BlueSci Issue 04 - Michaelmas 2005

Cambridge’s Science Magazine produced by

Issue 4

Michaelmas 2005

in association with

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Risk & Rationality When to trust your instincts

New Parts For Old The future of organ transplants

The Sound of Science New perspectives on music

• Artificial Intelligence • Obesity • • Women In Science • Genetic Counselling •

Michaelmas 2005

Issue 4

contents

Features

Don’t Believe Your Eyes

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Jamie Horder finds out why looks can be deceiving.........................................................................

Man vs Machine

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Anand Kulkarni and Swanand Gore puzzle out computer chess..................................................

Lies, Damned Lies and Statistics

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Tom Walters puts risk and rationality under the spotlight................................................................

The Transcendance of Tessellations

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Swanand Gore on a whole mosaic of disciplines..............................................................................

Fat Of The Land

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Helen Stimpson weighs up the evidence for the ‘obesity epidemic’ ...........................................

Regulars

Editorial .............................................................................................................................. 03 Cambridge News ............................................................................................................. 04 Focus ................................................................................................................................... 06 On the Cover ................................................................................................................... 20 A Day in the Life of... ...................................................................................................... 21 Away from the Bench ..................................................................................................... 22 Initiatives ............................................................................................................................ 23 History ............................................................................................................................... 24 Arts and Reviews .............................................................................................................26 Dr Hypothesis .................................................................................................................. 28 The front cover shows a droplet of YBCO superconducting ‘ink’ viewed with an optical microscope.The droplet has cracked during the drying process to produce the striking black fissures visible in the photograph.

Turn to page 20 for more details.

Article Submissions

Our contributors make BlueSci what it is.

Whether you’re a novice or an accomplished writer why not try your hand at an article for BlueSci?

Next Issue: January 2006

Submissions for our Lent Term issue must be received by 5pm on 14th November 2005.

submissions@bluesci.org enquiries@bluesci.org Photograph Competition

We want our readers to be able to see the science that’s going on in Cambridge. If you have an exciting image of your work then enter it into our

photograph competition for a chance to get it seen throughout Cambridge. Send your images by 5pm on 14th November. competitions@bluesci.org

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From The Editor New term, new BlueSci! Welcome to the latest edition of Cambridge’s popular science magazine.

Among the articles awaiting you in this issue is the FOCUS section, where we take an in-depth look at a particular scientific debate. This time, experts discuss the future of organ transplants, a thriving area of medical research encompassing topics as diverse as ethics and bioengineering.

On page 26, however, the focus is on the past, with a look at the history of the Cavendish, one of Cambridge’s most famous labs. As always, DR HYPOTHESIS answers your scientific queries on the inside back page: this issue’s topics range from life expectancy to life on other planets. If, like me, you’re a finalist beginning to wonder about a career after Cambridge, then turn to our regular feature DAY IN THE LIFE. This issue, Nerissa Hannink talks to a genetic counsellor.

In CRACKING CONDUCTORS on page 22, Tarek Mouganie talks about his work with superconductors and how he took the fantastic photo that adorns this term’s BlueSci. We are now accepting entries for

next issue’s cover image: photographs from all areas of science are welcome.

Send your picture and a brief explanation to competitions@bluesci.org by 14 November.

Ever been tricked by an optical illusion? In DON’T BELIEVE YOUR EYES, Jamie Horder explains how these apparently simple pictures manage to fool our eyes and brain. Find out about a groundbreaking interdisciplinary collaboration based here in Cambridge in THE SOUND OF SCIENCE. If you’ve been confused by conflicting reports about the so-called ‘obesity epidemic’ affecting the UK and US, discover the science behind the headlines with our article, FAT OF THE LAND. It’ll make you think twice about that second helping of chocolate cake…

Finally, an invitation: for your news, events and article submissions. See our website (www.bluesci.org) for more details.

Submissions from our readers make BlueSci what it is, so get writing!

Emily Tweed issue-editor@bluesci.org

From The Managing Editor

Happy First Birthday, BlueSci! It’s hard to believe how quickly things have evolved — not only have we set up a magazine and all its infrastructure, but we have also created a website with events listings and news articles not available in the print edition (www.bluesci.org). There is also a subscriptions service (subscriptions@bluesci.org) to get your own hard copies delivered each term. We have just begun a campaign to forge links with local schools to promote enthusiasm for science and offer local school students a chance to see their science writing published here in the future (schools@bluesci.org).

It’s our shared vision to continue to report science in Cambridge in the coming academic year as well as to facilitate

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interactions between scientists. To this end we are holding a first birthday celebration in association with CUSP at The Old Kitchen, Trinity College on Tuesday 18 October from 6.30pm. We’re hoping that as many people involved or interested in science communication within Cambridge will attend this event to meet other like-minded individuals over birthday cake and champagne. If you have not yet received an invitation and would like to attend, please email me at the address below.

Thanks again for your support — keep the feedback coming, Louise Woodley managing-editor@bluesci.org

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Issue 4: Michaelmas 2005 Produced by CUSP & Published by Varsity Publications Ltd Editor: Emily Tweed

Managing Editor: Louise Woodley Submissions Editor: Ewan Smith Business Manager: Chris Adams Design and Production

Production Manager: Tom Walters Pictures Editor: Tom Walters Production Team: Sheena Gordon, Helen Stimpson, Jonathan Zwart

Section Editors

News Editor: Laura Blackburn News and Events Team: Will Davies, Carolyn Dewey, Fiona McCahey, Richard Van Noorden Focus: Joanna Maldonado-Saldivia Features: Sheena Gordon, Helen Stimpson, Jonathan Zwart On the Cover: Tamzin Gristwood A Day in the Life of…: Nerissa Hannink Away from the Bench and Initiatives: Rob Young History: Victoria Leung Arts and Reviews: Owain Vaughan Dr Hypothesis: Rob Young CUSP Chairman: Björn Haßler

enquiries@bluesci.org

Varsity Publications Ltd 11/12 Trumpington Street Cambridge, CB2 1QA Tel: 01223 353422 Fax: 01223 352913 www.varsity.co.uk business@varsity.co.uk BlueSci is published by Varsity Publications Ltd and printed by Cambridge Printing Park. All copyright is the exclusive property of Varsity Publications Ltd. No part of this publication may be reproduced, stored in a retrieval system or transmitted in any form or by any means, without the prior permission of the publisher.

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Cambridge News

Cambridge News

Martin Jones

Art meets science in a collaboration between Professor Roberto Cipolla and Dr Carlos Hernandez-Esteban from the Department of Engineering, and Antony Gormley, the sculptor famous for creating the ‘Angel of the North’ in Gateshead.

Viewing sculptures in 2-D images is never the same as seeing them for real, so Cipolla and Hernandez-Esteban came up with a way of using a series of photographs of an object taken with a standard camera to create accurate 3-D computer

Dr Tamsin O’Connell at work

Crystal Clear Professor Harry Coles and Dr Mikhail Pivnenko of the Centre of Molecular Materials for Photonics and Electronics in the Department of Engineering have announced the discovery of a class of ‘blue-phase’ liquid crystals that remain stable over a wide range of temperatures.

Liquid crystals are substances with properties between those of a conventional liquid and a solid crystal; the liquid crystal may flow like a liquid but the molecules may have a highly organised structure, like in a solid crystal.The most common applications of liquid crystals are in liquid crystal displays, but they are also important in the manufacture of superstrength polymers such as Kevlar.

The blue phase of a liquid crystal refers to the thermodynamically stable state of the crystal and — despite the name — can be almost any colour. Blue-phase liquid crystals have a number of potential applications in photonics (the technology of generating and harnessing light) such as electrically switchable colour displays,

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models that can be viewed from any angle. The Digital Pygmalion project relies on a computer program which detects the important features of the object and its silhouette from multiple pictures, and then uses this information to calibrate the position of the camera. An algorithm creates an underlying ‘mathematical mesh’ which forms the basis of the 3-D reconstruction; next, the texture of the original sculpture can be laid on top and additional lighting effects can be added. Specially designed software allows viewing of the finished product.

Among other applications, this technique will revolutionize the digital archiving of museum collections and can be used to create low-resolution 3D models to help shoppers choose products sold online.

Gormley plans to use the high-resolution 3-D representation of one of his own sculptures produced by this technique to help him scale up the life-size original into a version more than 25 metres tall. LB www.eng.cam.ac.uk www.antonygormley.com

28,000 Years Ago

structed from mammoth bones, believed by archaeologists to be the best building material available at the time due to harsh weather conditions and a lack of nearby trees.

What makes the contribution of the Cambridge group to this collaboration so groundbreaking is that they are using scientific techniques that have never been applied to a site this old.The team will be using the latest biological and chemical methods to discover more about people’s diet and life in the cold and hostile Paleolithic environment.

These include soil micromorphology, which allows investigation of soil structure, and phytolith analysis, which gives researchers information on vegetation cover and plant use by humans. In addition, isotopic analysis of excavated bones will show what kind of diets people might have had. The team intend to return to the area for at least the next two years to unearth more information about the life of our species 28,000 years ago. FM www.arch.cam.ac.uk

A group of Cambridge archaeologists have begun a novel collaboration with researchers from the Czech Republic to study how hunter-gatherers lived 28,000 years ago. Professor Martin Jones and a group of archaeological scientists from the McDonald Institute and the Department of Archaeology are working with colleagues from the Academy of Sciences of the Czech Republic at the site of Dolní Vestonice in the Czech Republic.The area, which is approximately the size of central Cambridge, has been the focus of research since the 1920s and is an “amazing site” to study, according to Dr Tamsin O’Connell, one of the project’s researchers.

The group have made important discoveries about life in this era; finding for example that the hearth of the house was a focus of craft activities such as clay modelling and weaving as well as cooking and eating. Interestingly, many of the dwellings excavated in this area are conbut until now their sensitivity to temperature had hindered their widespread use.

The Cambridge researchers have discovered a solution to this instability.

They made 30 different mixtures of bimesogens (molecules that exhibit a liquid crystal phase) that show blue phases over a temperature range of 40–50°C. It is the unusual structure of these bimesogens that give the blue phase its stability. They consist of two rod-like components linked by a flexible chain, unlike normal blue phases in which liquid crystal molecules are arranged in a helix.The molecules are of the correct dimensions to reflect visible light, and by adjusting the twist of the molecule, red, green and blue reflections have been demonstrated.The researchers believe these materials will lead to a new generation of low-power-consumption liquid crystal displays. Another application is for tuneable optical filters, which could be used to sort through signals travelling at many different wavelengths down a single optical fibre in a fibre optic cable. FM

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Further information can be found in H. J. Coles, M. N. Pivnenko, Nature, 436: 997–1000 (2005) http://www-g.eng.cam.ac.uk/CMMPE

Harry Coles and Mikhail Pivnenko

An Extra Dimension

Photomicrograph of a wide temperature blue phase

Michaelmas 2005

Faber Maunsell/7-T

C a m b r i d g e N ew s

Artist’s impression of the Halley VI laboratory: construction is due to start on the Brunt Ice Shelf in 2007

Lab on Skis A new hi-tech laboratory is to be built in Antarctica for the Cambridge-based British Antarctic Survey (BAS).

Construction of Halley VI is due to start on the Brunt Ice Shelf in January 2007.

The laboratory is ingeniously designed to survive the hostile Antarctic conditions, including temperatures as low as -40°C, 80-mph winds, annual snowfall of 1.5 metres and days of near total darkness. The building’s unique feature is that it will stand upon a set of collapsi-

Tick Tock: Plant Clocks The circadian clock that governs key biochemical activities within plant cells enables plants to optimize their rates of photosynthesis and metabolism, according to research from the Department of Plant Sciences.

Plants possess an internal molecular clock which ensures that various physiological processes, such as stomatal opening, are cyclic, with a period of approximately one day-night cycle.This particular length of cycle was expected to hold a selective advantage on the basis that it would be optimal for plant metabolism.

Fighting Malaria Researchers from the Department of Genetics have won a prestigious grant from the Bill and Melinda Gates Foundation to investigate ways to reduce the incidence of malaria by targeting the insect which carries and transmits the parasite. Professor Michael Ashburner and Dr Steve Russell will share the £5 million award with colleagues at Imperial College London, the University of Washington and the Fred Hutchinson Cancer Research Centre in Seattle as part of the Gates Foundation project ‘Grand Challenges in Global Health’.

Dr Russell describes the statistics on

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ble ski-footed legs, permitting it to be moved around by bulldozer.This mobility will protect the base from being swept out to sea on an iceberg.The new installation, which will be continuously inhabited by a dedicated team of scientists and engineers, will enable the groundbreaking research performed by the BAS to continue at this invaluable site.The hole in the ozone layer was discovered due to observations and measurements taken on the Brunt Ice Shelf.

Future work at Halley VI will include experiments to predict the weather in

space — important for preventing damage to satellite communications and power systems — and investigations into the interactions between snow, air and sunlight and their resultant effects on the lower atmosphere. The director of the BAS, Professor Chris Rapley CBE said, “Our current research programme is attempting to answer big questions about the Earth’s climate system — so this remote and challenging place is vitally important for understanding our world.” WD www.antarctica.ac.uk

Researchers at the University of Cambridge decided to directly test this concept using plants with mutations in genes controlling periodicity. By growing wild-type, ‘long-period’ and ‘short-period’ mutants of the cress Arabidopsis thaliana under light-dark cycles of varying length, they measured the impact of periodicity on plant fitness. Fitness was assessed using indicators such as chlorophyll concentration, photosynthetic rate and degree of biomass accumulation.

It was found that plants thrived best when the intrinsic biological rhythm of the plant matched that of the external light-dark cycle, a condition known as

circadian resonance. The fitness benefits of circadian resonance were also evident in competition experiments, in which ‘long-period’ mutants out-competed ‘short-period’ mutants under long lightdark cycles and vice versa.

The molecular pathways through which the circadian clock controls the processes in question have yet to be elucidated. Further research in this area is likely to provide insights into ways of maximising crop yield and of increasing productivity in situations where lightdark cycles may vary. WD Further information can be found in Dodd et al., Science, 309: 630–633 (2005)

malaria as “frightening”: it is the second largest killer in the world, with 3 million deaths annually and 40% of the world’s population at risk.The most deadly form of the malarial parasite, Plasmodium falciparum, is transmitted in the bite of the female Anopheles gambiae mosquito.

There is no vaccine to protect against the parasite, and control efforts have been hampered by rapid increases in resistance of the parasite to anti-malarial drugs and of the mosquitoes to insecticides.

Researchers are now turning to genetic strategies to reduce the Anopheles mosquito population.

“Most of the methods that have been tried to control the insect population

have been spectacularly unsuccessful”, says Dr Russell. He and his team are, however, “very excited with this award and are hopeful that working with our colleagues in London and Seattle will yield significant results”. Over the next five years, the international team hope to develop a new technique which will disrupt genes essential for female reproduction, leading to female infertility and a population decline. Another approach under investigation is genetic manipulation of the mosquitoes so that they can no longer transmit the parasite. CD www.gen.cam.ac.uk www.grandchallengesgh.org

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Focus

New Parts for Old: t In 1954 a Boston doctor called Joseph Murray carried out the first successful organ transplant. The patient, a 23year-old man who received a kidney from his identical twin, was able to enjoy another eight years of life. His donor brother is still alive today. The success rates of kidney, heart, lung, cornea and liver transplants have improved steeply since this pioneering

The ethics of donation: a matter of trust and consent?

Organ transplantation from deceased donors is a successful therapeutic approach that can extend life expectancy and improve quality of life. Its success is, however, limited by the low availability of organs. Each year in the UK approximately 700 deceased individuals become major organ donors, while over 6,000 people wait for organs. In part, the shortfall in donations reflects an increase in the number of individuals who could benefit from a transplant, with the demand for organs and tissues set to escalate yet further in the near future. For instance, the UK kidney transplant waiting list rose by 26% between 1994 and 2003, and this figure is expected to increase to 33% by 2011. Some researchers have stated that the current organ shortage is not merely a problem of inadequate numbers of potential donors, but sub-optimal use of the available donor organ pool, exacerbated by the failure of health professionals to initiate the donation process.

Relatives of potential organ donors remain the most important link in maintaining organ supply, as they must express their lack of an objection before donation can take place. Across the UK, relatives’ refusal rates are around 40%, rising to 70% in non-white groups.These figures are significant, particularly as Asian and black populations have higher rates of renal failure than whites (mainly due to susceptibility to diabetes mellitus and hypertension), making up 52% of kidney transplant

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New legislation,The Human Tissue Act (2004), arose out of concern about organ retention and evidence that the law governing the post-mortem use of organs was not as comprehensive, clear or consistent as it might be.While the Act is to be welcomed with its guiding principles of informed consent and communication, it does raise certain challenges for health professionals and bereaved individuals, as well as the need to work increasingly in

Views persist among some congregations and their leaders that organ donation is culturally and religiously inappropriate

found effects, by affecting the suffering sustained by the dying and the consequent experience of those who care for them, potentially influencing their decisions about post-death organ donation.

Secondly, the lack of consent for the retention of organs following postmortem within a number of NHS Trusts came to public attention in 1999, when over 50,000 body parts or pre-term babies were discovered to be held by pathology services throughout the UK, sparking nationwide concern and prompting some 30,000 families to contact hospitals for information about their deceased relatives.

Subsequent inquires indicated that organs, particularly hearts, were routinely removed post-mortem and retained for use in research and teaching, without explicit consent of the next-of-kin. These investi-

Across the UK, relatives refusal rates are around 40%, rising to 70% in non-white groups

waiting lists in some areas. The reasons for refusal are poorly understood: although religious scholars in all major faiths perceive organ donation as a laudable practice and ultimately a matter of personal choice, views persist among some congregations and their leaders that organ donation is culturally and religiously inappropriate.

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Undoubtedly, there is a need to rebuild the trust the public is prepared to invest in health professionals responsible for the care of the dying and the bereaved, as two major health scandals and new legislation have highlighted. First, in the wake of the Harold Shipman affair, anecdotal reports are springing up throughout the UK about the restraint some doctors are exercising in prescribing analgesic medication to the dying. Such practice may have pro-

surgical intervention, yet hundreds of people die every year in the UK waiting for organs.We tend to feel uncomfortable thinking of our own death, and so few people register as organ donors. Moreover, medical advances and a decrease in the death rate of healthy individuals in road accidents mean that only a very small number of people become suitable donors.

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gations demonstrated weaknesses in the protocols for post-mortem consent, and that services for supporting bereaved families were fragmented and inadequate.

Good post-mortem practices, which respect the views of family members and include properly obtained consent, are essential to improve the donation process.

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partnership. For instance, the Act has provided that in the case of an adult “appropriate consent” rests with “a person who stood in a qualifying relationship to him immediately before he died”. There are a number of criteria listed defining qualifying relationships, which could raise difficulties for bereaved individuals and the responsibility they feel they have for decisions made on behalf of the deceased.

If organ transplantation is to remain a viable therapy, efforts must be made to facilitate donation. This involves helping relatives to make decisions which can impact upon their bereavement: it is important they do not regret these choices later. Western societies preserve the ethos of organ donation as a ‘gift of life’, a stand sensitive to relatives’ post-mortem distress that preserves the notion that the body is not property to be owned. Thus, although financial rewards or an offer to pay for funeral expenses of a donor could potentially help increase organ supply, the notion of organ trade is generally perceived as immoral. In addition, more could be done to highlight the benefits of donation to society. Not making relatives aware of the option of donation limits their postmortem choices and may deprive them of fulfilling the wish of the decedent.

Dr Magi Sque is a Senior Lecturer at the School of Nursing and Midwifery, University of Southampton

Michaelmas 2005

Fo c u s

: the Future of Organ Transplants

Challenges and advances in xenotransplantation The shortage of organs and tissues for donation has made xenotransplantation a realistic approach for the treatment of organ failure and disease. In the context of human xenotransplantation, it is envisaged that in the future, whole organs (heart, kidney) or tissue (pancreatic, islet cells or neural tissue) from pigs may be transplanted into human recipients.The comparable size of pig organs to their human equivalents and ease of breeding makes this animal the optimal donor for xenotransplants.These features also facilitate research into the immunology of xenograft rejection, and have led to the development of a number of genetically engineered pig lines.

Transplantation of tissue from one species to another carries two major problems, which are the focus of that research of numerous laboratories. The first is immunological rejection and the second is the risk of zoonotic infection (diseases communicable from animals to humans). Rejection of transplanted tissue has proven to be a major obstacle in all experimental studies to date. Porcine tissue expresses a number of specific epitopes (proteins and carbohydrates on the surface of cells) which trigger a very brisk human immune response. In the case of whole organ transplants, the rejection process mounted by the host is hyperacute and takes place in a matter of seconds or minutes. The main mediators of this rejection process are pre-formed human antibodies, which react with the epitopes on the transplanted organ, leading to rapid and irreversible damage of the blood vessels, ischaemia (inadequate oxygen delivery) and death of the transplanted organ. In order to overcome this rejection process, powerful immunosuppressive drugs, similar to those used for allografting (human-to-human transplants), would be necessary.

Immunosuppressive treatments for xenotransplants would need to be much more aggressive than those currently adopted prior to allografts, which already put patients in a susceptible position when

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driven several areas of scientific research to develop alternative treatments for organ failure. A century after a pig kidney and a goat liver were unsuccessfully transplanted to two different women in France, Roger Barker investigates the challenges facing the promising and extremely controversial area of xenotransplantation, the grafting of tissue from one species into

fighting opportunistic infections.

Strategies aiming to modify the transplanted porcine tissue so it becomes less immunogenic are increasingly successful.

They involve genetically engineering the porcine tissue, either to express factors that suppress the host immune response or to remove the epitopes that drive immune rejection. In the first case, this has been achieved by generating porcine tissue capable of expressing inhibitors of the human complement cascade, a series

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another. Finally, Ben Hanson describes the development of an artificial device designed to assist cardiac function which is being developed in Leeds.

Along with stem cell technology, xenotransplantation and ar tificial organs promise to open avenues previously considered purely fictional, but which may hold great benefits for human health.

of proteins whose activation in adverse immune reactions leads to rapid loss of tissue.This work was pioneered by David White and colleagues at Imutran, a company originally based here in Cambridge.

The second strategy, mainly undertaken

by David Cooper and David Sachs at Massachusetts General Hospital in Boston, has involved removing the major immunogenic epitope in pig tissue, called alpha 1,3-galactosyltransferase. Using this approach, the survival of transplanted

Indigo Goat, flickr.com

In this edition of BlueSci, we explore in detail some of the questions associated with human organ donation and transplantation.

Magi Sque looks at the possible reasons behind the severe shortage of organ donors in Britain and the issues related to obtaining consent from the relatives of deceased potential donors.

The scarcity of donated organs has

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Focus

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It seems possible that neural tissue could be grafted successfully into the adult brain of patients with neurological disorders

organs has been extended in experimental studies but is by no means longlasting.

To date, successful transplants using baboons have only prolonged the life of pig organs for months rather than years, but this does not exclude the very real possibility that modified animal organs may be one day used in the clinic.

The second major issue concerning xenotransplantation is the spread of infection, which at its simplest level can be in the form of bacteria and viruses commonly found in farm-bred animals. This is a particular problem for transplant recipients, whose immune systems are already weakened by the stress of invasive surgery and the drugs used to prevent rejection of the donor organ.The risk of such infections can be dramatically reduced if the animals are raised in special quarantine conditions. A more serious concern, however, relates to viruses that could spread from the pig and cause disease in humans. In particular, a class of viruses known as porcine endogenous retroviruses (PERVs) do not cause disease in pigs but could spread into the human recipient. Such infection could theoretically trigger a hitherto unknown disease in much the same way as has been postulated for the spread of AIDS from nonhuman primates, but based on tests on more than 160 patients who have been exposed to living porcine tissue, there is no evidence to support such risk. Data reported in 1999 by Khazal Paradis and colleagues at Imutran clearly demonstrated that, despite the presence of surviving pig cells years after transplantation, there was no evidence of infection or disease in human recipients. In contrast, subsequent studies, notably by Luc van der Laan and

Since 1 April 2005...

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colleagues in California, have included transplantation of pig tissue into severe combined immunodeficient (SCID) mice to show that the PERVs can spread throughout the host's body. In these mice there are no overt signs of disease, but clearly the fact that PERVs can escape and spread under such circumstances is a cause for concern. Still, it should be noted that immunosuppression in organ recipients is much less powerful than that seen with SCID mice.

A further uncertainty is whether pig organs and tissues have the capacity to perform the functions of their human equivalent with comparable efficiency.

Research suggests that this may depend on the specific organs.

Xenotransplantation of liver, for example, could be problematic because of the large number of essential and often speciesspecific proteins produced, whereas there is no reason to believe that pig dopamine neurons could not be used in patients with Parkinson’s disease, as the grafted cells should be able to produce the missing dopamine in sufficient concentrations to mediate a positive effect. Moreover, in

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people in the UK have received transplants

377

people have donated organs

6,331

people are still waiting for transplants

Figures from www.uktransplant.org; correct at time of going to press. the complement cascade and more on the other effector of the immune system, namely the T cells. While these cells do contribute to the chronic rejection of organ transplants in xenotransplantation, it seems possible that the engineering of neural tissue coupled to a strong immunosuppressive therapy would enable neural tissue to be grafted successfully into the adult brain of patients with neurological disorders.

Transplantation of tissue from one species to another carries two major problems: immunological rejection and the risk of zoonotic infection

terms of neurodegenerative disorders, rejection following transplantation of pig tissue into the brain has been shown to be much slower than with whole organs.

This process relies less on antibodies and

Further Reading For information on becoming an organ donor, go to www.uktransplant.org.uk or www.bbc.co.uk/health/donation For information on blood or bone marrow donations, go to www.blood.co.uk A discussion of the ethics involved in organ donation can be found at: www.studentbmj.com/issues/03/07/education/232.php

For the University of Southampton’s study on organ donation and care of bereaved relatives, go to www.nursingandmidwifery.soton.ac.uk/familybereavement

To explore the issues surrounding xenotransplantation further, read Nature Biotechnology 18: IT53–IT55 (2000).

To find out more about the work on cardiac assist devices at the University of Leeds, go to www.mech-eng.leeds.ac.uk/cardiacassist/home.htm

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The recent development of transgenic pig lines has enabled the field of xenotransplantation to advance yet closer to the clinic. As our understanding of the complex immune reactions induced by xenografts improve, so do strategies to overcome rejection. In the field of neural transplantation, emerging data suggests that cells transplanted from one species into another may have a primary advantage over their allografted equivalent. For example, xenografted pig cells appear to have a greater capacity to grow processes and migrate within the adult rodent brain than rodent cells of the same type. If this proves to be the case, then xenografted tissue would have great potential to replace cells lost in neurological conditions, as well as to recreate circuits through long-distance neuronal connections. It is, therefore, an exciting time for xenotransplantation and its potential applications in the treatment of clinical and neurological disorders.

Dr Roger Barker is a University Lecturer in Neurology and Honorary Consultant Neurologist at the Cambridge Centre for Brain Repair

Michaelmas 2005

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and blood vessels could be at risk of abrasion, so we have used a structure which separates the contracting bands from the heart's surface, provides a protective cushion, and maintains the shape of the device. To minimise interference with the heart during surgery, the device is constructed as a ‘sock’, slipped onto the ventricles in one motion, and secured in place. The motors are sheathed from the body with a bio-compatible sheet.

The difficulties associated with using human muscle have driven attempts to create a mechanical ‘artificial muscle’ assist device

different areas of the heart. Power for the device is provided by battery packs.

Control of the assistance force is crucial. If appropriate assistance is provided, allowing the heart muscle to rest, studies have shown that the heart muscle can start to regenerate. Assistance must be gentle to avoid damage to the coronary arteries that lie on the surface of the heart and supply blood to the heart muscle.

After contracting to pump blood out of the heart, the device must relax quickly and not restrict the refilling of the heart.

The time between heart-beats varies, and

Where a heart muscle is weakened or failing, the treatment options available are fairly limited and transplantable hearts are very rarely available

shoulder blade), and wrapping this around the heart. This muscle wrap is then electrically stimulated so that it contracts in sync with the heartbeat. This technique was shown to be successful in that the heart can be briefly assisted.

Ben Hanson

Replacement of diseased organs by artificial devices is an exciting challenge facing researchers with a diversity of scientific backgrounds. For instance, at the Biomedical Engineering Research Group in Leeds, mechanical and electrical engineers, material and computer scientists, physicists and biologists are joining forces to create joint replacements, synthetic tissues and devices to aid cardiovascular anomalies and disease.

Heart attacks or viral diseases can weaken the heart muscle, reducing its pumping power. When this happens, the heart often still has sufficient power to sustain life, but is unable to increase output to cope with greater pumping demands during exercise. Where a heart muscle is weakened or failing, the treatment options available are limited and transplantable hearts are rarely available.

Recently, efforts are increasingly being directed towards providing mechanical assistance to a weakened heart.

One strategy to increase pumping power is to implant a motorised pump into the bloodstream within the chest cavity. These pumps use a rapidly spinning impeller (similar to a propeller) to increase the flow of blood and have been found to work in the few cases of human implantation so far. There are, however, some problems with this approach, which are currently being tackled. The rapidly spinning impeller can damage the fragile blood cells and potentially instigate blood clots. Additionally, the immune system must be repressed with drugs in order to prevent rejection of the device. These complications are the result of blood flowing through an artificial chamber, which may be recognised as foreign and attacked by the recipient's immune system. Alternatively, to avoid contact between the implant and the blood, the heart can be assisted with direct cardiac compression (DCC), providing a compressive pressure to the heart's outer surface. One method of achieving this is through a surgical procedure known as a cardiomyoplasty, which involves detaching the patient's own latissimus dorsi muscle (a sheet-like muscle across the

Stimulation must, however, be carefully controlled since skeletal muscle — unlike healthy heart muscle — fatigues over time.

The difficulties associated with using human muscle have driven attempts to create a mechanical ‘artificial muscle’ assist device. Pneumatic pressure has been applied to hearts in different ways: by placing the heart within a pressure vessel, surrounding the heart with an inflatable cuff, or applying inflatable patches. The pneumatic actuators (cuffs, patches) have the benefit of high power to weight and power to volume ratios but the air hoses such a device requires pass through the skin and so are a potential source of infection, while attachment to a pneumatic pressure supply limits mobility.

Several new ‘artificial muscle’ technologies are being developed, but these new technologies are at early stages of development and are not yet suitable for an implantable cardiac compression device.

At the University of Leeds, we are developing a DCC device consisting of a series of bands to be placed circumferentially around the heart. These bands can contract in the same way a belt may be tightened around one’s waist. This contraction is powered by miniature motors, one per band, which are individually controlled.We can provide contraction in the form of a wave in order to squeeze blood up and out of the ventricles, and can apply varying levels of assistance to

Fo c u s

Artificial organs: direct cardiac compression heart assist device

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we are using a pacemaker as part of the system to sense when the heart beats and to synchronise the assist contraction.

The bands are inelastic in their circumference, but flexible. If these were directly on the surface of the heart, the tissue

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We have created a novel testing simulator that uses a computerised model of the heart and circulatory system, which is combined with a physical simulator representing a beating heart. This allows physcial testing of the mechanical performance of the assist device under realistic conditions. With the computer model we are also able to visualize how the assistance will affect the blood pressure and flow throughout the body; this can be repeated for many different states of heart failure and patient type.

We are developing new motor technologies that will hopefully be used to create a flexible sheet of ‘artificial muscle’ to replace the motorized belts currently used. The way the body reacts to assistance in the long term is yet to be determined, although avoiding direct contact with the bloodstream should greatly reduce the likelihood of immune system rejection.

Dr Ben Hanson is a Lecturer at the School of Mechanical Engineering, University College London, and a former Research Fellow at the University of Leeds

09

Don’t Believe Your Eyes The ancient Greeks knew that if they wanted a stone column to appear straight when viewed from a distance, they had to construct it with a slight bulge in the middle. What they didn’t know was how our eyes were tricked in this way. Today psychologists describe these effects as an optical or visual illusion and experimental psychology and neuroscience have revealed some of the brain processes behind them. Although many illusions are still as mysterious as ever, some of the simpler ones are well understood.

What happens when you look at a visual illusion? Light reflected from the illusion is focused by the lens in the eye to form an image on the retina. The retina consists of several layers of cells at the back of the eye, including cells known as photoreceptors — the famous rods and cones. These photoreceptors detect light and convert it into an electrical voltage that the nervous system can interpret. The magnitude of this

Figure 1. Koffka Ring The two semicircles are an identical shade of grey. The one which is seen on a pale grey background appears to be darker than the other, which is imposed on a dark grey background.

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Jon Heras

Jamie Horder finds out why looks can be decieving voltage is proportional to the intensity of light emitted from a particular point in the illusion. Brighter points generate larger signals than darker points.

Photoreceptors communicate these signals to a layer of neurons on the outer surface of the retina, known as retinal ganglion cells. The properties of these ganglion cells are critical to the functioning of vision and are also believed to be responsible for a number of common optical illusions. A single ganglion cell receives inputs from multiple photoreceptors via junctions called chemical synapses. A ganglion cell is ‘excited’ by light falling on photoreceptors in a small, circular area of the retina, but is ‘inhibited’ by light striking photoreceptors in a ring-shaped area surrounding this — a phenomenon known as lateral inhibition. The greater the net excitement of a ganglion cell, the brighter a particular point appears.

Lateral inhibition is crucial in explaining the Koffka Ring (Figure 1).

The ganglion cells are excited by photoreceptors responding to the two grey semicircles, but are laterally inhibited by photoreceptors responding to the surrounding pale or black region. The pale area causes a greater level of lateral inhibition than the black area because it reflects more light into the retina. The semicircle surrounded by the pale area therefore seems darker as the ganglion cells are excited less. Although the light falling on the retina is of the same intensity for both semicircles, the brain perceives the shades as being different because of lateral inhibition.

Lateral inhibition is also important for detecting edges and lines. A uniform level of light will lead to equal amounts of excitatory and inhibitory signals transmitted by the photoreceptors to each ganglion cell, which will cancel out the signal. Only a difference in light over a small area of the retina, such as a line, can be detected. A specialized region of the brain, called the visual

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cortex, is responsible for line detection.

The optic nerves carry signals from the eyes, through various areas of the brain, to the visual cortex, located in the occipital lobes at the back of the head.

Figure 2. Orbison s Illusion This is a square and a number of diagonal lines within a rectangle. Both shapes appear distorted — the square appears to be ‘squashed’ into a kite shape, while the rectangle looks wedge-shaped.

The visual cortex contains ‘simple cells’. Don’t let their name fool you, as simple cells are actually very clever.

Each simple cell is activated by a light or dark line in a particular area of the visual field. For example, one simple cell might respond to a vertical line at a specific place in the top left of your vision, while another might respond to a tilted line at a specific place in the bottom right of your vision. This happens because each simple cell receives input from a group of ganglion cells arranged in a line. If you’re thinking that there must be many simple cells to detect every possible line at any angle anywhere you look… you’d be right! The visual cortex also contains ‘complex cells’.These respond to lines of a particular orientation and other sophisticated patterns of stimulation, irrespective of their location in the visual field.

Lateral inhibition of simple and complex cells underlies Orbison’s Illusion (Figure 2) and the Ehrenstein Illusion (Figure 3). Simple and complex cells are

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arranged into ‘orientation hypercolumns’, or strips of tissue containing cells that respond to a particular orientation of a line. Adjacent columns have similar preferred orientations. These columns show lateral inhibition, in the same way as the retinal ganglion cells. If you simultaneously look at two lines of different orientation, lateral inhibition will cause them to appear at the wrong angles. It’s the same principle as in the Koffka Ring, but applied to direction rather than brightness.

Figure 3. The Ehrenstein Illusion The square in this illusion, superimposed on a number of concentric circles, appears almost like a four-pointed star.

Figure 4. The McCollough Effect

Another feature of the orientation hypercolumns is the ‘tilt after-effect’.

Each orientation-selective cell inhibits both its neighbours and itself. However, there is a delay built into this self-inhibition. The activity of particular cells is highest when you first look at an image and gradually declines as the cells adapt.

If you allow the cells long enough to adapt — typically one or two minutes — and then look at something else, strange things happen. For example, the cells responsible for detecting a 30degree tilt to the right have adapted and are active at a lower than normal level.

The brain interprets this as meaning that vertical lines are tilted to the left!

Many other visual features, such as motion and rotation, exhibit similar after-effects. With this in mind, it’s possible to decipher the basis of the McCollough Effect (Figure 4). After staring at the green- and purple-striped

squares for up to five minutes, switching between them every 15 seconds or so, the white stripes appear purple in the case of the vertical stripes and green for the horizontal ones.

Somewhere in the visual cortex there are red-vertical and green-horizontal edge-detecting cells. These cells can adapt: the mechanism of adaptation in this case must be different because the effect can last for days or weeks — but the underlying principle is the same.

Optical illusions can be fun, but they can also reveal information about the brain.These examples show that illusions are not random failures of our visual system, but, rather, necessary products of the way our brain processes the information it receives from our eyes. Maybe we can’t believe everything we see?

Jamie Horder is a third year Natural Scientist specializing in Experimental Psychology.

the

mays

4 books: £10

For fourteen years, Varsity has published THE MAYS, a renowned collection of poetry, prose and non-fiction writing from students in Cambridge & Oxford.

THE MAYS has become a major event in the literary calendar, renowned for helping to launch the careers of the likes of Zadie Smith, Jay Basu and many more. Each year a guest editor selects the best of hundreds of entries for publication in the latest edition. Past guest editors have included Ted Hughes, Stephen Fry, Philip Pullman & Andrew Motion.

For a limited time only, THE MAYS series has been re-issued at a special low price. Pick any of the anthologies for just £3, or you can choose four for £10. Buy from Heffer’s Bookshop during October, or use the order form to buy direct. And remember their names!

‘Maybe in a few years this lot will have me out of a job’ - Zadie Smith

THE MAYS – ORDER FORM

Choose any edition for £3, or 4 for £10. __ Mays 13 (2005) Robert McFarlance __ Mays 12 (2004) Ali Smith __ Mays 2003 - Ali Smith __ Mays 2002 - Andrew Motion/Nick Cave __ Mays 2001 Poetry - Michael Donaghy __ Mays 2000 Stories - Lawrence Norfolk __ Mays 2000 Poetry - Paul Mondoon __ Mays 1999 Stories - Penelope Lively __ Mays 1999 Poetry - John Kinsella __ Mays 1998 Stories - Sebastien Faulks __ Mays 1998 Poetry - JH Prynne

Please add £1 per book as a postage contribution.You can also buy from our offices (below) or from Heffer’s (during October).

Or, please send a cheque made payable to Varsity Publications Ltd to Varsity, 11–12 Trumpington Street, Cambridge CB2 1QA. Offer valid whilst stocks last

Man versus

Jon Heras

e n i h c a M

Anand Kulkarni and Swanand Gore puzzle out computer chess Britain’s highest ever ranked chess player, Michael Adams, recently suffered an overwhelming defeat by Hydra, the world’s most powerful computer. With this the most recent in a string of computerized triumphs, the chess world is gradually accepting that machines have essentially ‘solved’ the game. Until now, tasks like playing chess required human intelligence, an attribute that has taken millennia to emerge through countless cycles of evolution. In stark contrast, machines designed by us reached their current state within just two human life spans.

Does the triumph of machine over man on the chessboard imply that machine intelligence has surpassed

brute force refers to trying every possible solution until the best one is found. It does not rely on human-like intelligence but exploits the computer’s ability to examine every possible outcome. A second and much more complicated strategy tries to mimic the learning process of human chess grandmasters using sophisticated programming languages. To date, computer programmers have adopted a brute force approach to play to the strengths (calculating) rather than the shortcomings (learning) of the machine. Today’s computers, Hydra included, lack any real capacity to learn; it is the team of programmers that learns from Hydra’s bad experiences and fine-tunes the chess programs so as to overcome the computer’s weaknesses. In the

is much more than just “ Intelligence calculating power and should not be confused with computing speed human intelligence? Could the successful replication of human intelligence in machines jeopardize our existence on Earth?

Since the emergence of artificial intelligence (AI) in the 1950s, researchers have often used chess as an experimental model.

In the early days of computer chess, Claude Shannon, the computer science pioneer, proposed two strategies for designing chess programs.The first is called the ‘brute force’ strategy. In computer science language,

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early days, the brute force approach was of limited value, since the marginal processing power of contemporary computers made investigating every possible solution impractical. More recently, however, the many-fold increase in computing power has allowed the brute force search to become a viable strategy. As a result, the 1980s saw machines taking on the best players and sometimes sharing the honours. In 1997, the computer Deep Blue made history by beating Garry Kasparov,

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the most successful player in chess history.

Although human players fought on bravely, managing a few drawn encounters with machines such as Deep Blue and Deep Fritz, it was clear that the computer’s brute force was dominating over human intelligence; a fact which Hydra finally demonstrated by crushing Adams whilst running at only half of its design capacity.

What sort of black magic drives these computers? Major reasons for their triumph are both computational and technological. Computer chess programs view a chess game as a tree, with board positions as nodes and moves as branches. The root of the game tree is the starting position and the game tree branches out into nodes, each of which corresponds to a possible move.At the start of the game, the tree can branch out in 20 ways because white can play her first move in 20 different ways (four knight moves and 16 pawn moves). Black can then make a counter-move in 20 ways, leading to a massive 400 combinations for the first round alone. It is easy to imagine the exponential explosion of possibilities as the game proceeds: within 10 moves the number of possible outcomes surpasses the number of atoms in the universe. It is quixotic to take a brute force approach to search the entire game tree for the next best move.

This is where theoretical analysis paves the way by cutting down on search space.

The basic idea is to avoid unpromising paths in the tree, a process for which search algorithms are critical. Experts have devised some approximate ways to assess the relative merits of moves quantitatively. A simple heuristic is to assign points to pieces, for example, 1 to pawn, 3 to knight, 3 to bish-

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op, 5 to rook, 9 to queen and 200 to king.

One can also give a greater weight to centralized pieces, the pawn structure or the phase of the game. The ‘Minimax’ search algorithm makes use of such heuristics and works on the assumption that each contestant plays so as to minimise the possible damage caused by the opponent’s following move.This approach is depicted in Figure 1.

Over a span of more than 40 years, various improved algorithms have been devised. These have allowed computers with the same basic speed to play significantly better chess. One such algorithm, the ‘Alpha-beta pruning’ technique reduces the number of terminal evaluations by pruning out parts of the search tree that are so good for one player that the opponent will never allow them to be reached.

Along with sophisticated search algorithms and heuristics, hardware development has also had a major role in the remarkable performance of chess-playing computers. Moore’s law states that the number of transistors on an integrated circuit (a rough measure of computer processing power) doubles every 18 months. As processors get cheaper and faster with every generation, it has become possible to harness many of them together to vastly improve overall performance. Chess is also a problem that is easily parallelized. This means that we can give each of several computers a branch of the game tree to evaluate and then check which processor has found the best solution.Versions of the Alpha-beta pruning algorithm for parallel systems were developed throughout the 1980s and by the end of the decade the use of multiple processors within a single program was commonplace.

Another consequence of the declining cost of hardware is the ability to develop dedicated chess hardware. In 1980, Carnegie Mellon University in the US began developing specialized chips for implementing the Minimax algorithm exclusively for chess moves. Based on this special hardware, their 1988 chess machine HiTech was able to analyse up to one million board positions per second. The version of Deep Blue that defeated Gary Kasparov in 1997 had 256 special purpose chess processors working in parallel, analysing 200 million board positions per second.This hardware, Application Specific Integrated Circuit (ASIC), accelerates specific calculations needed for the Minimax algorithm using dedicated circuits to carry out a particular set of tasks. ASIC can implement a specific algorithm at least 100 times faster than programming the same algorithm in conventional software on a general-purpose computer.ASIC machines are efficient both in performance and power consumption, but lack flexibility in their dedicated hardware circuits, and so perform at a slower rate when the search algorithm is altered or when new chess knowledge is added.

Recently, an alternative to ASIC that avoids these problems has emerged.

Reconfigurable computing allows hardware circuits to be configured to suit the

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Figure 1. The approach used by the Minimax algorithm to pick the best next move.The nodes are board positions; oval nodes show positions where it is the computer’s move (marked A) and square nodes show those where the opponent is to move (marked C).The numbers show the computer’s score at each board position. Let us assume that the computer thinks only two moves ahead. According to the Minimax approach, the computer’s best action is A1 because the least gain with A1 is 15 and that with A2 is five, i.e. the worst score with A1 is better than the worst possible with other moves.This is a highly simplified scenario, in which just four terminal positions are evaluated; generally the computer searches many more moves ahead and the average number of legal moves in any position is 35.

particular tasks at hand. Reconfigurable systems make use of Field Programmable Gate Arrays (FPGA), semiconductor devices that process digital information and can be reprogrammed after manufacture without slowing performance.

This latest hardware technology forms Hydra’s basic building block. Hydra is a cluster of 32 processors assisted by the same number of FPGA chess cards. It has a processing power of 100 billion calculations — or 200 million chess moves — per second with this configuration and can project the game up to 40 moves ahead.

What are the implications of this significant chess achievement for other areas of AI? The public is often intrigued by the idea that intelligent machines could supersede us as the dominant life form on Earth.

The triumph of machines over humans on the chessboard tends to be misconstrued as a step towards this idea becoming a reality.

Despite the popular impression that Hydra and Deep Blue are masterpieces of AI, they are in fact no more capable of thought than a toaster. Intelligence is much more than just calculating power and should not be confused with computing speed. Hydra and Deep Blue are examples of ‘expert systems’, computers with large and powerful databases that enable them to perform narrowly defined tasks extremely well. The insights gained from designing such machines might tell us how to solve tedious problems quickly with the latest hardware technology, but hardly address large-scale issues in robotics and AI.These challenging problems include replicating a wide spectrum of human intelligence in a machine: knowledge, cognition and learning from experience.

Learning is an essential component of intelligence. Many AI researchers have been

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trying to make chess machines intelligent by including human-like learning processes in their programs, but there has been no great success to date.At present,the way we develop a computer chess machine is by trying to duplicate the knowledge and inference methods of human grandmasters. We have little idea of how to devise a system capable of learning in this way and also of inventing completely new games and negotiating their rules.This is because humanity has yet to unravel the mysteries of the brain. It is hoped that within the next 30 years, we will have a better understanding of how the human brain works, which will give us ‘templates of intelligence’ for developing stronger AI. Herbert Simon and John McCarthy, who are among the co-founders of AI, have both referred to chess as the Drosophila of AI: it is a simple model, a testbed. Hence, it may seem rash to expect fully intelligent machines within a few decades, when computers have barely matched the aptitude of an insect in a half-century of development. Instead, many long-time AI researchers suggest that a few centuries may be a more believable period.We have waited millions of years for the evolution of natural intelligence; we may have to wait centuries for its artificial equivalent. Until then at least, human intelligence rules. http://chess.about.com/od/computerchess www.hydrachess.com http://world.honda.com/ASIMO Anand Kulkarni is a PhD student in the Institute for Manufacturing.

Swanand Gore is a PhD student in the Department of Biochemistry

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Lies, Damned Lies and Statistics The London bombings of 7 July 2005 and the attempted attacks two weeks later caused many people to abandon travelling by bus and tube. Those who chose to stay away from the tube network did so because they perceived the risk of travelling on public transport as too great. But what governs our perception of risk and how easy is it to be misled by the statistics we hear?

Analysis of the risks that surround us is something that we have to do every day.

Cognitive psychologists suggest that there are two mechanisms by which humans can judge risk: the ‘experimental system’ and the ‘analytic system’.The former gives rise to our intuitive understanding of risk and relies on images and associations formed in our minds. This process occurs with little conscious control and it is the system which gives us a ‘gut feeling’ that something is wrong — that we shouldn’t eat some strangesmelling food, or walk down a dark alley.

By contrast, the analytic system requires much more conscious thought. This is the system by which we logically analyse evidence and statistics in order to reach reasoned conclusions.

We rely on our intuition in almost all situations in daily life; if you walk into a crowded pub and feel threatened for some reason, it’s not because you’ve performed an analysis of all the possible dangers and mitigating factors. If you had stopped to calculate the exact probability that the bunch of guys with lots of empty pint glasses and a certain team’s football shirt on were just up for a quiet night, and weren’t in fact going to take offence at your choice of wardrobe today, it might well have been too late.

We need to be able to inform our intuition by understanding and interpreting data on the dangers that face us, data that may come in many different

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forms. One factor in judging risks using our intuition is the availability of mental images related to an event about which we are concerned. Images which are particularly dramatic or disturbing, or which we are exposed to frequently, will be recalled more easily than other images and may make an event seem much more likely than it really is. The shocking nature and extensive media coverage of the London bombings made the images of them much more accessible in people’s minds, and thus made it seem more likely to them that the events would happen again. Conversely, hazards which are hard to visualise are often perceived as being less dangerous.

Control is also another key factor in the perception of risk. If a hazard seems to be outside of your control it can appear more serious. Psychologists have suggested that qualitative aspects of risk such as these can be roughly split into two categories: ‘dread’ and ‘unknown’.

Dread is typically associated with risks which appear uncontrollable or which have the potential for large-scale destruction, even though they may be far in the future. Hazards like nuclear power, radiation and climate change are seen as being high in both dread and unknown, whereas smoking and driving too fast are ranked much lower in both categories.

This may explain why people are much more likely to voluntarily expose themselves to risks of the latter type.

The channels through which information about risks passes can also increase or reduce their perceived severity. Trust in the source of information about a risk is crucial. Information from a trusted source will be taken much more seriously than information from an unknown or untrustworthy source, which can in some cases actually cause the recipient to take the opposing view.

Hazards which are hard to visualise are often perceived as being less dangerous

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Jon Heras

Tom Walters puts risk and rationality under the spotlight While the experimental system is a simple and robust method for assessing risk, there is the danger that some risks can be perceived as different from what they actually are — sometimes wildly so.

The analytic system can be seen as a kind of ‘reality check’ for our intuition.

If some real data are available against which we can check our ideas, then it would be a good idea to use them. Hard facts are useful, but again, there are dangers in assessing the statistics with which we are presented.

A lot of the confusion that is encountered when assessing statistics occurs simply because they are presented in a form that makes them difficult to comprehend. Percentages generally tell us very little. If there is a 10% rise in muggings per year, what does that mean; one more, making the total 11, or 1000 more, bringing the total to 11,000?

Furthermore, what is the overall population in which these muggings are occurring: is it your street? An entire city? The country?

One story which made front-page news in June 2005 was a four-year study that suggested that taking ibuprofen increases your risk of heart attack. The figure that many newspapers reported was that taking ibuprofen increases your risk of a heart attack by 24%. Pretty scary stuff by the sound of it. Statistics, especially on health-related stories, tend to get reported in this vague fashion. But is there a better way? Humans like dealing with real-life examples using numbers in a way which are easily comprehensible.

Natural frequencies, which use actual numbers rather than percentages, are a good way of expressing risks because they allow us to put the information in a realistic context.The actual data from the study stated that there would be one extra heart attack per 1,000 or so people on ibuprofen. All of a sudden the statistic isn’t quite so shocking.

Legal evidence is another area where there are numerous statistical pitfalls.

Although juries do not assess risk per se, they do have to deal with a great deal of evidence, some of it backed up by statistics or probabilities and some not. In the course of assessing probabilities it can be easy to fall for logical traps.

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independent; that the fact that one death had already occurred had no bearing on the probability of another death occurring. The probability that the second death occurred due to natural causes should be calculated as the probability of a case of SIDS occurring given that a case has already occurred in the same family. Due to the possibility of either a genetic predisposition to SIDS or shared environmental factors, it is reasonable to believe that the probability of this would be considerably greater than 1 in 8,500.

The Royal Statistical Society later criticized Meadow’s claim of 73 million to 1, saying that it had “no statistical basis”.

The second error of reasoning that helped the jury to reach a guilty verdict in this case is more subtle, but has misled juries in many cases. Many errors of reasoning (fallacies) such as this are so common that they have their own name. It seems that the trap that Meadow, unwittingly or not, led the jury into was the ‘prosecutor’s fallacy’: mixing up his conditional probabilities. (See ‘The Prosecutor’s Fallacy’, below.)

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Hard facts are useful, but there are dangers in assessing the statistcs with which we are presented

73 million. He then inferred this to be the probability that the defendant was innocent — damning testimony from an expert witness.

There were, however, two errors in Meadow’s reasoning. The first was the assumption that the two deaths were Try to spot the flaw in the standard example of the prosecutor’s fallacy, as illustrated in the following hypothetical scenario: Some cellular material belonging to the offender is found at a crime scene.This has been DNA profiled. A suspect has been arrested and DNA profiled, and the profiles match.The question for the jury is, did the suspect leave the sample at the crime?

The first assumption is that if two DNA samples were taken from a single person, they would give the same DNA profile.This is reasonable, as it is almost certain that two samples from the same person would give the same DNA profile. The second assumption is that it is very unlikely that two people would have the same DNA profile. So if the suspect had left the sample at the crime, it is almost certain that the profiles would match whereas if some other, unknown, person had left the crime sample there is a very small chance that they would match. So the expert witness says to the courtroom,

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The figure that the prosecution quoted was the probability of a double cot death occurring given that the defendant was innocent: very small indeed. The quantity that we are actually interested in, however, is the probability that the defendant is innocent, given that a dou-

The Prosecutor’s Fallacy

“the probability of a match if the sample left at the crime scene had come from someone else is one in a million”.

The jury then takes this to mean that there is a one in a million probability that the crime sample did come from someone else, and thus that there is only a one in a million chance that the suspect is innocent.

Can’t spot the flaw? Here’s a simpler example of the same fallacy.

An animal with four legs is on trial, accused of being an elephant. An expert on elephants is brought in and says, “if an animal is an elephant, there is a very high probability that it has four legs”. “Aha!” says the prosecution, “if an animal has four legs, there is a very high probability that it is an elephant, therefore there is a very high

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http://london-underground.blogspot.com

The recent notorious case of Roy Meadow, the paediatrician called as an expert witness in several cases where mothers were accused of killing their babies, is a prime example. In each case, the defendant claimed that the children had fallen victim to cot death or Sudden Infant Death Syndrome (SIDS).The testimony of Meadow as an expert witness was instrumental in the conviction of three mothers. However, this testimony was later called into question. Meadow was found to have misled the jury, causing him to be discredited as an expert witness, investigated by the General Medical Council and eventually struck off the medical register.

In the case of Sally Clark, the mother’s two children had both died in similar circumstances. Meadow claimed that the probability that the defendant was innocent in this case was about 1 in 73 million. It appears that he reasoned that since the incidence of SIDS is around 1 in 8,500, the probability of two cases occurring in the same family was that value squared, leading to the value of 1 in

ble cot death has occurred. These two quantities are not the same. That isn’t, of course, to say that the defendant was definitely innocent, but the crucial thing to remember when assessing statistics is that it must be done in context. In the case of a legal proceeding, that means evaluating the statistical and the non-statistical evidence simultaneously, quantifying what you can, and then leaving the jury to come to a reasoned conclusion.

So, the moral of the story seems to be: trust your intuition, but don’t forget to give yourself a reality check every so often. And, when dealing with statistics, remember to look beyond the numbers to check that the fancy figures mean what you think they do.

For more information, see BlueSci Online.

Tom Walters is a PhD student in the Centre for the Neural Basis of Hearing probability that this animal, which has four legs, is an elephant”.

This is an example of what statisticians call ‘transposing the conditional’.

Conditional probability is the probability that an event, A, occurs, if some other event, B, has occurred.

Mathematically, this is written P(A | B) where the ‘|’ means ‘given that’. So P(four legs | elephant) (the probability that the animal has four legs, given that it is an elephant) may be 0.99, but P(elephant | four legs) is not. In fact there is a way of converting between the two. This is called Bayes’ theorem and is written as follows: P(A|B)=P(B|A)P(A)/P(B). P(A) is the prior probability, in our case, the probability that the randomly selected animal we have in the stand is an elephant before we know anything about the number of legs it has. In the case of the DNA evidence, it is our prior knowledge of whether the suspect is likely to be innocent or guilty, and this can only be found by assessing the other evidence in the case.

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The Transcendence of Tessellations Swanand Gore on a whole mosaic of disciplines Science often seems like a maze of very specialized disciplines, but there are some universal ideas that transcend its boundaries. Tessellation is one such idea, in the league of other all-pervasive themes like potentials, graphs, memes and entropy.

Tessellation is the division of space without gaps or overlaps between the resulting regions. Flexible or growing entities compete for space; a gas expands to fill its vessel and cells grow in a petri dish until space or nutrients run out. This competition frequently results in tessellation, for example, beehives have hexagonal chambers because each bee grows its chamber in all directions until the hive is filled. A source of inspiration to scientists and mathematicians for centuries, tessellation offers both a way of describing the world and an effective tool. Tessellations have been rediscovered in different fields and rechristened; Thiessen polygons in geography, Blum’s transforms in biology and the domain of action in crystallography.

This ubiquity demonstrates tessellation’s utility as well as its place as a fundamental, unifying principle.

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every point in space to a generator using the definition of distance to quantify the proximity of a point to a generator. Figure 2 shows the territories formed by mouth-breeder fish, a clear example of tessellation in nature. The male mouth-breeder removes sand from the sand bed and spits it out towards the neighbouring diggers, creating breeding pits surrounded by sand walls. Here, a fish is a generator competing for space, and the assignment rule is that points enclosed by its sand walls are assigned to the nearest fish. The distance measure is straight line Euclidean geometry. The pits formed belong to the fish in them and are called the ‘dominance zones’ of the generators. A dominance zone is the set of points for which a particular generator is closer than all others.The set of dominance zone edges is called a ‘medial axis’ or ‘Voronoi skeleton’. Figure 3 depicts an abstract tessellation pattern: the generators are points, the distance is line-of-sight distance and the assignment rule is least distance.

In other cases, we can generalize the generators to lines, curves or circles, which for example can be used to model the contribution of different roads to pollution in a particular area.

Tessellation offers both a way of describing the world and an effective tool

Although they are often highly complicated, any tessellation can be described solely in terms of a ‘generator’, a ‘definition of distance’ and an ‘assignment rule’. A generator is a geometric entity competing for its share of space and an assignment rule assigns

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The distance definition can also be changed to account for, say, the direction-dependent cost of travel, whether uphill or downhill. The distance measure changes when space is curved or if obstacles obstruct the line of sight; you might need to drive a long way to reach

Figure 2. Territories of male mouthbreeder fish Tilapia mossambica. Reproduced from Barlow, G. W. 1974. Hexagonal territories.

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a supermarket visible from your house, for example.

Town planning is one field in which tessellation is a particularly important tool. A town planner aims to maximize the availability of urban infrastructure, because quality of life is influenced by how much daily travel people must undertake. Generators are hospitals, airports, schools or leisure centres, with their dominance zones roughly representing their catchment areas. If a tessellation of hospitals results in very large dominance zones, then the number of hospitals needs to be increased; if one of the zones is too big, hospitals need to be relocated. If the nearest ambulance is busy when you need it, then the next nearest must be called into service. The worst-case scenario can be examined using ‘farthest point’ tessellations, where the farthest, rather than the nearest, generator owns a particular point. If the maximum distance between a generator and its dominance zone is not too great in such a tessellation, it means that the farthest ambulance is not too far away and the town is well accommodated. Complications arise when one accounts for roads tra-

Figure 3. For a set of points (generators) in a plane, a simple tessellation can be defined by considering perpendicular bisectors of every pair of points (left).This results in one convex polygon (Voronoi region) per generator (middle).The corresponding Delaunnay tessellation is formed by joining the generators from adjacent regions (right). Delaunnay triangulation , a network of generators sharing dominance zone boundaries, is used for modelling the surfaces of solids. Reproduced from Poupon, A., ‘Voronoi and Voronoi-related tessellations in studies of protein structure and interaction’, Curr. Op. in Str. Biol., 14:233–241 (2004).

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Michaelmas 2005

versing the town. Typical networks are generally somewhere between the two extreme cases — grid (Manhattan or Milton Keynes) and radial (London or Karlsruhe). The design of road networks has inspired network-based tessellations, or ‘city Voronoi diagrams’, where distances are measured only along the road network. Tessellation changes dramatically when transport is restricted to roads and this influences decisions on the location of facilities.

Tessellation-based techniques can also be applied in biology. For instance, ‘medial axis inference’ is useful for characterizing changes in the shapes of body organs. These changes can be incredibly subtle, yet can be important indicators of disease: for example, the shapes of the amygdala and hippocampus, regions of the brain which are important for memory, learning and emotions, differ in shape considerably between those with and without schizophrenia. A tessellation-based quantitative morphogenic assessment can, therefore, assist in the diagnosis of disorders. Similarly, differences between twins give clues about growth and development.

At the molecular level, a variant of tessellation called ‘alpha-shapes’ can detect cavities in macromolecules such as proteins and DNA. Macromolecules are the cogs of cellular machinery and cavities on their surface can indicate important areas where they interact, identifying potential targets for drug design. Since the chemical properties of a molecule’s various constituent atoms differ, the distance definition must be adjusted using a weighted assignment rule to take these chemical differences and the interactions between the atoms into account.

The nineteenth-century German mathematician Dirichlet used his ideas about tessellation to study the distribution of galaxies in the cosmos and astronomers today still use tessellations for studying the large-scale structure of the universe. Mass is not randomly distributed in space, but occupies walls and filaments. The density of matter is least in the voids, greater in walls, still greater in filaments and greatest at ver-

Figure 5. Voronoi diagrams with generators consisting of points, straight lines and curves.

Reproduced with permission from K. Hoff et al., 1999.

Fast Computation of Generalized Voronoi Diagrams Using Graphics Hardware Proc. ACM SIGGRAPH

www.bluesci.org

Figure 1. Detail of Escher’s ‘Regular Division of the Plane Drawing #69’, 1948. ©2005 The M. C. Escher Company, the Netherlands. All rights reserved. Used by permission. www.mcescher.com

tices, where the galaxies are. Threedimensional tessellation models, with the voids as boundaries of dominance zones, have yielded insights into the large-scale structure of our universe, just as they have for other dynamic

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large, medium and small sizes, even though the size of eggs is naturally scattered. From the point of view of tessellation, clustered objects have crowded generators with smaller dominance zones.This is exploited by some pattern

Astronomers use tessellation for studying the large-scale structure of the universe

phenomena like the propagation of cracks in crystalline materials, the spread of bark beetles, epidemics and even forest fires.

In information theory, clustering and compression are two increasingly important applications of tessellation.

Information theory, a cornerstone of the computer revolution, describes a signal being transmitted or encoded over a noisy communication channel.

By compressing the data, one is able to transmit it more rapidly over a channel of a given bandwidth (those of you reading online are probably benefiting from this). Clustering is critical to any process for classifying objects with similar properties. For example, before they are packed up, eggs must be sorted into

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recognition and data clustering algorithms. Delaunnay triangulation (see figure 3) detects clusters by identifying neighbours and the distances between them.Automatic document analysis uses tessellation to identify word boundaries and word flow: the document is first scanned for characters and a tessellation computed, allowing adjacent characters, i.e. words, to be detected.

The human mind likes elegant, ordered constructs. It seems that nature does too. www.voronoi.com www.voronoigame.com Swanand Gore is a PhD student in the Department of Biochemistry

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Fat of the Land

Helen Stimpson weighs up the facts behind the ‘obesity epidemic’ We are a nation obsessed by our weight: Celebrity Fat Club and Dr Gillian McKeith’s You Are What You Eat are television staples and gossip magazines are full of reports documenting Pop Idol Michelle McManus’s weight loss. Obesity is now regarded as a major public health issue and talk of an ‘epidemic’ is everywhere. So, what are the facts? How heavy are we and why?

Obesity is traditionally determined by calculating the Body Mass Index (BMI), which relates height to weight. To work out your BMI, divide your weight in kilograms by your height in metres multiplied by itself. A BMI greater than 25 officially makes you overweight, while more than 30 classes you as obese. Using this measurement, the incidence of obesity in Britain is estimated to have tripled in the last 25 years, with over half of women and two-thirds of men now classed as overweight or obese. The World Health Organization estimates that over a billion people worldwide are overweight and around 300 million are clinically obese.

Obesity is associated with numerous health problems including diabetes, cardiovascular disease, high blood pressure, stroke, respiratory complications, and osteoarthritis.With around £2 billion per year of an already overstretched NHS budget being spent on obesity-related illnesses, it’s not surprising that public health officials are beginning to focus on reducing the population’s weight.

A simple principle governs bodyweight: if we take in more energy than we

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expend, we gain weight.

The most basic advice for losing weight is to exercise more and eat less.

However, in reality body-weight is the result of the complicated interplay between our genes and our environment — but which is the more important?

It is certainly true that our weight is determined by what we eat, but our desire for and response to eating has repeatedly been shown by scientists to have a genetic component. Eating too much causes us all to gain weight, but unfortunately for some it happens more quickly than for others!

Molecular studies have identified some of the genetic factors involved in our response to food. In 1994 work on mice led to the discovery of leptin, a hormone produced by fat cells. Leptin is detected by the hypothalamus, a region of the brain that controls appetite. In response to leptin, the hypothalamus sends out

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Over half of women and two-thirds of men in Britain are classed as obese

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appetite-suppressing signals.

Mutations in leptin genes and the protein in the brain which detects it (the leptin receptor) were found to cause obesity in mice.This was heralded as a breakthrough in our understanding of appetite and weight gain. Despite the initial furore surrounding this finding and the subsequent identification of other genes directly involved in appetite control, it has become evident that very few indi-

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viduals are obese or overweight because of such clear-cut mutations.

Rather, for most of us our genes specify a tendency to be larger or smaller.

Drug companies have poured millions of pounds into the study of obesity and the development of anti-obesity drugs.The result is just a handful of medicines that influence weight loss.

Medicines currently available fall into two categories. The most common are appetite suppressants, which modulate the activity of neurotransmitters that affect mood and appetite, such as catecholamine and serotonin. The second type perturbs the action of the intestinal enzyme lipase. When lipase is disrupted, only about 70% of ingested fat is absorbed into the bloodstream, leading to an immediate reduction in calorie intake and, theoretically, to weight loss. Scientists are also investigating the possibility of using a class of anti-cancer drugs to treat obesity.

These chemicals — known as angiogenesis inhibitors — limit the growth of blood vessels that feed tumours. Like tumours, fat cells need a blood supply and, in 2003, it was demonstrated that some of the angiogenesis inhibitors could suppress weight gain in mice.

To date, no miracle cure has been found. Current drugs are only prescribed in extreme cases and are not recommended for long-term use. The main problem with the drugs is that they do not alter behaviour and so do not target the root cause of weight gain.

In the end, rising rates of obesity can be traced to features of our modern lifestyle.

Food in the western world is now abundant and cheap, and we are increasingly inactive.With a metabolism evolutionarily designed to store energy for times of food scarcity, we can’t help but gain weight.These environmental factors must play a major role in the global rise in body-weight: our genetic make-up simply hasn’t changed enough in the last 25 years to account for the weight gain of the population.

Why though, are some of us more susceptible to weight gain than others? What controls our willpower, our sensation of taste, our tendency for depression, our moods, and our levels of anxiety? All these influence how and what we eat, but to what extent are they genetically predetermined?

In the modern world, we don’t just eat for sustenance and thus behaviour plays an enormous role in weight gain.

Research so far has centred on the mechanisms that physically control hunger, but the importance of behavioural studies is becoming increasingly apparent. Until we really understand human behaviour and combine this with our physiological knowledge, it is unlikely that we’ll truly know why we’re getting heavier.

Helen Stimpson is a postdoc in the MRC Laboratory of Molecular Biology

Michaelmas 2005

Graduate School of Biological, Medical and Veterinary Sciences

Thinking of a research degree? Why not stay in Cambridge?

The Graduate School of Biological, Medical and Veterinary Sciences encompasses over 20 departments and research institutes from Anatomy and Clinical Neurosciences to Veterinary Medicine and Zoology. All offer wide-ranging and internationally recognised research programmes, and provide an unparalleled range of opportunities for post-graduate students.

• Research degree opportunities at Doctorate (PhD) or Masters (MPhil) level • 4 year Wellcome Trust PhD Scheme in Developmental Biology, Infection and Immunity, and at the Sanger Institute for genome research.

• Over 50 Research Council and other studentships • A full programme of research training, career development and personal skills training organised by the Graduate School For details, including a searchable research project list and information on how to apply or visit our website: http://www.bio.cam.ac.uk/gradschool/ or contact us by email at gradbiol@mole.bio.cam.ac.uk

On the Cover

Cracking Conductors

Knowing nothing more about superconductors than the dictionary definition (materials with zero electrical resistivity at temperatures close to absolute zero), it was with some trepidation that I approached the Department of Materials Science and Metallurgy to meet Tarek Mouganie, the scientist behind our cover image. Thankfully Mouganie, a third year PhD student in the department’s Applied Superconductivity and Cryoscience Group, was not at all fazed by this and set about explaining to me what superconductors are, why he’s interested in them, and of course how his research came to produce the stunning image you see on the cover.

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Once set in motion, electrical current will flow forever in a closed loop of superconducting material

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Tarek Mouganie

Superconductivity was discovered in 1911 by the Dutch physicist Heike Kamerlingh Onnes. He observed that when mercury was cooled to the temperature at which helium is liquid — 4.2 K (-269ºC) — its electrical resistance suddenly disappeared. This lack of resistance means energy is not lost as it passes through a superconductor and so once set in motion, electrical current will flow forever in a closed loop of superconducting material. In addition, superconductors have interesting magnetic properties: the movement of a magnet over any conductor induces a current in the conductor but, in a superconductor, the induced current exactly mirrors the field that would otherwise have penetrated the material, causing the magnet to be repelled. This effect is so strong that a magnet can actually be made to levitate over a superconductor.

Probably the most well-known application of superconductors is Magnetic

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Resonance Imaging (MRI). By exposing the body to a strong superconductorderived magnetic field and then applying a pulse of radio frequency (RF) radiation, hydrogen atoms in the body absorb energy. The release of this energy upon removal of the RF radiation is detected and displayed graphically, providing doctors with a non-invasive method of looking inside the body. Other applications of superconductors include their use in ‘floating’ low-friction trains, high-energy particle colliders and in the development of ultra-fast computers.

Despite the extraordinary properties of superconductors, they are not as widely used as one might expect. This is due to the important fact that superconductors only exist below a certain critical temperature (Tc). Above the Tc superconductors behave like normal materials — a phenomenon which researchers are not yet able to fully explain. Commercially available metallic superconductors operate at Tcs in the region of 10 K (about -260ºC).

These incredibly low temperatures are expensive to achieve and are a major logistical problem in the development of superconductor applications.

Understandably, the discovery of a ‘high temperature’ superconductor in 1986 caused great excitement. Swiss researchers Müller and Berdnorz created a ceramic compound composed of lanthanum, barium, copper and oxygen that superconducted at the highest temperature then known: 30 K (-243ºC). This discovery — which was surprising because ceramics are normally insulators — sparked a surge of activity as scientists began creating ceramics of every imaginable combination in the hunt for higher and higher Tcs. In 1987, scientists substituted yttrium for lanthanum in the Müller and Berdnorz molecule to produce YBa2Cu3O7-5 (YBCO), a ceramic superconductor with an impressive 92 K (181ºC) Tc. Mouganie explained why people were so enthused by the quest for high Tcs, “The inter-metallic, ‘low temperature’ superconductors must be cooled using liquid helium in order to reach the incredibly low temperatures needed; liquid helium is comparable in price to the perfume Chanel No. 5. In contrast, ‘high temperature’ ceramic conductors like YBCO can be cooled using liquid nitrogen, which costs less than half the price of milk.”

Mouganie’s research involves the development of YBCO superconductors for commercial application. He described a challenge he faced when beginning this project, “Unlike metallic superconductors, which can be bent easily to form superconducting coils, the brittle nature of ceramics makes the formation of 3-D structures and 2-D patterns much more difficult.”

Mouganie approached this issue by devel-

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Jai Sin Tan

Tarek Mouganie, the scientist behind our cover image, talks to Tamzin Gristwood

oping an YBCO ‘ink’. The ink is a ‘sol-gel’; it is initially a solution but on heating converts to a gel. Using a specially built inkjet printer, Mouganie has been able to print a thin layer of YBCO onto a strip of metallic tape which can then be manipulated to form a ceramic superconducting coil.

The eye-catching cover image and the picture below left were taken during development of the YBCO ink. The former shows a segment of one droplet of YBCO ink viewed under an optical microscope.“In this case, the ink dried too rapidly, causing the surface of the droplet to crack.” The cover image is a close-up view of one of these cracks. The picture on this page highlights another problem: “During the heating step, the components of the ink have coagulated and precipitated to form large complexes.”

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The brittle nature of ceramics makes the formation of 3-D structures and 2-D patterns difficult

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Mouganie has successfully created a 5centimetre-long YBCO superconducting tape and the group are now collaborating with a German company to scale up the process.They plan to produce YBCO tape kilometres in length, which can be wound up to form coils. Although clearly pleased at the success of the project, Mouganie does have one small regret:“Unfortunately, when dried correctly the YBCO ink produces nothing more exciting than a transparent blue film, so it has put an end to the interesting photographs!” www.msm.cam.ac.uk/ascg www.superconductors.org Tamzin Gristwood is a PhD student in the Department of Biochemistry

Michaelmas 2005

A D ay i n t h e L i f e o f …

A Genetic Counsellor

The range of genetic tests available today mean we can learn more than ever about the medical conditions we, and our children, may develop. But for every test, patients need support and accurate interpretation of results, a role often fulfilled by a genetic counsellor. With the sequencing of the human genome, and the new information we may gain from it about our health, their role will be increasingly important. Ann Kershaw works as a counsellor in the Genetics department at Addenbrooke’s NHS Foundation Trust hospital, Cambridge.

How would you describe your role?

I work in the Department of Genetics, which comprises 13 medically trained doctors, six genetic counsellors and the molecular and cytogenetics laboratories.

Together, we provide the regional genetic service for about 2.5 million people in East Anglia. We also get a lot of referrals from outside the region as we hold several specialist clinics.

How did you become a genetic counseller?

I trained as a nurse and then worked as a health visitor in Cambridge.

Addenbrooke’s was looking for a new counsellor and I thought the role would enable me to spend more time with patients and develop new skills. As genetics evolves rapidly there isn’t an opportunity to get bored.You have to work hard to keep up with new developments in the field. We hold weekly meetings, journal clubs and seminars, and attend university lectures, study days and conferences.

Historically, genetic counsellors were nurses, midwives and health visitors who learnt ‘on the job’. Now there are also graduates coming with a science background and a Masters in Genetic Counselling. Both groups have something to offer, and have had different emphases during training, and it’s good to have a mix.

Are you the first person the patient sees?

Patients are allocated to the most appropriate member of staff. Patients needing a diagnosis will always see a doctor. A counsellor will usually see families with a known diagnosis.We see patients with single gene

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Jon Heras

Nerissa Hannink talks to Ann Kershaw about her work as a genetic counsellor disorders (such as cystic fibrosis), chromosomal anomalies (for example Down’s syndrome) or a family history of cancer.

Our patients are referred to us by GPs, consultants and other health professionals for a whole range of reasons. Someone may ask about breast cancer risk, and if we feel they do not fulfill our high-risk criteria we may write to him or her or see the patient only once. Or we may see someone with a family history of something like muscular dystrophy before a pre-natal test; support them during and after the test, and during future pregnancies.

What happens during a consultation on a typical day?

Normally I would see six families in a day with up to an hour per session. During a recent clinic I saw people with family histories of colon and breast cancer, cystic fibrosis and Huntington’s disease.The consultant will make a list of patients for me to see and then it’s up to me to prepare for that clinic, do the appropriate literature searches and organise any available testing.

I advise people whether a test is available, and its pros and cons. We provide nondirective counselling enabling the family to arrive at the decision that is best for them.

Do you spend time on your own research?

Primarily we have a clinical role and a busy case load, so any research tends to be done over and above the job, but we do encourage it. For example, I work with a neurologist researching Huntington’s disease.There is a lot of psychological research involved, such as how Huntington’s affects sleep and metabolism, which is the kind of study we could publish. As counsellors we are particularly interested in the psychosocial aspects of inherited disease.

With so much information available on the Internet, is it hard to clarify for people what is important and accurate?

The Internet has had a huge impact on our work. We now have a well-informed and educated client base. Because many of the conditions we see are rare,the first thing people do is to go on the Internet. It’s changed completely from when I first started nursing. People now come in knowing about the condition, so you have to be two steps ahead and not be defensive. I think

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that is empowering for patients. So my job is to help them sift through information, and direct them towards good quality sites.

Considering the decisions that might follow your discussions, is your work stressful?

The workload is big and that is a factor, but the intensity of the consultation can sometimes be draining. People may become upset if they don’t agree with what you’re saying, for example if they believe a test is available and it isn’t. Some families’ stories are very sad, so you have to deal with issues such as grief, bereavement and loss. Because we’re quite skilled in dealing with people, we can usually manage most challenging situations.

You develop coping strategies, and I have very supportive colleagues, which is very helpful. Counsellors have formal psychological supervision with an external supervisor.You can’t go home and discuss cases, as they are confidential so it took me a while to learn to ‘switch off ’ at home.

What skills are needed for the job?

A basic understanding of science, and the way the health system works. Genetic counselling is all about communication, so the skill is to get the message across in terms of the genetics and the person’s risk. You have to be interested in people and be able to put them at their ease quickly because you have a short time to establish a relationship, and obtain all the information you need in a consultation.

What are the benefits and downsides of your job?

It’s varied and diverse, I meet and work with nice people, and I cover all sorts of conditions and almost every aspect of medicine.Working with families is interesting and you can work with people for a long time and get to know them.

Although we’re busy, we build up relationships. I have worked with some of my Huntington’s families for 16 years.

Patients with chronic conditions need support and continuity of care.

For more information about the work of a genetic counsellor visit www.agnc.co.uk Nerissa Hannink is a postdoc in the Department of Plant Sciences

Michaelmas 2005 21

Away from the Bench

Out Of The Frying Pan...

When asked if I would like to spend three weeks on a field trip in the Azores, I didn’t have any hesitation in saying, “Yes please!”

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Faial is one of the most beautiful places I have been fortunate enough to visit

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This trip was part of an international project known as the International Transport of Ozone and its Precursors (ITOP) which has been set up to investigate the transport of pollutants such as nitric oxide and carbon monoxide from North America to Europe.These pollutants come from forest fires and the burning of biomass and fossil fuels. Though pollution is often seen as a local problem, gases produced in this way can be transported vast distances by weather systems: pollutants originating in North America can be deposited in Europe three to five days later.

In the presence of sunlight, these chemically active gases react with other chemical

compounds to produce ozone, which contributes to the high concentration of ozone observed over many parts of Europe.

The ITOP campaign involved groups from several UK universities, including the Universities of Cambridge, Leeds, Leicester and York.

Our team was based in Horta on the Atlantic island of Faial, the second largest of the nine islands that make up the Azores. Faial is one of the most beautiful places I have been fortunate enough to visit, with a varied mixture of lush green landscape and hills, volcanic craters, dramatic coastlines and, of course, the bright blue sea.

Most of our experiments were carried out via a suite of instruments on a BAe146 aircraft. I was involved in operating the on-board Tuneable Diode Laser Absorption Spectrometer, which measures the concentrations of carbon dioxide and methane. Flights, usually lasting between five and seven hours, took place over the Azores, Portugal and beyond. Even on the days we did not fly, there was work to be done: either in the hot and stuffy temporary labs that had been set up at the airport, or on the aircraft itself.

Doug Anderson/FAAM

Will Flynn investigates global pollution on holiday in the Azores

Mount Pico on Faial

The results of the ITOP study will contribute to furthering our understanding of the environmental impact of both local and global pollution. Despite the long hours, hard work, gruelling heat, constant sweating and all the itching from mosquito and other insect bites, we did enjoy one or two free days when we were able to go hiking and whale-watching.All in all it was a great experience and definitely one I would go through again! http://badc.nerc.ac.uk/data/itop Will Flynn is a PhD student at the Centre for Atmospheric Science, Department of Chemistry

…And Into The Freezer

Damien Carson

Samia Mantoura gets cold in the name of science

Samia in the snow

Located on the Western Antarctic Peninsula, surrounded by high mountains and glaciers, Rothera is the largest British Antarctic Survey base on this continent. For eight weeks, this outpost of a hundred or so people was to be my home, and the deep blue sea littered with giant icebergs, my office.

Scientists at Rothera study the process of sedimentation, where single-celled algae called diatoms take up the ‘greenhouse gas’ carbon dioxide from the atmosphere during photosynthesis, transporting it to the deep ocean as they sink.

I was working on a project to take samples from three places: algae living near the ocean surface, dead algae falling to the

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depths and accumulated algae on the ocean floor. Three times a week, three or four of us took a small boat to the sampling site, a few kilometres off shore. At times the sea was covered in broken ice, making progress slow. Wearing enormous dry suits, we collected seawater using silicone tubing and a pump running off a car battery.

The project was very much a team effort, with people collecting samples for each other and sharing the limited laboratory space. For example, sometimes we helped other scientists with a CTD cast, an instrument that measures the conductivity, temperature and density of water by depth.

This information is used by oceanographers to calculate the water’s physical properties and direction of movement.

There was a real cross-section of society on base with scientists, pilots, mechanics, cooks, domestic staff, doctors, electricians, divers and many more getting to know each other. Living on base was comfortable but basic and, thanks to the chefs, the food was fantastic considering it arrived dried, tinned or frozen. For those who had spent weeks in more remote parts of the continent, living in tents on dried food

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and without a shower, Rothera was the height of luxury!

This project taught me a great deal about the work done of other BAS scientists and about the importance of Antarctic science.

Antarctica is not just a natural wilderness but also a crucial part of our planet’s climate system.The removal of carbon dioxide by diatoms from the atmosphere could alleviate the problems of climate change, as it is thought to have been an important factor in the cooling of the earth during past ice ages. Identifying the factors that limit diatom growth is therefore an important task, and a controversial one. Some scientists believe that it is the availability of nutrients, such as iron, that is important, although calculations to determine this have provided contradictory results. Much work is still urgently required in this relatively new field.

For more information about the British Antarctic Survey, see www.bas.ac.uk.To find out about diatoms and sedimentation, see www.indiana.edu/~diatom/diatom.html Samia Mantoura is a PhD student in the Department of Earth Sciences

Michaelmas 2005

Cambridge scientists discuss networks for women in science, engineering and technology Did you think gender inequality in the sciences was a thing of the past?

These statistics may make you think again. Women still make up less than 20% of lecturing staff in science, engineering and technology (SET) at the University of Cambridge.

Although females account for approximately 50% of undergraduates studying biological sciences, this figure is much lower when one considers the physical sciences. The proportion of women involved in SET disciplines is lower at the graduate level, and declines yet further at more senior levels. These figures are not confined to the University of Cambridge; nationally, less than 10% of those

elected to Fellowships of the Royal Society are female.

Several factors have been suggested for this inequality, for example, the stereotypical scientist is a man – not a woman – in a white coat, and as there are relatively few prominent senior female scientists there are a lack of role models for girls considering a career in SET. There is concern that schools are often ill equipped to overcome these issues when offering careers advice to girls interested in SET. As in other professions, women often take careerbreaks to start a family but the rapid technological advances in SET make it especially difficult for women to return to the workplace, thus reducing the

number of women progressing to senior positions.

So what is being done to address these problems? Following the publication of a report entitled ‘The Rising Tide’ by HMSO in 1994, in which this underrepresentation of women in SET was documented, a number of groups that support women in SET have been set up. Nationally, these include the Association for Women in Science and Engineering (AWiSE), which is a regional network run by volunteers, and the Women in Science, Engineering and Technology Initiative (WiSETI), which is a Cambridge University-funded initiative. Both of which are currently active in Cambridge.

WiSETI

AWiSE is a national organisation with branches, meeting and events throughout Britain. Its objectives are to promote SET for girls and women, form a collective voice for women in SET, provide a network for mutual support, act as a centre of information and resources and act as a forum for discussion. In addition it is a valuable resource for keeping women in SET informed about topical and ongoing issues that affect them. Cambridge AWiSE achieves these aims by: • Organising local events and meetings on topics such as “Attitudes to Par t Time and Flexible Working” which include short talks but also plenty of opportunity to discuss the issues and to meet women from other fields within SET. • Setting up MentorSET which provides professional women in SET with independent mentors who can offer guidance, support and encouragement to help women further their careers.

The organisation’s strong networking initiative has provided members with many international opportunities and links with overseas. Today they network with US AWI, WISENET in Australia, NZ AWISE, SAWISE in South Africa, Femmes et Sciences in France, CES in Germany and with the Women in Science section of the European Commission.

WiSETI is a University organisation with a remit to increase the numbers of women studying SET at Cambridge, to improve the recruitment, retention and promotion rates of women in SET appointments and to raise the profile and enhance the self-confidence of women in SET through a range of initiatives. These include: • A recruitment programme aimed at encouraging women to apply for jobs in academic science and ensuring that they receive appropriate information about positions that may interest them.

• A Code of Practice and best practice guides for the SET workplace.

• Careers talks for undergraduate women, sponsored by Citigroup, in which a distinguished panel of guests speak about their careers.

• An annual WiSETI lecture, sponsored by Schlumberger, which was presented in May 2005 by Professor Kathy Sykes from the University of Bristol.

• MentorNet, an international e-mentoring programme which offers students in SET the opportunity to be paired with a mentor from industry or academia, and exchange regular emails about careers, courses, professional bodies etc.

• Springboard Personal Development Programme for undergraduates, which encourages personal and professional development through workshops, the Springboard workbook and opportunities for networking.

initiatives@bluesci.org

Katherine Borthwick

AWiSE

For information about AWiSE in Cambridge including details of forthcoming meetings visit their website: www.awise.org/?q=CambridgeBranch or email camawisemeetings@yahoo.co.uk.

For more information on MentorSET go to www.mentorset.org.uk.

Dr Nancy J. Lane is Director of WiSETI at the University of Cambridge; Dr Alison Maguire is Recruitment Office for WiSETI; Dr Jenny Koenig is Chair of Cambridge AWiSE and a Fellow of Lucy Cavendish College; Dr Bojana Popovic is a postdoc in the Department of Biochemistry.

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I n i t i at i ve s

A Woman’s Work?

To find out more, visit the website: www.admin.cam.ac.uk/offices/personnel/equality/wiseti.

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History

A Trip Down Free School Lane

Emily Tweed and Victoria Leung investigate the history of the Cavendish Laboratory

Cavendish laboratory

Imagine a university that taught science degrees but did not have any laboratories. Imagine studying for a degree in science that did not involve any practical work whatsoever.

Welcome to Cambridge in the midnineteenth century.

Unlike today, research was not considered part and parcel of being a university professor, and practical training was not a standard part of the curriculum.

Some favoured students were permitted to assist a professor in experiments but most graduated with no hands-on experience at all. The theories they were taught in lectures had mostly been elucidated by gentlemen amateurs like James Joule, who had a laboratory at home, or by academic men of science like Isaac Newton, who experimented in his college rooms. Private laboratories, rather than ones connected to institutions like universities, were the norm. Those labs that did exist in universities were small offshoots of lecture theatres where demonstrations were prepared, rather than spaces for research or teaching.

During the nineteenth century, however, institutional laboratories of the kind modern students and scientists might recognise did become increasingly common: first in Germany and France and then later in Britain and the United States. Accompanying this trend was a

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growing emphasis on precision measurement, partly driven by recognition of its role in industrial progress. Physicists in Britain made the link between Germany’s excellency in physics and its newfound industrial prosperity, using this to argue for better facilities and increased funding.

In the 1860s the University Senate recognised the growing clamour for new laboratories in Britain by setting up a committee to investigate the possibility of establishing one in Cambridge.This investigation came out firmly in favour of cre-

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Concerns over whether or not practical work was an appropriate part of a scientific education plagued the Cavendish’s early years

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ating a space for practical teaching and experimentation, fitted out with the latest apparatus and supervised by a new professor and his demonstrators. Several years later, the Cavendish Laboratory on Free School Lane opened amidst a great deal of

One of the earliest photographs of the practical class in the Cavendish, taken in 1933

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interest… and not a little controversy.

The Cavendish Laboratory was named after the University Chancellor who had provided most of the funding, the University itself being in a spot of financial bother at the time. James Clerk Maxwell, now renowned for his work on electricity and magnetism, was appointed the first Cavendish Professor and helped oversee the design and construction of the new laboratory. It was modelled on the pioneering teaching laboratories of the German universities, which emphasised the importance of systematic practical training and the use of elaborate instruments. As well as space for research it also contained lecture halls and a workshop for the construction and repair of equipment.

Strange as it may sound to us now, concerns over whether or not practical work was an appropriate part of a scientific education plagued the Cavendish’s early years. It was a time when the manipulation of instruments carried undesirable associations with factory work and manual labour, occupations considered entirely unsuitable for a student of the University of Cambridge.

Experimentation was considered by many to be an intellectual step-down from the more cerebral activities of calculating and theorizing. As Maxwell worried,“If we succeed too well, and corrupt the minds of youth till they observe vibrations and deflections and become Senior Ops. instead of Wranglers, we may bring the whole University and all the parents about our ears.” (A ‘Wrangler’ was someone who achieved a First in the Mathematical Tripos, whilst ‘Senior Ops.’ refers to a manual worker.)

All in all, the bill for the original Cavendish came to £8,450. An extravagant sum at the time, this amount represents but a fraction of what laboratories cost to build and equip now. In part, this reflects changes in the technology of physics research since the nineteenth century: then, an item of apparatus usually fitted on the workbench and was often pieced together from relatively basic and easily available materials. The twentieth century saw an incredible leap in the scale of experimental physics, both in cost and size. For example, the forthcoming extension of the Cavendish is likely to cost more than £137 million, while some modern physics instruments (such as the Large Hadron Collider in Geneva) are so expensive that they require financial support from several nations.

Research in the new laboratory was initially carried out by college fellows, mainly new graduates of the Mathematical Tripos which dominated Cambridge teaching in this era. It was several years before undergraduates came

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The Cavendish Laboratory was founded during a critical period in the history of physics

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the now familiar system where students move between a series of experiments, writing reports and aided by demonstrators. In examinations, students might be asked to measure the resistance of a length of wire or the focal length of a lens, or otherwise identify a piece of apparatus and take a measurement with it. One answer from this era has become infamous: one hapless student described in 100 Years and More of Cambridge Physics “recognised in a thermometer a machine for determining the specific gravity of water”!

Despite the odd undergraduate slip-up, the Cavendish soon gathered renown — particularly for the quality of its research.

The lab became particularly famous for

the technical expertise of its workers: ironic considering the initial objections made to its foundation. This experimental focus contrasted with the Cavendish’s counterparts on the Continent, which excelled at theoretical physics, and would serve as the foundation for the illustrious years ahead.

As in other laboratories, there was an overriding emphasis on precision measurement and quantification, particularly when it came to physical constants and standard units. As well as the demands from industry, this ethos of exactitude grew from a consensus among the physicists of the time that all the interesting, fundamental problems of their discipline had been solved and that their job was therefore to fine-tune these theories by working out the details and measuring the necessary constants with ever greater accuracy. One example of this was Lord Rayleigh’s work on the definition of standard electrical units such as the Ohm and Ampère.

Notoriously cramped and overcrowded, the Cavendish was extended through the 1880s and 1890s as the community of researchers grew. Its prestige attracted researchers from other universities and later from abroad, including the young Ernest Rutherford, famous for his research into atomic structure. It remained at the forefront of experimental physics throughout the twentieth century and the Cavendish can count no fewer

Further Reading 100 Years and More of Cambridge Physics, booklet available from Cavendish Laboratory.

When Physics Became King, Iwan Rhys Morus, University of Chicago Press, 2005

than 28 Nobel Prize recipients among its researchers past and present.

The laboratory was founded during a critical period in the history of physics. It was a time when science as a profession was gaining increasing recognition: the term ‘scientist’ was beginning to be widely used, and the people it described were growing in number. Both the modern university and modern physics as we know them were taking shape.

Cambridge was offering a greater range of courses, including the Natural Sciences Tripos and research degrees, and its facilities were expanding accordingly.

Physicists began to undertake systematic practical training and form organized groups of researchers, reporting their findings in specialist journals and at institutional seminars.

The new Cavendish Laboratory offered students a chance to move beyond purely theoretical study for the first time, giving them the skills to pursue a career in research — an option which, only a couple of decades before, would have been open to very few.

Looking at the sprawling complex in West Cambridge that the Cavendish now occupies, it seems a million miles away from the tiny laboratory on Free School Lane that cost only a few thousand pounds and which was almost not built for fear that practical work would “corrupt the minds of youth”.

History

to use the new facility, and several more before organised lab training and practical exams were incorporated into undergraduate degree courses. The latter was brought about by the second Cavendish Professor, Lord Rayleigh, who introduced

Emily Tweed is a third year Natural Scientist specializing in Pathology; Victoria Leung is a third year Natural Scientist specializing in Physics

The Cavendish Laboratory:The Early Years

1846 William Thompson, a Cambridge graduate, sets up Britain s first university physics laboratory in Glasgow.

1869 Senate committee reports in favour of founding a physics laboratory in Cambridge.

1871 Construction of the Cavendish Laboratory begins on Free School Lane. James Clerk Maxwell appointed first Cavendish Professor (after Thompson turns down the post).

1873 Maxwell publishes A Treatise on Electricity and Magnetism, a groundbreaking work which proved the fundamental connection between light and electro-magnetism and yielded a set of classic equations, which Einstein later acknowledged as the origins of special relativity.

1874 The Cavendish Laboratory officially opens, although it had been in informal use for several months already.

1877 First undergraduate lectures on basic practical topics introduced.

1879 Lord Rayleigh succeeds the late Maxwell as Cavendish Professor: he is later awarded a Nobel Prize for his work at the Cavendish.

1882 Women allowed to study at the Cavendish Lab for the first time: Maxwell had famously forbidden women students except at times when he was on holiday.

1884 J.J.Thomson appointed Cavendish Professor: he later wins a Nobel Prize for his discovery of the electron following his famous cathode ray experiments.

1895 Ernest Rutherford joins the Cavendish as a research student; after work in Canada and Manchester he rejoins the lab as Cavendish Professor in 1919.

www.bluesci.org

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Arts & Reviews

The Sound of Science

Owain Vaughan and Neta Spiro explore the biological and cultural phenomenon that is music

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When music induced a pleasurable response, it activated the same brain structures as those stirred by food, sex, and drugs

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In a quest that leads from decoding the ways in which we process music to fundamental questions about its origins and purpose, the field of science and music draws on aspects of both disciplines, including music analysis, experimental psychology and neuroscience.

One of the few centres specialising in this amalgamation is the Centre for Music and Science (CMS), directed by Dr Ian Cross, here in Cambridge.

Humans have the ability to perceive effortlessly the patterns of acoustic energy that we know as sound. After travelling through the outer and middle ear, sounds arrive at the inner ear (the cochlea) where they are sorted into their constituent elementary frequencies. This information is then transmitted from the cochlea as a string of neural discharges along individual fibres of the auditory nerve, finally arriving at the auditory cortex in the temporal lobe of the brain.

But this is only half the story. When it comes to listening to music, not only do numerous regions of the brain become involved in processing its various perceptual elements (such as melody, rhythm and harmony), but the very construction of the ear has an important influence on the details of this procedure.

Researchers in the field of psychoacoustics, for example, have demonstrated that the physiology of the ear has a

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Tom Walters

Music. Emotional, ineffable, an enigmatic and ethereal art form. Such descriptions are commonplace, and whilst there have been some attempts in the past to uncover the scientific basis of music, these have been limited and in some cases led only to exasperation and resignation. Take, for example, Claude Lévi-Strauss, who tried to describe the influence of music on human nature, including how we perceive musical time and its effects on the internal organs. Eventually he gave in, concluding that “music will remain the supreme mystery of human sciences”. But the mystery is slowly being unravelled as science meets music head on. direct effect on our perception of sounds as either pleasant or unpleasant (consonant or dissonant). Situated in the cochlea of the inner ear is the basilar membrane. This membrane has groups of sensory receptors, composed of hair cells running along its length, that become activated in response to sounds of specific frequencies. If the positions of excitation on the basilar membrane are too close, interference occurs, resulting in an unpleasant sensation for the listener.

When it comes to deciphering the role of the brain, our understanding has recently begun to flourish with the use of brain-imaging techniques such as positron emission tomography (PET) and functional magnetic resonance imaging (fMRI). Blood flow increases to those regions of the brain activated by particular cognitive tasks, and PET and fMRI techniques are able to pinpoint these activated regions by measuring certain properties of the blood.

Imaging studies of healthy individuals, together with evidence taken from patients with brain damage, have shown that there is no specialized ‘music centre’ in the brain. Instead, many areas distributed throughout the brain contribute to the processing of music, including those functioning in other kinds of cognition.

Scientists are gradually mapping these areas in greater detail. For example, the right temporal lobe of the auditory cortex is involved in perceiving aspects of melody, harmony and timbre. Different regions within the auditory cortex also process various features of rhythm.

A more precise understanding of certain brain structures has also been attained. Recent work at the John Hopkins University in Baltimore, Maryland, has revealed the existence of pitch-sensitive neurons. The pitch of a sound depends on its fundamental frequency, even when this frequency is physically missing from a complex

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sound. Individual cells have been found in the auditory cortex of marmoset monkeys that consistently responded in a similar way to various sounds that, although having no common frequency, shared the same fundamental frequency.

For example, a neuron that responds to 200 hertz also responds to the mixture of 800, 1000 and 1,200 hertz because all have the same fundamental frequency.

The location of these pitch-sensitive cells is consistent with the location of pitch-selective areas identified in human brain scans.

The response of the brain, however, is variable and depends on factors such as personal experience or musical training.

Studies have shown, for example, that the volume of the auditory cortex in musicians is 130 percent larger than that in non-musicians.

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Studies have shown that the volume of the auditory cortex in musicians is 130 percent larger than that in non-musicians

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Music is, of course, more than a catalogue of auditory aspects.The emotional response that music evokes is key to the listening experience, and the areas of the brain responsible are partially segregated from those that deal with the auditory processing of music. Though research into this area is still in its infancy, PET imaging studies carried out on volunteers listening to consonant or dissonant patterns of notes have revealed that at least two systems, each dealing with a separate type of emotion, are involved.

Furthermore, it has been shown that

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Music may have played a key role in the evolution of the human mind

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A comprehensive explanation of our musical experiences cannot, however, be achieved through studies of the ear and brain alone. To venture towards a more complete understanding, the science of sound is being placed in a broader context, both theoretically and experimentally. Research by Dr Ian Cross and other members of the Cambridge CMS emphasizes music as a biological and cultural phenomenon, studying such issues as the origins of music, the abilities that predispose humans to music, and the very reasons for its existence.

Consider, for example, the following three aspects of music, hitherto largely

neglected. The first is that music is an embodied action, inextricably bound to the movement of our bodies. The notion of sitting in a concert hall and simply listening to music is unique to Western classical music: most music involves some kind of movement or dance. Indeed many cultures do not distinguish between music and movement and have the same word for both. The Igbo of Nigeria, for example, use the word nkwa to denote “singing, playing instruments and dancing”. Secondly, the fact that music is embodied may provide the basis and explanation for music’s capacity for entrainment, the process that allows us to act together in time.

This is reflected in our ability, rare in the animal kingdom, to tap along to a beat. Thirdly, that music is embedded in social actions, playing an integral part in occasions like weddings, funerals, and parties.This provides yet another way in which music can be imbued with meaning, although the meaning may vary from person to person. Combined with the idea of entrainment, this social aspect of music allows it to create feelings of togetherness and of shared expe-

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rience that most forms of language are unable to achieve.

These ideas contribute to the intriguing suggestion that music - with the capabilities it requires, the positive effects it has on social cohesion, and the power it holds over our emotions - may have played a key role in the evolution of the human mind.

These fresh angles, and the questions that they evoke, are thus encouraging new ways to investigate the subject. Music and science started out using physics, psychophysics, psychology, artificial intelligence, and neuroscience. But things move quickly. Recognition of the wide-ranging impact of music, and our experience of it has led to additional fields such as biology, archaeology and sociology entering the score.The overture has ended; the opera is about to begin.

A r t s & R ev i ew s

when music induced a pleasurable response it activated the same brain structures as those stirred by food, sex, and drugs.

Owain Vaughan is a PhD student in the Department of Chemistry; Neta Spiro is a PhD student at the Institute for Logic, Language and Computation, University of Amsterdam and the Centre for Music and Science, Faculty of Music, University of Cambridge.

Engineers and Physicists Cambridge, Competitive salaries and benefit packages Sentec is a rapidly growing technology company offering an environment that provides challenge, excitement and variety.We create and develop technical solutions at our own risk, which are then licensed to manufacturers, as well as providing our technical skills and experience on a contract basis.

We want innovative people with a real passion for technology, first class understanding of the fundamental applied physics and/or engineering principles and with an outstanding academic background (A grades at A levels and at least a 2:1 in physics or engineering).

Practical experience in a laboratory or workshop and a desire to turn thought experiments into working prototypes is essential.

Graduate Engineer/Electronics Engineer (ref: 5912HJC) • Strong analogue electronics • Software programming experience (embedded preferred) • Problem solving skills Postgraduate Engineer (ref: 5912HJC) • Good understanding of fundamental engineering principles • Desire to work across traditional boundaries • World class PhD in a practical area (as appropriate) Postgraduate Physicist (ref: 5911HJC) • World class PhD in an applied physics topic • Desire to undertake a multidisciplinary role To apply for these roles, please send your CV to Bernadette Hempstead (email:bhempstead@sentec.co.uk) by 30th November.

NO AGENCIES PLEASE. www.sentec.co.uk

Dr Hypothesis

Dr Hypothesis Dr Hypothesis needs your problems!

If you have any worries (of a purely scientific nature, obviously) that you would like Dr Hypothesis to answer, please contact him by email at drhypothesis@bluesci.org He will award the author of the most intriguing question a £10 book voucher. Unfortunately, Dr Hypothesis cannot promise to answer every question, but he will do his best to see that the most fascinating are discussed in the next edition of BlueSci. Dear Dr Hypothesis, I have just returned from my summer holiday in the Caribbean which, as you can imagine, was much warmer than Cambridge! Normally I’m addicted to the wonders of my college buttery but while I was away I was much less hungry. It wasn’t just that I lay on the beach all day, and simply needed less energy, as I was an active sightseer.

Could there be a biological explanation as to why my appetite should be reduced in hot weather?

Ravenous Rita DR HYPOTHESIS SAYS: Rita, the explanation for this phenomenon is considered controversial by some but I will give you my favourite.This states that appetite is regulated not just by our need to consume food for energy, as many people think, but also by our need to control the amount of heat generated when food is broken down, so as to maintain a constant internal temperature. It follows from this that, on a cold day, you would need to eat quite a bit to keep your body temperature steady relative to the much cooler surroundings, whereas on a hot day you would be driven to eat less to reduce the energy generated and hence the heat produced.Therefore buttery food seems a lot less appealing in the heat of the Caribbean! http:/books.nap.edu/openbook/0309048400/html/189.

Dear Dr Hypothesis, I was brushing my teeth the other night and unfortunately forgot to follow the advice of switching the tap off while I brushed. I noticed that, as the water fell towards the sink, the stream of water appeared to become narrower. It looked as if the amount of water was decreasing! Surely the water was not just evaporating into thin air so, while I would not wish you to waste further water testing this phenomenon, I was wondering whether you could explain it to me?

Observant Oscar

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DR HYPOTHESIS SAYS: It is actually quite simple for me to answer this query, Oscar.The effect is known as a vena contracta — literally, a contracted vein. Inside the pipe, the water is under pressure from the column of water above it, with forces from the walls stopping it from leaking out sideways.The water jet is under less pressure from the air once outside the tap than it is from the pipe walls when it’s inside, which makes the water speed up as it is released. As you say, the water can’t just vanish (a consequence of it being incompressible at subsonic speeds), so the jet has to reduce its cross-sectional area to compensate for its greater velocity.

Dr Hypothesis is most grateful to Professor Mark Warner of the Cavendish Laboratory for useful discussions.

England in 1980 could expect to live to the age of 70.8, while girls could anticipate reaching 76.8 years old.You should always be careful when applying these figures to yourself as there can be a lot of variance around these averages, depending on lifestyle. So maybe by refusing fish and chips and going for a run instead we can all lift the average life expectancy of our groups! www.statistics.gov.uk mathworld.wolfram.com/LifeExpectancy.html In the last issue Dr Hypothesis asked you, the reader: Is there life ‘out there’?

Read some of the answers below…

“If you accept that the universe is infinite, then there is an infinite amount of chances for anything to happen.Therefore, eventually, everything will happen regardless of the likelihood. It follows from this that life must exist elsewhere in the universe but also life must exist in very similar forms to that which has evolved on this planet.”

“The answer to your question could be found using the famous Drake equation, which calculates the number of extraterrestrial civilizations (N) in our galaxy with which we can expect to make contact:

Dear Dr Hypothesis, I am to retire next year and am looking forward to having enough free time in which to do many of the things that I have always dreamed of, such as taking a road trip across the States.

Nevertheless, I am concerned about my financial situation and would like to stretch it as far as possible without running into problems in my last few years.

To this end, could you tell me how population scientists calculate life expectancies and what mine is likely to be?

Thrifty Trevor DR HYPOTHESIS SAYS: Life expectancy is usually defined as the average age until which a group of people of the same age and gender are likely to survive.This value is found from so-called ‘life tables’, compiled by statisticians using the death rate at each age.They use these figures to calculate the probability of members of a group surviving from one birthday to the next, from which life expectancy can be extrapolated. For example, figures released by the UK government estimate that boys born in

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Where R* is the rate at which stars are formed; fp is the fraction of those stars which have planets; ne is the average number of planets which could support life per star that has planets; fl is the fraction of these planets which actually do support intelligent civilizations; fc is the fraction of these which are then willing and able to communicate with us; and L is the expected lifetime of such a civilization. Current values for N range from 0.05 to 5000: obviously some of these values are more easily quantified than others, and the result obtained depends on the optimism of your estimate!”

Dr Hypothesis needs your problems!

He challenges you with this puzzle:

When I hold a copy of BlueSci up to a mirror the writing appears back-to-front.

But, given that the mirror doesn’t seem to have a preferred direction, why doesn’t the writing also appear upside down?

Please email him with answers, the best of which will be printed in the next edition.

Michaelmas 2005