SC PE The Scientific and Technical Journal of The Haberdashers’ Aske’s Boys’ School, Elstree
2019 I ssue 30
Elements Celebrating 150 Years of the Periodic Table Wilson’s disease
Fuel Cells
Changing the Way We React to Copper
A Path Towards A Better Future?
Silicon Semiconductors The Transformation of Quantum Computing
Letter From Editors Dear Reader, 2019 has been a very exciting year for science in many ways. The United Nations General Assembly during its 74th Plenary Meeting proclaimed 2019 as the International Year of the Periodic Table of Chemical Elements. 1869 is considered as the year of discovery of the Periodic System by the Russian scientist, Dmitri Mendeleev, and 2019 also commemorates the 150th anniversary of the establishment of the Periodic Table. This year aims to recognize the importance of the Periodic Table as one of the most important and influential achievements in modern science reflecting the essence not only of chemistry, but also of physics, biology and other basic scientific disciplines. Therefore, in honour of such a remarkable anniversary, we have dedicated this issue of SCOPE to the theme of ‘Elements’. With the standard of submissions outstanding as always, we have published a wonderfully wide range of articles from students across many year groups. This includes articles about the history and discovery of the elements, how vital certain elements are in the maintenance of our health, and the importance of studying elements for the future advancement of technology and energy. From chemistry to biology to physics, there are articles to attract all. Elements are the foundation of our universe and life as we know it, so we hope that by reading this magazine, you will better appreciate the wondrous nature of the Periodic Table and all that lies within. We hope that SCOPE 2019 uncovers some of its mysteries and inspires you to pursue some of these topics further, both now and in the future. Shrey Shah Aditya Varshney James Wirth
Dr A. Perera
Editors-in-Chief, Scope 2019
Staff Editor
SC PE
2019 I ssue 30
The Scientific and Technical Journal of The Haberdashers’ Aske’s Boys’ School, Elstree
Contents 2
14
26
40
Letter From Editors
Making Ice
By Shrey Shah, Aditya Varshney, James Wirth and Dr A. Perera
By Aditya Varshney
Mercury In Dental Amalgam Fillings: A Contentious Toxic Affair
The Elements And Composites That Conquered The Far Side Of The Moon
16
4
Fuel Cells – The Path Towards A Better Future?
Periodic Table
By Aryaman Bhuwania
6
18
The Development Of The Elements
Will We Reach The End Of The Periodic Table?
By Sohan Das
By Krish Nanavati
8 Will The Periodic Table Ever End? By Brandon Yong
10 It’s Called What? How Elements Are Named
20 Answering Chemistry’s Toughest Question
By Khaleel Jiwa
By TT Zhang
28
How Everything Is Stardust
By Abhisekh Chatterjee
By Thilan Kandeepan
30
44
Silicon: A Semiconductor With The Potential To Transform The Field Of Quantum Computing
Medical Research Work Experience Report
By Dr A. Chapman
22
The Role Of Aerodynamics In The Design Of F1 Cars
Our Favourite Elements
12
24
Employing Relativity To Explain Elemental Quirks
Wilson’s Disease: Changing The Way We React To Copper?
By James Wirth
Akshi Kumar
By Raunak Khanduja
46
By Mikeet Patel
33
By James Levy
42
Selenium, Selenocysteine And Amino Acids
Particle Physics Research Work Experience Report By Mikeet Patel
48
By Vivek Shah
36
The 2018 Nobel Laureates
The Elements Of The Elements By Shrey Shah
49
Black Hole
50
Citations
The Haberdashers’ Aske’s Boys’ School Butterfly Lane, Elstree, Hertfordshire WD6 3AF Telephone: 020 8266 1700 Registered charity no: 313996
The Development Of The Elements By Sohan Das 8S2
M
ankind has always been seeking insight into the origins of the universe and its components. After millennia of philosophical hypotheses and
scientific research, our understanding has reached a stage whereby the true answer is starting to break through. But how did we get here? Figure 1 The personalities of the classical elements
The Earliest Concepts Approximately 2500 years ago, ancient Greek philosopher Thales, thought there to be only one fundamental element in the universe: water. This idea seems bizarre now; however, if one considers the solid state of ice, the liquid phase of water, the gaseous form of steam and the life-giving properties
Later Aristotle added a fifth element, aether. This element
of water, it is possible to see why this proposition was
was also known as the void as it was thought to be the
deemed plausible. Then, about 100 years later, fellow Greek
material that filled the region of the universe above the
philosopher Empedocles suggested that the terrestrial
terrestrial sphere.
sphere (the region below the moon if the universe was
Other ancient cultures had similar understandings of the
modelled as geocentric, with the Earth at the centre) is made
composition of the universe; they believed it to be made
up of, not one, but four different elements: fire, earth, water
up of four or five different elements, each with their own
and air. The four terrestrial classical elements are connected
properties. These were the first ideas that mankind had in
in four different aspects of their ‘personality’ as shown in
a search of understanding how this planet and universe was
Figure 1. Empedocles also proposed that force of love mixed
created. Though now known to be inaccurate, this curiosity
these elements and the force of strife separated them.
about the makeup of our universe led to the discovery of all the chemical elements we know now.
6
The Development Of The Elements
The Elements
pudding’ model came shortly after his discovery of electrons
The ancient Egyptians recognised seven metallic elements:
and considers the atom as a spherical cloud of positive charge
gold, silver, iron, copper, lead, mercury and tin. However,
with negative charges scattered inside. Seven years later,
at this time, the Greeks still considered them to be some
Ernest Rutherford developed the ‘nuclear’ model, proposing
composition of the four ‘traditional’ elements. By AD 1, nine
a positive centre with rings of negative charge around it and
elements had been discerned: carbon, sulphur, iron, copper,
lots of empty space in between rings. This idea followed his
silver, tin, gold, mercury and lead.
famous ‘gold leaf experiment’, where this was the only viable
By the start of the 17th Century, four more elements had
explanation for the type of deflection that occurred. Niels
been discovered. Albertus Magnus discovered Arsenic in
Bohr modified the ‘nuclear’ model into the ‘planetary’ model,
1250, whilst bismuth, zinc and antimony were discovered
where electrons were moving in fixed orbits around a positive
between 1250 and 1500. However, even in 1650, it was
centre. In 1926, Erwin Schrödinger described the ‘quantum’
thought that all thirteen of these elements were mixtures of
model, where the atoms have a positive centre, but instead
the four traditional elements. Then, after a gap of 169 years
of the electrons having fixed orbits, clouds of probability
Hennig Brandt discovered phosphorus. In 1739, following
dictate where they are most likely to be found. In 1932, James
the discovery of cobalt a cascade of new elements were
Chadwick bombarded beryllium atoms with alpha particles,
identified, with a total of 78 elements discovered during
leading to him discovering unknown radiation: neutrons.
the 18th and 19th centuries. It was during this time that the
Chadwick modified Bohr’s model to include the newly-
scientific community were moving away from the idea of
discovered neutrons. His theory is widely accepted by the
four root elements and moving towards the atomic theory
scientific community and is the one taught around the world.
of elements. This change was greatly influenced by Dmitri Mendeleev, who discovered the periodic law, whereby when the elements are arranged in order of increasing atomic mass, certain sets of properties recur periodically. By arranging the 63 elements known at the time, he created a table based upon atomic mass, melting point, density and other properties. This ‘Periodic Table’ had gaps in it, which Mendeleev predicted would be filled in by undiscovered elements. This was later proven by the discoveries of gallium, scandium and germanium in 1875, 1879 and 1886 respectively. The current periodic table consists of 118 elements, with oganesson being the heaviest.
Figure 3 The development of the concept of the atom
Figure 2 Mendeleev’s incomplete Periodic Table
The Future The next few elements after oganesson are likely to have half-lives in the region of billionths of a second meaning identifying them will be difficult. The next possible island of
The Concept of Atoms
stability is element 122. One of its isotopes is said to have a
The smallest unit of an element is called an atom. However,
magic number of neutrons: 184, meaning that all its shells
the way we think of atoms has changed over time.
are filled, so it may be possible to create new detectable
The Greek philosopher Democritus first came up with the
trans-uranium elements.
concept of atoms, envisioning them as small brick-like
The way we think of elements has changed over the past
structures. John Dalton changed this model to small balls
three millennia and will continue to change as new research
of identically-sized invisible particles. J.J. Thomson’s ‘plum
into quantum physics emerges.
The Development Of The Elements
7
Will The Periodic Table Ever End? By Brandon Yong 8C
I
n 1937, Italian scientists Emilio Segrè and Carlo Perrier
Once every few billion times, the atoms will collide with
isolated Technetium (Tc), the first synthetically produced
the correct velocity and orientation so that they will merge
element [1]. Eventually, transuranium elements were
with each other, creating a new element [5]. However, the
found to exist – these are elements that are heavier than
elements created are inherently unstable and radioactive so
uranium in the periodic table and tend to be unstable. In
exist for only a short period of time before decaying into
1938, Enrico Fermi received a Nobel Prize “for demonstrating
other elements. For example, moscovium has a half-life of
of the existence of new radioactive elements produced by
only 0.8 s, and oganesson has a half-life of less than 1 ms [6].
neutron irradiation, and for related discovery of nuclear reactions brought about by slow neutrons” [2]. Then in 1939, Ernest Lawrence was also awarded a Nobel Prize in physics for his own work with transuranium elements [3]. These breakthroughs led scientists to explore the possibility of new synthetic elements leading to the development of the Periodic Table as we know it today. Twenty-four of the elements in the Periodic Table are now synthetic, compared to the 94 naturally found, with 4 new elements [4] named in 2016: nihonium [113-Nh], moscovium [115-Mc], tenessine [117-Ts] and oganesson [118-Og]. A method of creating synthetic elements has since been developed. It uses a particle accelerator to collide an atom of an element with a heavier target element.
8
Will The Periodic Table Ever End?
Figure 1 The inside of a particle accelerator
However, there is a possibility that the periodic table will never end. Some scientists believe that there exist ‘islands of stability’, where the number of neutrons work to quell Figure 2 Diagram of lithium atom
enough of the electrostatic repulsion to allow a more stable nucleus to form, hence allowing for more stable elements [10]. The possibility of multiple islands was suggested by Yuri
The discovery of new synthetic elements may be limited
Oganessian, a Russian nuclear physicist who is considered
due to the instability of the new elements with increasing
the world’s leading researcher in super-heavy chemical
atomic mass. The reason for the instability is the simple fact
elements, and only the second person living person to have
that the protons of an atom are positively charged so they
an element named in their honour. The crosses on the diagram
repel each other. In stable atoms, the strong nuclear force
show where islands with ‘magic numbers’ of neutrons and
between nucleons overcomes this repulsion, but unstable
protons are. In the example shown, a theoretical isotope with
atoms usually decay into lighter and more stable atoms [7].
184 neutrons and 114 protons is considered ‘stable’.
Furthermore, for an element to be recognised by IUPAC
More research needs to be carried out to confirm if this
(International Union of Pure and Applied Chemistry), it
is truly the case or if we will reach a natural limit and
must have a mean lifetime greater than 10-14 seconds, and
attrition to a ‘stable’ element. It is likely though that the
this is challenging for new elements because as the atomic
new elements created will only ever be used for research
number increases, the repulsive force becomes stronger [8].
purposes. For the foreseeable future, we will likely continue
A group of scientists who studied the Dirac equation, which
to use elements that are found naturally in the observable
is a relativistic wave equation postulated by the physicist
universe, although it is rather tantalising to wonder if there
Paul Dirac in 1928, suggested that neutral elements may no
remains an undiscovered heavy element that may have novel
longer be possible beyond element 173 [9].
applications for mankind.
Figure 3 The island of stability
Will The Periodic Table Ever End?
9
It’s Called What? How Elements Are Named By James Levy L6H1
A
t some point in everyone’s lives, there is a time where you
element: Carbon. He named it after the Latin ‘Carbo’ meaning
ask yourself this question: ‘If I could name an element
‘coal’, as that is what it looked a lot like. He then went to name
in the periodic table, what would it be called?’ I’ve
‘Oxygen’ in 1774, From two French words ‘oxy’ and ‘gene’ which
heard about every cringe worthy answer: Freshium, Fortnitium,
translates to ‘acidifying constituent,’ as he believed it was Oxygen
Chapmanium, and even Habsium, specifically so that the Habs
which made up acids (But you Year 11s know better, don’t you?)
Chemistry Department can no longer use it as a made-up
He also named Hydrogen, with the same principle, but using the
element in their Year 8 chemistry tests. Of these four, only one
Greek word ‘Hydro,’ for water. This one was right, which is good
would have a very slim chance of becoming an element; so, what
for Antoine if you ask me.
are the rules of naming an element?
Funnily enough, you may think that I will tell you he also
Let’s start with how elements were named in the ancient times.
created Nitrogen, but no! You were wrong! In fact, it was Daniel
The Romans named many abundant metals. Copper is named
Rutherford, who named it after nitre, the mineral he found the
after the Latin word ‘cuprum’ meaning ‘from the island of Cyprus,’
gas from.
because that’s where it was found. This also explains the symbol
Some elements were named based on the human senses.
‘Cu’. Gold, or Au, comes from the word ‘Aurum’, meaning ‘golden’.
Indium comes from the word indigo, as it shows blue colour on
Other metals include Iron Fe (‘Ferrum’ meaning Iron) and Silver
an emission spectrum, and Caesium also comes from the Latin
Ag (‘Argentum’ meaning shiny).
‘caesius’ meaning ‘sky blue’ as it also shows blue colour on the
Moving on, we are now travelling to the year 1694, where our
emission spectrum, shown within Figure 1.
good friend Antoine Lavoisier has now decided to name his first
10
How Elements Are Named
Figure 1 Emission Spectra for Elements 1 to 99
Figure 2 A plaque located in the village of Ytterby, located near Stockholm, Sweden
Bromine is an interesting one, named after the Greek word ‘Bromos,’
I hope you enjoyed the quiz! Did you win? The answers can be
which literally means ‘stench’. Why, you may ask? It stinks.
found at the end. My favourite fact about element names comes
Since 1947, the International Union of Applied Chemistry (IUPAC)
from the Swedish mining village of Ytterby (which you have never
decided to take all the fun out of naming elements and made it
heard of) where not one, or two, but four elements were named
into a long and dull process, which consists of adding the suffix
after! These elements are the well-known Ytterbium, Yttrium,
‘-ium’ to your name of choice and making sure this name has
Erbium and Terbium, as shown by the plaque in Figure 2, which
never been used before. What followed was a five-month waiting
we love so deeply (of course).
period before the board could reject it, so that you could do this
The third category is scientists. Thankfully, no scientist was so
fun process all over again! However, they did have their reasoning
arrogant as to actually name an element after themselves, but
for this and that was because of the 150-year petty squabble over
others have honoured them. A few are Curium, Einsteinium,
the name of element 41, America called it Columbium and Europe
Fermium and of course Mendelevium, in honour of the father of
called it Niobium. It was decided to be Niobium in 1949. IUPAC,
the modern Periodic Table.
from their triumph, then took over the process, making sure that
The final category allows elements to be named on a property it
there was never confusion again.
has. However, this has not been used so often since IUPAC has
There are now four categories of names an element can get. The
been founded, because the new super heavy elements do not
first category is Myth and Legend. Nickel and Cobalt have a great
stay intact, for long enough, to be observed before they break
story behind them, that you are welcome to tell your younger
apart into smaller, already named elements.
siblings before their bed time. According to the Germanic Folk
So that ends our journey through time, to see how elements
people, evil creatures used to swap out valuable ores in the
were named. If you are interested about the etymology of some
mines at night with less valuable ones, called ‘devil’ and ‘kobold’
of the other elements, take a look at the Periodic Table in this
which we now know as Nickel and Cobalt. Another element of
magazine. I hope that next time you ask yourself that time old
legend is Titanium, named after the Titans, the Greek God killers.
question you really give it thought and instead of coming up
The second category is geographical places. For this I thought I
with ‘spidermanium’ or something equally as dumb, you could
would do a fun quiz. If you win, give yourself a pat on the back.
actually use your time wisely to think of a mythical story that
Where did the following names come from?
resonates with you, or perhaps who your favourite chemistry
1.
Americium
teacher is!
2.
Polonium
3.
Nihonium Japan (Nihon in Japanese)
3.
Poland
2.
America
1. Answers:
How Elements Are Named
11
Employing Relativity To Explain Elemental Quirks By James Wirth L6S1
A
n unusual consequence of special relativity is that
The majority of metals in the periodic table have a silvery
the mass of a particle increases with its velocity
colour as they absorb light in the ultraviolet range whilst
v as given by the Lorentz factor,
reflecting most visible light. Gold, however, reflects yellow
1-v2 C
2
and red but absorbs blue light, giving it its distinctive hue. The contraction of its 6s orbital and expansion of its 5d
When applied to atomic electrons, this phenomenon can help
orbital results in the 5d to 6s electronic excitation having
to explain some peculiar properties of the heavier elements.
a lower energy requirement of 2.7eV which corresponds to
Under the Bohr model, the velocity of a 1s electron in an
that of blue light. The pale gold colour of caesium metal can
atom with atomic number Z can be approximated [1] using
also be attributed to this effect.
the formula
. By substituting into the Lorentz factor,
it can be shown that Z is proportional to the relativistic mass of the electron. Since the Bohr radius of the electron orbit is inversely proportional to this mass, the heavier the element, the greater the contraction of their s and p orbitals which have higher probability densities nearer the nucleus. In gold, for example, the 1s Bohr radius reduces by roughly 18%. Furthermore, the contraction of s and p orbitals increases the shielding for less penetrating d and f electrons, causing their Bohr radii to increase.
12
Employing Relativity To Explain Elemental Quirks
Figure 1 Gold Crystals
Figure 2 A typical organogold species
Figure 3 Liquid mercury
The high electron affinity of gold, boosted by up to 65%
Perhaps more surprising is that relativity is responsible
due to its contracted 6s orbital, has earned it the title of a
for the functioning of lead-acid batteries [5] used to power
‘pseudo-halogen’ [2]; not only is it surprisingly stable in the
vehicles – each galvanic cell in a battery can produce
form Au2, but it also forms intermetallic compounds like
a voltage of around 2.13V, 80% of which arises due to
caesium auride, an orange semiconductor crystal with a
relativistic effects. One electrode is coated with metallic lead
tendency toward [Cs] [Au] , with the gold taking an unusual
and the other with electronegative lead oxide, with a sulfuric
anionic form.
acid electrolyte. The contraction of electron orbitals in the
Aurophilicity [3], another consequence of relativity,
lead oxide species makes them act as lower energy wells that
concerns the ability of gold complexes to aggregate due
electrons will fall into more readily, increasing the potential
to the formation of Au–Au bonds, which have a strength
difference across the cell. This offers an explanation as to
comparable to that of a hydrogen bond. For example, the
why tin-acid batteries are inefficient: despite tin (which
compound shown in Figure 2 is stabilised by correlation
sits directly above lead in the periodic table) having similar
effects between electrons in the gold centres which is in part
chemical properties to lead, its higher energy s orbital is not
attributed to the expansion of the 5d10 orbital in the gold
as stable a place for electrons to reside.
atoms. Gold (I) complexes may even polymerise through Au–
Finally, α-polonium is the only elemental allotrope which
Au bonds to form nanoparticles which happen to have very
crystallises into a simple cubic structure [6] in ambient
high luminescence in the visible spectrum.
conditions. Pure quantum mechanics would suggest that it
Mercury is another metallic anomaly in that it exists in
take the hexagonal crystalline structure of tellurium, which
the liquid phase at room temperature [4]. Its stabilised,
occupies the slot above it in the periodic table. However,
lower-energy 6s orbital does not easily contribute its two
strong spin-orbit coupling in polonium – a relativistic
electrons to a delocalised sea, so weaker London forces hold
phenomenon in which the interaction between the electron
together the atoms resulting in a significantly lower melting
spin magnetic moment, angular momentum of the electron
temperature of -39 °C. The reluctance of elements in period
and the nucleus’ electrostatic field alters the electron energy
6 to use these electrons in bonding is named the inert 6s
levels within the atom – prevents the structure from becoming
+
–
2
pair effect; for example, despite [Th] having a larger ionic
unstable and transitioning to a trigonal configuration unless
radius than In , the energy required to increase the oxidation
higher pressures or temperatures are applied.
+
+
state of [Th] from +1 to +3 is 324kJ greater than that for In +
+
because of this relativistic contraction reducing the energy level of its 6s2 electrons.
Employing Relativity To Explain Elemental Quirks
13
Making Ice By Aditya Varshney L6H2
W
e all have an intuitive understanding of
bonds between molecules are formed so the reaction is
irreversibility. We know from experience that
exothermic. The product is at a lower energy level than the
“you can’t unscramble an egg”, crashed cars do
reactant so we often say that the product is more stable.
not simply reassemble themselves, and so on. Similarly, if
We might even be tempted to conclude that water freezes
we put water in a freezer set to -15 °C we know it will freeze
because the process is energetically favourable, i.e. because
to form ice. The reverse will never happen: at -15 °C ice will
ice is more stable. However, if that were the case, how can
never melt to form water no matter how long we wait. So,
endothermic reactions occur? We know water can also
what determines whether a reaction will ‘go’ or not?
evaporate to form water vapour which is at a higher energy
When ice is made from water, energy is released as hydrogen
level. Therefore, this idea that reactions take place only if they are ‘energetically favourable’ must be abandoned.
14
Making Ice
in which the molecules are already moving vigorously. This temperature dependence of entropy means that we must compute the entropy change of the surroundings from:
∆Ssurr =
qsurr Tsurr
where qsurr is the heat absorbed by the surroundings and
Tsurr is the absolute temperature (measured in Kelvin). The
heat absorbed by the surroundings is opposite to the heat absorbed by the system so
qsurr = -qsys and under conditions of constant pressure,
qsys = ∆H sys
Figure 1 Energy level diagram for an exothermic process
In fact, the true driving factor for a reaction is concerned with a quantity called entropy. A simple description of entropy is that it is a measure of the amount of disorder or randomness of a system. A gas has greater entropy than a liquid, which has a greater entropy than a solid. This can be rationalised
We can compute ∆Ssys using absolute entropies, and ∆Hsys
can be found using tabulated values as well. Now that we have an expression for ∆Ssurr we can go back to our original
equation to compute the entropy change of the universe simply as
∆Suniv =
by arguing that the freedom of molecules to move increases
-∆Hsys Tsurr
from a solid to a gas. Entropy is governed by the Second Law of Thermodynamics which is the key to predicting which processes will ‘go’ and
Performing the calculation for water → ice at -15 °C (258K) using data book [3] values:
which will not.
∆Suniv =
The Second Law: In a spontaneous process, the entropy of
described as spontaneous if it takes place without continuous intervention from us. Moreover, we must consider the entropy change of the Universe, not just that of the object of interest. To do this, we can divide the Universe into two parts: the object of interest, the system, and the rest of the Universe, called the surroundings. Then,
∆Suniv = ∆Ssurr + ∆Ssys These ideas are crucial to understanding why water can freeze to ice. Freezing is always an exothermic process so heat is given out to the surroundings and thus the entropy of the surroundings increases. However, ice has a lower entropy than liquid water, so freezing involves a decrease in entropy of the system. Therefore, it must be that ∆Ssurr outweighs
∆Ssys so the entropy of the Universe increases overall.
However, what we must not forget is that ice only forms at temperatures below 0 °C. It seems that ∆Ssurr>∆Ssys only
6.01×103 - 22.0 258
= +1.29 J K-1 mol-1 (3sf)
the Universe increases. This introduces the idea of spontaneity. A reaction is
+ ∆Ssys
Since ∆Suniv is positive, the Second Law dictates that this
process is spontaneous. Repeating the calculation at +15 °C (288 K):
∆Suniv =
6.01×103 - 22.0 288
= -1.13 J K-1 mol-1 (3sf) Now ∆Suniv is negative so this process is not feasible according to the Second Law.
As we expected, ice only forms spontaneously when the surroundings are cold enough. So, the reason why we put water in the freezer is so that the increase in entropy of the inside of the freezer is large enough to compensate for the decrease in entropy of the water freezing. What’s all this fuss about making ice? Well, it is easy to describe how the Second Law applies to phase changes. Applying these ideas to equilibrium reactions is more
at sufficiently low temperatures. This can be explained by
subtle, but we can nevertheless use the same tools in the
the fact that heating a cold object, in which the molecules
knowledge that they will not let us down. And so, just by
are not moving very much, causes a larger increase in
flicking pages of a data book, we can predict where the
entropy than does heating a hot object by the same amount,
position of equilibrium will lie.
Making Ice
15
Fuel Cells – The Path Towards A Better Future? By Aryaman Bhuwania L6J1
P
ower has always been important for mankind. From the
The fuel cell was first developed at the start of the 1800s by
rise and fall of empires to the desire for knowledge.
William Grove [1], as a ‘Gas Battery’, and since then, many
Power is knowledge. And the one advancement
different types have been made such as the hydrogen fuel
that has been pivotal to the progress of technology is the
cell, Phosphoric Acid Fuel Cell, alkali fuel cell and solid acid
development of electrical power and automation. Since
fuel cell. The hydrogen-oxygen fuel cell being the most
Alessandro Volta created the first electrochemical battery
rudimentary, in which the chemicals are stored separately
in 1800, humans have been searching for ways to improve
outside the cell and fed in when electricity is required [Fig 1].
and adapt our energy sources in order to achieve maximum efficiency and power. The fuel cell is potentially the end goal in this centuries-old search for efficient power.
Figure 1 Hydrogen Fuel Cell Diagram
16
Fuel Cells – The Path Towards A Better Future?
Figure 2 Hydrogen Fuel Cell
Hydrogen and oxygen gases are contained in two separate
These risks need to be considered when deciding the types of fuel
electrodes containing platinum, with partially permeable
cell to use in different scenarios as. For example, the phosphoric
membrane between the two, allowing anions and water to pass
acid may be dangerous if used in a vehicle as due to movement
through, but not the gases present [Fig 2]. The electrolyte is an
and extensive usage, there is a risk of acid leaks and therefore
aqueous alkaline solution of potassium hydroxide (KOH) solution.
can possibly damage the users of the vehicle. Another problem
The electrons flow from the negative electrode through an external
impacting widespread use of Phosphoric Acid Fuel Cells is the fact
circuit to the positive electrode. The OH- ions pass through the
that it has a reasonably small power density, which is a measure of
membrane towards the anode [2].
the amount of power per unit volume. This is essentially a measure
At the anode:
based on the internal capacity of the cell, rather than its external
2H2 (g) + 4OH– (aq) → 4H2O(l) + 4e– At the cathode:
size, measured in kWhm-3. Until now, the largest industrial uses of fuel cells have mainly been in electric vehicles with many famous car brands such as Toyota,
O2 (g)+ 2H2O(l) + 4e– → 4OH– (aq)
Hyundai and Honda having released many car designs and almost
Another fuel cell is the Phosphoric Acid Fuel Cell, which was first developed in the mid-1960s. This uses phosphoric acid (H3PO4) as its electrolyte, which is saturated in silicon carbide (SiC). The electrodes in this reaction are made of carbon paper coated with a platinum catalyst [3].
all other vehicle manufacturers have models under development currently. Since the first design was released in 2002, the Honda FCX-V4, the prices have rapidly dropped, with the leasing prices decreasing from $11,500 a month to $369 a month for the Honda Clarity and $349 for the Toyota Mirai [Fig. 3] [7].
Negative terminal:
2H2(g) → 4H+(aq)+ 4e– Positive terminal:
O2 (g )+ 4H+(aq)+ 4e– → 2H2O(l) The energy efficiency is an important part of deciding which fuel source to use and is shown by this calculation:
% Efficiency =
Useful Energy Output Total Energy Input
× 100%
According to the US Department of Energy [4], fuel cells are 40-60% efficient in comparison to 25% efficiency in internal combustion engines. This is the energy efficiency when looking at the useful energy being the main energy output. In a system which also captured useable heat, the figure for fuel cells increases to 85-90%.
Figure 3 - Toyota Mirai with Hydrogen Fuel Cell
These already have shown economic and environmental benefits over oil due to the fuel cell. There are a few possible problems, as the current price for hydrogen is £10-£15 per kg, and with the current average fuel tank capacity of 5kg, this would mean a full refill would cost between £50-£75, which is more expensive
The maximum theoretical efficiency is never reached due to factors
currently than internal combustion engines, however this should
such as transport, production and storage of the fuel. However,
come down in the future due to hydrogen being more readily
without taking these into account we can still make comparisons
available [8].
between different types of power generation methods. Statistics from the World Energy Council [5] show that the maximum theoretical energy efficiency of a fuel cell is 83% in comparison to 58% from an internal combustion engine. This shows that the energy efficiency of a fuel cell greatly exceeds that of an internal combustion engine, and hence it may be a viable alternative to organic fuels, not only providing a substantial amount of energy, but also producing less environmental damage.
Phosphoric Acid Fuel Cells in specific, have been researched extensively already and started to be used commercially in certain areas, replacing conventional energy sources. Some of the current uses includes stationary power generators with output in the 100kW- 400kW range [9], and they are also starting to be used in large vehicles such as buses, where they can be stored safely and kept isolated to ensure no spillage can occur, and if it does, no harm would come to passengers. In India, there is already research
Despite the positives of the Phosphoric Acid Fuel Cell, there are
at its National Defence Organisation [10] for an air-independent
some problems. The first is simply the phosphoric acid itself
propulsion for their submarines.
which, despite not being corrosive, does have many other risks, especially as the acid needs to be a very high concentration, or occasionally even pure acid. According to the National Institute for Occupational Safety and Health [6], it can cause damage, in many different ways, namely, pain and/or redness when exposed to skin or the eyes and possible shock and collapse if ingested.
The fuel cell is an alternative power source to diesel and oil cars and particularly, with the Phosphoric Acid Fuel Cell seems to have the largest benefit because of both outstanding efficiency and the extremely small amount of damage it causes to the environment in comparison to the other types of fuel cells.
Fuel Cells – The Path Towards A Better Future?
17
Will We Reach The End Of The Periodic Table? By Krish Nanavati 11R1
I
n early 2016, most Chemistry classrooms around the world had a slight update to their dĂŠcor as elements 113, 115, 117 and 118 completed the bottom row of the
periodic table, as shown in Figure 1. The International Union of Pure and Applied Chemistry (IUPAC) officially recognised their existence at the end of 2015, but most scientists were convinced of their existence years before that. The periodic table has a reputation for being reliable – since its conception 150 years ago, we have been able to predict the existence and nature of many elements well before we have experimental proof of their existence. The assumption since then was that this trend should surely continue, and the periodic table was never ending.
18
Will We Reach The End Of The Periodic Table?
Figure 1 Some of the newest elements
However, Einstein’s ground-breaking Theory of Special
a different reason. The quantum explanation of this issue did
Relativity put an end to this notion. It introduced revolutionary
not predict the electrons would be travelling too fast; instead
concepts, such as length contraction and consequentially time
it suggested that before that point was reached, there would
dilation, the universal and invariant speed limit of light and,
be so many protons that the nucleus wouldn’t be able to hold
most importantly in this context, the concept of energy-mass
itself together.
equivalence, characterised by the famous equation E = mc .
The force that causes similarly charged particles to repel is
What the theory showed was that as the mass of the atoms
known as the electrostatic force of repulsion, and it has infinite
increased, the speed at which the electrons orbited them also
range. It is a part of the electromagnetic interaction, one of
increased until eventually the innermost 1s electrons, would
the four Fundamental interactions of nature (see Figure 3). It
be travelling faster than the speed of light.
is incredibly strong compared to weak nuclear and gravity, two
Richard Feynman applied this concept to the Bohr model
other fundamental interactions. The fourth one, strong nuclear,
(in Figure 2) for an atom, the basic idea of how protons,
is about 100 times stronger than electromagnetism. The strong
neutrons and electrons are all placed within an atom. Using
nuclear force only works on a miniscule scale, but it is strong
the equations at his disposal, he calculated that there could
enough to overcome the electromagnetic repulsion of protons
not possibly exist an element with an atomic number greater
in an atom. This is what hold a nucleus together in all atoms.
than 137, for its electrons would be travelling faster than the
However, if an atom gets too large, the protons would be far
speed of light. This was the first estimate to be carried out with
apart enough for the nuclear force to be too weak to overcome
rigorous mathematics.
the electrostatic repulsion. Therefore, at some point, there
2
must be a nucleus that is too large to exist. The original attempts at the Dirac model predicted this limit would be 137, however after adjusting some of the parameters it was found to be 173, and that is the value that is often quoted now. However, the strong nuclear interaction is the most complicated interaction to understand, and there is still a lot about it we do not know. Most scientists agree that whilst 173 is a good estimate of the last element of the periodic table, we have very little idea as to the actual value. The next step would be to experimentally test this; however, it is unlikely that this will be possible anytime in the foreseeable future. In general, as elements become larger, Figure 2 Bohr atomic model
they become less stable. As such, they decay within fractions of a second and are unable to be examined. There are some exceptions, known as islands of stability, and one of these is
The issue with Feynman’s calculations were that the model he used was non-relativistic and he was presuming that the nucleus was a singular point. As such, his result was inaccurate. Further estimates were gathered using the Dirac equation, which stems from quantum mechanics and so takes into account factors that Feynman missed in his analysis. The Dirac equation also predicted a limit to the size of an atom, but for
around elements 120-126. However, the journey to element 173 (if it exists), with our current technology and methods, seems to be too far a reach. Nevertheless, with the current rate of technological evolution, combined with sufficient research into the nature of the forces of the universe, we may one day be able to complete what Dmitri Mendeleev started 150 years ago, and finish the Periodic Table.
Figure 3 The Four Fundamental Interactions
Will We Reach The End Of The Periodic Table?
19
Answering Chemistry’s Toughest Question By Dr A. Chapman
T
here are many questions that chemists dread being asked; “Why are d-orbitals those funny shapes?”, “What is organic chemistry really?”, or “how accurate is
Breaking Bad?” However, there’s a far simpler question which from my experience leads to much more head scratching by chemists: “What is your favourite element?” For anyone who has spent time in a Chemistry lesson it’s a familiar enquiry, and one that usually crops up a few minutes before the bell goes. For me there are two instantaneous thoughts: ‘Aha! Some wag is trying to veer of topic. Shall I go with it?” and “Um… I’ve never really decided. Best push on with the syllabus”. It’s a tough choice though, and all of the elements have a good case. Each has its own intriguing
some properties that are quite bizarre. At -198oC it is a liquid.
tales, solid scientific credentials, and more involvement of
Nothing unusual yet. Perhaps more surprising is that this liquid
economics that you’d probably expect. But, after about half
is blue (see Figure 1) and, due to the arrangement of electrons
a century of studying Chemistry, I feel it is time to finally
in the O2 molecule, it is attracted to magnets. There’s also the
commit. So, out of the 118 known elements this is it, and I’m
fact that it’s a very reactive substance, but unlike its neighbour
finally plumping for oxygen.
fluorine, it is quite happy floating around in the atmosphere
At first this might seem like a rather uninspiring choice. In the periodic table element 8 sits quite innocuously at the top of group 6, the chalcogens, just above more exotic sounding elements like selenium and tellurium. Everyone has heard of
minding its own business. In the same situation fluorine would be wildly pillaging electrons from any substance it could (i.e. pretty much everything). Like much of chemistry, the further you dig the more intriguing things become.
oxygen, and everyone understands why it is important. It is
Oxygen was first identified in the 1770’s, with the discovery
the third most common element in the universe, a colourless
generally attributed to one of two titans of chemistry: Joseph
gas here on Earth, and we breathe lungfuls of it in and out
Priestly or Antoine Lavoisier, though others are likely to have
several thousand times a day without really thinking about it.
isolated it previously. Its discovery was partly significant
However, oxygen’s every day familiarity perhaps conceals much of its real character. Looking a bit deeper there are
20
Figure 1 Blue Liquid Oxygen
Answering Chemistry’s Toughest Question
because oxygen was an element, and at the time only around 20 were known. However, its isolation also led to the end of the
wildly ‘imaginative’ concept of phlogiston, and the beginnings
energy valley. Consequently, more interesting and valuable
of our modern atomic theory. Lavoisier’s research into oxygen
oxidation products than combustion can be made. However
also gave the first real understanding of combustion, oxygen’s
pure oxygen is rarely used for obvious reasons. Instead, its
most reckless reaction. Unfortunately, Lavoisier’s research
inherent reactivity is controlled by connecting it to a metal
wasn’t entirely complete; he named the new element after the
atom, often chromium or manganese, then using this resultant
Greek words for “acid” and “producer”, which of course it isn’t
compound in a reaction. This works very well but it is often
(that would be hydrogen). But names tend to stick. Perhaps a
wasteful as these chemicals are generally good for one use.
better choice would have been pyrogen, or Firestarter, but I’m
This is where my work comes in.
not an 18th century chemist.
One seemingly madcap alternative is to use molecular oxygen
Oxygen’s proclivity to combust things is linked to the fact it’s
along with a catalyst such as platinum to mediate the reaction.
a small atom that is a couple of electrons short of its most
Under the correct conditions and with a lot of care selective
favourable arrangement. The positively charged nucleus
oxidation can be achieved producing very little waste and a
exhibits a strong pull on negatively charged electrons, so it will
high product yield. Win. Win. Win. The issue here is that pure
grab them from almost any other element. However, oxygen
oxygen has a bit of a tendency to just burn whichever delicate
usually exists as a molecule
starting material that we’re
of two atoms, which are held
trying to carefully react. Or even
together quite strongly as they
worse, ignite the solvent as they
share a couple of electrons
are often quite flammable. In
each. Quite a cosy arrangement.
my case the answer was to use
Contrast this with fluorine which
compressed carbon dioxide (or
only share one electron between
supercritical carbon dioxide if
two atoms in its molecules.
you are feeling technical) as
This makes them much easier
a reaction medium. Here CO2
to separate, unleashing its
acts wonderfully as a solvent
inherent energetic fury.
as it is already fully reacted
That’s not to say oxygen is
with oxygen so can’t burn. It
passive, it just needs a bit of
also completely mixes with
warm up before it really gets
oxygen, helping prevent large
going. Anyone who is familiar with the fire triangle will know
Figure 2 The Fire Triangle shows what is required for combustion to occur
that given some fuel and a bit of
concentrations
of
the
gas
build up which potentially could detonate with any other
energy, oxygen will unreservedly react with almost anything,
chemicals present. This is obviously undesirable if you want
and release lots of energy while doing so. And, provided there’s
your lab mates to continue to talk to you, and also pretty much
enough fuel to keep going, once it starts it is difficult to get it
how a diesel engine operates.
to stop (See Figure 2). As a result, oxygen is the only element
I’m pleased to say my research worked, or worked well enough to
that has the honour of having a whole branch of the emergency
pass my PhD. It was a complicated technique to get right, and I am
services based around stopping it reacting. Combustion does
just as pleased that I suffered no trips to A&E due to inadvertent
have its uses though, and we use oxygen’s ability to chew up
explosions. However, the sophistication of my oxidation system
carbon-based chemicals to generate much of our electricity and
pales into insignificance with what is going on in your body. Right
hot water, and to power most of our road vehicles. While useful,
now, oxygen is being extracted from the air, safely transported
this is quite unsophisticated chemistry. The reaction follows
around the body, before being delivered to cells. Here it is
the path of least resistance down to the bottom of an energy
carefully reacted with carbohydrates to produce carbon dioxide,
valley, producing carbon dioxide and water. Useful for releasing
water, and the energy that keeps the body running. All this is
energy, but there is far more to oxygen’s chemistry than setting
happening 24 hours a day without fail, and with the distinct lack
things on fire.
of an explosion. Having spent several years reacting oxygen with
At this point I must admit I have a personal reason for choosing
lots of things, mostly carefully, I’m still impressed by how much
oxygen, stemming from my own research work. Some reactions
better our bodies manage it.
involving oxygen are very important in industry for making all
So, there it is. Oxygen. Finally, I have a favourite element. Just
sorts of useful chemicals that end up all around us. These
don’t hold your breath if you ever ask for my second favourite.
“selective oxidations” require a much more delicate use of oxygen to avoid racing to the bottom of the aforementioned
Answering Chemistry’s Toughest Question
21
Our Favourite Elements
T
he six most common elements in living organisms
trends in the properties of the halogens. Perhaps the most
are hydrogen, carbon, oxygen, nitrogen, sulphur and
interesting fact about astatine is that its boiling point is
phosphorus. They are the arguably most important
just 337 °C so any visible quantity of it would be instantly
elements as their combinations make up most biological
vaporized by the thermal energy released due to its
molecules on Earth. Dr Chapman has already talked about
radioactive decay.” Phalgun Deevanapalli (7R)
his favourite element; now it is time for some junior students
“Arsenic naturally occurs in
to discuss a few of the lesser known, but perhaps more
many minerals and is also
interesting elements.
one of the few elements to “Astatine is the rarest naturally
sublime; however, its most
occurring element on Earth.
fascinating feature is perhaps
With a half-life of just 8.1
the fact that arsenic and
hours, only trace amounts of it
many of its compounds are
are present in the crust at any given time.
Figure 1 Astatine
22
Figure 2 Arsenic
especially potent poisons. The different allotropes of
When Mendeleev published
arsenic have different colours, with grey being the most
his periodic table, the space
common. Yellow arsenic is soft and waxy, and it is also the
directly below under iodine
more poisonous allotrope. So, how would you feel after
was empty; it was suggested that a fifth halogen belonged
ingesting arsenic? The symptoms of acute arsenic poisoning
there. Many scientists tried to find the element in nature,
(which is not enough to kill you) are vomiting, abdominal
but without success, given its rarity. Astatine was produced
pain, diarrhoea and muscle cramping. Contact with larger
synthetically by bombarding bismuth-209 with alpha
doses is likely to increase the chance of skin and liver cancer
particles in a particle accelerator. The scientists at Berkeley
and can even result in paralysis.
who first synthesised it noted that it was radioactive, thus
A variety of organoarsenic compounds were developed for
naming it from the Greek astatos meaning unstable.
chemical warfare during World War I, including vomiting
Like the other halogens, astatine is a non-metal, although
agents such as Adamsite. But arsenic also occupies a place
it shows more metallic character than the others. However,
as a healer in medical history, particularly in the treatment of
too little pure astatine has ever been assembled in one place
trypanosomiasis and syphilis. Such was its impact that the
to observe its physical properties. Therefore, many of its
first effective treatment for syphilis, Salvarsan, was hailed
bulk properties have had to be estimated by extrapolating
as ‘the arsenic that saved’.” Camran Aryan Singh Riaz (7J)
Our Favourite Elements
Figure 3 Chemical structure of lignin
“The elements we have discussed thus far are just that,
iron). Wood also contains other chemicals in trace quantities.
elements. They are not compounds or mixtures. Some such
Apart from water, there are three main organic compounds
as oxygen and nitrogen may be diatomic, but they are still
in wood: the polysaccharide cellulose, the irregularly
just elements. Lastly, I would like to write about the complex
structured hemicellulose, and the phenolic polymer
tree of organic compounds that make up wood.
lignin. There are several distinct types of wood due to the
We use wood in many industries and have been doing so since
varying growth conditions, but their properties all come
man has walked the earth. The elemental composition of
from fact that the three components are interwoven, with
wood varies between species but they are all approximately
microfibrils of cellulose impregnated with lignin reactions.�
50% carbon, 42% oxygen, 6% hydrogen, 1% nitrogen and
Aidan Cham (8M)
1% other elements (such as calcium, potassium, sodium and
Figure 4 Oxygen and its wonders
Our Favourite Elements
23
Wilson’s Disease: Changing The Way We React To Copper? Akshi Kumar L6M2
C
opper is one of the most widely appreciated and circulated
Wilson’s disease: A Background
elements that has been discovered and evidence shows
Wilson’s disease is a copper metabolism disorder which affects
that it has been used since 8700 BC in Northern Iraq [1],
around 1 in 30,000 people worldwide and is most prominent
having been extracted from its naturally occurring ore. This has
in China and Japan. Wilson’s disease is an autosomal recessive
not gone unnoticed in the medical world with its vital inclusion
disease and so in order for it to develop in offspring, two copies
in various metalloproteins to perform metabolic processes, fight
of the abnormal gene must be present. Its genetic pedigree (See
infections while neutralising free radicals and even creating
Figure 2) shows how 75% of offspring will likely carry the gene
new red blood cells. The human body usually contains between
from two carrier parents giving it a strong possibility of maintaining
1.4mg and 2.1mg of copper per kilogram of body mass. The
its existence in family lines. Wilson’s disease (coined by physician
recommended daily intake of copper is 1.2mg per day for an
Samuel Alexander Kinnier Wilson [3] affects the enzyme ATP7B
adult and as only 0.9mg is used per day, the excess is excreted,
[4] by inhibiting it from removing excess copper, by secreting it
being directed towards bile [2]. However, despite this apparent
into bile, and linking the copper to ceruloplasmin (a ferroxidase
positivity surrounding the intake of copper, it begs the question,
enzyme). This causes oxidative damage by impairing the balance
what happens when this system goes wrong?
between free radicals and the ability of the body to counteract their effects through antioxidants under what is known as Fenton chemistry. This can cause severe cirrhosis, chronic active hepatitis and various other ailments which all result in the need for either some sort of medication or in worse cases, transplantation which, when involving a liver, can be extremely dangerous.
Figure 1 Chalcopyrite, the most common form of copper ore (courtesy of https://en.wikipedia.org/wiki/Chalcopyrite)
24
Figure 2 The genetic pedigree of Wilson’s disease (courtesy of CGT, 2018)
Wilson’s Disease: Changing The Way We React To Copper?
Figure 3 Effects of Wilson’s disease and the role of the liver in copper transport (courtesy of Silbernagl/Lang from Colour of Physiology [2000])
What Does This Excess Of Copper Do?
irreversible extent. In order to tackle this problem, novel drugs
It is known that the effects of excess copper build up can be
are being tested which target the protection of LRP1 against this
fatal, with neurological, ophthalmological and hepatic systems
‘copper poisoning’ that takes place however, the research has
all at risk of permanent damage (See Figure 3). Neurologically,
been proven to be somewhat insufficient. The report, published
Parkinsonism, a clinical syndrome characterized by tremors,
in PNAS, describes the results as of ‘showing promise’ after
bradykinesia, rigidity, and postural instability, occurs and, as a
facing the uncertainties of copper excess as opposed to other
result, so do seizures. These come hand in hand with spasms,
metals such as aluminium that have been linked to the same
false tremors and sometimes slurred speech. What has
results. It also awaits to be confirmed whether the research is
become more apparent is the link between the development
applicable to humans because the experiments were carried out
of subcortical dementia and Wilson’s disease [5]. This type of
on mice and in specific conditions.
dementia often results in memory loss and the inability to make
Another interesting point of research is the rise in psychiatric
smart decisions which, as research into degenerative diseases
issues with Wilson’s disease. A study written in 2010 [8] recorded
progresses, poses an interesting situation for the question of
the case of a 20-year-old female patient who presented with
neurological pathology particularly dementia. However, less
acute psychiatric disturbances, and deteriorated over the next
obviously, Wilson’s is also known to affect the ophthalmological
few months, with apathy, lack of speech and drooling all part of
systems of patients causing what is known as a Kayser-Fleischer
her symptoms. Unexpectedly, she was diagnosed with Wilson’s
[6] rings on each eye which are circled around the iris due to
disease. Her symptoms were subdued with the subsequent
copper depositions on Descemet’s membrane. While they cause
electroconvulsive therapy (sending a current to the patient’s
no significant vision damage, they serve well as pathognomonic
brain, inducing an epileptic seizure). While it has questionable
signs to aid diagnosis. Sunflower cataracts form but again there
physical and mental side effects, it is a proven method of
is little vision damage done. Renal tubular acidosis means that
dealing with mental issues and it is another way of observing
aminoaciduria can take place in the kidneys causing nutrient
the neurological effect of Wilson’s disease. The disease’s effect
deficiencies. As well as effects on the heart’s rhythms and
on the brain has been an important step in the observation to
endocrinal co-ordination, it is observable that copper’s effect
investigate the relevance of other psychiatric disorders.
on organ systems causes anatomical debilitation, but will this change the way copper is seen by the medical world?
Conclusion It has become apparent that such a copper excess in the body
What will change about the way we view copper?
is toxic. However, what is more of an unforeseen consequence
One of the most topical discoveries of copper is its correlation to
is the effect on the neurological system and its relevance in
the increasing rates of Alzheimer’s [7]. A study carried out at the
modern day medicine as rates of Alzheimer’s rise as well as the
University of Rochester Medical Centre reportedly concluded
research into mental health soars. While we are exploring the
that copper presence affects the activity of protein LRP1 which
worrying increase in cases of degenerative diseases that lie in
helps to remove amyloid beta from the brain (a protein strongly
genetics and are non-communicable, the elements required for
associated with neurological dysfunction). Disorders such as
life are a point of call that should always be relied upon. Wilson’s
Wilson’s disease strongly point to such an excess of copper that
disease has given copper a different point of view and one that
can lead to damages being sustained in the brain often to an
should not be misjudged.
Wilson’s Disease: Changing The Way We React To Copper?
25
Mercury In Dental Amalgam Fillings: A Contentious Toxic Affair By Khaleel Jiwa L6J1
D
26
ental amalgam continues to serve as a widely popular
treaty initiated in 2013 aiming to protect the environment from
and effective restorative material used to fill cavities
mercury pollution, recently ratified by the EU regulation in 2017.
caused by tooth decay, predominantly for posterior teeth,
This paper will seek to explore the potential implications for the
and has been utilised globally for over 150 years in Dentistry. In
release and systemic uptake of mercury from dental amalgam,
terms of its composition, dental amalgam is an alloy of a mixture
both environmentally and toxicologically.
largely comprised of liquid (elemental) mercury and a powder,
This has emerged as such a contentious issue in public health,
consisting of silver (~22-23%); tin (~14%); copper (~8%); and
principally because such a large proportion of people are
other trace metals, such as zinc. Mercury within the dental sector
inadvertently exposed to it in order to obtain the unique benefits
is primarily encountered in two forms: elemental and ionic, and
that dental amalgam fillings offer. Therefore, it is critical to
it is this ‘toxic’ component that has sparked major controversy
consider the purpose of dental amalgam in clinical techniques.
regarding the safety of dental amalgam as a restorative
Dental caries is a widespread microbiological disease that
material. These potential implications have taken shape with
results in localised dissolution of the calcified structure of the
the inception of the Minimata Convention, an international
teeth, forming cavities. It is the interaction between primarily
Mercury In Dental Amalgam Fillings
soft acids and bases concept. The food chain facilitates the biomagnification of mercury levels and although all forms of mercury can bioaccumulate, methylmercury does so to a greater extent; therefore, increasing the concentration of this organic form in aquatic organisms and consequently raising levels of exposure for fish-eating predators and for humans. Toxicologically, mercury may present a risk to dental patients through temporal leaching out of amalgam restorations, as well as to dental personnel due to chronic exposure of the elemental form from repetition of clinical procedures. Low levels of mercury vapour are released, which can be inhaled and absorbed by the lungs. High doses of mercury vapour exposure are associated with adverse effects in the brain and on renal function, as they are target organs; however, extensive research has concluded that it is unlikely that such consequences, and other suspected toxicological effects, are as a result of the mercury in dental Figure 1 - Mercury in Dental Molar Filling
amalgam fillings. According to the British Dental Association, the 2017 EU regulation “advocates a phase-down of the use of
Streptococcus mutans in the oral biofilm, colonised during
dental amalgam, in line with the domestic circumstances of each
plaque formation, and the enamel at the tooth surface that is
country and in tandem with recommendations for prevention
the popular view in understanding caries initiation. Dental
programmes and increased research in to alternative restorative
restorations, such as amalgam, are therefore required in order
materials.”
to restore the function, integrity, and morphology of the missing tooth structure [Fig. 1].
Despite evidence highlighting the detrimental effect that mercury particle release from dental amalgam is having on the
Mercury is a dense d-block element in period 6 of the periodic
environment, contamination is minimal in comparison to vehicle
table, with a unique electron configuration that strongly resist
fossil fuel combustion and industrial pollution quantities.
the removal of an electron. Therefore, mercury forms weak
Therefore, the management of dental amalgam waste should
bonds and is a liquid at room temperatures, making it behave
be improved so that both the application of dental amalgam
similarly to noble gas elements [Fig. 2]. The chemical properties
as a highly effective restorative material and minimizing the
of mercury enable it to bind to the powdered alloy particles
environmental effects can be satisfied.
effectively, forming an amalgam in an amalgamation reaction, without the need for high melting temperatures. The prime concern for the environmental impact of dental amalgam encompasses its disposal in the aquatic ecosystem due to industrial discharge of elemental mercury via wastewater from dental practices. Lost or extracted teeth with amalgam fillings; surplus trituration capsules; minor amalgam particles produced during burnishing, carving, and polishing procedures are removed by the vacuum system, and so if no amalgam separating unit is used, this generated amalgam-contaminated sludge can be discharged in to the sewage system. Elementary mercury entering waterways is converted to methylmercury, an organometallic cation, mediated by methylcobalamin or sediment microorganisms and this raises concern, as it is a bio accumulative environmental toxicant. The subsequent uptake of mercury can occur via two methods: directly from the water due to mercury’s high affinity for sulphur and sulfhydryl groups, or through the food chain. Mercury has a high affinity for sulphur and thiols, (which are compounds with a –SH functional group),
Figure 2 - Mercury as a liquid at room temperature
as they are both ‘soft’ in their ionic forms and so combine to maximise covalency, in accordance with Pauling’s hard and
Mercury in Dental Amalgam Fillings
27
Selenium, Selenocysteine And Amino Acids By Abhisekh Chatterjee L6C2
B
efore diving into the proverbial deep end and discussing
biological compounds. All 20 standard amino acids contain
the intricacies of selenocysteine (Sec), establishing some
varying amounts of each of these; however, the 21st amino
basics might prove useful in navigating the treacherous,
acid, selenocysteine is the only amino acid to contain the
but devilishly enticing, waters of biochemistry.
trace element Selenium. Even pyrrolysine, the 22nd amino
When Francis Crick stated his central dogma of molecular
acid (another non-standard one) doesn’t have the audacity to
biology, ‘DNA → RNA → proteins’, he forgot to mention that
contain an element outside of CHNOPS. Selenocysteine really is
the building blocks of proteins are amino acids. An amino acid
a unique amino acid. Its seemingly innocuous structure is very
is a monomer; joining together many amino acids creates a
similar to those of serine and cysteine but in place of the sulphur
polypeptide. Proteins are made up of one or more polypeptides,
in Cys and the O in Ser, it has selenium.
with each amino acid linked to the next by a peptide bond. Now that you know how amino acids fit into the bigger picture, let’s take a closer look at them. Amino acids consist of a central carbon atom covalently bonded to one hydrogen atom, a carboxyl group, an amino group and a side-chain (R) group. This R group can be anything ranging from a simple hydrogen atom in glycine to a benzene ring in phenylalanine. Each amino acid is coded for by a variety of codons – each codon is a sequence, or triplet, of 3 DNA bases. The amino acids mentioned above are part of the 20 standard amino acids that are coded for by codons in the human genome. Selenocysteine, on the other hand, is a non-standard amino acid – it isn’t coded for in the normal fashion in the human genome. However, before we look at how Sec is coded for, we need to first examine its structure. The acronym CHNOPS stands for carbon, hydrogen, nitrogen, oxygen, phosphorus and sulfur - it describes the six most important elements which form the foundation for most
Figure 2 Codon wheel
The codon wheel in Figure 2 shows all the possible combinations of U, C, A and G in mRNA, and what amino acid each codon corresponds to. We can see that, for example, serine is coded for by 6 codons. Selenocysteine, on the other hand, is coded for by the UGA codon. Unfortunately, UGA is a normally a stop codon that would tell the tRNA which brings the amino acid
Figure 1 Structural formulae of Ser, Cys and Sec
28
Selenium, Selenocysteine And Amino Acids
to the ribosome to stop translation of mRNA into proteins.
However, to code for Sec, the UGA codon must be followed by a SECIS element. A SECIS element is an RNA element that adopts a hairpin-like stem-loop structure. In eukaryotic cells, the SECIS element code is contained in the 3’-UTR section of mRNA, a section of mRNA separate from the coding sequence that comes after a stop codon. However, in bacteria, SECIS is a 40-nucleotide long sequence that follows the single UGA codon it changes. This is the reason why the SECIS element in humans can modify many UGA codons within the translated section to code for Sec.
Figure 4 The SECIS delivery mechanism
The mechanism through with the SECIS element brings selenocysteine to the ribosome is also a complex (and almost surgical) procedure. To begin with, the SECIS element is identified by a special SECIS binding protein which recognises that the UGA codon in the middle of the translating sequence is not a normal stop codon. This binding protein then instructs not to terminate at this UGA codon but instead to bring in a special elongation factor called EFSEC. An elongation factor is a protein that brings tRNA to the ribosome during translation or protein Figure 3 A type 1 SECIS element
synthesis. EFSEC brings one tRNA molecule, which brings with it the all-important selenocysteine, and incorporates it into the polypeptide, as if the UGA codon coded for Sec. Without the
On the left, Figure 3 shows the shape that the SECIS element takes. Many structures that take this sort of shape, such as the tRNA molecule, which carries each amino acid to the ribosome, where proteins are made, are made up of RNA or DNA bases that are palindromic — in essence, they read the same in both
SECIS element, UGA would simply cause protein synthesis to stop in the middle of the translating synthesis. Notice, in the diagram, how the SECIS element follows the stop codon; this is the 3’-UTR region which directly affects the selenocysteine incorporation site inside the translating sequence.
directions, Imagine that DNA bases are letters, and that there
However, selenocysteine isn’t just a cool amino acid – it is
are two sequences of letter that run parallel to one another, like
used in a variety of metabolic processes, it is one of only two
the 2 strands in one DNA molecule. Imagine that both strands
proteinogenic amino acids coded for in a non-standard fashion
read ‘sex-at-noon-taxes’ or ‘nurses-run’, They are essentially
in the human genome, and its deregulation has found to be
the same strand but reversed, However, the SECIS element is
associated with neurodegenerative diseases and even the
not actually formed from palindromic DNA sequences — in fact,
development of neuronal disorders, one such being epilepsy.
it contains many ‘wobble’ base pairs, which are base pairings
While we may not yet fully understand why, we do know that the
that don’t follow the conventional Adenine binds to Thymine or
production of Sec in neuronal cells is essential to brain function,
Cytosine binds to Guanine format. This is an example of how
and further investigation on the specific role of this amino acid
the rules we used to govern biology, especially in conventional
may help us gain a clearer understanding of what the driving
education systems, are often ignored and disregarded by
forces behind these debilitating diseases that rob people of
nature itself, as function must come before form in every
their memory, autonomy and conviction are.
instance. However, we now have to understand how this SECIS element actually works to incorporate Sec into any given amino acid sequence.
Selenium, Selenocysteine And Amino Acids
29
Silicon: A Semiconductor With The Potential To Transform The Field Of Quantum Computing By Mikeet Patel L6H2
M
aking up 27.7% of the Earth’s crust, silicon is the
How quantum computers work?
second most abundant chemical element in the crust,
Firstly, an introduction to the mechanics of a quantum computer.
being surpassed only by oxygen. This accessibility
Conventional computers perform calculations by encoding
coupled with silicon’s semi-conductive nature and extremely
information as digital bits: 0s or 1s. Quantum computers also
high melting point give silicon its widespread use in the common
store information in bits; however, these quantum bits or qubits
integrated circuits which build conventional computers. However,
exist in quantum superposition, an ability of subatomic particles
advances in quantum mechanics over the past 50 years have led
to exist across all possible states at the same time. In this way,
to the development of quantum computers, which make use
qubits can exist as a state of combination of both 0 and 1, with
of the counterintuitive physics of subatomic particles and can
a certain probability of being 0 and a probability of being 1.
efficiently solve crucial problems that are not currently feasible
Quantum computers use a collection of qubits in superpositions
on conventional computers. Silicon is playing an increasingly
to efficiently solve calculations, by amplifying signals towards
large role in the development of quantum computing, and
the right answer and cancelling out the wrong answer. This
this article will explore how silicon-based technology has the
allows quantum computers to find a solution to certain
potential to dominate quantum computing, which could lead to
calculations in fewer steps than a conventional computer. These
astounding improvements in areas of science and technology.
qubits can also be entangled, meaning any operation on one has an immediate effect on the other qubit, and the qubits behave as a system. It is this immediate effect which makes quantum algorithms more powerful than classic ones. Some common examples of qubits include: • The spin of an electron which can be taken as spin up or spin down. • The polarisation of a photon which can be taken as vertical polarisation or horizontal polarisation. • The orientation of an individual atom, when levitated inside an electromagnetic field. Silicon spin qubits
Figure 1 A qubit exists as a combination of 0 and 1
Recently, researchers have developed a new type of a qubit called a silicon spin qubit, or silicon qubit. A silicon qubit
30
Silicon: A Semiconductor With The Potential To Transform The Field Of Quantum Computing
consists of a spin qubit, which stores its information in the spin
it is possible to connect qubits which are not directly adjacent to
momentum of an electron, trapped inside silicon chambers.
each other (up to a centimetre apart). Having wider separations
Silicon chambers are also known as quantum dots.
between individual qubits makes it easier to fit the circuitry
An experiment conducted by researchers at Princeton University
required to programme the qubits on the circuit board.
involved applying a magnetic field to a silicon qubit and
2. A silicon spin qubit is approximately one million times smaller
demonstrating that energy could be transferred from the spin
than a superconducting qubit used in traditional quantum
of an electron (which was held inside a silicon chamber) to a
computers. This means that more qubits can be packed onto an
photon, a particle of light. For this to occur, the electron needed
individual silicon chip.
to be isolated and its spin (or angular momentum) needed to
3. Silicon qubits can operate at slightly higher temperatures
stay constant. This is where silicon is essential. In a quantum
than superconducting qubits, meaning less cooling equipment
system such as a silicon qubit, there is a fixed time known as
is required allowing more qubits to be packed onto a silicon
the coherence time for which the state of that quantum system
quantum chip.
will be retained if the system is left still. In the case of a silicon qubit, the coherence time is the time for which the spin of an electron remains constant. Due to the unique capacity of silicon to be able to house the spin of an electron, or keep the spin of an electron constant, for a long period of time, silicon qubits have a long coherence time and were able to isolate the electron for long enough to interact with a photon in the experiment.
To summarise the above points, the wider separations between individual silicon qubits, coupled with the extremely small size and operating temperature of these qubits, allows the potential to scale up silicon quantum chips faster than regular superconducting quantum computers which have scaling issues due to the relatively large size of superconducting qubits.
Figure 2 In the experiment conducted by Princeton University, an electron (pink circle) interacts with a photon (pink waves)
In quantum computing, the primary challenge across all types of quantum computer is scaling up (adding more qubits) the quantum computer. This experiment demonstrates that it will be easier to scale up silicon quantum chips faster than regular superconducting quantum computers for three reasons: 1. The experiment shows that that it is possible for quantum
Jason Petta, a professor of physics at Princeton University affirmed the positive implications of this experiment for the future of quantum computing, and said that “This work expands our efforts in a whole new direction, because it takes you out of living in a two-dimensional landscape, where you can only do nearest-neighbour coupling, and into a world of all-to-all connectivity�.
information to be transferred via light to other qubits, meaning
Silicon: A Semiconductor With The Potential To Transform The Field Of Quantum Computing
31
Figure 3 Quantum volume
Lower error-rate of silicon qubits
with the environment. This minimises the error rate of the
This experiment also solves another problem. To increase the
silicon qubit, improving the power of silicon-based quantum
computational power of a quantum qubit, two improvements
computers. If this error rate remains constant, when silicon
are required:
quantum computers are scaled up in the future and contain
• Qubit count - the more qubits, the increased power of a
more qubits, as shown by Figure 3, their power will increase.
quantum computer. • Error rate - how well qubits interact with each other. Excessive
Despite showing positive signs, silicon-based quantum
noise and heat can cause qubits to decohere or lose their quantum
computing is at the beginning of its development; the first silicon
nature. This could flip 0s and 1s, or wipe out the superposition of a
quantum computer only contains two qubits. However, CQC2T
qubit, which would increase the error rate of a qubit.
(the Centre for Quantum Computation and Communicative
Quantum volume measures the power of a quantum computer by measuring the relationship between the number of qubits and the error rate of qubits. As Figure 3 shows, if the error rate is high, adding qubits does not increase the computational power of a quantum system. It is therefore vital that the qubits have low error rates. In the experiment, the electrons interacted with photons, which are light particles. These photons have a minimal effect on the position and state of the electron since they interact very little
32
A positive future for silicon-based technology
Technology) intend to build a 10-qubit prototype quantum computer using silicon by 2022. The advantages of silicon-based quantum computing in terms of scaling up and reducing errorrate are massive. It is therefore no surprise that silicon-based quantum computing is being heavily invested in, and, given that companies such as Intel are already specialising in silicon-based technology in the form of silicon integrated circuits, it seems likely that the element silicon will be key in the development of quantum computing.
Silicon: A Semiconductor with the Potential to Transform the Field of Quantum Computing
The Role Of Aerodynamics In The Design Of F1 Cars By Vivek Shah L6J1
T
he Ancient Greeks originally thought the 4 elements to be earth, air, water and fire. It is the element of air which plays an essential role in F1, through the concept of aerodynamics. Aerodynamics, a variant of fluid dynamics, can be described as the study of the motion of air flow, in this case, around a Formula 1 car. Formula 1 is the highest-tier of open seat racing and its Grand Prix cars are known to be the fastest and most complex circuit racing vehicles. The regulations set by the FIA result in cars that are incredibly low weight with high power, and the result is a car which tends to lack grip. This is where the importance of aerodynamics comes into action, the forces, downforce in particular, generated by various parts of an F1 car allow for greater stability and control of the car, which consequently enables a braking force of up to 5g, increasing the cornering speed of the car.
over its lower surface whereas an aircraft wing is designed so that air flows more rapidly over the upper surface [Fig. 1]. A simplified explanation of the fluid dynamics behind this can be explained by Bernoulli’s Principle, which states that the flow over the lower surface would create an increase in pressure on the top surface compared to the bottom and this resulting pressure difference creates a downward force.
When it comes to designing the best package, Formula 1 teams have two main objectives on the aerodynamic front: maximise downforce and minimise drag. Downforce is the vertical force directed downward, produced by airflow around an object. The generation of downforce is split into 3 different categories; the front wing, rear wing and the chassis. The principle of downforce can be compared to the principle of lift in aircraft, an F1 wing is designed so that air flows more rapidly
Figure 1 Pressure Flow Over a Wing.
The Role Of Aerodynamics In The Design Of F1 Cars
33
The downforce created by a given component can be expressed by: D= WHFρv2 Where: D = Downforce (N) W = Wingspan (m) H = Chord Length (m) F = Lift Coefficient (FC) ρ = Density of Air (kgm-3) ν = Velocity (m2) Figure 3 The Influence of Components of an F1 Car on Downforce
Figure 2 Chord Length
Drag is defined as the force acting opposite to the relative motion of any object with respect to the surrounding fluid (in this case, air). The minimisation of drag is vital as it allows an F1 car to reach higher speeds both quicker and more easily, as well as improving the efficiency of the car due to a lower resistant force. Furthermore, it reduces the wall of clean air that the car disturbs as it moves forward, this in turn will reduce the dirty wake flow. Skin friction is a type of drag between molecules of the air and the solid surface of the car. By smoothing out the surface as much as possible, the surface area of the car can be decreased and therefore, the skin friction can be reduced which can help to decrease the overall drag of the F1 car.
Arguably the most important aerodynamic component of an F1 car is the front wing this is because it is the only part which is exposed to clean, undisturbed air. It influences how the air flows over the rest of the car as well as into the sidepods and diffuser. The cascading winglets seen in the image below are responsible for generating downforce as well as directing air to the endplates which ensures that it passes around the tyres, this helps to reduce the drag caused by the tyres as well as improve the efficiency of the flow to the sidepods and bargeboards. The downforce generated by the front wing is enhanced by the presence of the ground effect underneath the wing. Located right behind the front wheels, the barge board is used to smooth out and redirect the disrupted airflow from the front wing and tyres. The distribution is split into two parts; the first sees the air directed into the sidepods to help with engine cooling and the second diverts the air around the outside of the car to reduce drag. Vortices, which are rotating fluids that create a lowpressure zone at the centre, are created around the edges of the bargeboards. This can help to seal the low-pressure system underneath the car.
The amount of drag that is created by an F1 car is given through: FD= CD ρv2 A Where: FD = Drag Force (N) CD = Drag Coefficient ρ = Density of air (kgm-3) ν = Velocity (m/s) A = Reference Area (m2) There are 4 main aerodynamic efficiency enhancing components; the front wing, rear wing, diffuser and barge boards.
Figure 4 Barge Boards Indicated by the Arrows
34
The Role Of Aerodynamics In The Design Of F1 Cars
The rear wing can be responsible for roughly 30% of the overall downforce produced, but as the air flow is disturbed even more by the shape of the wing, it can cause a large amount of drag force. It consists of 2 aerofoils which help push the air up, and due to Newton’s Third Law, the equal and opposite reaction is to push the car into the ground, generating large amounts of downforce. Since 2008, the rear wings have had an adjustable aerofoil, the Drag Reduction System (DRS). It was designed to allow closer slipstreaming from cars behind as the air will be able to flow straight through, reducing the drag caused by the rear wing. It allows drivers to get closer and promotes closer racing and more overtaking on straights. F1 teams will vary the size of the rear wing fitted to the car based on the track and its features, tracks which require less braking and more speed will have a smaller wing to decrease drag, whereas others have more corners and need more downforce, so a larger wing is fitted. The diffuser is a part of the floor of an F1 car, it sits on the
underside. It consists of many tunnels and splitters behind the rear axle which controls air flow. Diffusers are responsible for an aerodynamic effect called the ground effect which is based on Bernoulli’s Principle which states that as the speed of a fluid increases, its pressure decreases, an inverse relationship. As the air is travelling underneath the floor whilst the car is moving forward at speed, the pressure of this air decreases due to the increase in speed, this leads to a suction effect which helps to pull the car to the ground, therefore increasing the downforce generated. The high angle of attack combined with the splitters carefully control the airflow to help maximise this suction effect. The optimisation of downforce and drag are both key to the design of the aerodynamic components of an F1 car, and when designed correctly, they can increase lap times by multiple tenths of a second, providing the vital edge to a team over its competitors. Aerodynamics are therefore commonly seen as the “make or break” of a pole position lap as well as a race win, hence why arguably, it is the most important aspect of an F1 car.
Figure 5 The Closed Rear Wing of an Aston Martin Red Bull Figure 7 The Underside of an F1 Car, Showing the Splitters (On the LeftHand Side of the Photo)
Figure 6 The DRS Mechanism.
The Role Of Aerodynamics In The Design Of F1 Cars
35
The Elements Of The Elements Shrey Shah L6J1
W
hen first learning about the composition of everything
Elementary Fermions
around us, you are taught that atoms are the building
Elementary fermions are divided into two sets of six flavours
blocks of the universe. You are taught that an atom
(types) each. The first set, quarks, is composed of the up, down,
cannot be divided, that an atom is fundamental. In fact, the word
charm, strange, top and bottom flavours. The up and down
atom itself comes from the Greek atomos, meaning indivisible
quarks have the lowest masses and the highest stability so the
[1]. However, this is not true. You begin to learn that atoms
other four quarks decay into them quickly; therefore, the up
are formed from subatomic particles: protons, neutrons and
and down quarks are the most common in the universe. Quarks
electrons. Surely these must be the smallest things. Alas, not.
can interact via both the strong and the weak interactions. The
Protons and neutrons are merely composite subatomic particles
second set, leptons, is comprised of electrons, muons, tauons
which are comprised of different elementary subatomic
and their respective neutrinos. The electron, muon and tauon are
particles. These elementary particles are the true elements of
very similar but have different rest masses (the electron is the
the elements.
lightest and the tauon is the most massive). Their accompanying
The elementary, or fundamental, particles are thought to have
neutrinos follow the same trend in rest masses but are neutral.
no sub-structure, i.e. they are not made up of anything else; they
The leptons only interact via the weak interaction. These twelve
are truly atomos. They can be categorised, based on their spin,
fermions also have antiparticle counterparts, shown in Figure 1,
into elementary fermions (half-integer spin) and elementary
which have the same rest masses as their particles but quantum
bosons (integer-spin). Spin is an intrinsic form of angular
numbers such as charge are reversed.
momentum of a particle, relating to quantum mechanics [2].
36
The Elements Of The Elements
Figure 1 Standard Model of elementary particles and antiparticles
Elementary Bosons and Fundamental Interactions Elementary bosons, on the other hand, are the exchange particles which mediate the interactions between the fermions. Figure 1 also shows the six main elementary bosons: gluons, W bosons, the Z boson, the photon, the Higgs boson and the theorised graviton [3]. All the known forces of nature can be traced to four fundamental interactions (also called fundamental forces) that govern how objects or particles interact, and how some particles decay. The first of these is the weak interaction, which is capable of changing quark flavour. The name suggests that it is a feeble force; however, without it, life would not exist as the Sun would not be able to shine. The weak interaction is what stabilises the products of nuclear fusion (e.g. the helium atoms produced during hydrogen fusion in the Sun). Without this force, fusion could not occur and the nuclear
Figure 2 Nuclear Fusion in the Sun could not occur without the weak interaction
energy stored in the Sun would not be released as thermal
stay together if they repel each other? The answer lies with
and light energy, which allow for life to thrive on Earth [4].
the strong nuclear force, which, within the femtometre range
The weak interaction is mediated by the Z boson and W
[5], is 137 times stronger than the electromagnetic force, and
bosons (W+ and W- Bosons). The weak interaction is evident
can overcome the electrostatic repulsion. In the Periodic
in the processes of beta decay and electron capture. These
Table, elements up to calcium are stable with roughly an
processes are vital for allowing many elements to form
equal number of protons and neutrons. However, larger
stable structures, by letting the nucleus to decay until it
elements contain many more neutrons than protons in order
reaches the optimal proton/neutron ratio – without it, many
to have a stable nucleus, such as uranium-238 containing 92
of the elements that are used daily would be unstable and
protons and 146 neutrons. This is because the large number
radioactive [5].
of protons causes the electrostatic force of repulsion to
Have you ever wondered how positive protons in a nucleus
become much greater, and so only by adding more neutrons The Elements Of The Elements
37
can the strong force also increase and overcome the
second – without them, life could not survive [9].
repulsion. The gluon is the exchange particle of the strong
The last of the fundamental forces is the most well-known:
nuclear force, and it confines the quarks into their particles
the force of gravity. Currently, gravity is best described by
(such as a proton or neutron) and binds the protons and
Einstein’s General Theory of Relativity. Einstein postulates
neutrons to create the nucleus of atoms. Thus, without the
gravity as a consequence of the curvature of space-time
strong nuclear force, the nucleus of atoms would simply not
caused by the uneven distribution of mass. This explanation
exist and different elements could not form [6].
is generally approximated for objects with small masses (the
The third fundamental interaction is the essence of modern
weak-field limit) by Newton’s Law of Universal Gravitation [10],
life. The electromagnetic force has allowed mankind to
which describes gravity as a force which causes any two bodies
Figure 3 The electromagnetic spectrum
become technologically advanced. Without the flow of electric
to be attracted to each other with the force between them given
charge, anything with an electric circuit would not exist. No
by the equation in Figure 4. However, gravity currently cannot be
lights. No television. No phones. The exchange particle for
explained by the Standard Model. It is theorised that there is an
the electromagnetic force is the (virtual) photon. A photon
exchange particle called the graviton which is responsible for this
is a discrete wave packet of electromagnetic energy, which
force. The graviton is thought to be massless due to the range of
travels at the speed of light in a vacuum [7]. Without the
the gravitational force and due to the fact that it propagates at
electromagnetic force, the electromagnetic spectrum could
the speed of light [11]. The Theory of Gravitons states that the
not exist. Without the spectrum, there would be no visible
graviton can only exist if the force of gravity is quantised like the
light [5]. The electromagnetic interaction is also the root
other three fundamental forces. This means that gravity would
of all chemical reactions. Without the electrostatic force of
be described in accordance with the principles of quantum
attraction, there would be nothing keeping electrons in their
mechanics as opposed to classical physics, which Einstein’s
orbitals around the nucleus. Covalent bonds could not form
Theory of General Relativity does. [12]
as they occur due to the electrostatic attraction between the bonding pair of electrons and the common nuclei. Ionic bonds could not form as there would be no positive or negative ions in the first place. Metallic bonds would not exist as the delocalised electrons would not attract the metal ions. These bonds are central to chemistry. Reactions occur by breaking bonds and forming new ones; however, if there were no bonds to break and it was impossible to form new bonds, reactions would not occur [8]. There are roughly 1 X 1021 chemical reactions occurring in the human body every
38
The Elements Of The Elements
Gravitational Force, F F=
-Gm1m2 r2
F = gravitational force / N G = gravitational constant, 6.67 x 10-11 / Nm2kg2 m1 = mass of 2nd object / kg m2 = mass of 1st object r = distance between the two objects, m Figure 4 Newton’s Law of Universal Gravity
Figure 5 Example baryon and antibaryon compositions
Figure 6 Example meson compositions
The Higgs Boson is the last elementary boson and is associated
of such ‘anti-elements’ is mind-boggling. Is an ‘Anti-Periodic
with all the fundamental particles and forces. It is a result of the
Table’ possible? Could ‘anti-hydrogens’ and ‘anti-oxygen’
Higgs mechanism, which is responsible for all particles such as
combine to form ‘anti-water’? Unfortunately, the probability
the quarks and other fundamental bosons to acquire mass. The
of producing man-made, heavier ‘anti-atoms’ is very low, and
Higgs boson is heavily connected with the weak interaction as it
it is thought that forming even anti-lithium will be extremely
provides an explanation for the statistical improbabilities linked
unlikely [15], due to the extremely low frequency of collisions
with the W boson having a non-zero rest mass [13].
between the necessary particles to produce the ‘anti-atoms’.
Composite Fermions
But the larger question is why ‘anti-elements’ are not
Without the four fundamental interactions, the elementary particles would not be able to form composite subatomic particles, which in turn could not create the elements we know today. Composite fermions are groups of elementary fermions, bound by gluons. The type and number of quarks which form the compound particle dictate its properties. Hadrons are strongly-interacting particles and can be subcategorised into baryons and mesons. Baryons are made up of three quarks (antibaryons contain three antiquarks) whilst mesons contain one quark and one antiquark, as shown in Figures 5 and 6. The most basic atom, the hydrogen atom, is composed of a proton as the nucleus with a single electron in orbit. Thus, in terms of elementary particles, it is made of two up quarks, one down quark and one electron. What if you swap these particles with their antimatter counterparts? A positron orbiting an antiproton nucleus. The idea of this ‘antihydrogen’ seems fictitious. However, scientists from Swansea University, working as part of the ALPHA collaboration at CERN, published a paper in 2018 detailing how they had accumulated the ‘anti-atoms’ [14]. The thought
common in the universe. Theoretically, the Big Bang should have produced an equal amount of matter and antimatter. This in turn would mean that upon collision, matter and antimatter would annihilate. If there was an equal balance, there would be no matter in the universe, but only energy. However, around one particle per billion of matter survived and this makes up the universe today. Recent experiments have shown that the laws of nature do not apply equally to matter and antimatter, but the reasons remain yet unknown. It is thought that there was some unknown mechanism that could have interfered with the decay of oscillating particles, which should have decayed equally into matter and antimatter, causing the probability to shift towards an increase in the decay resulting in matter. [16] This mysterious mechanism is the reason as to why matter is in the majority and why the elements today could form. All of the 118 elements of the Periodic Table and their variety of isotopes can be broken down into their fundamental subatomic compositions just like the hydrogen atom. These elementary particles are the underlying units of the universe. They are the basic building blocks created by the Big Bang. They are the elements of the elements. The Elements Of The Elements
39
The Elements And Composites That Conquered The Far Side Of The Moon By TT Zhang 11S1
A
40
t 02:26 GMT in the morning of 3 January 2019, the first
the high quality of materials that have been used on the rover.
ever rover completed a soft landing onto the far side of
Space environment is incredibly harsh; the lunar rover will likely
the Moon, symbolising the beginning of a new era of
experience complex and unknown topography on the far side
space exploration. The rover was not made by NASA. Neither was
of the Moon. The exacting test of the environment, such as the
it made by Roscosmos. No, this significant feat was achieved by
diurnal temperature difference of over 300 °C, can easily cause
China’s Chang’e 4 space mission.
the components to undergo thermal deformation. Furthermore,
Landing on the far side of the Moon was never going to be
the lunar rover must withstand various collisions, extrusion,
simple business because of tidal locking; the Moon does not
friction, abrasion and so on. The process of landing on the
self-rotate like Earth – the side that faces us is always the side
far side of the Moon can be very tortuous, and even a slight
that faces us. This makes the mission of landing on the far side
miscalculation could initiate a domino effect possibly leading to
of the Moon almost impossible since the entire landing process
a failed landing. In fact, it is the walking pawl mechanism, which
must be controlled semi-remotely via a relay satellite. The lack
is the primary component in contact with the lunar surface, that
of communication with the rover meant that the past attempt by
poses a crucial problem. Solving this is perhaps the key for the
the USA’s Ranger 4 failed, with the rover crashing onto the lunar
lunar rover to land successfully on the Moon [2].
surface too quickly [1].
The National Key Laboratory of the Institute of Composite
How could have China achieved something that even the space
Materials at Shanghai Jiao Tong University has had a significant
giant, USA, failed to achieve? This can largely be credited to
influence on materials science research in China. It was co-
The Elements And Composites That Conquered The Far Side Of The Moon
Figure 1 Schematic of the Chang’e-4 communications
founded by my grandfather [3] who dedicated his career to the
were possible to fit particles of SiC into the aluminium structure,
establishment of this lab and to the research of silicon carbide
that would be the perfect material for making spacecrafts. Alas,
particle reinforced aluminium-matrix composite material.
success never comes so easily. Finding the perfect balance
Although he is now retired, the project that he led remains one
between the two components is undoubtedly difficult; the
of the most important achievements in the field of material
uncountable impurities in the structure can really frustrate the
science in China.
researchers and the SiC particles easily tangle up with each
The strong physical properties of silicon carbine (SiC) allow it
other. But after 20 years of theoretical and experimental work,
to be used in applications requiring strong physical and heat
a successful product was finally produced. The new SiC particle
endurance. SiC does not melt; like carbon dioxide, it does not
reinforced aluminium-matrix composite has all the desirable
have a liquid state, and instead sublimes at 2700 °C [4]. However,
characteristics: it is light weight, rigid, dimensionally stable, can
the disadvantage is that SiC is very brittle, and it could possibly
withstand high resistance, etc.
snap when in contact with the rough lunar terrain.
In conclusion, due to breakthroughs in the fields of materials
The second and perhaps most important part of the composite
science and growing knowledge of how different elements can
is aluminium. Aluminium is a relatively soft material; it is easily
be combined, scientists have been able to overcome one of
malleable and has a low melting point of 660 °C. It is also
the harshest topographies ever known to us, the far side of the
easily oxidised to aluminium oxide. It seems that neither of the
Moon. One could say that these developments were “one small
materials can be used in isolation of the lunar rover. But if it
step for a man, one giant leap for mankind”.
Figure 2 Chang’e-4 lunar lander
The Elements And Composites That Conquered The Far Side Of The Moon
41
How Everything Is Stardust By Thilan Kandeepan 11S1
T
he science vs. religion debate is an ongoing discussion;
The elements we are made from are essentially the remnants
however, something which we can all agree on is that
of stars, apart from hydrogen and helium. These two lightest of
99% of the human body consists of six main elements:
elements were the beginning of everything after the Big Bang
oxygen, hydrogen, calcium, carbon, nitrogen and phosphorus.
with hydrogen now accounting for around 75% of the mass in
As well as the philosophical arguments for the existence
the observable universe and helium being roughly 24%. The
of God, there is also a scientific cause for the creation of
products of the Big Bang, including gases and cosmic dust,
humans. Our very existence is linked to the Big Bang, as
soon cooled down to form stars. Our own galaxy, the Milky Way
well as stardust, which was the subject of a major scientific
is made up of at least 100m billion stars, so you can imagine the
breakthrough in 2016.
abundance of these resources in our space.
“ The nitrogen in our DNA, the calcium in our teeth, the iron in our blood, the carbon in our apple pies were made in the interiors of collapsing stars. We are made of star stuff.�
out proton-proton fusion in their core under extremely high
Carl Sagan
other atoms to create heavier elements which now compose
Why is this relevant to our creation? Fundamentally, stars carry pressures and temperatures. Here, two protons bind together to form a diproton which decays to deuterium. The deuterium then fuses with another proton to form a light isotope of helium. As this is not a terminating process, the helium atoms bind with our modern periodic table. In fact, it is the younger stars like our Sun that create helium atoms due to the abundance of hydrogen. Once a star begins to lack hydrogen, elements such as beryllium and carbon are created, and as they too are compressed in the core, elements from iron to oxygen are produced. The broad term for this process is nucleosynthesis as new nuclei are formed from to pre-existing nuclei. So now that we have a foundation and an understanding of how these elements are created, how are they dissipated all over our galaxy? The death of the star, also known as a supernova event, is the largest explosion that a star experiences at the end of its life. During this process, it ejects most of its mass, essentially scattering around 40 000 tonnes of cosmic dust out into space, Figure 1 Formation of a deuterium nucleus
42
How Everything Is Stardust
and towards our Earth.
However, scientists believe that distinct types of supernovae spread different elements across our galaxy. For instance, stars having a mass about eight times greater than our Sun experience a core-collapse supernova. This leads to elements such as oxygen and silicon to be distributed in excess. Another example of this would be white dwarfs, which dissipate vast quantities of nickel and iron. Analysing images from the Japanese satellite, Suzaku, has revealed that the ratios of these elements are consistent with the composition of stars, including the Sun. It was clear from study that the dispersal of the chemical elements of our universe is well mixed. Another finding of this study was that these ratios that determine the elemental composition of a galaxy apply generally, and thus to our solar system too. As of 1 February 2019, there are 49 potentially habitable exoplanets that have been discovered. Our Earth is likely not the only planet in the universe with life; extra-terrestrial life is bound to exist somewhere out there. So, the question is how can we relate to them? Well, at least we have one thing in common – we are all made of stardust. Figure 2 Data collected by the Suzaku satellite
How Everything Is Stardust
43
Medical Research Work Experience Report By Raunak Khanduja L6R2 Name of Organisation: St. Thomas’ Hospital (affiliated with Kings’ College, London)
heart cells (in our case). The antibodies then have a secondary antibody which sticks onto it, which can then be seen under a microscope. In this way, we can analyse the amount of protein/ distribution of different proteins around the heart.
O
n the first day at St Thomas’ Hospital [Fig. 1], myself and four other students met our supervisors for the week, Dr Heads and Dr Clark, who briefed us on the week
ahead as well as giving us a detailed timetable for the week. The
a solution containing the antibodies on the six heart samples (all of which came from mice). I found learning about this new concept extremely fascinating as it was an area of science in
first session on the timetable was a health and safety induction
which I had never delved into previously.
which lasted a long hour and a half. Following this, we received
The next day, we started by carrying out some cell culture which
a lecture from Dr Heads himself. As a senior lecturer in Kings’
was shortly followed by an ultrasound of a mouse. This was
College London, listening to him speaking was such a wonderful
a truly remarkable experience and we were frankly very lucky
opportunity. I learnt huge amounts about the cardiovascular
to witness the ultrasound. In the UK, there are only 5 of this
system and it was a great way to start the week. Following the
type of ultrasound machine and through this experience, my
lecture, we started work on immunohistochemistry. Prior to this,
knowledge of anatomy and physiology grew tremendously. We
I didn’t know what this word meant nor what it entailed.
were also taught how the Doppler Effect (something we touched
Immunohistochemistry is a lab test which uses specific
on in GCSE Physics) is used to make images on the ultrasound.
antibodies which stick onto the antigens of certain proteins on
During lunch on Tuesday, I got the chance to have a good
Figure 1 St Thomas’ Hospital
44
On the first day, we helped to carry out this lab test by squirting
Medical Research Work Experience Report
Figure 2 Nuclear Magnetic Resonance (NMR) Machine
conversation with Dr Clark about his job as well as some of
kind and I was excited for the day ahead. I remember watching
the material we had covered over the past two days. Having
Dr Clark expertly cutting open the mouse and showing us the
replied to some of our enquiries about the heart, he made us
organs surrounding the heart as well as the heart itself. I found
realise that there were many misconceptions at GCSE about the
looking at the mouse’s organ somewhat a surreal experience
cardiovascular system (and biology in general).
and it certainly sent a chill down my spine. The purpose of this
Following lunch, we saw the results of the immunohistochemistry
surgery was to give the beating heart a myocardial infarction (a
we had done the previous day. We saw the 6 heart samples
heart attack). This was done by tying up one side of the heart
under a microscope and it was amazing to see the different
with a suture and in doing so, cutting off its blood supply. This
types of proteins in certain areas of the heart. Having seen
would mean that unfortunately, the mouse died during surgery
the distribution of proteins in the heart, we were taught what
whilst under anaesthetics. This was very moving and I left the
implications this had on the heart itself e.g. an excess of collagen
surgery room with a sense of sorrow. However, I understood
implies that the heart may be stressed/ wouldn’t be able to beat
that without these surgeries, many hospitals wouldn’t be able
freely (from this, we can deduce that this particular heart has
to do as much (cardiovascular) research as they have and it
probably come from a fairly old mouse).
would hinder the amount of research they can do in the future.
On Wednesday, we carried out an interesting procedure called gel electrophoresis. This method is used to separate mixtures of proteins according to molecular size (the proteins coming again from the heart of a mouse). Therefore, we started this procedure by homogenising the heart in a buffer i.e. cutting it up using scissors as well as crushing it in a pestle and mortar tube (which brings out the different types of proteins). After doing this, we
Before the surgery, we even discussed the ethics behind using animals for research and it helped us come to terms with the situation. Later that day, we also spent time looking at imaging, particularly the way NMR spectroscopy [Fig. 2] and MRI scans work. I found this experience truly great as it improved my knowledge of physics and somewhat tied into the concepts we learnt at GCSE.
made the gel which would separate out these different proteins.
Finally, on my last day at St. Thomas’ Hospital, I spent the
To polymerise the gel, the following reagents were used: Tris
majority of the day cutting open and slicing the hearts of
buffer, water, 30% acrylamide, TEMED and 10% ammonium
some mice (known as cryosectioning). These small sections
p-sulphate (the catalyst). Having obtained the mixture of proteins
of heart which are 26 micrometres thick are required for other
and having made the gel, we put the mixture at the top of the
experimental procedures e.g. immunohistochemistry.
gel and passed a 90V downwards charge from the top of the gel.
Overall, I found this experience truly amazing, mostly down to
Then, we waited for the proteins to slowly move down the gel and
the wonderful teaching of both Dr Heads and Dr Clark. Both
separate themselves out (as they stop at different levels).
these scientists taught me concepts which I had never known
Thursday was a certainly a day to remember and one that I will
before and more importantly, showed me how exciting research
cherish forever. This was the day where we witnessed mouse
is as a career. This experience was also a true privilege as we
surgery! Prior to this experience, I had never seen surgery of any
studied material that most post graduate students would.
Medical Research Work Experience Report
45
Particle Physics Research Work Experience Report By Mikeet Patel L6H2 Name of Organisation: Rutherford Appleton Laboratory
then travel through neutron guides to various instruments, where the neutrons are used in neutron-scattering experiments. Neutron-scattering experiments use neutrons to learn about the
L
ast summer, I undertook one week of work experience at the Rutherford Appleton Laboratory (RAL) in Didcot, near Oxford. The RAL performs ground-breaking research in a
wide range of areas including particle physics, astronomy and biomedicine. Their research has impacted numerous fields, such as the environment, health, energy, technology and culture. Operated by the Science and Technology Facilities Council (STFC), the RAL employs 1,200 staff. The Harwell Campus, where the RAL is located, houses many scientific facilities; each facility is responsible for a different field of research, meaning jobs at the RAL range across different departments, from the Central Laser Facility, to the ISIS neutron and muon source, to RAL Space and Scientific Computing. During my placement I worked in the ISIS department. ISIS produced neutrons and muons, which are used in different scientific experiments to investigate materials. To produce neutrons, the ISIS synchrotron accelerator gives protons large amounts of kinetic energy. These high-energy protons are then fired at a target (ISIS contains 2 target stations), in what is known as the spallation process and releases neutrons. The neutrons
position and movement of atoms within a structure. Studying this enables scientists to learn about the various properties of materials, contributing to the pioneering research by the RAL. My main task throughout the week was to design the most efficient neutron guide, through which the neutrons would travel in neutron-scattering experiments. To do this, I had to use computer simulations to model different scenarios in order to optimise the number of neutrons reaching the sample (the material being analysed) from the neutron source (at the target). I also had to ensure that the neutrons that reached the sample were distributed in a homogeneous (uniform) way. For these requirements to be fulfilled, I had to run numerous simulations of neutron-scattering experiments using the software program, McStas. After each experiment, I analysed the graphs (showing the results) for uniformity of neutron distribution and number of neutrons. I then had to repeat the experiment adjusting numerous parameters on the C-code that simulated the experiment, such as the width, height and length of the neutron guide. One parameter new to me was the ‘m value’, referring to the angle at which the neutrons deflect. Running many simulations meant changing
Figure 1 An annotated diagram of my code for the elliptic neutron guide from the report
46
Particle Physics Research Work Experience Report
Reflecting upon my work experience, I found the work extremely fascinating because it was largely focused on computing and using coding for optimisation. I enjoy computing in my free time, so I therefore thoroughly enjoyed the work. The work was also very useful because I was able to learn the importance of computing in scientific research. Moreover, I enjoyed the additional activities, for example, I was given a tour of the ISIS particle accelerator, and talks about particle physics and the link between astronomy and art. I found the talk on astronomy and art particularly fascinating as it drew an unlikely link between the two fields, and was given in a very engaging way. The only aspect of the task which I found slightly less enjoyable was the monotonous nature of the work. However, repetitive work is common in many fields of work and I managed to cope with it well because I enjoy computing a lot. During my work experience, I did encounter a few problems, and learning how to deal with them was pivotal for improving my problem solving skills. Because I was working with code a lot, there were many circumstances where the code did not compile. In these circumstances, I had to rigorously check the code for the errors. With the help of my supervisor, I managed to trace down Figure 2 An annotated diagram of my code for the elliptic neutron guide from the report
the errors that I had made. By the end of the week, I feel that I had
several parameters many times. However, I was required to
making errors, I was able to resolve them more independently.
not only observe the effect of changing parameters, but also to
I have developed many skills from my work experience at RAL that
understand why this effect was produced, for example why the
will be of enormous benefit to me in whichever career I pursue.
first 3 neutron guides had to have the same dimensions, but the
For example, I believe that I have improved my skills in problem
4th required a higher m value. To understand why a certain effect
solving through having to recognise problems in my code and
was produced, I often drew diagrams of the neutron guides as I
then taking the appropriate steps to solve them. I have also learnt
adjusted it.
to work with others, since some of my work involved working
I experimented with not only linear (straight-edge) neutron
with a partner. This enabled me to learn from others and listen to
guides, but also elliptic neutron guides. This meant I had to work
their ideas. I asked my supervisor for feedback on my last day at
with a new component on the code, and alter the code for the
RAL, and he said I should work on my self-confidence. I have had
linear neutron guide to ensure it fits with the new component.
to present my research to my supervisor on numerous occasions,
Moreover, using elliptic neutron guides meant I had to alter much
and he advised me to present with more self-assurance. This is
more parameters; these parameters would change the shape of
a very valuable piece of advice that I will work on and which will
the ellipse. Because the work that I was doing contained a lot
benefit me when I start working after university.
of new, challenging material, I spend a lot of time researching
My work experience helped me largely with my future career
different scientific concepts, for example, reading scientific
choice since before this work experience, I did not think that
papers and online articles about elliptic neutron guides, and
scientific research would be the right career for me, despite
the reasons for using them. At the end of my work experience,
enjoying studying science at school. However, this work
I put together a six-page report, consisting of the data from the
experience has proved to me that a job in science can be
experiments I carried out (annotated diagrams of my code and
challenging and rewarding, two aspects of a job which appeal to
graphs), analysis from these experiments and the individual
me greatly.
learnt a lot from the mistakes I had made, and although I was still
research I did [Fig. 2].
Particle Physics Research Work Experience Report
47
The 2018 Nobel Laureates The Nobel Prize in Physics 2018 The Nobel Prize in Physics 2018 was awarded “for groundbreaking inventions in the field of laser physics” with one half to Arthur Ashkin “for the optical tweezers and their application to biological systems”, the other half jointly to Gérard Mourou and Donna Strickland “for their method of generating high-intensity,
The inventions being honoured this year have revolutionised laser physics. Extremely small objects and incredibly rapid processes are now being seen in a new light. Advanced precision instruments are opening up unexplored areas of research and a multitude of industrial and medical applications.
ultra-short optical pulses.”
Figure 1 Physics Nobel Laureates: Ashkin (Left), Mourou (Centre), Strickland (Right)
The Nobel Prize in Chemistry 2018
The 2018 Nobel Laureates in Chemistry have taken control
The Nobel Prize in Chemistry 2018 was divided, one half awarded to Frances H. Arnold “for the directed evolution of enzymes”, the other half jointly to George P. Smith and Sir Gregory P. Winter “for the phage display of peptides and antibodies.” The power of evolution is revealed through the diversity of life.
of evolution and used it for purposes that bring the greatest benefit to humankind. Enzymes produced through directed evolution are used to manufacture everything from biofuels to pharmaceuticals. Antibodies evolved using a method called phage display can combat autoimmune diseases and, in some cases, cure metastatic cancer.
Figure 2 Chemistry Nobel Laureates: Arnold (Left), Smith (Centre), Winter (Right)
48
The Nobel Laureates
“We have taken the first picture of a black hole,” said EHT project director Sheperd S. Doeleman of the Center for Astrophysics | Harvard & Smithsonian “This is an extraordinary scientific feat accomplished by a team of more than 200 researchers.”
The black hole in M87, which is located about 55 million light-years from Earth, is the first black hole whose mass has been calculated by three precise methods: measuring the motion of stars, the swirl of surrounding gases and now, thanks to the Event Horizon Telescope imaging project, the diameter of the black hole’s shadow.
Black Hole
49
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