RSR Spring 2014

Rutgers Vol 3 | Issue 2 | Spring 2014

Science Review

The Neuroscience of Effective Multitasking Azorubine’s Sensitivity to Changes in Viscosity Characterization of Microwave Plasma in Chemical Vapor Deposition

TABLE of

CONTENTS Features Letter to the Editor

05

The Neuroscience of Effective Multitasking

06

Interview with Dr. David Redlawsk

08

Aresty Abstracts

10

Research Papers

2 | Rutgers Science Review | Spring 2014

Azorubine’s Sensitivity to Changes in Viscosity

17

Something Old, Something New: Analysis of the Faunal Remains from the Middle Woodland Site of Pennella, Ocean County, NJ

22

Characterization of Microwave Plasma in Chemical Vapor Deposition

31

About

Letter from the Editor

The Rutgers Science Review (RSR) biannually publishes student-written scientific features, opinions, and research papers.

Dear Readers,

RSR is supported by RUSA Allocations. For more information, including submission guidelines, visit us at thersr.com Free copies can be found at the student centers and other various locations on campus.

Staff Co-Editors-in-Chief Alexandra DeMaio Stephanie Marcus

Features Editors Lauren Fish Christian Fernandez

Associate Editor

The 2013-2014 academic year has seen a lot of big changes for the RSR. We have recently expanded our writing and editing staff to include Rutgers graduate students as well as students of the newly integrated Rutgers Medical School (congratulations to everyone involved in the merger). We also established a new section dedicated specifically to Aresty Research Institute abstracts.

Thanks to the help and continued support of our visionary layout editor, Riasat Zaman, our journal will continue to undergo progressive thematic improvements. We would also like to thank RU WINS, the Douglass Project, and the Aresty Research Institute for their generous contributions. We have big dreams for the future of the RSR, and we invite YOU to participate not only as a reader, but also as a writer, photographer, editor - in whatever medium you feel best represents your talents! The RSR team always welcomes new members, and we’re happy to address any questions you may have about getting involved.

If you enjoy this edition, there are plenty more in our online archive at thersr.com. Best of luck with finals, and we wish you a wonderful summer break!

Sincerely, Stephanie Marcus and Alex DeMaio (Co-Editors-in-Chief)

Jessica Fellmeth

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Spring 2014 | Rutgers Science Review | 3

FEATURES

Letter to the Editor To the Editor,

I

write this letter to explain the political and economic forces behind the recent popularity of high fructose corn syrup (HFCS) in the media. HFCS is “the new trans-fat,” and its consumption has dipped for the first time in 40 years since it was integrated into the food industry. Many lay the rise in U.S. obesity rates at the feet of HFCS. Is this accurate? The trends are certainly compelling: in the late 1970s, domestic sugar prices were highly inflated, causing food producers to look for alternative sweeteners. As a corn byproduct, HFCS was especially low-priced and convenient to manufacture, and it quickly replaced cane sugar in soda, cereal, salad dressing, and many other processed foods. The rise in obesity levels also began to rise in the 1970s, making it appear correlated to this shift in the food industry.

Regardless, saying that HFCS is the sole cause of this trend is misleading.

Because obesity levels are on the rise in other countries where HFCS is not quite as ubiquitous, it is likely that other factors are at work. As a population, we lead more sedentary lifestyles, we consume more fats and sugars than our ancestors, and we eat more out more frequently.

The advent of canned soda, the progressively increasing convenience of food preparation, the popularity of chain restaurants with oversized portions (i.e. McDonald’s Supersize Me!), and basic genetics also have the capacity to influence our diet and health. At the government policy level, there have been many attempts in the past to pass a soda tax, a sugar tax, a HFCS tax, but none of them have ever gotten off the ground. Most recently, the Sugar Reform Act failed to pass in the House (206 to 221 against), and the number of sugar subsidies remained largely unchanged in the latest renewal of the Farm Bill in 2014. Clearly, the causes of obesity is a multifaceted issue. To combat this trend, our policies must start not with taxes - but with consumers, school administrators, food producers, and growers.

Many schools have banned soda from their vending machines and made their cafeteria lunches healthier. Farmers’ markets and joint community farms have been making vegetables and fruits more accessible as well. With the latest health fad against HFCS, it seems that consumer demand alone will accomplish what the anti-HFCS taxes attempted to do. For example, Yoplait recently switched from HFCS to refined sugar because of the tweets and Facebook messages the corporation has received from its customers. It is uncertain how effective these measures will be, but recently, the CDC reported that obesity rates in children between 2-5 years of age have declined. Only time will tell if this trend will continue, but this result is a hopeful sign that decades of health education and nutrition programs might finally be working.

For the first time in years, soda consumption has fallen as well, and beverage companies that saturated the market years ago are releasing “natural” and “retro” themed products in response. Pepsi Throwback and Mountain Dew Throwback (which echo nostalgia for the ‘70s) boast that they contain “real sugar,” not HFCS. The new products have been received positively; consumers report they have a “less chemical” taste. However, a can of regular Pepsi and a can of Pepsi Throwback both contain around 40 grams of sugar (12 fl oz), which exceeds the

American Medical Association’s recommendation of only 32 grams of sugar a day. Though many customers seem to prefer the Throwback because it contains the more “natural” sweetener, it should be kept in mind that sugar is still sugar, and should be consumed in moderation.

So both sugar-sweetened and HFCS-sweetened soda are bad for you.

But is one worse than the other? The debate continues. A controversial study from Princeton showed that rats with access to HFCS ended up with higher levels of fat accruel (a marker for obesity) and blood triglycerides (which can lead to heart problems) than rats with access to table sugar, even if their overall caloric intake was the same. It might indeed be that refined sugar is the lesser of two evils. However, I believe that the real impact of the Throwback is that it alters the current relationship between the sugar industry, HFCS manufacturers, and corporations like the Pepsi Bottling Company (PBG). High domestic prices of sugar are a large burden on soda and candy manufacturers, but because of HFCS, PBG was able to substitute for it in their sodas and maintain profits. Now that public opinion and consumer demand have turned away from HFCS, this may not be an option for much longer.

Right now, the Throwback is a niche product and seems to be going steadily out of stock in stores, despite immense popularity amongst those who’ve tried it. However Bevnet.com reports that in the summer the PBG will launch a new line of “real sugar” sodas to replace it, and soon after that, a low-calorie soda containing a new sweetener.

Two possibilities may result. Either domestic sugar will get the soda industry returned to them (and they’ll have even more funds for lobbying in later years to maintain their subsidies), or the real sugar sodas will be so popular (and the low calorie soda not) that Pepsi-Co will be galvanized to even more action for sugar reform.

Recall that the Bipartisan Sugar Reform Act failed by only a narrow margin, as many critics of our sugar policies claim that it’s an antiquated program has been negatively affecting the environment, food producers, and taxpayers for decades.

We might soon reach a tipping point that could finally end those billion dollar subsidies. In any case, give the Throwback sodas a try; that might be the flavor of the next decade! Refined sugar is certainly less questionable than HFCS, but, of course, avoid soda altogether is the best health option.

Sincerely, Lynn Ma

Spring 2014 | Rutgers Science Review | 5

The Neuroscience of Effective Multitasking HETALI MEHTA

Considering the fast-paced lifestyle of many individuals, multitasking is quickly becoming ubiquitous, although processing multiple streams of information intensifies the challenge for human cognition. While most individuals perform ineffective forms of multitasking, only effective multitasking can improve work flow and create adequate task completion. Ergo, this literature review examines the neuroscience behind multitasking and how it correlates with the specific qualifications that deem an individual an effective “supertasker”. When the brain tries to do two things at once, it divides and conquers, dedicating one-half of our gray matter to each task. Task management is thereby controlled by the prefrontal cortex. The anterior part of this brain region forms the goal and the posterior prefrontal cortex signals the rest of the brain to carry out the action. Only 2.5 percent of people have met the “supertasker” criteria. Thus, the examination of these supertaskers as well as ineffective multitaskers will elucidate the emergence of humans’ multitasking ability as an evolutionary change that help to distinguish humans from other animals. To explore the differences between the two, this literature review analyzes various scholarly articles regarding the multitasking mind.

S

tudying multitasking sheds light on how the brain reacts to simultaneous tasks. Tuning attention properly is pivotal to healthy cognition; a variety of mental conditions are related to improper (either heightened or unsufficient) sensitivity to environmental stimuli. For most people, the process of switching tasks heightens susceptibility to distractions and slows progress. However, a small subset of the population defies this trend, multitasking with ease. These individuals can concurrently excel at multiple tasks, as evidenced in their patterns of neural activation. These so-called “supertaskers” help elucidate the underlying neurological mechanisms that support multitasking and enable persistent attention. This literature review examines the characteristics that constitute an “effective multitasker” by analyzing the neurological effects that underly normal and privileged multitasker’s functional capacities. We seek to address the following questions: • How does the brain work when an individual is multitasking?

• Is multitasking advantageous in the long run?

• What constitutes a “supertasker” and what advantages to they have?

• How can multitasking be managed?

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Understanding the differences between the “supertasker” and the ordinary multitasking individual means understanding various connections among regions of the brain, particularly genetic/physiological features in “supertasker” brains that may be absent from typical human neuroanatomy.

How does the functionality of the brain work when an individual is multitasking?

Multitasking is an attempt to engage in more than one activity at the same time. When two tasks compete for attention, there is generally a switching that occurs between the neural processes involved (i.e. the processes are not truly concurrent).

The prefrontal cortex mediates this switching processes. The anterior portion of the prefrontal cortex forms the goal or intention (for example, “I want that cookie”), and the posterior prefrontal cortex activates the physiological processes necessary to accomplish that goal (in this case, pull a cookie out of the jar).

Multitasking has been shown to impair such cognitive performance, as each neural “switch” results in a reduced performance capacity. There is, however, growing evidence that the ability to multitask can be learned through practice (though

even acquired multitasking abilities tend to decrease with age).

People are remarkably good at eating while doing other things because the practiced motor skills involved in eating don’t overlap too heavily with those that interpret visual cues, control language, or run other complex processes. It has been found that multitasking becomes particularly problematic when individuals seek to undertake three or more independent tasks.

How is multitasking disadvantageous in the long run?

Research overwhelmingly reveals that the brain is a “one-thing-at-a-time” kind of machine. The human brain’s limited capacity for attention became strikingly apparent with the growth of aviation during World War II. As the task of piloting an airplane increased in complexity, the amount of information that the pilot was required to process also grew – and so did the number of airplane accidents unrelated to mechanical failures. The pioneering psychologist Donald Broadbent set out to investigate whether or not pilots could absorb all the information being displayed to them. Broadbent’s experiments supported the premise of “finite attention,” which is now a cornerstone of contemporary cognitive neuroscience. This theory posits that attention devoted to one activity is necessarily attention taken away from other activities. Attention is thought to amplify some signals and suppress others, two processes known as facilitation and inhibition. Tuning attention appropriately is key to healthy cognition, and several psychological disorders stem from the failure to do so, either from difficulties amplifying the appropriate input from the eyes, ears and other sense organs, or from trouble suppressing unimportant details of the environment. In some cases, excessive multitasking may even exacerbate attention-related psychological disorders.

Contrary to popular belief, multitasking is often less effective than focusing on one task at a time. Multitaskers often just “go through the motions” of multiple tasks rather than maintaining full immersion in and thereby fully experiencing one specific task.

What constitutes a “supertasker” and what advantages to they have?

After researchers tested approximately 700 people, 19 individuals met the criteria characterizing “supertaskers”.

These

individuals all ranked among the top 2.5 percent when doing a single task, and their performance did not deteriorate when completing two assignments at once.

Significant differences in the patterns of the neural activation of supertaskers and the control group were discovered. Supertaskers showed less neural activity at the more difficult levels of the multitasking test. For most people, a tougher challenge recruits more neurological resources, but supertaskers showed little or no change in brain activity as the tasks became more demanding, suggesting that somehow these individuals can achieve greater efficiencies and thereby perform better.

References Watson, J. W. (2012, April). Supertaskers and the multitasking brain. Scientific American Mind, 22-29.

Groeger, L. G. (2012, April). Manage your multitasking. Scientific American Mind, 26.

Anne, A. B. (n.d.). The 5 secrets of effective multi-tasking. Retrieved from http://www. evancarmichael.com/Work-Life/4322/The-5Secrets-of-Effective-MultiTasking.html Doering, S. D. (n.d.). Great at multitasking? that’s a bummer!. Retrieved from http://www. evancarmichael.com/Going-Green/2168/

To identify “supertasker” brains, researchers look for unique features in individuals’ genes and neurophysiology. Variants of one particular gene, COMT, for example, are associated with differences in working memory, executive attention, and (unfortunately) a predisposition for a broad number of psychological disorders. One reason to examine this gene is to study how its variants alter the efficiency of dopamine in the frontal cortex. It is thought that lower COMT enzyme activity may result in greater availability of dopamine for binding at the receptor sites in the frontal cortex.

Great-at-Multitasking--Well-Thats-a-Bummer. html Telis, G. T. (n.d.). Multitasking splits the brain.

Retrieved from http://news.sciencemag.org/ sciencenow/2010/04/multitasking-splitsthe-brain.html Costello, E. C. (1999, August 27). The cognitive and neuroanatomical correlates of multitasking.

Retrieved from http://www.sciencedirect.com/ science/article/pii/S0028393299001347 Gazzaley, A. G. (n.d.). How does the brain handle multitasking?. Retrieved from http://www.

How can multitasking be managed?

brainfacts.org/about-neuroscience/ask-an-

Training and practice can help individuals perfect their multitasking abilities. Simple, repetitive actions like typing can become almost automatic and thereby free up attention for additional uses. Professional musicians and athletes, for example, have mastered behaviors that would challenge beginners and, as a result, can focus on nuances like style and strategy. Researchers recommend learning to focus on one thing at a time, but even under the best conditions, it has been shown that most people cannot focus intensely for more than 20 to 30 minutes. Taking breaks is recommended (perhaps going for a walk outside or switching to a less demanding task) to shake loose new ideas and approaches when the challenge is resumed later. Checklists can also help manage the daily influx of new duties, and reconfiguring the workplace can limit distractions.

expert/articles/2012/multitasking/ Telis, G. T. (2010, April 15). Multitasking splits the brain. Retrieved from http://news.sciencemag. org/sciencenow/2010/04/multitaskingsplits-the-brain.html

Edited by Stephanie Marcus and Alexandra DeMaio.

Spring 2014 | Rutgers Science Review | 7

Interview with:

Dr. David Redlawsk

Conducted by Lauren Fish

Dr. David P. Redlawsk is a professor of Political Science and the Director of the Eagleton Center for Public Interest Polling, one of the nation’s first universitybased public opinion polls. His research in political psychology focuses on campaigning, elections, the role of information in voter decision-making, and emotional responses to campaign information. An award-winning writer, Dr. Redlawsk has contributed work to The New York Times and is currently in the process of publishing his latest book, The Positive Case for Negative Campaigning.

Q: What drew you to political science as a student?

Q: Can you tell us a little bit about your research?

A. I was interested in politics for as long as I can remember, and I don’t know why. It was apparently inborn. I really liked the political world, I loved my political science undergraduate studies, so I did my PhD in political science at Rutgers. It’s a weird dynamic how I got here- careers aren’t linear, but there’s a thread: I was always interested in why people were interested in politics, why they were involved, why they got active, because of my own background. I didn’t know why I was interested, so I was interested in the why of how people think about politics and I became not only a political scientist but a political psychologist as well.

A: I’m interested in why people make the decisions they do in the political world, and one of the things that is quite obvious is that we’re not the kind of cool rational processors that many assume. One of the really interesting things we find is that people often respond to new info counter to how we would expect. This is the idea of motivated reasoning, particularly with person perception. We like somebody, and we’re invested in that – be it our ego, our time, etc. When we have a strong positive evaluation and we encounter information that challenges that evaluation, we effectively fight against that information and we may end up evaluating the object even better. We reason in the service of maintaining our evaluations. We know empirically people do change their opinions from time to time, and the question is, what does it take to do it? Motivated reasoning has been the core of my research, and I’ve done papers on it, but I’ve written books on cognitive processes, the Iowa caucuses and the presidential primary process, and I’ve got a new book coming out on negative campaigning in which my colleague and I argue that negative campaigning is a good thing for the system. Without it, voters would not have enough information to make good decisions. One of the keys to what I’ve been doing is information, but I’ve done it from a number of different angles.

Q: What got you to make the switch from being involved in politics to researching politics?

A: In college, I was heavily involved in campus politics. When I went to an MBA program, got jobs, and didn’t do that, I found I missed it. I actually didn’t quit doing politics to go study it.

While I was a graduate student I stayed involved in the political process; I ran for office in Somerset county while I was a grad student studying voter decision-making. And that’s interesting because we tend to think of scientists as being objective observers.

There’s a sense that we could be biasing what we do if we’re participants. A lot of political scientists aren’t politically involved for exactly that reason. But I really liked the hands on stuff. I’m interested in human behavior in this really specific kind of way – voter decision making. How does the average voter make sense of all the information that I saw in the real world of politics? So for me, being involved in politics actually fed into my research agenda. It made me very interested in certain areas, and it fed tremendously into my teaching.

8 | Rutgers Science Review | Spring 2014

Q: How are the Rutgers Eagleton Poll Press Releases used?

A: The Rutgers Eagleton Poll is a public poll, we put out press releases, and our goal is to get media attention, and the primary reason to get media attention is to inform the public generally. So we use the media that way in terms of setting up the press releases, we now have a blog, we have a website, and we try to push this stuff out. For me, the Rutgers Eagleton poll is not necessarily on point with my main research area; on the other hand I make use of it for my research, for example some of my negative campaigning research. And so I find that there’s a thread through my work, including being involved in the Rutgers Eagleton

Poll- it really is about information and information availability.

The survey research side is something I fell into. I’m trained as an experimentalist in political science rather than as a survey researcher.

Q: How do you perform an experiment, if you don’t have a closed system to do it?

A: When we talk about experiments in social science, our intent is to identify the question, independent variables, the dependent variable, randomly assign people to levels of the independent variable, and then to see what happens. For example, we might do some survey experiments where we manipulate the wording of questions – that’s the treatment. The idea is we randomly assign people to one or the other version of a treatment, maybe a control or maybe two treatments, and then we compare (in this case the dependent variable would be how upset, on a scale) the means of the variables and we can see if something happened. In a sense we have a closed system if we define it carefully enough. Political scientists have also recently gone into this area of field experiments where they’re manipulating something going on in the real world.

Q: What difficulties do you face in your work?

A: We don’t cost as much as the natural sciences, but funding availability for the social sciences has been rough in recent years, just as it has been for other areas. Political science in particular has been the target of members of congress, who try to and sometimes successfully eliminate NSF funding specifically for political science.

Another problem we face is helping people understand why we have any relevance, particularly right now with the tremendous emphasis on STEM, where everybody can see what they’re doing for us. My strong feeling is that STEM’s great and it’s important, but you really need the broad understanding of humanity that you get from the social sciences and the arts and humanities, even if your primary focus is going to be in a STEM field. It’s an incredible position to be in – a faculty member at a research university. So, for all the frustration I might express, I can’t think of anything better to do.

Q: How has the field changed since you started and where do you hope to see your research go in the future?

A: When I started in 1990, a combination of qualitative and survey research was the dominant work. There was very little experimentation. My advisor, now my colleague here, trained as a social psychologist, but he came here for political science, and I ended up working with him on projects and getting trained on experimentation. From a research standpoint, the field that I’m in has been moved from being in a corner to being really mainstream.

Second has been the rise of political psychology itself, trying to understand behavior. What I’m doing now, with some young colleagues in various places, is looking at how social networks and environments influence information – how people really respond to all those social cues. We’ve got a paper in which we’re finding that social cues and sharing substitute for information. So I’m going off in completely different directions than I’ve ever been, but they still connect to this idea of information.

Spring 2014 | Rutgers Science Review | 9

Aresty

Wind Energy Harvesting Using an Inflatable, Variable-Diameter Cylinder DAVID ALONSO, JINGJIN XIE, AND DAVE OTTENSTEIN Our research addresses the application of vortex shedding to wind energy harvesting. We assess the response of a variable-diameter, inflatable cylinder and a voice coil generator to varying wind speeds. The diameter of the cylinder changes as a function of the incident wind speed to maintain resonant frequency of the system, thereby sustaining maximum vibration and extracting the greatest energy possible from the system. On a large scale, the purpose of our design is to generate clean wind energy, which may be used to supplement urban/ industrial power. Simulations indicate that one cylinder-generator pair can produce potentials of about 100-300 mV. The combination of many such systems shows practical potential for wind energy harvesting.

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ABstracts

Plastics: What can we do with them?

ERIN LACOSTA Recently, there has been an exciting expansion in research with graphene. Due to its high mechanical strength, supreme thermal and electrical conductivity, and an array of other striking qualities, graphene could have a variety of practical applications in areas including, but certainly not limited to, the automotive, aerospace, and biomaterials industries. Challenges currently keeping graphene out of the mainstream include its high price ($272,155 a pound), and harvesting it so that its properties are not diminished in any way. Poly (ether ether ketone) is a high engineering grade polymer that also exhibits many desirable properties, but is also very expensive, averaging $50 a pound. Our project involves using a novel injection molding machine to mechanically exfoliate the much cheaper, $1-a-pound graphite, into graphene, while simultaneously mixing the material with PEEK. If there is sufficient adhesion between the graphene and PEEK, we predict there will be excellent load transfer between phases, thus creating an economical composite that has properties even better suited for certain applications than either of its components alone. To prove the existence of enhanced properties we will characterize the mechanical and thermal properties of the composite and examine its morphology using scanning electron microscopy.

Spring 2014 | Rutgers Science Review | 11

Analysis of Pesticides’ Influence on β-amyloid Overexpression in Alzheimer’s disease MIRIAM LISCI Alzheimer’s disease is manifested by the accumulation of β-amyloid protein plaques proximal to neural cells in the central nervous system. Plaques and neurofibrillary tangles created by these peptides interfere with normal signal functioning by impairing memory, cognition, and behavior and they eventually cause the death of neural cells. The mechanisms which determine Alzheimer’s disease need further investigation, but thus far both genetic and environmental factors have been demonstrated to play a role in the onset of the disease. Our research studies the influence of organochlorines, such as pesticides, on the progression of this neurodegenerative condition in Drosophila melanogaster. We overexpress β-amyloid peptides processed from the Amyloid Precursor Protein in the central nervous system of Drosophila and we drive the expression of the phenotype through its compound eyes. We investigate the influence of pesticides on the accumulation of β-amyloid by monitoring the lifespan and rough eye phenotype of the model system. We further analyze the central nervous system of Drosophila by performing brain dissections and Elisa assays in order to assess the extent of β-amyloid intoxication. Our preliminary data suggests interesting patterns in the relationship between pesticides and levels of β-amyloid in the brain, thus opening new areas for further study of Alzheimer’s disease and the environmental threat posed by organochlorines.

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Using a Rat Model of Binge Eating to Highlight Changes in Cue Salience and Changes in Neuronal Activity DANIEL QUINTIN The purpose of this study is to explore cue salience in a rat model of binge eating disorders. We will do this by measuring neuronal activity in response to a food-associated cue in a simple Pavlovian experiment.

The objective is to support or disprove the proposed hypothesis that there is a positive correlation between binge eating behavior and neural activity in the nucleus accumbens (NAc). Beginning with eight weeks of a pre-treatment using an established binge eating paradigm, followed by a (still on-going) 10-day Pavlovian test using a conditioned stimulus paired with a sucrose reward, six Sprague Dawley rats are expected to exhibit more frequent approaches to the sucrose dipper as a result of the food-associated cue that is presented, relative to non-binged controls fed only lab chow. Results attained from ultrasonic vocalizations, which are used to measure a rat’s current affective state, and single unit recordings are predicted to show elevated positive affect and increased neural activity in the nucleus accumbens in response to the food-associated cue, relative to controls. The results of this research aim to show that there are changes in the neural activity of the nucleus accumbens as a consequence of binge eating, and perhaps in other eating disorders.

Spring 2014 | Rutgers Science Review | 13

Social Undermining: Backstabbing in the Workplace KELLY COYNE Social undermining - “behavior intended to hinder, over time, the ability to establish and maintain positive interpersonal relationships, work-related success, and favorable reputation”- has received increased attention from researchers in recent years, particularly in an organizational context (Duffy et al., 2002). Social undermining manifests through behaviors including discounting a person’s ideas, making demeaning remarks, and hindering information flow (Duffy et. al., 2002). Research has primarily focused on understanding how well-being and attitudinal outcomes result from social undermining; however, there is limited knowledge as to why social undermining occurs. We seek to further the understanding of social undermining by implementing a social network lens to increase understanding of when and why social undermining results. In order to answer pertinent research questions, longitudinal survey data has been collected from undergraduate student teams. We utilize social network software to evaluate measures of “in-degree” and “out-degree” centrality.

Results of the data should serve to replicate earlier findings from a smaller sample size, which indicated: (1) A mediating role of social undermining in the relationship between perceived competence and task and relationship conflict.

(2) Friendship network centrality as a moderating factor in this relationship (Edinger and Sharma, 2014).

Illuminating determinants of social undermining has both practical and theoretical implications. Increased understanding of social undermining will enable preventative action and improve workplace functionality.

Additionally, acquired knowledge will provide insight into areas of possible further research on precursors to social undermining.

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Studying the Effects of Eye-Movements and Interruptions in Multiple Object Tracking PRINCESS CHISOM EMEANA AND HANNAH CANUOTO Analogous to the eye movements a person makes while watching a sports game, this experiment examined where participants tend to look while tracking multiple objects. The human eye gathers relevant information from a visual scene. Studies of disrupted multiple object tracking (MOT) have shown tracking is easier when items halt while hidden than when they move. These results suggest that past object-locations are remembered when items disappear briefly from view. Here we examine where we look in MOT to learn whether eye-movements play a role.

Method. Subjects tracked 4 of 8 circles in three gaze conditions: (1) Subjects were free to move their eyes.

(2) Subjects fixated the center of the display.

(3) Subjects tracked the “centroid� of the targets.

Subjects blinked their eyes when they heard a sound. Eye-blinks triggered items to disappear, and to halt or move while hidden.

Results. MOT is better when subjects are free to move their eyes than when they fixate the center of the screen. Different factors can account for the impaired MOT in central fixation conditions: Cognitive effort needed to sustain fixation, or blurring of items in the periphery. More noteworthy is the robustness of the halt-move effect: Both fixation conditions produce better tracking when items halt. If the halt-move difference persists in (forthcoming) centroid condition, these findings will indicate that position-coding is not just due to eye movements, but rather due to covert attention.

Spring 2014 | Rutgers Science Review | 15

RESEARCH

Azorubine’s Sensitivity to Changes in Viscosity Ariella Kashi1 1

Rutgers University

We investigate the sensitivity of Azorubine to changes in the viscosity of surrounding media and asses the extent to which the substance can perform as a molecular rotor.

I. A.

INTRODUCTION

Review of Azorubine and Its Potential as a Probe for Viscosity

Azorubine is a synthetic red food dye in a group of molecules known as azo dyes. It has the molecular formula C20 H12 N2 Na2 O7 S2 and molecular weight of 502.44 g/mol. It is also highly soluble in water.

The structure of azorubine contains two nitrogen atoms bonded by a σ and a π bond with two aromatic attachments. The official IUPAC name for azorubine is disodium (E)-4-hydroxy-3-((4-sulfonatonaphthalen-1yl)diazenyl)naphthalene-1-sulfonate.

Due to its azo group, we speculate that azorubine can perform as a molecular rotor and will consequently be sensitive to changes in the viscosity of the surrounding medium. The term “molecular rotor” refers to a fluorescent molecule that undergoes a twisted intramolecular charge transfer (ICT) mechanism in its excited state. A molecular rotor typically contains an electron donor unit, an electron acceptor unit, and an electron-rich spacer unit that consists of σ and π bonds. Once excited by photons, an electron is transferred from the donor unit to the acceptor unit. When in its excited state, a molecule may return to the ground state through a twisting mech-

anism. However, if the molecule is immersed in a highly viscous environment, the fluid’s resistance to movement will restrain the rotational mobility of the molecule, resulting in intense fluorescent emission [1].

B.

Using Pyranine to Study the Local Environment

Previously, I conducted a study to determine azorubine’s sensitivity to changes in viscosity. This was achieved by adding azorubine to systems where the viscosity was manipulated using various methods, such as altering the temperature and water concentration of our solutions. In our data, there is a positive correlation between the viscosity of our solutions and the fluorescence emission intensity of the probe. These relationships had been characterized using an empirical model (Equation 1) whose parameters allow for the comparison of azorubine’s performance as a viscosity probe. We found that the parameters of the model varied, as can be seen in the table. The data were obtained during a previous study.

N I(η) = a +

η k1 + .k2 ∗ η

(1)

TABLE I: Parameters for the formulas derived by manipulating the viscosities of various substances in order to study the behavior of azorubine in several solutions.

Glycerol Temperature Study Glycerol and Water Sucrose Study Glucose Study a(-) 0.18 0.10 0.42 0.05 K1 (mPa s) 1335 246 271 59 K2 (-) 0.94 1.20 1.22 0.53 MSE 0.0005 0.0031 0.0003 0.0136

These results confirmed that, although azorubine was sensitive to viscosity changes, its sensitivity was not uniform among various substances used to modify the rheological characteristics of the medium. The slope of maximum intensity change was controlled to change the viscosity of the surrounding medium. The temperature of glycerol adjusted to modulate viscosity was significantly different than in other studies. In these previous works, the concentrations of several components (glycerol, su-

crose, and glucose) were controlled to change the viscosity of the surrounding medium. The slope’s inverse value is 1335 for glycerol, whereas, the inverse slope values in the other studies vary from 139 to 271. The higher the inverse of the slope value, the lower the impact that a change in viscosity has on the observed emission of azorubine in any given solution. It is hypothesized that the cause for these discrepancies is the compound’s differential effect, used to modulate bulk viscosity at the Spring 2014 | Rutgers Science Review | 17

2 local level. The small size of glycerol molecules indicates a tighter packing arrangement around the molecule, possibly restricting the movement of the fluorophore more than larger compounds.

To test this theory, pyranine was used to indirectly assess the composition (and consequently the mobility) of the solvation shell around the probe. Pyranine, 8hydroxy-1,3,6- pyrene trisulfonate, was used due to its sensitivity to the composition of solvent shell [4].

The ionizable hydroxyl’s dissociation from the pyranine fluorophore is responsible for the selective response in different environments [2–4].

In observing the emission data for pyranine, two peaks can normally be seen at approximately 435 and 510 nm, respectively. The band observed at approximately 510 nm is a consequence of the transfer of the dissociated proton to water. When there is an increase in hydration, or various other solutions that act as weak proton acceptors, extended proton transfer does not occur. Roche et al. [4] have reported that the addition of polyols, alcohol, and sugars to the environment hinder the proton transfer that is evidenced by a shift of the fluorescence peak to 435 nm. Therefore, the ratio between the intensity of the second peak and the first peak correlates to the composition and mobility of the solvent shell around the HPT. By extension, we hypothesize that pyranine can be used to obtain information about the characteristics of the environment surrounding a molecular rotor such as azorubine, and shed light on its differential sensitivity on several systems. To this end, data on pyranine in water, glycerol, and several carbohydrates were observed alongside the data collected from azorubine placed in equivalent media.

II.

MATERIALS AND METHODS

In my previous study, steps were taken to study the sensitivity of azorubine to changes in viscosity of the solutions that it was placed in. The first step taken was to determine the concentration of azorubine with which to conduct the study. A concentration of 30 µM of azorubine was ultimately chosen, which we continued to work with in this study. The concentration of 30 µM was chosen to avoid inaccurate results that might have been caused by the inner filter effect. The inner filter effect occurs when the presence of a large concentration of molecules obstructs the passage of light and prevents further excitation of the whole sample [5].

The next step involved modulating the viscosity of glycerol by manipulating the temperature in increments of 5◦ C, between 10◦ C and 50◦ C, using a thermoelectric temperature controller (Wavelength Electronics, Inc. Bozeman, MT). The viscosity of spectrophotometric grade glycerol (Alfa Aesar, Ward Hill, MA) was also manipulated by adding varying amounts of water and studying intensity as a function of glycerol/water concentrations using data. The viscosity of several water/glycerol 18 | Rutgers Science Review | Spring 2014

mixtures was obtained from the literature [6]. Next, the viscosity of sucrose and glucose solutions in water was altered by creating solutions at varying concentrations (60-70◦ Brix). Sucrose at a purity of >99.5, methylcellulose and carboxy methylcellulose from Sigma-Aldrich (St. Louis, MO) were used. Glucose Monohydrate (Cargill, Minneapolis, MN) was used for this step as well. Fluorescence spectra for azorubine and pyranine were gathered using a Fluoromax-3 (Horiba Scientific, Edison, NJ) and analyzed to establish relationships between viscosity and fluorescence intensity. All samples were run, at least, in duplicates.

A.

Determining The Proper Concentration Of Pyranine To Use

Our first step was to determine the concentration of pyranine that we should continue to use in our subsequent studies. Various solutions of pyranine and distilled water were prepared at concentrations of 0.5, 1, 2, 3, and 4 µM. These dilutions were prepared using a stock solution of 1 mM of pyranine in water. The solutions were then placed in quartz cuvettes (path length = 10 mm) (NSG Precision Cells, Farmingdale, NY, USA) and their fluorescence was recorded using a Fluoromax3 spectrophotometer (Horiba Scientific Inc., Edison, NJ, USA). The experimental parameters included an excitation wavelength of 350 nm and emission wavelengths at 365 nm to 600 nm, which were chosen based upon literature [4]. The solutions were maintained at a constant temperature of 20◦ C using a thermoelectric temperature controller (Wavelength Electronics, Inc. Bozeman, MT).

We ruled out 3 µM and 4 µM, because these concentrations exceeded the detection limit of the spectrophotometer. Additional tests were completed to decide between 0.5 µM and 1 µM. This was done by preparing solutions of spectrophotometric grade glycerol (Alfa Aesar, Ward Hill, MA) and distilled water at a ratio of 1:1. Pyranine was added using the bulk solution of 1 mM pyranine, forming solutions at the desired concentrations of 0.5 µM and 1 µM. We used glycerol for this concentration study to validate that the concentrations were appropriate for systems other than water. The solutions were placed into quartz cuvettes and tested in the spectrophotometer. Ultimately, we decided to continue the study using a concentration of 0.5 µM of pyranine, which is further explained in the results and conclusions.

B.

Calculating Amounts Needed to Prepare Various Solutions at Uniform Viscosities

Calculations were performed in order to determine how to prepare solutions of glucose, sucrose, glycerol, MC, and CMC that will exhibit the same viscosities, namely, 90 mPa s. This was done by fitting viscosity vs. concentration data with various models using Excel (Mi-

3 crosoft Corp., Seattle, WA) until a satisfying function was achieved based on goodness of fit measures. The sources and formulas that were selected are presented within the results and conclusions section.

C.

of 1.01 g of solution was mixed with 10 µL of 3000 uM azorubine in water to reach a concentration of 30 µM. In another sample of 1.01 g of MC in water, 0.5 µL of 1 mM pyranine in water was added. Both solutions were thoroughly mixed.

Steps for Preparing Solutions of Various Substances at a Viscosity of 90 mPa s 1.

Glycerol and Water

It was calculated that 84% glycerol and 16% water would be necessary to achieve a viscosity of 90 mPas. 10 µL of 3000 µM azorubine in water was added to a sample of 1.22 g of prepared solution. Additionally, 0.5 µL of 1 mM pyranine was added to a separate sample of 1.22 g of prepared solution. These were both thoroughly mixed.

2.

Glucose

It was determined that in order to prepare a solution of glucose in water at a viscosity of 90 mPas, the solution must be at a concentration of 68.1 Brix. We began by slowly heating 5 g of water. 15 g of glucose monohydrate (Cargill, Minneapolis, MN) was gradually added to the water until it was fully dissolved. The temperature was periodically checked and kept below 50◦ C in order to ensure the formation of undesirable compounds, e.g., furfural, etc. [7]. Once this was done, a refractometer (Atago N-4E, Bellevue, WA) was used to ensure that we had achieved the desired concentration of 68.1 Brix. The necessary adjustments were made. h probes, pyranine and azorubine, were added to the glucose solution. 10 µL of 3000 µM azorubine in water was added and thoroughly mixed. In the other, 0.5 µL of a solution of 1 mM pyranine was added and thoroughly mixed as well.

3.

5.

CMC

A solution of 1.35% CMC was prepared in water in order to achieve the desired viscosity. Once achieved, as in the previous solution of MC, a sample of 1.01 g of solution was mixed with 10 µL of 3000 µM azorubine in water to reach a concentration of 30 µM. In another sample of 1.01 g of CMC in water, 0.5 uL of 1 mM pyranine in water was added. Both solutions were thoroughly mixed.

Once these steps were taken to prepare the ten solutions, the solutions were placed in quartz cuvettes. Each separate solution sample was first placed into the spectrophotometer for five minutes in order to stabilize temperature at 20◦ C. The solutions with pyranine were studied in the spectrophotometer using an excitation wavelength of 350 nm and emission wavelengths of 365 nm to 600 nm. The solutions of azorubine were studied in the spectrophotometer at an excitation wavelength of 510 nM and emission wavelengths of 530 nm to 800 nm. This study was performed in duplicate.

III.

RESULTS AND DISCUSSION

During the concentration study, where various concentrations of pyranine in water were tested, it was decided that we should continue with either 0.5 uM or 1 uM of pyranine (higher sample concentrations had exceeded the detection limit of the spectrophotometer). The results can be seen in Figure 1.

Sucrose

It was determined that a sucrose solution at a concentration of 62.7 Brix will exhibit the target viscosity (90 mPa s). The steps for preparation were carried out in the same manner as glucose, however, replacing it with sucrose (Sigma-Aldrich St. Louis, MO) at a purity of >99.5. Just as was done with the glucose, two solutions of sucrose were prepared. One sample included 1.30 g of sucrose mixed with 10 µL of 3000 µM azorubine. The second included 1.30 g of sucrose mixed with 0.5 µL of 1 mM pyranine.

4.

MC

A solution of 1.36% MC was prepared in water to achieve the desired viscosity. Once achieved, a sample

FIG. 1: Fluorescence intensity of aqueous solutions of pyranine at various concentrations.

Additional tests were run in order to determine whether to use a concentration of 0.5 µM or 1 µM using Spring 2014 | Rutgers Science Review | 19

4 glycerol and water. The following graph was obtained in the study.

was done with the previous solutions, were derived using these experimental values.

MC: Concentration(η) = 0.5ln(η) − 0.89

(5)

Concentration(η) = 0.56ln(η) − 1.15

(6)

CMC:

FIG. 2: Intensity as a function of wavelength in solutions of .5 µM and 1 µM pyranine in 1:1 glycerol/water solutions and water by itself.

We decided to continue our study using 0.5 µM of pyranine, which eliminated our concern of exceeding the detection limit of the equipment and allowed us room to study various other systems.

Next, calculations were required to produce five solutions of different compositions at a constant viscosity (90 mPa s). The models used to characterize the relationship between concentration and viscosity for each compound is presented below.

An empirical model was used to characterize the relationship between concentration and viscosity of glycerol/water solutions. The original data was obtained from Dorsey (1984) [6]. The values were plotted and fitted.

Glycerol: η Concentration(η) = 49.7 + 0.64 + η ∗ 0.02

(2)

Solving the models for 90 mPa s allowed me to obtain the adequate concentration for all the compounds of interest. Azorubine was added to a sample of each solution in the amounts described previously. The spectra collected from the azorubine samples are shown in Figure 3.

FIG. 3: Fluorescence spectra of Azorubine (30µM) in several 90mPa s solutions.

Using the same solutions, pyranine was added to samples of each solution. Figure 4 displays the data obtained for this study.

The viscosities of glucose and sucrose at varying concentrations were taken from the CRC Handbook Of Chemistry And Physics 63rd Edition (Idem M17). The values were plotted and the following models describing concentration vs. viscosity were used to solve for 90 mPa s: Glucose:

Concentration(η) = 1.31 +

20000 − 1.31 1 + exp(0.12 ∗ (114.8 − η)) (3)

Sucrose: Concentration(η) = (5.1 ∗ 10

−5

)∗e

0.23η

.

(4)

MC and CMC, the viscosities of the solutions at varying concentrations were obtained experimentally using a Brookfield viscometer. Equations to describe the concentrations required to achieve specific viscosity values, as 20 | Rutgers Science Review | Spring 2014

FIG. 4: Fluorescence spectra of Pyranine in solutions at a viscosity of 90 mPa s . Pyranine was used at a concentration of 0.5 µM.

This study was replicated and the data were analyzed.

In each replication of the study in which azorubine had been added, we were able to observe that glycerol had

5 the highest intensity at 437 nm, followed by glucose, sucrose, MC, and CMC, apparently following a trend. As we can see, there is a correlation between the packing and mobility around the probe and the fluorescence intensity at 437 nm. The hydrocolloid solutions presented spectra similar to that of pyranine in pure water. (see Figure 2 for comparison).

We shift our focus over to the graph displaying the data regarding the solutions with pyranine. The first and second peaks of each solution were recorded. The wavelengths chosen to select the corresponding peaks were 437 nm for the first peaks and 509 nm for the second peaks.

The ratios between the first and second peaks were then calculated. Table II summarizes the data that was observed. In both replicates, the fluorescence intensity of the second peak (509 nm), ranked from lowest to highest, were that of glycerol, glucose, sucrose, MC, and CMC (although, MC and CMC might be very similar in terms of the intensity of their second peaks). The fluorescence

intensity at 437 nm for glycerol, glucose, and sucrose, are approximately equal. However, marked differences were observed when the ratio and the normalized intensity of the peak at 507 nm are compared for these three.

These differences show a correlation to the values of the viscosity sensitivity parameter of the azorubine sample (see Table I). In the case of the hydrocolloids (CMC and MC), the pyranine data suggest that the local environment around the probes is similar to that of water, which explains the reduced sensitivity of azorubine to changes in viscosity when the fluidity of the medium is modulated by the addition of hydrocolloids. However, these data do not explain why azorubine is more sensitive to changes in viscosity in MC solutions than in CMC ones.

The highest ratio corresponds to glycerol, which, as was aforementioned, relates to the hypothesis that the glycerol solution was significantly less hydrated then the other solutions studied.

TABLE II: First and second peaks in various solutions that contain 0.5 ÂľM pyranine and the ratios between the peaks.

Solution Normalized Fluorescence Intensity at 437 nm Normalized Fluorescence Intensity at 509 nm Ratio First Peak/Second Peak Glycerol 0.96 0.32 3.02 Glucose 1 0.55 1.81 Sucrose 0.91 0.68 1.33 CMC 0.28 0.94 0.30 MC 0.20 0.93 0.21

IV.

CONCLUSIONS

Although this study shed light on the properties of the solvation shell around each molecule, more research must be done. In the future, we intend to study differences at the bulk and local level that translate to differential sensitivity of azorubine to bulk viscosity.

Our data do not explain, as aforementioned, why azorubine is more sensitive to changes in the viscosity of MC solutions than in CMC solutions. This study must therefore be performed using a higher uniform viscosity,

[1] Scientific Opinion on the re-evaluation of Azorubine/Carmoisine (E 122) as a food additive1. EFSA 7(11):1332 (2009): 7-8. Print.

[2] Flora, K.K., Dabrowski, M.A., & Musson, S.P. (1999).

The effect of preparation and aging conditions on the internal environment of sol-gel derived materials as probed by 7-azaindole and pyranine fluorescence. Canadian Journal of Chemistry77(10): 1617-1625. Print.

[3] Huppart, D., Kolodney, E., Gutman, M., & Nachliel, E. (1982).Effect of water activity on the rate of proton dissociation.� J. Am. Chem. Soc.104(25): 6949-6953. Print.

[7] Smith, P.C. , Grethlein, H.C., &, Converse, A.O. (1982).

Glucose decomposition at high temperature, mild acid,

such as 400 mPa s in order to confirm our results regarding the MC and CMC data.

V.

ACKNOWLEDGEMENTS

Sincere thanks to Dr. Sophia Gershman for advice, instruction, and guidance throughout the two-year duration of this project. Funding and resources were provided

by Watchung Hills Regional High School.

Edited by Christian Fernandez.

[4] Roche, C.J., Guo, F., & Friedman, J.M. (2006.) Molecular level probing of preferential hydration and its its modulation by osmolytes through the use of pyranine complexed to hemoglobin. The Journal Of Biological Chemistry281: 38757-38768. Print.

[5] Kubista, M., Sjoback, R., Eriksson, S., & Albinsson B. (1994). Experimental correction for the inner-filter effect in fluorescence spectra . Analyst 119 (1994): 417-419.

Print.

6 [6] Dorsey, N.E. (1940). Properties of Ordinary WaterSubstance p 184 New York (Reinhold) and short residence times. Analyst 28.1: 41-48. Print.

Spring 2014 | Rutgers Science Review | 21

Site map of all Pennella excavations, 1972-1975 and 2001, including modern features such as house lots and roads, all built today 22 | Rutgers Science Review | Spring 2014

Something Old, Something New: Analysis of the Faunal Remains from the Middle Woodland Site of Pennella, Ocean County, NJ Devin L. Ward Faunal remains from the 1972 and 1974/5 excavations at the Pennella archaeological site in Ocean County, New Jersey, were studied for the purposes of (1) determining the paleoecology of the area and (2) analyzing Native American land usage practices. This analysis was used as a case study relevant to aging collections in museum storage at the New Jersey State Museum and in museums across the country.

I.

INTRODUCTION

The Pennella archaeological site is located in Ocean County, New Jersey, near Little Egg Harbor and the city of Tuckerton. Although all of the material excavated is associated with pre-contact Native American habitation, very little is known of the ethnohistory of the Native Americans in the area. Europeans began buying land in the surrounding coastal area in the 17th century, but did not seriously settle there until the 18th century. Their occupation was focused on the shoreline, most likely due to opportunities for commerce and trade provided by the access to the ocean. Occupation inland to the West was very limited. Documented historic land use included farming and forestry with an emphasis on logging. The nearby city of Tuckerton was settled in the late 18th century. Despite this, the area directly surrounding Pennella was still very undeveloped, and only in recent decades have residences and commercial and recreational zones been expanded, facilitated by newly constructed roads and public transportation [13, 24]. The current ecology of the area is fairly typical of a pineland environment. Local wildlife includes, waterfoul, small birds, and whitetail deer”, in addition to biting insects, “sometimes in annoying numbers”, asnoted by archaeologists in 2001. Currently, nearby development includes the Atlantis Golf Course and private residences. Lagoons have been dug out to provide these residences with direct access to water. In addition to historic farming, resulting in a significant plow zone, this modern development has significantly altered the surface landscape of the area [13, 24].

The site was first surveyed and described in Archaeology of New Jersey. After this, two main phases of excavation took place, one in 1972-1975 and the other in 2001; the New Jersey State Museum Bureau of Archaeology and Ethnology has accessioned material associated with all excavations. However, my analysis includes the faunal material recovered in the 1970s. Finds here were unsurprising because of the proximity of other archaeological sites and because of local knowledge of past Native American presence. Early 20th century archaeologist Francis Jordan made reference to Native American graves in the area around Tuckerton as early as 1906. He also is thought to have perpetrated an erroneous report of the discovery of a 7-foot-tall giant skeleton, an idea now firmly rooted in local legend. The Tuckerton Shell

Mound, at a distance of about 3000 feet from Pennella, was excavated in 1939 by the Indian Site Survey and is still visible today. Excavations in the region to date have, in sum, indicated small, short-term Native American occupations on drained ground near bodies of water facilitating the access to food [13].

Initial excavations in the 1970s by Andrew Stanzeski have associated excavated cultural material with the Fox Creek Phase of the Middle Woodland Period. A variety of artifacts were recovered along with diverse taxa of faunal remains, including, “side-notched points, performs, scrapers, hammerstones, sharpeners, a pestle, and a celt.” Several shell-filled features were also found and discarded [22]. David Parris, at the New Jersey State Museum, performed the initial faunal analysis on the bones excavated, and it is this assemblage on which my research is focused [19]. During my study of the faunal remains, I did refer occasionally to Parris, both in person and via his previous notes, and our conclusions do differ somewhat, although not in any significant manner. This difference is expected, being that we have different training, have differing levels and types of experience, and have conducted analysis with a significant chronological gap [13, 24].

The discovery of Native American graves at the site is also of importance. The human remains found at Pennella were sent to the Smithsonian Institution at the National Museum of Natural History, and were documented and analyzed by Dr. Douglas Ubelaker. The following information is available from his brief report. Skeletal remains from a minimum of seventeen individuals were recovered, and of these, fourteen were adults (for the most part elderly), one was an infant, one was 2.5 years, and one was 4 years [25]. This observed age-at-death distribution is consistent with an attritional mortality profile: “a high number of infant deaths, low numbers of adolescent deaths and a gradual increase in mortality throughout adulthood”, which is indicative of a healthy population [7]. The location of these remains is unfortunately currently unknown. This excavation occurred before the approval of the Native American Graves Protection and Repatriation Act in 1990 and little to nothing is known of the Native Americans previously occupying this region or of their descendants. Therefore, it may be assumed that these remains and associated funerary artifacts have not been repatriated and remain in storage, quite possibly at the Smithsonian Institution.

Spring 2014 | Rutgers Science Review | 23

2 Excavations in 2001, very close to those conducted in the 1970s, were contracted by MAAR Associates Inc, although Andrew Stanzeski was brought in to excavate the site again. This work was the initial stage of determining the potential of the land for development into residential lots between Country Club Boulevard and Overlook Drive. The final report was compiled by Alan Mounier on June 19, 2001, and is titled, Stage 1 Archaeological Survey of Block 326.01, Lots 8.04-8.14, Little Egg Harbor Township, Ocean County, New Jersey. The report concluded that the cultural materials found in the 2001 MAAR excavation were in all likelihood associated with Pennella, and that a progression into Stage II would be necessary to determine the boundaries ofoccupation in terms of the location of the planned development. Later in December of 2001, MARR published a report titled, Archaeological Investigations at a Portion of the Pennella Site 28OC60 Willis Creek, Ocean County, New Jersey, providing a more thorough investigation, in accordance with the suggested Stage II from June.

My personal assessment of the faunal assemblage from the 1972/73 and 1975 excavations by Andrew Stanzeski was conducted throughout 2013. Very little documentation is held with the faunal remains in the Bureau of Archaeology and Ethnology storage, accessioned to the museum as AE1985.26. Therefore, much of the information I have gathered on the history of the area in terms of archaeology and land use, along with the ecology and geology, is based off of the 2001 MAAR reports from Alan Mounier and Ronald Thomas. For the most part, my additional data comes from publications in the Journal of the Archaeology Society of New Jersey. After Stanzeski donated the collection to the museum in 1980, David Parris completed basic analysis of the collection in the early 1980s, during which he identified and conserved many specimens4 [19]. Since then, little work has been done with the assemblage. 14Carbon analysis, however, was done on charred wood taken from the bottom of Feature 33, producing a date of 153065 BP, and from a quahog shell from Feature 74, producing a date of 181050 BP [24].

Unfortunately, the preservation of the assemblage is poor. This inevitably prevented the identification of asmany specimens as precisely as would have been preferred. Specimens in the assemblages were small, commonlyless than 2 cm in length, and often lacked characteristics that would have allowed identification to taxon or element. This condition is most likely due to several factors, taphonomic and otherwise. Firstly, soil in the American Northeast is acidic [5]. Over time it eats away the cortical bone and, in the process, destroys articular surfaces and other identifying features. Many specimens in levels, squares, and features across the site also exhibit root etching. Root etching is caused by the secretion of acid from roots and fungi in the soil surrounding deposited bones and, “typically consists of multiple lines imparted in distinctive sinuous, or wavy, configurations that are macroscopically visible, have a U-shaped cross24 | Rutgers Science Review | Spring 2014

section, and are identified with little difficulty� [6]. This contributed to the degradation to cortical bone of specimens in the collection in combination with the acidic soil.

The surface of the bone does not exhibit features common to bone left above-ground to weather, like cracking or splintering, therefore they must not have been exposed for a long period of time [2]. Weathering as a result of taphonomic conditions is not at all unusual in archaeological sites, although it was particularly severe in Pennella [9]. I suspect that the wet, sandy, and marshy conditions around the site contributed to the less-than-ideal levels of bone preservation as well.

Compounding taphonomic conditions were the nonstandard methods of storage the collection experienced since its accession into the collections of the Bureau of Archaeology and Ethnology in 1980, and likely before its accession as well. Although the exact storage methods before the accession are unknown to me, I can at leastcomment upon the state in which I found the collections.

Fragments were stored in small Kodak boxes meant for film, brown paper bags stapled or taped closed, glass jars that previously held assorted foods, and thin plastic sandwich bags with paper labels stapled on the top.

In addition to the shells and bones I worked with, samples of charcoal, rock material, and sand were included in the collection. Unfortunately, these heavy samples were often placed in the same bags with delicate fragments, such as forest snail shells, causing damage to several shell and bones specimens. All of these discussed less-thandesirable preservation conditions should be taken into account when considering my findings and conclusions from the analysis of the faunal remains from Pennella.

My goal in studying the faunal remains from the 1972 and 1974/5 excavations at Pennella was two-fold. First, my proximate aim was to determine the paleoecology of the area and potentially how Native Americans used the land. Second, my ultimate objective was to use this analysis as a case study for work with aging collections often found in museum storage not only at the New Jersey State Museum, but across the country. In the process of completing these goals, I was able to accomplish several others. These include bringing the storage of the collection up to museum standards, identifying two human bones for separation and compliance with NAGPRA (Native American Graves Protection and Repatriation Act) regulations, and numbering hundreds of fragments previously left unidentified.

II.

METHODS

Initially, I began my analysis with re-bagging and labeling the collection. At this early point, I did not have access to maps of the excavation and was therefore unaware of the layers, squares, or any other contextual information. Re-curation of the entire collection therefore not only served to bring conditions up to museum standards but also to give me a general idea of the preser-

3 vation of the remains and also of the numbering system used to indicate the location of each find. Thankfully several maps were provided to me by Stanzeski in the fall of 2013, after I had completed most of my element identification. Levels listed for the material I worked with include:Surface, Level 1, Level 1A, Level 1 & 2, and Level 3. I indicated all material without a labeled level as Unknown. Level depth appears to have varied considerably, though I have no idea to what extent specifically in individual squares. Uniform and normal squares are labeled West to East alphabetically and are labeled North to South numerically. Each square is approximately 5 feet by 5 feet, although this varies throughout the site and many squares are irregularly shaped.

Following this initial stage, I systematically went through the entire collection again, this time identifying each element and fragment that I could, using comparative material in the museum and reference texts [15–18]. I took this data and recorded it either in an excel spreadsheet, for shells and other non-mammalian remains, or in MNISQL, for mammalian remains. MNISQL is an integrated Pascal computer program designed to, “cut the time and effort involved with MNI calculation, while simultaneously reducing the likelihood of calculation error” using explicit, “flexible assumptions”, and provides, “an inexpensive and compact way to store and retrieve bone data for manipulation by other programs” [3]. I used it to calculate the number of individual specimens (NISP) and the minimum number of individuals (MNI) for mammalian species. For non-mammalian species, such as shells, turtles, snakes, fish, and birds, I calculated number of individual specimens and the minimum number of individuals manually. I did not attempt to calculate the MNI in several cases, however, because I was unable to determine taxa. Because the number and small size of the unidentifiable fragments made counting

each individually impossible I weighed them, at 2328.3 g total [8]. I numbered and attempted to identify 1817 fragments, with the serial numbers of approximately 1100 through 2100 and then added number to identifiable fragments that were previously unnumbered of approximately 2300 through 3000. According to records from when the collection was accessioned to the New Jersey State Museum, I am missing numbers 0-1100.

Due to taphonomic conditions, I had to be more general with my identification of elements and taxa than I would have preferred. My determinations were certainly more general than David Parriss from the 1980s [19].

This may also be because the assemblage was in a better condition when he worked with it or because he has more experience in working with faunal remains from this region than I do. In particular, I was less specific with the identification of turtles, birds, and fish remains [17, 18].

Turtles were mainly represented by shell fragments of less than 2 cm in length, birds were mostly represented by shaft fragments of long bones, and all fish bones were highly weathered. Additionally, I initially separated the remains of medium herbivores into “Odocoilius virginianus”, “Unknown Medium Artiodactyl”, or “Ovis aries” [15, 16]. Poor preservation made several of my designations uncertain and instead combined all of these bones under “Odocoilius virginianus”. The reason for this is that although Bos taurus teeth and Odocoilius virginianus teeth were found, no Ovis aries teeth were identified. Combining all of these gives the opportunity for a more detailed analysis, and makes up for the fact that a temporal/stratigraphic analysis is impossible due to lack of contextualinformation for many fragments. I did not measure any fragments to determine the original size of the animal because few bones were preserved well enough to provide accurate measurements and the work would have contributed little to my analysis [26].

TABLE I: Results Linnean Names Vernacular Names Ursus sp.

Bear Tetsudo gracea-hermanni Turtle Rodentia Chipmunk, squirrel, and porcupine Sus scrofa Pig O. virginianus Deer Bos sp.

Domestic cow Procyon lotor Raccoon Lynx canadensis Lynx Ondatra zibethicus Muskrat Brezthion Beaver Unidentified snake Unidentified snake Unideintified bird Unidentified bird Unidentified fish Unidentified fish Unidentified frog Unidentified frog Unidentified lizard Unidentified lizard Unknown Unknown TOTAL

NISP MNI 3 1 860 3 75 7 5 1 301 7 116 2 11 2 1 1 1 1 1 1 10 – 46 – 260 – 8 – 7 – 112 – 1817 26 (identified)

Spring 2014 | Rutgers Science Review | 25

4 A.

Species Profiles

Although the majority of the shell deposits found by Stanzeski during the excavations were discarded, some shells remain in the collection. They include knobbed whelk, channeled whelk, soft shell clam, hard shellclam, oyster, scallop, sea snail, white-lipped forest snail, and slipper. I was able to identify these species using a combination of comparative material available to me through the Bureau of Natural History and through scientific literature [1, 4, 10, 12, 20, 21, 27, 28]. For the purposes of my work, I combined all species of whelk and also all species of clam. Whelk and clam, respectively, were the most common shell in the collection, with 39 and 38 fragments of each found. Oyster was the next most common, with 25 fragments identified. All unidentified fragments of shell were included in the weight of all unidentifiable fragments in the collection because they were very small and flaking. This distribution of mollusks is normal for this region of the New Jersey coastline, and many of these species are also found up and down the east coast of the United States (Anderson, n.d.).

A total of 46 fragments of bone were identified as bird, however due again to preservation no effort was made to identify the remains to genus or species. Of these, 25 fragments were identified to element. It should benoted that one bone, the lunate, was particularly large and probably belonged to a swan or turkey. These produced an MNI of 5, based on the presence of 9 humeri fragments. The likelihood of any of these fragments being from the same individual is quite low. The fragments were spread out across the site, with only two squares and one featureexhibiting more than one bird fragment (PP37, OO36, and F74 producing 2 fragments each and 5 with unknown layer) of the 28 squares and features exhibiting bird remains. The only location with a significant number of bird bones clustered with evidence of burning, NISP of 7, are squares “T1-T57�, which is a location that does not correlate to any location on the site map. A dispersed assemblage of bird bones with a consistently low concentration indicates a natural death pattern. Concentrations of broken or cut bird bones with evidence of burning, indicative of human involvement, is not seen. Analysis of bird bone deposition per layer yields no additional information, as the distribution is relatively consistent per layer and in the majority of cases the layer is unknown.

Turtle remains, with a NISP of 860, constituted both the majority of the non-mammalian specimens and of the collection overall. This is a slight exaggeration due to fragmentation of the shells and carapace: 818 fragments of carapace were identified, in comparison to 42 bones. Turtle carapace, being less dense than bone, will fragment into many small pieces, so the carapace NISP is exaggerated compared to the bone NISP. However, in such a wet and diverse marsh to woodland, saltwater to freshwater environment, a high number of turtles would not be unreasonable. The 2001 excavations found Dia26 | Rutgers Science Review | Spring 2014

mond Back Terrapin, Box Turtle, Snapper Turtle, and Sunk Pot Turtle [24]. Several different turtle carapaces and plastrons were partially reconstructed by both Dr. Parris and me, of Box Turtles and Snapping Turtles.

Three additional non-mammalian species identified in the collection were frog, lizard, and snake. Each was distinguished by its vertebrae and represents a small portion of the assemblage. Ten fragments of snake were found, 7 thoracic vertebrae and 3 ribs, producing an MNI of 1. All fragments not from an unknown level were from Level 2, and were found in F64, F74, CC38, and LL36. No features were available to distinguish the remains to genus or species, but they appear to be from snakes common in the area, such as the Northern scarlet snake (Cemophora coccinea copei), the Northern pine snake (Pituophis melanoleucus melanoleucus), the Queen snake (Regina septemvittata), the Smooth green snake (Opheodrys vernalis), the Northern copperhead (Agkistrodon contortrix mokasen), the Timber rattlesnake (Crotalus horridus horridus), or the Corn snake (Elaphe guttata guttata) (Snakes of New Jersey, n.d.). Eight fragments of frog were identified: 2 ilia, 2 humeri, 1 tibia, 1 fibula, and 3 of unknown element, producing an MNI of 1. Although the remains were not identified to genus or species, their size profile is not unusual for species of snake common in pineland habitat [24]. The remains are probably not from one individual, as they were found in two locations across the site and some were from an unknown location. I can only speculate on the lack of more frog remains in what should be an environment conducive to their habitation. According to Parris, many hibernating frogs, dead and alive, were discovered in the process of excavation. It seems possible that when these were removed from the collection, in situ frog remains were removed as well. Seven fragments of lizard were found, 1 tibia and 6 thoracic vertebrae, producing an MNI of 1. These bones most likely all came from one individual, as they were all found at level 2 of square VV39.

Bos Taurus, or a similar large bovid, was mostly found in the upper layers of the site. This makes sense based on Stanzeskis statement that Levels 1 and 1A are both plow zone and on historic information about the transition of the region into farming and grazing land in the 18th century. All teeth found belonging to this species had a high crown height. This suggests their premature death, most likely signifying their use as farm animals andslaughter for meat. No dental evidence of any species of small bovidae, goat or sheep, was found. An element representation profile across all levels reveals a high occurrence of ribs and thoracic vertebrae in comparison to other elements. According to the Schlep Effect, this indicates that the animal may have been processed for transportation to another location because elements lacking a significant meat association were left behind.

However, due to the fact that the Bos taurus remains were found mainly within the plow zone, and were not processed by hunter-gatherers, it is more probable that the elements are remnants of farming and not significant

5 of hunting. Odocoilius virginianus is present throughout all levels of the site. As previously stated, all medium herbivore remains were combined under the designation of “Odocoilius virginianus” because of the poor preservation at the site. All dentition found was permanent and very worn, up to a few millimeters above the dentoenamel junction, indicating that the individuals were all adult. Included among the fragments associated with the surface layer was a cervid pelvis fragment with the iliac crest cleanly cut off with a metal implement. This may indicate huntingin the area or at the very least quartering of the animal in the field. An element representation profile across all levels reveals a more complete and even representation of elements for Odocoilius virginianus than for Bos taurus. There indicated several things.

First, because Odocoilius virginianus is not a domesticated species in this area, it would have to be hunted instead of farmed. Therefore, the Schlep Effect applies and suggests that the animal was killed and butchered where it was also processed for consumption. Most of the remains were associated with upper levels, known to be plow zone, and could then be the effect of modern hunting. The few remains found in the lower strata of the site could indicate Native American presence and occupation.

The remains of one black bear, Ursus americanus, were identified in the assemblage, from one adult canine, one cervical vertebrae, and one metapodial. Unfortunately, the fragments were labeled with neither level nor square and did not exhibit any signs of damage other then root etching. Evidence of rodent presence was found in all levels. Remains were identified to beaver (Castor canadensis), chipmunk (Tamius stratius), porcupine (Hystricomorph hystricidae), and most likely squirrel (Sciuridae), which were all grouped under the category of Rodentia” in MNI and NISP analysis. In addition, evidence of raccoon (Procyon lotor), Lynx (Lynx canadensis), and muskrat (Ondatra zibethicus) was identified. The presence of all of these species is consistent with reports from the 2001 excavations [13, 24]. Fish remains were variably preserved throughout the site, and formed a NISP of 26021. This may be due to differential deposition but it may also be because flotation was used by Stansezki in some squares and not in others. Flotation was noted on the bags storing the flotation results. Unfortunately, the vast majority of the fish remains were associated with an unknown layer and negate their value for analysis of the human occupation at Pennella.

B.

Bone and Shell Alterations

A total of 27 fragments were identified as exhibiting the effects of burning, constituting 1.45% of the assemblage as a whole. The fragments found below the plow zone and from a known level have in general a burning stage of 3 or below. They were also not found in clusters, or in association with other burned bones in the assemblage. This would indicate that humans were not living

or cooking at this location. There was a cluster of bone with burning stages from 2-4 all belonging to the same deer, however the context numbers on the bones did notcorrelate to any of the other material I had available.

These were the same squares, “T1-T57”, that contained burned bird remains.

A total of 69 fragments were identified as exhibiting cut and scrape marks, constituting 3.70% of the assemblage as a whole. These fragments were mostly from Bos taurus or another large bovid. Because of the large body size of such animals, cut marks are expected to be more common. Separating the animal in to smallerpieces makes it easier to manage for transportation and further processing. Most of these marks werefound on bones associated with the plow zone and with Level 1 of the site.

The presence of cut marks on fragments in these layers is further evidence for the lands use as farmland. There appears to be no spatial significance to the location of these fragments by square in either the 1975 or 1973/4 excavations.

A total of 1280 specimens exhibited root-etching alteration. As previously discussed this most likely had a significant impact upon the preservation of the material deposited in the site because of cortical bone degradation.

A majority of these specimens belonged to turtles, and there are two factors that may have caused this. First, turtle specimens make up a majority of the assemblage in the overall NISP analysis, and would hence exaggerate their expression in this. Second, many of the turtle fragments were shell or carapace, a material more porous than bone and hence more easily degraded by the acid secreted by roots and fungus. Odocoilius virginianus and Bos Tauruswere the next most common species with root etching. This is most certainly due to their relatively high frequency in the collection. There appears to be no spatial distribution significance, as fragments with root etching are found all over the both excavation areas.

C.

Context/Geological Analysis

Although for the most part context was missing in this collection, some notes remain both on the maps and within the collection itself. I aligned the sediment notes from the wall maps that Stanzeski provided with their corresponding Munsell colors, although I do not know if Stanzeski was using a Munsell book at the time, in the following chart.

Most of the human remains found were located in features with dark yellowish brown soil. Level 2 seems to have the most abundance of naturally occurring local species (such as birds, turtles, and other non-mammals), Level 3 produced very little material in the first place, and Levels 1 and 1A were the most abundant in remains and remains with cut marks. This all makes sense in comparison with Stanzeskis conclusion that Levels 1 and 1A were both plow zone. I personally was not able to make many other significant conclusions from this, and Spring 2014 | Rutgers Science Review | 27

6 do not believe thatthere is any conclusion to be made simply due to the poor quality of the documentation. (A few samples of rocks and soil remained within the faunal collection, though without provenance, and so of little impact on my analysis).

Fortunately, in terms of general geological analysis, the reports from MAAR Associates, Inc. provide a basic description of the area and a more detailed description of the areas of the 2001 excavations. “The soils of the Pennella Site are made up of Hammonton organic matter, Downer soils and dredge material. Hammonton soils are deep, moderately well to somewhat poorly

drained. These soils consist of sandy loam subsoil over stratified loamy sand and sandy layers containing small amounts of rounded quartzose gravel. [The downer soil...] is well drained with a sandy loam sub-soil over stratified sand and loamy sand strata normally containing small amounts of gravel. [D]redge material composed of sand and gravel has been places over the Hammonton soils” [24].

Geological and faunal analysis agree that significant damage has been done to the ecosystem and topography of the area since it has been settled by Europeans.

Site Level Noted Traits Corresponding Munsell Level 1 & Plow ZoneDark brown sandy loam 10 YR 3/3; 7.5 YR 3/3, 3/3, 3/4 Level 1A Shell – Level 2 Yellowish brown sandy loam 10 YR 5/4, 5/6, 5/8

III. A.

CONCLUSION

Land Use Evolution - Paleoecology

The use of the land where Pennella is located fits with our knowledge of land use in the area in general. The MAAR analysis (2001) concluded that, “The Pennella Site now has fewer species than previously. The predominant mammals still in the area are deer, rabbit, mice, and chipmunk,” and the area is in the migratory zone of ”Canadian Geese, Mallard, Black Ducks, Brant and Snow Geese” [24]. All of these remaining species are taxa that have adapted to human settlement and development. Many of the low-lying areas have been dredged or built up in order for housing development, severely reducing habitat for local wildlife, and limiting the diversity of species seen today. The environment would have been excellent for native hunter-gatherers to exploit mammals, reptiles, and shells from 1500 to 1700 years BP (300 - 500 A.D.). The assemblage that I analyzed did not indicate this, however faunal remains found in the upper levels, plow zone, and surface, certainly indicate a transition to farming in the area. The presence of a Native American graveyard, however, indicates that evidence of a more permanent settlement may be located nearby. The proximity of the Tuckerton Shell Mound would certainly support this hypothesis.

B.

Lack of Context and Lost Potential

Some of the most important information in archaeology is derived from context, of which I had very little.

Fault for the lack of context remaining with faunal remains from Pennella does not lie exclusively with the 28 | Rutgers Science Review | Spring 2014

excavator or with the museum. Pennella does not represent the state of the vast majority of the collections held by the New Jersey State Museum or the materials excavated in the past 40 years.

Lack of evidence of burning and of cut marks on bones in the lower strata, unaffected by plowing, indicates that the area was most likely only used temporarily by Native Americans, and most definitely not as a regular homebase. The presence of human remains, although their location is not known, would indicate that Native Americans did attach some value to the area. These conclusions, however, are conspicuously in contest with conclusions madeby Ronald Thomas in the overall review of Pennella in 2001. He states that the site, “appears to represent a basecamp, occupied by a number of family groups and exhibiting a relatively high degree of sedentism as well as a wide range of activities, including tool maintenance and manufacturing, woodworking, and the procurement and processing of a variety of hunted and gathered resources, including animal and plant foods and shellfish” [24]. This conclusion is consistent with Stanzeskis conclusions from his work from the 1970s as well [22]. I believe that this can be attributed to the incomplete status of the assemblage that I worked with for my analysis. As stated previously, the assemblage was missing approximately 1200 numbered specimens, which the lack of shell material cannot account for alone. These may include the human remains sent to the Smithsonian for analysis and also some of the cultural artifacts and damaged (burned, cut, etc) faunal remains indicating the level of human occupation discussed by both MAAR Associates, Inc. reports. What I may have been left with is the less significant or less complete parts of the collection –the smaller more weathered fragments found around pits and features, lacking burning or other evidence of prehistoric behavior. The remaining parts of the collection

7 must certainly exist in storage somewhere, possibly under a site number associated with the 2001 excavations instead of the 1972-1975 excavations. They therefore pose an additional opportunity for study because those recent and additional faunal remains only received the same limited identification by Parris as the remains that I worked with [19]. In conclusion, when looking only at the material I received and analyzed from Stanzeskis original 1970s excavations, the presence of Native Americans is not strongly suggested by evidence provided by faunal remains. However, this interpretation is clearly incorrect when looking at the products of excavations in the area later by MAAR Associates and by Stanzeski himself. All other investigations could clearly and easily deduce continuous Native American occupation. I believe that the reason that I do not come to the same conclusions with the faunalmaterial that I analyze here is because the collection is incomplete. This interpretation is supported by the fact that I am missing several hundred supposedly numbered and identified fragments of bone and by the fact that there are many excavated squares from which I have no data. The assemblage may represent the transference of land use in the area as it was colonized and settled and represent the diversity of species occupying the environment, but it does not illustrate accurately Native American presence.

Given optimal preservation and documentation conditions, there are several other additional analyses that I would have liked to undertaken. If the shell deposits had been included with the collection or only partially discarded, I would have attempted to determine the pressure that Native Americans were putting on aquatic species as a source of food, particularly using whelk shells. When a population harvests shells for food, there is a bias towards picking the largest individuals, and therefore the average size of each individual whelk decreases [14, 23].

After measuring the length and breadth of the most complete shells and creating a population distribution of their sizes, I would have compared them to modern whelk demographics in order to determine if Native Americans were putting more or less pressure on whelks as a food source. The measurement of size would have also been useful given better preservation for other taxa, however there was no element complete enough for this.

C.

Potential Future Analysis

Future analysis on this faunal assemblage from Pennella is also possible. Of the fish bones in the collection, many were not as damaged by root etching and other taphonomy as some of the mammalian remains. There is definitely the potential for determination of species from some of these bones and from there a profile of the species present. This may have the capability of providing a more precise insight into the climate and water conditions both in salt and fresh water because of the unique marsh location of Pennella. The soil and rock samples in-

cluded in the collection may also be of use in determining the geology of the site more thoroughly than only from what was recorded. Also, if the charcoal samples are the same used for determining the radiocarbon date of levels 2 and 3 of the site, they could be re-analyzed with better technology for a more precise chronology.

Despite less-than-ideal conditions, this collection exhibits several important things. First, it represents a good example of the paleoecology of coastal pinelands in New Jersey from 1700-1500 years before present, particularly with non-mammalian taxa. It also exhibits how the conversion of the region to farming land and then to residential areas has effected stratification, topography, and ecology of the area. It especially shows the effect of a plow zone on the representation of fauna in strata in archaeological sites. All of this is despite the fact that my analysis is missing more than 1,000 fragments as well as context for many of the fragments that are not missing.

The Pennella Site faunal assemblage also illustrates the effect of how standards in archaeology have changed over time. In addition to highlighting the drawbacks of poorly recorded fragment contexts and less than ideal storage, the assemblage is still able to provide useful information about ecology and human occupation, if only toexhibit what the collection must be missing. Hopefully my analysis will prevent further degradation of the information associated with and available for this site as well as facilitate further research on the assemblage.

IV.

DISCUSSION

I have faith that the preservation and documentation of Pennella represents something closer to a “worst case scenario� for this type of analysis. I believe that although similar collections to this do exist in museum storage in the United States, there are also collections with good preservation and documentation, from which analysis of faunal and other remains can yet yield abundant information. To support my opinion, one may look at a similar analysis to this one which took place in 2009 with the Volk Collection from the Abbott Farm site in Middlesex County, New Jersey. Individuals, also at Rutgers University, studied the faunal remains with many of the difficulties that I encountered, though less severe in nature.

The analysis also struggled with undocumented excavation and the degradation of some material. Although working with fewer fragments, the fragments from the Volk Collection were much more complete and allowed an analysis with more depth, though less breadth than mine, and a focus on subsistence strategies [11]. Possibly if the missing numbered fragments from the Pennella Faunal Collection can be recovered a deeper and more complete analysis can occur.

Spring 2014 | Rutgers Science Review | 29

8 V.

ACKNOWLEDGEMENTS

I would like to thank the staff at the New Jersey State Museum Bureau of Archaeology and Ethnology, especially Jessie, Greg, and Dave, for their support throughout my work. I would also like to express my gratitude to the Douglass Residential College Alumnae Association

[1] Anderson, W. D. (n.d.). Knobbed Whelk, Busycon carica.

[2] Behrensmeyer, A. K. (1978). Taphonomic and ecologic information from bone weathering. Paleobiology, 4(2), 150162.

[3] Cruz-Uribe, K., & Klein, R. G. (1986). Pascal Programs for Computing Taxonomic Abundance in Samples of Fossil Mammals. Journal of Archaeological Science, (13), 171187.

[4] Eversole, A. G., Anderson, W. D., & Isely, J. J. (2008). Age and Growth of the Knobbed Whelk Busycon carica (Gmelin 1791) in South Carolina Subtidal Waters. Journal of Shellfish Research, 27(2), 423426. doi:10.2983/0730-8000(2008)27[423:AAGOTK]2.0.CO;2 [5] Fenn, M. E., Huntington, T. G., Mclaughlin, S. B., Eagar, C., Gomez, A., & Cook, R. B. (2006). Status of soil acidification in North America. Journal of ForestScience, 56, 313.

[6] Fisher, J. W. (1995). Bone Surface Modifications in Zooarchaeology. Journal of Archaeological Method and Theory, 2(1), 768.

[7] Gowland, R. L., & Chamberlain, A. T. (2005). Detecting plague: palaeodemographic characterisation of a catastrophic death assemblage. Antiquity, 79(October 2003), 146157.

[8] Klein, R. G., & Cruz-uribe, K. (1984). The Analysis of Animal Bones from Archaeological Sites. Chicago: University of Chicago Press.

[9] Landon, D. B. (2005). Zooarchaeology and Historical Archaeology: Progress and Prospects. Journal of Archaeological Method and Theory, 12(1), 136. doi:10.1007/s10816-005-2395-7 [10] Leavitt, D. F. (2010). Biology of the Atlantic Jacknife (Razor) Clam (Ensis directus Conrad , 1843). Northeast Regional Aquaculture Center, (217), 15.

[11] Lore, R. J., & Cushman, L. D. (2009). A Middle Woodland Period Pit and Prehistoric Subsistence: Faunal Remains from 28-Me-16. Archaeological Society of New Jersey Bulletin, 66, 2634.

[12] Mann, R., & Roegner, G. C. (n.d.). Hard Clam: Mercenaria mercenaria (pp. 117). Gloucester Point, Virginia: Virginia Institute of Marine Science.

[13] Mounier, A. (2001). Stage I Archaeological Survey of Block 326.01, Lots 8.04-8.14 Little Egg Harbor Township Ocean County, New Jersey.

[14] Nel, T. H. (2007). Analysis of tortoise size. Nyame Akuma, (68), 5261.

[15] Olsen, S. J. (1960). Post-Cranial Skeletal Characters of Bison and Bos. Papers of the Peabody Museum of Archaeology and Ethnology, 35(4), i15.

[16] Olsen, S. J. (1965). Mammal Remains from Archaeologi-

30 | Rutgers Science Review | Spring 2014

and the Aresty Research Center for providing me with research funding to travel to Trenton. Finally, I want to thank my advisor, Dr. Jason Lewis, for his invaluable guidance and advice throughout my research.

Edited by Stephanie Marcus and Alexandra DeMaio.

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Olsen, S. J. (1974). Osteology for the Archaeologist: The American Mastodon and the Woolly Mammoth, North American Birds: Skulls and Mandibles, North American Birds: Postcranial Skeletons. Papers of the Peabody Museum of Archaeology and Ethnology, 56(3,4,5).

Parris, D. (1981). Pennella Faunal Analysis. Unpublished raw data.

Perez, E. K. E., & Cordeiro, J. R. J. (2008). A Guide for Terrestrial Gastropod Identification. Carbondale, IL: Southern Illinois University.

Power, A. J., Selers, C. J., & Walker, R. L. (2009). Grrowth and Sexual Maturity of the Knobbed Whelk, Busycon carica (Gmelin, 1791), From a Commercially HArvested Population in Costal Georgia. Occasional Papers of the University of Georgia Marine Extension Service, 4, 129.

Stanzeski, A. J. (1996). Two Decades of Radiocarbon Dating from the New Jersey Shore. Bulletin of the Archaeological Society of New Jersey, 51, 4152.

Steele, T. E., & Klein, R. G. (2005). Mollusk and tortoise size as proxies for stone age population density in South Africa: Implications for the evolution of human cultural capacity. MUNIBE, 49(57), 221237.

Thomas, R. A., & Stanzeski, A. J. (2001). Archaeological Investigations at a Portion of the Pennella Site 28OC60 Willis Creek, Ocean County, New Jersey Principal.

Ubelaker, D. H. (1997). Human Skeletal Remains from the Pennella Site, Ocean County, New Jersey. Bulletin of the Archaeological Society of New Jersey, 52, 9296.

Von Den Driesch, A. (1976). A Guide to the Measurement of Animal Bones from Archaeological Sites. Peabody Museum Bulletins, Bulletin 1.

Walker, B. R. L., Power, A. J., Sweeney-reeves, M., Covington, E., Mitchell, M., & Recicar, T. (2008). Growth, Migration, Population Structure and Sex Ratio of Four Whelk Species (Family Melongenidae) Within Wassaw Sound, Georgia. Occasional Papers of the University of Georgia Marine Extension Service, 1, 152.

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Characterization of Microwave Plasma in Chemical Vapor Deposition Ajay Kashi1 and Kevin Chen2 2

1 Rutgers University Johns Hopkins University

The extraordinary tensile, thermal, and electrical properties of carbon nanotubes have made them a popular research subject. Microwave-plasma-enhanced chemical vapor deposition is one process used to synthesize these nanoparticles. In this study, a system was engineered for producing carbon nanotubes, applying Ar plasma generated within a 2.45 GHz microwave oven at vacuum conditions to a CH4 precursor. Plasma can be generated between 300 mTorr to 1.10 Torr in Ar and N2 environments. Visible and UV-range optical emission spectroscopy (OES) and diagnostics with a double symmetric Langmuir probe are used to analyze the deposition and plasma parameters. For regulation of the CVD process, the effect of gas composition on nanotube growth was studied. OES allowed the investigators to track the relative concentrations of neutral and excited species of Ar, N2 , and H2 . In addition, the rotational and vibrational temperatures of the plasma were computed with respect to bands in the second Positive Nitrogen System (C3 Π - B3 Πg ) to be 2100 K (±200 K) and between 4700 K 5700 K, respectively. Raman spectroscopy was carried out at Horiba Scientific and the Princeton Plasma Physics Laboratory to detect the presence of nanoparticles deposited onto the surface of the SiO2 substrates present in the reaction chamber.

I.

INTRODUCTION

Carbon nanotubes are allotropes of carbon that possess a hollow cylindrical nanostructure composed of sp2 hybridized bonds. Nanotubes can be single-walled or multi-walled and can behave like either semiconductors or metals, depending on their number of walls, diameters, chiral angles, and lengths. Individual nanotubes naturally align themselves into “ropes,” held together by π-stacking van der Waals forces. Owing to their extraordinary thermal conductivity and electrical and mechanical properties, they are valuable as an industrial material for building a variety of devices in computer, telecommunication, and medical industries. [1–3]. The deposition of these particlesis in high-energy processes such as thermal chemical vapor deposition and arc discharge, which involve temperatures spanning 700◦ C and 1000◦ C. The high temperatures required make nanotube synthesis very costly and unsuitable for large-scale production. Current systems cost up to tens of thousands of dollars. Microwave plasma-enhanced chemical vapor deposition offers a promising alternative method of depositing these particles by operating at lower temperatures (100◦ -500◦ C), thereby cutting heating and energy costs for large-scale production [4–6]. In addition, microwave plasma (generated in industrial microwave reactors) has been shown to produce carbon nanotubes over large areas in even distributions, potentially allowing for more precise control over the growth process [7]. The plasma itself is an electrodeless gas plume formed by microwaveinduced ionization. Operating under vacuum conditions, free electrons in the remaining air of the reaction chamber are quite far apart from one another. When a gas such as argon (Ar) is introduced into the chamber and the microwave is turned on,these electrons become excited by the alternating electric field and accelerate over a long mean free path, eventually elastically colliding with the Ar atoms. Through the elastic collisions that oc-

cur, the atoms either become excited or ionized, emitting electrons. More frequent collisions occur, causing the Townsend avalanche effect and producing plasma [5].

The chemical vapor deposition (CVD) process occurs via the decomposition of the CH4 precursor when stricken by the Ar plasma into its component C and H radicals.

The H radicals may diffuse into the reaction chambers walls, combine with O2 from the remaining air to form stable HOH, or be removed by the constant vacuum.

The C radicals are bombarded onto either the borosilicate walls of the chamber or onto SiO2 substrates placed on the chamber. SiO2 has been conventionally chosen as the preferred substrate material, as opposed to pure Si in order to avoid the silicidation reactions that occur with nonmetals. The C radicals continually build over one another, contributing to the growth of nanoscale, rod-like structures. The optimal method of carbon nanotube growth requires the presence of a transitionmetal-based catalyst sputtered onto the substrate. The metal particles are uniformly distributed over the surface of the substrate and act as the foundation on which carbon radicals deposit. Two methods have been proposed for nanotube growth based on substrate-catalyst interactions: the tip-growth model and the base-growth model [3]. In the tip-growth model (a), the substratecatalyst interaction is weak, resulting in the metal particles directing vertically-aligned carbon nanotubes underneath between the substrate and the catalyst. In the base growth model (b), the substrate-catalyst interaction is strong, resulting in carbon nanotube growth starting from a base composed of the catalyst partially diffused into the substrate [3, 6–9]. Diagnostics of plasma conditions require that the mode of analysis not disturb the plasmas behavior during the CVD process. One method of analysis used in this experiment is optical emission spectroscopy (OES). OES is used to analyze the gas composition present within the reaction chamber by splitting the UV and visible atomic and molecular radiation emitSpring 2014 | Rutgers Science Review | 31

2 ted by the plasma into distinct lines and bands, plotted by wavelength against intensity. The operating assumption is that the relative intensities of the line and band spectra are directly correlated with their relative concentrations inside the chamber. While atoms occurring naturally in the atmosphere fall in the visible range, molecules and other atoms fall in the UV range [10, 11].

Because of molecular vibrational and rotational motion, molecules exhibit band spectra as opposed to the line spectra exhibited by atoms. Each vibrational level contains rotational sublevels across which electron transitions occur. Under low resolution spectroscopic measurements, the close proximity of these transitions produces band formations. In addition to qualitatively estimating the composition of the chamber based on the relative concentrations of the gases present (controlled by their respective flow rates and the total pressure), OES allows characterization of the plasma itself in terms of its molecular and electron temperatures. Diatomic molecules such as N2 and O2 frequently occur in plasma emission, and can be treated as anharmonic oscillators, so that the energy of a vibrational stateis dependent on the particular vibrational quantum number = 1,2,3,4. Vibrational energy states can still however be approximated by treating the diatomic as a simple harmonic oscillator.

Rotational motion accounts for the energy of collisional molecules in a plasma, and thus the rotational temperature parameter gives an accurate estimate of the overall gas temperature. Because microwave plasma is in local thermal equilibrium, it can be assumed that the electrons follow a Maxwellian electron energy distribution function (EEDF) and that excitation in a plasma occurs solely due to electron collisions. Under these principles, electron temperature is directly related to the vibrational excitation temperature parameter obtainable from spectral information [12]. A second mode of analysis used in this experiment is Langmuir probe diagnostics using a double symmetric Langmuir probe. A Langmuir probe extends into a plasma and draws current when acted on by an AC voltage source, and can be used to compute the electron temperature and electron density parameters of the plasma by generating a plot of its I/V characteristic.

Double Langmuir probes offer the advantage of lessening disturbance to the plasmas behavior because the probe voltages are biased against each other, and not toward the ground. From an ideal I/V curve as the one presented below (modeled by a hyperbolic tangent function), electron temperature can be calculated from the saturation current:

qVbias I = Isat tanh .

(1) k B Te Electron density can be computed with the expression

I 1 M ne = exp − , (2) qAs 2 k B Te where As is the sheath area of the probe, and M is the ion mass [13–15].

32 | Rutgers Science Review | Spring 2014

II. EXPERIMENTAL DESIGN/METHODOLOGY

The system used to generate plasma and conduct the CVD procedure consists of a borosilicate glass chamber embedded inside a household 2.45 GHz microwave oven, connected to an oil pump vacuum and several gas connections.

A.

Microwave Diagnostics

The walls of the microwave oven were first stripped of their outer layers, and holes were drilled through the back (to accommodate the chamber) and through the side (to accommodate tubing). The next task was to determine the location inside the microwave wherein the chamber would experience the greatest intensities of microwave radiation due to constructive interference, or field maxima.

The wave density distribution of the oven was mapped out by layering sheets of mini marshmallows over one another, and then cooking them for 1-2 minutes. Areas where the marshmallows cooked the most corresponded to the areas of field maxima. The main region was found to be 16.5 cm from the left wall, 12.3 cm from the front wall, and 4 cm above the base. The chamber was positioned in this region for deposition. The result of the microwave test is displayed below, along with two other numerical simulations of a common household microwave with which it is compared.

B.

System Engineering

The experimental system, built in the first year of work, was set over a utility cart. The reaction chamber, which contains four ports, was placed through the back of the microwave oven such that only half of the chamber was exposed to the radiation. PFA tubing, valves, and standard Teflon adapters were used for allgas/vacuum connections. In the original design, tubing connected the front-end port to the vacuum pump. Tubing ran from the side ports to the individual gas sources, with the back port closed off. The total pressure of the chamber was monitored using a thermal conductivity gauge connected to the vacuum. Flowmeters and valves were installed along each gas line to regulate flow. The gas line extending from the Ar tank was hooked to a flowmeter reading in SCFH (standard cubic ft/hr), while the gas line extending from the natural gas inlet was connected to a flowmeter reading in sccm (standard cubic cm/min).

By the second year of work, modifications were made to improve experimental conditions. To carry out the CVD procedure along with OES and Langmuir probe diagnostics, the four ports of the chamber needed to be redesignated to include the fiber optic setup and the Langmuir probe. The investigators included a double T-joint that would merge the flows of Ar and CH4 before they entered

3 the chamber, thereby using only one of the side ports.

This however still allowed the two gases to be controlled by their respective flowmeters.

The entire cart was surrounded by a Faraday cage, used to isolate the internal electric field of the microwave from the external field, thereby preventing microwave leakage. The cage consisted of a poplar wooden frame and base entirely covered with copper mesh. Contact between the frame and base was ensured by using buckled cargo straps, copper tape, and duct tape. The whole cage was then grounded to a pipeline. When the cage was exposed to the microwaves, the electrons of the copper mesh were rearranged in response, isolating the internal and external electric fields. Before beginning the CVD process and/or modifying the setup, the Faraday cage was fastened, and a microwave leakage detector was used to pick up and seal off radiation along the edges.

Less than 0.5 MW/cm3 was picked up across the four edges of the cage. To access the microwave ovens buttons that lay inside the cage in order to turn it on, a foam block was put in place at a set distance between the cage and the microwave. Chopsticks were driven through the foam block in order to make contact with the buttons from the outside of the cage. To modify this and make a more permanent fixture, the investigators replaced the foam block with a block made of ABS plastic with holes drilled through it and chopsticks placed through them to access the designated buttons.

C.

Vacuum Testing Procedure

To achieve vacuum, each connection along the gas lines running to the chamber needed to be sealed tightly without distortion of the fittings. Teflon tape and O-rings were used to supplement the seal of the adapters used on the chamber. At the beginning of the vacuum testing procedure, the gauge was recalibrated to 760 Torr to match atmospheric conditions. When the vacuum was turned on, the pressure was brought down by turning the valve knob, thereby expanding the volume of the pump cylinder. The chamber reached its base pressure at maximum expansion. As the pressure decreased, isopropyl alcohol, a sufficiently volatile fluid, was dripped onto the connections of the chamber in order to check for sources of leakage. Via continuous vacuum testing and tightening of connections, the lowest base pressure reached for the chamber was 35.2 mTorr.

D.

Gas Flow Procedure/Plasma Generation 1.

Ar Plasma

When the chamber had reached a pressure of about 300 mTorr, Ar was introduced through copper and PFA tubing that extended from the chained Ar tank and was regulated via a rotary pin valve and the adjoining SCFH

flowmeter. Initially, the chamber was flooded with an abundance of Ar, such that the total pressure rose to about 10-20 Torr. The chamber was then closed off and evacuated. The pressure was then brought up again by increasing the flow rate of Ar to above 5 SCFH. Because Ar has a greater atomic weight than N2 and O2 (which are the predominant gases found in air) and flowed at high velocities from the pressurized tank, the process of evacuating and filling was used to push out as much of the remaining air as possible in order to make the composition inside the chamber as Ar-concentrated as possible for plasma formation. The flow rate was then brought down to 1.0 to 1.5 SCFH, such that the pressure equilibrated at 400 mTorr. The microwave was turned on, and the plasma was generated for two- to five-second durations (to avoid burning the connections and tubing). The Ar plasma consistently appeared to have a bright blue and white glow. The chamber was allowed to cool before the plasma was generated again. OES in the visible and UV ranges was conducted for analysis.

2.

N2 Plasma

In our second year’s work, it was found that plasma could be generated within just the existing air of the chamber after the vacuum was pulled to 400 mTorr.

Both gas lines were closed off, and the plasma formed in a bright purple glow that expanded to encompass the length of the chamber inside the oven. Based on flow rate and, later, spectroscopic measurements, the pressure range for the N2 plasma was determined to be between 200 mTorr and 1 Torr.

E.

CVD Procedure

In starting the chemical vapor deposition procedure, the chamber was first cleaned thoroughly using staticfree wipes and isopropanol solution. Substrates were then inserted along the length of the chamber - first bare Si wafers and then SiO2 wafers in the form of sterile, wellfree microscope slides. An additional wafer was added that had been sputtered with TiO2 catalyst. After all system connections were tightened and the Faraday cage was fastened, the chamber was placed under vacuum again. The chamber was evacuated again to base pressure and refilled with Ar at the same flow rate to reach 450 mTorr. After the evacuating and refilling procedure was repeated several times, CH4 was then introduced at 35 sccm, and the total pressure is regulated to be in the range of 450-600 mTorr. OES was run simultaneously to characterize the composition of the chamber. The microwave was then turned on and the plasma was run for two to five seconds. During the first year of work, over 64 deposition cycles were conducted along with OES analysis simultaneously. During the second year, 20 more deposition periods were performed in different flow rate and Spring 2014 | Rutgers Science Review | 33

4 pressure conditions to study the effects spectroscopically.

After the first phase of deposition trials, the substrates were taken out of the chamber, packaged into Petri dishes and sent to the Princeton Plasma Physics Laboratory for Raman Spectroscopy analysis to detect the presence of deposited carbon nanoparticles.

F.

OES Procedure

Optical emission spectroscopy was conducted in the visible and UV ranges for all plasma conditions. The setup involved an Ocean Optics fiber optic cable connected to a computer and spectrophotometer (calibrated to the specific range) interface, through which SpectraSuite software was run. SpectraSuite was used to plot the intensities of the gas emissions as a function of their respective wavelengths in real-time during plasma formation.

1.

Initial Setup

In the initial setup, the fiber optic cable was oriented toward the light emitted by the plasma and positioned over the chamber from the outside the microwave. However, owing to the low transmittance of UV rays through borosilicate glass, the first UV spectra of the Ar plasma and of the Ar-CH4 deposition mixture were produced in low intensities, giving a less accurate view of the molecular gas composition inside the chamber.

2.

Switch to Direct Fiber Optic Assembly

To solve this issue, the investigators engineered an assembly that would position the fiber optic cable directly into the deposition chamber. The tip of the fiber optic was secured inside a Teflon cylinder that housed an MgF quartz window. The window was placed in front of the fiber optic in order to protect the fiber from the plasma or carbon deposition, but still ensured high UV transmittance. Two compression fittings set over a #25 adapter were used to secure the cable tightly and ensure that the chamber was still vacuum-sealed. Additionally, the outer edge of the cable was covered with heat-shrink tubing for a stronger seal.

G.

Langmuir Probe Construction 1.

Probe Design

A double symmetric Langmuir probe was built to act as a secondary means of plasma characterization. Two tungsten rods 12 mm in length and 0.84 mm in diameter were chosen for their high melting points. The probe tips were shielded in a ceramic casing to ensure that 34 | Rutgers Science Review | Spring 2014

the current collected by the probe only flowed through the tips of the probe. Adhesive powder was mixed with water to form a paste, which was used to form an insulated connection between the ceramic casing and the probe tips. The length of the tip exposure was 5 mm, two times longer than the width of the ceramic casing to minimize the electron shadowing effects on the probe body during current collection [16]. The probe can be considered to have a collisional sheath since the mean free path was smaller than the sheath, which is smaller than the probe radius [17]. The double Langmuir probe was then built into the deposition chamber with compression fittings and a side-port #7 adapter. The probe tips were then soldered to the probe circuit.

2.

Probe Circuit

The probe circuit was used to provide an AC signal to the tips in order to draw in current from the plasma.

The network included a function generator, an oscilloscope, resistors, and isolation transformers. The input signal from the function generator provided the bias voltage sweep between the probes. The loop containing the probe tips was isolated from the function generator via an isolation transformer so that the loop that included the probe tips remained ungrounded. Within the loop there were also two additional connections to isolation transformers where the output signal for the probe voltage and probecurrent were displayed on the oscilloscope as a function of the voltage drop across the resistor. The display of the oscilloscope was set to Channel 2/Channel 1 to display the I-V characteristic of the plasma.

III. A.

RESULTS/DATA ANALYSIS

Raman Spectroscopy/CVD Analysis

At the beginning of our second year of work, Raman spectroscopy results were delivered back to the lab after the analysis of the Si and SiO2 substrates. Raman spectroscopy relies on Raman scattering of a visible, nearinfrared laser beam to pick up molecular vibrations based on the frequencies of the up or down shifts in the energies of laser photons. Raman spectroscopy provides both mechanical and electronic information about the carbon nanotube lattice, as well as about the imperfections that occur over the surface [18, 19]. Analysis of the substrates yielded no evidence of carbon particulate matter deposition, including the one sputtered with TiO2 . However, a noteworthy observation was the clouded, discolored appearance of the chamber walls after the allotted deposition period.

5 B.

OES Visible/UV Spectra

The main results obtained from the experiment came from the spectra obtained through visible and UV-range OES. The OES procedure with the placement of the fiber optic cable inside the deposition chamber was conducted on both the N2 and Ar plasmas before and during the deposition process, with the inclusion of CH4 . An observation to note in the spectra below is the higher relative intensity distribution, as compared to the spectrum resulting from direct UV exposure. All spectra were referenced to NIST and The Identification of Molecular Spectra (Pearse and Gaydon [11]).

C.

Determination of Plasma Temperatures 1.

Rotational Temperature

G(ν ) = ωe

1 ν + 2

+ωe ye

− ω e xe

1 ν + 2

3

1 ν + 2

(3)

+ ...,

where ν is the upper wave number ωe = 0.253818 eV, ωe xe eV, and ωe ye = 2.5892 ×10−4 eV . This relation assumes that N2 behaves as an anharmonic oscillator.

The function for the Boltzmann plot is given by

I ln , (4) f Aik

(5)

Langmuir Probe: Testing and Operation

Preliminary testing with the probe circuit positively demonstrated a 30 VAC bias voltage between the probes using a function generator and isolation transformers.

When the probes were connected, a linear I-Vgraph was produced on the oscilloscope. Continuity to the probe tips from the circuit was tested for and confirmed using a multimeter. When the probe was installed into the chamber and N2 plasma was generated, the Langmuir probe reached the peak bias of 30 VAC but collected very minimal current. Furthermore, no hyperbolic-tangent-shaped graph was produced on the oscilloscope.

IV.

2

1 . k B Tν

Two Boltzmann plots were constructed from data taken from the N2 bands that occured between 349 and 357 nm and 394 and 406 nm. Under 300 ms integration and corrected shifts, the first plot gave a slope of -2.528 with a correlation of -0.9208, which gives a temperature value of 4750 K, or 0.394 eV. The second plot gave a slope of 2.028 with a correlation of -0.9999, which gives a temperature of 5720 K, or 0.493 eV.

Vibrational Temperature

The vibrational temperature of the electrons in the plasma was found by generating a Boltzmann plot, which extracted the intensity and wavelength data of the three heads in a particular N2 band, and graphed the natural log of the intensity and other parameters as a function of the upper energy states under Maxwellian assumptions.

Specifically, the upper energy states were found for the three heads of the band by using the relationship:

slope = −

D.

The rotational temperature parameter of the plasma during the deposition procedure was found by applying a curve-fitting Excel macro to compare an experimental triple-headed N2 band (334-339 nm) from the second Positive system to a theoretical counterpart. The program takes into account N2 s characteristic vibrational and rotational behavior, namely its upper and lower vibrational levels, Jmax value (transition probability between rotational sublevels), and λ quantum number. As seen below, the rotational temperature computed was 2100 K (0.18 eV).

2.

where I is the intensity, f is the frequency at the given wavelength, and Aik is the transition probability as defined by the lower and upper wavenumbers. Vibrational temperature is calculated from the negative inverse slope of the plot:

A.

DISCUSSION

Absence of Deposited Carbon

The negative results of Raman spectroscopy indicate several reasons why carbon nanoparticles did not appear on any of the substrates tested. The most likely justification is that CVD is entirely catalyst- and timedependent. Because the process was run for two- to five-second intervals (10 seconds at the very maximum stretch) over the course of a few months, it would have been very unlikely that insufficient continuous time caused the carbon radicals to deposit and form a layer over the TiO2 -sputtered wafer that would have been detected by the laser beam. Literature suggests that most microwave reactors require at the very minimum, 10 minutes of continuous deposition [3–5]. Another possible explanation is the position of the substrate. While substrates did line the chamber, this only accounted for position in two dimensions. The clouded region on the walls of the borosilicate chamber suggests that the substrate position is farther away from the center of the plasma.

Raman spectroscopy may be conducted in the future over the chamber walls to draw a conclusion from this observation. A third possible factor is CH4 concentration. In the Spring 2014 | Rutgers Science Review | 35

6 last set of deposition trials, the methane concentration dramatically increased, and the microwave remained on for as long as the plasma could sustain itself. Ar plasma accounts for etching effects on the chamber, and so naturally, the rate of deposition must have been greater than the rate of etching considering that net carbon particles appeared.

B.

OES Results/Effect of Pressure onPlasma Generation 1.

Gas Composition

The results seen above from the visible/UV spectra taken show primarily heavy traces of Ar in the visible range and N2 in the UV range. This suggests the need either to continue evacuating the chamber before adding Ar, or to increase its flow rate to compensate for the remaining air. If this is not done, the plasma that forms will be a mixture of N2 and Ar plasmas, as both have been observed in the system individually. The increased intensities of H2 and H species when CH4 is introduced is however a promising sign that decomposition is in fact occurring, yielding C radicals. Reference tables of molecular spectra have invalidated the initial hypothesis that the unknown band that formed in part of the N2 band occurring between 380 and 390 nm was CH. This would have evidenced a two-step decomposition mechanism of CH4 in producing C radicals. However, the next closest band formation found in the tables was CO from the Herzberg System. Further comparisons and reading will be done to determine exactly what this is, and to distinguish it from the adjacent triple-headed N2 band.

2.

Time Limit to Plasma Generation

During the second year of our work, we increased the time that the microwave oven was on from two-second intervals, to eight-second intervals. Whether the plasma was formed in N2 or Ar, at higher pressures, it died off before the oven was turned off. This was observed spectroscopically from the fact that the intensities decreased sharply over the period during which the plasma sustained itself.

The main cause of this phenomenon is the fact that at higher pressures, the numerical density of ions and electrons in the plasma increases, causing the outer skin of the plasma to behave like a conducting surface, thereby reflecting incident microwaves, and thus losing ionization energy. The underlying speculation is that the rate of decay is proportional to the relative shift in the intensity distribution.

36 | Rutgers Science Review | Spring 2014

C.

Temperature Parameters

The rotational temperature calculated for the plasma during deposition was 2100 K. This value will need to be reevaluated as several authors have described low pressure microwave plasmas in ambient conditions. The vibrational temperature values calculated using the two N2 bands (0.394 eV and 0.493 eV) correspond very closely to each other, establishing a range for the average distributed energy among electrons according to Maxwellian conditions. However, electrons in this system appear to be very cold in the sense that literature values report a minimum of 0.8 eV [24]. This suggests a higher electron density in the plasma.

D.

Langmuir Probe Diagnostics

The Langmuir probe constructed was not able to generate a current-voltage graphfrom the plasma. The probe may have failed to collect current because the frequency of the input signal from the function generator was too low, or because the resistance in the circuit was too high.

The probe also may not have been in contact with the plasma as the probe tips were located outside the microwave oven, and the plasma appeared to be contained within the portion of the glass chamber that remained inside the oven. Future results might come from increasing the sweep frequency to a range between 100-500 MHz and/or reducing resistance in the circuit.

V.

CONCLUSION

The work presented herein was intended to investigate the deposition of carbon nanotubes via microwaveplasma-enhanced chemical vapor deposition and the parameters of the plasma itself. While carbon nanotubes were not synthesized in this work, key information regarding Ar microwave plasma was found using optical emission spectroscopy and Langmuir probe analysis techniques. The gas composition of the Ar-CH4 deposition environment was predominated with excited species of Ar and H2 as well as with N2 from the residual air.

Based on collected emission data, the rotational temperature of N2 in the gas mixture was calculated as 2100 K (0.18 eV) while the vibrational electron temperature of the plasma was found to be in the range of 4700-5700 K (0.39-0.49 eV). The constructed Langmuir probe successfully generated a sweep of Âą 30 VAC but was unable to draw in current from the plasma. In the future, evidence of carbon particles will be investigated on the chamber walls with Raman spectroscopy with further allotted deposition time. The use of other catalyst materials will be a secondary goal to aid in the deposition process, including experiments designed to test different silica-nonmetal complexes in finding appropriate substrate material. In addition, more spectra will be

7 collected and cross-referenced to observe other species present in the chamber. Modifications will be made to the existing probe circuit in order to reduce resistance and increase the frequency of the signal bias provided between the probes.

VI.

tion of this project. Funding and resources were provided

by Watchung Hills Regional High School.

ACKNOWLEDGEMENTS

Sincere thanks to Dr. Sophia Gershman for advice, instruction, and guidance throughout the two-year dura-

Edited by Stephanie Marcus and Alexandra DeMaio.

[1] J. Prasek, Mater et al. Methods for carbon nanotube synthesisreview. Chem., 2011, 21, 15872.

[2] Kossler, Maruicio et al. Patterning and Characterization of Carbon Nanotubes Grown in a Microwave Plasma Enhanced Chemical Vapor Deposition Chamber. Air Force Institute of Technology. 2009.

[3] Kumar, Mukul et al. Chemical Vapor Deposition of Carbon Nanotubes: A Review on Growth Mechanism and Mass Production. Journal of Nanoscience and Nanotechnology. 2010.

[4] Crossley, Benjamin et al. Characterizing Multi-Walled Carbon Nanotube Synthesis for Field Emission Applications. Air Force Research Laboratory.

[5] Bogaerts, Annemie et al. Gas discharge plasmas and their applications.Spectrochimica Acta Part B 57.June 6 2002.

[6] Choi, Young et al. Growth of carbon nanotubes by microwave plasma-enhanced chemical vapor deposition at low temperature. American Vacuum Society. 2000.

[7] Qin, L.C. et al. Growing carbon nanotubes by microwave plasma-enhanced vapor deposition. Applied Physics Letters. 1997.

[8] Meyyappan, M et al. Carbon nanotube growth by PECVD: a review. Institute of Physics Publishing. April 2003.

[9] Homma, Yoshikazu et al. Role of Transition Metal Catalysts in Single-Walled Carbon Nanotube Growth in Chemical Vapor Deposition. J. Phys. Chem. 107, 1216112164.2003.

[10] Goto, Motoshi: National Institute for Fusion Science. Introduction to the plasma spectroscopy.

[11] Pearse, R.W.B. and Gaydon, A.G. The Identification of Molecular Spectra. John Wiley & Sons, Inc., New York.

[12] Gershman, Sophia and A. Belkind. Plasma Diagnostics Part 2: Optical Emission Spectroscopy. Vacuum Tech-

nologies & Coating. July 2009.

[13] Chen, Francis. Lecture Notes on Langmuir Probe Diagnostics. Electrical Engineering Department, University of California, Los Angeles. 2003.

[14] Talukder, M. Diagnostics of High Pressure Microwave Discharge Plasma by Langmuir Probe. Journal of Bangladesh Academy of Science Vol. 29. 2005.

[15] Rousseau, A. Langmuir probe diagnostic studies of pulsed hydrogen plasmas in planar microwave reactor.

[16] Chen, Francis et al. Calibration of Langmuir Probes Against Microwaves and Plasma Oscillation Probes.

Electrical Engineering Department, University of California, Los Angeles. 2012.

[17] Furno, Ivo et al. Theory of electrostatic probes. cole Polytechnique, Fdrale De Lausanne. 2012.

[18] Dresselhaus, M.S. et al. Raman spectroscopy of carbon nanotubes. Physics Reports 409 4799. 2005.

[19] Dresselhaus, M.S. et al. Raman spectroscopy on isolated single wall carbon nanotubes. Carbon 4020432061. 2002.

[20] Herzberg, G. Molecular Spectra and Molecular Structure I. Spectra of Diatomic Molecules. 2ndedition. Van Nostrand. New York. 1950.

[21] Steinfeld, J.I. Molecules and Radiation, An Introduction to Modern Molecular Spectroscopy. 2nd Edition. MIT Press, Cambridge. 1986.

[22] Lofthus, Alf and Paul Krupenie. Spectrum of Molecular Nitrogen. J. PHys. Chem. Ref. Data, Vol 6, No. 1. 1977.

[23] Ding, Guowenet al. Effects of rapidly decaying plasmas on Langmuir probe measurements.Journal of Applied Physics84.3,1236-40.1998.

[24] Gershman, Sophia. 4.4. Discharge Investigation Using Emission Spectroscopy (from Dissertation). Rutgers University.

Spring 2014 | Rutgers Science Review | 37

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