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Bridget Murray
Professor Casey Barrier

A Geographic & Geophysical Analysis of Mississippian Archaeology in the American Bottom

The archaeological region of the United States known as the American Bottom, located east of the Mississippi River in Illinois, was the first site of urbanization in North America and has been studied largely via government-mandated cultural resource management (CRM) surveys at proposed construction sites since the 1970s. Part I of this project contextualizes these extensive surveys (numbering 500-600 for the counties included) as I build from scratch a geographic information system (GIS) database compiling site information (use, time period, size) and survey report details obtained through an Illinois CRM database. This database will enable analysis of settlement patterns from the Late Woodland thru Mississippian periods (A.D. 600-1350) along attribute and spatial parameters, the latter of which is particularly significant for describing the composition of an archaeologically dense area such as the American Bottom.

Part II of this project focuses specifically on the site of Cahokia through a series of geophysical surveys studying effects of early urbanization on the landscape. Other American Bottom sites show a period of settlement aggregation followed by rapid decline in the centuries prior to the period of growth this study addresses. This period, concurrent with maize domestication, will likely be marked by population clustering evident in habitation sites and farmsteads. Geophysical surveys using magnetic readings and ground penetrating radar (GPR) detect soil anomalies, producing maps showing features such as houses, fences, and fire pits which we would expect to see in a growing settlement. This information may be incorporated into the system developed in the first part of this project and analyzed alongside other American Bottom sites. 

Grisilda Bakiasi
Advisor's name: Gregory Davis

JH Regulation

In the G. Davis laboratory we study the evolution of development using the pea aphid, Acyrthosiphon pisum, as a model organism. The pea aphid is famous for its phenotypic plasticity. In one example, when exposed to short nights mothers produce embryos that will develop as asexual females, whereas when exposed to long nights mothers produce embryos that will develop as sexual females. A candidate for mediating this process is the insect hormone, Juvenile Hormone (JH). JH is best known for its role as a status quo hormone which determines the state of the aphid after each molt during development; if there are high levels of JH at molting the individual remains a nymph, and if there are low levels of JH the individual becomes an adult. In the context of reproductive fate JH is thought to induce the asexual fate: topically applied, JH can transform embryos that should have developed as sexual aphids into asexuals; additionally, JH titers inversely correlate with night length.Together this evidence suggests that JH mediates the induction of asexual fate under short night conditions. However, it remains unclear how JH titer is regulated by photoperiod.  This summer, in order to gain knowledge of how JH is regulated, I will look at the expression of pea aphid orthologues of genes known to regulate juvenile hormone. Some of these genes are JHAMTs, which catalyze the last step in the synthesis of JH. Others are JHEs which are known to degrade JH. I will examine expression of these genes in both mothers and embryonic progeny, under photoperiods promoting both sexual and asexual fates (i.e., long and short nights). Comparing the expression of these genes under these different conditions should reveal the mechanism of regulation.     

Erin Bonner ’17 and Emily Spiegel ’18
Dr. Greg Davis

Evolution of the Photoperiod Response in Pea Aphid Reproductive Polyphenism

We are studying the role of photoperiod response in the evolution of Acyrthosiphon pisum (pea aphid) reproductive plasticity. Pea aphids exhibit a remarkable evolutionary response to the challenges posed by seasonal fluctuations in climate. During warm summer months, female aphids reproduce asexually, allowing them to quickly produce vast numbers of genetically identical offspring. However, as nights grow longer in the fall, aphids switch to sexual reproduction. In response to longer night conditions, they are induced to produce sexual females and males that will mate to lay fertilized eggs. These eggs are durable and frost-resistant, allowing the species to survive through the cold winter months. In the spring, the eggs hatch into asexually-reproducing females, and the cycle continues. By alternating their mode of reproduction in response to seasonal fluctuations in night length, pea aphids are able to maximize their reproductive fitness: they reproduce rapidly and efficiently throughout the spring and summer, and by maintaining the ability to reproduce sexually, are able to survive the cold winter and generate beneficial genetic diversity. Previous research in our lab has suggested that Juvenile Hormone (JH) signaling mediates the switch between asexual and sexual reproduction. It is thought that JH sends an asexual-promoting signal during the spring and summer (short night conditions), thereby specifying asexual reproduction during favorable environmental conditions. The goal of our research this summer is to more critically evaluate the conditions that control this switch in reproductive fate, and to further investigate the role of JH in inducing this switch.

We are first testing the photoperiod response of three strains of aphids in order to ascertain whether strains collected from different latitudinal regions have undergone changes in their response to increasing night length. We will do this by attempting to identify the Critical Night Length (CNL) of each strain, in the belief that different strains will have different CNLs. The CNL refers to the minimum hours of darkness that aphids must be exposed to in order to produce 50% sexual offspring over 5 days. We will test multiple different photoperiods in the different strains, using a newly developed and efficient method: we are building a staggered light box with ten compartments, each of which will simulate a different night length in a 24 hour cycle. The three strains being tested are from Tucson, Arizona; Atlanta, Georgia; and upstate New York. The strain from Tucson does not produce sexuals in its natural habitat, because the warmer temperatures and less severe winters mean that they do not need to produce frost-resistant eggs. It is unknown whether the Georgia strain will produce sexuals. As a result of the latitudinal, and thus climatic, dissimilarities between these locations, it is believed that the more southern strains have evolved over time to require more darkness to induce sexual reproduction, in comparison to the more northern New York strain.This is because it would be disadvantageous for the more southern strains to produce sexuals if the winters were not severe enough to require this mode of reproduction. To support this theory, we aim to show that the CNL for more southern strains is longer, i.e. it requires longer exposure to darkness to induce sexual reproduction.

The second part of our research will involve testing a possible mechanism behind the differences in photoperiod response between the strains. As discussed earlier, JH has been implicated as specifying asexual fate in aphids. We postulate that the probable difference in CNL between the strains may be explained by an increased sensitivity to JH in the southern strains. We are applying Kinoprene, a JH analog, in varying doses to adult aphids, and scoring their progeny for asexual or sexual fate. Previous research from this lab has found a difference in JH sensitivity between Tucson and the New York strain using kinoprene. The Tucson strain was found to be more sensitive to JH, producing a greater percentage of asexuals than the New York strain given the same dosage treatment. This experiment needs to be repeated, and we will also be narrowing the dosage treatments and applying these treatments to the Georgia strain as well. 

Fransheska Clara
Dr. Peter Brodfuehrer

RNA interference analysis of non-NMDA receptors in Leech Swimming

In order to understand the structure and function of the nervous system, the analysis of motor behavior is necessary and has provided some insight, particularly in regard to rhythmic motor patterns (e.g. breathing and swimming). Although research over the last 50 years has provided some understanding into the nervous system, information on the cellular and ionic mechanisms that underlie the production of rhythmic behaviors is limited and not tacit. To overcome this, alternating or removing ion channel function during the expression of the behavior through the use of RNA interference can lead to understanding the roles of these specific ion channels in relation to the expression of the behavior. Knocking down the expression of specific mRNA and proteins can create changes in behavior, which then provides an achievable approach to describing ion channel function in behavior. 

Mian Horvath, Annie DeHart, and Lauren Sauers
Dr. Karen Greif

Effects of Synaptotagmin-1 on Filopodia Formation During Neuronal Development

While neuronal networks are the basis for most functions of many organisms, we have a limited understanding of their mechanisms. Within each neuronal network are thousands of axons, each of which produces many branches. While the lengthening of axons is well characterized, much less is known about the mechanisms behind axonal branching. In Dr. Greif’s lab, we will investigate the potential role a protein called Synaptotagmin-1 (syt1) may play in axonal branching of developing eight-day-old embryonic chick forebrain neurons.

Syt1 is a widely characterized Ca2+-binding protein responsible for vesicular exocytosis at the synapses of neurons. At presynaptic terminals, syt1 works as a calcium sensor within a SNARE complex, which expedites the merging of vesicles to the plasma membrane, and subsequently the release in neurotransmitters, in response to elevated Ca2+ levels. Our working hypothesis is that, in a similar fashion, syt1 merges vesicles to the plasma membrane of a developing neuron’s axon, adding additional membrane to allow for branching. Previous research has provided evidence that a surplus of syt1 leads to increases in the number of axonal branches and filopodia formed during development, while deficits in the protein result in a decrease in such branching. This evidence suggests that the syt1 produced during early development regulates the formation of new branches and filopodia. Filopodia are small extensions along the axon from which branches develop; they are distinguishable by a purely actin cytoskeleton, while branches incorporate microtubules.

To confirm our hypothesis, our experiments will test how overexpression of wild-type syt1 affects axonal branching and filopodia development as compared with a mutant form of sty1, which has impaired Ca2+-binding abilities. We will replicate this experiment with in ovo electroporation to simulate conditions in vitro. After using electroporation to incorporate our plasmids, filopodia formation and syt1 expression will be analyzed using immunocytochemistry techniques and fluorescence microscopy. Depending on the results of the initial experiments, they may be followed by rescue experiments. If the expression of mutated syt1 negatively affects filopodia development, the rescue experiments will investigate whether and how function may be restored to the mutated syt1.

Mandy Levine
Professor Peter Brodfuehrer

Creating expression vectors containing accessory proteins to leech glutamate receptors

The leech is an excellent model organism, widely utilized in the field of neuroscience because it exhibits a variety of distinct behaviors, including swimming, that are easily observed. Previous research has shown that glutamate receptors mediate all of the excitatory synaptic connections in the swim network. One approach to characterizing the role of glutamate receptors in swimming is through expression in Xenopus oocytes. In order to correctly express these glutamate receptors, however, several accessory proteins, including SOL-1 and STG, must also be expressed. The leech transcriptome database was searched for putative coding regions and primers were designed for these regions. Using PCR, postulated protein encoding sequences were amplified from an existing leech cDNA library. These regions were cloned into pGEM-T Easy for sequencing and compared to existing databases. The sequences were then cloned into expression vectors to be expressed in Xenopus oocytes so that glutamate receptors could be accurately studied. Sequences for STG1, STG2, and SOL-1B were isolated, sequenced, and cloned into expression vectors for later use. Based on BLAST searches, it is likely that these sequences do in fact code for the accessory proteins necessary for proper glutamate receptor activity and therefore, once cloned into expression vectors, will be useful in studying glutamate receptors in Xenopus oocytes.

Blanca Lopez
Dr. Peter Brodfuehrer

Biophysical Properties of AMPA Receptor on Xenopus oocytes

The α-amino-3-hydroxy-5-methyl-4-isoxazolepropionic acid (AMPA) receptors and kainite receptors are non-NMDA receptors which mediate all known excitatory synaptic connections in the leech central pattern generator (CPG). There is not much information about non-NMDA receptors, but by introducing mRNA of AMPA receptors into Xenopus oocytes their properties can be analyzed through two-electrode voltage clamp experiments. Then the distribution and location of AMPA receptors would be determined by in situ hybridization.

Mindy Reutter
Dr. Greg Davis

Measuring Whole-body, Hemolymph and Embryonic Juvenile Hormone Titers in the Pea Aphid

The cyclically parthenogenetic life cycle of the pea aphid Acyrthosiphon pisum involves both sexual and asexual reproduction. The reproductive mode of offspring is determined during embryogenesis within the mother. Previous research correlates long photoperiod (short nights) to high Juvenile Hormone (JH) titers and implicates the level of JH titer experienced by the embryo as the signal that determines whether it becomes sexual or asexual. It is unknown whether it is embryonic or maternal JH that is ultimately responsible for determining the embryo's reproductive fate. Our project aims to quantify maternal JH titers when mothers are producing sexual and asexual progeny, and to quantify embryonic JH titers in sexual and asexual fated embryos. The goal is to identify which sources of JH (maternal or embryonic or both) are correlated with changes in reproductive fate. To do this we will collect JH samples from both mothers and embryos exposed to varying photoperiod conditions. We will send these samples to Dr. Fernando Noriega, our collaborator at Florida International University, for quantitative analysis. Knowing which source of JH is responsible for the shift between reproductive fates will help us to focus our later studies on evolved changes in the response to photoperiod, which we believe to be due to changes in JH sensitivity.

Maritza Vazquez-Trejo
Dr. Greg Davis

Juvenile Hormone Detection in the Pea Aphid

The cyclically parthenogenetic life cycle of the pea aphid Acyrthosiphon pisum involves both sexual and asexual reproduction. The reproductive mode of offspring is determined during embryogenesis within the mother. Previous research correlates long photoperiod (short nights) to high JH titers and implicates the level of Juvenile Hormone titer experienced by the embryo as the signal that determines whether it becomes sexual or asexual. It is unknown whether it is embryonic or maternal JH that is ultimately responsible for determining the embryo's reproductive fate. Our project aims to quantify maternal JH titers when mothers are producing sexual and asexual progeny, and to quantify embryonic JH titers in sexual and asexual fated embryos. The goal is to identify which sources of JH (mother or embryo or both) are correlated with changes in reproductive fate. To do this we will collect JH samples from both mothers and embryos exposed to varied photoperiodic conditions. We will send these samples to Dr. Fernando Noriega, our collaborator at Florida International University, for quantitative analysis. Knowing which source of JH is responsible for the shift between reproductive fates will help us to focus our later studies on evolved changes in the response to photoperiod which we believe to be due to changes in JH sensitivity.

Brittney Beidelman
Dr. Sun
Temple University Chemistry Department

Synthesis of SiO2 Spherical Nanoparticles

Efficient energy conversion is important for increasing the performance of photovoltaic and photocatalyic devices for harvesting solar energy. The addition of metal plasmonic nanoparticles to a semiconductor, like SiO2, helps improve solar energy conversion by generating hot electrons, when in the presence of solar energy. SiO2 is a semiconductor with a large band gap that absorbs in the ultraviolet (UV) range. Since the major portion of the solar spectrum that reaches the surface of the earth is in the visible range, research is being done for new materials that have a high absorption in the visible range. SiO2 has a high electron-accepting capability, which is useful for the absorption of solar energy. Metal plasmonic nanoparticles, such as Cu, Al, Pd, At, and Au, can be added to SiO2 in order to shift the absorption spectrum from the UV into the visible spectrum. SiO2 is almost transparent in the visible region, so any change in absorption can be attributed to the addition of nanoparticles. We will use a modified Stöber process to synthesize the SiO2 particles, which utilizes hydrolysis and nucleation to create the spherical nanoparticles. The goal is to consistently obtain uniform nanoparticles of various sizes in the 200-350nm range and analyze their performance in photocatalysis.

Steffany Chou
Dr. Jason Schmink

Palladium Catalyzed Cross-Coupling of 1,3-Oxathiolanes and Aryl Bromides

Our lab explores palladium catalysis and the development of alternative nucleophiles. The focus of our research this summer will be to optimize the synthesis of aryl vinyl sulfides from the palladium catalyzed cross-coupling reaction of 1,3-oxathiolanes and aryl bromides. Such sulfide compounds are significant in organic chemistry syntheses, and have applications in both pharmaceuticals and materials sciences. We will be analyzing the data of reactions run under varying conditions to find the most efficient methods of synthesis, while striving to remain within the principles of green chemistry.

Alanna Goldberg
Advisor: Bill Malachowski

Enantioselective Synthesis of Polycyclic Structures via Intramolecular Heck Reactions 

Many vital drugs, including steroids such as prednisone, are made up of polycyclic ring structures. Modern synthetic chemistry lacks the efficiency and specificity that is needed to research and develop polycyclic structures. This research will investigate efficient methods of enantioselectively synthesizing polycyclic molecules. The reactions are carried out using Birch reduction-alkylation reactions, and intramolecular Heck reactions; Birch reduction-alklyation will create an alkene-containing ring bonded linearly to an aromatic ring, the main components to be used in an intramolecular Heck reaction. Using the intramolecular Heck reaction, we will use a palladium catalyst with chiral ligands to enantioselectively generate a C-C bond between the aromatic ring and alkene ring, thereby creating polycyclic structures. This research will determine efficient synthetic procedures as well as effective palladium ligands for enantioselectivity. 

Sarah Lew
Dr. Jason Schmink

Palladium-catalyzed cross-coupling of aryl bromides with 2,2-diphenyl-1,3-oxathiolaneThe palladium-catalyzed cross-coupling of aryl bromides with 2,2-diphenyl-1,3-oxathiolane creates vinyl sulfides. Palladium acts as a shuttle of electrons that allows for bonds to form and makes it possible to create leaving groups for there to be an E2 reaction. The methodology found from this research will allow pharmaceutical companies who need vinyl sulfides to create them. Currently the research has focused on finding the best method for making the starting material, 2,2-diphenyl-1,3-oxathiolane, as it cannot be bought.

Alexandra Nagelski
Dr. Sharon J. N. Burgmayer

The Investigation of Pterin Reduction Dynamics in Synthetic Molybdenum Cofactor Models

Molybdoenzymes catalyze oxygen atom transfer reactions and exist in nearly all organisms. In their catalytic site, molybdoenzymes contain the molybdenum cofactor (Moco). Moco is not stable outside of the protein matrix, therefore the use of small molecule analogues provides an alternate way to study Moco. This research focuses on the molybdopterin (MPT), which describes one or two conserved pyranopterin dithiolene ligands on Moco and its role in the catalytic function of Moco. Although there is little known about the relationship between MPT and the catalytic function of Moco, without MPT, Moco loses its catalytic efficiency. MPT is the most redox active ligand in all of biology, which suggests that the oxidation state may play a role in catalysis. The Burgmayer lab has created the model systems [TEA][Tp*Mo(O)(S2C2(pterin)(C(CH3)2R)], where TEA is tetraethylammonium, Tp* is tris(3,5-dimethylpyrazolyl)hydroborate, Mo exists in the Mo(IV) or Mo(V) oxidation state, and R can be a hydroxyl (1) or methyl (2). In (1), the complex experiences reversible intramolecular cyclization that is dependent upon the dielectric constant of the solvent, producing a pyran ring, as shown in Figure 1. The related complex (2), where the hydroxyl group (depicted in red in Figure 1) is isosterically replaced with a methyl group, prevents this intramolecular cyclization, thereby creating a standard to compare the behavior of (1).

The tetrahydropyranopterin form of (1), which has already been synthesized in our lab, closely resembles the Moco pyranopterin structure observed in molybdoenzymes crystal structures. We hope to achieve the reduced dihydro form and the fully reduced uncyclized tetrahydro form of (1) and (2). From reducing the oxidized pterin in these model complexes, we can learn more about the changes on the catalytic efficiency and the electronics that it may exhibit.

Figure 1: [TEA][Tp*Mo(O)S2BMOPP], where BMOPP is 6-(3-butynyl-2-methyl-2-ol)-2-pivaloyl pterin.

Nam Nguyen
Dr. Sharon J. N. Burgmayer

The pathway to Molybdenum pyranopterin dithiolene complex

The transition metal Molybdenum plays an important role in living organisms because of the ubiquitous molybdenum-containing enzymes. Despite its relevance in biological lives, there is still little understanding about the molybdopterin chemistry. The first goal is to create ligands 2-pivaloyl-6-chloropterin and BMOPP to further develop the molybdenum complex that our research group has already successfully modeled [TEA][Tp*Mo(X)pterin-C(CH3)2R-dithiolene], where TEA stands for tetraethylammonium and Tp* is tris(3,5-dimethylpyrazolyl)hydroborate, X is either oxygen or sulfur atom and investigate the molybdenum pterin dithiolene chemistry. The quality of the compounds will be evaluated through the characterization techniques including NMR, IR, GC-MS, etc. Apart from focusing on reproducing results to examine the complex, my summer research also seeks to optimize our current procedures and raise the standards of our materials. 

Ami Okazaki
Mentor: Jason Schmink

Palladium-catalyzed synthesis using 2,2-diphenyl-1,3-oxathiolanes

The characteristics of palladium-catalyzed chemistry is widely studied in the field of organometallics. As a transition metal, palladium’s multiple oxidation states help to facilitate the transfer of electrons and create bonds between two separate organic molecules that otherwise would not interact. In previous years, 2,2-dimethyl-1,3-oxathiolane was predicted to function as a nucleophile in palladium-catalyzed cross-coupling reactions with aryl halides, but due to the absence of electron-withdrawing groups, it unfortunately did not function as such nucleophile. This summer, we will focus on using 2,2-diphenyl-1,3-oxathiolanes instead, because this molecule contains electron-withdrawing groups and has the potential to undergo palladium-catalyzed cross-coupling with aryl bromides to create aryl vinyl sulfides, a synthetic compound in the field of organic chemistry not widely understood. In determining the optimal reagents and conditions needed for the efficient synthesis of our desired product, fundamental characteristics of individual atoms and electron-withdrawing groups will be considered in addition to varying the reaction time, temperature, and amount of catalyst used. By applying past understandings of thiolanes, oxathiolanes, and electron-withdrawing groups to our current project, we hope to gain a better understanding of the capabilities of palladium-catalyzed cross-coupling reactions.

Zauraiz Syeda
Mentor: Susan White

Stability of the L30e WT and Mutant Proteins

The Saccharomyces cerevisiae (yeast) ribosomal protein L30e can regulate its own gene splicing and translation by binding to pre-mRNA.  A kink turn motif in the structure of the RNA is needed in order for the protein to bind.  At the binding site, the protein has specific amino acids that interact with the RNA. Changing these amino acids to create mutated proteins can significantly impact the thermal stability of the protein as well as its ability to form an RNA complex. Mutants will be used in this experiment to make sure that the overall structure of the protein is not affected.

Differential scanning fluorimetry (DSF) will be used to measure the thermal stability of the mutated proteins (K28A, F85A, and F85W), which will be compared to the stability of the wild type L30e protein. Similar thermal stabilities will confirm that each mutation does not significantly change the rest of the protein structure.  Since these amino acids are involved in binding to the RNA, they are on the outside of the L30e protein, suggesting that there will be little structural adjustment. A thermal cycler instrument will use temperature to denature the protein, and, as it unfolds, a hydrophobic fluorescent dye will be able to bind to it. The increasing intensity of fluorescence will show the unfolding of the protein. This thermal denaturation experiment will determine the stability of each mutant.    

Nazifa Tabassum
Advisor: Sharon Burgmayer

Synthesis of Molybdopterins

Molybdenum-containing enzymatic cofactors (Moco) are found in most living organisms except for in saccharomyces cerevisiae (baker’s yeast) and catalyze vital reactions in their bodies. They are also a part of the carbon, sulfur and nitrogen cycles in the environment, and act primarily as redox cofactors. Despite being ubiquitous in nature, molybdenum cofactors have been studied very little. Hence it is of importance to investigate their character and activity.

Moco have several active parts in addition to the metal (molybdenum) which include dithiolene and pterin. Molybdopterin is one of the most redox active ligands of Moco. In order to study molybdopterins, they must be synthesized. This synthesis is a lengthy, multistep process. First, 6-chloropterin is synthesized from starting material in a four-step process. It is then pivolated to produce 2-pivaloyl-6-chloropterin, which is then used to make BMOPP. BMOPP is the specific pterin precursor that is then used in the model molybdopterin dithiolene to be studied. Although it is difficult to characterize and determine the purity of the pterin solids synthesized due to their insolubility in water, NMR and IR spectroscopy are used for characterization purposes.

Jingyi (Alice) Tang
Advisor: William P. Malachowski

IDO inhibitor

Inhibitors of indoleamine 2,3-dioxygenase (IDO) are designed to be potential drugs for the treatment of cancer. IDO is involved in controlling the host immune response to cancer. Cancer cells express IDO to limit the body’s immune response and thereby allow the cancer cells to grow. By creating inhibitors of IDO, we can limit the ability of cancer cells to evade detection.

Over the summer, I will be conducting synthetic organic chemistry to make newly designed inhibitors of IDO. These inhibitors are proposed to have a unique mechanism of inhibition: covalent or irreversible inhibition. That is, they are going to react with IDO and covalently link to the enzyme thereby killing it. My particular focus will be on irreversible inhibitors with a benzofuran core. The research activities in the lab on the IDO project include designing target compounds, ordering and gathering necessary chemicals and equipment to conduct the experiment, carrying out the experiment, monitoring the reaction, isolating target compounds using appropriate purification techniques, confirming purity and structure of the compound using NMR, GC/MS, LC/MS and IR techniques, and submitting the compounds to biological testing by the collaborator at Albert Einstein College of Medicine. 

Zidu Zeng
Advisor: Dr. Bill Malachowski

Indoleamine 2,3-dioxygenase inhibitor design and synthesis

My research project is currently targeting the synthesis of a new structural class of IDO enzyme inhibitors for the treatment of cancer. Due to the fact that tumors are capable of escaping immune control during their development, and IDO enzyme was found to enable these immune escape events, the study and synthesis of IDO enzyme inhibitors is critical to help the body reverse the immune system suppression that enables cancer’s growth.

To date, the Malachowski group has synthesized three IDO enzyme inhibitor structural classes that can be used as potential drugs for cancer treatment. During this summer, the Malachowski group is focusing on the synthesis of a new IDO inhibitor that will hopefully react with IDO via covalent or irreversible inhibition.The new inhibitor uses knowledge about the enzyme mechanism and, in particular, the radicals formed during the IDO catalyzed reaction to undermine the normal process.  To accomplish this, the synthesis of an indole derivative that contains a cyclopropane ring will be undertaken. A series of chemical reactions, including a tosylation reaction, a Wittig reaction, a cyclopropanation reaction, and a saponification reaction will be done. The effectiveness of these inhibitors in reducing IDO’s catalytic activity will be tested by our collaborators at Albert Einstein College of Medicine.

Dina Benedetto
Dr. Douglas Blank

Janx: The Educational Robot

Background

The educational system has a lack of providing a hands-on projects that cooperate the basics of computer science and its relation to the real world. By documenting the steps of this research project and procuring a tutorial of how to construct, build, and write simple code, students will have the opportunity to explore the different fields of Computer Science.

Research

Issues being solved: People are oblivious to the different features that robots can provide, such as responding to various situations. Therefore, this research will focus on providing users with ways to understand the logic behind feedback, utilizing the surrounding environment.

The design will focus on having a minimalistic figure with maximum performance. The robot, named Janx, will be a picture capturing moving robot. As a robot, Janx will include a variety of features, such as the ability to measure the surrounding temperature, and providing computer feedback to the user.  Janx will consist of three 3D printed wheels and base, will have 2 motors, a camera, a temperature sensor, and a controlling unit. For the purpose of this research project, the controlling unit will be an Arduino board.

The hardware construction: Janx will have a triangular chassis. Two of three 3D printed wheels will be mounted on motor shafts at the back two edges of the triangle. Wires will be connecting the two motors to the board. The third 3D printed wheel will be a free floating wheel (like a shopping cart wheel), pinned to the front of the triangle. The camera will be mounted to the front of the triangle, adjacent to the temperature sensor.

The software construction:The base code will be written in Java Programming Language with a help of Arduino Software (IDE). The code will include functions that move, steer, capture video, capture pictures, and sense surrounding temperature, as well as the code necessary to provide the various feedback to the user.

Why is this useful? The final outcome of the research can be used in different schools to spike and introduce students to a new component of Computer Science. Not only will students learn how to build a robot, write code, but will also be able to implement their own ideas into the real world.

Tu Luan
Advisor: Dianna Xu

Provably good quadrilateral mesh generation

Polygon meshes define the shape of digital objects like three-dimensional models. They are needed in all types of digital modeling and simulations. This projects focuses on the generation of quadrilateral meshes, which guarantees the quality of the meshes in terms of max/min angles and aspect ratios.

My research mainly focuses on the indirect conversion algorithm, which will convert a triangular mesh generated by a polygonal region to a quadrilateral mesh with bounded angles as well as aspect ratios.

If successful, this will be the first known algorithm that provides a provable bound on both angle and aspect ratio for a quadrilateral mesh.

Prakhya Malyala
Advisor: Professor Douglas Blank

TypeScript : Enhancing the Web’s Popular Language

My overarching goal is to be able to implement the TypeScript language so that it can assist Computer Science educators and projects such as robot development, sensory measure of water use, and the control system of deep learning. I want TypeScript to be used to teach introductory computer science courses and to be used in computer science projects. TypeScript is a programming language released by Microsoft in 2012 that will be built into all browsers. TypeScript adds classes to JavaScript and compiles into JavaScript, which most websites employ. I aim to become an expert on the difference between JavaScript and TypeScript and how the use of the latter enhances the programming experience. I am using a hands-on approach to code different programs in the web browser. I am first creating a TypeScript notebook on the college’s Jupyter installation, a platform for interactive computing in multiple programming languages. The notebook is a JSON document with an ordered list of input and output cells which can have code, text, animation, games, graphs, and more. I will then help connect TypeScript to an API framework that we will build. API stands for application program interface and is a set of routines, protocols, and tools for building software. It specifies how software components should interact. This framework will tie different projects relating to artificial intelligence, simulation, and robotics research with a central protocol and system. TypeScript should be implementable to the web framework and used in the browser itself. I hypothesize that TypeScript is a current and efficient language that will augment the experience of coding with javascript, one of the three core technologies of World Wide Web content production. If this language is successfully usable with different projects, then it will benefit the computer science program at ������̳. I test to see how the language can be used to complete the different projects and be integral to the API framework.

Flanagan, David (2011). JavaScript: The Definitive Guide (6th ed.). O'Reilly & Associates. ISBN 978-0-596-80552-4.

"API - Application Program Interface." What Is API. N.p., n.d. Web. 10 June 2016.

Ilisha Ramachandran
Advisor: Douglas Blank 

Sustainable living through technology

Development environments for Maker related boards such as the Raspberry Pi and Intel Edison can be fairly challenging to setup and use. This setup becomes even more challenging in an educational context. The aim of this project is to make these development environments more accessible and more effective for students and teachers by using a readily available, open source board such as the Intel Edison and explore building "real world" projects. I have chosen an Environmental Sensing project which includes tracking water usage and correlating that with temperature, humidity, and various other sensors. This is in an attempt to increase awareness about living a more sustainable lifestyle. The end goal of this project is not specifically to demonstrate the end use case, but to explore using different development tools, languages and online services. The actual end goal of the project will be to make concrete recommendations on “preferred” tool chains and platforms to enable students and teacher to rapidly develop projects and lesson plans. We will also provide a library for students to access and program different sensors through a web-based system. 

Alex Snow
Mentor: Douglas Blank

Explorations of Deep Learning in Robotics

A method of enabling machines to problem solve by exposing them to a collection of data and having them solve based on the data they learned, called deep learning, has become a popular research topic in recent years. For example, through deep learning, a computer can locate a certain object in a picture when commanded to if that computer was shown or trained with various images of the specific object. We will explore this by teaching an autonomous humanoid robot to reach out and look towards a fluorescent colored ball wherever the ball is within sight by training the robot with different images of the ball. To accomplish this task, we will write a series of code connecting the robot to an online deep learning system through a computer. From there, we will take images of the ball with varying surroundings, input them into the system, and hold the same ball in front of the robot. This will be a demonstration of deep learning in the field of robotics.

Ziyan Yang
Dr. Dianna Xu

Provably good quadrilateral mesh generation

Polygon meshes define the shape of digital objects and are needed in digital modeling and simulations of all types. In my summer research project, my mentor and I focus on quadrilateral mesh construction of 2D polygons. We have existing quadtree-based quadrilateral mesh construction algorithms to create a quadrilateral mesh of simple polygons that can have holes. Our existing algorithms guarantee the minimum/maximum angles and aspect ratios of elements of mesh but do not mesh a polygon completely: there still exist gaps between edges of original polygons and our constructed mesh boundaries. Our next step is to smooth the boundaries of mesh to make them as parallel as possible to the polygon edges. First, we need to classify all the possible mesh boundaries and figure out different ways to optimize them. Then, I will modify the codes to test our assumptions and the solutions for smoothing. Finally, after optimizing the mesh boundaries, we can start think of how to make up the space between mesh boundaries and polygon edges. It may be useful to add buffer zones and re-mesh the space to guarantee our original minimum/maximum angles and aspect ratios because these criterion are significant in determining the quality of the mesh.

Abby Letts
Dr. Don Barber

The effect of volcanic eruptions on carbon burial rates in salt marshes

Saltmarshes sequester large quantities of carbon due to the anaerobic conditions in coastal wetland soils. Deep saltmarsh peat layers can also provide proxy records of past environmental conditions at the coast. This summer research project investigates how and why carbon accumulation/burial rates have varied over the last two thousand years in the saltmarshes of eastern North America. I am analyzing the carbon concentration and stable carbon isotopic composition in salt marsh organic matter from cores in North Carolina, Delaware, and Massachusetts. Preliminary studies of cores from the study area suggest correspondence between volcanic eruptions and a subsequent drop in organic carbon content. My analyses target these intervals of known climate variations. The analyses will test hypotheses regarding the climate mechanisms by which large explosive volcanic eruptions induce the observed marsh responses; e.g., reduced organic matter preservation due to increased decomposition and/or reduced belowground plant growth.

Differential decomposition of belowground biomass fragments will be analyzed at sites with varying salinities, elevations and plant communities (e.g., Juncus, Spartina alterniflora or S. patens). Marsh vegetation comprises multiple organic fractions with different carbon isotope ratios. Measurements of these ratios will help determine whether changes in organic material production or preservation are associated with the drop in organic carbon content. The organic carbon content and carbon isotopic composition of the marsh peat will be compared across different time intervals and also among different coastal regions. Along with the carbon analyses described above, the studied marsh cores will be analyses for C/N ratio, bulk density and loss-on-ignition. Lastly selected samples will be submitted for radiocarbon dating in order to strengthen the core chronology.  Overall, the project aims to elucidate how effective saltmarshes are carbon sinks, and why carbon burial rates vary in response to short-lived climate perturbations.

Chloe Li
Mentor: Selby Cull-Hearth

Research on Mapping on Mars and Iceland,  Total Synthesis of Ferrihydrite, and Database Construction

This summer, I am working with Professor Selby Cull-Hearth on four laboratory research project investigating mapping minerals on Mars, mapping alteration of Basalts on Iceland, total synthesizing Ferrihydrite, and creating a database of current minerals found.

The distribution in space and time of liquid water on Mars is relevant to astrobiology and astroclimatology. To date, most orbital observations that attest to past fluvial and lacustrine activity on Mars have been dedicated to surficial landforms. This summer we focus on the Valles Marineris. By using the CRISM database and analysis of optical spectrum, we will locate precise latitude and longitude of relevant papers, and then map the minerals and CRISM ID on google earth.

Ferrihydrite is a widespread hydrous ferric oxyhydroxide mineral at the Earth’s surface, and a likely constituent in extraterrestrial materials. It forms in several types of environments, from freshwater to marine systems, aquifers to hydrothermal hot springs and scales, soils, and areas affected by mining. This summer we aim to find a feasible method to synthesize Ferrihydrite in lab by chemical reactions of iron chloride and iron nitrate, and analyze its optical spectrum.

The alteration of basalts includes metamorphism and weathering of basalts. Basalts are important within metamorphic belts, as they can provide vital information on the conditions of metamorphism within the belt. Also compared to other rocks found on Earth’s surface, basalts weather relatively fast, so the calcium released by basalts will bind up carbon dioxide from the atmosphere. Basalts often are associated with the release of large quantities of carbon dioxide into the atmosphere from volcanic gasses. So in this summer, we will access the database of the alteration of basalts on Iceland and map them in system to provide information to analyze and predict the volcanism on Iceland.

The last work is to create a database of all the minerals collected both within the U.S. and outside the U.S. The database will include the type of minerals, place found, collecting method, and other relative data of the minerals.

Helen Whitty

Advisor: Arlo Weil

Structural and Paleomagnetic Analyses of Structural Deformation in the South-Central Andean System

Along the western coast of South America, the Nazca Plate, composed of dense oceanic crust, is actively subducting beneath the South American Plate, which has caused the Andean orogeny. Deformation styles vary along the length of the orogen, which makes this region ideal for studying intraplate contractional deformation at a convergent ocean-continent boundary. Variations in crustal architecture may be influenced by a number of factors, including subduction geometry, shortening rates, stress/strain directions, and vertical axis rotation.

This research project seeks to better understand the factors that control variation in structural deformation along the Andean orogenic system, specifically in the south-central Andean system, which is made up of thick-skin, thin-skin, and hybrid components. Through structural and paleomagnetic studies of rocks from this region, we will test the relationships between subduction geometry, stress/strain directions, and vertical axis rotation.

Scientific knowledge gained through this research will contribute to a broader understanding of the previous and ongoing kinematic evolution of this particular orogenic system as well as that of convergent ocean-continent boundaries in general.

Matthew Willig
Advisor: Selby Cull-Hearth

This research aims to map morphologies and textures of hydrated deposits in the Valles Marineris, a Martian canyon system spanning roughly the length of the continental United States. We will be analyzing data from the High-Resolution Image Science Experiment (HiRISE) and Compact Reconnaissance Imaging Spectrometer for Mars (CRISM). CRISM was launched in 2005, designed to search for minerals indicative of the presence of water. Several other remote sensing instruments similar to CRISM orbit Mars as well. Many other research groups have already analyzed spectral data from these instruments and tentatively determined the composition of surface features across the planet. This research will be using a type of remote sensing software called ENVI to synthesize these analyses such that stratigraphic columns of regions within the Valles Marineris canyon system can be generated, a large step forward in the efforts to establish a geologic history of the planet.

A major complication of research dealing with this imaging spectroscopy is presence of “masking minerals” such as ferrihydrite. These minerals, even in small abundances, effectively prevent CRISM from recording the spectral signatures of surrounding mineral deposits. As a result, inferring past environments from a deposit containing masking mineral becomes far more complicated. To address this problem, a second component of this mapping project is synthesizing minerals that are known to mask other spectral signatures and mixing them with other hydrated Martian minerals to determine how strongly these certain minerals mask others. This research hopes to establish definite masking relationships between minerals that can subsequently be used to correct interpretations from spectral data gathered. This process will occur in the geochemistry lab and is intended to facilitate more accurate predictions of relative amounts of minerals in Martian deposits, and subsequently be able to more accurately infer ancient and current presences of water on the planet.

Martian mineralogists largely seek to infer past climates and surface conditions of the planet and more specifically, where water was present and how much was there. Such insights enable predictions regarding whether life has ever and could ever exist on Mars. These questions are particularly important as interest in Mars’ ability to sustain human life grows. 

Yezi Yang
Advisor: Katherine Marenco

Ordovician Receptaculitids from Western Utah: Investigating the Morphology and Paleobiology of an Enigmatic Fossil Group

Receptaculitids are enigmatic organisms that lived from the Early Ordovician through Permian Periods (488-250 million years ago), and are considered important components of Early Paleozoic shallow-water reefs along with sponges and microbial communities. Their body shapes vary widely but in general they share a distinctive helicospiral skeletal structure. Researchers have recognized similarities between receptaculitids and both sponges and algae, but currently there is no consensus on how this fossil group should be classified.

The goal of my research is to investigate the morphology and paleobiology of receptaculitids collected from the Early Ordovician Fillmore Formation of western Utah. Most of the receptaculitid specimens that I will be working with are incomplete and conical or cylindrical in shape, but one fossil is complete and goblet-shaped. I will make thin sections both parallel and perpendicular to the body axis of several of the receptaculitid specimens and polish the surfaces of other specimens in order to reconstruct the three-dimensional skeletal morphology and microstructure of these organisms. Based on my data and the existing literature, I will interpret the physiology and phylogenetic placement of these Fillmore Formation receptaculitids and explore their role within Early Ordovician reef habitats.

Emmeline Douglas-Mann
Advisor: David Schaffner

Construction of a Pulse-Forming Network

A plasma gun source requires the construction of a pulse-forming network (PFN) of capacitors. This circuit, consisting of 8 0.5mF capacitors and 8 inductors of optimised inductance, would give an ideal pulse with just sufficient current for plasma ejection over an extended period of time. This would make it possible to generate sustained plasma injection for studying turbulence. The first stage of construction is to design the PFN using LTSpice, and use simulations of current over time to determine the optimal magnitudes and combination of inductances that result in a long pulse of constant current. After simulating the network, it will be possible to construct it in the laboratory. A typical appropriate combination of inductances is expected to result in a flat current pulse that lasts for almost 300 microseconds. 

Codie Fiedler Kawaguchi
Mentor: David Schaffner 

Stainless Steel Proximity Experiment

Current pulsed through a copper coil will generate a magnetic field. When this occurs inside a stainless steel vacuum chamber, the resultant magnetic field will be modified due to Faraday’s law of induction. Using hall probes, as well as Bdot probes these effects can be measured.The goal of this research is to explore these effects, to help determine how to minimize the impact it has on the overall experiment. Furthermore, this information will help advance fusion research being conducted by ������̳ in collaboration with Swarthmore's SSX lab. It is expected that as the distance between the copper coil and stainless steel chamber is increased, the effects on the magnetic field will decrease.

Researchers have yet to achieve a self-sustaining fusion reaction in which the amount of energy put in is less than that being produced. ������̳ and Swarthmore  aim to develop new modules in which to accelerate and compress plasma plumes with relatively low energy input and high stability. Hall probes and Bdot probes are used to calculate the time of flight in order to know how fast the plasma is being accelerated. The use of the stainless steel is both a practical, and cost efficient design that will be more accessible for future research.  

Clare Allsopp-Shiner, Leyla Fahim, Carrie Filion
Dr. Michael Schulz

Black Hole Greybody Factors in Schwarzchild Spacetime

The goal of our project is to calculate the greybody factor of black holes in Schwarzchild spacetime. Black holes radiate the full thermal spectrum near the event horizon, and the amount that the observed radiation differs from this perfect spectrum is referred to as the greybody factor. The radiation created at the event horizon is referred to as Hawking radiation and is a result of quantum effects. Only a small portion of the Hawking radiation that is created will travel past the event horizon, largely due to the extremal geometry surrounding the black hole. Our research will focus on determining how much of the Hawking radiation created at the event horizon will travel outwards to infinity, i.e. how much will be able to tunnel out of the event horizon into the space beyond. In order to determine this, we will calculate the effective potential utilizing the Klein-Gordon Equation in Schwarzchild spacetime and then we will calculate transmission coefficient and the potential of tunneling through this potential. Calculating the tunneling potential and how the radiation at infinity differs from the perfect thermal spectrum emitted helps us further our understanding about black holes and their radiation. This is also applicable to the holography principle. 

Hayley Johnson
Professor David Schaffner

Stainless Steel Proximity Experiment

Generating and accelerating plasma in a conductive stainless steel chamber affects the magnetic fields inside, due to Faraday’s Law of Induction. These effects will interfere with measurements of the magnetic field due to a pulsed coil (which will later be used to accelerate plasma) inside the chamber. This work is being done in conjunction with work at the Swarthmore Spheromak Experiment, which uses a glass chamber instead of stainless steel. Both facilities are attempting to efficiently accelerate and compress plasma for the long-term goal of fusion technology as part of the project for Accelerating Low-Cost Plasma Heating and Assembly (ALPHA). Initial determinations of the effect of the stainless steel chamber will be made by using a B-dot probe to measure the magnetic field of a pulsed coil placed at incremental distances from a stainless steel plate. As the coil is moved farther from the plate, the plate’s interference with the magnetic field is expected to lessen. Preliminary data-taking suggests that at close proximity, the plate’s effects may be drastic enough to reverse the coil’s magnetic field entirely.

Zhimin (Cheryl) Liu and Jiayi (Rose) Lin
Mentor: Michael Noel

Investigating the Interactions among Ultracold Rubidium Atoms in Rydberg States

Rubidium atoms cooled to a velocity near zero and trapped at a certain location in space can be excited to high lying Rydberg States with a system of tunable diode lasers. These atoms have strong dipole moments, and can exchange energy through the dipole-dipole interaction.

The laser beams from the diode lasers are tuned to the appropriate wavelength and locked with circuits. Lasers operating at 780nm are used to cool and trap atoms in a magneto-optical trap (MOT). Two other diode lasers (766nm, 1265nm), are tuned to excite the Ultracold Rubidium atoms from the 5p3/2 state to the 5d5/2 state, and finally to the np3/2d state (the Rydberg State).

Our laboratory was recently moved so we will focus on rebuilding the previous laser system and MOT in the new laboratory. By the time the entire system is working effectively, we will start to observe the trapped Ultracold Rubidium atoms and to investigate their interactions.

Sarah Awad
Dr. Dustin Albert

Parenting Across Cultures: Normative Parenting and the Development of Executive Functions in ChildrenExecutive functioning refers to the cognitive functions involved in the control and coordination of attention, behavior, thoughts, and/or emotions to carry out goal-oriented actions. While research has investigated the maturation and development of executive functions in children, few studies have explored the influence of environmental factors, like parenting, that may contribute to individual differences in development. In addition, there is a notable lack of cross-cultural research evaluating whether parenting influences on the development of executive functions are culturally specific or universal. The present study investigates children’s executive functioning and parenting behaviors in 10-year-old children of 1297 families in nine countries (China, Columbia, Italy, Jordan, Kenya, Philippines, Sweden, Thailand, United States). In our analyses, we will evaluate unique and interactive effects of parenting and culture on the development of executive functions.

Janet Monroe
Dr. Laurel Peterson 

The influence of psychosocial and behavioral factors on self-reported stress in African Americans

A rich literature in health psychology illustrates the detrimental effects of stress on health outcomes, and points to stress as a potential mechanism contributing to health disparities between African American and white individuals. The effects of psychosocial stress can manifest in hypopituitary-adrenal-cortical axis responses, resulting in subclinical dysregulation of diurnal cortisol hormone profiles. Previous literature has established a relationship between negative health outcomes and the experience of chronic stress, which may be particularly prevalent in African Americans due to the added burden of racial discrimination. The Health and Racial Discrimination in Daily Life study in Professor Peterson’s lab collects data on physiological (via salivary cortisol) and self-reported stress, discrimination, and other psychosocial factors, using ambulatory assessment (i.e., sampling over the course of the day outside the lab). My SSR project will involve data collection from participants and examining the relationship between psychosocial and behavioral factors (e.g., discrimination, sleep quality) and self-reported stress in emerging adult African Americans. Through this research, it will be possible to explore risk factors that have an influence on the stress experienced by African Americans, providing preliminary data to launch a follow up study on hypopituitary-adrenal-cortical indicators. The identification of these influential factors offers the potential to understand the relationship between traditionally-measured self-report stress and bioindicators of trait stress-response among emerging adult African Americans.

Keywords: Health; Stress; Cortisol; Health disparities; Discrimination

Marea Newell
Professor Peterson

Examining the Relationship between Perceived Discrimination and Substance Use Among African American Young Adults

Research on stress and coping has demonstrated that stress is an important psychosocial factor that is predictive of substance use. African Americans experience disproportionate psychosocial stress due to interpersonal racial discrimination, which is implicated as a major contributor to racial health disparities. One of the ways individuals cope with stress is via substance use; therefore, it is important to research the relationship between racial discrimination and substance use among emerging adult African Americans. The current research will draw on the Health and Racial Discrimination in Daily Life (HRDDL1, Pittsburgh) study and the current HRDDL2 (Philadelphia) study, which examine perceived discrimination and substance use behaviors among African American emerging adults (18-30 years old). Participants complete questionnaires assessing discrimination, psychosocial constructs, as well as substance use behaviors and associated cognitions. Participants also report on these constructs using ecological momentary assessment, specifically, filling out brief questionnaires throughout the day via smartphones. My Summer Science Research project will involve recruitment, screening, and collecting data from participants. I plan to examine the relationship between perceived discrimination and substance use behaviors and associated cognitions.  I hypothesize that discrimination will be associated with greater substance use risk cognitions and behaviors among emerging adult African Americans. Additionally, I plan to conduct a review of the literature on potential mediators (e.g., negative affect) or potential buffers (e.g., social support) of the discrimination and substance use relationship. This study will use innovative methodologies to provide insight to how discrimination relates to engagement in substance use behaviors among the emerging adult African Americans.

Keywords: Discrimination; Substance Use; Health; Health Disparities

Jieni Zhou
Dr. Marc Schulz

Marital Satisfaction Trajectories over Life Course

Substantial research indicates that married people stay healthier and live longer. However, about 40% to 50% of marriages in the U.S end in divorce and many people in marriage report marital dissatisfaction. The quality of close relationships is important not only to couples but also to children’s mental and physical health. Thus, identifying factors that impact the quality of close relationships deserves attention with the ultimate purpose of educating and preparing families for inevitable strengths in their relationships.

My summer research project aims to construct trajectories of marital satisfaction over the life course by mining a prospective longitudinal dataset collected across a 75-year period on the lives and marriages of 743 men. The original participants, first contacted in the 1930s, were 267 sophomores at Harvard University and 476 adolescents from Boston's poorest neighborhoods between 1939-1944. A self-reported, multi-item questionnaire assessing marital quality along with social history information was collected at 7 points: 1954, 1967, 1972, 1983, 1989,1995 and 1999. We will utilize a newly digitized warehouse of information for each participant and combine major relationship events such as death of parents, birth of children and divorce with quantitative information on marital satisfaction collected across these 7 periods. By contextualizing marital functioning prospectively across 5 decades, we will be able to create a more comprehensive picture of factors that contribute to relationship quality.  Comparison within and between the two groups of men with distinct socioeconomic backgrounds will provide additional information. The results will help inform future interventions linked to key points in the marital life cycle to avoid and alleviate relationship distress and dysfunction.

References

Demir, M. (2007). Sweetheart, you really make me happy: Romantic relationship quality and personality as predictors of happiness among emerging adults. Journal of Happiness Studies J Happiness Stud, 9(2), 257-277. doi:10.1007/s10902-007-9051-8

Kaplan, R. M. (2006). Marital status and longevity in the United States population. Journal of Epidemiology & Community Health, 60(9), 760-765. doi:10.1136/jech.2005.037606