STAR Scholars Abstract

Recycling energy from heat  

Development of new methods of energy generation for meeting the growing energy needs of our society is an active area of research in the energy conversion and storage field. A relatively unexplored method of energy generation is the conversion of low-grade heat into electricity. Thermoelectric devices based on the Seebeck effect (the generation of electrical current when a temperature gradient is applied to dissimilar semiconductor materials) have been explored for this application, but thermoelectrics are expensive and time consuming to manufacture. Carbon materials are abundant and easily processed to have properties tailored to specific applications. Using carbon for such energy conversion devices could make them more suitable for use in electricity generation. Carbon can be casted into films that can generate current via the electrokinetic (EK) effect. The EK effect is created by the flow of polar solvent molecules through a material which causes electrical charges in the material to move with the solvent. This flow of charge induces a streaming potential which can be used for useful work. The EK effect is driven by the transport and evaporation of the solvent from the material, this effect can be enhanced using a temperature gradient, similar to the Seebeck effect. This project aims at optimizing porous carbon films to make them suitable for energy generation. Various compositions for the films were tested in order to achieve an optimized device.

1. STAR 2015

2. Ferroelectricity in KBNNO

Ferroelectric materials—materials with a spontaneous, switchable polarization when below their Curie temperature—have wide applications ranging from non-volatile memories to piezoelectric sensors. Recently, ferroelectric semiconductors have attracted considerable attention as an alternative to conventional semiconductor materials for photovoltaic solar energy conversion. 
One particularly promising class of ferroelectric, photovoltaic semiconductors is the single-phase solid-solution oxide: (1-x)[KNbO3]-x[BaNi0.5Nb0.5 O3- δ] (KBNNO). In the x = 0.1 composition, KBNNO has been reported to have exceptional photovoltaic and ferroelectric properties. An important property of ferroelectric materials is the Curie temperature, the maximum temperature at which ferroelectric materials retain their spontaneous polarization.  Here, the ferroelectric phase transitions of the x = 0 and x = 0.1 KBNNO compositions are identified with Raman spectroscopy. Raman spectroscopy uses Raman scattering, inelastic scattering where incident photon energy is shifted by lattice and molecular vibrational states in a material, to directly probe the lattice structure of a crystal. Because the ferroelectric transition is driven by a lattice structure change, Raman spectroscopy can be used to identify the Curie temperature. 
From these studies, we have identified the Curie temperature of the x = 0, or un-doped, composition as ~450 C. Remarkably, the x = 0.1 composition shows a Curie temperature of ~230 C.

Estuarine barrier islands in the Delaware Bay provide critical habitat for a variety of organisms, including nesting piping plovers and breeding horseshoe crabs. They also act as natural buffers for fragile salt-marsh ecosystems, diminishing physical energy from waves and currents. However, relatively little is known about their specific response to local relative sea level rise, which threatens to overtake these islands. Sea level rise will reduce available habitat and expose delicate salt marshes to heavy wave action. Our aim is to better understand the geological processes driving erosion and migration along these unique landforms. Our study site consists of several bayside barrier islands in the Delaware Bay off the coast of southern New Jersey. We took surface sediment samples at regular intervals along the islands in order to analyze cross-shore and longshore sediment transport. These sediment samples were analyzed using a Cam-Sizer particle analysis tool to generate cumulative distribution curves of grain sizes. The curves were analyzed according to standard granulometric parameters to understand sediment transport. This information will be integrated with further geological and historical analyses of the Delaware Bay to form a geomorphic response model. This model will provide a planning tool for future generations of researchers and coastal engineers. 

Solar photovoltaic energy is a clean and renewable source of electricity that has been researched heavily over the past 30 years. However, cost, toxicity, and rarity of precursor elements still limit widespread implementation of current technologies. Solution processing of these materials, such as hydrothermal synthesis, is desirable due to its low cost and scalability. Yet, these methods generally produce materials of lower electronic quality with defects and impurities that can limit carrier collection. Ferroelectrics may be able to withstand such drawbacks because of an internal electric field that can effectively separate carriers to reduce recombination rates. Antimony Sulfoiodide (SbSI) is a relatively unstudied ferroelectric with promising properties for solar cell absorber applications.    

In this work, the semiconductor SbSI was synthesized hydrothermally to produce crystals that were 650 microns long and 30 microns in diameter on average. These microrods were synthesized from a published procedure, but had variances in pH and seeding, where a decrease in pH increased crystal size. Scanning electron microscopy (SEM) showed SbSI is highly crystalline, while X-ray diffraction (XRD) confirmed the phase purity. Diffuse reflectance measurements for Tauc plots estimated an indirect band gap of 1.85 eV. Current work on measuring the carrier lifetimes and mobilities via ultrafast terahertz spectroscopy will help evaluate further pursuit of SbSI as an absorber material.

Year of participation in STAR: 2015

Abstract title: Osteonal Morphology, Distribution, & Drift in Porcine Femoral Midshaft

Abstract: Analysis of bone microstructure (i.e. primary and secondary osteons) in porcine femoral samples can be used to make statistical comparisons regarding bone quality.  The objective of this novel study is to quantify the osteonal morphology, distribution, and drift in the midshaft of the porcine femur.  Specifically, the 50% femoral site of two-month-old (n=5) and six-month-old (n=5) pigs was sectioned and mounted to prepare samples that hold cross-sections of bone.  These samples were then ground & polished with a Buehler PowerPro4000 (Buehler, Lake Bluff, IL) until they were adequately refined to be viewed under a microscope.  Each of the ten samples was then imaged with a Zeiss microscope at 10X magnification using reflective microscopy.  Next, the image portions for each sample were layered and flattened using the Adobe Photoshop program.  Once masked so that only bone was visible, these images were input into MATLAB software (Mathworks Inc., Natwick, MA) to identify endosteal and periosteal borders, as well as six wedges of interest.  After a distinction of endosteal versus periosteal bone was made in each image, two regions of interest were selected from each sample.  These regions will be reimaged at 5X magnification and the encompassed primary and secondary osteons will be traced using a custom MATLAB code.  The morphology and distribution of primary and secondary osteons will be computed to reveal differences between the microstructure of endosteal versus periosteal porcine femoral bone. 

                                          Interaction of Tip60 histone acetyltransferase with Abnormal-A, Hunchback, Squeeze and Zeste transcription factors
                                                                                                                                     John Gilligan, Songjun Xu, Felice Elefant
                                                                                                                  Department of Biology, Drexel University, Philadelphia, PA, 19104

Tip60 is an important histone acetyltransferase which modulates the packaging of DNA by histone proteins that have an important role in epigenetic gene regulation.  A group of proteins called transcription factors have the ability to recruit Tip60 to the promoter regions of DNA.  This influences what parts of the DNA strands go through transcription and what proteins will be expressed.  In the presence of amyloid precursor protein (APP), Tip60 plays an important role in neuronal development.  If Tip60 levels increase in AD mice, APP is overproduced in neurons.  This may cause Alzheimer’s and other neurodegenerative diseases in humans.        

In this project we test the hypothesis that Tip60 specifically interacts with the Hunchback, Squeeze, Abnormal-A and the Zeste transcription factors.  We studied these transcription factors experimentally by performing western blots analyses and by researching related scientific articles through databases such as PubMed.  We also studied whether Tip60 and these proteins have similar sequences called motifs.  Based on our research, it appears that Zeste transcription factor may manipulate how DNA is wrapped by histones.  This suggests that there is a potential interaction between Zeste and Tip 60.  This information could provide valuable insight into the discovery of medicines that could promote regular gene expression.                                

Since the dawn of humanity, people have looked at the stars for faith, for answers, and in recent years, for an understanding of how the universe works. This project examines the latter, as we perform multiple simulations of the early evolution of young star clusters. Astronomers recognize that all stars form in clusters, and know that over time, the resulting group will dissolve, expelling its stars into the galaxy; the life cycle of such a process is contingent upon the initial conditions of the fractal clusters. The first question is how much time is necessary for a given assemblage of stars to settle down, reaching an effective equilibrium.  The second physical effect we study is the degree of mass segregation in the final star cluster. As the system evolves,  we observe that heavier stars sink towards the center of the cluster. In both investigations, we modify the following parameters and analyze the effects they have on the resulting time scale for stabilization of the cluster:  the number of stars, the fractal dimension of our cluster, the scaling of the initial velocities, and the initial mass distribution of our stars. Each simulation is performed for numerous random realizations of the system and all calculations are continued until the cluster reaches dynamical equilibrium. We find that while neither the number of stars in the system nor the fractal dimension have significant effects on the time to reach equilibrium, the decrease in initial velocities causes the cluster to reach equilibrium faster.

There is both a higher asthma pevalence and mortality rate among Puerto Rican children than any other ethnic group in the United States. The disparity has been attributed to a variety of genetic and environmental factors. However, sociocultural factors also play a large role in a patient's understanding of their illness. Studies have shown that up to 89% of Hispanic patients are familiar with ethnomedical remedies for asthma. The aim of this study is to identify which alternative medical practices Puerto Rican families use in the treatment of their child's asthma. This knowledge will ultimately be used in order for clinicians to tailor education and clinical management of asthma for this population. In order to ascertain this data, surveys were created based on folk remedies recorded in previous medical-anthropological literature. The surveys are four pages long and assess a variety of ethnomedical practices for both the prevention and treatment of asthma attacks, as well as demographic information about the caregiver. The IRB-approved surveys are being distributed to eligible participants (parents of asthmatic children ages 2-18 who self-identify as Puerto Rican) in the asthma clinic at St. Christopher's Hospital for Children. To date, about thirty surveys have been conducted. When the goal of 135 completed surveys has been reached, statistical techniques will be will be carried out in order to identify trends in folk remedy use for the treatment of asthma for the Puerto Rican population served by St.Christopher's Hospital.