STAR Scholars Abstract

The New Jersey Pine Barrens is a globally rare ecosystem where the biota is well adapted to acidic, nutrient poor soil and water, and frequent wildfires. The Pine Barrens support ~14 species of anurans (i.e frogs and toads). Because anurans face a worldwide decline as a result of habitat loss and deforestation, it is important to understand the impact of water quality disturbance on anuran assemblages. I compared the difference in local species richness along a wetland disturbance gradient at the Warren Grove Gunnery Range to elucidate the effects of landscape change on anuran community structure. Anuran presence/absence, fire frequency, and water quality data were collected from ponds (n=23) from March – July 2016. Anuran community composition was correlated among environmental variables to determine the strength of relationships. Understanding the relationship between anuran species composition and abiotic parameters associated with land-use change will be imperative for the long-term conservation of these bio-indicator species.

Ultrasound contrast agents are used to enhance ultrasound images by increasing the impedance mismatch between tissues and consist of microbubbles which can also house drugs in their shells for targeted drug delivery. The contrast agent developed in our lab, SE61, is created by sonicating a surfactant solution composed of Span 60 and vitamin E under perfluorocarbon gas purging. A drawback to this method is its inability to form bubbles with uniform diameter and drug load. Microfluidics is a field in science which deals with manipulating liquids constrained on a micrometer scale and patterned on a chip. Recent research shows monodispersed droplets can be formed utilizing microfluidics. The aim of this project was to investigate the potential of microfluidics to produce uniform SE61 agents. A functional chip with an asymmetric flow focusing device structure was assembled in a flow regime employing two syringe pumps. The microchip was able to produce water-oil emulsions consistently having a uniform diameter of 75 microns. Valuable insight into the parameters necessary to create SE61 by microfluidics were obtained including the critical flow rates of the pumps and the need to break down the surfactant solutions particle size to a size small enough to be pumped through the chip.

Artificial Intelligence (AI) is the theory and development of computer systems able to perform
tasks that normally require human intelligence. In previous AI research, there has been little
success in creating biologically plausible models that mimic naturally intelligent behavior. This
research focuses on understanding how learning works through decision making and also
finding a practical application of emulating learning. The model developed is an adaptive finite
state automaton with probabilistic outputs. Through a series of experiments, we are determining
if the model presents key properties psychologists find in nature through classical and operant
conditioning. The objectives of this research are to reproduce past results to corroborate the
validity of the model, illustrate natural intelligence, and portray a biologically accurate structure.
This investigation will be accomplished through simulating 100 trials of each experiment to
compare the results to data found in nature. In the end, the results were positive and showed
that this model is a compelling candidate for mirroring low level natural intelligence and clearly
demonstrates many properties of conditioning studied by psychologists.

With the continuing depletion of nonrenewable energy sources, the demand for solar energy is rising. Perovskite oxide thin films are a promising material system that could advance technological progress in solar cell design, as little is known about their photovoltaic properties. They have a band gap in the visible range and are composed of non-toxic and chemically stable elements. These perovskite films are grown via molecular beam epitaxy by Prof. Steve May’s group (Drexel MSE). The carrier lifetimes and recombination mechanisms were studied by using ultrafast optical probe-pump spectroscopy. This method uses a single wavelength pump pulse which is fired into a material to excite charge carriers (electrons) across the band gap. A probe pulse is fired after a time delay to study the relaxation of photoexcited carriers. The data is obtained in terms of energy-resolved change in the reflectivity of the sample after excitation and then fitted to a recombination-diffusion transport model. In the model, parameters were set to study surface, trap-assisted and Auger recombination that occur in the material. Surface recombination limited carrier lifetimes in the thinnest films (~5 nm), but lifetimes of nanoseconds could be achieved in films with thicknesses >40 nm . Despite surface recombination being the limiting factor, increased research into perovskite oxide thin films could lead to possible solutions on how to increase carrier lifetimes and improve solar cell performance.

The purpose of this research is to explore the use of information and communications technology to improve home-school collaboration in special education. In special education, home-school collaboration is defined as active, equal partnerships based on mutual respect and complementary expertise with the ultimate goal of improving student outcomes. Much research has demonstrated higher achievement among students who benefit from the creation and maintenance of such relationships.  However, traditional paper systems of parent-teacher communication are unreliable and undetailed, which can cause frustration for all stakeholders and threaten student outcomes. We are developing a tool that extends Lilypad, a data collection and analysis system for special education classroom staff, which supports family-school partnerships in three ways: (1) giving parents access to behavioral data collected daily in the classroom, (2) including parents in long-term progress monitoring, and (3) providing a communication channel between family and school. In order to appeal to parents of all levels of availability, literacy and involvement, we primarily addressed the questions of which data to include, how much detail to provide, and which strategies of presentation make the data easily digestible. Our design process involved understanding data management in the classroom, and subsequently designing an interface to involve parents in the management and discussion of that data. We then held focus groups with expert behavioral psychologists and an interview with a parent of a child in a special education program. Use of this tool could foster improved home-school collaboration in special education without placing more demands on teachers.

Characterizing the Rheological Behavior of Novel Biomimetic Proteoglycans:

Proteoglycans (PGs) found within the body are responsible for encouraging cell growth,organizing the extracellular matrix (ECM) of tissues, influencing collagen fibrillogenesis, and regulating skin tensile strength. These macromolecules are composed of protein cores with attached glycosaminoglycan (GAG) chains. With aging, enzymes responsible for breaking down PGs become more active, reducing the overall concentration of PGs in the body. Therapy designed to increase the concentration of PGs in the body is challenging because natural PGs introduced into the body are still susceptible to enzymatic degradation. Biomimetic proteoglycans (BPGs) can be created using an enzymatically resistant polyacrylic acid (PAA) core with covalently attached natural chondroitin sulfate(CS) bristles that mimic the three dimensional bottlebrush architecture and hydrating properties of natural PGs. In this project, the rheological behavior of aqueous solutions of CS and BPGs was characterized using small amplitude oscillatory shear on a DHR-3 rheometer in order to better understand the flow behavior and molecular structure of BPGs in solution. Experimental variables include the concentration of CS and BPGs (10 mg/mL, 50 mg/mL) dissolved in aqueous solution, ionic strength (0.1X PBS, 1XPBS), and two different PAA sizes (PAA10kDa-CS, PAA250kDa-CS). This study explores how these variables affect the various solutions’ elastic modulus (G’), loss modulus (G”) and viscosity (η). An improved understanding of the underlying molecular structure and flow behavior of BPGs in solution would enable us to better predict how these solutions will behave when introduced into the body.

Eph receptors, such as EphA4 and EphB3, which are a subfamily of the Tyr kinase receptor superfamily, have been shown, in previous studies, to function as dependence receptors; in the absence of their respective ligand these trans-membrane receptors signal for programmed cell death, yet their mechanism for cell death induction has not been explicitly studied. To shed light on their function, we used mouse embryonic fibroblasts (MEFs) from EphA4-/-/EphB3-/- animals. The primary goal was to establish optimal conditions that would allow us to measure Eph-induced cell death in these cells. Afterwards, TrypanBlue exclusion assays were performed to quantify cell death in cells expressing either EphA4 alone, EphB3 alone, or EphA4/EphB3 together; the results were used to establish whether EphA4/EphB3 can cause effective apoptosis individually or if there is synergistic function between EphA4-EphB3 producing even greater cell death. Although inconclusive, our results suggest that EphB3 under our conditions is able to initiate apoptosis on its own in the absence of its respective ligand. Yet, further tests need to be conducted to better understand the function of EphA4 alone, as well as EphA4 and EphB3 in tandem.

First used commercially in the automotive industry, electrophoretic deposition (EPD) is an established, scalable method for applying coatings to conductive substrates via an applied electric field. When paired with colloidal semiconductor nanocrystals, EPD is an environmentally and economically advantageous method for large-scale manufacturing of photovoltaic cells due to its reduced waste and higher throughput compared to alternative methods. However, EPD typically uses high voltages in order to increase the electrostatic force and rate of deposition. This is problematic for semiconductor nanocrystals as high voltages may damage the depositing nanocrystals. Our research focuses on engineering the surface properties of copper zinc tin sulfide nanocrystals and the EPD bath composition in order to lower the process voltage, thus preserving the semiconductor. A new reactor was designed and implemented in order to directly observe the deposition process in situ. An automated amperometry apparatus was made to quantitatively measure the current that goes toward depositing the films during EPD. Theoretically, this current directly corresponds to the number of nanocrystals deposited. Therefore, by integrating the recorded current and comparing it against film thickness, we quantified the efficiency and the presence of additional electrochemical side-reactions that accompany the EPD process.