Neuronal Migration: How Do You Build a Brain?

Senior biology major Alex Burkard is working in the Walsh Neurodevelopment Laboratory at VCU to help answer the question, ‘How do you build a brain?’ Burkard is researching neuronal migration in Zebrafish and how cellular polarity affects hindbrain development

Design of quadrature mirror filter banks with canonical signed digit coefficients using genetic algorithms.

This thesis is about the use of a genetic algorithm to design QMF bank with canonical signed digit coefficients. A filter bank has applications in areas like video and audio coding, data communication, etc. Filter bank design is a multiobjective optimization problem. The performance depends on the reconstruction error of the overall filter bank and the individual performance of the composing lowpass filter. In this thesis we have used reconstruction error of the overall filter bank as our main objective and passband error, stopband error, stopband and passband ripples and transition width of the individual lowpass filter as constraints. Therefore filter bank design can be formulated as single objective multiple constraint optimization problem. A unique genetic algorithm is developed to optimize filer bank coefficients such that the corresponding system\u27s response matches that of an ideal system with an additional constraint that all coefficients are in canonical signed digit (CSD) format. A special restoration technique is used to restore the CSD format of the coefficients after crossover and mutation operators in Genetic algorithm. The proposed restoration technique maintains the specified word length and the maximum number of nonzero digits in filter banks coefficients. Experimental results are presented at the end. It is demonstrated that the designed genetic algorithm is reliable, and efficient for designing QMF banks.Dept. of Electrical and Computer Engineering. Paper copy at Leddy Library: Theses & Major Papers - Basement, West Bldg. / Call Number: Thesis2004 .U67. Source: Masters Abstracts International, Volume: 43-05, page: 1785. Thesis (M.A.Sc.)--University of Windsor (Canada), 2004

Fabrication of Nanoporous Gold and Biological Applications

FABRICATION OF NANOPOROUS GOLD AND BIOLOGICAL APPLICATIONS By Badharinadh Uppalapati A Dissertation submitted in partial fulfillment of the requirements for the degree of Master of Science at Virginia Commonwealth University. Virginia Commonwealth University, 2014 Major Director: Maryanne M. Collinson, Professor, Department of Chemistry Fabrication of nanoporous gold electrodes by dealloying Au:Ag alloys has attracted much attention in sensing applications. In the first part of this work, the electrochemical response of the redox active molecule, potassium ferricyanide, in a solution of bovine serum albumin in buffer, serum or blood was studied using nanoporous gold and comparisons made to planar gold. Nanoporous gold electrodes with different surface areas and porosity were prepared by dealloying Au:Ag alloy in nitric acid for different dealloying times, specifically, 7.5, 10, 12.5, 20 minutes. Characterization was done using scanning electron microscopy (SEM), X-ray photoelectron spectroscopy (XPS), energy dispersive X-ray spectroscopy (EDX), and cyclic voltammetry (CV). Using cyclic voltammetry, planar gold electrodes exposed to bovine serum albumin in buffer showed a decrease in Faradaic peak current and an increase in peak splitting for potassium ferricyanide. The time required for the peak Faradaic current to drop to one-half of its original value was 3 minutes. At nanoporous gold electrodes, however, no significant reduction in Faradaic peak current or increase in peak splitting was observed. Nanoporous gold electrodes having the smallest pore size and largest surface area showed ideal results to biofouling. These electrodes are believed to impede the mass transport of large biomolecules while allowing small redox molecules to exchange electrons effectively with the electrode. In the second part of this work, the open circuit potential (OCP) of biologic solutions (e.g., blood) was measured using nanoporous gold electrodes. Historically, the measurement of blood redox potential has been hindered due to significant fouling and surface passivation of the metal electrodes. As nanoporous gold electrodes retained electrochemical activity of redox probes like potassium ferricyanide in human serum and rabbit blood, they were used to measure the OCP of blood and plasma from various animals like pig, rabbit, rat, monkey and humans. Comparisons were made to planar gold electrodes. The OCP values at both the planar gold and nanoporous gold electrodes were different from each other and there was variability due to different constituents present in blood and plasma. The OCP of rabbit blood and crashed rabbit blood was measured and the values were found to be different from each other indicating that ORP helps in measuring the animal condition. Ascorbic acid was added to rabbit and sheep blood and OCP measured at the nanoporous electrodes. Addition of reducing agent to blood at different intervals and different concentrations showed a change in potential with concentration

Anxiety Reactivity in Monozygotic Twins Discordant for Major Depression

Transient anxiety is a healthy response to stress. However, constant anxiety elicits negative responses and threatens an individual’s day-to-day living. The onset of anxiety disorders excluding specific phobias is often childhood to late adolescence or early adulthood. Though depression is characterized as a low-energy state unlike anxiety, there is a high concordance between anxiety and depression. “Nearly one-half of those diagnosed with depression are also diagnosed with an anxiety disorder” (“Facts and Statistics”). There are two goals of the study: 1. To compare the individual response levels between monozygotic (MZ) twins discordant for major depressive disorder (MDD) during an anxiety-provoking task. 2. To evaluate the relationship between self-report measures and physiological responses in adolescent MZ twins discordant for MDD. To identify how physiological responses vary between MZ twins discordant for major depression during a resting baseline and the 7.5% carbon dioxide (CO2) breathing challenge task. The data was analyzed using multiple statistical methods including paired samples t-test and correlational models. We expected that MDD affected twins would self-report greater distress in response to an anxiety-provoking laboratory challenge and exhibit reduced physiological arousal. MDD affected twins demonstrated a somewhat reduced skin conductance response during the anxiety provoking task, suggesting blunted physiological response, which is consistent with other biological markers such as cortisol. There was a significant increase in sympathetic-vagal heart variability rate during the physiological baseline for the MDD affected twins. Although we did not observe any statistically significant differences for SUDS ratings assessed during baseline or inhalation of 7.5% CO2 enriched air, MDD affected twins reported higher levels of distress during the recovery period compared to their MDD unaffected co-twin. The results will shed light on the lasting impact of major depression on physiologic and subjective measures during rest and the biological challenge.https://scholarscompass.vcu.edu/uresposters/1160/thumbnail.jp

Organophosphates in Chlorpyrifos Insecticide: Neurobehavioral Development of Children in Agricultural Communities

The chemicals found in fertilizers and pesticides are known to adversely affect the human nervous system even at low levels of exposure. Neither the agricultural industry nor the EPA can deny scientific findings regarding the toxic qualities of organophosphates in the insecticide chlorpyrifos, but that does not deter pesticide manufacturers from selling harmful products. In fact, Dow AgroSciences, a pesticide company, states on its website that, “Insecticides, such as chlorpyrifos, provide important protection for our food supply and thus safeguard farm and consumer economy.” To understand the health risks associated with pesticide exposure, I studied the influence of organophosphates in the insecticide chlorpyrifos on children living in agricultural communities, primarily in Salinas Valley, California. I performed the review by analyzing a variety of articles and academic sources that focused on organophosphate exposure and child neurobehavioral functioning. The findings indicate that organophosphates found in the insecticide chlorpyrifos block the enzyme acetylcholinesterase and initiate the accumulation of the neurotransmitter acetylcholine, leading to impairments in attention and cognition. Farm children exposed to the chemicals via the mother during gestation period or who are exposed through inhalation or physical contact may be at higher risks for ADHD and autism than reference children who are typically only exposed to organophosphates through diet. Further study is needed to understand gender-based effects following organophosphate exposure. It is only through understanding the damaging effects of chemicals in pesticides that policies can be constructed to effectively reduce pesticide application and encourage alternatives of crop rotation, intercropping, crop diversity, and the use of pests to fight pests in the agricultural society.https://scholarscompass.vcu.edu/uresposters/1162/thumbnail.jp

Development of Application Program for Harmonic Analysis

Increased power quality problems due to intensive usage of power electronic devices resulted in development of software applications to perform quick harmonic analysis. However, the present harmonic analysis applications have special software or computer locks requirements and occupy huge memory and cost high. An application program (using Microsoft Visual C++) that is simple yet accurate in calculations; with no special software or high memory requirements is developed in this thesis work. The program uses the automatic acceptance criteria (AAC) and the harmonic penetration techniques in calculating the system voltages. Several userriendly features and tools that aid in better understanding of system harmonics are included in the program. Comparison of case study results with Superharm simulation results proves the program?s accuracy. This thesis work resulted in an informative and time saving program with which the user can document the study results and analyze them with minimum effort

Synthetic Approaches to C-1 Derivatives of Pancratistatin

The contents of this thesis describe a synthetic approach towards C-1 derivatives of pancratistatin, utilizing a previously published pathway to access a late-stage cis-diol. The key steps of the approach include enzymatic dihydroxylation to provide the C-ring backbone, Myers’ transposition to convert an allylic alcohol into an olefin, and nucleophilic substitution of a tosylate to insert carbon-based nucleophiles at C-1. Experimental and spectral data are provided for the novel compounds

Subjective Measures of MZ and DZ Twins during Anxiety-Provoking Tasks

Temporary anxiety is a healthy response to stress; however, continuous anxiety can threaten an individual’s day-to-day living by eliciting negative responses. In the study, monozygotic 84 (MZ) and 153 dizygotic (DZ) adolescent twins pairs, ages 15 to 20 years, participated in anxiety-provoking tasks and subjective experiences of anxiety were measured using subjective units of distress (SUDS). The twin participants were recruited through the Mid-Atlantic Twin Registry (MATR) at Virginia Commonwealth University. The twins participated in a carbon dioxide (CO2) breathing task and a trier social stress task (TSST). The study aims were to evaluate the relationship between anxiety-provoking tasks and subjective experiences of anxiety in MZ and DZ adolescent twins and to compare SUDS ratings in the CO2 task to SUDS ratings in the TSST to determine which task produces greater anxiety. The data was analyzed using correlational models. MZ twins reported more similar SUDS in both the CO2 task and trier task than the DZ twins, however, not at significant values. The mean SUDS ratings for MZ twins and DZ twins were higher in the trier task than the CO2 task, suggesting that the trier task was a better inducer of anxiety than the CO2 task. The goal of the research was to characterize etiological pathways involved in the development of internalizing disorders and to set the stage for advancement of effective intervention and prevention programs, specifically by determining the relationship between SUDS ratings and anxiety-provoking tasks in MZ and DZ twins. Further study is needed to evaluate the heritability of anxiety response.https://scholarscompass.vcu.edu/uresposters/1213/thumbnail.jp

Improved Periodicity Mining in Time Series Databases

Time series data represents information about real world phenomena and periodicity mining explores the interesting periodic behavior that is inherent in the data. Periodicity mining has numerous applications such as in weather forecasting, stock market prediction and analysis, pattern recognition, etc. Recently, the suffix tree, a powerful data structure that efficiently solves many strings related problems has been used to gather information about repeated substrings in the text and then perform periodicity mining. However, periodicity mining deals with large amounts of data which makes it difficult to perform mining in main memory due to the space constraints of the suffix tree. Thus, we first propose the use of the Compressed Suffix Tree (CST) for space efficient periodicity mining in very large datasets. Given the time-space trade-off that comes with any practical usage of the CST, we provide a comprehensive empirical analysis on the practical usage of CSTs and traditional suffix trees for periodicity mining.;Noise is an inherent part of practical time series data, and it is important to mine periods in spite of the noise. This leads to the problem of approximate periodicity mining. Existing algorithms have dealt with the noise introduced between the occurrences of the periodic pattern, but not the noise introduced in the structure of the pattern itself. We present a taxonomy for approximate periodicity and then propose an algorithm that performs periodicity mining in the presence of noise introduced simultaneously in both the structure of the pattern and between the periodic occurrences of the pattern

Examining Interaction Effects in 2D Fermi Gases Using Renormalization Group Theory

We use the Renormalization Group (RG) method within the perturbation theory framework to study properties of a balanced, two-dimensional Fermi gas with short-range, attractive interactions in non-superfluid (normal) phase. We find that the RG method allows for the evaluation of logarithmic corrections to Equations of State in various regimes of density and temperature. We present two calculations using RG with perturbation theory. The first being a simplified RG scheme with an interpolation of crossover between RG flow in different regimes. The second calculation features a rigorous derivation whereby the Green\u27s function within a standard perturbation theory is renormalized to derive the density Equation of State. Calculations of associated observables like particle number density and isothermal compressibility via both of our approaches show agreement with experimental data using trapped balanced gases to varying degrees