McNair Scholars Undergraduate Research Journal, 2011, Vol. 3

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    Zipf ’s Law and Its Correlation to the GDP of Nations
    (2011) Skipper, Rachel K.; Rosenberg, Jonathan
    This study looks at power laws, specifically Zipf ’s law and Pareto distributions, previously used to describe city size distribution, income distribution within firms, and word distribution within languages and documents among other things, and Gibrat’s law describing growth rate. This study seeks to discover if Zipf’s law can also be used to model the distribution of GDP’s worldwide using Gibrat’s law as a justification. The simplest method to determine Zipf's law’s applicability, and the one used in this study, was to create a log log plot, plotting rank versus size of the GDPs. Using that plot, Zipf ’s law was verified through two criteria. First the plot must appear linear and second it must have a slope of -1. For the purpose of this study, the data looked at was for all countries and then countries split into categories of emerging economies and advanced economies for the years 2005, 2006, 2007, and 2008. The results of this study showed that all countries and countries with emerging economies did not appear linear on the log log plot while advanced economies appeared linear with a slope roughly -.70, suggesting that GDP distribution of advanced economies instead follow a Pareto distribution. Advanced economies also showed a significantly smaller variation in growth rates over the four years as implied by Gibrat’s law. This was used as a possible explanation for the distribution discovered.
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    Does Situation Type Moderate the Relationship Between Maternal Attention-Deficit/Hyperactivity Disorder (ADHD) Symptoms and Observed Parenting?
    (2011) Santana, Erin Marie; O’Brien, Kelly; Chronis-Tuscano, Andrea
    Previous research has found associations between parental attention-deficit/hyperactivity disorder (ADHD) symptoms and maladaptive parenting. In contrast, some suggest a “similarity-fit hypothesis,” in which equal levels of ADHD symptoms between parents and children may be associated with a shared behavioral tempo, which may result in a better “fit.” However, this theory has only been tested in a free-play situation (Psychogiou et al., 2008a). This study tested the “similarity-fit hypothesis” using two samples of children with ADHD and their mothers across two tasks to examine the extent situational context is associated with ineffective parenting. Mother-child dyads were observed in an unstructured free-play task and a structured homework task in two studies of parent-child interactions consisting of a total of 175 elementary-aged children with DSM-IV ADHD. A significant main effect for situation type on positive parenting and ineffective commands was found in Study 2. Mothers displayed higher rates of positive parenting and ineffective commands in the homework task compared to the free-play task. A trend-level interaction (Situation Type x Maternal ADHD symptoms) was found in Study 1. Probing the interaction revealed that higher levels of maternal ADHD symptoms predicted higher levels of ineffective commands in the homework task, but not in the free-play task. Although, our results were both consistent and inconsistent with the literature examining families where ADHD is present in children and parents, our study’s findings may contribute to the limited literature using observational measures to examine associations between maternal ADHD symptoms and parenting. Our results suggest the challenging nature of the structured homework task may tax a mother’s core symptoms of ADHD, which contrasts with the “similarity-fit hypothesis.” Further research testing the “similarity-fit hypothesis” is needed to determine the extent situational context impacts the relationship between maternal ADHD symptoms and parenting.
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    Decline and Disparities in Mammography Use Trends by Socioeconomic Status and Race/Ethnicity
    (2011) Rattanawatkul, Kanokphan; Carter-Pokras, Olivia
    The second leading cause of death in women in the United States is breast cancer. While it remains the most common type of cancer in women, early detection through mammography screening has been used to combat and treat breast cancer. But after the 2000, the rates of mammography have been declining. The purpose of this study is to examine whether or not the decline has continued and whether all racial/ethnic and socioeconomic groups experienced the same rate of decline. The study further explores the reasons why there are greater decline rates and breast cancer disparities among African American women, and women with lower income and education. Data from the National Health Interview Survey (2003 to 2005) and the Behavioral Risk Factor Surveillance System (2002 to 2004) were used to calculate the percent decline for the total population and by race/ethnicity and socioeconomic status. Mammography rates declined between 2003-2005 (NHIS) and 2002-2004 (BRFSS). Data from both the NHIS and BRFSS show a greater rate of decline for African American women, and women with lower income and education. An expert sampling method is used to recruit participants to explore their views on the reasons why breast cancer disparities existed among African American women, women with lower income, and women with lower education. These results differ from previous studies which examined broader time interval (2000 to 2005). Further research is recommended to explore whether the rates of decline have continued, the impact of the decline in mammography rates on breast cancer incidence, mortality, and stage of diagnosis, as well as the underlying reasons for the observed decline in mammography rates and for disparities in the rates of decline.
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    Understanding the Abscisic Acid Pathway Using Guard Cell Specific Genes and the Anti-Aging Drug Spermidine
    (2011) Pearson, Deryck; Kwak, June M.; Villiers, Florent; Jammes, Fabien
    Plants must respond to environmental stress including drought and harsh winters. Overcoming these stresses depend heavily on timing of stomatal closure and seed germination. My research focused on both chemical and genetic aspects involved in the abscisic acid pathway that controls both stomatal closures in leaves and seed germination in Arabidopsis thaliana. My first study focused on recognizing specific proteins involved in the abscisic acid pathway for stomatal guard cell closure. Given specific promoters for their respective proteins, it is possible to determine whether or not proteins are guard cell specific. GatewayTM technology utilizes a series of reactions to create a clone containing a promoter of interest called an expression vector. By injecting this vector directly into the leaf of Arabidopsis, the plant will use the promoter to create the guard cell specific protein. The second study examined the effect of the anti-aging drug Spermidine on seed sensitivity to abscisic acid concentration during seed germination. By varying the concentration of Spermidine and abscisic acid exposure to seeds then observing the number of surviving seeds, the effects of Spermidine on seed germination can be measured. Spermidine is expected to reduce seed sensitivity to abscisic acid leading to increased seed germination.
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    A Comparison of the Inhibition of Nucleocytoplasmic Trafficking by Viral Effectors from Cardioviruses and Rhinoviruses
    (2011) Okafor, Obiageri; Palmenberg, Ann; Basta, Holly
    Cardioviruses and Enteroviruses of the Picornaviridae family exhibit similar infections. Viruses from the two genera inhibit nuclear import/export through the nuclear pore complex (NPC), a channel between the cytoplasm and nucleus. However, the diseases caused by viruses within these two genera vary in severity. Encephalomyocarditis virus (EMCV), a cardiovirus, uses a small potent protein called Leader (L) to inhibit trafficking through the NPC, thereby causing encephalitis in pigs and other animals. Human rhinovirus (HRV), an enterovirus, uses a protease, 2A, to inhibit trafficking through the nuclear pore and infection is associated with the common cold. It is unknown why cardioviruses and enteroviruses cause diseases of varying severity. In addition, little information is known about whether the mechanism of these viruses’ toxic proteins in inhibiting nuclear transport through the NPC, may correlate with the severity variation of the disease phenotypes of these viruses. To test this, we would compare the rates of nuclear efflux by three different Cardioviruses and three serotypes of HRV. Molecular techniques would be used to clone and express recombinant L proteins of the cardioviruses. Both nuclear efflux and nuclear import assays would be performed using recombinant green fluorescent protein (GFP) to track infection in HeLa cells for the effects of either L protein or 2A protease. This is done to determine the extent of inhibition of nuclear trafficking at the NPC. Knowledge of the kinetics between cardioviruses and HRV could hint at the different pathogenicities of these viruses. Also, it could add to our understanding of whether the genotype of a virus can infer the phenotype of the disease it causes.