Anthropology of the Crowd, Blog 10

Student blog posts from the Great VCU Bike Race Book

The importance of being divisible by three in alternative splicing

Alternative splicing events that are conserved in orthologous genes in different species are commonly viewed as reliable evidence of authentic, functionally significant alternative splicing events. Several recent bioinformatic analyses have shown that conserved alternative exons possess several features that distinguish them from alternative exons that are species-specific. One of the most striking differences between conserved and species-specific alternative exons is the high percentage of exons that preserve the reading frame (exons whose length is an exact multiple of 3, termed symmetrical exons) among the conserved alternative exons. Here, we examined conserved alternative exons and found several features that differentiate between symmetrical and non-symmetrical alternative exons. We show that symmetrical alternative exons have a strong tendency not to disrupt protein domain structures, whereas the tendency of non-symmetrical alternative exons to overlap with different fractions of protein domains is similar to that of constitutive exons. Additionally, skipping isoforms of non-symmetrical alternative exons are strongly underrepresented, compared with their including isoforms, suggesting that skipping of a large fraction of non-symmetrical alternative exons produces transcripts that are degraded by the nonsense-mediated mRNA decay mechanism. Non-symmetrical alternative exons also show a tendency to reside in the 5′ half of the CDS. These findings suggest that alternative splicing of symmetrical and non-symmetrical exons is governed by different selective pressures and serves different purposes

Low Rank Matrix-Valued Chernoff Bounds and Approximate Matrix Multiplication

In this paper we develop algorithms for approximating matrix multiplication with respect to the spectral norm. Let A\in{\RR^{n\times m}} and B\in\RR^{n \times p} be two matrices and \eps>0. We approximate the product A^\top B using two down-sampled sketches, \tilde{A}\in\RR^{t\times m} and \tilde{B}\in\RR^{t\times p}, where t\ll n such that \norm{\tilde{A}^\top \tilde{B} - A^\top B} \leq \eps \norm{A}\norm{B} with high probability. We use two different sampling procedures for constructing \tilde{A} and \tilde{B}; one of them is done by i.i.d. non-uniform sampling rows from A and B and the other is done by taking random linear combinations of their rows. We prove bounds that depend only on the intrinsic dimensionality of A and B, that is their rank and their stable rank; namely the squared ratio between their Frobenius and operator norm. For achieving bounds that depend on rank we employ standard tools from high-dimensional geometry such as concentration of measure arguments combined with elaborate \eps-net constructions. For bounds that depend on the smaller parameter of stable rank this technology itself seems weak. However, we show that in combination with a simple truncation argument is amenable to provide such bounds. To handle similar bounds for row sampling, we develop a novel matrix-valued Chernoff bound inequality which we call low rank matrix-valued Chernoff bound. Thanks to this inequality, we are able to give bounds that depend only on the stable rank of the input matrices...Comment: 15 pages, To appear in 22nd ACM-SIAM Symposium on Discrete Algorithms (SODA 2011

Intimate Partner Violence Against Ahtna (Alaska Native) Women in the Copper River Basin

This study examined the frequency, severity, and consequences of intimate partner violence against an availability sample of Athabaskan women (n=91) residing in the interior of Alaska. Data about victimization experiences as well as cultural involvement, residential mobility, living arrangements, social cohesion, alcohol use, and post-traumatic stress were gathered through interviews. Slightly less than two-thirds of respondents (63.7%) reported intimate partner violence victimization at some point in their lifetime. Nearly one out of five women surveyed (17.6%) reported that they had been physically assaulted by an intimate partner in the most recent 12 months. Intimate partner victimization was more prevalant and more frequent when compared to what has been reported by the National Violence Against Women Survey.National Institute of Justice, Office of Justice Programs, United States Department of Justice Grant No. 2000-WT-VX-0013Table of Contents / Table of Tables / Table of Figures / Abstract / Executive Summary / Acknowledgements / INTRODUCTION: The Setting; The Problem // METHODS: Collaboration and Cultural Sensitivity / Subject Recruitment / Subject Safety and the IRB / Survey Instrument // RESULTS: Prevalence and Incidence of Intimate Partner Violence / Comparison with Previous Estimates / Correlates and Risk Factors Associated with Intimate Partner Violence / Injury Among Victims of Intimate Partner Violence / Victims' Involvement with the Justice System // CONCLUSIONS / REFERENCES / APPENDICES: Main Survey Instrument; Detailed Physical Assault Incident Repor

Integrality gaps of semidefinite programs for Vertex Cover and relations to ℓ1\ell_1 embeddability of Negative Type metrics

We study various SDP formulations for {\sc Vertex Cover} by adding different constraints to the standard formulation. We show that {\sc Vertex Cover} cannot be approximated better than $2-o(1)$ even when we add the so called pentagonal inequality constraints to the standard SDP formulation, en route answering an open question of Karakostas~\cite{Karakostas}. We further show the surprising fact that by strengthening the SDP with the (intractable) requirement that the metric interpretation of the solution is an $\ell_1$ metric, we get an exact relaxation (integrality gap is 1), and on the other hand if the solution is arbitrarily close to being $\ell_1$ embeddable, the integrality gap may be as big as $2-o(1)$. Finally, inspired by the above findings, we use ideas from the integrality gap construction of Charikar \cite{Char02} to provide a family of simple examples for negative type metrics that cannot be embedded into $\ell_1$ with distortion better than 8/7-\eps. To this end we prove a new isoperimetric inequality for the hypercube.Comment: A more complete version. Changed order of results. A complete proof of (current) Theorem

The Relationship between high risk athletes risk perception of adventurous activities, their travel destinations and their vacation travel patterns

Adventure tourism is a growing market segment in the US; the decision to participate in adventurous activities and the selection of risky destinations while on vacation involves ones risk perception about the physical risks that can lead to fatal results from these activities. Existing literature suggest that risk perception is a determinate in choosing a leisure activity and destination while on vacation and that level of tolerance to uncertainty can determine travel behavior (Floyd & Gibson, 2004; Fuchs & Reichel, 2006; Hofstede, 2001; Iso- Ahola, 1980, 1982; Money & Crotts, 2003; Reisinger & Mavondo, 2005). People who have high tolerance to risk and uncertainty and are seeking high risk activities and destinations are defined in the literature as sensations seekers. Research shows that high risk athletes are sensation seekers that would take risks for the sake of novelty experience and that their risk perception of risky activities is different that of non-athletes (Straub, 1982; Woitas-Slubowska, 2006; Zuckerman, 2007). This research will look at high risk athletes risk perceptions of risky destinations and activities to determine the probability of them participating in adventure tourism

Hanging From the Poplar Tree: Kanye West and Racism in Internet Folklore

Folk ideas regarding African-Americans in nineteenth century America fueled racially charged stereotypes that served to promote segregation into the 1960s. Despite the belief of many Americans that the Civil Rights movement has ushered in an era of “postracism,” artifacts of digital culture prove that racism is still prevalent in American culture. Members of online social groups spread rumors and memes of popular African-American figures to propagate old racist stereotypes and spread conspiracy rumors among younger audiences. Folklorists Bill Ellis, Gary Fine, Véronique Campion-Vincente, and Patricia Turner provided foundational scholarship on rumors, conspiracy theories, and how they divide ethnic groups in wider American culture. This paper applies their works to an analysis of several memes and YouTube videos regarding Kanye West, an African-American rapper. It also considers how stereotypes of African-Americans as discussed in Marlon Riggs’ documentary Ethnic Notions still hold influence over current American attitudes towards African-Americans in the broader culture

Measurement Issues

Examining groups from a systems perspective may be natural for contemporary social workers. The systems perspective, or group-as a-whole orientation, provides a solid conceptual foundation for understanding groups (Agazarian, 1992). However, to engage in evidence-based group work practice or to conduct research on groups, abstract group concepts must be conceptualized and operationalized (Engel & Schutt, 2009). In qualitative approaches the conceptualization occurs after data have been collected to extract meaning from the observations. In quantitative approaches, operationalization is the process of assigning values to observable indicators of constructs prior to collecting data (Bonito, Ruppel, & Keyton, 2012). Whether inductive or deductive, the collection of observations is the process of measurement. This chapter discusses measurement issues in groups

Oxygen vacancies in strained SrTiO3_{3} thin films: formation enthalpy and manipulation

We report the enthalpy of oxygen vacancy formation in thin films of electron-doped SrTiO$_{3}$, under different degrees of epitaxial stress. We demonstrate that both compressive and tensile strain decrease this energy at a very similar rate, and promote the formation of stable doubly ionized oxygen vacancies. Moreover, we also show that unintentional cationic vacancies introduced under typical growth conditions, produce a characteristic rotation pattern of TiO$_6$ octahedra. The local concentration of oxygen vacancies can be modulated by an electric field with an AFM tip, changing not only the local electrical potential, but also producing a non-volatile mechanical response whose sign (up/down) can be reversed by the electric field.Comment: Physical Review B (accepted for publication