Robust computation of linear models by convex relaxation

Consider a dataset of vector-valued observations that consists of noisy inliers, which are explained well by a low-dimensional subspace, along with some number of outliers. This work describes a convex optimization problem, called REAPER, that can reliably fit a low-dimensional model to this type of data. This approach parameterizes linear subspaces using orthogonal projectors, and it uses a relaxation of the set of orthogonal projectors to reach the convex formulation. The paper provides an efficient algorithm for solving the REAPER problem, and it documents numerical experiments which confirm that REAPER can dependably find linear structure in synthetic and natural data. In addition, when the inliers lie near a low-dimensional subspace, there is a rigorous theory that describes when REAPER can approximate this subspace.Comment: Formerly titled "Robust computation of linear models, or How to find a needle in a haystack

APPRAISING OPPORTUNITIES TO BETTER UNDERSTAND WELL-BEING AND PERFORMANCE IN THE ORGANIZATIONAL SCIENCES

Despite a strong base of literature that shows appraisal (i.e., an individual’s assessment of the relevance of a possibly stressful situation to their own goals and their likelihood of effectively coping with it) is an important predictor of individual emotion, behavior, and performance, appraisal has been largely relegated to theory by the organizational sciences. The purpose of this work is to demonstrate why studying appraisal adds value to organizational science phenomena. This is accomplished through two empirical essays and a theory essay. First, a metaanalysis assesses the extent to which the challenge-hindrance framework, a perspective that explicitly suggests appraisal is unnecessary to understanding the effects of stressors (i.e., source of stress), applies to the context of entrepreneurship, where it is contended appraisal is most likely to play a role. Findings suggest that although the framework does apply, entrepreneurs (who operate in a more autonomous environment) experience better well-being and performance outcomes than non-entrepreneurs (who operate in more restrictive environments), and it is argued that appraisal is likely a factor in this difference. Second, a diary study tracks entrepreneurs’ daily appraisal, mood, and coping across a 20-day period in response to their self-identified largest source of stress. Results conclude that daily appraisal, which varies across time, directly affects daily mood and indirectly affects daily coping through mood, thus showing that appraisal predicts two important health indicators for entrepreneurs. Third, a theory on collective appraisal (i.e., the extent to which team members agree concerning which stressors are relevant to the team and how to respond to those stressors) is developed which turns appraisal from an individual-level construct to a team-level one. In so doing, the essay makes appraisal more useful to organizational science phenomena, which predominantly occur in team settings

Examining the Impacts of Virtual Mentoring On College Students\u27 Leadership Efficacy a Quantitative Study of C.A.M.P Osprey

Mentoring involves a collaborative and reciprocal sharing of knowledge for professional development. In leadership, a mentor is an individual who currently serves as a leader while guiding someone who aspires to be a leader in the future. This study evaluated how virtual mentoring compares to face-to-face mentoring on the development of leadership self-efficacy for college students. This study undertook a comparative analysis of face-to-face mentoring sessions and virtual mentoring sessions to explore the research question and hypotheses. The mentoring process involved a dyadic relationship where personalities create a positive and effective learning experience. A comparative analysis permitted the study to determine what differences occur in leadership efficacy for college students participating in virtual versus face-face mentoring. Efficacy was assessed on the students’ leadership abilities based on their evaluation of leadership mentoring sessions. The study realized that online learning was superior to relaying critical leadership skills to the student than face-to-face learning. As an implication, face-to-face mentoring experiences are not always possible due to geographical and budgetary constraints, virtual mentoring eliminates those barriers while still supplying a community learning experience. Additionally, virtual meetings also allow for access to marginalized populations that may not typically be available. The study was limited by the small sample population

Expression of transmembrane carbonic anhydrases, CAIX and CAXII, in human development

Background: Transmembrane CAIX and CAXII are members of the alpha carbonic anhydrase (CA) family. They play a crucial role in differentiation, proliferation, and pH regulation. Expression of CAIX and CAXII proteins in tumor tissues is primarily induced by hypoxia and this is particularly true for CAIX, which is regulated by the transcription factor, hypoxia inducible factor-1 (HIF-1). Their distributions in normal adult human tissues are restricted to highly specialized cells that are not always hypoxic. The human fetus exists in a relatively hypoxic environment. We examined expression of CAIX, CAXII and HIF-1 alpha in the developing human fetus and postnatal tissues to determine whether expression of CAIX and CAXII is exclusively regulated by HIF-1. Results: The co-localization of CAIX and HIF-1 alpha was limited to certain cell types in embryonic and early fetal tissues. Those cells comprised the primitive mesenchyma or involved chondrogenesis and skin development. Transient CAIX expression was limited to immature tissues of mesodermal origin and the skin and ependymal cells. The only tissues that persistently expressed CAIX protein were coelomic epithelium (mesothelium) and its remnants, the epithelium of the stomach and biliary tree, glands and crypt cells of duodenum and small intestine, and the cells located at those sites previously identified as harboring adult stem cells in, for example, the skin and large intestine. In many instances co-localization of CAIX and HIF-1 alpha was not evident. CAXII expression is restricted to cells involved in secretion and water absorption such as parietal cells of the stomach, acinar cells of the salivary glands and pancreas, epithelium of the large intestine, and renal tubules. Co-localization of CAXII with CAIX or HIF-1 alpha was not observed. Conclusion: The study has showed that: 1) HIF-1 alpha and CAIX expression co-localized in many, but not all, of the embryonic and early fetal tissues; 2) There is no evidence of co-localization of CAIX and CAXII; 3) CAIX and CAXII expression is closely related to cell origin and secretory activity involving proton transport, respectively. The intriguing finding of rare CAIX-expressing cells in those sites corresponding to stem cell niches requires further investigation

On Non-Abelian Symplectic Cutting

We discuss symplectic cutting for Hamiltonian actions of non-Abelian compact groups. By using a degeneration based on the Vinberg monoid we give, in good cases, a global quotient description of a surgery construction introduced by Woodward and Meinrenken, and show it can be interpreted in algebro-geometric terms. A key ingredient is the `universal cut' of the cotangent bundle of the group itself, which is identified with a moduli space of framed bundles on chains of projective lines recently introduced by the authors.Comment: Various edits made, to appear in Transformation Groups. 28 pages, 8 figure

Amino acid residues that are important for Hyal2 function as a receptor for jaagsiekte sheep retrovirus

BACKGROUND: Infection by jaagsiekte sheep retrovirus (JSRV) and by enzootic nasal tumor virus (ENTV) depends on cell-surface expression of the virus entry receptor, hyaluronidase 2 (Hyal2). Human Hyal2 binds the envelope (Env) proteins of these viruses and is functional as a receptor, but Hyal2 from mice does not bind Env nor does it mediate entry of either virus. Here we have explored the amino acid determinants that account for the difference in receptor function. RESULTS: Analysis of human-mouse Hyal2 chimeric proteins showed that amino acid differences responsible for the difference in Hyal2 receptor activity were localized to the central third of Hyal2. Human Hyal2 mutants containing single or double amino acid replacements with the respective mouse amino acids were generated across this region and were assayed for activity. None of the single or double mutation reduced the receptor activity of human Hyal2 by more than 10-fold, whereas mouse Hyal2 activity is reduced 1,000-fold from that of human Hyal2. While the 3-dimensional structures of mammalian Hyal2 proteins are unknown, bee venom hyaluronidase shows significant amino acid similarity to human and mouse Hyal2 and its structure has been determined. Many mutations having the largest negative effects on human Hyal2 function mapped to a small region of the bee venom hyaluronidase close to but not overlapping the active site of the enzyme, suggesting that this site represents the binding site for Env. Analysis of synonymous and non-synonymous nucleotide substitutions in the coding sequences of multiple mammalian Hyal2 proteins shows that the proteins are undergoing strong selection for amino acid conservation. We found no evidence for positive selection of amino acid changes that might reflect evolution of mammalian hosts to resist JSRV or ENTV infection. CONCLUSION: These results show that the greatly reduced receptor activity of mouse Hyal2 in comparison to that of human Hyal2 is determined by multiple amino acid changes acting in concert. In particular, no one amino acid change blocks infection. However, the most important amino acids map to a small patch on a predicted 3-dimensional Hyal2 structure, which may represent the binding site for Env

Return visits to the emergency department

A persistent problem for emergency physicians is the patient who returns unscheduled to the emergency department with a problem that either has not improved or has worsened. The purpose of this study was to evaluate the frequency of revisits and the nature of the problems. All patients returning within 72 hours of their initial visit were entered into the study. The charts were evaluated for classification of problem, unavoidable v avoidable returns, and errors in medical care or patient education. Of the 64,336 patients seen during the study, 255 returned within 72 hours. Eighty-three (32.5%) of the returns were found to be avoidable with better patient education or medical care on the initial visit. The revisit population is a high-risk group of patients who should be approached carefully by emergency physicians.Peer Reviewedhttp://deepblue.lib.umich.edu/bitstream/2027.42/26598/1/0000139.pd

Regulating the automobile

Division of Policy Research and Analysis. National Science Foundatio