De Sitter Bounces

By analytically continuing recently-found instantons, we construct time-dependent solutions of Einstein-Maxwell de Sitter gravity which smoothly bounce between two de Sitter phases. These deformations of de Sitter space undergo several stages in their time evolution. Four and five-dimensional de Sitter bounces can be lifted to non-singular time-dependent solutions of M-theory.Comment: Latex, 18 pages, 5 figure

Polymorphic Students

Objective: In an effort to break away from the stale classifications of community college students that stem from the hegemonic perspective of previous literature, this work utilizes the perceptions of community college practitioners to demonstrate new ways of understanding the identities of community college students. Method: By utilizing Gee’s identity theory and Grillo’s theory of intersectionality, we analyze interviews with community college practitioners from three different community colleges on the West coast of the United States to answer these questions: What identities (i.e., natural, institutional, and discursive) do faculty and administrators recognize in community college students? In what ways do community college faculty and administrators describe and conceptualize community college students? Findings: First, community college student identities are intricate and have changed with time; there are two different institutional views held by organizational members—the educational view and the managerial view—which both shape the construction of student identities and play a prominent role in determining which students are disadvantaged. Second, organizational members constructed meanings of student achievement and value (i.e., attributes or outcomes of the ideal student, or what policy makers and institutions refer to as success) according to organizational priorities and perspectives. Conclusion: This investigation encapsulates and elucidates the portrayals and understandings of community college students held by community college administrators and faculty as a means to acknowledge the diverse identities among these students. Scholars and practitioners are encouraged to acknowledge the polymorphic identities of this diverse population to improve scholarship and practice

Evidence of the presence of calcium/calmodulin-dependent protein kinase IV in human sperm and its involvement in motility regulation

The mechanisms involved in the regulation of mammalian sperm motility are not well understood. Calcium ions (Ca(2+)) have been suggested to play a key role in the maintenance of motility; nevertheless, how Ca(2+) modulates this process has not yet been completely characterized. Ca(2+) can bind to calmodulin and this complex regulates the activity of multiple enzymes, including Ca(2+)/calmodulin-dependent protein kinases (CaM kinases). Results from this study confirmed that the presence of Ca(2+) in the incubation medium is essential for maintaining human sperm motility. The involvement of CaM kinases in Ca(2+) regulation of human sperm motility was evaluated using specific inhibitors (KN62 and KN93) or their inactive analogues (KN04 and KN92 respectively). Sperm incubation in the presence of KN62 or KN93 led to a progressive decrease in the percentage of motile cells; in particular, incubation with KN62 also reduced sperm motility parameters. These inhibitors did not alter sperm viability, protein tyrosine phosphorylation or the follicular fluid-induced acrosome reaction; however, KN62 decreased the total amount of ATP in human sperm. Immunological studies showed that Ca(2+)/calmodulin-dependent protein kinase IV (CaMKIV) is present and localizes to the human sperm flagellum. Moreover, CaMKIV activity increases during capacitation and is inhibited in the presence of KN62. This report is the first to demonstrate the presence of CaMKIV in mammalian sperm and suggests the involvement of this kinase in the regulation of human sperm motility.Fil: Marin Briggiler, Clara Isabel. Consejo Nacional de Investigaciones Científicas y Técnicas. Instituto de Biología y Medicina Experimental. Fundación de Instituto de Biología y Medicina Experimental. Instituto de Biología y Medicina Experimental; ArgentinaFil: Jha, Kula N.. University of Virginia; Estados UnidosFil: Chertihin, Olga. University of Virginia; Estados UnidosFil: Buffone, Mariano Gabriel. Laboratorio de Estudios en Reproducción; ArgentinaFil: Herr, John C,. University of Virginia; Estados UnidosFil: Vazquez, Monica Hebe. Consejo Nacional de Investigaciones Científicas y Técnicas. Instituto de Biología y Medicina Experimental. Fundación de Instituto de Biología y Medicina Experimental. Instituto de Biología y Medicina Experimental; ArgentinaFil: Visconti, Pablo E.. University of Massachussets; Estados Unido