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Search Results: 1 - 10 of 10034 matches for " Marc Weiner "
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An Actin-Based Wave Generator Organizes Cell Motility
Orion D. Weiner,William A. Marganski,Lani F. Wu,Steven J. Altschuler,Marc W. Kirschner
PLOS Biology , 2012, DOI: 10.1371/journal.pbio.0050221
Abstract: Although many of the regulators of actin assembly are known, we do not understand how these components act together to organize cell shape and movement. To address this question, we analyzed the spatial dynamics of a key actin regulator—the Scar/WAVE complex—which plays an important role in regulating cell shape in both metazoans and plants. We have recently discovered that the Hem-1/Nap1 component of the Scar/WAVE complex localizes to propagating waves that appear to organize the leading edge of a motile immune cell, the human neutrophil. Actin is both an output and input to the Scar/WAVE complex: the complex stimulates actin assembly, and actin polymer is also required to remove the complex from the membrane. These reciprocal interactions appear to generate propagated waves of actin nucleation that exhibit many of the properties of morphogenesis in motile cells, such as the ability of cells to flow around barriers and the intricate spatial organization of protrusion at the leading edge. We propose that cell motility results from the collective behavior of multiple self-organizing waves.
An Actin-Based Wave Generator Organizes Cell Motility
Orion D Weiner ,William A Marganski,Lani F Wu,Steven J Altschuler,Marc W Kirschner
PLOS Biology , 2007, DOI: 10.1371/journal.pbio.0050221
Abstract: Although many of the regulators of actin assembly are known, we do not understand how these components act together to organize cell shape and movement. To address this question, we analyzed the spatial dynamics of a key actin regulator—the Scar/WAVE complex—which plays an important role in regulating cell shape in both metazoans and plants. We have recently discovered that the Hem-1/Nap1 component of the Scar/WAVE complex localizes to propagating waves that appear to organize the leading edge of a motile immune cell, the human neutrophil. Actin is both an output and input to the Scar/WAVE complex: the complex stimulates actin assembly, and actin polymer is also required to remove the complex from the membrane. These reciprocal interactions appear to generate propagated waves of actin nucleation that exhibit many of the properties of morphogenesis in motile cells, such as the ability of cells to flow around barriers and the intricate spatial organization of protrusion at the leading edge. We propose that cell motility results from the collective behavior of multiple self-organizing waves.
The DEEP2 Galaxy Redshift Survey: Clustering Dependence on Galaxy Stellar Mass and Star Formation Rate at z~1
Nick Mostek,Alison L. Coil,Michael C. Cooper,Marc Davis,Jeffrey A. Newman,Benjamin Weiner
Physics , 2012, DOI: 10.1088/0004-637X/767/1/89
Abstract: We present DEEP2 galaxy clustering measurements at z~1 as a function of stellar mass, star formation rate (SFR), and specific SFR (sSFR). We find a strong positive correlation between stellar mass and clustering amplitude on 1-10 h^-1 Mpc scales for blue, star-forming galaxies with 9.5 < log(M_*/M_sun) < 11 and no dependence for red, quiescent galaxies with 10.5 < log(M_*/M_sun) < 11.5. Using recently re-calibrated DEEP2 SFRs from restframe B-band magnitude and optical colors, we find that within the blue galaxy population at z~1, the clustering amplitude increases strongly with increasing SFR and decreasing sSFR. For red galaxies there is no significant correlation between clustering amplitude and either SFR or sSFR. Blue galaxies with high SFR or low sSFR are as clustered on large scales as red galaxies. We find that the clustering trend observed with SFR can be explained mostly, but not entirely, by the correlation between stellar mass and clustering amplitude for blue galaxies. We also show that galaxies above the star-forming "main sequence" are less clustered than galaxies below the main sequence, at a given stellar mass. These results are not consistent with the high sSFR population being dominated by major mergers. We also measure the clustering amplitude of our samples on small scales (< 0.3 h^-1 Mpc) and find an enhanced clustering signal relative to the best-fit large-scale power law for red galaxies with high stellar mass, blue galaxies with high SFR, and both red and blue galaxies with high sSFR. The increased small-scale clustering for galaxies with high sSFRs is likely linked to triggered star formation in interacting galaxies. These measurements provide strong constraints on galaxy evolution and halo occupation distribution models at z~1.
Reply to Jan Pouwer’s ‘The hidden flow’
James Weiner
Bijdragen tot de Taal-, Land- en Volkenkunde , 1991,
Abstract:
Preparing Nurses Internationally for Emergency Planning and Response
Elizabeth Weiner
Online Journal of Issues in Nursing , 2006,
Abstract: Competency-based education provides an international infrastructure for nurses to learn about emergency preparedness and response. The International Nursing Coalition for Mass Casualty Education (INCMCE) has developed competencies for all nurses, as well as online modules for meeting those competencies. In addition, other curriculum resources are available that range from face-to-face classes, web-based modules, and electronic journals, to complete pre-packaged materials. The author of this article describes competencies needed for emergency preparedness identified by Columbia University, Vanderbilt University, and the International Nursing Coalition for Mass Casualty Education, as well as various curriculum resources for emergency planning and response and also processes to prepare nurses for emergency responses. Examples of international "Best Practices" feature programs that provide examples of innovative educational strategies for preparing nurses for emergency response are presented. The author concludes that while curriculum resources are widely available, a better centralized clearinghouse could be made available for both faculty and students.
Book Review: Elinor Ostrom and Charlotte Hess (eds.). Understanding Knowledge as a Commons – From Theory to Practice. Cambridge, Mass.; MIT Press, 2006.
Maximiliane Weiner
Journal of International and Global Studies , 2011,
Abstract:
The Academic Journal: Has it a Future?
Gaby Weiner
Education Policy Analysis Archives , 2001,
Abstract: This article examines the current state of the academic journal. It does so for a number of reasons: the increasing expense of paper journals; the advent of electronic publishing; the use of publication in journals as an indicator of research quality (in addition to disseminating knowledge within a discipline) and consequent criticisms of systems of peer review and evaluation of scholarship; emergent issues of equity and access; and evidence of malpractice. These issues taken together constitute a critique of, and challenge to, the process whereby research papers become journal articles, which has in the past been viewed as unproblematic and straightforward. This paper brings together a wide range of literature in order to inform discussion about the future of the academic journal. It briefly examines the origins of the academic journal and then provides a comprehensive overview of current debates concerning how academic journals work today. In so doing, it raises questions about decisions that will need to be taken regarding the continuity or otherwise of the conventional academic journal, and how publishing practices may change in the future.
Research or "Cheerleading"? Scholarship on Community School District 2, New York City
Lois Weiner
Education Policy Analysis Archives , 2003,
Abstract: This article examines data on student achievement and school demographics not explored by the researchers who have promoted Community School District 2 (CSD 2) as a model of urban school reform that should be replicated elsewhere. Data on achievement indicate a remarkable degree of social and racial stratification among CSD 2's schools and levels of achievement that closely correlate with race, ethnicity, and poverty. In addition, when CSD 2's scores on state and city tests of mathematics are compared with results from CSD 25 in Queens, a school district that serves a population demographically similar, the superiority of its functioning becomes questionable. The article explains why the design of research on CSD 2 illustrates the perils to both research and policy when university-based researchers assume the role of “cheerleader” (Cuban, 1988), promoting reforms they have aided in implementing and assessing.
Ineffective Supersymmetry: Electroweak Symmetry Breaking from Extra Dimensions
Neal Weiner
Physics , 2001,
Abstract: Recently, a mechanism for electroweak symmetry breaking (EWSB) was discussed, in which the scale of EWSB is set by the scale of an additional dimension R ~ Tev^-1. The mechanism involves supersymmetry, but broken in such a fashion that high (four-dimensional) momentum loops are cut off by the finite size of the radius. In a Kaluza-Klein decomposition, a hard cutoff seems to give a strong cutoff dependence, while summing the entire tower is not only cutoff insensitive, but actually finite. Such behavior is easily understood in a formulation that respects five-dimensional locality. Finally, we note that certain models of this type naturally give operators which can ``fake'' the presence of a light Higgs in precision electroweak observables.
Unification without Unification
Neal Weiner
Physics , 2001,
Abstract: The logarithmic running of the gauge couplings alpha_1, alpha_2 and alpha_3, indicates that they may unify at some scale M_GUT ~ 10^16. This is often taken to imply that the standard model gauge group is embedded into some larger simple group in which quarks and leptons are placed in the same multiplet. These models have generic features, such as proton decay, and generic problems, namely the splitting of the Higgs doublet and triplet. Inspired by the recent discusion of dimensional deconstruction, we propose an interesting alternative: we postulate a strongly coupled SU(3)xSU(2)xU(1), which is not the remnant of a GUT, and is Higgsed with a weakly coupled SU(3)xSU(2)xU(1), which is the remnant of a GUT, or with a GUT group directly, into the diagonal subgroup. In this ``collapsed GUT'' mechanism, unification of coupling constants in the low energy theory is expected, but proton decay and the doublet/triplet splitting problem are entirely absent.
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