Stacks and D-Brane Bundles

In this paper we describe explicitly how the twisted ``bundles'' on a D-brane worldvolume in the presence of a nontrivial B field, can be understood in terms of sheaves on stacks. We also take this opportunity to provide the physics community with a readable introduction to stacks and generalized spaces.Comment: 24 pages, LaTeX; v2: references adde

Role of Id-2 in the maintenance of a differentiated and noninvasive phenotype in breast cancer cells. Cancer Res

ABSTRACT Id proteins are inhibitors of basic helix-loop-helix transcription factors and generally stimulate cell proliferation and inhibit differentiation. We have shown that ectopic expression of Id-1 in murine mammary epithelial cells resulted in loss of differentiation and gain of invasive and proliferative abilities. Moreover, Id-1 was highly expressed in aggressive breast cancer cells in culture and in biopsies from infiltrating carcinomas. In contrast to Id-1, we found that, in vitro and in vivo, Id-2 mRNA and protein were up-regulated as mammary epithelial cells lost proliferative capacity and initiated differentiation. We further determined that this up-regulation of Id-2 was a necessary step toward a fully differentiated phenotype in breast cells. Here we show that one of the components of the extracellular matrix network, laminin, is responsible for the increase in Id-2 expression during differentiation. We also show that Id-2 expression is inversely correlated with the rate of proliferation in murine mammary epithelial cells and that Id-2 is expressed at a higher level in differentiated human breast cancer cells in comparison with very aggressive and metastatic cells. When reintroduced in aggressive breast cancer cells, Id-2 is able to reduce their proliferative and invasive phenotypes and decrease their level of matrix metalloproteinase 9 secretion as well as increase syndecan-1 expression. Moreover, little Id-2 protein expression is detectable in human biopsies from aggressive and invasive carcinomas in comparison with in situ carcinomas. In conclusion, Id-2 expression not only follows a pattern opposite to that of Id-1 during mammary gland development and breast cancer progression but also appears to act as an important protein for the maintenance of a differentiated and noninvasive phenotype in normal and transformed breast cells

Risk estimation of distant metastasis in node-negative, estrogen receptor-positive breast cancer patients using an RT-PCR based prognostic expression signature

<p>Abstract</p> <p>Background</p> <p>Given the large number of genes purported to be prognostic for breast cancer, it would be optimal if the genes identified are not confounded by the continuously changing systemic therapies. The aim of this study was to discover and validate a breast cancer prognostic expression signature for distant metastasis in untreated, early stage, lymph node-negative (N-) estrogen receptor-positive (ER+) patients with extensive follow-up times.</p> <p>Methods</p> <p>197 genes previously associated with metastasis and ER status were profiled from 142 untreated breast cancer subjects. A "metastasis score" (MS) representing fourteen differentially expressed genes was developed and evaluated for its association with distant-metastasis-free survival (DMFS). Categorical risk classification was established from the continuous MS and further evaluated on an independent set of 279 untreated subjects. A third set of 45 subjects was tested to determine the prognostic performance of the MS in tamoxifen-treated women.</p> <p>Results</p> <p>A 14-gene signature was found to be significantly associated (p < 0.05) with distant metastasis in a training set and subsequently in an independent validation set. In the validation set, the hazard ratios (HR) of the high risk compared to low risk groups were 4.02 (95% CI 1.91–8.44) for the endpoint of DMFS and 1.97 (95% CI 1.28 to 3.04) for overall survival after adjustment for age, tumor size and grade. The low and high MS risk groups had 10-year estimates (95% CI) of 96% (90–99%) and 72% (64–78%) respectively, for DMFS and 91% (84–95%) and 68% (61–75%), respectively for overall survival. Performance characteristics of the signature in the two sets were similar. Ki-67 labeling index (LI) was predictive for recurrent disease in the training set, but lost significance after adjustment for the expression signature. In a study of tamoxifen-treated patients, the HR for DMFS in high compared to low risk groups was 3.61 (95% CI 0.86–15.14).</p> <p>Conclusion</p> <p>The 14-gene signature is significantly associated with risk of distant metastasis. The signature has a predominance of proliferation genes which have prognostic significance above that of Ki-67 LI and may aid in prioritizing future mechanistic studies and therapeutic interventions.</p

Impact of phytoplankton community size on a linked global ocean optical and ecosystem model

Author Posting. © The Author(s), 2011. This is the author's version of the work. It is posted here by permission of Elsevier for personal use, not for redistribution. The definitive version was published in Journal of Marine Systems 89 (2012): 61-75, doi:10.1016/j.jmarsys.2011.08.002.We isolated the effect phytoplankton cell size has on varying remote sensing reflectance spectra (Rrs(λ)) in the presence of optically active constituents by using optical and radiative transfer models linked in an offline diagnostic calculation to a global biogeochemical/ecosystem/circulation model with explicit phytoplankton size classes. Two case studies were carried out, each with several scenarios to isolate the effects of chlorophyll concentration, phytoplankton cell size, and size-varying phytoplankton absorption on Rrs(λ). The goal of the study was to determine the relative contribution of phytoplankton cell size and chlorophyll to overall Rrs(λ) and to understand where a standard band ratio algorithm (OC4) may under/overestimate chlorophyll due to Rrs(λ) being significantly affected by phytoplankton size. Phytoplankton cell size was found to contribute secondarily to Rrs(λ) variability and to amplify or dampen the seasonal cycle in Rrs(λ), driven by chlorophyll. Size and chlorophyll were found to change in phase at low to mid-latitudes, but were anti-correlated or poorly correlated at high latitudes. Phytoplankton size effects increased model calculated Rrs(443) in the subtropical ocean during local spring through early fall months in both hemispheres and decreased Rrs(443) in the Northern Hemisphere high latitude regions during local summer to fall months. This study attempts to tease apart when/where variability about the OC4 relationship may be associated with cell size variability. The OC4 algorithm may underestimate [Chl] when the fraction of microplankton is elevated, which occurs in the model simulations during local spring/summer months at high latitudes in both hemispheres.Funding for this study came from a NASA Earth and Space Science Fellowship and University of Rhode Island Graduate School Oceanography Alumni Fellowship, both awarded to C. Mouw. The CCSM-3 BEC simulations were generated with support from NASA Ocean Biology and Biogeochemistry Program (NNX07AL80G) and the NSF Center for Microbial Oceanography Research and Education (C-MORE, EF-0424599)

Life and the Technical Transformation of Différance: Stiegler and the Noopolitics of Becoming Non-Inhuman

Through a re-articulation of Derridean différance, Bernard Stiegler claims that the human is defined by an originary default that displaces all psychic and social life onto technical supplements. His philosophy of technics re-articulates the logic of the supplement as concerning both human reflexivity and its supports, and the history of the différance of life itself. This has been criticised for reducing Derrida’s work to a metaphysics of presence, and for instituting a humanism of the relation to the inorganic. By refuting these claims, this article will show that Stiegler’s doubling of différance enables him to articulate the human as constituted by both the individuation characteristic of ‘life’, and that of a technical, psychic and collective individuation. Putting forward a reading of the logic of the trace in life, and emphasising the aspects of Leroi-Gourhan, Simondon, and Canguilhem that Stiegler uses in his reading of Derrida, I will demonstrate that the political stakes of adaption and adoption in Noo-Politics require this re-articulation of différance. Technics shapes the human future, arising from this differential mutation; marking the invention of the human as the site of the political

Equal consideration of all – an aporetic project?

The article considers the relationships among three arguments that purport to establish the intrinsically contradictory or paradoxical nature of the modern project aiming at the equal consideration of all. The claim that the inevitable historical insertion of universal-egalitarian norms leads to always particular and untransparent interpretations of grammatically universal norms may be combined with the claim that the logic of determination of political communities tends to generate exclusions. The combination of these two claims lends specific force to the third argument according to which equal consideration perpetually requires the non-egalitarian project of understanding (excluded) individuals on their own terms. Hence, taking off from a recent debate between Christoph Menke and Jürgen Habermas, I argue that the former is right to diagnose an aporetic self-reflection in egalitarian universalism, while agreeing with the latter about the indispensability of deliberative democratic frameworks for the defence of both egalitarian and non-egalitarian norms

Customer-Driven Research: The Enhanced Focus Group to Establish Value and Service Quality

This paper discusses a customer-driven research approach which overcomes many of the problems of existing market research techniques and integrates qualitative and quantitative techniques to provide insights into what creates value for customers. The approach described provides a variation on the Gap model and is illustrated in the context of business-to-business marketing. A by-product of the approach is that it acts as a very powerful impetus for service quality improvement