Fearless Friday Naima Scott & Caroline Lewis

In this week’s edition of Fearless Friday, SURGE is honoring Naima Scott and Caroline Lewis for all the work they have done in our community as well as working on this year’s Vagina Monologues. [excerpt

Getting on the E List: E-Mail Use in a Community of Service Provider

This case examines how a community of organizations providing service to people experiencing homelessness made use of an electronic mail list. Current economic conditions have encouraged organizations in various sectors—including nonprofits—that might normally compete for scarce resources to collaborate with one another to increase their chances of survival. One set of tools likely to be of value in such relationships includes various online discussion technologies. An examination of this community’s email list use over a three-year period suggests a somewhat complex picture regarding technology use. More specifically, some issues both constrain and enable use. Additionally, seemingly basic and minimal uses of the list provided not only the greatest functionality for the users, but also led to several unanticipated consequences for those involved

Linear effects of perturbed recombination

Perturbations in the ionization fraction after recombination affect the Compton cooling of density perturbations. Once the gas temperature starts to decouple from the CMB temperature, ionization fraction perturbations can have a significant influence on the subsequent gas temperature perturbation evolution. This directly affects the 21cm spin temperature of the gas, and also modifies the small-scale baryon perturbation evolution via the difference in baryon pressure. The effect on the gas temperature perturbations can be significant on all scales, and galactic-scale baryon perturbations are modified at the percent level at redshifts z >~ 100 where numerical simulations are typically started.Comment: 5 pages; for more details of effect on 21cm see astro-ph/0702600; code available at http://camb.info/sources

The Law, Culture, and Economics of Fashion

Fashion is one of the world's most important creative industries. As the most immediate visible marker of self-presentation, fashion creates vocabularies for self-expression that relate individuals to society. Despite being the core of fashion and legally protected in Europe, fashion design lacks protection against copying under U.S. intellectual property law. This Article frames the debate over whether to provide protection to fashion design within a reflection on the cultural dynamics of innovation as a social practice. The desire to be in fashion - most visibly manifested in the practice of dress - captures a significant aspect of social life, characterized by both the pull of continuity with others and the push of innovation toward the new. We explain what is at stake economically and culturally in providing legal protection for original designs, and why a protection against close copies only is the proper way to proceed. We offer a model of fashion consumption and production that emphasizes the complementary roles of individual differentiation and shared participation in trends. Our analysis reveals that the current legal regime, which protects trademarks but not fashion designs from copying, distorts innovation in fashion away from this expressive aspect and toward status and luxury aspects. The dynamics of fashion lend insight into dynamics of innovation more broadly, in areas where consumption is also expressive. We emphasize that the line between close copying and remixing represents an often underappreciated but promising direction for intellectual property today. Published in Stanford Law Review, Vol. 61, March 2009.

Investigating dark matter substructure with pulsar timing: I. Constraints on ultracompact minihalos

Small-scale dark matter structure within the Milky Way is expected to affect pulsar timing. The change in gravitational potential induced by a dark matter halo passing near the line of sight to a pulsar would produce a varying delay in the light travel time of photons from the pulsar. Individual transits produce an effect that would either be too rare or too weak to be detected in 30-year pulsar observations. However, a population of dark matter subhalos would be expected to produce a detectable effect on the measured properties of pulsars if the subhalos constitute a significant fraction of the total halo mass. The effect is to increase the dispersion of measured period derivatives across the pulsar population. By statistical analysis of the ATNF pulsar catalogue, we place an upper limit on this dispersion of $\log \sigma_{\dot{P}} \leq -17.05$. We use this to place strong upper limits on the number density of ultracompact minihalos within the Milky Way. These limits are completely independent of the particle nature of dark matter.Comment: 9 pages, 5 figues, includes erratum published in MNRA

Mechanochemical Regulation of Epithelial Tissue Remodeling: A Multiscale Computational Model of the Epithelial-Mesenchymal Transition Program

Epithelial-mesenchymal transition (EMT) regulates the cellular processes of migration, growth, and proliferation - as well as the collective cellular process of tissue remodeling - in response to mechanical and chemical stimuli in the cellular microenvironment. Cells of the epithelium form cell-cell junctions with adjacent cells to function as a barrier between the body and its environment. By distributing localized stress throughout the tissue, this mechanical coupling between cells maintains tensional homeostasis in epithelial tissue structures and provides positional information for regulating cellular processes. Whereas in vitro and in vivo models fail to capture the complex interconnectedness of EMT-associated signaling networks, previous computational models have succinctly reproduced components of the EMT program. In this work, we have developed a computational framework to evaluate the mechanochemical signaling dynamics of EMT at the molecular, cellular, and tissue scale. First, we established a model of cell-matrix and cell-cell feedback for predicting mechanical force distributions within an epithelial monolayer. These findings suggest that tensional homeostasis is the result of cytoskeletal stress distribution across cell-cell junctions, which organizes otherwise migratory cells into a stable epithelial monolayer. However, differences in phenotype-specific cell characteristics led to discrepancies in the experimental and computational observations. To better understand the role of mechanical cell-cell feedback in regulating EMT-dependent cellular processes, we introduce an EMT gene regulatory network of key epithelial and mesenchymal markers, E-cadherin and N-cadherin, coupled to a mechanically-sensitive intracellular signaling cascade. Together these signaling networks integrate mechanical cell-cell feedback with EMT-associated gene regulation. Using this approach, we demonstrate that the phenotype-specific properties collectively account for discrepancies in the computational and experimental observations. Additionally, mechanical cell-cell feedback suppresses the EMT program, which is reflected in the gene expression of the heterogeneous cell population. Together, these findings advance our understanding of the complex interplay in cell-cell and cell-matrix feedback during EMT of both normal physiological processes as well as disease progression