Coasting cosmologies with time dependent cosmological constant

The effect of a time dependent cosmological constant is considered in a family of scalar tensor theories. Friedmann-Robertson-Walker cosmological models for vacumm and perfect fluid matter are found. They have a linear expansion factor, the so called coasting cosmology, the gravitational "constant" decreace inversely with time; this model satisfy the Dirac hipotesis. The cosmological "constant" decreace inversely with the square of time, therefore we can have a very small value for it at present time.Comment: 7 pages, latex file (ijmpal macro), accepted for publication in Int. Mod. Phys.

Analyzing the mechanisms that facilitate the subtype-specific assembly of γ-aminobutyric acid type A receptors

Impaired inhibitory signaling underlies the pathophysiology of many neuropsychiatric and neurodevelopmental disorders including autism spectrum disorders and epilepsy. Neuronal inhibition is regulated by synaptic and extrasynaptic γ-aminobutyric acid type A receptors (GABAARs), which mediate phasic and tonic inhibition, respectively. These two GABAAR subtypes differ in their function, ligand sensitivity, and physiological properties. Importantly, they contain different α subunit isoforms: synaptic GABAARs contain the α1–3 subunits whereas extrasynaptic GABAARs contain the α4–6 subunits. While the subunit composition is critical for the distinct roles of synaptic and extrasynaptic GABAAR subtypes in inhibition, the molecular mechanism of the subtype-specific assembly has not been elucidated. To address this issue, we purified endogenous α1- and α4-containing GABAARs from adult murine forebrains and examined their subunit composition and interacting proteins using liquid chromatography coupled with tandem mass spectrometry (LC-MS/MS) and quantitative analysis. We found that the α1 and α4 subunits form separate populations of GABAARs and interact with distinct sets of binding proteins. We also discovered that the β3 subunit, which co-purifies with both the α1 and α4 subunits, has different levels of phosphorylation on serines 408 and 409 (S408/9) between the two receptor subtypes. To understand the role S408/9 plays in the assembly of α1- and α4-containing GABAARs, we examined the effects of S408/9A (alanine) knock-in mutation on the subunit composition of the two receptor subtypes using LC-MS/MS and quantitative analysis. We discovered that the S408/9A mutation results in the formation of novel α1α4-containing GABAARs. Moreover, in S408/9A mutants, the plasma membrane expression of the α4 subunit is increased whereas its retention in the endoplasmic reticulum is reduced. These findings suggest that S408/9 play a critical role in determining the subtype-specific assembly of GABAARs, and thus the efficacy of neuronal inhibition

Looking Back, Looking Forward: How the Economic Downturn Continues to Impact School Districts

This study is the fourth in a series of studies conducted by the American Association of School Administrators on the impact of the economic downturn on schools. Collectively, the findings of the AASA Economic Impact Study series demonstrate that school districts in every part of the country are subject to the realities of the economic downturn. While this benchmark data cannot predict a trend, it is difficult to deny that the financial crisis is increasingly threatening the progress schools have obtained and the stability they have enjoyed in the past. This latest study, “Looking Back, Looking Forward: How the Economic Downturn Continues to Impact School Districts,” is based on a study of school administrators conducted in February and March 2009. This survey asked many of the same questions as the “AASA Study of the Impact of the Economic Downturn on Schools,” conducted in October 2008. Therefore, it is possible to compare and contrast key findings from the two studies

Hiring Criteria in Biology Departments of Academic Institutions

We surveyed faculty in the biology departments of US institutions of higher education to compare the experience and training valued by faculty at hiring institutions with the experience and training most graduate students receive. Our data show that associate, baccalaureate, and master\u27s institutions value teaching experience and skills more highly than research skills. In contrast, doctoral institutions place a higher value on the ability to publish research and obtain outside funding. These findings provide quantitative and qualitative insight into discrepancies between the values of those who train graduate students in biology and the expectations of the institutions likely to hire these individuals

Impact of the Economic Downturn on Schools

In Fall 2008, in response to the recent economic downturn, as evidenced in state budget shortfalls, federal buy‐outs and interventions, and a series of additional events characterizing a slowing, stagnant economy, AASA examined the impact on school districts across the nation. While there are regional differences, the findings of AASA’s Economic Impact Survey, presented here, demonstrate that superintendents in every part of the country are subject to the realities of the economic downturn. While this benchmark data cannot predict a trend, it is difficult to deny that superintendents, in increasing numbers, are confronted by the looming financial crisis that threatens the progress schools have obtained and the stability they have enjoyed in the past

ThYme: a database for thioester-active enzymes

The ThYme (Thioester-active enzYme; http://www.enzyme.cbirc.iastate.edu) database has been constructed to bring together amino acid sequences and 3D (tertiary) structures of all the enzymes constituting the fatty acid synthesis and polyketide synthesis cycles. These enzymes are active on thioester-containing substrates, specifically those that are parts of the acyl-CoA synthase, acyl-CoA carboxylase, acyl transferase, ketoacyl synthase, ketoacyl reductase, hydroxyacyl dehydratase, enoyl reductase and thioesterase enzyme groups. These groups have been classified into families, members of which are similar in sequences, tertiary structures and catalytic mechanisms, implying common protein ancestry. ThYme is continually updated as sequences and tertiary structures become available

Spectrin-beta 2 facilitates the selective accumulation of GABAA receptors at somatodendritic synapses

Fast synaptic inhibition is dependent on targeting specific GABAAR subtypes to dendritic and axon initial segment (AIS) synapses. Synaptic GABAARs are typically assembled from α1-3, β and γ subunits. Here, we isolate distinct GABAARs from the brain and interrogate their composition using quantitative proteomics. We show that α2-containing receptors co-assemble with α1 subunits, whereas α1 receptors can form GABAARs with α1 as the sole α subunit. We demonstrate that α1 and α2 subunit-containing receptors co-purify with distinct spectrin isoforms; cytoskeletal proteins that link transmembrane proteins to the cytoskeleton. β2-spectrin was preferentially associated with α1-containing GABAARs at dendritic synapses, while β4-spectrin was associated with α2-containing GABAARs at AIS synapses. Ablating β2-spectrin expression reduced dendritic and AIS synapses containing α1 but increased the number of synapses containing α2, which altered phasic inhibition. Thus, we demonstrate a role for spectrins in the synapse-specific targeting of GABAARs, determining the efficacy of fast neuronal inhibition