71 research outputs found
Continuous quantum measurement of a Bose-Einstein condensate: a stochastic Gross-Pitaevskii equation
We analyze the dynamics of a Bose-Einstein condensate undergoing a continuous
dispersive imaging by using a Lindblad operator formalism. Continuous strong
measurements drive the condensate out of the coherent state description assumed
within the Gross-Pitaevskii mean-field approach. Continuous weak measurements
allow instead to replace, for timescales short enough, the exact problem with
its mean-field approximation through a stochastic analogue of the
Gross-Pitaevskii equation. The latter is used to show the unwinding of a dark
soliton undergoing a continuous imaging.Comment: 13 pages, 10 figure
Fatty Acid Methyl Esters as Biosolvents of Epoxy Resins: A Physicochemical Study
The C8 to C18 fatty acid methyl esters (FAME) have been compared as solvents for two epoxy resin pre-polymers, bisphenol A diglycidyl ether (DGEBA) and triglycidyl paminophenol ether (TGPA). It was found that the solubilization limits vary according to the ester and that methyl caprylate is the best solvent of both resins. To explain these solubility performances, physical and chemical properties of FAME were studied, such as the Hansen parameters, viscosity, binary diffusion coefficient and vaporization enthalpy. Determination of the physicochemical parameters of FAME was carried out by laboratory experimentations and by calculation from bibliographic data. The Hansen parameters of FAME and epoxy resins pre-polymers were theoretically and experimentally determined. The FAME chain length showed a long dependence on the binary diffusion parameters and kinematic viscosity, which are mass and momentum transport properties. Moreover, the vaporization enthalpy of these compounds was directly correlated with the solubilization limits
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(3S)-3-(2,3-difluorophenyl)-3-methoxypyrrolidine (IRL752) - a novel cortical-preferring catecholamine transmission- and cognition-promoting agent
YesHere we describe for the first time the distinctive pharmacological profile for IRL752, a new phenyl-pyrrolidine derivative with regio-selective CNS transmission-enhancing properties. IRL752 (3.7-150 μmol/kg, s.c.) was characterised through extensive in vivo studies, using behavioural, tissue neurochemical and gene expression, as well as microdialysis methods. Behaviourally, the compound normalised tetrabenazine-induced hypoactivity, while unable to stimulate basal locomotion in normal animals or to either accentuate or reverse hyperactivity induced by amphetamine or MK-801. IRL752 induced but minor changes in monoaminergic tissue neurochemistry across NA- and DA-dominated brain regions. The expression of neuronal activity-, plasticity-, and cognition-related IEGs (immediate early genes) however increased by 1.5- to 2-fold. Furthermore, IRL752 dose-dependently enhanced cortical catecholamine dialysate output to 600-750% above baseline, while striatal DA remained unaltered and NA rose to ~250%; cortical and hippocampal dialysate ACh increased to ~250% and 190% above corresponding baseline, respectively. In line with this cortically preferential transmission-promoting action, the drug was also pro-cognitive in the novel object recognition and reversal learning tests. In vitro neurotarget affinity and functional data, coupled to drug exposure support the hypothesis that 5‑HT7 receptor and α2(C)-adrenoceptor antagonism are key contributors to the in vivo efficacy and original profile of IRL752. The cortical-preferring facilitatory impact on catecholamine (and ACh) neurotransmission, along with effects on IEG expression and cognition-enhancing features, are in line with the potential clinical usefulness of IRL752 in conditions where these aspects may be dysregulated, such as in axial motor and cognitive deficits in Parkinson's Disease
Two-dimensional hole precession in an all-semiconductor spin field effect transistor
We present a theoretical study of a spin field-effect transistor realized in
a quantum well formed in a p--doped ferromagnetic-semiconductor-
nonmagnetic-semiconductor-ferromagnetic-semiconductor hybrid structure. Based
on an envelope-function approach for the hole bands in the various regions of
the transistor, we derive the complete theory of coherent transport through the
device, which includes both heavy- and light-hole subbands, proper modeling of
the mode matching at interfaces, integration over injection angles, Rashba spin
precession, interference effects due to multiple reflections, and gate-voltage
dependences. Numerical results for the device current as a function of
externally tunable parameters are in excellent agreement with approximate
analytical formulae.Comment: 9 pages, 11 figure
Amyloid binding and beyond: a new approach for Alzheimer's disease drug discovery targeting Aβo–PrPC binding and downstream pathways
Amyloid β oligomers (Aβo) are the main toxic species in Alzheimer's disease, which have been targeted for single drug treatment with very little success. In this work we report a new approach for identifying functional Aβo binding compounds. A tailored library of 971 fluorine containing compounds was selected by a computational method, developed to generate molecular diversity. These compounds were screened for Aβo binding by a combined 19F and STD NMR technique. Six hits were evaluated in three parallel biochemical and functional assays. Two compounds disrupted Aβo binding to its receptor PrPC in HEK293 cells. They reduced the pFyn levels triggered by Aβo treatment in neuroprogenitor cells derived from human induced pluripotent stem cells (hiPSC). Inhibitory effects on pTau production in cortical neurons derived from hiPSC were also observed. These drug-like compounds connect three of the pillars in Alzheimer's disease pathology, i.e. prion, Aβ and Tau, affecting three different pathways through specific binding to Aβo and are, indeed, promising candidates for further development
An Observational Overview of Solar Flares
We present an overview of solar flares and associated phenomena, drawing upon
a wide range of observational data primarily from the RHESSI era. Following an
introductory discussion and overview of the status of observational
capabilities, the article is split into topical sections which deal with
different areas of flare phenomena (footpoints and ribbons, coronal sources,
relationship to coronal mass ejections) and their interconnections. We also
discuss flare soft X-ray spectroscopy and the energetics of the process. The
emphasis is to describe the observations from multiple points of view, while
bearing in mind the models that link them to each other and to theory. The
present theoretical and observational understanding of solar flares is far from
complete, so we conclude with a brief discussion of models, and a list of
missing but important observations.Comment: This is an article for a monograph on the physics of solar flares,
inspired by RHESSI observations. The individual articles are to appear in
Space Science Reviews (2011
A disease-associated gene desert directs macrophage inflammation through ETS2
Increasing rates of autoimmune and inflammatory disease present a burgeoning threat to human health1. This is compounded by the limited efficacy of available treatments1 and high failure rates during drug development2, highlighting an urgent need to better understand disease mechanisms. Here we show how functional genomics could address this challenge. By investigating an intergenic haplotype on chr21q22—which has been independently linked to inflammatory bowel disease, ankylosing spondylitis, primary sclerosing cholangitis and Takayasu’s arteritis3–6—we identify that the causal gene, ETS2, is a central regulator of human inflammatory macrophages and delineate the shared disease mechanism that amplifies ETS2 expression. Genes regulated by ETS2 were prominently expressed in diseased tissues and more enriched for inflammatory bowel disease GWAS hits than most previously described pathways. Overexpressing ETS2 in resting macrophages reproduced the inflammatory state observed in chr21q22-associated diseases, with upregulation of multiple drug targets, including TNF and IL-23. Using a database of cellular signatures7, we identified drugs that might modulate this pathway and validated the potent anti-inflammatory activity of one class of small molecules in vitro and ex vivo. Together, this illustrates the power of functional genomics, applied directly in primary human cells, to identify immune-mediated disease mechanisms and potential therapeutic opportunities
Microflares and the Statistics of X-ray Flares
This review surveys the statistics of solar X-ray flares, emphasising the new
views that RHESSI has given us of the weaker events (the microflares). The new
data reveal that these microflares strongly resemble more energetic events in
most respects; they occur solely within active regions and exhibit
high-temperature/nonthermal emissions in approximately the same proportion as
major events. We discuss the distributions of flare parameters (e.g., peak
flux) and how these parameters correlate, for instance via the Neupert effect.
We also highlight the systematic biases involved in intercomparing data
representing many decades of event magnitude. The intermittency of the
flare/microflare occurrence, both in space and in time, argues that these
discrete events do not explain general coronal heating, either in active
regions or in the quiet Sun.Comment: To be published in Space Science Reviews (2011
Diverse aging rates in ectothermic tetrapods provide insights for the evolution of aging and longevity
Comparative studies of mortality in the wild are necessary to understand the evolution of aging; yet, ectothermic tetrapods are underrepresented in this comparative landscape, despite their suitability for testing evolutionary hypotheses. We present a study of aging rates and longevity across wild tetrapod ectotherms, using data from 107 populations (77 species) of nonavian reptiles and amphibians. We test hypotheses of how thermoregulatory mode, environmental temperature, protective phenotypes, and pace of life history contribute to demographic aging. Controlling for phylogeny and body size, ectotherms display a higher diversity of aging rates compared with endotherms and include phylogenetically widespread evidence of negligible aging. Protective phenotypes and life-history strategies further explain macroevolutionary patterns of aging. Analyzing ectothermic tetrapods in a comparative context enhances our understanding of the evolution of aging.Animal science
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