155 research outputs found
A relativistically covariant stochastic model for systems with a fluctuating number of particles
We construct a relativistically covariant stochastic model for systems of
non-interacting spinless particles whose number undergoes random fluctuations.
The model is compared with the canonical quantization of the free scalar field
in the limit of infinite volume.Comment: 5 Pages; no figures; Plain REVTeX style. To be published in Phys.
Lett.
Evaluation of neuroactive steroid levels by liquid chromatography-tandem mass spectrometry in central and peripheral nervous system : effect of diabetes
The nervous system is a target for physiological and protective effects of neuroactive steroids. Consequently, the assessment of their levels in
nervous structures under physiological and pathological conditions is a top priority. To this aim, identification and quantification of pregnenolone
(PREG), progesterone (PROG), dihydroprogesterone (DHP), tetrahydroprogesterone (THP), testosterone (T), dihydrotestosterone (DHT), 5aandrostan-
3a, 17b-diol (3a-diol), 17a- and 17b-estradiol (17a-E and 17b-E) by liquid chromatography and tandem mass spectrometry (LC\u2013MS/
MS) has been set up. After validation, this method was applied to determine the levels of neuroactive steroids in central (i.e., cerebral cortex,
cerebellum and spinal cord) and peripheral (i.e., brachial nerve) nervous system of control and diabetic rats. In controls only the brachial nerve had
detectable levels of all these neuroactive steroids. In contrast, 17a-E in cerebellum, 17a-E, 17b-E, DHP and THP in cerebral cortex, and 17a-E,
17b-E and DHP in spinal cord were under the detection limit. Diabetes, induced by injection with streptozotocin, strongly affected the levels of
some neuroactive steroids. In particular, the levels of PREG, PROG and T in cerebellum, of PROG, T and 3a-diol in cerebral cortex, of PROG,
DHTand 3a-diol in spinal cord and of PREG, DHP, THP, T, DHTand 3a-diol in brachial nerve were significantly decreased. In conclusion, the data
here reported demonstrate that the LC\u2013MS/MS method allows the assessment of neuroactive steroids in the nervous system with high sensitivity
and specificity and that diabetes strongly affects their levels, providing a further basis for new therapeutic tools based on neuroactive steroids aimed
at counteracting diabetic neuropathy
Environmental isolation of black yeast-like fungi involved in human infection
The present study focuses on potential agents of chromoblastomycosis and
other endemic diseases in the state of ParanĂĄ, Southern Brazil. Using a
highly selective protocol for chaetothyrialean black yeasts and relatives,
environmental samples from the living area of symptomatic patients were
analysed. Additional strains were isolated from creosote-treated wood and
hydrocarbon-polluted environments, as such polluted sites have been supposed
to enhance black yeast prevalence. Isolates showed morphologies compatible
with the traditional etiological agents of chromoblastomycosis, e.g.
Fonsecaea pedrosoi and Phialophora verrucosa, and of agents of
subcutaneous or systemic infections like Cladophialophora bantiana
and Exophiala jeanselmei. Some agents of mild disease were indeed
encountered. However, molecular analysis proved that most environmental
strains differed from known etiologic agents of pronounced disease syndromes:
they belonged to the same order, but mostly were undescribed species. Agents
of chromoblastomycosis and systemic disease thus far are prevalent on the
human host. The hydrocarbon-polluted environments yielded yet another spectrum
of chaetothyrialean fungi. These observations are of great relevance because
they allow us to distinguish between categories of opportunists, indicating
possible differences in pathogenicity and virulence
Experimental evidence for 56Ni-core breaking from the low-spin structure of the N=Z nucleus 58Cu
Low-spin states in the odd-odd N=Z nucleus 58Cu were investigated with the
58Ni(p,n gamma)58Cu fusion evaporation reaction at the FN-tandem accelerator in
Cologne. Seventeen low spin states below 3.6 MeV and 17 new transitions were
observed. Ten multipole mixing ratios and 17 gamma-branching ratios were
determined for the first time. New detailed spectroscopic information on the
2+,2 state, the Isobaric Analogue State (IAS) of the 2+,1,T=1 state of 58Ni,
makes 58Cu the heaviest odd-odd N=Z nucleus with known B(E2;2+,T=1 --> 0+,T=1)
value. The 4^+ state at 2.751 MeV, observed here for the first time, is
identified as the IAS of the 4+,1,T=1 state in 58Ni. The new data are compared
to full pf-shell model calculations with the novel GXPF1 residual interaction
and to calculations within a pf5/2 configurational space with a residual
surface delta interaction. The role of the 56Ni core excitations for the
low-spin structure in 58Cu is discussed.Comment: 15 pages, 7 figures, submitted to Phys. Rev.
The mammalian gene function resource: The International Knockout Mouse Consortium
In 2007, the International Knockout Mouse Consortium (IKMC) made the ambitious promise to generate mutations in virtually every protein-coding gene of the mouse genome in a concerted worldwide action. Now, 5 years later, the IKMC members have developed highthroughput gene trapping and, in particular, gene-targeting pipelines and generated more than 17,400 mutant murine embryonic stem (ES) cell clones and more than 1,700 mutant mouse strains, most of them conditional. A common IKMC web portal (www.knockoutmouse.org) has been established, allowing easy access to this unparalleled biological resource. The IKMC materials considerably enhance functional gene annotation of the mammalian genome and will have a major impact on future biomedical research
Single-cell, whole-embryo phenotyping of mammalian developmental disorders
Mouse models are a critical tool for studying human diseases, particularly developmental disorders. However, conventional approaches for phenotyping may fail to detect subtle defects throughout the developing mouse. Here we set out to establish single-cell RNA sequencing of the whole embryo as a scalable platform for the systematic phenotyping of mouse genetic models. We applied combinatorial indexing-based single-cell RNA sequencing to profile 101 embryos of 22 mutant and 4 wild-type genotypes at embryonic day 13.5, altogether profiling more than 1.6âmillion nuclei. The 22 mutants represent a range of anticipated phenotypic severities, from established multisystem disorders to deletions of individual regulatory regions. We developed and applied several analytical frameworks for detecting differences in composition and/or gene expression across 52 cell types or trajectories. Some mutants exhibit changes in dozens of trajectories whereas others exhibit changes in only a few cell types. We also identify differences between widely used wild-type strains, compare phenotyping of gain- versus loss-of-function mutants and characterize deletions of topological associating domain boundaries. Notably, some changes are shared among mutants, suggesting that developmental pleiotropy might be 'decomposable' through further scaling of this approach. Overall, our findings show how single-cell profiling of whole embryos can enable the systematic molecular and cellular phenotypic characterization of mouse mutants with unprecedented breadth and resolution
Updated precision measurement of the average lifetime of B hadrons
The measurement of the average lifetime of B hadrons using inclusively reconstructed secondary vertices has been updated using both an improved processing of previous data and additional statistics from new data. This has reduced the statistical and systematic uncertainties and gives \tau_{\mathrm{B}} = 1.582 \pm 0.011\ \mathrm{(stat.)} \pm 0.027\ \mathrm{(syst.)}\ \mathrm{ps.} Combining this result with the previous result based on charged particle impact parameter distributions yields \tau_{\mathrm{B}} = 1.575 \pm 0.010\ \mathrm{(stat.)} \pm 0.026\ \mathrm{(syst.)}\ \mathrm{ps.
Momentum scale calibration of the LHCb spectrometer
For accurate determination of particle masses accurate knowledge of the momentum scale of the detectors is crucial. The procedure used to calibrate the momentum scale of the LHCb spectrometer is described and illustrated using the performance obtained with an integrated luminosity of 1.6 fb-1 collected during 2016 in pp running. The procedure uses large samples of J/Ï â ÎŒ + ÎŒ - and B+ â J/Ï K + decays and leads to a relative accuracy of 3 Ă 10-4 on the momentum scale
Curvature-bias corrections using a pseudomass method
Momentum measurements for very high momentum charged particles, such as muons from electroweak vector boson decays, are particularly susceptible to charge-dependent curvature biases that arise from misalignments of tracking detectors. Low momentum charged particles used in alignment procedures have limited sensitivity to coherent displacements of such detectors, and therefore are unable to fully constrain these misalignments to the precision necessary for studies of electroweak physics. Additional approaches are therefore required to understand and correct for these effects. In this paper the curvature biases present at the LHCb detector are studied using the pseudomass method in proton-proton collision data recorded at centre of mass energy â(s)=13 TeV during 2016, 2017 and 2018. The biases are determined using ZâÎŒ + ÎŒ - decays in intervals defined by the data-taking period, magnet polarity and muon direction. Correcting for these biases, which are typically at the 10-4 GeV-1 level, improves the ZâÎŒ + ÎŒ - mass resolution by roughly 18% and eliminates several pathological trends in the kinematic-dependence of the mean dimuon invariant mass
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