162 research outputs found
Monte-Carlo simulation method for the frequency comb spectrum of an atom laser
A theoretical particle-number conserving quantum field theory based on the
concept of imaginary time is presented and applied to the scenario of a
coherent atomic laser field at ultra-cold temperatures. The proposed
theoretical model describes the analytical derivation of the frequency comb
spectrum for an atomic laser realized from modeling a coherent atomic beam of
condensate and non-condensate quantum field components released from a trapped
Bose-Einstein condensate at a given repetition phase and frequency. The
condensate part of the atomic vapor is assumed to be subjected to thermal noise
induced by the temperature of the surrounding thermal atomic cloud. This new
quantum approach uses time periodicity and an orthogonal decomposition of the
quantum field in a complex-valued quantum field representation to derive and
model the quantum field's forward- and backward-propagating components as a
standing wave field in the same unique time and temperature domain without
quantitative singularities at finite temperatures. The complex-valued atom
laser field, the resulting frequency comb, and the repetition frequency
distribution with the varying shape of envelopes are numerically monitored
within a Monte-Carlo sampling method, as a function of temperature and trap
frequency of the external confinement.Comment: 7 pages, 11 figure
Information loss from dimensionality reduction in 5D-Gaussian spectral data
Understanding the loss of information in spectral analytics is a crucial
first step towards finding root causes for failures and uncertainties using
spectral data in artificial intelligence models built from modern complex data
science applications. Here, we show from a very simple entropy model analysis
with quantum statistics of spectral data, that the relative loss of information
from dimensionality reduction due to projection of an initial five-dimensional
state onto two-dimensional diagrams is less than one percent in the parameter
range of small data sets with sample sizes on the order of few hundreds data
samples. From our analysis, we also conclude that the density and expectation
value of the entropy probability distribution increases with the sample number
and sample size using artificial data models derived from random sampling
Monte-Carlo simulation methods.Comment: 4 pages, 3 figure
Number-conserving master equation theory for a dilute Bose-Einstein condensate
We describe the transition of weakly interacting atoms into a
Bose-Einstein condensate within a number-conserving quantum master equation
theory. Based on the separation of time scales for condensate formation and
non-condensate thermalization, we derive a master equation for the condensate
subsystem in the presence of the non-condensate environment under the inclusion
of all two body interaction processes. We numerically monitor the condensate
particle number distribution during condensate formation, and derive a
condition under which the unique equilibrium steady state of a dilute, weakly
interacting Bose-Einstein condensate is given by a Gibbs-Boltzmann thermal
state of non-interacting atoms
Sulfolipid-1 Biosynthesis Restricts Mycobacterium tuberculosis Growth in Human Macrophages
Mycobacterium tuberculosis (Mtb), the causative agent of tuberculosis, is a highly evolved human pathogen characterized by its formidable cell wall. Many unique lipids and glycolipids from the Mtb cell wall are thought to be virulence factors that mediate host-pathogen interactions. An intriguing example is Sulfolipid-1 (SL-1), a sulfated glycolipid that has been implicated in Mtb pathogenesis, although no direct role for SL-1 in virulence has been established. Previously, we described the biochemical activity of the sulfotransferase Stf0 that initiates SL-1 biosynthesis. Here we show that a stf0-deletion mutant exhibits augmented survival in human but not murine macrophages, suggesting that SL-1 negatively regulates the intracellular growth of Mtb in a species-specific manner. Furthermore, we demonstrate that SL-1 plays a role in mediating the susceptibility of Mtb to a human cationic antimicrobial peptide in vitro, despite being dispensable for maintaining overall cell envelope integrity. Thus, we hypothesize that the species-specific phenotype of the stf0 mutant is reflective of differences in antimycobacterial effector mechanisms of macrophages
Validation of multi-body models for simulation in authorisation of rail vehicles
An application of multi-body simulations is to reduce the amount of vehicle on-track testing and present an opportunity for saving the time and costs of vehicle acceptance in regard to running characteristics. One of the objectives of the EU project DynoTRAIN was to define criteria and limits for vehicle model validation. The paper presents investigations carried out by comparing simulations with measurements from a testing campaign using a test train with 4 types of vehicles and a total of 10 force measuring wheelsets and accompanied with continuous measurement of track irregularities and rail profiles. The simulations were performed by using several vehicle models, built in different simulation tools by different partners. The results of the investigations and the criteria and limits proposed for the validation of multi-body vehicle models, intended for simulations of on-track tests, in the framework of railway vehicle authorisations are presented.Une application des simulations multi-corps consiste à réduire la quantité d'essais en ligne et à offrir une opportunité pour économiser le temps et les coûts d'acceptation des Îhicules en ce qui concerne les caractéristiques de fonctionnement dynamiques. L'un des objectifs du projet de l'UE DynoTRAIN était de définir des critères et des limites pour la validation du modèle de Îhicule. Le document présente des recherches effectuées en comparant des simulations avec des mesures à partir d'une campagne de test utilisant un train d'essai avec 4 types de Îhicules et un total de 10 essieux de mesure de force roue-rail et accompagnés d'une mesure continue des irrégularités de voie et des profils de rail. Les simulations ont été réalisées en utilisant plusieurs modèles de Îhicules, construits dans différents outils de simulation par différents partenaires. Les résultats des enquêtes et les critères et limites proposés pour la validation des modèles de Îhicules multi-corps, destinés à des simulations de tests sur voie réelle, dans le cadre des autorisations de Îhicules ferroviaires sont présentés
Experimental evidence for temporal uncoupling of brain Aβ deposition and neurodegenerative sequelae
Brain A beta deposition is a key early event in the pathogenesis of Alzheimer ' s disease (AD), but the long presymptomatic phase and poor correlation between A beta deposition and clinical symptoms remain puzzling. To elucidate the dependency of downstream pathologies on A beta, we analyzed the trajectories of cerebral A beta accumulation, A beta seeding activity, and neurofilament light chain (NfL) in the CSF (a biomarker of neurodegeneration) in A beta-precursor protein transgenic mice. We find that A beta deposition increases linearly until it reaches an apparent plateau at a late age, while A beta seeding activity increases more rapidly and reaches a plateau earlier, coinciding with the onset of a robust increase of CSF NfL. Short-term inhibition of A beta generation in amyloid-laden mice reduced A beta deposition and associated glial changes, but failed to reduce A beta seeding activity, and CSF NfL continued to increase although at a slower pace. When short-term or long-term inhibition of A beta generation was started at pre-amyloid stages, CSF NfL did not increase despite some A beta deposition, microglial activation, and robust brain A beta seeding activity. A dissociation of A beta load and CSF NfL trajectories was also found in familial AD, consistent with the view that A beta aggregation is not kinetically coupled to neurotoxicity. Rather, neurodegeneration starts when A beta seeding activity is saturated and before A beta deposition reaches critical (half-maximal) levels, a phenomenon reminiscent of the two pathogenic phases in prion disease. The poor correlation between brain A beta deposition and clinical symptoms in Alzheimer ' s disease remains puzzling. Here, the authors show a temporal dissociation of A beta deposition and neurodegeneration
Teaching Intelligence Testing in APA-Accredited Programs: A National Survey
We surveyed instructors at APA-accredited clinical and school psychology programs across the United States and Canada to determine typical teaching practices in individual intelligence testing courses. The most recent versions of the Wechsler scales (Wechsler, 1989, 1991, 1997) and the Stanford-Binet (Thorndike, Hagan & Sattler, 1986) remain the primary tests taught in this course. Course instructors emphasized having students administer intelligence tests; however, relatively few instructors reported assessing students' final level of competence with regard to their test administration skills. The intelligence testing course appears quite time-intensive for instructors, and many teach the course with the aid of a teaching assistant. When compared with previous findings, current results suggest a good measure of stability over time regarding the core issues addressed and skills taught in the intelligence testing course.Yeshttps://us.sagepub.com/en-us/nam/manuscript-submission-guideline
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