10,111 research outputs found

    No Persistent Pulsations in Aquila X-1 as it Fades into Quiescence

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    We searched for coherent X-ray pulsations from Aql X-1 in a series of RXTE observations taken shortly after a recent outburst. During the course of these observations, Aql X-1 passes through an apparent "propeller" phase as its luminosity fades to its quiescent value. No pulsations were detected, and we place upper limits (ranging from 0.52% to 9.0%) on the fractional rms amplitude of any periodic signal contained in the various data sets searched. This result has implications for the geometry of the system, if the quiescent luminosity is due to continued low-level accretion. Alternatively, our result supports the idea that the quiescent luminosity may be due to thermal emission

    Modal Test of the NASA Mobile Launcher at Kennedy Space Center

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    The NASA Mobile Launcher (ML), located at Kennedy Space Center (KSC), has recently been modified to support the launch of the new NASA Space Launch System (SLS). The ML is a massive structureconsisting of a 345-foot tall tower attached to a two-story base, weighing approximately 10.5 million poundsthat will secure the SLS vehicle as it rolls to the launch pad on a Crawler Transporter, as well as provide a launch platform at the pad. The ML will also provide the boundary condition for an upcoming SLS Integrated Modal Test (IMT). To help correlate the ML math models prior to this modal test, and allow focus to remain on updating SLS vehicle models during the IMT, a ML-only experimental modal test was performed in June 2019. Excitation of the tower and platform was provided by five uniquely-designed test fixtures, each enclosing a hydraulic shaker, capable of exerting thousands of pounds of force into the structure. For modes not that were not sufficiently excited by the test fixture shakers, a specially-designed mobile drop tower provided impact excitation at additional locations of interest. The response of the ML was measured with a total of 361 accelerometers. Following the random vibration, sine sweep vibration, and modal impact testing, frequency response functions were calculated and modes were extracted for three different configurations of the ML in 0 Hz to 12 Hz frequency range. This paper will provide a case study in performing modal tests on large structures by discussing the Mobile Launcher, the test strategy, an overview of the test results, and recommendations for meeting a tight test schedule for a large-scale modal test

    Test of an Argumentative Skill Deficiency Model of Interspousal Violence

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    Presents a study that examined a model of communication and interpersonal physical violence among married people. Relation between communication and violence; Review of related literature on interspousal violence; Application of the model on abused wives and abused husbands

    Epidemiology of Any and Vaccine-Type Anogenital Human Papillomavirus Among 13-26-Year-Old Young Men After HPV Vaccine Introduction

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    PURPOSE: The aims of this study were to determine prevalence of and factors associated with any human papillomavirus (HPV) and vaccine-type HPV among young men after vaccine introduction, stratified by vaccination status. METHODS: Young men were recruited from clinical sites from 2013 to 2015, completed a survey, and were tested for 36 anogenital HPV types. We determined factors associated with ≥1 HPV type among all participants, and vaccine-type HPV (HPV6, 11, 16, and/or 18) among all, vaccinated and unvaccinated participants, using multivariable regression. RESULTS: Mean age was 21.5 years and 26% had received at least one HPV vaccine dose. HPV prevalence was lower in vaccinated versus unvaccinated young men (50.5% vs. 62.6%, p = .03). HPV positivity was discordant by anogenital site. At both sites, 59.4% were positive for ≥1 HPV type and 26.0% for ≥1 4-valent vaccine type. In multivariable logistic regression, factors associated with ≥1 HPV type among all participants were frequency of oral sex (odds ratio [OR] = 1.80, 95% confidence interval [CI] = 1.00-3.24), recent smoking (OR = 1.84, CI = 1.17-2.90), and sexually transmitted infection history (OR = 1.56, CI = 1.02-2.38). Factors associated with vaccine-type HPV among all participants were white versus black race (OR = 1.91, CI = 1.10-3.34) and gonorrhea history (OR = 2.52, CI = 1.45-4.38); among vaccinated participants were private versus Medicaid insurance (OR = 5.6, CI = 1.46-20.4) and private versus no insurance (OR = 15.9, CI = 3.06-83.3); and among unvaccinated participants was gonorrhea history (OR = 1.83, CI = 1.03-3.24). CONCLUSIONS: Anogenital HPV prevalence was high and vaccination rates low among young men 2-4 years after vaccine introduction, underscoring the urgency of increasing vaccination rates and vaccinating according to national guidelines

    Examining the reversibility of long-term behavioral disruptions in progeny of maternal SSRI exposure

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    Serotonergic dysregulation is implicated in numerous psychiatric disorders. Serotonin plays widespread trophic roles during neurodevelopment; thus perturbations to this system during development may increase risk for neurodevelopmental disorders. Epidemiological studies have examined association between selective serotonin reuptake inhibitor (SSRI) treatment during pregnancy and increased autism spectrum disorder (ASD) risk in offspring. It is unclear from these studies whether ASD susceptibility is purely related to maternal psychiatric diagnosis, or if treatment poses additional risk. We sought to determine whether maternal SSRI treatment alone or in combination with genetically vulnerable background was sufficient to induce offspring behavior disruptions relevant to ASD. We exposed C57BL/6J or Celf6(+/-) mouse dams to fluoxetine (FLX) during different periods of gestation and lactation and characterized offspring on tasks assessing social communicative interaction and repetitive behavior patterns including sensory sensitivities. We demonstrate robust reductions in pup ultrasonic vocalizations (USVs) and alterations in social hierarchy behaviors, as well as perseverative behaviors and tactile hypersensitivity. Celf6 mutant mice demonstrate social communicative deficits and perseverative behaviors, without further interaction with FLX. FLX re-exposure in adulthood ameliorates the tactile hypersensitivity yet exacerbates the dominance phenotype. This suggests acute deficiencies in serotonin levels likely underlie the abnormal responses to sensory stimuli, while the social alterations are instead due to altered development of social circuits. These findings indicate maternal FLX treatment, independent of maternal stress, can induce behavioral disruptions in mammalian offspring, thus contributing to our understanding of the developmental role of the serotonin system and the possible risks to offspring of SSRI treatment during pregnancy

    Length scale dependence of dynamical heterogeneity in a colloidal fractal gel

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    We use time-resolved dynamic light scattering to investigate the slow dynamics of a colloidal gel. The final decay of the average intensity autocorrelation function is well described by g_2(q,τ)1exp[(τ/τ_f)p]g\_2(q,\tau)-1 \sim \exp[-(\tau/\tau\_\mathrm{f})^p], with τ_fq1\tau\_\mathrm{f} \sim q^{-1} and pp decreasing from 1.5 to 1 with increasing qq. We show that the dynamics is not due to a continuous ballistic process, as proposed in previous works, but rather to rare, intermittent rearrangements. We quantify the dynamical fluctuations resulting from intermittency by means of the variance χ(τ,q)\chi(\tau,q) of the instantaneous autocorrelation function, the analogous of the dynamical susceptibility χ_4\chi\_4 studied in glass formers. The amplitude of χ\chi is found to grow linearly with qq. We propose a simple --yet general-- model of intermittent dynamics that accounts for the qq dependence of both the average correlation functions and χ\chi.Comment: Revised and improved, to appear in Europhys. Let
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