995 research outputs found
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The Association between Use of Online Social Networks to Find Sex Partners and Sexually Transmitted Infection Diagnosis among Young Men Who Have Sex with Men and Transgender Women Living with HIV.
We conducted a cross-sectional analysis of baseline data from the Adolescent Trials Network for HIV/AIDS Interventions to examine the association between the use of social media sites to find sex partners and recent diagnosis of sexually transmitted infections (STIs) among 13- to 24-year-old men who have sex with men and transgender women living with HIV. We used linear regression to determine the relationship between the number of STIs and the number of social media sites used to find sex partners with each type of sex act included in the analysis. Secondary analyses substituted frequency of social media site use for number of social media sites. Among 741 participants, for every 1 social media account used to find sex partners, there was a 2.53% (95% confidence interval: 0.28-5.54) increase in STIs. This association was mediated through condomless receptive anal intercourse or condomless insertive anal intercourse but not barrierless oral intercourse. Similar but attenuated associations were found when frequency of social media site use was substituted for number of social media sites. Future research should examine innovative interventions on these social media sites with respect for its users
Oscillatory oblique stagnation-point flow toward a plane wall
Two-dimensional oscillatory oblique stagnation-point flow toward a plane wall is investigated. The problem is a eneralisation of the steady oblique stagnation-point flow examined by previous workers. Far from the wall, the flow is composed of an irrotational orthogonal stagnation-point flow with a time-periodic strength, a simple shear flow of constant vorticity, and a time-periodic uniform stream. An exact solution of the Navier-Stokes equations is sought for which the flow streamfunction depends linearly on the coordinate parallel to the wall. The problem formulation reduces to a coupled pair of partial differential equations in time and one spatial variable. The first equation describes the oscillatory orthogonal stagnation-point flow discussed by previous workers. The second equation, which couples to the first, describes the oblique component of the flow. A description of the flow velocity field, the instantaneous streamlines, and the particle paths is sought through numerical solutions of the governing equations and via asymptotic analysis
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Internalizing symptomatology and academic achievement: bi-directional prospective relations in adolescence
Prior research has documented negative, concurrent relations between internalizing symptomatology and academic achievement among adolescents. The present study provided the first rigorous, longitudinal examination of the bi-directional, prospective relations between adolescent internalizing symptomatology and academic achievement. One hundred and thirty adolescents reported depression and anxiety annually from 6th through 10th grades, and GPA records were obtained annually from schools. Results showed that a) high depression and anxiety at the beginning of a school year predicted lower GPA during that school year, and b) low GPA in any school year predicted higher depression and anxiety at the beginning of the following school year. These findings underscore the tight link between adolescent internalizing symptomatology and academic achievement
On super free fall.
Villermaux & Pomeau (J. Fluid Mech., vol. 642, 2010, p. 147) analysed the motion of the interface of an inviscid liquid column released from rest in a vertical tube whose
area expands gradually downwards, with application to an inverted conical container for which experimental measurements were carried out. An error in the analysis is
found and corrected in the present investigation, which provides the new governing equation for the super-accelerated interface motion down gradually varying tubes in
general, and integrated results for interface trajectories, velocities and accelerations down a conical tube in particular. Interestingly, the error does not affect any of the conclusions given in the 2010 paper. Further new results are reported here such as the equation governing the centre of mass and proof that the end point acceleration is exactly that of gravit
Psychosocial Influences on Engagement in Care Among HIV-Positive Young Black Gay/Bisexual and Other Men Who Have Sex with Men
Young black gay/bisexual and other men who have sex with men (YB-GBMSM) living with HIV are at risk for poor engagement in HIV care. Relatively little is known about factors that impact engagement outcomes at various stages along the HIV care continuum in this specific population. The purpose of this analysis was to examine associations between various psychosocial factors and likelihood of engagement at each stage of the care continuum, among a geographically diverse sample of 132 YB-GBMSM living with HIV. Negative self-image, a component of HIV stigma, had an inverse association with early care seeking after HIV diagnosis (OR=1.05; 95% CI 1.01?1.10). Negative self-image was also inversely associated with adherence to medical appointments (OR=0.95; 95% CI 0.91?0.99), while employment (OR=0.30; 95% CI 0.12?0.75) and ethnic identity affirmation (OR=0.28; 95% CI 0.12?0.68) were both positively associated with appointment adherence. HIV-positive identity salience was associated with a higher likelihood of being on antiretroviral therapy (OR=1.06; 95% CI 1.02, 1.09). These findings highlight the importance of processes related to identity development, as both barriers and facilitators of engagement in care for HIV-positive YB-GBMSM.Peer Reviewedhttps://deepblue.lib.umich.edu/bitstream/2027.42/140188/1/apc.2014.0117.pd
Maternal Genistein Alters Coat Color and Protects A(vy) Mouse Offspring from Obesity by Modifying the Fetal Epigenome
Genistein, the major phytoestrogen in soy, is linked to diminished female reproductive performance and to cancer chemoprevention and decreased adipose deposition. Dietary genistein may also play a role in the decreased incidence of cancer in Asians compared with Westerners, as well as increased cancer incidence in Asians immigrating to the United States. Here, we report that maternal dietary genistein supplementation of mice during gestation, at levels comparable with humans consuming high-soy diets, shifted the coat color of heterozygous viable yellow agouti (A(vy)/a) offspring toward pseudoagouti. This marked phenotypic change was significantly associated with increased methylation of six cytosine–guanine sites in a retrotransposon upstream of the transcription start site of the Agouti gene. The extent of this DNA methylation was similar in endodermal, mesodermal, and ectodermal tissues, indicating that genistein acts during early embryonic development. Moreover, this genistein-induced hypermethylation persisted into adulthood, decreasing ectopic Agouti expression and protecting offspring from obesity. Thus, we provide the first evidence that in utero dietary genistein affects gene expression and alters susceptibility to obesity in adulthood by permanently altering the epigenome
Force acting on a rough disk spinning in a flow of noninteracting particles
Pressure force exerted on a rough disk spinning in a flow of noninteracting particles is determined by considering that a flow of point particles impinges on a body spinning around a fixed point. The rough disk is identical with the sequence of sets and thus the sets can be viewed as successive approximations of the rough disk. A proper choice of sequence of sets shows that the characteristic of billiard scattering is independent of n, and the billiard scattering on the rough set is defined. The pressure force exerted on the disk is independent of its angular velocity and that the characteristic of the interaction that is the moment of the pressure force slows down the rotation of the rough disk. The transverse force aligned with the instantaneous velocity of the front point of the body results in Magnus effect
An Integrable Shallow Water Equation with Linear and Nonlinear Dispersion
We study a class of 1+1 quadratically nonlinear water wave equations that
combines the linear dispersion of the Korteweg-deVries (KdV) equation with the
nonlinear/nonlocal dispersion of the Camassa-Holm (CH) equation, yet still
preserves integrability via the inverse scattering transform (IST) method.
This IST-integrable class of equations contains both the KdV equation and the
CH equation as limiting cases. It arises as the compatibility condition for a
second order isospectral eigenvalue problem and a first order equation for the
evolution of its eigenfunctions. This integrable equation is shown to be a
shallow water wave equation derived by asymptotic expansion at one order higher
approximation than KdV. We compare its traveling wave solutions to KdV
solitons.Comment: 4 pages, no figure
A mathematical model for top-shelf vertigo: the role of sedimenting otoconia in BPPV
Benign Paroxysmal Positional Vertigo (BPPV) is a mechanical disorder of the
vestibular system in which calcite particles called otoconia interfere with the
mechanical functioning of the fluid-filled semicircular canals normally used to
sense rotation. Using hydrodynamic models, we examine the two mechanisms
proposed by the medical community for BPPV: cupulolithiasis, in which otoconia
attach directly to the cupula (a sensory membrane), and canalithiasis, in which
otoconia settle through the canals and exert a fluid pressure across the
cupula. We utilize known hydrodynamic calculations and make reasonable
geometric and physical approximations to derive an expression for the
transcupular pressure exerted by a settling solid particle in
canalithiasis. By tracking settling otoconia in a two-dimensional model
geometry, the cupular volume displacement and associated eye response
(nystagmus) can be calculated quantitatively. Several important features
emerge: 1) A pressure amplification occurs as otoconia enter a narrowing duct;
2) An average-sized otoconium requires approximately five seconds to settle
through the wide ampulla, where is not amplified, which suggests a
mechanism for the observed latency of BPPV; and 3) An average-sized otoconium
beginning below the center of the cupula can cause a volumetric cupular
displacement on the order of 30 pL, with nystagmus of order /s, which
is approximately the threshold for sensation. Larger cupular volume
displacement and nystagmus could result from larger and/or multiple otoconia.Comment: 15 pages, 5 Figures updated, to be published in J. Biomechanic
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