2,603 research outputs found
Prevention effects on trajectories of African American adolescents\u27 exposure to interparental conflict and depressive symptoms.
The present study investigates the trajectory of children\u27s exposure to interparental conflict during adolescence, its effects on adolescents\u27 psychological adjustment, as well as the ability of a family-centered prevention program to alter this trajectory. A total of 331 African American couples with an adolescent or preadolescent child participated in a randomized control trial of the Promoting Strong African American Families program, a newly developed program targeting couple and cocaregiving processes. Using a multi-informant, latent growth curve approach, child exposure to interparental conflict during adolescence was found to be stable over a period of 2 years among families in the control group, but significantly declined among families in the treatment condition. Rates of change were significantly different between intervention and control groups based on parents\u27 report of youth exposure to interparental conflict, but not for child\u27s report. Structural equation models found trajectory parameters of interparental conflict predicted changes in adolescent depressive symptoms, with increasing rates of changes in conflict associated with increases in adolescent internalizing symptoms over the 2-year duration of the study. Finally, a significant indirect effect was identified linking treatment, changes in parents\u27 reports of child exposure to interparental conflict, and adolescent depressive symptoms. The implications for research and intervention are discussed
Modelling superradiant amplification of Casimir photons in very low dissipation cavities
Recent advances in nanotechnology and atomic physics may allow for a
demonstration of the dynamical Casimir effect. An array of film bulk acoustic
resonators (FBARs) coherently driven at twice the resonant frequency of a
high-quality electromagnetic cavity can generate a stationary state of Casimir
photons. These are detected using an alkali atom beam prepared in an inverted
population of hyperfine states, with an induced superradiant burst producing a
detectable radio-frequency signal. We describe here the results of the
simulations of the dynamics of superradiance and superfluorescence, with the
aim to optimize the parameters for the detectability of Casimir photons. When
the superradiant lifetime is shorter than the dissipation time, we find
superradiant evolution to be similar in character but dramatically slower than
in the usual lossy case.Comment: 7 pages, 2 figure
Corporate financing decisions: UK survey evidence
Despite theoretical developments in recent years, our understanding of corporate capital structure remains incomplete. Prior empirical research has been dominated by archival regression studies which are limited in their ability to fully reflect the diversity found in practice. The present paper reports on a comprehensive survey of corporate financing decision-making in UK listed companies. A key finding is that firms are heterogeneous in their capital structure policies. About half of the firms seek to maintain a target debt level, consistent with trade-off theory, but 60 per cent claim to follow a financing hierarchy, consistent with pecking order theory. These two theories are not viewed by respondents as either mutually exclusive or exhaustive. Many of the theoretical determinants of debt levels are widely accepted by respondents, in particular the importance of interest tax shield, financial distress, agency costs and also, at least implicitly, information asymmetry. Results also indicate that cross-country institutional differences have a significant impact on financial decisions
Walking the walk: a phenomenological study of long distance walking
Evidence suggests that regular walking can elicit significant psychological benefits although little evidence exists concerning long distance walking. The purpose of this study was to provide detailed accounts of the experiences of long distance walkers. Phenomenological interviews were conducted with six long distance walkers. Data were transcribed verbatim before researchers independently analyzed the transcripts. Participants reported a cumulative effect with positive feelings increasing throughout the duration of the walk. Long distance walking elicited positive emotions, reduced the effects of life-stress, and promoted an increased sense of well-being and personal growth. Results are aligned to theories and concepts from positive psychology
Why now? Examining antecedents for substance use initiation among African American adolescents
Current adolescent substance use risk models have inadequately predicted use for African Americans, with limited knowledge on differential predictability as a function of developmental period. Among a sample of 500 African American youth (ages 11–21), four risk indices (i.e., social, attitudinal, intrapersonal, and racial discrimination) were examined in the prediction of alcohol, marijuana, and cigarette initiation during early (ages 11–13), mid (ages 16–18) and late (ages 19–21) adolescence. Results showed that when developmental periods were combined, racial discrimination was the only index that predicted initiation for all three substances. However, when risk models were stratified based on developmental period, variation was found within and across substance types. Results highlight the importance of racial discrimination in understanding substance use initiation among African American youth and the need for tailored interventions based on developmental stage
One-loop graviton corrections to Maxwell's equations
We compute the graviton induced corrections to Maxwell's equations in the
one-loop and weak field approximations. The corrected equations are analogous
to the classical equations in anisotropic and inhomogeneous media. We analyze
in particular the corrections to the dispersion relations. When the wavelength
of the electromagnetic field is much smaller than a typical length scale of the
graviton two-point function, the speed of light depends on the direction of
propagation and on the polarisation of the radiation. In the opposite case, the
speed of light may also depend on the energy of the electromagnetic radiation.
We study in detail wave propagation in two special backgrounds, flat
Robertson-Walker and static, spherically symmetric spacetimes. In the case of a
flat Robertson-Walker gravitational background we find that the corrected
electromagnetic field equations correspond to an isotropic medium with a
time-dependent effective refractive index. For a static, spherically symmetric
background the graviton fluctuations induce a vacuum structure which causes
birefringence in the propagation of light.Comment: 15 pages, revte
Gas-Phase Oxygen Gradients in Strongly Interacting Galaxies: I. Early-Stage Interactions
A consensus is emerging that interacting galaxies show depressed nuclear gas
metallicities compared to isolated star-forming galaxies. Simulations suggest
that this nuclear underabundance is caused by interaction-induced inflow of
metal-poor gas, and that this inflow concurrently flattens the radial
metallicity gradients in strongly interacting galaxies. We present
metallicities of over 300 HII regions in a sample of 16 spirals that are
members of strongly interacting galaxy pairs with mass ratio near unity. The
deprojected radial gradients in these galaxies are about half of those in a
control sample of isolated, late-type spirals. Detailed comparison of the
gradients with simulations show remarkable agreement in gradient distributions,
the relationship between gradients and nuclear underabundances, and the shape
of profile deviations from a straight line. Taken together, this evidence
conclusively demonstrates that strongly interacting galaxies at the present day
undergo nuclear metal dilution due to gas inflow, as well as significant
flattening of their gas-phase metallicity gradients, and that current
simulations can robustly reproduce this behavior at a statistical level.Comment: Accepted for publication in Ap
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