1,020 research outputs found
Invading interfaces and blocking surfaces in high dimensional disordered systems
We study the high-dimensional properties of an invading front in a disordered
medium with random pinning forces. We concentrate on interfaces described by
bounded slope models belonging to the quenched KPZ universality class. We find
a number of qualitative transitions in the behavior of the invasion process as
dimensionality increases. In low dimensions the system is characterized
by two different roughness exponents, the roughness of individual avalanches
and the overall interface roughness. We use the similarity of the dynamics of
an avalanche with the dynamics of invasion percolation to show that above
avalanches become flat and the invasion is well described as an annealed
process with correlated noise. In fact, for the overall roughness is
the same as the annealed roughness. In very large dimensions, strong
fluctuations begin to dominate the size distribution of avalanches, and this
phenomenon is studied on the Cayley tree, which serves as an infinite
dimensional limit. We present numerical simulations in which we measured the
values of the critical exponents of the depinning transition, both in finite
dimensional lattices with and on the Cayley tree, which support our
qualitative predictions. We find that the critical exponents in are very
close to their values on the Cayley tree, and we conjecture on this basis the
existence of a further dimension, where mean field behavior is obtained.Comment: 12 pages, REVTeX with 2 postscript figure
Constraints on Type Ia Supernova Progenitor Companions from Early Ultraviolet Observations with Swift
We compare early ultraviolet (UV) observations of Type Ia Supernovae (SNe Ia)
with theoretical predictions for the brightness of the shock associated with
the collision between SN ejecta and a companion star. Our simple method is
independent of the intrinsic flux from the SN and treats the flux observed with
the Swift/Ultra-Violet Optical Telescope (UVOT) as conservative upper limits on
the shock brightness. Comparing this limit with the predicted flux for various
shock models, we constrain the geometry of the SN progenitor-companion system.
We find the model of a 1 M_sun red supergiant companion in Roche lobe overflow
to be excluded at a 95% confidence level for most individual SNe for all but
the most unfavorable viewing angles. For the sample of 12 SNe taken together,
the upper limits on the viewing angle are inconsistent with the expected
distribution of viewing angles for RG stars as the majority of companions with
high confidence. The separation distance constraints do allow MS companions. A
better understanding of the UV flux arising from the SN itself as well as
continued UV observations of young SNe Ia will further constrain the possible
progenitors of SNe Ia.Comment: accepted versio
Complementary and alternative medicines (CAMs) and adherence to mental health medications
BACKGROUND: Medication regimes are often poorly adhered to, and the negative consequences of this are well recognised. The dynamics underlying non-adherence are less understood. This paper examines adherence to prescription medications for mental health difficulties in relation to the use of complementary and alternative medicines (CAMs). This was based on suggestions that within medical pluralism, CAMs may reduce adherence to conventional prescription medications for reasons such as their further complicating the medication regime or their being perceived as a substitute with less adverse side effects than conventional prescription medications. METHODS: Data used was from the National Comorbidity Study Replication (NCS-R), specifically those 1396 individuals who reported taking a prescription drug for mental health difficulties within the last 12 months and under the supervision of a health professional. This subsample was selected due to their being the only subgroup questioned regarding their medication adherence. Other demographic and health factors were also considered. RESULTS: The use of complementary medicines alongside the conventional medicines bore no significant relation to odds of reporting adherence versus non adherence. Ethnicity and medication count were significant predictors of adherence versus non-adherence. CONCLUSIONS: The above findings are discussed from the point of both promoting the use of CAMs and increasing health professionals’ understanding of the dynamics underlying adherence, or the lack thereof, and subsequently informing interventions to reduce the problems associated with this issue in terms of increased health care needs and reduced quality of life
Religiosity and decreased risk of substance use disorders: is the effect mediated by social support or mental health status?
The negative association between religiosity (religious beliefs and church attendance) and the likelihood of substance use disorders is well established, but the mechanism(s) remain poorly understood. We investigated whether this association was mediated by social support or mental health status.
We utilized cross-sectional data from the 2002 National Survey on Drug Use and Health (n = 36,370). We first used logistic regression to regress any alcohol use in the past year on sociodemographic and religiosity variables. Then, among individuals who drank in the past year, we regressed past year alcohol abuse/dependence on sociodemographic and religiosity variables. To investigate whether social support mediated the association between religiosity and alcohol use and alcohol abuse/dependence we repeated the above models, adding the social support variables. To the extent that these added predictors modified the magnitude of the effect of the religiosity variables, we interpreted social support as a possible mediator. We also formally tested for mediation using path analysis. We investigated the possible mediating role of mental health status analogously. Parallel sets of analyses were conducted for any drug use, and drug abuse/dependence among those using any drugs as the dependent variables.
The addition of social support and mental health status variables to logistic regression models had little effect on the magnitude of the religiosity coefficients in any of the models. While some of the tests of mediation were significant in the path analyses, the results were not always in the expected direction, and the magnitude of the effects was small.
The association between religiosity and decreased likelihood of a substance use disorder does not appear to be substantively mediated by either social support or mental health status
Towards responsible use of cognitive-enhancing drugs by the healthy
In this article, we propose actions that will help society accept the benefits of enhancement, given appropriate research and evolved regulation. Prescription drugs are regulated as such not for their enhancing properties but primarily for considerations of safety and potential abuse. Still, cognitive enhancement has much to offer individuals and society, and a proper societal response will involve making enhancements available while managing their risks
Mammary tuberculosis – importance of recognition and differentiation from that of a breast malignancy: report of three cases and review of the literature
<p>Abstract</p> <p>Background</p> <p>While tuberculosis of the breast is an extremely uncommon entity seen in western populations, it accounts for up to 3% of all treatable breast lesions in developing countries.</p> <p>Case presentations</p> <p>We reviewed three female cases of mammary tuberculosis that were diagnosed and treated in Turkey during the same calendar year. All three patients presented with a painful breast mass. In all cases, fine needle aspiration was nondiagnostic for mammary tuberculosis. However, the diagnosis of mammary tuberculosis was confirmed by histopathologic evaluation at the time of open surgical biopsy. All three patients were treated with antituberculous therapy for six months. At the end of the treatment period, each patient appeared to be clinically and radiologically without evidence of residual disease.</p> <p>Conclusion</p> <p>The diagnosis of mammary tuberculosis rests on the appropriate clinical suspicion and the histopathologic findings of the breast lesion. Its recognition and differentiation from that of a breast malignancy is absolutely necessary. Antituberculous chemotherapy, initiated immediately upon diagnosis, forms the mainstay of treatment for mammary tuberculosis.</p
The Baryon Oscillation Spectroscopic Survey of SDSS-III
The Baryon Oscillation Spectroscopic Survey (BOSS) is designed to measure the
scale of baryon acoustic oscillations (BAO) in the clustering of matter over a
larger volume than the combined efforts of all previous spectroscopic surveys
of large scale structure. BOSS uses 1.5 million luminous galaxies as faint as
i=19.9 over 10,000 square degrees to measure BAO to redshifts z<0.7.
Observations of neutral hydrogen in the Lyman alpha forest in more than 150,000
quasar spectra (g<22) will constrain BAO over the redshift range 2.15<z<3.5.
Early results from BOSS include the first detection of the large-scale
three-dimensional clustering of the Lyman alpha forest and a strong detection
from the Data Release 9 data set of the BAO in the clustering of massive
galaxies at an effective redshift z = 0.57. We project that BOSS will yield
measurements of the angular diameter distance D_A to an accuracy of 1.0% at
redshifts z=0.3 and z=0.57 and measurements of H(z) to 1.8% and 1.7% at the
same redshifts. Forecasts for Lyman alpha forest constraints predict a
measurement of an overall dilation factor that scales the highly degenerate
D_A(z) and H^{-1}(z) parameters to an accuracy of 1.9% at z~2.5 when the survey
is complete. Here, we provide an overview of the selection of spectroscopic
targets, planning of observations, and analysis of data and data quality of
BOSS.Comment: 49 pages, 16 figures, accepted by A
Correlates of Employment Among Welfare Recipients: Do Psychological Characteristics and Attitudes Matter?
This study examines whether and how a wide range of potential barriers to work,including psychological characteristics and attitudes, are associated with current employment in a recent sample of welfare recipients in Michigan ( N = 672 ). Psychological factors include measures of depressive symptoms, work attitudes, and perceived risks associated with leaving welfare. Over and above demographic, economic, and contextual factors, positive psychological characteristics and attitudes were found to be moderately associated with currently being employed. Implications for welfare-to-work programs and policy are discussed.Peer Reviewedhttp://deepblue.lib.umich.edu/bitstream/2027.42/44056/1/10464_2004_Article_343149.pd
- …