286 research outputs found
Association of Mothers' Perception of Neighborhood Quality and Maternal Resilience with Risk of Preterm Birth.
We examined the associations of mothers' perception of neighborhood quality and maternal resilience with risk of preterm birth and whether maternal resilience moderated the effect of neighborhood quality perception. We analyzed data from 10,758 women with singleton births who participated in 2010-2012 Los Angeles Mommy and Baby surveys. Multilevel logistic regression models assessed the effects of mothers' perception of neighborhood quality and maternal resilience on preterm birth (yes/no), controlling for potential confounders and economic hardship index, a city-level measure of neighborhood quality. Interaction terms were assessed for moderation. Mothers' perception of neighborhood quality and maternal resilience were each uniquely associated with preterm birth, independent of potential confounders (p-values < 0.05). The risk of preterm birth among mothers who perceived their neighborhood as of poor quality was about 30% greater compared to mothers who perceived their neighborhood as of good quality; the risk was 12% greater among mothers with low resilience compared to those with high resilience. Effects of neighborhood quality were not modified by maternal resilience. The findings suggest that mothers' perception of neighborhood quality and resilience are associated with the risk of preterm birth. Further research should explore whether initiatives aimed at improving neighborhood quality and women's self-esteem may improve birth outcomes
Superconducting Phase with Fractional Vortices in the Frustrated Kagome Wire Network at f=1/2
In classical XY kagome antiferromagnets, there can be a novel low temperature
phase where has quasi-long-range order but is
disordered, as well as more conventional antiferromagnetic phases where
is ordered in various possible patterns ( is the angle of orientation
of the spin). To investigate when these phases exist in a physical system, we
study superconducting kagome wire networks in a transverse magnetic field when
the magnetic flux through an elementary triangle is a half of a flux quantum.
Within Ginzburg-Landau theory, we calculate the helicity moduli of each phase
to estimate the Kosterlitz-Thouless (KT) transition temperatures. Then at the
KT temperatures, we estimate the barriers to move vortices and effects that
lift the large degeneracy in the possible patterns. The effects we have
considered are inductive couplings, non-zero wire width, and the
order-by-disorder effect due to thermal fluctuations. The first two effects
prefer patterns while the last one selects a
pattern of supercurrents. Using the parameters of recent experiments, we
conclude that at the KT temperature, the non-zero wire width effect dominates,
which stabilizes a conventional superconducting phase with a current
pattern. However, by adjusting the experimental parameters, for example by
bending the wires a little, it appears that the novel superconducting
phase can instead be stabilized. The barriers to vortex motion are low enough
that the system can equilibrate into this phase.Comment: 30 pages including figure
Decolourisation of Acid orange 7 in a microbial fuel cell with a laccase-based biocathode: Influence of mitigating pH changes in the cathode chamber
Biocathodes may be a suitable replacement of platinum in microbial fuel cells (MFCs) if the cost of MFCs is to be reduced. However, the use of enzymes as bio-cathodes is fraught with loss of activity as time progresses. A possible cause of this loss in activity might be pH increase in the cathode as pH gradients in MFCs are well known. This pH increase is however, accompanied by simultaneous increase in salinity; therefore salinity may be a confounding variable.
This study investigated various ways of mitigating pH changes in the cathode of MFCs and their effect on laccase activity and decolourisation of a model azo dye Acid orange 7 in the anode chamber. Experiments were run with catholyte pH automatically controlled via feedback control or by using acetate buffers (pH 4.5) of various strength (100 mM and 200 mM), with CMI7000 as the cation exchange membrane. A comparison was also made between use of CMI7000 and Nafion 117 as the transport properties of cations for both membranes (hence their potential effects on pH changes in the cathode) are different
Prevalence and pattern of HIV-related malnutrition among women in sub-Saharan Africa: a meta-analysis of demographic health surveys
<p>Abstract</p> <p>Background</p> <p>The world's highest HIV infection rates are found in Sub-Saharan Africa (SSA), where adult prevalence in most countries exceeds 25%. Food shortages and malnutrition have combined with HIV/AIDS to bring some countries to the brink of crisis. The aim of this study was to describe prevalence of malnutrition among HIV-infected women and variations across socioeconomic status using data from 11 countries in SSA.</p> <p>Methods</p> <p>This study uses meta-analytic procedures to synthesize the results of most recent data sets available from Demographic and Health Surveys of 11 countries in SSA. Pooled prevalence estimates and 95% confidence intervals were calculated using random-and fixed-effects models. Subgroup and leave-one-country-out sensitivity analyses were also carried out.</p> <p>Results</p> <p>Pooling the prevalence estimates of HIV-related malnutrition yielded an overall prevalence of 10.3% (95% CI 7.4% to 14.1%) with no statistically significant heterogeneity (<it>I</it><sup>2 </sup>= 0.0%, p = .903). The prevalence estimates decreased with increasing wealth index and education attainment. The pooled prevalence of HIV-related malnutrition was higher among women residing in rural areas than among women residing in urban areas; and lower among women that were professionally employed than unemployed or women in agricultural or manual work.</p> <p>Conclusion</p> <p>Prevalence of HIV-related malnutrition among women varies by wealth status, education attainment, occupation, and type of residence (rural/urban). The observed socioeconomic disparities can help provide more information about population subgroups in particular need and high risk groups, which may in turn lead to the development and implementation of more effective intervention programs.</p
Contraceptive and reproductive health practices of unmarried women globally, 1999 to 2018: Systematic review and meta-analysis
Background: Premarital sex practices and contraceptive prevalence rate (CPR) among unmarried women worldwide remain unclear, even though unmarried women tend to have multiple sex partners over time, which makes their sexual behaviors particularly important to the sexual and reproductive health of society more broadly.
Methods: We searched the MEDLINE, PubMed, and Google Scholar databases for relevant articles published between January 1, 1999 and December 31, 2018. Data on prevalence of premarital sexual intercourse, use of highly prevalent contraceptive methods, as well as CPR overall and at first sexual intercourse were extracted and estimated using a DerSimonian- Laird random effects model.
Results: Of the 3918 articles identified, 37 covering 19 countries were included. The estimated overall prevalence of premarital sexual intercourse was 41.9% (95%CI 34.2-49.6%). Pooled CPR was 57.0% (95%CI 44.3-69.8%) overall and 57.6% (95% CI 39.5- 75.6%) at first intercourse. The overall prevalence of condom use was 51.2% (95%CI 42.7-59.7%), followed by oral contraceptives (20.5%, 95%CI 13.7-27.3%), withdrawal (12.7%, 95%CI 9.4-15.9%), and rhythm (12.1%, 95%CI 6.7-17.4%).
Conclusion: The findings of this global study indicate worrying trends in unprotected intercourse and contraceptive practices, suggesting the need for greater attention and resources aimed at educating unmarried adolescent women about sexual and reproductive health
Phase transitions in the antiferromagnetic XY model with a kagome lattice
The ground state of the antiferromagnetic XY model with a kagome lattice is
characterized by a well developed accidental degeneracy. As a consequence the
phase transition in this system consists in unbinding of pairs of fractional
vortices. Addition of the next-to-nearest neighbors (NNN) interaction leads to
stabilization of the long-range order in chirality (staggered chirality). We
show that the phase transition, related with destruction of this long-range
order, can happen as a separate phase transition below the temperature of the
fractional vortex pairs unbinding only if the NNN coupling is extremely weak,
and find how the temperature of this transition depends on coupling constants.
We also demonstarte that the antiferromagnetic ordering of chiralities and,
accordingly, the presence of the second phase transition are induced by the
free energy of spin wave fluctuations even in absence of the NNN coupling.Comment: 10 pages (Revtex) + 8 figures (in 2 postscript files
Quantum Interference in Superconducting Wire Networks and Josephson Junction Arrays: Analytical Approach based on Multiple-Loop Aharonov-Bohm Feynman Path-Integrals
We investigate analytically and numerically the mean-field
superconducting-normal phase boundaries of two-dimensional superconducting wire
networks and Josephson junction arrays immersed in a transverse magnetic field.
The geometries we consider include square, honeycomb, triangular, and kagome'
lattices. Our approach is based on an analytical study of multiple-loop
Aharonov-Bohm effects: the quantum interference between different electron
closed paths where each one of them encloses a net magnetic flux. Specifically,
we compute exactly the sums of magnetic phase factors, i.e., the lattice path
integrals, on all closed lattice paths of different lengths. A very large
number, e.g., up to for the square lattice, exact lattice path
integrals are obtained. Analytic results of these lattice path integrals then
enable us to obtain the resistive transition temperature as a continuous
function of the field. In particular, we can analyze measurable effects on the
superconducting transition temperature, , as a function of the magnetic
filed , originating from electron trajectories over loops of various
lengths. In addition to systematically deriving previously observed features,
and understanding the physical origin of the dips in as a result of
multiple-loop quantum interference effects, we also find novel results. In
particular, we explicitly derive the self-similarity in the phase diagram of
square networks. Our approach allows us to analyze the complex structure
present in the phase boundaries from the viewpoint of quantum interference
effects due to the electron motion on the underlying lattices.Comment: 18 PRB-type pages, plus 8 large figure
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