490 research outputs found
High‐sensitivity cardiac troponin after cardiac stress test: A systematic review and meta‐analysis
Dynamic origin of the morphotropic phase boundary - Soft modes and phase instability in 0.68Pb(Mg1/3Nb2/3O3)-0.32PbTiO3
We report neutron inelastic scattering on single crystal
0.68Pb(Mg1/3Nb2/3O3)-0.32PbTiO3 (PMN-0.32PT), a relaxor ferroelectric material
that lies within the compositional range of the morphotropic phase boundary
(MPB). Data were obtained between 100 K and 600 K under zero and non-zero
electric field applied along the cubic [001] direction. The lowest energy,
zone-center, transverse optic phonon is strongly damped and softens slowly at
high temperature; however the square of the soft mode energy begins to increase
linearly with temperature as in a conventional ferroelectric, which we term the
soft mode "recovery," upon cooling into the tetragonal phase at TC. Our data
show that the soft mode in PMN-0.32PT behaves almost identically to that in
pure PMN, exhibiting the same temperature dependence and recovery temperature
even though PMN exhibits no well-defined structural transition (no TC). The
temperature dependence of the soft mode in PMN-0.32PT is also similar to that
in PMN-0.60PT; however in PMN-0.60PT the recovery temperature equals TC. These
results suggest that the temperature dependence and the energy scale of the
soft mode dynamics in PMN-xPT are independent of concentration on the Ti-poor
side of the MPB, but scale with TC for Ti-rich compositions. Thus the MPB may
be defined in lattice dynamical terms as the concentration where TC first
matches the recovery temperature of the soft mode. High-resolution x-ray
studies show that the cubic-to-ferroelectric phase boundary shifts to higher
temperatures by an abnormal amount within the MPB region in the presence of an
electric field. This suggests that an unusual instability exists within the
apparently cubic phase at the MPB.Comment: 13 pages, 6 figure
Evaluating Neighborhood, Social, and Genetic Influences on Precursors of Alcohol Use Risk Behavior in African American Adolescents
Background: Using a socioecological framework, we examined neighborhood and social stressors in concert with genetic risk for alcohol dependence in relation to externalizing behaviors, important precursors to alcohol-related problems.
Methods: We used data from African American adolescents and their caregivers in the Gene, Environment, and Neighborhood Initiative, a subsample of the Mobile Youth and Poverty Study. Participants for the current analyses included 112 adolescents who reported ever having at least one full drink of alcohol. Empirical Bayes scores were used to estimate neighborhood-level violence and transitions. Multivariate models tested main effects and then interactions of family stressors, discrimination, and genetic risk with the neighborhood variables.
Results: In the main effects model, adolescent externalizing behaviors were positively associated with greater family stressors, more racial discrimination experiences, and genetic liability, while neighborhood variables were nonsignificant. We found three significant interactions. Specifically, the joint effects of neighborhood violence and transitions and between these neighborhood variables and family stressors were significantly associated with externalizing behaviors.
Conclusions: Our findings suggest genetic liability and complex interactions between neighborhood context and social stressors are important contributors that should be considered in the development of early prevention programs for adolescents who live in economically disadvantaged areas
The external benefits of higher education
The private market benefits of education are widely studied at the micro level, although the magnitude of their macroeconomic impact is disputed. However, there are additional benefits of education, which are less well understood. In this paper the macroeconomic effects of external benefits of higher education are estimated using the “micro-to-macro” simulation approach. Two types of externalities are explored: technology spillovers and productivity spillovers in the labour market. These links are illustrated and the results suggest they could be very large. However, this is qualified by the dearth of microeconomic evidence, for which we hope to encourage further work
Thermodynamics of nanodomain formation and breakdown in Scanning Probe Microscopy: Landau-Ginzburg-Devonshire approach
Thermodynamics of tip-induced nanodomain formation in scanning probe
microscopy of ferroelectric films and crystals is studied using the
Landau-Ginzburg-Devonshire phenomenological approach. The local redistribution
of polarization induced by the biased probe apex is analyzed including the
effects of polarization gradients, field dependence of dielectric properties,
intrinsic domain wall width, and film thickness. The polarization distribution
inside subcritical nucleus of the domain preceding the nucleation event is very
smooth and localized below the probe, and the electrostatic field distribution
is dominated by the tip. In contrast, polarization distribution inside the
stable domain is rectangular-like, and the associated electrostatic fields
clearly illustrate the presence of tip-induced and depolarization field
components. The calculated coercive biases of domain formation are in a good
agreement with available experimental results for typical ferroelectric
materials. The microscopic origin of the observed domain tip elongation in the
region where the probe electric field is much smaller than the intrinsic
coercive field is the positive depolarization field in front of the moving
counter domain wall. For infinitely thin domain walls local domain breakdown
through the sample depth appears. The results obtained here are complementary
to the Landauer-Molotskii energetic approach.Comment: 35 pages, 8 figures, suplementary attached, to be submitted to Phys.
Rev.
Noise Properties of the BOOMERANG Instrument
In this paper we report a short description of the BOOMERANG experiment explaining his scientific goal and the technologies implied. We concentrate then on the analysis of the noise properties discussing in particular the scan synchronous noise. Finally we present the calibration technique and the sensitivity of all the channels
Effects of gender and race on prognosis after myocardial infarction: Adverse prognosis for women, particularly black women
Controversy has arisen concerning whether gender influences the prognosis after myocardial infarction. Although some studies have shown there to be no difference between the sexes, most have indicated a worse prognosis for women, attributing this to differences in baseline characteristics. It has been further suggested that black women have a particularly poor prognosis after infarction. To determine the contribution of gender and race to the course of infarction, 816 patients with confirmed myocardial infarction who were enrolled in the Multi-center Investigation of the Limitation of Infarct Size (MILIS) were analyzed. Of those patients, 226 were women and 590 were men, 142 were black and 674 were white.The cumulative mortality rate at 48 months was 36% for women versus 21% for men (p < 0.001, mean follow-up 32 months). The cumulative mortality rate by race was 34% for blacks versus 24% for whites (p < 0.005). Both women and blacks exhibited more baseline characteristics predictive of mortality than did their male or white counterparts. It was possible to account for the greater mortality rate of blacks by identifiable baseline variables; however, even after adjustment, the mortality rate for women remained significantly higher (p < 0.002). The poorer prognosis for women was influenced by a particularly high mortality rate among black women (48%); the mortality rate for white women was 32%, for black men 23% and for white men 21%. The mortality for black women was significantly greater than that of the other subgroups. Thus, findings in the MILIS population indicate that the prognosis after myocardial infarction is worse for women, particularly black women
Experimental determination of translational starts using peptide mass mapping and tandem mass spectrometry within the proteome of Mycobacterium tuberculosis
Identification of protein translation start sites is largely a bioinformatics exercise, with relatively few confirmed by N-terminal sequencing. Translation start site determination is critical for defining both the protein sequence and the upstream DNA which may contain regulatory motifs. It is demonstrated here that translation start sites can be determined during routine protein identification, using MALDI-MS and MS/MS data to select the correct N-terminal sequence from a list of alternatives generated in silico. Applying the method to 13 proteins from Mycobacterium tuberculosis, 11 predicted translational start sites were confirmed, and two reassigned. The authors suggest that these data (be they confirmation or reassignments) are important for the annotation of both this genome and those of organisms with related genes. It was also shown that N-acetylation, reported to be rare in prokaryotes, was present in three of the 13 proteins (23 %), suggesting that in the mycobacteria this modification may be common, and an important regulator of protein function, although more proteins need to be analysed. This method can be performed with little or no additional experimental work during proteomics investigations
Polarized Spots in Anisotropic Open Universes
We calculate the temperature and polarization patterns generated in
anisotropic cosmological models drawn from the Bianchi classification. We show
that localized features in the temperature pattern, perhaps similar to the cold
spot observed in the Wilkinson Microwave Anisotropy Probe (WMAP) data, can be
generated in models with negative spatial curvature, i.e. Bianchi types V and
VII. Both these models also generate coherent polarization patterns. In
Bianchi VII, however, rotation of the polarization angle as light
propagates along geodesics can convert E modes into B modes but in Bianchi V
this is not necessarily the case. It is in principle possible, therefore, to
generate localized temperature features without violating existing
observational constraints on the odd-parity component of the polarization of
the cosmic microwave background.Comment: 6 pages, 1 figure, revisions to match version published in CQ
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