316 research outputs found
In-plane dipole coupling anisotropy of a square ferromagnetic Heisenberg monolayer
In this study we calculate the dipole-coupling-induced quartic in-plane
anisotropy of a square ferromagnetic Heisenberg monolayer. This anisotropy
increases with an increasing temperature, reaching its maximum value close to
the Curie temperature of the system. At T=0 the system is isotropic, besides a
small remaining anisotropy due to the zero-point motion of quantum mechanical
spins. The reason for the dipole-coupling-induced anisotropy is the disturbance
of the square spin lattice due to thermal fluctuations ('order-by-disorder'
effect). For usual ferromagnets its strength is small as compared to other
anisotropic contributions, and decreases by application of an external magnetic
field. The results are obtained from a Heisenberg Hamiltonian by application of
a mean field approach for a spin cluster, as well as from a many-body Green's
function theory within the Tyablikov-decoupling (RPA).Comment: 6 pages, 2 figures, accepted for publication in RP
Diquark condensation effects on hot quark star configurations
The equation of state for quark matter is derived for a nonlocal, chiral
quark model within the mean field approximation.We investigate the effects of a
variation of the formfactors of the interaction on the phase diagram of quark
matter. Special emphasis is on the occurrence of a diquark condensate which
signals a phase transition to color superconductivity and its effects on the
equation of state under the condition of beta- equilibrium and charge
neutrality. We calculate the quark star configurations by solving the Tolman-
Oppenheimer- Volkoff equations and obtain for the transition from a hot, normal
quark matter core of a protoneutron star to a cool diquark condensed one a
release of binding energy of the order of Delta M c^2 ~ 10^{53} erg. We find
that this energy could not serve as an engine for explosive phenomena since the
phase transition is not first order. Contrary to naive expectations the mass
defect increases when for a given temperature we neglect the possibility of
diquark condensation.Comment: 24 pages, 2 tables, 8 figures, references added, figures and text
improve
Nonextensive statistical effects in protoneutron stars
We investigate the bulk properties of protoneutron stars in the framework of
a relativistic mean field theory based on nonextensive statistical mechanics,
characterized by power-law quantum distributions. We study the relevance of
nonextensive statistical effects on the beta-stable equation of state at fixed
entropy per baryon, in presence and in absence of trapped neutrinos, for
nucleonic and hyperonic matter. We show that nonextensive statistical effects
could play a crucial role in the structure and in the evolution of the
protoneutron stars also for small deviations from the standard Boltzmann-Gibbs
statistics.Comment: 9 pages, 7 figure
PDF and scale uncertainties of various DY distributions in ADD and RS models at hadron colliders
In the extra dimension models of ADD and RS we study the dependence of the
various parton distribution functions on observable of Drell-Yan process to NLO
in QCD at LHC and Tevatron energies. Uncertainties at LHC due to factorisation
scales in going from leading to next-to-leading order in QCD for the various
distributions get reduced by about 2.75 times for a range . Further uncertainties arising from the error on experimental
data are estimated using the MRST parton distribution functions.Comment: 27 pages, 11 figures, the version to appear in European Physical
Journal
LOCV calculation for Beta-stable matter at finite temperature
The method of lowest-order constrained variational, which predicts reasonably
the nuclear matter semi-empirical data is used to calculate the equation of
state of beta-stable matter at finite temperature. The Reid soft-core with and
without the N- interactions which fits the N-N scattering data as well
as the potential plus the three-nucleon interaction are considered in
the nuclear many-body Hamiltonian. The electron and muon are treated
relativistically in the total Hamiltonian at given temperature, to make the
fluid electrically neutral and stable against beta decay. The calculation is
performed for a wide range of baryon density and temperature which are of
interest in the astrophysics. The free energy, entropy, proton abundance, etc.
of nuclear beta-stable matter are calculated.
It is shown that by increasing the temperature, the maximum proton abundance
is pushed to the lower density while the maximum itself increases as we
increase the temperature. The proton fraction is not enough to see any
gas-liquid phase transition. Finally we get an overall agreement with other
many-body techniques, which are available only at zero temperature.Comment: LaTex, 20 page
Measuring socioeconomic status in multicountry studies: Results from the eight-country MAL-ED study
Background: There is no standardized approach to comparing socioeconomic status (SES) across multiple sites in epidemiological studies. This is particularly problematic when cross-country comparisons are of interest. We sought to develop a simple measure of SES that would perform well across diverse, resource-limited settings. Methods: A cross-sectional study was conducted with 800 children aged 24 to 60 months across eight resource-limited settings. Parents were asked to respond to a household SES questionnaire, and the height of each child was measured. A statistical analysis was done in two phases. First, the best approach for selecting and weighting household assets as a proxy for wealth was identified. We compared four approaches to measuring wealth: maternal education, principal components analysis, Multidimensional Poverty Index, and a novel variable selection approach based on the use of random forests. Second, the selected wealth measure was combined with other relevant variables to form a more complete measure of household SES. We used child height-for-age Z-score (HAZ) as the outcome of interest. Results: Mean age of study children was 41 months, 52% were boys, and 42% were stunted. Using cross-validation, we found that random forests yielded the lowest prediction error when selecting assets as a measure of household wealth. The final SES index included access to improved water and sanitation, eight selected assets, maternal education, and household income (the WAMI index). A 25% difference in the WAMI index was positively associated with a difference of 0.38 standard deviations in HAZ (95% CI 0.22 to 0.55). Conclusions: Statistical learning methods such as random forests provide an alternative to principal components analysis in the development of SES scores. Results from this multicountry study demonstrate the validity of a simplified SES index. With further validation, this simplified index may provide a standard approach for SES adjustment across resource-limited settings.publishedVersio
The Public Repository of Xenografts enables discovery and randomized phase II-like trials in mice
More than 90% of drugs with preclinical activity fail in human trials, largely due to insufficient efficacy. We hypothesized that adequately powered trials of patient-derived xenografts (PDX) in mice could efficiently define therapeutic activity across heterogeneous tumors. To address this hypothesis, we established a large, publicly available repository of well-characterized leukemia and lymphoma PDXs that undergo orthotopic engraftment, called the Public Repository of Xenografts (PRoXe). PRoXe includes all de-identified information relevant to the primary specimens and the PDXs derived from them. Using this repository, we demonstrate that large studies of acute leukemia PDXs that mimic human randomized clinical trials can characterize drug efficacy and generate transcriptional, functional, and proteomic biomarkers in both treatment-naive and relapsed/refractory disease
Mapping child growth failure across low- and middle-income countries
Childhood malnutrition is associated with high morbidity and mortality globally1. Undernourished children are more likely to experience cognitive, physical, and metabolic developmental impairments that can lead to later cardiovascular disease, reduced intellectual ability and school attainment, and reduced economic productivity in adulthood2. Child growth failure (CGF), expressed as stunting, wasting, and underweight in children under five years of age (0�59 months), is a specific subset of undernutrition characterized by insufficient height or weight against age-specific growth reference standards3�5. The prevalence of stunting, wasting, or underweight in children under five is the proportion of children with a height-for-age, weight-for-height, or weight-for-age z-score, respectively, that is more than two standard deviations below the World Health Organization�s median growth reference standards for a healthy population6. Subnational estimates of CGF report substantial heterogeneity within countries, but are available primarily at the first administrative level (for example, states or provinces)7; the uneven geographical distribution of CGF has motivated further calls for assessments that can match the local scale of many public health programmes8. Building from our previous work mapping CGF in Africa9, here we provide the first, to our knowledge, mapped high-spatial-resolution estimates of CGF indicators from 2000 to 2017 across 105 low- and middle-income countries (LMICs), where 99 of affected children live1, aggregated to policy-relevant first and second (for example, districts or counties) administrative-level units and national levels. Despite remarkable declines over the study period, many LMICs remain far from the ambitious World Health Organization Global Nutrition Targets to reduce stunting by 40 and wasting to less than 5 by 2025. Large disparities in prevalence and progress exist across and within countries; our maps identify high-prevalence areas even within nations otherwise succeeding in reducing overall CGF prevalence. By highlighting where the highest-need populations reside, these geospatial estimates can support policy-makers in planning interventions that are adapted locally and in efficiently directing resources towards reducing CGF and its health implications. © 2020, The Author(s)
Early Life Child Micronutrient Status, Maternal Reasoning, and a Nurturing Household Environment have Persistent Influences on Child Cognitive Development at Age 5 years : Results from MAL-ED
Funding Information: The Etiology, Risk Factors and Interactions of Enteric Infections and Malnutrition and the Consequences for Child Health and Development Project (MAL-ED) is carried out as a collaborative project supported by the Bill & Melinda Gates Foundation, the Foundation for the NIH, and the National Institutes of Health/Fogarty International Center. This work was also supported by the Fogarty International Center, National Institutes of Health (D43-TW009359 to ETR). Author disclosures: BJJM, SAR, LEC, LLP, JCS, BK, RR, RS, ES, LB, ZR, AM, RS, BN, SH, MR, RO, ETR, and LEM-K, no conflicts of interest. Supplemental Tables 1–5 and Supplemental Figures 1–3 are available from the “Supplementary data” link in the online posting of the article and from the same link in the online table of contents at https://academic.oup.com/jn/. Address correspondence to LEM-K (e-mail: [email protected]). Abbreviations used: HOME, Home Observation for Measurement of the Environment inventory; MAL-ED, The Etiology, Risk Factors, and Interactions of Enteric Infections and Malnutrition and the Consequences for Child Health and Development Project; TfR, transferrin receptor; WPPSI, Wechsler Preschool Primary Scales of Intelligence.Peer reviewe
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