242 research outputs found
Anomalous magnetotransport in (YGd)Co alloys: interplay of disorder and itinerant metamagnetism
New mechanism of magnetoresistivity in itinerant metamagnets with a
structural disorder is introduced basing on analysis of experimental results on
magnetoresistivity, susceptibility, and magnetization of structurally
disordered alloys (YGd)Co. In this series, YCo is an
enhanced Pauli paramagnet, whereas GdCo is a ferrimagnet (T=400
K) with Gd sublattice coupled antiferromagnetically to the itinerant Co-3d
electrons. The alloys are paramagnetic for . Large positive
magnetoresistivity has been observed in the alloys with magnetic ground state
at temperatures TT. We show that this unusual feature is linked to
a combination of structural disorder and metamagnetic instability of itinerant
Co-3d electrons. This new mechanism of the magnetoresistivity is common for a
broad class of materials featuring a static magnetic disorder and itinerant
metamagnetism.Comment: 7 pages 7 figure
Association between household solid fuel use and tuberculosis: cross-sectional data from the Mongolian national tuberculosis prevalence survey
BACKGROUND: Tuberculosis (TB) and indoor air pollution (IAP) are equally critical public health issues in the developing world. Mongolia is experiencing the double burden of TB and IAP due to solid fuel combustion. However, no study has assessed the relationship between household solid fuel use and TB in Mongolia. The present study aimed to assess the association between household solid fuel use and TB based on data from the Mongolian National Tuberculosis Prevalence Survey (MNTP Survey). METHOD: The MNTP Survey was a nationally representative population-based cross-sectional survey targeting households in Mongolia from 2014 to 2015, with the aim of evaluating the prevalence of TB. The survey adopted a multistage cluster sampling design in accordance with the World Health Organization prevalence survey guidelines. Clusters with at least 500 residents were selected by random sampling. A sample size of 98 clusters with 54,100 participants was estimated to be required for the survey, and 41,450 participants were included in the final analysis of the present study. A structured questionnaire was used to collect information on environmental and individual factors related to TB. Physical examination, chest X-ray, and sputum examinations were also performed to diagnose TB. RESULTS: The use of solid fuels for heating (adjusted odds ratio (aOR): 1.5; 95% confidence interval (CI): 1.1-2.1), male gender (aOR: 2.2; 95% CI: 1.6-3.2), divorced or widowed (aOR: 2.6; 95% CI: 1.7-3.8), daily smoker (aOR: 1.8; 95% CI: 1.3-2.5), contact with an active TB case (aOR: 1.7; 95% CI: 1.2-2.3), being underweight (aOR: 3.7; 95% CI: 2.4-5.7), and previous history of TB (aOR: 4.3; 95% CI: 3.0-6.1) were significantly associated with bacteriologically confirmed TB after adjusting for confounding variables. CONCLUSION: The use of solid fuels for heating was significantly associated with active TB in Mongolian adults. Increased public awareness is needed on the use of household solid fuels, a source of IAP
Influence of large local and non-local bispectra on primordial black hole abundance
Primordial black holes represent a unique probe to constrain the early
universe on small scales - providing the only constraints on the primordial
power spectrum on the majority of scales. However, these constraints are
strongly dependent on even small amounts of non-Gaussianity, which is
unconstrained on scales significantly smaller than those visible in the CMB.
This paper goes beyond previous considerations to consider the effects of a
bispectrum of the equilateral, orthogonal and local shapes with arbitrary
magnitude upon the abundance of primordial black holes. Non-Gaussian density
maps of the early universe are generated from a given bispectrum and used to
place constraints on the small scale power spectrum. When small, we show that
the skewness provides an accurate estimate for how the constraint depends on
non-Gaussianity, independently of the shape of the bispectrum. We show that the
orthogonal template of non-Gaussianity has an order of magnitude weaker effect
on the constraints than the local and equilateral templates.Comment: 11 pages, 4 figures, updated to match published version in
JCAP02(2016)029, Journal of Cosmology and Astroparticle Physics, Volume 2016,
February 201
Anomalous resistivity and thermopower of the spinel-type compounds CuIr2S4 and CuIr2Se4
Resistivity (Ï) and thermopower (S) of spinel-type compounds CuIr2S4 and CuIr2Se4 have been measured at temperatures from 2 to 900 K under magnetic field from 0 to 15 T. The thermopower is positive in the metallic phase of both compounds at high temperatures, as well as in the low-temperature insulating state of CuIr2S4. The positive thermopower of the insulating phase implies p-type charge carriers, in agreement with the recent photoemission results. The low-temperature resistivity of CuIr2S4 is in good agreement with the Efros-Shklovskii variable-range hopping conductivity mechanism: Ï=Ï0exp[(T*/T)1/2]. The most striking result is that the resistivity of the metallic phases is well described by an exponential-type temperature dependence in a wide temperature range from 2 K to at least 900 K. This unusual result for metals type of the resistivity temperature dependence, as well as other features in the transport properties, imply a nonconventional conductivity mechanism. The magnetoresistivity ÎÏ is positive and proportional to H2, while magnetothermopower ÎS=S(H,T)-S(0,T) is very small for both compounds at all temperature
Weak itinerant ferromagnetism in Heusler type Fe2VAl0.95
We report measurements of the magnetic, transport and thermal properties of
the Heusler type compound Fe2VAl0.95. We show that while stoichiometric Fe2VAl
is a non-magnetic semi-metal a 5% substitution on the Al-site with the 3d
elements Fe and V atoms leads to a ferromagnetic ground state with a Curie
temperature TC = 33+-3 K and a small ordered moment ms = 0.12 mB/Fe in
Fe2VAl0.95. The reduced value of the ratio ms/mp = 0.08, where mp = 1.4 mB/Fe
is the effective Curie-Weiss moment, together with the analysis of the
magnetization data M(H,T), show magnetism is of itinerant nature. The specific
heat shows an unusual temperature variation at low temperatures with an
enhanced Sommerfeld coefficient, g = 12 mJK-2mol-1. The resistivity, r(T), is
metallic and follows a power law behavior r(T) = r0+AT^n with n = 1.5 below TC.
With applying pressure, TC decreases with the rate of (1/TC)(dTC /dP) = -0.061
GPa-1. We conclude substitution on the Al-site with Fe and V atoms results in
itinerant ferromagnetism with a low carrier density.Comment: 27 pages, 9 figure
Spectral Distortions of the CMB as a Probe of Inflation, Recombination, Structure Formation and Particle Physics
Following the pioneering observations with COBE in the early 1990s, studies
of the cosmic microwave background (CMB) have focused on temperature and
polarization anisotropies. CMB spectral distortions - tiny departures of the
CMB energy spectrum from that of a perfect blackbody - provide a second,
independent probe of fundamental physics, with a reach deep into the primordial
Universe. The theoretical foundation of spectral distortions has seen major
advances in recent years, which highlight the immense potential of this
emerging field. Spectral distortions probe a fundamental property of the
Universe - its thermal history - thereby providing additional insight into
processes within the cosmological standard model (CSM) as well as new physics
beyond. Spectral distortions are an important tool for understanding inflation
and the nature of dark matter. They shed new light on the physics of
recombination and reionization, both prominent stages in the evolution of our
Universe, and furnish critical information on baryonic feedback processes, in
addition to probing primordial correlation functions at scales inaccessible to
other tracers. In principle the range of signals is vast: many orders of
magnitude of discovery space could be explored by detailed observations of the
CMB energy spectrum. Several CSM signals are predicted and provide clear
experimental targets, some of which are already observable with present-day
technology. Confirmation of these signals would extend the reach of the CSM by
orders of magnitude in physical scale as the Universe evolves from the initial
stages to its present form. The absence of these signals would pose a huge
theoretical challenge, immediately pointing to new physics.Comment: Astro2020 Science White Paper, 5 pages text, 13 pages in total, 3
Figures, minor update to reference
Theoretical Engineering of the Gut Micro biome for the Purpose of Creating Superior Soldiers
The purpose of this review is to highlight research raising the possibility of exploiting the host-microbiome gut axis for military purposes. Through optimizing the gut-microbiome environment it is possible to enhance nutritional access to indigestible material, provide local and systemic analgesia, enhance psychological robustness to battlefield stress, produce endogenous steroids, reduce muscle fatigue, and promote peripheral wound healing. However, this approach is still in its early stages and thus has not been explored to its full potential. The challenges that are currently preventing the practical use of gut bacteria include the following: inconsistency of clinical outcomes, transient effects requiring continuous supplementation, the type of regimen selected, the initiation and cessation of regimen, and the broader clinical studies needed to validate this research. This review is intended to shed light on the numerous and varied positive impacts such an approach could have for the military if further developed
- âŠ