926 research outputs found
Formation of collective spins in frustrated clusters
Using magnetization, specific heat and neutron scattering measurements, as
well as exact calculations on realistic models, the magnetic properties of the
\lacuvo compound are characterized on a wide temperature range. At high
temperature, this oxide is well described by strongly correlated atomic =1/2
spins while decreasing the temperature it switches to a set of weakly
interacting and randomly distributed entangled pseudo spins and
. These pseudo-spins are built over frustrated clusters, similar to
the kagom\'e building block, at the vertices of a triangular superlattice, the
geometrical frustration intervening then at different scales.Comment: 10 page
In vitro Susceptibility and Evaluation of Techniques for Understanding the Mode of Action of a Promising Non-antibiotic Citrus Fruit Extract Against Several Pathogens
Copyright © 2019 de Nova, Carvajal, Prieto and Rubio. This is an open-access article distributed under the terms of the Creative Commons Attribution License (CC BY). The use, distribution or reproduction in other forums is permitted, provided the original author(s) and the copyright owner(s) are credited and that the original publication in this journal is cited, in accordance with accepted academic practice. No use, distribution or reproduction is permitted which does not comply with these terms.[EN] The screening for alternatives to antibiotics is an urgent need for the pharmaceutical industry. One of these alternatives seems to be the citrus fruit extracts, which are showing a significant antibacterial activity against Gram-negative and Gram-positive bacteria. One of these citrus extracts, named BIOCITRO®, is assessed in this study to elucidate its bacteriostatic and bactericidal effect and its mode of action on the important pathogens Campylobacter coli, C. jejuni, Escherichia coli, Salmonella enterica ssp. enterica, Clostridium difficile, C. perfringens, and Staphylococcus aureus. For most of the strains tested of these bacteria the product was bactericidal as well as bacteriostatic at the same concentration, and the minimum bactericidal concentrations ranged from 16 to 256 μg/mL. Regarding the mode of action, important changes in the permeability, structure, composition and morphology of the bacterial envelope were evidenced using flow cytometry, Fourier transform infrared spectroscopy and scanning electron microscopy. The main effect of the product was found over carbohydrates and polysaccharides, inducing the release of microvesicles by the cells in addition to other specific effects. During the study, the techniques used were evaluated to clarify their contribution to the knowledge of the mode of action of the product. The survival test elucidated whether the modifications displayed using other techniques affected the viability of the cells or on the contrary, the cells remained viable even with evident changes in their structure, composition or morphology. Flow cytometry showed that for some strains the proportion of cells detected with altered membrane permeability were higher than the number of non-viable cells, and therefore the damage did not affect the viability of some cells. On the contrary, some cells observed using scanning electron microscopy with no apparent damage, were demonstrated non-viable using the survival test, making this technique indispensable in studies of the mode of action of antimicrobials to make a correct interpretation of the data from other techniques.SIThe research was partly financed by PROBENA (2015/00119/001), the company commercializing BIOCITRO® in the EU, but without any influence over the experimental procedures neither results
Field-induced segregation of ferromagnetic nano-domains in PrSrMnO, detected by Mn NMR
The antiferromagnetic manganite PrSrMnO was investigated
at low temperature by means of magnetometry and Mn NMR. A field-induced
transition to a ferromagnetic state is detected by magnetization measurements
at a threshold field of a few tesla. NMR shows that the ferromagnetic phase
develops from zero field by the nucleation of microscopic ferromagnetic
domains, consisting of an inhomogeneous mixture of tilted and fully aligned
parts. At the threshold the NMR spectrum changes discontinuously into that of a
homogeneous, fully aligned, ferromagnetic state, suggesting a percolative
origin for the ferromagnetic transition.Comment: Latex 2.09 language. 4 pages, 3 figures, 23 references. Submitted to
physical Review
Investigating Social Ecological Contributors to Diabetes within Hispanics in an Underserved U.S.-Mexico Border Community
Hispanics bear a disproportionate burden of diabetes in the United States, yet relations of structural, socio-cultural and behavioral factors linked to diabetes are not fully understood across all of their communities. The current study examines disparities and factors associated with diabetes in adult Hispanics of Mexican-descent (N = 648) participating in a population survey of an underserved rural U.S.-Mexico border community. The overall rate of diabetes prevalence rate in the sample, based on self-report and a glucose testing, was 21%; much higher than rates reported for U.S. adults overall, for all Hispanic adults, or for Mexican American adults specifically. Acculturation markers and social determinants of health indicators were only significantly related to diabetes in models not accounting for age. Older age, greater BMI (>30), greater waist-to-hip ratio as well as lower fruit and vegetable consumption were significantly related to increased likelihood of diabetes when all structural, cultural, behavioral, and biological factors were considered. Models with sets of behavioral factors and biological factors each significantly improved explanation of diabetes relative to prior social ecological theory-guided models. The findings show a critical need for diabetes prevention efforts in this community and suggest that health promotion efforts should particularly focus on increasing fruit and vegetable consumption
Structure and magnetic order in Fe2+xV1-xAl
We present a detailed structural investigation via neutron diffraction of
differently heat treated samples Fe2VAl and Fe2+xV1-xAl. Moreover, the magnetic
behaviour of these materials is studied by means of mSR and
Mossbauer-experiments. Our structural investigation indicates that quenched
Fe2VAl, exhibiting the previously reported "Kondo insulating like" behaviour,
is off-stoichiometric (6%) in its Al content. Slowly cooled Fe2VAl is
structurally better ordered and stoichiometric, and the microscopic magnetic
probes establish long range ferromagnetic order below TC = 13K, consistent with
results from bulk experiments. The magnetic state can be modelled as being
generated by diluted magnetic ions in a non-magnetic matrix. Quantitatively,
the required number of magnetic ions is too large as to be explained by a model
of Fe/V site exchange. We discuss the implications of our findings for the
ground state properties of Fe2VAl, in particular with respect to the role of
crystallographic disorder.Comment: accepted for publication in J. Phys.: Condens. Matte
Self-trapped Exciton and Franck-Condon Spectra Predicted in LaMnO
Because the ground state has cooperative Jahn-Teller order, electronic
excitations in LaMnO are predicted to self-trap by local rearrangement of
the lattice. The optical spectrum should show a Franck-Condon series, that is,
a Gaussian envelope of vibrational sidebands. Existing data are reinterpreted
in this way. The Raman spectrum is predicted to have strong multiphonon
features.Comment: 5 pages with two embedded postscript figure
Approach to the metal-insulator transition in La(1-x)CaxMnO3 (0<x<.2): magnetic inhomogeneity and spin wave anomaly
We describe the evolution of the static and dynamic spin correlations of
LaCaMnO, for x=0.1, 0.125 and 0.2, where the system evolves
from the canted magnetic state towards the insulating ferromagnetic state,
approaching the metallic transition (x=0.22).
In the x=0.1 sample, the observation of two spin wave branches typical of two
distinct types of magnetic coupling, and of a modulation in the elastic diffuse
scattering characteristic of ferromagnetic inhomogeneities, confirms the static
and dynamic inhomogeneous features previously observed at x0.1. The
anisotropic q-dependence of the intensity of the low-energy spin wave suggests
a bidimensionnal character for the static inhomogeneities. At x=0.125, which
corresponds to the occurence of a ferromagnetic and insulating state, the two
spin wave branches reduce to a single one, but anisotropic. At this
concentration, an anomaly appears at {\bf q}=(1.25,1.25,0), that could be
related to an underlying periodicity, as arising from (1.5,1.5,0)
superstructures.
At x=0.2, the spin-wave branch is isotropic. In addition to the anomaly
observed at q, extra magnetic excitations are observed at larger q, forming
an optical branch. The two dispersion curves suggest an anti-crossing behavior
at some {\bf q'} value, which could be explained by a folding due to an
underlying perodicity involving four cubic lattice spacings
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