213 research outputs found
Percolative phase separation induced by nonuniformly distributed excess oxygens
The zero-field La and Mn nuclear magnetic resonances were
studied in with different oxygen
stoichiometry . The signal intensity, peak frequency and line
broadening of the La NMR spectrum show that excess oxygens have a
tendency to concentrate and establish local ferromagnetic ordering around
themselves. These connect the previously existed ferromagnetic clusters
embedded in the antiferromagnetic host, resulting in percolative conduction
paths. This phase separation is not a charge segregation type, but a
electroneutral type. The magnetoresistance peak at the temperature where
percolative paths start to form provides a direct evidence that phase
separation is one source of colossal magnetoresistance effect.Comment: 4 pages, 5 figure
Oral health status of patients over 18 years. Preventive Clinic Practicum I, UNNE School of Dentistry, Argentina, 2010
Introducción: con el propósito de conocer la situación de salud bucal de pacientes que asisten a la Cátedra Práctica Clínica Preventiva I de la Facultad de Odontología de la Universidad Nacional del Nordeste (UNNE), se realizó un estudio de corte transversal en septiembre y octubre del año 2010. Métodos: Las variables consideradas fueron: datos socio-demográficos, nivel de conocimientos en salud buco-dental, hábitos de higiene buco-dental y de consumo de hidratos de carbono, estado gingival, higiene bucal, estado de los dientes y acceso a la atención odontológica. Para la recolección de datos se utilizaron encuestas estructuradas auto-administradas y las historias clínicas de cada paciente. Se analizaron los datos con los programas estadísticos SPSS 15.0 y Epidat 3.1. Resultados y Conclusiones: si bien predomina un nivel de conocimientos de salud buco-dental bueno, esto no se refleja en los hábitos de higiene oral y en la periodicidad de búsqueda de atención odontológica preventiva. El examen clínico buco-dental reveló higiene buco-dental deficiente, alta prevalencia de gingivitis leve y elevada prevalencia de caries dental y de dientes obturados y perdidos como consecuencia de la misma. Es necesaria la búsqueda de estrategias programadas que permitan optimizar la educación sanitaria y mejorar los comportamientos preventivos de la población de estudio.Introduction: with the intention of identifying the oral health status of patients attending the Preventive Clinic Practicum I at the School of Dentistry, Universidad Nacional del Nordeste (UNNE), Argentina, a cross-sectional study was conducted between September and October 2010. Methods: the variables taken into account were: socio-demographic data, level of oral health knowledge, oral hygiene habits and carbohydrate consumption, gingival status, oral hygiene, teeth status, and access to dental care. The data were collected by means of structured self-administered surveys and the medical records of each patient, and they were analyzed with the statistical software SPSS® 15.0 and Epidat® 3.1. Results: although a good level of oral health knowledge is predominant, it is not reflected in oral hygiene habits or in the frequency in which individuals seek preventive dental care. The clinical examination revealed poor oral hygiene habits, high prevalence of mild gingivitis and high prevalence of dental caries as well as filled and missing teeth as a result of it. Conclusions: it is necessary to search for strategies to optimize health education and to improve preventive behaviors within the study population.Fil: Dho, María Silvina. Universidad Nacional del Nordeste. Facultad de Odontologia. Secretaria de Investigacion. Gabinete de Inv.interd.de Prevencion Salud y Epidemologia; Argentina. Consejo Nacional de Investigaciones Científicas y Técnicas; ArgentinaFil: Vila, Vilma G.. Universidad Nacional del Nordeste. Facultad de Odontologia. Departamento de Clinicas Integradas; ArgentinaFil: Palladino, Alberto C.. Universidad Nacional del Nordeste. Facultad de Medicina; Argentin
Controlling the exchange interaction using the spin-flip transition of antiferromagnetic spins in NiFe / -FeO
We report studies of exchange bias and coercivity in ferromagnetic
NiFe layers coupled to antiferromagnetic (AF) (0001),
(110), and (112) -FeO layers. We show that AF
spin configurations which permit spin-flop coupling give rise to a strong
uniaxial anisotropy and hence a large coercivity, and that by annealing in
magnetic fields parallel to specific directions in the AF we can control either
coercivity or exchange bias. In particular, we show for the first time that a
reversible temperature-induced spin reorientation in the AF can be used to
control the exchange interaction.Comment: 15 pages, 5 figures, submitted to Phys. Rev. Let
The effects of the next-nearest-neighbour density-density interaction in the atomic limit of the extended Hubbard model
We have studied the extended Hubbard model in the atomic limit. The
Hamiltonian analyzed consists of the effective on-site interaction U and the
intersite density-density interactions Wij (both: nearest-neighbour and
next-nearest-neighbour). The model can be considered as a simple effective
model of charge ordered insulators. The phase diagrams and thermodynamic
properties of this system have been determined within the variational approach,
which treats the on-site interaction term exactly and the intersite
interactions within the mean-field approximation. Our investigation of the
general case taking into account for the first time the effects of
longer-ranged density-density interaction (repulsive and attractive) as well as
possible phase separations shows that, depending on the values of the
interaction parameters and the electron concentration, the system can exhibit
not only several homogeneous charge ordered (CO) phases, but also various phase
separated states (CO-CO and CO-nonordered). One finds that the model considered
exhibits very interesting multicritical behaviours and features, including
among others bicritical, tricritical, critical-end and isolated critical
points.Comment: 12 pages, 7 figures; final version, pdf-ReVTeX; corrected typos in
reference; submitted to Journal of Physics: Condensed Matte
Evidence for Narrow N*(1685) Resonance in Quasifree Compton Scattering on the Neutron
The first study of quasi-free Compton scattering on the neutron in the energy
range of GeV is presented. The data reveals a narrow
peak at GeV. This result, being considered in conjunction with
the recent evidence for a narrow structure at GeV in the
photoproduction on the neutron, suggests the existence of a new nucleon
resonance with unusual properties: the mass GeV, the narrow width
MeV, and the much stronger photoexcitation on the neutron than
on the proton.Comment: Replaced with the version published in Phys. Rev.
Infections with Avian Pathogenic and Fecal Escherichia coli Strains Display Similar Lung Histopathology and Macrophage Apoptosis
The purpose of this study was to compare histopathological changes in the lungs of chickens infected with avian
pathogenic (APEC) and avian fecal (Afecal) Escherichia coli strains, and to analyze how the interaction of the bacteria with
avian macrophages relates to the outcome of the infection. Chickens were infected intratracheally with three APEC strains,
MT78, IMT5155, and UEL17, and one non-pathogenic Afecal strain, IMT5104. The pathogenicity of the strains was assessed by
isolating bacteria from lungs, kidneys, and spleens at 24 h post-infection (p.i.). Lungs were examined for histopathological
changes at 12, 18, and 24 h p.i. Serial lung sections were stained with hematoxylin and eosin (HE), terminal deoxynucleotidyl
dUTP nick end labeling (TUNEL) for detection of apoptotic cells, and an anti-O2 antibody for detection of MT78 and
IMT5155. UEL17 and IMT5104 did not cause systemic infections and the extents of lung colonization were two orders of
magnitude lower than for the septicemic strains MT78 and IMT5155, yet all four strains caused the same extent of
inflammation in the lungs. The inflammation was localized; there were some congested areas next to unaffected areas. Only
the inflamed regions became labeled with anti-O2 antibody. TUNEL labeling revealed the presence of apoptotic cells at 12 h
p.i in the inflamed regions only, and before any necrotic foci could be seen. The TUNEL-positive cells were very likely dying
heterophils, as evidenced by the purulent inflammation. Some of the dying cells observed in avian lungs in situ may also be
macrophages, since all four avian E. coli induced caspase 3/7 activation in monolayers of HD11 avian macrophages. In
summary, both pathogenic and non-pathogenic fecal strains of avian E. coli produce focal infections in the avian lung, and
these are accompanied by inflammation and cell death in the infected areas
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
Evidence of anisotropic magnetic polarons in laSrMnO by neutron scattering and comparison with Ca-doped manganites
Elastic and inelastic neutron scattering experiments have been performed in a
LaSrMnO untwinned crystal, which exhibits an
antiferromagnetic canted magnetic structure with ferromagnetic layers.
The elastic small q scattering exhibits a modulation with an anisotropic
q-dependence. It can be pictured by ferromagnetic inhomogeneities or polarons
with a platelike shape, the largest size () and largest
inter-polaron distance ( 38) being within the ferromagnetic
layers. Comparison with observations performed on Ca-doped samples, which show
the growth of the magnetic polarons with doping, suggests that this growth is
faster for the Sr than for the Ca substitution. Below the gap of the spin wave
branch typical of the AF layered magnetic structure, an additional spin wave
branch reveals a ferromagnetic and isotropic coupling, already found in
Ca-doped samples. Its q-dependent intensity, very anisotropic, closely reflects
the ferromagnetic correlations found for the static clusters. All these results
agree with a two-phase electronic segregation occurring on a very small scale,
although some characteristics of a canted state are also observed suggesting a
weakly inhomogeneous state.Comment: 11 pages, 11 figure
First evidence of luminescence in a He/CF gas mixture induced by non-ionizing electrons
Optical readout of Gas Electron Multipliers (GEM) provides very interesting
performances and has been proposed for different applications in particle
physics. In particular, thanks to its good efficiency in the keV energy range,
it is being developed for low-energy and rare event studies, such as Dark
Matter search. So far, the optical approach exploits the light produced during
the avalanche processes in GEM channels. Further luminescence in the gas can be
induced by electrons accelerated by a suitable electric field. The CYGNO
collaboration studied this process with a combined use of a triple-GEM
structure and a grid in an He/CF (60/40) gas mixture at atmospheric
pressure. Results reported in this paper allow to conclude that with an
electric field of about 11~kV/cm a photon production mean free path of about
1.0~cm was found
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