266 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
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
Ferromagnetic to spin glass cross over in (La,Tb)_{2/3}Ca_{1/3}MnO_{3}
In the series La_{2/3-x}Tb_{x}Ca_{1/3}MnO_{3}, it is known that the
compositions are ferromagnetic for smaller values of x and show spin glass
characteristics at larger values of x. Our studies on the magnetic properties
of various compositions in the La_{2/3-x}Tb_{x}Ca_{1/3}MnO_{3} series show that
the cross over from ferromagnetic to spin glass region takes place above x ~
1/8. Also, a low temperature anomaly at 30 K, observed in the ac susceptibility
curves, disappears for compositions above this critical value of x. A mixed
phase region coexists in the narrow compositional range 0.1 <= x <= 0.125,
indicating that the ferromagnetic to spin glass cross over is not abrupt.Comment: 5 pages, 5 figure
Effect of suppression of local distortion on magnetic, electrical and thermal transport properties of Cr substituted bi-layer manganite LaSrMnO
We have investigated magnetic, electrical and thermal transport properties
(Seebeck effect and thermal conductivity) of
LaSrMnCrO polycrystalline samples (=0.1, 0.2, 0.4
and 0.6). The Cr substitution for Mn sites causes a removal of
orbital of -electron resulting in a volume shrinkage of
lattice. Magnetic measurements reveal the appearance of a glassy behavior for
Cr-doped samples, accompanied by both a collapse of the A-type
antiferromagnetic structure and the growth of ferromagnetic clusters. Cr-doping
effect on electrical transport strongly enhances an insulating behavior over a
wide range of temperature, while it suppresses a local minimum of
thermoelectric power at lower temperatures. The phonon thermal conduction
gradually rises with increasing Cr content, which is contradictory to a typical
impurity effect on thermal conductivity. We attribute this to a suppression of
local lattice distortion through the introduction of Jahn-Teller inactive ions
of Cr.Comment: 8 pages, 9figure
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
Caracterización de pacientes según riesgo y/o actividad de caries y enfermedad periodontal
Introducción: El presente estudio se propone caracterizar a los pacientes que asistieron a la Facultad de Odontología de la UNNE, según riesgo y/o actividad de caries y enfermedad periodontal e identificar su asociación con variables sociodemográficas. Materiales y Métodos: Se realizó un estudio descriptivo transversal. Se recolectaron datos de las historias clínicas de pacientes que asistieron al Módulo Introducción a la Práctica Clínica en ciclo lectivo 2017. Se identificaron factores de riesgo e indicadores clínicos que permitieron caracterizar a los pacientes según riesgo y/o actividad de caries y enfermedad periodontal en relación al sexo y edad de cada individuo. Resultados: Se analizaron 166 historias clínicas. Se registró un predominio de pacientes con actividad de caries y riesgo de actividad periodontal. La condición de salud bucal no se asoció significativamente al sexo p=0,418, ni a la edad p=0,839. Conclusión: Se evidencia la necesidad de aplicar medidas preventivas para disminuir el riesgo de caries dental y enfermedad periodontal y aplicar tratamientos en lesiones de caries activas para impedir el avance de la enfermedad.
Local Ferromagnetism in Microporous Carbon with the Structural Regularity of Zeolite Y
Magnetization M(H,T) measurements have been performed on microporous carbon
(MC) with a three-dimensional nano-array structure corresponding to that of a
zeolite Y supercage. The obtained results unambiguously demonstrate the
occurrence of high-temperature ferromagnetism in MC, probably originating from
a topological disorder associated with curved graphene sheets. The results
provide evidence that the ferromagnetic behavior of MC is governed by isolated
clusters in a broad temperature range, and suggest the occurrence of
percolative-type transition with the temperature lowering. A comparative
analysis of the results obtained on MC and related materials is given.Comment: To be published in Physical Review B (2003
Hepoxilin A3 induces changes in cytosolic calcium, intracellular pH and membrane potential in human neutrophils
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