47,883 research outputs found
Observations of solar flare gamma-rays and protons
Solar flare gamma-rays (4 to 7 MeV) and protons (8 to 500 MeV) were simultaneously observed from six flares on 1 Apr., 4 Apr., 27, Apr. 13, May 1981, 1 Feb. and 6 June 1982 by the Hinotori and GMS satellites. The relationship between 4 to 7 MeV gamma-ray fluences and peak 16 to 34 MeV proton fluxes for these flares are analyzed. It does not reveal an apparent correlation between these two parameters. The present result implies that the protons producing gamma-rays and the protons observed near the Earth do not always belong to the same population
Intestinal Metaplasia —The Effect of Acid on the Gastric Mucosa and Gastric Carcinogenesis—
This review concerns stem cells and their relation to intestinal metaplasia. When
gastric regions of mice, Mongolian gerbils or several strains of rats were
irradiated with a total dose of 20 Gy of X-rays given in two fractions,
intestinal metaplasia was only induced in rats. In addition, it was greatly
influenced by rat strain and sex. Alkaline phosphatase (ALP) positive
metaplastic foci were increased by administration of ranitidine (H2
receptor antagonist), crude stomach antigens or subtotal resection of the fundus
and decreased by cysteamine (gastric acid secretion stimulator), histamine or
removal of the submandibular glands. Recent studies have shown that
Cdx2 transgenic mice with gastric achlorhydria develop
intestinal metaplasia and that in men and animals, Helicobacter
pylori (H. pyrlori) infection can cause intestinal metaplasias
that are reversible on eradication. Our results combined with findings for
H. pylori infection or eradication and transgenic mice
suggest that an elevation in the pH of the gastric juice due to disappearance of
parietal cells is one of the principal factors for development of reversible
intestinal metaplasia. When different organs were transplanted into the stomach
or duodenum, they were found to transdifferentiate into gastric or duodenal
mucosae, respectively. Organ-specific stem cells in normal non-liver tissues
(heart, kidney, brain and skin) also differentiate into hepatocytes when
transplanted into an injured liver. Therefore, stem cells have a multipotential
ability, transdifferentiating into different organs when transplanted into
different environments. Finally, intestinal metaplasia has been found to
possibly increase sensitivity to the induction of tumors by colon carcinogens of
the 1,2-dimethylhydrazine (DMH), azoxymethane (AOM) or
2-amino-1-methyl-6-phenylimidazo[4.5-b]pyridine (PhIP) type. This carcinogenic
process, however, may be relatively minor compared with the main gastric
carcinogenesis process induced by N-methy1-N’-nitro-N-nitrosoguanidine (MMNG) or
N-methylnitrosourea (MNU), which is not affected by the presence of intestinal
metaplasia. The protocol used in these experiments may provide a new approach to
help distinguish between developmental events associated with intestinal
metaplasia and gastric tumors
Efficient Implementations of Molecular Dynamics Simulations for Lennard-Jones Systems
Efficient implementations of the classical molecular dynamics (MD) method for
Lennard-Jones particle systems are considered. Not only general algorithms but
also techniques that are efficient for some specific CPU architectures are also
explained. A simple spatial-decomposition-based strategy is adopted for
parallelization. By utilizing the developed code, benchmark simulations are
performed on a HITACHI SR16000/J2 system consisting of IBM POWER6 processors
which are 4.7 GHz at the National Institute for Fusion Science (NIFS) and an
SGI Altix ICE 8400EX system consisting of Intel Xeon processors which are 2.93
GHz at the Institute for Solid State Physics (ISSP), the University of Tokyo.
The parallelization efficiency of the largest run, consisting of 4.1 billion
particles with 8192 MPI processes, is about 73% relative to that of the
smallest run with 128 MPI processes at NIFS, and it is about 66% relative to
that of the smallest run with 4 MPI processes at ISSP. The factors causing the
parallel overhead are investigated. It is found that fluctuations of the
execution time of each process degrade the parallel efficiency. These
fluctuations may be due to the interference of the operating system, which is
known as OS Jitter.Comment: 33 pages, 19 figures, add references and figures are revise
Phase Diagram of Spinless Fermions on an Anisotropic Triangular Lattice at Half-filling
The strong coupling phase diagram of the spinless fermions on the anisotropic
triangular lattice at half-filling is presented. The geometry of inter-site
Coulomb interactions rules the phase diagram. Unconventional charge ordered
phases are detected which are the recently reported pinball liquid and the
striped chains. Both are induced by the quantum dynamics out of classical
disordered states and afford extremely correlated metallic states and the
particular domain wall-type of excitations, respectively. The disorder once
killed by the quantum effect revives at the finite temperature, which is
discussed in the terms of the organic -ET.Comment: 4pages 6figure
Modelling of EIS spectrum drift from instrumental temperatures
An empirical model has been developed to reproduce the drift of the spectrum
recorded by EIS on board Hinode using instrumental temperatures and relative
motion of the spacecraft. The EIS spectrum shows an artificial drift in
wavelength dimension in sync with the revolution of the spacecraft, which is
caused by temperature variations inside the spectrometer. The drift amounts to
70 km s in Doppler velocity and introduces difficulties in velocity
measurements. An artificial neural network is incorporated to establish a
relationship between the instrumental temperatures and the spectral drift. This
empirical model reproduces observed spectrum shift with an rms error of 4.4 km
s. This procedure is robust and applicable to any spectrum obtained with
EIS, regardless of of the observing field. In addition, spectral curvatures and
spatial offset in the North - South direction are determined to compensate for
instrumental effects.Comment: 16 pages, 12 Figures, accepted for publication in Solar Physics.
Added description of neural networ
Nonequilibrium Green's Function Approach to Phonon Transport in Defective Carbon Nanotubes
We have developed a new theoretical formalism for phonon transport in
nanostructures using the nonequilibrium phonon Green's function technique and
have applied it to thermal conduction in defective carbon nanotubes. The
universal quantization of low-temperature thermal conductance in carbon
nanotubes can be observed even in the presence of local structural defects such
as vacancies and Stone-Wales defects, since the long wavelength acoustic
phonons are not scattered by local defects. At room temperature, however,
thermal conductance is critically affected by defect scattering since incident
phonons are scattered by localized phonons around the defects. We find a
remarkable change from quantum to classical features for the thermal transport
through defective CNTs with increasing temperature.Comment: 5 pages, 3 figures, accepted for publication in Phys. Rev. Let
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