2,278 research outputs found
Probing the Structure of Gamma-Ray Burst Jets with Steep Decay Phase of their Early X-ray Afterglows
We show that the jet structure of gamma-ray bursts (GRBs) can be investigated
with the tail emission of the prompt GRB. The tail emission which we consider
is identified as a steep-decay component of the early X-ray afterglow observed
by the X-ray Telescope onboard Swift. Using a Monte Carlo method, we derive,
for the first time, the distribution of the decay index of the GRB tail
emission for various jet models. The new definitions of the zero of time and
the time interval of a fitting region are proposed. These definitions for
fitting the light curve lead us an unique definition of the decay index, which
is useful to investigate the structure of the GRB jet. We find that if the GRB
jet has a core-envelope structure, the predicted distribution of the decay
index of the tail has a wide scatter and has multiple peaks, which cannot be
seen for the case of the uniform and the Gaussian jet. Therefore, the decay
index distribution tells us the information on the jet structure. Especially,
if we observe events whose decay index is less than about 2, both the uniform
and the Gaussian jet models will be disfavored according to our simulation
study.Comment: 21 pages, 10 figures, the paper with full resolution images is
http://theo.phys.sci.hiroshima-u.ac.jp/~takami/research/achievements/papers/003_full.pd
Quantum Markov Process on a Lattice
We develop a systematic description of Weyl and Fano operators on a lattice
phase space. Introducing the so-called ghost variable even on an odd lattice,
odd and even lattices can be treated in a symmetric way. The Wigner function is
defined using these operators on the quantum phase space, which can be
interpreted as a spin phase space. If we extend the space with a dichotomic
variable, a positive distribution function can be defined on the new space. It
is shown that there exits a quantum Markov process on the extended space which
describes the time evolution of the distribution function.Comment: Lattice2003(theory
Guanylate cyclase C as a target for prevention, detection, and therapy in colorectal cancer.
INTRODUCTION: Colorectal cancer remains the second leading cause of cancer death in the United States, and new strategies to prevent, detect, and treat the disease are needed. The receptor, guanylate cyclase C (GUCY2C), a tumor suppressor expressed by the intestinal epithelium, has emerged as a promising target. Areas covered: This review outlines the role of GUCY2C in tumorigenesis, and steps to translate GUCY2C-targeting schemes to the clinic. Endogenous GUCY2C-activating ligands disappear early in tumorigenesis, silencing its signaling axis and enabling transformation. Pre-clinical models support GUCY2C ligand supplementation as a novel disease prevention paradigm. With the recent FDA approval of the GUCY2C ligand, linaclotide, and two more synthetic ligands in the pipeline, this strategy can be tested in human trials. In addition to primary tumor prevention, we also review immunotherapies targeting GUCY2C expressed by metastatic lesions, and platforms using GUCY2C as a biomarker for detection and patient staging. Expert commentary: Results of the first GUCY2C targeting schemes in patients will become available in the coming years. The identification of GUCY2C ligand loss as a requirement for colorectal tumorigenesis has the potential to change the treatment paradigm from an irreversible disease of genetic mutation, to a treatable disease of ligand insufficiency
Interaction and Localization of One-electron Orbitals in an Organic Molecule: Fictitious Parameter Analysis for Multi-physics Simulations
We present a new methodology to analyze complicated multi-physics simulations
by introducing a fictitious parameter. Using the method, we study quantum
mechanical aspects of an organic molecule in water. The simulation is
variationally constructed from the ab initio molecular orbital method and the
classical statistical mechanics with the fictitious parameter representing the
coupling strength between solute and solvent. We obtain a number of
one-electron orbital energies of the solute molecule derived from the
Hartree-Fock approximation, and eigenvalue-statistical analysis developed in
the study of nonintegrable systems is applied to them. Based on the results, we
analyze localization properties of the electronic wavefunctions under the
influence of the solvent.Comment: 4 pages, 5 figures, the revised version will appear in J. Phys. Soc.
Jpn. Vol.76 (No.1
Spectroastrometry of rotating gas disks for the detection of supermassive black holes in galactic nuclei. I. Method and simulations
This is the first in a series of papers in which we study the application of
spectroastrometry in the context of gas kinematical studies aimed at measuring
the mass of supermassive black holes. The spectroastrometrical method consists
in measuring the photocenter of light emission in different wavelength or
velocity channels. In particular we explore the potential of spectroastrometry
of gas emission lines in galaxy nuclei to constrain the kinematics of rotating
gas disks and to measure the mass of putative supermassive black holes. By
means of detailed simulations and test cases, we show that the fundamental
advantage of spectroastrometry is that it can provide information on the
gravitational potential of a galaxy on scales significantly smaller (~ 1/10)
than the limit imposed by the spatial resolution of the observations. We then
describe a simple method to infer detailed kinematical informations from
spectroastrometry in longslit spectra and to measure the mass of nuclear mass
concentrations. Such method can be applied straightforwardly to integral field
spectra, which do not have the complexities due to a partial spatial covering
of the source in the case of longslit spectra.Comment: Accepted for publication in A&
Existence of the Wigner function with correct marginal distributions along tilted lines on a lattice
In order to determine the Wigner function uniquely, we introduce a new
condition which ensures that the Wigner function has correct marginal
distributions along tilted lines. For a system in dimensional Hilbert
space, whose "phase space" is a lattice with sites, we get different
results depending on whether is odd or even. Under the new condition, the
Wigner function is determined if is an odd number, but it does not exist if
is even.Comment: 18 page
Erratum: A spectro-astrometric study of southern pre-main sequence stars. Binaries, outflows, and disc structure down to AU scales
Peer reviewe
Erratum: A spectro-astrometric study of southern pre-main sequence stars. Binaries, outflows, and disc structure down to AU scales
Peer reviewe
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