2,227 research outputs found
Suzaku observations of the low surface brightness cluster A76
Context: We present results of Suzaku observations of a nearby galaxy cluster
A76 at z=0.0395. This cluster is characterized by extremely low X-ray surface
brightness and is hereafter referred to as the LSB cluster. Aims: To understand
the nature and thermodynamic evolution of the LSB cluster by studying the
physical properties of the hot intracluster medium in A76. Methods: We
conducted two-pointed Suzaku observations of A76 and examined the global gas
properties of the cluster by XIS spectral analysis. We also performed
deprojection analysis of annular spectra and derived radial profiles of gas
temperature, density and entropy out to approximately 850 kpc (~ 0.6 r_200) and
560 kpc (~0.4 r_200) in A76 East and A76 West, respectively. Results: The
measured global temperature and metal abundance are approximately 3.3 keV and
0.24 solar, respectively. From the deprojection analysis, the entropy profile
is found to be flat with respect to radius. The entropy within the central
region (r < 0.2r_200) is exceptionally high (~400 keV cm^2). This phenomenon is
not readily explained by either gravitational heating or preheating. The X-ray
morphology is clumped and irregular, and the electron density is extremely low
(1e-4 -- 1e-3 cm^-3) for the observed high temperature, suggesting that A76 is
in the early phase of cluster formation and the gas compression due to
gravitational potential confinement is lagging behind the gas heating.Comment: 7 pages, 5 figures, A&A accepte
Quantum walks and orbital states of a Weyl particle
The time-evolution equation of a one-dimensional quantum walker is exactly
mapped to the three-dimensional Weyl equation for a zero-mass particle with
spin 1/2, in which each wave number k of walker's wave function is mapped to a
point \vec{q}(k) in the three-dimensional momentum space and \vec{q}(k) makes a
planar orbit as k changes its value in [-\pi, \pi). The integration over k
providing the real-space wave function for a quantum walker corresponds to
considering an orbital state of a Weyl particle, which is defined as a
superposition (curvilinear integration) of the energy-momentum eigenstates of a
free Weyl equation along the orbit. Konno's novel distribution function of
quantum-walker's pseudo-velocities in the long-time limit is fully controlled
by the shape of the orbit and how the orbit is embedded in the
three-dimensional momentum space. The family of orbital states can be regarded
as a geometrical representation of the unitary group U(2) and the present study
will propose a new group-theoretical point of view for quantum-walk problems.Comment: REVTeX4, 9 pages, 1 figure, v2: Minor corrections made for
publication in Phys.Rev.
Asymmetric Patterns of Visual Field Defect in Primary Open-Angle and Primary Angle-Closure Glaucoma
Purpose: To compare the hemifield asymmetry of visual field (VF) loss in primary open-angle glaucoma (POAG) and primary angle-closure glaucoma (PACG) across all severity levels.
Methods: A total of 522 eyes of 327 patients with POAG (mean age ± SD, 54.1 ± 12.4 years) and 375 eyes of 204 patients with PACG (67.3 ± 8.9 years) were included. Subjects meeting the definitions of POAG or PACG were included. Means of the total deviation (TD) values (Humphrey 24-2 VF) in the Glaucoma Hemifield Test (GHT) regions were calculated in early (≥ −6 dB), moderate (< −6 dB and ≥ −12 dB), and advanced (< −12 dB) stages of POAG and PACG eyes. Then the differences of the TD values between superior and inferior hemifield GHT regions of POAG and PACG eyes were calculated. Also, the relationship between the values of pattern SD (PSD) and mean TD (mTD) was compared between POAG and PACG.
Results: In POAG eyes in the early stage, three regions (central, paracentral, and peripheral) in the superior hemifield had greater loss than their inferior counterparts; in moderate and advanced stages, all GHT regions in the superior hemifield had greater loss than their inferior counterparts. In PACG eyes, siginificantly fewer regions in the superior hemifield were significantly worse than their inferior counterpart, compared with POAG: one region (central) in early stage, two regions (central and peripheral) in moderate stage, and one region (central) in advanced stage. POAG eyes had greater PSD values than PACG eyes for given mean of TD values.
Conclusions: In both POAG and PACG eyes, VF damage was more pronounced in superior hemifield than inferior hemifield; however, this tendency was more obvious in POAG eyes than in PACG eyes
Inverse Anticipating Synchronization
We report a new type of chaos synchronization:inverse anticipating
synchronization, where a time delay chaotic system can drive another system in
such a way that the driven system anticipates the driver by synchronizing with
its inverse future state. We extend the concept of inverse anticipating chaos
synchronization to cascaded systems. We propose means for the experimental
observation of inverse anticipating chaos synchronization in external cavity
lasers.Comment: LaTex 6 pages, resubmitted to PR
Parameter Mismatches and Perfect Anticipating Synchronization in bi-directionally coupled external cavity laser diodes
We study perfect chaos synchronization between two bi-directionally coupled
external cavity semiconductor lasers and demonstrate for the first time that
mismatches in laser photon decay rates can explain the experimentally observed
anticipating time in synchronization.Comment: Latex 4 page
Extension of holomorphic functions and cohomology classes from non reduced analytic subvarieties
The goal of this survey is to describe some recent results concerning the L 2
extension of holomorphic sections or cohomology classes with values in vector
bundles satisfying weak semi-positivity properties. The results presented here
are generalized versions of the Ohsawa-Takegoshi extension theorem, and borrow
many techniques from the long series of papers by T. Ohsawa. The recent
achievement that we want to point out is that the surjectivity property holds
true for restriction morphisms to non necessarily reduced subvarieties,
provided these are defined as zero varieties of multiplier ideal sheaves. The
new idea involved to approach the existence problem is to make use of L 2
approximation in the Bochner-Kodaira technique. The extension results hold
under curvature conditions that look pretty optimal. However, a major unsolved
problem is to obtain natural (and hopefully best possible) L 2 estimates for
the extension in the case of non reduced subvarieties -- the case when Y has
singularities or several irreducible components is also a substantial issue.Comment: arXiv admin note: text overlap with arXiv:1703.00292,
arXiv:1510.0523
Expression of Cyclooxygenase Enhances Tumor Invasion and Metastasis in Human Gastric Carcinoma
Background: Expression of COX-2 in vitro has been shown to have a number of cellular effects including increasing proliferation, reducing apoptosis promoting angiogenesis, decreasing E-cadherin expression and increasing invasive/metastatic potential. Aims: To determine the role of COX-2 in the development and metastasis potential of gastric carcinoma in human subjects. Methods: Tissue samples were obtained from surgically removed specimens of 48 patients with primary gastric adenocarcinoma who underwent gastrectomy from January 1998 to December 1999. The specimens were stained for HE while COX-2 expressions in cancer fold and antrum site were evaluated immunohistochemically. Expression of COX-2 was defined as positive when either one of cancer lesion or antrum site showed immunoreactivity. Results: Preliminary result from 12 out of 48 cases, COX-2 immunoreactivity was detected in 50% (6 of 12 specimens). Expression of COX-2 were more frequent in tumor with serosal invasion (5 of 6 specimens), lymph node metastases (3 of 3 specimens), tumor size more than 4 cm and were significant, statistically (p<0.05). The expression of COX-2 in well differential carcinoma type was similar with in poorly differentiated carcinoma type. Conclusion: COX-2 expression in gastric carcinoma tissue is correlated closely with tumor size, serosal invasion and lymph node metastases, indicating that COX-2 is involved in the growth and metastases of gastric carcinoma
Characterization of a half-wave plate for cosmic microwave background circular polarization measurement with POLARBEAR
A half-wave plate (HWP) is often used as a modulator to suppress systematic
error in the measurements of cosmic microwave background (CMB) polarization. A
HWP can also be used to measure circular polarization (CP) through its optical
leakage from CP to linear polarization. The CP of the CMB is predicted from
various sources, such as interactions in the Universe and extension of the
standard model. Interaction with supernova remnants of population III stars is
one of the brightest CP sources. Thus, the observation of the CP of CMB is a
new tool for searching for population III stars. In this paper, we demonstrate
the improved measurement of the leakage coefficient using the transmission
measurement of an actual HWP in the laboratory. We measured the transmittance
of linearly polarized light through the HWP used in \textsc{Polarbear} in the
frequency range of \SIrange{120}{160}{GHz}. We evaluate properties of the HWP
by fitting the data with a physical model using the Markov Chain Monte Carlo
method. We then estimate the band-averaged CP leakage coefficient using the
physical model. We find that the leakage coefficient strongly depends on the
spectra of CP sources. We thus calculate the maximum fractional leakage
coefficient from CP to linear polarization as in the
Rayleigh--Jeans spectrum. The nonzero value shows that \textsc{Polarbear} has
sensitivity to CP. Additionally, because we use the bandpass of detectors
installed in the telescope to calculate the band-averaged values, we also
consider systematic effects in the experiment.Comment: 27 pages, 7 figure
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