2,107 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
Full bridge model study of a passive aerodynamic flutter suppression system
Peer reviewedPreprin
A travel guide to the canonical bundle formula
We survey known results on the canonical bundle formula and its applications
in algebraic geometry.Comment: 17 pages, to appear in the Proceedings of the conference Birational
Geometry and Moduli Space
Convection Patterns in Liquid Oxide Films on ZrB 2 –SiC Composites Oxidized at a High Temperature
Peer Reviewedhttp://deepblue.lib.umich.edu/bitstream/2027.42/66000/1/j.1551-2916.2007.01784.x.pd
Non-equilibrium Studies in Switching Arc Plasmas in Japan
This paper briefly introduce research work examples of non-equilibrium studies in switching arcs. In understanding arc behavior, one often assumes local thermodynamic equilibrium (LTE) condition in the arc plasma. However, actual arc plasmas are not completely and not always in LTE state because of strong temperature change temporally and spatially, and high electric field application etc. Recently, we have a collaboration work in numerical simulations and experimental approaches for decaying arcs without LTE assumption. First, our numerical model is presented for decaying arcs without chemical equilibrium assumption. Secondly, two experimental methods are introduced for measuring electron density in decaying arcs without LTE assumption: Laser Thomson Scattering method and the Schack-Hartmann method. Finally, comparison results is shown between the LTE simulation, the chemically non-equilibrium simulation, and the above experimental measurements
The landscape of nonlinear structural dynamics: an introduction.
Nonlinear behaviour is ever-present in vibrations and other dynamical motions of engineering structures. Manifestations of nonlinearity include amplitude-dependent natural frequencies, buzz, squeak and rattle, self-excited oscillation and non-repeatability. This article primarily serves as an extended introduction to a theme issue in which such nonlinear phenomena are highlighted through diverse case studies. More ambitiously though, there is another goal. Both the engineering context and the mathematical techniques that can be used to identify, analyse, control or exploit these phenomena in practice are placed in the context of a mind-map, which has been created through expert elicitation. This map, which is available in software through the electronic supplementary material, attempts to provide a practitioner's guide to what hitherto might seem like a vast and complex research landscape.This project has arisen from a collaboration between the five UK universities and eight industrial collaborators on the EPSRC ‘Engineering Nonlinearity’ Programme Grant (EPSRC grant no. EP/K003836/1). T.B. is funded by an RAEng/EPSRC Research Fellowship.This is the final version of the article. It was first available from Royal Society Publishing via http://dx.doi.org/10.1098/rsta.2014.040
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
Superconducting and structural properties of the type-I superconductor PdTe<sub>2</sub> under high pressure
The transition metal dichalcogenide PdTe has attractive features based on
its classification as a type-II Dirac semimetal and the occurrence of type-I
superconductivity, providing a platform for discussion of a topological
superconductor. Our recent work revealed that type-I superconductivity persists
up to pressures of GPa and the superconducting transition temperature
reaches a maximum at around 1 GPa, which is inconsistent with the
theoretical prediction. To understand its non-monotonic variation and
investigate superconductivity at higher pressures, we performed structural
analysis by x-ray diffraction at room temperature below 8 GPa and electrical
resistivity measurements at low temperatures from 1 to 8 GPa. With regard to
the superconductivity beyond 1 GPa, the monotonic decrease in is
reproduced without any noticeable anomalies; changes from 1.8 K at
1 GPa to 0.82 K at 5.5 GPa with K/GPa. The crystal
structure with spacegroup \={3}1 is stable in the pressure range we
examined. On the other hand, the normalized pressure-strain analysis (finite
strain analysis) indicates that the compressibility changes around 1 GPa,
suggesting that a Lifshitz transition occurs. We here discuss the effect of
pressure on the superconducting and structural properties based on the
comparison of these experimental results
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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