3,007 research outputs found
Ultrahigh magnetic field spectroscopy reveals the band structure of the 3D topological insulator BiSe
We have investigated the band structure at the point of the
three-dimensional (3D) topological insulator BiSe using
magneto-spectroscopy over a wide range of energies (\,eV) and in
ultrahigh magnetic fields up to 150\,T. At such high energies (\,eV) the
parabolic approximation for the massive Dirac fermions breaks down and the
Landau level dispersion becomes nonlinear. At even higher energies around 0.99
and 1.6 eV, new additional strong absorptions are observed with a temperature
and magnetic-field dependence which suggest that they originate from higher
band gaps. Spin orbit splittings for the further lying conduction and valence
bands are found to be 0.196 and 0.264 eV
The Radial Structure of the Cygnus Loop Supernova Remnant --- Possible evidence of a cavity explosion ---
We observed the North-East (NE) Limb toward the center region of the Cygnus
Loop with the ASCA Observatory. We found a radial variation of electron
temperature (kTe) and ionization timescale (log(\tau)) whereas no variation
could be found for the abundances of heavy elements. In this paper, we
re-analyzed the same data set and new observations with the latest calibration
files. Then we constructed the precise spatial variations of kTe, log(\tau),
and abundances of O, Ne, Mg, Si, and Fe over the field of view (FOV). We found
a spatial variation not only in kTe and in log(\tau) but also in most of heavy
elements. As described in Miyata et al. (1994), values of kTe increase and
those of log(\tau) decrease toward the inner region. We found that the
abundance of heavy elements increases toward the inner region. The radial
profiles of O, Ne, and Fe show clear jump structures at a radius of 0.9 Rs,
where Rs is the shock radius. Outside of 0.9 Rs, abundances of all elements are
constant. On the contrary, inside of 0.9 Rs, abundances of these elements are
20--30 % larger than those obtained outside of 0.9 Rs. The radial profile of
kTe also shows the jump structure at 0.9 Rs. This means that the hot and metal
rich plasma fills the volume inside of 0.9 Rs. We concluded that this jump
structure was the possible evidence for the pre-existing cavity produced by the
precursor. If the ejecta fills inside of 0.9 Rs, the total mass of the ejecta
was roughly 4\Msun. We then estimated the main-sequence mass to be roughly
15\Msun, which supports the massive star in origin of the Cygnus Loop supernova
remnant and the existence of a pre-existing cavity.Comment: 37 pages, 14 figures. Accepted for publication of Ap
Ten Years» Experience of Aortic Aneurysm Associated with Systemic Lupus Erythematosus
AbstractBackground: aortic aneurysm is a rare but life-threatening cardiovascular complication in patients with systemic lupus erythematosus (SLE). The purpose of this study was to clarify the characteristic clinical features and the pathological mechanism of aneurysmal formation in these patients. Methods: among 429 patients operated on for abdominal aortic aneurysm (AAA) during the past 10 years, five cases with SLE were treated surgically. Their clinical data were reviewed, and the resected aneurysmal wall of the five patients was also examined histologically. Results: the mean age of the patients with SLE was 55 years, which was statistically younger than that of the other patients (mean 77 years, s.d. 7.9, p <0.05). They had received long-term corticosteroid therapy for the treatment of SLE for a mean of 23 years. Histologically, destruction of the medial elastic lamina was characteristic. Four patients had no complications in the postoperative follow-up period (mean 4 years), while the remaining patient died of rupture of a dissecting aneurysm two years after operation.Conclusion : prolonged steroid therapy may play a major role in accelerating atherosclerosis, which can result in aortic aneurysmal enlargement, possibly together with primary aortic wall involvement and/or vasculitic damage in patients with SLE
Statics and Dynamics of the Wormlike Bundle Model
Bundles of filamentous polymers are primary structural components of a broad
range of cytoskeletal structures, and their mechanical properties play key
roles in cellular functions ranging from locomotion to mechanotransduction and
fertilization. We give a detailed derivation of a wormlike bundle model as a
generic description for the statics and dynamics of polymer bundles consisting
of semiflexible polymers interconnected by crosslinking agents. The elastic
degrees of freedom include bending as well as twist deformations of the
filaments and shear deformation of the crosslinks. We show that a competition
between the elastic properties of the filaments and those of the crosslinks
leads to renormalized effective bend and twist rigidities that become
mode-number dependent. The strength and character of this dependence is found
to vary with bundle architecture, such as the arrangement of filaments in the
cross section and pretwist. We discuss two paradigmatic cases of bundle
architecture, a uniform arrangement of filaments as found in F-actin bundles
and a shell-like architecture as characteristic for microtubules. Each
architecture is found to have its own universal ratio of maximal to minimal
bending rigidity, independent of the specific type of crosslink induced
filament coupling; our predictions are in reasonable agreement with available
experimental data for microtubules. Moreover, we analyze the predictions of the
wormlike bundle model for experimental observables such as the tangent-tangent
correlation function and dynamic response and correlation functions. Finally,
we analyze the effect of pretwist (helicity) on the mechanical properties of
bundles. We predict that microtubules with different number of protofilaments
should have distinct variations in their effective bending rigidity
Six topics on inscribable polytopes
Inscribability of polytopes is a classic subject but also a lively research
area nowadays. We illustrate this with a selection of well-known results and
recent developments on six particular topics related to inscribable polytopes.
Along the way we collect a list of (new and old) open questions.Comment: 11 page
Successful management of tracheo-innominate artery fistula with endovascular stent graft repair
AbstractTracheo-innominate artery fistula is a highly lethal complication after tracheostomy. A 37-year-old man who had undergone a tracheostomy 14 years earlier because of dysphagia after brain surgery had a tracheo-innominate artery fistula with exsanguinating hemorrhage from his tracheostomy site. After temporary control of the bleeding, a stent graft was implanted in the innominate artery through the brachial artery. The patient recovered uneventfully and remained well 14 months after the procedure, with no sign of infection. Endovascular stent grafting may be the treatment of choice for patients with tracheo-innominate artery fistula. (J Vasc Surg 2001;33:1280-2.
An X-Ray Study of Supernova Remnant N49 and Soft Gamma-Ray Repeater 0526-66 in the Large Magellanic Cloud
We report on the results from our deep Chandra observation (120 ks) of the
supernova remnant (SNR) N49 and soft Gamma-ray repeater (SGR) 0526-66 in the
Large Magellanic Cloud. We firmly establish the detection of an ejecta "bullet"
beyond the southwestern boundary of N49. The X-ray spectrum of the bullet is
distinguished from that of the main SNR shell, showing significantly enhanced
Si and S abundances. We also detect an ejecta feature in the eastern shell,
which shows metal overabundances similar to those of the bullet. If N49 was
produced by a core-collapse explosion of a massive star, the detected Si-rich
ejecta may represent explosive O-burning or incomplete Si-burning products from
deep interior of the supernova. On the other hand, the observed Si/S abundance
ratio in the ejecta may favor Type Ia origin for N49. We refine the Sedov age
of N49, tau_Sed ~ 4800 yr, with the explosion energy E_0 ~ 1.8 x 10^51 erg. Our
blackbody (BB) + power law (PL) model for the quiescent X-ray emission from SGR
0526-66 indicates that the PL photon index (Gamma ~ 2.5) is identical to that
of PSR 1E1048.1-5937, the well-known candidate transition object between
anomalous X-ray pulsars and SGRs. Alternatively, the two-component BB model
implies X-ray emission from a small (R ~ 1 km) hot spot(s) (kT ~ 1 keV) in
addition to emission from the neutron star's cooler surface (R ~ 10 km, kT ~
0.4 keV). There is a considerable discrepancy in the estimated column toward
0526-66 between BB+PL and BB+BB model fits. Discriminating these spectral
models would be crucial to test the long-debated physical association between
N49 and 0526-66.Comment: Accepted by ApJ, 27 pages in total (aastex preprint format) including
5 figures (4 in color) and 5 table
Schottky-based band lineups for refractory semiconductors
An overview is presented of band alignments for small-lattice parameter, refractory semiconductors. The band alignments are estimated empirically through the use of available Schottky barrier height data, and are compared to theoretically predicted values. Results for tetrahedrally bonded semiconductors with lattice constant values in the range from C through ZnSe are presented. Based on the estimated band alignments and the recently demonstrated p-type dopability of GaN, we propose three novel heterojunction schemes which seek to address inherent difficulties in doping or electrical contact to wide-gap semiconductors such as ZnO, ZnSe, and ZnS
Fermi Large Area Telescope Observations of the Cygnus Loop Supernova Remnant
We present an analysis of the gamma-ray measurements by the Large Area
Telescope(LAT) onboard the \textit{Fermi Gamma-ray Space Telescope} in the
region of the supernova remnant(SNR) Cygnus Loop(G74.08.5). We detect
significant gamma-ray emission associated with the SNR in the energy band
0.2--100 GeV. The gamma-ray spectrum shows a break in the range 2--3 GeV. The
gamma-ray luminosity is erg s between 1--100
GeV, much lower than those of other GeV-emitting SNRs. The morphology is best
represented by a ring shape, with inner/outer radii 0.7
0.1 and 1.6 0.1. Given the association among
X-ray rims, \halpha filaments and gamma-ray emission, we argue that gamma rays
originate in interactions between particles accelerated in the SNR and
interstellar gas or radiation fields adjacent to the shock regions. The decay
of neutral pions produced in nucleon-nucleon interactions between accelerated
hadrons and interstellar gas provides a reasonable explanation for the
gamma-ray spectrum.Comment: accepted by ApJ, 34 pages, 6 figure
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