1,302 research outputs found
Runaway Merging of Black Holes: Analytical Constraint on the Timescale
Following the discovery of a black hole (BH) with a mass of 10^3-10^6 M(sun)
in a starburst galaxy M82, we study formation of such a BH via successive
merging of stellar-mass BHs within a star cluster. The merging has a runaway
characteristic. This is because massive BHs sink into the cluster core and have
a high number density, and because the merging probability is higher for more
massive BHs. We use the Smoluchowski equation to study analytically the
evolution of the BH mass distribution. Under favorable conditions, which are
expected for some star clusters in starburst galaxies, the timescale of the
runaway merging is at most of order 10^7 yr. This is short enough to account
for the presence of a BH heavier than 10^3 M(sun) in an ongoing starburst
region.Comment: 10 pages, no figures, to appear in The Astrophysical Journal
(Letters
Large-Scale Regular Morphological Patterns in the Radio Jet of NGC 6251
We report on large-scale, regular morphological patterns found in the radio
jet of the nearby radio galaxy NGC 6251. Investigating morphological properties
of this radio jet from the nucleus to a radial distance of 300 arcsec
( 140 kpc) mapped at 1662 MHz and 4885 MHz by Perley, Bridle, &
Willis, we find three chains, each of which consists of five radio knots. We
also find that eight radio knots in the first two chains consist of three small
sub-knots (the triple-knotty substructures). We discuss the observational
properties of these regular morphological patterns.Comment: 8 figures, 15 pages, accepted for publication in A
SHG microscopic observations of polar state in Li-doped KTaO3 under electric field
Incipient ferroelectric KTaO3 with off-center Li impurity of the critical
concentration of 2.8 mol% was investigated in order to clarify the dipole glass
state under electric field. Using optical second-harmonic generation (SHG)
microscope, we observed a marked history dependence of SHG intensity through
zero-field cooling (ZFC), zero-field heating (ZFH), field heating after ZFC
(FH/ZFC) and FH after field cooling (FH/FC). These show different paths with
respect to temperature: In the ZFC/ZFH process, weak SHG was observed at low
temperature, while in the FH/ZFC process, relatively high SHG appears in a
limited temperature range below TF depending on the field strength, and in the
FC and FH/FC processes, the SHG exhibits ferroelectric-like temperature
dependence: it appears at the freezing temperature of 50K, increases with
decreasing temperature and has a tendency of saturation. These experimental
results strongly suggest that dipole glass state or polar nano-clusters which
gradually freezes with decreasing temperature is transformed into
semi-macroscopic polar state under the electric field. However at sufficiently
low temperature, the freezing is so strong that the electric field cannot
enlarge the polar clusters. These experimental results show that the polar
nano-cluster model similar to relaxors would be more relevant in KTaO3 doped
with the critical concentration of Li. Further experiments on the anisotropy of
SHG determine that the average symmetry of the field-induced polar phase is
tetragonal 4mm or 4, which is also confirmed by the X-ray diffraction
measurement.Comment: 26 pages, 8 figures, 1 tabl
An Origin of the Huge Far-Infrared Luminosity of Starburst Mergers
Recently Taniguchi and Ohyama found that the higher CO to CO
integrated intensity ratios at a transition =1--0, CO)CO) , in a sample of starburst merging
galaxies such as Arp 220 are mainly attributed to the depression of CO
emission with respect to CO. Investigating the same sample of galaxies
analyzed by Taniguchi & Ohyama, we find that there is a tight, almost linear
correlation between the dust mass and CO luminosity. This implies that
dust grains are also depressed in the high- starburst mergers, leading to
the higher dust temperature () in them because of the relative
increase in the radiation density. Nevertheless, the average dust mass () of the high- starburst mergers is higher significantly than that of
non-high galaxies. This is naturally understood because the galaxy mergers
could accumulate a lot of dust grains from their progenitor galaxies together
with supply of dust grains formed newly in the star forming regions. Since
(FIR) given the dust emissivity law, , the increases in both and
explain well why the starburst mergers are so bright in the FIR. We discuss
that the superwind activity plays an important role in destroying dust grains
as well as dense gas clouds in the central region of mergers.Comment: 10 pages (aaspp4.sty), 3 postscript figures (embedded). Accepted for
publication in Astrophysical Journal Letter
Brodalumab in patients with GPP and PsE
Background
A T‐helper (Th) cell subset Th17 preferentially produces interleukin (IL)‐17 and plays a pivotal role in the pathogenesis of psoriasis. However, the pathological roles of IL‐17 cascades in generalized pustular psoriasis (GPP) and psoriatic erythroderma (PsE) have not been well established.
Objectives
To evaluate the efficacy and safety of brodalumab, a human immunoglobulin G2 monoclonal antibody against human IL ‐17‐receptor A (IL‐17RA), in Japanese patients with GPP and PsE.
Methods
This was an open‐label, multicentre, long‐term phase III study in Japanese patients with rare and severe types of psoriasis. Patients received brodalumab 140 mg at day 1 and weeks 1 and 2, and then every 2 weeks until week 52. The primary endpoint was the Clinical Global Impression of Improvement (CGI). Safety evaluations included treatment‐emergent adverse events (AEs) and changes in laboratory parameters.
Results
A total of 12 patients with GPP and 18 with PsE were enrolled. Ten patients with GPP and 16 with PsE completed the study. At week 52 (last observation carried forward), CGI remission or improvement was achieved in 11 patients with GPP and 18 with PsE. The most commonly reported AE was nasopharyngitis (33·3%). Five serious AE s occurred during the study. However, none was considered treatment‐related.
Conclusions
Brodalumab significantly improved the symptoms of patients with GPP and PsE throughout the 52 weeks, and demonstrated favourable safety profiles without any new safety signals. Inhibition of IL‐17RA‐mediated signalling by brodalumab is expected to be a promising new treatment option for patients with GPP and PsE
Polar surface engineering in ultra-thin MgO(111)/Ag(111) -- possibility of metal-insulator transition and magnetism
A recent report [Kiguchi {\it et al.}, Phys. Rev. B {\bf 68}, 115402 (2003)]
that the (111) surface of 5 MgO layers grown epitaxially on Ag(111) becomes
metallic to reduce the electric dipole moment raises a question of what will
happen when we have fewer MgO layers. Here we have revealed, first
experimentally with electron energy-loss spectroscopy, that MgO(111) remains
metallic even when one-layer thick, and theoretically with the density
functional theory that the metallization should depend on the nature of the
substrate. We further show, with a spin-density functional calculation, that a
ferromagnetic instability may be expected for thicker films.Comment: 5 pages, 7 figure
Intersubband electronic Raman scattering in narrow GaAs single quantum wells dominated by single-particle excitations
We measured resonant Raman scattering by intersubband electronic excitations
in GaAs/AlAs single quantum wells (QWs) with well widths ranging from 8.5 to 18
nm. In narrow (less than 10 nm) QWs with sufficiently high electron
concentrations, only single-particle excitations (SPEs) were observed in
intersubband Raman scattering, which was confirmed by the well-width dependence
of Raman spectra. We found characteristic variations in Raman shift and line
shape for SPEs with incident photon energy in the narrow QWs.Comment: 5 pages including 4 figure
Scalability of spin FPGA: A Reconfigurable Architecture based on spin MOSFET
Scalability of Field Programmable Gate Array (FPGA) using spin MOSFET (spin
FPGA) with magnetocurrent (MC) ratio in the range of 100% to 1000% is discussed
for the first time. Area and speed of million-gate spin FPGA are numerically
benchmarked with CMOS FPGA for 22nm, 32nm and 45nm technologies including 20%
transistor size variation. We show that area is reduced and speed is increased
in spin FPGA owing to the nonvolatile memory function of spin MOSFET.Comment: 3 pages, 7 figure
Dominance of a single topological sector in gauge theory on non-commutative geometry
We demonstrate a striking effect of non-commutative (NC) geometry on
topological properties of gauge theory by Monte Carlo simulations. We study 2d
U(1) NC gauge theory for various boundary conditions using a new finite-matrix
formulation proposed recently. We find that a single topological sector
dictated by the boundary condition dominates in the continuum limit. This is in
sharp contrast to the results in commutative space-time based on lattice gauge
theory, where all topological sectors appear with certain weights in the
continuum limit. We discuss possible implications of this effect in the context
of string theory compactifications and in field theory contexts.Comment: 16 pages, 27 figures, typos correcte
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