650 research outputs found
Gravitational Lens Statistics and The Density Profile of Dark Halos
We investigate the influence of the inner profile of lens objects on
gravitational lens statistics taking into account of the effect of
magnification bias and both the evolution and the scatter of halo profiles. We
take the dark halos as the lens objects and consider the following three models
for the density profile of dark halos; SIS (singular isothermal sphere), the
NFW (Navarro Frenk White) profile, and the generalized NFW profile which has a
different slope at smaller radii. The mass function of dark halos is assumed to
be given by the Press-Schechter function. We find that magnification bias for
the NFW profile is order of magnitude larger than that for SIS. We estimate the
sensitivity of the lensing probability of distant sources to the inner profile
of lenses and to the cosmological parameters. It turns out that the lensing
probability is strongly dependent on the inner density profile as well as on
the cosmological constant. We compare the predictions with the largest
observational sample, the Cosmic Lens All-Sky Survey. The absence or presence
of large splitting events in larger surveys currently underway such as the 2dF
and SDSS could set constraints on the inner density profile of dark halos.Comment: 22 pages, minor changes and references added, accepted for
publication in Ap
Lithium production on a low-mass secondary in a black hole soft X-ray transient
We examine production of Li on the surface of a low-mass secondary in a black
hole soft X-ray transient (BHSXT) through the spallation of CNO nuclei by
neutrons which are ejected from a hot (> 10 MeV) advection-dominated accretion
flow (ADAF) around the black hole. Using updated binary parameters, cross
sections of neutron-induced spallation reactions, and mass accretion rates in
ADAF derived from the spectrum fitting of multi-wavelength observations of
quiescent BHSXTs, we obtain the equilibrium abundances of Li by equating the
production rate of Li and the mass transfer rate through accretion to the black
hole. The resulting abundances are found to be in good agreement with the
observed values in seven BHSXTs. We note that the abundances vary in a
timescale longer than a few months in our model. Moreover, the isotopic ratio
Li6/Li7 is calculated to be about 0.7--0.8 on the secondaries, which is much
higher than the ratio measured in meteorites. Detection of such a high value is
favorable to the production of Li via spallation and the existence of a hot
accretion flow, rather than an accretion disk corona system in quiescent BHSXT.Comment: 4 pages, 3 figures, and 2 tables, submitted to Astrophyscal Jounal
Letter
Analytical solutions of bound timelike geodesic orbits in Kerr spacetime
We derive the analytical solutions of the bound timelike geodesic orbits in
Kerr spacetime. The analytical solutions are expressed in terms of the elliptic
integrals using Mino time as the independent variable. Mino time
decouples the radial and polar motion of a particle and hence leads to forms
more useful to estimate three fundamental frequencies, radial, polar and
azimuthal motion, for the bound timelike geodesics in Kerr spacetime. This
paper gives the first derivation of the analytical expressions of the
fundamental frequencies. This paper also gives the first derivation of the
analytical expressions of all coordinates for the bound timelike geodesics
using Mino time. These analytical expressions should be useful not only to
investigate physical properties of Kerr geodesics but more importantly to
applications related to the estimation of gravitational waves from the extreme
mass ratio inspirals.Comment: A typo in the first expression in equation 21 was fixe
Characterization of two-dimensional fermionic insulating states
Inspired by the duality picture between superconductivity and insulator in
two spatial dimension, we conjecture that the order parameter, suitable for
characterizing 2D fermionic insulating state, is the disorder operator, usually
known in the context of statistical transformation. Namely, the change of the
phase of the disorder operator along a closed loop measures the particle
density accommodating inside this loop. Thus, identifying this (doped) particle
density with the dual counterpart of the magnetic induction in 2D SC, we can
naturally introduce the disorder operator as the dual order parameter of 2D
insulators. The disorder operator has a branch cut emitting from this
``vortex'' to the single infinitely far point. To test this conjecture against
an arbitrary 2D lattice models, we have chosen this branch cut to be compatible
with the periodic boundary condition and obtain a general form of its
expectation value for non-interacting metal/insulator wavefunction, including
gapped mean-field order wavefunction. Based on this expression, we observed
analytically that it indeed vanishes for a wide class of band metals in the
thermodynamic limit. In insulating states, on the other hand, it is quantified
by the localization length or the real-valued gauge invariant 2-from dubbed as
the quantum metric tensor
Orbital ferromagnetism and anomalous Hall effect in antiferromagnets on distorted fcc lattice
The Berry phase due to the spin wavefunction gives rise to the orbital
ferromagnetism and anomalous Hall effect in the non-coplanar antiferromagnetic
ordered state on face centered cubic (fcc) lattice once the crystal is
distorted perpendicular to (1,1,1) or (1,1,0)- plane. The relevance to the real
systems -FeMn and NiS is also discussed.Comment: 4 pages, 3 figure
The Outcome of Complex Hepato-Pancreato-Biliary Surgery for Elderly Patients: A Propensity Score Matching Analysis
Background/Aims: Postoperative mortality and morbidity rates after hepato-pancreato-biliary (HPB) surgery remain high, and the number of elderly patients requiring such surgery has been increasing. This study aimed to investigate postoperative outcomes of complex HPB surgery for elderly patients. Methods: We retrospectively reviewed perioperative data of 721 patients who underwent complex HPB surgery between 2010 and 2015. The patients were divided into 2 groups: elderly (≥75 years) and non-elderly (< 75 years). Surgical outcomes of both groups were compared after propensity score-matching analysis. Subsequently, risk factors for serious postoperative morbidity were identified by multivariate analysis. Results: Before matching, the elderly group (n = 170) had more comorbidities, such as cardiovascular and renal disease, than the non-elderly group (n = 551). Matching yielded elderly (n = 170) and non-elderly groups (n = 170) with similar preoperative backgrounds. The mortality and morbidity rates did not differ significantly between the groups. In multivariate analyses, operative time (OR 1.79; p = 0.005) and blood loss (OR 1.66; p = 0.03) were identified as independent risk factors for serious postoperative morbidity, whereas older age did not have a predictive impact (OR 1.16; p = 0.52). Conclusions: Although elderly patients had more comorbidities and higher incidences of postoperative mortality and several complications before matching, their postoperative outcomes were equivalent to those of non-elderly patients after matching
On the lack of strong O-line excess in the Coma cluster outskirts from Suzaku
About half of the baryons in the local Universe are thought to reside in the
so-called warm-hot intergalactic medium (WHIM) at temperatures of 0.1-10
million K. Thermal soft excess emission in the spectrum of some cluster
outskirts that contains OVII and/or OVIII emission lines is regarded as
evidence of the WHIM, although the origin of the lines is controversial due to
strong Galactic and solar system foreground emission. We observed the Coma-11
field, where the most prominent thermal soft excess has ever been reported,
with Suzaku XIS in order to make clear the origin of the excess. We did not
confirm OVII or OVIII excess emission. The OVII and OVIII intensity in Coma-11
is more than 5 sigma below that reported before and we obtained 2 sigma upper
limits of 2.8 and 2.9 photons cm^-2 s^-1 sr^-1 for OVII and OVIII,
respectively. The intensities are consistent with those in another field
(Coma-7) that we measured, and with other measurements in the Coma outskirts
(Coma-7 and X Com fields with XMM-Newton). We did not confirm the spatial
variation within Coma outskirts. The strong oxygen emission lines previously
reported are likely due to solar wind charge exchange.Comment: 5 pages, 3 figures. Accepted for publication in Ap
Chandra Observations of SDSS J1004+4112: Constraints on the Lensing Cluster and Anomalous X-Ray Flux Ratios of the Quadruply Imaged Quasar
We present results from Chandra observations of SDSS J1004+4112, a strongly
lensed quasar system with a maximum image separation of 15". All four bright
images of the quasar, as well as resolved X-ray emission originating from the
lensing cluster, are clearly detected. The emission from the lensing cluster
extends out to approximately 1.5 arcmin. We measure the bolometric X-ray
luminosity and temperature of the lensing cluster to be 4.7e44 erg s^-1 and 6.4
keV, consistent with the luminosity-temperature relation for distant clusters.
The mass estimated from the X-ray observation shows excellent agreement with
the mass derived from gravitational lensing. The X-ray flux ratios of the
quasar images differ markedly from the optical flux ratios, and the combined
X-ray spectrum of the images possesses an unusually strong Fe Kalpha emission
line, both of which are indicative of microlensing.Comment: 9 pages, 5 figures. Accepted for publication in ApJ. Version with
high-quality color figures at
http://cosmic.riken.jp/ota/publications/index.htm
A Radiobrominated Tyrosine Kinase Inhibitor for EGFR with L858R/T790M Mutations in Lung Carcinoma.
Activating double mutations L858R/T790M in the epidermal growth factor receptor(EGFR) region are often observed as the cause of resistance to tyrosine kinase inhibitors (TKIs). Third-generation EGFR-TKIs, such as osimertinib and rociletinib (CO-1686), was developed to target such resistance mutations. The detection of activating L858R/T790M mutations is necessary to select sensitive patients for therapy. Hence, we aimed to develop novel radiobromine-labeled CO-1686 as apositron emission tomography (PET) imaging probe for detecting EGFR L858R/T790M mutations. Nonradioactive brominated-CO1686 (BrCO1686) was synthesized by the condensation of N-(3-[{2-chloro-5-(trifluoromethyl)pyrimidin-4-yl}amino]-5-bromophenyl) acrylamide with the corresponding substituted 1-(4-[4-amino-3-methoxyphenyl]piperazine-1-yl)ethan-1-one. The radiobrominated [77Br]BrCO1686 was prepared through bromodestannylation of the corresponding tributylstannylated precursor with [77Br]bromide and N-chlorosuccinimide. Although we aimed to provide a novel PET imaging probe, 77Br was used as an alternative radionuclide for 76Br. We fundamentally evaluated the potency of [77Br]BrCO1686 as a molecular probe for detecting EGFR L858R/T790M using human non-small-cell lung cancer (NSCLC) cell lines: H1975 (EGFR L858R/T790M), H3255 (EGFR L858R), and H441 (wild-type EGFR). The BrCO1686 showed high cytotoxicity toward H1975 (IC50 0.18 0.06 M) comparable to that of CO-1686 (IC50 0.14 0.05 M). In cell uptake experiments, the level of accumulation of [77Br]BrCO1686 in H1975 was significantly higher than those in H3255 and H441 upon 4 h of incubation. The radioactivity of [77Br]BrCO1686 (136.3% dose/mg protein) was significantly reduced to 56.9% dose/mg protein by the pretreatment with an excess CO-1686. These results indicate that the binding site of the radiotracers should be identical to that of CO-1686. The in vivo accumulation of radioactivity of [77Br]BrCO1686 in H1975 tumor (4.51 0.17) was higher than that in H441 tumor (3.71 0.13) 1 h postinjection. Our results suggested that [77Br]BrCO1686 has specificity toward NSCLC cells with double mutations EGFR L858R/T790M compared to those in EGFR L858R and wild-type EGFR. However, the in vivo accumulation of radioactivity in the targeted tumor needs to be optimized by structural modification
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