4,608 research outputs found
Hippocampal Atrophy Correlated with Decreased Cortical Glucose Metabolism in Dementia: MRI and PET Study
開始ページ、終了ページ: 冊子体のページ付
Elemental Abundances in the Possible Type Ia Supernova Remnant G344.7-0.1
Recent studies on the Galactic supernova remnant (SNR) G344.7-0.1 have
commonly claimed its origin to be a core-collapse supernova (SN) explosion,
based on its highly asymmetric morphology and/or proximity to a star forming
region. In this paper, however, we present an X-ray spectroscopic study of this
SNR using Suzaku, which is supportive of a Type Ia origin. Strong K-shell
emission from lowly ionized Fe has clearly been detected, and its origin is
determined, for the first time, to be the Fe-rich SN ejecta. The abundance
pattern is highly consistent with that expected for a somewhat-evolved Type Ia
SNR. It is suggested, therefore, that the X-ray point-like source CXOU
J170357.8-414302 located at the SNR's geometrical center is not associated with
the SNR but is likely to be a foreground object. Our result further indicates
that G344.7-0.1 is the first possible Type Ia SNR categorized as a member of
the so-called "mixed-morphology" class. In addition, we have detected emission
from He-like Al at ~1.6 keV, the first clear detection of this element in the
spectrum of an extended X-ray source. The possible enhancement of the Al/Mg
abundance ratio from the solar value suggests that the ambient interstellar
medium has a relatively high metallicity (not less than 10% of the solar
value), if this SNR has indeed a Type Ia origin. We also report marginal
detection of Cr and Mn, although the measured fluxes have large statistical and
systematic uncertainties.Comment: ApJ in pres
Microscale flow dynamics of red blood cells in a circular microchannel
The blood flow dynamics in microcirculation depends strongly on the motion, deformation and interaction of
RBCs within the microvessel. This paper presents the application of a confocal micro-PTV system to track
RBCs through a circular polydimethysiloxane (PDMS) microchannel. This technique, consists of a spinning
disk confocal microscope, high speed camera and a diode-pumped solid state (DPSS) laser combined with a
single particle tracking (SPT) method. By using this system detailed motions of individual RBCs were measured
at a microscale level. Our results showed that this technique can provide detailed information about microscale
disturbance effects caused by RBCs in flowing blood
Light Higgsino in Heavy Gravitino Scenario with Successful Electroweak Symmetry Breaking
We consider, in the context of the minimal supersymmetric standard model, the
case where the gravitino weighs 10^6 GeV or more, which is preferred by various
cosmological difficulties associated with unstable gravitinos. Despite the
large Higgs mixing parameter B together with the little hierarchy to other soft
supersymmetry breaking masses, a light higgsino with an electroweak scale mass
leads to successful electroweak symmetry breaking, at the price of fine-tuning
the higgsino mixing mu parameter. Furthermore the light higgsinos produced at
the decays of gravitinos can constitute the dark matter of the universe. The
heavy squark mass spectrum of O(10^4) GeV can increase the Higgs boson mass to
about 125 GeV or higher.Comment: 13 pages, 3 figures; v2: version to appear in JHE
Quantum Search with Two-atom Collisions in Cavity QED
We propose a scheme to implement two-qubit Grover's quantum search algorithm
using Cavity Quantum Electrodynamics. Circular Rydberg atoms are used as
quantum bits (qubits). They interact with the electromagnetic field of a
non-resonant cavity . The quantum gate dynamics is provided by a
cavity-assisted collision, robust against decoherence processes. We present the
detailed procedure and analyze the experimental feasibility.Comment: 4 pages, 2 figure
Recent Developments of World-Line Monte Carlo Methods
World-line quantum Monte Carlo methods are reviewed with an emphasis on
breakthroughs made in recent years. In particular, three algorithms -- the loop
algorithm, the worm algorithm, and the directed-loop algorithm -- for updating
world-line configurations are presented in a unified perspective. Detailed
descriptions of the algorithms in specific cases are also given.Comment: To appear in Journal of Physical Society of Japa
Astrophysical and Cosmological Implications of Large Volume String Compactifications
We study the spectrum, couplings and cosmological and astrophysical
implications of the moduli fields for the class of Calabi-Yau IIB string
compactifications for which moduli stabilisation leads to an exponentially
large volume V ~ 10^{15} l_s^6 and an intermediate string scale m_s ~
10^{11}GeV, with TeV-scale observable supersymmetry breaking. All K\"ahler
moduli except for the overall volume are heavier than the susy breaking scale,
with m ~ ln(M_P/m_{3/2}) m_{3/2} ~ (\ln(M_P/m_{3/2}))^2 m_{susy} ~ 500 TeV and,
contrary to standard expectations, have matter couplings suppressed only by the
string scale rather than the Planck scale. These decay to matter early in the
history of the universe, with a reheat temperature T ~ 10^7 GeV, and are free
from the cosmological moduli problem (CMP). The heavy moduli have a branching
ratio to gravitino pairs of 10^{-30} and do not suffer from the gravitino
overproduction problem. The overall volume modulus is a distinctive feature of
these models and is an M_{planck}-coupled scalar of mass m ~ 1 MeV and subject
to the CMP. A period of thermal inflation can help relax this problem. This
field has a lifetime ~ 10^{24}s and can contribute to dark matter. It may be
detected through its decays to 2\gamma or e^+e^-. If accessible the e^+e^-
decay mode dominates, with Br(\chi \to 2 \gamma) suppressed by a factor
(ln(M_P/m_{3/2}))^2. We consider the potential for detection of this field
through different astrophysical sources and find that the observed gamma-ray
background constrains \Omega_{\chi} <~ 10^{-4}. The decays of this field may
generate the 511 keV emission line from the galactic centre observed by
INTEGRAL/SPI.Comment: 31 pages, 2 figures; v2. refs adde
Structural Insight into the Rotational Switching Mechanism of the Bacterial Flagellar Motor
Structural analysis of a clockwise-biased rotation mutant of the bacterial
flagellar rotor protein FliG provides a new model for the arrangement of FliG
subunits in the motor, and novel insights into rotation switching
Sparticle masses in deflected mirage mediation
We discuss the sparticle mass patterns that can be realized in deflected
mirage mediation scenario of supersymmetry breaking, in which the moduli,
anomaly, and gauge mediations all contribute to the MSSM soft parameters.
Analytic expression of low energy soft parameters and also the sfermion mass
sum rules are derived, which can be used to interpret the experimentally
measured sparticle masses within the framework of the most general mixed
moduli-gauge-anomaly mediation. Phenomenological aspects of some specific
examples are also discussed.Comment: 43 pages, 17 figures, references adde
- …