2,317 research outputs found
Evolution of Multiphase Hot Interstellar Medium in Elliptical Galaxies
We present the results of a variety of simulations concerning the evolution
of multiphase (inhomogeneous) hot interstellar medium (ISM) in elliptical
galaxies. We assume the gases ejected from stars do not mix globally with the
circumferential gas. The ejected gas components evolve separately according to
their birth time, position, and origin. We consider cases where supernova
remnants (SNRs) mix with local ISM. The components with high metal abundance
and/or high density cool and drop out of the hot ISM gas faster than the other
components because of their high metal abundance and/or density. This makes the
average metal abundance of the hot ISM low. Furthermore, since the metal
abundance of mass-loss gas decreases with radius, gas inflow from outer region
makes the average metal abundance of the hot ISM smaller than that of mass-loss
gas in the inner region. As gas ejection rate of stellar system decreases, mass
fraction of mass-loss gas ejected at outer region increases in a galaxy. If the
mixing of SNRs is ineffective, our model predicts that observed [Si/Fe] and
[Mg/Fe] should decrease towards the galactic center because of strong iron
emission by SNRs. In the outer region, where the cooling of time of the ISM is
long, the selective cooling is ineffective and most of gas components remain
hot. Thus, the metal abundance of the ISM in this region directly reflects that
of the gas ejected from stars. Our model shows that supernovae are not
effective heating sources in the inner region of elliptical galaxies, because
most of the energy released by them radiates. Therefore, cooling flow is
established even if the supernova rate is high. Mixing of SNRs with ambient ISM
makes the energy transfer between supernova explosion and ambient ISM more
effective.Comment: 21 pages (AASTeX), 14 figures, accepted for publication in The
Astrophysical Journa
Competing Spin-Gap Phases in a Frustrated Quantum Spin System in Two Dimensions
We investigate quantum phase transitions among the spin-gap phases and the
magnetically ordered phases in a two-dimensional frustrated antiferromagnetic
spin system, which interpolates several important models such as the
orthogonal-dimer model as well as the model on the 1/5-depleted square lattice.
By computing the ground state energy, the staggered susceptibility and the spin
gap by means of the series expansion method, we determine the ground-state
phase diagram and discuss the role of geometrical frustration. In particular,
it is found that a RVB-type spin-gap phase proposed recently for the
orthogonal-dimer system is adiabatically connected to the plaquette phase known
for the 1/5-depleted square-lattice model.Comment: 6 pages, to appear in JPSJ 70 (2001
Actin Gene-targeted RT-PCR Could Be a Useful Method for Evaluating In vitro Fungicidal Activity against Dermatophytes
Magnetic Susceptibility for
We examine experimental magnetic susceptibility for
CaVO by fitting with fitting function .
The function is a power series of 1/T and the lowest order
term is fixed as , where is the Curie constant as determined by the
experimental -value (g=1.96). Fitting parameters are , and
expansion coefficients except for the first one in .
We determine and as 0.73 and 0 for an
experimental sample. We interpret as the volume fraction of
CaVO in the sample and as the susceptibility for the
pure CaVO. The result of means that the sample includes
nonmagnetic components. This interpretation consists with the result of a
perturbation theory and a neutron scattering experiment.Comment: 4pages, 4figure
Meta-Plaquette Expansion for the Triplet Excitation Spectrum in CaVO
We study antiferromagnetic, Heisenberg models with nearest and second
neighbor interactions on the one-fifth depleted square lattice which describes
the spin degrees of freedom in the spin-gap system CaVO. The
meta-plaquette expansion for the triplet excitation spectrum is extended to
fifth order, and the results are compared with experimental data on
CaVO. We attempt to locate the phase boundary between magnetically
ordered and gapped phases.Comment: 4 figure
Pressure formulas for liquid metals and plasmas based on the density-functional theory
At first, pressure formulas for the electrons under the external potential
produced by fixed nuclei are derived both in the surface integral and volume
integral forms concerning an arbitrary volume chosen in the system; the surface
integral form is described by a pressure tensor consisting of a sum of the
kinetic and exchange-correlation parts in the density-functional theory, and
the volume integral form represents the virial theorem with subtraction of the
nuclear virial. Secondly on the basis of these formulas, the thermodynamical
pressure of liquid metals and plasmas is represented in the forms of the
surface integral and the volume integral including the nuclear contribution.
From these results, we obtain a virial pressure formula for liquid metals,
which is more accurate and simpler than the standard representation. From the
view point of our formulation, some comments are made on pressure formulas
derived previously and on a definition of pressure widely used.Comment: 18 pages, no figur
Collagen Iâmediated up-regulation of N-cadherin requires cooperative signals from integrins and discoidin domain receptor 1
Tumor cells undergo epithelial-to-mesenchymal transition (EMT) to convert from a benign to a malignant phenotype. Our recent focus has been signaling pathways that promote EMT in response to collagen. We have shown that human pancreatic cancer cells respond to collagen by up-regulating N-cadherin, which promotes tumor growth, invasion, and metastasis. Initial characterization showed that knocking down c-Jun NH2-terminal kinase prevented N-cadherin up-regulation and limited tumor growth and invasion in a mouse model for pancreatic cancer. The current study was designed to understand the pathway from collagen to N-cadherin up-regulation. Initiation of the signal requires two collagen receptors, α2ÎČ1 integrin and discoidin domain receptor (DDR) 1. Each receptor propagates signals through separate pathways that converge to up-regulate N-cadherin. Focal adhesion kinase (FAK)ârelated protein tyrosine kinase (Pyk2) is downstream of DDR1, whereas FAK is downstream of α2ÎČ1 integrin. Both receptor complexes rely on the p130 Crk-associated substrate scaffold. Interestingly, Rap1, but not Rho family guanosine triphosphatases, is required for the response to collagen I
Two-Dimensional Quantum Spin Systems with Ladder and Plaquette Structure
We investigate low-energy properties of two-dimensional quantum spin systems
with the ladder and plaquette structures, which are described by a generalized
antiferromagnetic Heisenberg model with both of the bond and spin alternations.
By exploiting a non-linear model technique and a modified spin wave
approach, we evaluate the spin gap and the spontaneous magnetization to discuss
the quantum phase transition between the ordered and disordered states. We
argue how the spin-gapped phase is driven to the antiferromagnetic phase in the
phase diagram.Comment: 8 pages (9 figures), accepted by JPS
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