8,920 research outputs found
Symmetries of supergravity black holes
We investigate Killing tensors for various black hole solutions of
supergravity theories. Rotating black holes of an ungauged theory, toroidally
compactified heterotic supergravity, with NUT parameters and two U(1) gauge
fields are constructed. If both charges are set equal, then the solutions
simplify, and then there are concise expressions for rank-2 conformal
Killing-Stackel tensors. These are induced by rank-2 Killing-Stackel tensors of
a conformally related metric that possesses a separability structure. We
directly verify the separation of the Hamilton-Jacobi equation on this
conformally related metric, and of the null Hamilton-Jacobi and massless
Klein-Gordon equations on the "physical" metric. Similar results are found for
more general solutions; we mainly focus on those with certain charge
combinations equal in gauged supergravity, but also consider some other
solutions.Comment: 36 pages; v2: minor changes; v3: slightly shorte
Elevated plasma homocysteine is associated with ischaemic heart disease in Hong Kong Chinese
published_or_final_versio
Comment on ``A new efficient method for calculating perturbative energies using functions which are not square integrable'': regularization and justification
The method recently proposed by Skala and Cizek for calculating perturbation
energies in a strict sense is ambiguous because it is expressed as a ratio of
two quantities which are separately divergent. Even though this ratio comes out
finite and gives the correct perturbation energies, the calculational process
must be regularized to be justified. We examine one possible method of
regularization and show that the proposed method gives traditional quantum
mechanics results.Comment: 6 pages in REVTeX, no figure
Hydrodynamics of the Kuramoto-Sivashinsky Equation in Two Dimensions
The large scale properties of spatiotemporal chaos in the 2d
Kuramoto-Sivashinsky equation are studied using an explicit coarse graining
scheme. A set of intermediate equations are obtained. They describe
interactions between the small scale (e.g., cellular) structures and the
hydrodynamic degrees of freedom. Possible forms of the effective large scale
hydrodynamics are constructed and examined. Although a number of different
universality classes are allowed by symmetry, numerical results support the
simplest scenario, that being the KPZ universality class.Comment: 4 pages, 3 figure
Fractal Formation Of A Y-Ba-Cu-O Thin-Film On Srtio3
Fractal formation has been observed after thermal annealing of the rf-sputtered Y-Ba-Cu-O thin film on SrTiO3 substrate. Through energy-dispersive x-ray analysis, it was found that the composition of the fractal was YBa2Cu3Ox and the surrounding film composition was Y2Ba2Cu3Ox. The fractal dimensions D ranging from 1.26 to 1.65 were obtained using the standard sandbox method with different thresholds
Comparison of 120Sn(6He,6He)120Sn and 120Sn(alpha,alpha)120Sn elastic scattering and signatures of the 6He neutron halo in the optical potential
Cross sections of Sn(,)Sn elastic scattering
have been extracted from the particle beam contamination of a recent
Sn(He,He)Sn experiment. Both reactions are analyzed
using systematic double folding potentials in the real part and smoothly
varying Woods-Saxon potentials in the imaginary part. The potential extracted
from the Sn(He,He)Sn data may be used as the basis for
the construction of a simple global He optical potential. The comparison of
the He and data shows that the halo nature of the He nucleus
leads to a clear signature in the reflexion coefficients : the relevant
angular momenta with and are shifted to
larger with a broader distribution. This signature is not present in the
scattering data and can thus be used as a new criterion for the
definition of a halo nucleus.Comment: 13 pages, 7 figures, accepted for publication in Phys. Rev.
Metallothionein 1E mRNA is highly expressed in oestrogen receptor-negative human invasive ductal breast cancer
Metallothioneins (MTs), a group of ubiquitous metalloproteins, comprise isoforms encoded by ten functional genes in humans. Different MT isoforms possibly play different functional roles during development or under various physiological conditions. The MT-1E isoform mRNA has been recently shown to be differentially expressed in oestrogen receptor (OR)-positive and OR-negative breast cancer cell lines. In this study, we evaluated MT-1E mRNA expression via semi-quantitative RT-PCR in 51 primary invasive ductal breast cancer tissues, concurrently with OR-positive and progesterone receptor (PR)-positive MCF7 cells, OR-negative and PR-negative MDA-MB-231 cells and PR-transfected MDA-MB-231 breast cancer cells (ABC28). We demonstrated significantly higher MT-1E mRNA expression in OR-negative compared with OR-positive breast cancer tissues (P= 0.026). MCF7 cells lacked MT-1E mRNA expression, while both OR- and PR-negative MDA-MD-231 cells exhibited a high level of MT-1E mRNA expression. The level of MT-1E mRNA expression in progesterone-treated and -untreated ABC28 cells remained similar as the parental cell line MDA-MB-231-C2 cells. The results suggest that MT-1E may have specific and functional roles in OR-negative invasive ductal breast cancers, possibly mediated via effector genes downstream of the oestrogen receptor, but not through the PR pathway. © 2000 Cancer Research Campaig
Phase transition in a mean-field model for sympatric speciation
We introduce an analytical model for population dynamics with intra-specific
competition, mutation and assortative mating as basic ingredients. The set of
equations that describes the time evolution of population size in a mean-field
approximation may be decoupled. We find a phase transition leading to sympatric
speciation as a parameter that quantifies competition strength is varied. This
transition, previously found in a computational model, occurs to be of first
order.Comment: accepted for Physica
On perturbations of Dirac operators with variable magnetic field of constant direction
We carry out the spectral analysis of matrix valued perturbations of
3-dimensional Dirac operators with variable magnetic field of constant
direction. Under suitable assumptions on the magnetic field and on the
pertubations, we obtain a limiting absorption principle, we prove the absence
of singular continuous spectrum in certain intervals and state properties of
the point spectrum. Various situations, for example when the magnetic field is
constant, periodic or diverging at infinity, are covered. The importance of an
internal-type operator (a 2-dimensional Dirac operator) is also revealed in our
study. The proofs rely on commutator methods.Comment: 12 page
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