8,183 research outputs found
Semi-analytical approach for the Vaidya metric in double-null coordinates
We reexamine here a problem considered in detail before by Waugh and Lake:
the solutions of spherically symmetric Einstein's equations with a radial flow
of unpolarized radiation (the Vaidya metric) in double-null coordinates. This
problem is known to be not analytically solvable, the only known explicit
solutions correspond to the constant mass case (Schwarzschild solution in
Kruskal-Szekeres form) and the linear and exponential mass functions originally
discovered by Waugh and Lake. We present here a semi-analytical approach that
can be used to discuss some qualitative and quantitative aspects of the Vaidya
metric in double-null coordinates for generic mass functions. We present also a
new analytical solution corresponding to -mass function.Comment: 5 pages, 6 figure
Parametric instabilities in the LCGT arm cavity
We evaluated the parametric instabilities of LCGT (Japanese interferometric
gravitational wave detector project) arm cavity. The number of unstable modes
of LCGT is 10-times smaller than that of Advanced LIGO (U.S.A.). Since the
strength of the instabilities of LCGT depends on the mirror curvature more
weakly than that of Advanced LIGO, the requirement of the mirror curvature
accuracy is easier to be achieved. The difference in the parametric
instabilities between LCGT and Advanced LIGO is because of the thermal noise
reduction methods (LCGT, cooling sapphire mirrors; Advanced LIGO, fused silica
mirrors with larger laser beams), which are the main strategies of the
projects. Elastic Q reduction by the barrel surface (0.2 mm thickness
TaO) coating is effective to suppress instabilities in the LCGT arm
cavity. Therefore, the cryogenic interferometer is a smart solution for the
parametric instabilities in addition to thermal noise and thermal lensing.Comment: 6 pages,3 figures. Amaldi7 proceedings, J. Phys.: Conf. Ser.
(accepted
Linguistics
Contains reports on one research project.U. S. Air Force (Electronics Systems Division) under Contract AF 19(628)-2487Joint Services Electronics Programs (U. S. Army, U. S. Navy, and U. S. Air Force) under Contract DA 36-039-AMC-03200(E)National Science Foundation (Grant GK-835)National Institutes of Health (Grant 2 PO1 MH-04737-06)National Aeronautics and Space Administration (Grant NsG-496
High field electro-thermal transport in metallic carbon nanotubes
We describe the electro-thermal transport in metallic carbon nanotubes
(m-CNTs) by a semi-classical approach that takes into account the high-field
dynamical interdependence between charge carrier and phonon populations. Our
model is based on the self-consistent solution of the Boltzmann transport
equation and the heat equation mediated by a phonon rate equation that accounts
for the onset of non-equilibrium (optical) phonons in the high-field regime.
Given the metallic nature of the nanostructures, a key ingredient of the model
is the assumption of local thermalization of charge carriers. Our theory
remarkably reproduces the room temperature electrical characteristics of m-CNTs
on substrate and free standing (suspended), shedding light on charge-heat
transport in these one dimensional nanostructures. In particular, the negative
differential resistance observed in suspended m-CNTs under electric stress is
attributed to inhomogeneous field profile induced by self-heating rather than
the presence of hot phonons.Comment: 10 pages, 10 figure
Mechanical quality factor of a sapphire fiber at cryogenic temperatures
A mechanical quality factor of was obtained for the 199
Hz bending vibrational mode in a monocrystalline sapphire fiber at 6 K.
Consequently, we confirm that pendulum thermal noise of cryogenic mirrors used
for gravitational wave detectors can be reduced by the sapphire fiber
suspension.Comment: To be published to Physiscs Letters A. Number of pages: 10 Number of
figures: 5 Number of tables:
Tosio Kato (1917–1999)
Tosio Kato was born August 25, 1917, in Kanuma City, Tochigi-ken, Japan. His early training was in physics. He obtained
a B.S. in 1941 and the degree of Doctor of Science in 1951, both at the University of Tokyo. Between these events he published
papers on a variety of subjects, including pair creation by gamma rays, motion of an object in a fluid, and results
on spectral theory of operators arising in quantum mechanics. His dissertation was entitled “On the convergence of the
perturbation method”.
Kato was appointed assistant professor of physics at the University of Tokyo in 1951 and was promoted to professor of
physics in 1958. During this time he visited the University of California at Berkeley in 1954–55, New York University in 1955,
the National Bureau of Standards in 1955–56, and Berkeley and the California Institute of Technology in 1957–58. He was
appointed professor of mathematics at Berkeley in 1962 and taught there until his retirement in 1988. He supervised
twenty-one Ph.D. students at Berkeley and three at the University of Tokyo.
Kato published over 160 papers and 6 monographs, including his famous book Perturbation Theory for Linear
Operators [K66b]. Recognition for his important work included the Norbert Wiener Prize in Applied Mathematics, awarded
in 1980 by the AMS and the Society for Industrial and Applied Mathematics. He was particularly well known for his work on
Schrödinger equations of nonrelativistic quantum mechanics and his work on the Navier-Stokes and Euler equations of
classical fluid mechanics. His activity in the latter area remained at a high level well past retirement and continued until his
death on October 2, 1999
Interspecific differences in the larval performance of Pieris butterflies (Lepidoptera: Pieridae) are associated with differences in the glucosinolate profiles of host plants
The tremendous diversity of plants and herbivores has arisen from a coevolutionary relationship characterized by plant defense and herbivore counter adaptation. Pierid butterfly species feed on Brassicales plants that produce glucosinolates as a chemical deterrent against herbivory. In turn, the larvae of pierids have nitrile specifier proteins (NSPs) that are expressed in their gut and disarm glucosinolates. Pierid butterflies are known to have diversified in response to glucosinolate diversification in Brassicales. Therefore, each pierid species is expected to have a spectrum of host plants characterized by specific glucosinolate profiles. In this study, we tested whether the larval performance of different Pieris species, a genus in Pieridae (Lepidoptera: Pieridae), was associated with plant defense traits of putative host plants. We conducted feeding assays using larvae of three Pieris species and 10 species of the Brassicaceae family possessing different leaf physical traits and glucosinolate profile measurements. The larvae of Pieris rapae responded differently in the feeding assays compared with the other two Pieris species. This difference was associated with differences in glucosinolate profiles but not with variations in physical traits of the host plants. This result suggests that individual Pieris species are adapted to a subset of glucosinolate profiles within the Brassicaceae. Our results support the idea that the host ranges of Pieris species depend on larval responses to glucosinolate diversification in the host species, supporting the hypothesis of coevolution between butterflies and host plants mediated by the chemical arms race
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