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Alkali- Metal Corrosion of Refractory Metals
This report talks about the Alkali- Metal Corrosion of Refractory Metal
Microcanonical statistics of black holes and bootstrap condition
The microcanonical statistics of the Schwarzschild black holes as well as the
Reissner-Nordstrm black holes are analyzed. In both cases we set
up the inequalities in the microcanonical density of states.
These are then used to show that the most probable configuration in the gases
of black holes is that one black hole acquires all of the mass and all of the
charge at high energy limit. Thus the black holes obey the statistical
bootstrap condition and, in contrast to the other investigation, we see that
U(1) charge does not break the bootstrap property.Comment: 16 pages. late
Follow-up observations of pulsating subdwarf B stars: Multisite campaigns on PG 1618+563B and PG 0048+091
We present follow-up observations of pulsating subdwarf B (sdB) stars as part
of our efforts to resolve the pulsation spectra for use in asteroseismological
analyses. This paper reports on multisite campaigns of the pulsating sdB stars
PG 1618+563B and PG 0048+091. Data were obtained from observatories placed
around the globe for coverage from all longitudes. For PG 1618+563B, our
five-site campaign uncovered a dichotomy of pulsation states: Early during the
campaign the amplitudes and phases (and perhaps frequencies) were quite
variable while data obtained late in the campaign were able to fully resolve
five stable pulsation frequencies. For PG 0048+091, our five-site campaign
uncovered a plethora of frequencies with short pulsation lifetimes. We find
them to have observed properties consistent with stochastically excited
oscillations, an unexpected result for subdwarf B stars. We discuss our
findings and their impact on subdwarf B asteroseismology.Comment: 50 pages including 17 figures and 10 tables. Accepted for publication
in the Astrophysical Journa
Suppression and enhancement of impurity scattering in a Bose-Einstein condensate
Impurity atoms propagating at variable velocities through a trapped
Bose-Einstein condensate were produced using a stimulated Raman transition. The
redistribution of momentum by collisions between the impurity atoms and the
stationary condensate was observed in a time-of-flight analysis. The
collisional cross section was dramatically reduced when the velocity of the
impurities was reduced below the speed of sound of the condensate, in agreement
with the Landau criterion for superfluidity. For large numbers of impurity
atoms, we observed an enhancement of atomic collisions due to bosonic
stimulation. This enhancement is analogous to optical superradiance.Comment: 4 pages, 4 figure
Holography and trace anomaly: what is the fate of (brane-world) black holes?
The holographic principle relates (classical) gravitational waves in the bulk
to quantum fluctuations and the Weyl anomaly of a conformal field theory on the
boundary (the brane). One can thus argue that linear perturbations in the bulk
of static black holes located on the brane be related to the Hawking flux and
that (brane-world) black holes are therefore unstable. We try to gain some
information on such instability from established knowledge of the Hawking
radiation on the brane. In this context, the well-known trace anomaly is used
as a measure of both the validity of the holographic picture and of the
instability for several proposed static brane metrics. In light of the above
analysis, we finally consider a time-dependent metric as the (approximate)
representation of the late stage of evaporating black holes which is
characterized by decreasing Hawking temperature, in qualitative agreement with
what is required by energy conservation.Comment: 11 pages, 2 figures, a few comments and references added, accepted
for publication in Phys. Rev.
Photophysics of the electronic states S0 and S1 for the coplanar molecular structures of the α,ω-diphenylpolyenes DPH and DPO
Spectroscopy of the monoclinic and orthorhombic crystalline forms of all-trans-diphenylhexatriene (DPH) and all-trans-diphenyloctatetraene (DPO) show absorption and emission bands that do not generate the widely known Stokes shift of the polyene compounds, discovered by Hausser et al. in 1953 and repeatedly studied over the last 60 years. It can be concluded from our study that the crystallization system, whether in a monoclinic or orthorhombic system, does not significantly influence the photophysics of DPH and DPO in the crystal phas
Is the giant radio galaxy M 87 a TeV gamma-ray emitter?
For the first time an excess of photons above an energy threshold of 730 GeV from the giant radio galaxy M 87 has been measured at a significance level above 4 σ. The data have been taken during the years 1998 and 1999 with the HEGRA stereoscopic system of 5 imaging atmospheric Cherenkov telescopes. The excess of 107.4 ± 26.8 events above 730 GeV corresponds to an integral flux of 3.3% of the Crab flux or Nγ (E > 730 GeV) = (0.96 ± 0.23) × 10-12 phot cm-2 s-1. M 87 is located at the center of the Virgo cluster of galaxies at a relatively small redshift of z = 0.00436 and is a promising candidate among the class of giant radio galaxies for the emission of TeV γ-radiation. The detection of TeV γ-rays from M 87 - if confirmed - would establish a new class of extragalactic source in this energy regime since all other AGN detected to date at TeV energies are BL Lac type objects.F. A. Aharonian ...G. P. Rowell...et al
From the cell membrane to the nucleus: unearthing transport mechanisms for Dynein
Mutations in the motor protein cytoplasmic dynein have been found to cause Charcot-Marie-Tooth disease, spinal muscular atrophy, and severe intellectual disabilities in humans. In mouse models, neurodegeneration is observed. We sought to develop a novel model which could incorporate the effects of mutations on distance travelled and velocity. A mechanical model for the dynein mediated transport of endosomes is derived from first principles and solved numerically. The effects of variations in model parameter values are analysed to find those that have a significant impact on velocity and distance travelled. The model successfully describes the processivity of dynein and matches qualitatively the velocity profiles observed in experiments
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