14,768 research outputs found
Are the reactions a challenge for the factorized Pomeron at high energies?
We would like to point to the strong violation of the putative factorized
Pomeron exchange model in the reactions in the
high-energy region where this model works fairly well in all other cases.Comment: 4 pages, LaTex, 1 fig. in postscript, minor typos corrected, to be
published in Phys. Rev. D 60, 117503 (1999
Discontinuity of the chemical potential in reduced-density-matrix-functional theory
We present a novel method for calculating the fundamental gap. To this end,
reduced-density-matrix-functional theory is generalized to fractional particle
number. For each fixed particle number, , the total energy is minimized with
respect to the natural orbitals and their occupation numbers. This leads to a
function, , whose derivative with respect to the particle
number has a discontinuity identical to the gap. In contrast to density
functional theory, the energy minimum is generally not a stationary point of
the total-energy functional. Numerical results, presented for alkali atoms, the
LiH molecule, the periodic one-dimensional LiH chain, and solid Ne, are in
excellent agreement with CI calculations and/or experimental data.Comment: 9 pages, 3 figures, version as publishe
Orbital Circularization of Hot and Cool Kepler Eclipsing Binaries
The rate of tidal circularization is predicted to be faster for relatively
cool stars with convective outer layers, compared to hotter stars with
radiative outer layers. Observing this effect is challenging, because it
requires large and well-characterized samples including both hot and cool
stars. Here we seek evidence for the predicted dependence of circularization
upon stellar type, using a sample of 945 eclipsing binaries observed by Kepler.
This sample complements earlier studies of this effect, which employed smaller
samples of better-characterized stars. For each Kepler binary we measure
based on the relative timing of the primary and secondary
eclipses. We examine the distribution of as a function of period
for binaries composed of hot stars, cool stars, and mixtures of the two types.
At the shortest periods, hot-hot binaries are most likely to be eccentric; for
periods shorter than 4 days, significant eccentricities occur frequently for
hot-hot binaries, but not for hot-cool or cool-cool binaries. This is in
qualitative agreement with theoretical expectations based on the slower
dissipation rates of hot stars. However, the interpretation of our results is
complicated by the largely unknown ages and evolutionary states of the stars in
our sample.Comment: Accepted for publication in Ap
On Quantum Mechanical Aspects of Microtubules
We discuss possible quantum mechanical aspects of MicroTubules (MT), based on
recent developments in quantum physics.We focus on potential mechanisms for
`energy-loss-free' transport along the microtubules, which could be considered
as realizations of Fr\"ohlich's ideas on the r\^ole of solitons for
superconductivity and/or biological matter. By representing the MT arrangements
as cavities,we present a novel scenario on the formation of macroscopic (or
mesoscopic) quantum-coherent states, as a result of the
(quantum-electromagnetic) interactions of the MT dimers with the surrounding
molecules of the ordered water in the interior of the MT cylinders. We suggest
specific experiments to test the above-conjectured quantum nature of the
microtubular arrangements inside the cell. These experiments are similar in
nature to those in atomic physics, used in the detection of the Rabi-Vacuum
coupling between coherent cavity modes and atoms. Our conjecture is that a
similar Rabi-Vacuum-splitting phenomenon occurs in the MT case.Comment: 26 pages LATEX (minor typos corrected no effect on conclusions
BANANA IV: Two aligned stellar rotation axes in the young eccentric binary system EP Crucis: primordial orientation and tidal alignment
With observations of the EP Cru system, we continue our series of
measurements of spin-orbit angles in eclipsing binary star systems, the BANANA
project (Binaries Are Not Always Neatly Aligned). We find a close alignment
between the sky projections of the rotational and orbital angular momentum
vectors for both stars (beta_p = -1.8+-1.6 deg and |beta_s|<17 deg). We also
derive precise absolute dimensions and stellar ages for this system. The EP Cru
and DI Her systems provide an interesting comparison: they have similar stellar
types and orbital properties, but DI Her is younger and has major spin-orbit
misalignments, raising the question of whether EP Cru also had a large
misalignment at an earlier phase of evolution. We show that tidal dissipation
is an unlikely explanation for the good alignment observed today, because
realignment happens on the same timescale as spin-orbit synchronization, and
the stars in EP Cru are far from syncrhonization (they are spinning 9 times too
quickly). Therefore it seems that some binaries form with aligned axes, while
other superficially similar binaries are formed with misaligned axes.Comment: ApJ accepted, 10 pages, 7 figure
Rho primes in analyzing e+e- annihilation, MARK III, LASS and ARGUS data
The results of an analysis are presented of some recent data on the reactions
, with the
subtracted events, , , , , the decays
,
, upon taking into account both the strong energy
dependence of the partial widths on energy and the previously neglected mixing
of the type resonances. The above effects are shown to exert an
essential influence on the specific values of masses and coupling constants of
heavy resonances and hence are necessary to be accounted for in establishing
their true nature.Comment: 20 pages, ReVTeX, 9 Postscript figures As compared to hep-ph/9607398,
new material concerning the analysis of the ARGUS data on the tau decays into
four pion hadronic states is adde
Local anaesthetic adjuncts for peripheral nerve blockade.
Moderate-to-severe pain is common and remains a significant problem. Compared with opioid analgesia alone, single-shot peripheral nerve blockade has been associated with improved pain relief and the potential of decreased side effects. Single-shot nerve blockade, however, is limited by its relatively short duration of action. In this review, we aim to summarize the evidence related to local anaesthetic adjuncts for peripheral nerve blockade.
Dexamethasone and dexmedetomidine exhibit characteristics that most closely resemble the ideal local anaesthetic adjunct. In upper limb block, dexamethasone has been demonstrated to be superior to dexmedetomidine regardless of administration route for the duration of sensory and motor blockade as well as the duration of analgesia. No clinically significant differences between intravenous and perineural dexamethasone were found. Perineural and intravenous dexamethasone have the potential to prolong sensory blockade to a greater extent than motor blockade. The evidence indicates that the mechanism of action of perineural dexamethasone in upper limb block is systemic in nature. Unlike perineural dexmedetomidine, intravenous dexmedetomidine has not been shown to result in differences in the characteristics of regional blockade compared with local anaesthetic alone.
Intravenous dexamethasone is the local anaesthetic adjunct of choice, increasing the duration of sensory and motor blockade as well as the duration of analgesia by 477, 289 and 478 min, respectively. In view of this, we recommend consideration of the intravenous administration of dexamethasone at a dose of 0.1-0.2 mg/kg for all patients undergoing surgery whatever the level of postoperative pain, mild, moderate or severe. Further research should focus on the potential synergism of action between intravenous dexamethasone and perineural dexmedetomidine
The extended narrow-line region of two type-I quasi-stellar objects
We investigate the narrow-line region (NLR) of two radio-quiet QSOs,
PG1012+008 and PG1307+085, using high signal-to-noise spatially resolved
long-slit spectra obtained with FORS1 at the Very Large Telescope. Although the
emission is dominated by the point-spread function of the nuclear source, we
are able to detect extended NLR emission out to several kpc scales in both QSOs
by subtracting the scaled central spectrum from outer spectra. In contrast to
the nuclear spectrum, which shows a prominent blue wing and a broad line
profile of the [O III] line, the extended emission reveals no clear signs of
large scale outflows. Exploiting the wide wavelength range, we determine the
radial change of the gas properties in the NLR, i.e., gas temperature, density,
and ionization parameter, and compare them with those of Seyfert galaxies and
type-II QSOs. The QSOs have higher nuclear temperature and lower electron
density than Seyferts, but show no significant difference compared to type-II
QSOs, while the ionization parameter decreases with radial distance, similar to
the case of Seyfert galaxies. For PG1012+008, we determine the stellar velocity
dispersion of the host galaxy. Combined with the black hole mass, we find that
the luminous radio-quiet QSO follows the local M_BH-sigma* relation of active
galactic nuclei.Comment: 7 pages, 5 figures, accepted for publication in Ap
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