18,810 research outputs found
Double-Mode Stellar Pulsations
The status of the hydrodynamical modelling of nonlinear multi-mode stellar
pulsations is discussed. The hydrodynamical modelling of steady double-mode
(DM) pulsations has been a long-standing quest that is finally being concluded.
Recent progress has been made thanks to the introduction of turbulent
convection in the numerical hydrodynamical codes which provide detailed results
for individual models. An overview of the modal selection problem in the HR
diagram can be obtained in the form of bifurcation diagrams with the help of
simple nonresonant amplitude equations that capture the DM phenomenon.Comment: 34 pages, to appear as a chapter in Nonlinear Stellar Pulsation in
the Astrophysics and Space Science Library (ASSL), Editors: M. Takeuti & D.
Sasselov (prints double column with pstops
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Effect of non-nicotinic moist snuff replacement and lobeline on withdrawal symptoms during 48-h smokeless tobacco deprivation
The present study investigated the effects of two herbal components (BACCOFFTM and DIPSTOP ™) of a commercially available smokeless tobacco treatment program for reducing subjective withdrawal symptoms during deprivation. One component, BACCOFF™, is a non-nicotinic chew. The second component, DIPSTOP™, is a liquid containing the alkaloid lobeline, which to some extent mimics peripheral nicotinic effects. All participants (N = 22 males) were placed in four conditions: BACCOFF™ + DIPSTOP™, BACCOFF™ + placebo control, DIPSTOP™ only, and placebo control only. The conditions involved 48 h of deprivation, and subjects were exposed to one condition per week for 4 weeks. Withdrawal measures were taken at baseline, 24 h, and 48 h of deprivation. Individuals were randomly assigned, and conditions were counterbalanced. Results showed that BACCOFF™, as compared with DIPSTOP™, significantly reduced withdrawal symptoms but not craving. These data suggest that behavioral/sensory substitutes’ influence on withdrawal might be routed through the product’s ability to approximate the preferred moist snuff
Local Isoelectronic Reactivity of Solid Surfaces
The quantity w^N(r) = ( 1/ k^2 T_el)[partial n(r, T_el) / partial
T_el]_(v(r),N) is introduced as a convenient measure of the local isoelectronic
reactivity of surfaces. It characterizes the local polarizability of the
surface and it can be calculated easily. The quantity w^N(r) supplements the
charge transfer reactivity measured e.g. by the local softness to which it is
closely related. We demonstrate the applicability and virtues of the function
w^N(r) for the example of hydrogen dissociation and adsorption on Pd(100).Comment: RevTeX, 13 pages, 3 figures, to appear in Phys. Rev. Let
Automorphisms of graphs of cyclic splittings of free groups
We prove that any isometry of the graph of cyclic splittings of a finitely
generated free group of rank is induced by an outer automorphism
of . The same statement also applies to the graphs of maximally-cyclic
splittings, and of very small splittings.Comment: 22 pages, 5 figures. Small modifications. To appear in Geometriae
Dedicat
Galaxy Mergers at z>1 in the HUDF: Evidence for a Peak in the Major Merger Rate of Massive Galaxies
We present a measurement of the galaxy merger fraction and number density
from observations in the Hubble Ultra Deep Field for 0.5<z<2.5. We fit the
combination of broadband data and slitless spectroscopy of 1308 galaxies with
stellar population synthesis models to select merging systems based on a
stellar mass of >10^10 M_sol. When correcting for mass incompleteness, the
major merger fraction is not simply proportional to (1+z)^m, but appears to
peak at z_frac~=1.3+-0.4. From this merger fraction, we infer that ~42% of
massive galaxies have undergone a major merger since z~1. We show that the
major merger number density peaks at z_dens~1.2, which marks the epoch where
major merging of massive galaxies is most prevalent. This critical redshift is
comparable to the peak of the cosmic star formation rate density, and occurs
roughly 2.6 Gyr earlier in cosmic time than the peak in the number density of
X-ray selected active galactic nuclei. These observations support an indirect
evolutionary link between merging, starburst, and active galaxies.Comment: Accepted to ApJ. 7 pages, 6 figures, 1 table. Uses and includes
emulateapj.cls. In the initial submission, Figures 1 and 2 where switche
Thermal denaturation of fluctuating finite DNA chains: the role of bending rigidity in bubble nucleation
Statistical DNA models available in the literature are often effective models
where the base-pair state only (unbroken or broken) is considered. Because of a
decrease by a factor of 30 of the effective bending rigidity of a sequence of
broken bonds, or bubble, compared to the double stranded state, the inclusion
of the molecular conformational degrees of freedom in a more general mesoscopic
model is needed. In this paper we do so by presenting a 1D Ising model, which
describes the internal base pair states, coupled to a discrete worm like chain
model describing the chain configurations [J. Palmeri, M. Manghi, and N.
Destainville, Phys. Rev. Lett. 99, 088103 (2007)]. This coupled model is
exactly solved using a transfer matrix technique that presents an analogy with
the path integral treatment of a quantum two-state diatomic molecule. When the
chain fluctuations are integrated out, the denaturation transition temperature
and width emerge naturally as an explicit function of the model parameters of a
well defined Hamiltonian, revealing that the transition is driven by the
difference in bending (entropy dominated) free energy between bubble and
double-stranded segments. The calculated melting curve (fraction of open base
pairs) is in good agreement with the experimental melting profile of
polydA-polydT. The predicted variation of the mean-square-radius as a function
of temperature leads to a coherent novel explanation for the experimentally
observed thermal viscosity transition. Finally, the influence of the DNA strand
length is studied in detail, underlining the importance of finite size effects,
even for DNA made of several thousand base pairs.Comment: Latex, 28 pages pdf, 9 figure
Biochemical and metabolic effects of a six- month exposure of small animals to a helium- oxygen atmosphere
Biochemical and metabolic effects of exposure of mice to helium-oxygen atmospher
On the String Consensus Problem and the Manhattan Sequence Consensus Problem
In the Manhattan Sequence Consensus problem (MSC problem) we are given
integer sequences, each of length , and we are to find an integer sequence
of length (called a consensus sequence), such that the maximum
Manhattan distance of from each of the input sequences is minimized. For
binary sequences Manhattan distance coincides with Hamming distance, hence in
this case the string consensus problem (also called string center problem or
closest string problem) is a special case of MSC. Our main result is a
practically efficient -time algorithm solving MSC for sequences.
Practicality of our algorithms has been verified experimentally. It improves
upon the quadratic algorithm by Amir et al.\ (SPIRE 2012) for string consensus
problem for binary strings. Similarly as in Amir's algorithm we use a
column-based framework. We replace the implied general integer linear
programming by its easy special cases, due to combinatorial properties of the
MSC for . We also show that for a general parameter any instance
can be reduced in linear time to a kernel of size , so the problem is
fixed-parameter tractable. Nevertheless, for this is still too large
for any naive solution to be feasible in practice.Comment: accepted to SPIRE 201
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