6,212 research outputs found
Hydrodynamic Interactions in Protein Folding
We incorporate hydrodynamic interactions (HI) in a coarse-grained and
structure-based model of proteins by employing the Rotne-Prager hydrodynamic
tensor. We study several small proteins and demonstrate that HI facilitate
folding. We also study HIV-1 protease and show that HI make the flap closing
dynamics faster. The HI are found to affect time correlation functions in the
vicinity of the native state even though they have no impact on same time
characteristics of the structure fluctuations around the native state
Stratospheric cruise emission reduction program
A recently implemented NASA effort specifically aimed at reducing cruise oxides of nitrogen from high-altitude aircraft is discussed. The desired emission levels and the combustor technology required to achieve them are discussed. A brief overview of the SCERP operating plan is given. Lean premixed-prevaporized combustion and some of the potential difficulties that are associated with applying this technique to gas turbine combustors are examined. Base technology was developed in several key areas. These fundamental studies are viewed as a requirement for successful implementation of the lean premixed combustion technique
Effects of Inelastic Neutrino-Nucleus Scattering on Supernova Dynamics and Radiated Neutrino Spectra
Based on the shell model for Gamow-Teller and the Random Phase Approximation
for forbidden transitions, we have calculated reaction rates for inelastic
neutrino-nucleus scattering (INNS) under supernova (SN) conditions, assuming a
matter composition given by Nuclear Statistical Equilibrium. The rates have
been incorporated into state-of-the-art stellar core-collapse simulations with
detailed energy-dependent neutrino transport. While no significant effect on
the SN dynamics is observed, INNS increases the neutrino opacities noticeably
and strongly reduces the high-energy tail of the neutrino spectrum emitted in
the neutrino burst at shock breakout. Relatedly the expected event rates for
the observation of such neutrinos by earthbound detectors are reduced by up to
about 60%.Comment: 4 pages, 2 figures, 1 tabl
Scaling of solvation force in 2D Ising strip
The solvation force for the 2D Ising strip is calculated via exact
diagonalization of the transfer matrix in two cases: the symmetric case
corresponds to identical surface fields, and the antisymmetric case to exactly
opposite surface fields. In the symmetric case the solvation force is always
negative (attractive) while in the antisymmetric case the solvation force is
positive (repulsive) at high temperatures and negative at low temperatures. It
changes sign close to the critical wetting temperature characterizing the
semi--infinite system. The properties of the solvation force are discussed and
the scaling function describing its dependence on temperature, surface field,
and strip's width is proposed
Orientation and solvatochromism of dyes in liquid crystals.
The orientation and solvatochromism of some dye molecules in a liquid crystal have been investigated. Interactions with the host and the structure of the dye molecule affect the macroscopic alignment of dichroic dye molecules in a liquid crystal: It was observed that some dye molecules show a large bathochromic shift of their absorption maxima in the liquid crystal host relative to the situation in isotropic solvents. It is suggested that this is due to the occurrence of a much weaker reaction field in the anisotropic, rigid host. These dye molecules show little or no apparent order in the anisotropic host despite the observation of a reduction in the electro optic switching time when the dye is present. The highest degree of macroscopic alignment was observed for a merocyanine compound, which showed the smallest solvatochromic shift in the liquid crystal host. These results are discussed in terms of the steric, dipolar and hydrogen bond interactions between the guest and the host
Nonclassicality of pure two-qutrit entangled states
We report an exhaustive numerical analysis of violations of local realism by
two qutrits in all possible pure entangled states. In Bell type experiments we
allow any pairs of local unitary U(3) transformations to define the measurement
bases. Surprisingly, Schmidt rank-2 states, resembling pairs of maximally
entangled qubits, lead to the most noise-robust violations of local realism.
The phenomenon seems to be even more pronounced for four and five dimensional
systems, for which we tested a few interesting examples.Comment: 6 pages, journal versio
Nanoscale fluid flows in the vicinity of patterned surfaces
Molecular dynamics simulations of dense and rarefied fluids comprising small
chain molecules in chemically patterned nano-channels predict a novel switching
from Poiseuille to plug flow along the channel. We also demonstrate behavior
akin to the lotus effect for a nanodrop on a chemically patterned substrate.
Our results show that one can control and exploit the behavior of fluids at the
nanoscale using chemical patterning.Comment: Phys. Rev. Lett. in pres
Comment on ``Measurement of the He mass diffusion coefficient in superfluid He over the 0.45--0.95 K temperature range
The role of 3He-3He collisions in our diffusion experiment is addressed and
shown to not be relevant to the measurement of 3He diffusion against phonons in
superfluid helium.Comment: Two pages, in Europhysics Letters forma
Improved Laboratory Transition Probabilities for Neutral Chromium and Re-determination of the Chromium Abundance for the Sun and Three Stars
Branching fraction measurements from Fourier transform spectra in conjunction
with published radiative lifetimes are used to determine transition
probabilities for 263 lines of neutral chromium. These laboratory values are
employed to derive a new photospheric abundance for the Sun: log (Cr
I) = 5.640.01 (). These Cr I solar abundances do
not exhibit any trends with line strength nor with excitation energy and there
were no obvious indications of departures from LTE. In addition, oscillator
strengths for singly-ionized chromium recently reported by the FERRUM Project
are used to determine: log (Cr II) = 5.770.03 (). Transition probability data are also applied to the spectra of three
stars: HD 75732 (metal-rich dwarf), HD 140283 (metal-poor subgiant), and CS
22892-052 (metal-poor giant). In all of the selected stars, Cr I is found to be
underabundant with respect to Cr II. The possible causes for this abundance
discrepancy and apparent ionization imbalance are discussed.Comment: 44 pages, 6 figure
Delineation of the Native Basin in Continuum Models of Proteins
We propose two approaches for determining the native basins in off-lattice
models of proteins. The first of them is based on exploring the saddle points
on selected trajectories emerging from the native state. In the second
approach, the basin size can be determined by monitoring random distortions in
the shape of the protein around the native state. Both techniques yield the
similar results. As a byproduct, a simple method to determine the folding
temperature is obtained.Comment: REVTeX, 6 pages, 5 EPS figure
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