37,947 research outputs found
Intrinsic Mean Square Displacements in Proteins
The thermal mean square displacement (MSD) of hydrogen in proteins and its
associated hydration water is measured by neutron scattering experiments and
used an indicator of protein function. The observed MSD as currently determined
depends on the energy resolution width of the neutron scattering instrument
employed. We propose a method for obtaining the intrinsic MSD of H in the
proteins, one that is independent of the instrument resolution width. The
intrinsic MSD is defined as the infinite time value of that appears in
the Debye-Waller factor. The method consists of fitting a model to the
resolution broadened elastic incoherent structure factor or to the resolution
dependent MSD. The model contains the intrinsic MSD, the instrument resolution
width and a rate constant characterizing the motions of H in the protein. The
method is illustrated by obtaining the intrinsic MSD of heparan sulphate
(HS-0.4), Ribonuclease A and Staphysloccal Nuclase (SNase) from data in the
literature
Foreign Policy Views and U.S. Standing in the World
What do Americans think about the US role in world affairs and why do they think the way they do? Americans typically do not think about foreign policy most of the time, and, as a consequence, know relatively little about it (Almond 1950, Lippmann 1955, Converse 1964, Erskine 1963, Edwards 1983, Sobel 1993, Holsti 2004, Canes-Wrone 2006, Page and Bouton 2006, Berinsky 2007). While foreign policy issues can become salient when major international events (like 9/11 and the Iraq War) arise or when political candidates focus on foreign policy (Aldrich, Sullivan and Borgida 1989), ceteris paribus, Americans know and care more about domestic politics (Delli-Carpini and Keeter 1996, Holsti 1994, Canes-Wrone 2006, Converse 1964). Consequently, typical Americans are broadly aware of foreign policy, and have some available attitudes about it (Page and Bouton 2006, Aldrich et al. 1989). However, except in the face of political priming by elites or exogenous shocks, such attitudes may not be broadly accessible when making political decisions, like voting.
Wind data from the 250-foot /76.2-meter/ tower at Wallops Island, Virginia
Statistical evaluation of sampled wind data from anemometers mounted on meteorological tower on Wallops Islan
Telecommunications reform in Malawi
In 1998 the Government of Malawi decided to reform its telecommunications sector. Although the reform was ambitious in some ways, it was modest when compared with the most ambitious reforms adopted elsewhere in Sub-Saharan Africa. The two main accomplishments were splitting the incumbent fixed line monopoly, the Malawi Post and Telecommunications Corporation, into two companies-Malawi Telecommunications Limited (MTL) and Malawi Post Corporation (MPC)-and issuing two new cellular licenses to two new private entrants. In addition, the Government also established a new regulator which was separate from, but heavily dependent on, the Ministry of Information and liberalized entry in value-added and Internet services. However, the Government had neither privatized the fixed-line telecommunications operator nor introduced competition in fixed-line services by the end of 2002. Clarke, Gebreab, and Mgombelo discuss sector performance before reform, details of the reform, the political motivation for reform, and events in the five years following the reform. The reform yielded mixed results. Although cellular penetration and Internet use expanded dramatically following reform, prices increased, especially for cellular calls, and fixed-line penetration remains low by regional standards.Public Sector Economics&Finance,Rural Communications,Telecommunications Infrastructure,ICT Policy and Strategies,Knowledge Economy,ICT Policy and Strategies,Rural Communications,Education for the Knowledge Economy,Knowledge Economy,Public Sector Economics&Finance
Procedures for estimating the effects of design and operational characteristics of jet aircraft on ground noise
Estimation procedures for effect of design and flight characteristics of jets on ground nois
Auxiliary-field quantum Monte Carlo calculations of molecular systems with a Gaussian basis
We extend the recently introduced phaseless auxiliary-field quantum Monte
Carlo (QMC) approach to any single-particle basis, and apply it to molecular
systems with Gaussian basis sets. QMC methods in general scale favorably with
system size, as a low power. A QMC approach with auxiliary fields in principle
allows an exact solution of the Schrodinger equation in the chosen basis.
However, the well-known sign/phase problem causes the statistical noise to
increase exponentially. The phaseless method controls this problem by
constraining the paths in the auxiliary-field path integrals with an
approximate phase condition that depends on a trial wave function. In the
present calculations, the trial wave function is a single Slater determinant
from a Hartree-Fock calculation. The calculated all-electron total energies
show typical systematic errors of no more than a few milli-Hartrees compared to
exact results. At equilibrium geometries in the molecules we studied, this
accuracy is roughly comparable to that of coupled-cluster with single and
double excitations and with non-iterative triples, CCSD(T). For stretched bonds
in HO, our method exhibits better overall accuracy and a more uniform
behavior than CCSD(T).Comment: 11 pages, 5 figures. submitted to JC
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