3,381 research outputs found
Multifractal spectra in homogeneous shear flow
Employing numerical simulations of 3-D homogeneous shear flow, the associated multifractal spectra of the energy dissipation, scalar dissipation and vorticity fields were calculated. The results for (128) cubed simulations of this flow, and those obtained in recent experiments that analyzed 1- and 2-D intersections of atmospheric and laboratory flows, are in some agreement. A two-scale Cantor set model of the energy cascade process which describes the experimental results from 1-D intersections quite well, describes the 3-D results only marginally
A Prototype Overview for Allocating USAID Foreign Aid
The United States Agency for International Development (USAID) is the federal government agency primarily responsible for administering civilian foreign aid. In fiscal year 2011, USAID spent approximately $15 billion in an effort to assist countries recovering from disaster, trying to escape poverty, and engaging in democratic reforms. Using Value-Focused Thinking, regression, and optimization techniques, this thesis utilizes overarching USAID objectives and underlying policy to develop a prototype overview model that is used to provide insight to a Decision Maker regarding how changes in funding allocation can lead to improved impact
Identifying networks with common organizational principles
Many complex systems can be represented as networks, and the problem of
network comparison is becoming increasingly relevant. There are many techniques
for network comparison, from simply comparing network summary statistics to
sophisticated but computationally costly alignment-based approaches. Yet it
remains challenging to accurately cluster networks that are of a different size
and density, but hypothesized to be structurally similar. In this paper, we
address this problem by introducing a new network comparison methodology that
is aimed at identifying common organizational principles in networks. The
methodology is simple, intuitive and applicable in a wide variety of settings
ranging from the functional classification of proteins to tracking the
evolution of a world trade network.Comment: 26 pages, 7 figure
Solwnd: A 3D Compressible MHD Code for Solar Wind Studies. Version 1.0: Cartesian Coordinates
Solwnd 1.0 is a three-dimensional compressible MHD code written in Fortran for studying the solar wind. Time-dependent boundary conditions are available. The computational algorithm is based on Flux Corrected Transport and the code is based on the existing code of Zalesak and Spicer. The flow considered is that of shear flow with incoming flow that perturbs this base flow. Several test cases corresponding to pressure balanced magnetic structures with velocity shear flow and various inflows including Alfven waves are presented. Version 1.0 of solwnd considers a rectangular Cartesian geometry. Future versions of solwnd will consider a spherical geometry. Some discussions of this issue is presented
Speech and language therapy versus placebo or no intervention for speech problems in Parkinson's disease
Parkinson's disease patients commonly suffer from speech and vocal problems including dysarthric speech, reduced loudness and loss of articulation. These symptoms increase in frequency and intensity with progression of the disease). Speech and language therapy (SLT) aims to improve the intelligibility of speech with behavioural treatment techniques or instrumental aids
Structure of human saposin A at lysosomal pH.
The saposins are essential cofactors for the normal lysosomal degradation of complex glycosphingolipids by acid hydrolase enzymes; defects in either saposin or hydrolase function lead to severe metabolic diseases. Saposin A (SapA) activates the enzyme β-galactocerebrosidase (GALC), which catalyzes the breakdown of β-D-galactocerebroside, the principal lipid component of myelin. SapA is known to bind lipids and detergents in a pH-dependent manner; this is accompanied by a striking transition from a `closed' to an `open' conformation. However, previous structures were determined at non-lysosomal pH. This work describes a 1.8 Å resolution X-ray crystal structure determined at the physiologically relevant lysosomal pH 4.8. In the absence of lipid or detergent at pH 4.8, SapA is observeed to adopt a conformation closely resembling the previously determined `closed' conformation, showing that pH alone is not sufficient for the transition to the `open' conformation. Structural alignments reveal small conformational changes, highlighting regions of flexibility.CHH is funded by a Wellcome Trust PhD studentship, RJR is supported by a Principal Research Fellowship funded by the Wellcome Trust (Grant No. 082961/Z/07/Z) and JED is supported by a Royal Society University Research Fellowship (UF100371). The Cambridge Institute for Medical Research is supported by a Wellcome Trust Strategic Award (100140).This is the final version of the article. It first appeared from Wiley via http://dx.doi.org/10.1107/S2053230X1500858
Spectral evidence for a powerful compact jet from XTE J1118+480
We present observations of the X-ray transient XTE J1118+480 during its
Low/Hard X-ray state outburst in 2000, at radio and sub-millimetre wavelengths
with the VLA, Ryle Telescope, MERLIN and JCMT. The high-resolution MERLIN
observations reveal all the radio emission (at 5 GHz) to come from a compact
core with physical dimensions smaller than 65*d(kpc) AU. The combined radio
data reveal a persistent and inverted radio spectrum, with spectral index
\~+0.5. The source is also detected at 350 GHz, on an extrapolation of the
radio spectrum. Flat or inverted radio spectra are now known to be typical of
the Low/Hard X-ray state, and are believed to arise in synchrotron emission
from a partially self-absorbed jet. Comparison of the radio and sub-millimetre
data with reported near-infrared observations suggest that the synchrotron
emission from the jet extends to the near-infrared, or possibly even optical
regimes. In this case the ratio of jet power to total X-ray luminosity is
likely to be P_J/L_X >> 0.01, depending on the radiative efficiency and
relativistic Doppler factor of the jet. Based on these arguments we conclude
that during the period of our observations XTE J1118+480 was producing a
powerful outflow which extracted a large fraction of the total accretion power.Comment: Accepted for publication as a Letter in MNRA
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