19,407 research outputs found
Post-flight analyses of the crystals from the M0003-14 quartz crystal microbalance experiment
Quartz Crystal Microbalances constructed by QCM Research were flown on the leading and trailing edges of LDEF as one of the sub-experiments of M0003. Response of the crystals coated with 150 A of In2O3 was recorded during the first 424 days of the mission. A second QCM with crystals coated with 150 A of ZnS was also flown but not monitored. After the flight, the QCM's were disassembled and analyzed in The Aerospace Corporation laboratories. The samples included the crystals from the leading and trailing edge samples of both types of coatings along with the reference crystals, which were inside the QCM housing. Analyses were performed by scanning electron microscopy, energy dispersive x-ray analyses, x-ray photoelectron spectroscopy, ion microprobe mass analysis, and reflectance spectroscopy in the infrared and UV/visible regions. The crystals are contaminated predominantly with silicone compounds. The contamination is higher on the leading edge than on the trailing edge and higher on the exposed crystals than on the reference crystals
Fast track children's hearing pilot: final report of the evaluation of the pilot
This report presents key findings of the evaluation of the Fast Track children’s hearings pilot in Scotland1. The research was undertaken by staff at the Universities of Glasgow, Stirling and Strathclyde between February 2003 and January 2005
On the accuracy of the melting curves drawn from modelling a solid as an elastic medium
An ongoing problem in the study of a classical many-body system is the
characterization of its equilibrium behaviour by theory or numerical
simulation. For purely repulsive particles, locating the melting line in the
pressure-temperature plane can be especially hard if the interparticle
potential has a softened core or contains some adjustable parameters. A method
is hereby presented that yields reliable melting-curve topologies with
negligible computational effort. It is obtained by combining the Lindemann
melting criterion with a description of the solid phase as an elastic
continuum. A number of examples are given in order to illustrate the scope of
the method and possible shortcomings. For a two-body repulsion of Gaussian
shape, the outcome of the present approach compares favourably with the more
accurate but also more computationally demanding self-consistent harmonic
approximation.Comment: 25 pages, 7 figure
Comment on `Renormalization-Group Calculation of the Dependence on Gravity of the Surface Tension and Bending Rigidity of a Fluid Interface'
It is shown that the interface model introduced in Phys. Rev. Lett. 86, 2369
(2001) violates fundamental symmetry requirements for vanishing gravitational
acceleration , so that its results cannot be applied to critical properties
of interfaces for .Comment: A Comment on a recent Letter by J.G. Segovia-L\'opez and V.
Romero-Roch\'{\i}n, Phys. Rev. Lett.86, 2369 (2001). Latex file, 1 page
(revtex
Topical decolonization does not eradicate the skin microbiota of community-dwelling or hospitalized adults
Topical antimicrobials are often employed for decolonization and infection prevention and may alter the endogenous microbiota of the skin. The objective of this study was to compare the microbial communities and levels of richness and diversity in community-dwelling subjects and intensive care unit (ICU) patients before and after the use of topical decolonization protocols. We enrolled 15 adults at risk for Staphylococcus aureus infection. Community subjects (n = 8) underwent a 5-day decolonization protocol (twice daily intranasal mupirocin and daily dilute bleach-water baths), and ICU patients (n = 7) received daily chlorhexidine baths. Swab samples were collected from 5 anatomic sites immediately before and again after decolonization. A variety of culture media and incubation environments were used to recover bacteria and fungi; isolates were identified using matrix-assisted laser desorption ionization–time of flight mass spectrometry. Overall, 174 unique organisms were recovered. Unique communities of organisms were recovered from the community-dwelling and hospitalized cohorts. In the community-dwelling cohort, microbial richness and diversity did not differ significantly between collections across time points, although the number of body sites colonized with S. aureus decreased significantly over time (P = 0.004). Within the hospitalized cohort, richness and diversity decreased over time compared to those for the enrollment sampling (from enrollment to final sampling, P = 0.01 for both richness and diversity). Topical antimicrobials reduced the burden of S. aureus while preserving other components of the skin and nasal microbiota
Coarse-graining microscopic strains in a harmonic, two-dimensional solid and its implications for elasticity: non-local susceptibilities and non-affine noise
In soft matter systems the local displacement field can be accessed directly
by video microscopy enabling one to compute local strain fields and hence the
elastic moduli using a coarse-graining procedure. We study this process for a
simple triangular lattice of particles connected by harmonic springs in
two-dimensions. Coarse-graining local strains obtained from particle
configurations in a Monte Carlo simulation generates non-trivial, non-local
strain correlations (susceptibilities), which may be understood within a
generalized, Landau type elastic Hamiltonian containing up to quartic terms in
strain gradients (K. Franzrahe et al., Phys. Rev. E 78, 026106 (2008)). In
order to demonstrate the versatility of the analysis of these correlations and
to make our calculations directly relevant for experiments on colloidal solids,
we systematically study various parameters such as the choice of statistical
ensemble, presence of external pressure and boundary conditions. We show that
special care needs to be taken for an accurate application of our results to
actual experiments, where the analyzed area is embedded within a larger system,
to which it is mechanically coupled. Apart from the smooth, affine strain
fields, the coarse-graining procedure also gives rise to a noise field made up
of non-affine displacements. Several properties of this noise field may be
rationalized for the harmonic solid using a simple "cell model" calculation.
Furthermore the scaling behavior of the probability distribution of the noise
field is studied and a master curve is obtained.Comment: 16 pages, 12 figure
Consistent thermodynamic derivative estimates for tabular equations of state
Numerical simulations of compressible fluid flows require an equation of
state (EOS) to relate the thermodynamic variables of density, internal energy,
temperature, and pressure. A valid EOS must satisfy the thermodynamic
conditions of consistency (derivation from a free energy) and stability
(positive sound speed squared). When phase transitions are significant, the EOS
is complicated and can only be specified in a table. For tabular EOS's such as
SESAME from Los Alamos National Laboratory, the consistency and stability
conditions take the form of a differential equation relating the derivatives of
pressure and energy as functions of temperature and density, along with
positivity constraints. Typical software interfaces to such tables based on
polynomial or rational interpolants compute derivatives of pressure and energy
and may enforce the stability conditions, but do not enforce the consistency
condition and its derivatives. We describe a new type of table interface based
on a constrained local least squares regression technique. It is applied to
several SESAME EOS's showing how the consistency condition can be satisfied to
round-off while computing first and second derivatives with demonstrated
second-order convergence. An improvement of 14 orders of magnitude over
conventional derivatives is demonstrated, although the new method is apparently
two orders of magnitude slower, due to the fact that every evaluation requires
solving an 11-dimensional nonlinear system.Comment: 29 pages, 9 figures, 16 references, submitted to Phys Rev
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