900 research outputs found
Estimations of electric field effects on the oxygen reduction reaction based on the density functional theory
Intravenous antibiotics given for 2 weeks do not eradicate persistent Staphylococcus aureus clones in cystic fibrosis patients
AbstractStaphylococcus aureus is the most commonly isolated pathogen in respiratory tract secretions from young patients with cystic fibrosis (CF), and several treatment strategies are used to control the infection. However, it is not known whether intensified treatment with antimicrobial agents causes eradication of S. aureus clones. We retrospectively determined the impact of intravenous (IV) antimicrobial agents on the suppression and eradication of S. aureus clones. One thousand and sixty-one S. aureus isolates cultured from 2526 samples from 130 CF patients during a 2-year study period were subjected to spa typing. Intervals between positive samples and the occurrence of clone replacements were calculated in relation to courses of IV antimicrobial agents. Of 65 patients chronically infected with S. aureus, 37 received 139 courses of IV antimicrobial agents with activity against S. aureus (mean duration, 15 days; range, 6–31 days). Administration of IV antibiotics increased the time to the next sample with growth of S. aureus: the mean interval between two positive samples was 68 days if IV treatment had been administered, in contrast to 49 days if no IV treatment had been administered (p 0.003). When S. aureus recurred in sputum after IV treatment, the isolate belonged to a different clone in 33 of 114 (29%) intervals, in comparison with 68 of 232 (29%) intervals where IV treatment had not been prescribed (OR 0.98, 95% CI 0.60–1.61). In conclusion, we show that 2 weeks of IV antimicrobial treatment can significantly suppress chronic staphylococcal infection in CF, but is not associated with the eradication of persistent bacterial clones
Bayesian Error Estimation in Density Functional Theory
We present a practical scheme for performing error estimates for Density
Functional Theory calculations. The approach which is based on ideas from
Bayesian statistics involves creating an ensemble of exchange-correlation
functionals by comparing with an experimental database of binding energies for
molecules and solids. Fluctuations within the ensemble can then be used to
estimate errors relative to experiment on calculated quantities like binding
energies, bond lengths, and vibrational frequencies. It is demonstrated that
the error bars on energy differences may vary by orders of magnitude for
different systems in good agreement with existing experience.Comment: 5 pages, 3 figure
Quantum Motion of Chemisorbed Hydrogen on Ni Surfaces
Quantum mechanical energy levels and wave functions have been calculated for the motion of chemisorbed hydrogen atoms on Ni surfaces. The results show considerable quantum effects for the adatom in both the ground and the excited states. The description of the adparticles as being delocalized along the surface offers a novel interpretation of several phenomena, in particular the vibrational excitations.Peer reviewe
Engineering Hybrid Epitaxial InAsSb/Al Nanowire Materials for Stronger Topological Protection
The combination of strong spin-orbit coupling, large -factors, and the
coupling to a superconductor can be used to create a topologically protected
state in a semiconductor nanowire. Here we report on growth and
characterization of hybrid epitaxial InAsSb/Al nanowires, with varying
composition and crystal structure. We find the strongest spin-orbit interaction
at intermediate compositions in zincblende InAsSb nanowires,
exceeding that of both InAs and InSb materials, confirming recent theoretical
studies \cite{winkler2016topological}. We show that the epitaxial InAsSb/Al
interfaces allows for a hard induced superconducting gap and 2 transport in
Coulomb charging experiments, similar to experiments on InAs/Al and InSb/Al
materials, and find measurements consistent with topological phase transitions
at low magnetic fields due to large effective -factors. Finally we present a
method to grow pure wurtzite InAsSb nanowires which are predicted to exhibit
even stronger spin-orbit coupling than the zincblende structure.Comment: 10 pages and 5 figure
Spectroscopic link between adsorption site occupation and local surface chemical reactivity
In this Letter we show that sequences of adsorbate-induced shifts of surface core level (SCL) x-ray photoelectron spectra contain profound information on surface changes of electronic structure and reactivity. Energy shifts and intensity changes of time-lapsed spectral components follow simple rules, from which adsorption sites are directly determined. Theoretical calculations rationalize the results for transition metal surfaces in terms of the energy shift of the d-band center of mass and this proves that adsorbate-induced SCL shifts provide a spectroscopic measure of local surface reactivity
Response to "comment on 'Trends in the exchange current for hydrogen evolution' [J. Electrochem. Soc., 152, J23 (2005)]"
A wideband heterodyne optical phase-locked loop for generation of 3-18 GHz microwave carriers
Coherent Optical Generation of a 6 GHz Microwave Signal with Directly Phase Locked Semiconductor DFB Lasers
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