1,495 research outputs found
Influence of Dopants on Defect Formation in GaN
Influence of p-dopants (Mg and Be) on the structure of GaN has been studied using Transmission Electron Microscopy (TEM). Bulk GaN:Mg and GaN:Be crystals grown by a high pressure and high temperature process and GaN:Mg grown by metal-organic chemical-vapor deposition (MOCVD) have been studied. Structural dependence on growth polarity was observed in the bulk crystals. Spontaneous ordering in bulk GaN:Mg on c-plane (formation of Mg-rich planar defects with characteristics of inversion domains) was observed for growth in the N to Ga polar direction (N polarity). On the opposite site of the crystal (growth in the Ga to N polar direction) Mg-rich pyramidal defects empty inside (pinholes) were observed. Both these defects were also observed in MOCVD grown crystals. Pyramidal defects were also observed in the bulk GaN:Be crystals
Lattice effects on the current-voltage characteristics of superconducting arrays
The lattice effects on the current-voltage characteristics of two-dimensional
arrays of resistively shunted Josephson junctions are investigated. The lattice
potential energies due to the discrete lattice structure are calculated for
several geometries and directions of current injection. We compare the energy
barrier for vortex-pair unbinding with the lattice pinning potential, which
shows that lattice effects are negligible in the low-current limit as well as
in the high-current limit. At intermediate currents, on the other hand, the
lattice potential becomes comparable to the barrier height and the lattice
effects may be observed in the current-voltage characteristics.Comment: 5 pages including 5 figures in two columns, to appear in Phys. Rev.
Positive pion absorption on 3He using modern trinucleon wave functions
We study pion absorption on 3He employing trinucleon wave functions
calculated from modern realistic NN interactions (Paris, CD Bonn). Even though
the use of the new wave functions leads to a significant improvement over older
calculations with regard to both cross section and polarization data, there are
hints that polarization data with quasifree kinematics cannot be described by
just two-nucleon absorption mechanisms.Comment: 14 pages, 6 figure
The role of interparticle heterogeneities in the selenization pathway of Cu Zn Sn S nanoparticle thin films a real time study
Real time energy dispersive X ray diffraction EDXRD analysis has been utilized to observe the selenization of Cu Zn Sn S nanoparticle films coated from three nanoparticle populations Cu and Sn rich particles roughly 5 nm in size, Zn rich nanoparticles ranging from 10 to 20 nm in diameter, and a mixture of both types of nanoparticles roughly 1 1 by mass , which corresponds to a synthesis recipe yielding CZTSSe solar cells with reported total area efficiencies as high as 7.9 . The EDXRD studies presented herein show that the formation of copper selenide intermediates during the selenization of mixed particle films can be primarily attributed to the small, Cu and Sn rich particles. Moreover, the formation of these copper selenide phases represents the first stage of the CZTSSe grain growth mechanism. The large, Zn rich particles subsequently contribute their composition to form micrometer sized CZTSSe grains. These findings enable further development of a previously proposed selenization pathway to account for the roles of interparticle heterogeneities, which in turn provides a valuable guide for future optimization of processes to synthesize high quality CZTSSe absorber layer
Oblique triangular antiferromagnetic phase in CsCuCoCl
The spin-1/2 stacked triangular antiferromagnet CsCuCoCl with
undergoes two phase transitions at zero field. The
low-temperature phase is produced by the small amount of Co doping. In
order to investigate the magnetic structures of the two ordered phases, the
neutron elastic scattering experiments have been carried out for the sample
with . It is found that the intermediate phase is identical to
the ordered phase of CsCuCl, and that the low-temperature phase is an
oblique triangular antiferromagnetic phase in which the spins form a triangular
structure in a plane tilted from the basal plane. The tilting angle which is
42 at K decreases with increasing temperature, and becomes
zero at K. An off-diagonal exchange term is proposed as the
origin of the oblique phase.Comment: 6 pages, 7 figure
Relativistic Mean Field Model with Generalized Derivative Nucleon-Meson Couplings
The quantum hadrodynamics (QHD) model with minimal nucleon-meson couplings is
generalized by introducing couplings of mesons to derivatives of the nucleon
field in the Lagrangian density. This approach allows an effective description
of a state-dependent in-medium interaction in the mean-field approximation.
Various parametrizations for the generalized couplings are developed and
applied to infinite nuclear matter. In this approach, scalar and vector
self-energies depend on both density and momentum similarly as in the
Dirac-Brueckner theory. The Schr\"{o}diger-equivalent optical potential is much
less repulsive at high nucleon energies as compared to standard relativistic
mean field models and thus agrees better with experimental findings. The
derivative couplings in the extended model have significant effects on
properties of symmetric nuclear matter and neutron matter.Comment: 35 pages, 1 table, 10 figure
An in situ transmission electron microscopy study of the ion irradiation induced amorphisation of silicon by He and Xe
Transmission electron microscopy with in situ ion irradiation has been used to examine the ionbeam-induced amorphisation of crystalline silicon under irradiation with light (He) and heavy (Xe) ions at room temperature. Analysis of the electron diffraction data reveal the heterogeneous amorphisation mechanism to be dominant in both cases. The differences in the amorphisation curves are discussed in terms of intra-cascade dynamic recovery, and the role of electronic and nuclear loss mechanisms
Growth differentiation factor 15 deficiency protects against atherosclerosis by attenuating CCR2-mediated macrophage chemotaxis
A 2-Year Pragmatic Trial of Antibiotic Stewardship in 27 Community Nursing Homes
OBJECTIVES: To determine if antibiotic prescribing in community nursing homes (NHs) can be reduced by a multicomponent antibiotic stewardship intervention implemented by medical providers and nursing staff and whether implementation is more effective if performed by a NH chain or a medical provider group. DESIGN: Two-year quality improvement pragmatic implementation trial with two arms (NH chain and medical provider group). SETTING: A total of 27 community NHs in North Carolina that are typical of NHs statewide, conducted before announcement of the US Centers for Medicare and Medicaid Services antibiotic stewardship mandate. PARTICIPANTS: Nursing staff and medical care providers in the participating NHs. INTERVENTION: Standardized antibiotic stewardship quality improvement program, including training modules for nurses and medical providers, posters, algorithms, communication guidelines, quarterly information briefs, an annual quality improvement report, an informational brochure for residents and families, and free continuing education credit. MEASUREMENTS: Antibiotic prescribing rates per 1000 resident days overall and by infection type; rate of urine test ordering; and incidence of Clostridium difficile and methicillin-resistant Staphylococcus aureus (MRSA) infections. RESULTS: Systemic antibiotic prescription rates decreased from baseline by 18% at 12 months (incident rate ratio [IRR] = 0.82; 95% confidence interval [CI] = 0.69-0.98) and 23% at 24 months (IRR = 0.77; 95% CI = 0.65-0.90). A 10% increase in the proportion of residents with the medical director as primary physician was associated with a 4% reduction in prescribing (IRR = 0.96; 95% CI = 0.92-0.99). Incidence of C. difficile and MRSA infections, hospitalizations, and hospital readmissions did not change significantly. No adverse events from antibiotic nonprescription were reported. Estimated 2-year implementation costs per NH, exclusive of medical provider time, ranged from 3653. CONCLUSIONS: Antibiotic stewardship programs can be successfully disseminated in community NHs through either NH administration or medical provider groups and can achieve significant reductions in antibiotic use for at least 2 years. Medical director involvement is an important element of program success
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