1,844 research outputs found
Prefect Transfer of Quantum States on Spin Chain with Dzyaloshinskii- Moriya interaction in inhomogeneous Magnetic field
In this work, we use the Hamiltonian of a modified Dzyaloshinskii-Moriya
model and investigate the perfect transfer of the quantum state on the spin
networks. In this paper, we calculate fidelity in which fidelity depends on
magnetic field and another parameters. Then, by using the numerical analysis we
show that the fidelity of the transferred state is determined by magnetic field
, exchange coupling and the Dzyaloshinskii- Moriya interaction . We
also found that the perfect transfer of the quantum state is possible with
condition where and
.Comment: 8 pages, 2 figure
Bistable perception in normal aging: perceptual reversibility and its relation to cognition
The effects of age on the ability to resolve perceptual ambiguity are unknown, though it depends
on fronto-parietal attentional networks known to change with age. We presented the bistable
Necker cube to 24 middle-aged and older adults (OA; 56–78 years) and 20 younger adults (YA;
18–24 years) under passive-viewing and volitional control conditions: Hold one cube percept and
Switch between cube percepts. During passive viewing, OA had longer dominance durations (time
spent on each percept) than YA. In the Hold condition, OA were less able than YA to increase
dominance durations. In the Switch condition, OA and YA did not differ in performance.
Dominance durations in either condition correlated with performance on tests of executive
function mediated by the frontal lobes. Eye movements (fixation deviations) did not differ between
groups. These results suggest that OA’s reduced ability to hold a percept may arise from reduced
selective attention. The lack of correlation of performance between Hold and executive-function
measures suggests at least a partial segregation of underlying mechanisms.Published versionAccepted manuscrip
Effect of the Heterogeneity of Metamaterials on Casimir-Lifshitz Interaction
The Casimir-Lifshitz interaction between metamaterials is studied using a
model that takes into account the structural heterogeneity of the dielectric
and magnetic properties of the bodies. A recently developed perturbation theory
for the Casimir-Lifshitz interaction between arbitrary material bodies is
generalized to include non-uniform magnetic permeability profiles, and used to
study the interaction between the magneto-dielectric heterostructures within
the leading order. The metamaterials are modeled as two dimensional arrays of
domains with varying permittivity and permeability. In the case of two
semi-infinite bodies with flat boundaries, the patterned structure of the
material properties is found to cause the normal Casimir-Lifshitz force to
develop an oscillatory behavior when the distance between the two bodies is
comparable to the wavelength of the patterned features in the metamaterials.
The non-uniformity also leads to the emergence of lateral Casimir-Lifshitz
forces, which tend to strengthen as the gap size becomes smaller. Our results
suggest that the recent studies on Casimir-Lifshitz forces between
metamaterials, which have been performed with the aim of examining the
possibility of observing the repulsive force, should be revisited to include
the effect of the patterned structure at the wavelength of several hundred
nanometers that coincides with the relevant gap size in the experiments.Comment: 9 pages, 13 figures. Rewriting equations (10) and (12) and increasing
the size of the lettering/numeral in figure
What is the right theory for Anderson localization of light?
Anderson localization of light is traditionally described in analogy to
electrons in a random potential. Within this description the disorder strength
-- and hence the localization characteristics -- depends strongly on the
wavelength of the incident light. In an alternative description in analogy to
sound waves in a material with spatially fluctuating elastic moduli this is not
the case. Here, we report on an experimentum crucis in order to investigate the
validity of the two conflicting theories using transverse-localized optical
devices. We do not find any dependence of the observed localization radii on
the light wavelength. We conclude that the modulus-type description is the
correct one and not the potential-type one. We corroborate this by showing that
in the derivation of the traditional, potential-type theory a term in the wave
equation has been tacititly neglected. In our new modulus-type theory the wave
equation is exact. We check the consistency of the new theory with our data
using a field-theoretical approach (nonlinear sigma model)
Drug resistance patterns of bacteria isolated from patients with nosocomial pneumonia at Tehran hospitals during 2009-2011
INTRODUCTION:
Nosocomial pneumonia remains an important cause of mortality and morbidity worldwide. Surveillance programs play an important role in the identification of common etiologic agents and local patterns of antimicrobial resistance.
METHODOLOGY:
In this study we determined the frequency and antimicrobial susceptibility of pathogens isolated from patients with nosocomial pneumonia during 2009 to 2011.
RESULTS:
A total of 642 bacteria were isolated from 516 suspected samples. Acinetobacter baumannii (21.1%, n = 136), was the commonest isolated pathogen followed by Pseudomonas aeruginosa (17.4%, n = 112), Staphylococcus aureus (15.8%, n = 102) and enterococci (8.4% n = 54). The most effective therapeutic agents against A. baumannii were polymyxin B (95.5% susceptible), ceftriaxone/tazobactam (72% susceptible) and levofloxacin (52.9% susceptible). Polymixin B (89.2% susceptible), ceftriaxone/tazobactam (89.2% susceptible) and piperacillin-tazobactam (80.3% susceptible) were found to be the most active agents against P. aeruginosa. Extended-spectrum beta-lactamases were detected among isolates of K. pneumoniae (45.4%) and E. coli (20.3%). Overall, the prevalence of methicillin-resistant S. aureus and vancomycin resistant enterococci were 80.4% and 40.7% respectively. Linezolid was found to be the most active antibiotic against these pathogens. The etiology of 50% of the nosocomial infection cases was polymicrobial.
CONCLUSIONS:
The combination of ceftriaxone/tazobactam seems to be beneficial agent against multidrug-resistant Gram-negative bacilli isolated form respiratory tract infections. The results of our study can be used for guiding appropriate empiric therapy in this geographic region
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