2,996 research outputs found
Electron irradiation induced reduction of the permittivity in chalcogenide glass (As2S3) thin film
We investigate the effect of electron beam irradiation on the dielectric
properties of As2S3 Chalcogenide glass. By means of low-loss Electron Energy
Loss Spectroscopy, we derive the permittivity function, its dispersive
relation, and calculate the refractive index and absorption coefficients under
the constant permeability approximation. The measured and calculated results
show, to the best of our knowledge, a heretofore unseen phenomenon: the
reduction in the permittivity of <40%, and consequently a modification of the
refractive index follows, reducing it by 20%, hence suggesting a significant
change on the optical properties of the material. The plausible physical
phenomena leading to these observations are discussed in terms of the homopolar
and heteropolar bond dynamics under high energy absorption.Comment: 22 pages, 7 figures, manuscript in preparation to send to Physical
Review
Tert-butyl benzoquinone: mechanism of biofilm eradication and potential for use as a topical antibiofilm agent
Objectives: Tert-butyl benzoquinone (TBBQ) is the oxidation product of tert-butyl hydroquinone (TBHQ), an antimicrobial food additive with >40 years of safe use. TBBQ displays potent activity against Staphylococcus aureus biofilms in vitro. Here, we report on studies to further explore the action of TBBQ on staphylococcal biofilms, and provide a preliminary preclinical assessment of its potential for use as a topical treatment for staphylococcal infections involving a biofilm component. Methods: The antibacterial properties of TBBQ were assessed against staphylococci growing in planktonic culture and as biofilms in the Calgary Biofilm Device. Established assays were employed to measure the effects of TBBQ on biofilm structure and bacterial membranes, and to assess resistance potential. A living skin equivalent was used to evaluate the effects of TBBQ on human skin. Results: TBBQ eradicated biofilms of S. aureus and other staphylococcal species at concentrations ≤64 mg/L. In contrast to other redox-active agents exhibiting activity against biofilms, TBBQ did not cause substantial destructuring of the biofilm matrix; instead, the antibiofilm activity of the compound was attributed to its ability to kill slow- and non-growing cells via membrane perturbation. TBBQ acted synergistically with gentamicin, did not damage a living skin equivalent following topical application, and exhibited low resistance potential. Conclusions: The ability of TBBQ to eradicate biofilms appears to result from its ability to kill bacteria regardless of growth state. Preliminary evaluation suggests that TBBQ represents a promising candidate for development as a topical antistaphylococcal biofilm agent
Configurable Version Management Hardware Transactional Memory for Multi-processor Platform
Programming on a shared memory multi-processor platforms in an efficient way is difficult as locked based synchronization limits the efficiency. Transactional memory (TM) is a promising approach in creating an abstraction layer for multi-threaded programming. However, the performance of TM is application-specific. In general, the configuration of a TM is divided into version management and conflict management. Each scheme has its strengths and weaknesses depending on executing application. Previous TM implementations for embedded system were built on fixed version management configuration which results in significant performance loss when transaction behaviour changes. In this paper, we propose a hardware transactional memory (HTM) with interchangeable version management. Random requests at different contention levels are used to verify the performance of the proposed TM. The proposed architecture is targeted for embedded applications and is area-efficient compared to current implementations that apply cache coherence protocols
Vortex Matter Transition in BiSrCaCuO under Tilted Fields
Vortex phase diagram under tilted fields from the axis in
BiSrCaCuO is studied by local magnetization
hysteresis measurements using Hall probes. When the field is applied at large
angles from the axis, an anomaly () other than the well-known
peak effect () are found at fields below . The angular dependence of
the field is nonmonotonic and clearly different from that of
and depends on the oxygen content of the crystal. The results suggest existence
of a vortex matter transition under tilted fields. Possible mechanisms of the
transition are discussed.Comment: Revtex, 4 pages, some corrections are adde
Diethyl 2,6-dimethyl-4-(5-phenyl-1H-pyrazol-4-yl)-1,4-dihydroÂpyridine-3,5-dicarboxylÂate
In the title compound, C22H25N3O4, the dihydroÂpyridine ring adopts a flattened boat conformation. The pyrazole ring makes a dihedral angle of 29.04 (5)° with the benzene ring. The molÂecular structure is stabilized by an intraÂmolecular C—H⋯O hydrogen bond which generates an S(9) ring motif. In the crystal, molÂecules are linked via N—H⋯O and C—H⋯N hydrogen bonds into a two-dimensional network parallel to the ab plane. The crystal structure is further consolidated by weak C—H⋯π interÂactions
Global three-dimensional flow of a neutron superfluid in a spherical shell in a neutron star
We integrate for the first time the hydrodynamic
Hall-Vinen-Bekarevich-Khalatnikov equations of motion of a -paired
neutron superfluid in a rotating spherical shell, using a pseudospectral
collocation algorithm coupled with a time-split fractional scheme. Numerical
instabilities are smoothed by spectral filtering. Three numerical experiments
are conducted, with the following results. (i) When the inner and outer spheres
are put into steady differential rotation, the viscous torque exerted on the
spheres oscillates quasiperiodically and persistently (after an initial
transient). The fractional oscillation amplitude () increases
with the angular shear and decreases with the gap width. (ii) When the outer
sphere is accelerated impulsively after an interval of steady differential
rotation, the torque increases suddenly, relaxes exponentially, then oscillates
persistently as in (i). The relaxation time-scale is determined principally by
the angular velocity jump, whereas the oscillation amplitude is determined
principally by the gap width. (iii) When the mutual friction force changes
suddenly from Hall-Vinen to Gorter-Mellink form, as happens when a rectilinear
array of quantized Feynman-Onsager vortices is destabilized by a counterflow to
form a reconnecting vortex tangle, the relaxation time-scale is reduced by a
factor of compared to (ii), and the system reaches a stationary state
where the torque oscillates with fractional amplitude about a
constant mean value. Preliminary scalings are computed for observable
quantities like angular velocity and acceleration as functions of Reynolds
number, angular shear, and gap width. The results are applied to the timing
irregularities (e.g., glitches and timing noise) observed in radio pulsars.Comment: 6 figures, 23 pages. Accepted for publication in Astrophysical
Journa
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