28,763 research outputs found
Quantum Doubles from a Class of Noncocommutative Weak Hopf Algebras
The concept of biperfect (noncocommutative) weak Hopf algebras is introduced
and their properties are discussed. A new type of quasi-bicrossed products are
constructed by means of weak Hopf skew-pairs of the weak Hopf algebras which
are generalizations of the Hopf pairs introduced by Takeuchi. As a special
case, the quantum double of a finite dimensional biperfect (noncocommutative)
weak Hopf algebra is built. Examples of quantum doubles from a Clifford monoid
as well as a noncommutative and noncocommutative weak Hopf algebra are given,
generalizing quantum doubles from a group and a noncommutative and
noncocommutative Hopf algebra, respectively. Moreover, some characterisations
of quantum doubles of finite dimensional biperfect weak Hopf algebras are
obtained.Comment: LaTex 18 pages, to appear in J. Math. Phys. (To compile, need
pb-diagram.sty, pb-lams.sty, pb-xy.sty and lamsarrow.sty
Topology of the polarization field in ferroelectric nanowires from first principles
The behaviour of the cross-sectional polarization field is explored for thin
nanowires of barium titanate from first-principles calculations. Topological
defects of different winding numbers have been obtained, beyond the known
textures in ferroelectric nanostructures. They result from the inward
accommodation of the polarization patterns imposed at the surface of the wire
by surface and edge effects. Close to a topological defect the polarization
field orients out of the basal plane in some cases, maintaining a close to
constant magnitude, whereas it virtually vanishes in other cases.Comment: 4 pages, 3 figure
In vitro and in vivo effects of salbutamol on neutrophil function in acute lung injury
Background: Intravenous salbutamol (albuterol) reduces lung water in patients with the acute respiratory
distress syndrome (ARDS). Experimental data show that it also reduces pulmonary neutrophil accumulation or
activation and inflammation in ARDS.
Aim: To investigate the effects of salbutamol on neutrophil function.
Methods: The in vitro effects of salbutamol on neutrophil function were determined. Blood and
bronchoalveolar lavage (BAL) fluid were collected from 35 patients with acute lung injury (ALI)/ARDS, 14
patients at risk from ARDS and 7 ventilated controls at baseline and after 4 days’ treatment with placebo or
salbutamol (ALI/ARDS group). Alveolar–capillary permeability was measured in vivo by thermodilution
(PiCCO). Neutrophil activation, adhesion molecule expression and inflammatory cytokines were measured.
Results: In vitro, physiological concentrations of salbutamol had no effect on neutrophil chemotaxis, viability
or apoptosis. Patients with ALI/ARDS showed increased neutrophil activation and adhesion molecule
expression compared with at risk-patients and ventilated controls. There were associations between alveolar–
capillary permeability and BAL myeloperoxidase (r = 0.4, p = 0.038) and BAL interleukin 8 (r = 0.38,
p = 0.033). In patients with ALI/ARDS, salbutamol increased numbers of circulating neutrophils but had no
effect on alveolar neutrophils.
Conclusion: At the onset of ALI/ARDS, there is increased neutrophil recruitment and activation. Physiological
concentrations of salbutamol did not alter neutrophil chemotaxis, viability or apoptosis in vitro. In vivo,
salbutamol increased circulating neutrophils, but had no effect on alveolar neutrophils or on neutrophil
activation. These data suggest that the beneficial effects of salbutamol in reducing lung water are unrelated to
modulation of neutrophil-dependent inflammatory pathways
Evidence for multiple impurity bands in sodium-doped silicon MOSFETs
We report measurements of the temperature-dependent conductivity in a silicon
metal-oxide-semiconductor field-effect transistor that contains sodium
impurities in the oxide layer. We explain the variation of conductivity in
terms of Coulomb interactions that are partially screened by the proximity of
the metal gate. The study of the conductivity exponential prefactor and the
localization length as a function of gate voltage have allowed us to determine
the electronic density of states and has provided arguments for the presence of
two distinct bands and a soft gap at low temperature.Comment: 4 pages; 5 figures; Published in PRB Rapid-Communication
Effects of post-anneal conditions on the dielectric properties of CaCu3Ti4O12 thin films prepared on Pt/Ti/SiO2/Si substrates
High-dielectric-constant CaCu3Ti4O12 (CCTO) thin films were prepared on
Pt/Ti/SiO2/Si(100) substrates by pulsed-laser deposition. The 480 nm thick
polycrystalline films have preferred orientation and show obvious
crystallization on the surface. The temperature-dependence of dielectric
constant and loss of the Pt/CCTO/Pt capacitors is comparable with that of
epitaxial CCTO films grown on oxides substrates. We found that the dielectric
properties are very sensitive to the post-annealing atmosphere and temperature.
Post-annealing in nitrogen atmosphere produces larger low-frequency dielectric
relaxation as the annealing temperature increases, while annealing in oxygen
atmosphere at high temperature suppresses the relaxation but lowers the
dielectric constant. Such results are attributed to the presence of insulating
grain boundary barrier layers.Comment: 10 pages, 3 figure
Membrane in M5-branes Background
In this paper, we investigate the properties of a membrane in the M5-brane
background. Through solving the classical equations of motion of the membrane,
we can understand the classical dynamics of the membrane in this background.Comment: 15 pages, typos correcte
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