7,353 research outputs found
Heat conduction in 2D strongly-coupled dusty plasmas
We perform non-equilibrium simulations to study heat conduction in
two-dimensional strongly coupled dusty plasmas. Temperature gradients are
established by heating one part of the otherwise equilibrium system to a higher
temperature. Heat conductivity is measured directly from the stationary
temperature profile and heat flux. Particular attention is paid to the
influence of damping effect on the heat conduction. It is found that the heat
conductivity increases with the decrease of the damping rate, while its
magnitude agrees with previous experimental measurement.Comment: 4 pages, 2 figures, presented in SCCS2008 conferenc
High regioselective acetylation of vitamin A precursors using lipase B from Candida antarctica in organic media
The effect of different reaction parameters was explored on the acylation of primary hydroxyl group of 1,6-diol by lipase B from Candida antarctica catalysis in organic solvent. First, the effect of the organic solvents was investigated, and the highest conversion rate was obtained in n-hexane. Then, the effect of the acyl donor was studied. Among several reactants, including acetic acid and two different acetates, vinyl acetate gave the best yield. A maximum monoester yield of 98.5% was obtained using vinyl acetate as acyl donor in n-hexane at 50°C. The substrate concentration was 25 mmol/L, while the diol to vinyl acetate molar ratio was 1:3. Substrate concentration had to be limited due to an inhibitory effect on enzyme by the diol that caused a decrease on initial reaction rate. To promote initial reaction rate, excess vinyl acetate was used. Under the optimum conditions, the conversion rate and monoacylation selectivity were 98.5 and 100%, respectively. The produced monoester was 6.1 mg/ml, and this amount can be further optimized base on the results presented here.Key word: Acetylation, regioselectivity, immobilized lipase B, biocatalytic processes, vitamin A precursors
Fast and robust population transfer in two-level quantum systems with dephasing noise and/or systematic frequency errors
We design, by invariant-based inverse engineering, driving fields that invert
the population of a two-level atom in a given time, robustly with respect to
dephasing noise and/or systematic frequency shifts. Without imposing
constraints, optimal protocols are insensitive to the perturbations but need an
infinite energy. For a constrained value of the Rabi frequency, a flat
pulse is the least sensitive protocol to phase noise but not to systematic
frequency shifts, for which we describe and optimize a family of protocols.Comment: 7 pages, 2 figure
Fast shuttling of a trapped ion in the presence of noise
We theoretically investigate the motional excitation of a single ion caused
by spring-constant and position uctuations of a harmonic trap during trap
shuttling processes. A detailed study of the sensitivity on noise for several
transport protocols and noise spectra is provided. The effect of slow
spring-constant drifts is also analyzed. Trap trajectories that minimize the
excitation are designed combining invariant-based inverse engineering,
perturbation theory, and optimal control
Coherent control of photon transmission : slowing light in coupled resonator waveguide doped with Atoms
In this paper, we propose and study a hybrid mechanism for coherent
transmission of photons in the coupled resonator optical waveguide (CROW) by
incorporating the electromagnetically induced transparency (EIT) effect into
the controllable band gap structure of the CROW. Here, the configuration setup
of system consists of a CROW with homogeneous couplings and the artificial
atoms with -type three levels doped in each cavity. The roles of three
levels are completely considered based on a mean field approach where the
collection of three-level atoms collectively behave as two-mode spin waves. We
show that the dynamics of low excitations of atomic ensemble can be effectively
described by an coupling boson model. The exactly solutions show that the light
pulses can be stopped and stored coherently by adiabatically controlling the
classical field.Comment: 10 pages, 6 figure
Self-Diffusion in 2D Dusty Plasma Liquids: Numerical Simulation Results
We perform Brownian dynamics simulations for studying the self-diffusion in
two-dimensional (2D) dusty plasma liquids, in terms of both mean-square
displacement and velocity autocorrelation function (VAF). Super-diffusion of
charged dust particles has been observed to be most significant at infinitely
small damping rate for intermediate coupling strength, where the
long-time asymptotic behavior of VAF is found to be the product of and
. The former represents the prediction of early theories in
2D simple liquids and the latter the VAF of a free Brownian particle. This
leads to a smooth transition from super-diffusion to normal diffusion, and then
to sub-diffusion with an increase of the damping rate. These results well
explain the seemingly contradictory scattered in recent classical molecular
dynamics simulations and experiments of dusty plasmas.Comment: 10 pages 5 figures, accepted by PR
Enhanced endothelial cell density on NiTi surfaces with sub-micron to nanometer roughness
The shape memory effect and superelastic properties of NiTi (or Nitinol, a nickel-titanium alloy) have already attracted much attention for various biomedical applications (such as vascular stents, orthodontic wires, orthopedic implants, etc). However, for vascular stents, conventional approaches have required coating NiTi with anti-thrombogenic or anti-inflammatory drug-eluting polymers which as of late have proven problematic for healing atherosclerotic blood vessels. Instead of focusing on the use of drug-eluting anti-thrombogenic or anti-inflammatory proteins, this study focused on promoting the formation of a natural anti-thrombogenic and anti-inflammatory surface on metallic stents: the endothelium. In this study, we synthesized various NiTi substrates with different micron to nanometer surface roughness by using dissimilar dimensions of constituent NiTi powder. Endothelial cell adhesion on these compacts was compared with conventional commercially pure (cp) titanium (Ti) samples. The results after 5 hrs showed that endothelial cells adhered much better on fine grain (<60 μm) compared with coarse grain NiTi compacts (<100 μm). Coarse grain NiTi compacts and conventional Ti promoted similar levels of endothelial cell adhesion. In addition, cells proliferated more after 5 days on NiTi with greater sub-micron and nanoscale surface roughness compared with coarse grain NiTi. In this manner, this study emphasized the positive pole that NiTi with sub-micron to nanometer surface features can play in promoting a natural anti-thrombogenic and anti-inflammatory surface (the endothelium) on a vascular stent and, thus, suggests that more studies should be conducted on NiTi with sub-micron to nanometer surface features
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Characterization of Laser-Resistant Port Wine Stain Blood Vessels Using In Vivo Reflectance Confocal Microscopy.
Background and objectivesPort wine stain (PWS) is a congenital vascular malformation of the human skin. Laser is the treatment of choice for PWS. Laser-resistant PWS is one crucial factor accounting for inadequate treatment outcome, which needs to be fully characterized. This study aims to quantitatively characterize the morphology of laser-resistant PWS blood vessels in the upper papillary dermis using in vivo reflectance confocal microscopy (RCM).Study design/materials and methodsA total of 42 PWS subjects receiving laser treatment from August 2016 through July 2018 were enrolled into this study. Thirty-three subjects had facial PWS; nine had extremity PWS. All subject's PWS received multiplex 585/1,064 nm laser treatment. RCM images were taken before and after treatment. The density, diameter, blood flow, and depth of PWS blood vessels were analyzed.ResultsWe found 44.4% PWS on the extremities (four out of nine subjects) were laser-resistant, which was significantly higher (P < 0.001) when compared with those PWS on the face (15.2%, 5 out of 33 subjects). The laser-resistant facial PWS blood vessels had significantly higher blood flow (1.35 ± 0.26 U vs. 0.89 ± 0.22 U, P < 0.001), larger blood vessel diameters (109.60 ± 18.24 µm vs. 84.36 ± 24.04 µm, P = 0.033) and were located deeper in the skin (106.01 ± 13.87 µm vs. 87.82 ± 12.57 µm, P < 0.001) in the skin when compared with laser-responsive PWS on the face. The average PWS blood vessel density (17.01 ± 4.63/mm2 vs. 16.61 ± 4.44/mm2 , P = 0.857) was not correlated to the laser resistance.ConclusionsLaser-resistant PWS blood vessels had significantly higher blood flow, larger diameters, and were located deeper in the skin. RCM can be a valuable tool for a prognostic evaluation on laser-resistant lesions before treatment, thereby providing guidance for tailored laser treatment protocols, which may improve the therapeutic outcome. The limitations for this study include relative small sample size and acquisitions of different blood vessels before and after 2 months of treatment. Lasers Surg. Med. © 2019 Wiley Periodicals, Inc
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