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111.
Zhi Ping Xu Zi Gu Xiaoxi Cheng Firas Rasoul Andrew K. Whittaker Gao Qing Max Lu 《Journal of nanoparticle research》2011,13(3):1253-1264
A novel nanocomposite film for sustained release of anionic ophthalmic drugs through a double-control process has been examined
in this study. The film, made as a drug-loaded contact lens, consists principally of a polymer hydrogel of 2-hydroxyethyl
methacrylate (HEMA), in whose matrix MgAl-layered double hydroxide (MgAl-LDH) nanoparticles intercalated with the anionic
drug are well dispersed. Such nanocomposite films (hydrogel-LDH-drug) contained 0.6–0.8 mg of MgAl-LDH and 0.08–0.09 mg of
the ophthalmic drug (ketorolac) in 1.0 g of hydrogel. MgAl-drug-LDH nanoparticles were prepared with the hydrodynamic particle
size of 40–200 nm. TEM images show that these nanoparticles are evenly dispersed in the hydrogel matrix. In vitro release
tests of hydrogel-LDH-drug in pH 7.4 PBS solution at 32 °C indicate a sustained release profile of the loaded drug for 1 week.
The drug release undergoes a rapid initial burst and then a monotonically decreasing rate up to 168 h. The initial burst release
is determined by the film thickness and the polymerization conditions, but the following release rate is very similar, with
the effective diffusion coefficient being nearly constant (3.0 × 10−12 m2/s). The drug release from the films is mechanistically attributed to anionic exchange and the subsequent diffusion in the
hydrogel matrix. 相似文献
112.
Yuliy Baryshnikov Wil Brady Andrew Bressler Robin Pemantle 《Journal of statistical physics》2011,142(1):78-107
We analyze several families of two-dimensional quantum random walks. The feasible region (the region where probabilities do
not decay exponentially with time) grows linearly with time, as is the case with one-dimensional QRW. The limiting shape of
the feasible region is, however, quite different. The limit region turns out to be an algebraic set, which we characterize
as the rational image of a compact algebraic variety. We also compute the probability profile within the limit region, which
is essentially a negative power of the Gaussian curvature of the same algebraic variety. Our methods are based on analysis
of the space-time generating function, following the methods of Pemantle and Wilson (J. Comb. Theory, Ser. A 97(1):129–161,
2002). 相似文献
113.
Symmetry-breaking perturbations destabilize the critical points of the two-channel and two-impurity Kondo models, thereby leading to a crossover from non-Fermi liquid behavior to standard Fermi liquid physics. Here we use an analogy between this crossover and one occurring in the boundary Ising model to calculate the full crossover Green function analytically. In remarkable agreement with our numerical renormalization group calculations, the single exact function applies for an arbitrary mixture of the relevant perturbations in each model. This rich behavior resulting from finite channel asymmetry, interlead charge transfer, and/or magnetic field should be observable in quantum dot or tunneling experiments. 相似文献
114.
Nicola J. van Leeuwen Henrik G. Kjaergaard Andrew C. Wilson 《Journal of Molecular Spectroscopy》2004,228(1):83-91
A highly sensitive cavity-enhanced frequency modulation spectroscopy technique has been used to measure ultraweak transitions in molecular oxygen that had not previously been characterized. The self-broadened half-width and line intensity of the measured transitions are reported. We include 12 high J transitions in the band of 16O2 (the so-called A band), 59 transitions in the hot band of 16O2, and 17 high J transitions in the band of 16O18O. Our measurements of line positions of the 16O18O transitions are used to determine improved molecular constants for the excited state of 16O18O. 相似文献
115.
Andrew P. Mendham Brian S. Potter Rex A. Palmer Trevor J. Dines John C. Mitchell Robert Withnall Babur Z. Chowdhry 《Journal of Raman spectroscopy : JRS》2010,41(2):148-159
Experimental Raman and FT‐IR spectra of solid‐state non‐deuterated and N‐deuterated samples of cyclo(L ‐Met‐L ‐Met) are reported and discussed. The Raman and FT‐IR results show characteristic amide I vibrations (Raman: 1649 cm−1, infrared: 1675 cm−1) for molecules exhibiting a cis amide conformation. A Raman band, assigned to the cis amide II vibrational mode, is observed at ∼1493 cm−1 but no IR band is observed in this region. Cyclo(L ‐Met‐L ‐Met) crystallises in the triclinic space group P1 with one molecule per unit cell. The overall shape of the diketopiperazine (DKP) ring displays a (slightly distorted) boat conformation. The crystal packing employs two strong hydrogen bonds, which traverse the entire crystal via translational repeats. B3‐LYP/cc‐pVDZ calculations of the structure of the molecule predict a boat conformation for the DKP ring, in agreement with the experimentally determined X‐ray structure. Copyright © 2009 John Wiley & Sons, Ltd. 相似文献
116.
The method of weakly nonlinear geometric optics is one of the main formal perturbation techniques used in analyzing nonlinear wave motion for hyperbolic systems. The tacit assumption in using such perturbation methods is that the corresponding solutions of the hyperbolic system remain smooth; since shock waves typically form in such solutions, these assumptions are rarely satisfied in practice. Nevertheless, in a variety of applied contexts, these methods give qualitatively reliable answers for discontinuous weak solutions. Here we give a rigorous proof for the validity of nonlinear geometric optics for general weak solutions of systems of hyperbolic conservation laws in a single space variable. The methods of proof do not mimic the formal construction of weakly nonlinear asymptotics but instead rely on structural symmetries of the approximating equations, stability estimates for intermediate asymptotic times, and the rapid decay in variation of weak solutions for large asymptotic times.Partially supported by NSF Grant No. DMS-8301135Partially supported by NSF Grant No. MCS-81-02360 and ARO Grant No. 483964-25530 相似文献
117.
118.
Adolph Baker 《Physics letters. A》1979,74(5):300-302
Correction of the Glaubner T-matrix to account for target particle motion and energy change in elastic scattering of charged particles from atomic systems is found to vanish to leading order. 相似文献
119.
We consider an extension of the affine scaling algorithm for linear programming problems with free variables to problems having infinitely many constraints, and explore the relationship between this algorithm and the finite affine scaling method applied to a discretization of the problem.This material is based on research supported by Air Force Office of Scientific Research Grant AFOSR 89-0410. 相似文献
120.
Ahlen S Ambrosio M Antolini R Auriemma G Baker R Baldini A Bam BB Barbarino GC Barish BC Battistoni G Bellotti R Bemporad C Bernandini P Bilokon H Bisi V Bloise C Bower C Bussino S Cafagna F Calicchio M Campana D Campana P Carboni M Cecchini S Cei F Chiarella V Cormack R Corona A Coutu S De Cataldo G Dekhissi H De Marzo C De Vincenzi M Di Credico A Diehl E Erriquez O Favuzzi C Ficenec D Forti C Fusco P Giacomelli G Giannini G Giglietto N Giubellino P Grassi M Green P Grillo A Guarino F 《Physical review letters》1994,72(5):608-612