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41.
It is shown that photorefractive wave-mixing gives saturable gain, saturable absorption and Kerr-like nonlinear phase retardation. An analogy between photorefractive two-beam coupling and two-level atom system is then drawn. We investigate optical bistability in a ring cavity, utilizing these phenomena, and compare our results with classical absorptive and dispersive optical bistability. 相似文献
42.
A model is introduced to investigate the transport properties of an inhomogeneously dense flexible chain particle. The specific model used is a sedimenting non-neutrally buoyant inhomogenously weighted flexible Brownian dumbbell, and it is shown that density inhomogeneity gives rise to a novel coupling effect between the "shape-fluctuation" and "size-fluctuation" dispersion mechanisms. The previously reported shape-fluctuation dispersion term stems from the dumbbell's nonspherical shape and the ensuing anisotropic mobility tensor, while the already investigated size fluctuation term is the result of the dependence of the overall dumbbell translational mobility on the separation distance between the constitutive spheres. Because the density of the constitutive spheres is unequal, the external force simultaneously reorients and deforms the flexible dumbbell, and it is this mutual dependence between dumbbell orientation and size that induces the coupling. Numerical results are presented for the case of a tethered dumbbell composed of two spheres, identical in size but differing in density. The "weak-field" limit is addressed, where the externally applied torque and particle deformation forces are dominated by the thermal fluctuations associated with rotational and deformation Brownian motion. This numerical solution, obtained by including a large number of higher order hydrodynamic interactions (120 terms), describes the Brownian particle's long-time transport without resorting to ad hoc approximations, such as preaveraging the hydrodynamic force or incorporating only first-order hydrodynamic interaction effects (such as employing the Burgers-Oseen tensor). Separate analytical solutions, based on these respective approximations, are also presented and it is concluded that in the limit of "long tethers," where the ratio of tether length to sphere size is greater than seven, no more than 15% error is introduced by neglecting higher-order hydrodynamic interactions. Similarly, the preaveraging approximation introduces no more than a few percent error in the limit of "almost-rigid" dumbbells, where the ratio of tether length to sphere size is less than three. For tethers of "intermediate" length, the full numerical solution must be employed. 相似文献
43.
Shimon Gross Alexander Brandis Louise Chen Varda Rosenbach-Belkin Susanne Roehrs Avigdor Scherz Yoram Salomon 《Photochemistry and photobiology》1997,66(6):872-878
Abstract— A model for studying the efficiency of photodynamic action with a photosensitizer placed exclusively on the bacterial cell wall has been used. Bacteriochlorophyllide molecules, conjugated to rabbit immunoglobulin G (IgG), were synthesized. The conjugated pigment bacteriochlo-rophyll (Bchl)-IgG bound with high specificity to protein-A residues naturally exposed on the cell wall of the bacterium Staphylococcus aureus Cowan I. In bacterial suspensions the phototoxicity of the targeted conjugates (0.5-2.5 pigment per IgG molecule) was dose dependent (LD50 = 1.7 μ M ) in the presence of light (Λ > 550 nm) and inhibited by native IgG but not by ovalbumin, suggesting selective interaction with protein-A on the bacterial cell wall. No dark toxicity was noticed even with the highest conjugate concentration tested. In contrast, the photocytotoxicity of bacteriochlorophyll-serine (Bchl-Ser, LD50 = 0.07 μ M ) used as a nontargeted control was not inhibited by IgG. In spite of its lower apparent potency, Bchl-IgG was found to be 30 times more efficacious than Bchl-Ser: At LD50 , only 66000 Bchl-IgG molecules were bound per bacterium compared to 1900 000 molecules of Bchl-Ser. The higher efficacy of Bchl-IgG is explained by its exclusive position on the bacterial cell wall. Consequently, photogeneration of oxidative species is confined to the cell wall and its vicinity, a seemingly highly susceptible domain for photodynamic action. In considering the design of cell-specific sensitizers for bacterial and cancer therapies, it would be beneficial to identify the more discretely sensitive subcellular domains as targets. 相似文献
44.
An infinite cardinal λ is Magidor if and only if . It is known that if λ is Magidor then for some , and the first such α is denoted by . In this paper we try to understand some of the properties of . We prove that can be the successor of a supercompact cardinal, when λ is a Magidor cardinal. From this result we obtain the consistency of being a successor of a singular cardinal with uncountable cofinality. 相似文献
45.
46.
Technical Physics - We report on the results of analysis of parameters of a laser-induced plasma, which were obtained using emission diagnostics of a laser torch plasma from a CuInSe2... 相似文献
47.
System with Potential Dual Modes of Metal–Ligand Cooperation: Highly Catalytically Active Pyridine‐Based PNNH–Ru Pincer Complexes 下载免费PDF全文
Dr. Peng Hu Dr. Gregory Leitus Dr. Linda J. W. Shimon Prof. Dr. David Milstein 《Chemistry (Weinheim an der Bergstrasse, Germany)》2014,20(48):15727-15731
Metal–ligand cooperation (MLC) plays an important role in catalysis. Systems reported so far are generally based on a single mode of MLC. We report here a system with potential for MLC by both amine–amide and aromatization–dearomatization ligand transformations, based on a new class of phosphino–pyridyl ruthenium pincer complexes, bearing sec‐amine coordination. These pincer complexes are effective catalysts under unprecedented mild conditions for acceptorless dehydrogenative coupling of alcohols to esters at 35 °C and hydrogenation of esters at room temperature and 5 atm H2. The likely actual catalyst, a novel, crystallographically characterized monoanionic de‐aromatized enamido–RuII complex, was obtained by deprotonation of both the N?H and the methylene proton of the N‐arm of the pincer ligand. 相似文献
48.
Dr. Orestes Rivada‐Wheelaghan Dr. Subrata Chakraborty Dr. Linda J. W. Shimon Yehoshoa Ben‐David Prof. David Milstein 《Angewandte Chemie (International ed. in English)》2016,55(24):6942-6945
Efficient iron‐catalyzed homocoupling of terminal alkynes and cross‐dimerization of aryl acetylenes with trimethylsilylacetylene is reported. The complex [Fe(H)(BH4)(iPr‐PNP)] ( 1 ) catalyzed the (cross‐)dimerization of alkynes at room temperature, with no need for a base or other additives, to give the corresponding dimerized products with Z selectivity in excellent yields (79–99 %). 相似文献
49.
Dr. You-Quan Zou Dr. Niklas von Wolff Dr. Michael Rauch Dr. Moran Feller Dr. Quan-Quan Zhou Dr. Aviel Anaby Dr. Yael Diskin-Posner Dr. Linda J. W. Shimon Dr. Liat Avram Yehoshoa Ben-David Prof. Dr. David Milstein 《Chemistry (Weinheim an der Bergstrasse, Germany)》2021,27(14):4715-4722
Glycolic acid is a useful and important α-hydroxy acid that has broad applications. Herein, the homogeneous ruthenium catalyzed reforming of aqueous ethylene glycol to generate glycolic acid as well as pure hydrogen gas, without concomitant CO2 emission, is reported. This approach provides a clean and sustainable direction to glycolic acid and hydrogen, based on inexpensive, readily available, and renewable ethylene glycol using 0.5 mol % of catalyst. In-depth mechanistic experimental and computational studies highlight key aspects of the PNNH-ligand framework involved in this transformation. 相似文献
50.