连续波锁模Pr3+:YLF激光器

本文报导了采用氩离子激光器来泵浦Pr³⁺:YLF晶体,应用声光调制器实现了主动锁模;同时应用振动─高反射平面镜也实现了被动锁模,两种锁模均得到了ps光脉冲.据作者了解这是这种晶体材料的第一次锁模运转.     

Geometrically designed,variable knot regression splines

A new method of Geometrically Designed least squares (LS) splines with variable knots, named GeDS, is proposed. It is based on the property that the spline regression function, viewed as a parametric curve, has a control polygon and, due to the shape preserving and convex hull properties, it closely follows the shape of this control polygon. The latter has vertices whose x-coordinates are certain knot averages and whose y-coordinates are the regression coefficients. Thus, manipulation of the position of the control polygon may be interpreted as estimation of the spline curve knots and coefficients. These geometric ideas are implemented in the two stages of the GeDS estimation method. In stage A, a linear LS spline fit to the data is constructed, and viewed as the initial position of the control polygon of a higher order (\(n>2\)) smooth spline curve. In stage B, the optimal set of knots of this higher order spline curve is found, so that its control polygon is as close to the initial polygon of stage A as possible and finally, the LS estimates of the regression coefficients of this curve are found. The GeDS method produces simultaneously linear, quadratic, cubic (and possibly higher order) spline fits with one and the same number of B-spline coefficients. Numerical examples are provided and further supplemental materials are available online.     

Some Higher-Order Nonlinear Evolution Equations

Nonlinear evolution equations are generated which correspond to isospectral differential-matrix eigenvalue problems. Although not discussed here, this procedure is appropriate for the analysis of the initial-value solution by the inverse-scattering method. In the 2 × 2 case the results obtained are consistent with other more general procedures. It yields the sine-Gordon equation, the reduced Maxwell-Bloch equations for self-induced transparency, and also a type of PBBM equation for long nonlinear water waves. In the n × n case, equations are derived corresponding to a new class of triad and multitriad resonant nonlinear interaction of wave envelopes.     

The numerical integration of relative equilibrium solutions. The nonlinear Schrodinger equation

We analyse different error propagation mechanisms for conservativeand nonconservative time-integrators of nonlinear Schrödingerequations. We use a geometric approach based on interpretingwaves as relative equilibria.     

Concerted and stepwise proton-coupled electron transfers in aquo/hydroxo complex couples in water: oxidative electrochemistry of [Os(II)(bpy)(2)(py)(OH(2))](2+)

Successive oxidation of transition metal(II) aqua complexes (M(II)OH(2) to M(III)OH) is a domain in which proton-coupled electron transfer reactions are extremely common. The mechanism of these PCET reactions-concerted or stepwise-is an important issue in the understanding and design of natural or artificial systems catalyzing the formation of dioxygen by four-electron oxidation of water. Concerted proton-coupled electron transfer from an aqua metal(II) to a hydroxo metal(III) complex requires the close proximity of a proton-accepting group with a pK value between those of the aqua complexes. Otherwise, stepwise electron-proton or proton-electron pathways involving high-energy intermediates are followed. Concerted proton-electron pathways involving water as proton-acceptor or proton-donor group are inefficient. Cyclic voltammetry of the title complex in buffered aqueous solution and re-examination of previous results for the same complex attached to an electrode surface are used to establish these conclusions, which provide a starting point on the route to higher degrees of oxidation, such as those involved in the catalysis of water oxidation.     

Nucleation of lead chromate from homogeneous solution

On the basis of the Christiansen-Nielsen model for nucleation, the nucleus of lead chromate precipitated from homogeneous solution has been found to consist of about five ions. The critical supersaturation values of solutions of lead chromate are dependent upon the method of filtration; however, a change in supersaturation of about 25 % is without effect on the size of the critical nucleus.     

Modulation of 8-Methoxypsoralen-Photoinduced Cutaneous Inflammatory Reactions by Various Chemotherapeutic Agents in vivo

Abstract— Exposure of albino rabbits to UVA-VIS (320-700 nm) radiation after the topical application of 8-methoxypsor-alen (8-MOP) cream is associated with acute cutaneous inflammatory reactions in situ. In the present studies the effects of various agents on 8-MOP plus light induced cutaneous inflammatory response viz. increase in vascular permeability (iVP), accumulation of polymorphonuclear leukocytes (aPMN) and erythema formation were investigated. The inflammatory reactions were induced by a single exposure of 8-MOP-sensitized sites to UVA-VIS (9.4J/cm²) light. Indomethacin, p-bromophenacyl bromide (BPAB), MK886 (trade name of Merck Sharpe & Dome), ibuprofen (IB), nordihydroguaiaretic acid (NDGA) or quinacrine were applied topically in cream base at various times prior to 8-MOP application. The iVP and aPMN were quantitated 24 h postirradiation using ^12SI-HSA and ⁵¹Cr-labeled PMN respectively, while erythema was graded visually. The rate of iVP, aPMN and erythema was inhibited almost completely by indomethacin (7.5-10%) when applied twice, 18 h and 3 h prior to 8-MOP. At lower concentrations of indomethacin (5%) iVP was inhibited whereas aPMN was augmented. The BPAB (0.25%) inhibited more than 90% of 8-MOP-photoinduced iVP and aPMN while there was partial reduction in erythema. The MK886 (0.1%) cream inhibited about 50% of iVP and aPMN but erythema persisted. The agents that are somewhat nonspecific such as IB, quinacrine and NDGA inhibited 8-MOP-photoinduced inflammation only marginally at the concentrations tested. The fact that iVP, aPMN and erythema can be dissociated suggests that there are independent variables in 8-MOP-photoinduced reactions, which involve multifactorial mechanisms probably controlled by different cell-signalling pathways and mediators.