Surface temperature measurement of dielectric materials heated by pulsed laser radiation

The temperature of a dielectric surface irradiated by a laser pulse can be measured by recording the time-resolved resistance change of a thin platinum stripe vapor-deposited on this surface. Results are reported for quartz and glass surfaces exposed to a pulsed CO₂ laser, showing heating rates in excess of 10⁸ K/s.     

A-stability of Runge-Kutta methods for systems with additive noise

Numerical stability of both explicit and implicit Runge-Kutta methods for solving ordinary differential equations with an additive noise term is studied. The concept of numerical stability of deterministic schemes is extended to the stochastic case, and a stochastic analogue of Dahlquist'sA-stability is proposed. It is shown that the discretization of the drift term alone controls theA-stability of the whole scheme. The quantitative effect of implicitness uponA-stability is also investigated, and stability regions are given for a family of implicit Runge-Kutta methods with optimal order of convergence.This author was partially supported by the Italian Consiglio Nazionale delle Ricerche.     

On the breakdown of classical solutions of the planar motion of an elastic string

We prove a result of formation of singularities for the classical solutions of the planar motion of a nonlinear elastic string. In a particular, but physically relevant, case we give a characterization of the global C¹ solutions with positive tension.     

An optimized protocol for anthraquinones isolation from Rhamnus frangula L.

Different from works described in the literature, which use expansive analytical methods to separation of anthraquinones derivatives (AQs), this communication reported a simple and inexpensive methodology to get them. In this way, the expensive commercial AQs: Chrysophanol, physcione and emodine were extracted from plant material (Rhamnus frangula L.) and isolated by classical column chromatography technique under optimised binary mobile phase gradients (CHCl₃ : AcOEt(a), a = 1 to 5%) in excellent yields.     

Potential psychotropic agents. 7-Chloro-9-phenyl-3,3-diethyl-3H-pyrazolo-[5, 1-b]quinazolin-10-ium-2-olate and 9-Chloro-2,3,4,5-tetrahydro-1-methyl-3,3-diethyl-7-phenyl-1H-benzo-1,5,6-triazonine-2,4-dione

2-Amino-5-chloro-α-phenylbenzylidene hydrazone ( 1 ) or its methyl derivative 2 or acetyl derivative 10 react with diethylmalonic esters to give the corresponding malonyl derivatives 3, 4 and 8 . These esters were hydrolyzed to the acids 5 and 6 . Treating 5 with dehydrating agents the mesoionic compound 7-chloro-9-phenyl-3,3-diethyl-3H-pyrazolo[5,1-b]quinazolin-10-ium-2-olate (14) was obtained, while the methyl derivative 6 afforded the desired 9-chloro-2,3,4,5-tetrahydro-1-methyl-3,3-diethyl-7-phenyl-1H-benzo-1,5,6-triazonine-2,4-dione ( 17 ). Some derivatives of these compounds were also described. The structures of the new compounds were confirmed by an alternative synthesis and by mass and prnr spectral data.     

Electrochemical production of NH2• radicals by the system Cu2+/VO2+/NH2OH and their reactions with benzene and toluene

Electroinitiated production of NH₂^. radicals was demonstrated to occur in aqueous acid solution when in the system Cu²⁺/VO²⁺/NH₂OH Cu²⁺ is reduced to metallic copper on a mercury cathode. The first stage of this process involves the reduction of vanadyl to V³⁺ by metallic copper. The electrochemical system Cu²⁺/VO²⁺ was demonstrated to follow a depolarization scheme of the type of the catalyzed electrode process.For the reaction Cu+2 VO²⁺k₁→Cu²⁺+2 V³⁺ a k₁ value of 32 M^?1 s^?1 at 50°C was calculated.The second stage of the process is the reduction of NH₂OH by V³⁺ to give aminyl radicals. In presence of benzene and toluene these radicals add to the aromatic ring to give new radicals which are oxidized by Cu²⁺ to the corresponding amines.The cuzrent yield of this process attains values as high as 70%. The yield dependence on H₂SO₄ concentration, electrolytic current and dioxane concentration is discussed.     

Strong enhancement of the two-photon absorption of tetrakis(4-sulfonatophenyl)porphyrin diacid in water upon aggregation

A strong enhancement of the two-photon absorption (TPA) cross section of tetrakis(4-sulfonatophenyl)porphyrin diacid (H(4)TPPS(2-)) at various wavelengths when a J-type aggregate is formed in water with respect to the one observed for the H(4)TPPS(2-) monomer in a mixture of water, dimethyl sulfoxide (DMSO), and urea is presented. The TPA properties are characterized by the open aperture Z-scan technique and the ultrafast two-photon absorption spectroscopy with white light continuum probe (TPA-WLCP) technique. The observed enhancement is discussed in terms of possible electronic cooperative effects in the aggregate.     

Interior path following primal-dual algorithms. part II: Convex quadratic programming

We describe a primal-dual interior point algorithm for convex quadratic programming problems which requires a total of number of iterations, whereL is the input size. Each iteration updates a penalty parameter and finds an approximate Newton direction associated with the Karush-Kuhn-Tucker system of equations which characterizes a solution of the logarithmic barrier function problem. The algorithm is based on the path following idea. The total number of arithmetic operations is shown to be of the order of O(n ³ L).     

Modified Hadamard transform microchip electrophoresis

Sensitivity is a crucial point in the development applications for medicine or environmental samples in which the analytes are present in the nanomolar range. Besides further technical development of detection systems, the multiplex sample injection technique can be applied for enhancing the signal-to-noise ratio. Hadamard transform is easily applied to microchip electrophoresis due to the fact that sample injection is generally achieved through cross, double-tee, or tee injector structures. This paper reports the first demonstration of a modified Hadamard transform electrophoresis on a microchip by using an amperometric detector. Contrary to the previous Hadamard applications, the resolution (number of points per unit of time) of electropherograms obtained is independent of the number of injections.