Experimental investigation and numerical simulation of the influence of resonator-length detuning on the output power,pulse duration and spectral width of a cw mode-locked picosecond optical parametric oscillator

We report on a cw mode-locked non-critically phase matched KTP optical parametric oscillator synchronously pumped by a picosecond Ti:Sapphire laser. High average signal output power of up to 950 mW over a large tuning range has been achieved. For this OPO the influence of resonator-length detuning on the output power, pulse duration and spectral bandwidth has been investigated. The measured data are in good agreement with the results of a numerical simulation using a split-step Fourier method which considers the group-velocity mismatch, the group-velocity dispersion and the self-phase modulation. The numerical simulation also describes the measured strong pump depletion and its influence on the OPO output and efficiency.     

Adiabatic passage Hartmann-Hahn cross polarization in NMR under magic angle sample spinning

We have recently demonstrated that polarization transfer using an adiabatic passage through the Hartmann-Hahn condition (APHH-CP) by a variation of the radio-frequency amplitude can substantially improve the transfer efficiency over Hartmann-Hahn cross polarization. Here we show that APHH-CP can be combined with fast magic angle sample spinning (MAS). The heteronuclear dipolar order, established in the course of the transfer, can indeed be created and preserved.     

An M/G/1 Retrial Queueing System with Two-Phase Service and Preemptive Resume

An M/G/1 retrial queueing system with additional phase of service and possible preemptive resume service discipline is considered. For an arbitrarily distributed retrial time distribution, the necessary and sufficient condition for the system stability is obtained, assuming that only the customer at the head of the orbit has priority access to the server. The steady-state distributions of the server state and the number of customers in the orbit are obtained along with other performance measures. The effects of various parameters on the system performance are analysed numerically. A general decomposition law for this retrial queueing system is established.     

Formation of a two-dimensional periodic structure of local melting regions on a silicon surface upon pulsed light irradiation

The first results regarding the formation of a two-dimensional periodic structure of local melting regions on a silicon surface upon pulsed light irradiation are presented. The conditions are established, and the mechanism of the formation of such structures is discussed. Zh. Tekh. Fiz. 67, 97–99 (December 1997)     

High quantum efficiency of intersubband transitions in coherent tunneling of electrons through asymmetric double-barrier structures

A converging perturbation series that can be summed analytically has been obtained for intersubband transitions of electrons coherently tunneling through the middle of a dimensionally quantized level in an asymmetric double-barrier structure in a high-frequency terahertz electric field. The possibility of a substantial increase in tunneling current accompanied by either absorption or emission of a photon has been demonstrated. The quantum efficiency of radiative transitions between dimensionally quantized levels can be up to 66%. Zh. éksp. Teor. Fiz. 112, 237–245 (July 1997)     

Interaction of 4-aminobenzofurazan with aryldiazonium salts

The reaction of 4-aminobenzofurazan with aryldiazonium salts leads to the formation of 4-amino-5-aryl-azobenzofurazans and 5-amino-2-aryl-4-nitroso-2H-benzotriazoles, products of the rearrangement of the initially formed 4-amino-7-(arylazo)benzofurazans. Oxidation of the benzofurazan as well as of the triazole derivatives gives 7-aryl-1,2,3-triazol[4,5-e]benzofurazans. The chemical properties of some of the compounds obtained have been investigated.Novosibirsk Institute of Organic Chemistry, Siberian Branch, Russian Academy of Sciences, Novosibirsk 630090. Translated from Khimiya Geterotsiklicheskikh Soedinenii, No. 10, pp. 1432–1438, October, 1994. Original article submitted July 25, 1994.     

Hydroxyl-containing mesogens. Synthesis and liquid-crystalline properties of 2-o-hydroxyarylpyrimidines

We have synthesized 5-alkyl(alkoxy)-2-(o-lzydroxy-p-alkoxyphenyl)pyrimidines and considered the effect of the OH group on the inesomorphism. We have found that in binuclear o-hydroxyarylpyrimidines, an ortho OH group forming an intramolecular hydrogen bond increases T_mp, inhibits the appearance of nematic properties, and promotes the appearance of a smectic A.Translated from Khimiya Geterotsiklicheskikh Soedinenii, Vol. 30, No. 1, pp. 90–92, January, 1994.