Synthesis of substituted anthranils by deoxidation of o-nitrosoacetylbenzenes

Substituted anthranils with both electron-donor and electron-acceptor substituents in the 6 position were obtained by deoxidation of o-nitrosoacylbenzenes with triphenylphosphine.     

Autoresonant control of nonlinear mode in ultrasonic transducer for machining applications

Experiments conducted in several countries have shown that the improvement of machining quality can be promoted through conversion of the cutting process into one involving controllable high-frequency vibration at the cutting zone. This is achieved through the generation and maintenance of ultrasonic vibration of the cutting tool to alter the fracture process of work-piece material cutting to one in which loading of the materials at the tool tip is incremental, repetitive and controlled. It was shown that excitation of the high-frequency vibro-impact mode of the tool-workpiece interaction is the most effective way of ultrasonic influence on the dynamic characteristics of machining. The exploitation of this nonlinear mode needs a new method of adaptive control for excitation and stabilisation of ultrasonic vibration known as autoresonance. An approach has been developed to design an autoresonant ultrasonic cutting unit as an oscillating system with an intelligent electronic feedback controlling self-excitation in the entire mechatronic system. The feedback produces the exciting force by means of transformation and amplification of the motion signal. This allows realisation for robust control of fine resonant tuning to bring the nonlinear high Q-factor systems into technological application. The autoresonant control provides the possibility of self-tuning and self-adaptation mechanisms for the system to keep the nonlinear resonant mode of oscillation under unpredictable variation of load, structure and parameters. This allows simple regulation of intensity of the process whilst keeping maximum efficiency at all times. An autoresonant system with supervisory computer control was developed, tested and used for the control of the piezoelectric transducer during ultrasonically assisted cutting. The system has been developed as combined analog-digital, where analog devices process the control signal, and parameters of the devices are controlled digitally by computer. The system was applied for advanced machining of aviation materials.     

Double chirped-pulse-amplification laser: a way to clean pulses temporally

We demonstrate a double chirped-pulse-amplification (CPA) Ti: sapphire laser system that includes two CPA stages with intermediate nonlinear temporal pulse filtering. The method makes it possible to reduce substantially the background of amplified spontaneous emission (ASE), including prepulses and postpulses. An ASE temporal contrast of 10(10) was demonstrated at 20 mJ of output energy and 50-fs pulse duration. The demonstrated scheme is applicable to petawatt power-level laser systems.     

Self-Assembly of Dendritic Micellar Structures Based on Triton X-100 and Branched Poly(ethylene oxide)-containing Cyclodextrins

Interaction between the branched poly(etylene oxide)-containing cyclodextrins and nonionic surfactant Triton X-100 was studied. Amphiphilic character of substituted cyclodextrins where poly(etylene oxide) fragments serve as the hydrophilic moiety and outer cyclodextrin surface, as the hydrophobic moiety. Using two groups of experimental methods, it was shown that substituted -cyclodextrin forms inclusion complexes with hydrophilic poly(ethylene oxide) fragment of Triton X-100 molecule, surfactant molecules being incorporated into a micelle composition. The first group of these methods includes viscometry of solutions and measurement of rotational diffusion coefficient, while the other group (tensiometry, gel permeation chromatography, and spectrophotometry) makes it possible to determine colloidal properties of components. The modified micelles consist of nonionic surfactant molecules, whose outer ends are strung with molecules of substituted cyclodextrins; moreover, their structure resembles that of dendrimers due to arising branchings. Note that the self-assembly method was employed to prepare such dendrimers for the first time.     

The detection of cyclodextrin self-association by titration with dyes

A simple procedure is proposed for the detection of association of cyclodextrins (CDs) and their derivatives in aqueous solutions by analyzing the curves of titration of these substances with dyes. Dissociation constants of cyclodextrin-dye complexes and concentrations of sites involved in the complexation are determined by the nonlinear regression analysis. The processes of CD association were characterized using deviations of the function of CD saturation with ligands from a simple scheme CD + ligand ? complex. Two association mechanisms were disclosed: cooperative association (for α-CD and dihydroxypropyl-β-CD) and step association (for β-CD, dimethyl-β-CD, hydroxypropyl-β-CD, and γ-CD). In the case of stepwise-associating compounds, association constants for head groups of cyclodextrins are found to vary from 3 × 10³ to 8 × 10³ M^?1. The titration data on CD association are confirmed by studying solutions of the above compounds using dynamic light scattering.