Lyudmil Lyutov

Instrument and methods for surface dilatational rheology measurements

We describe an instrument combining the advantages of two methods, axisymmetric drop shape analysis for well-deformed drops and capillary pressure tensiometry for spherical drops, both used for measuring the interfacial tension and interfacial rheological parameters. The rheological parameters are the complex interfacial elasticity, and the surface elasticity and viscosity of Kelvin-Voigt and Maxwell rheological models. The instrument is applicable for investigation of the effect of different types of surfactants (nonionic, ionic, proteins, and polymers) on the interfacial rheological properties both of air/water and oil/water interfaces, and of interfaces between liquids with equal mass densities. A piezodriven system and a specially designed interface unit, implemented in the instrument, ensure precise control for standard periodic waveforms of surface deformation (sine, square, triangle, and sawtooth) at a fixed frequency, or produce surface deformation at constant rate. The interface unit ensures accurate synchronization between the pressure measurement and the surface control, which is used for real-time data processing and feedback control of drop area in some of the applications.

Strontium atom laser excited by nanosecond pulsed longitudinal He-SrBr2 discharge

An investigation of a strontium bromide vapour laser excited by a nanosecond pulsed longitudinal discharge is presented. The optimal discharge conditions for laser oscillation on several Sr atom and ion lines are found. At multiline output an average laser power of 2.4 W is obtained, more than 80% of which is concentrated at the 6.45 µm Sr atom line.

Experimental study on the spectral and spatial characteristics of a high-power He–SrBr2 laser

An active volume scaling in the bore and length of a Sr atom laser excited in a nanosecond pulse longitudinal He–SrBr2 discharge is carried out. The optimal temperature regime is found for laser oscillation on several different Sr atom and ion lines. The optimal discharge conditions for achieving a maximal multiline average output power are also found. At multiline operation a record average output power of 4.25 W is obtained, more than 90% of which is concentrated on the 6.45 µm Sr atom line. The radial distribution of the laser intensity is obtained experimentally to be a high-beam-quality Gaussian profile.

High-Power Sr Atom Laser Excited in Nanosecond Pulsed Longitudinal

An active volume scaling in bore and length of an Sr atom laser excited in a nanosecond pulsed longitudinal He-SrBr2 discharge is carried out. The optimal discharge conditions for achieving of a maximal average output power at several Sr atom and ion lines are found. At multiline operation, a record average output power of 4.26 W is obtained, more than 90% of which is concentrated on the 6.45- mum Sr atom line.

\hbox{He-SrBr}_{2}

An investigation of a strontium bromide vapor laser excited by a nanosecond pulsed longitudinal discharge is presented. The optimal discharge conditions for laser oscillation on several Sr atom and ion lines are found. At multiline output an average laser power of 2.4 W is obtained, more than 80 % of which is concentrated at the 6.45-μm Sr atom line.

Discharge

Abstract We demonstrate a bottom-up synthesis of structures similar to graphene oxide via a two dimensional polymerization. Experimental evidence and discussion are conveyed as well as a general framework for this two dimensional polymerization. The proposed morphologies and lattice structures of these graphene oxides are derived from aldol condensation of alternating three nucleophilic and three electrophilic centers of benzenetriol.

Strontium bromide vapor laser excited by a nanosecond pulsed longitudinal discharge

Using a gas discharge tube typical for the middle infrared He-SrBr2 laser, a study on gas and electron temperatures of nanosecond pulsed longitudinal discharge in pure He, as well as with Ne admixture, is carried out. Thermal conductivities of Ne-He binary gas systems are obtained on the base of experimental data fit, rigid sphere and 12-6 Lennard-Jones inter-atomic interaction approximations. Assuming that the gas temperature varies only in the radial direction and using the calculated thermal conductivities, analytical solution of the steady-state heat conduction equation is found for uniform power input. Measurement of the relative intensities of some He and Ne spectral lines, originating from different upper levels has enabled us to determine the average electron temperature.

Two dimensional polymerization of graphene oxide: Bottom-up approach

An active volume scaling in bore and length of He-SrBr2 laser excited in nanosecond pulsed longitudinal discharge is carried out. The optimal temperature regime is found for laser oscillation at several different Sr atom and ion lines. Optimal discharge conditions, such as active zone diameter, vapor pressure, buffer-gas pressure, electrical excitation scheme parameters, average input power, pulse repetition frequency, are found. At multiline operation a record average output power of 4.30 W for the Sr atom lasers is obtained, more than 90 % of which is concentrated on the 6.45-μm Sr atom line. A new discharge tube with furtherly increased active volume in bore is developed. The effect of neon additive to the helium buffer gas on the gas and electron temperatures is investigated.