Self-similar gas motions in a gravity field

The decelerating effect of a homogeneous gravity field on the plane shock wave acceleration near the outside surface of a gas layer, initially in equilibrium, is analyzed within the framework of the self-similar formulation. A qualitative investigation is performed, the cases in which the first integrals exist are noted, and certain exact solutions of the problem are obtained at different power laws of the initial density variation.     

Uniform Expansion of a Gravitating Gas

Within the framework of the Newtonian mechanics, we studied the possibility of the formation of a uniformly expanding gravitating gas following the previous compression of a cold rarefied medium (dust). The variable detonation energy release is taken into account. The formulation of the problem is associated with the modeling of the formation of the observable large-scale expansion of the Universe. At the same time, the results obtained can also be applied to the calculation of the gravitational collapse of smaller masses.     

Optimum shape of a cavity for the collection of a soil-saturating viscous fluid

The process of inflow of an oil-bearing fluid from an infinite region of porous soil into a cavity (reservoir) and its subsequent pumping into a well located at the center of the reservoir is investigated. The cavity is chosen from the class of flattened ellipsoids of revolution. Thus, a combined problem of the optimization of the shape of a cavity of given volume for which the maximum seepage flow is achieved and the approximate determination of the additional constraints on the cavity dimensions necessary to ensure the outflow of the oil-bearing fluid is considered.     

Technique of Broadband Measurements of Frequency Conversion Efficiency for Each Harmonique in Frequency Multipliers up to Terahertz Range

The paper describes technique of quantitative analysis of a millimeter- and submillimeter-wave range multipliers performance in particular the measurement of the frequency conversion efficiency. The output power on each harmonic produced by the multiplier can be measured separately without any changes in the setup even in the case of simultaneous emission of all harmonics including the fundamental in a frequency range up to 1 THz and well above. The measuring technique primarily developed for high resolution microwave spectroscopy is based on absorption of radiation in spectral lines of rarefied sample gas and photo-acoustic method of the absorption detection. Sensitivity independence of the detection method on frequency and well known spectral parameters of the lines provide the technique with broadbandness, high spectral resolution and power measurement reliability. Principal limits of measurable radiation power may vary from nanowatts up to hundreds of watts. The technique permits real time operation convenient, e.g., for multiplier tuning. Practical examples include measurements of harmonic generation efficiency of multipliers of 78-118 GHz fundamental frequency range, and power measurement up to 6-th harmonic of 230 GHz fundamental radiation of phase locked Backward Wave Oscillator (BWO).     

Cycles in the Odd-Dimensional Models of Circular Gene Networks

The necessary and sufficient conditions are obtained for the existence of a cycle in an odd-dimensional nonlinear dynamical system that simulates the functioning of the simplest circular gene network. An invariant neighborhood of this cycle is described which is homeomorphic to a torus.     

Mathematical modeling of the first phase of morphogenesis of mechanoreceptors in <Emphasis Type="Italic">D. melanogaster</Emphasis>

The mechanoreceptors (in particular, macrochaetes) of drosophila pass three stages in its development (morphogenesis) whose genetic support is described in terms of gene networks. The key object of the gene networks of macrochaete morphogenesis is the achaete-scute (AS-C) complex of genes. Each mechanoreceptor develops from one parent cell distinguished by high concentration of the AS-C protein. The activity of this complex, which ensures the protein concentration critical for initiating morphogenesis, is determined by the central regulatory contour which includes a system of interactions among certain objects of the networks (genes and their products).     

Application of Gyrotrons for Molecular Gas Spectroscopy

Radiophysics and Quantum Electronics - We give a brief review of the results of using gyrotrons to study molecular spectra by means of a radioacoustic absorption detection (RAD) spectrometer....     

Compact Tunable Radiation Source at 180–1500 GHz Frequency Range

This paper is concerned with development of compact continuously tunable over all the submillimeterwave band (180 – 1500GHz) general purpose radiation source. The source consists of Backward Wave Oscillator (BWO) of the range 180 – 260 GHz or 250 – 375 GHz fixed in a small permanent magnet, followed by specially developed broadband frequency multiplier producing second, third, fourth, fifth and sixth harmonics of BWO fundamental frequency. The conversion losses for all the harmonics are measured. The estimations of output power of the source depending on frequency band are given. The examples of applications are presented in phase lock-in scanning BWO regime.