On a gas source in a constant force field

The nonbarochronic regular partially invariant submodel of the equations of gas dynamics is studied. The submodel reduces to an implicit ordinary differential equation of the first order for an auxiliary function X = X(x). The physical quantities (velocity, density, and pressure) are expressed in terms of the function X. The properties of the solutions of the equation are investigated and interpreted physically in terms of gas motion. The existence of a shock-wave solution is proved. The properties of the shock adiabat are studied. It is shown that the results obtained are new and differ significantly from the results for the case of no constant force. __________ Translated from Prikladnaya Mekhanika i Tekhnicheskaya Fizika, Vol. 47, No. 6, pp. 3–16, November–December, 2006.     

Chemical Transformations of Tetracyclo[3.3.1.1.3,7.0.1,3]decane (1,3-Dehydroadamantane): VIII. Reaction of 1,3-Dehydroadamantane with Aliphatic Aldehydes

Russian Journal of Organic Chemistry - The reaction of 1,3-dehydroadamantane with aliphatic aldehydes involves the Ca-H bond and forms hardly accessible branched 2-(1-adamantyl)alkylaldehydes in...     

Magnetic-field control of the transmission of a photonic crystal with a liquid-crystal defect

The method of modulation of transmittance of a multilayer photonic crystal with a nematic liquid-crystal defect upon the orientational transition from the homeotropic to the planar state is investigated. The orientation of the director of the nematic is controlled by a magnetic field in the B-effect mode. The method of recurrent relations is used for numerical simulation of transmission spectra of the photonic crystal structure under investigation.     

Atomic dynamics of a <Emphasis Type="Italic">d</Emphasis>-AlNiFe decagonal quasicrystal

The atomic dynamics of an Al_71.3Ni₂₄Fe_4.7 decagonal quasicrystal has been investigated using the isotopic contrast method for inelastic neutron scattering. The partial vibrational spectra of the Ni, Fe, and Al atoms and the spectrum of the thermal vibrations of the alloy have been reconstructed directly from the experimental data without any model assumptions. The cutoff energies and the positions of the main features of the spectra have been determined. It has been revealed that the average binding energy of the nickel atoms in the quasicrystal under investigation is lower than that of the iron atoms and the vibrational spectrum of the aluminum atoms is noticeably harder than the spectrum of the pure metal. The results obtained for the d-AlNiFe decagonal quasicrystal have been compared with the previously published data for an i-AlCuFe icosahedral quasicrystal.     

Melting curve of 4He: no sign of a supersolid transition down to 10 mK

We have measured the melting curve of 4He in the temperature range from 10 to 400 mK with the accuracy of about 0.5 micro bar. Crystals of different quality show the expected T4 dependence in the range from 80 to 400 mK without any sign of the supersolid transition, and the coefficient is in excellent agreement with available data on the sound velocity in liquid 4He and on the Debye temperature of solid 4He. Below 80 mK, we have observed a small deviation from T4 dependence, which, however, cannot be attributed to the supersolid transition, because instead of decrease the entropy of the solid rather remains constant, about 2.5 x 10(-6) R.     

On holomorphic representations of discrete Heisenberg groups

We define a class of monomial not necessary unitary representations of discrete Heisenberg groups. Their moduli space is a complex-analytic manifold. There exist characters of the representations which are automorphic forms on the moduli space.     

Experimental study of the characteristics of high-power laser diode radiation in the above-threshold mode for degradation analysis

The angular dependence of the intensity and contrast of the radiation of laser diodes (LDs) with a CW power of 1.25 W has been investigated in the above-threshold mode. An original method for detecting fundamental lasing is used to analyze the mode structure of the LD radiation at low pump currents. It is shown that this radiation contrast measurement makes it possible to detect the LD degradation in earlier stages than in power measurements.     

Determining the refractive index of a laser diode waveguide from the measured radiation pattern

It is shown that to find the transverse refractive-index profile of a semiconductor laser waveguide, it is sufficient to know the angle of the device’s radiation divergence and two values of the function describing the directional radiation pattern. A calculation technique is proposed and its use in the diagnostics of laser diode degradation is discussed.