On the first Townsend coefficient at high electric field

Based on the simplified approach it is shown and experimentally confirmed that gas gain in wire chambers at very low pressure becomes higher on thicker wires at the same applied high voltage. This is a consequence of the fact that the first Townsend coefficient at high reduced electric field depends almost entirely on the mean free path of electrons.Comment: 10 pages, 3 figures; version 2: revised, a few references adde

Influence of overload on low-frequency instability of working process in the combustion chamber of the solid propellant rocket engine

In the paper the real oscillatory process is reproduced by statement of direct numerical experiment and the mechanism of occurrence and refill of low-frequency acoustic instability in the combustion chamber of the solid propellant rocket engine with the account of flight overload is investigated for the first time. The direct numerical modeling of low-frequency acoustic instability is carried out by means of Davydov’s method (method of large particles), which is well-suited for the solutions of many problems of mechanics of the continuous media. The results of numerical modeling are presented here. The hydrodynamic highly nonlinear nature of low-frequency fluctuations connected to structure and character of current in the combustion chamber of the rocket engine on firm fuel are proved to be tru

A Variational Approach to Nonlocal Exciton-Phonon Coupling

In this paper we apply variational energy band theory to a form of the Holstein Hamiltonian in which the influence of lattice vibrations (optical phonons) on both local site energies (local coupling) and transfers of electronic excitations between neighboring sites (nonlocal coupling) is taken into account. A flexible spanning set of orthonormal eigenfunctions of the joint exciton-phonon crystal momentum is used to arrive at a variational estimate (bound) of the ground state energy for every value of the joint crystal momentum, yielding a variational estimate of the lowest polaron energy band across the entire Brillouin zone, as well as the complete set of polaron Bloch functions associated with this band. The variation is implemented numerically, avoiding restrictive assumptions that have limited the scope of previous assaults on the same and similar problems. Polaron energy bands and the structure of the associated Bloch states are studied at general points in the three-dimensional parameter space of the model Hamiltonian (electronic tunneling, local coupling, nonlocal coupling), though our principal emphasis lay in under-studied area of nonlocal coupling and its interplay with electronic tunneling; a phase diagram summarizing the latter is presented. The common notion of a "self-trapping transition" is addressed and generalized.Comment: 33 pages, 11 figure

Experimental Modeling of Cosmological Inflation with Metamaterials

Recently we demonstrated that mapping of monochromatic extraordinary light distribution in a hyperbolic metamaterial along some spatial direction may model the flow of time and create an experimental toy model of the big bang. Here we extend this model to emulate cosmological inflation. This idea is illustrated in experiments performed with two-dimensional plasmonic hyperbolic metamaterials. Spatial dispersion which is always present in hyperbolic metamaterials results in scale-dependent (fractal) structure of the inflationary "metamaterial spacetime". This feature of our model replicates hypothesized fractal structure of the real observable universe.Comment: 17 pages, 3 figures. This version is accepted for publication in Physics Letters

Search for Free Decay of Negative Pions in Water and Light Materials

We report on a search for the free decay component of pi- stopped in water and light materials. A non-zero value of this would be an indication of anomalous nu_e contamination to the nu_e and nu_mu_bar production at stopped-pion neutrino facilities. No free decay component of pi- was observed in water, Beryllium, and Aluminum, for which upper limits were established at 8.2E-4, 3.2E-3, and 7.7E-3, respectively

A Method for Regeneration of Spent Electrochemical Decontamination Solution and Its Treatment for Final Disposal

This paper describes the method of regeneration of spent electrochemical decontamination solution. The proposed method allows separation of radionuclides and stable metals from spent decontamination solution in a form suitable for final disposal and repeated use of the remaining solution for electrochemical decontamination. Development of this method was based on the results of the speciation studies which showed that Fe(III) can be precipitated in the presence of organic complexing agents, in a form of iron hydroxide, and Ag-110m, Co-60, Mn-54 radionuclides can be coprecipitated on it. In order to verify the conclusions made as a result of the speciation studies, the experiments with electrochemically prepared simulant solution and real solution were carried out. The test results proved that the proposed method can be applied in practice. Treatment of the ultimately spent decontamination solutions can be also made applying iron precipitation, which allows for removal of the bulk amount of contaminants, as the first step. Then, if necessary the remaining radionuclides can be removed by sorption. A series of novel absorbers has been tested for their potential for the sorption removal of the remaining radionuclides from the supernate. The test results showed that most of them were more effective in neutral or alkaline range of pH, however, the high efficiency of the sorption removal can be achieved only after the removal of the oxalic and citric acids from solution

On the vibron dressing in the α\alpha--helicoidal macromolecular chains

We present a study of the physical properties of the vibrational excitation in $\alpha$--helicoidal macromolecular chains, caused by the interaction with acoustical and optical phonon modes. The influence of the temperature and the basic system parameters on the vibron dressing has been analyzed by employing the simple mean--field approach based on the variational extension of the Lang--Firsov unitary transformation. Applied approach predicts a region in system parameter space where one takes place an abrupt transition from partially dressed (light and mobile) to fully dressed (immobile) vibron states. We found that the boundary of this region depends on system temperature and type of bond among structural elements in the macromolecular chain.Comment: 22 pages, 12 figures, title changed, the interaction with optical phonon modes jointly with acoustical ones added, consideration significantly enlarged, references added, the paper develops the results of arxiv:1210.3918, accepted for publication in Chinese Physics