Electron-phonon scattering at the intersection of two Landau levels

We predict a double-resonant feature in the magnetic field dependence of the phonon-mediated longitudinal conductivity $\sigma_{xx}$ of a two-subband quasi-two-dimensional electron system in a quantizing magnetic field. The two sharp peaks in $\sigma_{xx}$ appear when the energy separation between two Landau levels belonging to different size-quantization subbands is favorable for acoustic-phonon transitions. One-phonon and two-phonon mechanisms of electron conductivity are calculated and mutually compared. The phonon-mediated interaction between the intersecting Landau levels is considered and no avoided crossing is found at thermal equilibrium.Comment: 13 pages, 8 figure

Landau damping in thin films irradiated by a strong laser field

The rate of linear collisionless damping (Landau damping) in a classical electron gas confined to a heated ionized thin film is calculated. The general expression for the imaginary part of the dielectric tensor in terms of the parameters of the single-particle self-consistent electron potential is obtained. For the case of a deep rectangular well, it is explicitly calculated as a function of the electron temperature in the two limiting cases of specular and diffuse reflection of the electrons from the boundary of the self-consistent potential. For realistic experimental parameters, the contribution of Landau damping to the heating of the electron subsystem is estimated. It is shown that for films with a thickness below about 100 nm and for moderate laser intensities it may be comparable with or even dominate over electron-ion collisions and inner ionization.Comment: 15 pages, 2 figure

Resource-efficient low-loss four-channel active demultiplexer for single photons

We report a design and implementation of a resource-efficient spatial demultiplexer which produces 4 indistinguishable photons with efficiency of 39.7% per channel. Our scheme is based on a free-space storage/delay line which accumulates 4 photons and releases them by a controlled polarization rotation using a single Pockels cell.Comment: 8 pages, 7 figure

Future of superheavy element research: Which nuclei could be synthesized within the next few years?

Low values of the fusion cross sections and very short half-lives of nuclei with Z$>$120 put obstacles in synthesis of new elements. Different nuclear reactions (fusion of stable and radioactive nuclei, multi-nucleon transfers and neutron capture), which could be used for the production of new isotopes of superheavy (SH) elements, are discussed in the paper. The gap of unknown SH nuclei, located between the isotopes which were produced earlier in the cold and hot fusion reactions, can be filled in fusion reactions of $^{48}$Ca with available lighter isotopes of Pu, Am, and Cm. Cross sections for the production of these nuclei are predicted to be rather large, and the corresponding experiments can be easily performed at existing facilities. For the first time, a narrow pathway is found to the middle of the island of stability owing to possible $\beta^+$-decay of SH isotopes which can be formed in ordinary fusion reactions of stable nuclei. Multi-nucleon transfer processes at near barrier collisions of heavy (and very heavy, U-like) ions are shown to be quite realistic reaction mechanism allowing us to produce new neutron enriched heavy nuclei located in the unexplored upper part of the nuclear map. Neutron capture reactions can be also used for the production of the long-living neutron rich SH nuclei. Strong neutron fluxes might be provided by pulsed nuclear reactors and by nuclear explosions in laboratory conditions and by supernova explosions in nature. All these possibilities are discussed in the paper.Comment: An Invited Plenary Talk given by Valeriy I. Zagrebaev at the 11th International Conference on Nucleus-Nucleus Collisions (NN2012), San Antonio, Texas, USA, May 27-June 1, 2012. To appear in the NN2012 Proceedings in Journal of Physics: Conference Series (JPCS

Understanding of Active and Passive Constructions in 7- to 10-Year-Old Russian-Speaking Children: Reliance on Inflections or Word Order

Background. The background of the present study includes analysis of the understanding of active and passive grammatical constructions (GCs) in Russianspeaking aphasic patients and in children aged 3, 4 and 5 years (Akhutina, 1989; Akhutina, Velichkovskiy, & Kempe, 1988). Data regarding the reorganization of the children’s strategies are further compared to GC understanding in children speaking different languages, and their interpretations. Objective. To analyze the variable mechanisms of understanding of reversible GCs in primary-school-age children, namely, to reveal individual differences in reliance on word order or case endings. Design. Ninety-three first-graders, 93 second-graders, and 63 third-graders underwent a neuropsychological assessment and computer-based sentence-topicture test of their understanding of reversible GCs of active/passive voice with direct/reverse word order. The “productivity” of understanding GCs (percent of correct responses) was analyzed through cluster analysis. Results. The cluster analysis divided the children into four clusters. Cluster 1 consisted of eight children with low productivity, who were excluded from further analysis. Cluster 2 was characterized by low productivity in passive direct constructions (Group 1); Cluster 3 comprised children who had low productivity in passive reverse sentences (Group 2). Cluster 4 included children with good understanding of all GCs (Group 3). Between-group differences in productivity and time of correct responses in GCs, as well as neuropsychological indexes, were revealed. Conclusion. The results are consistent with the following hypotheses: (a) Group 1 relies on the rule “The first noun is the agent”, whereas the other two groups use morphological marking; (b) Group 1 is the weakest neuropsychologically, and syntactic understanding processes involve a more diffuse activation of the brain in this group, compared to more successful children; (c) changes in response times from the first to the second grade are under the influence of cerebral changes induced by reading acquisition