Band structure of (Sr3Sc2O5)Fe2As2 as a possible parent phase for new FeAs superconductors

By means of first-principles FLAPW-GGA calculations, we have investigated the electronic properties of the newly synthesized layered phase - (Sr3Sc2O5)Fe2As2. The electronic bands, density of states and Fermi surface have been evaluated. The resembling of our data for (Sr3Sc2O5)Fe2As2 with band structure pictures of known FeAs superconducting materials may be considered as the theoretical background specifying the possibility for (Sr3Sc2O5)Fe2As2 to become a parent phase for new FeAs superconductors.Comment: 10 pages, 4 figures, 3 table

On upstream influence in supersonic flows

The general problem of propagation of three-dimensional disturbances in viscous supersonic flows is considered in the framework of characteristic analysis. Unlike previous results for linear disturbances we deduce a condition determining nonlinear characteristic surfaces which is exact and therefore allows both qualitative and quantitative studies of the speed of propagation as a function of various physical phenomena. These include negative and adverse pressure gradients, and effects of wall cooling and suction–blowing, which are studied in this work as an illustration of the general theory

On the infeasibility of entanglement generation in Gaussian quantum systems via classical control

This paper uses a system theoretic approach to show that classical linear time invariant controllers cannot generate steady state entanglement in a bipartite Gaussian quantum system which is initialized in a Gaussian state. The paper also shows that the use of classical linear controllers cannot generate entanglement in a finite time from a bipartite system initialized in a separable Gaussian state. The approach reveals connections between system theoretic concepts and the well known physical principle that local operations and classical communications cannot generate entangled states starting from separable states.Comment: 6 pages, 3 figures. To appear in IEEE Transactions on Automatic Control, 201

Comment on `Measurement of the π+p⃗\pi^+ \vec p analyzing power at 68.3 MeV'

We comment on a recent paper by Weiser et al. [Phys. Rev. C {\bf 54}, 1930 (1996)]. The authors have performed a single-energy analysis of $\pi^+ p$ scattering data at 68.3 MeV, finding a value for the $S_{31}$ phase shift about 1^o smaller than found in the Karlsruhe-Helsinki (KH) partial-wave analysis. The authors use this result to argue for a dispersion relation analysis using recently measured data, so that their effect on the $\pi NN$ coupling constant (f^2) and $\Sigma$ amplitude can be determined. We note that these tasks were accomplished prior to the submission of the above paper. We clarify the effect of this new analyzing power data on f^2 and the $\Sigma$ amplitude.Comment: 5 pages of text. Revised according to Referee suggestion

Nanomechanics of a magnetic shuttle device

We show that self sustained mechanical vibrations in a model magnetic shuttle device can be driven by both the charge and the spin accumulated on the movable central island of the device. Different scenarios for how spin- and charge-induced shuttle instabilities may develop are discussed and shown to depend on whether there is a Coulomb blockade of tunneling or not. The crucial role of electronic spin flips in a magnetically driven shuttle is established and shown to cause giant magnetoresistance and dynamic magnetostriction effects

Influence of electric fields on dielectric properties of GPI ferroelectric

Using modified microscopic model of GPI by taking into account the piezoelectric coupling with strains $\varepsilon_i$ in the frames of two-particle cluster approximation, the components of polarization vector and static dielectric permittivity tensor of the crystal at applying the external transverse electric fields $E_1$ and $E_3$ are calculated. An analysis of the influence of these fields on thermodynamic characteristics of GPI is carried out. A satisfactory quantitative description of the available experimental data for these characteristics has been obtained at a proper choice of the model parameters.Comment: 17 pages, 17 figure

Nondispersive X-ray emission analysis for geochemical exploration

Nondispersive X-ray emission technique uses lightweight, and rugged X-ray fluorescence units. The X-ray pulse-height spectra is excited by radioactive isotope sources. The technique is applicable for quantitative and qualitative analyses on complex chemical systems, and satisfies the goals for a lunar geochemical exploration device