Electronic Structure and Thermoelectric Prospects of Phosphide Skutterudites

The prospects for high thermoelectric performance in phosphide skutterudites are investigated based on first principles calculations. We find that stoichiometric CoP_3 differs from the corresponding arsenide and antimonide in that it is metallic. As such the band structure must be modified if high thermopowers are to be achieved. In analogy to the antimonides it is expected that this may be done by filling with La. Calculations for LaFe_4P_12 show that a gap can in fact be opened by La filling, but that the valence band is too light to yield reasonable p-type thermopowers at appropriate carrier densities; n-type La filled material may be more favorable.Comment: 3 pages, 3 figures, 1 tabl

All fiber polarization insensitive detection for spectrometer based optical coherence tomography using optical switch

Polarization dependent image artifacts are common in optical coherence tomography imaging. Polarization insensitive detection scheme for swept source based optical coherence tomography systems is well established but is yet to be demonstrated for all fiber spectrometer-based Fourier domain optical coherence tomography systems. In this work, we present an all fiber polarization insensitive detection scheme for spectrometer based optical coherence tomography systems. Images from chicken breast muscle tissue were acquired to demonstrate the effectiveness of this scheme for the conventional Fourier domain optical coherence tomography system

Electronic structure and bond competition in the polar magnet PbVO3_3

Density functional electronic structure studies of tetragonal PbVO$_3$ are reported. The results show a an important role for both Pb 6$p$ - O 2$p$ and V $d$ - O $p$ bonding, with an interplay between these. This is discussed in relation to the possibility of obtaining magnetoelectric behavior.Comment: 5 page

Properties of large scale plasma flow during the early stage of the plasmaspheric refilling

The objective is to better characterize the macroscopic properties of the interhemisphere plasma flow by solving a more complete set of hydrodynamic equations than that solved previously. Specifically, the ion continuity, momentum and energy equations were solved for the plasma flow along the closed magnetic field lines. During the initial stage of the supersonic outflow in the equatorial region, the ions cool substantially. Using the hydrodynamic model for the large-scale plasma flow, the dynamics of shocks was examined which form in the geomagnetic flux tubes during the early stages of refilling. These shocks are more like those forming in neutral gases than the electrostatic shocks driven by microinstabilities involving ion-ion interaction. Therefore, the shocks seen in the hydrodynamic model are termed as hydrodynamic shocks. Such shocks are generally unsteady and therefore the usual shock jump conditions given by Rankine-Hugoniot relations are not strictly applicable to them. The density, flow velocity and temperature structures associated with the shocks are examined for both asymmetrical and symmetrical flows. In the asymmetrical flow the outflow from one of two conjugate ionospheres is dominant. On the other hand, in the symmetrical case outflows from the two ionospheric sources are identical. Both cases are treated by a two-stream model. In the late type of flow, the early-time refilling shows a relaxation type of oscillation, which is driven by the large-scale interactions between the two identical streams. After this early stage, the resulting temperature structure shows some interesting features. In the equatorial region the streams are isothermal, but in the off-equatorial regions the streams have quite different temperatures, and also densities and flow velocities. The dense and slow stream is found to be warmer than the low-density fast stream. In the late stage of refilling, the temperature is found to steadily increase from the conjugate ionospheres towards the equator; the equatorial temperature is found to be as high as about 8000 K compared to the ionospheric temperature of 3600 K

A New Narrow-Line Seyfert 1 galaxy : RXJ1236.9+2656

We report identification of a narrow-line Seyfert 1 galaxy RXJ1236.9+2656. X-ray emission from the NLS1 galaxy undergoes long-term variability with 0.1--2.0 keV flux changing by a factor of 2 within about 3 yr. The ROSAT PSPC spectrum of RXJ1236.9+2656 is well represented by a power-law of Gamma = 3.7 absorbed by matter in our own Galaxy (N_H = 1.33X10^20 cm**-2). Intrinsic soft X-ray luminosity of the NLS1 galaxy is estimated to be 1.5X10^43 erg/s in the energy band of 0.1-2.0 keV. The optical spectrum of RXJ1236.9+2656 is typical of NLS1 galaxies and shows narrow Balmer emission lines (1100 km/s < FWHM < 1700 km/s) of Hbeta, Halpha, and forbidden lines of [O III] and [N II]. Fe II multiplets, usually present in optical spectra of NLS1 galaxies, are also detected in RXJ1236.9+2656.Comment: 4 pages, A&A style Latex, To apear in A&A as a research not