The Distance to the Soft Gamma Repeater SGR 1627-41

We report millimeter observations of the line of sight to the recently discovered Soft Gamma Repeater, SGR 1627-41, which has been tentatively associated with the supernova remnant SNR G337.0-0.1 Among the eight molecular clouds along the line of sight to SGR 1627-41, we show that SNR G337.0-0.1 is probably interacting with one of the most massive giant molecular clouds (GMC) in the Galaxy, at a distance of 11 kpc from the sun. Based on the high extinction to the persistent X-ray counterpart of SGR 1627-41, we present evidence for an association of this new SGR with the SNR G337.0-0.1; they both appear to be located on the near side of the GMC. This is the second SGR located near an extraordinarily massive GMC. We suggest that SGR 1627-41 is a neutron star with a high transverse velocity (~ 1,000 \kms) escaping the young (~ 5,000 years) supernova remnant G337.0-0.1Comment: 17 pages, including 2 figures. Accepted for publication in the Astrophysical Journal Letter

Lifetimes of Confined Acoustic Phonons in Ultra-Thin Silicon Membranes

We study the relaxation of coherent acoustic phonon modes with frequencies up to 500 GHz in ultra-thin free-standing silicon membranes. Using an ultrafast pump-probe technique of asynchronous optical sampling, we observe that the decay time of the first-order dilatational mode decreases significantly from \sim 4.7 ns to 5 ps with decreasing membrane thickness from \sim 194 to 8 nm. The experimental results are compared with theories considering both intrinsic phonon-phonon interactions and extrinsic surface roughness scattering including a wavelength-dependent specularity. Our results provide insight to understand some of the limits of nanomechanical resonators and thermal transport in nanostructures

Produção e avaliação da qualidade do leite na microrregião de Castanhal.

bitstream/item/63529/1/Oriental-Doc95.PD

Cimetidine, C10H16N6S, formC: crystal structure and modelling of polytypes using suoperspace approach

An efficient method for modelling a polytypic family is presented with the example of cimetidine in the form C polymorph. The method exploits the (3 + 1)-dimensional superspace model, which is a powerful tool for the description, prediction and understanding of polytype modifications in small-molecule crystallography, as illustrated with this pharmaceutical example

New determinations of gamma-ray line intensities of the Ep = 550 keV and Ep = 1747 keV resonances of the 13-C(p,gamma)14-N reaction

Gamma-ray angular distributions for the resonances at Ep = 550 keV and 1747 keV of the radiative capture reaction 13-C(p,g)14-N have been measured, using intense proton beams on isotopically pure 13-C targets. Relative intensities for the strongest transitions were extracted with an accuracy of typically five per cent, making these resonances new useful gamma-ray standards for efficiency calibration in the energy range Egamma = 1.6 to 9 MeV.Comment: 17 pages, 6 figures, Nuclear Instruments and Methods, Sec. A, accepte

Effects of spatial dispersion in near-field radiative heat transfer between two parallel metallic surfaces

We study the heat transfer between two parallel metallic semi-infinite media with a gap in the nanometer-scale range. We show that the near-field radiative heat flux saturates at distances smaller than the metal skin depth when using a local dielectric constant and investigate the origin of this effect. The effect of non-local corrections is analysed using the Lindhard-Mermin and Boltzmann-Mermin models. We find that local and non-local models yield the same heat fluxes for gaps larger than 2 nm. Finally, we explain the saturation observed in a recent experiment as a manifestation of the skin depth and show that heat is mainly dissipated by eddy currents in metallic bodies.Comment: Version without figures (8 figures in the complete version

SPI observations of positron annihilation radiation from the 4th galactic quadrant: sky distribution

During its first year in orbit the INTEGRAL observatory performed deep exposures of the Galactic Center region and scanning observations of the Galactic plane. We report on the status of our analysis of the positron annihilation radiation from the 4th Galactic quadrant with the spectrometer SPI, focusing on the sky distribution of the 511 keV line emission. The analysis methods are described; current constraints and limits on the Galactic bulge emission and the bulge-to-disk ratio are presented.Comment: 4 pages, 2 figures, accepted for publication in the proceedings of the 5th INTEGRAL worksho