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Contains reports on two research projects

Communications Biophysics

Contains research objectives and reports on one research project.National Science Foundation(GrantG- 16526)National Institutes of Health (Grant MH-04737-03)National Aeronautics and Space Administration under Grant NsG-49

Intermetallic GaPd2_{2} Thin Films for Selective Hydrogenation of Acetylene

The preparation of single‐phase and catalytically active GaPd2 coatings was accomplished via DC magnetron sputtering using an intermetallic sputter target. Thin and uniform layers were deposited on borosilicate glass, Si(111) and planar as well as micro‐structured stainless steel foils. The specimens were examined regarding their phase composition, film morphology and microstructure. Thin films of different layer thickness were catalytically characterized in the semi‐hydrogenation of acetylene, which was conducted at 473 K and a feed gas composition of 0.5 vol.% C2H2, 5 vol.% H2 as well as 50 vol.% C2H4 in helium. Pre‐reduction of the catalyst was found to be essential to enhance the catalytic selectivity. Sputtered GaPd2 showed a high selectivity of 73 % for the hydrogenation to ethylene at conversion levels above 80 %. The surface‐specific activity was strongly increased to 8.97 molacetylene· (A 0· h)–1 compared to bulk‐ or nanoscale GaPd2 (1.93 and 0.30 molacetylene· (A 0· h)–1, respectively) caused by the high specific surface area of the thin films

Detection of x-rays from galaxy groups associated with the gravitationally lensed systems PG 1115+080 and B1422+231

Gravitational lenses that produce multiple images of background quasars can be an invaluable cosmological tool. Deriving cosmological parameters, however, requires modeling the potential of the lens itself. It has been estimated that up to a quarter of lensing galaxies are associated with a group or cluster which perturbs the gravitational potential. Detection of X-ray emission from the group or cluster can be used to better model the lens. We report on the first detection in X-rays of the group associated with the lensing system PG 1115+080 and the first X-ray image of the group associated with the system B1422+231. We find a temperature and rest-frame luminosity of 0.8 +/- 0.1 keV and 7 +/- 2 x 10^{42} ergs/s for PG 1115+080 and 1.0 +infty/-0.3 keV and 8 +/- 3 x 10^{42} ergs/s for B1422+231. We compare the spatial and spectral characteristics of the X-ray emission to the properties of the group galaxies, to lens models, and to the general properties of groups at lower redshift.Comment: Accepted for publication in ApJ. 17 pages, 5 figures. Minor changes to tex

Stellar Motion around Spiral Arms: Gaia Mock Data

We compare the stellar motion around a spiral arm created in two different scenarios, transient/co-rotating spiral arms and density-wave-like spiral arms. We generate Gaia mock data from snapshots of the simulations following these two scenarios using our stellar population code, SNAPDRAGONS, which takes into account dust extinction and the expected Gaia errors. We compare the observed rotation velocity around a spiral arm similar in position to the Perseus arm, and find that there is a clear difference in the velocity features around the spiral arm between the co-rotating spiral arm and the density-wave-like spiral arm. Our result demonstrates that the volume and accuracy of the Gaia data are sufficient to clearly distinguish these two scenarios of the spiral arms.Comment: 5 pages, 1 figure, to appear in the proceedings of "The Milky Way Unravelled by Gaia: GREAT Science from the Gaia Data Releases", Barcelona, 1-5 December 2014, eds. N. Walton, F. Figueras, C. Soubira

X-ray properties of the Parkes sample of flat-spectrum radio sources: dust in radio-loud quasars?

We investigate the X-ray properties of the Parkes sample of flat-spectrum radio sources using data from the ROSAT All-Sky Survey and archival pointed PSPC observations. In total, 163 of the 323 sources are detected. For the remaining 160 sources 2 sigma upper limits to the X-ray flux are derived. We present power-law photon indices for 115 sources, which were either determined with a hardness ratio technique or from direct fits to pointed PSPC data. For quasars, the soft X-ray photon index is correlated with redshift and with radio spectral index. Webster et al. (1995) discovered many sources with unusually red optical continua among the quasars of this sample and interpreted this result in terms of extinction by dust. Although the X-ray spectra in general do not show excess absorption, we find that low-redshift optically red quasars have significantly lower soft X-ray luminosities on average than objects with blue optical continua. The difference disappears for higher redshifts, as is expected for intrinsic absorption by cold gas associated with the dust. Alternative explanations are briefly discussed. We conclude, however, that dust does play an important role in some of the radio-loud quasars with red optical continua.Comment: 21 pages, 13 figures, to appear in MNRA

A variable neurodegenerative phenotype with polymerase gamma mutation

mtDNA replication and repair, causes mitochondrial diseases including autosomal dominant progressive external ophthalmoplegia (PEO),1 childhood hepato-encephalopathy (Alpers– Huttenlocher syndrome), adult-onset spinocerebellar ataxia, and sensory nerve degeneration with dysarthria and ophthalmoparesis (SANDO)

A Very Radio-Loud Narrow-Line Seyfert 1: PKS 2004-447

We have discovered a very radio-loud Narrow-Line Seyfert 1 candidate: PKS 2004-447. This Seyfert is consistent with the formal definition for NLS1s, although it does not have quite the same spectral features as some typical members of this subclass. Only ROSAT survey data is available at X-ray wavelengths, so it has not been possible to compare this source with other NLS1s at these wavelengths. A full comparison of this source with other members of the subclass will improve our physical understanding of NLS1s. In addition, using standard calculations, we estimate the central black hole to have a mass of $\sim 5 \times 10^6 M_{\odot}$. This does not agree with predictions in the literature, that radio-loud AGN host very massive black holes.Comment: 15 pages, 4 figures, accepted for publication in ApJ, minor typos change