2,221 research outputs found

    Phase diagram and optical conductivity of La1.8-xEu0.2SrxCuO4

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    La1.8-xEu0.2SrxCuO4 (LESCO) is the member of the 214 family which exhibits the largest intervals among the structural, charge ordering (CO), magnetic, and superconducting transition temperatures. By using new dc transport measurements and data in the literature we construct the phase diagram of LESCO between x = 0.8 and 0.20. This phase diagram has been further probed in ac, by measuring the optical conductivity {\sigma}1({\omega}) of three single crystals with x = 0.11, 0.125, and 0.16 between 10 and 300 K in order to associate the extra-Drude peaks often observed in the 214 family with a given phase. The far-infrared peak we detect in underdoped LESCO is the hardest among them, survives up to room temperature and is associated with charge localization rather than with ordering. At the CO transition for the commensurate doping x = 0.125 instead the extra-Drude peak hardens and a pseudogap opens in {\sigma}1({\omega}), approximately as wide as the maximum superconducting gap of LSCO.Comment: 6 pages, 6 figure

    THE CANADA-FRANCE REDSHIFT SURVEY IX: HST Imaging of High-Redshift Field Galaxies

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    HST B and I images are presented of 32 CFRS galaxies with secure redshifts in the range 0.5 < z < 1.2. These galaxies exhibit the same range of morphological types as seen locally, i.e., ellipticals, spirals and irregulars. The galaxies look far less regular in the BB images (rest-frame ultraviolet) than at longer wavelengths, underlining the fact that optical images of galaxies at still higher redshift should be interpreted with caution. Quantitative analyses of the galaxies yield disk sizes, bulge fractions, and colors for each component. At these redshifts, galaxy disks show clear evidence for surface brightness evolution. The mean rest-frame central surface brightness of the disks of normal late-type galaxies is mu_{AB}(B)=20.2 \pm 0.25 mag arcsec^{-2}, about 1.2 mag brighter than the Freeman (1970) value. Some degree of peculiarity is measurable in 10 (30%) of the galaxies and 4 (13%) show clear signs of interaction/mergers. There are 9 galaxies (30%) dominated by blue compact components. These components, which appear to be related to star formation, occur most often in peculiar/asymmetric galaxies (some of which appear to be interacting), but a few are in otherwise normal galaxies. Thus, of the galaxies bluer than present-day Sb, one-third are "blue nucleated galaxies", and half are late-type galaxies with disks which are significantly brighter than normal galaxies at z=0. Taken together, these two effects must be responsible for much of the observed evolution of the luminosity function of blue galaxies.Comment: uuencoded compressed postscript, 8 pages, 1 table + 5 figures in a separate part. Also available at http://www.astro.utoronto.ca/~lilly/CFRS/ . Accepted for publication in ApJ Letter

    Effects of Superconductivity and Charge Order on the sub-Terahertz reflectivity of La1.875_{1.875}Ba0.125−y_{0.125-y}Sry_{y}CuO4_4

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    The reflectivity R(ω)R (\omega) of both the abab plane and the c axis of two single crystals of La1.875_{1.875}Ba0.125−y_{0.125-y}Sry_{y}CuO4_4 has been measured down to 5 cm−1^{-1}, using coherent synchrotron radiation below 30 cm−1^{-1}. For yy = 0.085, a Josephson Plasma Resonance is detected at Tâ‰ȘTcT \ll T_c = 31 K in Rc(ω)R_{c} (\omega), and a far-infrared peak (FIP) appears in the optical conductivity below 50 K, where non-static charge ordering (CO) is reported by X-ray scattering. For yy = 0.05 (TcT_c = 10 K), a FIP is observed in the low-temperature tetragonal phase below the ordering temperature TCOT_{CO}. At 1/8 doping the peak frequency scales linearly with TCOT_{CO}, confirming that the FIP is an infrared signature of CO, either static or fluctuating.Comment: v2: longer version, 9 pages, 6 color figure

    Evolution of Cluster Ellipticals at 0.2 < z < 1.2 from Hubble Space Telescope Imaging

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    Two-dimensional surface photometry derived from Hubble Space Telescope imaging is presented for a sample of 225 early-type galaxies (assumed to be cluster members) in the fields of 9 clusters at redshifts 0.17<z<1.210.17 < z < 1.21. The 94 luminous ellipticals (MAB(B)<−20M_{AB}(B)<-20; selected by morphology alone with no reference to color) form tight sequences in the size-luminosity plane. The position of these sequences shifts, on average, with redshift so that an object of a given size at z=0.55 is brighter by ΔM(B)=−0.57±0.13\Delta M(B)=-0.57 \pm 0.13 mag than its counterpart (measured with the same techniques) in nearby clusters. At z=0.9 the shift is ΔM(B)=−0.96±0.22\Delta M(B)=-0.96 \pm 0.22 mag. If the relation between size and luminosity is universal so that the local cluster galaxies represent the evolutionary endpoints of those at high redshift, and if the size-luminosity relation is not modified by dynamical processes then this population of galaxies has undergone significant luminosity evolution since z=1 consistent with expectations based on models of passively evolving, old stellar populations.Comment: 7 pages, 3 figures, and 1 Tabl

    Liver Transplantation in Adults

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    Human liver transplantation has been possible since 1967. We report our experience in 32 adult patients who received liver transplants at the University of Pittsburgh over a 16‐month period. Survival data, method utilized for patient selection, costs, and morbidity of the procedure are discussed. Copyright © 1982 American Association for the Study of Liver Disease

    50 Ways To Save Your Heart

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    If you want to place a winning bet, bet that heart disease will kill you. Yes, you. Why? Because heart disease kills more people in the U.S. than any other disease, including cancer. We want to reverse that bet and save your life. How? You need to read this book and follow its simple recommendations. Many people have already jumped on the bandwagon and defied the probability of dying from heart disease. This book gives you the easy tools to do just that. Prevention costs practically nothing and you don’t have to give up anything. You only have to eat and be smart about saving your heart.https://digitalrepository.unm.edu/hsc_facbookdisplay/1000/thumbnail.jp

    Atmospheric methanol measurement using selective catalytic methanol to formaldehyde conversion

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    International audienceA novel atmospheric methanol measurement technique, employing selective gas-phase catalytic conversion of methanol to formaldehyde followed by detection of the formaldehyde product, has been developed and tested. The effects of temperature, gas flow rate, gas composition, reactor-bed length, and reactor-bed composition on the methanol conversion efficiency of a molybdenum-rich, iron-molybdate catalyst [Mo-Fe-O] were studied. Best results were achieved using a 1:4 mixture (w/w) of the catalyst in quartz sand. Optimal methanol to formaldehyde conversion (>95% efficiency) occurred at a catalyst housing temperature of 345°C and an estimated sample-air/catalyst contact time of <0.2 seconds. Potential interferences arising from conversion of methane and a number of common volatile organic compounds (VOC) to formaldehyde were found to be negligible under most atmospheric conditions and catalyst housing temperatures. Using the new technique, atmospheric measurements of methanol were made at the University of Bremen campus from 1 to 15 July 2004. Methanol mixing ratios ranged from 1 to 5 ppb with distinct maxima at night. Formaldehyde mixing ratios, obtained in conjunction with methanol by periodically bypassing the catalytic converter, ranged from 0.2 to 1.6 ppb with maxima during midday. These results suggest that selective, catalytic methanol to formaldehyde conversion, coupled with existing formaldehyde measurement instrumentation, is an inexpensive and effective means for monitoring atmospheric methanol
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