11,915 research outputs found

    Exact exchange optimized effective potential and self-compression of stabilized jellium clusters

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    In this work, we have used the exchange-only optimized effective potential in the self-consistent calculations of the density functional Kohn-Sham equations for simple metal clusters in stabilized jellium model with self-compression. The results for the closed-shell clusters of Al, Li, Na, K, and Cs with N=N=2, 8, 18, 20, 34, and 40 show that the clusters are 3% more compressed here than in the local spin density approximation. On the other hand, in the LSDA, neglecting the correlation results in a contraction by 1.4%.Comment: 7 pages, RevTex, 5 eps figures, 2 table

    Fatal lymphoproliferation and acute monocytic leukemia-like disease following infectious mononucleosis in the elderly

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    Three elderly patients are reported, in whom serologically confirmed recent infectious mononucleosis is followed by fatal lymphoproliferation (case 1), by acute monocytic leukemia (case 2), and by acute probably monocytic leukemia (case 3)

    Immature Sea Turtles in Gullivan Bay, Ten Thousand Islands, Southwest Florida

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    An in-water survey for immature endangered and threatened sea turtles in the coastal waters of southwest Florida during 1997-2003 yielded 191 Kemp\u27s ridley (Lepidochelys kempi), 15 loggerhead (Caretta caretta), 13 green (Chelonia mydas), and one hybrid hawksbill (Eretmochelys imbricata)-loggerhead turtle. Mean carapace lengths were 40.3 cm minimum straightline carapace length (MSCL) for Kemp\u27s ridley, 65.5 cm MSCL for loggerhead, and 51.6 cm MSCL for green turtles. Fibropapilloma tumors were found on seven of the green turtles and one loggerhead turtle. The mean growth rate of recaptured Kemp\u27s ridleys was 6.3 cm/yr. The nearshore waters of Gullivan Bay in the Ten Thousand Islands are an important developmental habitat for the highly endangered Kemp\u27s ridley turtle, and to a lesser degree, immature loggerhead and green turtles

    Seasonal Migration of Immature Kemp\u27s Ridley Turtles (Lepidochelys kempii Garman) Along the West Coast of Florida

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    Six immature Kemp\u27s ridley turtles (Lepidochelys hempii) were monitored via satellite telemetry to investigate their winter migration on the west coast of Florida. All turtles departed from Cedar Keys in late Nov., migrated southward in Dec., and overwintered in offshore waters from Anclote Keys to Captiva Island during Jan., 120 km and 296 km from Cedar Keys, respectively. Turtles migrated northward in Feb. and began returning to Cedar Keys in March. Five of the turtles occupied relatively small (3.8-48.0 km2) postmigration foraging ranges through Aug. The sixth turtle returned to Waccasassa Bay, east of Cedar Keys, but locational data were insufficient for postmigration analysis. Mean sea surface temperature (SST) used by turtles in Nov. decreased from 23.6 ± 1.9 C during the first 2 weeks to 17.1 ± 1.5 C during the latter 2 weeks, and corresponded to their departure from Cedar Keys. Mean SST used by turtles in Jan. increased from 14.0 ± 1.6 C during the first 2 weeks to 16.6 ± 1.4 C during the latter 2 weeks, and corresponded to the onset of their northward migration. Turtles traveled up to 13-56 km offshore to maximum depths of 15-31 m. Higher proportions of satellite location classes requiring four or more uplinks were obtained during winter months suggesting that turtles spent more time at the surface during their migrations. Further studies are needed to determine possible size-specific differences in depth use and migration patterns, to identify benthic habitats used by Kemp\u27s ridleys during winter migrations, and to determine what anthropogenic impacts occur within their migratory routes along the Florida coast

    Understanding the role of the anode on the polarization losses in high-temperature polymer electrolyte membrane fuel cells using the distribution of relaxation times analysis

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    To investigate the role of the anode on the polarization losses of a High-Temperature Polymer Electrolyte Membrane Fuel Cell (HT-PEMFC), we analyzed impedance data using the Distribution of Relaxation Times (DRT) method. Thereby, we varied the operating conditions of the anode (humidification, nitrogen dilution, and carbon monoxide (CO) impurities) to study its impact on Nyquist plot and DRT spectrum. Humidification of the hydrogen was found to dilute phosphoric acid, which is visible in the DRT. Nitrogen dilution of the anode gas slightly increases the Mass Transport (MT) resistance. Furthermore, CO was added to anode gas fed and it impacts the impedance throughout the whole frequency range, specifically the medium and low-frequency range, typically assigned to ORR kinetics and oxygen MT. For a more detailed analysis of the impedance data, a reference electrode was employed to separate the overpotential caused by each electrode. The DRT spectrum of the anode exhibits only one peak at 1 kHz. In the presence of CO, a second peak arises corresponding to side-reactions occurring as the anodic half-cell potential increases. It was found that the cathode is affected by CO on the anode merely by the lowered cell potential and not by CO directly

    Radiation studies for GaAs in the ATLAS Inner Detector

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    We estimate the hardness factors and the equivalent 1 MeV neutron fluences for hadrons fluences expected at the GaAs positions wheels in the ATLAS Inner Detector. On this basis the degradation of the GaAs particle detectors made from different substrates as a function of years LHC operation is predicted.Comment: 11 pages, 6 Postscript figures, uses elsart.cls, submitted to Nucl. Inst. and Met

    Vortex lattice dynamics in a-NbGe detected by mode-locking experiments

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    We observed mode-locking (ML) of rf-dc driven vortex arrays in a superconducting weak pinning a-NbGe film. The ML voltage shows the expected scaling V∝fBV\propto f\sqrt{B} with ff the rf-frequency and BB the magnetic field. For large dc-velocity (corresponding to a large ML frequency), the ML current step width exhibits a squared Bessel function dependence on the rf-amplitude as predicted for ML of a lattice moving elastically through a random potential.Comment: 2 pages, 2 figures. Contribution to M2S-HTSC Ri
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