86 research outputs found
Epitaxial and layer-by-layer growth of EuO thin films on yttria-stabilized cubic zirconia (001) using MBE distillation
We have succeeded in growing epitaxial and highly stoichiometric films of EuO
on yttria-stabilized cubic zirconia (YSZ) (001). The use of the Eu-distillation
process during the molecular beam epitaxy assisted growth enables the
consistent achievement of stoichiometry. We have also succeeded in growing the
films in a layer-by-layer fashion by fine tuning the Eu vs. oxygen deposition
rates. The initial stages of growth involve the limited supply of oxygen from
the YSZ substrate, but the EuO stoichiometry can still be well maintained. The
films grown were sufficiently smooth so that the capping with a thin layer of
aluminum was leak tight and enabled ex situ experiments free from trivalent Eu
species. The findings were used to obtain recipes for better epitaxial growth
of EuO on MgO (001).Comment: 10 pages, 15 figure
Photoproduction off Nuclei and Point-like Photon Interactions Part I: Cross Sections and Nuclear Shadowing
High energy photoproduction off nuclear targets is studied within the
Glauber-Gribov approximation. The photon is assumed to interact as a
-system according to the Generalized Vector Dominance Model and as a
``bare photon'' in direct scattering processes with target nucleons. We
calculate total cross sections for interactions of photons with nuclei taking
into account coherence length effects and point-like interactions of the
photon. Results are compared to data on photon-nucleus cross sections, nuclear
shadowing, and quasi- elastic -production. Extrapolations of cross
sections and of the shadowing behaviour to high energies are given.Comment: 15 pages, 12 figure
Magnetotransport of CeRhIn5
We report measurements of the temperature-dependent anisotropic resistivity
and in-plane magnetoresistance on single crystals of the tetragonal
heavy-fermion antiferromagnet (TN = 3.8 K) CeRhIn5. The measurements are
reported in the temperature range 1.4 K to 300 K and in magnetic fields to 18
tesla. The resistivity is moderately anisotropic, with a room-temperature
c-axis to in-plane resistivity ratio rho_c/rho_a(300 K) = 1.7. rho(T)
measurements on the non-magnetic analog LaRhIn5 indicate that the anisotropy in
the CeRhIn5 resistivity stems predominately from anisotropy in Kondo-derived
magnetic scattering. In the magnetically ordered regime an applied field H
reduces TN only slightly due to the small ordered moment (0.37mu_B) and
magnetic anisotropy. The magnetoresistance (MR) below TN is positive and varies
linearly with H. In the paramagnetic state a positive MR is present below 7.5
K, while a high-field negative contribution is evident at higher temperatures.
The positive contribution decreases in magnitude with increasing temperature.
Above 40 K the positive contribution is no longer observable, and the MR is
negative. The low-T positive MR results from interactions with the
Kondo-coherent state, while the high-T negative MR stems from single-impurity
effects. The H and T-dependent magnetotransport reflects the magnetic
anisotropy and Kondo interactions at play in CeRhIn5.Comment: submitted to Physical Review
Microbial sulfate reduction and metal attenuation in pH 4 acid mine water
Sediments recovered from the flooded mine workings of the Penn Mine, a Cu-Zn mine abandoned since the early 1960s, were cultured for anaerobic bacteria over a range of pH (4.0 to 7.5). The molecular biology of sediments and cultures was studied to determine whether sulfate-reducing bacteria (SRB) were active in moderately acidic conditions present in the underground mine workings. Here we document multiple, independent analyses and show evidence that sulfate reduction and associated metal attenuation are occurring in the pH-4 mine environment. Water-chemistry analyses of the mine water reveal: (1) preferential complexation and precipitation by H2S of Cu and Cd, relative to Zn; (2) stable isotope ratios of 34S/32S and 18O/16O in dissolved SO4 that are 2–3 ‰ heavier in the mine water, relative to those in surface waters; (3) reduction/oxidation conditions and dissolved gas concentrations consistent with conditions to support anaerobic processes such as sulfate reduction. Scanning electron microscope (SEM) analyses of sediment show 1.5-micrometer, spherical ZnS precipitates. Phospholipid fatty acid (PLFA) and denaturing gradient gel electrophoresis (DGGE) analyses of Penn Mine sediment show a high biomass level with a moderately diverse community structure composed primarily of iron- and sulfate-reducing bacteria. Cultures of sediment from the mine produced dissolved sulfide at pH values near 7 and near 4, forming precipitates of either iron sulfide or elemental sulfur. DGGE coupled with sequence and phylogenetic analysis of 16S rDNA gene segments showed populations of Desulfosporosinus and Desulfitobacterium in Penn Mine sediment and laboratory cultures
The emerging modern face of mood disorders: a didactic editorial with a detailed presentation of data and definitions
The present work represents a detailed description of our current understanding and knowledge of the epidemiology, etiopathogenesis and clinical manifestations of mood disorders, their comorbidity and overlap, and the effect of variables such as gender and age. This review article is largely based on the 'Mood disorders' chapter of the Wikibooks Textbook of Psychiatry http://en.wikibooks.org/wiki/Textbook_of_Psychiatry/Mood_Disorders
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