4,779 research outputs found
Amorphous thin film growth: theory compared with experiment
Experimental results on amorphous ZrAlCu thin film growth and the dynamics of
the surface morphology as predicted from a minimal nonlinear stochastic
deposition equation are analysed and compared. Key points of this study are (i)
an estimation procedure for coefficients entering into the growth equation and
(ii) a detailed analysis and interpretation of the time evolution of the
correlation length and the surface roughness. The results corroborate the
usefulness of the deposition equation as a tool for studying amorphous growth
processes.Comment: 7 pages including 5 figure
Phonon anomalies and charge dynamics in Fe_{1-x}Cu_{x}Cr_{2}S_{4} single crystals
A detailed investigation of phonon excitations and charge carrier dynamics in
single crystals of Fe_{1-x}Cu_{x}Cr_{2}S_{4} (x = 0, 0.2, 0.4, 0.5) has been
performed by using infrared spectroscopy. In FeCr_{2}S_{4} the phonon
eigenmodes are strongly affected by the onset of magnetic order. Despite
enhanced screening effects, a continuous evolution of the phonon excitations
can be observed in the doped compounds with x = 0.2 (metallic) and x = 0.4, 0.5
(bad metals), but the effect of magnetic ordering on the phonons is strongly
reduced compared to x = 0. The Drude-like charge-carrier contribution to the
optical conductivity in the doped samples indicates that the colossal
magneto-resistance effect results from the suppression of spin-disorder
scattering.Comment: 8 pages, 6 figure
Association of serum-soluble heat shock protein 60 with carotid atherosclerosis: clinical significance determined in a follow-up study
BACKGROUND AND PURPOSE: Previous work has shown that soluble heat shock protein 60 (HSP60; sHSP60), present in circulating blood, is associated with carotid atherosclerosis. In the current evaluation, we tested the hypothesis that sHSP60 levels are associated with the progression of carotid arteriosclerosis, prospectively. METHODS: The association of sHSP60 with early atherogenesis (5-year development and progression of nonstenotic carotid plaques) was investigated as part of the population-based prospective Bruneck Study. The current study focused on the follow-up period between 1995 and 2000 and, thus, included 684 subjects. RESULTS: sHSP60 levels measured in 1995 and 2000 were highly correlated (r=0.40; P<0.001), indicating consistency over a 5-year period. Circulating HSP60 levels were significantly correlated with antilipopolysaccharide and anti-HSP60 antibodies. It was also elevated in subjects with chronic infection (top quintile group of HSP60, among subjects with and without chronic infection: 23.8% versus 17.0%; P=0.003 after adjustment for age and sex). HSP60 levels were significantly associated with early atherogenesis, both in the entire population (multivariate odds ratio, for a comparison between quintile group V versus I+II: 2.0 [1.2 to 3.5] and the subgroup free of atherosclerosis at the 1995 baseline: 3.8 [1.6 to 8.9]). The risk of early atherogenesis was additionally amplified when high-sHSP60 and chronic infection were present together. CONCLUSIONS: Our study provides the first prospective data confirming an association between high levels of sHSP60 and early carotid atherosclerosis. This possibly indicates an involvement of sHSP60 in activating proinflammatory processes associated with early vessel pathology
Effect of inhomogeneity on s-wave superconductivity in the attractive Hubbard model
Inhomogeneous s-wave superconductivity is studied in the two-dimensional,
square lattice attractive Hubbard Hamiltonian using the Bogoliubov-de Gennes
(BdG) mean field approximation. We find that at weak coupling, and for
densities mainly below half-filling, an inhomogeneous interaction in which the
on-site interaction takes on two values, results in a larger
zero temperature pairing amplitude, and that the superconducting can also
be significantly increased, relative to a uniform system with on all
sites. These effects are observed for stripe, checkerboard, and even random
patterns of the attractive centers, suggesting that the pattern of
inhomogeneity is unimportant. Monte Carlo calculations which reintroduce some
of the fluctuations neglected within the BdG approach see the same effect, both
for the attractive Hubbard model and a Hamiltonian with d-wave pairing
symmetry.Comment: 5 pages, 4 figure
Polar phonons and spin-phonon coupling in HgCr2S4 and CdCr2S4
Polar phonons of HgCr2S4 and CdCr2S4 are studied by far-infrared spectroscopy
as a function of temperature and external magnetic field. Eigenfrequencies,
damping constants, effective plasma frequencies and Lyddane-Sachs-Teller
relations, and effective charges are determined. Ferromagnetic CdCr2S4 and
antiferromagnetic HgCr2S4 behave rather similar. Both compounds are dominated
by ferromagnetic exchange and although HgCr2S4 is an antiferromagnet, no phonon
splitting can be observed at the magnetic phase transition. Temperature and
magnetic field dependence of the eigenfrequencies show no anomalies indicating
displacive polar soft mode behavior. However, significant effects are detected
in the temperature dependence of the plasma frequencies indicating changes in
the nature of the bonds and significant charge transfer. In HgCr2S4 we provide
experimental evidence that the magnetic field dependence of specific polar
modes reveal shifts exactly correlated with the magnetization showing
significant magneto-dielectric effects even at infrared frequencies.Comment: 8 pages, 8 figure
An evaluation of Bradfordizing effects
The purpose of this paper is to apply and evaluate the bibliometric method Bradfordizing for information retrieval (IR) experiments. Bradfordizing is used for generating core document sets for subject-specific questions and to reorder result sets from distributed searches. The method will be applied and tested in a controlled scenario of scientific literature databases from social and political sciences, economics, psychology and medical science (SOLIS, SoLit, USB Köln Opac, CSA Sociological Abstracts, World Affairs Online, Psyndex and Medline) and 164 standardized topics. An evaluation of the method and its effects is carried out in two laboratory-based information retrieval experiments (CLEF and KoMoHe) using a controlled document corpus and human relevance assessments. The results show that Bradfordizing is a very robust method for re-ranking the main document types (journal articles and monographs) in today’s digital libraries (DL). The IR tests show that relevance distributions after re-ranking improve at a significant level if articles in the core are compared with articles in the succeeding zones. The items in the core are significantly more often assessed as relevant, than items in zone 2 (z2) or zone 3 (z3). The improvements between the zones are statistically significant based on the Wilcoxon signed-rank test and the paired T-Test
Compactification with Flux on K3 and Tori
We study compactifications of Type IIB string theory on a K3 \times T^2/Z_2
orientifold in the presence of RR and NS flux. We find the most general
supersymmetry preserving, Poincare invariant, vacua in this model. All the
complex structure moduli and some of the Kahler moduli are stabilised in these
vacua. We obtain in an explicit fashion the restrictions imposed by
supersymmetry on the flux, and the values of the fixed moduli. Some T-duals and
Heterotic duals are also discussed, these are non-Calabi-Yau spaces. A
superpotential is constructed describing these duals.Comment: Discussion of susy breaking vacua significantly altere
Middle Atmosphere Dynamics with Gravity Wave Interactions in the Numerical Spectral Model: Tides and Planetary Waves
As Lindzen (1981) had shown, small-scale gravity waves (GW) produce the observed reversals of the zonal-mean circulation and temperature variations in the upper mesosphere. The waves also play a major role in modulating and amplifying the diurnal tides (DT) (e.g., Waltersheid, 1981; Fritts and Vincent, 1987; Fritts, 1995a). We summarize here the modeling studies with the mechanistic numerical spectral model (NSM) with Doppler spread parameterization for GW (Hines, 1997a, b), which describes in the middle atmosphere: (a) migrating and non-migrating DT, (b) planetary waves (PW), and (c) global-scale inertio gravity waves. Numerical experiments are discussed that illuminate the influence of GW filtering and nonlinear interactions between DT, PW, and zonal mean variations. Keywords: Theoretical modeling, Middle atmosphere dynamics, Gravity wave interactions, Migrating and non-migrating tides, Planetary waves, Global-scale inertio gravity waves
Transport, magnetic, thermodynamic and optical properties in Ti-doped Sr_2RuO_4
We report on electrical resistivity, magnetic susceptibility and
magnetization, on heat capacity and optical experiments in single crystals of
Sr_2Ru_(1-x)Ti_xO_4. Samples with x=0.1 and 0.2 reveal purely semiconducting
resistivity behavior along c and the charge transport is close to localization
within the ab-plane. A strong anisotropy in the magnetic susceptibility appears
at temperatures below 100 K. Moreover magnetic ordering in c-direction with a
moment of order 0.01 mu_B/f.u. occurs at low temperatures. On doping the
low-temperature linear term of the heat capacity becomes reduced significantly
and probably is dominated by spin fluctuations. Finally, the optical
conductivity reveals the anisotropic character of the dc resistance, with the
in-plane conductance roughly following a Drude-type behavior and an insulating
response along c
Mitochondrial DNA mutations in renal cell carcinomas revealed no general impact on energy metabolism
Previously, renal cell carcinoma tissues were reported to display a marked reduction of components of the respiratory chain. To elucidate a possible relationship between tumourigenesis and alterations of oxidative phosphorylation, we screened for mutations of the mitochondrial DNA (mtDNA) in renal carcinoma tissues and patient-matched normal kidney cortex. Seven of the 15 samples investigated revealed at least one somatic heteroplasmic mutation as determined by denaturating HPLC analysis (DHPLC). No homoplasmic somatic mutations were observed. Actually, half of the mutations presented a level of heteroplasmy below 25%, which could be easily overlooked by automated sequence analysis. The somatic mutations included four known D-loop mutations, four so far unreported mutations in ribosomal genes, one synonymous change in the ND4 gene and four nonsynonymous base changes in the ND2, COI, ND5 and ND4L genes. One renal cell carcinoma tissue showed a somatic A3243G mutation, which is a known frequent cause of MELAS syndrome (mitochondrial encephalomyopathy, lactic acidosis, stroke-like episode) and specific compensatory alterations of enzyme activities of the respiratory chain in the tumour tissue. No difference between histopathology and clinical progression compared to the other tumour tissues was observed. In conclusion, the low abundance as well as the frequently observed low level of heteroplasmy of somatic mtDNA mutations indicates that the decreased aerobic energy capacity in tumour tissue seems to be mediated by a general nuclear regulated mechanism
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