1,663 research outputs found

    Results of the 1978 NASA/JPL balloon flight solar cell calibration program

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    The 1978 scheduled solar cell calibration balloon flight was successfully completed. Thirty six modules were carried to an altitude of above 36 kilometers. Recovery of telemetry and flight packages was without incident. These calibrated standard cells are used as reference standards in simulator testing of cells and arrays with similar spectral response characteristics. The factors affecting the spectral transmission of the atmosphere at various altitudes are summarized

    Predictors of ceasing or reducing statin medication following a large increase in the consumer co-payment for medications: A retrospective observation study

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    Objectives: Previous Australian research has shown that following the 21% increase in the patient co-payments in 2005, the use of lipid-lowering therapy declined by 5%. This study aimed to determine the demographic and clinical characteristics of individuals who continued, reduced or ceased their use of statin medication in 2005. Study type: Retrospective observational study using routinely collected administrative data. Method: Pharmaceutical claims, hospital separations, and mortality records from 2000–2005 were used from the Western Australian (WA) population. The cohort comprised stable users of statin medication in 2004. We identified individuals who i) continued using statins, ii) reduced their use by ≥20%, or iii) ceased therapy for at least the first six months in 2005, based on changes in statin use between 2004 and 2005. Multivariate logistic regression models were used to determine whether the demographic and clinical characteristics of the three groups differed. Results: There were 205 924 statin users identified in Australia in 2004. After the January 2005 Pharmaceutical Benefits Scheme (PBS) co-payment increase, 3.2% of individuals ceased their regular statin therapy, 12.9% reduced statin use and 83.9% continued statin usage. This was an increase of 2.1% in statin users reducing or ceasing therapy compared to 2004. Predictors of cessation and reduction of statin therapy included younger age, greater socio-economic disadvantage, residing in very remote areas, having general beneficiary status, being a new statin user, having no prior history of ischaemic heart disease, having no prior history of a coronary artery revascularisation procedure, taking no other cardiovascular medication or diabetic medication, taking an increased number of medications and having a lower adherence level to statin medication in 2004. Conclusion: Compared to 2004, an additional 2.1% of statin users reduced or discontinued medication use in 2005, which may be attributed to an increase in the medication co-payment. Individuals with general beneficiary status, younger and healthier people were at particular risk of cessation or reduction in statin use in 2005

    Spinless Two-Band Model in Infinite Dimensions

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    A spinless two-band model is studied in infinite dimension limit. Starting from the atomic limit, the formal exact solution of the model is obtained by means a perturbative treatment of the hopping and hybridisation terms. The model is solved in closed form in high dimensions assuming no local spin fluctuations. The non-Fermi liquid properties appearing in the metallic phase are analysed through the behaviour of the density of states and the self-energy near the Fermi level.Comment: 4 pages, 3 figures, to appear in PRB-Breif Repor

    Pedestrian Approach to the Two-Channel Kondo Model

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    We reformulate the two-channel Kondo model to explicitly remove the unscattered charge degrees of freedom. This procedure permits us to move the non-Fermi liquid fixed point to infinite coupling where we can apply a perturbative strong-coupling expansion. The fixed point Hamiltonian involves a three-body Majorana zero mode whose scattering effects give rise to marginal self-energies. The compactified model is the N=3 member of a family of "O(N)" Kondo models that can be solved by semiclassical methods in the large NN limit. For odd NN, {\em fermionic} "Kink" fluctuations about the N=N=\infty mean-field theory generate a fermionic NN-body bound-state which asymptotically decouples at low energies. For N=3, our semi-classical methods fully recover the non-Fermi liquid physics of the original two channel model. Using the same methods, we find that the corresponding O(3) Kondo lattice model develops a spin-gap and a gapless band of coherently propagating three-body bound-states. Its strong-coupling limit offers a rather interesting realization of marginal Fermi liquid behavior.Comment: 17 pages, Revtex 3.0. Replaced with fully compiled postscript file

    Knight Shift Anomalies in Heavy Electron Materials

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    We calculate non-linear Knight Shift KK vs. susceptibility χ\chi anomalies for Ce ions possessing local moments in metals. The ions are modeled with the Anderson Hamiltonian and studied within the non-crossing approximation (NCA). The Kvs.χK-vs.- \chi non-linearity diminishes with decreasing Kondo temperature T0T_0 and nuclear spin- local moment separation. Treating the Ce ions as an incoherent array in CeSn3_3, we find excellent agreement with the observed Sn K(T)K(T) data.Comment: 4 pages, Revtex, 3 figures available upon request from [email protected]

    Landau and dynamical instabilities of Bose-Einstein condensates with superfluid flow in a Kronig-Penney potential

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    We study the elementary excitations of Bose-Einstein condensates in a one-dimensional periodic potential and discuss the stability of superfluid flow based on the Kronig-Penney model. We analytically solve the Bogoliubov equations and calculate the excitation spectrum. The Landau and dynamical instabilities occur in the first condensate band when the superfluid velocity exceeds certain critical values, which agrees with the result of condensates in a sinusoidal potential. It is found that the onset of the Landau instability coincides with the point where the perfect transmission of low-energy excitations is forbidden, while the dynamical instability occurs when the effective mass is negative. It is well known that the condensate band has a peculiar structure called swallowtail when the periodic potential is shallow compared to the mean field energy. We find that the upper side of the swallowtail is dynamically unstable although the excitations have the linear dispersion reflecting the positive effective mass.Comment: 6 pages, 2 figures, Proceedings of the International Symposium on Quantum Fluids and Solids (QFS2006

    Small Energy Scale for Mixed-Valent Uranium Materials

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    We investigate a two-channel Anderson impurity model with a 5f15f^1 magnetic and a 5f25f^2 quadrupolar ground doublet, and a 5f25f^2 excited triplet. Using the numerical renormalization group method, we find a crossover to a non-Fermi liquid state below a temperature TT^* varying as the 5f25f^2 triplet-doublet splitting to the 7/2 power. To within numerical accuracy, the non-linear magnetic susceptibility and the 5f15f^1 contribution to the linear susceptibility are given by universal one-parameter scaling functions. These results may explain UBe13_{13} as mixed valent with a small crossover scale TT^*.Comment: 4 pages, 3 figures, REVTeX, to appear in Phys. Rev. Let

    Non-Fermi Liquid Behavior in Dilute Quadrupolar System Prx_{x}La1x_{1-x}Pb3_3 with xx\le0.05

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    We have studied the low-temperature properties of Prx_{x}La1x_{1-x}Pb3_{3} with non-Kramers Γ3\Gamma_{3} quadrupolar moments of the crystal-electric-field ground state, for a wide concentration range of Pr ions. For xx\le0.05, the specific heat C/TC/T increases monotonically below TT=1.5 K, which can be scaled with a characteristic temperature TT^{*} defined at each concentration xx. The electrical resistivity ρ\rho(T)(T) in the corresponding temperature region shows a marked decrease deviating from a Fermi-liquid behavior ρ\rho(T)(T)\proptoT2T^{2}. The Kondo effect arising from the correlation between the dilute Γ3\Gamma_{3} moments and the conduction electrons may give rise to such anomalous behavior
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