628 research outputs found

    Polaronic Signatures in Mid-Infrared Spectra: Prediction for LaMnO3 and CaMnO3

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    Hole-doped LaMnO3 and electron-doped CaMnO3 form self-trapped electronic states. The spectra of these states have been calculated using a two orbital (Mn eg Jahn-Teller) model, from which the non-adiabatic optical conductivity spectra are obtained. In both cases the optical spectrum contains weight in the gap region, whose observation will indicate the self-trapped nature of the carrier states. The predicted spectra are proportional to the concentration of the doped carriers in the dilute regime, with coefficients calculated with no further model parameters.Comment: 6 pages with 3 figures imbedde

    Temperature Dependence of Low-Lying Electronic Excitations of LaMnO_3

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    We report on the optical properties of undoped single crystal LaMnO_3, the parent compound of the colossal magneto-resistive manganites. Near-Normal incidence reflectance measurements are reported in the frequency range of 20-50,000 cm-1 and in the temperature range 10-300 K. The optical conductivity, s_1(w), is derived by performing a Kramers-Kronig analysis of the reflectance data. The far-infrared spectrum of s_1(w) displays the infrared active optical phonons. We observe a shift of several of the phonon to high frequencies as the temperature is lowered through the Neel temperature of the sample (T_N = 137 K). The high-frequency s_1(w) is characterized by the onset of absorption near 1.5 eV. This energy has been identified as the threshold for optical transitions across the Jahn-Teller split e_g levels. The spectral weight of this feature increases in the low-temperature state. This implies a transfer of spectral weight from the UV to the visible associated with the paramagnetic to antiferromagnetic state. We discuss the results in terms of the double exchange processes that affect the optical processes in this magnetic material.Comment: 7 pages, 5 figure

    Competition of charge, orbital, and ferromagnetic correlations in layered manganites

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    The competition of charge, orbital, and ferromagnetic interactions in layered manganites is investigated by magneto-Raman scattering spectroscopy. We find that the colossal magnetoresistance effect in the layered compounds results from the interplay of the orbital and ferromagnetic double-exchange correlations. Inelastic scattering by charge-order fluctuations dominates the quasiparticle dynamics in the ferromagnetic-metal state. The scattering is suppressed at low frequencies, consistent with the opening of a charge-density wave pseudogap.Comment: 10 pages, 4 figure

    Sporting embodiment: sports studies and the (continuing) promise of phenomenology

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    Whilst in recent years sports studies have addressed the calls ‘to bring the body back in’ to theorisations of sport and physical activity, the ‘promise of phenomenology’ remains largely under-realised with regard to sporting embodiment. Relatively few accounts are grounded in the ‘flesh’ of the lived sporting body, and phenomenology offers a powerful framework for such analysis. A wide-ranging, multi-stranded, and interpretatively contested perspective, phenomenology in general has been taken up and utilised in very different ways within different disciplinary fields. The purpose of this article is to consider some selected phenomenological threads, key qualities of the phenomenological method, and the potential for existentialist phenomenology in particular to contribute fresh perspectives to the sociological study of embodiment in sport and exercise. It offers one way to convey the ‘essences’, corporeal immediacy and textured sensuosity of the lived sporting body. The use of Interpretative Phenomenological Analysis (IPA) is also critically addressed. Key words: phenomenology; existentialist phenomenology; interpretative phenomenological analysis (IPA); sporting embodiment; the lived-body; Merleau-Pont

    The Oregon Experiment — Effects of Medicaid on Clinical Outcomes

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    Background: Despite the imminent expansion of Medicaid coverage for low-income adults, the effects of expanding coverage are unclear. The 2008 Medicaid expansion in Oregon based on lottery drawings from a waiting list provided an opportunity to evaluate these effects. Methods: Approximately 2 years after the lottery, we obtained data from 6387 adults who were randomly selected to be able to apply for Medicaid coverage and 5842 adults who were not selected. Measures included blood-pressure, cholesterol, and glycated hemoglobin levels; screening for depression; medication inventories; and self-reported diagnoses, health status, health care utilization, and out-of-pocket spending for such services. We used the random assignment in the lottery to calculate the effect of Medicaid coverage. Results: We found no significant effect of Medicaid coverage on the prevalence or diagnosis of hypertension or high cholesterol levels or on the use of medication for these conditions. Medicaid coverage significantly increased the probability of a diagnosis of diabetes and the use of diabetes medication, but we observed no significant effect on average glycated hemoglobin levels or on the percentage of participants with levels of 6.5% or higher. Medicaid coverage decreased the probability of a positive screening for depression (−9.15 percentage points; 95% confidence interval, −16.70 to −1.60; P=0.02), increased the use of many preventive services, and nearly eliminated catastrophic out-of-pocket medical expenditures. Conclusions: This randomized, controlled study showed that Medicaid coverage generated no significant improvements in measured physical health outcomes in the first 2 years, but it did increase use of health care services, raise rates of diabetes detection and management, lower rates of depression, and reduce financial strain.United States. Dept. of Health and Human Services. Office of the Assistant Secretary for Planning and EvaluationCalifornia HealthCare FoundationNational Institute on Aging (P30AG012810)National Institute on Aging (RC2AGO36631)National Institute on Aging (R01AG0345151)John D. and Catherine T. MacArthur FoundationRobert Wood Johnson FoundationAlfred P. Sloan FoundationSmith Richardson FoundationUnited States. Social Security Administration (5 RRC 08098400-03-00, to the National Bureau of Economic Research as part of the Retirement Research Consortium of the Social Security Administration)Centers for Medicare & Medicaid Services (U.S.

    On the Choice of Shear Correction Factor in Sandwich Structures

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    The first-order shear deformation theory (FSDT) is a relatively simple tool that has been found to yield accurate results in the non-local problems of sandwich structures, such as buckling and free vibration. However, a key factor in practical application of the theory is determination of the transverse shear correction factor (K), which appears as a coefficient in the expression for the transverse shear stress resultant. The physical basis for this factor is that it is supposed to compensate for the FSDT assumption that the shear strain is uniform through the depth of the cross section. In the present paper, the philosophies and results of K determination for homogeneous rectangular cross sections are first reviewed, followed by a review and discussion for the case of sandwich structures. The analysis presented in the paper results in the conclusion that K should be taken equal to unity, as a first approximation, for both two-skin as well as for multi-skin sandwich structures.Yeshttps://us.sagepub.com/en-us/nam/manuscript-submission-guideline

    Modeling the actinides with disordered local moments

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    A first-principles disordered local moment (DLM) picture within the local-spin-density and coherent potential approximations (LSDA+CPA) of the actinides is presented. The parameter free theory gives an accurate description of bond lengths and bulk modulus. The case of ÎŽ\delta-Pu is studied in particular and the calculated density of states is compared to data from photo-electron spectroscopy. The relation between the DLM description, the dynamical mean field approach and spin-polarized magnetically ordered modeling is discussed.Comment: 6 pages, 4 figure

    Pressure-dependence of electron-phonon coupling and the superconducting phase in hcp Fe - a linear response study

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    A recent experiment by Shimizu et al. has provided evidence of a superconducting phase in hcp Fe under pressure. To study the pressure-dependence of this superconducting phase we have calculated the phonon frequencies and the electron-phonon coupling in hcp Fe as a function of the lattice parameter, using the linear response (LR) scheme and the full potential linear muffin-tin orbital (FP-LMTO) method. Calculated phonon spectra and the Eliashberg functions α2F\alpha^2 F indicate that conventional s-wave electron-phonon coupling can definitely account for the appearance of the superconducting phase in hcp Fe. However, the observed change in the transition temperature with increasing pressure is far too rapid compared with the calculated results. For comparison with the linear response results, we have computed the electron-phonon coupling also by using the rigid muffin-tin (RMT) approximation. From both the LR and the RMT results it appears that electron-phonon interaction alone cannot explain the small range of volume over which superconductivity is observed. It is shown that ferromagnetic/antiferromagnetic spin fluctuations as well as scattering from magnetic impurities (spin-ordered clusters) can account for the observed values of the transition temperatures but cannot substantially improve the agreeemnt between the calculated and observed presure/volume range of the superconducting phase. A simplified treatment of p-wave pairing leads to extremely small (≀10−2\leq 10^{-2} K) transition temperatures. Thus our calculations seem to rule out both ss- and pp- wave superconductivity in hcp Fe.Comment: 12 pages, submitted to PR
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