3,641 research outputs found

    Non-Ergodic Behaviour of the k-Body Embedded Gaussian Random Ensembles for Bosons

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    We investigate the shape of the spectrum and the spectral fluctuations of the kk-body Embedded Gaussian Ensemble for Bosons in the dense limit, where the number of Bosons mm \to \infty while both kk, the rank of the interaction, and ll, the number of single-particle states, are kept fixed. We show that the relative fluctuations of the low spectral moments do not vanish in this limit, proving that the ensemble is non-ergodic. Numerical simulations yield spectra which display a strong tendency towards picket-fence type. The wave functions also deviate from canonical random-matrix behaviourComment: 7 pages, 5 figures, uses epl.cls (included

    Clinical Profile of Eprosartan: A Different Angiotensin II Receptor Blocker

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    Rationale. The goal of antihypertensive treatment is to reduce risk of cardiovascular morbidity and mortality. Apart from blood pressure lowering per se, also reducing the activities of the renin-angiotensin system and sympathetic nervous system appears to be important. Angiotensin II receptor blocker drugs (ARBs) have provided a useful class of anti-hypertensive drugs. Eprosartan is a relatively new ARB which is chemically distinct (non-biphenyl, non-tetrazole) from all other ARBs (biphenyl tetrazoles). An analysis has been made on available experimental and clinical data on eprosartan which not only is an effective and well tolerated antihypertensive agent, but also lowers the activities of the renin-angiotensin system and sympathetic nervous system. Experimental and pharmacokinetic studies on eprosartan have shown differences with the other ARBs. The distinct properties of this non-biphenyl, non-tetrazole ARB might be relevant in the effort to reduce cardiovascular risk, also beyond its blood pressure lowering capacity

    The Impact of Medicare's Prospective Payment System on Psychiatric Patients Treated in Scatterbeds

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    Medicare's Prospective Payment System (PPS) for hospitals was phased-in during the 1884 Federal Fiscal Year. While many providers of psychiatric inpatient care were exempted from PPS patients treated in general hospital beds outside of psychiatric units (scatterbeds) were not. This allows for an initial assessment of the impact of PPS on psychiatric patients. We use a single equation model of hospital length of stay to estimate the impact of PPS. We allow for the possibility of both anticipating behavior and slow adjustment to the new payment scheme. The results indicate a substantial response to PPS over the first year of implementation. The estimated response includes sizable anticipatory and slow adjustment components. The findings suggest that policy discussions may be weighted too heavily in the direction of concern over hospital financial status given the ability of hospitals to change their behavior.

    A Fast Converging Fractionally Spaced Equaliser

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    We present subband adaptive structures that can counteract the slow convergence which is imposed on the feed-forward part of a fractionally spaced equaliser by the spectral dynamics of the oversampled channel output. While the prewhitening of the subband approach is therefore beneficial to the feed-forward part, additionally operating the feedback part in subbands results in a more balanced and faster convergence, which is demonstrated in simulations

    The Separable Kernel of Nucleon-Nucleon Interaction in the Bethe-Salpeter Approach

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    The dispersion relations for nucleon-nucleon (NN) T-matrix in the framework of Bethe-Salpeter equation for two spin one-half particle system and with separable kernel of interaction are considered in the paper. The developed expressions are applied for construction of the separable kernel of interaction for S partial-waves in singlet and triplet channels. We calculate the low energy scattering parameters and the phase shifts and also the deuteron binding energy with the separable interaction. The approach can be easily extended to higher partial-waves for NN-scattering and other reactions (anti N N-, pi N-scattering).Comment: RevTex 4 style, 9 pages, 1 figur

    A Performance Comparison of Fullband and Different Subband Equalisers

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    We present two different fractionally spaced (FS) equalisers based on subband methods, with the aim of reducing the computational complexity and increasing the convergence rate of a standard fullband FS equaliser. This is achieved by operating in decimated subbands at a considerably lower update rate and by exploiting the prewhitening effect that a filter bank has on the considerable spectral dynamics of a signal received through a severely distorting channel. The two presented subband structures differ in their level of realising the feedforward and feedback part of the equaliser in the subband domain, with distinct impacts on the updating. Simulation results pinpoint the faster convergence at lower cost for the proposed subband equalisers

    NJL with eight quark interactions: Chiral phases at finite T

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    The thermodynamic potential and thermal dependence of low lying mass spectra of scalars and pseudoscalars are evaluated in a generalized Nambu -- Jona-Lasinio model, which incorporates eight-quark interactions. These are necessary to stabilize the scalar effective potential for the light and strange quark flavors, which would be otherwise unbounded from below. In addition it turns out that they are also crucial to i) lower the temperature of the chiral transition, in conformity with lattice calculations, ii) sharpen the temperature interval in which the crossover occurs, iii) or even allow for first order transitions to occur with realistic quark mass values, from certain critical values of the parameters. These are unprecedented results which cannot be obtained within the NJL approaches restricted to quartic and six-quark interactions.Comment: 6 pages, 3 figures, Talk presented at SCADRON 70 Workshop on Scalar Mesons and Related Topics, Lisbon, 11-16 February 200

    Two-step thermochemical solar-to-fuel efficiency computation of strontium and chromium doped lanthanum manganite perovskite oxides using CALPHAD

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    Reducing greenhouse gas emissions and profiting on novel synthetic fuels to store and buffer energy from renewable sources (such as solar or wind) is a prime strategy to encounter the global energy challenge. Here, two-step thermochemical fuel production is an energy technology utilizing intermittent solar power to convert water and carbon dioxide into syngas, a renewable fuel that can be stored easily and mitigate CO2 emissions. Success of the technology relies on the discovery of materials with a high thermochemical solar-to-fuel efficiency. Perovskites have attracted much attention recently due to impressive fuel productivity[1, 2]. Although a high fuel productivity shows the feasibility of a material, it does not imply that it is the optimum and most efficient material as it depends largely on the operation of the solar-to-fuel reactor [3, 4]. Literature on thermochemical solar-to-fuel efficiency of perovskites is limited and none of the existing studies measures the thermodynamic properties in the entire temperature range relevant for solar-to-fuel production, namely 1000-1800K. In this work, we use oxygen nonstoichiometry from CALPHAD data libraries on A-site doped La1-xSrxMnO3-δ and B-site doped perovskite La0.6Sr0.4Mn1-yCryO3-δ in a relevant temperature range of 1073-1873K to determine the solar thermochemical efficiency. The oxygen nonstoichiometry and thermodynamic properties extracted from CALPHAD libraries are compared to earlier studies of La1-xSrxMnO3-δ for thermochemical fuel production. We discuss diffferences between the earlier extrapolated models and the CALPHAD descriptions on the presented material examples. Specifically, we show thermochemical equilibrium models of fuel productivity supplemented by validations with experimental results on La1-xSrxMnO3-δ in literature. We make predictions on the most efficient material in the composition space La1-xSrxMn1-yCryO3-δ for different conditions. It is shown that the amount of experimental work can be reduced substantially by using the CALPHAD approach and further making predictions for multi-component systems that would be practically unattainable without this method. The solar-to-fuel field will benefit directly from additional thermodynamic data on perovskites in the relevant temperature range. Further, we provide guidelines in terms of key CALPHAD experiments that enables a mapping of the thermodynamic properties of a wide compositional space of perovskites to find materials with a high thermochemical efficiency. 1. McDaniel, A.H., et al., Sr-and Mn-doped LaAlO3−δ for solar thermochemical H2 and CO production. Energy & Environmental Science, 2013. 6(8): p. 2424-2428. 2. Bork, A.H., et al., Perovskite La0.6Sr 0.4Cr1− xCoxO3−δ solid solutions for solar-thermochemical fuel production: strategies to lower the operation temperature. Journal of Materials Chemistry A, 2015. 3(30): p. 15546-15557. 3. Scheffe, J.R., D. Weibel, and A. Steinfeld, Lanthanum–Strontium–Manganese Perovskites as Redox Materials for Solar Thermochemical Splitting of H2O and CO2. Energy & Fuels, 2013. 27(8): p. 4250-4257. 4. Yang, C.-K., et al., Thermodynamic and kinetic assessments of strontium-doped lanthanum manganite perovskites for two-step thermochemical water splitting. Journal of Materials Chemistry A, 2014. 2(33): p. 13612-13623
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