Four particle exchange in solid He-3

Calculations which demonstrate a physically important four-atom exchange process in bodycentered cubic He crystal and thus an important four-spin term in the exchange Hamiltonian are discussed. A simple, mean-field analysis of this Hamiltonian appears to account for a number of the perplexing properties of bodycentered cubic He crystal. It is suggested that an understanding of other properties may require treatment of the exact four-spin term

Thermodynamic and spectral properties of compressed Ce calculated by the merger of the local density approximation and dynamical mean field theory

We have calculated thermodynamic and spectral properties of Ce metal over a wide range of volume and temperature, including the effects of 4f electron correlations, by the merger of the local density approximation and dynamical mean field theory (DMFT). The DMFT equations are solved using the quantum Monte Carlo technique supplemented by the more approximate Hubbard I and Hartree Fock methods. At large volume we find Hubbard split spectra, the associated local moment, and an entropy consistent with degeneracy in the moment direction. On compression through the volume range of the observed gamma-alpha transition, an Abrikosov-Suhl resonance begins to grow rapidly in the 4f spectra at the Fermi level, a corresponding peak develops in the specific heat, and the entropy drops rapidly in the presence of a persistent, although somewhat reduced local moment. Our parameter-free spectra agree well with experiment at the alpha- and gamma-Ce volumes, and a region of negative curvature in the correlation energy leads to a shallowness in the low-temperature total energy over this volume range which is consistent with the gamma-alpha transition. As measured by the double occupancy, we find a noticeable decrease in correlation on compression across the transition; however, even at the smallest volumes considered, Ce remains strongly correlated with residual Hubbard bands to either side of a dominant Fermi-level structure. These characteristics are discussed in light of current theories for the volume collapse transition in Ce.Comment: 19 pages including 14 eps figure

Values of grass silage for finishing beef heifers : in vitrio studies

A two-year study was conducted with 98 growing/ finishing Hereford heifers to: (1) determine if the initial starting weight of heifers affects their use of forage; (2) determine if winter feeding level affects subsequent performance on high forage rations; (3) to collect data regarding the potential grain savings with a predominantly forage ration. Heifers weighing 500-550 pounds had significantly (P \u3c .05) higher final weights and carcass weights than 400-450 pound heifers. Lighter weight heifers had a greater economy of gain. Heifers on a restricted wintering level had slightly higher average daily gains in the feeding period directly following the wintering phase, however, overall average daily gains, final weights, and carcass weights were slightly higher for heifers fed ad libitum during the wintering period. There were no significant effects on carcass charac-teristics due to the initial weight of the heifers or to wintering level. Heifers finished on ground ear corn consumed 421 pounds (7.5 bu.) more corn per head than heifers finished on grass silage with limited concentrates. However, the finishing period was 75 days shorter for corn-fed heifers. In a second study, the chemical composition and in vitro dry matter digestibility (IVDDM) of ladino-orchardgrass silage and wheat silage were compared at four stages of maturity to determine: (1) the effect of stage of maturity on chemical composition and IVDDM; and (2) to compare the IVDDM of small grain silage and perennial grass silage. Comparisons of the pre-bloom, early bloom, late bloom, and post bloom stages of maturity showed that silage cut in the pre-bloom stage was higher in ash and crude protein and lower in lignin. IVDDM decreased with increasing maturity but this decrease was not significant for the first three cuttings. The IVDDM of wheat silage and ladino-orchardgrass silage was not significantly different

Happiness Comes Naturally: Engagement with Nature as a Route to Positive Subjective Well-Being

Empirical research consistently indicates that contact with the natural world is associated with broad psychological and physical benefit. Of particular interest are findings indicating that exposure to natural environments improves subjective well-being, suggesting that interacting with nature may be one route by which individuals may achieve and maintain a durable sense of happiness. In the current chapter, key concepts and influential theories concerning the effects of nature on well-being are described. Empirical research detailing the salutogenic effects of nature is then reviewed, with emphasis placed on four main areas of inquiry: (1) exposure to natural environments; (2) connectedness to nature and well-being; (3) physical proximity to nature; and (4) green exercise. Current limitations in the extant literature are discussed, and priorities for future research are outlined. Based on the present state of research in this domain, it is concluded that ample evidence documents the positive effects of nature on subjective well-being. However, additional research examining group differences in responses to nature, causal mechanisms accounting for the relationship between nature and well-being, and environmental factors impacting the effects of nature on well-being, among other topics, is necessary to develop a comprehensive and more nuanced understanding of the myriad ways in which happiness may be achieved through engagement with the natural world

Comparing Line and HR Executives’ Perceptions of HR Effectiveness: Services, Roles, and Contributions

This study compared HR and line executives’ evaluations of the effectiveness of the HR function in terms of its service delivery, roles, and contributions to the firm. Survey responses from 44 HR and 59 line executives from 14 companies indicated that (a) HR executives consistently rated the functions effectiveness higher than did line executives, and (b) the greatest differences were observed on the more important and/or strategic aspects of HR. Implications are discussed

Measurement Error in Research on Human Resource Decisions and Firm Performance: How Much Error is There and How Does its Influence Effect Size Estimates?

Recent empirical research finds that the relationship between human resource (HR) decisions and firm performance is significant in both statistical and practical terms. However, the typical research design in this area relies upon on a single respondent to validly assess firmwide HR practices. To date, no study has adequately addressed the reliability of such measures, a basic requirement of construct validity. Previous efforts have either defined reliability so narrowly as to miss a major source of measurement error (raters) or have estimated the unreliability due to raters using incorrect methods. In both cases, the result is upwardly biased estimates of reliability. We estimate reliabilities using intraclass correlation and generalizability coefficients. Our reliability estimates suggest substantial measurement error in the types of HR effectiveness and HR practice measures typically used to predict firm performance. We discuss how this degree of measurement influences research and policy implications

The electronic Hamiltonian for cuprates

A realistic many-body Hamiltonian for the cuprate superconductors should include both copper d and oxygen p states, hopping matrix elements between them, and Coulomb energies, both on-site and inter-site. We have developed a novel computational scheme for deriving the relevant parameters ab initio from a constrained occupation local density functional. The scheme includes numerical calculation of appropriate Wannier functions for the copper and oxygen states. Explicit parameter values are given for La2CuO4. These parameters are generally consistent with other estimates and with the observed superexchange energy. Secondly, we address whether this complicated multi-band Hamiltonian can be reduced to a simpler one with fewer basis states per unit cell. We propose a mapping onto a new two-band effective Hamiltonian with one copper d and one oxygen p derived state per unit cell. This mapping takes into account the large oxygen-oxygen hopping given by the ab initio calculations