1,019 research outputs found

    Heat capacity studies of Ce and Rh site substitution in the heavy fermion antiferromagnet CeRhIn_5;: Short-range magnetic interactions and non-Fermi-liquid behavior

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    In heavy fermion materials superconductivity tends to appear when long range magnetic order is suppressed by chemical doping or applying pressure. Here we report heat capacity measurements on diluted alloyes of the heavy fermion superconductor CeRhIn_5;. Heat capacity measurements have been performed on CeRh_{1-y}Ir_{y}In_5; (y <= 0.10) and Ce_{1-x}La_{x}Rh_{1-y}Ir_{y}In_5; (x <= 0.50) in applied fields up to 90 kOe to study the affect of doping and magnetic field on the magnetic ground state. The magnetic phase diagram of CeRh_{0.9}Ir_{0.1}In_5; is consistent with the magnetic structure of CeRhIn_5; being unchanged by Ir doping. Doping of Ir in small concentrations is shown to slightly increase the antiferromagnetic transition temperature T_{N} (T_{N}=3.8 K in the undoped sample). La doping which causes disorder on the Ce sublattice is shown to lower T_{N} with no long range order observed above 0.34 K for Ce_{0.50}La_{0.50}RhIn_5;. Measurements on Ce_{0.50}La_{0.50}RhIn_5; show a coexistence of short range magnetic order and non-Fermi-liquid behavior. This dual nature of the Ce 4f-electrons is very similar to the observed results on CeRhIn_5; when long range magnetic order is suppressed at high pressure.Comment: 8 pages, 9 figure

    The nature of social dominance orientation: theorizing and measuring preferences for intergroup inequality using the new SDO₇ scale

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    A new conceptualization and measurement of social dominance orientation-individual differences in the preference for group based hierarchy and inequality-is introduced. In contrast to previous measures of social dominance orientation that were designed to be unidimensional, the new measure (SDO7) embeds theoretically grounded subdimensions of SDO-SDO-Dominance (SDO-D) and SDO-Egalitarianism (SDO-E). SDO-D constitutes a preference for systems of group-based dominance in which high status groups forcefully oppress lower status groups. SDO-E constitutes a preference for systems of group-based inequality that are maintained by an interrelated network of subtle hierarchy-enhancing ideologies and social policies. Confirmatory factor and criterion validity analyses confirmed that SDO-D and SDO-E are theoretically distinct and dissociate in terms of the intergroup outcomes they best predict. For the first time, distinct personality and individual difference bases of SDO-D and SDO-E are outlined. We clarify the construct validity of SDO by strictly assessing a preference for dominance hierarchies in general, removing a possible confound relating to support for hierarchy benefitting the ingroup. Consistent with this, results show that among members of a disadvantaged ethnic minority group (African Americans), endorsement of SDO7 is inversely related to ingroup identity. We further demonstrate these effects using nationally representative samples of U.S. Blacks and Whites, documenting the generalizability of these findings. Finally, we introduce and validate a brief 4-item measure of each dimension. This article importantly extends our theoretical understanding of one of the most generative constructs in social psychology, and introduces powerful new tools for its measurement

    Localized f electrons in CexLa1-xRhIn5: dHvA Measurements

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    Measurements of the de Haas-van Alphen effect in CexLa1-xRhIn5 reveal that the Ce 4f electrons remain localized for all x, with the mass enhancement and progressive loss of one spin from the de Haas-van Alphen signal resulting from spin fluctuation effects. This behavior may be typical of antiferromagnetic heavy fermion compounds, inspite of the fact that the 4f electron localization in CeRhIn5 is driven, in part, by a spin-density wave instability.Comment: 4 pages, 4 figures, submitted to PR

    Field-induced magnetic transitions in the quasi-two-dimensional heavy-fermion antiferromagnets Ce_{n}RhIn_{3n+2} (n=1 or 2)

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    We have measured the field-dependent heat capacity in the tetragonal antiferromagnets CeRhIn5_{5} and Ce2_{2}RhIn8_{8}, both of which have an enhanced value of the electronic specific heat coefficient γ∼400\gamma \sim 400 mJ/mol-Ce K2^{2} above TNT_{N}. For T<TN,T<T_{N}, the specific heat data at zero applied magnetic field are consistent with the existence of an anisotropic spin-density wave opening a gap in the Fermi surface for CeRhIn5,_{5}, while Ce2_{2}RhIn8_{8} shows behavior consistent with a simple antiferromagnetic magnon. From these results, the magnetic structure, in a manner similar to the crystal structure, appears more two-dimensional in CeRhIn5_{5} than in Ce2_{2}RhIn8_{8} where only about 12% of the Fermi surface remains ungapped relative to 92% for Ce2_{2}RhIn8_{8}. When B∣∣c,B||c, both compounds behave in a manner expected for heavy fermion systems as both TNT_{N} and the electronic heat capacity decrease as field is applied. When the field is applied in the tetragonal basal plane (B∣∣aB||a), CeRhIn5_{5} and Ce2_{2}RhIn8_{8} have very similar phase diagrams which contain both first- and second-order field-induced magnetic transitions .Comment: 15 pages, 4 figure

    Bianchi type II,III and V diagonal Einstein metrics re-visited

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    We present, for both minkowskian and euclidean signatures, short derivations of the diagonal Einstein metrics for Bianchi type II, III and V. For the first two cases we show the integrability of the geodesic flow while for the third case a somewhat unusual bifurcation phenomenon takes place: for minkowskian signature elliptic functions are essential in the metric while for euclidean signature only elementary functions appear

    Gammaherpesvirus infection modulates the temporal and spatial expression of SCGB1A1 (CCSP) and BPIFA1 (SPLUNC1) in the respiratory tract

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    Murine γ-herpesvirus 68 (MHV-68) infection of Mus musculus-derived strains of mice is an established model of γ-herpesvirus infection. We have previously developed an alternative system using a natural host, the wood mouse (Apodemus sylvaticus), and shown that the MHV-68 M3 chemokine-binding protein contributes significantly to MHV-68 pathogenesis. Here we demonstrate in A. sylvaticus using high-density micro-arrays that M3 influences the expression of genes involved in the host response including Scgb1a1 and Bpifa1 that encode potential innate defense proteins secreted into the respiratory tract. Further analysis of MHV-68-infected animals showed that the levels of both protein and RNA for SCGB1A1 and BPIFA1 were decreased at day 7 post infection (p.i.) but increased at day 14 p.i. as compared with M3-deficient and mock-infected animals. The modulation of expression was most pronounced in bronchioles but was also present in the bronchi and trachea. Double staining using RNA in situ hybridization and immunohistology demonstrated that much of the BPIFA1 expression occurs in club cells along with SCGB1A1 and that BPIFA1 is stored within granules in these cells. The increase in SCGB1A1 and BPIFA1 expression at day 14 p.i. was associated with the differentiation of club cells into mucus-secreting cells. Our data highlight the role of club cells and the potential of SCGB1A1 and BPIFA1 as innate defense mediators during respiratory virus infection

    A systematic review of oil tanker truck disasters: Identifying prevention targets

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    Introduction: Oil tanker truck disasters have been reported worldwide; however, the circumstances, causes, and health effects of these disasters have not been described. To address this gap, we performed a systematic review using PRISMA criteria to better understand this public health problem and identify prevention targets. Methods: The academic and lay literatures were systematically searched for terms related to oil tanker truck disasters. Reports about civilian oil tanker truck disasters that occurred from 1997–2017 were included. Details about the disasters were summarized, including circumstances, identifiable causes, and health effects. Results: The search yielded 4713 Nexis Uni articles, 199 Google results, and one PubMed article; 951 records met inclusion criteria, describing 224 oil tanker truck explosions or fires. At least 2909 people died as a result of these disasters, and 3038 additional people were hospitalized. Almost all deaths (94%) occurred in low- and low-middle-income countries (LMIC). This may largely be due to scooping – the practice of collecting spilled oil from disabled tanker trucks for use or resale. Using the Haddon matrix, potential targets for future disaster prevention were identified. Conclusions: These data highlight the circumstances, causes, and health burden related to oil tanker truck disasters. Most began as collisions or rollovers, but nearly half of the fatalities involved scooping. The findings suggest opportunities to promote road safety, improve scene safety and security protocols used by drivers and first responders, and promote public understanding of the dangers of scooping to prevent mass casualty disasters from disabled tanker trucks, particularly in LMIC

    Eigenvalue computations in the context of data-sparse approximations of integral operators

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    In this work, we consider the numerical solution of a large eigenvalue problem resulting from a finite rank discretization of an integral operator. We are interested in computing a few eigenpairs, with an iterative method, so a matrix representation that allows for fast matrix-vector products is required. Hierarchical matrices are appropriate for this setting, and also provide cheap LU decompositions required in the spectral transformation technique. We illustrate the use of freely available software tools to address the problem, in particular SLEPc for the eigensolvers and HLib for the construction of H-matrices. The numerical tests are performed using an astrophysics application. Results show the benefits of the data-sparse representation compared to standard storage schemes, in terms of computational cost as well as memory requirements.This work was partially supported by the Spanish Ministerio de Ciencia e Innovacion under projects TIN2009-07519, TIN2012-32846 and AIC10-D-000600 and by Fundacao para a Ciencia e a Tecnologia - FCT under project FCT/MICINN proc 441.00.Román Moltó, JE.; Vasconcelos, PB.; Nunes, AL. (2013). Eigenvalue computations in the context of data-sparse approximations of integral operators. Journal of Computational and Applied Mathematics. 237(1):171-181. doi:10.1016/j.cam.2012.07.021S171181237
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