Anisotropy of the normal state properties of the superconducting Co1−x Ni x Zr2 system

Anisotropic behavior of the normal state thermoelectric power, electrical resistivity, and magnetic susceptibility is reported for the superconducting Co_1–x Ni _x Zr₂ system.This research was supported by the U.S. Department of Energy under Contract Number EY-76-S-03-0034-PA227-3 (ZH, WAF, MBM) and by the National Science Foundation under Grant Number NSF/DMR77-08469 (ZF, DCJ).Deceased.     

Intermediate valence behavior of ternary cerium and uranium transition metal borides

Low-temperature specific heat, electrical resistivity, ac magnetic susceptibility, and dc magnetization measurements were made on ternary cerium and uranium transition metal borides with the general formula CeT₃B₂ (T=Co, Ru, Rh, and Ir) and UT₃B₂ (T=Co, Ru, and Ir). The compound CeRu₃B₂ was found to exhibit superconductivity below 0.68 K. The values of the electronic specific heat coefficient range from 9.7 mJ/mole-K² for CeCo₃B₂ to 64 mJ/mole-K² for UIr₃B₂. The electrical resistivity versus temperature curves of all of the compounds exhibit negative curvature and are reminiscent of valence fluctuation behavior. In the case of CeIr₃B₂, the electrical resistivity attains a maximum value at 180 K, while the dc magnetic susceptibility has a temperature dependence that is typical of intermediate valence Ce compounds, approaching a finite value at zero temperature. The electrical resistivity of the ferromagnetic compound CeRh₃B₂ reveals a rapid decrease in spin disorder resistivity below 120 K. The dc magnetic susceptibility of this material can be described as the sum of a constant term and a Curie-Weiss contribution with an effective magnetic moment of 1.01 µ_B per formula unit and a Curie-Weiss temperature of 119 K. Magnetization measurements on CeRh₃B₂ yield a saturation magnetic moment of 0.37 µ_B per formula unit and a Curie temperature of 113 K.     

Anomalous pressure dependences of the superconducting transition temperature of dilute alloys of LaSn3 containing light rare earth impurities

The initial depressions of the superconducting transition temperature T _c of LaSn₃ by rare earth (RE) impurities are known to be anomalous. In an attempt to clarify this behavior, we have measured the pressure dependence of the T _c of (LaRE)Sn₃ alloys (RE = Y, Ce, Pr, Nd, Sm, Eu, Gd, and Lu) to pressures up to 25 kbar. The magnitude of the pressure dependence of the T _c of (LaRE)Sn₃ alloys containing RE impurities with partially filled 4f electron shells decreases monotonically with increasing RE atomic number. A general discussion of existing zero- and high-pressure data for various physical properties of (LaRE)Sn₃ alloys demonstrates that the association of large pressure dependences of T _c with the occurrence of unstable impurity 4f shells (the Kondo effect) should be made with caution. The experimental high-pressure results are analyzed in terms of appropriate theoretical models for magnetic and nonmagnetic localized impurity states in superconductors.Supported by the US DOE Contract E(04-3)-34PA227.National Science Foundation Postdoctoral Fellow.     

Examining the relative effectiveness of different message framing strategies for child passenger safety: Recommendations for increased comprehension and compliance

Background

Age-appropriate child restraints and rear seating dramatically reduce injury in vehicle crashes. Yet parents and caregivers struggle to comply with child passenger safety (CPS) recommendations, and frequently make mistakes when choosing and installing restraints. The purpose of this research was to evaluate various methods of framing CPS recommendations, and to examine the relative effectiveness on parents’ knowledge, attitudes, and behavioral intentions related to best practices and proper use of child restraints. Emphasis framing is a persuasion technique that involves placing focus on specific aspects of the content in order to encourage or discourage certain interpretations of the content.

Method

A 5 (flyer group) X 2 (time) randomized experiment was conducted in which 300 parent participants answered a pre-survey, viewed one of four flyer versions or a no-education control version, and completed a post-survey. Surveys measured CPS knowledge, attitudes, perceptions of efficacy and risk, and behavioral intentions. The four flyers compared in this study all communicated the same CPS recommendations, but several versions were tested which each employed a different emphasis frame: (1) recommendations organized by the natural progression of seat types; (2) recommendations which focused on avoiding premature graduation; (3) recommendations which explained the risk-reduction rationale behind the information given; or (4) recommendations which were organized by age. In a fifth no-education (control) condition, participants viewed marketing materials.

Results

Analyses of covariance and pairwise comparisons indicated the risk-reduction rationale flyer outperformed other flyers for many subscales, and significantly differed from no-education control for the most subscales, including restraint selection, back seat knowledge, rear-facing knowledge and attitudes, total efficacy, overall attitudes, and stated intentions.

Conclusions

This research provides insight for increasing caregiver understanding and compliance with CPS information. Recommendations for the field include communicating the rationale behind the information given, using behavior-based directives in headers, avoiding age-based headers, and incorporating back-seat positioning directives throughout.