Evolution of crystalline electric field effects, superconductivity, and heavy fermion behavior in the specific heat of Pr(Os1−x_{1-x}Rux_x)4_4Sb12_{12}

Specific heat $C(T)$ measurements were made on single crystals of the superconducting filled skutterudite series Pr(Os$_{1-x}$Ru$_x$)$_4$Sb$_{12}$ down to 0.6 K. Crystalline electric field fits in the normal state produced parameters which were in agreement with previous measurements. Bulk superconductivity was observed for all values of the Ru concentration $x$ with transition temperatures consistent with previous experiments, confirming a minimum in $T_{c}$ at $x=0.6$. The $C(T)$ data below $T_{c}$ appear to be more consistent with power law behavior for $x=0$ (PrOs$_4$Sb$_{12}$), and with exponential behavior for $0.05 \leq x \leq 0.2$. An enhanced electronic specific heat coefficient $\gamma$ was observed for $x \leq 0.4$, further supporting $x \simeq 0.6$ as a critical concentration where the physical properties abruptly change. Significant enhancement of $\Delta C/T_{c}$ above the weak coupling value was only observed for $x=0$ and $x=0.05$.Comment: 16 pages, 5 figures, submitted to Physical Review B. v2: text added and figures modifie

Unintended Consequences Of Equal Employment Opportunity: Unequal Parties In The Selection Process?

There arevarious regulations that are intended to promote equal employment opportunityand avoid illegal discrimination in the employment process. These regulationsdetermine what information employers may seek, and require that informationsought be job-related or it is illegal to seek such information as age, maritalstatus, or religion. Information that is not a bona fide occupationalqualification (BFOQ) is usually out of bounds as employers gather informationto determine the suitability of applicants for employment.  Since one of thebedrock laws affecting the employment relationship is the “at will” doctrinethat assumes both employer and applicant come together as equal partners in theformation of the employment contract, this paper raises the issues aboutwhether such regulations unintentionally leave the employer at an informationdisadvantage by negating the concept of equality assumed by the “at will”doctrine. Some suggestions for practical ways of reducing the identifiedemployer information disadvantages are provided

Helping HELP with limited resources: The Luquillo experience

By definition the HELP approach involves the active participation of individuals from a wide range of disciplines and backgrounds, including representatives of industry, academics, natural resource managers, and local officials and community leaders. While there is considerable enthusiasm and support for the integrated HELP approach, a central problem for all HELP basins is how to effectively engage individuals and groups with few, if any financial resources. In the Luquillo HELP project we have managed this issue by focusing our efforts on holding small, public meetings and workshops with technocrats and managers who are engaged in local water resource management. To date several forums have been organised, including: technical meetings with the directors of natural resource agencies; presentations and panel discussions at the meetings of local professional societies, including the societies of Civil Engineers and Architects, the Commonwealth Association of Tourism, the Association of Builders and Developers, and the Puerto Rican Association of Lawyers. During these forums HELP specialists gave presentations and led discussions on how integrated watershed management can help resolve local problems. Because the audience are directly involved with these issues, they are quite responsive to these discussions and have often provided unique solutions to common problems. Technical workshops are co-sponsored by local municipalities – these day-long workshops are hosted by a municipality and include managers from other municipalities, the local water authority, and local community leaders. Additional activities include: technical advice on water infrastructure projects is given; there are educational exchanges between local and international students, scientists, natural resource managers, and community leaders; and synthesis publications relevant to integrated water resource management are produced. Other activities have included compiling oral environmental histories and organising watershed restoration activities. This paper describes these activities and discusses the benefits and costs of each approach

The a-axis optical conductivity of detwinned ortho-II YBa_2Cu_3O_6.50

The a-axis optical properties of a detwinned single crystal of YBa_2Cu_3O_6.50 in the ortho II phase (Ortho II Y123, T_c= 59 K) were determined from reflectance data over a wide frequency range (70 - 42 000 cm^-1) for nine temperature values between 28 and 295 K. Above 200 K the spectra are dominated by a broad background of scattering that extends to 1 eV. Below 200 K a shoulder in the reflectance appears and signals the onset of scattering at 400 cm^-1. In this temperature range we also observe a peak in the optical conductivity at 177 cm^-1. Below 59 K, the superconducting transition temperature, the spectra change dramatically with the appearance of the superconducting condensate. Its spectral weight is consistent, to within experimental error, with the Ferrell-Glover-Tinkham (FGT) sum rule. We also compare our data with magnetic neutron scattering on samples from the same source that show a strong resonance at 31 meV. We find that the scattering rates can be modeled as the combined effect of the neutron resonance and a bosonic background in the presence of a density of states with a pseudogap. The model shows that the decreasing amplitude of the neutron resonance with temperature is compensated for by an increasing of the bosonic background yielding a net temperature independent scattering rate at high frequencies. This is in agreement with the experiments.Comment: 13 pages 16 figure

Equatorial symmetry/antisymmetry of stationary axisymmetric electrovac spacetimes

Two theorems are proved concerning how stationary axisymmetric electrovac spacetimes that are equatorially symmetric or equatorially antisymmetric can be characterized correctly in terms of the Ernst potentials \E and $\Phi$ or in terms of axis-data.Comment: 8 page

Mechanical Properties of Crosslinked Poly/methyl Methacrylate/ Polymers Under Space Environmental Conditions Final Report, Jun. 1, 1963 - Jan. 30, 1966

Mechanical properties determined for cross linked polymethyl methacrylate under stress-relaxation test metho