Some notes on the Kruskal - Szekeres completion

The Kruskal - Szekeres (KS) completion of the Schwarzschild spacetime is open to Synge's methodological criticism that the KS procedure generates "good" coordinates from "bad". This is addressed here in two ways: First I generate the KS coordinates from Israel coordinates, which are also "good", and then I generate the KS coordinates directly from a streamlined integration of the Einstein equations.Comment: One typo correcte

Performance Management in Portfolio School Districts

Explores the challenges of performance-based oversight of portfolio districts -- districts trying to provide diverse types of schools with common standards and accountability -- and the capacities needed. Includes profiles and best practices

Maximally extended, explicit and regular coverings of the Schwarzschild - de Sitter vacua in arbitrary dimension

Maximally extended, explicit and regular coverings of the Schwarzschild - de Sitter family of vacua are given, first in spacetime (generalizing a result due to Israel) and then for all dimensions $D$ (assuming a $D-2$ sphere). It is shown that these coordinates offer important advantages over the well known Kruskal - Szekeres procedure.Comment: 12 pages revtex4 5 figures in color. Higher resolution version at http://www.astro.queensu.ca/~lake/regularcoordinates.pd

Signatures of the Milky Way's Dark Disk in Current and Future Experiments

In hierarchical structure formation models of disk galaxies, a dark matter disk forms as massive satellites are preferentially dragged into the disk-plane where they dissolve. Here, we quantify the importance of this dark disk for direct and indirect dark matter detection. The low velocity of the dark disk with respect to the Earth enhances detection rates in direct detection experiments at low recoil energy. For WIMP masses M_{WIMP} >~ 50 GeV, the detection rate increases by up to a factor of 3 in the 5 - 20 keV recoil energy range. Comparing this with rates at higher energy is sensitive to M_{WIMP}, providing stronger mass constraints particularly for M_{WIMP}>~100 GeV. The annual modulation signal is significantly boosted by the dark disk and the modulation phase is shifted by ~3 weeks relative to the dark halo. The variation of the observed phase with recoil energy determines M_{WIMP}, once the dark disk properties are fixed by future astronomical surveys. The low velocity of the particles in the dark disk with respect to the solar system significantly enhances the capture rate of WIMPs in the Sun, leading to an increased flux of neutrinos from the Sun which could be detected in current and future neutrino telescopes. The dark disk contribution to the muon flux from neutrino back conversion at the Earth is increased by a factor of ~5 compared to the SHM, for rho_d/rho_h=0.5.Comment: 5 pages, 7 figures, To appear in the proceedings of Identification of Dark Matter 2008 (IDM2008), Stockholm, 18-22 August 2008; corrected one referenc

Design of FerroElectric MEMS energy harvesting devices

Waste heat is a widely available but little used source of power. Converting a thermal gradient into electricity is conventionally done using the Seebeck effect, but devices that use this effect are naturally inefficient. An alternate approach uses microelectromechanical systems (MEMS) to generate movement and time-varying temperature from a constant temperature gradient. Ferroelectric materials can harvest electricity from moving structures and temperature variations. This concept was realized using traditional silicon microprocessing techniques. A silicon on insulator (SOI) wafer was backside Deep Reactive Ion Etched (DRIE) to form a one mm2 by 7 micron thick silicon/silicon dioxide membrane. Lead zirconate titanate (PZT) was deposited on the membrane and acts as a ferroelectric material. Heating the bulk of the SOI substrate causes an increase in stress and upward deflection of the membrane. The membrane then enters into contact with a cold sink fixed above the substrate. Cooling of the membrane from contact with the cold sink causes actuation downwards of the membrane. The alternating heating and cooling of the PZT layer generates electricity from the pyroelectric effect. The actuation of the membrane generates stress on the PZT layer resulting in electricity from the piezoelectric effect

Rural Hospital Nursing Skill Mix and Work Environment Associated with Frequency of Adverse Events.

Introduction: Though rural hospitals serve about one fifth of the United States (U.S.), few studies have investigated relationships among nursing resources and rural hospital adverse events. Objectives: The purpose was to determine relationships among nursing skill mix (proportion of Registered Nurses (RNs) to all nursing staff), the work environment and adverse events (medication errors, patient falls with injury, pressure ulcers, and urinary tract infections) in rural hospitals. Methods: Using a cross-sectional design, nurse survey data from a large study examining nurse organizational factors, patient safety, and quality from four U.S. states were linked to the 2006 American Hospital Association data. The work environment was measured using the Practice Environment Scale of the Nursing Work Index (PES-NWI). Nurses reported adverse event frequency. Data analyses were descriptive and inferential. Results: On average, 72% of nursing staff were RNs (range = 45% to 100%). Adverse event frequency ranged from 0% to 67%, across 76 hospitals. In regression models, a 10-point increase in the proportion of RNs among all nursing staff and a one standard deviation increase in the PES-NWI score were significantly associated with decreased odds of frequent adverse events. Conclusion: Rural hospitals that increase the nursing skill mix and improve the work environment may achieve reduced adverse event frequency