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

Sudden future singularities in FLRW cosmologies

The standard energy conditions of classical general relativity are applied to FLRW cosmologies containing sudden future singularities. Here we show, in a model independent way, that although such cosmologies can satisfy the null, weak and strong energy conditions, they always fail to satisfy the dominant energy condition. They require a divergent spacelike energy flux in all but the comoving frame.Comment: revtex4. Added references and a definition. To appear in CQ

A preliminary investigation of finite-element modeling for composite rotor blades

The results from an initial phase of an in-house study aimed at improving the dynamic and aerodynamic characteristics of composite rotor blades through the use of elastic couplings are presented. Large degree of freedom shell finite element models of an extension twist coupled composite tube were developed and analyzed using MSC/NASTRAN. An analysis employing a simplified beam finite element representation of the specimen with the equivalent engineering stiffness was additionally performed. Results from the shell finite element normal modes and frequency analysis were compared to those obtained experimentally, showing an agreement within 13 percent. There was appreciable degradation in the frequency prediction for the torsional mode, which is elastically coupled. This was due to the absence of off-diagonal coupling terms in the formulation of the equivalent engineering stiffness. Parametric studies of frequency variation due to small changes in ply orientation angle and ply thickness were also performed. Results showed linear frequency variations less than 2 percent per 1 degree variation in the ply orientation angle, and 1 percent per 0.0001 inch variation in the ply thickness

Gravitational Collapse of Dust with a Cosmological Constant

The recent analysis of Markovic and Shapiro on the effect of a cosmological constant on the evolution of a spherically symmetric homogeneous dust ball is extended to include the inhomogeneous and degenerate cases. The histories are shown by way of effective potential and Penrose-Carter diagrams.Comment: 2 pages, 2 figures (png), revtex. To appear in Phys. Rev.

Junctions and thin shells in general relativity using computer algebra I: The Darmois-Israel Formalism

We present the GRjunction package which allows boundary surfaces and thin-shells in general relativity to be studied with a computer algebra system. Implementing the Darmois-Israel thin shell formalism requires a careful selection of definitions and algorithms to ensure that results are generated in a straight-forward way. We have used the package to correctly reproduce a wide variety of examples from the literature. We present several of these verifications as a means of demonstrating the packages capabilities. We then use GRjunction to perform a new calculation - joining two Kerr solutions with differing masses and angular momenta along a thin shell in the slow rotation limit.Comment: Minor LaTeX error corrected. GRjunction for GRTensorII is available from http://astro.queensu.ca/~grtensor/GRjunction.htm

Magnetic correlations of the quasi-one-dimensional half-integer spin-chain antiferromagnets SrM2M_2V2_2O8_8 (MM = Co, Mn)

Magnetic correlations of two iso-structural quasi-one-dimensional (1D) antiferromagnetic spin-chain compounds Sr$M_2$V$_2$O$_8$ ($M$ = Co, Mn) have been investigated by magnetization and powder neutron diffraction. Two different collinear antiferromagnetic (AFM) structures, characterized by the propagation vectors, $k$ = (0 0 1) and $k$ = (0 0 0), have been found below $\sim$ 5.2 K and $\sim$ 42.2 K for the Co- and Mn-compounds, respectively. For the Mn-compound, AFM chains (along the $c$ axis) order ferromagnetically within the $ab$ plane, whereas, for the Co-compound, AFM chains order ferro-/antiferromagnetically along the $a/b$ direction. The critical exponent study confirms that the Co- and Mn-compounds belong to the Ising and Heisenberg universality classes, respectively. For both compounds, short-range spin-spin correlations are present over a wide temperature range above $T_N$. The reduced ordered moments at base temperature (1.5 K) indicate the presence of quantum fluctuations in both compounds due to the quasi-1D magnetic interactions.Comment: 14 pages, 10 figures, 9 table

Stability of Transparent Spherically Symmetric Thin Shells and Wormholes

The stability of transparent spherically symmetric thin shells (and wormholes) to linearized spherically symmetric perturbations about static equilibrium is examined. This work generalizes and systematizes previous studies and explores the consequences of including the cosmological constant. The approach shows how the existence (or not) of a domain wall dominates the landscape of possible equilibrium configurations.Comment: 12 pages, 7 figures, revtex. Final form to appear in Phys. Rev.

Barriers to Effective Pain Management in Preterm and Critically Ill Neonates

The purpose of this dissertation is to explore potential barriers nurses experience in providing effective pain management for preterm and critically ill infants in neonatal intensive care units (NICUs). The specific aims of the study conducted are to examine (a) NICU caregivers’ knowledge about pain, (b) scales used to evaluate pain in infants, (c) NICU nurses’ documented pain practices, and (d) bias in treating pain of certain types of infants. This dissertation is comprised of three manuscripts. The first manuscript is an integrated review of the literature describing caregiver knowledge, barriers, and bias in the management of pain in neonates. The second manuscript is a systematic review of multidimensional pain scales developed for use in preterm and critically ill infants. The final manuscript reports a descriptive exploratory study designed to examine nurses’ knowledge of pain, knowledge of intensity and appropriate management of procedural pain, bias in treating pain of certain types of infants, and documented pain management practices. Over the past 25 years, caregiver knowledge of pain in preterm and critically ill infants has advanced from beliefs that neonates do not feel pain, to the knowledge that preterm infants experience more pain than term infants, older children, and adults. Nine multidimensional pain scales with varying levels of reliability and validity have been developed, yet a gold standard for pain assessment in preterm and critically ill neonates has not emerged. In this study, baccalaureate prepared nurses (BSN) and nurses with higher total years of nursing experience had better knowledge of pain in this population than associate degree nurses (ADN). However, pain management was inconsistent, resulting in pain that was untreated as often as 80% of the time. Nurses reported that physician practice was the primary obstacle to providing effective pain management. Additional concerns included knowledge deficits of nurses and physicians, lack of communication and teamwork, and rushed care. Nurses reported biases in managing pain and were less likely to invest time and energy treating the pain of infants experiencing neonatal abstinence syndrome