Why Solve the Hamiltonian Constraint in Numerical Relativity?

The indefinite sign of the Hamiltonian constraint means that solutions to Einstein's equations must achieve a delicate balance--often among numerically large terms that nearly cancel. If numerical errors cause a violation of the Hamiltonian constraint, the failure of the delicate balance could lead to qualitatively wrong behavior rather than just decreased accuracy. This issue is different from instabilities caused by constraint-violating modes. Examples of stable numerical simulations of collapsing cosmological spacetimes exhibiting local mixmaster dynamics with and without Hamiltonian constraint enforcement are presented.Comment: Submitted to a volume in honor of Michael P. Ryan, Jr. Based on talk given at GR1

Coulomb interacting Dirac fermions in disordered graphene

We study interacting Dirac quasiparticles in disordered graphene and find that an interplay between the unscreened Coulomb interactions and pseudo-relativistic quasiparticle kinematics can be best revealed in the ballistic regime, whereas in the diffusive limit the behavior is qualitatively (albeit, not quantitatively) similar to that of the ordinary 2DEG with parabolic dispersion. We calculate the quasiparticle width and density of states that can be probed by photoemission, tunneling, and magnetization measurements.Comment: Latex, 4 page

General Issues in the Evolution of Fermion Masses and Mixings

General issues in the renormalization group evolution of fermion masses and mixings is discussed. An effective fixed point in the top quark Yukawa coupling can strongly constrain its value at the electroweak scale. Predictions following from Yukawa coupling unification are affected by threshold corrections at the grand unified scale. The Landau pole translates into an upper limit on the strong gauge coupling $\alpha _3(M_Z)$. Given the hierarchy in the fermion sector, the evolution of the Cabbibo-Kobayashi-Maskawa matrix can be expressed in terms of a single scaling parameter $S$. Using this scaling factor and analogous scaling factors for the quark and lepton masses, we outline a systematic strategy that readily yields electroweak predictions for any GUT scale texture.}Comment: (Talk given at the SUSY93 Conference MSB), 9 pages + 3 PS figures not included (available on request), MAD/PH/75

Understanding Stress In The Operating Room: A Step Toward Improving The Work Environment

Job-related stress is an important factor predicting staff satisfaction and position turnover among nursing staff, particularly in the operating room. The purpose of this study was to examine the perceived amount of stress elicited by events in the perioperative environment, the frequency of those events, and the impact of those events on the perceived stress of operating room nurses (ORNs) and operating room technologists (ORTs). The Survey on Stress in the OR instrument, which was used to query the subjects, exhibited high internal consistency of all items. The findings indicated that the ORNs and the ORTs exhibited remarkable similarities between stressful events perceived as high and low impact. The two groups agreed that the highest impact stressful event was pressure to work more quickly. Using the results of this study, OR administrators may be able to redesign the OR environment to minimize the impact of stressful events and thereby improve job satisfaction and minimize nursing staff turnover

The Singularity in Generic Gravitational Collapse Is Spacelike, Local, and Oscillatory

A longstanding conjecture by Belinskii, Khalatnikov, and Lifshitz that the singularity in generic gravitational collapse is spacelike, local, and oscillatory is explored analytically and numerically in spatially inhomogeneous cosmological spacetimes. With a convenient choice of variables, it can be seen analytically how nonlinear terms in Einstein's equations control the approach to the singularity and cause oscillatory behavior. The analytic picture requires the drastic assumption that each spatial point evolves toward the singularity as an independent spatially homogeneous universe. In every case, detailed numerical simulations of the full Einstein evolution equations support this assumption.Comment: 7 pages includes 4 figures. Uses Revtex and psfig. Received "honorable mention" in 1998 Gravity Research Foundation essay contest. Submitted to Mod. Phys. Lett.

Implementation of a Virtual Journal Club in a Clinical Nursing Setting

Healthcare practice is increasingly focused on delivering care that is based on published research evidence. Staff development nurses can institute journal clubs to teach nursing staff critical appraisal of research articles and ways to translate research findings into clinical practice. Unfortunately, attending meetings regularly is often a challenge for nurses, and relatively few have the knowledge and expertise to adequately critique research articles. One way to bridge the limitations of accessibility and limited research expertise of journal club members is to establish a virtual journal club. This article describes one hospital\u27s experience with developing a virtual journal club