A Study of the Gravitational Wave Pulsar Signal with orbital and spindown Effects

In this work we present analytic and numerical treatments of the gravitational wave signal from a pulsar which includes spindown. We consider phase corrections to a received monochromatic signal due to rotational and elliptical orbital motion of the Earth, as well as perturbations due to Jupiter and the Moon. We discuss the Fourier transform of such a signal, which is expressed in terms of well known special functions and lends itself to a tractable numerical analysis.Comment: 8 pages, 8 figures. Write-up of talk given at Theory Canada I, June 2005, University of British Columbi

QED Effective Action Revisited

The derivation of a convergent series representation for the quantum electrodynamic effective action obtained by two of us (S.R.V. and D.R.L.) in [Can. J. Phys. vol. 71, p. 389 (1993)] is reexamined. We present more details of our original derivation. Moreover, we discuss the relation of the electric-magnetic duality to the integral representation for the effective action, and we consider the application of nonlinear convergence acceleration techniques which permit the efficient and reliable numerical evaluation of the quantum correction to the Maxwell Lagrangian.Comment: 20 pages, LaTeX, 1 table; minor additions and adjustments; to appear in Can. J. Phy

Diffeomorphism Invariance in the Hamiltonian formulation of General Relativity

It is shown that when the Einstein-Hilbert Lagrangian is considered without any non-covariant modifications or change of variables, its Hamiltonian formulation leads to results consistent with principles of General Relativity. The first-class constraints of such a Hamiltonian formulation, with the metric tensor taken as a canonical variable, allow one to derive the generator of gauge transformations, which directly leads to diffeomorphism invariance. The given Hamiltonian formulation preserves general covariance of the transformations derivable from it. This characteristic should be used as the crucial consistency requirement that must be met by any Hamiltonian formulation of General Relativity.Comment: 13 page

The Residual Stress Relaxation Behavior of Weldments During Cyclic Loading

Accurate measurement of residual stress is necessary to obtain reliable predictions of fatigue lifetime and enable estimation of time-to-facture for any given stress level. In this article, relaxation of welding residual stresses as a function of cyclic loading was documented on three common steels: AISI 1008, ASTM A572, and AISI 4142. Welded specimens were subjected to cyclic bending (R = 0.1) at different applied stresses, and the residual stress relaxation existing near the welds was measured as a function of cycles. The steels exhibited very different stress relaxation behaviors during cyclic loadings, which can be related to the differences in the microstructures of the specimens. A phenomenological model, which treats dislocation motion during cyclic loading as being analogous to creep of dislocations, is proposed for estimation of the residual stress relaxation

Safety and Pharmacokinetics of Nelfinavir During the Second and Third Trimesters of Pregnancy and Postpartum

Purpose: Evaluate the safety, tolerability, and pharmacokinetics (PK) of nelfinavir during pregnancy and postpartum in HIV-infected women. Methods: Phase IV, non-randomized, open-label study of nelfinavir 625 mg tablets (1250 mg) in combination with lamivudine/zidovudine twice daily. Primary endpoint was treatment-related or possibly treatment-related gastrointestinal or hepatic adverse events (AEs). Selected maternal and infant outcomes were recorded. Frequent plasma samples were collected for PK studies during the 2nd and 3rd trimesters, and 6 weeks postpartum, to analyze total and free nelfinavir and M8 concentrations. Results: Sixteen HIV+ pregnant women were enrolled. Six mild treatment-related AEs and 3 serious AEs occurred; 1 serious AE (elevated AST) met the primary endpoint. Compared with 6 weeks postpartum, levels of total nelfinavir were reduced by 44% and 46%, total M8 by 82% and 83%, free nelfinavir by 48% and 39%, and free M8 by 83% and 79% in the 2nd and 3rd trimesters, respectively. At 6 weeks postpartum, 75% and 50% of subjects maintained HIV-1 RNA levels <400 and <50 copies/mL, respectively. All pregnancies resulted in live births without transmission in 15 infants. Conclusions: Nelfinavir in combination with lamivudine/zidovudine was generally well tolerated. Total and free nelfinavir and M8 exposure were reduced in late pregnancy

The electronic properties of graphene nanoribbons and the offset logarithm function

International audienceGraphene Nanoribbons (GN), being an important class of next-generation carbon materials, are of immense interest and find innumerable applications in diverse fields. A variation of the generalized Lambert W function, called the Offset Logarithm function, has been found to have important applications in fields such as physics, engineering and nanotechnology. We study the electronic properties of zigzag GN and use the generalized Lambert W function to study the eigenvalue equations of the massless Dirac equation applied to zigzag GN. We have studied the effects of nanoribbon width and determined the parameters that significantly affect the obtained solutions

The accidental degeneracy of the hydrogen atom is no accident

The Schrödinger equation does not account for the 2n2 degeneracy of the hydrogen atom, which it dismisses as an accidental degeneracy. The factor of 2 in the 2n2 degeneracy is well-accounted-for in the relativistic formulation by the two spin states of the electron. The n2 degeneracy is nevertheless not quite an accident ; it is due to the SO(4), rather than SO(3), symmetry of the hydrogen atom. This result is well known, but is inadequately commented upon in most courses in quantum mechanics and atomic physics, leaving the student wondering about the origins of the n2 degeneracy of the hydrogen atom. A pedagogical analysis of this interesting aspect, which highlights the fundamental principles of quantum mechanics, is presented in this article. While doing so, not only is the n2 degeneracy of the hydrogen atom explained, but its energy spectrum and eigenfunctions are obtained without even using the Schrödinger equation, employing only the fundamental principles of quantum mechanics rather than the Schrödinger equation

Band structure and transport studies of half Heusler compound DyPdBi: An efficient thermoelectric material

The discovery of Heusler alloys has revolutionized the research field of intermetallics due to the ease with which one can derive potential candidates for multifunctional applications. During recent years, many half Heusler alloys have been investigated for their thermoelectric properties. The f-electron-based rare-earth ternary half Heusler compound DyPdBi has its f energy levels located close to the Fermi energy level. Other research efforts have emphasized that such materials have good thermoelectric capabilities. We have explored using first principles the electronic band structure of DyPdBi by use of different exchange correlation potentials in the density functional theoretical framework. Transport coefficients that arise in the study of thermoelectric properties of DyPdBi have been calculated and have illustrated its potential as an efficient thermoelectric material. Both the theoretically estimated Seebeck coefficient and the power factor agree well with the available experimental results. Our calculations illustrate that it is essential to include spin–orbit coupling in these models of f-electron half Heusler materials