Culture and Black Students\u27 Success

Black achievement measured in terms of cultural context

Taxation

Covers cases on inheritance tax—resident vendor\u27s interest in foreign lands as within taxing jurisdiction

Phase conjugate fluorozirconate fibre laser operating at 800nm

We report phase-conjugate feedback into a fluorozirconate optical fiber amplifier at infrared wavelengths. By using a semiconductor laser diode at 807 nm, a grating is established in photorefractive BaTiO3 that, in the ring configuration, provides feedback into the amplifier necessary for laser action. Once written, the grating is self-sustaining, and lasing is observed even after the laser diode is removed

Cosmic Vortons and Particle Physics Constraints

We investigate the cosmological consequences of particle physics theories that admit stable loops of superconducting cosmic string - {\it vortons}. General symmetry breaking schemes are considered, in which strings are formed at one energy scale and subsequently become superconducting in a secondary phase transition at what may be a considerably lower energy scale. We estimate the abundances of the ensuing vortons, and thereby derive constraints on the relevant particle physics models from cosmological observations. These constraints significantly restrict the category of admissible Grand Unified theories, but are quite compatible with recently proposed effects whereby superconducting strings may have been formed close to the electroweak phase transition.Comment: 33 pages, 2 figures, RevTe

Global Extensions of Spacetimes Describing Asymptotic Final States of Black Holes

We consider a globally hyperbolic, stationary spacetime containing a black hole but no white hole. We assume, further, that the event horizon, \tn, of the black hole is a Killing horizon with compact cross-sections. We prove that if surface gravity is non-zero constant throughout the horizon one can {\it globally} extend such a spacetime so that the image of $\cal N$ is a proper subset of a regular bifurcate Killing horizon in the enlarged spacetime. The necessary and sufficient conditions are given for the extendibility of matter fields to the enlarged spacetime. These conditions are automatically satisfied if the spacetime is static (and, hence ``$t$"-reflection symmetric) or stationary-axisymmetric with ``$t-\phi$" reflection isometry and the matter fields respect the reflection isometry. In addition, we prove that a necessary and sufficient condition for the constancy of the surface gravity on a Killing horizon is that the exterior derivative of the twist of the horizon Killing field vanish on the horizon. As a corollary of this, we recover a result of Carter that constancy of surface gravity holds for any black hole which is static or stationary- axisymmetric with the ``$t-\phi$" reflection isometry. No use of Einstein's equation is made in obtaining any of the above results. Taken together, these results support the view that any spacetime representing the asymptotic final state of a black hole formed by gravitational collapse may be assumed to possess a bifurcate Killing horizon or a Killing horizon with vanishing surface gravity.Comment: 20 pages, plain te

Donning a Novel Lower-Limb Restrictive Compression Garment During Training Augments Muscle Power and Strength

International Journal of Exercise Science 13(3): 890-899, 2020. The popularity of graduated compression garments (GCG) in sport and exercise is largely driven by the abundance of anecdotal claims suggesting their efficacy. A new line of compression apparel, restrictive compression garments (RCG), integrate novel resistance technology into lower-limb compression garments designed to provide variable resistance to movement. This study aimed to investigate the effect of donning an RCG during a 4-week training program on selected performance variables. Twelve college-aged males were recruited for four weeks of lower-body strength-power resistance training. Participants were randomized 1:1 and blinded to (i) an intervention group (RCG; n = 6) that donned a lower-body RCG during training or (ii) a control group (SHAM; n = 6) that donned a sham during identical training. Both groups demonstrated significant increases in 1-repetition maximum (1-RM) on a seated leg press after 4 weeks (both p \u3c 0.001), with RCG showing a significantly greater increase compared SHAM (p = 0.005, g = 3.35). Similarly, RCG demonstrated significantly greater increases in jump height, peak power, and average power compared to SHAM (p = 0.032, g = 3.44; p \u3c 0.001, g = 4.40; p \u3c 0.001, g = 4.50, respectively). Donning a RCG while engaging in lower-body strength-power training may augment increases 1-RM on a seated leg press, jump height, peak and average power, compared with same exercise training without an RCG

Harbors and Inland Waterways: An Overview of Federal Financing

This report outlines the commercial navigation system, how the federal government finances the system, some of the proposals to change federal financing, and challengess to the then future of harbors and inland waterways

On the topology of stationary black holes

We prove that the domain of outer communication of a stationary, globally hyperbolic spacetime satisfying the null energy condition must be simply connected. Under suitable additional hypotheses, this implies, in particular, that each connected component of a cross-section of the event horizon of a stationary black hole must have spherical topology.Comment: 7 pages, Late