Tridyne attitude control thruster investigation Final report

Experimental results of feasibility Tridyne attitude control thruste

Quantum Particles Constrained on Cylindrical Surfaces with Non-constant Diameter

We present a theoretical formulation of the one-electron problem constrained on the surface of a cylindrical tubule with varying diameter. Because of the cylindrical symmetry, we may reduce the problem to a one-dimensional equation for each angular momentum quantum number $m$ along the cylindrical axis. The geometrical properties of the surface determine the electronic structures through the geometry dependent term in the equation. Magnetic fields parallel to the axis can readily be incorporated. Our formulation is applied to simple examples such as the catenoid and the sinusoidal tubules. The existence of bound states as well as the band structures, which are induced geometrically, for these surfaces are shown. To show that the electronic structures can be altered significantly by applying a magnetic field, Aharonov-Bohm effects in these examples are demonstrated.Comment: 7 pages, 7 figures, submitted to J. Phys. Soc. Jp

Biharmonic pattern selection

A new model to describe fractal growth is discussed which includes effects due to long-range coupling between displacements $u$. The model is based on the biharmonic equation $\nabla^{4}u =0$ in two-dimensional isotropic defect-free media as follows from the Kuramoto-Sivashinsky equation for pattern formation -or, alternatively, from the theory of elasticity. As a difference with Laplacian and Poisson growth models, in the new model the Laplacian of $u$ is neither zero nor proportional to $u$. Its discretization allows to reproduce a transition from dense to multibranched growth at a point in which the growth velocity exhibits a minimum similarly to what occurs within Poisson growth in planar geometry. Furthermore, in circular geometry the transition point is estimated for the simplest case from the relation $r_{\ell}\approx L/e^{1/2}$ such that the trajectories become stable at the growing surfaces in a continuous limit. Hence, within the biharmonic growth model, this transition depends only on the system size $L$ and occurs approximately at a distance $60 \%$ far from a central seed particle. The influence of biharmonic patterns on the growth probability for each lattice site is also analysed.Comment: To appear in Phys. Rev. E. Copies upon request to [email protected]

A foundation for provitamin A biofortification of maize: genome-wide association and genomic prediction models of carotenoid levels.

Efforts are underway for development of crops with improved levels of provitamin A carotenoids to help combat dietary vitamin A deficiency. As a global staple crop with considerable variation in kernel carotenoid composition, maize (Zea mays L.) could have a widespread impact. We performed a genome-wide association study (GWAS) of quantified seed carotenoids across a panel of maize inbreds ranging from light yellow to dark orange in grain color to identify some of the key genes controlling maize grain carotenoid composition. Significant associations at the genome-wide level were detected within the coding regions of zep1 and lut1, carotenoid biosynthetic genes not previously shown to impact grain carotenoid composition in association studies, as well as within previously associated lcyE and crtRB1 genes. We leveraged existing biochemical and genomic information to identify 58 a priori candidate genes relevant to the biosynthesis and retention of carotenoids in maize to test in a pathway-level analysis. This revealed dxs2 and lut5, genes not previously associated with kernel carotenoids. In genomic prediction models, use of markers that targeted a small set of quantitative trait loci associated with carotenoid levels in prior linkage studies were as effective as genome-wide markers for predicting carotenoid traits. Based on GWAS, pathway-level analysis, and genomic prediction studies, we outline a flexible strategy involving use of a small number of genes that can be selected for rapid conversion of elite white grain germplasm, with minimal amounts of carotenoids, to orange grain versions containing high levels of provitamin A

Electrically Small Supergain Arrays

The theory, computer simulations, and experimental measurements are presented for electrically small two-element supergain arrays with near optimal endfire gains of 7 dB. We show how the difficulties of narrow tolerances, large mismatches, low radiation efficiencies, and reduced scattering of electrically small parasitic elements are overcome by using electrically small resonant antennas as the elements in both separately driven and singly driven (parasitic) two-element electrically small supergain endfire arrays. Although rapidly increasing narrow tolerances prevent the practical realization of the maximum theoretically possible endfire gain of electrically small arrays with many elements, the theory and preliminary numerical simulations indicate that near maximum supergains are also achievable in practice for electrically small arrays with three (and possibly more) resonant elements if the decreasing bandwidth with increasing number of elements can be tolerated.Comment: 10 pages, 11 figures, submitted to IEEE Transactions on Antennas and Propagation (December 2006

Variable contexts and levels of hypermutation in HIV-1 proviral genomes recovered from primary peripheral blood mononuclear cells

APOBEC-mediated cytidine cleamination of HIV-1 genomes during reverse transcription has been shown to be a potent mechanism of host restriction for HIV-1 infection ex vivo and in vitro. However, this defense system can be overcome by the viral protein Vif. Unlike other mechanisms of host restriction, the APOCEC-Vif interaction leaves an imprint on integrated proviruses in the form of G-A hypermutation. in the current work we systematically studied levels, contexts, and patterns of HIV-1 hypermutation in vivo. the analysis of 24 full-genome HIV-1 sequences retrieved from primary PBMCs, representing infections with several HIV-1 clades, and the inclusion of 7 cognate pairs of hypermutated/non-hypermutated sequences derived from the same patient sample, provided a comprehensive view of the characteristics of APOBEC-mediated restriction in vivo. Levels of hypermutation varied nearly 5-fold among the studied proviruses. GpG motifs were most frequently affected (22/24 proviruses). Levels of hypermutation varied across the genome. the reported twin peak pattern of hypermutation was observed in 18/24 hypermutants, but the remainder exhibited singular non-conforming patterns. These data suggest considerable complexity in the interplay of host restriction and viral defense during HIV-1 infection. (c) 2008 Elsevier Inc. All rights reserved.Henry M Jackson Fdn Advancement Mil Med, US Mil HIV Res Program, Rockville, MD 20850 USAUniversidade Federal de São Paulo, Paulista Sch Med, Div Infect Dis, BR-04039 São Paulo, BrazilWalter Reed Army Inst Res, Div Retrovirol, Rockville, MD 20850 USAUniversidade Federal de São Paulo, Paulista Sch Med, Div Infect Dis, BR-04039 São Paulo, BrazilWeb of Scienc

Mean flow and spiral defect chaos in Rayleigh-Benard convection

We describe a numerical procedure to construct a modified velocity field that does not have any mean flow. Using this procedure, we present two results. Firstly, we show that, in the absence of mean flow, spiral defect chaos collapses to a stationary pattern comprising textures of stripes with angular bends. The quenched patterns are characterized by mean wavenumbers that approach those uniquely selected by focus-type singularities, which, in the absence of mean flow, lie at the zig-zag instability boundary. The quenched patterns also have larger correlation lengths and are comprised of rolls with less curvature. Secondly, we describe how mean flow can contribute to the commonly observed phenomenon of rolls terminating perpendicularly into lateral walls. We show that, in the absence of mean flow, rolls begin to terminate into lateral walls at an oblique angle. This obliqueness increases with Rayleigh number.Comment: 14 pages, 19 figure

Dynamics and Selection of Giant Spirals in Rayleigh-Benard Convection

For Rayleigh-Benard convection of a fluid with Prandtl number \sigma \approx 1, we report experimental and theoretical results on a pattern selection mechanism for cell-filling, giant, rotating spirals. We show that the pattern selection in a certain limit can be explained quantitatively by a phase-diffusion mechanism. This mechanism for pattern selection is very different from that for spirals in excitable media

A COMPARATIVE MAPPING OF ENZYMES INVOLVED IN HEXOSEMONOPHOSPHATE SHUNT AND CITRIC ACID CYCLE IN THE BRAIN *

Peer Reviewedhttp://deepblue.lib.umich.edu/bitstream/2027.42/66082/1/j.1471-4159.1963.tb05042.x.pd