954 research outputs found
Supplementation of Opaque-2 and Normal Corn With Lysine and Tryptophan for Finishing Swine
The objective of this experiment was to evaluate the adequacy of normal and opaque-2 corn as sources of lysine and tryptophan for finishing swine. The criteria used to measure the value of these two amino acids were growth performance and carcass data
Relativistic coupled-cluster single-double method applied to alkali-metal atoms
A relativistic version of the coupled-cluster single-double (CCSD) method is
developed for atoms with a single valence electron. In earlier work, a
linearized version of the CCSD method (with extensions to include a dominant
class of triple excitations) led to accurate predictions for energies,
transition amplitudes, hyperfine constants, and other properties of monovalent
atoms. Further progress in high-precision atomic structure calculations for
heavy atoms calls for improvement of the linearized coupled-cluster
methodology. In the present work, equations for the single and double
excitation coefficients of the Dirac-Fock wave function, including all
non-linear coupled-cluster terms that contribute at the single-double level are
worked out. Contributions of the non-linear terms to energies, electric-dipole
matrix elements, and hyperfine constants of low-lying states in alkali-metal
atoms from Li to Cs are evaluated and the results are compared with other
calculations and with precise experiments.Comment: 12 page
Te-and Zn-Doped InSb Crystals Grown in Microgravity
In 2002, within the SUBSA (Solidification Using a Baffle in Sealed Ampoules) investigation, seven doped InSb crystals were grown in microgravity at the International Space Station. The key goals of the SUBSA investigation are: (a) to clarify the origin of the melt convection in space laboratories; (b) to reduce melt convection to the level which allows reproducible diffusion-controlled segregation; (e) to explore the submerged baffle process and liquid encapsulation in microgravity. 30 crystal growth experiments were conducted in the ground unit, to optimize the design of flight ampoules and to test the transparent SUBSA furnace developed by TecMasters Inc. The specially designed furnace, allowed observation of the crystal growth process (melting, seeding, motion of the solid-liquid interface, etc.). In the summer of 2002, eight crystal growth experiments were conducted in the Microgravity Science Glovebox (MSG) facility at the ISS. Four Te-doped (k = 0.5) and three Zn-doped (k2.9) crystals were grown on undoped seeds. In one experiment, we were not able to seed and grow. The seven grown crystals were sectioned and analyzed using SIMS. The design of the SUBSA ampoules, the segregation data and the video images obtained during the SUBSA flight experiments will be presented and discussed
Precision study of 6p 2Pj - 8s 2S1/2 relative transition matrix elements in atomic Cs
A combined experimental and theoretical study of transition matrix elements
of the 6p 2Pj - 8s 2S1/2 transition in atomic Cs is reported. Measurements of
the polarization-dependent two-photon excitation spectrum associated with the
transition were made in an approximately 200 cm-1 range on the low frequency
side of the 6s 2S1/2 - 6p 2P3/2 resonance. The measurements depend
parametrically on the relative transition matrix elements, but also are
sensitive to far-off-resonance 6s 2S1/2 - np 2Pj - 8s 2S1/2 transitions. In the
past, this dependence has yielded a generalized sum rule, the value of which is
dependent on sums of relative two-photon transition matrix elements. In the
present case, best available determinations from other experiments are combined
with theoretical matrix elements to extract the ratio of transition matrix
elements for the 6p 2Pj - 8s 2S1/2 (j = 1/2,3/2) transition. The resulting
experimental value of 1.423(2) is in excellent agreement with the theoretical
value, calculated using a relativistic all-order method, of 1.425(2)
Heat transfer between a nano-tip and a surface
We study quasi-ballistic heat transfer through air between a hot
nanometer-scale tip and a sample. The hot tip/surface configuration is widely
used to perform nonintrusive confined heating. Using a Monte-Carlo simulation,
we find that the thermal conductance reaches 0.8 MW.m-2K-1 on the surface under
the tip and show the shape of the heat flux density distribution
(nanometer-scale thermal spot). These results show that a surface can be
efficiently heated locally without contact. The temporal resolution of the heat
transfer is a few tens of picoseconds.Comment: 4 page
Angle-resolved photoemission and first-principles electronic structure of single-crystalline -uranium (001)
Continuing the photoemission study begun with the work of Opeil et al. [Phys.
Rev. B \textbf{73}, 165109 (2006)], in this paper we report results of an
angle-resolved photoemission spectroscopy (ARPES) study performed on a
high-quality single-crystal -uranium at 173 K. The absence of
surface-reconstruction effects is verified using X-ray Laue and low-energy
electron diffraction (LEED) patterns. We compare the ARPES intensity map with
first-principles band structure calculations using a generalized gradient
approximation (GGA) and we find good correlations with the calculated
dispersion of the electronic bands
Functional Quantum Nodes for Entanglement Distribution over Scalable Quantum Networks
We demonstrate entanglement distribution between two remote quantum nodes
located 3 meters apart. This distribution involves the asynchronous preparation
of two pairs of atomic memories and the coherent mapping of stored atomic
states into light fields in an effective state of near maximum polarization
entanglement. Entanglement is verified by way of the measured violation of a
Bell inequality, and can be used for communication protocols such as quantum
cryptography. The demonstrated quantum nodes and channels can be used as
segments of a quantum repeater, providing an essential tool for robust
long-distance quantum communication.Comment: 10 pages, 7 figures. Text revised, additional information included in
Appendix. Published online in Science Express, 5 April, 200
Influence of GaInP ordering on the electronic quality of concentrator solar cells
The ordering phenomenon produces a reduction in the band gap of the GaInP material. Though a drawback for many optoelectronic applications, ordering can be used as an additional degree of material and device engineering freedom. The performance of the record efficiency GaInP/GaAs/Ge multijunction solar cells depends on the quality and design of the GaInP top cell, which can be affected also by ordering. The tradeoff existing between band gap and minority carrier properties, and the possibility of creating a back surface field (BSF) structure based on an order–disorder GaInP heterostructure makes the study of the ordering appealing for solar cell applications. In this work, the ordering dependency with the growth conditions and substrate orientation is studied. The results obtained are presented to enrich and extend the data available in the literature. Then the properties of order–disorder GaInP heterostructures are assessed by using them as BSF in GaInP concentrator solar cells. The external quantum efficiency (EQE) shows a good behavior of these BSF layers, but unexpectedly poor electronic quality in the active layers. Although the exact origin of this problem remains to be known, it is attributed to traps introduced by the ordered/disordered domains matrix or growth native defects. EQE measurements with bias light show a recovery of the minority carrier properties, presumably due to the saturation of the traps
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