1,486 research outputs found
Pyramidal Atoms: Berylliumlike Hollow States
Based on the idea that four excited electrons arrange themselves around the
nucleus in the corners of a pyramid in order to minimize their mutual
repulsion, we present an analytical model of quadruply excited states. The
model shows excellent comparison with ab initio results and provides a clear
physical picture of the intrinsic motion of the four electrons. The model is
used to predict configuration-mixing fractions and spectra of these highly
correlated states.Comment: 4 pages, 2 figure
High Altitude Ozone Research Balloon
In order to create a mission model of the high altitude ozone research balloon (HAORB) several options for flight preparation, altitude control, flight termination, and payload recovery were considered. After the optimal launch date and location for two separate HAORB flights were calculated, a method for reducing the heat transfer from solar and infrared radiation was designed and analytically tested. This provided the most important advantage of the HAORB over conventional balloons, i.e., its improved flight duration. Comparisons of different parachute configurations were made, and a design best suited for the HAORB's needs was determined to provide for payload recovery after flight termination. In an effort to avoid possible payload damage, a landing system was also developed
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Synthesis of refractory-oxide materials by skull melting
Skull melting is a cold-crucible technique for obtaining high-purity melts of refractory materials, particularly oxides. This technique has been used to synthesize high-purity minerals and to prepare single crystals of uraninite (UO/sub 2/) and thorianite (ThO/sub 2/) directly from the melt. A description of the crystal-growing technique is discussed. Los Alamos is also interested in developing the skull-melting technique to zone-refine spent UO/sub 2/ nuclear reactor fuel pins. Since metallic fission products and actinides will behave as solute impurities in a UO/sub 2/ solvent, the success of the zone-refining process will depend on the distribution of the impurities between molten and solid UO/sub 2/. An effective distribution coefficient for Y/sub 2/O/sub 3/ segregated between molten and solid UO/sub 2/ was experimentally determined by zone melting. An effective distribution coefficient of k = 0.75 +- 0.05 was obtained, in good agreement with an equilibrium value of k/sub 0/ = 0.6, estimated from the Y/sub 2/O/sub 3/-UO/sub 2/ phase diagram
Effects of Activation Drills Combined with Dynamic Warmup on Performance Field Tests
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Chemical Vapor Deposition Model of Polysilicon in a Trichlorosilane and Hydrogen System
The traditional polysilicon processes should be refined when addressing the low energy consumption requirement for the production of solar grade silicon. This paper addresses the fluid dynamic conditions required to deposit polysilicon in the traditional Siemens reactor. Analytical solutions for the deposition process are presented, providing information on maximizing the rate between the amount of polysilicon obtained and the energy consumed during the deposition process. The growth rate, deposition efficiency, and power-loss dependence on the gas velocity, the mixture of gas composition, the reactor pressure, and the surface temperature have been analyzed. The analytical solutions have been compared to experimental data and computational solutions presented in the literature. At atmospheric pressure, the molar fraction of hydrogen at the inlet should be adjusted to the range of 0.85–0.90, the gas inlet temperature should be raised within the interval of 673 and 773 K, and the gas velocity should reach the Reynolds number 800. The resultant growth rate will be between 6 and 6.5 _m min−1. Operation above atmospheric pressure is strongly recommended to achieve growth rates of 20 _m min−1 at 6 atm
Intermanifold similarities in partial photoionization cross sections of helium
Using the eigenchannel R-matrix method we calculate partial photoionization
cross sections from the ground state of the helium atom for incident photon
energies up to the N=9 manifold. The wide energy range covered by our
calculations permits a thorough investigation of general patterns in the cross
sections which were first discussed by Menzel and co-workers [Phys. Rev. A {\bf
54}, 2080 (1996)]. The existence of these patterns can easily be understood in
terms of propensity rules for autoionization. As the photon energy is increased
the regular patterns are locally interrupted by perturber states until they
fade out indicating the progressive break-down of the propensity rules and the
underlying approximate quantum numbers. We demonstrate that the destructive
influence of isolated perturbers can be compensated with an energy-dependent
quantum defect.Comment: 10 pages, 10 figures, replacement with some typos correcte
Examination of Curcumin and Fenugreek Soluble Fiber Supplementation on Submaximal and Maximal Aerobic Performance Indices
This study examined the effects of curcumin and fenugreek soluble fiber supplementation on the ventilatory threshold (VT) and peak oxygen consumption (VO2 peak). Methods: Forty-five untrained men and women were randomly assigned to one of three supplementation groups: placebo (PLA, n = 13), 500 mg·day−1 CurQfen® (CUR, n = 14), or 300 mg·day−1 fenugreek soluble fiber (FEN, n = 18). Participants completed a maximal graded exercise test on a cycle ergometer to determine the VT and VO2 peak before (PRE) and after (POST) 28 days of daily supplementation. Separate, one-way analyses of covariance (ANCOVAs) were used to examine the between-group differences for adjusted POST VT and VO2 peak values, covaried for the respective PRE-test values. Results: The adjusted POST VT VO2 values for the CUR (mean SD = 1.593 0.157 L·min−1) and FEN (1.597 0.157 L·min−1) groups were greater than (p = 0.039 and p = 0.025, respectively) the PLA (1.465 0.155 L·min−1) group, but the FEN and CUR groups were not different (p = 0.943). There were no differences in the adjusted VO2 peak values (F = 0.613, p = 0.547) among groups. Conclusion: These findings indicated that fenugreek soluble fiber was responsible for the improvements in the submaximal performance index for both CUR and FEN groups
Resonance structure in the Li^- photodetachment cross section
We report on the first observation of resonance structure in the total cross
section for the photodetachment of Li^-. The structure arises from the
autodetaching decay of doubly excited ^1P states of Li^- that are bound with
respect to the 3p state of the Li atom. Calculations have been performed for
both Li^- and H^- to assist in the identification of these resonances. The
lowest lying resonance is a symmetrically excited intrashell resonance. Higher
lying asymmetrically excited intershell states are observed which converge on
the Li(3p) limit.Comment: 4 pages, 2 figure, 19 references, RevTeX, figures in ep
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Management application of an empirical model of sardine–climate regime shifts
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