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141.
Argon crystals were doped with 0.2 ppm of 41K through the nuclear reaction 40Ar (n, β-) 41K. The absorption spectrum from 300 nm to 800 nm was measured as a function of the annealing temperature. Absorption ← 42s transition of the free atom could be bands corresponding to the 42p, ← 42s and 52p, ← 42s transition of the free atom could be observed. The absorption bands depend strongly on the annealing temperature. An increase in the annealing temperature results in a blue shift of the absorption bands. 相似文献
142.
Valfredo Azevedo Lemos Moacy Selis Santos Márcio José Silva dos Santos Daniel Rodrigues Vieira Cleber Galvão Novaes 《Mikrochimica acta》2007,157(3-4):215-222
Cloud point extraction employing the new reagent 6-[2′-(6′-methyl-benzothiazolylazo)]-1,2-dihydroxy-3,5-benzenedisulfonic
acid as complexing agent and Triton X-114 as the surfactant is proposed for copper determination. A sample volume of 10 mL
was used. Dilution of the surfactant-rich phase with acidified methanol was performed after phase separation, and the copper
contents were measured by flame atomic absorption spectrometry. Variables affecting the system were optimized using factorial
design and Doehlert matrix. Signals were measured as peak height using an instrument software. Using the experimental conditions
defined in the optimization, the method allowed copper determination with a detection limit of 1.5 μg L−1. The calculated enrichment factor is 14. The effects of foreign ions are reported. The accuracy of the procedure was tested
by analyzing certified reference material. The method was successfully applied to copper determination in natural and drinking
water samples. 相似文献
143.
Measurements have been made of the magnetic susceptibility X in ternary titanium-vanadium hydrides Ti1?yVyHx in the range 0<y< 0.5 and with a hydrogen to metal ratio from 1.6 to 1.92; they cover the temperature interval from 80 to 440 K. The x?T curves of some of the ternary hydrides possess a maximum similar to that seen in binary hydrides. Its occurrence depends upon both hydrogen and vanadium concentration. Comparison with the lattice constants shows that this dependence is related to the transition from the cubic γ-phase to the tetragonal δ-phase. The x?T curves of those samples showing the phase transition were extrapolated from the cubic phase down to lower temperatures. Conclusions were drawn from the measured and extrapolated susceptibility values, as to the influence of both hydrogen and vanadium concentrations on the electronic structure of these hydrides. The dependence of the magnetic susceptibility on the vanadium concentration shows that, in the cubic phase, the fermi energy lies on the increasing side of a maximum in the density of states curve. The degree of occupation of the conduction band does not depend on the hydrogen concentration. The rigid band model cannot be used in the hydrides studied here to account for the effects of varying their hydrogen concentration. 相似文献
144.
Jorge C.G. Calado Edmundo J.S. Gomes de Azevedo Virgílio A.M. Soares Klaus Lucas Keshawa P. Shukla 《Fluid Phase Equilibria》1984,16(2):171-183
The total vapour pressure of the xenon + methyl chloride system has been measured as a function of composition at 175.44 and 182.32 K. The resulting data have been used to evaluate the excess Gibbs functions GE at the same temperatures. The excess enthalpy and excess molar volume have also been measured at 182.32 K. The system shows large positive deviations from Raoult's law but negative volumes on mixing. These results are compared with theoretical predictions of a recent molecular theory and of standard engineering methods. The calculations show the superiority of the molecular theory over more empirical procedures such as those based on the Redlich-Kwong equation of state or the regular-solution model. 相似文献
145.
146.
It is shown, starting from a nearly-free electron approximation, how correlations can occur in the atomic positions of binary liquid and glassy alloys. In particular, it follows from energy considerations that for an alloy of a transition metal with a metalloid there is a concentration region where there should be no metalloid-metalloid nearest neighbors. This concentration region is just the same as that where glass formation is often observed in these systems. 相似文献
147.
In this paper we are concerned with a special class of bicriterion path problems. For the considered class of bicriterion problems at least one of the objectives is type MAXMIN. For the other one, besides an objective type MAXMIN also a MINSUM and a MINRATIO type objective are considered. Two algorithms are presented for the considered class of bicriterion path problems. The first one only determines the minimal complete set of nondominated paths and the second one determines the entire set of nondominated paths. Both algorithms can be used for any type of bicriterion path problems, since one of the objectives is type MAXMIN and an algorithm exists to determine the best path for the other objective. Computational statistics for the three types of considered bicriterion path problems are also presented. 相似文献
148.
We report both experimental and theoretical studies of the optical properties in KCl of a defect-associated In center whose sole previously identified optical transition was a strong absorption band peaking at 610 nm. With the aid of an optical tagging technique, we have been able to identify with that center two new but much weaker absorption bands peaking at 860 and 960 nm, respectively. We show that the energy splittings, relative strengths, and less perfectly, the polarizations of those three transitions make fit to the In0(1) center model, i.e., the model, initially developed for the Tl0(1) center, of a neutral atom perturbed by the field of an adjacent anion vacancy. However, in contrast to the Tl0(1) center, the In0(1) center lacks a significant emission, excluding its use as a laser gain medium. 相似文献
149.
C.K. Chen J. Knowles D. Martin J.M. Scarr I.O. Skillicorn K. Smith P. Joos A. Ladage H. Meyer P. Stein G. Wolf S. Yellin C. Benz G. Drews D. Hoffmann J. Knobloch W. Kraus H. Nagel K. Wacker 《Nuclear Physics B》1978,133(1):13-37
Electroproduction of hadrons is studied in the kinematic region W < 2.8 GeV and 0.3 < Q2 < 1.4 GeV2 using the DESY streamer chamber. Prong cross sections, charged-particle multiplicities and inclusive π? distributions are presented. The average charged multiplicity is found to be independent of Q2 in the Q2 range studied here; however it is lower than in photoproduction. The fraction of forward π? is found to be significantly less in electroproduction than in photoproduction. The 〈p⊥2〉 for inclusive π? is, for all x values, similar to that found in photoproduction. 相似文献
150.