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101.
Non-linear ion acoustic waves are excited by a positive voltage step applied on a grid in a quiescent plasma. The distortion of the excited wave packet during propagation agrees with Ichikawa and Taniuti's theory. 相似文献
102.
E. Galvão da Silva R. B. Scorzelli F. Sánchez-Sinencio Octavio-Alvarez-F J. G. Mendoza-Alvarez 《Hyperfine Interactions》1990,57(1-4):1839-1843
CEMS studies have been performed on Cd0.95 Fe0.05 Te films grown by r.f. supttering on quartz and silicon substrates. The dependence of the relative amount of Fe2+ and Fe3+ on substrate type, substrate temperature and annealing temperature is discussed. 相似文献
103.
Mössbauer absorption of Fe57, for four equivalent but differently oriented sites, in naturally occuring FeS2 (pyrite) crystals has been studied in the ideal absorber thickness, as a function of the orientation of the crystal axes with respect to the linearly polarized gamma rays from Co57/LiNbO3 source and the direction of the polarization. Eperimental peak area ratio of ~ 1 in the polycrystalline absorber and the monocrystalline absorbers is independent of the crystal orientation. The analysis of the present experiment shows that the Mössbauer fraction, f, is isotropic and that the asymmetry parameter, η, is zero. 相似文献
104.
105.
Mössbauer spectroscopy and X-ray diffraction measurements have been done on (Ti1–x
Nb
x
)Fe2 compounds in order to investigate the effect of Nb on the magnetic properties of TiFe2. The experimental results show that Nb enters the lattice by filling Ti sites, thereby forming a continuous phase over the whole range of Nb concentrations. The Mössbauer spectra at 80 K fitted with a magnetic hyperfine field distribution show a continuous decrease of the average magnetic hyperfine field with increasing Nb concentration, as well as several different magnetic configurations forx0.3. 相似文献
106.
R. B. Scorzelli E. Galvão da Silva C. Kaito Y. Saito M. McElfresh M. Elmassalami 《Hyperfine Interactions》1994,94(1):2337-2342
Iron-nickel ultrafine particles with a composition in the Invar region (38–50% Ni) were prepared by the gas-evaporation-coalescence technique. The chemical composition was checked by electronprobe microanalysis, while X-ray diffraction Rietveld refinement was used to characterize the structure as well as to estimate the particle size. The temperature and field dependence of the magnetizationM(B, T) was measured for 0B25 kOe in the temperature range 4.2 KT400 K. Transmission Mössbauer spectra were taken at room temperature and at liquid helium temperature. The results obtained show that the predominant phase is a disordered Ni-rich alloy.On leave from Physics Department, University of Khartoum, P.O. Box 321, Khartoum, Sudan. 相似文献
107.
Noé Zúñiga-Villarreal Juan Manuel Germán-Acacio Ana Adela Lemus-Santana Marisol Reyes-Lezama Rubén A. Toscano 《Journal of organometallic chemistry》2004,689(17):2827-2832
The halocarbonyls BrM(CO)5, M = Mn and Re, were reacted with the KN(SePPh2)2 salt in equimolar amounts; the reactions were thermally carried out and resulted in the generation of the hexacoordinated isostructural complexes [M(CO)4{Ph2P(Se)NP(Se)Ph2-Se,Se′}] with a twist MSePNPSe ring conformation. Complexes’ characterizations were achieved by IR, mass, NMR (1H, 13C, 31P, 77Se) spectroscopies, and by single-crystal X-ray diffraction. 相似文献
108.
Paul Chiy Miguel de la Fuente Enrique Barrado Marisol Vega C. Phillips 《Fresenius' Journal of Analytical Chemistry》1998,361(4):343-348
The optimum conditions for microwave digestion of herbage and faeces to determine mineral concentrations were obtained by
varying sample mass, reagent and heating programme, and it was confirmed that the resulting element concentrations were the
same as for certified reference material. The effects of feeding cadmium to sheep at a level that is typical of polluted
regions (1 mg/kg) for ten days were investigated, as well as the possible amelioration of cadmium effects by adding 30 mg/kg
Zn to the diet. Cadmium in the feed increased the cadmium balance and produced several mineral disturbances, in particular
a reduction in sodium balance which is typical of renal tubular disorders. Including zinc in the diet as well as cadmium reduced
the cadmium balance to a level similar to that of sheep that did not receive cadmium or zinc, which suggests that the zinc
status is critical in determining whether cadmium in feed increases the cadmium balance in sheep.
Received: 1 August 1997 / Revised: 8 December 1997 / Accepted: 10 December 1997 相似文献
109.
Martins VL de Almeida LF de Castro SL Galvão RK de Araújo MC da Silva EC 《Journal of chemical information and computer sciences》2003,43(6):1725-1732
Instrumental analysis techniques that employ measurements based on inflection points may have their accuracy compromised due to the need for signal differentiation, which is very sensitive to instrumental noise. This paper presents a strategy for localizing inflection points that exploits the multiscale processing capability of the Wavelet Transform and avoids the need for explicit signal differentiation. The strategy is illustrated in simulated examples and also in a real analytical problem involving the determination of Pb and Cd by potentiometric stripping analysis. In this application, the results were in good agreement with the expected values and were slightly better than those obtained from the first derivative of the curves after smoothing by a Windowed Fourier Transform. 相似文献
110.
Here we present Adun, a new molecular simulator that represents a paradigm shift in the way scientific programs are developed. The traditional algorithm centric methods of scientific programming can lead to major maintainability and productivity problems when developing large complex programs. These problems have long been recognized by computer scientists; however, the ideas and techniques developed to deal with them have not achieved widespread adoption in the scientific community. Adun is the result of the application of these ideas, including pervasive polymorphism, evolutionary frameworks, and refactoring, to the molecular simulation domain. The simulator itself is underpinned by the Adun Framework, which separates the structure of the program from any underlying algorithms, thus giving a completely reusable design. The aims are twofold. The first is to provide a platform for rapid development and implementation of different simulation types and algorithms. The second is to decrease the learning barrier for new developers by providing a rigorous and well-defined structure. We present some examples on the use of Adun by performing simple free-energy simulations for the adiabatic charging of a single ion, using both free-energy perturbation and the Bennett's method. We also illustrate the power of the design by detailing the ease with which ASEP/MD, an elaborated mean field QM/MM method originally written in FORTRAN 90, was implemented into Adun. 相似文献