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71.
The two emission lines, Kα1α3h and Kα2α3h resulting from the two-electron transitions and were resolved for elemental nickel. Their measured energies agree well with calculations. Their relative intensity and their intensity relative to that of the Kα diagram lines is about 10?4. This is some 104 times larger than both theoretical results and the results of ion-atom collision experiments. 相似文献
72.
The tetradentate Schiff-base ligands, N,N′-bis(salicylidene)-ethylenediamine (Salen), N,N′-bis(salicylidene) butylenediamine (Salbut), and N,N′-bis(salicylidene)-o–phenylenediamine, (sal-o-phen) are very strongly sorbed by cation exchange resin (Dowex-50W) with Fe2+ ions as a counter ion, forming stable complexes. The kinetics of the catalytic decomposition of H2O2 using these complexes was studied in ethanolic medium. The reaction was first-order with salen and sal-o-phen and second-order with salbut with respect to [H2O2]. The rate of the H2O2 decomposition increased either from salen to salbut or from salen to sal-o-phen. Also, the k (per g dry resin) values decreased with increasing both the particle size and the degree of resin cross-linkage. The active species formed at the beginning of the reaction, had an inhibiting effect on the reaction rate. The corresponding activation parameters were calculated from a least-squares fit of the temperature dependence of the rate constant. A reaction mechanism is proposed. © 1994 John Wiley & Sons, Inc. 相似文献
73.
J. Stephanidou-Stephanatou N. E. Alexandrou G. Salem A. Terzis 《Journal of heterocyclic chemistry》1985,22(3):673-675
The crystal and molecular structure of the title compound, derived by lead tetraacetate oxidation of the bis-p-methoxybenzoylhydrazone of 3,3-dimethylpentane-2,4-dione, is studied by an X-ray crystallographic analysis. 相似文献
74.
75.
Electrical conductivity measurements of 2,4-dinitrosoresorcinol (DNR) and its complexes were measured in the temperature range 20–115°C to give faint semiconducting behaviour for these systems. The conductivity values of the bis Co, Ni, Cu and Zn systems indicated that the metal ion forms a bridge between the two ligands facilitating the transfer of current carriers with some degree of delocalization in the excited state. As the iron content in the complexes increased, a gradual increase of electrical conductivity occurred, that might be due to lattice imperfections. 相似文献
76.
Essam Nasser 《Zeitschrift für Physik A Hadrons and Nuclei》1963,172(4):405-428
Extending earlier studies on spark breakdown, the development of the impulse prebreakdown streamers leading to complete breakdown were investigated. By taking advantage of the proportionality between point potential and length of the positive Lichtenberg figure produced, the potential of the streamer tips progressing from a point anode towards a plane cathode were determined. It was found that the streamer tip potential decreases as streamer advances. At voltages much lower than sparking potential this decrease is rapid. By approaching the sparking potential the loss of tip potential diminishes considerably near the anode. The decrease of potential remains very rapid near the cathode until sparking potential is reached. At the cathode the tip potential increases with the applied potential. At a certain value electrons are emitted from the cathode under the influence of high tip fields. These electrons are accelerated towards the tips forming avalanches by collision. These avalanches appear on the photographic film as minute dots whose number and density depend on the intensity of tip fields. If the applied potential exceeds the sparking voltage, tip potentials are recorded on the cathode between 15 and 25 kV. The avalanches formed in the high intensity field region reach the critical size and form negative, anode — directed streamers. These streamers appear on the film as negative Lichtenberg figures. This ionising potential wave, known as return stroke, travels along the channel of the positive primary streamer. It increases its ionisation to such a degree that the main stroke can take place. 相似文献
77.
78.
The tight-binding method is used to describe the electronic waves of metals in the atomic orbital language familiar to chemists. It is shown that (in both fcc and bcc crystals) k vectors with components (0, 0, 1) or (1, 1, 1) carry hybrids between the s waves and Z2 waves whose axis Z is parallel to the direction of the wave vector. In particular the higher-energy hybrid waves are strongly pointed along the wave vector direction. Furthermore, using the finite cube model, with excellent analytical approximations to the orbitals, the existence of privileged wave vector directions perpendicular to the surface approached by an incoming substrate is demonstrated. A preliminary discussion of the favorable conditions for catalysis emphasizes the extremely favorable role of such pointed hybrids if their sub-band lies (empty) just above the Fermi level of the metal. 相似文献
79.
Transparent glass-nanocomposite sample [50Li2B4O7-50(SrO-Bi2O3-Nb2O5)] (mol %) was prepared by a conventional melt-quenching technique. Fluorite (Bi3NbO7) and SrBi2Nb2O9 (SBN) was produced by heat-treating the as-prepared sample at 773 K for 6 h (HT773). The nanocrystallites of fluorite and SBN phases in the Li2B4O7 glass matrix were established by differential thermal analysis (DTA) which is confirmed by X-ray powder diffraction (XRD), infrared spectroscopy and transmission electron microscopic (TEM) studies. The influence of heat-treating the as-prepared sample on the optical properties (transmission, optical band gap and Urbach energy) has been investigated. Properties such as dielectric constant and dielectric loss as a function of frequency (120 Hz -100 k Hz) and temperature (300-829 K) are reported. 相似文献
80.
Jabbar A Tufail M Arshed W Bhatti AS Ahmad SS Akhter P Dilband M 《Isotopes in environmental and health studies》2010,46(4):495-505
In Rechna Doab, samples of the most common vegetation, perennial grass Desmostachya bipinnata (dab), were collected along with soil samples from 29 sites. Natural radioactivity of 22?Ra, 232Th/22?Ac and ??K was measured by using high purity germanium-based gamma ray spectrometer. Activity concentration levels of 22?Ra, 232Th/22?Ac and ??K in soil were found to be 46.8 ± 6.2 (36.0-57.6), 61.4 ± 5.9 (48.2-73.2) and 644.8 ± 73.9 (537.7-868.4) Bq kg?1 (dry mass), respectively, and those in vegetation were 2.74 ± 1.70 (1.00-6.39), 2.24 ± 0.59 (1.56-2.61) and 172.72±113.37 (53.14-469.24) Bq kg?1 (dry mass), respectively. The measured values of the activity concentration in vegetation are comparable with some other international data. Calculated soil to vegetation transfer factors of 22?Ra, 22?Ac and ??K were 0.06 ± 0.03 (0.02-0.14), 0.04 ± 0.01 (0.03-0.04) and 0.26 ± 0.16 (0.09-0.69). The mean outdoor absorbed dose rate in air for the area under study was determined as 8.22 nGy h?1 and the mean indoor absorbed dose rate in air was 11.52 nGy h?1. The total annual effective dose to the general public from the vegetation was found to be (0.02-0.16) mSv, which is below the recommended limit value of 1 mSv y?1 for the general public. The dab vegetation under study was found to be radiologically safe for the population and environment. 相似文献