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991.
Bogdan Ptaszyński 《Thermochimica Acta》1980,38(3):277-283
Thermal studies have been carried out on crystalline complexes formed between antimony(III) bromide and hydrobromides of some aromatic amines in concentrated hydrobromic acid solutions. Thermal analysis curves of the compounds under study are presented. Kinetic parameters of the thermal decomposition reactions were calculated from the TG curves using the Horowitz—Metzger method. A comparison of the thermal stabilities of the complexes was made. 相似文献
992.
993.
Uniaxial stress experiments were used to investigate the nature of the luminescence lines observed at low temperatures in ZnTe in the vicinity of the absorption edge. The single crystals used in this experiment were grown from solution of ZnTe in tellurium. Both “as-grown” crystals and crystals annealed in Zn vapour were investigated. The most intense line in “as-grown” crystals is attributed to an exciton bound to a neutral acceptor. The binding energy of the exciton in this center is 6 meV. After annealing a new center appears in the same spectral region. Stress experiments as well as the temperature dependence of the intensity of the luminescence indicate that this center is a complex consisting of an exciton and an ionized donor. Splitting of J = 1 (Γ5) and J = 2 (Γ3 + Γ4) levels was found to be 1.2 meV. 相似文献
994.
The second-order intensity correlation function g(2)(0) of a laser beam passing through a nonlinear medium has been experimentally found to be a decreasing function of the power density in the medium. 相似文献
995.
A. Budzanowski K. Chyla R. Czabański K. Grotowski L. Jarczyk B. Kamys A. Kapus̀cik S. Micek J. Płoskonka A. Strzałkowski J. Szmider Z. Wróbel L. Zastawniak R. Zybert 《Nuclear Physics A》1973,211(3):463-472
Excitation functions for the elastic scattering of α-particles from Ni, Co and Cu at θlab = 179° were measured in the lab energy range 22.75–28.40 MeV, as well as some angular distributions for Co(α, α). Broad maxima with a width of about 2.5 MeV were found in the excitation functions. It is shown that a simple four-parameter optical model of the interaction is able to reproduce the angular distributions as well as the excitation functions. Examination of the Argand diagrams leads to the conclusion that the maxima in the excitation curves are formed as a result of a coherent superposition of a number of partial waves, none of which behaves in itself in a resonance-like manner. 相似文献
996.
M. Szymański J. Karolczak F. Kaczmarek 《Applied Physics A: Materials Science & Processing》1979,19(3):345-351
PrP5O14, PrxLa1−xP5O14, and PrxY1−xP5O14 (0≦x≦1) single crystals of laser quality were synthesized and their crystallographic and optical parameters measured. Laser
emissions in the visible (λ=637.4 nm) with no mirrors in place (superradiance) and also in various optical resonators have
been observed. 相似文献
997.
The Cerofolini procedure for obtaining multilayer adsorption isotherms on heterogeneous surfaces is generalized, to take into account the full form of the BET equation as the local adsorption isotherm. 相似文献
998.
U. Domańska 《Journal of solution chemistry》1989,18(2):173-188
Three long-chain ethylene glycol monoesters of stearic, eicosanoic and behenic acids have been synthesized and carefully purified. Their solubilities in 25 pure solvents and in 28 binary solvent systems have been investigated by a synthetic method over a temperature range from 280 to 320 K. The systems containing cyclohexane+alcohols and chlorohydrocarbons+alcohols mixed solvents were found to exhibit a solubility synergistic effect. The results of these measurements were correlated by the Wilson equation utilizing temperature dependent ij parameters. 相似文献
999.
A. Golański 《Journal of Radioanalytical and Nuclear Chemistry》1969,3(3-4):161-173
A study of the possibility of using half-lives between 0.55 and 873 msec in activation analysis with 14 MeV neutrons is presented
here. The cyclic counting method is used: irradiation and detection are repeated several times and counts are memorised during
all successive cycles until good final statistics are reached. The theoretical aspect of the cyclic counting method and the
influence of neutron pulse shape on the activation results are discussed. The sample is activated and its activity measured
in the same geometry: the sample and the scintillation detector are placed close to the target of the neutron generator. An
electronic gating system is used to avoid photomultiplier gain fluctuations involved in neutron bombardment. Detection limits
are measured for the following elements: Be, B, Al, Ca, As, Zr, In, Tl, Pb, Bi.
Work carried out at: Centre d'Etudes Nucleaires de Grenoble, France. 相似文献
1000.
Matczak-Jon E Videnova-Adrabińska V Burzyńska A Kafarski P Lis T 《Chemistry (Weinheim an der Bergstrasse, Germany)》2005,11(8):2357-2372
The crystal structures of 3-methylpiperid-1-ylmethane-1,1-diphosphonic (2), 4-methylpiperid-1-ylmethane-1,1-diphosphonic (3), 2-ethylpiperid-1-ylmethane-1,1-diphosphonic (4), and 2-methylpiperid-1-ylmethane-1,1-diphosphonic (5) acids have been determined and are discussed with respect to their molecular organization and crystal-packing preferences. The chair conformation, predominant also in solution, favors equatorial positioning of the bulky substituents of the heterocyclic N and C atoms. The molecular geometry also provides access to intramolecular hydrogen-bond formation between the axial protons located on the nitrogen atoms, as well as the carbon atoms closest to it, and phosphonic/phosphonate oxygen atoms. The molecules preferably arrange in monolayers, observed in all crystals with an exception of 3. The layers are held in place in the third direction through van der Waals interactions. The analysis of two-dimensional hydrogen-bonded networks is concentrated on revealing how the substituent's topology of the molecule affects the solid-state organization in well-defined structures and is aimed at unraveling the consequences and the possible conformational changes by stepwise network disruption upon crystal dissolution in water. The solution NMR studies are focused on revealing the role that the topochemistry of the substituent plays for the stereodynamics in 2-5. It is demonstrated that in contrast to piperid-1-ylmethane-1,1-diphosphonic acid (1), in which the ring inversion/rotation around the C-N bond concerted with the N-H...O hydrogen-bond breaking/formation process leads to a mixture of two interconverting conformers, the concerted N-H...O breaking/rotation/N-H...O formation process in 2 and 3 allows for a predominance of one conformer in solution. However, placement of a substituent at 2-position in the ring hampers the rotation around the C-N bond; this makes 4 and 5 significantly less flexible relative to compounds 1-3. In addition, both compounds 4 and 5 are proved to exist as a mixture of two conformers, the equilibrium of which in acidic solution is shifted towards the conformer found in solid state. In alkaline solutions of 4 and 5, the equilibrium is shifted towards the conformer that is forced by the flipping of the heterocyclic ring. These results correlate well with recently documented differences in the biological potency of this group of compounds. 相似文献