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1.
The retention indices of synthesized alkyl derivatives of carane and of cycloheptane in capillary columns with tricresyl phosphate and squalane at 70°C have been determined. The influence of the structure of the hydrocarbons studied on the values of their retention parameters is considered. An estimate is given of the nature of the interrelationship between the physical properties of these hydrocarbons and their retention indices on a nonpolar stationary phase.  相似文献   
2.
3.
Derivatives of 3-O-acetyl-18-H-glycyrrhetic acid were synthesized. Their structures and membrane activities were studied.  相似文献   
4.
Crystallographic characteristics of six new phases of idealized composition Ca8R5F31 which are formed in the CaF2RF3 (R = Y, HoLu) systems are reported. All the phases have a similar structure derived from CaF2 with slight distortion and pseudocubic unit cell parameters aord = 13adis (where adis is the parameter of the fluorite subcell). The degree of ordering increases in the lanthanide series with decrease of ionic radius and, in every system given, with an increase in the RF3 content of the solid solution. Significant influence of temperature and time of annealing on the degree of ordering was not detected.  相似文献   
5.
Two crystalline polymorphic forms of α-(N-benzoxazolin-2-one)acetic acid (BAA) are prepared by changing the temperature of its crystallization from solution in ethanol. Crystallographic data of the α-form are determined: a = 12.7769(17) Å, b = 8.2574(9) Å, c = 16.7390(19) Å, β = 105.087(13)°, space group C2/c, V = 1705.2(4) Å3, and Z = 8, while those of β form are a = 5.2854(4) Å, b = 5.9880(4) Å, c = 13.4509(5) Å, β = 94.666(4)°, space group P21, V = 424.30(4) Å3, and Z = 2. It is found that BAA molecules of the α form combine into infinite one-dimensional chains arranged along axis b by means of O?H···O and C?H···O hydrogen bonds, and these chains are crosslinked via C?H···O hydrogen bonds to form a threedimensional structure. The β form has another system of hydrogen bonds, one of which is bifurcated (O4···O2, O4···O3), and the π–π-interactions between the benzoxazolinone fragments of BAA molecules combined into a chain also arranged along axis b are observed. Calorimetric analysis shows that the polymorphic transition from the α form to the β form occurs at 129°C.  相似文献   
6.
The structure of polymer films modified with zinc oxide nanocrystals was studied by the optical absorption and small-angle X-ray scattering methods. Small-angle X-ray scattering allows determination of the nanoparticle size distribution function, which is the decisive factor in predicting the optical properties of heterophase materials, including filled polymer films. The optical absorption spectrum of an acrylate polymer film doped with 1.6 wt % zinc oxide nanocrystals approaches the ideal absorber spectrum, which allows this material to be recommended for use as a protective color filter.  相似文献   
7.
Carbon nanotubes are prepared by the method of self-propagating high-temperature synthesis for the first time. The initial components for this synthesis are carboniferous materials (soda, limestone, and Teflon) and reducers (magnesium, lithium, and sodium) with addition of a nickel or iron catalyst. The morphology of the nanotubes (straight multiwall nanotubes apparently free of a catalyst, bent nanotubes completely filled with a catalyst, and carbon nanofibers) is similar to that of nanotubes grown by chemical methods. The nanotubes account for 2–4 wt % of the product synthesized.  相似文献   
8.
Glycine-nitrate combustion method was used to obtain powders based on CeFeO3 nanocrystals with average crystallite size in the range from 33 ± 3 to 51 ± 5 nm. The influence exerted by parameters of the glycine-nitrate combustion process and, in particular, by the glycine-nitrate ratio (G/N) on the composition and crystallite size of the synthesis products was determined. The optimal G/N ratio at which nanocrystalline cerium orthoferrite is formed with the minimum amount of impurity phases Fe2O3 and CeO2 was found to be 0.8. It was demonstrated that the composition of the starting solution affects the nature of the phase heterogeneity in the resulting product, crystallite size, and porosity of the nanocrystalline powders being formed. The patterns determined in the study make it possible to optimize the technology of nanocrystalline powders based on CeFeO3 in order to obtain powders with prescribed phase composition and crystallite sizes to enable their use as a basis for photocatalytic materials.  相似文献   
9.
Asymptotic terms are constructed for a solution to the three-dimensional elasticity problem for a thin cylindrical isotropic plate clamped at its lateral side except for a part (crack) that is in contact with a rigid profile without friction. The existence and uniqueness theorems are established. The behavior of solutions at infinity is studied. Bibliography: 38 titles. Illustrations: 1 figure.  相似文献   
10.
The crystal structure of the complex of 18-dehydroglycyrrhetic acid (GLD) with DMSO (C30H41O4·C2H6OS) has been determined by x-ray structural analysis. Syntex P21 diffractometer, CuK radiation, 1309 reflections, R = 0.080. A conformational analysis has been made of the GLD molecule in comparison with that of glycyrrhetic acid. The conformations of rings A and B in the GLD molecule do not differ from the conformations of the corresponding rings of glycyrrhetic acid. Differences arise in ringsC,D, andE because of the presence of the double bond between the C18 and C19 atoms.Translated from Khimiya Prirodnykh Soedinenii, No. 3, pp. 362–366, May-June, 1996. Original article submitted Novemher 11, 1995.  相似文献   
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