Gas-chromatographic analysis of alkylated derivatives of carane and of cycloheptane in capillary columns

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.     

Synthesis, Structure, and Membrane Activity of New Glycyrrhetic Acid Derivatives

Derivatives of 3-O-acetyl-18-H-glycyrrhetic acid were synthesized. Their structures and membrane activities were studied.     

三阶泛函微分方程的周期解的存在性

本文利用重合度理论研究了一类三阶泛函微分方程方程的2π-周期解的问题,获得了该方程存在2π-周期解的若干新结论,改进推广了有关文献中的已有结果．     

New phases with fluorite-derived structure in CaF2(Y,Ln)F3 systems

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 a_ord = 13a_dis (where a_dis 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.     

Two crystalline polymorphic forms of α-(<Emphasis Type="Italic">N</Emphasis>-benzoxazolin-2-one)acetic acid

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) ų, 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) ų, 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.     

Distribution of Zinc Oxide Nanocrystals in a Polymer Film

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.     

Production of carbon nanotubes by self-propagating high-temperature synthesis

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.     

氢链系统中的非线性问题

考虑氢原子之间的非谐相互作用,分别用代数方法和变分法求得氢链系统中扭结与反扭结孤波解,解的特点是在非谐项的影响下,正孤波与反孤波不再对称,从而解释了实验中观察到的冰分子中L缺陷和D缺陷的对称性破缺现象,进一步的计算表明,由于非谐项的存在,正孤波与反孤波携带的能量也失去对称性,且代数方法和变分法给出一致的结果.     

Glycine-nitrate combustion synthesis of CeFeO<Subscript>3</Subscript>-based nanocrystalline powders

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.