Thermodynamic characteristics of the formation of α- and β-cyclodextrin complexes with lumichrome, lumazine, and uracil in aqueous solution

Interactions of α- and β-cyclodextrins with lumichrome and its structural fragments, lumazine and uracil, were studied by means of solubility and 1H NMR spectroscopy. α-Cyclodextrin was found to have a weak complexing ability toward the studied compounds. It was established that β-cyclodextrin forms stable complexes with lumichrome and does not complex with lumazine and uracil. It was shown that only the benzene ring of lumichrome penetrates the β-cyclodextrin cavity, leading to a substantial increase in the solubility of lumichrome in water. We concluded that β-cyclodextrin complexation with lumichrome is highly exothermic due to the van der Waals interactions and hydrogen bonding between polar groups of the reagents.     

Hydroxyethyl cellulose/bentonite/magnetite hybrid materials: structure,physicochemical properties,and antifungal activity

Bentonite/magnetite powder was synthesized and characterized using laser diffraction, scanning electron microscopy, X-ray diffraction, low-temperature nitrogen adsorption–desorption technique, and magnetization measurements, revealing it to be a ferromagnetic material with mesopores. Hydroxyethyl cellulose was filled with bentonite/magnetite particles by mechanical dispersion to produce hybrid film materials that were studied using various methods. X-ray diffraction analysis showed that the interlayer distance in the clay was increased due to intercalation of polymer molecules. A concentration effect of the filling agent on the tensile properties of the hybrid material was revealed. Infrared (IR) spectrometry indicated an increase in the density of the hydrogen-bonding network. Microbiological tests showed that the HEC/bentonite/magnetite films exhibited antifungal effect against Candida albicans.     

The dielectric properties and flow of electrorheological fluids based on polymer-coated nanodispersed barium tetraacetate titanyl particles upon a dynamic shear in electric fields

The shear stress in flowing electrorheological fluids consisting of PMS-20 poly(dimethylsiloxane) filled with nanodispersed barium tetraacetate titanyl particles coated with polymers (polyethyleneimine, poly(ethylene glycol), and polyethyloxazoline) has been studied as depending on the strengths of direct- and alternating-current (f = 50 Hz) electric fields. Results of analyzing the dielectric spectra of electrorheological fluids in a frequency range of 25–10⁶ Hz have been presented. The values of the shear stress in the flowing fluids as depending on the nature of a polymer adsorbed on the particle surface decrease in a series corresponding to a reduction in the Maxwell–Wagner relaxation times of the suspensions. The current-voltage characteristics of the electrorheological fluids at high voltages (up to 5 kV) indicate the realization of the mechanism of currents limited by the space charge. The influence of an adsorbed polymer on the magnitude of the electrorheological effect is reduced to blocking polar groups on the particle surface and variations in the conductivity, effective dielectric permittivity, and loss tangents of filler materials. An increase in the contribution from these factors leads to a gradual decrease in the magnitude of the electrorheological effect.     

Kinetics of the total oxidation of para-xylene and its mixtures with carbon monoxide over supported copper catalysts

The kinetics of the total oxidation of para-xylene and its mixtures with CO over alumina-supported copper catalysts has been investigated at atmospheric pressure in the temperature range from 200 to 270°C. The reactions over the catalysts 10%CuO/γ-Al₂O₃ and (10%CuO + 20%CeO₂)/γ-Al₂O₃ obey the same kinetic equations in fractional rational form. These equations imply that the reactions occur at medium surface coverages of adsorbed substances and differ only in numerical values of constants. The simultaneous oxidation of para-xylene and CO reveals a complicated mutual influence associated with the formation of new intermediates inducing a change in the kinetics of the process.     

Consideration of viscosity during subsonic penetration of a solid body into isotropic barriers

In solving the problem of the reaction of solids with isotropic barriers during their impact, one of the main questions is determination of the penetration resistance of the solid into the barrier. Currently in calculating this resistance as a basic phenomenological approach use is made of the hydrodynamic anomaly in accordance with which the penetration resistance in the plastic region is assumed to be equivalent to the resistance of an ideal liquid.Translated from Zhurnal Prikladnoi Mekhaniki i Tekhnicheskoi Fiziki, No. 3, pp. 120–125, May–June, 1986.     

不同生长期当归1H NMR指纹图谱的研究

利用¹H NMR法测定27个不同生长期的当归提取物,对当归的主要活性成分阿魏酸、藁本内酯、当归多糖进行了初步归属,用特征峰相对峰面积表示3种活性成分的相对含量,并对它们在生长过程中的含量变化进行分析. 数据分析显示,当归中阿魏酸、藁本内酯、当归多糖的含量在第1年变化较为平稳,第2年和第3年变化相对较为活跃,而在当归的生长周期内,当归多糖的含量变化明显大于其他两种活性成分,为参与代谢活动的主要活性成分. 结果证实,通过对照¹H NMR指纹图谱, 将相对含量法与主成分分析法相结合,能对不同生长期的当归药材中的活性成分进行宏观评价和分析,可作为植物药材代谢组学的研究方法.     

无机-有机杂化非线性光学晶体材料LAP和d-LAP晶体红外吸收边计算

根据双原子谐振子模型近似,提出了估算分子晶体材料红外吸收边的理论方法,然后利用超分子量子化学从头算,计算了L-精氨酸一水磷酸盐(LAP)晶体和氘化L-精氨酸一水磷酸盐(d-LAP)晶体单元超分子的红外振动光谱,其中LAP晶体超分子计算值与晶体红外光谱实验值吻合,表明超分子计算能有效地模拟无机-有机杂化非线性光学晶体的红外振动光谱。在归属了超分子重要基频线后,分析其红外强度,并估算了泛频频率。根据我们提出的方法,估算了这两种晶体的红外吸收边,结果与实验值较吻合。表明我们建议的理论方法是合理的。此外,通过计算表明,如果非线性光学晶体材料的红外吸收边是由与活泼H有关的伸缩振动泛频频率决定,那么活泼H的氘化是一种改善红外吸收边的有效途径。     

在RHIC的极限碎裂和Φ介子产生(英文)

利用强子和串级联模型LUCIAE研究了PHOBOS的极限碎裂等以及在PHIC进行的Au+Au碰撞中带电粒子多重性的经验标度规律. 对Φ介子的产生机制也通过与带电粒子多重性的比较进行类似的研究. 结果似乎表明在串级碎裂模型中带电粒子和Φ介子有共同的产生机制. 还讨论了PHOBOS经验标度规律的模型依赖性.The PHOBOS’s limiting fragmentation etc. three empirical scaling rules for charged multiplicity in Au+Au collisions at RHIC are investigated by ahadron and string cascade model LUCIAE. Similar studies are performed for the meson exploring its production mechanism via comparing with the charged multiplicity. The LUCIAE results for charged multiplicity are compatible with PHOBOS observations. However, for the  meson the three empirical scaling rules are either kept only or kept better in the LUCIAE calculations without reduction mechanism of the s quark suppression extra introduced for the strangeness in LUCIAE model. These results seem indicating a universal production mechanism for charged particle and  meson in string fragmentation regime. It is discussed that the PHOBOS’s empirical scaling rules are model dependent indeed.     

Determination of the reaction rate constant and activation energy for pressure-induced 2+2 cycloaddition of the C60 fullerene

The kinetics of fullerene solid-phase dimerization proceeding through the 2+2 cycloaddition of C₆₀ at a pressure of 1.5 GPa is investigated by vibrational spectroscopy in the temperature range 373–473 K. Kinetic curves for the formation of (C₆₀)₂ dimers are obtained using the analytical band at 796 cm^?1 in the IR spectra of the (C₆₀)₂ dimer molecule. Under the assumption that the pressure-induced dimerization of C₆₀ is an irreversible second-order reaction, the reaction rate constants are determined at different temperatures. The activation energy and the preexponential factor are found to be equal to 134±6 kJ/mol and (1.74±0.24)×10¹⁴ s^?1, respectively.