Biodegradable Electrostatic Complexes of Chitosan Cationic Microparticles and Anionic Liposomes

Using the electrostatic adsorption of anionic liposomes on the surface of cationic microparticles of ion-crosslinked chitosan, complexes in which each microparticle can bind up to 110 intact (undestroyed) liposomes are prepared. The saturated complex 350–400 nm in diameter does not dissociate to initial components in aqueous solutions with pH 7 and a NaCl concentration of 0.15 mol/L, but decomposes to 10-nm particles in the presence of proteolytic enzymes. The chitosan–liposome complex and its biodegradation products are characterized by a low cytotoxicity. The described technique may be used to obtain biodegradable multiliposomal containers for the encapsulation and delivery of drugs.     

Thermodynamics of intercalation from solution for PbI2

IR and diffuse-reflection spectroscopy have been used to detect the concentration threshold in intercalation, whose temperature dependence has been examined for systems composed of PbI₂ with solutions of aniline and quinoline in benzene. The thermodynamic nature of the threshold has been established, and it is found that the penetration of the organic molecules between the layers involves the formation of an order intercalation phase. The enthalpies and entropies of formation have been calculated for the intercalation compounds. It is found that intercalation leads in the main to changes in the vibrational bands of the amino group, which indicates that it participates in forming the bond between the amine and the inorganic layered matrix.Translated from Teoreticheskaya i Éksperimental'naya Khimiya, Vol. 21, No. 1, pp. 123–127, January–February, 1985.     

Heterophase polymerization of styrene in the presence of organosilicon compounds of various natures

The heterophase polymerization of styrene has been carried out in the presence of surfactants—organosilicon compounds with different solubilities in aqueous and styrene phases and surface activities at the interface. It has been demonstrated that the stability of polymer suspensions prepared with water-insoluble organosilicon compounds is much higher than that in the presence of organosilicon surfactants soluble in organic and aqueous phases. In the former case, suspensions with narrower particle-size distributions are produced. The stability of polymer microspheres prepared at various monomer-to-water volume ratios has been tested. An increase in the monomer concentration above 25 vol % leads to the loss of system stability.     

Determination of Epoxy and Isocyanate Groups in the Presence of Each Other

Analytical reactions for the determination of epoxy and isocyanate groups in the presence of each other in epoxy–isocyanate compositions were studied. For the determination of epoxy groups in the presence of isocyanate groups, a test with HBr in glacial acetic acid was proposed; acetic acid reacts with isocyanate groups and, hence, masks them. Isocyanate groups in the presence of epoxy groups were determined by potentiometric titration with a solution of piperidine in ethyl methyl ketone. The addition of toluene to the test solution decreases the fraction of the enol form of ethyl methyl ketone, which interferes with the determination.     

New syntheses and13C NMR spectra of the methyl ethers of methyl α-L-arabinopyranoside

A method is described for obtaining the methyl ethers of methyl -L-arabinopyranoside that is based on the partial methylation of methyl -L-arabinopyranoside followed by the liquid chromatography of the methyl ethers. The¹³C NMR spectra of the methyl ethers of methyl -L-arabinopyranoside have been studied.Pacific Ocean Institute of Bioorganic Chemistry, Far Eastern Scientific Center, Academy of Sciences of the USSR, Vladivostok. Translated from Khimiya Prirodnykh Soedinenii, No. 2, pp. 178–181, March–April, 1985.     

Gas-liquid chromatography of carbohydrates

A review is given of materials on the use of the method of gas-liquid chromatography in carbohydrate chemistry.Pacific Ocean Institute of Bioorganic Chemistry, Far Eastern Scientific Center, Academy of Sciences of the USSR, Vladivostok. Translated from Khimiya Prirodnykh Soedinenii, No. 4, pp. 411–428, July–August, 1984.     

Effective conversion of copper-vapor laser emission in a β-BaB2O4 crystal

Our results lead to the following conclusions.

Application of the Fast Automatic Differentiation Technique for Solving Inverse Coefficient Problems

Computational Mathematics and Mathematical Physics - Results obtained by the authors in solving inverse coefficient problems are overviewed. The inverse problem under consideration is to determine...     

Cluster generation under pulsed laser ablation of zinc oxide

Neutral and cationic Zn _n O _m clusters of various stoichiometry have been produced by nanosecond laser ablation of ZnO in vacuum and investigated by time-of-flight mass spectrometry. Particular attention was paid to the effect of laser wavelength (in the range from near-IR to UV) on cluster composition. Under 193-nm laser ablation, the charged clusters are essentially substoichiometric with Zn_nO_n-1⁺\mathrm{Zn}_{n}\mathrm{O}_{n-1}^{+} and Zn_nO_n-3⁺\mathrm{Zn}_{n}\mathrm{O}_{n-3}^{+} being the most abundant series. Both sub- and stoichiometric cationic clusters are generated in abundance at 532- and 1064-nm ablation whose composition depends on the cluster size. The reactivity of small stoichiometric Zn_nO_n⁺\mathrm{Zn}_{n}\mathrm{O}_{n}^{+} clusters (n<11) toward hydrogen is found to be high, while oxygen-deficient species are less reactive. The neutral plume particles are mainly stoichiometric with Zn₄O₄ tetramer being a magic cluster. It is suggested that the Zn₄O₄ loss is the dominant fragmentation channel of large zinc oxide clusters upon electron impact. Plume expansion conditions under ZnO ablation with visible and IR laser pulses are shown to be favorable for stoichiometric cluster formation.