A study of the oxidation of vegetable oils by inverse gas chromatography

Summary Inverse gas chromatography is shown to be suitable for the study of the oxidation of vegetable oils. With air as carrier gas characteristic plots of retention index versus time are obtained for hydroxylic test solutes that are consistent with the oxidation behaviour of vegetable oils. Shifts of retention are found to be accompanied by changes of column efficiency due to the oxidative crosslinking of polyunsaturated vegetable oils. The technique also leads to useful information concerning the oxidation of antioxidant inhibited systems. Presented at the 15th International Symposium on Chromatography, Nürnberg, October 1984     

(2-甲基丙烯酰氧乙基)三甲基氯化铵-丙烯酰胺反相微乳液共聚合研究

采用SPAN-OP复合乳化剂和K_2S_2O_8-Na_2SO_3氧化还原引发剂,进行(2-甲基丙烯酰氧乙基)三甲基氯化铵-丙烯酰胺的反相微乳液共聚合。测得单体的竞聚率r_(DM·MC)=1.11±0.16,r_(AM)=0.53±0.08。在单体总浓度为20—40％(wt),引发剂浓度为0.01—0.05％,乳化剂浓度为10—18％,聚合温度为299K的条件下,得到共聚反应动力学方程:R_p=k[M]~(1.07)[I]~(0.52)[E]~(0.90),文中对上述结果做了解释。     

Irreversible and reversible phase transitions of alkyl monolayers. Gas chromatographic evidence of polar solvent influence on the adsorbing properties of the layer

Summary Further to Gilpin's observations in liquid chromatography of the irreversible transformation of alkyl grafts, following the replacement of an organic mobile phase by an aqueous one, we describe some gas chromatographic experiments which lead to similar (log V_s, I/T) plots, as a consequence of the same solvent release process.We use paraffin films on siliceous supports or hydroxylated liquid substrates or C₂₂-alkyl bonded silica. These experiments demonstrate that this irreversible transition and the melting-like reversible transition are completely different phenomena. They confirm the existence of at least three kinds of monomeric alkyl films.     

Studies on the porous structure of di(methacryloyloxymethyl) naphthalene-divinylbenzene copolymers by inverse exclusion chromatography

Summary Using inverse exclusion chromatography the porous structure of the copolymers of di(methacryloyloxymethyl)naphthalenes and divinylbenzene was investigated.In order to determine the pore size distributions of the copolymers, toluene, alkylphenones, phthalates and polystyrene standards were used as the probes.The measurements proved that the existence of micropores depend on the method of copolymerization. The copolymers obtained by suspension and emulsion methods are more or less microporous, but the copolymer prepared by thermal polymerization in mass does not include micropores in its internal structure.     

Study of modified silicas by inverse gas chromatography. Influence of chain length on the conformation of n-alcohols grafted on a pyrogenic silica

Summary A fumed silica surface was systematically modified by the grafting of n-alkyl chains with increasing carbon numbers. The samples were characterized by the dispersive component of the surface energy, their specific interaction potential and enthalpies of adsorption of polar, in particular, alcohol probes. It is shown that the variation of the surface properties and adsorption capacities depend on the chain length of the graft. For instance, minimum values are recorded when the surface coverage by methylene groups corresponds either to one or two CH₂ surface layers. This behaviour is related to the mobility of the grafted alkyl chains, mobility which was examined by solid state NMR.     

Surface characterization of macroporous glycidyl methacrylate based copolymers by inverse gas chromatography

Two samples of macroporous crosslinked poly(glycidyl methacrylate-co-ethylene glycol dimethacrylate), PGME, with different porosity parameters were synthesized by suspension copolymerization and modified by ring-opening reaction of the pendant epoxy groups with ethylene diamine, EDA. Inverse gas chromatography at infinite dilution was used for the determination of adsorption properties of PGME, and copolymer modified with ethylene diamine, PGME-en. Thermodynamic parameters of adsorption, dispersive components of the surface free energies, and the acid/base constants for the copolymer samples were calculated. The calculated dispersive surface energy values, , for PGME and PGME-en are comparable with the literature data for nonconductive polymers.     

反相乳液聚合制备壳聚糖接枝共聚物及应用

以壳聚糖、丙烯酰胺、甲基丙烯酰氧乙基三甲基氯化铵为原料,硝酸铈铵为引发剂,Span-20为乳化剂,通过反相乳液聚合技术,合成壳聚糖阳离子接枝共聚物。分析讨论了乳化剂用量、引发剂浓度、油水体积比、单体配比、反应时间、反应温度对共聚物接枝率的影响,并采用正交试验方法对合成条件进行了优化。研究了其对重金属离子Cu2 、Cd2 、Zn2 的吸附性能。结果表明,在Cu2 、Cd2 、Zn2 的混合离子体系中,该共聚物对Cu2 、Zn2 有选择性吸附。     

Study of modified silicas by inverse gas chromatography part II: Influence of chain length on surface properties of silicas grafted withα−ω diols

Summary The surface properties of silicas modified with – diols having between 4 and 16 carbon atoms were investigated by inverse gas chromatography. It is shown, that the value of the dispersive component of the surface energy does not change monotonously: a minimum value is recorded when the surface is covered by a monolayer of methylene groups. Further, when measuring the adsorption enthalpies of polar probes, an alternation of their H values is observed: grafts having an odd number of carbon atoms systematically show higher H values than the others. A trans-trans configuration of the grafted chains which allows optimum interactions is proposed, suggesting a preferential diesterification reaction of both terminal hydroxyl groups of odd diols.     

聚丙烯酰胺固定化糖化酶特性的研究

本研究以丙烯酰胺单体通过反向悬浮聚合技术合成聚丙烯酰胺作为载体材料，采用包埋—交联法固定化葡萄糖淀粉酶，并对其特性进行了研究．结果表明，该固定化酶最适pH值为5．0，最适温度为55～58℃，而且具有较好的贮存稳定性和操作稳定性，8个月后该固定化酶的残余活力仍保持在94％左右，可重复使用43批次，此固定化酶酶活回收率达到56％．实验表明丙烯酰胺悬浮聚合固定化糖化酶的方法是简便可行的．     

Fast folding and comparison of RNA secondary structures

Summary Computer codes for computation and comparison of RNA secondary structures, the Vienna RNA package, are presented, that are based on dynamic programming algorithms and aim at predictions of structures with minimum free energies as well as at computations of the equilibrium partition functions and base pairing probabilities.An efficient heuristic for the inverse folding problem of RNA is introduced. In addition we present compact and efficient programs for the comparison of RNA secondary structures based on tree editing and alignment.All computer codes are written in ANSI C. They include implementations of modified algorithms on parallel computers with distributed memory. Performance analysis carried out on an Intel Hypercube shows that parallel computing becomes gradually more and more efficient the longer the sequences are.

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Schnelle Faltung und Vergleich von Sekundärstrukturen von RNA

Zusammenfassung Die im Vienna RNA package enthaltenen Computer Programme für die Berechnung und den Vergleich von RNA Sekundärstrukturen werden präsentiert. Ihren Kern bilden Algorithmen zur Vorhersage von Strukturen minimaler Energie sowie zur Berechnung von Zustandssumme und Basenpaarungswahrscheinlichkeiten mittels dynamischer Programmierung.Ein effizienter heuristischer Algorithmus für das inverse Faltungsproblem wird vorgestellt. Darüberhinaus präsentieren wir kompakte und effiziente Programme zum Vergleich von RNA Sekundärstrukturen durch Baum-Editierung und Alignierung.Alle Programme sind in ANSI C geschrieben, darunter auch eine Implementation des Faltungs-algorithmus für Parallelrechner mit verteiltem Speicher. Wie Tests auf einem Intel Hypercube zeigen, wird das Parallelrechnen umso effizienter je länger die Sequenzen sind.