Increase in the para selectivity in the nitration of alkylbenzenes in the presence of aryl iodides

Conclusions Additives of iodobenzene, para-iodotoluene, and ortho-iodotoluene increase the relative yield of the para isomer in the nitration of toluene, ethylbenzene, and cumene as well as the yield of 4-nitro-o-xylene in the KNO₃/CF₃CO₂H system.Translated from Izvestiya Akademii Nauk SSSR, Seriya Khimicheskaya, No. 3, pp. 714–716, March, 1988.     

水凝胶中物质扩散过程研究进展

主要从模型理论和实验研究方法两个方面综述了国内外聚合物水凝胶中物质扩散行为研究进展.水凝胶中扩散理论模型主要有自由体积模型、流体力学模型、位阻效应模型三大类;实验研究方法主要分为间接法和实时法两种.     

Change in the rate of decomposition of dioxetanes in sulfolane solutions in the transition from the liquid to the solid phase

Conclusions It has been established that the rate of decompostion of dioxetanes changes in in sulfolane solutions on transition from the liquid to the solid phase, which is explained in terms of structural changes of the molecular complexes dioxetane-sulfolane in the solid phase of the solvent.Translated from Izvestiya Akademii Nauk SSSR, Seriya Khimicheskaya, No. 10, pp. 2238–2243, October, 1988.     

On the feasibility of the numerical Laplace Transform in the calculation of the statistical moments in GC

Summary Statistical moments may be used to augment the information content of stored GC data. Their calculation can be performed either directly by the methods of statistics or by the numerical Laplace Transform. It was found that the direct statistical computation will yield the better results.

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Zur Frage der Anwendbarkeit der numerischen Laplace-Transformation in der Berechnung der Statistischen Momente in der Gas-Chromatographie

Zusammenfassung Die statistischen Momente können zur Erhöhung der Aussagekraft von GC-Daten verwendet werden. Diese Berechnungen können auf dem Weg der Statistik direkt oder mittels numerischer Laplace-Transformation durchgeführt werden. Es wurde festgestellt, daß die direkte statistische Bestimmung der numerischen Laplace-Transformation vorzuziehen ist.

     

Use of the Garner balance in the investigation of errors in the carbon-hydrogen determination

Summary The reproducibility of weighing the mass of small-size glass Ascartte and Drierite absorption tubes with 0.25-mm capillaries on the Garner balance has been investigated. A standard error of estimate for the Ascarite tube was found to be ±1.65g and for the Drierite tube ±2.65g. Corresponding figures for light-weight aluminum absorption tubes with 0.34-mm capillaries were considerably higher. Filled glass absorption tubes standing idle in the room were found to exhibit weight increases with respect to time of the order of 0.201g/min. for Ascarite and 0.251g/min, for indicating Drierite. Tubes with larger capillaries (0.34mm) showed a more rapid weight gain.Absorption tubes filled with oxygen undergo a loss in weight, which remains the predominating phenomenon during the first 2 hours.A limiting factor is indicated by failure to obtain consistent blanks.

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Zusammenfassung Die Gewichtskonstanz kleiner C-H-Absorptionsröhrchen aus Glas mit kapillaren Verengungen von 0,25 mm innerem Durchmesser wurde mit der Garner-Mikrowaage untersucht. Die mittleren Fehler der Schätzungen wurden zu ±1,65g für das Ascariteröhrchen und zu ±2,65g für das Drieriteröhrchen berechnet. Die entsprechenden Zahlen für leichte Absorptionsröhrchen aus Aluminium mit Kapillaren von 0,34 mm innerem Durchmesser wurden merklich größer gefunden. Die Gewichtszunahme beim Liegen der gefüllten Glasabsorptionsapparate betrug 0,20g/Minute für das Ascariteröhrchen und 0,25g/Minute für das mit Indikator-Drierite gefüllte Röhrchen. Absorptionsapparate mit Kapillaren von 0,34 mm innerem Durchmesser zeigten entsprechend größere Gewichtszunahmen.Sauerstoffgefüllte Absorptionsröhrchen zeigen außerdem einen durch Austausch toit der Atmosphäre verursachten Gewichtsverlust, der während der ersten zwei Stunden überwiegt.Bisher unbekannte Faktoren verhindern es, in Leerversuchen gleichbleibende Gewichtsänderungen der Absorptionsapparate zu erhalten.

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Résumé La reproductibilité des pesées des petits tubes d'absorption en verre à ascarite et à drierite avec des capillaires de 0,25 mm sur la balance de Garner a été étudiée. On a trouvé une erreur standard de ±1, 65g pour le tube d'ascarite et de ±2,65g pour le tube de drierite et des chiffres considérablement plus élevés avec des tubes d'absorption très légers en aluminium ayant des capillaires de 0,34 mm. Des tubes d'absorption en verre remplis et suspendus inutilisés dans la pièce présentent des gains de poids par rapport au temps de l'ordre de 0,20g/min pour l'ascarite et de 0,25g/min pour la drierite. Les tubes avec capillaire plus grand (0,34 mm) ont présenté un gain de poids plus rapide. Les tubes d'absorption remplis d'oxygène subissent une perte de poids qui reste le phénomène prédominant pendant les deux premières heures. On donne un facteur limite dans l'impossibilité de fixer une valeur déterminée pour l'essai à blanc.

     

Recent Advances in the Application of the Antimicrobial Peptide Nisin in the Inactivation of Spore-Forming Bacteria in Foods

Conventional thermal and chemical treatments used in food preservation have come under scrutiny by consumers who demand minimally processed foods free from chemical agents but microbiologically safe. As a result, antimicrobial peptides (AMPs) such as bacteriocins and nisin that are ribosomally synthesised by bacteria, more prominently by the lactic acid bacteria (LAB) have appeared as a potent alternative due to their multiple biological activities. They represent a powerful strategy to prevent the development of spore-forming microorganisms in foods. Unlike thermal methods, they are natural without an adverse impact on food organoleptic and nutritional attributes. AMPs such as nisin and bacteriocins are generally effective in eliminating the vegetative forms of spore-forming bacteria compared to the more resilient spore forms. However, in combination with other non-thermal treatments, such as high pressure, supercritical carbon dioxide, electric pulses, a synergistic effect with AMPs such as nisin exists and has been proven to be effective in the inactivation of microbial spores through the disruption of the spore structure and prevention of spore outgrowth. The control of microbial spores in foods is essential in maintaining food safety and extension of shelf-life. Thus, exploration of the mechanisms of action of AMPs such as nisin is critical for their design and effective application in the food industry. This review harmonises information on the mechanisms of bacteria inactivation from published literature and the utilisation of AMPs in the control of microbial spores in food. It highlights future perspectives in research and application in food processing.     

Licensing in the italian regulatory system in the use of radioisotopes

The regulatory system in force in Italy concerning radioisotopes is based on two statutes dating back to 1962 and 1964; the latter is based on a 1962 Directive of European Community, of which Italy is a Member. European Directives of 1980, 1984, 1989, 1990 and 1992 will be enacted into Italian legislation by January 1^st, 1996. In the statutes in force the basic rules are established governing the holding and use of, trading in and disposal of radioactive material. These activities are subject to notification and licensing. Notification and licensing are based on two tiered system: a local, regional or provincial level and a national one, depending on the intersection of a number of parameters. The role of the governmental organs, state agencies such as ANPA (National Agency for Environmental Protection), local administrative bodies, their competence and their powers are discussed with regard to notification and licensing.     

Change in the lipid composition of lichens in the spring period

The dynamics of the amount of total lipids, the ratio of the main classes of lipids, the amount of fatty acids, and the ratio of individual phospholipids in three epiphytic species of lichens from the Zhigulevsk reserve have been followed. It has been shown that all the classes of lipids of the lichens change to some degree or other in this period. The dynamics of the fatty acids has also confirmed a known rule: an increase in the amount of saturated and a decrease in the number of unsaturated fatty acids of the membranes with a rise in the temperature of the environment. This is the first time that the dynamics of the hydroxy acids have been followed.     

Change in the lipid composition of lichens in the spring period

The dynamics of the amount of total lipids, the ratio of the main classes of lipids, the amount of fatty acids, and the ratio of individual phospholipids in three epiphytic species of lichens from the Zhigulevsk reserve have been followed. It has been shown that all the classes of lipids of the lichens change to some degree or other in this period. The dynamics of the fatty acids has also confirmed a known rule: an increase in the amount of saturated and a decrease in the number of unsaturated fatty acids of the membranes with a rise in the temperature of the environment. This is the first time that the dynamics of the hydroxy acids have been followed.Institute of the Ecology of the Volga Basin, Tol'yatti. Translated from Khimiya Prirodnykh Soedinenii, No. 5, pp. 660–664, September–October, 1993.     

Role of the special pair in the charge-separating event in photosynthesis

We synthesized special-pair/electron-acceptor systems consisting of a complementary slipped cofacial dimer of imidazolyl-substituted zinc porphyrin, bearing pyromellitdiimide as the electron acceptor. In the case of the dimer, the first and second oxidation potentials were split into a total of four peaks in the differential pulse voltammetry measurement. Furthermore, the shift values of the first oxidation potentials obtained by changing the solvent polarity for the dimer were almost half of those observed for the monomer. These results indicate that the radical cation is delocalized over the whole pi system of the dimer. Time-resolved transient absorption measurements revealed that, relative to the corresponding monomer, the dimer accelerated the charge separation rate, but decelerated the charge recombination rate. The smaller reorganization energy of the slipped cofacial dimer relative to that of the monomeric system demonstrates the significance of the special-pair arrangement for efficient charge separation in photosynthesis.