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.     

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.     

Application of IR spectroscopy in the analysis of the woody-fibrous mass in the process of hydrolysis

The possibility has been shown of using IR spectroscopy in the investigation of the changes in the polysaccharide component of wood in the process of acid hydrolysis. The method of determining the relative optical density (ROD) was used for the quantitative evaluation of the changes in the functional groups of the lignocellulose.Deceased.Siberian Scientific Research Institute of Cellulose and Board, Bratsk. Translated from Khimiya Prirodnykh Soedinenii, No. 5, pp. 683–687, September–October, 1990.     

Variation of the composition of asphaltenes in the course of bitumen aging in the presence of antioxidants

Chemical aging of BND 40/60 bitumen in the presence of an oxidation inhibitor under the conditions of heating in a thin film at 163°C for 5, 10, 15, and 20 h was studied. An increase in the asphaltene content, associated with the new formation of a colloid-unstable high-molecular-weight fraction A1 of increased aromaticity, was observed to a lesser extent than in the straight bitumen.     

Distribution of phospholipids in the organs of the cotton plant in the period of mass fruit-formation

The distribution of phosphorus in the vegetative and generative organs of the cotton plant of variety 159-F has been studied. It has been established that the various organs of the cotton plant differ with respect to the qualitative and quantitative compositions of their phospholipids.     

Application of IR spectroscopy in the analysis of the woody-fibrous mass in the process of hydrolysis

The possibility has been shown of using IR spectroscopy in the investigation of the changes in the polysaccharide component of wood in the process of acid hydrolysis. The method of determining the relative optical density (ROD) was used for the quantitative evaluation of the changes in the functional groups of the lignocellulose.     

贵阳市红枫湖底栖生物体中多溴联苯醚的初步研究

为了研究贵阳市红枫湖底栖生物体中多溴联苯醚(polybrominateddiphenyl ethers,PBDEs)的污染情况,通过索氏抽提、凝胶色谱柱和多层硅胶/氧化铝层析柱净化,对红枫湖底栖生物体中PBDEs的含量、分布模式、来源进行分析。结果表明,红枫湖样品中Σ18PBDEs为105.71～43902.73 pg/g(干重),各单体含量为1.05～20045.38 pg/g。红枫湖底栖生物体中PBDEs的污染尚处于较低水平。     

Progress in the chemistry of the cycloartanes

The review, which considers advances in the chemistry of the cycloartanes, covers literature devoted to compounds of plants of the genusAstragalus and other publications appearing in the period from 1984 to 1987 and, in part, 1988.Institute of the Chemistry of Plant Substances, Uzbek SSR Academy of Sciences, Tashkent. Translated from Khimiya Prirodnykh Soedinenii, No. 2, pp. 156–175, March–April, 1989.     

自然流产孕妇体内微量元素含量的变化

为了解自然流产孕妇体内微量元素的变化,检测了50例正常妊娠妇女和50例自然流产妇女（其中忆查明流产原因的33例,不明原因流产17例）头发中微量元素。结果显示,查明原因流产组发锌、铜、铁、钙和不明原因流产组发锌、铜、铁含量均明显低于正常妊娠组;而发铅含量则明显高于正常妊娠组,经统计学处理分析,差别有显著性。提示妊娠期微量元素平衡与否,对宫内胎儿的发育乃至安危均有一定的影响。     

Amounts of arachidonic acid in the buds of Populus balzamifera in the course of the annual cycle

The paper gives information on the amount of arachidonic acid in the buds ofPopulus balzamifera. The presence of arachidonic acid in the buds was confirmed by TLC, GLC, coulometric titration, and an iodine number calculation. The dynamics of the amount of arachidonic acid in the buds during the annual cycle are given.     

Application of capillary gas chromatography in the analysis of hydrocarbons in the environment

Summary Hydrocarbons are emitted into the environment in quantity and diversity. Some of these can be detrimental in low concentration, many can be active in photochemical smog production. For combatment there is also interest in the sources of hydrocarbons in the atmosphere. For source recognition fine-structured chromatographic fingerprints are essential. This also holds for oil pollution. A complicating factor in the determination of hydrocarbon pollutants may arise from the occurrence of recently biosynthesized hydrocarbons. For distinguishing between these two types the application of capillary gas chromatography is preferred to packed column gc. It will be clear that the application of capillary gc in the analysis of hydrocarbons in the environment is of great practical value. The modified Grob method used by us for the analysis of hydrocarbons in air is discussed. For the characterization and source recognition of oil pollution in water and soil application of capillary gc fingerprinting is essential; in this way valuable information can be gathered about weathering of oil pollution. Sources of oil pollution in water areas and harbour regions can be traced in certain cases. Also the possibility of measurement of residence time is present. Typical examples are given.Publication No. 601 of the TNO Research Institute for Environmental Hygiene.     

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.     

Analysis of the principles of the theory of metal solution in electrolytes in the anode region

The main aspects of the mechanism of anode solution of metals in aqueous electrolytes are outlined. All states of the metal surface (i.e., the states of active solution, active-passive transition, passive state proper, and transpassive states) are considered. Special attention is paid to self-consistency of all processes. The principles of the theory of these phenomena are formulated.     

Amounts of arachidonic acid in the buds of Populus balzamifera in the course of the annual cycle

The paper gives information on the amount of arachidonic acid in the buds ofPopulus balzamifera. The presence of arachidonic acid in the buds was confirmed by TLC, GLC, coulometric titration, and an iodine number calculation. The dynamics of the amount of arachidonic acid in the buds during the annual cycle are given.Siberian Branch of the Technological Institute, Krasnoyarsk. Translated from Khimiya Prirodnykh Soedinenii, No. 4, pp. 513–516, July–August, 1987.     

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.     

脂质组学分析中样品前处理技术的研究进展

脂质不仅是细胞膜的主要组成部分,还参与一些生命活动如能量存储、信号传导等,在生命体中发挥着重要作用。近年来,越来越多的研究表明脂质的变化与一些重大疾病的发生发展密切相关,脂质组学研究对理解疾病的发生机制及过程具有重要意义。在脂质分析过程中,由于样品基质的干扰或被分析物浓度的限制,通常需要对样品进行前处理,以得到最佳的分析性能。该文综述了脂质组学分析中的样品前处理技术,包括脂质的提取方法（如液液萃取、固相萃取等）和针对不同类脂质的化学衍生化技术在各领域,尤其是生命分析和代谢组学中的应用,并对脂质组学分析中的样品前处理技术的发展进行了展望。     

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.     

Distribution of phospholipids in the organs of the cotton plant in the period of mass fruit-formation

The distribution of phosphorus in the vegetative and generative organs of the cotton plant of variety 159-F has been studied. It has been established that the various organs of the cotton plant differ with respect to the qualitative and quantitative compositions of their phospholipids.Institute of the Chemistry of Plant Substances, Academy of Sciences of the Uzbek SSR, Tashkent. Translated from Khimiya Prirodnykh Soedinenii, No. 6, pp. 706–710, November–December, 1981.     

Study of the early deactivation in pyrolysis of polymers in the presence of catalysts

In this work, the early degradation step of the pyrolysis of some polymers in the presence of certain catalysts has been studied using thermogravimetric analysis (TGA). Three commercial polymers (PE, PP and EVA) and three catalysts were studied (ZSM-5, MCM-41a, and MCM-41b), and the MCM-41a catalyst has been selected for the analysis of the earlier steps of the pyrolysis process carried out in the presence of catalysts. Several cycles of heating–cooling were performed using a thermobalance, in order to analyze the influence of the first stages of decomposition on the activity of the more accessible active sites involved. In this way, the behaviour of the polymer–catalyst mixtures (20% (w/w) of catalyst) was studied and compared with that observed in the corresponding thermal degradation as well as in the pyrolysis in the presence of catalysts, in a single heating cycle.The results obtained clearly show the existence of an early degradation step. For a polymer–catalyst system with low steric hindrances such as PE-MCM-41, this early degradation step causes a noticeable decrease of the catalyst activity for the main decomposition step (i.e., cracking of the chain). The decrease of the catalytic activity is lower for a polymer–catalyst system with higher steric restrictions, as occurs in the EVA-MCM-41 degradation process. However, in this case, the catalyst activity in the first decomposition step (i.e., the loss of the acetoxi groups) is noticeable decreased after one pyrolysis run, thus reflecting that the active sites involved are mainly the most accessible ones.     

Quantum-chemical study of the mechanism of the hydrolysis of amides in the gas phase and in aqueous solution

The MNDO, AM1, and MNDO/M methods have been used to calculate the profile of the potential energy surface for the hydrolysis of formamide in the gas phase and in aqueous solution. Estimates have been made of the changes in the energy barrier in specific acid and base catalysis, and it is shown that in the absence of proton exchange between the reacting system and the solvent the interaction of the charged reactants with a polar medium impedes the reaction.Translated from Izvestiya Akademii Nauk SSSR, Seriya Khimicheskaya, No. 8, pp. 1785–1792, August 1989.