Ac transport studies in polymers by a resistor network and transfer matrix approaches: application to polyaniline

A statistical model of resistor network is proposed to describe a polymer structure and to simulate the real and imaginary components of its ac resistivity. It takes into account the polydispersiveness of the material as well as intrachain and interchain charge transport processes. By the application of a transfer matrix technique, it reproduces ac resistivity measurements carried out with polyaniline films in different doping degrees and at different temperatures. Our results indicate that interchain processes govern the resistivity behavior in the low frequency region while, for higher frequencies, intrachain mechanisms are dominant.Comment: LaTeX file, 15 pages, 5 ps figures, to appear in Phys. Rev.

Результаты испытаний перспективных инсектицидов из химического класса антранилдиамидов на культуре огурца в защищенном грунте

Relevance. The adaptive-integrated plant protection system is the basis of biologized protective measures against harmful organisms. This system provides for careful treatment of natural resources, prevents contamination of soil and water with pesticides and agrochemicals. In recent years, legislation and sanitary regulations have increasingly tightened the regulations governing the use of pesticides in crop production. Organic farming is becoming increasingly common. Leading global chemical companies are expanding their research on the biology of manufactured plant protection products: they give them a selective character, reduce the period of their inactivation, respectively, the waiting period. FMC manufactures and supplies to Russia new generation insecticides Verimark® and Benevia® from the chemical class of diamides compatible with the biomethode and having a short waiting time.Methods. In 2020-2021, in the greenhouse complex of the FSVC, an assessment of the biological effectiveness of the insecticides Verimark® and Benevia® on cucumber culture has been carried out. Verimark® was applied by shedding seedlings under the root and applying through a drip system, Benevia® was introduced by ground spraying of vegetating plants.Results. The most problematic cucumber pests in greenhouse are tobacco trips (Thrips tabaci) and greenhouse whitefly (Trialeurodes vaporarium). As a result of successive additions of the Verimark® (for the root) and Benevia® (for the leaves), the number of tobacco thrips was reduced by 90,8-98,9%. Spraying the plants with Benevia® in admixture with Codacide oil also provided a high positive effect against the greenhouse whitefly. Already on the third day, the number of pests decreased by 90,3%. Protective measures made it possible to increase crop yield by 26.3% in the first turnover and 28.3% in the second. The highest rates of biological efficacy were observed in the use of preparations before the start of pest settlement, which is fully supported by the recommendations of the manufacturer.Актуальность. Адаптивно-интегрированная система защиты растений является основой биологизированных защитных мероприятий от вредных организмов. Данная система предусматривает бережное отношение к природным ресурсам, предотвращает загрязнение почвы и воды пестицидами и агрохимикатами. Законодательные акты и санитарные нормы в последние годы все более ужесточают регламент применения пестицидов в растениеводстве. Все большее распространение находит органическое земледелие. Ведущие мировые химические компании расширяют свои исследования по биологизации производимых препаратов: придают им избирательный характер, сокращают период их инактивации, соответственно, срок ожидания. Компания FMC (ЭфЭмСи) производит и поставляет в Россию инсектициды нового поколения Веримарк® и Беневия® из химического класса антранилдиамиды, совместимые с биометодом и имеющие короткий срок ожидания.Методика. В 2020-2021 годах в тепличном комплексе ФГБНУ ФНЦО проведена оценка биологической эффективности препаратов Веримарк® и Беневия® на культуре огурца. Веримарк® вносили через систему капельного полива, Беневия® – методом наземного опрыскивания вегетирующих растений в смеси с масляным адъювантом Кодасайд.Результаты. Наиболее проблемными насекомыми-вредителями огурца в защищенном грунте являются трипс табачный (Thrips tabaci) и белокрылка тепличная (Trialeurodes vaporarium). В результате последовательных внесений препаратов Веримарк® (капельным способом) и Беневия® (по листьям) удалось сократить численность трипса табачного на 90,8-98,9%. Опрыскивание растений препаратом Беневия® в смеси с Кодасайд также обеспечило высокую техническую эффективность против белокрылки. Уже на третий день численность вредителей сократилась на 90,3%. Проведенные защитные мероприятия позволили повысить урожайность культуры на 26,3% в первом обороте и 28,3% – во втором. Наиболее высокие показатели биологической эффективности были отмечены при применении препаратов до начала заселения растений вредителями, что полностью подтверждается рекомендациями фирмы-изготовителя

Mechanical, electrical, and melt flow properties of polyurethane elastomer/surface-modified carbon nanotube composites

Carbon nanotube-reinforced polyurethane elastomer composites were prepared by melt-mixing. Nitric acid oxidation and silanization were applied to carbon nanotube surfaces to achieve better interfacial interactions with polyurethane elastomer. Tensile and hardness tests, differential scanning calorimetry, melt flow index test, dielectric measurements, and morphological studies of composites were reported. The best results were obtained for surface-modified carbon nanotubes containing composites with lower loading levels. Addition of carbon nanotubes leads to almost two-fold increase in strain and modulus compared to pristine polyurethane elastomer. Tensile strength of composites was also improved by inclusion of carbon nanotubes. However, strength values drop down with increasing carbon nanotube content. Shore hardness increased with the inclusion of modified carbon nanotube to polyurethane elastomer while pristine carbon nanotube caused remarkable decrease in hardness of polyurethane elastomer. Relatively higher melting points and slightly lower glass transition temperatures were observed for carbon nanotube-loaded composites compared to polyurethane elastomer because of plasticizing effect of carbon nanotube. Incorparation of carbon nanotube to polyurethane elastomer matrix caused reduction in melt flow index values due to formation of agglomarates, and n the contrary, surface modifications of carbon nanotube exhibited increase in melt flow index thanks to enhanced interfacial interactions between carbon nanotube and polyurethane elastomer. Significant increase in dielectric constant of composites was observed. Better dispersion of surface modified carbon nanotubes into polyurethane elastomer was also concluded from SEM micrographs of composites