Distribution of periphytic diatoms in the rivers of the Lake Ladoga basin (Northwestern Russia).

Relationships between distribution of periphytic diatoms and environmental variables in 19 rivers of the Lake Ladoga basin (Northwestern Russia) were examined using gradient analysis. On the basis of geology and river water chemistry, the Lake Ladoga basin could be separated into twomain parts, the northern and the southern sub-basin. The rivers in the northern sub-basin are slightly acidic and low in conductivity (mean value 53 mS cm–1); the rivers in the southern sub-basin have neutral to slightly alkaline waters with higher conductivities (mean value 168 mS cm–1). A detrended correspondence analysis (DCA)defined two groups of rivers generally corresponding to the two main parts of the Lake Ladoga basin. Fragilaria capucina var. rumpens, Frustulia saxonica and Tabellaria flocculosa were the typical species for the northern sub-basin, whereas Cocconeis placentula var. euglypta, Ulnaria ulna and Gomphonema parvulum were characteristic species for the southern sub-basin. A canonical correspondence analysis (CCA) identified conductivity, pH, bicarbonate, total phosphorus and water colour as the most important environmental variables related to changes in assemblage structure. Both DCA and CCA ordination showed that conductivity related to geology was the most important variable,while concentration of total phosphorus was the second most important variable.Weighted averaging was used to infer total phosphorus from relative biomass of diatoms. The predictive ability of the inference model was sufficiently strong with r2 = 0.71 and RMSEP = 1.9 mg L–1. These results strongly support the use of a diatom-based inference phosphorus model for indicating eutrophication in the rivers of the Lake Ladoga basin

Elastic deformation due to tangential capillary forces \ud

A sessile liquid drop can deform the substrate on which it rests if the solid is sufficiently “soft.” In this paper we compute the detailed spatial structure of the capillary forces exerted by the drop on the solid substrate using a model based on Density Functional Theory. We show that, in addition to the normal forces, the drop exerts a previously unaccounted tangential force. The resultant effect on the solid is a pulling force near the contact line directed towards the interior of the drop, i.e., not along the interface. The resulting elastic deformations of the solid are worked out and illustrate the importance of the tangential force

Contact angles on a soft solid: from Young's law to Neumann's law

The contact angle that a liquid drop makes on a soft substrate does not obey the classical Young's relation, since the solid is deformed elastically by the action of the capillary forces. The finite elasticity of the solid also renders the contact angles different from that predicted by Neumann's law, which applies when the drop is floating on another liquid. Here we derive an elasto-capillary model for contact angles on a soft solid, by coupling a mean-field model for the molecular interactions to elasticity. We demonstrate that the limit of vanishing elastic modulus yields Neumann's law or a slight variation thereof, depending on the force transmission in the solid surface layer. The change in contact angle from the rigid limit (Young) to the soft limit (Neumann) appears when the length scale defined by the ratio of surface tension to elastic modulus $\gamma/E$ reaches a few molecular sizes

Sharp change over from compound nuclear fission to shape dependent quasi fission

Fission fragment mass distribution has been measured from the decay of $^{246}$Bk nucleus populating via two entrance channels with slight difference in mass asymmetries but belonging on either side of the Businaro Gallone mass asymmetry parameter. Both the target nuclei were deformed. Near the Coulomb barrier, at similar excitation energies the width of the fission fragment mass distribution was found to be drastically different for the $^{14}$N + $^{232}$Th reaction compared to the $^{11}$B + $^{235}$U reaction. The entrance channel mass asymmetry was found to affect the fusion process sharply.Comment: 4 pages,6 figure

Согласование тягово-сцепных качеств движителей сельскохозяйственных мобильных энергетических средств с допустимым максимальным давлением на почву

Modern highly mechanized agricultural production is characterized by the incompatibility of simultaneous matching of the maximum pressure of agricultural mobile equipment movers on the soil and the possibility of increasing the tractors energy saturation when equipping them with existing wheel engines.(Research purpose) To coordinate the maximum pressure on the soil with the permissible norms, weight utilization factors and the level of tractors energy saturation.(Materials and methods) The authors used a calculated method for determining the maximum pressure on the soil using a universal tire characteristic.(Results and discussion) The authors found that when performing spring works on closing moisture and sowing row crops at a maximum pressure of 80 kilopascals, corresponding to all types of soil, the most mass universal row tractor Belarus 1020 had a maximum pressure of 150 kilopascals, which was 70 kilopascals higher than the permissible one for the corresponding crop shortage. They found that replacing ordinary tires with agrophilic tires could increase the area of the contact spot by 16 percent, while reducing the coefficient of unevenness and increasing the coefficient of use of the adhesion weight. The main condition for replacing ordinary tires with agrophilic tires was to keep the traction force unchanged.(Conclusions) Summarizing the results of the research as agrophilic direction, ensuring the compliance impacts on soil and positively solving the problems of saturation, it is possible to recommend the development of navigation systems in achieving utilization hitch weight equal to 0.5 (low tire pressure), equal to 0.6 (rubber joint with torsion bar suspension) and 0.7 (rubber track). It was found that the conducted research, taking into account the available data on traction tests of the T-250 tractor, would allow to include an agrophilic concept with a hypothetical dependence of the adhesion weight use factor on the longitudinal unevenness coefficient in the revised State Standard 27021-86 “Agricultural and forestry Tractors. Traction classes”.Современное высокомеханизированное сельскохозяйственное производство характеризуется несовместимостью одновременной реализации требований экологических организаций к максимальному давлению движителей сельскохозяйственной мобильной техники на почву и возможностей повышения энергонасыщенности тракторов при оснащении их существующими колесными движителями.(Цель исследования) Согласовать максимальное давление на почву с допустимыми нормами, коэффициентами использования сцепного веса и уровнем энергонасыщенности тракторов.(Материалы и методы) Использовали расчетный метод определения максимального давления на почву с помощью универсальной характеристики шины.(Результаты и обсуждение) Установили, что при выполнении весенних работ по закрытию влаги и проведению посева пропашных культур при допустимом максимальном давлении 80 килопаскалей, соответствующем всем типам почв, самый массовый универсально-пропашной трактор Беларус 1020 имеет максимальное давление 150 килопаскалей, что на 70 килопаскалей превышает допустимое при соответствующем недоборе урожая. Установили, что замена ординарных шин на агрофильные позволяет увеличить площадь пятна контакта на 16 процентов с одновременным уменьшением коэффициента неравномерности и увеличением коэффициента использования сцепного веса. Принципиальным условием замены ординарных шин на агрофильные служит сохранение неизменным создаваемого трактором тягового усилия.(Выводы) Определили оптимальные значения коэффициента использования сцепного веса: для шин сверхнизкого давления – 0,5, для резинометаллического шарниира с торсионной подвеской -- 0,6, для резиноармированной гусеницы – 0,7. Установили, что проведенные исследования с учетом имеющихся данных о тяговых испытаниях гусеничного трактора Т-250, позволят включить агрофильную концепцию с гипотетической (предполагаемой) зависимостью коэффициента использования сцепного веса от коэффициента продольной неравномерности в пересматриваемый ГОСТ 27021-86 «Тракторы сельскохозяйственные и лесохозяйственные. Тяговые классы»

Experimental evidence for the separability of compound-nucleus and fragment properties in fission

The large body of experimental data on nuclear fission is analyzed with a semi-empirical ordering scheme based on the macro-microscopic approach and the separability of compound-nucleus and fragment properties on the fission path. We apply the statistical model to the non-equilibrium descent from saddle to scission, taking the influence of dynamics into account by an early freeze out. The present approach reveals a large portion of common features behind the variety of the complex observations made for the different systems. General implications for out-of-equilibrium processes are mentioned.Comment: 11 pages, 3 figure