Electron-electron interaction in carbon nanostructures

The electron-electron interaction in carbon nanostructures was studied. A new method which allows to determine the electron-electron interaction constant $\lambda_c$ from the analysis of quantum correction to the magnetic susceptibility and the magnetoresistance was developed. Three types of carbon materials: arc-produced multiwalled carbon nanotubes (arc-MWNTs), CVD-produced catalytic multiwalled carbon nanotubes (c-MWNTs) and pyrolytic carbon were used for investigation. We found that $\lambda_c$=0.2 for arc-MWNTs (before and after bromination treatment); $\lambda_c$ = 0.1 for pyrolytic graphite; $\lambda_c >$ 0 for c-MWNTs. We conclude that the curvature of graphene layers in carbon nanostructures leads to the increase of the electron-electron interaction constant $\lambda_c$.Comment: 12 pages, 18 figures, to be published in the Proceedings of the NATO Advanced Research Workshop on Electron Correlation in New Materials and Nanosystems, NATO Science Series II, Springer, 200

Planning algorithm for efficient and sustainable crop production

The process of agricultural production is associated with a complex of factors of a different nature: systemic, technological, biological, socio-economic, climatic, reproductive, environmental. All of them influence the size and stability of economic and financial results. There is a threshold level of enterprise management complexity, the excess of which motivates agribusiness to switch to computerized methods. Management of an agricultural enterprise should be based on planning results, updated in a rolling mode. When developing the annual plan, it is necessary to take into account a lot of heterogeneous information and tend to the optimal solution – the achievement of the target indicators with the minimum expenditure of resources. As the basis of the optimal annual planning system, the article proposes an economic-mathematical model for optimizing the production and industry structure of an agricultural enterprise, which includes the following modules: assessment of the parameters of the yield production functions based on field history, the formation of a fertilizer application plan with justification of economically feasible yield levels, solving the problem of optimizing the sectoral structure of crop production, taking into account the forecrop influence in the crop rotation. The algorithm for finding an effective and stable production structure under various combinations of environmental conditions implements the following sequence of procedures: generation of parameter combinations of the economic-mathematical model; obtaining the optimal solution for each combination of these parameters; assessment of the mathematical expectation of the efficiency criterion and variance for each optimal solution on a variety of parameter combinations; choice of a highly effective solution with a low dispersion of this efficiency. To implement this algorithm, the method of simulation experiments in the space of system parameters is used. The optimal solution is chosen by minimizing the distance to the “ideal point” (maximum efficiency, minimum dispersion).El proceso de producción agrícola está asociado con un complejo de factores de diferente naturaleza: sistémicos, tecnológicos, biológicos, socioeconómicos, climáticos, reproductivos, ambientales. Todos ellos influyen en el tamaño y la estabilidad de los resultados económicos y financieros. Existe un nivel umbral de complejidad de gestión empresarial, cuyo exceso motiva a los agronegocios a cambiar a métodos computarizados. La gestión de una empresa agrícola debe basarse en resultados de planificación, actualizados en un modo continuo. Al desarrollar el plan anual, es necesario tener en cuenta mucha información heterogénea y tender a la solución óptima: el logro de los indicadores objetivo con el gasto mínimo de recursos. Como base del sistema óptimo de planificación anual, el artículo propone un modelo económico-matemático para optimizar la producción y la estructura industrial de una empresa agrícola, que incluye los siguientes módulos: evaluación de los parámetros de las funciones de producción de rendimiento en función del historial de campo, la formación de un plan de aplicación de fertilizantes con justificación de niveles de rendimiento económicamente factibles, resolviendo el problema de optimizar la estructura sectorial de la producción de cultivos, teniendo en cuenta la influencia de la cosecha en la rotación de cultivos. El algoritmo para encontrar una estructura de producción efectiva y estable bajo diversas combinaciones de condiciones ambientales implementa la siguiente secuencia de procedimientos: generación de combinaciones de parámetros del modelo económico-matemático; obtener la solución óptima para cada combinación de estos parámetros; evaluación de la expectativa matemática del criterio de eficiencia y la varianza para cada solución óptima en una variedad de combinaciones de parámetros; elección de una solución altamente efectiva con una baja dispersión de esta eficiencia. Para implementar este algoritmo, se utiliza el método de experimentos de simulación en el espacio de los parámetros del sistema. La solución óptima se elige minimizando la distancia al "punto ideal" (máxima eficiencia, mínima dispersión)

Interplay between lattice, orbital, and magnetic degrees of freedom in the chain-polymer Cu(II) breathing crystals

The chain-polymer Cu(II) breathing crystals C21H19CuF12N4O6 were studied using the x-ray diffraction and ab initio band structure calculations. We show that the crystal structure modification at T=146 K, associated with the spin crossover transition, induces the changes of the orbital order in half of the Cu sites. This in turn results in the switch of the magnetic interaction sign in accordance with the Goodenough-Kanamori-Andersen theory of the coupling between the orbital and spin degrees of freedom.Comment: 6 pages, 7 figure

Synthesis of nitroxyl radical by direct nucleophilic functionalization of a C-H bond in the azadiene systems

Cyclic dinitrones underwent nucleophilic substitution of the hydrogen atom in the reaction with a paramagnetic carbanion, the lithium derivative of 4,4,5,5-tetramethyl-4,5-dihydro-1H-imidazol-1-oxyl 3-oxide, to give polyfunctional nitronyl nitroxyls. © 2012 Springer Science+Business Media New York

The dependence of antihypoxic activity on the chemical structure in a series of N-(3-methyl-7-acetylmethylxanthinyl)-8-piperazine ammonium salts

The comparative investigation of the dependence of antihypoxic activity on chemical structure in a series of N-(3-methyl-7-acetylmethylxanthinyl)- 8-piperazine ammonium salts has been conducted on the model of acute atmospheric hypoxia with hypercapnia in tests on white Wistar line rats. It has been found that among the tested compounds aminoacetic ammonium salt showed the lowest antihypoxic activity, and the highest one was shown by N-(3-methyl-7-acetylmethylxanthinyl)-8-piperazine succinate that increased the life time of rats by 79,9% in the conditions of acute atmospheric hypoxia and exceeded by 9,2% the activity of the reference drug of mexidol. The series of N-(3-methyl-7-acetylmethylxanthinyl)-8-piperazine ammonium salts are the promising group of organic compounds for the further synthesis and pharmacological screening for the purpose of using them as effective antihypoxic drugs.Сравнительное исследование зависимости антигипоксической активности от химической структуры в ряду аммониевых солей N-(3-метил-7-ацетилметилксантинил)-8-пиперазиния проведено на модели острой нормобарической гипоксии с гиперкапнией в опытах на белых крысах линии Вистар. Обнаружено, что среди исследованных соединений наименьшую антигипоксическую активность проявила аминоацетатная аммониевая соль, а наибольшую – сукцинат N-(3-метил-7-ацетилметилксантинил)-8-пиперазиния, который увеличивал продолжительность жизни крыс на 79,9% в условиях острой нормобарической гипоксии и превышал активность препарата сравнения мексидола на 9,2%. Аммониевые соли, в ряду производных N-(3-метил-7-ацетилметилксантинил)-8-пиперазиния, являются перспективной группой органических соединений для последующего синтеза и фармакологического скрининга с целью создания на их основе эффективных антигипоксических препаратов

Influence of the atomic-wall collision elasticity on the coherent population trapping resonance shape

We studied theoretically a coherent population trapping resonance formation in cylindrical cell without buffer gas irradiated by a narrow laser beam. We take into account non-zero probabilities of elastic ("specular") and inelastic ("sticking") collision between the atom and the cell wall. We have developed a theoretical model based on averaging over the random Ramsey pulse sequences of times that atom spent in and out of the beam. It is shown that the shape of coherent population trapping resonance line depends on the probability of elastic collision.Comment: 18 pages, 5 figure