New classes of stable exact solutions for a nonlinear rotational DNA model

We consider a system of two coupled nonlinear partial differential equations for describing the rotational motions of bases in both polynucleotide chains of the DNA molecule. The model was proposed by L.V. Yakushevich and it is well known that the model supports, for some operating regimes, traveling wave solutions as kink–(antikink) soliton solutions. We have tried to make some progress by performing an analysis of the classical symmetries of this model. Our study shows that the model does not have enough symmetries as to reduce the equations to ordinary differential equations. Nevertheless, the known symmetries have been useful for finding several classes of exact solutions, by imposing adequate Ansätze. Some of them are kink–(antikink) like solutions, but other ones are not traveling wave solutions. For some of the new solutions, we have carried out a qualitative study and analyzed some stability properties. We think that they could be significant for the description of the DNA molecule as well as for some other applications.DGYCYT project MTM2006-05031Junta de Andalucía FQM 201. P06-FQM-0144

Estudio de viabilidad para la emisión de títulos de deuda para financiar la ampliación del colegio balandra cruz del sur

empresas. Nuestra empresa a analizar, PREDUCA S.A, se ha desenvuelto en el sector educativo clase alta, manteniendo un prestigio por 17 años, lo cual la coloca como una de las mejores dentro de su estrato social. Su objetivo de reestructuración de pasivos y expansión futura, nos llevaron a establecer pautas para la utilización de nuevas herramientas de financiamiento. La emisión de obligaciones es una herramienta, conocida y utilizada en varios países incluidos el nuestro, que ha dado paso a un mayor desarrollo en el mercado de capitales ya que se muestra como una opción rentable al momento de invertir. Los análisis de los estados financieros de nuestra empresa en mención fueron factores cruciales para poder determinar la factibilidad de una emisión, además de una estrategia de introducción de este tipo de empresas en el mercado de valores, ya que de incursionar PREDUCA S.A. en este mercado sería la primera en su clase y sector. Las oportunidades y amenazas que una decisión como esta conlleva y los beneficios futuros asociados son tratados en nuestro estudio, a fin de dar al lector una visión del entorno de la empresa y proporcionar una guía de procedimientos a seguir en caso de realizarse una emisión de obligaciones. Todo ello asociado con la experiencia tanto al interior de nuestro país, la realidad que se ha vivido en los últimos años en nuestro mercado de obligaciones conjuntamente con lo sucedido en países latinoamericanos, nos muestra el escenario en que se desenvolvería PREDUCA S.A. al momento de emitir una obligación

Regulation of brain endothelial barrier function by microRNAs in health and neuroinflammation

Brain endothelial cells constitute the major cellular element of the highly specialized blood–brain barrier (BBB) and thereby contribute to CNS homeostasis by restricting entry of circulating leukocytes and blood-borne molecules into the CNS. Therefore, compromised function of brain endothelial cells has serious consequences for BBB integrity. This has been associated with early events in the pathogenesis of several disorders that affect the CNS, such as multiple sclerosis, HIV-associated neurologic disorder, and stroke. Recent studies demonstrate that brain endothelial microRNAs play critical roles in the regulation of BBB function under normal and neuroinflammatory conditions. This review will focus on emerging evidence that indicates that brain endothelial microRNAs regulate barrier function and orchestrate various phases of the neuroinflammatory response, including endothelial activation in response to cytokines as well as restoration of inflamed endothelium into a quiescent state. In particular, we discuss novel microRNA regulatory mechanisms and their contribution to cellular interactions at the neurovascular unit that influence the overall function of the BBB in health and during neuroinflammatio

Optimizacion del diseino de una red de distribucion de agua potable

En el presente reporte se present an los resultados obtenidos por el grupo de trabajo que estudio el problema de disenar de manera optima, una red de distribucion de agua potable. Esencialmente se discuten dos clases de estrategias. En primer lugar, aquellas cuya finalidad es reducir significativamente los recursos computacionales requeridos por los algoritmos im- plementados por el IMTA. Estos algoritmos son de caracter heuristico y generan una solucion factible que no es optima. En ciertos casos se sabe que las soluciones obtenidas por dichos algoritmos estan relativamente lejos del optima y no son aceptables desde el punto de vista del disenador. La segunda clase de estrategias propuestas, esta destinada precisamente a aliviar este problema. Se sugieren tecnicas originadas en optimizacion continua yen flujo en redes

The neonicotinoid insecticide Imidacloprid repels pollinating flies and beetles at field-realistic concentrations

Neonicotinoids are widely used systemic insecticides which, when applied to flowering crops, are translocated to the nectar and pollen where they may impact upon pollinators. Given global concerns over pollinator declines, this potential impact has recently received much attention. Field exposure of pollinators to neonicotinoids depends on the concentrations present in flowering crops and the degree to which pollinators choose to feed upon them. Here we describe a simple experiment using paired yellow pan traps with or without insecticide to assess whether the commonly used neonicotinoid imidacloprid repels or attracts flying insects. Both Diptera and Coleoptera exhibited marked avoidance of traps containing imidacloprid at a field-realistic dose of 1 μg L-1, with Diptera avoiding concentrations as low as 0.01 μg L-1. This is to our knowledge the first evidence for any biological activity at such low concentrations, which are below the limits of laboratory detection using most commonly available techniques. Catch of spiders in pan traps was also slightly reduced by the highest concentrations of imidacloprid used (1 μg L-1), but catch was increased by lower concentrations. It remains to be seen if the repellent effect on insects occurs when neonicotinoids are present in real flowers, but if so then this could have implications for exposure of pollinators to neonicotinoids and for crop pollination. © 2013 Easton, Goulson

Bistability in the Tunnelling Current through a Ring of NN Coupled Quantum Dots

We study bistability in the electron transport through a ring of N coupled quantum dots with two orbitals in each dot. One orbital is localized (called b orbital) and coupling of the b orbitals in any two dots is negligible; the other is delocalized in the plane of the ring (called d orbital), due to coupling of the d orbitals in the neighboring dots, as described by a tight-binding model. The d orbitals thereby form a band with finite width. The b and d orbitals are connected to the source and drain electrodes with a voltage bias V, allowing the electron tunnelling. Tunnelling current is calculated by using a nonequilibrium Green function method recently developed to treat nanostructures with multiple energy levels. We find a bistable effect in the tunnelling current as a function of bias V, when the size N>50; this effect scales with the size N and becomes sizable at N~100. The temperature effect on bistability is also discussed. In comparison, mean-field treatment tends to overestimate the bistable effect.Comment: Published in JPSJ; minor typos correcte

The Essential Interactions in Oxides and Spectral Weight Transfer in Doped Manganites

We calculate the value of the Fr\"ohlich electron-phonon interaction in manganites, cuprates, and some other charge-transfer insulators and show that this interaction is much stronger than any relevant magnetic interaction. A polaron shift due to the Fr\"ohlich interaction, which is about 1 eV, suggests that carriers in those systems are small (bi)polarons at all temperatures and doping levels, in agreement with the oxygen isotope effect and other data. An opposite conclusion, recently suggested in the literature, is shown to be incorrect. The frequency and temperature dependence of the optical conductivity of ferromagnetic manganites is explained within the framework of the bipolaron theory.Comment: 6 pages, REVTeX 3.1 with 3 eps-figures. Journal versio

Search for the standard model Higgs boson in the H to ZZ to 2l 2nu channel in pp collisions at sqrt(s) = 7 TeV

A search for the standard model Higgs boson in the H to ZZ to 2l 2nu decay channel, where l = e or mu, in pp collisions at a center-of-mass energy of 7 TeV is presented. The data were collected at the LHC, with the CMS detector, and correspond to an integrated luminosity of 4.6 inverse femtobarns. No significant excess is observed above the background expectation, and upper limits are set on the Higgs boson production cross section. The presence of the standard model Higgs boson with a mass in the 270-440 GeV range is excluded at 95% confidence level.Comment: Submitted to JHE