Importance of force decomposition for local stress calculations in biomembrane molecular simulations

Local stress fields are routinely computed from molecular dynamics trajectories to understand the structure and mechanical properties of lipid bilayers. These calculations can be systematically understood with the Irving-Kirkwood-Noll theory. In identifying the stress tensor, a crucial step is the decomposition of the forces on the particles into pairwise contributions. However, such a decomposition is not unique in general, leading to an ambiguity in the definition of the stress tensor, particularly for multibody potentials. Furthermore, a theoretical treatment of constraints in local stress calculations has been lacking. Here, we present a new implementation of local stress calculations that systematically treats constraints and considers a privileged decomposition, the central force decomposition, that leads to a symmetric stress tensor by construction. We focus on biomembranes, although the methodology presented here is widely applicable. Our results show that some unphysical behavior obtained with previous implementations (e.g. nonconstant normal stress profiles along an isotropic bilayer in equilibrium) is a consequence of an improper treatment of constraints. Furthermore, other valid force decompositions produce significantly different stress profiles, particularly in the presence of dihedral potentials. Our methodology reveals the striking effect of unsaturations on the bilayer mechanics, missed by previous stress calculation implementations

Sobre la convergencia del modelo GARCH(1,1)-M al movimiento geométrico browniano con reversión a la media

This paper shows, under certain conditions, the convergence of the GARCH (1.1)-M model to the geometric Brownian motion with mean reversion (diffusion GARCH process). The importance from this result is that the problem of inference on the parameters of the valuation models of options with stochastic volatility can be reduced by estimating the model GARCH (1.1)-M. It is also carried out a discussion on the assumptions that ensure the existence and uniqueness of the limit process. Finally, it is provided a quick demonstration of the convergence, which is less formal, but more intuitive and easy to remember.Convergencia de procesos estocásticos, valuación de derivados, volatilidad estocástica

Measurement of the neutron-induced fission cross section of 230Th at the CERN n_TOF facility

Euratom "Support safe operation of nuclear systems" program MIS 5033021European Union (EU) European Social Fund (ESF)Greek national funds through the action 84755

Análisis y evaluación de la condición física en estudiantes de educación primaria de un medio rural y urbano

El objetivo de este trabajo ha sido analizar y evaluar la condición física de escolares estudiantes de educación primaria para conocer la diferencia que existe entre los alumnos que viven en un medio rural y los que viven en un medio urbano. Para ello se seleccionaron 253 estudiantes de segundo y tercer ciclo de educación primaria. La muestra fue clasificada según el tipo de colegio en dos grupos, urbano y rural. A todos los estudiantes se les realizó una valoración antropométrica (talla, masa, IMC, ratio CC), evaluación del salto vertical (CMJ), flexibilidad (test Sit and Reach), fuerza (dinamometría manual) y resistencia (test course na­vette). Los resultados muestran diferencias a nivel antropométrico donde los alumnos del colegio rural han presentado mayores índices de sobrepeso. En cambio, los resultados obtenidos en la evaluación de la condición física muestran como en las pruebas de fuerza, resistencia y flexibilidad los alumnos del colegio rural obtienen mayores resultados que los alumnos del colegio urbano, mientras que en el salto vertical los alumnos rurales presentan mayores valores

Nuevos datos sobre la sedimentación terciaria en La Mancha (Ciudad Real)

Los datos obtenidos de la investigación geofísica y perforación de sondeos en la parte occidental de La Mancha han permitido determinar la estructura del sustrato del Neógeno: un conjunto de fosas controladas por fallas, que se generaron en periodos de tectónica distensiva. Se han separado tres  unidades litoestratigráficas: Unidad detrítica de la base, Unidad lutítica roja intermedia y Unidad carbonatada superior

Nondiffractive sonic crystals

We predict theoretically the nondiffractive propagation of sonic waves in periodic acoustic media (sonic crystals), by expansion into a set of plane waves (Bloch mode expansion), and by finite difference time domain calculations of finite beams. We also give analytical evaluations of the parameters for nondiffractive propagation, as well as the minimum size of the nondiffractively propagating acoustic beams.Comment: 7 figures, submitted to J. Acoust. Soc. A

On the interaction between Autonomous Mobility-on-Demand systems and the power network: models and coordination algorithms

We study the interaction between a fleet of electric, self-driving vehicles servicing on-demand transportation requests (referred to as Autonomous Mobility-on-Demand, or AMoD, system) and the electric power network. We propose a model that captures the coupling between the two systems stemming from the vehicles' charging requirements and captures time-varying customer demand and power generation costs, road congestion, battery depreciation, and power transmission and distribution constraints. We then leverage the model to jointly optimize the operation of both systems. We devise an algorithmic procedure to losslessly reduce the problem size by bundling customer requests, allowing it to be efficiently solved by off-the-shelf linear programming solvers. Next, we show that the socially optimal solution to the joint problem can be enforced as a general equilibrium, and we provide a dual decomposition algorithm that allows self-interested agents to compute the market clearing prices without sharing private information. We assess the performance of the mode by studying a hypothetical AMoD system in Dallas-Fort Worth and its impact on the Texas power network. Lack of coordination between the AMoD system and the power network can cause a 4.4% increase in the price of electricity in Dallas-Fort Worth; conversely, coordination between the AMoD system and the power network could reduce electricity expenditure compared to the case where no cars are present (despite the increased demand for electricity) and yield savings of up $147M/year. Finally, we provide a receding-horizon implementation and assess its performance with agent-based simulations. Collectively, the results of this paper provide a first-of-a-kind characterization of the interaction between electric-powered AMoD systems and the power network, and shed additional light on the economic and societal value of AMoD.Comment: Extended version of the paper presented at Robotics: Science and Systems XIV, in prep. for journal submission. In V3, we add a proof that the socially-optimal solution can be enforced as a general equilibrium, a privacy-preserving distributed optimization algorithm, a description of the receding-horizon implementation and additional numerical results, and proofs of all theorem