Effects of constraints in general branched molecules: A quantitative ab initio study in HCO-L-Ala-NH2

A general approach to the design of accurate classical potentials for protein folding is described. It includes the introduction of a meaningful statistical measure of the differences between approximations of the same potential energy, the definition of a set of Systematic and Approximately Separable and Modular Internal Coordinates (SASMIC), much convenient for the simulation of general branched molecules, and the imposition of constraints on the most rapidly oscillating degrees of freedom. All these tools are used to study the effects of constraints in the Conformational Equilibrium Distribution (CED) of the model dipeptide HCO-L-Ala-NH2. We use ab initio Quantum Mechanics calculations including electron correlation at the MP2 level to describe the system, and we measure the conformational dependence of the correcting terms to the naive CED based in the Potential Energy Surface (PES) without any simplifying assumption. These terms are related to mass-metric tensors determinants and also occur in the Fixman's compensating potential. We show that some of the corrections are non-negligible if one is interested in the whole Ramachandran space. On the other hand, if only the energetically lower region, containing the principal secondary structure elements, is assumed to be relevant, then, all correcting terms may be neglected up to peptides of considerable length. This is the first time, as far as we know, that the analysis of the conformational dependence of these correcting terms is performed in a relevant biomolecule with a realistic potential energy function.Comment: 8 pages, 1 figure, LaTeX, aipproc style (included

Flow damping in stellarators close to quasisymmetry

Quasisymmetric stellarators are a type of optimized stellarators for which flows are undamped to lowest order in an expansion in the normalized Larmor radius. However, perfect quasisymmetry is impossible. Since large flows may be desirable as a means to reduce turbulent transport, it is important to know when a stellarator can be considered to be sufficiently close to quasisymmetry. The answer to this question depends strongly on the size of the spatial gradients of the deviation from quasisymmetry and on the collisionality regime. Recently, formal criteria for closeness to quasisymmetry have been derived in a variety of situations. In particular, the case of deviations with large gradients was solved in the $1/\nu$ regime. Denoting by $\alpha$ a parameter that gives the size of the deviation from quasisymmetry, it was proven that particle fluxes do not scale with $\alpha^{3/2}$, as typically claimed, but with $\alpha$. It was also shown that ripple wells are not necessarily the main cause of transport. This paper reviews those works and presents a new result in another collisionality regime, in which particles trapped in ripple wells are collisional and the rest are collisionless.Comment: 14 pages, 2 figures. To appear in Plasma Physics and Controlled Fusio

The effect of tangential drifts on neoclassical transport in stellarators close to omnigeneity

In general, the orbit-averaged radial magnetic drift of trapped particles in stellarators is non-zero due to the three-dimensional nature of the magnetic field. Stellarators in which the orbit-averaged radial magnetic drift vanishes are called omnigeneous, and they exhibit neoclassical transport levels comparable to those of axisymmetric tokamaks. However, the effect of deviations from omnigeneity cannot be neglected in practice. For sufficiently low collision frequencies (below the values that define the $1/\nu$ regime), the components of the drifts tangential to the flux surface become relevant. This article focuses on the study of such collisionality regimes in stellarators close to omnigeneity when the gradient of the non-omnigeneous perturbation is small. First, it is proven that closeness to omnigeneity is required to preserve radial locality in the drift-kinetic equation for collisionalities below the $1/\nu$ regime. Then, it is shown that neoclassical transport is determined by two layers in phase space. One of the layers corresponds to the $\sqrt{\nu}$ regime and the other to the superbanana-plateau regime. The importance of the superbanana-plateau layer for the calculation of the tangential electric field is emphasized, as well as the relevance of the latter for neoclassical transport in the collisionality regimes considered in this paper. In particular, the tangential electric field is essential for the emergence of a new subregime of superbanana-plateau transport when the radial electric field is small. A formula for the ion energy flux that includes the $\sqrt{\nu}$ regime and the superbanana-plateau regime is given. The energy flux scales with the square of the size of the deviation from omnigeneity. Finally, it is explained why below a certain collisionality value the formulation presented in this article ceases to be valid.Comment: 36 pages. Version to be published in Plasma Physics and Controlled Fusio

Cuando de salud se trata, ¿a dónde acuden las personas?

Cartel presentado en la Segunda Conferencia Internacional de Comunicación en Salud, celebrada el 23 de octubre de 2015 en la Universidad Carlos III de MadridEsta investigación pretendió conocer las relaciones vecinales y sociales de los/as habitantes de dos de los barrios de la localidad de Bosa y de la localidad de Engativá (Bogotá) con las droguerías como instituciones de respuesta a las situaciones de salud, y si éstas pueden ser consideradas consideradas como lugares en donde se suple la falencia del servicio de salud y asimismo, se instauran relaciones sociales que van más allá de la venta de un producto. Asimismo, conocer las razones por las que los/las habitantes de las localidades de Bosa y Engativá, en dos de sus barrios acuden a las droguerías antes que a las entidades de salud; y qué tipo de población acude con más frecuencia. De acuerdo con lo anterior, se consideró como objetivo general analizar las relaciones sociales y vecinales generadas por los servicios de salud que prestan las droguerías de las dos localidades en su zona central respectivamente como instituciones de respuesta a las situaciones o crisis de salud en estas zonas específicas. Esta investigación tuvo un enfoque hermenéutico interpretativo y tuvo tres etapas: Diagnóstico: A través de observación participante en las droguerías seleccionadas; Trabajo de campo: aplicando las técnicas de entrevista a farmaceutas de las droguerías seleccionadas y encuestas escritas a los clientes consumidores de la farmacia y a habitantes de sus alrededores; Sistematización mediante la recopilación de datos e información y análisis de los mismos, obteniendo como principal respuesta a las preguntas de investigación que las personas prefieren las droguerías antes que los establecimiento de salud como EPS y hospitales por la cercanía, confianza, mejor atención, efectividad en diagnóstico y formulación ya que estando las droguerías dentro de los barrios, y su cercanía con la comunidad, se convierten en un espacio de interrelaciones vecinales

Cooler and bigger than thought? Planetary host stellar parameters from the InfraRed Flux Method

Effective temperatures and radii for 92 planet-hosting stars as determined from the InfraRed Flux Method (IRFM) are presented and compared with those given by other authors using different approaches. The IRFM temperatures we have derived are systematically lower than those determined from the spectroscopic condition of excitation equilibrium, the mean difference being as large as 110 K. They are, however, consistent with previous IRFM studies and with the colors derived from Kurucz and MARCS model atmospheres. Comparison with direct measurements of stellar diameters for 7 dwarf stars, which approximately cover the range of temperatures of the planet-hosting stars, suggest that the IRFM radii and temperatures are reliable in an absolute scale. A better understanding of the fundamental properties of the stars with planets will be achieved once this discrepancy between the IRFM and the spectroscopic temperature scales is resolved.Comment: 15 pages, 4 figures. Accepted for publication in Ap

Negocios inclusivos. Un modelo de metáfora biológica para el sector agropecuario

The agricultural sector was one of the sectors that was most compromised during the confinements in the COVID-19 pandemic, guaranteeing the value chain and the necessary inputs. But even so, the problems of the sector are still evident: poverty, inequity, lack of rural and non-rural employment, low profit rates, lack of distribution chains and market development, among others. An alternative that is presented to achieve successful productive chains is that of inclusive businesses, for its better application and understanding, the application of a biological metaphor of coevolution and mutualism is presented in this document, noting that inclusive businesses should not occur. only on occasions of vulnerable producers, but to recognize in them their skills, knowledge, and capacities that they can share and put in favour of the integration model to achieve joint developments with the other organizations in the chain.The proposal focuses on strengthening inclusive models from the recognition of diversity and difference, and the development of management alternatives for the entire chain in general.El sector agropecuario fue uno de los más comprometidos durante los confinamientos en la pandemia de COVID-19, garantizando la cadena de valor y los insumos necesarios. Pero, aun así, los problemas del sector siguen siendo evidentes, pobreza, inequidad, falta de empleo rural y no rural, bajas tasas de ganancia, falta de cadenas de distribución y desarrollode mercados, entre otros. Una alternativa para lograr encadenamientos productivos exitosos es la de los negocios inclusivos. Para una mejor aplicación y entendimiento, este documento presenta la aplicación de una metáfora biológica de la coevolución y el mutualismo, señalando que los negocios inclusivos no solo deben darse en productores vulnerables,sino que deben reconocer sus habilidades, conocimientos y capacidades que pueden compartir y utilizar a favor del modelo de integración, para lograr desarrollos conjuntos con otras organizaciones de la cadena. La propuesta se centra en fortalecer los modelos inclusivos desde el reconocimiento de la diversidad y la diferencia, y el desarrollo de alternativas de gestión para toda la cadena en general

Twisted Nano-optics: Manipulating Light at the Nanoscale with Twisted Phonon Polaritonic Slabs

Recent discoveries have shown that when two layers of van der Waals (vdW) materials are superimposed with a relative twist angle between their respective in-plane principal axes, the electronic properties of the coupled system can be dramatically altered. Here, we demonstrate that a similar concept can be extended to the optics realm, particularly to propagating polaritons, hybrid light-matter interactions. To do this, we fabricate stacks composed of two twisted slabs of a polar vdW crystal (MoO3) supporting low-loss anisotropic phonon polaritons (PhPs), and image the propagation of the latter when launched by localized sources (metal antennas). Our images reveal that under a critical angle the PhPs isofrequency curve (determining the PhPs momentum at a fixed frequency) undergoes a topological transition. Remarkably, at this angle, the propagation of PhPs is strongly guided along predetermined directions (canalization regime) with no geometrical spreading (diffraction-less). These results demonstrate a new degree of freedom (twist angle) for controlling the propagation of polaritons at the nanoscale with potential for nano-imaging, (bio)-sensing, quantum applications and heat management

Análisis del confort térmico en escuela modelo de la sierra peruana y evaluación de mejoramiento térmico mediante el uso de principios bioclimáticos

La investigación consiste en la evaluación del confort térmico en las aulas de una escuela modelo tipo Sierra, ubicada en la ciudad de Cusco, así como una propuesta de mejora térmica basada en un diseño bioclimático. En la introducción, se presentan los antecedentes de la arquitectura vernácula. Se explica la problemática energética producto de la masificación de sistemas constructivos y la aparición de sistemas de aire acondicionado cuyo fin se justifica en satisfacer requerimientos de confort interno. La revisión de literatura presenta los estudios relacionados al confort interno de edificaciones así como estrategias bioclimáticas que permitan alcanzar la zona de confort según las variables climáticas de los emplazamientos. Para la evaluación del confort en el caso práctico se utiliza el programa computacional “Design Builder” que brinda resultados del confort para ser analizados. Finalmente, en la evaluación de resultados se discute el análisis del confort del caso práctico y cómo la propuesta de diseño bioclimático contribuye a alcanzar los niveles de confort deseados en la escuela