Temperature dependence of surface stress across an order-disorder transition: p(1x2)O/W(110)

Strain relaxations of a p(1x2) ordered oxygen layer on W(110) are measured as a function of temperature across the disordering transition using low-energy electron diffraction. The measured strains approach values of 0.027 in the [1-10] and -0.053 in the [001] direction. On the basis of the measured strain relaxations, we give quantitative information on temperature-dependent surface stress using the results of ab initio calculations. From the surface formation energy for different strains, determined by first-principles calculations, we estimate that surface stress changes from -1.1 for the ordered phase to -0.2N/m for the disordered one along [1-10], and from 5.1 to 3.4 N/m along [001]. Moreover, our observation that the strains scale inversely with domain size confirms that the strain relaxation takes place at the domain boundaries.Comment: 8 pages, 5 figure

Stress engineering at the nanometer scale: Two-component adlayer stripes

Spontaneously formed equilibrium nanopatterns with long-range order are widely observed in a variety of systems, but their pronounced temperature dependence remains an impediment to maintain such patterns away from the temperature of formation. Here, we report on a highly ordered stress-induced stripe pattern in a two-component, Pd-O, adsorbate monolayer on W(110), produced at high temperature and identically preserved at lower temperatures. The pattern shows a tunable period (down to 16 nm) and orientation, as predicted by a continuum model theory along with the surface stress and its anisotropy found in our DFT calculations. The control over thermal fluctuations in the stripe formation process is based on the breaking/restoring of ergodicity in a high-density lattice gas with long-range interactions upon turning off/on particle exchange with a heat bath.Comment: 6 pages, 4 figure

Strain relaxation in small adsorbate islands: O on W(110)

The stress-induced lattice changes in a p(1x2) ordered oxygen layer on W(110) are measured by low-energy electron diffraction. We have observed that small oxygen islands show a mismatch with the underlying lattice. Our results indicate that along [1-10] the average mismatch scales inversely with the island size as 1/L for all oxygen coverages up to 0.5 ML, while along [001] it is significant only for the smallest oxygen islands and scales as a higher power of the inverse island size. The behaviour along [1-10] is described by a one-dimensional finite-size Frenkel-Kontorova model. Using this model, together with calculated force constants, we make a quantitative estimate for the change of surface-stress upon oxygen adsorption. The result is consistent with our ab-initio calculations, which give a relative compressive stress of -4.72 N/m along [1-10] and a minute relative tensile stress of 0.15 N/m along [001]. The scaling along [001] is qualitatively explained as an effect induced by the lattice relaxation in the [1-10] direction.Comment: 22 pages, 5 figure

Electrostatic internal energy using the method of images

For several configurations of charges in the presence of conductors, the method of images permits us to obtain some observables associated with such a configuration by replacing the conductors with some image charges. However, simple inspection shows that the potential energy associated with both systems does not coincide. Nevertheless, it can be shown that for a system of a grounded or neutral conductor and a distribution of charges outside, the external potential energy associated with the real charge distribution embedded in the field generated by the set of image charges is twice the value of the internal potential energy associated with the original system. This assertion is valid for any size and shape of the conductor, and regardless of the configuration of images required. In addition, even in the case in which the conductor is not grounded nor neutral, it is still possible to calculate the internal potential energy of the original configuration through the method of images. These results show that the method of images could also be useful for calculations of the internal potential energy of the original system.Comment: 5 pages, 3 figures. New discussions added. Minor change

Combination of DROOL rules and Protégé knowledge bases in the ONTO-H annotation tool

ONTO-H is a semi-automatic collaborative tool for the semantic annotation of documents, built as a Protégé 3.0 tab plug-in. Among its multiple functionalities aimed at easing the document annotation process, ONTO-H uses a rule-based system to create cascading annotations out from a single drag and drop operation from a part of a document into an already existing concept or instance of the domain ontology being used for annotation. It also gives support to the detection of name conflicts and instance duplications in the creation of the annotations. The rule system runs on top of the open source rule engine DROOLS and is connected to the domain ontology used for annotation by means of an ad-hoc programmed Java proxy

phase coexistence in two dimensional fe 0 70 ni 0 30 films on w 110

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Discretización exacta de un robot móvil con retardo de transporte

An exact discrete time model of a mobile robot of the type (2,0) that includes the time-delay induced by a communication network between the sensors and actuators on the mobile robot and the remote control system is presented. Simulations results are provided to show the performance of the proposed exact discrete time model. The performance of obtained model is better compared to the approximate model because it does not need a sampling period sufficiently small.En este trabajo se presenta la obtención del modelo exacto en tiempo discreto de un robot móvil tipo (2,0), bajo la consideración de la existencia de retardos de transporte en la señal de control, producidos por la propagación de las señales entre los sensores y actuadores del robot y el control remoto. El modelo obtenido es evaluado mediante simulación, comparando su desempeño con un modelo discreto aproximado que incluye también retardos de transporte y con el modelo en tiempo continuo del mismo sistema

Modelamiento y simulación de un quadrotor mediante la integración de Simulink y SolidWorks

El propósito de este trabajo fue el de realizar el modelo dinámico de un vehículo aéreo no tripulado (VANT) tipo quadrotor, que simule el comportamiento real del mismo, de tal manera que el quadrotor pueda realizar sus movimientos básicos con el mínimo error posible. Para realizar dicho modelo matemático se consideró al quadrotor como un cuerpo rígido de seis grados de libertad en donde el sistema es dividido en coordenadas traslacionales y rotacionales al manejar una técnica para la modelación, mediante las ecuaciones de Euler-Lagrange, y así obtener la función de transferencia, expresada en las plantas del modelo dinámico que describe el comportamiento del quadrotor. La dinámica rotacional del VANT fue definida por los principales momentos de inercia, los cuales fueron hallados en el centro de masa del vehículo, dichos momentos fueron estimados a través del software de entorno CAD Solidworks. Para ello, el quadrotor se ensambló allí con el mínimo de partes posibles y luego el diseño se exportó a Simulink para complementar los resultados de la simulación con una animación en 3D del movimiento. Al diseño de la estructura se le implementó una estrategia de control que estabiliza las plantas ya descritas y se corroboró el funcionamiento del sistema al aplicar al mismo, perturbaciones externas como lo son las ráfagas de viento y masas variables que puedan producir inestabilidad durante el vuelo, logrando que ante este tipo de señales el sistema reaccione de forma controlada. En los resultados se observó que la simulación de una ráfaga de viento en donde el VANT cambio su posición en los ejes de desplazamiento horizontal, este mismo logró llegar nuevamente a su posición de referencia en menos de doce (12) segundos. Lo anterior constituye una importante aplicación de la dinámica rotacional del Vehículo Aéreo No Tripulado, al utilizar Simulink y la librería Simscape Multibody en conjunto con Solidworks, lográndose una herramienta de gran interés y por ende un aporte significativo para el estudio de los VANT, dando posibilidad del uso de una herramienta práctica para el diseño de quadrotores, enfocados en diferentes aplicaciones, tales como la agricultura de precisión

Examining national and district-level trends in neonatal health in Peru through an equity lens:A success story driven by political will and societal advocacy

Abstract Background Peru has impressively reduced its neonatal mortality rate (NMR). We aimed, for the period 2000–2013, to: (a) describe national and district NMR variations over time; (b) assess NMR trends by wealth quintile and place of residence; (c) describe evolution of mortality causes; (d) assess completeness of registered mortality; (e) assess coverage and equity of NMR-related interventions; and (f) explore underlying driving factors. Methods We compared national NMR time trends from different sources. To describe NMR trends by wealth quintiles, place of residence and districts, we pooled data on births and deaths by calendar year for neonates born to women interviewed in multiple surveys. We disaggregated coverage of NMR-related interventions by wealth quintiles and place of residence. To identify success factors, we ran regression analyses and combined desk reviews with qualitative interviews and group discussions. Results NMR fell by 51 % from 2000 to 2013, second only to Brazil in Latin America. Reduction was higher in rural and poorest segments (52 and 58 %). District NMR change varied by source. Regarding cause-specific NMRs, prematurity decreased from 7.0 to 3.2 per 1,000 live births, intra-partum related events from 2.9 to 1.2, congenital abnormalities from 2.4 to 1.8, sepsis from 1.9 to 0.8, pneumonia from 0.9 to 0.4, and other conditions from 1.2 to 0.7. Under-registration of neonatal deaths decreased recently, more in districts with higher development index and lower rural population. Coverage of family planning, antenatal care and skilled birth attendance increased more in rural areas and in the poorest quintile. Regressions did not show consistent associations between mortality and predictors. During the study period social determinants improved substantially, and dramatic out-of-health-sector and health-sector changes occurred. Rural areas and the poorest quintile experienced greater NMR reduction. This progress was driven, within a context of economic growth and poverty reduction, by a combination of strong societal advocacy and political will, which translated into pro-poor implementation of evidence-based interventions with a rights-based approach. Conclusions Although progress in Peru for reducing NMR has been remarkable, future challenges include closing remaining gaps for urban and rural populations and improving newborn health with qualified staff and intermediate- and intensive-level health facilities

Evaluación de las Actividades Antioxidante y Antitopoisomerasa de Extractos de Plantas de la Ecorregión Cafetera Colombiana

De la parte aérea de 29 especies de plantas recolectadas en la Ecorregión Cafetera Colombiana se obtu­vieron por maceración pasiva los extractos de diclorometano y metanol a los cuales se les determinó la activi­dad antitopoisomerasa empleando cepas mutadas de Saccharomyces cerevisiae por el método de difusión en agar; adicionalmente, se les evaluó la capacidad captadora de radicales libres por los métodos de los radicales 1,1-Difenil-2-picrilhidrazilo (DPPH•) y ácido 2,2' azinobis-(3-etilbenzotiazolina)-6-sulfónico (ABTS•+). Así mismo, se determinó el contenido de fenoles totales por el método de Folin-Ciocalteu a todos los extractos que pre­sentaron capacidad antioxidante igual o superior al 25% en el ensayo de DPPH•. Se encontraron 8 extractos de diclorometano y 15 de metanol con actividad antioxidante superior al 25% y alto contenido de fenoles totales. Los extractos de metanol de Hyeronima sp. y Acalypha diversifolia (Euphorbiaceae) presentaron los porcen­tajes de actividad antioxidante más altos con valores de 41.83% (45.56 μmolTrolox/g extracto) y 41.79% (45.51 μmolTrolox/g extracto) mediante el método del DPPH•, respectivamente. Ninguno de los extractos evaluados mostró actividad antitopoisomerasa a través del método empleado