Niche overlap in sympatric Rocio (Teleostei: Cichlidae) of Guatemala

Rocio is a small genus of Neotropical freshwater fishes that is distributed in Atlantic drainages of northern Middle America. Two species in the genus exhibit sympatry in the Río Dulce basin (in Izabal, Guatemala), where one species is endemic (R. spinosissima), while the other only includes this area as part of a larger geographic range (R. octofasciata). Unfortunately, the ecology of these species has been poorly studied. This study sought to determine the ecological and morphological differences between these two closely related sympatric freshwater fishes. We hypothesized that R. octofasciata would exhibit greater ecological and morphological variation, showing an overlap with R. spinosissima. We also hypothesized that morphological divergence would be associated with character displacement. Local-scale environmental data suggest habitat characteristics overlap between the two species, with a greater use of slow-flowing to lentic, poorly oxygenated and with a larger range of pH, environments by R. spinosissima, and R. octofasciata inhabiting areas with a greater range of environmental characteristics. Drainage-scale data also indicate that land cover, soil, precipitation and temperature largely define the distribution of both species, with some noticeable differences. Additionally, the mean body shape is different between specimens from the two species when they are in sympatry, while specimens from outside of the sympatric area tend to show similar shape characteristics between the two species, following a pattern of character displacement

Trans-Neptunian Objects with Hubble Space Telescope ACS/WFC

We introduce a novel search technique that can identify trans-neptunian objects in three to five exposures of a pointing within a single Hubble Space Telescope orbit. The process is fast enough to allow the discovery of candidates soon after the data are available. This allows sufficient time to schedule follow up observations with HST within a month. We report the discovery of 14 slow-moving objects found within 5\circ of the ecliptic in archival data taken with the Wide Field Channel of the Advanced Camera for Surveys. The luminosity function of these objects is consistent with previous ground-based and space-based results. We show evidence that the size distribution of both high and low inclination populations is similar for objects smaller than 100 km, as expected from collisional evolution models, while their size distribution differ for brighter objects. We suggest the two populations formed in different parts of the protoplanetary disk and after being dynamically mixed have collisionally evolved together. Among the objects discovered there is an equal mass binary with an angular separation ~ 0."53.Comment: 16 page, 10 figures, accepted by Ap

Propuesta de diseño hidráulico a nivel de prefactibilidad del sistema de abastecimiento de agua potable de la comunidad “Los López”, Municipio de Villa El Carmen, Departamento de Managua, en el periodo de Junio – Noviembre 2016

Este documento está enfocado en describir de la forma más simple posible, los aspectos técnicos relacionados con el estudio y diseño hidráulico del sistema de abastecimiento de agua potable de la comunidad rural “Los López”, ubicada en el municipio de Villa el Carmen, departamento de Managua, el cual consiste en la propuesta de un Mini acueducto por bombeo eléctrico (MABE). Dentro de este documento se abarca una reseña histórica de la comunidad en mención. Los datos y recopilación de información se obtuvieron de Normas técnicas para el diseño de abastecimiento y potabilización de agua potable (NTON 09 Rural) y las Normas Regionales de Calidad del Agua para el Consumo Humano, editada por CAPRE, donde se obtuvieron los parámetros de diseño de sistemas de abastecimiento de agua potable e Instituciones gubernamentales como: Alcaldía de Villa El Carmen, Ministerio de Salud (MINSA), y la Empresa Nacional de Acueductos y Alcantarillados (ENACAL), Instituto Nacional de Información de Desarrollo (INIDE), Instituto Nicaragüense de Estudios Territoriales (INETER), COSUD

Using Simulation To Evaluate Web-Based Bidding in Construction

The Internet is changing the whole business model by allowing companies to communicate instantly with suppliers, partners, and customers on a worldwide scale. To enjoy realtime data exchange and higher transaction efficiencies, companies need to use information technology (IT) solutions and change how they distribute goods and how they collaborate within the company with contractors and suppliers. While the Internet is the channel that allows instant interaction between all components of a company, IT provides the ability to streamline the structure and to influence and control the flow of information. In this paper, we evaluate the impact that using the Internet can have on the procurement aspect of the construction industry. Specifically, we describe how the traditional service procurement process in construction is affected by the use of a web-based bidding tool (WBBT). We use a simulation model on a case study to evaluate how the WBBT affected service procurement in a large pharmaceutical company. The paper describes the potential impact of IT solutions in the Construction Industry and on the procurement aspect in particular, before discussing the case study in detail

Modeling bone healing by boundary element method

El proceso de curación de fracturas es iniciado y regulado principalmente por los factores de crecimiento y por el entorno mecánico en el callo. Este fenómeno ha sido analizado desde un punto de vista biomecánico. La mayoría de los modelos computacionales están basados en el método de los elementos finitos y muchos de ellos estudian los niveles de tensiones y deformaciones producidos en los diferentes tejidos como el principal estímulo mecánico que afecta la diferenciación celular y el patrón de osificación ósea. En este trabajo se incorporó esa hipótesis en un entorno basado en el método de los elementos de contorno (BEM) para problemas axialmente simétricos. La idea principal es proponer el método de elementos de contorno como una alternativa atractiva a los métodos de dominio comúnmente utilizados en esta clase de problemas: diferencias finitas y elementos finitos. Los resultados obtenidos fueron cotejados con los reportados por la literatura comprobando la versatilidad y efectividad del método numérico propuesto. Como una primera aproximación, se realizó un análisis elástico-lineal para modelar los efectos de estimulación e inhibición que ejerce el estado de deformación sobre el proceso de diferenciación tisular, siguiendo la metodología propuesta por Claes and Heigele. Luego, en un modelo bifásico poroelástico en régimen estacionario, se incorpora la presión de poro como variable adicional dentro de la hipótesis, lo que permitió complementar las conclusiones hechas por Claes and Heigele. De esta manera, existe una nueva correlación de valores que permitirán a los modelos actuales comparar la evolución de propiedades tales como el modulo de elasticidad (E) y relación de Poisson (À), en base al estado de deformación presente en el modelo en análisis poroelásticos.Peer Reviewe

Initial Planetesimal Sizes and the Size Distribution of Small Kuiper Belt Objects

The Kuiper Belt is a remnant from the early solar system and its size distribution contains many important constraints that can be used to test models of planet formation and collisional evolution. We show, by comparing observations with theoretical models, that the observed Kuiper Belt size distribution is well matched by coagulation models, which start with an initial planetesimal population with radii of about 1 km, and subsequent collisional evolution. We find that the observed size distribution above R ~ 30 km is primordial, i.e., it has not been modified by collisional evolution over the age of the solar system, and that the size distribution below R ~ 30 km has been modified by collisions and that its slope is well matched by collisional evolution models that use published strength laws. We investigate in detail the resulting size distribution of bodies ranging from 0.01 km to 30 km and find that its slope changes several times as a function of radius before approaching the expected value for an equilibrium collisional cascade of material strength dominated bodies for R ≾0.1 km. Compared to a single power-law size distribution that would span the whole range from 0.01 km to 30 km, we find in general a strong deficit of bodies around R ~ 10 km and a strong excess of bodies around 2 km in radius. This deficit and excess of bodies are caused by the planetesimal size distribution left over from the runaway growth phase, which left most of the initial mass in small planetesimals while only a small fraction of the total mass is converted into large protoplanets. This excess mass in small planetesimals leaves a permanent signature in the size distribution of small bodies that is not erased after 4.5 Gyr of collisional evolution. Observations of the small Kuiper Belt Object (KBO) size distribution can therefore test if large KBOs grew as a result of runaway growth and constrained the initial planetesimal sizes. We find that results from recent KBO occultation surveys and the observed KBO size distribution can be best matched by an initial planetesimal population that contained about equal mass per logarithmic mass bin in bodies ranging from 0.4 km to 4 km in radius. We further find that we cannot match the observed KBO size distribution if most of the planetesimal mass was contained in bodies that were 10 km in radius or larger simply because their resulting size distribution cannot be sufficiently depleted over 4.5 Gyr to match observations

Dynamically excited outer solar system objects in the Hubble Space Telescope archive

We present the faintest mid-ecliptic latitude survey in the second part of Hubble Space Telescope archival search for outer solar system bodies. We report the discovery of 28 new trans-Neptunian objects and one small centaur (R similar to 2 km) in the band 5°-20° off the ecliptic. The inclination distribution of these excited objects is consistent with the distribution derived from brighter ecliptic surveys. We suggest that the size and inclination distribution should be estimated consistently using suitable surveys with calibrated search algorithms and reliable orbital information

La modelización espacial de las zonas litorales, una herramienta para el análisis de la sostenibilidad en las zonas costeras. Aplicación a la zona litoral del Mar Menor.

El artículo analiza la importancia de disponer de sistemas de representación y modelización de las zonas costeras y la franja litoral, que sean consistentes con los modelos terrestres y que permitan analizar con mayor rigor los efectos que la actividad humana genera en el medio marino. La investigación se ha centrado en el desarrollo de un prototipo de visualizador tridimensional del medio marino para el área de la Reserva Marina de Cabo de Palos-Islas Hormigas en el Mar Menor