On the Extreme Positive Feedback Star-Forming Mode from Massive and Compact Superstar Clusters

The force of gravity acting within the volume occupied by young, compact and massive superstar clusters, is here shown to drive in situ all the matter deposited by winds and supernovae into several generations of star formation. These events are promoted by radiative cooling which drains the thermal energy of the ejected gas causing its accumulation to then rapidly exceed the gravitational instability criterion. A detailed account of the integrated ionizing radiation and mechanical luminosity as a function of time is here shown to lead to a new stationary solution. In this, the mass deposition rate $\dot M$, instead of causing a wind as in the adiabatic solution, turns into a positive feedback star-forming mode equal to the star formation rate. Some of the implications of this extreme positive feedback mode are discussed.Comment: 4 pages, 4 figures, accepted for publication in The Astrophysical Journal Letter

Schwannoma primario renal: revisión de la literatura a propósito de un caso

El schwannoma es un tumor mesenquimal que se origina de las vainas de mielina que revisten los nervios periféricos. Lo más frecuente es que se localice en cabeza, cuello y extremidades, siendo extraordinariamente raro a nivel renal. Presentamos el caso de un paciente de 47 años, asintomático, al que se le descubrió de manera incidental (por una prueba de imagen debido a otro motivo) una lesión en el riñón izquierdo. Se realizó nefrectomía parcial por laparoscopia, diagnosticándose un schwannoma primario renal. Además de detallar el caso, se explican en este trabajo las características macroscópicas, microscópicas e inmunohistoquímicas de este tumor y comparamos nuestros hallazgos con los descritos en la literatura.<br /

Tumor de células de Leydig: revisión de la literatura a propósito de un caso.

En este trabajo presentamos el caso de un tumor de células de Leydig estudiado en el HCU Lozano Blesa. Explicamos sus características macroscópicas, microscópicas e inmunohistoquímicas más relevantes y comparamos nuestros hallazgos con los descritos en la literatura.<br /

Physical properties of wood from thinned pines in northwest Spain

Se estudió la densidad, contracción, higroscopicidad y punto de saturación de la pared celular en la madera de ejemplares jóvenes de tres especies importantes en la producción maderera española: Pinus pinaster, Pinus sylvestris y Pinus radiata. Se muestrearon 29 pinos procedentes de raleos efectuados en diferentes masas forestales de Galicia (noroeste de España). El material de ensayo fueron probetas de pequeñas dimensiones sin defectos. La madera de Pinus pinaster resultó semipesada y más inestable en dimensiones ante los cambios de humedad que las de Pinus radiata y Pinus sylvestris, que resultaron ligeras y relativamente estables, especialmente Pinus radiata. La densidad en Pinus pinaster fue similar a la obtenida en estudios anteriores sobre pies adultos. Pinus radiata y Pinus sylvestris presentaron madera más ligera que la de pies adultos. Las propiedades relativas a la estabilidad dimensional fueron similares en la madera joven analizada y en la madera de pies adultos, a excepción de la madera de Pinus radiata, que resultó más estable en la muestra que en la madera adulta. La variación entre zonas del fuste y entre individuos fue notable para las variables densidad y peso específico, aun en el caso de árboles muestreados en un mismo rodal y estación.Wood density, shrinkage, hygroscopicity and fibre saturation point were studied in young trees corresponding to three important species in the spanish timber production (Pinus pinaster, Pinus sylvestris and Pinus radiata). Twenty-nine thinned pines from different stands of Galicia (northwestern Spain) were sampled. The test material was small size defect-free specimens. The wood of Pinus pinaster exhibited intermediate density and more instability in dimensions, due to environmental moisture changes, than wood of Pinus radiata and Pinus sylvestris. These woods were light and relatively stable, especially Pinus radiata. The density in Pinus pinaster was similar to that obtained in previous studies on adult trees. Pinus radiata and Pinus sylvestris showed lower density than adult trees. The shrinkage properties were similar in the analyzed young wood and in the wood of adult trees, excepting the wood sampled for Pinus radiata, more stable than adult wood. Even with a sample of trees from the same stand in a specific site, there were significant differences in wood density among positions in each tree and among trees.S

Can the life-history strategy explain the success of the exotic trees Ailanthus altissima and Robinia pseudoacacia in Iberian floodplain forests?

Ailanthus altissima and Robina pseudoacacia are two successful invasive species of floodplains in central Spain. We aim to explain their success as invaders in this habitat by exploring their phenological pattern, vegetative and sexual reproductive growth, and allometric relations, comparing them with those of the dominant native tree Populus alba. During a full annual cycle we follow the timing of vegetative growth, flowering, fruit set, leaf abscission and fruit dispersal. Growth was assessed by harvesting two-year old branches at the peaks of vegetative, flower and fruit production and expressing the mass of\ud current-year leaves, stems, inflorescences and infrutescences per unit of previous-year stem mass. Secondary growth was\ud assessed as the increment of trunk basal area per previous-year basal area. A. altissima and R. pseudoacacia showed\ud reproductive traits (late flowering phenology, insect pollination, late and long fruit set period, larger seeds) different from P. alba and other native trees, which may help them to occupy an empty reproductive niche and benefit from a reduced competition for the resources required by reproductive growth. The larger seeds of the invaders may make them less dependent on gaps for seedling establishment. If so, these invaders may benefit from the reduced gap formation rate of flood-regulated rivers of the study region. The two invasive species showed higher gross production than the native, due to the higher size of pre-existing stems rather than to a faster relative growth rate. The latter was only higher in A. altissima for stems, and in R. pseudoacacia for reproductive organs. A. altissima and R. pseudoacacia showed the lowest and highest reproductive/vegetative mass ratio, respectively. Therefore, A. altissima may outcompete native P. alba trees thanks to a high potential to overtop coexisting plants whereas R. pseudoacacia may do so by means of a higher investment in sexual reproduction

Levantamiento topográfico de 8,771.95 m2 para el mejoramiento del campo de fútbol de la villa victoria de julio en el Municipio de Tipitapa, Departamento de Mangua

Presente levantamiento se realizo con una descripción del modelo topográfico empleado para la elaboración de diferentes cálculos relativos a la definición de rasante, movimiento de tierra etc. Del proyecto de terraza El proyecto tienecomo objetivo mejorar la calidad de vida de los niños y jóvenes de nuestro municipio, por lo que se propone este estudio topográfico, dirigido a proporcionar los datos necesarios para que sean aprovechados en beneficio de mejorar el campo de futbol del barrio Villa victoria de Julio del Municipio de Tipitapa. Se propone el estudio por medio de un levantamiento topográfico, así como un estudio basado en los datos recopilados en campo, para que sirva como una herramienta necesaria y útil, capaz de presentar los fundamentos para que se pueda realizar, gestionar o diseñar un proyecto que sea idóneo para resolver la problemática existente en el sitio, de los niños, jóvenes y familias que habitan los alrededores del barrio. Se necesita este proyecto para que los niños y jóvenes tengan una manera de recreación así tengan una oportunidad de mantenerse en el deporte y estén fuera de vicios que puedan inducirlos a realizar actos negativos ante la sociedad. Se adjuntan fotografías tomadas del lugar en el cual se propone llevar a cabo dicho estudio, en las cuales se pueden observar la necesidad de dicha obra. (Ver fotos en anexos

A Jordan Canonical Form for nilpotent elements in an arbitrary ring

En este poster resumimos una nueva forma de calcular la forma canónica de un elemento nilpotente dentro de un álgebra asociativa.Universidad de Málaga. Campus de Excelencia Internacional Andalucía Tech

Can the life-history strategy explain the success of the exotic trees Ailanthus altissima and Robinia pseudoacacia in Iberian floodplain forests?

Ailanthus altissima and Robina pseudoacacia are two successful invasive species of floodplains in central Spain. We aim to explain their success as invaders in this habitat by exploring their phenological pattern, vegetative and sexual reproductive growth, and allometric relations, comparing them with those of the dominant native tree Populus alba. During a full annual cycle we follow the timing of vegetative growth, flowering, fruit set, leaf abscission and fruit dispersal. Growth was assessed by harvesting two-year old branches at the peaks of vegetative, flower and fruit production and expressing the mass of current-year leaves, stems, inflorescences and infrutescences per unit of previous-year stem mass. Secondary growth was assessed as the increment of trunk basal area per previous-year basal area. A. altissima and R. pseudoacacia showed reproductive traits (late flowering phenology, insect pollination, late and long fruit set period, larger seeds) different from P. alba and other native trees, which may help them to occupy an empty reproductive niche and benefit from a reduced competition for the resources required by reproductive growth. The larger seeds of the invaders may make them less dependent on gaps for seedling establishment. If so, these invaders may benefit from the reduced gap formation rate of flood-regulated rivers of the study region. The two invasive species showed higher gross production than the native, due to the higher size of pre-existing stems rather than to a faster relative growth rate. The latter was only higher in A. altissima for stems, and in R. pseudoacacia for reproductive organs. A. altissima and R. pseudoacacia showed the lowest and highest reproductive/vegetative mass ratio, respectively. Therefore, A. altissima may outcompete native P. alba trees thanks to a high potential to overtop coexisting plants whereas R. pseudoacacia may do so by means of a higher investment in sexual reproduction

Water harvesting for young trees using Peltier modules powered by photovoltaic solar energy

Young trees transplanted from nursery into open field require a minimum amount of soil moisture to successfully root in their new location, especially in dry-climate areas. One possibility is to obtain the required water from air moisture. This can be achieved by reducing the temperature of a surface below the air dew point temperature, inducing water vapor condensation on the surface. The temperature of a surface can be reduced by applying the thermoelectric effect, with Peltier modules powered by electricity. Here, we present a system that generates electricity with a solar photovoltaic module, stores it in a battery, and finally, uses the electricity at the moment in which air humidity and temperature are optimal to maximize water condensation while minimizing energy consumption. Also, a method to reduce the evaporation of the condensed water is proposed. The objective of the system is to sustain young plants in drier periods, rather than exclusively irrigating young plants to boost their growth