Influence of primary-particle density in the morphology of agglomerates

Agglomeration processes occur in many different realms of science, such as colloid and aerosol formation or formation of bacterial colonies. We study the influence of primary-particle density in agglomerate structures using diffusion-controlled Monte Carlo simulations with realistic space scales through different regimes (diffusion-limited aggregation and diffusion-limited colloid aggregation). The equivalence of Monte Carlo time steps to real time scales is given by Hirsch's hydrodynamical theory of Brownian motion. Agglomerate behavior at different time stages of the simulations suggests that three indices (the fractal exponent, the coordination number, and the eccentricity index) characterize agglomerate geometry. Using these indices, we have found that the initial density of primary particles greatly influences the final structure of the agglomerate, as observed in recent experimental works.This work has been supported by the Spanish Ministerio de Economía y Competitividad Grant No. FIS2011-28838-C02-01 and by the Autonomous Region of Madrid Grant No. P2009/ENE-1597 (HYSYCOMB).Publicad

Fair weather induced charges and currents on tall wind turbines and experiments with kites

Earth’s atmospheric potential rapidly increases up to few tens of kilovolts below 200 m altitude. This potential drop will induce charge to tall objects at ground by virtue of electrostatic induction. In this work we investigate the induced electric charges in fair weather to a 1.5 MW and 5 MW wind turbines. The effect of rotation is included and the current calculated result in currents of few micro-amps. The production of point discharge and corona is investigated and some experiments are conducted by means of instrumented kites.Preprin

Cartilage in pulmonary valves of Syrian Hamsters

En el campo "Centro"(centro de origen del ítem) he seleccionado la Facultad de Ciencias ya que este artículo se publicó durante mi adscripción al departamento de Biología Animal.El cartílago y/o el hueso se desarrollan en el esqueleto cardíaco de varias especies de mamíferos. Se observó depósitos cartilaginosos en la válvula aórtica, trígonos fibrosos y tabique interventricular. También se conoce la presencia de cartílago en la válvula pulmonar en aves, pero no en mamíferos. En este trabajo se describe la aparición de tejido cartilaginoso en las válvulas pulmonares de 40 de 351 hámsteres sirios examinados mediante técnicas histológicas, histoquímicas y/o inmunohistoquímicas. Los depósitos cartilaginosos se localizaron en las uniones fibrosas de las valvas de la válvula a la pared del tronco de la arteria pulmonar. Nuestros hallazgos indican que las uniones proximales de las valvas a sus respectivos senos, y especialmente la de la valva ventral, son las regiones valvulares más propensas a desarrollar focos cartilaginosos. No obstante, la posible función de estos focos sigue siendo una cuestión sin resolver. La formación de cartílago en la válvula pulmonar comienza durante el primer mes de vida, es decir en el período en el que la válvula alcanza la maduración histológica. La evidencia más temprana de condrogénesis es la presencia de pequeños grupos de células incrustadas en una matriz extracelular positiva para colágeno tipo II. Estos grupos celulares aumentan de tamaño y se diferencian en tejido cartilaginoso hialino. Se supone que los precursores de las células cartilaginosas son elementos derivados de la cresta neural. Sin embargo, se desconoce el factor o factores implicados en la diferenciación de estos precursores en condrocitos. Cabe destacar que, tanto en aves como en mamíferos, la formación de cartílago en las válvulas aórtica y pulmonar son eventos independientes. Esto encaja con la hipótesis de que la morfogénesis de las válvulas semilunares cardíacas puede estar mediada por subpoblaciones específicas de células de la cresta neural cardíaca, que actúan por separado en ambos lados del tracto de salida cardíaco embrionario.D.G.E.S. (Ministerio de Educaci6n y Cultura, España): PB98-1418-C02-0

First data of the Colombia Lightning Mapping Array - COLMA

The first data set of VHF lightning mapping using a Lightning Mapping Array system - LMA in a tropical region is presented in this paper. Six sensors were installed at the north of Colombia near Santa Marta city. Since the installation of the LMA network in 2015, up to 7000 intra-cloud (IC) discharges from September to November 2015 have been analyzed. The data suggests that, the electrical charge distribution in tropical thunderstorms shows higher vertical development reaching higher altitudesPreprin

Multi-Proxy Approach for Identifying Heinrich Events in Sediment Cores from Hatton Bank (NE Atlantic Ocean)

A series of six gravity cores has been used to reconstruct the depositional history of Hatton Bank (Rockall Plateau, NE Atlantic Ocean). The cores have been studied for magnetic susceptibility (MS), geochemical composition, grain size distribution, and a semi-quantitative foraminiferal association. Two main interbedded facies have been described: (i) calcareous ooze; and (ii) lithogenous silt. The study reveals prominent peaks from the MS signal, silt, Mg/Ca, Fe/Ca, Al/Ca, and Rare Earth Elements normalised by Continental Crust (REE/CC), which are sensitive indicators for Heinrich events (H1, H2, H3, H4, and H5) and ash layers. These peaks may relate to alternations in dominance of the calcareous and lithogenic facies. The sediment displays a high percentage of carbonate in interglacial layers but is lithogenic-dominated in glacial stages. The layers with prominent lithic-rich and foraminifera-poor sediments (established as Heinrich layers) may be related to a possible palaeoclimatic effect, where freshwater discharged during iceberg melting may have reduced the formation of North Atlantic Deep Water (NADW). In the study area, the mean sedimentation rates for the last glacial as ~4.2 cm ka−1 and ~1.4 cm ka−1 for the last ~18 ka (interglacial period) have been estimated. Besides this evidence, Fe/Ca and MS peaks may reflect the presence of basalt, either introduced through ice-rafting or transported and redistributed by bottom currents in the study area. Certain indices, including MS and Fe/Ca, are proposed as good proxies for detecting Heinrich events and ash layers in the Hatton Bank sediments and, in consequence, are parameters that can be used to infer strengthened/weakened NADW formation, according to stadials/interstadials. Moreover, we suggest that the northernmost boundary of the area with evidence of Heinrich events may be situated around 57°38′ N in the Hatton–Rockall area, at least for H4, based on the variation of the Mg/Ca and Fe/Ca curves

Evaluación continuada sin morir en el intento

Entre los objetivos de la evaluación continuada podemos destacar: ayudar a que el alumno organice su estudio a lo largo del curso, proporcionarle feedback y ofrecer la posibilidad que no se juegue toda su nota en un único acto evaluador, sino en varios actos. A la hora de implementar este tipo de evaluación hay diversas metodologías, pero muchas reciben la queja de un elevado coste, tanto para el estudiante como para el profesor. En este artículo se presenta un modelo de evaluación que nos permite alcanzar los objetivos de la evaluación continuada, con un coste para el alumno y el profesor similar al de la evaluación tradicional. Los resultados muestran que los objetivos planteados han sido alcanzados.Este trabajo ha sido apoyado por el Ministerio de Educación y Ciencia, bajo proyecto TIN 2004-07739-C02-01

High altitude leaders mapped by the Colombia lightning mapping array

On April 2015 a Lightning Mapping Array network (COL-LMA) was installed at the north of Colombia. This network provides 3D mapping of the development of lightning leaders. For the first time such network has been setup in the tropics. That allows us to investigate the high altitude development of lightning leaders. Here we present the results of the first measurements to confirm that negative leaders at altitudes of 15 km are common in the observed thunderstorms.Postprint (published version

Selection and characterization of biofuel-producing environmental bacteria isolated from vegetable oil-rich wastes

Fossil fuels are consumed so rapidly that it is expected that the planet resources will be soon exhausted. Therefore, it is imperative to develop alternative and inexpensive new technologies to produce sustainable fuels, for example biodiesel. In addition to hydrolytic and esterification reactions, lipases are capable of performing transesterification reactions useful for the production of biodiesel. However selection of the lipases capable of performing transesterification reactions is not easy and consequently very few biodiesel producing lipases are currently available. In this work we first isolated 1,016 lipolytic microorganisms by a qualitative plate assay. In a second step, lipolytic bacteria were analyzed using a colorimetric assay to detect the transesterification activity. Thirty of the initial lipolytic strains were selected for further characterization. Phylogenetic analysis revealed that 23 of the bacterial isolates were Gram negative and 7 were Gram positive, belonging to different clades. Biofuel production was analyzed and quantified by gas chromatography and revealed that 5 of the isolates produced biofuel with yields higher than 80% at benchtop scale. Chemical and viscosity analysis of the produced biofuel revealed that it differed from biodiesel. This bacterial-derived biofuel does not require any further downstream processing and it can be used directly in engines. The freeze-dried bacterial culture supernatants could be used at least five times for biofuel production without diminishing their activity. Therefore, these 5 isolates represent excellent candidates for testing biofuel production at industrial scale

Radiopharmacokinetics and uptake of 99m Tc-cRGD in av B3 integrins for imaging angiogenesis in induced malignant tumors in athymic mice

The multistep process of angiogenesis offers several targets for therapeutic interventions. One molecular target structure is the alfa five beta three (av b3 ) integrin which is expressed on vascular endothelial cells and over-expressed in cancer tumor angiogenesis. To image neoangiogenesis in athymic mice with induced pancreatic, breast and prostate malignant tumors a new radiopharmaceutical was developed. The 99mTc-EDDA/HYNIC-cyclic-Arg-Gly- Asp-D-Phe-Lys (99mTc-cRGD) targets integrin receptors av b3 and was prepared with an average radiochemical purity > 95 %. 99mTc-cRGD shows high in vivo stability, fast blood clearance and rapid renal excretion in mice. There are statistical differences between tumor/muscle ratios for the 3 tumors studied. The highest tumor/non-target ratio was found in breast cancer (7.2 after 24 h) and a representative dorsal SPECT image was obtained where the tumor showed up very clearly over the background tissue. The high resolution of the image implies that 99mTc-cRGD will be of great value in nuclear medicine as a potential radiopharmaceutical for av b3 integrins receptor uptake and for imaging neoangiogenesis in neoplastic tissue and to follow up cancer tumor progression