466 research outputs found

    870 micron continuum observations of the bubble-shaped nebula Gum 31

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    We are presenting here a study of the cold dust in the infrared ring nebula Gum 31. We aim at deriving the physical properties of the molecular gas and dust associated with the nebula, and investigating its correlation with the star formation in the region, that was probably triggered by the expansion of the ionization front. We use 870 micron data obtained with LABOCA to map the dust emission. The obtained LABOCA image was compared to archival IR,radio continuum, and optical images. The 870 micron emission follows the 8 micron (Spitzer), 250 micron, and 500 micron (Herschel) emission distributions showing the classical morphology of a spherical shell. We use the 870 micron and 250 micron images to identify 60 dust clumps in the collected layers of molecular gas using the Gaussclumps algorithm. The clumps have effective deconvolved radii between 0.16 pc and 1.35 pc, masses between 70 Mo and 2800 Mo, and volume densities between 1.1x10^3 cm^-3 and 2.04x10^5 cm^-3. The total mass of the clumps is 37600 Mo. The dust temperature of the clumps is in the range from 21 K to 32 K, while inside the HII region reaches ~ 40 K. The clump mass distribution is well-fitted by a power law dN/dlog(M/Mo) proportional to M^(-alpha), with alpha=0.93+/-0.28. The slope differs from those obtained for the stellar IMF in the solar neighborhood, suggesting that the clumps are not direct progenitors of single stars/protostars. The mass-radius relationship for the 41 clumps detected in the 870 microns emission shows that only 37% of them lie in or above the high-mass star formation threshold, most of them having candidate YSOs projected inside. A comparison of the dynamical age of the HII region with the fragmentation time, allowed us to conclude that the collect and collapse mechanism may be important for the star formation at the edge of Gum 31, although other processes may also be acting.Comment: 15 pages, 10 figures. Accepted for publication in A&

    Pentamethylcyclopentadienyl halo- and alkyl-alkoxo tantalum(V) complexes. Crystal structure of TaCp*(CH2SiMe3) 2{η2-O(2-CH2-6-MeC6H3)}

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    Reaction of TaCp" C! 4 with MOR (M - Li, Na) in different molar ratios gives halo alkoxides TaCp" CI,(OR)4_,, (n - 3: R -tBu 1; iPh32;2,6Me2C6H33;n2:R Bu4;SiPh35;2,6Me2C6H36;a!:RSiMe37)ingoodyields.ThealkylidenecomplexTaCp(CH2SiMe,02(CHSiMe )ishydrolyzedinthepresenceoftracesofwatertogivetheoxodialkylderivative[TaCp(CH2SiM¢3) O],,8,andreactswithIequivalentof2,6MezC6H NCaffordinganewq2iminoacyicompoundTaCp"(CH2iPh 3 2; 2,6-Me2C6H 3 3; n -- 2: R -~Bu 4; SiPh 3 5; 2,6-Me2C6H3 6; a - !: R - SiMe 3 7) in good yields. The alkylidene complex TaCp'(CH2SiMe,02(CHSiMe ~) is hydrolyzed in the presence of traces of water to give the oxo dialkyl derivative [TaCp'(CH2SiM¢3)~O],, 8, and reacts with I equivalent of 2,6-MezC6H~NC affording a new 'q2-iminoacyi compound TaCp" (CH 2iMe3XCHSiMe3){~ 2"C(CH 2SiMe3 ) = N(2,6"MeaC6 H 3)} 9. Reactions of TaCp "(CH 2SiMe3)a(CHSiMe3 ) with I equivalent of C6HsOH and 4-MeC6H3(OH) 2 result in the formation of the alkyl phenoxo TaCp'(CH2SiMe3)3(OC6Hs) 10 and 4-methyl pyrocatecholate TaCp'(CH2SiMe~)2(O2C6H3Me) 11, whereas the related re,",,:don with 2,6-Me2C6H 3OH leads to the cyclic alkyi-aikoxo compound TaCp (CH2SiMej)2(~2-O(2-CH2-6-MeC6H3)) 12. All the complexes were characterized by IR and NMR (tH and 13C) spectroscopy. The crystal and molecular structure of 12 has been determine~i. C~ystals of 12 are triclinic, space group P'[ with Z - 2 in a unit cell of dimensions a- 9.151(5) ~, b- 11.835(5) ~,, c- 14.045(4) A, a- 89.35(3) °, /3- 72.34(3) 0 and 'y-88.51(4) °, V- 1449(I) ~s. Final values of R -0.025 and Rw -0.0655 were obtained from 554'7 reflections measured (50'70, > 2o'(i))

    Reuse of Zeolite By-Products Derived from Petroleum Refining for Sustainable Roads

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    The reduction in consumption of natural resources (fuel, gas, etc.) and contaminant emissions (CO2, CO, NOx, etc.) during the production of asphalt mixtures has become one of the main challenges in road engineering. Warm mix asphalts (WMAs) have been developed in order to achieve this objective while ensuring the mechanical performance and durability of traditional hot mix asphalts (HMAs). However, these materials are commonly manufactured using additives or products whose production could reduce both their environmental benefits and cost effectiveness. /is paper presents a research study that aims to analyse the reuse of zeolite wastes derived from petroleum refining in the production of warm mix asphalts. For this purpose, two different types of zeolite wastes were analysed as additives for the manufacture of two warm mix asphalts, whose mechanical performance was compared with conventional WMA and hot mix asphalt. /e results indicate that zeolite wastes with a lower particles size presented higher capacity to absorb water, while its dosage at 0.3% allows for producing warm mix asphalts at temperatures around 145°C, with comparable workability and densification to conventional HMA at 165°C without reducing its bearing capacity, fatigue life, and resistance to water action and plastic deformation.“Soluciones de Pavimentación Ecológicamente Sostenibles: Ecoasfaltos” funded by the Ministry of Economy and Knowledge of Andalusia and the Ministry of Economy and Competitiveness of Spain in the framework of CTA (Corporación Tecnológica de Andalucía)

    ZnO-mesoporous glass scaffolds loaded with osteostatin and mesenchymal cells improve bone healing in a rabbit bone defect.

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    The use of 3D scaffolds based on mesoporous bioactive glasses (MBG) enhanced with therapeutic ions, biomolecules and cells is emerging as a strategy to improve bone healing. In this paper, the osteogenic capability of ZnO-enriched MBG scaffolds loaded or not with osteostatin (OST) and human mesenchymal stem cells (MSC) was evaluated after implantation in New Zealand rabbits. Cylindrical meso-macroporous scaffolds with composition (mol %) 82.2SiO2–10.3CaO–3.3P2O5–4.2ZnO (4ZN) were obtained by rapid prototyping and then, coated with gelatin for easy handling and potentiating the release of inorganic ions and OST. Bone defects (7.5 mm diameter, 12 mm depth) were drilled in the distal femoral epiphysis and filled with 4ZN, 4ZN+MSC, 4ZN+OST or 4ZN+MSC+OST materials to evaluate and compare their osteogenic features. Rabbits were sacrificed at 3 months extracting the distal third of bone specimens for necropsy, histological and microtomography (µCT) evaluations. Systems investigated exhibited bone regeneration capability. Thus, trabecular bone volume density (BV/TV) values obtained from µCT showed that the good bone healing capability of 4ZN was significantly improved by the scaffolds coated with OST and MSC. Our findings in vivo suggest the interest of these MBG complete systems to improve bone repair in the clinical practice

    Geometrical isotropy in perforated plates with subwavelength holes decorated with Archimedean patterns

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    The design and use of small apertures perforated in opaque plates to control the transmission of ultrasonic waves has been widely studied in recent years. The ultrasonic transmission response of brass plates perforated with Archimedean patterns of subwavelength hole arrays immersed in water is reported, both numerically and experimentally, in this work. It is shown that an increase in the geometrical isotropy of the elementary cells of the Archimedean patterns gives rise to a suppression of both minimum and maximum transmission corresponding to the destructive and constructive interferences, leading to uniformity within the angle-dependent transmitted sound power coefficient. The experimental results are in close agreement with the calculated ones. This property can be used to design ultrasonic devices such as filters and sensors.This work has been supported by the Spanish MICINN (MAT2010-16879) and Generalitat Valenciana (PROM-ETEOII/2014/026).Gómez Lozano, V.; Rubio Michavila, C.; Candelas Valiente, P.; Belmar Ibáñez, F.; Uris Martínez, A. (2015). Geometrical isotropy in perforated plates with subwavelength holes decorated with Archimedean patterns. EPL. 111(3):34002p1-34002p5. https://doi.org/10.1209/0295-5075/111/34002S34002p134002p5111

    Unveiling the stellar origin of the Wolf-Rayet nebula NGC6888 through infrared observations

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    We present a comprehensive infrared (IR) study of the iconic Wolf-Rayet (WR) wind-blown bubble NGC6888 around WR136. We use Wide-field Infrared Survey Explorer (WISE), Spitzer IRAC and MIPS and Herschel PACS IR images to produce a sharp view of the distribution of dust around WR136. We complement these IR photometric observations with Spitzer IRS spectra in the 5-38 μ\mum wavelength range. The unprecedented high-resolution IR images allowed us to produce a clean spectral energy distribution, free of contamination from material along the line of sight, to model the properties of the dust in NGC6888. We use the spectral synthesis code Cloudy to produce a model for NGC6888 that consistently reproduces its optical and IR properties. Our best model requires a double distribution with the inner shell composed only of gas, whilst the outer shell requires a mix of gas and dust. The dust consists of two populations of grain sizes, one with small sized grains asmalla_\mathrm{small}=[0.002-0.008] μ\mum and another one with large sized grains abiga_\mathrm{big}=[0.05-0.5] μ\mum. The population of big grains is similar to that reported for other red supergiants stars and dominates the total dust mass, which leads us to suggest that the current mass of NGC6888 is purely due to material ejected from WR136, with a negligible contribution of swept up interstellar medium. The total mass of this model is 25.52.8+4.7^{+4.7}_{-2.8} M_{\odot}, a dust mass of Mdust=M_\mathrm{dust}=0.140.01+0.03^{+0.03}_{-0.01} M_{\odot}, for a dust-to-gas ratio of 5.6×1035.6\times10^{-3}. Accordingly, we suggest that the initial stellar mass of WR136 was \lesssim50 M_{\odot}, consistent with current single stellar evolution models.Comment: 13 pages, 11 figures, 6 tables; Accepted to MNRA

    Hackathon in teaching: Machine Learning applied to Life Sciences

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    La programación ha sido tradicionalmente una competencia perteneciente a las ingenierías, que recientemente está adquiriendo una importancia significativa en áreas como Ciencias de la Vida, donde resulta fundamental para la resolución de problemas de análisis de datos. Este trabajo es un caso de estudio enmarcado en la necesidad de mejorar las habilidades, sobre análisis de datos en el alumnado de Ciencias de la Vida y de la base temática en los estudiantes de ingeniería. Mediante la herramienta del hackathon y el trabajo en equipo, se combinó al alumnado de ambas disciplinas y se le enfrentó a una serie de problemas de análisis de datos. Se establecieron equipos de trabajo que recibieron una formación previa al comienzo de la competición. De cada equipo, se valoró la metodología empleada para la obtención de los datos, su análisis, interpretación de resultados, y exposición de las diversas tareas. Se hizo un análisis descriptivo de los resultados del Proyecto mediante encuestas al alumnado, así como su percepción sobre las actividades realizadas. El Proyecto ha conseguido que el alumnado resuelva los problemas planteados, difícilmente abordables con equipos unidisciplinares, generando un aprendizaje común y una experiencia multidisciplinar altamente satisfactoria tanto para el alumnado como para el profesorado.Programming has traditionally been an engineering competence, but recently it is acquiring significant importance in several areas, such as Life Sciences, which is considered essential for problem-solving based on data analysis. This work is a case study framed within the need to improve not only the data analysis skills of life science students, but also the biological background concerning the given issue of engineering students. Using hackathon and teamwork-based tools, students from both disciplines have been made and challenged with a series of problems in the area of Life Sciences. To solve these problems, we established work teams trained before the competition's beginning. Their results were assessed concerning the approach to obtain the data, perform the analysis, and finally interpret and present the results to solve the challenges. The project outcomes were assessed using structured surveys for students and their overall perception. The project succeeded, meaning students solved the proposed problems and achieved the activity's goals. These goals would have been difficult to address with teams composed of students from the same field of study. The hackathon succeeded in generating a shared learning and a multidisciplinary experience for their professional training, being highly rewarding for both students and faculty members

    EVIDENCIA DE VALIDEZ DE CONTENIDO DE LA ESCALA INHUMAPS: UN ESTUDIO SOBRE PRÁCTICAS INNOVADORAS EN GESTIÓN HUMANA

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    Este artículo presenta resultados de validez de contenido de la escala Innovative Human Management Practices Scale (INHUMAPS) a partir de juicios de expertos y análisis de los ítems; la cual se diseñó y hace parte de los productos de la investigación sobre prácticas innovadoras de gestión humana realizada por Rubio, Agudelo, Mena y Mejía (2021). El análisis de contenido incluyó nueve expertos según los siguientes criterios: con conocimientos en la temática, experiencia en investigación o diseño de pruebas en el campo organizacional. A partir de los resultados de la valoración se clasifican los ítems de acuerdo con Tristán (2008): en esencial, útil pero no esencial y no necesario. Las calificaciones permitieron calcular la razón de validez de contenido (RVC), encontrando que los 36 ítems se mantuvieron, 27 aprobados y 9 revisados. Demostrando criterios de suficiencia, relevancia, coherencia y claridad. En general los ítems, tienden a presentar homogeneidad indicando discriminación en la respuesta. Las evidencias demuestran la validez de contenido de INHUMAPS, como una herramienta para identificar niveles de implementación en prácticas innovadoras de gestión humana

    Submesoscale physicochemical dynamics directly shape bacterioplankton community structure in space and time

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    Submesoscale eddies and fronts are important components of oceanic mixing and energy fluxes. These phenomena occur in the surface ocean for a period of several days, on scales between a few hundred meters and few tens of kilometers. Remote sensing and modeling suggest that eddies and fronts may influence marine ecosystem dynamics, but their limited temporal and spatial scales make them challenging for observation and in situ sampling. Here, the study of a submesoscale filament in summerly Arctic waters (depth 0–400 m) revealed enhanced mixing of Polar and Atlantic water masses, resulting in a ca. 4 km wide and ca. 50 km long filament with distinct physical and biogeochemical characteristics. Compared to the surrounding waters, the filament was characterized by a distinct phytoplankton bloom, associated with depleted inorganic nutrients, elevated chlorophyll a concentrations, as well as twofold higher phyto- and bacterioplankton cell abundances. High-throughput 16S rRNA gene sequencing of bacterioplankton communities revealed enrichment of typical phytoplankton bloom-associated taxonomic groups (e.g., Flavobacteriales) inside the filament. Furthermore, linked to the strong water subduction, the vertical export of organic matter to 400 m depth inside the filament was twofold higher compared to the surrounding waters. Altogether, our results show that physical submesoscale mixing can shape distinct biogeochemical conditions and microbial communities within a few kilometers of the ocean. Hence, the role of submesoscale features in polar waters for surface ocean biodiversity and biogeochemical processes need further investigation, especially with regard to the fate of sea ice in the warming Arctic Ocean

    Reciprocal responses in the interaction between Arabidopsis and the cell-content feeding chelicerate herbivore spider mite

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    Most molecular-genetic studies of plant defense responses to arthropod herbivores have focused on insects. However, plant-feeding mites are also pests of diverse plants, and mites induce different patterns of damage to plant tissues than do well-studied insects (e.g. lepidopteran larvae or aphids). The two-spotted spidermite (Tetranychus urticae) is among the most significant mite pests in agriculture, feeding on a staggering number of plant hosts. To understand the interactions between spider mite and a plant at the molecular level, we examined reciprocal genome-wide responses of mites and its host Arabidopsis (Arabidopsis thaliana). Despite differences in feeding guilds, we found that transcriptional responses of Arabidopsis to mite herbivory resembled those observed for lepidopteran herbivores. Mutant analysis of induced plant defense pathways showed functionally that only a subset of induced programs, including jasmonic acid signaling and biosynthesis of indole glucosinolates, are central to Arabidopsis's defense to mite herbivory. On the herbivore side, indole glucosinolates dramatically increased mite mortality and development times. We identified an indole glucosinolate dose-dependent increase in the number of differentially expressedmite genes belonging to pathways associated with detoxification of xenobiotics. This demonstrates that spider mite is sensitive to Arabidopsis defenses that have also been associated with the deterrence of insect herbivores that are very distantly related to chelicerates. Our findings provide molecular insights into the nature of, and response to, herbivory for a representative of a major class of arthropod herbivores
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