2,082 research outputs found
Dimensión óptima de una planta industrial cuando los coeficientes de la fución de costes no están especificados: aplicación al caso de una fábrica de azúcar en Valladolid
CONSERVACIÓN ex situ DE SEMILLAS DE CUATRO ESPECIES ANDINAS DE Pasiflora
Colombia has endemic species of Passiflora L. mainly located in the Andean region, where they face a high risk of extinctiondue to deforestation, fragmentation and destruction of habitats. The studies of seed ecophysiology are important forprocesses of selection and ex situ conservation of native species, in addition to being an input for the improvement oftropical fruit trees. In this regard, the Botanical Garden of Bogota “José Celestino Mutis” has a live collection of 32 speciesof Pasiflora, of which seven species are represented in the ex situ germplasm seed bank. The objective was to evaluatethe germinative response under different treatments and the tolerance from the drying of eight pre-accessions of fourspecies of Pasiflora of rural areas of Bogotá Distrito Capital (P. tripartia; P. tarminiana, P. pinnatistipula and P. mixta).Several tests were performed of moisture content, desiccation tolerance and germination, evaluating the percentage ofgermination (PG), and the Average Time of Germination (ATG). An effect of the treatments on PG andATG was not observed, nor endogenous latency in the seeds, and it was determined that although atreatment can reach a smaller ATG, it not always obtains a higher PG. Six pre-accessions showeda clear orthodox behavior (seeds that survive desiccation), being useful sources of seed for theex situ conservation of these species.Colombia tiene especies endémicas de Pasiflora L., ubicadas en la región andina, donde afrontan un alto riesgo deextinción por la deforestación, fragmentación y destrucción de hábitats. Los estudios ecofisiológicos en semillas, sonimportantes para los procesos de selección y conservación ex situ de especies nativas, además son un insumo parael mejoramiento de los frutales tropicales. Al respecto, el Jardín Botánico de Bogotá José Celestino Mutis cuenta conuna colección viva de 32 especies de Pasiflora, de las cuales siete están representadas en el banco de germoplasma desemillas ex situ. El objetivo fue evaluar la respuesta germinativa bajo diferentes tratamientos y la tolerancia a la desecaciónde ocho pre-accesiones de cuatro especies de Pasiflora de zonas rurales de Bogotá Distrito Capital (P. tripartita; P.tarminiana; P. pinnatistipula y P. mixta). Se realizaron pruebas de contenido de humedad, de tolerancia a la desecacióny de germinación, evaluando el porcentaje de germinación (PG) y tiempo medio de Germinación (TMG). No se observóefecto de los tratamientos sobre el PG y el TMG, ni latencia endógena en las semillas, y se determinó que, aunque untratamiento alcance un menor TMG no siempre se obtiene un mayor PG. Seis pre-accesiones presentaron un clarocomportamiento Ortodoxo (semillas que sobreviven a desecación), siendo fuentes semilleras útiles para la conservaciónex situ de estas especies
La seca de encinas y alcornoques en Andalucía : decaimiento y enfermedad
El decaimiento forestal es una enfermedad de
etiología compleja, resultado de la acción de un
número variable de factores bióticos y abióticos que
causan un deterioro gradual y general de los árboles
afectados, hasta su muerte. Los factores implicados en
el decaimiento de los Quercus en Andalucía son
factores predisponentes de tipo selvícola, alteraciones
climáticas como factor incitante, y plagas y
enfermedades como factores contribuyentes. Entre las
enfermedades implicadas en Seca de los Quercus
destacan, por orden de importancia, la podredumbre
radical causada por Phytophthora cinnamomi, los
chancros de tronco y ramas causados por
Botryosphaeria spp. y el chancro carbonoso causado
por Biscogniauxia mediterranea. No obstante, las dos
primeras enfermedades tienen una especial incidencia
en distintas zonas de Andalucía de forma
independiente, no asociadas al decaimiento. En el
presente artículo se exponen las medidas de control
disponibles contra estas enfermedades de los Quercus
y se plantea la necesidad de disponer de un
diagnóstico preciso en cada caso para abordar dicho
control con garantías, ya que no cabe encontrar
soluciones únicas que resulten eficaces con
independencia de la naturaleza del problema._____________________________________The forestry decline is a complex disease, as a result
of the action of a changeable number of biotic and
abiotic factors that cause a gradual and general
deterioration of the affected trees, until their death.
The factors involved in the Quercus decline in
Andalusia are predisposing factors like silvic,
climatic alterations as inciting factor, and insect pest
and diseases as contributing factors. Between the
diseases involved in oak decline stand out, in order
of importance, the root roting caused by
Phytophthora cinnamomi, the chancres of trunk and
branches caused by Botryosphaeria spp. and the
charcoal canker caused by Biscogniauxia
mediterranea. Nevertheless, the first two diseases
have a special effect on different zones of Andalusia
in different ways, not associated with the decay. In
this article we expose the available tools of disease
control. We emphasizes the need of having a precise
diagnosis in every case to approach the control with
guarantees, since there is no chance of finding only
one efficient solution regardless of the nature of the
problem
Comparison of Mechanical Properties of Hemp-Fibre Biocomposites Fabricated with Biobased and Regular Epoxy Resins
[EN] Bio- and green composites are mainly used in non-structural automotive elements like interior panels and vehicle underpanels. Currently, the use of biocomposites as a worthy alternative to glass fibre-reinforced plastics (GFRPs) in structural applications still needs to be fully evaluated. In the current study, the development of a suited biocomposites started with a thorough review of the available raw materials, including both reinforcement fibres and matrix materials. Based on its specific properties, hemp appeared to be a very suitable fibre. A similar analysis was conducted for the commercially available biobased matrix materials. Greenpoxy 55 (with a biocontent of 55%) and Super Sap 100 (with a biocontent of 37%) were selected and compared with a standard epoxy resin. Tensile and three-point bending tests were conducted to characterise the hemp-based biocomposite.The authors acknowledge financial support from the Spanish Government, Project PID2019-108807RB-I00.Colomer Romero, V.; Rogiest, D.; García Manrique, JA.; Crespo, J. (2020). Comparison of Mechanical Properties of Hemp-Fibre Biocomposites Fabricated with Biobased and Regular Epoxy Resins. Materials. 13(24):1-8. https://doi.org/10.3390/ma13245720181324Mohanty, A. K., Misra, M., & Hinrichsen, G. (2000). Biofibres, biodegradable polymers and biocomposites: An overview. Macromolecular Materials and Engineering, 276-277(1), 1-24. doi:10.1002/(sici)1439-2054(20000301)276:13.0.co;2-wLa Mantia, F. P., & Morreale, M. (2011). Green composites: A brief review. Composites Part A: Applied Science and Manufacturing, 42(6), 579-588. doi:10.1016/j.compositesa.2011.01.017Hansen, O., Habermann, C., & Endres, H.-J. (2019). BIO-BASED MATERIALS FOR EXTERIOR APPLICATIONS – PROJECT BIOHYBRIDCAR. Zukunftstechnologien für den multifunktionalen Leichtbau, 189-200. doi:10.1007/978-3-662-58206-0_18Gholampour, A., & Ozbakkaloglu, T. (2019). A review of natural fiber composites: properties, modification and processing techniques, characterization, applications. Journal of Materials Science, 55(3), 829-892. doi:10.1007/s10853-019-03990-yPatil, N. V., Rahman, M. M., & Netravali, A. N. (2017). «Green» composites using bioresins from agro‐wastes and modified sisal fibers. Polymer Composites, 40(1), 99-108. doi:10.1002/pc.24607Verma, D., & Senal, I. (2019). Natural fiber-reinforced polymer composites. Biomass, Biopolymer-Based Materials, and Bioenergy, 103-122. doi:10.1016/b978-0-08-102426-3.00006-0Adekomaya, O. (2020). Adaption of green composite in automotive part replacements: discussions on material modification and future patronage. Environmental Science and Pollution Research, 27(8), 8807-8813. doi:10.1007/s11356-019-07557-xKim, Y. K., & Chalivendra, V. (2020). Natural fibre composites (NFCs) for construction and automotive industries. Handbook of Natural Fibres, 469-498. doi:10.1016/b978-0-12-818782-1.00014-6Potluri, R., & Chaitanya Krishna, N. (2020). Potential and Applications of Green Composites in Industrial Space. Materials Today: Proceedings, 22, 2041-2048. doi:10.1016/j.matpr.2020.03.218Mann, G. S., Singh, L. P., Kumar, P., & Singh, S. (2018). Green composites: A review of processing technologies and recent applications. Journal of Thermoplastic Composite Materials, 33(8), 1145-1171. doi:10.1177/0892705718816354Standard Test Method for Tensile Properties of Polymer Matrix Composite Materials https://www.astm.org/Standards/D3039https://www.pecepoxy.co.uk/data-sheets/TDS_100_1000_v4.pdfhttp://www.matrix-composites.co.uk/prod-data-sheet/old/greenpoxy-55-ft-uk.pdfCzłonka, S., Strąkowska, A., & Kairytė, A. (2020). The Impact of Hemp Shives Impregnated with Selected Plant Oils on Mechanical, Thermal, and Insulating Properties of Polyurethane Composite Foams. Materials, 13(21), 4709. doi:10.3390/ma13214709Madhu, P., Mavinkere Rangappa, S., Khan, A., Al Otaibi, A., Al‐Zahrani, S. A., Pradeep, S., … Siengchin, S. (2020). Experimental investigation on the mechanical and morphological behavior of
Prosopis juliflora
bark fibers/E‐glass/carbon fabrics reinforced hybrid polymeric composites for structural applications. Polymer Composites, 41(12), 4983-4993. doi:10.1002/pc.2576
The bang of a white hole in the early universe from a 6D vacuum state: Origin of astrophysical spectrum
Using a previously introduced model in which the expansion of the universe is
driven by a single scalar field subject to gravitational attraction induced by
a white hole during the expansion (from a 6D vacuum state), we study the origin
of squared inflaton fluctuations spectrum on astrophysical scales.Comment: Final version to be published in Eur. Phys. J.
Noncommutative Quantum Cosmology
We consider noncommutative quantum cosmology in the case of the low-energy
string effective theory. Exacts solutions are found and compared with the
commutative case.The Noncommutative quantum cosmology is considered in the case
of the low-energy string effective theory. Exacts solutions are found and
compared with the commutative case.Comment: Revtex4, 3 pages, 2 figures, to appear in Gen.Rel.Gra
Evolución del abandono de tierras de cultivo en la comarca oriental de la Región de Murcia
En la Comarca Oriental de la Región de Murcia, se analiza la superficie, distribución y
evolución de tierras de cultivo abandonadas, mediante análisis espacial con herramientas
SIG. Se observa un progresivo aumento del abandono en las últimas décadas, fomentado
tanto por factores ambientales como económicos. Alrededor de un 15% de la superficie
estudiada se encuentra en abandono y sometida a pérdidas de suelo, producidas por notables
procesos de erosión. Por ello, el conocimiento del estado de estas áreas es fundamental para
la toma de decisiones encaminadas a mitigar este grave problema
Multi-dimensional gyrokinetic parameter studies based on eigenvalue computations
Plasma microinstabilities, which can be described in the framework of the linear gyrokinetic equations, are routinely computed in the context of stability analyses and transport predictions for magnetic confinement fusion experiments. The GENE code, which solves the gyrokinetic equations, has been coupled to the SLEPc package for an efficient iterative, matrix-free, and parallel computation of rightmost eigenvalues. This setup is presented, including the preconditioner which is necessary for the newly implemented Jacobi-Davidson solver. The fast computation of instabilities at a single parameter set is exploited to make parameter scans viable, that is to compute the solution at many points in the parameter space. Several issues related to parameter scans are discussed, such as an efficient parallelization over parameter sets and subspace recycling. © 2011 Elsevier B.V. All rights reserved.E. Romero and J.E. Roman were supported by the Spanish Ministry of Science and Innovation (MICINN) under project number TIN2009-07519.Merz, F.; Kowitz, C.; Romero Alcalde, E.; Román Moltó, JE.; Jenko, F. (2012). Multi-dimensional gyrokinetic parameter studies based on eigenvalue computations. Computer Physics Communications. 183(4):922-930. https://doi.org/10.1016/j.cpc.2011.12.018S922930183
Sub-arcsecond radio and optical observations of the likely counterpart to the gamma-ray source 2FGL J2056.7+4939
We have searched and reviewed all multi- wavelength data available for the
region towards the gamma-ray source 2FGL J2056.7+4939 in order to con- strain
its possible counterpart at lower energies. As a result, only a point-like
optical/infrared source with flat-spectrum radio emission is found to be
consistent with all X-ray and gamma-ray error circles. Its struc- ture is
marginally resolved at radio wavelengths at the sub-arcsecond level. An
extragalactic scenario appears to be the most likely interpretation for this
object.Comment: 5 pages, 3 figures, 1 tabl
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