6,942 research outputs found
TORCH: A Cherenkov Based Time-of-Flight Detector
TORCH is a novel high-precision time-of-flight detector suitable for large area applications and
covering the momentum range up to 10 GeV/c. The concept uses Cherenkov photons produced
in a fused silica radiator which are propagated to focussing optics coupled to fast photodetectors.
For this purpose, custom MCP-PMTs are being produced in collaboration with industrial partners.
The development is divided into three phases. Phase 1 addresses the lifetime requirements for
TORCH, Phase 2 will customize the MCP-PMT granularity and Phase 3 will deliver prototypes
that meet the TORCH requirements. Phase 1 devices have been successfully delivered and initial
tests show stable gain performance for integrated anode current >5 C/cm2
and a single photon
time resolution of †30 ps. Initial simulations indicate the single photon timing resolution of the
TORCH detector will be âŒ70 ps
Synthesis of Enantioenriched Amines by Iron-Catalysed Amination of Alcohols Employing at Least One Achiral Substrate
The synthesis of a broad range of enantioenriched amines by the direct Fe-catalysed coupling of amines with alcohols through the borrowing hydrogen strategy, while at least one of these substrates is achiral is reported. When starting from α-chiral amines and achiral alcohols, a wide range of enantioenriched amine products, including N-heterocyclic moieties can be obtained with complete retention of stereochemistry and the power of this method is demonstrated in the one-step synthesis of known pharmaceuticals from commercially available, simple enantiopure primary amines and achiral alcohols. It was also found that the use of ÎČ-branched enantioenriched primary alcohols and achiral amines as reaction partners leads to a partial loss of stereochemical integrity in the final product, however, a systematic optimization enabled partial retention of enantiopurity and possible parameters effecting for racemization were identified.</p
Understanding herbivore-plant-soil feedbacks to improve grazing management on Mediterranean mountain grasslands
The surface of many European mountain grasslands is decreasing due to global change and extensive grazing stands out as a key tool for their conservation. Sound knowledge of grassland ecosystem functioning and its feedback processes is required to implement sustainable grazing management. This study aimed to understand the effect of different grazing intensities on herbivore-plant-soil feedbacks in Mediterranean mountain grasslands. We estimated spatial distribution of sheep grazing intensity using GPS technology in order to assess the effect of grazing pressure on vegetation and soil properties measured throughout the study area. Our results showed that grazing intensity ranged from 0.06 to 2.85 livestock units / ha, corresponding to a gradient of pasture utilisation rates varying from 2.38% to 45.60% of annual productivity from pasture. Increasing grazing pressure was associated with smaller relative cover and species richness of non-leguminous forbs, while the opposite trends were observed for graminoids. Forage had a greater concentration of N and smaller C:N ratio in more heavily grazed areas. Increasing grazing intensity was also associated with higher values of total soil N, NO3-, NH4+, soil organic carbon, microbial biomass C and activity of Ă-glucosidase. Higher litter quality was the main factor explaining greater content of soil organic matter, which favoured both soil microbes and plant productivity. Grazing induced changes in the plant community triggered positive hervibore-plant-soil feedbacks, as they ultimately improved forage quality and productivity, which significantly influenced the pasture preference of free-ranging domestic grazers. Our work showed that grazing management aiming pasture utilisation rates of around 45% is critical in sustaining positive herbivore-plant-soil feedbacks and preserving or enhancing the whole ecosystem functioning in the Mediterranean mountain grasslands studied. © 2021 The Author
A finite element approach to model high-velocity impact on thin woven GFRP plates
A finite element model to predict the ballistic behaviour of woven GFRP laminates is presented. This finite element model incorporates a new constitutive model based on a continuum damage mechanics approach able to predict the performance of these laminates under high-velocity impacts. The material parameters of the model are identified from the literature and original experiments conducted in this work. The predictive capability of the model is verified against experimental impact tests. Finally, the model is used to analyse the influence of laminate thickness on different energy absorption mechanisms at velocities near the ballistic limit. This analysis allows for the determination of the principal deformation and failure mechanisms governing the perforation process.L. Alonso, S.K.GarcĂa Castillo and C.Navarro are indebted to the project 'AcciĂłn EstratĂ©gica en Materiales Compuestos y AnĂĄlisis NumĂ©rico simplificado de Estructuras y protecciones ligeras sometidas a impacto balĂstico' (2010/00309/002) of the University Carlos III of Madrid for the financial support of this work. F. MartĂnez-Hergueta acknowledges support from PECRE1819_02 from the Scottish Research Partnership in Engineering. D. Garcia-Gonzalez acknowledges support from the Talent Attraction grant (CM 2018 - 2018-T2/IND-9992) from the Comunidad de Madrid
Effects of Low-Energy Laser Irradiation on Sperm Cells Dynamics of Rabbit (Oryctolagus Cuniculus)
Infertility is a world disease in which a couple is unable to achieve pregnancy. There are numerous parameters to determinate fertility; nevertheless, sperm motility is by consensus one of the most important attributes to evaluate male fertility. Contributions to a better understanding of this crucial parameter are imperative; hence, the aim of this investigation was to assess the effect of low-energy laser irradiation on sperm cell dynamics in thawed samples that were cryopreserved. We used a 405 nm blue laser beam to irradiate spermatic cells from rabbit inside a temperature-controlled dispersion chamber at 37 °C; then, we applied an image recognizing system to calculate individual sperm trajectories and velocities. We found that sperms raise its motility after irradiation suggesting that λ=405 nm is an optimal wavelength for spermatic photo-stimulation
Olive Actual âon Yearâ Yield Forecast Tool Based on the Tree Canopy Geometry Using UAS Imagery
Olive has a notable importance in countries of Mediterranean basin and its profitability
depends on several factors such as actual yield, production cost or product price. Actual âon
yearâ Yield (AY) is production (kg tree-1) in âon yearsâ, and this research attempts to relate it with
geometrical parameters of the tree canopy. Regression equation to forecast AY based on manual
canopy volume was determined based on data acquired from different orchard categories and
cultivars during different harvesting seasons in southern Spain. Orthoimages were acquired with
unmanned aerial systems (UAS) imagery calculating individual crown for relating to canopy volume
and AY. Yield levels did not vary between orchard categories; however, it did between irrigated
orchards (7000â17,000 kg ha-1) and rainfed ones (4000â7000 kg ha-1). After that, manual canopy
volume was related with the individual crown area of trees that were calculated by orthoimages
acquired with UAS imagery. Finally, AY was forecasted using both manual canopy volume and
individual tree crown area as main factors for olive productivity. AY forecast only by using individual
crown area made it possible to get a simple and cheap forecast tool for a wide range of olive orchards.
Finally, the acquired information was introduced in a thematic map describing spatial AY variability
obtained from orthoimage analysis that may be a powerful tool for farmers, insurance systems,
market forecasts or to detect agronomical problems
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