1,776 research outputs found

    Can soil moisture be mapped onto the terrain?

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    International audienceSoil moisture heterogeneity has an effect on the rainfall?runoff characteristics of a landscape. The aggregate effect on the mean water balance over an area can be quantified successfully using models such as the PDM (Moore, 1986) and TOPMODEL (Beven and Kirkby, 1979). These rainfall?runoff models have been embedded in the large-scale land surface schemes used in meteorological models. However, there is also a requirement (e.g. model validation) to identify the spatial structure of the fine-scale soil moisture heterogeneity that makes up these aggregate models. In some types of landscape, this will be dictated by topography, in others by soil characteristics, or by a combination of both. A method to distribute area-average soil moisture according to the likely effect of local topography is presented and tested. The heterogeneity of the soil moisture is described by the Xinanxiang distribution (Zhao et al., 1980), commonly used to describe the natural spatial heterogeneity of the landscape. This distribution is then mapped onto the terrain using a topographic index to locate the wettest and driest areas. Soil moisture data from the Wye catchment in Wales and from the Pang catchment in Berkshire, England, are used to test the method. It is found that soil moisture data from the Wye catchment follow the topographic index reasonably well, whereas data from the quick-draining, chalky Pang catchment do not. The conclusion that topographic index is a useful indicator only in some landscapes applies equally to using this mapping method and those models that use topographic index directly. Keywords: soil moisture, heterogeneity, topographic index, dat

    A Fixed-Target ExpeRiment at the LHC (AFTER@LHC) : luminosities, target polarisation and a selection of physics studies

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    We report on a future multi-purpose fixed-target experiment with the proton or lead ion LHC beams extracted by a bent crystal. The multi-TeV LHC beams allow for the most energetic fixed-target experiments ever performed. Such an experiment, tentatively named AFTER for "A Fixed-Target ExperRiment", gives access to new domains of particle and nuclear physics complementing that of collider experiments, in particular at RHIC and at the EIC projects. The instantaneous luminosity at AFTER using typical targets surpasses that of RHIC by more than 3 orders of magnitude. Beam extraction by a bent crystal offers an ideal way to obtain a clean and very collimated high-energy beam, without decreasing the performance of the LHC. The fixed-target mode also has the advantage of allowing for spin measurements with a polarised target and for an access over the full backward rapidity domain up to xF ~ - 1. Here, we elaborate on the reachable luminosities, the target polarisation and a selection of measurements with hydrogen and deuterium targets.Comment: 6 pages. Proceedings of the Sixth International Conference on Quarks and Nuclear Physics QNP2012 (16-20 April 2012, Ecole Polytechnique, Palaiseau,France

    Differentiation between decomposed remains of human origin and bigger mammals

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    This study is a follow-up study in the search for a human specific marker in the decomposition where the VOC-profile of decomposing human, pig, lamb and roe remains were analyzed using a thermal desorber combined with a gas chromatograph coupled to a mass spectrometer in a laboratory environment during 6 months. The combination of 8 previously identified human and pig specific compounds (ethyl propionate, propyl propionate, propyl butyrate, ethyl pentanoate, 3-methylthio-1-propanol, methyl(methylthio)ethyl disulfide, diethyl disulfide and pyridine) was also seen in these analyzed mammals. However, combined with 5 additional compounds (hexane, heptane, octane, N-(3-methylbutyl)- and N-(2-methylpropyl)acetamide) human remains could be separated from pig, lamb and roe remains. Based on a higher number of remains analyzed, as compared with the pilot study, it was no longer possible to rely on the 5 previously proposed esters to separate pig from human remains. From this follow-up study reported, it was found that pyridine is an interesting compound specific to human remains. Such a human specific marker can help in the training of cadaver dogs or in the development of devices to search for human remains. However, further investigations have to verify these results.</p

    Spin physics at A Fixed-Target ExpeRiment at the LHC (AFTER@LHC)

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    We outline the opportunities for spin physics which are offered by a next generation and multi-purpose fixed-target experiment exploiting the proton LHC beam extracted by a bent crystal. In particular, we focus on the study of single transverse spin asymetries with the polarisation of the target.Comment: Contributed to the 20th International Spin Physics Symposium, SPIN2012, 17-22 September 2012, Dubna, Russia, 4 pages, LaTe

    Continuous Uniform Finite Time Stabilization of Planar Controllable Systems

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    Continuous homogeneous controllers are utilized in a full state feedback setting for the uniform finite time stabilization of a perturbed double integrator in the presence of uniformly decaying piecewise continuous disturbances. Semiglobal strong C1\mathcal{C}^1 Lyapunov functions are identified to establish uniform asymptotic stability of the closed-loop planar system. Uniform finite time stability is then proved by extending the homogeneity principle of discontinuous systems to the continuous case with uniformly decaying piecewise continuous nonhomogeneous disturbances. A finite upper bound on the settling time is also computed. The results extend the existing literature on homogeneity and finite time stability by both presenting uniform finite time stabilization and dealing with a broader class of nonhomogeneous disturbances for planar controllable systems while also proposing a new class of homogeneous continuous controllers

    Prospectives for A Fixed-Target ExpeRiment at the LHC: AFTER@LHC

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    We argue that the concept of a multi-purpose fixed-target experiment with the proton or lead-ion LHC beams extracted by a bent crystal would offer a number of ground-breaking precision-physics opportunities. The multi-TeV LHC beams will allow for the most energetic fixed-target experiments ever performed. The fixed-target mode has the advantage of allowing for high luminosities, spin measurements with a polarised target, and access over the full backward rapidity domain --uncharted until now-- up to x_F ~ -1.Comment: 6 pages, 1 table, LaTeX. Proceedings of the 36th International Conference on High Energy Physics (ICHEP2012), 4-11 July 2012, Melbourne, Australi

    Postoperative urinary retention:Risk factors, bladder filling rate and time to catheterization: an observational study as part of a randomized controlled trial

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    Background: Knowledge of risk factors for postoperative urinary retention may guide appropriate and timely urinary catheterization. We aimed to determine independent risk factors for postoperative urinary catheterization in general surgical patients. In addition, we calculated bladder filling rate and assessed the time to spontaneous voiding or catheterization. We used the patients previously determined individual maximum bladder capacity as threshold for urinary catheterization.Methods: Risk factors for urinary catheterization were prospectively determined in 936 general surgical patients. Patients were at least 18 years of age and operated under general or spinal anesthesia without the need for an indwelling urinary catheter. Patients measured their maximum bladder capacity preoperatively at home, by voiding in a calibrated bowl after a strong urge that could no longer be ignored. Postoperatively, bladder volumes were assessed hourly with ultrasound. When patients reached their maximum bladder capacity and were unable to void, they were catheterized by the nursing staff. Bladder filling rate and time to catheterization were determined.Results: Spinal anesthesia was the main independent modifiable risk factor for urinary catheterization (hyperbaric bupivacaine, relative risk 8.1, articaine RR 3.1). Unmodifiable risk factors were a maximum bladder capacity &lt;500 mL (RR 6.7), duration of surgery &gt;= 60 min (RR 5.5), first scanned bladder volume at the Post Anesthesia Care Unit &gt;= 250mL (RR 2.1), and age &gt;= 60 years (RR 2.0). Urine production varied from 100 to 200 mL/h. Catheterization or spontaneous voiding took place approximately 4 h postoperatively.Conclusion: Spinal anesthesia, longer surgery time, and older age are the main risk factors for urinary retention catheterization. Awareness of these risk factors, regularly bladder volume scanning (at least every 3 h) and using the individual maximum bladder capacity as volume threshold for urinary catheterization may avoid unnecessary urinary catheterization and will prevent bladder overdistention with the attendant risk of lower urinary tract injury.</p

    Avaliação do potencial de cinco cultivares de videiras americanas para sucos de uva no sul de Minas Gerais.

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    Objetivou-se, no presente trabalho realizar uma caracterização dos sucos de uva de cinco cultivares de videira americana Vitis labrusca (Folha de Figo, Alwood, Concord, BRS-RĂșbea e Isabel) segundo suas caracterĂ­sticas visuais, olfativas e gustativas, utilizando um mĂ©todo descritivo por um painel de degustadores da Embrapa Uva e Vinho (EMBRAPA/CNPUV) de Bento Gonçalves e da Associação Brasileira de Enologia (ABE), constituĂ­do por doze degustadores. De acordo com os resultados, os sucos das cultivares Isabel e Folha de Figo foram superiores aos demais, segundo a anĂĄlise de componentes principais (ACP), principalmente pelas variĂĄveis limpidez, equilĂ­brio olfativo, intensidade e corpo gustativo, persistĂȘncia olfato-gustativa e julgamento geral (notas). O suco Folha de Figo foi superior ao Isabel quanto Ă  tonalidade, sendo o primeiro caracterizado como vermelho-violĂĄceo. A cultivar Folha de Figo Ă© a mais utilizada na regiĂŁo para a produção de suco, podendo os produtores utilizarem tambĂ©m a cultivar Isabel, que mostrou potencial nas condiçÔes edafo-climĂĄticas do sul de Minas Gerais.DisponĂ­vel tambĂ©m on-line

    Linear Protection Schemes Analysis in Scattered Placement Fiber-To-The Home-Passive Optical Network Using Customer Access Protection Unit Solution

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    <STRONG>Problem statement:</STRONG> This study highlights on restoration scheme proposed against failure in working line at the drop region for Fiber-To-The Home (FTTH) with a Passive Optical Network (PON). Whereas PON is a system that brings optical fiber cable and signals all or most of the way to the end user.<STRONG> Approach:</STRONG> Survivability scheme against failure is focused on scattered residence architectures and it is applied in the ring and tree topology respectively by means of Customer Access Protection Unit (CAPU). CAPU will be installed before the ONU and ensure the signal will find the alternative path when failure occurs at the specific line. Our proposal scheme is low cost and applicable to any residence architecture. The advantage of this scheme is the failure at fiber line can be recovered until three levels to make sure the optic signal flow continuously to avoid any application disturbance. Two type of restoration scheme is proposed by means of linear protection (tree) and migrated protection (ring). FTTH based network design is simulated by using Opti System 7.0 in order to investigate the power output and BER performance at each node in the tree and ring protection scheme in scattered placement. This study we perform an analysis on linear protection scheme that consisting of two model a) Line to Line (L2L) protection and CAPU to CAPU (C2C) or Shared protection. However the migration of tree to ring topology to enable the signal flow continuously in the case of failure occurs specifically in random or scattered placement topology has been highlighted in our previous publication. <STRONG>Results:</STRONG> The signal will be divided into section; drop and pass through and the ratio is significant to determine the number of user allowed and achievable distance. Output power for optical nodes could be slightly improved by varying the pass through and drop signal ratio. <STRONG>Conclusion:</STRONG> Our proposal is the first reported up to this time in which the upstream signal flows in anticlockwise in ring topology when the restoration scheme activated
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