728 research outputs found

    The 2mrad horizontal crossing angle IR layout for a TeV ILC

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    The current status of the 2mrad crossing angle layout for the ILC is reviewed. The scheme developed in the UK and France is described and the performance discussed for a TeV machine. Secondly, the scheme developed at SLAC and BNL is then studied and modified for a TeV machine. We find that both schemes can handle the higher energy beam with modifications, and share many common features.Comment: The proceedings of the 2005 International Linear Collider Workshop, March 2005. 4 pages, 5 figure

    Movimiento Arte del Cambio: una iniciativa del Trabajo Social antiopresivo

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    This article presents the Art of Change Movement (Movimiento Arte del Cambio), which has developed out of a project of the Association of Social Workers Without Boundaries (AsociaciĂłn Trabajadores/as Sociales Sin Fronteras), with the collaboration of the Faculty of Social Work at Universidad de Granada and of education professionals, incorporating theatrical creativity and musical expression as pedagogical and social intervention tools. The aim is for the initiative to become another instrument in the fight against oppression. Through a laboratory for collective creativity involving students and professionals from social work and other social science disciplines, the movement seeks social transformation through artistic expression, based on political commitment and sustainable development that empowers participant

    Atomic-scale investigation of hydrogen distribution in a Ti–Mo alloy

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    Ingress of hydrogen is often linked to catastrophic failure of Ti-alloys. Here, we quantify the hydrogen distribution in fully β and α + β Ti–Mo alloys by using atom probe tomography. Hydrogen does not segregate at grain boundaries in the fully β sample but segregates at some α/β phase boundaries with a composition exceeding 20 at.% in the α + β sample. No stable hydrides were observed in either sample. The hydrogen concentration in β phases linearly decreases from ~13 at. % to ~4 at. % with increasing Mo-content, which is ascribed to the suppression of hydrogen uptake by Mo addition

    A laser triggered electron source for pulsed radiolysis

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    We present the design of a photo-injector based accelerator for pulsed radiolysis applications. This machine is destined to meet the needs of the physical chemistry community at the Universite de Paris XI. A 4 MeV Energy electron pulse of a few picoseconds duration and with a charge in the range of 1 to 10 nC is produced from a Cs/sub 2 /Te photocathode. The photocathode is placed in the half energy spread cell of a 1-1/2 cell, 3 GHz RF gun, whose design is based on the gun used for the drive beam of the CERN CLIC Test facility. A 4 cell "booster" cavity is then used to accelerate the beam to an energy of 9 MeV. The transport system consists of a quadrupole triplet downsteam of the booster, two rectangular, 30 degree bend, dipoles with a pair of quadrupoles between them and a second triplet downstream of the second dipole. Energy dependent path length effects in the two dipoles allow the possibility of magnetic bunch compression depending on the phase-energy correlation of the bunch exiting the booster cavity. The beam envelope and the bunch length have been calculated through the transport line using TRACE-3d and PARMELA. These codes allow us to verify the required beam parameters at the experimental areas. We discuss the adjustment of the optics, aimed at producing the minimum electron bunch length at the experimental targets. (4 refs)

    Onderzoek naar de trekvissoorten in het Schelde-estuarium. Voortplantings-en opgroeihabitat van rivierprik en fint

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    Migratory fish such as river lamprey and twaite shad are important indicators of ecosystem functioning. Over the past century, most migratory fish have disappeared from the river Scheldt due to human impacts. The previous study on migratory fishes in the Scheldt showed however that most species show the first signs of recovery (Stevens et al., 2009). For both river lamprey and twaite shad there are strong indications that they reproduce in the Scheldt. However, the spawning and nursery habitats of both species are unknown and it is unclear whether the preconditions for a sustainable recovery are met. The spawning and nursery habitat of river lamprey can be located through targeted sampling of the larvae in the sediment. Sampling with fyke nets showed that adult river lamprey migrate mainly to the Bovenschelde and Zwalmbeek. In both rivers a number of locations were selected, which are, according to the literature, expected to be suitable habitats for the larvae of river lamprey. Wadable sites were sampled with a specially designed sediment pump and the deeper sites with a Van Veen grab. In neither of these rivers, however, river lamprey larvae could be found and no spawning sites could be identified. Possible reasons for the lack of larvae in the samples are (1) that no suitable larval habitat is present in the studied areas, (2) that the larval density in the investigated habitats is low and hence sampling frequency should be increased, (3) that the River Bovenschelde and the River Zwalm are not the main spawning grounds for river lamprey in the Scheldt. Telemetry of adult river lamprey could be a possible solution to locate the spawning grounds. In order to improve the reproduction and survival of river lamprey in the River Bovenschelde, the migration barriers in the Scheldt and its tributaries should be cleared and sufficient larval habitat should be availability. Larval habitat could be created in the River Zwalm and other tributaries through the restoration of natural banks. In addition, mud and sand banks in the Bovenschelde should be protected as much as possible as potential larval habitat.The population of twaite shad in the Scheldt is too small to identify the critical habitats by sampling in the field. Therefore, a habitat suitability model for spawning and larval shad was constructed based on literature data. Hereto, we first selected the environmental variables that determine habitat suitability. Next, for each variable the tolerance range was determined. Finallly, the variables were combined using fuzzy logic in order to determine the degree of suitability of a habitat. The model predicts the presence of suitable spawning habitat in the Upper Zeeschelde, upstream of the River Durme. Later in the season, when the water temperature rises, suitable spawning habitat is also present in the Rivers Kleine Nete and Grote Nete. Suitable habitat for larval shad is located mainly in the Upper Zeeschelde upstream Rupelmonde and in the River Rupel. Spawning of twaite shad takes place in the main channel and during their ontogeny the larvae migrate to the edges of the main channel and to side channels.Therefore, in areas with suitable spawning and larval habitat, both the main and side channels need protection. In particular mudflats, sand flats and subtidal low dynamic habitats should be safeguarded. Dredging of these habitats thus mortgages the recovery of the twaite shad population in the Scheldt. The oxygen concentration in the estuary has been greatly improved in recent years.However, in summer a low-oxygen zone in the freshwater area persists, comprising the upstream migration of adults and the survival of larvae. Periodic hypoxic conditions should therefore be avoided and a minimum oxygen content of 5 mg / l is essential for both adults and larvae. During the last century, hydrodynamics in the estuary has increased markedly. As a result, larvae have more difficulties in maintaining their position in suitable habitat. Actions that increase the river/tidal flow or eliminate local retention areas should therefore be avoided
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