539 research outputs found
A model of horse mussel reef formation in the Bay of Fundy based on population growth and geological processes
From a total of 14 geological sediment provinces recognized in the Bay of Fundy only five: sand with bioherms, gravel/cobble, gravel /scallop bed, mottled gravel and glacio-marine mud were found to have significant populations of the horse mussel, Modiolus modiolus. Valve increment measures of annual growth rings in the early years of life of populations of these Bay of Fundy horse mussels, suggest that growth rates vary with the geological province where they are found. Horse mussel populations grow fastest on sand with bioherms, closely followed by those growing on gravel/scallop bed; the slowest growing are found on gravel/ cobble and mottled gravel geological provinces.
Multibeam bathymetry and backscatter data have been collected in an area of mussel reefs in the central part of the Bay of Fundy. The data indicates that the mussel reefs (bioherms) tend to occur on the eastern side of small, gravel covered, glacial ridges on the seabed and form a variety of single and multiple, long and short reefs that rise above the seabed up to 3 m high. They are always associated with sand in transport at the seabed in a variety of bedforms. A conceptual model of formation and location is presented that considers: current velocity and turbulence, well-mixed water masses, seabed morphology, sediment distribution and sediment transport, as causative factors.
RĂSUMĂ
Dâun total de 14 classes de sĂŠdiments gĂŠologiques reconnues dans la baie de Fundy, seulement cinq (biohermes, gravier/galets, gravier/fond de pĂŠtoncle, gravier tachetĂŠ et boue glacio-marine) renfermaient des populations importantes de modiole Modiolus modiolus. Les mesures de lâaugmentation valvaire des cernes dâaccroissement annuels durant les premières annĂŠes de vie des populations de modioles dans la baie de Fundy indiqueraient que les taux de croissance varient selon la classe de sĂŠdiment gĂŠologique oĂš ils se trouvent. Les populations de modioles croissent plus rapidement dans le sable renfermant des biohermes, et la croissance est presque aussi grande chez les modioles prĂŠsents dans les classes de sĂŠdiments composĂŠes de gravier/fond de pĂŠtoncles; la croissance la plus lente a ĂŠtĂŠ observĂŠe dans les classes de sĂŠdiments gĂŠologiques composĂŠes de gravier/galets et de gravier tachetĂŠ.
Des donnĂŠes ont ĂŠtĂŠ recueillies au moyen de la bathymĂŠtrie par secteurs et de la rĂŠtrodiffusion dans une zone de rĂŠcifs de moules de la partie centrale de la baie de Fundy. Les donnĂŠes indiquent que les rĂŠcifs de moules (biohermes) semblent se former sur le cĂ´tĂŠ est de petites crĂŞtes glaciaires recouvertes de gravier sur le plancher sousâmarin, et quâils forment divers rĂŠcifs uniques et multiples, longs et courts, qui sâĂŠlèvent sur le plancher sous-marin jusquâĂ une hauteur de trois mètres. Ils sont toujours associĂŠs avec le sable dĂŠplacĂŠ sur le plancher sous-marin dans diverses morphologies de fond. On prĂŠsente un modèle conceptuel de la formation et de lâemplacement qui considère comme facteurs de causalitĂŠ les ĂŠlĂŠments suivants : la vitesse et la turbulence actuelles, les masses dâeau homogènes, la morphologie du plancher sous-marin, la rĂŠpartition des sĂŠdiments et les transports sĂŠdimentaires. [Traduit par la redaction
CMS Software Distribution on the LCG and OSG Grids
The efficient exploitation of worldwide distributed storage and computing
resources available in the grids require a robust, transparent and fast
deployment of experiment specific software. The approach followed by the CMS
experiment at CERN in order to enable Monte-Carlo simulations, data analysis
and software development in an international collaboration is presented. The
current status and future improvement plans are described.Comment: 4 pages, 1 figure, latex with hyperref
Distributed Computing Grid Experiences in CMS
The CMS experiment is currently developing a computing system capable of serving, processing and archiving the large number of events that will be generated when the CMS detector starts taking data. During 2004 CMS undertook a large scale data challenge to demonstrate the ability of the CMS computing system to cope with a sustained data-taking rate equivalent to 25% of startup rate. Its goals were: to run CMS event reconstruction at CERN for a sustained period at 25 Hz input rate; to distribute the data to several regional centers; and enable data access at those centers for analysis. Grid middleware was utilized to help complete all aspects of the challenge. To continue to provide scalable access from anywhere in the world to the data, CMS is developing a layer of software that uses Grid tools to gain access to data and resources, and that aims to provide physicists with a user friendly interface for submitting their analysis jobs. This paper describes the data challenge experience with Grid infrastructure and the current development of the CMS analysis system
Experience with fibre channel in the environment of the ATLAS DAQ protoype "-1" project
Fibre Channel equipment has been evaluated in the environment of the ATLAS DAQ prototype "-1". Fibre Channel PCI and PMC cards have been tested on PwerPC-based VME processor boards running LynxOS and on Pentium-based personal computers running Windows NT. The performance in terms of overhead and bandwidth has been measured in point-to-point, arbitrated loop and fabric configuration with a Fibre Ch annel switch. The possible used of the equipment for event building in the ATLAS DAQ prototype "-1" has been studied
Using Linux PCs in DAQ applications
ATLAS Data Acquisition/Event Filter "-1" (DAQ/EF1) project provides the opportunity to explore the use of commodity hardware (PCs) and Open Source Software (Linux) in DAQ applications. In DAQ/EF-1 there is an element called the LDAQ which is responsible for providing local run-control, error-handling and reporting for a number of read- out modules in front end crates. This element is also responsible for providing event data for monitoring and for the interface with the global control and monitoring system (Back-End). We present the results of an evaluation of the Linux operating system made in the context of DAQ/EF-1 where there are no strong real-time requirements. We also report on our experience in implementing the LDAQ on a VMEbus based PC (the VMIVME-7587) and a desktop PC linked to VMEbus with a Bit3 interface both running Linux. We then present the problems encountered during the integration with VMEbus, the status of the LDAQ implementation and draw some conclusions on the use of Linux in DAQ applications. (18 refs)
Performance of the CMS Cathode Strip Chambers with Cosmic Rays
The Cathode Strip Chambers (CSCs) constitute the primary muon tracking device
in the CMS endcaps. Their performance has been evaluated using data taken
during a cosmic ray run in fall 2008. Measured noise levels are low, with the
number of noisy channels well below 1%. Coordinate resolution was measured for
all types of chambers, and fall in the range 47 microns to 243 microns. The
efficiencies for local charged track triggers, for hit and for segments
reconstruction were measured, and are above 99%. The timing resolution per
layer is approximately 5 ns
Performance and Operation of the CMS Electromagnetic Calorimeter
The operation and general performance of the CMS electromagnetic calorimeter
using cosmic-ray muons are described. These muons were recorded after the
closure of the CMS detector in late 2008. The calorimeter is made of lead
tungstate crystals and the overall status of the 75848 channels corresponding
to the barrel and endcap detectors is reported. The stability of crucial
operational parameters, such as high voltage, temperature and electronic noise,
is summarised and the performance of the light monitoring system is presented
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