2,452 research outputs found
The second generation of optimized beam orbit measurement (BOM) system of LEP: hardware and performance description
The BOM System with its 504 Beam Position Monitors and 40 Processing Electronics Stations, distributed along the 27 km of the LEP tunnel, has been optimized for all beam conditions and modes of operation. The description of the Beam Position Monitors (or PU) behavior in the tunnel is given. The guiding approaches for obtaining both main aspects of the critical BOM performances were: a) high reliability, since most of the electronics is not accessible during operation, and b) resolution, precision and stability of the signal processing equipment for the management of the LEP optics, polarization and energy calibration. The finalized analog signal processing chains, both Wide-Band and Narrow-Band, are described. Since local memories allow for the recording of data at each bunch passage during more than 1000 revolutions, it can be followed by a powerful digital signal processing allowing for many modes of beam observation. Examples are presented of beam and machine behavior studies. The BOM System has been a key instrument for the success of LEP operation
Crystal to Liquid-Crystal Transition Studied by Raman Scattering
Phase transitions of the nematic liquid crystal p-methoxy-benzylidine, pân butyl-aniline were studied by recording the low-frequency Raman spectrum. The intensity of the lattice Raman bands undergoes abrupt change at the crystalline-to-nematic phase transition temperature, with an indication of a hysteresis. The band totally disappears at the isotropic (liquid) phase
Impact of alpha-tocopherol deficiency and supplementation on sacrocaudalis and gluteal muscle fiber histopathology and morphology in horses.
BackgroundA subset of horses deficient in alpha-tocopherol (α-TP) develop muscle atrophy and vitamin E-responsive myopathy (VEM) characterized by mitochondrial alterations in the sacrocaudalis dorsalis medialis muscle (SC).ObjectivesTo quantify muscle histopathologic abnormalities in subclinical α-TP deficient horses before and after α-TP supplementation and compare with retrospective (r)VEM cases.AnimalsProspective study; 16 healthy α-TP-deficient Quarter Horses. Retrospective study; 10 retrospective vitamin E-responsive myopathy (rVEM) cases .MethodsBlood, SC, and gluteus medius (GM) biopsy specimens were obtained before (day 0) and 56âdays after 5000âIU/450âkg horse/day PO water dispersible liquid α-TP (n = 8) or control (n = 8). Muscle fiber morphology and mitochondrial alterations were compared in samples from days 0 and 56 and in rVEM cases.ResultsMitochondrial alterations more common than our reference range (<2.5% affected fibers) were present in 3/8 control and 4/8 treatment horses on day 0 in SC but not in GM (mean, 2.2; range, 0%-10% of fibers). Supplementation with α-TP for 56âdays did not change the percentage of fibers with mitochondrial alterations or anguloid atrophy, or fiber size in GM or SC. Clinical rVEM horses had significantly more mitochondrial alterations (rVEM SC, 13%â±â7%; GM, 3%â±â2%) and anguloid atrophy compared to subclinical day 0 horses.Conclusions and clinical importanceClinically normal α-TP-deficient horses can have mitochondrial alterations in the SC that are less severe than in atrophied VEM cases and do not resolve after 56âdays of α-TP supplementation. Preventing α-TP deficiency may be of long-term importance for mitochondrial viability
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Mobile robot operator for downstream Oil & Gas industrial facilities
This thesis considers the application of robots in downstream Oil & Gas facilities. Automation is important in industrial facilities where improvements in safety, efficiency, and environmental performance are becoming increasingly important. Here we present a mobile robotic platform for the performance of inspection and survey tasks in downstream facilities. We demonstrate a hybrid localization strategy using a novel metric which allows for long term autonomy in large distributed industrial environments. An environmental sensing package and gas source localization algorithm are deployed on the platform to identify and localize fugitive emission sources. Our mobile robotic platform, hybrid localization strategy, and gas source localization algorithm form an autonomous remote operator capable of meaningfully contributing to the advancement of automation in industrial facilities.Mechanical Engineerin
The effects of mismatches on hybridization in DNA microarrays: determination of nearest neighbor parameters
Quantifying interactions in DNA microarrays is of central importance for a
better understanding of their functioning. Hybridization thermodynamics for
nucleic acid strands in aqueous solution can be described by the so-called
nearest-neighbor model, which estimates the hybridization free energy of a
given sequence as a sum of dinucleotide terms. Compared with its solution
counterparts, hybridization in DNA microarrays may be hindered due to the
presence of a solid surface and of a high density of DNA strands. We present
here a study aimed at the determination of hybridization free energies in DNA
microarrays. Experiments are performed on custom Agilent slides. The solution
contains a single oligonucleotide. The microarray contains spots with a perfect
matching complementary sequence and other spots with one or two mismatches: in
total 1006 different probe spots, each replicated 15 times per microarray. The
free energy parameters are directly fitted from microarray data. The
experiments demonstrate a clear correlation between hybridization free energies
in the microarray and in solution. The experiments are fully consistent with
the Langmuir model at low intensities, but show a clear deviation at
intermediate (non-saturating) intensities. These results provide new
interesting insights for the quantification of molecular interactions in DNA
microarrays.Comment: 31 pages, 5 figure
The functional role of biodiversity in ecosystems: incorporating trophic complexity
Understanding how biodiversity affects functioning of ecosystems requires integrating diversity within trophic levels (horizontal diversity) and across trophic levels (vertical diversity, including food chain length and omnivory). We review theoretical and experimental progress toward this goal. Generally, experiments show that biomass and resource use increase similarly with horizontal diversity of either producers or consumers. Among prey, higher diversity often increases resistance to predation, due to increased probability of including inedible species and reduced efficiency of specialist predators confronted with diverse prey. Among predators, changing diversity can cascade to affect plant biomass, but the strength and sign of this effect depend on the degree of omnivory and prey behaviour. Horizontal and vertical diversity also interact: adding a trophic level can qualitatively change diversity effects at adjacent levels. Multitrophic interactions produce a richer variety of diversityâfunctioning relationships than the monotonic changes predicted for single trophic levels. This complexity depends on the degree of consumer dietary generalism, tradeâoffs between competitive ability and resistance to predation, intraguild predation and openness to migration. Although complementarity and selection effects occur in both animals and plants, few studies have conclusively documented the mechanisms mediating diversity effects. Understanding how biodiversity affects functioning of complex ecosystems will benefit from integrating theory and experiments with simulations and networkâbased approaches
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