The Future of RICH Detectors through the Light of the LHCb RICH

The limitations in performance of the present RICH system in the LHCb experiment are given by the natural chromatic dispersion of the gaseous Cherenkov radiator, the aberrations of the optical system and the pixel size of the photon detectors. Moreover, the overall PID performance can be affected by high detector occupancy as the pattern recognition becomes more difficult with high particle multiplicities. This paper shows a way to improve performance by systematically addressing each of the previously mentioned limitations. These ideas are applied in the present and future upgrade phases of the LHCb experiment. Although applied to specific circumstances, they are used as a paradigm on what is achievable in the development and realisation of high precision RICH detectors

Analysis and correction of the magnetic field effects in the Hybrid Photo-Detectors of the RICH2 Ring Imaging Cherenkov detector of LHCb

The Ring Imaging Cherenkov detectors of the LHCb experiment at the Large Hadron Collider at CERN are equipped with Hybrid Photo-Detectors. These vacuum photo-detectors are affected by the stray magnetic field of the LHCb magnet, which degrades their imaging properties. This effect increases the error on the Cherenkov angle measurement and would reduce the particle identification capabilities of LHCb. A system has been developed for the RICH2 Ring Imaging Cherenkov detector to perform a detailed characterisation of the magnetic distortion effects. It is described, along with the methods implemented to correct for these effects, restoring the optimal resolution.Comment: 16 pages, 11 figure

Genetic diversity of Amblyomma variegatum (Acari:Ixodidae), the main vector of Ehrlichia ruminantium in Indian Ocean Islands

The hard ticks Amblyomma variegatum is the main vector of Ehrlichia ruminantium which is the pathogen responsible for heartwater or cowdriosis, a disease of ruminants. This tick originates from sub-Saharan Africa and is now widely widespread. A. variegatum has been described in 1899 for the first time in Madagascar, but its introduction is probably older and very likely concomitant with livestock introduction from Africa. A. variegatum has also been described in the Comoros, Mayotte, La Reunion and Mauritius islands. The aim of this study was to investigate the genetic and demographic phenomena that have shaped the present distribution and structure of A. variegatum populations in the Indian Ocean area. A first phylogeographic approach has been carried out, by analysing two mitochondrial-DNA genes at an intra-specific level through the analysis of tick samples from Madagascar and from the other Indian Ocean Islands included in this study. These samples have been compared to samples from Africa, where this species is originated from, and samples from the French West Indies where A. variegatum was introduced around the 18th century. This study will help to elucidate A. variegatum introduction history in the different Indian Ocean Islands. A population genetics approach, using microsatellite markers, focused on Madagascar and some other islands (La Reunion, Comoros and Mayotte islands), has given an insight into the present population structure. This study has led to two main lineages identification: one covering all the species distribution and one restricted to East Africa and Indian Ocean area. These two lineages are in sympatry in Madagascar. The results seemed to be in keeping with the historical data concerning the introduction of the tick in the Indian Ocean area. In Madagascar, a high genetic diversity has been described whereas a lower genetic diversity is observed in the other islands. In Madagascar tick populations are clearly structured but in a heterogeneous way. This structure is probably shaped by the complex interaction of geographic, climatic and anthropic factors. (Texte intégral

Intracellular targeting and functional analysis of single-chain Fv fragments in mammalian cells

In the past decade, intracellular antibodies have proven to be a useful tool in obtaining the phenotypic knock-out of selected gene function in different animal and plant systems. This strategy is based on the ectopic expression of recombinant forms of antibodies targeted towards different intracellular compartments, exploiting specific targeting signals to confer the new intracellular location. The functional basis of this technology is closely linked to the ability of intracellular antibodies to interact with their target antigens in vivo. This interaction allows either a direct neutralising effect or the dislodgement of the target protein from its normal intracellular location and, by this mechanism, the inactivation of its function. By using this approach, the function of several antigens has been inhibited in the cytoplasm, the nucleus, and the secretory compartments. In this article, we shall describe all the steps required for expressing single-chain Fv fragments in different subcellular compartments of mammalian cells and their subsequent use in knock-out experiments, starting from a cloned single-chain Fv fragment. This will include the analysis of the solubility properties of the new scFv fragment in transfected mammalian cells, the intracellular distribution of the antigen-antibody complex, and the resulting phenotype

Upper limb vibration prototype with sports and rehabilitation applications : development, evaluation and preliminary study

Acknowledgment: This work was supported by the North East of Scotland Technology Seed Fund (NESTech) grant from Scottish Funding Council (SFC)Peer reviewedPublisher PD

A mechanistic model linking insect (Hydropsychidae) silk nets to incipient sediment motion in gravel‐bedded streams

Plants and animals affect stream morphodynamics across a range of scales, yet including biological traits of organisms in geomorphic process models remains a fundamental challenge. For example, laboratory experiments have shown that silk nets built by caddisfly larvae (Trichoptera: Hydropsychidae) can increase the shear stress required to initiate bed motion by more than a factor of 2. The contributions of specific biological traits are not well understood, however. Here we develop a theoretical model for the effects of insect nets on the threshold of sediment motion, τ * crit , that accounts for the mechanical properties, geometry, and vertical distribution of insect silk, as well as interactions between insect species. To parameterize the model, we measure the tensile strength, diameter, and number of silk threads in nets built by two common species of caddisfly, Arctopsyche californica and Ceratopsyche oslari . We compare model predictions with new measurements of τ * crit in experiments where we varied grain size and caddisfly species composition. The model is consistent with experimental results for single species, which show that the increase in τ * crit above the abiotic control peaks at 40–70% for 10–22 mm sediments and declines with increasing grain size. For the polyculture experiments, however, the model underpredicts the measured increase in τ * crit when two caddisfly species are present in sediments of larger grain sizes. Overall, the model helps explain why the presence of caddisfly silk can substantially increase the forces needed to initiate sediment motion in gravel‐bedded streams and also illustrates the challenge of parameterizing the behavior of multiple interacting species in a physical model. Key Points Caddisfly silk nets are incorporated into a model of incipient sediment motion Silk nets increase critical shear stress in gravel‐bedded streams Species‐specific silk and behaviors control the range of grain sizes affectedPeer Reviewedhttp://deepblue.lib.umich.edu/bitstream/2027.42/109329/1/jgrf20303.pd

Une Approche filière pour limiter les risques d'infection par Salmonella des consommateurs des produits de volaille à la Réunion

A la Réunion, la production de volailles est en constante augmentation malgré la menace perpétuelle de nombreuses pathologies et notamment le spectre du virus H5N1. La viande de poulet représente les apports majeurs en protéines animales des consommateurs réunionnais. Ces derniers, caractérisés par une multiplicité culturelle et religieuse, sont notamment très friands de charcuterie 100% volaille comme certaines saucisses ou pâtés à consommer quasiment crus. Or, les poulets de chair sont souvent infectés par Salmonella spp.,une des deux bactéries les plus incriminées dans les toxi-infections alimentaires dans le monde. Outre le problème de santé publique, la présence de cette bactérie constitue aussi un péril économique pour la filière avicole. L'objectif général de notre étude est donc d'identifier les mesures spécifiques pour limiter la contamination des produits avicoles par Salmonella spp. offerts aux consommateurs réunionnais. Nos objectifs spécifiques sont d'évaluer (1) d'évaluer le niveau d'infection des volailles et de contamination des produits avicoles, (2) de confirmer si la consommation de produits avicoles peut avoir un impact sur la santé du consommateur (3) d'identifier les facteurs de risque majeurs d'infection des volailles ou de contamination des produits pour prendre les mesures correctives. En fin de période d'élevage, plus de 22% des bandes (60 élevages enquêtés) sont infectés par Salmonella spp. avec quatre sérovars majoritaires S. Blockley, S. Typhimurium, S. Virchow et S. Livingstone. En fin d'abattoir, 56% des lots de carcasses (110 lots prélevés) sont contaminés avec S. Blockley S. Typhimurium, S. Virchow et S. Hadar comme sérovars majeurs. L'électrophorèse à champs pulsés nous a permis de comparer les souches de Salmonella spp. isolées chez la volaille ou ses produits, l'environnement et chez l'homme. Les souches humaines proviennent de patients présentant une diarrhée aigue nécessitant un prélèvement ou une hospitalisation. Cette méthode met en évidence une proximité génétique (plus de 80% d'homologie) entre les souches animales et humaines au sein des sérovars majoritaires. Enfin, les facteurs de risque d'infection des volailles ont été déterminés : proximité des champs de cannes (OR=7.92; [1.10;90.05]), statut de la bande précédente vis à vis de Salmonella (OR=6.89; [1.30;36.45]), age des poulaillers (OR=5.36; [1.20;29.52]) et administration d'antibiotiques aux poussins d'un jour sont associés avec un risque élevé d'infection par Salmonella. Néanmoins, l'application rigoureuse des étapes de nettoyage et désinfection peuvent réduire le risqué d'infection (OR=0.05; [0.01;0.79]). Ces résultats permettent de prendre les mesures prioritaires pour lutter plus efficacement contre les contaminations liées aux salmonelles dans la filière volaille à la Réunion. Ils confirment aussi la nécessité de maintenir une surveillance des contaminations bactériennes potentiellement liées aux productions animales et de renforcer celle-ci par rapport aux phénomènes de résistance aux antibiotiques. (Texte intégral

How Does Restored Habitat For Chinook Salmon ( Oncorhynchus Tshawytscha ) In The Merced River In California Compare With Other Chinook Streams?

The amount of time and money spent on restoring rivers for declining populations of salmon has grown substantially in recent decades. But despite the infusion of resources, many studies suggest that salmon populations are continuing to decline, leading some to question the effectiveness of restoration efforts. Here we examine whether a particular form of salmon restoration—channel reconfiguration with gravel augmentation—generates physical and biological habitat that is comparable with other streams that support salmon. We compared a suite of habitat features known to influence the various life stages of Chinook salmon in a restoration project in California's Merced River with 19 other streams that also support Chinook that we surveyed in the same geographic region. Our survey showed that riffle habitats in the restored site of the Merced River have flow discharge and depth, substrate and food web characteristics that cannot be distinguished from other streams that support Chinook, suggesting that these factors are unlikely to be bottlenecks to salmon recovery in the Merced. However, compared with other streams in the region, the Merced has minimal riparian cover, fewer undercut banks, less woody debris and higher water temperatures, suggesting that these factors might limit salmon recovery. After identifying aspects in the Merced that differ from other streams, we used principal components analysis to correlate salmon densities to independent axes of environmental variation measured during our survey. These analyses suggested that salmon densities tend to be greatest in streams that have more undercut banks and woody debris and lower water temperatures. These are the same environmental factors that appear to be missing from the Merced River restoration effort. Collectively, our results narrow the set of candidate factors that may limit salmon recovery in channel reconfiguration restoration efforts. Copyright © 2012 John Wiley & Sons, Ltd.Peer Reviewedhttp://deepblue.lib.umich.edu/bitstream/2027.42/97512/1/rra1604.pd

Miglustat Reverts the Impairment of Synaptic Plasticity in a Mouse Model of NPC Disease

Niemann-Pick type C disease is an autosomal recessive storage disorder, characterized by abnormal sequestration of unesterified cholesterol within the late endolysosomal compartment of cells and accumulation of gangliosides and other sphingolipids. Progressive neurological deterioration and insurgence of symptoms like ataxia, seizure, and cognitive decline until severe dementia are pathognomonic features of the disease. Here, we studied synaptic plasticity phenomena and evaluated ERKs activation in the hippocampus of BALB/c NPC1-/- mice, a well described animal model of the disease. Our results demonstrated an impairment of both induction and maintenance of long term synaptic potentiation in NPC1-/- mouse slices, associated with the lack of ERKs phosphorylation. We then investigated the effects of Miglustat, a recent approved drug for the treatment of NPCD. We found that in vivo Miglustat administration in NPC1-/- mice was able to rescue synaptic plasticity deficits, to restore ERKs activation and to counteract hyperexcitability. Overall, these data indicate that Miglustat may be effective for treating the neurological deficits associated with NPCD, such as seizures and dementia