11,492 research outputs found

    RPCs as trigger detector for the ATLAS experiment: performances, simulation and application to the level-1 di-muon trigger

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    In the muon spectrometer different detectors are used to provide trigger functionality and precision momentum measurements. In the pseudorapidity range |eta|<1 the first level muon trigger is based on Resistive Plate Chambers, gas ionization detectors which are characterized by a fast response and an excellent time resolution (<1.5ns). The working principles of the Resistive Plate Chambers will be illustrated in chapter 3. Given the long time of operation expected for the ATLAS experiment (~10 years), ageing phenomena have been carefully studied, in order to ensure stable long-term operation of all the subdetectors. Concerning Resistive Plate Chambers, a very extensive ageing test has been performed at CERN's Gamma Irradiation Facility on three production chambers. The results of this test are presented in chapter 4. One of the most commonly used gases in RPCs operation is C2H2F4, which during the gas discharge can produce fluorine ions. Being F one of the most aggressive elements in nature, the presence of F- ions on the plate surface is dangerous for the integrity of the surface itself. For this reason a significant effort has been put in the last years to understand the mechanisms of F- production in RPCs operated with C2H2F4-based gas mixtures. The results of the measurements performed in the INFN-Roma2 ATLAS laboratories, in collaboration with the Dept. of Science and Chemical Technology of the Univeristy of Rome "Tor Vergata", are presented in chapter 5. The old Geant3 software toolkit, which has been the de facto standard for high energy physics simulation in the last 15 years, is being progressively replaced by the completely re-written toolkit Geant4. The migration from Geant3 to Geant4 has required, in the case of the ATLAS experiment, a re-writing from scratch of most of the simulation software. In chapter 6 the work done on RPC Geant4 simulation will be described. Many interesting physics processes to be observed in ATLAS will be characterized by the presence of pairs of muons in the final state. For this reason, the ATLAS first level muon trigger has been designed to allow to select di-muon events. While foreseen in the design of the trigger system, this possibility was never intensively tested with the final detector layout. In chapter 7 the first results of such a test will be summarized

    Measurement of W/Z cross-sections in the ATLAS experiment

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    The propects for the measurements of the production cross-section for W and Z bosons in the ATLAS experiment will be briefly presented here, together with a discussion on the strategy for controlling the main sytematic effects

    Analysis of the isolation valve system in water distribution networks using the segment graph

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    The mechanical reliability of Water Distribution Networks (WDNs) is a relevant technical and scientific issue. During planned maintenance or unplanned interruptions, the affected area must be isolated by valves shutdown. This operation involves the alteration of the network structure, i.e., the domain of the hydraulic system, and for this reason the isolation valve system plays a central role. Some studies started to consider the presence of the isolation valve system in WDNs reliability analysis. Accordingly, this work uses the Complex Network Theory to analyse the isolation valve system performance and to assess the importance of the segments generated by valves shutdown. Differently from the classic complex network theory approach, in this work the recently proposed WDN-relevance-based betweenness centrality is applied to the segment graph to introduce information about the relevance of the different elements into the network, considering geometric and hydraulic parameters, such as length, demand, risk of disconnection, etc. The proposed strategy also suggests an improvement in the representation of the segment graph with respect to the presence of parallel edges. The strategy is presented using a small network, while it is demonstrated and discussed using a real WDN. The results indicate that the WDN-relevance-based betweenness centrality allows to effectively assess the importance of the segments generated by valves shutdowns, also providing indications to improve the isolation valve system design

    Diversity of cervical microbiota in asymptomatic chlamydia trachomatis genital infection: a pilot study

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    Chlamydia trachomatis genital infection continues to be an important public health problem worldwide due to its increasing incidence. C. trachomatis infection can lead to severe sequelae, such as pelvic inflammatory disease, obstructive infertility, and preterm birth. Recently, it has been suggested that the cervico-vaginal microbiota may be an important defense factor toward C. trachomatis infection as well as the development of chronic sequelae. Therefore, the investigation of microbial profiles associated to chlamydial infection is of the utmost importance. Here we present a pilot study aiming to characterize, through the metagenomic analysis of sequenced 16s rRNA gene amplicons, the cervical microbiota from reproductive age women positive to C. trachomatis infection. The main finding of our study showed a marked increase in bacterial diversity in asymptomatic C. trachomatis positive women as compared to healthy controls in terms of Shannon's diversity and Shannon's evenness (P = 0.031 and P = 0.026, respectively). More importantly, the cervical microbiota from C. trachomatis positive women and from healthy controls significantly separated into two clusters in the weighted UniFrac analysis (P = 0.0027), suggesting that differences between the two groups depended entirely on the relative abundance of bacterial taxa rather than on the types of bacterial taxa present. Furthermore, C. trachomatis positive women showed an overall decrease in Lactobacillus spp. and an increase in anaerobes. These findings are part of an ongoing larger epidemiological study that will evaluate the potential role of distinct bacterial communities of the cervical microbiota in C. trachomatis infection

    Development and reproduction of Cataclysta lemnata, a potential natural enemy of the invasive alien duckweed Lemna minuta in Italy

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    Life cycle of the aquatic moth Cataclysta lemnata (Lepidoptera: Crambidae) was studied in laboratory conditions to obtain a basic biological knowledge useful for predicting the possible success of the herbivorous larvae of this insect as potential control agents in limiting the spread of the invasive American duckweed Lemna minuta (Alismatales: Araceae) in Italy. The multivoltinism of C. lemnata, as well as the high overall emergence from the pupal stage (85%), the high success in mating among the formed couples (>90%), and the high number of larvae born from each egg laying (on average 310 individuals), suggest that the insect can be successfully bred in the laboratory for the purposes of an augmentative biological control. Under experimental conditions, larvae developed in 23 days (through six larval instars, distinguishable by cephalic capsule dimensions) and pupae in 10, with no difference in duration between females and males. The larval phase resulted longer than the adult one (23 vs 10 days), therefore it can be considered the most suitable stage for releasing the insect in field for biocontrol purposes. Indeed, the larvae having a herbivorous diet might consume large amount of the invasive plant, contrarily to the adult phase which is focused exclusively on reproduction. The results emerged not only allow to contribute to the knowledge on aquatic lepidoptera that are scarcely known, but also support the effectiveness of a possible protocol for an augmentative biological control of the invasive alien duckweed L. minuta

    Kaon physics with the KLOE detector

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    In this paper we discuss the recent finalized analyses by the KLOE experiment at DAΦ\PhiNE: the CPT and Lorentz invariance test with entangled K0Kˉ0K^0 \bar{K}^0 pairs, and the precision measurement of the branching fraction of the decay K+→π+π−π+(γ){ K^+} \rightarrow \pi^+\pi^-\pi^+(\gamma). We also present the status of an ongoing analysis aiming to precisely measure the K±K^{\pm} mass
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