Effects of High Charge Densities in Multi-GEM Detectors

A comprehensive study, supported by systematic measurements and numerical computations, of the intrinsic limits of multi-GEM detectors when exposed to very high particle fluxes or operated at very large gains is presented. The observed variations of the gain, of the ion back-flow, and of the pulse height spectra are explained in terms of the effects of the spatial distribution of positive ions and their movement throughout the amplification structure. The intrinsic dynamic character of the processes involved imposes the use of a non-standard simulation tool for the interpretation of the measurements. Computations done with a Finite Element Analysis software reproduce the observed behaviour of the detector. The impact of this detailed description of the detector in extreme conditions is multiple: it clarifies some detector behaviours already observed, it helps in defining intrinsic limits of the GEM technology, and it suggests ways to extend them.Comment: 5 pages, 6 figures, 2015 IEEE Nuclear Science Symposiu

On the General Analytical Solution of the Kinematic Cosserat Equations

Based on a Lie symmetry analysis, we construct a closed form solution to the kinematic part of the (partial differential) Cosserat equations describing the mechanical behavior of elastic rods. The solution depends on two arbitrary analytical vector functions and is analytical everywhere except a certain domain of the independent variables in which one of the arbitrary vector functions satisfies a simple explicitly given algebraic relation. As our main theoretical result, in addition to the construction of the solution, we proof its generality. Based on this observation, a hybrid semi-analytical solver for highly viscous two-way coupled fluid-rod problems is developed which allows for the interactive high-fidelity simulations of flagellated microswimmers as a result of a substantial reduction of the numerical stiffness.Comment: 14 pages, 3 figure

SpBase: the sea urchin genome database and web site

SpBase is a system of databases focused on the genomic information from sea urchins and related echinoderms. It is exposed to the public through a web site served with open source software (http://spbase.org/). The enterprise was undertaken to provide an easily used collection of information to directly support experimental work on these useful research models in cell and developmental biology. The information served from the databases emerges from the draft genomic sequence of the purple sea urchin, Strongylocentrotus purpuratus and includes sequence data and genomic resource descriptions for other members of the echinoderm clade which in total span 540 million years of evolutionary time. This version of the system contains two assemblies of the purple sea urchin genome, associated expressed sequences, gene annotations and accessory resources. Search mechanisms for the sequences and the gene annotations are provided. Because the system is maintained along with the Sea Urchin Genome resource, a database of sequenced clones is also provided

Charge Transfer Properties Through Graphene Layers in Gas Detectors

Graphene is a single layer of carbon atoms arranged in a honeycomb lattice with remarkable mechanical, electrical and optical properties. For the first time graphene layers suspended on copper meshes were installed into a gas detector equipped with a gaseous electron multiplier. Measurements of low energy electron and ion transfer through graphene were conducted. In this paper we describe the sample preparation for suspended graphene layers, the testing procedures and we discuss the preliminary results followed by a prospect of further applications.Comment: 2014 IEEE Nuclear Science Symposium and Medical Imaging Conference with the 21st Symposium on Room-Temperature Semiconductor X-Ray and Gamma-Ray Detectors, 4 pages, 8 figure

Effect of boat noise on the behaviour of bluefin tuna Thunnus thynnus in the Mediterranean Sea

The effect of boat noise on the behaviour of bluefin tuna Thunnus thynnus was investigated in the Egadi Islands, Sicily, during spring 2005 using a fixed tuna trap set near shipping routes. Tuna behaviour was observed when exposed to both natural ambient sound and sound generated by hydrofoil passenger ferries, small boats and large car ferries. Acoustical and behavioural analyses were conducted with and without extraneous sound to define a list of behavioural categories. Each vessel produced different engine sounds with regard to their composition and bandwidth, and all were distinctly different from ambient sound levels. In the absence of boat noise, tuna assumed a concentrated coordinated school structure with unidirectional swimming and without a precise shape. When a car ferry approached, tuna changed swimming direction and increased their vertical movement toward surface or bottom; the school exhibited an unconcentrated structure and uncoordinated swimming behaviour. Hydrofoils appeared to elicit a similar response, but for shorter periods. Agonistic behaviour was more evident when exposed to sounds from outboard motors of small boats. This study showed that local noise pollution generated by boats produced behavioural deviations in tuna schools. Schooling enhances tuna homing accuracy during their spawning migration, and an alteration in schooling behaviour can affect the accuracy of their migration to spawning and feeding grounds

Mercury in fishes from Augusta Bay (southern Italy): Risk assessment and health implication

Our study reports on the total mercury (HgT) concentrations measured in the muscles and livers of several benthic, demersal and pelagic fish species caught inside and outside of Augusta Bay (southern Italy), a semi-enclosed marine area, highly contaminated by the uncontrolled (since the 1950s to 1978s) discharge of the largest European petrochemical plant. Mercury levels in fish tissues are discussed with regard to specific habitat, size and/or age of the specimens and HgT distribution in the bottom sediments. Results suggest a still active Hg release mechanism from the polluted sediments to the marine environment. Also, the high HgT concentrations measured in fishes caught in the external area of the bay imply a potential role of Augusta Bay as a pollutant source for the Mediterranean ecosystem. Finally, values of hazard target quotient (THQ) and estimated weekly intake (EWI) demonstrate that consumption of fishes caught inside the bay represents a serious risk for human health. Also, data indicate that intake of fishes caught from the external area of the bay, especially for that concern demersal and benthic species, could be represent a significant component of risk for the local population

Grip Force Reveals the Context Sensitivity of Language-Induced Motor Activity during “Action Words

Studies demonstrating the involvement of motor brain structures in language processing typically focus on \ud time windows beyond the latencies of lexical-semantic access. Consequently, such studies remain inconclusive regarding whether motor brain structures are recruited directly in language processing or through post-linguistic conceptual imagery. In the present study, we introduce a grip-force sensor that allows online measurements of language-induced motor activity during sentence listening. We use this tool to investigate whether language-induced motor activity remains constant or is modulated in negative, as opposed to affirmative, linguistic contexts. Our findings demonstrate that this simple experimental paradigm can be used to study the online crosstalk between language and the motor systems in an ecological and economical manner. Our data further confirm that the motor brain structures that can be called upon during action word processing are not mandatorily involved; the crosstalk is asymmetrically\ud governed by the linguistic context and not vice versa

EMRI_MC: A GPU-based code for Bayesian inference of EMRI waveforms

We describe a simple and efficient Python code to perform Bayesian forecasting for gravitational waves (GW) produced by Extreme-Mass-Ratio-Inspiral systems (EMRIs). The code runs on GPUs for an efficient parallelised computation of thousands of waveforms and sampling of the posterior through a Markov-Chain-Monte-Carlo (MCMC) algorithm. EMRI_MC generates EMRI waveforms based on the so--called kludge scheme, and propagates it to the observer accounting for cosmological effects in the observed waveform due to modified gravity/dark energy. Extending the code to more accurate schemes for the generation of the waveform is straightforward. Despite the known limitations of the kludge formalism, we believe that the code can provide a helpful resource for the community working on forecasts for interferometry missions in the milli-Hz scale, predominantly, the satellite-mission LISA.Comment: 14 pages, 2 figures, code available at https://doi.org/10.5281/zenodo.1020418

Construction and Performance of Large-Area Triple-GEM Prototypes for Future Upgrades of the CMS Forward Muon System

At present, part of the forward RPC muon system of the CMS detector at the CERN LHC remains uninstrumented in the high-\eta region. An international collaboration is investigating the possibility of covering the 1.6 < |\eta| < 2.4 region of the muon endcaps with large-area triple-GEM detectors. Given their good spatial resolution, high rate capability, and radiation hardness, these micro-pattern gas detectors are an appealing option for simultaneously enhancing muon tracking and triggering capabilities in a future upgrade of the CMS detector. A general overview of this feasibility study will be presented. The design and construction of small (10\times10 cm2) and full-size trapezoidal (1\times0.5 m2) triple-GEM prototypes will be described. During detector assembly, different techniques for stretching the GEM foils were tested. Results from measurements with x-rays and from test beam campaigns at the CERN SPS will be shown for the small and large prototypes. Preliminary simulation studies on the expected muon reconstruction and trigger performances of this proposed upgraded muon system will be reported.Comment: 7 pages, 25 figures, submitted for publication in conference record of the 2011 IEEE Nuclear Science Symposium, Valencia, Spai

THGEM-based detectors for sampling elements in DHCAL: laboratory and beam evaluation

We report on the results of an extensive R&D program aimed at the evaluation of Thick-Gas Electron Multipliers (THGEM) as potential active elements for Digital Hadron Calorimetry (DHCAL). Results are presented on efficiency, pad multiplicity and discharge probability of a 10x10 cm2 prototype detector with 1 cm2 readout pads. The detector is comprised of single- or double-THGEM multipliers coupled to the pad electrode either directly or via a resistive anode. Investigations employing standard discrete electronics and the KPiX readout system have been carried out both under laboratory conditions and with muons and pions at the CERN RD51 test beam. For detectors having a charge-induction gap, it has been shown that even a ~6 mm thick single-THGEM detector reached detection efficiencies above 95%, with pad-hit multiplicity of 1.1-1.2 per event; discharge probabilities were of the order of 1e-6 - 1e-5 sparks/trigger, depending on the detector structure and gain. Preliminary beam tests with a WELL hole-structure, closed by a resistive anode, yielded discharge probabilities of <2e-6 for an efficiency of ~95%. Methods are presented to reduce charge-spread and pad multiplicity with resistive anodes. The new method showed good prospects for further evaluation of very thin THGEM-based detectors as potential active elements for DHCAL, with competitive performances, simplicity and robustness. Further developments are in course.Comment: 15 pages, 11 figures, MPGD2011 conference proceedin