168 research outputs found

    Development of the readout electronics for the high luminosity upgrade of the CMS outer strip tracker

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    The High-luminosity upgrade of the LHC will deliver the dramatic increase in luminosity required for precision measurements and to probe Beyond the Standard Model theories. At the same time, it will present unprecedented challenges in terms of pileup and radiation degradation. The CMS experiment is set for an extensive upgrade campaign, which includes the replacement of the current Tracker with another all-silicon detector with improved performance and reduced mass. One of the most ambitious aspects of the future Tracker will be the ability to identify high transverse momentum track candidates at every bunch crossing and with very low latency, in order to include tracking information at the L1 hardware trigger stage, a critical and effective step to achieve triggers with high purity and low threshold. This thesis presents the development and the testing of the CMS Binary Chip 2 (CBC2), a prototype Application Specific Integrated Circuit (ASIC) for the binary front-end readout of silicon strip detectors modules in the Outer Tracker, which also integrates the logic necessary to identify high transverse momentum candidates by correlating hits from two silicon strip detectors, separated by a few millimetres. The design exploits the relation between the transverse momentum and the curvature in the trajectory of charged particles subject to the large magnetic field of CMS. The logic which follows the analogue amplification and binary conversion rejects clusters wider than a programmable maximum number of adjacent strips, compensates for the geometrical offset in the alignment of the module, and correlates the hits between the two sensor layers. Data are stored in a memory buffer before being transferred to an additional buffer stage and being serially read-out upon receipt of a Level 1 trigger. The CBC2 has been subject to extensive testing since its production in January 2013: this work reports the results of electrical characterization, of the total ionizing dose irradiation tests, and the performance of a prototype module instrumented with CBC2 in realistic conditions in a beam test. The latter is the first experimental demonstration of the Pt-selection principle central to the future of CMS. Several total-ionizing-dose tests highlighted no functional issue, but observed significant excess static current for doses <1 Mrad. The source of the excess was traced to static leakage current in the memory pipeline, and is believed to be a consequence of the high instantaneous dose delivered by the x-ray setup. Nevertheless, a new SRAM layout aimed at removing the leakage path was proposed for the CBC3. The results of single event upset testing of the chip are also reported, two of the three distinct memory circuits used in the chip were proven to meet the expected robustness, while the third will be replaced in the next iteration of the chip. Finally, the next version of the ASIC is presented, highlighting the additional features of the final prototype, such as half-strip resolution, additional trigger logic functionality, longer trigger latency and higher rate, and fully synchronous stub readout.Open Acces

    Human memory retrieval and inhibitory control in the brain: Beyond correlational evidence

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    Retrieving information from long-term memory can result in the episodic forgetting of related material. One influential account states that this retrieval-induced forgetting (RIF) phenomenon reflects inhibitory mechanisms called into play to decrease retrieval competition. Recent neuroimaging studies suggested that the prefrontal cortex, which is critically engaged in inhibitory processing, is also involved in retrieval competition situations. Here, we used transcranial direct current stimulation (tDCS) to address whether inhibitory processes could be causally linked to RIF. tDCS was administered over the right dorsolateral prefrontal cortex during the retrieval-practice phase in a standard retrieval-practice paradigm. Sixty human participants were randomly assigned to anodal, cathodal, or sham-control groups. The groups showed comparable benefits for practiced items. In contrast, unlike both the sham and anodal groups, the cathodal group exhibited no RIF. This pattern is interpreted as evidence for a causal role of inhibitory mechanisms in episodic retrieval and forgetting

    Assessing the effects of tDCS over a delayed response inhibition task by targeting the right inferior frontal gyrus and right dorsolateral prefrontal cortex

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    Many situations in our everyday life call for a mechanism deputed to outright stop an ongoing course of action. This behavioral inhibition ability, known as response stopping, is often impaired in psychiatric conditions characterized by impulsivity and poor inhibitory control. Transcranial direct current stimulation (tDCS) has recently been proposed as a tool for modulating response stopping in such clinical populations, and previous studies in healthy humans have already shown that this noninvasive brain stimulation technique is effectively able to improve response stopping, as measured in a stop-signal task (SST) administered immediately after the stimulation. So far, the right inferior frontal gyrus (rIFG) has been the main focus of these attempts to modulate response stopping by the means of noninvasive brain stimulation. However, other cortical areas such as the right dorsolateral prefrontal cortex (rDLPFC) have been implicated in inhibitory control with other paradigms. In order to provide new insight about the involvement of these areas in response stopping, in the present study, tDCS was delivered to 115 healthy subjects, using five stimulation setups that differed in terms of target area (rIFG or rDLPFC) and polarity of stimulation (anodal, cathodal, or sham). The SST was performed 15 min after the offset of the stimulation. Consistently with previous studies, only anodal stimulation over rIFG induced a reliable, although weak, improvement in the SST, which was specific for response stopping, as it was not mirrored in more general reaction time measures

    Continuous Queries and Real-time Analysis of Social Semantic Data with C-SPARQL

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    Abstract. Social semantic data are becoming a reality, but apparently their streaming nature has been ignored so far. Streams, being unbounded sequences of time-varying data elements, should not be treated as persistent data to be stored “forever ” and queried on demand, but rather as transient data to be consumed on the fly by queries which are registered once and for all and keep analyzing such streams, producing answers triggered by the streaming data and not by explicit invocation. In this paper, we propose an approach to continuous queries and realtime analysis of social semantic data with C-SPARQL, an extension of SPARQL for querying RDF streams

    Observations of field and cluster RR Lyræ with Spitzer. Towards high precision distances with Population II stellar tracers

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    Indexación: Scopus.We present our project to calibrate the RR Lyræ period-luminosity-metallicity relation using a sample of Galactic calibrators in the halo and globular clusters.https://www.epj-conferences.org/articles/epjconf/pdf/2017/21/epjconf_puls2017_07004.pd

    A Sub-Electron-Noise Multi-Channel Cryogenic Skipper-CCD Readout ASIC

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    The \emph{MIDNA} application specific integrated circuit (ASIC) is a skipper-CCD readout chip fabricated in a 65 nm LP-CMOS process that is capable of working at cryogenic temperatures. The chip integrates four front-end channels that process the skipper-CCD signal and performs differential averaging using a dual slope integration (DSI) circuit. Each readout channel contains a pre-amplifier, a DC restorer, and a dual-slope integrator with chopping capability. The integrator chopping is a key system design element in order to mitigate the effect of low-frequency noise produced by the integrator itself, and it is not often required with standard CCDs. Each channel consumes 4.5 mW of power, occupies 0.156 mm2{^2} area and has an input referred noise of 2.7μνrms{\mu\nu}_{rms}. It is demonstrated experimentally to achieve sub-electron noise when coupled with a skipper-CCD by means of averaging samples of each pixel. Sub-electron noise is shown in three different acquisition approaches. The signal range is 6000 electrons. The readout system achieves 0.2e−{e^{-}} RMS by averaging 1000 samples with MIDNA both at room temperature and at 180 Kelvin

    Correction to: Bone metabolism in patients with anorexia nervosa and amenorrhoea.

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    Unfortunately, the sixth author name was incorrectly spelled as "S. Fassio" instead of "A. Fassio" in the original publication
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