There are many ways to simulate handrim wheelchair propulsion in the laboratory. Ideally, these would be able to, at least mechanically, simulate field conditions. This narrative review provides an ...overview of the lab-based equipment used in published research and critically assesses their ability to simulate and measure wheelchair propulsion performance. A close connection to the field can only be achieved if the instrument can adequately simulate frictional losses and inertia of real-life handrim wheelchair propulsion, while maintaining the ergonomic properties of the wheelchair-user interface. Lab-based testing is either performed on a treadmill or a wheelchair ergometer (WCE). For this study WCEs were divided into three categories: roller, flywheel, and integrated ergometers. In general, treadmills are mechanically realistic, but cannot simulate air drag and acceleration tasks cannot be performed; roller ergometers allow the use of the personal wheelchair, but calibration can be troublesome; flywheel ergometers can be built with commercially-available parts, but inertia is fixed and the personal wheelchair cannot be used; integrated ergometers do not employ the personal wheelchair, but are suited for the implementation of different simulation models and detailed measurements. Lab-based equipment is heterogeneous and there appears to be little consensus on how to simulate field conditions.
The upgrade of the LHC to the High Luminosity LHC will challenge the silicon strip detector performance with high fluence and long operation time. Sensors have been designed and tests on charge ...collection and electrical performance have been carried out in order to evaluate their behaviour. Besides that, it is important to understand and predict the long-term evolution of the sensor properties. In this work, detailed studies on the annealing behaviour of ATLAS12 strip sensors designed by the ITK Strip Sensor Working Group and irradiated from 5×1013neqcm−2 to 2×1015neqcm−2 are presented. Systematic charge collection and leakage current measurements have been carried out during the annealing process until break-down or the appearance of charge multiplication. The annealing was carried out, separating the sensors into two groups being either annealed at 23°C or 60°C. Sensors showing charge multiplication have been then kept at high voltage for a long time in order to monitor their stability. The difference in the annealing behaviour between the two temperatures has been analysed and compared to similar measurements on n-type sensors and with a theoretical model. From the impedance measurements for the samples irradiated to low fluences it was possible to extract the effective doping concentration. This was compared to similar measurements on n-type sensors and with a theoretical model.
Abstract
Collider experiments as the upcoming Phase II-LHC or the future circular collider (FCC) will increase the demands on tracking detectors. In the FCC hadron collider, sensors will not only ...face fluences up to 1 × 10
17
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/cm
2
, but also high pile-up scenarios. Therefore, sensors will be required not only to have a good spatial resolution and a very high radiation hardness, but also an excellent time resolution of the order of 5 ps. Currently, Low Gain Avalanche Diodes (LGADs) are one of the main candidates when it comes to timing, achieving a resolution well below 30 ps. However, their radiation hardness is not sufficient for future colliders. 3D sensors are an interesting alternative due to their superior radiation hardness. In 3D sensors, which already have been thoroughly investigated for tracking purposes, the drift distances are short, the depletion voltage is very low and the electric field can be very high, thus the signals are fast and short.
In this study, the time resolution of different 3D sensors was investigated with signals generated by MIP-like electrons, as well as by measurements using a laser with an infrared wavelength. It is shown that 3D pixel sensors can achieve time resolutions competitive with those of LGADs. Additionally, Transient Current Technique (TCT) timing measurements have been conducted. These allow to study the position dependence of the time resolution, which is interesting for 3D sensors due to their complex electric field structure. The measurements prove the direct correlation between the time resolution and the electric field configuration. Furthermore, the performance of the sensors is demonstrated before and after irradiation with reactor neutrons.
AbstractThe potential for the discovery of a Standard Model Higgs boson in the mass range mH < 2 mZ in the vector boson fusion mode has been studied for the ATLAS experiment at the LHC. The ...characteristic signatures of additional jets in the forward regions of the detector and of low jet activity in the central region allow for an efficient background rejection. Analyses for the H → WW(*) and H → ττ decay modes have been performed using a realistic simulation of the expected detector performance. The results obtained demonstrate the large discovery potential in the H → WW(*) decay channel and the sensitivity to Higgs boson decays into τ-pairs in the low-mass region around 120 GeV/c2.
This study investigates the charge collection efficiency of silicon strip detectors, produced by MICRON Semiconductor Co., Ltd. within the CERN RD50 collaboration, designed specifically to understand ...the effect of design parameters on the onset and magnitude of charge multiplication. Charge collection measurements are performed before and after irradiation with a proton fluence of 1×1015 1MeVneq/cm2 (neq/cm2) and neutron fluence ranging from 1–5×1015neq/cm2. Structures on these devices include varying diffusion times and energies for the implantation process, different sensor thicknesses, the use of intermediate biased or floating strips between the readout strips, and several different strip width and pitch geometries. The charge collection for these devices is studied as a function of the bias voltage, looking for indications of charge multiplication. Results are compared to standard float zone 300μm thick silicon strip sensors having a strip width of 25μm and pitch of 80μm.
•Specially designed silicon detectors were developed to investigate charge multiplication.•Charge collection measurements were performed before and after irradiation.•Charge multiplication only seen ≥5×1015neq/cm2.•Decreasing width/pitch increases collected charge.•Increasing implant energy/diffusion time increased collected charge.
We discuss the physics potential and the experimental challenges of an upgraded LHC running at an instantaneous luminosity of 1035 cm-2s-1. The detector R&D needed to operate ATLAS and CMS in a very ...high radiation environment and the expected detector performance are discussed. A few examples of the increased physics potential are given, ranging from precise measurements within the Standard Model (in particular in the Higgs sector) to the discovery reach for several New Physics processes.
The new silicon microstrip sensors of the End-cap part of the HL-LHC ATLAS Inner Tracker (ITk) present a number of challenges due to their complex design features such as the multiple different ...sensor shapes, the varying strip pitch, or the built-in stereo angle. In order to investigate these specific problems, the “petalet” prototype was defined as a small End-cap prototype. The sensors for the petalet prototype include several new layout and technological solutions to investigate the issues, they have been tested in detail by the collaboration. The sensor description and detailed test results are presented in this paper. New software tools have been developed for the automatic layout generation of the complex designs. The sensors have been fabricated, characterized and delivered to the institutes in the collaboration for their assembly on petalet prototypes. This paper describes the lessons learnt from the design and tests of the new solutions implemented on these sensors, which are being used for the full petal sensor development. This has resulted in the ITk strip community acquiring the necessary expertise to develop the full End-cap structure, the petal.
Stimulation of phosphoinositide-hydrolysing phospholipase C (PLC) generating inositol-1,4,5-trisphosphate is a major calcium signalling pathway used by a wide variety of membrane receptors, ...activating distinct PLC-β or PLC-γ isoforms. Here we report a new PLC and calcium signalling pathway that is triggered by cyclic AMP (cAMP) and mediated by a small GTPase of the Rap family. Activation of the adenylyl cyclase-coupled β2-adrenoceptor expressed in HEK-293 cells or the endogenous receptor for prostaglandin E1 in N1E-115 neuroblastoma cells induced calcium mobilization and PLC stimulation, seemingly caused by cAMP formation, but was independent of protein kinase A (PKA). We provide evidence that these receptor responses are mediated by a Rap GTPase, specifically Rap2B, activated by a guanine-nucleotide-exchange factor (Epac) regulated by cAMP, and involve the recently identified PLC- isoform.
Celotno besedilo
Dostopno za:
DOBA, IJS, IZUM, KILJ, NUK, PILJ, PNG, SAZU, UILJ, UKNU, UL, UM, UPUK
The ATLAS detector is a general purpose experiment designed to fully exploit the discovery potential of the Large Hadron Collider (LHC) at a nominal luminosity of 10
34
cm
−2
s
−1. It is expected ...that after several years of successful data-taking, the LHC physics program will be extended by increasing the peak luminosity by one order of magnitude. For ATLAS, an upgrade scenario will imply the complete replacement of the Inner Detector (ID), since the current tracker will not provide the required performance due to cumulated radiation damage and a dramatic increase in the detector occupancy.
In this paper, a proposal of a double-sided silicon micro-strip module for the short-strip region of the future ATLAS ID is presented. The expected thermal performance based upon detailed FEA simulations is discussed. First electrical results from a prototype version of the next generation readout front-end chips are also shown.
Sphingolipids such as sphingosine‐1‐phosphate (SPP) and sphingosylphosphorylcholine (SPPC) can act both intracellularly and at G‐protein‐coupled receptors, some of which were cloned and designated as ...Edg‐receptors.
Sphingolipid‐induced vascular effects were determined in isolated rat mesenteric and intrarenal microvessels. Additionally, sphingolipid‐induced elevations in intracellular Ca2+ concentration were measured in cultured rat aortic smooth muscle cells.
SPPC and SPP (0.1–100 μmol l−1) caused concentration‐dependent contraction of mesenteric and intrarenal microvessels (e.g. SPPC in mesenteric microvessels pEC50 5.63±0.17 and Emax 49±3% of noradrenaline), with other sphingolipids being less active. The vasoconstrictor effect of SPPC in mesenteric microvessels was stereospecific (pEC50 D‐erythro‐SPPC 5.69±0.08, L‐threo‐SPPC 5.31±0.06) and inhibited by pretreatment with pertussis toxin (Emax from 44±5 to 19±4%), by chelation of extracellular Ca2+ with EGTA and by nitrendipine (Emax from 40±6 to 6±1 and 29±6%, respectively). Mechanical endothelial denudation or NO synthase inhibition did not alter the SPPC effects, while indomethacin reduced them (Emax from 87±3 to 70±4%).
SPP and SPPC caused transient increases in intracellular Ca2+ concentrations in rat aortic smooth muscle cells in a pertussis toxin‐sensitive manner.
Our data demonstrate that SPP and SPPC cause vasoconstriction of isolated rat microvessels and increase intracellular Ca2+ concentrations in cultured rat aortic smooth muscle cells. These effects appear to occur via receptors coupled to pertussis toxin‐sensitive G‐proteins. This is the first demonstration of effects of SPP and SPPC on vascular tone and suggests that sphingolipids may be an hitherto unrecognized class of endogenous regulators of vascular tone.
British Journal of Pharmacology (2000) 130, 1871–1877; doi:10.1038/sj.bjp.0703515
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