1,530 research outputs found
Concept of a novel fast neutron imaging detector based on THGEM for fan-beam tomography applications
The conceptual design and operational principle of a novel high-efficiency,
fast neutron imaging detector based on THGEM, intended for future fan-beam
transmission tomography applications, is described. We report on a feasibility
study based on theoretical modeling and computer simulations of a possible
detector configuration prototype. In particular we discuss results regarding
the optimization of detector geometry, estimation of its general performance,
and expected imaging quality: it has been estimated that detection efficiency
of around 5-8% can be achieved for 2.5MeV neutrons; spatial resolution is
around one millimeter with no substantial degradation due to scattering
effects. The foreseen applications of the imaging system are neutron tomography
in non-destructive testing for the nuclear energy industry, including
examination of spent nuclear fuel bundles, detection of explosives or drugs, as
well as investigation of thermal hydraulics phenomena (e.g., two-phase flow,
heat transfer, phase change, coolant dynamics, and liquid metal flow).Comment: 11 Pages; 6 Figures; Proceeding of the International Workshop on Fast
Neutron Detectors and Application FNDA2011, Ein Gedi, Israel, November 2011.
Published on the Journal of Instrumentation; 2012 JINST 7 C0205
Clinical significance of epithelial-to-mesenchymal transition in laryngeal carcinoma: Its role in the different subsites
Background: During epithelial-to-mesenchymal transition, cancer cells lose adhesion capacity gaining migratory properties. The role of the process on prognosis has been evaluated in 50 cases of laryngeal carcinoma. Methods: E-cadherin, N-cadherin, ÎČ-catenin, α-catenin, Îł-catenin, caveolin-1, and vimentin immunohistochemical expression were evaluated using a double score based on staining intensity and cellular localization. Results: Cytoplasmic E-cadherin and α/Îł catenin staining were associated with a decrease in survival, cytoplasmic ÎČ-catenin was associated with advanced stage, and N-cadherin and vimentin expression were associated with poor differentiation and tumor relapse. On the basis of cancer cells, epithelial or mesenchymal morphological and immunophenotypic similarity we identified 4 main subgroups correlated with a transition to a more undifferentiated phenotype, which have a different pattern of relapse and survival. Conclusion: The negative prognostic role of epithelial-to-mesenchymal transition has been confirmed and a predictive role in glottic tumors has been suggested, leading us to propose epithelial-to-mesenchymal transition as an additional adverse feature in laryngeal carcinoma
Advances in imaging THGEM-based detectors
The thick GEM (THGEM) [1] is an "expanded" GEM, economically produced in the
PCB industry by simple drilling and etching in G-10 or other insulating
materials (fig. 1). Similar to GEM, its operation is based on electron gas
avalanche multiplication in sub-mm holes, resulting in very high gain and fast
signals. Due to its large hole size, the THGEM is particularly efficient in
transporting the electrons into and from the holes, leading to efficient
single-electron detection and effective cascaded operation. The THGEM provides
true pixilated radiation localization, ns signals, high gain and high rate
capability. For a comprehensive summary of the THGEM properties, the reader is
referred to [2, 3]. In this article we present a summary of our recent study on
THGEM-based imaging, carried out with a 10x10 cm^2 double-THGEM detector.Comment: 3 pages, 3 figures. Presented at the 10th Pisa Meeting on Advanced
Detectors; ELBA-Italy; May 21-27 200
THGEM operation in Ne and Ne/CH4
The operation of Thick Gaseous Electron Multipliers (THGEM) in Ne and Ne/CH4
mixtures, features high multiplication factors at relatively low operation
potentials, in both single- and double-THGEM configurations. We present some
systematic data measured with UV-photons and soft x-rays, in various Ne
mixtures. It includes gain dependence on hole diameter and gas purity,
photoelectron extraction efficiency from CsI photocathodes into the gas,
long-term gain stability and pulse rise-time. Position resolution of a 100x100
mm^2 X-rays imaging detector is presented. Possible applications are discussed.Comment: Submitted to JINST, 25 pages, 33 figure
Passive drag in young swimmers: Effects of body composition, morphology and gliding position
The passive drag (Dp) during swimming is affected by the swimmerâs morphology, body density and body position. We evaluated the relative contribution of morphology, body composition, and body position adjustments in the prediction of a swimmerâs Dp. This observational study examined a sample of 60 competitive swimmers (31 male and 29 female) with a mean (±SD) age of 15.4 ± 3.1 years. The swimmerâs Dp was measured using an electro-mechanical towing device and the body composition was assessed using a bioelectrical impedance analyser. Body lengths and circumferences were measured in both the standing position and the simulated streamlined position. Partial correlation analysis with age as a control variable showed that Dp was largely correlated (p < 0.05) with body mass, biacromial-and bi-iliac-breadth, streamline chest circumference and breadth. Body mass, Body Mass Index, chest circumference and streamline chest circumference showed a significant and moderate to strong effect (η2 > 0.55) on Dp. Body mass was the best predictor of Dp explaining 69% of the variability. These results indicate that swimmers with lower Dp values were: (i) slimmer, with lower fat and fat-free mass; (ii) thinner, with lower shoulder breadth, chest circumference, and streamline trunk diameters (iii), shorter, with lower streamline height. These findings can be used for talent identification in swimming, with particular reference to the gliding performance
Arm-stroke descriptor variability during 200-M front crawl swimming
The present study aimed to explore the variability of the arm-stroke temporal descriptors between and within laps during middle-distance swimming event using IMMUs. Eight male swimmers performed a 200-m maximum front-crawl in which the inter-lap and intra-lap variability of velocity, stroke rate, stroke-phases duration and arm-coordination index were measured through five units of IMMU. An algorithm computes the 3D coordinates of the wrist by means the IMMU orientation and the kinematic chain of upper arm biomechanical model, and it recognizes the start events of the four arm-stroke phases. Velocity and stroke rate had a mean value of 1.47 ± 0.10 m·sâ1 and 32.94 ± 4.84 cycles·minâ1, respectively, and a significant decrease along the 200-m (p < 0.001; η2 = 0.80 and 0.47). The end of each lap showed significantly lower stroke rate compared to the start and the middle segment (p < 0.05; η2 = 0.55). No other significant inter-lap and intra-lap differences were detected. The two main findings are: (i) IMMUs technology can be an effective solution to continuously monitor the temporal descriptors during the swimming trial; (ii) swimmers are able to keep stable their temporal technique descriptors in a middle-distance event, despite the decrease of velocity and stroke rate
Observation-based Fine Grained Access Control of Data
In this paper, we propose an observation-based fine grained access control (OFGAC) mechanism where data are made accessible at various levels of abstractions according to their sensitivity levels. In this setting, unauthorized users are not able to infer the exact content of the confidential data, while they are allowed to get partial information out of it, according to their access rights. The traditional fine grained access control (FGAC) can be seen as a special case of the OFGAC framework
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