1,130 research outputs found
VACUUM PERFORMANCE OF AMORPHOUS CARBON COATING AT CRYOGENIC TEMPERATURE WITH PRESENCE OF PROTON BEAMS
No full textAmorphous carbon (a-C) coating is the baseline electron multipacting mitigation strategy proposed for the Inner Triplets (IT) in the High Luminosity upgrade of the Large Hadron Collider (HL-LHC). As of 2014, the COLD bore EXperiment (COLDEX) is qualifying the performance of a-C coating at cryogenic temperature in a LHC type cryogenic vacuum system. In this paper, the experimental results following a cryogenic vacuum characterization of a-C coating in the 5 to 150 K temperature range are reviewed. We discuss the dynamic pressure rise, gas composition, dissipated heat load and electron activity observed within an accumulated beam time of 9 Ah. The results of dedicated experiments including pre-adsorption of different gas species (H2, CO) on the a-C coating are iscussed. Based of phenomenological modeling, up-to-date secondary emission input parameters for a-C coatings are retrieved for electron cloud build-up simulations.
Finally, first implications for the HL-LHC ITs design are drawn
Intravitreal ranibizumab injection for choroidal neovascularization in Strumpell-Lorrain Syndrome
No full textStrumpell-Lorrain syndrome, or hereditary spastic paraplegia is a genetic disease of the central nervous system affecting the spinal cord and cerebellum. It represents a clinically heterogenous group of neurodegenerative disorders characterized by progressive spasticity and hyperreflexia of the lower limbs. Ocular abnormalities include keratitis, macular pigmentary abnormalities, juxtafoveolar retinal telangiectasis and choroidal neovascularization. We report the first case of choroidal neovascularization associated with Strupell-Lorrain syndrome treated successfully with intravitreal ranibizumab injection. (C) 2012 Elsevier Masson SAS. All rights reserved
Amorphous Carbon Coatings at Cryogenic Temperatures with LHC Type Beams: First Results with the COLDEX Experiment
No full textExtrapolations of electron cloud data from the Large Hadron Collider (LHC) Run 1 to the High Luminosity upgrade (HL-LHC) beam parameters predict an intolerable increase of heat load on the beam screens of the inner triplets. Amorphous carbon (a-C) coating of the beam screen surface is proposed to reduce electron cloud production, thereby minimising its dissipated power. To validate this solution, the COLDEX experiment has been re-commissioned. Such equipment mimics the performance of the LHC cold bore and beam screen cryogenic vacuum system in presence of LHC beams in the Super Proton Synchrotron (SPS). The main objective of the study is the performance evaluation of a-C coatings while operating the beam screen in the 10 to 60 K temperature range and cold bore below 3 K. This paper reviews the status of COLDEX and the results obtained during its first experimental runs
Measurement of NEG Coating Performance Variation in the LHC after the First Long Shutdown
No full textDuring the Long Shutdown 1 (LS1) of the Large Hadron Collider, 90% of the Non-Evaporable Getter (NEG) coated beam pipes in the Long Straight Sections (LSS) were vented to undertake the planned upgrade and consolidation programmes. After each intervention, an additional bake-out and NEG activation were performed to reach the vacuum requirements. An analysis of the coating performance variation after the additional activation cycle has been carried out by using ultimate pressure and pressure build-up measurements. In addition, laboratory measurements have been carried out to mimic the LHC coated beam pipe behaviour. The experimental data have been compared with calculation obtained by Molflow+
Asteroseismology of OB stars with CoRoT
No full textThe CoRoT satellite is revolutionizing the photometric study of massive O-type and B-type stars. During its long runs, CoRoT observed the entire main sequence B star domain, from typical hot β Cep stars, via cooler hybrid p- and g-mode pulsators to the SPB stars near the edge of the instability strip. CoRoT lowers the sensitivity barrier from the typical mmagprecision reached from the ground, to the μ mag-level reached from space. Within the wealth of detected and identified pulsation modes, relations have been found in the form of multiplets, combination of frequencies, and frequency- and period spacings. This wealth of observational evidence is finally providing strong constraints to test current models of the internal structure and pulsations of hot stars. Aside from the expected opacity driven modes with infinite lifetime, other unexpected types of variability are detected in massive stars, such as modes of stochastic nature. The simultaneous observation of all these light curve characteristics implies a challenge for both observational asteroseismology and stellar modelling. © 2010 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim
A novel role for CD36 in VLDL-enhanced platelet activation
No full textType 2 diabetes is characterized by increased plasma triglyceride levels and a fourfold increase in ischemic heart disease, but the mechanism is unclear. CD36 is a receptor/transporter that binds fatty acids of lipoproteins. CD36 deficiency has been linked with insulin resistance. There is strong evidence of in vivo interaction between platelets and atherogenic lipoproteins suggesting that atherogenic triglyceride-rich lipoproteins, such as VLDL, that are increased in diabetic dyslipidemia are important in this process. This study demonstrates that VLDL binds to the platelet receptor CD36, enhances platelet thromboxane A2 production, and causes increased collagen-mediated platelet aggregation. VLDL enhanced collagen-induced platelet aggregation by 1) shortening the time taken for aggregation to begin (lag time) to 70% of control (P = 0.001); 2) increasing maximum aggregation to 170% of control (P = 0.008); and 3) increasing thromboxane production to 3,318% of control (P = 0.004), where control represents platelets stimulated with collagen (100%). A monoclonal antibody against CD36 attenuated VLDL-enhanced collagen-induced platelet aggregation by 1) inhibiting binding of VLDL to platelets by 75% (P = 0.041); 2) lengthening lag time to 190% (P < 0.001); and 3) decreasing thromboxane production to 8% of control (P < 0.001). In support of this finding, platelets from Cd36-deficient rats showed no increase in aggregation, thromboxane production, and VLDL binding in contrast to platelets from rats expressing CD36. These data suggest that platelet Cd36 has a key role in VLDL-induced collagen-mediated platelet aggregation, possibly contributing to atherothrombosis associated with increased VLDL levels
Impedance analysis of deformable RF contact bridges for high luminosity LHC
No full textIn order to maintain the continuity of the vacuum system wall and comply with beam stability limits, radio frequency contact bridges are utilised as transitional elements in beam vacuum line interconnections. These radio frequency contact bridges must absorb and correct longitudinal, angular, and transverse misalignments brought on by mechanical motions during assembly, alignment, operating phases and thermal influences during accelerator operation. A deformable thin-walled copper beryllium structure is the foundation of a novel deformable radio frequency contact bridge concept that satisfies the above criteria without using conventional sliding contacts. To assess the feasibility of implementing such deformable radio frequency contact bridges in the High-Luminosity LHC, the longitudinal, dipolar, and quadrupolar components of the beam impedance in the two transverse planes were determined using electromagnetic simulations
DOES THE CLINICAL PRESENTATION AND EXTENT OF VENOUS THROMBOSIS PREDICT LIKELIHOOD AND TYPE OF RECURRENCE? A PATIENT LEVEL META-ANALYSIS OF 2,554 UNSELECTED PATIENTS AFTER A FIRST THROMBOSIS
No full textImpedances of the cold bore experiment, COLDEX, installed in the SPS machine
No full textThis paper focuses on the impedances evaluation of the cold bore experiment called COLDEX, and installed in the SPS machine. A comparison between analytical model and numerical results is presented. Tests on power losses are also shown. (c) 2006 Elsevier B.V. All rights reserved
DOES THE CLINICAL PRESENTATION OF VENOUS THROMBOEMBOLISM PREDICT THE RISK FOR AND TYPE OF THROMBOSIS RECURRENCE?
No full text- …
