Performance analysis of correlation techniques for noise measurements

The cross-correlation technique makes it possible to perform noise measurements with a sensitivity that would otherwise be unreachable, well below the noise floor of the amplifiers. Not all noise contributions from the amplifiers can however be eliminated or even just attenuated by cross-correlation: therefore it is important to take into consideration the detailed characteristics of the DUT (Device Under Test) and of the amplifiers when setting up the measurement system. Here we discuss the relative advantages of the different (“series” and “parallel”) configurations coupled with our technique for the accurate evaluation of the transimpedance between the noise source to be measured and the amplifier output. In particular, we show (i) the importance of the comparison between the real and the imaginary part of the cross-spectrum due to the asymmetry of the correlation amplifiers and (ii) how to estimate the maximum number of averages in the cross-spectrum evaluation that leads to an actual advantage from the point of view of the measurement accuracy. Finally we discuss the issue of shielding from external spurious signals, whose relevance is often underestimated

Mechanical support concept of the DEMO breeding blanket

The DEMO tokamak architecture is based on large vertical breeding blanket (BB) segments that are accessed from a maintenance hall above the tokamak and are vertically replaced through large upper ports of the vacuum vessel (VV). The feasibility of the BB segments mechanical supports is a prerequisite of this vertical segment architecture. Their design directly impacts on the removal kinematics and the remote handling operations required for release and engagement. The supports must withstand large forces acting on the BB in particular due to electromagnetic (EM) loads. At the same time, they must ensure a sufficiently precise positioning of the BB first wall. Their design also takes into account the significant thermal expansion of the blanket segments that are operated at high temperature avoiding excessive support reaction forces. The BB support concept described in this article does not require fasteners or electrical straps to the VV and therefore much reduces the complexity of the BB remote replacement – a valuable characteristic that would make this concept a milestone in meeting one of the goals defined for the DEMO project: to develop a maintainable fusion power plant design [1]. Each blanket segment is individually supported by the VV without any physical contact to the other blankets or in-vessel components. It relies instead on vertical pre-compression inside the VV due to obstructed thermal expansion and radial pre-compression due to the ferromagnetic force acting on the BB material in the toroidal magnetic field. The verification process did not identify show stoppers. Nonetheless, a further evolution of the concept is required including design improvements to mitigate the high stress levels found in the inboard blankets during plasma disruptions. The fact that no excessively high support reaction forces or large BB deflections were found suggests though that the further development of the concept could be successful

MIRA: a Multiphysics Approach to Designing a Fusion Power Plant

Fusion systems codes (SCs) are deployed to produce the baseline of the European fusion power reactor (DEMO) within its conceptual design. A DEMO baseline is mostly defined by a radial/vertical reactor sketch and major reactor parameters, such as fusion and net electric power, magnetic fields, and plasma burn time. A baseline shall also meet a set of prescribed reactor requirements, constraints, and architectural features. According to the conceptual design workflow implemented within the EU-DEMO programme, the output from the SC is transferred to the detailed physics and engineering design codes. Presently-available fusion SCs rely on rather basic physics and engineering models (mostly at zero or one-dimensional level). The design codes, instead, are very detailed but run on much longer computing times. To fill the gap between systems and design codes, the multi-fidelity systems/design tool modular integrated reactor analysis (MIRA)—has been recently developed. MIRA incorporates the physics and the engineering insights of the utmost domains of tokamak reactors and relies on a higher spatial resolution, spanning from 1D up to 3D modelling frames. The MIRA approach has been applied to the DEMO 2017 baseline, generated by the EU reference SC PROCESS and used as input to MIRA. In the paper, the architectural and mathematical insights of the MIRA package are described, along with an EU-DEMO 2017 baseline analysis

Antinociceptive effects of tetrazole inhibitors of endocannabinoid inactivation: Cannabinoid and non-cannabinoid receptor-mediated mechanisms

Background and purpose: Tetrazoles were recently developed as inhibitors of the cellular uptake of the endocannabinoid anandamide or of its hydrolysis by fatty acid amide hydrolase (FAAH), but were proposed to act also on non-endocannabinoid-related serine hydrolases. Experimental approach: We tested, in a model of inflammatory pain induced in mice by formalin, five chemically similar inhibitors: (i) OMDM119 and OMDM122, two potent carbamoyl tetrazole FAAH inhibitors with no effect on anandamide uptake; (ii) LY2183240, a carbamoyl tetrazole with activity as both FAAH and uptake inhibitor; (iii) OMDM132, a non-carbamoyl tetrazole with activity only as uptake inhibitor and iv) OMDM133, a non-carbamoyl tetrazole with no activity at either FAAH or uptake. Results: All compounds (2.5-10 mg kg -1, i.p.) inhibited the second phase of the nocifensive response induced by intraplantar injection of formalin. The effects of OMDM119, OMDM122 and OMDM133 were not antagonized by pretreatment with cannabinoid CB 1 receptor antagonists, such as rimonabant or AM251 (1-3 mg kg -1, i.p.). The effects of LY2183240 and OMDM132 were fully or partially antagonized by rimonabant, respectively, and the latter compound was also partly antagonized by the CB 2 receptor antagonist, AM630. Conclusions and implications: (i) non-FAAH hydrolases might be entirely responsible for the antinociceptive activity of some, but not all, tetrazole FAAH inhibitors, (ii) the presence of a carbamoylating group is neither necessary nor sufficient for such compounds to act through targets other than FAAH and (iii) inhibition of anandamide uptake is responsible for part of this antinociceptive activity, independently of effects on FAAH. © 2008 Macmillan Publishers Limited All rights reserved

Calcium as a key player in arrhythmogenic cardiomiopathy : adhesion disorder or intracellular alteration?

Arrhythmogenic cardiomyopathy (ACM) is an inherited heart disease characterized by sudden death in young people and featured by fibro-adipose myocardium replacement, malignant arrhythmias, and heart failure. To date, no etiological therapies are available. Mutations in desmosomal genes cause abnormal mechanical coupling, trigger pro-apoptotic signaling pathways, and induce fibro-adipose replacement. Here, we discuss the hypothesis that the ACM causative mechanism involves a defect in the expression and/or activity of the cardiac Ca2+ handling machinery, focusing on the available data supporting this hypothesis. The Ca2+ toolkit is heavily remodeled in cardiomyocytes derived from a mouse model of ACM defective of the desmosomal protein plakophilin-2. Furthermore, ACM-related mutations were found in genes encoding for proteins involved in excitation\u2012contraction coupling, e.g., type 2 ryanodine receptor and phospholamban. As a consequence, the sarcoplasmic reticulum becomes more eager to release Ca2+, thereby inducing delayed afterdepolarizations and impairing cardiac contractility. These data are supported by preliminary observations from patient induced pluripotent stem-cell-derived cardiomyocytes. Assessing the involvement of Ca2+ signaling in the pathogenesis of ACM could be beneficial in the treatment of this life-threatening disease