Modelling of power exhaust in fusion plasmas

This PhD thesis deals with the thorny problem of “Modelling of power exhaust in fusion plasmas”, a challenge concerning the development of a system able to withstand the large loads expected in the fusion power plant divertor. After an introduction to fusion and to the key concepts modelling the behaviour of the plasma during plasma-surface interactions and describing the power exhaust, an overview of the state-of-the-art in the research field on power exhaust is given. A brief introduction on theoretical basis of the plasma boundary reconstruction precedes the author first contribution in the design and vertical stability analysis of plasma alternative magnetic configurations for a demonstration fusion power plant (DEMO). The second contribution concerns an assessment of the DEMO divertor target tiles lifetime in case of strike-point sweeping. This technique is one of the most promising candidate solution to the power exhaust issue but its main drawback is related to the periodical heating and cooling of the plasma facing components inducing the thermal-fatigue phenomenon. To evaluate the lifetime of the DEMO divertor target tiles, different 2D and 3D thermo-mechanical models are presented. Finally, a preliminary analysis on the wobbling technique applied to a DEMO Double Null plasma magnetic configuration is illustrated

The use of functional tests and planned coronary angiography after percutaneous coronary revascularization in clinical practice. Results from the AFTER multicenter study

Background: The follow-up strategies after percutaneous coronary intervention (PCI) have relevant clinical and economic implications. The purpose of this prospective observational multicenter study was to evaluate the effect of clinical, procedural and organizational variables on the execution of functional testing (FT) and planned coronary angiography (CA) after PCI, and to assess the impact of American College of Cardiology (ACC)/American Heart Association (AHA) guidelines on clinical practice. Methods: Four hundred twenty consecutive patients undergoing PCI were categorized as class I, IIB and III indications for follow-up FT according to ACC/AHA guidelines recommendations. Furthermore, all patients were grouped according to the presence or absence of FT and/or planned CA over 12 months after PCI. Multivariable analysis was used to assess the potential predictors of test execution. Results: During the 12-month follow-up at least one test was performed in 72% of patients with class I indication, 63% of patients with class IIB indication and 75% of patients with class III indication (p=ns). A total of 283 patients (67%) underwent testing. The use of tests was associated with younger age (R. R. 0.94, C. I. 0.91 +/- 0.97, p<0.001), a lower number of diseased vessels (R.R. 0.60, C.I. 0.43 +/- 0.84, p=0.003), follow-up by the center performing PCI (R. R. 2.64, C. I. 1.43 +/- 4.86, p=0.002), and the specific center at which PCI was performed. Most asymptomatic patients completed their testing prematurely with respect to the risk period for restenosis. Conclusions: The use of FT and planned CA after PCI is unrelated to patient's symptom status, and depends on patient's age and logistics. ACC/AHA guidelines have no influence in clinical practice, and test timing is not tailored to the risk period for restenosis. (C) 2008 Elsevier Ireland Ltd. All rights reserved

Design and Optimization of a Boost Interface for Magnetostrictive Energy Harvesting

Magnetostrictive alloys are very promising for Vibration Energy Harvesting applications to supply power to Wireless Sensor Network (WSN) and Internet of Things (IoT) devices, especially because of their intrinsic robustness. Typically, vibration energy sources are random in nature, usually providing exploitable voltages much lower than the electronic standards 1.6, 3.3 and 5 V. Therefore, a Power Electronic Interface (PEI) is needed to improve the conversion to DC output voltage from AC input&nbsp;over a wide range of frequencies and amplitudes. Very few or no conversion techniques are available for magnetostrictive devices, although several have been presented over the years for other smart materials, such as piezoelectrics. For example, hybrid buck&ndash;boost converters for piezoelectrics use one or more external inductors with a high-frequency switching technique. However, because of the intrinsic nature of harvesters based on magnetostrictive materials, such energy conversion techniques are proved to be neither efficient nor applicable. An improved AC&ndash;DC boost converter seems very promising for our purpose instead. The key feature is represented by the direct exploitation of the active harvester coil as a storage element of the boost circuit, without using other passive inductors as in other switching methods. Experimental tests of such a converter, driven with a real-time operating Arduino controller to detect the polarity of the input voltage, are presented with the aim to assess the potentiality of the scheme with both sinusoidal and impulse-like inputs. Simulations have been performed with LTspice, and the performance and efficiency have been compared with other energy conversion techniques

Management of multivessel coronary disease after ST elevation myocardial infarction treated by primary angioplasty

Background: Optimal treatment strategy of patients with ST elevation myocardial infarction (STEMI) and multivessel coronary artery disease (CAD) undergoing primary angioplasty is still unclear. Percutaneous coronary intervention (PCI) of non-culprit vessels simultaneously or soon after primary angioplasty is feasible and safe, but available data failed to consistently show a benefit in long-term clinical outcomes. Methods: We retrospectively compared in-hospital and long-term outcomes for patients with STEMI and multivessel CAD treated by primary angioplasty with (Group 1, n=64) or without (Group 2, n=46) early, staged PCI of other angiographically significant coronary lesions. In-hospital major adverse cardiovascular events (MACE) were defined as a composite of death, periprocedural myocardial infarction after staged, elective PCI, stroke, stent thrombosis, major bleeding, and vascular complications. MACE at follow-up were defined as a composite of death, stroke, stent thrombosis, any coronary revascularization, and re-hospitalization for acute coronary syndrome. Results: Group 1 patients underwent staged PCI 5.9 ± 3.5 days after primary angioplasty. The mean length of follow-up was 13 months (392 ± 236 days). The incidence of in-hospital MACE was 20.3% in Group 1 and 10.8% in Group 2 (P=0.186); the incidence of out of hospital MACE was 9.3% in Group 1 and 23.9% in Group 2 (P=0.037). In Group 1 in-hospital MACE were driven by periprocedural myocardial infarction after the elective procedure, which occurred in 15.6% of patients. Conclusions: Our data show that multivessel, staged PCI in STEMI patients is associated with a low incidence of adverse events at follow-up but with a higher incidence of in-hospital MACE, mainly driven by periprocedural myocardial infarction during the elective procedure. © Authors

Power-Efficient Design of Large-Aperture Magnets for High-Energy Physics

Anovel and sustainability-oriented approach to the design of large-aperture iron-dominated magnets is proposed, focusing on its application to charged particle momentum detection in highenergy experimental physics. As compared to classical design techniques, a broader number of goals and constraints is taken into account, considering jointly the detection performance, the minimization of both the electrical power and magnet size, and the electromagnetic efficiency. A case study is considered for the detector magnet of a specific experiment, where the optimal design is pursued with semi-analytical tools, duly introducing the main quantities’ scaling laws in analytical form and successively validating the results with 3D numerical tools. A solution at higher energy efficiency is obtained, as compared to a more traditional design point of view. The proposed methodology can be fruitfully employed also in the design of magnets with a reduced ecological footprint in a number of other industrial and medical applications

Exploring the course of metals between the Sardinian Bronze Age and Iberia. New data from Monte Sa Idda hoard provenance studies

The hoard of Monte Sa Idda (Decimoputzu, Cagliari), is one of the classic metal hoards of Nuragic archaeology in Sardinia (Taramelli 1921). The hoard was uncovered with all its goods grouped into a large pottery container, and located within a Nuragic building. It was composed of over three hundred artefacts, most of them fragmentary, which are characteristic of the Late Bronze Age period in Sardinia. In addition, some of the represented objects within this hoard are usually related with Iberian typologies as, for example, the Sa Idda swords. Furthermore, other Iberian artefacts have been also connected within Sa Idda¿s types like the wax-lost handles. The present study focuses on a group of 11 copper-based artefacts recovered from this hoard and are composed of six copper ingots, one socketed axe, one ferrule, one dagger and two swords. The applied methodology consisted of elemental analysis performed by a pXRF and lead isotope analysis (LIA) performed by MC-ICP-MS in the Frankfurt Laboratory (Klein et al. 2009). The main goal of this research is to approach the provenance of these metal artefacts and, if possible, relate them to the original ore source. Results show that six objects and ingots present isotopic coincidences with three different Iberian copper ore areas and the remaining five artefacts can be related with local Sardinian minerals. These results, in combination with other lead isotopic results from Late Bronze Age metal artefacts in Iberia and also in the Balearic Islands, permit us to reconstruct the trade dynamics that would have connected the Iberian Peninsula and Sardinia during this period. Thus, this information seems to be relevant for a better understanding of the hoarding practices, and also to follow Late Bronze Age metal trade courses in the Central and Western Mediterranean

Thrombus aspiration during primary angioplasty for cardiogenic shock

We sought to assess the clinical efficacy of thrombus aspiration during primary percutaneous coronary interventions (PCI) in patients presenting with ST-elevation myocardial infarction (STEMI) complicated by cardiogenic shock (CS). We retrospectively selected 44 patients with CS out of a population of 842 STEMI patients treated with primary PCI at our Hospital between March 2003 and October 2007. Twenty-six patients died during hospital stay (59.1%, Group 1), whereas the remaining 18 were discharged (40.9%, Group 2). Post-procedural ST-segment resolution was greater (68.0% ± 35.6 vs. 43.0% ± 35.0; p = 0.06) and in-hospital mortality was significantly lower (21.4% vs 76.6%; p < 0.01) in patients treated by TA as compared to patients undergoing standard PCI. At multivariate logistic regression analysis, TA was the only variable independently associated with survival. © 2008 Elsevier Ireland Ltd. All rights reserved