Machine learning applied to X-ray tomography as a new tool to analyze the voids in RRP Nb3Sn wires.

The electro-mechanical and electro-thermal properties of high-performance Restacked-Rod-Process (RRP) Nb3Sn wires are key factors in the realization of compact magnets above 15 T for the future particle physics experiments. Combining X-ray micro-tomography with unsupervised machine learning algorithm, we provide a new tool capable to study the internal features of RRP wires and unlock different approaches to enhance their performances. Such tool is ideal to characterize the distribution and morphology of the voids that are generated during the heat treatment necessary to form the Nb3Sn superconducting phase. Two different types of voids can be detected in this type of wires: one inside the copper matrix and the other inside the Nb3Sn sub-elements. The former type can be related to Sn leaking from sub-elements to the copper matrix which leads to poor electro-thermal stability of the whole wire. The second type is detrimental for the electro-mechanical performance of the wires as superconducting wires experience large electromagnetic stresses in high field and high current conditions. We analyze these aspects thoroughly and discuss the potential of the X-ray tomography analysis tool to help modeling and predicting electro-mechanical and electro-thermal behavior of RRP wires and optimize their design.

High-field superconductivity in C-doped MgB2 bulk samples prepared by a rapid synthesis route.

The upper critical field sets the thermodynamic limit to superconductivity. A big gap is present between the upper-critical-field values measured in MgB2 polycrystalline bulk superconductors and those of thin films, where values as high as ~ 50 T have been achieved at 4.2 K. Filling this gap would unlock the potential of MgB2 for magnet applications. This work presents the results of an extensive experimental campaign on MgB2 bulk samples, which has been guided by a Design of Experiment. We modeled the dependence of the upper critical field on the main synthesis parameters and established a new record (~ 35 T at 4.2 K) preparing C-doped bulk samples by a non-conventional rapid-synthesis route. This value appears to be an upper boundary for the upper critical field in bulk samples. Structural disorder in films seems to act selectively on one of the two bands where superconductivity in MgB2 takes place: this enhances the upper critical field while reducing the critical temperature only by few Kelvins. On the other hand, the critical temperature in bulk samples decreases monotonically when structural disorder increases, and this imposes a limit to the maximum achievable upper critical field.

Ivabradine improves quality of life in subjects with chronic heart failure compared to treatment with ß-blockers: results of a multicentric observational APULIA study.

OBJECTIVES: Ivabradine (IVA), a selective If current inhibitor decreasing the heart rate (HR) in patients with sinus rhythm, has been added to the most recent European Guidelines on heart failure. This selective treatment reduces HR exclusively while fully preserving myocardial contractility and relaxation, atrioventricular conduction, and ventricular repolarization, as well as blood pressure. The aim of this study was to evaluate the improvement of quality of life (QOL) in patients with chronic heart failure (CHF) treated with IVA versus two ß-blockers (bisoprolol and carvedilol). METHODS: We evaluated if a 1-month treatment with IVA (5 mg b.i.d.) or ß-blockers (carvedilol 6.25 mg b.i.d. or bisoprolol 1.25 mg b.i.d.) improves the QOL (assessed by SF-36 questionnaire) in patients with CHF with reduced left ventricular ejection fraction (<50%). SF-36 was tested in 221 CHF patients (mean age 64 ± 6 years) randomized into two groups (IVA group - 110 patients; ß-blockers group - 111 patients). Data of QOL questionnaire and HR were collected by an interview during a clinical visit both at prescription time (basal) and after 1 month of therapy with IVA or ß-blockers. QOL life and HR results after 1-month of therapy (T1) with IVA were compared with basal values (T0). RESULTS: The IVA versus ß-blockers treatment was associated with a significant improvement of physical functioning (p < 0.001 vs. p < 0.01), physical role functioning (p < 0.001 vs. p < 0.01), emotional role functioning (p < 0.01 vs. p < 0.85), and mental health scales (p < 0.001 vs. p < 0.01). HR in the IVA group was significantly lower compared to the group of patients treated with ß-blockers (63 vs. 67 bpm; p < 0.001). CONCLUSIONS: IVA treatment significantly improves the QOL in patients with CHF without any deleterious impact on hemodynamics, and may be beneficial in these patients without other adverse effects associated with ß-blockers.