Potential adverse cardiac remodelling in highly trained athletes: still unknown clinical significance

Moderate endurance exercise has long been considered an essential element to maintain cardiovascular health, and sedentary behaviour in the general population has been related to a significant increase in all-causes of mortality, cardiovascular disease mortality and cardiovascular disease incidence. However, a growing group of people performs an intense exercise that leads to multiple heart adaptive changes that are collectively called “athlete’s heart”. In this review, we discussed the evidence of cardiac remodelling process secondary to repetitive and strenuous exercise in some predisposed athletes that produces intense and probably deleterious changes in cardiac morphology and function with no clear clinical significance in long-term follow-up. Moreover, we also discussed the individual biological response to exercise assessed by myocardial damage, inflammation, oxidative stress, fibrosis and ventricular hypertrophy biomarkers showing different intensities with equivalent exertion.     

Suppression of DC-link voltage unbalance in three-level neutral-point clamped converters

Two different control approaches for suppressing DC-link voltage unbalance in Three-Level Neutral-Point Clamped Converters (NPCs) are presented in this paper. They both guarantee DC-link voltage equalization over any NPC operating conditions, i.e. when the NPC feeds or is supplied by the main AC grid at different active and/or reactive power rates. The proposed control approaches consist of either a hysteresis or a proportional regulator, each of which synthesizes the most suitable control action based on the actual DC-link voltage unbalance. Particularly, two different PWM techniques have been developed in order to achieve DC-link voltage equalization successfully, preserving NPC voltage and current waveforms at the same time. The performances achievable by means of both the proposed control approaches have been compared to each other through an extensive simulation study in order to highlight their most important advantages and drawbacks, as well as their effectiveness over any operating conditions. Particularly, both control approaches are validated in the Matlab-Simulink environment referring to DC-link voltage equalization of an NPC that represents the point of common coupling between a DC microgrid and the main AC grid.     

Geographic dispersion and co-location in global R&D portfolios: Consequences for firm performance

We examine how the ways in which firms geographically configure their global portfolios of R&D units influence the effectiveness of firms’ own R&D investments and of external technical knowledge in enhancing firm performance. Our analysis indicates that the strength of these effects depends on the extent to which firms spread their R&D units across countries (geographic dispersion of R&D) and the extent to which firms establish multiple R&D units within each country (co-location of R&D). We show that geographic dispersion and co-location are associated with distinct value creation and value capture mechanisms and in turn lead to different performance outcomes. Although geographic dispersion enhances the effects of a firm’s own R&D on its performance, R&D co-location limits such effects. These relationships are reversed when we consider the effects of external technical knowledge on firm performance. R&D co-location, rather than geographic dispersion, is what renders the exploitation of external knowledge more effective in enhancing firm performance. Our results suggest that future research should shift its focus from the degree of R&D globalization to how a portfolio is globalized and geographically structured.