Reduced frequency noise in superconducting resonators

We report a reduction of the frequency noise in coplanar waveguide superconducting resonators. The reduction of 7 dB is achieved by removing the exposed dielectric substrate surface from the region with high electric fields and by using NbTiN. In a model-analysis the surface of NbTiN is found to be a negligible source of noise, experimentally supported by a comparison with NbTiN on SiOx resonators. The reduction is additive to decreasing the noise by widening the resonators.Comment: 4 pages, 4 figure

Nutrition for master athletes: From challenges to optimisation strategies

Master athletes are genuine examples of successful ageing thanks to their capacity of maintaining a high level of sports performance during their entire life. Within the last decade many studies have focused on the evolution of performance in many sports with ageing, as well as on the training modalities to reach such performance. On the contrary, there is a paucity of data on the nutritional habits of master athletes and the question of whether they need to adapt their nutrition to the ageing process remains unsolved. This is within this context of the optimisation of nutrition for master athletes that this review stands. The aim is to identify the potential nutritional challenges encountered by master athletes and how to handle them through adapted nutritional strategies. Given the lack of data specific to master athletes, studies including master athletes are considered as a priority, though we also make inferences based on nutrition for young adults and perturbations induced by ageing in non-athletic populations. The first part of this opinion paper tackles the first challenge faced by master athletes which is the gradual reduction in energy intake with ageing. The second challenge is the anabolic resistance and the need for increased protein intake. The third nutritional challenge we present is the episodes of metabolic crisis master athletes may face throughout life. Finally, we gather the main nutritional recommendations for master athletes and suggest the next stage of research. © 2019 ACAPS

Epitaxial aluminium-nitride tunnel barriers grown by nitridation with a plasma source

High critical current-density (10 to 420 kA/cm^2) superconductor-insulator-superconductor tunnel junctions with aluminium nitride barriers have been realized using a remote nitrogen plasma from an inductively coupled plasma source operated in a pressure range of 10^{-3} to 10^{-1} mbar. We find a much better reproducibility and control compared to previous work. From the current-voltage characteristics and cross-sectional TEM images it is inferred that, compared to the commonly used AlO_x barriers, the poly-crystalline AlN barriers are much more uniform in transmissivity, leading to a better quality at high critical current-densities.Comment: 3 pages, 3 figures, accepted for publication in AP

Nutrition for master athletes: is there a need for specific recommendations?

Master athletes are often considered exemplars of successful aging, thanks to their capacity to maintain a high sports performance during their entire life. A high training capacity, regular participation in sporting competitions, and delayed alterations in body composition and physiological capacities have been listed among the main factors contributing to impressive master athletes’ performances. However, there is a paucity of data on the metabolism and dietary habits of master athletes, and the question of whether they need to adapt their nutrition to the aging process remains open. Herein, the authors presented a contemporary overview of themetabolic challenges associated with aging, including the risk of low energy availability, anabolic resistance, and periods of metabolic crisis due to forced immobilization. After assembling scientific evidence to show that master athletes must adapt their dietary intake, the authors proposed a summary of nutritional recommendations for master athletes and suggested the next stage of research

Downhill Running: What Are The Effects and How Can We Adapt? A Narrative Review

Downhill running (DR) is a whole-body exercise model that is used to investigate the physiological consequences of eccentric muscle actions and/or exercise-induced muscle damage (EIMD). In a sporting context, DR sections can be part of running disciplines (off-road and road running) and can accentuate EIMD, leading to a reduction in performance. The purpose of this narrative review is to: (1) better inform on the acute and delayed physiological effects of DR; (2) identify and discuss, using a comprehensive approach, the DR characteristics that affect the physiological responses to DR and their potential interactions; (3) provide the current state of evidence on preventive and in-situ strategies to better adapt to DR. Key findings of this review show that DR may have an impact on exercise performance by altering muscle structure and function due to EIMD. In the majority of studies, EIMD are assessed through isometric maximal voluntary contraction, blood creatine kinase and delayed onset muscle soreness, with DR characteristics (slope, exercise duration, and running speed) acting as the main influencing factors. In previous studies, the median (25th percentile, Q1; 75th percentile, Q3) slope, exercise duration, and running speed were − 12% (− 15%; − 10%), 40 min (30 min; 45 min) and 11.3 km h−1 (9.8 km h−1; 12.9 km h−1), respectively. Regardless of DR characteristics, people the least accustomed to DR generally experienced the most EIMD. There is growing evidence to suggest that preventive strategies that consist of prior exposure to DR are the most effective to better tolerate DR. The effectiveness of in-situ strategies such as lower limb compression garments and specific footwear remains to be confirmed. Our review finally highlights important discrepancies between studies in the assessment of EIMD, DR protocols and populations, which prevent drawing firm conclusions on factors that most influence the response to DR, and adaptive strategies to DR

Editorial: From Physiological Adaptations to Endurance Performance: It Is Time to Bridge the Gap

Editorial on the Research Topic From Physiological Adaptations to Endurance Performance: It Is Time to Bridge the Ga

The time course of different neuromuscular adaptations to short‑term downhill running training and their specific relationships with strength gains

Purpose: Due to its eccentric nature, downhill running (DR) training has been suggested to promote strength gains through neuromuscular adaptations. However, it is unknown whether short-term chronic DR can elicit such adaptations. Methods: Twelve untrained, young, healthy adults (five women, seven men) took part in four weeks’ DR, comprising 10 sessions, with running speed equivalent to 60-65% maximal oxygen uptake (V̇O2max, assessed at weeks 0 and 4). Isometric and isokinetic knee-extensor maximal voluntary torque (MVT), vastus lateralis (VL) muscle morphology/architecture (anatomical cross-sectional area, ACSA; physiological CSA, PCSA; volume; fascicle length, Lf; pennation angle, PA) and neuromuscular activation (VL EMG) were assessed at weeks 0, 2 and 4. Results: MVT increased by 9.7-15.2% after four weeks (p<0.01). VL EMG during isometric MVT increased by 35.6±46.1% after four weeks (p<0.05) and correlated with changes in isometric MVT after two weeks (r=0.86, p=0.001). VL ACSA (+2.9±2.7% and +7.1±3.5%) and volume (+2.5±2.5% and +6.6±3.2%) increased after two and four weeks, respectively (p<0.05). PCSA (+3.8±3.3%), PA (+5.8±3.8%) and Lf (+2.7±2.2%) increased after four weeks (p<0.01). Changes in VL volume (r=0.67, p=0.03) and PCSA (r=0.71, p=0.01) correlated with changes in concentric MVT from two-to-four weeks. V̇O2max (49.4±6.2 vs. 49.7±6.3 mL∙kg-1∙min-1) did not change after four weeks (p=0.73). Conclusion: Just four weeks’ moderate-intensity DR promoted neuromuscular adaptations in young, healthy adults, typically observed after high-intensity eccentric resistance training. Neural adaptations appeared to contribute to most of the strength gains at two and four weeks, while muscle hypertrophy seemed to contribute to MVT changes from two-to-four weeks only