Improving the performance of superconducting microwave resonators in magnetic fields

The operation of superconducting coplanar waveguide cavities, as used for circuit quantum electrodynamics and kinetic inductance detectors, in perpendicular magnetic fields normally leads to a reduction of the device performance due to energy dissipating Abrikosov vortices. We experimentally investigate the vortex induced energy losses in such Nb resonators with different spatial distributions of micropatterned pinning sites (antidots) by transmission spectroscopy measurements at 4.2 K. In comparison to resonators without antidots we find a significant reduction of vortex induced losses and thus increased quality factors over a broad range of frequencies and applied powers in moderate fields

Magnetic hysteresis effects in superconducting coplanar microwave resonators

We performed transmission spectroscopy experiments on coplanar half wavelength niobium resonators at a temperature T=4.2 K. We observe not only a strong dependence of the quality factor Q and the resonance frequency f_res on an externally applied magnetic field but also on the magnetic history of our resonators, i.e. on the spatial distribution of trapped Abrikosov vortices in the device. We find these results to be valid for a broad range of frequencies and angles between the resonator plane and the magnetic field direction as well as for resonators with and without antidots near the edges of the center conductor and the ground planes. In a detailed analysis we show, that characteristic features of the experimental data can only be reproduced in calculations, if a highly inhomogeneous rf-current density and a flux density gradient with maxima at the edges of the superconductor is assumed. We furthermore demonstrate, that the hysteretic behaviour of the resonator properties can be used to considerably reduce the vortex induced losses and to fine-tune the resonance frequency by the proper way of cycling to a desired magnetic field

Optimizing the spin sensitivity of grain boundary junction nanoSQUIDs -- towards detection of small spin systems with single-spin resolution

We present an optimization study of the spin sensitivity of nanoSQUIDs based on resistively shunted grain boundary Josephson junctions. In addition the dc SQUIDs contain a narrow constriction onto which a small magnetic particle can be placed (with its magnetic moment in the plane of the SQUID loop and perpendicular to the grain boundary) for efficient coupling of its stray magnetic field to the SQUID loop. The separation of the location of optimum coupling from the junctions allows for an independent optimization of the coupling factor $\phi_\mu$ and junction properties. We present different methods for calculating $\phi_\mu$ (for a magnetic nanoparticle placed 10\,nm above the constriction) as a function of device geometry and show that those yield consistent results. Furthermore, by numerical simulations we obtain a general expression for the dependence of the SQUID inductance on geometrical parameters of our devices, which allows to estimate their impact on the spectral density of flux noise $S_\Phi$ of the SQUIDs in the thermal white noise regime. Our analysis of the dependence of $S_\Phi$ and $\phi_\mu$ on the geometric parameters of the SQUID layout yields a spin sensitivity $S_\mu^{1/2}=S_\Phi^{1/2}/\phi_\mu$ of a few $\mu_{\rm{B}}/\rm{Hz^{1/2}}$ ($\mu_B$ is the Bohr magneton) for optimized parameters, respecting technological constraints. However, by comparison with experimentally realized devices we find significantly larger values for the measured white flux noise, as compared to our theoretical predictions. Still, a spin sensitivity on the order of $10\,\mu_{\rm B}/\rm{Hz^{1/2}}$ for optimized devices seems to be realistic.Comment: 10 pages, 5 figures, Superconductor Science and Technology (submitted

Impact of 3 months of detraining after high intensity exercise on menopause-related symptoms in early postmenopausal women – results of the randomized controlled actlife project

Regular exercise might reduce postmenopausal symptoms, however even short-moderate periods of absence from exercise training might significantly reduce these positive effects. The aim of the study was thus to determine detraining effects on postmenopausal symptoms after a 3-month detraining period in early post-menopausal women. After 13 months, the exercise group (EG: n = 27; 54.6 ± 2.0; 23.6 ± 3.3 kg/m2) had to abruptly stop their supervised, facility-based, high intensity aerobic and resistance group exercise conducted three times per week due to the COVID-19 pandemic and the corresponding lockdown of all training facilities in Germany. In parallel, the control group (CG: n = 27; 55.6 ± 1.6 years, 25.2 ± 5.2 kg/m2) had to terminate their low-intensity exercise program performed once per week. Study endpoint as determined after 3 months of detraining was menopausal symptoms as determined by the Menopausal Rating Scale II (MRS II). The intention to treat principle with multiple imputation was applied. After 13 months of intense multicomponent exercise and significant exercise-induced effects on menopausal symptoms, a further 3 months of detraining resulted in non-significant deteriorations (p = .106) in the exercise group, while non-significant improvements were observed in the control group (p = .180). Corresponding group differences were significant (p = .036) after detraining. Of importance, self-reported individual outdoor activities increased by about 40% in both groups during the three-month lock-down period. Three months of absence from a supervised high-intensity group exercise protocol resulted in detraining effects on postmenopausal symptoms even when outdoor physical activity was increased significantly. Trial registration numberClinicalTrials.gov: NCT0395999

Phase-sensitive evidence for dx2-y2-pairing symmetry in the parent-structure high-Tc cuprate superconductor Sr1-xLaxCuO2

Even after 25 years of research the pairing mechanism and - at least for electron doped compounds - also the order parameter symmetry of the high transition temperature (high-Tc) cuprate superconductors is still under debate. One of the reasons is the complex crystal structure of most of these materials. An exception are the infinite layer (IL) compounds consisting essentially of CuO2 planes. Unfortunately, these materials are difficult to grow and, thus, there are only few experimental investigations. Recently, we succeeded in depositing high quality films of the electron doped IL compound Sr1-xLaxCuO2 (SLCO), with x approximately 0.15, and on the fabrication of well-defined grain boundary Josephson junctions (GBJs) based on such SLCO films. Here we report on a phase sensitive study of the superconducting order parameter based on GBJ SQUIDs from a SLCO film grown on a tetracrystal substrate. Our results show that also the parent structure of the high-Tc cuprates has dx2-y2-wave symmetry, which thus seems to be inherent to cuprate superconductivity.Comment: Submitted to PRL, 5 pages, 3 figures, supplementary information included (4 pages, 4 figures

Effects of whole-body electromyostimulation with different impulse intensity on blood pressure changes in hyper- and normotensive overweight people. A pilot study

Hypertension is a frequent condition in untrained middle-aged to older adults, who form the core group of whole-body electromyostimulation (WB-EMS) applicants. So far, the acute effects of varying impulse intensities on blood pressure responses have not been evaluated in normo- and hypertensive people. Thirteen hypertensive and twelve normotensive overweight WB-EMS novices, 40–70 years old, conducted the same WB-EMS protocol (20 min, bipolar, 85 Hz, 350 µs, 4 s impulse-4 s rest; combined with easy movements) with increasing impulse intensity (low, moderate, advanced) per session. Mean arterial blood pressure (MAP) as determined by automatic sphygmomanometry rose significantly (p < .001) from rest, 5 min pre-WB-EMS to immediately pre-WB-EMS assessment. Of importance, a 20-min WB-EMS application does not increase MAP further. In detail, maximum individual MAP does not exceed 128 mmHg (177 mmHg systolic or 110 mmHg diastolic) in any case. Two-min post-WB-EMS, MAP was significantly lower (p = .016) compared to immediately pre-WB-EMS. In contrast, heart rate increased significantly from immediately pre to immediately post-exercise (p < .001), though individual peak values did not exceed 140 beats/min−1 and heart rate decreased rapidly (p < .001) post-exercise. No significant differences in MAP and HR kinetics were observed for impulse intensity categories or hypertensive status. In summary, largely independently of impulse intensity and status, the acute effect of WB-EMS on MAP in novice applicants seem to be largely negligible. Although definite evidence might not have been provided by the present study, we conclude that hypertension, at least under treatment, should not be considered as a barrier for WB-EMS application in moderately old or older cohorts

Changes of Maximum Leg Strength Indices During Adulthood a Cross-Sectional Study With Non-athletic Men Aged 19–91

Age-related loss of muscle mass and function, also called sarcopenia, was recently added to the ICD-10 as an independent condition. However, declines in muscle mass and function are inevitable during the adulthood aging process. Concerning muscle strength as a crucial aspect of muscle function, maximum knee extension strength might be the most important physical parameter for independent living in the community. In this study, we aimed to determine the age-related decline in maximum isokinetic knee extension (MIES) and flexion strength (MIFS) in adult men. The primary study hypothesis was that there is a slight gradual decrease of MIES up to ≈age 60 years with a significant acceleration of decline after this “changepoint.” We used a closed kinetic chain system (leg-press), which is seen as providing functionally more relevant results on maximum strength, to determine changes in maximum isokinetic hip/leg extensor (MIES) and flexor strength (MIFS) during adulthood in men. Apart from average annual changes, we aimed to identify whether the decline in maximum lower extremity strength is linear. MIES and MIFS data determined by an isokinetic leg-press of 362 non-athletic, healthy, and community-dwelling men 19–91 years old were included in the analysis. A changepoint analysis was conducted based on a multiple regression analysis adjusted for selected co-variables that might confound the proper relationship between age and maximum strength. In summary, maximum isokinetic leg-strength decline during adulthood averaged around 0.8–1.0% p.a.; however, the reduction was far from linear. MIES demonstrated a non-significant reduction of 5.2 N/p.a. (≈0.15% p.a.) up to the estimated breakpoint of 52.0 years and an accelerated loss of 44.0 N/p.a. (≈1.3% p.a.; p < 0.001). In parallel, the decline in MIFS (10.0 N/p.a.; ≈0.5% p.a.) prior to the breakpoint at age 59.0 years was significantly more pronounced. Nevertheless, we observed a further marked accelerated loss of MIFS (25.0 N/p.a.; ≈1.3% p.a.) in men ≥60 years. Apart from the “normative value” and closed kinetic chain aspect of this study, the practical application of our results suggests that sarcopenia prophylaxis in men should be started in the 5th decade in order to address the accelerated muscle decline of advanced age

Detraining Effects on Musculoskeletal Parameters in Early Postmenopausal Osteopenic Women: 3-Month Follow-Up of the Randomized Controlled ACTLIFE Study

Periods of absence from supervised group exercise while maintaining physical activity might be a frequent pattern in adults’ exercise habits. The aim of the present study was to determine detraining effects on musculoskeletal outcomes after a 3-month detraining period in early post-menopausal, osteopenic women. Due to the COVID-19 pandemic, we terminated the 18-month randomized controlled ACTLIFE exercise intervention immediately after the 13-month follow-up assessment. This put an abrupt stop to the high-intensity aerobic and resistance group exercise sessions undertaken three times per week by the exercise group (EG: n = 27) and the gentle exercise program performed once per week for the attention control group (CG: n = 27); but both groups were permitted to conduct individual outdoor activity for the 3-month lock-down period. Study endpoints were lean body mass (LBM), bone mineral density (BMD) at the lumbar spine (LS), maximum hip-/leg extension strength and power. Detraining-induced reductions of LBM, hip/leg strength and power (but not BMD-LS) were significantly greater (p < 0.001 to p = 0.044) compared with the CG. Significant exercise effects, i.e. differences between EG and CG, present after 13 months of exercise, were lost after 3 months of detraining for LBM (p = 0.157) and BMD-LS (p = 0.065), but not for strength (p < 0.001) and power (p < 0.001). Of note, self-reported individual outdoor activities and exercise increased by about 40% in both groups during the lock-down period. Three months’ absence from a supervised group exercise protocol resulted in considerable detraining effects for musculoskeletal parameters. Thus, exercise programs for adults should be continuous rather than intermittent. Trial registration number: ClinicalTrials.gov: NCT04420806, 06.05.2020