Assessment of Galileo High Accuracy Service (HAS) test signals and preliminary positioning performance.

The Galileo High Accuracy Service (HAS) is a GNSS augmentation that provides precise satellite corrections to users worldwide for free directly through Galileo's E6 signal. The HAS service provides free PPP corrections from the Galileo constellation and the Internet, with targeted real-time 95% positioning performance of better than 20 cm horizontal and 40 cm vertical error after 5 min of convergence time globally and shorter in Europe. The HAS initial service, under validation at the time of writing, provides these capabilities with a reduced performance (based on the current Galileo stations network). Live HAS test signals broadcasted from the Galileo satellites during summer 2022 have been decoded and analyzed. Corrections include Galileo and GPS orbit, clock, and code bias corrections, with SISRE of 10.6 cm and 11.8 cm for Galileo and GPS, respectively. Code bias corrections showed good performance as well, with rms of 0.28 ns, 0.26 ns, and 0.22 ns for Galileo C1C-C5Q, C1C-C7Q, and C1C-C6C, respectively, and 0.20 ns for GPS C1C-C2L. Float PPP positioning performance results show that the combined Galileo and GPS solution can already achieve the HAS full service accuracy performance target and is close in terms of convergence time, with 95% rms of 13.1 cm and 18.6 cm horizontally and vertically, respectively, in kinematic mode, and with a 95% convergence time of 7.5 min. The latter is expected to be improved with the inclusion of satellite phase bias and local atmospheric corrections. With these early Galileo HAS test signals, this preliminary analysis indicates that the HAS full service targets are attainable. Finally, a correction latency analysis is performed, showing that even with latency of up to 60 s, positioning can remain within the targeted HAS accuracy performance.

Effects of Gradient and Speed on Uphill Running Gait Variability.

BACKGROUND: The aim of this study was to investigate the effects of gradient and speed on running variability (RV) and local dynamic stability (LDS) during uphill running. HYPOTHESES: (1) Both gradient and speed increase metabolic effort, in terms of heart rate (HR) and perceived exertion (CR10), in line with the contemporary literature, and (2) gradient increases RV and impairs LDS. STUDY DESIGN: "Crossover" observational design. LEVEL OF EVIDENCE: Level 3. METHODS: A total of 25 runners completed 10-minute running trials in 3 different conditions and in a randomized order: gradient at 0% (0CON), 2% (2CON), and 2% at isoefficiency speed (2IES). 0CON and 2CON speeds were calculated as the "best 10-km race performance" minus 1 km·h-1, whereas 2IES speed was adjusted to induce the same metabolic expenditure as 0CON. HR and perceived exertion as well as running kinematic variables were collected across all trials and conditions. Running variability was calculated as the standard deviation of the mean stride-to-stride intervals over 100 strides, while LDS was expressed by the Lyapunov exponent (LyE) determined on running cycle time over different running conditions. RESULTS: Increases in HR and CR10 were observed between 0CON and 2CON (P < 0.001) and between 2IES and 2CON (P < 0.01). Higher RV was found in 2CON compared with 0CON and 2IES (both P < 0.001). Finally, the largest LyE was observed in 2IES compared with 0CON and 2CON (P = 0.02 and P = 0.01, respectively). CONCLUSION: Whereas RV seems to be dependent more on metabolic effort, LDS is affected by gradient to a greater extent. CLINICAL RELEVANCE: Running variability could be used to monitor external training load in marathon runners.

Derivation of harmonised high-level safety requirements for self-driving cars using railway experience.

The development and manufacture of self-driving cars (SDCs) have triggered unprecedented challenges among car manufacturers and smart road operators to accelerate awareness and implementation of innovative technologies for cooperative, connected and automated mobility (CCAM), especially those with a high level of automation and safety. Safety improvement is a pre-requisite to justify and unleashing a mass deployment of connected and driverless cars to reach the goal of zero-accident in 2050 set by the European Commission. Behind these motivations a well-justified and widely acceptable high-level safety target for SDCs is mandatory. The aim of this article is to contribute to the derivation of an harmonised high-level safety target for SDCs, starting from the safety requirements and the state of the art achieved by train and airplane operations. The novelty of our approach is to leverage the Common Safety Method-Design Targets (CSM-DT) already adopted and widely accepted by the railway community. According to this approach, the derived, justified and harmonised high-level design safety target for SDCs, defined as the average probability of a dangerous failure PFSDC per 1 h, should be 1 × 10-7/h. An example of PFSDC allocation to individual SDC safety functions, including position determination based on Global Navigation Satellite System (GNSS), is described using a fault tree. The proposed methodology can speed up the validation and certification process needed to authorise the SDCs, by capitalising the know-how and best practices in use since many years for the train management.

Large Polarons as Key Quasiparticles in SrTiO_{3} and SrTiO_{3}-Based Heterostructures.

Despite its simple structure and low degree of electronic correlation, SrTiO_{3} (STO) features collective phenomena linked to charge transport and, ultimately, superconductivity, that are not yet fully explained. Thus, a better insight into the nature of the quasiparticles shaping the electronic and conduction properties of STO is needed. We studied the low-energy excitations of bulk STO and of the LaAlO_{3}/SrTiO_{3} two-dimensional electron gas (2DEG) by Ti L_{3} edge resonant inelastic x-ray scattering. In all samples, we find the hallmark of polarons in the form of intense dd+phonon excitations, and a decrease of the LO3-mode electron-phonon coupling when going from insulating to highly conducting STO single crystals and heterostructures. Both results are attributed to the dynamic screening of the large polaron self-induced polarization, showing that the low-temperature physics of STO and STO-based 2DEGs is dominated by large polaron quasiparticles.

Shoes and Insoles: The Influence on Motor Tasks Related to Walking Gait Variability and Stability.

The rhythmic control of the lower limb muscles influences the cycle-to-cycle variability during a walking task. The benefits of insoles, commonly used to improve the walking gait, have been little studied. Therefore, the aim of this study was to assess the walking gait variability and stability on different walking conditions (without shoes, WTS, with shoes, WS, with shoes and insoles, WSI) related to brain activity. Twelve participants randomly (WTS/WS/WSI) walked on a treadmill at 4 km/h for 10 min. Kinematic analysis (i.e., footstep and gait variability), brain activation (beta wave signal), rating of perceived exertion (RPE, CR-10 scale), and time domain measures of walking variability were assessed. The maximum Lyapunov exponent (LyE) on the stride cycle period's datasets was also calculated. Stride length and cycle calculated for all walking conditions were 61.59 ± 2.53/63.38 ± 1.43/64.09 ± 2.40 cm and 1.11 ± 0.03/1.14 ± 0.03/1.15 ± 0.04 s (F1,10 = 4.941/p = 0.01, F1,10 = 4.938/p = 0.012) for WTS, WS, WSI, respectively. Beta wave (F1,10 = 564.201/p = 0.0001) was higher in WTS compared to WS and WSI. Analysis of variance's (ANOVA) LyE showed a F1,10 = 3.209/p = 0.056, while post hoc analysis showed a significant effect between WS and WSI with p = 0.023, and nonsignificant effects between WTS and WS/WSI (p = 0.070/0.607), respectively. Small perturbations of the foot can influence the control of gait rhythmicity by increasing the variability in a dissipative deterministic regimen.

Eumelanin Graphene-Like Integration: The Impact on Physical Properties and Electrical Conductivity.

The recent development of eumelanin pigment-based blends integrating "classical" organic conducting materials is expanding the scope of eumelanin in bioelectronics. Beyond the achievement of high conductivity level, another major goal lays in the knowledge and feasible control of structure/properties relationship. We systematically investigated different hybrid materials prepared by in situ polymerization of the eumelanin precursor 5,6-dihydroxyindole (DHI) in presence of various amounts of graphene-like layers. Spectroscopic studies performed by solid state nuclear magnetic resonance (ss-NMR), x-ray photoemission, and absorption spectroscopies gave a strong indication of the direct impact that the integration of graphene-like layers into the nascent polymerized DHI-based eumelanin has on the structural organization of the pigment itself, while infrared, and photoemission spectroscopies indicated the occurrence of negligible changes as concerns the chemical units. A tighter packing of the constituent units could represent a strong factor responsible for the observed improved electrical conductivity of the hybrid materials, and could be possible exploited as a tool for electrical conductivity tuning.

Supplementing π-systems: eumelanin and graphene-like integration towards highly conductive materials for the mammalian cell culture bio-interface.

Organic (bio)electronics appears to be the first target for competitive exploitation in the materials science of eumelanins, black insoluble photoprotective human biopolymers. Nonetheless, the low conductivity of these pigments is limiting the implementation of eumelanin-based devices. Here we present a novel organic/organic hybrid material (EUGL) by integration of conductive graphene-like (GL) layers within the EUmelanin pigment (EU). GL layers were obtained by a two-step oxidation/reduction of carbon black. The stability of GL layers over a wide pH range and the self-assembling tendency place this material in a leading position for the fabrication of hybrid materials in aqueous media. EUGL was obtained by inducing the polymerization of eumelanin precursors (5,6-dihydroxyindole, DHI and 5,6-dihydroxyindole-2 carboxylic acid, DHICA) in aqueous media containing GL layers. The new material featured promising biocompatibility and an increased conductivity with respect to eumelanin by four orders of magnitude.

Wet chemical method for making graphene-like films from carbon black.

Reduction of strongly oxidized carbon black by hydrazine hydrate yields water-insoluble graphene-like sheets that undergo to self-assembling in thin film on surfaces after drying. The height of a drop-casted graphene-like film was determined by atomic force microscopy (AFM) to be around 20 nm, corresponding to approximately 25 graphene-like layers. The oxidized carbon black and the corresponding reduced form were carefully characterized.

Pedaling time variability is increased in dropped riding position.

Variability of cycle-to-cycle duration during a pedaling task is probably related to the rhythmic control of the lower limb muscles as in gait. Although walking variability has been extensively studied for its clinical and physiological implications, pedaling variability has received little attention. The present contribution determines the variability of the cycling time during a 10-min exercise as a function of upper body position. Nine healthy males were required to pedal on cycle-ergometer at a self-selected speed for 10 min in two different upper body positions [hands on upper handlebars (UP) or lower handlebars (DP)]. Time domain measures of cycling variability [total standard deviation (SDtot), mean standard deviation cycle-to-cycle intervals over 100 cycles (SD100), standard deviation of the average cycle-to-cycle intervals over 100 cycles (SDA100)] were measured. Moreover, the same time domain measures were also calculated for heart rate in order to discriminate possible involvements of autonomic regulation. Finally, the structure of the cycle variations has been analyzed in the framework of deterministic chaos calculating the maximum Lyapunov exponents. Significant increases in cycle-to-cycle variability were found for SDtot, SD100 in DP compared to UP, whereas cardiac parameters and other cycling parameters were not changed in the two positions. Moreover, the maximum Lyapunov exponent was significantly more negative in DP. The results suggest that small perturbations of upper body position can influence the control of cycling rhythmicity by increasing the variability in a dissipative deterministic regimen.