Theoretical evidence supporting harmonic reaching trajectories

Minimum Jerk trajectories have been long thought to be the reference trajectories for human movements due to their impressive similarity with human movements. Nevertheless, minimum jerk trajectories are not the only choice for C∞ (i.e., smooth) functions. For example, harmonic trajectories are smooth functions that can be superimposed to describe the evolution of physical systems. This paper analyses the possibility that motor control plans using harmonic trajectories, will be experimentally observed to have a minimum jerk likeness due to control signals being transported through the Central Nervous System (CNS) and muscle-skeletal system. We tested our theory on a 3-link arm simulation using a recently developed planner that we reformulated into a motor control architecture, inspired by the passive motion paradigm. The arm performed 100 movements, reaching for each target defined by the clock experiment. We analysed the shape of the trajectory planned in the CNS and executed in the physical simulator. We observed that even under ideal conditions (i.e., absence of delays and noise) the executed trajectories are similar to a minimum jerk trajectory; thus, supporting the thesis that the human brain might plan harmonic trajectories

Geometrical postural optimisation of 7-DoF limb-like manipulators

Robots are moving towards applications in less structured environments, but their model-based controllers are challenged by the tasks’ complexity and intrinsic environmental unpredictability. Studying biological motor control can provide insights into overcoming these limitations due to the high dexterity and stability observable in humans and animals. This work presents a geometrical solution to the postural optimisation of 7-DoF limbs-like mechanisms, which are robust to singularities and computationally efficient. The theoretical formulation identified two separate decoupled optimisation strategies. The shoulder and elbow strategy align the plane of motion with the expected plane of motion and guarantee the reachability of the end-posture. The wrist strategy ensures the end-effector orientation, which is essential to retain manipulability when nearing a singular configuration. The numerical results confirmed the theoretical observations and allowed us to identify the effect of different grasp strategies on system manipulability. The geometrical method was numerically tested in thousands of configurations proving to be both robust and accurate. The tested scenarios include left and right arm postures, singular configurations, and walking scenarios. The proposed geometrical approach can find application in developing efficient and robust interaction controllers that could be applied in computational neuroscience and robotics

Recombinant C1 inhibitor in the prevention of severe COVID-19: a randomized, open-label, multi-center phase IIa trial.

BACKGROUND Conestat alfa (ConA), a recombinant human C1 inhibitor, may prevent thromboinflammation. METHODS We conducted a randomized, open-label, multi-national clinical trial in which hospitalized adults at risk for progression to severe COVID-19 were assigned in a 2:1 ratio to receive either 3 days of ConA plus standard of care (SOC) or SOC alone. Primary and secondary endpoints were day 7 disease severity on the WHO Ordinal Scale, time to clinical improvement within 14 days, and safety, respectively. RESULTS The trial was prematurely terminated because of futility after randomization of 84 patients, 56 in the ConA and 28 in the control arm. At baseline, higher WHO Ordinal Scale scores were more frequently observed in the ConA than in the control arm. On day 7, no relevant differences in the primary outcome were noted between the two arms (p = 0.11). The median time to defervescence was 3 days, and the median time to clinical improvement was 7 days in both arms (p = 0.22 and 0.56, respectively). Activation of plasma cascades and endothelial cells over time was similar in both groups. The incidence of adverse events (AEs) was higher in the intervention arm (any AE, 30% with ConA vs. 19% with SOC alone; serious AE, 27% vs. 15%; death, 11% vs. 0%). None of these were judged as being related to the study drug. CONCLUSION The study results do not support the use of ConA to prevent COVID-19 progression. CLINICAL TRIAL REGISTRATION https://clinicaltrials.gov, identifier NCT04414631

Current trends in cannulation and neuroprotection during surgery of the aortic arch in Europe†‡

OBJECTIVES To conduct a survey across European cardiac centres to evaluate the methods used for cerebral protection during aortic surgery involving the aortic arch. METHODS All European centres were contacted and surgeons were requested to fill out a short, comprehensive questionnaire on an internet-based platform. One-third of more than 400 contacted centres completed the survey correctly. RESULTS The most preferred site for arterial cannulation is the subclavian-axillary, both in acute and chronic presentation. The femoral artery is still frequently used in the acute condition, while the ascending aorta is a frequent second choice in the case of chronic presentation. Bilateral antegrade brain perfusion is chosen by the majority of centres (2/3 of cases), while retrograde perfusion or circulatory arrest is very seldom used and almost exclusively in acute clinical presentation. The same pumping system of the cardio pulmonary bypass is most of the time used for selective cerebral perfusion, and the perfusate temperature is usually maintained between 22 and 26°C. One-third of the centres use lower temperatures. Perfusate flow and pressure are fairly consistent among centres in the range of 10-15 ml/kg and 60 mmHg, respectively. In 60% of cases, barbiturates are added for cerebral protection, while visceral perfusion still receives little attention. Regarding cerebral monitoring, there is a general tendency to use near-infrared spectroscopy associated with bilateral radial pressure measurement. CONCLUSIONS These data represent a snapshot of the strategies used for cerebral protection during major aortic surgery in current practice, and may serve as a reference for standardization and refinement of different approache

Modelling and development of heterogeneous wireless networks for Vehicle-to-Vehicle (V2V) and Vehicle-to-Infrastructure (V2I) applications with emphasis on harsh transmission environments

This dissertation aims at modeling and development of heterogeneous wireless networks for Vehicle-to-Vehicle (V2V) and Vehicle-to-Infrastructure (V2I) applications with emphasis on harsh transmission environments. Specifically, the dissertation addresses the problem of the lack of reliability of the simulations due to their differentiation compared to the experimental measurements and in particular in the case of wireless transmission within the tunnel for surveillance applications within mobile nodes (vehicles) using different networks. For this purpose, channel models have been studied in great detail to find the most appropriate one. The primary objective of the dissertation as mentioned above is the selection / development of a representative model channel for wireless mobile networks. More specifically, based on experimental measurements, a wireless channel model which operates at 5.4 - 5.9 GHz frequency band was selected for railways and motorways tunnel applications. The second main objective of the present thesis was to design a handover algorithm in order to optimize the performance in conditions where vehicles - trains are traveling on opposite tracks within a tunnel during the WiMAX FBSS (Fast Base Station Switching process) and compare with the Vertical handover algorithm (VHO). The next objective was to design an algorithm that aims to optimize the QoS of the wireless channel, therefore an heterogeneous IEEE 802.11p - LTE (HetNet) wireless network was deployed under SISO and MIMO conditions within a suburban environment. The algorithm includes dynamic grouping of vehicles in clusters as well as Cluster Header (CH) selection and the corresponding gateway for the IEEE 802.11p - LTE Het-Net. For this purpose, the proposed Cluster Selection Algorithm is simulated using the Veins library of the OMNeT ++ simulator and the SUMO (Simulation of Urban Mobility) simulator. A separate contribution of the dissertation was the development of the innovative Virtual Drive test method by simulating a vehicular LTE model for a predefined route using a LTE base station simulator, a Channel simulator, a RayTracing tool, and an UE node. Finally, the research expanded into the design and simulation of the proposed Break-Point-PathLoss model in a tunnel-channel environment and then applied to a WiMAX-WLAN networks. Using the proposed Break-Point-PathLoss channel model, the user can now accurately simulate each wireless network in the OMNeT ++ simulator and produce reliable results for wireless network applications in a tunnel as long as we know the geometric dimensions.Η παρούσα διατριβή έχει ως θέμα τη μοντελοποίηση και ανάπτυξη ετερογενών κινητών δικτύων οχήματος-προς-όχημα (Vehicle to-Vehicle) και οχήματος-προς-υποδομή (Vehicle-to-Infrastructure) με έμφαση σε δύσκολα περιβάλλοντα μετάδοσης. Ειδικότερα η διατριβή προσέγγισε το πρόβλημα της έλλειψης αξιοπιστίας των εξομοιώσεων λόγω της διαφοροποίησης τους σε σύγκριση με πειραματικές μετρήσεις και ειδικότερα κατά την περίπτωση ασύρματης μετάδοσης εντός σήραγγας για εφαρμογές επιτήρησης εντός κινούμενων κόμβων (τρένο-οχήματα) με χρήση ετερογενών δικτύων. Για το σκοπό αυτό μελετήθηκαν με μεγάλη λεπτομέρεια μοντέλα καναλιού για την εξεύρεση του πλέον κατάλληλου. Ο πρώτος κατά σειρά στόχος της διατριβής όπως προαναφέρθηκε είναι η επιλογή/ανάπτυξη ενός αντιπροσωπευτικού μοντέλου καναλιού, για ασύρματα κινούμενα δίκτυα. Πιο συγκεκριμμένα, προτάθηκε με βάση πειραματικές μετρήσεις και επιλέχθηκε μοντέλο ασύρματου καναλιού για την περιοχή συχνοτήτων 5.4-5.9 GHz σε περιβάλλοντα σήραγγας αμαξοστοιχίας και αυτοκινητοδρόμου. Ο δεύτερος βασικός στόχος της παρούσας διατριβής ήταν ο σχεδιασμός και η αναπτύξη ενός αλγόριθμου μεταπομπής για τη βελτιστοποίηση των επιδόσεων σε συνθήκες μετάδοσης-λήψης οχημάτων – συρμών τρένων τα οποία κινούνται σε αντιπαράλληλες τροχίες εντός σήραγγας, κατά τη διαδικασία του WiMAX FBSS (Fast Base Station Switching) Handover και η σύγκρισή του με τον αντίστοχο Vertical Handover (VHO). O επόμενος στόχος ήταν ο σχεδιασμός ενός αλγόριθμου που στοχεύει στην βελτιστοποίηση του QoS του ασύρματου καναλιού κατά την περίπτωση ενός ασύρματου κινούμενου ετερογενούς (HetNet) IEEE 802.11p - LTE δικτύου οχημάτων με χρήση των τεχνικών SISO (single-input & single-output)και MIMO (multiple-input & multiple-output) εντός προαστιακού περιβάλλοντος. Ο αλγόριθμος περιλαμβάνει τη δυναμική ομαδοποίηση των οχημάτων σε clusters καθώς και την επιλογή Cluster Header (CH) και του αντίστοιχου Gateway για το Het-Net IEEE 802.11p – LTE. Για την πληρέστερη τεκμηρίωση των αποτελεσμάτων συγκρίθηκαν τα αποτελέσματα με αντίστοιχους Handover αλγόριθμους βασισμένους στην τεχνική του Clustering και αντιστοίχως για διαφορετική πυκνότητα και ταχύτητα οχημάτων. Για το σκοπό αυτό ο προτεινόμενος Handover αλγόριθμος εξομοιώθηκε μέσω της βιβλιοθήκης Veins του εξομοιωτή OMNeT++, με τη χρήση του SUMO – (Simulation of Urban Mοbility) εξομοιωτή. Μια ξεχωριστή συνεισφορά της διατριβής αποτέλεσε η ανάπτυξη της καινοτόμου μεθόδου του Virtual Drive testing μέσω της προσομοίωσης ενός αυτοκινούμενου LTE προτύπου για μια προεπιλεγμένη διαδρομή, με τη χρήση ενός LTE base station emulator, ενός Channel emulator, ενός RayTracing tool και μιας φορητής συσκευής σε ρόλο LTE κινούμενου κόμβου. Απώτερος στόχος του Virtual Drive testing είναι η χαρτογράφηση του LTE δικτύου ενός κινούμενου οχήματος σε μια προεπιλεγμένη περιοχή ενδιαφέροντος και η ρεαλιστική απεικόνιση των συνθηκών μετάδοσης με τη χρήση ενός Ray Tracing μοντέλου καναλιού σε προαστικό περιβάλλον. Τέλος, η έρευνα επεκτάθηκε στο σχεδιασμό και την εξομοίωση του προτεινόμενου Break-Point-PathLoss μοντέλου καναλιού σε περιβάλλον σήραγγας και εν συνεχεία εφαρμόστηκε σε ετερογενή WiMAX-WLAN δίκτυα. Με τη χρήση του προτεινόμενου Break-Point-PathLoss μοντέλου καναλιού ο χρήστης δύναται πλέον να εξομοιώσει με ακρίβεια οποιοδήποτε ασύρματο δίκτυο στον εξομοιωτή OMNeT++ και να παράξει αξιόπιστα αποτελέσματα για εφαρμογές ασύρματων δικτύων σε σήραγγα αρκεί να γνωρίζει τις γεωμετρικές διαστάσεις της

Exploiting spherical projections to generate human-like wrist pointing movements

The mechanism behind the generation of human movements is of great interest in many fields (e.g. robotics and neuroscience) to improve therapies and technologies. Optimal Feedback Control (OFC) and Passive Motion Paradigm (PMP) are currently two leading theories capable of effectively producing human-like motions, but they require solving nonlinear inverse problems to find a solution. The main benefit of using PMP is the possibility of generating path-independent movements consistent with the stereotypical behaviour observed in humans, while the equivalent OFC formulation is path-dependent. Our results demonstrate how the path-independent behaviour observed for the wrist pointing task can be explained by spherical projections of the planar tasks. The combination of the projections with the fractal impedance controller eliminates the nonlinear inverse problem, which reduces the computational cost compared to previous methodologies. The motion exploits a recently proposed PMP architecture that replaces the nonlinear inverse optimisation with a nonlinear anisotropic stiffness impedance profile generated by the Fractal Impedance Controller, reducing the computational cost and not requiring a task-dependent optimisation