Design and optimal control of a multistable, cooperative microactuator

In order to satisfy the demand for the high functionality of future microdevices, research on new concepts for multistable microactuators with enlarged working ranges becomes increasingly important. A challenge for the design of such actuators lies in overcoming the mechanical connections of the moved object, which limit its deflection angle or traveling distance. Although numerous approaches have already been proposed to solve this issue, only a few have considered multiple asymptotically stable resting positions. In order to fill this gap, we present a microactuator that allows large vertical displacements of a freely moving permanent magnet on a millimeter-scale. Multiple stable equilibria are generated at predefined positions by superimposing permanent magnetic fields, thus removing the need for constant energy input. In order to achieve fast object movements with low solenoid currents, we apply a combination of piezoelectric and electromagnetic actuation, which work as cooperative manipulators. Optimal trajectory planning and flatness-based control ensure time- and energy-efficient motion while being able to compensate for disturbances. We demonstrate the advantage of the proposed actuator in terms of its expandability and show the effectiveness of the controller with regard to the initial state uncertainty

Movement plans for posture selection do not transfer across hands

Schütz C, Schack T. Movement plans for posture selection do not transfer across hands. Frontiers in Psychology. 2015;6: 1358.In a sequential task, the grasp postures people select depend on their movement history. This motor hysteresis effect results from the reuse of former movement plans and reduces the cognitive cost of movement planning. Movement plans for hand trajectories not only transfer across successive trials, but also across hands. We therefore asked whether such a transfer would also be found in movement plans for hand postures. To this end, we designed a sequential, continuous posture selection task. Participants had to open a column of drawers with cylindrical knobs in ascending and descending sequences. A hand switch was required in each sequence. Hand pro/supination was analyzed directly before and after the hand switch. Results showed that hysteresis effects were present directly before, but absent directly after the hand switch. This indicates that, in the current study, movement plans for hand postures only transfer across trials, but not across hands

A simple model to estimate the percentage of motor plan reuse from hysteresis effect size

Schütz C, Schack T. A simple model to estimate the percentage of motor plan reuse from hysteresis effect size. Frontiers in Psychology. 2019;10: 561.In sequential tasks, a partial reuse of former motor plans results in a persistence in the former posture (termed hysteresis). The cost-optimization hypothesis states that the percentage of reuse depends on the relative cognitive and mechanical cost of each movement. These costs should be constant across all drawers, yet previous studies found a larger hysteresis effect at the central drawers and declining effects toward the periphery. In the current study, we show that a simple mathematical model that assumes a sigmoid optimal grasp angle function and a fixed percentage of motor plan reuse explains the posture variance in a randomized and an ordered sequential drawer opening task. This finding indicates that (1) the optimal pro/supination angle is a sigmoid function of drawer height, (2) the percentage of motor plan reuse is constant across drawers, and (3) a constant percentage of reuse results in a larger hysteresis effect at the central drawers. Based on the model, the percentage of motor plan reuse in future studies can be estimated from the size of the motor hysteresis effect

A Simple Model to Estimate the Percentage of Motor Plan Reuse From Hysteresis Effect Size

In sequential tasks, a partial reuse of former motor plans results in a persistence in the former posture (termed hysteresis). The cost-optimization hypothesis states that the percentage of reuse depends on the relative cognitive and mechanical cost of each movement. These costs should be constant across all drawers, yet previous studies found a larger hysteresis effect at the central drawers and declining effects toward the periphery. In the current study, we show that a simple mathematical model that assumes a sigmoid optimal grasp angle function and a fixed percentage of motor plan reuse explains the posture variance in a randomized and an ordered sequential drawer opening task. This finding indicates that (1) the optimal pro/supination angle is a sigmoid function of drawer height, (2) the percentage of motor plan reuse is constant across drawers, and (3) a constant percentage of reuse results in a larger hysteresis effect at the central drawers. Based on the model, the percentage of motor plan reuse in future studies can be estimated from the size of the motor hysteresis effect

Fine discrimination of volatile compounds by graphene-immobilized odorant-binding proteins

Abstract We describe the fabrication and performance of a biosensor for odorants, using wildtype and engineered mutants of the Italian honeybee (Apis mellifera ligustica) odorant binding protein 14 (OBP14), immobilized onto a reduced graphene oxide field-effect transistor (rGO-FET). The binding properties of the protein when immobilized on the biosensor are similar to those measured in solution, thus providing a method for measuring affinities to small molecules as an alternative to the current fluorescence assay. Out of the 14 chemicals tested, the best ligands for wildtype OBP14 were eugenol, homovanillic acid and related compounds sharing a phenol-methoxy backbone. Other chemicals, including methyl eugenol, showed affinities to OBP14 100–1000 times lower. We have also tested two mutants of OBP14. The first, bearing a HisTag at its N-terminus for better orientation on the sensor surface, showed only minor differences in its binding properties for chemicals when compared to the wildtype. The second contained an additional disulfide bond between helices α3 and α6, thus reducing the dynamics of OBP14 and leading to a higher affinity for eugenol. These data also demonstrate that it is feasible to produce biosensors with desired ligand specificities by introducing selected mutations into the structure of OBPs or other active proteins

Habitual vs Non- Habitual Manual Actions: An ERP Study on Overt Movement Execution

Westerholz J, Schack T, Schütz C, Koester D. Habitual vs Non- Habitual Manual Actions: An ERP Study on Overt Movement Execution. PLoS ONE. 2014;9(4): e93116.This study explored the neurophysiological mechanisms underlying the planning and execution of an overt goal- related handle rotation task. More specifically, we studied the neural basis of motor actions concerning the influence of the grasp choice. The aim of the present study was to differentiate cerebral activity between grips executed in a habitual and a nonhabitual mode, and between specified and free grip choices. To our knowledge, this is the first study to differentiate cerebral activity underlying overt goal-related actions executed with a focus on the habitual mode. In a handle rotation task, participants had to use thumb-toward (habitual) or thumb- away ( non- habitual) grips to rotate a handle to a given target position. Reaction and reach times were shorter for the habitual compared to the non- habitual mode indicating that the habitual mode requires less cognitive processing effort than the non- habitual mode. Neural processes for action execution ( measured by event-related potentials ( ERPs)) differed between habitual and non-habitual conditions. We found differential activity between habitual and non- habitual conditions in left and right frontal areas from -600 to 200 ms time- locked to reaching the target position. No differential neural activity could be traced for the specification of the grip. The results suggested that the frontal negativity reflected increased difficulty in movement precision control in the non- habitual mode compared to the habitual mode during the homing in phase of grasp and rotation actions

A Simple Model to Estimate the Percentage of Motor Plan Reuse From Hysteresis Effect Size

In sequential tasks, a partial reuse of former motor plans results in a persistence in the former posture (termed hysteresis). The cost-optimization hypothesis states that the percentage of reuse depends on the relative cognitive and mechanical cost of each movement. These costs should be constant across all drawers, yet previous studies found a larger hysteresis effect at the central drawers and declining effects toward the periphery. In the current study, we show that a simple mathematical model that assumes a sigmoid optimal grasp angle function and a fixed percentage of motor plan reuse explains the posture variance in a randomized and an ordered sequential drawer opening task. This finding indicates that (1) the optimal pro/supination angle is a sigmoid function of drawer height, (2) the percentage of motor plan reuse is constant across drawers, and (3) a constant percentage of reuse results in a larger hysteresis effect at the central drawers. Based on the model, the percentage of motor plan reuse in future studies can be estimated from the size of the motor hysteresis effect

Zur Effektivität aktiver Arbeitsmarktpolitik : Erfahrungen aus einer integrierten Wirkungs- und Implementationsstudie

"Die hohen Ausgaben der aktiven Arbeitsmarktpolitik, die jährlich bis zu 50 Milliarden DM ausmachen, werden zunehmend in Frage gestellt. Die Meinungen über ihre Effektivität gehen nicht nur in der öffentlichen Debatte, sondern auch in der Wissenschaft weit auseinander. Der Beitrag möchte Argumente, Evidenzen, Analysen und internationale Erfahrungen für eine Klärung bieten. Zunächst wird ein Überblick zum Stand der Wirkungsforschung gegeben. Der Beitrag konzentriert sich auf die noch wenigen bekannten Makrostudien, die den Einfluss der Arbeitsmarktpolitik auf regionaler oder nationaler Ebene einzuschätzen versuchen. Die verschiedenen Ansatzweisen werden aufgeführt und deren Ergebnisse resümiert. Diese sind, wie auch bei mikroökonometrischen Ansätzen, noch recht widersprüchlich und unbefriedigend. Der Beitrag plädiert daher für Makrostudien auf mittlerer, d.h. regionaler Ebene, um die bisher gänzlich vernachlässigte Implementationsebene in die Analyse mit einbeziehen zu können. Er analysiert quantitativ den Einsatz arbeitsmarktpolitischer Instrumente in allen 142 Arbeitsamtsbezirken in Westdeutschland in der Zeit von 1994 bis 1997, ergänzt durch qualitative Fallstudien in drei ausgewählten Arbeitsamtsbezirken. Dabei stellt sich heraus, dass der Einsatz von Weiterbildung, Arbeitsbeschaffung und Lohnsubventionen trotz zentraler Regulierung sowohl im Niveau als auch in der Mischung der Instrumente erheblich variiert, und dies selbst nach statistischer Kontrolle von Niveau und Struktur der Arbeitslosigkeit sowie anderer - außerhalb der Arbeitsmarktpolitik liegender - Einflussgrößen. Aktive Arbeitsämter, denen es im besonderen Maße gelingt, die Langzeitarbeitslosen zu erreichen, zeichnen sich vor allem durch Kooperation mit einer professionaliiserten Trägerstruktur und durch konstruktive Einbindung der Unternehmensseite aus. Es stellt sich die Frage, ob die festgestellte große Variation im Einsatz aktiver Arbeitsmarktpolitik einen Unterschied im Erfolg zur Bekämpfung der Arbeitslosigkeit macht. In einer gepoolten multivariaten Regressionsanalyse werden folgende, zum Teil überraschenden, Effekte festgestellt: Weiterbildung reduziert das Niveau der Langzeitarbeitslosigkeit signifikant um einen Faktor von 0,1; eine ähnliche Wirkung ergibt sich auch für die Struktur der Langzeitarbeitslosigkeit. Arbeitsbeschaffungsmaßnahmen tragen dagegen nicht signifikant und nachhaltig zum Abbau von Langzeitarbeitslosigkeit bei. Lohnsubventionen sind vor allem bei den 'langen Langzeitarbeitslosen' (über zwei Jahre) wirksam. Auch die Implementation macht einen Unterschied. So weisen Arbeitsämter mit kürzeren Weiterbildungsmaßnahmen signifikant bessere Ergebnisse auf als Arbeitsämter mit längeren Maßnahmen. Bei den Lohnsubventionen ist es umgekehrt, hier scheinen Arbeitsämter mit Maßnahmen von durchschnittlich längerer Subventionsdauer erfolgreicher zu sein als Arbeitsämter mit kürzerer Subventionsdauer. International vergleichbare Studien unterstützen diese Ergebnisse in der Tendenz und ergänzen sie um wichtige Gesichtspunkte." (Autorenreferat, IAB-Doku)Arbeitsmarktpolitik - Erfolgskontrolle, Weiterbildung, Arbeitsbeschaffungsmaßnahme, Lohnsubvention, Langzeitarbeitslosigkeit, Arbeitsamtsbezirke, regionale Disparität

Remote Training for Medical Staff in Low-Resource Environments Using Augmented Reality

This work aims to leverage medical augmented reality (AR) technology to counter the shortage of medical experts in low-resource environments. We present a complete and cross-platform proof-of-concept AR system that enables remote users to teach and train medical procedures without expensive medical equipment or external sensors. By seeing the 3D viewpoint and head movements of the teacher, the student can follow the teacher’s actions on the real patient. Alternatively, it is possible to stream the 3D view of the patient from the student to the teacher, allowing the teacher to guide the student during the remote session. A pilot study of our system shows that it is easy to transfer detailed instructions through this remote teaching system and that the interface is easily accessible and intuitive for users. We provide a performant pipeline that synchronizes, compresses, and streams sensor data through parallel efficiency

Directed evolution of G protein-coupled receptors in yeast for higher functional production in eukaryotic expression hosts

Despite recent successes, many G protein-coupled receptors (GPCRs) remained refractory to detailed molecular studies due to insufficient production yields, even in the most sophisticated eukaryotic expression systems. Here we introduce a robust method employing directed evolution of GPCRs in yeast that allows fast and efficient generation of receptor variants which show strongly increased functional production levels in eukaryotic expression hosts. Shown by evolving three different receptors in this study, the method is widely applicable, even for GPCRs which are very difficult to express. The evolved variants showed up to a 26-fold increase of functional production in insect cells compared to the wild-type receptors. Next to the increased production, the obtained variants exhibited improved biophysical properties, while functional properties remained largely unaffected. Thus, the presented method broadens the portfolio of GPCRs accessible for detailed investigations. Interestingly, the functional production of GPCRs in yeast can be further increased by induced host adaptation