Streifenförmige Ablagerung des Reaktionsprodukts bei einer Gasphasenreaktion

The gas-phase reaction of NH3 with HCl in a glas tube (length 150 cm, diameter 1–6 cm) leads to solid depositions of NH4Cl on the glaswall, with a regularpattem of stripes. The peculiar structure is also observed with other volatile reactants leading to a salt as the only solid product. Variations of tubediameters and temperatures indicate a broad validity of the observations

Autonomes Parken mit Parkl¨uckenerkennung

Anl¨asslich des ProjektseminarsElektrotechnik/Informationstechnik an der Otto-von-Guericke-Universit¨at Magdeburg sollte ein Roboter entwickelt werden, der die Funktionsweise eines Parkassistenten simuliert. In nachfolgender Arbeit wird veranschaulicht, wie sich diesmithilfe von Lego Mindstorms realisieren ließ. Dabei wird auch grafisch auf die Umsetzung des Roboters eingegangen. Neben Konstruktion und Programmierung erfolgt zudem eine Analyse der dabei aufgetretenen Schwierigkeiten und Probleme. Im Zuge des Projekts ist dabei ein Fahrzeug entstanden, das seine Parkl¨ucke selbstst¨andig erkennt und sowohl ein- als auch ausparken kann. Hierbei wird zwischen L¨angs und Querparken, sowie zwischen verschiedenen Gr¨oßen derParklücke differenziert

Indigo : a new tribological substance class for non-toxic and ecological gliding surfaces on ice, snow, and water

The biogenic substance E-indigo can form supramolecular, hydrophobic structures using self-organization. These structures show a low coefficient of friction as a gliding layer against polar surfaces. The formation of primary particles with platelet morphology based on hydrogen-bonded E-indigo molecules is ideal to produce the gliding layer. Structures with excellent gliding properties can be achieved by means of directed friction and high pressure, as well as through tempering. The resulting hard, thin gliding layer of E-indigo does not easily absorb dirt and, thus, prevents a rapid increase in friction. Field tests on snow, with cross-country skis, have shown promising results in comparison to fluorinated and non-fluorinated waxes. Based on quantitative structure–activity relationship (QSAR) data for E-indigo, and its isomers and tautomers, it has been demonstrated that both the application and abrasion of the thin indigo layers are harmless to health, and are ecologically benign and, therefore, sustainable

Design and Evaluation of a Fiber-Optic Grip Force Sensor with Compliant 3D-Printable Structure for (f)MRI Applications

Grip force sensors compatible with magnetic resonance imaging (MRI) are used in human motor control and decision-making research, providing objective and sensitive behavioral outcome measures. Commercial sensors are expensive, cover limited force ranges, rely on pneumatic force transmission that cannot detect fast force changes, or are electrically active, which increases the risk of electromagnetic interference. We present the design and evaluation of a low-cost, 3D-printed, inherently MRI-compatible grip force sensor based on a commercial intensity-based fiber-optic sensor. A compliant monobloc structure with flexible hinges transduces grip force to a linear displacement captured by the fiber-optic sensor. The structure can easily be adapted for different force ranges by changing the hinge thickness. A prototype designed for forces up to 800 N was manufactured and showed a highly linear behavior (nonlinearity of 2.37%) and an accuracy of 1.57% in a range between zero and 500 N. It can be printed and assembled within one day and for less than $300. Accurate performance was confirmed, both inside and outside a 3 T MRI scanner within a pilot study. Given its simple design allowing for customization of sensing properties and ergonomics for different applications and requirements, the proposed grip force handle offers researchers a valuable scientific tool

Mixed methods usability evaluation of an assistive wearable robotic hand orthosis for people with spinal cord injury

BACKGROUND Robotic hand orthoses (RHO) aim to provide grasp assistance for people with sensorimotor hand impairment during daily tasks. Many of such devices have been shown to bring a functional benefit to the user. However, assessing functional benefit is not sufficient to evaluate the usability of such technologies for daily life application. A comprehensive and structured evaluation of device usability not only focusing on effectiveness but also efficiency and satisfaction is required, yet often falls short in existing literature. Mixed methods evaluations, i.e., assessing a combination of quantitative and qualitative measures, allow to obtain a more holistic picture of all relevant aspects of device usability. Considering these aspects already in early development stages allows to identify design issues and generate generalizable benchmarks for future developments. METHODS We evaluated the short-term usability of the RELab tenoexo, a RHO for hand function assistance, in 15 users with tetraplegia after a spinal cord injury through a comprehensive mixed methods approach. We collected quantitative data using the Action Research Arm Test (ARAT), the System Usability Scale (SUS), and timed tasks such as the donning process. In addition, qualitative data were collected through semi-structured interviews and user observations, and analyzed with a thematic analysis to enhance the usability evaluation. All insights were attributed and discussed in relation to specifically defined usability attributes such as comfort, ease of use, functional benefit, and safety. RESULTS The RELab tenoexo provided an immediate functional benefit to the users, resulting in a mean improvement of the ARAT score by 5.8 points and peaking at 15 points improvement for one user (clinically important difference: 5.7 points). The mean SUS rating of 60.6 represents an adequate usability, however, indicating that especially the RHO donning (average task time = 295 s) was perceived as too long and cumbersome. The participants were generally very satisfied with the ergonomics (size, dimensions, fit) of the RHO. Enhancing the ease of use, specifically in donning, increasing the provided grasping force, as well as the availability of tailoring options and customization were identified as main improvement areas to promote RHO usability. CONCLUSION The short-term usability of the RELab tenoexo was thoroughly evaluated with a mixed methods approach, which generated valuable data to improve the RHO in future iterations. In addition, learnings that might be transferable to the evaluation and design of other RHO were generated, which have the potential to increase the daily life applicability and acceptance of similar technologies

Culture and labour productivity: an empirical investigation

Culture is considered as one of the most powerful forces that shape human behaviour and thereby economic activity. This paper investigates the effects of culture on labour productivity and examines the cultural traits driving this relationship. Using panel data analysis, empirical evidence is provided covering a sample of 34 OECD countries over a wide period of three decades. Our empirical results suggest a significant positive relationship between the cultural background and labour productivity. The main channels of this positive impact are control and work ethic environment, while obedience has a negative impact on productivity. These findings are robust to a series of robustness checks, including alternative cultural measures, additional control variables, various country samples, and alternative specifications

Fully Wearable Actuated Hand Exoskeleton for Assistance in Daily Life and Therapy

Human hands combine unique dexterity and somatosensory abilities which are exceptional in living organisms and not reached in technology. How important hands are for our daily living becomes evident when we temporarily or permanently lose the ability to use them and simple tasks like eating or grooming suddenly require assistance from a third person. Worldwide, far more than 50 million individuals suffer from upper limb impairment following neurological diseases or trauma such as stroke or spinal cord injury. Pain, spasticity, contractures, and weakness lead to disabilities ranging from poor finger individuation to complete paralysis of the hand and, consequently, to a major loss of independence and quality of life. In subjects with neuromotor hand impairment, it is well acknowledged that through robotics high dose and intensity in the training and a positive effect on the outcome of the rehabilitation therapy can be reached. However, many individuals remain with persistent hand impairment when they are discharged from the hospital after the typical treatments to restore the hand function have been applied. Whether or not there is potential for further recovery of the nervous system, the use of the hand and the therapy must be continued to at least maintain the residual hand function. The potential of wearable hand exoskeletons for assistance in daily living and continued home rehabilitation therapy has been recognized in research and industry, and numerous devices have been developed. However, the human hand is highly dexterous, powerful, and of leanest design. The emulation of its functions requires complex mechanical systems, and the trade-off between functionality and usability in daily life is challenging. Thus, no device has been presented that successfully combines the required capability for functional grasping tasks, full wearablility for use in daily living, and reliable, intuitive control. The aim of this work is to develop and evaluate a wearable robotic system fusing the concepts of assistance and therapy in the design of RELab tenoexo, a fully wearable actuated hand exoskeleton for assistance in daily life and with the potential for wearable all-day rehabilitation in the clinic or at home for subjects with neuromotor hand impairments. We identify the key design factors and requirements for such a device in continuous discussion with expert clinicians, interviews with users, and various usability studies. We realize that, in a first step, a fully wearable hand exoskeleton for assistance in daily living has to be designed, and only in a second step, through control based on physiological signals, this device can turn into a wearable system for assistance and rehabilitation. Based on the defined requirements and a previously presented hand exoskeleton, we suggest a detailed design concept for RELab tenoexo. We reduce the dexterity of the hand to few basic functions needed to perform the four most frequently used grasp types. With strict attention paid to ease of use, we present various options to customize the modular device. For optimal assistance, we develop an automated tailor algorithm which allows to automatically generate a virtual model of the hand exoskeleton based on hand size, kinematic relations, and desired wrist angles of individual users. As perceived weight is paramount for the acceptance of assistive devices, we investigate the use of a remote actuation system to move the mass of the actuators from the hand to the back. We summarize various approaches for remote actuation in a literature review and objectively compare advantages and disadvantages of the three most frequently used principles (pneumatic, hydraulic, and mechanical power transmission), focusing on usability during activities of daily living. We build and evaluate test benches to quantitatively compare the approaches' performance and propose guidelines for the design of the tested remote actuation systems based on desired key properties. Finally, we digitize these guidelines and present an automatic component selector that can be used to select and automatically dimension the best matching remote actuation system for most fully wearable robotics. The most promising remote actuation system for RELab tenoexo, a Bowden-cable-based force transmission system, is iterated and improved. We develop power-saving control strategies and integrate a cable bending angle sensor that turns backlash from a common drawback of cable transmission systems into an advantage. The new sensor allows to accurately control the force with no need for electronics at the output of the remote actuation system. The final Bowden-cable-based force transmission system achieves output forces as well as power-to-mass ratios that outperform state-of-the-art remote actuation systems and can be integrated into an extremely lightweight backpack for RELab tenoexo. The mechanical evaluation of the fully assembled RELab tenoexo shows that the defined requirements in terms of grasp types, fingertip force, range of motion, as well as weight and dimensions are largely met. In a user test, we evaluate the usability in daily life including comfort, appearance, and perceived weight. The potential as assistive device is highlighted in a standardized assessment of the upper extremity performance where a subject with spinal cord injury showed an immediate clinically meaningful difference in hand function when assisted by RELab tenoexo. Building on the hypothesis that control based on physiological signals can promote neuroplasticity, we target to convert RELab tenoexo from a promising purely assistive device into a platform for continued rehabilitation and present a framework for a real-time myoelectric intention detection system. In contrast to other systems which often require extensive cabling, electrode placement, and connection to external computers, this system is stand-alone and fully wearable. In combination with a short software routine to train a classification algorithm on the recognition of custom grasp types, this system provides a unique ease of use. Testing demonstrated that the proposed system can offline classify five hand gestures with high accuracy and online classify the three gestures needed to control RELab tenoexo performed by subjects with mild to strong neuromotor impairment. Finally, we adapt RELab tenoexo to the size and functional requirements of children and introduce the first wearable pediatric full hand exoskeleton PEXO. In a test with a 6 years old subject with stroke, we evaluate the feasibility of PEXO-assisted task-oriented training and show promising first results. With strict focus on the overall usability including functionality, ease of use, and human factors, we successfully combine advantages of rigid link structures and tendon-based-mechanisms with kinematic considerations, and condense the complexity of the human hand to few functions. With a lightweight, low-profile, and fully wearable design, RELab tenoexo assists subjects with neuromotor hand impairment with the most frequently used grasp types in activities of daily living, and generates an immediate clinically important difference in the functional ability. In combination with the integrated myoelectric intention detection system, RELab tenoexo is a promising candidate for assistance in daily living for individuals with strong hand impairments, and as a platform for continuous wearable neurorehabilitation

Eine Studie über Südsudanesen in Khartum

The dissertation deals with marginalisation in Sudan and examines the relations between southern Sudanese in Khartoum, the majority society of Khartoum and the state. The research arose from the assumption that the settlement of war between North and South Sudan, in January 2005, and the corresponding official termination of hostilities affects the reality of civilians in Khartoum. While majority of southern Sudanese in Khartoum live in squatter areas or camps where they are geographically set apart from the majority society, for this project an elite group of privileged and educated southern Sudanese has been chosen. Members of this group live in the city centre alongside their northern Sudanese countrymen; they work in local (northern) companies, non-governmental and international organisations or for newspapers or political parties; they teach at schools and study at universities. Some were born in Khartoum; others came as children with their parents; some came unaccompanied in search of education or work. All look back at a long stay in Khartoum; in fact, they spent the larger parts of their lives here. Their offspring were brought up in Khartoum and most of the times were born there. They are considerably well off and can afford the costly life in the centre of the capital. This group of southern Sudanese is a small elite and a clear minority among their own people. Worth mentioning, interview partners have considerable influence on the political opinion-making in the southern community in the North and even in the South. Their work in ethnic communities, church groups and political parties – and the general acceptance that they are more educated than the majority of southern Sudanese – allows them to seriously influence the southern community. Following guidelines of grounded theory, it has been surveyed, how accessible society and the system are for southern Sudanese, who have been living and working in Khartoum for at least two decades. Furthermore, it has been analysed, how relations between the distinct groups change over time. Apparently, in the consideration of process, the Comprehensive Peace Agreement (CPA) is of particular importance. The study looks at if the CPA has changed relations and whether it has made unity attractive to the research group, which, at least from an economical perspective, is able to lead a better life in the North than is currently possible in the South. The research takes the challenge of looking into everyday matters and strategic, long-sighted projects under drastically transformed conditions, namely the termination of war, the potential division of the country into two parts and changing perspectives for return to the South. Moreover, it analyses the construction of identity and different forms of belonging after the signature of the CPA in 2005 and before the formation of the new state in July 2011.Die Dissertation beschäftigt sich mit der Marginalisierung von ethnischen Minoritäten im Sudan und untersucht die Beziehungen von in Khartum lebenden Südsudanesen zur nordsudanesischen Mehrheitsgesellschaft und dem Staat. Das Forschungsinteresse ist der Annahme entsprungen, dass der Abschluss des Friedensvertrages zwischen Nordsudan und Südsudan im Januar 2005, sowie der offizielle Waffenstillstand zwischen den Krieg führenden Parteien, auch die Situation von Zivilisten in Khartum beeinflussen. Die meisten Südsudanesen in Khartum leben außerhalb des Stadtzentrums in Armenvierteln und Lagern und sind so schon rein geographisch von der Mehrheitsgesellschaft abgeschnitten. Mitglieder der Forschungsgruppe hingegen leben Seite an Seite mit ihren nordsudanesischen Landsmännern im Zentrum Khartums. Es handelt sich bei der Forschungsgruppe um eine kleine, gut ausgebildete Elite, die durch einen relativ hohen sozioökonomischen Status charakterisiert ist. Interviewpartner arbeiten in lokalen (nordsudanesischen) Unternehmen, in Nichtregierungsorganisationen und internationalen Organisationen oder z.B. für Zeitungsredaktionen und politische Parteien. Andere lehren an Schulen oder studieren an Universitäten. Manche von ihnen wurden bereits in Khartum geboren, andere kamen als Kinder mit ihren Eltern und wieder andere alleine auf der Suche nach Bildung oder Arbeit. Sie alle blicken auf eine lange Zeit in Khartum zurück und haben den größten Teil ihres Lebens hier verbracht. Ihre Kinder wurden entweder in Khartum geboren oder wuchsen zumindest hier auf. Die Gruppe ist relativ wohl situiert und kann sich das kostspielige Leben im Zentrum der Hauptstadt leisten. Damit bildet sie eine klare Minderheit innerhalb der eigenen Gruppe. Durch ihre Arbeit in ethnischen Gruppierungen, Kirchen und politischen Parteien sowie durch die allgemeine Akzeptanz, dass sie besser gebildet sind als die Mehrheit der Südsudanesen, haben Mitglieder der Forschungsgruppe nennenswerten Einfluss auf die politische Meinungsbildung innerhalb der südsudanesischen Gemeinschaft im Norden und sogar im Süden. Mit Methoden der Grounded Theory wurde eruiert, wie zugänglich die Gesellschaft und das System für Südsudanesen, die seit mindestens zwei Jahrzehnten in Khartum leben, sind. Es wurde untersucht, wie die Beziehungen der einzelnen Gruppen sich mit der Zeit verändern, wobei der Einfluss des Friedensabkommens besondere Berücksichtigung fand. Es wurde hinterfragt, ob es dem Friedensabkommen gelungen ist, Einheit mit dem Norden für Interviewpartner, die zumindest aus ökonomischer Sicht im Norden ein besseres Leben führen als es derzeit im Süden möglich wäre, attraktiv zu machen. Die Forschung untersucht alltägliche Angelegenheiten und strategische, langfristige Planungen unter sich drastisch und rapide verändernden Bedingungen, nämlich die Beendigung des Krieges, die mögliche Zweiteilung des Landes und die mögliche Rückkehr in den Südsudan. Die Forschung beschäftigt sich darüber hinaus mit Identitätskonstruktionen und Formen der Zugehörigkeit im Sudan nach dem Friedensabkommen von 2005 und vor der Unabhängigkeit des Südsudans im Juli 2011