Geometric Basics and Calculation Methods for the Design of a Technical Saddle Joint based on Owl Neck Vertebrae

A saddle joint enables the movement of two components relative to each other primarily about two axes of rotation and, to a limited extent, in translational direction. This type of joint is primarily found in nature, for example in the human thumb, in the ossicles and the cervical spine of owls. Motivated by the high degree of the owls’ head mobility, the authors aim to make this high motion potential technically accessible by defining relevant design parameters and developing calculation methods for dimensioning the saddle joint components. First, an abstracted contact geometry model based on the owls’ saddle joints is de-fined. A method for calculating the kinematics of the joint as a function of the previously introduced design parameters of the contact is derived mathematically. Regarding the implementation in a design process, this model is used to calculate the restoring forces required to stabilize the joint parts as well as the actuator torque needed for a specific rotational movement around those axes. Furthermore, the rotational stiffness of a specific joint geometry is calculated as an important design criterion. In summary, the defined contact geometry, the kinematics, and the computable forces serve as basis for designing technical saddle joints in the future

Interaction of Acid-sensing Ion Channel (ASIC) 1 with the Tarantula Toxin Psalmotoxin 1 is State Dependent

Acid-sensing ion channels (ASICs) are Na+ channels gated by extracellular H+. Six ASIC subunits that are expressed in neurons have been characterized. The tarantula toxin psalmotoxin 1 has been reported to potently and specifically inhibit homomeric ASIC1a and has been useful to characterize ASICs in neurons. Recently we have shown that psalmotoxin 1 inhibits ASIC1a by increasing its apparent affinity for H+. However, the mechanism by which PcTx1 increases the apparent H+ affinity remained unclear. Here we show that PcTx1 also interacts with ASIC1b, a splice variant of ASIC1a. However, PcTx1 does not inhibit ASIC1b but promotes its opening; under slightly acidic conditions, PcTx1 behaves like an agonist for ASIC1b. Our results are most easily explained by binding of PcTx1 with different affinities to different states (closed, open, and desensitized) of the channel. For ASIC1b, PcTx1 binds most tightly to the open state, promoting opening, whereas for ASIC1a, it binds most tightly to the open and the desensitized state, promoting desensitization

The Tarantula Toxin Psalmotoxin 1 Inhibits Acid-sensing Ion Channel (ASIC) 1a by Increasing Its Apparent H+ Affinity

Acid-sensing ion channels (ASICs) are ion channels activated by extracellular protons. They are involved in higher brain functions and perception of pain, taste, and mechanical stimuli. Homomeric ASIC1a is potently inhibited by the tarantula toxin psalmotoxin 1. The mechanism of this inhibition is unknown. Here we show that psalmotoxin 1 inhibits ASIC1a by a unique mechanism: the toxin increases the apparent affinity for H+ of ASIC1a. Since ASIC1a is activated by H+ concentrations that are only slightly larger than the resting H+ concentration, this increase in H+ affinity is sufficient to shift ASIC1a channels into the desensitized state. As activation of ASIC1a has recently been linked to neurodegeneration associated with stroke, our results suggest chronic desensitization of ASIC1a by a slight increase of its H+ affinity as a possible way of therapeutic intervention in stroke

Die assessering en voorstelling van strategieë vir die belyning van Werknemerhulpprogramme (WHPs) met 'n ontwikkelingsgerigte maatskaplike welsynbenadering

Die navorser het gepoog om strategieë te assesseer en voor te stel vir die belyning van Werknemerhulpprogramme (WHPs) met die ontwikkelingsgerigte maatskaplike welsynsbenadering. Die doelstelling van die studie was om die belyning van WHPs met die ontwikkelingsgerigte maatskaplike welsynsbenadering te ondersoek en te beskryf. Die oogmerk van die studie was om vas te stel of ‘n belyning tussen WHPs en die ontwikkelingsgerigte maatskaplike welsynsbenadering bestaan. Die doelstelling en doelwitte is bereik. Die literatuurstudie het getoon dat daar bykans geen navorsing oor die onderwerp bestaan nie. Die studie was kwantitatief, ondersoekend en beskrywend van aard deurdat die navorser gepoog het om die belyning tussen WHPs en ontwikkelingsgerigte maatskaplike welsyn te ondersoek en te beskryf. Die navorsingsvraelys was in elektroniese formaat en respondente het toegang tot die vraelys verkry deur middel van ‘n internet-skakel (link) wat per epos verskaf is. Die oorspronklike studie-populasie het die lede van EAPA-SA ingesluit. Weens veranderinge in die lidmaatskapvereistes van EAPA-SA en gevolglike veranderinge in die struktuur, het die teiken-populasie kleiner geword. Weens verdere administratiewe tekortkominge het die navorser uiteindelik slegs op die EAPA-SA se Vrystaat-tak gefokus vir respondente. Die bevindinge was dat WHP-personeel se kennis rakende die ontwikkelingsgerigte maatskaplike welsynsbenadering nie op standaard was nie. Alhoewel WHP-personeel se kennis van die benadering (volgens die vyf temas van ontwikkelingsgerigte maatskaplike welsyn) nie goed was nie, toon die data dat verskeie WHPs reeds besig is om gedeeltelik aan die beginsels daarvan te voldoen. Alhoewel die studie-populasie slegs ‘n klein aantal WHP-personeellede ingesluit het, is die navorser van mening dat die studie tog waardevolle inligting na vore gebring het ten einde WHP-personeel in Suid Afrika bewus te maak van die belyning van WHPs met die ontwikkelingsgerigte maatskaplike welsynsbenadering. Dit is belangrik dat WHP-personeel sal begryp dat hul dienste deel vorm van die ontwikkelingsgerigte maatskaplike welsynbenadering soos uiteengesit word in die Witskrif vir Maatskaplike Welsyn van 1997. Vir WHPs om meer vanuit ‘n ontwikkelingsgerigte maatskaplike welsynbenadering te funksioneer is dit van kardinale belang dat hul dienste binne die temas van ontwikkelingsgerigte maatskaplike welsyn se parameters moet val. Laastens, weens die feit dat die Witskrif vir Maatskaplike Welsyn van 1997 tans hersien word, sal dit nodig wees om in die toekoms verdere navorsing oor die onderwerp te onderneem.Mini Dissertation (MSW)--University of Pretoria, 2017.Social Work and CriminologyMSWUnrestricte

Cache-effiziente Block-Matrix-Löser für die Partition of Unity Methode

Die Partition of Unity Methode findet Anwendung in gitterlosen Diskretisierungsverfahren zum Lösen elliptischer partieller Differentialgleichungen. Die bei der Diskretisierung entstehenden Gleichungssysteme besitzen eine Blockstruktur, die sich mittels der Multilevel Partition of Unity Methode asymptotisch optimal lösen lassen. Ein alternatives Verfahren zum Lösen dieser Gleichungssysteme stellen die vorkonditionierten Krylow- Unterraumverfahren dar. In dieser Arbeit wird ein auf der ILU-Zerlegung basierenders CG-Verfahren für Block-Matrizen implementiert, das auf Cache-effizienten Algorithmen basiert. Der Ausgangspunkt stellt die Bibliothek TifaMMy dar. Die in den letzten Jahren entwickelte Bibliothek basiert auf inhärent Cache-effiziente Algorithmen für dicht- und dünnbesetzte Matrizen. Dabei wird eine neue Datenstruktur für Blockmatrizen (BCRS) und die nötigen Algorithmen implementiert. Die Leistung des Block-Matrix-Löser wird mit der Multilevel Partition of Unity Methode verglichen