Pupil Size in Spider Eyes Is Linked to Post-Ecdysal Lens Growth

In this study we describe a distinctive pigment ring that appears in spider eyes after ecdysis and successively decreases in size in the days thereafter. Although pigment stops in spider eyes are well known, size variability is, to our knowledge, reported here for the first time. Representative species from three families (Ctenidae, Sparassidae and Lycosidae) are investigated and, for one of these species (Cupiennius salei, Ctenidae), the progressive increase in pupil diameter is monitored. In this species the pupil occupies only a fourth of the total projected lens surface after ecdysis and reaches its final size after approximately ten days. MicroCT images suggest that the decrease of the pigment ring is linked to the growth of the corneal lens after ecdysis. The pigment rings might improve vision in the immature eye by shielding light rays that would otherwise enter the eye via peripheral regions of the cornea, beside the growing crystalline lens

Understanding the retinal basis of vision across species

The vertebrate retina first evolved some 500 million years ago in ancestral marine chordates. Since then, the eyes of different species have been tuned to best support their unique visuoecological lifestyles. Visual specializations in eye designs, large-scale inhomogeneities across the retinal surface and local circuit motifs mean that all species' retinas are unique. Computational theories, such as the efficient coding hypothesis, have come a long way towards an explanation of the basic features of retinal organization and function; however, they cannot explain the full extent of retinal diversity within and across species. To build a truly general understanding of vertebrate vision and the retina's computational purpose, it is therefore important to more quantitatively relate different species' retinal functions to their specific natural environments and behavioural requirements. Ultimately, the goal of such efforts should be to build up to a more general theory of vision

A record of spontaneous subduction initiation in the Izu–Bonin–Mariana arc

The initiation of tectonic plate subduction into the mantle is poorly understood. If subduction is induced by the push of a distant mid-ocean ridge or subducted slab pull, we expect compression and uplift of the overriding plate. In contrast, spontaneous subduction initiation, driven by subsidence of dense lithosphere along faults adjacent to buoyant lithosphere, would result in extension and magmatism. The rock record of subduction initiation is typically obscured by younger deposits, so evaluating these possibilities has proved elusive. Here we analyse the geochemical characteristics of igneous basement rocks and overlying sediments, sampled from the Amami Sankaku Basin in the northwest Philippine Sea. The uppermost basement rocks are areally widespread and supplied via dykes. They are similar in composition and age—as constrained by the biostratigraphy of the overlying sediments—to the 52–48-million-year-old basalts in the adjacent Izu–Bonin–Mariana fore-arc. The geochemical characteristics of the basement lavas indicate that a component of subducted lithosphere was involved in their genesis, and the lavas were derived from mantle source rocks that were more melt-depleted than those tapped at mid-ocean ridges. We propose that the basement lavas formed during the inception of Izu–Bonin–Mariana subduction in a mode consistent with the spontaneous initiation of subduction

Spritzgießen von faserverstärkten Kunststoffen mit drehendem Werkzeugkern. Rheologie - praktische Untersuchungen - Auslegungsmethodik

Beim Spritzgießen von länglichen rotationssymmetrischen Bauteilen führen Fertigungsrestriktionen sowie komplexe Geometrien oftmals dazu, dass die Bauteilfüllung in axialer Richtung erfolgt. Strömungsbedingt richten sich die Moleküle sowie ggf. vorhandene Verstärkungsfasern hierbei in Fließrichtung aus. Da bei faserverstärkten Kunststoffen die maximale Verstärkungswirkung erzielt wird, wenn ein Großteil der Fasern in Belastungsrichtung ausgerichtet ist, ist diese axiale Ausrichtung bei innendruckbelasteten Bauteilen nachteilig und führt zu einer ineffizienten Materialausnutzung. In dieser Arbeit wird gezeigt, wie bei solchen Bauteilen durch einen drehenden Werkzeugkern die Faserorientierung und die daraus resultierende Mechanik gezielt beeinflusst und für Innendruckbelastung optimiert werden kann. Um wichtige Einflussgrößen und deren Auswirkung bei dieser Prozesstechnologie zu charakterisieren, wird zu Beginn der Arbeit eine rheologische Vorbetrachtung vorgestellt. Diese zeigt u.a., dass sich die Einspritzgeschwindigkeit und die Rotationsgeschwindigkeit maßgeblich auf den resultierenden Schergeschwindigkeitsvektor auswirken und damit den größten Einfluss auf die Faserumorientierung haben. Die Berechnungen zeigen zudem, dass die absolute Schergeschwindigkeit zwar maßgeblich von der Wanddicke und der Strukturviskosität der Polymerschmelze abhängen, diese Größen jedoch die Ausrichtung des resultierenden Schergeschwindigkeitsvektors nur geringfügig verändern. Im Anschluss folgen Kapitel, in denen die Prozessumsetzung des Spritzgießens mit drehendem Werkzeugkern sowie Methodiken zur direkten und indirekten Quantifizierung der Faserumorientierung vorgestellt werden. Darauf aufbauend werden umfangreiche Untersuchungen an kurz- und langfaserverstärktem Polypropylen und Polyamid u.a. zum Einfluss der Drehzahl, der Wanddicke, des Fasergehalts sowie von Spritzgießprozessparametern vorgestellt. Hierbei können die rheologischen Voruntersuchungen zum Teil bestätigt werden und es zeigt sich, dass unabhängig vom Material und der Wanddicke mit zunehmender Drehzahl ein Großteil der Fasern in tangentiale Richtung umorientiert werden kann. Mit steigender Drehzahl führt die rotationsinduzierte Scherung dazu, dass die ursprüngliche Schichtstruktur der Faserorientierung mit in Fließrichtung ausgerichteten Fasern in den Randschichten sowie quer zur Fließrichtung orientierten Fasern in der Kernschicht nicht mehr vorhanden ist. Durch die Drehung werden die Randschichten schmaler und der Großteil der Fasern in diesen Schichten kann tangential ausgerichtet werden. Auch in der Kernschicht ist es möglich, die Fasern noch stärker auszurichten, wodurch beispielsweise der mittlere tangentiale Orientierungsgrad für ein kurzfaserverstärktes Polypropylen (PP-GF50) von 0,32 (ungedreht) auf 0,73 (gedreht mit 4,4 s-¹) erhöht werden kann. Kurzfassung Durch die vermehrt tangential ausgerichteten Fasern kann die Berstdruckfestigkeit signifikant, in vielen Versuchsreihen um über 100 %, gesteigert werden. Für ein kurzfaserverstärktes PP (PP-GF50) ist somit eine Steigerung von 58 bar auf 120 bar und für ein kurzfaserverstärktes Polyamid (PA-GF50) von 85 bar auf 159 bar möglich. Um den positiven Einfluss des drehenden Werkzeugkerns auf die Mechanik in der Simulation berücksichtigen zu können, folgt anschließend die Entwicklung einer Simulationsmethodik, mit der die beeinflusste Faserorientierung in der Struktursimulation abgebildet werden kann. Diese Simulationsmethodik kann an den Ergebnissen der Berstdruckprüfungen erfolgreich validiert werden. Darauf aufbauend wird eine Auslegungsmethodik für Bauteile, die mit einem drehenden Werkzeugkern hergestellt werden sollen, vorgestellt und auf zwei Bauteile aus der Industrie übertragen. Die Anwendung der Auslegungsmethodik bei diesen Bauteilen verdeutlicht zum Abschluss der Arbeit das große Potential der Prozesstechnologie: Bei einem innendruckbelasteten Bauteil mit einfacher Geometrie kann der Auslastungsgrad je nach Lastfall deutlich von u.a. 0,81 auf 0,47 reduziert werden. Bei einem Pumpengehäuse mit komplexer Geometrie kann durch die Rotation der Auslastungsgrad von 0,58 auf 0,4 gesenkt werden. Zudem führt die höhere Steifigkeit bei diesem Bauteil durch die in Belastungsrichtung ausgerichteten Fasern zu einer deutlich geringeren Verformung und der Reduktion von Spannungsspitzen.In the injection moulding of elongated, rotationally symmetrical components, manufacturing restrictions and complex geometries often result in the component being filled in the axial direction. As a result of this flow, the molecules and possible reinforcement fibres are aligned in the direction of flow. Since the maximum strengthening effect is achieved with fibre-reinforced plastics when the majority of the fibres are aligned in the direction of the load, this axial alignment is disadvantageous for components exposed to internal pressure and leads to inefficient material utilization. In this work, it is shown how the fibre orientation and the resulting mechanics can be intentionally influenced and optimized for internal pressure loading in such structural parts by using a rotating mould core. In order to characterise important influencing variables and their effect in this process technology, a preliminary rheological analysis is presented at the beginning of this thesis. The rheological analysis shows, among other things, that the injection speed and the rotation speed have a significant effect on the resulting shear velocity vector and thus have the greatest influence on the fibre reorientation. The analyses also show that the absolute shear rate depends significantly on the wall thickness and the structural viscosity of the polymer melt, but that these parameters only slightly change the orientation of the resulting shear rate vector. Afterwards, chapters are presented in which the process implementation of injection moulding with a rotating mould core as well as methods for the direct and indirect quantification of the fibre reorientation are presented. Based on this, comprehensive investigations of short and long fibre-reinforced polypropylene and polyamide are presented, including the influence of speed, wall thickness, fibre content and injection moulding process parameters. The preliminary rheological analysis can be partially confirmed and it is shown that, regardless of the material and the wall thickness, the majority of the fibres can be reoriented in the tangential direction with increasing rotational speed. By increasing the rotational speed, the rotation-induced shear has the effect that the originally layered structure of the fibre orientation with fibres oriented in the flow direction in the outer layers and fibres oriented transversely to the flow direction in the core layer is no longer present. Due to the rotation, the outer layers become narrower and the majority of the fibres in these layers can be oriented tangentially. It is also possible to further align the fibres in the core layer, whereby, for example, the average degree of tangential orientation for a short-fibre reinforced polypropylene (PP-GF50) can be increased from 0,32 (unrotated) to 0,73 (rotated with 4,4 s-¹). Through the increased tangentially oriented fibres, the bursting strength can be significantly increased, in many test series by more than 100 %. Consequently, for a short-fibre x Abstract reinforced PP (PP-GF50) an increase from 58 bar to 120 bar and for a short-fibre reinforced polyamide (PA-GF50) from 85 bar to 159 bar is achieved. In order to be able to consider the positive effect of the rotating mould core on the mechanics in the simulation, a methodology is developed with which the influenced fibre orientation can be taken into account in the structural simulation. This simulation methodology is validated on the results of the bursting pressure tests. Based on this, a design methodology for components that are to be manufactured with a rotating mould core is presented and applied to two structural components from industry. The application of the design methodology to these components demonstrates the significant potential of the process technology at the end of this thesis: For a component with simple geometry that is subjected to internal pressure, the load factor can be significantly reduced from 0,81 to 0,47 depending on the load case. For a pump casing with complex geometry, the rotation can reduce the load factor from 0,58 to 0,4. In addition, the higher stiffness in this component due to the fibres aligned in the direction of the load leads to significantly lower deformation and the reduction of stress

Focus of attention and motor performance: From theory to analysis

Land WM, Philippen P. Focus of attention and motor performance: From theory to analysis. Presented at the 2nd Annual Summer School, Center of Excellence Cognitive Interaction Technology (CITEC)

Diagnosing and Measuring the Yips in Golf Putting: A Kinematic Description of the Involuntary Movement Component That Is the Yips

Philippen P, Legler A, Land WM, Schütz C, Schack T. Diagnosing and Measuring the Yips in Golf Putting: A Kinematic Description of the Involuntary Movement Component That Is the Yips. Sport, Excercise and Performance Psychology. 2014;3(3):149-162

Quasi Static and Fatigue Properties of Long Carbon Fiber Reinforced Polyamide

In this experimental work, the quasi static and fatigue properties of a 40 wt.% long carbon fiber reinforced partially aromatic polyamide (Grivory GCL-4H) were investigated. For this purpose, microstructural parameter variations in the form of different thicknesses and different removal directions from injectionmolded plates were evaluated. Mechanical properties decreased by increasing misalignment away from the melt flow direction. By changing the specimen thickness, no change in the general fiber distribution pattern transversal and normal to the axis of melt flow was observed. It has shown that with increasing specimen thickness the quasi static properties along the melt flow direction decreased and vice versa resulting in superior properties normal to the melt flow axis. At around 5 mm, an intersection suggests quasi-isotropic behavior. In addition, the fatigue strength of the material was significantly higher in the flow direction than normal to the flow direction. No change in fatigue life was observed while changing specimen thickness. The Basquin equation seems to describe the effect of stress amplitude on the fatigue strength of this composite. Scanning electron microscopy was used to investigate fracture surfaces of tested specimens. Results show that mechanical properties and morphological structures depend highly on fiber orientation

Tagespflegeboersen Vermittlung und Qualifizierung von Tagespflegepersonen in Hamburg-Altona, -Wandsbek und -Harburg

UuStB Koeln(38)-960106175 / FIZ - Fachinformationszzentrum Karlsruhe / TIB - Technische InformationsbibliothekSIGLEDEGerman

Citizen Science in the Digital World of Apps

Book cover The Science of Citizen Science pp 461–474Cite as Citizen Science in the Digital World of Apps Rob Lemmens, Vyron Antoniou, Philipp Hummer & Chryssy Potsiou Chapter First Online: 12 January 2021 16k Accesses 8 Citations Abstract In this chapter, we highlight the added value of mobile and web apps to the field of citizen science. We provide an overview of app types and their functionalities to facilitate appropriate app selection for citizen science projects. We identify different app types according to methodology, data specifics, and data collection format. The chapter outlines good practices for creating apps. Citizen science apps need to ensure high levels of performance and usability. Social features for citizen science projects with a focus on mobile apps are helpful for user motivation and immersion and, also, can improve data quality via community feedback. The design, look and feel, and project identity are essential features of citizen science apps. We provide recommendations aimed at establishing good practice in citizen science app development. We also highlight future developments in technology and, in particular, how artificial intelligence (AI) and machine learning (ML) can impact citizen science projects