Ocean waves offer an uninterrupted, rich resource of globally available renewable energy. However, because of their high cost and low power production, commercial wave energy converters are not ...operational at present. In this paper, we numerically evaluated the performance of a novel feedback-controlled lift-based cycloidal wave energy converter (CycWEC) at various sea states of the Humboldt Bay wave climate. The device comprised of two hydrofoils attached eccentrically to a shaft at a radius, submerged at a distance under the ocean surface. The pitch of the blades was feedback-controlled based on estimation of the incoming wave. The simulations were performed for regular waves and irregular waves approximated with a JONSWAP spectrum. Climate data from Humboldt Bay, CA was used to estimate the yearly power generation. The results underline the importance of a well-tuned control algorithm to maximize the annual energy production. The estimated annual energy production of the CycWEC was 3000MWh from regular wave simulations and 1800MWh from irregular wave simulations, showing that it can be a commercially viable means of electricity production from ocean waves.
Purpose
We have developed a second‐generation virtual‐pinhole (VP) positron emission tomography (PET) device that can position a flat‐panel PET detector around a patient's body using a robotic arm to ...enhance the contrast recovery coefficient (CRC) and detectability of lesions in any region‐of‐interest using a whole‐body PET/computed tomography (CT) scanner.
Methods
We constructed a flat‐panel VP‐PET device using 32 high‐resolution detectors, each containing a 4 × 4 MPPC array and 16 × 16 LYSO crystals of 1.0 × 1.0 × 3.0 mm3 each. The flat‐panel detectors can be positioned around a patient's body anywhere in the imaging field‐of‐view (FOV) of a Siemens Biograph 40 PET/CT scanner by a robotic arm. New hardware, firmware and software have been developed to support the additional detector signals without compromising a scanner's native functions. We stepped a 22Na point source across the axial FOV of the scanner to measure the sensitivity profile of the VP‐PET device. We also recorded the coincidence events measured by the scanner detectors and by the VP‐PET detectors when imaging phantoms of different sizes. To assess the improvement in the CRC of small lesions, we imaged an elliptical torso phantom measuring 316 × 228 × 162 mm3 that contains spherical tumors with diameters ranging from 3.3 to 11.4 mm with and without the VP‐PET device. Images were reconstructed using a list mode Maximum‐Likelihood Estimation‐Maximization algorithm implemented on multiple graphics processing units (GPUs) to support the unconventional geometries enabled by a VP‐PET system. The mean and standard deviation of the CRC were calculated for tumors of different sizes. Monte Carlo simulation was also conducted to image clusters of lesions in a torso phantom using a PET/CT scanner alone or the same scanner equipped with VP‐PET devices. Receiver operating characteristic (ROC) curves were analyzed for three system configurations to evaluate the improvement in lesion detectability by the VP‐PET device over the native PET/CT scanner.
Results
The repeatability in positioning the flat‐panel detectors using a robotic arm is better than 0.15 mm in all three directions. Experimental results show that the average CRC of 3.3, 4.3, and 6.0 mm diameter tumors was 0.82%, 2.90%, and 5.25%, respectively, when measured by the native scanner. The corresponding CRC was 2.73%, 6.21% and 10.13% when imaged by the VP‐PET insert device with the flat‐panel detector under the torso phantom. These values may be further improved to 4.31%, 9.65% and 18.01% by a future dual‐panel VP‐PET insert device if DOI detectors are employed to triple its detector efficiency. Monte Carlo simulation results show that the tumor detectability can be improved by a VP‐PET device that has a single flat‐panel detector. The improvement is greater if the VP‐PET device employs a dual‐panel design.
Conclusions
We have developed a prototype flat‐panel VP‐PET device and integrated it with a clinical PET/CT scanner. It significantly enhances the contrast of lesions, especially for those that are borderline detectable by the native scanner, within regions‐of‐interest specified by users. Simulation demonstrated the enhancement in lesion detectability with the VP‐PET device. This technology may become a cost‐effective solution for organ‐specific imaging tasks.
PET combined with CT has proven to be a valuable multimodality imaging device revealing both functional and anatomic information. Although PET/CT has become completely integrated into routine ...clinical application and also has been used in small-animal imaging, CT provides only limited soft-tissue contrast and, in preclinical studies, exposes the animal to a relatively high radiation dose. Unlike CT, MRI provides good soft-tissue contrast even without application of contrast agents and, furthermore, does not require ionizing radiation.
This project focused on combining a high-resolution PET scanner with a 7-T MRI system for animal research. Because classic PET detectors based on photomultiplier tubes cannot be used in high magnetic fields, we used a detector technology based on 10 x 10 lutetium oxyorthosilicate crystal arrays and 3 x 3 avalanche photodiode arrays. A ring of such PET detectors will ultimately be used as an insert for the 119-mm-diameter MRI bore.
Initial measurements with 1 PET detector module in the 7-T field during application of MRI sequences were encouraging. Position profiles from the PET detectors and a first MR image of a mouse could be acquired simultaneously.
Further work will concentrate on the construction of a full PET detector ring with compact, integrated electronics.
The exoskeleton of the American lobster Homarus americanus is a hierarchical nanocomposite consisting of chitin–protein fibers, reinforced with amorphous calcium carbonate (ACC) and a small amount of ...crystalline calcite. Crystallographic pole‐figure analysis reveals two texture components of the crystalline α‐chitin in the exoskeleton. One component represents the well‐known twisted plywood structure of chitin–protein fibers within the cuticle plane, and the second component represents fibers oriented roughly perpendicular to the cuticle surface. These perpendicular fibers interpenetrate the open canals of the planar honeycomblike structure originating from the well‐developed pore‐canal system present in this material. The calcite crystallites reveal fiber texture with the crystallographic c‐axis oriented perpendicular to the cuticle surface, suggesting an orientation relationship between calcite and the organic chitin–protein fibers. Local orientation analysis using X‐ray microdiffraction reveals that the crystalline calcium carbonate fraction is associated with the chitin–protein fibers oriented perpendicular to the surface. Calcite is exclusively found in the exocuticle and is mostly restricted to a thin layer in the outermost region, while the major part of the exocuticle and the whole endocuticle contain ACC exclusively. It is therefore speculated that the most likely function of calcite in the exoskeleton of the American lobster is related to impact‐ and wear‐resistance.
Local orientation analysis using X‐ray microdiffraction reveals that the crystalline calcium carbonate fraction in lobster cuticle is associated with the chitin/protein fibers oriented perpendicular to the surface. The calcite crystallites show a fiber texture with the crystallographic c‐axis pointing perpendicular to the cuticle surface, suggesting an orientation relationship between calcite and the organic chitin/protein fibers.
For the systematic development of feedback flow controllers, a numerical model that captures the dynamic behaviour of the flow field to be controlled is required. This poses a particular challenge ...for flow fields where the dynamic behaviour is nonlinear, and the governing equations cannot easily be solved in closed form. This has led to many versions of low-dimensional modelling techniques, which we extend in this work to represent better the impact of actuation on the flow. For the benchmark problem of a circular cylinder wake in the laminar regime, we introduce a novel extension to the proper orthogonal decomposition (POD) procedure that facilitates mode construction from transient data sets. We demonstrate the performance of this new decomposition by applying it to a data set from the development of the limit cycle oscillation of a circular cylinder wake simulation as well as an ensemble of transient forced simulation results. The modes obtained from this decomposition, which we refer to as the double POD (DPOD) method, correctly track the changes of the spatial modes both during the evolution of the limit cycle and when forcing is applied by transverse translation of the cylinder. The mode amplitudes, which are obtained by projecting the original data sets onto the truncated DPOD modes, can be used to construct a dynamic mathematical model of the wake that accurately predicts the wake flow dynamics within the lock-in region at low forcing amplitudes. This low-dimensional model, derived using nonlinear artificial neural network based system identification methods, is robust and accurate and can be used to simulate the dynamic behaviour of the wake flow. We demonstrate this ability not just for unforced and open-loop forced data, but also for a feedback-controlled simulation that leads to a 90% reduction in lift fluctuations. This indicates the possibility of constructing accurate dynamic low-dimensional models for feedback control by using unforced and transient forced data only.
The relative autonomy of Pädagogik (education) as an academic field has always been in jeopardy. Consequently, we take a closer look at its past, present, and future. We begin by retracing the ...historical development of this field of study in the German-speaking context. In the second part, we look at the current state of the discipline and spotlight current developments threatening education’s autonomy, first and foremost the steep rise and dominance of Empirische Bildungsforschung (empirical educational research). In the last part, we argue for education as an independent discipline and outline how educationalists can strengthen its autonomy and disciplinary identity.
To prospectively use compact avalanche photodiodes instead of photomultiplier tubes to integrate a positron emission tomographic (PET) detector and a 7-T magnetic resonance (MR) imager.
All animal ...experiments were performed in accordance with the University of Tübingen guidelines and the German law for the protection of animals. A compact lutetium oxyorthosilicate-avalanche photodiode PET detector was built and optimized to operate within a 7-T MR imager. The detector performance was investigated both outside and inside the magnet, and MR image quality was evaluated with and without the PET detector. Two PET detectors were set up opposite each other and operated in coincidence to acquire PET images in the step-and-shoot mode in a mouse head specimen after injection of fluorine 18 fluorodeoxyglucose.
The performance of the PET detector when operated inside the magnet during MR image acquisition showed little degradation in energy resolution (increase from 14.6% to 15.9%). The PET detector did not influence MR imaging. The fused PET and MR images showed an anatomic match and no degradation of image quality.
Simultaneous PET and MR imaging with a 7-T system was deemed feasible.
Abstract Background and objectives Attentional processes have been suggested to play a crucial role in resilience defined as positive adaptation facing adversity. However, research is lacking on ...associations between attentional biases to positive and threat-related stimuli, attentional control and trait resilience. Methods Data stem from the follow-up assessment of a longitudinal study investigating mental health and related factors among German soldiers. Trait resilience was assessed with the Connor-Davidson Resilience Scale and attentional control with the Attentional Control Scale. A subset of n = 198 soldiers also completed a dot probe task with happy, neutral and threatening faces. Results Attentional control was positively related to trait resilience. Results revealed no associations between both attentional biases and trait resilience. However, there was a negative association between attentional bias to threat and trait resilience when attentional control was low and a positive association between attentional bias to threat and trait resilience when attentional control was high. No such associations were found for attentional bias to positive stimuli. Limitations Generalizability to other populations may be limited since we exclusively focused on male soldiers. Also, the cross-sectional design does not allow for causal conclusions. Conclusions Findings suggest that attentional processing may promote trait resilience. Future research on preventive interventions should consider these findings.
Für die Aus- und Weiterbildung im Pflegebereich stehen zahlreiche Erklärvideos auf der weit verbreiteten Videostreaming-Plattform YouTube zur Verfügung. Allerdings werden die Videos weitgehend ...unkontrolliert veröffentlicht und sie zeichnen sich durch ein hohes Mass an Heterogenität aus. Lehrende und Lernende stehen vielfach vor der Frage, welches Video aus der umfangreichen Ergebnisliste einer Suche am besten geeignet ist. Im Mittelpunkt dieser Studie steht die qualitative Gestaltung von Erklärvideos, da auch fachlich korrekte Lehr-Lerninhalte angemessen präsentiert werden müssen, um die Wahrscheinlichkeit eines Lernerfolgs zu erhöhen. Zur qualitativen Bewertung von jeweils drei Erklärvideos zu den grundlegenden Pflegethemen Infusionsvorbereitung und 30-Grad-Positionierung wird ein disziplinübergreifendes Analyseraster verwendet, das pädagogisch-didaktische, (lern-)psychologische und filmanalytische Merkmale berücksichtigt. Die Ergebnisse der empirischen Untersuchung zeigen eine durchwachsene Qualität von Erklärvideos für den Pflegebereich. Die evaluierten Erklärvideos berücksichtigen jeweils unterschiedlich umfangreich die Qualitätskriterien und erfüllen kaum (medien-)pädagogisch-didaktische Qualitätskriterien. Die Autoren arbeiten heraus, wann die Erklärvideos dennoch für unterschiedliche Zielgruppen geeignet sind und wie (lern-)psychologische und filmgestalterische Kriterien ineinandergreifen.
For nursing education and training, numerous explanatory videos are available on the widely used video streaming platform YouTube. However, the videos are published largely uncontrolled, and they are characterized by a great heterogeneity. Teachers and learners are often faced with the question of which video is most suitable from the extensive list of results in a search. The focus of this study is the qualitative design of explainer videos, since even subject-specific content must be presented appropriately in order to increase the likelihood of learning progress. For the qualitative evaluation of three explanatory videos each on the nursing topics of infusion preparation and 30-degree positioning, a cross-disciplinary analysis grid is used that considers pedagogical-didactic, (instructional) psychological, and film-analytical features. The results of the empirical investigation show a mixed quality of explanatory videos for nursing. The evaluated explanatory videos each consider the quality criteria to varying extents and hardly fulfill (media) pedagogical-didactic quality criteria. The authors discuss why the explanatory videos are suitable for different target groups and how (instructional) psychological and film design criteria intertwine.
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