Studie zum One-Shot Prozess an Holz-Kunststoff-Verbunden

Environmental changes force industries to use renewable and degradable materials for lightweight solutions to solve weight and therefore CO2. One highly prioritized topic is the combination of wood materials with biodegradable plastics. Especially when processing these materials, it is essential to develop efficient processes to reduce obstacles and enable the application in serial use. To take advantage of the mechanical behaviour of the wood structure it is necessary to investigate the combination of thin solid wood with plastic. Regarding large-scale production, an injection moulding process is addressed in this study. When processing raw material cutting operations are used. To use the shear cutting process has several advantages: it is a cost effective process with short cycle times. Also no thermal influence or water immersion occur on the working material (like in laser beam or water jet methods), so material sensitive on this can be worked by shearing. But as a disadvantage a working force is applied. This work aims to show the findings this working fore on 5mm wood solids and the influence of the created surface on the bonding between plastic and wood cutting edge. The process connections and dependencies of shear cutting and injection moulding are investigated. Different wood materials were used to analyse the effects of cutting and material parameters (e.g. moisture, forces) on the cutting edge quality (e.g. structural damage). To detect the effect of different cutting edge qualities on the joint between wood and plastic component tensile specimen were tested.Umweltveränderungen zwingen die Industrie, erneuerbare und abbaubare Materialien für Leichtbaulösungen zu verwenden, um Gewicht und damit CO2 einzusparen. Ein hochpriorisiertes Thema ist die Kombination von Holzwerkstoffen mit biologisch abbaubaren Kunststoffen. Besonders bei der Verarbeitung dieser Materialien ist es wichtig, effiziente Prozesse zu entwickeln, um Hindernisse für den Markteintritt zu reduzieren und die Anwendung im Serieneinsatz zu ermöglichen. Um das mechanische Verhalten der Holzfaserstruktur auszunutzen, ist es notwendig, die Kombination von dünnem Holz mit Kunststoff zu untersuchen. Im Hinblick auf die Großserienproduktion wird in dieser Studie das Spritzgussverfahren adressiert. Die Anwendung des Scherschneidverfahrens hat einige Vorteile: Es ist ein kostengünstiges Verfahren mit kurzen Zykluszeiten. Auch findet keine thermische Beeinflussung oder Eintauchen in Wasser auf das zu bearbeitende Material statt (wie beim Laserstrahl- oder Wasserstrahlverfahren), sodass darauf empfindliches Material durch Schneiden bearbeitet werden kann. Als Nachteil wird jedoch eine Arbeitskraft aufgebracht. Ziel dieser Arbeit ist es, die Erkenntnisse zu zeigen, die die scherende Bearbeitung an 5mm Holzwerkstoffen und der folgende Einfluss der erzeugten Oberfläche auf die Verbindung zwischen Kunststoff und Holz hat. Die Prozesszusammenhänge und -abhängigkeiten von Scherschneiden und Spritzgießen werden untersucht. Es wurden verschiedene Holzwerkstoffe verwendet, um die Auswirkungen von Schnitt- und Materialparametern (z.B. Feuchtigkeit, Kräfte) auf die Schnittkantenqualität (z.B. Strukturschäden) zu analysieren. Um den Einfluss unterschiedlicher Schnittkantenqualitäten auf die Verbindung zwischen Holz- und Kunststoffbauteil zu erkennen, wurden Zugproben untersucht

E-Learning in der fachdidaktischen Ausbildung von Mathematiklehrkräften. Effekte verschiedener Lehrveranstaltungsangebote auf den Studienerfolg

Die universitäre Ausbildung von Lehrkräften umfasst in der Mathematik traditionell sowohl fachmathematische als auch fachdidaktisch-pädagogische Inhalte. In der empirischen Forschung rückt häufiger die fachmathematische Seite in den Fokus. Für fachdidaktische Lehrveranstaltungen eines Mathematiklehramtsstudiengangs ist die Befundlage deutlich geringer.Der Einfluss der COVID-19-Pandemie auf das Lehrangebot an den Hochschulen in Deutschland war und ist enorm. Der Großteil der Veranstaltungen in den letzten Semestern konnte nicht als Präsenzangebot ausgestaltet werden, was mit erheblichen technischen, methodischen und organisatorischen Herausforderungen für Lehrende und Lernende einherging. In Bezug auf den Einfluss digitaler Lehrangebote auf den Studienerfolg sind bisher wenige Ergebnisse bekannt. Selbstauskünfte von Studierenden verschiedener Studiengänge lassen darauf schließen, dass Vorteile beim Lernen eher auf Seiten der Präsenzlehre gesehen werden.Dies legt die Vermutung nahe, dass Studierende, die ausschließlich an digitalen Lehrformaten teilnehmen, im Mittel auch schlechtere Leistungen erzielen als jene Studierenden, die an vergleichbaren Präsenzlehrveranstaltungen teilnehmen. Eine Untersuchung dieser Frage erfolgt am Beispiel des Grundkurs Didaktik der Mathematik, einer fachdidaktischen Lehrveranstaltung des Lehramts für Sekundarstufen im Fach Mathematik. Die Ergebnisse bestätigen die obige Vermutung insbesondere für Lehrveranstaltungen mit einem hohen Aktivitätsgrad, wie Übungen

The Complexity of Computing Minimal Unidirectional Covering Sets

Given a binary dominance relation on a set of alternatives, a common thread in the social sciences is to identify subsets of alternatives that satisfy certain notions of stability. Examples can be found in areas as diverse as voting theory, game theory, and argumentation theory. Brandt and Fischer [BF08] proved that it is NP-hard to decide whether an alternative is contained in some inclusion-minimal upward or downward covering set. For both problems, we raise this lower bound to the Theta_{2}^{p} level of the polynomial hierarchy and provide a Sigma_{2}^{p} upper bound. Relatedly, we show that a variety of other natural problems regarding minimal or minimum-size covering sets are hard or complete for either of NP, coNP, and Theta_{2}^{p}. An important consequence of our results is that neither minimal upward nor minimal downward covering sets (even when guaranteed to exist) can be computed in polynomial time unless P=NP. This sharply contrasts with Brandt and Fischer's result that minimal bidirectional covering sets (i.e., sets that are both minimal upward and minimal downward covering sets) are polynomial-time computable.Comment: 27 pages, 7 figure

Multi-input synapses, but not LTP-strengthened synapses, correlate with hippocampal memory storage in aged mice

Long-lasting changes at synapses enable memory storage in the brain. Although aging is associated with impaired memory formation, it is not known whether the synaptic underpinnings of memory storage differ with age. Using a training schedule that results in the same behavioral memory formation in young and aged mice, we examined synapse ultrastructure and molecular signaling in hippocampus after contextual fear conditioning. Only in young, but not old mice contextual fear memory formation was associated with synaptic changes that characterize well-known long-term potentiation,a strengthening of existing synapses with one input. Instead old age memory was correlated with generation of multi-innervated dendritic spines (MIS), which are predominantly two-input synapses formed by the attraction of an additional excitatory, presynaptic terminal onto an existing synapse. Accordingly, a blocker used to inhibit MIS generation impaired contextual fear memory only in old mice. Our results reveal how the synaptic basis of hippocampal memory storage changes with age and they suggest that these distinct memory-storing mechanisms may explain impaired updating in old age

Come, tell me how you live: Habitat suitability analysis for Ostrea edulis restoration

Against the background of the UN decade on ecosystem restoration and the new EU Biodiversity Strategy for 2030, and in the context of marine spatial planning and complex maritime user conflicts, reliable information on habitat suitability for large-scale restoration is an important prerequisite for implementing conservation management and for supporting successful, sustainable, and ecologically efficient restoration measures. In this study, habitat suitability was assessed using multicriteria decision analysis (MCDA) for the restoration of the European oyster, Ostrea edulis, in marine protected areas (MPAs) of the German Bight in the North Sea: Borkum Reef Ground (Borkum Riffgrund, BRG) and Sylt Outer Reef – Eastern German Bight (Sylter Außenriff, SAR). Based on site selection criteria, exclusion and suitability factors for the MCDA were defined. Results were integrated with the available geodata to produce habitat suitability maps for oyster restoration in the area of interest. Suitable as well as unsuitable habitats have been successfully identified for both MPAs: several hundred square kilometres (≥97.2% of BRG) or several thousand square kilometres (≥74.5% of SAR) were classified as ecologically and logistically suitable for oyster restoration measures in the respective MPAs. As oyster restoration is significantly limited by human activities (e.g. bottom trawl fisheries), the management of fisheries is an important prerequisite for successful oyster restoration in both MPAs. Results show that designated fishery management measures will increase the possibilities for oyster restoration. In BRG, our results correspond to the known historical distribution. In SAR, our results significantly exceed the historically known distribution. The habitat suitability analysis will facilitate decision-making regarding ocean use, and will reduce restoration costs through targeted management activities in areas of high suitability and expand species recovery by improving the survival of reintroduced individuals. The habitat suitability analysis procedure is easily adaptable for application to other areas, other species, or other habitat restoration projects, or to other conservation management settings. The software applied is open source and the suitability calculation is described in detail to inform wider applications

Fluorescence optical imaging feature selection with machine learning for differential diagnosis of selected rheumatic diseases

Background and objectiveAccurate and fast diagnosis of rheumatic diseases affecting the hands is essential for further treatment decisions. Fluorescence optical imaging (FOI) visualizes inflammation-induced impaired microcirculation by increasing signal intensity, resulting in different image features. This analysis aimed to find specific image features in FOI that might be important for accurately diagnosing different rheumatic diseases.Patients and methodsFOI images of the hands of patients with different types of rheumatic diseases, such as rheumatoid arthritis (RA), osteoarthritis (OA), and connective tissue diseases (CTD), were assessed in a reading of 20 different image features in three phases of the contrast agent dynamics, yielding 60 different features for each patient. The readings were analyzed for mutual differential diagnosis of the three diseases (One-vs-One) and each disease in all data (One-vs-Rest). In the first step, statistical tools and machine-learning-based methods were applied to reveal the importance rankings of the features, that is, to find features that contribute most to the model-based classification. In the second step machine learning with a stepwise increasing number of features was applied, sequentially adding at each step the most crucial remaining feature to extract a minimized subset that yields the highest diagnostic accuracy.ResultsIn total, n = 605 FOI of both hands were analyzed (n = 235 with RA, n = 229 with OA, and n = 141 with CTD). All classification problems showed maximum accuracy with a reduced set of image features. For RA-vs.-OA, five features were needed for high accuracy. For RA-vs.-CTD ten, OA-vs.-CTD sixteen, RA-vs.-Rest five, OA-vs.-Rest eleven, and CTD-vs-Rest fifteen, features were needed, respectively. For all problems, the final importance ranking of the features with respect to the contrast agent dynamics was determined.ConclusionsWith the presented investigations, the set of features in FOI examinations relevant to the differential diagnosis of the selected rheumatic diseases could be remarkably reduced, providing helpful information for the physician

Old World megadroughts and pluvials during the Common Era

Climate model projections suggest widespread drying in the Mediterranean Basin and wetting in Fennoscandia in the coming decades largely as a consequence of greenhouse gas forcing of climate. To place these and other “Old World” climate projections into historical perspective based on more complete estimates of natural hydroclimatic variability, we have developed the “Old World Drought Atlas” (OWDA), a set of year-to-year maps of tree-ring reconstructed summer wetness and dryness over Europe and the Mediterranean Basin during the Common Era. The OWDA matches historical accounts of severe drought and wetness with a spatial completeness not previously available. In addition, megadroughts reconstructed over north-central Europe in the 11th and mid-15th centuries reinforce other evidence from North America and Asia that droughts were more severe, extensive, and prolonged over Northern Hemisphere land areas before the 20th century, with an inadequate understanding of their causes. The OWDA provides new data to determine the causes of Old World drought and wetness and attribute past climate variability to forced and/or internal variability

The Electron Capture in 163^{163} Ho Experiment - a Short Update

The definition of the absolute neutrino mass scale is one of the main goals of the Particle Physics today. The study of the end-point regions of the β- and electron capture (EC) spectrum offers a possibility to determine the effective electron (anti-)neutrino mass in a completely model independent way, as it only relies on the energy and momentum conservation. The ECHo (Electron Capture in 163Ho) experiment has been designed in the attempt to measure the effective mass of the electron neutrino by performing high statistics and high energy resolution measurements of the 163 Ho electron capture spectrum. To achieve this goal, large arrays of low temperature metallic magnetic calorimeters (MMCs) implanted with with 163Ho are used. Here we report on the structure and the status of the experiment

Minimum joint space width and tibial cartilage morphology in the knees of healthy individuals: A cross-sectional study

<p>Abstract</p> <p>Background</p> <p>The clinical use of minimum joint space width (mJSW) and cartilage volume and thickness has been limited to the longitudinal measurement of disease progression (i.e. change over time) rather than the diagnosis of OA in which values are compared to a standard. This is primarily due to lack of establishment of normative values of joint space width and cartilage morphometry as has been done with bone density values in diagnosing osteoporosis. Thus, the purpose of this pilot study is to estimate reference values of medial joint space width and cartilage morphometry in healthy individuals of all ages using standard radiography and peripheral magnetic resonance imaging.</p> <p>Design</p> <p>For this cross-sectional study, healthy volunteers underwent a fixed-flexion knee X-ray and a peripheral MR (pMR) scan of the same knee using a 1T machine (ONI OrthOne™, Wilmington, MA). Radiographs were digitized and analyzed for medial mJSW using an automated algorithm. Only knees scoring ≤1 on the Kellgren-Lawrence scale (no radiographic evidence of knee OA) were included in the analyses. All 3D SPGRE fat-sat sagittal pMR scans were analyzed for medial tibial cartilage morphometry using a proprietary software program (Chondrometrics GmbH).</p> <p>Results</p> <p>Of 119 healthy participants, 73 were female and 47 were male; mean (SD) age 38.2 (13.2) years, mean BMI 25.0 (4.4) kg/m². Minimum JSW values were calculated for each sex and decade of life. Analyses revealed mJSW did not significantly decrease with increasing decade (p > 0.05) in either sex. Females had a mean (SD) medial mJSW of 4.8 (0.7) mm compared to males with corresponding larger value of 5.7 (0.8) mm. Cartilage morphometry results showed similar trends with mean (SD) tibial cartilage volume and thickness in females of 1.50 (0.19) μL/mm²and 1.45 (0.19) mm, respectively, and 1.77 (0.24) μL/mm²and 1.71 (0.24) mm, respectively, in males.</p> <p>Conclusion</p> <p>These data suggest that medial mJSW values do not decrease with aging in healthy individuals but remain fairly constant throughout the lifespan with "healthy" values of 4.8 mm for females and 5.7 mm for males. Similar trends were seen for cartilage morphology. Results suggest there may be no need to differentiate a t-score and a z-score in OA diagnosis because cartilage thickness and JSW remain constant throughout life in the absence of OA.</p