554 research outputs found
Guest Lecture – Foundation Engineering for Gravity Structures in the Northern North Sea
During the past 10 years, 15 gravity structures have been installed in the northern North Sea. As new gravity structures are being designed for installation on softer soils and at greater depths, they still pose a great challenge to soil mechanics and foundation engineering. Great improvements have been made during the 10-year period. This applies to soil investigations, in-situ measurements, undisturbed sampling, laboratory testing and design analyses. Compared to structures on land, offshore gravity structures are characterised by large foundation areas, the installation method, and the cyclic wave loading state. The paper reviews investigation methods, site and soil conditions, construction principles, instrumentation and installation. The main emphasis, however, is given to current foundation design practice and experiences from full scale measurements
Students' experiences with short videos in a flipped classroom design in physic
We have implemented a methodology for using short videos as a part of a flipped classroom design in an introductory, multi-campus physics course for engineering students. These pre-recorded videos introduced theory and concepts to students ahead of in-class sessions, which enabled a reduction in the time used for traditional lectures. The time spent in classes puts emphasis on student activities, such as quizzes, Q&A sessions with the lecturer answering student-submitted questions, and problem solving. The physics course has a modular design for customized delivery to a multitude of study programmes and is coordinated by a team of teachers who provide localized classes at several campuses. Although teachers manage individual classes, the course uses an open learning environment which allows enrolled students access to all study materials published by any teacher. We present results from a questionnaire investigating student experiences with the use of short videos, by measuring the overall level of satisfaction with the videos, as well as collecting students’ comments to the videos. We investigate correlations between student satisfaction with the videos and the comments they make, and whether students whose teacher is featured in the video are more satisfied than students without a personal relationship with the featured teacher. Students report overall satisfaction with video length and level of precision, while requesting more worked examples and detailed calculations. We identify a set of good practices for flipped classroom designs, based on the students’ feedback
Longevity and growth of Acacia tortilis; insights from 14C content and anatomy of wood
Background: Acacia tortilis is a keystone species across arid ecosystems in Africa and the Middle East. Yet, its life-history, longevity and growth are poorly known, and consequently ongoing changes in tree populations cannot be managed in an appropriate manner. In other arid areas parenchymatic bands marking growth zones in the wood have made dendrochronological studies possible. The possibilities for using pre- and post-bomb 14C content in wood samples along with the presence of narrow marginal parenchymatic bands in the wood is therefore tested to gain further insight into the age, growth and growth conditions of A. tortilis in the hyper-arid Eastern Desert of Egypt. Results: Based on age scenarios and the Gompertz growth equation, the age of trees studied seems to be from 200 up to 650 years. Annual radial growth estimated from calibrated dates based on the post-bomb 14C content of samples is up to 2.4 mm, but varies both spatially and temporally. Parenchymatic bands are not formed regularly. The correlation in band pattern among trees is poor, both among and within sites. Conclusion: The post-bomb 14C content of A. tortilis wood gives valuable information on tree growth and is required to assess the age scenario approach applied here. This approach indicates high longevities and slow growth of trees. Special management measures should therefore be taken at sites where the trend in tree population size is negative. The possibilities for dendrochronological studies based on A. tortilis from the Eastern Desert are poor. However, marginal parenchymatic bands can give insight into fine scale variation in growth conditions and the past management of trees
The immunology of the periodic fever, aphthous stomatitis, pharyngitis and cervical adenitis syndrome; what can the tonsils reveal. A literature review.
Under embargo until: 25.11.2020Objectives: Tonsillectomy (TE) or adenotonsillectomy (ATE) may have a beneficial effect on the clinical course in children with the periodic fever, aphthous stomatitis, pharyngitis and cervical adenitis (PFAPA) syndrome. However, an immunological reason for this effect remains unknown. This literature review summarizes the current knowledge regarding the immunological role of the tonsils in the PFAPA syndrome. Methods: We searched PubMed, Medline, EMBASE and Cochrane for papers written in English dated from 1 January 1987 to 30 April 2019. The search included all studies reporting histological, immunological or microbiological workup of tonsil specimens from children aged 0–18 years with PFAPA. Results: Thirteen articles reported histological, immunological or microbiological workup of tonsil specimens in children with PFAPA. The histology of tonsil specimens from children with PFAPA displayed chronic tonsillar inflammation with lymphoid hyperplasia. No uniform immunological pattern was identified, but some studies found fewer B-lymphocytes and smaller germinal centers in PFAPA compared to controls. A difference in tonsillar microbiota between PFAPA and controls was found in one study. Conclusion: A uniform immunological or microbiological pattern explaining the clinical effect of TE in children with PFAPA has not been revealed. Future targeted immunological studies of tonsils in PFAPA patients could possibly illuminate the understanding of the immunology in this disease.acceptedVersio
Maternal investment, sibling competition, and offspring survival with increasing litter size and parity in pigs (Sus scrofa)
The aim of this study was to examine the effects of litter size and parity on sibling competition, piglet survival, and weight gain. It was predicted that competition for teats would increase with increasing litter size, resulting in a higher mortality due to maternal infanticide (i.e., crushing) and starvation, thus keeping the number of surviving piglets constant. We predicted negative effects on weight gain with increasing litter size. Based on maternal investment theory, we also predicted that piglet mortality would be higher for litters born late in a sow's life and thus that the number of surviving piglets would be higher in early litters. As predicted, piglet mortality increased with increasing litter size both due to an increased proportion of crushed piglets, where most of them failed in the teat competition, and due to starvation caused by increased sibling competition, resulting in a constant number of survivors. Piglet weight at day 1 and growth until weaning also declined with increasing litter size. Sows in parity four had higher piglet mortality due to starvation, but the number of surviving piglets was not affected by parity. In conclusion, piglet mortality caused by maternal crushing of piglets, many of which had no teat success, and starvation caused by sibling competition, increased with increasing litter size for most sow parities. The constant number of surviving piglets at the time of weaning suggests that 10 to 11 piglets could be close to the upper limit that the domestic sow is capable of taking care of
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