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Search Results: 1 - 10 of 201517 matches for " N. Bj?rn? "
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Loss of trophic complexity in saline prairie lakes as indicated by stable-isotope based community-metrics
Ryan N Cooper, Bjrn Wissel
Aquatic Biosystems , 2012, DOI: 10.1186/2046-9063-8-6
Abstract: Lakes of the northern Great Plains are strongly influenced by a high variability in climate and hydrology and, as a result, are very diverse in water chemistry and lake morphometry [1,2]. Glacial retreat has left the local terrain flat and without relief [3]. Yet, 1000s of kettle lakes formed as chunks of ice broke off glaciers, forming small depressions scattered across the landscape [4]. The semi-arid to sub-humid climate in combination with the low relief resulted in the formation of closed (endorheic) drainage basins [4]. As the continuous flushing with dilute waters that is typical for boreal lakes is absent in these systems, inflows are almost exclusively associated with spring snow melt while surface water evaporation during summer is the most important loss of water [5].Water chemistry in prairie lakes is largely a function of the flux of particulate and dissolved substances that are being delivered to the lakes during the spring snow melt, and the intensity of evaporative concentration of solutes during summer. Accordingly, lakes across the Canadian prairies show a large variability in nutrient levels, and salinity ranges from freshwater to hypersaline. Water depth includes shallow-mixed (< 3 m) systems and deep-meromictic lakes (> 20 m), and lake size ranges over several orders of magnitude [1,6]. Subsequently, the taxonomic composition of the biota in these lakes also changes with water chemistry [6]. Salinity has been reported to be most important in controlling species assemblages but other environmental factors, such as nutrient content, calcium and water depth can play crucial roles as well [7]. A recent analysis across 20 prairie lakes indicated that the strength of salinity effects differs among major taxonomic groups [8]. Accordingly, fishes were excluded with increasing salinity (> 2 g L-1) while littoral macroinvertebrates were ubiquitous. In contrast, zooplankton were encountered over the whole salinity range, but showed a clear transition in ta
Alternating-code experiment for plasma-line studies
P. Guio,N. Bjrn,W. Kofman
Annales Geophysicae (ANGEO) , 2003,
Abstract: We present results of the first plasma-line measurement of the incoherent spectrum using the alternating-code technique with the EISCAT VHF radar. This technique, which has earlier mostly been used to measure high-resolution E-region ion-line spectra, turned out to be a very good alternative to other techniques for plasma-line measurements. The experiment provides simultaneous measurement of the ion line and downshifted and upshifted plasma-line spectra with an altitude resolution of 3 km and a temporal resolution of 10 s. The measurements are taken around the peak of the F region, but not necessarily at the peak itself, as is the case with the long-pulse technique. The condition for success is that the scale height should be large enough such that the backscattered signal from the range extent of one gate falls inside the receiver filter. The data are analysed and the results are combined with the results of the ion-line data analysis to estimate electron mean drift velocity and thereafter electric currents along the line of sight of the radar using both the standard dispersion relation assuming a Maxwellian electron velocity distribution and the more recent model including a heat-flow correction term.
Interactive effects of chemical and biological controls on food-web composition in saline prairie lakes
Cooper Ryan N,Wissel Bjrn
Aquatic Biosystems , 2012, DOI: 10.1186/2046-9063-8-29
Abstract: Salinity is restricting habitatability for many biota in prairie lakes due to limited physiological abilities to cope with increasing osmotic stress. Yet, it remains unclear how salinity effects vary among major taxonomic groups and what role other environmental parameters play in shaping food-web composition. To answer these questions, we sampled fish, zooplankton and littoral macroinvertebrates in 20 prairie lakes (Saskatchewan, Canada) characterized by large gradients in water chemistry and lake morphometry. We showed that salinity thresholds differed among major taxonomic groups, as most fishes were absent above salinities of 2 g L-1, while littoral macroinvertebrates were ubiquitous. Zooplankton occurred over the whole salinity range, but changed taxonomic composition as salinity increased. Subsequently, the complexity of fish community (diversity) was associated with large changes in invertebrate communities. The directional changes in invertebrate communities to smaller taxa indicated that complex fish assemblages resulted in higher predation pressure. Most likely, as the complexity of fish community decreased, controls of invertebrate assemblages shifted from predation to competition and ultimately to productivity in hypersaline lakes. Surprisingly, invertebrate predators did not thrive in the absence of fishes in these systems. Furthermore, the here identified salinity threshold for fishes was too low to be a result of osmotic stress. Hence, winterkill was likely an important factor eliminating fishes in low salinity lakes that had high productivity and shallow water depth. Ultimately, while salinity was crucial, intricate combinations of chemical and biological mechanisms also played a major role in controlling the assemblages of major taxonomic groups in prairie lakes.
Application of Pedagogical Perspectives in the Teaching and Training of New Cataract Surgeons—A Literature-Based Essay  [PDF]
Bjrn Johansson
Open Journal of Ophthalmology (OJOph) , 2013, DOI: 10.4236/ojoph.2013.33015
Abstract:

Cataract is the most common cause of visual impairment that can be effectively treated by surgery and cataract surgery is the most commonly performed surgical procedure in the world. With modern cataract operation techniques, patients expect excellent results. Teaching and training of new surgeons involve both pedagogical and ethical challenges for teachers and trainees, and also may pose a potential risk to patients. This literature-based essay aims to describe how behavioristic, cognitive and conceptual learning perspectives can be recognized during the trainee surgeons progress. It also describes how teacher-pupil relationships may vary during the training process. Finally it presents the concept of situational tutorship, where the teacher adapts to the stages that the trainee passes through with increasing experience. Teaching and trainee surgeons who are aware of pedagogical concepts such as teacher-pupil relationships and tutoring strategies may use this knowledge to optimize the learning process. Further research is needed to clarify how using this knowledge may affect the training of new cataract surgeons.

Reviewing the Learning Process through Creative Puzzle Solving  [PDF]
Bjrn Petter Jelle
Creative Education (CE) , 2017, DOI: 10.4236/ce.2017.813137
Abstract: Human beings are at a continuous learning process at various levels and with different motivations during their whole lifetime. Puzzle solving may beneficially be applied to increase the motivation, enhance the mastering apprehension, promote the creative processes, expand the ability to engage and solve miscellaneous challenges from various viewpoints, and hence lead to an improved learning process and problem solving capability. That is, the application of puzzles may lead to better learning and increased knowledge in general, stimulating the reasoning process and the apprehension of the need for both creativity and hard work. Thus, teachers of both students and teachers may find it beneficial to utilize the art of puzzle solving. Typically, the puzzles are very suitable for and mostly used in mathematics and natural science classes. Nevertheless, the puzzles are in general also applicable for any type of class. The aim of this study is to examine and discuss the learning process through applying creative puzzle solving as a teaching tool. These aspects are illustrated through a review of several selected puzzle examples.
Tectonic Control of the Reykjanes Geothermal Field in the Oblique Rift of SW Iceland: From Regional to Reservoir Scales  [PDF]
Maryam Khodayar, Sveinbj?rn Bj?rnsson, Egill árni Guenason, Steintór Níelsson, Gueni Axelsson, Catherine Hickson
Open Journal of Geology (OJG) , 2018, DOI: 10.4236/ojg.2018.83021
Abstract: This paper presents a multidisciplinary structural analysis of the Reykjanes Peninsula where Holocene deformation of a young oblique rift controls the geothermal processes in presence of a transform segment. The new structural map from aerial images and outcrops is correlated with selected surface and subsurface data and shows a complex pattern: NNE extensional rift structures, N-S dextral and ENE sinistral oblique-slip Riedel shears of the transform zone, and WNW and NW dextral oblique-slip faults. Shear fractures are more common, and along with the NNE fractures, they compartmentalise the crustal blocks at any scale. The fractures are within two ENE Riedel shear zones, indicating a minimum 7.5 km wide transform zone. The greatly deformed Southern Riedel Shear Zone is bounded to the north and the south by the 1972 and the 2013 earthquake swarms. This shear zone contains the geothermal field in a highly fractured block to the west of a major NW structure. Some of the deformations are: a) clockwise rotation of rift structures by the 1972 earthquake zone, inducing local compression; b) magma injection into extensional and oblique-slip shear fractures; c) reactivation of rift structures by transform zone earthquakes; d) tectonic control of reservoir boundaries by WNW and ENE shear fractures, and the distribution of surface alteration, fumaroles, CO2 flux, reservoir fluid flow and the overall shape of pressure drawdown by N-S, ENE, WNW/NW and NNE fractures. Results demonstrate the role of seismo-tectonic boundaries beyond which fault types and density change, with implications for permeability.
A cross-sectional study of Tritrichomonas foetus infection among healthy cats at shows in Norway
Kristoffer Tysnes, Bjrn Gjerde, Ane N?dtvedt, Ellen Skancke
Acta Veterinaria Scandinavica , 2011, DOI: 10.1186/1751-0147-53-39
Abstract: The sample population consisted of 52 cats participating in three cat shows in Norway in 2009. Samples were examined for motile T. foetus by microscopy, after culturing and for T. foetus-DNA by species-specific nested PCR, as well as for Giardia cysts and Cryptosporidium oocysts by immunofluorescent antibody test (IFAT).By PCR, T. foetus-DNA was demonstrated in the faeces of 11 (21%) of the 52 cats tested. DNA-sequencing of five positive samples yielded 100% identity with previous isolates of T. foetus from cats. Only one sample was positive for T. foetus by microscopy. By IFAT, four samples were positive for Giardia cysts and one for Cryptosporidium oocysts, none of which was co-infected with T. foetus. No significant associations were found between the presence of T. foetus and the various risk factors examined.T. foetus was found to be a common parasite in clinically healthy cats in Norway.During the last decade, the protozoan parasite Tritrichomonas foetus has been identified as an important cause of chronic large-bowel diarrhoea in cats, especially among purebred cats in multi-cat households. T. foetus was first associated with diarrhoea in cats in the USA [1,2], but has since been reported from diarrhoeic and/or non-diarrhoeic cats in the UK [3,4], Norway [5], Australia [6], Switzerland [7,8], Italy [9], the Netherlands [10], and New Zealand [11]. The many recent reports of this parasite in cats might give the impression of feline trichomoniasis as an emerging disease. However, Stockdale et al. [12] suggested that the increasingly frequent diagnosis of T. foetus in cats might be due to a rise in the awareness about the parasite among veterinarians and improved diagnostic methods, rather than an actual increase in the incidence.In Norway, T. foetus was originally detected in the uterine contents of a cat with pyometra, as well as in the faeces of three other cats in the same household, one of which had a history of diarrhoea [5]. Following this discovery, T. fo
Next Generation Sequencing of miRNAs – Strategies, Resources and Methods
Susanne Motameny,Stefanie Wolters,Peter Nürnberg,Bjrn Schumacher
Genes , 2010, DOI: 10.3390/genes1010070
Abstract: miRNAs constitute a family of small RNA species that have been demonstrated to play a central role in regulating gene expression in many organisms. With the advent of next generation sequencing, new opportunities have arisen to identify and quantify miRNAs and elucidate their function. The unprecedented sequencing depth reached by next generation sequencing technologies makes it possible to get a comprehensive miRNA landscape but also poses new challenges for data analysis. We provide an overview of strategies used for miRNA sequencing, public miRNA resources, and useful methods and tools that are available for data analysis.
Risk Reduction Technologies in General Practice and Social Work
Devin Rexvid,Bjrn Blom,Lars Evertsson,Annika Forssén
Professions & Professionalism , 2012, DOI: 10.7577/pp.409
Abstract: General practitioners (GPs) and social workers (SWs) are professions whose professional autonomy and discretion have changed in the so-called risk and audit society. The aim of this article is to compare GPs’ and SWs’ responses to Evidence-Based and Organizational Risk Reduction Technologies (ERRT and ORRT). It is based on a content analysis of 54 peer-reviewed empirical articles. The results show that both professions held ambivalent positions towards ERRT. The response towards ORRT differed in that GPs were sceptical whilst SWs took a more pragmatic view. Furthermore the results suggest that SWs might experience professional benefits by adopting an adherent approach to the increased dissemination of risk reduction technologies (RRT). GPs, however, did not seem to experience such benefits. Keywords: Profession, risk, social worker, general practitioner, risk reduction technologies, evidence-based practice/medicine
Anomalous echoes observed with the EISCAT UHF radar at 100-km altitude
E. Malnes,N. Bjrn,T. L. Hansen
Annales Geophysicae (ANGEO) , 2003,
Abstract: We have observed a number of strong echoes with the European incoherent-scatter (EISCAT) UHF (930-MHz) radar at angles 83.5° and 78.6° with the geomagnetic field and at about 100-km altitude north in the auroral zone. The echoes are short-lived and occur in single 2- or 10-s data dumps. They are offset by 125–130 kHz with respect to the transmitted frequency. In most cases the offset compares well with the frequency of gyro lines in the incoherent-scatter spectrum, as given by the standard linear dispersion relation. But sometimes the measured offsets deviate significantly from the model calculations, and the interpretation in terms of gyro lines becomes questionable. The discrepancy could possibly be explained by local deviations in the magnetic field from the model (IGRF 1987), which are generated by incoming particle beams. A more serious problem with the gyro-line theory is how the line can be excited at altitudes where the collisional damping is substantial. The high intensity and short lifetime of the signal point to a fast-growing plasma instability as the likely excitation mechanism, if the gyro-line interpretation is correct. The cause of the instability could be the same particle beams as those causing the disturbances in the magnetic field. Alternatively, the observations may be interpreted as meteor head echoes. The large Doppler shifts, the short lifetimes and the altitudes of the signals support this explanation. The main difficulty is that the distribution of measured offsets appears to be different in magnetically active conditions and in less active conditions. Also, the occurrence of echoes does not seem to follow the expected changes in meteor density. More observations in different conditions are needed to decide between the two interpretations. As it is, we are inclined to believe in the meteor head echo theory, the objections to the gyro-line theory being more fundamental.
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