859 research outputs found
Cross - fertilization between three different teaching modes for geo - informatics education
Objective of this study was to determine if the use and student appreciation of course
materials differs for native materials (materials that were developed for that course type in
which they are used) and foreign materials (materials that were developed for another course
type) and if the way the materials are used, (compulsory versus optional, interchangeable
versus the only source of information) affects the student appreciation.
A comparison was made between a face-to-face course, a blended learning course and a
distance course. The comparison was based on a questionnaire, the course evaluation and the
statistics from the digital learning environments. Results show no difference between native
and foreign course materials, but do however show the influence of the way the materials
were used. Appreciation for compulsory, non-interchangeable materials is higher than for
optional interchangeable ones, but even for this last category the general appreciation is high.
Distance students have the highest overall appreciation for study materials, followed by the
face-to-face students
Comprehensive Characterization of Escherichia coil O104:H4 Isolated from Patients in the Netherlands
In 2011, a Shiga toxin-producing Enteroaggregative Escherichia coli (EAEC Stx2a+) O104:H4 strain caused a serious outbreak of acute gastroenteritis and hemolytic-uremic syndrome (HUS) in Germany. In 2013, E. coli O104:H4 isolates were obtained from a patient with HUS and her friend showing only gastrointestinal complaints. The antimicrobial resistance and virulence profiles of these isolates together with three EAEC Stx2a+ O104:H4 isolates from 2011 were determined and compared. Whole-genome sequencing (WGS) was performed for detailed characterization and to determine genetic relationship of the isolates. Four additional genomes of EAEC Stx2a+ O104:H4 isolates of 2009 and 2011 available on NCBI were included in the virulence and phylogenetic analysis. All E. coli O104:H4 isolates tested were positive for stx2a, aatA, and terD but were negative for escV. All, except one 2011 isolate, were positive for aggR and were therefore considered EAEC. The EAEC Stx2a+ O104:H4 isolates of 2013 belonged to sequence type (ST) ST678 as the 2011 isolates and showed slightly different resistance and virulence patterns compared to the 2011 isolates. Core-genome phylogenetic analysis showed that the isolates of 2013 formed a separate cluster from the isolates of 2011 and 2009 by 27 and 20 different alleles, respectively. In addition, only a one-allele difference was found between the isolate of the HUS-patient and that of her friend. Our study shows that EAEC Stx2a+ O104:H4 strains highly similar to the 2011 outbreak clone in their core genome are still circulating necessitating proper surveillance to prevent further outbreaks with these potentially pathogenic strains. In addition, WGS not only provided a detailed characterization of the isolates but its high discriminatory power also enabled us to discriminate the 2013 isolates from the isolates of 2009 and 2011 expediting the use of WGS in public health services to rapidly apply proper infection control strategies
Using the right slope of the 970nm absorption feature for estimating canopy water content
Canopy water content (CWC) is important for understanding the functioning of terrestrial ecosystems.
Biogeochemical processes like photosynthesis, transpiration and net primary production are related to foliar
water. The first derivative of the reflectance spectrum at wavelengths corresponding to the left slope of the
minor water absorption band at 970 nm was found to be highly correlated with CWC and PROSAIL model
simulations showed that it was insensitive to differences in leaf and canopy structure, soil background and
illumination and observation geometry. However, these wavelengths are also located close to the water
vapour absorption band at about 940 nm.
In order to avoid interference with absorption by atmospheric water vapour, the potential of estimating
CWC using the first derivative at the right slope of the 970 nm absorption feature was studied.
Measurements obtained with an ASD FieldSpec spectrometer for three test sites were related to CWC
(calculated as the difference between fresh and dry weight). The first site was a homogeneous grassland
parcel with a grass/clover mixture. The second site was a heterogeneous floodplain with natural vegetation
like grasses and various shrubs. The third site was an extensively grazed fen meadow.
Results for all three test sites showed that the first derivative of the reflectance spectrum at the right slope of
the 970 nm absorption feature was linearly correlated with CWC. Correlations were a bit lower than those at
the left slope (at 942.5 nm) as shown in previous studies, but better than those obtained with water band
indices. FieldSpec measurements showed that one may use any derivative around the middle of the right
slope within the interval between 1015 nm and 1050 nm. We calculated the average derivative at this
interval. The first site with grassland yielded an R2 of 0.39 for the derivative at the previously mentioned
interval with CWC (based on 20 samples). The second site at the heterogeneous floodplain yielded an R2 of
0.45 for this derivative with CWC (based on 14 samples). Finally, the third site with the fen meadow yielded
an R2 of 0.68 for this derivative with CWC (based on 40 samples). Regression lines between the derivative
at the right slope of the 970 nm absorption feature and CWC for all three test sites were similar although
vegetation types were quite different. This indicates that results may be transferable to other vegetation
types and other sites
Resolving cryptic species complexes in marine protists: phylogenetic haplotype networks meet global DNA metabarcoding datasets
Marine protists have traditionally been assumed to be lowly diverse and cosmopolitan. Yet, several recent studies have shown that many protist species actually consist of cryptic complexes of species whose members are often restricted to particular biogeographic regions. Nonetheless, detection of cryptic species is usually hampered by sampling coverage and application of methods (e.g. phylogenetic trees) that are not well suited to identify relatively recent divergence and ongoing gene flow. In this paper, we show how these issues can be overcome by inferring phylogenetic haplotype networks from global metabarcoding datasets. We use the Chaetoceros curvisetus (Bacillariophyta) species complex as study case. Using two complementary metabarcoding datasets (Ocean Sampling Day and Tara Oceans), we equally resolve the cryptic complex in terms of number of inferred species. We detect new hypothetical species in both datasets. Gene flow between most of species is absent, but no barcoding gap exists. Some species have restricted distribution patterns whereas others are widely distributed. Closely related taxa occupy contrasting biogeographic regions, suggesting that geographic and ecological differentiation drive speciation. In conclusion, we show the potential of the analysis of metabarcoding data with evolutionary approaches for systematic and phylogeographic studies of marine protists
logarithmic conformal field theories of type Bn; p = 2 and symplectic fermions
In the first part, I present a well-known algebraic object, a *vertex
operator algebra* (VOA) *V* associated to a given lattice. I describe its
representation theory and define some maps acting on it, called *screening
operators*. The established program by B. Feigin et. al. to which my master project contributes asks to consider a sub lattice VOA *W* of *V*, by taking the intersection of the kernels of some screenings. Many conjectures were made in the past years about this new object *W*.
In particular it was conjectured that this is a *Logarithmic Conformal Field Theory* (LCFT), i.e. a VOA with a finite but non-semisimple representation theory. Not many LCFT are nowadays known, and the program outlined above has only been completed for rank 1 so far.
My master project is to study and completely understand a new example of
this construction, where the lattice is a Lie algebra root lattice of type
B_n, rescaled by p=2. In the second part I indeed calculate and discuss the screening operators, the representations of *W*, their decomposition
behaviour and their graded characters.
In the third part I prove that *W* is isomorphic to a known LCFT, the
*Symplectic Fermions* VOA. In particular this implies that our *W* is in this case a LCFT. This is hence the first higher rank example, where the program has been successfully completed
Gewaspatronen H-WodKa: Studie Atlas
Deze atlas bevat kaarten met gewaspatronen voor 10 agrarische percelen in de Hoeksche Waard voor de periode 2006-2010. De kaarten geven een indicatie van de biomassa voor drie momenten in een groeiseizoen (twee in 2010). Deze momenten betreffen het begin, het midden en het eind van het groeiseizoen. De timing van de opnames is afhankelijk van de beschikbaarheid van geschikte remote sensing beelden
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