888 research outputs found
Rota's basis conjecture for paving matroids
Rota conjectured that, given n disjoint bases of a
rank-n matroid M, there are n disjoint transversals of these bases
that are all bases of M. We prove a stronger statement for the
class of paving matroids
Online discussion compensates for suboptimal timing of supportive information presentation in a digitally supported learning environment
This study used a sequential set-up to investigate the consecutive effects of timing of supportive information presentation (information before vs. information during the learning task clusters) in interactive digital learning materials (IDLMs) and type of collaboration (personal discussion vs. online discussion) in computer-supported collaborative learning (CSCL) on student knowledge construction. Students (N = 87) were first randomly assigned to the two information presentation conditions to work individually on a case-based assignment in IDLM. Students who received information during learning task clusters tended to show better results on knowledge construction than those who received information only before each cluster. The students within the two separate information presentation conditions were then randomly assigned to pairs to discuss the outcomes of their assignments under either the personal discussion or online discussion condition in CSCL. When supportive information had been presented before each learning task cluster, online discussion led to better results than personal discussion. When supportive information had been presented during the learning task clusters, however, the online and personal discussion conditions had no differential effect on knowledge construction. Online discussion in CSCL appeared to compensate for suboptimal timing of presentation of supportive information before the learning task clusters in IDLM
Humane risicobeoordeling in zicht : een inventarisatie van de mogelijkheden voor het optimaliseren van het gebruik van humane data bij de risicobeoordeling van chemische stoffen in de voeding
Het doel van deze studie was het identificeren van visies op het huidige risicobeoordelingsproces, het optimaliseren van het gebruik van humane data en de samenwerking tussen toxicologie en epidemiologie. Gegevens zijn verkregen middels 23 semigestructureerde interview
On Binary Matroid Minors and Applications to Data Storage over Small Fields
Locally repairable codes for distributed storage systems have gained a lot of
interest recently, and various constructions can be found in the literature.
However, most of the constructions result in either large field sizes and hence
too high computational complexity for practical implementation, or in low rates
translating into waste of the available storage space. In this paper we address
this issue by developing theory towards code existence and design over a given
field. This is done via exploiting recently established connections between
linear locally repairable codes and matroids, and using matroid-theoretic
characterisations of linearity over small fields. In particular, nonexistence
can be shown by finding certain forbidden uniform minors within the lattice of
cyclic flats. It is shown that the lattice of cyclic flats of binary matroids
have additional structure that significantly restricts the possible locality
properties of -linear storage codes. Moreover, a collection of
criteria for detecting uniform minors from the lattice of cyclic flats of a
given matroid is given, which is interesting in its own right.Comment: 14 pages, 2 figure
Ventricular tachycardia after administration of sildenafil citrate: a case report
<p>Abstract</p> <p>Background</p> <p>It has not previously been reported that sildenafil citrate causes malignant arrhythmias in humans.</p> <p>Case presentation</p> <p>A 41-year-old man developed sustained ventricular tachycardia following sildenafil citrate administration.</p> <p>Conclusion</p> <p>It cannot be dismissed that this patient experienced ventricular tachycardia as an adverse effect of sildenafil citrate administration.</p
Mobile extracorporeal membrane oxygenation after traumatic freshwater submersion using bi-caval dual lumen catheter
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