13,112 research outputs found
MRI E-Conference electronic conference on ‘Marine Research Infrastructures (MRI): The need for better Information and Co-ordination’ 26-30 april 2004, final report
The MRI E-conference was an initiative of VLIZ and AWI in collaboration with EurOcean, ESF/Marine Board and IOC/UNESCO. The objective of this forum was to discuss the needs and expectations of the Scientific Community towards a common European approach for optimizing the coordination of marine research infrastructure. All the points made by the contributors are summarised and bundled in this final report
Deformation of Silica Aerogel During Fluid Adsorption
Aerogels are very compliant materials - even small stresses can lead to large
deformations. In this paper we present measurements of the linear deformation
of high porosity aerogels during adsorption of low surface tension fluids,
performed using a Linear Variable Differential Transformer (LVDT). We show that
the degree of deformation of the aerogel during capillary condensation scales
with the surface tension, and extract the bulk modulus of the gel from the
data. Furthermore we suggest limits on safe temperatures for filling and
emptying low density aerogels with helium.Comment: 8 pages, 5 figures, submitted to PR
Raising awareness of the accessibility challenges in mathematics MOOCs
MOOCs provide learning environments that make it easier for learners to study from anywhere, at their own pace and with open access to content. This has revolutionised the field of eLearning, but accessibility continues to be a problem, even more so if we include the complexity of the STEM disciplines which have their own specific characteristics. This work presents an analysis of the accessibility of several MOOC platforms which provide courses in mathematics. We attempt to visualise the main web accessibility problems and challenges that disabled learners could face in taking these types of courses, both in general and specifically in the context of the subject of mathematics
Development of a System for Directed Evolution of \u3cem\u3eArabidopsis\u3c/em\u3e Formate Dehydrogenase to Utilize NADP as a Cofactor
Formate dehydrogenase (FDH) is a NAD-dependent enzyme found in methylotrophic bacteria, yeast and plants. This enzyme catalyzes the reversible oxidation of formate to carbon dioxide. The goal of this research was to determine the feasibility of using a directed evolution approach to generate an altered Arabidopsis FDH with a high affinity for NADP as a cofactor. A PCR procedure that induced approximately 1.5 mutations in the wild-type Arabidopsis FDH sequence per thousand base pairs was developed and the amplified products were transformed into E. coli cells. Approximately 1300 cell lines were assayed in 96-well microplates for activity with NADP+ and 100 putative mutants were selected for further study. One particular mutant line, pFDH-18, possessed reproducible NADP+-FDH activity. Sequence analysis showed that a single T in the wild-type DNA sequence had been changed to a G. The result of this mutation was that an isoleucine (Ile) residue at position 188 in the wild-type enzyme was converted to a methionine. This particular Ile residue is conserved in the known FDH sequences from higher plants and is located in the region of the enzyme that contains the binding domain for the NAD cofactor
An empirical test for cellular automaton models of traffic flow
Based on a detailed microscopic test scenario motivated by recent empirical
studies of single-vehicle data, several cellular automaton models for traffic
flow are compared. We find three levels of agreement with the empirical data:
1) models that do not reproduce even qualitatively the most important empirical
observations,
2) models that are on a macroscopic level in reasonable agreement with the
empirics, and 3) models that reproduce the empirical data on a microscopic
level as well.
Our results are not only relevant for applications, but also shed new light
on the relevant interactions in traffic flow.Comment: 28 pages, 36 figures, accepted for publication in PR
Sparse Randomized Kaczmarz for Support Recovery of Jointly Sparse Corrupted Multiple Measurement Vectors
While single measurement vector (SMV) models have been widely studied in
signal processing, there is a surging interest in addressing the multiple
measurement vectors (MMV) problem. In the MMV setting, more than one
measurement vector is available and the multiple signals to be recovered share
some commonalities such as a common support. Applications in which MMV is a
naturally occurring phenomenon include online streaming, medical imaging, and
video recovery. This work presents a stochastic iterative algorithm for the
support recovery of jointly sparse corrupted MMV. We present a variant of the
Sparse Randomized Kaczmarz algorithm for corrupted MMV and compare our proposed
method with an existing Kaczmarz type algorithm for MMV problems. We also
showcase the usefulness of our approach in the online (streaming) setting and
provide empirical evidence that suggests the robustness of the proposed method
to the distribution of the corruption and the number of corruptions occurring.Comment: 13 pages, 6 figure
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