1,253 research outputs found
Epidemiology and integrated control of Potato Late Blight in Europe
No full textPhytophthora infestans, the causal agent of late blight, is a major threat to potato production in northwestern Europe. Before 1980, the worldwide population of P. infestans outside Mexico appeared to be asexual and to consist of a single clonal lineage of A1 mating type characterized by a single genotype. It is widely believed that new strains migrated into Europe in 1976 and that this led to subsequent population changes including the introduction of the A2 mating type. The population characteristics of recently collected isolates in NW Europe show a diverse population including both mating types, sexual reproduction and oospores, although differences are observed between regions. Although it is difficult to find direct evidence that new strains are more aggressive, there are several indications from experiments and field epidemics that the aggressiveness of P. infestans has increased in the past 20 years. The relative importance of the different primary inoculum sources and specific measures for reducing their role, such as covering dumps with plastic and preventing seed tubers from becoming infected, is described for the different regions. In NW Europe, varieties with greater resistance tend not to be grown on a large scale. From the grower’s perspective, the savings in fungicide input that can be achieved with these varieties are not compensated by the higher (perceived) risk of blight. Fungicides play a crucial role in the integrated control of late blight. The spray strategies in NW Europe and a table of the specific attributes of the most important fungicides in Europe are presented. The development and use of decision support systems (DSSs) in NW Europe are described. In The Netherlands, it is estimated that almost 40% of potato growers use recommendations based on commercially available DSS. In the Nordic countries, a new DSS concept with a fixed 7-day spray interval and a variable dose rate is being tested. In the UK, commercially available DSSs are used for c. 8% of the area. The validity of Smith Periods for the new population of P. infestans in the UK is currently being evaluated
Experimental control strategies reducing the fungicide input at a practical scale
No full textPhytophthora infestans is the most devastating disease in potato cultivation. Chemical control is necessary to ensure a healthy crop. At the same time Dutch governmental policy asks for a reduction of the environmental impact of potato late blight control by 75% in 2012 as compared to 1996-1998. The aim of the experiments was to compare Decision Support Systems with different approaches to blight risk management for their ability to reduce the fungicide input without compromising control efficacy. Considerable savings, up to 81% when compared to weekly, full dose rate, spray schedules, can be achieved by using information on cultivar resistance, length of the critical period and disease pressure to decide whether or not to spray. The subroutine calculating the potential for viable transport of spores is only effective on resistant varieties as the threshold was exceeded with every critical period on less resistant cultivars. Implications of the experimental control strategies for agricultural practise are discusse
Appreciating Johann Schepers.
No full textAs an expert leader in psychometrics, eminent scholar, gatekeeper, study leader and mentor, Johann M. Schepers has had a profound effect on the development of Psychology and Industrial Psychology in South Africa. By means of an appreciative inquiry the outstanding ability of this man has been highlighted in stories which resulted in a rich profile and a legacy that needs to be protected and nurtured
TS2PACK: A Two-Level Tabu Search for the Three-dimensional Bin Packing Problem
No full textThree-dimensional orthogonal bin packing is a problem NP-hard in the strong sense where a set of boxes must be orthogonally packed into the minimum number of three-dimensional bins. We present a two-level tabu search for this problem. The first-level aims to reduce the number of bins. The second optimizes the packing of the bins. This latter procedure is based on the Interval Graph representation of the packing, proposed by Fekete and Schepers, which reduces the size of the search space. We also introduce a general method to increase the size of the associated neighborhoods, and thus the quality of the search, without increasing the overall complexity of the algorithm. Extensive computational results on benchmark problem instances show the effectiveness of the proposed approach, obtaining better results compared to the existing one
Pharmacological blockade of GPR17 promotes functional and structural remyelination in the murine cuprizone model
No full textMultiple sclerosis (MS) is a chronic demyelinating disease of the central nervous system. Current therapies are very efficacious in reducing inflammatory MS relapses but do not prevent the progression of the disease. One of the drivers of disability progression has been linked to chronic demyelination which can lead to irreversible axonal damage and neuronal death. Remyelination, the generation of new myelin in the adult nervous system, is an endogenous repair mechanism that provides metabolic support to axons and restores axonal functions. A significant drive in development of MS therapeutics is to address this high unmet medical need and to identify drug targets that can promote remyelination by engaging oligodendrocyte precursor cells (OPC) to form new myelin. G protein-coupled receptor 17 (GPR17) has been identified as an important regulator in oligodendrocytes development and remyelination. Here, we demonstrate that blocking GPR17 using a novel proprietary orally acting small molecule (RWT001) enhances remyelination in an acute cuprizone model. Male C57Bl/6 mice were fed with a diet containing 0.3% cuprizone for 6 weeks to induce demyelination, followed by 9 days of daily p.o. treatment with RWT001 during normal diet feeding to induce remyelination. Non-invasive visual evoked potential (VEP) latency time was recorded to assess the myelin status of the optic nerve. Compared to baseline, the VEP latency was significantly delayed following 6 weeks of cuprizone treatment. Treatment with RWT001 significantly stimulated recovery of the VEP latency time as compared to the vehicle, indicating improved in vivo remyelination of the optic nerve during the treatment period. In agreement with the functional VEP data, histological analysis of markers of myelination showed increased remyelination in the corpus callosum following treatment with RWT001 as compared to the vehicle. Collectively, our study provided evidence that the small molecule compound RWT001, which selectively and potently inhibits the GPR17 receptor, accelerates functional remyelination in the cuprizone model and as such might contribute to the repair-inducing treatments for myelin-related disorders
Synthesis and evaluation of hexitol nucleoside congeners as ambiguous nucleosides
No full textA series of anhydrohexitol nucleoside congeners was synthesized as ambiguous or so-called universal nucleosides and was evaluated for their hybridization potential and discrimination properties. The 1,5-anhydro-2,3-dideoxy-2-(5-nitroindazol-1-yl)-d-arabino-hexitol 4e showed the lower spread in Tm values upon hybridization to the natural bases, with minimal destabilization, and therefore behaved as a true ambiguous nucleoside
Precision phrase linking and pulling – ispantu
No full textPrecision semantic linking and pulling:
The semantic web can be interpreted as a web of sem
antic units – or ideas. An idea
can occasionally be found succinctly expressed in a
phrase on a remote web-page. To
make sense of the semantic web we ought to be able
to link precisely to such a text-
phrase, plucking it from its surroundings and re-pr
esenting it, while intrinsically
attributing its derivation: its semantic context.
A new page could be built from a
mosaic of such verbatim citations pulled
in situ
from over the web. For this to be of
enduring value the integrity of phrases once cited
should be verifiable later. All this
becomes less of an academic exercise when one consi
ders the multilingual field –
where, for challenging translations, re-tracing the
precise source-language context
often assists a broader comprehension
Synthesis and base pairing properties of 1',5'-anhydro-l-hexitol nucleic acids (l-HNA)
No full textOligonucleotides composed of 1,5-anhydro-arabino-hexitol nucleosides belonging to the L series (L-HNA) were prepared and preliminarily studied as a novel potential base-pairing system. Synthesis of enantiopure L-hexitol nucleotide monomers equipped with a 2-(N6-benzoyladenin-9-yl) or a 2-(thymin-1-yl) moiety was carried out by a de novo approach based on a domino reaction as key step. The L oligonucleotide analogues were evaluated in duplex formation with natural complements as well as with unnatural sugar-modified oligonucleotides. In many cases stable homo- and heterochiral associations were found. Besides Tm measurements, detection of heterochiral complexes was unambiguously confirmed by LC-MS studies. Interestingly, circular dichroism measurements of the most stable duplexes suggested that L-HNA form left-handed helices with both D and L oligonucleotides
Final results from the EU project AVATAR: aerodynamic modelling of 10 MW wind turbines
No full textThis paper presents final results from the EU project AVATAR in which aerodynamic models are improved and validated for wind turbines on a scale of 10 MW and more. Special attention is paid to the improvement of low fidelity engineering (BEM based) models with higher fidelity (CFD) models but also with intermediate fidelity free vortex wake (FVW) models. The latter methods were found to be a good basis for improvement of induction modelling in engineering methods amongst others for the prediction of yawed cases, which in AVATAR was found to be one of the most challenging subjects to model. FVW methods also helped to improve the prediction of tip losses. Aero-elastic calculations with BEM based and FVW based models showed that fatigue loads for normal production cases were over predicted with approximately 15% or even more. It should then be realised that the outcome of BEM based models does not only depend on the choice of engineering add-ons (as is often assumed) but it is also heavily dependent on the way the induced velocities are solved. To this end an annulus and element approach are discussed which are assessed with the aid of FVW methods. For the prediction of fatigue loads the so-called element approach is recommended but the derived yaw models rely on an annulus approach which pleads for a generalised solution method for the induced velocities
Geometry of Configuration Spaces of Tensegrities
No full textConsider a graph G with n vertices. In this paper we study geometric conditions for an n-tuple of points in a"e (d) to admit a nonzero self-stress with underlying graph G. We introduce and investigate a natural stratification, depending on G, of the configuration space of all n-tuples in a"e (d) . In particular we find surgeries on graphs that give relations between different strata. Further we discuss questions related to geometric conditions defining the strata for plane tensegrities. We conclude the paper with particular examples of strata for tensegrities in the plane with a small number of vertices.sponsorship: F. Doray and J. Schepers supported by VICI-grant 639.033.402 of NWO. O. Karpenkov partially supported by RFBR grant SS-709.2008.1 and by NWO-DIAMANT grant 613.009.001. (NWO|639.033.402, RFBR|SS-709.2008.1, NWO-DIAMANT|613.009.001)status: Publishe
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