| 1. |
- van Haarlem, M. P., et al.
(author)
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LOFAR : The LOw-Frequency ARray
- 2013
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In: Astronomy and Astrophysics. - : EDP Sciences. - 0004-6361 .- 1432-0746. ; 556, s. 1-53
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Journal article (peer-reviewed)abstract
- LOFAR, the LOw-Frequency ARray, is a new-generation radio interferometer constructed in the north of the Netherlands and across europe. Utilizing a novel phased-array design, LOFAR covers the largely unexplored low-frequency range from 10–240 MHz and provides a number of unique observing capabilities. Spreading out from a core located near the village of Exloo in the northeast of the Netherlands, a total of 40 LOFAR stations are nearing completion. A further five stations have been deployed throughout Germany, and one station has been built in each of France, Sweden, and the UK. Digital beam-forming techniques make the LOFAR system agile and allow for rapid repointing of the telescope as well as the potential for multiple simultaneous observations. With its dense core array and long interferometric baselines, LOFAR achieves unparalleled sensitivity and angular resolution in the low-frequency radio regime. The LOFAR facilities are jointly operated by the International LOFAR Telescope (ILT) foundation, as an observatory open to the global astronomical community. LOFAR is one of the first radio observatories to feature automated processing pipelines to deliver fully calibrated science products to its user community. LOFAR’s new capabilities, techniques and modus operandi make it an important pathfinder for the Square Kilometre Array (SKA). We give an overview of the LOFAR instrument, its major hardware and software components, and the core science objectives that have driven its design. In addition, we present a selection of new results from the commissioning phase of this new radio observatory.
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| 2. |
- Müller, M, et al.
(author)
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Central sleep apnoea syndrome in chronic heart failure : an underestimated and treatable comorbidity.
- 2010
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In: Netherlands heart journal : monthly journal of the Netherlands Society of Cardiology and the Netherlands Heart Foundation. - 1568-5888. ; 18:5, s. 260-3
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Journal article (peer-reviewed)abstract
- Chronic heart failure is a clinical syndrome with a high mortality and morbidity. Despite optimal therapy, five-year survival is still only 50%. Central sleep apnoea syndrome is seen in approximately 40% of patients with congestive heart failure. Sleep apnoea syndrome can be divided into two forms in these patients: obstructive sleep apnoea syndrome (OSAS) and central sleep apnoea syndrome (CSAS, Cheyne-Stokes respiration), of which CSAS is the most common. CSAS is a form of sleep apnoea in congestive heart failure which is driven by changes in pCO(2). As a consequence of apnoea-hypopnoea an imbalance in myocardial oxygen delivery/consumption ratio will develop, sympathetic and other neurohormonal systems will be activated and right and left ventricular afterload will be increased. Sleep apnoea is associated with an increased mortality in patients with systolic heart failure. Treatment of sleep apnoea increases left ventricular ejection fraction and transplant-free survival. Because of its high prevalence, poor quality of life, poor outcome, and the beneficial effects of treatment, physicians treating patients with heart failure should be aware of central sleep apnoea. There are different treatment options, but the exact effects and indications of each option have not yet been fully determined. Further studies should be done to further investigate its prevalence, and to establish the most adequate therapy for the individual patient. (Neth Heart J 2010;18:260-3.).
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| 3. |
- Nieuwenhuis, Bart P. S., et al.
(author)
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Evolution of uni- and bifactorial sexual compatibility systems in fungi
- 2013
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In: Heredity. - : Springer Science and Business Media LLC. - 0018-067X .- 1365-2540. ; 111:6, s. 445-455
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Research review (peer-reviewed)abstract
- Mating systems, that is, whether organisms give rise to progeny by selfing, inbreeding or outcrossing, strongly affect important ecological and evolutionary processes. Large variations in mating systems exist in fungi, allowing the study of their origin and consequences. In fungi, sexual incompatibility is determined by molecular recognition mechanisms, controlled by a single mating-type locus in most unifactorial fungi. In Basidiomycete fungi, however, which include rusts, smuts and mushrooms, a system has evolved in which incompatibility is controlled by two unlinked loci. This bifactorial system probably evolved from a unifactorial system. Multiple independent transitions back to a unifactorial system occurred. It is still unclear what force drove evolution and maintenance of these contrasting inheritance patterns that determine mating compatibility. Here, we give an overview of the evolutionary factors that might have driven the evolution of bifactoriality from a unifactorial system and the transitions back to unifactoriality. Bifactoriality most likely evolved for selfing avoidance. Subsequently, multiallelism at mating-type loci evolved through negative frequency-dependent selection by increasing the chance to find a compatible mate. Unifactoriality then evolved back in some species, possibly because either selfing was favoured or for increasing the chance to find a compatible mate in species with few alleles. Owing to the existence of closely related unifactorial and bifactorial species and the increasing knowledge of the genetic systems of the different mechanisms, Basidiomycetes provide an excellent model for studying the different forces that shape breeding systems.
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| 4. |
- Nieuwenhuis, Bart P. S., et al.
(author)
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On the asymmetry of mating in natural populations of the mushroom fungus Schizophyllum commune
- 2013
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In: Fungal Genetics and Biology. - : Elsevier BV. - 1087-1845 .- 1096-0937. ; 56, s. 25-32
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Journal article (peer-reviewed)abstract
- Before a mycelium of a mushroom-forming basidiomycete develops mushrooms, the monokaryotic mycelium needs to become fertilized. Although the mechanistic details of mating in mushrooms have been studied thoroughly in laboratory research, very little is known on mating patterns in nature. In this study, we performed fine-scale analyses of three populations of Schizophyllum commune from their natural substrate (i.e. dead beech branches). From the three branches, 24, 12, and 24 fruiting bodies were isolated and for each mushroom, the origins of its nuclei and cytoplasm were reconstructed using DNA markers. Nuclear genotypes were determined using sequencing data and mating types, and mitochondrial haplotypes using SNP markers. From these combined data we reconstructed colonization and mating patterns of the mycelia. On each branch, we found multiple dikaryons (3, 3, and 8, respectively); in two instances one nuclear haplotype was shared between two dikaryons and in two other cases a nuclear haplotype was shared between three dikaryons. Each dikaryon always had a single mitochondrial haplotype. These findings indicate that mating usually is not symmetrical and that a monokaryon is most likely fertilized by a small monokaryon, a spore or a dikaryon. Sharing of nuclear haplotype between different dikaryons resulted either from multiple fertilizations of a single monokaryon, if the dikaryons had identical mitochondrial haplotypes, or, if the dikaryons had different mitochondria] haplotypes, most likely from secondary matings between a monokaryon and a dikaryon (Buller phenomenon). We conclude that mating in S. commune between same-sized monokaryons with reciprocal migration, as generally described in textbooks, is rare in nature. We discuss the implications of non-symmetric mating for basidiomycete evolution.
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