468 research outputs found
On seed physiology, biomechanics and plant phenology in Eragrostis tef
No full text • Key words: Teff (Eragrostis tef (Zuccagni) Trotter), germination, temperature, model, leaf appearance, phyllochron, development rate, lodging, biomechanics, safety factor, flowering, heading, day length, photoperiod. • Background Teff (Eragrostis tef (Zuccagni) Trotter) is a C4 annual grass species (Poaceae) originating from Ethiopia. Teff cultivation in the Netherlands is thought to be economically feasible because teff grains and flour do not contain gluten and are rich in iron. These two characteristics make teff a desirable ingredient in health products, particularly for celiac disease patients. At the start of this project Dutch teff yields were modest (1.0 - 1.5 Mg•ha-1). The sowing and harvest dates were (too) late in the season and the crop was sensitive to lodging. Here, lodging is defined as the permanent displacement of shoots from their vertical due to root or shoot failure. • The objective of this research is to detail some processes that underlie the sensitivity to lodging and the late harvest. Therefore we studied seed germination, lodging resistance, day length response, pace of leaf appearance. • Germination of teff can be described by assuming a normally distributed rate of germination within the seed population. Minimal and maximal temperatures required for germination depend on water availability (water potential). Conversely, the minimal required water potential for germination depends on temperature. • Lodging was inevitable for teff grown on a Dutch sandy soil. We identified that not only the shoots of teff are prone to lodging, but that the roots are also a major factor in the lodging process. Furthermore, water adhering to the shoots alone, without wind action, could induce lodging in the studied cultivars. • Flowering in teff is significantly delayed by exposure to long days. Teff is therefore a short day plant; not only panicle initiation, but also development and outgrowth of the panicle were influenced by photoperiod. • Phyllochron, defined as the time required between the appearance of two successive teff leaves, increased abruptly for the last few leaves on the main stem of teff. After re-evaluation of literature data this abrupt increase in phyllochron seemed to be also present in both wheat and rice. The delay is most likely independent of temperature, but might be related to the moment of panicle initiation. • In conclusion, the study on teff identified clear targets for breeding towards a high-yielding cultivar in the Netherlands. </p
Met de Triton en Iris naar de zuidwestkust van Nieuw Guinea in 1828 : de reisverhalen van Justin Modera en Arnoldus Johannes van Delden /
No full textIn april 1828 vertrokken Z.M. korvet Triton en Z.M. koloniale schoener Iris van Ambon naar Nieuw-Guinea om een westelijk gedeelte van dat eiland bij proclamatie voor Nederland in bezit te nemen en er een militaire nederzetting te vestigen. De marineofficieren verrichtten er hydrografische opnamen voor zeekaarten teneinde de Nieuw-Guineese wateren voor scheepvaart te ontsluiten.0Meevarende leden van de ?Natuurkundige commissie voor Nederlands-Indië? onderzochten de planten ? en dierenwereld van het onder Europeanen nagenoeg onbekende eiland. De reis, in opdracht van de gouverneur van de Molukken, was ingegeven door de angst dat Engelsen zich vanuit Australië op het door nog geen enkele koloniale macht geclaimde Nieuw-Guinea zouden vestigen. Van Engelse activiteit was geen spoor te bekennen en Fort Du Bus, zoals de nederzetting werd genoemd, kende een kort bestaan. Het voor Europeanen fnuikende klimaat, aanvallen door Molukse en Papoease zeerovers en een vrijwel doorlopend gebrek aan voedsel, kostte talloze levens waardoor het fort in 1836 moest worden verlaten.00'Met de Triton en Iris naar Nieuw-Guinea' bevat de transcripties van twee journalen die tijdens de reis van 1828 zijn bijgehouden. Het eerste is van Justin Modera, die bij vertrek uit Nederland tweeëntwintig jaar was, en luitenant ter zee op de Triton Het tweede is van de enkele maanden jongere bestuursambtenaar Arnoldus Johannes van Delden, die als gouvernementscommissaris was belast met de formele inbezitneming van Nieuw-Guinea.Includes bibliographic references and indexes. - With a summary in English.In april 1828 vertrokken Z.M. korvet Triton en Z.M. koloniale schoener Iris van Ambon naar Nieuw-Guinea om een westelijk gedeelte van dat eiland bij proclamatie voor Nederland in bezit te nemen en er een militaire nederzetting te vestigen. De marineofficieren verrichtten er hydrografische opnamen voor zeekaarten teneinde de Nieuw-Guineese wateren voor scheepvaart te ontsluiten.0Meevarende leden van de ?Natuurkundige commissie voor Nederlands-Indië? onderzochten de planten ? en dierenwereld van het onder Europeanen nagenoeg onbekende eiland. De reis, in opdracht van de gouverneur van de Molukken, was ingegeven door de angst dat Engelsen zich vanuit Australië op het door nog geen enkele koloniale macht geclaimde Nieuw-Guinea zouden vestigen. Van Engelse activiteit was geen spoor te bekennen en Fort Du Bus, zoals de nederzetting werd genoemd, kende een kort bestaan. Het voor Europeanen fnuikende klimaat, aanvallen door Molukse en Papoease zeerovers en een vrijwel doorlopend gebrek aan voedsel, kostte talloze levens waardoor het fort in 1836 moest worden verlaten.00'Met de Triton en Iris naar Nieuw-Guinea' bevat de transcripties van twee journalen die tijdens de reis van 1828 zijn bijgehouden. Het eerste is van Justin Modera, die bij vertrek uit Nederland tweeëntwintig jaar was, en luitenant ter zee op de Triton Het tweede is van de enkele maanden jongere bestuursambtenaar Arnoldus Johannes van Delden, die als gouvernementscommissaris was belast met de formele inbezitneming van Nieuw-Guinea
Genetic variation for oviposition behavior in Drosophila melanogaster: II. Oviposition preferences and differential survival
No full textSeveral behavioral traits connected with oviposition were studied inDrosophila melanogaster strains which had been kept on regular and ethanol-supplemented food. All strains preferred food with a low agar content for oviposition, though this tendency was more pronounced in an ethanol-adapted strain. Oviposition on regular and ethanol-supplemented food was tested both under choice and no-choice conditions. Though dependent on the alcohol dehydrogenase genotype, adapted strains in general preferred ethanol food, while control strains preferred regular food. There was a strong tendency for oviposition on the vertical sides, when food blocks were offered. This tendency was more pronounced in the ethanol adapted strains. For egg insertion (for which the genetic basis was analyzed in the preceding paper; Kamping and van Delden, 1990), it was shown that inserted eggs laid on ethanol food hatched more often than noninserted eggs. The adaptive significance of the genetic differences in oviposition behavioral traits is discussed
Euthanasia and other medical decisions concerning the end of life
No full texttag=1 data=Euthanasia and other medical decisions concerning the end of life.
tag=2 data=van der Maas, Paul J.%van Delden, Johannes J.M.%Pijnenborg, Loes%Looman, Caspar W.N.
tag=3 data=The Lancet, Vol 338
tag=6 data=^d14^mSep ^y1991
tag=8 data=DEATH
tag=9 data=EUTHANASIA%NETHERLANDS
tag=15 data=JO
Effect of urbanization on soil methane and nitrous oxide fluxes in subtropical Australia
No full textIncreasing population densities and urban sprawl are causing rapid land use change from natural and agricultural ecosystems into smaller, urban residential properties. However, there is still great uncertainty about the effect that urbanization will have on biogeochemical C and N cycles and associated greenhouse gas (GHG) budgets. We aimed to evaluate how typical urbanization related land use change in subtropical Australia affects soil GHG exchange (N2O and CH4) and the associated global warming potential (GWP). Fluxes were measured from three land uses: native forest, a long-term pasture, and a turf grass lawn continuously over two years using a high-resolution automated chamber system. The fertilized turf grass had the highest N2O emissions, dominated by high fluxes >100 g N2O-N day−1 immediately following establishment though decreased to just 0.6 kg N2O-N ha−1 in the second year. Only minor fluxes occurred in the forest and pasture, with the high aeration of the sandy topsoil limiting N2O emissions while promoting substantial CH4uptake. Native forest was consistently the strongest CH4 sink (−2.9 kg CH4-C ha−1 year−1), while the pasture became a short-term CH4 source after heavy rainfall when the soil reached saturation. On a two-year average, land use change from native forest to turf grass increased the non-CO2 GWP from a net annual GHG sink of −83 CO2-e ha–1 year−1 to a source of 245 kg CO2-e ha–1 year−1. This study highlights that urbanization can substantially alter soil GHG exchange by altering plant soil water use and by increasing bulk density and inorganic N availability. However, on well-drained subtropical soils, the impact of urbanization on inter-annual non-CO2 GWP of turf grass was low compared to urbanized ecosystems in temperate climates
Methods for estimating the quality of multisource statistics
No full textWith the increasing availability of data, official business statistics are more often based on multiple data sources. Evaluating accuracy, i.e. bias and variance, of output based on multiple sources has therefore become an important topic. Estimating the accuracy is important to inform users about data quality, and it can be a trigger to adjust processing steps when accuracy drops below an acceptable level. An inventory of methods to estimate output accuracy of multisource statistics has been made in the European project KOMUSO. The bias and variance of multisource statistics are affected by errors on the representation side (units and populations) and by errors on the measurement side. Additionally, when combining sources at microlevel, unit-level linkage errors may occur. We will introduce recently developed methods to estimate bias and variance of outputs as affected by representation error, linkage error, and measurement error, illustrated by examples for business statistics.</p
Constructed Tidal Marshes: An analysis on how model configurations influence accretion
No full textAlong river banks, on the transition zone between the river and see, tidal marshes can develop. The tidal marshes accommodate multiple plant and fish species. As a result of the stressful conditions in tidal marshes, unique intertidal ecology develops. However, due to the densifying of the river banks, tidal marshes are disappearing. Restoration of tidal marshes can reintroduce the unique intertidal ecology on several locations in the estuary. To obtain restoration of tidal marshes, constructed tidal marshes come into play, which can be built at designated places along the river. However, constructed tidal marshes are not necessarily built to restore the unique tidal nature, but can also have other functions as recreation and contribution in green city area.Nevertheless, is it still unknown how constructed tidal marshes behave and what the optimal design is. Namely, a mismatch exists between the policymakers and designers on the one side and academic knowledge on the other side. To fill up this gap, accessible knowledge from the experts should be available for designers. Therefore, this research provides guidelines for designers and gains more insight into the behaviour of constructed tidal marshes. This thesis focusses on extracting general knowledge from the results of a numerical model, applied on a case study.Simulations of a numerical 1D Sobek model applied on the case study achieves the influence of model configurations on accretion. Therefore, tidal forcing, marsh design and system adjustments are divided into multiple components. The model simulations of the separate components give the influence on bed shear stress and potential sedimentation. Furthermore, executed fieldwork calibrates the model on measured flow velocities. Besides, the Manning coefficient is estimated, and cross-sections are obtained by gps measurements. The parameters are subsequently used as model input. From the simulations, it can be concluded that tidal asymmetry determines the duration of stagnant water and thus the settling of fine particles. A considerable increase in sedimentation is reached when flats are participating. However, an increasing flat area encourages ebb-dominance and can even lead to erosion. Next, when the width of the cross-section is large compared to the depth, more sedimentation is predicted. With flood-dominant bed shear stresses, a broad cross-section leads to accretion.In the case study, the presence of sand particles is not expected, as sand is deposited close to the inlet, where the bed shear stress is ebb-dominant. In contrast, silt settles throughout the system. Especially at low energetic conditions, such as bends, silt settles. As the occurring bed shear stress is mostly flood-directed, it is likely that sediment entering the system, does not leave the system anymore, and accretion of the bends is presumed. The placement of gate culverts in flood direction leads to higher accretion rates due to the longer slack duration. However, at the exact locations of structures, higher bed shear stresses can develop, and erosion is expected.Water Managemen
Living in fragments: Genetic variation in spatially structured populations
No full textIn de Achterhoek gaat het met de boomkikker weer wat beter dankzij beschermingsmaatregelen. Men heeft geprobeerd de lokale populaties in vijf clusters te verstevigen door in de directe omgeving nieuwe poelen te graven, het landhabitat te verbeteren en verbindingen te maken tussen lokale poelen. Toch ligt het gevaar van uitsterving ook hier nog steeds op de loer omdat de leefgebieden relatief klein en geïsoleerd zijn. Dit maakt de eveneens relatief kleine populaties kwetsbaar, bijvoorbeeld voor inteelt, omdat de genetische variatie in de populaties laag is. Inteelt, op zijn beurt, maakt populaties extra gevoelig voor toevallige omstandigheden als droogte of andere extreme (weers)omstandigheden. Paul Arens constateerde dat er tussen de clusters weinig genetische uitwisseling is, terwijl de genetische variatie binnen het hele gebied nu al gevaarlijk laag is. Recent is de belangrijkste populatie in een van de clusters bijvoorbeeld uitgestorven. Volgens Arens moeten er daarom met spoed natuurlijke verbindingen, zogenaamde corridors, tussen de clusters worden aangelegd. Dit geldt ook voor de leefgebieden van de heikikker, hoewel de genetische variatie binnen deze soort tot nu toe minder te lijden lijkt te hebben gehad van landschapsversnippering dan de boomkikker. Het leefgebied van planten en dieren in Nederland is in de laatste honderd jaar dramatisch kleiner geworden en versnipperd. Paul Arens onderzocht de consequenties voor de genetische variatie van deze natuurverarming niet alleen bij de boom- en de heikikker maar ook bij de zwarte populier, de boszegge en het dalkruid. Hij vond bij alle vijf de soorten schadelijke effecten van de versnippering van het leefgebied en/of ander menselijk handelen. Voor de drie plantensoorten lijkt vooral het ontbreken van voldoende dynamiek, die condities voor bloei en/of zaadkieming creëren, de belangrijkste oorzaak voor de achteruitgang van lokale populaties
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