917 research outputs found
Variability of the 13C-acetate breath test for gastric emptying of liquids in healthy children.
No full textNew Pliocene and Pleistocene acritarchs from the North Atlantic, Arctic Ocean and Bering Sea
No full textAcritarchs have received limited attention in palynological studies of the Cenozoic, although they have much potential both for refining Neogene and Quaternary stratigraphy, especially in mid- and high northern latitudes, and developing palaeoceanographical reconstructions. Here we formally describe and document the stratigraphical and palaeotemperature ranges (from foraminiferal Mg/Ca) of four new acritarch species: Cymatiosphaera? aegirii sp. nov., Cymatiosphaera? fensomei sp. nov., Cymatiosphaera? icenorum sp. nov. and Lavradosphaera canalis sp. nov. In reviewing the stratigraphical distributions of all species of the genus Lavradosphaera De Schepper & Head, 2008, we demonstrate their correlation potential between the North Atlantic and Bering Sea in the Pliocene. Additionally, Lavradosphaera lucifer De Schepper & Head, 2008 and Lavradosphaera canalis sp. nov., while not themselves overlapping stratigraphically, have morphological intermediates that do partially overlap and may represent an evolutionary trend consequent upon climate cooling in the Late Pliocene. Finally, we show that the highest abundances of the acritarchs presented here were living in the eastern North Atlantic, in surface-water temperatures not very different from today
Response to “Comment on ‘The viscoelastic response of Brownian suspensions’?” [J. Chem. Phys. 114, 3339 (2001)]
No full textOur original article presented computer simulation results for the viscoelastic response of a simple model colloidal suspension. We compared our results for the viscosity with a theoretical prediction of Verberg et al. [R. Verberg, I. M. de Schepper, and E. G. D. Cohen, Phys. Rev. E 55, 3143 (1997)] and found poor agreement. It is suggested in the previous comment that a comparison with a modified expression is more appropriate. In response we explain the basis of our comparison and expand on how a different interpretation could be made, leading to an expression of the form Felderhof suggests is appropriate. Nonetheless, as stated in the comment, the agreement with simulation is poor, no matter which of the two possible theoretical expressions is used. We also seek to clarify our position concerning the form of the high frequency response at low volume fraction. Our finding is that the ratio of this to the high frequency response in the zero density limit is not the radial distribution function at contact, as predicted by Verberg et al. [R. Verberg, I. M. de Schepper, M. J. Feigenbaum, and E. G. D. Cohen, J. Stat. Phys. 87, 1037 (1997)], but is a rather smaller quantity.Computational PhysicsApplied Science
Stochastic approximations of present value functions.
No full textThe aim of the paper is to apply the method proposed by Denuit, Genest and Marceau (1999) for deriving stochastic upper and lower bounds on the present value of a sequence of cash flows, where the discounting is performed under a given stochastic return process. The convex approximation provided by Goovaerts, Dhaene and De Schepper (1999) and Goovaerts and Dhaene (1999) is then compared to these stochastic bounds. On the basis of several numerical examples, it will be seen that the convex approximation seems reasonable.Value; Functions;
Spin-echo development for a time-of-flight neutron reflectometer
No full textNeutron scattering techniques are a useful tool to determine structures in samples with sizes ranging from 1 x 10-10 up to 1 x 10-5 meter. Unfortunately powerful neutron sources are scares and expensive, which demands an efficient use of the available neutrons. This thesis focuses mainly on the practical realisation of a combination of two neutron scattering techniques; neutron reflectometry and neutron spin-echo angle labelling. This special combination will not only result in more efficient neutron scattering measurements but will also open up possibilities for new types of measurements. OffSpec is a new dedicated spin-echo reflectometer which is designed to accommodate the fusion of the two techniques and is located at the Second Target Station at ISIS in the United Kingdom. It will be ready for user operation mid 2009. Delft University of Technology has been responsible for the development and production of the spin-echo components for OffSpec. A flexible mechanical design results in five different applications for this spectrometer: ultra small-angle scattering by spin-echo, high intensity measurements on in-plane - nanometre to micrometre - correlations, high resolution measurements for bent or wavy samples, possibility to separate specular and off-specular scattering within a detector pixel, and inelastic spin-echo in transmission or in reflection. A large part of this thesis work consists of the design and build of these spin-echo components. A dedicated beam at the Reactor Institute Delft was used to test the components and built a number of prototypes spectrometers. These prototypes were used to perform proof of principle measurements for several different instrumental modes which are described in this thesis.Radiation, radionuclides & reactorsApplied Science
New late Cenozoic acritarchs: evolution, palaeoecology and correlation potential in high latitude oceans
No full text<div><p>Acritarchs have received limited attention in palynological studies of the Cenozoic, although they have much potential both for refining Neogene and Quaternary stratigraphy, especially in mid- and high northern latitudes, and developing palaeoceanographical reconstructions. Here we formally describe and document the stratigraphical and palaeotemperature ranges (from foraminiferal Mg/Ca) of four new acritarch species: <i>Cymatiosphaera</i>? <i>aegirii</i> sp. nov., <i>Cymatiosphaera</i>? <i>fensomei</i> sp. nov., <i>Cymatiosphaera</i>? <i>icenorum</i> sp. nov. and <i>Lavradosphaera canalis</i> sp. nov. In reviewing the stratigraphical distributions of all species of the genus <i>Lavradosphaera</i> De Schepper & Head, 2008, we demonstrate their correlation potential between the North Atlantic and Bering Sea in the Pliocene. Additionally, <i>Lavradosphaera lucifer</i> De Schepper & Head, 2008 and <i>Lavradosphaera canalis</i> sp. nov., while not themselves overlapping stratigraphically, have morphological intermediates that do partially overlap and may represent an evolutionary trend consequent upon climate cooling in the Late Pliocene. Finally, we show that the highest abundances of the acritarchs presented here were living in the eastern North Atlantic, in surface-water temperatures not very different from today.</p><p><a href="http://zoobank.org/urn:lsid:zoobank.org:pub:7AB934D1-E452-4117-9D38-76C3FCFC00B8" target="_blank">http://zoobank.org/urn:lsid:zoobank.org:pub:7AB934D1-E452-4117-9D38-76C3FCFC00B8</a></p></div
A method to minimize test times for accelerated testing of pHEMT's by analysis of the elctronic fingerprint of the initial stage of degradation
No full textAccelerated life testing provides a necessary tool for reliability validation but is generally very time-consuming as standard test take up to 2000 hours to proceed. In this article, results on the early stages of the ageing of pHEMT transistors are presented and it is shown that the necessary test time can be decreased from 2000 hours to 144 hours without loss of data confidence. This has been enabled by the application of an insitu measurement method where the ageing of the device under test is characterized during the stress phase. Two main degradation factors can be identified in good agreement with findings reported in literature. The data have been successfully correlated with standard test results performed on a 2000 hours time scale
A fundamental study on materials for Li-ion batteries
No full textIn April 1997 the program "Decentralized Production and Storage for Large-Scale Application of Renewable Energy" of the Delft Interfaculty Research Centre (DIOC) was launched. In this program various groups from several Faculties of the Delft University of Technology studied the feasibility of large scale application of renewable energy. Energy produced by a renewable source will not only be produced at moments that it is needed (as is the case with the conventionally produced energy) but also at moments that it is barely needed. Therefore one will have to store this energy to make it available at all times. Energy can be stored in many ways, e.g. converting water into hydrogen and oxygen and back again when the energy is needed. One of the most convenient and easiest ways is to store electrical energy in rechargeable batteries, e.g. lithium-ion batteries. Favourable characteristics of lithium-ion batteries include a high energy density, a high voltage and a low weight. In the study presented here we focussed on two materials for an all solid-state lithium-ion battery, the ceramic electrolyte BPO4 + z% Li2O and the cathode LiMn2O4. By using several techniques, i.e. Neutron Diffraction, Quasi Elastic Neutron Scattering, 1-dimensional NMR and 2-dimensional NMR, the crystal structure and Li-dynamics of these materials have been studied. The results will be shown and discussed.Applied Science
Placcaet en[de] ordinantie [...] des Conincx, op tstuc van het crijchsvolck zoo wel te voete als te peerde, loopende den huysman afteeren, verdrucken ende oppresseren. Ten Nyemeghen den xxix. dach van Ianuario, xvc.Lxxij.
No full textCockx-Indestege, E. Belgica typographica ; 2650Machiels, J. Catalogus van de boeken gedrukt vóór 1600 ; P 510Vanderhaeghen, F. Bib. gantoise ; 256Europeana-GoogleBooksVander Haeghen, Ferdinand François ErnestDe Schepper, Marcu
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