1,110 research outputs found
Biological Carbon Sequestration and Carbon Trading Re-Visited
No full textUnder Kyoto, biological activities that sequester carbon can be used to create CO2 offset credits that could obviate the need for lifestyle-changing reductions in fossil fuel use. Credits are earned by storing carbon in terrestrial ecosystems and wood products, although CO2 emissions are also mitigated by delaying deforestation, which accounts for one-quarter of anthropogenic CO2 emissions. However, nonpermanent carbon offsets from biological activities are difficult to compare with each other and with emissions reduction because they differ in how long they prevent CO2 from entering the atmosphere. This is the duration problem; it results in uncertainty and makes it difficult to determine the legitimacy of biological activities in mitigating climate change. While there is not doubt that biological sink activities help mitigate climate change and should not be neglected, in this paper we demonstrate that these activities cannot be included in carbon trading schemes.carbon offset credits, climate change, duration of carbon sinks, Environmental Economics and Policy,
The discovery of SycO reveals a new function for type three secretion effector chaperones
No full textThe Type Three Secretion (T3S) system is a device used by many Gram-negative pathogens that allows bacteria to deliver effector proteins straight into the eukaryotic cell cytosol. These effectors interfere with various signaling pathways to subvert the host cell functions. The secretion machinery of the T3S system consist of a basal body spanning the bacterial inner and outer membrane followed by a stiff hollow needle outside the bacterium. The fully assembled secretion apparatus constitute a continuous hollow conduit that connects the bacteria to the eukaryotic target cell. After cell contact, virulence proteins -called effectors- are injected directly into the cytosol of the host cell via the T3S apparatus. Several effectors of the T3S system require the assistance of specific cytosolic chaperones to be efficiently exported. There are three classes of T3S chaperones. Effector proteins are assisted by Class I chaperones. Although Class I chaperones are well characterized, their main function is still a matter of controversy. In this thesis, we demonstrate that orf155 encodes a specific chaperone for the effector YopO that we called SycO. We showed that SycO enhances YopO secretion in vitro and is required for translocation of YopO into infected cells. By pulldown assay we demonstrated that residues 20 to 77 of YopO are required and sufficient for SycO binding. Using crosslinking experiments and size exclusion chromatography analysis, we determined the stoichiometry of purified SycO and YopO-SycO complexes. SycO alone forms dimers in solution and the YopO-SycO complex has a 1:2 stoichiometry. These results suggested that SycO is a typical chaperone of the Class I. YopO is a serine/theronine kinase that interacts with Rho and Rac and disrupts the cytoskeleton of the target cells. YopO has been shown to localize at the cell plasma-membrane. By transfection of YopO-EGFP hybrid proteins into HEK293T cells, we demonstrated that the chaperone-binding domain (CBD) coincides with the membrane localization domain of YopO. Nevertheless, the CBD was not needed for the kinase activity of YopO. By ultracentrifugation, we also showed that the CBD causes YopO aggregation in the bacteria, when SycO does not cover it. Further, we show that the CBD of YopE and YopT also caused aggregation in the bacteria in the absence of SycE and SycT respectively. YopE, YopT and T3S effectors in other systems also act at the membrane of the eukaryotic host cell. We propose a new hypothesis concerning the role of T3S chaperones. The sub-cellular localization domain of effectors is aggregation-prone and creates the need for a chaperone inside bacteria. We propose that masking such aggregation-prone localization domains may be a general function for type III effector chaperones
A non-reflective boundary condition for LBM based on the assumption of non-equilibrium symmetry
No full textIn this study a new type of non-reflective boundary condition (NRBC) for the Lattice Boltzmann Method (LBM) is proposed; the Non-equilibrium Symmetry Boundary Condition (NSBC). The idea behind this boundary condition is to utilize the characteristics of the non-equilibrium distribution function to assign values to the incoming populations. A simple gradient based extrapolation technique and a far-field criterion are used to predict the macroscopic fluid variables. To demonstrate the non-reflective behaviour of the NSBC, two different tests have been carried out, examining the capability of the boundary to absorb acoustic waves respectively vortices. The results for both tests show that the amount of reflection generated by the NSBC is nearly zero.Green Open Access added to TU Delft Institutional Repository ‘You share, we take care!’ – Taverne project https://www.openaccess.nl/en/you-share-we-take-care Otherwise as indicated in the copyright section: the publisher is the copyright holder of this work and the author uses the Dutch legislation to make this work public.Numerical Analysi
The Master-Slave Splitting Extended to Power Flow Problems on Integrated Networks with an Unbalanced Distribution Network
No full textAn integrated network consists of a transmission network and at least one distribution network which are connected to each other via a substation. One way to do power flow simulations on these integrated networks is the Master-Slave splitting method. This method splits the integrated network and iterates between the separate transmission (the master) and distribution (the slave) network. In this paper, we extend the method to hybrid networks: a network consisting of a balanced transmission and an unbalanced distribution network. An extra handling is necessary to get the Master-slave splitting to work on hybrid networks. We explain two approaches to use the Master-Slave splitting on a hybrid network and compare these approaches on accuracy, computational time, and convergence, by doing test-simulations. The Master-Slave splitting is interesting when distribution and transmission systems have different characteristics, are in geographically distinct locations, or when system operators are not able or allowed to share data of their network with each other. The extension to hybrid networks makes this method generally applicable and an interesting choice to do power flow simulations on integrated networks.Green Open Access added to TU Delft Institutional Repository ‘You share, we take care!’ – Taverne project https://www.openaccess.nl/en/you-share-we-take-care Otherwise as indicated in the copyright section: the publisher is the copyright holder of this work and the author uses the Dutch legislation to make this work public.Numerical Analysi
Modelling Turbulent Combustion Coupled with Conjugate Heat Transfer in OpenFOAM
No full textThis paper verifies a mathematical model that is developed for the open source CFD-toolbox OpenFOAM, which couples turbulent combustion with conjugate heat transfer. This feature already exists in well-known commercial codes. It permits the prediction of the flame’s characteristics, its emissions, and the consequent heat transfer between fluids and solids via radiation, convection, and conduction. The verification is based on a simplified 2D axisymmetric cylindrical reactor. In the first step, the combustion part of the solver is compared against experimental data for an open turbulent flame. This shows good agreement when using the full GRI 3.0 reaction mechanism. Afterwards, the flame is confined by a cylindrical wall and simultaneously conjugate heat transfer is activated and analysed. It is shown that the combustion and conjugate heat transfer are successfully coupled.Green Open Access added to TU Delft Institutional Repository ‘You share, we take care!’ – Taverne project https://www.openaccess.nl/en/you-share-we-take-care Otherwise as indicated in the copyright section: the publisher is the copyright holder of this work and the author uses the Dutch legislation to make this work public.Numerical AnalysisMathematical Physic
Scaling of the Steady-State Load Flow Equations for Multi-Carrier Energy Systems
No full textCoupling single-carrier networks (SCNs) into multi-carrier energy systems (MESs) has recently become more important. Steady-state load flow analysis of energy systems leads to a system of nonlinear equations, which is usually solved using the Newton-Raphson method (NR). Due to various physical scales within a SCN, and between different SCNs in a MES, scaling might be needed to solve the nonlinear system. In single-carrier electrical networks, per unit scaling is commonly used. However, in the gas and heat networks, various ways of scaling or no scaling are used. This paper presents a per unit system and matrix scaling for load flow models for a MES consisting of gas, electricity, and heat. The effect of scaling on NR is analyzed. A small example MES is used to demonstrate the two scaling methods. This paper shows that the per unit system and matrix scaling are equivalent, assuming infinite precision. In finite precision, the example shows that the NR iterations are slightly different for the two scaling methods. For this example, both scaling methods show the same convergence behavior of NR in finite precision.Green Open Access added to TU Delft Institutional Repository ‘You share, we take care!’ – Taverne project https://www.openaccess.nl/en/you-share-we-take-care Otherwise as indicated in the copyright section: the publisher is the copyright holder of this work and the author uses the Dutch legislation to make this work public.Numerical Analysi
A Direct Projection to Low-Order Level for p-Multigrid Methods in Isogeometric Analysis
No full textIsogeometric Analysis (IgA) can be considered as the natural extension of the Finite Element Method (FEM) to high-order B-spline basis functions. The development of efficient solvers for discretizations arising in IgA is a challenging task, as most (standard) iterative solvers have a detoriating performance for increasing values of the approximation order p of the basis functions. Recently, p-multigrid methods have been developed as an alternative solution strategy. With p-multigrid methods, a multigrid hierarchy is constructed based on the approximation order p instead of the mesh width h (i.e. h-multigrid). The coarse grid correction is then obtained at level p = 1, where B-spline basis functions coincide with standard Lagrangian P1 basis functions, enabling the use of well known solution strategies developed for the Finite Element Method to solve the residual equation. Different projection schemes can be adopted to go from the high-order level to level p = 1. In this paper, we compare a direct projection to level p = 1 with a projection between each level 1 ≤ k ≤ p in terms of iteration numbers and CPU times. Numerical results, including a spectral analysis, show that a direct projection leads to the most efficient method for both single patch and multipatch geometries.Green Open Access added to TU Delft Institutional Repository ‘You share, we take care!’ – Taverne project https://www.openaccess.nl/en/you-share-we-take-care Otherwise as indicated in the copyright section: the publisher is the copyright holder of this work and the author uses the Dutch legislation to make this work public.Numerical Analysi
Korte historiael, ende journaels aenteyckeninge, van verscheyden voyagiens in de vier deelen des wereldts-ronde, als Europa, Africa, Asia, ende Amerika gedaen /
No full textIllustrated with numerous copperplate engravings. Frontispiece portrait of the author by Cornelis Visscher.Mode of access: Internet
Cornelis Ketel en zijn familie: een revisie
No full textAbstractIn 1964 this journal published an article by J. Schouten with a family tree of the Ketel family of Gouda; most of the archive records consulted by the author for that purpose were already public. His principal theme, however, was the hypothesis of a third painter in the family by the name of Cornelis Ketel. The first Cornelis, who died in 1567, was the now forgotten uncle and teacher of the second, the well-known painter Cornelis Ketel who died in Amsterdam in 1616; the third Cornelis was the first one's son and thus a cousin of the second. Fresh archive research has yielded a corrected and more extensive family trcc of the Ketel family (fig. 1). Another result of this investigation is the untenability of Schouten's hypothesis: a third Cornelis did exist, but died at an early age before 1582, and there are no indications that he was an artist. Consequently, all Gouda archive records post-dating 1582 or thereabouts refer to the Cornclis Ketel who lived in Amsterdam at that time. Although he did live in Gouda for a few years after 1590/91, it was not in a 'Gasthuis' (almshouse), a misunderstanding caused by an incorrcctly transcribed archive record (fig. 6). A number of paintings which an 'old' tradition - much younger, incidentally, than Schouten would have us believe - ascribes to the second Ketel, and which because of their inferior quality arc attributed by Schouten to the third Cornelis, can therefore not be the work of the latter (figs. 7, 8, 9). Nor are they by the well-known Ketel. The addition of 'de Jonge' (the Younger) to the Amsterdam Ketel's name occurs sporadically in a few Gouda records. This suffix was not meant, as Schouten presumed, to distinguish him from his cousin, who in any case was younger than the Amsterdam Ketel, but to distinguish him as a painter from his elder uncle and teacher. Until work by this teacher is discovered, there is no point in dubbing the pupil 'the Younger'. Ketel did not suffer from gout; his brushless painting is a facet of his artistic versatility. As a matter of fact he did paint a number of works with the brush after 1600. A brother of the third Cornelis, the engineer Jacob whom Van Mander mentions in his biography of Ketel, is apparently identical with the painter Jacques Que(s)tel who lived successively in Orleans, Milan and Paris (fig. 2). He probably did not take up painting until after 1602. In 1608 he made decorations for Queen Maria de Medici's ceremonial entrance into Chartres. No work by him has come to light thus far, but a number of engravings after a portrait he painted in 1609 have survived (figs. 3 and 4). Appendix i traces how a legacy of another uncle of Ketel was distributed and passed on to his descendants. Appendix 2 lists a number of archive records pertaining to Jacob Ketel/Jacques Questel.
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Portret van twee negentiende-eeuwse meesters: Leven en werk van Hendrik Jan en Cornelis Hendrik van Ameron
No full textLeven en werk van de kunstschilder Hendrik Jan (1776-1833) en diens zoon Cornelis Hendrik van Amerom (1804-1874) zijn nauw verbonden met het kunstonderwijs in Arnhem en Leiden. De vroegste geschiedenis van de Arnhemse Kunstakademie is niet te denken zonder de invloed van Hendrikjan van Amerom. Als "eerste tekenmeester" bepaalde hij dertig jaar lang het onderwijs aan deze instelling. Zijn zoon, Cornelis Hendrik, speelde een belangrijke rol in het tekenonderricht te Leiden, waar hij les gaf aan diverse kostscholen voor jongens en meisjes uit de "betere standen". Cornelis Hendrik van Amerom kan tot de vroegste fotografen in Nederland worden gerekend. Tevens mag hij worden beschouwd als ontdekker van het Gelderse landschap, dat inspiratiebron werd voor vele kunstenaars. Hiermee is hij een directe voorloper van de schilders van de "Oosterbeekse Schildersbent" en de "Haagse School". Van uitzonderlijke (kunst)historische betekenis is zijn "Memorie-boekje". In dit tot nu toe onopgemerkt gebleven ego-document maakte hij belangrijke aantekeningen over zijn familie en zijn werk als kunstenaar en fotograaf. Het "Memorie-boekje" wordt in deze uitgave, met een geïllustreerde oeuvrecatalogus van beide kunstenaars, integraal gepubliceerd. Uitgave van Stichting Leids Kunsthistorisch Jaarboek
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