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Search Results: 1 - 10 of 200901 matches for " P. Dekker "
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The Electromigration Force in Metallic Bulk
A. Lodder,J. P. Dekker
Physics , 1998, DOI: 10.1063/1.54652
Abstract: The voltage induced driving force on a migrating atom in a metallic system is discussed in the perspective of the Hellmann-Feynman force concept, local screening concepts and the linear-response approach. Since the force operator is well defined in quantum mechanics it appears to be only confusing to refer to the Hellmann-Feynman theorem in the context of electromigration. Local screening concepts are shown to be mainly of historical value. The physics involved is completely represented in ab initio local density treatments of dilute alloys and the implementation does not require additional precautions about screening, being typical for jellium treatments. The linear-response approach is shown to be a reliable guide in deciding about the two contributions to the driving force, the direct force and the wind force. Results are given for the wind valence for electromigration in a number of FCC and BCC metals, calculated using an {\it ab initio} KKR-Green's function description of a dilute alloy.
Accurate evaluation of the interstitial KKR-Green function
J. P. Dekker,A. Lodder,R. Zeller,A. F. Tatarchenko
Physics , 1996, DOI: 10.1103/PhysRevB.54.4531
Abstract: It is shown that the Brillouin zone integral for the interstitial KKR-Green function can be evaluated accurately by taking proper care of the free-electron singularities in the integrand. The proposed method combines two recently developed methods, a supermatrix method and a subtraction method. This combination appears to provide a major improvement compared with an earlier proposal based on the subtraction method only. By this the barrier preventing the study of important interstitial-like defects, such as an electromigrating atom halfway along its jump path, can be considered as being razed.
Theory for the electromigration wind force in dilute alloys
J. P. Dekker,A. Lodder,J. van Ek
Physics , 1997, DOI: 10.1103/PhysRevB.56.12167
Abstract: A multiple scattering formulation for the electromigration wind force on atoms in dilute alloys is developed. The theory describes electromigration via a vacancy mechanism. The method is used to calculate the wind valence for electromigration in various host metals having a close-packed lattice structure, namely aluminum, the noble metals copper, silver and gold and the $4d$ transition metals. The self-electromigration results for aluminum and the noble metals compare well with experimental data. For the $4d$ metals small wind valences are found, which make these metals attractive candidates for the experimental study of the direct valence.
Resistivity due to low-symmetrical defects in metals
J. P. Dekker,A. Lodder,J. van Ek
Physics , 1998, DOI: 10.1103/PhysRevB.57.12719
Abstract: The impurity resistivity, also known as the residual resistivity, is calculated ab initio using multiple-scattering theory. The mean-free path is calculated by solving the Boltzmann equation iteratively. The resistivity due to low-symmetrical defects, such as an impurity-vacancy pair, is calculated for the FCC host metals Al and Ag and the BCC transition metal V. Commonly, 1/f noise is attributed to the motion of such defects in a diffusion process.
GC- and AT-rich chromatin domains differ in conformation and histone modification status and are differentially modulated by Rpd3p
Job Dekker
Genome Biology , 2007, DOI: 10.1186/gb-2007-8-6-r116
Abstract: We have compared GC- and AT-rich isochores of yeast with respect to chromatin conformation, histone modification status and transcription. Using 3C analysis we show that, along chromosome III, GC-rich isochores have a chromatin structure that is characterized by lower chromatin interaction frequencies compared to AT-rich isochores, which may point to a more extended chromatin conformation. In addition, we find that throughout the genome, GC-rich and AT-rich genes display distinct levels of histone modifications. Interestingly, elimination of the histone deacetylase Rpd3p differentially affects conformation of GC- and AT-rich domains. Further, deletion of RPD3 activates expression of GC-rich genes more strongly than AT-rich genes. Analyses of effects of the histone deacetylase inhibitor trichostatin A, global patterns of Rpd3p binding and effects of deletion of RPD3 on histone H4 acetylation confirmed that conformation and activity of GC-rich chromatin are more sensitive to Rpd3p-mediated deacetylation than AT-rich chromatin.We find that GC-rich and AT-rich chromatin domains display distinct chromatin conformations and are marked by distinct patterns of histone modifications. We identified the histone deacetylase Rpd3p as an attenuator of these base composition-dependent differences in chromatin status. We propose that GC-rich chromatin domains tend to occur in a more active conformation and that Rpd3p activity represses this propensity throughout the genome.Chromosomes are characterized by regions that differ in base composition [1,2]. These so-called isochores correspond to functionally distinct domains that are cytologically visible as R- and G-bands [2-4]. Functional differences between the two types of regions include higher and lower levels of transcription and meiotic recombination and earlier and later firing of replication origins.Isochores in the yeast Saccharomyces cerevisiae range in size from 5-90 kb [5-9]. Clear evidence that isochores are correlated wi
Mind the gap: suggestions for bridging the divide between formal and informal social security
AH Dekker
Law, Democracy & Development , 2008,
Abstract: Adriette Dekker argues that the protection provided by social security is necessary not only to achieve social justice but is also an indispensable tool in the fight against poverty. Formal government-regulated social security in South Africa comprises both social insurance and social assistance. Due to the legacy of apartheid, this formal social security system is not comprehensive and excludes many of those who need it most, leading many people and communities to devise their own social security mechanisms. These alternatives can be termed informal social security which, although providing a certain degree of security, functions outside the protection and recognition of the formal system. The article offers suggestions for mechanisms to enhance offers cooperation between these two social security systems that can assist government in providing improved and more comprehensive social security.
Christiaan Maurits van den Heever.
G. Dekker
Koers : Bulletin for Christian Scholarship , 1958, DOI: 10.4102/koers.v26i2.1992
Abstract: Met die dood van C. M. van den Heever het ons ’n figuur ontvalwat ’n betekenisvolle rol in ons literêre lewe en in ons volkslewe gespeel het.
Kort woord van waardering. Vir prof. Labuschagne.
G. Dekker
Koers : Bulletin for Christian Scholarship , 1960, DOI: 10.4102/koers.v28i5&6.1562
Abstract: Waar ek weens my vertrek na diebuiteland nie in die geleentheid wasom breedvoeriger te ken getuig vanwat prof. Labuschagne beteken het enbeteken vir ons inrigting.
Rembrandt en die Bybel.
G. Dekker
Koers : Bulletin for Christian Scholarship , 1951, DOI: 10.4102/koers.v18i4.1739
Abstract: Onlangs het ek in ’n Nederlandse weekblad iets gelees wat tot diepnadenke stem. Dit was die uitspraak van ’n ontwikkelde Oosterling wat sy groot bewondering vir die Westerse kultuur betuig het en sy besef van wat dit nog vir die Ooste sal beteken. Maar, het hy besluit,wat die Weste tot daardie hoogte laat styg het, is die Christendom, en die Christelike geloof is nie ineer die bronaar van sy geestelike lewe nie.
Enkele gedagtes oor kuns
G. Dekker
Koers : Bulletin for Christian Scholarship , 1955, DOI: 10.4102/koers.v22i5&6.1951
Abstract: Dis nie sonder ’n sekere mate van skroom nie dat ek op versoek van u bestuur onderneem het om voor U as Filosofiese Vereniging op te tree en dit nogal met hierdie onderwerp wat ryk is aan so’n verskeidenheid vanaspekte en probleme wat die wysgeer en die estetiese beskouer vanuit sulke uiteenlopende standpunte benader—selis as dieselfde terminologiegebruik word, is die konnotasie daarvan dikwels so verskillend by die filosoof en die stetikus dat liulle gevaar loop om heltemal by mekaar verby te praat.
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