Towards device-size atomistic models of amorphous silicon

The atomic structure of amorphous materials is believed to be well described by the continuous random network model. We present an algorithm for the generation of large, high-quality continuous random networks. The algorithm is a variation of the "sillium" approach introduced by Wooten, Winer, and Weaire. By employing local relaxation techniques, local atomic rearrangements can be tried that scale almost independently of system size. This scaling property of the algorithm paves the way for the generation of realistic device-size atomic networks.Comment: 7 pages, 3 figure

The Early Royal Society and Visual Culture

Recent studies have fruitfully examined the intersection between early modern science and visual culture by elucidating the functions of images in shaping and disseminating scientific knowledge. Given its rich archival sources, it is possible to extend this line of research in the case of the Royal Society to an examination of attitudes towards images as artefacts –manufactured objects worth commissioning, collecting and studying. Drawing on existing scholarship and material from the Royal Society Archives, I discuss Fellows’ interests in prints, drawings, varnishes, colorants, images made out of unusual materials, and methods of identifying the painter from a painting. Knowledge of production processes of images was important to members of the Royal Society, not only as connoisseurs and collectors, but also as those interested in a Baconian mastery of material processes, including a “history of trades”. Their antiquarian interests led to discussion of painters’ styles, and they gradually developed a visual memorial to an institution through portraits and other visual records.AH/M001938/1 (AHRC

Partitioning 3D space for parallel many-particle simulations

In a common approach for parallel processing applied to simulations of manyparticle systems with short-ranged interactions and uniform density, the simulation cell is partitioned into domains of equal shape and size, each of which is assigned to one processor. We compare the commonly used simple-cubic (SC) domain shape to domain shapes chosen as the Voronoi cells of BCC and FCC lattices. The latter two are found to result in superior partitionings with respect to communication overhead. Other domain shapes, relevant for a small number of processors, are also discussed. The higher e#ciency with BCC and FCC partitionings is demonstrated in simulations of the sillium model for amorphous silicon. Key words: parallel computing, particle simulations, space partitioning PACS: 02.70.Ns, 82.20.Wt, 61.43.Dq

Abstract Partitioning 3D space for parallel many-particle simulations

In a common approach for parallel processing applied to simulations of manyparticle systems with short-ranged interactions and uniform density, the simulation cell is partitioned into domains of equal shape and size, each of which is assigned to one processor. We compare the commonly used simple-cubic (SC) domain shape to domain shapes chosen as the Voronoi cells of BCC and FCC lattices. The latter two are found to result in superior partitionings with respect to communication overhead. Other domain shapes, relevant for a small number of processors, are also discussed. The higher efficiency with BCC and FCC partitionings is demonstrated in simulations of the sillium model for amorphous silicon

Structure and rheological properties of acid-induced egg white protein gels

This study compares the rheological properties of acid-induced gels prepared of industrial spray-dried egg white proteins (EWP) with the acid-induced gels prepared of ovalbumin (OA) and whey protein isolate (WPI). Also we aimed to form transparent gels of EWP by means of the cold-gelation process. We showed that it was not possible to prepare cold-set gels because ovotransferrin (OT), present in EWP, was found to interfere with fibril formation. Therefore, we developed a new purification method in which first OT was selectively denatured by a heating step, subsequently precipitated by acidification and removed by centrifugation. Finally, the supernatant was desalted by ultra filtration. This resulted in a preheated EWP preparation, which mainly contains OA (>80%). By removing OT using this new preheat procedure transparent gels were obtained after acid-induced gelation. Fracture properties of various EWP preparations were determined and compared with those of acid-induced gels of OA and WPI. Gels formed from different EWP preparations were weak (fracture stress 1-15 kPa, fracture strain 0.3-0.7), and the networks consisted of thin strands with hardly any additional disulphide bonds formed during the gelation step. In conclusion, the microstructure of the aggregates formed in the first step of the cold-gelation process and the amount of additional disulphide bonds formed during the second step appeared to be the determining factors contributing to the hardness and deformability of acid-induced gels of egg white proteins. © 2005 Elsevier Ltd. All rights reserved