High-performance explicit transient structural analysis

The continuous development of finite element programs creates code which is increasingly difficult to maintain, due to the increasing complexity as well as the chosen programming language. At the same time, the desire to analyse increasingly more complex and larger models requires the use of powerful tools capable of solving these problems in a reasonable amount of time. The research described in this thesis aims to solve these issues of maintainability and performance. For that purpose a new code structure has been designed, and the new finite element program has been adapted to make use of modern high-performance computers. The two principle parts in this thesis are: Design of an object-oriented code base In order to improve maintainability and ease of development, an object-oriented framework for finite element programs, written in C++, has been designed. The structure of the framework is set up in such a way, that the existing computational routines from the old Fortran program can be integrated in the new object-oriented code. Adaptation for high-performance computing Although object-oriented code generates more overhead than traditional procedural programming, the restructuring of the program together with the use of certain advantages of C++ created a new program executable which is faster than the old program. The object-oriented code made the adaptation of the code for parallel computing relatively easy and allowed the programming of the communication to be implemented transparently. New element types and new material models have been implemented to demonstrate the flexibility and ease of development of the new code. Three applications are presented to demonstrate the possibilities of the new finite element program

Maatschappelijk vastgoed uitbesteden? Onderzoeksrapport

In dit rapport is onderzoek gedaan naar het uitbesteden van maatschappelijk vastgoed. Hierbij gaat het om het uitbesteden van het technische beheer. Dit onderzoek is gehouden in opdracht van de gemeente Assen. De gemeente Assen is geïnteresseerd in de keuzes die andere gemeenten gemaakt hebben met betrekking tot het uitbesteden. In het verleden is er nog niet veel onderzoek naar uitbesteding van vastgoed gedaan. Om toch een duidelijk beeld te krijgen van het proces richting uitbesteden zijn verscheidene gemeenten en experts benaderd. Aanvankelijk richtte dit onderzoek zich enkel op het uitbesteden van het technisch beheer. Tijdens het onderzoek zijn er interessantere onderwerpen aan het licht gekomen, die tevens een aanvulling waren op het onderzoek. Daarmee is het oorspronkelijke onderzoeksontwerp uitgebreid. Er zijn een aantal gemeenten die hun maatschappelijk vastgoed reeds uitbesteden. Hoe zijn zij tot die keuze gekomen? Welke ervaringen hebben zij op gedaan en waar zijn zij tegenaan gelopen? Het onderzoeksdoel is : ’Een inzicht verkrijgen in de criteria die aan de beslissing voorafgaan om maatschappelijk vastgoed wel of niet uit te besteden’. Studentonderzoek in het kader van het thema Leefomgeving

Cigarette smoke extract induced exosome release is mediated by depletion of exofacial thiols and can be inhibited by thiol-antioxidants

Introduction: Airway epithelial cells have been described to release extracellular vesicles (EVs) with pathological properties when exposed to cigarette smoke extract (CSE). As CSE causes oxidative stress, we investigated whether its oxidative components are responsible for inducing EV release and whether this could be prevented using the thiol antioxidants N-acetyl-L-cysteine (NAC) or glutathione (GSH). Methods: BEAS-2B cells were exposed for 24 h to CSE, H2O2, acrolein, 5,5'-dithiobis-(2-nitrobenzoic acid) (DTNB), bacitracin, rutin or the anti-protein disulfide isomerase (PDI) antibody clone RL90; with or without NAC or GSH. EVs in media were measured using CD63(+)CD81(+) bead-coupled flow cytometry or tunable resistive pulse sensing (TRPS). For characterization by Western Blotting, cryo-transmission electron microscopy and TRPS, EVs were isolated using ultracentrifugation. Glutathione disulfide and GSH in cells were assessed by a GSH reductase cycling assay, and exofacial thiols using Flow cytometry. Results: CSE augmented the release of the EV subtype exosomes, which could be prevented by scavenging thiol-reactive components using NAC or GSH. Among thiol-reactive CSE components, H2O2 had no effect on exosome release, whereas acrolein imitated the NAC-reversible exosome induction. The exosome induction by CSE and acrolein was paralleled by depletion of cell surface thiols. Membrane impermeable thiol blocking agents, but not specific inhibitors of the exofacially located thiol-dependent enzyme PDI, stimulated exosome release. Summary/conclusion: Thiol-reactive compounds like acrolein account for CSE-induced exosome release by reacting with cell surface thiols. As acrolein is produced endogenously during inflammation, it may influence exosome release not only in smokers, but also in ex-smokers with chronic obstructive pulmonary disease. NAC and GSH prevent acrolein-and CSE-induced exosome release, which may contribute to the clinical benefits of NAC treatment

Developments in B2000: A review of time-integration methods

Aerospace Engineerin