Diversity, ecology and domoic acid production of <i>Pseudo-nitzschia</i> spp. in Scottish waters

Some diatoms of the genus Pseudo-nitzschia produce the toxin domoic acid (DA). Accumulation of DA in shellfish has led to harvesting closures in western Scottish waters since 1999. This thesis investigated the diversity, ecology and distribution of toxic and non-toxic Pseudo-nitzschia species in western Scottish waters and physiological aspects of growth and toxin production dynamics of P. seriata. The temporal and spatial distribution of phytoplankton was analysed in two separate field studies. 1) Temporal changes were followed by sampling a site in coastal Scottish waters weekly to fortnightly over a period of three years. 2) The spatial distribution of the phytoplankton community was investigated by sampling a transect across the shelf. Within both studies, physical, biological and chemical parameters were measured and correlated to temporal and spatial distribution patterns in the phytoplankton community, indicating seasonality, and differences in the distribution of toxic and non-toxic Pseudo-nitzschia species between coastal and offshore waters. From those samplings 59 clonal cultures of Pseudo-nitzschia, comprising 7 species (2 of them toxic), were established. Strains were identified via classic morphological and genetic techniques. Phylogenetic relationships were established between Scottish Pseudo-nitzschia strains. P. seriata was identified for the first time in Scottish waters as a DA producer. Laboratory experiments with cultured strains showed a) enhanced toxin production by P. seriata under silicate (Si) and phosphate (P) limitation, with higher DA production under Si than under P limitation b) similar cell yields of P. seriata, when grown in nitrate or ammonia based media c) a preference for spring light conditions (short day length) in a non-toxic P. delicatissima strain and summer light conditions (long day length) for a toxic P. seriata strain, expressed by enhanced biomass yield under the respective light condition. It was also shown that the presence of bacteria enhanced the growth of single P. seriata cells

Female Maquila Workers in Nicaragua - How can the State Enhance the Women’s Human Security?

This thesis explores the insecurities of female maquila workers in Nicaragua in order to derive policy implications for the Nicaraguan state. These workers are deeply embedded in gendered and neoliberal structures of the global political economy. Based on theories of the social contract, the state is identified as being responsible for ensuring human security for its citizens. Using observations, text analysis and focus groups with female maquila workers, the female workers’ everyday insecurities are identified. The analysis is guided by the human security framework employing a gender perspective. The results are contrasted to feminist policy proposals by Barrientos and Kabeer (2004). Violence, economy and health have been identified as main insecurities of these workers. As a result it is argued that Barrientos and Kabeer’s (2004) proposals are too narrowly focused on the productive and reproductive role of women, but do not consider other issues that seriously constrain the workers’ security like violence and health

Algorithms for massively parallel generic hp-adaptive finite element methods

Efficient algorithms for the numerical solution of partial differential equations are required to solve problems on an economically viable timescale. In general, this is achieved by adapting the resolution of the discretization to the investigated problem, as well as exploiting hardware specifications. For the latter category, parallelization plays a major role for modern multi-core and multi-node architectures, especially in the context of high-performance computing. Using finite element methods, solutions are approximated by discretizing the function space of the problem with piecewise polynomials. With hp-adaptive methods, the polynomial degrees of these basis functions may vary on locally refined meshes. We present algorithms and data structures required for generic hp-adaptive finite element software applicable for both continuous and discontinuous Galerkin methods on distributed memory systems. Both function space and mesh may be adapted dynamically during the solution process. We cover details concerning the unique enumeration of degrees of freedom with continuous Galerkin methods, the communication of variable size data, and load balancing. Furthermore, we present strategies to determine the type of adaptation based on error estimation and prediction as well as smoothness estimation via the decay rate of coefficients of Fourier and Legendre series expansions. Both refinement and coarsening are considered. A reference implementation in the open-source library deal.II is provided and applied to the Laplace problem on a domain with a reentrant corner which invokes a singularity. With this example, we demonstrate the benefits of the hp-adaptive methods in terms of error convergence and show that our algorithm scales up to 49,152 MPI processes.Für die numerische Lösung partieller Differentialgleichungen sind effiziente Algorithmen erforderlich, um Probleme auf einer wirtschaftlich tragbaren Zeitskala zu lösen. Im Allgemeinen ist dies durch die Anpassung der Diskretisierungsauflösung an das untersuchte Problem sowie durch die Ausnutzung der Hardwarespezifikationen möglich. Für die letztere Kategorie spielt die Parallelisierung eine große Rolle für moderne Mehrkern- und Mehrknotenarchitekturen, insbesondere im Kontext des Hochleistungsrechnens. Mit Hilfe von Finite-Elemente-Methoden werden Lösungen durch Diskretisierung des assoziierten Funktionsraums mit stückweisen Polynomen approximiert. Bei hp-adaptiven Verfahren können die Polynomgrade dieser Basisfunktionen auf lokal verfeinerten Gittern variieren. In dieser Dissertation werden Algorithmen und Datenstrukturen vorgestellt, die für generische hp-adaptive Finite-Elemente-Software benötigt werden und sowohl für kontinuierliche als auch diskontinuierliche Galerkin-Verfahren auf Systemen mit verteiltem Speicher anwendbar sind. Sowohl der Funktionsraum als auch das Gitter können während des Lösungsprozesses dynamisch angepasst werden. Im Besonderen erläutert werden die eindeutige Nummerierung von Freiheitsgraden mit kontinuierlichen Galerkin-Verfahren, die Kommunikation von Daten variabler Größe und die Lastenverteilung. Außerdem werden Strategien zur Bestimmung des Adaptierungstyps auf der Grundlage von Fehlerschätzungen und -prognosen sowie Glattheitsschätzungen vorgestellt, die über die Zerfallsrate von Koeffizienten aus Reihenentwicklungen nach Fourier und Legendre bestimmt werden. Dabei werden sowohl Verfeinerung als auch Vergröberung berücksichtigt. Eine Referenzimplementierung erfolgt in der Open-Source-Bibliothek deal.II und wird auf das Laplace-Problem auf einem Gebiet mit einer einschneidenden Ecke angewandt, die eine Singularität aufweist. Anhand dieses Beispiels werden die Vorteile der hp-adaptiven Methoden hinsichtlich der Fehlerkonvergenz und die Skalierbarkeit der präsentierten Algorithmen auf bis zu 49.152 MPI-Prozessen demonstriert

UHPC Compressive Strength Test Specimens: Cylinder or Cube?

AbstractUltra High Performance Concrete (UHPC) is a new cement-based material developed in the era of modern concrete technology. The present of fiber in UHPC composition is necessary to increase strengths and durability, which then lead to name the material as Ultra High Performance Fiber Reinforced Concrete (UHPFRC). However, the exact determination of UHPC and UHPFRC have challenges due to its very high compression strength. Some issues are the limited capability to purchase high load capacity testing machines, and the surface preparation requirement for cylinder specimens. In this study, three series of experimental programs were conducted to investigate the compressive strength of UHPC and UHPFRC using cylinder and cube specimens, and to determine its converting factors (ratio). The results show that the compressive strength relationships between specimens differ from those of conventional concrete