Plasma turbulence on a uniform density gradient with unfavorable magnetic curvature is investigated extensively in the Helimak device. The turbulence is strong with density and electrostatic potential fluctuation levels in excess of 40%. Measurements of the dispersion relation, k[subscript z], and k[subscript parallel lines] identify the the fluctuations with drift-waves, which propagate in the poloidal direction at the diamagnetic drift velocity and have a small, but nite parallel wavenumber. A non-zero phase shift between the density and potential fluctuations gives rise to turbulent cross-eld particle transport, which is measured using spectral techniques. In addition, the electrostatic drift-wave fluctuations have a small magnetic component that is driven by the turbulent parallel current [scientific symbols]. An examination of nonlinear processes associated with the plasma turbulence uncovers high levels of intermittency near the plasma edge and long-time persistence of the density fluctuations on the order of the parallel confinement time. An analysis of the bispectrum conrms the existence local and nonlocal three-wave interactions between unstable drift-waves although the turbulent saturation of the density fluctuation spectrum is likely due nonlinear processes acting in the time domain. / text

In biochemical systems, stochastic e↵ects can be caused by the presence of small numbers of certain reactant molecules. In this setting, discrete state-space and stochastic simulation approaches were proved to be more relevant than continuous state-space and deterministic ones. These stochastic models constitute the theory of stochastic reaction networks (SRNs). Furthermore, in some cases, the dynamics of fast and slow time scales can be well separated and this is characterized by what is called sti↵ness. For such problems, the existing discrete space-state stochastic path simulation methods, such as the stochastic simulation algorithm (SSA) and the explicit tau-leap method, can be very slow. Therefore, implicit tau-leap approxima- tions were developed to improve the numerical stability and provide more e cient simulation algorithms for these systems. One of the interesting tasks for SRNs is to approximate the expected values of some observables of the process at a certain fixed time T. This is can be achieved using Monte Carlo (MC) techniques. However, in a recent work, Anderson and Higham in 2013, proposed a more computationally e cient method which combines multi-level Monte Carlo (MLMC) technique with explicit tau-leap schemes. In this MSc thesis, we propose new fast stochastic algorithm, particularly designed 5 to address sti↵ systems, for approximating the expected values of some observables of SRNs. In fact, we take advantage of the idea of MLMC techniques and drift-implicit tau-leap approximation to construct a drift-implicit MLMC tau-leap estimator. In addition to accurately estimating the expected values of a given observable of SRNs at a final time T , our proposed estimator ensures the numerical stability with a lower cost than the MLMC explicit tau-leap algorithm, for systems including simultane- ously fast and slow species. The key contribution of our work is the coupling of two drift-implicit tau-leap paths, which is the basic brick for constructing our proposed drift-implicit MLMC tau-leap estimator. As an example of sti↵ problem, we used the decaying-dimerizing reaction as a test example to show the advantage of our drift-implicit method over the explicit one. Through our numerical experiments, we checked the convergence properties of our coupling algorithm and showed that our proposed estimator is outperforming the explicit MLMC estimator about three times in terms of computational work. We also illustrated in a second example how our drift-implicit MLMC tau-leap estimator can be forty times faster than the explicit MLMC.

No description available.

Öringens gälar (Salmo trutta) fungerar inte bara som ett andningssystem för fisken utan också som ett fastsättningsställe för flodpärlmusslans (Margaritifera margaritifera) parasitiska larver. Larverna kallas glochidielarver och när de släpps ifrån modermusslan måste de hitta sin värd relativt snabbt för att inte dö. Om de lyckas hitta sig en öring så fäster de sig på fiskens gälar där de sedan kapslas in av fiskens epitelceller. Glochidielarverna lever sedan där i ca 3-10 månader främst beroende på temperaturen. Eftersom mussellarven är en parasit tar den sin näring och energi ifrån värdfisken. I denna studie undersöktes skillnader mellan låginfekterade och höginfekterade odlade öringar (+0, medelvikt 1,77g +/- 0,11) och hur deras beteende skilde sig åt när det gäller rörlighet och antal fångade byten. Fiskarna testades både individuellt och i par. Experimentet utfördes i ett strömakvarium och hypoteserna var att låginfekterade öringar tar fler byten än höginfekterade, och att de individuella fiskarna tar mer byten än fiskarna i par. Det undersöktes också i vilken omfattning fiskarna simmade uppströms eller nedströms när de fångade sina byten och om det var någon skillnad mellan låg- och höginfekterade öringar. Resultatet visade att det fanns en signifikant skillnad (p=0,0046) mellan låg- och höginfekterade öringar när det gäller antal tagna byten, där låginfekterade öringar tar mer byten än höginfekterade. Det fanns igen signifikant skillnad mellan antlal simrörelser nedströms/uppströms mellan låg- och höginfekterade, däremot fanns det en signifikant skillnad (p=0,0027) mellan antal simrörelser uppströms och nedströms oavsett låg- eller höginfekterad, där det visade sig att öringen simmar mer nedströms än uppströms från sin focal point när den fångar byten. När det gäller antal tagna byten hos de individuella fiskarna vs. fiskarna i par, så tog de individuella fiskarna fler byten än vad var och en av fiskarna i par gjorde (medeltal: fiskar i par 28, individuella 36), men det fanns ingen signifikant skillnad (p=0,06). Utifrån resultaten kan man antyda att infektering av flodpärlmusslans glochidielarver kan ha en negativ effekt på öringens fysiska prestanda. Öringen får mindre energi till födosök och därmed sämre förutsättningar till t.ex. tillväxt.

This thesis takes an innovative approach to examining health care policy by applying the concept of policy drift to the issue of access to abortion across Canada through analyzing three explanations: the structure of Canadian federalism, women’s organizations, and rights litigation. The Supreme Court of Canada ruled that section 251 of the Criminal Code of Canada was unconstitutional in R v. Morgentaler (1988). Section 251 forced women to secure the approval of a panel of medical experts in order to gain legal consent to seek an abortion. As a result of this decision, women are now able to undergo a therapeutic abortion procedure without facing criminal sanctions. However, the issue of equitable access to abortion services across Canada is still unresolved. For example, women living in Prince Edward Island have to travel out of province at their own expense to undergo an abortion procedure. Meanwhile, women in Ontario are able to undergo an abortion procedure at a number of hospitals and private clinics with provincial insurance subsidizing the financial burdens. Abortion is a time-sensitive procedure and different from other health care procedures because it is also gender-sensitive. Findings within this thesis suggest that the model of Canadian federalism contributes to the inability of women’s organizations to gain audience from the federal government and inhibits the courts from assisting in expanding provincial access, which further facilitates policy drift. Recognizing policy drift concerning access to abortion is significant because it is an issue that involves gender equity at its core as well as discussions over what society deems is a right and what society deems is fair.

No description available.

Broadly speaking, art can be described as man’s emotion made tangible, providing a visual memory of the past. Resistance art is no different save the strength of its embedded meaning bound to context through signs and cultural references. In a pre-liberation South Africa, resistance art formed one of the critical voices of opposition to the apartheid regime and from the Rorke’s Drift Art and Craft Centre in Zululand this voice resounded. The memory of this together with the memory of the Rorke’s Drift artists has become dissociated from the actual place resulting in a gap in the history of South African art as well as the history of KwaZulu-Natal and South Africa. In light of this, this document explores the potential of art to generate built-form. By examining the link between man, society and art through the review of relevant literature, it is found that memory can be revived as a key driver behind the meaning of art and built-form through the provision of place as governed by issues of cultural identity, symbols and meaning context and the experiential. This conclusion is extended through precedent studies to include the art in question and is proved through the use of a case study. The significance suggested is that there is a global opportunity for art to provide meaning to the built environment and a local potential to directly address the loss of meaning and memory of Rorke’s Drift. In other words, it is proposed that meaning can be returned to Rorke’s Drift if the fundamental issues of memory are addressed, thereby continuing the narrative of South African art and contributing to it in the future. / Thesis (M.Arch.)-University of KwaZulu-Natal, Durban, 2012.

Well integrity is an important topic in oil and gas well operations. The intention is to control the reservoir fluids and well pressures, by technical, operational and organizational barriers. Inadequate barriers can lead to unwanted influx and cause a kick, which can escalate further into a blowout. The Deepwater Horizon accident in the Gulf of Mexico in 2010 raised concerns about the safety of offshore deepwater drilling. This rig was considered to be an efficient and safe drilling unit, until the fatal blowout occurred leading to the loss of eleven lives, and the worst environmental disaster in US history.The main objective of a well barrier is to prevent leakage from the wellbore to the external environment during the various well operations. Well barriers are classified as primary or secondary barriers. The primary barriers are the barriers closest to the hydrocarbons and are the first obstacle to unwanted flow of formation fluid. The secondary barrier acts as a backup barrier. Barriers can further be classified as static or dynamic. The static barriers apply for the production phase, meaning that they are present over a longer period of time. Dynamic barriers occur during drilling and well intervention, and these are the once that are most difficult to assess because of the constantly changing parameters involved.Various drilling types such as overbalanced (conventional) and underbalanced drilling are used in the search for oil and gas. The main difference between these types, is how the pressure in the wellbore is maintained, and for this different barriers are needed.Laws and regulations dictate the requirements the industry has to follow. The Petroleum Safety Authority governs the regulations in Norway, and gives requirements to well barriers. In their regulations, they also refer to other guidelines and standards for more detailed requirements. NORSOK D-010 from 2013, “Well integrity in drilling and well operations”, is a widely used standard which defines requirements and guidelines relating to well integrity in drilling and well activities. Ways to regulate is found to vary between countries, such as for Norway and the US. During drilling, a dynamic barrier situation applies, where the activation of the barrier depends on the current situation, and there is no pre-made sequence of barrier activation. Overall, this makes the assessment a difficult task. Various approaches have been suggested for the assessment of dynamic barriers over the years, with contributions to the topic from oil-companies, standards and research papers. Most of what has been suggested has some kind of weaknesses, and no common approach has been accepted and put into use by the industry. As a contribution a new approach has been suggested in this thesis. An overbalanced drilling operation in deep waters initiated by a kick is selected as case study. The approach is based on using two different types of analysis, in combination. An event tree is used to illustrate the dynamics of the event, and various fault trees are used to analyze the barriers involved. To understand what can cause a kick, the possibility of avoiding it, and what to do if it happens are given attention. From the suggested approach, it emerges that the human factor plays an important role in the kick evaluation and to maintain the well integrity. If the primary barrier is lost, there will be a kick. For this to escalate into a blowout, the secondary barrier must also be lost. If the control equipment functions as intended, lack of detection and understanding, together with insufficient training and competence of personnel can make this happen.To prevent major accidents and hazardous events in the future, it is important to learn and gain experience from previous incidents and learn from each other, and the ability to work together, also between companies, on these difficult topics.

A proper understanding of the effects of turbulence on the diffusion and drift of cosmic-rays in the heliosphere is imperative for a better understanding of cosmic-ray modulation. This study presents an ab initio model for cosmic-ray modulation, incorporating for the first time the results yielded by a two-component turbulence transport model. The latter model is solved for solar minimum heliospheric conditions, utilizing boundary values chosen in such a way that the results of this model are in fair to good agreement with spacecraft observations of turbulence quantities, not only in the ecliptic plane, but also along the out-of-ecliptic trajectory of the Ulysses spacecraft. These results are employed as inputs for modelled slab and 2D turbulence energy spectra, which in turn are used as inputs for parallel mean free paths based on those derived from quasi-linear theory, and perpendicularmean free paths from extended nonlinear guiding center theory. The modelled 2D spectrum is chosen based on physical considerations, with a drop-off at the very lowest wavenumbers commencing at the 2D outerscale. There currently exist no models or observations for this quantity, and it is the only free parameter in this study. The use of such a spectrum yields a non-divergent 2D ultrascale, which is used as an input for the reduction terms proposed to model the effects of turbulence on cosmic-ray drifts. The resulting diffusion and drift coefficients are applied to the study of galactic cosmic-ray protons, electrons, antiprotons, and positrons using a three-dimensional, steady-state numerical cosmic-ray modulation code. The magnitude and spatial dependence of the 2D outerscale is demonstrated to have a significant effect on computed cosmic-ray intensities. A form for the 2D outerscale was found that resulted in computed cosmic-ray intensities, for all species considered, in reasonable agreement with multiple spacecraft observations. Computed galactic electron intensities are shown to be particularly sensitive to choices of parameters pertaining to the dissipation range of the slab turbulence spectrum, and certain models for the onset wavenumber of the dissipation range could be eliminated in this study. / Thesis (PhD (Physics))--North-West University, Potchefstroom Campus, 2013

A proper understanding of the effects of turbulence on the diffusion and drift of cosmic-rays in the heliosphere is imperative for a better understanding of cosmic-ray modulation. This study presents an ab initio model for cosmic-ray modulation, incorporating for the first time the results yielded by a two-component turbulence transport model. The latter model is solved for solar minimum heliospheric conditions, utilizing boundary values chosen in such a way that the results of this model are in fair to good agreement with spacecraft observations of turbulence quantities, not only in the ecliptic plane, but also along the out-of-ecliptic trajectory of the Ulysses spacecraft. These results are employed as inputs for modelled slab and 2D turbulence energy spectra, which in turn are used as inputs for parallel mean free paths based on those derived from quasi-linear theory, and perpendicularmean free paths from extended nonlinear guiding center theory. The modelled 2D spectrum is chosen based on physical considerations, with a drop-off at the very lowest wavenumbers commencing at the 2D outerscale. There currently exist no models or observations for this quantity, and it is the only free parameter in this study. The use of such a spectrum yields a non-divergent 2D ultrascale, which is used as an input for the reduction terms proposed to model the effects of turbulence on cosmic-ray drifts. The resulting diffusion and drift coefficients are applied to the study of galactic cosmic-ray protons, electrons, antiprotons, and positrons using a three-dimensional, steady-state numerical cosmic-ray modulation code. The magnitude and spatial dependence of the 2D outerscale is demonstrated to have a significant effect on computed cosmic-ray intensities. A form for the 2D outerscale was found that resulted in computed cosmic-ray intensities, for all species considered, in reasonable agreement with multiple spacecraft observations. Computed galactic electron intensities are shown to be particularly sensitive to choices of parameters pertaining to the dissipation range of the slab turbulence spectrum, and certain models for the onset wavenumber of the dissipation range could be eliminated in this study. / Thesis (PhD (Physics))--North-West University, Potchefstroom Campus, 2013