published_or_final_version / abstract / Chemistry / Doctoral / Doctor of Philosophy

Alkali-Surfactant-Polymer (ASP) or Surfactant-Polymer (SP) flooding are attractive chemical enhanced oil recovery (EOR) methods. However, some reservoir conditions are not favorable for the use of polymers or their use would not be economically attractive due to low permeability, high salinity, or some other unfavorable factors. In such conditions, gas can be an alternative to polymer for improving displacement efficiency in chemical-EOR processes. The co-injection or alternate injection of gas and chemical slug results in the formation of foam. Foam reduces the relative permeability of injected chemical solutions that form microemulsion at ultra-low interfacial tension (IFT) conditions and generates sufficient viscous pressure gradient to drive the foamed chemical slug. We have named this technique of foam assisted enhanced oil recovery as Alkali/Surfactant/Gas (ASG) process. The concept of ASG flooding as an enhanced oil recovery technique is relatively new, with very little experimental and theoretical work available on the subject. This dissertation presents a systematic study of ASG process and its potential as an EOR method. We performed a series of high performance surfactant-gas tertiary recovery corefloods on different core samples, under different rock, fluid, and process conditions. In each coreflood, foamed chemical slug was chased by foamed chemical drive. The level of mobility control in corefloods was evaluated on the basis of pressure, oil recovery, and effluent data. Several promising surfactants, with dual properties of foaming and emulsification, were identified and used in the coreflood experiments. We observed a strong synergic effect of foam and ultra-low IFT conditions on oil recovery in ASG corefloods. Oil recoveries in ASG corefloods compared reasonably well with oil recoveries in ASP corefloods, when both were conducted under similar conditions. We found that the negative salinity gradient concept, generally applied to chemical floods, compliments ASG process by increasing foam strength in displacing fluids (slug and drive). A characteristic increase in foam strength was observed, in nearly all ASG corefloods conducted in this study, as the salinity first changed from Type II(+) to Type III environment and then from Type III to Type II(-) environment. We performed foaming and gas-microemulsion flow experiments to study foam stability in different microemulsion environments encountered in chemical flooding. Results showed that foam in oil/water microemulsion (Type II(-)) is the most stable, followed by foam in Type III microemulsion. Foam stability is extremely poor (or non-existent) in water/oil microemulsion (Type II (+)). We investigated the effects of permeability, gas and liquid injection rates (injection foam quality), chemical slug size, and surfactant type on ASG process. The level of mobility control in ASG process increased with the increase in permeability; high permeability ASG corefloods resulting in higher oil recovery due to stronger foam propagation than low permeability corefloods. The displacement efficiency was found to decrease with the increase in injection foam quality. We studied the effect of pressure on ASG process by conducting corefloods at an elevated pressure of 400 psi. Pressure affects ASG process by influencing factors that control foam stability, surfactant phase behavior, and rock-fluid interactions. High solubility of carbon dioxide (CO₂) in the aqueous phase and accompanying alkali consumption by carbonic acid, which is formed when dissolved CO₂ reacts with water, reduces the displacement efficiency of the process. Due to their low solubility and less reactivity in aqueous phase, Nitrogen (N₂) forms stronger foam than CO₂. Finally, we implemented a simple model for foam flow in low-IFT microemulsion environment. The model takes into account the effect of solubilized oil on gas mobility in the presence of foam in low-IFT microemulsion environment. / text

<p>Mobile communication systems are experiencing a huge growth. While traditional communication paradigms deal with fixed networks, mobility raises a new set of questions, techniques, and solutions. This work focuses on wireless sensor networks (WSNs) where each node is a mobile device. The main objectives of this thesis have been to develop algorithms and protocols enabling WSNs with a special interest in overcoming mobility support limitations of standards such as Bluetooth and Zigbee. The contributions of this work may be divided in four major parts related to mobility support. The first part describes the implementation of local positioning services in Bluetooth since local positioning is not supported in Bluetooth v1.1. The obtained results are used in later implemented handover algorithms in terms of deciding when to perform the handover. Moreover local positioning information may be used in further developed routing protocols. The second part deals with handover as a solution to overcome the getting out of range problem. Algorithms for handover have been implemented enabling mobility in Bluetooth infrastructure networks. The principal achievement in this part is the significant reduction of handover latency since sensor cost and quality of service are directly affected by this parameter. The third part solves the routing problems originated with handovers. The main contribution of this part is the impact of the Bluetooth scatternet formation and routing protocols, for multi-hop data transmissions, in the system quality of service. The final part is a comparison between Bluetooth and Zigbee in terms of mobility support. The main outcome of this comparison resides on the conclusions, which can be used as a technology election guide.</p><p>The main scientific contribution relies on the implementation of a mobile WSN with Bluetooth v1.1 inside the scope of the ”Multi Monitoring Medical Chip (M3C) for Homecare Applications” European Union project (Sixth Framework Program (FP6) Reference: 508291) offering multi-hop routing support and improvements in handover latencies with aid of local positioning services.</p>

Research at the site of San Estevan, Belize begins with the premise that more serious attention must be paid to the significance of residential variability in archaeological modelings of the lowland Maya. A classification of structure groupings is used to track the distribution of San Estevan's diverse residential arrangements across the site. Norms of social structure and economic inequality prove inadequate frameworks to account for the spatial and temporal variation manifest by San Estevan's residential classes, nor do they help to explain the spatial regularities underlying the distributions of these classes. I suggest, instead, that the site's residential units best effect divergent organizational strategies adopted by San Estevan's prehispanic domestic groups. Whereas diffuse political authority, impoverished political economies, and kingroup self-sufficiency traditionally have been invoked to account for Maya residential patterns, domestic strategies at San Estevan gained their shape directly in relation to the functions housed in the community's precincts of monumental architecture. I conclude that prehispanic Maya residential distributions formed through stringent economic and political entailments of community life.

SgrAI is a restriction endonuclease (ENase) that cuts a long recognition sequence and exhibits self-modulation of cleavage activity and sequence specificity. Previous research has shown that SgrAI forms large oligomers when bound to particular DNA sequences and under the same conditions where SgrAI exhibits accelerated DNA cleavage kinetics. However, the detailed structure and stoichiometry of SgrAI:DNA as well as the basic building block of the oligomers, has not been fully characterized. Ion mobility mass spectrometry (IM-MS) was employed to analyze SgrAI/DNA complexes and show that the basic building block of the oligomers is the DNA-bound SgrAI dimer (DBD). The oligomers are heterogeneous containing a mixture of species with variable numbers of DBD. The collision cross sections (CCS) of the oligomers were found to have a linear relationship with the number of DBD. Models of the SgrAI/DNA oligomers were constructed and a head-to-tail arrangement was most consistent with the experimental CCS.

Background. The Swedish government states that participation and influence are among the most fundamental prerequisites of public health. Mobility services provide professional and high quality information, advice, and assessment to individuals with a medical condition or recovering from an accident or injury that may affect their ability to drive, access, or egress a motor vehicle. Although Swedish physicians must report drivers with medical conditions, rehabilitative training for driving licenses following injury or severe medical conditions does not exist within contemporary Swedish healthcare systems. Aim. This study aimed primarily to describe and compare two driving assessment models, i.e., the model used by Traffic Medicine Center (TRMC) Stockholm in 1998 and the model provided by Mobilitetscenter.se (MC.se) Gothenburg in 2007. The study also sought to determine the context of the changed provision of driving assessments and identify the significant components of this change. Method A literature review, synthesised with the author’s research and complemented by practice-based evidence, provided the knowledge base and starting point of this essay. Action research paired with intervention propelled the changes in the provision of mobility services in Sweden between 1998 and 2007. The author used John Ovretveit’s identification of significant change components to illuminate the complex change process that occurred.  Selection of an appropriate list of variables to compare the two assessment models derived from FORUM of Mobility Centres, the umbrella organization of British Mobility Centres that developed national guidelines for driving ability assessments in the UK; the QEF Mobility Centre was a member of that organization. The author used a questionnaire and a semi-structured interview to gather relevant data from the compared centers. Results TRMC aims primarily to provide services for society through its contributions to road safety. A Mobility Center focuses on providing assessment and rehabilitation services, optimizing impaired drivers’ mobility potential and minimizing collision risks. Cognitive assessment at TRMC accounted for a large part of this study’s time allotment. MC.se’s practical driving test in a suitably modified car provides the most significant difference between the two models.  In addition, MC.se has replaced physicians and psychologists with occupational therapists. Conclusion TRMC aims to ensure that current drivers comply with medical driving laws and regulations. MC.se provides assessments that maximize mobility potential and also ensure low collision rates. Thus, safety is balanced against the right to mobility. The study also explores coping strategies, training, adaptations, and choice of vehicle. / <p>ISBN 978-91-85721-58-0</p>

Migration and the concomitant crossing of borders is a growing world wide theme in literature. This phenomenon can be attributed to growing mobility and globalisation which allow people to move freely across national borders. Mobility is a key concept for the 21st century and can be used as an umbrella term for the crossing of borders and migration, also connecting with concepts such as displacement, diaspora, nomad, travel, exile and (post)colonialism. Migration as demographic phenomenon does not only include the borders of countries but also social, cultural, psychological and language borders. Memory as border can be added to this since it acts as a link between time and space. The crossing of (national) borders also holds certain consequences, amongst others the problem of origin and identity, outsidership and/or marginalization as well as the experience of loss. Two novels which can be classified as migrant literature – Idil, een meisje (Yasmine Allas) and De reis van de lege flessen (Kader Abdolah), and one novel which explores the problem of migration thematically – Anderkant die stilte (André P. Brink) – are analysed in this dissertation. Idil, een meisje (Yasmine Allas) portrays a female perspective by a female migrant writer, while De reis van de lege flessen (Kader Abdolah) offers a male perspective by a male migrant writer. Anderkant die stilte (André P. Brink) adds an additional dimension to gender analysis since a female perspective is portrayed by a male writer. These three novels, one from Afrikaans and two from Dutch literature, will be analysed to determine the manifestation of migration and displacement and the outcome(s) thereof with emphasis on gendered experience in these literature texts. / Thesis (MA (Afrikaans en Nederlands))--North-West University, Vaal Triangle Campus, 2013

Gas-phase analytical techniques provide very valuable tools for tackling the structural complexity of macromolecular structures such as those encountered in biological systems. Conformational dynamics of polypeptides and polypeptide assemblies underlie most biological functionalities, yet great difficulties arise when investigating such phenomena with the well-established techniques of X-ray crystallography and NMR. In areas such as these ion mobility interfaced with mass spectrometry (IMMS) and molecular modelling can make a significant contribution. During an IMMS experiment analyte ions drift in a chamber filled with an inert gas; measurement of the transport properties of analyte ions under the influence of a weak electric field can lead to determination of the orientationally-averaged collision cross-section of all resolved ionic species. A comparison with cross-sections estimated for model molecular geometries can lead to structural assignments. Thus IMMS can be used effectively to separate gas-phase ions based on their conformation. The drift tube employed in the experiments described herein is thermally regulated, which also enables the determination of collision cross-sections over a range of temperatures, and can provide a view of temperature-dependent conformational dynamics over the experimental (low microsecond) timescale. Studies described herein employ IMMS and a gamut of other MS-based techniques, solution spectroscopy and – importantly – molecular mechanics simulations to assess a) conformational stability of isolated peptide ions, with a focus on small model peptides and proteins, especially the Trp cage miniprotein; and b) structural characteristics of oligomeric aggregates of an amyloidogenic peptide. The results obtained serve to clarify the factors which dominate the intrinsic stability of non-covalent structure in isolated peptides and peptide assemblies. Strong electrostatic interactions are found to play a pivotal role in determining the conformations of isolated proteins. Secondary structures held together by hydrogen bonding, such as helices, are stable in the absence of solvent, however gas-phase protein structures display loss of their hydrophobic cores. The absence of a polar solvent, “self-solvation” is by far the most potent force influencing the gas-phase configuration of these systems. Geometries that are more compact than the folded state observed in solution are routinely detected, indicating the existence of intrinsically stable compact non-native states in globular proteins, illuminating the nature of proteins’ ‘unfolded’ states.

Approved for public release; distribution is unlimited / Virtual Private Networks (VPNs) are designed to use the Transmission Control Protocol (TCP) or User Datagram Protocol (UDP) to establish secure communication tunnels over public Internet. Multipath TCP (MPTCP) extends TCP to allow data to be delivered over multiple network paths simultaneously. This thesis first builds a testbed and investigates the potential of using MPTCP tunnels to increase the goodput of VPN communications and support seamless mobility. Based on the empirical results and an analysis of the MPTCP design in Linux kernels, we further introduce a full-multipath kernel, implementing a basic Multipath UDP (MPUDP) protocol into an existing Linux MPTCP kernel.We demonstrate the MPUDP protocol provides performance improvements over single path UDP tunnels and in some cases MPTCP tunnels. The MPUDP kernel should be further developed to include more efficient scheduling algorithms and path managers to allow better performance and mobility benefits seen with MPTCP. / Outstanding Thesis / Lieutenant, United States Navy

This study is a thematic analysis of written plan-descriptions associated to valid detail-plans in the city of Umeå. These plan-descriptions are used as gateways to how planners and architects have reasoned when it comes to planning decisions. The thematic analysis is conducted on 24 selected detail-plans in the city of Umeå and has the starting point of the three themes of Mobility, Green space and Safety. The themes are identified as important to study in the light of the sustainable development concept where new modes of transportation, better knowledge about how nature affects us and a safe environment for everyone are propagated. By making better use of the fine source of information and insights that are the detail-plans students, researchers and practitioners can more effectively steer their efforts towards areas that really are in need of change. There is also something to be learned about the connection between process and outcome in physical planning. The results of this study show first of all that the scope and the thoroughness of detail-planning have changed over time. During the 1950’s, 60’s and 70’s the plans generally covered larger areas and the descriptions where short and concise. In present time the plans generally cover smaller areas but are very exhausting in their investigative preparing work and associated documents. Other findings are that the goal of a safe environment in the detail-plans mostly is connected to traffic-safety.