The silent frontier: deaf people and their social use of cell phones in Cape Town

Includes abstract.Includes bibliographical references.This thesis seeks to understand the ways in which the Deaf negotiate and embrace the cell phone socially. The Deaf, who can be seen as a linguistic and sensory minority within the predominant hearing society, use the cell phone to negotiate their marginalised position as people living with a hearing impairment. By doing so, the Deaf are able to extend and intensify their social relationships, which are used to overcome language barriers

Long-term chemical characterization of tropical and marine aerosols at the Cape Verde Atmospheric Observatory (CVAO) from 2007 to 2011

The first long-term aerosol sampling and chemical characterization results from measurements at the Cape Verde Atmospheric Observatory (CVAO) on the island of São Vicente are presented and are discussed with respect to air mass origin and seasonal trends. In total 671 samples were collected using a high-volume PM10 sampler on quartz fiber filters from January 2007 to December 2011. The samples were analyzed for their aerosol chemical composition, including their ionic and organic constituents. Back trajectory analyses showed that the aerosol at CVAO was strongly influenced by emissions from Europe and Africa, with the latter often responsible for high mineral dust loading. Sea salt and mineral dust dominated the aerosol mass and made up in total about 80% of the aerosol mass. The 5-year PM10 mean was 47.1 ± 55.5 μg m−2, while the mineral dust and sea salt means were 27.9 ± 48.7 and 11.1 ± 5.5 μg m−2, respectively. Non-sea-salt (nss) sulfate made up 62% of the total sulfate and originated from both long-range transport from Africa or Europe and marine sources. Strong seasonal variation was observed for the aerosol components. While nitrate showed no clear seasonal variation with an annual mean of 1.1 ± 0.6 μg m−3, the aerosol mass, OC (organic carbon) and EC (elemental carbon), showed strong winter maxima due to strong influence of African air mass inflow. Additionally during summer, elevated concentrations of OM were observed originating from marine emissions. A summer maximum was observed for non-sea-salt sulfate and was connected to periods when air mass inflow was predominantly of marine origin, indicating that marine biogenic emissions were a significant source. Ammonium showed a distinct maximum in spring and coincided with ocean surface water chlorophyll a concentrations. Good correlations were also observed between nss-sulfate and oxalate during the summer and winter seasons, indicating a likely photochemical in-cloud processing of the marine and anthropogenic precursors of these species. High temporal variability was observed in both chloride and bromide depletion, differing significantly within the seasons, air mass history and Saharan dust concentration. Chloride (bromide) depletion varied from 8.8 ± 8.5% (62 ± 42%) in Saharan-dust-dominated air mass to 30 \textpm 12% (87 ± 11%) in polluted Europe air masses. During summer, bromide depletion often reached 100% in marine as well as in polluted continental samples. In addition to the influence of the aerosol acidic components, photochemistry was one of the main drivers of halogenide depletion during the summer; while during dust events, displacement reaction with nitric acid was found to be the dominant mechanism. Positive matrix factorization (PMF) analysis identified three major aerosol sources: sea salt, aged sea salt and long-range transport. The ionic budget was dominated by the first two of these factors, while the long-range transport factor could only account for about 14% of the total observed ionic mass

Long-term chemical characterization of tropical and marine aerosols at the Cape Verde Atmospheric Observatory (CVAO) from 2007 to 2011

The first long-term aerosol sampling and chemical characterization results from measurements at the Cape Verde Atmospheric Observatory (CVAO) on the island of São Vicente are presented and are discussed with respect to air mass origin and seasonal trends. In total 671 samples were collected using a high-volume PM10 sampler on quartz fiber filters from January 2007 to December 2011. The samples were analyzed for their aerosol chemical composition, including their ionic and organic constituents. Back trajectory analyses showed that the aerosol at CVAO was strongly influenced by emissions from Europe and Africa, with the latter often responsible for high mineral dust loading. Sea salt and mineral dust dominated the aerosol mass and made up in total about 80% of the aerosol mass. The 5-year PM10 mean was 47.1 ± 55.5 μg m−2, while the mineral dust and sea salt means were 27.9 ± 48.7 and 11.1 ± 5.5 μg m−2, respectively. Non-sea-salt (nss) sulfate made up 62% of the total sulfate and originated from both long-range transport from Africa or Europe and marine sources. Strong seasonal variation was observed for the aerosol components. While nitrate showed no clear seasonal variation with an annual mean of 1.1 ± 0.6 μg m−3, the aerosol mass, OC (organic carbon) and EC (elemental carbon), showed strong winter maxima due to strong influence of African air mass inflow. Additionally during summer, elevated concentrations of OM were observed originating from marine emissions. A summer maximum was observed for non-sea-salt sulfate and was connected to periods when air mass inflow was predominantly of marine origin, indicating that marine biogenic emissions were a significant source. Ammonium showed a distinct maximum in spring and coincided with ocean surface water chlorophyll a concentrations. Good correlations were also observed between nss-sulfate and oxalate during the summer and winter seasons, indicating a likely photochemical in-cloud processing of the marine and anthropogenic precursors of these species. High temporal variability was observed in both chloride and bromide depletion, differing significantly within the seasons, air mass history and Saharan dust concentration. Chloride (bromide) depletion varied from 8.8 ± 8.5% (62 ± 42%) in Saharan-dust-dominated air mass to 30 \textpm 12% (87 ± 11%) in polluted Europe air masses. During summer, bromide depletion often reached 100% in marine as well as in polluted continental samples. In addition to the influence of the aerosol acidic components, photochemistry was one of the main drivers of halogenide depletion during the summer; while during dust events, displacement reaction with nitric acid was found to be the dominant mechanism. Positive matrix factorization (PMF) analysis identified three major aerosol sources: sea salt, aged sea salt and long-range transport. The ionic budget was dominated by the first two of these factors, while the long-range transport factor could only account for about 14% of the total observed ionic mass

Glyoxal and methylglyoxal in Atlantic seawater and marine aerosol particles: method development and first application during the Polarstern cruise ANT XXVII/4

An analytical method for the determination of the alpha dicarbonyls glyoxal (GLY) and methylglyoxal (MGLY) from seawater and marine aerosol particles is presented. The method is based on derivatization with o-(2,3,4,5,6-Pentafluorobenzyl)-hydroxylamine (PFBHA) reagent, solvent extraction and GC-MS (SIM) analysis. The method showed good precision (RSD < 10%), sensitivity (detection limits in the low ng L−1 range), and accuracy (good agreement between external calibration and standard addition). The method was applied to determine GLY and MGLY in oceanic water sampled during the Polarstern cruise ANT XXVII/4 from Capetown to Bremerhaven in spring 2011. GLY and MGLY were determined in the sea surface microlayer (SML) of the ocean and corresponding bulk water (BW) with average concentrations of 228 ng L−1 (GLY) and 196 ng L−1 (MGLY). The results show a significant enrichment (factor of 4) of GLY and MGLY in the SML. Furthermore, marine aerosol particles (PM1) were sampled during the cruise and analyzed for GLY (average concentration 0.19 ng m−3) and MGLY (average concentration 0.15 ng m−3). On aerosol particles, both carbonyls show a very good correlation with oxalate, supporting the idea of a secondary formation of oxalic acid via GLY and MGLY. Concentrations of GLY and MGLY in seawater and on aerosol particles were correlated to environmental parameters such as global radiation, temperature, distance to the coastline and biological activity. There are slight hints for a photochemical production of GLY and MGLY in the SML (significant enrichment in the SML, higher enrichment at higher temperature). However, a clear connection of GLY and MGLY to global radiation as well as to biological activity cannot be concluded from the data. A slight correlation between GLY and MGLY in the SML and in aerosol particles could be a hint for interactions, in particular of GLY, between seawater and the atmosphere

(R)evolutionary improvements in the design of interventional X-ray systems

Interventional X-ray systems are used to acquire 2D and 3D images of complex anatomical structures (e.g. the cardiovascular system). These images provide a clinician with feedback in a medical procedure, which enables advanced minimally invasive treatments. A typical interventional X-ray system contains an X-ray source and detector, connected by a C-shaped arm. Several stacked motion systems enable the C-arm and imaging equipment to move spherically around an isocentre. This allows for 2D X-ray images to be taken at various projection angles. Other imaging techniques such as 3D computed tomography are enabled by this core functionality. Developments in interventional X-ray systems are often a compromise between performance, clinical usability, and cost. This paper presents three novel mechatronic architectures, which are designed to break through this trade-off. The proposed designs aim to improve the interventional X-ray system on multiple, application-specific levels. The first system focusses on improved image quality and clinical usability of 3D scans (high-end applications). A dual stage design allows for significantly extended and faster scanning motions, with a 55% smaller footprint in the operating room. It is based on a quasi-kinematic roll guide design, resulting in less nonlinear behaviour, and improved alignment of the imaging equipment. The second system decreases cost and installation requirements, while maintaining and adding to the current imaging capability (low-end applications). By reconsidering the degrees of freedom needed, a lightweight design is created (&gt;50% mass reduction), with an improved stiffness to mass ratio. Both system 1 and 2 present an evolutionary improvement on existing architectures. As a revolutionary alternative, the third system pursues high-end performance and optimised workflow, at reduced overall cost. It features a compact and lightweight (~500 kg) mechatronic design which makes optimal use of the space available in the operating room. A full scale mock-up of this system has been built. Currently, a detailed design, including hardware realisation is being made for experimental performance validation at subsystem level.</p

(R)evolutionary improvements in the design of interventional X-ray systems

Interventional X-ray systems are used to acquire 2D and 3D images of complex anatomical structures (e.g. the cardiovascular system). These images provide a clinician with feedback in a medical procedure, which enables advanced minimally invasive treatments. A typical interventional X-ray system contains an X-ray source and detector, connected by a C-shaped arm. Several stacked motion systems enable the C-arm and imaging equipment to move spherically around an isocentre. This allows for 2D X-ray images to be taken at various projection angles. Other imaging techniques such as 3D computed tomography are enabled by this core functionality. Developments in interventional X-ray systems are often a compromise between performance, clinical usability, and cost. This paper presents three novel mechatronic architectures, which are designed to break through this trade-off. The proposed designs aim to improve the interventional X-ray system on multiple, application-specific levels. The first system focusses on improved image quality and clinical usability of 3D scans (high-end applications). A dual stage design allows for significantly extended and faster scanning motions, with a 55% smaller footprint in the operating room. It is based on a quasi-kinematic roll guide design, resulting in less nonlinear behaviour, and improved alignment of the imaging equipment. The second system decreases cost and installation requirements, while maintaining and adding to the current imaging capability (low-end applications). By reconsidering the degrees of freedom needed, a lightweight design is created (&gt;50% mass reduction), with an improved stiffness to mass ratio. Both system 1 and 2 present an evolutionary improvement on existing architectures. As a revolutionary alternative, the third system pursues high-end performance and optimised workflow, at reduced overall cost. It features a compact and lightweight (~500 kg) mechatronic design which makes optimal use of the space available in the operating room. A full scale mock-up of this system has been built. Currently, a detailed design, including hardware realisation is being made for experimental performance validation at subsystem level.</p

Seasonal variation of aliphatic amines in marine sub-micrometer particles at the Cape Verde islands

Monomethylamine (MA), dimethylamine (DMA) and diethylamine (DEA) were detected at non-negligible concentrations in sub-micrometer particles at the Cap Verde Atmospheric Observatory (CVAO) located on the island of São Vicente in Cape Verde during algal blooms in 2007. The concentrations of these amines in five stage impactor samples ranged from 0–30 pg m−3 for MA, 130–360 pg m−3 for DMA and 5–110 pg m−3 for DEA during the spring bloom in May 2007 and 2–520 pg m−3 for MA, 100–1400 pg m−3 for DMA and 90–760 pg m−3 for DEA during an unexpected winter algal bloom in December 2007. Anomalously high Saharan dust deposition and intensive ocean layer deepening were found at the Atmospheric Observatory and the associated Ocean Observatory during algal bloom periods. The highest amine concentrations in fine particles (impactor stage 2, 0.14–0.42 μm) indicate that amines are likely taken up from the gas phase into the acidic sub-micrometer particles. The contribution of amines to the organic carbon (OC) content ranged from 0.2–2.5% C in the winter months, indicating the importance of this class of compounds to the carbon cycle in the marine environment. Furthermore, aliphatic amines originating from marine biological sources likely contribute significantly to the nitrogen content in the marine atmosphere. The average contribution of the amines to the detected nitrogen species in sub-micrometer particles can be non-negligible, especially in the winter months (0.1% N–1.5% N in the sum of nitrate, ammonium and amines). This indicates that these smaller aliphatic amines can be important for the carbon and the nitrogen cycles in the remote marine environment