A quantitative evaluation of single photon emission computed tomography (SPECT) and planar scintigraphic imaging may be valuable for both diagnostic and therapeutic purposes. For an accurate quantification it is usually necessary to correct for attenuation and scatter and in some cases also for septal penetration. For planar imaging a background correction for the contribution from over- and underlying tissues is needed. In this work a few correction methods have been evaluated and further developed. Much of the work relies on the Monte Carlo method as a tool for evaluation and optimisation. A method for quantifying the activity of I-125 labelled antibodies in a tumour inoculated in the flank of a mouse, based on planar scintigraphic imaging with a pin-hole collimator, has been developed and two different methods for background subtraction have been compared. The activity estimates of the tumours were compared with measurements in vitro. The major part of this work is attributed to SPECT. A method for attenuation and scatter correction of brain SPECT based on computed tomography (CT) images of the same patient has been developed, using an attenuation map calculated from the CT image volume. The attenuation map is utilised not only for attenuation correction, but also for scatter correction with transmission dependent convolution subtraction (TDCS). A registration method based on fiducial markers, placed on three chosen points during the SPECT examination, was evaluated. The scatter correction method, TDCS, was then optimised for regional cerebral blood flow (rCBF) SPECT with Tc-99m, and was also compared with a related method, convolution scatter subtraction (CSS). TDCS has been claimed to be an iterative technique. This requires however some modifications of the method, which have been demonstrated and evaluated for a simulation with a point source. When the Monte Carlo method is used for evaluation of corrections for septal penetration, it is important that interactions in the collimator are taken into account. A new version of the Monte Carlo program SIMIND with this capability has been evaluated by comparing measured and simulated images and energy spectra. This code was later used for the evaluation of a few different methods for correction of scatter and septal penetration of I-123 brain SPECT. The methods were CSS, TDCS and a method where correction for scatter and septal penetration are included in the iterative reconstruction. This study shows that quantitative accuracy in I-123 brain SPECT benefits from separate modelling of scatter and septal penetration.

<p>The time bound agenda of the Millennium Development Goals (MDG&rsquo / s) aims at reducing poverty, extending gender equality and advancing opportunities for health and education by addressing current and future water resource and sanitation needs. In many rural areas of South Africa, the cost implication of routing surface water supplies and providing water borne sewerage may far exceed the budgets of local water service authorities. This has resulted in a major thrust in service provision via localised sources, mainly boreholes and springs as well as on site sanitation options. Whilst the National Water Act (Act 36 of 1998) mandates the South African government to provide potable water to all citizens in an equitable manner, this needs to be balanced against the preservation of the country&rsquo / s water resources both quantitatively and qualitatively to ensure sustainability. It is imperative that this fine balance between protection and effecting societal demands and economic development through large-scale water provision be maintained, as successful strategising will be resultant of integrated social, economic and environmental issues especially in economically developing countries. In order to fulfil the mandate of the NWA, policies and strategies for effective protection and use of groundwater resources have been drawn up and are in the process of being drawn up by the national Department of Water Affairs and Forestry (DWAF). The major scope of research in this thesis stems from feasibility studies commissioned by the DWAF for the implementation of a groundwater protection zoning policy for the management and protection of groundwater resource quality. The research work focuses on specifically the microbiological zone of protection and attempts to determine the fate of various pathogens that emanate from on site sanitation facilities as they move through the subsurface. The research was predominantly proposed as a desktop collation and analysis of existing published data however / it was later decided to include a local case study site.</p>

The major advantage of position sensitive radiation detector systems lies in their ability to non invasively map the regional distribution of the emitted radiation in real-time. Three of such detector systems were studied in this thesis, gamma-cameras, positron cameras and CMOS image sensors. A number of physical factors associated to these detectors degrade the qualitative and quantitative properties of the obtained images. These blurring factors could be divided into two groups. The first group consists of the general degrading factors inherent to the physical interaction processes of radiation with matter, such as scatter and attenuation processes which are common to all three detectors The second group consists of specific factors inherent to the particular radiation detection properties of the used detector which have to be separately studied for each detector system. Therefore, the aim of this thesis was devoted to the development of computational methods to enable quantitative molecular imaging in PET, SPET and in vivo patient dosimetry with CMOS image sensors. The first task was to develop a novel quantitative dual isotope method for simultaneous assessments of regional lung ventilation and perfusion using a SPET technique. This method included correction routines for photon scattering, non uniform attenuation at two different photon energies (140 and 392 keV) and organ outline. This quantitative method was validated both with phantom experiments and physiological studies on healthy subjects. The second task was to develop and clinically apply a quantitative method for tumour to background activity uptake measurements using planar mammo-scintigraphy, with partial volume compensation. The third stage was to produce several computational models to assess the spatial resolution limitations in PET from the positron range, the annihilation photon non-collineairy and the photon depth of interaction. Finally, a quantitative image processing method for a CMOS image sensor for applications in ion beam therapy dosimetry was developed. From the obtained phantom and physiological results it was concluded that the methodologies developed for the simultaneous measurement of the lung ventilation and perfusion and for the quantification of the tumour malignancy grade in breast carcinoma were both accurate. Further, the obtained models for the influence that the positron range in various human tissues, and the photon emission non-collinearity and depth of interaction have on PET image spatial resolution, could be used both to optimise future PET camera designs and spatial resolution recovery algorithms. Finally, it was shown that the proton fluence rate in a proton therapy beam could be monitored and visualised by using a simple and inexpensive CMOS image sensor.

Auxiliary absorbers provide an effective means to attenuate the vibrations of a structural or mechanical system (the "primary structure"). The simplest auxiliary absorber, a tuned mass damper (TMD), provides reliable narrow-band attenuation but is not robust to the effects of detuning. Strongly nonlinear tuned mass dampers (NTMDs) are capable of wide-band, irreversible energy transfer known as "energy pumping" but can also exhibit high amplitude solutions which significantly amplify the response of the primary structure. Semi-active tuned mass dampers (STMDs) incorporate an actuating element in order to achieve real-time tuning adjustment capability. This thesis presents a global dynamic analysis of the response of a primary structure with an NTMD and then explores the performance of a novel absorber configuration consisting of an NTMD and STMD attached to the primary structure in series. The global dynamic analysis is conducted using a new cell mapping method developed by the author and introduced within the thesis: the parallelized multi-degrees-of-freedom cell mapping (PMDCM) method. The benefits of the additional STMD component are explored for two distinct applications: (1) restoring the performance of a linear TMD which develops a weak nonlinearity due to operation outside of the intended range or other means, and (2) acting as a safety device to eliminate or minimize convergence to the detached high-amplitude response. In the weakly nonlinear case, the STMD is shown to reduce the effects of the nonlinearity and improve attenuation capability by constraining the motion of the NTMD. In the strongly nonlinear case, the STMD effectively eliminates the complex response behavior and high amplitude solutions which were present in the original system, resulting in a single low amplitude response. Experimental tests using an adjustable-length pendulum STMD verify the numerical results.

A wave digital filter is derived from an analog filter, which is realized as classical doubly resistively terminated reactancefilters. Perfectly designed wave digital filters express good dynamic signal range, low roundoff noise and excellent stabilitycharacteristics with respect to nonlinearity which are produced due to finite wordlength effects. Wave digital filters inheritthe sensitivity properties from analog filters, therefore, coefficients values can be selected to favorable values.Wave digital filters, derived from ladder filters, have low coefficient sensitivity in the passband and stopband. These WDFsare very complicated and are non-modular. The lattice wave digital filters are modular and are not complex. However, theyhave very high sensitivity in the stopband and thus require large coefficient wordlengths. The number of coefficients equalsthe filter order which have to be odd.This thesis discusses the wave digital filter structures that are modular because they are designed by cascading the first-orderand second-order sections. These WDFs can be pipelined. They also exhibit all the above mentioned favorable properties.Similar to lattice WDFs, these structures are restricted to symmetrical and antisymmetrical transfer functions. The synthesisof these structures is based on the factorization of the scattering matrix of lossless two-ports.In this thesis work, lowpass wave digital filters based on circulator-tree structure are designed with different orders startingfrom 3 and going upto 13. In parallel to these circulator-tree wave digital filters, the simple digital filters are also designedwith the same specification. The results of the two filters are compared with each other. It is observed that impulse responseand attenuation response of the two kind of filters perfectly match. Therefore, it is can be concluded that circulator-tree WDFupto Nth order can be synthesized. The implementation examples of two filter with order 3 and order 7 is presented in thisdocumentation for ready reference. It has also been shown that the order of sections does not affect the transfer function ofthe filter. Noise has been introduced and adaptor sections are penetrated. From the results it is concluded that the order of theadaptor sections does not matter and also that the noise does not affect the other adaptors sections, it only propagates throughother adaptors sections.

This degree project handles acoustic measurements of the heat pump EcoAir 107, made by Enertech CTC AB. The sound from the three sound sources of the heat pump, fan, compressor and four way valve, have been measured to find out how they affect the total sound level of the product. Measures to attenuate the sound level have been developed and tested. By comparing these with the sound of the heat pump, in its original state, we have found out the measures which have best effects. The best attenuating measures came to be: taped openings and holes around the compressor space, isolating the top and the bottom of the whole construction, support of the fan bottom part and shielding of the sound source with a screen at a distance of 110 mm These measures have been tested together and an average attenuation of the total sound level with 3,9 dB have been accomplished. In the front of the fan where the continuous sound is the strongest, the attenuation was 4,7 dB. This project is meant to be used as a guide by Enertech CTC AB:s during their future developing process. / Detta examensarbete behandlar akustiska undersökningar på luftvärmepumpen EcoAir 107 från Enertech CTC AB. Ljudbilden över värmepumpens tre ljudkällor, fläkt, kompressor och fyrvägsventil, har mätts upp för att se hur dessa påverkar produktens totala ljudnivå. Åtgärder för att försöka dämpa ljudnivån har sedan tagits fram och testats. Genom att jämföra dessa med ljudbilden på värmepumpen i standardutförande har vi kommit fram till de åtgärder som fungerar bäst. De bästa dämpningsåtgärderna visade sig vara: Tejpade lister och hål runt kompressorutrymmet, isolering i tak och botten av hela konstruktionen, stadgning av fläktutrymmets bottendel och avskärmning av ljudkällan med skärm på 110 mm avstånd. Dessa åtgärder har testats tillsammans och en genomsnittlig sänkning på totala ljudnivån med 3,9 dB har åstadkommits. Fläktljudet rakt framifrån, som är det starkaste ihållande ljudet från värmepumpen, sänktes med 4,7 dB. Detta arbete är tänkt att användas som hjälp vid Enertech CTC AB:s framtida utvecklingsarbete.

Virtual three-dimensional (3D) auditory displays utilize signal-processing techniques to alter sounds presented through headphones so that they seem to originate from specific spatial locations around the listener. In some circumstances bone-conduction headsets (bonephones) can provide an alternative sound presentation mechanism. However, existing 3D audio rendering algorithms need to be adjusted to use bonephones rather than headphones. This study provided anchor points for a function of shift values that could be used to adapt virtual 3D auditory displays for use with bonephones. The shift values were established by having participants adjust phase and amplitude of two waves in order to cancel out the signal and thus produce silence. These adjustments occurred in a listening environment consisting of air-conducted and bone-conducted tones, as well as air- conducted masking. Performance in the calibration condition suggested that participants understood the task, and could do this task with reasonable accuracy. In the bone-to-air listening conditions, the data produced a clear set of anchor points for an amplitude shift function. The data did not reveal, however, anchor points for a phase shift function the data for phase were highly variable and inconsistent. Application of shifts, as well as future research to establish full functions and better understand phase are discussed, in addition to validation and follow-up studies.

This thesis considers four nonlinear systems with parametric forcing. The first problem involves an inverted pendulum with asymmetric elastic restraints subjected to harmonic vertical base excitation. On linearizing trigonometric terms the pendulum is governed by an asymmetric Mathieu equation. Solutions to this equation are scaleable. The stability regions in the parameter plane are studied numerically. Periodic solutions at the boundaries of stable regions in the parameter plane are found numerically and then their existence is proved theoretically. The second problem involves use of the method of multiple scales to elucidate the dynamics associated with early and delayed ejection of ions from Paul traps. A slow flow equation is developed to approximate the solution of a weakly nonlinear Mathieu equation to describe ion dynamics in the neighborhood of the nominal stability boundary of ideal traps. Since the solution to the unperturbed equation involves linearly growing terms, some care in identification and elimination of secular terms is needed. Due to analytical difficulties, harmonic balance approximations are used within the formal implementation of the method. The third problem involves the attenuation, caused by weak damping, of harmonic waves through a discrete, periodic structure with wave frequency nominally within the Propagation Zone. Adapting the transfer matrix method and using the harmonic balance for nonlinear terms, a four-dimensional map governing the dynamics is obtained. This map is analyzed by applying the method of multiple scales upto first order. The resulting slow evolution equations give the amplitude decay rate in the structure. The fourth problem involves the dynamic response of a strongly nonlinear single-degree-of-freedom oscillator under a constant amplitude, parametric, periodic, impulsive forcing, e.g., a pendulum with strongly nonlinear torsional spring that is periodically struck in the axial direction. Single-term harmonic balance gives an approximate, but explicit, 2-dimensional map governing the dynamics. The map exhibits many fixed points (both stable and unstable), higher period orbits, transverse intersections of stable and unstable manifolds of unstable fixed points, and chaos.

Es wurde eine Arsenkontamination von Boden und Grundwasser im Bereich einer Zellstofffabrik untersucht, die auf Ablagerungen von Eisenoxidschlacken (Rückstände aus der Pyritröstung) mit hohem Gehalt an verschiedenen Spurenelementen zurückzuführen ist. Der Standort ist dadurch gekennzeichnet, dass über viele Jahre Lösungen aus der Celluloseproduktion („Sulfitablauge“) versickerten. Hierdurch gelangten größere Mengen an Sulfat und organischen Stoffen in den Untergrund. Infolgedessen weist das Grundwasser einen stark reduzierten, sulfidischen Chemismus auf. Ein Großteil der Spurenelemente wurde aus der Schlacke im Oberboden in den darunter liegenden wassergesättigten Bereich transportiert und dort in Form von sulfidischen Niederschlägen festgelegt. Eine Ausnahme bildet Arsen, das unter den spezifischen Milieubedingungen im Schadenzentrum lösliche schwefelhaltige Verbindungen bildet (max. 4 mg As/L). Diese Arsen-Schwefel-Spezies wurden erstmals mit einer neu entwickelten IC-ICP/MS- Methode in einem Grundwasser nachgewiesen. Die Grundwasser- und Bodenuntersuchungen sowie begleitende hydrogeologische Messungen ergaben, dass die Arsen-Schwefel-Spezies innerhalb einer Fließstrecke von 30-80 m im Abstrom des Schadenzentrums vollständig immobilisiert werden. Bei der Festlegung von Arsen spielt die biologische Sulfatreduktion, die durch versickerte Sulfitablauge ermöglicht wurde, eine entscheidende Rolle. Anhand dieser Erkenntnisse wurde im Jahr 2000 ein natural attenuation-Konzept zur Sicherung des Standortes ausgearbeitet. Nach Auswertung der Ergebnisse der Standortuntersuchungen aus den Jahren 1999-2005 sowie einer Literaturrecherche zur Arsen-Schwefel-Chemie wurden die Struktur und das Verhalten der unbekannten Arsen-Schwefel-Spezies sowie die Vorgänge bei der Festlegung von Arsen im Boden genauer untersucht. Das wesentlichste Ergebnis der Arbeiten ist, dass in sulfidischen Systemen, z.B. in Grundwässern unter Sulfat reduzierenden Bedingungen, Thioarsenate gebildet werden. In Lehrbüchern und Fachpublikationen aus den vergangenen Jahrzehnten wurde bislang ausschließlich die Existenz von Thioarseniten vermutet. Ursache für die Bildung von Thioarsenaten ist eine hohe Affinität zwischen Arsen und Schwefel, die eine Oxidation von As(III) durch Anlagerung eines Schwefelatoms an dessen freiem Elektronenpaar „erzwingt“. In sulfidhaltigen Lösungen wird hierzu ein Teil des As(III) zu elementarem Arsen reduziert. Das zunächst gebildete Monothioarsenat wird weiter zu den schwefelhaltigeren Thioarsenaten sulfidiert. In sulfidischen Grundwässern bestimmen deshalb die Anionen von Oxomonothioarsenat, Oxodithioarsenat, Oxotrithioarsenat und Tetrathioarsenat das Verhalten von Arsen. Wesentlich für das Verständnis der Arsen-Schwefel-Chemie ist auch die Instabilität der As-SH-Gruppen, die entsprechend dem Dissoziationsverhalten der jeweiligen Arsen-Schwefel-Spezies gebildet werden. Dies erfolgt bei pH-Werten im Bereich von ca. 7-8,5, wobei die monomeren Anionen unter Abspaltung von Schwefelwasserstoff kondensieren. Infolgedessen muss in Grundwässern auch mit polymeren Thioarsenaten gerechnet werden. In saurer Lösung zerfallen die Thioarsenate in arsenige Säure und Schwefel bzw. fallen als Arsenpentasulfid aus. Arsen wird in sulfidischen Aquiferen als Sulfid (z.B. As4S4), als Arsenpyrit (FeAsS) oder durch Einbau von Arsen als Schwefelsubstituent in das Kristallgitter von Mackinawite bzw. Pyrit (FeS, FeS2) festgelegt. Die ermittelten Prozesse können ggf. zur Sanierung bzw. Sicherung von Standorten mit arsenhaltigen Rückständen im Boden bzw. von arsenbelasteten Grundwässern eingesetzt werden. Dabei ist auch von Bedeutung, dass Thioarsenate nach derzeitigem Kenntnisstand relativ gering toxisch sind. Im Umgang mit Thioarsenaten, z.B. auch bei der Analyse von Arsen in sulfidischen Proben, ist jedoch deren Umwandlung in arsenige Säure bei einer pH-Absenkung und auch bei Sauerstoffzutritt zu berücksichtigen. Die biologische Sulfatreduktion spielt eine wesentlich größere Rolle für die Mobilität von Arsen in Grundwässern als bisher angenommen. Im Hinblick auf die weltweit große gesundheitliche Relevanz von Arsen im Trinkwasser und auf mögliche Sanierungsverfahren sollten die Umsetzungen von Arsen unter Sulfat reduzierenden Bedingungen eingehender untersucht werden. / The motivation for the thesis was a project at an industrial site conducted in 1999 to define a remediation concept for soil and groundwater contaminated with arsenic. The contamination resulted from the deposition of residuals from pyrite burning (iron oxides containing different trace elements) in the upper soil many years ago. Because of long-term pollution with process waters rich in organic substances and sulfate, the aquifer is strongly reduced (sulfidic). Most of the arsenic was transferred out of the contaminated soil into the saturated zone in a depth of 7-10 m. There it is partly immobilized as sulfide precipitations, but part of it is solved in the groundwater in form of arsenic-sulfur-complexes (up to 4 ppm). These complexes were detected for the first time in a groundwater by means of an improved IC-ICP-MS method. It was also found that approx. 80 m downstream of the contaminated spot the concentrations of arsenic in soil and groundwater were not increased. On this basis a natural attenuation concept was proposed in 2000. The data from the investigated site was evaluated and specific laboratory tests were carried out in order to identify the unknown arsenic species as well as the processes which lead to their immobilization in the aquifer. The key role of the soluble arsenic-sulfur complexes for the mobility and toxicity of arsenic in sulfate-reducing environments is commonly accepted. In the past, thioarsenites were assumed to be the existing species in sulfidic systems. In this study, however, thioarsenates were identified in solutions spiked with in arsenite and hydrogen sulfide as well as in the contaminated groundwater. The unexpected finding of an oxidation of arsenite to thioarsenates in strongly reducing systems can be explained by the high affinity between As(III) and sulfur. In sulfide containing solutions without any oxidant, arsenite therefore undergoes disproportionation to thioarsenates and elemental arsenic. This was already found out in the 19th century, but has been neglected in publications from the last decades. According to the results of this study the anions of oxomonothioarsenate, oxodithioarsenate, oxotrithioarsenate und tetrathioarsenate are the dominating arsenic species in sulfidic waters. The partitioning of the four species is governed mainly by the sulfide concentration. Beside the high affinity between arsenic and sulfur, the instability of the As-SH group is essential to understand the reactions in the arsenic-sulfur system. As soon as the arsenic-sulfur complexes form As-SH groups (according to their dissociation characteristics) they condensate in separating hydrogen sulfide. Thioarsenates form polymers in the pH range of approx. 7-8.5. Therefore beside the mentioned monomers, thioarsenate polymers can also be important in natural environments. In more acidic solutions they decay into arsenite and sulfur or precipitate as arsenic-pentasulfide. When analyzing arsenic in sulfide containing solutions, it has always to be taken into account that thioarsenates are highly sensitive to oxygen and pH. Therefore, e.g. arsenic speciation by means of HG-AAS is not suitable for sulfidic waters and can wrongly indicate a mixture of arsenite and arsenate. It has previously been supposed that the mobility as well as the toxicity of arsenic increase if the redox state decreases. For sulfidic waters the opposite is probably the case owing to the formation of thioarsenates. The toxicity of arsenite is due to the high reactivity of the As(III) towards sulfohydroxyl groups in proteins. Without a free electron pair and sulfur already incorporated, thioarsenates should be less toxic compared to arsenite. Arsenic can be mobilized out of contaminated soils in form of thioarsenates via infiltration of sulfide solutions or by input of sulfate and biodegradable organic matter. In the presence of iron, thioarsenates can be fixated in sulfidic aquifers as a minor substitute in mackinawite and biogenic pyrite or as arsenic pyrite. Bacterial sulfate reduction is a crucial factor for the mobilization and immobilization of arsenic in reduced aquifers. Considering the negative health impacts of arsenic for millions of people worldwide, as well as the implementation of the mentioned remediation strategies the arsenic-sulfur chemistry deserves closer attention.

<p>This degree project handles acoustic measurements of the heat pump EcoAir 107, made by Enertech CTC AB. The sound from the three sound sources of the heat pump, fan, compressor and four way valve, have been measured to find out how they affect the total sound level of the product.</p><p>Measures to attenuate the sound level have been developed and tested. By comparing these with the sound of the heat pump, in its original state, we have found out the measures which have best effects.</p><p>The best attenuating measures came to be: taped openings and holes around the compressor space, isolating the top and the bottom of the whole construction, support of the fan bottom part and shielding of the sound source with a screen at a distance of 110 mm</p><p>These measures have been tested together and an average attenuation of the total sound level with 3,9 dB have been accomplished. In the front of the fan where the continuous sound is the strongest, the attenuation was 4,7 dB.</p><p>This project is meant to be used as a guide by Enertech CTC AB:s during their future developing process.</p> / <p>Detta examensarbete behandlar akustiska undersökningar på luftvärmepumpen EcoAir 107 från Enertech CTC AB. Ljudbilden över värmepumpens tre ljudkällor, fläkt, kompressor och fyrvägsventil, har mätts upp för att se hur dessa påverkar produktens totala ljudnivå. Åtgärder för att försöka dämpa ljudnivån har sedan tagits fram och testats. Genom att jämföra dessa med ljudbilden på värmepumpen i standardutförande har vi kommit fram till de åtgärder som fungerar bäst.</p><p>De bästa dämpningsåtgärderna visade sig vara: Tejpade lister och hål runt kompressorutrymmet, isolering i tak och botten av hela konstruktionen, stadgning av fläktutrymmets bottendel och avskärmning av ljudkällan med skärm på 110 mm avstånd.</p><p>Dessa åtgärder har testats tillsammans och en genomsnittlig sänkning på totala ljudnivån med 3,9 dB har åstadkommits. Fläktljudet rakt framifrån, som är det starkaste ihållande ljudet från värmepumpen, sänktes med 4,7 dB.</p><p>Detta arbete är tänkt att användas som hjälp vid Enertech CTC AB:s framtida utvecklingsarbete.</p>