We present a calculation of vector and axial-vector form factors for each of the octet hyperon semi-leptonic transition matrix elements by using the techniques of lattice QCD where simulations were performed with Nf = 2 + 1 flavours of dynamical O(a)-improved Wilson fermions. We also study the electromagnetic form factors, axial charges and other properties of octet baryons. Errors due to extrapolation to zero transferred momentum are reduced by applying a twist to the boundary conditions on the lattice. Our form factor results compare favourably with experiment and other lattice QCD determinations. By considering an expansion about the SU(3)-flavour symmetric limit we seek to investigate and quantify the symmetry breaking effects in these matrix elements due to the mass splitting between the strange and light quarks. We find good agreement with the Ademollo-Gatto theorem for the vector form factor, a measurable amount of breaking in the axial-vector form factor and significant effects in the weak magnetism form factor. Knowledge of the parameterisation of SU(3)-flavour symmetry breaking allows for a series of constrained fits to be made to the form factor results which are used to arrive at a 'baryonic' estimation of the Cabibbo-Kobayashi-Maskawa matrix element |Vus|.

No description available.

Fluorescence microscopy is an important tool for biological research. However, the resolution of a standard fluorescence microscope is limited by diffraction, which makes it difficult to observe small details of a specimen’s structure. We have developed two fluorescence microscopy methods that achieve resolution beyond the classical diffraction limit. The first method represents an extension of localisation microscopy. We used nonnegative matrix factorisation (NMF) to model a noisy dataset of highly overlapping fluorophores with intermittent intensities. We can recover images of individual sources from the optimised model, despite their high mutual overlap in the original dataset. This allows us to consider blinking quantum dots as bright and stable fluorophores for localisation microscopy. Moreover, NMF allows recovery of sources each having a unique shape. Such a situation can arise, for example, when the sources are located in different focal planes, and NMF can potentially be used for three dimensional superresolution imaging. We discuss the practical aspects of applying NMF to real datasets, and show super-resolution images of biological samples labelled with quantum dots. It should be noted that this technique can be performed on any wide-field epifluorescence microscope equipped with a camera, which makes this super-resolution method very accessible to a wide scientific community. The second optical microscopy method we discuss in this thesis is a member of the growing family of structured illumination techniques. Our main goal is to apply structured illumination to thick fluorescent samples generating a large out-of-focus background. The out-of-focus fluorescence background degrades the illumination pattern, and the reconstructed images suffer from the influence of noise. We present a combination of structured illumination microscopy and line scanning. This technique reduces the out-of-focus fluorescence background, which improves the quality of the illumination pattern and therefore facilitates reconstruction. We present super-resolution, optically sectioned images of a thick fluorescent sample, revealing details of the specimen’s inner structure. In addition, in this thesis we also discuss a theoretical resolution limit for noisy and pixelated data. We correct a previously published expression for the so-called fundamental resolution measure (FREM) and derive FREM for two fluorophores with intermittent intensity. We show that the intensity intermittency of the sources (observed for quantum dots, for example) can increase the “resolution” defined in terms of FREM.

Thesis (MBA (Business Management))--University of Stellenbosch, 2005. / ENGLISH ABSTRACT: The matrix structure has had varying degrees of success over the last 35 years. During this period the major factors, seen as critical to achieving matrix effectiveness, have been identified as: • communication; • strong leader; • culture; • rewards; • skills in teams; • clear and defined goals; • senior management support; • defined responsibility; • accountability; and • procedures and standards. A matrix structure (In the form of Category Management) was introduced into our organisation (USABCO) in 1999 and three years later it was replaced with the previous structure (Hierarchical Structure). In hind light the category management structure, if implemented correctly with the relevant preparation, training, and support,would have improved new product development efficiency. Eleven recent articles related to matrix effectiveness were selected and analysed, and the results used to establish the following for each of the above and other critical factors: • proposed actions that can be taken to improve matrix effectiveness; and • reported benefits of these actions. This is not an exhaustive list but rather a summary of results from current research, empirical studies and surveys. / AFRIKAANSE OPSOMMING: Die matriks struktuur het oor die laaste 35 jaar verskillende suksesse behaal. Gedurende hierdie periode, was die volgende hoof faktore gesien as krities tot die bereiking van matriks doeltreffendheid: • kommunikasie; • sterk leiers; • kultuur; • vergoeding; • vaardighede in spanne; • duidelike doelwitte; • bemagtiging van lede; • senior bestuur ondersteuning; • gedefinieerde verantwoordlikheid; • toerekenbaarheid; en • prosedures en standaarde. Die matriks struktuur (in die vorm van kategoriebestuur) was in 1999 in ons maatskappy bekend gestel en na 3 jaar was dit weer vervang met die vorige struktuur (hierargiese struktuur). Die "kategorie bestuur struktuur" kon nuwe produk ontwikkeling doeltreffendheid verbeter, as dit reg geimplementeer was met die nodige voorbereiding, opleiding en ondersteuning. Elf onlangse artikels, wat verband hou met matriks doeltreffendheid, was geselekteer en geanaliseer en die resultate gebruik om die volgende vas te stel vir elkeen van die bogenoemde hooffaktore: • voorgestelde aksies om matriks doeltreffendheid te verbeter; en • gepubliseerde voordele van die aksies. Dit is nie 'n volledige lys nie, maar eerder 'n opsomming van huidige navorsing, empiriese studies en ondersoeke.

Thesis (MBA)--Stellenbosch University, 2003. / ENGLISH ABSTRACT: Matrix organizations still remain a successful competitor in a hyper networked and borderless world. Matrix organizations are a multidimensional structure that tries to maximize the strength of a functional organization and minimize the weaknesses of both the project and functional organizations. It combines the vertical hierarchical structure with a horizontal structure of an input coordinator and provides advantages in terms of creativity, innovation, integration of knowledge and responsiveness to customer needs (Stebbins, Sena & Shani, 1997: 1). Project managers in a matrix organization have control over three factors: what has to be done, when it must be done, and how much in terms of resources must be dedicated to the project. The probable risk here is that the project manager may become isolated from a technical foundation and loss the technical skills that is needed to manage the matrix organization effectively. Some of the other key issues in a matrix organization is the "two bosses" or sharing of authority, the difficult balance between the organizations need for cost effectiveness and the project manager's need to achieve perfection and the problems associated with the resources and functional managers' reluctance to give up these resources. The solution for most of these problems is that the project manager should have sufficient authority in the organization and the back up and support of top management. The project manager of the matrix organization needs the personal skills to effectively communicate and motivate the project team and allow for greater collaboration among differing functional specialties, and political skills to handle all the relevant stakeholders. The transition into a predominantly knowledge-based economy with knowledge workers manning the workstations, the need for managing interpersonal complexity at work is also driving the matrix. The discipline of matrix management, however, remains more an art than a science. / AFRIKAANSE OPSOMMING: Matriks organisasies is nog steeds 'n suksesvolle mededinger in 'n wereld met netwerke sonder grense. Matriks organisasies is multi-dimensionele strukture wat probeer om die sterk punte van funksionel organisasies te maksimaliseer en die swak punte te minimaliseer van beids projek en funksionele organisasies. Dit kombineer die vertikale hierargiese strukture met die horisontale strukture van 'n koordineerder wat verantwoordelik is vir insette, en voorsien voordele in terme van kreatiwiteit, innovering, integrasie van kennis en reaksie op wat kliente benodig (Stebbins, Sena & Shani, 1997: 1 ). Projekbestuurders in 'n matriks organisasie het beheer oor drie faktore: wat moet gedoen word, wanneer moet dit gedoen word en hoeveel, in terme van hulpbronne, moet toegewys word aan die projek. Die moontlike risiko is dat die projekbestuurder geisoleer kan word van 'n tegniese grondslag en die tegniese vaardigheid, wat nodig is om die matriks organisasie effektief te bestuur, verloor. Sommige van die ander belangrike punte in 'n matriks organisasie is die "twee hoofde"of die gedeelde autoriteit, die moeilike balans tussen die organisasie se noodsaaklikheid van koste effektiwiteit en die projek bestuurder se strewe na volmaakheid, asook die probleme wat geassosieer word met die hulpbronne en die funksionele bestuurder se huiwering om dit op te gee. Die oplossing van die meeste van hierdie probleme is dat die projekbestuurder voldoende autoriteit moet hê in die organisasie en die ondersteuning van die top bestuur. Die projekbestuurder van die matriks organisasie benodig die persoonlike vaardigheid om effektief met die projekspan te kommunikeer en hul te motiveer. Groter samewerking tussen die verskillende funksionele spesialiteite moet toe gelaat word en die projek bestuurder benodig ook die politieke vaardigheid om alle relevante insethouers te hanteer. Soos die verandering plaasvind in 'n hoofsaaklike kennis gebaseerde ekonomie met opgeleide werkers wat die werkstasies beman, word die matriks ook gedryf deur die behoefte om interpersoonlike gekompliseerdheid te bestuur. Die disipline van matriksbestuur is meer 'n kuns, as 'n wetenskap.

Thesis (PhD (Mathematics))--University of Stellenbosch, 2010. / ENGLISH ABSTRACT: THE concept of a k-matrix in the full 2 2 matrix ring M2(R=hki), where R is an arbitrary unique factorization domain (UFD) and k is an arbitrary nonzero nonunit in R, is introduced. We obtain a concrete description of the centralizer of a k-matrix bB in M2(R=hki) as the sum of two subrings S1 and S2 ofM2(R=hki), where S1 is the image (under the natural epimorphism fromM2(R) toM2(R=hki)) of the centralizer in M2(R) of a pre-image of bB, and where the entries in S2 are intersections of certain annihilators of elements arising from the entries of bB. Furthermore, necessary and sufficient conditions are given for when S1 S2, for when S2 S1 and for when S1 = S2. It turns out that if R is a principal ideal domain (PID), then every matrix in M2(R=hki) is a k-matrix for every k. However, this is not the case in general if R is a UFD. Moreover, for every factor ring R=hki with zero divisors and every n > 3 there is a matrix for which the mentioned concrete description is not valid. Finally we provide a formula for the number of elements of the centralizer of bB in case R is a UFD and R=hki is finite. / AFRIKAANSE OPSOMMING: DIE konsep van ’n k-matriks in die volledige 2 2 matriksring M2(R=hki), waar R ’n willekeurige unieke faktoriseringsgebied (UFG) en k ’n willekeurige nie-nul nie-inverteerbare element in R is, word bekendgestel. Ons verkry ’n konkrete beskrywing van die sentraliseerder van ’n k-matriks bB in M2(R=hki) as die som van twee subringe S1 en S2 van M2(R=hki), waar S1 die beeld (onder die natuurlike epimorfisme van M2(R) na M2(R=hki)) van die sentraliseerder in M2(R) van ’n trubeeld vanbB is, en die inskrywings van S2 die deursnede van sekere annihileerders van elemente afkomstig van die inskrywings van bB is. Verder word nodige en voldoende voorwaardes gegee vir wanneer S1 S2, vir wanneer S2 S1 en vir wanneer S1 = S2. Dit blyk dat as R ’n hoofideaalgebied (HIG) is, dan is elke matriks in M2(R=hki) ’n k-matriks vir elke k. Dit is egter nie in die algemeen waar indien R ’n UFG is nie. Meer nog, vir elke faktorring R=hki met nuldelers en elke n > 3 is daar ’n matriks waarvoor die bogenoemde konkrete beskrywing nie geldig is nie. Laastens word ’n formule vir die aantal elemente van die sentraliseerder van bB verskaf, indien R ’n UFG en R=hki eindig is.

published_or_final_version / abstract / Biochemistry / Master / Master of Philosophy

published_or_final_version / abstract / Mechanical Engineering / Doctoral / Doctor of Philosophy

published_or_final_version / Orthopaedics and Traumatology / Master / Master of Philosophy

published_or_final_version / Mechanical Engineering / Master / Master of Philosophy