Recurrence and ergodicity in unital *-algebras

Results concerning recurrence and ergodicity are proved in an abstract Hilbert space setting based on the proof of Khintchine's recurrence theorem for sets, and on the Hilbert space characterization of ergodicity. These results are carried over to a non-commutative *-algebraic setting using the GNS-construction. This generalizes the corresponding measure theoretic results, in particular a variation of Khintchine's Theorem for ergodic systems, where the image of one set overlaps with another set, instead of with itself.Comment: 16 page

Noncommutative recurrence over locally compact Hausdorff groups

We extend previous results on noncommutative recurrence in unital *-algebras over the integers, to the case where one works over locally compact Hausdorff groups. We derive a generalization of Khintchine's recurrence theorem, as well as a form of multiple recurrence. This is done using the mean ergodic theorem in Hilbert space, via the GNS construction.Comment: 11 page

Preoperative risk evaluation of postoperative morbidity in IBD patients-impact of the POSSUM score

Ziel der Studie war die Erfassung der Morbidität und Mortalität nach operativer Therapie von Patienten mit Chronisch Entzündlichen Darmerkrankungen mit speziellem Fokus auf die Anwendbarkeit eines Risiko-Score-Systems, dem POSSUM score (Physiological and Operative Severity Score for the Enumeration of Mortality and Morbidity) zur präoperativen Risikoabschätzung und Prognose der postoperativen MorbiditätThe aim of this study was to assess the morbidity and mortality of patients undergoing surgery for infIammatory bowel disease (IBD) with special focus of the predictive value of the Physiological and Operative Severity Score for the Enumeration of Mortality and Morbidity (POSSUM) scoring system for preoperative risk adjustment of postoperative morbidity

An experimental study of organisational change and communication management

More than ever, organisations are recognising that they need to build and sustain healthy relationships with stakeholders in order to survive, grow and be successful. When an organisation is threatened by environmental changes – such as a crisis or competition as a result of information technology developments, increased customer demands, new legislations, even the threat of AIDS – the need for better communication increases. Successful organisations use the potential of communication management, not only to ease the transformation process, but also to improve their relationships with key stakeholders and the environment, and uphold their reputation. In this sense, communication practitioners are playing managerial, ethical and strategic roles during times of instability because change complexities involve having to deal with stakeholders’ trust and commitment. This thesis attempts to clarify the growing importance of communication management, particularly the role of relationship management. Proposed here is a different way of thinking about change communication strategies and building healthy relationships when organisations and their stakeholders have to make or adjust to change. Existing literature shows that most organisations tend to take a planned approach to change which is structured, consists of specific goals and objectives, and tightly controlled by management. Management sees its role within this paradigm as reducing conflict, creating order, controlling chaos and simplifying all the complexities created by the environment. Possible outcomes are predicted and alternatives for action are planned. Structures determine the information needed, and perceptions are managed by feeding the ‘right’ information or withholding information that might give rise to disorder and chaos. An alternative paradigm is the postmodern perspective, drawing specifically from chaos and complexity theories. These ‘emergent’ approaches to management consider organisations as living and holistic systems, more organic and ecological, seeking less control and more freedom. Organisations that operate like living systems are open, flexible, creative, caring and willing to adjust their strategies to adapt to the environment. While strategic planning is still considered important within the positivistic paradigms of management, it is nevertheless moving from the basic premise of control and prediction to scenario planning and processes of open communication, facilitation and networking. The emphasis is on relationship building via the full participation of the stakeholders involved. This two-way, symmetrical approach is also considered the more ethical. When an organisation is confronted by a problem, and if the constraints on communication are low, the organisation’s publics (employees/stakeholders) tend to feel connected to the problem and want to do something about it. Their need to actively seek information about the problem opens up many communication potentialities, including a willingness to change their attitudes, beliefs and behaviours. The result is a culture of shared responsibility, participation in decision-making, open and honest communication, which leads to a positive working climate and higher productivity. So an important assumption that can be made here is that an empowered public will strive for a positive relationship with the organisation. It can further be derived that a positive relationship between an organisation and its publics, particularly its internal stakeholders (employees), will lead to greater communication and a greater willingness to change. These assumptions were tested in this study. The research questions were: (1) What is the connection between the communication management strategy followed during change in organisations and the relationship and behavioural effects on internal stakeholders (employees)? (2) What are the effects of the communication management strategy followed during high change on relationships and behaviours with internal stakeholders (employees)? The methodology was an experimental approach which allows for the manipulation of independent variables and measurement of influences thereof on dependent variables. The independent variables were the communication and change strategies followed in organisations; the dependent variables were the relationship characteristics (trust, control mutuality, commitment, and satisfaction). The use of scenarios was most effective in this experimental context because different scenarios can project different outcomes. The researcher, therefore, had the opportunity to analyse the effects of the change strategies, as well as the changes that would take place. Data collection from 9 different organisations resulted in, more or less, 10–40 employees from different levels of management and non-management of each organisation. Each respondent evaluated 2 different scenarios, which resulted in 372 evaluations in total (186 for each scenario). The scenarios addressed changes in general and were about various issues. Basic descriptive statistics, as well as hypotheses testing using MANOVA (to test for meaningful differences between groups), were conducted. Other data analyses included testing for validity and reliability, analysis of variance and the Scheffe’s Test for significance of correlations. The findings showed significant proof of the internal validity of the experimental design used, indicating that: (a) the experimental manipulation (the two different change management strategies) had a definite effect on the relationship that internal stakeholders would have with organisations, and that except for the size of the organisation and the educational level of the employees, no other variables had an influence; (b) strong correlations exist between the strategy followed during change and the resulting projected relationships with internal stakeholders of the organisation; (c) high participation during high change led to significantly more positive overall relationships between an organisation and its internal stakeholders, as compared to low participation with a planned approach. In brief, the findings support a strong participative, two-way public relations strategy to be followed when organisations go through major change processes. The significance of these findings calls for a new paradigm in strategic communication and relationship management. Change cannot be solely based on plans and projections, but rather on understanding the complexities of situations and weighing different options available. Well-developed organisational change, therefore, is a strategically managed process that takes into consideration all the possibilities of change in the environment. Traditional studies and models of change management have either ignored the importance of strategic communication as a contribution to successful change, or saw communication as only a tool in the first stages of ransformation. However, to facilitate successful strategic change management is to recognise communication management as contributing significantly to guiding the complete transformation process in building important relationships internally and externally. Alternative emergent approaches to change recognise that change and, more specifically, transformation should be viewed as a continuous process linking to the complexities of the changing market, nature of work environments, new management approaches, organisational boundaries and relationships. Chaos and complexity theories, in particular, stress the importance of interconnectivity between subsystems of societies and organisations. Central to these theories is the observation that relationships built on open communication have the potential of producing something greater for an organisation. The complex and dynamic nature of the environment, structural alteration, and the need for employee flexibility are all recognised. Another important insight is the view that organisations can create visions and perform strategic planning around scenarios that guide actions. Another way of adapting to change is to influence back on change, that is, steer change through relationship building and participative decision-making. To become a true learning organisation requires the building of knowledge architecture with a strong supporting technical infrastructure. The main function of the communication manager, therefore, is to establish networks and structures for the collection and dissemination of information, and ultimately, the translation to knowledge. Communication leaders can connect teams and workgroups by driving communication and building trust. Involving staff in change management decision-making stimulates debate and criticisms, thus creates opportunities for innovation and revolutionary change. These are some of the main preconditions for sustainable change, and all can be achieved through sound communication management and the building of relationships with stakeholders.Thesis (PhD)--University of Pretoria, 2006.Communication ManagementPhDUnrestricte

Zur Versicherungsfunktion von Rücküberweisungen von Migranten: Eine Untersuchung in Südafrika

In den meisten Entwicklungs- und Schwellenländern bestehen keine umfas - senden Systeme der sozialen Sicherung. Private Versicherungen sind für einen Großteil der Bevölkerung meist schwer zugänglich oder sehr teuer. Von Risiken sind jedoch alle Menschen betroffen und arme Bevölkerungsschichten häufig sogar noch stärker. Da es für Menschen mit geringen und häufig unregelmäßigen Einkommen schwierig ist, größere Ausgaben zu decken, benutzen sie unterschiedliche Mechanismen der Vorsorge und des Finanzmanagements, um mit Risiken umzugehen. Die hier vorgestellte Studie untersucht, ob Rücküberweisungen von Migranten Versicherungen ersetzen oder eher zum Abschluss von Versicherungen führen.Rücküberweisung (Migranten) Soziale Sicherung Sozialversicherung Südafrika

Structural Analysis and Glycan Receptor Binding Specificities of Human Polyomaviruses

This thesis investigates the atomic structures and cell surface glycan receptor specificities of six human polyomaviruses. In healthy individuals, polyomaviruses establish usually asymptomatic chronic infections, but they may cause severe disease in immunocompromised patients. High-resolution X-ray structures of the major capsid protein VP1 alone and in complex with its specific glycan receptors allowed to analyze the molecular basis for underlying recognition events during early steps of the infection. The findings from crystallographic studies were corroborated with cell-based binding experiments using flow cytometry, interaction studies in solution by NMR spectroscopy, and infection studies in cell culture. The presented results highlight the enormous complexity of virus-glycan interactions and demonstrate that subtle differences in both the viral attachment protein and the cell-surface glycan receptor modulate binding specificities and affinities and thus, are key determinants for tissue and host tropism, viral infectivity, and pathogenesis. JC Polyomavirus (JCPyV) causes the fatal demyelinating disease Progressive Multifocal Leukoencephalopathy (PML) in immunocompromised individuals. A brain isolate of JCPyV, a genotype 1 strain, requires α2,6-linked sialic acids on the LSTc glycan for attachment to host cells, whereas a kidney isolate, a genotype 3 strain, was reported to interact with gangliosides featuring α2,3- and α2,8-linked sialic acids. Comprehensive structural and functional analyses of these two representative strains and their glycan receptor specificities show that engagement of LSTc is a prerequisite for functional receptor engagement for all seven JCPyV genotypes while the weaker-binding gangliosides are not required for infection. Interestingly, the majority of JCPyV isolates from PML patients contain distinct mutations within or in proximity to the LSTc binding site on VP1. The presented results reveal that binding of these mutant viruses to glycans is abolished or severely compromised rendering them not infectious. Thus, these viruses likely utilize a so far unknown receptor for the infectious entry and/or play alternative roles in PML pathogenesis. In order to explore potential strategies for the development of antiviral compounds against PML a fragment-based screening approach was carried out and subsequent X-ray structure analysis identified a novel compound binding site inside the hydrophobic cavity of the JCPyV VP1 pentamer. Further studies show that modifications to the five-fold pore of the VP1 pentamer result in a severe reduction of infectivity, suggesting that the pore is an important structural feature of polyomaviruses. Thus, targeting this pore may be proven to be an effective antiviral therapy. Crystal structures of VP1 from Trichodysplasia spinulosa-associated Polyomavirus (TSPyV) in complex with three different glycans reveal a sialic acid binding site that is shifted by about 18 Å from the ‘classical’ sialic acid binding sites of JCPyV and other polyomaviruses. Functional and cell-based studies confirm the importance of these novel interactions with sialic acids and suggest that glycolipids play an important role during TSPyV infection. Surprisingly, this new sialic acid binding site is also conserved in VP1 of Human Polyomavirus 12 (HPyV12), whereas the human New Jersey Polyomavirus (NJPyV) employs a third location for the recognition of an Neu5Ac-α2,3-Gal-containing receptor. A structure-based phylogenetic analysis suggests that TSPyV, HPyV12, and NJPyV share their sialic acid binding site with closely related non-human polyomaviruses providing initial clues about determinants of host specificity and evolution of these viruses. In contrast, Human Polyomavirus 6 and 7 (HPyV6 and HPyV7, respectively) carry uniquely elongated loops that cover the bulk of the outer virion surfaces, and moreover, obstruct the groove that binds sialylated glycan receptors in related viruses. Consistently, cell attachment and NMR studies further suggest that sialylated glycans are not required for cell attachment of both, HPyV6 and HPyV7. In conclusion, with its relatively high sequence homology and a conserved overall architecture, the growing Polyomaviridae family forms an excellent platform to analyze principles and molecular determinants of receptor specificity and antigenicity as well as critical factors for viral pathogenesis. A detailed understanding of the underlying molecular principles is important to establish a comprehensive toolbox, which can be used for new approaches for antiviral therapies and for the design of therapeutic gene vectors.Diese Dissertation untersucht die atomaren Strukturen von sechs menschlichen Polyomaviren und das spezifische Andocken dieser Viren an Zuckerstrukturen auf Zelloberflächen der Wirtszellen. Bei gesunden Menschen verursachen Polyomaviren meist chronische asymptomatische Infektionen, jedoch können einige dieser Viren bei immungeschwächten Patienten schwere Erkrankung auslösen. Mit Hilfe von Röntgenstrukturen der Kapsidproteine in Komplexen mit Zuckerverbindungen konnten die molekularen Grundlagen für das spezifische Andocken dieser Viren an Zellen identifiziert werden. Anschließend wurden die Erkenntnisse aus den kristallographischen Studien mit zellbasierten Bindungsexperimenten mittels Durchflusszytometrie, Interaktionsstudien mittels NMR-Spektroskopie in Lösung und Infektionsstudien in Zellkultur überprüft und weiter analysiert. Die erhaltenen Ergebnisse unterstreichen die enorme Komplexität von Interaktionen zwischen Viren und Zuckerstrukturen auf der Zelloberfläche und zeigen, dass feine Unterschiede in den viralen Proteine oder den gebundenen Zuckermolekülen eine wichtige Rolle für die Erkennungsprozess und die Bindungsaffinität spielen. Diese spezifischen und gut regulierten Wechselwirkungen zwischen Virus und Rezeptoren auf der Wirtszelle sind nicht nur für die initiale Erkennung wichtig sondern auch die viralen Infektiosität und Pathogenese. JC Polyomavirus (JCPyV) kann bei immungeschwächten Personen die tödliche Gehirnerkrankung Progressive Multifokale Leukoenzephalopathie (PML) auslösen. Ein JCPyV Stamm aus dem Gehirn bindet an α2,6-verknüpfte Sialinsäure der linearen Zuckerstruktur LSTc auf der Wirtszelle, während Untersuchungen für einen anderen JCPyV Stamm, der aus der Niere isoliert wurde, zeigten, dass auch Gangliosiden mit α2,3- oder α2,8- verknüpfter Sialinsäure gebunden werden. Eine umfassende strukturelle und funktionelle Analyse der zwei repräsentative Virusstämme zeigt hier jedoch deutlich, dass die Bindung an LSTc eine Voraussetzung für die Infektion für alle sieben JCPyV Genotypen ist, während die schwächer gebundenen Ganglioside nicht für die Infektion erforderlich sind. Interessanterweise besitzen JCPyV Isolate von PML-Patienten oft eine kleine Anzahl von konservierten Mutationen innerhalb oder in unmittelbarer Nähe der LSTc-Bindungsstelle auf dem Kapsidprotein. Die hier vorgestellten Ergebnisse zeigen, dass die Bindung an Zuckerstrukturen durch die Veränderungen in VP1 verhindert oder stark beeinträchtigt ist und daher diesen Viren nicht mehr infektiös sind. Somit verwenden diese PML-assoziierten Viren wahrscheinlich ein bisher unbekanntes Molekül auf der Zelloberfläche für den infektiösen Eintritt und/oder sie tragen in einer anderen Weise zur PML-Pathogenese bei. Ein Fragment-basiertes Screening wurde durchgeführt um mögliche Strategien für die Entwicklung von antiviralen Verbindungen gegen PML zu testen. Die Bindung von einem Fragment im Innenraum des hydrophoben VP1 Pentamers wurde mittels Strukturanalyse bestätigt. Zusätzlich konnte in einer Untersuchung gezeigt werden, dass Änderungen der fünffachen Pore der VP1-Pentamere die Virusinfektion verringern. Diese Erkenntnisse deuten darauf hin, dass die Poren ein wichtiger struktureller Bestandteil des Viruskapsids ist. Somit stellt auch die Pore oder gar der hydrophobe Innenraum des VP1 Pentamers einen möglichen Angriffsort für die Entwicklung von wirksamen antiviralen Therapien dar. Kristallstrukturen von VP1 des Trichodysplasia spinulosa-assoziierten Polyomavirus (TSPyV) im Komplex mit drei verschiedenen Zuckermolekülem zeigen eine Sialinsäure-Bindungsstelle, die um etwa 18 Å von der "klassischen" Sialinsäure-Bindungsstellen von JCPyV und anderer Polyomaviren entfernt ist. Funktionelle Untersuchungen bestätigen die Wichtigkeit dieser neuartigen Sialinsäure-Interaktion für die TSPyV Infektion und lassen zudem vermuten, dass besonders Glycolipide hierbei eine wichtige Rolle einnehmen. Diese neue Bindungsstelle ist auch im Kapsid des menschlichen Polyomavirus 12 (HPyV12) strukturell konserviert, während der menschliche New Jersey Polyomavirus (NJPyV) in einem dritten Bereich von VP1 mit einer spezifischer Zuckerstruktur wechselwirkt. Strukturbasierte phylogenetische Analysen zeigen, dass die Sialinsäure-Bindungsstellen von TSPyV, HPyV12 und NJPyV vermutlich auch in verwandten aber nicht-menschlichen Polyomaviren vorhanden sind und geben Hinweise über Determinanten der Wirtsspezifität und Evolution dieser Viren. Die humanen Polyomaviren 6 und 7 (HPyV6 und HPyV7) besitzen im Gegensatz dazu verlängerte VP1-Schleifenstrukturen, die den Großteil der Kapsidoberflächen abdecken und das Erkennen von Zuckermolekülen verhindert. Zusätzlich zeigen NMR-spektroskopische Untersuchungen, dass sialylierte Zucker nicht für das initiale Andocken von HPyV6 und HPyV7 an Zellen erforderlich sind. Zusammenfassend lässt sich sagen, das die wachsende Familie der Polyomaviren mit einer hohen Sequenzhomologie und konservierten Gesamtarchitektur eine hervorragende Plattform bildet, um Einblicke in grundlegende Prinzipien und molekularen Determinanten für Rezeptorspezifität, viraler Antigenität und Pathogenese zu erhalten. Ein detailliertes Verständnis der molekularen Grundlagen ist wichtig für neue Ansätze in der Entwicklung von antiviralen Therapien und auch therapeutische Genvektoren

‘Kyk hoe elk in die ander pas’: Landskap, liggaam en die visuele in enkele gedigte van Johann de Lange

In hierdie artikel word ondersoek ingestel na die rol van landskap en die visuele in die poësie van Johann de Lange, sowel as na die verbintenis of verbondenheid tussen liggaam en landskap. Die meervoudige rol wat landskap in De Lange se oeuvre speel en die gepaardgaande visuele ingesteldheid word in enkele sleutelgedigte uit resente bundels verken en bespreek deur van relevante teoretiese konsepte (hoofsaaklik soos uiteengesit deur Wylie 2007) gebruik te maak. De Lange leun aan by die fenomenologiese denkskool vir wie visie en liggaam, liggaam en landskap ten nouste verweef is, maar ook by tendense van die nuwe materialisme en die ekologiese gedagte. Daar word gevolglik aangetoon dat die saambestaan van liggaam en landskap bowenal verband hou met relasionaliteit. Die digterlike proses en die wyse waarop landskap en liggaam as inspirasie vir die skryf van poësie dien, word ondersoek, en daar word aandag geskenk aan voyeurisme en die landskap van die erotiek. ‘See how each fits into the other’: Landscape , body and visual in some poems of Johann de Lange. In this article we investigated the function of landscape and the visual in Johann de Lange’s poetry as well as the bond or connectedness between body and landscape. The multiple functions of landscape in De Lange’s oeuvre as well as the concomitant visual disposition amongst selected key poems from recent volumes are investigated by using relevant theoretical concepts (mainly as discussed by Wylie 2007). De Lange also gleans from the phenomenological school of thought in which vision and body, body and landscape are closely interwoven. He also makes use of other trends such as new materialism and ecological thought. Consequently it is shown that the coexistence of body and landscape can be closely connected with relationality. The poetical process and the manner in which body and landscape serve as inspiration for the poetical writing are explored with special reference to voyeurism and the erotic landscape. Keywords: Johan De Lange; landskap; visie; liggaa