22282 research outputs found
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Fingerprinting Codes and Separating Hash Families
No full textThe thesis examines two related combinatorial objects, namely fingerprinting codes and separating hash families. Fingerprinting codes are combinatorial objects that have been studied for more than 15 years due to their applications in digital data copyright protection and their combinatorial interest. Four well-known types of fingerprinting codes are studied in this thesis; traceability, identifiable parent property, secure frameproof and frameproof. Each type of code is named after the security properties it guarantees. However, the power of these four types of fingerprinting codes is limited by a certain condition. The first known attempt to go beyond that came out in the concept of two-level traceability codes, introduced by Anthapadmanabhan and Barg (2009). This thesis extends their work to the other three types of fingerprinting codes, so in this thesis four types of two-level fingerprinting codes are defined. In addition, the relationships between the different types of codes are studied. We propose some first explicit non-trivial con- structions for two-level fingerprinting codes and provide some bounds on the size of these codes. Separating hash families were introduced by Stinson, van Trung, and Wei as a tool for creating an explicit construction for frameproof codes in 1998. In this thesis, we state a new definition of separating hash families, and mainly focus on improving previously known bounds for separating hash families in some special cases that related to fingerprinting codes. We improve upper bounds on the size of frameproof and secure frameproof codes under the language of separating hash families
A Secure and Trusted Channel Protocol for User Centric Smart Cards
No full textThe User Centric Smart Card Ownership Model (UCOM) provides an open and dynamic smart card environment enabling cardholders to request installation/deletion of an application to which they are entitled. As in this model, smart cards are not under the control of a centralised authority; hence, it is difficult for an application provider to ascertain their trustworthiness. At present, proposed secure channel protocols for the smart card environment do not provide adequate assurance required by the UCOM. In this paper, we explore the reasons behind their failure to meet the UCOM requirements and then propose a secure and trusted channel protocol that meets them. In addition, the proposed protocol is also suitable to GlobalPlatform's consumer-centric smart cards. A comparison of the proposed protocol with existing smart card and selected Internet protocols is provided. Then we analyse the protocol with the CasperFDR tool. Finally, we detail the implementation and the performance measurement
Exploring the Use of Accounting History in Post-Enron Stories
No full textThis study uses the concept of “popular history” to address the use of accounting history in post-Enron stories on corporate collapse and accounting failure. The study extends the work of Carnegie and Napier (2010), which focuses on how professional accountants and their firms and organizations were portrayed in post-Enron books that were published during the period 2002 to 2005. These books can be characterized as “popular histories”, and the paper illustrates how the scholarly work of academic accounting historians is given little attention by the authors of these post-Enron stories. It points to the largely untapped potential for accounting historians to make their research findings and insights available for a general readership
Enhancing multiphoton rates with quantum memories
No full textSingle photons are a vital resource for optical quantum information processing. Efficient and deterministic single photon sources do not yet exist, however. To date, experimental demonstrations of quantum processing primitives have been implemented using non-deterministic sources combined with heralding and/or postselection. Unfortunately, even for eight photons, the data rates are already so low as to make most experiments impracticable. It is well known that quantum memories, capable of storing photons until they are needed, are a potential solution to this `scaling catastrophe'. Here, we analyze in detail the benefits of quantum memories for producing multiphoton states, showing how the production rates can be enhanced by many orders of magnitude. We identify the quantity as the most important figure of merit in this connection, where and are the efficiency and time-bandwidth product of the memories, respectively
Curating Science in an Age of Empire: Kew's Museum of Economic Botany
No full textThis thesis considers the history and significance of the Museum of Economic Botany at the Royal Botanic Gardens, Kew, focussing especially on the period from its opening in 1847 to the eve of the First World War. Looking specifically at the Museum’s collection of wood specimens and artefacts, it seeks to understand the nature of economic botany during this period, and to evaluate the contribution made to the field by the Kew Museum. Through examination of the Museum’s practices, networks, spaces, and objects, it sets out to address the question: how do museums produce scientific knowledge? Part One sets the context. Chapter One provides a brief historical account of nineteenth-century economic botany and the Museum. Chapter Two offers a critical overview of literatures on Kew and economic botany; on the role of place in the production, circulation, and reception of scientific knowledge; and on the role of the public museum in Victorian science and culture. It also outlines the conceptual framework of the thesis. Chapter Three presents an account of the methodology and sources. Part Two highlights museum practices. Chapters Four to Six are devoted respectively to the practices of ‘exhibition’ (the spatialities, rhetorics, and rationalities of display); ‘instruction’ (the educational uses of museum objects); and ‘supply’ (the circulation of objects). Part Three turns to specific objects and their biographies. Chapters Seven and Eight trace respectively the production, circulation and reception of a totem pole from British Columbia and a timber trophy from Tasmania, to demonstrate how objects acquire diverse meanings in diverse contexts, and how they are used to impart meaning to particular sites. In conclusion, Chapter Nine reflects on the cumulative findings of the thesis and on its potential outcomes, and it looks beyond the thesis to recommend areas for future research and practice
Curating Science in an Age of Empire: Kew's Museum of Economic Botany
No full textThis thesis considers the history and significance of the Museum of Economic Botany at the Royal Botanic Gardens, Kew, focussing especially on the period from its opening in 1847 to the eve of the First World War. Looking specifically at the Museum’s collection of wood specimens and artefacts, it seeks to understand the nature of economic botany during this period, and to evaluate the contribution made to the field by the Kew Museum. Through examination of the Museum’s practices, networks, spaces, and objects, it sets out to address the question: how do museums produce scientific knowledge? Part One sets the context. Chapter One provides a brief historical account of nineteenth-century economic botany and the Museum. Chapter Two offers a critical overview of literatures on Kew and economic botany; on the role of place in the production, circulation, and reception of scientific knowledge; and on the role of the public museum in Victorian science and culture. It also outlines the conceptual framework of the thesis. Chapter Three presents an account of the methodology and sources. Part Two highlights museum practices. Chapters Four to Six are devoted respectively to the practices of ‘exhibition’ (the spatialities, rhetorics, and rationalities of display); ‘instruction’ (the educational uses of museum objects); and ‘supply’ (the circulation of objects). Part Three turns to specific objects and their biographies. Chapters Seven and Eight trace respectively the production, circulation and reception of a totem pole from British Columbia and a timber trophy from Tasmania, to demonstrate how objects acquire diverse meanings in diverse contexts, and how they are used to impart meaning to particular sites. In conclusion, Chapter Nine reflects on the cumulative findings of the thesis and on its potential outcomes, and it looks beyond the thesis to recommend areas for future research and practice
Clostridium difficile: Infection and Immunity
No full textClostridium difficile is a Gram positive pathogen of significant importance in the UK, Europe and the USA. No vaccine has been developed and current treatments are focused on hospital management and the use of antibiotics. The disease is spread in hospitals in the spore form and the role of spores in C. difficile infecton is poorly understood. In this project spores of C. difficile have been characterised. The proteins from the outermost layers of the spore were identified and the genes cloned. Three of these surface proteins have unique enzymatic properties that maybe important for symptoms of disease. The ability of C. difficile spores to adhere to intestinal cells was found to be far greater than with live cells and through this we have identified that the spore may play an important role in colonisation. The regulation of spore coat gene expression during sporulation was also examined and temporal phases of genes expression identified. A major part of this project was to develop a mucosal vaccine to C. difficile. The approach used was to clone the C-terminus of toxin A onto the surface of Bacillus subtilis spores and use these recombinant spores to immunise mice and hamsters. We found that oral delivery of these spores conferred 75% protection to C. difficile infection in a hamster model of infection. Further, parenteral immunisation of the same antigens (toxin A and B) failed to generate mucosal responses and this showed that mucosal immunisation is critical for good protection. Finally, we found that antibodies to the C-terminus of toxin A were cross reactive to the C-terminus of toxin B. This showed that mucosal delivery of just the C-terminus of toxin A is sufficient to confer protection in an animal model of infection. The outcome of this work is that we have shown the parameters for successful immunisation and vaccination against C. difficile
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