Purine and pyrimidine bases as growth substances for lactic acid bacteria

In 1936 Richardson (1) showed that uracil was essential for the anaerobic growth of Staphylococcus aureus, but not for aerobic growth of the same organism. Of five strains tested three required uracil, while one required both guanine and uracil for growth. Thymine or cytosine did not replace uracil for this organism. These experiments suggested that hydrolytic products of nucleic acids might become factors limiting growth of various organisms under certain conditions. Bonner and Haagen-Smit (2) in 1939 showed that adenine greatly stimulated growth of leaves under defined conditions, while Möller (3) showed that adenine was required for growth of Streptobacterium plantarum. Pappenheimer and Hottle (4) recently showed that adenine was necessary for the growth of a strain of Group A hemolytic streptococci; it could be replaced by hypoxanthine, guanine, anthine, guanylic acid or adenylic acid. They made the very interesting observation that adenine was unnecessary for growth of this organism if the carbon dioxide tension was maintained at a sufficiently high level

‘I don’t make out how important it is or anything’: identity and identity formation by part-time higher education students in an English further education college.

Policymakers in England have recently, in common with other Anglophone countries, encouraged the provision of higher education within vocational Further Education Colleges. Policy documents have emphasised the potential contribution of college-based students to widening participation: yet the same students contribute in turn to the difficulties of this provision. This article draws on a study of part-time higher education students in a college, a group whose perspectives, identities and voices have been particularly neglected by educational research. Respondents’ narratives of non-participation at 18 indicated the range of social and geographical constraints shaping their decisions and their aspirations beyond higher education; whilst they drew on vocational and adult traditions to legitimate college participation, their construction of identity was also shaped by the boundaries between further education and the university. These distinctive processes illustrate both possibilities and constraints for future higher education provision within collegesN/

'Bridging' the gap between VET and higher education: permeability or perpetuation?

Demands for admission to higher education from vocational routes are widespread across Eu-rope but take different forms, depending on the recognition of tertiary VET or whether sharp-er distinctions between VET and higher education exist. In England, alongside policies pro-moting more employer-responsive tertiary provision, opportunities for ‘bridging’ from voca-tional routes to general university education, and vice versa, have been discussed. The study reported here examined four cases of existing provision supporting transitions into higher edu-cation, potential sites of practices supporting bridging across pathways. Each case provided valued support for progression to higher levels of study; yet these practices focused on exist-ing routes rather than transitions between more academic or vocationally-oriented sites. It is suggested, therefore, that the explicit denotation of separate tertiary provision may be more likely to constrain ‘bridging’ provision than for the latter to help students move beyond their existing route into substantially different forms of higher education.The paper draws on a study funded by the Gatsby Charitable Foundation GAT3398/J

Beyond comparative institutional analysis: a workplace turn in English TVET

Vocational education analyses often compare national patterns seen to favour industry-based training, state schooling or personal investment in skills acquisition: these are increasingly offered as ‘templates’ to new and established industrial economies. Institutionalist scholarship has correspondingly foregrounded skill formation as key to national policy differences; in particular historical institutionalism has focused on the role of labour market and state actors in negotiating and contesting arrangements for skill formation. Whilst paying relatively little direct attention to educational practice, these approaches provide theoretical tools to understand policy differences and to identify possibilities, limitations and strategies for change. This paper draws on their application in England, where apprenticeship and technical education reforms are periodically represented as relocating skills formation to the point of production on the model of collectivist systems: case study data is examined for evidence of institutional change strategies within emerging educational practices. Whilst the absence of engaged labour market actors renders the adoption of a substantially different model improbable, contestation over knowledge, control and educational roles is nevertheless evident, indicating the deployment of strategies for significant change. Their outcomes will determine the availability of transitions, with a layering of selective opportunities threatening to diminish the opportunities available to others.N/

The Reverse Cuthill-McKee Algorithm in Distributed-Memory

Ordering vertices of a graph is key to minimize fill-in and data structure size in sparse direct solvers, maximize locality in iterative solvers, and improve performance in graph algorithms. Except for naturally parallelizable ordering methods such as nested dissection, many important ordering methods have not been efficiently mapped to distributed-memory architectures. In this paper, we present the first-ever distributed-memory implementation of the reverse Cuthill-McKee (RCM) algorithm for reducing the profile of a sparse matrix. Our parallelization uses a two-dimensional sparse matrix decomposition. We achieve high performance by decomposing the problem into a small number of primitives and utilizing optimized implementations of these primitives. Our implementation shows strong scaling up to 1024 cores for smaller matrices and up to 4096 cores for larger matrices

An alternative audio web browsing solution: viewing web documents through a tree structural approach

This thesis examines methods to aid in the non-visual browsing of web based documcnts, primarily using synthetic speech output. The serial nature of speech ensures that it is a difficult medium in which to browse documents. Much of the structure implied in the visual appearance of the content is not available through specch. Only a narrow region in the content is perceivable at any given time, and it can bc difficult to navigate to the important segments of the document. This is in contrast to visual interaction, where cues such as changcs in font or colour establish contextual changes in the content and guide the user accordingly. A number of browsing/navigation strategies are presented to offset these problems. These are implemented through WebTree. This is a highly customisable web browser which rcnders documents through a dynamically expandable tree structural view. This mirrors the arrangement of mark-up elements in the source file. Contextual information about each element is provided as appropriate. By expanding and collapsing individual tree elements, thc user decides how much of the content is rendered at any given time. The user can also dctermine whether a certain element is automatically expanded in the rendcring when cncountercd, or whether it appcars in the rendering at all, effectively allowing for the easy gencration of alternative document views. To speed up navigation the user can move through the document based on the element of their choice. Specialiscd element search functions are also available. Additional navigational functionality is provided to deal with the specific requirements of or elements. The thesis reviews different methods previously employed to offset problems with auditory interfaces and compares these with WebTree. Initial user tests and evaluations of WebTrec are prescnted, which show that the approaches taken provide a viable solution, particularly for thc browsing of large or complex wcb-bascd documcnts, by blind users