The degradation of starch by the oral streptococci.

A thesis submitted to the Faculty or Science, University of the Witwatersrand Johannesburg, in fulfilment of the requirements for the degree of Doctor of Philosophy.Two carbohydrates predominate in modern diets namely sucrose and starch. They are metabolized by oral microorganisms to products implicated in dental caries. The influence of sucrose and its metabolites is well documented but starches have received less attention. This study investigated the secretion of starch hydrolysing enzymes by oral streptococci and the production of sugars, acids and polysaccharides from the two ccmponents of starch, amylose and amylopectin. ( Abbreviation abstract )AC201

A novel fluorescent tracer for real-time tracing of clay transport over soil surfaces

Clay is an important vector for the transport of pollutants in the environment, including nutrients, pesticides and metals; therefore, the fate of many chemicals in soil systems is closely linked to that of clay. Understanding the mechanisms responsible for clay transport has been hampered by the lack of a suitable tracer. Producing a tracer that accurately mimics clay transport is challenging, due to the small size of the particles and their unique physical properties. Here we describe the design and synthesis of a tracer using natural clay particles as a foundation, exploiting the natural ability of clay to sorb molecules to coat the clay with a thin layer of fluorophore. Application of the tracer has been demonstrated through the collection of real-time images of the tracer moving over the surface of a soil box during a rainfall event. These images allow, for the first time, clay to be tracked spatially and temporally without need to remove soil for analysis, thus resulting in minimal experimental artefacts. Custom written software has been used to extract high resolution data describing tracer movement and extent throughout the experiment

AccessRI

AccessRI, a studio team comprised of ten graduate students in the Department of Urban Affairs and Planning at Hunter College, was commissioned by New York State Senator José M. Serrano to identify and provide strategies to address residents’ concerns regarding the quality of life on Roosevelt Island. Roosevelt Island, located between Manhattan and Queens in the East River, is an exceptional place within the varied fabric of New York City. The island provides its residents with an existence apart from the typical hassles associated with urban life, yet its proximity to the rest of the city allows residents to partake in countless amenities. Not only does the island possess a unique geographic location, but its history as a master-planned community has helped to create its distinct character, while simultaneously creating many challenges. Roosevelt Island was virtually abandoned after decades of service as a place for New York’s sick and infirmed. The city, under the Lindsay administration, embarked on an ambitious redevelopment plan. The master plan designed by architects Philip Johnson and John Burgee in 1969, utilized the island’s exceptional views and established a framework for an idealized, “auto-free,” mixed-use development. The development scheme included low and moderate-income housing, a parking garage, the preservation of six historic structures, abundant public spaces and a commercial corridor. The original master plan successfully established a distinctive community that enjoys some of the finest views and greatest amounts of open space that the city has to offer. Yet despite these advantages, the current residents of the island are struggling with a myriad of issues that range from problems caused by aging and neglected infrastructure to demographic and social changes resulting from an influx of residents moving into newly built or renovated residential developments. These concerns are coupled with residents’ perceptions of inadequate governance, that result in the feeling that their concerns are ignored and will never be addressed. Through initial investigation, AccessRI found that the best way to assist residents in improving their quality of life would be to improve access to the facilities and services necessary for well-being