Problems in the physical chemistry of polysaccharides: the structure and solution behaviour of potato amylose

Physical techniques, including rotational viscometry and several ultracentrifugal methods not previously used in these laboratories have been detailed.The viscometric behaviour of the amylose component of potato starch dissolved in aqueous alkaline solution was found to depend on pH and counter-ion concentration. Maximum [π]- values occur- red at a pH of approximately 13 and these were reduced, on the addition of salt, to values below those found in neutral solution. In these solvents, where [π]-values were minimal, the solution behaviour resembled ideal θ-conditions. Changes in [π] were interpreted as changes in the conformation of the amylose molecule due to the ionisation of hydroxyl groups. These effects were confirmed for amylose fractions of varying molecular-weight.The absolute viscosity of solutions of amylose in 0.33M KCl, 0.15M KOH and 1M KOH was found to be dependent on the average shear rate G, between G = 0 -1200 sec⁻¹. Limiting viscosity numbers, [[π], were however, independent of shear rate even for the largest molecular weight samples of amylose.The subfractionation of both total-amylose and linear-amylose has been studied in detail, and the fractional precipitation of amylose from a dimethyl-sulphoxide solution with acetone was found the most efficient method. In the subfractionation of total - amylose, a heterogeneity was evident in some subfractions, and its presence was related to the ß- amylolysis limit. It was shown that this heterogeneity was natural to the polysaccharide, and probably represented branched material.From a study of the properties of subfractions of linear amylose, the polysaccharide was found to behave as a random coil in 0.50M KCl/10⁻²M KOH (an aqueous 9- solvent), 0.15M KCl, and 0.15M KOH. The amylose molecule was in a more expanded form in the latter two solvents. Moreover, there was some evidence for association in neutral aqueous solutions of natural amylose.The concentration dependence of sedimentation coefficient was negligible for amylose dissolved in the above θ-solvent, but increased with solvent power in accord with theory. In addition, the apparent sedimentation coefficient was dependent on forcefield.By fractionating total potato starch, the presence of polysaccharide-material intermediate in structure between linear amylose and highly ramified amylopectin was confirmed. These results suggest that a continuous range in molecular structure may be present in the starch granule. Intermediate material was composed of branched polysaccharides similar to both amylose and amylopectin

Use of computer-aided detection (CAD) tools in screening mammography: a multidisciplinary investigation

We summarise a set of analyses and studies conducted to assess the effects of the use of a computer-aided detection (CAD) tool in breast screening. We have used an interdisciplinary approach that combines: (a) statistical analyses inspired by reliability modelling in engineering; (b) experimental studies of decisions of mammography experts using the tool, interpreted in the light of human factors psychology; and (c) ethnographic observations of the use of the tool both in trial conditions and in everyday screening practice. Our investigations have shown patterns of human behaviour and effects of computer-based advice that would not have been revealed by a standard clinical trial approach. For example, we found that the negligible measured effect of CAD could be explained by a range of effects on experts' decisions, beneficial in some cases and detrimental in others. There is some evidence of the latter effects being due to the experts using the computer tool differently from the intentions of the developers. We integrate insights from the different pieces of evidence and highlight their implications for the design, evaluation and deployment of this sort of computer tool

Mineral Potential of Arctic Canada

Canada is on the threshold of a major new phase in the development of its Arctic resources. The Prudhoe Bay discovery triggered a boom in northern petroleum exploration that is just getting into high gear this year. Mining activity also has greatly expanded in the last few years with some 73 active exploration programs underway and several large new mines just coming into production. The size of these ventures is indicated by ore reserves of two lead-zinc mines to the value of 900 million dollars at Pine Point in southern Northwest Territories, and 1.2 billion dollars at the Anvil property in the southern Yukon Territory. Other properties with very large reserves are currently under development. Approximately 465,000 sq. miles of the 1.5 million square miles of Canada north of the 60th parallel are underlain by sedimentary rocks. A volumetric estimate of petroleum potential on the basis of rather scanty evidence is made at 54 billion barrels. With the current activity in the area it should be possible to improve this estimate considerably in the next 2 or 3 years. The two most promising areas are the Arctic Coastal Plains containing large volumes of young sedimentary rock and large structures, and the Mesozoic Sverdrup Basin also with many potential hydrocarbon traps. The Interior Plains of the mainland and the Arctic lowlands, as well as the fold belts of the Franklinian miogeosyncline indicate lesser potential

Standardisation, Innovation and Implementation of Information Technology

This paper looks at the mutual interplay between information technology (IT) and its environment. Exploring specifically the issues surrounding innovations in the field of corporate IT systems we show that a distinction has to be made between different categories of information technology (IT) systems regarding their introduction, subsequent diffusion, and particularly their corporate usage. We will show that strategic deployment of e-mail will only happen if and when it is no longer considered an infrastructural technology. However, apparently this has rarely happened thus far. Strong relations and dependencies exist between standardiation, innovation and the subsequent implementation of IT systems. We argue that these activities must not be considered separately, especially as standards-based components are playing an increasingly important role in implementation processes. Consequently, the role of the users in, and their influence on, standards setting are addressed as well. The findings and conclusions presented are largely based on a number of interview

The elements of a computational infrastructure for social simulation

Applications of simulation modelling in social science domains are varied and increasingly widespread. The effective deployment of simulation models depends on access to diverse datasets, the use of analysis capabilities, the ability to visualize model outcomes and to capture, share and re-use simulations as evidence in research and policy-making. We describe three applications of e-social science that promote social simulation modelling, data management and visualization. An example is outlined in which the three components are brought together in a transport planning context. We discuss opportunities and benefits for the combination of these and other components into an e-infrastructure for social simulation and review recent progress towards the establishment of such an infrastructure

Towards Detecting Rumours in Social Media

The spread of false rumours during emergencies can jeopardise the well-being of citizens as they are monitoring the stream of news from social media to stay abreast of the latest updates. In this paper, we describe the methodology we have developed within the PHEME project for the collection and sampling of conversational threads, as well as the tool we have developed to facilitate the annotation of these threads so as to identify rumourous ones. We describe the annotation task conducted on threads collected during the 2014 Ferguson unrest and we present and analyse our findings. Our results show that we can collect effectively social media rumours and identify multiple rumours associated with a range of stories that would have been hard to identify by relying on existing techniques that need manual input of rumour-specific keywords