4 resultados para Step potential well

em Greenwich Academic Literature Archive - UK


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Summary form only given. Currently the vast majority of adhesive materials in electronic products are bonded using convection heating or infra-red as well as UV-curing. These thermal processing steps can take several hours to perform, slowing throughput and contributing a significant portion of the cost of manufacturing. With the demand for lighter, faster, and smaller electronic devices, there is a need for innovative material processing techniques and control methodologies. The increasing demand for smaller and cheaper devices pose engineering challenges in designing a curing systems that minimize the time required between the curing of devices in a production line, allowing access to the components during curing for alignment and testing. Microwave radiation exhibits several favorable characteristics and over the past few years has attracted increased academic and industrial attention as an alternative solution to curing of flip-chip underfills, bumps, glob top and potting cure, structural bonding, die attach, wafer processing, opto-electronics assembly as well as RF-ID tag bonding. Microwave energy fundamentally accelerates the cure kinetics of polymer adhesives. It provides a route to focus heat into the polymer materials penetrating the substrates that typically remain transparent. Therefore microwave energy can be used to minimise the temperature increase in the surrounding materials. The short path between the energy source and the cured material ensures a rapid heating rate and an overall low thermal budget. In this keynote talk, we will review the principles of microwave curing of materials for high density packing. Emphasis will be placed on recent advances within ongoing research in the UK on the realization of "open-oven" cavities, tailored to address existing challenges. Open-ovens do not require positioning of the device into the cavity through a movable door, hence being more suitable for fully automated processing. Further potential advantages of op- - en-oven curing include the possibility for simultaneous fine placement and curing of the device into a larger assembly. These capabilities promise productivity gains by combining assembly, placement and bonding into a single processing step. Moreover, the proposed design allows for selective heating within a large substrate, which can be useful particularly when the latter includes parts sensitive to increased temperatures.

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RATIONALE & OBJECTIVES: The food multimix (FFM)concept states that limited food resources can be combined using scientific knowledge to meet nutrient needs of vulnerable groups at low cost utilizing the ‘nutrient strengths’ of individual or candidate foods in composite recipes within a cultural context. METHODS: The method employed the food-to-food approach for recipe development using traditional food ingredients. Recipes were subjected to proximate and micronutrient analysis and optimized to meet at tleast 40% of recommended daily intakes. End products including breads, porridge and soup were developed. RESULTS: FMM products were employed in a feeding trial among 120 healthy pregnant women in Gauteng, South Africa resulting in improvements in serum iron levels from baseline values of 14.59 (=/-7.67) umol/L and 14.02 (=/-8.13) umol/L for control and intervention groups (p=0.71), to 16.03 (=/-5.67) umol/L and 18.66 (=/-9.41) umol/L (p=0.19). The increases from baseline to post-intervention were however statistically significant within groups. Similarly Mean Cell Volume values improved from baseline as well as serum ferritin and transferritin levels. CONCLUSION: The FMM concept has potential value in feeding programs for vulnerable groups including pregnant and lactating mothers.

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Research This paper outlines some of the key findings from an evaluation of the project and demonstrates that EC funded projects such as this, which seek to promote cross border collaboration and understanding (i.e. across organisational, sectoral and geographical boundaries) offer considerable learning potential – not least about variances in health politics across different communities. However, for this learning to be realised a comprehensive system of knowledge management needs to be an integral part of project planning alongside a system for sustaining embryonic professional networks. The concept of managing relationships was also a key part of the projects success. Executing a project funded by the EU demands the development of complex organisational skills to negotiate all the administrative challenges en route to successful completion and this project in particular relied for its success on the development of social relationships of trust and mutual respect across national, professional and social boundaries. Context A three–year European Commission funded project designed to exchange a wide range of staff (professional semiprofessional and voluntary staff in health and social care) project led by the University of Greenwich (UK) and the Université Catholique de Lille, France was completed this year (February 2008). The project was complex because it involved working in different national contexts, was multi-disciplinary, and demanded the negotiation of multiple boundaries. Theories A mixed method evaluation including written reports gathered immediately after each exchange visit and a post hoc series of individual interviews and focus groups was conducted in order to gain qualitative information (from the participants perspective) on their experiences and to identify any learning gained. Results Analysis of the data provided evidence of learning on a number of levels; personally, inter and intra professionally and organisationally as well as across sectors and also from a project management perspective. The learning crystallised around the extent of the differences noted by the participants between the UK and the French health and social care systems despite geographical proximity, common membership of the EU and many shared challenges in health and social care. The extent of these differences, noted at every level from policy to practice proved a rich source for reflection on organisational philosophies, ways of working, distribution of resources, professional roles and autonomy and professional registration and mobility - in short on health politics at ‘macro’ and ‘micro’ levels.

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A library of 19 cycloruthenated derivatives is constructed by making use of the well-known cyclometalation reaction. Their geometries are modified in a straightforward manner by addition of either mono- or bidentate ligands, such as bipyridine, phenanthroline, 1,2-bis(diphenylphosphanyl)ethane, dimethylphenylphosphane, triphenylphosphane, and 1,3,5-triaza-7-phosphatricyclo[3.3.1.1]decane (PTA) ligands, to cationic cycloruthenated centers. The antitumor properties of the compounds thus obtained are investigated in order to compare them with recently reported ruthenium complexes and cisplatin. IC50 values against mammalian cells (A-172, HCT-116, and RDM-4) are determined for the library compounds and some of them, such as those derived from orthoruthenated phenylpyridine and a bidentate N,N ligand, display activity of the same order of magnitude as cisplatin.