Composite gaskets are compatible with liquid oxygen, resist compression set

Gaskets fabricated by laminating fluorocarbon polymers with fiber glass cloth have a low compression set. Their flexibility is not subject to drastic changes at the temperature of liquid oxygen with which they are used. The fabrication process is controlled so that the fibers are not impregnated with the polymer

Photovoltaic water pumping : a case study in Kwazulu

This is the first thorough evaluation of the viability and appropriateness of photovoltaic (PV) water pumping in South Africa. It is a case study of the operation of a PV water pumping system installed in a rural community vegetable garden in KwaZulu. The system comprised a 574 WP array, DC power maximizer, DC motor and a Mono (positive displacement) pump. The pump delivered an average of 15 m3 I day over a static head of 12.5 metres for a Standard Solar Day of 5 kWh/m2/d. Three facets were considered: technical, economic, and social. · For the technical evaluation the operation of the whole system as well as that of each component under various conditions were monitored in the field using a data logger. The economic evaluation compared the Life Cycle Costs of PV water pumping with those of diesel, petrol, and electric pumps. The social evaluation was based on three sets of interviews over a period of five years ranging from before the introduction of the pump to four years afterwards. The following are the most important conclusions. Technical: the system Daily Energy Efficiency was 2.22%. This is low in comparison with values given in Halcrow's authoritative report of 2.35% for their average systems and 3.28% for their best systems. The reason for this was the low efficiency of the Mono Pump: 39% in comparison with 41.5% for Halcrow's average systems and 59% for their best. This was because the head of 12.5 metres at Sondela was not ideal for the Mono Pump which is designed for 45 metres. All the low-cost PV pumping systems available in South Africa, however, use positive displacement pumps and are thus inefficient at low heads. But because PV pumps are more competitive economically at low heads and low flow rates, it is important that an efficient pump for these applications is designed. Submersible centrifugal pumps should be considered. · Economics: the applicability of various assumptions to developing areas has been thoroughly evaluated. This has laid U1e groundwork for a accurate computer program which would accurately compare the Life Cycle Costs of PV, diesel, petrol and electric pumps under a range of conditions. Connecting to the grid has many advantages and should be considered first. However, the costs of the normal tariff are affected strongly by the site and this option is out of the question for more remote sites. PV pumps are at the moment competitive with diesel pumps at only low hydraulic heads (around 40 m4/day). However, if a PV pump which was efficient at low heads were designed and if the path of the sun were physically tracked, then PV pumps could possibly be competitive up to hydraulic heads of 1400 m4/day. Social: the study showed that installing pumps in community vegetable gardens can almost double the productivity of the gardeners' time. The gardeners interviewed indicated that, because of the many advantages of PV pumps, they would prefer them to diesel pumps if their amortized costs were up to twice those of the diesel pump., But few, if any, community gardens would be able to raise the capital required for a PV pump. For this reason, a scheme similar to that just introduced by ESKOM could make a crucial difference to the marketability of PV pumps: ESKOM will buy and maintain the pump recovering the costs from the user at a fixed monthly rate stipulated before installation. This scheme obviates the two major barriers to the sale of PV pumps: I) high initial cost and ii) the risk of damage or loss of expensive equipment due to floods, theft, or vandalism

Technical assessment for quality control of resins

Survey visits to companies involved in the manufacture and use of graphite-epoxy prepregs were conducted to assess the factors which may contribute to variability in the mechanical properties of graphite-epoxy composites. In particular, the purpose was to assess the contributions of the epoxy resins to variability. Companies represented three segments of the composites industry - aircraft manufacturers, prepreg manufacturers, and epoxy resin manufacturers. Several important sources of performance variability were identified from among the complete spectrum of potential sources which ranged from raw materials to composite test data interpretation

Quality of Life of Zambians Living with HIV & AIDS

Introduction: The HIV/AIDS disease has changed individual lifestyles and quality of life, as the HIV disease progresses, quality of life deteriorates. It is vital that the quality of life of PLWHA is assessed regularly so that they are given holistic care that is able to ameliorate the symptoms of ill health and improve their quality of life.Purpose: The purpose of this study was to determine the quality of life of Zambians living with HIV/AIDSMethod: The study used a cross-sectional descriptive design. This study was conducted in both rural and urban antiretroviral clinics in Zambia on 160 PLWHAof various HIV ranging from asymptomatic to full blown AIDS. Three scales, “Zambian WHOQOL-HIV Scale” (á = .896); “Zambian WHOHIV SRPB Scale” (á = .699); “Zambian WHOHIV medication dependence Scale” (á = .801); derived from the WHOQOL-HIV were used to assess quality of life.Results: A third of the participants reported very high medication dependence (32.5%). Two thirds of the participants (66%) had good or very good spirituality. Majority of the participants (82.2%) had good or very good quality of life. The results show that the quality of life, medication dependence and spirituality for the Zambian sample were all above average. Quality of life had significant positive relationships with all of its domains and a significant positive relationship with spirituality.Conclusion: Because little investigation has been done on quality of life in HIV/AIDS in developing countries such as Zambia, the current study is a vital step in addressing the issue of quality of life. The finding that quality of life of Zambian people living with HIV/AIDS is above average may mean that thepreventive and health care programs that are being used for education and provision of antiretroviral medication are yielding good results, this progress should be harnessed.Keywords: Quality of Life, HIV & AIDS, Zambia

The development of structural adhesives systems suitable for use with liquid oxygen Annual summary report, 1 Jul. 1963 - 30 Jun. 1964

Fluorinated, chlorinated, and halogenated polymer adhesives prepared and tested for compatibility with liquid oxyge

The magnetic-resonance force microscope: a new tool for high-resolution, 3-D, subsurface scanned probe imaging

The magnetic-resonance force microscope (MRFM) is a novel scanned probe instrument which combines the three-dimensional (3-D) imaging capabilities of magnetic-resonance imaging with the high sensitivity and resolution of atomic-force microscopy. It will enable nondestructive, chemical-specific, high-resolution microscopic studies and imaging of subsurface properties of a broad range of materials. The MRFM has demonstrated its utility for study of microscopic ferromagnets, and it will enable microscopic understanding of the nonequilibrium spin polarization resulting from spin injection. Microscopic MRFM studies will provide unprecedented insight into the physics of magnetic and spin-based materials. We will describe the principles and the state-of-the-art in magnetic-resonance force microscopy, discuss existing cryogenic MRFM instruments incorporating high-Q, single-crystal microresonators with integral submicrometer probe magnets, and indicate future directions for enhancing MRFM instrument capabilities

Risk and management of ocular bleeding associated with oral anticoagulants

Deep vein thrombosis, pulmonary embolism, ischemic stroke and myocardial infarction are the major thromboembolic diseases which affect millions of North Americans. Most of these patients are managed long term with oral anticoagulants that can increase the risk of bleeding including ocular hemorrhages. As primary eye care providers, optometrists do encounter patients presenting with ocular bleeding secondary to oral anticoagulants. This article provides an overview and update of oral anticoagulants, and discusses ways to manage ocular bleeding associated with oral anticoagulants via two clinical cases. Interruption of anticoagulation temporarily increases thromboembolic risk, and continuing anticoagulation increases the risk of bleeding, both scenarios adversely affect patient’s overall health. Eye care providers must work closely with primary care provider and/or anticoagulation team to come up with the best decision on an individual patient basis with respect to each ocular bleeding occurrence

Power Transmission Control using Distributed Max-Flow

Existing maximum flow algorithms use one processor for all calculations or one processor per vertex in a graph to calculate the maximum possible flow through a graph\u27s vertices. This is not suitable for practical implementation. We extend the max-flow work of Goldberg and Tarjan to a distributed algorithm to calculate maximum flow where the number of processors is less than the number of vertices in a graph. Our algorithm is applied to maximizing electrical flow within a power network where the power grid is modeled as a graph. Error detection measures are included to detect problems in a simulated power network. We show that our algorithm is successful in executing quickly enough to prevent catastrophic power outages