7,901 research outputs found
Two color holographic interferometry for microgravity application
Holographic interferometry is a primary candidate for determining temperature and concentration in crystal growth experiments designed for space. The method measures refractive index changes within the fluid of an experimental test cell resulting from temperature and/or concentration changes. When the refractive index changes are caused by simultaneous temperature and concentration changes, the contributions of the two effects cannot be separated by single wavelength interferometry. By using two wavelengths, however, two independent interferograms can provide the additional independent equation required to determine the two unknowns. There is no other technique available that provides this type of information. The primary objectives of this effort were to experimentally verify the mathematical theory of two color holographic interferometry (TCHI) and to determine the practical value of this technique for space application. In the foregoing study, the theory of TCHI has been tested experimentally over a range of interest for materials processing in space where measurements of temperature and concentration in a solution are required. New techniques were developed and applied to stretch the limits beyond what could be done with existing procedures. The study resulted in the production of one of the most advanced, enhanced sensitivity holographic interferometers in existence. The interferometric measurements made at MSFC represent what is believed to be the most accurate holographic interferometric measurements made in a fluid to date. The tests have provided an understanding of the limitations of the technique in practical use
Market-Oriented Strategies to Improve Household Access to Food: Experience from Sub-Saharan Africa
The objectives of this report are to identify market-oriented strategies to alleviate both chronic and transitory food insecurity, and to examine the interactions between short-run targeting mechanisms and longer-run strategies designed to alleviate the chronic causes of inadequate access to food. The main premise of the report is that sustained improvements in household access to food in Sub-Saharan Africa require the development of more reliable food and input markets that (a) create incentives to adopt cost-reducing investments at various stages in the food system; and (b) offer incentives for rural households to shift from a subsistence-oriented pattern of production and consumption to more productive systems based on specialization and gains from exchange. Sustained productivity growth in most parts of the world has typically entailed some form of structural transformation, which, in the historical development processes of other regions, has been a prerequisite for broad-based and sustained growth in productivity, real incomes and purchasing power throughout society. Structural transformation involves a movement away from subsistence-oriented, household-level production toward an integrated economy based on specialization and exchange. But specialization makes households dependent on the performance of exchange systems. The ability to capture the productivity gains from new technology and specialization thus depends on reducing the risks and uncertainty of market-based exchange, thereby facilitating greater participation in the types of specialized production and consumption patterns involved in the process of structural transformation. Section 3 presents empirical evidence from research conducted in Africa to draw conclusions about how the design of agricultural policies and transfer programs have affected household access to food in both rural and urban areas. Based on the foregoing, section 4 presents the following guidelines for the design of strategies to promote access to food in Africa: (1.) Focus on achieving productivity gains in the food system. (2.) Focus on how food and income transfer programs can be designed to promote the long-run development of the food system- the basis for providing food for most people over the long run in addition to providing food to people in the short run. (3.) Focus on reducing consumer food costs by expanding the range of products available to produce and consume. (4.) Focus on the cost and reliability of food supplies to rural areas as a component of non-farm, livestock, and other income diversification strategies designed to promote access to food over the longer run. (5.) Focus on developing local analytical expertise to help guide food system development.Food Security and Poverty, Downloads July 2008-June 2009: 12,
Enabling Small-Scale Maize Marketing and Processing to Assure Supplies of Low-Cost Staples
Crop Production/Industries, Downloads December 2008 - July 2009: 6,
Diversification as a Strategy: A Research-Based Plan for Arts Organizations to Cultivate New Audiences
Building a more inclusive audience is not a far-fetched idea; system diversification by its very nature is a performance strategy, not a performance goal. Changing audience demographics requires well laid out plans, achievable goals, effective processes, and a total organizational commitment to diversification. This report was created to provide perspectives that inform executive leaders in arts organizations who plan to attract diverse audiences. It highlights nine research-based recommendations for audience diversification. The report is unique in that it layers four approaches that, if used simultaneously, have the potential to both increase the likelihood of success and decrease the amount of time it will take to achieve results by framing audience diversification as a strategy, not a goal
Diversification as a Strategy: A Research-Based Plan to Cultivate New Audiences at the Richmond Symphony
Building a more inclusive audience is not a far-fetched idea; system diversification by its very nature is a performance strategy, not a performance goal. Changing audience demographics requires well laid out plans, achievable goals, effective processes, and a total organizational commitment to diversification. This report was created to provide perspectives that inform executive leaders in arts organizations who plan to attract diverse audiences. It highlights nine research-based recommendations for audience diversification. Our report is unique in that it layers four approaches that, if used simultaneously, have the potential to both increase the likelihood of success and decrease the amount of time it will take to achieve results by framing audience diversification as a strategy, not a goal
Surgical Helmets and SARS Infection
Performance testing of two brands of surgical helmets indicated that their efficiency at in vivo filtration of sub–micrometer-sized particles is inadequate for their use as respirators. These helmets are not marketed for respiratory protection and should not be used alone for protection against severe acute respiratory syndrome when performing aerosol-generating procedures
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Apportionment of primary and secondary organic aerosols in Southern California during the 2005 Study of Organic Aerosols in Riverside (SOAR-1)
Ambient sampling was conducted in Riverside, California during the 2005 Study of Organic Aerosols in Riverside to characterize the composition and sources of organic aerosol using a variety of state-of-the-art instrumentation and source apportionment techniques. The secondary organic aerosol (SOA) mass is estimated by elemental carbon and carbon monoxide tracer methods, water soluble organic carbon content, chemical mass balance of organic molecular markers, and positive matrix factorization of high-resolution aerosol mass spectrometer data. Estimates obtained from each of these methods indicate that the organic fraction in ambient aerosol is overwhelmingly secondary in nature during a period of several weeks with moderate ozone concentrations and that SOA is the single largest component of PM1 aerosol in Riverside. Average SOA/OA contributions of 70−90% were observed during midday periods, whereas minimum SOA contributions of ~45% were observed during peak morning traffic periods. These results are contrary to previous estimates of SOA throughout the Los Angeles Basin which reported that, other than during severe photochemical smog episodes, SOA was lower than primary OA. Possible reasons for these differences are discussed
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