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  • Author or Editor: D.F. Cox x
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Three trials, beginning June, July, and September 1991, examined the breakdown of photodegradable plastic bags. The plastic contained a light-sensitive compound dissolved in the polymer to hasten degradation. The bags were placed in east-west rows on bare ground. Other factors studied included turning the bags over either every 3 or 7 days and either filling the bags with fresh grass clippings or leaving them empty. Strength loss was determined with a hand-held puncture tester. Strength increased initially by 36%, 32%, and 63% in the three trials, respectively. The bags took 33, 35, and 64 days to reach brittleness (puncture strength of 180 g) in the three trials, respectively. Once degradation began, all trials showed similar rates of decline. However, the degradation began 7 days after exposure in the first two trials, but not until 14 days after exposure in the September trial. The addition of grass clippings to the bags increased the initial strength and delayed the onset of degradation. Turning the bags every 3 days rather than every 7 did not affect degradation.

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BioBLAST is a NASA-funded multimedia curriculum supplement, targeted to enrich high school biology classes. It is modeled after the CELSS scenario and currently is being developed by the Classroom of the Future at Wheeling Jesuit College. Through innovative applications of educational technologies and interactions with active researchers in life sciences based at the various NASA centers and by incorporating alternative assessment measures, the BioBLAST project seeks to improve student learning and assist biology teachers. The studentsed life-support system, which uses biological processes to supply astronauts with recycled food, water, and oxygen. The students will be encouraged to formulate hypotheses, devise hands-on experiments to investigate key processes, and use computer simulations to investigate what systems are required to achieve stability of these life-support systems in a simulated lunar base. To succeed in their mission, students will learn basic principles in plant physiology, microbiology, human physiology, nutrition, and the interdependence of systems, and the impact of physical constraints such as temperature, light, and water availability on biological system functioning. BioBLAST will be supported by extensive interactive CD-ROM-based materials and World Wide Web and other internet resources, together with intelligent tutor, frequently asked question lists, and mentor networks that will include the ability to contact NASA and other scientists on-line. An early version of this software will be prototyped to selected schools throughout the United States in Fall 1996.

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Sap nitrate was determined with the ion-selective electrodes, HACH combination nitrate electrode, and the CARDY nitrate meter on pepper petioles over five sample dates (n = 160). The electrode values were compared to the Cd reduction method performed on a Lachat automated ion analyzer with flow injection analysis. Thirty petioles were collected from plots of each of several N rate studies and the sap expressed by a hand-held garlic press. Correlation among the techniques were similar (r > 0.9), but the CARDY meter constantly read 100 to 175 ppm higher than the HACH. Across all dates the standard deviation of the difference, compared with the Cd reduction, for the HACH = 16 ppm, while for the CARDY it was 50. While the CARDY meter is easier to use and has fewer steps, the HACH electrode values were closer to the true readings and less erratic. One must use care when interpreting nitrate sufficiency value ranges with different quick-test techniques.

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Wireless sensor networks (WSNs) transmit sensor data and control signals over long distances without the need for expensive infrastructure, allowing WSNs to add value to existing irrigation systems since they provide the grower with direct feedback on the water needs of the crop. We implemented WSNs in nine commercial horticulture operations. We provide an overview of the integration of sensors with hardware and software to form WSNs that can monitor and control irrigation water applications based on one of two approaches: 1) “set-point control” based on substrate moisture measurements or 2) “model-based control” that applied species-specific irrigation in response to transpiration estimates. We summarize the economic benefits, current and future challenges, and support issues we currently face for scaling WSNs to entire production sites. The series of papers that follow either directly describe or refer the reader to descriptions of the findings we have made to date. Together, they illustrate that WSNs have been successfully implemented in horticultural operations to greatly reduce water use, with direct economic benefits to growers.

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