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961.
Sustainable development and technology 总被引:2,自引:0,他引:2
Amin U. Sarkar 《The Environmentalist》1997,17(2):97-102
962.
Bioabsorbable soy protein plastic composites: Effect of polyphosphate fillers on water absorption and mechanical properties 总被引:7,自引:0,他引:7
The use of synthetic and natural bioabsorbable plastics has been severely limited due to their low stiffness and strength
properties as well as their strong tendency to absorb moisture. This research focused on the development of bioabsorbable
polyphosphate filler/soy protein plastic composites with enhanced stiffness, strength, and water resistance. Bioabsorbable
polyphosphate fillers, biodegradable soy protein isolate, plasticizer, and adhesion promoter were homogenized and compression-molded.
Physical, mechanical, and water absorption testing was performed on the molded specimens. Results showed improvements in stiffness,
strength, and water resistance with increasing polyphosphate filler content up to 20% by weight. Application of a coupling
agent produced further mechanical property enhancements and a dramatic improvement in water resistance, interpreted by an
interfacial chemical bonding model. Examination of the fracture surfaces of the materials revealed that the addition of the
polyphosphate fillers changed the failure mode from brittle to pseudo-ductile. These results suggest that these materials
are suitable for many load-bearing applications in both humid and dry environments where current soy protein plastics are
not usable. 相似文献
963.
ABSTRACT: Past historical evidence indicates that droughts have had great impacts on human life. Drought (or scarcity of water) is assessed based on two key factors, namely, the estimated water demand, and the expected water supply. The formulation of these key factors for a region largely depends on the agro-climatic and economic conditions. Consideration of one such key factor is the relationship between the crop yield and water deficit in the assessment and prediction of agricultural droughts. The varying nature of this relationship from crop to crop adds to the complexity of agricultural drought analysis. To overcome this difficulty in analyzing agricultural droughts of a region, it is adequate to consider and place emphasis on a single crop (i.e., an index crop) grown homogeneously over the major area of the region. From one year to another year, the pattern of water requirement during the growing season of an index crop is rather stationary, and the water supply in arid and semi-arid area is mainly from seasonal random precipitation. In a region, grain yield of the index crop and, in turn, assessment of the severity of drought can reasonably be predicted as a function of the time of crop sowing and the distribution of rainfall, provided that temporal and spatial effects of other contributing factors (crop variety, soil fertility status, crop disease, pest control, cultivation practices etc.) on grain yield are considered to be uniformly distributed (i.e., stable). A predictive method of assessing agricultural droughts in an arid area of western India is presented. The major crop (Pearl Millet) of this region is grown from. July through September. The formulation of the proposed predictive method inherently implies that the grain yield of the main crop is a reliable indicator of agricultural drought. In the development of this predictive relationship (i.e., a regression type model) a number of potential yet simple variables affecting the grain yield in the region were investigated. The soil moisture index, although generally considered significant compared to the simple variables, has been found to account for insignificant variation in the grain yield. Results of our investigations suggest that it would be advisable to exclude the soil moisture index variable from the model. The proposed regression model can be used in the prediction of grain yield of the main crop several months ahead of crop harvesting operations and, in turn, the assessment of agricultural drought severity as mild, moderate, or severe. Such an assessment is expected to be helpful to planners for arranging appropriate measures to effectively combat agricultural drought situations. 相似文献
964.
Davies IM Minchin A Bauer B Harding MJ Wells DE 《Journal of environmental monitoring : JEM》1999,1(3):233-238
The disruption of the endocrine systems of gastropod molluscs and consequential physiological changes (imposex and intersex) are used as biomarkers for environmental contamination by tributyltin compounds. The first international laboratory performance study on the determination of imposex and intersex in neogastropod molluscs, Nucella lapillus and Littorina littorea has been undertaken by the QUASIMEME (Quality Assurance of Information for Marine Environmental Monitoring in Europe) project. Samples of live gastropods were distributed and participants were asked to record shell height and sex, together with penis length and vas deferens sequence stage (VDS) in Nucella or the intersex stage (IS) and prostate length in Littorina. Calculations were made of vas deferens sequence index (VDSI) and the relative penis size index (RPSI) in Nucella and of intersex stage index (ISI) and the average female prostate length (FPrL) in Littorina. Thirteen (87%) of the 15 participating laboratories returned data. The remaining two laboratories asked to participate in later exercises. For Nucella, seven laboratories reported sex ratios significantly different from the reference laboratory data. Differences in penis length measurements between laboratories were largely random, although there were indications of systematic errors affecting the data from three laboratories. Seven laboratories reported satisfactory data (Z-score magnitude of Z < 2) for VDSI. The inclusion of a high proportion of sub-adults in the Nucella samples may have made separation of the sexes more difficult than in mature adults. The sub-adults will have had smaller pene than mature adults in the same population, and therefore any errors (random or systematic) in the measurement of penis length or observation of reproductive organs would have a potentially greater impact on the final reported values of the summary imposex indices. The Littorina sample did not show a high degree of intersex (ISI = 0.41). The laboratories could determine the sex of Littorina reliably and only one laboratory reported data significantly different from the reference laboratory. All except two laboratories reported satisfactory data for ISI. 相似文献
965.
966.
967.
968.
969.
970.
The Influence of Atmospheric N Deposition on Nitrous Oxide and Nitric Oxide Fluxes and Soil Ammonium and Nitrate Concentrations 总被引:2,自引:0,他引:2
U. Skiba C. Pitcairn L. Sheppard V. Kennedy D. Fowler 《Water, Air, & Soil Pollution: Focus》2004,4(6):37-43
The deposition of atmospheric N to soils provides sources of available N to the nitrifying and denitrifying microbial community and subsequently influences the rate of NO and N2O emissions from soil. We have investigated the influence of three different sources of enhanced N deposition on NO and N2O emissions 1) elevated NH3 deposition to woodlands downwind of poultry and pig farms, 2) increased wet cloud and occult N deposition to upland forest and moorland and 3) enhanced N deposition to trees as NO
3
–
and NH
4
+
aerosol. Flux measurements of NO and N2O were made using static chambers in the field or intact and repacked soil cores in the laboratory and determination of N2O by gas chromatography and of NO by chemiluminescence analysis. Rates of N deposition to our study sites were derived from modelled estimates of N deposition, NH3 concentrations measured by passive diffusion and inference from measurements of the 210Pb inventory of soils under tree canopies compared with open grassland. NO and N2O emissions and KCl-extractable soil NH
4
+
and NO
3
–
concentrations all increased with increasing N deposition rate. The extent of increase did not appear to be influenced by the chemical form of the N deposited. Systems dominated by dry-deposited NH3 downwind of intensive livestock farms or wet-deposited NH
4
+
and NO
3
–
in the upland regions of Britain resulted in approximately the same linear response. Emissions of NO and N2O from these soils increased with both N deposition and KCl extractable NH
4
+
, but the relationship between NH
4
+
and N deposition (ln NH
4
+
= 0.62 ln Ndeposition + 0.21, r
2 = 0.33, n = 43) was more robust than the relationship between N deposition and soil NO and N2O fluxes. 相似文献