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101.
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Elisée Ouédraogo Leo Stroosnijder Abdoulaye Mando Lijbert Brussaard Robert Zougmoré 《Nutrient Cycling in Agroecosystems》2007,77(3):245-256
A field experiment was conducted in Gampela (Burkina Faso) in 2000 and 2001 to assess the impact of organic and mineral sources
of nutrients and combinations thereof in optimising crop production in till and no-till systems and to assess the economic
benefit of these options. The study showed that under conditions of rainfall deficiency, the use of a single organic resource
at an equivalent dose of 40 kg N ha−1 better secured crop yield than the application of an equivalent amount as urea-N, while a combination of organic resources
and fertiliser was better in increasing crop yield than the application of the same N amount in the form of urea. In a year
of rainfall deficiency, a mix of organic resources and fertiliser in both till and no-till systems increased crop water use
efficiency, with the result that the farmer was able to purchase only half of the normal quantity of N fertiliser to obtain
a higher yield that he would have done when all of the N was supplied in the form of urea. Under conditions where soil N is
deficient, an economic benefit was achieved when urea was combined with easily decomposable organic material (e.g. sheep dung);
mixing the urea at a dose of 40 kg N ha−1 with maize straw was not sufficient in alleviating the negative interaction due to the enhanced N immobilisation. The results
demonstrate that the use of N fertiliser alone was risky and that a higher yield, with the accompanying economic benefit,
was scarcely achieved under the prevailing rainfall conditions. The application of soil and water conservation measures can
contribute greatly to increasing the economic benefit of mineral, organic or combined organic and mineral-derived nutrient
application under semi-arid conditions. 相似文献
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P. W. Griffiths M. di Leo P. Cartwright P. C. Eames P. Yianoulis G. Leftheriotis B. Norton 《Solar Energy》1998,63(4):243-249
An indium-based seal augmented with an adhesive, developed to maintain a vacuum between two sheets of glass, avoids the high temperatures required to produce a seal in evacuated glazings to date. An experimentally-validated three-dimensional transient model has been used to predict heat transfer for an indium/adhesive sealed 1 m2 area evacuated window with a highly insulating frame. An overall heat loss coefficient of 0.9 W m−2 K−1, with a midplane value of 0.36 W m−2 K−1, can be achieved with 0.72 visible transmittance for two 6 mm panes separated by 0.2 mm diameter pillars 40 mm apart. The conduction through a 3 mm edge-seal was 1.14 W m−2 K−1. Detailed three-dimensional isothermal contour plots through the system are presented. 相似文献
106.
Adams Gerald R.; Ryan Bruce A.; Ketsetzis Maria; Keating Leo 《Canadian Metallurgical Quarterly》2000,14(2):237
This study examined the associations among family processes (cohesion, control, and conflict), school-focused parent–child interactions (support and pressure about achievement), and the child's own characteristics (assertiveness, frustration tolerance, intellectual effectiveness, and self-esteem) as correlates of rule compliance and peer sociability in the classroom. The sample consisted of 161 Grade 4 and 151 Grade 7 children. Family processes and parent-child interactions about school issues were associated with children's personal characteristics, which, in turn, predicted children's rule compliance and peer sociability. Some differences were found between the 4th- and 7th-grade samples; however, many variables consistently predicted the same outcomes across grades. (PsycINFO Database Record (c) 2010 APA, all rights reserved) 相似文献
107.
Concentrations of ergosterol as low as 1.2 mM are effective in satisfying the essential high specificity microrequirement
for C5,6 unsaturated sterol in yeast. In a sterol auxotroph supplemented with saturated sterol (cholestanol), aqueous extracts
of yeast provide a growth factor that eliminates the ergosterol microrequirement. The factor is easily differentiated from
ergosterol by solubility, thermostability, and thin layer and liquid chromatography and is functional at levels equivalent
to those of vitamins, hormones and pheromones. 相似文献
108.
Cerri G. De Leo R. Primiani V.M. Russo P. 《IEEE transactions on instrumentation and measurement》2008,57(2):242-247
This paper presents two test benches for the characterization of a plasma column used as a radiating element. In particular, the main parameters to be quantified are the efficiency of the plasma antenna, the turn-on time of the column, and the conductivity of the plasma. The first two parameters are evaluated by measuring the field radiated by the plasma antenna compared with that of an equivalent copper antenna. For the conductivity, a reflectometric technique is used, wherein the plasma column is inserted inside a waveguide. The accuracy of the method is limited by the ill-conditioned relationship between the reflection coefficient and the plasma conductivity; nevertheless, it is sufficient to subdivide the range of the conductivity values into three regions (i.e., low, medium, and high conductivities) to determine the best operating conditions of the antenna. 相似文献
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