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In wetland ecosystems, such as rice fields, methanogenic bacteria (MB) play important roles in global carbon cycling as terminal organic decomposers and in hydrogen cycling as hydrogen consumers, leading to methane production (Jorgensen 1982). In the global atmosphere, concentration of methane has been increasing by about 1% per year (Blake and Rowland 1986; Bouwman 1989; Dlugokensky et al. 1994) and it is considered that 80% is of biological origin (Seiler 1984). The environmental impact of methane on global warming has also been confirmed (Chappellaz et al. 1990). Rice paddy fields contribute to an estimated 10% of the global methane emission (Bouwman 1989; IPCC 1992) and the intensification of paddy cultivation may contribute considerably to the gradual increase of atmospheric methane (Rasmussen and Khalil 1981). From 1970 to 1990, rice production increased by 110% in West Africa (FAO 1970, 1990), as a direct result of encroachment on new lands throughout most of West Africa (Windmeijer and Andriesse 1993; Issaka et al. 1996a, b). In Burkina Faso, about 85% of the rice cultivation areas are lowlands (Sié 1991). In recent years, many studies on methane emission from paddy fields and limited ecological studies on methanogenic populations have been conducted (Schütz et al. 1989; Asakawa and Hayano 1995; Adachi et al. 1996). However, studies on both methane emission and populations of methanogens in African paddy fields are very limited. Garcia et al. (1974) enumerated methanogenic populations in Sénégal rice soils by the most probable number (MPN) method. With the gradual increase in the land area under rice cultivation, more information is needed on methane fluxes, populations, and species of methanogens in paddy fields of West Africa. We reported here the enumeration of methanogenic populations in the soils of lowland paddy fields located in the Sudan and Guinea Savanna zones of Burkina Faso (West Africa) by the MPN method. 相似文献
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酸性染料由于颜色丰富,价格低廉而成为现阶段木材工业常用的染料。木材的染色效果通常与染料的渗透深度和分布均匀性密切相关。为了提高染料的染色效果,同时充分利用丰富的国产速生材,以杉木边材为试材,研究恒温浸渍法、冷热交替法和真空浸注法3种工艺对染料纵向和横向渗透性的影响。结果表明:(1)恒温浸渍法中,横向渗透性随着染液温度升高而增加,纵向渗透性则相反。横向渗透在染液温度为90℃时最大,为0.66~0.94 mm,而纵向渗透在染液温度为28℃时最大,为3.2~4.67 mm。在恒温浸渍中,染料的渗透深度随染色时间的延长呈现出无规则变化;(2)冷热交替法中,染料渗透性介于真空注入与恒温浸渍之间,温度差对横向渗透性的影响远大于对纵向渗透性的影响;相同时间内,交替次数的增加能显著提高染料在横向的渗透性,而纵向渗透性远低于横向渗透性;(3)真空注入中,染料在纵向和横向渗透性均最大,比恒温90℃浸渍2 h提高2.0~3.0倍。 相似文献
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Prosper Bovien 《Journal of pest science》1929,5(5):60-62
Ohne Zusammenfassung 相似文献
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Glazer I Masaphy S Marciano P Bar-Ilan I Holland D Kerem Z Amir R 《Journal of agricultural and food chemistry》2012,60(19):4841-4848
Aqueous extracts of pomegranate peels were assayed in vitro for their antifungal activity against six rot fungi that cause fruit and vegetable decay during storage. The growth rates of Alternaria alternata , Stemphylium botryosum , and Fusarium spp. were significantly inhibited by the extracts. The growth rates were negatively correlated with the levels of total polyphenolic compounds in the extract and particularly with punicalagins, the major ellagitannins in pomegranate peels. Ellagitannins were also found to be the main compounds in the bioactive fractions using bioautograms, and punicalagins were identified as the main bioactive compounds using chromatographic separation. These results suggest that ellagitannins, and more specifically punicalagins, which are the dominant compounds in pomegranate peels, may be used as a control agent of storage diseases and to reduce the use of synthetic fungicides. 相似文献
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