Lepidium meyeniiWalp. （Maca）, a perennial herbaceous plant with narrow distdbution in the Andean region, was cultivated by local residents as early as 1600 B.C. It has high nutritional values and multiple medicinal ...Lepidium meyeniiWalp. （Maca）, a perennial herbaceous plant with narrow distdbution in the Andean region, was cultivated by local residents as early as 1600 B.C. It has high nutritional values and multiple medicinal effects. In recent years the plant source of Maca has been greatly scarce since Maca products are increasingly becoming popular in the world. This makes the study urgent on the identification and quality evaluation of Maca materials. In present work, four Mace samples of different origins or handlings and three other natural plants, including radish, odental ginseng and American ginseng, were investigated. Their essential oils （steam distillates） of the hypogeal parts were weighed and analyzed by GC/MS. Through comparison of the characteristics of their chromatograms, it was found that the essential oil of Maca had unique GC/MS behaviors, and the characteristic peaks produced by the major essential oil components （Phenylacetonitrile, Benzaldehyde, 3-Methoxyphenylacetonitrile, etc） were distinct. Furthermore, the chromatograms of several Maca samples showed a similar qualitative pattern except for some differences in the quantitative composition, and the percentage of total essential oils in the samples varied from 0.88 % to 1.59 %. These behaviors and technologies can be applied to the identification of Maca materials in the markets and be a supplement to assess the quality of Maca matedals.展开更多
This paper analyzes the corn production cost in China, the U.S. and Brazil from 1997 to 2014. According to the results,（1） corn production cost in China is the highest among these three countries;（2） the rapid gro...This paper analyzes the corn production cost in China, the U.S. and Brazil from 1997 to 2014. According to the results,（1） corn production cost in China is the highest among these three countries;（2） the rapid growth of labor cost and land cost is the major factor that promotes the increase of total corn production cost in China;（3） the level of agricultural mechanization in China has been gradually improving, and the gap between agricultural mechanization levels in China and other two countries is constantly narrowing;（4） differing from the U.S. and Brazil,China exhibits a ＂high input, low output＂ agricultural production mode. Based on the above analyses, corresponding suggestions have been presented to reduce corn production cost in China.展开更多
How to teach creative writing at school？ If the procedures inherited from writing workshops have undoubtedly proved efficient as regards text production, it is also clear that in Switzerland, as elsewhere in Europe a...How to teach creative writing at school？ If the procedures inherited from writing workshops have undoubtedly proved efficient as regards text production, it is also clear that in Switzerland, as elsewhere in Europe and in the Anglo-Saxon world, the present use of evaluation grids with their numerous items prevents secondary school pupils from adopting the stance of an author. Why？ Simply because the most innovative and ＂literary＂ texts are always surprising： They are ＂different＂, and could not possibly result from writing guidelines devised only to facilitate a mechanical evaluation itself conceived for the sake of some illusory objectivity... Now, in our postmodern age with its rejection of models, what is more difficult than assessing the quality of creative writing？ In our approach, we suggest restoring confidence in the teacher, an expert reader if any, who, acting as a publisher, dramaturge, or mere aesthete, knows how to take his pupils＇ texts seriously, acknowledge their aesthetic value, and look at apparent clumsiness as a possible promise of innovation. The teaching of creative writing lies both in this specific reception of budding works and in the teacher＇s performative utterances that, then and there, make the pupil a writer.展开更多
文摘Lepidium meyeniiWalp. （Maca）, a perennial herbaceous plant with narrow distdbution in the Andean region, was cultivated by local residents as early as 1600 B.C. It has high nutritional values and multiple medicinal effects. In recent years the plant source of Maca has been greatly scarce since Maca products are increasingly becoming popular in the world. This makes the study urgent on the identification and quality evaluation of Maca materials. In present work, four Mace samples of different origins or handlings and three other natural plants, including radish, odental ginseng and American ginseng, were investigated. Their essential oils （steam distillates） of the hypogeal parts were weighed and analyzed by GC/MS. Through comparison of the characteristics of their chromatograms, it was found that the essential oil of Maca had unique GC/MS behaviors, and the characteristic peaks produced by the major essential oil components （Phenylacetonitrile, Benzaldehyde, 3-Methoxyphenylacetonitrile, etc） were distinct. Furthermore, the chromatograms of several Maca samples showed a similar qualitative pattern except for some differences in the quantitative composition, and the percentage of total essential oils in the samples varied from 0.88 % to 1.59 %. These behaviors and technologies can be applied to the identification of Maca materials in the markets and be a supplement to assess the quality of Maca matedals.
文摘This paper analyzes the corn production cost in China, the U.S. and Brazil from 1997 to 2014. According to the results,（1） corn production cost in China is the highest among these three countries;（2） the rapid growth of labor cost and land cost is the major factor that promotes the increase of total corn production cost in China;（3） the level of agricultural mechanization in China has been gradually improving, and the gap between agricultural mechanization levels in China and other two countries is constantly narrowing;（4） differing from the U.S. and Brazil,China exhibits a ＂high input, low output＂ agricultural production mode. Based on the above analyses, corresponding suggestions have been presented to reduce corn production cost in China.
文摘How to teach creative writing at school？ If the procedures inherited from writing workshops have undoubtedly proved efficient as regards text production, it is also clear that in Switzerland, as elsewhere in Europe and in the Anglo-Saxon world, the present use of evaluation grids with their numerous items prevents secondary school pupils from adopting the stance of an author. Why？ Simply because the most innovative and ＂literary＂ texts are always surprising： They are ＂different＂, and could not possibly result from writing guidelines devised only to facilitate a mechanical evaluation itself conceived for the sake of some illusory objectivity... Now, in our postmodern age with its rejection of models, what is more difficult than assessing the quality of creative writing？ In our approach, we suggest restoring confidence in the teacher, an expert reader if any, who, acting as a publisher, dramaturge, or mere aesthete, knows how to take his pupils＇ texts seriously, acknowledge their aesthetic value, and look at apparent clumsiness as a possible promise of innovation. The teaching of creative writing lies both in this specific reception of budding works and in the teacher＇s performative utterances that, then and there, make the pupil a writer.
