水稻密码全破了     

雷永青 《发现．图形科普》2002,(12):14-16

  相似文献   

竖直埋管地源热泵技术   总被引：3，自引：1，他引：3  

刘冬生  孙友宏 《世界地质》2002,21(4):406-410

竖直埋管地源热泵技术的重点和核心是地下埋管换热器。地下埋管换热器的设计包括：换热器形式和回路形式的选择，地下换热器尺寸设计，水平间距及热短路，管材的选用和换热能力等。地下埋管换热器的施工主要包括：钻孔，下管，注浆、回填和换热器的安装。  相似文献   

人类基因测序为何被提前     

格子 《发现．图形科普》2001,(2):35-37

继2000年6月26日人类基因组”工作框架图”绘制完成后．参与人类基因组计划的6国科学家2月12日共同宣布，经过初步测定和分析，人类基因组共有32亿个碱基对，包含了大约3万到4万个蛋白编码基因。题为《人类基因组的初步测定和分析》的学术论，发表在权威科学刊物《自然》上。据悉，这篇论长达60多页，是人类首次全面介绍人类基因组工作框架图的“基本信息”。  相似文献   

渭北旱原农业生态系统物能转化效率及综合效益评估     

张转放  梁宏儒 《地域研究与开发》1992,11(2):44-47

以渭北旱原合阳县甘井乡为例,对其物能产投关系进行了研究。氮、磷素及能量的转化效率在产量中等(约2550kg/ha)时最高,低产和高产时都下降;水分转化效率与产量呈正相关。根据物能产投关系及其它有关指标,对农业生态经济系统效益进行了综合评估,其结果能客观反映农业生态建设的成就。  相似文献   

计算高能原电子能量损失率的方法     

谢爱根  郭胜利  裴元吉 《南京气象学院学报》2007,30(5):720-722

提出了计算属于同一个能区高能原电子在金属发射体内的沿程能量损失率的方法,用实验数据分别计算出属于两个能区的高能原电子在金属金发射体内的沿程能量损失率,并用实验数据计算出属于同一个能区的高能原电子在金属铝发射体内的沿程能量损失率,结果显示,计算高能原电子在金属发射体内的沿程能量损失率的方法是可行的.  相似文献   

四川南部珙县早侏罗世一新蜥脚类恐龙   总被引：3，自引：0，他引：3  

何信禄  王长生  刘尚忠  周凤云  刘图强  蔡开基  代兵 《四川地质学报》1998,(1)

简介在珙县下侏罗统自流井组东岳庙段中,发现的原始蜥脚类恐龙化石的一新属种石碑珙县龙。成年个体长约１４ｍ。化石材料相当丰富,除头骨不完全外,其他部分乃至全部均保存完好。它是早期的原始的蜥脚类,但又和蜥脚类有不少共同点。它对研究蜥脚类的起源和进化,具有重要意义  相似文献   

The Complete Sequence of Mitochondrial COⅡ Gene of Fenneropenaeus chinensis and Its Applicability as a Marker for Phylogenetic Analysis     

YU Shanshan KONG Xiaoyu LI Yulong XU Hui 《中国海洋大学学报(英文版)》2007,6(2):187-192

The complete mitochondrial cytochrome oxidase subunit Ⅱ （COⅡ） gene of Penaeinae shrimp Fenneropenaeus chinensis was cloned and sequenced. The gene is 688 bp in length and codes for 229 amino acids. It shows 83.2%, 87.0% and 83.8% sequence similarity to Marsupenaeus Japonicus, Penaeus monodon and Farfantepenaeus notialis, respectively. The A＋T content of the whole gene and that at the third position of codons are 64.7% and 78.2%, respectively. The phylogenetic relationship between F. chinensis and three other species representing genera Farfanatepenaeus, Marsupenaeus and Penaeus was analyzed. Results showed that the genetic distances among the four taxa ranged from 0.144 0 to 0.200 5, exceeding those estimated with COⅠ and partial 16S rRNA gene sequences among Marsupenaeus, Litopenaeus and Melicertus, and being therefore larger than the value among subgenera. It has been suggested that the COⅡ gene has a faster evolutionary rate than that of the COⅠ gene and partial 16S rRNA gene and could be used for phylogenetic analysis at genus or species level. The results of the present study indicated that Farfantepenaeus, Fenneropenaeus, Marsupenaeus and Penaeus are at a higher phylogenetic level than subgenus, which supports the opinion of the elevation of phylogenetic status of the four subgenera to genus level.  相似文献   

Positive effect of porphyrans on the lifespan and vitality of Drosophila melanogaster     

赵婷婷  张全斌  綦慧敏  李智恩 《中国海洋湖沼学报》2007,25(4):373-377

The effects of degraded porphyran (P1) and natural porphyran (P) on the lifespan and vitality of Drosophila melanogaster are studied. The porphyrans, added daily to the food medium at 0.2% and 1% concentrations, can significantly increase the lifespan in average of 55.79 and 58.23 d in 0.2% P1 diet females and 1% P1 diet males, extending by 12.29% and 8.60% over the corresponding controls, respectively. The effects of porphyrans on D. melanogaster in heat-stress condition were also examined, and found a remarkable increase in survival time. The results which are consistently associated with the use of porphyrans are related to their free radical scavenger action. Considerable increase in vitality demonstrated that vitalities of middle-aged fly (assessed by measuring their mating capacity) was observed after porphyrans addition. Therefore, porphyrans are effective in reducing the rate of aging, and P1 in low molecular weight is better than natural P.  相似文献   

面包霉菌也有用处     

《海洋世界》2008,(6):9-9

看见面包上长了霉菌，大多数人会立刻将其扔掉；然而，有些人却可以从这些小型真菌中看到诸多可能性，美国密苏里大学的科学家帕特里克·许和他的研究小组发现了霉菌生殖过程中的一种新机制——该机制通过在减数分裂中“关闭”不匹配基因（“关闭”后该基因将无法表达），避免了非正常的遗传突变。许说：“对霉菌的这种‘定位不匹配基因并关闭之’机制的研究。  相似文献   

全球海洋微生物普查发现大量新基因     

《海洋世界》2007,(4):6-6

在一支美国科研小组的领导下,各国科学家利用2年的时间完成了至今最为彻底的海洋微生物普查,记录下了600多万种新蛋白质的基因编码,使全球基因数据库的总量增加了一倍。  相似文献