英语网络教学中的交流与沟通     

刘红  贾思明 《北京农业职业学院学报》2003,17(Z1):33-35

沟通和交流在英语网络教学中有着重要的作用.目前,英语网络教学存在着沟通与交流被忽视或简单化,学术讨论缺乏目的性,学生对书面交流缺乏认识等问题.学分制和合作学习可以使学生有更多机会参与交流并增强合作能力,教师主导制和实名制可以保证讨论规范进行,培养学生的书面交流技巧可以增强学生沟通的准确性.  相似文献   

药用植物牛至的组织培养技术研究     

沙红  廖康 《新疆农业大学学报》2003,26(4):49-51

讨论了以牛至种子为外植体的组织培养繁殖技术。在增殖培养基的筛选过程中发现 ,以茎尖为外植体时 ,最适宜的增殖培养基为MS中加入BA 2 .0mg·L-1,IBA 0 .0 2mg·L-1,增殖倍数最高可达 5 .5 4 ;而茎段的增殖倍数较小为 2 .83。在生根培养基的筛选中发现 ,牛至在不含激素的 1/ 2MS、MS培养基上生根率可达 96 %～10 0 % ,但获得根较细 ,侧根少 ,移栽不易成活 ,加入激素后 ,生根数量增多 ,同时侧根数量明显增加 ,试验数据表明NAA ,IBA ,IAA 3种激素均可提高生根数量 ,浓度以 0 .5～ 1.0mg·L-1较好。  相似文献   

西农莎能奶山羊遗传检测的研究     

耿社民  常洪  胡建宏 《西北农林科技大学学报(自然科学版)》1995,23(5):57-60

通过对西农莎能奶山羊九个血液蛋白位点和四项外形特征的遗传抽样检测，结果表明：西农莎能奶山羊在七个血液蛋白位点和四项外形特征上具有多态性，并存在有原种瑞士莎能奶山羊不具有的Ｈｂ￣Ｂ和Ｔｆ￣Ｂ基因，以及其他莎能羊种中不具有的Ａｃｐ￣Ａ和Ｃａｔ￣Ｂ基因。  相似文献   

基于畜禽废弃物管理的发酵床技术研究Ⅱ.接种剂的应用效果研究   总被引：7，自引：0，他引：7  

朱洪  常志州  王世梅  费辉盈  陈欣 《江苏农业科学》2007,(2):228-232

用腐熟猪粪堆肥为材料制作微生物接种菌剂,在室内模拟条件下,研究了木屑、木屑与稻壳混合两种不同垫料发酵床应用接种剂后,垫料中pH值、无机氮及部分酶活性变化,探析应用接种剂对猪粪的原位降解效果。试验结果表明,菌剂能降低垫料环境pH值;垫料铵态氮和硝态氮含量在第5 d均降到最低值,其中混合垫料铵态氮含量最大时接种组与CK差异极显著;过氧化氢酶活性在第5 d达到最大值,其中木屑垫料过氧化氢酶活性最大时接种组与CK差异极显著;脲酶活性在第10 d达到最大值,两种垫料脲酶活性最大时接种组与CK均达到极显著水平;纤维素酶活性在第5 d达到最大值,两种垫料纤维素酶活性最大时接种组与CK均达到极显著水平;蛋白酶在整个试验过程中保持旺盛的酶活性,呈逐渐增加趋势,应用接种剂加快了猪粪原位降解速率。  相似文献   

Effects of Zinc Deficiency and Drought on Plant Growth and Metabolism of Reactive Oxygen Species in Maize （Zea mays L.）   总被引：1，自引：0，他引：1  

WANG Hong JIN Ji-yun 《中国农业科学(英文版)》2007,6(8):988-995

The combinative effects of applied zinc (Zn) and soil moisture on the plant growth, Zn uptake, and the metabolism of reactive oxygen species (ROS) in maize (Zea mays L.) plants were examined through two pot experiments under greenhouse conditions. Maize variety Zhongdan 9409 was used. In experiment 1, maize plants were grown in cumulic cinnamon soil with five Zn treatments (0, 3.0, 9.0, 27.0, and 81.0 mg Zn kg-1 soil). Three treatments of soil moisture including serious drought, mild drought, and adequate water supply were set at 30-35 %, 40-45 %, and 70-75 % (w/w) of soil saturated water content, respectively. Soil saturated water content was 36% (w/w). The dry matter weights of shoots were enhanced by Zn application and adequate water supply. There was no apparent difference in plant growth among Zn application rates from 3.0 to 81.0 mg Zn kg-1 soil. The increases of plant growth and Zn uptake due to Zn application were found more significant under well-watered condition than under drying condition. In experiment 2, two levels of Zn (0 and 5.0 mg Zn kg-1 soil) and soil moisture regimen (40-45 % and 70-75 % of soil saturated water content, respectively) were set. Zn deficiency or water stress resulted in higher concentrations of O2-· and malondiadehyde in the first fully expanded leaves.Zn deficiency lowered the activity of superoxide dismutase (SOD, EC 1.15.1.1) in leaves. Drought stress increased SOD activity in leaves regardless of Zn supply. The activity of guaiacol peroxidase (POD, EC1.11.1.11) was found to be enhanced by Zn supply only in well-watered leaves. Zinc deficiency or water stress had little effect on the activity of catalase (CAT, EC 1.11.1.6). The higher ROS level in early maize leaves due to water stress seemed not to be alleviated or lowered partially by Zn application. However, Zn fertilizer was recommended to apply to maize plants irrigated or supplied with adequate water, otherwise Zn deficiency would reduce the water use for plant biomass production.  相似文献   

播期对饲料大麦盐丰一号生长发育及籽粒产量的影响   总被引：1，自引：0，他引：1  

陈晓静  陶红  陈和  陈健  沈会权  乔海龙 《河北农业科学》2007,11(6):1-2,5

为了探讨弱春性六棱饲料大麦盐丰一号的适宜播期,研究了不同播期对盐丰一号群体茎蘖动态、个体发育和产量的影响.结果表明:盐丰一号在10月12～30日播种,群体茎蘖动态合理,产量三要素关系协调,易获得高产.  相似文献   

The composite genome of the legume symbiont Sinorhizobium meliloti     

Galibert F  Finan TM  Long SR  Puhler A  Abola P  Ampe F  Barloy-Hubler F  Barnett MJ  Becker A  Boistard P  Bothe G  Boutry M  Bowser L  Buhrmester J  Cadieu E  Capela D  Chain P  Cowie A  Davis RW  Dreano S  Federspiel NA  Fisher RF  Gloux S  Godrie T  Goffeau A  Golding B  Gouzy J  Gurjal M  Hernandez-Lucas I  Hong A  Huizar L  Hyman RW  Jones T  Kahn D  Kahn ML  Kalman S  Keating DH  Kiss E  Komp C  Lelaure V  Masuy D  Palm C  Peck MC  Pohl TM  Portetelle D  Purnelle B  Ramsperger U  Surzycki R  Thebault P  Vandenbol M  Vorholter FJ 《Science (New York, N.Y.)》2001,293(5530):668-672

The scarcity of usable nitrogen frequently limits plant growth. A tight metabolic association with rhizobial bacteria allows legumes to obtain nitrogen compounds by bacterial reduction of dinitrogen (N2) to ammonium (NH4+). We present here the annotated DNA sequence of the alpha-proteobacterium Sinorhizobium meliloti, the symbiont of alfalfa. The tripartite 6.7-megabase (Mb) genome comprises a 3.65-Mb chromosome, and 1.35-Mb pSymA and 1.68-Mb pSymB megaplasmids. Genome sequence analysis indicates that all three elements contribute, in varying degrees, to symbiosis and reveals how this genome may have emerged during evolution. The genome sequence will be useful in understanding the dynamics of interkingdom associations and of life in soil environments.  相似文献   

非线性传染率的流行病模型的周期解与Hopf分支的存在性   总被引：1，自引：0，他引：1  

汪宏喜 《安徽农业大学学报》2002,29(2):199-202

本文讨论一类具有非线性传染率的流行病模型的动力形态,并给出该系统出现同宿分支与周期轨道分支的条件.  相似文献   

Discovery and directed evolution of a glyphosate tolerance gene   总被引：2，自引：0，他引：2  

Castle LA  Siehl DL  Gorton R  Patten PA  Chen YH  Bertain S  Cho HJ  Duck N  Wong J  Liu D  Lassner MW 《Science (New York, N.Y.)》2004,304(5674):1151-1154

The herbicide glyphosate is effectively detoxified by N-acetylation. We screened a collection of microbial isolates and discovered enzymes exhibiting glyphosate N-acetyltransferase (GAT) activity. Kinetic properties of the discovered enzymes were insufficient to confer glyphosate tolerance to transgenic organisms. Eleven iterations of DNA shuffling improved enzyme efficiency by nearly four orders of magnitude from 0.87 mM-1 min-1 to 8320 mM-1 min-1. From the fifth iteration and beyond, GAT enzymes conferred increasing glyphosate tolerance to Escherichia coli, Arabidopsis, tobacco, and maize. Glyphosate acetylation provides an alternative strategy for supporting glyphosate use on crops.  相似文献   

Sirt5 is a NAD-dependent protein lysine demalonylase and desuccinylase   总被引：1，自引：0，他引：1  

Du J  Zhou Y  Su X  Yu JJ  Khan S  Jiang H  Kim J  Woo J  Kim JH  Choi BH  He B  Chen W  Zhang S  Cerione RA  Auwerx J  Hao Q  Lin H 《Science (New York, N.Y.)》2011,334(6057):806-809

Silent information regulator 2 (Sir2) proteins (sirtuins) are nicotinamide adenine dinucleotide-dependent deacetylases that regulate important biological processes. Mammals have seven sirtuins, Sirt1 to Sirt7. Four of them (Sirt4 to Sirt7) have no detectable or very weak deacetylase activity. We found that Sirt5 is an efficient protein lysine desuccinylase and demalonylase in vitro. The preference for succinyl and malonyl groups was explained by the presence of an arginine residue (Arg(105)) and tyrosine residue (Tyr(102)) in the acyl pocket of Sirt5. Several mammalian proteins were identified with mass spectrometry to have succinyl or malonyl lysine modifications. Deletion of Sirt5 in mice appeared to increase the level of succinylation on carbamoyl phosphate synthase 1, which is a known target of Sirt5. Thus, protein lysine succinylation may represent a posttranslational modification that can be reversed by Sirt5 in vivo.  相似文献