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1.
我国热带土地退化问题及持续农业发展对策   总被引:4,自引:0,他引:4  
对国内外土地退化研究现状趋势和我国热带地区土地退化问题进行了分析,并提出了治理热带土地退化及实现持续发展的对策。  相似文献   
2.
This paper deals with the immune reaction betweenTrypanosoma gambiense and monoclonal IgM mouse antibody at equivalence with or without rabbit complement. Antibody-mediated trypanosome clumps formed in the absence of complement, and were readily dissociated by complement to become free. In the presence of complement, on the other hand,T. gambiense were not aggregated by the antibody. Free parasites adhered readily to cultured peritoneal macrophages. Complement-mediated dissociation of the clumped trypanosomes in the equivalence area released a large number of previously bound surface antigens. These antigens were capable of binding again to fresh IgM antibody. Experimental results further indicated that the complement system caused a functional alteration, changing the multivalent nature of the IgM antibody in the immune complex into a univalent one. This phenomenon is of great advantage to the infected host in clearing pathogens in vivo, as it allows more antibodies to attach to trypanosomes and subsequently initiate complement activity.  相似文献   
3.
BaMnZnCoTi-W型铁氧体微波吸收特性的研究   总被引:2,自引:1,他引:1  
对用Co2+,Ti4+置换Fe3+的BaMnZn-W型平面六角晶系微波铁氧体吸收材料的制备和吸收性能进行分析研究,发现涂层厚度为1.06mm在7-12GHz频率范围内有三个吸收峰,峰值最高达34dB以上;同时比较了在相同工艺条件下,随着Co2+,Ti4+含量的增加,材料的吸收频率特性和涂层厚度的关系。  相似文献   
4.
Kinesins are microtubule-based motor proteins that perform diverse functions[1―6], including the transloca- tion of vesicles, organelles, chromosomes, proteincomplexes, RNA-binding proteins (RNPs), etc. They also help to orchestrate microtubule dynamics …  相似文献   
5.
本文用 S—C 变换法,研究极尖为任意角度的磁头场,导出了一般实数型的理论公式,并对其应用作了讨论。  相似文献   
6.
Moderate leaf rolling is one of the most important morphological traits in rice breeding for plant ideotype. Previous studies have shown that the rl(t) gene has a high breeding potential for developing hybrid-rice varieties with an ideal ideotype, because it leads to an appropriate leaf rolling index (LRI) of about 30 % in the heterozygous state, and had a positive effect on grain yield. In this study, we isolated rl(t) and performed a preliminary investigation of its function in regulating leaf rolling in rice. DNA sequencing identified a single base change (G to T) in the finely mapped region (11 kb) containing rl(t), and this is located in 3′-untranslated region (3′-UTR) of the only predicted gene, Roc5 (Rice outermost cell-specific). The expression level of Roc5 is significantly higher in the rl(t) mutant than in the wild-type. Using RNAi and overexpression analysis, we found that the expression level of Roc5 correlated with LRI and leaf bulliform area, and wasalso associated with leaf abaxial or adaxial rolling. These results confirmed that Roc5 controls leaf rolling in a dosagedependent manner. Bioinformatics analysis revealed a conserved 17-nt sequence (called the GU-rich element) in the 3′-UTR of HD-GL2 (Homeodomain-Glabra2) family genes including Roc5. Based on the model of this element in regulating mRNA stability in mammals, we speculate that the single nucleotide change in this element accounts for the higher expression level of Roc5 in the rl(t) mutant compared to the wild-type, which ultimately leads to adaxial rolling of the leaf. This discovery further enhances our knowledge of the molecular mechanisms underlying leaf rolling in rice.  相似文献   
7.
用反应动力学方法对Cl~-影响COD_(cr)测定进行研究.通过理论推导和实验测定,K_2Cr_2O_7和Cl~-属于二级动力学反应.给出不同温度下的反应速率常数、一定温度范围内的活化能、回流温度下(147.5℃)[HgCl_4]~2-的不稳定常数;并与文献中数据比较、验证,结果有助于判断Cl-对COD_(cr)测定的影响程度.  相似文献   
8.
桉树+粗果相思混交林模式及其效益   总被引:3,自引:0,他引:3  
在各种混交模式中,桉树高生长以行间混交模式高于带状混交和纯林模式;胸径生长因受到密度效应作用,行间与带状混交模式均低于纯林模式;单株材积以纯林最高,行间混交次之,带状混交模式最小;林木树冠长度以混交模式大于纯林模式.各模式中粗果相思的生长,以雷林33 号行间混交模式的单株材积最大,达到0-102 1 m3 ,粗果相思的群体蓄积为带状混交< 雷林33 号行间混交< MLA(尾叶桉无性系) 行间混交;从粗果相思的群体保存率看,MLA行间混交模式最高(90-4% ) ,远大于雷林33 号(47-1 % ) 行间混交和MLA的(43-9% ) 带状混交模式;从群体总产量来看,MLA行间混交模式最高,其它模式依次为MLA 纯林> 雷林33 号行间混交模式> MLA带状混交模式> W5 纯林模式> 雷林1 号桉与大叶相思混交模式;从生物量测定结果看,纯林MLA 单株生物量高于混交模式;群体生物量则以行间混交模式最高,达到71 414-1 kg/hm2 ,MLA带状混交与纯林模式分别为36 501-4 kg/hm2 和63 434-3 kg/hm2 ;各模式枯落物现存量以带状模式最高(9 794.0 kg/hm2) ,MLA行间混交模式次之(9 262.0 k  相似文献   
9.
Genetic analysis and fine mapping of genes controlling leaf rolling were conducted using two backcrossed generations (BC4F2, BC4F3) derived from a cross between QMX, a non-rolled leaf cultivar as a recurrent parent, and JZB, a rolled leaf NIL of ZB as a donor parent. Results indicated that leaf rolling was mainly controlled by an incompletely recessive major gene, namely rl(t), and at the same time, affected by quantitative trait loci (QTLs) and/or the environment. A genetic linkage map was constructed using MAPMAKER/EXP3.0 with eight polymorphic markers on chromosome 2, which were screened by BAS method from 500 SSR markers and 15 newly developed insertion/deletion (InDel) markers. The position of rl(t) was estimated with composite interval mapping (CIM) method using WinQTLcart2.5. Gene rl(t) was mapped between markers InDel 112 and RM3763, and 1.0 cM away from InDel 112 using 241 plants in BC4F2 population. To fine map r(t), one BC4F3 line with 855 plants was generated from one semi-rolled leaf plant in BC4F2. Four new polymorphic InDel markers were developed, including InDel 112.6 and InDel 113 located between markers InDe1112 and RM3763. Based on the information of recombination offered by 191 rolled leaf plants and 185 non-rolled leaf plants from the BC4F3 line ,we mapped r(t) to a 137-kb region between markers InDel 112.6 and InDel 113. Homologous gene analysis suggested that r(t)was probably related to the process of leaf development regulated by microRNA.  相似文献   
10.
The kinetochore is structurally composed of four layers,We know that three microtubule-based motor protcins such as CENP-E,dynein,and MCAK are located at the outmost region of the kinctochore,Experimentation of these motot functions betters our understanding of mitotic regulation,and chromaosme movements in particular,With real-time studies of chromosome movements in live cells,we hope to illustrate the molecular mechanisms under lying mitotic regulation.  相似文献   
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