首页 | 本学科首页   官方微博 | 高级检索  
相似文献
 共查询到20条相似文献,搜索用时 46 毫秒
1.
利用空速、氧醇比、反应温度研究了Ag/ZSM-5分子筛催化剂对催化乙醇制乙醛的反应活性的影响。结果表明,该催化剂在340℃就有相当高的催化活性:乙醛产率达93.0%(空速为9.6s ̄(-1),氧醇比为0.50)。XRD和SEM等研究表明,Ag是以单质的形式负载在ZSM-5分子筛上。由此提出催化反应机理。  相似文献   

2.
制备了5′端共价连接EDTA的寡聚核苷酸与生命金属的螯合物ODN-5′-EDTAM(n+),其中M(n+)为Fe(Ⅱ),Co(Ⅱ)或Cu(Ⅱ);分析、计算了这3个螯合物形成的最佳pH值范围,ODN-EDTAFe(Ⅱ)为pH5.8~8.6,ODN-EDTACo(Ⅱ)为PH4.6~8.1,ODN-EDTACu(Ⅱ)为pH3.4~5.7;在此条件下,剪切反应必须的Mg2+并不与Fe(Ⅱ),Co(Ⅱ)或Cu(Ⅱ)竞争EDTA,也不会形成沉淀;讨论了ODN-EDTAM(n+)切割DNA双链的反应机理:修饰寡核苷酸通过氢键在DNA双链的大沟结合形成三链体,在O2和还原剂DTT作用下,Fe作为催化剂,产生羟基自由基,氧化糖环,切割EDTAFe(Ⅱ)附近的DNA双链.  相似文献   

3.
用光度法研究了Ag(Ⅰ)-α,α’-DiPy.-K2S3O8-ECR催化体系.确定了最佳测定条件为:3.0×10-3Mα,α’-Dipy,3.8×10-2M K2S3O8,1.2X10-4M ECR和pH5.0.方法灵敏,其检测限为1× 10-9g/ml.本法用于测定氯化银溶度积,经果与文献值相符.  相似文献   

4.
旋扭山绿豆根瘤菌抗药菌株筛选及结瘤竞争   总被引:2,自引:0,他引:2  
本实验获得了抗链霉素突变株MXDI6S_m ̄R,此菌株既有稳定的抗药性又保持良好的固氮能力.菌株间竞争结瘤表明MXDI6S_m ̄R竞争能力量强,并有双侵染出现.MXDI6S_m ̄R与土著根瘤菌竞争时,竞占瘤率达90%.生长在TY培养基上的MXDI6K_m ̄R与生长在YEM培养基上的MXDI6S_m ̄R竞争时MXDI6K_m ̄R占瘤率为零.  相似文献   

5.
由HMnO4和(NH4)6Mo7O24;4H2O合成了标题化合物K0.5(NH4)5.5「MnMo9O32」.6H2O用X-射线测定了晶体结构,该化合物的晶体属三方晶系,空间群R32;a=15.846(4),C=12.396(30)A,Mr=1657.28,V=2695.6A^3,Z=3,Dc=3.82g/cm^3,μ41.5=cm^-1,F(000)=2967和3024个可观测衍射「Fp≥3σ(  相似文献   

6.
研究了新合成试剂4-(4,5-二甲基噻唑偶氮)-1,3-二氨基甲苯(DMTADAB)与钴(Ⅱ)的显色反应及其配合物在溶液中的质子化行为.实验表明,在pH为6.5~9.5范围内试剂与钴(Ⅱ)定量配合,加入适量强酸时配合物非但不被破坏反而形成一种颜色较前更深的蓝绿色配合物,使其灵敏度和选择性都有所提高.该配合物的λmax=600nm,表观ε600=9.1×104,钴(Ⅱ)浓度在0~10μg/25mL范围内服从比耳定律.从而建立了一种测定钴(Ⅱ)的新体系.  相似文献   

7.
由KMnO4和(NH4)6Mo7O244H2O合成了标题化合物K0.5(NH4)5.5[MnMo9O32]6H2O,用x-射线测定了晶体结构.该化合物的晶体属三方晶系,空间群R32;a=15.846(4),C=12.396(3),Mr=1657.28,V=2695.63,Z=3,Dc=3.82g/cm3,μ=41.5cm-1,F(000)=2967.对3024个可观测衍射[F0≥3σ(F0)]最终偏离因子R=0.037,Rw=0.043.结构测定表明:Mn(Ⅳ)与6个氧配位形成键长相同的MnO6八面体,它位于[MnMo9O32]6-阴离子的中心,而Mo(Ⅵ)均与氧原子六配位,形成9个畸变的MoO6八面体.  相似文献   

8.
用化学共沉淀工艺制备了可望用作高密度垂直磁记录介质的Co-Sn替代钡铁氧体系列微软样品BaFe_(12-2x)Co_xSn_xO_(19),其中x可取值为0,0.2,0.4,0.5,0.6,0.8,1.2.给出了最佳制备条件:反应温度t=80℃,体系的pH值pH=11.8,热处理温度T_h=925℃。对所制备的系列样品进行了透射电镜(TEM)观测和x光衍射(XRD)测试,给出了颗粒的形貌和大小以及晶体结构和晶格常数。用振动样品磁强计(VSM)对宏观磁性进行了测试,给出了宏观磁性与替代浓度关系。  相似文献   

9.
探讨了培养基成分、培养时间、高渗缓冲液成分和pH、溶菌酶浓度以及酶解温度和时间对苏云金杆菌SD-5菌株原生质体形成和再生的影响;结果表明,SD-5菌株原生质形成和再生的最佳条件组合为:PBG培养基、30℃培养14h再活化5h,以SMMpH6.5作酶解缓冲液,溶菌酶浓度0.6mg/ml,34℃处理60min。  相似文献   

10.
铝镁复合氢氧化物的合成研究   总被引:4,自引:0,他引:4  
以硝酸铝、硝酸镁为原料,NaOH 为沉淀剂,采用变化pH 值法,经过共沉淀水热合成了铝镁层状复合氢氧化物。详细测定了不同镁铝摩尔比混合盐溶液的碱滴定曲线,利用正交设计探讨各个主要因素在合成过程中的影响,借助XRD鉴定合成物相结构。结果表明,当混合盐溶液中n(Mg)/n(Al)= 1.0~10.0 时,在pH= 5.0~10.0 下,与NaOH 共沉淀物经回流处理后,均能合成层状复合氢氧化物;最佳合成条件为:n(Mg)/n(Al)= 1.0~6.0,pH= 8.0~9.0,110℃,3 h 的水热处理。  相似文献   

11.
Language markedness is a common phenomenon in languages, and is reflected from hearing, vision and sense, i.e. the variation in the three aspects such as phonology, morphology and semantics. This paper focuses on the interpretation of markedness in language use following the three perspectives, i.e. pragmatic interpretation, psychological interpretation and cognitive interpretation, with an aim to define the function of markedness.  相似文献   

12.
何延凌 《科技信息》2008,(4):258-258
Language is a means of verbal communication. People use language to communicate with each other. In the society, no two speakers are exactly alike in the way of speaking. Some differences are due to age, gender, statue and personality. Above all, gender is one of the obvious reasons. The writer of this paper tries to describe the features of women's language from these perspectives: pronunciation, intonation, diction, subjects, grammar and discourse. From the discussion of the features of women's language, more attention should be paid to language use in social context. What's more, the linguistic phenomena in a speaking community can be understood more thoroughly.  相似文献   

13.
王慧 《科技信息》2008,(10):240-240
Wuthering Heights, Emily Bronte's only novel, was published in December of 1847 under the pseudonym Ellis Bell. The book did not gain immediate success, but it is now thought one of the finest novels in the English language. Catherine is the key character of this masterpiece, because everybody and everything center on her though she had a short life. We can understand this masterpiece better if we know Catherine well.  相似文献   

14.
The Williston Basin is a significant petroleum province, containing oil production zones that include the Middle Cambrian to Lower Ordovician, Upper Ordovician, Middle Devonian, Upper Devonian and Mississippian and within the Jurassic and Cretaceous. The oils of the Williston Basin exhibit a wide range of geochemical characteristics defined as "oil families", although the geochemical signature of the Cambrian Deadwood Formation and Lower Ordovician Winnipeg reservoired oils does not match any "oil family". Despite their close stratigraphic proximity, it is evident that the oils of the Lower Palaeozoic within the Williston Basin are distinct. This suggests the presence of a new "oil family" within the Williston Basin. Diagnostic geochemical signatures occur in the gasoline range chromatograms, within saturate fraction gas chromatograms and biomarker fingerprints. However, some of the established criteria and cross-plots that are currently used to segregate oils into distinct genetic families within the basin do not always meet with success, particularly when applied to the Lower Palaeozoic oils of the Deadwood and Winnipeg Formation.  相似文献   

15.
理论推导与室内实验相结合,建立了低渗透非均质砂岩油藏启动压力梯度确定方法。首先借助油藏流场与电场相似的原理,推导了非均质砂岩油藏启动压力梯度计算公式。其次基于稳定流实验方法,建立了非均质砂岩油藏启动压力梯度测试方法。结果表明:低渗透非均质砂岩油藏的启动压力梯度确定遵循两个等效原则。平面非均质油藏的启动压力梯度等于各级渗透率段的启动压力梯度关于长度的加权平均;纵向非均质油藏的启动压力梯度等于各渗透率层的启动压力梯度关于渗透率与渗流面积乘积的加权平均。研究成果可用于有效指导低渗透非均质砂岩油藏的合理井距确定,促进该类油藏的高效开发。  相似文献   

16.
As an American modern novelist who were famous in the literary world, Hemingway was not a person who always followed the trend but a sharp observer. At the same time, he was a tragedy maestro, he paid great attention on existence, fate and end-result. The dramatis personae's tragedy of his works was an extreme limit by all means tragedy on the meaning of fearless challenge that failed. The beauty of tragedy was not produced on the destruction of life, but now this kind of value was in the impact activity. They performed for the reader about the tragedy on challenging for the limit and the death.  相似文献   

17.
Location based services is promising due to its novel working style and contents.A software platform is proposed to provide application programs of typical location based services and support new applications developing efficiently. The analysis shows that this scheme is easy implemented, low cost and adapt to all kinds of mobile nework system.  相似文献   

18.
正The periodicity of the elements and the non-reactivity of the inner-shell electrons are two related principles of chemistry,rooted in the atomic shell structure.Within compounds,Group I elements,for example,invariably assume the+1 oxidation state,and their chemical properties differ completely from those of the p-block elements.These general rules govern our understanding of chemical structures and reactions.Using first principles calcula-  相似文献   

19.
We have developed an adiabatic connection to formulate the ground-state exchange-correlation energy in terms of pairing matrix linear fluctuations.This formulation of the exchange-correlation energy opens a new channel for density functional approximations based on the many-body perturbation theory.We illustrate the potential of such approaches with an approximation based on the particle-particle Random Phase Approximation(pp-RPA).This re-  相似文献   

20.
正The electronic and nuclear(structural/vibrational)response of 1D-3D nanoscale systems to electric fields gives rise to a host of optical,mechanical,spectral,etc.properties that are of high theoretical and applied interest.Due to the computational difficulty of treating such large systems it is convenient to model them as infinite and periodic(at least,in first approximation).The fundamental theoretical/computational problem in doing so is that  相似文献   

设为首页 | 免责声明 | 关于勤云 | 加入收藏

Copyright©北京勤云科技发展有限公司  京ICP备09084417号