R2Fe17C化合物的结构与内禀磁性的研究

本文系统研究了R₂Fe₁₇C(R=Y.Sm,Gd,Tb.Dy,Er)化合物的结构与内禀磁性,并与相应的R₂Fe₁₇化合物进行了比较。R₂Fe₁₇C的居里温度比相应R₂Fe₁₇的居里温度增加大约200K。本文讨论了C原子对该化合物结构与磁性的影响,同时,还对Sm₂(Fe_1-xCo_{x 关键词：}     

激光加热Cu和NaF靶产生的1.2keV区X射线转换效率的测量

介绍了激光加热Cu靶和NaF靶发射的在1.2keV区X射线转换效率的测量方法和实验结果。结果表明,在激光辐照功率密度为1×10¹³—1×10¹⁴W·cm^-2条件下,激光波长为1.06μm或0.53μm时,Cu等离子体发射的1.2KeV区X射线的转换率为NaF等离子体的4—5倍;对此两种等离子体,激光波长为0.53μm的X射线转换效率是波长为1.06μm的2倍左右。 关键词：     

用^1HNMR芳烃质子鉴定α—卤代桂皮酰胺类化合物的构型

桂皮酰胺类化合物的Z或E—构型,影响其对中枢神经的药理作用(兴奋或抑制),根据NMR测定结果,该类烯氢未取代的化合物,可以用两个烯氢的偶合常数大小来鉴定其构型(J_E>J_Z);α—卤代的桂皮酰胺,可根据β—烯氢的化学位移(δ_(H(z))>δ_(H(E)),差别大于1 ppm)和NH的化学位移(δ_(H(z))>δ_(H(E)))来区分.但对α—卤代的桂皮酰哌啶类化合物,其哌啶环的氮上无氢,两种构型的β—烯氢的化学位移的差别也不大,可以利用(?)C=O与β—烯氢的偶合常数~3J_(CH)来区别.但~3J_(CH)不易测定,干扰因素也多.有些化合物可根据N上取代基的大小,导致(?)C(?)键和芳环自由转动程度不同及优势构象各异、面角改变等来鉴定构型(Z或E).综合和比较这些化合物的~1H谱发现α—卤代桂皮酰胺类化合物,不论酰胺氮上带有何种取代基,苯环上取代基的种类与数目,芳烃质子的化学位移与峰形,Z型和E型有显著的不同,特别是α—位为较大的溴原子取代时,这种差别更明显,可用于鉴定这些化合物的构型.     

1.8—4.2K GaAs1-xPx注N+,注Zn+光荧光谱

本文研究了1.8—4.2K下离子注N,注ZnGaAs_1-xP_x样品的光致发光行为。实验结果表明由N-Zn跃迁完全转变到N束缚激子复合的x值依赖N,Zn的浓度。利用Campbell局域化模型计算了N-Zn跃迁与N束缚激子复合的几率比。这一几率比是组分x和N-Zn浓度的函数。在1.8K,在同一样品上我们清晰地观测到对应N-Zn跃迁与N束缚激子复合的光谱。 关键词：     

黄河水体无机固体粒子与镉、铜相互作用的离子交换等温线

报道了本实验室测得的河流等温线是“台阶型”多级离子交换等温线，具体讨论了形成这类新型等温线的原因。     

高压浸取-火焰原子吸收光谱法测定重晶石中铅

研究了在高压消解瓶内升温增压下,用王水对重晶石中铅浸取,并用火焰原子吸收光谱法测定浸出的铅。试验表明,在180℃加热3h,铅的浸取量最大,用该法浸取铅比在常温常压下更完全,相对标准偏差为2.20%～3.72%,回收率为95.2%～100.4%,方法检出限为0.12mg·L-1。     

TOTAL SYNTHESIS OF YEAST ALANINE TRANSFER RIBONUCLEIC ACID

By a combination of chemical and enzymatic methods, small oligonucleotides with lengths varying from 2 to 8 nucleotides were synthesized from mononucleotides. The small oligonucleotides were then ligated with T_4 RNA ligase into six laxge ligonucleotides (9 to 19 nucleotides long) which were further ligated to form two half molecules with 35 and 41 nucleotides respectively, Finally, the two synthetic half molecules were annealed and ligated to obtain the whole molecule of yeast alanine tRNA (tRNA_y~(Ala)). Prior to this, two semi-syntheses were performed, i. e. ligation of the synthetic 5'-half molecule with the natural 3'-half molecule and that of the natural 5'-half molecule with the synthetic 3'-half molecule.     

中科院手性分析技术合作研究中心成立

药物结构也有“左右手”之分，就像人的左右手一样，许多人工合成的药物是由两种互为镜像的形态构成的。前不久，为加快手性化合物的开发与制造，中科院上海有机化学研究所与大赛璐（中国）投资有限公司在沪成立中科院手性分析技术合作研究中心。合作双方将本着“平等互惠、优势互补、资源共享、风险共担”的原则，就色谱法手性分析技术及其在手性合成中的应用研究等方面开展合作。该中心的目标是将国内手性技术的研究和生产提高到国际先进水平。     

Surface Modification of Montmorillonites by Chlorosilanes

Montmorillonite was modified by chlorosilane derivatives (trimethylchlorosilane and tert-butyldimethylchlorosilane)based on the reaction between OH group and chlorosilane,Fourier-transformed infrared spectra(FTIR)confirmed that chlorosilanes did react with the OH groups of montmorillonite.The effect of reaction time and dispersing agents on the intercalation was studied by wide angle X-ray diffraction(WAXD) method.Further experiments proved that there is no reactive OH group on the surface of layers in the interlayer galleries of montmorillonite.The cation exchange capacity(CEC) of montmorillonites was measured.showing that after modification by chlorosilane derivatives,CEC values drastically decreased.The dispersibility measurements of montmorillonites were conducted.which showed that the dispersibility of modified montmorillonites both in H2O and toluene wer improved due to the decrease of attractions of particles and layers.