邻香草醛缩丙氨酸盐及邻菲咯啉与Ln(Ⅲ)三元配合物的合成与表征

某些水扬醛类氨基酸的金属配合物具有特殊的性质和应用[1 ,2 ] ,近年来 ,过渡金属离子的此类希夫碱配合物有不少报道。本工作在无水乙醇体系中 ,用稀土硝酸盐与邻香草醛缩丙氨酸钾及邻菲咯啉作用合成了未见文献报道的三种混配配合物 ,并对其组成和配位方式进行了研究。1　实验部分1 1　主要仪器与试剂美国Ｂｉｏ ＲａｄＦＩＳ1 65型红外光谱仪 ,ＫＢｒ压片 ;美国ＰＥ2 4 0 0 (Ⅱ )型元素分析仪 ;岛津ＵＶ 30 0 0双光束分光光度计 ;ＤＤＳ 1 1Ａ型电导率仪 ;德国ＳＴＡ40 9ＺＰ热分析仪。Ｌｎ2 Ｏ3纯度高于 99 9% ;ＤＬ α 丙氨酸为生化试剂…     

Quantum chemical characterization of the cytosine: 2‐Aminopurine base pair

The nature of the base pairing between cytosine and 2‐aminopurine is investigated by means of quantum mechanical calculations including electron correlation and accounting for the effects of aqueous solvation. At neutral pH, both a neutral wobble base pair and a Watson–Crick‐like base pair having a protonated 2‐aminopurine are predicted to be close to one another in energy; other previously proposed forms are found to be too high in energy to be of significant chemical interest. Accounting for the energetics of helix embedding suggests that the equilibrium between the two low‐energy motifs is quite sensitive to local environment. © 2001 John Wiley & Sons, Inc. J Comput Chem 22: 1167–1179, 2001     

水杨醛缩苯胺类席夫碱构象异构体的稳定性及其非线性光学性质的理论研究

运用量子化学有限场FF/PM3方法,对水杨醛缩苯胺类席夫碱几种异构体稳定构象的能量、结构、非线性光学系数进行了分析,探讨氢键及氢迁移过程对体系稳定性和非线性光学性质的影响.结果表明:水杨醛缩苯胺类席夫碱分子具有较好的二阶非线性光学性质,并可能成为一类良好的光学材料.     

茂金属聚乙烯和低密度聚乙烯共混物的流变行为

研究了茂金属催化乙烯丁烯1共聚物mPE和LDPE共混物的流变行为.测定了一系列共混物的稳态剪切粘度和动态粘弹性,用改进Cross模型拟合实验数据.mPE的零切粘度η₀较小,从牛顿型转变为非牛顿型所需的剪切速率较大,转变应力较高,在挤出加工剪切速率范围内熔体粘度高,对剪切敏感性差,这是由于它有较低的重均分子量、窄的分子量分布(M_w/M_n=21)所致.对于对数加和规律,共混物η₀在mPE/LDPE为50/50和25/75时有强烈的正偏差,这是由于共混物自由体积减小所致.共混物的转变应力τ^*和非牛顿指数n随LDPE加入量增大而降低,表明共混物对剪切的敏感性提高,加工性得到改善.G'和G”的一致性说明mPE和LDPE共混是相容的.     

席夫碱的合成及热色性研究Ⅲ——二取代苯甲醛-二-对-氨基苯甲烷类席夫碱

本文合成了二取代苯甲醛-二-对-二氨基苯基甲烧类席夫碱类的7个化合物,并应用物理方法进行了表征.通过加热显微观察,这些化合物都具热色性,而其中4种具有可逆热色性.此外应用差热分析阐述了这类席夫碱的吸热峰的ΔH(ΔS)与其结构的关系.     

一氧化氮在Nafion-钴席夫碱膜修饰电极上的电催化氧化及其测定

将一种杂环席夫碱N,N′-2 ,6 -二乙酰吡啶缩双苯胺和Nafion修饰在铂电极上 ,然后与钴 (Ⅱ )反应 ,得到Nafion -钴席夫碱膜修饰电极。实验结果表明 ,该修饰电极具有良好的机械、化学和电化学稳定性 ,对生物分子一氧化氮的电化学氧化有显著的催化作用。以1.5次微分线性扫描伏安法测定一氧化氮 ,当浓度在2.8×10-6～8.4×10-8 mol/L范围时 ,氧化电流与浓度有良好的线性关系 ,抗坏血酸、精氨酸及亚硝酸根不干扰测定。     

Asymmetric nitrogen

Reactions of the Tröger base (1) with HgBr₂ and Mel proceed with the participation of only one N atom. According to the data of X-ray diffraction analysis, the complex [(±)-1]₂·HgBr₂ crystallizes in the achiral space groupP _n . Unlike the complex [(+)-1]₂·HgBr₂, methiodide of (+)-1 in MeOH undergoes racemization at 20°C. The virtual spin-spin coupling constants⁴ J _HH observed for the base (C ₂ symmetry) are transformed into the “usual” constants in the case of the desymmetrized methiodide system.     

Determination of the rates of formation and hydrolysis of the Schiff bases formed by pyridoxal 5′-phosphate and hydrazinic compounds

The macroscopic rate constants of formation (k₁) and hydrolysis (k₂) for the reactions of pyridoxal 5′-phosphate (PLP) with hydrazine (PLP-HY system), carbidopa (-hydrazino--methyl-β-(3,4-dihydroxyphenyl)propionic acid, PLP-CD system), hydralazine (1-hydrazinophthalazine, PLP-HL system) and isoniazid (4-pyridinecarboxylic acid hydrazide, PLP-ISO system) were fitted to a kinetic scheme that considers the different ionic species present in the medium, their protonation constants, and their individual rates of formation (k₁ⁱ) and hydrolysis (k₂ⁱ). The results obtained for the molecules bearing the hydrazine group are compared with those for the reactions of PLP with n-hexylamine (PLP-NHA system) and poly- -lysine (PLP-LYS system). Some structural effects on the individual rate constants are also examined.     

高温真实气体底部流动的NS方程数值计算

本文数值模拟了高超音速飞行时钝锥的底部流动。采用轴对称NS方程并考虑真实气体效应。湍流模型采用修正的Baldwin-Lomax涡粘性代数模型,数值方法空间离散对流项采用显式NND格式,粘性项采用中心差。时间离散采用三阶的龙格-库塔法。真实气体模型采用考虑七种组分四种反应的汉森模型。给出了底部流场的压力和温度分布及各组分的浓度分布。可以看出在近底部区域高速流-绕过拐角就产生一回流旋涡区。由于温度变化很大,气体的热力学特性受气体离解、复合和振动能激发的影响。所以整个流动过程变得十分复杂。     

Right closure of martingale sequences in the sense of theA-integral

In this paper new sufficient (necessary and sufficient for martingales of special form) conditions for the martingale closure from the right in the sense of theA-integral are given. These results follow from the theorem about passing to the limit under theA-integral. The theorem is established using the criterion for transposing iterated limits with respect to the base. It is shown that the sufficient conditions thus obtained are stronger than those previously known. Translated fromMatematicheskie Zametki, Vol.68, No. 1, pp. 98–104, July, 2000.