Automated inductively-coupled plasma optical emission spectrometry based on a sequential reading monochromator

An automated computer-controlled sequential reading monochromator system for optical emission spectrometry with an inductively-coupled plasma as source is described. The system selects the set of emission lines which are best suited for each type of sample. Multi-element analysis of major and trace elements is done automatically, including sample changing, calibration, background correction and presentation of results.     

Long-term stability of glass electrodes in aqueous media

The stability of the potential of glass electrodes has been studied. The potential changes only slightly during the hydration of freshly etched electrodes. With glass electrodes previously used in alkaline solutions, structural transformations within the gel-layer give rise to large potential drifts in neutral or acidic test solutions. In alkaline solutions all glass electrodes are attacked, especially the low-temperature type, and the potential changes with time. Drying hydrated electrodes affects the stability only slightly. Alternating transfers between acidic and basic solutions decrease the stability. Recommendations for precise measurements with glass electrodes are given.     

钼铁硫原子簇化合物的结构规则

本文将过渡金属原子簇化合物的9N-L结构规则, 用于讨论Mo-Fe-S原子簇化合物, 得到了它们的结构和自旋性质之间的关系,推得的理论最大自旋值与实验事实吻合. 进而, 对各种Mo-Fe-S原子簇化合物的典型分子或模型分子, 进行了EHMO量子化学计算, 得到了与上述讨论相一致的结果, 进 一步揭示和验证了上述讨论的本质.     

Echo-time independent signal modulations using PRESS sequences: a new approach to spectral editing of strongly coupled AB spin systems

In clinical MR spectroscopy, double spin-echo point resolved spectroscopy (PRESS) sequences are routinely used for volume selection. For strongly coupled AB spin systems under PRESS excitation, the dependence of the signal on the echo time TE has been thoroughly investigated, whereas less attention has been paid to the signal modulation which occurs at constant TE with varying interpulse delays. A substantial TE-independent J modulation is here predicted from analytical solutions of the Liouville equation and density matrix simulations, and verified with experiments on citrate at 1.5 and 3T. It is also shown that this modulation effect could be exploited for editing of strongly coupled AB resonances or for removal of singlets in spectra-by means of difference spectroscopy-just using a standard PRESS sequence. The applicability in vivo of this new spectral editing approach is also demonstrated, with selective detection of citrate resonances in the human prostate. This novel approach has the advantages of being simple, and directly applicable on standard clinical MR scanners, provided that the exact behavior of the resonance is known.     

绝热式热动力学的研究I:可逆反应动力学的数学模型

本文提出了几类可逆反应通用的微分动力学方程.并应用无量纲参数法,建立了可逆反应动力学的数学模型.还给出了一个解析实例.     

阳离子－π体系相互作用的理论研究 3: 碱金属阳离子－苯 复合物体系的量子 化学研究

运用abinitioHartree-Fock从头算,微扰MP2和密度泛函B3LYP方法在不同的基组水平上对碱金属阳离子－苯复合物体系的可能构型进行了自由优化,得到了复合物的能量最低构型为碱金属阳离子位于苯环平面的正上方,频率计算结果表明该结构为稳定结构.复合物的键长、原子净电荷、分子轨道、前沿轨道能量、Mullicken键级等都表明,碱金属阳离子和苯环碳原子之间的作用包含p-π作用方式,碱金属阳离子与苯结合时电子从苯环向碱金属阳离子转移,形成电荷转移复合物.它们之间的结合方式和氢键的结合方式相似,但计算得到的热力学参数表明复合物中碱金属阳离子与苯之间的结合强度远远大于典型的氢键,尤其是锂离子－苯复合物的生成焓已和普通的化学键相当.复合物的红外特征振动频率位于200^-^1附近,对应于碱金属阳离子垂直于苯环平面的来回振动,同时形成复合物后,原来位于3200cm^-^1的苯的C--H振动红外活性消失。     

联苯在β-蒎烯光氧化中的电子中继

β-蒎烯的长时间单重态氧光氧化导致复杂的产物分布。二氰基蒽(DCA)敏化的电子转移光氧化使桃金娘烯醇的产率略有改善, 但是, 添加联苯作共敏化剂使产率几乎翻了一番。在向DCA的竞争性单电子转移中, 联苯超过了β-蒎烯。MNDO计算证实其原因是联苯的HOMO较高。联苯正离子游离基从β-蒎烯回收一个电子, 再生联苯和生成β-蒎烯正离子游离基, 它再与经基态氧与(DCA)^-之间电子转移而生成的超氧负离子(O^-~2)复合。     

静电势方法研究分子间的电子转移 II: 在光电转移模拟体系中的应用

用从头算和静电势方法研究了光电转换模拟体系C~6H~7N+C~6H~8N^+中的分子间电荷转移。通过计算分子间的静电势分布, 确定了电子在分子间运动所需穿透势垒的特性, 对电子穿透几率及穿透弛时间等参数作了理论预测并研究了外接基团的影响。在分子间距d=0.35nm时, 穿透几率P=2.94x10^-^4, 穿透弛豫时间τ=3.4x10^-^1^0s, 在此情况下, 由模型分子组成的截面积为10x1mm^2的多层分子膜, 在光照条件下可能产生的理论光电流为0.28A。     

Furyl-maleimidein situ generated ab-monomers: Synthesis,characterization, and Diels-Alder polymerization

2-Furoyl chloride reacted with the monomaleamic acids 1a-1d derived from a aromatic diamine to yield a new series of maleamic acids 2a–2d . The latter were cyclodehydrated to afford maleimides 3a-3d which behaved as AB-monomers for a Diels-Alder polymerization. In addition, the monomaleamic acid 4 derived from 4-aminophenol reacted with 2-furoyl chloride to yield maleamic acid 5 . It was cyclodehydrated to maleimide 6 which is a novel polymer precursor. The monomers were characterized by IR and ¹H-NMR spectroscopy. Their thermal polymerization was investigated by DTA. Maleamic acids 2a–2d and 5 were cured at 280°C for 22 h to yield polymers which were characterized by TGA and isothermal gravimetric analysis (IGA). They were stable up to 340–376°C and afforded anaerobic char yield of 55–64% at 800°C. © 1992 John Wiley & Sons, Inc.