Bi-Ce二元氧化物催化剂上丙烯氧化脱氢二聚的动力学与反应机理

丙烯在氧化物催化剂上氧化脱氢二聚反应的研究,文献上主要是在Bi-Sn系催化剂上进行的,不同研究者根据各自的结果,对这一步反应提出了两种不同的机理:一种认为是催化剂表面上吸附丙烯间的二聚(Langmuir-Hinshelwood型机)理;另一种认为是气相丙烯与吸附丙烯间的二聚(Eley-Rideal型机理).我们发现Bi-Ce二元氧化物显示出与Bi-

Eu~(2+)和Ce~(3+)激活的BaYF_5荧光性质

本文讨论了BaYF_5中Eu~(2+)和Ce~(3+)的光谱特征及浓度对光谱的影响。Eu~(2+)和Ce~(3+)均表现为d—f跃迁的特征激发和发射。由于Eu~(2+)—Eu~(2+),Ce~(3+)—Ce~(3+)能量迁移的存在,两者猝灭浓度偏低,其猝灭机理为偶极-偶极相互作用。根据BaYF_5基质中Eu~(2+)和Ce~(3+)的能级关系,发现Ce~(3+)对Eu~(2+)的发射具有明显的敏化作用。其机理主要为非辐射多极子作用,但也存在辐射传递。

助熔剂法合成RPO_4(R=La、Ce、Tb)晶体的研究

本文研究了以(NH_4)_2HPO_4-Li_2CO_3-MoO_3(PbF_2)为助熔剂合成 RPO_4(R=La~(3+),Ce~(3+),Tb~(3+))晶体的工艺,测试和分析了晶胞参数和晶体结构。对 CePO_4和 TbPO_4晶体的激发光谱和荧光光谱进行了讨论和分析。

K_5LnLi_2F_(10)(Ln=La,Gd,Y)的合成和Ce~(3+)在其中的发光

在Ar气氛中,采用高温固相反应法合成了K_5LnLi_2F_(10)(Ln=La,Ce,Gd,Y)化合物。X射线衍射图表明:除K_5YLi_2F_(10)外,均具有与K_5NdLi_2F_(10)(KNLF)相同的结构。计算了K_5LnLi_2F_(10)(Ln=La,Ce,Gd)的晶胞参数和晶胞体积,它们随着La~(3+),Ce(3+),Gd~(3+)的离子半径减小而有规律地减小。测定了K_5Ce_?Ln_(1-?)Li_2F_(10)化合物的激发光谱和荧光光谱。发现Ce~(3+)的激发波长和发射波长随着La~(3+),Gd~(3+),Y~(3+)离子的改变几乎不变,并对这种现象进行了讨论。

Photosynthetic parameters of sexually different parts of Porphyra katadai var. hemiphylla (Bangiales, Rhodophyta) during dehydration and re-hydration

Physiological data from extreme habitat organisms during stresses are vital information for comprehending their survival. The intertidal seaweeds are exposed to a combination of environmental stresses, the most influential one being regular dehydration and re-hydration. Porphyra katadai var. hemiphylla is a unique intertidal macroalga species with two longitudinally separated, color distinct, sexually different parts. In this study, the photosynthetic performance of both PSI and PSII of the two sexually different parts of P. katadai thalli during dehydration and re-hydration was investigated. Under low-grade dehydration the variation of photosystems of male and female parts of P. katadai were similar. However, after the absolute water content reached 42%, the PSI of the female parts was nearly shut down while that of the male parts still coordinated well and worked properly with PSII. Furthermore, after re-hydration with a better conditioned PSI, the dehydrated male parts were able to restore photosynthesis within 1 h, while the female parts did not. It is concluded that in P. katadai the susceptibility of photosynthesis to dehydration depends on the accommodative ability of PSI. The relatively lower content of phycobiliprotein in male parts may be the cause for a stronger PSI after severe dehydration.

中太平洋海区富钴结壳地球化学特征及成因机制

本文利用ICP-AES、EPMA、X-ray衍射等测试技术以及聚类分析和因子分析等多种数理统计方法，系统地对中太平洋海区富钴结壳的元素地球化学特征、矿物组成和微观组构进行了研究，并探讨了其成因机制，获得以下主要认识： 1中太平洋海区富钴结壳类型多样，均为水成成因，其矿物相主要由锰矿物相、铁矿物相和非金属矿物相组成；富钴结壳壳层发育多种原生和次生构造类型。 2磷酸盐化作用不仅强烈改变富钴结壳元素初始含量，而且造成富钴结壳某些元素间的相关性发生改变，这些敏感型元素对可用于指示富钴结壳是否发生磷酸盐化。在不同水深段内，未磷酸盐化型富钴结壳的主要元素随经向、纬向的变化趋势相似，表明其受水体化学障、表面生产力和物质来源等环境参数控制；而随水深的变化则具有区域一致性，表明水体化学具有区域成层性。 3未磷酸盐化富钴结壳稀土元素含量和轻重稀土分馏程度随水深发生规律变化，这种变化不仅与它们在海洋中的含量和行为有关，也与海洋背景颗粒的吸附有关；铈(Ce)在富钴结壳中基本上呈4价，且动力学因素控制了其富集过程，因此Ce异常不能用于指示富钴结壳形成环境的氧化程度。 4基于富钴结壳微层呈锯齿状且同一微层生长速率不同，提出了富钴结壳在各种基底表面生长以及后继发育过程受固液界面双电层控制的发育模式。在富钴结壳整个发育过程中，经历了从贫氧环境向富氧环境的转变，但微环境则呈富氧-低氧过程的交替。 关键词： 富钴结壳；中太平洋；元素地球化学；界面双电层

CE determination of 2-(9-carbazole)ethyl chloroformate-labeled oligopeptides

A pre-column derivatization method for sensitive determination of oligopeptides, using the tagging reagent 2-(9-carbazole)ethyl chloroformate (CEOC-Cl) followed by capillary electrophoresis (CE) with diode-array detection, has been developed. Maximum yield close to 100% were observed when a three to fourfold molar excess of reagent was used at pH 9.0-10.0. Excess reagent was extracted with n-hexane-ethyl acetate 9:1-10:1 (v/v); this enabled direct analysis using CE with no significant disturbance from the major fluorescent reagent degradation by-products. The effects on the results of buffer pH and of SDS and organic modifier concentrations were examined. Good baseline resolution in the separation of five CEOC-peptides was achieved with a 48.5-cm total length (effective length 40 cm) 50-mu m inner diameter capillary column.

Comparative analysis of allantoin quercetin, and 1-methyl-1,2,3,4-tetrahydro-beta-carboline-3-carboxylic acid in Nitraria tangutorum Bobr. Seed by HPLC-APCI-MS and CE

This paper describes the simultaneous determination of allantoin, quercetin, and 1-methyl-1,2,3,4-tetrahydro-beta-carboline-3-carboxylic acid (MTCCA) in Nitraria tangutorum Bobr seed by HPLC-APCI-MS and CE (capillary electrophoresis) methods. The final optimized chromatographic conditions were investigated in a reversed-phase Eclipse XDB-C8 column (150 x 4.6 mm, 5 mu m). A seventeen-minute gradient elution, (A: aqueous acetonitrile 20% (v/v); B: aqueous acetonitrile 60% (v/v); C: pure acetonitrile 100%) at a flow rate of 1.0 mL/min was selected for the separation of three natural products with diode array detection (DAD) at 220 nm. A CE experiment was carried out in a fused silica capillary with 32 mmol/L boric acid (pH 10), 32 mmol/L SDS and acetonitrile (10.0%, v/v). The applied potential and temperature was, respectively, set at 19 kV and 25 degrees C. After development, the validation was performed in parallel for HPLC and CE, with the same standards and sample to avoid differences due to the manipulation. The validation parameters of both techniques were adequate for the intended purpose.

CE环境下面向产品竞争力设计与经营决策集成系统研究

从提升产品市场竞争力的角度,提出了面向产品竞争力设计和经营决策的理念,建立了有关的结构模型和框架模型。在此基础上,进一步提出了并行工程环境下实现基于产品开发周期的面向产品竞争力设计与经营决策一体化的设想;研究了面向产品竞争力设计与经营决策集成系统的特征、结构和功能。最后以汽车车身为例对并行工程环境下的车身设计与经营决策集成系统进行了应用研究。

碳酸盐岩风化成土过程中REE超常富集及Ce强烈亏损的地球化学机理

碳酸盐岩的REE含量极低，但最近在贵州一些碳酸盐岩风化表土层底部首次发现了REE的超常富集层，REE总量最高可达近31000μg/g;Ce强烈亏损，δCe值最低达0.007。这种低背景、高富集、强分异的REE富集现象在贵州碳酸盐岩风化壳中具有一定的普遍性。选取发育在下三叠统花溪灰岩和平坝白云岩之上的两个较具代表性的碳酸盐岩风化壳进行研究，结果表明，这种富集现象与碳酸盐岩风化成土的两阶段性密切相关。（1）在残积土形成阶段（风化早期），碳酸盐的快速溶解导致风化前缘形成一个垂直方向相对狭窄、突变的碱性障(pH值为8左右）。此障既能有效地将碳酸盐岩分解释放的REE以及下渗水携带的REE分解沉淀和以吸附于粘土矿物上的方式富集，也容易使Ce^3+氧化成Ce^4+，与HCO3^-形成稳定的可溶性络合物随下渗雨水流走，从而使Ce进一步亏损。（2）残积土演化阶段，轻、重稀土发生明显分异，Ce^3+氧化成Ce^4+并发生水解沉淀，致使下渗水富重稀土而贫Ce，最终使REE在剖面上显示出一般风化壳共有的分异特征。另外，根据对碳酸盐岩中的酸不溶物、可溶性稀土的提取以及质量平衡计算，碳酸盐岩能够提供足够的REE物源；以可溶态为主的赋存状态有利于REE的淋滤（活化）。

NO reduction and CO oxidation over Cu/Ce/Mg/Al mixed oxide catalyst in FCC operation

Simultaneous NO reduction and CO oxidation in the presence of O-2,H2O and SO2 over Cu/Mg/AUO (Cu-cat), Ce/Mg/Al/O (Ce-cat) and Cu/Ce/Mg/Al/O (CuCe-cat) were studied. At low temperatures (<340 degreesC), the presence of O-2 or H2O enhanced the activity of CuCe-cat for NO and CO conversions, but significantly suppressed the activity of Cu-cat and Ce-cat, At high temperature (720 degreesC), the presence of O-2 or H2O had no adverse effect on the NO and CO conversions over these catalysts. The addition of SO2 to NO + CO + O-2 + H2O system had no effect on the, reaction of CO + O-2 over Cu-cat, but deactivated this catalyst for NO + CO and CO + H2O reactions; over Ce-cat, all of these reactions of NO + CO, CO + O-2 and CO + H2O were suppressed significantly; over CuCe-cat, NO + CO and CO + O-2 reactions were not affected while the reaction of CO + H2O was slightly inhibited. (C) 2002 Elsevier Science B.V. All rights reserved.