KZnF_3∶Eu的水热合成及其光谱性质

采用中温水热法合成了立方钙钛矿单相 KZn F3 及 KZn F3 ∶ Eu,通过 SEM观察了产物形态 ;XPS测定结果表明 ,产物含氧量不高 ;荧光光谱及 ESR谱表明 ,KZn F3 ∶ Eu体系中 Eu2 +与 Eu3 +共存 ,进一步讨论了不等价取代中的电荷补偿途径

Brittle-ductile transition in high-density polyethylene/glass-bead blends: Effects of interparticle distance and temperature

The toughness of high-density polyethylene (HDPE)/glass-bead blends containing various glass-bead contents as a function of temperature was studied. The toughness of the blends was determined from the notch Izod impact test. A sharp brittle-ductile transition was observed in impact strength-interparticle distance (ID) curves at various temperatures. The brittle-ductile transition of HDPE/glass-bead blends occurred either with reduced ID or with increased temperature. The results indicated that the brittle-ductile-transition temperature dropped markedly with increasing glass-bead content. Moreover, the correlation between the critical interparticle distance (ID.) and temperature was obtained. Similar to the ID, of polymer blends with elastomers, the ID, nonlinearly increased with increasing temperature. However, this was the first observation of the variation of the ID, with temperature for polymer blends with rigid particles. (C) 2001 John Wiley & Sons, Inc. J Polym. Sci Part B: Polym. Phys 39: 1855-1859, 2001.

Ce3+ -> Eu2+ energy transfer in BaLiF3 phosphor

Photoluminescence characteristics and the energy transfer between Ce3+ and Eu2+ in BaLiF3 host lattice have been investigated. A series of concentrations of Ce3+ ion with a fixed Eu2+ concentration in doubly doped BaLiF3:Ce3+,Eu2+ have been studied. According to the defects forming after Eu2+ and Ce3+ entering the host lattice, cerium ions occupy the positions of nearest neighbors of the europium ions. The energy transfer probability and critical distance are calculated. (C) 1999 Elsevier Science Ltd. All rights reserved.

ELECTROCHEMICAL STUDY OF ISOPOLY-OXOMETALLATE AND HETEROPOLY-OXOMETALLATE FILM MODIFIED MICROELECTRODES .2. ELECTROCHEMICAL-BEHAVIOR OF ISOPOLYMOLYBDIC ACID MONOLAYER MODIFIED CARBON-FIBER MICROELECTRODES

In this paper the electrochemical properties of isopolymolybdic anion thin film modified carbon fibre (CF) microelectrode prepared by simple dip coating have been described. The modified electrode shows three couples of surface redox waves between + 0.70 and - 0.1 V vs. sce in 2 M H2SO4 solution with good stability and reversibility. The pH of solution has a marked effect on the electrochemical behaviour and stability of the film, the stronger the acidity of electrolyte solution is, the better the stability and reversibility of isopolymolybdic anion film CF microelectrode will be. The scanning potential range strongly influences on the electrochemical behaviour of the film. The isopolymolybdic anion film prepared by the dip coating resulting a monolayer with estimated surface concentration (F) 2.8 x 10(-11) mol cm-2. From the half-peak widths and peak areas of the surface redox waves of the film electrode, the first three surface waves are corresponding to two-electron processes. The electron energy spectra show the products by six electrons reduction are a mixture of Mo(VI) and Mo(V) species. The electrochemical reaction of the isopolymolybdic anion monolayer can be expressed as Mo8O264- + mH+ + 2ne half arrow right over half arrow left [HmMo8-2n(VI)Mo2n(V)O26](4,2n-m)-n = 1, 2, 3; m = 2, 5, 7.

(η~5-C_9H_7)_3Ln·OC_4H_8(Ln=Nd、Gd、Er)的合成及晶体结构

合成了三茚基稀土配合物(η~5-C_9H_7)_3Ln·OC_4H_8(Ln=Nd、Gd、Er),经元素分析、红外光谱、水解产物核磁共振谱及质谱表征,并测得了(η~5-C_9H_7)_3Nd·OC_4H_8(1)及(η~5-C_9H_7)_3Gd·OC_4H_8(2)的晶体结构。(1)、(2)均属六方晶系,P6_3空间群,Z=2。(1)的晶体学参数为a=b=1.1843(3)nm,c=1.0304(4)nm,V=1.25165(87)nm~3,D_c=1.49g·cm~(-3),最后一致性因子R=0.049;(2)的晶体学参数a=b=1.1805(2)nm,c=1.0236(2)nm,V=1.23536(56)nm~3,D_c=1.54 g·cm~(-3),R=0.023。平均Nd-C=0.2812nm,Gd-C=0.2795nm;Nd-O=0.2557(21)nm,Gd—O=0.2459(13)nm。配合物中四氢呋喃的四个碳原子处于完全无序状态。

Life history strategies of Calanus sinicus in the southern Yellow Sea in summer

Ecological and physiological features of the planktonic copepod Calanus sinicus in the southern Yellow Sea in summer were studied to reveal its life history strategy. From the coastal shallow waters to the central part of the southern Yellow Sea, a shift of the stage composition occurs from being dominated by the egg-nauplius stage to being dominated by the fifth copepodite (CV) stage. Most CVs reside in the Yellow Sea Cold Water Mass (YSCWM), where both temperature and food abundance are low. CVs in the YSCWM have longer body lengths, heavier body weights and higher carbon contents than those outside the YSCWM. Onboard incubations show that the development of CVs in the YSCWM is suspended. Energy conservation, development suspension and lack of diel vertical migration (DVM) behavior suggest a diapause status for the CVs in the YSCWM, although vertical distribution patterns indicate the CV individuals are not fully synchronous in physiology and development. This adaptive oversummering strategy would help C. sinicus to live through the warm and food-limited summer in the central part of the southern Yellow Sea; both low temperature and low food supply are necessary for CV to maintain the resting state in the YSCWM. Calanus sinicus exhibits different life history strategies in different regions of the southern Yellow Sea in summer.

Bromophenols coupled with methyl gamma-ureidobutyrate and bromophenol sulfates from the red alga Rhodomela confervoides

Four new bromophenols C-N coupled with methyl gamma-ureidobutyrate (1-4), a phenylethanol bromophenol (5), and three phenylethanol sulfate bromophenols (6-8) have been isolated from polar fractions of an ethanolic extract of the red alga Rhodomela confervoides. On the basis of spectroscopic evidence including HRMS and 2D NMR data, the structures of the new compounds were determined as methyl N'-(2,3-dibromo-4,5-dihydroxybenzyl)-gamma-ureidobutyrate (1), methyl N,N'-bis(2,3-dibromo-4,5-dihydroxybenzyl)-gamma-ureidobutyrate (2), methyl N'-[3-bromo-2-(2,3-dibromo-4,5-dihydroxybenzyl)-4,5-dihydroxybenzyl]-gamma-ureidobutyrate (3), methyl N'-(2,3-dibromo-4,5-dihydroxybenzyl)-A7-[3-bromo2-(2,3-dibromo-4,5-dihydroxybenzyl)-4,5-dihydroxybenzyl]-gamma-ureidobutyrate (4), 2,3-dibromo-4,5-dihydroxyphenylethanol (5), 2,3-dibromo-4,5-dihydroxyphenylethanol Sulfate (6), 3-bromo-4,5-dihydroxyphenylethanol sulfate (7), and 3-bromo2-(2,3-dibromo-4,5-dihydroxybenzyl)-4,5-dihydroxyphenylethanol sulfate (8). The cytotoxicity of all compounds was evaluated against several human cancer cell lines including human colon cancer (HCT-8), hepatoma (Bel7402), stomach cancer (BGC-823), lung adenocarcinoma (A549), and human ovarian cancer (A2780). Among them, the phenylethanol and the phenylethanol sulfate bromophenols (5-8) showed moderate cytotoxicity against all tested cell lines.

高寒草甸不同海拔梯度下多年生黄帚橐吾的克隆生长特征

通过对多年生植物黄帚橐吾(Ligularia virgaurea)在四个不同海拔梯度下的克隆生长行为进行研究,结果表明:(1)资源水平(土壤养分)、干扰和群落性质影响间隔物(spacer)长度的变化.在第一和第四海拔梯度中(土壤养分较丰富)间隔物长度较短,而在第二和第三海拔梯度中(土壤养分较贫乏)间隔物长度较长,说明其能对资源水平和生境优劣作出反应.(2)分枝强度(branching intensity)随资源水平的增加而上升.(3)在高海拔、寒冷和资源较丰富的生境中,其生物量的投资偏向于地下部分生物量,说明黄帚橐吾的资源分配方式受到环境资源条件和群落性质的影响.

一个数控自动编程系统的自然语言接口

本文简要介绍了一个数控自动编程专家系统的自然语言接口的实现.该自然语言接口是以我们研制的数控自动编程专家系统为背景,运行在 SUN3/4 工作站的 UNIX 下和 IBM/AT 机的 DOS 下,用 C语言编程.该自然语言接口由词法分析、句法分析、语义语用分析、目标生成和图形仿真五个模块及相应的知识库构成.该接口能够接受数控编程系统所需的对工件的英语自然语言描述并处理一些比较简单的英语语言现象.

智能机器人基于作业子空间划分的自学习自适应控制方法

现有的机器人自适应控制基本上都是在建立机器人线性化的动力学模型的基础上,采用某种显式或隐式参数辨识的方法,在线地修正控制作用.本文针对机器人运动和动力学参数变化的固有特点,提出一种完全不同的自学习自适应方法.这种方法基于智能机器人分级系统中的两级结构,并且在空间域里而不是在时间域里处理机器人参数的变化.把机器人的作业空间划分成子空间,其中包括重力载荷的作用,每个子空间对应一组控制器.规划的轨迹映射到作业空间形成子空间序列.用自学习方法选择与这个序列对应的最佳控制器序列.该方法算法简单,计算量小.避开了通常的自适应方法遇到的一系列困难问题.

菲和萘的非线性吸附过程研究

分配模型认为疏水性有机物在土壤上的吸附过程是一种分配的过程[1,2],平衡分配系数与土壤有机碳的含量存在线性相关关系.Weber和Huang[3,4]提出土壤吸附有机污染物的三端员模式.认为无机矿物表面和无定形有机质对有机污染物的吸附以相分配为主,而凝聚态有机质对有机污染物吸附则表现为非线性的.Pignatello和Xing[5,6]指出双模式吸附模型可将土壤有机质分为溶解相和孔隙填充相两个部分;认为有机污染物在溶解相上的吸附是一个分配过程,而在孔隙填充相中的吸附则服从兰格缪尔吸附等温模型,表现为非线性.可以肯定土壤有机质是引起疏水性有机物非线性吸附过程的主要组分.因此,本研究利用现代分析方法表征土壤有机质的化学组成和结构;定量研究多环芳技烃化合物菲和萘在吸附剂上的等温吸附过程;探讨疏水性有机污染物的非线性等温吸附与吸附剂中有机质化学组成和结构之间的关系.

(古)盐度研究的一种重要工具——锶同位素

本文详细地阐述了海水－陆表水双元体系中锶同位素的混合原理、混合水体中＾８７Ｓｒ／＾８６Ｓｒ值与盐度的定量关系。利用Ｓｒ同位素不随生物、何尝作用过程发生分馏作用及Ｓｒ与Ｃａ化学性质相似等特征，地层、沉积物中生物壳体和碳酸盐岩＾８７Ｓｒ／＾８６Ｓｒ值可作为沉积水体（古）盐度确定的一种有用工具。文中详细地综述了国内外在这方面的研究进展，并讨论了成岩后生作用对生物壳体和碳酸盐岩＾８７Ｓｒ／＾８６Ｓｒ原始值

An in-situ modified sol-gel process for monolith catalyst preparation used in the partial oxidation of methane

An in-situ modified sol-gel method for the preparation of a Ni-based monolith-supported catalyst is reported. With the presence of a proper amount of plasticizer and binder, and at an optimized pH value, the stable boehmite sol was modified with metal ions (Ni, Li, La) successfully without distinct growth of the particle size. Monolith-supported Ni-based/gamma-Al2O3 catalysts were obtained using the modified sol as the coating medium with several cycles of dip-coating and calcination. Combined BET, SEM-EDS, XRD and H-2-TPR investigations demonstrated that the derived monolith catalysts had a high specific surface area, a relatively homogeneous surface composition, and a high extent of interaction between the active component and the support. These catalysts showed relatively stable catalytic activities for partial oxidation of methane (POM) to syngas under atmospheric pressure. The monolith catalysts prepared by this sol-gel method also demonstrated an improved resistance to sintering and loss of the active component during the reaction process.

Widzieć siebie — z czasu minionego ("Tamten" Bolesława Leśmiana i "Kilkunastoletnia" Wisławy Szymborskiej)

The article presents a juxtaposition of the following two brilliant poems "Tamten" (from the collection of poems entitled "Napój cienisty", 1936) and "Kilkunastoletnia" (from the collection of poems entitled "Tutaj", 2009) that employ the same idea of an encounter with oneself – an adolescent person (in the former poem) and a teenage girl (in the latter). The poems exceed the literary convention of just a lyrical reminiscence of the past, they rather form a particular dialogue with the narrator as he/she was years ago, or even propose a kind of a confrontation. Both poems indirectly feature reflections on the passing time and on the author's identity. The poem written by Leśmian fits perfectly into his poetical system, both in terms of the introduction of metaphysical threads and the application of the elements of a love poem and in terms of the plot outline, somewhat reminiscent of his ballads. Szymborska's poem also concurs with her own poetics mostly due to the characteristic subtle auto-irony.