酸雨对重庆地区不同植被下土壤的影响

在地处亚热带，酸雨污染严重的重庆地区土壤上，近一年的定位研究表明：1）酸雨促进了马尾松针叶林林内降水的酸化和元素的淋失。在重污染的城区针叶林，其冠流和干流pH分别为3.71和2.75，离子含量分别是郊区冠流、干流的1.2-3.2倍和1.1-2.7倍。2）森林死地被物层对酸性降水有中和、缓冲作用，其中阔叶林死地被物层作用大于针叶林。3）酸雨有助于马尾松针叶林黄壤的酸化和土壤溶液中离子含量的增加。重污染的城区与轻污染的郊区比较，土壤溶液pH低0.2-0.8，而离子含量却普遍增高。4）在重庆地区的土壤溶液中，SO~(2-)_4是优势阴离子，占所测阴离子总量的60-90％，但土壤溶液中Al~(3+)含量却很低。目前土壤溶液中Al~(3+)不可能对树木产生毒害作用。

Gas permeability and permselectivity of polyimides prepared from phenylenediamines with methyl substitution at the ortho position

Polyimides were prepared from diamines: 2,4,6-trimethyl-1,3-phenylenediamine (3MPDA) and 2,3,4,5-tetramethyl-1,4-phenylenediamine (4MPDA). 1,4-Bis(3,4-dicarboxyphenoxy)benzene dianhydride (HQDPA), 3,3',4,4'-benzophenone tetracarboxylic dianhydride (BTDA), 3,3'-4,4'-diphenylsulphone tetracarboxylic dianhydride (SO(2)PDA), 3,3',4,4'-diphenylsulphide tetracarboxylic dianhydride (SPDA), pyromellitic dianhydride (PMDA), and 2,2'-bis(3,4-dicarboxyphenyl)hexa-fluoroisopropane dianhydride (6FDA) were used as dianhydride. The gas permeabilities of H-2, O-2 and N-2 through the polyimides were measured at temperatures from 30 degrees C to 90 degrees C. The results show that as methyl and trifluoromethyl substitution groups densities increase from 7.73 x 10(-3) molcm(-3) to 13.50 x 10(-3)molcm(-3), the peameability of H-2 increases 10-fold at 60% loss of permselectivity of H-2/N-2 however, the permeability of O-2 increases 20-fold at 20% loss of permselectivity of O-2/N-2. For O-2/N-2 separation, PMDA-3MPDA has similar performance to 6FDA-3MPDA and 6FDA-4MPDA; all have higher permeabilities for O-2 than normal polyimides, and the P(O-2)/alpha(O-2/N-2) trade-off relationships lie on the upper bound line for polymers. (C) 1999 Society of Chemical Industry.

贵州乌江水系河水硫同位素组成研究

对乌江丰水期河水硫酸盐的硫同位素组成特征进行了研究。SO^2- 4平均浓度为0．48mmol／L，δ^34S值为-11．5‰～8．3‰，干流河水834S值为-6．7％。～-3．9‰。河水的硫同位素组成主要受岩石风化及大气降水的影响，具有明显的区域性分异特征：上游碳酸盐岩地区河水的SO^2- 4浓度高而834s值低，SO^2- 4主要来源于煤中黄铁矿的氧化、矿床硫化物的氧化和大气降水；下游碳酸盐岩夹碎屑岩地区河水中的SO^2- 4浓度低而δ^34 S值高，SO^2- 4主要来源于大气降水和石膏溶解，煤中黄铁矿氧化生成的硫酸盐所占比重较低。乌江河水向贵州省外输出的SO^2- 4。通量为172×10^10g／a，丰水期占全年SO^2- 4输出总量的72％。来自煤、硫化物、雨水和蒸发岩的硫对丰水期河水中SO^2- 4的平均贡献分别为：50％、25％、20％和5％。H2s04对碳酸盐岩的侵蚀速率为35．1t／km^2／a（17．5mm／ka），由此降低大气CO2消耗速率3．66×10^5moL／km^2／a.

贵州喀斯特地区河流的地球化学研究

河水的地球化学研究可以获得有关流域盆地化学风化、气候、上地壳的平均化学和同位素组成以及化学元素在大陆－河流－海洋系统中外生循环过程的重要信息。作为岩溶环境分异强烈的贵州碳酸盐岩区，其地表岩石土壤的风化侵蚀过程，必然具有很大的特殊性，也必然对地表环境系统产生重要的影响。构成该地区生态环境脆弱性和地球化学敏感性的一个重要特性。本论文通过对喀期特地区河流中河水的主量元素、微量元素及其锶同位素组成和分布特征的研究，得出如下主要结论和几点新认识。（1）贵州喀斯特地区河流水化学及地球化学特征主要受控于亚热带湿润气候条件下碳酸盐岩的溶解过程，以高Ca、Mg和高碱度区别亚洲和其它地区河流，其主量元素含量的沿程变化是由流域的岩石和土壤的化学成分、矿物组成及流域的物理、化学风化作用决定的。（2）碳酸盐的溶解－沉淀平衡是制约贵州喀斯特地区河流水化学的重要因素，高Ca、Mg和高碱度导致贵州喀斯特地区河流河水具有沉积性特征，河水相对于CaCO_3处于过饱和状态。（3）贵州喀斯特地区河流大多数河水样品的Sr同位素组成均落在显生宙海水的变化范围内。贵州喀斯特地区河流的Sr同位素组成主要受自然风化过程的影响，河水中Sr的浓度及其同位素组成主要来源于两个端员即具有高的Sr浓度、低的~(86)Sr/~(87)Sr比值的碳酸盐岩端员的风化和具有低的Sr浓度、高的~(86)Sr/~(87)Sr比值的硅酸盐岩端员的风化的混合。Sr同位素组成与元素比值（如Na/Ca、Mg/Ca等）的变化同时辨别出以白云岩为主和以石灰岩为主的溶解端员，贵州喀斯特地区河流的化学组成主要受石灰岩风化作用的控制。（4）通过对贵州喀斯特地区河流河水的主量元素、特别是阴离子（SO~(2-)_4、NO~-_3）和微量元素的含量及其控制因素的研究，表明贵州喀斯特地区河流受污染的程度远低于许多发达国家的河流。贵州乌江水系河流受工业污染的程度高于沅江水系的河流，而沅江水系河流受农业污染的程度高于乌江水系的河流，这与乌江流域的工业比沅江流域的工业发达相一致。（5）对贵州喀斯特地区河流中的一些重金属元素分布的初步研究表明，碳酸盐岩地区河流的高碱度使得河水中重金属离子的停留时产不长，其自然净化能力可能比硅酸盐岩地区的河流高。

长江水环境的地球化学初步研究

1）长江沿程水溶态#delta#~(34)SO~(2-)_4的变化范围为-3.474～+5.938 per thousand，算术平均值为2.254 per thousand；悬浮态#delta#~(34)S之间的变化范围为-4.031 approx +4.580 per thousand。长江中水溶态#delta#~(34)SO~(2-)_4与悬浮态#delta#~(34)S之间存在相关性；2）根据长江中水溶态#delta#~(34)SO~(2-)_4的平均和它的径流量，估算中国河流#delta#~(34)SO~(2-)_4的加权平均值为+2.7 per thousand。结合中国长江、黄河的硫同位素组成和亚洲其它主要河流水溶态SO~(2-)_4的含量，推测亚洲河流的#delta#~(34)SO~(2-)_4加权平均值可能为+5 per thousand；3）长江流域内的区域地质条件决定了河流悬浮物中稀土元素和微量元素的背景含量－－悬浮物中稀土元素和大多数微量元素的含量为东高西低；4）悬浮物中大多数元素的含量随时间的变化基本保护不变，其变化幅度在自然波动范围之内；而砷元素在悬浮物中的含量随时间有明显的增高趋势，这显示了长江流域内的As污染源的增加。

社会冲突信息加工的事件相关电位研究

Processing of discrepant information is an important part in our everyday life. According to the social attributes of information, it can be categorized into two parts: social discrepancy and nonsocial discrepant information. The researches focused on nonsocial discrepancy are much mature than those of social discrepancy processing. This serial study employed three ERP experiments to explore the attributes of social discrepancy cognition. Experiment one compared the ERP differences between social and nonsocial discrepancy processing, experiment two adopted single stimulus paradigm to explore the negativity attention biases of social emotions, experiment three investigated the affective mechanism of emotions to social discrepancy information with cue-target paradigm, based on the experiment one and two. We invited healthy undergraduates to participate in our researches, in which social gender words and affective images were stimuli to explore the temporal sequences, activated modes and affective mechanisms of social discrepancy. The results were as below: 1. The differences of attention resource distributions between social and nonsocial information processing exhibited as early as 200 ms, since which P2 was evoked in both blocks. The larger P2 in nonsocial block represented the more attention to physical and nonsocial attributes of objects. N300/400 indicated the differences of evaluating systems in each block. The cognitive mechanisms of social and nonsocial tasks were specific, based on the fact: (1) the discrepancy evaluating system was activated earlier in nonsocial block than that of social block; (2) the social cognition performed right hemisphere advantage, but nonsocial task did not so. 2. Social emotions also could raise a negativity bias on attention. The latency of P2 evoked by social sad images was shorter than that of social happiness and neutral images. The latencies of P2 indicated that sad emotions attracted attention earlier, and possessed a processing advantage. The phenomenon that the larger N2 was evoked by social sadness showed that people was easily moved by sad emotions and sympathized the sadness. 3. Emotions affected social discrepancy processing. Positive affective mood magnified the discrepancy effect, based on the smaller latencies of difference N400 and larger amplitudes. Persons with happy mood synthesized social stereotypes to accelerate the social tasks. 4. Three experiments all showed the right hemisphere advantages of social cognition and social emotions, offered more proof in laterality hypothesis of social cognition. Above all, social cognition had essential distinctions with nonsocial cognition; they two had their own specific characteristics. The fact that social cognition was prone to be affected by different emotional mood made it more complex.

Internal resonance of an L-shaped beam with a limit stop .2. Forced vibration

A limit stop is placed at the elbow of an L-shaped beam whose linear natural frequencies are nearly commensurable. As a result of this hardening device the non-linear system exhibits multiple internal resonances, which involve various degree of coupling between the first five modes of the beam in free vibration. A point load is so placed as to excite several modes and the resulting forced vibration is examined. In the undamped case, three in-phase and two out-of-phase solution branches have been found. The resonance curve is extremely complicated, with multiple branches and interactions between the first four modes. The amplitudes of the higher harmonics are highly influenced by damping, the presence of which can effectively attenuate internal resonances. Consequently parts of the resonance curve may be eliminated, with the resulting response comprising different distinctive branches. (C) 1996 Academic Press Limited

The kinetic-theory for dilute solid liquid 2-phase flow

On the basis of a brief review of the continuum theory for macroscopic descriptions and the kinetic theory for microscopic descriptions in solid/liquid two-phase flows, some suggestions are presented, i.e. the solid phase may be described by the Boltzmann equation and the liquid phase still be described by conservation laws in the continuum theory. Among them the action force on the particles by the liquid fluid is a coupling factor which connects the phases. For dilute steady solid/liquid two-phase flows, the particle velocity distribution function can be derived by analogy with the procedures in the kinetic theory of gas molecules for the equilibrium state instead of being assumed, as previous investigators did. This done, more detailed information, such as the velocity probability density distribution, mean velocity distribution and fluctuating intensity etc. can be obtained directly from the particle velocity distribution function or from its integration. Experiments have been performed for dilute solid/liquid two-phase flow in a 4 x 6 cm2 sized circulating square pipe system by means of laser Doppler anemometry so that the theories can be examined. The comparisons show that the theories agree very well with all the measured data.

Influence of carbon on the thermoluminescence and optically stimulated luminescence of α -Al2O3:C crystals

alpha-Al2O3:C crystal shows excellent thermoluminescence (TL) and optically stimulated luminescence (OSL) properties but the real role carbon plays in this crystal is still not clearly understood so far. In this work, alpha-Al2O3:C crystal doping with different amounts of carbon were grown by the temperature gradient technique, and TL and OSL properties of as-grown crystals were investigated. Additionally, a mechanism was proposed to explain the role of carbon in forming the TL and OSL properties of alpha-Al2O3:C. TL and OSL intensities of as-grown crystals increase with the increasing amount of carbon doping in the crystal, but no shift is found in the glow peak location at 465 K. As the amount of carbon doping in the crystals decreases, OSL decay rate becomes faster. With the increase in heating rate, the integral TL response of as-grown crystals decreases and glow peak shifts to higher temperatures. TL response decrease rate increases with the increasing amount of carbon doping in the crystals. All the TL and OSL response curves of as-grown crystals show linear-sublinear-saturation characteristic, and OSL dose response exhibits higher sensitivity and wider linear dose range than that of TL. The crystal doping with 5000 ppm carbon shows the best dosimetric properties. Carbon plays the role of a dopant in alpha-Al2O3:C crystal and four-valent carbon anions replace the two-valent anions of oxygen during the crystal growth process, and large amounts of oxygen vacancies were formed, which corresponds to the high absorption coefficient of F and F+ centers in the crystals.

SO(n)规范势的可分解理论

使用几何代数方法 ,研究了n维紧致黎曼流形上SO(n)规范势 (自旋联络 )的一般分解理论 ,建立了SO(n)规范场用球丛上单位矢量场n分解的一般表达式 .由此 ,分别得到了U(1 )规范场和U(2 )规范场用单位矢量场n分解的一般形式 .

板栗壳吸附Cu~(2+)的平衡与动力学研究及工艺设计

研究了板栗壳吸附Cu2+的平衡、动力学和热力学特征并对吸附工艺进行设计.采用Langmuir和Freundlich等温线对静态吸附平衡数据进行了拟合,同时采用准一级动力学和准二级动力学模型对静态吸附动力学数据进行了拟合,并计算了吸附过程的热力学参数自由能变(ΔGo)、焓变(ΔHo)和熵变(ΔSo).结果表明,平衡实验数据符合Langmuir等温吸附模型,分离因子RL值在0～1之间,为有利吸附;动力学实验数据符合准二级动力学方程,平衡吸附量随Cu2+起始浓度增大而增大;ΔHo和ΔSo分别为12.206kJ·mol-1和21.534J·mol-·1K-1,ΔGo为负值,表明板栗壳吸附Cu2+为放热过程,可以自发进行,吸附过程增加了固液界面的混乱度.基于Langmuir等温吸附模型推导出的板栗壳用量计算公式可用于预测将一定体积一定起始浓度Cu2+溶液经过吸附降至所需浓度的板栗壳用量.

Synthesis and self-assembly of poly(ethylene oxide)-b-poly(2-hydroxyethyl methacrylate)

Poly(ethylene oxide)-b-poly(2-hydroxyethyl methacrylate) (PEO-b-PHEMA) was synthesized by successive atom transfer radical polymerization (ATRP) of 2-hydroxyethyl methacrylate(HEMA) monomer using PEO-Br macroinitiator as initiator, CuBr/CuBr2 and 2,2.-bipyridyl (bpy) as catalyst and ligand. IR, H-1 NMR, and GPC analysis indicate that PEO-b-PHEMA block copolymer with low polydispersity index (M-w/M-n approximate to 1.1) has been formed. Self-assembly of this double hydrophilic block copolymer in the selective solvent and water was also studied. Owing to the high hydrophilic nature of the PEO and PHEMA blocks, this double hydrophilic block copolymer cannot disperse well in water. So block copolymer was modified by part esterification of PEO-b-PHEMA with acetic anhydride, which increased the hydrophobic group of the PHEMA block. The TEM results show that this block copolymer spontaneously form well-defined micelles in water.

Electrochemiluminescent detection based on solid-phase extraction at tris(2,2 '-bipyridyl)ruthenium(II)-modified ceramic carbon electrode

A sensitive electrochemiluminescent detection scheme by solid-phase extraction at Ru(bpy)(3)(2+)-modified ceramic carbon electrodes (CCEs) was developed. The as-prepared Ru(bpy)(3)(2+)-modified CCEs show much better long-term stability than other Nafion-based Ru(bpy)(3)(2+)-modified electrodes and enjoy the inherent advantages of CCEs. The log-log calibration plot for dioxopromethazine is linear from 1.0 x 10(-9) to 1.0 x 10(-4) mol L-1 using the new detection scheme. The detection limit is 6.6 x 10(-10) mol L-1 at a signal-to-noise ratio of 3. The new scheme improves the sensitivity by similar to 3 orders of magnitude, which is the most sensitive Ru(bpy)(3)(2+) ECL method. The scheme allows the detection of dioxopromethazine in a urine sample within 3 min. Since Ru(bpy)(3)(2+) ECL is a powerful technique for determination of numerous amine-containing substances, the new detection scheme holds great promise in measurement of free concentrations, investigation of protein-drug interactions and DNA-drug interactions, pharmaceutical analysis, and so on.