厚度对非极性聚合物薄膜驻极体电荷储存及电荷动态特性的影响

以Du Pont公司的商用Teflon FEP A型薄膜为例，通过热脉冲技术、等温表面电位衰减测量和开路热刺激放电电流谱分析等实验结果，讨论了经常温和高温电晕充电后样品厚度对薄膜驻极体的沉积电荷密度、薄膜驻极体的内电场、体电导率以及电荷储存稳定性的影响.通过热脉冲技术组合电导率温度曲线的测量，研究了在不同温度条件下样品厚度对沉积电荷层的平均电荷重心移动的影响.结果表明：在充电参数一定的条件下，随着膜厚的降低，储存电荷密度上升，但电荷稳定性有所下降.因此，合理地调控薄膜厚度，可以有效地优化驻极体的电荷储存能 关键词： 厚度 驻极体 电荷储存能力 电荷稳定性     

Maintenance of Soft Calibration Models in the Determination of Zinc,Cadmium, Lead and Copper by Differential Pulse Anodic Stripping Voltammetry

A strategy for constructing a global multivariate calibration model that includes calibration samples measured over time on different days is developed and applied in electroanalysis. Both synthetic and real samples (tap, extracted and river water) are analyzed by differential‐pulse anodic stripping voltammetry, showing the suitability of the global model constructed that provides successful results similar to those of the usual multivariate calibration. In addition the capability of discrimination of this model is evaluated in prediction for the mean of three replicates with estimation of probability of false noncompliance, α, and false compliance, β, being found 3.1, 11.2, 6.7 and 64.7 nM for nominal concentrations of zinc, cadmium, lead and copper of 96.0, 40.4, 37.3 and 328.0 nM respectively when α=β=0.05. It has been proven that the use of the global calibration does not imply a loss of multivariate analytical sensitivity, using this parameter as quality index of the analytical procedure. The viability of using calibration maintenance strategies with electroanalytical techniques is shown, providing a way to save time and experimental effort when these techniques are used in routine analysis.     

A Tin(IV) Porphyrin with Two Axial Organometallic NCN‐Pincer Platinum Units

A tin(IV) porphyrin was combined with two axial NCN‐pincer platinum(II) fragments by utilizing the oxophilicity of the apical positions on the tin atom and the acidic nature of the NCN‐pincer platinum derived benzoic acid. The solid‐state structure determined by X‐ray crystallography revealed some close contacts between the pincer complexes and the meso‐p‐tolyl subsitutents of the porphyrin. It was shown by ¹H NMR spectroscopy that these close contacts were not present in solution and that this compound can potentially act as a novel building block for supramolecular architectures.     

建筑施工高处坠落的原因及对策

高处坠落事故是建筑施工伤亡事故的主要原因之一,有效防止高处坠落事故对预防建筑施工安全事故有着十分重要的意义.本文针对建筑施工高处坠落事故现象,进行了原因分析,并提出预防高处坠落的具体措施.     

广义线性模型(六)

本讲座是广义线性模型这个题目的一个比较系统的介绍。主要分 3部分 :建模、统计分析与模型选择和诊断。写作时依据的主要参考资料是L .Fahrmeir等人的 :《MultivariateStatisticalModel ingBasedonGeneralizedLinearModles》。     

6σ管理中需要澄清的几个问题

6σ管理作为组织实施连续质量改进的一种经营策略,已引起企业界和学术界的极大兴趣,并在一些企业中得到很好应用。正确实施6σ,需要对其基本概念、假设条件、相关约束等有一个较为全面的了解和认识。本文探讨了6σ文献和应用过程中需要关注的几个问题,其中包括6σ的基本概念和特点;分布假设;过程均值1.5σ漂移的可行性;过程能力指数;短期波动和长期波动;6σ改进和6σ设计等。     

甲醛与乙腈相互作用的理论研究

在HF/ 6 311G(d ,p)、MP2 / 6 311G(d ,p)和B3LYP/ 6 311G(d ,p)水平上 ,对H2 CO和CH3 CN以及设计的 4种结构H2 CO…CH3 CN复合物等进行几何全优化和振动频率计算 ,排除振动频率为负值的非局域极小点结构 ,并对稳定的环状构型复合物结合能进行基组重叠误差校正和零点振动能校正 .分子间相互作用的能量分解分析显示 ,静电能在H2 CO…CH3 CN相互作用能量中占主导地位 ,电荷转移能居第二位 .     

回填材料膨润土对放射性气体滞留能力模拟研究

利用各种分析手段对膨润土的物理特性进行了表征 .X射线衍射分析表明钠基膨润土呈典型的六方晶胞 ,晶胞参数是 :a轴 4 .913,c轴 5 .4 0 5 ;差热分析曲线在低温区和高温区有明显的吸热峰出现 ;元素分析钠、钾离子的含量大于钙、镁离子的含量 ,在性能上表现为钠质膨润土具有较强的离子交换能力 ;显微分析表明其表面呈皱隙状 ,测定比表面积高达 2 4 .5 2m2 /g;吸水率测定表明膨胀率大 ,说明它具有密封功能 ,可有效阻滞地下水的渗入 .利用SF6示踪技术 ,通过采集不同时间段取样池样品 ,分析样品中示踪气体浓度 ,绘制取样池示踪气体浓度随时间的变化关系曲线 ,根据费克扩散定律计算扩散系数 .实验结果表明 ,随着压实膨润土密度的增大 ,示踪气体扩散系数迅速减小 ,当密度大于 1.8g/cm3 时 ,扩散系数降至 10 -9m2 /s.研究结果表明 ,膨润土性能优化是通过在膨润土中添加适量的活性炭 ,可明显改善其对气体的阻滞能力 ;增加其对放射性气体滞留能力 ;添加少量的石英砂增加其机械性能、导热性和减少蠕变性 ,将引起对气体阻滞能力的下降 .综合考虑 ,在膨润土中各添加 5 %活性炭和石英砂 ,既对气体具有较好的滞留能力 ,又具有较好的工程特性 .     

Synthesis of an Anti-1,3-Diol Type Chiral Building Block

Duringthelastdecade,1,3-dioltypechiralbuildingbIocksofvariousconfigurationshavebeensynthesizedandappliedwidelyinthetotalsynthesisofnaturalpolyenemacrolideantibiotics1'2andla,25-dihydroxyvitaminD3analogues'.RecentlyWeigandandBrucker4synthesizedachiralbuildingblock(4R,6R)-2,2-dimethyl-5-tert-butyldip4-hydroxymethyl-l,3-dioxane1inlOsteps.Herein,wereportasyntheticrouteofnewbuildingblock(4S,6S)-2,2-dimethyl-5-tert-butyldip2,anenantiomerofl,startingfromreadilyavailableandinexpensiveD( )-xylose3i…     

Validation of HPLC Analysis of 2-Phenoxyethanol, 1-Phenoxypropan-2-ol, Methyl, Ethyl, Propyl, Butyl and Benzyl 4-Hydroxybenzoate (Parabens) in Cosmetic Products, with Emphasis on Decision Limit and Detection Capability

The Commission Decision of August 12, 2002 on the performance of analytical methods and the interpretation of results was applied to the HPLC method for the analysis of parabens, 2-phenoxyethanol and 1-phenoxypropan-2-ol in cosmetic products. This method is published in the seventh Directive 96/45/EC of the European Commission. Non-compliant concentrations, taking into account the data distribution (CC) and the probability of false negative values (CC) were determined. The repeatability and reproducibility amount to <4% and <7%, respectively. These values were obtained with blanc samples that were fortified in the laboratory. Calibration linearity was confirmed by absence of lack of fit for all seven preservatives. Matrix effects on the determinations of the preservatives in body milk or shampoo are negligible.