甲基丙烯酸甲酯悬浮聚合实验教学的改进

选用氢氧化镁为分散剂,甲基丙烯酸甲酯(MMA)为单体,进行悬浮聚合反应,研究了分散剂用量、引发剂用量、水和单体比、搅拌速度、反应温度及反应时间对聚合物珠粒大小、均匀程度和产率的影响。结果表明:与目前高分子实验教材普遍选用的以聚乙烯醇(PVA)为分散剂的悬浮聚合反应相比,以氢氧化镁为分散剂,具有操作简单、聚合时间短、体系稳定性高等优点,可代替原有的悬浮聚合反应实验,作为高分子化学实验的教学课程内容。     

Preconcentration of samples in sandwich tanks for continuous thin-layer chromatography

It is demonstrated that horizontai sandwich tank with two cover plates can be used to preconcentrate sample solutions. Narrow sharply-defined starting zones are obtained just outside the smaller cover plate when the series of spots of the sample solution are applied on the thin layer and predeveloped with a volatile solvent. After evaporation of the solvent, the whole area of the TLC-plate is covered with two plates and developed with a suitable solvent.     

Simultaneous estimation of Poisson means

In the simultaneous estimation of means from independent Poisson distributions, an estimator is developed which incorporates a prior mean and variance for each Poisson mean estimated. This estimator possesses substantially smaller risk than the usual estimator in a region of the parameter space and seems superior to other estimators proposed to estimate p Poisson means. It is indicated through two asymptotic results that, unlike the conjugate Bayes estimator, the risk of the estimator does not greatly exceed the risk of the usual estimator outside of the region of risk improvement.     

还原偶氮测定硝基苯方法中样品背景存在的问题及改进

对还原偶氮法测定水中硝基苯分析方法中样品背景等方面存在的问题,以及对分析测定产生的影响进行了较为深入的分析和研究;提出了测定方法的改进意见.并通过硝基苯环境标准样品的实际测定,对改进前后的方法进行了对比和验证,取得了满意的结果.     

Improvement of amine-modification with piperazine for the adsorption of CO2

Both selectivity and capacity of CO₂ adsorption were considerably increased when PZ (piperazine) was added in MDEA (methyldiethylamine) that used to modify the surface of silica gels. The adsorbent saturated with CO₂ was regenerated at ambient temperature through nitrogen purge. A set of PSA (pressure swing adsorption) operation with 200 cycles was carried out and applicability of the modified adsorbent was thus illustrated. The CO₂ content in the column-top stream decreased from 13% to below 0.05% at steady state.     

聚乙烯醇缩丁醛LB膜制备及其对硬脂酸镉LB膜的修饰

研究了PVB单分子膜的π～A曲线和稳定性,沉积了优质LB膜,发现将PVB与CdSt₂形成交替异质的LB膜能提高膜的光学质量;在CdSt₂LB膜的上面封装PVBLB膜能保持CdSt₂LB膜的结构。     

苯甲醇和苯甲酸制备实验的改进与创新设计

以苯甲醛为原料,通过Cannizarro反应制备苯甲醇和苯甲酸是有机化学实验教学中的经典内容。鉴于现有实验方案已难满足日益提升的教学要求,对其进行了改进与创新设计:采用微波辐射法合成,引入正交设计优化条件;采用紫外分光光度法定量测定粗产品中苯甲醇的含量;采用柱层析法分离得到苯甲醇。改进结果表明:KOH溶液浓度50%(质量百分比),微波功率500 W时,反应15 min完成。光度法定量显示苯甲醇产率可达82.0%。萃取分离后的粗产品用50:1和15:1石油醚/乙酸乙酯(体积比)梯度洗脱,柱层析分离后可得苯甲醇纯品,水相酸化重结晶后得到苯甲酸。产物的相关测试与表征结果与文献吻合良好。与传统方案相比,新方案时间锐减99%,产率提高约15%,萃取剂更安全,产率测定快速准确,产物纯化方法优化。将之用于教学,可通过各要点功能的分别承载,综合实现研究性思维与方法的培养目标。     

水中总氮测定分析方法的改进

用"碱性过硫酸钾消解紫外分光光度法"测定水中的总氮时, 通过减少氧化剂中氢氧化钠的浓度, 使消解后溶液可以直接在波长210 nm处进行测定. 与原法相比, 简化了分析步骤, 节约了试剂;而且灵敏度提高了约2倍, 保证有很好的精密度和准确度.     

Forecasting mortality in subpopulations using Lee–Carter type models: A comparison

The relative performance of multipopulation stochastic mortality models is investigated. When targeting mortality rates, we consider five extensions of the well known Lee–Carter single population extrapolative approach. As an alternative, we consider similar structures when mortality improvement rates are targeted. We use a dataset of deaths and exposures of Italian regions for the years 1974–2008 to conduct a comparison of the models, running a battery of tests to assess the relative goodness of fit and forecasting capability of different approaches. Results show that the preferable models are those striking a balance between complexity and flexibility.     

Exposed crystal surface-controlled TiO2 nanorods having rutile phase from TiCl3 under hydrothermal conditions

Size-, shape-, and phase structure-controlled synthesis of TiO₂ nanocrystallites has long been one of the main themes in TiO₂ research. Many synthetic techniques have been utilized in the preparation of TiO₂ nanocrystals, among which hydrothermal treatment has been drawing much attention because it directly produces well-crystallized nanocrystallities of a wide range of compositions of crystal phases within a short reaction time. In this study, we carried out hydrothermal growth of rutile TiO₂ rods by using aqueous titanium trichloride (TiCl₃) solutions containing NaCl. Uniform ultrafine rutile TiO₂ particles were obtained, and developed crystal faces were observed by TEM, SEM, XRD, and specific surface area measurements. The obtained rutile fine particles showed high levels of activity for degradation of 2-propanol and acetaldehyde under UV irradiation compared to the activity levels of anatase fine particles (ST-01) developed for environmental clean-up. The surface chemistry of the rutile TiO₂ particles was also investigated. From photodeposition of Pt and PbO₂, we suggest that the (1 1 0) face provides reductive sites and that the (1 1 1) face provides oxidative sites. These results indicate that the crystal faces facilitate the separation of electrons and holes, resulting in improvement of photocatalytic activity.