Films formed from polystyrene latex/clay composites: A fluorescence study

This study reports a steady-state fluorescence (SSF) technique for studying film formation from surfactant-free polystyrene (PS) latex and Na-montmorillonite (SNaM) composites. The composite films were prepared from pyrene (P)-labeled PS particles and SNaM clay at room temperature and annealed at elevated temperatures in 10-min intervals above glass transition temperature (t₃) of polystyrene. During the annealing processes, the transparency of the film improved considerably. Scattered light (I_s) and fluorescence intensity (I_p) from P were measured after each annealing step to monitor the stages of film formation. Evolution of transparency of composite films was monitored by using photon transmission intensity, I_tr. Scanning electron microscopy (SEM) was used to detect the variation in physical structure of annealed composite films. Minimum film formation temperature, T_q, and healing temperatures, T_h, were determined. Void closure and interdiffusion stages were modeled and related activation energies were determined. It was observed that both activation energies increased as the percent of SNaM was increased in composite films.     

Sodium molybdate—a possible alternate additive for sodium dichromate in the electrolytic production of sodium chlorate

Sodium dichromate is commonly used in sodium chlorate production to maintain high current efficiency; however, it is also a well documented carcinogen. To reduce the environmental impact, identification of a suitable alternative with similar buffering characteristics to dichromate and without adverse effect on the electrolytic performance of sodium chlorate production is important; sodium molybdate is a good candidate. Molybdate ion and its conjugated acid work as a buffer pair at pH 5–6, a lower and slightly narrower pH window than the typical buffer region of dichromate. Nonetheless, the molybdate buffer works effectively during the electrolytic process by maintaining pH at 5.9. Although the use of molybdate buffer will lower the overpotential of hydrogen evolution reaction (HER) by 100 mV, the average off-gas oxygen content is noticeably compromised at 3.6–4.6%, measured using a pilot cell operated at 3 kA m⁻²and 80 °C during a 3-day trial. The resulting current efficiency of 91 92% is significantly lower than when dichromate is employed as the process additive (> 96%). Mixtures of different dichromate and molybdate ratio were also investigated in terms of the resulting cathode surface potential.     

Developmental variations in plasma leptin,leptin soluble receptor and their molar ratio in healthy infants

Background  

Leptin and its soluble receptor (sOB-R) are important to regulation of body composition but there are no data on the developmental variations in these plasma variables and their relationship with body composition measurements,     

The influence of preparation conditions on electrochemical properties of LiNi0.5Mn1.5O4 thin film electrodes by PLD

LiNi_0.5Mn_1.5O₄ thin films were prepared by pulsed laser deposition (PLD) on stainless steel substrates. The growth of the films has been studied as a function of substrate temperature and oxygen partial pressure in deposition, using X-ray diffraction (XRD) and field-emission scanning electron microscopy (FESEM). Electrochemical properties of LiNi_0.5Mn_1.5O₄ thin film cathodes were investigated using cyclic voltammetry and galvanostatic charge/discharge against a lithium anode. The initial capacity and capacity retention of the films are highly dependent on the crystallinity and purity of the films. LiNi_0.5Mn_1.5O₄ thin films grown at 600 °C in an oxygen partial pressure of 200 mTorr are well crystallized with high purity, exhibiting excellent capacity retention between 3 and 5 V with a LiPF₆-based electrolyte.     

Synthesis of highly crystalline spinel LiMn2O4 by a soft chemical route and its electrochemical performance

Highly crystalline spinel LiMn₂O₄ was successfully synthesized by annealing lithiated MnO₂ at a relative low temperature of 600 °C, in which the lithiated MnO₂ was prepared by chemical lithiation of the electrolytic manganese dioxide (EMD) and LiI. The LiI/MnO₂ ratio and the annealing temperature were optimized to obtain the pure phase LiMn₂O₄. With the LiI/MnO₂ molar ratio of 0.75, and annealing temperature of 600 °C, the resulting compounds showed a high initial discharge capacity of 127 mAh g⁻¹ at a current rate of 40 mAh g⁻¹. Moreover, it exhibited excellent cycling and high rate capability, maintaining 90% of its initial capacity after 100 charge-discharge cycles, at a discharge rate of 5 C, it kept more than 85% of the reversible capacity compared with that of 0.1 C.     

TSP203Plus超前地质预报技术在贵广铁路客运专线长大隧道施工中的应用技术研究

贵广铁路线路中特大长隧道、特大断面的隧道所占比例达到75%以上,隧道穿越某些地质情况复杂地区,可能遇到的工程地质问题及地质灾害较一般浅埋隧道更多、更严重。因此,在隧道施工中开展超前地质预报工作非常有必要。TSP203plus的工作原理和系统工作特点能满足工程预报需要。在贵广铁路部分隧道超前地质预报中证实了TSP203plus作为一种隧道地质预报手段的合理性和有效性。在对TSP203plus超前地质预报产生的误差原因进行分析的同时,提出了提高预报精度对策,从而指导不良地质条件下的隧道安全快速施工。     

现行农村土地制度的弊端

我国农村土地制度几经变迁,形成了现阶段农村土地集体所有、农户承包经营为主的农村土地制度架构.随着我国经济的迅猛发展,传统的农村土地制度已经不能适应社会主义新农村建设的要求,其弊端主要表现在土地的产权不完整、相应的法律法规规范性不足和管理体系紊乱.     

国内外大学生就业政策的比较分析及对策研究

将我国促进大学生就业政策与美、日、英、德等西方国家促进大学生就业政策进行了全面的介绍和比较分析,总结出我国现行大学生就业政策存在的优势和不足以及国外可借鉴的相关经验。通过对不同领域和不同层面促进就业的制度和政策内容及实施效果的分析,提出了从源头上解决大学生就业难的高校教育改革措施和完善政府促进就业的举措。     

微波条件下树形分子核单元的合成及优化

聚酰胺胺树形分子因其独特的分子结构使其在药物载体、生物化学、催化剂等方向有着潜在的应用.但常温下合成树形分子的周期较长,致使其成本高.从乙二胺出发,利用微波技术,通过反复摸索,优化得到了微波辅助合成聚酰胺胺树形分子核单元的最佳条件.     

一种基于无约束总变分模型的阴影检测方法

阴影检测是进行阴影处理前的重要步骤,总变分模型可以用于影像阴影检测.通过对总变分模型进行改进,提出了一种基于无约束总变分模型的阴影检测方法.经实验及统计分析证明,在合适的迭代条件下,该方法对于单一阴影影像的处理效果理想.