Characterization of hydraulic mortars by means of simultaneous thermal analysis

The properties of hydraulic mortars were studied by means of simultaneous thermal analysis (STA), according to a procedure proposed in the literature. Hydraulic limes, cement and/or slaked lime were mixed using different proportions of both inert and reactive aggregates, in order to test the effectiveness of such procedure in distinguishing the different degree of hydraulicity of such samples. The use of the normalized coordinates suggested in the literature results in overlapping of the clusters of different kinds of mortars. Modified coordinates are proposed, which give promising results in view of outlining a ‘master curve’ of hydraulicity.     

Aptamer sensor for cocaine using minor groove binder based energy transfer

We report on an optical aptamer sensor for cocaine detection. The cocaine sensitive fluorescein isothiocyanate (FITC)-labeled aptamer underwent a conformational change from a partial single-stranded DNA with a short hairpin to a double-stranded T-junction in the presence of the target. The DNA minor groove binder Hoechst 33342 selectively bound to the double-stranded T-junction, bringing the dye within the Förster radius of FITC, and therefore initiating minor groove binder based energy transfer (MBET), and reporting on the presence of cocaine. The sensor showed a detection limit of 0.2 μM. The sensor was also implemented on a carboxy-functionalized polydimethylsiloxane (PDMS) surface by covalently immobilizing DNA aptamers. The ability of surface-bound cocaine detection is crucial for the development of microfluidic sensors.     

Synthesis of carbon nanofibers@MnO2 3D structures over copper foil as binder free anodes for lithium ion batteries

A 3D structured composite of carbon nanofibers@MnO₂ on copper foil is reported here as a binder free anode of lithium ion batteries, with high capacity, fast charge/discharge rate and good stability. Carbon nanofiber yarns were synthesized directly over copper foil through a floating catalyst method. The growth of carbon nanofiber yarns was significantly enhanced by mechanical polishing of the copper foils, which can be attributed to the increased surface roughness and surface area of the copper foils. MnO₂ was then grown over carbon nanofibers through spontaneous reduction of potassium permanganate by the carbon nanofibers. The obtained composites of carbon nanofibers@MnO₂ over copper foil were tested as an anode in lithium ion batteries and they show superior electrochemical performance. The initial reversible capacity of carbon nanofibers@MnO₂ reaches up to around 998 mAh·g^?1 at a rate of 60 mmA·g^?1 based on the mass of carbon nanofibers and MnO₂. The carbon nanofibers@MnO₂ electrodes could deliver a capacity of 630 mAh·g^?1 at the beginning and maintain a capacity of 440 mmAh·g^?1 after 105 cycles at a rate of 600 mA·g^?1. The high initial capacity can be attributed to the presence of porous carbon nanofiber yarns which have good electrical conductivity and the MnO₂ thin film which makes the entire materials electrochemically active. The high cyclic stability of carbon nanofibers@MnO₂ can be ascribed to the MnO₂ thin film which can accommodate the volume expansion and shrinking during charge and discharge and the good contact of carbon nanofibers with MnO₂ and copper foil.     

Novel affinity chromatography method for the efficient purification of recombinant Binder of SPerm homolog proteins

In mammalian species, a family of proteins named the Binder of SPerm proteins, which are expressed in the male reproductive tract, have been shown to play a role in epididymal sperm maturation and sperm capacitation. Recently, one homolog from human and two homologs from mouse were characterized. In order to further investigate the biochemical activity of these proteins, efficient purification procedures are required to isolate the proteins. Since these proteins are produced in very minute quantities, we exploited the high capacity of Escherichia coli to produce larger quantities of recombinant proteins that were subsequently purified using affinity chromatography on a diethylaminoethyl‐Sephadex A‐25 column. Binder of SPerm proteins have been shown to interact with pseudo‐choline groups such as diethylaminoethyl through affinity rather than ionic interactions. The aim of the current study was to develop a novel method for purifying these recombinant proteins, produced in Escherichia coli cells. Diethylaminoethyl is positively charged and is a weak anion exchanger, but binder of sperm proteins interacts with affinity to this resin. This study presents a new, rapid, and cost‐effective purification method that provides with an exceptional purity level, which can be used to study their roles in mammalian fertilization.     

INDUCTION OF CRYSTALLIZATION OF SPECIFIC CALCIUM OXALATE HYDRATES IN MICELLAR SOLUTIONS OF SURFACTANTS

ABSTRACT

The influence of octaethylene glycol mono-n-hexadecyl ether (C₁₆EO₈) and sodium dodecyl sulphate (SDS) on the crystallization of calcium oxalate from 0.3 mol dm^?3 sodium chloride solutions has been investigated. The critical micellar concentration (CMC) of C₁₆EO₈ in water and 0.3 mol dm^?3 NaCl was determined by surface tension measurements (CMC_H2O=CMC_NaCl = 7.2.10^?6 mol dm^?3). The kinetics of precipitation of calcium oxalate was followed by Coulter counter, and solid phases were characterized by polarized microscopy, thermal analysis and X-ray powder diffraction patterns. Under the precipitation conditions employed, the thermodynamically stable monohydrate, CaC₂O₄?H₂O (COM) was the predominant crystalline form. In the presence of micellar solutions of C₁₆EO₈ precipitation of this phase was facilitated as evidenced by higher initial precipitation rates and higher precipitate volume and number of particles, as compared to the controls. Micellar solutions of 50S retarded precipitation but induced crystallization of calcium oxalate dihydrate, CaC₂O₄?(2+×)H₂O (COD, x≤0.5). Thus at c(SDS>CMC the precipitates contained ≥85 mass % COD. The results are discussed in relation to previously reported data on the precipitation of calcium oxalate in the presence of dodecyl ammonium chloride     

A Quartz Crystal Microbalance Characterization of Metal‐Oil Interfaces and Interactions with Wax Molecules

The solid‐liquid interface between stainless steel and model petroleum fluids is investigated at isothermal conditions using a quartz crystal microbalance. AISI 316 (Fe/Cr18/Ni10/Mo3) stainless steel is chosen to represent the metal surface. Paraffin components dissolved in dodecane constitute the petroleum fluid phase. Commercial macro‐crystalline and micro‐crystalline waxes provide primarily linear and branched paraffin components, respectively. Paraffin solubility conditions are established through a van't Hoff relationship. Model fluids prepared with the single‐component alkanes n‐C₃₆ or n‐C₃₀ paraffin provide well‐defined solubility conditions. Monitored changes in resonance frequency and energy dissipation of the quartz crystal resonator immersed in the model fluids confirm that no continual deposition of paraffin components occurs at isothermal conditions. Solid paraffin crystals dispersed in solution show no adherence to the stainless steel surface. The absence of attractive interactions between the stainless steel surface and the dispersed paraffin crystals suggests that a surface adsorption and/or surface nucleation mechanism is responsible for the formation of incipient paraffin wax deposits under nonquiescent conditions.     

Stabilization of Paraffin Emulsions Used in the Manufacture of Chipboard Panels by Liquid Crystalline Phases

Paraffin emulsions are commonly used in the manufacture of chipboard panels to provide resistance to water and humidity. The quality and performance of chipboards are improved with the use of paraffin emulsions stabilized by mixed surfactant systems, although little is known about the basic colloidal chemistry of such systems and their implications in the manufacturing and processing of the chipboard panels. In the present work, the stability and the phase behavior of paraffin emulsions stabilized by a mixture of anionic and nonionic surfactants, are described. Stability is studied by applying thermal and ultracentrifugation cycles, and also by rheology (steady state and dynamic determinations). A significant increase of stability is observed at high {anionic surfactant/(anionic surfactant+nonionic surfactant)} ratios. Phase behavior studies have demonstrated the presence of hexagonal liquid crystalline structures at high ionic surfactant/nonionic surfactant ratios and the presence of lamellar structures at low ratios. The stability of emulsions could be related to phase behavior, and, thus, providing a qualitative tool to predict stability.     

ZrO2/ SiO2多层膜的化学法制备研究

 分别以ZrOCl₂·8H₂O 和正硅酸乙酯为原料,采用溶胶-凝胶工艺制备了性能稳定的ZrO₂和SiO₂溶胶。用旋转镀膜法分别在K9玻璃和单晶硅片上制备了ZrO₂/ SiO₂多层膜。采用溶剂替换和紫外光处理等手段,有效地解决了ZrO₂/SiO₂多层膜中膜层开裂和膜间渗透等问题。应用扫描电子显微镜观测了薄膜的表面和剖面微观形貌,并用椭偏仪测得薄膜的厚度和折射率,研究了薄膜厚度、折射率与热处理温度、紫外光处理时间的关系,对所获得薄膜的紫外-可见、红外光谱进行了分析。用输出波长1064nm ,脉宽15ns 的电光调Q光系统产生的强激光进行了单层膜的辐照实验,结果发现溶剂替换后激光损伤阈值有所提高。     

固体石蜡碳糊—磷钼酸根电极的研制与应用

研究了以固体石蜡作粘和剂的碳糊电极,在磷钼酸溶液中活化一定时间后,该电极对1.0×10~(-6)～5.0×10~(-4)mol·L~(-1)的磷钼酸有能斯特响应,斜率约为30mV,检出限为3.2×10~(-7)mol·L~(-1).电极的稳定性和选择性较好,已用于矿石、水样中磷的测定,结果满意.     

乳胶粒化学改性酚醛树脂合成闸片的制动性能研究

采用自制的环保型乳胶粒化学改性酚醛树脂为粘结剂制备了和谐号电力机车用轮装式有机合成闸片,参照欧洲标准UIC 541-3: 2006和我国铁道部标准TB/T 3118-2005规定的试验程序,在铁道部产品质量监督检验中心机车车辆检验站进行了闸片的制动性能试验（最高速度200 km/h时制动闸片中心线速度为41.8 m/s）。试验结果表明该闸片在不同初始速度干燥条件下的平均摩擦系数在0.29 ~ 0.57,静摩擦系数平均值为0.47,36闸后的磨损率约为0.2 cm3/MJ,满足UIC 541-3: 2006中规定的指标。表面形貌观察发现制动试验后闸片无开裂、掉渣、塌边和皴裂等现象,红外分析发现闸片摩擦表面化学结构与基体基本一致,粘结剂未发生明显摩擦化学反应。该闸片在和谐号电力机车的制动中将有广阔的应用前景.