Capillary Electrophoresis Separation Techniques and Mechanisms in Dilute Polymer Matrices

Capillary electrophoresis in ultradilute derivatized solutions is used to separate nucleic acid fragment mixtures. Pulsed field techniques are used to improve resolution. Protocols in which pulse parameters are varied during the course of the separation are used to increase the range of fragment sizes separated. Fluorescence microscopy is used to study the separation mechanism in ultradilute solution.     

Electrochemical Detection of Artemisinin Using Cobalt Sulphide/Reduced Graphene Oxide Nanocomposite

Solvothermally synthesized cobalt sulphide/reduced graphene oxide (CoS/rGO) was used to fabricate an electrochemical sensor for detection of artemisinin. Microscopic techniques were used to characterize CoS/rGO nanocomposite. The electrochemical sensor was fabricated by modifying the surface of glassy carbon electrode with CoS/rGO nanocomposite. [Fe(CN)6]^3−/4− was used as a mediator to aid oxidation of artemisinin. Differential pulse voltammetric technique was used for the detection of artemisinin. A linear range of 30–100 μM was used. Experimentally, a detection limit of 0.5 μM was obtained. Therefore, the developed sensor can be used for quality control of artemisinin.     

Exact solutions of lattice polymer models

We consider directed path models of a selection of polymer and vesicle problems. Each model is used to illustrate an important method of solving lattice path enumeration problems. In particular, the Temperley method is used for the polymer collapse problem. The ZL method is used to solve the semi-continuous vesicle model. The Constant Term method is used to solve a set of partial difference equations for the polymer adsorption problem. The Kernel method is used to solve the functional equation that arises in the polymer force problem. Finally, the Transfer Matrix method is used to solve a problem in colloid dispersions. All these methods are combinatorially similar as they all construct equations by considering the action of adding an additional column to the set of objects.     

Gas-phase optrode measurements of oxygen in calorimetric vessels

Simultaneous measurements of oxygen and heat rates are useful for the determination of thermodynamics and kinetics of metabolic and chemical reactions involving oxygen. Optrodes have not previously been used to measure oxygen inside calorimetric vessels. The optrode used in this study produces <2 μW and can be used to make measurements in both gaseous and aqueous systems. An external syringe injection of air was used to calibrate the optrode, and zinc–air batteries were used to evaluate the system. Data on maple leaf buds were collected to demonstrate application to respiration measurements.     

Computer monitoring of sugars,acids and volatile compounds in fermentations

Head-space gas chromatography coupled to computer-assisted mass spectrometry is used to follow the formation kinetics of ethanol in fermentations. High-performance liquid chromatography, coupled to a computerized integrator, is used to follow the kinetics of disappearance of sugars and the formation of acids during the fermentation process. Flow injection analysis is used to monitor feed streams of low sugar content during downstream processing and recovery of the lactic acid. The kinetics pattern of volatile and nonvolatile products can be used in order to control fermentation parameters.     

Thermochemical and physical properties of printed circuit board laminates and other polymers used in the electronics industry

Theories behind four thermal analysis techniques are reviewed, and relevant case studies are used to illustrate the application of these techniques to measure; various parameters relevant to printed circuit board laminates and engineering polymers.Thermogravimetric analysis (TGA) is used to determine the filler content of polymers and composites and when combined with Fourier transform infrared (FTIR) spectroscopy can be used for the chemical analysis of evolved gases.Differential scanning calorimetry (DSC) is used to measure the melting point of polymers and the degree of cure of prepregs, laminates and adhesives.Thermomechanical analysis (TMA) is used to measure the coefficient of thermal expansion (CTE) and the glass transition temperature (Tg) of laminates, and dynamic mechanical analysis (DMA) is used to measure the storage modulus, loss; modulus and Tan δ of polymers.     

金纳米粒子组装体系中偶联单分子层膜结构的SERS光谱表征与分析

通过分子自组装方法制备4,4′-二硫联吡啶(PySSPy)单分子膜修饰的金电极. 利用所形成的对巯基吡啶自组装单分子膜(SAMs)作为偶联层进行金纳米粒子有序膜的组装. 对该纳米粒子组装体系进行Raman光谱测定, 得到了具有良好信噪比的对巯基吡啶单分子膜的表面增强拉曼散射(SERS)光谱. 在此基础上, 进一步采用电化学现场SERS光谱技术研究了该纳米粒子组装体系的SERS光谱随电位变化的规律. 在该体系稳定的电位范围内表征对巯基吡啶单分子膜的特征谱峰1011与1093 cm^-1、1575与1610 cm^-1以及1206与1215 cm^-1这三对谱峰其强度随着所施加电位的改变呈现出明显的规律性. 分析表明, 偶联单分子层中吡啶环芳香性随着所施加电位的改变而有规律地变化是SERS光谱特征改变的内在原因.     

脂肪醛和脂肪酮的沸点与分子结构关系的拓扑化学研究

根据分子拓扑学原理,通过采用信息量丰富的染色分子图代替隐氢图,借助于距离矩阵表征分子图中顶点的连接性和标识分子图中顶点性质的差异,发展了一种适用于含杂原子分子体系结构性能研究的新方法,据此探讨了脂肪醛和脂肪酮的沸点与分子结构之间的关系,提出一个既能合理表征结构性能关系、又能预测沸点的定量关系式。结果表明,沸点预测值与实验值的一致性令人满意,平均误差0.21%。     

Photosensitized degradation of organic pollutants in water: processes and analytical applications

Photosensitized degradation has been used to remove a broad range of organic pollutants, generally with mineralization to CO₂ and other inorganic products such as Cl⁻ and . TiO₂ and Fe³⁺ are the photosensitizers mainly used to accelerate the degradation of persistent organic chemicals. Various analytical techniques were used to identify the degradation products and to monitor the degradation kinetics. Chromatographic techniques such as high-performance liquid chromatography (HPLC), gas chromatography (GC) and ion-exchange were used. Other analytical techniques, such as total organic carbon analysis, UV–visible spectrophotometry, spectrofluorimetry, and potentiometry, were also used. When the photodegradation is carried out in water, extraction methods such liquid–liquid extraction or solid-phase extraction need to be used, followed by GC or HPLC analysis. We review the analytical methods used for the identification of the products formed in photodegradation studies. Kinetic studies of the degradation are also reported.     

Implementation of a system for reagent selection and library enumeration, profiling, and design

We describe an integrated suite of computational tools which are used to assist in the selection of compounds for biological assays and the design of combinatorial libraries. These functions are delivered in a platform-independent manner via a corporate intranet and are used by computational experts and nonexperts alike. While the system was primarily designed to be used prior to synthesis, it can also be used to provide structural information for library registration and for decoding beads in tagged libraries. We describe a simple statistical method for monomer selection and compare it to computationally more demanding approaches.     

A visualization study of poly(ethylene terephthalate) flow using potential chain-ordering die geometries

Streak-photographic and stress birefringence techniques were used to analyze the flow of poly(ethylene terephthalate) through potential chain-ordering die geometries. The streak photographs were used to determine velocity distributions and streamlines in various convergent dies. The different contours were seen to have a significant effect on the polymer streamlines and velocity distributions. The measured velocities were used to develop empirical equations, specific for each geometry, which relate velocity to position within the die and to throughput rate. Flow birefringence was used to determine the extent of molecular ordering. The optimum chain-ordering die geometry was determined to be one which included a rapid initial decrease in cross-sectional area. Birefringence was also used to monitor polymer flow instability. An unusual mechanism for instability was observed at intermediate throughput rates.     

Evaluating changes of writhe in computer simulations of supercoiled DNA

We compute changes in the writhe of a polygonal space curve when one of the vertices is displaced. The resulting expressions can be used in simulations of supercoiled DNA. For Brownian dynamics simulations, the expressions can be used to eliminate the explicit twisting degree of freedom. For Monte Carlo simulations, they can be used in fast local moves. Preliminary Monte Carlo simulations using only such fast local moves show that these can be used to efficiently simulate small DNA supercoils.     

Modeling of carbonic acid pretreatment process using ASPEN-plusŖ

ASPEN-Plus^Ŗ process modeling software is used to model carbonic acid pretreatment of biomass. ASPEN-Plus was used because of the thorough treatment of thermodynamic interactions and its status as a widely accepted process simulator. Because most of the physical property data for many of the key components used in the simulation of pretreatment processes are not available in the standard ASPEN-Plus property databases, values from an in-house database (INHSPCD) developed by the National Renewable Energy Laboratory were used. The standard non-random-two-liquid (NRTL) or renon route was used as the main property method because of the need to distill ethanol and to handle dissolved gases. The pretreatment reactor was modeled as a “black box” stoichiometric reactor owing to the unavailability of reaction kinetics. The ASPEN-Plus model was used to calculate the process equipment costs, power requirements, and heating and cooling loads. Equipment costs were derived from published modeling studies. Wall thickness calculations were used to predict construction costs for the high-pressure pretreatment reactor. Published laboratory data were used to determine a suitable severity range for the operation of the carbonic acid reactor. The results indicate that combined capital and operating costs of the carbonic acid system are slightly higher than on H₂SO₄-based system and highly sensitive to reactor pressure and solids concentration.     

Pyrolysis-FTIR and TGA techniques as tools in the characterization of blends of natural rubber and SBR

The employment of used tyres as a new source of raw materials for different applications can be a partial solution to the great environmental problems generated by these products concerning their disposal at waste depots. In this study, high-resolution thermogravimetric analysis (Hi-Res TGA) is used to quantify the elastomer composition of SBR/NR in tyre formulations. This technique provides the ability to generate TGA derivative profiles (DTGA), which can be used to distinguish different formulations from appropriate calibration curves. Infrared spectroscopy (FTIR) is also employed for composition quantification of used tyres and the results are compared to those obtained by Hi-Res TGA. Both analysis methods give satisfactory results when applied to elastomer mixtures of known composition and to tyre rubbers of unknown composition. The study confirms the accuracy of high-resolution TGA-DTGA technique for rapid quantitative determination of elastomer blends in used tyres.     

Breathing air from protein foam

Protein foams can be used to extinguish fires. If foams are to be used to extinguish fires where people are present, such as in high-rise buildings or ships, then a method for allowing people to breathe in a foam-filled environment is needed. It is proposed that the air, used to create the foam be used for breathing. A canister that will break incoming air-filled foam has been designed for attachment to a standard gas mask, in order to provide breathable air to a trapped person. Preliminary results for the modified mask indicate feasibility of breathing air from air-filled protein foam.     

Applications of nuclear methods in the automotive industry

Over the years nuclear methods have proved to be a valuable asset to industry in general and to the automotive industry in particular. This paper summarizes some of the most important recent contributions of nuclear technology to the development of vehicles having high quality and long-term durability. Radiotracer methods are used to measure engine oil consumption and the wear rates of inaccessible components. Radiographic and tomographic methods are used to image fluids and structures in engines and accessory components. Tracers are used to understand combustion chemistry and quantify fluid flow. Gauging methods are used for inspection and process control. Nuclear analytical methods are used routinely for materials characterization and problem solving. Although nuclear methods are usually considered as the means of last resort, they can often be applied more easily and quickly than conventional methods when those in industrial engineering and R&D are aware of their unique capabilities.     

化学废旧电池的环境污染和利用

本文就化学电池的种类、废旧电池的危害、电池工业的发展方向、国内外废旧电池的再生和利用情况进行了讨论,并对我国废旧电池的回收提出一些合理的建议。     

Targeted use of exoglycosidase digestion for the structural elucidation of neutral O-linked oligosaccharides

Exoglycosidase digestion in combination with the catalog-library approach (CLA) is used with matrix-assisted laser desorption/ionization Fourier transform mass spectrometry (MALDI-FTMS) to obtain the complete structure of oligosaccharides. The CLA is a collision-induced dissociation (CID)-based method used to determine the structure of O-linked neutral oligosaccharides. It provides both linkage and stereochemical information. Exoglycosidases are used to confirm independently the validity of the CLA. In some cases, the CLA provides structural information on all but a single residue. Exoglycosidase is used to refine these structures. In this way, exoglycosidase use is targeted employing only a small number of enzymes. Exoglycosidase arrays, which have been used with N-linked oligosaccharides, is avoided despite the larger variations in structures of O-linked species.     

衍生化-离子阱气相色谱质谱联用检测乳粉中三聚氰胺时不同质谱检测方法研究

利用N,O-双三甲基硅基三氟乙酰胺(BSTFA)和三甲基氯硅烷(TMCS)衍生化试剂对乳粉中三聚氰胺进行衍生化处理,利用离子阱气相色谱质谱联用仪,建立了全扫描、选择离子监测、二级质谱3种测定三聚氰胺的质谱方法.选择离子监测以三聚氰胺衍生物的特征离子m/z342,327,171,99为定性离子,以m/z327为定量离子;全扫描法二级质谱特征峰为定性依据,以特征离子m/z327为定量离子;二级质谱法以衍生物二级质谱m/z285,171,213为定性离子,以m/z 285为定量离子.3种方法的线性范围为0.05～2.0 mg/L,线性相关系数分别为0.9986、0.9990、0.9988;检测限分别为0.005、0.002、0.003 mg/kg,RSD分别为6.3%、5.7%、6.1%(n=6),方法的回收率为84%～105%.3种不同质谱检测方法应用到乳粉的检测中效果良好,均能够满足乳粉中三聚氰胺的检测要求.