一种提高色谱指纹谱保留时间重现性的新方法

通过色谱热力学分析发现，在相同的分析条件下，即使采用不同的液相色谱系统或不同的色谱柱，组分的保留时间存在简单的线性关系，应用该线性关系可提高不同反相C18柱间保留时间重现性，经过实际样品在不同操作条件下的验证，表明该方法是正确而可行的。     

Standardization of Raman spectra for transfer of spectral libraries across different instruments

In this paper we evaluate methods for standardization of Raman spectra that are required to improve spectral correlation computations between spectra measured on different instruments. Five commercially-available 785 nm Raman spectrometers from different vendors were included in the study. These spectrometers have diverse specifications and performance levels and range in size from laboratory-based instruments to field-deployable portable and handheld platforms. Since each Raman spectrometer has different characteristics, spectra obtained on one instrument cannot readily be compared to a library acquired on a different instrument without performing various types of spectral corrections (standardization). We outline a procedure that combines previously established Raman shift and intensity correction protocols with a resolution matching step to facilitate the comparison of a centralized master library with spectra acquired on different geographically distributed Raman spectrometers. The standardization procedure is effective in reducing the inherent instrument-to-instrument variability so that spectra from different spectrometers can be compared and reliable results obtained using library-based spectral correlation methods. The findings have important implications for the ability to transfer Raman spectral libraries between instruments.     

毛细管电中中性溶质在氰基柱上分离机理的研究

 对中性溶质在氰基柱上的毛细管电色谱（CEC）分离特征进行了研究 ,讨论了流动相中有机调节剂种类及其体积分数、缓冲液种类等对溶质迁移速率的影响。通过对样品在氰基柱上的分离行为与其在反相ODS柱和正相SI柱上的分离行为的比较 ,说明中性溶质在氰基柱上的分离机理既具有部分反相特征又具有部分正相特征。受两种机理的影响 ,在不同的操作条件下极性不同的中性溶质在氰基柱上的迁移速率差别很大 ,较一般的正相和反相电中更易出现出峰顺序变化的现象 ,也说明这种分离模式更易于进行分离选择性调节。     

具有不同活性中心的固体催化剂的失活模式

 An approach is suggested to distinguish different types of active sites responsible for different reactions on bifunctional catalysts. The model assumes a non-uniform vulnerability of active sites that depends on their location. Problems on the relationship between the dispersion of the active phase and selectivity are discussed. The effect of coke formation on the activity change of different sites is analyzed.     

Synthesis of a new family of four deoxycholic acid derived chiral stationary phases and their evaluation in the HPLC resolution of racemic compounds

Four new chiral selectors obtained by suitable derivatization of the hydroxyl groups of the deoxycholic acid with two identical (homoderivatized) or different (heteroderivatized) arylisocyanates have been prepared and linked covalently to silica gel to obtain new chiral stationary phases (CSPs) for the HPLC separation of enantiomers. The CSPs containing two identical substituents are able to enantiodiscriminate different classes of racemic compounds, or the same racemates to a different extent, a property which depends on the different electronic character of the arylcarbamate moieties. The heteroderivatized CSPs retain the character of the two homoderivatized phases: however, the relative position of the two different arylcarbamate moieties on the deoxycholic backbone strongly affects the enantiodiscrimination capability of these two CSPs.     

Multicolor imaging of cell surface proteins

We report on a method for the multicolor imaging of cell surface proteins which is based on the labeling of carrier protein (CP) fusion proteins with different fluorophores. In one application, different generations of a cell surface protein can be sequentially labeled to discriminate between old and newly made copies. In another application, fusions to different CPs can be selectively labeled with different fluorophores in one sample. Both applications open up new ways for studying the properties of cell surface proteins of living cells.     

表面吸附质对银亚胶体吸光特性的影响

纯银溶胶在390nm处有一吸收峰。当银溶胶吸附了1-苯基-5-巯基四氮唑(PMT)或2-巯基苯骈噻唑(MBT)时, 银溶胶由亮黄色转变为橙红色, 即在510～550nm处出现一个新的吸收峰。研究发现, 卤素离子在银溶胶颗粒上与PMT和MBT有竞争吸附作用。但是卤离子对银溶胶的光谱吸收的影响完全不同于PMT和MBT。在讨论这种差别时应首先考虑金属银溶胶颗粒表面性质因吸附不同物质所产生的变化。     

Adhesion of Pseudomonas fluorescens on magnetic surfaces

The adhesion of Pseudomonas fluorescens (ATCC 700830) to perpendicularly polarized magnetic surfaces was recently discovered. The findings have found that the magnetic free surfaces from different magnetic polarities have different profound effects on the P. fluorescens bacterial adhesion to its surfaces. These phenomena can be explained by the surface magnetic effect, which was found to affect the surface free energy. An in situ experiment, by contrast microscopy and under static conditions, was conducted to determine the influence of magnetic surfaces, that are polarized under different external magnetizing field strengths, on bacterial adhesion. The effect of different magnetic polarities on the surface free energy has also been investigated.     

两种填料片表面润湿性能及其对CO2吸收传质的影响

为提高CO2吸收填料塔的传质效率,研究了填料片表面润湿性能变化对传质过程的影响．设计了一种能够进行CO2吸收的气液接触传质实验装置,并对两种具有不同液固接触角的平板进行了吸收传质对比实验,实验采用15wt％的MEA溶液为吸收剂,原料气CO2与空气比例为1：3．通过实验给出了润湿性能对吸收传质效率的影响．为进一步了解不同润湿条件下的流动和传质行为细节,建立了基于VOF方法的三维计算流体力学模型,模拟了与传质实验对应的不同液固接触角时液体降膜流动与传质行为,得到了不同润湿性能时的降膜流动速度分布及浓度分布图像,模拟结果与实验值吻合较好,定量解释了接触角变化导致液膜流动结构和吸收传质效果变化的原因．     

Effect of surface charge of polymeric micelles on in vitro cellular uptake

This work focuses on the interaction between polymeric micelles with different charged surfaces and cancer cells in order to study the influence of surface charge on the in vitro cellular uptake efficiency. The amphiphilic diblock copolymers poly(ε-caprolactone)-b-poly(ethylene oxide) (PCL-b-PEO) with different functional groups at the end of hydrophilic block were synthesized. The functional groups endue the micelles with different charges on the surfaces. The cellular uptake of micelles to T-24 cells (human bladder tumor cells), HepG2 cells (human liver hepatocellular carcinoma cell line) and Hela cells (human epithelial cervical cancer cells) was studied by means of flow cytometer and confocal laser scanning microscopy. The results indicate that the surface charges showed great influence on zeta potential of micelles at different pH values. The in vitro cellular uptake efficiency of micelles with different charged surfaces demonstrated different cellular uptake patterns to three kinds of cancer cells.     

Surface-enhanced Raman scattering of a series of n-hydroxybenzoic acids (n = P, M and O) on the silver nano-particles

Surface-enhanced Raman scattering (SERS) spectra of a series of n-hydroxybenzoic acids (n-HBA, n = P, M and O) adsorbed on the silver nano-particles were studied, respectively, in the silver colloidal solution and on the dried silver-coated filter paper. On the same substrate, the different molecules' SERS spectra were different, while on the different substrates the same molecules' SERS spectra were also different. Significant changes were found in the SERS spectra of PHBA molecules adsorbed on the two substrates, and the changes found in MHBA's spectra on two substrates were next to PHBA's, while almost no changes were found in the spectra of OHBA molecules. Moreover, it was found, on the filter paper, that the SERS spectra of the same molecules would change with the coverage density of the silver nano-particles. The analyses showed that the origins of these changes were the different adsorption behavior of molecules adsorbed on the silver nano-particles. Because in these three molecules the relative positions of the carboxyls and hydroxyls on the benzenes are different, the adsorption behaviors of these three molecules adsorbed on the silver surfaces are also different. The experimental results suggest that the surface characteristic of the substrate and the surface configuration of the adsorbate could exert a great influence on the adsorption behavior of the adsorbates on the substrates.     

The stone decay of monuments in relation to atmospheric environment

In order to explain why different forms of decay are present on a building facade some samples were taken from different areas of many monuments. Macroscopic observations of the forms of decay were correlated with quantitative analytical data in order to build up a simple model which was able to explain in a general way the decay phenomena. This simplified model was tested on several Venetian monuments and the features visible on stone surfaces correspond to different degree of deterioration. The quantitative analytical data were associated with the different forms of decay, which were defined as white washing, dirt accumulation and dirt washing. The results obtained showed that the features visible on stone surfaces corresponded to different degree of deterioration and the sulphate formation is greatest in the black dendrite-shaped crusts which are generally formed at the interface between the white washing areas and the sheltered ones, which were defined as dirt washing area.     

Process dependence of pressure-specific volume-temperature measurement for amorphous polymer: Acrylonitrile-butadiene-styrene

The process dependence of pressure-specific volume-temperature (pvT) measurement for an amorphous polymer, acrylonitrile-butadiene-styrene (ABS), was investigated. The influences of different measurement processes (heating, cooling, compression, and decompression with different rates) were considered in the pvT measurements. The pvT measurements of isobaric cooling and heating with different cooling and heating rates (2, 5, and 10 °C/min) and isothermal compression and decompression with different compression and decompression rates (up to 920 bar/s) were conducted. The testing temperature ranged between 40 and 230 °C and the pressure ranged between 20 and 2200 bar. The obtained results demonstrated that the pvT diagram will be significantly different depending on the direction in which the pressure or temperature is changing and also on the rate of the change. Isobaric pvT diagrams are different between cooling and heating. Fast cooling accelerates phase transitions, while fast heating reverses. Specific volume at the same pressure and temperature in decompression process is lower than that in compression. Compression and decompression leads to different pvT curves. Compression and decompression rates have different effects on specific volume in different states.     

分子动力学模拟多巴在自组装膜上的黏附性

为了更好地理解贻贝在表面的黏附机理,实现水下胶黏,采用分子动力学方法研究了多巴在自组装膜上的黏附性:采用伞形取样和加权柱状图分析方法计算了多巴在不同自组装膜表面的黏附自由能,使用拉伸分子动力学模拟研究了多巴在不同自组装膜表面上黏附后的脱附力.结果表明,多巴在带负电的羧基自组装膜上的黏附能比在带正电的氨基自组装膜上的大,多巴更容易黏附到带负电表面;多巴在带电表面的黏附能比未带电表面的黏附能更强,表明在带电表面黏附更稳定.进一步分析了多巴在不同表面的取向分布,发现多巴与不同表面相互作用的方式不同:与疏水表面主要通过苯环相互作用;与亲水表面主要通过羟基相互作用;与负电表面主要通过氨基相互作用;与正电表面主要通过羧基相互作用.通过模拟比较了多巴在不同自组装膜上的脱附力,发现多巴在带电表面的脱附力比在未带电表面的大,与黏附能的趋势一致.对比4种非带电表面的脱附力,发现多巴在疏水性甲基自组装膜表面的脱附力最大,黏附更稳定,随着表面疏水性的增加,脱附力增大,黏附稳定性增强.本工作可为研发新型水下胶黏剂提供理论指导.     

Examination of Selectivities of Thermally Stable Geminal Dicationic Ionic Liquids by Structural Modification

Dicationic ionic liquids (ILs) are widely used as gas chromatography (GC) stationary phases as they show higher thermal stabilities, variety of polarities, and unique selectivities towards certain compounds. An important aspect contributing to them is that they show multiple solvation interactions compared to the traditional GC stationary phases. Dicationic ILs are considered as combination of three structural moieties: (1) cationic head groups; (2) a linkage chain; and (3) the counter anions. Modifications in these structural moieties can alter the chromatographic properties of IL stationary phases. In this study, a series of nine thermally stable IL stationary phases were synthesized by the combination of five different cations, two different linkage chains, and two different anions. Different test mixtures composed of a variety of compounds having different functional groups and polarities were analyzed on these columns. A comparison of the separation patterns of these different compounds on nine different IL columns provided some insights about the effects of structural modifications on the selectivities and polarities of dicationic ILs.     

External field induced crystallization of poly(3-dodecylthiophene)

In order to investigate the effect of external field on the crystallization behavior of poly(3-dodecylthiophene) (P3DDT), the samples were recrystallized with different electrostatic field intensity, different pressure and different solidification direction in temperature gradient field. Measurements of differential scanning calorimetry and X-ray diffraction were operated to characterize these samples for analysis. The results suggest that after recrystallization, whether the external field is added or not, a more compact packing of molecular chains in P3DDT could be obtained without the change of the crystal structure model. Moreover, the addition of electrostatic field has greater effects on the crystallization of rigid main chains than on that of flexible side chains. Merely great pressure field can effect the rearrangements of molecular chains greatly. As for the temperature gradient field induced crystallization, different oriented solidification direction will lead to different effects on the compact degree and perfect degree of molecular chains packing.     

Environmental biodegradation of synthetic polymers I. Test methodologies and procedures

Biodegradation of synthetic polymers is an important property that is used in many applications. Evaluation of the extent of biodegradation has used different methods in recent years. For each environmental compartment, different approaches have to be made in order to obtain valuable data on biodegradability.This review describes validated and accepted methods based on standardized biodegradation tests, analytical tests, enzymatic tests or tests of physical properties to evaluate the biodegradability of synthetic polymers for different types of environmental compartments (e.g., soil, compost or aqueous media).Part II of this review will subsequently report on the environmental biodegradation of different groups of synthetic polymers.     

Impedance measurements of self-assembled lipid bilayer membranes on the tip of an electrode

Supported lipid membranes were self-assembled on the tip of a freshly cleaved silver wire, in the presence of an appropriate polarization voltage, to facilitate, during the membrane formation, the organization of the lipids into an ordered structure. Radiowave impedance spectroscopy measurements have been carried out to provide information on the relaxation properties of the system. We have measured the conductometric and dielectric properties of bilayers built up of different lipids [dipalmitoylphosphatidic acid (DPPA), 1,2-dipalmitoyl-sn-glycero-3-phosphocholine (DPPC), linoleic acid (LIN)] in a wide frequency range (from 10(3) to 10(6) Hz) and in electrolyte solutions of different ionic strengths, in the presence of uni-univalent (KCl) and di-univalent (CaCl(2), MgCl(2), ZnCl(2)) electrolytes. This made it possible to measure the influence of different cations and different lipid compositions on the membrane properties. In particular, we have found a different capacitive behaviour of the supported lipid bilayer membrane (s-BLM) structure in the presence of different counterions in the electrolyte solution. This peculiarity offers the opportunity for the preparation of a variety of biosensors with diverse applications in membrane biophysics, biochemistry and biotechnology.     

Grand canonical Monte Carlo simulation of the adsorption isotherms of water molecules on model soot particles

The grand canonical Monte Carlo method is used to simulate the adsorption isotherms of water molecules on different types of model soot particles. The soot particles are modeled by graphite-type layers arranged in an onionlike structure that contains randomly distributed hydrophilic sites, such as OH and COOH groups. The calculated water adsorption isotherm at 298 K exhibits different characteristic shapes depending both on the type and the location of the hydrophilic sites and also on the size of the pores inside the soot particle. The different shapes of the adsorption isotherms result from different ways of water aggregation in or/and around the soot particle. The present results show the very weak influence of the OH sites on the water adsorption process when compared to the COOH sites. The results of these simulations can help in interpreting the experimental isotherms of water adsorbed on aircraft soot.