Small angle X-ray scattering investigations of thermodynamic properties of fluid mixtures

Absolute small angle X-ray studies of concentration fluctuations were performed in order to determine thermodynamic properties of a model blend, consisting ofn-hexane and perfluoro-n-hexane. The quantities which we determined were the second derivate of the Gibbs free energy of mixing with respect to the concentration of the components, the location of the spinodal, interaction and solubility parameters, the energy gradient density coefficient as well as the correlation length of the fluctuations at various compositions and temperatures, particularly in the neighbourhood of the spinodal and the critical point. The data obtained were compared with those obtainable from the well known location of the binodal, to test the reliability of the scattering method.     

Two-dimensional double-quantum 2H NMR spectroscopy in the solid state under OMAS conditions: correlating 2H chemical shifts with quasistatic line shapes.

Solid-state 2H NMR spectroscopy is a well-established and versatile method to study molecular orientation and dynamics in selectively deuterated samples. Herein, we introduce a 2D 2H double-quantum (DQ) NMR experiment performed under fast magic-angle spinning with a slight offset of the magic angle (OMAS). The experiment combines 2H chemical-shift resolution with DQ-filtered quasistatic 2H line shapes. In this way, it is possible to separate 2H resonances and to independently determine 2H quadrupole couplings at multiple sites. While 2H chemical shifts are resolved in the 2H DQ dimension, the quadrupole parameters can be obtained from characteristic line shapes which are reintroduced in the second dimension by the magic-angle offset. The 2D 2H DQ OMAS experiment is demonstrated on L-histidine which was deuterated at multiple sites by recrystallisation from D2O.     

Metabolic profiling of normal and hypertensive rat kidney tissues by hrMAS-NMR spectroscopy

Intact kidney tissue samples of normal and spontaneously hypertensive rats (SHRs) were analyzed by hrMAS-NMR spectroscopy and principal component analysis (PCA). Radial components (cortex, outer stripe of the outer medulla, inner stripe of the outer medulla, and papilla) were sampled from various regions across the kidney from multiple animals in order to establish inter- and intra-animal variability. The effects of temperature were also measured. Papilla was differentiated from the other tissue types, and this variation by tissue type was greater than the effect of temperature on the samples (spectra were compared from samples at 2 and 30 °C). This study also revealed long term stability issues of tissue storage at -80 °C. The PCA showed that the greatest differentiation between normal rats and SHRs was found in the cortex and the regions in the NMR spectra that were correlated with this variation were identified.Abbreviations hrMAS High-resolution magic angle spinning - NMR Nuclear magnetic resonance - PCA Principal component analysis - CSA Chemical shift anisotropy - DD Dipolar coupling - SHR Spontaneously hypertensive rat     

Effect of the Coil Angle in an Inductively Coupled Plasma Torch: A Novel Two-Dimensional Model

A two-dimensional model has been developed for the calculation of the electromagnetic (EM) fields generated by spiral coil currents, in order to obtain a better representation of the actual configuration used in a typical inductively coupled plasma (ICP) torch. In order to obtain the EM fields in a two-dimensional model, the change of EM field in tangential direction is neglected and the coil is assumed to be a concentric cylinder. In order to justify our assumption, the EM, flow and temperature fields resulting from five-ring coil and concentric cylinder coil are compared and the results are almost the same except for the EM field in the vicinity of the coil. In the case of the spiral coil, the coil current is inclined with respect to the horizontal plane. Therefore current in the cylinder coil is assumed to have the same inclined angle, which is split into tangential and axial components. The axial electric field and hence an axial current in plasma is induced by the axial component of the spiral coil current. Charge density is accumulated in the plasma, since the axial current cannot form a loop. In order to obtain the EM field and the charge distribution in the plasma generated by the spiral coil, the equations of axial vector potential and electrostatic potential have been derived. Due to the swirling Lorentz force (J_z×B_r) an axisymmetrical swirling fluid model is used to simulate the plasma flow in an axisymetrical configuration. With an inclined angle of the coil current being 3.7° and the frequency being 3 MHz, computational results show that the swirling Lorentz force causes plasma swirling with a maximum speed of 3.41 m/s near the plasma center when the injected sheath gas and central gas are not swirling. In these conditions, the real and imaginary parts of the maximum electrostatic potential are 0.95 V and 1.66 V, respectively. When the electrostatic field is neglected, the swirling velocity of the plasma is 3.95 m/s.     

透射电镜像转角的测定及应用

论述了完全标定透射电镜像转角所需拍摄的二次曝光电子显微像的数量,推导了由已测的像转角间接计算其它像转角的一般公式,以Philips Cm200电镜为实例,说明了测定像转角的基本步骤,并以实例说明怎样利用像转角,把衍射花样的晶体学信息传递给电子显微像。     

Sulfide Gels and Films: Products of Non-Oxide Gelation

The preparation of concentrated sols and transparent stiff gels of II-VI semiconductors nanocrystals is reported. A two-step process for the production of cadmium sulfide is reported. Sol stabilization and gelation control are achieved through successive passivation and depassivation of the surface of the nanocrystals which are complexed with thiols. The mechanisms driving the aggregation and the gelation are explained on the basis of NMR and SAXS experiments. Thin films as well as monoliths can be produced. The general principles of the method presented are not restricted to chalcogenide systems and thus enlarge the domain of application of the inorganic sol-gel process.     

Characterization of proteins separated by displacement chromatography using low angle laser light scattering photometry

Summary -Lactoglobulin A and B (-LACT) were separated by displacement chromatography (DSC) on an ionexchange column using dextran sulfate as the displacer. A LALLS photometer and a UV detector, in series, were used to determine the molecular weight (MW) of the proteins, on-line. The results indicate that both, -LACT A and B, were present as dimers in the buffer used for the mobile phase. The MWs of the proteins were about 6–8% higher than the theoretical MW of a dimer (37,000). Additional control studies have shown the presence of a high molecular weight species in both the proteins, which could possibly be an aggregate. This species was observed in the LALLS signal but was nearly absent in the UV signal. Our work has demonstrated the feasibility of interfacing LALLS with displacement chromatography for detecting impurities or aggregates which may be difficult to detect by conventional detectors used for chromatography.     

Surface properties of Reactive Yellow 2 immobilised pHEMA and HEMA/chitosan membranes: characterisation of their selectivity to different proteins

Poly(hydroxyethyl methacrylate), pHEMA, and a composite pHEMA/chitosan networks were synthesized in the membrane form via UV initiated photo-polymerisation in the presence of an initiator ,′-azoisobutyronitrile. Reactive Yellow 2 (RY-2) was covalently immobilised as a dye–ligand onto both membranes. The polarity and surface energy of the investigated membranes were determined by contact angle measurement. The incorporation of chitosan in the pHEMA networks produced more hydrophilic surface, as indicated by contact angle analysis. The binding characteristics of lysozyme, γ-globulins, human serum albumin (HSA) and bovine serum albumin (BSA) to pHEMA-RY-2 and pHEMA/chitosan-RY-2 affinity membranes have been investigated from aqueous solution and their dye–ligand free forms were used as control systems. When chitosan was incorporated in the pHEMA network as a cationic polymer led to higher adsorption capacity for the lysozyme. Selective adsorption behaviour was also observed in the case of pHEMA/chitosan-RY-2 membrane for the lysozyme. The non-specific adsorptions of the lysozyme on the pHEMA and pHEMA/chitosan membranes were about 1.9 and 7.2 mg/ml, respectively. These were negligible for all others investigated proteins. The lysozyme adsorption data was analysed using the first-order and the second-order models. The first-order equation in both affinity membrane systems is the most appropriate equation to predict the adsorption capacities of the adsorbents. The adsorption isotherms well fitted the combined Langmuir–Freundlich model. A theoretical analysis has been conducted to estimate the thermodynamic contributions (changes in enthalpy, entropy and Gibbs free energy) for the adsorption of lysozyme to both dye–ligand immobilised membranes. The adsorption capacities of both dye–ligand immobilised membranes increased with increasing the temperature while decreased with increasing the NaCl concentration. Both affinity membranes are stable when subjected to sanitization with sodium hydroxide after repeated separation–elution cycles.     

RELATIONSHIPS BETWEEN X—H STRETCHING OVERTONE FREQUENCIES AND BOND LENGTHS/BOND ANGLES

A relationship between the X-H (X = N, O, C, and so on) equilibrium bond length in a Morse oscillator and the X-H stretching overtone frequency shifts is obtained theoretically. We use the equation to discuss the empirical linear relationships that have been proposed for heterocyclics, alkanes and fluorinated benzenes. On the other hand, a unified relationship between the X-H bond angles and the experimental quantities (ω(?) and the coupling strength λ) is also presented for XH2, XH, and XH4 molecules or molecular fragments. Calculations of X-H bond angles for a number of molecules show that the results from our equations are in excellent agreement with the experimental values. Also we can extract the information of relative magnitude of bond coupling force field.     

A method for correcting the contact angle from the θ/2 method

The θ/2 method, a widely used technique on measuring the contact angle of a sessile drop, assumes that the drop profile is part of a sphere. However, the shape profile of a sessile drop is governed by the Young–Laplace equation and is different from a sphere, especially for drops with a large bound number (e.g. large volume or small surface tension). The spherical assumption, therefore, causes errors on evaluating the contact angles. The deviation of contact angle from the θ/2 method is evaluated from a theoretical calculation in this work. A simple means is given for correcting the measurement error. The corrected angle results from the drop volume, surface tension, liquid density and the contact angle from θ/2 method. An algorithm for finding the correct contact angle without knowing the density and surface tension is also given. At the end, two examples of pendant drops are given for the illustration.