Direct visualization of collapse process of porphyrin monolayers and porphyrin exclusion for mixed monolayers at the air-water interface

The collapse process of porphyrin monolayers at the air-water interface was studied by Brewster angle microscopy and by compression-recompression isotherms. It was found that the start of collapse observed by BAM is accordant with that measured by compression-recompression isotherms. The behavior of mixed monolayers was studied also and the results showed that porphyrin islands were excluded from mixed monolayers at 35mN/m.

A method to identify the collapse of monolayers at the air-water interface

The collapse behaviour of phthalocyanine monolayers at the air-water interface was studied by means of compression-expansion isotherms. Measurements of two cycles of compression-expansion isotherms of copper tetrakis (4'-benzyloxy-4-phenylsulfonylphenoxy) phthalocyanine showed that the difference in the area per molecule at target pressure between the first cycle and the second cycle was dependent on the target pressure. This difference was used to identify the collapse of monolayers at the air-water interface. The transfer behaviour of monolayers at the air-water interface onto a substrate at different target pressures was also studied.

ELECTRON-DIFFRACTION STUDY ON MONOLAYER LB FILMS OF LIQUID-CRYSTALLINE POLYACRYLATE CONTAINING PARA-NITRO AZOBENZENE

Monolayers of liquid-crystalline polyacrylate containing para-nitro azobenzene (HP6) on the water subphase were characterized by the surface pressure (pi)-area per monomer unit (A) isotherm and were successfully transferred onto glass substrates by the vertical lifting method. The monolayer Langmuis-Blodgett (LB) films transferred at different surface pressures were studied by electron diffraction. The thickness of the monolayer LB film was measured by the transmission electron microscopy folding method. The results of the electron diffraction of the monolayer LB films of HP6 showed that a two-dimensional arrangement exists in the transferred films. According to the results of the pi-A isotherm, electron diffraction and the measured thickness of the monolayer LB film, a molecular arrangement model of HP6 on the water subphase was proposed. The ordered monolayer formation of HP6 showed it to be promising as a second-order non-linear optical material.

Synthesis and properties of thermotropic liquid crystalline copolyesters containing bis(4-hydroxyphenyl)methanone(V)

A new series of fully aromatic thermotropic liquid crystalline copolyesters were synthesized by thermal polycondensation of p-hydroxybenzoic acid (PHB), terephthalic acid (TPA), resorcinol (RES) and bis (4-hydroxyphenyl) methanone (BHP). The DSC traces of copolyesters exhibited two or three endotherms, the low temperature endotherm(Tm) of which indicated the transition from solid state to anisotropic phase. Observation under polarizing microscope and WAXD measurements suggested that the LC-phase formed immediately above Tm had a nematic character.

AN INFRARED SPECTROSCOPIC CHARACTERIZATION OF THE SOLID SOLID BEHAVIOR OF DODECYLAMMONIUM CHLORIDE

The infrared spectra of the bilayer system dodecylammonium chloride has been studied as a function of temperature. Unusual splitting of some vibrational modes helps us to characterize the structure of different solid states. This study provided the evidence for the occurrence of an order-disorder phase transition whose onset occurs at 327 K and its completion ends at 339 K. In the low temperature phase below 327 K, the virgin crystals form a well-ordered phase with all-transhydrocarbon chains. In the intermediate state between 327 and 339 K, the data demonstrate the introduction of intramolecular as well as intermolecular disorder. The coexistence of solid and liquid-crystal-like states is shown by the persistence of factor group splittings together with the existence of defect bands in the wide intermediate temperature range. In the high temperature phase over 339 K the crystals convert to a liquid-crystal-like system with extensive motional and conformational disorder, but still show characteristics in their infrared spectra which indicate the presence of ordered segments in the hexagonal solid phase.

HIGH-TEMPERATURE SUPERCONDUCTOR, YBA2CU3O7-X AS ALL-SOLID-STATE LITHIUM CELL

The utility of the high-temperature superconductor, YBa2Cu3O7-x as the cathode material for an all-solid-state lithium cell has been examined. The capacity of YBa2Cu3O7-x is 223 mA h g-1 and the discharge efficiency is > 92%. Measurements of a.c. impedance show that the charge-transfer resistance at the interface of the electrolyte/cathode is very low and increases with the depth-of-discharge of the battery. Studies using X-ray photoelectron spectroscopy (XPS) reveal that the cathode becomes doped with Li+ ions as the cell discharges.

ANESTHETIC LIDOCAINE AND DICAINE TRANSFER ACROSS LIQUID LIQUID INTERFACES

Lidocaine transfer across the water/1,2-dichloroethane and the water/nitrobenzene interfaces has been investigated by chronopotentiometry with linear current scanning and cyclic voltammetry. The irreversible hydrolysis occurring in the phase transfer of dicaine at the water/nitrobenzene interface is discussed.

AN ALL-SOLID-STATE LITHIUM POLYANILINE RECHARGEABLE CELL

The performance of an all-solid-state cell having a lithium negative electrode, a modified polyethylene oxide (PEO)-epoxy resin (ER) electrolyte, and a polyaniline (PAn) positive electrode has been studied using cyclic voltammetry, charge/discharge cycling, and polarization curves at various temperatures. The redox reaction of the PAn electrode at the PAn/modifed PEO-ER interface exhibits good reversibility. At 50-80-degrees-C, the Li/PEO-ER-LiClO4/PAn cell shows more than 40 charge/discharge cycles, 90% charge/discharge efficiency, and 54 W h kg-1 discharge energy density (on PAn weight basis) at 50-mu-A between 2 and 4 V. The polarization performance of the battery improves steadily with increase in temperature.

THE USE OF CHEMICALLY MODIFIED ELECTRODES FOR LIQUID-CHROMATOGRAPHY AND FLOW-INJECTION ANALYSIS

The use of chemically modified electrodes (CMEs) for liquid chromatography and flow-injection analysis is reviewed. Electrochemical detection with CMEs based on electrocatalysis, permselectivity, ion flow in redox films, and ion transfer across the water-solidified nitrobenzene interface is discussed in terms of improving the stability, selectivity, and scope of electrochemical detectors, and the detection of electroinactive substances. More than 90 references are included.

ELECTROCHEMICAL INVESTIGATION OF LIQUID/LIQUID SYSTEMS USING VARIOUS ORGANIC SOLVENTS

The potential windows of the system water/pure solvent (W/P) and water/solvent mixtures(W/S) have been investigated by cyclic voltammetry with solvents whose dielectric constants lie between 5.87 and 34.82. In the presence of LiCI in the aqueous phase and tetrabutytammoniumtetraphenylborate(TBATPB) in the organic phase, the systems water/allyl iso-thiocyanate (W/AIT) and water/nitrobensene (W/NB) show a same wide epotential window. thermodynamic parameters of ion transfer W/AIT interface were determined. In systems of W/P and V/S the influence solvent effect on the standard gibbs energies of transfer of was discussed.

Analysis of urinary 8-hydroxydeoxyguanosine by capillary electrophoresis and solid-phase extraction

Urinary 8-hydroxydeoxyguanosine (80HdG) has been considered as an excellent marker of individuals at high risk of developing cancer. Until now, urinary 80HdG has largely been measured by high-performance liquid chromatography with electrochemical detection. A new method for the analysis of urinary 80HdG by high-performance capillary electrophoresis has been developed and optimized in our laboratory. A single step solid-phase extraction procedure was optimized and used for extracting 80HdG from human urine. Separations were performed in an uncoated silica capillary (50 cm x 50 tm i.d.) using a P/ACE MDQ system with UV detection. The separation of 80HdG from interfering urinary matrix components is optimized with regard to pH, applied voltage, pressure injection time and concentration of SDS in running buffer. The detection limit of this method is 0.4 mug/ml, the linear range is 0.8-500 mug/ml, the correlation coefficients levels is better than 0.999. The developed method is simple, fast and good reproducibility, furthermore, it requires a very small injection volumes and low costs of analysis, which makes it possible to provide a new noninvasive assay for an indirect measurement of oxidative DNA damage.

Tracing the reactive melting of glass-forming silicate batches by in situ Na-23 NMR

Winter, Rudolf; Jones, A.R.; Florian, P.; Massiot, D., (2005) 'Tracing the reactive melting of glass-forming silicate batches by in situ Na-23 NMR', Journal of Physical Chemistry B 109(10) pp.4324-4332 RAE2008

Mathematical modelling of the solidification of liquid tin with electromagnetic stirring

It is well known that during alloy solidification, convection currents close to the so-lidification front have an influence on the structure of dendrites, the local solute concentration, the pattern of solid segregation, and eventually the microstructure of the casting and hence its mechanical properties. Controlled stirring of the melt in continuous casting or in ingot solidification is thought to have a beneficial effect. Free convection currents occur naturally due to temperature differences in the melt and for any given configuration, their strength is a function of the degree of superheat present. A more controlled forced convection current can be induced using electro-magnetic stirring. The authors have applied their Control-Volume based MHD method [1, 2] to the problem of tin solidification in an annular crucible with a water-cooled inner wall and a resistance heated outer one, for both free and forced convection situations and for various degrees of superheat. This problem was studied experimentally by Vives and Perry [3] who obtained temperature measurements, front positions and maps of electro-magnetic body force for a range of superheat values. The results of the mathematical model are compared critically against the experimental ones, in order to validate the model and also to demonstrate the usefulness of the coupled solution technique followed, as a predictive tool and a design aid. Figs 6, refs 19.

Dynamics of an axisymmetric electromagnetic ‘crucible’ melting

Different industrial induction melting processes involve free surface and melt-solid interface of the liquid metal subject to dynamic change during the technological operation. Simulation of the liquid metal dynamics requires to solve the non-linear, coupled hydrodynamic-electromagnetic-heat transfer problem accounting for the time development of the liquid metal free boundary with a suitable turbulent viscosity model. The present paper describes a numerical solution method applicable for various axisymmetric induction melting processes, such as, crucible with free top surface, levitation, semi-levitation, cold crucible and similar melting techniques. The presented results in the cases of semi-levitation and crucible with free top surface meltings demonstrate oscillating transient behaviour of the free metal surface indicating the presence of gravity-inertial-electromagnetic waves which are coupled to the internal fluid flow generated by both the rotational and potential parts of the electromagnetic force.

Modelling induction melting energy savings

Electromagnetic processing of liquid metals involves dynamic change of the fluid volume interfacing with a melting solid material, gas or vacuum, and possibly a different liquid. Electromagnetic field and the associated force field are strongly coupled to the free surface dynamics and the heat-mass transfer. We present practical modelling examples of the flow and heat transfer using an accurate pseudo-spectral code and the k-omega turbulence model suitable for complex and transitional flows with free surfaces. The 'cold crucible' melting is modelled dynamically including the melting front gradual propagation and the magnetically confined free surrounding interface. Intermittent contact with the water-cooled segmented wall and the radiation heat losses are parts of the complex problem.