Preparation and characterization of iron oxide thin films by spray pyrolysis using methanolic and ethanolic solutions

Iron oxide thin films have been obtained by spray pyrolysis using 100% methanolic and ethanolic solutions of iron tri-chloride. The films were deposited onto ITO-coated glass substrates. The preparative conditions have been optimized to obtain compact, pin-hole-free and smooth thin films which are adherent to the substrate. The structural, morphological and compositional characterizations have been carried out by X-ray diffraction, scanning electron microscopy and energy dispersive X-ray analysis. The films deposited using ethanolic solution results into pure hematite; α-Fe₂O₃ thin films, however, films deposited using methanolic solution consists of hematite and maghemite-c phases of iron oxide. The films are nanocrystalline with particle size of 30-40 nm. The optical absorbance of the film was of the order of 10⁵ cm⁻¹. The optical band gap of films was found to be 2.26 and 2.20 eV for the films deposited using methanolic and ethanolic solutions, respectively.     

Influence of humic substances on sorption and methylation processes of inorganic- and organo-tin species

The influence of humic substances on sorption and methylation processes for inorganic- and organotin species is presented. Four sediment samples from different locations of the Rivers Elbe, Mulde and Spittelwasser, Germany, with different organotin and humic contents were selected to extract the humic and fulvic acids. The various fractions—the original sediment, the humic acid, the fulvic acid and the residual sediment—were analysed for their organotin content. The individual buyltin species show quite different distribution patterns. Monobutyltin is found mostly associated with humic acids. Dibutyltin shows a nonunique behaviour. At low total organotin content, dibutyltin is found bonded to humic and fulvic acids, whereas at high organotin content dibutyltin is distributed more with the residual sediment. Most of the tributyltin remains in the sediment unextracted; only small quantities of it are in the fulvic acid fraction. Tetrabutyltin is only in the humic acid fraction when it binds to humic matter; it mostly remains in the sediment. General observations indicate that ionic butyltin species bind to fulvic acids whereas the non-polar tetrabutyltin is not found in the fulvic acid fractions in any of the samples. The appearance of monomethyl- and dimethyl-tin species in the humic and fulvic acid fractions after the alkaline extraction was surprising. There is a correlation between the humic content of the sample and the formation of methyltin species. Evidence is provided by experiments that humic substances act as methylation agents.     

Role of orientation in kinetics of nucleation and growth of crystals in polymers

A theoretical framework is provided for generalizing the inferences drawn from the results of earlier experimental studies of kinetics of crystallization in oriented poly(ethylene terephthalate). The framework is obtained by combining extensions of classical nucleation theories in polymers^3,4 and a theory of crystal growth with anisotropic incorporation of segments into growing crystals.¹⁵ It is shown that, while a very strong dependence of rate of primary nucleation on orientation does exist, there is a only a much weaker dependence of rate of crystal growth on the orientation of the crystallizing polymer. The theoretical formulation provided here would allow qualitative estimates for comparison with experiments.     

Stoichiometry-dependent formation of quantum dot-antibody bioconjugates: a complementary atomic force microscopy and agarose gel electrophoresis study

The unique advantages of quantum dot (QD) bioconjugates have motivated their application in biological assays. However, physical characterization of bioconjugated QDs after surface modification has often been overlooked. Here, biotinylated antibodies (biotin-IgG) were attached to commercial streptavidin-conjugated quantum dots (strep-QDs) at different stoichiometric ratios, and these QD bioconjugates were characterized with atomic force microscopy and discontinuous sodium dodecyl sulfate agarose gel electrophoresis (SDS-AGE). The results from these complementary analytical techniques showed that the molar ratio determined the relative sizes, molecular weights and morphologies of the QD bioconjugates. Additionally, the novel discontinuous SDS-AGE analysis confirmed specific binding between biotin-IgG and strep-QDs. Researchers who design QD bioconjugates for cell-based assays should consider stoichiometry-dependent differences in the physical properties of their QD bioconjugates.     

Thermal and microwave-assisted N-formylation using solid-supported reagents

A rapid and easy route to formamides by microwave assisted N-formylation of primary and secondary amines is described. Using an insoluble polymer or an inorganic solid-supported reagent as a formylating agent, microwave irradiation furnished the corresponding formamides in high yields, with reduced reaction time and solvent volume over the conventional approach.     

Decreased insulin binding to mononuclear leucocytes and erythrocytes from dogs after S-Nitroso-N-Acetypenicillamine administration

Background

Nitric oxide (NO) and oxygen free-radicals play an important part in the destruction of beta-cells in auto- immune diabetes although the precise mechanism of interaction is still not known. This study was designed to examine any possible diabetogenic effect of NO by investigating any differences in cellular binding of insulin to its receptor on the cell membranes of erythrocytes and mononuclear leucocytes of dogs treated with the NO donor, S-nitroso-N-acetylpenicillamine (SNAP) and controls treated with captopril.

Results

The result obtained showed decreased binding of insulin to its receptor on the cell membranes of erythrocytes and mononuclear leucocytes. Mononuclear leucocytes from SNAP-treated dogs had decreased ability to bind insulin (16.30 ± 1.24 %) when compared to mononuclear leucocytes from captopril-treated controls (20.30 ± 1.93 %). Similar results were obtained for erythrocytes from dogs treated with SNAP (27.20 ± 1.33 %) compared with dogs treated with captopril (34.70 ± 3.58 %). Scatchard analysis demonstrated that this decrease in insulin binding was accounted for by a decrease in insulin receptor sites per cell, with mononuclear leucocytes of SNAP-treated dogs having 55 % less insulin receptor sites per cell compared with those of captopril-treated controls (P < 0.05). Average affinity and kinetic analysis revealed a 35 % decrease in the average receptor affinity, with mononuclear leucocytes from captopril-treated controls having an empty site affinity of 12.36 ± 1.12 × 10^-8 M^-1 compared with 9.64 ± 0.11 × 10^-8 M^-1 in SNAP-treated dogs (P < 0.05).

Conclusion

These results suggest that acute alteration of the insulin receptor on the membranes of mononuclear leucocytes and erythrocytes occurred in dogs treated with S-nitroso-N-acetylpenicillamine. These findings suggest the first evidence of the novel role of NO as a modulator of insulin binding and the involvement of NO in the aetiology of diabetes mellitus.     

Molecular mass distribution of sodium alginate by high-performance size-exclusion chromatography

A sensitive high-performance size-exclusion chromatography (HPSEC) method with simple UV detection was developed for the molecular mass analysis of sodium alginate. It was used to evaluate alginates of varying molecular mass and the results were compared with the viscosity measurements. This HPSEC method was sensitive to serve as the stability indicating method for alginate after storage under different conditions. The information of relative molecular mass distribution of alginate was provided with reference to pullulan molecular mass standards. The comparison of the HPSEC chromatograms of alginate, pullulan and dextran revealed the effect of chemical composition of a polysaccharide and its effect on apparent molecular mass distribution.     

Ligand discrimination in the reaction of nitrones with [PtCl2(PhCN)2]. Selective formation of mono-oxadiazoline and mixed bis-oxadiazoline complexes under thermal and microwave conditions

[2+3] Cycloaddition of nitrones to the nitrile ligands in the complexes cis- or trans-[PtCl2(PhCN)2] occurs under ligand differentiation and allows for selective synthesis of complexes of the type cis- or trans-[PtCl2(oxadiazoline)(PhCN)]. Microwave irradiation enhances the reaction rates of the cycloaddition considerably and further favours the selectivity towards the mono-cycloadduct with respect to thermal conditions, because the first cycloaddition is accelerated to a higher extent than the second one. Reaction of the trans-substituted mono-oxadiazoline complexes with a nitrone different from the one used for the first cycloaddition step gives access to mixed bis-oxadiazoline compounds of the composition trans-[PtCl2(oxadiazoline-a)(oxadiazoline-b)]. The corresponding cis-configured complexes, however, do not undergo further cycloaddition. All reactions described occur without isomerisation of the stereochemistry around the platinum center, independently of whether thermal or microwave heating is applied.     

Estimation of effective diffusion coefficients of model solutes through gastric mucus: assessment of a diffusion chamber technique based on spectrophotometric analysis.

A diffusion chamber technique based on spectrophotometric analysis to determine effective diffusion coefficients for solutes with various relative molecular mass (Mr) values and properties, passing through native mucus gel, is reported. For all solutes studied, a reduction in effective diffusion coefficients is observed with a retardation of solute flux by a factor of at least two. For the solutes investigated (with Mr values ranging from 126-14,400 u), no consistent effect of solutes of low Mr was evident with regard to the retarding effect of mucus; however, at high Mr values (greater than 4000 u) the retardation was greatly enhanced. A possible relationship between charged solutes of low Mr and the degree of retardation was observed, which possibly suggests the presence of ionic interactions of the solutes with the largely negatively charged mucus gel. The results provide further evidence for the suggestion that mucus is acting more than simply as a gel support for an unstirred water layer and is perhaps a more potent diffusion barrier to specific solutes.