A visual flow study of mixed convection in the entry region of a vertical internally heated annulus

The velocity distribution in laminar upward flow of water (Pr 7.25) in the entry of a vertical internally heated annulus (radius ratio 4:1) has been determined by visual observation. Photographic measurements have been made of the motion of hydrogen bubble clusters, which were generated by a carefully controlled process of electrolysis, to assess the effects of free convection effects on the forced flow.For heat fluxes up to 2500 W/m² and at a Reynolds number of approximately 450, local heat transfer coefficients have been obtained in a length of about 23 equivalent diameters. Heat transfer rate in the immediate entry was found to be insensitive to change in heat flux over the range of variables considered. As the distance downstream increased, the heat transfer rate was found to be dependent on the heat flux.     

Fourier transform ion cyclotron resonance mass spectrometry of principal components in oilsands naphthenic acids

Naphthenic acids present formidable challenges for the petroleum industry and are a growing concern in the aquatic environment. For example, these acids are responsible for corrosion of refinery equipment, leading to the incurrence of additional costs to the consumer, and are toxic to aquatic wildlife, making disposal and remediation of contaminated waters and sediments a significant problem. The detection and characterization of naphthenic acids is therefore of considerable importance. Fourier transform ion cyclotron resonance mass spectrometry is presented as a technique with inherently ultra-high mass accuracy and resolution, affording unequivocal assignments. The suitability of the technique for environmental applications is demonstrated to characterize two different commercial mixtures of naphthenic acids and one oilsands tailings pond sample.     

On-line high-performance liquid chromatography/mass spectrometric investigation of amyloid-beta peptide variants found in Alzheimer's disease

Abeta peptides are the major components of amyloid deposits in Alzheimer's disease. The presence of N-terminally truncated Abeta variants in amyloid may be a critical factor in Alzheimer's disease pathogenesis. These Abeta variants are less soluble and more amyloidogenic than full-length Abeta, making their separation, purification and identification difficult. High-performance liquid chromatography (HPLC) at elevated temperatures, coupled to electrospray ionization (ES) mass spectrometry (MS), enables rapid separation and identification of N-terminally truncated Abeta variants. This methodology provides a potential tool for exploring the importance of these Abeta variants in both the pathogenesis and diagnosis of Alzheimer's disease.     

Determination of crystalline silica in silica fume

Silica fume is formed as a by-product in the manufacture of silicon from quartzite. This paper describes an analytical method for the determination of crystalline silica in silica fume. The crystalline silica was determined after removal of amorphous silica from the fume. A gravimetric method was developed for the determination of the total crystalline silica in the fume, while the cascade impactor technique was used to determine the crystalline content in the -10 microm fraction. X-Ray diffraction, scanning electron microscopy and particle size distributions were used to validate the steps in the analytical procedure. The total crystalline silica content was found to vary from 2.7 to 8.6% with an RSD of +/-2%, while the crystalline silica content of the -10 microm fraction was 0.23 to 0.55% with an RSD of +/-10%. A knowledge of the crystalline silica content of silica fume is of great importance in the area of Occupational Health and Safety. The samples surveyed were shown to have levels of crystalline silica in the respirable fraction well within the draft guidelines for silica fume. It is proposed that this method be accepted as a standard method for the determination of crystalline silica in silica fume.     

Principles of Fourier transform ion cyclotron resonance mass spectrometry and its application in structural biology

Fourier transform ion cyclotron resonance (FT-ICR) mass spectrometry has become increasingly significant within recent years. The inherently ultra-high resolution and mass accuracy allow unequivocal assignments of chemical formulae to be made and further structural elucidation can be conducted through the utilization of tandem mass spectrometry techniques. With the advent of electrospray ionization (ESI), FT-ICR mass spectrometry has become a powerful tool for the investigation of biological macromolecules, such as the study of non-covalent interactions of proteins. In this article, the basic principles are highlighted, some of the techniques employed are described and examples of applications are provided, with particular respect being paid to the field of characterization of biomolecules.     

Continuous molecular enrichment in microfluidic systems

Highly efficient molecular extractions in continuous flow microfluidic systems are demonstrated utilising the rapid mixing properties of biphasic segmented flow in conjunction with suspended micro-particulate adsorbents. A continuous flow technique providing potential for continual on-line sample enrichment, purification and clean-up in chemical synthesis, and sample preparation.