Life Sciences Commons^™

Caesium On Si(100) Studied By Biassed Secondary Electron Microscopy, M. Azim, C. J. Harland, T. J. Martin, R. H. Milne, J. A. Venables

Scanning Microscopy

An ultra-high vacuum scanning electron microscope (UHV-SEM) has been used to study sub-monolayers of Cs on Si(100) surface. Cs adsorption on the surface causes a considerable change in the work function. Coverages below 1/2 monolayer (ML) have been estimated by correlating the work function changes with the secondary electron (SE) signal. It has been found that this signal is sensitive down to ~ 0.005 ML when the sample is biassed to a few hundred volts.

Electron trajectories from a biassed sample have been simulated for electrons originating from different areas with different work functions across the sample. This indicates that …

Atomic Force Microscopy Study Of Human Tooth Enamel Surfaces, Ph. Schaad, E. Paris, F. J. G. Cuisinier, J. -C. Voegel

Scanning Microscopy

Human enamel features from individual crystals up to prisms were observed by atomic force microscopy (AFM). Low magnification images of vestibular tooth surfaces show the existence of enamel prisms appearing as deep holes. Individual, parallel enamel crystals show lateral faces elongated and formed by the (100) planes of hydroxyapatite (HA). Height differences between (001) faces create the roughness of enamel surface. Individual (001) crystal faces can be observed clearly at higher magnification and show the characteristic hexagonal shape with 60° angles between (100) faces. This study confirms the applicability of AFM for studying biological hydroxyapatite crystals.

The Stabilisation Of Air In Foods Containing Fat - A Review, B. E. Brooker

Food Structure

Foods containing aqueous solutions of proteins readily foam when air is introduced into them. When fat is also present, interaction between the two components at the air/water interface may produce a stable foam with characteristic bulk properties. In the case of dairy foams (such as whipped cream), bubbles produced in the whipping process are initially stabilised by the adsorption of protein at the air/water interfaces.

Commonly encountered defects in whipping cream arise when large triglyceride crystals, formed in masses of free fat, adsorb to the air/water interface during whipping at the expense of fat globules.

In other food systems , …

The Stabilisation Of Air In Cake Batters - The Role Of Fat, B. E. Brooker

Food Structure

The role of fat crystals in the stabilisation of air bubbles in cake batters was studied with aqueous phase aerations prepared by the "all in one" method using shortening containing emulsifier. During mixing, fat crystals become coated with an interfacial layer of ad sorbed protein (crystal -water interface). They adsorb to the surface of bubbles (that have been transiently stabilised by egg proteins) by a process which involves the fu sion of the crystal-water interface with the air-water interface.

The adsorption of fa t crystals helps to stabilise large numbers of small bubbles which must expand without rupturing during baking …