Evanescently coupled interface states in the gap between two Bragg reflectors.

Interface states are known to exist at the surface of an appropriately structured Bragg reflector. If such reflectors are present on the surfaces of two prisms separated by a narrow gap, the evanescently coupled interface states can interact to produce a pair of very narrow transmission lines, the separation of which can be adjusted by varying the size of the gap between the two prisms. Thus, although only a single cavity is involved, the spectral properties of the system are similar to those of a dual-cavity photonic microstructure. In addition to other potential applications, we propose that such a structure could form the basis of an adjustable beat-frequency emitter in the terahertz regime.

Leveraging differences for collaborative advantage: enhancing student learning through an international educational collaboration.

This case study in collaboration development describes the relationship from initiation through maintenance over three years between a high profile research-focused school of nursing in the U.S. and a school in the UK known for learning and teaching innovation. The ultimate goal of the collaboration is to enhance nursing student learning opportunities to best prepare students to function in the complex and ever-changing world of nursing practice. This goal has been, and continues to be, achieved through implementation of innovative teaching and learning strategies including the use of high fidelity simulation. The authors describe the intellectual collaborative advantage that the relationship between the schools has made possible as well as key principles to be considered when any organization is contemplating a collaboration.

A new quantitative optical biosensor for protein characterisation.

A new optical biosensor is described based on a dual waveguide interferometric technique. By addressing the waveguide structure with alternate polarisations the optogeometrical properties (density and thickness) of adsorbed protein layers at the sensor (solid)-liquid interface have been determined. Differences in the waveguide mode dispersion between the transverse electric (TE) and transverse magnetic (TM) modes allow unique solutions for adlayer thickness and refractive index to be determined at all stages during the formation process. The technique has been verified using standard protein systems and by comparing the data with published work using X-ray crystallography and neutron reflection techniques. The data obtained was found to be in excellent agreement with previously reported X-ray experiments given that typical film thicknesses for streptavidin layers were in the range 5.5-6.5 nm compared with the short axis crystal structure of between 4.8 and 5.6 nm. The precision of the measurements taken was of the order of 40 pm with respect to adsorbed adlayer thicknesses. This biosensor approach provides measurements of both thickness and density of adlayers to a high precision, simultaneously and in real time enabling detail of the structure and function of proteins to be elucidated. From such data it is possible to obtain information on the orientation, distortion and efficiency of immobilisation procedures as well as the interaction event of interest. The technique is expected to find utility with those interested in protein structure and function. This is an area of growing importance within the life sciences as the demand for quantitative analytical techniques increases with the growth in "proteomics".

Reduction in vitro of red cell glutathione reproduces defects of cellular sodium transport seen in oedematous malnutrition

Red cells in oedematous malnutrition (kwashiorkor) have an increased sodium content, 'leakiness' to sodium and enhanced sodium pumping. In non-oedematous malnutrition (marasmus) there is a reduction in the sodium pump activity. The explanation has hitherto been unknown but the glutathione content of red cells is low in kwashiorkor and normal in marasmus. We artifically lowered the glutathione content of normal red cells to values characteristic of mild oedematous malnutrition, using the enzyme inhibitors bischloronitrosourea (BCNU) and buthionine sulfoximine (BSOX). After preincubation, the cells were washed to remove the inhibitors and oxidized glutathione. Cellular content of sodium and potassium, and 86Rb influx were then measured. The reduction in glutathione reproduce the abnormalities of sodium content and flux observed in kwashiorkor. We suggest that oxidant stress in kwashiorkor, by reducing cellular glutathione, may affect cell membrane electrolyte transport. This may act through alterations in membrane sulfhydryl groups. Glutathione depletion may therefore play an important role in the clinical picture and natural history of oedematous malnutrition and may have relevance to other conditions where oxidant stress occurs. (AU)