5,070 research outputs found
Optical control of electric-field poling in LiTaO<sub>3</sub>
We present a room temperature technique for optically inducing periodic domain-inverted structures in bulk (0.2mm thick) LiTaO3. By simultaneous application of an electric field and patterned illumination using UV wavelengths (351nm and 364nm) we demonstrate modulation of the resulting domain profile. We discuss the origins of the observed optical effect and describe our results from repeated domain switching, by cycling the electric field
Biosensor measurement of purine release from cerebellar cultures and slices
We have previously described an action-potential
and Ca2+-dependent form of adenosine release in the
molecular layer of cerebellar slices. The most likely source
of the adenosine is the parallel fibres, the axons of granule cells. Using microelectrode biosensors, we have therefore investigated whether cultured granule cells (from postnatal day 7–8 rats) can release adenosine. Although no purine release could be detected in response to focal electrical stimulation, purine (adenosine, inosine or hypoxanthine) release occurred in response to an increase in extracellular K+ concentration from 3 to 25 mM coupled with addition of 1 mM glutamate. The mechanism of purine release was transport from the cytoplasm via an ENT transporter.
This process did not require action-potential firing but
was Ca2+dependent. The major purine released was not
adenosine, but was either inosine or hypoxanthine. In
order for inosine/hypoxanthine release to occur, cultures
had to contain both granule cells and glial cells; neither
cellular component was sufficient alone. Using the same
stimulus in cerebellar slices (postnatal day 7–25), it was
possible to release purines. The release however was not
blocked by ENT blockers and there was a shift in the Ca2+
dependence during development. This data from cultures
and slices further illustrates the complexities of purine
release, which is dependent on cellular composition and
developmental stage
Early Integrators and the Passive Majority: An evaluation study of a large web-based bibliographic reference database
An evaluation is reported of user responses to zetoc, a service that provides access to the British Library electronic table of contents database and an email alerting service. Two questionnaire surveys and an interview programme gave data on over 800 users. The results show that about 17% are active users who are achieving a personal information management routine by integrating zetoc with other services (the early integrators). The other 83%, the `passive majority', make limited use of zetoc and do not achieve integration with other services. The interviews reveal that some of this group have a stable but restricted usage routine that limits information overload. The usage by others is less controlled and they make little use of the information they receive. The paper examines the impact of enhancements to the zetoc service to support integration and it discusses the barriers that prevent many users exploiting the potential of services available to them
Growth of single and multilayer sesquioxide crystal films for lasing applications via pulsed laser deposition
Sesquioxides, materials of the form RE2O3 (RE: rare earth), are of great interest for lasing applications. These materials offer high thermal conductivities, are mechanically stable, can easily be doped with various rare earth ions and are optically isotropic. Members of the sesquioxide family have the same crystal structure but differing refractive indices, and hence are ideal candidates for multilayer as well as single film growth. Sesquioxides can be challenging to grow from the melt, however, due to their high melting points (>2400 °C)
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