Crystallisation in basaltic magmas revealed via in situ 4D synchrotron X-ray microtomography.

Magma crystallisation is a fundamental process driving eruptions and controlling the style of volcanic activity. Crystal nucleation delay, heterogeneous and homogeneous nucleation and crystal growth are all time-dependent processes, however, there is a paucity of real-time experimental data on crystal nucleation and growth kinetics, particularly at the beginning of crystallisation when conditions are far from equilibrium. Here, we reveal the first in situ 3D time-dependent observations of crystal nucleation and growth kinetics in a natural magma, reproducing the crystallisation occurring in real-time during a lava flow, by combining a bespoke high-temperature environmental cell with fast synchrotron X-ray microtomography. We find that both crystal nucleation and growth occur in pulses, with the first crystallisation wave producing a relatively low volume fraction of crystals and hence negligible influence on magma viscosity. This result explains why some lava flows cover kilometres in a few hours from eruption inception, highlighting the hazard posed by fast-moving lava flows. We use our observations to quantify disequilibrium crystallisation in basaltic magmas using an empirical model. Our results demonstrate the potential of in situ 3D time-dependent experiments and have fundamental implications for the rheological evolution of basaltic lava flows, aiding flow modelling, eruption forecasting and hazard management.

The development of module evaluation: a Delphi approach.

This paper outlines an innovatory approach to curriculum evaluation in one of the six colleges of nursing that developed an English National Board (ENB) pilot scheme in nurse education (ENB 1987a). The method of evaluation is promoted as a means of facilitating a working partnership between student and teacher in which they can share in the dynamic process of systematic monitoring and reviewing of learning programmes to ensure changing needs are met. It is envisaged the strategy would interest planners or implementers of health care courses who seek a deeper insight into the perceptions and values their learners hold.

A low-copy-number vector utilizing beta-galactosidase for the analysis of gene control elements.

A low-copy-number vector, pFZY1, with the multiple restriction site linker of M13mp18 inserted upstream from a promoterless beta-galactosidase (beta Gal)-coding lacZ gene has been constructed to provide a convenient and accurate system to analyze regulatory elements in vivo. The plasmid contains the oriF replication origin without the par locus and is present in the cell in one to two copies per genome. It is retained in the host by the presence of ampicillin, and each inserted promoter yielded consistent values of beta Gal activity under all the conditions tested. A series of tetracycline resistance (TcR) promoter fragments and lac promoter fragments have been compared in pFZY1 and the high-copy-number pKO-vector series. The transcriptional activity measured for different fragments containing the same TcR promoter varied within a six-fold range among the several constructs tested. Regulation of the wild-type lac promoter and mutants in pFZY1 was similar to that observed for lac promoters in the chromosome while their regulation in pKO-1mp18 was significantly affected by the high copy number, as expected.