Newton's method on Riemannian manifolds and a geometric model for the human spine

To study a geometric model of the human spine we are led tofinding a constrained minimum of a real valued function definedon a product of special orthogonal groups. To take advantgeof its Lie group structure we consider Newton's method on thismanifold. Comparisons between measured spines and computed spinesshow the pertinence of this approach.     

Use of labelled nitrogen to measure gross and net rates of mineralization and microbial activity in permanent pastures following fertilizer applications at different time intervals

Measurements of some of the main internal N-cycling processes in soil were obtained by labelling the inorganic N pool with the stable isotope of nitrogen ((15)N). The (15)N mean pool dilution technique, combined with other field measurements, enabled gross and net N-mineralization rates to be resolved in grassland soils, which had previously either received fertilizer N (F), or had remained unfertilized (U) for many years. The two soils were subdivided into plots that received N at different time intervals (over 3 weeks), prior to (15)N measurements being made. By this novel approach, possible 'priming' effects over time were investigated to try to overcome some of the temporal problems of isotopic labelling of soil N (native plus fertilizer) and to identify possible changes in a range of primary N-transformation processes. The results suggested that an overall stimulation of microbially mediated processes occurred with all N treatments, but there were inconsistencies associated with the release of N, both in the timing and the degree to which different processes responded to the application of fertilizer N. The rates of these processes were, however, within the range of previously reported data and the (15)N measurements were not adversely affected by the differences in N pools created by the treatments. Thus, the mean pool dilution technique was shown to be applicable to agricultural soils, under conditions relevant to grass swards receiving fertilizer. For example, between the U and F treatments, the size of inorganic N pools increased by five-fold and gross rates of mineralization reached 3.5 and 4.8 microg N g(-1) (dry soil) d(-1), respectively, but did not vary greatly with the timing of N applications. A correlation (r(2) = 0.57) was found between soil respiration (which is relatively simple to measure) and net mineralization (which is more time consuming), suggesting that the former might be used as an indicator of the latter. Although this relationship was stronger in previously unfertilized soils, the similarities found with fertilized soils suggest that this approach could be used to obtain information of wider agronomic value and would, therefore, warrant further work under a range of soil conditions.     

Electroluminescence in ruthenium(II) complexes

We have investigated the electrochemical, spectroscopic, and electroluminescent properties of a family of diimine complexes of Ru featuring various aliphatic side chains as well as a more extended pi-conjugated system. The performance of solid-state electroluminescent devices fabricated from these complexes using indium tin oxide (ITO) and gold contacts appears to be dominated by ionic space charge effects. Their electroluminescence efficiency was limited by the photoluminescence efficiency of the Ru films and not by charge injection from the contacts. The incorporation of di-tert-butyl side chains on the dipyridyl ligand was found to be the most beneficial substitution in terms of reducing self-quenching of luminescence.     

Phenylpropanoids from Umbilicus pendulinus

Phytochemical investigation of the leaves of Umbilicus pendulinus afforded in addition to 2-O-caffeoyl malate, isoquercitrin and Z-venusol, the new isomer E-venusol. Special NMR experiments were carried out to elucidate the configuration of the two latter compounds.     

Auditorium acoustic modelling now

Acoustic scale modelling of auditoria now has a history extending back half a century. Although progress has been intermittent, the essential viability of the modelling process has guaranteed continued elaboration of testing techniques. Modelling techniques have now achieved a certain sophistication and auditorium models have proved very valuable as consultancy and research aids. The work of Jordan and other groups involved in acoustic modelling of auditoria is reviewed briefly with a discussion of the scale factors used and the nature of testing. The current techniques for both objective and subjective model testing are discussed, concluding in each case with an assessment of the level of contribution each can make to auditorium design.