A geochemical model of mid-ocean ridge magma chambers

A computer model of mid-ocean ridge basalt generation using trace element geochemistry has been developed. The model simulates a periodically replenished, continually cooled and fractionated magma chamber, with periodic lava extrusion. Primitive basalts from the ocean floor are used to generate likely evolution paths for the magma chamber. The steady state variant of this model has led to the isolation of several variables which critically affect the basalt composition. Although the fraction of cumulates is an important parameter, other variables such as the volume of incoming magma batches, their frequency, and the volume of the mixing cell, play a critical part especially on slow-spreading ridges. The growing magma chamber model uses random number generators to simulate the initiation and growth of a chamber. This model predicts a rapid increase in incompatible element concentrations, immediately after chamber initiation on a fast-spreading ridge. This would occur in situations such as propagating rifts and may help in the understanding of ferrobasalt generation.     

Whole-bird models for the magnetic cleansing of oiled feathers

Iron powder, a promising dry-cleansing agent for oiled feathers where both the contaminant and the cleansing agent may be harvested magnetically, has been tested on the plumage of whole-bird models. The breast and back plumage of Mallard Duck (Anas platyrhynchos) and Little Penguin (Eudyptula minor) carcasses were patch-contaminated with commercial-grade engine oil, three different crude oils, and an oil/seawater emulsion. The plumage was then subjected to a magnetic cleansing protocol. The contaminant removal was assessed gravimetrically and was found to reflect the outcomes for a previously reported in vitro study using feather clusters. Between 92-98% of the contaminants, and effectively all of the cleansing agent, were removed from the feathers.     

Cation ordering in omphacite and effect on deformation mechanism and lattice preferred orientation (LPO)

We present microstructural data and lattice preferred orientations (LPOs) of omphacites from a suite of eclogites, from the Adula/Cima Lunga nappe (Central Alps). Our work shows a surprisingly strong correlation between the measured LPO and the ordering state of cations in omphacite. Estimates of deformation temperature from metamorphic petrology, together with measured omphacite compositions and LPOs, determine the field (ordering state), on the omphacite phase diagram, into which each sample falls. LPOs dominated by L-type and S-type signatures are developed in samples that fall in the P2/n field (ordered structure) and C2/c field (disordered structure), respectively.Dislocations with b=1/2−110 or b=[001] are observed in the transmission electron microscope (TEM) in all samples. The former change from a perfect dislocation in the C2/c structure to a partial in P2/n. Any movement of a partial dislocation requires the formation or growth of a stacking fault. Furthermore, in order to pass an obstacle a partial dislocation has to constrict to a unit dislocation. The energy to form a constriction is high in omphacite due to the large separation width. Thus, the activity of the b=1/2−110 dislocation is hindered in the P2/n structure relative to the C2/c structure, which change the balance between the two and might give rise to the different LPOs.     

Bianchi Type-III String Cosmological Model with Bulk Viscous Fluid in General Relativity

A Bianchi type-III string cosmological model with bulk viscous fluid for massive string is investigated. To get a determinate solution, a supplementary condition B=C ⁿ, between metric potentials, is used whereB and C are function of time alone. The behaviour of the model in presence and absence of bulk viscosity, is discussed. This revised version was published online in July 2006 with corrections to the Cover Date.     

A multi-site campaign on the long period variable subdwarf b star PG 1627+017

We report on the outcome of the first major multi-site campaign on a long-period variable subdwarf B star. The target PG 1627+017 was observed for a total of 334 h during April/May/June 2003 from the lynchpin observatory at Mt. Bigelow, Arizona, with important contributions coming from co-observations at SAAO, Calar Alto and Siding Spring. Preliminary analysis indicates the presence of 8–10 probable periods in the range ～4500 to ～8900 s with relative amplitudes between 0.1 and 0.5%;. The range over which the periods are found is in qualitative agreement with theoretical predictions and the number of periods found shows potential for an in-depth asteroseismological analysis. Multi-colour observations show that the relative amplitudes of pulsation are larger in the U-band than in the R, which again is in agreement with theory. However, more multi-colour observations are needed to be able to make statements at the quantitative level.     

Investigations into an unknown organism on the martian meteorite Allan Hills 84001

Abstract— Examination of fracture surfaces near the fusion crust of the martian meteorite Allan Hills (ALH) 84001 have been conducted using scanning electron microscopy (SEM) and atomic force microscopy (AFM) and has revealed structures strongly resembling mycelium. These structures were compared with similar structures found in Antarctic cryptoendolithic communities. On morphology alone, we conclude that these features are not only terrestrial in origin but probably belong to a member of the Actinomycetales, which we consider was introduced during the Antarctic residency of this meteorite. If true, this is the first documented account of terrestrial microbial activity within a meteorite from the Antarctic blue ice fields. These structures, however, do not bear any resemblance to those postulated to be martian biota, although they are a probable source of the organic contaminants previously reported in this meteorite.