Do vesicle cells of the red alga Asparagopsis (Falkenbergia stage) play a role in bromocarbon production?

The Rhodophyceae (red algae) are an established source of volatile halocarbons in the marine environment. Some species in the Bonnemaisoniaceae have been reported to contain large amounts of halogens in structures referred to as vesicle cells, suggesting involvement of these specialised cells in the production of halocarbons. We have investigated the role of vesicle cells in the accumulation and metabolism of bromide in an isolate of the red macroalga Asparagopsis (Falkenbergia stage), a species known to release bromocarbons. Studies of laboratory-cultivated alga, using light microscopy, revealed a requirement of bromide for both the maintenance and formation of vesicle cells. Incubation of the alga in culture media with bromide concentrations below 64 mg l-1 (the concentration of Br- in seawater) resulted in a decrease in the proportion of vesicle cells to pericentral cells. The abundance of vesicle cells was correlated with bromide concentration below this level. Induction of vesicle cell formation in cultures of Falkenbergia occurred at concentrations as low as 8 mg l-1, with the abundance of vesicle cells increasing with bromide concentration up to around 100 mg l-1. Further studies revealed a positive correlation between the abundance of vesicle cells and dibromomethane and bromoform production. Interestingly, however, whilst dibromomethane production was stimulated by the presence of bromide in the culture media, bromoform release remained unaffected suggesting that the two compounds are formed by different mechanisms.

Mathematical prerequisites for learning statistics in Psychology: Assessing core skills of numeracy and mathematical reasoning among undergraduates.

This study sought to extend earlier work by Mulhern and Wylie (2004) to investigate a UK-wide sample of psychology undergraduates. A total of 890 participants from eight universities across the UK were tested on six broadly defined components of mathematical thinking relevant to the teaching of statistics in psychology - calculation, algebraic reasoning, graphical interpretation, proportionality and ratio, probability and sampling, and estimation. Results were consistent with Mulhern and Wylie's (2004) previously reported findings. Overall, participants across institutions exhibited marked deficiencies in many aspects of mathematical thinking. Results also revealed significant gender differences on calculation, proportionality and ratio, and estimation. Level of qualification in mathematics was found to predict overall performance. Analysis of the nature and content of errors revealed consistent patterns of misconceptions in core mathematical knowledge , likely to hamper the learning of statistics.

Multidimensional DSP Core Synthesis for FPGA

This paper, chosen as a best paper from the 2004 SAMOS Workshop on Computer Systems: describes a novel, efficient methodology for automatically creating embedded DSP computer systems. The novelty arises since now embedded electronic signal processing systems, such as radar or sonar, can be designed by anyone from the algorithm level, i.e. no low level system design experience is required, whilst still achieving low controllable implementation overheads and high real time performance. In the chosen design example, a bank of Normalised Lattice Filter (NLF) components is created which a four-fold reduction in the required processing resource with no performance decrease.

Proof of polar ejection from the close-binary core of the planetary nebula Abell 63

We present the first detailed kinematical analysis of the planetary nebula Abell 63, which is known to contain the eclipsing close-binary nucleus UU Sge. Abell 63 provides an important test case in investigating the role of close-binary central stars on the evolution of planetary nebulae. Longslit observations were obtained using the Manchester echelle spectrometer combined with the 2.1-m San Pedro Martir Telescope. The spectra reveal that the central bright rim of Abell 63 has a tube-like structure. A deep image shows collimated lobes extending from the nebula, which are shown to be high-velocity outflows. The kinematic ages of the nebular rim and the extended lobes are calculated to be 8400 +/- 500 and 12900 +/- 2800 yr, respectively, which suggests that the lobes were formed at an earlier stage than the nebular rim. This is consistent with expectations that disc-generated jets form immediately after the common envelope phase. A morphological-kinematical model of the central nebula is presented and the best-fitting model is found to have the same inclination as the orbital plane of the central binary system; this is the first proof that a close-binary system directly affects the shaping of its nebula. A Hubble-type flow is well-established in the morphological-kinematical modelling of the observed line profiles and imagery. Two possible formation models for the elongated lobes of Abell 63 are considered, (i) a low-density, pressure-driven jet excavates a cavity in the remnant asymptotic giant branch (AGB) envelope; (ii) high-density bullets form the lobes in a single ballistic ejection event.

Ionization energies of beryllium in strong magnetic fields: a frozen core approximation

An effective frozen core approximation has been developed and applied to the calculation of energy levels and ionization energies of the beryllium atom in magnetic field strengths up to 2.35 x 10(5) T. Systematic improvement over the existing results for the beryllium ground and low-lying states has been accomplished by taking into account most of the correlation effects in the four-electron system. To our knowledge, this is the first calculation of the electronic properties of the beryllium atom in a strong magnetic field carried out using a configuration interaction approximation and thus allowing a treatment beyond that of Hartree-Fock. Differing roles played by strong magnetic fields in intrashell correlation within different states are observed. In addition, possible ways to gain further improvement in the energies of the states of interest are proposed and discussed briefly.

Simple models of complex aggregation: Vesicle formation by soft repulsive spheres with dipolelike interactions

Structural and thermodynamic properties of spherical particles carrying classical spins are investigated by Monte Carlo simulations. The potential energy is the sum of short range, purely repulsive pair contributions, and spin-spin interactions. These last are of the dipole-dipole form, with however, a crucial change of sign. At low density and high temperature the system is a homogeneous fluid of weakly interacting particles and short range spin correlations. With decreasing temperature particles condense into an equilibrium population of free floating vesicles. The comparison with the electrostatic case, giving rise to predominantly one-dimensional aggregates under similar conditions, is discussed. In both cases condensation is a continuous transformation, provided the isotropic part of the interatomic potential is purely repulsive. At low temperature the model allows us to investigate thermal and mechanical properties of membranes. At intermediate temperatures it provides a simple model to investigate equilibrium polymerization in a system giving rise to predominantly two-dimensional aggregates.

Negative photoion spectroscopy of the core-excited bromo- chloro-alkanes, Br(CH2)(n) Cl, n=1-4

Polar photodissociation of a set of bromo-chloro-alkanes in the vicinity of the Br 3d core edge has been observed for the first time. It is shown that negative photoion spectroscopy is a powerful tool for investigating the various decay mechanisms of core-excited molecules. Analysis of these results indicates that the observed polar photodissociation arises from two competing spectator Auger decay processes in which the molecule can dissociate either before or after the core hole relaxation.

The pathobiology of the septin gene family.

Septins are an evolutionarily conserved group of GTP-binding and filament-forming proteins that belong to the large superclass of P-loop GTPases. While originally discovered in yeast as cell division cycle mutants with cytokinesis defects, they are now known to have diverse cellular roles which include polarity determination, cytoskeletal reorganization, membrane dynamics, vesicle trafficking, and exocytosis. Septin proteins form homo- and hetero-oligomeric polymers which can assemble into higher-order filaments. They are also known to interact with components of the cytoskeleton, ie actin and tubulin. The precise role of GTP binding is not clear but a current model suggests that it is associated with conformational changes which alter binding to other proteins. There are at least 12 human septin genes, and although information on expression patterns is limited, most undergo complex alternative splicing with some degree of tissue specificity. Nevertheless, an increasing body of data implicates the septin family in the pathogenesis of diverse disease states including neoplasia, neurodegenerative conditions, and infections. Here the known biochemical properties of mammalian septins are reviewed in the light of the data from yeast and other model organisms. The data implicating septins in human disease are considered and a model linking these data is proposed. It is posited that septins can act as regulatable scaffolds where the stoichiometry of septin associations, modifications, GTP status, and the interactions with other proteins allow the regulation of key cellular processes including polarity determination. Derangements of such septin scaffolds thus explain the role of septins in disease states. Copyright © 2004 Pathological Society of Great Britain and Ireland.