Tree-ring series offer considerable potential for the development of environment-sensitive proxy records. However, with traditional increment cores, only small amounts of wood are often available from annual tree-ring sequences. For this reason, it is important to understand the reliability (and reproducibility) of radiocarbon measurements obtained from small-sized samples. Here we report the F14C results from the Chronos 14Carbon-Cycle Facility of modern tropical Australian tree samples over a range of four graphite target sizes from the same rings. Our study shows that similar precision can be obtained from full-sized, half-sized, as well as small-sized graphite targets using standard pretreatment and analysis procedures. However, with a decline in sample size, there was an increase seen in the associated variance of the ages and the smallest target weights started showing a systematic bias. Wiggle-matching accuracy tests, comparing the Southern Hemisphere post-bomb atmospheric calibration curve to the different sample weight sequences, were all significant except for the 200 μgC graphite targets. Our results indicate that samples smaller than 350 μgC have limited accuracy and precision. Overall, reliable measurements of F14C sequences from tree-ring records across a range of sample sizes, with best results found using graphitized samples >350 μgC.

Experiments on the National Ignition Facility show that multi-dimensional effects currently dominate the implosion performance. Low mode implosion symmetry and hydrodynamic instabilities seeded by capsule mounting features appear to be two key limiting factors for implosion performance. One reason these factors have a large impact on the performance of inertial confinement fusion implosions is the high convergence required to achieve high fusion gains. To tackle these problems, a predictable implosion platform is needed meaning experiments must trade-off high gain for performance. LANL has adopted three main approaches to develop a one-dimensional (1D) implosion platform where 1D means measured yield over the 1D clean calculation. A high adiabat, low convergence platform is being developed using beryllium capsules enabling larger case-to-capsule ratios to improve symmetry. The second approach is liquid fuel layers using wetted foam targets. With liquid fuel layers, the implosion convergence can be controlled via the initial vapor pressure set by the target fielding temperature. The last method is double shell targets. For double shells, the smaller inner shell houses the DT fuel and the convergence of this cavity is relatively small compared to hot spot ignition. However, double shell targets have a different set of trade-off versus advantages. Details for each of these approaches are described.

Experiments reporting magnetic-field generation by the ablative nonlinear Rayleigh–Taylor (RT) instability are reviewed. The experiments show how large-scale magnetic fields can, under certain circumstances, emerge and persist in strongly driven laboratory and astrophysical flows at drive pressures exceeding one million times atmospheric pressure.

We are developing a purely commensal survey experiment for fast (<5 s) transient radio sources. Short-timescale transients are associated with the most energetic and brightest single events in the Universe. Our objective is to cover the enormous volume of transients parameter space made available by ASKAP, with an unprecedented combination of sensitivity and field of view. Fast timescale transients open new vistas on the physics of high brightness temperature emission, extreme states of matter and the physics of strong gravitational fields. In addition, the detection of extragalactic objects affords us an entirely new and extremely sensitive probe on the huge reservoir of baryons present in the IGM. We outline here our approach to the considerable challenge involved in detecting fast transients, particularly the development of hardware fast enough to dedisperse and search the ASKAP data stream at or near real-time rates. Through CRAFT, ASKAP will provide the testbed of many of the key technologies and survey modes proposed for high time resolution science with the SKA.

The odor produced by male Ips grandicollis attacking caged loblolly pine bolts was not very effective in attracting marked beetles. Only 2.4% of the 9,417 beetles released around the attracting attacks were recaptured.Unscreened infested bolts lost their attractiveness to responding beetles when about 27 attacks per square foot of bark surface had been reached. More beetles attacked bolts placed outside of a beetle producing area than those within. The latter indicates that a dispersal flight may be needed before response takes place.

Five trap designs were evaluated for sampling the insect complex attracted to severed shortleaf (Pinus echinata Mill.), Virginia (P. virginiana Mill.), and loblolly (P. taeda L.) pines. The baffled flight trap was superior for capturing Coleoptera. Plexiglas®, saran screen, and 4-directional Plexiglas traps were most efficient in trapping Diptera and Hymenoptera. The results indicate that the choice of any particular trap depends on the group of insects to be sampled.

The possibility of using the Vlasov fluid model to describe large ion Larmor radius effects in a Z pinch is discussed. It is shown that the Vlasov fluid formulation can be applied to the m = 0 mode, but the comparison theorem which states that systems which are MHD stable are also Vlasov fluid stable, is shown to be inapplicable in this case.

A magnetically confined two-fluid plasma is considered in which the Ohmic heating of the electrons by a current driven parallel to an applied magnetic field is balanced by bremsstrahlung and equipartition to the ions. It is found that for a steady state the applied electric field must be below a critical value which in absence of bremsstrahlung is given by where the electrical conductivity is and the total pressure is p. Under this condition it is found that there are two /Futions for Te/Ti which satisfy the steady electron energy balance equation in a homogeneous, fully ionized plasma. One of these /Futions always has values above the critical value of Te/Ti (= 132 in absence of bremsstrahlung) for the onset of the electrothermal instability in a fully ionized gas. Inclusion of electron thermal conduction transverse to the magnetic field (with Hall parameter ) yields a wavelength for maximum growth of the instability of about , where ae is the electron Larmor radius. The steady non linear profiles showing current filamentation have been calculated. Runaway electrons and ion-acoustic instabilities can occur in the spatial maximum of the current density and electron temperature. Inclusion of bremsstrahlung loss reduces the value of Te/Ti for the onset of the instability, and at Te = Ti yields a maximum ion temperature obtainable by Ohmic heating in a stable plasma.

An electron thermal instability is proposed, which could explain the occurrence of the break-up of a plasma shell into separated current elements during the early history of a discharge. Inclusion of electron thermal conduction and Faraday's law leads to an optimum wavelength for growth, in good agreement with recent results on a θ pinch at NRL, Washington. Finally, the addition of ion motion leads to a modification of the stability criterion. The non-convective instability exists only at low temperature and high density; but a convective instability now appears, which persists at high temperature, and could be relevant to fusion conditions.

A stability analysis is presented of the electrothermal modes of perturbation of a spatially homogeneous, two-temperature and fully ionized plasma with wave-vector K perpendicular to the magmetic field. It is found that the wavelength of the fastest growing unstable, non-convective mode is of the order of (mi/ me)½ ae, with maximum growth rate of the order of (me/ mi) vei, where ae and vei are the electron Larmor radius and electorn-ion collision frequency respectively. Depending on the values of ωτ and β, this analysis also shows the presence of a convective mode which persists in the limit of long wavelengths. This theory has been consistently examined with homogeneous equilibrium plasma models constructed under the assumption of either a scalar or a tensor electric conductivity. A comparison of these results with the previous steady-state profiles obtained in parts 1 and 2 of this series indicates that current filamentation can take place as a result of electrothermal instabilities in the plasma.

A study of the ideal magnetohydrodynamic linear eigenvalue spectrum for free-boundary modes in the Z-pinch is presented. The application of a variational method to estimate eigenvalues is described and limitations imposed by the nature of the spectrum are discussed. An analytic expression for the long-wavelength m = 0 growth rate is derived

A tensor conductivity model for a fully ionized, two-temperature, cylindrical and diffuse pinch is constructed and its properties analyzed under energy and momentum equilibria conditions. The set of Braginskii's classical two-temperature tensor transport equations are solved for the strict steady state and the radial equilibria profiles of the relevant parameters produced. Unlike the scalar conductivity model (part 1 of this series) tensor coefficients yield profiles with the appropriate ideal boundary conditions, namely zero pressure and temperatures at the plasma radius. Furthermore, spatial oscillations of the electron temperature only occur for extreme values of the free parameters.

Numerical solutions of the momentum and energy equilibria in a two-temperature diffuse pinch show that it is possible for the electron temperature to have a radially oscillating component with a wavelength of the order of ae(mi/me)1/2, where ae is the electron Larmor radius. This is also the order of magnitude of the optimum wavelength for growth of an electro-thermal instability in a homogeneous plasma (studied in part 3 of this series) and suggests this kind of instability as a possible primary source of a current filamentation in the plasma. It has also been revealed both analytically and computationally in this strictly steady state model that the pressure of one species (ions or electrons) is finite at the wall boundary; the same study carried out on a neo-classical model shows, however, that strict confinement is possible provided some restrictions are imposed upon its free parameters. This is also found with a model employing classical tensor conductivity (studied in part 2).

The dense Z-pinch project at Imperial College is aimed at achieving radiative collapse to high density in a hydrogen plasma, and also to study plasmas close to controlled fusion conditions. To this end, the MAGPIE generator (2.4 MV, 1.25, and 200 ns) has been built and tested, and is now giving preliminary experimental data at 60% of full voltage for carbon and CD2 fibers. These discharges are characterized by an initial radial expansion followed by the occurrence of m = 0 structures with transient X-ray emission from bright spots. Late in the discharge a disruption can occur, accompanied by hard X-ray emission from the anode due to an energetic electron beam and, in the case of CD2 fibers, a neutron burst. Concomitant theoretical studies have solved the linear stability problem for a Z-pinch with large ion Larmor radii, showing that a reduction in growth rate of m = 0 and m = 1 modes to about 20% of the magnetohydrodynamic (MHD) value can occur for a parabolic density profile when the Larmor radius is optimally 20% of the pinch radius. Two dimensional MHD simulations of Z-pinches in two extremes of focussed short-pulse laserplasma interactions and of galactic jets reveal a nonlinear stabilizing effect in the presence of sheared flow. One-dimensional simulations show that at low line density the lower hybrid drift instability can lead to coronal radial expansion of a Z-pinch plasma.

The star-formation histories, masses and structural properties of galaxies are strongly dependent on their environment: massive, passively-evolving spheroids dominate cluster cores, while in field regions, galaxies are typically low-mass, star-forming and disk-dominated (e.g Blanton et al. 2005). Equally the global properties of galaxies have been found to be bimodally distributed around a stellar mass of ~3 × 1010 M⊙ (~M*+1) (e.g. Kauffmann et al. 2003). Large-scale spectroscopic surveys have shown that the evolution of massive galaxies is primarily driven by their merger history, rather than through direct interection with the cluster environment, as demonstrated by the finding of massive passively-evolving galaxies in all environments, mild observed environmental trends for their mean stellar ages, and the gradual SF-density relation in which star-formation is still seen to be suppressed in galaxies 3–4 virial radii from the nearest cluster. In contrast, in the dwarf regime (>M*+2) dramatic changes are seen in both the luminosity function and red galaxy fraction between those galaxies in the cores of clusters and those at the virial radius (Mercurio et al. 2006, Haines et al. 2006a).

We have examined the origins of the bimodality observed in the global properties of galaxies by comparing the environmental dependencies of star-formation for giant and dwarf galaxy populations. Using SDSS DR4 spectroscopic data to create a volume-limited sample complete to M*+3, we find that the environmental dependences of giant and dwarf galaxies are quite different, implying fundamental differences in their evolution (Haines et al. 2006b). Whereas the star-formation histories of giant galaxies are determined primarily by their merger history, this is not the case for dwarf galaxies. In particular, we find that old or passive dwarf galaxies are ONLY found as satellites within massive halos (clusters, groups or giant galaxies), with none in the lowest density regions. This implies that star-formation in dwarf galaxies must be much more resilient to the effects of mergers, and that the evolution of dwarf galaxies is primarily driven by the mass of their host halo, through effects such as suffocation, ram-pressure stripping or galaxy harassment.

We studied ~ 2 deg2 region in the Shapley Supercluster (SSC) core at z~0.05 in two bands (B and R). By studying the galaxy luminosity function (LF) and the colour distribution of galaxies we find that processes directly related to the supercluster environment are responsible for transforming faint galaxies, rather than galaxy merging.