Atypical size selection of captive school prawns,Metapenaeus macleayi,by three recreational fishing gears in south‐eastern Australia

Three manipulative experiments were done to estimate the selectivity of conventional and new sizes and configurations of mesh for school prawns, Metapenaeus macleayi, in three south‐eastern Australian recreational fishing gears (haul, push, and scoop nets). The treatment meshes examined were: (1) conventional‐sized, diamond‐shaped mesh used in all gears (20 mm in scoop nets and 30 mm in push and haul nets); (2) 30 mm in scoop nets; and (3) 40‐mm diamond‐ and (4) 23‐mm square‐shaped mesh in all gears. In all experiments, known quantities of school prawns (6–24 mm carapace length (CL)) were placed in purpose‐built enclosures, monitored to ensure no experimental‐induced stress (as measured by changes in L‐lactate in their haemolymph) and the replicate treatments of the various gear configurations deployed. Escapees from the various treatment nets were collected from the enclosures using fine‐meshed nets. Logistic selection curves were derived for all treatment nets and specific comparisons made within and among gears. All nets had 50% retention lengths (L₅₀) comparable to other penaeid‐catching gears with similar mesh sizes, but most had selection ranges (SRs) that were atypically inflated. The large SRs were attributed to a combination of factors that included the mesh geometry and towing speed of the gears and the behaviour of school prawns. The 20‐mm scoop net had the smallest selection parameters, retaining >99% of individuals larger than 13 mm CL. Mesh size in this gear would need to be increased to at least 30 mm to allow some maturing prawns (>18 mm CL) to escape.     

Drained cavity expansions in soils of finite radial extent subjected to two boundary conditions

The problem of drained cavity expansion in soils of finite radial extent is investigated. Cylindrical and spherical cavities expanded from zero radius subjected to either constant stress or zero displacement at the finite boundary are considered. The generalised analytical solution procedure presented enables more advanced constitutive models to be implemented than have been possible in previous studies. Results generated for Sydney quartz sand highlight substantial differences between cavity limit pressures for the two boundary conditions and for boundaries of finite and infinite radial extent. This is of significance in accounting for boundary effects when interpreting cone penetration tests conducted in calibration chambers. Copyright © 2011 John Wiley & Sons, Ltd.     

Multispacecraft Observations of Magnetic Clouds and Their Solar Origins between 19 and 23 May 2007

We analyze a series of complex interplanetary events and their solar origins that occurred between 19 and 23 May 2007 using observations by the STEREO and Wind satellites. The analyses demonstrate the new opportunities offered by the STEREO multispacecraft configuration for diagnosing the structure of in situ events and relating them to their solar sources. The investigated period was characterized by two high-speed solar wind streams and magnetic clouds observed in the vicinity of the sector boundary. The observing satellites were separated by a longitudinal distance comparable to the typical radial extent of magnetic clouds at 1 AU (fraction of an AU), and, indeed, clear differences were evident in the records from these spacecraft. Two partial-halo coronal mass ejections (CMEs) were launched from the same active region less than a day apart, the first on 19 May and the second on 20 May 2007. The clear signatures of the magnetic cloud associated with the first CME were observed by STEREO B and Wind while only STEREO A recorded clear signatures of the magnetic cloud associated with the latter CME. Both magnetic clouds appeared to have interacted strongly with the ambient solar wind and the data showed evidence that they were a part of the coronal streamer belt. Wind and STEREO B also recorded a shocklike disturbance propagating inside a magnetic cloud that compressed the field and plasma at the cloud’s trailing portion. The results illustrate how distant multisatellite observations can reveal the complex structure of the extension of the coronal streamer into interplanetary space even during the solar activity minimum. Electronic Supplementary Material  The online version of this article () contains supplementary material, which is available to authorized users.     

Gelification of victorian tertiary soft brown coal wood. II. Changes in chemical structure associated with variation in the degree of gelification

The gross chemical structures of xylites and gelified soft brown coal woods, Latrobe Valley, Victoria, Australia, as determined by solid state nuclear magnetic resonance spectroscopy, are compared with those of present-day wood-derived materials prepared from an angiosperm, Eucalyptus regnans, and a gymnosperm (conifer), Pinus radiata. Also examined are the changes in the gross chemical structures of soft brown coal woods with increase in their degree of gelification and the relationship between these changes and variations in their chemical composition and microscopic appearance.The Victorian xylites exhibit greater affinities with the present-day gymnosperm than the present-day angiosperm. The progressive removal of cellulose with increasing degree of gelification can be equated with an increase in huminite reflectance, elimination of humotelinite autofluorescence and changes in the relative proportions of the humotelinite submacerals. The lignin structure of xylite is also modified during the gelification process, including the progressive loss of methoxyl groups and evidence of minor oxidation.     

Temporal trends in abundance of fish in the tidal Delaware River

Water quality in the tidal Delaware River has improved dramatically over the last several decades. Areas near Philadelphia that were once anoxic and formed a pollution block to migratory fish passage now rarely experience dissolved oxygen concentrations less than 3 ppm. To assess whether these improvements in water quality led to increased abundance of juvenile fishes, data from a beach seine survey conducted annually since 1980 were examined. The number of species captured increased throughout the tidal river, but the increase was greatest in the areas downstream of Philadelphia, wheare water quality has improved the most. Abundance of juvenile striped bass and American shad, two important game species in the river whose migratory patterns make them susceptible to water quality problems, both increased more than, 1,000-fold during the last decade. Correlatations between the temporal abundance patterns of these species in the tidal Delaware River and in other East Coast systems were poor, suggesting that increases in their numbers were related more closely to improving conditions within the Delaware than to factors affecting coastal stocks.     

Dawn; the Vesta–HED connection; and the geologic context for eucrites,diogenites, and howardites

The Dawn mission has provided new evidence strengthening the identification of asteroid Vesta as the parent body of the howardite, eucrite, and diogenite (HED) meteorites. The evidence includes Vesta's petrologic complexity, detailed spectroscopic characteristics, unique space weathering, diagnostic geochemical abundances and neutron absorption characteristics, chronology of surface units and impact history, occurrence of exogenous carbonaceous chondritic materials in the regolith, and dimensions of the core, all of which are consistent with HED observations and constraints. Global mapping of the distributions of HED lithologies by Dawn cameras and spectrometers provides the missing geologic context for these meteorites, thereby allowing tests of petrogenetic models and increasing their scientific value.