VARIATION IN THE AGE AT FIRST SPAWNING OF FEMALE TWAITE SHAD (ALOSA FALLAX FALLAX) FROM THE RIVER SEVERN, ENGLAND.

The mean age of maturity of female Alosa fallax fallax based on annual samples ranged from 4.28 to 5.26 years, with an overall mean ± 95 % CI of 4.80 ± 0.021 years. The mean age at first spawning was determined for the 1973 – 1992 year classes and ranged from 4.41 years to 5.40 years. A significant power relationship existed between the mean age at first spawning and the combined biomass of the 0-2 and 0-3 age groups (P < 0.05), explaining 40.7 % and 31.6 % of the variability in the age at which a year class matures. The relationship between maturity and biomass indicates that the onset of maturity was related to density-dependent processes and fish, that matured early had significantly faster growth rates compared to those that matured later (P < 0.05). The findings suggest that the immature fish at sea congregate in a fairly restricted area where it is likely that the older year classes impact younger ones. The fact that the relationship between maturity and the biomass of various components of the stock breaks down after the age of four may relate to the onset of maturity, as the mature fish enter the rivers to spawn and are effectively isolated from the main population

Crystallite Orientation Discontinuities and the Evolution of Mammalian Enamel – Or, When is a Prism?

The nature and relationship of crystallite domains have been explored in fossil and extant enamels spanning an evolutionary period of 200 x 106 years. Minor crystallite orientation discontinuities, either linear or planar, were found to be consistent characteristics of all specimens examined. The earliest minor discontinuity is linear (convergence line), shown here in Oligokyphus and Eozostrodon. The convergence line would be the result of the occasional development of a conical Tomes\u27 process to the parent ameloblast. An increase in number and regularity of convergence lines, shown here in Haldanodon, marks the appearance of a regular pseudoprismatic enamel structure. The second minor discontinuity to appear is planar (seam), shown here in a dryolestid eupantothere. The seam has previously been deduced to relate developmentally to a central groove on the sloping floor-wall of the Tomes\u27 process pit. Coincident with the appearance of the seam is that of a rudimentary major planar discontinuity which does not enclose a domain to constitute what would normally be acknowledged as a prism. Its developmental basis would be the establishment of a steep wall and floor (however partial in circumference) to the Tomes\u27 process pit. The extent of the major planar discontinuities was found to increase subsequently to enclose a classically recognizable prismatic domain, shown here in Amphiperatherium, Hassianycteris, Smilodon and Felis. This would be consistent with the further development of a definitive floor and wall to the Tomes\u27 process pit. The sequential appearance of minor linear, minor planar and major planar discontinuities in crystallite orientation is seen as fundamental to the evolution of mammalian enamel structure

Dayside convection and auroral morphology during an interval of northward interplanetary magnetic field

International audienceWe investigate the dayside auroral dynamics and ionospheric convection during an interval when the interplanetary magnetic field (IMF) had predominantly a positive Bz component (northward IMF) but varying By. Polar UVI observations of the Northern Hemisphere auroral emission indicate the existence of a region of luminosity near local noon at latitudes poleward of the dayside auroral oval, which we interpret as the ionospheric footprint of a high-latitude reconnection site. The large field-of-view afforded by the satellite-borne imager allows an unprecedented determination of the dynamics of this region, which has not previously been possible with ground-based observations. The location of the emission in latitude and magnetic local time varies in response to changes in the orientation of the IMF; the cusp MLT and the IMF By component are especially well correlated, the emission being located in the pre- or post-noon sectors for By By > 0 nT, respectively. Simultaneous ground-based observations of the ionospheric plasma drift are provided by the CUTLASS Finland HF coherent radar. For an interval of IMF By \approx 0 nT, these convection flow measurements suggest the presence of a clockwise-rotating lobe cell contained within the pre-noon dayside polar cap, with a flow reversal closely co-located with the high-latitude luminosity region. This pattern is largely consistent with recent theoretical predictions of the convection flow during northward IMF. We believe that this represents the first direct measurement of the convection flow at the imaged location of the footprint of the high-latitude reconnection site

An evaluation of metal removal during wastewater treatment: The potential to achieve more stringent final effluent standards

This is the author's accepted manuscript. The final published article is available from the link below. Copyright @ 2011 Taylor & Francis.Metals are of particular importance in relation to water quality, and concern regarding the impact of these contaminants on biodiversity is being encapsulated within the latest water-related legislation such as the Water Framework Directive in Europe and criteria revisions to the Clean Water Act in the United States. This review undertakes an evaluation of the potential of 2-stage wastewater treatment consisting of primary sedimentation and biological treatment in the form of activated sludge processes, to meet more stringent discharge consents that are likely to be introduced as a consequence. The legislation, sources of metals, and mechanisms responsible for their removal are discussed, to elucidate possible pathways by which the performance of conventional processes may be optimized or enhanced. Improvements in effluent quality, achievable by reducing concentrations of suspended solids or biochemical oxygen demand, may also reduce metal concentrations although meeting possible requirements for the removal of copper my be challenging

A Cation-π Interaction in the Binding Site of the Glycine Receptor Is Mediated by a Phenylalanine Residue

Cys-loop receptor binding sites characteristically contain many aromatic amino acids. In nicotinic ACh and 5-HT3 receptors, a Trp residue forms a cation-{pi} interaction with the agonist, whereas in GABAA receptors, a Tyr performs this role. The glycine receptor binding site, however, contains predominantly Phe residues. Homology models suggest that two of these Phe side chains, Phe159 and Phe207, and possibly a third, Phe63, are positioned such that they could contribute to a cation-{pi} interaction with the primary amine of glycine. Here, we test this hypothesis by incorporation of a series of fluorinated Phe derivatives using unnatural amino acid mutagenesis. The data reveal a clear correlation between the glycine EC50 value and the cation-{pi} binding ability of the fluorinated Phe derivatives at position 159, but not at positions 207 or 63, indicating a single cation-{pi} interaction between glycine and Phe159. The data thus provide an anchor point for locating glycine in its binding site, and demonstrate for the first time a cation-{pi} interaction between Phe and a neurotransmitter

First simultaneous observations of flux transfer events at the high-latitude magnetopause by the cluster spacecraft and pulsed radar signatures in the conjugate ionosphere by the CUTLASS and EISCAT radars

Cluster magnetic field data are studied during an outbound pass through the post-noon high-latitude magnetopause region on 14 February 2001. The onset of several minute perturbations in the magnetospheric field was observed in conjunction with a southward turn of the interplanetary magnetic field observed upstream by the ACE spacecraft and lagged to the subsolar magnetopause. These perturbations culminated in the observation of four clear magnetospheric flux transfer events (FTEs) adjacent to the magnetopause, together with a highly-structured magnetopause boundary layer containing related field features. Furthermore, clear FTEs were observed later in the magnetosheath. The magnetospheric FTEs were of essentially the same form as the original “flux erosion events” observed in HEOS-2 data at a similar location and under similar interplanetary conditions by Haerendel et al. (1978). We show that the nature of the magnetic perturbations in these events is consistent with the formation of open flux tubes connected to the northern polar ionosphere via pulsed reconnection in the dusk sector magnetopause. The magnetic footprint of the Cluster spacecraft during the boundary passage is shown to map centrally within the fields-of-view of the CUTLASS SuperDARN radars, and to pass across the field-aligned beam of the EISCAT Svalbard radar (ESR) system. It is shown that both the ionospheric flow and the backscatter power in the CUTLASS data pulse are in synchrony with the magnetospheric FTEs and boundary layer structures at the latitude of the Cluster footprint. These flow and power features are subsequently found to propagate poleward, forming classic “pulsed ionospheric flow” and “poleward-moving radar auroral form” structures at higher latitudes. The combined Cluster-CUTLASS observations thus represent a direct demonstration of the coupling of momentum and energy into the magnetosphere-ionosphere system via pulsed magnetopause reconnection. The ESR observations also reveal the nature of the structured and variable polar ionosphere produced by the structured and time-varying precipitation and flow