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Concentrations of elements in the sagittal otoliths of juvenile white anglerfish (Lophius piscatorius) from five locations in the north-east Atlantic were measured to test for evidence of segregation in the early life stages. The concentrations of some elements, notably copper, were different between locations. As such, the results suggest limited exchange between locations during some period of the early life history. The relevance of these results to our understanding of population structuring is discussed in relation to recent information on anglerfish movements and genetic structuring.
Forage based feeding systems are often disadvantaged compared with those based on high cereal usage in terms of feed intake, live weight gain and efficiency of utilisation of dietary energy and protein. Furthermore, under some situations, particularly with animals fed on grass silage, cattle often have higher fat:protein carcass ratios than those fed other forage-diets. However, other factors such as age, genotype and physiological state may also influence nutrient partitioning. An experiment was conducted to investigate the effect of diet (based on silage alone or supplemented with additional energy and/or protein) and stage of development on the partitioning of nutrients between fat and lean deposition. Overall effects of diet on animal performance and carcass composition were reported by Scollan et al. (1999).
Metalorganic chemical vapour deposition (MOCVD) is a promising technique for the deposition of the pyroelectric oxide lead scandium tantalate, Pb(Sc0.5Ta0.5)O3. In order to exploit the full potential of the method, it is important to identify the optimum combination of precursors so that process parameters and film properties are optimised. In this paper, the molecular design of new, more compatible Ta and Sc oxide precursors is described and it is shown how the use of carefully matched precursors allows the growth of Pb(Sc0.5Ta0.5)O3 in the required perovskite phase at low substrate temperatures.
We have investigated the use of focused ion beam (FIB) etching for the fabrication of GaN-based devices. Although work has shown that conventional reactive ion etching (RME) is in most cases appropriate for the GaN device fabrication, the direct write facility of FIB etching - a well-established technique for optical mask repair and for IC failure analysis and repair - without the requirement for depositing an etch mask is invaluable. A gallium ion beam of about 20nm diameter was used to sputter GaN material. The etching rate depends linearly on the ion dose per area with a slope of 3.5 × 10-4 μm3/pC. At a current of 3nA, for example, this corresponds to an etch rate of 1.05μm3/s. Good etching qualities have been achieved with a side wall roughness significantly below 0.1μm. Changes in the roughness of the etched surface plane stay below 8nm.
Single crystalline (0001) gallium nitride layers were implanted with beryllium and subsequently annealed within the range of 300-1100°C for 10-60 minutes under a flux of atomic nitrogen obtained using a rf plasma source. The nitrogen flux protected the GaN surface from decomposition in vacuum at high temperatures. SIMS measurements revealed that no long range diffusion of the implanted Be occurred at 900 or 1100°C. XRD spectra showed defect-related peaks in the as-implanted samples; these peaks disappeared upon annealing at 900°C and higher for 10 minutes. Photoluminescence (PL) measurements showed one new line at 3.35 eV which provided strong evidence for the presence of optically active Be acceptors.
Fertilisation in the brown alga Fucus involves species-specific interactions between biflagellate sperm and spherical eggs (Bolwell et al., 1977; Evans, Callow & Callow, 1982; Callow, Callow & Evans, 1985; Callow, Stafford & Green, 1992). We are interested in two related aspects of Fucus gamete cell surfaces: 1) How are the cell surface molecules organised? and 2) What is the molecular basis of recognition and the associated cell responses that occur within a few seconds or minutes of gamete fusion? Such studies in higher plants are difficult because the gametes are embedded within tissues, and plasma membrane based receptors have limited accessibility because of intervening cell walls. In addition, it is still relatively difficult to obtain gametes in sufficient numbers from higher plants compared with Fucus from which naked gametes are released in large enough quantities to allow detailed biochemical studies (Bolwell, Callow & Evans, 1980; Stafford, Callow & Green, 1992a). Thus the Fucus system has much to offer, and hopefully the findings will be relevant to gamete interactions in higher plants. This review will focus on how we have used a combination of biochemical and immunological approaches to study: 1) the organisation of the Fucus egg cell surface and 2) the role of sperm proteins in egg binding and the triggering of cell wall release.
Six clusters forming part of the Hydra-Cen Supercluster and its extension on the opposite side of the galactic plane are under study at 21 cm with the Parkes radiotelescope. The infrared Tully-Fisher relation is used to determine the relative distances of the clusters. These clusters exhibit significant and generally positive peculiar velocities ranging from essentially zero for the Hydra cluster to as much as 1000 km/sec for the Pavo and Centaurus clusters. An upper limit of 500 km/sec was previously found in the study of clusters accessible from Arecibo. Data collection is not yet complete, however, and is further subject to unstudied systematic errors due to present reliance on photographic galaxy diameters. Nevertheless, these preliminary results support the notion of a large scale (and presumably gravitationally) disturbed velocity field in the second and third quadrants of the supergalactic plane.
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