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We review the state of our chemical evolution models for spiral and low mass galaxies. We analyze the consequences of using different stellar yields, infall rate laws and star formation prescriptions in the time/redshift evolution of the radial distributions of abundances, and other quantities as star formation rate or gas densities, in the Milky Way Galaxy; In particular we will study the evolution of the oxygen abundance radial gradient analyzing its relation with the ratio SFR/infall. We also compare the results with our old chemical evolution models, cosmological simulations and with the existing data, mainly with the planetary nebulae abundances.
The Magellanic System represents one of the best places to study the formation and evolution of galaxies. Photometric surveys of various depths, areas and wavelengths have had a significant impact on our understanding of the system; however, a complete picture is still lacking. VMC (the VISTA near-infrared YJKs survey of the Magellanic System) will provide new data to derive the spatially resolved star formation history and to construct a three-dimensional map of the system. These data combined with those from other ongoing and planned surveys will give us an absolutely unique view of the system opening up the doors to truly new science!
The abundance of the neutron-rich magnesium isotopes observed in metal-poor stars is explained quantitatively with a chemical evolution model of the local Galaxy that considers — for the first time — the metallicity-dependent contribution from intermediate mass stars. Previous models that simulate the variation of Mg isotopic ratios with metallicity in the solar neighbourhood have attributed the production of 25Mg and 26Mg exclusively to hydrostatic burning in massive stars. These models match the data well for [Fe/H] > –1.0 but severely underestimate 25,26Mg/24Mg at lower metallicities. Earlier studies have noted that this discrepancy may indicate a significant role played by intermediate mass stars. Only recently have detailed calculations of intermediate mass stellar yields of 25Mg and 26Mg become available with which to test this hypothesis. In an extension of previous work, we present a model that successfully matches the Mg isotopic abundances in nearby Galactic disk stars through the incorporation of nucleosynthesis predictions of Mg isotopic production in asymptotic giant branch stars.
Nutrition has a major impact on the fatty acid composition of beef, despite high levels of biohydrogenation of dietary polyunsaturated fatty acids (PUFA) in the rumen (Scollan et al., 2006). The latter may be ameliorated by feeding rumen-protected lipid. Grass relative to concentrate feeding results in beef characterised by a higher content of n-3 PUFA and excellent colour shelf life. This study investigated the effects of including a PUFA-rich lucerne-based plant extract (PX) on the fatty acid composition and meat quality in beef.
It is the practise for some farmers to supplement new season lambs with concentrates, often as a creep feed, in order to get them to market early before the price declines. This concentrate is usually based on cereals and would be high in n-6 fatty acids, diluting the beneficial effect of grass grazing which promotes the n-3 polyunsaturated fatty acid (PUFA) content in the meat (Fisher et al., 2000). The purpose of this trial was to assess the addition of linseed to the concentrate, fed in a creep-feed system, which would maintain or enhance the n-3 fatty acid composition of the meat of animals fed concentrates at grass during the finishing period (Cooper et al., 2004).
Didymobothrium rudolphii (Cestoda: Spathebothriidea) was collected seasonally from the sand sole, Solea lascaris, off the northern, central and southern areas of the Portuguese coast. Morphological and molecular analyses were conducted in order to examine the possible existence of cryptic species and to facilitate the circumscription of their morphological boundaries. Data were compared between D. rudolphii specimens from each of the 3 geographical areas and 4 seasons, and principal components analysis of 18 morphological characters was used to detect differences. Two distinct genotypes were present with sequence divergences of 1·9% and 2·1% in the large subunit (lsrDNA) and second internal transcribed spacer (ITS-2) of ribosomal DNA (rDNA), respectively. The less common ‘central’ genotype was present only off the central area from summer to winter, whereas the ‘common’ genotype was present throughout the year off the northern and southern areas, but only during spring in the central area. No sequence variation was found within each genotype. The presence of 2 distinct genetic entities was supported by morphological analyses, which showed the ‘central’ genotype specimens to be more slender and elongate, although morphometric ranges overlapped considerably for most characters. Molecular phylogenetic analysis of 4 of the 5 known genera of the Spathebothriidea showed Spathebothrium to be the earliest branching lineage and the 2 genotypes of Didymobothrium formed a sister group to Cyathocephalus. The concordance of genetic differences with variation in host diet according to season and locality could account for sympatric speciation occurring in the central region of the Portuguese coast.
Robinia aurata n. g., n. sp. is described from Liza aurata (Mugilidae), the golden grey mullet, from the Ebro Delta, Spanish Mediterranean. The new genus differs from all other hemiurid genera in the combined possession of muscular flanges and a vestigial ecsoma. Within the Bunocotylinae, which currently accommodates 2 genera, Bunocotyle and Saturnius, the new genus exhibits a unique combination of blind caeca, Juel's organ, post-ovarian bulk of the uterus in the hind-body, and tegumental papillae surrounding the oral and ventral sucker apertures. Furthermore, Robinia n. g. differs from both Bunocotyle and Saturnius in the nature of the muscular extensions around the oral sucker, with the shape of a muscular belt in the latter and numerous muscular papillae in the former. The phylogenetic hypothesis for the Bunocotylinae developed from sequence data analyses based on partial lsrDNA and complete ssrDNA combined (22 species) and V4 domain of the ssrRNA gene (37 species) supports the erection of the new genus and confirms its position within the Hemiuroidea. Both molecular analyses confirmed the monophyly of the Hemiuroidea, its division into 2 major clades and the polyphyly of the Derogenidae, as in previous studies, and suggest that the Gonocercinae (with 2 genera, Gonocerca and Hemipera), may require a distinct familial status. Finally, there was poor support for the distinct status of the Lecithasteridae and Hemiuridae, following previous suggestions based on different sequence data sets. A key to genera of the Bunocotylinae is presented.
Physiological studies of elite and sub-elite black South African runners show that these athletes are typically about 10–12 kg lighter than white athletes and that they are able to sustain higher exercise intensities for longer than white runners. Such superior performance is not a result of higher V O2max values and hence cannot be due to superior oxygen delivery to the active muscles during maximal exercise, as is predicted by the traditional cardiovascular/anaerobic/catastrophic models of exercise physiology. A marginally superior running economy is also unlikely to be a crucial determinant in explaining this apparent superiority. However, black athletes are able to sustain lower rectal and thigh, but higher mean skin, temperatures during exercise. Furthermore, when exercising in the heat, lighter black athletes are able to maintain higher running speeds than are larger white runners matched for running performance in cool environmental conditions. According to the contrasting theory that the body acts as a complex system during exercise, the superiority of black African athletes should be sought in an enhanced capacity to maintain homeostasis in all their inter-dependent biological systems despite running at higher relative exercise intensities and metabolic rates. In this case, any explanation for the success of East African runners will be found in the way in which their innate physiology, training, environment, expectations and genes influence the function of those parts of their subconscious (and conscious) brains that appear to regulate the protection of homeostasis during exercise as part of an integrative, complex biological system.
Effect of moisture on the oxidation of copper was studied using in situ UHV-TEM. The ultra high vacuum condition is required for minimum contamination effects. The initial observations show that the water vapor reduces the oxide as well as reduces the rate of oxidation if both oxygen gas and water vapor are simultaneously used. Based on these observations, we have speculated on the role of moisture in the solid state reactions involved in copper oxidation
Amorphous silicon formed by ion-implantation of crystalline silicon is investigated with the use of VC-TEM (variable-coherence transmission electron microscopy). This technique is sensitive to medium-range-order structures. The results from high-energy Si implanted samples showed a striking similarity to sputtered amorphous silicon. We found that both ion-implanted and sputtered samples have paracrystalline structures, rather than the expected continuous random network (CRN). We also observed the structural relaxation of the ion-implanted amorphous silicon after ex-situ thermal annealing towards the random network. The more disordered structures are favored and a large heat of relaxation is released as the temperature increases. Finally, we show some preliminary results on the structural variation with the sample depth.