Application of Neural Networks to the study of stellar model solutions

Artificial neural networks (ANN) have different applications in Astronomy, including data reduction and data mining. In this work we propose the use ANNs in the identification of stellar model solutions. We illustrate this method, by applying an ANN to the 0.8M$_\odot$ star CG Cyg B. Our ANN was trained using 60,000 different 0.8M$_\odot$ stellar models. With this approach we identify the models which reproduce CG Cyg B's position in the HR diagram. We observe a correlation between the model's initial metal and helium abundance which, in most cases, does not agree with a helium to metal enrichment ratio $\Delta$Y/$\Delta$Z=2. Moreover, we identify a correlation between the model's initial helium/metal abundance and both its age and mixing-length parameter. Additionally, every model found has a mixing-length parameter below 1.3. This means that CG Cyg B's mixing-length parameter is clearly smaller than the solar one. From this study we conclude that ANNs are well suited to deal with the degeneracy of model solutions of solar type stars.Comment: Accepted for publication in New Astronom

Mineral deficiency and the presence of Pinus sylvestris on mires during the mid- to late Holocene: Palaeoecological data from Cadogan's Bog, Mizen Peninsula, Co. Cork, southwest Ireland

Pollen records across parts of Ireland, England and northern Scotland show a dramatic collapse in Pinus pollen percentages at approximately 4000 radiocarbon years BP. This phenomenon has attracted much palaeoecological interest and several hypotheses have been put forward to account for this often synchronous and rapid reduction in pine from mid-Holocene woodland. Explanations for the 'pine decline' include prehistoric human activity, climatic change, in particular a substantial increase in precipitation resulting in increased mire wetness, and airborne pollution associated with the deposition of tephra. Hitherto, one largely untested hypothesis is that mineral deficiency could adversely affect pine growth and regeneration on mire surfaces. The discovery of pine-tree remains (wood pieces, stumps and trunks) within a peat located at Cadogan's Bog on the Mizen Peninsula, southwest Ireland, provided an opportunity to investigate the history of Pinus sylvestris and also to assess the importance of mineral nutrition in maintaining pine growth on mires. Pollen, plant macrofossils, microscopic charcoal and geochemical data are presented from a radiocarbon dated monolith extracted from this peat together with tree ring-width data and radiocarbon dated age estimates from subfossil wood. Analyses of these data suggest that peat accumulation commenced at the site around 6000 years BP when pine was the dominant local tree. Thereafter Pinus pollen percentages diminish in two stages, with the second decline taking place around 4160 ± 50 years BP. Concomitant with this decline in Pinus pollen, there is a noticeable, short-lived increase in wet-loving mire taxa and a decrease in the concentration of phosphorus, potassium, magnesium, calcium, sodium, iron and zinc. These results suggest that increased mire surface wetness, possibly the result of a change in climate, created conditions unsuitable for pine growth c. 4000 years BP. Mire surface wetness, coupled with a period of associated nutrient deficiency, appears to be a possible explanation for a lack of subsequent pine-seedling establishment for most of the later Holocene

The changing landscape of Clara Bog: the history of an Irish raised bog

Clara Bog is one of the few raised bogs that has not been fully exploited in the Irish midlands and is a reminder of how the landscape of this region once appeared. This paper describes how the Clara Bog landscape has been changing since the commencement of the Holocene 11,500 years ago. Initially change was relatively slow as the bog naturally developed from its origins in an early Holocene lake, which became in-filled to form a fen circa 8000 years ago, before it continued to develop into an acid raised bog reaching its maximum extent by the beginning of the nineteenth century. Clara Bog has changed dramatically in the last 200 years due to human activity. Today less than 50% of its original bog surface remains. The changes in the bog during the historic past have been driven by population change, poverty, economic growth, construction of the Grand Canal, the building of roads, the need for fuel and farmland, nature conservation and tourism. The prehistoric development of the bog and land use in its hinterland was reconstructed from a detailed analysis of published archaeological records, palaeoecological studies and stratigraphical studies. Published maps and historical records have been vital in establishing a chronology for the changes that have occurred on Clara Bog since the beginning of the nineteenth centur

Activity patterns and resource use by sheep and red deer grazing across a grass/heather boundary

Diet selection and activities of sheep and red deer grazing alone and together across a grass (primarily Lolium perenne/Agrostis capillaris) and heather (Calluna vulgaris) boundary, between July and October, are described.\ud \ud Throughout the experiment, both animal species had a much higher proportion of grass than heather in their diet. Time spent grazing on each type of vegetation was similarly greater on grass, and the bite rates of the animals were also more rapid on the grass than on the heather.\ud \ud Red deer spent more time grazing per 24 hours than did sheep, with sheep grazing less during darkness hours than red deer. Total grazing time of both species did not decrease with decreasing daylength from July to October.\ud \ud There were no consistent differences in the diurnal patterns of activity of sheep and red deer, with both species showing 2-3 large grazing peaks per day.\ud \ud There were no consistent effects of mixing sheep and deer on their grazing behaviour and diet composition

Depositional and post-depositional history of warm stage deposits at Knocknacran, Co. Monaghan, Ireland: implications for preservation of Irish last interglacial deposits

Organic-rich deposits, uncovered during overburden removal from mantled gypsum karst at Knocknacran opencast gypsum mine, Co. Monaghan, are the best candidate to date for a last interglacial record in Ireland. The two till and organic-rich deposits (preserved at different quarry elevations) were emplaced on to a Tertiary dolerite surface during high-energy flood events and subsequently folded and faulted by movement towards sinkholes in underlying gypsum. Uranium-thorium disequilibrium dating suggests that the organic-rich deposits in the upper section were hydrologically isolated at ca. 41 ka and those in the lower section at ca. 86 ka. Interpretation of the pollen content, although tentative because of the depositional and post-depositional history of the material, suggests that the organic material originated in a warm stage possibly warmer than the post-Eemian interstadials. The unusual setting of preservation may indicate that in situ, last interglacial deposits have generally been removed by erosion in Ireland