45 research outputs found
Detailed Chemical Abundances of Globular Clusters in Local Group Dwarf Galaxies
We present detailed chemical abundances of Fe, Ca and Ba for 17 globular
clusters (GCs) in 5 Local Group dwarf galaxies: NGC 205, NGC 6822, WLM, the SMC
and LMC. These abundances are part of a larger sample of over 20 individual
elements measured in GCs in these galaxies using a new analysis method for high
resolution, integrated light spectra. Our analysis also provides age and
stellar population constraints. The existence of GCs in dwarf galaxies with a
range of ages implies that there were episodes of rapid star formation
throughout the history of these galaxies; the abundance ratios of these
clusters suggest that the duration of these burst varied considerably from
galaxy to galaxy. We find evolution of Fe, Ca, and Ba with age in the LMC, SMC,
and NGC 6822 that is consistent with extended, lower-efficiency SF between
bursts, with an increasing contribution of low-metallicity AGB ejecta at late
times. Our sample of GCs in NGC 205 and WLM are predominantly old and
metal-poor with high [Ca/Fe] ratios, implying that the early history of these
galaxies was marked by consistently high SF rates.Comment: 2 pages, To appear in the proceedings of the conference "A Universe
of Dwarf Galaxies" (Lyon, June 14-18, 2010
Measuring children’s involvement as an indicator of curriculum effectiveness : a curriculum evaluation of a selected child study centre in Singapore
This paper presents one aspect of a research project evaluating a curriculum model of a selected child study centre in Singapore. An issue of worldwide interest and concern is the ‘quality of learning’ debate as it relates to early childhood centres. In Singapore, the government is focusing on expansion in child care settings and increases in the amount of funded training. One of the issues surrounding prior-to-school education raises the question of how one measures the quality of teaching and learning, to describe the value of using, funding and promoting early education. The research reported in this study used a quasi experimental research paradigm to assess one aspect of the quality of a curriculum programme in a child study centre in Singapore. Children aged between 18 months and 6 years (N = 81) participated in the research. Using the observation scale of Laevers’ Child Involvement Scale, the active involvement of children in learning experiences was measured. The findings are presented and discussed
Students’ Ontological Security and Agency in Science Education—An Example from Reasoning about the Use of Gene Technology
The Tichborne Claimant and the people Investigations into popular culture 1867-1886
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Environmental impacts of the control with organophosphate pesticides and explosions of the red-billed quelea bird Quelea quelea in Africa
Both spraying with pesticides and using explosions to kill red-billed quelea birds may affect non-target organisms and leave hazardous contaminants in the environment. Results of monitoring such effects in Botswana and Tanzania showed that although few non-target mortalities were noted, indirect effects in terms of depressed cholinesterases in birds and small mammals were marked and pesticides and contaminants from products used for the explosions persisted at controlled sites at unacceptable levels and for long periods (at least 188 days for sprays and at least 11 months for petroleum products and plastics)