1,380 research outputs found

    Studiet av bruket av naturen

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    How do you spell 'support'? Multiple methods of library support to distributed education programs

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    This paper consists of librarians from two universities, one in the US and one in Canada, discussing and demonstrating the various ways they offer support to multiple distributed education programs. Because different programs on the same campus often offer distributed courses in different formats, libraries are required to become expert in all formats offered. This presentation will discuss library support via WebCT, Blackboard, FirstClass, proprietary courseware, email, the web, and Conferencing software. Where appropriate, differences between library support in the US and Canada will be noted and examined

    The realm of the Galactic globular clusters and the mass of their primordial clouds

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    By adopting the empirical constraints related to the estimates of Helium enhancement (ΔY\Delta Y), present mass ratio between first and second stellar generations (M1G/M2GM_{1G}/M_{2G}) and the actual mass of Galactic globular clusters (MGCM_{GC}), we envisage a possible scenario for the formation of these stellar systems. Our approach allows for the possible loss of stars through evaporation or tidal interactions and different star formation efficiencies. In our approach the star formation efficiency of the first generation (ϵ1G\epsilon_{1G}) is the central factor that links the stellar generations as it not only defines both the mass in stars of the first generation and the remaining mass available for further star formation, but it also fixes the amount of matter required to contaminate the second stellar generation. In this way, ϵ1G\epsilon_{1G} is fully defined by the He enhancement between successive generations in a GC. We also show that globular clusters fit well within a ΔY\Delta Y {\it vs} M1G/M2GM_{1G}/M_{2G} diagram which indicates three different evolutionary paths. The central one is for clusters that have not loss stars, through tidal interactions, from either of their stellar generations, and thus their present MGCM_{GC} value is identical to the amount of low mass stars (MM_* \le 1 M_\odot) that resulted from both stellar generations. Other possible evolutions imply either the loss of first generation stars or the combination of a low star formation efficiency in the second stellar generation and/or a loss of stars from the second generation. From these considerations we derive a lower limit to the mass (MtotM_{tot}) of the individual primordial clouds that gave origin to globular clusters.Comment: 17 pages, 2 figures, accepted for publication in the Astrophysical Journa

    Star Formation in Tadpole Galaxies

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    Tadpole Galaxies look like a star forming head with a tail structure to the side. They are also named cometaries. In a series of recent works we have discovered a number of issues that lead us to consider them extremely interesting targets. First, from images, they are disks with a lopsided starburst. This result is firmly established with long slit spectroscopy in a nearby representative sample. They rotate with the head following the rotation pattern but displaced from the rotation center. Moreover, in a search for extremely metal poor (XMP) galaxies, we identified tadpoles as the dominant shapes in the sample- nearly 80% of the local XMP galaxies have a tadpole morphology. In addition, the spatially resolved analysis of the metallicity shows the remarkable result that there is a metallicity drop right at the position of the head. This is contrary to what intuition would say and difficult to explain if star formation has happened from gas processed in the disk. The result could however be understood if the star formation is driven by pristine gas falling into the galaxy disk. If confirmed, we could be unveiling, for the first time, cool flows in action in our nearby world. The tadpole class is relatively frequent at high redshift - 10% of resolvable galaxies in the Hubble UDF but less than 1% in the local Universe. They are systems that could track cool flows and test models of galaxy formation.Comment: arXiv admin note: text overlap with arXiv:1302.435

    Atmosphere Extinction at the ORM on La Palma: A 20 yr Statistical Database Gathered at the Carlsberg Meridian Telescope

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    The Observatorio del Roque de los Muchachos (ORM), in the Canary Islands (Spain), was one of the candidates to host the future European Extremely Large Telescope (E-ELT) and is the site of the Gran Telescopio Canarias (GTC), the largest optical infrared facility to date. Sky transparency is a key parameter as it defines the quality of the photometry to be acquired in the astronomical observations. We present a study of the atmosphere extinction at the ORM, carried out after analysis of a database spanning more than 20 yr, to our knowledge, the longest and most complete and homogeneous in situ database available for any observatory. It is based on photometric measurements in the V band and r' band (transformed to the V -band extinction coefficient kV) using the Carlsberg Meridian Telescope (CMT). Clear seasonal variations that repeat yearly are observed. The median value of kV is 0.13 mag/airmass; the mean value has a maximum in the summer months (June- September), corresponding to the season with maximum frequency of nights affected by dust or cirrus (~29% in summer, but only ~13% during the rest of the year). Two volcanic eruptions took place during the database baseline, which has enabled the study of the impact of volcanoes on the global atmosphere extinction. For the 5 yr of available information, we have estimated the average monthly weather downtime from the CMT data log, obtaining a result (20.7%) in reasonable agreement with earlier studies. The main conclusion of our study is that there is no significant evidence from the CMT data for any secular changes in kV over the 20 yr database baseline.Comment: 13 pages, 9 figures, 6 tables, published at PAS

    A Review of Action Research in Teaching and Learning: A Practical Guide to Conducting Pedagogical Research in Universities

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    Action Research in Teaching and Learning: A Practical Guide to Conducting Pedagogical Research in Universities by Lynn S. Norton provides a useful resource for those in higher education interested in using action research. Action research takes place when educational practitioners reflect on their approach to education and test pedagogical theories with research that is then presented for consideration within the institution and in the wider academic arena. After making a case for the use of action research as an important part of the scholarship of teaching and learning that should take place in higher education, the author discusses the steps for conducting action research— from identifying the problem to addressing quantitative and qualitative research approaches and publishing the results

    The pressure confined wind of the massive and compact superstar cluster M82-A1

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    The observed parameters of the young superstar cluster M82-A1 and its associated compact HII region are here shown to indicate a low heating efficiency or immediate loss, through radiative cooling, of a large fraction of the energy inserted by stellar winds and supernovae during the early evolution of the cluster. This implies a bimodal hydrodynamic solution which leads to a reduced mass deposition rate into the ISM, with a much reduced outflow velocity. Furthermore, to match the observed parameters of the HII region associated to M82-A1, the resultant star cluster wind is here shown to ought to be confined by a high pressure interstellar medium. The cluster wind parameters, as well as the location of the reverse shock, its cooling length and the radius of the standing outer HII region are derived analytically. All of these properties are then confirmed with a semi-analytical integration of the flow equations, which provides us also with the run of the hydrodynamic variables as a function of radius. The impact of the results is discussed and extended to other massive and young superstar clusters surrounded by a compact HII region.Comment: 19 pages, 4 figures, accepted for publication in Ap
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