2,688 research outputs found

    Gods lewende woord en die mens

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    In sy proefskrif: „Klaarheid en interpretasie” praat dr. H. W. Rossouw, net soos vele in ons tyd wat allerlei reserwes daarop nahou t.o.v. die letterlike inspirasie van die Skrif, dik- wels van „Gods lewende Woord”. Hy het dit veral teen die Ortodoksie wat na die Reformasietyd 'n teologie probeer uit- bou het, waarby hulle formeel die Aristotelies-skolastiese metodiek van metafisika en logika gebruik het om 'n leer- sisleem van stabiele waarhede en sillogistiese konklusies op te stel wat dan in die plek van die „lewende Woord” gefunk- sioneer het

    Is Barth gereformeerd?

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    Daar het ’n tydjie gelede ’n boek verskyn van dr. G. C. van Niftrikin Nederland. Die boek is getitel „Een beroerder Israels” en dit behandeld ie teologie van Barth. Alhoewel Van Niftrik op enkele punte van Barthverskil, is hy ’n bewonderaar van hom en vergelyk hy hierdie geleerde metElia van ouds, wat deur koning Agab ’n „beroerder van Israel” genoemis

    PEE6: PROSTAMIDES VS. COMBINATION PRODUCTS FOR GLAUCOMA TREATMENT: EFFECTIVENESS AND COST CONSIDERATIONS

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    Molecular Line Observations of Infrared Dark Clouds: Seeking the Precursors to Intermediate and Massive Star Formation

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    We have identified 41 infrared dark clouds from the 8 micron maps of the Midcourse Space Experiment (MSX), selected to be found within one square degree areas centered on known ultracompact HII regions. We have mapped these infrared dark clouds in N2H+(1-0), CS(2-1) and C18O(1-0) emission using the Five College Radio Astronomy Observatory. The maps of the different species often show striking differences in morphologies, indicating differences in evolutionary state and/or the presence of undetected, deeply embedded protostars. We derive an average mass for these clouds using N2H+ column densities of ~2500 solar masses, a value comparable to that found in previous studies of high mass star forming cores using other mass tracers. The linewidths of these clouds are typically ~2.0 - 2.9 km/s. Based on the fact that they are dark at 8 micron, compact, massive, and have large velocity dispersions, we suggest that these clouds may be the precursor sites of intermediate and high mass star formation.Comment: Accepted to ApJS, 22 pages, 10 pages of figures. For full-resolution images, see http://www.astro.lsa.umich.edu/~seragan/pubs/fcrao/figures.tar.g

    How do methanol masers manage to appear in the youngest star vicinities and isolated molecular clumps?

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    General characteristics of methanol (CH3OH) maser emission are summarized. It is shown that methanol maser sources are concentrated in the spiral arms. Most of the methanol maser sources from the Perseus arm are associated with embedded stellar clusters and a considerable portion is situated close to compact HII regions. Almost 1/3 of the Perseus Arm sources lie at the edges of optically identified HII regions which means that massive star formation in the Perseus Arm is to a great extent triggered by local phenomena. A multiline analysis of the methanol masers allows us to determine the physical parameters in the regions of maser formation. Maser modelling shows that class II methanol masers can be pumped by the radiation of the warm dust as well as by free-free emission of a hypercompact region hcHII with a turnover frequency exceeding 100 GHz. Methanol masers of both classes can reside in the vicinity of hcHIIs. Modelling shows that periodic changes of maser fluxes can be reproduced by variations of the dust temperature by a few percent which may be caused by variations in the brightness of the central young stellar object reflecting the character of the accretion process. Sensitive observations have shown that the masers with low flux densities can still have considerable amplification factors. The analysis of class I maser surveys allows us to identify four distinct regimes that differ by the series of their brightest lines.Comment: 8 pages, 4 figures, invited presentation at IAU242 "Astrophysical Masers and their environments

    On the Identification of High Mass Star Forming Regions using IRAS: Contamination by Low-Mass Protostars

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    We present the results of a survey of a small sample (14) of low-mass protostars (L_IR < 10^3 Lsun) for 6.7 GHz methanol maser emission performed using the ATNF Parkes radio telescope. No new masers were discovered. We find that the lower luminosity limit for maser emission is near 10^3 Lsun, by comparison of the sources in our sample with previously detected methanol maser sources. We examine the IRAS properties of our sample and compare them with sources previously observed for methanol maser emission, almost all of which satisfy the Wood & Churchwell criterion for selecting candidate UCHII regions. We find that about half of our sample satisfy this criterion, and in addition almost all of this subgroup have integrated fluxes between 25 and 60 microns that are similar to sources with detectable methanol maser emission. By identifying a number of low-mass protostars in this work and from the literature that satisfy the Wood & Churchwell criterion for candidate UCHII regions, we show conclusively for the first time that the fainter flux end of their sample is contaminated by lower-mass non-ionizing sources, confirming the suggestion by van der Walt and Ramesh & Sridharan.Comment: 8 pages with 2 figures. Accepted by Ap

    ‘Doing’ health policy analysis: methodological and conceptual reflections and challenges

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    The case for undertaking policy analysis has been made by a number of scholars and practitioners. However, there has been much less attention given to how to do policy analysis, what research designs, theories or methods best inform policy analysis. This paper begins by looking at the health policy environment, and some of the challenges to researching this highly complex phenomenon. It focuses on research in middle and low income countries, drawing on some of the frameworks and theories, methodologies and designs that can be used in health policy analysis, giving examples from recent studies. The implications of case studies and of temporality in research design are explored. Attention is drawn to the roles of the policy researcher and the importance of reflexivity and researcher positionality in the research process. The final section explores ways of advancing the field of health policy analysis with recommendations on theory, methodology and researcher reflexivity

    New Periodic 6.7 GHz Class II Methanol Maser Associated with G358.460-0.391

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    Eight new class II methanol masers selected from the 6.7 GHz Methanol Multibeam survey catalogues I and II were monitored at 6.7 GHz with the 26m Hartebeesthoek Radio Astronomy Observatory (HartRAO) radio telescope for three years and seven months, from February 2011 to September 2014. The sources were also observed at 12.2 GHz and two were sufficiently bright to permit monitoring. One of the eight sources, namely G358.460-0.391, was found to show periodic variations at 6.7 GHz. The period was determined and tested for significance using the Lomb-Scargle, epoch-folding and Jurkevich methods, and by fitting a simple analytic function. The best estimate for the period of the 6.7 GHz class II methanol maser line associated with G358.460-0.391 is 220.0 ±\pm 0.2 day.Comment: 8 pages, 11 figures, accepted for publication in MNRAS. The appendix of 4 pages (with 16 figures) will be published as online versio

    Methanol masers : Reliable tracers of the early stages of high-mass star formation

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    The GLIMPSE and MSX surveys have been used to examine the mid-infrared properties of a statistically complete sample of 6.7 GHz methanol masers. The GLIMPSE point sources associated with methanol masers are clearly distinguished from the majority, typically having extremely red mid-infrared colors, similar to those expected of low-mass class 0 young stellar objects. The intensity of the GLIMPSE sources associated with methanol masers is typically 4 magnitudes brighter at 8.0 micron than at 3.6 micron. Targeted searches towards GLIMPSE point sources with [3.6]-[4.5] > 1.3 and an 8.0 micron magnitude less than 10 will detect more than 80% of class II methanol masers. Many of the methanol masers are associated with sources within infrared dark clouds (IRDC) which are believed to mark regions where high-mass star formation is in its very early stages. The presence of class II methanol masers in a significant fraction of IRDC suggests that high-mass star formation is common in these regions. Different maser species are thought to trace different evolutionary phases of the high-mass star formation process. Comparison of the properties of the GLIMPSE sources associated with class II methanol masers and other maser species shows interesting trends, consistent with class I methanol masers tracing a generally earlier evolutionary phase and OH masers tracing a later evolutionary phase.Comment: 45 pages, 19 figures, accepted for publication in Ap
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