2,688 research outputs found
Gods lewende woord en die mens
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?
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
Molecular Line Observations of Infrared Dark Clouds: Seeking the Precursors to Intermediate and Massive Star Formation
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?
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
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
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
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
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
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
- …