Pumping of the 4.8 GHz H2_{\text{2}}CO masers and its implications for the periodic masers in G37.55+0.20

Periodic or regular flaring of class II methanol masers in nine high mass star forming regions is now a well established phenomenon. Amongst the nine star forming regions, G37.55+0.20 is the only case at present where apart from the presence of a periodic class II methanol maser, correlated flaring of another masing species, formaldehyde in this case, has been detected. We perform numerical calculations to investigate under which conditions the 4.8 GHz transition of ortho-formaldehyde is inverted in order to address the question of the correlated flaring of the 6.7 GHz methanol and 4.8 GHz formaldehyde masers in G37.55+0.20. We developed a numerical code to study the population inversion of o-formaldehyde. Equilibrium solutions for the level populations are found by integrating the rate equations using Heun's method. It is found that collisional excitation with H$_2$ as well as radiative excitation by the free-free radio continuum radiation from a nearby ultra- or hyper-compact HII region can invert the 4.8 GHz transition. It is also found that radiative excitation by the dust infrared radiation field does not lead to an inversion of the 4.8 GHz transition. The 14.5 GHz and 28.9 GHz transitions are inverted only in the presence of the free-free continuum radiation field of a very compact HII region. Due to the different pumping mechanisms of the formaldehyde and methanol masers it is unlikely that the near simultaneous flaring of the methanol and formaldehyde masers in G37.55+0.20 is due to changes in the pumping of the masers.Comment: Accepted for publication in Astronomy and Astrophysic

Literatuur en lewensbeskouing — met besondere verwysing na die moderne afrikaanse kunsprosa*

Een van die belangrikste sake wat vir ons opnuut geak- tualiseer is deur tendensies in die hedendaagse Afrikaanse letterkunde ên veral deur die bekroning met die Hertzogprys van Sewe dae by die Silbersteins, is die verhouding tussen lewensbeskouing en kunsbeskouing in die algemeen, en meer in besonder dié tussen lewensbeskouing en letterkunde. Hier­ die laasgenoemde aspek wil ek graag behandel, maar dan in sy konteks en slegs so volledig as wat die tydsbeperking my toelaat

’n Literêre aspek van ons Latynse erfenis

Dit is die Romeine, en by name die veldheer Julius Casesar en sy legioene, wat die “Insula Batavorum” uit die mistige skemering van die prehistorie gehaal het kort voor die begin van die Christelike jaartelling. Hierdie “eiland van die Bataviere” moet verstaan word as die gebied tussen die Waal en die Ryn — die kern van die Lae Lande by die See, die latere staat Nederland. Die Bataviere was een van die baie Germaanse stamme, die ou bewoners van Noordwes-Europa, teen wie die Romeine gestuit het in hulle veroweringstogte. Volgens die Latynse geskiedskrywer Cornelius Tacitus was hulle gedugte vegters maar het vroeg ’n bondgenootskap met die Romeine aangegaan — hoewel daar ook in die verwarring wat in die Ryk gevolg het op die dood van Nero (68 nC), ’n mislukte opstand van die Bataviere was onder leiding van Cajus Julius Civilis

The role of Cytochrome P450 17-alpha-Hydroxylase/ 17,20-Lyase (CYP17) in the stress coping ability in a divergently selected Merino sheep population

South African Merino sheep were selected divergently from the same base population for their ability to rear multiples. Two distinct populations were formed over a period of more than 20 years of selection. Reproduction (and therefore presumably fitness) in the line selected in the upward direction (H-line) was substantially improved compared to the line selected in the downward direction (L-line). In the present study, it was demonstrated that the H-line was more stresstolerant than the L-line in terms of their glucose and cortisol response when challenged with insulin. Sheep from the breeding program were genotyped according to one of two cytochrome P450 17α-hydroxylase/17-20 lyase (CYP17) alleles, as these genotypes were previously linked to the ability of Angora goats to cope with external stressors. However, no association was found between CYP17 genotype and selection line. The difference in insulin induced stress response between the H- and the L-line can therefore not be attributed to CYP17 genotype

A deep learning approach to diabetic blood glucose prediction

We consider the question of 30-minute prediction of blood glucose levels measured by continuous glucose monitoring devices, using clinical data. While most studies of this nature deal with one patient at a time, we take a certain percentage of patients in the data set as training data, and test on the remainder of the patients; i.e., the machine need not re-calibrate on the new patients in the data set. We demonstrate how deep learning can outperform shallow networks in this example. One novelty is to demonstrate how a parsimonious deep representation can be constructed using domain knowledge

A near-infrared study of the star forming region RCW 34

We report the results of a near-infrared imaging study of a $7.8 \times 7.8$ arcmin$^2$ region centered on the 6.7 GHz methanol maser associated with the RCW 34 star forming region using the 1.4m IRSF telescope at Sutherland. A total of 1283 objects were detected simultaneously in J, H, and K for an exposure time of 10800 seconds. The J-H, H-K two-colour diagram revealed a strong concentration of more than 700 objects with colours similar to what is expected of reddened classical T Tauri stars. The distribution of the objects on the K {\it vs} J-K colour-magnitude diagram is also suggestive that a significant fraction of the 1283 objects is lower mass pre-main sequence stars. We also present the luminosity function for the subset of about 700 pre-main sequence stars and show that it suggests ongoing star formation activity for about $10^7$ years. An examination of the spatial distribution of the pre-main sequence stars shows that the fainter (older) part of the population is more dispersed over the observed region and the brighter (younger) subset is more concentrated around the position of the O8.5V star. This suggests that the physical effects of the O8.5V star and the two early B-type stars on the remainder of the cloud out of which they formed, could have played a role in the onset of the more recent episode of star formation in RCW 34.Comment: Accepted for publication in The Astronomical Journa