Discrete ordinates-Monte Carlo coupling: A comparison of techniques in NERVA radiation analysis

In the radiation analysis of the NERVA nuclear rocket system, two-dimensional discrete ordinates calculations are sufficient to provide detail in the pressure vessel and reactor assembly. Other parts of the system, however, require three-dimensional Monte Carlo analyses. To use these two methods in a single analysis, a means of coupling was developed whereby the results of a discrete ordinates calculation can be used to produce source data for a Monte Carlo calculation. Several techniques for producing source detail were investigated. Results of calculations on the NERVA system are compared and limitations and advantages of the coupling techniques discussed

Studies in the mulga pastoral zone. 2. Some aspects of the value of the mulga scrub

THE mulga pastoral zone is so named since most of its area is dominated by Mulga (Acacia aneura). The mulga is found associated with shrubs and grasses in almost all plant habitats. In its various forms it can associate with spinifex (Triodia basedowi), Wandarrie Grasses (Danthonia, Eragostis and Eriachne spp.) and with low shrubs on flood plains, hills and breakaways. It may even attempt to become established in salty communities, though this is never completely successful. The scene the area offers from its low hills is one of a succession of low undulations, occasionally scarred by creeks or breakaways and completely dominated by the dull green or blue grey overmantle of the mulga tree

Studies in the mulga pastoral zone. 1. The grazing of Wandarrie grass associations

THE establishment of the Wiluna office of the North-West Branch marked the commencement of a series of investigations into the pastures of the mulga zone. Unlike the agricultural areas where a fund of knowledge exists on the growth habits of the pastures, the pastures of this area were completely unknown. The preliminary investigations had to be aimed at forming an understanding of the reactions of the various plants to rain, to temperature and seasonal conditions and to grazing in an area of extremely low rainfall reliability

Range evaluation using aerial photography

The Department of Agriculture, in association with the University of Western Australia, recently undertook a study of the application of aerial photography to range condition monitoring in three rangeland types in the mulga zone of Western Australia. The project was financed by the Rural Credits Development Fund and the C.S.l.R.O. Rangelands Research Unit. This article deals in a general way with the possible use of aerial photography in rangeland administration

Pastures for the pastoral areas

The pastoral areas lie generally outside the zone where cultivated crops are grown. The rainfall is erratic and the basic pastures for sheep and cattle consist of native plants. In some favoured areas however, and in particular situations, sown pasture species are becoming increasingly important

Antibodies to acetylcholine receptor in parous women with myasthenia: evidence for immunization by fetal antigen

The weakness in myasthenia gravis (MG) is mediated by autoantibodies against adult muscle acetylcholine receptors (AChR) at the neuromuscular junction; most of these antibodies also bind to fetal AChR, which is present in the thymus. In rare cases, babies of mothers with MG, or even of asymptomatic mothers, develop a severe developmental condition, arthrogryposis multiplex congenita, caused by antibodies that inhibit the ion channel function of the fetal AChR while not affecting the adult AChR. Here we show that these fetal AChR inhibitory antibodies are significantly more common in females sampled after pregnancy than in those who present before pregnancy, suggesting that they may be induced by the fetus. Moreover, we were able to clone high-affinity combinatorial Fab antibodies from thymic cells of two mothers with MG who had babies with arthrogryposis multiplex congenita. These Fabs were highly specific for fetal AChR and did not bind the main immunogenic region that is common to fetal and adult AChR. The Fabs show strong biases to VH3 heavy chains and to a single Vk1 light chain in one mother. Nevertheless, they each show extensive intraclonal diversification from a highly mutated consensus sequence, consistent with antigen-driven selection in successive steps. Collectively, our results suggest that, in some cases of MG, initial immunization against fetal AChR is followed by diversification and expansion of B cells in the thymus; maternal autoimmunity will result if the immune response spreads to the main immunogenic region and other epitopes common to fetal and adult AChR

Visit of working party on North Kimberley Agricultural Development to the area in July 1977

Report suggests that the area of land suitable for Townsville Stylo in the North Kimberley above the 750 mm rainfall isohyet is about 1.25 million hectares. The regions in which land suitable for Stylosanthes can be found are shown. A brief description of the suitability of the land systems of the region for Stylosanthes is given