Chemistry of the CO dimer at low temperatures

Researchers conducted a series of experiments on the chlorine-catalyzed photodecomposition of O sub 3 both in the gas and in inert solvents such as CF sub 4 and CO sub 2 in the temperature range about 190 to 225 K. The liquid medium was chosen in order to minimize possible surface loss of long-lived ClO dimer, and to aid in the stabilization of transient excited intermediates. The mechanism of dimer formation was as follows: (1) Cl sub 2 + hv yields Cl + Cl; (2) Cl + O sub 3 yields ClO + O sub 2; (3) ClO + ClO yields Cl sub 2 O sub 2. The experiments were done in cooled low temperature cells, with irradiation from an Osram high pressure mercury arc, filtered to remove radiation below 325 nm. Spectral analysis was by means of a Cary Model 2200 UV spectrometer. The principal objectives were: (1) to determine the lifetime of the dimer as a function of temperature; (2) to observe spectral changes in the mixtures which could be attributed to dimer or related products; and (3) to observe chemical or photochemical reactions of the dimer

Letter from W. J. Roux to T. B. Larimore

Letter from W. J. Roux to T. B. Larimore. The two-page handwritten letter is dated 12 November 1912. There is a transcript of the correspondence in the item PDF

Equilibrium onions?

We demonstrate the possibility of a stable equilibrium multi-lamellar ("onion") phase in pure lamellar systems (no excess solvent) due to a sufficiently negative Gaussian curvature modulus. The onion phase is stabilized by non-linear elastic moduli coupled to a polydisperse size distribution (Apollonian packing) to allow space-filling without appreciable elastic distortion. This model is compared to experiments on copolymer-decorated lamellar surfactant systems, with reasonable qualitative agreement

Characteristics of Wetting-Induced Bacteriophage Blooms in Biological Soil Crust.

Biological soil crusts (biocrusts) are photosynthetic "hot spots" in deserts and cover ∼12% of the Earth's terrestrial surface, and yet they face an uncertain future given expected shifts in rainfall events. Laboratory wetting of biocrust communities is known to cause a bloom of Firmicutes which rapidly become dominant community members within 2 days after emerging from a sporulated state. We hypothesized that their bacteriophages (phages) would respond to such a dramatic increase in their host's abundance. In our experiment, wetting caused Firmicutes to bloom and triggered a significant depletion of cyanobacterial diversity. We used genome-resolved metagenomics to link phage to their hosts and found that the bloom of the genus Bacillus correlated with a dramatic increase in the number of Caudovirales phages targeting these diverse spore-formers (r = 0.762). After 2 days, we observed dramatic reductions in the relative abundances of Bacillus, while the number of Bacillus phages continued to increase, suggestive of a predator-prey relationship. We found predicted auxiliary metabolic genes (AMGs) associated with sporulation in several Caudovirales genomes, suggesting that phages may influence and even benefit from sporulation dynamics in biocrusts. Prophage elements and CRISPR-Cas repeats in Firmicutes metagenome-assembled genomes (MAGs) provide evidence of recent infection events by phages, which were corroborated by mapping viral contigs to their host MAGs. Combined, these findings suggest that the blooming Firmicutes become primary targets for biocrust Caudovirales phages, consistent with the classical "kill-the-winner" hypothesis.IMPORTANCE This work forms part of an overarching research theme studying the effects of a changing climate on biological soil crust (biocrust) in the Southwestern United States. To our knowledge, this study was the first to characterize bacteriophages in biocrust and offers a view into the ecology of phages in response to a laboratory wetting experiment. The phages identified here represent lineages of Caudovirales, and we found that the dynamics of their interactions with their Firmicutes hosts explain the collapse of a bacterial bloom that was induced by wetting. Moreover, we show that phages carried host-altering metabolic genes and found evidence of proviral infection and CRISPR-Cas repeats within host genomes. Our results suggest that phages exert controls on population density by lysing dominant bacterial hosts and that they further impact biocrust by acquiring host genes for sporulation. Future research should explore how dominant these phages are in other biocrust communities and quantify how much the control and lysis of blooming populations contributes to nutrient cycling in biocrusts

Inflation dynamics in a dollarised economy: The case of Zimbabwe

This paper explores the dynamics of inflation in the dollarised Zimbabwean economy using the autoregressive distributed lag (ARDL) model with monthly data from 2009:1 to 2012:12. The main determinants of inflation were found to be the US dollar/South African rand exchange rate, international oil prices, lagged Zimbabwean inflation rate and South African inflation rate. During the local currency era, inflation dynamics in Zimbabwe were explained by excess growth in money supply, changes in import and administered prices, unit labour costs and output (Chhibber, Cottani, Firuzabadi & Walton 1989). According to Makochekanwa (2007), hyperinflation during the same era was attributed to excess money supply growth, lagged infl ation and political factors. Coorey, Clausen, Funke, Munoz & Ould-Abdallah (2007) affirmed these findings by identifying excess money supply growth as a source of high inflation in Zimbabwe during the local currency era. In essence, the findings of this study point to a shift in infl ation dynamics in Zimbabwe. This shift in inflation dynamics means that policies, which were used to respond to both internal and external shocks that have an impact on price formation, might not be applicable in a dollarised economy.Keywords: inflation, dollarisation, autoregressive distributed lag mode

Vertical activity estimation using 2D radar

Understanding airspace activity is essential for airspace control. Being able to detect vertical activity in aircraft allows prediction of aircraft intent, thereby allowing more accurate situation awareness and correspondingly more appropriate airspace control response. The method for qualitative vertical activity estimation as presented is characterised by a very fast response time and requires minimal sensor input. The method relies on the interplay of two opposing motion prediction models. The efficacy of the method is demonstrated in both simulated and real-world data. Scientia Militaria: South African Journal of Military Studies Vol. 36 (2) 2008: pp. 60-7

A dynamic modelling of safety nets

The nonlinear dynamic modelling of safety net systems is approached at different scales. For this purpose, the fundamental rope dynamic tests are the reference for two basic tools. One hand an anaytical bidimensional model with explicit geometrical nonlinearity and bilnear material law is proposed for preliminary design. On the other hand, a nonlinear explicit finite element is defined for numerical modelling of net systems. Semi-scale and full scale dynamic tests are performed to validate complete finite element models, suitable for global qualification of safety systems. The direct applications of these tools deal with explicit certification of safety systems for high-speed sport, such as downhill competitions

Production and reproduction norms of fine woolled Merino sheep on natural pastures in the Karoo

The objective of this study was to establish a fine woolled Merino flock at the Grootfontein Agricultural Development Institute in order to evaluate the production and reproduction performance of fine woolled animals against a control line on natural pastures in the Karoo. Data collected from 1989 to 1999 were used to evaluate the production and reproduction performance of these two lines. It is evident from the results of this study that the control lambs had a slightly better growth rate than the fine woolled lambs. However, body weight and reproduction of the adult ewes did not differ. The fine woolled animals produced significantly less wool compared to the control line. It can therefore be concluded that it would be possible to produce finer wool effectively under natural pastures in the Karoo. Keywords: Fibre diameter, body weight, fleece weight South African Journal of Animal Science Vol. 37 (1) 2007: pp. 31-3