Emergent behaviour in a chlorophenol-mineralising three-tiered microbial `food web'

Anaerobic digestion enables the water industry to treat wastewater as a resource for generating energy and recovering valuable by-products. The complexity of the anaerobic digestion process has motivated the development of complex models. However, this complexity makes it intractable to pin-point stability and emergent behaviour. Here, the widely used Anaerobic Digestion Model No. 1 (ADM1) has been reduced to its very backbone, a syntrophic two-tiered microbial food chain and a slightly more complex three-tiered microbial food web, with their stability analysed as function of the inflowing substrate concentration and dilution rate. Parameterised for phenol and chlorophenol degradation, steady-states were always stable and non-oscillatory. Low input concentrations of chlorophenol were sufficient to maintain chlorophenol- and phenol-degrading populations but resulted in poor conversion and a hydrogen flux that was too low to sustain hydrogenotrophic methanogens. The addition of hydrogen and phenol boosted the populations of all three organisms, resulting in the counterintuitive phenomena that (i) the phenol degraders were stimulated by adding hydrogen, even though hydrogen inhibits phenol degradation, and (ii) the dechlorinators indirectly benefitted from measures that stimulated their hydrogenotrophic competitors; both phenomena hint at emergent behaviour.Comment: 19 pages, 8 figure

Ground Anchors Stabilize Highway Bridge Abutments

Calgary\u27s Glenmore Causeway, constructed in 1962 across the Elbow River, consists of an earthfill embankment with a waterway spanned by a 43 m long bridge, the abutments of which are supported on spread footings founded in the embankment fill. Between the 25 m deep sand and gravel embankment fill and the sub-horizontal bedrock surface is a compressible clay layer up to 5 m thick. To improve abutment stability during peak river flows, 126 post-tensioned Dywidag ground anchors up to 60 m long were installed through the concrete slabs armouring the abutment slopes. Twenty-two anchors were terminated in the embankment fill and the rest were grouted into bedrock. After a series of lift-off tests and anchor retensioning to compensate for ground consolidation, a procedure for predicting the rate of anchor load relaxation was developed. It was concluded the anchors are performing satisfactorily although periodic re-tensioning will be required

Optimal Grazing Termination Date for Dual-Purpose Winter Wheat Production

Dual-purpose winter wheat (fall-winter forage plus grain) production is an important economic enterprise in the southern Great Plains. Grazing termination to enable grain production is a critical decision. The objective is to determine the optimal grazing termination date for dual-purpose wheat. The value of knowing the occurrence of first hollow stem (FHS), a wheat growth threshold for grazing termination, is also determined. Results indicate that for most price situations grazing should be terminated at or before FHS. Marginal wheat returns from extended grazing were negative and the value of FHS information ranges from $1.50 to$10 per acre.dual-purpose, first hollow stem, plateau function, stocker cattle, value of information, wheat, Agribusiness, Agricultural Finance, Crop Production/Industries, Farm Management, Land Economics/Use, Livestock Production/Industries, Production Economics, Q12, Q16,

A MiMeS analysis of the magnetic field and circumstellar environment of the weak-wind O9 sub-giant star HD 57682

I will review our recent analysis of the magnetic properties of the O9IV star HD 57682, using spectropolarimetric observations obtained with ESPaDOnS at the Canada-France-Hawaii telescope within the context of the Magnetism in Massive Stars (MiMeS) Large Program. I discuss our most recent determination of the rotational period from longitudinal magnetic field measurements and Halpha variability - the latter obtained from over a decade's worth of professional and amateur spectroscopic observations. Lastly, I will report on our investigation of the magnetic field geometry and the effects of the field on the circumstellar environment.Comment: 2 pages, 2 figures, IAUS272 - Active OB Stars: Structure, Evolution, Mass Loss and Critical Limit

Discovery of the first tau Sco analogues: HD 66665 and HD 63425

The B0.2 V magnetic star tau Sco stands out from the larger population of massive OB stars due to its high X-ray activity, peculiar wind diagnostics and highly complex magnetic field. This paper presents the discovery of the first two tau Sco analogues - HD 66665 and HD 63425, identified by the striking similarity of their UV spectra to that of tau Sco. ESPaDOnS spectropolarimetric observations were secured by the Magnetism in Massive Stars CFHT Large Program, in order to characterize the stellar and magnetic properties of these stars. CMFGEN modelling of optical ESPaDOnS spectra and archived IUE UV spectra showed that these stars have stellar parameters similar to those of tau Sco. A magnetic field of similar surface strength is found on both stars, reinforcing the connection between the presence of a magnetic field and wind peculiarities. However, additional phase-resolved observations will be required in order to assess the potential complexity of the magnetic fields, and verify if the wind anomalies are linked to this property.Comment: 6 pages, 2 tables, 3 figures. Accepted for publication in MNRAS. The definitive version will be available at www.blackwel-synergy.co