Longitudinal trends in river functioning: Patterns of nutrient and carbon processing in three Australian rivers

Understanding longitudinal trends in the processing of carbon in rivers represents a much conceptualised, but infrequently tested, issue in aquatic ecology. In this study, we conducted concurrent longitudinal examinations of three very different rivers in eastern Australia to determine whether general principles in river functioning exist across broad geographic and hydrologic scales. Specifically, we examined trends in ambient basic water chemistry, nutrient concentrations, dissolved organic carbon (DOC), extracellular enzymes and food web structure and functioning and conducted bioassays to examine the degree to which DOC and nutrients limit heterotrophic bacterial respiration. These parameters revealed striking similarities across all sites. For metazoan communities, stable isotope analysis showed that algal carbon was the dominant basal resource utilised by consumers in all three rivers, suggesting that in‐stream primary producers strongly underpin trophic pathways regardless of the position within a catchment or catchment condition. Analyses of extracellular enzymes revealed that microbial communities are actively utilising DOC at all sites. In fact, heterotrophic microbial respiration was strongly limited by DOC at all sites, with nutrient additions resulting in only relatively minor increases in respiration. Ultimately, this study demonstrates that DOC and algal carbon are critically important drivers of ecosystem processes in Australian riverine ecosystems. Furthermore, across all of our sites and rivers, ambient nutrient concentrations did not influence carbon processing. The consistent longitudinal trends in river function identified in this study provide useful insights for catchment managers and modellers with respect to identifiying key principles that underpin ecosystem functioning in Australian rivers. Copyright © 2009 John Wiley & Sons, Ltd.     

The fracture behaviour of two Co-Mo-Cr-Si wear resistant alloys (“Tribaloys”)

The room temperature modulus of rupture (MOR) and the plane strain fracture toughness (K _IC) of two Co-Mo-Cr-Si wear resistant alloys in various microstructure conditions have been determined. The modulus of rupture varied from 304 to 927 MN m^–2 and as such was more structure sensitive thanK _IC, which was in the range 15 to 26 MN m^–3/2 for all conditions of the alloys. The best combination of room-temperature properties was associated with an f c c solid solution whereas h c p solid solution with a Widmanstätten precipitate produced the poorest properties. The industrial significance of these results are discussed.     

Compliance with growth hormone therapy in chronic renal failure and post transplant

An anonymous questionnaire to investigate non-compliance with recombinant human growth hormone (rhGH), its causes and correlation with growth response, was sent to 60 children with renal disease; 48% returned the questionnaires; 69% reported that they were concerned about their size and 83% reported being treated as younger than they were. Understanding of the purpose and administration of rhGH was good; 62% missed some rhGH injections, but there was no correlation with understanding or difficulty with the injections, concern regarding size or growth response.     

Robust delay‐dependent sliding mode control for uncertain time‐delay systems

In this paper, the problem of robust sliding mode control for a class of linear continuous time‐delay systems is studied. The parametric uncertainty considered is a modelling error type of mismatch appearing in the state. A delay‐dependent sufficient condition for the existence of linear sliding surfaces is developed in terms of linear matrix inequality, based on which the corresponding reaching motion controller is designed. A numerical example is given to show the potential of the proposed techniques. Copyright © 2007 John Wiley & Sons, Ltd.     

Measurements of impulse response of a wideband radio channel at 910 MHz from a moving vehicle

A set-up for impulse response measurement is described using short RF pulses and a wideband receiver. A fast wave form digitiser digitises the detected impulse response and a minicomputer stores the data on a hard disc. First results are presented showing the rapid change of the impulse response during vehicle movement.     

Non-polymeric binders for ceramic powders: utilization of neutral and ionic species derived from decaborane(14)

The pyrolytic conversion of bis-Lewis base adducts of decaborane(14), L·B₁₀H₁₂·L (L=neutral monophosphine) and phosphonium salts of the [B₁₀H₁₀]^2– anion (e.g. [Ph₄P⁺]₂, etc.), to ceramic materials has been studied. All species examined served as binders for a variety of non-oxide refractory ceramic powders (e.g. B₄C, BN, BP, B₁₃P₂, SiC, Si₃N₄, B, C, AIN).     

The aerobic deterioration of grass silage and its effect on the water-soluble carbohydrate and the associated heat production

Experiments are described which investigated the aerobic deterioration of silage under laboratory conditions. Relationships were established between: (i) dry matter (DM) loss and the temperature rise (t) of the silage (° C) (percentage DM loss = 0.17t?1.480; r=0.9646, significant at the 0.01% level); (ii) daily DM loss, depth and time (percentage daily DM loss = ?0.1394–0.00633 × depth (mm) + 0.780 × day ?0.059 × day²; r = 0.9576, significant at the 0.1 % level); and (iii) total DM loss and the final pH of the silage (pH = 3.79 + 0.13 percentage DM loss; r = 0.8355, significant at the 0.01% level). The indications were that most if not all of the DM loss was accounted for by the losses of water-soluble carbohydrate. The field application of the work is discussed.     

Effect of the New York State cigarette fire safety standard on ignition propensity, smoke constituents, and the consumer market

Objectives: This study examines empirical evidence from the New York experience testing tobacco industry arguments made in opposition to fire safety standards for cigarettes. Design: Percentages of cigarettes exhibiting full length burns (FLBs), cigarette sales before and following the implementation of the New York standards, a sample of retail cigarette prices, brand availability, and selected smoke constituent yields were compared between cigarettes sold in New York and two other states. Cigarette paper analysis was conducted on cigarettes sold in New York. Results: New York cigarette brands averaged 10.0% FLBs as compared to 99.8% for California and Massachusetts brands. Reduced ignition propensity (RIP) appears to have been achieved by cigarette paper banding. Cigarette sales, prices, and brand availability do not appear to have been affected by the New York standards. Yields of the majority of smoke constituents tested did not differ substantially between RIP cigarettes sold in New York as compared to the same brands sold in Massachusetts. Average yields of tar, carbon monoxide, and two compounds were slightly higher, the yields of seven compounds were higher for one brand only, and nicotine was lower, among New York brands tested. Conclusions: RIP cigarette brands have been designed to meet the New York fire safety standards. Their introduction has not affected cigarette sales or prices in New York. There is no evidence that the small increases in smoke constituent yields affect the already highly toxic nature of cigarette smoke. Data on smoking caused fires, deaths, and injuries dating from after the change in law are not yet available. Such data will be able to address the question of whether the demonstrated reduced ignition standards are associated with reduced fires and injuries. Based on the New York experience, prior industry objections to producing RIP cigarettes are unfounded. Other states and nations should adopt similar standards.