A hedging point strategy - balancing effluent quality, economy and robustness in the control of wastewater treatment plants

An operational space map is an efficient tool to compare a large number of operational strategies to find an optimal choice of setpoints based on a multicriterion. Typically, such a multicriterion includes a weighted sum of cost of operation and effluent quality. Due to the relative high cost of aeration such a definition of optimality result in a relatively high fraction of the effluent total nitrogen in the form of ammonium. Such a strategy may however introduce a risk into operation because a low degree of ammonium removal leads to a low amount of nitrifiers. This in turn leads to a reduced ability to reject event disturbances, such as large variations in the ammonium load, drop in temperature, the presence of toxic/inhibitory compounds in the influent etc. Hedging is a risk minimisation tool, with the aim to "reduce one's risk of loss on a bet or speculation by compensating transactions on the other side" (The Concise Oxford Dictionary (1995)). In wastewater treatment plant operation hedging can be applied by choosing a higher level of ammonium removal to increase the amount of nitrifiers. This is a sensible way to introduce disturbance rejection ability into the multi criterion. In practice, this is done by deciding upon an internal effluent ammonium criterion. In some countries such as Germany, a separate criterion already applies to the level of ammonium in the effluent. However, in most countries the effluent criterion applies to total nitrogen only. In these cases, an internal effluent ammonium criterion should be selected in order to secure proper disturbance rejection ability.

Molecular evidence for the common origin of snap-traps among carnivorous plants

The snap-trap leaves of the aquatic waterwheel plant (Aldrovanda) resemble those of Venus' flytrap (Dionaea), its distribution and habit are reminiscent of bladderworts (Utricularia), but it shares many reproductive characters with sundews (Drosera). Moreover, Aldrovanda has never been included in molecular phylogenetic studies, so it has been unclear whether snap-traps evolved only once or more than once among angiosperms. Using sequences from nuclear 18S and plastid rbcL, atpB, and matK genes, we show that Aldrovanda is sister to Dionaea, and this pair is sister to Drosera. Our results indicate that snap-traps are derived from flypaper-traps and have a common ancestry among flowering plants, despite the fact that this mechanism is used by both a terrestrial species and an aquatic one. Genetic and fossil evidence for the close relationship between these unique and threatened organisms indicate that carnivory evolved from a common ancestor within this caryophyllid clade at least 65 million years ago.

Dry matter production and boron concentrations of vegetative and reproductive tissues of canola and sunflower plants grown in nutrient solution

Canola (Brassica napus L.) and sunflower (Helianthus annuus L.), two important oilseed crops, are sensitive to low boron (B) supply. Symptoms of B deficiency are often more severe during the reproductive stage, but it is not known if this is due to a decreased external B supply with time or an increased sensitivity to low B during this stage. Canola and sunflower were grown for 75 days after transplanting (DAT) in two solution culture experiments using Amberlite (IRA-743) B-specific resin to maintain constant B concentration in solution over the range 0.6 - 53 muM. Initially, the vegetative growth of both crops was good in all treatments. With the onset of the reproductive stage, however, severe B deficiency symptoms developed and growth of canola and sunflower was reduced with less than or equal to 0.9 and less than or equal to 0.7 muM B, respectively. At these concentrations, reproductive parts failed to develop. The critical B concentration (i.e. 90% of maximum shoot dry matter yield) in the youngest opened leaf was 18 mg kg(-1) in canola and 25 mg kg(-1) in sunflower at 75 DAT. The results of this study indicate that the reproductive stage of these two oilseed crops is more sensitive than the vegetative stage to low B supply.

Discovery and structures of the cyclotides: novel macrocyclic peptides from plants

Circular disulfide-rich polypeptides were unknown a decade ago but over recent years a large family of such molecules has been discovered, which we now refer to as the cyclotides. They are typically about 30 amino acids in size, contain an N- to C-cyclised backbone and incorporate three disulfide bonds arranged in a cystine knot motif. In this motif, an embedded ring in the structure formed by two disulfide bonds and their connecting backbone segments is penetrated by the third disulfide bond. The combination of this knotted and strongly braced structure with a circular backbone renders the cyclotides impervious to enzymatic breakdown and makes them exceptionally stable. This article describes the discovery of the cyclotides in plants from the Rubiaceae and Violaceae families, their chemical synthesis, folding, structural characterisation, and biosynthetic origin. The cyclotides have a diverse range of biological applications, ranging from uterotonic action, to anti-HIV and neurotensin antagonism. Certain plants from which they are derived have a history of uses in native medicine, with activity being observed after oral ingestion of a tea made from the plants. This suggests the possibility that the cyclotides may be orally bioavailable. They therefore have a range of potential applications as a stable peptide framework.

Assessing the self-heating behaviour of Callide coal using a 2-metre column

A 2-m, adiabatic column has been successfully refurbished and recommissioned for coal self-heating research at The University of Queensland. Subbituminous coal from the Callide Coalfields reached thermal runaway in just under 19 days from a starting temperature of 20-22 degreesC. The coal was loaded as two layers, with an R-70 index of 2.73 degreesC h(-1) and 5.90 degreesC h(-1) for the upper layer and lower layer respectively. Initially, a hotspot developed in the upper layer between 120 and 140 cm from the air inlet due to moisture adsorption. After 7 days, self-heating in the lower half of the column began to take over, consistent with the higher R-70 index of this coal. The location of the final hotspot was approximately 60 cm from the air inlet. Further tests on Australian coals, with the column, will enable a better understanding of coal self-heating under conditions closely resembling mining, transport and storage of coal. The results from the column will also provide industry with the information needed to manage the coal self-heating hazard. (C) 2002 Elsevier Science Ltd. All rights reserved.

Ultra-high-temperature (UHT) treatment of milk: comparison of direct and indirect modes of heating

UHT processing of milk and its subsequent storage causes several changes which affect the shelf-life of UHT milk although it remains 'commercially sterile'. These changes include whey protein denaturation, protein-protein interaction, lactose-protein interaction, isomerisation of lactose, Maillard browning, sulphydryl compound formation, formation of a range of carbonyl and other flavoursome compounds, and formation of insoluble substances. They ultimately reduce the quality and limit the shelf life of UHT milk through development of off-flavours, fat separation, age gelation and sedimentation. The extent of these changes depends on many factors, a major one being the type of UHT heating. This review compares the effect heating milk by direct and indirect modes on various aspects of processing and quality of UHT milk.

Behavior of argon gas release from manganese oxide minerals as revealed by Ar-40/Ar-39 laser incremental heating analysis

Manganese oxides in association with paleo-weathering may provide significant insights into the multiple factors affecting the formation and evolution of weathering profiles, such as temperature, precipitation, and biodiversity. Laser probe step-heating analysis of supergene hollandite and cryptomelane samples collected from central Queensland, Australia, yield well-defined plateaus and consistent isochron ages, confirming the feasibility, dating very-fined supergene manganese oxides by Ar-40/(39) Ar technique. Two distinct structural sites hosting Ar isotopes can be identified in light of their degassing behaviors obtained by incremental heating analyses. The first site, releasing its gas fraction at the laser power 0.2-0.4 W, yields primarily Ar-40(atm), Ar-38(atm), and Ar-36(atm), (atmospheric Ar isotopes). The second sites yield predominantly Ar-40* (radiogenic Ar-40), Ar-39(K), and Ar-38(K) (nucleogenic components), at similar to0.5-1.0 W. There is no significant Ar gas released at the laser power higher than 1.0 W, indicating the breakdown of the tunnel sites hosting the radiogenic and nucleogenic components. The excellent match between the degassing behaviors of Ar-40*, Ar-39(K), and Ar-38(K) suggests that these isotopes occupy the same crystallographic sites and that Ar-39(K) loss from the tunnel site by recoil during neutron irradiation and/or bake-out procedure preceding isotopic analysis does not occur. Present investigation supports that neither the overwhelming atmospheric Ar-40 nor the very-fined nature of the supergene manganese oxides poses problems in extracting meaningful weathering geo-chronological information by analyzing supergene manganese oxides minerals.

A synthetic xylanase as a novel reporter in plants

Transient gene expression assays are often used to screen promoters before stable transformation. Current transient quantification methods have several problems, including a lack of reporter gene stability and expense. Here we report a synthetic, codon-optimised xylanase gene (sXynA) as a reporter gene for quantitative transient analyses in plants. Azurine-crosslinked xylan (AZCL-xylan) was used as a substrate for assaying xylanase activity. The enzymatic nature of the protein allows for sensitive assays at the low levels of transgene protein found in transiently transformed tissue extracts. The xylanase (XYN) protein is stable, activity slopes are linear over long time periods and assays are cost-effective. Coupled with the GUSPlus reporter gene, the XYN reporter allows sensitive and accurate quantification of gene control sequences in transient expression systems.

Physiological profiles of restricted endemic plants and their widespread congenors in the North Queensland wet tropics, Australia

Little is known about causes of endemic rarity in plants. This study pioneered an approach that determined environmental variables in the rainforest habitat and generated physiological profiles for light, water, and nutrient relations for three endemically restricted versus widespread congeneric species' pairs. We found no overall consistent differences in the physiological variables between the group of restricted species and the group of widespread species, and congeneric species pairs were therefore examined individually. Availability of soil nutrients did not differ between restricted-widespread species sites suggesting that species grow under comparable nutrient conditions. Under ambient and manipulated higher light conditions, widespread Gardenia ovularis had a greater photosynthetic activity than restricted Gardenia actinocarpa suggesting that the two species differ in their photosynthetic abilities. Differences between Xanthostemon species included lower photosynthetic activity, higher transpiration rate, and a higher foliar manganese concentration in restricted Xanthostemon formosus compared to widespread Xanthostemon chrysanthus. It is suggested that X. formosus is restricted by its high water use to its current rainforest creek edge habitat, while X. chrysanthus grows in a range of environments, although naturally found in riparian rainforest. Restricted Archidendron kanisii had higher electron transport rates, greater dissipative capacity for removal of excess light, and more efficient investment of nitrogen into photosynthetic components, than its widespread relative Archidendron whitei. These observations and previous research suggest that restricted Archidendron kanisii is in the process of expanding its range. Physiological profiles suggest a different cause of rarity for each species. This has implications for the conservation strategies required for each species. (C) 2002 Elsevier Science Ltd. All rights reserved.

The effect of heat transfer mode on heart rate responses and hysteresis during heating and cooling in the estuarine crocodile Crocodylus porosus

The effect of heating and cooling on heart rate in the estuarine crocodile Crocodylus porosus was studied in response to different heat transfer mechanisms and heat loads. Three heating treatments were investigated. C. porosus were: (1) exposed to a radiant heat source under dry conditions; (2) heated via radiant energy while half-submerged in flowing water at 23degreesC and (3) heated via convective transfer by increasing water temperature from 23degreesC to 35degreesC. Cooling was achieved in all treatments by removing the heat source and with C. porosus half-submerged in flowing water at 23degreesC. In all treatments, the heart rate of C. porosus increased markedly in response to heating and decreased rapidly with the removal of the heat source. Heart rate during heating was significantly faster than during cooling at any given body temperature, i.e. there was a significant heart rate hysteresis. There were two identifiable responses to heating and cooling. During the initial stages of applying or removing the heat source, there was a dramatic increase or decrease in heart rate ('rapid response'), respectively, indicating a possible cardiac reflex. This rapid change in heart rate with only a small change or no change in body temperature (

Kinetic parameters associated with self-heating of New Zealand coals under adiabatic conditions

Adiabatic self-heating tests were carried out on five New Zealand coal samples ranging in rank from lignite to high-volatile bituminous. Kinetic parameters of oxidation were obtained front the self-heating curves assuming Arrhenius behaviour. The activation energy E (kJ mol(-1)) and the pre-exponential factor A (s(-1)) were determined in the temperature range of 70-140 degreesC. The activation energy exhibited a definite rank relationship with a minimum E of 55 kJ mol(-1) occurring at a Suggate rank of similar to6.2 corresponding to subbituminous C. Either side of this rank there was a noticeable increase in the activation energy indicating lower reactivity of the coal. A similar rank trend was also observed in the R-70 self-heating rate index values that were taken from the initial portion of the self-heating curve front 40 to 70 degreesC. From these results it is clear that the adiabatic method is capable of providing reliable kinetic parameters of coal oxidation.

Towards the on-farm conservation of the assassin bug Pristhesancus plagipennis (Walker) (Hemiptera : Reduviidae) during winter using crop plants as refuges

Habitat instability associated with seasonal crop succession in broad-acre farming systems presents a problem for the conservation and utilisation of beneficial insects in annual field crops. The present paper describes two experiments used to measure the potential of seven plant species to be utilised as winter refuges to support and conserve the predatory bug Pristhesancus plagipennis (Walker). In the first experiment, replicated plots of canola (Brassica napus ), red salvia (Salvia coccinea ), niger (Guizotia abyssinica ), linseed (Linum usitatissimum ), lupins (Lupinus angustifolius ), and lucerne (Medicago falcata ) were planted in a randomized experiment during Autumn 1998. Upon crop establishment, adults and nymphs of P. plagipennis were released into treatment plots and their numbers were assessed, along with those of their potential prey, throughout the ensuing winter months. Post-release sampling suggested that canola and niger retained a proportion of adult P. plagipennis , while niger, lucerne and canola retained some nymphs. The other plant species failed to support P. plagipennis nymphs and adults postrelease. In the second experiment, niger was compared with two lines of sunflower (Helianthus annus ). Both sunflower lines harboured significantly higher (P < 0.05) densities of P. plagipennis nymphs than did niger. The more successful refuge treatments (sunflower, niger and canola) had an abundance of yellow flowers that were attractive to pollinating insects, which served as supplementary prey on which P. plagipennis were observed to feed. Sunflower and niger also supported high densities of the prey insect Creontiades dilutus (Stal) and provided protective leafy canopies which supplied shelter during the winter months. The potential and limitations for using each plant species as a winter refuge to retain P. plagipennis during winter are discussed.

New fluorescence parameters for monitoring photosynthesis in plants - 1. The effect of illumination on the fluorescence parameters of the JIP-test

Chlorophyll fluorescence measurements have a wide range of applications from basic understanding of photosynthesis functioning to plant environmental stress responses and direct assessments of plant health. The measured signal is the fluorescence intensity (expressed in relative units) and the most meaningful data are derived from the time dependent increase in fluorescence intensity achieved upon application of continuous bright light to a previously dark adapted sample. The fluorescence response changes over time and is termed the Kautsky curve or chlorophyll fluorescence transient. Recently, Strasser and Strasser (1995) formulated a group of fluorescence parameters, called the JIP-test, that quantify the stepwise flow of energy through Photosystem II, using input data from the fluorescence transient. The purpose of this study was to establish relationships between the biochemical reactions occurring in PS II and specific JIP-test parameters. This was approached using isolated systems that facilitated the addition of modifying agents, a PS II electron transport inhibitor, an electron acceptor and an uncoupler, whose effects on PS II activity are well documented in the literature. The alteration to PS II activity caused by each of these compounds could then be monitored through the JIP-test parameters and compared and contrasted with the literature. The known alteration in PS II activity of Chenopodium album atrazine resistant and sensitive biotypes was also used to gauge the effectiveness and sensitivity of the JIP-test. The information gained from the in vitro study was successfully applied to an in situ study. This is the first in a series of four papers. It shows that the trapping parameters of the JIP-test were most affected by illumination and that the reduction in trapping had a run-on effect to inhibit electron transport. When irradiance exposure proceeded to photoinhibition, the electron transport probability parameter was greatly reduced and dissipation significantly increased. These results illustrate the advantage of monitoring a number of fluorescence parameters over the use of just one, which is often the case when the F-V/F-M ratio is used.