Showing papers by "Cooperative Research Centre published in 2009"

Tailored titanium dioxide photocatalysts for the degradation of organic dyes in wastewater treatment: A review

Abstract: Organic dyes are one of the largest groups of pollutants released into wastewaters from textile and other industrial processes. Because of potential toxicity of the dyes and their visibility in surface waters, removal and degradation of organic dyes have been a matter of considerable interest. A wide range of methods have been developed, amongst which the heterogeneous photocatalysis involving titanium dioxide (TiO2) appears to be the most promising technology. This paper presents a critical review of novel achievements in the modification of TiO2 photocatalytic systems aimed at: enhanced TiO2 photocatalytic efficiency; complete mineralization of organic dyes; efficient utilization of visible and/or solar light; stability and reproducibility of the modified TiO2; recycle and reuse in real wastewater treatment.

High-resolution palaeoclimatology of the last millennium: a review of current status and future prospects:

Abstract: This review of late-Holocene palaeoclimatology represents the results from a PAGES/CLIVAR Intersection Panel meeting that took place in June 2006. The review is in three parts: the principal high-resolution proxy disciplines (trees, corals, ice cores and documentary evidence), emphasizing current issues in their use for climate reconstruction; the various approaches that have been adopted to combine multiple climate proxy records to provide estimates of past annual-to-decadal timescale Northern Hemisphere surface temperatures and other climate variables, such as large-scale circulation indices; and the forcing histories used in climate model simulations of the past millennium. We discuss the need to develop a framework through which current and new approaches to interpreting these proxy data may be rigorously assessed using pseudo-proxies derived from climate model runs, where the `answer' is known. The article concludes with a list of recommendations. First, more raw proxy data are required from the diverse disciplines and from more locations, as well as replication, for all proxy sources, of the basic raw measurements to improve absolute dating, and to better distinguish the proxy climate signal from noise. Second, more effort is required to improve the understanding of what individual proxies respond to, supported by more site measurements and process studies. These activities should also be mindful of the correlation structure of instrumental data, indicating which adjacent proxy records ought to be in agreement and which not. Third, large-scale climate reconstructions should be attempted using a wide variety of techniques, emphasizing those for which quantified errors can be estimated at specified timescales. Fourth, a greater use of climate model simulations is needed to guide the choice of reconstruction techniques (the pseudo-proxy concept) and possibly help determine where, given limited resources, future sampling should be concentrated.

Characteristics of cutting forces and chip formation in machining of titanium alloys

Abstract: Chip formation during dry turning of Ti6Al4V alloy has been examined in association with dynamic cutting force measurements under different cutting speeds, feed rates and depths of cut. Both continuous and segmented chip formation processes were observed in one cut under conditions of low cutting speed and large feed rate. The slipping angle in the segmented chip was 55°, which was higher than that in the continuous chip (38°). A cyclic force was produced during the formation of segmented chips and the force frequency was the same as the chip segmentation frequency. The peak of the cyclic force when producing segmented chips was 1.18 times that producing the continuous chip. The undeformed surface length in the segmented chip was found to increase linearly with the feed rate but was independent of cutting speed and depth of cut. The cyclic force frequency increased linearly with cutting speed and decreased inversely with feed rate. The cutting force increased with the feed rate and depth of cut at constant cutting speed due to the large volume of material being removed. The increase in cutting force with increasing cutting speed from 10 to 16 and 57 to 75 m/min was attributed to the strain rate hardening at low and high strain rates, respectively. The decrease in cutting force with increasing cutting speed outside these speed ranges was due to the thermal softening of the material. The amplitude variation of the high-frequency cyclic force associated with the segmented chip formation increased with increasing depth of cut and feed rate, and decreased with increasing cutting speed from 57 m/min except at the cutting speeds where harmonic vibration of the machine occurs.

Chronic exposure of arsenic via drinking water and its adverse health impacts on humans.

Abstract: Worldwide chronic arsenic (As) toxicity has become a human health threat. Arsenic exposure to humans mainly occurs from the ingestion of As contaminated water and food. This communication presents a review of current research conducted on the adverse health effects on humans exposed to As-contaminated water. Chronic exposure of As via drinking water causes various types of skin lesions such as melanosis, leucomelanosis, and keratosis. Other manifestations include neurological effects, obstetric problems, high blood pressure, diabetes mellitus, diseases of the respiratory system and of blood vessels including cardiovascular, and cancers typically involving the skin, lung, and bladder. The skin seems to be quite susceptible to the effects of As. Arsenic-induced skin lesions seem to be the most common and initial symptoms of arsenicosis. More systematic studies are needed to determine the link between As exposure and its related cancer and noncancer end points.

Reduced calcification in modern Southern Ocean planktonic foraminifera

Abstract: The oceans are becoming more acidic as they absorb anthropogenic carbon dioxide—this may limit the ability of marine organisms to secrete carbonate. A sediment-trap study shows that in the Southern Ocean the shell weights of a surface-dwelling single-celled organism with a calcite shell are lower than pre-industrial values, probably as a result of increasing ocean acidity. Anthropogenic carbon dioxide has been accumulating in the oceans, lowering both the concentration of carbonate ions and the pH (ref. 1), resulting in the acidification of sea water. Previous laboratory experiments have shown that decreased carbonate ion concentrations cause many marine calcareous organisms to show reduced calcification rates2,3,4,5. If these results are widely applicable to ocean settings, ocean acidification could lead to ecosystem shifts. Planktonic foraminifera are single-celled calcite-secreting organisms that represent between 25 and 50% of the total open-ocean marine carbonate flux6 and influence the transport of organic carbon to the ocean interior7. Here we compare the shell weights of the modern foraminifer Globigerina bulloides collected from sediment traps in the Southern Ocean with the weights of shells preserved in the underlying Holocene-aged sediments. We find that modern shell weights are 30–35% lower than those from the sediments, consistent with reduced calcification today induced by ocean acidification. We also find a link between higher atmospheric carbon dioxide and low shell weights in a 50,000-year-long record obtained from a Southern Ocean marine sediment core. It is unclear whether reduced calcification will affect the survival of this and other species, but a decline in the abundance of foraminifera caused by acidification could affect both marine ecosystems and the oceanic uptake of atmospheric carbon dioxide.

GM-CSF- and M-CSF-dependent macrophage phenotypes display differential dependence on Type I interferon signaling

Abstract: M-CSF and GM-CSF are mediators involved in regulating the numbers and function of macrophage lineage populations and have been shown to contribute to macrophage heterogeneity. Type I IFN is an important mediator produced by macrophages and can have profound regulatory effects on their properties. In this study, we compared bone marrow-derived macrophages (BMM) and GM-CSF-induced BMM (GM-BMM) from wild-type and IFNAR1(-/-) mice to assess the contribution of endogenous type I IFN to the phenotypic differences between BMM and GM-BMM. BMM were capable of higher constitutive IFN-beta production, which contributed significantly to their basal transcriptome. Microarray analysis found that of the endogenous type I IFN-regulated genes specific to either BMM or GM-BMM, 488 of these gene alterations were unique to BMM, while only 50 were unique to GM-BMM. Moreover, BMM displayed enhanced basal mRNA levels, relative to GM-BMM, of a number of genes identified as being dependent on type I IFN signaling, including Stat1, Stat2, Irf7, Ccl5, Ccl12, and Cxcl10. As a result of prior type I IFN "priming," upon LPS stimulation BMM displayed increased activation of the MyD88-independent IRF-3/STAT1 pathways compared with GM-BMM, which correlated with the distinct cytokine/chemokine profiles of the two macrophage subsets. Furthermore, the autocrine type I IFN signaling loop regulated the production of the M1 and M2 signature cytokines, IL-12p70 and IL-10. Collectively, these findings demonstrate that constitutive and LPS-induced type I IFN play significant roles in regulating the differences in phenotype and function between BMM and GM-BMM.

Grain unloading of arsenic species in rice.

Abstract: Rice (Oryza sativa) is the staple food for over half the world's population yet may represent a significant dietary source of inorganic arsenic (As), a nonthreshold, class 1 human carcinogen. Rice grain As is dominated by the inorganic species, and the organic species dimethylarsinic acid (DMA). To investigate how As species are unloaded into grain rice, panicles were excised during grain filling and hydroponically pulsed with arsenite, arsenate, glutathione-complexed As, or DMA. Total As concentrations in flag leaf, grain, and husk, were quantified by inductively coupled plasma mass spectroscopy and As speciation in the fresh grain was determined by x-ray absorption near-edge spectroscopy. The roles of phloem and xylem transport were investigated by applying a ± stem-girdling treatment to a second set of panicles, limiting phloem transport to the grain in panicles pulsed with arsenite or DMA. The results demonstrate that DMA is translocated to the rice grain with over an order magnitude greater efficiency than inorganic species and is more mobile than arsenite in both the phloem and the xylem. Phloem transport accounted for 90% of arsenite, and 55% of DMA, transport to the grain. Synchrotron x-ray fluorescence mapping and fluorescence microtomography revealed marked differences in the pattern of As unloading into the grain between DMA and arsenite-challenged grain. Arsenite was retained in the ovular vascular trace and DMA dispersed throughout the external grain parts and into the endosperm. This study also demonstrates that DMA speciation is altered in planta, potentially through complexation with thiols.

Nitric oxide‐mediated dispersal in single‐ and multi‐species biofilms of clinically and industrially relevant microorganisms

Abstract: Strategies to induce biofilm dispersal are of interest due to their potential to prevent biofilm formation and biofilm-related infections. Nitric oxide (NO), an important messenger molecule in biological systems, was previously identified as a signal for dispersal in biofilms of the model organism Pseudomonas aeruginosa. In the present study, the use of NO as an anti-biofilm agent more broadly was assessed. Various NO donors, at concentrations estimated to generate NO levels in the picomolar and low nanomolar range, were tested on single-species biofilms of relevant microorganisms and on multi-species biofilms from water distribution and treatment systems. Nitric oxide-induced dispersal was observed in all biofilms assessed, and the average reduction of total biofilm surface was 63%. Moreover, biofilms exposed to low doses of NO were more susceptible to antimicrobial treatments than untreated biofilms. For example, the efficacy of conventional chlorine treatments at removing multi-species biofilms from water systems was increased by 20-fold in biofilms treated with NO compared with untreated biofilms. These data suggest that combined treatments with NO may allow for novel and improved strategies to control biofilms and have widespread applications in many environmental, industrial and clinical settings.

Evidence for the accelerations of sea level on multi-decade and century timescales.

Abstract: A modification in the rate of change of sea level (i.e. an ‘acceleration’ or ‘nonlinear trend’) is an important climate-related signal, which requires confirmation and explanation. In this study, the evidence for accelerations in regional and global average sea level on timescales of several decades and longer is reviewed by inter-comparison of the recent findings of different researchers and by inspection of original tide gauge records. Most sea-level data originate from Europe and North America, and both the sets display evidence for a positive acceleration, or ‘inflexion’, around 1920–1930 and a negative one around 1960. These inflexions are the main contributors to reported accelerations since the late 19th century, and to decelerations during the mid- to late 20th century. However, these characteristic features are not always found in records from other parts of the world. Although some aspects of the sea-level time series are consistent with changes in rates of globally averaged temperature changes, volcanic eruptions and natural climate variability, modelling undertaken so far has been unable to describe these features adequately. This emphasizes the need for a major enhancement of the sea-level data set, especially for those parts of the world without long tide gauge records, in order to obtain greater insight into the spatial dependence of accelerations. A number of complementary methods must be employed, of which salt marsh techniques offer the possibility of obtaining time series similar to those that would have been obtained from coastal tide gauges. Copyright © 2008 Royal Meteorological Society

Quantifying uncertainty in estimation of hydrologic metrics for ecohydrological studies

Abstract: Hydrologic metrics have been used extensively in ecology and hydrology to summarize the characteristics of riverine flow regimes at various temporal scales but there has been limited evaluation of the sources and magnitude of uncertainty involved in their computation Variation in bias, precision and overall accuracy of these metrics influences the ability to correctly describe flow regimes, detect meaningful differences in hydrologic characteristics through time and space, and define flow-ecological response relationships Here, we examine the effects of two primary factors—discharge record length and time period of record—on uncertainty in the estimation of 120 separate hydrologic metrics commonly used by researchers to describe ecologically relevant components of the hydrologic regime Metric bias rapidly decreased and precision and overall accuracy markedly increased with increasing record length, but tended to stabilize >15 years and did not change substantially >30 years We found a strong positive relationship between the degree of overlap of discharge record and similarity in hydrologic metrics when based on 15- and 30-year discharge periods calculated within a 36-year temporal window (1965–2000), although hydrologic metrics calculated for a given stream gauge tended to vary only within a restricted range through time Our study provides critical guidance for selecting an appropriate record length and temporal period of record given a degree of metric bias and precision deemed acceptable by a researcher We conclude that: (1) estimation of hydrologic metrics based on at least 15 years of discharge record is suitable for use in hydrologic analyses that aim to detect important spatial variation in hydrologic characteristics; (2) metric estimation should be based on overlapping discharge records contained within a discrete temporal window (ideally >50% overlap among records); and (3) metric uncertainty varies greatly and should be accounted for in future analyses Copyright © 2009 John Wiley & Sons, Ltd

Predicting the natural flow regime: models for assessing hydrological alteration in streams

Abstract: Understanding the extent to which natural streamflow characteristics have been altered is an important consideration for ecological assessments of streams. Assessing hydrologic condition requires that we quantify the attributes of the flow regime that would be expected in the absence of anthropogenic modifications. The objective of this study was to evaluate whether selected streamflow characteristics could be predicted at regional and national scales using geospatial data. Long-term, gaged river basins distributed throughout the contiguous US that had streamflow characteristics representing least disturbed or near pristine conditions were identified. Thirteen metrics of the magnitude, frequency, duration, timing and rate of change of streamflow were calculated using a 20–50 year period of record for each site. We used random forests (RF), a robust statistical modelling approach, to develop models that predicted the value for each streamflow metric using natural watershed characteristics. We compared the performance (i.e. bias and precision) of national- and regional-scale predictive models to that of models based on landscape classifications, including major river basins, ecoregions and hydrologic landscape regions (HLR). For all hydrologic metrics, landscape stratification models produced estimates that were less biased and more precise than a null model that accounted for no natural variability. Predictive models at the national and regional scale performed equally well, and substantially improved predictions of all hydrologic metrics relative to landscape stratification models. Prediction error rates ranged from 15 to 40%, but were ≤25% for most metrics. We selected three gaged, non-reference sites to illustrate how predictive models could be used to assess hydrologic condition. These examples show how the models accurately estimate pre-disturbance conditions and are sensitive to changes in streamflow variability associated with long-term land-use change. We also demonstrate how the models can be applied to predict expected natural flow characteristics at ungaged sites. Copyright © 2009 John Wiley & Sons, Ltd.

Arsenic contamination in groundwater in the Southeast Asia region.

Abstract: The adverse impact of groundwater contaminated with arsenic (As) on humans has been reported worldwide, particularly in Asian countries. In this study, we present an overview of the As crisis in the Southeast Asian region where groundwater is contaminated with naturally occurring As and where contamination has become more widespread in recent years. In this region more than 100 million people are estimated to be at risk from groundwater As contamination, and some 700,000 people are known so far to have been affected by As-related diseases. Despite investments exceeding many millions of dollars, there are still substantial knowledge gaps about the prevalence and impact of As, notably in its epidemiology, temporal variations, social factors, patient identification, treatment, etc. Arsenic-affected people in the affected regions also face serious social problems. Of major concern is the fact that many researchers from different countries have been conducting research in SE Asia region but with a lack of coordination, thus duplicating their work. There is an urgent need to coordinate these various studies to ensure better delivery of research outcomes. Further research is needed to improve field testing and monitoring of drinking water sources, and to develop new treatments for chronic As toxicity and new sources of safe drinking water.

Selenium increases seed production in Brassica

Abstract: Selenium (Se) is essential for humans and animals but is not considered to be essential for higher plants. Although researchers have found increases in vegetative growth due to fertiliser Se, there has been no definitive evidence to date of increased reproductive capacity, in terms of seed production and seed viability. The aim of this study was to evaluate seed production and growth responses to a low dose of Se (as sodium selenite, added to solution culture) compared to very low-Se controls in fast-cycling Brassica rapa L. Although there was no change in total biomass, Se treatment was associated with a 43% increase in seed production. The Se-treated Brassica plants had higher total respiratory activity in leaves and flowers, which may have contributed to higher seed production. This study provides additional evidence for a beneficial role for Se in higher plants.

Gene expression patterns during intramuscular fat development in cattle.

Abstract: Deposition of intramuscular fat, or "marbling," in beef cattle contributes significantly to meat quality variables, including juiciness, flavor, and tenderness. The accumulation of intramuscular fat is largely influenced by the genetic background of cattle, as well as their age and nutrition. To identify genes that can be used as early biomarkers for the prediction of marbling capacity, we studied the muscle transcriptome of 2 cattle crossbreeds with contrasting intramuscular fat content. The transcriptomes of marbling LM tissue of heifers from Wagyu x Hereford (WxH; n = 6) and Piedmontese x Hereford (PxH; n = 7) crosses were profiled by using a combination of complementary DNA microarray and quantitative reverse transcription-PCR. Five biopsies of LM were taken from each animal at approximately 3, 7, 12, 20, and 25 mo from birth. Tissue was also collected from the LM of each animal at slaughter (approximately 30 mo). Microarray experiments, conducted on the first 3 biopsies of 2 animals from each crossbreed, identified 97 differentially expressed genes. The gene expression results indicated that the LM transcriptome of animals with high marbling potential (WxH) could be reliably distinguished from less marbled animals (PxH) when the animals were as young as 7 mo of age. At this early age, one cannot reliably determine meaningful differences in intramuscular fat deposition. We observed greater expression of a set of adipogenesis- and lipogenesis-related genes in the LM of young WxH animals compared with their PxH contemporaries. In contrast, genes highly expressed in PxH animals were associated with mitochondrial oxidative activity. Further quantitative reverse transcription-PCR experiments revealed that the messenger RNA of 6 of the lipogenesis-related genes also peaked at the age of 20 to 25 mo in WxH animals. The messenger RNA expression of ADIPOQ, SCD, and THRSP was highly correlated with intramuscular fat content of an individual in WxH animals. Our study provides clear evidence of early molecular changes associated with marbling and also identifies specific time frames when intramuscular fat development in cattle muscle can be detected by using gene expression. This information could be used by animal scientists to design optimal nutrition for high marbling potential. In addition, the genes found to be highly expressed during development of marbling could be used to develop genetic markers or biomarkers to assist with beef production strategies.

Effects of Minor Components in Carbon Dioxide Capture Using Polymeric Gas Separation Membranes

Abstract: The capture of carbon dioxide by membrane gas separation has been identified as one potential solution to reduce greenhouse gas emissions. In particular, the application of membranes to CO2 capture from both pre‐ and post‐combustion strategies is of interest. For membrane technology to become commercially viable in CO2 capture, a number of factors need to be overcome, one being the role of minor components in the process on membrane performance. This review considers the effects of minor components in both pre‐ and post‐combustion use of polymeric membranes for CO2 capture. In particular, gases such as SOx, NOx, CO, H2S, NH3, as well as condensable water and hydrocarbons are reviewed in terms of their permeability through polymeric membranes relative to CO2, as well as their plasticization and aging effects on membrane separation performance. A major conclusion of the review is that while many minor components can affect performance both through competitive sorption and plasticization, much rema...

Evaluating ten spectral vegetation indices for identifying rust infection in individual wheat leaves

Abstract: Ten, widely-used vegetation indices (VIs), based on mathematical combinations of narrow-band optical reflectance measurements in the visible/near infrared wavelength range were evaluated for their ability to discriminate leaves of 1 month old wheat plants infected with yellow (stripe), leaf and stem rust. Narrow band indices representing changes in non-chlorophyll pigment concentration and the ratio of non-chlorophyll to chlorophyll pigments proved more reliable in discriminating rust infected leaves from healthy plant tissue. Yellow rust produced the strongest response in all the calculated indices when compared to healthy leaves. No single index was capable of discriminating all three rust species from each other. However the sequential application of the Anthocyanin Reflectance Index to separate healthy, yellow and mixed stem rust/leaf rust classes followed by the Transformed Chlorophyll Absorption and Reflectance Index to separate leaf and stem rust classes would provide for the required species discrimination under laboratory conditions and thus could form the basis of rust species discrimination in wheat under field conditions.

Improving estimates of savanna burning emissions for greenhouse accounting in northern Australia: limitations, challenges, applications

Abstract: Although biomass burning of savannas is recognised as a major global source of greenhouse gas emissions, quantification remains problematic with resulting regional emissions estimates often differing markedly. Here we undertake a critical assessment of Australia’s National Greenhouse Gas Inventory (NGGI) savanna burning emissions methodology. We describe the methodology developed for, and results and associated uncertainties derived from, a landscape-scale emissions abatement project in fire-prone western Arnhem Land, northern Australia. The methodology incorporates (i) detailed fire history and vegetation structure and fuels type mapping derived from satellite imagery; (ii) field-based assessments of fuel load accumulation, burning efficiencies (patchiness, combustion efficiency, ash retention) and N : C composition; and (iii) application of standard, regionally derived emission factors. Importantly, this refined methodology differs from the NGGI by incorporation of fire seasonality and severity components, and substantial improvements in baseline data. We consider how the application of a fire management program aimed at shifting the seasonality of burning (from one currently dominated by extensive late dry season wildfires to one where strategic fire management is undertaken earlier in the year) can provide significant project-based emissions abatement. The approach has wider application to fire-prone savanna systems dominated by anthropogenic sources of ignition.

A Lamb-wave-based technique for damage detection in composite laminates

Abstract: This paper presents the application of Lamb waves to inspect damage in composite laminates. The proposed methodology employs a network of transducers that are used to sequentially scan the structure before and after the presence of damage by transmitting and receiving Lamb wave pulses. A damage localization image is reconstructed by analyzing the cross-correlation of the scatter signal envelope with the excitation pulse envelope for each transducer pair. A potential damage area is then reconstructed by superimposing the image observed from each actuator and sensor signal path. Both numerical and experimental case studies are used to verify the proposed methodology for composite laminates. Three-dimensional finite element models with a transducer network consisting of four transducer elements are used in the numerical case studies. The experimental case studies employ a transducer network using four piezoelectric transducers as transmitter elements and a laser vibrometer to measure the response signals at four locations close to the transducers. The results show that the method enables the reliable detection of structural damage with locating inaccuracies of the order of a few millimeters inside as well as outside of an inspection area of 100 x 100 mm(2).

Establishment, immortalisation and characterisation of pteropid bat cell lines.

Abstract: Background Bats are the suspected natural reservoir hosts for a number of new and emerging zoonotic viruses including Nipah virus, Hendra virus, severe acute respiratory syndrome coronavirus and Ebola virus. Since the discovery of SARS-like coronaviruses in Chinese horseshoe bats, attempts to isolate a SL-CoV from bats have failed and attempts to isolate other bat-borne viruses in various mammalian cell lines have been similarly unsuccessful. New stable bat cell lines are needed to help with these investigations and as tools to assist in the study of bat immunology and virus-host interactions. Methodology/Findings Black flying foxes (Pteropus alecto) were captured from the wild and transported live to the laboratory for primary cell culture preparation using a variety of different methods and culture media. Primary cells were successfully cultured from 20 different organs. Cell immortalisation can occur spontaneously, however we used a retroviral system to immortalise cells via the transfer and stable production of the Simian virus 40 Large T antigen and the human telomerase reverse transcriptase protein. Initial infection experiments with both cloned and uncloned cell lines using Hendra and Nipah viruses demonstrated varying degrees of infection efficiency between the different cell lines, although it was possible to infect cells in all tissue types. Conclusions/Significance The approaches developed and optimised in this study should be applicable to bats of other species. We are in the process of generating further cell lines from a number of different bat species using the methodology established in this study.

Hypoxia prolongs monocyte/macrophage survival and enhanced glycolysis is associated with their maturation under aerobic conditions.

Abstract: In chronic inflammatory lesions macrophages are abundant and adapt to the low oxygen concentrations often present there. In low oxygen some cell types die by apoptosis, as reported for macrophage cell lines, while others survive better as they shift their metabolism to anaerobic glycolysis. It was found here that hypoxia prolongs the survival of murine bone marrow-derived macrophages, either in the absence or presence of low CSF-1 (M-CSF) concentrations. Although Akt activity increased in bone marrow-derived macrophages in the low oxygen conditions, the levels of both anti- and proapoptotic Bcl-2 family members decreased. Glycolysis was enhanced as judged by increased glucose uptake, glucose transporter expression, lactate dehydrogenase mRNA expression, and lactate secretion. Human monocytes responded similarly to low oxygen, and a number of genes associated with glycolysis were shown by microarray analysis and quantitative PCR to be up-regulated. Interestingly, human monocyte-derived macrophages showed evidence of enhanced glycolysis even under aerobic conditions. It is proposed that certain monocyte/macrophage populations survive better under conditions of low oxygen, thereby contributing to their increased numbers at sites of chronic inflammation and tumors; it is also proposed that as macrophages differentiate from monocytes they begin to adopt a glycolytic metabolism allowing them to adapt readily when exposed to low oxygen conditions.

Invasive Andropogon gayanus (gamba grass) is an ecosystem transformer of nitrogen relations in Australian savanna

Abstract: Invasion by the African grass Andropogon gayanus is drastically altering the understory structure of oligotrophic savannas in tropical Australia. We compared nitrogen (N) relations and phenology of A. gayanus and native grasses to examine the impact of invasion on N cycling and to determine possible reasons for invasiveness of A. gayanus. Andropogon gayanus produced up to 10 and four times more shoot phytomass and root biomass, with up to seven and 2.5 times greater shoot and root N pools than native grass understory. These pronounced differences in phytomass and N pools between A. gayanus and native grasses were associated with an altered N cycle. Most growth occurs in the wet season when, compared with native grasses, dominance of A. gayanus was associated with significantly lower total soil N pools, lower nitrification rates, up to three times lower soil nitrate availability, and up to three times higher soil ammonium availability. Uptake kinetics for different N sources were studied with excised roots of three grass species ex situ. Excised roots of A. gayanus had an over six times higher uptake rate of ammonium than roots of native grasses, while native grass Eriachne triseta had a three times higher uptake rate of nitrate than A. gayanus. We hypothesize that A. gayanus stimulates ammonification but inhibits nitrification, as was shown to occur in its native range in Africa, and that this modification of the soil N cycle is linked to the species' preference for ammonium as an N source. This mechanism could result in altered soil N relations and could enhance the competitive superiority and persistence of A. gayanus in Australian savannas.

Modelling and testing spatially distributed sediment budgets to relate erosion processes to sediment yields

Abstract: Identifying the erosion processes contributing to increased basin fine sediment yield is important for reducing downstream impacts on aquatic ecosystems. However, erosion rates are spatially variable, and much eroded sediment is stored within river basins and not delivered downstream. A spatially distributed sediment budget model is described that assesses the primary sources (hillslope soil erosion, gully and riverbank erosion) and sinks (floodplain and reservoir deposition) of fine sediment for each link in a river network. The model performance is evaluated in a 17,000-km^2 basin in south-east Australia using measured suspended sediment yields from eight catchments within the basin, each 100-700km^2 in area. Spatial variations within the basin in yield and area-specific yield were reliably predicted. Observed yields and area-specific yields varied by 17-fold and 15-fold respectively between the catchments, while predictions were generally within a factor of 2 of observations. Model efficiency at predicting variations in area-specific yield was good outside forested areas (0.58), and performance was weakly sensitive to parameter values. Yields from forested areas were under-predicted, and reducing the predicted influence of riparian vegetation on bank erosion improved model performance in those areas. The model provided more accurate and higher resolution predictions than catchment area interpolation of measured yields from neighbouring river basins. The model is suitable for guiding the targeting of remediation measures within river basins to reduce downstream sediment yields.

Composition and significance of picophytoplankton in Antarctic waters

Abstract: Filter fractionated picophytoplankton from Antarctic coastal waters (summer 2001) represented only 7–33% of total phytoplankton, even though total stocks were low (average Chl a = 0.32 μg l−1, range = 0.13–1.03 μg l−1). Though all cells passed a 2 μm filter, electron microscopy revealed most cells were over 2 μm, principally Parmales, Phaeocystis sp., and small diatoms. CHEMTAX analysis of HPLC pigment data suggested type 8 haptophytes (e.g. Phaeocystis sp. plus Parmales and pelagophytes) contributed 7–58% of picoplanktonic chlorophyll a, type 6 haptophytes (e.g. coccolithophorids) 18–59%, diatoms 0–18% (mostly type 2 diatoms, e.g. Pseudonitzschia sp., 0–15%), prasinophytes 0–17%, with cell fragments of cryptophytes 0–40%, and dinoflagellates 0–11%. Only stocks of type 8 haptophytes and prasinophytes differed significantly due to successional changes. Zeaxanthin concentrations exceeded estimates from previous cyanobacterial counts and may derive from non-photosynthetic bacteria.

Prediction of the probability of large fires in the Sydney region of south-eastern Australia using fire weather

Abstract: The probability of large-fire (≥1000 ha) ignition days, in the Sydney region, was examined using historical records Relative influences of the ambient and drought components of the Forest Fire Danger Index (FFDI) on large fire ignition probability were explored using Bayesian logistic regression The preferred models for two areas (Blue Mountains and Central Coast) were composed of the sum of FFDI (Drought Factor, DF = 1) (ambient component) and DF as predictors Both drought and ambient weather positively affected the chance of large fire ignitions, with large fires more probable on the Central Coast than in the Blue Mountains The preferred, additive combination of drought and ambient weather had a marked threshold effect on large-fire ignition and total area burned in both localities This may be due to a landscape-scale increase in the connectivity of available fuel at high values of the index Higher probability of large fires on the Central Coast may be due to more subdued terrain or higher population density and ignitions Climate scenarios for 2050 yielded predictions of a 20–84% increase in potential large-fire ignitions days, using the preferred model

A geographic mosaic of genetic variation within a foundation tree species and its community-level consequences.

Abstract: Knowledge of the manner in which genetic variation within a tree species affects associated communities and ecosystem processes across its entire range is important for understanding how geographic mosaics of genetic interactions might develop and support different communities. While numerous studies have investigated the community and ecosystem consequences of genetic variation at the hybrid cross type or genotype level within a species, none has investigated the community-level effects of intraspecific genetic variation across the geographic range of a widespread species. This is the scale at which geographic mosaics of coevolution are hypothesized to exist. Studies at this level are particularly important for foundation tree species, which typically support numerous microbial, fungal, plant, and animal communities. We studied genetic variation across eight geographical races of the forest tree Eucalyptus globulus representing its natural distribution across southeastern Australia. The study was conducted in a 15-year-old common garden trial based on families derived from single-tree open-pollinated seed collections from the wild. Neutral molecular genetic variation within E. globulus was also assessed and compared with genetic divergence in the phenotypic and community traits. Three major findings emerged. First, we found significant genetically based, hierarchical variation in associated communities corresponding to geographical races of E. globulus and families within races. Second, divergence in foliar communities at the racial level was associated with genetically based divergence in specific leaf morphological and chemical traits that have known defensive functions. Third, significant positive correlations between canopy community dissimilarity and both neutral molecular genetic and leaf quantitative genetic dissimilarity at the race level supported a genetic similarity rule. Our results argue that genetic variation within foundation tree species has the potential to be a significant driver of the geographical mosaics of variation typical of forest communities, which could have important ecological and evolutionary implications.