Anabranching and maximum flow efficiency in Magela Creek, northern Australia

Anabranching is the prevailing river pattern found along alluvial tracts of the world's largest rivers. Hydraulic geometry and bed material discharge are compared between single channel and anabranching reaches up to 4 times bank-full discharge in Magela Creek, northern Australia. The anabranching channels exhibit greater sediment transporting capacity per unit available stream power, i.e., maximum flow efficiency (MFE). Simple flume experiments corroborate our field results showing the flow efficiency gains associated with anabranching, and highlight the prospect of a dominant anabranch, which is found in many anabranching rivers. These results demonstrate that anabranching can constitute a stable river pattern in dynamic equilibrium under circumstances in which a continuous single channel would be unable to maintain sediment conveyance. We propose the existence of a flow efficiency continuum that embraces dynamic equilibrium and disequilibrium (vertically accreting) anabranching rivers

A comparison of sequential total and activated white cell count in patients undergoing coronary artery bypass grafting, using cardiopulmonary bypass, with and without a white cell filter

Introduction Cardiopulmonary bypass (CPB) has been shown to induce a systemic inflammatory response similar to the local reaction seen after tissue damage [1]. This leads to the release of toxic substances, such as elastase, which cause endothelial damage and may adversely affect outcome [2]. Use of a leucocyte depleting arterial line filter is one of many anti-inflammatory strategies that are undergoing evaluation. Leucocyte depleting filters may be capable of selectively removing activated white cells [3], but this has not been proved in vivo. The aim of the present study was to compare sequential total and activated white cells during CPB, using either a leucocyte depleting or standard arterial line filter. Materials and methods After local ethical committee approval, 20 patients undergoing coronary artery bypass grafting using CPB were prospectively randomly allocated to have either a Leukogard LG–6 (Pall Biomedical, Portsmouth, UK) or a nonleucocyte depleting filter inserted into the arterial line of the CPB circuit. Arterial limb blood samples were taken immediately after institution of CPB (0min) and at 10–min intervals throughout the bypass period. Activated white cells were identified using nitroblue tetrazolium, then both total and activated white cell numbers counted after staining with Leucoplate.Results Table 1 shows the number of white cells counted/1.25 ? l (volume of a single channel of Nageotte counting chamber) using light microscopy (× 25).Conclusion The LG6 leucocyte filter reduces the total white cell count and is capable of selectively removing activated white cells during CPB. The exact relationship between leucocyte depletion and improved patient outcome still remains unclear

Beating heart coronary surgery and renal function: a prospective randomised study (Presented at 18th Spring Meeting of the Association of Cardiothoracic Anaesthetists: Selected abstracts, Cambridge, UK. 22 June 2001)

Introduction Cardiopulmonary bypass (CPB) is widely regarded as an important contributor to renal failure, a well recognised complication, following coronary artery surgery (CABG). Off-pump coronary surgery (OPCAB) is intuitively considered renoprotective. We examine the extent of renal glomerular and tubular injury in low-risk patients undergoing either OPCAB or on-pump coronary artery bypass (ONCAB).Methods Forty patients awaiting elective CABG were prospectively randomized into those undergoing OPCAB (n = 20) and ONCAB (n = 20). Table 1 illustrates the exclusion criteria. Glomerular and tubular injury were assessed, respectively, by urinary excretion of microalbumin and retinol binding protein (RBP) indexed to urinary creatinine [1]. Daily measurements were made from admission to postoperative day 5. Fluid balance, serum creati-nine and blood urea were also monitored. Results No mortality or renal complication was observed. Both groups had similar demographic make-up. The OPCAB group received fewer coronary grafts than their counterparts (1.8 versus 2.8; P = 0.002). Serum creatinine and blood urea remained normal in both groups throughout the study. A dramatic and similar rise in mean ± 2SD urinary RBP:creatinine ratio occurred in both groups peaking on day 1 (3183 ± 2534 versus 4035 ± 4078; P = 0.43) before returning to baseline levels. These trends were also observed with the urinary microalbumin:creatinine ratio (5.05 ± 2.66 versus 6.77 ± 5.76; P = 0.22). ONCAB patients had a significantly more negative fluid balance on postoperative day 2 (-183 ± 1118 versus 637 ± 847 ml; P < 0.05). Conclusions Although renal dysfunction did not clinically occur in any patient, sensitive indicators revealed significant and similar injury to both renal tubules and glomeruli following either OPCAB or ONCAB. These suggest that avoidance of CPB per se does not offer additional renoprotection to patients at low risk of perioperative renal insult during CABG

Lowland river responses to intraplate tectonism and climate forcing quantified with luminescence and cosmogenic 10Be

Intraplate tectonism has produced large-scale folding that steers regional drainage systems, such as the 1600 km-long Cooper Ck, en route to Australia’s continental depocentre at Lake Eyre. We apply cosmogenic 10Be exposure dating in bedrock, and luminescence dating in sediment, to quantify the erosional and depositional response of Cooper Ck where it incises the rising Innamincka Dome. The detachment of bedrock joint-blocks during extreme floods governs the minimum rate of incision (17.4±6.5 mm/ky) estimated using a numerical model of episodic erosion calibrated with our 10Be measurements. The last big-flood phase occurred no earlier than ~112–121ka. Upstream of the Innamincka Dome long-term rates of alluvial deposition, partly reflecting synclinal-basin subsidence, are estimated from 47 luminescence dates in sediments accumulated since ~270 ka. Sequestration of sediment in subsiding basins such as these may account for the lack of Quaternary accumulation in Lake Eyre, and moreover suggests that notions of a single primary depocentre at base-level may poorly represent lowland, arid-zone rivers. Over the period ~75–55 ka Cooper Ck changed from a bedload- dominant, laterally-active meandering river to a muddy anabranching channel network up to 60 km wide. We propose that this shift in river pattern was a product of base-level rise linked with the slowly deforming syncline–anticline structure, coupled with a climate-forced reduction in discharge. The uniform valley slope along this subsiding alluvial and rising bedrock system represents an adjustment between the relative rates of deformation and the ability of greatly enhanced flows at times during the Quaternary to incise the rising anticline. Hence, tectonic and climate controls are balanced in the long term

Floodplains : the forgotten and abused component of the fluvial system

River restoration is strongly focussed on in-channel initiatives driven by fisheries interests and a continued desire for river stability. This contrasts greatly with the inherently mobile nature of watercourses. What is often overlooked is the fact that many rivers have developed floodplain units that would naturally operate as integrated functional systems, moderating the effects of extreme floods by distributing flow energy and sediment transport capacity through out of bank flooding. Floodplain utilisation for farming activities and landowner intransigence when it comes to acknowledging that the floodplain is part of the river system, has resulted in floodplains being the most degraded fluvial morphologic unit, both in terms of loss of form and function and sheer levels of spatial impact. The degradation has been facilitated by the failure of regulatory mechanisms to adequately acknowledge floodplain form and function. This is testament to the ‘inward looking’ thinking behind national assessment strategies. This paper reviews the state of floodplain systems drawing on quantitative data from England and Wales to argue for greater consideration of the floodplain in relation to river management. The database is poor and must be improved, however it does reveal significant loss of watercourse-floodplain connectivity linked to direct flood alleviation measures and also to altered flood frequency as a result of river downcutting following river engineering. These latter effects have persisted along many watercourses despite the historic nature of the engineering interventions and will continue to exacerbate the risk of flooding to downstream communities. We also present several examples of the local and wider values of reinstating floodplain form and function, demonstrating major ecological gains, improvement to downstream flood reduction, elevation of water quality status and reductions in overall fine sediment loss from farmland. A re-think is required regarding our approach to managing floodplains and funding floodplain restoration, arguing for greater recognition of the natural role of the floodplain as a resource for upstream flood management and as an agent for overall biotic improvement in line with restoration objectives

Solution-processable 2,1,3-benzothiadiazole containing compound based on the novel 1-dodecyl-6-dodecoxynaphthyridine-2-one unit for organic field-effect transistors

Small molecule organic semiconductors have well-defined structures and can be used in place of polymers which often show batch-to-batch variation. Many different electron-rich donor and electron-deficient acceptor units have been used to design materials with reduced HOMO-LUMO gaps and improved mobilities. Here we introduce a novel acceptor unit, 1-dodecyl-6-dodecoxynaphthyridine-2-one. This acceptor unit has been used in the synthesis of two novel compounds, with thiophene and 2,1,3-benzothiadiazole (BT) cores. The BT-containing compound shows a narrower HOMO-LUMO gap, broad solid-state absorption and has been applied to organic field-effect transistors, showing a mobility of 0.022 cm2 V−1 s−1 after optimisation of devices using self-assembled monolayers

Arran Stibbe. Ecolinguistics: Language, Ecology and the Stories We Live By.

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Flood energy dissipation in anabranching channels

This study examines the character of developing anabranched channel networks on the River Wear, north England using metre-scale aerial LiDAR. DSM-DTM interpretation reveals a well-developed vegetation structure and a locally diverse terrain, dominated by an interlinked channel network split by low elevation depositional areas with the gross morphology of the reach resembling that of a strongly active meandering / wandering channel suggesting that an anabranching network may develop within systems that were initially active meandering and wandering, evolving in line with floodplain vegetative succession. Utilisation of the LiDAR DEM in the hydrological component of the CAESAR-Lisflood (version 1.4) morpho-dynamic model has generated local hydraulic variable estimates through the anabranched reaches for a range of flows. These data clearly demonstrate how elevated flows are transferred out of the primary channel and distributed along the interconnected secondary channel network, creating a diverse set of hydraulic environments. Areas between the channels rapidly become inundated as flows increase, dissipating flow energy. Shear stress estimates throughout the study site reveal a generally reduced ability to mobilise sediments and erode channel margins, in comparison to a single-thread reach immediately downstream. Anabranched secondary channels appear to operate in disequilibrium and act predominantly as aggradational zones, although with some evidence of scour at channel bifurcation and confluence points. It would appear that the topographic character of anabranching sites efficiently manages flood flow energy, activating secondary channels and low elevation areas to distribute flood flows. These findings contrast with the hydraulic data from an adjacent single-thread reach, characterised by flood flows concentrated in-channel creating a high erosive potential. We propose that anabranching rivers could play an important role in natural flood and sediment management in many UK river systems

Classification of river morphology and hydrology to support management and restoration

The work leading to this paper has received funding from the European Union’s FP7 programme under Grant Agreement No. 282656 (REFORM