ORCID Profile
0000-0002-5257-3172
Current Organisations
Australian National University
,
Commonwealth Scientific and Industrial Research Organisation
,
CSIRO
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Publisher: Elsevier BV
Date: 06-2020
Publisher: Wiley
Date: 17-06-2021
DOI: 10.1002/ESP.5171
Abstract: Topographic models provide a useful tool for understanding gully occurrence in the landscape but require reliable estimates of gully head drainage areas. Modern high‐resolution topography data (collected using structure from motion photogrammetry or light detection and ranging) is increasingly used for topographic studies of gullies, but little work has been done to assess the variability of gully head drainage area estimates using different methods. This study evaluated alternative approaches to using high‐resolution digital elevation models (DEMs) so that gully topographic models can be more readily applied to any area with suitably high‐resolution data. Specifically, we investigated the impact of single‐ or multiple‐direction flow routing algorithms, DEM hydrologic‐enforcement procedures and spatial resolution on gully head drainage area estimation. We tested these methods on a 40 km 2 site centred on Weany Creek, a low‐relief semi‐arid landscape draining towards the Great Barrier Reef, Australia. Using a subroutine to separate gully heads into those with ergent or convergent flow patterns upslope, we found that ergent flow conditions occurred at half of 484 studied gullies. Drainage areas estimated by different flow routing algorithms were more variable in these ergent cases than for convergent cases. This variation caused a significant difference between topographic threshold parameters (slope b and intercept k ) derived from single‐ or multiple‐direction flow routing algorithms, respectively. Different methods of hydrologic enforcement (filling or breaching) also affected threshold analysis, resulting in estimates of the exponent b being ~188% higher if the DEM was filled than if breached. The testing of the methods to date indicates that a finer resolution (≤2 m) DEM and a multiple‐direction flow routing algorithm achieve the most realistic drainage area estimates in low‐relief landscapes. For Weany Creek we estimated threshold parameters k = 0.033 and b = 0.189, indicating that it is highly susceptible to gully erosion.
Publisher: Elsevier BV
Date: 05-2023
Publisher: Springer Science and Business Media LLC
Date: 12-01-2007
DOI: 10.1007/S00421-006-0372-9
Abstract: Patients with mitochondrial myopathy (MM) have a reduced capacity to perform exercise due to a reduced oxidative capacity. We undertook this study to determine whether skeletal muscle metabolism could be improved with oxygen therapy in patients with MM. Six patients with MM and six controls, matched for age, gender and physical activity, underwent (31)P-magnetic resonance spectroscopy ((31)P-MRS) examination. (31)P-MR spectra were collected at rest and in series during exercise and recovery whilst breathing normoxic (0.21 O(2)) or hyperoxic (1.0 O(2)) air. At rest, MM showed an elevated [ADP] (18 +/- 3 micromol/l) and pH (7.03 +/- 0.01) in comparison to the control group (12 +/- 1 micromol/l, 7.01 +/- 0.01) (P 0.05). Inferred maximal ATP synthesis rate improved by 33% with oxygen in MM (21 +/- 3 vs. 28 +/- 5 mmol/(l min), P 0.05). We conclude that oxygen therapy is associated with significant improvements in muscle metabolism in patients with MM. These data suggest that patients with MM could benefit from therapies which improve the provision of oxygen.
Publisher: Elsevier BV
Date: 11-2017
Location: Australia
Location: No location found
No related grants have been discovered for Simon Walker.