ORCID Profile
0000-0003-1061-3356
Current Organisation
University of Cape Town
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Publisher: Elsevier
Date: 2019
Publisher: MDPI AG
Date: 10-06-2021
DOI: 10.3390/JMSE9060647
Abstract: Frazil ice, consisting of loose disc-shaped ice crystals, is the first ice that forms in the annual cycle in the marginal ice zone (MIZ) of the Antarctic. A sufficient number of frazil ice crystals form the surface “grease ice” layer, playing a fundamental role in the freezing processes in the MIZ. As soon as the ocean waves are sufficiently d ed by a frazil ice cover, a closed ice cover can form. In this article, we investigate the rheological properties of frazil ice, which has a crucial influence on the growth of sea ice in the MIZ. An in situ test setup for measuring temperature and rheological properties was developed. Frazil ice shows shear thinning flow behavior. The presented measurements enable real-data-founded modelling of the annual ice cycle in the MIZ.
Publisher: Elsevier BV
Date: 11-2021
Publisher: Elsevier BV
Date: 02-2008
Publisher: Elsevier BV
Date: 02-2013
Publisher: Elsevier BV
Date: 10-2012
Publisher: Elsevier BV
Date: 10-2016
Publisher: Elsevier BV
Date: 03-2016
Publisher: Elsevier BV
Date: 05-2020
Publisher: Springer Berlin Heidelberg
Date: 2011
Publisher: CRC Press
Date: 15-08-2013
DOI: 10.1201/B15963-112
Publisher: Wiley
Date: 26-12-2013
DOI: 10.1002/CNM.2610
Abstract: Myocardial infarction is an increasing health problem worldwide. Because of an under-supply of blood, the cardiomyocytes in the affected region permanently lose their ability to contract. This in turn gradually weakens the overall heart function. A new therapeutic approach based on the injection of a gel into the infarcted area aims to support the healing and to inhibit adverse remodelling that can lead to heart failure. A computational model is the basis for obtaining a better understanding of the heart mechanics, in particular, how myocardial infarction and gel injections affect its pumping performance. A strain invariant-based stored energy function is proposed to account for the passive mechanical behaviour of the model, which also makes provision for active contraction. To incorporate injections an additive homogenization approach is introduced. The numerical framework is developed using an in-house code based on the element-free Galerkin method. The main focus of this contribution is to investigate the influence of gel injections on the mechanics of the left ventricle during the diastolic filling and systolic isovolumetric (isochoric) contraction phases. It is found that gel injections are able to reduce the elevated fibre stresses caused by an infarct.
Publisher: ACTAPRESS
Date: 2013
Publisher: Elsevier BV
Date: 2009
Publisher: CRC Press
Date: 31-08-2016
Publisher: Elsevier BV
Date: 05-2020
Publisher: Elsevier BV
Date: 2015
Publisher: Elsevier BV
Date: 06-2010
Publisher: Springer Science and Business Media LLC
Date: 11-07-2020
DOI: 10.1007/S10741-020-09993-1
Abstract: Rheumatic heart disease (RHD) is a major cause of cardiovascular morbidity and mortality in low- and middle-income countries, where living conditions promote spread of group A β-haemolytic streptococcus. Autoimmune reactions due to molecular mimicry of bacterial epitopes by host proteins cause acute rheumatic fever (ARF) and subsequent disease progression to RHD. Despite knowledge of the factors that predispose to ARF and RHD, determinants of the progression to valvular damage and the molecular events involved remain incompletely characterised. This review focuses on altered protein expression in heart valves, myocardial tissue and plasma of patients with RHD and pathogenic consequences on RHD. Proteins mainly involved in structural organization of the valve matrix, blood homeostasis and immune response were altered due to RHD pathogenesis. Study of secreted forms of these proteins may aid the development of non-invasive biomarkers for early diagnosis and monitoring outcomes in RHD. Valve replacement surgery, the single evidence-based strategy to improve outcomes in severe RHD, is costly, largely unavailable in low- and middle-income countries (LMIC) and requires specialised facilities. When diagnosed early, penicillin prophylaxis may be used to delay progression to severe valvular damage. Echocardiography and cardiovascular magnetic resonance and the standard imaging tools recommended to confirm early diagnosis remain largely unavailable and inaccessible in most LMIC and both require expensive equipment and highly skilled persons for manipulation as well as interpretation of results. Changes in protein expression in heart valves and myocardium are associated with progressive valvular deformation in RHD. Understanding these protein changes should shed more light on the mechanisms of pathogenicity, while secreted forms of these proteins may provide leads towards a biomarker for non-invasive early detection of RHD.
Publisher: CRC Press
Date: 31-08-2016
Publisher: CRC Press
Date: 31-08-2016
Publisher: Informa UK Limited
Date: 20-03-2007
Publisher: Elsevier BV
Date: 05-2020
Publisher: Copernicus GmbH
Date: 20-07-2022
Abstract: Abstract. As part of the 2019 Southern oCean seAsonal Experiment (SCALE) Winter Cruise of the South African icebreaker SA Agulhas II, first-year ice was s led at the advancing outer edge of the Antarctic marginal ice zone along a 150 km Good Hope Line transect. Ice cores were extracted from four solitary pancake ice floes of 1.83–2.95 m diameter and 0.37–0.45 m thickness as well as a 12×4 m pancake ice floe of 0.31–0.76 m thickness that was part of a larger consolidated pack ice domain. The ice cores were subsequently analysed for temperature, salinity, texture, anisotropic elastic properties and compressive strength. All ice cores from both solitary pancake ice floes and consolidated pack ice exhibited predominantly granular textures. The vertical distributions of salinity, brine volume and mechanical properties were significantly different for the two ice types. High salinity values of 12.6±4.9 PSU were found at the topmost layer of the solitary pancake ice floes but not for the consolidated pack ice. The uniaxial compressive strengths for pancake ice and consolidated pack ice were determined as 2.3±0.5 and 4.1±0.9 MPa, respectively. Young's and shear moduli in the longitudinal core direction of solitary pancake ice were obtained as 3.7±2.0 and 1.3±0.7 GPa, respectively, and of consolidated pack ice as 6.4±1.6 and 2.3±0.6 GPa, respectively. Comparing Young's and shear moduli measured in longitudinal and transverse core directions, a clear directional dependency was found, in particular for the consolidated pack ice.
Publisher: Elsevier BV
Date: 07-2013
Publisher: Copernicus GmbH
Date: 13-08-2021
DOI: 10.5194/TC-2021-209
Abstract: Abstract. As part of the 2019 Southern oCean seAsonal Experiment (SCALE) Winter Cruise of the South African icebreaker SA Agulhas II first-year ice was s led at the advancing outer edge of the Antarctic marginal ice zone along a 150 km-Good Hope Line transect. Ice cores were extracted from four solitary pancake ice floes of 1.83–2.95 m diameter and 0.37–0.45 m thickness as well as a 12 × 4 m2 pancake ice floe of 0.31–0.76 m thickness part of a larger consolidated pack ice domain. The ice cores were subsequently analyzed for temperature, salinity, texture, anisotropic elastic properties and compressive strength. All ice cores from both, solitary pancake ice floes and consolidated pack ice, exhibited predominantly granular textures. The vertical distributions of salinity, brine volume and mechanical properties were significantly different for the two ice types. High salinity values of 12.6 ± 4.9 PSU were found at the topmost layer of the solitary pancake ice floes but not for the consolidated pack ice. The uniaxial compressive strength for pancake ice and consolidated pack ice were determined as 2.3 ± 0.5 MPa and 4.1 ± 0.9 MPa, respectively. The Young’s and shear moduli in longitudinal core direction of solitary pancake ice were obtained as 3.7 ± 2.0 GPa and 1.3 ± 0.7 GPa, and for consolidated pack ice as 6.4 ± 1.6 GPa and 2.3 ± 0.6 GPa, respectively. Comparing Young’s and shear moduli measured in longitudinal and transverse core directions, a clear directional dependency was found, in particular for the consolidated pack ice.
Publisher: CRC Press
Date: 21-08-2019
Publisher: Elsevier BV
Date: 03-2009
Publisher: CRC Press
Date: 15-08-2013
DOI: 10.1201/B15963-81
Publisher: Wiley
Date: 02-02-2021
Publisher: MDPI AG
Date: 29-04-2021
Abstract: The marginal ice zone is a highly dynamical region where sea ice and ocean waves interact. Large-scale sea ice models only compute domain-averaged responses. As the majority of the marginal ice zone consists of mobile ice floes surrounded by grease ice, finer-scale modelling is needed to resolve variations of its mechanical properties, wave-induced pressure gradients and drag forces acting on the ice floes. A novel computational fluid dynamics approach is presented that considers the heterogeneous sea ice material composition and accounts for the wave-ice interaction dynamics. Results show, after comparing three realistic sea ice layouts with similar concentration and floe diameter, that the discrepancy between the domain-averaged temporal stress and strain rate evolutions increases for decreasing wave period. Furthermore, strain rate and viscosity are mostly affected by the variability of ice floe shape and diameter.
Publisher: Springer Vienna
Date: 2012
Publisher: American Geophysical Union (AGU)
Date: 12-06-2019
DOI: 10.1029/2019GL082457
Publisher: CRC Press
Date: 21-08-2019
Publisher: ECCOMAS
Date: 2013
Publisher: CRC Press
Date: 21-08-2019
No related grants have been discovered for Sebastian Skatulla.