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Your search keyword '"Ward, Colin R."' showing total 151 results
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151 results on '"Ward, Colin R."'

1. Bicuspid Aortic Valve Disease with Early-Onset Complications: Characteristics and Aortic Outcomes.

Author

Selbst, Maximilian A., Ward, Colin R., Svetgoff, Megan L., Michelena, Hector I., Sabate-Rotes, Anna, De Backer, Julie, Mosquera, Laura Muiño, Yetman, Anji T., Bissell, Malenka M., Andreassi, Maria Grazia, Foffa, Ilenia, Hui, Dawn S., Caffarelli, Anthony, Kim, Yuli Y., Guo, Dongchuan, Citro, Rodolfo, De Marco, Margot, Tretter, Justin T., Morris, Shaine A., and McBride, Kim L.

Subjects
*CONGENITAL heart disease, *YOUNG adults, *THORACIC aneurysms, *MITRAL valve, *AORTIC valve diseases
Abstract

Bicuspid aortic valve (BAV) is the most common congenital heart malformation in adults, but it can also cause childhood-onset complications. The presentation and clinical course of young adults who present due to BAV complications are relatively uncharacterized. In a multicenter study, we found that young people who experience significant complications related to BAV disease before age 30 are distinguished from the majority of BAV cases that manifest after age 50 by a relatively severe clinical course, with higher rates of surgical interventions, more frequent second interventions, and a greater burden of congenital heart malformations. These observations highlight the need for prompt recognition, regular lifelong surveillance, and targeted interventions to address the significant health burdens of patients with early-onset BAV complications. [ABSTRACT FROM AUTHOR]

Published
2024
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5. Valuable elements in Chinese coals: a review

Author

Dai, Shifeng, primary, Yan, Xiaoyun, additional, Ward, Colin R., additional, Hower, James C., additional, Zhao, Lei, additional, Wang, Xibo, additional, Zhao, Lixin, additional, Ren, Deyi, additional, and Finkelman, Robert B., additional

Published
2020
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39. Evaluation of mineral matter transformations in low-temperature ashes of South African coal feedstock samples and their density separated cuts using high-temperature X-ray diffraction

Author

20682972 - Strydom, Christiena Adriana, 20164200 - Bunt, John Reginald, 21166625 - Matjie, Ratale Henry, 21667373 - Rautenbach, Rudelle, Rautenbach, Rudelle, Matjie, Ratale H., Strydom, Christien A., Bunt, John R., Ward, Colin R., 20682972 - Strydom, Christiena Adriana, 20164200 - Bunt, John Reginald, 21166625 - Matjie, Ratale Henry, 21667373 - Rautenbach, Rudelle, Rautenbach, Rudelle, Matjie, Ratale H., Strydom, Christien A., Bunt, John R., and Ward, Colin R.

Abstract

Coal mineral matter is the leading cause of inevitable ash problems (fouling and slagging) during the combustion of coal. Low-temperature ash (LTA) samples of feed coals and the density separated fractions were subjected to high-temperature X-ray diffraction (HT-XRD) to identify the mineral reactions occurred at elevated temperatures under oxidizing conditions. Excluded minerals were mainly contained in the sink fractions, while included minerals were mainly present in the float fractions. QEMSCAN results indicate that the mineral associations in carbominerites and included minerals in Feeds A, B and C and sinks B and C are responsible for the melt formation during HT-XRD experiments. HT-XRD results indicate the presence of mullite, anorthite, and amorphous aluminosilicate materials formed in the thermally treated LTA samples. The formation of these slagging crystalline and glassy phases could be attributed to either crystallization during the cooling of the molten solution, or via solid-state reactions at elevated temperatures. A comprehensive knowledge of the included and excluded minerals can be used to prepare a blended feedstock for combustion processes. The operational ash-related problems in the combustion and gasification processes could be minimized by implementing this comprehensive knowledge of the transformation of coal minerals at elevated temperatures

Published
2020

42. Corrigendum: Earliest signs of life on land preserved in ca. 3.5 Ga hot spring deposits

Author

Djokic, Tara, Van Kranendonk, Martin J., Campbell, Kathleen A., Walter, Malcolm R., and Ward, Colin R.

Subjects
Corrigenda, Article
Abstract

The ca. 3.48 Ga Dresser Formation, Pilbara Craton, Western Australia, is well known for hosting some of Earth’s earliest convincing evidence of life (stromatolites, fractionated sulfur/carbon isotopes, microfossils) within a dynamic, low-eruptive volcanic caldera affected by voluminous hydrothermal fluid circulation. However, missing from the caldera model were surface manifestations of the volcanic-hydrothermal system (hot springs, geysers) and their unequivocal link with life. Here we present new discoveries of hot spring deposits including geyserite, sinter terracettes and mineralized remnants of hot spring pools/vents, all of which preserve a suite of microbial biosignatures indicative of the earliest life on land. These include stromatolites, newly observed microbial palisade fabric and gas bubbles preserved in inferred mineralized, exopolymeric substance. These findings extend the known geological record of inhabited terrestrial hot springs on Earth by ∼3 billion years and offer an analogue in the search for potential fossil life in ancient Martian hot springs., Some of the earliest life on Earth flourished in terrestrial hot springs. Here, the authors present evidence for ca. 3.5 Ga hot spring deposits from the Dresser Formation, Pilbara Craton, Australia, that host some of the earliest known life in the form of stromatolites and other microbial biosignatures.

Published
2017

43. Discussion of 'roofing slate standards: a critical review' by V. Cardenes et al. [Construction and Building Materials 115(2016) 93-104]

Author

Gomez-Fernandez, Fernando, Herrero-Hernandez, Antonio, Ward, Colin R., and Castanon, Ana Maria

Subjects
Concrete -- Analysis -- Mechanical properties, Roofing -- Analysis, Business, Construction and materials industries
Abstract

The paper by Cardenes et al. [1] reviews the roofing slate standards of different countries, analysing and comparing the current methods of testing. This is always an important and interesting [...]

Published
2017
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44. Evaluation of mineral matter transformations in low-temperature ashes of South African coal feedstock samples and their density separated cuts using high-temperature X-ray diffraction.

Author

Rautenbach, Rudelle, Matjie, Ratale H., Strydom, Christien A., Bunt, John R., Ward, Colin R., French, David, and Van Alphen, Chris

Subjects
X-ray diffraction, COAL sampling, COAL combustion, HIGH temperatures, AMORPHOUS substances
Abstract

Coal mineral matter is the leading cause of inevitable ash problems (fouling and slagging) during the combustion of coal. Low-temperature ash (LTA) samples of feed coals and the density separated fractions were subjected to high-temperature X-ray diffraction (HT-XRD) to identify the mineral reactions occurred at elevated temperatures under oxidizing conditions. Excluded minerals were mainly contained in the sink fractions, while included minerals were mainly present in the float fractions. QEMSCAN results indicate that the mineral associations in carbominerites and included minerals in Feeds A, B and C and sinks B and C are responsible for the melt formation during HT-XRD experiments. HT-XRD results indicate the presence of mullite, anorthite, and amorphous aluminosilicate materials formed in the thermally treated LTA samples. The formation of these slagging crystalline and glassy phases could be attributed to either crystallization during the cooling of the molten solution, or via solid-state reactions at elevated temperatures. A comprehensive knowledge of the included and excluded minerals can be used to prepare a blended feedstock for combustion processes. The operational ash-related problems in the combustion and gasification processes could be minimized by implementing this comprehensive knowledge of the transformation of coal minerals at elevated temperatures. [ABSTRACT FROM AUTHOR]

Published
2020
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49. Valuable elements in Chinese coals: a review

Author

Dai, Shifeng, primary, Yan, Xiaoyun, additional, Ward, Colin R., additional, Hower, James C., additional, Zhao, Lei, additional, Wang, Xibo, additional, Zhao, Lixin, additional, Ren, Deyi, additional, and Finkelman, Robert B., additional

Published
2016
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50. Valuable elements in Chinese coals: a review.

Author

Dai, Shifeng, Yan, Xiaoyun, Ward, Colin R., Hower, James C., Zhao, Lei, Wang, Xibo, Zhao, Lixin, Ren, Deyi, and Finkelman, Robert B.

Subjects
COAL industry, RARE earth metals, COAL combustion, COAL products, ORE deposits
Abstract

China is, and in the coming decades should continue to be, the largest producer and user of coal in the world. The high volume of coal usage in China has focused attention not only on the toxic trace elements that may be released from coal combustion but also on the valuable elements that may occur in the coal and associated ash. Valuable elements in several coals (or coal ashes) and some coal-bearing strata in China (e.g. Ge, Ga, U, rare earth elements and Y, Nb, Zr, Se, V, Re, Au, and Ag, as well as the base metal Al) occur at concentrations comparable to or even higher than those in conventional economic deposits. Several factors are responsible for these elevated concentrations: (1) injection of exfiltrational solutions during peat accumulation or as part of later epigenetic activity; (2) injection of infiltrational epigenetic solutions; (3) introduction of syngenetic alkali volcanic ashes into the peat-forming environment or into associated non-coal-forming terrestrial environments; (4) input of terrigenous materials into the coal-forming environment; (5) leaching of non-coal partings by groundwater/hydrothermal solutions; and (6) mixed processes involving both hydrothermal solutions and volcanic ash. The valuable elements in Chinese coals may be associated with either the organic matter or mineral matter, or have a mixed organic- and inorganic-affinity. For example, the Ge and U in coal-hosted ore deposits dominantly occur in the organic matter, with only traces of U-bearing minerals being present; gallium mainly occurs in boehmite and kaolinite, and to a lesser extent, in the organic matter. Rare earth elements and Y occur as carbonate-minerals (e.g. florencite, parisite), phosphate-minerals (e.g. rhabdophane, silico-rhabdophane, and xenotime), and in part are associated with the organic matter. Some metals (e.g. Ge, Al, Ga) have been successfully extracted at an industrial scale from Chinese coals, and others have significant potential for such extraction. Major challenges remaining for coal scientists include the development of economic extraction methods from coal ash, and the control of toxic elements released during the metal extraction process to protect human health and to avoid environmental pollution. [ABSTRACT FROM AUTHOR]

Published
2018
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