Author
Jorge D. Abad
Other affiliations: University of Engineering and Technology, Lahore, University of Illinois at Urbana–Champaign, Pontifical Catholic University of Peru
Bio: Jorge D. Abad is an academic researcher from University of Pittsburgh. The author has contributed to research in topics: Meander & Turbulence. The author has an hindex of 24, co-authored 71 publications receiving 3075 citations. Previous affiliations of Jorge D. Abad include University of Engineering and Technology, Lahore & University of Illinois at Urbana–Champaign.
Topics: Meander, Turbulence, Bank erosion, Beach morphodynamics, Bedform
Papers published on a yearly basis
Papers
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TL;DR: Improved understanding of the fate and transport of contaminants of concern and increased long-term monitoring and data dissemination will help effectively manage water-quality risks associated with unconventional gas industry today and in the future.
Abstract: Unconventional natural gas resources offer an opportunity to access a relatively clean fossil fuel that could potentially lead to energy independence for some countries. Horizontal drilling and hydraulic fracturing make the extraction of tightly bound natural gas from shale formations economically feasible. These technologies are not free from environmental risks, however, especially those related to regional water quality, such as gas migration, contaminant transport through induced and natural fractures, wastewater discharge, and accidental spills. We review the current understanding of environmental issues associated with unconventional gas extraction. Improved understanding of the fate and transport of contaminants of concern and increased long-term monitoring and data dissemination will help manage these water-quality risks today and in the future.
1,263 citations
TL;DR: In this article, a morphodynamic model for river meander migration is presented, in which separate relations are developed for the migration of the eroding bank and the depositing bank.
Abstract: Many models of river meander migration rely upon a simple formalism, whereby the eroding bank is cut back at a rate that is dictated by the flow, and the depositing bank then migrates passively in response, so as to maintain a constant bankfull channel width. Here a new model is presented, in which separate relations are developed for the migration of the eroding bank and the depositing bank. It is assumed that the eroding bank consists of a layer of fine-grained sediment that is cohesive and/or densely riddled with roots, underlain by a purely noncohesive layer of sand and/or gravel. Following erosion of the noncohesive layer, the cohesive layer fails in the form of slump blocks, which armor the noncohesive layer and thereby moderate the erosion rate. If the slump block material breaks down or is fluvially entrained, the protection it provides for the noncohesive layer diminishes and bank erosion is renewed. Renewed bank erosion, however, rejuvenates slump block armoring. At the depositing bank, it is assumed that all the sediment delivered to the edge of vegetation due to the transverse component of sediment transport is captured by encroaching vegetation, which is not removed by successive floods. Separate equations describing the migration of the eroding and depositing banks are tied to a standard morphodynamic formulation for the evolution of the flow and bed in the central region of the channel. In this model, the river evolves toward maintenance of roughly constant bankfull width as it migrates only to the extent that the eroding bank and depositing bank ‘talk’ to each other via the medium of the morphodynamics of the channel center region. The model allows for both (a) migration for which erosion widens the channel, forcing deposition at the opposite bank, and (b) migration for which deposition narrows the channel forcing erosion at the opposite bank. Copyright © 2010 John Wiley & Sons, Ltd.
282 citations
TL;DR: For example, the authors found that only rare evidence of contamination of surface and groundwaters in Pennsylvania showed that incidents that impact PA waters have been relatively rare and that contaminants were quickly diluted; however, firm conclusions are hampered by the lack of information about location and timing of incidents due to liability or confidentiality agreements.
262 citations
TL;DR: In this article, the authors present a new approach that calculates rates of river meander migration using physically-based streambank erosion formulations, which can capture the complex long-term migration patterns of natural channels which cannot be merely predicted from hydrodynamics only.
127 citations
TL;DR: In this paper, the effect of bend orientation on bed morphodynamics in a periodic, asymmetric, Kinoshita meandering channel was investigated. But the results were limited to the case of bends oriented upstream valley, whereas for the case with bends oriented downstream valley they are observed around the upstream inflection point, and the downstream-skewed condition produces the deepest scour region, which is located downstream of the bend apex.
Abstract: [1] Experiments carried out under flat smooth bed condition in a periodic, asymmetric, Kinoshita meandering channel showed that bend skewness controls the three-dimensional mean flow (e.g., primary and secondary flow) and turbulence structure (e.g., location of shear layers and turbulent shear stresses). In this paper, similar hydraulic conditions are used to perform movable-bed experiments with uniform sediment size in order to study the effect of bend orientation on bed morphodynamics. Two main differences between the upstream- and downstream-skewed meander configurations are found: (1) for the case of bends oriented upstream valley, the bed forms are produced just upstream of the bend apex, whereas for the case of bends oriented downstream valley they are observed around the upstream inflection point, and (2) the downstream-skewed condition produces the deepest scour region, which is located downstream of the bend apex. A comparison with observations at two bends on the Wabash River, Illinois, shows some remarkable similarities with the bed morphology observed in the Kinoshita channel. Further analysis of the bed form celerity, bed load transport during evolution, and superimposition of migrating bed forms and their implications on bend migration are presented.
121 citations
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28 Jul 2005
TL;DR: PfPMP1）与感染红细胞、树突状组胞以及胎盘的单个或多个受体作用，在黏附及免疫逃避中起关键的作�ly.
Abstract: 抗原变异可使得多种致病微生物易于逃避宿主免疫应答。表达在感染红细胞表面的恶性疟原虫红细胞表面蛋白1（PfPMP1）与感染红细胞、内皮细胞、树突状细胞以及胎盘的单个或多个受体作用，在黏附及免疫逃避中起关键的作用。每个单倍体基因组var基因家族编码约60种成员，通过启动转录不同的var基因变异体为抗原变异提供了分子基础。
18,940 citations
TL;DR: In this article, molecular-level design approaches for membrane materials, focusing on how these materials address the urgent requirements of water treatment applications, are reviewed for water scarcity and the pollution of aquatic environments.
Abstract: Membranes have an increasingly important role in alleviating water scarcity and the pollution of aquatic environments. Promising molecular-level design approaches are reviewed for membrane materials, focusing on how these materials address the urgent requirements of water treatment applications.
1,900 citations
TL;DR: Improved understanding of the fate and transport of contaminants of concern and increased long-term monitoring and data dissemination will help effectively manage water-quality risks associated with unconventional gas industry today and in the future.
Abstract: Unconventional natural gas resources offer an opportunity to access a relatively clean fossil fuel that could potentially lead to energy independence for some countries. Horizontal drilling and hydraulic fracturing make the extraction of tightly bound natural gas from shale formations economically feasible. These technologies are not free from environmental risks, however, especially those related to regional water quality, such as gas migration, contaminant transport through induced and natural fractures, wastewater discharge, and accidental spills. We review the current understanding of environmental issues associated with unconventional gas extraction. Improved understanding of the fate and transport of contaminants of concern and increased long-term monitoring and data dissemination will help manage these water-quality risks today and in the future.
1,263 citations
TL;DR: Analysis of published data reveals evidence for stray gas contamination, surface water impacts in areas of intensive shale gas development, and the accumulation of radium isotopes in some disposal and spill sites.
Abstract: The rapid rise of shale gas development through horizontal drilling and high volume hydraulic fracturing has expanded the extraction of hydrocarbon resources in the U.S. The rise of shale gas development has triggered an intense public debate regarding the potential environmental and human health effects from hydraulic fracturing. This paper provides a critical review of the potential risks that shale gas operations pose to water resources, with an emphasis on case studies mostly from the U.S. Four potential risks for water resources are identified: (1) the contamination of shallow aquifers with fugitive hydrocarbon gases (i.e., stray gas contamination), which can also potentially lead to the salinization of shallow groundwater through leaking natural gas wells and subsurface flow; (2) the contamination of surface water and shallow groundwater from spills, leaks, and/or the disposal of inadequately treated shale gas wastewater; (3) the accumulation of toxic and radioactive elements in soil or stream sediments near disposal or spill sites; and (4) the overextraction of water resources for high-volume hydraulic fracturing that could induce water shortages or conflicts with other water users, particularly in water-scarce areas. Analysis of published data (through January 2014) reveals evidence for stray gas contamination, surface water impacts in areas of intensive shale gas development, and the accumulation of radium isotopes in some disposal and spill sites. The direct contamination of shallow groundwater from hydraulic fracturing fluids and deep formation waters by hydraulic fracturing itself, however, remains controversial.
1,255 citations