52 research outputs found
Modeling of Acid Fracturing in Carbonate Reservoirs
The acid fracturing process is a thermal, hydraulic, mechanical, and geochemical (THMG)-coupled phenomena in which the behavior of these variables are interrelated. To model the flow behavior of an acid into a fracture, mass and momentum balance equations are used to draw 3D velocity and pressure profiles. Part of the fluid diffuses or leaks off into the fracture walls and dissolves part of the fracture face according to the chemical reaction below.
2H^(+)(aq) + CO((2-)/3) → H_(2 )CO_(3)(aq) → CO_(2)(g) + H_(2)O (l)
An acid balance equation is used to draw the concentration profile of the acid and to account for the quantity of rock dissolved. An algorithm is developed for this process to generate the final conductivity distribution after fracture closure. The objective of modeling acid fracturing is to determine the optimum condition that results in a petroleum production rate increase.
The conductivity value and acid penetration distance both affect the final production rate from a fracture. Treatment parameters are simulated to draw a conclusion about the effect of each on the conductivity and acid penetration distance. The conductivity distribution file from an acid fracturing simulator is imported into the ECLIPSE reservoir simulator to estimate the production rate. Reservoir permeability is the determining factor when choosing between a high- conductivity value and a long penetration distance.
For the model to be more accurate, it needs to be coupled with heat transfer and geomechanical models. Many simulation cases cannot be completed because of numerical errors resulting from the hydraulic model (Navier-Stokes equations). The greatest challenge for the simulator before coupling it with any other phenomena is building a more stable hydraulic solution
Copper selenide film electrodes prepared by combined electrochemical/chemical bath depositions with high photo-electrochemical conversion efficiency and stability
Copper selenide (of the type Cu2-xSe) film electrodes, prepared by combined electrochemical (ECD)
followed by chemical bath deposition (CBD), may yield high photo-electrochemical (PEC) conversion
efficiency (~14.6%) with no further treatment. The new ECD/CBD-copper selenide film electrodes show
enhanced PEC characteristics and exhibit high stability under PEC conditions, compared to the ECD or the
CBD films deposited separately. The electrodes combine the advantages of both ECD-copper selenide
electrodes (in terms of good adherence to FTO surface and high surface uniformity) and CBD-copper
selenide electrodes (suitable film thickness). Effect of annealing temperature, on the ECD/CBD film
electrode composition and efficiency, is discussed.The results of this work are partly based on K. Murtada M.Sc.
Thesis, under direct supervision of H.S. Hilal. Other experimental
measurements and calculations, including dark current experiments,
film thickness measurement, electrical conductivity, SEM
analysis, XRD &AFM analysis revisions were performed by A. Zyoud
after the thesis completion. Additional film electrode stability experiments
under PEC conditions, were also performed by A. Zyoud
after the Thesis completion. SEM micrographs and EDX spectra
were measured by T.W. Kim and H-J.C. at the KIER, Korea. The XRD
patterns were measured by D-H. Park and H. Kwon at PUK. M.H.S.
Helal and H. Bsharat contributed with literature search, discussions
and modeling. M. Faroun measured AFM micrographs at Al-Quds
University. H.S. Hilal acknowledges financial support from ANU,
Islamic Development Bank, Al-Maqdisi Project and Union of Arab
Universities. T.W. Kim and H-J. Choi acknowledge financial support
from the framework of the Research and Development Program of
the Korea Institute of Energy Research (B6-2523)
Paradoxical aortic stiffening and subsequent cardiac dysfunction in Hutchinson-Gilford progeria syndrome
[EN] Hutchinson-Gilford progeria syndrome (HGPS) is an ultra-rare disorder with devastating sequelae resulting in early death, presently thought to stem primarily from cardiovascular events. We analyse novel longitudinal cardiovascular data from a mouse model of HGPS (Lmna(G609G/G609G)) using allometric scaling, biomechanical phenotyping, and advanced computational modelling and show that late-stage diastolic dysfunction, with preserved systolic function, emerges with an increase in the pulse wave velocity and an associated loss of aortic function, independent of sex. Specifically, there is a dramatic late-stage loss of smooth muscle function and cells and an excessive accumulation of proteoglycans along the aorta, which result in a loss of biomechanical function (contractility and elastic energy storage) and a marked structural stiffening despite a distinctly low intrinsic material stiffness that is consistent with the lack of functional lamin A. Importantly, the vascular function appears to arise normally from the low-stress environment of development, only to succumb progressively to pressure-related effects of the lamin A mutation and become extreme in the peri-morbid period. Because the dramatic life-threatening aortic phenotype manifests during the last third of life there may be a therapeutic window in maturity that could alleviate concerns with therapies administered during early periods of arterial development.This work was supported, in part, by grants from the US National Institutes of Health: R01 HL105297 (J.D.H.) and P01 HL134605 (Dan Rifkin) and R01 AG047632 and R33 ES025636 (G.S.S.)Murtada, SI.; Kawamura, Y.; Caulk, AW.; Ahmadzadeh, H.; Mikush, N.; Zimmerman, K.; Kavanagh, D.... (2020). Paradoxical aortic stiffening and subsequent cardiac dysfunction in Hutchinson-Gilford progeria syndrome. Journal of The Royal Society Interface. 17(166):1-12. https://doi.org/10.1098/rsif.2020.00661121716
Excessive adventitial stress drives inflammation-mediated fibrosis in hypertensive aortic remodelling in mice
Hypertension induces significant aortic remodeling, often adaptive but sometimes not. To identify immuno-mechanical mechanisms responsible for differential remodeling, we studied thoracic aortas from 129S6/SvEvTac and C57BL/6J mice before and after continuous 14-day angiotensin II infusion, which elevated blood pressure similarly in both strains. Histological and biomechanical assessments of excised vessels were similar at baseline, suggesting a common homeostatic set-point for mean wall stress. Histology further revealed near mechano-adaptive remodeling of the hypertensive 129S6/SvEvTac aortas, but grossly maladaptive remodeling of C57BL/6J aortas. Bulk RNA sequencing suggested that increased smooth muscle contractile processes promoted mechano-adaptation of 129S6/SvEvTac aortas while immune processes prevented adaptation of C57BL/6J aortas. Functional studies confirmed an increased vasoconstrictive capacity of the former while immunohistochemistry demonstrated marked increases in inflammatory cells in the latter. We then used multiple computational biomechanical models to test the hypothesis that excessive adventitial wall stress correlates with inflammatory cell infiltration. These models consistently predicted that increased vasoconstriction against an increased pressure coupled with modest deposition of new matrix thickens the wall appropriately, restoring wall stress toward homeostatic consistent with adaptive remodeling. In contrast, insufficient vasoconstriction permits high wall stresses and exuberant inflammation-driven matrix deposition, especially in the adventitia, reflecting compromised homeostasis and gross maladaptation
Is the Public willing to help the Nigerian Police during the Boko Haram crisis? A look at moderating factors.
This paper sought the opinion of 200 Nigerians on their willingness to cooperate with the Police during the Boko Haram crisis. Public perceptions of Police effectiveness during the crisis, residence location, gender and religious affiliation were used as moderators. Data was analysed using an explanatory factor analysis and structural equation modelling. Results indicated a strong association between perceived effectiveness and willingness to report to the Police with respondents who question the effectiveness of the Police being less likely to be willing to report criminal activity about Boko Haram. Further to this, the impact of religion on willingness to report was at least partially mediated by perceived effectiveness of the Police with the results showing that Christian respondents perceived the Police as less effective. Females and those living in the North were significantly less willing to report criminal activity to the Police The findings are then discussed in relation to the BH crises and directions for future research are given
Pharmacologically Improved Contractility Protects Against Aortic Dissection in Mice With Disrupted Transforming Growth Factor-β Signaling Despite Compromised Extracellular Matrix Properties
Reduced Biaxial Contractility in the Descending Thoracic Aorta of Fibulin-5 Deficient Mice
The precise role of smooth muscle cell contractility in elastic arteries remains unclear, but accumulating evidence suggests that smooth muscle dysfunction plays an important role in the development of thoracic aortic aneurysms and dissections (TAADs). Given the increasing availability of mouse models of these conditions, there is a special opportunity to study roles of contractility ex vivo in intact vessels subjected to different mechanical loads. In parallel, of course, there is a similar need to study smooth muscle contractility in models that do not predispose to TAADs, particularly in cases where disease might be expected. Multiple mouse models having compromised glycoproteins that normally associate with elastin to form medial elastic fibers present with TAADs, yet those with fibulin-5 deficiency do not. In this paper, we show that deletion of the fibulin-5 gene results in a significantly diminished contractility of the thoracic aorta in response to potassium loading despite otherwise preserved characteristic active behaviors, including axial force generation and rates of contraction and relaxation. Interestingly, this diminished response manifests around an altered passive state that is defined primarily by a reduced in vivo axial stretch. Given this significant coupling between passive and active properties, a lack of significant changes in passive material stiffness may help to offset the diminished contractility and thereby protect the wall from detrimental mechanosensing and its sequelae
Reduced Biaxial Contractility in the Descending Thoracic Aorta of Fibulin-5 Deficient Mice
The precise role of smooth muscle cell contractility in elastic arteries remains unclear, but accumulating evidence suggests that smooth muscle dysfunction plays an important role in the development of thoracic aortic aneurysms and dissections (TAADs). Given the increasing availability of mouse models of these conditions, there is a special opportunity to study roles of contractility ex vivo in intact vessels subjected to different mechanical loads. In parallel, of course, there is a similar need to study smooth muscle contractility in models that do not predispose to TAADs, particularly in cases where disease might be expected. Multiple mouse models having compromised glycoproteins that normally associate with elastin to form medial elastic fibers present with TAADs, yet those with fibulin-5 deficiency do not. In this paper, we show that deletion of the fibulin-5 gene results in a significantly diminished contractility of the thoracic aorta in response to potassium loading despite otherwise preserved characteristic active behaviors, including axial force generation and rates of contraction and relaxation. Interestingly, this diminished response manifests around an altered passive state that is defined primarily by a reduced in vivo axial stretch. Given this significant coupling between passive and active properties, a lack of significant changes in passive material stiffness may help to offset the diminished contractility and thereby protect the wall from detrimental mechanosensing and its sequelae
Reduced Biaxial Contractility in the Descending Thoracic Aorta of Fibulin-5 Deficient Mice
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