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Computational fluid dynamics

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https://www.readbyqxmd.com/read/27917102/euler-lagrange-computational-fluid-dynamics-for-bio-reactor-scale-down-an-analysis-of-organism-lifelines
#1
Cees Haringa, Wenjun Tang, Amit T Deshmukh, Jianye Xia, Matthias Reuss, Joseph J Heijnen, Robert F Mudde, Henk J Noorman
The trajectories, referred to as lifelines, of individual microorganisms in an industrial scale fermentor under substrate limiting conditions were studied using an Euler-Lagrange computational fluid dynamics approach. The metabolic response to substrate concentration variations along these lifelines provides deep insight in the dynamic environment inside a large-scale fermentor, from the point of view of the microorganisms themselves. We present a novel methodology to evaluate this metabolic response, based on transitions between metabolic "regimes" that can provide a comprehensive statistical insight in the environmental fluctuations experienced by microorganisms inside an industrial bioreactor...
October 2016: Engineering in Life Sciences
https://www.readbyqxmd.com/read/27913993/antifreeze-glycopeptides-from-structure-and-activity-studies-to-current-approaches-in-chemical-synthesis
#2
REVIEW
Małgorzata Urbańczyk, Jerzy Góra, Rafał Latajka, Norbert Sewald
Antifreeze glycopeptides (AFGPs) are a class of biological antifreeze agents found predominantly in Arctic and Antarctic species of fish. They possess the ability to regulate ice nucleation and ice crystal growth, thus creating viable life conditions at temperatures below the freezing point of body fluids. AFGPs usually consist of 4-55 repetitions of the tripeptide unit Ala-Ala-Thr that is O-glycosylated at the threonine side chains with β-D-galactosyl-(1 → 3)-α-N-acetyl-D-galactosamine. Due to their interesting properties and high antifreeze activity, they have many potential applications, e...
December 2, 2016: Amino Acids
https://www.readbyqxmd.com/read/27908677/haemodynamic-variations-of-flow-to-renal-arteries-in-custom-made-and-pivot-branch-fenestrated-endografting
#3
J Ou, A Y S Tang, T L Chiu, K W Chow, Y C Chan, S W K Cheng
OBJECTIVE: This study aimed to investigate variation of blood flow to renal arteries in custom-made and pivot branch (p-branch) fenestrated endografting, using a computational fluid dynamics (CFD) technique. METHODS: Idealised models of custom-made and p-branch fenestrated grafting were constructed on a basis of a 26 mm stent graft. The custom-made fenestration was designed with a 6 mm diameter, while the 5 mm depth renal p-branch was created with a 6 mm inner and 15 mm outer fenestration...
November 28, 2016: European Journal of Vascular and Endovascular Surgery
https://www.readbyqxmd.com/read/27905492/high-fidelity-computational-simulation-of-thrombus-formation-in-thoratec-heartmate-ii-continuous-flow-ventricular-assist-device
#4
Wei-Tao Wu, Fang Yang, Jingchun Wu, Nadine Aubry, Mehrdad Massoudi, James F Antaki
Continuous flow ventricular assist devices (cfVADs) provide a life-saving therapy for severe heart failure. However, in recent years, the incidence of device-related thrombosis (resulting in stroke, device-exchange surgery or premature death) has been increasing dramatically, which has alarmed both the medical community and the FDA. The objective of this study was to gain improved understanding of the initiation and progression of thrombosis in one of the most commonly used cfVADs, the Thoratec HeartMate II...
December 1, 2016: Scientific Reports
https://www.readbyqxmd.com/read/27904980/a-resolved-two-way-coupled-cfd-6-dof-approach-for-predicting-embolus-transport-and-the-embolus-trapping-efficiency-of-ivc-filters
#5
Kenneth I Aycock, Robert L Campbell, Keefe B Manning, Brent A Craven
Inferior vena cava (IVC) filters are medical devices designed to provide a mechanical barrier to the passage of emboli from the deep veins of the legs to the heart and lungs. Despite decades of development and clinical use, IVC filters still fail to prevent the passage of all hazardous emboli. The objective of this study is to (1) develop a resolved two-way computational model of embolus transport, (2) provide verification and validation evidence for the model, and (3) demonstrate the ability of the model to predict the embolus-trapping efficiency of an IVC filter...
November 30, 2016: Biomechanics and Modeling in Mechanobiology
https://www.readbyqxmd.com/read/27902924/simple-mechanisms-of-early-life-simulation-model-on-the-origin-of-semi-cells
#6
Adrian Klein, Martin Bock, Wolfgang Alt
The development of first cellular structures played an important role in the early evolution of life. Early evolution of life probably took place on a molecular level in a reactive environment. The iron-sulfur theory postulates the formation of cell-like structures on catalytic surfaces. Experiments show that H2S together with FeS and other metallic centers drive auto-catalytic surface reactions, in which organic molecules such as pyruvic and amino acids occur. It is questionable which mechanisms are needed to form cell-like structures under these conditions...
November 27, 2016: Bio Systems
https://www.readbyqxmd.com/read/27901333/fractional-flow-reserve-lessons-from-platform-and-future-perspectives
#7
Gianluca Pontone, Patrizia Carità, Massimo Verdecchia, Dario Buccheri, Daniele Andreini, Andrea I Guaricci, Mark Rabbat, Mauro Pepi
In the treatment of stable coronary artery disease (CAD) the identification of patients who may gain the highest benefit from further invasive treatments is of pivotal importance for the healthcare system. In this setting, it has been established that an ischemia-guided revascularization strategy yields improved clinical outcomes in a cost- effective fashion compared with anatomy-guided revascularization alone. Invasive fractional flow reserve (FFR) is considered the gold standard, especially in the intermediate-range atherosclerotic lesions, for assessing lesion specific ischemia at the time of invasive coronary angiography and has now become the standard of reference for studies assessing the diagnostic performance of the various non-invasive stress tests...
November 30, 2016: Minerva Cardioangiologica
https://www.readbyqxmd.com/read/27893059/the-localized-hemodynamics-of-drug-eluting-stents-are-not-improved-by-the-presence-of-magnetic-struts
#8
P R S Vijayaratnam, T J Barber, J A Reizes
The feasibility of implementing magnetic struts into drug-eluting stents (DESs) to mitigate the adverse hemodynamics which precipitate stent thrombosis is examined. These adverse hemodynamics include platelet-activating high wall shear stresses (WSS) and endothelial dysfunction-inducing low wall shear stresses. By magnetizing the stent struts, two forces are induced on the surrounding blood: (1) magnetization forces which reorient red blood cells to align with the magnetic field and (2) Lorentz forces which oppose the motion of the conducting fluid...
January 1, 2017: Journal of Biomechanical Engineering
https://www.readbyqxmd.com/read/27891248/synchrotron-4-dimensional-imaging-of-two-phase-flow-through-porous-media
#9
F H Kim, D Penumadu, P Patel, X Xiao, E J Garboczi, S P Moylan, M A Donmez
Near real-time visualization of complex two-phase flow in a porous medium was demonstrated with dynamic 4-dimensional (4D) (3D + time) imaging at the 2-BM beam line of the Advanced Photon Source (APS) at Argonne National Laboratory. Advancing fluid fronts through tortuous flow paths and their interactions with sand grains were clearly captured, and formations of air bubbles and capillary bridges were visualized. The intense X-ray photon flux of the synchrotron facility made 4D imaging possible, capturing the dynamic evolution of both solid and fluid phases...
2016: MRS Adv
https://www.readbyqxmd.com/read/27891172/vortex-analysis-of-intra-aneurismal-flow-in-cerebral-aneurysms
#10
Kevin Sunderland, Christopher Haferman, Gouthami Chintalapani, Jingfeng Jiang
This study aims to develop an alternative vortex analysis method by measuring structure ofIntracranial aneurysm (IA) flow vortexes across the cardiac cycle, to quantify temporal stability of aneurismal flow. Hemodynamics were modeled in "patient-specific" geometries, using computational fluid dynamics (CFD) simulations. Modified versions of known λ2 and Q-criterion methods identified vortex regions; then regions were segmented out using the classical marching cube algorithm. Temporal stability was measured by the degree of vortex overlap (DVO) at each step of a cardiac cycle against a cycle-averaged vortex and by the change in number of cores over the cycle...
2016: Computational and Mathematical Methods in Medicine
https://www.readbyqxmd.com/read/27890537/computational-fluid-dynamics-modeling-of-contrast-transport-in-basilar-aneurysms-following-flow-altering-surgeries
#11
Alireza Vali, Adib A Abla, Michael T Lawton, David Saloner, Vitaliy L Rayz
In vivo measurement of blood velocity fields and flow descriptors remains challenging due to image artifacts and limited resolution of current imaging methods; however, in vivo imaging data can be used to inform and validate patient-specific computational fluid dynamics (CFD) models. Image-based CFD can be particularly useful for planning surgical interventions in complicated cases such as fusiform aneurysms of the basilar artery, where it is crucial to alter pathological hemodynamics while preserving flow to the distal vasculature...
November 11, 2016: Journal of Biomechanics
https://www.readbyqxmd.com/read/27889286/computational-fluid-analysis-of-symptomatic-chronic-type-b-aortic-dissections-managed-with-the-streamliner-multilayer-flow-modulator
#12
Florian Stefanov, Sherif Sultan, Liam Morris, Ala Elhelali, Edel P Kavanagh, Violet Lundon, Mohamed Sultan, Niamh Hynes
OBJECTIVE: Managing symptomatic chronic type B aortic dissection (SCTBAD) by the Streamliner Multilayer Flow Modulator (SMFM) stent (Cardiatis, Isnes, Belgium) is akin to provisional structural support to induce complete attachment of the dissection flap, but with the ability of aortic remolding. This study investigated the SMFM's capability to enact healing of SCTBAD. METHODS: Clinical data for 12 cases comprising preoperative and postoperative treatment of SCTBAD were obtained from a multicenter database hosted by the Multilayer Flow Modulator Global Registry, Ireland...
November 23, 2016: Journal of Vascular Surgery
https://www.readbyqxmd.com/read/27888933/review-on-modeling-heat-transfer-and-thermoregulatory-responses-in-human-body
#13
REVIEW
Ming Fu, Wenguo Weng, Weiwang Chen, Na Luo
Several mathematical models of human thermoregulation have been developed, contributing to a deep understanding of thermal responses in different thermal conditions and applications. In these models, the human body is represented by two interacting systems of thermoregulation: the controlling active system and the controlled passive system. This paper reviews the recent research of human thermoregulation models. The accuracy and scope of the thermal models are improved, for the consideration of individual differences, integration to clothing models, exposure to cold and hot conditions, and the changes of physiological responses for the elders...
December 2016: Journal of Thermal Biology
https://www.readbyqxmd.com/read/27886512/angular-dynamics-of-a-small-particle-in-turbulence
#14
F Candelier, J Einarsson, B Mehlig
We compute the angular dynamics of a neutrally buoyant nearly spherical particle immersed in an unsteady fluid. We assume that the particle is small, that its translational slip velocity is negligible, and that unsteady and convective inertia are small perturbations. We derive an approximation for the torque on the particle that determines the first inertial corrections to Jeffery's equation. These corrections arise as a consequence of local vortex stretching and can be substantial in turbulence, where local vortex stretching is strong and closely linked to the irreversibility of turbulence...
November 11, 2016: Physical Review Letters
https://www.readbyqxmd.com/read/27885825/multiphase-fluid-solid-coupled-analysis-of-shock-bubble-stone-interaction-in-shockwave-lithotripsy
#15
K G Wang
A novel multiphase fluid-solid coupled computational framework is applied to investigate the interaction of a kidney stone immersed in liquid with a lithotripsy shock wave (LSW) and a gas bubble near the stone. The main objective is to elucidate the effects of a bubble in the shock path to the elastic and fracture behaviors of the stone. The computational framework couples a finite volume two-phase computational fluid dynamics (CFD) solver with a finite element (FE) computational solid dynamics (CSD) solver...
November 24, 2016: International Journal for Numerical Methods in Biomedical Engineering
https://www.readbyqxmd.com/read/27885707/spatial-resolution-and-velocity-field-improvement-of-4d-flow-mri
#16
Fraser M Callaghan, Stuart M Grieve
PURPOSE: 4D-flow MRI obtains a time-dependent 3D velocity field; however, its use for the calculation of higher-order parameters is limited by noise. We present an algorithm for denoising 4D-flow data. THEORY AND METHODS: By integrating a velocity field and eliminating streamlines in noisy flow, depicted by high curvature, a denoised dataset may be extracted. This method, defined as the velocity field improvement (VFIT) algorithm, was validated in an analytical dataset and using in vivo data in comparison with a computation fluid dynamics (CFD) simulation...
November 24, 2016: Magnetic Resonance in Medicine: Official Journal of the Society of Magnetic Resonance in Medicine
https://www.readbyqxmd.com/read/27882440/hemodynamic-changes-in-a-middle-cerebral-artery-aneurysm-at-follow-up-times-before-and-after-its-rupture-a-case-report-and-a-review-of-the-literature
#17
A Sejkorová, K D Dennis, H Švihlová, O Petr, G Lanzino, A Hejčl, D Dragomir-Daescu
Hemodynamic parameters play a significant role in the development of cerebral aneurysms. Parameters such as wall shear stress (WSS) or velocity could change in time and may contribute to aneurysm growth and rupture. However, the hemodynamic changes at the rupture location remain unclear because it is difficult to obtain data prior to rupture. We analyzed a case of a ruptured middle cerebral artery (MCA) aneurysm for which we acquired imaging data at three time points, including at rupture. A patient with an observed MCA aneurysm was admitted to the emergency department with clinical symptoms of a subarachnoid hemorrhage...
November 24, 2016: Neurosurgical Review
https://www.readbyqxmd.com/read/27882278/heat-transfer-analysis-of-underground-u-type-heat-exchanger-of-ground-source-heat-pump-system
#18
Guihong Pei, Liyin Zhang
BACKGROUND: Ground source heat pumps is a building energy conservation technique. The underground buried pipe heat exchanging system of a ground source heat pump (GSHP) is the basis for the normal operation of an entire heat pump system. METHODS: Computational-fluid-dynamics (CFD) numerical simulation software, ANSYS-FLUENT17.0 have been performed the calculations under the working conditions of a continuous and intermittent operation over 7 days on a GSHP with a single-well, single-U and double-U heat exchanger and the impact of single-U and double-U buried heat pipes on the surrounding rock-soil temperature field and the impact of intermittent operation and continuous operation on the outlet water temperature...
2016: SpringerPlus
https://www.readbyqxmd.com/read/27878837/thrombotic-depositions-on-right-impeller-of-double-ended-centrifugal-total-artificial-heart-in-vivo
#19
Jamshid H Karimov, David J Horvath, Shinji Okano, Mark Goodin, Gengo Sunagawa, Nicole Byram, Nader Moazami, Leonard A R Golding, Kiyotaka Fukamachi
The development of total artificial heart devices is a complex undertaking that includes chronic biocompatibility assessment of the device. It is considered particularly important to assess whether device design and features can be compatible long term in a biological environment. As part of the development program for the Cleveland Clinic continuous-flow total artificial heart (CFTAH), we evaluated the device for signs of thrombosis and biological material deposition in four animals that had achieved the intended 14-, 30-, or 90-day durations in each respective experiment...
November 23, 2016: Artificial Organs
https://www.readbyqxmd.com/read/27876371/approaches-for-treatment-of-aortic-arch-aneurysm-a-numerical-study
#20
Asaph Nardi, Idit Avrahami
Aortic arch aneurysm is a complex pathology which requires coverage of one or more aortic arch vessels. In this study we explore the hemodynamic behavior of the aortic arch in aneurysmatic and treated cases with three currently available treatment approaches: Surgery Graft, hybrid Stent-Graft and chimney Stent Graft. The analysis included four models of the time-dependent fluid domains of aneurysmatic arch and of the surgery, hybrid and chimney endovascular techniques. Dimensions of the models are based on typical anatomy, and boundary conditions are based on typical physiological flow...
November 12, 2016: Journal of Biomechanics
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