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Hui Meng

Bio: Hui Meng is an academic researcher from University at Buffalo. The author has contributed to research in topics: Aneurysm & Particle image velocimetry. The author has an hindex of 51, co-authored 214 publications receiving 9500 citations. Previous affiliations of Hui Meng include State University of New York System & East China Normal University.


Papers
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Journal ArticleDOI
TL;DR: It is proposed that the “high-versus-low wall shear stress” controversy is a manifestation of the complexity of aneurysm pathophysiology, and both high and low wallShear stress can drive intracranial aneurYSm growth and rupture.
Abstract: Summary: Increasing detection of unruptured intracranial aneurysms, catastrophic outcomes from subarachnoid hemorrhage, and risks and cost of treatment necessitate defining objective predictive parameters of aneurysm rupture risk. Image-based computational fluid dynamics models have suggested associations between hemodynamics and intracranial aneurysm rupture, albeit with conflicting findings regarding wall shear stress. We propose that the “high-versus-low wall shear stress” controversy is a manifestation of the complexity of aneurysm pathophysiology, and both high and low wall shear stress can drive intracranial aneurysm growth and rupture. Low wall shear stress and high oscillatory shear index trigger an inflammatory-cell-mediated pathway, which could be associated with the growth and rupture of large, atherosclerotic aneurysm phenotypes, while high wall shear stress combined with a positive wall shear stress gradient trigger a mural-cell-mediated pathway, which could be associated with the growth and rupture of small or secondary bleb aneurysm phenotypes. This hypothesis correlates disparate intracranial aneurysm pathophysiology with the results of computational fluid dynamics in search of more reliable risk predictors.

670 citations

Journal ArticleDOI
01 Jan 2011-Stroke
TL;DR: Hemodynamics is as important as morphology in discriminating aneurysm rupture status with high AUC values, and all 3 models—morphological only, hemodynamic only, and combined—discriminate intracranial aneurYSm rupturestatus with highAUC values.
Abstract: Background and purpose the purpose of this study was to identify significant morphological and hemodynamic parameters that discriminate intracranial aneurysm rupture status using 3-dimensional angiography and computational fluid dynamics. Methods one hundred nineteen intracranial aneurysms (38 ruptured, 81 unruptured) were analyzed from 3-dimensional angiographic images and computational fluid dynamics. Six morphological and 7 hemodynamic parameters were evaluated for significance with respect to rupture. Receiver operating characteristic analysis identified area under the curve (AUC) and optimal thresholds separating ruptured from unruptured aneurysms for each parameter. Significant parameters were examined by multivariate logistic regression analysis in 3 predictive models-morphology only, hemodynamics only, and combined-to identify independent discriminants, and the AUC receiver operating characteristic of the predicted probability of rupture status was compared among these models. Results morphological parameters (size ratio, undulation index, ellipticity index, and nonsphericity index) and hemodynamic parameters (average wall shear stress [WSS], maximum intra-aneurysmal WSS, low WSS area, average oscillatory shear index, number of vortices, and relative resident time) achieved statistical significance (P Conclusions all 3 models-morphological (based on size ratio), hemodynamic (based on WSS and oscillatory shear index), and combined-discriminate intracranial aneurysm rupture status with high AUC values. Hemodynamics is as important as morphology in discriminating aneurysm rupture status.

628 citations

Journal ArticleDOI
01 Jun 2007-Stroke
TL;DR: Strong localization of aneurysm-type remodeling to the region of accelerating flow suggests that a combination of high wallShear stress and a high gradient in wall shear stress represents a “dangerous” hemodynamic condition that predisposes the apical vessel wall to aneurYSm formation.
Abstract: Background and Purpose— Arterial bifurcation apices are common sites for cerebral aneurysms, raising the possibility that the unique hemodynamic conditions associated with flow dividers predispose the apical vessel wall to aneurysm formation. This study sought to identify the specific hemodynamic insults that lead to maladaptive vascular remodeling associated with aneurysm development and to identify early remodeling events at the tissue and cellular levels. Methods— We surgically created new branch points in the carotid vasculature of 6 female adult dogs. In vivo angiographic imaging and computational fluid dynamics simulations revealed the detailed hemodynamic microenvironment for each bifurcation, which were then spatially correlated with histologic features showing specific tissue responses. Results— We observed 2 distinct patterns of vessel wall remodeling: (1) hyperplasia that formed an intimal pad at the bifurcation apex and (2) destructive remodeling in the adjacent region of flow acceleration that resembled the initiation of an intracranial aneurysm, characterized by disruption of the internal elastic lamina, loss of medial smooth muscle cells, reduced proliferation of smooth muscle cells, and loss of fibronectin. Conclusions— Strong localization of aneurysm-type remodeling to the region of accelerating flow suggests that a combination of high wall shear stress and a high gradient in wall shear stress represents a “dangerous” hemodynamic condition that predisposes the apical vessel wall to aneurysm formation.

526 citations

Journal ArticleDOI
TL;DR: Size ratio and aneurysm angle are promising new morphological metrics for IA rupture risk assessment because these parameters account for vessel geometry and may bridge the gap between morphological studies and more qualitative location-based studies.
Abstract: Intracranial aneurysms (IA) affect approximately 2 to 5% of the entire population (23, 25) Ruptured IAs typically cause subarachnoid hemorrhage (SAH) and its sequelae, resulting in significant morbidity and mortality Among patients who have SAH, 50 to 60% will die from the initial hemorrhage and a further 20 to 25% will experience complications (30) However, despite their expected common occurrence, only 1% of all IAs actually rupture (25) Although the morbidity and mortality associated with rupture may suggest that an incidentally detected aneurysm should be treated to forestall the catastrophic event of SAH, the two current methods of treatment (open microsurgical aneurysm clip ligation or endovascular aneurysm coil embolization) are not without some risk of major morbidity and mortality (8, 31) Therefore, an accurate metric (or several metrics) to judge the risk of rupture of an aneurysm is critical to aid in generating the best possible treatment algorithm Hemodynamics has been shown to play an important role in IA pathophysiology and rupture Using computational fluid dynamics, Hassan et al (11) suggested that high wall shear stress (WSS) may be responsible for IA growth and rupture in high-flow aneurysms, whereas the predominant factors causing rupture in low-flow aneurysms are high intra-aneurysmal pressure and flow stasis Cebral et al (6) demonstrated that ruptured IAs have unstable flow patterns, smaller impinging jet diameters, and smaller impingement zones Shojima et al (24) found that ruptured IAs have a higher average WSS in the aneurysm sac than unruptured IAs They observed recirculation zones and blood stasis at the apex of ruptured IAs It is important to realize that IA hemodynamics are strongly dependent on the geometry of the aneurysmal sac and its feeding vessel (11, 13, 26) For a given geometry, Cebral et al (5) showed that hemodynamics do not vary significantly with physiological variations of flow rate, blood pressure, and waveform Therefore, suitable parameters characterizing IA geometry can capture the characteristic hemodynamics and potentially predict rupture risk Several past studies have investigated such parameters The most ubiquitous parameter is IA size Although aneurysms exceeding 10 mm in size are considered to be dangerous, several studies have shown that a large percentage of ruptured aneurysms are, in fact, smaller than 10 mm (2, 9, 22, 23, 26, 27, 30) The relationship between IA rupture risk and IA size has yet to be completely elucidated Aneurysm shape has been studied as well, and certain shape parameters show stronger correlation with rupture than IA size Aspect ratio (AR), defined as IA height divided by neck diameter, is the most commonly studied shape parameter Although most findings affirm its importance, they do not converge on a common threshold value (2, 22, 26, 27, 29) Other, more sophisticated, shape parameters such as undulation index (UI), nonsphericity index (NSI), and ellipticity index (EI) have been proposed (22) in an attempt to account for the three-dimensional (3D) nature of IA Such 3D parameters show promise to be better predictors than lower-dimensional parameters such as size or AR, and they are further examined in the current study Previous studies have also investigated additional factors that correlate with IA rupture risk, such as familial preponderance, smoking, hypertension, female sex, connective tissue disorder, aneurysm growth rate, and presence of multiple IAs (15-17, 32) However, these studies have not yielded quantifiable metrics that can be readily integrated into the clinical decision-making process Adding complexity from such diverse variables into our current study would make risk assessment analysis unwieldy Currently, morphometric evaluation, typically using size alone, is the mainstay of applied aneurysm rupture risk assessment in day-to-day clinical practice Our aim is to improve such morphological evaluation and better the accuracy of aneurysm rupture risk assessment, something that is fundamental to the current practice of cerebrovascular neurosurgery A limitation of previous morphology-based rupture risk studies, including those investigating 3D parameters, is that the geometry of the parent artery is typically ignored Parent artery geometry has a significant influence on the resultant IA hemodynamics and, consequently, the rupture risk Castro et al (4) have demonstrated that upstream vessel tortuosity can critically influence intra-aneurysmal hemodynamics Hassan et al (11) observed that a greater parent vessel incidence angle shifts the high WSS area toward the aneurysm dome, where rupture-prone blebs often are present, whereas Hoi et al (13) noted that highly curved parent vessels subject IAs to higher hemodynamic stresses at the inflow zone that might promote growth or rupture Thus, parent vessel geometry should be accounted for when defining morphological parameters for IA rupture risk prediction Furthermore, numerous studies have observed a connection between IA rupture risk and vessel location (3, 4, 9, 21, 26, 30) Because vessel location is strongly related to vessel geometry, this finding affirms the importance of vessel geometry for IA rupture risk Incorporating parent vessel geometry in morphology parameters can, at least to some extent, capture the influence of IA location as well In the current study, we address the above-mentioned issues and define three new morphology parameters that incorporate IA parent vessel geometry We analyze a group of 45 IAs (20 ruptured, 25 unruptured) to evaluate new IA rupture parameters, in comparison with five “traditional” parameters that have been described in earlier studies

448 citations

Journal ArticleDOI
TL;DR: It is postulate that lateral saccular aneurysms located on more curved arteries are subjected to higher hemodynamic stresses, and the large impact zone at the distal side of theAneurysm neck correlates well with other findings, implicating this zone as the most likely site of aneurYSm growth or regrowth of treated lesions.
Abstract: Object. Few researchers have quantified the role of arterial geometry in the pathogenesis of saccular cerebral aneurysms. The authors investigated the effects of parent artery geometry on aneurysm hemodynamics and assessed the implications relative to aneurysm growth and treatment effectiveness. Methods. The hemodynamics of three-dimensional saccular aneurysms arising from the lateral wall of arteries with varying arterial curves (starting with a straight vessel model) and neck sizes were studied using a computational fluid dynamics analysis. The effects of these geometric parameters on hemodynamic parameters, including flow velocity, aneurysm wall shear stress (WSS), and area of elevated WSS during the cardiac cycle (time-dependent impact zone), were quantified. Unlike simulations involving aneurysms located on straight arteries, blood flow inertia (centrifugal effects) rather than viscous diffusion was the predominant force driving blood into aneurysm sacs on curved arteries. As the degree of arterial c...

293 citations


Cited by
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Journal ArticleDOI
01 Jun 2012-Stroke
TL;DR: Evidence-based guidelines are presented for the care of patients presenting with aneurysmal subarachnoid hemorrhage and offer a framework for goal-directed treatment of the patient with aSAH.
Abstract: Purpose—The aim of this guideline is to present current and comprehensive recommendations for the diagnosis and treatment of aneurysmal subarachnoid hemorrhage (aSAH). Methods—A formal literature s...

2,713 citations

01 Jan 2000
TL;DR: In this article, the authors propose a method to use the information of the user's interaction with the system to improve the performance of the system. But they do not consider the impact of the interaction on the overall system.
Abstract: Статья посвящена вопросам влияния власти на поведение человека. Авторы рассматривают данные различных источников, в которых увеличение власти связывается с напористостью, а ее уменьшение - с подавленностью. Конкретно, власть ассоциируется с: а) позитивным аффектом; б) вниманием к вознаграждению и к свойствам других, удовлетворяющим личные цели; в) автоматической переработкой информации и резкими суждениями; г) расторможенным социальным поведением. Уменьшение власти, напротив, ассоциируется с: а) негативным аффектом; б) вниманием к угрозам и наказаниям, к интересам других и к тем характеристикам я, которые отвечают целям других; в) контролируемой переработкой информации и совещательным типом рассуждений; г) подавленным социальным поведением. Обсуждаются также последствия этих паттернов поведения, связанных с властью, и потенциальные модераторы.

2,293 citations

Journal Article
TL;DR: The Social Psychology of Groups as discussed by the authors is a seminal work in the field of family studies, where the authors introduced, defined, and illustrated basic concepts in an effort to explain the simplest of social phenomena, the two-person relationship.
Abstract: The Social Psychology of Groups. J. W Thibaut & H. H. Kelley. New York: alley, 1959. The team of Thibaut and Kelley goes back to 1946 when, after serving in different units of the armed services psychology program, the authors joined the Research Center for Group Dynamics, first at M.LT and then at the University of Michigan. Their continued association eventuated in appointments as fellows at the Center for Advanced Study in the Behavioral Sciences, 19561957. It is during these years that their collaboration resulted in the publication of The Social Psychology of Groups. The book was designed to "bring order and coherence to present-day research in interpersonal relations and group functioning." To accomplish this aim, the authors introduced, defined, and illustrated basic concepts in an effort to explain the simplest of social phenomena, the two-person relationship. These basic principles and concepts were then employed to illuminate larger problems and more complex social relationships and to examine the significance of such concepts as roles, norm, power, group cohesiveness, and status. The lasting legacy of this book is derived from the fact that the concepts and principles discussed therein serve as a foundation for one of the dominant conceptual frameworks in the field of family studies today-the social exchange framework. Specifically, much of our contemporary thinking about the process of interpersonal attraction and about how individuals evaluate their close relationships has been influenced by the theory and concepts introduced in The Social Psychology of Groups. Today, as a result of Thibaut and Kelley, we think of interpersonal attraction as resulting from the unique valence of driving and restraining forces, rewards and costs, subjectively thought to be available from a specific relationship and its competing alternatives. We understand, as well, that relationships are evaluated through complex and subjectively based comparative processes. As a result, when we think about assessing the degree to which individuals are satisfied with their relationships, we take into consideration the fact that individuals differ in terms of the importance they attribute to different aspects of a relationship (e.g., financial security, sexual fulfillment, companionship). We also take into consideration the fact that individuals differ in terms of the levels of rewards and costs that they believe are realistically obtainable and deserved from a relationship. In addition, as a result of Thibaut and Kelley's theoretical focus on the concept of dependence and the interrelationship between attraction and dependence, there has evolved within the field of family studies a deeper appreciation for the complexities and variability found within relationships. Individuals are dependent on their relationships, according to Thibaut and Kelley, when the outcomes derived from the existing relationship exceed those perceived to be available in competing alternatives. Individuals who are highly dependent on their relationships are less likely to act to end their relationships. This dependence and the stability it engenders may or may not be voluntary, depending on the degree to which individuals are attracted to and satisfied with their relationships. When individuals are both attracted to and dependent on their relationships, they can be thought of as voluntarily participating in their relationship. That is, they are likely to commit themselves to the partner and relationship and actively work for its continuance. Thibaut and Kelley termed those relationships characterized by low levels of satisfaction and high levels of dependence "nonvoluntary relationships. …

1,894 citations

Journal ArticleDOI
TL;DR: A review of the current state-of-the-art experimental and computational techniques for turbulent dispersed multiphase flows, their strengths and limitations, and opportunities for the future can be found in this paper.
Abstract: Turbulent dispersed multiphase flows are common in many engineering and environmental applications. The stochastic nature of both the carrier-phase turbulence and the dispersed-phase distribution makes the problem of turbulent dispersed multiphase flow far more complex than its single-phase counterpart. In this article we first review the current state-of-the-art experimental and computational techniques for turbulent dispersed multiphase flows, their strengths and limitations, and opportunities for the future. The review then focuses on three important aspects of turbulent dispersed multiphase flows: the preferential concentration of particles, droplets, and bubbles; the effect of turbulence on the coupling between the dispersed and carrier phases; and modulation of carrier-phase turbulence due to the presence of particles and bubbles.

1,401 citations

Journal ArticleDOI
TL;DR: In this article, a review of scale-invariance properties of high-Reynolds-number turbulence in the inertial range is presented, focusing on dynamic and similarity subgrid models and evaluating how well these models reproduce the true impact of the small scales on large scale physics and how they perform in numerical simulations.
Abstract: ▪ Abstract Relationships between small and large scales of motion in turbulent flows are of much interest in large-eddy simulation of turbulence, in which small scales are not explicitly resolved and must be modeled. This paper reviews models that are based on scale-invariance properties of high-Reynolds-number turbulence in the inertial range. The review starts with the Smagorinsky model, but the focus is on dynamic and similarity subgrid models and on evaluating how well these models reproduce the true impact of the small scales on large-scale physics and how they perform in numerical simulations. Various criteria to evaluate the model performance are discussed, including the so-called a posteriori and a priori studies based on direct numerical simulation and experimental data. Issues are addressed mainly in the context of canonical, incompressible flows, but extensions to scalar-transport, compressible, and reacting flows are also mentioned. Other recent modeling approaches are briefly introduced.

1,395 citations