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Emelia J Benjamin - One of the best experts on this subject based on the ideXlab platform.
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evolution of mitral valve prolapse insights from the framingham heart study
Circulation, 2016Co-Authors: Francesca N Delling, Jian Rong, Martin G Larson, Birgitta T Lehman, Deborah L Fuller, Ewa Osypiuk, Plamen Stantchev, Brianne Hackman, Warren J Manning, Emelia J BenjaminAbstract:Background —Longitudinal studies of mitral valve prolapse (MVP) progression among unselected individuals in the community, including those with non-diagnostic MVP morphologies (NDM), are lacking. Methods and Results —We measured longitudinal changes in annular diameter, leaflet Displacement, Thickness, anterior/posterior leaflet projections onto the annulus, coaptation height, and mitral regurgitation (MR) jet height in 261 Framingham Offspring participants at Examination 5 who had available follow-up imaging 3 to 16 years later. Study participants included MVP (N=63), NDM - 9minimal systolic Displacement9 or MSD (N=50) and the 9abnormal anterior coaptation9 (AAC) phenotype (N=10, with coaptation height >40% of the annulus similar to posterior MVP), plus 138 healthy referents without MVP or NDM. At follow-up, individuals with MVP (52% women, 57±11 years) had greater increases of leaflet Displacement, Thickness, and jet height compared with referents (all p<0.05). Eleven participants with MVP (17%) had ≥ moderate MR (jet height ≥5 mm) and 5 others (8%) underwent mitral valve repair. Of the individuals with NDM, 8 (80%) AACs progressed to posterior MVP; 17 (34%) MSDs were reclassified as either posterior MVP (12) or AAC (5). Compared with the 33 MSDs who did not progress, the 17 who progressed had greater leaflet Displacement, Thickness, coaptation height, and MR jet height (all p<0.05). Conclusions —NDM may evolve into MVP, highlighting the clinical significance of mild MVP expression. MVP progresses to significant MR over a period of 3 to 16 years in a quarter of individuals in the community. Changes in mitral leaflet morphology are associated with both NDM and MVP progression.
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mild expression of mitral valve prolapse in the framingham offspring expanding the phenotypic spectrum
Journal of The American Society of Echocardiography, 2014Co-Authors: Francesca N Delling, Martin G Larson, Birgitta T Lehman, Warren J Manning, Emelia J Benjamin, Philimon Gona, Robert A Levine, Ramachandran S VasanAbstract:Background Mitral valve (MV) prolapse (MVP) is a common disorder associated with mitral regurgitation, endocarditis, heart failure, and sudden death. Nondiagnostic morphologies have been described in the familial context and may represent early expression of MVP in those genetically predisposed. The aim of this study was to explore the spectrum of MVP abnormalities in the community and compare their clinical and echocardiographic features. Methods We measured annular diameter MV leaflet Displacement, Thickness, anterior and posterior leaflet projections onto the annulus, MV leaflet coaptation height (posterior MV leaflet projection/annular diameter), and MR jet height in 296 individuals of the Framingham Offspring Study with MVP (n = 77), the "abnormal anterior coaptation" (AAC) phenotype (n = 11) or "minimal systolic Displacement" (MSD) (n = 57), and 151 age-matched and sex-matched referents with no MVP or its nondiagnostic forms. Results AAC did not meet diagnostic Displacement criteria but resembled MVP with regard to annular diameter and leaflet Thickness ( P > .05 for both). AAC was similar to posterior MVP with regard to posterior leaflet asymmetry and an anteriorly shifted coaptation ( P = .91). Compared to patients with MSD and referents, patients with AAC had greater leaflet coaptation height, Thickness, and annular diameter ( P P P Conclusions Nondiagnostic morphologies are observed in the community and share the common feature of posterior leaflet asymmetry with MVP. AAC and MSD may thus represent early expressions of MVP. Longitudinal studies are warranted to elucidate the natural history of these phenotypes.
H Babinsky - One of the best experts on this subject based on the ideXlab platform.
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effect of microvortex generators on separated normal shock boundary layer interactions
Journal of Aircraft, 2007Co-Authors: H A Holden, H BabinskyAbstract:Experiments have been performed in a blowdown supersonic wind tunnel to investigate the effect of subboundary layer vortex generators placed upstream of a normal shock/turbulent boundary layer interaction at a Mach number of 1.5 and a freestream Reynolds number of 28 x 10 6 . The Reynolds number based on the inflow boundary layer Displacement Thickness was 26,000. Two types of subboundary layer vortex generators were investigated: wedge-shaped and counter-rotating vanes. It was found that the vane-type subboundary layer vortex generators eliminated and the wedge-type subboundary layer vortex generators greatly reduced the shock-induced separation. When placed in the supersonic part of the flow, both types of subboundary layer vortex generators caused a wave pattern consisting of a shock, reexpansion, and shock. The reexpansion and double shocks are undesirable features because they equate to increased total pressure losses. Furthermore there are indications that the vortex intensity is reduced by the normal shock/boundary layer interaction. Overall, the vane-type subboundary layer vortex generators were the more effective devices as they eliminated the shock-induced separation and had the least detrimental effect on the shock structure.
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micro ramp control for oblique shock wave boundary layer interactions
37th AIAA Fluid Dynamics Conference and Exhibit, 2007Co-Authors: Cwp Ford, H BabinskyAbstract:Supersonic engine intakes operating supercritically feature shock wave / boundary layer interactions (SBLIs), which are conventionally controlled using boundary layer bleed. The momentum loss of bleed flow causes high drag, compromising intake performance. Micro-ramp sub-boundary layer vortex generators (SBVGs) have been proposed as an alternative form of flow control for oblique SBLIs in order to reduce the bleed requirement. Experiments have been conducted at Mach 2.5 to characterise the flow details on such devices and investigate their ability to control the interaction between an oblique shock wave and the naturally grown turbulent boundary layer on the tunnel floor. Micro-ramps of four sizes with heights ranging from 25% to 75% of the uncontrolled boundary layer Thickness were tested. The flow over all sizes of microramp was found to be similar, featuring streamwise counter-rotating vortices which entrain high momentum fluid, locally reducing the boundary layer Displacement Thickness. When installed ahead of the shock interaction it was found that the positioning of the micro-ramps is of limited importance. Micro-ramps did not eliminate flow separation. However, the previously two-dimensional separation was broken up into periodic three-dimensional separation zones. The interaction length was reduced and the pressure gradient across the interaction was increased.
Francesca N Delling - One of the best experts on this subject based on the ideXlab platform.
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evolution of mitral valve prolapse insights from the framingham heart study
Circulation, 2016Co-Authors: Francesca N Delling, Jian Rong, Martin G Larson, Birgitta T Lehman, Deborah L Fuller, Ewa Osypiuk, Plamen Stantchev, Brianne Hackman, Warren J Manning, Emelia J BenjaminAbstract:Background —Longitudinal studies of mitral valve prolapse (MVP) progression among unselected individuals in the community, including those with non-diagnostic MVP morphologies (NDM), are lacking. Methods and Results —We measured longitudinal changes in annular diameter, leaflet Displacement, Thickness, anterior/posterior leaflet projections onto the annulus, coaptation height, and mitral regurgitation (MR) jet height in 261 Framingham Offspring participants at Examination 5 who had available follow-up imaging 3 to 16 years later. Study participants included MVP (N=63), NDM - 9minimal systolic Displacement9 or MSD (N=50) and the 9abnormal anterior coaptation9 (AAC) phenotype (N=10, with coaptation height >40% of the annulus similar to posterior MVP), plus 138 healthy referents without MVP or NDM. At follow-up, individuals with MVP (52% women, 57±11 years) had greater increases of leaflet Displacement, Thickness, and jet height compared with referents (all p<0.05). Eleven participants with MVP (17%) had ≥ moderate MR (jet height ≥5 mm) and 5 others (8%) underwent mitral valve repair. Of the individuals with NDM, 8 (80%) AACs progressed to posterior MVP; 17 (34%) MSDs were reclassified as either posterior MVP (12) or AAC (5). Compared with the 33 MSDs who did not progress, the 17 who progressed had greater leaflet Displacement, Thickness, coaptation height, and MR jet height (all p<0.05). Conclusions —NDM may evolve into MVP, highlighting the clinical significance of mild MVP expression. MVP progresses to significant MR over a period of 3 to 16 years in a quarter of individuals in the community. Changes in mitral leaflet morphology are associated with both NDM and MVP progression.
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mild expression of mitral valve prolapse in the framingham offspring expanding the phenotypic spectrum
Journal of The American Society of Echocardiography, 2014Co-Authors: Francesca N Delling, Martin G Larson, Birgitta T Lehman, Warren J Manning, Emelia J Benjamin, Philimon Gona, Robert A Levine, Ramachandran S VasanAbstract:Background Mitral valve (MV) prolapse (MVP) is a common disorder associated with mitral regurgitation, endocarditis, heart failure, and sudden death. Nondiagnostic morphologies have been described in the familial context and may represent early expression of MVP in those genetically predisposed. The aim of this study was to explore the spectrum of MVP abnormalities in the community and compare their clinical and echocardiographic features. Methods We measured annular diameter MV leaflet Displacement, Thickness, anterior and posterior leaflet projections onto the annulus, MV leaflet coaptation height (posterior MV leaflet projection/annular diameter), and MR jet height in 296 individuals of the Framingham Offspring Study with MVP (n = 77), the "abnormal anterior coaptation" (AAC) phenotype (n = 11) or "minimal systolic Displacement" (MSD) (n = 57), and 151 age-matched and sex-matched referents with no MVP or its nondiagnostic forms. Results AAC did not meet diagnostic Displacement criteria but resembled MVP with regard to annular diameter and leaflet Thickness ( P > .05 for both). AAC was similar to posterior MVP with regard to posterior leaflet asymmetry and an anteriorly shifted coaptation ( P = .91). Compared to patients with MSD and referents, patients with AAC had greater leaflet coaptation height, Thickness, and annular diameter ( P P P Conclusions Nondiagnostic morphologies are observed in the community and share the common feature of posterior leaflet asymmetry with MVP. AAC and MSD may thus represent early expressions of MVP. Longitudinal studies are warranted to elucidate the natural history of these phenotypes.
Yizhao Wang - One of the best experts on this subject based on the ideXlab platform.
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application of boundary layer Displacement Thickness in wind erosion protection evaluation case study of a salix psammophila sand barrier
International Journal of Environmental Research and Public Health, 2019Co-Authors: Shuai Zhang, Guodong Ding, Guanglei Gao, Yuanyuan Zhao, Long Wang, Yizhao WangAbstract:Since the establishment of blown sand physics, surface roughness has been widely used in current research to indicate the ability of a surface to resist wind erosion and to evaluate the windproof effect of protective measures. However, since the calculation of surface roughness can result in different values and its applicability is poor, there are disadvantages to its use. Therefore, it is proposed that the boundary layer Displacement Thickness should be used rather than roughness as an indicator to solve such problems. To analyze the new indicator’s accuracy and applicability when evaluating the effect of protective measures, a wind tunnel simulation experiment on a typical mechanical protection measure commonly used for sand control in China was conducted. Indicators of roughness and boundary layer Displacement Thickness were compared in evaluating the windproof performance of a Salix psammophila sand barrier of differing heights, side lengths, and porosities. The wind speed acceleration rate and effective protection area, which can directly reflect the protective effect of a sand barrier, were analyzed as evaluation criteria. The results show that roughness can only reflect the influence of height on the windbreak effect of sand barriers, whereas the boundary layer Displacement Thickness accurately showed the influence of height, side length, and porosity on the windproof effect of the sand barriers. Compared with roughness, the boundary layer Displacement Thickness was more strongly correlated with the effective protection area. Therefore, the boundary layer Displacement Thickness, rather than roughness, should be used as a new indicator when evaluating the windproof effect of protective measures.
Holger Babinsky - One of the best experts on this subject based on the ideXlab platform.
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normal shock boundary layer control with various vortex generator geometries
Computers & Fluids, 2011Co-Authors: Eric Loth, Holger BabinskyAbstract:Various vortex generators which include ramp, split-ramp and a new hybrid concept “ramped-vane” are investigated under normal shock conditions with a diffuser at Mach number of 1.3. The dimensions of the computational domain were designed using Reynolds Average Navier-Stokes studies to be representative of the flow in an external-compression supersonic inlet. Using this flow geometry, various vortex generator concepts were studied with Implicit Large Eddy Simulation. In general, the ramped-vane provided increased vorticity compared to the other devices and reduced the separation length downstream of the device centerline. In addition, the size, edge gap and streamwise position respect to the shock were studied for the ramped-vane and it was found that a height of about half the boundary Thickness and a large trailing edge gap yielded a fully attached flow downstream of the device. This ramped-vane also provided the largest reduction in the turbulent kinetic energy and pressure fluctuations. Additional benefits include negligible drag while the reductions in boundary layer Displacement Thickness and shape factor were seen compared to other devices.
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wind tunnel setup for investigations of normal shock wave boundary layer interaction control
AIAA Journal, 2006Co-Authors: Hideaki Ogawa, Holger BabinskyAbstract:The use of wind-tunnel setup for study of normal shock wave/boundary layer interaction control, was investigated. The rectangular working section that was 114 mm wide, and 178 mm high at the straight downstream of the nozzle was used. The incoming airflow was partitioned by a plate of 6 mm Thickness to overcome the problem of shock wave instability. The height of the upper and lower passage was maintained at 91 and 122 mm respectively. The incoming boundary layer Thickness was 5.7 mm and the Reynolds number based on boundary-layer Displacement Thickness was approximately 25,000. It was observed that shock can be located above 3-D bump and large ?-shock structure whose front shock leg starts at the onset of control cab be analyzed. Result shows that wind-tunnel setup can be used to test various types of shock control at positions where conventional setups are unable to hold shock system due to shock instability.