Incorporating the Aortic Valve into Computational Fluid Dynamics Models using Phase-Contrast MRI and Valve Tracking

The American Heart Association states about 2% of the general population have a bicuspid aortic valve (BAV). BAVs exist in 80% of patients with aortic coarctation (CoA) and likely influences flow patterns that contribute to long-term morbidity post-surgically. BAV patients tend to have larger ascending aortic diameters, increased risk of aneurysm formation, and require surgical intervention earlier than patients with a normal aortic valve. Magnetic resonance imaging (MRI) has been used clinically to assess aortic arch morphology and blood flow in these patients. These MRI data have been used in computational fluid dynamics (CFD) studies to investigate potential adverse hemodynamics in these patients, yet few studies have attempted to characterize the impact of the aortic valve on ascending aortic hemodynamics. To address this issue, this research sought to identify the impact of aortic valve morphology on hemodynamics in the ascending aorta and determine the location where the influence is negligible. Novel tools were developed to implement aortic valve morphology into CFD models and compensate for heart motion in MRI flow measurements acquired through the aortic valve. Hemodynamic metrics such as blood flow velocity, time-averaged wall shear stress (TAWSS), and turbulent kinetic energy (TKE) induced by the valve were compared to values obtained using the current plug inflow approach. The influence of heart motion on these metrics was also investigated, resulting in the underestimation of TAWSS and TKE when heart motion was neglected. CFD simulations of CoA patients exhibiting bicuspid and tricuspid aortic valves were performed in models including the aortic sinuses and patient-specific valves. Results indicated the aortic valve impacted hemodynamics primarily in the ascending aorta, with the BAV having the greatest influence along the outer right wall of the vessel. A marked increase in TKE is present in aortic valve simulations, particularly in BAV patients. These findings suggest that future CFD studies investigating altered hemodynamics in the ascending aorta should accurately replicate aortic valve morphology. Further, aortic valve disease impacts hemodynamics in the ascending aorta that may be a predictor of the development or progression of ascending aortic dilation and possible aneurysm formation in this region

Henry Cabot Lodge :

Analysis of Lodge's career not only provided insight into the process of political apprenticeship in nineteenth century America but also contributed to an understanding of the evolution of political conservatism. Lodge's change from a conservative defender of American fishing rights in 1886 to an attitude of expansionism in 1898 was representative of the growing nationalism of the last decade of the century.While the biography began with Lodge's birth in 1850, the focus was on the period, 1882-1901. In those years, Lodge changed from a reform-minded, Liberal Republican to a Republican party loyalist. Lodge's rapid rise in stature in Congress placed him at the center of national politics in the crucial decade of the 1890's, but he remained essentially a regional figure with his loyalties most firmly attached to the interests of Massachusetts and New England.This study placed Henry Cabot Lodge in the context of Gilded Age politics both in the nation and in Massachusetts. Lodge was interpreted as a Neo-Hamiltonian conservative who attempted to bridge the change from the politics of William McKinley to the politics of Theodore Roosevelt

Relationship Between Gene Frequencies and Indices of Physiological Stress in the Estuarine Gastropod, Thais Haemastoma.

The relationship between individual energy budgets and genetic variability was examined in Thais haemastoma acclimated to 7.5, 20 and 35(\u27o)/oo S at 21(DEGREES)C. Energy budgets, after the equations of Crisp (1971), were determined by measuring rates of caloric ingestion, absorption efficiencies, oxygen consumption and ammonia and primary amine excretion. Genotypes at six polymorphic loci coding for soluble enzymes, of 25 total loci assayed, were determined using starch gel electrophoresis. The polymorphic loci examined were those encoding for (alpha)-L-amino peptidase (LAP), phosphoglucomutase (PGM), glucose-6-phosophate dehydrogenase (G6PDH), a non-specific esterase (Est) and two dipeptidases (L-leucyl-L-proline and L-phenylalanyl-L-proline dipeptidases). The genetic variability observed in T. haemastoma was similar to that reported for other marine invertebrates. There was a significant positive relationship between total heterozygosity and whole animal Scope for Growth at all three salinities. This relationship was due in part to the greater size of the more heterozygous individuals since Scope for Growth increases with size. Analysis of covariance also revealed a significant positive effect of total heterozygosity on weight corrected Scope for Growth. These results provide physiological evidence of superiority of heterozygotes over homozygotes, for growth, survival and potential reproductive output. The increased Scope for Growth measured in heterozygotes was caused by significantly greater feeding rates. Heterozygous individuals at 20 and 35(\u27o)/oo S had lower metabolic maintanence costs, expressed as calories lost per unit weight than more highly homozygous ones. However, greater metabolic efficiency did not account for much of the differences in Scope for Growth between heterozygotes and homozygotes. Heterozygotic overdominance, or heterozygote superiority over homozygotes across all loci is the most likely explanation of the observed differences in Scope for Growth. The heterozygote contribution at each locus is small, but cumulative, resulting in a statistically significant relationship. Mean Scope for Growth was significantly greater for LAP heterozygotes at the stressful salinities, 7.5 and 35(\u27o)/oo S, but not at the optimum salinity, 20(\u27o)/oo S. This indicates the possibility of direct selective pressure from salinity extremes on genetic variability at the LAP locus

Trumpet slices of the Schwarzschild-Tangherlini spacetime

We study families of time-independent maximal and 1+log foliations of the Schwarzschild-Tangherlini spacetime, the spherically-symmetric vacuum black hole solution in D spacetime dimensions, for D >= 4. We identify special members of these families for which the spatial slices display a trumpet geometry. Using a generalization of the 1+log slicing condition that is parametrized by a constant n we recover the results of Nakao, Abe, Yoshino and Shibata in the limit of maximal slicing. We also construct a numerical code that evolves the BSSN equations for D=5 in spherical symmetry using moving-puncture coordinates, and demonstrate that these simulations settle down to the trumpet solutions.Comment: 11 pages, 6 figures, submitted to PR

Treating a 20 mm Hg Gradient Alleviates Myocardial Hypertrophy in Experimental Aortic Coarctation

Background Children with coarctation of the aorta (CoA) can have a hyperdynamic and remodeled left ventricle (LV) from increased afterload. Literature from an experimental model suggests the putative 20 mm Hg blood pressure gradient (BPG) treatment guideline frequently implemented in CoA studies may permit irreversible vascular changes. LV remodeling from pressure overload has been studied, but data are limited following correction and using a clinically representative BPG. Materials and methods Rabbits underwent CoA at 10 weeks to induce a 20 mm Hg BPG using permanent or dissolvable suture thereby replicating untreated and corrected CoA, respectively. Cardiac function was evaluated at 32 weeks by magnetic resonance imaging using a spoiled cine GRE sequence (TR/TE/FA 8/2.9/20), 14 × 14-cm FOV, and 3-mm slice thickness. Images (20 frames/cycle) were acquired in 6-8 short axis views from the apex to the mitral valve annulus. LV volume, ejection fraction (EF), and mass were quantified. Results LV mass was elevated for CoA (5.2 ± 0.55 g) versus control (3.6 ± 0.16 g) and corrected (4.0 ± 0.44 g) rabbits, resulting in increased LV mass/volume ratio for CoA rabbits. A trend toward increased EF and stroke volume was observed but did not reach significance. Elevated EF by volumetric analysis in CoA rabbits was supported by concomitant increases in total aortic flow by phase-contrast magnetic resonance imaging. Conclusions The indices quantified trended toward a persistent hyperdynamic LV despite correction, but differences were not statistically significant versus control rabbits. These findings suggest the current putative 20 mm Hg BPG for treatment may be reasonable from the LV\u27s perspective

Gender-grade-gap zeroed out under a specific intro-physics assessment regime

Evidence is presented that offering introductory physics courses with an explicit focus on mastery can reduce the gender gap to zero. Taken together with a previous study showing that a concepts-first course may zero out another demographic gap leads one to speculate that demographic grade gaps in introductory physics are just artifacts of the design of the courses and that none of these classes/grades should be assumed to be demographically neutral