Persistent fenestration may be a marker for physiologic intolerance after Fontan completion

BackgroundWe sought to evaluate the medium-term implications of fenestration status.MethodsBetween 1994 and 2012, 326 patients received an extracardiac Fontan (hospital mortality n = 6, 1.8%). A fenestration was routinely created (n = 306, 94%) unless there was technical difficulty. Three hundred patients discharged with an open fenestration were included. The primary end points were death and Fontan failure. Secondary outcomes were Fontan complications such as venovenous collaterals, protein-losing enteropathy, pacemaker requirement, and arrhythmias.ResultsThe fenestration was closed in 260 patients: 185 as a catheter intervention (62%) and 75 (25%) spontaneously. Forty patients (13%) had the fenestration open at a median follow-up period of 5.05 years. Of these patients, catheter-based closure failed in 10 (3%). There was no statistically significant difference in pre-Fontan hemodynamic parameters, such as pulmonary artery pressure and pulmonary vascular resistance between the patients with open fenestration and the ones with closed fenestration. Patients with an open fenestration had significantly more late deaths (P < .001), Fontan failure (P = .021), and Fontan complications (P = .011) compared with those with a closed fenestration. Multivariable Cox regression revealed open fenestration (P < .001) and indeterminate ventricular morphology (P = .002) as risk factors for death/Fontan failure, and ventricular dysfunction (P = .014) and open fenestration (P = .009) as risk factors for Fontan complications.ConclusionsPersistent fenestration was a marker for physiologic intolerance as noted by increased rates of mortality and a higher incidence of Fontan failure/complications. The specificity of pre-Fontan physiologic data for fenestration status may not have the fidelity needed for long-term care and thus, the consequences of decision making regarding fenestration status may not be determined until well after the operation

A Boltzmann-based finite volume algorithm for surface water flows on cells of arbitrary shapes

An explicit two-dimensional conservative finite volume model for shallow water equations is formulated and tested. The algorithm for the mass and momentum fluxes at the control surface of the finite volume is obtained from the solution of the Bhatnagar-Gross-Krook (BGK) Boltzmann equation. Unlike classical methods, BGK schemes do not require an ad-hoc splitting of advection and diffusion. The BGK scheme is second order in both time and space. The formulation of the BGK algorithm is performed for a cell of arbitrary irregular shape, but the test cases are conducted using a structured grid of quadrilateral cells. Two approximate Riemann solvers, the HLLC scheme and the two-stage Hancock-HLLC scheme, where HLL stands for Harten, Lax and van Leer and C stands for contact discontinuity, are also considered. The second-order accuracy of HLL and Hancock-HLLC schemes is obtained by MUSCL approach, where MUSCL is the acronym for Monotone Upstream-centered Schemes for Conservation Laws. The data reconstruction for all three schemes is carried out by the Van Leer limiter. The test cases involve strong shocks and expansion waves. The accuracy of the schemes are measured using an absolute error norm and a waviness error norm. The HLLC scheme is highly oscillatory for Courant number larger than 0.5, while the BGK and the Hancock-HLLC schemes are applicable for Courant numbers as high as 1.0. For a fixed value of the central processing unit (CPU) time, the absolute error of the Hancock-HLLC is slightly smaller than that of the BGK while the waviness error of the BGK is quite close to that of Hancock-HLLC. This is because (i) the Hancock-HLLC is a two-step method while the BGK is a single-step method (i.e., the Hancock-HLLC requires storage of intermediate variables, but the BGK does not), and (ii) the Hancock-HLLC schemes requires larger number of grid points than the BGK scheme for the same level of accuracy. For example, to achieve an absolute error of 0.01, the BGK requires about 600 grid points while the Hancock-HLLC requires about 800 grid points. Both the BGK and Hancock-HLLC schemes have similar convergence properties. Unlike exact or approximate Riemann solvers, BGK fluxes accounts for both waves and diffusion. The ability of the BGK scheme to model diffusion is illustrated using a viscous flow problem. Excellent agreement between the analytical and computed viscous flow solution is found. Although the BGK and Hancock-HLLC schemes perform similarly for hyperbolic problems, BGK schemes have the added advantage of being able to solve hyperbolic-parabolic problems without the need for an ad-hoc operator splitting. This is important given that the artificial splitting of advection and diffusion is known to cause artificial widening in shear layers and introduces artificial transient in regions with sharp gradients. Such problems arise when the splitting operation fails to faithfully represent the correct coupling between the physics of advection and the physics of waves

A Boltzmann-based mesoscopic model for contaminant transport in flow systems

objective of this paper is to demonstrate the formulation of a numerical model for mass transport based on the Bhatnagar-Gross-Krook (BGK) Boltzmann equation. To this end, the classical chemical transport equation is derived as the zeroth moment of the BGK Boltzmann differential equation. The relationship between the mass transport equation and the BGK Boltzmann equation allows an alternative approach to numerical modeling of mass transport, wherein mass fluxes are formulated indirectly from the zeroth moment of a difference model for the BGK Boltzmann equation rather than directly from the transport equation. In particular, a second-order numerical solution for the transport equation based on the discrete BGK Boltzmann equation is developed. The numerical discretization of the first-order BGK Boltzmann differential equation is straightforward and leads to diffusion effects being accounted for algebraically rather than through a second-order Fickian term. The resultant model satisfies the entropy condition, thus preventing the emergence of non-physically realizable solutions including oscillations in the vicinity of the front. Integration of the BGK Boltzmann difference equation into the particle velocity space provides the mass fluxes from the control volume and thus the difference equation for mass concentration. The difference model is a local approximation and thus may be easily included in a parallel model or in accounting for complex geometry. Numerical tests for a range of advection-diffusion transport problems, including one- and two-dimensional pure advection transport and advection-diffusion transport show the accuracy of the proposed model in comparison to analytical solutions and solutions obtained by other schemes. (C) 2001 Published by Elsevier Science Ltd

Host and environmental factors influencing 'Candidatus Liberibacter asiaticus' acquisition in Diaphorina citri

Background: Diaphorina citri is a vector of ‘Candidatus Liberibacter asiaticus’ (CLas) associated with citrus Huanglongbing. In this study, the infection and titers of CLas in the psyllid, were monitored for life cycle stage, sex, host‐plant CLas titer, host‐plant genotype, and ambient temperature. Results: Acquisition efficiency of CLas by D. citri was highest in nymphs reared at 25 °C on a host plant with high CLas titers but was independent of the host genotypes assessed and of vector sex. We further observed that D. citri nymphs acquired CLas more rapidly than adults based on acquisition access periods (AAPs). CLas did not multiply in the alimentary canal, hemolymph, and salivary glands of adults for 18 days after a 3‐day AAP as adult. However, CLas multiplication was detected in hemolymph and salivary gland of adults after the bacterium was acquired by nymphs. Eighty percent of salivary glands of adults contained CLas 18 days after a 3‐day AAP as nymph compared to 10% 18 days after a 3‐day AAP as adults. Conclusion:Different factors tested herein influenced CLas acquisition efficiency of D. citri, CLas multiplication and spread inside the psyllid. These observations serve to better understand mechanisms of CLas infection in D. citri

Bioaerosol Concentrations and Size Distributions during the Autumn and Winter Seasons in an Industrial City of Central China

The ambient bioaerosols were measured in PM2.5 and PM10 samples taken in Huangshi City, Hubei Province, China, during autumn and winter from November 2017 to February 2018. Both the bioaerosol number concentration and size distribution (0.37-16 mu m) were obtained by direct fluorescent staining coupled with microscopic imaging. The bioaerosol number concentrations ranged from 0.05 to 3.4 # cm(-3) for PM2.5 and from 0.17 to 5.7 # cm(-3) for PM10, with averages of 0.90 # cm(-3) and 1.9 # cm(-3), respectively. In terms of particle number, the bioaerosols were dominated by fine particles (0.37-2.5 mu m in diameter), with a larger proportion of submicron than supermicron particles. Assuming a unit density of 1 g cm(-3) and a spherical shape for the particles, the mass abundances of the bioaerosols were estimated to be 2.4 +/- 1.9% and 4.8 +/- 3.2% of the PM2.5 and PM10, respectively, as measured by a nearby compliance monitor. Higher bioaerosol concentrations were observed in winter than autumn and on polluted than non-polluted days. During heavily polluted conditions, bioaerosols in the PM2.5 and PM10 were enriched by 6 and 3.7 times, respectively, compared to non-polluted days and contributed up to 15% of the PM10 mass. Rainfall and snowfall appeared to lower the bioaerosol levels. As enhanced emission controls on combustion and dust sources decrease PM levels in China, the bioaerosol fraction in measured PM concentrations will likely increase