CFD Study of the Flow Field and Particle Dispersion and Deposition in the Upper Human Respiratory System

Das Einatmen von Partikeln in den menschlichen Körper hat zwei verschiedene Aspekte im Hinblick auf die Gesundheit des Menschen. Einerseits existieren schädliche Partikel wie beispielsweise Feinstaub in der Umwelt, der nach Eintreten in den menschlichen Körper Krankheiten wie Herzerkrankungen und Erkrankungen der Atemwege auslösen kann, und der sogar zum Tod führen kann. Hier sind insbesondere Partikel, die kleiner als 2,5 µm sind, relevant. Andererseits ist es in der medizinischen Therapie einiger Atemwegerkrankungen wünschenswert, gezielt Partikel den Atemwegen zuzuführen. Die medikamentöse Aerosol-Therapie, bei der das Medikament durch den nasalen oder oralen Atemweg in die Lunge oder einen anderen Ort des Atemtrakts gebracht wird, wird gern verwendet, um Krankheiten wie z.B. Asthma oder chronisch obstruktive Lungenerkrankungen zu behandeln. Diese Therapie hat den Vorteil der kleinen Dosierung, der minimalen systemischen Nebenwirkungen und der schnellen Wirkung. Das Medikament soll hier tief in die Lunge, in der die Krankheit auftritt, eindringen. Die typische Größe dieser Partikel liegt im Bereich von 1 bis 5 µm. Fokus ist die gezielte Steuerung des Medikaments in spezielle Regionen wie beispielsweise zu einer Tumorposition, sodass Nebenwirkungen durch Ablagerung in anderen Regionen vermieden werden. Ein verbessertes Verständnis des Gesamtprozesses beinhaltet die Kenntnis der charakteristischen Luftströmung und des Partikeltransports sowie deren gegenseitige Beeinflussung. In der vorliegenden Arbeit, in der die Luftströmung sowie die Partikelverteilung und -ablagerung in den menschlichen oberen Atemwegen untersucht werden, werden vier verschiedene Geometrien verwendet: die verengte Luftröhre, das auf einem Gussstück basierende Mund-Rachen-Modell, das auf Computertomographie (CT) basierende Mund-Rachen-Modell und das auf CT-Skans basierende Nasenhöhlen-Modell. Die Software NeuRa2 wird zur Generierung des numerischen Oberflächengitters verwendet und ANSYS ICEM CFD-11.0, um Volumengitter zu erzeugen. Ein-Weg- und Zwei-Wege-Kopplung zwischen der Gasphase und den Partikeln werden in der Arbeit in Abhängigkeit verschiedener Partikelvolumenanteile angewendet. Dreidimensionale inkompressible Navier-Stokes (N-S) Gleichungen werden zur Beschreibung der Luftströmung verwendet. Large Eddy Simulation (LES) wird zur Modellierung der turbulenten Strömung herangezogen, und das Smagorinsky Feinskalen-Modell sowie das dynamische Smagorinsky Modell dienen der Beschreibung der kleinen turbulenten Skalen. Unter der Annahme eines großen Partikel-Luft Dichteverhältnisses, der Vernachlässigbarkeit der Partikelrotation und der Kollision zwischen den Partikeln sowie der Annahme, dass die Trägheitskraft die Partikelbewegung dominiert, werde Lagrange-Gleichungen herangezogen, um die Bewegung der Partikel zu modellieren. Im Falle von Partikeln, die kleiner als ein Mikrometer sind, wird die Brownsche Kraft zusätzlich berücksichtigt. Zur Lösung der Gleichungen wird die Software-Plattform OpenFOAM 1.5 benutzt, für die neue Solver entwickelt werden, die die Luftströmung mit LES und die Teilchenbewegung mit Hilfe einer Lagrange-Formulierung lösen können. Abhängig von der Partikelbeladung wird Ein-Weg- oder Zwei-Wege-Kopplung mit oder ohne Berücksichtigung des Einflusses des Partikelimpulses auf die Gasphase verwendet. Zunächst wird die Luftgeschwindigkeit an der Mittellinie und in unterschiedlichen Querschnitten stromabwärts der Glottis in der verengten Luftröhre mit numerischen Ergebnissen und experimentellen Daten aus der Literatur verglichen, hier wird ein Modell der Reynolds-gemittelten Navier-Stokes-Gleichungen (RANS) bei niedriger Reynolds-Zahl, das k-omega; Modell, verwendet. Die hier verwendete Methode verbessert die vorliegenden Literaturergebnisse, sodass sie die Basis für weitere Berechnungen in den verbleibenden Geometrien bildet. Die Luftströmung wird im Gussstück-basierten Mund-Rachen-Modell für drei verschiedene Inhalationsgeschwindigkeiten simuliert. Die numerischen Ergebnisse zeigen, dass das Geschwindigkeitsfeld der instationären Luftströmung sehr stark vom mittleren Geschwindigkeitsfeld abweicht, dies gilt insbesondere für das Auftreten von Wirbeln. Die numerische Simulation zeigt, dass die Partikelablagerung von der Partikelgröße, ihrer Ausgangsposition, der Inhalationsgeschwindigkeit sowie von der Geometrie abhängt. Turbulenz und Existenz von Rezirkulationszonen haben ebenfalls großen Einfluss auf den Partikeltransport. Eine polydisperse Partikelverteilung, die aus Messungen an einem Trockenpulver-Inhalator zur Verfügung steht, wird ebenfalls zur Simulation herangezogen. In diesem Fall wird Zwei-Wege-Kopplung verwendet. Polydisperse Partikelablagerung zeigt im Vergleich zur monodispersen Partikelablagerung stark unterschiedliche Charakteristika. Deshalb ist es notwendig, polydisperse Partikelverteilung und Zwei-Wege-Kopplung zu verwenden, wenn die reale medikamentöse Dosis eines Hubs berücksichtigt wird, die bei der klinischen Behandlung Anwendung findet. Um das Strömungsfeld bei einer realistischeren zeitabhängigen Inhalation zu untersuchen, wird eine numerische Simulation für das Gussstück-basierte Mund-Rachen-Modell unter den gleichen Bedingungen durchgeführt. Die Untersuchung zeigt, dass das Strömungsfeld signifikant verschieden ist in der beschleunigenden und der verlangsamenden Phase der Inhalation: In der Beschleunigungsphase ist die Luftströmung laminar während sie in der verlangsamenden Phase eher turbulent ist. Zur Untersuchung des Einflusses geometrischer Eigenschaften auf die Partikelablagerung werden numerische Simulationen für das CT-basierte Mund-Rachen-Modell durchgeführt. Im Ergebnis ist das Strömungsfeld im CT-basierten Mund-Rachen-Modell sehr verschieden von dem im Gussstück-basierten Mund-Rachen-Modell. Obwohl das Geschwindigkeitsfeld sowohl im mittleren als auch im zeitabhängigen Fall ähnlich ist, hat das Strömungsfeld ein sehr kompliziertes Wirbelfeld mit hoher räumlicher und zeitlicher Dynamik. Partikel der Größe 2 µm können den Pharynx passieren, sich in der Luftröhre ablagern oder weiter in die Lungenregion vordringen. Um die Eigenschaften des Geschwindigkeitsfelds in der Nasenhöhle zu untersuchen, wurde ein geometrisches Modell der Nasenhöhle aus CT-Skans konstruiert. Die numerischen Ergebnisse zeigen, dass die Luft durch die Hauptluft-Passage der Nasenhöhle fließt und nur wenig Luft die Spitzen der Nasengänge und der olfaktorischen Region erreicht

A sufficient and necessary condition of existence of blow-up radial solutions for a k-Hessian equation with a nonlinear operator

In this paper, we establish the results of nonexistence and existence of blow-up radial solutions for a k-Hessian equation with a nonlinear operator. Under some suitable growth conditions for nonlinearity, the result of nonexistence of blow-up solutions is established, a sufficient and necessary condition on existence of blow-up solutions is given, and some further results are obtained.&nbsp

Numerical Simulation of the Dispersion and Deposition of a Spray Carried by a Pulsating Airflow in a Patient-Specific Human Nasal Cavity

[EN] The present numerical study concerns the dispersion and deposition of a nasal spray in a patient-specific human nose. The realistic three-dimensional geometry of the nasal cavity is reconstructed from computer tomography (CT) scans. Identification of the region of interest, removal of artifacts, segmentation, generation of the .STL file and the triangulated surface grid are performed using the software packages ImageJ, meshLab, and NeuRA2. An unstructured computational volume grid with approximately 15 million tetrahedral grid cells is generated using the software Ansys ICEM-CFD 11.0. An unsteady Eulerian-Lagrangian formulation is used to describe the airflow and the spray dispersion and deposition in the realistic human nasal airway using two-way coupling. A new solver called pimpleParcelFoam is developed, which combines the lagrangianParcel libraries with the pimpleFoam solver within the software package OpenFOAM 3.0.0. A large eddy simulation (LES) with the dynamic sub-grid scale (SGS) model is performed to study the spray in both a steady and a pulsating airflow with an inflow rate of 7.5 L/min (or maximum value in case of the pulsating spray) and a frequency of 45 Hz for pulsation as used in commercial inhalation devices. 10,000 mono-disperse particles with the diameters of 2.4 µm and 10 µm are uniformly injected at the nostrils. In order to fulfil the stability conditions for the numerical solution, a constant time-step of 10−5 s is implemented. The simulations are performed for a real process time of 1 s, since after the first second of the process, all particles have escaped through the pharynx or they are deposited at the surface of the nasal cavity. The numerical computations are performed on the high-performance computer bwForCluster MLS&WISO Production using 256 processors, which take around 32 and 75 hours for steady and pulsating flow simulation, respectively. The study shows that the airflow velocity reaches its maximum values in the nasal valve, in parts of the septum and in the nasopharynx. A complex airflow is observed in the vestibule and in the nasopharynx region, which may directly affect the dispersion and deposition pattern of the spray. The results reveal that the spray tends to deposit in the nasal valve, the septum and in the nasopharynx due to the change in the direction of the airflow in these regions. Moreover, it is found that due to the pulsating airflow, the aerosols are more dispersed and penetrate deeper into the posterior regions and the meatuses where the connections to the sinuses reside.The authors thank Dr. H. Mentzel from PARI Respiratory Equipment, Inc. for intense discussions about the pulsating spray initial conditions. The current study is part of a project supported by the German Research Foundation (DFG) through a research fellowship of the HGS MathComp. Furthermore, high-performance computing time at the bwForCluster MLS&WISO Production which is funded by the state of Baden-Württemberg through bwHPC and DFG through grant INST 35/1134-1 FUGG.Farnoud, A.; Cui, X.; Baumann, I.; Gutheil, E. (2017). Numerical Simulation of the Dispersion and Deposition of a Spray Carried by a Pulsating Airflow in a Patient-Specific Human Nasal Cavity. En Ilass Europe. 28th european conference on Liquid Atomization and Spray Systems. Editorial Universitat Politècnica de València. 529-536. https://doi.org/10.4995/ILASS2017.2017.4628OCS52953

Solvability and asymptotic properties for an elliptic geophysical fluid flows model in a planar exterior domain

In this paper, we study the solvability and asymptotic properties of a recently derived gyre model of nonlinear elliptic Schrödinger equation arising from the geophysical fluid flows. The existence theorems and the asymptotic properties for radial positive solutions are established due to space theory and analytical techniques, some special cases and specific examples are also given to describe the applicability of model in gyres of geophysical fluid flows

Existence and asymptotic analysis of positive solutions for a singular fractional differential equation with nonlocal boundary conditions

In this paper, we focus on the existence and asymptotic analysis of positive solutions for a class of singular fractional differential equations subject to nonlocal boundary conditions. By constructing suitable upper and lower solutions and employing Schauder’s fixed point theorem, the conditions for the existence of positive solutions are established and the asymptotic analysis for the obtained solution is carried out. In our work, the nonlinear function involved in the equation not only contains fractional derivatives of unknown functions but also has a stronger singularity at some points of the time and space variables

Comparison of Efficacy of Deep Brain Stimulation of Different Targets in Parkinson's Disease: A Network Meta-Analysis

Background: Deep brain stimulation (DBS) is considered an effective treatment option for Parkinson's disease (PD). Several studies have demonstrated the efficacy of neurostimulation in patients with advanced PD. The subthalamic nucleus (STN), the internal globus pallidus (GPi), ventral intermediate nucleus (Vim), and pedunculopontine nucleus (PPN) are reportedly effective DBS targets for control of Parkinsonian tremors. However, there is no consensus on the ideal target for DBS in patients with Parkinson's disease. Only a few studies have directly compared the efficacy of DBS of the Vim, STN, and GPi. Therefore, we searched PubMed, Embase, Cochrane Library, and other databases for observational studies, extracted data on unified Parkinson's disease rating scale (UPDRS) scores and performed a comprehensive network meta-analysis of different strategies of DBS and compared the efficiency of DBS at different targets.Methods: Forest plot was used to examine the overall efficiency of DBS; cumulative probability value was used to rank the strategies under examination. A node-splitting model was employed to assess consistency of reported outcomes inconsistency. A total of 16 studies which focused on UPDRS improvement were included in the network meta-analysis.Results: By comparing the overall efficiency associated with each target, we confirmed the efficacy of DBS therapy in PD. Our findings revealed similar efficacy of DBS targeted at GPi and STN in the on-medication phase [GPi-3.9 (95% CI −7.0 to −0.96); STN-3.1 (−5.9 to −0.38)]; however, in the off-medication phase, Vim-targeted DBS was associated with better improvement in UPDRS scores and could be a choice as a DBS target for tremor-dominant Parkinsonism.Conclusions: Our findings will help improve clinical application of DBS

Inverse Estimation of an Annual Cycle of California's Nitrous Oxide Emissions

Nitrous oxide (N_2O) is a potent long‐lived greenhouse gas (GHG) and the strongest current emissions of global anthropogenic stratospheric ozone depletion weighted by its ozone depletion potential. In California, N_2O is the third largest contributor to the state's anthropogenic GHG emission inventory, though no study has quantified its statewide annual emissions through top‐down inverse modeling. Here we present the first annual (2013–2014) statewide top‐down estimates of anthropogenic N_2O emissions. Utilizing continuous N_2O observations from six sites across California in a hierarchical Bayesian inversion, we estimate that annual anthropogenic emissions are 1.5–2.5 times (at 95% confidence) the state inventory (41 Gg N_2O in 2014). Without mitigation, this estimate represents 4–7% of total GHG emissions assuming that other reported GHG emissions are reasonably correct. This suggests that control of N_2O could be an important component in meeting California's emission reduction goals of 40% and 80% below 1990 levels of the total GHG emissions (in CO_2 equivalent) by 2030 and 2050, respectively. Our seasonality analysis suggests that emissions are similar across seasons within posterior uncertainties. Future work is needed to provide source attribution for subregions and further characterization of seasonal variability

Improving the storage quality and suppressing off-flavor generation of winter jujube by precise micro-perforated MAP

IntroductionTraditional modified atmosphere packaging (MAP) cannot meet the preservation requirements of winter jujube, and the high respiration rate characteristics of winter jujube will produce an atmosphere component with high CO2 concentration in traditional MAP. Micro-perforated MAP is suitable for the preservation of winter jujube due to its high permeability, which can effectively remove excess CO2 and supply O2. In this study, a microporous film preservation system that can be quickly applied to winter jujube was developed, namely PMP-MAP (precise micro-perforated modified atmosphere packaging). An experiment was designed to store winter jujube in PMP-MAP at 20°C and 2°C, respectively. The quality, aroma and antioxidant capacity, etc. of winter jujube at the storage time were determined.MethodsIn this study, the optimal micropore area required for microporous film packaging at different temperatures is first determined. To ensure the best perforation effect, the effects of various factors on perforation efficiency were studied. The gas composition within the package was predicted using the gas prediction equation to ensure that the gas composition of the perforated package achieved the desired target. Finally, storage experiments were designed to determine the quality index of winter jujube, including firmness, total soluble solids, titratable acid, reddening, and decay incidence. In addition, sensory evaluation, aroma and antioxidant capacity were also determined. Finally, the preservation effect of PMP-MAP for winter jujube was evaluated by combining the above indicators.Results and discussionAt the end of storage, PMP-MAP reduced the respiration rate of winter jujube, which contributed to the preservation of high total soluble solids and titratable acid levels, and delayed the reddening and decay rate of winter jujube. In addition, PMP-MAP maintained the antioxidant capacity and flavor of winter jujube while inhibiting the occurrence of alcoholic fermentation and off-flavors. This can be attributed to the effective gas exchange facilitated by PMP-MAP, thereby preventing anaerobic stress and quality degradation. Therefore, the PMP-MAP approach is an efficient method for the storage of winter jujube

Atmospheric observation-based estimation of fossil fuel CO_2 emissions from regions of central and southern California

Combustion of fossil fuel is the dominant source of greenhouse gas emissions to the atmosphere in California. Here, we describe radiocarbon (^(14)CO_2) measurements and atmospheric inverse modeling to estimate fossil fuel CO_2 (ffCO_2) emissions for 2009–2012 from a site in central California, and for June 2013–May 2014 from two sites in southern California. A priori predicted ffCO_2 mixing ratios are computed based on regional atmospheric transport model (WRF-STILT) footprints and an hourly ffCO_2 prior emission map (Vulcan 2.2). Regional inversions using observations from the central California site suggest that emissions from the San Francisco Bay Area (SFBA) are higher in winter and lower in summer. Taking all years together, the average of a total of fifteen 3-month inversions from 2009 to 2012 suggests ffCO_2 emissions from SFBA were within 6 ± 35% of the a priori estimate for that region, where posterior emission uncertainties are reported as 95% confidence intervals. Results for four 3-month inversions using measurements in Los Angeles South Coast Air Basin (SoCAB) during June 2013–May 2014 suggest that emissions in SoCAB are within 13 ± 28% of the a priori estimate for that region, with marginal detection of any seasonality. While emissions from the SFBA and SoCAB urban regions (containing ~50% of prior emissions from California) are constrained by the observations, emissions from the remaining regions are less constrained, suggesting that additional observations will be valuable to more accurately estimate total ffCO_2 emissions from California as a whole