ORCID Profile
0000-0002-2812-6188
Current Organisations
Johns Hopkins School of Medicine
,
Melbourne Centre for Nanofabrication
,
RMIT University Bundoora Campus
,
Victoria University
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Simulation and Modelling | Numerical Computation | Artificial Intelligence and Image Processing
Expanding Knowledge in Engineering | Environmentally Sustainable Manufacturing not elsewhere classified | Occupational Health |
Publisher: MDPI AG
Date: 28-02-2020
Abstract: This paper presents a computational and experimental study of steady inhalation in a realistic human pharyngeal airway model. To investigate the intricate fluid dynamics inside the pharyngeal airway, the numerical predicted flow patterns are compared with in vitro measurements using Particle Image Velocimetry (PIV) approach. A structured mesh with 1.4 million cells is used with a laminar constant flow rate of 10 L/min. PIV measurements are taken in three sagittal planes which showed flow acceleration after the pharynx bend with high velocities in the posterior pharyngeal wall. Computed velocity profiles are compared with the measurements which showed generally good agreements with over-predicted velocity distributions on the anterior wall side. Secondary flow patterns on cross-sectional slices in the transverse plane revealed vortices posterior of pharynx and a pair of secondary flow vortexes due to the abrupt cross-sectional area increase. Finally, pressure and flow resistance analysis demonstrate that greatest pressure occurs in the superior half of the airway and maximum in-plane pressure variation is observed at the velo-oropharynx junction, which expects to induce a high tendency of airway collapse during inhalation. This study provides insights of the complex fluid dynamics in human pharyngeal airway and can contribute to a reliable approach to assess the probability of flow-induced airway collapse and improve the treatment of obstructive sleep apnea.
Publisher: Informa UK Limited
Date: 05-06-2015
DOI: 10.1080/10255842.2014.921682
Abstract: The aim of this study is to elucidate the correlation between coronary artery branch angulation, local mechanical and haemodynamic forces at the vicinity of bifurcation. Using a coupled fluid-structure interaction (FSI) modelling approach, five idealized left coronary artery models with various angles ranging from 70° to 110° were developed to investigate the influence of branch angulations. In addition, one CT image-based model was reconstructed to further demonstrate the medical application potential of the proposed FSI coupling method. The results show that the angulation strongly alters its mechanical stress distribution, and the instantaneous wall shear stress distributions are substantially moderated by the arterial wall compliance. As high tensile stress is hypothesized to cause stenosis, the left circumflex side bifurcation shoulder is indicated to induce atherosclerotic changes with a high tendency for wide-angled models.
Publisher: Springer Science and Business Media LLC
Date: 29-12-2018
DOI: 10.1007/S11095-017-2280-6
Abstract: Nose-to-brain drug administration along the olfactory and trigeminal nerve pathways offers an alternative route for the treatment of central nervous system (CNS) disorders. The characterization of particle deposition remains difficult to achieve in experiments. Alternative numerical approach is applied to identify suitable aerosol particle size with maximized inhaled doses. This study numerically compared the drug delivery efficiency in a realistic human nasal cavity between two aerosol drug administration systems targeting the olfactory region: the aerosol mask system and the breath-powered bi-directional system. Steady inhalation and exhalation flow rates were applied to both delivery systems. The discrete phase particle tracking method was employed to capture the aerosol drug transport and deposition behaviours in the nasal cavity. Both overall and regional deposition characteristics were analysed in detail. The results demonstrated the breath-powered drug delivery approach can produce superior olfactory deposition with peaking olfactory deposition fractions for diffusive 1 nm particles and inertial 10 μm. While for particles in the range of 10 nm to 2 μm, no significant olfactory deposition can be found, indicating the therapeutic agents should avoid this size range when targeting the olfactory deposition. The breath-powered bi-directional aerosol delivery approach shows better drug delivery performance globally and locally, and improved drug administration doses can be achieved in targeted olfactory region.
Publisher: SAGE Publications
Date: 21-02-2018
Abstract: Aerosol transport and deposition in human lungs has attracted considerable attention in the past few years, as it has significant value to the study of toxicity consequence as well as therapeutic potential in occupational health and medical applications. In reproducing human tracheobronchial airways, two approaches were frequently taken: (1) anatomical realistic reconstruction through image scans (e.g. CT and MRI) or cadaver casts and (2) mathematical description using simplified models. Strengths and limitations are primarily focused on accuracy, resolution, repeatability, and computational\\physical expenses. While both approaches were reported in literature, detailed comparison of aerosol transport and deposition in the two representations were scarcely performed, largely due to the challenge to acquire comprehensive data from the irregular structured airway replicas (approach 1). To fill the gap, the current study performed a numerical comparison of nanoparticle transport and deposition in human upper tracheobronchial airways by using an anatomical realistic reconstruction (through CT scans) and a mathematically simplified airway model. As the first step, the current study was focused on the variation in breathing airflow pattern and the effect towards fate of the inhaled nanoparticles in human upper tracheobronchial airways. The study provided important information to understand geometric sensitivity of nanoparticle modeling in the human tracheobronchial tree and is of significant value to predict the whole lung uptake of inhaled nanoparticles in the human respiratory system.
Publisher: Elsevier BV
Date: 02-2022
Publisher: Springer Science and Business Media LLC
Date: 03-2019
Publisher: WORLD SCIENTIFIC (EUROPE)
Date: 12-09-2017
Publisher: Elsevier BV
Date: 08-2023
Publisher: Elsevier BV
Date: 11-2017
Publisher: Elsevier BV
Date: 02-2022
Publisher: Elsevier BV
Date: 2018
Publisher: MDPI AG
Date: 08-2017
DOI: 10.3390/EN10081129
Publisher: Elsevier BV
Date: 08-2022
DOI: 10.1016/J.COMPBIOMED.2022.105676
Abstract: Air conditioning in the nasal airways plays an important role in regulating ambient atmospheric temperature and humidity conditions of the inhaled air. Inevitably, it may alter the behaviour and fate of inhaled ambient aerosols within the human respiratory airways due to hygroscopic growth and droplet evaporation, which is a phenomena of variations in particle sizes due to physical and chemical reactions on particle surfaces in different temperature and humidity fields. Although laboratory animals have been widely used to predict health effects of human exposure to ambient substances, the nasal temperature and humidity responses in animal surrogates and human nasal cavities are still less-investigated. This paper provides a comparative study between two monkey and two human nasal subjects under the same ambient temperature and humidity conditions, where nasal models were reconstructed from CT images and the heat and mass transfer process incorporating with the intricate nose anatomy were modelled by the computational fluid dynamics (CFD) approach. Present model comparison revealed that the monkey nasal models can reach equilibrium temperature and moisture state for inhaled ambient air in a much shorter distance compared to the human models. This indicate that heat transfer in the monkey models is more effective compared to the human models due to having a higher complexity coefficient and a smaller hydraulic radius. Hence, in order to achieve comparable or similar inhalation exposure patterns in animal surrogates, corresponding adjustments such as changing the size of released particles, or the inhalation flow rates, to achieve comparable particle Stokes number are needed. The outcomes of this study would provide informative insights for future inhalation toxicology studies related to hygroscopic materials and targeted drug delivery through nasal airways.
Publisher: MDPI AG
Date: 04-06-2022
Abstract: Background: As common pathogens in the human respiratory tract, fungal-spore-related health risks have been challenging to evaluate properly. This paper presents numerical simulations of particle deposition of Aspergillus niger spores in human nasal cavities. Methods: 30 healthy adults (including 60 nasal chambers) who lived in northwest China were recruited to conduct a nasal cavity numerical simulation using computational fluid dynamics–discrete phase model (CFD-DPM). The deposition rate in each anatomic area and its influencing variables, such as body position and respiratory flow rate, were analyzed. Results: (1) Under a resting condition, only about 5.57% ± 1.51% Aspergillus niger spores were deposited in the nasal cavity, while most of them escaped from the nasopharynx, and 0.31% ± 0.20% spores entered the maxillary sinus (2) under an exercising condition, spores deposited in the nasal cavity were about 2.09 times as many as that in the resting state (3) in a lying position, the A. niger spores deposited evenly on the lateral wall of the nasal cavity and the sinus when compared with a standing position. However, the deposition rate in each anatomic area did not change significantly.
Publisher: Elsevier BV
Date: 05-2021
Publisher: Elsevier BV
Date: 05-2022
Publisher: Wiley
Date: 27-12-2022
DOI: 10.1002/CNM.3565
Abstract: As a primary determinant of nasal physiological functions, the nasal morphology and its effects on the airflow dynamics have been extensively studied in literature. However, gross flow features reported in literature are mostly obtained from subjects at similar ages, while studies focusing on nasal subjects with distinct age differences are significantly less. To advance current understandings of nasal airflow dynamics in the context of age ersity, this study employed three anatomically accurate nasal cavity models with distinct age features (5‐, 24‐ and 77‐year‐old models) and numerically compared the physiological nasal airflow fields within these nasal cavity models. To demonstrate the validity of the present numerical models, in vivo rhinomanometry measurement was conducted on the 24‐year‐old female nasal model, and key anatomical features and pressure‐flow curves of all three models were compared with models with similar age features in literature work. Apart from results comparison based on conventional velocity flow fields and wall shear stress distributions, a method for quantifying flow partitions in confined airway spaces was developed to reveal the proportions of fractional flow that enters the olfactory region. Our results revealed dramatic intersubject discrepancies between considered nasal cavity models, especially for the fractional flow that enters the olfactory region. Specifically, the 5‐year‐old girl nasal model received the highest proportion of fractional flow, which accounts for 13.3% ~ 15% of overall inhalation flow rates under different activity levels. For the 24‐year‐old female model, on the contrary, the olfactory fractional flow was dramatically reduced (with a local to overall percentage around 4.3%–7.7%). Finally, for the elderly subject—77‐year‐old male model, minimum level of olfactory flux was observed with a local to overall percentage ranging between 3.1% and 4.9% for considered wide range of inhalation flow rates. Therefore, the local flow intersubject variation can reach nearly fourfold. The vast local flow difference is mainly due to the inherent anatomical features (e.g., immature nasal turbinate structure in the child model, the partial narrowing superior nasal valve in the elder model). The results may further lead to discrepant health effects associated with inhalation exposure to airborne particles.
Publisher: Springer Science and Business Media LLC
Date: 31-05-2023
Publisher: Elsevier BV
Date: 2019
Publisher: Elsevier BV
Date: 04-2023
Publisher: Elsevier BV
Date: 10-2022
Publisher: Elsevier BV
Date: 12-2022
DOI: 10.1016/J.SCITOTENV.2022.158770
Abstract: Inhaled particulate matter is associated with nasal diseases such as allergic rhinitis, rhinosinusitis and neural disorders. Its health risks on humans are usually evaluated by measurements on monkeys as they share close phylogenetic relationship. However, the reliability of cross-species toxicological extrapolation is in doubt due to physiological and anatomical variations, which greatly undermine the reliability of these expensive human surrogate models. This study numerically investigated in-depth microparticle transport and deposition characteristics on human and monkey (Macaca fuscata) nasal cavities that were reconstructed from CT-images. Deposition characteristics of 1-30μm particles were investigated under resting and active breathing conditions. Similar trends were observed for total deposition efficiencies and a single correlation using Stokes Number was fitted for both species and both breathing conditions, which is convenient for monkey-human extrapolation. Regional deposition patterns were carefully compared using the surface mapping technique. Deposition patterns of low, medium and high inertial particles, classified based on their total deposition efficiencies, were further analyzed in the 3D view and the mapped 2D view, which allows locating particle depositions on specific nasal regions. According to the particle intensity contours and regional deposition profiles, the major differences were observed at the vestibule and the floor of the nasal cavity, where higher deposition intensities of medium and high inertial particles were shown in the monkey case than the human case. Comparisons of airflow streamlines indicated that the cross-species variations of microparticle deposition patterns are mainly contributed by two factors. First, the more oblique directions of monkey nostrils result in a sharper airflow turn in the vestibule region. Second, the monkey's relatively narrower nasal valves lead to higher impaction of medium and high inertial particles on the nasal cavity floor. The methods and findings in this study would contribute to an improved cross-species toxicological extrapolation between human and monkey nasal cavities.
Publisher: SAGE Publications
Date: 03-2017
Abstract: Vehicular toxic emissions can easily contaminate the air quality of the enclosed tunnel environment, especially during rush hours with traffic jam events or low vehicle speeds, which poses serious health hazards to road utilizers. The piston effect generated by moving vehicles was normally considered adequate to discharge vitiated air out of short tunnel based on a typical driving speed. However, complex traffic conditions may yield unexpected consequences on in-tunnel air quality levels. This study numerically investigated the CO 2 concentration to identify the in-tunnel pollutant dispersion under three traffic conditions including severe traffic congestion and traffic flow with low vehicle speeds. Fan conditions were considered to model the influence of mechanical winds on pollutant dispersion and comparison with vehicular piston effect was also performed. The results revealed elevated pollutant concentration regions were found at the vicinity of near-ground region and tunnel downstream. The vehicular piston effect can sufficiently remove the in-tunnel vehicular emissions when vehicles travel at relatively higher speed. However, pollutant accumulation occurs when vehicles are idling or moving at slow speed. Compared with traffic piston effect at high travelling speed, the mechanical ventilation of ceiling mounted fans only generate a limited contribution to the removal of emissions.
Publisher: Elsevier BV
Date: 07-2018
DOI: 10.1016/J.MEDENGPHY.2018.04.010
Abstract: A major functional role of the nasal cavity is air conditioning of the inspired environmental air to near alveolar conditions. It is well known that the anatomical disparities among nasal passages can change airflow patterns to a great extent. However, its effect on nasal air conditioning performance remains largely unexplored. This research investigated the nasal air conditioning performance among nasal models with distinct vestibule phenotypes, including subjects with and without vestibule notches. For the mass transfer, we used a two-film theory model to determine the species transport. Airflow patterns, heat and mass transfer between the inhaled airflow and the nasal mucosa were analysed and compared. Results showed that the nasal air conditioning performance is closely related to nasal passage structures. The anatomical variations, especially the geometry changes in the anterior vestibule region, can increase both heat and mass transfer rate between nasal mucous and respiratory air at the vicinity of the notched regions, while for other regions such as the anterior superior nasal cavity, the heat transfer is greatly reduced to even zero heat flux due to lack of active airflow passing.
Publisher: MDPI AG
Date: 23-02-2017
DOI: 10.3390/ATMOS8030043
Abstract: In this study, the effect of seasonal variation on air flow and pollutant dispersion characteristics was numerically investigated. A three-dimensional urban canopy model with unit aspect ratio (H/D = 1) was used to calculate surface temperature distribution in the street canyon. Four representative time events (1000 LST, 1300 LST, 1600 LST and 2000 LST) during typical clear summer and winter days were selected to examine the air flow diurnal variation. The results revealed the seasonal variation significantly altered the street canyon microclimate. Compared with the street canyon surface temperature distribution in summer, the winter case showed a more evenly distributed surface temperature. In addition, the summer case showed greater daily temperature fluctuation than that of the winter case. Consequently, distinct pollutant dispersion patterns were observed between summer and winter scenarios, especially for the afternoon (1600 LST) and night (2000 LST) events. Among all studied time events, the pollutant removal performance of the morning (1000 LST) and the night (2000 LST) events were more sensitive to the seasonal variation. Lastly, limited natural ventilation performance was found during the summer morning and the winter night, which induced relatively high pollutant concentration along the pedestrian height level.
Publisher: Elsevier BV
Date: 09-2023
Publisher: Elsevier BV
Date: 11-2023
Publisher: Elsevier BV
Date: 2021
Publisher: IEEE
Date: 04-2017
Publisher: Elsevier BV
Date: 06-2019
DOI: 10.1016/J.CLINBIOMECH.2017.10.006
Abstract: A major issue among computational respiratory studies is the wide variety of nasal morphologies being studied, caused by both inter-population and inter-subject variations. Six nasal cavity geometries exhibiting erse geometry variations were subjected to steady inhalation flow rate of 15L/min. to determine if any consistent flow behaviour could be found. Despite vastly different geometries we were able to identify consistent flow patterns including relatively high velocity in the nasal valve region, followed by flow continuing predominantly in the inferior half of the airway. We also found conformity among models where the inhaled air reached a near-conditioned state by the middle of the nasal cavity. Air from the front of the face reached the olfactory regions while air from the lateral sides of the face moved through the inferior half of the nasal cavity. The ability to predict gross flow features provides a baseline flow field to compare against. This contributes towards establishing well defined flow predictions and be used as a comparison for future larger studies.
Publisher: Elsevier BV
Date: 09-2018
Publisher: Elsevier BV
Date: 07-2018
Publisher: Elsevier BV
Date: 10-2024
Publisher: Elsevier BV
Date: 02-2022
Publisher: Elsevier BV
Date: 03-2015
Publisher: MDPI AG
Date: 18-07-2019
Abstract: Rats have been widely used as surrogates for evaluating the adverse health effects of inhaled airborne particulate matter. This paper presents a computational fluid and particle dynamics (CFPD) study of particle transport and deposition in an approximate rat central airway model. The geometric model was constructed based on magnetic resonance (MR) imaging data sourced from previous study. Lung-inhalable particles covering a diameter range from 20 nm to 1.0 µm were passively released into the trachea, and the Lagrangian particle tracking approach was used to predict in idual particle trajectories. Overall, regional and local deposition patterns in the central airway were analyzed in detail. A preliminary interspecies data comparison was made between present rat models and previously published human data. Results showed deposition “hot spots” were mainly concentrated at airway bifurcation apexes, and a gravitational effect should also be considered for inertia particles when using a rat as a laboratory animal. While for humans, this may not happen as the standing posture is completely different. Lastly, the preliminary interspecies data comparison confirms the deposition similarity in terms of deposition enhancement factors, which is a weighted deposition concentration parameter. This interspecies comparison confirms feasibility of extrapolating surrogate rat deposition data to humans using existing data extrapolation approach, which mostly relies on bulk anatomical differences as dose adjustment factors.
Publisher: Oxford University Press (OUP)
Date: 13-05-2016
Abstract: To gain a better understanding of nanoparticle exposure in human nasal cavities, laboratory animals (e.g. rat) are used for in vivo studies. However, due to anatomical differences between human and rodent nasal cavities, direct particle deposition comparisons between species are difficult. This paper presents a comparative nanoparticle (1 nm, 10 nm, and 100 nm) deposition study using anatomically realistic models of a human and rat nasal cavity. The particle deposition fraction was highest consistently in the main nasal passage, for all nanoparticles tested, in the human model whereas this was only the case for 10 nm, and 100 nm particles for the rodent model, where greater deposition was found in the anterior nose for 1 nm particles. A deposition intensity (DI) term was introduced to represent the accumulated deposition fraction on cross-sectional slices. A common and preferential deposition site in the human model was found for all nanoparticles occurring at a distance of 3.5 cm inside the nasal passage. For the rodent model maximum DI occurred in the vestibule region at a distance of 0.3 cm, indicating that the rodent vestibule produces exceptionally high particle filtration capability. We also introduced a deposition flux which was a ratio of the regional deposition fraction relative to the region's surface area fraction. This value allowed direct comparison of deposition flux between species, and a regional extrapolation scaling factor was found (e.g. 1/10 scale for vestibule region for rat to human comparison). This study bridges the in vitro exposure experiments and in vivo nanomaterials toxicity studies, and can contribute towards improving inter-species exposure extrapolation studies in the future.
Publisher: Stichting Nase
Date: 04-2020
DOI: 10.4193/RHIN19.387
Publisher: Elsevier BV
Date: 10-2016
DOI: 10.1016/J.COMPBIOMED.2016.08.002
Abstract: In this study, the effects of nasal drug delivery device and the spray nozzle orientation on sprayed droplets deposition in a realistic human nasal cavity were numerically studied. Prior to performing the numerical investigation, an in-house designed automated actuation system representing mean adults actuation force was developed to produce realistic spray plume. Then, the spray plume development was filmed by high speed photography system, and spray characteristics such as spray cone angle, break-up length, and average droplet velocity were obtained through off-line image analysis. Continuing studies utilizing those experimental data as boundary conditions were applied in the following numerical spray simulations using a commercially available nasal spray device, which was inserted into a realistic adult nasal passage with external facial features. Through varying the particle releasing direction, the deposition fractions of selected particle sizes on the main nasal passage for targeted drug delivery were compared. The results demonstrated that the middle spray direction showed superior spray efficiency compared with upper or lower directions, and the 10µm agents were the most suitable particle size as the majority of sprayed agents can be delivered to the targeted area, the main passage. This study elaborates a comprehensive approach to better understand nasal spray mechanism and evaluate its performance for existing nasal delivery practices. Results of this study can assist the pharmaceutical industry to improve the current design of nasal drug delivery device and ultimately benefit more patients through optimized medications delivery.
Publisher: Elsevier BV
Date: 10-2015
Publisher: Elsevier BV
Date: 05-2018
DOI: 10.1016/J.IJPHARM.2018.03.046
Abstract: The complex nasal structure poses obstacles for efficient nasal drug administration beyond the nasal valve, especially when targeting the olfactory region. This study numerically detailed the naturally inhaled nanoparticle transport process from the initial releasing locations to the final deposited sites using a realistic human nasal passage. Dispersed nanoparticles at different coronal cross-sections were partitioned into multiple groups according to their final deposited locations. Results showed inhaled nanoparticles are more likely to move along the septum. Olfactory deposited particles entered the nose through the inner superior corner of the nostril the middle meatus deposited particles entered the nose through the top third of the nostril the inferior deposited particles entered via the bottom floor regions of the nostril. Therefore, targeted nasal inhalation therapies that intentionally release therapeutic particles from these recognized regions at the nostril plane can considerably improve the resultant topical disposition doses. However, it remains challenging to completely prevent undesired particle depositions as particles coming from the same location may produce multiple-sites depositions due to partition overlapping. Nevertheless, the fraction of undesired particle deposition is anticipated to be reduced at a great extent compared to unplanned releasing approaches.
Publisher: Informa UK Limited
Date: 02-01-2018
DOI: 10.1080/08958378.2018.1439549
Abstract: Rats have been widely used as surrogates for evaluating the health effects of inhaled airborne particulate matter. To provide a thorough understanding of particle transport and deposition mechanisms in the rat nasal airway, this article presents a computational fluid dynamics (CFD) study of particle exposure in a realistic rat nasal passage under a resting flow condition. Particles covering a diameter range from 1 nm to 4 µm were passively released in front of the rat's breathing zone, and the Lagrangian particle tracking approach was used to calculate in idual particle trajectories. Detailed particle deposition analysis shows the deposition of inertial particles >2 µm is high in the rat nasal vestibule and more than 70% of all inhaled inertial particles were trapped in this region. While for diffusive nanoparticles, the vestibule filtration effect is reduced, only less than 60% of inhaled nanoparticles were blocked by the anterior nasal structures. The particle exposure in the olfactory region only shows notable deposition for diffusive nanoparticles, which peaks at 9.4% for 5 nm particles. Despite the olfactory deposition remains at a low level, the ratio between the olfactory and the main passage is kept around 30-40% for 10-800 nm particles, which indicates a particle-size-independent distribution pattern in the main nasal passage and olfactory. This study provides a deep understanding of particles deposition features in a rat nasal passage, and the research findings can aid toxicologist in inter-species exposure-response extrapolation study.
Publisher: Elsevier BV
Date: 12-2023
Publisher: Elsevier BV
Date: 08-2012
Publisher: Springer Science and Business Media LLC
Date: 24-05-2017
Publisher: Elsevier BV
Date: 12-2013
Publisher: Springer Science and Business Media LLC
Date: 02-09-2022
Publisher: Informa UK Limited
Date: 28-01-2019
Publisher: Elsevier BV
Date: 10-2018
Publisher: Elsevier BV
Date: 2019
DOI: 10.1016/J.CLINBIOMECH.2018.12.006
Abstract: Understanding respiratory physiology can aid clinicians in diagnosing the cause of respiratory symptoms or shed light on drug delivery inhaler device optimisation. However, the sheer complexity of the human lung prohibits a full-scale study. In this study, a realistic respiratory airway model including large-to-small conducting airways was built. This airway model consists of subject-specific upper and lower airways, extending from nasal and oral openings to terminal bronchioles (up to the 15th generation). Based on the subject-specific airway model, topological information was extracted and a digital reference model that exhibits strong asymmetry and multi-fractal properties was provided. Inhalation flow rates 18 L/min and 50 L/min were adopted to understand inspiratory conditions subjecting to resting and light exercise inhalation modes. Regional airflow in terms of axial velocity and secondary flow vortices along the lung airway model was extracted. Obvious secondary flow currents were seen in the larynx-trachea segment and left main bronchus, while for the terminal conducting airway in the right lower lobe, the airflow tends to be much smoother with no secondary flow currents. This paper provides insights on respiratory physiology, especially in the lower lung airways, and will be potentially useful for diagnosis of lower airway diseases.
Publisher: Frontiers Media SA
Date: 23-02-2023
DOI: 10.3389/FPED.2023.1083699
Abstract: Adenoid hypertrophy (AH) is an obstructive condition due to enlarged adenoids, causing mouth breathing, nasal blockage, snoring and/or restless sleep. While reliable diagnostic techniques, such as lateral soft tissue x-ray imaging or flexible nasopharyngoscopy, have been widely adopted in general practice, the actual impact of airway obstruction on nasal airflow and inhalation exposure to drug aerosols remains largely unknown. In this study, the effects of adenoid hypertrophy on airflow and micron particle inhalation exposure characteristics were analysed by virtually comparing pre- and postoperative models based on a realistic 3-year-old nasal airway with AH. More specifically, detailed comparison focused on anatomical shape variations, overall airflow and olfactory ventilation, associated particle deposition in overall and local regions were conducted. Our results indicate that the enlarged adenoid tissue can significantly alter the airflow fields. By virtually removing the enlarged tissue and restoring the airway, peak velocity and wall shear stress were restored, and olfactory ventilation was considerably improved (with a 16∼63% improvement in terms of local ventilation speed). Furthermore, particle deposition results revealed that nasal airway with AH exhibits higher particle filtration tendency with densely packed deposition hot spots being observed along the floor region and enlarged adenoid tissue area. While for the postoperative model, the deposition curve was shifted to the right. The local deposition efficiency results demonstrated that more particles with larger inertia can be delivered to the targeted affected area following Adenoidectomy (Adenoid Removal). Research findings are expected to provide scientific evidence for adenoidectomy planning and aerosol therapy following Adenoidectomy, which can substantially improve present clinical treatment outcomes.
Publisher: SAGE Publications
Date: 23-01-2017
Abstract: This paper presents an improved annular water–air jet pump concept design through integrating a self-induced oscillation mixing chamber with the conventional annular jet pump (AJP). The internal flow characteristics for both conventional and improved AJP were numerically investigated and compared by a validated computational fluid dynamics model. The numerical comparison demonstrated an approximately 10% pumping performance increase compared with the conventional pump, which is mostly attributed to the improved mass and energy transfer along the oscillating phase interface. Furthermore, transient flow analysis was conducted to resolve the unsteady self-introduced oscillation. The results revealed the self-introduced oscillation induces a continuous break-up and formation of fresh water–air interfaces, which exhibits a periodic feature with a dominant frequency of 147 Hz for the current design under given operational conditions. This study contributes toward a better understanding of the internal annular water–air jet pump flow patterns, and also demonstrates the feasibility of incorporating self-introduced oscillation chamber into AJP design.
Publisher: Taiwan Association for Aerosol Research
Date: 2022
DOI: 10.4209/AAQR.210338
Publisher: Oxford University Press (OUP)
Date: 10-06-2011
DOI: 10.1093/HMG/DDR270
Publisher: Springer Science and Business Media LLC
Date: 15-04-2021
Publisher: Taiwan Association for Aerosol Research
Date: 2018
Publisher: Elsevier BV
Date: 08-2017
Publisher: Elsevier BV
Date: 2023
Publisher: Elsevier BV
Date: 09-2012
Publisher: Informa UK Limited
Date: 18-11-2017
Publisher: MDPI AG
Date: 23-02-2022
Abstract: Although many parametric studies have been conducted in developing standardized nasal geometry and analysing associated airflow dynamics, most of them are based on symmetrical nasal chambers assumption, while the inter-chamber variations due to the morphological asymmetry of the two nasal chambers are much less investigated. To address this issue, this paper presents an inter-chamber anatomical variability study by developing a shape comparison method to quantify inter-chamber anatomical differences. Then the anatomical deviation is correlated with the flow apportionment and the associated nanoparticle deposition patterns using CFD method. Results show that noticeable inter-chamber difference is observed especially in the inferior and middle passages where most inhaled flow is distributed to. Additionally, the shape of vestibule notch and septum deviation contributes to the discrepancy flow behaviour between two chambers. Consequently, these differences lead to variations in regional nanoparticle deposition, especially for 1 nm particles in the olfactory region, where the inter-chamber differences can reach up to 400%. Our results suggest that the inter-chamber anatomical variation should be considered when developing standardized nasal models.
Publisher: Elsevier BV
Date: 2023
Publisher: Trans Tech Publications, Ltd.
Date: 05-2011
DOI: 10.4028/WWW.SCIENTIFIC.NET/AMR.236-238.1653
Abstract: A numerical approach was used to investigate the flow characteristics around a butterfly valve with the diameter of 2108 mm by the commercial computational fluid dynamics (CFD) code FLUENT6.3. The simulation was carried out to predict flow field structure, flow resistance coefficient, hydrodynamics torque and so on, when the large diameter butterfly valve operated at various opening degrees. The three-dimensional simulation results shown that there are vortexes presented near valve back region as the opening degree smaller than 40 degree the flow resistance coefficient reduces rapidly with the increasing of opening degree and the resistance coefficient is quite small as the angle larger than 50 degree the hydrodynamic torque reduces with the increasing of opening degree and the hydrodynamic torque is smaller than 20% of maximum torque the torque ratio and the pressure drop ratio are reduce with the increasing of opening degree, the pressure drop ratio reduces rapidly as the opening degree is smaller than 50 degree.
Publisher: Elsevier BV
Date: 03-2017
Publisher: Elsevier BV
Date: 02-2012
Publisher: Elsevier BV
Date: 03-2017
DOI: 10.1016/J.IJCARD.2017.01.001
Abstract: Vascular disease (VD), as assessed by history of myocardial infarction or peripheral artery disease or aortic plaque, increases stroke risk in atrial fibrillation (AF), and is a component of risk assessment using the CHA We analysed data from the ARAPACIS study, an observational study including 2027 Italian patients with non-valvular AF, in whom CP was detected using Doppler Ultrasonography. VD was reported in 351 (17.3%) patients while CP was detected in 16.6% patients. Adding CP to the VD definition leaded to higher VD prevalence (30.9%). During a median [IQR] follow-up time of 36months, 56 (2.8%) stroke/TIA events were recorded. Survival analysis showed that conventional VD alone did not increase the risk of stroke (Log-Rank: 0.009, p=0.924), while addition of CP to conventional VD was significantly associated to an increased risk of stroke (LR: 5.730, p=0.017). Cox regression analysis showed that VD+CP was independently associated with stroke (HR: 1.78, 95% CI: 1.05-3.01, p=0.0318). Reclassification analysis showed that VD+CP allowed a significant risk reclassification when compared to VD alone in predicting stroke at 36months (NRI: 0.192, 95% CI: 0.028-0.323, p=0.032). In non-valvular AF patients the addition of ultrasound detection of carotid plaque to conventional VD significantly increases the predictive value of CHA
Publisher: MDPI AG
Date: 28-07-2022
Abstract: Airway stenosis is a global respiratory health problem that is caused by airway injury, endotracheal intubation, malignant tumor, lung aging, or autoimmune diseases. A precise understanding of the airflow dynamics and pharmaceutical aerosol transport through the multi-stenosis airways is vital for targeted drug delivery, and is missing from the literature. The object of this study primarily relates to behaviors and nanoparticle transport through the multi-stenosis sections of the trachea and upper airways. The combination of a CT-based mouth–throat model and Weibel’s model was adopted in the ANSYS FLUENT solver for the numerical simulation of the Euler–Lagrange (E-L) method. Comprehensive grid refinement and validation were performed. The results from this study indicated that, for all flow rates, a higher velocity was usually found in the stenosis section. The maximum velocity was found in the stenosis section having a 75% reduction, followed by the stenosis section having a 50% reduction. Increasing flow rate resulted in higher wall shear stress, especially in stenosis sections. The highest pressure was found in the mouth–throat section for all flow rates. The lowest pressure was usually found in stenosis sections, especially in the third generation. Particle escape rate was dependent on flow rate and inversely dependent on particle size. The overall deposition efficiency was observed to be significantly higher in the mouth–throat and stenosis sections compared to other areas. However, this was proven to be only the case for a particle size of 1 nm. Moreover, smaller nanoparticles were usually trapped in the mouth–throat section, whereas larger nanoparticle sizes escaped through the lower airways from the left side of the lung this accounted for approximately 50% of the total injected particles, and 36% escaped from the right side. The findings of this study can improve the comprehensive understanding of airflow patterns and nanoparticle deposition. This would be beneficial in work with polydisperse particle deposition for treatment of comprehensive stenosis with specific drugs under various disease conditions.
Publisher: Elsevier BV
Date: 08-2023
Publisher: Wiley
Date: 21-11-2013
DOI: 10.1002/CNM.2529
Abstract: The study of cardiovascular models was presented in this paper based on medical image reconstruction and computational fluid dynamics. Our aim is to provide a reality platform for the purpose of flow analysis and virtual intervention outcome predication for vascular diseases. By connecting two porous mediums with transient permeability at the downstream of the carotid bifurcation branches, a downstream peripheral impedance model was developed, and the effect of the downstream vascular bed impedance can be taken into consideration. After verifying its accuracy with a healthy carotid bifurcation, this model was implemented in a diseased carotid bifurcation analysis. On the basis of time-averaged wall shear stress, oscillatory shear index, and the relative residence time, fractions of abnormal luminal surface were highlighted, and the atherosclerosis was assessed from a hemodynamic point of view. The effect of the atherosclerosis on the transient flow ision between the two branches because of the existence of plaque was also analysed. This work demonstrated that the proposed downstream peripheral vascular impedance model can be used for computational modelling when the outlets boundary conditions are not available, and successfully presented the potential of using medical imaging and numerical simulation to provide existing clinical prerequisites for diagnosis and therapeutic treatment.
Publisher: Elsevier BV
Date: 2019
Publisher: Informa UK Limited
Date: 25-09-2015
DOI: 10.3109/08958378.2015.1088600
Abstract: Micron-sized particle deposition in anatomically realistic models of a rat and human nasal cavity was numerically investigated. A steady laminar inhalation flow rate was applied and particles were released from the outside air. Particles showing equivalent total particle deposition fractions were classified into low, medium and high inertial particle. Typical particle sizes are 2.5, 9 and 20 μm for the human model and 1, 2 and 3 μm for the rat model, respectively. Using a surface-mapping technique the 3D nasal cavity surface was "unwrapped" into a 2D domain and the particle deposition locations were plotted for complete visual coverage of the domain surface. The total surface area comparison showed that the surface area of the human nasal model was about ten times the size of the rat model. In contrast, the regional surface area percentage analysis revealed the olfactory region of the rat model was significantly larger than all other regions making up ∼55.6% of the total surface area, while that of the human nasal model only occupying 10.5%. Flow pattern comparisons showed rapid airflow acceleration was found at the nasopharynx region and the nostril region for the human and rat model, respectively. For the human model, the main passage is the major deposition region for micro-particles. While for the rat model, it is the vestibule. Through comparing the regional deposition flux between human and rat models, this study can contribute towards better extrapolation approach of inhalation exposure data between inter-subject species.
Publisher: Taiwan Association for Aerosol Research
Date: 2020
Publisher: Elsevier BV
Date: 11-2013
Publisher: Elsevier BV
Date: 2017
Publisher: Elsevier BV
Date: 12-2014
Publisher: Elsevier BV
Date: 06-2010
Publisher: American Society of Mechanical Engineers
Date: 13-11-2015
Abstract: To improve the understanding of dose-response extrapolation from rat to human, regional micro-particle deposition patterns are numerically investigated and compared between human and rat realistic nasal cavities using Computational Fluid Dynamics (CFD). Resting breathing conditions are chosen and airflow patterns are visualised by streamlines. To have better comparisons of deposition patterns, deposited particles are projected into pre- ided 2D domains based on anatomical features using surface-mapping technique. The results show significant differences between human and rat due to the different nasal geometries, especially at vestibule regions. In human case, large micro-particles deposit primarily in vestibule, septum and pharynx and small micro-particles relatively scattered in the whole cavity. On the contrary, in the rat case, large and small micro-particles are captured by the first and second bend of vestibule region.
Publisher: American Society of Hematology
Date: 13-01-2022
Abstract: ALK-positive histiocytosis is a rare subtype of histiocytic neoplasm first described in 2008 in 3 infants with multisystemic disease involving the liver and hematopoietic system. This entity has subsequently been documented in case reports and series to occupy a wider clinicopathologic spectrum with recurrent KIF5B-ALK fusions. The full clinicopathologic and molecular spectra of ALK-positive histiocytosis remain, however, poorly characterized. Here, we describe the largest study of ALK-positive histiocytosis to date, with detailed clinicopathologic data of 39 cases, including 37 cases with confirmed ALK rearrangements. The clinical spectrum comprised distinct clinical phenotypic groups: infants with multisystemic disease with liver and hematopoietic involvement, as originally described (Group 1A: 6/39), other patients with multisystemic disease (Group 1B: 10/39), and patients with single-system disease (Group 2: 23/39). Nineteen patients of the entire cohort (49%) had neurologic involvement (7 and 12 from Groups 1B and 2, respectively). Histology included classic xanthogranuloma features in almost one-third of cases, whereas the majority displayed a more densely cellular, monomorphic appearance without lipidized histiocytes but sometimes more spindled or epithelioid morphology. Neoplastic histiocytes were positive for macrophage markers and often conferred strong expression of phosphorylated extracellular signal-regulated kinase, confirming MAPK pathway activation. KIF5B-ALK fusions were detected in 27 patients, whereas CLTC-ALK, TPM3-ALK, TFG-ALK, EML4-ALK, and DCTN1-ALK fusions were identified in single cases. Robust and durable responses were observed in 11/11 patients treated with ALK inhibition, 10 with neurologic involvement. This study presents the existing clinicopathologic and molecular landscape of ALK-positive histiocytosis and provides guidance for the clinical management of this emerging histiocytic entity.
Publisher: Springer Science and Business Media LLC
Date: 03-08-2018
DOI: 10.1007/S11739-018-1922-Y
Abstract: In the original publication, one of the ARAPACIS collaborators Dr. "Leonardo Di Gennaro" name has been erroneously mentioned as "Leonardo De Gennaro".
Publisher: Springer Science and Business Media LLC
Date: 25-05-2021
Publisher: Elsevier BV
Date: 09-2021
Publisher: Informa UK Limited
Date: 07-01-2021
Publisher: Elsevier BV
Date: 10-2013
DOI: 10.1016/J.COMPBIOMED.2013.06.013
Abstract: Widely accepted treatment for carotid artery stenosis includes stenting as well as carotid endoarterectomy (CEA), despite complications associated with distal embolism. Therefore pre-screening for evaluating the extent of a stenosis is critically important before undertaking surgical procedures. This study presents and evaluates the feasibility of implementing a virtual computational hemodynamics platform for clinical use to determine the severity of a stenosis and give guidance for surgical decision making. The virtual platform incorporates high-resolution three-dimensional angiography results with Computational Fluid Dynamics modeling to determine clinically related indicators. This includes wall shear stress (WSS), the spatial and temporal hemodynamic changes of blood flow within patient-specific carotid bifurcations, pressure drop coefficient, and severity stratification. The turn-around time for each computational modeling stage was examined which showed that the total time cost is practical and the proposed hemodynamics evaluation platform is reasonably efficient for clinical diagnosis. Furthermore the virtual platform may be used to detect the hemodynamic consequence of atherogenesis, which can then be addressed and quantified based on the distribution of WSS related flow indicators on the abnormal luminal fractions. Additional functional evidence and data can be used by the overseeing physician to enrich and complement the anatomical information for more in-depth evaluation of stenosis in a reasonable time duration.
Publisher: Springer Science and Business Media LLC
Date: 03-03-2013
DOI: 10.1038/NG.2578
Publisher: Elsevier BV
Date: 08-2018
Publisher: Wiley
Date: 29-05-2019
DOI: 10.1002/CNM.3215
Publisher: Wiley
Date: 03-01-2021
DOI: 10.1002/CNM.3414
Publisher: Elsevier BV
Date: 2024
Publisher: Elsevier BV
Date: 2012
Location: United States of America
Start Date: 2021
End Date: 12-2023
Amount: $395,775.00
Funder: Australian Research Council
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