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Luo Q, Yang X, Hang J, Fan X, Luo Z, Gu Z, Ou C. Influence of natural ventilation design on the dispersion of pathogen-laden droplets in a coach bus. Sci Total Environ 2023; 885:163827. [PMID: 37121320 PMCID: PMC10147445 DOI: 10.1016/j.scitotenv.2023.163827] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Track Full Text] [Figures] [Subscribe] [Scholar Register] [Received: 02/08/2023] [Revised: 04/19/2023] [Accepted: 04/25/2023] [Indexed: 05/04/2023]
Abstract
Natural ventilation is an energy-efficient design approach to reduce infection risk (IR), but its optimized design in a coach bus environment is less studied. Based on a COVID-19 outbreak in a bus in Hunan, China, the indoor-outdoor coupled CFD modeling approach is adopted to comprehensively explore how optimized bus natural ventilation (e.g., opening/closing status of front/middle/rear windows (FW/MW/RW)) and ceiling wind catcher (WCH) affect the dispersion of pathogen-laden droplets (tracer gas, 5 μm, 50 μm) and IR. Other key influential factors including bus speed, infector's location, and ambient temperature (Tref) are also considered. Buses have unique natural ventilation airflow patterns: from bus rear to front, and air change rate per hour (ACH) increases linearly with bus speed. When driving at 60 km/h, ACH is only 6.14 h-1 and intake fractions of tracer gas (IFg) and 5 μm droplets (IFd) are up to 3372 ppm and 1394 ppm with ventilation through leakages on skylights and no windows open. When FW and RW are both open, ACH increases by 43.5 times to 267.50 h-1, and IFg and IFd drop rapidly by 1-2 orders of magnitude compared to when no windows are open. Utilizing a wind catcher and opening front windows significantly increases ACH (up to 8.8 times) and reduces IF (5-30 times) compared to only opening front windows. When the infector locates at the bus front with FW open, IFg and IFd of all passengers are <10 ppm. More droplets suspend and further spread in a higher Tref environment. It is recommended to open two pairs of windows or open front windows and utilize the wind catcher to reduce IR in coach buses.
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Affiliation(s)
- Qiqi Luo
- School of Atmospheric Sciences, Sun Yat-sen University, Southern Marine Science and Engineering Guangdong Laboratory (Zhuhai), Zhuhai, PR China; Key Laboratory of Tropical Atmosphere-Ocean System (Sun Yat-sen University), Ministry of Education, Zhuhai 519000, PR China
| | - Xia Yang
- Guangdong Province Engineering Laboratory for Air Pollution Control, Guangzhou, PR China
| | - Jian Hang
- School of Atmospheric Sciences, Sun Yat-sen University, Southern Marine Science and Engineering Guangdong Laboratory (Zhuhai), Zhuhai, PR China; Key Laboratory of Tropical Atmosphere-Ocean System (Sun Yat-sen University), Ministry of Education, Zhuhai 519000, PR China
| | - Xiaodan Fan
- School of Atmospheric Sciences, Sun Yat-sen University, Southern Marine Science and Engineering Guangdong Laboratory (Zhuhai), Zhuhai, PR China; Key Laboratory of Tropical Atmosphere-Ocean System (Sun Yat-sen University), Ministry of Education, Zhuhai 519000, PR China
| | - Zhiwen Luo
- Welsh School of Architecture, Cardiff University, UK
| | - Zhongli Gu
- Guangdong Fans-tech Agro Co., Ltd., PR China
| | - Cuiyun Ou
- School of Atmospheric Sciences, Sun Yat-sen University, Southern Marine Science and Engineering Guangdong Laboratory (Zhuhai), Zhuhai, PR China; Key Laboratory of Tropical Atmosphere-Ocean System (Sun Yat-sen University), Ministry of Education, Zhuhai 519000, PR China.
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Song H, Li X, Huang H, Xie C, Qu W. Postoperative virtual pressure difference as a new index for the risk assessment of liver resection from biomechanical analysis. Comput Biol Med 2023; 157:106725. [PMID: 36913851 DOI: 10.1016/j.compbiomed.2023.106725] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/09/2022] [Revised: 02/21/2023] [Accepted: 02/27/2023] [Indexed: 03/05/2023]
Abstract
In the realm of hepatectomy, traditional methods for postoperative risk assessment are limited in their ability to provide comprehensive and intuitive evaluations of donor risk. To address this issue, there is a need for the development of more multifaceted indicators to assess the risk in hepatectomy donors. In an effort to improve postoperative risk assessments, a computational fluid dynamics (CFD) model was developed to analyze blood flow properties, such as streamlines, vorticity, and pressure, in 10 eligible donors. By comparing the correlation between vorticity, maximum velocity, postoperative virtual pressure difference and TB, a novel index - postoperative virtual pressure difference - was proposed from a biomechanical perspective. This index demonstrated a high correlation (0.98) with total bilirubin values. Donors who underwent right liver lobe resections had greater pressure gradient values than those who underwent left liver lobe resected donors due to the denser streamlines and higher velocity and vorticity values of the former group. Compared with traditional medical methods, the biofluid dynamic analysis using CFD offers advantages in terms of accuracy, efficiency, and intuition.
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Affiliation(s)
- Hongqing Song
- University of Science and Technology Beijing, Beijing, 100083, China
| | - Xiaofan Li
- University of Science and Technology Beijing, Beijing, 100083, China
| | - Hao Huang
- Liver Transplantation Section, Department of General Surgery, Beijing Friendship Hospital, Capital Medical University, Beijing, 100050, China
| | - Chiyu Xie
- University of Science and Technology Beijing, Beijing, 100083, China
| | - Wei Qu
- Liver Transplantation Section, Department of General Surgery, Beijing Friendship Hospital, Capital Medical University, Beijing, 100050, China.
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Ganesapillai M, Mondal B, Sarkar I, Sinha A, Ray SS, Kwon YN, Nakamura K, Govardhan K. The face behind the Covid-19 mask - A comprehensive review. Environ Technol Innov 2022; 28:102837. [PMID: 35879973 PMCID: PMC9299984 DOI: 10.1016/j.eti.2022.102837] [Citation(s) in RCA: 7] [Impact Index Per Article: 3.5] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Received: 06/24/2022] [Revised: 07/16/2022] [Accepted: 07/16/2022] [Indexed: 05/07/2023]
Abstract
The threat of epidemic outbreaks like SARS-CoV-2 is growing owing to the exponential growth of the global population and the continual increase in human mobility. Personal protection against viral infections was enforced using ambient air filters, face masks, and other respiratory protective equipment. Available facemasks feature considerable variation in efficacy, materials usage and characteristic properties. Despite their widespread use and importance, face masks pose major potential threats due to the uncontrolled manufacture and disposal techniques. Improper solid waste management enables viral propagation and increases the volume of associated biomedical waste at an alarming rate. Polymers used in single-use face masks include a spectrum of chemical constituents: plasticisers and flame retardants leading to health-related issues over time. Despite ample research in this field, the efficacy of personal protective equipment and its impact post-disposal is yet to be explored satisfactorily. The following review assimilates information on the different forms of personal protective equipment currently in use. Proper waste management techniques pertaining to such special wastes have also been discussed. The study features a holistic overview of innovations made in face masks and their corresponding impact on human health and environment. Strategies with SDG3 and SDG12, outlining safe and proper disposal of solid waste, have also been discussed. Furthermore, employing the CFD paradigm, a 3D model of a face mask was created based on fluid flow during breathing techniques. Lastly, the review concludes with possible future advancements and promising research avenues in personal protective equipment.
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Affiliation(s)
- Mahesh Ganesapillai
- Mass Transfer Group, School of Chemical Engineering, Vellore Institute of Technology, Vellore, Tamil Nadu, India
| | - Bidisha Mondal
- Mass Transfer Group, School of Chemical Engineering, Vellore Institute of Technology, Vellore, Tamil Nadu, India
| | - Ishita Sarkar
- Mass Transfer Group, School of Chemical Engineering, Vellore Institute of Technology, Vellore, Tamil Nadu, India
| | - Aritro Sinha
- Mass Transfer Group, School of Chemical Engineering, Vellore Institute of Technology, Vellore, Tamil Nadu, India
| | - Saikat Sinha Ray
- Department of Urban and Environmental Engineering, Ulsan National Institute of Science and Technology, Republic of Korea
| | - Young-Nam Kwon
- Department of Urban and Environmental Engineering, Ulsan National Institute of Science and Technology, Republic of Korea
| | - Kazuho Nakamura
- Faculty of Engineering, Division of Material Science and Chemical Engineering, Yokohama National University, Tokiwadai, Yokohama, Kanagawa 240-8501, Japan
| | - K Govardhan
- Department of Micro and Nano-Electronics, School of Electronics Engineering, Vellore Institute of Technology, Vellore, Tamil Nadu, India
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Qu W, Li X, Huang H, Xie C, Song H. Mechanisms of the ascites volume differences between patients receiving a left or right hemi-liver graft liver transplantation: From biofluidic analysis. Comput Methods Programs Biomed 2022; 226:107196. [PMID: 36367484 DOI: 10.1016/j.cmpb.2022.107196] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 07/25/2022] [Revised: 10/17/2022] [Accepted: 10/19/2022] [Indexed: 06/16/2023]
Abstract
BACKGROUND AND OBJECTIVE Post-transplant refractory ascites (RA) is common in patients receiving living donor liver transplantation (LDLT) using a left hemi-liver graft than in those using a right hemi-liver graft. However, there is currently no clear mechanism explaining the effect of grafts on ascites drainage. The purpose of this study is to analyze the values of blood flow parameters in the portal vein under different grafts using computational fluid dynamics (CFD) to interpret the relationship between portal pressure values with ascites drainage. METHODS In this work, ascites drainage was counted in 30 patients who underwent left-sided liver transplantation and 26 patients who underwent right-sided liver transplantation. The portal vein flow models of the transplanted liver under different flow rates were established based on computed tomography (CT) images and finite element theory. Ascites drainage and blood flow parameters were qualitatively compared. RESULTS The results show that the ascites drained from patients who received LDLT with a left hemi-liver is three times as that with a right hemi-liver. The simulation results show that the coefficient of the pressure-velocity curve of the left-liver is 1.7 times of the right-liver under the same hydrodynamic conditions, which qualitatively agrees with the clinical data. Moreover, the streamline of the transplanted left liver shows more vortexes compared with the right liver, which is a major reason for the left liver's higher pressure value. CONCLUSION This clinical phenomenon is reproduced and comprehensively explained by the hemodynamic parameters of the portal vein. This work establishes the relationship between portal pressure values and floating water drainage, and offers a new way for physicians to predict postoperative risks intuitively.
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Affiliation(s)
- Wei Qu
- Liver Transplantation Section, Department of General Surgery, Beijing Friendship Hospital, Capital Medical University, Beijing 100050, China; Tsinghua University, Beijing 100084, China
| | - Xiaofan Li
- University of Science and Technology Beijing, Beijing 100083, China
| | - Hao Huang
- Liver Transplantation Section, Department of General Surgery, Beijing Friendship Hospital, Capital Medical University, Beijing 100050, China
| | - Chiyu Xie
- University of Science and Technology Beijing, Beijing 100083, China
| | - Hongqing Song
- University of Science and Technology Beijing, Beijing 100083, China.
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Fallah A, Altunbek M, Bartolo P, Cooper G, Weightman A, Blunn G, Koc B. 3D printed scaffold design for bone defects with improved mechanical and biological properties. J Mech Behav Biomed Mater 2022; 134:105418. [PMID: 36007489 DOI: 10.1016/j.jmbbm.2022.105418] [Citation(s) in RCA: 8] [Impact Index Per Article: 4.0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/26/2022] [Revised: 07/28/2022] [Accepted: 08/12/2022] [Indexed: 10/15/2022]
Abstract
Bone defect treatment is still a challenge in clinics, and synthetic bone scaffolds with adequate mechanical and biological properties are highly needed. Adequate waste and nutrient exchange of the implanted scaffold with the surrounded tissue is a major concern. Moreover, the risk of mechanical instability in the defect area during regular activity increases as the defect size increases. Thus, scaffolds with better mass transportation and mechanical properties are desired. This study introduces 3D printed polymeric scaffolds with a continuous pattern, ZigZag-Spiral pattern, for bone defects treatments. This pattern has a uniform distribution of pore size, which leads to uniform distribution of wall shear stress which is crucial for uniform differentiation of cells attached to the scaffolds. The mechanical, mass transportation, and biological properties of the 3D printed scaffolds are evaluated. The results show that the presented scaffolds have permeability similar to natural bone and, with the same porosity level, have higher mechanical properties than scaffolds with conventional lay-down patterns 0-90° and 0-45°. Finally, human mesenchymal stem cells are seeded on the scaffolds to determine the effects of geometrical microstructure on cell attachment and morphology. The results show that cells in scaffold with ZigZag-Spiral pattern infilled pores gradually, while the other patterns need more time to fill the pores. Considering mechanical, transportation, and biological properties of the considered patterns, scaffolds with ZigZag-Spiral patterns can mimic the properties of cancellous bones and be a better choice for treatments of bone defects.
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Affiliation(s)
- Ali Fallah
- Integrated Manufacturing Technologies Research and Application Center, Sabanci University, Istanbul, 34906, Turkey; Nanotechnology Research and Application Center, Sabanci University, Istanbul, 34956, Turkey; Faculty of Engineering and Natural Sciences, Sabanci University, Istanbul, 34956, Turkey
| | - Mine Altunbek
- Nanotechnology Research and Application Center, Sabanci University, Istanbul, 34956, Turkey; Faculty of Engineering and Natural Sciences, Sabanci University, Istanbul, 34956, Turkey
| | - Paulo Bartolo
- School of Mechanical, Aerospace and Civil Engineering, Manchester Institute of Biotechnology, University of Manchester, Manchester, M13 9PL, UK; Singapore Centre for 3D Printing, School of Mechanical and Aerospace Engineering, Nanyang Technological University, Singapore, 639798, Singapore
| | - Glen Cooper
- School of Mechanical, Aerospace and Civil Engineering, Manchester Institute of Biotechnology, University of Manchester, Manchester, M13 9PL, UK
| | - Andrew Weightman
- School of Mechanical, Aerospace and Civil Engineering, Manchester Institute of Biotechnology, University of Manchester, Manchester, M13 9PL, UK
| | - Gordon Blunn
- School of Pharmacy and Biomedical Sciences, University Portsmouth, Portsmouth, PO1 2UP, UK
| | - Bahattin Koc
- Integrated Manufacturing Technologies Research and Application Center, Sabanci University, Istanbul, 34906, Turkey; Nanotechnology Research and Application Center, Sabanci University, Istanbul, 34956, Turkey; Faculty of Engineering and Natural Sciences, Sabanci University, Istanbul, 34956, Turkey.
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Zhang H, Zhang L, An C, Zhang Y, Shao F, Gao Y, Zhang Y, Li H, Zhang Y, Ren C, Sun K, He W, Cheng F, Wang H, Weitz DA. Large-scale single-cell encapsulation in microgels through metastable droplet-templating combined with microfluidic-integration. Biofabrication 2022; 14. [PMID: 35593920 DOI: 10.1088/1758-5090/ac7168] [Citation(s) in RCA: 5] [Impact Index Per Article: 2.5] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/03/2021] [Accepted: 05/05/2022] [Indexed: 11/11/2022]
Abstract
Current techniques for the generation of cell-laden microgels are limited by numerous challenges, including poorly uncontrolled batch-to-batch variations, processes that are both labor- and time-consuming, the high expense of devices and reagents, and low production rates; this hampers the translation of laboratory findings to clinical applications. To address these challenges, we develop a droplet-based microfluidic strategy based on metastable droplet-templating and microchannel integration for the substantial large-scale production of single cell-laden alginate microgels. Specifically, we present a continuous processing method for microgel generation by introducing amphiphilic perfluoronated alcohols to obtain metastable emulsion droplets as sacrificial templates. In addition, to adapt to the metastable emulsion system, integrated microfluidic chips containing 80 drop-maker units are designed and optimized based on the computational fluid dynamics simulation. This strategy allows single cell encapsulation in microgels at a maximum production rate of 10 ml hr-1 of cell suspension while retaining cell viability and functionality. These results represent a significant advance toward using cell-laden microgels for clinical-relevant applications, including cell therapy, tissue regeneration and 3D bioprinting.
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Affiliation(s)
- Haoyue Zhang
- Dalian University of Technology, Dalian University of Technology, No.2 Linggong Road, High-tech District, Dalian, 116024, P.R.China, Dalian, Liaoning, 116024, CHINA
| | - Liyuan Zhang
- Harvard School of Engineering and Applied Sciences, Harvard University, Pierce Hall, 29 Oxford Street, Cambridge, MA 02138, Cambridge, Massachusetts, MA 02138, UNITED STATES
| | - Chuanfeng An
- Dalian University of Technology, Dalian University of Technology, No.2 Linggong Road, High-tech District, Dalian, 116024, P.R.China, Dalian, Liaoning, 116024, CHINA
| | - Yang Zhang
- Shenzhen University, Laboratory of Regenerative Biomaterials, Department of Biomedical Engineering, Health Science Center, Shenzhen University, Shenzhen, 518037, P.R. China, Shenzhen, Guangdong, 518037, CHINA
| | - Fei Shao
- Dalian University of Technology, Dalian University of Technology, No.2 Linggong Road, High-tech District, Dalian, 116024, P.R.China, Dalian, Liaoning, 116024, CHINA
| | - Yijie Gao
- Dalian Municipal Central Hospital Affiliated of Dalian Medical University, 42 Xuegong Street, Shahekou district, Dalian, Liaoning province, Dalian, Liaoning, 116033, CHINA
| | - Yonghao Zhang
- Dalian University of Technology, Dalian University of Technology, No.2 Linggong Road, High-tech District, Dalian, 116024, P.R.China, Dalian, Liaoning, 116024, CHINA
| | - Hanting Li
- Dalian University of Technology, Dalian University of Technology, No.2 Linggong Road, High-tech District, Dalian, 116024, P.R.China, Dalian, Liaoning, 116024, CHINA
| | - Yujie Zhang
- Dalian University of Technology, Dalian University of Technology, No.2 Linggong Road, High-tech District, Dalian, 116024, P.R.China, Dalian, Liaoning, 116024, CHINA
| | - Changle Ren
- Dalian Municipal Central Hospital Affiliated of Dalian Medical University, 42 Xuegong Street, Shahekou district, Dalian, Liaoning province, Dalian, Liaoning, 116033, CHINA
| | - Kai Sun
- Dalian University of Technology, Dalian University of Technology, No.2 Linggong Road, High-tech District, Dalian, 116024, P.R.China, Dalian, Liaoning, 116024, CHINA
| | - Wei He
- Dalian University of Technology, Dalian University of Technology, No.2 Linggong Road, High-tech District, Dalian, 116024, P.R.China, Dalian, Liaoning, 116024, CHINA
| | - Fang Cheng
- Dalian University of Technology, Dalian University of Technology, No.2 Linggong Road, High-tech District, Dalian, 116024, P.R.China, Dalian, Liaoning, 116024, CHINA
| | - Huanan Wang
- dalian university of technology, Dalian University of Technology, Dalian University of Technology, No.2 Linggong Road, High-tech District, Dalian, 116024, P.R.China, Dalian, 116024, CHINA
| | - David A Weitz
- Harvard School of Engineering and Applied Sciences, Harvard University, Pierce Hall, 29 Oxford Street, Cambridge, MA 02138, Cambridge, Massachusetts, MA 02138, UNITED STATES
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Zhao Z, Xiao Q, Tchivelekete GM, Reilly J, Jiang H, Shu X. Quantification of computational fluid dynamics simulation assists the evaluation of protection by Gypenosides in a zebrafish pain model. Physiol Behav 2020; 229:113223. [PMID: 33127465 DOI: 10.1016/j.physbeh.2020.113223] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/27/2020] [Revised: 10/02/2020] [Accepted: 10/24/2020] [Indexed: 10/23/2022]
Abstract
In recent years, due to its rapid reproduction rate and the similarity of its genetic structure to that of human, the zebrafish has been widely used as a pain model to study chemical influences on behavior. Swimming behaviors are mediated by motoneurons in the spinal cord that drive muscle contractions, therefore a knowledge of internal muscle mechanics can assist the understanding of the effects of drugs on swimming activity. To demonstrate that the technique used in our study can supplement biological observations by quantifying the contribution of muscle effects to altered swimming behaviours, we have evaluated the pain/damage caused by 0.1% acetic acid to the muscle of 5 dpf zebrafish larvae and the effect of protection from this pain/damage with the saponin Gypenosides (GYP) extracted from Gynostemma pentaphyllum. We have quantified the parameters related to muscle such as muscle power and the resultant hydrodynamic force, proving that GYP could alleviate the detrimental effect of acetic acid on zebrafish larvae, in the form of alleviation from swimming debility, and that the muscle status could be quantified to represent the degree of muscle damage due to the acetic acid and the recovery due to GYP. We have also linked the behavioral changes to alteration of antioxidant and inflammation gene expression. The above results provide novel insights into the reasons for pain-related behavioral changes in fish larvae, especially from an internal muscle perspective, and have quantified these changes to help understand the protection of swimming behaviors and internal muscle by GYP from acetic acid-induced damage.
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Affiliation(s)
- Zhenkai Zhao
- Department of Naval Architecture, Ocean, and Marine Engineering, University of Strathclyde, Glasgow G4 0LZ, UK
| | - Qing Xiao
- Department of Naval Architecture, Ocean, and Marine Engineering, University of Strathclyde, Glasgow G4 0LZ, UK.
| | - Gabriel Mbuta Tchivelekete
- Department of Biological and Biomedical Sciences, Glasgow Caledonian University, Glasgow G4 0BA, United Kingdom
| | - James Reilly
- Department of Biological and Biomedical Sciences, Glasgow Caledonian University, Glasgow G4 0BA, United Kingdom
| | - Huirong Jiang
- Strathclyde Institute of Pharmacy and Biomedical Sciences, Glasgow G4 0RE, United Kingdom
| | - Xinhua Shu
- Department of Biological and Biomedical Sciences, Glasgow Caledonian University, Glasgow G4 0BA, United Kingdom; Department of Vision Science, Glasgow Caledonian University, Glasgow G4 0BA, United Kingdom; School of Basic Medical Sciences, Shaoyang University, Shaoyang, Hunan 422000, P. R. China.
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Luo N, Weng W, Xu X, Hong T, Fu M, Sun K. Assessment of occupant-behavior-based indoor air quality and its impacts on human exposure risk: A case study based on the wildfires in Northern California. Sci Total Environ 2019; 686:1251-1261. [PMID: 31412521 DOI: 10.1016/j.scitotenv.2019.05.467] [Citation(s) in RCA: 12] [Impact Index Per Article: 2.4] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 04/16/2019] [Revised: 05/26/2019] [Accepted: 05/30/2019] [Indexed: 05/27/2023]
Abstract
The recent wildfires in California, U.S., have caused not only significant losses to human life and property, but also serious environmental and health issues. Ambient air pollution from combustion during the fires could increase indoor exposure risks to toxic gases and particles, further exacerbating respiratory conditions. This work aims at addressing existing knowledge gaps in understanding how indoor air quality is affected by outdoor air pollutants during wildfires-by taking into account occupant behaviors (e.g., movement, operation of windows and air-conditioning) which strongly influence building performance and occupant comfort. A novel modeling framework was developed to simulate the indoor exposure risks considering the impact of occupant behaviors by integrating building energy and occupant behaviour modeling with computational fluid dynamics simulation. Occupant behaviors were found to exert significant impacts on indoor air flow patterns and pollutant concentrations, based on which, certain behaviors are recommended during wildfires. Further, the actual respiratory injury level under such outdoor conditions was predicted. The modeling framework and the findings enable a deeper understanding of the actual health impacts of wildfires, as well as informing strategies for mitigating occupant health risk during wildfires.
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Affiliation(s)
- Na Luo
- Institute of Public Safety Research, Department of Engineering Physics, Tsinghua University, Beijing 100084, PR China; Beijing Key Laboratory of City Integrated Emergency Response Science, Tsinghua University, Beijing, 100084, PR China; Building Technology and Urban Systems Division, Lawrence Berkeley National Laboratory, USA
| | - Wenguo Weng
- Institute of Public Safety Research, Department of Engineering Physics, Tsinghua University, Beijing 100084, PR China; Beijing Key Laboratory of City Integrated Emergency Response Science, Tsinghua University, Beijing, 100084, PR China.
| | - Xiaoyu Xu
- Institute of Public Safety Research, Department of Engineering Physics, Tsinghua University, Beijing 100084, PR China; Beijing Key Laboratory of City Integrated Emergency Response Science, Tsinghua University, Beijing, 100084, PR China
| | - Tianzhen Hong
- Building Technology and Urban Systems Division, Lawrence Berkeley National Laboratory, USA
| | - Ming Fu
- Hefei Institute for Public Safety Research, Tsinghua University, Hefei, Anhui Province 320601, PR China
| | - Kaiyu Sun
- Building Technology and Urban Systems Division, Lawrence Berkeley National Laboratory, USA
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Chung SK, Byun S, Na Y. Investigation of flow characteristics in the maxillary sinus where polypoid changes develop. Comput Biol Med 2018; 102:180-90. [PMID: 30300763 DOI: 10.1016/j.compbiomed.2018.10.001] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [What about the content of this article? (0)] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/16/2018] [Revised: 10/01/2018] [Accepted: 10/01/2018] [Indexed: 11/22/2022]
Abstract
Flow behavior in the maxillary sinus where polypoid changes develop was investigated using computational fluid dynamics. A nasal cavity model was constructed, after performing a virtual polypectomy based on computed tomography images of a patient, using a computer-aided design software to artificially remove polypoid changes inside the maxillary sinus. Local flow characteristics in the maxillary sinus were examined for one full respiration period. The results showed that the epithelial surfaces where polypoid changes occur are located in the lower part of the maxillary sinus which contains a protruding zone of the sinus and are characterized by stagnation of air during the entire respiration period. Due to the geometric characteristics, a very slow recirculating motion was found to occur in the bulging area for approximately half of the respiration period as a result of interaction with a larger-scale, counter-rotating vortex filling the middle of the maxillary sinus. With a much smaller velocity inside the maxillary sinus compared to that typically found in the airway passage through the middle meatus, both wall shear and pressure changes were found to be vanishingly small along the epithelial surface of the maxillary sinus where polypoid changes were found.
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Chung SK, Kim DW, Na Y. Numerical study on the effect of uncinectomy on airflow modification and ventilation characteristics of the maxillary sinus. Respir Physiol Neurobiol 2016; 228:47-60. [PMID: 26996072 DOI: 10.1016/j.resp.2016.03.011] [Citation(s) in RCA: 11] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [What about the content of this article? (0)] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/20/2015] [Revised: 02/12/2016] [Accepted: 03/15/2016] [Indexed: 11/21/2022]
Abstract
In this study, we examined the effect of uncinectomy on the alteration in local airflows and on the resulting effect on gas exchange in the maxillary sinus, by using computational fluid dynamics in two nasal cavity models: one with a preserved uncinate process, and the other with the uncinate process removed virtually. Uncinectomy distinctively changed the local flow topology by triggering the formation of counter-rotating vortices in the ostiomeatal complex, except for the instants with relatively low airflow rate when the respiration phase changed, ultimately leading to a change in the velocity field inside the ostium and maxillary sinus. Despite a significant increase in the maximum air velocity through the maxillary ostium, ventilation was found to increase only slightly when the uncinate process was removed. Furthermore, the degree of maxillary sinus ventilation by inhaled air was comparable to that by exhaled air. This was true to both models and was independent of the presence of the uncinate process.
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11
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Chung SK, Jo G, Na Y. Investigation of flow characteristics in regions of nasal polypoid change. Comput Biol Med 2016; 70:148-156. [PMID: 26845472 DOI: 10.1016/j.compbiomed.2016.01.011] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/20/2015] [Revised: 01/13/2016] [Accepted: 01/14/2016] [Indexed: 10/22/2022]
Abstract
We used computational fluid dynamics to study the airflow characteristics in the ostiomeatal complex/middle turbinate of the human upper airway, where clinically relevant nasal polypoid changes occur (designated Regions A1-A4). We assessed six different flow rates representing one full period of respiration, based on realistic human respiration data, in an anatomically correct numerical model of a patient with a history of polypectomy. The simulation results showed that Regions A1-A4 were not correlated with the local stagnation points where a locally high level of wall pressure was achieved. They, however, exhibited a very distinctive feature in that the positive wall-normal pressure gradients evaluated at the epithelial surface were persistent at six different flow rates spanning the whole respiration period in these areas. Therefore, the regions where polypoid changes developed were thought to be subject to mechanical irritation of the epithelium constantly via locally accelerating airflow moving towards the surface from the airway. On the contrary, relatively large or small values for local wall shear stress were not correlated with Regions A1-A4.
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Affiliation(s)
- Seung-Kyu Chung
- Department of Otorhinolaryngology, Head and Neck Surgery, Samsung Medical Center, Sungkyunkwan University, School of Medicine, Seoul, Republic of Korea
| | - Gyehwan Jo
- Department of Mechanical Engineering, Konkuk University, Seoul 143-701, Republic of Korea
| | - Yang Na
- Department of Mechanical Engineering, Konkuk University, Seoul 143-701, Republic of Korea.
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Karbaschi M, Taeibi Rahni M, Javadi A, Cronan C, Schano K, Faraji S, Won J, Ferri J, Krägel J, Miller R. Dynamics of drops – Formation, growth, oscillation, detachment, and coalescence. Adv Colloid Interface Sci 2015; 222:413-24. [PMID: 25466690 DOI: 10.1016/j.cis.2014.10.009] [Citation(s) in RCA: 7] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [What about the content of this article? (0)] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/10/2014] [Revised: 10/29/2014] [Accepted: 10/30/2014] [Indexed: 10/24/2022]
Abstract
Single drops or bubbles are frequently used for the characterization of liquid-fluid interfaces. Their advantage is the small volume and the various protocols of their formation. Thus, several important methods are based on single drops and bubbles, such as capillary pressure and profile analysis tensiometry. However, these methods are often applied under dynamic conditions, although their principles are defined under equilibrium conditions. Thus, specific attention has to be paid when these methods are used beyond certain limits. In many cases, computational fluid dynamics (CFD) simulations have allowed researchers, to extend these limits and to gain important information on the interfacial dynamics. Examples discussed here are the capillary pressure tensiometry used for short time and profile analysis tensiometry for long time dynamic interfacial tension measurements, the oscillating drop methods for measuring dilational visco-elasticity. For measuring the coalescence of two drops the liquid dynamics of the subsequently formed liquid bridges have to be considered. In this paper, a thorough review of important experimental and computational findings, related to the dynamics of drops, including its formation, growth, oscillation, detachment, and coalescence is presented. Emphasis is however on some selected important developments. In addition, the paper tries to predict the main directions of advancement in interfacial research for the near future.
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Chung SK, Jo G, Kim SK, Na Y. The effect of a middle meatal antrostomy on nitric oxide ventilation in the maxillary sinus. Respir Physiol Neurobiol 2014; 192:7-16. [PMID: 24333403 DOI: 10.1016/j.resp.2013.12.003] [Citation(s) in RCA: 14] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [What about the content of this article? (0)] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/23/2012] [Revised: 11/30/2013] [Accepted: 12/02/2013] [Indexed: 10/25/2022]
Abstract
The effects of middle meatal antrostomy (MMA) on air and nitric oxide exchange in the human maxillary sinus were quantified using the computational fluid dynamics technique. One full period of respiration was considered in the anatomically correct numerical domain. The simulation results showed that MMA did not cause any noticeable change in the velocity or pressure fields at a global level but induced local velocity as high as 0.21m/s inside the maxillary. Therefore, enlargement of the ostium area by MMA allows inspiratory and expiratory nasal airflow to induce significant convective flows in the sinus, which in turn enhances gas exchange dramatically. At the end of the inspiration phase, NO concentration in the maxillary sinus decreased to about 54% of the initial value. NO concentration decreased only by about 30% during the expiration phase. This difference in reduction rate is thought to result from the difference in airflow velocity in the extended ostium during inspiration vs. expiration.
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Amaral F, Gross-Hardt S, Timms D, Egger C, Steinseifer U, Schmitz-Rode T. The spiral groove bearing as a mechanism for enhancing the secondary flow in a centrifugal rotary blood pump. Artif Organs 2013; 37:866-74. [PMID: 23635098 DOI: 10.1111/aor.12081] [Citation(s) in RCA: 8] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/30/2022]
Abstract
The rapid evolution of rotary blood pump (RBP) technology in the last few decades was shaped by devices with increased durability, frequently employing magnetic or hydrodynamic suspension techniques. However, the potential for low flow in small gaps between the rotor and pump casing is still a problem for hemocompatibility. In this study, a spiral groove hydrodynamic bearing (SGB) is applied with two distinct objectives: first, as a mechanism to enhance the washout in the secondary flow path of a centrifugal RBP, lowering the exposure to high shear stresses and avoiding thrombus formation; and second, as a way to allow smaller gaps without compromising the washout, enhancing the overall pump efficiency. Computational fluid dynamics was applied and verified via bench-top experiments. An optimization of selected geometric parameters (groove angle, width and depth) focusing on the washout in the gap rather than generating suspension force was conducted. An optimized SGB geometry reduced the residence time of the cells in the gap from 31 to 27 ms, an improvement of 14% compared with the baseline geometry of 200 μm without grooves. When optimizing for pump performance, a 15% smaller gap yielded a slightly better rate of fluid exchange compared with the baseline, followed by a 22% reduction in the volumetric loss from the primary pathway. Finally, an improved washout can be achieved in a pulsatile environment due to the SGB ability to pump inwardly, even in the absence of a pressure head.
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Affiliation(s)
- Felipe Amaral
- Institute of Applied Medical Engineering, Helmholtz Institute, Aachen, Germany
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