scholarly journals The Build-Up of Aerosols Carrying the SARS-CoV-2 Coronavirus, in Poorly Ventilated, Confined Spaces

2021 ◽  
Author(s):  
Björn Birnir
Keyword(s):  
Decay Time ◽  
Air Flow ◽  
Time Frame ◽  
Aerosol Concentration ◽  
Confined Space ◽  
Confined Spaces ◽  
Turbulent Air Flow ◽  
Short Time ◽  
Respiratory Droplets ◽  
Standard Ventilation

Abstract A model of the distribution of respiratory droplets and aerosols by Lagrangian turbulent air-flow is developed and used to show how the SARS-CoV-2 Coronavirus can be dispersed by the breathing of an infected person. It is shown that the concentration of viruses in the exhaled cloud can increase to infectious levels with time (grow linearly), in a confined space where the air re-circulates. The model is used to analyze the air-flow and SARS-CoV-2 Coronavirus build-up in a restaurant in Guangzhou, China [32, 30]. It is concluded that the outbreak of Covid-19 pandemic in the restaurant in January 2020, is due to the build-up of the airborne droplets and aerosols carrying the SARS-CoV-2 Coronavirus and would not have been prevented by standard ventilation. A comparison with standard models for aerosol concentration shows that, in the absence of ventilation, the decay of the aerosol concentration is also controlled by the decay time of the virions in aerosols. This decay time is very long, with low relative humidity, and a steady state is not achieved in the time-frame of the contagion. Instead the concentration exhibits a polynomial increase and reaches infectious levels in a relatively short time, explaining the outbreak in the restaurant in Guangzhou.

scholarly journals The Build-Up of Aerosols Carrying the SARS-CoV-2 Coronavirus, in Poorly Ventilated, Confined Spaces

2020 ◽  
Author(s):  
Bjorn Birnir ◽  
Luiza Angheluta
Keyword(s):  
Decay Time ◽  
Air Flow ◽  
Time Frame ◽  
Aerosol Concentration ◽  
Confined Space ◽  
Confined Spaces ◽  
Turbulent Air Flow ◽  
Short Time ◽  
Respiratory Droplets ◽  
Standard Ventilation

Abstract A model of the distribution of respiratory droplets and aerosols by Lagrangian turbulent air-flow is developed and used to show how the SARS-CoV-2 Coronavirus can be dispersed by the breathing of an infected person. It is shown that the concentration of viruses in the exhaled cloud can increase to infectious levels with time (grow linearly), in a confined space where the air re-circulates. The model is used to analyze the air-flow and SARS-CoV-2 Coronavirus build-up in a restaurant in Guangzhou, China [23, 21]. It is concluded that the outbreak of Covid-19 pandemic in the restaurant in January 2020, is due to the build-up of the airborne droplets and aerosols carrying the SARS-CoV-2 Coronavirus and would not have been pre- vented by standard ventilation. A comparison with standard models for aerosol concentration shows that, in the absence of ventilation, the decay of the aerosol concentration is also con- trolled by the decay time of the virions in aerosols. This decay time is very long and a steady state is not achieved in the time-frame of the contagion. Instead the concentration exhibits a polynomial increase and reaches infectious levels in a relatively short time, explaining the outbreak in the restaurant in Guangzhou.

scholarly journals The Build-Up of Aerosols Carrying the SARS-CoV-2 Coronavirus, in Poorly Ventilated, Confined Spaces

2020 ◽  
Author(s):  
Björn Birnir
Keyword(s):  
Decay Time ◽  
Air Flow ◽  
Time Frame ◽  
Aerosol Concentration ◽  
Confined Space ◽  
Confined Spaces ◽  
Turbulent Air Flow ◽  
Short Time ◽  
Respiratory Droplets ◽  
Standard Ventilation

AbstractA model of the distribution of respiratory droplets and aerosols by Lagrangian turbulent air-flow is developed and used to show how the SARS-CoV-2 Coronavirus can be dispersed by the breathing of an infected person. It is shown that the concentration of viruses in the exhaled cloud can increase to infectious levels with time (grow linearly), in a confined space where the air re-circulates. The model is used to analyze the air-flow and SARS-CoV-2 Coronavirus build-up in a restaurant in Guangzhou, China [30, 28]. It is concluded that the outbreak of Covid-19 pandemic in the restaurant in January 2020, is due to the build-up of the airborne droplets and aerosols carrying the SARS-CoV-2 Coronavirus and would not have been prevented by standard ventilation. A comparison with standard models for aerosol concentration shows that, in the absence of ventilation, the decay of the aerosol concentration is also controlled by the decay time of the virions in aerosols. This decay time is very long and a steady state is not achieved in the time-frame of the contagion. Instead the concentration exhibits a polynomial increase and reaches infectious levels in a relatively short time, explaining the outbreak in the restaurant in Guangzhou.

scholarly journals Ventilation and the SARS-CoV-2 Coronavirus Analysis of outbreaks in a restaurant and on a bus in China,and at a Call Center in South Korea

2020 ◽  
Author(s):  
Bjorn Birnir
Keyword(s):  
Call Center ◽  
Air Conditioning ◽  
Air Flow ◽  
Second Step ◽  
Infected Person ◽  
Confined Space ◽  
Air Conditioning System ◽  
Turbulent Air Flow ◽  
Lay Buddhists ◽  
Respiratory Droplets

In a previous paper [10] a model of the distribution of respiratory droplets and aerosols by Lagrangian turbulent air-flow was developed. It is used to show how the SARS-CoV-2 Coronavirus can be spread by the breathing of single infected person. The model shows that the concentration of viruses in the cloud, exhaled by one person, can increase to infectious levels within a certain amount of time, in a confined space where the air re-circulates. In [10] the model was used to analyze the air-flow and SARS-CoV-2 Coronavirus build-up in a restaurant in Guangzhou, China [19,18]. In this paper, we add the analysis of two more cases, an outbreak among lay-Buddhists, on a bus [26], traveling to a ceremony in Zhejiang province, China, and an outbreak in a Call Center in Seoul, Korea [20]. The analysis and comparison of these three cases, leads to the conclusion that the SARS-CoV-2 Coronavirus attacks in two steps: The first step is a linear spread between individuals with a couple of days delay. The second step is an exponential spread effected by the air-conditioning system affecting a much larger number of people. Thus in the second step, the ventilation becomes the super-spreader.

Humidity Control in Confined Building Spaces Using Liquid Desiccant Dehumidifier-Conceptual Investigation

Solar Energy ◽  
2004 ◽  
Author(s):  
D. Dong ◽  
M. Liu
Keyword(s):  
Physical Models ◽  
Conceptual System ◽  
Confined Space ◽  
Short Time Period ◽  
Liquid Desiccant ◽  
Humidity Control ◽  
Confined Spaces ◽  
Time Period ◽  
Short Time ◽  
Simultaneous Heat

Moisture and moisture-related problems often originate from the confined spaces such as bathrooms and kitchens, where large amounts of moisture are released within a short time period. These problems are identified by signs including condensation on windows and walls as well as mold and fungi growth in corners of interior surfaces of walls and ceiling. To prevent condensation and formations of mold and fungi in the confined spaces, a special desiccant dehumidification system may be used. This system uses ambient space air to regenerate when the spaces produce no moisture. To investigate the feasibility of the desiccant dehumidification system for confined space humidity control, a conceptual system and physical models were developed. Numerical simulations were conducted to calculate simultaneous heat and mass transfer involved among moisture source, space air and liquid desiccant. This paper presents the methods and simulated results. The results show that use of the desiccant dehumidification system can substantially reduce the room humidity level.

scholarly journals Polyethylene Migration from Food Packaging on Cheese Detected by Raman and Infrared (ATR/FT-IR) Spectroscopy

Materials ◽  
2021 ◽  
Vol 14 (14) ◽  
pp. 3872
Author(s):  
Klytaimnistra Katsara ◽  
George Kenanakis ◽  
Zacharias Viskadourakis ◽  
Vassilis M. Papadakis
Keyword(s):  
Vibrational Spectroscopy ◽  
Food Packaging ◽  
Time Frame ◽  
Low Density Polyethylene ◽  
Low Density ◽  
Ft Ir ◽  
Comparative Results ◽  
Short Time ◽  
And Storage ◽  
Ft Ir Spectroscopy

For multiple years, food packaging migration has been a major concern in food and health sciences. Plastics, such as polyethylene, are continuously utilized in food packaging for preservation and easy handling purposes during transportation and storage. In this work, three types of cheese, Edam, Kefalotyri and Parmesan, of different hardness were studied under two complementary vibrational spectroscopy methods, ATR-FTIR and Raman spectroscopy, to determine the migration of low-density polyethylene from plastic packaging to the surface of cheese samples. The experimental duration of this study was set to 28 days due to the degradation time of the selected cheese samples, which is clearly visible after 1 month in refrigerated conditions at 4 °C. Raman and ATR-FTIR measurements were performed at a 4–3–4–3 day pattern to obtain comparative results. Initially, consistency/repeatability measurement tests were performed on Day0 for each sample of all cheese specimens to understand if there is any overlap between the characteristic Raman and ATR-FTIR peaks of the cheese with the ones from the low-density polyethylene package. We provide evidence that on Day14, peaks of low-density polyethylene appeared due to polymeric migration in all three cheese types we tested. In all cheese samples, microbial outgrowth started to develop after Day21, as observed visually and under the bright-field microscope, causing peak reverse. Food packaging migration was validated using two different approaches of vibrational spectroscopy (Raman and FT-IR), revealing that cheese needs to be consumed within a short time frame in refrigerated conditions at 4 °C.

scholarly journals Breeding Strategies to Improve Miscanthus as a Sustainable Source of Biomass for Bioenergy and Biorenewable Products

Agronomy ◽  
2019 ◽  
Vol 9 (11) ◽  
pp. 673 ◽  
Author(s):  
John Clifton-Brown ◽  
Kai-Uwe Schwarz ◽  
Danny Awty-Carroll ◽  
Antonella Iurato ◽  
Heike Meyer ◽  
...  
Keyword(s):  
Significant Contribution ◽  
Perennial Grass ◽  
Time Frame ◽  
Eastern Asia ◽  
Germplasm Collections ◽  
Naturally Occurring ◽  
Wide Range ◽  
Yield Quality ◽  
Short Time ◽  
Commercial Expansion

Miscanthus, a C4 perennial grass native to Eastern Asia, is being bred to provide biomass for bioenergy and biorenewable products. Commercial expansion with the clonal hybrid M. × giganteus is limited by low multiplication rates, high establishment costs and drought sensitivity. These limitations can be overcome by breeding more resilient Miscanthus hybrids propagated by seed. Naturally occurring fast growing indigenous Miscanthus species are found in diverse environments across Eastern Asia. The natural diversity provides for plant breeders, the genetic resources to improve yield, quality, and resilience for a wide range of climates and adverse abiotic stresses. The challenge for Miscanthus breeding is to harness the diversity through selections of outstanding wild types, parents, and progenies over a short time frame to deploy hybrids that make a significant contribution to a world less dependent on fossil resources. Here are described the strategies taken by the Miscanthus breeding programme at Aberystwyth, UK and its partners. The programme built up one of the largest Miscanthus germplasm collections outside Asia. We describe the initial strategies to exploit the available genetic diversity to develop varieties. We illustrate the success of combining diverse Miscanthus germplasm and the selection criteria applied across different environments to identify promising hybrids and to develop these into commercial varieties. We discuss the potential for molecular selections to streamline the breeding process.

Forced ignition of dispersions of liquid fuel in turbulent air flow

2017 ◽  
Author(s):  
Pedro M. de Oliveira ◽  
Epaminondas Mastorakos ◽  
Patton M. Allison
Keyword(s):  
Liquid Fuel ◽  
Air Flow ◽  
Turbulent Air Flow

Ranking the explanatory power of factors associated with worldwide new Covid-19 cases

2021 ◽  
Author(s):  
Aristides Moustakas
Keyword(s):  
Explanatory Power ◽  
Interdisciplinary Approach ◽  
Time Frame ◽  
Variance Partitioning ◽  
Total Variance ◽  
Disease Spread ◽  
Spatial Spread ◽  
Global Pandemic ◽  
Governmental Intervention ◽  
Short Time

Abstract Disease spread is a complex phenomenon requiring an interdisciplinary approach. Covid-19 exhibited a global spatial spread in a very short time frame resulting in a global pandemic. Data of new Covid-19 cases per million were analysed worldwide at the spatial scale of a country and time replicated from the end of December 2019 to late May 2020. Data driven analysis of epidemiological, economic, public health, and governmental intervention variables was performed in order to select the optimal variables in explaining new Covid-19 cases across all countries in time. Sequentially, hierarchical variance partitioning of the optimal variables was performed in order to quantify the independent contribution of each variable in the total variance of new Covid-19 cases per million. Results indicated that from the variables available new tests per thousand explained the vast majority of the total variance in new cases (51.6%) followed by the governmental stringency index (15.2%). Availability of hospital beds per 100k inhabitants explained 9% extreme poverty explained 8.8%, hand washing facilities 5.3%, the fraction of the population aged 65 or older explained 3.9%, and other disease prevalence (cardiovascular diseases plus diabetes) explained 2.9%. The percentage of smokers within the population explained 2.6% of the total variance, while population density explained 0.6%.

Crossword Puzzles: Active Learning in Undergraduate Pathology and Medical Education

2009 ◽  
Vol 133 (9) ◽  
pp. 1457-1462
Author(s):  
Anurag Saxena ◽  
Raenelle Nesbitt ◽  
Punam Pahwa ◽  
Sheryl Mills
Keyword(s):  
Student Perceptions ◽  
Small Groups ◽  
Time Frame ◽  
Teaching Tool ◽  
Internet Resource ◽  
Cooperative Groups ◽  
Key Concepts ◽  
Second Year ◽  
Peer Teachers ◽  
Short Time

Abstract Context.—Second-year medical students are introduced to many new terms and concepts in a short time frame in the hematology system and the neoplasia section of the undergraduate pathology course. It is a challenge to provide adequate practice and necessary repetition to reinforce key concepts. Objective.—To determine student perceptions of the usefulness of crosswords as a quick and effective way to reinforce essential concepts and vocabulary. Design.—Crosswords with ensured content validity built on a free Internet resource were completed by the students in collaborative and cooperative groups of 6 to 7 with a reward for the first group to successfully complete the puzzle. Student perceptions of the value of crosswords for their learning were examined in 2003 (39 students) with a survey of yes or no responses and in 2004 (41 students) with a survey using questions with a 5-point Likert scale. Results.—Many students (37 of 39 in 2003 and 24 of 41 in 2004) indicated that crosswords were useful and contributed to their learning. Specifically, crosswords were found to be useful for identifying key concepts and vocabulary and for their collaborative and competitive aspects. Written and informal comments indicated student enthusiasm for and a desire to participate in more of these exercises. Students have transferred this review strategy to other classes and the peer teachers have expressed an interest in it as an adjunct teaching tool. Conclusions.—The judicious use of crosswords was useful for near transfer content and provided an opportunity to discuss and recall essential concepts, think critically, and collaborate in small groups.

scholarly journals Cockroaches traverse crevices, crawl rapidly in confined spaces, and inspire a soft, legged robot

2016 ◽  
Vol 113 (8) ◽  
pp. E950-E957 ◽  
Author(s):  
Kaushik Jayaram ◽  
Robert J. Full
Keyword(s):  
Body Weight ◽  
High Speed ◽  
Stride Length ◽  
Body Height ◽  
Legged Robot ◽  
Confined Space ◽  
Performance Limits ◽  
Biological Inspiration ◽  
Confined Spaces ◽  
Postural Changes

Jointed exoskeletons permit rapid appendage-driven locomotion but retain the soft-bodied, shape-changing ability to explore confined environments. We challenged cockroaches with horizontal crevices smaller than a quarter of their standing body height. Cockroaches rapidly traversed crevices in 300–800 ms by compressing their body 40–60%. High-speed videography revealed crevice negotiation to be a complex, discontinuous maneuver. After traversing horizontal crevices to enter a vertically confined space, cockroaches crawled at velocities approaching 60 cm⋅s−1, despite body compression and postural changes. Running velocity, stride length, and stride period only decreased at the smallest crevice height (4 mm), whereas slipping and the probability of zigzag paths increased. To explain confined-space running performance limits, we altered ceiling and ground friction. Increased ceiling friction decreased velocity by decreasing stride length and increasing slipping. Increased ground friction resulted in velocity and stride length attaining a maximum at intermediate friction levels. These data support a model of an unexplored mode of locomotion—“body-friction legged crawling” with body drag, friction-dominated leg thrust, but no media flow as in air, water, or sand. To define the limits of body compression in confined spaces, we conducted dynamic compressive cycle tests on living animals. Exoskeletal strength allowed cockroaches to withstand forces 300 times body weight when traversing the smallest crevices and up to nearly 900 times body weight without injury. Cockroach exoskeletons provided biological inspiration for the manufacture of an origami-style, soft, legged robot that can locomote rapidly in both open and confined spaces.

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