scholarly journals Drying of virus-containing particles: modelling effects of droplet origin and composition

2021 ◽  
Author(s):  
Michael C. Jarvis
Keyword(s):  
Liquid Droplet ◽  
Solute Concentration ◽  
Ambient Relative Humidity ◽  
Kohler Theory ◽  
Emissions Modelling ◽  
Drying Behaviour ◽  
Virus Survival ◽  
Droplet Drying ◽  
Respiratory Droplets ◽  
Solute Composition

Abstract Background and purpose Virus-containing aerosol droplets emitted by breathing, speech or coughing dry rapidly to equilibrium with ambient relative humidity (RH), increasing in solute concentration with effects on virus survival and decreasing in diameter with effects on sedimentation and respiratory uptake. The aim of this paper is to model the effect of ionic and macromolecular solutes on droplet drying and solute concentration. Methods Deliquescence-efflorescence concepts and Kohler theory were used to simulate the evolution of solute concentrations and water activity in respiratory droplets, starting from efflorescence data on mixed NaCl/KCl aerosols and osmotic pressure data on respiratory macromolecules. Results In NaCl/KCl solutions total salt concentrations were shown to reach 10-13 M at the efflorescence RH of 40-55%, depending on the K:Na ratio. Dependence on K:Na ratio implies that the evaporation curves differ between aerosols derived from saliva and from airway surfaces. The direct effect of liquid droplet size through the Kelvin term was shown to be smaller and restricted to the evolution of breath emissions. Modelling the effect of proteins and glycoproteins showed that salts determine drying equilibria down to the efflorescence RH, and macromolecules at lower RH. Conclusion Differences in solute composition between airway surfaces and saliva are predicted to lead to different drying behaviour of droplets emitted by breathing, speech and coughing. These differences may influence the inactivation of viruses.

scholarly journals Drying of virus-containing aerosol particles: Modelling effects of droplet origin and composition.

2021 ◽  
Author(s):  
Michael C. Jarvis
Keyword(s):  
Droplet Size ◽  
Liquid Droplet ◽  
Aerosol Particles ◽  
Solute Concentration ◽  
Airway Surface Liquid ◽  
Pressure Measurements ◽  
Ambient Relative Humidity ◽  
Surface Liquid ◽  
Drying Behaviour ◽  
Virus Survival

Virus-containing aerosol droplets emitted by breathing, speech or coughing dry rapidly to equilibrium with ambient relative humidity (RH), increasing in solute concentration with effects on virus survival and decreasing in diameter with effects on sedimentation and respiratory uptake. In simulations starting from drying data on mixed NaCl/KCl aerosols, the supersaturated salt concentrations were shown to reach 20-25M at the efflorescence RH of 40-55%, depending on the K:Na ratio. These salt concentrations may inactivate some viruses. The dependence on K:Na ratio implies that the evaporation curves differ between aerosols derived from saliva and from airway surfaces. Differences in drying behaviour are consequently predicted between breathing, speech and coughing emissions and between droplet size fractions within these. The direct effect of liquid droplet size through the Kelvin term was shown to be smaller and restricted to breath emissions. Comparative simulations starting from osmotic pressure measurements on airway surface liquid showed that salts are the primary determinants of drying equilibria down to the efflorescence RH, and macromolecules at lower RH.

scholarly journals Non-respiratory Particles Emitted by Guinea Pigs in Airborne Disease Transmission Experiments

2021 ◽  
Author(s):  
Sima Asadi ◽  
Manilyn J. Tupas ◽  
Ramya S. Barre ◽  
Anthony S. Wexler ◽  
Nicole M. Bouvier ◽  
...  
Keyword(s):  
Guinea Pig ◽  
Disease Transmission ◽  
Guinea Pigs ◽  
Liquid Droplet ◽  
Particle Count ◽  
Air Exchange Rate ◽  
Influenza Transmission ◽  
Particle Sizer ◽  
Airborne Disease ◽  
Respiratory Droplets

Abstract Animal models are often used to assess the airborne transmissibility of various pathogens, which are typically assumed to be carried by expiratory droplets emitted directly from the respiratory tract of the infected animal. We recently established that influenza virus is also transmissible via “aerosolized fomites,” micron-scale dust particulates released from virus-contaminated surfaces (Asadi et al., Nature Communications, 2020). Here we expand on this observation, by counting and characterizing the particles emitted from guinea pig cages using an Aerodynamic Particle Sizer (APS) and an Interferometric Mie Imaging (IMI) system. Of over 9,000 airborne particles emitted from guinea pig cages and directly imaged with IMI, none had an interference pattern indicative of a liquid droplet. Separate measurements of the particle count using the APS indicate that particle concentrations spike upwards immediately following animal motion, then decay exponentially with a time constant commensurate with the air exchange rate in the cage. Taken together, the results presented here raise the possibility that a non-negligible fraction of airborne influenza transmission events between guinea pigs occurs via aerosolized fomites rather than respiratory droplets, though the relative frequencies of these two routes have yet to be definitively determined.

scholarly journals INFLUENCE OF BRINE COMPOSITION AND CONCENTRATION ON MICROBIAL GROWTH DURING WHOLE COMMON BEAN (Phaseolus vulgaris L) FERMENTATION USING Lb.plantarum BFE 5092

2018 ◽  
Vol 1 (2) ◽  
pp. 22
Author(s):  
Vivian Chepchirchir Kitum ◽  
Peter Kinyanjui Kahenya ◽  
Julius Mathaara Maina ◽  
Daniel Ndaka Sila
Keyword(s):  
Common Bean ◽  
Fermentation Process ◽  
Starter Culture ◽  
Solute Concentration ◽  
Microbial Safety ◽  
Spontaneous Fermentation ◽  
Significant Difference ◽  
Solute Composition ◽  
Fermentation Technology ◽  
Made In

Fermentation technology improves the flavour and shelf life of foods while lowering antinutrient levels. Common bean, though a highly nutritious food, contains high levels of anti-nutrients. Fermentation can be exploited to lower antinutrients in common bean. Though significant strides have been made in bean milk and flour fermentation, common bean is majorly consumed as whole grain. This study, therefore, was aimed at developing a fermentation protocol for whole common bean. Lactobacillus plantarum BFE 5092 was used as starter culture for fermentation. Salt and salt-sugar at 1%, 2% and 3% solute concentrations were used as brine. The effect of starter culture, solute composition and concentration on the growth of lactic acid bacteria (LAB) was monitored. pH and microbial safety were also monitored during the fermentation process. Inoculation with Lb. plantarum BFE 5092 caused a significant increase (P<0.05) of LAB counts in salt brines compared to spontaneous fermentation but no significant difference (P>0.05) in salt-sugar brines. The pH of salt sugar brine solutions was significantly (P<0.05) lowered during the fermentation process from 6.07 to ≤ 3.75. This inhibited enterobacteria growth while promoting the growth of yeast. In salt brines, the pH was ≥ 4.8 favoring enterobacterial growth while inhibiting yeast growth. Solute concentration had no significant effect (P>0.05) on the growth of LAB, pH and microbial safety during fermentation. The study established that use of salt-sugar brine was effective in promoting the growth of LAB during common bean fermentation. It also lowered the pH to ≤ 3.75 and inhibited enterobacterial growth unlike salt brines.

scholarly journals Non-respiratory particles emitted by guinea pigs in airborne disease transmission experiments

2021 ◽  
Vol 11 (1) ◽  
Author(s):  
Sima Asadi ◽  
Manilyn J. Tupas ◽  
Ramya S. Barre ◽  
Anthony S. Wexler ◽  
Nicole M. Bouvier ◽  
...  
Keyword(s):  
Guinea Pig ◽  
Disease Transmission ◽  
Guinea Pigs ◽  
Liquid Droplet ◽  
Particle Count ◽  
Air Exchange Rate ◽  
Influenza Transmission ◽  
Particle Sizer ◽  
Airborne Disease ◽  
Respiratory Droplets

AbstractAnimal models are often used to assess the airborne transmissibility of various pathogens, which are typically assumed to be carried by expiratory droplets emitted directly from the respiratory tract of the infected animal. We recently established that influenza virus is also transmissible via “aerosolized fomites,” micron-scale dust particulates released from virus-contaminated surfaces (Asadi et al. in Nat Commun 11(1):4062, 2020). Here we expand on this observation, by counting and characterizing the particles emitted from guinea pig cages using an Aerodynamic Particle Sizer (APS) and an Interferometric Mie Imaging (IMI) system. Of over 9000 airborne particles emitted from guinea pig cages and directly imaged with IMI, none had an interference pattern indicative of a liquid droplet. Separate measurements of the particle count using the APS indicate that particle concentrations spike upwards immediately following animal motion, then decay exponentially with a time constant commensurate with the air exchange rate in the cage. Taken together, the results presented here raise the possibility that a non-negligible fraction of airborne influenza transmission events between guinea pigs occurs via aerosolized fomites rather than respiratory droplets, though the relative frequencies of these two routes have yet to be definitively determined.

scholarly journals Extended lifetime of respiratory droplets in a turbulent vapour puff and its implications on airborne disease transmission

2020 ◽  
Author(s):  
Kai Leong Chong ◽  
Chong Shen Ng ◽  
Naoki Hori ◽  
Rui Yang ◽  
Roberto Verzicco ◽  
...  
Keyword(s):  
Relative Humidity ◽  
Disease Transmission ◽  
Droplet Evaporation ◽  
Collective Effects ◽  
Ambient Conditions ◽  
Airborne Transmission ◽  
Ambient Relative Humidity ◽  
Respiratory Event ◽  
Poor Ventilation ◽  
Respiratory Droplets

To mitigate the COVID-19 pandemic, it is key to slow down the spreading of the life-threatening coronavirus (SARS-CoV-2). This spreading mainly occurs through virus-laden droplets expelled at speaking, screaming, shouting, singing, coughing, sneezing, or even breathing [1-7]. To reduce infections through such respiratory droplets, authorities all over the world have introduced the so-called "2-meter distance rule" or "6-foot rule". However, there is increasing empirical evidence, e.g. through the analysis of super-spreading events [6, 8-11], that airborne transmission of the coronavirus over much larger distances plays a major role [1-3, 7, 12-15], with tremendous implications for the risk assessment of coronavirus transmission. It is key to better and fundamentally understand the environmental ambient conditions under which airborne transmission of the coronavirus is likely to occur, in order to be able to control and adapt them. Here we employ direct numerical simulations of a typical respiratory aerosol in a turbulent jet of the respiratory event within a Lagrangian-Eulerian approach [16-18] with 5000 droplets, coupled to the ambient velocity, temperature, and humidity fields to allow for exchange of mass and heat [19] and to realistically account for the droplet evaporation under different ambient conditions. We found that for an ambient relative humidity of 50% the lifetime of the smallest droplets of our study with initial diameter of 10 μm gets extended by a factor of more than 30 as compared to what is suggested by the classical picture of Wells [20, 21], due to collective effects during droplet evaporation and the role of the respiratory humidity [22], while the larger droplets basically behave ballistically. With increasing ambient relative humidity the extension of the lifetimes of the small droplets further increases and goes up to 150 times for 90% relative humidity, implying more than two meters advection range of the respiratory droplets within one second. Smaller droplets live even longer and travel further. Our results may explain why COVID-19 superspreading events can occur for large ambient relative humidity such as in cooled-down meat-processing plants [10] or in pubs with poor ventilation. We anticipate our tool and approach to be starting points for larger parameter studies and for optimizing ventilation and indoor humidity controlling concepts, which in the upcoming autumn and winter both will be key in mitigating the COVID-19 pandemic.

Discrepancies between soil solute concentration estimates obtained by TDR and aqueous extracts

Soil Research ◽  
1997 ◽  
Vol 35 (3) ◽  
pp. 527 ◽  
Author(s):  
Arie Nadler
Keyword(s):  
Soil Water ◽  
Clay Soil ◽  
Clay Content ◽  
Solute Concentration ◽  
Aqueous Extracts ◽  
Soluble Salts ◽  
Dissolved Ions ◽  
Salinity Levels ◽  
Adsorption Desorption ◽  
Solute Composition

Soil moisture (θ) changes modify the electrical conductivity of the soil solution (ECw) by varying the amount and composition of dissolved ions, their activity coefficients, and soil tortuosity. Theoretically expected, it was experimentally confirmed that the contribution of common reactions (precipitation–dissolution, adsorption–desorption, and complexation) to solute composition is not always a linear function of soil : water ratios. Using the driest or wettest q as references, correcting for dilution only when θ changed, did not fully reconstruct the salinity. Bulk soil EC (ECa)–ECw linkage, based on the same mechanisms, is shown to have variable, curvilinear relations for soils of medium salinity levels, which are enhanced by the presence of sparingly soluble salts and clay content. An extreme disagreement between ECw and ECc (EC of 1 : 1 soil : water extracts adjusted for θ) was found for a clay soil, where up to ~2 dS/m the slope was negative.

scholarly journals Growth of respiratory droplets in cold and humid air

2020 ◽  
Author(s):  
Chong Shen Ng ◽  
Kai Leong Chong ◽  
Rui Yang ◽  
Mogeng Li ◽  
Roberto Verzicco ◽  
...  
Keyword(s):  
Numerical Simulations ◽  
Disease Transmission ◽  
Liquid Droplet ◽  
Quantitative Agreement ◽  
Droplet Growth ◽  
Liquid Droplets ◽  
Ambient Conditions ◽  
Ambient Temperatures ◽  
Saturated Vapour ◽  
Respiratory Droplets

The ambient conditions surrounding liquid droplets determine their growth or shrinkage. However, the precise fate of a liquid droplet expelled from a respiratory puff as dictated by its surroundings and the puff itself has not yet been fully quantified. From the view of airborne disease transmission, such as SARS-CoV-2, knowledge of such dependencies are critical. Here we employ direct numerical simulations (DNS) of a turbulent respiratory vapour puff and account for the mass and temperature exchange with respiratory droplets and aerosols. In particular, we investigate how droplets respond to different ambient temperatures and relative humidity (RH) by tracking their Lagrangian statistics. We reveal and quantify that in cold and humid environments, as there the respiratory puff is supersaturated, expelled droplets can first experience significant growth, and only later followed by shrinkage, in contrast to the monotonic shrinkage of droplets as expected from the classical view by William F. Wells (1934). Indeed, cold and humid environments diminish the ability of air to hold water vapour, thus causing the respiratory vapour puff to super-saturate. Consequently, the super-saturated vapour field drives the growth of droplets that are caught and transported within the humid puff. To analytically predict the likelihood for droplet growth, we propose a model for the axial RH based on the assumption of a quasi-stationary jet. Our model correctly predicts super-saturated RH conditions and is in good quantitative agreement with our DNS. Our results culminate in a temperature-RH map that can be employed as an indicator for droplet growth or shrinkage.Significance StatementInfluence of environmental conditions on airborne diseases transmission is an important issue, especially during the pandemic of COVID-19. Human-to-human transmission is mediated by the transport of virus-laden respiratory droplets. Here we investigate the problem from a fluid mechanics perspective by conducting numerical simulations to quantify the fate of respiratory droplets in a warm humid coughing puff under different ambient conditions. We reveal a non-intuitive regime with considerable growth of respiratory droplets, dominated by a super-saturated vapour field, preferentially occurring in cold and humid environments. We further propose a theoretical model that accurately predicts the condition for droplet growth. Our work should inform socializing policies and ventilation strategies for controlling indoor ambient conditions to mitigate dispersion of droplets from asymptomatic individuals.

scholarly journals Fluid dynamics of COVID-19 airborne infection suggests urgent data for a scientific design of social distancing

2020 ◽  
Vol 10 (1) ◽  
Author(s):  
M. E. Rosti ◽  
S. Olivieri ◽  
M. Cavaiola ◽  
A. Seminara ◽  
A. Mazzino
Keyword(s):  
Initial Distribution ◽  
Scientific Basis ◽  
Liquid Droplets ◽  
Social Distancing ◽  
Airborne Infection ◽  
Ambient Relative Humidity ◽  
Droplet Sizes ◽  
Key Issues ◽  
Respiratory Droplets ◽  
Infectious Potential

AbstractThe COVID-19 pandemic is largely caused by airborne transmission, a phenomenon that rapidly gained the attention of the scientific community. Social distancing is of paramount importance to limit the spread of the disease, but to design social distancing rules on a scientific basis the process of dispersal of virus-containing respiratory droplets must be understood. Here, we demonstrate that available knowledge is largely inadequate to make predictions on the reach of infectious droplets emitted during a cough and on their infectious potential. We follow the position and evaporation of thousands of respiratory droplets by massive state-of-the-art numerical simulations of the airflow caused by a typical cough. We find that different initial distributions of droplet size taken from literature and different ambient relative humidity lead to opposite conclusions: (1) most versus none of the viral content settles in the first 1–2 m; (2) viruses are carried entirely on dry nuclei versus on liquid droplets; (3) small droplets travel less than $$2.5\,{\mathrm{m}}$$ 2.5 m versus more than $$7.5\,{\mathrm{m}}$$ 7.5 m . We point to two key issues that need to be addressed urgently in order to provide a scientific foundation to social distancing rules: (I1) a careful characterisation of the initial distribution of droplet sizes; (I2) the infectious potential of viruses carried on dry nuclei versus liquid droplets.

Droplet drying behaviour of docosahexaenoic acid (DHA)-containing emulsion

2014 ◽  
Vol 106 ◽  
pp. 181-189 ◽  
Author(s):  
Yang Wang ◽  
Liming Che ◽  
Cordelia Selomulya ◽  
Xiao Dong Chen
Keyword(s):  
Docosahexaenoic Acid ◽  
Drying Behaviour ◽  
Droplet Drying

Analytical Electron Microscopy of Surface-Modified Ceramics

1985 ◽  
Vol 43 ◽  
pp. 276-279
Author(s):  
P. S. Sklad
Keyword(s):  
Electron Microscopy ◽  
Analytical Electron Microscopy ◽  
Theoretical Models ◽  
Ceramic Materials ◽  
Solute Concentration ◽  
Second Phase ◽  
Analytical Electron ◽  
Implantation Techniques ◽  
Lattice Damage ◽  
Surface Modified

Over the past several years, it has become increasingly evident that materials for proposed advanced energy systems will be required to operate at high temperatures and in aggressive environments. These constraints make structural ceramics attractive materials for these systems. However it is well known that the condition of the specimen surface of ceramic materials is often critical in controlling properties such as fracture toughness, oxidation resistance, and wear resistance. Ion implantation techniques offer the potential of overcoming some of the surface related limitations.While the effects of implantation on surface sensitive properties may be measured indpendently, it is important to understand the microstructural evolution leading to these changes. Analytical electron microscopy provides a useful tool for characterizing the microstructures produced in terms of solute concentration profiles, second phase formation, lattice damage, crystallinity of the implanted layer, and annealing behavior. Such analyses allow correlations to be made with theoretical models, property measurements, and results of complimentary techniques.

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