Aerosol Droplets Research Articles

Investigation of Island Growth on Fluidized Particles Coated by Means of Aerosol

In this study, an aerosol fluidized bed is used to coat particles. A new aerosol generator is used to obtain coating solution droplets with a diameter of around 1 μm or smaller. Glass particles, which have a mean diameter of 653 μm, were the non-porous core material and the coating solution was sodium benzoate. Scanning electron microscope pictures were analyzed by MATLAB image processing for evaluating the coverage with the curvature effect. Monte Carlo simulation was used to describe the coating of fluidized particles by aerosol droplets. The purpose of this work was the determination of possible island growth on particles, and investigation of the reasons of it by comparing the experimental and simulation results. The preferential deposition of droplets on already occupied positions is seen as the main possible reason for island growth.

Significantly Accelerated Hydroxyl Radical Generation by Fe(III)–Oxalate Photochemistry in Aerosol Droplets

Fe(III)-oxalate complexes are ubiquitous in atmospheric environments, which can release reactive oxygen species (ROS) such as H2O2, O•2-, and OH• under light irradiation. Although Fe(III)-oxalate photochemistry has been investigated extensively, the understanding of its involvement in authentic atmospheric environments such as aerosol droplets is far from enough, since the current available knowledge has mainly been obtained in bulk-phase studies. Here, we find that the production of OH• by Fe(III)-oxalate in aerosol microdroplets is about 10-fold greater than that of its bulk-phase counterpart. In addition, in the presence of Fe(III)-oxalate complexes, the rate of photo-oxidation from SO2 to sulfate in microdroplets was about 19-fold faster than that in the bulk phase. The availability of efficient reactants and mass transfer due to droplet effects made dominant contributions to the accelerated OH• and SO42- formation. This work highlights the necessary consideration of droplet effects in atmospheric laboratory studies and model simulations.

Caution Regarding Enclosures for Airway Procedures

Article| January 2023 Caution Regarding Enclosures for Airway Procedures Uday Jain, BSEE, MD, PhD, FASA Uday Jain, BSEE, MD, PhD, FASA Search for other works by this author on: This Site PubMed Google Scholar ASA Monitor January 2023, Vol. 87, 29. https://doi.org/10.1097/01.ASM.0000911788.66274.ff Views Icon Views Article contents Figures & tables Video Audio Supplementary Data Peer Review Share Icon Share Facebook Twitter LinkedIn MailTo Cite Icon Cite Get Permissions Search Site Citation Uday Jain; Caution Regarding Enclosures for Airway Procedures. ASA Monitor 2023; 87:29 doi: https://doi.org/10.1097/01.ASM.0000911788.66274.ff Download citation file: Ris (Zotero) Reference Manager EasyBib Bookends Mendeley Papers EndNote RefWorks BibTex toolbar search Search Dropdown Menu toolbar search search input Search input auto suggest filter your search All ContentAll PublicationsASA Monitor Search Advanced Search Topics: airway procedure, airway device Several enclosures for placement around the head and upper torso have been described during this pandemic (Anesth Analg 2020;131:e135-36; J Cardiothorac Vasc Anesth 2021;35:966-67). They are usually made of frames covered by transparent sheets. The enclosures have access ports for the operator's arms, supplemental oxygen, and airway equipment. The enclosures do not form an airtight seal around the patient's head and torso. They provide partial source control by suctioning aerosol and infectious droplets. If suction devices currently available in hospitals are utilized, the enclosure may only slightly reduce interior pressures relative to the ambient pressure. Hopefully most infectious material remains inside the enclosure, but during doffing and disposal contaminated material may escape. Although an enclosure may reduce health care personnel (HCP) exposure, full personal protective equipment (PPE) is still required. No studies demonstrate safety, efficacy, or usability. What is unambiguous is that airway enclosures adversely affect visibility... You do not currently have access to this content.

Single liquid aerosol nano-impact electrochemistry: accessing the droplet|air interface

Fabrication of a dual-barrel platinum ultramicroelectrode allows for the stochastic detection of a single liquid aerosol droplet. The new measurement technique has significant potential for studying the microdroplet|air interface using electrochemistry.

Acceleration of chemical processes in aerosol

The evolution of the state of aerosol droplets containing a reaction mixture with volatile components is accompanied by a change in the size and composition of the droplets, changes in the concentrations of reagents and the rates of chemical reactions. The methods of formal chemical kinetics and equilibrium thermodynamics describe size effects that lead to a significant acceleration of chemical processes in aerosols. The dependence of the rate of chemical processes on the initial size and composition of droplets, as well as on the composition of the gas phase, is described. The main regularities are modeled on the example of the condensation reaction of glycine with glucose (Maillard reaction). Keywords: aerosol, size effect, chemical kinetics, spray technology.

Ускорение химических процессов в аэрозоле

The evolution of the state of aerosol droplets containing a reaction mixture with volatile components is accompanied by a change in the size and composition of the droplets, changes in the concentrations of reagents and the rates of chemical reactions. The methods of formal chemical kinetics and equilibrium thermodynamics describe size effects that lead to a significant acceleration of chemical processes in aerosols. The dependence of the rate of chemical processes on the initial size and composition of droplets, as well as on the composition of the gas phase, is described. The main regularities are modeled on the example of the condensation reaction of glycine with glucose (Maillard reaction).

Secondary ultrasonic atomisation mechanisms

Liquid atomisation is the basis for various practical applications such as pharmaceuticals, cosmetics, food industry, etc. In this case, the main challenge is the development of high-performance, highly dispersed atomisation systems. Generally, high-throughput atomisation systems form aerosol with large droplet sizes, and high-disperse atomisation systems have low performance. Secondary ultrasonic atomisation can solve this problem by allowing non-contact crushing of already formed aerosol droplets with large droplet sizes by means of a high-intensity ultrasonic field. For this purpose, a pre-generated stream of liquid droplets is directed into a cylindrical region formed by an emitter in which a high-intensity ultrasonic field is generated. Ultrasonic radiator, is a tube of stepped-variable cross-section, providing the formation of bending-diametral or diametral oscillations at a frequency above 20 kHz. At sufficiently high ultrasound intensity, conditions for further crushing of liquid droplets are realised, which leads to the formation of a highly dispersed aerosol. This paper describes the proposed mathematical model of the atomisation process and finds the regularities of the process depending on the determining parameters of the ultrasonic field and physical and chemical properties of the liquid. Two mechanisms of jet destruction are revealed: direct destruction of droplets when they hit the ultrasonic wave front and cavitation mechanism of droplet and jet destruction. The dominant crushing mechanism depends on the problem parameters and, in turn, determines the minimum size of the resulting droplets. The results of this work will help to optimise the secondary ultrasonic atomisation process and improve liquid atomisation technologies in various applications.

Fate of Exhaled Droplets From Breathing and Coughing in Supermarket Checkouts and Passenger Cars.

The global pandemic of COVID-19 has highlighted the importance of understanding the role that exhaled droplets play in virus transmission in community settings. Computational Fluid Dynamics (CFD) enables systematic examination of roles the exhaled droplets play in the spread of SARS-CoV-2 in indoor environments. This analysis uses published exhaled droplet size distributions combined with terminal aerosol droplet size based on measured peak concentrations for SARS-CoV-2 RNA in aerosols to simulate exhaled droplet dispersion, evaporation, and deposition in a supermarket checkout area and rideshare car where close proximity with other individuals is common. Using air inlet velocity of 2 m/s in the passenger car and ASHRAE recommendations for ventilation and comfort in the supermarket, simulations demonstrate that exhaled droplets <20 μm that contain the majority of viral RNA evaporated leaving residual droplet nuclei that remain aerosolized in the air. Subsequently ~ 70% of these droplet nuclei deposited in the supermarket and the car with the reminder vented from the space. The maximum surface deposition of droplet nuclei/m2 for speaking and coughing were 2 and 819, 18 and 1387 for supermarket and car respectively. Approximately 15% of the total exhaled droplets (aerodynamic diameters 20-700 µm) were deposited on surfaces in close proximity to the individual. Due to the non-linear distribution of viral RNA across droplet sizes, however, these larger exhaled droplets that deposit on surfaces have low viral content. Maximum surface deposition of viral RNA was 70 and 1.7 × 103 virions/m2 for speaking and 2.3 × 104 and 9.3 × 104 virions/m2 for coughing in the supermarket and car respectively while the initial airborne concentration of viral RNA was 7 × 106 copies per ml. Integrating the droplet size distributions with viral load distributions, this study helps explain the apparent importance of inhalation exposures compared to surface contact observed in the pandemic.

Detection of Rubella Antibodies in Women with Repeated Miscarriage During Different Seasons in Mosul City

Background: Rubella or German measles is a viral disease transmitted via aerosol droplets affecting mainly children, Mostly, rubella is a simple and self-limiting disease with no chronic consequences, except in infected pregnant women which may result in devastating outcomes depending on the trimester of pregnancy. Materials and methods: the study enrolled 1004 women suffering from spontaneous miscarriage tested for rubella IgM antibodies using ELISA. The sampling was conducted in two different seasons, summer and winter. Results: Test reading showed that 15.23% of all tested women were positive for rubella IgM antibodies i.e. 153 out of 1004 women. Seasonal change showed no significant variation in the percentage of the infection, where 15.8% of all participants were positive in summer versus 14.35% seropositive in the winter season (p˃ 0.05). Conclusion: Rubella infection is affecting a relatively high number of women suffering from a spontaneous miscarriage in Mosul city, and there was no seasonal variation in the rate of infection.

Numerical Modeling of Laser Heating and Evaporation of a Single Droplet

Laser technology is being widely studied for controlled energy deposition for a range of applications, including flow control, ignition, combustion, and diagnostics. The absorption and scattering of laser radiation by liquid droplets in aerosols affects propagation of the laser beam in the atmosphere, while the ignition and combustion characteristics in combustion chambers are influenced by the evaporation rate of the sprayed fuel. In this work, we present a mathematical model built on OpenFOAM for laser heating and evaporation of a single droplet in the diffusion-dominated regime taking into account absorption of the laser radiation, evaporation process, and vapor flow dynamics. The developed solver is validated against available experimental and numerical data for heating and evaporation of ethanol and water droplets. The two main regimes—continuous and pulsed laser heating—are explored. For continuous laser heating, the peak temperature is higher for larger droplets. For pulsed laser heating, when the peak irradiance is close to transition to the boiling regime, the temporal dynamics of the droplet temperature does not depend on the droplet size. With the empirical normalization of time, the dynamics of the droplet shrinkage and cooling are found to be independent of droplet sizes and peak laser intensities.

Textile Functionalization Using LTA and FAU Zeolitic Materials.

COVID-19 has drawn worldwide attention to the need for personal protective equipment. Face masks can be transformed from passive filters into active protection. For this purpose, it is sufficient to apply materials with oligodynamic effect to the fabric of the masks, which makes it possible to destroy infectious agents that have fallen on the mask with aerosol droplets from the air stream. Zeolites themselves are not oligodynamic materials, but can serve as carriers for nanoparticles of metals and/or compounds of silver, zinc, copper, and other materials with biocidal properties. Such a method, when the particles are immobilized on the surface of the substrate, will increase the lifetime of the active oligodynamic material. In this work, we present the functionalization of textile materials with zeolites to obtain active personal protective equipment with an extended service life. This is done with the aim to extend the synthesis of zeolitic materials to polymeric fabrics beyond cotton. The samples were characterized using XRD, SEM, and UV-Vis spectroscopy. Data of physicochemical studies of the obtained hybrid materials (fabrics with crystals grown on fibers) will be presented, with a focus on the effect of fabrics in the growth process of zeolites.

INFLUENCE OF LIQUID SUPPLY WORKING PRESSURE ON POTATO PROCESSING AREA

The doctrine of food security lists critical products for Ukraine and the minimum level of their own production. Potatoes are among these products. Despite the fact that the country's needs are almost completely covered by potatoes produced on the territory of our state, in recent years more and more attention has been paid to increasing the yield of the crop. Pre-sowing treatment helps to increase the yield of crops. The main method of pre-sowing preparation of potatoes is to treat the planting material with drugs to protect against pests and diseases. The main method of pre-sowing seed preparation is poisoning with chemical preparations against pests and diseases. It is widely used in intensive agricultural technology and allows to reduce potential crop losses by 50-55%. The applied technical means, which ensure uniform and complete coverage of the surface of the seed material, have distributors that create drops of different diameters. In the best case, it is possible to control the average particle size, and large weight fractions of different particle sizes reduce the processing efficiency and negatively affect the uniformity of the coating. In this regard, one of the main tasks of the used technical means is to obtain drops of the same (monodisperse) size. Moreover, their size should be within 20 - 50 μm.. It is quite time-consuming to select the correct parameters of a technical device to achieve these aerosol sizes experimentally, therefore it is necessary to develop mathematical models of seed processing with different types of sprayers, which will tell in which direction scientific developments should be conducted .\ For the model of the technological process of processing, the design and technological parameters and operating modes of the spraying system can be used as initial conditions, and the parameters of the distribution system of aerosol droplets, seed material and drug as boundary conditions (the speed of the air flow created by the fan, the amount of working fluid that provided, design parameters of the processing chamber).

New dose-response model and SARS-CoV-2 quanta emission rates for calculating the long-range airborne infection risk

Predictive models for airborne infection risk have been extensively used during the pandemic, but there is yet still no consensus on a common approach, which may create misinterpretation of results among public health experts and engineers designing building ventilation. In this study we applied the latest data on viral load, aerosol droplet sizes and removal mechanisms to improve the Wells Riley model by introducing the following novelties i) a new model to calculate the total volume of respiratory fluid exhaled per unit time ii) developing a novel viral dose-based generation rate model for dehydrated droplets after expiration iii) deriving a novel quanta-RNA relationship for various strains of SARS-CoV-2 iv) proposing a method to account for the incomplete mixing conditions. These new approaches considerably changed previous estimates and allowed to determine more accurate average quanta emission rates including omicron variant. These quanta values for the original strain of 0.13 and 3.8 quanta/h for breathing and speaking and the virus variant multipliers may be used for simple hand calculations of probability of infection or with developed model operating with six size ranges of aerosol droplets to calculate the effect of ventilation and other removal mechanisms. The model developed is made available as an open-source tool.

Integration of IoT Sensors to Determine Life Expectancy of Face Masks.

Personal protective equipment (PPE) is widely used around the world to protect against environmental hazards. With the emergence of the COVID-19 virus, the use of PPE domestically has increased dramatically. People use preventive and protective mechanisms now more than ever, leading to the important question of how protective is the PPE that is being used. Face masks are highly recommended or mandatory during the time of the COVID-19 pandemic due to their protective features against aerosol droplets. However, an issue faced by many users of face masks is that they are entirely manual, with users having to decide for themselves whether their mask is still protective or if they should replace their mask. Due to the difficulty in determining this, people tend to overuse masks beyond their optimal usage. The research presented in this paper is an investigation of the viability of integrating IoT sensors into masks that are capable of collecting data to determine its usage. This paper demonstrates the usage of humidity and temperature sensors for the purpose of determining a mask's usage status based on changes in these variables when a mask is put on and taken off. An evaluation was made on the usage of the two sensors, with the conclusion that a humidity sensor provides more accurate results. From this, we present a framework that takes into consideration the factors that affect a mask's performance, such as time, humidity and temperature, to calculate the life expectancy of a mask.

Investigation of aerosol droplets diameter generated in aerosol jet printing

Abstract Aerosol jet printing is a contactless direct-write technique that could be used for the deposition of a variety of materials. First, used for electric paths, the technology was explored for many applications. The substantial part of the process is the generation of aerosols. The size of the droplets and the stability of the process affect the quality of the sprayed lines. This article investigates the diameter of the sprayed droplets, allowing future comparison of the results with sprayed lines. Droplets from ultrasonic and pneumatic generators were sprayed at their outlet on the polyethylene terephthalate (PET) foil. Using a digital microscope and the built-in algorithm, the diameter of the droplets was measured, and the dataset was collected as CSV files and served as a background to the box plot. Scanning electron microscopy (SEM) and atomic force microscopy (AFM) scans were applied to verify the results obtained. The ink parameters used in the process have an influence on the aerosol generation and droplet diameter, whereas the carrier gas pressure has an impact mostly on the droplet diameter. In this case, the aerosol was produced from three types of ink in combination with two generators. For inks with a dynamic viscosity below 6.5 m·Pa−1·s−1 a stable range of 5–10 μm droplet diameter was observed. A high-viscosity ink (7.5–10.5 m·Pa−1·s−1) produced droplets with diameter in the range of 6–25 μm. The diameter of the droplet decreased from 7–22 μm to 1–5 μm with a reduction in the dynamic viscosity from 7.5–10.5 m·Pa−1·s−1 to 4.5–5.5 m·Pa−1·s−1.

Learning Coagulation Processes With Combinatorial Neural Networks

AbstractSimulating the evolution of a coagulating aerosol or cloud of droplets in a key problem in atmospheric science. We present a proof of concept for modeling coagulation processes using a novel combinatorial neural network (CombNN) architecture. Using two types of data from a high‐detail particle‐resolved aerosol simulation, we show that CombNN models outperform standard neural networks and are competitive in accuracy with traditional state‐of‐the‐art sectional models. These CombNN models could have application in learning coarse‐grained coagulation models for multi‐species aerosols and for learning coagulation models from observed size‐distribution data.

Toward unraveling the mechanisms of aerosol generation during phonation

Aerosol droplets made from respiratory liquid are of fundamental importance for airborne transmission of several virus-based diseases, such as COVID-19. While the transmission route in the air has been intensively studied in the last two years, only few papers deal with the formation of these droplets. It seems to be accepted that such droplets are generated by upper airway activity such as talking, sneezing, or coughing. Especially talking is associated with disease transmission, although the droplet formation mechanisms have not been fully resolved yet. Thus, we focus on the investigation of the atomization process of respiratory liquid attached to the vocal folds. A new experimental setup has been installed that emulates the vocal folds and their oscillating movement in a simplified manner. A model liquid mimicking the respiratory mucus is dispersed at the vocal folds. The primary atomization of the model liquid into an air stream is observed qualitatively. This new insight shows that in contrast to the typical assumption that only liquid bridges form between the vocal folds and breakup into droplets, rather bubbles are generated, which can breakup into much smaller particles than filaments. Furthermore, droplet size distributions downstream of the vocal folds are evaluated. The influence of the oscillation frequency and amplitude as well as air flow rate on the droplet size distributions are analyzed. It is found that an increase in both frequency and amplitude leads to smaller particle sizes, while raising the air flow rate results in a higher proportion of larger particles.

Increased aerosols can reverse Twomey effect in water clouds through radiative pathway

Aerosols play important roles in modulations of cloud properties and hydrological cycle by decreasing the size of cloud droplets with the increase of aerosols under the condition of fixed liquid water path, which is known as the first aerosol indirect effect or Twomey-effect or microphysical effect. Using high-quality aerosol data from surface observations and statistically decoupling the influence of meteorological factors, we show that highly loaded aerosols can counter this microphysical effect through the radiative effect to result both the decrease and increase of cloud droplet size depending on liquid water path in water clouds. The radiative effect due to increased aerosols reduces the moisture content, but increases the atmospheric stability at higher altitudes, generating conditions favorable for cloud top entrainment and cloud droplet coalescence. Such radiatively driven cloud droplet coalescence process is relatively stronger in thicker clouds to counter relatively weaker microphysical effect, resulting the increase of cloud droplet size with the increase of aerosol loading; and vice-versa in thinner clouds. Overall, the study suggests the prevalence of both negative and positive relationships between cloud droplet size and aerosol loading in highly polluted regions.

Coronavirus-mimicking nanoparticles (CorNPs) in artificial saliva droplets and nanoaerosols: Influence of shape and environmental factors on particokinetics/particle aerodynamics

Severe acute respiratory syndrome coronavirus 2, abbreviated as SARS-CoV-2, has been associated with the transmission of infectious COVID-19 disease through breathing and speech droplets emitted by infected carriers including asymptomatic cases. As part of SARS-CoV-2 global pandemic preparedness, we studied the transmission of aerosolized air mimicking the infected person releasing speech aerosol with droplets containing CorNPs using a vibrating mesh nebulizer as human patient simulator. Generally speech produces nanoaerosols with droplets of <5 μm in diameter that can travel distances longer than 1 m after release. It is assumed that speech aerosol droplets are a main element of the current Corona virus pandemic, unlike droplets larger than 5 m, which settle down within a 1 m radius. There are no systemic studies, which take into account speech-generated aerosol/droplet experimental validation and their aerodynamics/particle kinetics analysis. In this study, we cover these topics and explore role of residual water in aerosol droplet stability by exploring drying dynamics. Furthermore, a candle experiment was designed to determine whether air pollution might influence respiratory virus like nanoparticle transmission and air stability.

Trepanation revisited in COVID-19 era: A perspective on craniotomy during current pandemic, surgical technique, and complications avoidance.

Craniotomy creates maximum aerosols threatening the health care workers (HCWs) of operation room. The technique of trepanation and measures to avoid complications has never been described in the literature. The time taken for craniotomy by different instruments has also never been compared. The study included only COVID-positive patients who underwent surgery. Craniotomy was performed using trephine, pneumatic/power drill (PD), and Hudson brace-Gigli saw (HB-GS). Trepanation as done in 32 patients. The generation of aerosols and time taken for craniotomy by these instruments was observed. The droplet spread over a waterproof graph paper of 10 × 10 sq. cm was calculated in 13 cases of all the three craniotomy methods. The technique of trepanation and maneuvers to overcome complications was discussed. There was a gross difference in aerosol production and soiling of the surgical drapes, floor, surgeon's glove, gowns, face shield, goggles, etc. The average number of droplet aerosol in trepanation group was 4.76, 23.6 in drill and 21.3 in Gigli saw method. The average time taken for trepanation, PD, and HB-GS craniotomy was 4.8, 22.8, and 24.4 min, respectively. One mortality secondary to COVID was noted. All the HCWs assisting trepanation were negative for COVID-19 during postoperative follow-up of 7 days. However, 13 members of the surgical team which assisted in electric drill and HB-GS methods were COVID-positive. Trepanation should be the preferred method of craniotomy during COVID-19 pandemic as it is associated with the least aerosolization and is the most time efficient.