Aerosol Droplet Size Research Articles

A multi-nozzle nebuliser does not improve tissue drug delivery during PIPAC

BackgroundMulti-nozzle nebulisers for pressurised intraperitoneal aerosol chemotherapy (PIPAC) are implemented in clinical practice to improve the homogeneity of tissue drug delivery. Nonetheless, the advantages of such devices over one-nozzle nebulisers have not been demonstrated thus far. In this study, we compared the performance of multi- and one-nozzle nebulisers by conducting physical and ex vivo pharmacological experiments.MethodsThe one-nozzle nebuliser Capnopen® and the multi-nozzle nebuliser were the subjects of this study. In physical experiments, the aerosol droplet size was measured by laser diffraction spectroscopy. Spatial spray patterns were depicted on blotting paper. Pharmacological experiments were performed on the enhanced inverted bovine urinary bladder model, demonstrating real-time tissue drug delivery, aerosol sedimentation and homogeneity of doxorubicin and cisplatin tissue distribution.ResultsThe multi-nozzle nebuliser had a sixfold greater aerosolisation flow and a threefold greater angle of aerosolisation than Capnopen®. The aerosol particle size and distribution range were higher than that of Capnopen®. Spray patterns on blotting paper were more extensive with the multi-nozzle nebuliser. Real-time tissue drug delivery with the multi-nozzle nebuliser was over 100 ml within 1 min, and the aerosol sedimentation was 48.9% ± 21.2%, which was not significantly different from that of Capnopen®. The doxorubicin and cisplatin tissue concentrations were greater with Capnopen®. Although there was no significant difference in the homogeneity of doxorubicin distribution between the two devices, the homogeneity of cisplatin distribution was significantly higher with Capnopen®.ConclusionThe multi-nozzle PIPAC nebuliser did not fulfil expectations. Even though the surface spray patterns were broader with the multi-nozzle nebuliser, the tissue drug homogeneity and concentration were greater with Capnopen®.Graphical

Microfluidics produced ATRA-loaded PLGA NPs reduced tuberculosis burden in alveolar epithelial cells and enabled high delivered dose under simulated human breathing pattern in 3D printed head models

Tuberculosis, caused by Mycobacterium tuberculosis (Mtb), is second only to COVID-19 as the top infectious disease killer worldwide. Multi-drug resistant TB (MDR-TB) may arise because of poor patient adherence to medications due to lengthy treatment duration and side effects. Delivering novel host directed therapies (HDT), like all trans retinoic acid (ATRA) may help to improve drug regimens and reduce the incidence of MDR-TB. Local delivery of ATRA to the site of infection leads to higher bioavailability and reduced systemic side effects. ATRA is poorly soluble in water and has a short half-life in plasma. Therefore, it requires a formulation step before it can be administered in vivo. ATRA loaded PLGA nanoparticles suitable for nebulization were manufactured and optimized using a scalable nanomanufacturing microfluidics (MF) mixing approach (MF-ATRA-PLGA NPs). MF-ATRA-PLGA NPs demonstrated a dose dependent inhibition of Mtb growth in TB-infected A549 alveolar epithelial cell model while preserving cell viability. The MF-ATRA-PLGA NPs were nebulized with the Aerogen Solo vibrating mesh nebulizer, with aerosol droplet size characterized using laser diffraction and the estimated delivered dose was determined. The volume median diameter (VMD) of the MF-ATRA-PLGA NPs was 3.00 ± 0.18 μm. The inhaled dose delivered in adult and paediatric 3D printed head models under a simulated normal adult and paediatric breathing pattern was found to be 47.05 ± 3 % and 20.15 ± 3.46 % respectively. These aerosol characteristics of MF-ATRA-PLGA NPs supports its suitability for delivery to the lungs via inhalation. The data generated on the efficacy of an inhalable, scalable and regulatory friendly ATRA-PLGA NPs formulation provides a foundation on which further pre-clinical testing can be built. Overall, the results of this project are promising for future research into ATRA loaded NPs formulations as inhaled host directed therapies for TB.

A method of spraying based on hydrodynamic and ultrasonic influence on the sprayed liquid

The article is devoted to the development of a sprayer based on the method of simultaneous hydrodynamic and ultrasonic influence on the flow of sprayed liquid. The proposed spraying method makes it possible to increase spraying productivity while reducing the size of aerosol droplets. By establishing optimal conditions, with a nozzle diameter of 0.7 mm, an ultrasonic tool diameter of 8 mm and an excess pressure of the sprayed liquid of 0.7 MPa, the atomizer provides a productivity of 9 ml/s and forms an aerosol with droplet sizes D32 = 40 μm. This is primarily due to the establishment of the optimal operating mode and conditions in the cavitation zone, which make it possible to ensure the highest quantitative concentration of cavitation bubbles.

Numerical Simulation of Pyrethrin Aerosol Deposition

Highlights A steady state, laminar CFD model was developed to simulate the airflow inside an aerosol exposure chamber. The CFD model predicted the droplet tracks and deposition of various sizes of aerosol droplets. Larger aerosol droplets had higher deposition efficiency. A Higher flow rate, but still within the laminar flow regime, caused lower deposition efficiency for all droplet sizes. Abstract. Aerosol insecticides (e.g., pyrethrin) are widely used for the control of stored products insects inside food facilities. To optimize pyrethrin aerosol application, computational fluid dynamics (CFD) was used to predict airflow and aerosol transport inside a vertical flow aerosol exposure chamber operated under laminar flow conditions. A discrete phase model in ANSYS FLUENT 2021 R1 was developed, and simulations were conducted to track pyrethrin droplets of various diameters (0.1 to 20 µm) and determine their deposition onto Petri dishes located near the center of the chamber. The deposition efficiency of the different aerosol droplet sizes and the effect of two flow rates (5 × 10-4 m3 s-1 and 4 × 10-4 m3 s-1) on deposition efficiency were determined. The results showed that the predicted deposition of pyrethrin aerosol increased with increasing droplet size, largely due to inertial and gravitational effects. Deposition efficiencies decreased with the higher flow rate—with 0.1% to 96.6% predicted deposition efficiencies for the low flow rate and 0.1% to 93.8% for the high flow rate. Results of this study can be used to improve aerosol application methods for stored product insect control. Keywords: Aerosol deposition, Aerosol insecticide, Computational fluid dynamics, Confused flour beetle, Deposition efficiency, Discrete phase model, Numerical simulation, Particle tracking, Pyrethrins, Stored product insect.

Aerosolized Insecticide Spray Distributions and Relationships to Efficacy against Stored Product Pests.

Aerosol insecticides are widely used in stored product insect management programs in food facilities. Previous research has shown spatial variation in aerosol efficacy within facilities, but information on how spatial patterns of aerosol droplet concentration, size distribution, dispersal, and deposition contribute to this variation in efficacy is limited. This study involved two aerosol application systems: a high-pressure cylinder containing TurboCide Py-75® with pyriproxyfen IGR (ChemTech Ltd., Des Moines, IA, USA) and a hand-held fogger containing Pyrocide 100® (MGK, Minneapolis, MN, USA) with Diacon II which contains methoprene IGR (Wellmark, Schaumburg, IL, USA). These systems were used at single or multiple application locations. The spray trials were conducted in a small-scale flour mill, Hall Ross Flour Mill (Kansas State University, Manhattan, KS, USA). The droplet size distributions were monitored at multiple positions within the room using nine aerodynamic particle sizing (APS, TSI Incorp, Shoreview, MN, USA) instruments. The APS data collected over the treatment period were summarized into a mass concentration index (MCI), which ranged from 155 to 2549 mg/m3 for Turbocide and 235-5658 mg/m3 for Pyrocide. A second parameter called the Deposition Index (Dep.Idx) was derived to estimate potential insecticide depositions on the floor and has units of g/m2. The Dep.Idx was below 5.3 g/m2 for most Turbocide applications, while the Dep.Idx was below 8.4 g/m2 for most Pyrocide applications. The MCI and Dep.Idx values varied with APS position and spray application location, with proximity to the aerosol application location and degree of obstruction between the release point and APS position contributing to this variation. We assessed the relationship between aerosol droplet parameters and insect efficacy using Tribolium confusum Jacqueline DuVal, the confused flour beetle. The adults were treated directly, while the larvae were treated two weeks later during the residual test (previously published). For Turbocide, efficacy against adults increased with MCI and Dep.Idx values, but for residual efficacy of the IGR, efficacy was high at all aerosol droplet values, so no relationship was apparent. In contrast, the relationship between Pyrocide deposition and adult insect efficacy was highly variable. But with larval insect efficacy, residual larvae control was directly related to increases in Pyrocide MCI and Dep.Idx. Contour plots of Dep.Idx values were developed, which could be used to predict areas of the mill that are not receiving an adequate application rate, and this could be used to develop more effective application strategies for aerosol insecticides in food facilities.

Machinability and tribological analysis of used cooking oil for MQL applications in drilling AISI 304 using a low-cost pneumatic operated MQL system

Developing low-cost MQL systems and application of used/waste cooking oil (generated in restaurants/homes), which poses a health risk if it enters the food chain again, as feedstock for MQL applications can increase the adoption of MQL by smaller manufacturing industries. A low-cost pneumatic-based MQL system that works only on compressed air is developed and tested. The droplet size and velocity of the MQL aerosol are analysed using CFD to arrive at an optimum nozzle design and the nozzle spray characteristics are studied using a Phase Doppler Particle Analyzer. Drilling of AISI 304 using the MQL system with commercial MQL oil and used cooking oil is carried out and the results are compared with flood cooling. The thrust and radial forces are comprehensively analysed and related to the tool wear, built-up edge (BUE) formation along the drill cutting edges, and chip morphology. It is found that a steady drilling process is obtained with used cooking oil because of its superior viscosity (resulting in lower friction) and lower surface tension (leading to smaller droplet size and better wettability).

Abstracts from The Aerosol Society Drug Delivery to the Lungs 33.

Abstracts from The Aerosol Society Drug Delivery to the Lungs 33.

Computational fluid dynamics and experimental validation of aerosol jet printing with multi-stage flow focusing lenses

A 3D computational fluid dynamics (CFD) framework is presented to model and explain critical aerodynamic interactions occurring in the printhead during aerosol jet printing (AJP) with multi-stage flow focusing lenses. AJP has demonstrated great potential to fabricate complex circuits and conductive devices for numerous applications, including flexible electronics, medical diagnostic devices, and fuel cells. However, the devices manufactured by AJP are currently relegated to prototype roles due to poor repeatability of the deposited structures. The lack of process consistency in AJP arises from an incomplete understanding of causal aerodynamic interactions that influence the structure and repeatability of the printed features. Herein, a comprehensive CFD framework is presented to analyze the effects of gas flow rates, nozzle geometry, stand-off distance, printhead design, and aerosol droplet size on the resolution and morphology of printed features. Compressible Navier-Stokes equations with a k-ε turbulence model are solved to simulate flow conditions in the aerosol jet printhead. Additionally, a Lagrangian discrete phase model is used to simulate the transport of aerosolized ink droplets through the turbulent shear flow. The results highlight the crucial role of the design of the mist tube and the first aerodynamic lens, the density of the sheath gas, and the size of the droplets in the aerosol stream in determining print resolution and quality. A favorable comparison was found between numerically calculated results and experimental data obtained using the NanoJet™ system. CFD models presented in this work are expected to aid in identifying optimal process windows a priori, to improve process consistency.

Correlation between concentration, droplet size, turbulent intensity and explosion parameters of gas-liquid two-phase mixture

In this study, concentration and droplet size of aerosol and turbulence distribution in the 20 L vessel over time under pneumatic pressure of 1 MPa–2MPa were observed and correlation between actual concentration, droplet size, turbulent intensity of the ethanol aerosol and pneumatic pressure were analyzed. The effect of concentration, droplet size, and turbulent intensity on aerosol explosion parameters of the ethanol aerosol were examined. The actual concentration of ethanol aerosol in the vessel is much lower than the design concentration. The ratio between the actual concentration and the designed concentration is about 65%–90% at the pneumatic pressure from 1.0 MPa to 2.0 MPa. The concentration of ethanol aerosol in the vessel increases with time from 0 ms to 50 ms, maintains a stead state from 50 ms to 100 ms and decreases gradually after 100 ms. In the initial stage of injecting, the size of aerosol droplets in the vessel changes with time sharply and tends to constant at 50 ms. The turbulence intensity from 10sm to 50 ms is higher and decreases rapidly from 50 ms to 100 ms. The effect of the pneumatic pressure on the maximum rate of explosion pressure rise of ethanol aerosol is much higher than that on the peak explosion pressure. The maximum rate of explosion pressure rise of the ethanol aerosol is lower than that of ethanol vapor/air. The explosion index of ethanol vapor/air is higher than that of ethanol aerosol. Ethanol vapor/air has a higher explosion hazard, compared with ethanol aerosol with the same concentration.

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.

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.

Choice of buffer in mobile phase can substantially alter peak areas in quantification of lipids by HPLC-ELSD

Evaporative light scattering detectors (ELSD) are commonly used with high-performance liquid chromatography (HPLC) to separate and quantify lipids, which are typically not easily detectable by more conventional methods such as UV–visible detectors. In many HPLC-ELSD methods to analyze lipids, a volatile buffer is included in the mobile phase to control the pH and facilitate separation between lipid species. Here, we report an unintended effect that buffer choice can have in HPLC-ELSD analysis of lipids – the identity and concentration of the buffer can substantially influence the resulting ELSD peak areas. To isolate this effect, we use a simple isocratic methanol mobile phase supplemented with different concentrations of commonly used buffers for ELSD analysis, and quantify the effect on peak width, peak shape, and peak area for seven different lipids (POPC, DOPE, cholesterol, sphingomyelin, DOTAP, DOPS, and lactose ceramide). We find that the ELSD peak areas for different lipids can change substantially depending on the mobile phase buffer composition, even in cases where the peak width and shape are unchanged. For a subset of analytes which are UV-active, we also demonstrate that the peak area quantified by UV remains unchanged under different buffer conditions, indicating that this effect is particular to ELSD quantification. We speculate that this ELSD-buffer effect may be the result of a variety of physical phenomenon, including: modification of aerosol droplet size, alteration of clustering of analytes during evaporation of the mobile phase, and mass-amplification or ion-pair effects, all of which could lead to differences in observed peak areas. Such effects would be expected to be molecule-specific, consistent with our data. We anticipate that this report will be useful for researchers designing and implementing HPLC-ELSD methods, especially of lipids.

Experimental research on surface acoustic wave microfluidic atomization for drug delivery

This paper demonstrates that surface acoustic wave (SAW) atomization can produce suitable aerosol concentration and size distribution for efficient inhaled lung drug delivery and is a potential atomization device for asthma treatment. Using the SAW device, we present comprehensive experimental results exploring the complexity of the acoustic atomization process and the influence of input power, device frequency, and liquid flow rate on aerosol size distribution. It is hoped that these studies will explain the mechanism of SAW atomization aerosol generation and how they can be controlled. The insights from the high-speed flow visualization studies reveal that it is possible by setting the input power above 4.17 W, thus allowing atomization to occur from a relatively thin film, forming dense, monodisperse aerosols. Moreover, we found that the aerosol droplet size can be effectively changed by adjusting the input power and liquid flow rate to change the film conditions. In this work, we proposed a method to realize drug atomization by a microfluidic channel. A SU-8 flow channel was prepared on the surface of a piezoelectric substrate by photolithography technology. Combined with the silicon dioxide coating process and PDMS process closed microfluidic channel was prepared, and continuous drug atomization was provided to improve the deposition efficiency of drug atomization by microfluidic.

One year of surgical mask testing at the University of Bologna labs: Lessons learned from data analysis

The outbreak of SARS-CoV-2 pandemic highlighted the worldwide lack of surgical masks and personal protective equipment, which represent the main defense available against respiratory diseases as COVID-19. At the time, masks shortage was dramatic in Italy, the first European country seriously hit by the pandemic: aiming to address the emergency and to support the Italian industrial reconversion to the production of surgical masks, a multidisciplinary team of the University of Bologna organized a laboratory to test surgical masks according to European regulations. The group, driven by the expertise of chemical engineers, microbiologists, and occupational physicians, set-up the test lines to perform all the functional tests required. The laboratory started its activity on late March 2020, and as of the end of December of the same year 435 surgical mask prototypes were tested, with only 42 masks compliant to the European standard. From the analysis of the materials used, as well as of the production methods, it was found that a compliant surgical mask is most likely composed of three layers, a central meltblown filtration layer and two external spunbond comfort layers. An increase in the material thickness (grammage), or in the number of layers, does not improve the filtration efficiency, but leads to poor breathability, indicating that filtration depends not only on pure size exclusion, but other mechanisms are taking place (driven by electrostatic charge).The study critically reviewed the European standard procedures, identifying the weak aspects; among the others, the control of aerosol droplet size during the bacterial filtration test results to be crucial, since it can change the classification of a mask when its performance lies near to the limiting values of 95 or 98%.

Uncertainties in Evaluating Global Electric Circuit Interactions With Atmospheric Clouds and Aerosols, and Consequences for Radiation and Dynamics

AbstractObservations and theory relevant to evaluating the importance of the effect of Ionosphere‐Earth current density, JZ, in the global electric circuit on cloud microphysics and cloud opacity at high latitudes, with presumed consequences for surface pressure, are reviewed and updated. The day‐to‐day input variations are less than 10% of their mean values, as are the reported cloud and pressure effects, but could be indicative of more important longer‐term effects, and of neglected processes in aerosol‐cloud interactions. There is consistent evidence for responses to both externally (solar‐wind) and internally (thunderstorm and shower‐cloud) generated changes in JZ and cloud opacity. The pressure correlations show non‐stationary behavior, with changes in phase relative to that of the solar wind input and JZ variations on interdecadal timescales. These might be due to the non‐stationary nature of the solar wind, and non‐stationary aerosol populations. For modeling the cloud effects there are considerable uncertainties in the size and charge distributions of aerosol particles, droplets, and ice particles. The cloud radiative coupling with periodic solar wind inputs may nudge internal tropospheric waves into phase coherence at times when the amplitude of the solar input and the duration of the input trains exceed minimum values.

Development of a rat capnoperitoneum phantom to study drug aerosol deposition in the context of anticancer research on peritoneal carcinomatosis

Pressurized Intraperitoneal Aerosol Chemotherapy (PIPAC) is a promising approach with a high optimization potential for the treatment of peritoneal carcinomatosis. To study the efficacy of PIPAC and drugs, first rodent cancer models were developed. But inefficient drug aerosol supply and knowledge gaps concerning spatial drug distribution can limit the results based on such models. To study drug aerosol supply/deposition, computed tomography scans of a rat capnoperitoneum were used to deduce a virtual and a physical phantom of the rat capnoperitoneum (RCP). RCP qualification was performed for a specific PIPAC method, where the capnoperitoneum is continuously purged by the drug aerosol. In this context, also in-silico analyses by computational fluid dynamic modelling were conducted on the virtual RCP. The physical RCP was used for ex-vivo granulometric analyses concerning drug deposition. Results of RCP qualification show that aerosol deposition in a continuous purged rat capnoperitoneum depends strongly on the position of the inlet and outlet port. Moreover, it could be shown that the droplet size and charge condition of the drug aerosol define the deposition efficiency. In summary, the developed virtual and physical RCP enables detailed in-silico and ex-vivo analyses on drug supply/deposition in rodents.

Exploring high pressure nebulization of Pluronic F127 hydrogels for intraperitoneal drug delivery

Peritoneal metastasis is an advanced cancer type which can be treated with pressurized intraperitoneal aerosol chemotherapy (PIPAC). Here, chemotherapeutics are nebulized under high pressure in the intraperitoneal (IP) cavity to obtain a better biodistribution and tumor penetration. To prevent the fast leakage of chemotherapeutics from the IP cavity, however, nebulization of controlled release formulations is of interest.In this study, the potential of the thermosensitive hydrogel Pluronic F127 to be applied by high pressure nebulization is evaluated. Therefore, aerosol formation is experimentally examined by laser diffraction and theoretically simulated by computational fluid dynamics (CFD) modelling. Furthermore, Pluronic F127 hydrogels are subjected to rheological characterization after which the release of fluorescent model nanoparticles from the hydrogels is determined.A delicate equilibrium is observed between controlled release properties and suitability for aerosolization, where denser hydrogels (20% and 25% w/v Pluronic F127) are able to sustain nanoparticle release up to 30 h, but cannot effectively be nebulized and vice versa. This is demonstrated by a growing aerosol droplet size and exponentially decreasing aerosol cone angle when Pluronic F127 concentration and viscosity increase. Novel nozzle designs or alternative controlled release formulations could move intraperitoneal drug delivery by high pressure nebulization forward.

Recognition of Inter‐Cloud Versus Intra‐Cloud Controls on Droplet Dispersion With Applications to Microphysics Parameterization

AbstractAerosols in the atmosphere can have a large impact on weather and climate. One of its lesser‐known impacts is the aerosol‐dispersion effect, which refers to the feedback between the aerosol (or cloud droplet) concentration and the relative dispersion of the droplet size distribution. This study attempts to reconcile the inconsistent sign of the correlation between aerosol number and droplet dispersion found in past studies by distinguishing local correlation from cloud‐mean correlation. We find that while the cloud‐mean correlation between aerosol concentration and droplet size relative dispersion is largely nonexistent, in‐cloud regions with high relative dispersion are typically associated with low local droplet concentration. Even stronger correlation is found with respect to the local activation fraction (the ratio of droplet concentration to total droplet and aerosol concentration). Based on this local correlation, we propose a new equation to diagnose the shape parameter in marine stratocumulus clouds for double moment bulk schemes in cloud‐resolving or large‐eddy simulations. This new equation is more physically realistic than many existing ones that are based on the weak cloud‐mean correlation.

Pt-WO3 oxydehydrates fructose to furans in the gas phase

Bio-feedstocks are destined to replace fossil fuels for specialty chemicals, but current bio-refineries mainly ferment monosaccharides to ethanol, a commodity chemical that is blended with gasoline as a fuel. The market price of biofuels is several-fold lower than specialty chemicals and monomers. Rather than cracking the C6-sugars ethanol, here, develop dehydration and oxydehydration processes to valuable platform C6-chemicals like 5-hydroxymethyl furfural (HMF), 2,5-dimethyl furan (DFF), and 2,5-furandicarboxylic acid. This gas-phase process atomizes an aqueous solution of fructose into a fluidized bed reactor operating at 350°C. The solution forms an aerosol (droplet size of 30µm), which contacts the hot Pt-WO3/TiO2 catalyst and reacts to HMF rather than caramelizing. The maximum yield reached 21% and it increased slightly with temperature, and decreased with increasing catalyst inventory; it was less sensitive to O2 concentration, Pt loading on the catalyst, liquid feed flow rate, and fructose feed concentration. At the optimal condition, selectivity continued to increase with time even after 3h reaction. Selectivity to 2,5-diformyl furan reached 42% at 250°C with HMF as a feedstock.

Modeling the viral load expelled in saliva droplets carrying SARS-CoV-2

One of the most likely routes of transmission of COVID-19 is through the saliva droplets that are produced while speaking, coughing or sneezing by infected people. The expelled droplets, measuring between 0.4 and 450 μm, follow trajectories determined, mainly, by the gravitational, and air frictional forces. We solve numerically the equations of motion in which the linear and quadratic velocity terms in the drag force are considered. In order to model the virus load expelled during respiratory events, we assume log-log Gaussian distributions, with peaks around 10 μm, and analyze four size ranges: the aerosol (0.4–5 μm), the small (5.1–10 μm), the middle (10.1–100 μm), and big (100.1–450 μm) droplet size regimes. In the aerosol regime, the frictional forces quickly stop the droplets in their horizontal movement and they fall extremely slowly pulled down by the gravitational force. The residence time, in a calm environment, goes from 3.83 days to 33.3 min. More massive droplets take shorter times and hit the ground meters away from the source. By assuming a constant density of virions per milliliter, we estimate the expelled amount into the environment. The middle and small size droplets contain the highest amount but since the aerosol droplets remain in the air such a long time, they represent also a high risk for infection. We emphasize the importance of face protection to minimize COVID-19, transmission.