Features of metastable superheated water atomization when being discharged through convergent-divergent nozzles at different superheat values

Experiments with the metastable superheated water atomization proved the significant increase of the submicron droplets mass fraction at the outlet of convergent-divergent nozzle from 0.45-0.55 to 0.75-0.9 with an increase of the inlet water temperature from170to255°C. Two different approaches to dimensionless treatment of the atomization processdata and determining the boundary of the zone of flashing predominance are compared. The analysis of two approaches to dimensionless treatment of experimental and calculating results concerning transition to predominating role of nucleation in the process of superheated liquid atomization in convergent-divergent nozzles is done.

Modeling Aerial Transmission of Pathogens (Including the SARS-CoV-2 Virus) through Aerosol Emissions from E-Cigarettes

We examine the plausibility of aerial transmission of pathogens (including the SARS-CoV-2 virus) through respiratory droplets that might be carried by exhaled e-cigarette aerosol (ECA). Given the lack of empiric evidence on this phenomenon, we consider available evidence on cigarette smoking and respiratory droplet emission from mouth breathing through a mouthpiece as convenient proxies to infer the capacity of vaping to transport pathogens in respiratory droplets. Since both exhaled droplets and ECA droplets are within the Stokes regime, the ECA flow acts effectively as a visual tracer of the expiratory flow. To infer quantitatively the direct exposure distance, we consider a model that approximates exhaled ECA flow as an axially symmetric intermittent steady starting jet evolving into an unstable puff, an evolution that we corroborate by comparison with photographs and videos of actual vapers. On the grounds of all this theoretical modeling, we estimate for low-intensity vaping (practiced by 80–90% of vapers) the emission of 6–210 (median 39.9, median deviation 67.3) respiratory submicron droplets per puff and a horizontal distance spread of 1–2 m, with intense vaping possibly emitting up to 1000 droplets per puff in the submicron range with a distance spread over 2 m. The optical visibility of the ECA flow has important safety implications, as bystanders become instinctively aware of the scope and distance of possible direct contagion through the vaping jet.

MECHANICAL PROPERTIES OF POLYSULFONE-ZnO NANOCOMPOSITE MEMBRANE

Large quantities of wastewater are generated by the petroleum refining process. Micron-scale emulsion droplets and submicron droplets are difficult to remove from oil-refined wastewater, and addressing these issues has been a major challenge for researchers. Membrane technology is widely used in water treatment because it is very selective and effective in the filtration process. his research focuses on oil refinery water treatment using a polysulfone membrane (PSF)-nano-ZnO membrane with the addition of polyethylene glycol (PEG). This research aims to determine the PEG ratio that produces the optimum PSF-ZnO membrane in terms of mechanical properties, including thickness, tensile strength, and molecular weight cut-off (MWCO) value. The membranes with the optimum clearance were obtained at 3% PEG with a thickness of 0.0077 mm, Young's modulus of 8800 N/m2, and Morphological analysis was performed using the SEM (Scanning Electron Microscopy) method on the membrane which had the highest and lowest permeability values.. The best membrane MWCO value was achieved by the addition of 19% PSF-nano-ZnO 1% wt at 5 minutes of UV irradiation. This shows that the addition of PEG composite affects pore openings. The membrane formed with variations in PEG concentrations affecting the thickness of the membrane. Higher concentrations make the membrane thicker, resulting in a higher Young’s modulus.

Room Temperature Nanoencapsulation of Bioactive Eicosapentaenoic Acid Rich Oil within Whey Protein Microparticles

In this study, emulsion electrospraying assisted by pressurized gas (EAPG) has been performed for the first time to entrap ca. 760 nm droplets of the bioactive eicosapentaenoic acid (EPA)-rich oil into whey protein concentrate (WPC) at room temperature. The submicron droplets of EPA oil were encapsulated within WPC spherical microparticles, with sizes around 5 µm. The EPA oil did not oxidize in the course of the encapsulation performed at 25 °C and in the presence of air, as corroborated by the peroxide value measurements. Attenuated Total Reflection—Fourier Transform Infrared spectroscopy and oxygen consumption tests confirmed that the encapsulated EPA-rich oil showed increased oxidative stability in comparison with the free oil during an accelerated oxidation test under ultraviolet light. Moreover, the encapsulated EPA-rich oil showed increased thermal stability in comparison with the free oil, as measured by oxidative thermogravimetric analysis. The encapsulated EPA-rich oil showed a somewhat reduced organoleptic impact in contrast with the neat EPA oil using rehydrated powdered milk as a reference. Finally, the oxidative stability by thermogravimetric analysis and organoleptic impact of mixtures of EPA and docosahexaenoic acid (DHA)-loaded microparticles was also studied, suggesting an overall reduced organoleptic impact compared to pure EPA. The results here suggest that it is possible to encapsulate 80% polyunsaturated fatty acids (PUFAs)-enriched oils by emulsion EAPG technology at room temperature, which could be used to produce personalized nutraceuticals or pharmaceuticals alone or in combination with other microparticles encapsulating different PUFAs to obtain different targeted health and organoleptic benefits.

Aerial transmission of SARS-CoV-2 virus (and pathogens in general) through environmental e-cigarette aerosol

We examine the plausibility, scope and risks of aerial transmission of pathogens (including the SARS-CoV-2 virus) through respiratory droplets carried by exhaled e–cigarette aerosol (ECA). Observational and laboratory data suggests considering cigarette smoking and mouth breathing through a mouthpiece as convenient proxies to infer the respiratory mechanics and droplets sizes and their rate of emission that should result from vaping. To infer distances for possible direct contagion we model exhaled ECA flow as an intermittent turbulent jet evolving into an unstable puff, estimating for low intensity vaping (practiced by 80-90% of vapers) ECA expirations the emission of 2-230 respiratory submicron droplets per puff a horizontal distance spread of 1-2 meters, with intense vaping possibly carrying hundreds and up to 1000 droplets per puff in the submicron range a distance spread over 2 meters. Bystanders exposed to low intensity expirations from an infectious vaper in indoor spaces (home and restaurant scenarios) face a 1% increase of risk of indirect contagion with respect to a “control case” scenario defined by exclusively rest breathing without vaping. This relative added risk becomes 5 – 17% for high intensity vaping, 40 – 90% and over 260% for speaking or coughing (without vaping). This risk evaluation remains practically unchanged in shared spaces with universal usage of face masks. We estimate that disinfectant properties of glycols in ECA are unlikely to act efficiently on pathogens carried by vaping expirations under realistic conditions.

Evaluation of Novel “No-Touch” Technologies for Decontamination of Toys in Pediatric Healthcare Settings

Background: Toys in playrooms are often shared among patients in pediatric healthcare settings; they can present a risk for transmission of bacterial and viral pathogens. Effective cleaning and disinfection of toys using disinfectant wipes is labor intensive and difficult due to irregular surfaces. Methods: We conducted a point-prevalence culture survey to determine the frequency of contamination of in-use toys and high-touch surfaces in playrooms in a pediatric healthcare facility with methicillin-resistant Staphylococcus aureus (MRSA), vancomycin-resistant enterococci (VRE), and Clostridioides difficile. Using a variety of toys inoculated with pathogens, we evaluated efficacy and ease-of-use of 3 novel “no-touch” technologies: (1) an electrostatic sprayer, (2) a small ultraviolet-C (UV-C) box (18.9 × 9.9 × 1.8 inches) for smaller toys, and (3) a high-level disinfection cabinet using ultrasonic submicron droplets of peracetic acid and hydrogen peroxide. Test pathogens included C. difficile, MRSA, and Candida auris. Results: Of 135 items cultured in playrooms, 6 (4.4%) were contaminated with MRSA, 1 (0.7%) was contaminated with VRE, and none were contaminated with C. difficile. Each of the technologies reduced all pathogens by >4 log10 CFU on all types of toys tested (plastic, soft rubber, and tablet). The electrostatic sprayer was considered the easiest to use by all users because large numbers of toys could be processed much more quickly (ie, spray for 20 seconds and allow to air dry) than with disinfectant wipes. The disinfection cabinet required 21 minutes for cycle completion, whereas the decontamination cycle for the UV box was only 30–90 seconds but with limited capacity to hold toys. Conclusions: Three “no-touch” technologies were effective for disinfection of toys contaminated with healthcare-associated pathogens. The electrostatic spray application of disinfectant was considered the easiest to use for rapid decontamination of toys.Funding: NoneDisclosures: None

Spontaneous nano-emulsification with tailor-made amphiphilic polymers and related monomers

In general, nano-emulsions are submicron droplets composed of liquid oil phase dispersed in liquid aqueous bulk phase. They are stable and very powerful systems when it regards the encapsulation of lipophilic compounds and their dispersion in aqueous medium. On the other hand, when the properties of the nano-emulsions aim to be modified, e.g. for changing their surface properties, decorating the droplets with targeting ligands, or modifying the surface charge, the dynamic liquid / liquid interfaces make it relatively challenging. In this study, we have explored the development of nano-emulsions which were not anymore stabilized with a classical low-molecular weight surfactant, but instead, with an amphiphilic polymer based on poly(maleic anhydride-alt-1-octadecene) (PMAO) and Jeffamine®, a hydrophilic amino-terminated PPG/PEG copolymer. Using a polymer as stabilizer is a potential solution for the nano-emulsion functionalization, ensuring the droplet stabilization as well as being a platform for the droplet decoration with ligands (for instance after addition of function groups in the terminations of the chains). The main idea of the present work was to understand if the spontaneous emulsification –commonly performed with nonionic surfactants– can be transposed with amphiphilic polymers, and a secondary objective was to identify the main parameters impacting on the process. PMAO was modified with two different Jeffamine®, additionally different oils and different formulation conditions were evaluated. As a control, the parent monomer, octadecyl succinic anhydride (OSA) was also modified and studied in the similar way as that of polymer. The generated nano-emulsions were mainly studied by dynamic light scattering and electron microscopy, that allows discriminating the crucial parameters in the spontaneous process, originally conducted with polymers as only stabilizer.

Numerical simulation of micron and submicron droplets in jet impinging

Micron droplet deposition onto a wall in an impinging jet is important for various applications like spray cooling, coating, fuel injection, and erosion. The impinging process is featured by abrupt velocity changes and thus complicated behaviors of the droplets. Either modeling or experiment for the droplet behaviors is still challenging. This study conducted numerical modeling and compared with an existing experiment in which concentric dual-ring deposition patterns of micron droplets were observed on the impinging plate. The modeling fully took into account of the droplet motion in the turbulent flow, the collision between the droplets and the plate, as well as the collision, that is, agglomeration among droplets. Different turbulence models, that is, the v2− f model, standard k–ε model, and Reynolds stress model, were compared. The results show that the k–ε model failed to capture the turbulent flow structures and overpredicted the turbulent fluctuations near the wall. Reynolds stress model had a good performance in flow field simulation but still failed to reproduce the dual-ring deposition pattern. Only the v2− f model reproduced the dual-ring pattern when coupled with droplet collision models. The results echoed the excellent performance of the v2− f model in the heat transfer calculation for the impinging problems. The agglomeration among droplets has insignificant influence on the deposition.

Simulations of femtosecond laser pulse interaction with spray target

Laser interactions with spray targets (clouds of submicron droplets) are studied here via numerical simulations using two-dimensional particle-in-cell codes. Our simulations demonstrate an efficient absorption of laser pulse energy inside the spray. The energy absorption efficiency depends on the inter-droplet distance, size of the cloud of droplets, and laser pulse intensity, as well as on the pre-evaporation of droplets due to laser pulse pedestal. We investigate in detail proton acceleration from the spray. Energy spectra of protons in various acceleration directions vary significantly depending on the density profile of the plasma created from the droplets and on laser intensity. The spray target can be alternative of foil targets for high intensity high repetition ultrahigh contrast femtosecond lasers. However, at intensities >1021 W/cm2, the efficiency of laser absorption and ion acceleration from the droplets drops significantly in contrast to foils.