Aerosol Research Articles

Pemberdayaan Warga Binaan dalam Upaya Pencegahan TB Paru di Lapas Perempuan Kelas II A Pontianak

Pulmonary Tuberculosis is a direct infectious disease caused by the tuberculosis germ (Mycobacterium tuberculosis) which is transmitted through the air (droplet nuclei) when a patient coughs and splashes of saliva containing the bacteria are inhaled by another person while breathing. The risk factors for the incidence of pulmonary TB are, occupancy density, lack of ventilation, poor lighting, access to inadequate facilities. The problems that exist in partners are the lack of counseling activities, especially related to health education on the prevention of pulmonary TB, the condition of densely populated prisons, inadequate ventilation and inadequate lighting are risk factors for the development of pulmonary TB. The first step is to collect pre-test data before being given health information on TB prevention. Furthermore, health education was given about prevention of pulmonary TB to the inmates. At the evaluation stage, post-test data were collected. Based on the results of community service activities with the target of assisted residents in the Pontianak class II women's correctional prison, it went well. Participants can participate in activities from start to finish with enthusiasm. After participating in this activity, it was found that there was an increase in knowledge in efforts to prevent pulmonary TB in prisons. It is hoped that the prison can increase health education activities, especially pulmonary TB, this is necessary to prevent transmission of pulmonary TB in prisons.

Evaluation of effective operation parameter on High Efficiency Particulate Air and Ultra Low Particulate Air filters

The particle penetration removal efficiency of the High Efficiency Particulate Air (HEPA) and Ultra Low Particulate Air (ULPA) filters were studied by using of mono-disperse liquid aerosols of Di-Octyl Phethalate (DOP) under vary operational conditions. The effects of different operational factors, including the particle size, the face velocity and pressure drop were investigated in this study. The results indicated that the most penetrating particle size through the ULPA and HEPA filters was approximately 0.1-0.12 µm. Brown diffusion effect is suggested mechanism for particle size removal mechanism of 0.1 µm and less while impaction and interception mechanisms are explained the behavior of HEPA and ULPA filters for removal of 0.12 µm and more particle size. The penetrations of particle through both kind of filters were increased with increasing of face velocity. Additionally, the pressure drop of filter is increased versus the rising of face velocity. The cost of energy is lower in low face velocity of filters.

Effects of pulse power on evaporation characteristics of an n-heptane droplet in a microtube

When combustion instability arises in liquid rocket engines, heat release fluctuations cause local temperature oscillations and affect the evaporation of fuel droplets. In this study, to investigate the responses of droplet evaporation characteristics to temperature oscillations, an n-heptane droplet is formed by continuous fuel injection, and a pulse power is applied to generate temperature oscillations. The pulse power outputs a square wave with a frequency of 0.1–10 Hz and a power of 16.6–30.0 W. A transient heat transfer and droplet evaporation model is established, and measured droplet diameters serve to validate the model. The effects of heating frequency, heating power, and waveforms on droplet vaporization are studied. The results show that pulse power induces oscillations in air temperature, droplet diameter, and evaporation rate, which correspond to the applied heating frequency. Due to heat transfer within the tube, a phase lag is observed in the air temperature relative to the applied power. The dynamic equilibrium between the evaporation rate and fuel flow rate causes the evaporation rate phase to lag behind the droplet diameter phase by a constant of 0.5π, and to lead slightly ahead of the air temperature phase. Increases in heating frequency reduce the amplitudes of air temperature, droplet diameter, and evaporation rate while maintaining their averages constant. Decreases in heating power lower the air temperature, consequently increasing the evaporation rate amplitude and average droplet diameter. At 16.6 W, the droplet descends due to exceeding the critical diameter of 2.02 mm. Replacing the square wave of pulse power with a sinusoidal or triangular wave only results in a decline in air temperature amplitude, consequently reducing the evaporation rate amplitude by an equivalent degree. The amplitude percentage ratio between them remains unchanged at 4.77 but is subject to interference from their phase difference. As frequency increases from 0.1 to 1 Hz, the phase difference rises from −0.08π and converges to 0, while the amplitude percentage ratio increases from 4.77, converging to 4.87.

The classification of atmospheric hydrometeors and aerosols from the EarthCARE radar and lidar: the A-TC, C-TC and AC-TC products

Abstract. The EarthCARE mission aims to probe the Earth's atmosphere by measuring cloud and aerosol profiles using its active instruments, the Cloud Profiling Radar (CPR) and ATmospheric LIDar (ATLID). The correct identification of hydrometeors and aerosols from atmospheric profiles is an important step in retrieving the properties of clouds, aerosols and precipitation. Ambiguities in the nature of atmospheric targets can be removed using the synergy of collocated radar and lidar measurements, which is based on the complementary spectral response of radar and lidar relative to atmospheric targets present in the profiles. The instruments are sensitive to different parts of the particle size distribution and provide independent but overlapping information in optical and microwave wavelengths. ATLID is sensitive to aerosols and small cloud particles, and CPR is sensitive to large ice particles, snowflakes and raindrops. It is therefore possible to better classify atmospheric targets when collocated radar and lidar measurements exist compared to using a single instrument. The cloud phase, precipitation and aerosol type within the column sampled by the two instruments can then be identified. ATLID-CPR target classification (AC-TC) is the product created for this purpose by combining the ATLID target classification (A-TC) and CPR target classification (C-TC). AC-TC is crucial for the subsequent synergistic retrieval of cloud, aerosol and precipitation properties. AC-TC builds upon previous target classifications using CloudSat and CALIPSO synergy while providing richer target classification using the enhanced capabilities of EarthCARE's instruments, specifically CPR's Doppler velocity measurements to distinguish snow and rimed snow from ice clouds and ATLID's lidar ratio measurements to objectively discriminate between different aerosol species and optically thin ice clouds. In this paper, we first describe how the single-instrument A-TC and C-TC products are derived from ATLID and CPR measurements. Then the AC-TC product, which combines the A-TC and C-TC classifications using a synergistic decision matrix, is presented. Simulated EarthCARE observations based on combined cloud-resolving and aerosol model data are used to test the processors generating the target classifications. Finally, the target classifications are evaluated by quantifying the fractions of ice and snow, liquid clouds, rain, and aerosols in the atmosphere that can be successfully identified by each instrument and their synergy. We show that radar–lidar synergy helps better detect ice and snow, with ATLID detecting radiatively important optically thin cirrus and cloud tops, while CPR penetrates most deep and highly concentrated ice clouds. The detection of rain and drizzle is entirely due to C-TC, while that of liquid clouds and aerosols is due to A-TC. The evaluation also shows that simple assumptions can be made to compensate for when the instruments are obscured by extinction (ATLID) or surface clutter and multiple scattering (CPR); this allows for the recovery of the majority of liquid cloud not detected by the active instruments.

Detectable Anthropogenic Intensification of the Summer Compound Hot and Dry Events Over Global Land Areas

AbstractCompound hot and dry events (CHDEs) pose an increasing threat to global warming and have received growing attention in recent decades. We conducted a detection and attribution analysis (D&A) using the optimal fingerprint technique to analyze the changes in observed CHDEs at continental and sub‐continental scales from 1961 to 2014. The responses of CHDEs changes to anthropogenic (ANT), greenhouse gases (GHG), aerosols (AER), and natural (NAT) forcings were obtained from the Coupled Model Intercomparison Project phase 6 forcing experiment. In a two‐signal D&A analysis that considered ANT and NAT simultaneously, ANT signals were robustly detected and separated from NAT in all continental domains and more than 65% of subcontinental domains (29 out of 44 domains). The trend attributed to the ANT forcing is comparable to the observed trend over domains where the ANT signal is detectable. We also conducted a three‐signal D&A analysis that regressed observation onto GHG, AER, and NAT simultaneously. The GHG signals were detectable in all continents except Oceania, and it contributed dominantly to the observed trend over 22 out of 29 regions where ANT signals had emerged. Multivariate biases correction can largely reduce the models' biases in simulating the marginal distribution and the dependence structure, which can provide a more accurate future risk of CDHEs. We found that limiting global warming to 1.5℃ rather than 2.0℃ can significantly mitigate the impact of compound events in most areas of global land, particularly in South America, Africa, and Oceania.

Impact of aerosol in-situ peroxide formations induced by metal complexes on atmospheric H2O2 budgets

Hydrogen peroxide (H2O2), hydroxyl radicals (OH), hydroperoxyl (HO2), and superoxide (O2−) radicals interacting with aerosol particles significantly affect the atmospheric pollutant budgets. A multiphase chemical kinetic box model (PKU-MARK), including the multiphase processes of transition metal ions (TMI) and their organic complexes (TMI-OrC), was built to numerically drive H2O2 chemical behaviors in the aerosol particle liquid phase using observational data obtained from a field campaign in rural China. Instead of relying on fixed uptake coefficient values, a thorough simulation of multiphase H2O2 chemistry was performed. In the aerosol liquid phase, light-driven TMI-OrC reactions promote OH, HO2/O2−, and H2O2 recycling and spontaneous regenerations. The in-situ generated aerosol H2O2 would offset gas-phase H2O2 molecular transfer into the aerosol bulk phase and promote the gas-phase level. When combined with the multiphase loss and in-situ aerosol generation involving TMI-OrC mechanism, the HULIS-Mode significantly improves the consistency between modeled and measured gas-phase H2O2 levels. Aerosol liquid phase could be a pivotal potential source of aqueous H2O2 and influence the multiphase budgets. Our work highlights the intricate and significant effects of aerosol TMI and TMI-OrC interactions on the multiphase partitioning of H2O2 when assessing atmospheric oxidant capacity.

Multielemental analysis of oils and animal fat by using deep eutectic solvents assisted by an aerosol phase extraction procedure

In the present study, thirteen elements (Ag, Al, Ba, Cd, Cr, Cu, Fe, K, Li, Mg, Mn, Ni, Pb) have been extracted from used cooking oils, olive oils and animal fat. Either inductively coupled plasma optical emission spectrometry (ICP-OES) or tandem mass spectrometry (ICP-MS/MS) have been chosen as detection techniques. Due to the difficulty of directly introducing highly viscous organic samples into the spectrometer, a fast dispersive liquid – liquid aerosol phase extraction (DLLAPE) method has been selected to isolate the analytes from the sample matrix. The DLLAPE is based on the generation of an aerosol from the extracting phase with the help of a pneumatic nebulizer. This high velocity aerosol impacts and penetrates in the liquid sample. Consequently, the liquid – liquid exchange surface area becomes high, thus leading to high extraction yields. A hydrophilic deep eutectic solvent (DES) consisting of choline chloride and ethylene glycol (1:2 mass ratio) has been selected as the extracting solvent. Prior to undertaking the experiments, the extraction method has been evaluated in terms of precision under suitable conditions. In comparison with conventional methods based on sample digestion, sample dilution and shot analysis or extraction assisted by vortex agitation, the DLLAPE shows several advantages, because it is faster, and it provides lower limits of detection than the reference methodologies. The procedural limits of quantification for the determined elements with the DLLAPE in ICP-OES were 0.046 (Ag), 0.396 (Al), 0.013 (Cd), 0.033 (Cr), 0.040 (Cu), 0.20 (Fe), 0.026 (K), 0.026 (Li), 0.33 (Mg), 0.013 (Mn), 2.64 (Ni) and 0.53 (Pb) mg kg−1. Meanwhile, pLOQ in ICP-MS/MS lowered by roughly one order of magnitude. The accuracy of the aerosol phase extraction method has been evaluated through the determination of the recoveries for four representative analytes (Ca, Cu, Mg and Ni) from spiked real samples. For these elements, recovery has taken values of (100 ± 20)%. Moreover, a comparison of the multielemental concentration obtained with conventional methods (c.a., sample dilution and shot ICP analysis and liquid-liquid extraction using a vortex agitator) against that measured with the DLLAPE has been carried out. Multiemelemental concentrations have been obtained for real samples and the found levels have been similar to those encountered in previously published works.

Aeromicelle—A new form of liquid aerosol for delivering aqueous samples into a single-particle mass spectrometer

For applying highly sensitive mass spectrometry to chemical analysis of aqueous samples, we have developed a novel technique using a new form of liquid droplets, which we call “aeromicelle” (AM), to deliver aqueous sample solutions directly into the vacuum region of a single-particle mass spectrometer in liquid form and conduct immediate mass analysis. AMs are generated by spraying an aqueous solution containing a surfactant at a concentration significantly lower than its critical micelle concentration (CMC). When the solution is sprayed, liquid droplets containing the surfactant are formed, which gradually dry in an air flow. Upon drying, the surfactant concentration in the droplet exceeds its CMC, and consequently, the surfactant molecules begin to cover the droplet surface. Finally, the surface is expected to be fully covered with surfactant molecules such as reverse micelles. The surface coverage helps suppress the evaporation of water, thereby enhancing the residence time of the liquid droplet. Our experimental results show that the AMs retained a liquid form for at least 100 s in air and survived even under vacuum conditions for further mass analysis: each AM delivered in the vacuum region of a single-particle mass spectrometer is ablated with an intense laser pulse and then, mass analyzed. Individual AMs generated from an aqueous solution containing CsCl were analyzed using a single-particle mass spectrometer. The Cs+ ion peak was observed even in AMs generated from the 10 nM solution. The number of Cs atoms in each AM was estimated to be approximately 7 × 103, which corresponds to 1.2 × 10−20 mol (12 zmol). Meanwhile, in the mass analysis of tyrosine, both positive and negative fragmentation ions from tyrosine in AMs were observed in the mass spectrum and 4.6 × 105 (760 zmol) tyrosine molecules were detected.

Combustion Characteristics of Coal-Water Slurry Droplets in High-Temperature Air with the Addition of Syngas

An experimental study of the ignition and combustion processes of coal-water slurry (CWS) droplets based on coal enrichment waste in a high-temperature oxidizer at 650–850 °C with a syngas addition was carried out. The fuel slurry was a mixture of finely dispersed solid combustible particles (coal sludge, 10–100 µm in size) and water. The syngas was a product of biomass pyrolysis and two waste-derived fuels in a laboratory gasifier. Composition of the syngas was controlled by a precision analytical gas analyzer. The feasibility of co-firing CWS with syngas was experimentally established. Under such conditions, the CWS droplets ignition process was intensified by 15–40%, compared to fuel combustion without the addition of syngas to the combustion chamber. The greatest positive effect was achieved by adding the gas obtained during the biomass pyrolysis. The ignition delay times of CWS droplets are 5.2–12.5 s versus 6.1–20.4 s (lower by 15–39%) when ignited in a high-temperature medium without adding syngas to the combustion chamber. Based on the results obtained, a concept for the practical implementation of the CWS combustion technology in a syngas-modified oxidizer medium is proposed.

Evaluation of Probes to Measure Oxidizing Organic Triplet Excited States in Aerosol Liquid Water.

Oxidizing triplet excited states of organic matter (3C*) drive numerous reactions in fog/cloud drops and aerosol liquid water (ALW). Quantifying oxidizing triplet concentrations in ALW is difficult because 3C* probe loss can be inhibited by the high levels of dissolved organic matter (DOM) and copper in particle water, leading to an underestimate of triplet concentrations. In addition, illuminated ALW contains high concentrations of singlet molecular oxygen (1O2*), which can interfere with 3C* probes. Our overarching goal is to find a triplet probe that has low inhibition by DOM and Cu(II) and low sensitivity to 1O2*. To this end, we tested 12 potential probes from a variety of compound classes. Some probes are strongly inhibited by DOM, while others react rapidly with 1O2*. One of the probe candidates, (phenylthiol)acetic acid (PTA), seems well suited for ALW conditions, with mild inhibition and fast rate constants with triplets, but it also has weaknesses, including a pH-dependent reactivity. We evaluated the performance of both PTA and syringol (SYR) as triplet probes in aqueous extracts of particulate matter. While PTA is less sensitive to inhibition than SYR, it results in lower triplet concentrations, possibly because it is less reactive with weakly oxidizing triplets.

Impact of Coronavirus Disease (COVID-19) on Reproductive Health

The coronavirus disease (COVID-19) is a communicable respiratory disease caused by a new strain of coronavirus that causes illness in humans. The disease is caused by a pathogen called Severe Acute Respiratory Syndrome Coronavirus-2 and can be transmitted from person to person through infected air droplets that are projected during sneezing or coughing. The coronavirus disease has generally affected all sectors of the society, including the health sector and reproductive health in particular. Reproductive health contributes greatly to physical and psychosocial comfort and closeness between individuals. Adequate and balanced reproductive health can be impaired and deprived by diseases, abuse, exploitation, unwanted pregnancy, and death. This review paper looked into possible effects of COVID-19 pandemic on reproductive health. Human and nonhuman primate literatures were examined to extract empirical data detailing the impact of COVID-19 on reproductive health. Literatures were sourced from Ovid MEDLINE, SCOPUS, the Cochrane Library, Ovid EMBASE, CINAHL Plus, PROQUEST, PUBMED, and Web of Science. Experimental and clinical evidence were used to examine whether COVID-19 adversely impacted on the reproductive health of infected and non-infected population. The global outbreak of COVID-19 has led to measures driven by the pandemic, to prevent further spread and effectual treatment of those affected. This has literally caused decrease in sexual and reproductive health care services due to global lockdowns and closures of health sectors deemed to be non-essential in combating the disease.

ANTIMICROBIAL PROPERTIES OF FILTERING FIBROUS MATERIALS IMPREGNATED BY AMINOMETHANESULPHONIC ACIDS

Background. The spread of a new strain of SARS-CoV-2 and the pandemic that caused it has led to huge changes around the world. So, it reminded us again about the importance of developing measures for the prevention of infections that transmitted by air droplets.
 Aim: investigation of the antimicrobial activity of aminomethanesulfonic acid (AMSA) and its derivatives (N-(2-hydroxyethyl)-(HEAMSA), N-benzyl-(BnAMSA) and N-(tert-butyl)-(t-BuAMSA)) which impregnated on filtering fibrous material and can be used for the manufacture of anti-aerosol elements of individual respiratory protection against strains of Staphylococcus aureus with different level of antibiotics resistance.
 Materials and methods. The standard method of Kirby and Bauer disks is used for the investigation of the specific activity of antimicrobial drugs. The 24-hour cultures of microorganisms that contained (1.2+0.2)x109 CFU/ml were diluted according to the turbidity standard. The results were detected after 18-20 hours of incubation at 37°C. The 0.5 cm diameter filter fibrous discs contained the following compounds: AMSA, HEAMSA, BzAMSA, t-BuAMSA and streptocide (sulfanilamide) as a reference with active compound content (Q) at a final concentration of 0.047 and 0.236 mmol/g.
 Results. All test samples with aminomethanesulfonic acids at a final concentration of 0.236 mmol/g that were applied to the filter fibrous material had a higher level of inhibition of the growth of the microorganisms than the prototype using streptocide (sulfanilamide) e against the strains of Staphylococcus aureus 2781 and Staphylococcus aureus Kunda.
 Conclusions. Samples based on HEAMSA showed the greatest antimicrobial activity against the studied strains of Staphylococcus aureus from all research samples of filter fibrous material with YAMSA. They were characterized by the maximum hydrophilicity and the minimum value of the empirical pKa function lgPow. AMSA and HEAMSA were characterized by the smallest particle sizes on the surface of lavsan fiber according to electron microscopy analysis. This provides the largest boundary of contact between the phases of these biocides in the composition of the filtering fibrous material with bio aerosols during respiratory air purification.

Predicting Athlete Intentions for Using Sports Complexes in the Post-Pandemic Era.

In recent years, the concept of health has gradually fit into people's lives through the government's promotion. The indoor sports complex is becoming more and more popular, offering people the opportunity to engage in physical and recreational activities regardless of weather conditions. Psychological and social abundance is the key to improving happiness, and the most important thing is to treat and care for yourself. Many fitness venues have emerged to provide athletes with a wide range of choices. However, the advent of the COVID-19 pandemic, which is caused by a virus mainly transmitted through direct contact or air droplets, has had a severe impact on indoor gym users. Therefore, based on the Theory of Planned Behavior (TPB) and Health-Promoting Lifestyle (HPL), this research investigated athletes' behavioral intentions regarding sports halls and perceived risks as interfering variables. For data collection, we collected data samples from sports complexes athletes in Taiwan. A total of 263 responses were analyzed via SPSS 20.0 (IBM Corporation, New York, NY, USA) and AMOS 20.0 (IBM Corporation, New York, NY, USA) seis tests. The study's results indicate that health-promoting lifestyle cognition has a positive and significant effect on behavioral intention; athletes' attitudes, subjective norms, and perceived behavioral control significantly affects the behavioral intention of using the facilities in a sports complex. Athletes' risk perceptions have an interference effect between HPL, attitude, subjective norm, perceived behavioral control, and behavioral intentions of using the facilities in a sports complex. Sports venue managers can refer to the results of this project to develop marketing strategies and promoting.

Experimental and numerical studies on the spray cooling of deionized water in non-boiling regime

High-efficiency spray cooling technology has received increase of interest for high heatflux applications. Experimental and numerical investigations on spray heat transfer in single-phase deionized water are reported in this paper. The 3D numerical model is established based on Discrete Phase Model and Lagrange Wall Film model, comprehensively considering the exchange of mass, momentum and energy between the air (continuous phase) and water droplets (discrete phase), and the heat transfer in liquid film at the heated surface. PDA is adopted to measure Sauter Mean Diameter (SMD) of near-wall droplets. The influences of mass flow rates, nozzle diameters and spray heights on spray heat transfer characteristics are discussed. Results indicate that increasing mass flow rate can reduce SMD due to high We number and improve heat transfer coefficient. Liquid-film thickness is high at either low or high mass flow rate, but has minor influence on cooling performance. The optimal nozzle diameter is 0.6 mm rather than the smaller or higher diameter because the spray area is similar to the heated area. Similar reason is for the optimal spray height of 20 mm.

Temperature-Responsive, Femtosecond Laser-Ablated Ceramic Surfaces with Switchable Wettability for On-Demand Droplet Transfer.

Reversible wettability transition has drawn substantial interest because of its importance for widespread applications, but facile realization of such transition on ceramic surfaces, which is promising for achieving on-demand droplet manipulation under harsh conditions, remains rare. Herein, superhydrophobic zirconia ceramic surfaces that can reversibly and repeatedly transit between superhydrophobicity and superhydrophilicity after alternate heating treatments have been fabricated using a femtosecond laser. The underlying mechanisms of the complex wettability transitions on the laser-ablated zirconia surfaces are elucidated. Hydrophilic polished zirconia surfaces immediately become superhydrophilic after laser ablation, which is mainly attributed to the amplification effect of the laser-induced micro/nanostructures and has no obvious relationship with oxygen vacancies. The obtained superhydrophilic surfaces are transformed into superhydrophobic surfaces because of rapid adsorption of airborne organic compounds driven mainly by physical interaction under heating conditions. With the alternate removal and re-adsorption of organic compounds, reversible and repeatable wettability transition between superhydrophobicity and superhydrophilicity happens on the zirconia surfaces. The laser-induced micro/nanostructures also contribute to the wettability transitions. Furthermore, utilizing the superhydrophobic zirconia surfaces with switchable wettability, on-demand transfer of strong acid droplet in air and oil droplet under strong acid solution has been achieved. This work will inspire the environmentally friendly fabrication of switchable superhydrophobic ceramic surfaces and their multifunctional applications under harsh conditions.

Qualitative and quantitative studies on two commercial specifications of Polygonatum odoratum.

The rhizoma of Polygonatum odoratum (PO) is used to treat yin injuries of the lung and stomach in traditional Chinese medicine. The chemical constituents of this herb are steroidal saponins, homoisoflavanones, and alkaloids. Xiangyuzhu (XPO) and Guanyuzhu (GPO) are available in the market as two specifications of the commodity. Nonetheless, systematic research on the identification and comparison of chemical constituents of these two commercial specifications is yet lacking. Herein, an integrated method combing ultra-high-performance liquid chromatography-quadruple time-of-flight mass spectrometry (UHPLC-Q-TOF/MS) with ultra-high-performance liquid chromatography-charged aerosol detection (UHPLC-CAD) was employed for the comprehensively qualitative and quantitative analyses of PO. A total of 62 compounds were identified by UHPLC-Q-TOF/MS, among which 13 potential chemical markers were screened out to distinguish two commercial specifications. Subsequently, the absolute determination method for polygodoraside G, polygonatumoside F, and timosaponin H1 was established and validated by UHPLC-CAD. The contents of the three compounds were 13.33-236.24μg/g, 50.55-545.04μg/g, and 13.34-407.83μg/g, respectively. Furthermore, the ratio of timosaponin H1/polygodoraside G could be applied to differentiate the two specifications. Samples with a ratio <2 are considered XPO and >5 are considered GPO. Therefore, the above results provide a valuable means for the quality control of PO.

Dependence of polyethylene combustion dynamics in a 1 m&lt;sup&gt;3&lt;/sup&gt; chamber on particle size

Introduction. The results of a standard study on the explosion hazard of polyethylene air suspensions (PES) can contribute to the theory of turbulent combustion. For example, analysis of polydispersity data and values of the PES lean combustion limit in a 1 m3 chamber helped to identify the maximum size of explosive particles d*m,t ≈ 100 µm (Poletaev, 2014). In this work, a relationship was obtained between the dynamics of PES combustion in a 1 m3 chamber and the average particle size of the suspension, which is understood as the average particle size of its explosive fraction d*50.Initial data. Well-known findings of a study on the explosion of 28 polyethylene specimens in a 1 m3 chamber were used. Continuous functions of specimen particles distribution by size, necessary for calculating d*50, were represented using the Rosin-Rammler distribution.Combustion dynamics. The dynamics of PES turbulent combustion in a 1 m3 chamber is described by the maximum rate of air suspension burnout Ub. Ub was calculated according to the formula (Kumar, 1992) intended for gas-air mixtures by substituting PES explosion parameters into this formula.Results and its discussion. The graph, describing the dependence of the complex d*50Ub on d*50, is provided. The averaged value of the complex (≈ 45 µm · (m/s)) is constant in the range 40 µm &lt; d*50 &lt; 90 µm. The latter is typical for the product of the particle size and the normal velocity of laminar flame in liquid aerosols (Myers, 1986), which indicates similarity between the effect of particle dispersion and dynamics of turbulent and laminar combustion of the aforementioned heterogeneous mixtures.Conclusions. The dispersive capacity of an explosive polydisperse polyethylene specimen is determined by the average particle size of the explosive fraction of the specimen d*50. The similarity of combustion patterns indicates the proximity of propagation mechanisms typical for turbulent flame, typical for PES, and laminar flame, typical for liquid aerosols.

Explosive properties of selected aerosols determined in a spherical 5-L test chamber

Combustible liquids in the form of aerosols are important for many industrial processes. Therefore the problem of explosion hazards posed by the aerosols becomes increasingly more prominent. To correctly assess the explosion risk and fulfil the requirements of the ATEX directive, it is necessary to obtain information regarding the flammable and explosive properties of the aerosols. Unlike in the case of gases and dusts, no standard procedures aimed at obtaining quantitative information of this type exist. Factors that influence the explosion dynamics of aerosols include: concentration, droplet size, temperature etc. Some of these factors are strongly dependent on the aerosol generation methods. A prototype apparatus was designed and constructed to address that dependence. The apparatus was used in an attempt to determine the basic explosion parameters of liquid flammable aerosols. The device consisted of a 5-L spherical vessel equipped with a pump-injection system that generated aerosols as well as a spark ignition source. A wide variety of injection settings were tested to select the most suitable conditions over a broad range of concentrations and fluid properties. A measurement procedure was developed for operating the device. Prototype tests were carried out with fluids commonly used in industry: isopropanol and kerosene. The tests demonstrated the significant influence of the vessel wall temperature on the result accuracy. Correct temperature control made it possible to obtain relationships between the aerosol concentration and the following explosion parameters: maximum explosion pressure and maximum rate of pressure rise.

Knowledge, Risk Perceptions and Preventive Behaviors Regarding to COVID-19 Pandemic in General Population of Sindh, Pakistan

Aim: The purpose of this research was to evaluate how Pakistanis feel about and understand COVID-19 Methods: To conduct the cross-sectional survey, we used Google forms to digitize a questionnaire with 17 items, which we then sent to a sample of the general population. Results: There was a total of 615 questionnaires collected from residents of Sindh Province. Most people 75.1% believe that the disease is spread through direct contact with an infected person or through inhaling air droplets expelled by a sick person while they sneeze or cough. When asked how they had avoided contracting COVID-19 over the preceding 14 days, the vast majority, 39.4%, reported consistently washing and sanitizing their hands. Other steps include not shaking hands with people 33.0% and staying at least one meter away from them (24.9%), not letting people share utensils at meals 38.1%, and masking their faces even when they don't feel sick 28.8%. Additionally, 56.1% of the respondents admitted that they had not taken any special precautions to protect themselves. It is duty of every citizen to obey the government’s steps to avoid from COVID-19. Conclusion: In general, the people who took part knew a lot about the disease and felt good about taking precautions. The government and the public are taking effective steps to stop the spread of disease, but there is still a need for more awareness campaigns and knowledge of safe ways to stop the spread of disease. Keywords: SARS-Cov-2, COVID-19, Sindh, pandemic, epidemic

Three-dimensional modeling of Venus photochemistry and clouds

We present here three-dimensional simulations of the Venus photochemistry and clouds from the ground to the bottom of the thermosphere. For that purpose, we have implemented a state-of-the-art photochemical and equilibrium cloud model in the Venus Planetary Climate Model (Venus PCM). The interactive coupling between dynamics, radiation, chemistry and clouds allows a comprehensive description of the CO2, CO, sulfur, chlorine, oxygen, and hydrogen species, with tracking of the condensed phase. Regarding the clouds, the Venus PCM calculates the composition, number density, and sedimentation rates of the binary H2SO4-H2O liquid aerosols, based on observed altitude-dependent size distributions. The article describes in detail the new components implemented in the Venus PCM. It then presents an overview of the results concerning clouds and atmospheric chemistry, which are compared with a wide range of observations. The modeled cloud characteristics and vertical profiles of minor species are found to be in broad agreement with most of the measurements available between 30 and 100 km. In particular, the Venus PCM reproduces the steep decrease of H2O and SO2 mixing ratio inside the cloud layer, as well as the observed vertical distribution of species well identified above the clouds, such as CO and O3. The model also agrees with the ground-based measurements of HCl, but not with the conflicting HCl vertical profiles derived from Venus Express. On the quasi-horizontal plane, latitudinal contrasts in the modeled trace species mostly result from the Hadley-type mean meridional circulation. Large-scale longitudinal variations are essentially created by the diurnal thermal tide above the clouds, and by photolysis above 80 km.