This book contains twenty-one original papers and one review paper published by internationally recognized experts in the Atmosphere Special Issue "Recent Advances in Urban Ventilation Assessment and ...Flow Modelling", years 2017–2019. The Special Issue includes contributions on recent experimental and modelling works, techniques, and developments mainly tailored to the assessment of urban ventilation on flow and pollutant dispersion in cities. The study of ventilation is of critical importance, as it addresses the capacity with which a built urban structure is capable of replacing the polluted air with ambient fresh air. Here, ventilation is recognized as a transport process that improves local microclimate and air quality and closely relates to the term “breathability”. The efficiency with which street canyon ventilation occurs depends on the complex interaction between the atmospheric boundary layer flow and the local urban morphology.The individual contributions to this Issue are summarized and categorized into four broad topics: (1) outdoor ventilation efficiency and application/development of ventilation indices, (2) relationship between indoor and outdoor ventilation, (3) effects of urban morphology and obstacles to ventilation, and (4) ventilation modelling in realistic urban districts. The results and approaches presented and proposed will be of great interest to experimentalists and modelers, and may constitute a starting point for the improvement of numerical simulations of flow and pollutant dispersion in the urban environment, for the development of simulation tools, and for the implementation of mitigation strategies.
Organic peroxides (OPs) are an important component of dissolved organic matter (DOM), detected in various aquatic media. Despite their unique functions as redox agents in water ecosystems, the ...complete mechanisms and factors controlling their transformation are not explicitly established. Here, we evaluate the pH effect on the aqueous-phase reaction of three selected OPs (methyl hydroperoxide (MHP), peracetic acid (PAA), and benzoyl peroxide (BZP)) with dissolved SO.sub.2 . Results show that due to the presence of the hydroperoxyl group in their structures, MHP and PAA are susceptible to forming inorganic sulfate and organosulfate (methyl sulfate for MHP and acetyl sulfate for PAA) depending on the pH, while BZP exclusively forms organosulfate (benzoyl sulfate) in the pH range investigated. Moreover, it is seen that the ability of PAA to form inorganic sulfate relative to organosulfate is more pronounced, which is supported by a previous experimental observation. The effective rate constants of the transformation of these peroxides within the pH 1-10 and 240-340 K ranges exhibit positive pH and temperature dependencies, and BZP is seen to degrade more effectively than MHP and PAA. In addition to the pH impact, it is highlighted that the formation of organic and/or inorganic sulfate strongly depends on the nature of the substituents on the peroxy function. Namely, PAA and BZP are more reactive than MHP, which may be attributed to the electron-withdrawing effects of -C(O)R (R = -CH.sub.3 and -C.sub.6 H.sub.5 for PAA and BZP, respectively) substituents that activate the peroxy function. The results further indicate that the aqueous-phase degradation of OPs can adequately drive the change in the chemical composition of DOM, both in terms of organic and inorganic sulfate mass fractions.
In order to cope with heavy haze pollution in China, the Air Pollution Prevention and Control Action Plan including phased goals of the fine particulate matter (PM2.5) was issued in 2013. In this ...study, China's emission inventories in the baseline 2012 and the future scenarios of 2017 and 2020 have been developed based on this Action Plan. Beijing-Tianjin-Hebei (Jing-Jin-Ji) region, one of the most polluted regions in China, was taken as a case to assess the impact of phased emission control measures on PM2.5 concentration reduction using WRF-CMAQ model system. With the implementation of the Action Plan, the emissions of sulfur dioxide (SO2), nitrogen oxides (NOX), PM2.5, non-methane volatile organic compound (NMVOC), and ammonia (NH3) in 2017 will decrease by36%, 31%, 30%,12%, and −10% from the 2012 levels in Jing-Jin-Ji, respectively. In 2020, the emissions of SO2, NOX, PM2.5, NMVOC, and NH3 will decrease by 40%, 44%, 40%, 22%, and −3% from the 2012 levels in Jing-Jin-Ji, respectively. Consequently, the ambient annual PM2.5 concentration under the scenarios of 2017 and 2020 will be 28.3% and 37.8% lower than those in 2012, respectively. The Action Plan provided an effective approach to alleviate PM2.5 pollution level in Jing-Jin-Ji region. However, emission control of NMVOC and NH3 should be paid more attention and be strengthened in future. Meanwhile, emission control of NOx, SO2, NH3 and NMVOC synergistically are highly needed in the future because multiple pollutants impact on PM2.5 and O3 concentrations nonlinearly.
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•Multiple-pollutants emission inventory for 2012 and two scenarios for 2017 and 2020 are developed based on the Action Plan.•WRF-CMAQ model system is used to simulate PM2.5 concentrations in Jing-Jin-Ji region during 2012-2020.•PM2.5 concentrations under the scenarios of 2017 and 2020 will be 28.3% and 37.8% lower than those in 2012, respectively.•NMVOC and NH3 should be strictly controlled in the future.
We apply laser light to induce the asymmetric heating of Janus colloids adsorbed at water-oil interfaces and realize active micrometric "Marangoni surfers." The coupling of temperature and surfactant ...concentration gradients generates Marangoni stresses leading to self-propulsion. Particle velocities span 4 orders of magnitude, from microns/s to cm/s, depending on laser power and surfactant concentration. Experiments are rationalized by finite elements simulations, defining different propulsion regimes relative to the magnitude of the thermal and solutal Marangoni stress components.
The widespread use of antibiotics has led to their ubiquitous presence in water and wastewater and raised concerns about antimicrobial resistance. Clinical antibiotic susceptibility assays have been ...repurposed to measure removal of antimicrobial activity during water and wastewater treatment processes. The corresponding protocols have mainly employed growth inhibition of Escherichia coli. The present work focused on optimizing bacteria selection to improve the sensitivity of residual antimicrobial activity measurements by broth microdilution assays. Thirteen antibiotics from four classes (i.e., fluoroquinolones, macrolides, sulfonamides, tetracyclines) were investigated against three gram-negative organisms, namely E. coli, Mycoplasma microti, and Pseudomonas fluorescens. The minimum inhibitory concentration (MIC) and half-maximal inhibitory concentration (IC50) were calculated for each antibiotic-bacteria pair. P. fluorescens produces a fluorescent siderophore, pyoverdine, that was used to assess sublethal effects and further enhance the sensitivity of antimicrobial activity measurements. The optimal antibiotic-bacteria pairs were as follows: fluoroquinolone-E. coli (growth inhibition); macrolide- and sulfonamide-M. microti (growth inhibition); and, tetracycline-P. fluorescens (pyoverdine inhibition). Compared to E. coli growth inhibition, the sensitivity of antimicrobial activity analysis was improved by up to 728, 19, and 2.7 times for macrolides (tylosin), sulfonamides (sulfamethoxazole), and tetracyclines (chlortetracycline), facilitating application of these bioassays at environmentally-relevant conditions.
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•IC50 was a more accurate and precise measurement of antimicrobial activity than MIC•Fluoroquinolones were most potent against E. coli growth inhibition•M. microti improved the sensitivity of analysis for macrolides and sulfonamides•Pyoverdine inhibition in P. fluorescens was the optimal endpoint for tetracyclines•Sensitivity of antimicrobial activity analysis was improved by bacteria selection
With the increasingly widespread use of titanium dioxide nanoparticles (TiO2 NPs), the particles' environmental impacts have attracted concern, making it necessary to understand the fate and ...transport of TiO2 NPs in aqueous media. In this study, we investigated TiO2 NP aggregation caused by the effects of humic acid (HA), ionic strength (IS) and different pH using dynamic light scattering (DLS) to monitor the size distribution of the TiO2 NPs continuously. It was determined that HA can influence the stability of TiO2 NPs through charge neutralization, steric hindrance and bridging effects. In the absence of IS, aggregation was promoted by adding HA only when the pH (pH=4) is less than the point of zero charge for the TiO2 NPs (pHPZC≈6) because HA reduces the zeta potential of the TiO2 NPs via charge neutralization. At pH=4 and when the concentration of HA is 94.5μg/L, the zeta potential of TiO2 NPs is close to zero, and they reach an aggregation maximum. A higher concentration of HA results in more negatively charged TiO2 NP surfaces, which hinder their aggregation. When the pH is 5.8, HA enhances the negative zeta potential of the TiO2 NPs and increases their stability via electrostatic repulsion and steric hindrance. When the pH (pH=8) is greater than pHpzc, the zeta potential of the TiO2 NPs is high (~40mV), and it barely changes with increasing HA concentration. Thus, the TiO2 NPs are notably stable, and their size does not grow at pH8. The increase in the critical coagulation concentration (CCC) of TiO2 NPs indicated that there is steric hindrance after the addition of HA. HA can enhance the coagulation of TiO2 NPs, primarily due to bridging effect. These findings are useful in understanding the size change of TiO2 NPs, as well as the removal of TiO2 NPs and HA from aqueous media.
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•Charge neutralization was observed when pH=4 and ionic strength is very low.•Steric hindrance only occurs when ionic strength is lower than CCC.•Humic acid plays a bridging effect when ionic strength is higher than CCC.
This paper is devoted to an investigation of blow-up phenomena occurring in high-contrast fiber-reinforced composites. When the distance between perfect conductors or between the conductors and the ...matrix boundary tends to zero, the electric field may appear blow-up. The major objective of this paper is to give a precise description for the singular behavior of such a high concentration in the presence of C1,α-inclusions with extreme conductivities. Our results contain the boundary and interior asymptotics of the concentrated field in all dimensions. In particular, the blow-up factor for each dimension is accurately captured.
•An exploratory randomized, controlled trial of baloxavir marboxil and favipiravir in COVID-19 patients were conducted.•The free drug concentrations of baloxavir acid and favipiravir are generally ...lower than their respective EC50 values.•Add-on either baloxavir or favipiravir to the current standard treatment resulted in no additional antiviral benefit.
Background: Effective antiviral drugs for COVID-19 are still lacking. This study aims to evaluate the clinical outcomes and plasma concentrations of baloxavir acid and favipiravir in COVID-19 patients.
Methods: Favipiravir and baloxavir acid were evaluated for their antiviral activity against SARS-CoV-2 in vitro before the trial initiation. We conducted an exploratory trial with 3 arms involving hospitalized adult patients with COVID-19. Patients were randomized assigned in a 1:1:1 ratio into baloxavir marboxil group, favipiravir group, and control group. The primary outcome was the percentage of subjects with viral negative by Day 14 and the time from randomization to clinical improvement. Virus load reduction, blood drug concentration and clinical presentation were also observed. The trial was registered with Chinese Clinical Trial Registry (ChiCTR 2000029544).
Results: Baloxavir acid showed antiviral activity in vitro with the half-maximal effective concentration (EC50) of 5.48 μM comparable to arbidol and lopinavir, but favipiravir didn't demonstrate significant antiviral activity up to 100 μM. Thirty patients were enrolled. The percentage of patients who turned viral negative after 14-day treatment was 70%, 77%, and 100% in the baloxavir marboxil, favipiravir, and control group respectively, with the medians of time from randomization to clinical improvement was 14, 14 and 15 days, respectively. One reason for the lack of virological effect and clinical benefits may be due to insufficient concentrations of these drugs relative to their antiviral activities. One of the limitations of this study is the time from symptom onset to randomization, especially in the baloxavir marboxil and control groups, which is higher than the favipiravir group.
Conclusions: Our findings could not prove a benefit of addition of either baloxavir marboxil or favipiravir under the trial dosages to the existing standard treatment.
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The aim of this study was to explore the utility of target‐concentration controlled infusion (TCI) as a prophylactic antibiotic administration method based on the results of a population ...pharmacokinetic model of cefazolin. In patients undergoing elective gastric surgery, 2 g of cefazolin was dissolved in 50 mL of saline and administered for 10 min prior to skin incision. Arterial blood samples were obtained at preset intervals to measure the total and free plasma concentrations of cefazolin. Population pharmacokinetic analysis was performed using non‐linear mixed‐effects modelling. To evaluate the effectiveness of the TCI method, stochastic simulation was performed based on the model construction results. In total, 360 total and 360 free plasma concentration measurements from 40 patients were used to characterise the pharmacokinetics of cefazolin. The changes in the total concentration of cefazolin over time were well‐explained by the three‐compartment mammillary model. Fat‐free mass and estimated glomerular filtration rate were significant covariates. The probability of target attainment (PTA) to reach the target 100% fraction of time that the free plasma concentration of cefazolin was maintained above its minimal inhibitory concentration (fT > MIC) at MIC of 4 mg/L was also notably higher in the TCI method (90.7%) than in the standard method (17.0%). When cefazolin is administered by the TCI method, patient‐tailored antibiotic dosing may be possible. The potential benefits of administering prophylactic antibiotics by the TCI method were observed. Further research is warranted to confirm the effectiveness of the TCI method.
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