In Situ Electrochemistry of Formate on Cu Thin Films Using ATR-FTIR Spectroscopy and X-ray Photoelectron Spectroscopy.

Formate (HCOO-) is the most dominant intermediate identified during carbon dioxide electrochemical reduction (CO2ER). While previous studies showed that copper (Cu)-based materials that include Cu(0), Cu2O, and CuO are ideal catalysts for CO2ER, challenges to scalability stem from low selectivity and undesirable products in the -1.0-1.0 V range. There are few studies on the binding mechanism of intermediates and products for these systems as well as on changes to surface sites upon applying potential. Here, we use an in situ approach to study the redox surface chemistry of formate on Cu thin films deposited on Si wafers using a VeeMAX III spectroelectrochemical (SEC) cell compatible with attenuated total reflectance Fourier transform infrared spectroscopy (ATR-FTIR). Spectra for surface species were collected in real time as a function of applied potential during cyclic voltammetry (CV) experiments. Results showed the reproducibility of CV curves on freshly prepared Cu/Si wafers with relatively high signal-to-noise ATR-FTIR absorbance features of surface species during these electrochemical experiments. The oxidation reaction of HCOO- to bicarbonate (HCO3-) was observed using ATR-FTIR at a voltage of 0.27 V. Samples were then subjected to reduction in the CV, and the aqueous phase products below the detection limit of the SEC-ATR-FTIR were identified using ion chromatography (IC). We report the formation of glycolate (H3C2O3-) and glyoxylate (HC2O3-) with trace amounts of oxalate (C2O42-), indicating that C-C coupling reactions proceed in these systems. Changes to the oxidation state of surface Cu were measured using X-ray photoelectron spectroscopy, which showed a reduction in Cu(0) and an increase in Cu(OH)2, indicating surface oxidation.

Model-free characterization of topological edge and corner states in mechanical networks.

Topological materials can host edge and corner states that are protected from disorder and material imperfections. In particular, the topological edge states of mechanical structures present unmatched opportunities for achieving robust responses in wave guiding, sensing, computation, and filtering. However, determining whether a mechanical structure is topologically nontrivial and features topologically protected modes has hitherto relied on theoretical models. This strong requirement has limited the experimental and practical significance of topological mechanics to laboratory demonstrations. Here, we introduce and validate an experimental method to detect the topologically protected zero modes of mechanical structures without resorting to any modeling step. Our practical method is based on a simple electrostatic analogy: Topological zero modes are akin to electric charges. To detect them, we identify elementary mechanical molecules and measure their chiral polarization, a recently introduced marker of topology in chiral phases. Topological zero modes are then identified as singularities of the polarization field. Our method readily applies to any mechanical structure and effectively detects the edge and corner states of regular and higher-order topological insulators. Our findings extend the reach of chiral topological phases beyond designer materials and allow their direct experimental investigation.

Non-orientable order and non-commutative response in frustrated metamaterials.

From atomic crystals to animal flocks, the emergence of order in nature is captured by the concept of spontaneous symmetry breaking1-4. However, this cornerstone of physics is challenged when broken symmetry phases are frustrated by geometrical constraints. Such frustration dictates the behaviour of systems as diverse as spin ices5-8, confined colloidal suspensions9 and crumpled paper sheets10. These systems typically exhibit strongly degenerated and heterogeneous ground states and hence escape the Ginzburg-Landau paradigm of phase ordering. Here, combining experiments, simulations and theory we uncover an unanticipated form of topological order in globally frustrated matter: non-orientable order. We demonstrate this concept by designing globally frustrated metamaterials that spontaneously break a discrete [Formula: see text] symmetry. We observe that their equilibria are necessarily heteregeneous and extensively degenerated. We explain our observations by generalizing the theory of elasticity to non-orientable order-parameter bundles. We show that non-orientable equilibria are extensively degenerated due to the arbitrary location of topologically protected nodes and lines where the order parameter must vanish. We further show that non-orientable order applies more broadly to objects that are non-orientable themselves, such as buckled Möbius strips and Klein bottles. Finally, by applying time-dependent local perturbations to metamaterials with non-orientable order, we engineer topologically protected mechanical memories11-19, achieve non-commutative responses and show that they carry an imprint of the braiding of the loads' trajectories. Beyond mechanics, we envision non-orientability as a robust design principle for metamaterials that can effectively store information across scales, in fields as diverse as colloidal science8, photonics20, magnetism7 and atomic physics21.

Uma análise documental do atendimento psicológico das vítimas de violência sexual infantil no pronto socorro / A documental analysis of the psychological care for victims of child sexual abuse in the emergency room / Un análisis documental de la atención psicológica a víctimas de violencia sexual en urgencias

INTRODUÇÃO: O Hospital Odilon Behrens é um dos hospitais de referência que atende Vítimas de Violência Sexual (VVS) em Belo Horizonte nas primeiras 72 horas após a ocorrência da violência. OBJETIVO: Identificar os sinais e sintomas desenvolvidos após a violência sexual assim como os diversos fatores contextuais que devem ser considerados para compreender o impacto da violência sofrida no sujeito no atendimento no pronto socorro de um hospital de referência. MÉTODOS: Foi realizada uma análise de dados qualitativos coletados a partir de 187 relatórios realizados de todos os pacientes que foram atendidos pela equipe de psicologia no Pronto Socorro e que foram consequentemente encaminhados ao Conselho Tutelar, considerando os pacientes de sexo masculino e feminino com idade inferior a 18 anos que foram atendidos no período de janeiro a dezembro do ano 2021. RESULTADOS: 79,8% dos casos eram do sexo feminino, 38,4% entre os 6 a 12 anos, o tipo de revelação sexual mais incidente foi a detecção acidental, os sinais de violência sexual mais frequentes foram os sinais físicos seguido de sinais emocionais. DISCUSSÃO: Foi percebido que a incidência de violência sexual é subnotificada e que há um grande desconhecimento do fluxo de atendimento dos diversos dispositivos da rede. CONCLUSÃO: Não foi possível um único quadro psicopatológico ou sintomatologia característica para todos os casos de violência sexual, sublinhando a relevância da análise da subjetividade do sujeito e dos fatores contextuais no atendimento à vítima de violência sexual.

INTRODUCTION: Hospital Odilon Behrens is one of the reference hospitals that assist Victims of Sexual Abuse in Belo Horizonte in the first 72 hours after the occurrence of the abuse. OBJECTIVE: To identify the signs and symptoms developed after sexual violence as well as the various contextual factors that must be considered to understand the impact of the violence suffered on the subject when treated in the emergency room of a reference hospital. METHODOLOGY: An analysis of qualitative data collected from 187 reports made of all patients who were assisted by the psychology team at the Emergency Room and who were consequently referred to the Tutelary Council, considering male and female patients under the age of 18 years old who were assisted from January to December of 2021 was carried out. RESULTS: 79.8% of the cases were female, 38.4% were between 6 and 12 years old, the most common type of sexual disclosure was accidental detection, and the most common signs of sexual abuse were physical signs followed by emotional signs. DISCUSSION: It was noticed that the incidence of sexual abuse is underreported and that there is a great lack of knowledge about the service flow of the various devices in the network. CONCLUSION: It was not possible to find a single psychopathological profile or characteristic symptomatology for all cases of sexual abuse, underlining the relevance of analyzing the subject's subjectivity and contextual factors in caring for victims of sexual abuse.

INTRODUCCIÓN: El Hospital Odilon Behrens es uno de los hospitales de referencia que asiste a Víctimas de Violencia Sexual en Belo Horizonte en las primeras 72 horas después de la ocurrencia de la violencia. OBJETIVO: Identificar los signos y síntomas desarrollados después de la violencia sexual, así como los diversos factores contextuales que deben ser considerados para comprender el impacto de la violencia sufrida en el sujeto cuando es atendido en la sala de emergencia de un hospital de referencia. MÉTODO: Se realizó un análisis de los datos cualitativos recolectados de 187 informes realizados de todos los pacientes que fueron consultados por el equipo de psicología en el Servicio de Urgencias y que fueron derivados al Consejo Tutelar, considerando pacientes a los hombres y mujeres menores de 18 años, quienes fueron consultados de enero a diciembre de 2021. RESULTADOS: El 79,8% de los casos fueron mujeres, el 38,4% entre 6 y 12 años, el tipo de revelación sexual más frecuente fue la detección accidental, las señales de violencia sexual fueron las físicas seguidas de las emocionales. DISCUSIÓN: Se notó que la incidencia de violencia sexual es sub-reportada y que existe un gran desconocimiento sobre el flujo de servicio de los diversos dispositivos en la red. CONCLUSIÓN: No fue posible encontrar un cuadro psicopatológico único o sintomatología característica para todos los casos de violencia sexual, lo que subraya la relevancia de analizar la subjetividad del sujeto y los factores contextuales en el cuidado de las víctimas de violencia sexual.

Oxidation of Phenolic Aldehydes by Ozone and Hydroxyl Radicals at the Air-Solid Interface.

Biomass burning emissions contain abundant phenolic aldehydes (e.g., syringaldehyde, vanillin, and 4-hydroxybenaldehyde) that are oxidized during atmospheric transport, altering the physicochemical properties of particulates. Herein, the oxidative processing of thin films made of syringaldehyde, vanillin, and 4-hydroxybenaldehyde is studied at the air-solid interface under a variable O3(g) molar ratio (410 ppbv-800 ppmv) and relative humidity (0-90%). Experiments monitored the absorption changes of C=C, C=O, and -COOH vibration changes during the oxidation of thin films by transmission Fourier transform infrared spectroscopy (FTIR). Selected spectroscopic features of aromatic ring cleavage by O3(g) revealed the production of carboxylic acids. Instead, monitoring O-H stretching provided a comparison of a hydroxylation channel from in situ produced hydroxyl radical. The overall oxidation reactivity trend syringaldehyde > vanillin > 4-hydroxybenzladehyde can be explained based on the additional electron density from methoxide substituents to the ring. The reactive uptake coefficient of O3(g) increases for higher relative humidity, e.g., for syringaldehyde by 18 and 215 times at 74% and 90% relative humidity (RH), respectively, as compared to dry conditions. A Langmuir-Hinshelwood mechanism fits well the kinetics of oxidation under a variable O3(g) molar ratio at 74% RH, providing useful information that should be included in atmospheric chemistry models.

Oxidation of Catechols at the Air-Water Interface by Nitrate Radicals.

Abundant substituted catechols are emitted to, and created in, the atmosphere during wildfires and anthropogenic combustion and agro-industrial processes. While ozone (O3) and hydroxyl radicals (HO•) efficiently react in a 1 µs contact time with catechols at the air-water interface, the nighttime reactivity dominated by nitrate radicals (NO3) remains unexplored. Herein, online electrospray ionization mass spectrometry (OESI-MS) is used to explore the reaction of NO3(g) with a series of representative catechols (catechol, pyrogallol, 3-methylcatechol, 4-methylcatechol, and 3-methoxycatechol) on the surface of aqueous microdroplets. The work detects the ultrafast generation of nitrocatechol (aromatic) compounds, which are major constituents of atmospheric brown carbon. Two mechanisms are proposed to produce nitrocatechols, one (equivalent to H atom abstraction) following fast electron transfer from the catechols (QH2) to NO3, forming NO3- and QH2•+ that quickly deprotonates into a semiquinone radical (QH•). The second mechanism proceeds via cyclohexadienyl radical intermediates from NO3 attack to the ring. Experiments in the pH range from 4 to 8 showed that the production of nitrocatechols was favored under the most acidic conditions. Mechanistically, the results explain the interfacial production of chromophoric nitrocatechols that modify the absorption properties of tropospheric particles, making them more susceptible to photooxidation, and alter the Earth's radiative forcing.

Interfacial Oxidative Oligomerization of Catechol.

The heterogeneous reaction between thin films of catechol exposed to O3(g) creates hydroxyl radicals (HO•) in situ, which in turn generate semiquinone radical intermediates in the path to form heavier polyhydroxylated biphenyl, terphenyl, and triphenylene products. Herein, the alteration of catechol aromatic surfaces and their chemical composition are studied during the heterogeneous oxidation of catechol films by O3(g) molar ratios ≥ 230 ppbv at variable relative humidity levels (0% ≤ RH ≤ 90%). Fourier transform infrared micro-spectroscopy, atomic force microscopy, electrospray ionization mass spectrometry, and reverse-phase liquid chromatography with UV-visible and mass spectrometry detection provide new physical insights into understanding the surface reaction. A Langmuir-Hinshelwood mechanism is accounted to report reaction rates, half-lives, and reactive uptake coefficients for the system under variable relative humidity levels. The reactions reported explain how the oligomerization of polyphenols proceeds at interfaces to contribute to the formation of brown organic carbon in atmospheric aerosols.

Chemical State of Potassium on the Surface of Iron Oxides: Effects of Potassium Precursor Concentration and Calcination Temperature.

Potassium is used extensively as a promoter with iron catalysts in Fisher-Tropsch synthesis, water-gas shift reactions, steam reforming, and alcohol synthesis. In this paper, the identification of potassium chemical states on the surface of iron catalysts is studied to improve our understanding of the catalytic system. Herein, potassium-doped iron oxide (α-Fe2O3) nanomaterials are synthesized under variable calcination temperatures (400-800 °C) using an incipient wetness impregnation method. The synthesis also varies the content of potassium nitrate deposited on superfine iron oxide with a diameter of 3 nm (Nanocat®) to reach atomic ratios of 100 Fe:x K (x = 0-5). The structure, composition, and properties of the synthesized materials are investigated by X-ray diffraction, differential scanning calorimetry, thermogravimetric analysis, Fourier-transform infrared, Raman spectroscopy, inductively coupled plasma-atomic emission spectroscopy, and X-ray photoelectron spectroscopy, as well as transmission electron microscopy, with energy-dispersive X-ray spectroscopy and selected area electron diffraction. The hematite phase of iron oxide retains its structure up to 700 °C without forming any new mixed phase. For compositions as high as 100 Fe:5 K, potassium nitrate remains stable up to 400 °C, but at 500 °C, it starts to decompose into nitrites and, at only 800 °C, it completely decomposes to potassium oxide (K2O) and a mixed phase, K2Fe22O34. The doping of potassium nitrate on the surface of α-Fe2O3 provides a new material with potential applications in Fisher-Tropsch catalysis, photocatalysis, and photoelectrochemical processes.

Surface Oxidation of Phenolic Aldehydes: Fragmentation, Functionalization, and Coupling Reactions.

Substantial amounts of phenolic aldehydes, represented by the structures of syringaldehyde, vanillin, and 4-hydroxybenzaldehyde, are emitted to the atmosphere during biomass burning. The oxidative transformation of phenolic aldehydes during atmospheric transport has the potential to modify the physicochemical properties of particulates, which play a vital role in Earth's climate and human health. Herein, thin solid films made of syringaldehyde, vanillin, and 4-hydroxybenzaldehyde are oxidized in contact with O3(g) under a relative humidity of 74% representative of average global conditions. New physical insights into the surface reactions are achieved by analyzing isopropanol-extracted films before and during oxidation by multiple techniques. Changes in electronic transitions at 220, 310, and 350-400 nm registered by UV-vis spectroscopy show that the oxidized films have enhanced mass absorption coefficients at λ > 300 nm. Electrospray ionization (ESI) mass spectrometry (MS) and ion chromatography with conductivity and MS detection of extracted oxidized films confirm aromatic ring cleavage of syringaldehyde and vanillin by O3(g) with the production of carboxylic acids. Carboxylic acids were observed as anions ([M - H]-) at m/z 45 (formic acid), 73 (glyoxylic acid), 75 (glycolic acid), 89 (oxalic acid), 115 (maleic acid), 117 (mesoxalic acid), 119 (tartronic acid), and 129 (maleic acid monomethyl ester), while other polyfunctional products were registered by ultrahigh-pressure liquid chromatography with UV-vis and MS detection. In situ production of hydroxyl radicals is confirmed by demethoxylation products and ipso attack at the C1 ring position holding the -C(H)═O group. The order of reactivity increased with the number of methoxy substituents that donate electron density to the aromatic ring. Combined oxidation mechanisms for the three compounds are proposed based on all of the experimental observations and explain the contribution of aged biomass burning material to secondary organic aerosol formation.

Characteristics and health effects of particulate matter emitted from a waste sorting plant.

Solid waste components can be recycled in waste paper and cardboard sorting plants (WPCSP) through a multistep process. This work collected 15 samples every six days from each of the 9 points selected to study the processes taking place in a WPCSP (135 particulate matter samples total). Examining the concentration and size fraction of particulate matter (i.e., PM1, PM2.5 and PM10) in WPCSP is an essential issue to notify policy makers about the health impacts on exposed workers. The major activities for increasing of the concentration of PM in various processing units in the WPCSP, especially in hand-picking routes I and II were related to manual dismantling, mechanical grinding, mechanical agitation, and separation and movement of waste. The results of this work showed that a negative correlation between temperature and particulate matter size followed the order PM10 > PM2.5 > PM1. Exposure to PM2.5 and PM10 in the WPCSP lead to possible risk (HI = 5.561 and LTCRs = 3.41 × 10-6 to 9.43 × 10-5 for PM2.5 and HI = 7.454 for PM10). The exposure duration and the previous concentrations had the most effect on the ILCRs and HQs for PM2.5 and PM10 in all sampling sites. Hence, because WPCSP are infected indoor environments (I/O ratio > 1), the use of control methods such as isolation of units, misting systems, blower systems equipped with bag houses, protective equipment, a mechanical ventilation system, and additional natural ventilation can reduce the amount of suspended PM, enhance worker safety, and increase the recycling rate.

Characteristics and assessing biological risks of airborne bacteria in waste sorting plant.

Examining the concentration and types of airborne bacteria in waste paper and cardboard sorting plants (WPCSP) is an urgent matter to inform policy makers about the health impacts on exposed workers. Herein, we collected 20 samples at 9 points of a WPCSP every 6 winter days, and found that the most abundant airborne bacteria were positively and negatively correlated to relative humidity and temperature, respectively. The most abundant airborne bacteria (in units of CFU m-3) were: Staphylococcus sp. (72.4) > Micrococcus sp. (52.2) > Bacillus sp. (30.3) > Enterococcus sp. (24.0) > Serratia marcescens (20.1) > E. coli (19.1) > Pseudomonas sp. (16.0) > Nocardia sp. (1.9). The lifetime average daily dose (LADD) for the inhalation and dermal routes for the intake of airborne bacteria ranged from 3.7 × 10-3 ≤ LADDInhalation ≤ 2.07 × 101 CFU (kg d)-1 and 4.75 × 10-6 ≤ LADDDermal ≤ 1.64 × 10-5 CFU (kg d)-1, respectively. Based on a sensitivity analysis (SA), the concentration of airborne bacteria (C) and the exposure duration (ED) had the most effect on the LADDInhalation and LADDDermal for all sampling locations. Although the Hazard Quotient of airborne bacteria was HQ < 1, an acceptable level, the indoor/outdoor ratio (1.5 ≤ I/O ≤ 6.6) of airborne bacteria typically exceeded the threshold value (I/O > 2), indicating worker's exposure to an infected environment. Therefore, in the absence of sufficient natural ventilation the indoor ambient conditions of the WPCSP studied should be controlled by supplying mechanical ventilation.

Reactivity of aminophenols in forming nitrogen-containing brown carbon from iron-catalyzed reactions.

Nitrogen-containing organic carbon (NOC) in atmospheric particles is an important class of brown carbon (BrC). Redox active NOC like aminophenols received little attention in their ability to form BrC. Here we show that iron can catalyze dark oxidative oligomerization of o- and p-aminophenols under simulated aerosol and cloud conditions (pH 1-7, and ionic strength 0.01-1 M). Homogeneous aqueous phase reactions were conducted using soluble Fe(III), where particle growth/agglomeration were monitored using dynamic light scattering. Mass yield experiments of insoluble soot-like dark brown to black particles were as high as 40%. Hygroscopicity growth factors (κ) of these insoluble products under sub- and super-saturated conditions ranged from 0.4-0.6, higher than that of levoglucosan, a prominent proxy for biomass burning organic aerosol (BBOA). Soluble products analyzed using chromatography and mass spectrometry revealed the formation of ring coupling products of o- and p-aminophenols and their primary oxidation products. Heterogeneous reactions of aminophenol were also conducted using Arizona Test Dust (AZTD) under simulated aging conditions, and showed clear changes to optical properties, morphology, mixing state, and chemical composition. These results highlight the important role of iron redox chemistry in BrC formation under atmospherically relevant conditions.

Aqueous Photochemistry of 2-Oxocarboxylic Acids: Evidence, Mechanisms, and Atmospheric Impact.

Atmospheric organic aerosols play a major role in climate, demanding a better understanding of their formation mechanisms by contributing multiphase chemical reactions with the participation of water. The sunlight driven aqueous photochemistry of small 2-oxocarboxylic acids is a potential major source of organic aerosol, which prompted the investigations into the mechanisms of glyoxylic acid and pyruvic acid photochemistry reviewed here. While 2-oxocarboxylic acids can be contained or directly created in the particles, the majorities of these abundant and available molecules are in the gas phase and must first undergo the surface uptake process to react in, and on the surface, of aqueous particles. Thus, the work also reviews the acid-base reaction that occurs when gaseous pyruvic acid meets the interface of aqueous microdroplets, which is contrasted with the same process for acetic acid. This work classifies relevant information needed to understand the photochemistry of aqueous pyruvic acid and glyoxylic acid and motivates future studies based on reports that use novel strategies and methodologies to advance this field.

Modes of Transmission of Severe Acute Respiratory Syndrome-Coronavirus-2 (SARS-CoV-2) and Factors Influencing on the Airborne Transmission: A Review.

The multiple modes of SARS-CoV-2 transmission including airborne, droplet, contact, and fecal-oral transmissions that cause coronavirus disease 2019 (COVID-19) contribute to a public threat to the lives of people worldwide. Herein, different databases are reviewed to evaluate modes of transmission of SARS-CoV-2 and study the effects of negative pressure ventilation, air conditioning system, and related protection approaches of this virus. Droplet transmission was commonly reported to occur in particles with diameter >5 µm that can quickly settle gravitationally on surfaces (1-2 m). Instead, fine and ultrafine particles (airborne transmission) can stay suspended for an extended period of time (≥2 h) and be transported further, e.g., up to 8 m through simple diffusion and convection mechanisms. Droplet and airborne transmission of SARS-CoV-2 can be limited indoors with adequate ventilation of rooms, by routine disinfection of toilets, using negative pressure rooms, using face masks, and maintaining social distancing. Other preventive measures recommended include increasing the number of screening tests of suspected carriers of SARS-CoV-2, reducing the number of persons in a room to minimize sharing indoor air, and monitoring people's temperature before accessing a building. The work reviews a body of literature supporting the transmission of SARS-CoV-2 through air, causing COVID-19 disease, which requires coordinated worldwide strategies.

Dark Iron-Catalyzed Reactions in Acidic and Viscous Aerosol Systems Efficiently Form Secondary Brown Carbon.

Iron-driven secondary brown carbon formation reactions from water-soluble organics in cloud droplets and aerosols create insoluble and soluble products of emerging atmospheric importance. This work shows, for the first time, results on dark iron-catalyzed polymerization of catechol forming insoluble black polycatechol particles and colored water-soluble oligomers under conditions characteristic of viscous multicomponent aerosol systems with relatively high ionic strength (I = 1-12 m) and acidic pH (∼2). These systems contain ammonium sulfate (AS)/nitrate (AN) and C3-C5 dicarboxylic acids, namely, malonic, malic, succinic, and glutaric acids. Using dynamic light scattering (DLS) and ultra high pressure liquid chromatography-mass spectrometry (UHPLC-MS), we show results on the rate of particle growth/agglomeration and identity of soluble oligomeric reaction products. We found that increasing I above 1 m and adding diacids with oxygen-to-carbon molar ratio (O:C > 1) significantly reduced the rate of polycatechol formation/aggregation by a factor of 1.3 ± 0.4 in AS solution in the first 60 min of reaction time. Using AN, rates were too slow to be quantified using DLS, but particles formed after 24 h reaction time. These results were explained by the relative concentration and affinity of ligands to Fe(III). We also report detectable amounts of soluble and colored oligomers in reactions with a slow rate of polycatechol formation, including organonitrogen compounds. These results highlight that brown carbon formation from iron chemistry is efficient under a wide range of aerosol physical states and chemical composition.

An overview of the effect of bioaerosol size in coronavirus disease 2019 transmission.

The fast spread of coronavirus disease 2019 (COVID-19) constitutes a worldwide challenge to the public health, educational and trade systems, affecting the overall well-being of human societies. The high transmission and mortality rates of this virus, and the unavailability of a vaccine or treatment, resulted in the decision of multiple governments to enact measures of social distancing. Such measures can reduce the exposure to bioaerosols, which can result in pathogen deposition in the respiratory tract of the host causing disease and an immunological response. Thus, it is important to consider the validity of the proposal for keeping a distance of at least 2 m from other persons to avoid the spread of COVID-19. This work reviews the effect of aerodynamic diameter (size) of particles carrying RNA copies of severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2). A SARS-CoV-2 carrier person talking, sneezing or coughing at distance of 2 m can still provide a pathogenic bioaerosol load with submicron particles that remain viable in air for up to 3 h for exposure of healthy persons near and far from the source in a stagnant environment. The deposited bioaerosol creates contaminated surfaces, which if touched can act as a path to introduce the pathogen by mouth, nose or eyes and cause disease.

Application of a Small Unmanned Aerial System to Measure Ammonia Emissions from a Pilot Amine-CO2 Capture System.

The quantification of atmospheric gases with small unmanned aerial systems (sUAS) is expanding the ability to safely perform environmental monitoring tasks and quickly evaluate the impact of technologies. In this work, a calibrated sUAS is used to quantify the emissions of ammonia (NH3) gas from the exit stack a 0.1 MWth pilot-scale carbon capture system (CCS) employing a 5 M monoethanolamine (MEA) solvent to scrub CO2 from coal combustion flue gas. A comparison of the results using the sUAS against the ion chromatography technique with the EPA CTM-027 method for the standard emission sampling of NH3 shows good agreement. Therefore, the work demonstrates the usefulness of sUAS as an alternative method of emission measurement, supporting its application in lieu of traditional sampling techniques to collect real time emission data.

Oxidation of Phenolic Aldehydes by Ozone and Hydroxyl Radicals at the Air-Water Interface.

Biomass burning releases highly reactive methoxyphenols into the atmosphere, which can undergo heterogeneous oxidation and act as precursors for secondary organic aerosol (SOA) formation. Understanding the reactivity of such methoxyphenols at the air-water interface is a matter of major atmospheric interest. Online electrospray ionization mass spectrometry (OESI-MS) is used here to study the oxidation of two methoxyphenols among three phenolic aldehydes, 4-hydroxybenzaldehyde, vanillin, and syringaldehyde, on the surface of water. The OESI-MS results together with cyclic voltammetry measurements at variable pH are integrated into a mechanism describing the heterogeneous oxidative processing of methoxyphenols by gaseous ozone (O3) and hydroxyl radicals (HO•). For a low molar ratio of O3 ≤ 66 ppbv, the OESI-MS spectra show that the oxidation is dominated by in situ produced HO• and results in the production of polyhydroxymethoxyphenols. When the level of O3 increases (i.e., ≥78 times), the ion count of polyhydroxymethoxyphenols increases, while new ring fragmentation products are generated, including conjugated aldehydes and double bonds as well as additional carboxylic acid groups. The interfacial reactivity of methoxyphenols with O3 and HO• is enhanced as the number of methoxy (-OCH3) groups increases (4-hydroxybenzaldehyde < vanillin < syringaldehyde). The experimental observations are summarized in two reaction pathways, leading to the formation of (1) hydroxylated methoxyphenols and (2) multifunctional carboxylic acids from fragmentation of the aromatic ring. The new highly oxygenated products with low volatility are excellent precursors for aqueous SOA formation.

Hyperuniform states generated by a critical friction field.

Hyperuniform states are an efficient way to fill up space for disordered systems. In these states the particle distribution is disordered at the short scale but becomes increasingly uniform when looked at large scales. Hyperuniformity appears in several systems, in static or quasistatic regimes, as well as close to transitions to absorbing states. Here, we show that a vibrated granular layer, at the critical point of the liquid-to-solid transition, displays dynamic hyperuniformity. Prior to the transition, patches of the solid phase form, with length scales and mean lifetimes that diverge critically at the transition point. When reducing the wave number, density fluctuations encounter increasingly more patches that block their propagation, resulting in a static structure factor that tends to zero for small wave numbers at the critical point, which is a signature of hyperuniformity. A simple model demonstrates that this coupling of a density field to a highly fluctuating scalar friction field gives rise to dynamic hyperuniform states. Finally, we show that the structure factor detects better the emergence of hyperuniformity, compared to the particle number variance.

Production of Singlet Oxygen (1O2) during the Photochemistry of Aqueous Pyruvic Acid: The Effects of pH and Photon Flux under Steady-State O2(aq) Concentration.

The photochemistry of pyruvic acid (PA) in aqueous atmospheric particles contributes to the production of secondary organic aerosols. This work investigates the fate of ketyl and acetyl radicals produced during the photolysis (λ ≥ 305 nm) of 5-100 mM PA under steady state [O2(aq)] = 260 µM (1.0 ≤ pH ≤ 4.5) for photon fluxes between 1 and 10 suns. The radicals diffuse quickly into the water/air interface of microbubbles and react with dissolved O2 to produce singlet oxygen (1O2*). Furfuryl alcohol is used to trap and bracket the steady-state production of 2 × 10-12 ≤ [1O2*] ≤ 1 × 10-11 M. Ion chromatography mass spectrometry shows that 2,3-dimethyltartaric acid (DMTA), 2-(3-oxobutan-2-yloxy)-2-hydroxypropanoic acid (oxo-C7 product), and 2-(1-carboxy-1-hydroxyethoxy)-2-methyl-3-oxobutanoic acid (oxo-C8 product) are formed under all conditions investigated. The sigmoidal dependence of initial reaction rates with pH resembles the dissociation curve of PA. For increasing photon fluxes, the branching ratio of products shifts away from the radical recombination that favors DMTA toward multistep radical chemistry forming more complex oxocarboxylic acids (oxo-C7 + oxo-C8). The large steady-state production of 1O2 indicates that PA in aerosols can be a significant source of atmospheric oxidants on par with natural organic matter.