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Outdoor air pollution is an increasing public health burden. Fine particulate matter (PM2.5) is a pollutant of major concern for human health, and it also affects the climate and ecosystems. Understanding and quantifying emission sources and their impact on particulate air pollution is critical for improving global health and for informing climate action. Poor air quality across the globe disproportionately affects middle- and lower-income countries. Delhi, the capital of India, is one of the most populated and polluted megacities in the world, where in 2017 almost 12,000 premature deaths were attributed to outdoor air pollution. My thesis aims to advance our understanding of outdoor air pollution in Delhi megacity, with a focus on the impact of on-road transport emissions on surface levels of PM2.5 and its implications for air quality policymaking. To do this, I use a combination of a state of the art regional atmospheric chemistry transport model, recently developed local emissions inventories, and sensitivity analysis techniques. In the first research chapter I use the WRF-Chem atmospheric chemical transport model to understand the regional influence on air quality over Delhi. As part of this work, I characterise seasonal anthropogenic, pyrogenic, and biogenic influences on fine particulate matter and one of its main constituents, organic aerosol (OA), over the Indo-Gangetic Plain (IGP). My results show that anthropogenic emissions influence the magnitude and distribution of PM2.5 and OA throughout the year, especially over cities including Delhi, while pyrogenic emissions from crop residues burning result in localized contributions over the central and upper parts of IGP in all non-monsoonal seasons, with the highest impact during the post-monsoon season that correspond to the post-harvest season in the agricultural calendar. Biogenic emissions play an important role in the magnitude and distribution of PM2.5 and OA during the monsoon season, particularly over the lower IGP. In all seasons mean values of PM2.5 still exceed the recommended levels, indicating that air pollution is a year-round problem. In the second research chapter I develop the WRF-Chem model used in my first chapter to include local emission inventories, in order to quantify the contribution of the on-road transport sector to surface PM2.5 over Delhi during the highly polluted post-monsoon season. This contribution is compared to the contributions of other local (within Delhi) and regional (within the National Capital Region, NCR) anthropogenic sectors. My results show that emissions from the local transport sector contribute typically less than 10% to daily mean PM2.5 values over Delhi, rising to 17% when regional transport sources are included. The contribution from the local transport sector is largest (18%) during the evening traffic peak. The total transport impact is dominated by contributions from twoand three-wheelers (50%) and heavy-duty vehicles (30%). The largest individual contributions to daily mean PM2.5 values are found to be from regional power and industry (14%) and domestic (11%) sectors. In the third research chapter I drive the WRF-Chem model with future transport emissions scenarios to investigate the potential impact of electric and clean-fuel vehicles on surface PM2.5 and ozone (O3) over Delhi for two contrasting seasons, pre-monsoon and post-monsoon. My results show that the conversion of diesel vehicles to compressed natural gas (CNG) brings a greater reduction in PM2.5 concentrations than the full electrification of two- and three-wheelers. However, the maximum reduction of daily mean PM2.5 concentrations for all scenarios is within 5% compared to baseline values for both seasons. Electrification of two- and three-wheelers increases average 8-hour daily maximum (MDA8) ozone (1.3-3.5% in pre-monsoon 5-13% in post-monsoon) compared to baseline values. On the other hand, conversion of all diesel vehicles to CNG reduces MDA8 O3 in both seasons (by 2.3-5.3% in pre-monsoon and by 1-1.5% in post-monsoon) compared to baseline values. In conclusion, the findings of my thesis highlight different factors that can be relevant for designing effective policies to meet PM2.5 air quality standards over Delhi megacity, with a focus on mitigating the impact from the on-road transport sector. First, air quality over Delhi is strongly influenced by regional and seasonal pollution sources from the IGP. As such, effective mitigation of PM2.5 pollution over Delhi will require a range of regional and state-level policies. In particular, cooperative mitigation strategies between the Delhi megacity and the broader NCR is needed if PM2.5 pollution is to be reduced. Second, two-and three-wheelers and heavy-duty vehicles dominate on-road transport impact on PM2.5, thus emissions reductions from these vehicles should be given priority, both within Delhi and in the NCR. Third, cleaner mobility plans of electrification of two- and threewheelers should be accompanied by diesel vehicles conversion to compressed natural gas, to limit ozone pollution increase and further reduce PM2.5 concentrations. This also highlights the importance of coordinated control of PM2.5 and other pollutants such as O3 when considering emission control strategies for transport over Delhi.

Supplemental Digital Content is available in the text., Background: Hutchinson-Gilford progeria syndrome (HGPS) is a rare disorder characterized by premature aging and death mainly because of myocardial infarction, stroke, or heart failure. The disease is provoked by progerin, a variant of lamin A expressed in most differentiated cells. Patients look healthy at birth, and symptoms typically emerge in the first or second year of life. Assessing the reversibility of progerin-induced damage and the relative contribution of specific cell types is critical to determining the potential benefits of late treatment and to developing new therapies. Methods: We used CRISPR-Cas9 technology to generate LmnaHGPSrev/HGPSrev (HGPSrev) mice engineered to ubiquitously express progerin while lacking lamin A and allowing progerin suppression and lamin A restoration in a time- and cell type–specific manner on Cre recombinase activation. We characterized the phenotype of HGPSrev mice and crossed them with Cre transgenic lines to assess the effects of suppressing progerin and restoring lamin A ubiquitously at different disease stages as well as specifically in vascular smooth muscle cells and cardiomyocytes. Results: Like patients with HGPS, HGPSrev mice appear healthy at birth and progressively develop HGPS symptoms, including failure to thrive, lipodystrophy, vascular smooth muscle cell loss, vascular fibrosis, electrocardiographic anomalies, and precocious death (median lifespan of 15 months versus 26 months in wild-type controls, P

The term open-air factor (OAF) was coined following microbiological research in the 1960s and 1970s which established that rural air had powerful germicidal properties and attributed this to Criegee intermediates formed in the reaction of ozone with alkenes. We have re-evaluated those early experiments applying the current state of knowledge of ozone–alkene reactions. Contrary to previous speculation, neither Criegee intermediates nor the HO radicals formed in their decomposition are directly responsible for the germicidal activity attributed to the OAF. We identify other potential candidates, which are formed in ozone–alkene reactions and have known (and likely) germicidal properties, but the compounds responsible for the OAF remain a mystery. There has been very little research into the OAF since the 1970s, and this effect seems to have been largely forgotten. In this opinion piece we remind the community of the germicidal open-air factor. Given the current global pandemic spread by an airborne pathogen, understanding the natural germicidal effects of ambient air, solving the mystery of the open-air factor and determining how this effect can be used to improve human welfare should be a high priority for the atmospheric science community.

International audience; Abstract. This article, the eighth in the series, presents kinetic and photochemical data sheets evaluated by the IUPAC Task Group on Atmospheric Chemical Kinetic Data Evaluation. It covers the gas-phase thermal and photochemical reactions of organic species with four, or more, carbon atoms (≥ C4) available on the IUPAC website in 2021, including thermal reactions of closed-shell organic species with HO and NO3 radicals and their photolysis. The present work is a continuation of volume II (Atkinson et al., 2006), with new reactions and updated data sheets for reactions of HO (77 reactions) and NO3 (36 reactions) with ≥ C4 organics, including alkanes, alkenes, dienes, aromatics, oxygenated, organic nitrates and nitro compounds in addition to photochemical processes for nine species. The article consists of a summary table (Table 1), containing the recommended kinetic parameters for the evaluated reactions, and a supplement containing the data sheets, which provide information upon which recommendations are made.

This article, the seventh in the series, presents kinetic and photochemical data sheets evaluated by the IUPAC Task Group on Atmospheric Chemical Kinetic Data Evaluation. It covers an extension of the gas-phase and photochemical reactions related to Criegee intermediates previously published in Atmospheric Chemistry and Physics (ACP) in 2006 and implemented on the IUPAC website up to 2020. The article consists of an introduction, description of laboratory measurements, a discussion of rate coefficients for reactions of O3 with alkenes producing Criegee intermediates, rate coefficients of unimolecular and bimolecular reactions and photochemical data for reactions of Criegee intermediates, and an overview of the atmospheric chemistry of Criegee intermediates. Summary tables of the recommended kinetic and mechanistic parameters for the evaluated reactions are provided. Data sheets summarizing information upon which the recommendations are based are given in two files, provided as a Supplement to this article.

Sustainable design methods and tools abound, but their implementation in practice remains marginal. This article brings together results from previous literature reviews and analyses of sustainable design methods and tools, as well as input from design researchers and professional practitioners to identify the needs and gaps in the area. It results in a shared vision of how sustainable design methods and tools can be more tightly integrated into mainstream product design and development, as well as the current state of practice and research in relation to four central questions: What are the needs and values of industry regarding sustainable design? What improvements in sustainable design methods and tools would most drive industry forward? How should researchers move forwardwith developingmore useful sustainable designmethods and tools? Howcan sustainable design be more effectively integrated into industry? A roadmap for the international sustainable design research community is proposed with descriptions of short-, medium-, and long-term tasks for addressing each question. The purpose is to support collective progress and discussions on method and tool development and adoption, and to enablemore tangible success inmainstreaming sustainable design practices in industry. © 2020 by the authors. open access

In the present work, a 5-component gasoline surrogate chemical kinetic mechanism has been developed and validated. The first novelty of this mechanism is that a recently advanced H2/O2/CO/C1 detailed sub-mechanism is adopted for accurately predicting the laminar flame speeds over a wide range of operating conditions and a recently advanced C2-C3 detailed sub-mechanism is used due to its potential benefits on accurate flame propagation simulation in order to overcome the drawbacks in the original decoupling methodology. The second novelty of this mechanism is that the sub-mechanisms of propyne and allene which are important for soot formation from non-aromatics have been improved significantly. For each of the five gasoline surrogate components (iso-octane, n-heptane, iso-hexane, 1-hexene, and toluene) a skeletal sub-mechanism, which determines the simulation of ignition delay times, is constructed for species C4-Cn. The five skeletal sub-mechanisms are coupled with the new C2-C3 and H2/O2/CO/C1 detailed sub-mechanisms. Together with a reduced NOx (oxides of nitrogen) sub-mechanism, the 5-component gasoline surrogate chemical kinetic mechanism has 214 species and 1233 reactions, which are feasible currently for CFD simulation of gasoline engine combustion, emissions, and knock. The new H2/O2/CO/C1 and C2-C3 detailed sub-mechanisms were validated with selected experimental data of ignition delay times, laminar flame speeds, and important species profiles in the literature. The reaction rate constants of the five skeletal sub-mechanisms were optimized in this work to match available experimental data of either pure fuels or fuel blends, including real gasoline fuels. The validation results show that the prediction accuracy of the 5-component gasoline surrogate chemical kinetic mechanism of the present work can be less than 5% for various fuel blends under a pressure range of 1.0 80.0 bar, a temperature range of 300 1260 K, and an equivalence ratio range of 0.5 2.5. This work was partially funded by a URP (University Research Program) of Ford Motor Company. Shiyou Yang of Ford thanks Dr. Chitral Naik of Reaction Design (now ANSYS) for help in using the CHEMKIN-PRO software, also SY thanks Dr. Snehasish Panigrahy of National University of Ireland-Galway for implementing the latest propyne detailed sub-mechanism into MCCh v2.0 mechanism and providing the experimental data for validation. James Yi, Steven Wooldridge, Brad VanDerWege, Claudia Iyer, Foo-Chern Ting, and Cindy Zhou of Ford Motor Company are thanked for helpful discussions and suggestions. peer-reviewed

An Al-Mg-Si aluminium alloy was shaped by using a two-pass equal-channel angular pressing (ECAP) process. This led to fragmentation of the coarse Fe-rich intermetallics (IMCs), a decrease in grain size and an increase in the high angle grain boundary (HAGB) density, with overconcentration of HAGBs around the IMCs. Corrosion tests in NaCl solution showed that, before and after ECAP, only pitting corrosion occurred. However, for ECAP samples, pits were more numerous due to the fragmentation of the IMCs; they were also larger and less deep, their propagation being strongly influenced by the presence of very small grains around the IMCs.

International audience

We present a digital, freely available, searchable, and evaluated compilation of rate coefficients for the gas-phase reactions of organic compounds with OH, Cl, and NO3 radicals and with O3. Although other compilations of many of these data exist, many are out of date, most have limited scope, and all are difficult to search and to load completely into a digitized form. This compilation uses results of previous reviews, though many recommendations are updated to incorporate new or omitted data or address errors, and includes recommendations on many reactions that have not been reviewed previously. The database, which incorporates over 50 years of measurements, consists of a total of 2765 recommended bimolecular rate coefficients for the reactions of 1357 organic substances with OH, 709 with Cl, 310 with O3, and 389 with NO3, and is much larger than previous compilations. Many compound types are present in this database, including naturally occurring chemicals formed in or emitted to the atmosphere and anthropogenic compounds such as halocarbons and their degradation products. Recommendations are made for rate coefficients at 298 K and, where possible, the temperature dependences over the entire range of the available data. The primary motivation behind this project has been to provide a large and thoroughly evaluated training dataset for the development of structure–activity relationships (SARs), whose reliability depends fundamentally upon the availability of high-quality experimental data. However, there are other potential applications of this work, such as research related to atmospheric lifetimes and fates of organic compounds, or modelling gas-phase reactions of organics in various environments. This database is freely accessible at https://doi.org/10.25326/36 (McGillen et al., 2019).

This paper presents an experimental study into the flow behaviour of lubricant in a reciprocating contact simulating a piston ring–cylinder liner pair. The aim was to understand the effects of cavitation, starvation and surface texture, as well as the interaction between these, in order to improve automotive engine performance. A custom-built test rig was used, in which a section of piston ring is loaded against a reciprocating, laser-textured, fused silica pad representing the liner. A fluorescence microscope focusses through the silica specimen onto the contact in order to image the distribution of dyed oil. Tests were performed using a range of texture geometries and orientations, under starved and fully-flooded lubrication conditions, with measurements being compared against those from a non-textured reference. Under limited oil supply conditions, the non-textured reciprocating contact sweeps oil towards the reversal points (TDC and BDC), leading to starvation and increased friction. This issue is alleviated by the presence of surface texturing, with each pocket transferring oil from the inlet to the outlet of the contact as it passes; the result being 33% lower friction and oil distributed evenly over the liner surface. Even under fully flooded conditions, starvation is shown to occur following each reversal, as the change in sliding direction causes the cavitated outlet to become the oil-deprived inlet. This proof of cavitation-reversal-starvation, which occurs for up to the first 5% of the stroke length, depending on the lubricant’s viscosity, corresponds to regions of high wear, measured in this study and on actual cylinder liners reported in the literature. This process is also counteracted by the presence of surface texture, with each pocket depositing oil into the cavitated region prior to reversal. Fluorescence data also provides insights into other mechanisms with which different textures geometries control friction. Grooves oriented parallel to sliding direction increase friction as they appear to connect the high pressure inlet with the low pressure outlet, leading to oil film collapse. Grooves oriented transverse to sliding direction produce localised cavitation inside each pocket, which supports the theory that texture draws lubricant into the contact through the ‘inlet suction’ mechanism. These findings can aid texture design by showing how pockets can be used in practice to simultaneously control oil consumption, and reduce friction and wear along the stroke. It should be noted that the lubricant transport mechanisms described above should also result from other types of depressions, such those produced by porous coatings (provided they are smaller than the contact area).

This paper presents a comparison between the results from numerical modelling and experiments to shed light on the mechanisms by which surface texture can reduce friction when applied to an automotive cylinder liner. In this configuration, textured features move relative to the piston-liner conjunction and to account for this our approach is to focus on the transient friction response to individual pockets as they pass through, and then leave, the sliding contact. The numerical approach is based on the averaged Reynolds’ equation with the Patir & Cheng's flow factors and the p-θ Elrod-Adams mass-conserving cavitation model. The contact pressures that arise from the asperity interactions are solved simultaneously to the fluid flow solution using the Greenwood and Tripp method. The experimental data is produced using a pin-on-disc set up, in which laser textured pockets have been applied to the disc specimen. Under certain conditions in the mixed and boundary lubrication regimes, both model and experimental results show i ) an increase in friction as the pocket enters the contact, followed by ii ) a sharp decrease as the pocket leaves the contact, and then iii ) a gradual decay back to the pre-entrainment value. From the evidence obtained for the first time from the proposed combined modelling and experimental investigation conducted under carefully controlled conditions, we suggest that these three stages occur due to the following mechanisms: i ) a reduction in fluid pressure due to the increased inlet gap, ii ) inlet suction as the cavitated fluid within the pocket draws lubricant into the contact, and iii ) film thickness decay as oil is squeezed out of the contact. The interplay of these three mechanisms is shown to control the response of micro-textured surfaces under all lubrication regimes.

In order to determine a material's hydrogen storage potential, capacity measurements must be robust, reproducible, and accurate. Commonly, research reports focus on the gravimetric capacity, and often times the volumetric capacity is not reported. Determining volumetric capacities is not as straight-forward, especially for amorphous materials. This is the first study to compare measurement reproducibility across laboratories for excess and total volumetric hydrogen sorption capacities based on the packing volume. The use of consistent measurement protocols, common analysis, and figure of merits for reporting data in this study, enable the comparison of the results for two different materials. Importantly, the results show good agreement for excess gravimetric capacities amongst the laboratories. Irreproducibility for excess and total volumetric capacities is attributed to real differences in the measured packing volume of the material.

International audience; Gasoline soot nanoparticles (SNPs) were studied by performing in situ compression tests on individual nanoparticles inside a transmission electron microscope. After consecutive compressions, the SNPs exhibited an elasto-plastic behavior, and an increasing trend in Young's modulus and hardness values. Molecular dynamics were used to simulate compression cycles, the results of which confirmed the observations made during the experiments. The simulations were used to investigate how the different structural components of the nanoparticles affect their elastic and plastic response. By comparing the behavior of gasoline and diesel SNPs under compression, differences were observed both experimentally and in the simulations: the former were found to be more elastic and less prone to become hard under compression compared to the latter.

From the earliest observations of ozone in the lower atmosphere in the 19th century, both measurement methods and the portion of the globe observed have evolved and changed. These methods have different uncertainties and biases, and the data records differ with respect to coverage (space and time), information content, and representativeness. In this study, various ozone measurement methods and ozone datasets are reviewed and selected for inclusion in the historical record of background ozone levels, based on relationship of the measurement technique to the modern UV absorption standard, absence of interfering pollutants, representativeness of the well-mixed boundary layer and expert judgement of their credibility. There are significant uncertainties with the 19th and early 20th-century measurements related to interference of other gases. Spectroscopic methods applied before 1960 have likely underestimated ozone by as much as 11% at the surface and by about 24% in the free troposphere, due to the use of differing ozone absorption coefficients. There is no unambiguous evidence in the measurement record back to 1896 that typical mid-latitude background surface ozone values were below about 20 nmol mol–1, but there is robust evidence for increases in the temperate and polar regions of the northern hemisphere of 30–70%, with large uncertainty, between the period of historic observations, 1896–1975, and the modern period (1990–2014). Independent historical observations from balloons and aircraft indicate similar changes in the free troposphere. Changes in the southern hemisphere are much less. Regional representativeness of the available observations remains a potential source of large errors, which are difficult to quantify. The great majority of validation and intercomparison studies of free tropospheric ozone measurement methods use ECC ozonesondes as reference. Compared to UV-absorption measurements they show a modest (~1–5% ±5%) high bias in the troposphere, but no evidence of a change with time. Umkehr, lidar, and FTIR methods all show modest low biases relative to ECCs, and so, using ECC sondes as a transfer standard, all appear to agree to within one standard deviation with the modern UV-absorption standard. Other sonde types show an increase of 5–20% in sensitivity to tropospheric ozone from 1970–1995. Biases and standard deviations of satellite retrieval comparisons are often 2–3 times larger than those of other free tropospheric measurements. The lack of information on temporal changes of bias for satellite measurements of tropospheric ozone is an area of concern for long-term trend studies.

International audience; Peroxy radicals (HO 2 and RO 2 ) are key species in atmospheric chemistry, which together with the hydroxyl radical (OH), are involved in oxidation processes leading to the formation of secondary pollutants such as ozone and organic aerosols. Monitoring these short-lived species during intensive field campaigns and comparing the measured concentrations to box model simulations allow assessing the reliability of chemical mechanisms implemented in atmospheric models. However, ambient measurements of peroxy radicals are still considered challenging and only a few techniques have been used for field measurements. Three complementary instruments capable of ambient measurements of pe roxy radicals have been deployed together at the HELIOS atmospheric simulation chamber (Orléans, France) in October 2018. These instruments rely on the PEroxy Radical Chemical Amplification (PERCA), Laser Induced Fluorescence-Fluorescent Assay by Gas Expansion (LIF-FAGE), and Chemical Ionisation Mass Spectrometry (CIMS) techniques. Several chamber experiments have been conducted under dark and irradiated conditions, including oxidation experiments of dihydrogen, methane, pentene, isoprene, and α-pinene. In this presentation, the agreement between the different instruments will be discussed in the light of supporting measurements of volatile organic compounds and inorganic species (O3, NO, NO2), photolysis frequencies, as well as box modelling of the chamber chemistry.