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Several studies have investigated new particle formation (NPF) events from various sites ranging from pristine locations, including forest sites, to urban areas. However, there is still a dearth of studies investigating NPF processes and subsequent aerosol growth in coastal yet semi-urban sites, where the tropospheric layer is a concoction of biogenic and anthropogenic gases and particles. The investigation of factors leading to NPF becomes extremely complex due to the highly dynamic meteorological conditions at the coastline especially when combined with both continental and oceanic weather conditions. Herein, we engage in a comprehensive study of particle number size distributions and aerosol-forming precursor vapors at the coastal semi-urban site in Helsinki, Finland. The measurement period, 25 June–18 August 2019, was timed with the recurring cyanobacterial summer bloom in the Baltic Sea region and coastal regions of Finland. Our study recorded several regional/local NPF and aerosol burst events during this period. Although the overall anthropogenic influence on sulfuric acid (SA) concentrations was low during the measurement period, we observed that the regional or local NPF events, characterized by SA concentrations on the order of 107 molec.cm-3, occurred mostly when the air mass traveled over the land areas. Interestingly, when the air mass traveled over the Baltic Sea, an area enriched with algae and cyanobacterial blooms, high iodic acid (IA) concentration coincided with an aerosol burst or a spike event at the measurement site. Further, SA-rich bursts were seen when the air mass traveled over the Gulf of Bothnia, enriched with cyanobacterial blooms. The two most important factors affecting aerosol precursor vapor concentrations, and thus the aerosol formation, were speculated to be (1) the type of phytoplankton species and intensity of bloom present in the coastal regions of Finland and the Baltic Sea and (2) the wind direction. During the events, most of the growth of sub-3 nm particles was probably due to SA, rather than IA or methane sulfonic acid (MSA); however much of the particle growth remained unexplained indicative of the strong role of organics in the growth of particles, especially in the 3–7 nm particle size range. Further studies are needed to explore the role of organics in NPF events and the potential influence of cyanobacterial blooms in coastal locations.

Background and Purpose: Elamipretide is a mitochondrial-targeting agent being developed for the treatment of mitochondrial dysfunction-associated diseases. While prior studies have shown that subcutaneous elamipretide is generally safe/well tolerated, injection site reactions (ISRs) were reported in most subjects. We evaluated the efficacy of interventions to mitigate ISRs, identify underlying ISR mechanisms, and evaluate the pharmacokinetic and safety profile of subcutaneous elamipretide. Experimental Approach: Subcutaneous elamipretide 60 mg was administered to healthy subjects (N=10) on six separate occasions with/without potential ISR interventions (mometasone furoate, ice application, tacrolimus ointment, doxepin cream, and oral diphenhydramine). ISR clinical/self-assessments, blood samples, and safety data were collected at predetermined intervals. Preclinical studies investigated mast cell-specific receptor MRGPRX2 mediation of ISRs. Key Results: Mometasone significantly reduced the incidence of induration/swelling and pruritus. Diphenhydramine significantly decreased the incidence of induration; 50% reported somnolence. Ice application significantly reduced the incidence of pain, although it reduced elamipretide’s maximum plasma concentration and area-under-the-curve from time 0-6hrs versus elamipretide alone. Preclinical data suggest that SQ-elamipretide induced ISRs by activating MRGPRX2 in humans and its ortholog Mrgprb2 in mice. Conclusion and Implications: Elamipretide activated MRGPRX2 and Mrgprb2 receptors, resulting in activation of mast cells and inflammation in mouse models, suggesting that targeting mast-cell activation may ameliorate elamipretide ISRs. Topical mometasone prior to subcutaneous elamipretide demonstrated significant reductions in ISR signs and symptoms and did not cause significant changes in elamipretide plasma exposure or additional adverse events. Therefore, mometasone prior to subcutaneous injection of elamipretide warrants further investigation in clinical studies for alleviating ISRs.

Iodine is a reactive trace element in atmospheric chemistry that destroys ozone and nucleates particles. Iodine emissions have tripled since 1950 and are projected to keep increasing with rising O3 surface concentrations. Although iodic acid (HIO3) is widespread and forms particles more efficiently than sulfuric acid, its gas-phase formation mechanism remains unresolved. Here, in CLOUD atmospheric simulation chamber experiments that generate iodine radicals at atmospherically relevant rates, we show that iodooxy hypoiodite, IOIO, is efficiently converted into HIO3 via reactions (R1) IOIO + O3 → IOIO4 and (R2) IOIO4 + H2O → HIO3 + HOI + (1)O2. The laboratory-derived reaction rate coefficients are corroborated by theory and shown to explain field observations of daytime HIO3 in the remote lower free troposphere. The mechanism provides a missing link between iodine sources and particle formation. Because particulate iodate is readily reduced, recycling iodine back into the gas phase, our results suggest a catalytic role of iodine in aerosol formation.

In this study, we modeled the aerosol particle formation along air mass trajectories arriving at the remote Arctic research stations Gruvebadet (67 m a.s.l.) and Zeppelin (474 m a.s.l.), Ny-Ålesund, during May 2018. The aim of this study was to improve our understanding of processes governing secondary aerosol formation in remote Arctic marine environments. We run the Lagrangian chemistry transport model ADCHEM, along air mass trajectories generated with FLEXPART v10.4. The air masses arriving at Ny-Ålesund spent most of their time over the open ice-free ocean. In order to capture the secondary aerosol formation from the DMS emitted by phytoplankton from the ocean surface, we implemented a recently developed comprehensive DMS and halogen multi-phase oxidation chemistry scheme, coupled with the widely used Master Chemical Mechanism (MCM). The modeled median particle number size distributions are in close agreement with the observations in the marine-influenced boundary layer near-sea-surface Gruvebadet site. However, while the model reproduces the accumulation mode particle number concentrations at Zeppelin, it overestimates the Aitken mode particle number concentrations by a factor of ∼5.5. We attribute this to the deficiency of the model to capture the complex orographic effects on the boundary layer dynamics at Ny-Ålesund. However, the model reproduces the average vertical particle number concentration profiles within the boundary layer (0–600 m a.s.l.) above Gruvebadet, as measured with condensation particle counters (CPCs) on board an unmanned aircraft system (UAS). The model successfully reproduces the observed Hoppel minima, often seen in particle number size distributions at Ny-Ålesund. The model also supports the previous experimental findings that ion-mediated H2SO4–NH3 nucleation can explain the observed new particle formation in the marine Arctic boundary layer in the vicinity of Ny-Ålesund. Precursors resulting from gas- and aqueous-phase DMS chemistry contribute to the subsequent growth of the secondary aerosols. The growth of particles is primarily driven via H2SO4 condensation and formation of methane sulfonic acid (MSA) through the aqueous-phase ozonolysis of methane sulfinic acid (MSIA) in cloud and deliquescent droplets.

As part of the COVID-19 pandemic response, the Ontario Ministry of Health funded a virtual care pilot program intended to support emergency department (ED) diversion of patients with low acuity complaints and reduce the need for face-to-face contact. The objective was to describe the demographic characteristics, outcomes and experience of patients using the provincial pilot program.This was a prospective cohort study of patients using virtual care services provided by 14 ED-led pilot sites from December 2020 to September 2021. Patients who completed a virtual visit were invited by email to complete a standardized, 25-item online survey, which included questions related to satisfaction and patient-reported outcome measures.There were 22,278 virtual visits. When patients were asked why they contacted virtual urgent care, of the 82.7% patients who had a primary care provider, 31.0% said they could not make a timely appointment with their family physician. Rash, fever, abdominal pain, and COVID-19 vaccine queries represented 30% of the presenting complaints. Of 19,613 patients with a known disposition, 12,910 (65.8%) were discharged home and 3,179 (16.2%) were referred to the ED. Of the 2,177 survey responses, 94% rated their overall experience as 8/10 or greater. More than 80% said they had answers to all the questions they had related to their health concern, believed they were able to manage the issue, had a plan they could follow, and knew what to do if the issue got worse or came back.Many presenting complaints were low acuity, and most patients had a primary care provider, but timely access was not available. Future work should focus on health equity to ensure virtual care is accessible to underserved populations. We question if virtual urgent care can be safely and more economically provided by non-emergency physicians.RéSUMé: INTRODUCTION: Dans le cadre de la réponse à la pandémie de COVID-19, le ministère de la Santé de l'Ontario a financé un programme pilote de soins virtuels visant à soutenir la réorientation vers les services d'urgence des patients présentant des problèmes de faible acuité et à réduire le besoin de contact en personne. L'objectif était de décrire les caractéristiques démographiques, les résultats et l'expérience des patients utilisant le programme pilote provincial. MéTHODES: Il s'agissait d'une étude de cohorte prospective de patients utilisant des services de soins virtuels fournis par 14 sites pilotes dirigés par des services d'urgence, de décembre 2020 à septembre 2021. Les patients qui ont effectué une visite virtuelle ont été invités par courriel à répondre à une enquête en ligne standardisée de 25 questions, qui comprenait des questions relatives à la satisfaction et aux résultats rapportés par les patients. RéSULTATS: Il y a eu 22 278 visites virtuelles. Lorsqu'on a demandé aux patients pourquoi ils avaient contacté les soins urgents virtuels, sur les 82,7 % de patients qui avaient un prestataire de soins primaires, 31,0 % ont répondu qu'ils n'avaient pas pu obtenir un rendez-vous en temps voulu avec leur médecin de famille. Les éruptions cutanées, la fièvre, les douleurs abdominales et les interrogations sur le vaccin COVID-19 représentaient 30 % des plaintes présentées. Sur les 19 613 patients dont la disposition était connue, 12 910 (65,8 %) ont été renvoyés chez eux et 3 179 (16,2 %) ont été orientés vers les urgences. Sur les 2 177 réponses à l'enquête, 94 % ont attribué une note de 8/10 ou plus à leur expérience globale. Plus de 80 % d'entre eux ont déclaré avoir obtenu des réponses à toutes les questions qu'ils se posaient sur leur problème de santé, se croire capables de le gérer, avoir un plan qu'ils pouvaient suivre et savoir quoi faire si le problème s'aggravait ou revenait. CONCLUSIONS: De nombreuses plaintes présentées étaient de faible acuité, et la plupart des patients avaient un fournisseur de soins primaires, mais l'accès en temps opportun n'était pas disponible. Les travaux futurs devraient se concentrer sur l'équité en matière de santé pour s'assurer que les soins virtuels sont accessibles aux populations mal desservies et nous nous demandons si ces services peuvent être fournis en toute sécurité et de manière plus économique par des médecins non urgentistes.

The equality and work well-being group at the Institute for Atmospheric and Earth System Research (INAR) has comprised a list of everyday behavior patterns that we shouldpay attention to when striving to make the workplace culture welcoming to people with diverse backgrounds. The examples in the list are broadly categorized as 1) Accept and be interested in people as multidimensional beings, restricting manifestation of fear of differences 2) Be aware of the space and time different people are taking in workplace meetings and social situations 3) Support a balance between work and private life and recovery from work equally for different genders as well as for people with different ages and family situations 4) Be aware that discussions focusing in competition, status, hierarchies, and comparing the achievements of people (those present or not present) make many people uncomfortable 5) Be aware that discussing people in terms of being ‘smart’, ‘intelligent’, ‘brilliant’, ‘genius’ is not gender and culture neutral 6) Avoid boss-centric atmosphere where the role of the boss is to decide alone and be revered by the rest 5) Avoid discussing the physical appearance or capabilities of other people even if they are not present 6) In both work related discussions and when telling jokes, stories and anecdotes in social situations, keep in mind you position with respect to people present when choosing the content or style 7) Don’t use gender specific words etc as a compliment: ‘real man’, ‘has got balls’, ‘strong for a woman’ 8) Remember to consider the language barrier(s) when a multinational set of people is present We recommend that the list is discussed, for example, in a departmental seminar: our approach was to have three members of the equality and work well being group perform some of the examples in the list as a dialogue, after which the audience discussed whether they have encountered something similar and how that has affected them. Afterwards, the complete list was distributed to the staff on the unit. We received encouraging feedback on the session with requests to organize similar events in the meetings of the individual INAR research groups. We want to remind that non-one is perfect, and our vision is not to construct strict foolproof rules to avoid all situations leading to feelings of discomfort. However, a little change goes a long way in making the working environment better for everyone. Opening the eyes to how other people might experience common encounters can be aided by using an externally constructed list of examples as a starting point.

Various culture media are used to propagate keratinocytes (KCs) in vitro. The COVID-19 pandemic resulted in supply chain shortages necessitating substitutions to standard laboratory protocols, which resulted in many laboratories having to use culture media different from those they typically use. We screened available media on the KC line N/TERT2G and found that biological responses varied considerably across three culture media: KC serum-free media, KC growth medium 2, and defined media. We observed qualitative and quantitative differences in proliferation; KCs cultured in defined media had significantly lower proliferative capacity. KC differentiation was assessed by western blot for CLDN1, occludin, cytokeratin-10, and loricrin. Elevated expression of differentiation markers was observed in cells cultured in either KC growth medium 2 or defined media compared with those in cells cultured in KC serum-free media. KC barrier function was measured by transepithelial electrical resistance. KCs cultured in KC growth medium 2 and defined media developed significantly higher transepithelial electrical resistance than those cultured in KC serum-free media, and when treated with IL-4 and IL-13 or IL-17A, we observed variable responses. HE staining on day 5 -post-differentiation showed greater epithelial thickness in KCs cultured in defined media and KC growth medium 2 than in those cultured in KC serum-free media. These findings show that the choice of culture media impacts the biological response of KCs in a manner that persists through differentiation in the same media.

Skin barrier dysfunction, a defining feature of atopic dermatitis (AD), arises from multiple interacting systems. In AD, skin inflammation is caused by host-environment interactions involving keratinocytes as well as tissue-resident immune cells such as type 2 innate lymphoid cells, basophils, mast cells, and T helper type 2 cells, which produce type 2 cytokines, including IL-4, IL-5, IL-13, and IL-31. Type 2 inflammation broadly impacts the expression of genes relevant for barrier function, such as intracellular structural proteins, extracellular lipids, and junctional proteins, and enhances

Sulfuric acid (H2SO4, SA) is the key compound in atmospheric new particle formation. Therefore, it is crucial to observe its concentration with sensitive instrumentation, such as chemical ionisation inlets coupled to Atmospheric Pressure interface Time-of-Flight mass spectrometers (CI-APi-TOF). However, there are environmental conditions and physical reasons when chemical ionisation cannot be used, for example in certain remote places or flight measurements with limitations regarding chemicals. In these cases, it is important to estimate the SA concentration based on ambient ion composition and concentration measurements that are achieved by APi-TOF alone. Here we derive a theoretical expression to estimate SA concentration and validate it with accurate CI-APi-TOF observations. The developed estimate works very well during daytime and with SA concentrations above 2⋅106 cm-3.

Life-threatening viral diseases such as eczema herpeticum (EH) and eczema vaccinatum (EV) occur in5% of individuals with atopic dermatitis (AD). The diagnosis of AD, however, excludes all individuals with AD from smallpox vaccination.We sought to identify circulatory and skin lipid biomarkers associated with EH and EV.Stratum corneum and plasma samples from 15 subjects with AD and a history of EH, 13 age- and gender-matched subjects with AD and without EH history, and 13 healthy nonatopic (NA) controls were analyzed by liquid chromatography tandem mass spectrometry for sphingolipid content. Sphingosine-1-phosphate (S1P) and ceramide levels were validated in plasma samples from the Atopic Dermatitis Vaccinia Network/Atopic Dermatitis Research Network repository (12 NA, 12 AD, 23 EH) and plasma from 7 subjects with EV and 7 matched subjects with AD. S1P lyase was downregulated in human primary keratinocytes to evaluate its effect on herpes simplex virus 1 (HSV-1) replication in vitro.The stratum corneum of patients with EH demonstrated significantly higher levels of free sphingoid bases than those in patients who were NA, indicating enhanced sphingolipid turnover in keratinocytes (P .05). Plasma from 2 independent cohorts of patients with EH had a significantly increased S1P/ceramide ratio in subjects with EH versus those with AD and or who were NA (P .01). The S1P level in plasma from subjects with EV was twice the level in plasma from subjects with AD (mean = 1,533 vs 732 pmol/mL; P .001). Downregulation of S1P lyase expression with silencing RNA led to an increased S1P level and doubled HSV-1 titer in keratinocytes.Our data point to long-term abnormalities in the S1P signaling system as a biomarker for previous disseminated viral diseases and a potential treatment target in recurring infections.

We study an approximation scheme for a variational theory of cohesive fracture in a one-dimensional setting. Here, the energy functional is approximated by a family of functionals depending on a small parameter $0 < \varepsilon \ll 1$ and on two fields: the elastic part of the displacement field and an eigendeformation field that describes the inelastic response of the material beyond the elastic regime. We measure the inelastic contributions of the latter in terms of a non-local energy functional. Our main result shows that, as $\varepsilon \to 0$, the approximate functionals $\Gamma$-converge to a cohesive zone model., Comment: Comments are welcome!

Aerosols can originate from different sources and undergo various formation pathways. New Particle formation (NPF) events occur when precursor vapors nucleate and vapors with low volatility condense on the critical nuclei enabling them to grow to cloud condensation nuclei (CCN) relevant sizes. As CCN, these aerosols affect the occurrence of clouds and their lifetime on local, regional and global level. Many studies have investigated new particle formation events from various sites ranging from urban areas, boreal forests to pristine locations; however, there is still a dearth of studies investigating coastal new particle formation, which is a complex phenomenon due to the dynamic and ever-changing atmospheric conditions at the coast. A comprehensive study of particle number distributions and aerosol forming precursor vapors was carried out in a coastal capital city of Finland, Helsinki, during the summer of 2019. The experimental setup comprising of a nitrate-based chemical ionization atmospheric pressure interface time of flight mass spectrometer (CI-APi-TOF), a neutral cluster-air ion spectrometer (NAIS) and a particle size magnifier (PSM) were housed in and around the SMEAR III station in Kumpula Science campus. SMEAR III is a unique site situated in a semi-urban yet coastal location. The period of experiment coincided with the cyanobacterial bloom in the coastal areas of Finland and in the Baltic Sea region. Our study recorded several regional NPF and aerosol burst events during this period. High concentrations of sulfuric acid was found to be associated with the regional NPF events whereas increasing iodic acid concentrations was mostly associated with the initiation of burst events. The sources of sulfuric acid and iodic acid has been carefully evaluated in this study.

In the high Arctic, the climate is warming faster than in the lower latitudes due to the Arctic amplification. Sea ice is melting and permafrost is thawing, and the scarce vegetation of the Arctic is changing rapidly. All these varying conditions will have an impact on possible emission sources of aerosol precursor gases, thus affecting the New Particle Formation (NPF) in the Arctic atmosphere, of which we still know very little. It is important to study the NPF events, which parameters affect the aerosol phase and how these newly formed aerosols can grow into cloud condensation nuclei sizes. Only then, it is possible to understand how climate change is affecting the aerosol population, clouds and regional climate of the pristine Arctic. The role of the precursor gases like Sulphuric Acid (SA), Iodic Acid (IA), Methane Sulphonic Acid (MSA) and Highly Oxygenated organic Molecules (HOM) in NPF in boreal and urban environments has been explored to a great extent. However, the role of these precursor gases in NPF events in remote locations - devoid of pollution sources and the vegetation - is still ambiguous. Therefore, it is crucial to conduct long-term measurements to study the composition and concentrations of aerosol precursors molecules, nanoparticles and air ions in remote and climatically fragile place like Ny-Ålesund in the Arctic. This research location is not only a natural pristine laboratory to understand the atmospheric processes but also acts as a climate mirror reflecting the most drastic changes happening in the atmosphere and cryosphere. In this study, we aim to enhance the understanding of the role of aerosol precursor gases in new particle formation in Ny-Ålesund, Svalbard. We have studied aerosol particle formation now for almost three years in the Ny-Ålesund research village in Svalbard (78° 55' 24.7368'' N, 11° 54' 35.6220'' E.) with the Neutral cluster and Air Ion Spectrometer (NAIS) measuring ~1-40 nm particles and ions. We have conducted measurements with a Chemical Ionization Atmospheric Pressure interface Time Of Flight (CI-APi-TOF) mass spectrometer to understand the chemical composition of organic precursors vapours and abundance of inorganic aerosol precursor gases such as SA, MSA and IA. Additionally, we have studied the emission and composition of volatile organic compounds on the site during summer-time. In this study, we report the time series concentrations of the most common aerosol precursor gases like SA, MSA, IA and HOM from the period 28.6.-25.7.2019, which are responsible for the initiation and/or growth of particles. The variability in the concentrations of these vapours is compared between NPF event and non-event days. The study explores also the role of meteorological parameters like wind speed, wind direction, temperature and humidity on NPF processes.

Significance Recycling of reactive iodine from heterogeneous processes on sea-salt aerosol was hypothesized over two decades ago to play an important role in the atmospheric cleansing capacity. However, the understanding of this mechanism has been limited to laboratory studies and has not been confirmed in the atmosphere until now. We present atmospheric measurement of gas-phase iodine interhalogen species and show that their production via heterogeneous processing on marine aerosols is remarkably fast. These observations reveal that the atmospheric recycling of atomic iodine through photolysis of iodine interhalogen species is more efficient than previously thought, which is ultimately expected to lead to higher ozone loss and faster new particle formation in the marine environment., Reactive iodine plays a key role in determining the oxidation capacity, or cleansing capacity, of the atmosphere in addition to being implicated in the formation of new particles in the marine boundary layer. The postulation that heterogeneous cycling of reactive iodine on aerosols may significantly influence the lifetime of ozone in the troposphere not only remains poorly understood but also heretofore has never been observed or quantified in the field. Here, we report direct ambient observations of hypoiodous acid (HOI) and heterogeneous recycling of interhalogen product species (i.e., iodine monochloride [ICl] and iodine monobromide [IBr]) in a midlatitude coastal environment. Significant levels of ICl and IBr with mean daily maxima of 4.3 and 3.0 parts per trillion by volume (1-min average), respectively, have been observed throughout the campaign. We show that the heterogeneous reaction of HOI on marine aerosol and subsequent production of iodine interhalogens are much faster than previously thought. These results indicate that the fast formation of iodine interhalogens, together with their rapid photolysis, results in more efficient recycling of atomic iodine than currently considered in models. Photolysis of the observed ICl and IBr leads to a 32% increase in the daytime average of atomic iodine production rate, thereby enhancing the average daytime iodine-catalyzed ozone loss rate by 10 to 20%. Our findings provide direct field evidence that the autocatalytic mechanism of iodine release from marine aerosol is important in the atmosphere and can have significant impacts on atmospheric oxidation capacity.

11 pags., 4 figs., New particle formation in the Arctic atmosphere is an important source of aerosol particles. Understanding the processes of Arctic secondary aerosol formation is crucial due to their significant impact on cloud properties and therefore Arctic amplification. We observed the molecular formation of new particles from low-volatility vapors at two Arctic sites with differing surroundings. In Svalbard, sulfuric acid (SA) and methane sulfonic acid (MSA) contribute to the formation of secondary aerosol and to some extent to cloud condensation nuclei (CCN). This occurs via ion-induced nucleation of SA and NH and subsequent growth by mainly SA and MSA condensation during springtime and highly oxygenated organic molecules during summertime. By contrast, in an ice-covered region around Villum, we observed new particle formation driven by iodic acid but its concentration was insufficient to grow nucleated particles to CCN sizes. Our results provide new insight about sources and precursors of Arctic secondary aerosol particles., The authors acknowledge European Research Council (GASPARCON, Grant no. 714621 and COALA, Grant no. 638703), Academy of Finland (Project nos. 296628, 306853, 317380, 316114, and 320094), INTERACT, European Regional Development Fund (project MOBTT42), Austrian Science Fund (FWF, Project J3951-N36), the European Union's Horizon 2020 Research and Innovation Program (Grant no. 689443) via project iCUPE (Integrative and Comprehensive Understanding on Polar Environments) and Project ERC-2016- COG 726349 CLIMAHAL, National Research Foundation (NRF) of the Ministry of Science, ICT and Future Planning (NRF-2018R1A2A1A19019281), Knut-and-Alice-Wallenberg Foundation within the Arctic Climate Across Scales (Project No. \,2016.0024), the Swedish EPA's (Naturvårdsverket) Environmental monitoring program (Miljöövervakning), the Swedish Research Council FORMAS (Project "Interplay between water, clouds and Aerosols in the Arctic," \# 2016-01427), Climate Change Tower – Integrated Project of the National Research Council of Italy and the National Interest Project by the Italian Minister of Education, University and Research (PRIN2007 and PRIN2009). The authors thank Department of Earth System Sciences and Technologies for the Environment, Department of Earth Sciences and Technology of the Environment of CNR and the doctoral program in atmospheric sciences at the University of Helsinki for financial support. Aarhus University acknowledge financial support from Danish Ministry of Environment and food and Ministry of Climate, Energy and Utilities by means of DANCEA.

EGU General Assembly 2020 in the online format, 4-8 May 2020

Trace iodine vapours have a significant impact on atmospheric chemistry, influencing catalytic ozone destruction and the HOx / NOx cycles. Oxidized iodine species also form aerosols in coastal and polar regions (O’Dowd et al, 2002), playing a direct role in Earth’s radiation balance. It was recently shown that iodic acid (HIO3) has a significant impact on coastal new particle formation processes (Sipilä et al., 2016). However, neutral HIO3 molecules have only been measured in two sites (Sipilä et al., 2016).In this study, a global observation of HIO3 has been carried out in ten sites around the globe, including city sites, Arctic and Antarctica sites, a remote island site, a coastal site and a boreal forest site. While the existence of HIO3 is unambiguously revealed in all of the sites, its concentration varies significantly among them. Dedicated laboratory experiments are required to examine the particle formation rates from iodine-containing species to be able to predict their global importance in particle formation, and further, in cloud condensation nuclei formation. O’Dowd, C. D. et al. Marine aerosol formation from biogenic iodine emissions. Nature 417, 632–6 (2002)Sipilä, M. et al. Molecular-scale evidence of aerosol particle formation via sequential addition of HIO3. Nature 537, 532–534 (2016).

Highly-oxygenated organic molecules (HOMs) contribute substantially to the formation and growth of atmospheric aerosol particles, which affect air quality, human health and Earth's climate. HOMs are formed by rapid, gas-phase autoxidation of volatile organic compounds (VOCs) such as α-pinene, the most abundant monoterpene in the atmosphere. Due to their abundance and low volatility, HOMs can play an important role for new-particle formation (NPF) and the early growth of atmospheric aerosols, even without any further assistance of other low-volatility compounds such as sulfuric acid. Both the autoxidation reaction forming HOMs and their new-particle formation rates are expected to be strongly dependent on temperature. However, experimental data on both effects are limited. Dedicated experiments were performed at the CLOUD (Cosmics Leaving OUtdoor Droplets) chamber at CERN to address this question. In this study, we show that a decrease in temperature (from +25 to −50 °C) results in a reduced HOM yield and reduced oxidation state of the products, whereas the new-particle formation rates (J1.7 nm) increase substantially. Measurements with two different chemical ionization mass spectrometers (using nitrate and protonated water as reagent ion, respectively) provide the molecular composition of the gaseous oxidation products and a 2-dimensional volatility basis set model (2D-VBS) provides their volatility distribution. The HOM yield decreases with temperature from 6.2 % at 25 °C to 0.7 % at −50 °C. However, there is a strong reduction of the saturation vapor pressure of each oxidation state as the temperature is reduced. Overall, the reduction in volatility with temperature leads to an increase in the nucleation rates by up to three orders of magnitude at −50 °C compared with 25 °C. In addition, the enhancement of the nucleation rates by ions decreases with decreasing temperature, since the neutral molecular clusters have increased stability against evaporation. The resulting data quantify how the interplay between the temperature-dependent oxidation pathways and the associated vapor pressures affect biogenic new-particle formation at the molecular level. Our measurements therefore improve our understanding of pure biogenic new-particle formation for a wide range of tropospheric temperatures and precursor concentrations.

Ions enhance the formation rate of atmospheric aerosol particles, which play an important role in Earth’s radiative balance. Ion-induced nucleation involves the stepwise accretion of neutral monomers onto a molecular cluster containing an ion, which helps to stabilize the cluster against evaporation. Although theoretical frameworks exist to calculate the collision rate coefficients between neutral molecules and ions, they need to be experimentally confirmed, ideally under atmospherically relevant conditions of around 1000 ion pairs cm−3. Here, in experiments performed under atmospheric conditions in the CERN CLOUD chamber, we have measured the collision rate coefficients between neutral iodic acid (HIO3) monomers and charged iodic acid molecular clusters containing up to 11 iodine atoms. Three methods were analytically derived to calculate ion-polar molecule collision rate coefficients. After evaluation with a kinetic model, the 50% appearance time method is found to be the most robust. The measured collision rate coefficient, averaged over all iodine clusters, is (2.4 ± 0.8)×10−9 cm3 s−1, which is close to the expectation from the surface charge capture theory.

We study pointwise convergence properties of weakly* converging sequences $\{u_i\}_{i \in {\mathbb N}}$ in $\mathrm{BV}({\mathbb R}^n)$. We show that, after passage to a suitable subsequence (not relabeled), we have pointwise convergence $u_i^*(x)\to u^*(x)$ of the precise representatives for all $x\in {\mathbb R}^n \setminus E$, where the exceptional set $E \subset {\mathbb R}^n$ has on the one hand Hausdorff dimension at most $n-1$, and is on the other hand also negligible with respect to the Cantor part of $|D u|$. Furthermore, we discuss the optimality of these results., Comment: 22 pages, comments are welcome

In the present-day atmosphere, sulfuric acid is the most important vapour for aerosol particle formation and initial growth. However, the growth rates of nanoparticles (

In this paper linear stochastic transport and continuity equations with drift in critical $L^{p}$ spaces are considered. In this situation noise prevents shocks for the transport equation and singularities in the density for the continuity equation, starting from smooth initial conditions. Specifically, we first prove a result of Sobolev regularity of solutions, which is false for the corresponding deterministic equation. The technique needed to reach the critical case is new and based on parabolic equations satisfied by moments of first derivatives of the solution, opposite to previous works based on stochastic flows. The approach extends to higher order derivatives under more regularity of the drift term. By a duality approach, these regularity results are then applied to prove uniqueness of weak solutions to linear stochastic continuity and transport equations and certain well-posedness results for the associated stochastic differential equation (sDE) (roughly speaking, existence and uniqueness of flows and their $C^\alpha$ regularity, strong uniqueness for the sDE when the initial datum has diffuse law). Finally, we show two types of examples: on the one hand, we present well-posed sDEs, when the corresponding ODEs are ill-posed, and on the other hand, we give a counterexample in the supercritical case., Comment: 64 pages, 1 figure, comments are welcome

We consider a class of vectorial integrals with linear growth, where, as a key feature, some degenerate/singular behavior is allowed. For generalized minimizers of these integrals in BV, we establish interior gradient regularity, and | as a consequence | uniqueness up to constants. In particular, these results apply, for 1 < p < 2, to the singular model integrals Z (1 + jrw(x)j p ) 1 p dx

We report on new techniques and results in the regularity theory of general non-uniformly elliptic variational integrals. By means of a new potential theoretic approach we reproduce, in the non-uniformly elliptic setting, the optimal criteria for Lipschitz continuity known in the uniformly elliptic one and provide a unified approach between non-uniformly and uniformly elliptic problems.

We study the minimization of convex, variational integrals of linear growth among all functions in the Sobolev space $W^{1,1}$ with prescribed boundary values (or its equivalent formulation as a boundary value problem for a degenerately elliptic Euler--Lagrange equation). Due to insufficient compactness properties of these Dirichlet classes, the existence of solutions does not follow in a standard way by the direct method in the calculus of variations and in fact might fail, as it is well-known already for the non-parametric minimal surface problem. Assuming radial structure, we establish a necessary and sufficient condition on the integrand such that the Dirichlet problem is in general solvable, in the sense that a Lipschitz solution exists for any regular domain and all prescribed regular boundary values, via the construction of appropriate barrier functions in the tradition of Serrin's paper [19]., Comment: 19 pages, 2 figures. Comments are welcome!