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Dimethyl sulfide (DMS) is an important trace gas emitted from the ocean. The oxidation of DMS has long been recognised as being important for global climate through the role DMS plays in setting the sulfate aerosol background in the troposphere. However, the mechanisms in which DMS is oxidised are very complex and have proved elusive to accurately determine in spite of decades of research. As a result the representation of DMS oxidation in global chemistry–climate models is often greatly simplified. Recent field observations and laboratory and ab initio studies have prompted renewed efforts in understanding the DMS oxidation mechanism, with implications for constraining the uncertainty in the oxidation mechanism of DMS as incorporated in global chemistry–climate models. Here we build on recent evidence and develop a new DMS mechanism for inclusion in the UK Chemistry Aerosol (UKCA) chemistry–climate model. We compare our new mechanism (CS2-HPMTF) to a number of existing mechanisms used in UKCA (including the highly simplified three-reactions–two-species mechanism used in CMIP6 studies with the model) and to a range of recently developed mechanisms reported in the literature through a series of global and box model experiments. Global model runs with the new mechanism enable us to simulate the global distribution of hydroperoxylmethyl thioformate (HPMTF), which we calculate to have a burden of 2.6–26 Gg S (in good agreement with the literature range of 0.7–18 Gg S). We show that the sinks of HPMTF dominate uncertainty in the budget, not the rate of the isomerisation reaction forming it and that, based on the observed DMS / HPMTF ratio from the global surveys during the NASA Atmospheric Tomography mission (ATom), rapid cloud uptake of HPMTF worsens the model–observation comparison. Our box model experiments highlight that there is significant variance in simulated secondary oxidation products from DMS across mechanisms used in the literature, with significant divergence in the sensitivity of the rates of formation of these products to temperature exhibited; especially for methane sulfonic acid (MSA). Our global model studies show that our updated DMS scheme performs better than the current scheme used in UKCA when compared against a suite of surface and aircraft observations. However, sensitivity studies underscore the need for further laboratory and observational constraints. In particular our results suggest that as a priority long-term DMS observations be made to better constrain the highly uncertain inputs into the system and that laboratory studies be performed that address (1) the uptake of HPMTF onto aerosol surfaces and the products of this reaction and (2) the kinetics and products of the following reactions: CH3SO3 decomposition, CH3S + O2, CH3SOO decomposition, and CH3SO + O3.

We present the first incorporation of the Common Representative Intermediates version 2.2 tropospheric chemistry mechanism, CRI v2.2, combined with stratospheric chemistry, into the global chemistry–climate United Kingdom Chemistry and Aerosols (UKCA) model to give the CRI-Strat 2 mechanism. A rigorous comparison of CRI-Strat 2 with the earlier version, CRI-Strat, is performed in UKCA in addition to an evaluation of three mechanisms, CRI-Strat 2, CRI-Strat and the standard UKCA chemical mechanism, StratTrop v1.0, against a wide array of surface and airborne chemical data. CRI-Strat 2 comprises a state-of-the-art isoprene scheme, optimized against the Master Chemical Mechanism v3.3.1, which includes isoprene peroxy radical isomerization, HOx recycling through the addition of photolabile hydroperoxy aldehydes (HPALDs), and isoprene epoxy diol (IEPOX) formation. CRI-Strat 2 also features updates to several rate constants for the inorganic chemistry, including the reactions of inorganic nitrogen and O(1D). The update to the isoprene chemistry in CRI-Strat 2 increases OH over the lowest 500 m in tropical forested regions by 30 %–50 % relative to CRI-Strat, leading to an improvement in model–observation comparisons for surface OH and isoprene relative to CRI-Strat and StratTrop. Enhanced oxidants also cause a 25 % reduction in isoprene burden and an increase in oxidation fluxes of isoprene and other biogenic volatile organic compounds (BVOCs) at low altitudes with likely impacts on subsequent aerosol formation, atmospheric lifetime, and climate. By contrast, updates to the rate constants of O(1D) with its main reactants relative to CRI-Strat reduces OH in much of the free troposphere, producing a 2 % increase in the methane lifetime, and increases the tropospheric ozone burden by 8 %, primarily from reduced loss via O(1D)+H2O. The changes to inorganic nitrogen reaction rate constants increase the NOx burden by 4 % and shift the distribution of nitrated species closer to that simulated by StratTrop. CRI-Strat 2 is suitable for multi-decadal model integrations and the improved representation of isoprene chemistry provides an opportunity to explore the consequences of HOx recycling in the United Kingdom Earth System Model (UKESM1). This new mechanism will enable a re-evaluation of the impact of BVOCs on the chemical composition of the atmosphere and further probe the feedback between the biosphere and the climate.

The evolution of volcanic sulfur and the resulting radiative forcing following explosive volcanic eruptions is well understood. Petrological evidence suggests that significant amounts of halogens may be co-emitted alongside sulfur in some explosive volcanic eruptions, and satellite evidence indicates that detectable amounts of these halogens may reach the stratosphere. In this study, we utilise an aerosol–chemistry–climate model to simulate stratospheric volcanic eruption emission scenarios of two sizes, both with and without co-emission of volcanic halogens, in order to understand how co-emitted halogens may alter the life cycle of volcanic sulfur, stratospheric chemistry, and the resulting radiative forcing. We simulate a large (10 Tg of SO2) and very large (56 Tg of SO2) sulfur-only eruption scenario and a corresponding large (10 Tg SO2, 1.5 Tg HCl, 0.0086 Tg HBr) and very large (56 Tg SO2, 15 Tg HCl, 0.086 Tg HBr) co-emission eruption scenario. The eruption scenarios simulated in this work are hypothetical, but they are comparable to Volcanic Explosivity Index (VEI) 6 (e.g. 1991 Mt Pinatubo) and VEI 7 (e.g. 1257 Mt Samalas) eruptions, representing 1-in-50–100-year and 1-in-500–1000-year events, respectively, with plausible amounts of co-emitted halogens based on satellite observations and volcanic plume modelling. We show that co-emission of volcanic halogens and sulfur into the stratosphere increases the volcanic effective radiative forcing (ERF) by 24 % and 30 % in large and very large co-emission scenarios compared to sulfur-only emission. This is caused by an increase in both the forcing from volcanic aerosol–radiation interactions (ERFari) and composition of the stratosphere (ERFclear,clean). Volcanic halogens catalyse the destruction of stratospheric ozone, which results in significant stratospheric cooling, offsetting the aerosol heating simulated in sulfur-only scenarios and resulting in net stratospheric cooling. The ozone-induced stratospheric cooling prevents aerosol self-lofting and keeps the volcanic aerosol lower in the stratosphere with a shorter lifetime. This results in reduced growth by condensation and coagulation and a smaller peak global-mean effective radius compared to sulfur-only simulations. The smaller effective radius found in both co-emission scenarios is closer to the peak scattering efficiency radius of sulfate aerosol, and thus co-emission of halogens results in larger peak global-mean ERFari (6 % and 8 %). Co-emission of volcanic halogens results in significant stratospheric ozone, methane, and water vapour reductions, resulting in significant increases in peak global-mean ERFclear,clean (> 100 %), predominantly due to ozone loss. The dramatic global-mean ozone depletion simulated in large (22 %) and very large (57 %) co-emission scenarios would result in very high levels of UV exposure on the Earth's surface, with important implications for society and the biosphere. This work shows for the first time that co-emission of plausible amounts of volcanic halogens can amplify the volcanic ERF in simulations of explosive eruptions. It highlights the need to include volcanic halogen emissions when simulating the climate impacts of past or future eruptions, as well as the necessity to maintain space-borne observations of stratospheric compounds to better constrain the stratospheric injection estimates of volcanic eruptions.

The evolution of tropospheric ozone from 1850 to 2100 has been studied using data from Phase 6 of the Coupled Model Intercomparison Project (CMIP6). We evaluate long-term changes using coupled atmosphere–ocean chemistry–climate models, focusing on the CMIP Historical and ScenarioMIP ssp370 experiments, for which detailed tropospheric-ozone diagnostics were archived. The model ensemble has been evaluated against a suite of surface, sonde and satellite observations of the past several decades and found to reproduce well the salient spatial, seasonal and decadal variability and trends. The multi-model mean tropospheric-ozone burden increases from 247 ± 36 Tg in 1850 to a mean value of 356 ± 31 Tg for the period 2005–2014, an increase of 44 %. Modelled present-day values agree well with previous determinations (ACCENT: 336 ± 27 Tg; Atmospheric Chemistry and Climate Model Intercomparison Project, ACCMIP: 337 ± 23 Tg; Tropospheric Ozone Assessment Report, TOAR: 340 ± 34 Tg). In the ssp370 experiments, the ozone burden increases to 416 ± 35 Tg by 2100. The ozone budget has been examined over the same period using lumped ozone production (PO3) and loss (LO3) diagnostics. Both ozone production and chemical loss terms increase steadily over the period 1850 to 2100, with net chemical production (PO3-LO3) reaching a maximum around the year 2000. The residual term, which contains contributions from stratosphere–troposphere transport reaches a minimum around the same time before recovering in the 21st century, while dry deposition increases steadily over the period 1850–2100. Differences between the model residual terms are explained in terms of variation in tropopause height and stratospheric ozone burden.

Abstract We document the implementation of the Common Representative Intermediates Mechanism version 2, reduction 5 into the United Kingdom Chemistry and Aerosol model (UKCA) version 10.9. The mechanism is merged with the stratospheric chemistry already used by the StratTrop mechanism, as used in UKCA and the UK Earth System Model, to create a new CRI‐Strat mechanism. CRI‐Strat simulates a more comprehensive treatment of non‐methane volatile organic compounds (NMVOCs) and provides traceability with the Master Chemical Mechanism. In total, CRI‐Strat simulates the chemistry of 233 species competing in 613 reactions (compared to 87 species and 305 reactions in the existing StratTrop mechanism). However, while more than twice as complex than StratTrop, the new mechanism is only 75% more computationally expensive. CRI‐Strat is evaluated against an array of in situ and remote sensing observations and simulations using the StratTrop mechanism in the UKCA model. It is found to increase production of ozone near the surface, leading to higher ozone concentrations compared to surface observations. However, ozone loss is also greater in CRI‐Strat, leading to less ozone away from emission sources and a similar tropospheric ozone burden compared to StratTrop. CRI‐Strat also produces more carbon monoxide than StratTrop, particularly downwind of biogenic VOC emission sources, but has lower burdens of nitrogen oxides as more is converted into reservoir species. The changes to tropospheric ozone and nitrogen budgets are sensitive to the treatment of NMVOC emissions, highlighting the need to reduce uncertainty in these emissions to improve representation of tropospheric chemical composition.

Introduction: Given the shortage of studies on parental perceived benefits of OROS-methylphenidate treatment in Asian populations, we assessed parental response to OROS-methylphenidate treatment of Korean children with attention- deficit/hyperactivity disorder (ADHD), in relation to children's academic performance and behavioral symptoms as well as parental rearing stress and depressive symptoms. Methods: We enrolled 132 medication-naïve children with ADHD into a multicenter, openlabel, 12-week trial of OROS-MPH. The outcome measures were the ADHD rating scale-IV (ADHDRS), the comprehensive attention test and academic performance rating scale, and the clinical global impression (CGI)- severity/improvement instrument (for the children) and Beck depression inventory and parenting stress index (for their parents). Results: We found parent-perceived improvements in children's ADHD-related behavioral symptoms and academic function and their parents' depressive symptoms and parenting stress. Investigator-rated ADHD symptoms and subjects' neuropsychological function were also improved (p < 0.001). Discussion: Parents of Korean children with ADHD perceive that OROS-methylphenidate treatment improves their children's academic function and behavior as well as their own childrearing stress and emotional state. These findings must be interpreted with caution, due to a non-comparative open-label trial. [ABSTRACT FROM AUTHOR]

Streptolysin O (SLO) is known to bacterial proteins that form very large pores in the plasma membrane of mammalian cells. SLO has been used in the delivery of proteins into living cells following permeabilization. The objective of this study was to investigate the effect of permeabilization of donor cells using SLO on in vitro development of porcine reconstructed embryos. Porcine fetal fibroblast cells were treated with Ca2?-free DMEM medium containing 200 ng mL-1 of SLO for 50 min before or after trypsinization. Those SLO-treated donor cells were injected into enucleated oocytes, fused with 2 DC pulses (1.2 kV cm-1, 30 s) and cultured in procine zygote medium-3 (PZM-3) for 6 days. In vitro development of the reconstructed embryos was examined. SLO treatment after trypsinzation significantly increased (P < 0.05) the percentage of fusion rates and blastocyst developmental rates compared with that before trypsinization or in the nontreated group. Additionally there were no significant differences in fusion rates, cleavage rates, blastocyst developmental rates, and total cell number of blastocysts between the SLO-treated group before trypsinzation and the nontreated group. Next, after the trypsinzation treatment, fetal fibroblast cells were incubated in Ca2?-free DMEM containing 200 ng mL-1 of SLO for 0, 30, 50, and 70 min and SLO-treated donor cells were also tested for fusion rate and developmental capability following reconstruction. The 50-min group of SLO-treated cells significantly increased (P < 0.05) the percentage of fusion rates (90.6 vs. 77.6, 85.4, and 78.5?) and blastocyst developmental rates (24.7 vs. 13.5, 11.2, and 13.5?) compared with the other groups (Table 1). However, there was no significant difference in the total cell number of blastocysts among SLO-treated groups. Although cleavage rates the in SLO-treated groups were not significantly different from those of the nontreated group, there the cleavage rates were slightly in SLO-treated groups. In conclusion, permeabilization of porcine fetal fibroblast cells with SLO improves the fusion rates and in vitro development of porcine reconstructed embryos. [ABSTRACT FROM AUTHOR]

Transgenic animals can be generated by nuclear transfer with genetically modified somatic cells in which the essential procedure of transgene transfection is required. Most transgene vectors are constructed to contain transgene and drug-resistant genes to enrich for somatic cells in which transgene integration has occurred. However, construction of transgene vectors along with drug-resistant genes may not be easy, due to inappropriate restriction sites. Therefore, in this study, two separate constructs, human tPA cDNA fused to ?-casein promoter sequence as a transgene vector and neomycin-resistant gene (Neor) driven by PGK promoter as a drug-selectable gene, were co-transfected into pig and goat fetal fibroblast cells to estimate the efficiency of transgene transfection following G418 selection. First, goat fetal fibroblasts (GFF) and pig fetal fibroblasts (PFF) were tested for G418 resistance with different concentrations of G418. The pertinent concentrations of G418 were 800 g mL-1 for GFF and 200 g mL-1 for PFF. The linearized tPA vector and Neor gene vector were co-transfected into goat fetal fibroblasts and pig fetal fibroblasts with FuGENE6 transfection reagent (Roche Diagnostics, Mannheim, Germany). The cells were selected following exposure of 800 g mL-1 and 200 g mL-1 G418 for GFF and PFF, respectively, for 14 days. Cell colonies surviving G418 selection were assayed by PCR amplification with tPA-specific primers. Initially 2 106 GFF and PFF were transfected. Resistant colonies were counted and transferred to 24-well plates for expansion and PCR analysis. The results of co-transfection experiments are summarized in Table 1. The transfection of 2 106 GFF and PFF yielded an estimated 96 and 93 colonies, respectively, which survived as the G418 selection. However, 54 colonies of GFF and 39 colonies of PFF proliferated during expansion and were subjected to PCR analysis. Twenty-three and 5 of these colonies were identified to contain tPA transgene in GFF and PFF colonies, respectively. Transfection frequencies for tPA gene were 42.6? and 12.8? in GFF and PFF, respectively. These results suggest that co-transfection of transgene vector with Neor gene can be an alternative method for transfection of transgenes into fetal fibroblast cells. [ABSTRACT FROM AUTHOR]