Nitrous oxide (N2O) is a potent greenhouse gas (GHG) and ozone destructing agent; yet global estimates of N2O emissions are uncertain. Marine N2O stems from nitrification and denitrification ...processes which depend on organic matter cycling and dissolved oxygen (O2). We introduce N2O as an obligate intermediate product of denitrification and as an O2‐dependent by‐product from nitrification in the Bern3D ocean model. A large model ensemble is used to probabilistically constrain modern and to project marine N2O production for a low (Representative Concentration Pathway (RCP)2.6) and high GHG (RCP8.5) scenario extended to A.D. 10,000. Water column N2O and surface ocean partial pressure N2O data serve as constraints in this Bayesian framework. The constrained median for modern N2O production is 4.5 (±1σ range: 3.0 to 6.1) Tg N yr−1, where 4.5% stems from denitrification. Modeled denitrification is 65.1 (40.9 to 91.6) Tg N yr−1, well within current estimates. For high GHG forcing, N2O production decreases by 7.7% over this century due to decreasing organic matter export and remineralization. Thereafter, production increases slowly by 21% due to widespread deoxygenation and high remineralization. Deoxygenation peaks in two millennia, and the global O2 inventory is reduced by a factor of 2 compared to today. Net denitrification is responsible for 7.8% of the long‐term increase in N2O production. On millennial timescales, marine N2O emissions constitute a small, positive feedback to climate change. Our simulations reveal tight coupling between the marine carbon cycle, O2, N2O, and climate.
Key Points
A new parameterization for marine N2O production by nitrification and denitrification is developed
Modern marine N2O emissions are constrained by observations to 4.3 (2.8 to 5.9) Tg N yr‐1
Probabilistic projections yield massive reductions in O2 and a long‐term increase in N2O emissions
Innate lymphoid cells (ILC) are a new family of innate immune cells that have emerged as important regulators of tissue homeostasis and inflammation. However, limited data are available concerning ...the relative abundance and characteristics of ILC in the human lung.
The aim of this study was to characterize and enumerate the different ILC subsets in human lung by multi-color flow cytometry.
Within the CD45+ Lin- CD127+ pulmonary ILC population, we identified group 1 (ILC1), group 2 (ILC2) and group 3 (ILC3) innate lymphoid cells using specific surface markers (i.e. IL12Rβ2, CRTH2 and CD117 respectively) and key transcription factors (i.e. T-bet, GATA-3 and RORγT respectively). Based on the presence of NKp44, ILC3 were further subdivided in natural cytotoxicity receptor (NCR)+ and NCR- ILC3. In addition, we demonstrated the production of signature cytokines IFN-γ, IL-5, IL-17A, IL-22 and GM-CSF in the pulmonary ILC population. Interestingly, we observed a tendency to a higher frequency of NCR- ILC3 in lungs of patients with chronic obstructive pulmonary disease (COPD) compared with controls.
We show that the three main ILC subsets are present in human lung. Importantly, the relative abundance of ILC subsets tended to change in COPD patients in comparison to control individuals.
Chronic obstructive pulmonary disease (COPD) is a heterogeneous syndrome associated with abnormal inflammatory immune responses of the lung to noxious particles and gases. Cigarette smoke activates ...innate immune cells such as epithelial cells and macrophages by triggering pattern recognition receptors, either directly or indirectly via the release of damage-associated molecular patterns from stressed or dying cells. Activated dendritic cells induce adaptive immune responses encompassing T helper (Th1 and Th17) CD4+ T cells, CD8+ cytotoxicity, and B-cell responses, which lead to the development of lymphoid follicles on chronic inflammation. Viral and bacterial infections not only cause acute exacerbations of COPD, but also amplify and perpetuate chronic inflammation in stable COPD via pathogen-associated molecular patterns. We discuss the role of autoimmunity (autoantibodies), remodelling, extracellular matrix-derived fragments, impaired innate lung defences, oxidative stress, hypoxia, and dysregulation of microRNAs in the persistence of the pulmonary inflammation despite smoking cessation.
Background Asthma is classified according to severity and inflammatory phenotype and is likely to be distinguished by specific microRNA (miRNA) expression profiles. Objective We sought to associate ...miRNA expression in sputum supernatants with the inflammatory cell profile and disease severity in asthmatic patients. Methods We investigated miRNA expression in sputum supernatants of 10 healthy subjects, 17 patients with mild-to-moderate asthma, and 9 patients with severe asthma using high-throughput, stem-loop, reverse transcriptase quantitative real-time PCR miRNA expression profiling (screening cohort, n = 36). Differentially expressed miRNAs were validated in an independent cohort (n = 60; 10 healthy subjects and 50 asthmatic patients). Cellular miRNA origin was examined by using in situ hybridization and reverse transcriptase quantitative real-time PCR. The functional role of miRNAs was assessed by using in silico analysis and in vitro transfecting miRNA mimics in human bronchial epithelial cells. Results In 2 independent cohorts expression of miR-629-3p, miR-223-3p, and miR-142-3p was significantly upregulated in sputum of patients with severe asthma compared with that in healthy control subjects and was highest in patients with neutrophilic asthma. Expression of the 3 miRNAs was associated with sputum neutrophilia, and miR-223-3p and miR-142-3p expression was associated also with airway obstruction (FEV1 /forced vital capacity). Expression of miR-629-3p was localized in the bronchial epithelium, whereas miR-223-3p and miR-142-3p were expressed in neutrophils, monocytes, and macrophages. Transfecting human bronchial epithelial cells with miR-629-3p mimic induced epithelial IL-8 mRNA and protein expression. IL-1β and IL-8 protein levels were significantly increased in sputum of patients with severe asthma and were positively associated with sputum neutrophilia. Conclusions Expression of miR-223-3p, miR-142-3p, and miR-629-3p is increased in sputum of patients with severe asthma and is linked to neutrophilic airway inflammation, suggesting that these miRNAs contribute to this asthma inflammatory phenotype.
Information on the relationship between cumulative fossil CO2 emissions and multiple climate targets is essential to design emission mitigation and climate adaptation strategies. In this study, the ...transient response of a climate or environmental variable per trillion tonnes of CO2 emissions, termed TRE, is quantified for a set of impact-relevant climate variables and from a large set of multi-forcing scenarios extended to year 2300 towards stabilization. An ∼ 1000-member ensemble of the Bern3D-LPJ carbon–climate model is applied and model outcomes are constrained by 26 physical and biogeochemical observational data sets in a Bayesian, Monte Carlo-type framework. Uncertainties in TRE estimates include both scenario uncertainty and model response uncertainty. Cumulative fossil emissions of 1000 Gt C result in a global mean surface air temperature change of 1.9 °C (68 % confidence interval (c.i.): 1.3 to 2.7 °C), a decrease in surface ocean pH of 0.19 (0.18 to 0.22), and a steric sea level rise of 20 cm (13 to 27 cm until 2300). Linearity between cumulative emissions and transient response is high for pH and reasonably high for surface air and sea surface temperatures, but less pronounced for changes in Atlantic meridional overturning, Southern Ocean and tropical surface water saturation with respect to biogenic structures of calcium carbonate, and carbon stocks in soils. The constrained model ensemble is also applied to determine the response to a pulse-like emission and in idealized CO2-only simulations. The transient climate response is constrained, primarily by long-term ocean heat observations, to 1.7 °C (68 % c.i.: 1.3 to 2.2 °C) and the equilibrium climate sensitivity to 2.9 °C (2.0 to 4.2 °C). This is consistent with results by CMIP5 models but inconsistent with recent studies that relied on short-term air temperature data affected by natural climate variability.
•The DPF code predicts well the Weber numbers within a droplet-laden compressor flow.•The applicability of a simplified implementation of the NLTAB3 model is approved.•Maximum deformation plots ...reveal the disparity between applied TAB and NLTAB3 model.•Breakup criteria from shock tube results show deficiency in gradually accelerated flow.•One recombined secondary breakup model is identified to reproduce experimental results.
Different secondary breakup models are assessed to simulate gas-droplet flows that involve large velocity gradients and yield relative velocities between both phases (e.g. wet compression flows). For the simulation of such two-phase flows, the Euler-Lagrange approach is employed, using a commercial flow solver and an in-house FORTRAN source code. The droplet deformation models: Taylor Analogy Breakup (TAB) and a simplified implementation of the Non-linear TAB (NLTAB3) are each tested with two different breakup criteria to evaluate the adequacy for considered droplet-laden compressor flows. A detailed atomization model is applied to account for a temporal fragmentation process. By contrast with experimental results good agreements are found for Weber number distributions in the inter blade flow. Though, different sensitivities and locations for secondary breakup occurrence are observed in dependence of applied droplet deformation model and breakup criterion. In spite of incisive model simplifications to reduce its computational effort, the non-linear droplet deformation model (NLTAB3) in combination with a physically substantiated breakup criterion showed good agreements with qualitative experimental data.
The response of forest growth to climate variability varies along environmental gradients. A growth increase and decrease with warming is usually observed in cold‐humid and warm‐dry regions, ...respectively. However, it remains poorly known where the sign of these temperature effects switches. Here we introduce a newly developed European tree ring network that has been specifically collected to reconstruct forest aboveground biomass increment (ABI). We quantify, how the long‐term (1910–2009) interannual variability of ABI depends on local mean May–August temperature and test, if a dynamic global vegetation model ensemble reflects the resulting patterns. We find that sites at 8 °C mean May–August temperature increase ABI on average by 5.7 ± 1.3%, whereas sites at 20 °C decrease ABI by 3.0 ± 1.8% m−2 year−1 Δ°C−1. A threshold temperature between beneficial and detrimental effects of warming and the associated increase in water demand on tree growth emerged at 15.9 ± 1.4 °C mean May–August temperature. Because interannual variability increases proportionally with mean growth rate—that is, the coefficient of variation stays constant—we were able to validate these findings with a much larger tree ring data set that had been established following classic dendrochronological sampling schemes. While the observed climate sensitivity pattern is well reflected in the dynamic global vegetation model ensemble, there is a large spread of threshold temperatures between the individual models. Also, individual models disagree strongly on the magnitude of climate impact at the coldest and warmest locations, suggesting where model improvement is most needed to more accurately predict forest growth and effectively guide silvicultural practices.
Key Points
Central and Northern European forest growth is expected to benefit (suffer) from additional warming in regions with a mean growing season temperature below (above) 15.9 plus‐minus 1.4 degrees Celsius
A vegetation model ensemble mean agrees with this threshold but is too sensitive to temperature changes at coldest and warmest locations
Model improvements are needed to predict forest growth more accurately and guide silvicultural practices
Atmospheric CO2 was ∼90 ppmv lower at the Last Glacial Maximum (LGM) compared to the late Holocene, but the mechanisms responsible for this change remain elusive. Here we employ a carbon ...isotope‐enabled Earth System Model to investigate the role of ocean circulation in setting the LGM oceanic δ13C distribution, thereby improving our understanding of glacial/interglacial atmospheric CO2 variations. We find that the mean ocean δ13C change can be explained by a 378 ± 88 Gt C(2σ) smaller LGM terrestrial carbon reservoir compared to the Holocene. Critically, in this model, differences in the oceanic δ13C spatial pattern can only be reconciled with a LGM ocean circulation state characterized by a weak (10–15 Sv) and relatively shallow (2000–2500 m) North Atlantic Deep Water cell, reduced Antarctic Bottom Water transport (≤10 Sv globally integrated), and relatively weak (6–8 Sv) and shallow (1000–1500 m) North Pacific Intermediate Water formation. This oceanic circulation state is corroborated by results from the isotope‐enabled Bern3D ocean model and further confirmed by high LGM ventilation ages in the deep ocean, particularly in the deep South Atlantic and South Pacific. This suggests a poorly ventilated glacial deep ocean which would have facilitated the sequestration of carbon lost from the terrestrial biosphere and atmosphere.
Key Points
Oceanic δ13C model/data comparison suggests weaker and shallower North Atlantic Deep Water at the LGM compared to the Holocene
δ13C and ventilation ages model/data comparison further suggests very weak Antarctic Bottom Water (AABW) transport at the LGM
A poorly ventilated ocean at the LGM would contribute to enhanced deep ocean carbon storage and particularly respired carbon
Mammalian mitochondrial DNA (mtDNA) is packaged by mitochondrial transcription factor A (TFAM) into mitochondrial nucleoids that are of key importance in controlling the transmission and expression ...of mtDNA. Nucleoid ultrastructure is poorly defined, and therefore we used a combination of biochemistry, superresolution microscopy, and electron microscopy to show that mitochondrial nucleoids have an irregular ellipsoidal shape and typically contain a single copy of mtDNA. Rotary shadowing electron microscopy revealed that nucleoid formation in vitro is a multistep process initiated by TFAM aggregation and cross-strand binding. Superresolution microscopy of cultivated cells showed that increased mtDNA copy number increases nucleoid numbers without altering their sizes. Electron cryo-tomography visualized nucleoids at high resolution in isolated mammalian mitochondria and confirmed the sizes observed by superresolution microscopy of cell lines. We conclude that the fundamental organizational unit of the mitochondrial nucleoid is a single copy of mtDNA compacted by TFAM, and we suggest a packaging mechanism.
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