Atmospheric Partial Pressure Research Articles

Effect of thermal treatment on TiO2 varistor properties in different atmospheres

TiO2 is a typical nonstoichiometric compound and defects such as oxygen vacancies in TiO2 grains and at TiO2 grain boundaries are very sensitive to the oxygen partial pressure in the environment. In this paper, commercial TiO2 doped with Nb2O5 and Bi2O3 was used as the raw material to prepare TiO2 varistors. The samples were thermally treated in three kinds of atmospheres: H2, vacuum, and O2 at 600°C. In the two low oxygen partial pressure atmospheres of vacuum and H2, due to the volatilization of lattice oxygen in TiO2, the oxygen vacancy concentration and the number of semiconducting grains increase, while the height and width of the potential barrier and the varistor voltage decrease. After the oxygen atmosphere thermal treatment, the acceptor state density and the height and width of the potential barriers increase, the conductivity decreases, and the varistor voltage improves significantly as a result of oxygen accumulation at grain boundaries.

Singlet oxygen feedback delayed fluorescence of protoporphyrin IX in organic solutions.

Delayed fluorescence (DF) of protoporphyrin IX (PpIX) has been recently proposed as a tool for monitoring of mitochondrial oxygen tension in vivo as well as for observation of the effectiveness of photodynamic therapy (PDT) [E. G. Mik, Anesth. Analg., 2013, 117, 834-346; F. Piffaretti et al., J. Biomed. Opt., 2012, 17, 115007]. However, the efficiency of the mechanism of thermal activation (E-type DF), which was considered in the papers, is limited due to a large energy gap between the first excited singlet and the first triplet state of PpIX at room or body temperatures. Moreover, the energy gap is roughly equal to other porphyrinoid photosensitizers that generate DF mostly through the Singlet Oxygen Feedback-Induced mechanism (SOFDF) under certain conditions [M. Scholz and R. Dědic, Singlet Oxygen: Applications in Biosciences and Nanosciences, 2016, vol. 2, pp. 63-81]. The mechanisms of delayed fluorescence of PpIX dissolved either in dimethylformamide (DMF) or in the mixture of DMF with ethylene glycol (EG) were investigated at atmospheric partial pressure of oxygen by means of a simultaneous time-resolved detection of 1O2 phosphorescence and PpIX DF which makes a direct comparison of the kinetics and lifetimes of both the luminescence channels possible. Samples of PpIX (100 μM) exhibit concave DF kinetics, which is a typical footprint of the SOFDF mechanism. The dramatic decrease in the DF intensity after adding a selective 1O2 quencher sodium azide (NaN3, 10 mM) proves that >90% of DF is indeed generated through SOFDF. Moreover, the analysis of the DF kinetics in the presence of NaN3 implies that the second significant mechanism of DF generation is the triplet-triplet annihilation (P-type DF). The bimolecular mechanism of DF was further confirmed by the decrease of the DF intensity in the more viscous mixture DMF/EG and by the increase of the ratio of DF to the prompt fluorescence (PF) intensity with the increasing excitation intensity. These results show the significant role of the SOFDF mechanism in the DF of PpIX at high concentrations and at atmospheric partial pressure of oxygen and should be considered when developing diagnostic tools for clinical applications.

Influence of oxygen partial pressure on the characteristics of human hepatocarcinoma cells

Most of the in vitro studies using liver cell lines have been performed under atmospheric oxygen partial pressure (21% O2). However, the oxygen concentrations in the liver and cancer cells are far from this value. In the present study, we have evaluated the influence of oxygen on 1) the tumor cell lines features (growth, steady-state ROS levels, GSH content, activities of antioxidant enzymes, p66 Shc and SOD expressions, metalloproteinases secretion, migration, invasion, and adhesion) of human hepatocellular carcinoma cell lines, and b) the response of the cells to an oxidant stimulus (aqueous leaf extract of the V. baccifera plant species). For this purpose, three hepatocarcinoma cell lines with different p53 status, HepG2 (wild-type), Huh7 (mutated), and Hep3B (deleted), were cultured (6–30 days) under atmospheric (21%) and more physiological (8%) pO2. Results showed that after long-term culturing at 8% versus 21% O2, the cellular proliferation rate and the steady-state levels of mitochondrial O2- were unaffected. However, the intracellular basal ROS levels were higher independently of the characteristics of the cell line. Moreover, the lower pO2 was associated with lower glutathione content, the induction of p66 Shc and Mn-SOD proteins, and increased SOD activity only in HepG2. This cell line also showed a higher migration rate, secretion of active metalloproteinases, and a faster invasion. HepG2 cells were more resistant to the oxidative stress induced by V. baccifera. Results suggest that the long-term culturing of human hepatoma cells at a low, more physiological pO2 induces antioxidant adaptations that could be mediated by p53, and may alter the cellular response to a subsequent oxidant challenge. Data support the necessity of validating outcomes from studies performed with hepatoma cell cultures under ambient O2.

Low Hesperian PCO2 constrained from in situ mineralogical analysis at Gale Crater, Mars

Carbon dioxide is an essential atmospheric component in martian climate models that attempt to reconcile a faint young sun with planetwide evidence of liquid water in the Noachian and Early Hesperian. In this study, we use mineral and contextual sedimentary environmental data measured by the Mars Science Laboratory (MSL) Rover Curiosity to estimate the atmospheric partial pressure of CO2 (PCO2) coinciding with a long-lived lake system in Gale Crater at ∼3.5 Ga. A reaction-transport model that simulates mineralogy observed within the Sheepbed member at Yellowknife Bay (YKB), by coupling mineral equilibria with carbonate precipitation kinetics and rates of sedimentation, indicates atmospheric PCO2 levels in the 10s mbar range. At such low PCO2 levels, existing climate models are unable to warm Hesperian Mars anywhere near the freezing point of water, and other gases are required to raise atmospheric pressure to prevent lake waters from being lost to the atmosphere. Thus, either lacustrine features of Gale formed in a cold environment by a mechanism yet to be determined, or the climate models still lack an essential component that would serve to elevate surface temperatures, at least locally, on Hesperian Mars. Our results also impose restrictions on the potential role of atmospheric CO2 in inferred warmer conditions and valley network formation of the late Noachian.

Strong thermal acclimation of photosynthesis in tropical and temperate wet-forest tree species: the importance of altered Rubisco content.

Understanding of the extent of acclimation of light-saturated net photosynthesis (An ) to temperature (T), and associated underlying mechanisms, remains limited. This is a key knowledge gap given the importance of thermal acclimation for plant functioning, both under current and future higher temperatures, limiting the accuracy and realism of Earth system model (ESM) predictions. Given this, we analysed and modelled T-dependent changes in photosynthetic capacity in 10 wet-forest tree species: six from temperate forests and four from tropical forests. Temperate and tropical species were each acclimated to three daytime growth temperatures (Tgrowth ): temperate - 15, 20 and 25°C; tropical - 25, 30 and 35°C. CO2 response curves of An were used to model maximal rates of RuBP (ribulose-1,5-bisphosphate) carboxylation (Vcmax ) and electron transport (Jmax ) at each treatment's respective Tgrowth and at a common measurement T (25°C). SDS-PAGE gels were used to determine abundance of the CO2 -fixing enzyme, Rubisco. Leaf chlorophyll, nitrogen (N) and mass per unit leaf area (LMA) were also determined. For all species and Tgrowth , An at current atmospheric CO2 partial pressure was Rubisco-limited. Across all species, LMA decreased with increasing Tgrowth . Similarly, area-based rates of Vcmax at a measurement T of 25°C (Vcmax25 ) linearly declined with increasing Tgrowth , linked to a concomitant decline in total leaf protein per unit leaf area and Rubisco as a percentage of leaf N. The decline in Rubisco constrained Vcmax and An for leaves developed at higher Tgrowth and resulted in poor predictions of photosynthesis by currently widely used models that do not account for Tgrowth -mediated changes in Rubisco abundance that underpin the thermal acclimation response of photosynthesis in wet-forest tree species. A new model is proposed that accounts for the effect of Tgrowth -mediated declines in Vcmax25 on An , complementing current photosynthetic thermal acclimation models that do not account for T sensitivity of Vcmax25 .

Predation of freshwater fish in environments with elevated carbon dioxide

Carbon dioxide (CO2) in fresh-water environments is poorly understood, yet in marine environments CO2 can affect fish behaviour, including predator–prey relationships. To examine changes in predator success in elevated CO2, we experimented with predatory Micropterus salmoides and Pimephales promelas prey. We used a two-factor fully crossed experimental design; one factor was 4-day (acclimation) CO2 concentration and the second factor CO2 concentration during 20-min predation experiments. Both factors had three treatment levels, including ambient partial pressure of CO2 (pCO2; 0–1000 μatm), low pCO2 (4000–5000 μatm) and high pCO2 (8000–10000 μatm). Micropterus salmoides was exposed to both factors, whereas P. promelas was not exposed to the acclimation factor. In total, 83 of the 96P. promelas were consumed (n=96 trials) and we saw no discernible effect of CO2 on predator success or time to predation. Failed strikes and time between failed strikes were too infrequent to model. Compared with marine systems, our findings are unique in that we not only saw no changes in prey capture success with increasing CO2, but we also used CO2 treatments that were substantially higher than those in past experiments. Our work demonstrated a pronounced resiliency of freshwater predators to elevated CO2 exposure, and a starting point for future work in this area.

High-Altitude Pulmonary Vascular Diseases

More than 140 million people permanently reside in high-altitude regions of Asia, South America, North America, and Africa. Another 40 million people travel to these places annually for occupational and recreational reasons, and are thus exposed to the low ambient partial pressure of oxygen. This review will focus on the pulmonary circulatory responses to acute and chronic high-altitude hypoxia, and the various expressions of maladaptation and disease arising from acute pulmonary vasoconstriction and subsequent remodeling of the vasculature when the hypoxic exposure continues. These unique conditions include high-altitude pulmonary edema, high-altitude pulmonary hypertension, subacute mountain sickness, and chronic mountain sickness.

D/H fractionation during the sublimation of water ice

Experiments of sublimation of pure water ice have been performed in the temperature range −105 °C to −30 °C and atmospheric partial pressures ranging from 10−6 to 10−1mb. Sampling of both vapour and residual ice fractions has been performed with the use of a vacuum line designed for the extraction and purification of gases before the measurement of their D/H ratios. Sublimation was responsible for sizable isotopic fractionation factors in the range 0.969–1.123 for temperatures lying between −105 °C and −30 °C. The fractionation factor exhibits a cross-over at temperatures around −50 °C with the water vapour fraction being D-depleted relative to the residual ice fraction at T<−50 °C (αice-vapour= 0.969–0.995). This cross-over has implications for the understanding of the atmospheric water cycle of some terrestrial planets such as the Earth or Mars. The magnitude of deuterium enrichment or depletion between ice and water vapour cannot explain the differences in the D/H ratios amongst Jupiter comets and long–period comets families nor those that have been documented between Earth's and cometary water.

Differential protein expression using proteomics from a crustacean brine shrimp (Artemia sinica) under CO2-driven seawater acidification

Gradually increasing atmospheric CO2 partial pressure (pCO2) has caused an imbalance in carbonate chemistry and resulted in decreased seawater pH in marine ecosystems, termed seawater acidification. Anthropogenic seawater acidification is postulated to affect the physiology of many marine calcifying organisms. To understand the possible effects of seawater acidification on the proteomic responses of a marine crustacean brine shrimp (Artemia sinica) three groups of cysts were hatched and further raised in seawater at different pH levels (8.2 as control and 7.8 and 7.6 as acidification stress levels according to the predicted levels at the end of this century and next century, respectively) for 1, 7 and 14 days followed by examination of the protein expression changes via two-dimensional gel electrophoresis. Searches of protein databases revealed that 67 differential protein spots were altered due to lower pH level (7.6 and 7.8) stress in comparison to control groups (pH 8.2) by mass spectrometry. Generally, these differentially expressed proteins included the following: 1) metabolic process-related proteins involved in glycolysis and glucogenesis, nucleotide/amino acid/fatty acid metabolism, protein biosynthesis, DNA replication and apoptosis; 2) stress response-related proteins, such as peroxiredoxin, thioredoxin peroxidase, 70-kDa heat shock protein, Na/K ATPase, and ubiquinol-cytochrome c reductase; 3) immune defence-related proteins, such as prophenoloxidase and ferritin; 4) cytoskeletal-related proteins, such as myosin light chain, TCP1 subunit 2, tropomyosin and tubulin alpha chain; and 5) signal transduction-related proteins, such as phospholipase C-like protein, 14-3-3 zeta, translationally controlled tumour protein and RNA binding motif protein. Taken together, these data support the idea that CO2-driven seawater acidification may affect protein expression in the crustacean A. sinica and possibly also in other species that feed on brine shrimp in the ecosystem, particularly marine food webs.

A Pleistocene ice core record of atmospheric O 2 concentrations

The history of atmospheric O2 partial pressures (Po2) is inextricably linked to the coevolution of life and Earth's biogeochemical cycles. Reconstructions of past Po2 rely on models and proxies but often markedly disagree. We present a record of Po2 reconstructed using O2/N2 ratios from ancient air trapped in ice. This record indicates that Po2 declined by 7 per mil (0.7%) over the past 800,000 years, requiring that O2 sinks were ~2% larger than sources. This decline is consistent with changes in burial and weathering fluxes of organic carbon and pyrite driven by either Neogene cooling or increasing Pleistocene erosion rates. The 800,000-year record of steady average carbon dioxide partial pressures (Pco2) but declining Po2 provides distinctive evidence that a silicate weathering feedback stabilizes Pco2 on million-year time scales.

Dissociation Oxygen Partial Pressure of CaPd3O4 from 1023 to 1328 K

Introduction The high level radioactive wastes in spent fuels are immobilized in borosilicate glass. The spent fuels is mixed with borosilicate glass and the mixture is heated by joule heat directly supplied by electrical current. The oxides of platinum group metals (Rh, Pd or Ru) exist in the spent fuels. Since the oxides are easily reduced resulting in low resistivity, their thermodynamic properties are indispensable to establish the immobilizing process. The object of this study is to make clear the dissociation oxygen pressure over the Pd-CaO-CaPd3O4 coexistence by using the electrochemical cell. Experimental The dissociation of CaPd3O4 is represented by 2CaPd3O4 → 2CaO + 6Pd + 3O2 (1).Equilibrium oxygen partial pressures of the above reaction were measured by oxygen concentration cells using CaO stabilized ZrO2 solid electrolyte.The cell is described as Pt, CaO, CaPd3O4, Pd, O2(sample) |CSZ| O2(air), Pt.Electromotive force (emf) of the cell from 1023 to 1328 K was measured by a digital volt meter with impedance of 109 Ω. Results and discussion The equilibrium value was adopted from an average of emfs for last 30 s when the changes in the emfs were within 1 mV par 30 ks. The least squares fits give the emf's of the cell in the following expression. E/V = 0.6781 − (5.177x10-4) T From the obtained emf values, the equilibrium oxygen partial pressures of Pd-CaO-CaPd3O4 coexistence is represented by log p(O2)/bar = 51.8 - 72.6x103/T.Therefore, the dissociation oxygen partial pressure is higher than atmospheric oxygen partial pressure above 1310 K.From the obtained equilibrium oxygen partial pressure, the standard Gibbs energy change of the reaction (1) is represented by ∆G 0(1) / kJ mol-1 = -262.0 + 0.1871 T.Using the reported values of the standard Gibbs energy of formation of CaO, we obtained the standard Gibbs energy of formation of CaPd3O4 as follows.Δf G 0(CaPd3O4) / kJ mol-1 = -1034 + 0.3904T.

Reduced plant water status under sub-ambient pCO2 limits plant productivity in the wild progenitors of C3 and C4 cereals.

The reduction of plant productivity by low atmospheric CO2 partial pressure (pCO2) during the last glacial period is proposed as a limiting factor for the establishment of agriculture. Supporting this hypothesis, previous work has shown that glacial pCO2 limits biomass in the wild progenitors of C3 and C4 founder crops, in part due to the direct effects of glacial pCO2 on photosynthesis. Here, we investigate the indirect role of pCO2 mediated via water status, hypothesizing that faster soil water depletion at glacial (18 Pa) compared to post-glacial (27 Pa) pCO2, due to greater stomatal conductance, feeds back to limit photosynthesis during drying cycles. We grew four wild progenitors of C3 and C4 crops at glacial and post-glacial pCO2 and investigated physiological changes in gas exchange, canopy transpiration, soil water content and water potential between regular watering events. Growth parameters including leaf area were measured. Initial transpiration rates were higher at glacial pCO2 due to greater stomatal conductance. However, stomatal conductance declined more rapidly over the soil drying cycle in glacial pCO2 and was associated with decreased intercellular pCO2 and lower photosynthesis. Soil water content was similar between pCO2 levels as larger leaf areas at post-glacial pCO2 offset the slower depletion of water. Instead the feedback could be linked to reduced plant water status. Particularly in the C4 plants, soil-leaf water potential gradients were greater at 18 Pa compared with 27 Pa pCO2, suggesting an increased ratio of leaf evaporative demand to supply. Reduced plant water status appeared to cause a negative feedback on stomatal aperture in plants at glacial pCO2, thereby reducing photosynthesis. The effects were stronger in C4 species, providing a mechanism for reduced biomass at 18 Pa. These results have added significance when set against the drier climate of the glacial period.

Novel Glass-free LTCC Material co-fired with Cupper-Electrodes

Abstract Low Temperature Co-fired Ceramics (LTCC) have excellent high-frequency characteristics and have widely been used for microwave electronic components. By lowering the sintering temperature of the ceramics used as insulating layers, LTCC was co-fired with a high-conductivity wiring conductor, such as Cu or Ag. LTCC substrate has been expected as one of the most promising technologies to realize miniaturization of RF circuits in the field of wireless communications. There is no limitation to demand for further downsizing of RF circuits, suppression of electric loss and high mechanical strength of the substrate. However, conventional LTCC materials for substrates contain glass frit which causes defects, such as pores or cracks, and low mechanical strength. In this work, we have developed a novel LTCC material system BaO-Al2O3-SiO2-MnO-TiO2, without any glass frits. The material was co-fired with cupper electrodes, which have low resistivity and show less diffusion than silver in LTCC, under a low-oxygen partial pressure atmosphere (mixture of N2 and H2) at 980°C. Thin layers (8μm) of the material showed high insulating resistivity and reliability due to few defects, such as pores, in LTCC. Its dielectric and mechanical properties were measured as 6.8 (low-εr), 350 at 3GHz (high-Q-value) and 341MPa (high mechanical strength) respectively. This LTCC material will contribute to further miniaturizing of microwave applications and integration of passive elements.

Restructuring of Epibacterial Communities on Fucus vesiculosus forma mytili in Response to Elevated pCO2 and Increased Temperature Levels.

Marine multicellular organisms in composition with their associated microbiota—representing metaorganisms—are confronted with constantly changing environmental conditions. In 2110, the seawater temperature is predicted to be increased by ~5°C, and the atmospheric carbon dioxide partial pressure (pCO2) is expected to reach approximately 1000 ppm. In order to assess the response of marine metaorganisms to global changes, e.g., by effects on host-microbe interactions, we evaluated the response of epibacterial communities associated with Fucus vesiculosus forma mytili (F. mytili) to future climate conditions. During an 11-week lasting mesocosm experiment on the island of Sylt (Germany) in spring 2014, North Sea F. mytili individuals were exposed to elevated pCO2 (1000 ppm) and increased temperature levels (Δ+5°C). Both abiotic factors were tested for single and combined effects on the epibacterial community composition over time, with three replicates per treatment. The respective community structures of bacterial consortia associated to the surface of F. mytili were analyzed by Illumina MiSeq 16S rDNA amplicon sequencing after 0, 4, 8, and 11 weeks of treatment (in total 96 samples). The results demonstrated that the epibacterial community structure was strongly affected by temperature, but only weakly by elevated pCO2. No interaction effect of both factors was observed in the combined treatment. We identified several indicator operational taxonomic units (iOTUs) that were strongly influenced by the respective experimental factors. An OTU association network analysis revealed that relationships between OTUs were mainly governed by habitat. Overall, this study contributes to a better understanding of how epibacterial communities associated with F. mytili may adapt to future changes in seawater acidity and temperature, ultimately with potential consequences for host-microbe interactions.

Demonstration of Copper Co‐Fired (Na, K)NbO3 Multilayer Structures for Piezoelectric Applications

A Li and Ta modified (Na, K)NbO3 piezoelectric ceramic has been successfully co‐fired with inner copper electrodes in a reduced atmosphere. Highly dense NKN ceramics (95% relative density, 4.64 g/cm3) were obtained by sintering the samples in a low oxygen partial pressure (low pO2) atmosphere at 1050°C. The poly(propylene carbonate) binder system was used to permit a clean burnout at low temperature in N2 atmosphere, and also prevent the electrode copper particles from undergoing any oxidation. No interdiffusion of copper, chemical reactions, and/or carbon residues were observed in the grains, grain boundaries, or at the electrode–ceramic interface of the co‐fired samples from a detailed transmission electron microscopy (TEM) analysis. Dielectric and piezoelectric properties were characterized from those co‐fired prototyped samples. The samples displayed high relative dielectric permittivity above 800, with low dielectric loss about 3.6%. A normalized strain coefficient (max. strain/max. electric field) of = 220 pm/V was obtained under unipolar converse electromechanical measurement at 20 kV/cm. This paper presents the feasibility of co‐firing a Cu inner electrode with NKN ceramics toward multilayer lead‐free piezoelectric applications, providing an engineering route to narrow the performance differences between soft lead‐based piezoelectrics and lead‐free materials.

The occurrence of &amp;lt;italic&amp;gt;Quercus heqingensis&amp;lt;/italic&amp;gt; n. sp. and its application to palaeo-CO&amp;lt;sub&amp;gt;2&amp;lt;/sub&amp;gt; estimates

Many leaf fossils belonging to Quercus sect. Heterobalanus were collected from the Upper Pliocene Sanying Formation in Heqing County, Yunnan Province, China. Leaves are oblong, elliptic or obovate with entire margin or spinous serrations, 3.1–8.7 cm in length and 1.8–5.7 cm in width. Leaf apex is round, mucronate or blunt round, while leaf base is heart-shaped, slightly heart-shaped or blunt round, and occasionally asymmetric. The petiole is slightly sturdy, straight or a bit curved, with 1.8–4.9 mm in length. The main vein of these specimens is slightly zigzagging, with a sturdy base attenuating to the apex. Secondary veins are pinnate, 7–12 pairs, alternate and parallel with the stretching angles from 40° to 73°, bifurcating near 1/3 to 1/2 of the leaf margin. Tertiary veins are, relatively thin, 5–7 bands in 1 cm2, and perpendicular to secondary veins. Quaternary, blind and marginal veins are not clear. The upper epidermis has both unicellular and multicellular trichomes without stomata, and most of the epidermal cells are nearly quadrangular. The lower epidermis has only unicellular trichomes and cyclocytic stomatal apparatuses, and the epidermal cells are nearly quadrangular or pentagonal. The stomatal apparatuses are 20–33 m m in length, 17–27 m m in width , with 2–6 m m wide in apertures. They spread casually with the stomatal density of 503±98 mm - 2 and the stomatal index of 8.90%±0.32%. The guard cells show kidney-shaped, with 5–7 subsidiary cells. These features are similar to Q. rehderiana, Q. guyavifolia , Q. preguyavifolia and some other extant or fossil species of Q . sect. Heterobalanus , but they are different in terms of density and type of trichomes. Both Q . guyavifolia and Q . preguyavifolia have more trichomes in total, and multicellular trichomes in lower epidermis which spread in veins and between veins. The fossil leaves of Q . sect. Heterobalanus in Heqing and Q . rehderiana have less trichomes, and the former has no multicellular trichome in lower epidermis, while the latter’s multicellular trichome are just found in veins. Hence, it was designated as a new species— Quercus heqingensis n. sp. The estimates of palaeoatmospheric-CO2 using the positive relationships between stomatal frequency and atmospheric CO2 partial pressure in its Nearest Living Relatives (NLRs)— Q . guyavifolia show that, the palaeo-CO2 levels in the late Pliocene reconstructed by Q. heqingensis were 263.42±24.86 ppm (equation with extant field collections) and 234.25±22.49 ppm (equation with historical herbarium samples). These results are slightly lower than most previous estimates of the same age. Our results are in agreement with other estimates when palaeoaltitude is considered. This indicates that it is feasible to apply the stomatal index of Q . heqingensis to the positive relationship between stomatal index of Q . guyavifolia and atmospheric p CO2 to reconstruct palaeo-CO2 levels. Meanwhile, the results further support lower palaeo-CO2 level in the late Pliocene than present. This study provides credible evidence for future palaeo-CO2 estimates using NLRs as proxies.

Exomoon climate models with the carbonate-silicate cycle and viscoelastic tidal heating

The habitable zone for exomoons with Earth-like properties is a non-trivial manifold, compared to that of Earth-like exoplanets. The presence of tidal heating, eclipses and planetary illumination in the exomoon energy budget combine to produce both circumstellar and circumplanetary habitable regions. Analytical calculations suggest that the circumplanetary habitable region is defined only by an inner edge (with its outer limits determined by orbital stability). Subsequent calculations using 1D latitudinal climate models indicated that the combined effect of eclipses and ice-albedo feedback can produce an outer edge to the circumplanetary habitable zone. But is this outer edge real, or an artefact of the climate model's relative simplicity? We present an upgraded 1D climate model of Earth-like exomoon climates, containing the carbonate-silicate cycle and viscoelastic tidal heating. We conduct parameter surveys of both the circumstellar and circumplanetary habitable zones, and we find that the outer circumplanetary habitable edge remains provided the moon's orbit is not inclined relative to that of the planet. Adding the carbonate-silicate cycle pushes the circumplanetary habitable zone outward, by allowing increases in atmospheric partial pressure of carbon dioxide to boost the greenhouse effect. Viscoelastic tidal heating widens the habitable zone compared to standard, fixed-Q models. Weakening the tidal heating effect due to melting allows moons to be habitable at higher eccentricity, and pushes the inner circumstellar and circumplanetary habitable zone boundary inward.

Fighting global warming by greenhouse gas removal: destroying atmospheric nitrous oxide thanks to synergies between two breakthrough technologies.

Even if humans stop discharging CO2 into the atmosphere, the average global temperature will still increase during this century. A lot of research has been devoted to prevent and reduce the amount of carbon dioxide (CO2) emissions in the atmosphere, in order to mitigate the effects of climate change. Carbon capture and sequestration (CCS) is one of the technologies that might help to limit emissions. In complement, direct CO2 removal from the atmosphere has been proposed after the emissions have occurred. But, the removal of all the excess anthropogenic atmospheric CO2 will not be enough, due to the fact that CO2 outgases from the ocean as its solubility is dependent of its atmospheric partial pressure. Bringing back the Earth average surface temperature to pre-industrial levels would require the removal of all previously emitted CO2. Thus, the atmospheric removal of other greenhouse gases is necessary. This article proposes a combination of disrupting techniques to transform nitrous oxide (N2O), the third most important greenhouse gas (GHG) in terms of current radiative forcing, which is harmful for the ozone layer and possesses quite high global warming potential. Although several scientific publications cite "greenhouse gas removal," to our knowledge, it is the first time innovative solutions are proposed to effectively remove N2O or other GHGs from the atmosphere other than CO2.

New insights into &amp;lt;i&amp;gt;f&amp;lt;/i&amp;gt;CO&amp;lt;sub&amp;gt;2&amp;lt;/sub&amp;gt; variability in the tropical eastern Pacific Ocean using SMOS SSS

Abstract. Complex oceanic circulation and air–sea interaction make the eastern tropical Pacific Ocean (ETPO) a highly variable source of CO2 to the atmosphere. Although the scientific community have amassed 70 000 surface fugacities of carbon dioxide (fCO2) data points within the ETPO region over the past 25 years, the spatial and temporal resolution of this data set is insufficient to fully quantify the seasonal to interannual variability of the region, a region where fCO2 has been observed to fluctuate by &gt; 300 μatm. Upwelling and rainfall events dominate the surface physical and chemical characteristics of the ETPO, with both yielding unique signatures in sea surface temperature and salinity. Thus, we explore the potential of using a statistical description of fCO2 within sea-surface salinity–temperature space. These SSS/SST relationships are based on in situ surface ocean CO2 atlas (SOCAT) data collected within the ETPO. This statistical description is then applied to high-resolution (0.25°) Soil Moisture and Ocean Salinity (SMOS) sea surface salinity (SSS) and Operational Sea Surface Temperature and Sea Ice Analysis (OSTIA) sea surface temperature (SST) in order to compute regional fCO2. As a result, we are able to resolve fCO2 at sufficiently high resolution to elucidate the influence that various physical processes have on the fCO2 of the surface ETPO. Normalised (to 2014) oceanic fCO2 between July 2010 and June 2014 within the entire ETPO was 39 (±10.7) μatm supersaturated with respect to 2014 atmospheric partial pressures, and featured a CO2 outgassing of 1.51 (±0.41) mmol m−2 d−1. Values of fCO2 within the ETPO were found to be broadly split between the Gulf of Panama region and the rest of the tropical eastern Pacific Ocean. The northwest, central and offshore regions were supersaturated, with wintertime wind-jet-driven upwelling found to constitute the first-order control on fCO2 values. This contrasts with the southeastern/Gulf of Panama region, where heavy rainfall combined with rapid stratification of the upper water column act to dilute dissolved inorganic carbon, and yield fCO2 values undersaturated with respect to atmospheric fugacities of CO2.

Selective catalytic oxidation of benzene over Cu/Ti/HZSM-5 under low oxygen pressure for one step synthesis of phenol

The direct hydroxylation of benzene to phenol over a Cu impregnated zeolite catalyst (Cu/HZSM-5) is performed in airflow. Phenol is obtained as a main product in a yield of 2.5%, however, the selectivity of phenol is low (44.0%) due to the formation of by-products such as hydroquinone, p-benzoquinone, CO, and CO2. The use of Cu/HZSM-5 leads to a significantly higher selectivity of phenol (94.0%) under an O2 partial pressure that is lower than the atmospheric O2 partial pressure. It is found that excess O2 in the gas-phase causes the formation of by-products, whereas a decrease of O2 partial pressure prevents the by-products from forming. Moreover, the addition of Ti to Cu/HZSM-5 leads to improved phenol formation activity. Good yield (4.3%) and selectivity (88.0%) of phenol are achieved over Cu/Ti/HZSM-5 under a low O2 partial pressure. The addition of Ti is found to accelerate the formation of Cu+ as an active site. It is therefore speculated that phenol can be formed selectively over Cu/Ti/HZSM-5 under lower O2 partial pressure owing to the increase of Cu+ sites by Ti addition and the prevention of by-product formation by the decreased O2 partial pressure.