Mixture Of Oxides Research Articles

Chemistry Informed Machine Learning-Based Heat Capacity Prediction of Solid Mixed Oxides.

Knowing heat capacity is crucial for modeling temperature changes with the absorption and release of heat and for calculating the thermal energy storage capacity of oxide mixtures with energy applications. The current prediction methods (ab initio simulations, computational thermodynamics, and the Neumann-Kopp rule) are computationally expensive, not fully generalizable, or inaccurate. Machine learning has the potential of being fast, accurate, and generalizable, but it has been scarcely used to predict mixture properties, particularly for mixed oxides. Here, we demonstrate a method for the generalizable prediction of heat capacity of solid oxide pseudobinary mixtures using heat capacity data obtained from computational thermodynamics and descriptors from ab initio databases. Models trained through this workflow achieved an error (mean absolute error of 0.43 J mol-1 K-1) lower than the uncertainty in differential scanning calorimetry measurements, and the workflow can be extended to predict other properties derived from the Gibbs free energy and for higher-order oxide mixtures.

Corrosion behavior of δ-ferrite in AISI 316 austenitic stainless steel exposed to oxygen-saturated lead‑bismuth eutectic at 550 °C

δ-ferrite is usually found in the 300 series austenitic stainless steels (ASS), but the role of δ-ferrite on corrosion behaviors exposed to oxygen-controlled lead–bismuth eutectic (LBE) has not yet been elucidated. The corrosion behaviors of AISI 316 ASS containing δ-ferrite in the oxygen-saturated static LBE at 550 °C were studied in terms of their solution-treated and accelerated-aging treated conditions. The δ-ferrite and decomposed δ-ferrite exhibit the superior resistance to oxidation attack compared to the austenite, and the δ-ferrite possesses a better corrosion resistance than the decomposed δ-ferrite. Compared with the austenite, the higher diffusivities of Cr and Si in δ-ferrite cause a reduction in the critical concentration required for the formation of chromium oxide and Si-rich oxide. A mixture of Cr2O3 oxide and Fe-Cr-Si spinel oxide developed on the surface of δ-ferrite can effectively impede the metal transfer, leading to the superior resistance to oxidation attack. The retained δ-ferrite and M23C6 carbides in the decomposed δ-ferrite oxidizes independently into FeCr2O4 and Cr2O3 oxides, respectively. The presence of Cr2O3 scale around the retained δ-ferrite decreases its oxidation rate, resulting in the non-uniform oxide phenomenon.

Hf-W dating of zircon in mesosiderite with high-pressure sintered standard

New standard zircons applicable to in situ analysis of Hf/W ratio by Nanoscale secondary ion mass spectrometer (NanoSIMS) were prepared and applied to Hf-W dating of a differentiated meteorite classified as mesosiderite. The standard zircons were synthesized by high-pressure experiment from starting materials which were mixture of hafnium oxide, tungsten oxide and high-purity zircon powder. The mixed powders were stirred and pulverized by a high-energy ball mill. They were then sintered at 1000 °C and 6 GPa using multi-anvil apparatus. Homogeneity of Hf/W ratios of synthesized zircons was examined by SEM–EDS, EPMA, and Laser Ablation Inductively Coupled Plasma Mass Spectrometer (LA-ICPMS). Hf/W ratios of the same zircons were measured by a NanoSIMS with 2 nA oxygen primary beam and mass resolving power of 10,000. The relative sensitivity factor (RSF) of Hf/W ratio was determined by comparing zircon data measured by LA-ICPMS and NanoSIMS. Observed RSF (Hf/W) of zircon is 0.585 ± 0.180 (hereafter all error 2σ) consistent with 0.855 ± 0.468 of previous work within experimental error margin. The value is higher than observed RSF of glass matrix, 0.301 ± 0.062, and significantly higher than glass data of 0.21–0.22 in references. Based on the RSF, the Hf/W ratios of zircons extracted from mesosiderite “Asuka 882,023” were measured together with W isotopic compositions by NanoSIMS. Observed data in 180Hf/186W–182W/186W diagram are fitted by a straight line, yielding a slope (182Hf/180Hf) of 8.19 ± 3.50 × 10–6. This slope is converted into an absolute zircon Hf-W age of 4536.5+4.6–7.2 Ma using the age anchor of CV3 chondrite. This age agrees well with a reference value of 4532.0+11.4–20.8 Ma.

Remarkably High Separation of Neodymium from Praseodymium by Selective Dissolution from their Oxide Mixture using an Ionic Liquid Containing aβ-Diketone.

A simple, efficient, direct and economical method for the mutual separation of Nd and Pr was developed by the selective dissolution of Nd2O3 from their oxide mixtures in an ionic liquid containing 2-thenoyltrifluoroacetone (HTTA) resulting in an unprecedented separation factor (βNd/Pr)>500, which is 277 times more than the thus far reported βNd/Pr values. The proposed mechanism was supported by DFT computations.

Failure analysis of leaking firefighting pipeline used in nuclear power plant: Corrosion development process and key influence factors

A penetrating hole has been found in the inner wall of the firefighting pipeline (A106 steel) used for 20 years in a nuclear power plant of China, and the pipeline is filled with almost stagnant tap water before failure. The failed pipeline is taken from a vertically placed water outlet pipeline. The corrosion process and key influence factors of the failed firefighting pipeline were studied using optical microscopy (OM), scanning electron microscopy (SEM) and X-ray diffraction (XRD). The results show that there exist two typical corrosion characteristics on the inner wall of the failed pipeline besides leakage hole, that is, corrosion nodulation and corrosion bulge. The corrosion nodulation, mainly consisting of a mixture of calcium and iron oxides, is the initiation position of perforation corrosion, and the iron-oxidizing bacteria (IOB) play a key role in the formation of corrosion nodulation. Then the sulfate-reducing bacteria (SRB) is involved in the propagation of corrosion nodulation when the dissolved oxygen concentration is low. The corrosion nodulation gradually become loose and form large bulge with extended service time. The corrosion pits under the corrosion bulge also develop gradually. Eventually, the inner wall of the pipeline is thinned and perforated.

Enhancing thermal efficiency in MHD kerosene oil-based ternary hybrid nanofluid flow over a stretching sheet with convective boundary conditions

The increasing demand for thermal management due to the high heat density heat exchangers for different technological and industrial processes draw the attention of researchers in heat transfer analysis to investigate the simultaneous solution to this problem. Keeping this in mind, the current work addressed the utilization of ternary hybrid nanofluid, a mixture of graphene oxide with silver and copper, to examine the heat and mass transfer enhancement of MHD Maxwell fluid. In the current model, the author discussed heat and mass transfer analysis of Maxwell MHD ternary hybrid nanofluid flow across a porous medium over an extending sheet. The energy and concentration equations are expressed to include the effects of Brownian motion and thermophoretic diffusion. Additionally, the effects of thermal radiation, activation energy, chemical reactions, and convective boundary conditions are considered. The similarity transformations are used to convert the nonlinear PDEs into ODEs. The impact of embedded factors on velocity, temperature, and concentration profiles is perceived graphically and mathematically by using the HAM technique. The convergence of computed solutions is ensured by h-curves. The significant outcomes from the analysis expressed that the flow distribution increases with slip and suction/injection factors. The concentration of the ternary hybrid nanofluid increases with an increase in thermophoretic diffusion (0.1–0.5), thermal biot number, and solutal biot number (0.1–0.5), however, a declining behavior is perceived with rising quantity of Schmidt number (0.6–0.8) and Brownian motion (0.1–0.5) parameters. Nusselt number shows a dominant behaviour with a higher magnetic factor. Similarly, the skin friction increases with an increase in thermal biot number and thermophoresis factor. It is revealed that the skin friction along x− direction increases from (0.78138, 0.833702, 0.897022, and 0.972526) for ternary hybrid nanofluid. Nusselt number increases from 2 to 5% (0.208936, 0.214288, 0.219799, 0.22555) when the volume fraction varies from 0.01 to 0.04 respectively.

Morphological and structural analysis of ceramic materials composite by Kaolinite and Alumina

In this work, we report the preparation, structural and electrical characterization, morphological analysis and hardness measurements of ceramic materials composed of kaolinite Al2(Si2O5(OH)4 and alumina AL2O3. Samples were prepared from mixtures of precursor oxides starting with 100% alumina and increased the kaolinite concentration on steps of 10% up to complete 100% of kaolinite. The samples were sintered by the method of solid state reaction at temperatures of 1150, 1250 and 1350 °C. We found that the alumina samples are stable at the different temperatures of synthesis. The samples of kaolinite at 100% suffer a change phase depending on the sinterization temperature, noting that at 1350 °C yields 87% mullite and 13% cristobalite. The presence of quartz was only detected in samples with 100% kaolinite for sinterization temperatures of 1150 and 1250 °C. All samples with a mixture of alumina and kaolinite showed the presence of mullite, which is increased when the content of kaolínite is high or when the sinterization temperature is increased. This allows us to infer that the introduction of alumina optimizes the process of mullite formation hy their reaction with the SiO2 that remainder from the kaolinite. The sample with 100% alumina has a Mohs hardness of about 5, and this is increased with the content of kaolinite, until a Mohs hardness of about 6 to the sample with 100% kaolinite. The dielectric constant of these materials is around 27.82.

Highly sensitive humidity sensor based on composite film of partially reduced graphene oxide and bacterial cellulose

Breathing is an important physiological activity of human body, which not only reflects the state of human movement, but also is one of the important health indicators. Breathing can change the concentration of water molecules, so monitoring humidity has gradually become a hot topic in modern research. In this study, a humidity sensing composite film with high sensitivity and short response time was made by using the mixture of graphene oxide (GO) and bacterial cellulose (BC) with simple dry film-forming method. L-ascorbic acid was used as reducing agent to reduce GO and improve the conductivity of GO/BC composite film (BG). The influence of different BC contents and the different reduction degree on the resistance change rate of composite film was investigated in details. The maximum resistance change rate of partially reduced BG humidity sensitive composite film reached up to 94%, and the response and recovery time were 13 s and 47 s respectively. Furthermore, the sensor shows obvious resistance change in noncontact sensing test and different breathing states. This kind of humidity sensitive film with fast response and high sensitivity has great potential in human health monitoring and noncontact sensing, and is of great significance in promoting health detection and intelligent life.

Selective extraction of high-added value carboxylic acids from aqueous fermentative effluents with new hydrophobic eutectic solvents (HES)

SummaryRecovering these carboxylic acids from the fermentative streams in a sustainable, green, and economical way is a significant challenge. This work assessed hydrophobic eutectic solvents (HES) – water-immiscible – for the selective recovery of carboxylic acids via liquid–liquid extraction. Different trioctylphosphine oxide (TOPO) mixtures with menthol and thymol were studied and deeply characterized by 1H and 31P NMR to yield stable eutectic solvents, including a novel experiment of 31P NMR at variable temperatures for the first time. Those stable eutectic solvents were tested in the liquid extraction of complex aqueous mixtures containing C2–C6 carboxylic acids and simple sugars (glucose and xylose). The back-extraction of the carboxylic acids for the recovery of the HES was optimized, being necessary in three stages for the complete cleaning of the eutectic solvent using NaOH 0.1 M. The eutectic mixture of TOPO and thymol in a molar ratio of 1:2 exhibited an overall recovery of C5 and C6 carboxylic acids over 70 %, allowing its selective extraction from the rest of the compounds in the complex mixture. Likewise, this HES (after back extraction) was successfully reused in a second extraction cycle, keeping the performance of the fresh one. Therefore, this study demonstrated that HES can have a high extraction selectivity for carboxylic acids of ≥C5. Moreover, these solvents were stable and allowed reusability, reducing the environmental impact and process costs.

Formation of Calcium Ferrite Containing Aluminum (CFA) in Sintering of Iron Ore Fines

Calcium ferrite containing aluminum (CFA) is a precursor of the low-temperature bonding phase in the sintering process of iron ore fines for blast furnace ironmaking. Thus, improving the formation of CFA at lower temperature is very important for saving energy, improving efficiency and production. In this paper, the formation process of CFA was investigated at 1200 °C by reactions of alumina (Al2O3), respectively with a mixture of calcium oxide (CaO) and hematite (Fe2O3) and monocalcium ferrite (CF) as a recognized initial product, as well as reaction of Al-containing hematite (Hss) with CF. The result confirmed that CF is an intermediate product formed easily in the sintering process, and it may react with excessive Fe2O3 to generate an alpha-calcium iron oxide (Ca2Fe15.50O25) as a new phase. It was found that CFA can be formed directly by reactions of CF with Hss and Ca2Fe15.50O25 with Al2O3, while the reaction of CF with Al2O3 is more helpful in generating Ca2Fe15.5O25 rather than CFA, simultaneously forming a calcium aluminum oxide (CaAl2O4, CA; CaAl4O7, CA2). It was revealed that the appearance of CA and CA2 is a main reason to hinder CFA formation in the sintering process of iron ore fines.

Detonation Cell Size Prediction Using Artificial Neural Networks (ANNs) for Hydrogen/Hydrocarbon/Ammonia/Nitrous Oxide Mixtures

In this work, a previously developed three-feature Artificial Neural Network (ANN) model with dimensional inputs is directly applied to predict the cell size of hydrocarbon/ammonia/nitrous oxide mixtures and compare these to experimental data. This model uses as inputs three ZND parameters (MCJ, ΔI, and σ˙max), which are mainly calculated using Konnov’s and Mével’s mechanisms. A similar prediction is obtained with the two mechanisms for the biogas–O2, H2–O2, H2–N2O, and NH3–O2 mixtures, indicating that the model is not only limited to Konnov’s chemical kinetic mechanism which was used for its training. The overall good agreement between the ANN predictions and the actual experimental values for the aforementioned mixtures, which are not used in the original training of the ANN model, is promising and shows its potential for application and extension to other mixtures and initial conditions, provided that the chemical kinetic parameters describing the ideal reaction zone structure could be computed. The model is then used to compare experimental cell size data from two detonation tube facilities, and also different chemical kinetic mechanisms for NH3-N2O mixtures. In the end, the original ANN model is expanded with the inclusion of additional cell size data, showing a slightly lower mean error for the predicted cell sizes if the data for the mixtures considered in this study are taken into account for the training of the new ANN model.

Successful synthesis of proton-conducting high-entropy (La0.2Nd0.2Ho0.2Lu0.2Y0.2)2ZrO5 ceramics

Using mechanical activation of an oxide mixture containing 0.2 wt% hexagonal boron nitride, followed by high-temperature firing (1400–1500 °C), we prepared single-phase (La0.2Nd0.2Ho0.2Lu0.2Y0.2)2ZrO5 ceramic, a high-entropy oxide (HEO) analog of Gd2ZrO5, whereas we failed to obtain single-phase Gd2ZrO5 under similar conditions: the material consisted of two phases, with the fluorite and bixbyite structures, like in the case of conventional synthesis or coprecipitation in previous work. Thus, the use of the HEOs allowed us to obtain a phase-pure compound with the fluorite structure at a markedly lower synthesis temperature. An important role was played by 0.2 wt% hyperstoichiometric hexagonal BN additions, which ensured considerable amorphization of the starting oxides. The start powders and resulting ceramics were studied by X-ray diffraction, SEM analyses and conductivity was measured by impedance spectroscopy method in dry and wet air.The highest proton conductivity, ∼2.5 × 10−5 S/cm at 630 °C, was offered by the (La0.2Nd0.2Ho0.2Lu0.2Y0.2)2ZrO5 HEO ceramic. The use of HEO analogs of various compounds can be helpful for not only assessing thermodynamic properties of ceramics (reduction in synthesis and polymorphic transformation temperatures), but also preparing proton conductors when it is necessary to enhance hydrating properties of the cation sublattice.

Numerical illustration of diffusive flow of blood-based tri-hybrid nanofluid generated by a curved stretching sheet using law of porosity

The study of flow of blood through the blood vessels carries nanoparticles which opens new ways in the research. This study explores one such flow of trihybrid nanoparticles suspended in blood over a curved stretching surface which undergoes the Darcy-Forchheimer porosity model. The analysis employs Cattaneo-Christov heat flux model along with chemical reaction, linear heat source allowing the surface to slip with heat and mass convection. The trihybrid nanofluids consist of a mixture of titanium dioxide, iron oxide, and silica nanoparticles mixed with base fluid (blood) to generate TiO 2 - Fe 3 O 4 - SiO 2 /blood hybrid nanofluids. Runge-Kutta-Fehlberg 4th–5th order technique, a robust numerical technique, was employed to obtain mathematical solutions. Throughout the numerical process, all parameters, except those under examination, were kept at their default values. Additionally, various plots were generated based on numerical results to illustrate the obtained data. The findings indicate that an increase in the Forchheimer number and porosity results in a reduction in the velocity profile. Furthermore, an increase in the radiation parameter and thermal Biot number leads to an increase in the temperature profile, while the temperature profile decreases with an increase in the thermal relaxation parameter. Additionally, an increase in the chemical reaction parameter and concentration Biot number results in an increase in the concentration profile. Moreover, higher Brinkman and Prandtl numbers enhance the Nusselt number.

Emerging pollutants in textile wastewater: an ecotoxicological assessment focusing on surfactants.

Water and several chemicals, including dyestuffs, surfactants, acids, and salts, are required during textile dyeing processes. Surfactants are harmful to the aquatic environment and induce several negative biological effects in exposed biota. In this context, the present study aimed to assess acute effects of five surfactants, comprising anionic and nonionic classes, and other auxiliary products used in fiber dyeing processes to aquatic organisms Vibrio fischeri (bacteria) and Daphnia similis (cladocerans). The toxicities of binary surfactant mixtures containing the anionic surfactant dodecylbenzene sulfonate + nonionic fatty alcohol ethoxylate and dodecylbenzene sulfonate + nonionic alkylene oxide were also evaluated. Nonionic surfactants were more toxic than anionic compounds for both organisms. Acute nonionic toxicity ranged from 1.3mg/L (fatty alcohol ethoxylate surfactant) to 2.6mg/L (ethoxylate surfactant) for V. fischeri and from 1.9mg/L (alkylene oxide surfactant) to 12.5mg/L (alkyl aryl ethoxylated and aromatic sulfonate surfactant) for D. similis, while the anionic dodecylbenzene sulfonate EC50s were determined as 66.2mg/L and 19.7mg/L, respectively. Both mixtures were very toxic for the exposed organisms: the EC50 average in the anionic + fatty alcohol ethoxylate mixture was of 1.0mg/L ± 0.11 for V. fischeri and 4.09mg/L ± 0.69 for D. similis. While the anionic + alkylene oxide mixture, EC50 of 3.34mg/L for D. similis and 3.60mg/L for V. fischeri. These toxicity data suggested that the concentration addition was the best model to explain the action that is more likely to occur for mixture for the dodecylbenzene sulfonate and alkylene oxide mixtures in both organisms. Our findings also suggest that textile wastewater surfactants may interact and produce different responses in aquatic organisms, such as synergism and antagonism. Ecotoxicological assays provide relevant information concerning hazardous pollutants, which may then be adequately treated and suitably managed to reduce toxic loads, associated to suitable management plans.

Photocatalytic Decomposition of Amoxicillin Using Zinc Ferrite Nanoparticles

Catalysts enriched in Zinc ferrite (ZFO) were synthesized using coprecipitation and hydrothermal methods. Mixtures of crystalline nanoparticles (ZFO and α-Fe2O3, several allotropic varieties of FeO) were characterized by various techniques such as X-ray diffraction (XRD), transmission electron microscopy (TEM, SEM), N2 sorption, UV-visible spectrophotometry (UV-Vis) and X-ray photoelectron spectroscopy (XPS). After detailed characterizations, the catalytic performance of the solids (1 g/L) in the degradation of amoxicillin (AMX) (10 mg/L) as an antibiotic pollutant in water was evaluated. In addition, we used air as the oxygen source and adjusted the pH to 5.0. Consequently, the catalysts obtained via the hydrothermal method HT-ZFO had a high activity (100% of AMX removal in less than 100 min when an LED (75 W) light was used) compared to a similar mixture of oxides with graphene HT-ZFO-GO (a longer time of 150 min) that was necessary for the complete degradation of AMX. Impregnation with an aqueous solution containing 80 mg of GO obtained using Hummer’s method, reduced into RGO by an ultrasound treatment, enhances the initial reaction rate but is associated with a prolonged time for complete AMX removal (10 ppm in water) that we attribute to its spontaneous corrosion.

Electrocatalytic reduction of simulated industrial CO2 and CO mixtures: Revising chronoamperometry to enable selective gas mixture reduction via cyclic voltammetry

While substantial advancements have been achieved in the electrocatalytic reduction of pure CO2 or CO, the reduction of carbon oxide mixtures remains underexplored, a key limitation in scaling the technology for industrial applications. This underexplored domain gains practical importance by considering carbon oxide mixtures, given that CO and CO2 together constitute a large proportion of diverse industrial gas streams. However, the simultaneous reduction of mixed CO and CO2 poses a potential challenge due to their differing optimal reduction potentials, which complicates an efficient reduction process. While cyclic voltammetry (CV) is typically used for characterization, which involves sweeping between positive and negative potentials, we utilized it to conduct reduction reactions within a defined negative potential window. This approach, serving as an alternative to conventional chronoamperometry that maintains a constant potential, ensures a continuous reduction reaction throughout the entire cycling process. By employing cycling between the optimized reduction potentials of CO2 (−1.4 V) and CO (−1.6 V), CV achieved an increase in production efficiency, ranging from 25 % to 40 % for predominant products (HCOOH and C2H4), in comparison to chronoamperometry. Meanwhile, the results underscored the dependency of performance enhancement on the scan rate of cycling, revealing plausible correlations with mass transfer and electrode surface dynamics. Furthermore, the findings indicated that the selectivity towards HCOOH and C2H4 is closely related to the CO2/CO ratios of gas sources. This provides insight into the potential for modulating selectivity of industrial gas reduction for improved product quality and customization.

Innovative syntheses of immobilized CuxO semiconductors grown on 3D prints and their photoelectrochemical activity for sulfamethoxazole degradation

Traditional copper oxide manufacturing processes require high energy consumption, high synthesis temperatures, and long process times. This study proposes an innovative additive manufacturing process to support immobilized copper oxide, offering greater design flexibility and customization. CuxO semiconductors were synthesized on 3D-printed substrates via the anodization process and evaluated for their effectiveness in degrading sulfamethoxazole (SMX). XRD analysis of the samples revealed the presence of both CuO and Cu2O crystalline phases, this mixture of oxides helps to expand the absorption range of visible light. The immobilized CuxO semiconductors exhibited band gaps ranging between 1.6 and 1.8 eV. Negative current densities and Mott-Schottky analysis confirmed the nature of the p-type semiconductor. Semiconductors grown by 3D printing demonstrated remarkable degradation capacity for the antibiotic sulfamethoxazole (SMX), achieving 60% degradation after 360 minutes under visible light. Kinetic degradation tends to be a first-order and zero-order model. TOC analysis further revealed the formation of reaction intermediates during SMX degradation, ultimately leading to the mineralization of the contaminant. Based on these results, we report, for the first time CuxO semiconductors grown on large 3D-printed substrates as promising photocatalysts for the degradation of emerging water pollutants. Based on these results, we report, for the first time, that CuxO semiconductors grown on large 3D-printed substrates are promising photocatalysts for the degradation of emerging water contaminants. Furthermore, it should be emphasized that the proposed method is faster and does not require subsequent thermal treatments for its functionalization, making it attractive for various industrial applications.

Sustainable methyl formate generation by dehydrogenation of green methanol over Cu_SiO2/MgO

Copper impregnated SiO2 and MgO catalysts were prepared, characterised, and tested for the synthesis of methyl formate (MF) from methanol by dehydrogenation. Compared to the Cu-impregnated pure oxides, MF formation was improved when SiO2/MgO mixtures were used as support. For further comparison, a silver impregnated mixed oxide catalyst, known for its dehydrogenation ability, and a typical methanol catalyst (Cu/ZnO/Al2O3) were tested. Both catalysts displayed non or poorer performance under tested reaction conditions. High catalytic activity was assigned, besides the Cu content, to the presence of both medium acidic and basic sites. At 240 °C and 1 bar, the highest MF yield of 34 % has been obtained with the mixture of oxides containing the highest MgO ratio of 35 mol%. By exposing the prepared catalyst to a methanol/water mixture (36 wt% water), methanol conversion drops to 5 %, but compared to the reference Cu/ZnO/Al2O3 catalyst, two times the selectivity towards MF was obtained. With respect to sustainable technology development, direct coupling of green methanol synthesis from CO2/H2 gas feed and MF production without water removal is not recommended, since the yield to MF is below 2 % in this case.

The effects of local variations in conditions on carbon storage and release in the continental mantle.

Recent advances indicate that the amount of carbon released by gradual degassing from the mantle needs to be revised upwards, whereas the carbon supplied by plumes may have been overestimated in the past. Variations in rock types and oxidation state may be very local and exert strong influences on carbon storage and release mechanisms. Deep subduction may be prevented by diapirism in thick sedimentary packages, whereas carbonates in thinner sequences may be subducted. Carbonates stored in the mantle transition zone will melt when they heat up, recognized by coupled stable isotope systems (e.g. Mg, Zn, Ca). There is no single 'mantle oxygen fugacity', particularly in the thermal boundary layer (TBL) and lowermost lithosphere, where very local mixtures of rock types coexist. Carbonate-rich melts from either subduction or melting of the uppermost asthenosphere trap carbon by redox freezing or as carbonate-rich dykes in this zone. Deeply derived, reduced melts may form further diamond reservoirs, recognized as polycrystalline diamonds associated with websteritic silicate minerals. Carbon is released by either edge-driven convection, which tears sections of the TBL and lower lithosphere down so that they melt by a mixture of heating and oxidation, or by lateral advection of solids beneath rifts. Both mechanisms operate at steps in lithosphere thickness and result in carbonate-rich melts, explaining the spatial association of craton edges and carbonate-rich magmatism. High-pressure experiments on individual rock types, and increasingly on reactions between rocks and melts, are fine-tuning our understanding of processes and turning up unexpected results that are not seen in studies of single rocks. Future research should concentrate on elucidating local variations and integrating these with the interpretation of geophysical signals. Global concepts such as average sediment compositions and a uniform mantle oxidation state are not appropriate for small-scale processes; an increased focus on local variations will help to refine carbon budget models.

Substance use disorder of equimolar oxygen-nitrous oxide mixture in French sickle-cell patients: results of the PHEDRE study

BackgroundIn many countries, nitrous oxide is used in a gas mixture (EMONO) for short-term analgesia. Cases of addiction, with significant misuse, have been reported in hospitalized patients. Patients suffering from sickle cell disease (SCD) could represent a high-risk population for substance use disorder (SUD) due to their significant pain crisis and repeated use of EMONO. The objective of the PHEDRE study was to assess the prevalence of SUD for EMONO in French SCD patients.ResultsA total of 993 patients were included. Among 339 EMONO consumers, only 38 (11%) had a SUD, with very few criteria, corresponding mainly to a mild SUD due to a use higher than expected (in quantity or duration) and relational tensions with the care teams. Almost all patients (99.7%) were looking for an analgesic effect, but 68% of patients were also looking for other effects. The independent risks factors associated with at least one SUD criterion were: the feeling of effects different from the expected therapeutic effects of EMONO, at least one hospitalization for vaso occlusive crisis in the past 12 months and the presence of a SUD for at least one other analgesic drug.ConclusionsThe use of EMONO was not problematic for the majority of patients. Manifestations of SUD that led to tensions with healthcare teams should alert and lead to an evaluation, to distinguish a true addiction from a pseudoaddiction which may be linked to an insufficient analgesic treatment related to an underestimation of pain in SCD patients.Trial registration: Clinical Trials, NCT02580565. Registered 16 October 2015, https://clinicaltrials.gov/