An activity model for phase equilibria in the H2O–CO2–NaCl system

We present a semi-empirical thermodynamic model with uncertainties that encompasses the full range of compositions in H2O–CO2–NaCl mixtures in the range of 10–380 °C and 1–3500 bars. For binary H2O–CO2 mixtures, the activity–composition model is built from solubility experiments. The parameters describing interactions between H2O and CO2 are independent of the absolute thermodynamic properties of the end-members and vary strongly non-linearly with pressure and temperature. The activity of water remains higher than 0.88 in CO2-saturated solutions across the entire pressure–temperature range. In the H2O–NaCl system, it is shown that the speciation of aqueous components can be accounted for by a thermodynamic formalism where activities are described by interaction parameters varying with intensive properties such as pressure and temperature but not with concentration or ionic strength, ensuring consistency with the Gibbs–Duhem relation.The thermodynamic model reproduces solubility experiments of halite up to 650 °C and 10 kbar, and accounts for ion pairing of aqueous sodium and chloride ions with the use of associated and dissociated aqueous sodium chloride end-members whose relative proportions vary with salinity. In the H2O–CO2–NaCl system, an activity–composition model reproduces the salting-out effect with interactions parameters between aqueous CO2 and the aqueous species created by halite dissolution. The proposed thermodynamic properties are compatible with the THERMOCALC database (Holland and Powell, 2011) and the equations used to retrieve the activity model in H2O–CO2 can be readily applied to other systems, including minerals

Very-low-grade phyllosilicates in the Aravis massif (Haute-Savoie, France) and the di-trioctahedral substitution in chlorite

Very-low-grade mineral veins investigated in the impure limestone massif of the Aravis (Haute-Savoie, France) yielded a rich mineral assemblage typified by dolomite, calcite, quartz, illitic mica, fluorite and three types of chlorite. The vein network extends over more than 5 km and was probably emplaced around peak burial of the limestone (∼7 km depth, 190 ∘C). The mineralogy has been investigated with electron microscopy, mass spectrometry and X-ray diffraction, with emphasis on chlorite types. The first chlorite type is a chamosite often interlayered with illitic mica. The second type is a Mg-rich, Al-depleted cookeite. The third type is a Li-rich sudoite. Presence of the three chlorite types shows limited solubility between di-trioctahedral chlorite phase components (sudoite and cookeite) and with tri-trioctahedral chlorite (chamosite). Departure of the Li-rich sudoite and Mg-rich cookeite from the ideal end-member compositions suggests solid solutions towards a Li-sudoite component. The associated illitic mica does not contain Li in significant proportion but shows pyrophyllitic and di-trioctahedral substitution, without a Tschermak component. These results call for systematic studies of the Li content of chlorite and for better modelling of di-trioctahedral substitution in chlorite and mica.</p

Near-future CO2 levels impair the olfactory system of a marine fish

This is the author accepted manuscript. The final version is available from Springer Nature via the DOI in this recordData availability: All raw sequence data are accessible at the NCBI Sequence Read Archive through accession number SRP097118. Water chemistry, behaviour and electrophysiology data are available through Pangaea (https://doi.pangaea.de/10.1594/PANGAEA.884674).Survival of marine fishes that are exposed to elevated near-future CO2levels is threatened by their altered responses to sensory cues. Here we demonstrate a physiological and molecular mechanism in the olfactory system that helps to explain altered behaviour under elevated CO2. We combine electrophysiology measurements and transcriptomics with behavioural experiments to investigate how elevated CO2affects the olfactory system of European sea bass (Dicentrarchus labrax). When exposed to elevated CO2(approximately 1,000 µatm), fish must be up to 42% closer to an odour source for detection, compared with current CO2levels (around 400 µatm), decreasing their chances of detecting food or predators. Compromised olfaction correlated with the suppression of the transcription of genes involved in synaptic strength, cell excitability and wiring of the olfactory system in response to sustained exposure to elevated CO2levels. Our findings complement the previously proposed impairment of γ-aminobutyric acid receptors, and indicate that both the olfactory system and central brain function are compromised by elevated CO2levels.This study was supported by grants from Association of European Marine Biology Laboratories (227799), the Natural Environment Research Council (R.W.W.; NE/H017402/1), the Biotechnology and Biological Sciences Research Council (R.W.W.; BB/D005108/1), Fundação para a Ciência e Tecnologia (Portuguese Science Ministry) (UID/Multi/04326/2013) and a Royal Society Newton International Fellowship to C.S.P. C.S.P. is also a beneficiary of a Starting Grant from AXA

HSP90 regulates temperature-dependent seedling growth in Arabidopsis by stabilizing the auxin co-receptor F-box protein TIR1

Recent studies have revealed that a mild increase in environmental temperature stimulates the growth of Arabidopsis seedlings by promoting biosynthesis of the plant hormone auxin. However, little is known about the role of other factors in this process. In this report we show that increased temperature promotes rapid accumulation of the TIR1 auxin co-receptor, an effect that is dependent on the molecular chaperone HSP90. In addition, we show that HSP90 and the co-chaperone SGT1 each interact with TIR1, confirming that TIR1 is an HSP90 client. Inhibition of HSP90 activity results in degradation of TIR1 and interestingly, defects in a range of auxin-mediated growth processes at lower as well as higher temperatures. Our results indicate that HSP90 and SGT1 integrate temperature and auxin signaling in order to regulate plant growth in a changing environment

Thermodynamic modelling of clay dehydration, stability and compositional evolution with temperature, pressure and H2O activity

We propose a thermodynamic approach to model the stepwise dehydration with increasing temperature or decreasing H2O activity of K, Na, Ca and Mg-smectite. The approach relies on the relative stability of the different solid-solutions that describe the hydration of di- or trioctahedral-smectites containing 0, 1, 2 or 3 interlayer water layers. The inclusion of anhydrous mica end-members makes it possible to cover, with the same solid-solution model, the entire range of composition from low-charge smectite to mica, through high-charge smectite and illite. Non-ideal Margules parameters were used to describe the non-ideality of the solid solutions between the hydrated and dehydrated smectite end-members. Standard state properties of all smectite end-members as well as Ca- and Mg-muscovite and -phlogopite were initially estimated by oxide summation. These values were then refined and the other non-ideal interactions were estimated on the basis of different experimental data. The stepwise dehydration of smectite, and its stability and compatibility relations were calculated by Gibbs free energy minimising. Our results account for the progressive evolution of smectite to interlayered illite/smectite and then to mica, as observed in nature and experiments, and our model provides an explanation for the thermodynamic stability of smectite and illite/smectite compared to mica + kaolinite or pyrophyllite assemblages. The results suggest that the enthalpic contribution of interlayer water is a function of the ionic potential of the interlayer cation and the number of interlayer water molecules. This evolution makes possible to estimate the standard-state thermodynamic parameters and hydration-temperature behaviour of smectite of virtually all possible compositions. For the four-interlayer cations considered in the study, our model reproduces the 3 --> 2 --> 1 water-layer transitions that accompany a reduction of water activity or an increase of temperature at ambient pressure. The range of water content and interlayer distance calculated for the 3w, 2w and 1w states are also in fair agreement with the experimental values at ambient pressure.</p

Kolmogorov Complexity and Cellular Automata Classification

We present a new approach to cellular automata (CA for short) classification based on algorithmic complexity. We construct a parameter which is based only on the transition table of CA and measures the &quot;randomness&quot; of evolutions; is better, in a certain sense, than any other parameter defined on rule tables. We investigate the relations between the classical approach based on topology and ours based on algorithmic randomness. We also compare our parameter with Langton&apos;s one: we prove that ours is theoretically better and also agrees with some practical evidences reported in literature. Finally we propose a protocol to approximate and to make experiments on CA dynamical behavior

Les minéraux enregistreurs de l’histoire des continents

National audienc

Crustal stacking and expulsion tectonics during continental subduction: P-T deformation constraints from Oman

The northeastern continental margin of Oman in the Saih Hatat region is characterized by high-pressure (HP) chloritoid- or carpholite-bearing metasediments and highly deformed mafic eclogites and blueschists in a series of tectonic units bounded by high-strain ductile shear zones. New data on the upper cover units of this HP nappe stack indicate that all of them underwent similar P conditions to the underlying Hulw structural unit (with a cooler exhumation pressure-temperature path). Early SSW directed crustal thickening during ophiolite emplacement created recumbent folds and strong schistose fabrics in these Permian-Mesozoic shelf carbonates and was followed by later NNE dipping normal sense shear zones and normal faults. The Mayh unit shows high strain in a 15-25 km long sheath fold that likely formed at carpholite grade pressures of 8-10 kbar. We show that there are no significant P differences across the Hulw shear zone (upper plate-lower plate discontinuity) or between the overlying Mayh, Yenkit-Yiti, and Ruwi units. Postpeak metamorphic exhumation of the HP rocks was therefore accomplished by bottom-to-SSW (rather than top-to-NNE) active footwall extrusion beneath a fixed, static, passive hanging wall. Footwall uplift beneath these passive roof faults resulted in progressive expulsion of the HP rocks from depths of ∼80-90 km (eclogites) and mainly 30-35 km (blueschists and chloritoid-/carpholite-bearing units) during the Campanian-Early Maastrichtian. Oman thus provides a detailed record of how continental material (thick platform shelf carbonates) progressively jammed a subduction zone and emphasizes the contrasting behavior between cover units and their underlying basement. Copyright 2010 by the American Geophysical Union

Dehydration of dioctahedral aluminous phyllosilicates: thermodynamic modelling and implications for thermobarometric estimates

We propose a solid-solution model for dioctahedral aluminous phyllosilicates accounting for the main compositional variations, including hydration, observed in natural smectites, interlayered illite/smectite, illites, and phengites from diagenetic to high-grade metamorphic conditions. The suggested formalism involves dehydrated micas and hydrated pyrophyllite-like thermodynamic end-members. With these end-members, the equilibrium conditions of quartz + water + K-bearing mica-like phyllosilicates of fixed 2:1 composition are represented by a line in P–T space along which the interlayer water content varies. The relevant thermodynamic properties required for the calculation of equilibrium conditions were derived using a set of 250 natural data of known maximal temperature and pressure conditions, which covers a range between 25°C and few MPa to 800°C and 5 GPa. The temperatures calculated at fixed pressure with our model are in fair agreement with those reported in the literature for the 250 natural data. At low temperature and pressure, the amount of interlayer water in K-deficient phengite and illite is predicted to reach 100% of the apparent vacancies, which is consistent with previous values reported in the literature. Although the amount of interlayer water is predicted to decrease with pressure and temperature, it is calculated to be significant in K-deficient phengite from LT–HP pelites metamorphosed at about 350°C, 10 kbar. The presence of molecular water in the interlayer site of such phengites has been confirmed by FTIR mapping. Its implications for P–T estimates are discussed