Minor Amounts Of Water Research Articles

Molecular dynamics of vegetable oil extraction and degumming: Analysis of micelles and phospholipid bilayers in different solvents

AbstractUnderstanding the molecular‐level mechanisms of vegetable oil extraction and degumming remains limited. This study aimed to investigate these processes using molecular dynamics (MD), with a focus on the challenges associated with replacing n‐hexane with ethanol. MD simulations with a coarse‐grained force field (Martini 3) were conducted to examine the behavior of phospholipid mono/bilayers with and without triacylglycerol in various solvents, including water, absolute and aqueous ethanol (with 0%–10% water content by weight), and n‐hexane. Trilinolein and phospholipids with 16–18 carbon tails and 0–2 unsaturations were considered. The degree of unsaturation and tail size of phospholipids did not significantly affect bilayer formation in water. However, they influenced bilayer organization, as measured by the order parameter, bilayer thickness, and area. The phospholipid bilayer, composed of 1‐palmitoyl‐2‐oleoyl‐sn‐glycero‐3‐phosphocholine (POPC), exhibited a well‐defined structure in water, partial disruption in ethanol, and complete disruption in n‐hexane. The presence of triacylglycerol had no effect on phospholipid monolayers in water but increased lipid disorder in ethanol. Minor amounts of water in ethanol did not significantly alter the behavior of the lipid layers. MD simulations, combined with artificial intelligence, identified and quantified the formation of micelles during the degumming process, both in conjunction with n‐hexane extraction and independently as a function of water concentration. The volume and number of micelles were strongly influenced by the water content. Molecular dynamics in food engineering is relatively limited and scarce because of the complex nature of the systems. However, this study successfully demonstrates its applicability in this context.

2nd generation PLA; Lactide formation directly from aqueous lactic acid

In order to develop a 2nd generation polylactic acid (PLA) process, lactide (LD) was synthesized directly from a commercially available 90% aqueous lactic acid (LA) solution. Experiments were conducted in an ordinary continuous flow fixed bed reactor. The reaction was carried out over various zeolites and γ-Al2O3 catalysts. Furthermore, the influence of pressure, temperature and water content in the inlet was studied. The highest LD selectivity of 98.9% was obtained using 90% LA and γ-Al2O3 as catalyst. In addition, it is concluded that LD yield increases when using highly concentrated LA oligomer with a minor amount of water. The catalysts were characterized by inductively coupled plasma atomic emission spectroscopy (ICP-AES), X-ray powder diffraction (XRD), nitrogen adsorption isotherms (BET), temperature programmed desorption of ammonia (NH3-TPD) and pyridine Fourier transformed infrared spectroscopy (Py-FTIR).

Water Recycling in the Deep Earth: Insights From Integrated μ‐XRF, THz‐TDS Spectroscopy, TG, and DCS of High‐Pressure Granulite

AbstractSubduction‐related dehydration and exhumation‐related rehydration play an important role in water recycling on Earth. Water can be transported to the deep mantle through crustal subduction, whereas the behavior of water in the subducted crust during exhumation remains enigmatic. Here, we use an integrated micro X‐ray fluorescence spectrometry, transmission terahertz time‐domain, thermogravimetry, and differential scanning calorimetry approach for the first time on high‐pressure mafic granulite and amphibolite to investigate the water species and contents, as well as exhumation rehydration reactions. Our study demonstrates that garnet, hornblende, and ilmenite contain considerable amounts, and plagioclase contains minor amounts of water as molecular and structural species, whereas quartz contains only a minor amount of structural water. Water released from garnet and external fluids from the grain boundary will either migrate into hornblende, plagioclase, ilmenite, and quartz, or stored in the mantle wedge, or further subducted into the deep mantle. We suggest that water recycling between the Earth's surface and deep mantle is an unequilibrium process, and the lower crust and mantle may store a significant amount of water in deep Earth and can function as a container to feed and maintain the water recycling balance.

Copper-Catalyzed Ligand-Controlled Selective Borocarbonylation of α-Substituted Styrenes Toward β-Boryl Aldehydes and Cyclopropyl Boronate Esters

Copper-Catalyzed Ligand-Controlled Selective Borocarbonylation of α-Substituted Styrenes Toward β-Boryl Aldehydes and Cyclopropyl Boronate Esters

Moisture effect on the separation of CO2/CH4 mixtures with amine-functionalised porous silicas

The effect of minor amounts of water on the CO2 and CH4 adsorption on primary and secondary amine-functionalised mesoporous silicas (APTES@SBA-15 and DEAPTES@SBA15, respectively) was studied with a combination of high-pressure gas adsorption, solid state NMR of labelled 13CO2 and density functional theory (DFT) calculations. Known amounts of water were pre-adsorbed on the materials (0.047 to 0.157 mmol∙g−1) and the adsorption performance for CO2 and CH4 was compared to the performance of the dry samples. We observed that even when only minor amounts of water are present, the tertiary amine-functionalised material revealed a significant enhancement of the selectivity for CO2 (from ca. 5.8 to 208) while the one with primary amine maintained the same adsorption properties. This is related to the change in the adsorption mechanism in DEAPTES@SBA15 when water is present since water participates in the reaction of the tertiary amine with CO2 to produce bicarbonate (confirmed by NMR and DFT results). Such species was not observed in APTES@SBA-15 with water. From a broader perspective, the results presented in this work are relevant to confirm the suitability of this type of hybrid adsorbents in industrial applications related with CO2 adsorption, where minor amounts of water may be present in the process streams, such as during bio, landfill, or natural gas upgrading, or also in carbon capture applications.

Contributions to the stereochemistry of zirconium oxysalts\u2014part IV: syntheses and crystal structures of Zr2(OH)2(XO4)3\xb74H2O (X\u2009=\u2009S, Se), Zr(SO4)2\xb74H2O, and Zr(SeO3)2

Zr2(OH)2(XO4)3·4H2O (X = S, Se), Zr(SO4)2·4H2O, and Zr(SeO3)2 were synthesized at low-hydrothermal conditions from mixtures of Zr2O2(CO3)(OH)2, the respective acids, and minor amounts of water. While Zr2(OH)2(XO4)3·4H2O (X = S, Se) and Zr(SO4)2·4H2O form crystals up to several tenths of a mm, Zr(SeO3)2 was mainly obtained as microcrystalline powder, single crystals rarely exceeded 10 μm in size. Samples were investigated by single-crystal X-ray techniques and in the case of Zr(SeO3)2 also by X-ray powder diffraction. The compounds Zr2(OH)2(XO4)3·4H2O (X = S, Se) crystallize in the Ce2(OH)2(SO4)3·4H2O structure type (C2/c, Z = 4, a = 13.034(2) / 13.308(3), b = 6.500(1) / 6.683(2), c = 15.056(3) / 15.383(4) Å, β = 96.27(1) / 96.81(1)°, V = 1267.9(4) / 1358.5(6) Å3 for X = S / Se, respectively). Tetragonal aniprisms Zr[8]O8 are edge-connected to dimers that share corners with XO4 tetrahedra forming a three-dimensional network. Zr(SO4)2·4H2O (Fddd, Z = 8, a = 5.498(1), b = 11.618(3), c = 25.893(6) Å, V = 1653.9(6) Å3) is isotypic with the respective selenate compound. Occasionally, pseudomerohedral twinning is observed, simulating a larger monoclinic C-centered unit cell. Again, tetragonal antiprisms Zr[8]O8 are formed; however, they are corner-linked with SO4 tetrahedra to Zr(SO4)2 layers interconnected solely by hydrogen bonds. Zr(SeO3)2 crystallizes in P21/c, Z = 2; a = 4.9724(3), b = 8.5992(5), c = 6.9447(3) Å, β = 110.128(3)°, V = 278.81(3) Å3 (unit cell from powder data) and belongs to the β-Sn(SeO3)2 structure type established further for Ti(SeO3)2 and Pb(SeO3)2. Isolated ZrO6 octahedra share corners with the selenite groups forming a three-dimensional network.Graphical abstract

ASSESSMENT OF RESIDUAL SOIL PROPERTIES FOR SLOPE STABILITY ANALYSIS

Slope instability is a common natural geological hazard in tropical countries like Malaysia, with abundant residual soil and frequent rainfall. Over the years, these rainfalls have induced instabilities that lead to significant human and economic loss. To reduce the expected disastrous impacts due to rainfall-induced slope failure characterization of residual soil is necessary for evaluation of slope stability assessment. Therefore, this study aims to characterize the residual soil for numerical modelling of rainfall-induced slope failure and preliminary slope stability assessment so that future slope failure can be reduced. A series of experiments involving index properties tests and engineering properties tests were carried out on the residual soil samples collected from a slope located in UniversitiTeknologi Malaysia (UTM). Based on the particle size distribution and consistency the soil can be classified as high plasticity silt (MH). The maximum dry unit weight and optimum moisture content are 13.17kN/m3 and 30 %, respectively. Saturated hydraulic conductivity from the falling head test is 2.32055E-07 m/s, while the saturated gravimetric water content was 54%. The effective cohesion and angle of the internal fraction were 8 kPa and 32°, respectively. The average undrained shear strength and unconfined compressive strength were 105 kPa and 43 kPa, respectively. The result obtained in this study was utilized for the preliminary rainfall slope stability assessment in tropical residual soils by simulating rainfall of different intensities and duration on a typical slope profile using PLAXIS 2d. The results show that due to the low hydraulic conductivity and fine-grained nature of the soil, the slopes in the study area are more critical to the low intensity and long duration rainfall events (I≤4Ks). The highly intense and short-duration rainfall (I≥8Ks) has no significant effect on the safety of the soil, as most of the precipitation will contribute to runoff, and only a minor amount of water will infiltrate into the slope.

Odour-active compounds in liquid malt extracts for the baking industry

An odorant screening by gas chromatography–olfactometry (GC–O) and a crude aroma extract dilution analysis (AEDA) applied to the volatiles isolated from a light and a dark liquid malt extract (LME) by solvent extraction and solvent-assisted flavour evaporation (SAFE) identified 28 odorants. Fifteen major odorants were subsequently quantitated and odour activity values (OAVs) were calculated as ratio of the concentration to the respective odour threshold value (OTV). Important odorants in the light LME included 3-(methylsulfanyl)propanal (OAV 1500), (E)-β-damascenone (OAV 430), and 4-ethenyl-2-methoxyphenol (OAV 91). In the dark LME, sotolon (OAV 780), 3-(methylsulfanyl)propanal (OAV 550), (E)-β-damascenone (OAV 410), acetic acid (OAV 160), and maltol (OAV 120) were of particular importance. To get an insight into the changes during malt extract production, the quantitations were extended to the malt used as the starting material for both LMEs. Addition of a minor amount of water to malt before volatile extraction was shown to be effective to cover the free as well as the bound malt odorants. Results showed that some LME odorants originated from the starting material whereas others were formed during processing. Important process-induced LME odorants included (E)-β-damascenone and 4-ethenyl-2-methoxyphenol in the light LME as well as maltol, sotolon, (E)-β-damascenone, and 2-methoxyphenol in the dark LME. In summary, the odorant formation during LME production was shown to be more important than the transfer of odorants from the malt.

Contributions to the stereochemistry of zirconium oxysalts\u2014part III: syntheses and crystal structures of M2+Zr(SO4)3 with M\u2009=\u2009Mg, Mn, Co, Ni, Zn and Cd, and a note on (Fe3+,2+,Zr)2(SO4)3 and Fe2(SO4)3

The novel compounds M2+Zr(SO4)3 with M = Mg, Mn, Co, Ni, Zn, and Cd as well as (Fe3+,2+,Zr)2(SO4)3 were synthesized at mild hydrothermal conditions (Teflon-lined stainless steel vessels, 220 °C) from the mixtures of Zr2O2(CO3)(OH)2, the respective M2+(SO4)·nH2O hydrated salts, H2SO4 and a minor amount of water. Crystals up to several tenths of a mm in size were obtained within a few days and studied at 200 K by single-crystal X-ray diffraction techniques. All these compounds belong to the structure type of monoclinic Fe2(SO4)3; they are either isotypic in space group P21/n (No. 14), Z = 4, i.e. M2+Zr(SO4)3 with M = Mn, Co, Ni, Zn, and Cd as well as the mixed valence sulfate (Fe3+,2+,Zr)2(SO4)3 or in the case of MgZr(SO4)3, closely related but with a larger unit cell, in space group Pc and Z = 8. The framework of the monoclinic Fe2(SO4)3 structure is characterized by two types of isolated Fe3+O6 octahedra, corner-linked with three types of sulfate groups. In the isotypic M2+Zr(SO4)3 series, the Fe3+ atom on the Fe(1) position is substituted by Zr4+ while M2+ ions occupy the Fe(2) site in the ferric sulfate structure type. Mean cation-oxygen bond lengths (S[4]: 1.462–1.472 Å; Zr[6]: 2.053–2.060 Å as well as M2+–O distances) are generally rather short, but still within the range reported in literature.Graphic abstract

Origin and formation mechanisms of low oil saturation reservoirs in Nanpu Sag, Bohai Bay Basin, China

Abstract Low oil saturation reservoirs are increasingly encountered in superimposed sedimentary basins, however, the uncertainty about the origin of the low oil saturation becomes a major factor impeding further hydrocarbon exploration. Routine core analysis, (fluorescence) thin section, scanning electron microscope (SEM) and nuclear magnetic resonance (NMR) measurements were used to understand the characteristics and formation mechanisms of the low oil saturation reservoirs in the Paleogene Dongying Formation in the Nanpu sag, Bohai Bay Basin, East China. Irreducible water saturation was determined from sealed coring oil saturation testing and NMR logs. Wide ranges of porosity and permeability were observed, and the samples with moderate reservoir quality have the best oil bearing property. Low oil saturation oil layers are characterized by low oil saturation ( 40%), with only oil being produced whereas no water or only minor amounts of water being produced. The low oil saturation oil-water reservoirs refer to the low oil saturation layers in which both oil and water will be produced during oil testing. Irreducible water saturation increases with total clay content, with the authigenic clays (kaolinite, illite and mixed layer illite/smectite) blocking pore spaces, and resulting in high irreducible water saturations. Fluorescence thin sections combined with NMR measurements show that the NMR T2 (transversal relaxation time) distribution is uni-modal, with large intergranular pores being rare. Almost the entire pore-size range is oil bearing for the low oil saturation oil reservoirs. The large intergranular pores are fluorescence-free, while the intragranular dissolution pores and micropores emit fluorescence in the low oil saturation oil-water reservoirs. The NMR T2 distribution of low oil saturation oil-water reservoirs is bi-modal and right-skewed, and the main oil-bearing NMR pore size distribution ranges from 0.1 to 100 ms. High irreducible water content was encountered in the low oil saturation oil reservoirs and low oil saturation oil-water reservoirs, and only part of the large intergranular pores are oil saturated, and in some cases only the intragranular pores are saturated with oils forming low oil saturation oil reservoirs. The results help improve the knowledge of characteristics and formation of the low oil saturation oil layers, and could provide insights in enhancing oil recovery.

Mars: Formation and fate of a frozen Hesperian ocean

Late Hesperian-aged, circum-Tharsis floods interpreted to have formed by catastrophic release of groundwater cut large channels and debouched significant quantities of water into the northern lowlands of Mars. The floods are thought by many to have formed an ocean of significant volume and depth, encircled by contacts that have been interpreted as shorelines. Models of catastrophic groundwater release require a thick and continuous cryosphere with mean annual temperatures well below freezing much like those today. In this environment, the bodies of liquid formed by individual outflow events would have been very short lived, undergoing rapid freezing. We investigate the case where floods repeatedly flowed into the northern lowlands under climatic conditions that resemble those of the present day; the water from each flood froze in a geologically short period of time to form an ice layer. Successive ice layers accumulated to form an ocean-sized body of ice that filled the basin up to the -3650 contour, thereby enclosing a 110 m global equivalent layer (GEL) of water. Subsequent to the filling of the basin the ice slowly sublimated into the atmosphere to be lost to space or to accumulate in various surface and near-surface cold traps, such as the polar layered deposits. Where is this excess water today? The presence of the thick global cryosphere meant that only minor amounts of water were lost from the surface back into the global groundwater system. Approximately 20-30 m GEL of water is estimated to be at or near the surface today and exchanging with the atmosphere on geologic time scales (this includes the polar layered deposits and deposits elsewhere at depths less than approximately 80 m). Below the exchangeable reservoir is a non-exchangeable reservoir of unknown capacity. Present day loss rates to space fall far short of those needed to eliminate the mid-Hesperian ice ocean and those needed to cause the observed doubling of the D/H of the exchangeable reservoir since the mid-Hesperian. The discrepancy implies earlier loss rates must have been higher. Assuming a linear increase in loss rates because of the higher early EUV output of the Sun, we estimate that for a present inventory of 30 m GEL, 42 m GEL remains to be accounted for. Possibilities include greater dependence of losses of EUV than assumed, and enhanced losses during periods of high obliquity. In addition, large volumes of ice may be present near the surface at high latitudes outside the polar layered deposits as indicated by recent discoveries of ice layers in cliffs.

Impact ionisation mass spectrometry of platinum-coated olivine and magnesite-dominated cosmic dust analogues

Impact ionisation mass spectrometry enables the composition of cosmic dust grains to be determined in situ by spacecraft-based instrumentation. The proportion of molecular ions in the impact plasma is a function of the impact velocity, making laboratory calibration vital for the interpretation of the mass spectra, particularly at the low velocities typical of lunar or asteroid encounters. Here we present an analysis of laboratory impact ionisation mass spectra from primarily low (<15 km s−1) velocity impacts of both olivine and magnesite-dominated particles onto the SUrface Dust Mass Analyzer (SUDA) laboratory mass spectrometer.The cation mass spectra show characteristic peaks due to their constituent elements, with Mg, Al, Si, C, Ca, O and Fe frequently present. Contaminant species from the conductive coating process (B, Na, K, C, Pt) also occur, at varying frequencies. Possible saponite or talc inclusions in the magnesite particles are revealed by the presence of Si, Fe, Ca and Al in the magnesite mass spectra. Magnesium is clearly present at the lowest impact velocities (3 km s−1), at which alkali metals were presumed to dominate. Peaks attributed to very minor amounts of water or hydroxyl present in the grains are also seen at low velocities in both cation and anion mass spectra, demonstrating the feasibility of impact ionisation mass spectrometry in identifying hydrated or hydrous minerals, during very low velocity encounters or with very low abundances of water or hydroxy groups, in the impinging grains.Velocity thresholds for the reliable identification of the major elements within the magnesite and olivine cation spectra are presented. Additionally, relative sensitivity factors for Mg (5.1), Fe (1.5) and O (0.6) with respect to Si, in the olivine particles, at impact speeds >19 km s−1, were found to be very similar to those previously determined for orthopyroxene-dominated particles, despite different target and projectile materials. This confirms that quantitative analyses of mineral dust grain composition in space is viable despite initially poorly-constrained mineralogy.

Nanostructured lime-based materials for the conservation of calcareous substrates

Nanostructured lime-based materials for the conservation of calcareous substrates

Genesis of volatiles in suprasubduction basaltic melts from Tolbachik Volcano, Kamchatka

Vitreous basalts and plagioclase lapilli from Tolbachik Volcano studied by high-temperature gas chromatography reveal features of a fluid regime uncommon to suprasubduction melts. Prominent depletion in volatiles confirms the anomalous behavior of the Tolbachik fluid systems. Vitreous basalts contain minor amounts of water (0.16-0.27 wt.%) and carbon dioxide (95-440 ppm). New data on volatiles in the Tolbachik plagioclase lapilli show very low contents of CO2 and total gas (exclusive of H2O) and enrichment in reduced fluids (CO and CH4) relative to the basalts. In general, analysis of basalts and plagioclase lapilli from different eruptions trace a progressive increase in reduced fluids (CO and CH4) and decrease in CO2 and total gas from past to present events. The concentrations of CO2 decrease, while those of CO and CH4 in basalts and plagioclase lapilli increase systematically with an increase in FeO/MgO ratios and K2O contents in the lavas and in anorthite component in plagioclase.

Nanostructured lime-based materials for the conservation of calcareous substrates

Nanostructured lime-based materials for the conservation of calcareous substrates

Nanostructured lime-based materials for the conservation of calcareous substrates

Nanostructured lime-based materials for the conservation of calcareous substrates

Room-Temperature Self-Healing Polymers Based on Dynamic-Covalent Boronic Esters

Cross-linked polymers constructed with dynamic-covalent boronic esters were synthesized via photoinitiated radical thiol–ene click chemistry. Because the reversibility of the boronic ester cross-links was readily accessible, the resulting materials were capable of undergoing bond exchange to covalently mend after failure. The reversible bonds of the boronic esters were shown to shift their exchange equilibrium at room temperature when exposed to water. Nevertheless, the materials were observed to be stable and hydrophobic and absorbed only minor amounts of water over extended periods of time when submerged in water or exposed to humid environments. The facile reversibility of the networks allowed intrinsic self-healing under ambient conditions. Highly efficient self-healing of these bulk materials was confirmed by mechanical testing, even after subjecting a single site to multiple cut–repair cycles. Several variables were considered for their effect on materials properties and healing, including cross-lin...

Water in the slab: A trilogy

Abstract The geological and geophysical phenomena associated with water in the slab can be grouped into three different categories: those related to 1) the storage of water in the oceanic lithosphere at the surface, 2) the subduction of a hydrated slab and 3) its dehydration that ultimately leads to mantle regassing. Widespread hydration of the uppermost oceanic lithosphere occurs at mid-ocean ridges and more pervasively at the trench–rise system in response to bending-related fracturing and faulting. The amount of water stored in the upper lithosphere appears to be proportional to the spreading slowness and amount of bending. Hydrothermal alteration of the oceanic plate may also occur more locally along transform margins, fracture zones and volcanic ridges. Subduction of a hydrated slab should be observed from a reduction of seismic velocities, anomalous Vp/Vs ratios and seismic anisotropy in its uppermost portions, and shift of the main phase transformation boundaries characteristic of the mantle. Because of the increased buoyancy and weakness, hydrated or wet slabs should tend to stagnate over the 660 km discontinuity, favoring layered mantle convection patterns. Slab dehydration takes place according to the plate thermal regime function of the slab age and sinking velocity. Hydrous minerals in the oceanic crust and mantle are stable down to a maximum of 300 km and 1200 km depth, respectively, after which minor amounts of water can be retained in nominally anhydrous minerals. There is abundant geophysical evidence for dehydration of the slab crust and sub-Moho mantle, while fragmentary and often indirect evidence supports the presence of water in the lower plane of the Double Seismic Zone and at depths > 300 km.

Photochemical Electron Transfer Mediated Addition of Naphthylamine Derivatives to Electron-Deficient Alkenes

Using photochemical electron transfer, N,N-dimethylnaphthylamine derivatives are added to α,β-unsaturated carboxylates. The addition takes place exclusively in the α-position of electron-deficient alkenes and mainly in the 4-position of N,N-dimethylnaphthalen-1-amine. A minor regioisomer results from the addition in the 5-position of this naphthylamine. A physicochemical study reveals that the fluorescence quenching of N,N-dimethylnaphthalen-1-amine is diffusion-controlled and that the back electron transfer is highly efficient. Therefore no transformation is observed at lower concentrations. To overcome this limitation and to induce an efficient transformation, minor amounts of water or another proton donor as well as an excess of the naphthylamine derivative are necessary. A mechanism involving a contact radical ion pair is discussed. Isotopic labeling experiments reveal that no hydrogen is directly transferred between the substrates. The hydrogen transfer to the furanone moiety observed in the overall reaction therefore results from an exchange with the reaction medium. An electrophilic oxoallyl radical generated from the furanone reacts with the naphthylamine used in excess. Concerning some mechanistic details, the reaction is compared with radical and electrophilic aromatic substitutions. The transformation was carried out with a variety of electron-deficient alkenes. Sterically hindered furanone derivatives are less reactive under standard conditions. In a first experiment, such a compound was transformed using heterogeneous electron transfer photocatalysis with TiO(2).

Effect of water on the electrical conductivity of lower crustal clinopyroxene

[1] The electrical conductivity of lower crustal clinopyroxene was measured at 6–12 kbar, 250–1000°C, and Ni-NiO buffer conditions. The dependence of electrical conductivity on water content was studied using both natural and preannealed samples separated from a fresh xenolith granulite, with water contents from 0 to 375 ppm. An end-loaded piston cylinder apparatus and a Solarton-1260 Impedance/Gain Phase Analyzer were used in the study over a frequency range of 0.01–106 Hz to obtain the complex impedance spectra. The results show that the influence of pressure is very weak relative to temperature and water content and that two distinct mechanisms with different activation enthalpies dominate electrical conduction under dry and wet conditions. For the dry sample, the activation enthalpy is ∼102 kJ/mol and the main charge carriers are small polarons, i.e., hopping of electron holes between ferrous and ferric irons. For wet samples, the electrical conductivity is significantly enhanced with an activation enthalpy of ∼70 kJ/mol and the charge carriers are likely to be protons. Under hydrous conditions, the activation enthalpies are nearly independent of water content and the conductivity is a function of water content with an exponent of ∼1. As a major constituent of granulites with >60% modal volume in some regions, clinopyroxene containing minor amounts of water may contribute significantly to the high electrical conductivity in the lower crust, especially under stable continental regions.