Sulfur Partition Research Articles

Glucose enhances indolic glucosinolate biosynthesis without reducing primary sulfur assimilation.

The effect of glucose as a signaling molecule on induction of aliphatic glucosinolate biosynthesis was reported in our former study. Here, we further investigated the regulatory mechanism of indolic glucosinolate biosynthesis by glucose in Arabidopsis. Glucose exerted a positive influence on indolic glucosinolate biosynthesis, which was demonstrated by induced accumulation of indolic glucosinolates and enhanced expression of related genes upon glucose treatment. Genetic analysis revealed that MYB34 and MYB51 were crucial in maintaining the basal indolic glucosinolate accumulation, with MYB34 being pivotal in response to glucose signaling. The increased accumulation of indolic glucosinolates and mRNA levels of MYB34, MYB51, and MYB122 caused by glucose were inhibited in the gin2-1 mutant, suggesting an important role of HXK1 in glucose-mediated induction of indolic glucosinolate biosynthesis. In contrast to what was known on the function of ABI5 in glucose-mediated aliphatic glucosinolate biosynthesis, ABI5 was not required for glucose-induced indolic glucosinolate accumulation. In addition, our results also indicated that glucose-induced glucosinolate accumulation was due to enhanced sulfur assimilation instead of directed sulfur partitioning into glucosinolate biosynthesis. Thus, our data provide new insights into molecular mechanisms underlying glucose-regulated glucosinolate biosynthesis.

The role of crystallization‐driven exsolution on the sulfur mass balance in volcanic arc magmas

AbstractThe release of large amounts of sulfur to the stratosphere during explosive eruptions affects the radiative balance in the atmosphere and consequentially impacts climate for up to several years after the event. Quantitative estimations of the processes that control the mass balance of sulfur between melt, crystals, and vapor bubbles is needed to better understand the potential sulfur yield of individual eruption events and the conditions that favor large sulfur outputs to the atmosphere. The processes that control sulfur partitioning in magmas are (1) exsolution of volatiles (dominantly H2O) during decompression (first boiling) and during isobaric crystallization (second boiling), (2) the crystallization and breakdown of sulfide or sulfate phases in the magma, and (3) the transport of sulfur‐rich vapor (gas influx) from deeper unerupted regions of the magma reservoir. Vapor exsolution and the formation/breakdown of sulfur‐rich phases can all be considered as closed‐system processes where mass balance arguments are generally easier to constrain, whereas the contribution of sulfur by vapor transport (open system process) is more difficult to quantify. The ubiquitous “excess sulfur” problem, which refers to the much higher sulfur mass released during eruptions than what can be accounted for by amount of sulfur originally dissolved in erupted melt, as estimated from melt inclusion sulfur concentrations (the “petrologic estimate”), reflects the challenges in closing the sulfur mass balance between crystals, melt, and vapor before and during a volcanic eruption. In this work, we try to quantify the relative importance of closed‐ and open‐system processes for silicic arc volcanoes using kinetic models of sulfur partitioning during exsolution. Our calculations show that crystallization‐induced exsolution (second boiling) can generate a significant fraction of the excess sulfur observed in crystal‐rich arc magmas. This result does not negate the important role of vapor migration in sulfur mass balance but rather points out that second boiling (in situ exsolution) can provide the necessary yield to drive the excess sulfur to the levels observed for crystal‐rich systems. In contrast, in crystal‐poor systems, magma recharge that releases sulfur‐rich bubbles is necessary and most likely the primary contributor to sulfur mass balance. Finally, we apply our model to account for the effect of sulfur partitioning during second boiling and its impact on sulfur released during the Cerro Galan supereruption in Argentina (2.08 Ma) and show the potential importance of second boiling in releasing a large amount of sulfur to the atmosphere during the eruption of large crystal‐rich ignimbrites.

Structural biology and regulation of the plant sulfation pathway

In plants, sulfur is an essential nutrient that must be converted into usable metabolic forms for the formation of sulfur-containing amino acids and peptides (primary route) and for the modification of diverse metabolites (secondary route). In plants, the fate of assimilated sulfate depends on the three enzymes – ATP sulfurylase, adenosine-5′-phosphate (APS) reductase, and APS kinase - that form a branchpoint in the pathway. ATP sulfurylase catalyzes the formation of the critical intermediate APS, which can either be used in the primary assimilatory route or be phosphorylated to 3′-phospho-APS (PAPS) for a variety of sulfation reactions. Recent biochemical and structural studies of the branchpoint enzymes in plant sulfur metabolism suggest that redox-regulation may control sulfur partitioning between primary and secondary routes. Disulfide-based redox switches differentially affect APS reductase and APS kinase. Oxidative conditions that promote disulfide formation increase the activity of APS reductase and decreases PAPS production by APS kinase. Here we review recent work on the ATP sulfurylase and APS kinase from plants that provide new insight on the regulation of PAPS formation, the structural evolution of these enzymes in different organisms, and redox-control of this key branchpoint in plant sulfur metabolism.

Sulphide Capacity of CaO–SiO<sub>2</sub>–Al<sub>2</sub>O<sub>3</sub>–MgO System Relevant to Low MgO Blast Furnace Slags

Desulphurization has been of more importance to control the quality of hot metal in blast furnace (BF) with increasing utilization of low-grade iron ores and poor-quality fuels as well as reducing the slag volume by decreasing MgO concentration. To improve performance with better understanding the desulphurization in BFs, sulphide capacities of CaO-SiO -Al O -MgO system relevant to BF slags were experimentally determined using gas-slag equilibration technique. The results show that sulphide capacity increases with the increase in temperature, CaO/SiO weight ratio and MgO at fixed Al O concentration. The experimental results were further compared with sulphide capacity obtained from available models in open literature. In addition, the equilibrium sulphur partition ratio between slag and hot metal was calculated from sulphide capacity with oxygen activity in the melt, which is also compared with industrial data and the laboratory experiments of kinetic desulphurization of hot metal.

Fluid-melt partitioning of sulfur in differentiated arc magmas and the sulfur yield of explosive volcanic eruptions

The fluid-melt partitioning of sulfur (DSfluid/melt) in differentiated arc magmas has been experimentally investigated under oxidizing conditions (Re–ReO2 buffer) from 800 to 950°C at 200MPa. The starting glasses ranged in composition from trachyte to rhyolite and were synthesized targeting the composition of the residual melt formed after 10–60% crystallization of originally trachy-andesitic, dacitic and rhyodacitic magmas (Masotta and Keppler, 2015). Fluid compositions were determined both by mass balance and by Raman spectroscopy of fluid inclusions. DSfluid/melt increases exponentially with increasing melt differentiation, ranging from 2 to 15 in the trachytic melt, from 20 to 100 in the dacitic and rhyodacitic melts and from 100 to 120 in the rhyolitic melt. The variation of the DSfluid/melt is entirely controlled by the compositional variation of the silicate melt, with temperature having at most a minor effect within the range investigated. Experiments from this study were used together with data from the literature to calibrate the following model that allows predicting DSfluid/melt for oxidized arc magmas: lnDSfluid/melt=9.2-31.4·nbot-1.8·ASI-29.5·Al#+4.2·Ca#where nbot is the non-bridging oxygen atoms per tetrahedron, ASI is the alumina saturation index, Al# and Ca# are two empirical compositional parameters calculated in molar units (Al#=XAl2O3XSiO2+XTiO2+XAl2O3 and Ca#=XCaOXNa2O+XK2O).The interplay between fluid-melt partitioning and anhydrite solubility determines the sulfur distribution among anhydrite, melt and fluid. At increasing melt polymerization, the exponential increase of the partition coefficient and the decrease of anhydrite solubility favor the accumulation of sulfur either in the fluid phase or as anhydrite. On the other hand, the higher anhydrite solubility and lower partition coefficient for less polymerized melts favor the retention of sulfur in the melt. At equilibrium conditions, these effects yield a maximum of the sulfur fraction in the fluid phase for slightly depolymerized melts (nbot=0.05–0.15). Our data allow quantitative predictions of the sulfur yield of explosive volcanic eruptions over a wide range of magma compositions.

The Effect of High Temperature Thermal Cycling on Near-Surface Sulphur Partitioning in Gamma and Gamma Prime Phases and Its Implications on Sulphur Segregation in Coated Ni-Base Superalloys

Secondary ion mass spectrometry (SIMS) was used to study the near-surface segregation of sulphur during; (a) the thermal processing stages (diffusion annealing after application of Pt bond coat and after secondary ageing following subsequent deposition of the Y2O3-stabilised ZrO2 top coat) and (b) thermal cycling in the Ni-base superalloy, CMSX4. In the thermal processing stages, an increased segregation of sulphur was observed within the upper regions of the Pt bond coat after diffusion annealing, while following secondary ageing, the sulphur segregation in this layer became heterogeneous with discrete pockets of enrichment (≫1 ppm) and regions of depletion (≪1 ppm). During thermal cycling, partitioning of sulphur occurred to the Pt-enriched γ′ region characterised by the finger-like morphology, while examination of TBC spalled specimens showed significant depletion of sulphur within the substrate in the vicinity of the surface. The reservoir for sulphur-depletion within the substrate was definitively identified as the Pt-enriched γ′ region. A quantitative method for the calculation of sulphur-segregation at the surface in terms of mono-layers is presented.

Crustal‐scale degassing due to magma system destabilization and magma‐gas decoupling at Soufrière Hills Volcano, Montserrat

AbstractActivity since 1995 at Soufrière Hills Volcano (SHV), Montserrat has alternated between andesite lava extrusion and quiescence, which are well correlated with seismicity and ground deformation cycles. Large variations in SO2 flux do not correlate with these alternations, but high and low HCl/SO2 characterize lava dome extrusion and quiescent periods respectively. Since lava extrusion ceased (February 2010) steady SO2 emissions have continued at an average rate of 374 tonnes/day (± 140 t/d), and incandescent fumaroles (temperatures up to 610oC) on the dome have not changed position or cooled. Occasional short bursts (over several hours) of higher (∼ 10x) SO2 flux have been accompanied by swarms of volcano‐tectonic earthquakes. Strain data from these bursts indicate activation of the magma system to depths up to 10 km. SO2 emissions since 1995 greatly exceed the amounts that could be derived from 1.1 km3 of erupted andesite, and indicating extensive partitioning of sulfur into a vapour phase, as well as efficient decoupling and outgassing of sulfur‐rich gases from the magma. These observations are consistent with a vertically extensive, crustal magmatic mush beneath SHV. Three states of the magmatic system are postulated to control degassing. During dormant periods (103 to 104 years) magmatic vapour and melts separate as layers from the mush and decouple from each other. In periods of unrest (years) without eruption, melt and fluid layers become unstable, ascend and can amalgamate. Major destabilization of the mush system leads to eruption, characterized by magma mixing and release of volatiles with different ages, compositions and sources.

Partitioning of sulfur and chlorine between aqueous fluid and basaltic melt at 1050°C, 100 and 200 MPa

The partitioning of S and Cl between aqueous fluid and basaltic melt of Mt. Etna has been experimentally investigated at 1050°C, logfO2~FMQ+0.5, FMQ+2.3, and FMQ+2.8 at 200MPa as well as at ~FMQ+2.8 at 100MPa by using HCl(aq) and native S as chlorine and sulfur source. At given P–T–fO2 conditions, the partitioning of S and Cl between fluid and melt typically demonstrates non-linear dependence on S and Cl contents in the system, and only at low concentrations of S (below ~2wt.%) and Cl (below ~1wt.%) in the fluid is the Henrian behavior observed. The partition coefficients of S (DS, wt.% Sfluid/wt.% Smelt) ranged between 3±1 and 96±24 at 200MPa and between 6±2 and 73±18 at 100MPa at logfO2≥FMQ+2.3, and between 164±13 and 236±26 at 200MPa and FMQ+0.5. The partition coefficients of Cl (DCl, wt.% Clfluid/wt.% Clmelt) ranged between ~2±1 and 17±1 at 200MPa and between ~3±2 and 19±1 at 100MPa at logfO2≥FMQ+2.3, and between ~2±1 and 9±1 at 200MPa and at FMQ+0.5.At oxidizing conditions (FMQ+2.3 and FMQ+2.8) sulfur and chlorine demonstrate mutual interaction by favoring partitioning of both volatiles into the fluid relative to melt together with effective extraction of Ca and K from the melt into the fluid. Such interaction indicates that both, S and Cl may change their speciation by effective extraction of Ca and K from the melt and by mutual reactions between species rather than by competitive bonding with extracted cations. These observations are also an indication that bulk activity coefficients of S and Cl in the fluid are decreased, which in turn decrease non-ideality of mixing between interacting fluid species compared to S-deficient aqueous chloridic fluids.The non-linear dependence of Cl fluid–melt partitioning on the concentration of Cl in the fluid can be described by a simple square root function.The data also indicate that Cl may affect the solubility of H2O in basaltic melt which increases by 0.5mol of H2O per 1mol of Cl. It can be presumably attributed to the incorporation mechanism of HCl into the melt structure, i.e. Cl− may complex with network-modifying cation(s) and H+ may bond with half of non-bridging oxygen. The square root behavior of Cl partitioning between many aluminosilicate melts and aqueous fluid may thus be explained by the exchange reaction of one Cl ion from the fluid with two oxygen ions in the melt. Correlations between the mechanisms and the partitioning behavior of S between fluid and melt could not be carved out.At 100MPa and oxidizing conditions (~FMQ+2.3 and FMQ+2.8), the S/Cl ratio in the fluids and S contents in the coexisting melts closely match the compositions of fluids and compositions of olivine hosted melt inclusions from the 2002–2003 eruption of Mt. Etna. At S/Cl fluid ratios of ~5 to 7, measured during passive degassing, experimentally determined melt S contents were similar to primitive magma which contains ~0.27 to 0.33wt.% S. Whereas at S/Cl fluid ratios of ~2 to 4 determined during mild strombolian activity, coexisting melts contained 0.18 to 0.27wt.% S which is similar to partially degassed, slightly evolved melts. This indicates that primitive melts of Mt. Etna might have been more oxidizing than previously determined on melt inclusions.

Flourishing ocean drives the end-Permian marine mass extinction

The end-Permian mass extinction, the most severe biotic crisis in the Phanerozoic, was accompanied by climate change and expansion of oceanic anoxic zones. The partitioning of sulfur among different exogenic reservoirs by biological and physical processes was of importance for this biodiversity crisis, but the exact role of bioessential sulfur in the mass extinction is still unclear. Here we show that globally increased production of organic matter affected the seawater sulfate sulfur and oxygen isotope signature that has been recorded in carbonate rock spanning the Permian-Triassic boundary. A bifurcating temporal trend is observed for the strata spanning the marine mass extinction with carbonate-associated sulfate sulfur and oxygen isotope excursions toward decreased and increased values, respectively. By coupling these results to a box model, we show that increased marine productivity and successive enhanced microbial sulfate reduction is the most likely scenario to explain these temporal trends. The new data demonstrate that worldwide expansion of euxinic and anoxic zones are symptoms of increased biological carbon recycling in the marine realm initiated by global warming. The spatial distribution of sulfidic water column conditions in shallow seafloor environments is dictated by the severity and geographic patterns of nutrient fluxes and serves as an adequate model to explain the scale of the marine biodiversity crisis. Our results provide evidence that the major biodiversity crises in Earth's history do not necessarily implicate an ocean stripped of (most) life but rather the demise of certain eukaryotic organisms, leading to a decline in species richness.

Atmospheric evolution of sulfur emissions from Kı̅lauea: real-time measurements of oxidation, dilution, and neutralization within a volcanic plume.

The high atmospheric concentrations of toxic gases, particulate matter, and acids in the areas immediately surrounding volcanoes can have negative impacts on human and ecological health. To better understand the atmospheric fate of volcanogenic emissions in the near field (in the first few hours after emission), we have carried out real-time measurements of key chemical components of the volcanic plume from Kı̅lauea on the Island of Hawai'i. Measurements were made at two locations, one ∼ 3 km north-northeast of the vent and the other 31 km to the southwest, with sampling at each site spanning a range of meteorological conditions and volcanic influence. Instrumentation included a sulfur dioxide monitor and an Aerosol Chemical Speciation Monitor, allowing for a measurement of the partitioning between the two major sulfur species (gas-phase SO2 and particulate sulfate) every 5 min. During trade wind conditions, which sent the plume toward the southwest site, sulfur partitioning exhibited a clear diurnal pattern, indicating photochemical oxidation of SO2 to sulfate; this enabled the quantitative determination of plume age (5 h) and instantaneous SO2 oxidation rate (2.4 × 10(-6) s(-1) at solar noon). Under stagnant conditions near the crater, the extent of SO2 oxidation was substantially higher, suggesting faster oxidation. The particles within the plume were extremely acidic, with pH values (controlled largely by ambient relative humidity) as low as -0.8 and strong acidity (controlled largely by absolute sulfate levels) up to 2200 nmol/m(3). The high variability of sulfur partitioning and particle composition underscores the chemically dynamic nature of volcanic plumes, which may have important implications for human and ecological health.

Fate and behavior of inorganic constituents of RDF in a two stage fluid bed-plasma gasification plant

To accelerate progress in the industrial use of RDF as an alternative fuel in gasification plants, the problems associated with hazardous solid residues and ash deposition must be resolved. The practical approach to reduce these problems must be aimed at preventing the accumulation of fly ash/condensable vapours on heat transfer surface areas while minimising the amount of residual materials that have to be treated before the disposal. One such approach is adopted in an advanced two-stage thermal process which incorporates a plasma processing stage for conditioning the gas generated from a primary waste gasification unit, primarily for the treatment of household and industrial wastes. This paper presents a comprehensive examination of ashes sampled under different operational conditions and in different locations of a two-stage fluid bed-plasma demonstration plant. A demonstration test miming the normal commercial operation was conducted over 44h of operation with RDF from a standard UK municipal solid waste. The results are presented according to solid samples composition, gas composition, and further specific data (e.g., enrichment factor, XRD analysis, leaching test, etc.). An investigation on pollutant removal from the hot syngas, focusing on the partitioning and chemistry of sulphur and chlorine along with other relevant components, is also carried out. Experimental trials revealed a reduced extent of alkali and metals availability in the gas phase, i.e. a minor deposit forming potential into downstream equipment. From 85% to 91% of the fly ash was captured and vitrified within the plasma converter and made non-leachable with respect to non-volatile heavy metals, allowing for near complete landfill diversion.

OPTIMIZATION OF DESULFURIZATION PROCESS THROUGH STUDYING THE LADLE REFINING FURNACE PARAMETERS

This research aims to optimize of the desulfurization process through the ladle-refining furnace in the melting shop ofAbu Zaabal for Industrial Engineering Company. The Optimization of desulfurization process has been studied in the LadleRefining Furnace of the melting shop with respect to the amount of desulfurizing agent, deoxidation power of Silicon, Stirring energy, and the temperature as well as The composition and the sulfur content of slag have been determined to calculate the partition coefficient of sulfur at different deoxidizer content, and different content of desulfurizing agent. Y. Yang and Sosinsky- Sommerville modelshave been used to determine the deviation between the measured and computational method for sulfur partition coefficient. The results refer tothe desulfurization efficiency of lime is entirely dependent on the oxygen content. On the other hand, the desulfurizing rate has its maximum value at 0.25% Si. The stirring energy has a linear relationship with the desulfurizing rate, as well as the desulfurizing rate has its ultimatum at 1893K. Eventually, the measured sulfur partition coefficient has closed values to that have been calculated from the Oxygen activity considered model.

Metal–silicate partitioning of sulphur, new experimental and thermodynamic constraints on planetary accretion

Partitioning of sulphur between liquid Fe-rich metals and silicates (DSmet/sil) was investigated at temperatures from 1800 °C to 2400 °C, pressures from 2 to 23 GPa and oxygen fugacities from 3.5 to 1.5 log units below the iron–wüstite buffer, using multi-anvil apparatus. The results are combined with previous experimental works to refine a multi-variable thermodynamic model of DSmet/sil. Sulphur appears to become more siderophile with increasing pressure and FeO content of the silicate melt, and less siderophile with increasing temperature and with Si, C, O, Fe and Ni contents of the metal. We then modelled the behaviour of sulphur in the course of planetary accretion, using different possible scenarios of mantle dynamics and evolution with time of oxygen fugacity. We investigated three end-member models for metal–silicate segregation of the incoming impactors: (i) the planetary mantle does not mix and is kept chemically stratified, (ii) the magma ocean is continuously mixed chemically, and (iii) both the magma ocean and the solid lower mantle are well mixed.We show that if S is accreted along the accretion, whatever the oxidation path, its distribution between core and mantle can lead to the observed S concentration of the mantle (200±80 ppm) and to the estimations of S content of the core (from its depletion in the mantle relative to the other elements with the same volatility). In the case of an Earth built with reduced material, to explain the present-day 200(±80) ppm S found in the mantle, it is necessary that both the magma ocean and the solid lower mantle mix at each major step of the planetary accretion. S could also be accreted in the last 10 to 20% of Earth's growth and reach its observed present terrestrial abundances if the magma ocean is chemically mixed along the accretion. Consequently, our models show that the S terrestrial abundances do not formally require an S accretion in a late veneer but can be explained by a core–mantle equilibration alone.

Characteristics of Deoxidation and Desulfurization during LF Refining Al-killed Steel by Highly Basic and Low Oxidizing Slag

Steel and slag samples were taken at the start and the end of LF refining for steel plate cold common (SPCC), in the compact strip production (CSP) process, and at the same time, the temperature and oxygen activity a[O] were measured by using an oxygen sensor. Furthermore, inclusions in steel samples were monitored by scanning electron microscopy (SEM) combined with energy dispersive spectroscopy (EDS). It was confirmed that a[O] in liquid steel was in equilibrium with inclusion rather than with top slag during LF refining. Desulfurization was related to deoxidation since a[O] at slag-steel interface was clarified to be very close to that in liquid steel under the specific condition in LF with intense stirring by argon blowing and refined by highly basic low oxidizing slag for Al-killed steel. Sulfur partition ratio (LS) was very sensitive to a[O]. Since a[O] increased rapidly with temperature rise, it not only offset promotion to desulfurization reaction with temperature rise but decreased LS. For Al-killed steel, the modification of Al2O3 for lowering the activity of Al2O3 in inclusion was believed to be favorable for both deoxidation and desulfurization during LF refining.

Deep Desulfurization of Fuels by Extraction with 4-Dimethylaminopyridinium-Based Ionic Liquids

In this work, three 4-dimethylaminopyridinium-based ionic liquids (ILs), N-ethyl-4-dimethylaminopyridinium dicyanamide ([C24DMAPy][N(CN)2]), N-butyl-4-dimethylaminopyridinium dicyanamide ([C44DMAPy][N(CN)2]) and N-hexyl-4-dimethylaminopyridinium dicyanamide ([C64DMAPy][N(CN)2]), were synthesized and then demonstrated to be efficient for aromatic sulfur compounds extraction from fuels. The mutual solubility evaluating results indicated that 4-dimethylaminopyridinium-based ILs hardly dissolved in the fuels, while the solubility of 97# gasoline in ILs varies from 7.0 wt % for [C24DMAPy][N(CN)2] to 12.4 wt % for [C64DMAPy][N(CN)2] and the solubility of 0# diesel in ILs varies from 6.7 wt % for [C24DMAPy][N(CN)2] to 9.7 wt % for [C64DMAPy][N(CN)2]. Also, the sulfur partition coefficient was evaluated. In the case of model gasoline, the thiophene (TS) partition coefficient in model gasoline varies from 0.885 for [C24DMAPy][N(CN)2] to 1.218 for [C64DMAPy][N(CN)2]. In the case of model diesel, 4-dimethylaminopyridinium-based ILs exhibit a relatively higher sulfur partition coefficient, compared to alkyl modified pyridinium-based ILs. 1H NMR results confirmed that the high aromatic π-electron density of the dimethylaminopyridinium cation was the main reason for the good extraction performance. 1H NMR results also confirmed the KN sequence for each IL ([C24DMAPy][N(CN)2] < [C44DMAPy][N(CN)2] < [C64DMAPy][N(CN)2]) is mainly due to the sulfur compounds and ILs structures. Furthermore, the extractive selectivity results indicated a more preferable extraction of TS than toluene with 4-dimethylaminopyridinium-based ILs. To have a better evaluation of the overall sulfur extraction performance, the three 4-dimethylaminopyridinium-based ILs were compared to other typical ILs (e.g., pyridinium-based ILs and imidazolium-based ILs), which suggested our synthesized 4-dimethylaminopyridinium-based ILs exhibited good balance between mutual solubility and the sulfur partition coefficient. ILs after use were regenerated by a water dilution process. Based on these results, 4-dimethylaminopyridinium-based ILs can be used as potential extractants for EDS processes.

Genetic regulation of glucoraphanin accumulation in Beneforté® broccoli

Diets rich in broccoli (Brassica oleracea var italica) have been associated with maintenance of cardiovascular health and reduction in risk of cancer. These health benefits have been attributed to glucoraphanin that specifically accumulates in broccoli. The development of broccoli with enhanced concentrations of glucoraphanin may deliver greater health benefits.Three high-glucoraphanin F1 broccoli hybrids were developed in independent programmes through genome introgression from the wild species Brassica villosa. Glucoraphanin and other metabolites were quantified in experimental field trials. Global SNP analyses quantified the differential extent of B. villosa introgressionThe high-glucoraphanin broccoli hybrids contained 2.5–3 times the glucoraphanin content of standard hybrids due to enhanced sulphate assimilation and modifications in sulphur partitioning between sulphur-containing metabolites. All of the high-glucoraphanin hybrids possessed an introgressed B. villosa segment which contained a B. villosa Myb28 allele. Myb28 expression was increased in all of the high-glucoraphanin hybrids. Two high-glucoraphanin hybrids have been commercialised as Beneforté® broccoli.The study illustrates the translation of research on glucosinolate genetics from Arabidopsis to broccoli, the use of wild Brassica species to develop cultivars with potential consumer benefits, and the development of cultivars with contrasting concentrations of glucoraphanin for use in blinded human intervention studies.

Compositional instability of Earth's solid inner core

All models that invoke convection to explain the observed seismic variations in Earth's inner core require unstable inner core stratification. Previous work has assumed that chemical effects are stabilizing and focused on thermal convection, but recent calculations indicate that the thermal conductivity at core temperatures and pressures is so large that the inner core must cool entirely by conduction. We examine partitioning of oxygen, sulfur, and silicon in binary iron alloys and show that inner core growth results in a variable light element concentration with time: oxygen concentration decreases, sulfur concentration decreases initially and increases later, and silicon produces a negligible effect to within the model errors. The result is a net destabilizing concentration gradient. Convective stability is measured by a Rayleigh number, which exceeds the critical value for reasonable estimates of the viscosity and diffusivity. Our results suggest that inner core convection models, including the recently proposed translational mode, can be viable candidates for explaining seismic results if the driving force is compositional.

Fluid-present melting of sulfide-bearing ocean-crust: Experimental constraints on the transport of sulfur from subducting slab to mantle wedge

To constrain the sulfur enrichment of arc magma source-regions and the agent of sulfur transport from subducting slab to mantle wedge, here we report experimental measurements of sulfur content at sulfide saturation (SCSS) of slab-derived hydrous partial melts at 2.0 and 3.0GPa and from 800 to 1050°C, using Ni–NiO (NNO) and Co–CoO (CCO) external oxygen fugacity (fO2) buffers. A synthetic H2O-saturated MORB with 1wt.% S (added as pyrite) was used as starting material. All experiments produced pyrrhotite- and fluid-saturated assemblages of silicate glass, clinopyroxene, garnet, quartz, and rutile (plus amphibole at 2GPa/800°C and phengite at 3GPa/850°C). The silicate partial melt composition evolves from rhyolitic to rhyodacitic compositions with increasing temperature and melting degree in equilibrium with an eclogitic residue, showing substantial decrease in SiO2 and Mg# and increase in FeOT, TiO2 and Na2O. At all temperatures melt sulfur concentrations are very low, with an average of 110±50ppm S, similar to previous measurements at lower pressures. Melt SCSS appears to be mainly controlled by the melt composition, the activity of water, aH2O and the sulfur fugacity, fS2 (calculated from the composition of pyrrhotite). Mass-balance calculations show that the proportion of bulk sulfur dissolved in the silicate melt is negligible (<0.005wt.% of the bulk sulfur). In contrast, diminishing proportion of pyrrhotite with increasing temperature suggests that the fluid phase at equilibrium may contain as much as 10–15wt.% S at ⩾1050°C, and more than 40wt.% of the bulk sulfur initially present in the slab may be transferred to the aqueous fluid. Our data also suggest that fluid/melt sulfur partitioning increases with increasing temperature, from ∼300 at 900°C to ∼1200 at 1050°C, whereas pressure appears to have less of an effect. With respect to fO2, no real difference of fluid/melt S partitioning, within data uncertainties, between NNO and CCO at 2 and 3GPa was observed. This is interpreted as a consequence of comparable S speciation in the hydrous fluid phase in fO2 conditions ranging from NNO−0.5 to CCO−1.0 at 2 and 3GPa and 850 to 1050°C. Under these reducing conditions, the hydrous fluid phase is composed mainly of H2S and H2O, and to a lesser extent of S2 and H2, and S in melt is dissolved almost totally as S2− (i.e., S6+/Stotal∼0). Our study suggests that slab-derived aqueous fluids with reduced sulfur species could be sufficient vectors for the transport of sulfur from the slab to the mantle wedge and only ∼0.3 to 1.5wt.% of slab fluids are required for the mantle wedge enrichment in sulfur over background mantle concentrations. Also, depending on the initial amount of sulfur in the slab, recycling of sulfide to the deep mantle may be favored in cold to intermediate subduction zones, whereas warm subduction zones will cause fluid-mediated slab-mantle wedge transfer of sulfur.

Effect of Silicon on the Desulfurization of Al-Killed Steels: Part I. Mathematical Model

Recent observations suggest that increased silicon levels improve ladle desulfurization of aluminum-killed steel. While the overall desulfurization reaction of Al-killed steels does not show a direct role of silicon in desulfurization, model calculations are presented which test the idea that silicon suppresses the reduction of silica which can consume aluminum at the slag/metal interface. Consumption of aluminum would increase the oxygen potential at the slag/metal interface and decrease the sulfur partition coefficient between slag and metal. The model considers the coupled reactions of the reduction of silica, iron oxide, and manganese oxide in the slag and desulfurization of the steel by aluminum. The results show that silicon can indeed suppress consumption of aluminum at the slag/metal interface by side reactions other than desulfurization, with silicon affecting both the kinetics and the equilibrium of desulfurization.

Electronic and topological properties of interactions between imidazolium-based ionic liquids and thiophenic compounds: a theoretical investigation

To deepen the understanding the interactions of thiophenic compounds in ionic liquids, we have performed a systemic study on the electronic structures, and topological properties of interactions between N-ethyl-N-ethylimidazolium diethyl phosphate ([EEIM][DEP]) ionic liquid and 3-methylthiophene (3-MT), benzothiophene (BT), or dibenzothiophene (DBT) using density functional theory. From NBO atomic charges and electrostatic potential analyses, most of the positive charge is located on C2–H2 in the [EEIM] cation, and the negative charge is focused on oxygen atoms in [DEP] anion, implying oxygen atoms in [DEP] should easily attack C2–H2 in [EEIM]. The electrostatic interaction between anion and cation may be dominant for the formation of the [EEIM]–[DEP] ion pair. The large stabilizing effect is due to the strong orbital interactions between the antibonding orbital of proton donor σ*(C2–H2) in [EEIM] cation and the lone pairs of proton acceptor LP(O) in [DEP] anion. A common feature of [EEIM][DEP], [EEIM][DEP]-3-MT/BT/DBT complexes is the presence of hydrogen bonds between [EEIM] cation and [DEP] anion. This work has also given the interacting mechanism of 3-MT, BT, and DBT adsorption on [EEIM][DEP] ionic liquid. Both [EEIM] cation and [DEP] anion are shown to play important roles in interactions between 3-MT, BT, DBT and [EEIM][DEP], which has been corroborated by NBO and AIM analyses. The π···π, π···C–H and hydrogen bonding interactions occur between [EEIM][DEP] and 3-MT, BT, DBT. The strength of sulfur involved interactions between 3-MT, BT, DBT and [EEIM][DEP] follows the order of 3-MT > BT > DBT. The order of interaction energies between [EEIM][DEP] and 3-MT, BT, DBT is 3-MT BT > 3-MT) in terms of sulfur partition coefficients.