Absence Of Minerals Research Articles

Hydrothermal carbon reduction in the absence of minerals

Abiotic synthesis of CH4 in seafloor hydrothermal fluids is generally assumed to occur via heterogeneous reactions on mineral surfaces. Stepwise homogeneous reduction of CO2 has, however, been suggested as an alternative (but sluggish) abiotic pathway to CH4, potentially via metastable species of intermediate oxidation states. In this study, we examine the effect of two temperature-dependent methylated species − methanol (CH3OH) and methanethiol (CH3SH), on homogeneous CH4 formation rates under long-term simulated hydrothermal conditions. Aqueous solutions containing formic acid (H13COOH, generating 13CO2 and H2) were heated with and without H2S at 300–325 °C (35 MPa) in a flexible Au reaction cell over several years without added minerals. Substantial 13C-labeled CH4 and CH3OH production from 13CO2 was observed over 4.3 yr, with aqueous CH4 formation varying with CH3OH abundance – a strong function of dissolved H2 abundance and, inversely, temperature. CH4 production was slower at 325 °C with lower CH3OH concentrations (in equilibrium with CO2 and H2), and faster at 300 °C, accompanying an equilibrium-controlled increase in CH3OH. Fastest CH4 production occurred at 300 °C following injection of H2S and H13COOH, which led to rapid formation (<4 days) of 13C-labeled CH3SH that subsequently decomposed over a further 0.8 yr, partly to 13CH4. Heating aqueous 13CH4 to 345–387 °C (33–35 MPa) in the presence of an oxidizing hematite-magnetite-pyrite assemblage, however, yielded no detectable CH3SH after 112 days indicating the reverse reaction is inhibited under favorable thermodynamics. Neither direct reduction of CO2 to CH3SH nor CO2-CH3SH equilibrium were evident at 300 °C, implying CH3SH and CH3OH play disparate roles in homogeneous carbon reduction to CH4. Longer chain hydrocarbons (C2+ alkanes) remained low throughout the experiments.CH3SH abundances previously reported in vent fluids at the Von Damm hydrothermal field correlate strongly with demonstrably abiotic HCOOH there, suggesting the reduction of HCOOH to CH3SH observed in this study may also occur in vent fluids. A comparison of mineral-free 13CH4 production rates reported here with 13CO2 reduction experiments involving minerals indicates that homogeneous reduction proceeds at similar rates to purported transition metal-catalyzed 13CH4 production, and is generally faster than experiments with either added olivine or ultramafic rock. Previous claims of substantial mineral-catalyzed abiogenic CH4 production are therefore not supported by our study. Homogeneous CO2 reduction may be a significant source of methylated compounds and CH4 in hydrothermal fluids characterized by decadal (or longer) residence times, such as those found in mineral-hosted inclusions or occluded fractures in igneous basement, requiring only moderate temperatures and abundant H2 to proceed.

Relationships between matrix mineralization, oxidative metabolism, and mitochondrial structure during ATDC5 murine chondroprogenitor cell line differentiation.

The mechanistic relationships betweenthe progression of growth chondrocyte differentiation, matrix mineralization, oxidative metabolism, and mitochondria content and structure were examined in the ATDC5 murine chondroprogenitor cell line. The progression of chondrocyte differentiation was associated with a statistically significant (p ≤ 0.05)~2-fold increase in oxidative phosphorylation. However, as matrix mineralization progressed, oxidative metabolism decreased. In the absence of mineralization, cartilage extracellular matrix mRNA expression for Col2a1, Aggrecan, and Col10a1 were statistically (p ≤ 0.05)~2-3-fold greater than observed in mineralizing cultures. In contrast, BSP and Phex that are associated with promoting matrix mineralization showed statistically (p ≤ 0.05) higher ~2-4 expression, while FGF23 phosphate regulatory factor was significantly lower (~50%) in mineralizing cultures. Cultures induced to differentiate under both nonmineralizing and mineralizing media conditionsshowed statistically greater basal oxidative metabolism and ATP production. Maximal respiration and spare oxidative capacity were significantly elevated (p ≤ 0.05) in differentiated nonmineralizing cultures compared to those that mineralized. Increased oxidative metabolism was associated with both an increase in mitochondria volume per cell and mitochondria fusion, while mineralization diminishedmitochondrial volume and appeared to be associated with fission. Undifferentiated and mineralized cells showed increased mitochondrial co-localization with the actin cytoskeletal. Examination of proteins associated with mitochondria fission and apoptosis and mitophagy, respectively, showed levels of immunological expression consistent with the increasing fission and apoptosis in mineralizing cultures. These results suggest that chondrocyte differentiation is associated with intracellular structural reorganization, promoting increased mitochondria content and fusion that enables increased oxidative metabolism. Mineralization, however, does not need energy derived from oxidative metabolism; rather, during mineralization, mitochondria appear to undergofission and mitophagy. In summary, these studies show that as chondrocytes underwent hypertrophic differentiation, they increased oxidative metabolism, but as mineralization proceeds, metabolism decreased. Mitochondria structure also underwent a structural reorganization that was further supportive of their oxidative capacity as the chondrocytes progressed through their differentiation. Thus, the mitochondria first underwent fusion to support increased oxidative metabolism, then underwent fission during mineralization, facilitating their programed death.

Оценка длительного воздействия бессменного выращивания различных сельскохо зяйственных культур на микробные сообщества почвы

The study of soil microbial communities under different agricultural crops (flax, clover, barley, potato, winter rye) grown in permanent cropping and crop rotation was carried out. The effect of permanent cropping and crop rotation on the taxonomic profile of the prokaryotic and fungal components of the soil microbiome was studied. The effect of permanent cropping and crop rotation on the metabolic intensity and stability of soil biota in the absence of mineral and organic fertilisers was assessed. The subject of the research was the long-term experience established in 1912 by Professor A.G. Doyarenko at the Russian State Agrarian University – Moscow Timiryazev Agricultural Academy, founded in 1912 by Professor A.G. Doyarenko. It was shown that the highest OUT (operational taxonomic units) values for fungi were found in soils under fallow and crop rotation. For prokaryotes, however, the crop rotation variant had the lowest number of OTUs. Ascomycetes were found to be the dominant fungal taxon in all samples studied. Prokaryotes were dominated by Proteobacteria and Acidobacteriota, followed by Actinobacteriota and Firmicutes, and Chloroflexi were represented to a lesser extent. Among the archaea, the Crenarcheota phylum was dominant. It was shown that continuous cultivation of crops generally has a negative effect on the functioning of the microbial community. With an optimal metabolic coefficient of 0.2 in monoculture, they reached 0.6. The sustainability of the soil microbial community is reduced by the continuous cultivation of potatoes, flax and clover without organic and mineral fertilizers, as well as by the “perpetual fallow” option. Particularly unfavorable conditions were found in potato monoculture. Continuous cultivation of cereals, especially winter rye, does not lead to a significant decrease in the activity of soil biota and the stability of soil microbial communities. Crop rotation makes it possible to optimize microbiological processes in the soil and to increase the stability of the soil microbial community.

Nitrogen fixation of lablab and finger millet in South‐India

AbstractBackgroundIn a long‐term rotation experiment (2016–2022) with different nitrogen (N) fertilizer levels in subtropical South‐India, crop yields of low N plots were unexpectedly high. We therefore hypothesized that in the absence of mineral N application, these yields are largely due to N inputs by N2 fixation in the component crops. To assess the diazotrophic N2‐fixation of lablab (Lablab purpureus L. Sweet) and possible associative N2‐fixation of finger millet (Eleusine coracana L. Gaertn), a controlled experiment was conducted during the 2021 monsoon season within the above‐mentioned long‐term field study. Two approaches were used to estimate the quantity of N derived from the atmosphere (Ndfa): the dilution method using a 15N‐labeled fertilizer and the natural abundance method.MethodFor the 15N dilution method irrigated maize (Zea maize L.), finger millet and lablab were labeled with two split applications of 10% 15N fertilizer (50:50 15N‐urea and 15N‐ammonium sulfate) amounting to a total of 15 kg N ha−1. Maize was selected as the non‐fixing reference plant to estimate diazotrophic N2‐fixation. The entire aboveground biomass of the labeled plants was harvested at maturity and analyzed for total DM, N concentration, and the 15N isotope ratio.ResultsN2 fixation efficiency for lablab was 52%–69% depending on the calculation method, corresponding to 40–53 kg N ha−1. For finger millet, the natural abundance method resulted in an estimated N2‐fixation of 5 kg N ha−1, which was suggested by the results of the dilution method whereby the reference plant maize was only poorly labeled.ConclusionLabeling of maize might have been diluted due to unexpected associative N2‐fixation or N‐uptake from unlabeled deep soil N pools. The data underline the importance of symbiotic N2‐fixation in crop rotation systems of South‐India.

Free Radical and Cationic Addition due to Clay Minerals Found in Bitumen Froth at 250 °C Probed with Use of α-Methylstyrene and 1-Octene

Following previous evidence that hydrothermal treatment of bitumen froth does not lead to bitumen upgrading at 250 °C and promotes viscosity increase, the current study explores the free radical and cationic reactivity of clay minerals found in bitumen froth in promoting heavier material formation through addition reactions. The current investigation employed α-methylstyrene (AMS) and 1-octene as probe molecules instead of bitumen froth, and their conversion at 250 °C in the presence of clay minerals kaolinite and illite was studied in batch reactors. Thermal conversion of AMS and 1-octene at 250 °C in the absence of minerals was observed to be low. In the presence of clay minerals, not only the conversion of AMS and 1-octene was increased but also reactions such as dimerization of AMS and alkylation of 1-octene and toluene (used as solvents) were mainly promoted, leading to heavier product formation. Double-bond isomerization of 1-octene and cumene formation from AMS was side reactions that were also promoted by the clay minerals. Suppression of mineral-related conversion by pyridine and selectivity to different reaction products that enabled differentiation between free radical and cationic reaction pathways indicated that the mineral-related conversion was predominantly cationic in nature. Using the reactions in the presence of minerals and pyridine as surrogates for alkaline bitumen froth, it was concluded that even under alkaline conditions, minerals could promote heavier material formation through cationic addition.

Traditional Multiwell Plates and Petri Dishes Limit the Evaluation of the Effects of Ultrasound on Cells In Vitro.

Ultrasound accelerates healing in fractured bone; however, the mechanisms responsible are poorly understood. Experimental setups and ultrasound exposures vary or are not adequately characterized across studies, resulting in inter-study variation and difficulty in concluding biological effects. This study investigated experimental variability introduced through the cell culture platform used. Continuous wave ultrasound (45 kHz; 10, 25 or 75 mW/cm2, 5 min/d) was applied, using a Duoson device, to Saos-2 cells seeded in multiwell plates or Petri dishes. Pressure field and vibration quantification and finite-element modelling suggested formation of complex interference patterns, resulting in localized displacement and velocity gradients, more pronounced in multiwell plates. Cell experiments revealed lower metabolic activities in both culture platforms at higher ultrasound intensities and absence of mineralization in certain regions of multiwell plates but not in Petri dishes. Thus, the same transducer produced variable results in different cell culture platforms. Analysis on Petri dishes further revealed that higher intensities reduced vinculin expression and distorted cell morphology, while causing mitochondrial and endoplasmic reticulum damage and accumulation of cells in sub-G1 phase, leading to cell death. More defined experimental setups and reproducible ultrasound exposure systems are required to study the real effect of ultrasound on cells for development of effective ultrasound-based therapies not just limited to bone repair and regeneration.

Separation of Mineral from Brown Algae Extract using Micro Filtration (MF) and Ultra Filtration (UF) Membrans – Review

Brown algae ( Phaeophyta ) contain active compounds such as carbohydrates, proteins, phenolics, fats, pigments, vitamins and minerals. The mineral content of brown algae is around 8% to 40% consisting of cations Na + , K + , Mg ++ , Fe ++ , Zn ++ , Mn ++ and heavy metals. Bioactive brown algae has many benefits, including Fucoidan as a cancer drug. The barrier of using Fucoidan as a medicine is its high mineral content. Therefore, the minerals must be separated. The extraction process of brown algae using various methods has been carried out with the aim of isolating the active component of Fucoidan that is free from minerals that will be an obstacle in utilizing the active component. This paper will describe some of the latest methods of extracting the active ingredients of brown algae and mineral separation processes using Micro Filtration (MF) and Ultra Filtration (UF) membrane. MF and UF membrane can separate small molecules such as cations (minerals) that can pass through the membrane so that macromolecules such as carbohydrates, fats, proteins, pigments, phenolics and vitamins can be separated from minerals and active ingredients in the absence of minerals can be obtained. The purpose of this paper is to provide research directions in the exploration of the active ingredients of brown algae for pharmaceutical and cosmetic applications without side effects caused by high metal or mineral content above the threshold value in brown algae extracts.

VITAMIN SUFFICIENCY OF MILITARY SEAFAFRERS DURING LONGTERM VOYAGE

The purpose of work— to justify the conclusion of compliance of vitamin level in military personnel with real energy expenditure and job factors during the long-term voyage basing on education of their real nutrition.Materials and methods.To carry out the study, a sample of 30 people from the personnel of surface ships was made. The amount of water-soluble and fat-soluble vitamins in the blood of the military was measured by means of highefficiency liquid chromatography (HELC) and photometry.Results and discussion.Relationship between dietary vitamin content and in the blood of the military that is specified by food habits during the long-term voyage. During the voyage, the supplying of seafarers with food products providing water-soluble vitamins А, В1, В2, В6, РР and С is of key importance. Vitamin deficiency in a sea ration is corrected by giving out multivitamin preparation «Geksavit». However, this preparation is not optimal in view of limited set of vitamins and absence of minerals in it. Actual ration needs correcting by introduction relevant vitamin mineral complexes in the ration.

ВЕТЕРИНАРНО-САНИТАРНАЯ ЭКСПЕРТИЗА МЯСА ЦЫПЛЯТ-БРОЙЛЕРОВ УРАЛЬСКИХ ПРОИЗВОДИТЕЛЕЙ

Poultry farming, providing replenishment of the food basket with high-quality and inexpensive products, plays an important role in the formation of food security in Russia. Veterinary and sanitary examination of poultry products in the context of the ecological component of the safety of agricultural raw materials is an important and timely task within the framework of government documents of the Russian Federation in the field of health protection of the country's population. According to the results of the physical, chemical and microbiological tests of chilled broiler chicken carcasses of the 1st grade of the Ural processors («Ravis – Sosnovskaya poultry farm», «Argayashskaya poultry farm», «Nagaybak poultry complex»), the raw materials were recognized as fresh, in terms of the amount of pesticides, antibiotics and heavy metals – safe. The content of protein, fat and moisture in all studied samples corresponded to the average values. A detailed study of the mineral composition revealed negative deviations in the amount of Fe and Se in all carcass samples. The products of the Argayash poultry farm against the background of analogous samples contained less fat and moisture with identical protein values, occupied an intermediate position in the amount of essential elements – Ca, Fe, Na, P, Zn, was distinguished by the absence of minerals that increase the toxic load on the human body – Ni, Ti , Ba, Ga, Li, which formed its competitive advantages.

COMPREHENSIVE ASSESSMENT OF QUALITY AND SAFETY OF BERRY SAUCE WITH IODINE-CONTAINING ADDITIVE

One of the acute problems of our time is iodine deficiency in human nutrition, which is typical for both countries with economies in transition and economically developed ones. Today, about a third of the world's population live in conditions of natural iodine deficiency. The most common solution to iodine deficiency is salt iodization, but this can lead to excessive iodine intake. In addition, it is much healthier to eat organic iodine, which is found in large quantities in brown algae. It is the development of new types of food products using brown algae as a biologically active additive that is a new promising direction for solving the problem of insufficient iodine consumption. Taking into account the relevance of solving the problem of iodine deficiency and the constantly growing demand for fruit and berry sauces, the technology of berry sauces based on blueberries, cranberries, dogwood, sea buckthorn and viburnum with the addition of brown algae has been developed. However, the mass introduction into production and consumption of the developed sauces will make a significant contribution to solving the global problem of insufficient consumption of organic iodine, requires research to establish their compliance with the typical quality and safety indicators for these products. The physicochemical indicators of the developed berry sauces were investigated, confirming the high quality in terms of the content of soluble solids – 25.0 ... 28.5%, the mass fraction of titratable acids – 1.9%, and indicate the complete absence of mineral, vegetable and foreign substances in the product. It was found that the developed sauces with iodine-containing algal additive have high microbiological quality indicators when stored for up to 14 days, even without adding preservatives. The complete safety of the developed berry sauces was established in terms of the content of toxic elements, as well as the absence of genetically modified organisms in the finished product

Adaptations for Wear Resistance and Damage Resilience: Micromechanics of Spider Cuticular “Tools”

AbstractIn the absence of minerals as stiffening agents, insects and spiders often use metal‐ion cross‐linking of protein matrices in their fully organic load‐bearing “tools.” In this comparative study, the hierarchical fiber architecture, elemental distribution, and the micromechanical properties of the manganese‐ and calcium‐rich cuticle of the claws of the spider Cupiennius salei, and the Zn‐rich cuticle of the cheliceral fangs of the same animal are analyzed. By correlating experimental results to finite element analysis, functional microstructural and compositional adaptations are inferred leading to remarkable damage resilience and abrasion tolerance, respectively. The results further reveal that the incorporation of both zinc and manganese/calcium correlates well with increased biomaterial's stiffness and hardness. However, the abrasion‐resistance of the claw material cross‐linked by incorporation of Mn/Ca‐ions surpasses that of many other non‐mineralized biological counterparts and is comparable to that of the fang with more than triple Zn content. These biomaterial‐adaptation paradigms for enhanced wear‐resistance may serve as novel design principles for advanced, high‐performance, functional surfaces, and graded materials.

New guidelines for the application of Stokes' models to the sinking velocity of marine aggregates

AbstractNumerical simulations of ocean biogeochemical cycles need to adequately represent particle sinking velocities (SV). For decades, Stokes' Law estimating particle SV from density and size has been widely used. But while Stokes' Law holds for small, smooth, and rigid spheres settling at low Reynolds number, it fails when applied to marine aggregates complex in shape, structure, and composition. Minerals and zooplankton can alter phytoplankton aggregates in ways that change their SV, potentially improving the applicability of Stokes' models. Using rolling cylinders, we experimentally produced diatom aggregates in the presence and absence of minerals and/or microzooplankton. Minerals and to a lesser extent microzooplankton decreased aggregate size and roughness and increased their sphericity and compactness. Stokes' Law parameterized with a fractal porosity modeled adequately size‐SV relationships for mineral‐loaded aggregates. Phytoplankton‐only aggregates and those exposed to microzooplankton followed the general Navier‐Stokes drag equation suggesting an indiscernible effect of microzooplankton and a drag coefficient too complex to be calculated with a Stokes' assumption. We compared our results with a larger data set of ballasted and nonballasted marine aggregates. This confirmed that the size‐SV relationships for ballasted aggregates can be simulated by Stokes' models with an adequate fractal porosity parameterization. Given the importance of mineral ballasting in the ocean, our findings could ease biogeochemical model parameterization for a significant pool of particles in the ocean and especially in the mesopelagic zone where the particulate organic matter : mineral ratio decreases. Our results also reinforce the importance of accounting for porosity as a decisive predictor of marine aggregate SV.

Intra-amniotic administration (Gallus gallus) of TiO2, SiO2, and ZnO nanoparticles affect brush border membrane functionality and alters gut microflora populations

Metal oxide nanoparticles (NP) are increasingly used in the food and agriculture industries, making human consumption nearly unavoidable. The goal of this study was to use the Gallus gallus (broiler chicken) intra-amniotic administration of physiologically relevant concentrations of TiO2, SiO2, and ZnO to better understand the effects of NP exposure on gut health and function. Immediately after hatch, blood, cecum, and small intestine were collected for assessment of iron (Fe)-metabolism, zinc (Zn)-metabolism, brush border membrane (BBM) functional, and pro-inflammatory related proteins gene expression; blood Fe and Zn levels; cecum weight; and the relative abundance of intestinal microflora. NP type, dose, and the presence or absence of minerals was shown to result in altered mineral transporter, BBM functional, and pro-inflammatory gene expression. Metal oxide NP also altered the abundance of intestinal bacterial populations. Overall, the data suggest that the in vivo results align with in vitro studies, and that NP have the potential to negatively affect intestinal functionality and health.

The effects of minerals on oil cracking in confined pyrolysis experiments

Confined pyrolysis experiments of oil in the presence and absence of minerals were conducted to reveal the effects of minerals on the oil cracking process. The results indicated that the methane generation rates decreased in the following order: oil alone > oil with clastic minerals > oil with carbonate minerals > oil with clay minerals, and the yields of C2-5 decreased in the order: oil with clay minerals > oil with carbonate minerals > oil with clastic minerals > oil alone. That means these minerals inhibited the cracking of C2-5 into methane. The inhibiting effect were decreased in the order: clay minerals > carbonate minerals > clastic minerals. Meanwhile, the ratios of i-C4/n-C4 decreased in the order: oil with clay minerals > oil with carbonate minerals > oil with clastic minerals > oil alone. That means the efficiencies of isomerization catalysed by minerals were decreased in the order: clay minerals > carbonate minerals > clastic minerals. Meanwhile, the ratios of C2H4/C2H6 increased with the order: oil with clay minerals < oil with carbonate minerals < oil with clastic minerals < oil alone. The hydrogenation rates of olefins increased in the following order: clay minerals < carbonate minerals < clastic minerals. The extent of enrichment12C for the generated methane and ethane increased in the order: clastic minerals < carbonate minerals < clay minerals. Such carbon isotopic fractionation during methane and ethane formation was probably induced by the catalytic effect of mineral surface on the terminal methyl group of hydrocarbons. The study of minerals effects on oil cracking may enhance our understanding on the evolution of petroleum reservoirs.

The Influence of Thermal Differences and Variation of Cl–F–OH Ratios on Cu-Ni-PGE Mineralization in the Contact Aureole of the South Kawishiwi Intrusion, Duluth Complex

In the contact metamorphic aureole of the Duluth Complex, Cu-Ni-PGE mineralization occurs locally up to 100 m from the intrusion-footwall contact (Spruce Road area), whereas elsewhere (Dunka Pit deposit) the footwall granite and metapelite (Serpentine deposit) are barren. This study aimed to understand the effect of temperature and halogen fugacity variations on the presence or absence of mineralization in these footwall units. The mafic mineral assemblages, two-pyroxene, titanium-in-quartz, and biotite-apatite thermometers indicate that temperatures could be as high as 920 °C in the mineralized areas of the footwall, whereas the maximum temperature was lower by about 100 °C in the unmineralized part of the intrusion. Variation of the halogen concentrations and fugacities was monitored with the analysis of halogen concentrations in biotite and apatite. Fluorine and chlorine concentrations in biotite increase as a function of the distance from contact in the mineralized drill core and decrease in the unmineralized zones. Chlorine concentrations in apatite increase parallel with the distance from contact in the mineralized zones, whereas fluorine concentrations show only minor variation. Concentrations of these elements may have had subtle effect on the partial melting in the footwall units and indirectly facilitated the infiltration of the sulfide liquid into the footwall.

Are phloem-derived amino acids the origin of the elevated malate concentration in the xylem sap following mineral N starvation in soybean?

A substantial increase in malate in the xylem sap of soybean subjected to mineral N starvation originates mainly from aspartate, a prominent amino acid of the phloem. A substantial increase in xylem malate was found when non-nodulated soybean plants were transferred to a N-free medium. Nodulated plants growing in the absence of mineral N and, therefore, dependent on symbiotic N2 fixation also contained elevated concentrations of malate in the xylem sap. When either nitrate or ammonium was supplied, malate concentrations in the xylem sap were low, both for nodulated and non-nodulated plants. Evidence was obtained that the elevated malate concentration of the xylem was derived from amino acids supplied by the phloem. Aspartate was a prominent component of the phloem sap amino acids and, therefore, a potential source of malate. Supplying the roots of intact plants with 13C-aspartate revealed that malate of the xylem sap was readily labelled under N starvation. A hypothetical scheme is proposed whereby aspartate supplied by the phloem is metabolised in the roots and the products of this metabolism cycled back to the shoot. Under N starvation, aspartate metabolism is diverted from asparagine synthesis to supply N for the synthesis of other amino acids via transaminase activity. The by-product of aspartate transaminase activity, oxaloacetate, is transformed to malate and its export accounts for much of the elevated concentration of malate found in the xylem sap. This mechanism represents a new additional role for malate during mineral N starvation of soybean, beyond that of charge balance.

The effects of selected minerals on laboratory simulated thermochemical sulfate reduction

Improved understanding of the reservoir mineral effects on the occurrence of thermochemical sulfate reduction (TSR) and possible mechanisms is critical for petroleum exploration and production. A series of hydrous pyrolysis experiments were conducted with and without the presence of montmorillonite, illite and quartz (silicates), calcite and dolomite (carbonates) at 360 °C and 50 MPa for 12 h, 48 h and 312 h. Gaseous compounds, C7–8 light hydrocarbons, n-C9+ and organic sulfur compounds as well as compound-specific δ34S analysis were conducted subsequently. The results show that with the heating time increasing or TSR advancing, n–C9+ decrease gradually accompanied by the increases of TSR products, H2S, alkylbenzenes, benzothiophenes (BTs) and dibenzothiophenes (DBTs). The δ34S values of BTs and DBTs progressively approached that of MgSO4 and the difference in their average δ34S values (Δ34SBT-DBT) decreased. Compared to experiments with the absence of minerals, the experiments with silicates, in particular montmorillonite, are depleted in n–C9+ and enriched in H2S, light monoaromatics and organosulfur compounds and smaller Δ34SBT-DBT. Experiments with carbonates demonstrated the opposite trend. This indicates that silicates, in particular montmorillonite, accelerated TSR rates while carbonates reduced them. Under the experimental conditions, the exchange cations within montmorillonite and on the surface of clays and talc precipitation can increase the concentrations of H+ and hence HSO4− and then catalyze the generation of isoalkanes, which are prone to be oxidized in TSR. This can reduce the activation energy required for the occurrence of TSR. It might therefore be possible for TSR to occur at relatively low temperatures in silicate reservoirs and source rocks in natural environments. Carbonate dissolution can reduce the concentrations of H+ and HSO4−, and hence reduce the TSR rates. This study demonstrates the importance of minerals in regulating the TSR occurrence and suggests that TSR can occur in siliciclasitic as well as carbonate formations in nature. Therefore, the significance of minerals should be considered in the evaluation of TSR and sour gas risk in TSR-altered hydrocarbon accumulations in different geological contexts.

Effects of CO2 atmosphere on slow pyrolysis of high-ash lignite

Slow pyrolysis of a typical high-ash lignite in China was carried out in atmospheres of N2, 20%CO2/N2, 40%CO2/N2, and 60%CO2/N2 in a fixed bed reactor. The evolution of char, tar, and gases in yield and characteristics, and the physico-chemical characteristics of chars in different atmospheres were compared. Results revealed that CO2 almost behaves as an inert gas in the evolution of char and CO before 600 °C. The decrease in char and CO2 yields and the increase in CO yield at temperatures higher than 600 °C are ascribed to the occurrence of char-CO2 gasification. The higher the CO2 level present in the atmosphere, the higher the severity of the gasification becomes. Introducing CO2 into the atmosphere raises tar and water yields but cuts down H2, CH4, and C2H6 yields. The promotion of tar yield results from the higher phenols and aliphatics yields in the presence of CO2. The reduction of H2 yield is associated with the increase in water yield, while the decline of light hydrocarbon gases is connected with the suppression effects of CO2 on methyl decomposition. The role of inherent minerals was also investigated by comparing product yields from raw coal and demineralized coal. The comparison indicated that the char-CO2 gasification rate is sharply reduced to nearly zero without the catalytic effects of calcium, iron, and magnesium minerals. The evolution of tar and light hydrocarbon gases in the CO2-containing atmosphere greatly depends on inherent minerals. Without minerals, tar yield is inhibited in the presence of CO2. In the absence of minerals, CO2 hardly has influences on CH4 and C2H6 yields.

Interactions between organic nitrogen and inorganic matter in the pyrolysis zone of underground coal gasification: Insights from controlled pyrolysis experiments

In recent years, a variety of N-heterocyclic compounds and inorganic nitrogen species were identified during the field-scale experiment on underground coal gasification (UCG), leading to concerns about the environmental impact. In an attempt to unravel the kinetics responsible for the generation of various nitrogen compounds (NCs), carbazole is selected in this paper as a model organic nitrogen compound in coal matrix. Hydrous pyrolysis experiments on carbazole were conducted using an autoclave in the presence and absence of minerals or their main active components in coal. Effects of inorganic matter, reaction mechanism and chemical kinetics were investigated on the basis of the experimental data. The results demonstrate negligible influence of water on thermal destruction of carbazole. However, the combination of water and aluminium oxide may play a role in the N – O atom exchange, resulting in a new ammonia formation mechanism. Pyrite exhibits extremely higher reactivity during carbazole cracking than other minerals. The calculated apparent activation energies for carbazole co-pyrolysis with inorganic matter range from 202 to 305 kJ/mol. According to the influence of inorganic matter on carbazole cracking, the pyrolysis zone of UCG could be further divided into positive effect subzone, transition subzone and negative effect subzone.

Evolution of ribozymes in the presence of a mineral surface.

Mineral surfaces are often proposed as the sites of critical processes in the emergence of life. Clay minerals in particular are thought to play significant roles in the origin of life including polymerizing, concentrating, organizing, and protecting biopolymers. In these scenarios, the impact of minerals on biopolymer folding is expected to influence evolutionary processes. These processes include both the initial emergence of functional structures in the presence of the mineral and the subsequent transition away from the mineral-associated niche. The initial evolution of function depends upon the number and distribution of sequences capable of functioning in the presence of the mineral, and the transition to new environments depends upon the overlap between sequences that evolve on the mineral surface and sequences that can perform the same functions in the mineral's absence. To examine these processes, we evolved self-cleaving ribozymes in vitro in the presence or absence of Na-saturated montmorillonite clay mineral particles. Starting from a shared population of random sequences, RNA populations were evolved in parallel, along separate evolutionary trajectories. Comparative sequence analysis and activity assays show that the impact of this clay mineral on functional structure selection was minimal; it neither prevented common structures from emerging, nor did it promote the emergence of new structures. This suggests that montmorillonite does not improve RNA's ability to evolve functional structures; however, it also suggests that RNAs that do evolve in contact with montmorillonite retain the same structures in mineral-free environments, potentially facilitating an evolutionary transition away from a mineral-associated niche.