Lithological and Geochemical Heterogeneity of the Organo-Mineral Matrix in Carbonate-Rich Shales

The paper discusses the issues of interaction of the organic matter and the siliceous-carbonate mineral matrix in unconventional reservoirs of the Upper Devonian Domanik Formation of the Upper Kama Depression of the Volga-Ural Basin. The Domanik Formation is composed of organic-rich low-permeability rocks. Lithological and geochemical peculiarities of rocks were studied using light microscopy, X-ray diffraction analysis (XRD), scanning electronic microscopy (SEM), and evaporation method. Organic matter was examined by the Rock-Eval pyrolysis with quantitative and qualitative evaluation of generation potential and maturity degree. Integrated analysis of results of lithological and geochemical studies allowed identifying intervals in the studied section where organic matter can form a complex association with the siliceous-carbonate matrix. It was fixed experimentally that in some cases the mineral carbonate matrix and the organic matter form a one-whole high-molecular compound. The authors supposed that in the course of sedimentation, organic matter is immobilized into the structure of the mineral carbonate matrix. At the deposition and diagenesis stage, the carbonate matter interacts with acids of the organic matter and forms natural organo-mineral polymers. Special physicochemical properties of such organo-mineral associations shed new light onto the problems of producing from hard-to-develop nonconventional carbonate reservoirs and evaluating the associated risks.

Multifunctional layered composite material used for construction purposes

Introduction. The adjustability of electrical properties of materials, that have hydraulic setting characteristics, has been studied over the last decades. It is emphasized that any change in electrical properties, triggered by various additives, causes negative side effects, including low corrosive resistance and modified physical and mechanical characteristics. The purpose of this research is to design a multifunctional layered material that features localized electrical conductivity. The objective is to track the influence of modifiers, capable of regulating electrical properties. Materials and methods. Samples were made of Portland cement I 42.5; the cement, having the fineness modulus of 0.7, was used as the aggregate; samples also contained ground Sulphur type 9998 (GOST 127.1-93), soot slurry, and calcium nitrate. The co-authors have identified the unit resistance values of each layer of this composite material, mechanical properties and features of each layer, and the structure of contact layers. Results. The co-authors have determined that the addition of pre-treated Sulphur in the amount of 7 % of the binder mass facilitates the formation of a nonconductive layer, whose unit resistance reaches 29.57 kiloohm cm on the 28th day. The conductive layer, generated by adding soot in the amount of 7 % of the binder mass, ensures the stable passage of electric current. The co-authors have identified that calcium nitrate influences the morphology of secondary crystalline hydrates and the non-crystalline phase of the mineral matrix, made of Portland cement, and it also ensures the required concrete strength. Conclusions. The layered method of formation of new compositions allows to make composite materials having adjustable electrical characteristics. New materials are made of Portland cement, and they contain no non-conductors. The co-authors have proven the efficiency of Sulphur, an integrated modifier made of soot and calcium nitrite, used as the modifiers of the mineral matrix, since they regulate the electrical properties of the artificial stone.

The Effects of Calcium, Magnesium, Phosphorus, Fluoride, and Lead on Bone Tissue

Bones are metabolically active organs. Their reconstruction is crucial for the proper functioning of the skeletal system during bone growth and remodeling, fracture healing, and maintaining calcium–phosphorus homeostasis. The bone metabolism and tissue properties are influenced by trace elements that may act either indirectly through the regulation of macromineral metabolism, or directly by affecting osteoblast and osteoclast proliferation or activity, or through becoming part of the bone mineral matrix. This study analyzes the skeletal impact of macroelements (calcium, magnesium, phosphorus), microelements (fluorine), and heavy metals (lead), and discusses the concentration of each of these elements in the various bone tissues.

Effects of Radiation Intensity, Mineral Matrix, and Pre-Irradiation on the Bacterial Resistance to Gamma Irradiation under Low Temperature Conditions

Ionizing radiation is one of the main factors limiting the survival of microorganisms in extraterrestrial conditions. The survivability of microorganisms under irradiation depends significantly on the conditions, in which the irradiation occurs. In particular, temperature, pressure, oxygen and water concentrations are of great influence. However, the influence of factors such as the radiation intensity (in low-temperature conditions) and the type of mineral matrix, in which microorganisms are located, has been practically unstudied. It has been shown that the radioresistance of bacteria can increase after their exposure to sublethal doses and subsequent repair of damage under favorable conditions, however, such studies are also few and the influence of other factors of extraterrestrial space (temperature, pressure) was not studied in them. The viability of bacteria Arthrobacter polychromogenes, Kocuria rosea and Xanthomonas sp. after irradiation with gamma radiation at a dose of 1 kGy under conditions of low pressure (1 Torr) and low temperature (−50 °C) at different radiation intensities (4 vs. 0.8 kGy/h) with immobilization of bacteria on various mineral matrices (montmorillonite vs. analogue of lunar dust) has been studied. Native, previously non-irradiated strains, and strains that were previously irradiated with gamma radiation and subjected to 10 passages of cultivation on solid media were irradiated. The number of survived cells was determined by culturing on a solid medium. It has been shown that the radioresistance of bacteria depends significantly on the type of mineral matrix, on which they are immobilized, wherein montmorillonite contributes to an increased survivability in comparison with a silicate matrix. Survivability of the studied bacteria was found to increase with decreasing radiation intensity, despite the impossibility of active reparation processes under experimental conditions. Considering the low intensity of radiation on various space objects in comparison with radiobiological experiments, this suggests a longer preservation of the viable microorganisms outside the Earth than is commonly believed. An increase in bacterial radioresistance was revealed even after one cycle of irradiation of the strains and their subsequent cultivation under favourable conditions. This indicates the possibility of hypothetical microorganisms on Mars increasing their radioresistance.

Citrate Supplementation Restores the Impaired Mineralisation Resulting from the Acidic Microenvironment: An In Vitro Study

Chronic metabolic acidosis leads to bone-remodelling disorders based on excessive mineral matrix resorption and inhibition of bone formation, but also affects the homeostasis of citrate, which is an essential player in maintaining the acid–base balance and in driving the mineralisation process. This study aimed to investigate the impact of acidosis on the osteogenic properties of bone-forming cells and the effects of citrate supplementation in restoring the osteogenic features impaired by the acidic milieu. For this purpose, human mesenchymal stromal cells were cultured in an osteogenic medium and the extracellular matrix mineralisation was analysed at the micro- and nano-level, both in neutral and acidic conditions and after treatment with calcium citrate and potassium citrate. The acidic milieu significantly decreased the citrate release and hindered the organisation of the extracellular matrix, but the citrate supplementation increased collagen production and, particularly calcium citrate, promoted the mineralisation process. Moreover, the positive effect of citrate supplementation was observed also in the physiological microenvironment. This in vitro study proves that the mineral matrix organisation is influenced by citrate availability in the microenvironment surrounding bone-forming cells, thus providing a biological basis for using citrate-based supplements in the management of bone-remodelling disorders related to chronic low-grade acidosis.