Changes In Mineral Composition Research Articles

Изменения химического состава кислотных вытяжек по глубине торфяной залежи внутриболотных экосистем Васюганского болота (Западная Сибирь)

Актуальность работы. Анализ изменений химического и минерального состава органогенных и минеральных грунтов является важным этапом поисков полезных ископаемых, разработки соответствующей методологии, а также методологии экологического мониторинга. Цель работы: выявление закономерностей изменения химического состава кислотных вытяжек по глубине торфяной залежи на примере восточного участка Васюганского болота. Методы исследования: ландшафтно-геохимический и статистические методы, методы определения химического и минерального состава, имитационное математическое моделирование. Результаты и выводы. По данным опробования торфов и минерального грунта в марте 2017 и 2018 гг. в восточной части Васюганского болота (Западная Сибирь, Российская Федерация) выполнен анализ: химического состава кислотных вытяжек из торфов, органо-минеральных отложений и минерального грунта с использованием метода масс-спектрометрии с индуктивно связанной плазмой; состава минеральных включений в торфа и минерального состава подстилающего грунта методом сканирующей электронной микроскопии и рентгенодифракционного анализа. По результатам исследования определены концентрации 73 химических элементов, среди которых выделены три группы: 1) с относительно устойчивым увеличением от поверхности к минеральным грунтам и/или ярко выраженным максимумом в минеральных грунтах; 2) с хорошо выраженными максимумами в верхней и нижней частях разреза; 3) с иными типами распределения. Основными факторами пространственных изменений химического состава грунтов являются преимущественно природные биогеохимические условия, интенсивность водообмена, соотношение атмосферного и грунтового водного и минерального питания, определяющие общую доступность воды и питательных веществ для болотной растительности, отвод токсичных для этой растительности веществ.

The effect of foliar fertilization with sulphur on changes in mineral composition of leaves and fruits of Malus × domestica ‘Gloster’

The two-year field trial was focused on the effect of foliar fertilization with different forms of sulphur on the concentration of mineral elements in leaves (N, P, K, Ca, Mg, S and B) and fruits (S, K, Mg, Ca and B) of Malus × domestica 'Gloster'. The treatments were as follows: 1) unfertilized control, 2) foliar application of elemental sulphur with boron (Sulfika SB-C), 3) foliar application of magnesium sulphate (EPSO Top), 4) foliar fertilization with thiosulphates with potassium (SK sol), and 5) foliar application of fungicide with elemental sulphur (Kumulus). The same dose of Sulphur, i.e., 3.2 kg S ha-1 per vegetation, was applied in each treatment (except the control). Results obtained within two years (2014-2015) show the highest concentration of sulphur in leaves in treatment 4 (0.190% in dry matter) in comparison with treatments 2 (0.164% in dry matter) and 3 (0.175% in dry matter). A similar trend was observed in fruits, however the differences between the treatments were not significant. The concentration of sulphur in leaves was followed by the concentration of total nitrogen in 2014. It was significantly higher in treatment 4 (2.585% in dry matter) than in treatments 2 (2.390% in dry matter) and 3 (2.373% in dry matter). Sulfika SB-C significantly increased the concentration of boron in leaves and fruits and seems to be a good source of this element.

The three-stage petrochemical evolution of the Steens Basalt (southeast Oregon, USA) compared to large igneous provinces and layered mafic intrusions

The Steens Basalt, southeast Oregon, USA, initiated at 17 Ma as the earliest pulse of the Columbia River Flood Basalt of the northwestern USA. New and existing stratigraphically controlled data reveal temporal changes in lava flow character, and whole-rock and mineral compositions, which we use to evaluate how the balance of magma differentiation processes change in time. Temporal petrochemical variations in the Steens Basalt are analogous to the transition from Imnaha Basalt to Grande Ronde Basalt units of the Columbia River Flood Basalt and have parallels to the temporal evolution of the Deccan and Siberian traps, in India and Russia, respectively, as well as to the stratigraphic sequences of the Bushveld, of South Africa, and Stillwater, in southern Montana, USA, layered mafic intrusions. The excellent stratigraphic control from the Steens Basalt provides a detailed record for comparison across this variety of large mafic systems, providing ability to focus on commonalities among differentiation processes in time.

Effect of high temperature on physical and mechanical properties of Jalore granite

Underground nuclear waste disposal is an important area of research which requires concepts related to thermal cracking in brittle rock. The disposed canister produces residual heat that results from the decay of radionuclide's; increase the heat in the surrounding rock.The changes of mineral composition and pore water content of the rock after heating lead to the variation of the physical and mechanical properties of the host rock.In this study, an experiment was carried out to study the thermal effect (from 25 °C to 600 °C) on stress-strain behavior, elastic modulus, peak stress, thermal damage, and tensile strength of Jalore granite, India and compared with similar properties of granite from other countries. Scanning electron microscope (SEM) analyses have been done to determine the changes in growth of thermal cracks due to heating of Jalore granite at different elevated temperature. Based on the temperature interval (between 25 °C and 600 °C) can be divided into two zones from 25 °C–300 °C to 300 °C–600 °C. It was observed that the compressive strength and tensile strength of rock increased as the temperature was gradually increased up to 300 °C, but decreased sharply above this temperature. In the temperature range of 300 °C–600 °C, stress-strain curves showed plasticity behavior in which brittle-ductile transition was observed. It was observed that thermally-inducedmicro-cracks because of its complexity in thermal expansivity, the densification stage is longer which increases the crack density rapidly, at the same time, the elastic modulus, compressive strength, and thermal damage are higher. Heating at high temperature will make the tensile strength of granite change due to the loss of water and minerals and the effect of thermal stress that the most conspicuous effect is the expansion of quartz.It is found that 300 °C is the critical temperature for Jalore granite above which the physicomechanical behavior reduces sharply. A very strong correlation was found between the compressive strength and tensile strength of Jalore granite rock with very high coefficients of determination.

Microscopic Failure Mechanism Analysis of Sandstone Under Triaxial Compression

Mineral composition and microstructure changes under loading greatly influence the macroscopic mechanical strength of rocks. In this study, the chemical and mineral composition of sandstone from a coal mine in China were analyzed with energy dispersive spectrometry and X-ray diffraction. Triaxial compression tests of three sandstone samples with different compositions were carried out by using a servo-controlled rock mechanics testing system to obtain macroscopic failure characteristics and complete stress–strain curves. Fracture morphologies of the sandstone samples were observed by scanning electron microscopy (SEM), and the fracture origins, defects, grain size, pore structure and distribution, microfracture characteristics and grain boundaries were determined. Finally, the fracture mechanism of the rocks was analyzed, and the microstructure and fracture characteristics of three samples were obtained. The results showed that the stress–strain curve of samples under triaxial compression can be divided into four stages: microfractures compressed-closed, elastic deformation, plastic-failure and post-failure. Under triaxial compression, shear failure occurred in the samples, and the slip occurred along the plane of maximum shear stress. The SEM results showed grooves and steps on the fracture surface, where the debris was piled up in angular and granular shapes. Higher quartz and feldspar content is positively correlated with sample strength. There were some microcracks in the fracture surface of the clastic sandstone with higher hydrophilic clay minerals, which indicates the fracture was easily extended during the shear process. Thus, tensile fractures are more likely to be generated along the bedding plane, resulting in the low strength of clastic sandstone.

Modern methods of studying the phase composition of clay raw material at kiln process

It was developed methods for study of change clay rocks mineral phase composition at kiln process. The object of study was clay feed which is used to produce of ceramic materials. The main method of investigation was X-ray diffraction analysis. An additional method was synchronous thermal analysis (STA).At work was used X-ray diffractometer Shimadzu XRD-7000S (Japan) with a high-temperature furnace. Such equipment allows carrying out research of samples composition from 25°C to 1200°C. Experimentally established optimal temperatures of research: 20, 100, 200, 300, 400, 500, 600, 700, 750, 800, 850, 900, 950, 1000, 1050, 1100, 1150 and 1200°C. Data at these temperatures were processed in the DIFFRAC.EVA software. The result was quantitative information and graphs of the change in clay phase mineral composition during (burning?) firing process. At the same time was a studied quantitative change of the amorphous phase at different temperatures.The STA was used as an additional method of investigation. Sample analysis was carried on Netzsch STA 449 F3 Jupiter device (Germany), which allowing measurements of mass changes and thermal effects at temperatures up to 1200°C. We fixed changes using thermogravimetric measurements (TG) and curves of differential thermal analysis (DTA).The integration of methods allowed to obtain obtaining important information about the qualitative and quantitative changes of clays samples composition during firing process. Also results of our study showed reactions of minerals transformation due exothermic and endothermic processes. The overall result is a diagram of phase and quantitative transformations of minerals at temperatures from 20 to 1200°C including amorphous phase.

Influence of Supercritical CO2 Exposure on CH4 and CO2 Adsorption Behaviors of Shale: Implications for CO2 Sequestration

The interaction of shale–CO2 during the CO2 sequestration and enhanced shale gas recovery process has significant influence on the adsorption properties of shale. In this study, the influence of supercritical CO2 (ScCO2) exposure on CH4 and CO2 adsorption behavior of shale was studied. The pore structure and functional groups of different shale samples before and after ScCO2 (P = 8 MPa, 12 MPa, 16 MPa; T = 35 °C) exposure were measured by low-pressure nitrogen adsorption and the Fourier transform infrared spectroscopy (FTIR) method, respectively. Moreover, CH4 and CO2 adsorption isotherms of shale samples before and after ScCO2 exposure were also obtained to reveal the mechanism of the influence of ScCO2 exposure on CH4 and CO2 adsorption behaviors of shale. The results indicated that after treatment by ScCO2 the adsorption capacity of CO2 and CH4 in all tested samples was decreased. The main reason for the decrease is the change of pore structures, mineral compositions, and surface chemistry in shale cau...

Varietal differences in nutrient, amino acid and mineral composition and in vitro rumen digestibility of grape (Vitis vinifera) pomace from the Cape Winelands vineyards in South Africa and impact of preservation techniques

Grape pomace, a by-product of the winemaking industry, is a potential source of animal feed but its nutrient and chemical composition is not sufficiently studied in South Africa. The current study investigated the changes in nutrient, amino acid and mineral composition, and in vitro digestibility of neutral detergent fiber of grape (Vitis vinifera var. Pinotage, Shiraz and Sauvignon Blanc) pomace after three drying treatments: sun (7d), freeze (72 h) and oven drying (72 h at 60 °C). Oven-dried Shiraz had the greatest dry matter, crude protein and the least ash content (P < 0.05), while sun-dried Shiraz had the highest neutral detergent fiber, acid detergent fiber and acid detergent lignin compared to other grape pomace treatments (P < 0.05). Freeze-dried Sauvignon Blanc had the highest starch content, whereas freeze-dried Shiraz had the highest ether extract content relative to other grape pomace treatments (P < 0.05). The in vitro digestibility of neutral detergent fiber at 24- and 48 h were highest in freeze-dried Pinotage followed by freeze-dried Shiraz and Sauvignon Blanc treatments (P < 0.05). Freeze-dried Pinotage had the majority of amino acids in highest concentration, followed by freeze-dried Shiraz (P < 0.05). Freeze- and oven-dried Pinotage exhibited higher contents of potassium, magnesium, sulfur, sodium, iron and aluminum than other treatments. Overall, sun- and oven-dried Shiraz had the higher dry matter, crude protein, neutral detergent fiber, acid detergent fiber and acid detergent lignin contents, freeze- and oven-dried Pinotage had the best mineral composition, while freeze-dried Pinotage had the best amino acid profile and in vitro digestibility of neutral detergent fiber at 24 and 48 h.

Synthetic seismic model of a Permian biosiliceous carbonate – carbonate depositional system (Spitsbergen, Svalbard Archipelago)

Abstract The non-unique correspondence between seismic and subsurface geology is a fundamental problem when interpreting seismic data sets. Synthetic seismic models of outcrop analogs are commonly constructed to cover the gap between the small-scale outcrop observations and low-resolution seismic data. The Permian biosiliceous carbonate – carbonate sediments on Spitsbergen are characterized by a wide variability in lithologies and microfacies determining the petrophysical properties (e.g., porosity, acoustic properties) that consequently complicate seismic interpretation. This study uses 1D and 2D synthetic seismic modelling techniques (at different resolutions) to gain an understanding of how seismic reflectors are expressed with respect to the sediment distribution, aiming to facilitate real seismic interpretation. In the study area, nine microfacies were defined that were used to produce a geological model displaying small-scale microfacies variations within a well-defined sequence stratigraphic framework. Laboratory derived petrophysical properties (Vp, ρBulk and AI) were assigned to each predefined microfacies body in the geological models in order to construct acoustic impedance models that were used to produce synthetic seismograms. The appearance of the seismic reflectors in the synthetic seismic profiles is primarily controlled by changes in mineral composition and link to spatial microfacies distributions within the depositional sequences. Differences in acoustic impedance and the origin of synthetic seismic reflections within a single microfacies type are mainly caused by porosity contrasts (varying between 5 and 20%) and diagenetic modifications such as chertification and cementation. This detailed information cannot be derived from the low-frequency seismograms (25–100 Hz) resulting in changes in seismic expression when seismic resolution diminishes. Comparison with time equivalent, real and synthetic seismic data of the Finnmark Platform reveals similarities with the synthetic seismic reflection patterns of Spitsbergen. In both areas, the pronounced seismic traces follow abrupt microfacies transitions, which are coherent with cycle boundaries and timelines.

Stromatolite Growth in Lagoa Vermelha, Southeastern Coast of Brazil: Evidence of Environmental Changes

AbstractAmong the oldest remains of living beings to have inhabited the Earth’s surface, there are the stromatolites—laminated sedimentary rocks associated with lithified mats of layered phototrophic microbial communities—which grow in specific environmental conditions. In the present work, we study a recent carbonatic stromatolite from Lagoa Vermelha (Rio de Janeiro, Brazil), a shallow coastal hypersaline lagoon. X-ray diffraction was associated to a depth chronological model defining three different sections based on changes in mineral composition of the stromatolite with increased dolomite content. Although a mean growth rate of 0.19±0.03 mm/yr is observed, the model discloses decreasing growth rates among the sections. Since dolomite formation can be related to high availability of Mg+2, confirmed by an expressive presence of (Ca, Mg)CO3, the lower growth rates were associated to a more arid environment, until approximately 1440 cal AD, with higher temperatures and consequently promoting water evaporation and salinity enhancement.

The late Neoproterozoic Dahanib mafic-ultramafic intrusion, South eastern Desert, Egypt: Is it an Alaskan-type or a layered intrusion?

In Egypt, mafic-ultramafic complexes have been classified into three major types: incomplete ophiolite sequences; Alaskan-type intrusions, concentrically-zoned bodies formed in a subduction arc environment; and layered intrusions, vertically-zoned bodies intruded in post-collisional tectonic environments and rift-related bodies associated with the opening of the Red Sea. We present new field work, geochemical data, mineral chemistry and interpretations for the late Neoproterozoic Dahanib mafic-ultramafic intrusion in the South Eastern Desert of Egypt (northernmost Arabian–Nubian Shield, ANS). The Dahanib intrusion shows no evidence of metamorphism or deformation, with excellent preservation of intrusive contacts, well-preserved textures and primary mineralogy. Field relations indicate that it is younger than the surrounding metamorphic rocks and syn-tectonic granitoids. The intrusion is composed of a basal suite of ultramafic rocks (dunite, lherzolite, wehrlite and pyroxenite) and an overlying suite of mafic rocks (olivine gabbronorite, gabbronorite and anorthosite). It displays evident layering of modal abundance, visible directly in outcrop, as well as cryptic layering discernible through changes in mineral compositions. The western and eastern lobes of the Dahanib intrusion occur in the form of a lopolith with readily correlated layers, especially in the upper mafic unit. The present-day dip of the layering decreases from the ultramafic units into the mafic sequence. Structural and compositional relations show that the ultramafic units are cumulates from a high-Mg tholeiitic parent magma emplaced at deep crustal levels and evolved via fractional crystallization rather than any kind of residual mantle sequence. Fo content of olivine and Mg# of pyroxenes display a systematic decrease from ultramafic to mafic rocks, well-correlated with whole-rock Mg#. Spinels in ultramafic samples vary from Cr-rich to Al-rich and have Mg# and Fe^(3+)# similar to spinels from typical stratiform complexes and clearly different from those found in ophiolitic and Alaskan-type complexes. Although the mafic and ultramafic units are clearly related and can be derived from common parent magma, they were not emplaced coevally; rather, they represent different pulses of magma. The Dahanib mafic–ultramafic intrusion does not display any features that convincingly identify it as a typical Alaskan-type body, particularly the lack of clinopyroxenite and hornblendite, rarity of primary hornblende, and the notable abundance of orthopyroxene and plagioclase in its rocks. Our results confirm that it is more akin to a layered mafic-ultramafic intrusion with a multistage evolution. It was emplaced into a stable post-orogenic cratonic setting, with a trace element signature indicating contamination of the mantle source by previous subduction events.

Determination of the elastic modulus of fly ash-based stabilizer applied in the trackbed

This paper describes a unique application of a fly ash-based stabilizer in the trackbed of a railway main line. The key goals of the stabilizer application are to protect the subgrade against the ingress of rain water, to increase the frost resistance and to remediate the natural ground constituted of weathered rock. The stabilizer was designed as a mixture of fly ash, generated as a waste material from coal plants, gypsum, calcium oxide and water. The mixture recipe was developed in a laboratory over several years. In 2005, a trial section of a railway line with subgrade consisting of clay limestone (weathered marlite) was built in the municipality of Smiřice. Since then, periodical measurements including collection of samples for laboratory evaluation of the fly ash-based stabilizer have taken place. Over the time span of the measurements, changes in mineral composition and development of fly ash transforming structures leading to the formation of C-A-S-H gel were detected. This paper describes the experimental laboratory investigation of the influence of dynamic loading on the elastic modulus of fly ash stabilizer samples and the development of permanent deformation of the samples with increasing number of loading cycles.

Changes in Fatty Acid and Mineral Compositions of Rose-Shrimp Croquettes During Production Process

Changes in Fatty Acid and Mineral Compositions of Rose-Shrimp Croquettes During Production Process

Control of facies, maturation and primary migration on biomarkers in the Barnett Shale sequence in the Marathon 1 Mesquite well, Texas

A great deal is known about the genetic relationships between biomarkers and their biogenic precursors in organic rich rocks. The same is true of the way in which biomarker compound ratios change during maturation. On the other hand, very little is known about whether a crude oil can fully retain its inherent compositional ancestry during expulsion from a source rock. Thanks to shales being characterized in great detail for their unconventional resource potential, new information is gradually coming to light. Here we report on observations in biomarker geochemistry of a thermally mature core of the Barnett Shale, in which organofacies and maturity are essentially the same, but where intraformational sources and reservoirs have already been reported.Our results indicate that most biomarkers are not fractionated as the primary migration of petroleum within source rocks takes place. The 20S/(20S + 20R) ratio of C27 steranes is uniform in the whole source-rock sequence, while the 20S/(20S + 20R) ratio of C29 steranes shows indistinctly high values in the reservoir unit. The 20S/(20S + 20R) ratio of diasteranes and the 22S/(22S + 22R) ratio of C31 17α-hopanes do not appear to have been fractionated, which may be a result of the thermal isomerization reactions predominating over and masking out the possible fractionation effects. Diasteranes/steranes ratios do not exhibit features that suggest an association with fractionation, but rather are broadly correlated with lithology. However, compared to the diasteranes/steranes ratios, the Ts/(Ts + Tm) ratio is much more sensitive to changes in mineral compositions. Variations in the Ts/(Ts + Tm) ratio show a positive correlation (R2 = 0.73) with mixed-layer illite-smectite content. Fractionation in the Ts/(Ts + Tm) ratio, if it has so occurred, may be subsequently overprinted by in-situ clay-catalyzed reactions.

Whitefish (Coregonus lavaretus) Response to Varying Potassium and Sodium Concentrations: A Model of Mining Water Toxic Response

Boreal waters are typically low in minerals and oligotrophic, and therefore particularly sensitive to changes in mineral composition. We investigated the effects of potassium and the potassium: sodium (K+: Na+) ratio in freshwater on growth performance and oxidative stress in a typical northern species of whitefish, Coregonus lavaretus. Fish were subjected to 0.8 mM Na and 4.4 mM K, which corresponds to the K+:Na+ ratio in a lake contaminated by mining wastes from the Kostomuksha iron mine and ore dressing mill in northwestern Russia. The control group was subjected to water with similar mineralization levels and equal amounts of Na and K (approximately 0.3 mM of each). Potassium excess caused a decrease in fish growth rate and oxidative stress, as indicated by the level of lipid peroxidation product malondialdehyde (MDA). Glutathione-S-transferase (GST) activity and the level of reduced glutathione (GSH) were not affected by cation composition.

Synergistic Action of a Microbial-based Biostimulant and a Plant Derived-Protein Hydrolysate Enhances Lettuce Tolerance to Alkalinity and Salinity.

In the coming years, farmers will have to deal with growing crops under suboptimal conditions dictated by global climate changes. The application of plant biostimulants such as beneficial microorganisms and plant-derived protein hydrolysates (PHs) may represent an interesting approach for increasing crop tolerance to alkalinity and salinity. The current research aimed at elucidating the agronomical, physiological, and biochemical effects as well as the changes in mineral composition of greenhouse lettuce (Lactuca sativa L.) either untreated or treated with a microbial-based biostimulant (Tablet) containing Rhizophagus intraradices and Trichoderma atroviride alone or in combination with a PH. Plants were sprayed with PH at weekly intervals with a solution containing 2.5 ml L-1 of PH. Lettuce plants were grown in sand culture and supplied with three nutrient solutions: standard, saline (25 mM NaCl) or alkaline (10 mM NaHCO3 + 0.5 g l-1 CaCO3; pH 8.1). Salt stress triggered a decrease in fresh yield, biomass production, SPAD index, chlorophyll fluorescence, leaf mineral composition and increased leaf proline concentration, without altering antioxidant enzyme activities. The decrease in marketable yield and biomass production under alkali stress was not significant. Irrespective of nutrient solution, the application of Tablet and especially Tablet + PH increased fresh marketable yield, shoot and root dry weight. This was associated with an improvement in SPAD index, Fv/Fm ratio, CAT and GPX activities and a better nutritional status (higher P, K, and Fe and lower Na with NaCl and higher P and Fe with NaHCO3) via an increase of total root length and surface. The combination of microbial biostimulant with foliar application of PH synergistically increased the marketable fresh yield by 15.5 and 46.7% compared to the Tablet-treated and untreated plants, respectively. The improved crop performance of Tablet + PH application was attributed to a better root system architecture (higher total root length and surface), an improved chlorophyll synthesis and an increase in proline accumulation. Combined application of Tablet and PH could represent an effective strategy to minimize alkalinity and salinity stress in a sustainable way.

The detrital record of Cretaceous to Pliocene sandstones across the NE South American margin

The Cretaceous to Pliocene erosional history of the NE South American margin depicts the increasing influence of the uplifting Caribbean Mountain belt. Petrographic analyses of 59 Cretaceous to Late Pliocene sandstone samples derived from across the islands of Trinidad and Barbados, demonstrate systematic mineralogical changes whereby Early Cretaceous arkosic arenites gave way to mature quartz arenites by the Late Cretaceous and Caribbean Mountain-derived lithic-rich arenites during the Neogene. Changes in the framework compositions are accompanied by changes in textural attributes, with Caribbean Mountain detritus being notably finer grained than cratonic input. Silica cements predominate in quartzose sandstones and sericitic and clay cements within litharenites. The changing mineralogical compositions record the gradual deformation of the northern South American passive margin and initiation of the Andean–Caribbean Mountain foreland basin system, with incipient orogenic detritus evident from the latest Eocene and unambiguous orogenic input by the Late Oligocene. The preponderance of finer grain sizes within deltaic Pliocene sandstones records the later fill of an established foredeep with sediments sourced primarily from erosion of the Andean hinterland. These interpretations agree with heavy mineral compositional changes and the timing of uplift from geo- and thermo-chronological data across the margin. Supplementary material : Qualitative descriptions, sample coordinates and raw point counts are available at https://doi.org/10.6084/m9.figshare.c.3659381

Influence of viscoelastic surfactant fracturing fluid on permeability of coal seams

Hydraulic fracturing is an effective way of improving permeability of coal seams. Performance of the fracturing fluid is a key factor affecting the extent of improvement. Coal-seam permeability directly affects the difficulty of coal-bed methane extraction and is mainly related to the pore size. Comparison of the influence of water, which is widely used in underground fracturing, and viscoelastic surfactant fracturing fluid on the composition, pore structure, and gas permeability at different buried depths of coal samples were experimentally investigated. The X-ray diffraction and atomic emission spectrometry results showed that the viscoelastic surfactant fracturing fluid decreased the content of clay minerals that easily block pores and fractures in the coal. Scanning electron microscopy observations of coal pores were consistent with these changes of mineral composition. Low-temperature N2 adsorption showed that the cumulative pore volume of coal samples processed with the viscoelastic surfactant fracturing fluid was 0.00092cm3/g, which was an increase of 33.3% compared with that of coal samples processed with water. Analysis of the pore structure showed that the influence of fracturing fluid adsorption on gas permeability was mainly affected by its surface tension. Use of the viscoelastic surfactant fracturing fluid reduced the occupation of migration channels and improved the gas flow compared with water. Permeability contrast tests conducted on the coal samples processed with viscoelastic surfactant fracturing fluid and water showed that permeability of the former was greater by almost 178%, which verified the results of the above analyses. As the effective stress increased, the permeability decreased exponentially.

Caries prevention with fluoridated and iodinated salt in school-aged children living in areas with fluoride and iodine deficiency

The aim of the study was to evaluate the efficacy of dental caries prevention program with 3 years follow-up in children living in areas with fluoride and iodine deficiency. The study involved 625 school-aged children aged 6, 12 and 15 years receiving endogenous prevention with fluoridated and iodinated salt (300±50 mgF/kg and 40±10 mgI/kg). Enamel and dentine concentrations of CA, P, F and I were measured in 98 intact deciduous teeth by X-ray microanalysis before and after prevention program. Enamel and dentin microhardness was assessed in the same 98 teeth by Vickers Hardness Test. Obtained reduction of DMFT growth, positive changes of mineral composition and dental hard tissues microhardness prove high clinical efficacy of applied prevention program.

Chemical and Mineral Composition of Defatted Flaxseed Flour Incorporated Crackers

The suitability of defatted flaxseed flour for cracker preparation was investigated in this study. The defatted flaxseed flour was blended with refined wheat flour in the ratios of 100: 0, 95: 5, 90: 10, 85: 15, 80: 20, 75: 25 and 70: 30. The developed products were packed in laminate aluminium pouches and stored for 90 days at room temperature to ascertain the changes in chemical and mineral composition. From the results it was concluded that with the incorporation of roasted and partially defatted flaxseed the mean antioxidant activity was 33.87%, total phenolic content 113.33 mg/100g, free fatty acid 0.57% as oleic acid and peroxide value 0.29 meq. peroxide/kg of sample were observed the highest in treatment S7 (30% flaxseed flour). However, minimum mean calcium and potassium content of 491.64 and 94.59 mg per 100 g were recorded in S1 (0% flaxseed flour), respectively. In general, with the incorporation of roasted and partially defatted flaxseed flour, all the chemical parameters increased whereas, with the advancement of storage period decreased.