Magnesium Ion Concentration Research Articles

Influence of sea salt on the interfacial adhesion of bitumen–aggregate systems by molecular dynamics simulation

• Sea salt damaged bitumen’s original colloidal structure by disaggregating asphaltenes. • Saturates played the major role by most extensively diffusing to the surface of silica. • SARA fractions’ redistribution was driven by water with ions only acting as catalysts. • Number of SARA fractions in model decreased the adhesion energy in all environments. • Spatiotemporal distribution of SARA fractions at the interface determined the adhesion. This research investigated the influence of sea salt on the adhesion properties of bitumen–aggregate systems by molecular dynamics simulations in order to fundamentally understand the mechanism of damage in the seawater environment. The seawater environment was simulated by high concentrations of chloride, sodium, sulfate, magnesium, and calcium ions in water. Bitumen was represented by 3-, 4-, and 12-component models using the COMPASS force field, while the bitumen–seawater–aggregate interfacial model was discontinued by a vacuum layer of 60 Å in thickness. The results demonstrated that the presence of seawater affected the adhesion by facilitating the molecular migrations of bitumen components and by weakening the agglomeration of asphaltene. Consequently, this gradually damaged the colloidal structure of bitumen in the interfacial zone. Saturates played a dominant role in the adhesion in the seawater environment because they were the most likely to diffuse away from the silica surface. Besides the composition of bitumen, the spatiotemporal distribution of its components in the region of the interface was also identified as extremely important for the interpretation of the intrinsic factors which control the adhesion behaviour of thesesystems.

Impact of Magnesium on Oxytocin Receptor Function.

Simple SummaryWhat is already known: Mg2+ levels modulate the affinity of oxytocin receptors for oxytocin in vitro, low serum Mg2+ is correlated with migraine headache onset. What this study adds: Electrophysiologic and behavioral assays demonstrate that Mg2+ increases the efficacy of oxytocin; oxytocin efficacy is limited by Mg2+ availability. Clinical significance: Modulating Mg2+ levels may enhance oxytocin efficacy for pain, other uses, and endogenous processes.Background and Purpose: The intranasal administration of oxytocin (OT) reduces migraine headaches through activation of the oxytocin receptor (OTR). Magnesium ion (Mg2+) concentration is critical to the activation of the OTR, and a low serum Mg2+ concentration is predictive of a migraine headache. We, therefore, examined the functional impact of Mg2+ concentration on OT-OTR binding efficacy using two complimentary bioassays. Experimental Approach: Current clamp recordings of rat trigeminal ganglia (TG) neurons measured the impact of Mg2+ on an OT-induced reduction in excitability. In addition, we assessed the impact of Mg2+ on intranasal OT-induced craniofacial analgesia in rats. Key Results: While OT alone dose-dependently hyperpolarized TG neurons, decreasing their excitability, the addition of 1.75 mM Mg2+ significantly enhanced this effect. Similarly, while the intranasal application of OT produced dose-dependent craniofacial analgesia, Mg2+ significantly enhanced these effects. Conclusions and Implications: OT efficacy may be limited by low ambient Mg2+ levels. The addition of Mg2+ to OT formulations may improve its efficacy in reducing headache pain as well as for other OT-dependent processes.

Programmable protein topology via SpyCatcher-SpyTag chemistry in one-pot cell-free expression system.

Protein-based biomaterials play a significant role in biomedicine and biocatalysis due to their intrinsic biocompatibility and biodegradability. Topological biomaterials show certain advantages without changing the wild-type sequence of the protein, such as unique biofunctions and exceptional stabilities. However, the tuning for the synthesis and assembly of topological protein materials was limited. In this study, we combined the SpyCatcher/SpyTag (SC/ST) chemistry and proposed a cell-free one-pot transcription-translation-assembly system for flexibly regulating the production of topological protein materials. Dimers, trimers, and multimers of proteins with topological structures were designed. Next, the cell-free system was optimized by adjusting the magnesium ion concentration and the molar ratio of different plasmids to obtain the greatest degree of polymerization. The optimal Mg ion concentration was finally determined to be 15 mM, and their most appropriate plasmid molar ratios (SC:ST) were 7:3 for dimers, trimers, and multimers. Finally, based on the topological structure of the polymer, the function was verified with the fusion of xylanase, and it was found that the xylanase activity of the polymer was three times that of the xylanase monomer. Universally, the cell-free system in this study can be used to synthesize protein materials with different topologies based on various covalent or non-covalent methods, and it is likely to have potential in topological structure exploration and bioapplications.

Influence of Metal Concentration and Plumbing Materials on Legionella Contamination.

Legionella colonization of water supply pipes is a significant public health problem. The objective of this work was to evaluate Legionella colonization in hotel hot water systems and to investigate the relationship between metal concentrations, piping materials (galvanized iron pipes and plastic pipes), and Legionella proliferation. Concentrations of calcium and magnesium ions and the presence of Legionella pneumophila were determined in a total of 108 water samples from the hot water systems of four hotels in Split-Dalmatia County over a 12-month period, and additional data on piping materials were collected. L. pneumophila was isolated in 23.1% of all samples—in 28.8% (15/52) of water samples from galvanized iron pipes and in 17.8% (10/56) of samples from plastic pipes. L. pneumophila serogroups 2–14 were isolated from all samples. This study found higher prevalence of L. pneumophila at higher concentrations of Ca and Mg ions (except for Mg and plastic pipes). The metal parts of the water supply may be important factors in Legionella contamination due to the possibility of lime scale or roughness of the pipes. Higher Ca and Mg ion concentrations increased the risk of Legionella colonization.

Distribution and abundance of freshwater snails in Warwade Dam, Dutse, Northern Nigeria

Preliminary investigation in August, 2017 reported the presence of Lymnaea natalensis, Bellamya unicolor, Melanoides tuberculata and Bulinus globosus in order of increasing abundance and distribution in Warwade dam, Dutse, Jigawa State, Nigeria. A follow up study was carried out from April to October, 2019 to reveal further details on the abundance and distribution of freshwater snails in relation to some physiochemical factors of the dam. Four sampling sites; human activity, vegetation cover, lentic and lotic were selected for the study along the bank of the dam. Freshwater snails were collected using long handled scoop net with mesh 0.2mm complemented by hand picking methods in the four sampling sites. Water samples from the sampling sites were analyzed in the laboratory using standard procedures. A total of 2,027 of freshwater snails belonging to ten species were identified. Bulinus globosus 12(0.6%) and Lymnaea natalensis 12(0.6%) had the lowest abundance and distribution while Melanoides tuberculata 1553(76.6%) had the highest. Snail abundance was highest in site characterized by human activities (670) followed by vegetation (482), lotic (442) and lentic (433) waters. Most of the physico-chemical factors measured appeared to favour the growth and survival of fresh water snails. pH (p = 0.01), water current (p = <0.01) and magnesium ion concentration (p = < 0.01) varied significantly across the four sites. Only calcium ion concentration was significantly associated with snail abundance (p = 0.04). Snail abundance showed weak positive relationship with water temperature, color, turbidity and concentration of magnesium ion. The dam habours about ten species of freshwater snails in different abundance and distribution with M. tuberculata being the most abundant throughout the period of investigation. The dominance of M. tuberculata over other species particularly those of medical and veterinary importance could have positive implication for their control in the dam.

31 P MRSI at 7 T enables high-resolution volumetric mapping of the intracellular magnesium ion content in human lower leg muscles.

The non-invasive determination of the free magnesium ion concentration ([Mg2+free ]) using 31 P MRSI in vivo is of interest in research on various pathologies, e.g. diabetes. The purpose of this study was to demonstrate the potential of 31 P MRSI at 7 T to enable volumetric, high-resolution mapping of [Mg2+free ]. 3D 31 P MRSI datasets from the lower leg of three healthy volunteers were acquired at B0 = 7 T with a nominal spatial resolution of (8× 8× 16)mm3 in 56 min. Volumetric [Mg2+free ] maps were calculated based on the quantified local chemical shift difference between the α- and β-resonance of adenosine triphosphate (ATP) considering also local pH values. Mean [Mg2+free ] values from three different muscle groups were compared. To demonstrate the potential of reducing the measurement time, the analysis was repeated on the acquired MRSI data retrospectively reconstructed with fewer averages. The generated [Mg2+free ] maps revealed local differences, and mean [Mg2+free ] values of (1.08 ± 0.03)mM were found in the tibialis anterior, (0.91 ± 0.04)mM in the soleus and (0.98 ± 0.03)mM in the gastrocnemius medialis. The time-reduced 28-min scan resulted in comparable [Mg2+free ] maps, and mean values being in agreement with the values from the 56-min scan. 31 P MRSI at 7 T enables volumetric, high-resolution mapping of free magnesium ion content in human lower leg muscles. The measurement time of the 31 P MRSI acquisition can be reduced to 28 min, opening the potential to apply volumetric [Mg2+free ] mapping for the investigation of pathologies with altered magnesium homeostasis.

Habitat preference of blackflies in Omo Gibe river basin (southwest Ethiopia): Implications for onchocerciasis elimination and control.

Ecological control of blackflies (Simulium damnosum) can be an alternative or additional tool to enhance onchocerciasis elimination efforts. However, limited research is conducted on the ecology of blackflies in Ethiopia. In this study, we determined the habitat preference of blackfly larvae and their relationship with aquatic macroinvertebrate predators in the Omo Gibe river basin of southwest Ethiopia. Environmental and biological data were collected from 150 sampling sites during both dry and wet seasons in 2019. Generalized Linear Models (GLMs) were used to identify factors affecting the occurrence and abundance of S. damnosum larvae. Canonical Correspondence Analysis (CCA) was used to investigate the relationship between environmental and biological variables and the abundance of S. damnosum larvae. The findings of this study indicated the abundance of S. damnosum larvae increased with increasing turbidity, alkalinity and altitude, but decreased with increasing concentrations of five-day Biological Oxygen Demand (BOD5), orthophosphate and magnesium ion. Both the presence and abundance of S. damnosum larvae decreased with the increasing abundance of stonefly larvae (Perlidae). Simulium damnosum larvae were found less likely in the presence of mayfly larvae (Baetidae) and were less abundant where Chironomidae are abundant. In conclusion, the findings of this study showed that the habitat preference of S. damnosum larvae is determined by environmental factors and that the presence and abundance of the larvae are affected by macroinvertebrate predators. It is essential to establish buffer zones as a part of watershed management to retain pollutants and prevent them from entering directly into water courses to improve water quality and the assemblages of macroinvertebrate predators and enhance biocontrol of blackflies.

Improvement of substrate recognition in branched-chain aminoacyl-tRNA synthetases from Escherichia coli under conditions of pyrophosphate amplification

Isoleucyl-tRNA synthetase (IleRS), leucyl-tRNA synthetase (LeuRS), and valyl-tRNA synthetase (ValRS) are enzymes that have potential for the determination of l-isoleucine, l-leucine, and l-valine in food products and plasma. However, the disadvantages of these enzymes are their specificity and sensitivity. Here, we examined the substrate specificity of IleRS, LeuRS, and ValRS under various conditions of pyrophosphate amplification to improve their specificity and sensitivity. The amount of pyrophosphate produced in IleRS, LeuRS, and ValRS reactions was amplified after the addition of excess adenosine-5'-triphosphate and magnesium ions, and was approximately 9-, 8-, and 7-fold higher, respectively, for each of the initial l-amino acid substrates (50μM). However, in addition to their target amino acids, IleRS, LeuRS, and ValRS also reacted with l-valine, l-lysine, and l-threonine, respectively. This substrate misrecognition was overcome by making the reaction pH more acidic and by increasing the magnesium ion concentration. The pyrophosphate amplification in IleRS, LeuRS, and ValRS reactions resulted in the production of p1, p4-di (adenosine) 5'-tetraphosphate. We also observed a strong positive correlation (R= 0.99) between the amount of pyrophosphate produced and the initial concentration of l-amino acid with 5 and 50μM l-isoleucine, l-leucine, and l-valine. Our results suggest that amino acid assays using IleRS, LeuRS, and ValRS are promising methods to accurately measure l-valine, l-isoleucine, and l-leucine in food products and plasma.

Stable ionic liquid-based polymer inclusion membranes for lithium and magnesium separation

The separation of lithium and magnesium is crucial for the exploitation of lithium resources with a high concentration of magnesium ions (Mg2+). In this study, polymer inclusion membranes (PIMs) based on the stable ionic liquid (IL) extractant system were developed for separating lithium ions (Li+) from Mg2+ in aqueous solutions. The mixture of 1-butyl-3-methylimidazolium bis(trifluoromethylsulfonyl)imide ([C4mim][NTf2]) and tributylphosphate (TBP) was used as the carrier to transfer Li+, and the cellulose triacetate (CTA) polymer was chosen as the matrix due to its high compatibility with [C4mim][NTf2] via hydrogen bond. The TBP was kept in the membrane matrix without obvious leakage in the membrane extraction process, and the lithium selectivity and extraction percentage of the membranes decrease by less than 10% after five continuous extraction operation cycles. In the transport experiment using the feed containing 7.2 mmol/L Li+ and 2.06 mmol/L Mg2+, the PIM with 40 wt% TBP-[C4mim][NTf2] exhibits the separation factor of 2.24 for Li+/Mg2+ and an initial flux of 0.89 × 10−6 mol m−2 s−1 for Li+, much higher than the results of the pure CTA membranes, indicating that TBP-[C4mim][NTf2] system is efficient for Li+ extraction in PIM membrane. Besides, the PIMs we prepared were applied to extract Li+ from simulative salt-lake brines with a high Li+/Mg2+ selectivity of 23.87. The IL-based PIMs provide a possible membrane technology to extract Li+ from salt-lake brines with high stability, low energy consumption and environment-friendly.

Degradation of methylene blue using co-dopants Mg and Se in an hydroxyapatite composite.

In this work, a comparative study was made of different magnesium ion content incorporated into hydroxyapatite (HAP) and modified with selenite ions, with the aim to develop the degradation performance of methylene blue. Although the dopant metal (Mg2+ ) was present at a relatively low ratio, it induced a change in the microstructure, morphology, surface area, external surface charge, particle size, and degradation performance. The effect of magnesium and selenium binary doping on microstructure and degradation of methylene blue was evaluated. The external surface charge measured by zeta potential clarified that the highest negativity was -11.8 mV and this was accomplished in 1.0 Mg/Se-HAP. Furthermore, the roughness average increased from 36.8 nm, reaching 59.2 nm upon the addition of Mg(II). Moreover, transmission electron microscope micrographs showed that compositions were formed as rod shapes. The process of degradation was optimized, showing effectiveness in methylene blue degradation of 62.4% after 150 min of exposure to visible light. Electrostatic attraction and H-bonding, and coordination played vital roles in the adsorption process. The recyclability of the as-prepared compositions demonstrated that the effectiveness had been reduced to ~54.2% after five times of re-use.

Optimization of persistent luminescence via dopant concentration in LiNbO3

Manipulating the concentrations of magnesium ions was found to be an effective strategy to tune persistent luminescence in lithium niobite crystals. The photoluminescence excitation and emission spectra indicated that the dopant concentration exhibits a significant regulating effect toward the photoluminescent properties of LiNbO3 crystals. A series of thermoluminescence experiments revealed that the electron trap depths played a crucial role in persistent luminescence. Computational analysis based on DFT method elucidated the changes of defect structures in co-doped Mg2+:Pr3+:LiNbO3 crystals as the doping concentration varies. A dynamic model was proposed to explain the variation of afterglow luminescence intensity with doping concentration.

A systematic exploration of local network state space in neocortical mouse brain slices

The ex vivo cortical slice is an extremely versatile preparation, but its utility ultimately depends on understanding its limitations and functional constraints. A question for experimentalists new to the field of cortical slice electrophysiology might be — what are the different network dynamical states available to a cortical slice as a function of excitatory drive? The purpose of this study is to provide a coherent answer to this question, within the context of extracellularly recorded population field potentials.Cortical slices (400 µm) were prepared from adult male or female C57 mice. Evoked responses were recorded within cortical layer III/IV using extracellularly positioned metal electrodes. In the first part of the study, slice excitatory drive was increased by reducing the concentration of magnesium ions in the artificial cerebrospinal fluid — and the evoked responses categorized during the transition. In the second part, each of the identified functional states were explored in greater detail with tissue perfusion conditions and excitatory drive optimised for the requisite response state.As expected, rodent cortical slices did not generate spontaneous, persistent EEG-like field potential activity. However, distinct response states (spontaneous and evoked) characterized by intermittent population bursts could be differentiated as a function of excitatory drive. Each state reflected different modes of neocortical activation: “monosynaptic” responses were brief, non-propagating activations, reflecting an inhibited cortex with sensory processing blocked; polysynaptic and epileptiform activity propagated intra-cortically, the latter reflecting a hyperactivated, hypersynchronous “seizing” cortex. Polysynaptic activity most closely resembled sensory “up states” associated with intracortical sensory processing.Understanding the functional distinction between the different cortical slice response states is the starting point for designing experiments that maximise the utility of this ex vivo model. The results and descriptions in this study should help slice experimentalists less experienced in the nuances of cortical slice neurophysiology to make informed choices about how to tailor the parameters of the model to suit the specific aims of their research.

Dynamic RNA Fitness Landscapes of a Group I Ribozyme during Changes to the Experimental Environment.

Fitness landscapes of protein and RNA molecules can be studied experimentally using high-throughput techniques to measure the functional effects of numerous combinations of mutations. The rugged topography of these molecular fitness landscapes is important for understanding and predicting natural and experimental evolution. Mutational effects are also dependent upon environmental conditions, but the effects of environmental changes on fitness landscapes remains poorly understood. Here, we investigate the changes to the fitness landscape of a catalytic RNA molecule while changing a single environmental variable that is critical for RNA structure and function. Using high-throughput sequencing of in vitro selections, we mapped a fitness landscape of the Azoarcus group I ribozyme under eight different concentrations of magnesium ions (1–48 mM MgCl2). The data revealed the magnesium dependence of 16,384 mutational neighbors, and from this, we investigated the magnesium induced changes to the topography of the fitness landscape. The results showed that increasing magnesium concentration improved the relative fitness of sequences at higher mutational distances while also reducing the ruggedness of the mutational trajectories on the landscape. As a result, as magnesium concentration was increased, simulated populations evolved toward higher fitness faster. Curve-fitting of the magnesium dependence of individual ribozymes demonstrated that deep sequencing of in vitro reactions can be used to evaluate the structural stability of thousands of sequences in parallel. Overall, the results highlight how environmental changes that stabilize structures can also alter the ruggedness of fitness landscapes and alter evolutionary processes.

Incidence of ionized hypomagnesemia in adult patients undergoing noncardiac major surgery: a prospective observational trial

The present study aimed to investigate the incidence of preoperative ionized hypomagnesemia and compare with that of total hypomagnesemia. This prospective observational study included 536 patients aged >20 years who were scheduled for elective surgery. Total and ionized magnesium levels were evaluated before and after the surgery. Based on these levels, patients were classified into the following groups: ionized hypo- (<0.42 mmol/L), normo- (0.42-0.59 mmol/L) and hypermagnesemia (>0.59 mmol/L), as well as total hypo- (<1.9 mg/dL[0.78 mmol/L]), normo- (1.9-2.7 mg/dL[0.78-1.11 mmol/L]) and hypermagnesemia (>2.7 mg/dL [1.11 mmol/L]). The primary objective was to establish the incidence of preoperative ionized hypomagnesemia. There was a marked difference between the incidence of preoperative ionized and total hypomagnesemia (28% vs. 19%; p<0.001). The postoperative values of ionized magnesium, ionized calcium, and albumin were significantly lower than the respective preoperative values (p<0.001 for all three variables). The incidence of hypomagnesemia, determined by ionized magnesium concentration, was higher than that determined by total magnesium concentration.

ИССЛЕДОВАНИЕ ТЕРМОРЕАГЕНТНОГО МЕТОДА ВОССТАНОВЛЕНИЯ РЕГЕНЕРАЦИОННЫХ РАСТВОРОВ NA-КАТИОНИТОВЫХ ФИЛЬТРОВ

In this paper, we analyzed a method for the thermochemical recovery of spent regeneration solutions of Na-cation exchange filters containing chlorides, calcium and magnesium ions, with the introduction of one precipitant (soda ash) and heating in an autoclave at a pressure of 0.2–0.41 MPa, as well as proposed on its basis the technology of recycling solutions of sodium chloride. Spent regeneration solutions after the process are still discharged into wastewater or directly into natural reservoirs. The concentration of chlorides in such effluents significantly exceeds the MAC for wastewater sent to water bodies (MAC = 350 mg/dm3), which affects the properties of water in natural water bodies.It should also be noted that the MAC of wastewater discharged after regeneration and washing of cationexchangers is also higher in terms of magnesium content (MAC Mg = 50 mg/dm3), and in regeneration solutions the concentration reaches 200 mg-eq/l. Known reagent methods for the recovery of sodium chloride solutions (alkaline, lime-sulfate, phosphate, oxalate, etc.) allow the precipitation of hardness salts only when they are used in combination, which leads to a multi-stage purification process, and also increases the number of pieces of equipment used.According to technical and economic indicators, these methods are not implemented in production. The method developed and proposed in the article can eliminate and prevent the discharge of spent sodium chloride solutions into water bodies while obtaining products suitable for sale, which will ensure the recycling of Na-cationite filter solutions and the low-waste technology for their purification. When developing the method, special attention was paid to indicators of residual hardness and filtering properties of the resulting suspension.Guided by the results obtained on the content of calcium and magnesium ions and the removal of the solid phase, the influence of the content of sodium carbonate and sodium chloride on the solubility of calcium and magnesium carbonates in aqueous systems is also considered: NaCl − CaCO3 − H2O, NaCl – CaCO3 – Na2CO3 − H2O and NaCl − (MgOH)2 CO3 − H2O и NaCl – (MgOH)2 CO3 – Na2CO3 − H2O in the temperature range 120÷140 0C.

ASSESSMENT OF THE ECOLOGICAL STATE OF WATERS BY THE SPECIES COMPOSITION OF ZOOPLANKTON AND PHYTOPLANKTON

Presented the results of studies of macrophytes, zooplankton and phytoplankton and the chemical composition of water polluted by sewage from a livestock enterprise and a conditionally clean pond. It was established that changes in the chemical composition of water after entering the reservoir of wastewater from a livestock enterprise due to an increase in the concentration of mineral and ammonium nitrogen, sodium ions, a decrease in the content of calcium and magnesium ions and hydrogen carbonate ions, at constant values of the pH indicator, total mineralization, potas-sium ions, chlorides and sulfates. Compared to a conditionally clean reservoir, it became polluted with sewage and was characterized by the intensive development of higher aquatic plants, a smaller number of zooplankton species, and its abundance and biomass underwent changes due to a decrease in the number of rotifers (Rotatoria) and an increase in the number of spiny (Sladocera) and copepods (Copepoda) crustaceans. Studies of the species composi-tion, number and biomass of phytoplankton in a pond polluted with wastewater from a livestock enterprise estab-lished the predominance of euglena algae over other species in the reservoir, a significant increase in the number of blue-green (Cyanophyta) and diatom (Bacillariophyta) algae in biomass, the presence of small-celled flagellates with department of cryptophytic and bacterial-fungal accumulations, in contrast to a conditionally clean water body. A conclusion was drawn on the expediency of using the species composition of phytoplankton and zooplankton, as well as individual indicators of the chemical composition of water as criteria for assessing the ecological state of ponds located in the area of activity of livestock enterprises when polluted by sewage.

Direct evidence of nitric oxide production induced by lactoferrin and its enhancement by magnesium ions in cultured endothelial cells.

Bovine lactoferrin (BLF) reportedly lowers blood pressure and induces vasorelaxation, but its effect on nitric oxide (NO) production has not been established. Accordingly, we aimed to determine whether BLF induces NO production in bovine aortic endothelial cells, and the effects of extracellular free magnesium (Mg) ion concentrations on this NO production. BLF induced NO production time-dependently. NO production was markedly inhibited by the NO synthase inhibitor, NG-nitro-L-arginine methyl ester, in an effect abolished by L-arginine, but not D-arginine. NO production was suppressed at low concentrations, and enhanced at high concentrations, of Mg ions in culture medium. These results suggest that BLF has an important role in hypotensive effects. Mg ions may affect BLF-induced NO production.

Reusing Flowback and Produced Water with Different Salinity to Prepare Guar Fracturing Fluid

Economical and environmental concerns have forced the oil and gas industry to consider reusing flowback and produced water for fracturing operations. The major challenge is that the high-salinity of flowback water usually prevents its compatibility with several fracturing fluid additives. In this paper, the authors explored an economic and effective method to prepare guar fracturing fluids with different salinity waters. The main research idea was to use chelating agents to mask metal ions, such as calcium and magnesium, that are harmful to crosslinking. Firstly, a complexometric titration test was conducted to measure the chelating ability of three chelating agents. Secondly, through viscosity, crosslinking, and hanging tests, it was verified that the complex masking method could cope with the problem of high-valence metal ions affecting crosslinking. Thirdly, the preferred chelating agent was mixed with several other additives, including thickeners, crosslinkers, and pH regulators, to prepare the novel guar fracturing fluid. The comprehensive performances of the novel fluid system were tested such as temperature and shear resistance, friction reduction, gel-breaking performance, and core damage rate. The results show that the organophosphate chelating agent (i.e., CA-5) had the greatest ability to chelate calcium and magnesium ions. There was a good linear relationship between the dosage of CA-5 and the total molar concentration of calcium and magnesium ions in brine water. The main mechanism was that the chelating agent formed a complex with calcium and magnesium ions at a chelation ratio of 1:5. The test results of the comprehensive performance evaluation indicate that the prepared guar fracturing fluid met the requirements for field application, and the lower the salinity of the flowback water, the more it is economical and effective.

Diversity Variation of Silica-Scaled Chrysophytes Related to Differences in Physicochemical Variables in Estuaries of Rivers in an Arctic Watershed

The present study examined the taxonomic diversity of silica-scaled chrysophytes in the estuaries of the Arctic watershed of Yakutia in the context of global climate change, as these aquatic organisms are highly sensitive to environmental changes. Previously, 41 species of silica-scaled chrysophytes were recorded in the waters of Yakutia. In the present study, we supplemented this list with 55 species. We observed a high species richness (82 taxa) of silica-scaled chrysophytes in the study area. Of these, eight species were recorded in the waters of Russia for the first time. At present, the study area represents the northernmost habitat for most species observed during the study. The diversity of silica-scaled chrysophytes in Arctic rivers is comparable to or even greater than the diversity of chrysophycean flora at the middle latitudes. Most of these chrysophytes are represented by polyzonal and ubiquitous species. During 2008–2010, we noted increased relative numbers of boreal species in northern waters compared with data obtained during the previous 30 years. Overall, the species richness of silica-scaled chrysophytes in the studied rivers increased with increase in water transparency, temperature, and magnesium ion concentration, but decreased with increase in surfactant concentration. The origin of samples from a certain river; distance of the sampling site from the estuary; water temperature, transparency, and colour; and concentration of carbon dioxide, magnesium ions, total iron, surfactants, and oil products affect the species composition of silica-scaled chrysophytes in the study area. Our findings are fundamental to evaluate the current status of Arctic aquatic microflora and its further monitoring in the context of anthropogenic and climatic impacts.

The suitability of groundwater in Mosul city for various civilizational uses.

: In the current research, 23 wells were chosen from some residential neighborhoods located in the city of Mosul. To study some of the physical properties of well water represented by temperature, electrical conductivity, and total dissolved salts, as well as, the study of chemical analyzes are: (sulfates, chlorides, phosphates, nitrates, sodium, potassium, calcium, magnesium, dissolved oxygen and pH). The results of the study refer to the height of the electrical conductivity, which ranged between (791-2456) µmhos/cm. The results showed that a lot of water is free of dissolved oxygen, as it recorded the highest value of 4.6 mg/l. Whereas, the temperature of the studied water ranged between (20-28.4)Cº, and it is considered warm water. In the current study, the calcium ion concentration was greater than the magnesium ion concentration in all well water, and the highest concentration reached (264 and 134) mg/L at well 22 and 23, respectively. There was an increase in the concentration of chloride ion, which reached (204) mg/L and the lowest concentration (32) mg/l at wells 11 and 7, respectively. When comparing the values of the electrical conductivity of the well water with the global determinants of drinking, it was determined that they are not suitable for drinking. When applying the relationship between the value of the electrical conductivity and the ratio of sodium adsorption to well water, it was found that all water from wells Class (C3 - S1) except for wells (11 and 19) are classified as Class (C4 - S1)