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The structure of an aqueous solution of potassium dihydrogen phosphate (KH2PO4, KDP) was studied by small-angle X-ray scattering (SAXS) and molecular dynamics (MD). According to SAXS data, the octameric species (KH2PO4)8 are formed in solution in addition to K+, (H2PO4)−, and KH2PO4, while the presence of other types of oligomers is not observed. When the temperature drops below the saturation temperature (~60 °C), the volume fraction of octamers increases sharply, reaching 50% at 4 °C. The results of MD calculations of the temporal stability relationships of dimers (KH2PO4)2, tetramers (KH2PO4)4, and octamers (KH2PO4)8 show that the dimers and tetramers disintegrate rapidly (50–100 ps), while the octamers remain stable. A comparative analysis of the bonds between the octamers and the KDP crystal lattice was carried out when the octamer was inserted during crystal growth in the directions [001] and [100]. The possible relationship of the obtained results with the changes in the anisotropy of growth rates (habitus) of KDP crystals at different degrees of supersaturation is discussed. [ABSTRACT FROM AUTHOR]

The article describes the experiment on the upward percolating mass transfer by water solution according to the natural mechanism of movement of solutions toward ground surface with water evaporation in atmosphere. Useful components settle out from the solutions and concentrate on the evaporation barrier. The experiment simulates a complete cycle of processes for flotation tailings of complex ore: feed of solutions in boreholes from surface to bottom of a tailings body; spreading of the solutions in the tailings body; capillary ascent to the surface; settling out and concentration of useful salts on the evaporation barrier. The usability of this approach and some parameters of the mass transfer process can be found from the relevant research. [ABSTRACT FROM AUTHOR]

The phenomenon of the formation of microheterogeneities (MHs) in solutions, which, according to chemical handbooks, are considered true solutions, has been known for a long time. MHs have been found in more than 100 binary solutions, many of which are used both in various scientific studies and in life. However, the nature of this phenomenon is largely unclear. It is only well-known that MHs are stable areas of increased concentration of one of the components of the solution. The main reason for the poor knowledge of MHs is the use of very few experimental methods, mainly light scattering methods. In this paper, the terahertz time-domain spectroscopy method was used for the first time to study MHs using the example of aqueous solutions of three sugars: glucose, fructose, and sucrose. This method gives the spectra of complex permittivity in the terahertz range, which are very informative when studying the hydrate shells of molecules in solutions. The idea of this study was that structuring sugar molecules with the formation of MHs changes their hydration. The characteristics of sugar hydration in solutions before and after filtration through a 20 nm filter, leading to the destruction of MHs, were compared. It has been shown that the water binding in the MHs of all three solutions is increased compared with the hydrate shells of individual sugar molecules. Also, for MHs' fructose solution, a decrease in the number of hydrogen bonds between water molecules and an increase in the number of free water molecules was shown, which is not observed in MH glucose and sucrose solutions. This is explained by mutarotations of fructose molecules, leading to permanent significant rearrangements of the water structure in MHs. Thus, terahertz time-domain spectroscopy provides fundamentally new information about the MHs of aqueous solutions at the level of their hydration characteristics. The presence of MHs in solutions is a significant factor that has never been taken into account when studying the hydrate shells of various molecules in solutions using THz spectroscopy. [ABSTRACT FROM AUTHOR]

The object of research is a new, potentially effective and practical process for the decontamination of radioactive soil, based on combination of plasma hydroseparation and plasma activation. The cleaning effect is ensured by the destruction of the bonds of radionuclides with soil particles due to a series of electrophysical discharges at which active particles and shock waves appear. In a designed setup, the process of plasma-chemical treatment is implemented in a plasma cell with a self-sustaining pulsating mode of burning an electric discharge, which occurs in an aqueous solution. The setup realizes a resonant increase in the intensity of shock waves, turbulence and multiple expansion of the core, such that the expansion of the plasma-liquid interface becomes a real basis for scaling up the setup. Regardless of the material of the electrodes and in a wide range of electrical conductivity (measured from 100 to 5,000 μS/cm), the restructuring of the combustion regime is accompanied by an increase in the size and stabilization of the luminous zone, fragmentation of bubbles, and an increase in the rate of their evacuation from the discharge zone. The main factors of such a restructuring are the channel dimensions and temperature of the solution. Various materials of the walls of plasma-chemical reactor have been tested: plexiglass, ceramics and stainless steel with the thickness of 2 mm. The maximum increase in the amplitude of resonance oscillations depends on the cell radius. A dynamic pressure, which in an individual discharge is about 5–15 mm of the water column at the mouth of the discharge, increases to 150–200 mm of the water column at the bottom of the plasma cell at resonance. An increase in efficiency is achieved by an optimal choice of the duration of the current phase and the distance between the electrodes, which is 15–30 mm. The voltage drop is 70–80 % across the spark discharge, the rest falls across the solution. The transition of the discharge to a periodic pulsating current mode with an increase in the temperature of the solution has been found. Tests on a mobile plasma-chemical facility for the process of plasma co-precipitation of radionuclides 137Cs, 134Cs and 90Sr with ferrocyanide sorbents under real conditions of hydroseparation of contaminated soil from fields around the Fukushima Daiichi have shown a decrease in organic substances in water by 40 times, and of radioactivity by 75 times. [ABSTRACT FROM AUTHOR]

Elementary building blocks for the growth of KDP crystals were established. The solution of potassium dihydrogen phosphate (KH2PO4–KDP) has been experimentally studied by the small-angle X-ray scattering (SAXS) method. The analysis of SAXS data in the temperature range of 2.5–90 °C using a set of models of 3D fragments of the crystal structure showed that the saturated solution contains above K+, H2PO4− and KH2PO4 monomers, as well as mainly octamers. The 3D model of the octamer isolated from the crystal structure has dimensions of 17.443 Å along the [001] axis and 5.963 Å along the [100] and [010] axes. As the temperature is decreased, starting from the saturation temperature of the solution, the volume fraction of octamers sharply increases while the volume fraction of monomers decreases. The results indicate that the monomers and octamers represent major components in the solution with the presence of minor populations of other oligomers. The significant dominance of octamers in the supersaturated solution indicates that they are elementary building blocks for the growth of KDP crystals of tetragonal modification. [ABSTRACT FROM AUTHOR]

The effects of deoxyribose and phosphate substitutions on the hydrogen bond strength of adenine-thymine (AT) base pair in the gas phase and water solution were computationally investigated. According to the gas phase complexation energies, the parent molecule is the least stable complex among all of the structures. Our results clearly show that the attachment of deoxyribose substitution significantly increased the stability of dAT and ATd derivatives. While the phosphate addition has an opposite effect. In addition, the binding of the deoxyribose substitution from thymine side further increased the stability of ATd compared to adenine side in the dAT structures. Surprisingly, in the water solution, the binding of the phosphate group increased the additive effect of the deoxyribose substitution on the hydrogen bond strength. It is interesting to note that these substitutions in both phases further effect on the C–H···O hydrogen bond than the other units. Also the highest amount of its energy in the gas phase and water solution belongs to the dAT and ATdp, respectively and these structures have the highest values of total energy of hydrogen bonds. Finally, we introduced some good descriptors for estimation of the individual and the total hydrogen bond energies in these biomolecules. [ABSTRACT FROM AUTHOR]

The structure of an aqueous solution of potassium dihydrogen phosphate (KH2PO4, KDP) was studied by small-angle X-ray scattering (SAXS) and molecular dynamics (MD). According to SAXS data, the octameric species (KH2PO4)8 are formed in solution in addition to K+, (H2PO4)−, and KH2PO4, while the presence of other types of oligomers is not observed. When the temperature drops below the saturation temperature (~60 °C), the volume fraction of octamers increases sharply, reaching 50% at 4 °C. The results of MD calculations of the temporal stability relationships of dimers (KH2PO4)2, tetramers (KH2PO4)4, and octamers (KH2PO4)8 show that the dimers and tetramers disintegrate rapidly (50–100 ps), while the octamers remain stable. A comparative analysis of the bonds between the octamers and the KDP crystal lattice was carried out when the octamer was inserted during crystal growth in the directions [001] and [100]. The possible relationship of the obtained results with the changes in the anisotropy of growth rates (habitus) of KDP crystals at different degrees of supersaturation is discussed.

Enterprises of fuel and energy complex are the main sources of carcinogenic and mutagenic potentially toxic elements (PTEs). Their particulate and gaseous emissions, wastes, and effluents enforce migration processes of PTEs in atmosphere, soil, and then in water bodies, creating a danger to the functioning of aquatic ecosystems. Vulnerable objects include water bodies with slow water exchange, due to the accumulation of PTEs in the bottom sediments and the threat of secondary contamination. Among them it is necessary to note cooling ponds of thermal power plants (TPP). In this study, the ecological and geochemical state of components of "water-suspended sediments-bottom sediments" aquatic system is assessed on the example of the Gusinoye Lake (the Republic of Buryatia), which is used as cooling pond for the largest in the region TPP, burning brown coal from local deposits. The Gusinoye Lake is the second largest lake in Buryatia after the Baikal Lake and a valuable source of water supply, place of recreation, and fish breeding. To study the distribution of PTEs in the waters of the lake, a network of 19 monitoring stations was deployed in the summer of 2019. In contrast to the previous researches, detailed studies of the central deep-water part of the lake were carried out. As a result, data on the concentration of PTEs in the dissolved and suspended forms and also in bottom sediments was obtained. To study the balance of chemicals in the lake, its main tributaries were surveyed, as well as the drainage channel of TPP. For the first time, for the Lake Gusinoye, bulk concentrations of As, Cd, Pb, Zn, Co, Mo, Cu, Sb, Cr, V, Mn, Sr, and Ag were determined using the inductively coupled plasma mass spectrometry. The highest concentrations of dissolved PTEs in the lake water are confined to the mouths of tributaries in the northern part of the lake. Dissolved Sr, Mo, and Cu in the lake exceed maximum permissible concentrations (MPCs) for fishery. The maximum concentrations of Sr and Cu are almost 3 MPCs and that of Mo is 22 MPCs near the TPP. The suspended sediments of the Gusinoye Lake are depleted of all studied PTEs as compared to the regional clarkes (natural abundances) of the lithosphere. Mn has the highest concentrations in the suspension, and its maximum concentration was due to the surface runoff from the solid waste landfill and an abandoned coal mine. Concentrations of Cu, Zn, Sr, Mo, and Pb in bottom sediments are higher than in suspended sediments, thus indicating the accumulation of pollutants. The maximum intensity of accumulation is characteristic of the deep central basin of the lake and its eastern part, where Sr, Ag, and Mo accumulate most intensively near the coal field. The main sources of PTE pollution are concentrated in the northern and northeastern parts of the lake catchment area. Significant amount of dissolved Mo, Sr, and As enter the lake with the waters of quarries and mines of the coal fields, the solid waste landfill of the town of Gusinoozyorsk, and northern rivers-tributaries, draining the dumps of the large Zagustaj coal field. [ABSTRACT FROM AUTHOR]

The phenomenon of the formation of microheterogeneities (MHs) in solutions, which, according to chemical handbooks, are considered true solutions, has been known for a long time. MHs have been found in more than 100 binary solutions, many of which are used both in various scientific studies and in life. However, the nature of this phenomenon is largely unclear. It is only well-known that MHs are stable areas of increased concentration of one of the components of the solution. The main reason for the poor knowledge of MHs is the use of very few experimental methods, mainly light scattering methods. In this paper, the terahertz time-domain spectroscopy method was used for the first time to study MHs using the example of aqueous solutions of three sugars: glucose, fructose, and sucrose. This method gives the spectra of complex permittivity in the terahertz range, which are very informative when studying the hydrate shells of molecules in solutions. The idea of this study was that structuring sugar molecules with the formation of MHs changes their hydration. The characteristics of sugar hydration in solutions before and after filtration through a 20 nm filter, leading to the destruction of MHs, were compared. It has been shown that the water binding in the MHs of all three solutions is increased compared with the hydrate shells of individual sugar molecules. Also, for MHs’ fructose solution, a decrease in the number of hydrogen bonds between water molecules and an increase in the number of free water molecules was shown, which is not observed in MH glucose and sucrose solutions. This is explained by mutarotations of fructose molecules, leading to permanent significant rearrangements of the water structure in MHs. Thus, terahertz time-domain spectroscopy provides fundamentally new information about the MHs of aqueous solutions at the level of their hydration characteristics. The presence of MHs in solutions is a significant factor that has never been taken into account when studying the hydrate shells of various molecules in solutions using THz spectroscopy.

Combination of several films from polymerizable liquid crystal (PLC) into single device system with complex properties faces a fabrication issue due to chemical compatibility and mutual alignment effect of the neighbouring layers. Eco-friendly green technology of high anchoring azo-dye photoalignment layer coating from water solvent provides efficient solution to hinder interlayer interaction of bottom PLC layer avoiding its chemical damage and providing unique photoalignment pattern for top PLC retarder. The advanced possibilities of green technology of photoalignment layers coated from H2O solution are demonstrated through fabrication of achromatic quarter-wave retarder system comprising formation of polimerizable liquid crystal layers on top of one another with arbitrary azimuthal photoalignment direction. The merge of photoaligned PLC retarders into single multi-layer anisotropic structure opens new approach to fabrication of thin-film phase devices with complex optical properties. [ABSTRACT FROM AUTHOR]

Elementary building blocks for the growth of KDP crystals were established. The solution of potassium dihydrogen phosphate (KH2PO4–KDP) has been experimentally studied by the small-angle X-ray scattering (SAXS) method. The analysis of SAXS data in the temperature range of 2.5–90 °C using a set of models of 3D fragments of the crystal structure showed that the saturated solution contains above K+, H2PO4− and KH2PO4 monomers, as well as mainly octamers. The 3D model of the octamer isolated from the crystal structure has dimensions of 17.443 Å along the [001] axis and 5.963 Å along the [100] and [010] axes. As the temperature is decreased, starting from the saturation temperature of the solution, the volume fraction of octamers sharply increases while the volume fraction of monomers decreases. The results indicate that the monomers and octamers represent major components in the solution with the presence of minor populations of other oligomers. The significant dominance of octamers in the supersaturated solution indicates that they are elementary building blocks for the growth of KDP crystals of tetragonal modification.

This paper describes a new method for measuring the spectra of infrared radiation emitted by protein solutions in the native state without any external excitation. Radiation is detected using a vacuum Fourier-transform infrared spectrometer, and the tested sample itself is a source of radiation. The necessary conditions for detecting radiation from a sample are the use of a highly sensitive cooled detector and the presence of a cold background. In this work, the background was a black body at the boiling point of nitrogen. It is also important to select the optimal vacuum pumping depth for the spectrometer and sample thickness. Radiation occurs due to spontaneous radiative transitions from excited vibrational energy states to the ground state of molecules. The intensity of radiation is determined by the population of the respective energy states, which, according to the Boltzmann distribution, depends on temperature and frequency. Using solution of human interferon gamma as an example, it has been shown for the first time that proteins have intrinsic radiation. The described method allows detecting spectral lines with a radiation power of about 10−8 W or even less. It has also been demonstrated that emission spectroscopy offers advantages in the signal-to-noize ratio compared to absorption spectroscopy and allows analyzing the structural characteristics of a protein, in particular, providing information about its secondary structure. Another significant advantage of the method described in the article is its noninvasiveness. At the sample temperature of 25°С, emission spectra can be detected in the range from 400 to 3,600 cm−1, which covers almost the entire frequency range of existing stretching and bending vibrations of molecules. At the same time, in the fingerprint region from 500 to 1,600 cm−1 (the most informative part of the infrared spectrum), the highest sensitivity of the method is demonstrated. There is also potential for extending the available frequency range into the far infrared and terahertz ranges. Being applicable to the study of protein solutions in low concentrations, the proposed approach is not only interesting from the point of view of fundamental science but also can have applied significance in biological and medical research.

[Display omitted] • A general and direct one-step operational strategy has been developed for the synthesis of 1,2-diols from various simple alkenes using oxone in aqueous medium. • This reaction used the relatively low loadings of reagents under organic solvent- and transition-metal-free conditions, well overcoming the shortcomings in previous methods. • Both broad substrate scope and good functional group tolerance were demonstrated in this reaction, and the reaction can be conducted at the gram scale. An efficient one-pot direct dihydroxylation of alkenes has been achieved. This reaction proceeds under transition-metal-free conditions and in water solution, producing the corresponding 1,2-diols in good to excellent yields. The discovery of an optimal pH environment is identified as a key factor in the current system, which ensures the generality and good functional group compatibility of this reaction. Moreover, the gram-scale dihydroxylation of alkenes was demonstrated and without significant decrease of the yield of product, making this protocol very practical. [ABSTRACT FROM AUTHOR]

The article presents the results of obtaining hydrogels based on polyacrylonitrile, with potassium-phosphorus fertilizers in the composition used as agricultural fertilizers. As a potassium-phosphate fertilizer used fertilizer - potassium dehydrogenase orthophosphate. Comparative analysis was carried out using the obtained hydrogel cultures of wheat, safflower and barley. It is established that the polymer hydrogel containing potassium and phosphorus increases the moisture content of the soil, improves its water-retaining properties, improves the process of air exchange, increases the water-resistance of soil aggregates, and increases the productivity of plants while reducing the amount of polymer hydrogel per hectare. In this work, it was obtained a hydrogel containing potassium, magnesium and phosphorus impregnated by mixing with the addition of the same amount of the hydrogel, with the addition of soluble caliciviridae and magnetohydrostatic. In the drying Cabinet, increased twice the volume obtained, dried for two hours at a temperature of 90-950C. Several samples containing potassium, magnesium and phosphorus were sampled for plants. [ABSTRACT FROM AUTHOR]

Background: Present of p-chloro phenol in the environment due to high toxicity, mutagenic and carcinogenic effects, powerful odor production and stability in the environment caused to be categorized as priority pollutants. The aim of this study was to investigate the removal of p-chloro phenol from aqueous solution using chestnut shell modified by sulfuric acid. Methods: This study was an experimental study and chestnut shell (Quercus brantii Var. persica) was used as an adsorbent. The effects of pH, contact time, adsorbent dosage, and initial concentration on the adsorption process were evaluated, in a batch scale. The characterizations of the raw and modified adsorbent were investigated by Fourier transform infrared (FTIR) spectroscopy, scanning electron microscopy (SEM) and X-ray diffractometer (XRD). Langmuir and Fruindlich isotherm models and pseudo-first order kinetic, pseudo-second order kinetic were evaluated by experimental data. Results: The results showed that the removal efficiency of p-chloro phenol increased with increasing of the contact time and adsorbent dosage, and had a reverse effect with increasing of pH and p-chloro phenol initial concentration. The maximum adsorption capacity of p-chloro phenol by modified chestnut shell adsorbent was achieved of 3.33 mg/g and the maximum removal efficiency of p-chloro phenol was 87 percent at pH=4. The experimental data were well descripted by Freundlich isotherm (R2>0.92) and pseudo-second order kinetic (R2>0.94). Conclusion: This study showed that the chestnut shell could be effectively used at removal of p-chloro phenol from aqueous solutions. As the chestnut shell is a waste, so it can be applied as an adsorbent for removal of pollutants such as p-chloro phenol.

Abstract The emission of organic fluorophores is usually quenched in water solution. In this paper, strong emission of 7-hydroxyindazolo[2,3- b ]isoquinolin-12(7 H)-one derivatives were disclosed in aqueous solution. The absorption and fluorescence spectra of the ten derivatives were reported, they show absorption at 349–374 nm and emission at 409–483 nm. Among of them, the fluorescence quantum yield of 1c with alkyl groups is up to 85.9% in water; Compound 1g with benzyl group showed the maximum fluorescence intensity at 486 nm in water, which was attributed to S 1 →S 0 transition and intramolecular hydrogen bond. While the fluorescence of 1j with m -methoxyphenyl group was quenched by photo-induced electron transfer process. The fluorescence intensities of selected compounds were stable in pH 3.0–9.0. Thus this work expands the study of new fluorophores which produce strong fluorescence in aqueous condition. Graphical abstract Image 1 Highlights • The optical properties of 7-hydroxyindazolo[2,3- b ]isoquinolin-12(7 H)-one derivatives are reported. • Strong emission in water solution. • The fluorescence quantum yields are up to 85.9%. [ABSTRACT FROM AUTHOR]

In this research, tungsten disulfide (WS 2 ) nanosheets as sonocatalyst were synthesized through a sonochemical route. Characterization of as-synthesized sonocatalyst was carried out by X-ray diffraction (XRD), scanning electron microscopy (SEM), electron dispersive X-ray spectroscopy (EDX), Dot-mapping, high resolution transmission electron microscopy (HRTEM), Brunauer-Emmett-Teller (BET), Fourier transform infrared spectroscopy (FTIR), and ultraviolet-visible diffuse reflectance spectroscopy (UV–vis DRS) analysis. WS 2 nanosheets were evaluated for their sonocatalytic performance in order to remove basic violet 10 (BV10) under ultrasonic irradiation. The removal efficiency was maximized (94.01%) via the use of 1 g L −1 catalyst and 10 mg L −1 BV10 at pH = 4.5 and an ultrasonic power of 400 W within a reaction time of 150 min. In addition to BV10, the sonocatalytic elimination for a number of organic dyes viz. direct blue 71, acid blue 92, methylene blue, basic orange 2 and basic red 46 was examined to demonstrate the performance of WS 2 nanosheets under the ultrasonic irradiation. The experimentation of trapping was conducted using edetate disodium (EDTA-2Na), tert-butyl alcohol ( t -BuOH), and benzoquinone (BQ). According to the results, all radicals participated in the sonocatalytic activity. OH played a more prominent role than h + and O 2 - ∙ in the process of BV10 separation. Following five repetitive runs, the nanocomposites revealed a reusability of circa 18% drop in the elimination efficiency. The main removal intermediates were recognized by GC–MS technique. [ABSTRACT FROM AUTHOR]

Non-nutritive sweeteners have been used as substitutes for nutritive sweeteners with the goal of preventing obesity and dental caries. The main factor responsible for the difference in taste between beverages containing a nutritive sweetener and those containing a non-nutritive sweetener is the temporal profile of sensory attributes. In this study, untrained panelists performed a time-intensity evaluation of sweetness, using one coffee beverage containing a nutritive sweetener (sucrose) and two coffee beverages containing non-nutritive sweeteners (sucralose or acesulfame potassium (acesulfame K)). They evaluated continuously perceived intensity of sweetness for 150 s after swallowing each coffee beverage. We did not detect a significant difference in temporal profiles among the three coffee beverages. To investigate why the temporal profiles of the three coffee beverages followed similar traces, all untrained participants who had participated in the coffee beverage session also performed a time-intensity evaluation of sweetness using three water solutions (sucrose-sweetened, sucralose-sweetened, and acesulfame K-sweetened deionized water). We observed a significant difference in temporal profiles among the three water solutions. These results indicate that differences in the temporal profiles of coffee beverages might be masked by factors other than the sweetness of the sweetener. [ABSTRACT FROM AUTHOR]

Remediation of heavy metal–contaminated soil and water bodies necessitates the continuous development of effective decontamination techniques. To address this issue, ferromanganese binary oxide–biochar composites (FMBC) were prepared using impregnation/sintering methods, and their physicochemical properties and morphologies were examined. Kinetic modeling and adsorption isotherms were used to characterize the adsorption of Cu(II) and Cd(II) on FMBC, revealing that adsorption was well represented by pseudo-second-order kinetics ( R 2 > 0.99) and the Langmuir isotherm model. The prepared FMBC exhibited maximum Cu(II) and Cd(II) adsorption capacities of 64.9 and 101.0 mg/g, respectively, exceeding the corresponding values of biochar (21.7 and 28.0 mg/g, respectively). Moreover, adsorption was favored by increased pH and high humic acid concentration. X-ray photoelectron spectroscopy and Fourier transform infrared analyses confirmed that the heavy metal ions adsorbed on FMBC were divalent, indicating that the uptake of Cu(II) and Cd(II) was mainly due to the formation of strong mono- or multidentate inner-sphere complexes (e.g., COO–M (M = Cu or Cd) and Fe–Mn–O–M). Thus, the prepared composites exhibited potential applications as excellent adsorbents for Cu(II) and Cd(II) removal from contaminated water. [ABSTRACT FROM AUTHOR]

Efficiently sensing target ions in water solution is still an intriguing challenge. Herein, we report a novel and efficient approach for high fluorescent detection ions in water by a pillar[5]arene-based supramolecular sensors. This novel approach is illustrated as follows. Firstly, water soluble cationic pillar[5]arene ( P5 ) and acid functionalized naphthalene monoimide derivative ( N2 ) were self-assembled in water and formed supramolecular sensor ( P5N2 ). Then, competitive coordination was rationally introduced into the supramolecular sensor P5N2 by adding Al 3+ in suit and formed new supramolecular sensor ( P5N2Al ). Interestingly, the supramolecular sensor P5N2 could sense Al 3+ in water, while the supramolecular sensor P5N2Al could sense CN − in water with high selectivity and sensitivity, respectively. Therefore, it's a novel and facile way for the design of sensor which could efficiently sense ions in water. [ABSTRACT FROM AUTHOR]

Detection of dissolved methane and volatile hydrocarbons in water is a problem met inleakage localization during exploitation of underwater pipelines, oil and oil product spill over watersurface, geological exploration work for the localization of oil and gas fields under water, etc. Thisproblem can be solved by the application of detection system based on tubular selective membranepermeable for volatile organics and impenetrable for liquid water. Carrier gas (air) flowing throughthis tube is saturated with dissolved gas and then gas concentration is measured usingsemiconductor or other gas sensor. The system prototype was tested under laboratory conditionsand demonstrated low limit of gas detection (~20 ppb by mass of dissolved methane in water) andshort response time (~10 s).

In this study, an ultrasonic nebulizer unit was established to improve the quantitative analysis ability of laser-induced breakdown spectroscopy (LIBS) for liquid samples detection, using solutions of the heavy metal element Pb as an example. An analytical procedure was designed to guarantee the stability and repeatability of the LIBS signal. A series of experiments were carried out strictly according to the procedure. The experimental parameters were optimized based on studies of the pulse energy influence and temporal evolution of the emission features. The plasma temperature and electron density were calculated to confirm the LTE state of the plasma. Normalizing the intensities by background was demonstrated to be an appropriate method in this work. The linear range of this system for Pb analysis was confirmed over a concentration range of 0-4,150ppm by measuring 12 samples with different concentrations. The correlation coefficient of the fitted calibration curve was as high as 99.94% in the linear range, and the LOD of Pb was confirmed as 2.93ppm. Concentration prediction experiments were performed on a further six samples. The excellent quantitative ability of the system was demonstrated by comparison of the real and predicted concentrations of the samples. The lowest relative error was 0.043% and the highest was no more than 7.1%. [ABSTRACT FROM AUTHOR]

The coagulation characteristics of bisphenol A (BPA) with polyaluminum chloride (PACl) as a coagulant and the influence of UV irradiation as a complementary process were investigated. The influences of various coagulation parameters such as coagulant dose, pH, solution turbidity, and initial BPA concentrations were analyzed. The possible dominate mechanisms, formation, and performance of flocs over coagulation process were discussed. A coagulant dose of 17.5 mg/L was chosen as optimum dosage. Compared with other ranges of the pH, it can be seen that pH 8 was more effective. It was indicated that turbidity 16 NTU and BPA initial concentration 0.25 mg/L were as optimum conditions in the coagulation process. In this study, elimination mechanism of BPA included colloids entrapment and sweep flocs, predominantly. The results showed that the contact time of UV irradiation was an important factor in the removal efficiency of the BPA residual supernatant. The combination of C/F followed by UV irradiation showed an efficient removal method for treatment of water solutions containing BPA. [ABSTRACT FROM PUBLISHER]

In this work we study by means of Nuclear Magnetic Resonance spectroscopy the dynamics of the different water clusters that form within a solution with LiCl at eutectic concentration in the temperature range 320–205 K. This solution is considered a model system allowing the investigation of water properties in the deep supercooled regime in its bulk phase. Our data reveal two important dynamical changes occurring at two relevant temperatures for water: the highest temperature coincides with that of the water density maximum (277 K) and the lowest with that of the so-called dynamical crossover ( ≃ 225 K ). We interpret our data in terms of the different influence that the ions exert on water by lowering the temperature and of the tendency that water displays to develop its characteristic hydrogen bond network. [ABSTRACT FROM AUTHOR]

The structural and thermodynamic properties of pure water and sodium chloride solutions at high temperatures and pressures are studied by using molecular dynamics simulations and quantum molecular simulations. Properties are calculated as functions of temperature and pressure. The results show that the structure of pure water becomes looser as temperature increases from 298 to 400 K, with the collapse of the traditional tetrahedral structure. For sodium chloride solutions, the same collapse is also found with the increased concentration. Moreover, a critical point for the diffusion coefficient ofandis evident when the temperature increases linearly under 100 atm. At the critical points, the ions are abnormally clustered, due to the weakly hydrogen-bonded water molecules. The cluster size of the ions is synchronous with the corresponding diffusion coefficients. [ABSTRACT FROM AUTHOR]

The precipitation of a heterogeneous polydisperse suspension of low hydrophylicity onto an aluminosilicate substrate is used to obtain ceramic membranes with an asymmetric structure. The average pore size of the ceramic membrane is 0.3-0.5 μm. The problem of matching the shrinkage of the ceramic substrate and membrane layers is solved. A technology for obtaining micro- and ultrafiltration membranes using suspensions based on water and alcohol-water solutions of carboxymethyl cellulose is presented. [ABSTRACT FROM AUTHOR]

An experiment was conducted in solution culture to understand the response of dissimilar maize (Zea mays L.) genotypes against salinity in green house at Saline Agriculture Research Centre, Institute of Soil and Environmental Sciences, University of Agriculture, Faisalabad, Pakistan. Maize plants at two leaf phase were transplanted at three different levels of water salinity [(T1 (Control) T2 [EC 2.0 dS m-1, SAR 15.0 (mmol L-1)1/2 and RSC 2.25 mmolcL-1] andT3 [EC 4.0 dS m-1, SAR 25.0 (mmol L-1)1/2, RSC 5.0 mmolc L-1 ]. The mixtures of four salts (NaHCO3, Na2SO4, CaCl2.2H2O and MgSO4.7H2O) were used to formulate saline water levels through quadratic equation. Half strength Hoagland's nutrient solution was applied for nourishment throughout experiment. After 30 days of salinity evolution, maize plants were harvested and data for shoot fresh weight, root fresh weight, shoot dry weight root dry weight, shoot length and root length were recorded. From leaf juice Na+ and K+ contents were resolute and K+: Na+ proportion was calculated. All the growing components of maize varieties were significantly abridged owing to salinity effects and genotypic dissimilarity for salt lenience was also noticed between the maize varieties. The genotypes Sahiwal-2002 and Afgoi were classified as salt lenient genotype as these produced the highest shoot biomass (21.6 g and 17.3g) and retained higher K+: Na+(0.90 and 0.67) ratio, however Sadaf, FH-963 and FH-722 were categorized as salt sensitive genotypes and produced the least shoot weight (8.8 g, 7.7g and 7.9g) and could retain the lowest K+: Na+(0.34, 0.19 and 0.21) proportions under salinity. [ABSTRACT FROM AUTHOR]

Highlights: [•] Boron can be removed from water by adsorption on layered double hydroxide (LDH). [•] Both boric acid and borate species are adsorbed on the LDH. [•] Adsorption of borate is due to anion exchange and electrostatic interactions. [•] Adsorption of boric acid is attributed to acid–base reaction. [•] Solution pH plays a key role on the adsorption of the boron species onto LDH. [ABSTRACT FROM AUTHOR]

Highlights: [•] Calculation results indicate that luminol can form an extended hydrogen-bonding network. [•] The simulated adsorption spectrums of the network model are in accordance with the experimental results. [•] The changes induced by hydrogen bonds are discussed. [ABSTRACT FROM AUTHOR]

Pyriproxyfen is an insect growth regulator that affects the physiology of morphogenesis, reproduction and embryogenesis of insects. The molecule of pyriproxyfen bears little resemblance to endogenous insect juvenile hormone (JH), but it affects JH and ecdysteroid titers in a variety of arthropods. High-performance liquid chromatography with diode array (HPLC-DAD) method is a widely used method for the analyses of pyriproxyfen. Although the methods have been remarkably improved, tandem mass spectrometry (LC-MS/MS) systems with significant advantages have gradually replaced HPLC-DAD in many analyses. The aim of this study, was the evaluation of the two methods for linearity, limit of detection (LOD), limit of quantification (LOQ) selectivity and repeatability for the determination of pyriproxyfen in water solutions. Using HPLC-DAD the obtained LOD was 0.01 µg/ml with the LOQ of 0.03 µg/ml. The linearity was over 0.99 for the concentrations from 0.1 to 1.0 µg/ml with the repeatability RSD less than 11.7%. The LC-MS/MS method showed high reproducibility, as evident from the RSD values for intra-day and inter-day variability being 1.0-6.8% and 2.0-7.7%. The LC-MS/MS method exhibits linearity (R2>0.99) for the concentrations from 1.0 to 100.0 ng/ml with the repeatability RSD less than 12.7%. The obtained LOD and LOQ was 0.1 ng/ml and 1.0 ng/ml, respectively. The HPLC-DAD performed well in terms of various validation parameters, but showed a very high LOD and LOQ (considering low concentration level of pyriproxyfen used in mosquito treatment) compared to LC-MS/MS. [ABSTRACT FROM AUTHOR]

A magnetic composite of silver/iron oxides/carbon nanotubes (Ag/Fe3O4/CNTs) was synthesized and used as an adsorbent for the preconcentration of mercury ions in water solutions at room temperature (25°C) in this study. The silver nanoparticles were supported on the magnetic CNTs. The modification enabled the composite had not only a high adsorption capacity for mercury ions (Hg2+) but also the magnetic isolation properties. A fast, sensitive, and simple method was successfully developed for the preconcentration and determination of trace amount of Hg2+in water using the synthesized nanocomposite as adsorbent. The mercury concentration was determined by an atomic fluorescence spectrometer (AFS). The experimental conditions such as pH value, extraction temperature, extraction time, sample volume, eluent composition and concentration, sorbent amount, and coexisting ions were investigated for the optimization. A 500 mL of sample volume resulted in a preconcentration factor of 125. When a 200 mL of sample was employed, the limit of detection for Hg2+was as low as 0.03 ng mL−1with relative standard deviation of 4.4% at 0.1 ng mL−1(n = 7). The ease of synthesis and separation, the good adsorption capacity, and the satisfactory recovery will possibly make the composite an attractive adsorbent for the preconcentration of ultratrace Hg2+in waters. [ABSTRACT FROM AUTHOR]

Highlights: [•] We have measured the hydrogen gas yield from the dietary tablets dissolved in water. [•] We observed the oil emulsification due to the presence of nanobubbles. [•] We considered a simple model to estimate the lifetime of nanobubbles. [•] NMR proton spectra were measured at different times after adding the tablet to the water. [•] Proton NMR is a useful method to estimate the volume and lifetime of nanobubbles. [ABSTRACT FROM AUTHOR]

Using the method that was offered before in our previous work we determined an effective diffusion coefficient of ions for water-NaCl solution with dextran admixtures with molecular mass 40000 and without them in temperature interval (283-353) K. It was shown that leading dextran admixtures to solution results in penetration of ions inside the dextran balls and further movement of these ions and balls as a whole and thus in decrease of effective diffusion coefficient of ions. It was determined the concentration of ions inside the balls. [ABSTRACT FROM AUTHOR]

At present, there are no system solutions for preventing extensive oxidation of the dispersed metal in electric arc metallizing (EM). To solve the problem of reducing the negative effect of oxidation, investigations were carried out at the GOSNITI GNU Institute into the application of the metal–carbothermal processes. [ABSTRACT FROM PUBLISHER]

Reactions of gold(III) complexes with ethylene and propylene in water provide the first such examples not accompanied by reduction of the gold. HAuCl4 and AuCl3(TPPTS) produce organic products (alcohol, aldehyde/ketone, etc.) with gold reduction to the metal. However, [Au(bipy)Cl2] CI in water produces the gold(III) β-hydroxy complexes, [Au(bipy)(CH2CH2OH)2]X (X = C1-, PF6-) and [Au(bipy)(CH2CH(OH)CH3]Cl, which are stable in solution. These complexes could not be isolated, but were characterized by NMR and high-resolution mass spectra. [Au(terpy)Cl]Cl2 fails to react with ethylene in water, even at elevated temperatures. DFT computations were performed to investigate the reaction mechanism. [ABSTRACT FROM AUTHOR]

We have used Terahertz time-domain spectroscopy (THz-TDS) to investigate the complex dielectric function of water solutions containing different ions. Using HCl and NaCl solutions with different concentrations we study the changes of the dielectric response introduced by the ions. We find a linear increase of the real and imaginary part of the dielectric function compared with pure water with increasing ion concentrations. We use an expanded model for fitting the dielectric function based on a combination of a Debye relation and damped harmonic oscillators for the anions and cations. A good agreement between the model and the experimental results is obtained. [ABSTRACT FROM AUTHOR]

In this paper, an investigation of silicon nanocrystals-based sandwiched slot waveguides which are dispersion engineered for exciting optical solitons inside very short structures (only 3 mm long) is proposed. The possibility of using these structures for efficient surface sensing devices has been explored for the first time in cases of either air or water solution cover. [ABSTRACT FROM PUBLISHER]

In this paper, we present radio-frequency electro-magnetic field characterization of an electrooptic (EO) probe. This probe is able to simultaneously measure temperature and one component of the electric field (e-field) in a continuous wave (CW) or in a pulsed regime. For this purpose, linearity, selectivity, and sensitivity measurements are performed in air and in a cuvette filled with a water solution. The media are exposed to 1800-MHz CW electromagnetic wave through a transverse electromagnetic cell. Numerical characterization is also performed using finite-difference time-domain simulations. The EO probe presents a dynamic range exceeding 70 dB. Selectivity up to 25 dB is measured, demonstrating the ability of the EO probe to measure one unique component of the e-field. The EO probe sensitivity is equal to 0.77 and to 0.18 V · m-1Hz-½, in the air and in the water solution, respectively. This millimeter-sized EO probe is particularly suited for the measurement of ultrawide bandwidth and high-voltage e-fields up to a few megavolts per meter. [ABSTRACT FROM AUTHOR]

Abstract: The potential nitric oxide scavenging activity of polyhydroxylated derivative of fullerene C60(OH)24, called fullerenol, has been tested using the computer simulation (MD) method. The study is motivated by the expected diverse biological applications of water-soluble fullerenols. The static structure factor of the nitric oxide and fullerenol mixture in water solvent, related to the neutron scattering experiment, has been calculated and discussed. The distribution of nitric oxide NO molecules near fullerenol in water solution have been observed by calculating the partial radial distribution function at several temperatures, from 300 to 325K. The slight uptake of nitric oxide molecules by fullerenol has been detected at physiological temperature T =310K. The temperature dependence of the nitric oxide scavenging by fullerenol has been estimated. [Copyright &y& Elsevier]

This study is aimed at explaining the preference for AT and CG pairings and the possible insertion of other tautomeric DNA base pairs such as GenolT, that respect energetic and steric requirements including at least two hydrogen bonds and 11 ± 0.5Å distance between the 9-CH3 of purine and 5-CH3 of pyrimidine. The calculated free energy of formation ΔΔG at the DFT B3LYP/6-31G*-PCM/BEM level pointed out the CG and AT pairs as the most favored, followed closely by GenolT, in good agreement with Michaelis–Menten first order kinetics (CG ≈ AT > GenolT). Unusual DNA base pairs complexes such as AG (BEM) and CT (PCM) resulted to be stable, but it is very difficult to assume that they are likely to be included in the double strand DNA. The calculated enthalpy and dipole moments of isolated DNA bases agree well with experiment. The free energy of hydration, ΔGhyd, was found to depend on the electrostatic term, while cavitation-dispersion components are almost constant. The stability of DNA complexes in water resulted from PCM calculations is markedly influenced by the free energy of hydration. © 2009 Wiley Periodicals, Inc. Int J Quantum Chem, 2010 [ABSTRACT FROM AUTHOR]

The reaction mechanism for the dehydration of 1,4-butanediol in hot water has been investigated by means of the hybrid quantum mechanical/molecular mechanical approach combined with the theory of energy representation (QM/MM-ER). We have assumed that the proton transfers along the hydrogen bonds of the water molecules catalyze the reaction, where the transition state (TS) forms a singlet biradical electronic structure. It has been revealed by the simulation that the biradical electronic state at the TS changes to zwitterionic structure in solution due to the hydration of the polar solvent. Such the electronic structure change gives rise to the substantial stabilization of the TS in hot water. As a result, the water-catalytic path becomes more favorable in aqueous solution than another possible path that proceeds without proton transfers as opposed to the reaction mechanism in the gas phase. Furthermore, the activation free energy computed by the present method is in excellent agreement with the experimental result. [ABSTRACT FROM AUTHOR]