Search

Environmental context Dimethyl trisulfide (DMTS) is a malodorous compound formed from decomposing algal matter and can severely compromise the quality of drinking water. The reactivity of DMTS toward cyanide was studied in aqueous solutions at environmentally relevant conditions. It was found that the half-lives of DMTS in the presence of free cyanide varied from several months to several thousand years depending on environmental conditions. Abstract Organically bound sulfur in the form of mono-, di- and polysulfide bridges constitutes a significant fraction of this element in recent and ancient sediments. In water columns of lakes, the concentrations of organo-sulfur compounds are much lower, and they are present in the form of malodorous dimethyl polysulfides. Currently, information regarding reactivity of organic polysulfides towards nucleophiles that are stronger than hydroxyl anions is lacking. In this work, the reaction kinetics of dimethyl trisulfide (DMTS) with the strong nucleophile and important environmental pollutant cyanide as a function of concentrations of reactants, pH and temperature were studied. It was found that the reaction rate constant as well as the activation energy of the reaction strongly depend on pH. The experimental data agree well with the existence of two distinct pathways: slow reaction between protonated cyanide and DMTS under acidic and neutral conditions and fast reaction between cyanide anion and DMTS under highly alkaline conditions. However, reactions of DMTS with the iron cyanide complexes hexacyanoferrate(ii) and hexacyanoferrate(iii) have no environmental significance since they are slower than the rate of DMTS decomposition. Under environmentally relevant conditions, rates of reactions of free cyanide with DMTS will be lower than the reaction with inorganic polysulfides or tetrathionate, but faster than the reaction with thiosulfate. Examples of application of kinetic parameters for calculation of rates of cyanide consumption in industrial and non-polluted natural aquatic systems as well as a protocol for quantification of organic polysulfide sulfur based on reaction with cyanide are provided.

Phosphorite deposits in southern Israel alternate between low phosphorous pristine phosphorites and high phosphorous reworked phosphorites. Deposition of pristine phosphorites occurs at high productivity and sedimentation rates under suboxic to anoxic conditions, whereas deposition of reworked phosphorites has been attributed to oxidizing conditions at low sedimentation rates during high-energy episodes accompanied by bioturbation. In this study, iron speciation in primary and reworked phosphates was used for investigating paleoenvironmental conditions of the two phosphate facies. Studied phosphates include low iron sections (Zin and Rotem synclines, North Negev) and iron-rich phosphates deposit (Ein-Ofarim, North Arava). Iron speciation in different synclines provides information on diagenetic processes during phosphogenesis and reworking processes.Pristine phosphorites are associated with substantially higher total iron (FeT) and highly reactive iron (FeHR) contents compared to the reworked phosphorites. On the other hand, the FeHR to FeT ratio is higher in reworked phosphorites. The pyrite Fe (Fepy) fraction to FeHR ratio is diagnostic for non-sulfidic water conditions for all studied phosphorites. The combination of FeHR/FeT and Fepy/FeHR paleoredox proxies points to possibly anoxic to anoxic-ferruginous sedimentary settings for pristine phosphorites while reworked phosphorites seem to be formed under more anoxic conditions. However, this observation opposes the general concept of reworked facies formation under aerated conditions. As ferruginous conditions are implausible, an alternative explanation for the observed iron speciation could be external input (possibly aeolian dust) of iron-rich particles during initial phosphate. During the reworking processes, removal of poorly reactive iron-rich smectites during reworking processes, although both fractions were depleted by up to 90%. Thus, the observed differences in FeHR to FeT ratio between pristine and reworked phosphates were likely caused by physical processes rather than changes in environmental redox conditions.

In aquatic systems a reaction between tetrathionate and cyanide results in the formation of thiocyanate. We have studied kinetics of the reactions of tetrathionate with free cyanide and two cyanide complexes, hexacyanoferrate(II) and hexacyanoferrate(III), at the environmentally relevant conditions. For the reaction between tetrathionate and free cyanide, the rate constant and the activation energy, but not the reaction order, strongly depend on pH. Our observations allow to propose the following pathways of thiocyanate formation by the reactions of free cyanide with tetrathionate: (1) tetrathionate reacts relatively slow with hydrogen cyanide at acidic and neutral conditions; and (2) tetrathionate reacts relatively fast with cyanide anion under highly alkaline conditions. Depending on environmental conditions, the half-lives of the reaction between free cyanide and tetrathionate will be in the ranges of hours to several years. Reactions of tetrathionate with hexacyanoferrate(II) and hexacyanoferrate(III) have no environmental significance as they are slower than the decomposition of tetrathionate. Strategy for improvement of analytical protocols for analysis of tetrathionate and cyanide is proposed based on the detected kinetics parameters.

The mammalian target of rapamycin is not only a central regulator of lipid metabolism that controls the processes of adipogenesis and lipolysis but also a regulator of the immunometabolism of immune cells that infiltrate adipose tissue. In turn, the level of progression of diabetes is significantly influenced by the Treg subpopulation, the complexity and heterogeneity of which is confirmed by the detection of numerous tissue-specific Tregs, including the so-called VAT Tregs (visceral adipose tissue CD4+Foxp3+ regulatory T cells). Therefore, the purpose of the study was to determine the mRNA expression levels of mTOR, Foxp3, IL1β, and IL17A genes in rat parapancreatic adipose tissue with experimental streptozotocin-induced diabetes mellitus, with or without metformin administration. The experiments were performed on male Wistar rats with induced diabetes as a result of streptozotocin administration. Molecular genetic studies were performed using real-time reverse transcription-polymerase chain reaction. The development of diabetes caused transcriptional activation of the mammalian target of rapamycin protein kinase gene, as well as increased mRNA expression of the pro-inflammatory cytokines IL1β and IL17A, but did not affect Foxp3 mRNA expression. The intervention with metformin in diabetic rats inhibited the mammalian target of rapamycin mRNA expression and caused an increase in the transcriptional activity of the Foxp3 gene in parapancreatic adipose tissue.

Low-cost metallic nanoink based on nickel–silver core–shell nanoparticles (Ni@Ag NPs) was used for the formation of conductive metallic coatings with low sintering temperature, which can be successfully applied for replacement of currently used silver-based nanoinks in printed electronics. The effect of oxalic acid (OA) on the sintering temperature and conductivity of coatings formed by Ni@Ag NPs was evaluated. It was found that the addition of OA to the ink formulation and post-printing treatment of deposited films with this acid provided a noticeable decrease in the sintering temperature required for obtaining conductive patterns that is especially important for utilizing the polymeric substrates. The obtained resistivity of metallic coatings after sintering at temperature as low as 100 °C was found to be 30 µΩ·cm, only ~4 times higher compared to the resistivity of bulk Ni that is promising for future application of such materials for fabrication of low-cost flexible printed patterns.

Reactions between cyanide and compounds, which contain S–S bonds, in aqueous media result in formation of thiocyanate. In this work, we studied the kinetics of reactions of thiosulfate with free cyanide and its complexes under environmental conditions. Rates of reactions between cyanide species and thiosulfate decrease in the following order: CN− > HCN > [Fe(CN)6]3− > [Fe(CN)6]4−. However, at neutral and slightly acidic pH range, reaction of thiosulfate with iron-cyanide complexes outcompetes its reaction with free cyanide, which exists in equilibrium with complexed cyanide. At environmentally relevant conditions, the characteristic time of reaction between free cyanide and thiosulfate was found to be tens of thousands of years, while for iron-cyanide complexes it was found to be hundreds to millions of years. Examples of application of kinetic parameters for calculation of rates of cyanide consumption in industrial (coke oven wastewater) and non-polluted natural aquatic system (Delaware Great Marsh) are provided.

The review is focused on bimetallic nanoparticles composed of a core formed by low-cost metal having high electrical conductivity, such as Cu and Ni, and a protective shell composed of stable to oxidation noble metal such as Ag or Au. We present the chemical and physical approaches for synthesis of such particles, as well as the combination of the two, the stability to oxidation of core-shell nanoparticles at various conditions, and the formulation of conductive compositions and their application in conductive coatings and printed electronics.

Lake Sevan is a meso-eutrophic water body, which was severely impacted by anthropogenic level decrease, pollution and eutrophication during the last century. Starting in the 1970s, these processes resulted in the formation of an oxygen-depleted hypolimnion during summer-autumn stratification of the lake. In this work, we demonstrate for the first time that eutrophication of the lake leads not only to the full depletion of oxygen and nitrate in the hypolimnion but as well to the presence of sulfate-reducing microorganisms and toxic hydrogen sulfide. Concentrations of hydrogen sulfide in the hypolimnion of Major and Minor Sevan in October were as high as 9 and 39 μM, respectively. In October 2019, 66 % of lake's bottom was covered by sulfidic waters, while the fraction of sulfidic water volume reached 19 %. Values of δ34S for hypolimnetic sulfide are lower by only 7-12 ‰ compared to epilimnetic sulfate, while δ33S values of sulfide are similar to the δ33S values of sulfate. These isotopic fingerprints are not consistent with microbial sulfate reduction as the sole source of hydrogen sulfide in the hypolimnion. We attribute the formation of a sulfidic deep-water layer to a combination of microbial sulfate reduction in the water column and diffusion of hydrogen sulfide from the sediments.

The high fluxes of iron minerals associated with aeolian dry deposition may result in an anomalously high reactive iron content and the rapid reoxidation of hydrogen sulfide in sediments. This will prevent the formation of pyrite and result in a ‘cryptic’ sulfur cycle. We studied the cycling of iron and sulfur in deep water (>800 m water depth) sediments of the Red Sea and its northern extension, the Gulf of Aqaba. We found that the reactive iron content in the surface sediments of the Gulf of Aqaba and the Red Sea is high, whereas the amount of sulfur-bound iron is very low and decreases with the water depth. The presence of trace amounts of pyrite and zero-valent sulfur, as well as the isotopic compositions of sulfate and pyrite, which are consistent with sulfate reduction under substrate-limiting conditions, suggest that cryptic sulfur cycling is likely to be a result of the rapid reoxidation of hydrogen sulfide rather than the suppression of microbial sulfate reduction. The low amount of reactive iron and high organic carbon content in the sediments of the Shaban Deep, which are overlain by hypersaline hydrothermal brines, result in a non-cryptic sulfur cycle characterized by the preservation of pyrite in the sediments. Supplementary material: Data for sulfur speciation, iron speciation and sulfur isotope composition are available at https://doi.org/10.6084/m9.figshare.c.5508155 Thematic collection: This article is part of the Sulfur in the Earth system collection available at: https://www.lyellcollection.org/cc/sulfur-in-the-earth-system

Deep-sea hydrothermal vents are a significant source of dissolved metals to the global oceans, producing midwater plumes enriched in metals that are transported thousands of kilometers from the vent source. Particle precipitation upon emission of hydrothermal fluids controls metal speciation and the magnitude of metal export. Here, we document metal sulfide particles, including pyrite nanoparticles, within the first meter of buoyant plumes from three high-temperature vents at the East Pacific Rise. We observe a zone of particle settling 10–20 cm from the orifice, indicated by stable sulfur isotopes; however, we also demonstrate that nanoparticulate pyrite (FeS2) is not removed from the plume and can account for over half of the filtered Fe (≤0.2 µm) up to one meter from the vent orifice. The persistence of nanoparticulate pyrite demonstrates that it is an important mechanism for near-vent Fe stabilisation and highlights the potential role of nanoparticles in element transport., There has been much interest recently in the transport mechanisms of metals from hydrothermal vents. Here the authors found that nanoparticulate pyrite is not removed from the plume and can account for over 50% of filtered iron one metre from the vent mouth.

A detailed study of kinetics of reaction between hydrogen sulfide and orthorhombic cyclooctasulfur at environmentally relevant conditions, which results in formation of inorganic polysulfides, was performed. Rates of reaction were measured as a function of pH, temperature and concentrations of S2− and S0 in airtight stirred batch reactor. Reaction was carried out at [S0]/[S2−]

Organic-rich carbonate sediments are deposited in a range of environments today and in the geologic past. A significant part of organic matter (OM) degradation in such sediments often occurs by microbial reduction of seawater sulfate, and the sulfide product may be preserved in pyrite and in organic sulfur (S) compounds. The isotopic composition (δ34S) of these phases can provide valuable information about S cycling in the ocean and in sediment porewaters, but only insofar as the processes governing these δ34S values are understood. To this end, we investigated the pathways, timing and interactions between pyrite and organic S formation during the deposition of organic-rich chalks. As a test case, we studied cores representing the thickest (∼350 m) and most complete Late Cretaceous organic-rich sequence along the southern Paleotethyan margin (central Israel). The organic S and OM contents show an inverse relation with the pyritic S content, which together with the uniform FePy/FeHR ratio (∼40%), suggest competition between organic S and pyrite formation. Both kerogen and pyritic S are 34S-depleted relative to Late Cretaceous marine sulfate (δ34S∼17–20‰), but the kerogen S is consistently and unusually 34S-enriched relative to coexisting pyrite by up to ∼38‰. Large S isotope fractionation (∼60‰) during microbial sulfate reduction necessary to reproduce the lowest pyrite δ34S values in the core, and relatively invariant δ34S values in organic S suggests that this large fractionation was approximately constant during deposition of the chalks in the core. Higher pyrite δ34S values observed in the most organic-rich parts of the core may be explained by Fe-limited pyrite formation, perhaps due to the reaction of Fe (e.g., complexation, sorption) with organic compounds. Lesser Fe availability, relative to the OM available for sulfate reduction, limits the ultimate abundance of pyrite, but importantly, it delays the formation of pyrite to deeper below the sediment-water interface, from 34S-enriched sulfide produced by Rayleigh distillation of a dwindling sulfate reservoir. Thus, it appears that competing Fe-OM, S-OM and Fe-S reactions can significantly affect the δ34S values recorded in pyrite in organic-rich carbonate sediments despite large and relatively constant microbial S isotope fractionation.

The early evolution of life on Earth was intimately coupled with the evolution of ocean chemical composition and redox conditions in Archean ocean. However, the measurements of chemical and isotopic compositions of Archean sedimentary rocks does not provide sufficient information for understanding the biogeochemical processes that characterized oceans during this period. In this research, the cycling of the redox-sensitive elements in the water column and sediments of the seasonally stratified Lake Sihailongwan, China, was studied. It was found that during the stratification, the concentrations of sulfate ions in the epilimnion were −1. The hypolimnion of the lake becomes anoxic and contains iron, manganese and low concentrations of hydrogen sulfide. These conditions are similar to those suggested to exist in the Archean ocean, and therefore the biogeochemical cycles in Lake Sihailongwan may be analogous to those in the Archean ocean. In Lake Sihailongwan, the chemocline is always deeper than the thermocline. The hypolimnion is supersaturated with respect to iron sulfide in August, while in May and October, this supersaturation is present only in the lower hypolimnion. The concentration profiles of the redox species in the water column and in the sediments show that dissolved iron(II) and manganese(II) diffuse from the sediments into the water column, while hydrogen sulfide and sulfate diffuse into the sediment. At the hypolimnion, the sulfur isotope fractionation values are consistent with microbial sulfate reduction, possibly combined, to a minor extent, with disproportionation of zero-valent sulfur. The absolute sulfur isotope fractionation factor increases between spring and autumn and decreases with water depth, possibly due to precipitation of iron sulfide in the lower hypolimnion. The fraction of highly reactive iron in the sediments is mainly composed of iron(II) carbonates and the most reactive iron(III) (hydr)oxide phases. Iron-based redox proxies are consistent with sediment deposition under ferruginous water column conditions. In the sediment, concentrations of sulfate and hydrogen sulfide are low, and sulfur isotope composition of sedimentary pyrite is equal to that of the epilimnetic sulfate. The obtained results demonstrated that despite a low sulfate concentration in the water column, sulfur isotope fractionation is high. However, due to the complete consumption of the sulfate reservoir, the large isotope fractionation is not preserved in the sedimentary record.

Soft robotics is a growing field of research, focusing on constructing motor-less robots from highly compliant materials, some are similar to those found in living organisms. Soft robotics has a high potential for applications in various fields such as soft grippers, actuators, and biomedical devices. 3D printing of soft robotics presents a novel and promising approach to form objects with complex structures, directly from a digital design. Here, recent developments in the field of materials for 3D printing of soft robotics are summarized, including high-performance flexible and stretchable materials, hydrogels, self-healing materials, and shape memory polymers, as well as fabrication of all-printed robots (multi-material printing, embedded electronics, untethered and autonomous robotics). The current challenges in the fabrication of 3D printed soft robotics, including the materials available and printing abilities, are presented and the recent activities addressing these challenges are also surveyed.

The search for new high-performance antimicrobial compounds remains one of the most important tasks of modern pharmaceutical chemistry, despite the wide range of modern natural, synthetic and semi-synthetic drugs for the treatment of infectious diseases.This is especially true for the naturally occurring compounds, new non-toxic and effective drugs can be created by their chemical modification for the treatment of various infectious pathologies. Recent researches in this area point to significant prospect of new synthetic derivatives of xanthine. The aim of this work is to develop simple laboratory methods for synthesizing 8-aminoderivatives of 7-alkyl-3-methylxanthines and to study their physical and chemical peculiarities and antimicrobial properties. The meltingpoint has been determined with the help of an open capillary method with TAP device (M). Elemental analysis has been performed with the help of the instrument ElementarVario L cube, NMR-spectra have been taken on a spectrometer Bruker SF-400 (operating frequency of 400 MHz, solvent DMSO-d6, internal standard – TMS). These data correspond to the calculated elemental analysis. For the initial screening study of the newly-synthesized substances benchmark testing-cultures of both gram-positive and gram-negative bacteria have been used, which belong to clinically significant groups of infections agents which are differing by their morpho-physiological properties. Through the reaction of 7-alkyl-3-methylxanthines with primary and secondary amines in water, water-ethanol, water-dioxane or cellosolve environment a range of 8-aminoderivativeshas been obtained which was not described earlier. Developing accessible laboratory methods to synthesize new 8-aminoderivatives of 7-alkyl-3-methylxanthines, which are potential bioactive compounds. Studying NMR-spectral characteristics of the obtained substances. Initial screening research of antimicrobial activity of the synthesized compounds has shown that 8-aminoxanthines (4, 6–12) can be used in medical practice as antistaphylococcal drugs, and 3-methyl-8-(4-methylpiperidine-1-yl)-7-n-propilxanthine (5)– antifungal agentafter additional studies.

Oxygen profiles were measured in the sediments of the Gulf of Aqaba (Red Sea), an oligotrophic marine system affected by episodic seasonal flash floods and intense aeolian dry deposition. Sediment cores were retrieved from shallow (15–45 m), intermediate (250–561 m) and deep (700 m) water sites of south–north and east–west transects. Dissolved oxygen concentrations were measured simultaneously by using microelectrodes and microoptodes immediately after sampling and after transportation. Oxygen penetration depths were found to increase from 2 to 5 mm at the shallow water sites with sandy permeable sediments to 10–21 mm at the deeper sites with cohesive muddy sediments. This increase corresponds to decrease in oxygen diffusive fluxes at the sediment–water interface and oxygen consumption rates with depth. Oxygen consumption rates exhibit local maxima at the oxic–anoxic sediment boundary, which may be attributed to oxygen reduction coupled to oxidation of dissolved Fe(II) and Mn(II) at deep and intermediate water sites and of hydrogen sulfide at shallow water sites. Microelectrodes and microoptodes measurements of cohesive sediments from deep and intermediate water sites yielded similar results. By comparison, the microoptodes displayed more robust measurements than microelectrodes in sandy near-shore sediments. This was attributed to their flexible fiber structure that is less likely to break or to abruptly displace sand particles. After transportation of sediment cores from Eilat to Beer Sheva followed by ≤ 24-h storage, no changes in oxygen fluxes and consumption rates were detected.

Special attention of pharmaceutical scientists is attracted to the creation of new potential substances. They select natural heterocyclic molecules that exhibit various types of pharmacological activity as basic structures. Adamantane derivatives, as well as a number of other framework compounds, in the vast majority are biologically active substances. This fact causes interest to the given classes of organic compounds as potential sources for the development of new drugs. Due to the high pharmacological action of 1,2,4-triazole derivatives, the combination of adamantane and 1,2,4-triazole in one molecule can lead to the formation of high-level pharmacological substances. The aim of this work is the synthesis of some 2- (2 - ((5- (adamantane-1-yl) -4-R-1,2,4-triasole-3-yl) thio) acetyl) -N-R1-hydrazine-carbothioamides, study of their physical and chemical properties, antimicrobial and antifungal activity. Materials and methods. The chemical names of the compounds are given in accordance with the requirements of the IUPAC nomenclature (1979) and the recommendations of the IUPAC (1993). Study of the physical and chemical properties of 2-(2-((5-(adamantane-1-yl)-4-R-1,2,4-triazole-3-yl)thio)acetyl)-N-R1-hydrazine-carbothioamides have been carried out on the certified and licensed equipment in the ZSMU physical-chemical laboratories. The melting temperature was determined by an open capillary method on the Opti Melt MPA 100. The elemental composition of the synthesized compounds was determined on the universal analyzer Elementar Vario L cube (CHNS) (standard – sulfanilamide). 1H NMR spectra were recorded on a spectrometer Varian Mercury VX-200 (1H, 200 MHz) in dimethylsulfoxide-d6solvent (tetramethylsilane - internal standard) and are decoded using ADVASP(tm)Analyzer program (Umatek International Inc.). Chromatographic mass spectral studies were performed on a gas-liquid chromatograph Agilent 1260 Infinity HPLC equipped with an Agilent 6120 mass spectrometer (ionization in an electric spray (ESI). Results. New 2-(2-((5-(adamantane-1-yl)-4-R-1,2,4-triazole-3-yl)thio)acetyl)-N-R1-hydrazine-carbothioamides are firstly synthesized, their structure is established by means of modern physical chemical methods of analysis (elemental analysis, IR-, NMR 1H-spectroscopy), and their individuality is done by HPLC-MS method. In all cases, the meanings of the investigated physical and chemical constants coincide with the estimated theoretical indicators. Determination of antimicrobial and antifungal activity was carried out by 2-fold serial dilutions method in liquid nutrient media. As a result of conducted investigations the compounds which levels of antimicrobial and antifungal action approaching, and in some cases exceeding comparison drug trimethoprim were revealed among the synthesized compounds. Conclusions. A compound of 2-(2-((5-(adamantane-1-yl)-4-phenyl-1,2,4-triazole-3-yl)thio)acetyl)-N-ethyl-hydrazine-carbothioamide occurred as the most active in relation to all test-strains among the synthesized substances, the force of antimicrobial and antifungal activity of it several times exceeds the comparison standard trimethoprim.