Phase Behavior of Aqueous Na-K-Mg-Ca-CI-NO3 Mixtures: Isopiestic Measurements and Thermodynamic Modeling

A comprehensive model has been established for calculating thermodynamic properties of multicomponent aqueous systems containing the Na{sup +}, K{sup +}, Mg{sup 2+}, Ca{sup 2+}, Cl{sup -}, and NO{sub 3}{sup -} ions. The thermodynamic framework is based on a previously developed model for mixed-solvent electrolyte solutions. The framework has been designed to reproduce the properties of salt solutions at temperatures ranging from the freezing point to 300 C and concentrations ranging from infinite dilution to the fused salt limit. The model has been parameterized using a combination of an extensive literature database and new isopiestic measurements for thirteen salt mixtures at 140 C. The measurements have been performed using Oak Ridge National Laboratory's (ORNL) previously designed gravimetric isopiestic apparatus, which makes it possible to detect solid phase precipitation. Water activities are reported for mixtures with a fixed ratio of salts as a function of the total apparent salt mole fraction. The isopiestic measurements reported here simultaneously reflect two fundamental properties of the system, i.e., the activity of water as a function of solution concentration and the occurrence of solid-liquid transitions. The thermodynamic model accurately reproduces the new isopiestic data as well as literature data for binary, ternary and higher-order subsystems. Because of its high accuracy in calculating vapor-liquid and solid-liquid equilibria, the model is suitable for studying deliquescence behavior of multicomponent salt systems

Geochemical features of the ashy layer («zol'nic») at the Bronze Age settlement of Streletskoe-1 in the forest-steppe Trans-Urals

The paper summarizes the results of a geo-chemical study of the soil samples collected from the ashy layer (zol’nic) at the Bronze Age settlement Streletskoye I in the Southern Trans-Urals and from the nearby natural deposition. The site is located on the left bank of the Ui river in Chelyabinsk region, Russia. The data on the distribution of phosphorus, potassium, calcium, manganese, sulfur, iron, titanium, rubidium, vanadium, cobalt, zinc and strontium are considered. The comparison demonstrates that concentrations of such elements as phosphorus, calcium, manganese, sulfur, rubidium exceed background values 2–3 times, while levels of potassium, iron, titanium, vanadium, cobalt, and strontium are below background values. At the same time, humus of buried soil underneath the ashy layer demonstrates highest values that exceed the usual one 2–4 times. The statistical analysis (t-statistics) supported the conclusion of very different proportions of elements between the cultural layer and the natural soil deposition, except for vanadium, cobalt, and strontium. There are two zones of element accumulations within the cross-section of the cultural layer, which are the ashy layer and the humus horizon. The conducted analysis contributes to the understanding of the subsistence strategies and craft. The high levels of phosphorus, potassium, calcium, possibly sulfur and zinc suggest the dominance of livestock breeding. The pre-sence of pottery production indicated by concentrations of manganese, iron, titanium, rubidium, strontium, vanadium and cobalt which could come with raw materials (clay) and broken ceramics. The discovered ashy layer is interpreted as a midden where wastes were repeatedly burned. Thus, layers of ash are complex objects that accumulate information of the economic activities and are unique for each ancient settlement

Droplet microfluidic device for chemoenzymatic sensing.

The rapid detection of pollutants in water can be performed with enzymatic probes, the catalytic light-emitting activity of which decreases in the presence of many types of pollutants. Herein, we present a microfluidic system for continuous chemoenzymatic biosensing that generates emulsion droplets containing two enzymes of the bacterial bioluminescent system (luciferase and NAD(P)H:FMN-oxidoreductase) with substrates required for the reaction. The developed chip generates "water-in-oil" emulsion droplets with a volume of 0.1 μL and a frequency of up to 12 drops per minute as well as provides the efficient mixing of reagents in droplets and their distancing. The bioluminescent signal from each individual droplet was measured by a photomultiplier tube with a signal-to-noise ratio of up to 3000/1. The intensity of the luminescence depended on the concentration of the copper sulfate with the limit of its detection of 5 μM. It was shown that bioluminescent enzymatic reactions could be carried out in droplet reactors in dispersed streams. The parameters and limitations required for the bioluminescent reaction to proceed were also studied. Hereby, chemoenzymatic sensing capabilities powered by a droplet microfluidics manipulation technique may serve as the basis for early-warning online water pollution systems

Geological expediency for inclusion of the “easy” methods complex into the geological exploration for oil and gas

The article presents a triad of “easy” field methods for geological exploration of subsoil areas in the exploration and prospecting-evaluation stages of geological exploration for oil and gas. The triad of field surveys includes the following sequentially performed works: 1) remote sensing and interpretation of space images of the Earth, 2) areal helium survey (He-survey), and 3) areal microseismic survey (MC-survey) as a single triad of field surveys. Based on the results of these surveys, areal and quantitative parameters of the anomalies of registered useful signals are estimated, which are predictably associated with potentially oil and gas promising zones on the licensed area where the types and volumes of field seismic operations, and then deep exploratory drilling can be located. Expert and automated methods based on the data of triad of field surveys can be used to assess the prospects of oil and gas potential and localized resources of each subsoil area. Their economic attractiveness is assessed taking into account geological and economic risks. The economic assessment of the licensed area uses the generally accepted indicators in the oil and gas industry for the stages of geological exploration. In addition, the conduct of the described work by the triad of field surveys at the pre-licensing stage can be carried out in the winter, and they are appropriate to be carried out on the initiative of the state authorities on subsoil use: a complete cycle of analysis of geological and economic attractiveness will help attract new subsoil users to participate in auctions and increase the cost of initial payments at the auction

Structural, electrical and luminescent characteristics of ultraviolet light emitting structures grown by hydride vapor phase epitaxy

Electrical and luminescent properties of near-UV light emitting diode structures (LEDs) prepared by hydride vapor phase epitaxy (HVPE) were studied. Variations in photoluminescence and electroluminescence efficiency observed for LEDs grown under nominally similar conditions could be attributed to the difference in the structural quality (dislocation density, density of dislocations agglomerates) of the GaN active layers, to the difference in strain relaxation achieved by growth of AlGaN/AlGaN superlattice and to the presence of current leakage channels in current confining AlGaN layers of the double heterostructure