Prediction of Aqueous Solution Surface Tension of Some Surfactant Mixtures and Composition of Their Monolayers at the Solution–Air Interface

Measurements of the surface tension of the aqueous solution of SDDS mixture with fluorocarbon surfactants (FC) were carried out and considered in light of the surface tension of aqueous solutions of individual surfactants. Similar analyses were made for many other aqueous solutions of binary and ternary mixtures, taking into account the literature data of the surface tension of aqueous solutions of TX100, TX114, TX165, SDDS, SDS, CTAB, CPyB and FC. The possibility of predicting the surface tension of the aqueous solution of many surfactant mixtures from that of the mixture components using both the Szyszkowski, Fainerman and Miller and Joos concepts was analyzed. The surface tension of the aqueous solutions of surfactant mixtures was also considered based on the particular mixture component contribution to the water surface tension reduction. As a result, the composition of the mixed surface layer at the solution–air interface was discussed and compared to that which was determined using the Hua and Rosen concept. As follows from considerations, the surface tension of the aqueous solution of binary and ternary surfactant mixtures can be described and/or predicted.

Are Efficient-Dose Mixtures a Solution to Reduce Fungicide Load and Delay Evolution of Resistance? An Experimental Evolutionary Approach

Pesticide resistance poses a critical threat to agriculture, human health and biodiversity. Mixtures of fungicides are recommended and widely used in resistance management strategies. However, the components of the efficiency of such mixtures remain unclear. We performed an experimental evolutionary study on the fungal pathogen Z. tritici to determine how mixtures managed resistance. We compared the effect of the continuous use of single active ingredients to that of mixtures, at the minimal dose providing full control of the disease, which we refer to as the “efficient” dose. We found that the performance of efficient-dose mixtures against an initially susceptible population depended strongly on the components of the mixture. Such mixtures were either as durable as the best mixture component used alone, or worse than all components used alone. Moreover, efficient dose mixture regimes probably select for generalist resistance profiles as a result of the combination of selection pressures exerted by the various components and their lower doses. Our results indicate that mixtures should not be considered a universal strategy. Experimental evaluations of specificities for the pathogens targeted, their interactions with fungicides and the interactions between fungicides are crucial for the design of sustainable resistance management strategies.

Fractional diffusant model of a multicomponent inhomogeneous gas mixture as a basis for the diffusant approximation

It can be shown that for a correct description of the motion of an inhomogeneous multicomponent mixture of gases, such concepts as a multi-velocity continuum and interpenetrating motion are not enough. This is the basis for the introduction of the concept of “poly-velocity motion”. The reason for the need to use this concept is that to describe the motion of each component of an inhomogeneous mixture, it is necessary to use not one, but two velocity fields. The use of two velocity fields to describe the motion of a mixture component is the basis for constructing a fractional model of the mixture component, in which each component is divided into two fractions. This model serves as the basis for constructing the proposed fractional diffusant model of a multicomponent inhomogeneous gas mixture.

Mixed-Gas Selectivity Based on Pure Gas Permeation Measurements: An Approximate Model

An approximate model based on friction-coefficient formalism is developed to predict the mixed-gas permeability and selectivity of polymeric membranes. More specifically, the model is a modification of Kedem’s approach to flux coupling. The crucial assumption of the developed model is the division of the inverse local permeability of the mixture component into two terms: the inverse local permeability of the corresponding pure gas and the term proportional to the friction between penetrants. Analytical expressions for permeability and selectivity of polymeric membranes in mixed-gas conditions were obtained within the model. The input parameters for the model are ideal selectivity and solubility coefficients for pure gases. Calculations have shown that, depending on the input parameters and the value of the membrane Peclét number (the measure of coupling), there can be both a reduction and an enhancement of selectivity compared to the ideal selectivity. The deviation between real and ideal selectivity increases at higher Peclét numbers; in the limit of large Peclét numbers, the mixed-gas selectivity tends to the value of the ideal solubility selectivity. The model has been validated using literature data on mixed-gas separation of n-butane/methane and propylene/propane through polymeric membranes.

Why do fungicide mixtures delay the evolution of resistance? An experimental evolutionary approach

Pesticide resistance poses a critical threat to agriculture, human health and biodiversity. Mixtures of fungicides are recommended and widely used in resistance management strategies. However, the components of the efficiency of such mixtures remain unclear. We performed an experimental evolution study on the fungal pathogen Z. tritici, to determine how mixtures managed resistance. We compared the effect of the continuous use of single active ingredients to that of mixtures, at the minimal dose providing full control of the disease, which we refer to as the "efficient" dose. We found that the performance of efficient-dose mixtures against an initially susceptible population depended strongly on the components of the mixture. Such mixtures were either as durable as the best mixture component used alone, or worse than all components used alone. Moreover, efficient-dose mixture regimes probably select for generalist resistance profiles as a result of the combination of selection pressures exerted by the various components and their lower doses. Our results indicate that mixtures should not be considered a universal strategy. Experimental evaluations of specificities for the pathogens targeted, their interactions with fungicides and the interactions between fungicides are crucial for the design of sustainable resistance management strategies.

Числове та експериментальне дослідження наповнення резервуару компонентом газової суміші

The subject of the research is mathematical models of a gas-dynamic non-stationary process of filling a vessel with a component of a gas mixture. The aim of the study is the scientific and experimental substantiation of the choice of a model of filling a vessel with a component of a gas mixture with a given accuracy. The objectives of the study are to conduct full-scale experiments on filling the vessel with gas for further verification of the gas mixture generation control system, as well as in the development of adequate mathematical models of gas-dynamic flow, the analysis of simulation results, and the use of verified results in the system of automated generation of a gas mixture of a given accuracy by assessing the mass of its components depending on the filling parameters. The tasks are solved by studying the results of numerical modeling of the process and full-scale experiments. The following results are obtained. A series of full-scale experiments on filling a vessel with high-frequency monitoring of the pressure and temperature of the gas being filled was carried out. Significant factors were analyzed. The use of SAS SST turbulence models was substantiated. Models of the gas-dynamic unsteady process of filling the vessel with a component of the gas mixture for various values of the mass flow rate had been built. All the simulations were carried out using the ANSYS CFX software package. The influence of considering a heat exchange with the vessel walls on the studied parameters of the mixture is determined, namely: pressure, gas temperature averaged over the volume, gas temperature in a control point, mass of the component of a gas mixture. It was found that the deviation of the calculated data when using a model with an adiabatic condition on the wall compared to a model with a constant temperature regime is: for pressure – no more than 5 %, for averaged temperature – 6 %, for the temperature at the monitor point – 9 %, for mass – 1.5 %. The discrepancy between the simulation results and the full-scale experiment does not exceed 12 % in pressure and temperature at the monitor point, as well as 4 % in the mass of the component. By the experimentally determined accuracy parameter of the gas mixture (the mass of the mixture component in particular), the numerical models had been corrected to provide the mass value error of no more than 0.5 %.

One-Layer vs. Two-Layer SOM in the Context of Outlier Identification: A Simulation Study

In this work, we applied a stochastic simulation methodology to quantify the power of the detection of outlying mixture components of a stochastic model, when applying a reduced-dimension clustering technique such as Self-Organizing Maps (SOMs). The essential feature of SOMs, besides dimensional reduction into a discrete map, is the conservation of topology. In SOMs, two forms of learning are applied: competitive, by sequential allocation of sample observations to a winning node in the map, and cooperative, by the update of the weights of the winning node and its neighbors. By means of cooperative learning, the conservation of topology from the original data space to the reduced (typically 2D) map is achieved. Here, we compared the performance of one- and two-layer SOMs in the outlier representation task. The same stratified sampling was applied for both the one-layer and two-layer SOMs; although, stratification would only be relevant for the two-layer setting—to estimate the outlying mixture component detection power. Two distance measures between points in the map were defined to quantify the conservation of topology. The results of the experiment showed that the two-layer setting was more efficient in outlier detection while maintaining the basic properties of the SOM, which included adequately representing distances from the outlier component to the remaining ones.

Software package for calculation of fertilizer mixture component doses

A methodology and a software package for calculating the fertilizer mixture component doses depending on the data on the variability of agrochemical indicators and agricultural crops planned for cultivation are discussed. The software package can be used by both agricultural enterprises and fertilizer manufacturers with fertilizer mixing plants for the production of fertilizer mixtures for the soil, climatic and economic conditions of the end consumer.

Density Measurements of an Air-Like Binary Mixture over the Temperature Range from 100 K to 298.15 K at Pressures up to 8.0 MPa

Densities of an air-like binary mixture (0.2094 oxygen + 0.7906 nitrogen, mole fractions) were measured along six isotherms over the temperature range from 100 K to 298.15 K at pressures up to 8.0 MPa, using a low-temperature single-sinker magnetic suspension densimeter. The measurements were carried out at T = (100, 115, and 130) K in the homogeneous gas and liquid region, and at T = (145, 220, and 298.15) K in the supercritical region (critical temperature TC = 132.35 K); in total, we present results for 52 (T, p) state points. The relative expanded combined uncertainty (k = 2) of the experimental densities was estimated to be between 0.03 % and 0.13 %, except for four values near the critical point. The largest error is caused by the magnetic suspension coupling in combination with the mixture component oxygen, which is strongly paramagnetic; the resulting force transmission error is up to 1.1 %. However, this error can be corrected with a proven correction model to an uncertainty contribution in density of less than 0.044 %. Due to a supercritical liquefaction procedure and the integration of a special VLE-cell, it was possible to measure densities in the homogeneous liquid phase without changing the composition of the liquefied mixture. Moreover, saturated liquid and saturated vapor densities were determined at T = (100, 115, and 130) K by extrapolation of the experimental single-phase densities to the saturation pressure. The new experimental results were compared with the mixture model of Lemmon et al. for the system (nitrogen + argon + oxygen) and the GERG-2008 equation of state.