Initial Concentrations Of Components Research Articles

Phase equilibria of the propylene glycol/CO2 and propylene glycol/ethanol/CO2 systems

The high-pressure vapour–liquid phase equilibria (P–T–x–y) of the binary mixture propylene glycol/CO2 have been experimentally investigated at temperatures of (398.2, 423.2 and 453.2)K over the pressure range from (2.5 to 55.0)MPa using a static-analytic method. Furthermore, the high-pressure vapour–liquid phase equilibria (P–T–x–y) of the ternary mixture propylene glycol/CO2/ethanol at constant temperatures of (398.2, 423.2 and 453.2)K and at constant pressure of 15.0MPa have been determined using a static-analytic method. Initial concentrations of components in propylene glycol (PG)/ethanol (EtOH) mixture vary from 10 up to 90wt.%. In general, for binary system it was observed that the solubility of CO2 in the heavy propylene glycol reach phase increases with increasing pressure at constant temperature. On the contrary, the composition of gaseous phase is not influenced by the pressure or the temperature. On average the solubility of PG in light phase of CO2 amounts to 30wt.%. The system behaviour at temperature of 398.2K was investigated up to 70.0MPa and a single-phase region was not observed. Above the pressure 60.0MPa a single-phase region of the system was observed for the temperature of 423.2K. For the temperature of 453.2K the single-phase was observed above the pressure of 48.0MPa. For ternary system it was observed that the composition of heavy phase is slightly influenced by the temperature when the mass fraction of EtOH in initial mixture is higher than 50wt.%. If the mass fraction of PG in initial mixture is higher than 50wt.%, the composition of heavy phase is not influenced by the temperature anymore. The composition of the PG, EtOH and CO2 in light phase remains more or less unchanged and it is not influenced by the conditions.

MATHEMATICAL MODELLING OF STRENGTH CHARACTERISTICS OF ELECTROCONSOLIDATED ZrO2-Al2O3 MATERIALS

In this article the way of forecasting of quality indicators (fracture toughness, hardness) ofelectroconsolidated materials of ZrO2 - Al2O3 nanosystem is considered by a method of mathematicalmodeling.The main patterns of influence of technological factors eleсtroсonsolidation and concentration ofinitial components for the synthesis of materials using zirconia and alumina nanopowders on the strengthcharacteristics of the materials were identified. The mathematical models were built. The model is easy toassess the extent and impact of the results of each of the factors (temperature, holding time and Al2O3concentration) on the characteristics of the object, find it optimal regimes operation. The active experimentallows putting the artificial indignation on object under study and measuring the corresponding valuesoutput parameters. The size and mix of revolting influences introduced into the facility in accordance with adefinite plan, for any optimal criteria.

Removal of 4-nitrophenol from binary aqueous solution with aniline by granular activated carbon using Taguchi’s design of experimental methodology

This paper reports the studies on the simultaneous removal of aniline and 4�nitrophenol from aqueous solutions of the binaries using granular activated carbon as an adsorbent. The effect of operating parameters such as initial component concentrations, temperature, adsorbent dosage and contact time on the adsorption of the above said mixtures of solutes in the binary aqueous solution was studied. Taguchi's method of design of experiments was used to study the effect of each parameter at three levels on the selected response characteristic (total amount of solutes adsorbed on granular activated carbon (qtot, mmol/g)).The analysis of variance shows that the adsorbent dosage is the most significant parameter affecting the adsorption process with 22.42 and 37.62% contribution to qtot and signal-to-noise ratio data. The contribution of interactions between initial concentration of binary components is also significant. Confirmation experiments were car� ried out to check the effectiveness of the Taguchi's methodology at the optimum levels of process parameters.

Preparation of mixture of free-flowing materials in double-shaft paddle mixers

Results are presented for investigation of the movement of free-flowing materials in double-shaft paddle mixers. A method of reducing the mixing times of these free-flowing materials, and the design of the doubleshaft paddle mixer for this reduction, which provides for intensification of mixing due to an additional loop for particle movement are examined. Paddle mixers are widely used in various branches of industry. A number of investigations relative to mixing of freeflowing materials have been conducted in these mixers for the purpose of shortening the time required for preparation of the mixture, and improvement of its quality [1, 2]. Let us isolate two basic types of double-shaft paddle mixers: without intersection of the rotational trajectories of the paddles of the parallel shafts (Fig. 1a); and, with intersecting rotational trajectories of the paddles of the parallel shafts (Fig. 2a). It is proposed to shorten the preparation time of the mixture in the mixers with allowance for charging rules by rapid equalization of the initial components along the tiers of the effective members, intensification of convective and diffusion mixing [3, 4], and organization of large-flow discharge of the mixture without loss of its uniformity due to variation in the rotational direction of the shafts and variation of the position of the paddles on these shafts. Two methods of charging the initial components into the mixer are: uniform charging in order of decreasing sizes (the concentration of initial components in each tier of effective members is essentially the same); and, simultaneous charging via different devices (positioning of the initial components is strictly isolated with respect to the tiers of effective members) [4]. Let us examine a mixer (see Fig. 1a) in the housing of which paddles 2 are located on shafts 1 such that the material is mixed from one terminal section of the mixer in one direction, and to the other terminal section in the other direction, while at the end, one or two pairs of paddles are mounted at the opposite angle for agitation of the mixture in the opposite direction. The rotational trajectory of paddles 2 on shafts 1 do not intersect. The interaxial distance between the shafts a 1 > 2R (R is the radius of the rotational trajectory of the paddles). For the method of simultaneous loading of the initial components, a largeflow counter-movement of particles 3 is formed from one terminal section to the other in the initial stage to equalize their concentration along the shafts in each tier of effective members, and intensify convective mixing (see Fig. 1b). Shafts 1 rotate in opposite directions, displacing the free-flowing material from the center of the mixer toward the lateral walls of the housing. Formation of zones of material slip (A) is possible near the terminal walls of the housing in the mixer, resulting in a nonuniform load over the length of the shaft, and slowing of the process of uniform movement of the material. Movement of material is insignificant between the effective zones of the shafts; this renders equalization of the concentration of initial components difficult within the entire reaction space (see Fig. 1b). Charging requires organization within the central zone along the mixer. The charging consumes from 0.1 to 0.3 of the total time required for mixing. To intensify diffusion mixing, the direction of rotation of the shafts is reversed, mixing the material from the lateral walls of the housing toward the center of the mixer. Active exchange of particles occurs between the opposing flows in the central portion of the mixer (see Fig. 1c).

Adsorptive removal of aniline by granular activated carbon from aqueous solutions with catechol and resorcinol

In the present paper, the removal of aniline by adsorption process onto granular activated carbon (GAC) is reported from aqueous solutions containing catechol and resorcinol separately. The Taguchi experimental design was applied to study the effect of such parameters as the initial component concentrations (C 0, i ) of two solutes (aniline and catechol or aniline and resorcinol) in the solution, temperature (T), adsorbent dosage (m) and contact time (t). The L27 orthogonal array consisting of five parameters each with three levels was used to determine the total amount of solutes adsorbed on GAC (q tot, mmol/g) and the signal-to-noise ratio. The analysis of variance (ANOVA) was used to determine the optimum conditions. Under these conditions, the ANOVA shows that m is the most important parameter in the adsorption process. The most favourable levels of process parameters were T=303 K, m=10 g/l and t=660 min for both the systems. q tot values in the confirmation experiments carried out at optimum conditions were 0.73 and 0.95 mmol/g for aniline–catechol and aniline–resorcinol systems, respectively.

FUSIBLE BISMUTHCONTAIN GLASSES

The processes of glass-making, crystallizations were investigated. The physical and chemical properties of the system SiO2-B2O3-Bi2O3-ZnO-BaO at the different concentrations of initial components are studied. The optimal compositions of fusible glasses for solders, resistance and conductive thick-film elements of the electronics are offered.

Dynamics of the reaction glucose-catalase-glucose oxidase-hydrogen peroxide

Glucose-catalase-glucose oxidase-hydrogen peroxide reaction is one of the few known enzymatic systems studied in vitro in the field of nonlinear chemical dynamics. This reaction belongs to the family of oscillatory enzymatic reactions, which form a natural basis of oscillations in biological systems. A parametric study of dependence on mixing, temperature and initial concentrations of components in a batch stirred reactor was carried out. A newly proposed mathematical model of the reaction conforms to the obtained experimental data. Results of our experiments and simulations hint at further directions of research of non-linear dynamics in this reaction.

Adsorptive removal of phenol from binary aqueous solution with aniline and 4-nitrophenol by granular activated carbon

This paper reports the studies on the simultaneous adsorptive removal of phenol and aniline, and phenol and nitrophenol from aqueous solutions using granular activated carbon (GAC). The effect of operating parameters such as initial component concentrations, temperature, adsorbent dosage and contact time on the adsorption of mixtures of solutes in the binary aqueous solution were studied. Taguchi's method of design of experiments was used to study the effect of each parameter at three levels on the total amount of solutes adsorbed on GAC ( q tot, mmol/g). The analysis of variance shows that the contribution of interactions between initial concentrations of binary components is significant. Confirmation experiments were carried out to check the effectiveness of the Taguchi's methodology at the optimum levels of process parameters. The q tot value at optimum condition for P–AN and P–NP systems were found to be 0.85 and 0.88 mmol/g, respectively.

10.1007/s11494-008-2005-5

The effect of a decrease in the inhibiting action of antioxidants (InH) was found in the model oxidation reaction of methyl oleate in the presence of phospholipids (egg phosphatidylcholine and dipalmitoylphosphatidylcholine), which increased with growing the oxidation extent of the substrate and initial concentrations of components of the mixture. It was shown that the decrease in the inhibition efficiency is due to the interaction of InH with the nitrogen-containing moiety of phospholipids, as demonstrated by spectrophotometric data and by similarity in the features of retardation of ethylbenzene oxidation by InH mixtures with phospholipids and N,N,N′,N′-tetramethylethylenediamine.

The effect of precipitation of the complexes of streptavidin with biotinylated proteins in agar gel

The effect of precipitation of complexes of streptavidin with biotinylated proteins under conditions of simple (according to Mancini) and double (according to Ouchterlony) radial diffusion in agar gel was studied. The position and form of precipitation lines depended primarily on the initial concentration of components and the degree of protein biotinylation. Free biotin, 1% SDS, and 6 M urea contained in the gel, as well as thermal denaturation of streptavidin inhibited the precipitate formation. Mannose, glucose, fucose, galactose, sucrose, and NaCl at high concentrations had no effect on biospecific precipitation. A model of interaction of streptavidin with biotinylated macromolecules is suggested, which accounts for the observed effect, and the prospects of practical application of the precipitation effect are discussed.

Role of the nitrogen-containing moiety of phosphatidylcholines in the mechanism of inhibiting action of their mixtures with natural and synthetic antioxidants

The effect of a decrease in the inhibiting action of antioxidants (InH) was found in the model oxidation reaction of methyl oleate in the presence of phospholipids (egg phosphatidylcholine and dipalmitoylphosphatidylcholine), which increased with growing the oxidation extent of the substrate and initial concentrations of components of the mixture. It was shown that the decrease in the inhibition efficiency is due to the interaction of InH with the nitrogen-containing moiety of phospholipids, as demonstrated by spectrophotometric data and by similarity in the features of retardation of ethylbenzene oxidation by InH mixtures with phospholipids and N,N,N′,N′-tetramethylethylenediamine.

Morphological evolution and characterization of hydrothermal synthesized Na 2CuP 2O 7 crystals

Na 2CuP 2O 7 crystals were synthesized by hydrothermal technique at moderate pressure–temperature conditions. The maximum degree of crystallinity is observed at critical concentration of initial components, beyond which the crystallinity collapses sharply to minimum. Solubility studies have revealed, positive thermal coefficient of solubility in a H 3PO 4 solvent with relatively high enthalpy. Thermal behaviour and structural coordination of the prepared materials were investigated, respectively, using DTA/TGA and FTIR measurements. Magnetic results have revealed; it is a frequency and temperature dependent prospective paramagnetic material.

Hydrothermal synthesis, morphological evolution and characterization of Na 2CoP 2O 7 crystals

Na 2CoP 2O 7 crystals are synthesized by hydrothermal technique at moderate pressure–temperature conditions. The maximum degree of crystallinity is observed at the critical concentration of initial components, beyond which the crystallinity collapses sharply to a minimum. Solubility studies have revealed positive thermal coefficient of solubility in a H 3PO 4 solvent with relatively high enthalpy. DTA results revealed this compound to undergo a phase transition at 380 °C.

Computation and analysis of time-dependent sensitivities in Generalized Mass Action systems

Understanding biochemical system dynamics is becoming increasingly important for insights into the functioning of organisms and for biotechnological manipulations, and additional techniques and methods are needed to facilitate investigations of dynamical properties of systems. Extensions to the method of Ingalls and Sauro, addressing time-dependent sensitivity analysis, provide a new tool for executing such investigations. We present here the results of sample analyses using time-dependent sensitivities for three model systems taken from the literature, namely an anaerobic fermentation pathway in yeast, a negative feedback oscillator modeling cell-cycle phenomena, and the Mitogen Activated Protein (MAP) kinase cascade. The power of time-dependent sensitivities is particularly evident in the case of the MAPK cascade. In this example it is possible to identify the emergence of a concentration of MAPKK that provides the best response with respect to rapid and efficient activation of the cascade, while over- and under-expression of MAPKK relative to this concentration have qualitatively different effects on the transient response of the cascade. Also of interest is the quite general observation that phase-plane representations of sensitivities in oscillating systems provide insights into the manner with which perturbations in the envelope of the oscillation result from small changes in initial concentrations of components of the oscillator. In addition to these applied analyses, we present an algorithm for the efficient computation of time-dependent sensitivities for Generalized Mass Action (GMA) systems, the most general of the canonical system representations of Biochemical Systems Theory (BST). The algorithm is shown to be comparable to, or better than, other methods of solution, as exemplified with three biochemical systems taken from the literature.

Investigation of Belousov–Zhabotinsky reaction kinetics using thermal lens spectrometry

Thermal lensing is proposed for monitoring unstirred Belousov–Zhabotinsky reaction with a mixture of free Fe(II) and its chelate with 1,10-phenanthroline as a catalyst and a photometric indicator of the reaction process. The optimum initial concentrations of components for stable oscillations in system are found. The sensitivity and reproducibility of thermal lensing was compared to spectrophotometry and potentiometry by the model determination of bromide ions by its inhibition effect on the reaction kinetics.

Processes controlling the episodic streamwater transport of atrazine and other agrichemicals in an agricultural watershed

Episodic streamwater transport of atrazine (a common agricultural herbicide) and nutrients has been observed throughout agricultural watersheds in the United States and poses a serious threat to the quality of its water resources. Catchment-scale atrazine and nutrient transport processes after agricultural application are still poorly understood, and predicting episodic streamwater composition remains an elusive goal. We instrumented a 1.2-km 2 agricultural catchment near Harrisonburg, Virginia, and examined streamwater, overland flow, soil water, groundwater, and rainfall during the summer of 1998. Storm chemographs demonstrated different patterns for constituents derived primarily from weathering (silica and calcium), compared to constituents derived primarily from early spring land applications (nitrate, atrazine, DOC, potassium, chloride, and sulfate). During storms, the concentrations of silica and calcium decreased, the atrazine response was variable, and the concentrations of nitrate, DOC, potassium, chloride, and sulfate increased; the elevated nitrate signal lagged several hours behind the other elevated constituents. Graphical and statistical analyses indicated a relatively stable spring-fed baseflow was modified by a mixture of overland flow and soil water. A rapid, short-duration overland-flow pulse dominated the streamflow early in the event and contributed most of the potassium, DOC, chloride, suspended sediment, and atrazine. A longer-duration soil–water pulse dominated the streamflow later in the event and contributed the nitrate as well as additional potassium, DOC, sulfate, and atrazine. The contributions to the episodic streamflow were quantified using a flushing model in which overland-flow and soil–water concentrations decreased exponentially with time during an episode. Flushing time constants for the overland-flow and soil–water reservoirs were calculated on a storm-by-storm basis using separate tracers for each time-variable reservoir. Initial component concentrations were estimated through regression analyses. Mass-balance calculations were used for flow separations and to predict the observed streamwater composition. Model forecasts indicated that reduced fertilizer and pesticide application (rather than elimination of overland-flow or soil–water contributions) was necessary to improve the episodic streamwater composition. This study provides important additional understanding of the catchment-scale processes by which land-applied pesticides and nutrients can move through agricultural systems.

Hydrodynamic instability in a three-component electrochemical system

The Raleigh-Benard thermodynamic instability in electrochemical systems containing three types of univalent ionic components is considered for the case of a galvanostatic electrolysis. Dimensionless parameters characterizing the stability threshold and their critical values are found. Influence of an indifferent-electrolyte type and its concentration on the system stability is analyzed. A procedure is suggested for calculating the critical current from the dimensionless parameters at fixed physical characteristics of the system and initial concentrations of components

An Evolutionary Algorithm for Initial State and Parameter Estimation in Complex Biochemical Models

An evolutionary strategy has been used for the estimation of parameters in a complex biochemical model. The basic characteristics of the strategy are demonstrated with a simple example which is a parameter estimation for a Haldane inhibition kinetic model. The strategy is then applied to a complex activated sludge model describing the removal of organic compounds, nitrogen and phosphorus from wastewater. 49 parameters and 19 initial component concentrations were simultaneously estimated. The method is easy to implement and robust against numerical difficulties.

PLS “self-calibration” method for the evaluation of rate constants and/or initial concentrations in multicomponent kinetic analysis

An algorithm is presented where the Partial Least Squares (PLS) regression estimation calibration method is used to calculate initial concentrations or rate constant parameters. The calibration matrix is obtained by a “selfmodeling” process calculating theoretical curves, while following two, three or more levelfactorial design. The new calibration objects are included in the calibration matrix or replacing the old ones and the calibration space is eventually reduced until satisfactory results are obtained. Prediction of the kinetic parameters as good as that achievable by the traditional minimizing routines can be obtained. The properties, behavior, advantages and problems of the proposed PLS “self-calibration” method are discussed. It has been shown that it is possible to determine analytes in mixtures quite rapidly and precisely without prior knowledge of the initial concentrations of components.

Autooscillation and autowave processes in belousov-zhabotinskii reactions involving ?-ketoglutaric acid and iron(II, III) complexes

Concentration regions for the existence of temporal autooscillations and spacetime structures are determined, as well as dependences of the autooscillation parameters on initial concentrations of components for the reactions of sodium bromate, α-ketoglutaric acid, and the complex of iron(II) with o-phenanthroline and of sodium bromate, α-ketoglutaric acid, and the complex of iron(II) with 2,2′-bipyridyl. The experimental results allow the conclusion that the relationships of the parameters of these systems to concentration are similar and that their mechanisms are probably similar. An advantage of these systems is the practically complete absence of gas formation and of the inhibiting effect of oxygen.