Effects Of Changes In Concentration Research Articles

Spectral and luminescence properties of Sm3+ doped sodium lead alumino borosilicate glasses

Sm3+-doped sodium lead alumino borosilicate glasses with the composition 20Na2O-10PbO-(5-x)Al2O3-40B2O3-25SiO2:xSm2O3 have been prepared by the melt-quenching technique and are characterized through various physical parameters. Optical absorption spectrum from the near infrared to visible region is taken and the Judd-Ofelt analysis is carried out in order to determine Ωλ (λ = 2, 4, 6) parameters. Transition probabilities, branching ratios and radiative lifetime of 4G5/2 level of Sm3+ ions in the present glass under investigation have been predicted using different parameters. Photoluminescence spectra are used to analyze the luminescence behavior of the prepared glasses. Effect of change in concentration of Sm3+ ions on the luminescence properties is investigated. Branching ratios, stimulated emission cross-section are estimated from the luminescence spectra. CIE chromaticity coordinates are calculated to evaluate the glass performance on color luminescence. The results are analyzed for potential application of the title glass as a new laser material.

Parametric, equilibrium and kinetic studies on the removal of mercury using ion exchange resin

This experimental research was an investigation into removal of mercury by using a strong acid cation resin, 001 × 7. Parametric experiments were conducted to determine the optimum pH, resin dosage, agitation speed and the effect of change in concentration in the range of 50–200 mg/L. High resin dosages favoured better removal efficiency but resulted in lower uptakes. Equilibrium experiments were performed and fitted to Langmuir and Freundlich isotherm models. Langmuir model suited well to this study confirming the homogeneity of the resin surface. The Langmuir constants were estimated as qmax = 110.619 mg/g and KL = 0.070 L/g at 308 K. Kinetic experiments were modeled using Pseudo second order model and higher values of R2 (>0.97) were obtained. The Pseudo second order kinetic constants, namely, equilibrium uptake (qe) and rate constant (k2), were evaluated as 59.17 mg/g and 40.2 × 10−4 g mg−1 min−1 at an initial mercury concentration of 100 mg/L and temperature of 308 K.

Exploration of the Effect of Chitosan and Crosslinking Agent Concentration on the Properties of Dual Responsive Chitosan-g-Poly (N-Isopropylacrylamide) Co-polymeric Particles

The objective of the present study was to synthesize and evaluate the effect of change in concentration of chitosan (CS) and N,N-methylenebisacrylamide (MBA)- a cross linking agent, on various properties such as lower critical solution temperature (LCST), zeta potential, particle size and poly dispersity index (PDI) of the synthesized co-polymer. Nine different formulations of chitosan-g-poly (N-isopropylacrylamide) (CS-g-PNIPAAm) co-polymer with varying CS and MBA concentrations were synthesized by a surfactant free dispersion copolymerization method. The synthesized co-polymer was further characterized and confirmed for its structure, morphology, particle size, zeta-potential, thermo and pH responsive properties, in-vitro cyto-compatability and stability studies using various analytical tools. The data confirms the successful synthesis of co-polymer. The increase in the concentrations of CS and MBA during the polymerization of co-polymer, resulted in proportional increase of LCST and zeta potential with decrease in particle size of co-polymeric nanoparticles. pH responsive studies showed that as the pH of the medium increases particle size and zeta potential decreases with increase in LCST of co-polymeric nanoparticles. From the results, it can be inferred that the synthesized co-polymeric nanoparticles exerted thermo and pH responsive properties with biocompatibility. By varying the CS and MBA concentrations in the co-polymer, desired LCST, particle size and zeta potential for co-polymeric nanoparticles can be obtained and thus the synthesized co-polymer may have great potential to be used as a drug carrier (nanoform) with both thermo and pH responsiveness.

Change in nutrient loading pattern due to coupled effect of change in concentration and hydroclimatic forces

ABSTRACTIncrease in nutrient loading into large riverine systems is of interest because of long-lasting negative effects on downstream water bodies. We know little of this phenomenon with respect to long-term relationships between water quality metrics and trends in river flow. Here we present a multi-decadal (1937–2014) examination of nutrient transport patterns of the South Saskatchewan and Red Deer Rivers, Canada. Using a multi-method approach, we show a slightly increasing trend in annual volume of water reaching a mid-watershed reservoir (Lake Diefenbaker) concomitant with a change in seasonal variability of flow events from the 1970s. Both total nitrogen (TN) and total phosphorus (TP) flux increased during the period of record. TN concentration increased, while TP concentration decreased. On average, the high-flow season transported 95% of annual TP flux, 75% of annual TN flux, and 65% of annual flow. Inter-annually, high-flow season contributions decreased with respect to water volume, but increased with respect to both TN and TP flux. We believe that changes in variability but also timing of hydroclimatic forces are responsible for observed patterns. Higher flows and more precipitation during the high-flow season are most likely responsible for increasing nutrient load regardless of overall decreases in nutrient concentration.

Effects of change in concentration of lead on the properties of Bi-2223 superconductor prepared through solid state reaction.

In this work, superconducting pellets without lead (Pb) as well as with different concentrations of lead are prepared by solid state reaction. The prepared samples are then characterized using X-ray powder diffraction (XRD), scanning electron microscope (SEM), and energy-dispersive X-ray spectroscopy (EDX). The superconducting properties are examined using electrical resistivity and transport critical current density J c . Our results show that the sample prepared with calcination of 48 hours with intermediate grinding has the ideal value of the superconducting transition temperature T c and transport critical current density J c .

Partial Molar Volumes of 15-Crown-5 Ether in Mixtures of N,N-Dimethylformamide with Water

The density of 15-crown-5 ether (15C5) solutions in the mixtures of N,N-dimethylformamide (DMF) and water (H2O) was measured within the temperature range 293.15–308.15 K using an Anton Paar oscillatory U-tube densimeter. The results were used to calculate the apparent molar volumes (V Φ) of 15C5 in the mixtures of DMF + H2O over the whole concentration range. Using the apparent molar volumes and Redlich and Mayer equation, the standard partial molar volumes of 15-crown-5 were calculated at infinite dilution ( V_{text{m}}^{^circ } ). The limiting apparent molar expansibilities (α) were also calculated. The data are discussed from the point of view of the effect of concentration changes on interactions in solution.

Physicochemical and Rheological Behavior of African Star Apple Chrysophyllum Albidium) Juice as Affected by Concentration and Temperature Variation

The viscosity, shear stress and shear rate of African star apple juice (Chrysophyllum albidium) at different concentrations of 8 % to 32% total solid concentration and temperature range of 20°C to 70°C were obtained in order to determine the effect of changes in concentration and temperature on the rheological properties of the juice. Also, the physico-chemical analyses of the sample were carried out. Plot of shear stress against shear rate showed that at all concentrations, African star apple juice behaved as a non-Newtonian fluid at temperature below 60°C. At 70°C, however, lower concentration (8% and 12%) behaves non-Newtonian while higher concentrations behave Newtonian. Increase temperature decreases the viscosity of the juice. The knowledge of rheological properties of African star apple juice is essential for the design and optimization of energy process and heat transfer.

Fatty acids in the de novo lipogenesis pathway and risk of coronary heart disease: the Cardiovascular Health Study

De novo lipogenesis (DNL) is an endogenous pathway whereby carbohydrates and proteins are converted to fatty acids. DNL could affect coronary heart disease (CHD) or sudden cardiac arrest (SCA) via generation of specific fatty acids. Whether these fatty acids are prospectively associated with SCA or other CHD events is unknown. The objective was to investigate the relations of 4 fatty acids in the DNL pathway-palmitic acid (16:0), palmitoleic acid (16:1n-7), 7-hexadecenoic acid (16:1n-9), and cis-vaccenic acid (18:1n-7)-with incident CHD, including fatal CHD, nonfatal myocardial infarction (NFMI), and SCA. A community-based prospective study was conducted in 2890 men and women aged ≥65 y, who were free of known CHD at baseline and who were followed from 1992 to 2006. Cardiovascular disease risk factors and plasma phospholipid fatty acids were measured at baseline by using standardized methods. Incident CHD was ascertained prospectively and was centrally adjudicated by using medical records. Risk was assessed by using multivariable-adjusted Cox proportional hazards. During 29,835 person-years of follow-up, 631 CHD and 71 SCA events occurred. Both 18:1n-7 and 16:1n-9 were associated with a higher risk of SCA [multivariable-adjusted hazard ratio (95% CI) for the interquintile range: 7.63 (2.58, 22.6) for 18:1n-7 and 2.30 (1.16, 4.55) for 16:1n-9] but not of total CHD, fatal CHD, or NFMI. In secondary analyses censored to mid-follow-up (7 y) to minimize the effects of changes in concentrations over time, 16:1n-9 was also associated with a significantly higher risk of total CHD (2.11; 1.76, 2.54), including a higher risk of CHD death, NFMI, and SCA; 16:0 and 16:1n-7 were not associated with clinical CHD outcomes. Higher plasma phospholipid 18:1n-7 and 16:1n-9 concentrations were prospectively associated with an elevated risk of SCA but not of other CHD events, except in secondary analyses.

Statistical Optimization of Anaerobic Biological Processes for Dye Treatment

In the present study both the synthetic media composition as well as some process parameters in the anaerobic decolorization of Reactive Black 5 (RB5) by activated sludge were studied and optimized using statistical design of experiments (DOEs). Statistical analysis of the results of Plackett–Burman DOE showed that the addition of Mn or Fe, or increase in concentration of Mg, had a positive effect on the anaerobic decolorization efficiency whereas the effect of increase in concentration of glucose, ammonium chloride, and calcium chloride was negative. The effect of change in the concentration of glucose, mixed liquor suspended solid (MLSS), and RB5 on the anaerobic decolorization efficiency and rate and chemical oxygen demand (COD) removal was studied using central composite design methodology. Statistical analysis of the data showed that all the factors had significant effect on both the dye decolorization efficiency and rate. The interaction of glucose with MLSS and with dye and the interaction of MLSS with glucose and with dye were significant when the response was decolorization efficiency and rate, respectively. When COD removal was the response, the effect of change in glucose and MLSS concentration and the interaction between these two factors had statistically significant effect on the response.

Synthesis and characterization of graft copolymers of 2-hydroxyethyl methacrylate and some comonomers onto extracted cellulose for use in separation technologies

To develop low-cost and environmentally friendly polymeric materials for enrichment, separation, and remediation of metal ions from water, graft copolymers based on cellulose extracted from pine needles were synthesized by grafting of 2-hydroxy methacrylate (HEMA) alone and with comonomers acrylic acid, acrylamide, and acrylonitrile by benzoyl peroxide initiation. The effects of change in concentrations of monomer and initiator, reaction time and temperature; and nature and composition of solvent system on graft yield and grafting efficiency were evaluated. At the optimum reaction conditions evaluated for the grafting of HEMA alone, comonomers as acrylamide, acrylic acid, and acrylonitrile at their five different concentrations were also co-grafted along with HEMA onto cellulose backbone polymer. Graft copolymers were further functionalized by partial hydrolysis, and were characterized by water uptake, FTIR, and elemental analysis. Sorption of Fe2+, Cu2+ and Cr6+ ions on graft copolymers were investigated to define their end-uses in separation technologies.

Solar photoassisted advanced oxidation process of azo dyes

Advanced oxidation processes assisted with natural solar radiation in CPC type reactors (parabolic collector compound), was applied for the degradation of three azo dyes: acid orange (AO7), acid red 151 (AR151) and acid blue 113 (AB113). Fenton, Fenton like and ferrioxalate-type complexes showed to be effective for degrade the azo linkage and moieties in different extensions. Initially, the best dose of reagents (Fe(3 + )-H(2)O(2)) was determined through a factorial experimental design, next, using response surface methodologies, the reagent consumption was reduced up to 40%, maintaining in all cases high decolourisation percentages (>98%) after 60 min. of phototreatment. In this work, it was also studied the effect of concentration changes of the influent between 100-300 mg/L and the operation of the photocatalytic process near neutral conditions (pH 6.0-6.5) by using ferrioxalate type complex (FeOx).

Numerical study of IP3-induced Ca2+ spiral pattern evolution

The effect of change in concentration of messenger molecule inositol 1,4,5-trisphosphate (IP3) on intracellular Ca2+ spiral pattern evolution is studied numerically. The results indicate that when the IP3 concentration decreases from 0.27 μM, a physiologically reasonable value, to different values, the spiral centre drifts to the edge of the medium and disappears for a small enough IP3 concentration. The instability of spiral pattern can be understood in terms of excitability-change controlled by the IP3 concentration. On the other hand, when the IP3 concentration increases from 0.27 μM, a homogeneous area with a high Ca2+ concentration emerges and competes with the spiral pattern. A high enough IP3 concentration can lead the homogeneous area to occupy the whole medium. The instability of spiral pattern is ascribed to the change in stability of a stationary state with a high Ca2+ concentration.

Concentration history and market power in US manufacturing industries

For a 1963–1992 panel of US manufacturing industries, the relationship between seller concentration and both price-cost margins (PCMs) and prices is investigated for industries divided by whether concentration has recently increased or decreased. Regressions of PCM in levels and first differences, and price equations in first differences, establish that the positive effect of concentration on prices and profits is always weaker in industries where concentration has recently increased and always stronger in industries where concentration has recently decreased. These results are attributed to the different endogeneity biases in the two samples. Increasing concentration industries are more likely the ones where leading firms have lowered prices to gain share, while decreasing concentration industries are more likely the ones where smaller firms have lowered concentration by lowering prices. An additional conclusion is that the cost-reducing effects of changes in concentration are greater for increasing concentration industries, meaning that increasing concentration industries have lower price increases compared to decreasing concentration industries.

COMPUTATIONAL ANALYSIS FOR INVESTIGATING THE EFFECTS OF O2 AND CO2 CONCENTRATION CHANGES IN THE GAS LAYER ON GASEOUS TRANSFERS IN AN OXYGENATOR

We have been trying to establish a numerical estimation of O2 and CO2 transfers in an oxygenator by our computational fluid dynamics (CFD) method. Our CFD method could calculate distributions of O2 and CO2 concentrations in both blood and gas layers simultaneously using nonlinear relational expressions of O2 and CO2 reactions with blood and equations of membrane permeations. This method enables to deal also CO2 transfer, which was unsuitable to be assumed as constant in the gas layer because of low difference of concentration. In this study, we analyzed distributions of O2 and CO2 concentrations with a staggered arranged hollow fibers (225 μm outer diameter) model. The hollow fibers model was a part of the blood inlet side and the gas inlet side of a referred oxygenator, which had a rectangular bundle consisting of parallel hollow fibers and had a right angle of the blood flow and the gas flow. In results of 1 L/min blood and 3 L/min gas flow rate, O2 concentration decreased from 710.0 to 506.1 mmHg, CO2 concentration increased from 1.5 to 45.0 mmHg (achieved equilibrium) in the gas layer at the blood inlet side. At the blood outlet side, O2 concentration decreased from 712.5 to 629.7 mmHg, CO2 concentration increased from 0.2 to 28.8 mmHg in the gas layer. These results suggested that our CFD method could estimate the gaseous transfers into the blood with considerable effects of concentration changes in the gas layer.

Reactions of Hf-Ag and Zr-Ag alloys with Al2O3 at elevated temperatures

We are studying reactions of Ti, V, Zr, and Hf with ceramics as part of a program to understand fundamental reaction and bonding mechanisms in active metal brazing of ceramics. In this paper we present results of experiments with model systems comprising Ag alloys that contain different amounts of Hf or Zr that were reacted with sapphire or 99.6% alumina for different times and temperatures in a controlled atmosphere furnace. In these alloys the Ag functions as an inert solvent, which allowed us systematically to determine the effects of changes in concentration of the active element. We observed qualitative wetting and spreading tendencies of the alloys during heating and examined cross sections after cooling using electron analytical techniques. For all reaction times studied, the Hf/Ag alloys formed a discontinuous reaction layer, which was consistent with earlier high-resolution electron microscopy that showed sub-micrometer HfO2 particles embedded in the surfaces of the Al2O3 grains. By contrast, initial reaction of the Zr/Ag alloys with Al2O3 produced a continuous interface layer. With longer reaction times, the ZrO2 reaction product became much thicker and exhibited three distinct zones at the interface. The results suggest that the rate limiting step in the Zr/Ag reaction is the chemical reaction at the interface, whereas with Hf/Ag reaction diffusion of products away from the interface is rate limiting.

1-6.石炭と各種試薬の相互作用における試薬濃度の影響(Session 1 石炭・重質油)

1-6.石炭と各種試薬の相互作用における試薬濃度の影響(Session 1 石炭・重質油)

The uptake of caesium and strontium radioisotopes onto clays

Montmorillonite and illite clays have been examined for their ability to take up caesium and strontium radioisotopes from solution. Uptakes onto near homoionic Na, K, NH4, Mg, Ca, and Sr clays have been assessed by the construction of ion exchange isotherms. Effects of changes in concentration (total normality) and temperature have been assessed. Where possible, thermodynamic constants have been calculated and selectivity series constructed. It is shown that both clays are suitable for uptake of Cs, but not Sr.

Market concentration and technological innovation in a dynamic model of growth and distribution

This paper develops a post Keynesian macromodel of growth and distribution in which endogenous technological innovation plays a pivotal role. The innovationrate is made quadratic in market concentration, to capture a plausible neo-Schumpeterian non-linear influence of market structure on firms' propensity to innovate. Concentration is endogenous, though, since under neo-Schumpeterian competition the relation between market structure and technical change cuts both ways. Investment will then be non-linear in concentration, and the effect of changes in concentration on capacity utilisation, growth and distribution will depend on the level of concentration. Demand also plays a role, with capacity utilisation and growth rising with the wage share. The dynamic stability properties of the system will depend on the direction and relative strength of the technological innovation effects with respect to the demand ones, and on the relative bargaining power of workers and capitalists. JEL Codes: O41, E25, O32, L10

Effect of Concentration Change on the Viscosity of Antifreeze Solutions.

Working fluids and heat transfer fluids used in energy systems such as refrigerating plants and heat pumps cannot avoid concentration changes due to contamination with lubricating oils, water or other impurities. In the case of aqueous solutions of glycols, which are used as antifreeze heat-transfer media, the change in concentration means a large change in viscosity, since the viscosity of glycol is significantly higher than that of water. In the present study, the dependencies of viscosity on concentration and on temperature were experimentally investigated for aqueous solutions of ethylenglycol and of propyleneglycol. Ubbelohde viscometers were used in the range of concentration from 40 to 100 wt% and of temperature from 253 to 313 K.

1H and 2H NMR Studies of Mixtures 2,6-Lutidine/Water Near the Lower Critical Solution Point

Abstract Deuteron spin-lattice relaxation time (TJ measurements of binary mixtures 2,6-lutidine/D20 have been done near the lower critical solution point (TC, L), ε = (T - TC, L)/TC, L ≧10-5. Singularities are observed at TC, L. The changes in the slope of T1 (2H) = ƒ ( T ) can be interpreted as due to the effect of concentration changes on Ty and simultaneously strong overlaping of 2H NMR signals from coexisting phases. In the two-phase region, ca. 2°C above TC, L two D2O signals with very strong temperature evolution have been detected. Similar doubling of 2,6-lutidine 1H NMR signals has been observed already at T - TC, L ≦ 1 °C. It is shown that the two signals arise from the nuclei in two coexisting phases; they are not due to pecularities of hydrogen bond. The difference between chemical shifts of both D2O signals δ’ - δ” possess the property of an order parameter, i.e. δ’ - δ” ~ εβ with β = 0.336±0.030