KMnO4 chemical kinetics in high diluted solvents

Background: A number of theoretical and experimental approaches have been signalizing towards a induction of some solvent structural order or dynamical behavior, whenever a High Dilution (HD) is prepared. These works have been performed using different spectroscopic techniques, calorimetric studies, electrical and optical measurements, among others, which results are interpreted under many different approaches. The understanding of the physicochemical nature of HDs is still far from to be clarified, despite the evidences on their biological activity. Assuming that physicochemical changes induced by shaking and dilution (potentization) are true, one could expect that the changed solvent could interfere in the chemical kinetics of a complex reaction. The reduction of Mn7+ to Mn2+ (color change) observed when KMnO4 in transferred into an acidic solvent is a self-catalyzed reaction dependent on pH, temperature and concentration with many reaction pathways, but converging usually to the colorless Mn2+ state (the Mn2+ produced in the Mn7+ reduction is the reaction catalyzer). Method: We have performed this reaction using oxalic and sulphuric acid as solvent, observing the time dependence of the absorbance at λ = 525 nm. Some solvent variants were proofed: G0: normal solvent; G1: potentized solvent at 12x; G2: Mn2+ potentized in normal solvent until 12x. If the potentization itself could change the solvent, we would expect differences in G1 compared to G0. If some Mn2+ information were imprinted into the solvent due the potentization we would expect differences in G2 to G1 and G0. It was recorded 10 spectra for each solvent variant and the experiment was performed twice (different weeks), with different fresh starting solutions (KMnO4, acid solvent and variants). Averaged values and standart deviations were compared. Results: The only difference observed were a randomic time delay (few seconds) to start the decrease in the absorbance at λ = 525 nm. This delay was associated to the natural diffusion of KMnO4 in the solvent and the time left to insert the cuvette into the spectrometer as well to turn the measurements on. After delay correction, all curves showed similar behavior (unsignificant differences), that its typical decrease. Conclusion: If potentization is able to induce changes in the solvent, these were not able to affect the chemical kinetics of the KMnO4 in acidic medium. One could hypothetize this model is not responsive to those putative changes either by the unspecificity of a chemical solution (no similitude is achieved) or by the lack of a biological sensor able to interpret such changes. Another conclusion would be that no changes are induced on the solvent due potentization.

The Solution Behavior of Dopamine in the Presence of Mono and Divalent Cations: A Thermodynamic Investigation in Different Experimental Conditions

The interactions of dopamine [2-(3,4-Dihydroxyphenyl)ethylamine, (Dop-)] with methylmercury(II) (CH3Hg+), magnesium(II), calcium(II), and tin(II) were studied in NaCl(aq) at different ionic strengths and temperatures. Different speciation models were obtained, mainly characterized by mononuclear species. Only for Sn2+ we observed the formation of binuclear complexes (M2L2 and M2LOH (charge omitted for simplicity); M = Sn2+, L = Dop−). For CH3Hg+, the speciation model reported the ternary MLCl (M = CH3Hg+) complex. The dependence on the ionic strength of complex formation constants was modeled by using both an extended Debye–Hückel equation that included the Van’t Hoff term for the calculation of enthalpy change values of the formation and the Specific Ion Interaction Theory (SIT). The results highlighted that, in general, the entropy is the driving force of the process. The sequestering ability of dopamine towards the investigated cations was evaluated using the calculation of pL0.5 parameter. The sequestering ability trend resulted to be: Sn2+ > CH3Hg+ > Ca2+ > Mg2+. For example, at I = 0.15 mol dm−3, T = 298.15 K and pH = 7.4, pL0.5 = 3.46, 2.63, 1.15, and 2.27 for Sn2+, CH3Hg+, Ca2+ and Mg2+ (pH = 9.5 for Mg2+), respectively. For the Ca2+/Dop- system, the precipitates collected at the end of the potentiometric titrations were analyzed by thermogravimetry (TGA). The thermogravimetric calculations highlighted the formation of solid with stoichiometry dependent on the different metal:ligand ratios and concentrations of the starting solutions.

Biocompatible Sulphonated PEEK Spheres: Influence of Processing Conditions on Morphology and Swelling Behavior

This work aimed to develop and evaluate the influence of processing variables on the morphology and swelling of sulfonated poly(ether ether ketone) (SPEEK) spheres for possible applications as a biomaterial. We used the drip method to obtain spheres with the polymer starting solutions SPEEK-6 (w/v: 6%) and SPEEK-10 (w/v: 10%), drip rates (20 and 30 mL/h), and drip heights (5 and 10 cm) in experimental planning. The samples were characterized by Fourier-transform infrared spectroscopy (FTIR), optical microscopy (OM), the absorption capacity of phosphate-buffered saline (PBS) by swelling (%), and statistical analysis of data through Design of Experiments (DOE). The obtained results evidenced that the processing variables influenced the morphology and swelling. Spheres with a bigger concentration of the polymer solution presented a greater degree of sulfonation (DS). We verified that the diameter of the spheres was directly related to the variable height and the sphericity was associated with the speed and viscosity of the solution. Bigger and more pores in a greater amount were observed in the spheres with a greater DS, influencing the behavior of the swelling in PBS. The better variable combinations with a high DS, regular sphericity, a smaller diameter, and greater swelling were the samples S2-10-20-5 e S10-10-20-5. The cytotoxicity indicated that the best samples obtained in the experimental planning (S2-10-20-5 and S10-10-20-5) were not toxic. In that regard, the evaluated spheres presented cell viability and swelling capacity, suggesting their possible applications as biomaterials.

"Permanent solutions for some motions of UCM fluids with power-law dependence of viscosity on the pressure"

Steady motion of two types of incompressible Maxwell fluids with power-law dependence of viscosity on the pressure is analytically studied between infinite horizontal parallel plates when the gravity effects are taken into consideration. Simple and exact expressions are established for the permanent components of starting solutions corresponding to two oscillatory motions induced by the lower plate that oscillates in its plane. Such solutions are very important for the experimentalists who want to eliminate the transients from their experiments. The similar solutions for the simple Couette flow of the same fluids, as well as the permanent solutions corresponding to ordinary incompressible Maxwell fluids performing the same motions, are obtained as limiting cases of general solutions. The convergence of starting solutions to their permanent components as well as the influence of physical parameters on the fluid motion is graphically underlined and discussed.

Mathematical Analysis of Maxwell Fluid Flow through a Porous Plate Channel Induced by a Constantly Accelerating or Oscillating Wall

Exact expressions for dimensionless velocity and shear stress fields corresponding to two unsteady motions of incompressible upper-convected Maxwell (UCM) fluids through a plate channel are analytically established. The porous effects are taken into consideration. The fluid motion is generated by one of the plates which is moving in its plane and the obtained solutions satisfy all imposed initial and boundary conditions. The starting solutions corresponding to the oscillatory motion are presented as sum of their steady-state and transient components. They can be useful for those who want to eliminate the transients from their experiments. For a check of the obtained results, their steady-state components are presented in different forms whose equivalence is graphically illustrated. Analytical solutions for the incompressible Newtonian fluids performing the same motions are recovered as limiting cases of the presented results. The influence of physical parameters on the fluid motion is graphically shown and discussed. It is found that the Maxwell fluids flow slower as compared to Newtonian fluids. The required time to reach the steady-state is also presented. It is found that the presence of porous medium delays the appearance of the steady-state.

Sustainability nudges in the context of customer co-design for consumer electronics

In this study, we shed light on the unexplored potential of customer co-design in a mass customization (MC) setting to contribute to the promotion of sustainable consumption. We theoretically derive and empirically test several opportunities for companies to improve sustainable consumption and production in a joint effort with consumers. Our research bridges between the MC and the sustainability literature and shows that MC enables consumers to cohere attitude and action, based on individual sustainability preferences. We empirically assess whether MC companies can nudge their customers successfully towards more sustainable choices by designing sustainability-based starting solutions (Study 1) and by providing transparent sustainability information (Study 2) in MC configuration systems. We do so by portraying a simulated online buying process of a customizable TV with a realistic web-based product configurator. We find that sustainable defaults can play a significant role in promoting sustainable consumption, while providing detailed sustainability information does not show an effect. To get more insights into our results, we discuss the results on a supplementary qualitative analysis based on think-aloud consumer tests (Study 3), revealing several suggestions for further research. Using these findings, we revisit sustainability information in Study 4 and find that intuitive labels significantly influence consumers to choose more sustainably.