Acid–base equilibria of the aqua adducts of Ru(II) arene complexes with functionalised pyridines

Acid?Cbase equilibria of the aqua adducts of Ru(II) arene complexes, general formulae [(??⁶-p-cymene)Ru (L^1?3)Cl₂] where L¹?=?3-acetylpyridine (1), L²?=?4-acetylpyridine (2) and L³?=?2-amino-5-chloropyridine (3), then [(??⁶-p-cymene)Ru(HL⁴)Cl₂] with HL⁴?=?isonicotinic acid (4); [(??⁶-p-cymene)Ru(HL^5?8)Cl] where H₂L⁵?=?2,3-pyridine dicarboxylic acid (5), H₂L⁶?=?2,4-pyridine dicarboxylic acid (6), H₂L⁷?=?2,5-pyridine dicarboxylic acid (7) and H₂L⁸?=?2,6-pyridine dicarboxylic acid (8) have been studied. pK _a values were determined by potentiometry at 25?°C and constant ionic strength of 0.1?M NaNO₃. The assumed equilibria were confirmed by UV and ¹H-NMR spectroscopy.     

Co-continuous morphology on spin coating produced thin TiO2 films

Biological research has shown good cell response to dense TiO₂ films. Good surface chemistry of the implant can be further improved by introducing optimal topology, which in the case of osseointegration means porosity features in the nm and ??m range. TiO₂ films are produced by spin coating and the obtained morphologies are characterized qualitatively and quantitatively from the scanning electron microscope images of the surface and in focused ion beam cross-sections. Infrared spectroscopy, thermogravimetry/differential thermal analysis, and X-ray diffraction were used to characterize chemical changes and crystallization processes in the bulk gels and thin films. Mechanical properties of the films are characterized using Nano Scratch Test. Results show that the increase in acetyl acetone (ACAC) concentration from 1?mol ACAC:1?mol Ti(IV) n-butoxide used for dense films to 1.5:1 and simultaneous polyethylene glycol (PEG) presence led to a change in morphology from a dense to highly porous, co-continuous morphology. This is a result of pronounced phase separation with respect to gelation due to (1) the presence of uncomplexed ACAC, which is highly dissimilar, in a sense of polarity, to the other components of the sol and (2) the additional reaction between PEG and TiO₂ oligomers. This porous morphology is found to be very sensitive to production parameters such as viscosity, spinning velocity and the amount of PEG added to the sol. It was also detected that, in addition to the phase separation, PEG also influences the crystallization process of the film.     

Ice photolysis of 2,2′,4,4′,6-pentabromodiphenyl ether (BDE-100): Laboratory investigations using solid phase microextraction

Here, we report for the first time a laboratory investigation into the photochemical degradation of 2,2′,4,4′,6-pentabromodiphenyl ether (BDE-100) in ice solid samples using an artificial UV light source. Solid phase microextraction (SPME) was used as a sensitive extraction technique for monitoring trace amounts of the hydrophobic pollutant and its photoproducts. The results showed that ice photolysis kinetics for BDE-100 is similar to the one observed in the aqueous counterpart. The eight photoproducts identified consisted of brominated diphenyl ethers with lower bromine content and polybrominated dibenzofurans, suggesting two important photodegradation pathways for BDE-100 in ice solid samples: (i) stepwise reductive debromination and (ii) intramolecular elimination of HBr. Similarities in photochemical product arrays observed in the ice and water photolysis of BDE-100 were attributed to a similar mechanism for photochemical decomposition for both phases. Possible involvement of the water molecules in the reactions has been excluded by performing photolysis in D₂O ice solid and water samples. Taking advantage of the high preconcentration factor obtained with SPME at low temperatures, a SPME fiber cooled with liquid carbon dioxide down to 0 °C was used as a photoreaction support for BDE-100 allowing the identification of a greater number of photoproducts.     

Calibrating continuous multi-objective heuristics using mixture experiments

A genetic algorithm heuristic that uses multiple rank indicators taken from a number of well established evolutionary algorithms including NSGA-II, IBEA and SPEA2 is developed. It is named Multi-Indicator GA (MIGA). At every iteration, MIGA uses one among the available indicators to select the individuals which will participate as parents in the next iteration. MIGA chooses the indicators according to predefined probabilities found through the analysis of mixture experiments. Mixture experiments are a particular type of experimental design suitable for the calibration of parameters that represent probabilities. Their main output is an explanatory model of algorithm performance as a function of its parameters. By finding the point that provides the maximum we also find good algorithm parameters. To the best of our knowledge, this is the first paper where mixture experiments are used for heuristic tuning. The design of mixture experiments approach allowed the authors to identify and exploit synergy between the different rank indicators. This is demonstrated by our experimental results in which the tuned MIGA compares favorably to other well established algorithms, an uncalibrated multi-indicator algorithm, and a multi-indicator algorithm calibrated using a more conventional approach.     

Spatial arrangement of the structural elements ofvocal fold layers: An adjustment to the vibration process

It is well established that the multilayered structure of the vocal fold is highly adjusted to the requirements of the vibration process during phonation. There is also some partial data indicating that the spatial arrangement of each vocal fold layer corresponds to the functional requirements, and thus facilitate the phonation process. Nevertheless, all reports on the spatial arrangement of the vocal fold structures deal only with an individual element of the vocal fold histologic structure. The present study encompasses the spatial histologic analysis of all major elements of the vocal fold layers. It was demonstrated that the vocal fold epithelial cells, the connective and muscle fibers, and even the blood vessels run parallel to the vocal fold free edge, which indicates a high adjustment to the phonation requirements and the vibration process.     

Generalized group actions in a global setting

We study generalized group actions on differentiable manifolds in the Colombeau framework, extending previous work on flows of generalized vector fields and symmetry group analysis of generalized solutions. As an application, we analyze group invariant generalized functions in this setting.     

Natural convection in shallow water

Starting from the 3D Boussinesq model and taking the limit as the domain thickness tends to zero, we derive rigorously the 2D model for natural convection in shallow water. The model reduces to a degenerated elliptic equation for the pressure, an explicit formula for horizontal components of the velocity and a vertical diffusion for the vertical component. The macroscopic flow is driven by temperature variations as well as the bottom topography.     

Mostar index

We propose and investigate a new bond-additive structural invariant as a measure of peripherality in graphs. We first determine its extremal values and characterize extremal trees and unicyclic graphs. Then we show how it can be efficiently computed for large classes of chemically interesting graphs using a variant of the cut method introduced by Klav?ar, Gutman and Mohar. Explicit formulas are presented for several classes of benzenoid graphs and Cartesian products. At the end we state several conjectures and list some open problems.     

Differences in coating mechanism of structurally different aluminosilicates observed through the thermal analysis

Systematic modification of three structurally different minerals (zeolite, mica, and vermiculite) was carried out with the aim of determining the modification mechanism and exposing the hydrophobic surface that can be used as a sorbent for many organic compounds. Mechanism of modification with cationic surfactant depends strongly on the mineral type. In order to identify the influence of aluminosilicates structural differences on the modification process, adsorption experiments with organic matter and water vapor, supplemented with the DTA/TG analysis, were performed. The cation exchange capacity (CEC) value was 1454?>?560?>?28 meq kg^?1 for zeolite (clinoptilolite), vermiculite, and mica (muscovite), respectively. Despite its CEC value, vermiculite adsorbed three times the amount of organic matter than did clinoptilolite due to the porous structure of zeolite, which acted to limit the adsorption only on the external exchangeable cations. If the loading amount is equal to the CEC or the external cation exchange capacity for clinoptilolite (ECEC?≈?10% CEC), the monolayer will form while mineral surface will have hydrophobic character. Only one active center exists at the surface of the clinoptilolite that was identified by DTA curves with a sharp and defined peak around 300 °C and by the mass loss at the TG diagrams. Two significant and equal active centers were observed in vermiculite, one for the exchange of the surface cations and the other for the interlayer cations and H₂O molecules. Muscovite CEC is negligible, and due to the absence of any other functional groups, the modification of this mineral was impossible.