Preparation and characterization of poly(vinyl alcohol)‐based magnetic nanocomposites. 1. Thermal and mechanical properties

CoFe₂O₄ magnetic nanoparticles were prepared by in situ precipitation and oxidation of Co²⁺ and Fe²⁺ within a sulfonated polystyrene resin. The nanometric particles were characterized by X‐ray diffraction. A ferrofluid was prepared from the CoFe₂O₄ mineralized polymer resin and water. Poly(vinyl alcohol) (PVA)‐based nanocomposite materials were obtained by mixing different amounts of ferrofluid (compositions ranging within 0–51 wt % of mineralized resin) with an aqueous solution of the polymer. The PVA composite materials were characterized by TGA, DSC, and stress–strain testing. The thermal and mechanical properties of PVA change with filler content, exhibiting an initial increase in these properties due to polymer–filler interactions. After a maximum value, at about 15 wt % of mineralized resin, the mechanical properties decrease probably due to particle aggregation which causes phase separation. The results obtained show that the nanoparticles are dispersed in the amorphous regions of the polymer, the crystalline zones remaining unaltered up to compositions as high as 30 wt %. © 2001 John Wiley & Sons, Inc. J Appl Polym Sci 82: 3215–3222, 2001     

Triggers for chemical product design: A systematic literature review

The product design project is a complex problem because objectives and constraints must be considered simultaneously, the sustainability context is highly relevant and specific, decision-making involves not only customer needs but also of other stakeholders, especially the organization in which the design project takes place. This work presents a systematic literature review of design methodologies for chemical products to identify how that problem has been addressed and which are the future challenges to be met. The review involved the analysis of 262 research papers and 336 patents, classified according to the chemical product type, the design phase studied, and whether they consider association with a business context. The study highlights the need for holistic product design methodologies applicable from the early design stages, covering the assessment of customer needs and the requirements of other stakeholders, as well as the business context where the design process is carried out.     

Endothelial Dysfunction: An Intermediate Clinical Feature between Urolithiasis and Cardiovascular Diseases

An epidemiological relationship between urolithiasis and cardiovascular diseases has extensively been reported. Endothelial dysfunction is an early pathogenic event in cardiovascular diseases and has been associated with oxidative stress and low chronic inflammation in hypertension, coronary heart disease, stroke or the vascular complications of diabetes and obesity. The aim of this study is to summarize the current knowledge about the pathogenic mechanisms of urolithiasis in relation to the development of endothelial dysfunction and cardiovascular morbidities. Methods: A non-systematic review has been performed mixing the terms “urolithiasis”, “kidney stone” or “nephrolithiasis” with “cardiovascular disease”, “myocardial infarction”, “stroke”, or “endothelial dysfunction”. Results: Patients with nephrolithiasis develop a higher incidence of cardiovascular disease with a relative risk estimated between 1.20 and 1.24 and also develop a higher vascular disease risk scores. Analyses of subgroups have rendered inconclusive results regarding gender or age. Endothelial dysfunction has also been strongly associated with urolithiasis in clinical studies, although no systemic serum markers of endothelial dysfunction, inflammation or oxidative stress could be clearly related. Analysis of urine composition of lithiasic patients also detected a higher expression of proteins related to cardiovascular disease. Experimental models of hyperoxaluria have also found elevation of serum endothelial dysfunction markers. Conclusions: Endothelial dysfunction has been strongly associated with urolithiasis and based on the experimental evidence, should be considered as an intermediate and changeable feature between urolithiasis and cardiovascular diseases. Oxidative stress, a key pathogenic factor in the development of endothelial dysfunction has been also pointed out as an important factor of lithogenesis. Special attention must be paid to cardiovascular morbidities associated with urolithiasis in order to take advantage of pleiotropic effects of statins, angiotensin receptor blockers and allopurinol.     

Effect of Empagliflozin on Sphingolipid Catabolism in Diabetic and Hypertensive Rats

The profile of sphingomyelin and its metabolites shows changes in the plasma, organs, and tissues of patients with cardiovascular, renal, and metabolic diseases. The objective of this study was to investigate the effect of empagliflozin on the levels of sphingomyelin and its metabolites, as well as on the activity of acid and neutral sphingomyelinase (aSMase and nSMase) and neutral ceramidase (nCDase) in the plasma, kidney, heart, and liver of streptozotocin-induced diabetic and Angiotensin II (Ang II)-induced hypertension rats. Empagliflozin treatment decreased hyperglycemia in diabetic rats whereas blood pressure remained elevated in hypertensive rats. In diabetic rats, empagliflozin treatment decreased sphingomyelin in the plasma and liver, ceramide in the heart, sphingosine-1-phosphate (S1P) in the kidney, and nCDase activity in the plasma, heart, and liver. In hypertensive rats, empagliflozin treatment decreased sphingomyelin in the plasma, kidney, and liver; S1P in the plasma and kidney; aSMase in the heart, and nCDase activity in the plasma, kidney, and heart. Our results suggest that empagliflozin downregulates the interaction of the de novo pathway and the catabolic pathway of sphingolipid metabolism in the diabetes, whereas in Ang II-dependent hypertension, it only downregulates the sphingolipid catabolic pathway.     

Effect of ceramic veneer thickness and cement shade on the CIELAB system after bonding—an in vitro study

In restoration dentistry clinicians need to control the effect of the ceramic thickness and cement shade to achieve successful colorimetric results when all‐ceramic veneers are bonded. The purpose of this study was to evaluate the in vitro effects of cement color and the thickness of the final shade on porcelain discs. The study sample comprised 120 e.max Press HT A‐2 ceramic discs of two thicknesses (60 of 1 mm thick and 60 of 0.5 mm thick). Three different lightnesses of Variolink Veneer cement were used (?3, 0, and +3) for the cementation process. An Easyshade spectrophotometer was used to measure color coordinates (L*, C*, h, a*, and b*) on the discs both before and after cementation. To a large extent, color changes (ΔE ) after the cementation process were found to depend on cement thickness, ceramic thickness, and cement lightness. This model predicted 52% of the observed variability. The most marked change in color appeared on discs 0.5 mm thick and a cement lightness of ?3 (ΔE = 12.0 units). By contrast, color was more stable (minor changes) on discs with a cement lightness of +3 (ΔE = 2.3 units). All color coordinates were significantly modified after bonding, both on thin and thick discs and in all three cement color groups (?3, 0, and +3). However the difference in color (ΔE ) is significantly greater in discs 0.5 mm thick as compared with ceramic discs 1 mm thick. The most prominent change after bonding was found in the h (hue) coordinate. © 2015 Wiley Periodicals, Inc. Col Res Appl, 41, 642–648, 2016     

Inverse gas chromatography study of polyvinylacetate–solvent and polyethylene–solvent systems

In this article, the thermodynamic behavior of polyvinylacetate (PVAc)–solvent, and polyethylene (PE)–solvent mixtures have been studied by determining the thermodynamic sorption parameters (enthalpy, entropy, and free energy), the mass‐based solvent activity coefficients (Ω) and the Flory Huggins parameters (χ), by means of inverse gas chromatography (IGC) measurements. According to the Flory Huggins parameters of the PE–solvent mixtures, determined between 40 and 60°C the compatibility (the ability to interact with each other) of this polymer with the different types of solvents follows this order: dispersion solvents > polar solvents > association solvents. In the case of PVAc mixtures, the thermodynamic parameters were determined between 60 and 80°C, only for polar‐type and association‐type solvents due to, in the studied temperature range, the retention diagrams of dispersion solvents show that there are not bulk interactions. The Hildebrand solubility parameters of both polymers were also determined, according to Guillet procedure. The higher values of PVAc material (14.1 MPa^0.5 for PE and 19.8 MPa^0.5 for PVAc, at 60°C) are related to the strong interactions of vinyl acetate monomer. POLYM. ENG. SCI., 56:36–43, 2016. © 2015 Society of Plastics Engineers     

Three‐component solids velocity measurements in the outlet section of a riser

Coincident (simultaneous) three‐component particle velocity measurements performed using two laser Doppler anemometry probes at the outlet section of a 9 m high cylindrical riser are for the first time presented for dilute flow conditions. Near the blinded extension of the T‐outlet a solids vortex is formed. Particle downflow along the riser wall opposite the outlet tube is observed, which is restricted to higher riser heights at higher gas flow rates. Increased velocity fluctuations are observed in the solids vortex and downflow region as well as at heights corresponding to the outlet tube. Contrary to the rest of the riser, in the downflow region time and ensemble velocity averages are not equal. Given the local bending of the streamlines, axial momentum transforms to radial and azimuthal momentum giving rise to the corresponding shear stresses. Turbulence intensity values indicate the edges of the downflow region. © 2016 The Authors AIChE Journal published by Wiley Periodicals, Inc. on behalf of American Institute of Chemical Engineers AIChE J, 62: 3575–3584, 2016     

Synthesis of N-heteroaryl retinals and their artificial bacteriorhodopsins

N-Heteroaryl retinals derived from indole, 1-indolizine and 3-indolizine (10 a-c) have been synthesized after their UV/Vis red-shifted absorption properties had been predicted by time-dependent density functional theory (TD-DFT) computations. The three new analogues form artificial pigments upon recombination with bacterioopsin: indolyl retinal 10 a undergoes fast and efficient reconstitution to form a species with a UV/Vis absorbance maximum similar to that of wild-type bacteriorhodopsin, whilst the indolizinyl retinals 10 b and 10 c also reconstitute in significant proportion to give noticeably red-shifted, although unstable, pigments. Significant changes in the pK(a) values of these artificial bacteriorhodopsins are interpreted as arising from nonoptimal binding-site occupancy by the chromophore due to steric constraints.     

Comparison of the superelasticity of different nickel–titanium orthodontic archwires and the loss of their properties by heat treatment

The aim of this work is to describe and compare mechanical properties of eight widely used nickel–titanium orthodontic wires under uniform testing conditions and to determine the influence of the heat treatments on the loss of the superelasticity. Ten archwires from two batches from eight different manufacturers were evaluated. A three-point bending test was performed, in accordance with ISO 15841:2006, on 80 round nickel–titanium archwire segments of 0.016?inch. To obtain a load-deflection curve, the centre of each segment was deflected to 3.1?mm and then unloaded until force became zero. On the unloading curve, deflection at the end of the plateau and forces delivered at that point, and at 3, 2, 1 and 0.5?mm of deflection, were recorded. Plateau slopes were calculated from 3 and from 2?mm of deflection. Data obtained were statistically analysed to determine inter-brand, intra-brand and inter-batch differences (P?<?0.05). The results show that at 2?mm of deflection, maximum differential force exerted among brands [Nitinol SuperElastic (1.999N)—Sentalloy M (1.001?N)] was 0.998?N (102?gf). The Nitinol SuperElastic plateau slope (0.353?N/mm) was the only one that was statistically different from 2?mm of deflection, as compared with the other brand values (0.129–0.155?N/mm). Damon Optimal Force described the gentlest slope from 3?mm of deflection (0.230?N/mm) and one of the longest plateaus. Titanol and Orthonol showed the most notable intra-brand differences, whereas inter-batch variability was significant for Nitinol (Henry Schein), Euro Ni–Ti and Orthonol. Superelasticity degree and exerted forces differed significantly among brands. Superelasticity of Nitinol SuperElastic was not observed, while Damon Optimal Force and Proclinic Ni–Ti Superelástico (G&H) showed the most superelastic curves. Intra-brand and inter-batch differences were observed in some brands. In all cases, the heat treatment at 600?°C produces precipitation in the matrix. The precipitates are rich in titanium and this fact produce changes in the chemical composition of the matrix and the loss of the superelasticity. At 400?°C these precipitates are not produced and the forces delivered by the wires are very similar with wires untreated.     

A comparative study of lignocellulosic ethanol productivities by <Emphasis Type="Italic">Kluyveromyces marxianus</Emphasis> and <Emphasis Type="Italic">Saccharomyces cerevisiae</Emphasis>

The yeast Saccharomyces cerevisiae is commonly employed in industrial ethanol production, regardless of the capability of Kluyveromyces marxianus strains to produce ethanol at similar or higher levels and on inhibitory conditions. Therefore, in this work strains of S. cerevisiae (ethanol RED and AR5) and K. marxianus (SLP1 and OFF1) were compared for ethanol production from sugarcane bagasse (SCB) and wheat straw (WS) hydrolysates. As it is known, during the lignocellulosic hydrolysis not only free sugars were obtained (SCB, g L^?1: glucose 7.64, xylose 8.38, arabinose 2.43; and WS, g L^?1: glucose 6.07, xylose 6.36, arabinose 2.09) but also growth inhibitors of yeast such as hydroxymethylfurfural and furfural that could modify the fermentation capability. The volumetric ethanol productivity (Q _p) was evaluated, and it was observed that the K. marxianus SLP1 was the most efficient for ethanol production reaching a Q _p of 0.292 and 0.250 g L^?1 h^?1 on SCB and WS hydrolysates, respectively. In contrast, S. cerevisiae AR5 and ethanol RED exhibited a reduced Q _p on SCB, but similar values of Q _p to K. marxianus OFF1 on WS. The results obtained show that it is possible to select K. marxianus yeast strains for ethanol production using SCB and WS hydrolysates obtaining higher Q _p than S. cerevisiae yeast strains. Considering the efficiency of ethanol production and the tolerance to inhibitors, K. marxianus strain SLP1 possesses a great potential as an industrial yeast for lignocellulosic ethanol production.