Structure of zeolites used in hydrogen evolution from water

The structure of zeolite-type materials used in hydrogen evolution from water is described. The formula of these porous crystalline solids based essentially on tetrahedral networks which include channels and cavities is: M_m/z[mAlO₂ · nSiO₂] · qH₂O. Mordenite is one of the siliceous zeolites and a typical formula of a synthetic mordenite is: M_2/zO · [Al₂O₃ · (9–10)SiO₂] · 6H₂O. The spatial formula of modified zeolites is discussed in connection with the ability of some of them to generate hydrogen from hot steam after their vacuum activation.     

Recovery of carboxylic acids C1?C3 with organophosphine oxide solvating extractants

This study was aimed at examining the use of the organophosphine oxides Cyanex^®921 and Cyanex^®923 for the extraction of formic, acetic and propionic acids from aqueous solutions. The stripping of monocarboxylic acids with water from the loaded extractants was also examined. The studies were aimed at determining the equilibrium conditions for extraction and stripping. Overall, the effect of the kind of extractant was not significant although Cyanex^®921 extracted carboxylic acids slightly better than Cyanex^®923 with 1:1 complexes being formed by both extractants with the acids during extraction. The efficiency of extraction depended on temperature, acid concentration and solvent, with toluene a better diluent for the extractants than octane or Exxsol^®D 220/230. Extraction efficiency increased as the concentration of acid in the feed decreased and, also, as the temperature increased, the amount of acid extracted decreased. The extraction and stripping isotherms were determined. The apparent enthalpy and entropy of the extraction reaction were determined. Distribution data for the transfer of carboxylic acids from aqueous (NaCl) solutions to organic solvents in the presence of trialkylphosphine oxide were determined at 293 K with the distribution ratios increasing as the concentration of NaCl increased. Copyright © 2005 Society of Chemical Industry     

Polyurethanes: Products of 4,4′‐bis(6‐hydroxyhexylthio)diphenyl ether and methylene bis(4‐phenyl isocyanate)

New linear polyurethanes derived from 4,4′‐bis(6‐hydroxyhexylthio)diphenyl ether and methylene bis(4‐phenyl isocyanate) were synthesized by either melt or solution polymerization with a strictly equimolar ratio of the monomers. In the solution method, good results were obtained with the aprotic solvent N,N‐dimethylformamide at an approximately 20 wt % concentration of the monomers, with dibutyltin dilaurate as a catalyst, the process being conducted at 90–100°C for 4 h. The basic physicochemical properties of the polymers were investigated with thermogravimetric analysis and differential scanning calorimetry. The molecular weight distribution was determined by gel permeation chromatography. Shore hardness and tensile test results were also examined. The structures of the resulting products were confirmed with elemental analysis, Fourier transform infrared, and X‐ray diffractometry. The properties of the copolyurethanes, containing various amounts of poly(oxytetramethylene) diol (～1000) or polycaprolactone diol (～1250) and synthesized under the conditions for the nonsegmented polyurethanes, were also examined. © 2003 Wiley Periodicals, Inc. J Appl Polym Sci 88: 380–388, 2003     

New degradable polyesters from deoxycholic acid and oligo(ethylene glycol)s

A new class of polyesters was prepared by polycondensation of a bile acid, deoxycholic acid, and an oligo(ethylene glycol) (OEG) with molar mass ranging from 100 to 1500. The chemical structure and composition of the polyesters were confirmed by ¹H‐NMR, Fourier transform infrared spectroscopy and HPLC analysis. Polyester molar masses measured by gel permeation chromatography were between 5000 and 20 000. Thermal stability and glass transition temperature decreased with increasing length of OEG. Hydrolytic degradation was also enhanced by the presence of longer chain OEG. Polyesters obtained from OEG with molar mass ≥ 1000 were water soluble, semicrystalline and thermosensitive. As a function of the OEG length used for their preparation, the new polyesters can be useful for biomedical or industrial applications. © 2012 Society of Chemical Industry     

Determination of free radicals and flavan-3-ols content in fermented and unfermented teas and properties of their infusions

The objective of this study was to analyse selected brands of fermented (red and black) and unfermented (white and green) teas for free radical content with the use of electron paramagnetic resonance (EPR) spectroscopy and for contents of flavan-3-ols by means of high-performance liquid chromatography. Analyses were also conducted for the polyphenolic profile of infusions of the analysed teas (with the Folin–Ciocalteu’s method) and their antioxidant activity (in reaction with a DPPH radical) at three brewing times (5, 10 and 15 min). The obtained results showed the possibility of using rapid spectroscopic method EPR to evaluate the oxidative changes in tea leaves caused by enzymatic fermentation. The number of free radicals in teas was negatively correlated with contents of flavan-3-ols, (?)-EGCG in particular. The main signals observed in EPR spectra of teas were attributed to semiquinone radicals; however, also signals attributed to carbohydrate radicals were detected. Regarding unfermented teas, it was ascertained that teas with the highest content of flavan-3-ols, (?)-EGCG in particular, were characterised by the lowest content of semiquinone radicals and a high content of carbohydrate radicals. The group of fermented teas demonstrated to contain mainly semiquinone radicals. The total phenolic content and antioxidant activity of the tea infusions were strongly diversified depending on the kind and brand of tea as well as on the extraction time. The predominating flavan-3-ol in the analysed teas was epigallocatechin gallate (?)-EGCG, the content of which was additionally highly correlated with the antioxidant activity of the tea infusions.     

Experimental Study on Ultrasonic Monitoring of Splitting Failure in Reinforced Concrete

This paper investigates inspection of reinforced concrete elements sensitive to the splitting failure. The behaviour of a reinforced concrete specimen subjected to a tensile stress is considered. The damage detection procedure is based on the ultrasonic wave propagation technique. The piezoelectric transducers are located on both ends of the specimen and the measurements are taken periodically during the incrementally increased loading. The features of measured signals in time and frequency domains as well as wavelet transforms before and after the splitting failure are studied. The experimental results show that proposed method can be used for monitoring of damage evolution in concrete elements. The method makes possible detection of the moment just before the splitting failure occurs.     

Influence of body composition on the technological properties and mineralogy of stoneware: A DOE and mineralogical-microstructural study

This paper reports a systematic and comprehensive investigation of the effects of the starting mixture composition on the mineralogy and properties of porcelain stoneware tiles using mixture design and full quantitative phase analyses by the Rietveld method. Functional relationships between properties and the raw material mixture proportions were obtained and related to the mineralogical composition of the fired product. Mullite crystallisation depended on the chemical environment. Dissolved quartz mounted to 10 wt% of the dry body regardless on initial amount, indicating saturation of the surrounding melt. The paramount role of the amorphous content on the stoneware properties was disclosed quantitatively. Open porosity decreased with increasing amount of amorphous content, and consequently both the stain and wear resistance increased. The CIE-Lab colour parameters a* and b* increased with increased amorphous content due to interaction with surface iron in hematite. The mullite content increased wear resistance, thus supporting the mullite strengthening theory.     

Food safety implications of the distribution of azaspiracids in the tissue compartments of scallops ( Pecten maximus )

Azaspiracids, a new class of shellfish toxins, have been implicated in several recent incidents of human intoxications following the consumption of mussels ( Mytilus edulis ). A study was undertaken to examine the distribution of azaspiracid poisoning (AZP) toxins in scallops ( Pecten maximus ) and individual shellfish were dissected into five tissue fractions for the determination of toxin composition. Separation of the predominant azaspiracids, AZA1-3, was achieved using reversed-phase liquid chromatography with detection by positive electrospray multiple tandem mass spectrometry. The AZP toxin composition was determined in the adductor muscle (meat), gonad (roe), hepatopancreas (digestive glands), mantle and gill of scallops. Substantial differences in the AZP toxin levels between tissue compartments were observed and toxins were concentrated predominantly, about 85%, in the hepatopancreas. There was also a significant variation in the total toxin levels between individual scallops from the same sample batch and the RSD was 60% (n = 9). Interestingly, although all three AZP toxins were present in phytoplankton and mussels, AZA3 was not detected in the scallop samples examined. It was concluded that to improve food safety, only the adductor muscle and gonad of scallops should be permitted for sale to the public.     

Assessment of 21st century ICT skills in Chile: Test design and results from high school level students

This paper describes a study that evaluates fifteen-year-old Chilean students Information and Communication Technology (ICT) skills. The paper presents an operational definition of ICT skills, an instrument measuring these skills as well as the students' results in the test. The definition of ICT skills used considers Chile's curricular framework, functional and cognitive skills. Specifically, ICT skills were defined as the capacity to solve problems of information, communication and knowledge in digital environments. A performance-based assessment was designed in a virtual environment to measure these skills. The analysis of the results showed that the majority of students were able to solve tasks related to the use of information as consumers, i.e., approximately three quarters of the students were able to search for information and half of them were also able to organize and manage digital information. Additionally, they show that very few students were able to succeed in tasks related to the use of information as producers, i.e., only one third of the students were able to develop their own ideas in a digital environment and less than one fifth were able to refine digital information and create a representation in a digital environment. Socioeconomic group, access, daily use and confidence in doing ICT-related activities were all positively associated with higher scores, showing the need to implement strategies to compensate this inequality, possibly by explicitly defining these aims in the national curriculum.     

Effects of rainbow trout freshness on n‐3 polyunsaturated fatty acids in fish offal

The effects of rainbow trout cold storage on the quality of offal left after fish processing to fillets with skin were determined. The intact farmed rainbow trout were kept at 2 °C in ice for 0, 4, 7, and 14 days of storage. The offal was, immediately after processing, frozen at ?20 °C and analysed after a month‐long frozen storage; fillets (non‐frozen) were analysed as well. Non‐protein nitrogen, volatile bases, trimethylamine, lipid oxidation (peroxide value, anisidine value, UV‐VIS spectra, and fluorescence) and fatty acid composition were determined. The offal consists in 15% of protein and in about 20% of chloroform/methanol‐extractable lipids, with n‐3 polyunsaturated fatty acids (n‐3 PUFA) accounting for 20.37 ± 1.25% of the fatty acids. The fish storage duration was found to exert a significant (p = 0.05) effect on the changes in lipids and nitrogen compounds. No losses of long‐chain n‐3 PUFA in the offal were detected during the 2 wk of storage in ice plus 1 month at ?20 °C. The rainbow trout offal is a valuable – rich and stable – source of n‐3 PUFA.