Raw halloysite as reusable heterogeneous catalyst for esterification of lauric acid

The methylic and ethylic esterifications of lauric acid were investigated using raw halloysite as a catalyst, in heterogeneous media. The reactions were conducted with different molar ratios (alcohol:lauric acid) and proportions of catalyst, at 160 °C for 2 h in a pressurized steel reactor. Halloysite produced lauric acid conversion of 95.02% and 87.11% for the methylic and ethylic esterifications, respectively. These results were better than those obtained from thermal conversion (75.61% and 59.86% for methanol and ethanol, respectively). After four consecutive reaction cycles, halloysite was recovered and could be reused after washing and drying. The results showed that halloysite is a promising inexpensive and reusable material for esterification reactions involving fatty acids.     

On the arithmetic of the endomorphisms ring {{\rm End}(\mathbb{Z}_{p} \times \mathbb{Z}_{p^{2}})}

For a prime number p, Bergman (Israel J Math 18:257–277, 1974) established that End(\mathbbZ_p×\mathbbZ_p²){{\rm End}(\mathbb{Z}_{p}\times \mathbb{Z}_{p^{2}})} is a semilocal ring with p ⁵ elements that cannot be embedded in matrices over any commutative ring. We identify the elements of End(\mathbbZ_p ×\mathbbZ_p²){{\rm End}(\mathbb{Z}_{p} \times \mathbb{Z}_{p^{2}})} with elements in a new set, denoted by E _p , of matrices of size 2 × 2, whose elements in the first row belong to \mathbbZ_p{\mathbb{Z}_{p}} and the elements in the second row belong to \mathbbZ_p²{\mathbb{Z}_{p^{2}}}; also, using the arithmetic in \mathbbZ_p{\mathbb{Z}_{p}} and \mathbbZ_p²{\mathbb{Z}_{p^{2}}}, we introduce the arithmetic in that ring and prove that the ring End(\mathbbZ_p ×\mathbbZ_p²){{\rm End}(\mathbb{Z}_{p} \times \mathbb{Z}_{p^{2}})} is isomorphic to the ring E _p . Finally, we present a Diffie-Hellman key interchange protocol using some polynomial functions over E _p defined by polynomials in \mathbbZ[X]{\mathbb{Z}[X]}.     

Model-based testing of software for automation systems using heuristics and coverage criterion

Software and Systems Modeling - The aim of this work is to increase the confidence on software for automation systems defining a coverage criterion to measure the quality level of generated tests...     

Dendritic Zinc Growth in Acid Electrolyte: Effect of the pH

In this paper, dendritic growth at the edges of electrogalvanized steel strip has been studied using a specially designed rotating washer electrode which simulates the fluid dynamic conditions and the current density distribution at the steel strip edge found in a production line. The effect of electrolyte pH and current density on dendritic growth in an acidic zinc plating bath (ZnSO₄ and H₂SO₄) was addressed. The temperature was kept constant at 60 °C. Solution pH was adjusted to 1, 2 or 3 using different amounts of H₂SO₄. In addition, the influence of temperature on the pH of the solution was determined. The current density was set at 40 or 60 A/dm², similar to that used in the industry. Deposits were characterized using SEM and XRD. The results showed that pH strongly affects dendrites shape, length and texture. Furthermore, the morphology of dendrites at the washer edge and of deposits on the flat portion of the washer changed considerably as solution pH was increased from 1 to 3. It was found that the morphology of dendrites at the washer edge stems from the morphology of the deposit on its flat portion, which in turn determines their shape.     

Functional diversity in studies of aquatic macroinvertebrates community

We have compiled information from scientific articles from the ISI Web of Knowledge database (Thomson Reuters) to monitor trends and identify gaps in the use of functional diversity in studies of macroinvertebrates in stream ecosystems. We identified regions, periodicals, taxa and set of functional traits, which were more frequently used. The use of functional diversity with stream macroinvertebrates has proved to be recent, intended to answer the negative effects of land use on the community, especially of aquatic insects and mainly distributed in the European and North American continents. The meaning of terms used in the functional approach differ from concepts found in earlier studies, which may cause misunderstandings in interpretations and comparisons between articles. In addition to this issue, absence of species lists and functional values, and the combination of binary or continuous data and different taxonomic levels also hinder these comparisons. The standardization of terminology has been proposed previously and would simplify the use of functional traits, facilitating the understanding and the search for articles. We highlight the need for funding agencies to determine measures that force researchers to provide the databases after a certain period of time, thus contributing to the creation of a database in other continents, as has been occurring especially in Europe. Such initiative strengthens research, especially those distributed in areas undergoing intense human pressure.     

Sintering,high temperature strength and oxidation resistance of liquid-phase-pressureless-sintered SiC–AlN ceramics with addition of rare-earth oxides

SiC–AlN composites can be pressureless sintered with the addition of rare-earth oxides (RE = Y, Yb, Er, Lu, Ho, Sm, Ce) and without protective powder bed. Sintered bodies showed high density (≥97% T.D.) and were mainly composed by 2H SiC–AlN solid solution with additive containing grain boundary phases. The high temperature strength and oxidation resistance of the composites were also investigated and correlated with the cationic radii of the oxide additives. The flexural strength at 1500 °C increased from 269 MPa to 587 MPa as direct consequence of the rare-earth cationic radius decrease. The specific weight gain during oxidation at 1500 °C for 200 h showed the same behaviour, decreasing from 12.60 mg/cm² to 3.13 mg/cm².     

The effects of unpaved roads on suspended sediment concentration at varying spatial scales – a case study from Southern Brazil

Unpaved roads may induce adverse effects on downstream water resources by increasing suspended sediment concentration (SSC). This study documents the localized impacts on stream SSC of six unpaved road–stream crossings in the rural Guabiroba River Catchment, in southern Brazil. Results demonstrated that SSC values downstream of road–stream crossings was between 3.5 and 10 times higher than upstream SSC at all third‐ and fourth‐order stream locations. However, downstream values were statistically undistinguishable from those collected upstream of road–stream crossings at fifth‐order sampling sites. These findings suggest that localized road effects on stream SSCs are scale‐dependent in that these are important for low‐order headwater streams yet undetectable for their higher order counterparts. Findings point to the importance of low‐order stream crossings in increasing SSC and the need to further explore the role of unpaved roads as agents of water quality degradation in agriculturally active rural settings.