The use of solution microcalorimetry to evaluate chemically modified fish scales as a viable adsorbent for heavy metals

Here, we report for the first time the direct and simultaneous determination of kinetic and energetic parameters of Cr(VI) sorption on chemically modified fish scales (GA-scale) using solution microcalorimetry. Characterization has suggested that electrostatic interactions between scales collagen positive charges and chromate negative charges constitute the majority of the interactions. The microcalorimetric kinetic data of Cr(VI) sorption on GA-scale were successful adjusted to a three-parameter exponential function. The enthalpies of Cr(VI) sorption on GA-scale are highly exothermic (from −226.43 to −183.79 kJ mol⁻¹), and Cr(VI) interaction energies decrease as initial Cr(VI) in solution increases. The kinetic and thermodynamic from solution microcalorimetry results suggest that the interactions GA-scale/Cr(VI) occur mainly by surface reactions. The maximum adsorption capacity of GA-scale for Cr(VI) was found to be comparable with some commercial adsorbent samples.     

Steering in computational science: Mesoscale modelling and simulation

This paper outlines the benefits of computational steering for high performance computing applications. Lattice-Boltzmann mesoscale fluid simulations of binary and ternary amphiphilic fluids in two and three dimensions are used to illustrate the substantial improvements which computational steering offers in terms of resource efficiency and time to discover new physics. We discuss details of our current steering implementations and describe their future outlook with the advent of computational grids.     

First integrals and analytical solutions of the nonlinear fin problem with temperature-dependent thermal conductivity and heat transfer coefficient

Fin materials can be observed in a variety of engineering applications. They are used to ease the dissipation of heat from a heated wall to the surrounding environment. In this work, we consider a nonlinear fin problem with temperature-dependent thermal conductivity and heat transfer coefficient. The equation(s) under study are highly nonlinear. Both the thermal conductivity and the heat transfer coefficient are given as arbitrary functions of temperature. Firstly, we consider the Lie group analysis for different cases of thermal conductivity and the heat transfer coefficients. These classifications are obtained from the Lie group analysis. Then, the first integrals of the nonlinear straight fin problem are constructed by three methods, namely, Noether’s classical method, partial Noether approach and Ibragimov’s nonlocal conservation method. Some exact analytical solutions are also constructed. The obtained result is also compared with the result obtained by other methods.     

Thermal properties and morphology of high-density polyethylene filled with coffee dregs

Composites of high-density polyethylene (HDPE) and coffee dregs (COFD) were elaborated using four different types (integral, extracted, major size, and minor size) of COFD. The aim was to study the effects of particle size and soluble extraction over the properties of the HDPE. Four blends were made at the proportion of 90–10 % polymer-filler. The materials were evaluated through optical and scanning electron microscopy, differential scanning calorimetry and thermogravimetry/derivative thermogravimetry. The results showed that the integral COFD has a performance similar to the minor size one, and superior to the extracted. The composites degraded in two steps. The first one was in a temperature lower than the neat HDPE, but higher than the processing temperature of the polymer. The melting temperature and the degree of crystallinity of the composites resulted similar to the neat HDPE ones. In general, extraction and particle size of the COFD have little influence on the behavior of the HDPE. The results show that COFD can be used as filler in polymeric composites.     

Kinetics of interaction of hardened oil-well cement slurries with acidic solutions from isothermal heat-conduction calorimetry

The kinetics of interaction of hydrochloric acid with oil-well cement slurries treated with the silane coupling agents, tetraethyl orthosilicate, 3-(trimethoxysilyl)-1-propanethiol and 3-(chloropropyl)-trimethoxysilane have been investigated isothermal heat-conduction calorimetry at 298.15 K. The Avrami kinetic model gives a better fit to the experimental data than the traditional Lagergren kinetics models. A pore diffusion model suggests acid diffusion only for the standard slurry. The results indicate that isothermal heat-conduction calorimetry is suitable to evaluate the protective role of silane coupling agents on hardened oil-well cement slurries.     

On regularity of block triangular fuzzy matrices

Necessary and sufficient conditions are given for the regularity of block triangular fuzzy matrices. This leads to characterization of idempotency of a class of triangular Toeplitz matrices. As an application, the existence of group inverse of a block triangular fuzzy matrix is discussed. Equivalent conditions for a regular block triangular fuzzy matrix to be expressed as a sum of regular block fuzzy matrices is derived. Further, fuzzy relational equations consistency is studied.     

A comparative study of two marine catfish (Siluriformes,Ariidae): Cytogenetic tools for determining cytotaxonomy and karyotype evolution

The family Ariidae comprises approximately 130 catfish species on both warm-temperate and tropical continental shelves around the world. The systematics of the group is problematic, with several misidentification problems. In order to better understand the evolutionary relationships in the family, the present study used a cytogenetic approach to characterize two populations of Genidens genidens and two populations of Aspistor luniscutis from the southern coast of Brazil using conventional techniques and fluorescent in situ hybridization with 18S rDNA probes. The two species had the same diploid number (2n = 56), high fundamental numbers and similar banding patterns, thereby corroborating the karyotypic homogeneity proposed for the group. Single nucleolus organizer regions (NORs) were found in the genus Genidens and multiple NORs were found in Aspistor, which are considered an important cytotaxonomic marker for this genus. Karyotypic evolution trends were hypothesized, providing a better understanding of the karyotype diversity and chromosome evolution processes.     

Preparation and properties of europium-doped phosphosilicate glasses obtained by the sol–gel method

In this work, we report the synthesis of europium-doped phosphosilicate glasses from tetraethylorthosilicate (TEOS), phenyltrietoxysilane (PTES) and ammonium phosphate (NH₄H₂PO₄) prepared by the sol–gel process. The matrix was synthesized by modified Stöber methodology. The alkoxide precursors PTES and TEOS were mixed with NH₄H₂PO₄, in the presence of europium III chloride, using ethanol as solvent in basic catalysis. These materials were studied by photoluminescence spectroscopy (PL), thermal analysis (TGA/DTA), transmission electron microscopy (TEM) and energy-dispersive spectroscopy (EDS). The results obtained for the materials show the formation of conchoidal-fractures, which are characteristics of glass materials. The thermal analysis showed the thermal stability of materials up to 300 °C. Eu III has been used as structural probe due to its photophysical properties. The PL spectra displays the lines characteristics of the Eu (III) ion ⁵D₀ → ⁷F_J (J = 0, 1, 2, 3 and 4). Wide bands were observed, indicating non-homogeneous sites that are characteristic of amorphous systems.     

Kinetics and equilibrium parameters of Hg(II) adsorption on silica-dithizone

Sílica-dithizone (Sil-dtz) was synthesized and used to adsorb Hg(II) in solution at pH 6.0. Increasing the temperature accelerates the mass transfer of Hg(II) to the silica surface. The kinetic data were evaluated using the traditional pseudo-first-order Lagergren equation and an alternative Avrami kinetic equation. From the latter equation, two regions presenting distinct kinetic parameters were found, at 25 and 35 degrees C, and the use of the parameter n was also related to the determination of distinct kinetic orders. Variations of the adsorption kinetic rate in relation to the time and the temperature were also calculated and are discussed. The adsorption isotherms data were well fitted to the Freundlich model. Interestingly, good adsorption data correlation of the Langmuir model and experimental values was observed only at 45 and 50 degrees C, suggesting, for this temperature range, the formation of complexes with the proportion Hg:dithizone 1:1 on the silica surface.     

A pericyclic cascade to the stereocontrolled synthesis of 9-cis-retinoids

A domino reaction that is pericyclic in nature is thought to be triggered upon treatment of alkenynol 10 with arylsulfenyl chlorides. The process comprises an ordered sequence of sigmatropic rearrangements: a reversible [2,3]-allyl sulfenate to allyl sulfoxide shift, followed by a [2,3]-propargyl sulfenate to allenyl sulfoxide rearrangement, and last a stereodifferentiating [1,5]-sigmatropic hydrogen migration leading to polyene 13. The occurrence of the C7 to C11 hydrogen migration has been demonstrated by labeling experiments. The double diastereoselection of the [1,5]-sigmatropic hydrogen shift to afford a single isomer of the final polyene 13 is thought to arise from a combination of the electronic effect of the sulfoxide at one terminus, and the steric effect imparted by the bulky trimethylcyclohexenyl substituent at the other terminus. The overall process thus constitutes a stereoselective synthesis of an E,Z,Z-triene fragment from an alkenynol and, in particular, a retinoid with the 7E,9Z,11Z,13E configuration on the conjugated polyenic side chain. Application of this method to the synthesis of retinoids, including labeled analogues, is straightforward.