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This work proposes a new mathematical model for reproducing desertification and vegetation patterns. The model consists of two nonlinear partial differential equations. One of them describes the Spatio-temporal dynamic of vegetation in an analogous way to Lefever’s model, while the precipitation dynamic is given by one equation of Hardenberg’s model. The model’s equations are solved using a numerical-functional difference method for the Spatio-temporal terms. The numerical results reproduce various bi-dimensional (2D) patterns observed in water-limited regions, including stripes, spots, hollows, and labyrinths. 2D patterns with these morphologies are characterized by their Fourier spectra and quantified their dimension fractal. The numerical solutions of the model also predict transitions from bare soil at low precipitation to homogeneous vegetation at high rainfall. These results reveal an underlying mechanism for the local desertification process and the vegetation self-organization. The broad context of matter order-disorder transitions. The proposed model even reproduces the desertification patterns for local instabilities of the hydrodynamic type beyond the instability induced by diffusion.

In this research, it is presented a detailed study of the structural and thermoelectric properties of the pyrochlore zirconium Pr2Zr2O7 compound prepared by solid-state reaction (SSR) in air at ambient pressure. The synthesized sample was characterized using powder X-ray diffraction. The thermal stability of the thermoelectric compound (TE) Pr2Zr2O7 was tested by thermogravimetric analysis (TGA) and differential thermal analysis (DTA). Scanning electron microscopy shows that the crystal size varies between 0.69 and 2.81μm. Electrical conductivity (\sigma) of the sample calcined at 1400 °C presented values increase irregularly with the increasing temperature from 0.001 to 0.018 S cm-1 as expected in a semiconductor material. The thermal conductivity is lower than 0.44 - 775 W m-1 K-1 which is quite anomalous in comparison with the thermal conductivity of other oxides.

The article presents a new methodology that employs 3D printing technology to generate a microporous composite material of polylactic acid, sodium alginate and hydroxyapatite, whose microstructure is designed by means of the 3D numerical solution from a mathematical model. This model represents the spatio-temporal dynamics of the interaction between osteoblasts and osteoclasts in the bone remodeling. The microporosity of composite material mimics the structure of human trabecular bone. This material has density with microporosity pretty close to the one that is exhibited by the natural bone tissue. Close relationship between the material processing and its elasticity module is observed. When subjecting this composite material to a simulated body fluid treatment, the mechanical resistance to compression is increased due to induced mineralization of hydroxyapatite crystals on its surface. The methodology shows potential to generate structures that allow the control of the composite material properties. The material presents a microporosity that has morphological and chemical properties suitable for future applications in tissue engineering as bone scaffold.

This research addresses the synthesis of silver phosphate microcrystals with complex polyhedral morphologies as rhombic dodecahedral, trapezoidal, tetrahedral and cuadri-hexahedral polyhedrons as well as structures of shape corners and edges. These structures are obtained simultaneously by means of few modifications to the hydrothermal method using microwave and basic medium for the chemical synthesis. The photo-degradation activity of silver phosphate microcrystals was measured using methylene blue (MB) under sunlight while stirring. The degradation time of the MB was reported at 4 min using 0.1 gr of microparticles suspended on 50 mL of MB at 5 × 10 5 mol/L concentration. These Ag3PO4 polyhedric microcrystals were characterized by different techniques: energy-dispersive X-ray spectroscopy (EDX), X-ray diffraction (DRX), atomic force microscopy (AFM), scanning electron microscopy (SEM) and Nitrogen adsorption at 77 K. Reaction order and rate law were determined as well. A particle pore size distribution with order diameter of 4.862 nm and pore families between 5 and 20 nm linked to interstitial mesopores were well identified. Furthermore, these type of materials synthesis is environmental friendly due to its basic nature.

Zinc oxide nanoparticles (ZnONPs) synthesis was studied in multiscale modeling, proposing a reaction-diffusion system based on its three-stage reaction mechanism by the hydrothermal method: (1) dissociation of the precursor, (2) formation of the anion complex, and (3) obtaining the ZnO nanoparticle. Chemical compounds present in the reaction mechanism were evaluated under the Density Functional Theory (DFT) to find its reactivity through the B3LYP/6–311+G method. Reaction-diffusion model Computational simulation and numerical solution allow reproducing ZnONPs three-dimensional morphologies reported experimentally, such as rods, spheres, pseudo-spheres, octahedral, sheet-like, nut-like, and hollow spheres.

The search for novel materials and the development of improved processes for water purification have attracted the interest of researchers worldwide and the use of titanium dioxide in photocatalytic processes for the degradation of organic pollutants contained in water has been one of the benchmarks. Compared to crystalline titanium dioxide (cTiO2), the amorphous material has the advantages of having a higher adsorption capacity and being easier to dope with metal and non-metal elements. In this work, we take advantage of these two features to improve its photocatalytic properties in the degradation of Rhodamine B. The structural characterization by XRD analysis gives evidence of its amorphous nature and the SEM micrographs portray the disc morphology of 300 nm in diameter with heterogeneous grain boundaries. The degradation of Rhodamine B tests with the amorphous TiO2 using visible light confirm its improved catalytic activity compared to that of a commercial product, Degussa P25, which is a well-known crystalline material.

The search for novel materials and the development of improved processes for water purification have attracted the interest of researchers worldwide and the use of titanium dioxide in photocatalytic processes for the degradation of organic pollutants contained in water has been one of the benchmarks. Compared to crystalline titanium dioxide (cTiO2), the amorphous material has the advantages of having a higher adsorption capacity and being easier to dope with metal and non-metal elements. In this work, we take advantage of these two features to improve its photocatalytic properties in the degradation of Rhodamine B. The structural characterization by XRD analysis gives evidence of its amorphous nature and the SEM micrographs portray the disc morphology of 300 nm in diameter with heterogeneous grain boundaries. The degradation of Rhodamine B tests with the amorphous TiO2 using visible light confirm its improved catalytic activity compared to that of a commercial product, Degussa P25, which is a well-known crystalline material.

A functional with interactions short-range and long-range low coarse-grained approximation is proposed. This functional satisfies models with dissipative dynamics A, B and the stochastic Swift-Hohenberg equation. Furthermore, terms associated with multiplicative noise source are added in these models. These models are solved numerically using the method known as fast Fourier transform. Results of the spatio-temporal dynamic show similarity with respect to patterns behaviour in ferrofluids phases subject to external fields (magnetic, electric and temperature), as well as with the nucleation and growth phenomena present in some solid dissolutions. As a result of the multiplicative noise effect over the dynamic, some microstructures formed by changing solid phase and composed by binary alloys of Pb-Sn, Fe-C and Cu-Ni, as well as a NiAl-Cr(Mo) eutectic composite material. The model A for active-particles with a non-potential term in form of quadratic gradient explain the formation of nanostructured particles of silver phosphate. With these models is shown that the underlying mechanisms in the patterns formation in all these systems depends of: (a) dissipative dynamics; (b) the short-range and long-range interactions and (c) the appropiate combination of quadratic and multiplicative noise terms.

Electrochemical oxidation depends enormously on the electrode materials used during electrolysis. Dimensionally Stable Anodes (DSA) represent a good option for electrochemical oxidation applied to wastewater treatment due to the ability of generating hydroxyl radicals. These radicals are strong, non-selective oxidizing agents, which are able to react with organic pollutants and mineralize them. However, this kind of electrodes is commonly synthesized from chloride precursors, which represents an environmental problem, because they can form undesirable chlorinated by-products during the electrolysis. Some DSA electrodes such as PbO2, SnO2-Sb2O5 and TiO2 are promising anodes due to their high over-potential for oxygen evolution, which leads to the ability of OH radical production; however, their main drawback is the low chemical stability [1, 2]. This disadvantage prevents their use in environmental applications and causes the search for other materials with better properties. In this work we present the synthesis as well as its electrochemical application of a DSA electrode composed of Ti|IrO2-SnO2-Sb2O3. The purpose is enhancing the chemical stability and prolonging the electrode lifetime. The Pechini concept was used to this material, but with the advantage that no chloride precursors were employed [3]. Cyclic voltammetry (CV), X-ray diffraction (DRX), Energy-dispersive X-ray spectroscopy (EDS) and scanning electron microscopy (SEM) were used to characterize the as-prepared electrode. The electrocatalytic properties were evaluated by electrochemical degradation of tartrazine in aqueous media as well as dibenzothiophene in organic media. Results showed that noncracked oxide layers were obtained and that the electrode has a great capability for the electrochemical degradation of both molecules. Keywords: DSA electrode, Ti|IrO2-SnO2-Sb2O3, tartrazine, dibenzothiophene X. Chen, G. Chen, Anodic oxidation of dyes at novel Ti/B-diamond electrodes, Chem. Eng. Sci. 58 (2003) 995. X. Chen, G. Chen, F. Gao, P. Yue, High-performance Ti/BDD electrodes for pollutant oxidation, Environ. Sci. Technol. 37 (2003) 5021. M. H. P. Santana, L. M. Da Silva, L. A. De Faria, (2003). Investigation of Surface Properties of Ru-Based Oxide Electrodes Containing Ti, Ce and Nb. Electrochim. Acta, 48 (13), 1885.