Pyrolysis of atmospheric residue of petroleum (ATR) using AlSBA-15 mesoporous material by TG and Py-GC/MS

The mesoporous material AlSBA-15 with Si/Al molar ratio of 25 was synthesized by the hydrothermal method and characterized by X-ray diffraction and nitrogen adsorption. This is a promising material in the field of catalysis, particularly for petroleum refining, since their mesopores facilitate the accessibility of large hydrocarbon molecules to the active sites of AlSBA-15, producing light hydrocarbons. In order to evaluating the catalytic activity of AlSBA-15, a sample of ca. 10 % in mass of this solid was physically mixed with atmospheric residue of petroleum (ATR) and heated in a thermobalance from room temperature up to 900 °C, under nitrogen atmosphere. From TG curves, it was observed a reduction in the onset temperature, when AlSBA-15 was used as catalyst for the degradation process of ATR. The kinetic model proposed by Ozawa–Flynn–Wall yielded some kinetic parameters to determine the apparent activation energy of the degradation, evidencing the efficiency of the mesoporous material, since there was a decrease in the activation energy for the catalytic degradation. The ATR alone and mixed with AlSBA-15 was also heated in a pyrolysis reactor coupled to a gas chromatograph and mass spectrometer (Py-GC/MS). From the chromatograms, it was observed an increase in the yield of hydrocarbons in the range of gasoline and diesel derived from the catalytic process. These results are due to the combination of the mesoporosity and acidity of the AlSBA-15 for application in the process of pyrolysis of hydrocarbons molecules constituents of the ATR.     

Existence of solutions and optimal control for a model of tissue invasion by solid tumours

In this paper we study the distributed optimal control problem for the two-dimensional mathematical model of cancer invasion. Existence of optimal state-control and stability is proved and an optimality system is derived.     

Marine sponge melanin: a new source of an old biopolymer

Various types of melanin have already been found in the majority of organisms, being this biopolymer considered as one of the major pigments present in nature. The presence of this pigment in marine sponges (Phylum Porifera, one of the simplest multicellular organisms) was postulated, but never characterized. In this context this work aims the extraction and characterization of a dark pigment observed in four different marine sponges species (Erylus mamillaris, Erylus discophorus var. deficiens, Pachymatisma johnstonia, Dercitus bucklandi). Characterization of the extracted biopolymer was performed using solid state analytical techniques, due to the characteristic non-solubility of melanin. Therefore, characterization techniques like SEM–EDS, IR, UV–vis, MALDI-MS, elemental analysis and X-ray powder diffraction (XRD) were used to identify the biopolymer. The results showed that the extracted material was obtained with high purity, being identified as melanin. The results also emphasize a large structure variability present in this pigment, showing different structure arrangements and composition depending on its source, which influences the UV behaviour. The structural characterization of this class of pigments is fundamental, allowing a better understanding of melanin properties.     

On explicit L∞(QT)‐estimates for a model of tissue invasion by solid tumors

In this paper, we prove that if the initial data is small enough, we obtain an explicit L^∞(Q_T)‐estimate for a two‐dimensional mathematical model of cancer invasion, proving an explicit bound with respect to time T for the estimate of solutions. Copyright © 2017 John Wiley & Sons, Ltd.     

Comparative α‐Helicity of Cyclic Pentapeptides in Water

Helix‐constrained polypeptides have attracted great interest for modulating protein–protein interactions (PPI). It is not known which are the most effective helix‐inducing strategies for designing PPI agonists/antagonists. Cyclization linkers (X₁–X₅) were compared here, using circular dichroism and 2D NMR spectroscopy, for α‐helix induction in simple model pentapeptides, Ac‐cyclo(1,5)‐[X₁‐Ala‐Ala‐Ala‐X₅]‐NH₂, in water. In this very stringent test of helix induction, a Lys1→Asp5 lactam linker conferred greatest α‐helicity, hydrocarbon and triazole linkers induced a mix of α‐ and 3₁₀‐helicity, while thio‐ and dithioether linkers produced less helicity. The lactam‐linked cyclic pentapeptide was also the most effective α‐helix nucleator attached to a 13‐residue model peptide.     

Solution Equilibria of Ternary Systems Involving Nickel(II) Ion,Picolinic Acid,and the Amino Acids Histidine,Cysteine, Aspartic and Glutamic Acids

Solution equilibria of the ternary systems Ni(II)–picolinic acid (Hpic) and the amino acids aspartic acid (H₂asp), glutamic acid (H₂glu), cysteine (H₂cys) and histidine (Hhis), where the amino acids are denoted as H _i L, have been studied pH-metrically. The formation constants of the resulting mixed ligand complexes have been determined at 25 °C using a ionic strength 1.0 mol·dm^?3 NaCl. In the Ni(II)–Hpic–H₂asp and Ni(II)–Hpic–H₂glu systems, the complexes [Ni(pic)H₂L]⁺, Ni(pic)HL, [Ni(pic)L]^? and [Ni(pic)L(OH)]^2? were detected. In the Ni(II)–Hpic–H₂cys system the complexes [Ni(pic)H₂L]⁺ and [Ni(pic)L]^? are present. Additionally, in the Ni(II)–Hpic–Hhis system the species [Ni(Hpic)HL]²⁺, Ni(pic)L and [Ni(pic)L(OH)]^? were identified. The species distribution diagrams as functions of pH are briefly discussed.