Cover Image,Volume 66, Issue 10

The cover image, by Bruna A. Bregadiolli et al., is based on the Research Article Towards the synthesis of poly(azafulleroid)s: main chain fullerene oligomers for organic photovoltaic devices, DOI: 10.1002/pi.5419 .

     

Colloidal synthesis of Au nanoparticles using polyelectrolytes with 1,3,4-thiadiazole as reducing agents

Heterocyclic compounds are well known for their biological activity and coordination properties. Some heterocyclic compounds have been employed in the stabilization against coalescence of metallic nanoparticles in colloidal solutions, for example, tetrazole, triazole, and pyrazole. The aim of this work is to design new polyelectrolytes with heterocyclic pendant groups useful as reducing agents of Au³⁺ and as stabilizing agents for the synthesis of colloidal Au nanoparticles. Thus, polyelectrolytes with thiosemicarbazone and 1,3,4-thiadiazole pendant groups were used as reducing agents of Au³⁺ ions and stabilizing agents of Au nanoparticles. The voltammetry study of the polyelectrolytes showed that one with thiosemicarbazone pendant groups is the better reducing agent than polyelectrolytes with heterocyclic pendant groups. The polyelectrolytes can control the growth of the nanoparticles, obtaining structures with an average size of 9 nm. In this study, it was concluded that the nature of the heterocyclic group does not have an effect on the shape of nanoparticles and quasi-spherical nanoparticles were obtained with all polyelectrolytes. © 2019 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2019 , 136, 47790.     

Combining 1,3-Ditriazolylbenzene and Quinoline to Discover a New G-Quadruplex-Interactive Small Molecule Active against Cancer Stem-Like Cells

Quadruplex nucleic acids are promising targets for cancer therapy. In this study we used a fragment-based approach to create new flexible G-quadruplex (G4) DNA-interactive small molecules with good calculated oral drug-like properties, based on quinoline and triazole heterocycles. G4 melting temperature and polymerase chain reaction (PCR)-stop assays showed that two of these compounds are selective G4 ligands, as they were able to induce and stabilize G4s in a dose- and DNA sequence-dependent manner. Molecular docking studies have suggested plausible quadruplex binding to both the G-quartet and groove, with the quinoline module playing the major role. Compounds were screened for cytotoxicity against four cancer cell lines, where 4,4′-(4,4′-(1,3-phenylene)bis(1H-1,2,3-triazole-4,1-diyl))bis(1-methylquinolin-1-ium) ( 1 d ) showed the greater activity. Importantly, dose–response curves show that 1 d is cytotoxic in the human colon cancer HT-29 cell line enriched in cancer stem-like cells, a subpopulation of cells implicated in chemoresistance. Overall, this study identified a new small molecule as a promising lead for the development of drugs targeting G4 in cancer stem cells.     

Regioselective analysis of the fatty acid composition of triacylglycerols with conventional high-performance liquid chromatography

A new method for regioselective analysis of triacyglycerols via conventional high-performance liquid chromatography (HPLC) has been developed. The method is simple and avoids the time-consuming purification processes normally characteristics of regioselective analyses. The procedure utilizes an sn-1,3-specific lipase from Rhizopus arrhizus to deacylate the fatty acid residues located at the sn-1 and sn-3 positions of triacylglycerols. The fatty acid residues esterified at the sn-2 position are determined by subtraction of the results of the sn-1,3 analysis from an overall composition analysis based on complete saponification of the original sample. The fatty acid mixtures are converted to p-bromophenacyl esters and analyzed using conventional HPLC techniques. The analytical procedure has been verified using a standard structured triacylglycerol. The analytical results for three edible vegetable oils are compared with those obtained via the method proposed by P.J. Williams and co-workers.     

Alumina–Aluminide Alloys (3A) Technology: I, Model Development

The general reaction behavior of the 3A process under the thermal explosion mode of synthesis has been investigated via a continuum model. The continuum model uses mass and energy balances to predict temperature difference ( T _s,avg− T _f) curves, as well as profile curves of the reactant conversions and sample temperature. In particular, the effect of the dimensionless parameters associated with the rate of local heat generation (β, the thermicity factor), the activation energy (γ, the Arrhenius number), the rate of heat redistribution (α, the modified thermal diffusivity), the rate of heat transfer by convection (Bi, the Biot number or convective heat transfer parameter), and the rate of heat transfer by radiation (Ω, the radiative heat transfer parameter) were investigated. Conditions to control the reaction process, which should produce high-density final products, were determined. It was found that the overall maximum temperature may be reduced for high γ, low β, high α, and high Bi and Ω. In terms of processing conditions, this may be obtained by reducing the initial reactant concentrations, optimizing the particle size, using small sample sizes and high compaction pressure, and increasing the heat loss by using a high thermal conductivity inert gas.     

Möglichkeiten und Problemlösungen der Stromerzeugung mit Windkraftwerken

Scope and problem solutions of power generation by wind-driven plant. The importance of wind power has changed in the course of history with the advent of competing energy converters for power production from coal, oil, and nuclear energy. The known physical laws of aerodynamics and geographical location ascribe wind power a market share of no more than a few percent of power generation. Among the many designs of wind turbines, only 2- and 3-blade propeller turbines have been produced in large quantities with power ratings up to ca. 4 MW. Market developments have so far been determined by government funding. The power generation costs of 0.25 to 0.30 DM/kWh are still too high by a factor of 2 to 3. With regard to future developments it remains to be seen whether the use of more sophisticated generator systems will permit the expected large savings on the mechanical side and thus open the path to economic large production runs also in the case of medium and large-scale units.     

Wetting angles and photocatalytic activities of illuminated TiO2 thin films

TiO₂ thin films have been prepared by physical vapour deposition (PVD) and plasma enhanced chemical vapour deposition (PECVD) to study the UV-induced photo-activity of this material. Wetting angle variations and photo-catalytic activity for the degradation of dyes upon UV illumination have been compared for thin films with different crystalline structure (amorphous, rutile and anatase), microstructure (columnar, compact, etc.) and porosities as estimated from the values of their refraction indices and their direct assessment with a quartz crystal monitor. The surface of the thin films became superhydrophilic upon UV light irradiation and then it recovered its original state by keeping the samples in the dark. Wetting angle decays follow very similar kinetics for amorphous and crystalline films, independently of their actual porosities. By contrast the photo-catalytic activity was very dependent on the crystalline structure of the films (anatase > rutile > amorphous) and on their porosities. The different behaviour depicted by the films with regard to these two properties suggests that they respond to different though related mechanisms and that they cannot be considered as equivalent when trying to prove the photo-activity of TiO₂.     

Kinetic modeling of catalytic conversion of methylcyclohexane over USY zeolites: Adsorption and reaction phenomena

Catalytic conversion of cycloparaffins is a complex process involving competing reaction steps. To understand this process, FCC experiments using methylcyclohexane (MCH) on USY zeolite catalysts were carried out in the mini‐fluidized CREC riser simulator. Runs were developed under relevant FCC process conditions in terms of partial pressures of MCH, temperatures (450–550°C), contact times (3–7 s), catalyst‐oil mass ratios (5), and using fluidized catalysts. MCH overall conversions ranged between 4 to 16 wt %, with slightly higher conversions obtained using the larger zeolite crystallites. Moreover, it was found that MCH undergoes ring opening, protolytic cracking, isomerization, hydrogen transfer and transalkylation. A heterogeneous kinetic model for MCH conversion including thermal effects, adsorption and intrinsic catalytic reaction phenomena was established. Adsorption and kinetic parameters were determined, including the heat of adsorption (?40 kJ/mol), as well as thermal and primary catalytic intrinsic activation energies, which were in the range of 43–69 kJ/mol, and 50–74 kJ/mol, respectively. © 2009 American Institute of Chemical Engineers AIChE J, 2009