Ozonation of Pyrolytic Aqueous Phase: Changes in the Content of Phenolic Compounds and Color

Ozonation on the phenols present in pyrolytic aqueous phases attained from biomass thermochemical conversion was evaluated. During ozonation, the dark color of original samples was found to decrease as a function of ozonation time. The oxidation kinetics of phenols was quantified by a method based on the color changes of samples. The oxidation profiles showed different behaviors and in some cases the phenols presented a positive correlation with the relative R color parameter, except eugenol, syringol, and vanillin which were markedly different. Finally, the color changes observed seem to be associated with the changes in the overall content of phenols and with the change in the molecular weight of the heavy fractions that include lignin oligomers.     

Dry Fractionation of Cupuassu (Theobroma grandiflorum) Fat: Physical–Chemical Properties and Polymorphic Behavior

Physical chemical properties of cupuassu fat were modified by dry fractionation. Stearin and olein fractions were obtained at 29, 26, and 24 °C. Polymorphic behavior of unfractionated cupuassu fat (UCF) and its fractions were studied in situ by small-angle (SAXS) and wide-angle (WAXS) X-ray scattering using synchrotron light. Polymorphic transitions were followed in real time tempering samples with a thermal cycle. For UCF, the main polymorphic form crystallized under selected conditions was the β’₂. α and β’₁-forms appeared in trace amounts. β₂-form was obtained after storage at 25 °C for 3 months. Stearins obtained at 26 (S-26) and 24 °C (S-24) showed a similar polymorphic behavior. However, S-26 with improved physical properties might be more suitable for chocolate production or as a trans-fat alternative than UCF. Stearin fraction obtained at 29 °C (S-29) had a complex polymorphic behavior. The α-form was the first polymorphic form detected followed by β’₂-form. There was a polymorphic transition from α to β’₁-form but no transition between β’-forms. They were independent to each other showing fractionation in two different solid solutions. Increased contents of the triacylglycerols (TAG) SOA and SOB together with lower contents of SOO compared to UCF led to co-crystallization because there was no complete compatibility among all TAG present in S-29. β₁-form crystallized after storage forming crystals with a double-layer arrangement and a characteristic morphology. This form could be useful for accelerating crystallization process in melted liquid systems.     

Computation offloading balance in small cell networks with mobile edge computing

Wireless Networks - As a promising way to offset the low computation capacity of user equipments (UEs), mobile edge computing (MEC) has attracted great attention of academy and industrial recently....     

Synthesis and characterization of a titanium phosphate-tellurite glass for Faraday rotators

This work is focused on investigation of thermal, structural, optical, magnetic, and magneto-optical properties of novel titanium phosphate-tellurite glass applied as Faraday rotators. The glass belonging to the system 35Li₂O–10Al₂O₃–5TiO₂–45P₂O₅–5TeO₂ was prepared by a nonconventional wet route of raw materials processing, followed by melting-quenching-annealing steps. Some important physical properties of the investigated glass have been measured and calculated, providing knowledge related to glass compactness, electronic structure, glass forming capability, etc. XRD analysis evidenced an amorphous network structure of the investigated glass. The optical absorption in the Vis domain is mainly due to Ti³⁺ ions and Te₂ clusters formed during the glass melting process. A relatively low optical absorption is noticed over 600 nm that activates a significant Faraday magneto-optical effect. Photoluminescence bands in the blue, red, and infrared domains are observed, caused by Te₂ clusters formed during the glass melting process. The magnetization in dependency on applied magnetic field reveals a complex behavior of the glass, depending on temperature. Thus, it is found a ferromagnetic behavior up to 2000 Oe, a paramagnetic component up to 40 000 Oe, followed by a diamagnetic one over 40 000 Oe. Faraday rotation angle and Verdet constant values in the visible domain are correlated with the reduced TeO₂ content of the glass.     

Kinetic mobility and connectivity in nanopore networks

Experimental results for methane and carbon dioxide diffusion in coal, as reported in the literature, often lead to diffusion rates of CO₂ appearing to be much greater than that of CH₄. The interpretation sometimes offered that the diffusion coefficient for CO₂ is 1–2 orders of magnitude higher than that of CH₄, violates fundamental principles. Nevertheless, the experimental observations require explanation. In this article, we: (a) Develop simplified models for the fast estimation of transport coefficients. These are compared with comprehensive grand canonical Monte Carlo (GCMC) and molecular dynamic (MD) simulations, collectively defined as molecular simulations (MS), which provide theoretical adsorption isotherms and various transport coefficients based on multicenter potential energy equations. The simplified models are shown to have acceptable accuracies. (b) Use the simplified models to compare diffusivities of CO₂ and CH₄ in carbon nanopores. For all cases examined, the diffusivity of CH₄ is always larger than that of CO₂. (c) Offer two explanations for the apparently contradictory experimental observations (that CO₂ sometimes appears to diffuse much faster than the CH₄ molecule, even though CH₄ is lighter and has smaller adsorption affinity): (i) CH₄ mobility could be significantly reduced by directional forces resulting from irregular pore geometries; and (ii) if pores contain throats with sizes close to the CH₄ molecular diameter, the energy barrier that the methane molecules must overcome to proceed through is much larger than that required for CO₂. (d) Demonstrate that both mobility and connectivity issues can be addressed using kinetic theory in association with percolation analysis. Furthermore, this method of understanding pore networks provides a number of important quantitative measures including percolation threshold, size of largest cluster, shortest path and tortuosity. Separating different transport mechanisms, as we propose here, provides improved insights into the complex transport phenomena that occur in carbonaceous porous media. In many cases, diffusivities reported in the literature with mixed mechanisms are better named “apparent transport coefficients,” because they lump in other unrelated phenomena, violating the fundamental basis of, or mathematical assumptions imposed on, the definition of diffusion. © 2011 American Institute of Chemical Engineers AIChE J, 2012     

SEM‐EDX and microftir studies on evaluation of protection capacity of some thin phosphate layers

This article presents the SEM‐EDX and microFTIR study and the corrosion behavior of new five types of phosphated coatings obtained by coprecipitation in acid aqueous medium of some metal cations, pursuing the influence of the addition of other cations and a moderator of precipitation, on the uniformity and compactness of the layers and on the morphology of dendritic structure of Zn(II) and Fe(II) phosphates. Microsc. Res. Tech. 2012. © 2012 Wiley Periodicals, Inc.     

Influence of Surface Morphology on the Torsion Fracture of NiTi Endodontic Instruments

This study analyzed the influences of manufacturing process (twisting and machining) and surface finishing on the angular distortion, maximum torque, and toughness of two NiTi endodontic instruments (Race—FKG Dentaire and TF—Twisted Files, SybronEndo). Statistical analysis of results showed that TF instruments (twisted) had higher distortion angle (p < 0.05) and lower maximum torque to fracture (p < 0.05) than Race instruments (machined). SEM analysis of fractured instruments showed a surface morphology characteristic of ductile fracture, with plastic deformation in the helical shafts. The results suggest that both instruments are equally suitable for clinical applications. This study is purely scientific as it evaluates only some material properties, and is not intended to endorse a commercial product.