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Abstract: In this work, the parameters of the equation of state formed by the Patel–Teja pressure–volume–temperature relationship and the alpha function of Heyen have been estimated for 184 polar substances. To obtain the parameters of the proposed model, pseudo-experimental data have been generated using the DIPPR correlations for vapor pressure and liquid density. The proposed model in conjunction with the Wong–Sandler mixing rules and the NRTL activity model have been used to describe the vapor liquid equilibria of some complex mixtures. Three kinds of binary systems have been analyzed and they are those of the type: polar substance/aromatic, polar substance/n-alkane and polar substance/n-alkanol. Based on the homologous series concept, generalized expressions for the binary interaction parameters in the Wong–Sandler-NRTL mixing rules were developed in order to correlate vapor–liquid equilibrium at low pressures for the selected mixtures. For n-alkanes and aromatic compounds, the acentric factor has been used to generalize the binary interaction parameters for mixtures with a polar substance and these kinds of compounds. In the case of systems composed by a polar substance and an alcohol, the reduced dipole moment of the alcohols is used to develop the generalized expressions. Ninety-two binary mixtures were analyzed and a relative average absolute deviation of 1.21% was estimated for the bubble pressure. Finally, the model was validated by predicting binary vapor–liquid equilibrium at high pressures and for ternary mixtures. In both cases, the results are satisfactory. The average absolute deviations in bubble pressure are 2.34% for high pressure predictions and 1.15% for ternary mixtures. [Copyright &y& Elsevier]

Abstract: A generalized cubic equation of state is proposed for non-polar substances, including heavy hydrocarbons. The new model is based on the Patel–Teja cubic equation of state and the alpha function of Heyen. The proposed equation is compared with the Peng–Robinson, the Peng–Robinson–Gasem, the original Patel–Teja and the translated Peng–Robinson model proposed by Ahlers and Gmehling. Results show that the model proposed in this work is the best of the models evaluated to represent the saturated thermodynamic properties of non-polar substances, especially in the cases of heavy hydrocarbons and hydrogen. The new model improves the capability of the Patel–Teja equation to predict the second virial coefficient and the Boyle temperature of gases and hydrocarbons. Finally, some generalized expressions are developed to predict the vapor liquid equilibria for aromatic/alkane and aromatic/aromatic system using the proposed model and the Wong–Sandler mixing rules. [Copyright &y& Elsevier]

Abstract: A comparative study was made to establish how is altered the performance of Patel–Teja EoS and Peng–Robinson EoS, to represent thermodynamic properties of saturated pure fluids when the alpha function of Soave is substituted by an exponential function with one, two or three parameters. Results show that the Soave function should be replaced by a two parameter exponential function to get adequate representation of the vapor pressure and the saturated vapor volume of pure substances; especially in the low pressure zone (1–101.325kPa). Additionally the performance of equations of state to represent saturated liquid volume and vaporization enthalpy was found practically independent of the alpha function. Comparison between the two equations of state, show that Patel–Teja EoS is superior than Peng–Robinson EoS to represent the saturated liquid volume of pure substances with critical compressibility factor lower than 0.25 or higher than 0.285. Also it has been demonstrated that using the two-parameter alpha function of Heyen with the Wong–Sandler-NRTL mixing rules the capability of cubic EoS to represent the vapor liquid equilibria below 1atm for alcohol/alkane and alcohol/aromatic systems can be improved. [Copyright &y& Elsevier]

Abstract Conventional radiotherapy is mainly applied by linear accelerators. Although linear accelerators provide dual (electron/photon) radiation beam modalities, both of them are intrinsically produced by a megavoltage electron current. Modern radiotherapy treatment techniques are based on suitable devices inserted or attached to conventional linear accelerators. Thus, precise control of delivered beam becomes a main key issue. This work presents an integral description of electron beam deflection control as required for novel radiotherapy technique based on convergent photon beam production. Theoretical and Monte Carlo approaches were initially used for designing and optimizing device´s components. Then, dedicated instrumentation was developed for experimental verification of electron beam deflection due to the designed magnets. Both Monte Carlo simulations and experimental results support the reliability of electrodynamics models used to predict megavoltage electron beam control. Highlights • Novel method for high energy electron beam control is presented and investigated. • Deflection systems based on permanent magnets demonstrated promising capability. • Experiments, theory and Monte Carlo characterized radiotherapy beam deflection. • Electron beam from clinical linear accelerators can be suitably controlled. • Very good agreement was found between theory, simulation and experiments. [ABSTRACT FROM AUTHOR]

Abstract International dosimetry protocols are based on determinations of absorbed dose to water. Ideally, the phantom material should be water equivalent; that is, it should have the same absorption and scatter properties as water. This study presents theoretical, experimental and Monte Carlo modeling of water-equivalence of Fricke and polymer (NIPAM, PAGAT and itaconic acid ITABIS) gel dosimeters. Mass and electronic densities along with effective atomic number were calculated by means of theoretical approaches. Samples were scanned by standard computed tomography. Photon mass attenuation coefficients and electron stopping powers were examined. Theoretical, Monte Carlo and experimental results confirmed good water-equivalence for all gel dosimeters. Overall variations with respect to water in the low energy radiology range (up to 130 kVp) were found to be less than 3% in average. Highlights • Water-equivalence for radiology applications was evaluated for gel dosimeters. • Fricke and polymer (NIPAM, PAGAT and itaconic acid) gel dosimeters investigated. • Experimental, theory and Monte Carlo approaches were applied. • Variations less than 3% were found for radiology energy range (up to 130kVp). • Results suggest promising performance of gel dosimetry for radiology applications. [ABSTRACT FROM AUTHOR]

Complexity in modern radiotherapy treatments demands advanced dosimetry systems for quality control. These systems must have several characteristics, such as high spatial resolution, tissue equivalence, three-dimensional resolution, and dose-integrating capabilities. In this scenario, gel dosimetry has proved to be a very promising option for quality assurance. In this study, the feasibility of Fricke and polymer gel dosimeters suitably shaped in form of thin layers and optically analyzed by visible light transmission imaging has been investigated for quality assurance in external radiotherapy. Dosimeter irradiation was carried out with a 6-MV photon beam (CLINAC 600C). The analysis of the irradiated dosimeters was done using two-dimensional optical transmission images. These dosimeters were compared with a treatment plan system using Monte Carlo simulations as a reference by means of a gamma test with parameters of 1 mm and 2%. Results show very good agreement between the different dosimetric systems: in the worst-case scenario, 98% of the analyzed points meet the test quality requirements. Therefore, gel dosimetry may be considered as a potential tool for the validation of other dosimetric systems. [ABSTRACT FROM AUTHOR]

Abstract: The oxidation of soda lignin extracted from sugar cane bagasse was studied in acid medium. Soda lignin was precipitated from black liquor by adding (36N) sulphuric acid until the pH of the resultant solution was close to 2. The resultant, dried, material was oxidized using hydrogen peroxide. Soda lignin oxidized at different times was investigated by CHNS and EDX chemical analysis, GPC, FTIR and solid state CP-MAS 13C NMR spectroscopy. Oxidation increased the amount of carboxylic groups, while that of associated carbohydrates decreased. In addition, self-condensation with increase of molecular weight was observed. [Copyright &y& Elsevier]

This work describes the development of hyperbranched polymer from eucalyptus Kraft lignin for the removal of heavy metals present in water. The lignin versatile structure and reactive functional groups, such as phenolic hydroxyl groups have been explored. The oxidation of Kraft lignin was prepared under acid conditions, triazine was added in order to incorporate nitrogen heteroatoms and modify the lignin structure generating a hyperbranched polymer. Infrared spectroscopy, gel permeation chromatography, SEM-EDS Microscopy and Physisorption of N 2 at 77 K were employed fot the characterization of adsorbents. It was also made a comparison of the amount of heavy metal removal using Kraft lignin (KL), oxidized Kraft lignin (OKL) and oxidized Kraft lignin cross-linked with triazine (OKL-CC). These were used in the adsorption of nickel and cadmium at 20 ppm, a pH of 4 and at 25 °C, with an amount of adsorbent of 25 mg. By atomic absorption was determined the concentration of the metals. The removal of cadmium was 96.1% for OKL-CC, 92.48% for OKL, while for KL it was 24.4%. The nickel removal with OKL-CC was 80.4%, with OKL was 68.8% and for the KL was 20.99%. • Use of an industrial waste as raw material for the development of a bioadsorbent. • Obtaining a hyperbranched material from a biomolecule and crosslinking with triazine. • Oxidation with hydrogen peroxide as a treatment to increase adsorption removal of metals. [ABSTRACT FROM AUTHOR]