Vapor–liquid equilibrium data for the nitrogen + n-octane system from (344.5 to 543.5) K and at pressures up to 50 MPa

A static-analytical apparatus with visual sapphire windows and pneumatic capillary samplers has been used to obtain new vapor–liquid equilibrium data for the N₂ + n-octane system over the temperature range from (344.5 to 543.5) K and at pressures up to 50 MPa. Equilibrium phase compositions and vapor–liquid equilibrium ratios are reported. The new results were compared with solubility data reported by other authors. The comparison showed that the solubility data reported in this work at 344.5 K are in good agreement with those determined by others at 344.3 K. The experimental data were modeled with the PR and PC-SAFT equations of state by using one-fluid mixing rules and a single temperature-independent interaction parameter. Results from the modeling effort showed that the PC-SAFT equation was superior to the PR equation in correlating the experimental data of the N₂ + n-octane system.     

Intercalation and functionalization of zinc hydroxide nitrate with mono- and dicarboxylic acids

The intercalation of ions derived from succinic, glutaric, and adipic acid into layered zinc hydroxide nitrate by ionic exchange reaction is reported. Different reaction conditions are investigated and the materials are characterized by powder X-ray diffraction, Fourier transform infrared spectroscopy, thermal analysis (simultaneous thermogravimetry and differential scanning calorimetry) and elemental analysis. The dicarboxylic acids can be grafted to the matrix slab by one carboxylate group and the second hydrated carboxylate group is hanging between the layers. Benzoate ions have also been intercalated by both ionic exchange reaction and stirring in acetonitrile. The two benzoate-intercalated materials exchange the organic moiety by sulfate ions if stirred in magnesium sulfate solution, but the sample obtained by anion exchange also allows the unusual incorporation of neutral magnesium sulfate in addition to free solvated sulfate ion. A schematic arrangement of the intercalated species between the layers is presented.     

Structural Studies by NMR and X-Ray Crystallography of N-(p-Toluenesulfonyl)-Amino Acids

N-(p-Toluenesulfonyl)-glycine 7 and analogous derivatives of d,l-alanine 8, L-valine 9, L-leucine 10, L-isoleucine 11, and L-phenylalanine 12 were synthesized by condensation of the amino acid with p-toluenesulfonyl chloride. The presence of intermolecular hydrogen bonding was established by variable NMR spectroscopy. The molecular structure and intermolecular interactions of N-(p-toluenesulfonyl)–d,l-alanine and N-(p-toluenesulfonyl)–L-valine were corroborated by X-ray diffraction (XRD) experiments.     

Modeling of the hydrolysis of sugar cane bagasse with hydrochloric acid

Sugar cane bagasse was hydrolyzed under different concentrations of hydrochloric acid (2–6%), reaction times (0–300 min), and temperatures (100–128°C). Sugars obtained (xylose, glucose, arabinose, and glucose) and deg-radation products (furfural and acetic acid) were determined. Based on the Saeman model and the two-fraction model, kinetic parameters for predicting these compounds in the hydrolysates were developed. The influence of temperature was studied using the Arrhenius equation. The optimal conditions selected were 128°C, 2% HCl, and 51.1 min. Using these conditions, 22.6g xylose/L, 3.31 garabinose/L, 3.77 g glucose/L, 3.59 g acetic acid/L, and 1.54 g furfural/L were obtained.     

Predominant environmental noise classification over sound mixing based on source-specific dictionary

This paper presents a methodology to classify predominant urban acoustic sources in real mixed signals. This is based on a source-specific dictionary with atoms in the time–frequency domain using the Orthogonal Matching Pursuit (OMP) algorithm and identifying the class through a proposed selection criterion with a dynamic number of iterations involving a lower algorithm complexity. Several time–frequency atoms were evaluated considering retained energy and relative error to build a source-specific dictionary in the relevant classes. The source-specific dictionary has better results up to 7% in retained energy than to use an individual dictionary such as based on wavelet or Gabor functions, improving classification of predominant sources over sound mixing up to 9% compared to using standard dictionaries. Experimental results on classification are applied to mixture inter-class signals of two or more sources recorded by a real permanent monitoring system in an urban soundscape. The classification performance has successfully achieved identifying a predominant source in real inter-class mixtures of urban soundscapes.     

Markov Control Processes with the Expected Total Cost Criterion: Optimality, Stability, and Transient Models

This paper studies the expected total cost (ETC) criterion for discrete-time Markov control processes on Borel spaces, and possibly unbounded cost-per-stage functions. It presents optimality results which include conditions for a control policy to be ETC-optimal and for the ETC-value function to be a solution of the dynamic programming equation. Conditions are also given for the ETC-value function to be the limit of the -discounted cost value function as 1, and for the Markov control process to be `stable" in the sense of Lagrange and almost surely. In addition, transient control models are fully analized. The paper thus provides a fairly complete, up-dated, survey-like presentation of the ETC criterion for Markov control processes on Borel spaces.     

Electrochemical studies of nafion–trimethylsilyl and nafion–trimethylsilyl/Ru complex-modified electrodes

In this work, we report the electrochemical properties of the nafion–trimethylsilyl (Naf–TMS) polymer. First, we introduce a procedure to dissolve Naf–TMS polymer and the incorporation of ruthenium catalyst complexes into it. The inclusion of the catalysts involved two strategies. The first one concerned the direct formation of a Naf–TMS/Ru complex solution. The second one consists of depositing Naf–TMS solution on a glassy carbon electrode, followed by the incorporation of Ru complexes under potentiodynamic conditions. Electrochemical studies showed the good ion permeation capability of Naf–TMS membranes and its use as a good alternative approach to Nafion ion-conducting membranes. The analytical capabilities of Naf–TMS- and Naf–TMS/Ru-modified glassy carbon electrodes have been tested for the detection of dopamine in standard solutions. Detection limits in the order of nanomolar have been achieved with working ranges extending over three decades in concentration at pH 7.2. Further enhancement in the dopamine oxidation current was achieved by the incorporation of Ru complexes into the Naf–TMS polymer. This study offers a new insight into the investigation of Naf–TMS resin as an ion-conducting polymer.     

Numerical simulation of building evacuation in emergency conditions

In the present work, pedestrian behaviour in crowds is assumed to be a coupled phenomena. Therefore, the use of continuousand individual-models in different regions according to its local density is suggested. (© 2008 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim)     

Improvement in the Thermostability of a Recombinant β-Glucosidase Immobilized in Zeolite under Different Conditions

β-Glucosidase is part of the cellulases and is responsible for degrading cellobiose into glucose, a compound that can be used to produce biofuels. However, the use of the free enzyme makes the process more expensive. Enzyme immobilization improves catalytic characteristics and supports, such as zeolites, which have physical-chemical characteristics and ion exchange capacity that have a promising application in the biotechnological industry. This research aimed to immobilize by adsorption a recombinant β-glucosidase from Trichoderma reesei, obtained in Escherichia coli BL21 (DE3), in a commercial zeolite. A Box Behnken statistical design was applied to find the optimal immobilization parameters, the stability against pH and temperature was determined, and the immobilized enzyme was characterized by SEM. The highest enzymatic activity was determined with 100 mg of zeolite at 35 °C and 175 min. Compared to the free enzyme, the immobilized recombinant β-glucosidase presented greater activity from pH 2 to 4 and greater thermostability. The kinetic parameters were calculated, and a lower K_M value was obtained for the immobilized enzyme compared to the free enzyme. The obtained immobilization parameters by a simple adsorption method and the significant operational stability indicate promising applications in different fields.