Biogas steam reformer for hydrogen production: Evaluation of the reformer prototype and catalysts

This work aims to investigate a biogas steam reforming prototype performance for hydrogen production by mass spectrometry and gas chromatography analyses of catalysts and products of the reform. It was found that 7.4% Ni/NiAl₂O₄/γ-Al₂O₃ with aluminate layer and 3.1% Ru/γ-Al₂O₃ were effective as catalysts, given that they showed high CH₄ conversion, CO and H₂ selectivity, resistance to carbon deposition, and low activity loss. The effect of CH₄:CO₂ ratio revealed that both catalysts have the same behavior. An increase in CO₂ concentration resulted in a decrease in H₂/CO ratio from 2.9 to 2.4 for the Ni catalyst at 850 °C, and from 3 to 2.4 for the Ru catalyst at 700 °C. In conclusion, optimal performance has been achieved in a CH₄:CO₂ ratio of 1.5:1. H₂ yield was 60% for both catalysts at their respective operating temperature. Prototype dimensions and catalysts preparation and characterization are also presented.     

Sequential experimental design based on multiobjective optimization procedures

Model-based sequential experimental designs are frequently applied for discrimination of rival models and/or estimation of precise model parameters. Although the development and use of a single design criterion to perform the simultaneous model discrimination and precise parameter estimation seem appealing, published material indicates that previous attempts to develop such a single design criterion have not been successful. Despite that, this problem has rarely been analyzed with the help of multiobjective optimization procedures. In this work, a multiobjective optimization method based on the particle swarm optimization procedure is used to build the Pareto fronts in experimental design problems where distinct design criteria used for discrimination of rival models and/or estimation of precise model parameters are considered simultaneously. It is shown through the rigorous analysis of the Pareto sets that both design objectives are frequently conflicting, which means that optimum discrimination of rival models and estimation of precise model parameters cannot be performed simultaneously in many cases. However, it is also shown that the use of the posterior covariance matrix of estimated model parameters for model discrimination makes the design of experiments for the simultaneous optimum model discrimination and estimation of model parameters possible in many experimental design problems.     

Nanoindentation and nanoscratch behaviour of reactive sputtered deposited W–S–C film

Transition metal dichalcogenides having layered structure are promising self lubricating film and can be considered as substitute for carbon based films in several varieties of environmental conditions. The macrotribological properties of these films are studied extensively and are fairly well understood. However, mechanical and tribological behaviour of these films in millinewton load range have hardly been reported. Study of mechanical and tribological properties at applied load in the millinewton range is useful for possible application related to microelectro mechanical systems or micromechanical assemblies. In view of the above, the present work is undertaken to understand the indentation behaviour and scratch behaviour under constant and low applied load of reactive sputtered deposited W–S–C thin films. Towards that purpose, W–S films containing various amount of C are deposited on 100Cr6 steel using a radio frequency magnetron sputtering unit. The load vs. displacement curves of all these films are generated for four different loads to assess the load effect, substrate effect and size effect on the hardness and the load displacement curves of these films. Curves showing the variation of load as a function of the square of displacement are also evaluated in order to understand deformation and fracture mechanisms of these films and the interface between various microstructures of these films. The scratch behaviour of these films under constant load is determined to examine the friction and wear performance. The results show that the film containing 54 at.% carbon has the maximum hardness and the minimum scratch depth. In contrast, the minimum friction coefficient is exhibited by the film containing the maximum carbon.     

The pulsing structure of science: Ortega y Gasset,Saint Matthew,fractality and transfractality

By a new fractal/transfractal geometry of the Unified Scientometric Model, it is possible to demonstrate that science presents an oscillating or pulsing dynamic. It goes alternatively through two types of phases. Some phases are fractal, with crystalline networks, where the Matthew effect clearly manifests itself with regard to the most notable actors and those that provide the best contributions. The other phases are transfractal, with deformed, amorphous networks, in which the actors, considered mediocre, present greater capacity to restructure the network than the more renowned actors. The result after any transfractal deformation is a new crystalline fractal network. Behind this vision lies the Kuhn paradigms. As examples, the scientific fields of surfactants and autism have been analysed.     

Dynamic Routing and Wavelength Assignment in Optical Networks by Means of Genetic Algorithms

We propose a novel genetic algorithm for solving the dynamic routing and wavelength assignment (DRWA) problem in wavelength-routed optical networks. The algorithm not only obtains low call blocking probability, but it also employs a very short computation time. Moreover, it is capable of providing fairness among connections, that is, to offer approximately the same quality of service (in terms of blocking probability) for all source-destination node pairs. Since requirements on optical network availability are highly severe, we also propose an extension of the algorithm to provide fault-tolerance capability at the optical layer. It is achieved by means of protection, where each optical connection request is provided with a pair of lightpaths (a primary and a backup lightpath). Again, the genetic algorithm proves to be highly efficient, in this case, at performing routing and wavelength assignment of pairs of lightpaths.     

Crystallization kinetics of poly(ethylene oxide) diluted with xylene

The crystallization kinetics of poly(ethylene oxide)-xylene mixtures with volume fractions of solvent v₁ = 0.52, 0.93 and 0.99 has been investigated by means of dilatometry. At low extents of crystallinity, isotherms are well expressed by the free growth approximation with exponent n = 3 for the concentrated systems (v₁ = 0.52 and 0.93) and n = 4 for the more dilute solution (v₁ = 0.99). The overall rate temperature coefficient was analysed using the theory pertinent to polymer-diluent mixtures. Assuming that the product σ′_eσ_u, where σ′_e is the apparent basal free energy and σ_u is the lateral free energy of the critical nucleus, is independent of concentration, the dissolution temperature for different dilutions as well as the interaction parameter χ₁ have been estimated.     

Analysis of molecular weight distribution of purified cellulose pulp

The molecular weight distribution of purified cellulose pulp is analyzed by using empiric distribution functions. The data are also analyzed by the direct binomial method and the results are compared with those obtained by the method of Beall.     

Random-coil configurations of alicyclic polyformals

A sample of poly (trans-1,4-cyclohexylene-dimethylene-oxymethylene oxide) (PTCDM) was synthesized by condensation of trans-1,4-cyclohexane dimethanol and paraformaldehyde using p-toluene sulphonic acid as catalyst. A fraction having M_n=6500 and a melting point of 86°C was isolated and purified; its n.m.r. spectrum does not change with temperature in the range 20°–50°C which indicates a rigid distribution of methylene substituents in the cyclohexane ring; its dipole moment, measured in benzene solution at several temperatures between 20° and 60°C, yielded values of $\text{D}{}_{\mathrm{n}}\text{=}\text{[μ}{}^2\text{]}\text{nm}{}^2\text{=0.17–0.21}$ and a temperature coefficient dln $\text{{gm}{}^2\text{}}\text{d}\text{T}\text{= 5.5 × 10}{}^{\mathrm{?3}}\text{K}{}^{\mathrm{?1}}$, similar to those reported in the literature for acyclic polyformals. Agreement between experimental and calculated (using rotational isomeric states theory) values is satisfactory.     

CES2, ABCG2, TS and Topo-I Primary and Synchronous Metastasis Expression and Clinical Outcome in Metastatic Colorectal Cancer Patients Treated with First-Line FOLFIRI Regimen

Enzymatic activation of irinotecan (CPT-11) is due to carboxylesterase (CES), and its pharmacological behavior is influenced by drug resistance-related proteins. We previously reported that the clinical response and prognosis of metastatic colorectal cancer (mCRC) patients did not differ in tumors with different thymidylate synthase (TS) or topoisomerase-I (Topo-I) expression. Using immunohistochemistry (IHC), we evaluated the biological role of CES2 and the expression of breast cancer resistance protein (BCRP/ABCG2) in 58 consecutive mCRC patients, who had undergone a first-line CPT-11/5-FU/leucovirin (FOLFIRI) regimen. The expression of these proteins was also examined in a group of synchronous lymph nodes and liver metastases. Furthermore, all samples were revaluated for TS and Topo-I expression. High expression of CES2, ABCG2, TS and Topo-I was observed in 55%, 56%, 38% and 49% of patients, respectively. There was a significant association between high TS and high ABCG2 expression (p = 0.049). Univariate analysis showed that only TS expression significantly impacted on time to progression (p = 0.005). Moreover, Cox’ multivariate analysis revealed that TS expression was significantly associated with overall survival (p = 0.01). No significant correlation was found between investigated markers expression and clinical response. Topo-I expression resulted in being significantly higher in liver metastases with respect to the corresponding primary tumors (p < 0.0001), emphasizing the role of Topo-I expression in metastatic cancer biology. In primary tumor tissues, CES2 expression tended to be higher than that observed in liver metastasis tissues (p = 0.05). These preliminary data may suggest CES2 over-expression as a potential marker of malignant phenotype. In light of these findings, we suggest that Topo-I expression together with TS expression could be associated with metastatic progression of CRC. Further studies are warranted with the aim of evaluating the potential predictive and prognostic role of CES2 and ABCG2 in larger series of patients.