Ni–Nb-Based Mixed Oxides Precursors for the Dry Reforming of Methane

Perovskite-related mixed-oxides based on La Ni Nb and La Sr Ni Nb were synthesized by the auto combustion method to use as precursors materials for the catalytic reforming of methane at 700 ºC, atmospheric pressure, CH₄:CO₂ = 1:1. LaNiO₃ and LaNbO₄ were used as reference. XRD analysis show that the synthesis method produce a new series of precursor family formed by a mixture of oxides where Ni crystallized as part of a perovskite and Ruddlesden–Popper structure while Nb formed lanthanum orthoniobate LaNbO₄, a scheelite-type structure alternating with oxide layers, with phase distribution depending on niobium content. For Nb (x ≤ 0.3) Ni crystallizes as LaNiO₃ perovskite-type oxide while for Nb (x ≥ 0.7) it forms mainly the orthoniobate phase LaNbO₄ a scheelite-type structure. At higher calcined temperatures (~1100 °C) La₂Ni_0.8Nb_0.2O₄ was formed with a Ruddlesden–Popper structure consisting of three perovskite type layers along the c-axis alternating with a layer of the rock salt type phase. TEM analysis showed the presence of cubic particles with sizes varying between 5 and 60 nm depending on the extent of substitution of Ni by Nb. Reduction of the perovskite-related precursor oxides produced a series of Ni⁰/La₂O₃–NbOx oxides with high metallic dispersion which favors the activity and stability of the catalysts. Introduction of doping quantities of Sr into LaNi_0.8Nb_0.2O_3±λ structure produced a mixture of oxides with Sr dissolved in the lanthanum orthoniobate LaNbO₄ scheelite-type structure due to the similarity of ionic radii of La and Sr. Under the reaction conditions conversions near the thermodynamic equilibrium were attained which remains for long periods of time assessing the stability of the synthesized catalysts.     

High performance of low cost soft magnetic materials

The consistent interest in supporting research and development of magnetic materials during the last century is revealed in their steadily increasing market. In this work, the soft magnetic nanocrystalline FINEMET alloy was prepared with commercial purity raw materials and compared for the first time with the generally studied high purity one. The exhaustive characterization covers several diverse techniques: X-ray diffraction, Mössbauer spectroscopy, differential scanning calorimetry, differential thermal analysis and magnetic properties. In addition, a brief economic analysis is presented. For the alloys annealed at 813 K, the value of the grain size was 16 nm with 19·5% of Si, the coercivity was 0·30 A m^?1 while the saturation was 1·2 T. These results prove that structural, magnetic and thermal properties of this material are very close to the expensive high purity FINEMET alloy, while a cost reduction of almost 98% seems highly attractive for laboratories and industry. The analysis should be useful not only for the production of FINEMETs, but for other type of systems with similar constitutive elements as well, including soft and hard magnetic materials.     

Alteration of N-terminal phosphoesterase signature motifs inactivates Saccharomyces cerevisiae Mre11

Saccharomyces cerevisiae Mre11, Rad50, and Xrs2 function in a protein complex that is important for nonhomologous recombination. Null mutants of MRE11, RAD50, and XRS2 are characterized by ionizing radiation sensitivity and mitotic interhomologue hyperrecombination. We mutagenized the four highly conserved phosphoesterase signature motifs of Mre11 to create mre11-11, mre11-2, mre11-3, and mre11-4 and assessed the functional consequences of these mutant alleles with respect to mitotic interhomologue recombination, chromosome loss, ionizing radiation sensitivity, double-strand break repair, and protein interaction. We found that mre11 mutants that behaved as the null were sensitive to ionizing radiation and deficient in double-strand break repair. We also observed that these null mutants exhibited a hyperrecombination phenotype in mitotic cells, consistent with previous reports, but did not exhibit an increased frequency of chromosome loss. Differential ionizing radiation sensitivities among the hypomorphic mre11 alleles correlated with the trends observed in the other phenotypes examined. Two-hybrid interaction testing showed that all but one of the mre11 mutations disrupted the Mre11-Rad50 interaction. Mutagenesis of the phosphoesterase signatures in Mre11 thus demonstrated the importance of these conserved motifs for recombinational DNA repair.     

In vitro protein digestibility and mineral availability of green beans (Phaseolus vulgarisL) as influenced by variety and pod size

Three varieties of green beans (Cleo, Strike and Sentry) were harvested and sorted into four fractions according to pod size (diameter <7 mm; 7–8·5 mm; 8·6–10 mm and >10 mm). Ash content and dietary fibre increased significantly as pod size increased mainly in Cleo and Strike beans. Strike showed the highest fibre content (378·0 g kg⁻¹) but the lowest carbohydrate (364·6 g kg⁻¹) and ash (68·4 g kg⁻¹) values. Mean values for Fe and Mg content were higher in Cleo beans (70·9 and 27·1 mg kg⁻¹, respectively), Zn, Cu and Mg were higher in Strike beans (48·7 mg kg⁻¹, 22·4 mg kg⁻¹ and 3·15 g kg⁻¹, respectively) while Na and Ca values were maximum in Sentry (459·1 mg kg⁻¹ and 7·11 g kg⁻¹, respectively). Trypsin inhibitor was negatively related to in vitro protein digestibility but no relationship was found between this last parameter and phytic acid content. This antinutrient, together with dietary fibre, and a negative influence on in vitro mineral dialysability of green beans. © 1998 SCI     

Anti‐symmetrical curved composite laminate subject to delamination induced by thermal cycling

Composite structures usually undergo to temperature variations in aircraft during landing/taking off and when cruising at high altitude. Under these conditions and in combination with curved structures, they can generate severe thermal stresses that induce delaminations. Considering the importance of studying delamination in these conditions, this research imposed an anti‐symmetrical laminate to cyclic temperature variations of 130 °C and ?70 °C with the objective of inducing varied curvatures and, consequently, crack growth. Different from standardized test procedures, this test setup elastically deformed coupons without external forces and forward experimentally and numerically evaluated the strain energy release rate (SERR) during crack propagation. This procedure enabled the assessment of delamination rate (da/dN) as a function of maximum SERR. The experimental results were compared with numerical results obtained by ABAQUS Finite Element code. Despite large scatter in experimental results, a reasonable correlation between experimental and numerical results was obtained in terms of crack growth rate (da/dN) as a function of the maximum SERR.     

A nitrilase-like protein interacts with GCC box DNA-binding proteins involved in ethylene and defense responses

Ethylene-responsive element-binding proteins (EREBPs) of tobacco (Nicotiana tabacum L.) bind to the GCC box of many pathogenesis-related (PR) gene promoters, including osmotin (PR-5). The two GCC boxes on the osmotin promoter are known to be required, but not sufficient, for maximal ethylene responsiveness. EREBPs participate in the signal transduction pathway leading from exogenous ethylene application and pathogen infection to PR gene induction. In this study EREBP3 was used as bait in a yeast two-hybrid interaction trap with a tobacco cDNA library as prey to isolate signal transduction pathway intermediates that interact with EREBPs. One of the strongest interactors was found to encode a nitrilase-like protein (NLP). Nitrilase is an enzyme involved in auxin biosynthesis. NLP interacted with other EREBP family members, namely tobacco EREBP2 and tomato (Lycopersicon esculentum L.) Pti4/5/6. The EREBP2-EREBP3 interaction with NLP required part of the DNA-binding domain. The specificity of interaction was further confirmed by protein-binding studies in solution. We propose that the EREBP-NLP interaction serves to regulate PR gene expression by sequestration of EREBPs in the cytoplasm.     

Social support and adjustment among Puerto Rican adolescent mothers: The moderating effect of acculturation.

Associations between grandmother and partner involvement and adjustment were examined among 61 Puerto Rican adolescent mothers. Results indicated that associations between grandmother involvement and adjustment were moderated by the adolescents' level of acculturation. Greater support was related to less symptomatology and parenting stress when acculturation scores were low but to more symptomatology and parenting stress when acculturation scores were high. Social support from partners was related to less symptomatology (but not parenting stress). Although coresidence with a partner was related to greater symptomatology, a significant interaction effect revealed that coresidence was associated with greater symptomatology mainly when mothers perceived their partners as providing low levels of support. Results are discussed in light of Latino cultural values and normative developmental issues. Implications for intervention strategies are also discussed. (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

On the selection and classification of independent features

This paper is focused on the problems of feature selection and classification when classes are modeled by statistically independent features. We show that, under the assumption of class-conditional independence, the class separability measure of divergence is greatly simplified, becoming a sum of unidimensional divergences, providing a feature selection criterion where no exhaustive search is required. Since the hypothesis of independence is infrequently met in practice, we also provide a framework making use of class-conditional Independent Component Analyzers where this assumption can be held on stronger grounds. Divergence and the Bayes decision scheme are adapted to this class-conditional representation. An algorithm that integrates the proposed representation, feature selection technique, and classifier is presented. Experiments on artificial, benchmark, and real-world data illustrate our technique and evaluate its performance.     

Multilayer silica-methacrylate hybrid coatings prepared by sol-gel on stainless steel 316L: Electrochemical evaluation

AISI 316L stainless steel is a biocompatible alloy used in prosthetic devices for many years. However this alloy tends to suffer localized corrosion and needs external fixation to hard tissues. This work describes the development of a coating system of two layers with complementary properties. The inner layer is prepared using TEOS and MTES that has already shown good anticorrosion properties. The top layer is a new hybrid organic-inorganic coating prepared with TEOS, 3-methacryloxypropyl trimethoxysilane (MPS), and 2-hydroxyethyl methacrylate (HEMA). The properties of this sol let to produce a thick and porous coating formed by two interpenetrating (organic and inorganic) networks. This coating could be an excellent container for the later aggregate of bioactive particles as the following step in a future work based on its high thickness, plasticity and open structure to allow the electrolyte access to induce the formation of hydroxyapatite. The coating is electrochemically characterised in simulated body fluid at 37 °C after 1, 10 and 30 days of immersion by means of assays as electrochemical impedance spectroscopy (EIS) and polarization curves. The dual coating seems to join the best properties of the individual ones in time: their thickness restrict the passage of potentially toxic ions to the body fluid, the breakdown potential (Eb) remains high and far from the corrosion potential (Ecorr) and the film presents the open structure of the outer layer that allows the entrance of the electrolyte to react with the particles when added to the sol meanwhile the inner layer maintain its corrosion protective features.