Quantitative assessment of alkali silica reaction potential of quartz-rich aggregates: comparison of chemical test and accelerated mortar bar test improved by SEM-PIA

Bulletin of Engineering Geology and the Environment - The alkali silica reaction (ASR), which originates in highly alkaline conditions in concrete where reactive forms of silica are available,...     

Can we identify who will adhere to long-term physical activity? Signal detection methodology as a potential aid to clinical decision making.

Signal detection methodology was used to identify the best combination of predictors of long-term exercise adherence in 269 healthy, initially sedentary adults ages 50-65 years. Less educated individuals who were assigned to supervised home-based exercise of either higher or lower intensity and who were less stressed and less fit at baseline than other individuals had the greatest probability of successful adherence by the 2nd year. Overweight individuals assigned to a group-based exercise program were the least likely to be successful 2 years later. Predictors of short-term (1-year) adherence were generally similar to predictors of 2-year adherence. Signal detection analysis may be useful for identifying subgroups of people at risk for underadherence who subsequently might be targeted for intervention. (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Assessment of green cleaning effectiveness on polychrome surfaces by MALDI‐TOF mass spectrometry and microscopic imaging

This article proposes an innovative methodology which employs nondestructive techniques to assess the effectiveness of new formulations based on ionic liquids, as alternative solvents for enzymes (proteases), for the removal of proteinaceous materials from painted surfaces during restoration treatments. Ionic liquids (ILs), also known as “designer” solvents, because of their peculiar properties which can be adjusted by selecting different cation‐anion combinations, are potentially green solvents due totheir low vapour pressure. In this study, two ionic liquids were selected: IL1 (1‐butyl‐3‐methylimidazolium tetrafluoroborate ([BMIM][BF₄])) and IL2 (1‐ethyl‐3‐methylimidazolium ethylsulphate ([EMIM][EtSO₄])). New formulations were prepared with these ILs and two different proteases (E): one acid (E1—pepsin) and one alkaline (E2—obtained from Aspergillus sojae). These formulations were tested on tempera and oil mock‐up samples, prepared in accordance with historically documented recipes, and covered with two different types of protein‐based varnishes (egg white and isinglass—fish glue). A noninvasive multiscale imaging methodology was applied before and after the treatment to evaluate the cleaning's effectiveness. Different microscopic techniques—optical microscopy (OM) with visible and fluorescent light, scanning electron microscopy (SEM) and atomic force microscopy (AFM)—together with Matrix‐Assisted Laser Desorption/Ionization—Time of Flight Mass Spectrometry (MALDI‐TOF MS) were applied on areas cleaned with the new formulations (IL + E) and reference areas cleaned only with the commercial enzyme formulations (gels). MALDI‐TOF proved particularly very useful for comparing the diversity and abundance of peptides released by using different enzymatic systems. Microsc. Res. Tech. 77:574–585, 2014. © 2014 Wiley Periodicals, Inc.     

A numerical study of prestressed high strength steel tubular members

The structural behavior of prestressed high strength steel (HSS) tubular members is investigated through the execution of advanced finite element modeling. Numerical models are developed and validated against published experimental data on HSS tubular members subjected to different levels of initial prestress and loaded either in tension or compression. The effect of the presence or absence of grouting on the strength and ductility of the members is also considered. To numerically replicate the structural response recorded in the tests, some key modeling features including the employed numerical solver, the adopted material models and the element types warrant careful consideration. Upon developing of the finite element models, the numerically generated ultimate loads, the corresponding failure modes and the full load-deformation curves are compared to the experimental ones, indicating a successful validation. As anticipated, prestressing enhances the load-bearing capacity for the tensile members, whereas it is detrimental for the compressive ones. A series of parametric studies is performed to assess the influence of key factors on the structural response of prestressed HSS members and the obtained results are discussed. Design guidance for tensile and compressive prestressed tubular members is also provided.     

Investigation on strategies for optimizing process definition in rubber processing: A study on mechanical and chemical properties of vulcanizates as basis for the development of a new calculation model for quality prediction

Rubber compounds may exhibit significant batch variations due to multiple different ingredients mixed in one compound. Hence, defining the manufacturing process for constant part quality can be challenging. Common strategies in considering batch variations in rubber processing include the determination of reaction kinetics, and the definition of process parameters according to normalized vulcanization isotherms. Thereby, maintenance of the degree of cure is targeted. With this path, information on the mechanical properties of vulcanizates is lost, despite its visibility from the kinetic data and part quality assurance is missed. This contribution points out the differences obtained for parts produced to the same degree of cure at various temperatures and intends to emphasize new strategies in process definitions. Therefore, compression molded parts were produced from styrene-butadien rubber, which was then characterized with mechanical and chemical methods. Each of the methods revealed a significant difference in part behavior, which were manufactured to the same degrees of cure but at different temperatures. It was concluded that a temperature-dependent reaction rate should be considered when quality maintenance is targeted in the production. Only then will it be possible to predict the properties adequately, with simultaneous effect of enhancing sustainability policies in rubber processing.     

Inorganic Salts of N-phenylbiguanidium(1+)—Novel Family with Promising Representatives for Nonlinear Optics

Seven inorganic salts containing N-phenylbiguanide as a prospective organic molecular carrier of nonlinear optical properties were prepared and studied within our research of novel hydrogen-bonded materials for nonlinear optics (NLO). All seven salts, namely N-phenylbiguanidium(1+) nitrate (C2/c), N-phenylbiguanidium(1+) perchlorate (P-1), N-phenylbiguanidium(1+) hydrogen carbonate (P2₁/c), bis(N-phenylbiguanidium(1+)) sulfate (C2), bis(N-phenylbiguanidium(1+)) hydrogen phosphate sesquihydrate (P-1), bis(N-phenylbiguanidium(1+)) phosphite (P2₁), and bis(N-phenylbiguanidium(1+)) phosphite dihydrate (P2₁/n), were characterised by X-ray diffraction (powder and single-crystal X-ray diffraction) and by vibrational spectroscopy (FTIR and Raman). Two salts with non-centrosymmetric crystal structures—bis(N-phenylbiguanidium(1+)) sulfate and bis(N-phenylbiguanidium(1+)) phosphite—were further studied to examine their linear and nonlinear optical properties using experimental and computational methods. As a highly SHG-efficient and phase-matchable material transparent down to 320 nm and thermally stable to 483 K, bis(N-phenylbiguanidium(1+)) sulfate is a promising novel candidate for NLO.     

High surface area SiC(O)-based ceramic by pyrolysis of poly (ethylene glycol) methacrylate-modified polycarbosilane

In the present work, a high surface area SiC(O)-based ceramic powder was synthesized upon thermal transformation of a polymer-derived macromolecular precursor, which was obtained by the chemical modification of a allylhyldrido polycarbosilane with poly(ethylene glycol) methaacrylate under argon environment. The pyrolysis of developed precursor led to the formation of amorphous and high surface area SiC(O)-based ceramic powder with in situ generated micro/meso-porosity. The specific surface area of the obtained powders depends on the processing temperature. It decreases from 363 to 122 m²/g as the pyrolysis temperature increases from 600 to 1200°C, respectively. Furthermore the promising samples were fabricated using pressing technique, which led to crack-free SiC(O) monoliths on subsquent heat treatment. The present study also emphasizes the potential of produced SiC(O) ceramic powder to support NiO catalyst. The impregnation method were used to produce high surface area NiO@SiC(O) ceramic powder (NiO as a catalyst; SiC(O) as a catalyst support) for further catalytic applications. Interestingly, the distribution of the NiO was shown to strongly depend on the oxygen content present in the SiC(O) matrix. Thus, larger oxygen contents induce homogeneously distributed flower-like NiO catalyst onto SiC(O).