Preparation of barium hexaferrite coatings using atmospheric plasma spraying

Thick coatings of barium hexaferrite with the compositions BaFe₁₂O₁₉ and BaCoTiFe₁₀O₁₉ were prepared using atmospheric plasma spraying (APS) technology. The coatings were prepared from pre-reacted powders of the desired composition. The as-deposited coatings were poorly crystallized, but their crystallinity was improved with a subsequent annealing. The crystallization mechanism of the sprayed hexaferrites was studied during annealing up to 1300 °C, using X-ray powder diffraction combined with thermal analysis and with electron microscopy including microanalysis. Single-phase coatings were obtained after annealing treatments at 1100–1300 °C. Their magnetic properties showed that they would be suitable for absorbers at microwave and mm-wave frequencies, depending on the coating phase's composition, the crystallinity and the thicknesses.     

Poly(2,6-dimethyl-1,4-phenylene oxide)/polystyrene blends: thermodynamic interactions from glass transition data

Summary The glass transition temperatures of several blends of poly(2,6-dimethyl-1,4-phenylene oxide) and polystyrene have been measured by DSC, and the T _g -composition data have been described on the basis of a thermodynamic treatment. A negative enthalpy of mixing and a positive entropy of mixing have been found, in agreement with the well known miscibility of the blend. The presence of a singolarity point in the T _g -composition plot has been evidenced and considered at the light of a theoretical treatment recently proposed. Received: 27 November 1998/Accepted: 13 March 1999     

Interplay of strengthening mechanisms in the interaction of a ½〈1 1 1〉 screw dislocation with Cr precipitates in bcc Fe: An atomistic study

The interaction of Cr precipitates with a ½〈1 1 1〉 screw dislocation in bcc Fe is studied using molecular static calculations to evaluate the contributions from different strengthening mechanisms. The total interaction energy of the precipitate and the dislocation, the surface energy created due to the precipitate shearing and the shear modulus misfit interaction energy were estimated separately. Based on these data the shear modulus misfit was concluded to be the main mechanism determining the precipitate resisting force for the passage of a ½〈1 1 1〉 screw dislocation.     

Some problems related to an environmental factual database: the case Aeolian project

Factual databanks can make an important contribution to environmental management. They help considerably with the difficult processes of integrating the various scientific languages used, and also with the development of valid methods for interdisciplinary research. In the planning the Aeolian project (a multidisciplinary study of an Archipelago north of Sicily), it was considered useful to include a group of workers on methodology and computer science. The hope is that they will help to facilitate the exchange of data and thus contribute to a better understanding of the various phenomena occurring on the islands. This paper discusses the conceptual working aspects of environmental information, together with those characteristics that render it suitable for inclusion in a modern computer‐based system.     

First carbon ring closures started by the combustive radical addition of propargyl to butadiyne. A theoretical study

Formation of the first ring structure from small aliphatic molecules is often regarded as the rate-determining step (and in any case as a step of paramount importance) in the combustive growth of larger aromatic systems and soot lamellae. Among possible reactions able to start off this process, the radical addition of the propargyl radical to butadiyne (diacetylene) has been recently studied theoretically [G. da Silva, A. Trevitt, Phys. Chem. Chem. Phys. 13 (2011) 8940] and shown to lead preferentially to a 5-membered ring intermediate. The same reaction is here addressed focusing instead on the possible formation of 6-membered rings. The large variety of partially intertwined reaction pathways is the basis for a subsequent RRKM study (carried out at different combustion temperatures). It confirms, on one hand, the favored formation of fulvenallenyl radical indicated by da Silva and Trevitt, but also indicates the possible formation of six-membered cyclic systems as minor products. In particular, at high pressure, six-membered ring system yields are very low, but at lower pressures a more significant yield of six-membered ring product is predicted.     

Model-based dynamic compensation of load cell response in weighing machines affected by environmental vibrations

This work proposes and validates experimentally a model-based scheme for the compensation of environmental vibrations affecting load cell measurements in automatic weighing machines. Weighing machines are often adversely affected by low frequency vibrations which may arise from the coupled effects of machine frame flexibility and the excitation induced by internal (inertial) or external (impact) vibration sources. These vibrations are generally named “environmental vibrations”, since they seem to arise from the environment around the machine. Environmental vibrations have a detrimental effect on load cell responses and can in turn deteriorate machine performances. It is usually ineffective to try overcoming this problem by low-pass filtering load cell measurements: low cut-off frequencies usually downgrade machine speed by both introducing delay and increasing filtered signal rise time. Since automatic weighing machines need to operate at ever increasing speed, alternative approaches must be investigated. In this work it is suggested to make use of the mechanical models of the weighing machine and the load cells to process supplementary accelerometer measurements and compute an effective compensation of the effect of environmental vibrations on load cell response. The technique is here applied to a multi-head weighing machine in order to prove its effectiveness and implementability in industrial devices with real-time controllers.     

The variable sample size t control chart for monitoring short production runs

Starting the online monitoring of a quality characteristic by means of a control chart at the beginning of a short production run is often a challenging issue for quality practitioners: in fact, the frequent absence of preliminary information prevents from getting a precise estimate of the characteristic mean and standard deviation. Furthermore, for short runs having a finite rolling horizon, the number of inspections scheduled within the run can be too small to get sufficient samples allowing the phase I implementation of the chart to be completed. Recently, t control charts have been proposed as efficient means to overcome this problem because they do not need any phase I tentative control limits definition or preliminary process knowledge. In this paper, a variable sample size (VSS) version of the t chart is proposed. Adaptive control charts have been implemented with success in long runs: here, the performance of the variable sample size strategy is investigated for a chart used in a short run. The statistical performance of the VSS t chart is compared with the one of the fixed-parameter (FP) t chart for both scenarios of fixed and unknown shift size, with the latter situation being frequent in short-run manufacturing environments. An extensive numerical investigation reveals the potential benefits of the proposed chart. When the statistical design is optimized with respect to a fixed value of the shift size δ, the VSS t chart has a better statistical performance than the FP t chart for moderate to large values of δ. Conversely, for the unknown shift size condition, the VSS t chart always outperforms the FP t chart for in-control average sample sizes ASS₀?>?7. An illustrative example shows the implementation of the VSS during the production of a finite lot of mechanical parts.     

Mechanisms of Action of Non-Steroidal Anti-Inflammatory Drugs (NSAIDs) and Mesalazine in the Chemoprevention of Colorectal Cancer

Colorectal cancer (CRC) is the third most common malignant neoplasm worldwide. Although conclusive evidence is still lacking, epidemiologic studies suggest that long-term use of non-steroidal anti-inflammatory drugs (NSAIDs) has chemopreventive properties against CRC. Similarly, regular consumption of mesalazine, a drug structurally related to NSAIDs, seems to reduce the risk of CRC in patients with ulcerative colitis. These observations are supported by a large body of experimental data showing the ability of such drugs to inhibit multiple pathways that sustain colon carcinogenesis. This review summarizes the current information on the molecular mechanisms by which NSAIDs and mesalazine could interfere with CRC cell growth and survival.     

Fast patterning of poly(methyl methacrylate) by a novel soft molding approach and its application to the fabrication of silver structures

A novel single-step approach for the fabrication of poly(methyl methacrylate) structures by soft molding of a 5 wt% solution in acetone is reported. The use of a low weight solution and of a solvent with high volatility ensures a very fast patterning, down to 10 s. In addition, the process is extremely simple and cost-effective, since just one elastomeric mold is needed, and areas as large as 1 cm² were patterned uniformly and defect-free. The process was applied to the fabrication of silver structures by silver deposition via electroless plating or evaporation followed by poly(methyl methacrylate) removal. Structures of various shapes and sizes, with dimensions in the micrometer and submicrometer range were successfully fabricated, showing the versatility of the process. This silver patterning process is particularly well suited for applications in microelectronics and optoelectronics, such as the fabrication of transparent electrodes for solar cells and displays, manufacturing of metal etching masks and wiring of printed circuits.