45S5 bioactive glass coatings by atmospheric plasma spraying obtained from feedstocks prepared by different routes

45S5 bioactive glass powders with the composition of 45 SiO₂, 6 P₂O₅, 24.5 CaO and 24.5 wt% Na₂O were melted and quenched in water to obtain a frit. The frit was milled using two different routes: dry milling followed by sieving to obtain glass particles and wet milling followed by spray drying to obtain a powder comprising porous agglomerates. All feedstocks showed adequate characteristics that make them suitable to be deposited by atmospheric plasma spraying. The powders and coatings were characterised by field-emission gun environmental scanning electron microscope and X-ray diffraction. The roughness and the contact angle of the coatings were also determined. The bioactivity of the powders and coatings was assessed by immersion in simulated body fluid. It was found that bioactive glass prepared from bioglass frit by dry milling exhibited similar bioactivity as that of a commercial bioactive glass. All coatings produced showed good adhesion to the substrate as well as suitable surface properties to ensure efficient contact with body fluid. Regardless of the characteristics of the feedstocks or plasma spray conditions used, all coatings were exclusively made up of an amorphous phase. On the other hand, micrographs revealed that the characteristics of the feedstock strongly impact on the final coating microstructure. The most homogeneous microstructure was obtained when the feedstock was prepared by fine dry grinding of the frit. For this coating, the formation of a bioactive layer was also proved by Fourier transform infrared spectroscopy and X-ray diffraction.     

Obtaining S–N curves from crack growth curves: an alternative to self-similarity

A crack growth model that allows us to obtain the S–N curves from the crack growth rate curves is presented in an attempt to harmonize the stress based and fracture mechanics approaches in lifetime prediction of long cracks propagation. First, using the Buckingham theorem, the crack growth rate curve $\frac{da}{dN}-\varDelta K$ is defined over all its range as a cumulative distribution function based on a normalized dimensionless stress intensity factor range $\varDelta K^+$ . Then, a relevant theorem is derived that provides an alternative to self-similarity allowing significant reduction of experimental planning. In this way, different $a-N$ crack growth curves for different stress ranges $\varDelta \sigma $ and initial crack lengths $a_0$ can be obtained from a particular crack growth curve under some conditions. The S–N field is obtained from the crack growth curves, showing the close relation between the fracture mechanics and stress approaches. Finally, the model is applied to a particular set of experimental data to obtain the crack growth rate curve and the S–N curves of a certain material for a subsequent fatigue lifetime assessment     

Understanding web site redesigns in small- and medium-sized enterprises (SMEs): a U.K.-based study on the applicability of e-commerce Stage Models

Despite the efforts of governments and the various support programmes, achievement of advanced stages of e-commerce by small- and medium-sized enterprises (SMEs) is still very low. There have been some attempts to study the dynamic nature of websites, but there is still little research evidence to explain why and how SMEs evolve their web presence. This paper aims to develop a comprehensive classification of drivers for web site redesign based on interviews with various members of staff from SMEs in the U.K. that have recently redesigned their web sites. A sequential mixed-methodological analysis, involving the use of qualitative and quantitative data analysis, was used to develop the classification. This enabled the development of a framework that classified seven main categories of drivers for web site redesign. The drivers identified were: changing business requirements, evolving internet strategies, addressing user needs, maintenance, changing technology, pressure from peers/competitors, and the influence of developers. However, only the first four were found to be significant in the study. The categorisation and the findings suggest a number of key determinants not explicitly addressed by other work. In addition, the findings provide little support for the staged approach to e-commerce progression as few companies reported the implementation of sophisticated internet technology features as a main reason for their web site redesigns. The contributions of this paper are firstly, to provide an instrument to the academic and practitioner communities interested in the topic of web site evolution. Secondly, the categorisation of drivers for redesign and the individual reasons found in this study are expected to provide assistance to SME managers to justify, plan and strategise internet investments realistically and effectively.     

High‐resolution solid‐state NMR investigation of the filler–rubber interaction: 2. High‐speed [1H] magic‐angle spinning NMR spectroscopy in carbon‐black‐filled polybutadiene

This work investigates the behaviour of elastomeric chains (polybutadienes of identical molecular weight but different microstructures) in the close vicinity of carbon black surfaces in order to attain a better understanding of the structure and properties of interphases. Elastomer–filler interactions are assessed through the study of the thermal properties and NMR relaxation characteristics of the corresponding materials. Three series of samples were compared: pure polymers, raw polymer–filler blends (filler loading ratio: 50 phr) and solvent‐extracted blends (so as to get rid of any polymer which is not under the influence of the solid surface). While differential scanning calorimetry points to the existence of an elastomer fraction which is not detected as undergoing the glass transition, ie is strongly immobilized, [¹H] high‐resolution high‐speed magic‐angle spinning solid‐state NMR provides information on the effect exerted by polymer–filler interactions on the mobility of the various constitutive species of the macromolecular backbone. A systematic study of the evolution of the spectral lines yielded by the samples indicates that 1,2‐polybutadiene moieties have a particular affinity towards the carbon black surface which suggests the occurrence of specific interactions at the elastomer–filler interface. © 2001 Society of Chemical Industry     

Oil and fungal biomass dispersion in a stirred tank containing a simulated fermentation broth

The production of γ‐decalactone by the filamentous fungus Trichoderma harzianum involves four phases (oil–water–air–mycelium) and its dispersion is crucial during fermentation. Oil and biomass (when present) dispersion, as a function of the volumetric power drawn (P/V), was characterized, in two; three‐ and four‐phase systems agitated with Rushton turbines. Trichoderma harzianum mycelium was used as the solid phase in the four‐phase system. Two stages of the fermentation were simulated: the beginning (15% oil and 1.4 kgm^?3 of mycelium) and the end (2% oil and 10.6 kg m^?3 of mycelium). In the two‐phase system, the use of exhausted broth achieved higher oil dispersions at low P/V values as compared with distilled water. Aeration decreased the oil dispersion for the high‐oil system, but enhanced oil dispersion for the low‐oil system. Compared with the P/V used in the actual fermentation (0.2 kW m^?3), a high segregation of the system was observed for the high‐oil/low‐biomass system, due to the difficulty of mixing the thick oil–air emulsion present at the top of the tank. The system simulating the end of the fermentation reached almost complete homogeneity of oil and biomass, a phenomenon due to the high biomass/oil ratio and the biomass acting as an oil carrier. © 2001 Society of Chemical Industry     

On multivariate order statistics. Application to ranked set sampling

Two new concepts of order statistics for multivariate samples are introduced. In one of the versions it turns out that not every multivariate order statistic is present in every sample. These order statistics have application in multivariate ranked set sampling and can be used to generate broad classes of multivariate densities in the sense of Jones. In this case the likelihood for the sample values and their corresponding ranks can be calculated based on the conditional density of a multivariate order statistics given its sample value, and such that its integral gives the probability for the multivariate order statistics under discussion to be observed. An alternative version of multivariate order statistics is also introduced, for which multivariate order statistics are always well defined and expressions for their marginal densities are derived. Since these multivariate order statistics are tailor made for multivariate ranked set sampling, their densities allow for parameter inference based on ranked set sampling. Some simulations show that both multivariate order statistics densities can be used with advantage with respect to simple random sampling.     

Easy extrusion of honeycomb-shaped monoliths using Moroccan natural clays and investigation of their dynamic adsorptive behavior towards VOCs

In the present work, honeycomb-shaped monoliths were easily extruded using local natural clays without the need of chemical binders. This finding allows significant cost reduction, in terms of not only additives and solvents but also the energy consumption required for their elimination by thermal treatment. The extruded monoliths were subject to mechanical strength testing in addition to the study of their thermal behavior, structural and textural properties. Moreover, one of their potential uses as VOCs adsorbents was evaluated in comparison with conventional packed bed by investigating their dynamic adsorptive and desorption behavior towards a model VOC of o-xylene type.     

Process Optimisation of In Situ H2 Generation From Ammonia Using Ni on Alumina Coated Cordierite Monoliths

A catalyst of Ni supported on alumina coated monolith has been prepared, characterized and tested in NH₃ decomposition. The characterization of the catalyst by XPS and TPR showed that there is no formation of aluminates after catalyst use. It is studied the effect of the space velocity, by varying the feed flow rate and the catalyst??s length. Some evidences are shown about the reaction inhibition by produced H₂ and about the reasons for the better performance of the monolith than packed bed catalyst.     

A multiplatform Java wrapper for the BioAPI framework

We present a solution for the development of multiplatform and web-oriented Java applications for biometric authentication based on the BioAPI framework. Our proposal is a single Java Native Interface wrapper that is compatible with the BioAPI instantiations of Windows and Linux/Unix operating systems. Following a study of existing wrappers, we extended the open-source Linux/Unix wrapper to include Windows support. In order to show the utility of this multiplatform Java wrapper, we discuss some of its possible uses and present a real-life application.