Multi-scale friction modeling for manufacturing processes: The boundary layer regime

This paper presents a multi-scale friction model for largescale forming simulations. A friction framework has been developed including the effect of surface changes due to normal loading and straining the underlying bulk material. A fast and efficient translation from micro to macro modeling, based on stochastic methods, is incorporated to reduce the computational effort. Adhesion and ploughing effects have been accounted for to characterize friction conditions on the micro scale. A discrete model has been adopted which accounts for the formation of contact patches ploughing through the contacting material. To simulate metal forming processes a coupling has been made with an implicit Finite Element code. Simulations on a typical metal formed product shows a distribution of friction values. The modest increase in simulation time, compared to a standard Coulomb-based FE simulation, proves the numerical feasibility of the proposed method

Real-life effectiveness of once-daily calcipotriol and betamethasone dipropionate gel vs. ointment formulations in psoriasis vulgaris: final analysis of the 52-week PRO-long study

Background: Topical therapies are the mainstay of treatment for psoriasis vulgaris. The fixed combination of calcipotriol (Cal) 50 mu g/g plus betamethasone 0.5 mg/g (as dipropionate; BD) is a first-line topical treatment and available as a gel or ointment. The use of these fixed combination products was compared in PRO-long, a long-term noninterventional study, for which interim results (4 and 12 weeks) have previously been reported. Objective: To describe and compare patients' perspectives on the fixed combination gel and ointment formulations; to include efficacy, adherence behaviour, treatment satisfaction and health-related quality of life (HRQoL) aspects during long-term real-life psoriasis management. Methods: PRO-long was a multicentre, prospective, observational, 52-week study of patients prescribed fixed combination Cal/BD gel or ointment in clinical practice. For final analysis the following were assessed at weeks 24, 36 and 52: differences in the proportion of patients with 'mild'/'very mild' disease according to patient's global assessment of disease severity, adherence behaviour, treatment satisfaction (nine-item treatment satisfaction questionnaire for medication) and HRQoL (Skindex-29). Results: Patients (n = 328) were prescribed once-daily Cal/BD gel (n = 152) or ointment (n = 176). At week 52, a higher proportion of patients reported that the severity of their psoriasis was 'mild'/'very mild' vs. baseline (gel: 60.2 vs. 47.1%; ointment: 58.8 vs. 42.4%), with greater treatment satisfaction reported in patients using gel vs. those using ointment. A higher proportion of patients found the gel 'easy' to use compared with the ointment (66.7 vs. 45.2%). Daily application of treatment took <= 5 min for 86.1% of patients using gel and 71.0% of patients using ointment. Conclusion: This real-life study has demonstrated similar effectiveness between the Cal/BD formulations. However, over a 52-week treatment period, patients reported greater treatment satisfaction with the gel, which was considered easier to use, faster to apply and overall a more convenient product

Bio-reduction of sulfide minerals to recover invisible gold

Sulfide minerals, like pyrite and arsenopyrite, are of economical interest due to the presence of invisible gold locked inside these minerals. As fine grinding is often not sufficient to liberate the gold from these minerals, additional destruction techniques, based on chemical and biological oxidation processes, are required to access the gold via cyanidation. These techniques have proven to be successful to reach satisfactory gold recoveries, but operation costs are high and challenging waste streams (sulfuric acid) are produced. As an alternative to the oxidation methods in this thesis the bio-reduction of sulfide minerals was proposed and investigated. Bio-reduction, the use of hydrogen to convert mineral-sulfur to hydrogen sulfide, has as major advantage that the hydrogen sulfide can be recovered from the solution (to produce bio-sulfur) leaving a waste stream without diluted sulfuric acid. Furthermore, electrical energy will be saved. Theoretically, this more environmental friendly alternative should work, but no bio-reduction reaction was observed in practice. It appeared that sulfur/sulfate reducing bacteria were not able to use sulfur when fixed in the crystal lattice of pyrite and arsenopyriteat the selected conditions (pH 5, 35ºC). In order to make the mineral-sulfur bio-available for these bacteria the sulfur should first enter the solution. As alternative the combination between partial bio-oxidation and bio-reduction was therefore investigated. Partial bio-oxidation at pH 2 results in the formation of elemental sulfur, which can serve as a substrate at pH 5 for the sulfur/sulfate reducing bacteria. This combined method was found to be successful at 35°C, as the gold leachability of the used concentrate was increased from 6% to 39%. Optimization of this process is needed to reach gold recoveries >90% in 1 or 2 ox/red cycles, but when successful a new method (called the Paroxsul process) with a lower environmental impact, less costs, and application to a large number of minerals, is ready to be introduced to the precious metal industry. </p

Two distinct AFLP types in three populations of marram grass (Ammophila arenaria in Wales)

The genetic structure of marram grass populations at coastal and inland locations, 200 m apart, was investigated at three sites by means of amplified fragment length polymorphism (AFLP) DNA markers. We expected a genetic differentiation between coastal and inland populations and more genetic variation in the coastal areas as a result of different events of colonization by different plant materials. An assignment test showed that the sampled Ammophila arenaria could be assigned to two groups based on AFLP data. The spatial distribution of the two AFLP types of A. arenaria varied with sampling location. In two of the three locations, mainly one type (1) was found in the newly formed dunes. This type did also occur further landward, but the second type (2) was preferentially found in inland populations. Genetic diversity was very low and of similar value in both coastal and inland populations. For each site, outlier loci with respect to FST value were identified, which may be indicative of different selection pressures in coastal compared with inland clusters. However, no identical outlier loci were found at all three sites. Possible explanations for the observed difference in distribution of type 1 and 2 populations between coastal and inland sites are discusse