Dietary supplement for energy and reduced appetite containing the β-agonist isopropyloctopamine leads to heart problems and hospitalisations

In 2013 the Dutch authorities issued a warning against a dietary supplement that was linked to 11 reported adverse reactions, including heart problems and in one case even a cardiac arrest. In the UK a 20-year-old woman, said to have overdosed on this supplement, died. Since according to the label the product was a herbal mixture, initial LC-MS/MS analysis focused on the detection of plant toxins. Yohimbe alkaloids, which are not allowed to be present in herbal preparations according to Dutch legislation, were found at relatively high levels (400–900 mg kg^–1). However, their presence did not explain the adverse health effects reported. Based on these effects the supplement was screened for the presence of a β-agonist, using three different biosensor assays, i.e. the validated competitive radioligand β2-adrenergic receptor binding assay, a validated β-agonists ELISA and a newly developed multiplex microsphere (bead)-based β-agonist assay with imaging detection (MAGPIX^®). The high responses obtained in these three biosensors suggested strongly the presence of a β-agonist. Inspection of the label indicated the presence of N-isopropyloctopamine. A pure standard of this compound was bought and shown to have a strong activity in the three biosensor assays. Analysis by LC-full-scan high-resolution MS confirmed the presence of this ‘unknown known’ β3-agonist N-isopropyloctopamine, reported to lead to heart problems at high doses. A confirmatory quantitative analysis revealed that one dose of the preparation resulted in an intake of 40–60 mg, which is within the therapeutic range of this compound. The case shows the strength of combining bioassays with chemical analytical techniques for identification of illegal pharmacologically active substances in food supplements.     

Modeling and simulation of asymmetrical three-roll bending process

Asymmetrical three-roll bending is one of the three-roll bending processes widely used in metal forming due to its simple configuration. Modeling and simulation of the process based on finite element analyses has great interests to industrial practices. This paper deals with the prediction of the position of the lateral roll during cylindrical roll bending. In the numerical model, the rolls are assumed to be rigid bodies and the plate is assumed to be made of elasto-plastic material, with a bilinear material model corresponding to the results from tensile tests. Shell elements are applied to the plate and automatic node-to-surface contacts are selected for the interfaces between the plate and the rolls. The nonlinear equations are resolved by fully integrated Belytschko–Tsay shell formulation under the well-known ANSYS/LS-DYNA environment with explicit time integration. The positions of the lateral roll predicted by the numerical simulations agree well with experiments.     

Geopolymers from Algerian metakaolin. Influence of secondary minerals

The influence of secondary phases (illite, quartz) on the geopolymerization reaction of metakaolin has been investigated by comparing two metakaolins, one prepared from a pure kaolinite and the other from illite- and quartz-containing Algerian kaolin from the Tamazert region, respectively. Geopolymerization was achieved by mixing the metakaolins with an alkaline sodium silicate solution at room temperature and curing at 50 °C. The products were characterized by X-ray diffraction and ²⁹Si and ²⁷Al MAS-NMR. The results show that the secondary phases, at the concentration used in this work, do not prevent the geopolymerization reaction.     

On the relevance of non-standard theories of uncertainty in modeling and pooling expert opinions

Wu, Apostolakis and Okrent¹ have recently analyzed the current status of emerging alternatives to classical probabilistic methods in the modeling and pooling of expert opinions in safety analysis of engineering systems. They have pointed out some difficulties faced by these theories, due to their relative lack of maturity. This paper pursues the investigation so as to clarify some aspects of belief functions and possibility theories, and also to point out the need for further research. A comparison between the mathematical models of expert opinion pooling offered by Bayesian probabilities, belief functions and possibility theory is carried out. It is proved that the Bayesian approach that these authors advocate suffers from the same numerical stability problems as possibilistic and evidential rules of combination in the presence of strongly conflicting information due to their strong structural similarities. The problem of dependence between experts is briefly addressed. The other main point of this paper is that a single combination rule cannot reasonably address all situations where expert opinions must be pooled. It is suggested that the framework of possibility and evidence theories offers a more flexible framework for representing and combining subjective uncertain judgments than the one of subjective probability alone although some progress is required to reach the maturity of the Bayesian theory.     

Nonlinear state affine identification methods: Applications to electrical power plants

A nonlinear identification method by simple state-space models is proposed in the discrete-time case. This approach is suggested by theoretical results similar to the approximation property known for a long time for Volterra series. The proposed technique uses extensions with polynomial inputs of bilinear systems called state-affine systems. This modelling requires a small computing time and enables us to obtain nonlinear models which can be easily implemented on microprocessors and remain valid over a wide range of operating conditions. Several physical examples concerning electric power plants are also reported.     

Periodic-polynomial interpretation for structural properties of linear periodic discrete-time systems

The structural properties of linear periodic discrete-time systems are analyzed in the periodic polynomial representation. It is shown that the classical polynomial approach for linear time-invariant systems can be extended to periodic systems. New definitions and properties are given in terms of skew polynomial rings and periodic difference algebra. Necessary and sufficient conditions for the characterization of reachability, controllability, observability and reconstructibility are given in this framework.