Stereoselective Synthesis of Methyl 15,16-Epoxypimarates

Methyl 15,16-epoxypimarates are stereoselectively obtained from 15-hydroxy-16-tosyl derivatives by an intramolecular substitution     

Evaluating the reliability of analytical results using a probability criterion: a Bayesian perspective

Methods validation is mandatory in order to assess the fitness of purpose of the developed analytical method. Of core importance at the end of the validation is the evaluation of the reliability of the individual results that will be generated during the routine application of the method. Regulatory guidelines provide a general framework to assess the validity of a method, but none address the issue of results reliability. In this study, a Bayesian approach is proposed to address this concern. Results reliability is defined here as "the probability (π) of an analytical method to provide analytical results (X) within predefined acceptance limits (±λ) around their reference or conventional true concentration values (μ(T)) over a defined concentration range and under given environmental and operating conditions." By providing the minimum reliability probability (π(min)) needed for the subsequent routine application of the method, as well as specifications or acceptance limits (±λ), the proposed Bayesian approach provides the effective probability of obtaining reliable future analytical results over the whole concentration range investigated. This is summarised in a single graph: the reliability profile. This Bayesian reliability profile is also compared to two frequentist approaches, the first one derived from the work of Dewé et al. [W. Dewé, B. Govaerts, B. Boulanger, E. Rozet, P. Chiap, Ph. Hubert, Chemometr. Intell. Lab. Syst. 85 (2007) 262-268] and the second proposed by Govaerts et al. [B. Govaerts, W. Dewé, M. Maumy, B. Boulanger, Qual. Reliab. Eng. Int. 24 (2008) 667-680]. Furthermore, to illustrate the applicability of the Bayesian reliability profile, this approach is also applied here to a bioanalytical method dedicated to the determination of ketoglutaric acid (KG) and hydroxymethylfurfural (HMF) in human plasma by SPE-HPLC-UV.     

N‐tert‐Butyl‐N′‐(2‐cyclohexylamino‐5‐nitrobenzenesulfonyl)urea,BM531, a dual‐acting agent for thromboxane receptor antagonism and thromboxane synthase inhibition

The title compound (BM531), C₁₇H₂₆N₄O₅S, has been designed for use as both a thromboxane synthase inhibitor (TXSI) and a thromboxane receptor antagonist (TXRA). We report here the X‐ray crystal structure determination of the compound.     

Mathematical Level Raising Through Collaborative Investigations with the Computer

Investigations with the computer can have different functions in the mathematical learning process, such as to let students explore a subject domain, to guide the process of reinvention, or to give them the opportunity to apply what they have learned. Which function has most effect on mathematical level raising?We investigated that question in the context of developing learning materials for 16-year-old students in the domain of probability theory,consisting of computer simulations based on a gambling game and investigation tasks about these games. We compared the difference in level raising between three versions of the learning materials: investigations with the computer before, during or after the learning of a mathematical concept. It was shown that there was no significant difference in the final mathematical level that students attained in the three conditions (the product). However, there were differences in the level on which students approached the investigation tasks (the process). Furthermore,we found evidence of new categories in the students' answers, lying between the perceptual and conceptual levels, which may give important insight into the process of level raising. This revised version was published online in July 2006 with corrections to the Cover Date.     

Yielding of magnesium: From single crystal to polycrystalline aggregates

Hexagonal close-packed (hcp) metals show a deformation behavior, which is quite different from that of materials with cubic crystalline structure. As a consequence, rolled or extruded products of magnesium and its alloys exhibit a strong anisotropy and an unlike yielding in tension and compression. In this work, the microstructural mechanisms of deformation in pure magnesium are modeled by visco-plastic constitutive equations of crystal plasticity. Single crystals and textured polycrystals are analyzed numerically. By means of virtual mechanical tests of representative volume elements mesoscopic yield surfaces are generated. The linking of micro- and mesoscale provides a procedure for the simulation of the yielding and hardening behavior of arbitrarily textured solids with hcp structure such as extruded bars or rolled plates.     

(2RS,5SR,6SR)‐Methyl 4‐{cis‐2‐[3‐fluoro‐5‐(4‐methoxy‐3,4,5,6‐tetrahydro‐2H‐pyran‐4‐yl)phenoxy­methyl]‐6‐hydroxy‐3‐phenylmorpholino}­benzene­sulfinate

The title compound, C₃₀H₃₄FNO₇S, is a key inter­mediate in the design of dual 5‐LOX (5‐lipoxygenase)/COX‐2 (cyclo­oxygenase‐2) inhibitors. The compound crystallizes as a racemate. Linear hydrogen‐bonded chains are aligned along the [201] direction, and stacked π–π inter­actions and C—H⋯O contacts stabilize the crystal structure.     

Fuzzy implication operators for difference operations for fuzzy sets and cardinality-based measures of comparison

In this paper, we determine by means of fuzzy implication operators, two classes of difference operations for fuzzy sets and two classes of symmetric difference operations for fuzzy sets which preserve properties of the classical difference operation for crisp sets and the classical symmetric difference operation for crisp sets respectively. The obtained operations allow us to construct as in [B. De Baets, H. De Meyer, Transitivity-preserving fuzzification schemes for cardinality-based similarity measures, European Journal of Operational Research 160 (2005) 726–740], cardinality-based similarity measures which are reflexive, symmetric and transitive fuzzy relations and, to propose two classes of distances (metrics) which are fuzzy versions of the well-known distance of cardinality of the symmetric difference of crisp sets.     

Multistep and semibatch nitroxide‐mediated controlled free‐radical emulsion polymerization: A significant step toward conceivable industrial processes

Nitroxide‐mediated emulsion polymerizations of n‐butyl acrylate and styrene were performed with a monofunctional, water‐soluble alkoxyamine initiator and a difunctional one. Two different processes were applied, either in two steps or under semibatch conditions. In particular, the polymerization times were strongly reduced, while high conversions and good control over the polymer characteristics were maintained. In all cases, stable latexes were recovered; with the difunctional initiator in particular, they exhibited small particles and narrow particle size distributions. © 2006 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 44: 4142–4153, 2006     

Une approche formelle unifiée des théories de plaques et poutres linéairement élastiques

In this Note we present a formal scaling method that allows for the deduction from three-dimensional linearized elasticity of the equations of shearable structures such as Reissner–Mindlin's equations for plates and Timoshenko's equations for rods, as well as other models of thin structures. This method is based on the requirement that a scaled energy functional possibly including second-gradient terms stay bounded in the limit of vanishing ‘thinness’. To cite this article: B. Miara, P. Podio-Guidugli, C. R. Acad. Sci. Paris, Ser. I 343 (2006).