Adaptative Biaryl Phosphite–Oxazole and Phosphite–Thiazole Ligands for Asymmetric Ir‐Catalyzed Hydrogenation of Alkenes

A library of readily available phosphite–oxazole/thiazole ligands ( L1 a – g – L7 a – g ) was applied in the Ir‐catalyzed asymmetric hydrogenation of several largely unfunctionalized E‐ and Z‐trisubstituted and 1,1‐disubstituted terminal alkenes. The ability of the catalysts to transfer chiral information to the product could be tuned by choosing suitable ligand components (bridge length, the substituents in the heterocyclic ring and the alkyl backbone chain, the configuration of the ligand backbone, and the substituents/configurations in the biaryl phosphite moiety), so that enantioselectivities could be maximized for each substrate as required. Enantioselectivities were therefore excellent (enantiomeric excess (ee) values up to >99 %) for a wide range of E‐ and Z‐trisubstituted and 1,1‐disubstituted terminal alkenes. The biaryl phosphite moiety was a very advantageous ligand component in terms of substrate versatility.     

Relaxed loading conditions for higher order homogenisation approaches

The present paper deals with the formulation of minimal loading conditions for the application of numerical homogenisation techniques, namely the FE² methodology. Based on the set of volume averaging rules connecting the heterogeneous micro and the homogeneous macro scale, the minimal constraints on the deformation of a micro volume are derived for a classical Cauchy continuum as well as for a micromorphic continuum theory. For both cases, numerical studies are included highlighting the main aspects of the proposed procedure within the context of small deformations. (© 2011 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim)     

On the Bergman Theory for Solenoidal and Irrotational Vector Fields. II. Conformal Covariance and Invariance of the Main Objects

This is a continuation of our work (González-Cervantes et al. in On the Bergman theory for solenoidal and irrotational vector fields. I. General theory. Operator theory: advances and applications. Birkhauser, accepted) where for solenoidal and irrotational vector fields theory as well as for the Moisil–Théodoresco quaternionic analysis we introduced the notions of the Bergman space and the Bergman reproducing kernel and studied their main properties. In particular, we described the behavior of the Bergman theory for a given domain whenever the domain is transformed by a conformal map. The formulas obtained hint that the corresponding objects (spaces, operators, etc.) can be characterized as conformally covariant or invariant, and in the present paper we construct a series of categories and functors which allow us to give such characterizations in precise terms.     

A new diversity induction mechanism for a multi-objective ant colony algorithm to solve a real-world time and space assembly line balancing problem

Time and space assembly line balancing considers realistic multi-objective versions of the classical assembly line balancing industrial problems. It involves the joint optimisation of conflicting criteria such as the cycle time, the number of stations, and/or the area of these stations. The different problems included in this area also inherit the precedence constraints and the cycle time limitations from assembly line balancing problems. The presence of these hard constraints and their multi-criteria nature make these problems very hard to solve. Multi-objective constructive metaheuristics (in particular, multi-objective ant colony optimisation) have demonstrated to be suitable approaches to solve time and space assembly line balancing problems. The aim of this contribution is to present a new mechanism to induce diversity in an existing multi-objective ant colony optimisation algorithm for the 1/3 variant of the time and space assembly line balancing problem. This variant is quite realistic in the automative industry as it involves the joint minimisation of the number and the area of the stations given a fixed cycle time limit. The performance of our proposal is validated considering ten real-like problem instances. Moreover, the diversity induction mechanism is also tested on a real-world instance from the Nissan plant in Barcelona (Spain).     

Trends in aircraft noise annoyance: the role of study and sample characteristics

Recently, it has been suggested that the annoyance of residents at a given aircraft noise exposure level increases over the years. The objective of the present study was to verify the hypothesized trend and to identify its possible causes. To this end, the large database used to establish earlier exposure-response relationships on aircraft noise was updated with original data from several recent surveys, yielding a database with data from 34 separate airports. Multilevel grouped regression was used to determine the annoyance response per airport, after which meta-regression was used to investigate whether study characteristics could explain the heterogeneity in annoyance response between airports. A significant increase over the years was observed in annoyance at a given level of aircraft noise exposure. Furthermore, the type of annoyance scale, the type of contact, and the response percentage were found to be sources of heterogeneity. Of these, only the scale factor could statistically account for the trend, although other findings rule it out as a satisfactory explanation. No evidence was found for increased self-reported noise sensitivity. The results are of importance to the applicability of current exposure-annoyance relationships for aircraft noise and provide a basis for decisions on whether these need to be updated.     

Slow light in molecular-aggregate nanofilms

We study slow-light performance of molecular aggregates arranged in nanofilms by means of coherent population oscillations. The molecular cooperative behavior inside the aggregate enhances the delay of input signals in the gigahertz range in comparison with other coherent population oscillation-based devices. Moreover, the problem of residual absorption present in coherent population oscillation processes is removed. We also propose an optical switch between different delays by exploiting the optical bistability of these aggregates.     

Adaptive optics wide-field microscopy using direct wavefront sensing

We report a technique for measuring and correcting the wavefront aberrations introduced by a biological sample using a Shack-Hartmann wavefront sensor, a fluorescent reference source, and a deformable mirror. The reference source and sample fluorescence are at different wavelengths to separate wavefront measurement and sample imaging. The measurement and correction at one wavelength improves the resolving power at a different wavelength, enabling the structure of the sample to be resolved.