Ring-opening polymerization of DD-lactide catalyzed by Novozyme 435

In contrast to LLA, DLA is converted in toluene solution under mild reaction conditions (50-70 degrees C) using Novozyme 435 (immobilized CALB) to form the corresponding polymer. The influence of several parameters, such as enzyme concentration, temperature and monomer concentration, on the polymerization rate and the monomer conversion was studied. In contrast to the Novozyme 435 catalyzed polymerization of epsilon-caprolactone, enzyme deactivation occurs. It is attributed to the deprivation of water from the enzyme. This work points out that by careful selection of the reaction conditions, it is possible to obtain poly(D-lactide) in reasonable molecular weights and in high yields using Novozyme 435 catalysis.     

A reference-gene-based quantitative PCR method as a tool to determine <Emphasis Type="Italic">Fusarium</Emphasis> resistance in wheat

In recent years, plant breeders made great progress in breeding Fusarium-tolerant wheat lines. However, total resistance to this genus of plant pathogenic fungi has not yet been achieved as the resistance genes are located on several distinct genetic regions. Visual scoring of disease symptoms in combination with the analysis of mycotoxins is commonly applied to assess the tolerance of new lines. Both approaches are indirect methods and do not mandatorily determine the accumulated fungal biomass. Quantitative PCR is a useful tool to assess fungal biomass based on the abundance of organism-specific DNA. The aim of this study was the development of a quantitative PCR assay for trichothecene-producing Fusarium species and to adapt this method for resistance assessment of wheat lines artificially infected with Fusarium graminearum and Fusarium culmorum. Several DNA-extraction methods for wheat samples were evaluated and optimized for downstream real-time PCR analysis and furthermore, a new reference-gene-based approach for more accurate quantification of Fusarium biomass in cereals is presented. The co-determination of a plant gene was used to compensate for unequal DNA-extraction efficiencies.     

Ant colony optimization with a specialized pheromone trail for the car-sequencing problem

This paper studies the learning process in an ant colony optimization algorithm designed to solve the problem of ordering cars on an assembly line (car-sequencing problem). This problem has been shown to be NP-hard and evokes a great deal of interest among practitioners. Learning in an ant algorithm is achieved by using an artificial pheromone trail, which is a central element of this metaheuristic. Many versions of the algorithm are found in literature, the main distinction among them being the management of the pheromone trail. Nevertheless, few of them seek to perfect learning by modifying the internal structure of the trail. In this paper, a new pheromone trail structure is proposed that is specifically adapted to the type of constraints in the car-sequencing problem. The quality of the results obtained when solving three sets of benchmark problems is superior to that of the best solutions found in literature and shows the efficiency of the specialized trail.     

An axiomatic analysis of concordance–discordance relations

Outranking methods propose an original way to build a preference relation between alternatives evaluated on several attributes that has a definite ordinal flavor. Indeed, most of them appeal the concordance/non-discordance principle that leads to declaring that an alternative is “superior” to another, if the coalition of attributes supporting this proposition is “sufficiently important” (concordance condition) and if there is no attribute that “strongly rejects” it (non-discordance condition). Such a way of comparing alternatives is rather natural. However, it is well known that it may produce binary relations that do not possess any remarkable property of transitivity or completeness. This explains why the axiomatic foundations of outranking methods have not been much investigated, which is often seen as one of their important weaknesses. This paper uses conjoint measurement techniques to obtain an axiomatic characterization of preference relations that can be obtained on the basis of the concordance/non-discordance principle. It emphasizes their main distinctive feature, i.e. their very crude way to distinguish various levels of preference differences on each attribute. We focus on outranking methods, such as ELECTRE I, that produce a reflexive relation, interpreted as an “at least as good as” preference relation. The results in this paper may be seen as an attempt to give such outranking methods a sound axiomatic foundation based on conjoint measurement.     

Existence of non-trivial harmonic functions on Cartan–Hadamard manifolds of unbounded curvature

The Liouville property of a complete Riemannian manifold M (i.e., the question whether there exist non-trivial bounded harmonic functions on M) attracted a lot of attention. For Cartan–Hadamard manifolds the role of lower curvature bounds is still an open problem. We discuss examples of Cartan–Hadamard manifolds of unbounded curvature where the limiting angle of Brownian motion degenerates to a single point on the sphere at infinity, but where nevertheless the space of bounded harmonic functions is as rich as in the non-degenerate case. To see the full boundary the point at infinity has to be blown up in a non-trivial way. Such examples indicate that the situation concerning the famous conjecture of Greene and Wu about existence of non-trivial bounded harmonic functions on Cartan–Hadamard manifolds is much more complicated than one might have expected.      

Examples of scalar-flat hypersurfaces in $${\mathbb{R}^{n+1}}$$

Given a hypersurface M of null scalar curvature in the unit sphere , n ≥ 4, such that its second fundamental form has rank greater than 2, we construct a singular scalar-flat hypersurface in as a normal graph over a truncated cone generated by M. Furthermore, this graph is 1-stable if the cone is strictly 1-stable.     

Hybrid Flow-Shop: a Memetic Algorithm Using Constraint-Based Scheduling for Efficient Search

The paper considers the hybrid flow-shop scheduling problem with multiprocessor tasks. Motivated by the computational complexity of the problem, we propose a memetic algorithm for this problem in the paper. We first describe the implementation details of a genetic algorithm, which is used in the memetic algorithm. We then propose a constraint programming based branch-and-bound algorithm to be employed as the local search engine of the memetic algorithm. Next, we present the new memetic algorithm. We lastly explain the computational experiments carried out to evaluate the performance of three algorithms (genetic algorithm, constraint programming based branch-and-bound algorithm, and memetic algorithm) in terms of both the quality of the solutions produced and the efficiency. These results demonstrate that the memetic algorithm produces better quality solutions and that it is very efficient.