Hybrid flowshop with unrelated machines, sequence-dependent setup time, availability constraints and limited buffers

This paper presents a genetic algorithm for an important production scheduling problem. Since the problem is NP-hard, we focus on suboptimal scheduling solutions for the hybrid flowshop with unrelated machines, sequence-dependent setup time, availability constraints, and limited buffers. The production environment of a television assembly line for inserting electronic components is considered. The proposed genetic algorithm is a modified and extended version of the algorithm for a problem without limited buffers. It takes into account additional limited buffer constraints and uses a new crossover operator and stopping criteria. Experimental results carried out on real production settings show an improvement in scheduling when the proposed algorithm is used.     

Meta-QSAR: a large-scale application of meta-learning to drug design and discovery

We investigate the learning of quantitative structure activity relationships (QSARs) as a case-study of meta-learning. This application area is of the highest societal importance, as it is a key step in the development of new medicines. The standard QSAR learning problem is: given a target (usually a protein) and a set of chemical compounds (small molecules) with associated bioactivities (e.g. inhibition of the target), learn a predictive mapping from molecular representation to activity. Although almost every type of machine learning method has been applied to QSAR learning there is no agreed single best way of learning QSARs, and therefore the problem area is well-suited to meta-learning. We first carried out the most comprehensive ever comparison of machine learning methods for QSAR learning: 18 regression methods, 3 molecular representations, applied to more than 2700 QSAR problems. (These results have been made publicly available on OpenML and represent a valuable resource for testing novel meta-learning methods.) We then investigated the utility of algorithm selection for QSAR problems. We found that this meta-learning approach outperformed the best individual QSAR learning method (random forests using a molecular fingerprint representation) by up to 13%, on average. We conclude that meta-learning outperforms base-learning methods for QSAR learning, and as this investigation is one of the most extensive ever comparisons of base and meta-learning methods ever made, it provides evidence for the general effectiveness of meta-learning over base-learning.     

Towards nanoporous membranes based on ABC triblock terpolymers

Block copolymers represent an exciting class of complex materials as they self-assemble into highly regular structures of nanoscopic dimensions. When prepared as thin films, such structures can be used for a variety of applications including lithographic masks or nanoporous membranes. Reported here are nanostructures in thin films of structurally analogous polybutadiene-block-poly(2-vinyl pyridine)-block-poly(tert-butyl methacrylate) (BVT) and polystyrene-block-poly(2-vinyl pyridine)-block-poly(tert-butyl methacrylate) (SVT) triblock terpolymers, which are synthesized via sequential living anionic polymerization. The morphological behavior of annealed SVT and BVT films is investigated by scanning force and electron microscopies. The difference in the terpolymer composition results in the formation of an ordered perforated lamella phase in SVT films and hexagonally packed core/shell cylinders in BVT films. Further, the BVT films show high potential for the fabrication of composite membranes using track-etched poly(ethylene terephthalate) macroporous filters as a support.     

Light scattering study of sodium caseinate + dextran sulfate in aqueous solution: Relationship to emulsion stability

Using combined static and dynamic light scattering, various structural and thermodynamic parameters have been determined for the complex particles formed from sodium caseinate (0.5 wt/v%) + dextran sulfate (0.01, 0.1 or 1.0 wt/v%) in aqueous solution at pH = 6.0. The polysaccharide contents refer, respectively, to three polysaccharide/protein molar ratios (R = 1, 10 and 100) calculated on the basis of the measured values of the weight-average molar masses of sodium caseinate particles and dextran sulfate molecules. The complexes were prepared by mixing together the two biopolymer components in bulk solution or bringing them together at the interface in a protein-stabilized foam. The results indicate dissociation of the original sodium caseinate particles in response to associative interactions with excess amounts of negatively charged polysaccharide. A significant difference was observed between properties of complexes formed in solution and those formed at the interface, especially for R = 100. We identify a possible correlation between the structures of these complexes and the recently reported stability properties of oil-in-water emulsions containing the same biopolymers (Jourdain, L., Leser, M. E., Schmitt, C., Michel, M., & Dickinson, E. (2008). Food Hydrocolloids, 22, 647–659). In particular, we infer that the greater hydrophilicity and the more open/bulky architecture of complexes formed in the bulk aqueous phase are better able to provide effective steric/electrostatic stabilization of the so-called “mixed” emulsions, as compared with the interfacial complexes formed in the so-called “bilayer” emulsions. We also present results on the effect of ionic strength on the structural parameters of the complexes, and we attempt to interpret the data in the context of previously determined stability behaviour of the corresponding emulsions.     

Design,Synthesis, and Biological Evaluation of (+)-Camphor- and (−)-Fenchone-Based Derivatives as Potent Orthopoxvirus Inhibitors

In this work, a library of (+)-camphor and (−)-fenchone based N-acylhydrazones, amides, and esters, including para-substituted aromatic/hetaromatic/cyclohexane ring was synthesized, with potent orthopoxvirus inhibitors identified among them. Investigations of the structure-activity relationship revealed the significance of the substituent at the para-position of the aromatic ring. Also, the nature of the linker between a hydrophobic moiety and aromatic ring was clarified. Derivatives with p-Cl, p-Br, p-CF_3, and p-NO₂ substituted aromatic ring and derivatives with cyclohexane ring showed the highest antiviral activity against vaccinia virus, cowpox, and ectromelia virus. The hydrazone and the amide group were more favourable as a linker for antiviral activity than the ester group. Compounds 3 b and 7 e with high antiviral activity were examined using the time-of-addition assay and molecular docking study. The results revealed the tested compounds to inhibit the late processes of the orthopoxvirus replication cycle and the p37 viral protein to be a possible biological target.