Managing the tabu list length using a fuzzy inference system: an application to examination timetabling

In this paper, we present an application of Tabu Search (TS) to the examination timetabling problem. One of the drawbacks of this meta-heuristic is related to the need of tuning some parameter (like tabu tenure) whose value affects the performance of the algorithm. The importance of developing an automatic procedure is clear considering that most of the users of timetabling software, like academic staff, do not have the expertise to conduct such tuning. The goal of this paper is to present a method to automatically manage the memory in the TS using a Decision Expert System. More precisely a Fuzzy Inference Rule Based System (FIRBS) is implemented to handle the tabu tenure based on two concepts, “Frequency” and “Inactivity”. These concepts are related respectively with the number of times a move is introduced in the tabu list and the last time (in number of iterations) the move was attempted and prevented by the tabu status. Computational results show that the implemented FIRBS handles well the tuning of the tabu status duration improving, as well, the performance of Tabu Search.     

The role of excluded volume and electrostatics from coarse-grain modeling of the interaction of gemini surfactants with like-charged membranes

Cationic systems composed of lipids and/or surfactants are of paramount importance in a variety of applications. Within these, gemini have attracted particular attention, mainly due to their improved aggregation properties and to the possibility of tuning offered by the presence of a spacer. In this work, a Monte Carlo simulation study with a coarse-grained model was employed to assess the interaction of cationic gemini surfactants with a like-charged model membrane. Separating the contribution of the excluded volume and that of the electrostatic effects in the organization of gemini–lipid membranes was the first goal of this work and the role of these factors was assessed varying the concentration, the spacer length and the headgroup charge of gemini surfactants. The results provide a new insight on the organization of lipid headgroups in the vicinity of gemini surfactants. It was found that the surfactant–lipid interaction is strongly affected by the surfactant spacer length, being controlled by an overall balance between excluded volume and surfactant–lipid and surfactant–surfactant electrostatic effects. It is also seen that the out-of-plane motion of the spacer has a significant effect upon membrane organization and counterion condensation. Good agreement was found with results previously obtained from atomistic simulation.     

Does cation dehydration drive the binding of metal ions to polyelectrolytes in water? What we can learn from the behaviour of aluminium(III) and chromium(III)

Much stronger binding is seen in aqueous solutions between the anionic polyelectrolyte potassium poly(vinyl sulfate) and the substitution labile aluminium(III) than with the kinetically inert chromium(III). This strongly supports the idea that entropy driven water loss from the hydration sphere of the metal ion plays a major role in driving binding of the trivalent metal ion to the polyelectrolyte.     

Structure and order of DODAB bilayers modulated by dicationic gemini surfactants

Cationic liposomes have been extensively studied from the experimental and theoretical standpoints, motivated both by their fundamental interest and by potential applications in drug delivery and gene therapy. However, a detailed understanding of the nature of interactions within mixed bilayers containing cationic gemini surfactants is still lacking. This work focuses on the structural and dynamic properties of DODAB membranes in the presence of dicationic gemini surfactants. A thermodynamic characterization of the phase transitions in the mixed systems has been carried out by differential scanning calorimetry, while insight into the molecular interactions in the bilayer has been provided by molecular dynamics. For this purpose, variations in the gemini spacer and tail length, as well as in the respective molar fraction, have been included in both experimental and simulation studies. The results indicate that the influence of cationic gemini surfactants upon the thermotropic behavior and degree of order of DODAB structures is controlled by a complex interplay between charge density, conformation and hydrophobic effects, for which a detailed rationale is provided.     

Pre-analytical method for NMR-based grape metabolic fingerprinting and chemometrics

Although metabolomics aims at profiling all the metabolites in organisms, data quality is quite dependent on the pre-analytical methods employed. In order to evaluate current methods, different pre-analytical methods were compared and used for the metabolic profiling of grapevine as a model plant. Five grape cultivars from Portugal in combination with chemometrics were analyzed in this study. A common extraction method with deuterated water and methanol was found effective in the case of amino acids, organic acids, and sugars. For secondary metabolites like phenolics, solid phase extraction with C-18 cartridges showed good results. Principal component analysis, in combination with NMR spectroscopy, was applied and showed clear distinction among the cultivars. Primary metabolites such as choline, sucrose, and leucine were found discriminating for ‘Alvarinho’, while elevated levels of alanine, valine, and acetate were found in ‘Arinto’ (white varieties). Among the red cultivars, higher signals for citrate and GABA in ‘Touriga Nacional’, succinate and fumarate in ‘Aragonês’, and malate, ascorbate, fructose and glucose in ‘Trincadeira’, were observed. Based on the phenolic profile, ‘Arinto’ was found with higher levels of phenolics as compared to ‘Alvarinho’. ‘Trincadeira’ showed lowest phenolics content while higher levels of flavonoids and phenylpropanoids were found in ‘Aragonês’ and ‘Touriga Nacional’, respectively. It is shown that the metabolite composition of the extract is highly affected by the extraction procedure and this consideration has to be taken in account for metabolomics studies.     

Port wine spectronephelometry

The main purpose of this research was to create a portable equipment capable of measuring colour and turbidity during production of port wine. Actually, human, chemical and colour analysis are performed in key production stages for quality control. Several wine transformation processes are done without any kind of control. By using a fibre optic illuminator with a tungsten/halogen light source and a small spectrometer with fibre optic input, it was possible to perform angular measurements in wine samples. We have adapted these optical devices with a specially designed mechanical equipment which allows the passage of the wine during production. The spectral measurements were acquired in four different angular positions in a bypass of the mechanical support. This way we could determine colour coordinates and spectral transmittance and turbidity for three stages of a Ruby production. The entire equipment assembly had been previously calibrated in terms of colour and turbidity determination. The obtained results are in agreement with wine transformations between measurements, showing a small variation in colour and a high diminishing in spectral turbidity when filtration was performed. Transmittance has also increased after filtration turning the wine more limpid as it should be for human appreciation.     

Organic Fluorescent Thermometers Based on Borylated Arylisoquinoline Dyes

Borylated arylisoquinolines with redshifted internal charge‐transfer (ICT) emission were prepared and characterized. Upon heating, significant fluorescence quenching was observed, which forms the basis for a molecular thermometer. In the investigated temperature range (283–323 K) an average sensitivity of ?1.2 to ?1.8 % K^?1 was found for the variations in fluorescence quantum yield and lifetime. In the physiological temperature window (298–318 K) the average sensitivity even reaches values of up to ?2.4 % K^?1. The thermometer function is interpreted as the interplay between excited ICT states of different geometry. In addition, the formation of an intramolecular Lewis pair can be followed by ¹¹B NMR spectroscopy. This provides a handle to monitor temperature‐dependent ground‐state geometry changes of the dyes. The role of steric hindrance is addressed by the inclusion of a derivative that lacks the Lewis pair formation.