Multiobjective vehicle routing problem with fixed delivery and optional collections

We present an adaption on the formulation for the vehicle routing problem with fixed delivery and optional collections, in which the simultaneous minimization of route costs and of collection demands not fulfilled is considered. We also propose a multiobjective version of the iterated local search (MOILS). The performance of the MOILS is compared with the $\epsilon $ -constrained ( $P_{\epsilon }$ ) ILS, the NSGA-II and the indicator-based multi-objective local search methods in the solution of 14 problem instances containing between 50 and 199 customers plus the depot. The results indicate that the MOILS outperformed the other approaches, obtaining significantly better average values for coverage, hypervolume and cardinality.     

Mechanism of generation of volatile species by aqueous boranes: Towards the clarification of most controversial aspects

The state of knowledge of the mechanisms involved in the chemical generation of volatile species (CHG) arising from aqueous phase reaction of classical hydride forming elements, transition and noble metals with borane complexes (mainly NaBH₄), has been critically reviewed in the light of evidences and literature data published in the last fifty years. The mechanisms, which are necessary to describe the reactivity of CHG system, are essentially: (i) the mechanism of hydrolysis of borane complexes, (ii) the mechanism of formation of volatile species, (iii) the mechanism of liquid phase interference and (iv) the mechanism of action of additives. Only the mechanisms (i) and (ii) have reached a good degree of rationalization, whereas more experimental evidences are necessary for the mechanisms (iii) and (iv). A more general reaction model for analytical CHG can be drawn according to the present state of knowledge, which is valid for both classical hydride forming elements and transition and noble metals. It is based on the formation of analyte–borane complex (ABC) intermediates through which takes place the direct, stepwise transfer of hydrogen atoms from boron to analyte substrate ML_n, (M is a metal or semi-metal, L is a ligand). By this way the original analyte substrate is stepwise converted to hydrido metal complexes MH_xL_y, then to the final products (hydride, metal atoms, etc). The clarification of several controversial aspects and the ruling out of wrong concepts, among them the “nascent” hydrogen theory, can been achieved in the light of the present state of knowledge.     

The Baeyer–Villiger oxidation of ketones: A paradigm for the role of soft Lewis acidity in homogeneous catalysis

The Baeyer–Villiger oxidation of ketones to the corresponding esters or lactones is a valuable transformation that has been upgraded several times over the last century, from the original use of monopersulfuric acid as oxidant to more atom efficient and environmentally friendly oxidants such as hydrogen peroxide. The latter requires activation with organometallic complexes to explicate its oxidizing power. The catalytic version of the reaction can be achieved with several transition metal catalysts, but major differences are present among the various catalysts proposed in terms of scope of the reaction. In particular, most of the catalytic systems are active towards four-membered ring ketones leading to the corresponding substituted γ-butyro-lactones. Pt^II complexes characterized by the employment of chelating diphosphines turned out to be the most efficient in catalyzing the BV oxidation of a wider range of substrates, in particular cyclohexanones are suitable substrates and acyclic ketones can be converted into the corresponding esters, albeit with low turnover. As long as organometallic catalyzed BV reaction is concerned, Pt^II catalysts show the most versatile activity and selectivity. Such peculiar features are the result of the unique electronic properties of such metal combined with an easily tailored soft Lewis acid character modulated by the proper choice of the ancillary ligands. The enantioselective version of the reaction benefits from these properties and the compatibility of Pt^II species with water enabled the development of asymmetric catalytic BV reactions in water aided by the presence of micelles as dynamic self-assembled environments.     

One‐Pot Preparation of Imines from Nitroarenes by a Tandem Process with an Ir–Pd Heterodimetallic Catalyst

A new tandem catalytic process has been studied for a heterodimetallic complex containing both iridium and palladium fragments connected by a 1,2,4‐trimethyltriazolyldiylidene ligand. The process implies the unprecedented preparation of imines from the direct reaction of nitroarenes and primary alcohols. The global process comprises the following steps: 1) reduction of the nitroarene to an amine, 2) oxidation of the alcohol to aldehyde, and 3) condensation of the aldehyde and the amine to form the corresponding imine. The oxidation of the alcohol to aldehyde is promoted by the iridium fragment, while the reduction of the nitro group to amine is facilitated by palladium. A wide set of different catalytic systems has been studied, showing that the Ir/Pd complex 1 is a highly active and stable catalyst in the preparation of imines.     

Probing dynamic protein ensembles with atomic proximity measures

The emerging role of internal dynamics in protein fold and function requires new avenues of structure analysis. We analyzed the dynamically restrained conformational ensemble of ubiquitin generated from residual dipolar coupling data, in terms of protruding and buried atoms as well as interatomic distances, using four proximity-based algorithms, CX, DPX, PRIDE and PRIDE-NMR (http://hydra.icgeb.trieste.it/protein/). We found that Ubiquitin, this relatively rigid molecule has a highly diverse dynamic ensemble. The environment of protruding atoms is highly variable across conformers, on the other hand, only a part of buried atoms tends to fluctuate. The variability of the ensemble cautions against the use of single conformers when explaining functional phenomena. We also give a detailed evaluation of PRIDE-NMR on a wide dataset and discuss its usage in the light of the features of available NMR distance restraint sets in public databases.     

Structural and Optical Properties of Novel Surfactant Coated TiO<Subscript>2</Subscript>–Ag Based Nanoparticles

Stable dispersions of surfactant-coated TiO₂–Ag based nanoparticles in apolar medium have been prepared by performing sequentially the hydrolysis of titanium(IV) isopropoxide and the reduction of Ag⁺ in the confined space of sodium bis(2-ethylhexyl)sulfosuccinate (NaAOT) reverse micelles. Depending on the sequence length, this novel procedure allowed the synthesis of semiconductor–metal nanoparticles, nominally indicated as TiO₂/Ag, TiO₂/Ag/TiO₂, and TiO₂/Ag/TiO₂/Ag, stabilized by a monolayer of oriented surfactant molecules. The structural characterization of these nanoparticles has been performed by High Resolution Transmission Electron Microscopy (HR-TEM), while optical properties were investigated by UV–Vis absorption and fluorescence spectroscopies. TEM investigation showed the presence of globular nanoparticles with an average diameter of about 10 nm composed by distinct amorphous TiO₂ and crystalline Ag glued domains whose structure depends on the sequence length. UV–Vis absorption measurements highlighted the mutual metal–semiconductor influence on the TiO₂ energy band gap and on the Ag plasmon resonance. Steady-state fluorescence spectra analysis allowed to reveal the strong inhibition of the electron–hole radiative recombination in the TiO₂ domains due to the Ag and the appearance of a new emission band centred in the 484–545 nm range. Possible attributions of the involved electronic transition of this last emission are discussed.     

An SPME–GC–MS method using an octadecyl silica fibre for the determination of the potential angiogenesis modulators 17β-estradiol and 2-methoxyestradiol in culture media

A simple and easily automable method based on solid-phase microextraction followed by gas chromatographic–mass spectrometric analysis was developed for the determination of two potential angiogenesis modulators 17β-estradiol (17-BE) and 2-methoxyestradiol (2-MEOE) in culture media. Trifluoroacetic anhydride was used as the derivatising agent. A homemade octadecyl silica coating, characterised by a coating thickness of 72 ± 10 μm and a good thermal stability until 250 °C, was prepared. Experimental design was used to optimise the extraction conditions in terms of derivatisation time, derivatisation temperature and time of extraction. As for method validation, lower limits of quantification of 0.17 and 0.015 μg/l for 17β-estradiol and 2-methoxyestradiol, respectively, were obtained. Finally, the capabilities of the developed fibres were evaluated for the analysis of the investigated analytes developed by granulosa cells in culture media maintained under normoxic, hypoxic and anoxic conditions, in order to better elucidate their possible role in the angiogenic process. An increase of the production of both 17-BE and 2-MEOE in hypoxic and anoxic conditions seems to be related to the effect of oxygen deprivation.