Preliminary study of multi-objective features selection for evolving software product lines

When dealing with software-intensive systems, it is often beneficial to consider families of similar systems together. A common task is then to identify the particular product that best fulfils a given set of desired product properties. Software Product Lines Engineering (SPLE) provides techniques to design, implement and evolve families of similar systems in a systematic fashion, with variability choices explicitly represented, e.g., as Feature Models. The problem of picking the ‘best’ product then becomes a question of optimising the Feature Configuration. When considering multiple properties at the same time, we have to deal with multi-objective optimisation, which is even more challenging. While change and evolution of software systems is the common case, to the best of our knowledge there has been no evaluation of the problem of multi-objective optimisation of evolving Software Product Lines. In this paper we present a benchmark of large scale evolving Feature Models and we study the behaviour of the state-of-the-art algorithm (SATIBEA). In particular, we show that we can improve both the execution time and the quality of SATIBEA by feeding it with the previous configurations: our solution converges nearly 10 times faster and gets an 113% improvement after one generation of genetic algorithm

Electrochemically Induced C−Br and C−I Bond Activation by the Pd₃(dppm)₃CO²⁺ Cluster, and Characterization of the Reactive Pd₃(dppm)₃CO⁺ Intermediate: The First Confidently Identified Paramagnetic Pd Cluster

Electrochemically Induced C−Br and C−I Bond Activation by the Pd3(dppm)3CO2+ Cluster, and Characterization of the Reactive Pd3(dppm)3CO+ Intermediate:  The First Confidently Identified Paramagnetic Pd Cluste

Stoichiometric and Catalytic Activation of the α- and β-2,3,4-Tri-<i>O</i>-Acetyl-5-Thioxylopyranosyl Bromide Inside the Cavity of the Pd₃(dppm)₃(CO)²⁺ Cluster

The title cluster (Pd32+) exhibits a pronounced affinity for Br- ions to form the very stable Pd3(Br)+ adduct. Upon a 2-electron reduction, a dissociative process occurs generating Pd30 and eliminating Br- according to an ECE mechanism (electrochemical, chemical, electrochemical). At a lower temperature (i.e. −20 °C), both ECE and EEC processes operate. This cluster also activates the C−Br bond, and this work deals with the reactivity of Pd32+ with 2,3,4-tri-O-acetyl-5-thioxylopyranosyl bromide (Xyl−Br), both α- and β-isomers. The observed inorganic product is Pd3(Br)+ again, and it is formed according to an associative mechanism involving Pd32+···Xyl−Br host−guest assemblies. In an attempt to render the C−Br bond activation catalytic, these species are investigated under reduction conditions at two potentials (−0.9 and −1.25 V vs SCE). In the former case, the major product is Xyl−H, issued from a radical intermediate Xyl• abstracting an H atom from the solvent. Evidence for Xyl• is provided by the trapping with TEMPO (2,2,6,6-tetramethyl-1-piperidinyloxy) and DMPO (5,5‘-dimethylpyrroline-N-oxyde). In the second case, only one product is observed, 3,4-di-O-acetyl-5-thioxylal, which is issued from the Xyl- intermediate anion

Thermodynamic and Kinetic Control over the Reduction Mechanism of the Pd₃(dppm)₃(CO)(I)⁺ Cluster

The reduction mechanism of the title cluster has been investigated by means of cyclic voltammetry (CV), rotating disk electrode (RDE) voltammetry, and coulometry. The 2-electron reduction proceeds via two routes simultaneously. The first one involves two 1-electron reduction steps, followed by an iodide elimination to form the neutral Pd3(dppm)3(CO)0 cluster (EEC mechanism). The second one is a 1-electron reduction process, followed by an iodide elimination, then by a second 1-electron step (ECE mechanism) to generate the same final product. Control over these two competitive mechanisms can be achieved by changing temperature, solvent polarity, iodide concentration, or sweep rate. The reoxidation of the Pd3(dppm)3(CO)0 cluster in the presence of iodide proceeds via a pure ECE pathway. The overall results were interpreted with a six-member square scheme, and the cyclic and RDE voltammograms were simulated, in order to extract the reaction rate and equilibrium constants for iodide exchange for all three Pd3(dppm)3(CO)(I)n (n = +1, 0, −1) adducts

Thermal and Electrochemically Assisted Pd−Cl Bond Cleavage in the d⁹−d⁹ Pd₂(dppm)₂Cl₂ Complex by Pd₃(dppm)₃(CO)<i>ⁿ</i>⁺ Clusters (<i>n</i> = 2, 1, 0)

A new aspect of reactivity of the cluster [Pd3(dppm)3(μ3-CO)]n+, ([Pd3]n+, n = 2, 1, 0) with the low-valent metal−metal-bonded Pd2(dppm)2Cl2 dimer (Pd2Cl2) was observed using electrochemical techniques. The direct reaction between [Pd3]2+ and Pd2Cl2 in THF at room temperature leads to the known [Pd3(dppm)3(μ3-CO)(Cl)]+ ([Pd3(Cl)]+) adduct and the monocationic species Pd2(dppm)2Cl+ (very likely as Pd2(dppm)2(Cl)(THF)+, [Pd2Cl]+) as unambiguously demonstrated by UV−vis and 31P NMR spectroscopy. In this case, [Pd3]2+ acts as a strong Lewis acid toward the labile Cl- ion, which weakly dissociates from Pd2Cl2 (i.e., dissociative mechanism). Host−guest interactions between [Pd3]2+ and Pd2Cl2 seem unlikely on the basis of computer modeling because of the strong screening of the Pd−Cl fragment by the Ph-dppm groups in Pd2Cl2. The electrogenerated clusters [Pd3]+ and [Pd3]0 also react with Pd2Cl2 to unexpectedly form the same oxidized adduct, [Pd3(Cl)]+, despite the known very low affinity of [Pd3]+ and [Pd3]0 toward Cl- ions. The reduced biproduct in this case is the highly reactive zerovalent species “Pd2(dppm)2” or “Pd(dppm)” as demonstrated by quenching with CDCl3 (forming the well-known complex Pd(dppm)Cl2) or in presence of dppm (forming the known Pd2(dppm)3 d10−d10 dimer). To bring these halide-electron exchange reactions to completion for [Pd3]+ and [Pd3]0, 0.5 and 1.0 equiv of Pd2Cl2 are necessary, respectively, accounting perfectly for the number of exchanged electrons. The presence of a partial dissociation of Pd2Cl2 into the Cl- ion and the monocation [Pd2Cl]+, which is easier to reduce than Pd2Cl2, is suggested to explain the overall electrochemical results. It is possible to regulate the nature of the species formed from Pd2Cl2 by changing the state of charge of the title cluster

Enhanced Stability of a Paramagnetic Palladium Complex Promoted by Interactions with Ethynyl Substrates

The highly reactive palladium-centered radical cluster [Pd3(dppm)3(CO)]•+ exhibits only a limited stability in solution at room temperature (about an hour). This stability can be extended significantly to several hours by adding organic substrates such as the symmetric and asymmetric alkynes Ph−C⋮C−H and MeO2C−C⋮C−CO2Me, which reversibly bind to the Pd3 triangle. The presence of the substrate inside the cavity protects the palladium centers from reacting with the “outside world”, hence enhancing the stability. Both adducts are stable as the cluster is always totally recovered. The paramagnetic complexes along with their corresponding dications were characterized by EPR, variable-temperature 31P NMR, UV−vis and MALDI-TOF spectroscopy, and electrochemistry. For the MeO2C−C⋮C−CO2Me/[Pd3(dppm)3(CO)]2+ complex, the analysis of the low-temperature 31P NMR spectra strongly suggests a major structure modification of the ligand and substrate with respect to the starting materials

Surfactant Behavior of Ionic Liquids Involving a Drug: From Molecular Interactions to Self-Assembly

Aggregates formed in an aqueous medium by three ionic liquids C_<i>n</i>MImIbu made up of 1-alkyl-3-methyl-imidazolium cation (<i>n</i> = 4, 6, 8) and ibuprofenate anion are investigated. Dynamic light scattering (DLS), cryogenic transmission electron microscopy (cryo-TEM), ¹H nuclear magnetic resonance measurements, and atom-scale molecular dynamics simulations are used to shed light on the main interactions governing the formation of the aggregates and their composition. At high concentration, mixed micelles are formed with a composition that depends on the imidazolium alkyl chain length. For the shortest alkyl chain, micelles are mainly composed of ibuprofenate anions with some imidazolium cations intercalated between the anions. Upon increasing the alkyl chain length, the composition of the aggregates gets enriched in imidazolium cations and aggregates of stoichiometric composition are obtained. Attractive interactions between these aggregates led to the formation of larger aggregates. As suggested by molecular simulations, these larger aggregates might constitute the early stage of phase separation. Transitions from micelles to vesicles or ribbons are observed due to dilution effects and changes in the chemical composition of the aggregates. We also show that aggregation can be probed using simple microscopic quantities such as radial distribution functions and average solvation numbers

Enhanced Stability of a Paramagnetic Palladium Complex Promoted by Interactions with Ethynyl Substrates

The highly reactive palladium-centered radical cluster [Pd3(dppm)3(CO)]•+ exhibits only a limited stability in solution at room temperature (about an hour). This stability can be extended significantly to several hours by adding organic substrates such as the symmetric and asymmetric alkynes Ph−C⋮C−H and MeO2C−C⋮C−CO2Me, which reversibly bind to the Pd3 triangle. The presence of the substrate inside the cavity protects the palladium centers from reacting with the “outside world”, hence enhancing the stability. Both adducts are stable as the cluster is always totally recovered. The paramagnetic complexes along with their corresponding dications were characterized by EPR, variable-temperature 31P NMR, UV−vis and MALDI-TOF spectroscopy, and electrochemistry. For the MeO2C−C⋮C−CO2Me/[Pd3(dppm)3(CO)]2+ complex, the analysis of the low-temperature 31P NMR spectra strongly suggests a major structure modification of the ligand and substrate with respect to the starting materials

Ionic Liquid Mediated Sol-Gel Synthesis in the Presence of Water or Formic Acid: Which Synthesis for Which Material?

Sol-gel syntheses involving either neutral water or formic acid as a reactant have been investigated (1) to determine the best conditions to confine a maximum of ionic liquid (IL) inside silica-based matrixes and (2) to reach the highest porosity after removing the IL from the ion gels (washed gels). Several sets of ionogels were prepared from various 1-butyl-3-methylimidazolium ILs and various silica or organosilica sources. The study evidenced a critical effect of the anion on the morphology (monolith, powder) and texture of the resulting washed gels. Particularly, tetrafluoroborate anion led to monolith ionogels by a simple hydrolytic method, affording highly condensed mesoporous silicas with some fluorinated surface sites. Such sites have never been reported before and were evidenced by ¹⁹F NMR. On the other hand, formic acid solvolysis turned out to be the only method to get non-exuding, crack-free, and transparent monoliths from ILs containing bis­(trifluoromethylsulfonyl)­imide [NTf₂] anion, with promising applications in photochemistry or photosensing. With bulky imidazolium and pyridinium cations, removal of the IL led to highly porous silicas with pore diameters and pore volumes as high as 10–15 nm and 3 cm³ g^–1, respectively. These silicas could find applications as supports for immobilizing bulky molecules