Cavitand supported tetraphosphine: cyclodextrin offers a useful platform for Suzuki-Miyaura cross-coupling

The cyclodextrin-tetraphosphine hybrid coined α-Cytep allows turnover numbers up to 340,000,000,000 and turnover frequencies up to 1,000,000,000 h(-1) to be reached in Suzuki-Miyaura reactions. These exceptional figures are clearly linked to the outstanding longevity of the reactive species induced by the ligand α-Cytep and illustrates the rising potential of cyclodextrins in catalytic applications.     

Hydrogen bonded supramolecular polymers in moderately polar solvents

Hydrogen bonded assemblies are usually decomposed by polar organic solvents. However, we have succeeded in preparing a strongly associated supramolecular polymer which forms viscous solutions in competitive solvents such as tetrahydrofuran.     

Indirect controllability of locally coupled systems under geometric conditions

We consider systems of two wave/heat/Schrödinger-type equations coupled by a zero order term, only one of them being controlled. We prove an internal and a boundary null-controllability result in any space dimension, provided that both the coupling and the control regions satisfy the Geometric Control Condition. This includes several examples in which these two regions have an empty intersection.     

Theoretical prediction of the onset of thermoacoustic instability from the experimental transfer matrix of a thermoacoustic core

The aim of this paper is to propose a method to predict the onset conditions of the thermoacoustic instability for various thermoacoustic engines. As an accurate modeling of the heat exchangers and the stack submitted to a temperature gradient is a difficult task, an experimental approach for the characterization of the amplifying properties of the thermoacoustic core is proposed. An experimental apparatus is presented which allows to measure the transfer matrix of a thermoacoustic core under various heating conditions by means of a four-microphone method. An analytical model for the prediction of the onset conditions from this measured transfer matrix is developed. The experimental data are introduced in the model and theoretical predictions of the onset conditions are compared with those actually observed in standing-wave and traveling-wave engines. The results show good agreement between predictions from the model and experiments.     

Polydispersity and Optimal Relaxation in the Hard Sphere Fluid

We consider the mass heterogeneity in a gas of polydisperse hard particles as a key to optimizing a dynamical property: the kinetic relaxation rate. Using the framework of the Boltzmann equation, we study the long time approach of a perturbed velocity distribution toward the equilibrium Maxwellian solution. We work out the cases of discrete as well as continuous distributions of masses, as found in dilute fluids of mesoscopic particles such as granular matter and colloids. On the basis of analytical and numerical evidence, we formulate a dynamical equipartition principle that leads to the result that no such continuous dispersion in fact minimizes the relaxation time, as the global optimum is characterized by a finite number of species. This optimal mixture is found to depend on the dimension $d$ of space, ranging from five species for $d=1$ to a single one for $d\ge 4$ . The role of the collisional kernel is also discussed, and extensions to dissipative systems are shown to be possible.     

Solid‐State Hierarchical Cyclodextrin‐Based Supramolecular Polymer Constructed by Primary,Secondary, and Tertiary Azido Interactions

The crystallization of a di‐azido‐α‐cyclodextrin revealed a polymeric self‐assembly involving a variety of azido‐type interactions. The crystal arrangement relies on the cooperativity of a primary azido inclusion, a secondary azido–azido interaction involving an unprecedented distribution of canonical forms, and a tertiary azido–groove interaction. The second azido group brings in a major contribution to the supramolecular structure illustrating the benefit of a difunctionalization for the generation of hierarchy.     

TG-FTIR kinetic study of the thermal cleaning of wood laminated flooring waste

The enhancement of wood waste is a promising solution for the production of energy from renewable resources. Nevertheless, wood waste often needs a preliminary treatment step to remove pollutants present in the material. The thermal cleaning of wood laminated flooring (WLF) waste is studied through thermogravimetric and FTIR analyses. As a first step, it has been shown, through non iso-thermal tests, that degradation temperature ranges for wood and additives (aminoplast resins) are different, making it possible to proceed to a thermal cleaning through a low temperature pyrolysis. It has also been highlighted that chemical linkages between the different components of WLF waste influence their own thermal behaviour making it difficult to predict the thermal behaviour of the whole material. Fourier transform infra-red spectrometry analyses reveal that NH₃ and HNCO are the main nitrogen-containing gases produced during pyrolysis, which highlights the pyrolysis efficiency in terms of nitrogen (i.e., resin) removing. Lastly, thermal degradation of wood and WLF has been modelled to provide information for reactor designing.     

Confining Phosphanes Derived from Cyclodextrins for Efficient Regio‐ and Enantioselective Hydroformylation

Two confining phosphane ligands derived from either α‐ or β‐cyclodextrin produce singly P^III‐ligated metal complexes with unusual coordination spheres. High‐pressure NMR studies have revealed that rhodium hydride complexes of the same type are also formed under hydroformylation conditions. This unique feature strongly favors the formation of the branched aldehyde at the expense of the linear one with high enantioselectivity in the rhodium‐catalyzed hydroformylation of styrene.     

Total Lipid Extraction of Food Using d-Limonene as an Alternative to n-Hexane

A useful and green method for the extraction of fats and oils with a new procedure combining Soxhlet extraction and Clevenger distillation using d-limonene (bio-solvent) as a substitute for n-hexane (petroleum solvent) is reported. This method using green solvent is a laboratory exercise which easily teaches fundamental green analytical chemical lessons and successfully incorporates green “analytical chemistry” into the teaching and the research laboratory to both developed and developing nations.