Cu−NHC Complex for Chan-Evans-Lam Cross-Coupling Reactions of N-Heterocyclic Compounds and Arylboronic Acids

An efficient copper(II) N-heterocyclic carbene (NHC) complex with an NCN coordination mode was optimized to catalyze the Chan–Evans-Lam (CEL) cross-coupling reaction of imidazole and other N-heterocyclic nucleophiles with arylboronic acid. This air-stable copper catalyst shows robust catalytic performance and tolerates a diverse array of functional groups on both the N-nucleophile and arylboronic acid coupling partners in C−N bond forming reactions with up to 95 % yield. Formation of the Cu−NHC complex in situ generated similar catalytic performance for CEL coupling. Alternative metal ions (Mn²⁺, Fe²⁺, Co²⁺, Ni²⁺, Zn²⁺, Ru²⁺, and Pd²⁺) were also screened in the presence of the NHC precursor as CEL catalysts.     

A Computational Intelligence-Based Genetic Programming Approach for the Simulation of Soil Water Retention Curves

Soil water retention curves are a key constitutive law used to describe the physical behavior of an unsaturated soil. Various computational modeling techniques, that formulate retention curve models, are mostly based on existing soil databases, which rarely consider any effect of stress on the soil water retention. Such effects are crucial in the case of swelling soils. This study illustrates and explores the ability of computational intelligence-based genetic programming to formulate the mathematical relationship between the water content, in terms of degree of saturation, and two input variables, i.e., net stress and suction for three different soils (sand–kaolin mixture, Gaduk Silt and Firouzkouh clay). The predictions obtained from the proposed models are in good agreement with the experimental data. The parametric and sensitivity analysis conducted validates the robustness of our proposed model by unveiling important parameters and hidden non-linear relationships.     

The crystallization kinetics and morphology of nitric acid trihydrate

Crystallization kinetics of stable and metastable nitric acid trihydrate (NAT) were investigated by time dependent X-ray powder diffraction (XRD) measurements. Kinetic conversion curves were evaluated adopting the Avrami model. The growth and morphology of the respective crystallites were monitored in situ on the cryo-stage of an environmental scanning electron microscope (ESEM) under a partial pressure of nitrogen gas (0.3 Torr, 40 Pa). The results show a close relationship between the presence of ice in the sample and the crystallization mechanism of NAT, which results in different shapes and sizes of NAT crystal particles.     

Apparent molar volumes of urea in several solvents as functions of temperature and concentration

Apparent molar volumes of urea are measured over a temperature range in water, methanol, ethanol, formamide, DMF and DMSO. The limiting apparent molar volumes show a large variation in different solvents. In marked contrast to the situation in water, the temperature dependence of the limiting apparent molar volumes in the nonaqueous solvents is slight. The concentration dependence is discussed qualitatively in terms of solute association.Now Diane Beaumont.     

How to generalise demonic composition

Semigroup Forum - Demonic composition is defined on the set of binary relations over the non-empty set X, $$Rel_X$$ , and is a variant of standard or “angelic” composition. It arises...     

The generation of tunable near IR radiation using a nitrogen laser pumped dye laser

Excitation transfer between the two components of a dye mixture has allowed a near IR dye laser to be pumped by a nitrogen laser. Several dye mixtures were employed to achieve lasing at all wavelengths within the range 6400–7720 Å. The output pulse powers were in excess of 10 kW over most of this range.