Tris-ACE-(6,6′-bipyridyl)-α-cyclodextrin: synthesis and chirality of the tripodal metal complexes

This Letter describes the synthesis of a C₃-symmetrical tris-^ACE-(6,6′-bipyridyl)-α-CyD via ‘one-pot’ Staudinger-Aza-Wittig reaction (SAW). Metal complexation behavior was investigated by UV–vis and Circular Dichroism. Coordination of 6,6′-bipyridyl units with Cu^II and Ni^II cations, spontaneously generates a strong exciton coupling-type positive Cotton effect proving the formation of a Λ-helix with a left-handed screw propeller (M).     

Three-element zoom lens with fixed distance between focal points

This work deals with a theoretical analysis of zoom lenses with a fixed distance between focal points. Equations are derived for the primary (paraxial) design of the basic parameters of a three-element zoom lens. It is shown that the number of optical elements for such a lens must be larger than two.     

Chromatic aberrations of thin refractive variable-focus lens

We present an approach to an analysis of the third order chromatic aberrations of thin refractive fluid lenses with a variable focal length. A detailed theoretical analysis is performed for a simple fluidic variable-focus lens and formulas are derived for an optical design of such lenses. Aberration coefficients of the third order of the variable-focus lens can be completely characterized by three parameters which depend only on refractive indices of fluids forming the variable-focus lens. Formulas were derived for the change of the third-order aberration coefficients with the wavelength. Calculations are provided for Varioptic lens Arctic-416.     

Capillary pressure and contact line force on a soft solid

The surface free energy, or surface tension, of a liquid interface gives rise to a pressure jump when the interface is curved. Here we show that a similar capillary pressure arises at the interface of soft solids. We present experimental evidence that immersion of a thin elastomeric wire into a liquid induces a substantial elastic compression due to the solid capillary pressure at the bottom. We quantitatively determine the effective surface tension from the elastic displacement field and find a value comparable to the liquid-vapor surface tension. Most importantly, these results also reveal the way the liquid pulls on the solid close to the contact line: the capillary force is not oriented along the liquid-air interface, nor perpendicularly to the solid surface, as previously hypothesized, but towards the interior of the liquid.     

The Oberbeck–Boussinesq Approximation as a Singular Limit of the Full Navier–Stokes–Fourier System

We consider the asymptotic limit for the complete Navier–Stokes–Fourier system as both Mach and Froude numbers tend to zero. The limit is investigated in the context of weak variational solutions on an arbitrary large time interval and for the ill-prepared initial data. The convergence to the Oberbeck–Boussinesq system is shown.      

New Prospects toward the Synthesis of Difluoromethylated Phosphate Mimics

The difluoromethyl phosphonate motif plays a crucial role in the development of bioactive molecules as it is considered as a phosphate bioisoster. Since 2010, a renewal of interest to enlarge the panel of reactions to access these difluoromethylated phosphonate‐containing molecules has been witnessed. This Concept article charts the recent progress that has been made.     

Kinetic Resolution in the [2+2] Cycloaddition of Ketenes: An Experimental and Theoretical Study

The kinetic resolution of Z and E olefins by [2+2] cycloaddition with ketenes allows the isolation of pure E olefin, as well as the synthesis of pure cis‐cyclobutanones, starting from Z/E mixtures. A computational rationale for this kinetic difference is reported. The obtained difference of energy of activation matches with the experimental results.     

Hémisynthèse d''un nouvel isomère de la vinblastine

The reaction of the chloroindolenine of secopandoline $\text{2}$ with vindoline in acidic medium gives an isomer of the antitumor vinblastine $\text{1}$. This new compound is 14′-epi-20′-epivinblastine $\text{7}$.