Boundary Representations of λ-Harmonic and Polyharmonic Functions on Trees

Potential Analysis - The upper escape rate for a Markov process is a natural partial generalization of the celebrated Khintchine’s law of the iterated logarithm. In this article, we present a...     

Trifluoromethylation of Allenes: An Expedient Access to α-Trifluoromethylated Enones at Room Temperature

A silver(I) catalyzed regioselective trifluoromethylation of allenes using Langlois's salt (NaOSOCF₃) is demonstrated. This transformation enables direct expedient access to α-trifluoromethylated acroleins, which are valuable synthons for a number of pharmaceuticals and agrochemicals containing vinyl-CF₃ moieties. Versatility of this trifluoromethylation method has been established with good yield and excellent regioselectivity. Preliminary experiments and computational studies were carried out to elucidate the mechanistic insight of this protocol.     

Immobilization of an Iridium Pincer Complex in a Microporous Polymer for Application in Room-Temperature Gas Phase Catalysis

An iridium dihydride pincer complex [IrH₂(POCOP)] is immobilized in a hydroxy-functionalized microporous polymer network using the concepts of surface organometallic chemistry. The introduction of this novel, truly innocent support with remote OH-groups enables the formation of isolated active metal sites embedded in a chemically robust and highly inert environment. The catalyst maintained high porosity and without prior activation exhibited efficacy in the gas phase hydrogenation of ethene and propene at room temperature and low pressure. The catalyst can be recycled for at least four times.     

Design and kinematic optimization of a novel underactuated robotic hand exoskeleton

This study presents the design and the kinematic optimization of a novel, underactuated, linkage-based robotic hand exoskeleton to assist users performing grasping tasks. The device has been designed to apply only normal forces to the finger phalanges during flexion/extension of the fingers, while providing automatic adaptability for different finger sizes. Thus, the easiness of the attachment to the user’s fingers and better comfort have been ensured. The analyses of the device kinematic pose, statics and stability of grasp have been performed. These analyses have been used to optimize the link lengths of the mechanism, ensuring that a reasonable range of motion is satisfied while maximizing the force transmission on the finger joints. Finally, the usability of a prototype with multiple fingers has been tested during grasping tasks with different objects.     

Hybrid materials with an increased resistance to hard X‐rays using fullerenes as radical sponges

The protection of organic and hybrid organic–inorganic materials from X‐ray damage is a fundamental technological issue for broadening the range of applications of these materials. In the present article it is shown that doping hybrid films with fullerenes C₆₀ gives a significant reduction of damage upon exposure to hard X‐rays generated by a synchrotron source. At low X‐ray dose the fullerene molecules act as `radical scavengers', considerably reducing the degradation of organic species triggered by radical formation. At higher doses the gradual hydroxylation of the fullerenes converts C₆₀ into fullerol and a bleaching of the radical sinking properties is observed.     

Surface-Initiated RAFT Polymerization of 2,3-Dimethyl-1,3-butadiene on Silica Nanoparticles for Matrix-free Methyl Rubber Nanocomposites

Reversible addition-fragmentation chain transfer (RAFT) polymerization of 2,3-dimethyl-1,3-butadiene (DMB) in solution and on the surface of silica nanoparticles was investigated and PDMB-grafted silica nanoparticles (PDMB-g-SiO₂ NPs) with different chain densities and molecular weights were prepared. The kinetic studies of DMB polymerization mediated by silica anchored RAFT agents at different graft densities were investigated and compared to the polymerization mediated by the corresponding free RAFT agent. The PDMB-g-SiO₂ NPs were cured to prepare rubbery films and obtain matrix-free nanocomposites, which exhibited a good dispersion of silica nanoparticles and improved mechanical properties compared to the unfilled crosslinked rubber. © 2020 Wiley Periodicals, Inc. J. Polym. Sci. 2020 , 58, 417–427     

Templated Synthesis of Copper(II) Azacyclam Complexes Using Urea as a Locking Fragment and Their Metal‐Enhanced Binding Tendencies towards Anions

Copper(II) azacyclam complexes 3 ²⁺ and 4 ²⁺ were obtained through a metal‐templated procedure involving the pertinent open‐chain tetramine, formaldehyde and a phenylurea derivative as a locking fragment. Both metal complexes can establish interactions with anions through the metal centre and the amide NH group. Equilibrium studies in DMSO by a spectrophotometric titration technique were carried out to assess the affinity of 3 ²⁺ and 4 ²⁺ towards anions. While the NH group of an amide model compound and the metal centre of the plain Cu^II(azacyclam)²⁺ complex do not interact at all with anions, 3 ²⁺ and 4 ²⁺ establish strong interactions with oxo anions, profiting from a pronounced cooperative effect. In particular, 1) they form stable 1:1 and 1:2 complexes with H₂PO₄^? ions in a stepwise mode with both hydrogen‐bonding and metal–ligand interactions, and 2) in the presence of CH₃COO^?, they undergo deprotonation of the amido NH group and thus profit from axial coordination of the partially negatively charged carbonyl oxygen atom in a scorpionate binding mode.     

Entire radial and nonradial solutions for systems with critical growth

In this paper we establish existence of radial and nonradial solutions to the system

$$\begin{aligned} {\left\{ \begin{array}{ll} \displaystyle -\Delta u_1 = F_1(u_1,u_2) &{}\quad \text {in }{\mathbb R}^N,\\ -\Delta u_2 = F_2(u_1,u_2) &{}\quad \text {in }{\mathbb R}^N,\\ u_1\geqslant 0,\ u_2\geqslant 0 &{}\quad \text {in }{\mathbb R}^N,\\ u_1,u_2\in D^{1,2}({\mathbb R}^N), \end{array}\right. } \end{aligned}$$

where \(F_1,F_2\) are nonlinearities with critical behavior.

     

On the shape factor of interaction laws for a non-local approximation of the Sobolev norm and the total variation

We consider the family of non-local and non-convex functionals introduced by H. Brézis and H.-M. Nguyen in a recent paper. These functionals Gamma-converge to a multiple of the Sobolev norm or the total variation, depending on a summability exponent, but the exact values of the constants are unknown in many cases.We describe a new approach to the Gamma-convergence result that leads in some special cases to the exact value of the constants, and to the existence of smooth recovery families.