Determining the role of the underlying orbital‐dependence of PBE0‐DH and PBE‐QIDH double‐hybrid density functionals

We study the orbital‐dependence of three (parameter‐free) double‐hybrid density functionals, namely the PBE0‐DH, the PBE‐QIDH models, and the SOS1‐PBE‐QIDH spin‐opposite‐scaled variant of the latter. To do it, we feed all their energy terms with different sets of orbitals obtained previously from self‐consistent density functional theory calculations using several exchange‐correlation functionals (e.g., PBE, PBE0, PBEH&H), or directly with HF‐PBE orbitals, to see their effect on selected datasets for atomization and reaction energies, the latter proned to marked self‐interaction errors. We find that the PBE‐QIDH double‐hybrid model shows a great consistency, as the best results are always obtained for the set of orbitals corresponding to its hybrid scheme, which prompts us to recommend this model without any other fitting or reparameterization. © 2017 Wiley Periodicals, Inc.     

Polydiacetylene‐Tb3+ Nanosheets of Which Both the Color and the Fluorescence Can Be Reversibly Switched between Two Colors

Polydiacetylenes (PDAs), an organic layered compound, show a series of intriguing properties, such as thermochromism and fluorescence emission in the red‐phase. However, their irreversible color change, and weak and single‐color fluorescence emitted only from the red‐phase PDAs, have limited their applications. Herein, we report double‐reversible PDA‐Tb³⁺ nanosheets of which both the color and the fluorescence can be reversibly switched between two colors. PDA‐Tb³⁺ nanosheets have the nearly defect‐free intercalated structure in which a layer of Tb³⁺ ions was intercalated in between each two PDA bilayers to tether almost all of the carboxyl groups at the end of the side chains of the PDA. When the PDA is in the blue phase, the PDA‐Tb³⁺ nanosheets emit the green fluorescence of Tb³⁺ ions. When the PDA is in the red phase, the Tb³⁺ fluorescence disappears while the intrinsic red fluorescence of PDA is effectively enhanced through the fluorescence resonance energy transfer (FRET) process; the PDA‐Tb³⁺ nanosheets emit stronger red fluorescence compared with the PDA in red phase. Moreover, the tethering of almost all of the carboxyl groups at the end of the side chains of the PDA endows the nanosheets with the double reversibility in both the color and fluorescence transitions.     

XNBR/LDH nanocomposites: Effect of vulcanization and organic modifier on nanofiller dispersion and strain‐induced crystallization

In elastomer/organo clay nanocomposites, the morphological characteristics, and hence the mechanical properties, of the vulcanizates are strongly influenced by the organic modifier and the vulcanization process. When the elastomer itself undergoes strain‐induced crystallization, both the organic modifier and the dispersed filler particles could significantly influence the crystallization process. These phenomena are very common in case of natural rubber‐based vulcanizates. In this study, the similar effects have been demonstrated with carboxylated nitrile rubber (XNBR) and organically modified layered double hydroxide (O‐LDH)‐based nanocomposites. The effect of size of the organic modifier was obviously visible on the interlayer distance of O‐LDH and also on the morphological reorganization of the dispersed O‐LDH particles during vulcanization process. The strain‐induced crystallization of the XNBR was found to be strongly dependent on the morphological change that occurs during vulcanization process. © 2010 Wiley Periodicals, Inc. J Polym Sci Part B: Polym Phys, 2010     

Recent results for single meson production from the Crystal-Barrel/TAPS experiment at ELSA

The present focus of the CBELSA/TAPS experiment is on meson-photoproduction off the nucleon using polarized photons and polarized targets. Here first preliminary results on the reactions γp → pπ and γp → pπ for both circularly and linearly polarized photons and a longitudinally polarized target are presented. Preliminary results for the beam asymmetry ∑ and the double polarization observable G have been extracted for both reactions using the linear polarization data. From the circular polarization data the observable E has been determined. Due to the near 4π angular coverage of the detector system these results cover almost the full solid angle.     

Volume of Hyperbolic 3-Manifolds with Iterated Pseudo-Anosov Amalgamations (Dedicated to Professor Mitsuyoshi Kato on his sixtieth birthday)

Let : be a pseudo-Anosov homeomorphism. We will study an asymptotic behaviour of the volume of closed hyperbolic 3-manifolds N _n obtained from certain 3-manifolds M, M by attaching their boundaries by the n-th iteration ⁿ of .     

The standard double bubble is the unique stable double bubble in

We prove that the only equilibrium double bubble in which is stable for fixed areas is the standard double bubble. This uniqueness result also holds for small stable double bubbles in surfaces, where it is new even for perimeter-minimizing double bubbles.

     

Trivalent Cation Substitution Effect into Layered Double Hydroxides Co2Fey Al1−y(OH)6Cl·nH2O: Study of the Local Order: Ionic Conductivity and Magnetic Properties

A series of layered double hydroxide materials of composition Co₂Fe_yAl_1−y(OH)₆Cl·nH₂O (0≤y≤1) was prepared via chimie douce. The crystalline parameter related to the cation to cation distance obeys the expected variation, showing that the substitution is effective over the entire range. Local order around Co and Fe cations is studied by X-ray absorption spectroscopy. Moduli of the Fourier transform at the Fe K-edge are superimposable, in agreement with an ordered model, although present in small domains since no superlattice is depicted. The ionic resistivity of the samples is highly dependent on the water molecule content. The conductivity is found to be thermally assisted, and the variation of the slope in the Arrhenius diagram is explained by a Vogel-Tamman-Fulcher-type behavior. Magnetic susceptibility measurements support the proposed cation composition and indicate the onset of local magnetic order at low temperature (below 10 K). The inter-sheet distance influences the magnetic response at low temperature, showing the presence of weak interactions between lamellae.     

Acoustic Waves in Channels with Porous and Permeable Walls

The propagation of acoustic disturbances in a porous medium crossed by numerous cracks (double porosity medium) is a complex problem that we here simplify by investigating the acoustics of a permeable channel. We consider a fluidfilled channel in two possible geometries, a slit or a cylindric pipe. The channel is surrounded by a porous medium (saturated with the same fluid) and is itself surrounded by an external medium. To simulate the average properties of the cracked rock, the external medium is either nonpermeable (few connections between cracks) or highly permeable (numerous connections). We present analytical and numerical results concerning acoustic disturbances of small amplitude generated in the channel, such as harmonic waves, step disturbanses and pulses.     

A boundary integral formulation for elastically deformable particles in a viscous fluid

This paper reports a formulation and implementation of a mixed (both direct and indirect) boundary element method using the double layer and its adjoint in a form suitable for solving Stokes flow problems involving elastically deformable particles. The formulation is essentially the Completed Double Layer Boundary Element Method for solving an exterior traction problem for the surrounding fluid or solid phase, followed by an interior displacement, and a mobility problem (if required) for the elastic particles. At the heart of the method is a deflation procedure that allows iterative solution strategies to be adopted, effectively opens the way for large-scale simulations of suspensions of deformable particles to be performed. Several problems are considered, to illustrate and benchmark the method. In particular, an analytical solution for an elastic sphere in an elongational flow is derived. The stresslet calculations for an elastic sphere in shear and elongational flows indicate that elasticity of the inclusions can potentially lead to positive second normal stress difference in shear flow, and an increase in the tensile resistance in elongational flow.This work is supported by a grant from the Australian Research Grant Council. X-J F wishes to acknowledge the support of the National Natural Science Foundation of China.