Effective permittivity of a fiber-reinforced composite with transversely isotropic constituents

Simple closed-form expressions for effective permittivity of fiber-reinforced composites with transversely isotropic constituents are found using asymptotic homogenization. Circular cylindrical fibers are distributed in a square array. The analysis considers four orientations of constituents transverse symmetry axis relative to fibers direction. Local problems defined on a periodic square unit cell are solved by means of complex potential theory using Weierstrassian and Natanzon's functions, assuming that the contrast of permittivities is small. Derived closed-form formulas are compared with finite element calculations and, in the isotropic case, with standard mixture rules and classical bounds, obtaining excellent results even when contrast is large.     

Quasi-classical rate constants for the inelastic process O2(υi≫ 1) + O2 → O2(υf) + O2

Rate constants have been calculated using quasi-classical trajectories (QCT) for the vibrational relaxation of highly excited O₂:O₂(X³Σ?,v_i) + O₂(X³Σ?,0) → O₂(X³Σ?,v_f) + O₂(X³Σ?) with 22 ≤v_i≤28. The present full-dimensional QCT results agree very well with recent quantum reduced dimensionality calculations, giving further support to the hypothesis that the observed experimental jump in depletion rates would be due partially to enhanced vibrational relaxation.     

Providing support in favor of the existence of a Pd(II)/Pd(IV) catalytic cycle in a Heck-type reaction

The complex [Pd(O,N,C-L)(OAc)], in which L is a monoanionic pincer ligand derived from 2,6-diacetylpyridine, reacts with 2-iodobenzoic acid at room temperature to afford the very stable pair of Pd(IV) complexes (OC-6-54)- and (OC-6-26)-[Pd(O,N,C-L)(O,C-C(6)H(4)CO(2)-2)I] (1.5:1 molar ratio, at -55?°C). These complexes and the Pd(II) species [Pd(O,N,C-L)(OX)] and [Pd(O,N,C-L')(NCMe)]ClO(4), (X = MeC(O) or ClO(3), L' = another monoanionic pincer ligand derived from 2,6-diacetylpyridine), are precatalysts for the arylation of CH(2)=CHR (R = CO(2)Me, CO(2)Et, Ph) using IC(6)H(4)CO(2)H-2 and AgClO(4). These catalytic reactions have been studied and a tentative mechanism is proposed. The presence of two Pd(IV) complexes was detected by ESI(+)-MS during the catalytic process. All the data obtained strongly support a Pd(II)/Pd(IV) catalytic cycle.     

Solution Structure of a Parallel-Stranded Oligoisoguanine DNA Pentaplex Formed by d(T(iG)(4) T) in the Presence of Cs(+) Ions

What a pentaplexing situation: Isoguanine (iG) is an isomer of guanine, where the positions of the C2 amino group and the C6 carboxy group are swapped. iG can self-assemble into pentads in the presence of alkali metal cations. Cs(+) ions were found to stabilize a pentaplex of d(T(iG)(4) T). Solution NMR studies of this pentaplex in the presence of Cs(+) ions (or Na(+) , K(+) , Rb(+) , or NH(4) (+) cations) demonstrate its stability and structure.     

Periodic motions in forced problems of Kepler type

A Newtonian equation in the plane is considered. There is a central force (attractive or repulsive) and an external force λh(t), periodic in time. The periodic second primitive of h(t) defines a planar curve and the number of periodic solutions of the differential equation is linked to the number of loops of this curve, at least when the parameter λ is large.     

On the Sobolev embedding theorem for variable exponent spaces in the critical range

In this paper we study the Sobolev embedding theorem for variable exponent spaces with critical exponents. We find conditions on the best constant in order to guaranty the existence of extremals. The proof is based on a suitable refinement of the estimates in the Concentration–Compactness Theorem for variable exponents and an adaptation of a convexity argument due to P.L. Lions, F. Pacella and M. Tricarico.     

Mechanisms,Methods of Tracking and Applications of DNA Walkers: A Review

In recent years, DNA nanotechnology expanded its scope from structural DNA nanoarchitecture towards designing dynamic and functional nanodevices. This progress has been evident in the development of an advanced class of DNA nanomachines, the so-called DNA walkers. They represent an evolution of basic switching between distinctly defined states into continuous motion. Inspired by the naturally occurring walkers such as kinesin, research on DNA walkers has focused on developing new ways of powering them and investigating their walking mechanisms and advantages. New techniques allowing the visualization of walkers as single molecules and in real time have provided a deeper insight into their behavior and performance. The construction of novel DNA walkers bears great potential for applications in therapeutics, nanorobotics or computation. This review will cover the various examples and breakthrough designs of recently reported DNA walkers that pushed the limits of their performance. It will also mention the techniques that have been used to investigate walker nanosystems, as well as discuss the applications that have been explored so far.     

Structure and Dynamical Evolution of Low Lying Nucleon Resonances

Within a multi-channels multi-resonances reaction model of pion nucleon reactions, we examine the properties of the nucleon resonances with masses less than 2?GeV. The Roper resonance and the second resonance in P ₁₁ are found to evolve dynamically from the same bare state. With the exception of the P ₁₃ and P ₃₁ resonances, our resonance pole positions agree well with the 3 and 4 star resonances listed by the Particle Data Group.