A Tethered Porphyrin Dimer with π Overlap of a Single Pyrrole Ring

The special pair of the bacterial photosystem has been modeled with a porphyrin dimer (the partial structure is shown). As with the natural system, only one pyrrole ring from each monomer subunit participates in π overlap.     

Confocal zero-angle dynamic depolarized light scattering

We present a novel Dynamic Depolarized Scattering method based on a tight confocal, zero scattering angle, heterodyne scheme. The method is highly immune from parasitic multiple-scattering contributions, so that it can operate with non-index-matched samples presenting large turbidity. It provides measurements of both rotational and translational diffusion coefficients, the latter via number fluctuation spectroscopy. In addition, the amplitude ratio between the two baselines for the fast rotational mode and the slow translational mode can be used to determine the particles intrinsic birefringence.     

Three structures containing (E)‐1,2‐bis­(benzimidazol‐2‐yl)ethene groups

Two of the title compounds, namely (E)‐1,2‐bis­(1‐methyl­benzimidazol‐2‐yl)ethene, C₁₈H₁₆N₄, (Ib), and (E)‐1,2‐bis­(1‐ethyl­benzimidazol‐2‐yl)ethene, C₂₀H₂₀N₄, (Ic), consist of centrosymmetric trans‐bis­(1‐alkyl­benzimidazol‐2‐yl)ethene mol­ecules, while 3‐eth­yl‐2‐[(E)‐2‐(1‐ethyl­benzimidazol‐2‐yl)­ethen­yl]benzimidazol‐1‐ium perchlorate, C₂₀H₂₁N₄⁺·ClO₄⁻, (II), contains the monoprotonated analogue of compound (Ic). In the three structures, the benzimidazole and benzimidazolium moieties are essentially planar; the geometric parameters for the ethene linkages and their bonds to the aromatic groups are consistent with double and single bonds, respectively, implying little, if any, conjugation of the central C=C bonds with the nitro­gen‐containing rings. The C—N bond lengths in the N=C—N part of the benzimidazole groups differ and are consistent with localized imine C=N and amine C—N linkages in (Ib) and (Ic); in contrast, the corresponding distances in the benzimidazolium cation are equal in (II), consistent with electron delocalization resulting from protonation of the amine N atom. Crystals of (Ib) and (Ic) contain columns of parallel mol­ecules, which are linked by edge‐over‐edge C—H⋯π overlap. The columns are linked to one another by C—H⋯π inter­actions and, in the case of (Ib), C—H⋯N hydrogen bonds. Crystals of (II) contain layers of monocations linked by π–π inter­actions and separated by both perchlorate anions and the protruding eth­yl groups; the cations and anions are linked by N—H⋯O hydrogen bonds.     

Structural control design and defective systems

The intersection between the two concepts of structural control and defectiveness is discussed. Two simple oscillators differently connected by serial spring-dashpot arrangement are used to simply simulate technically relevant cases: dissipatively coupled adjacent free-standing structures, structures equipped by TMD and base-isolated structures. Eigensolution loci of the two classes of systems are tracked against one or more significant parameters to determine the potential benefits realized by different combinations of stiffness and viscosity. In both studied cases, codimension-two manifolds in the four-parameter space corresponding to coalescing eigenvalues are determined by analytical expressions. Conditions to discern semi-simple eigenvalues from defective ones confirm that the latter is the generic case laying in a two-parameter space while the former span a one-parameter subspace. The knowledge of the location of the defective systems in the parameter space permits to determine regions with specific dynamical properties useful for control design purpose.     

Characteristics and Trends of Telecom Italia Transport Networks

Abstract

The realization of a new transport backbone for the Telecom Italia network has multiple objectives: to increase transport capacity, network flexibility, and reliability through the adoption of evolved management and control planes, and to go beyond the present architecture, which is based on point-to-point systems. This article describes the present status of the network and the evolutionary trends.     

A simple model system for the study of carbohydrate--aromatic interactions

A molecular scaffold was identified which enables the establishment of intramolecular interactions between a monosaccharide and a nearby phenyl ring. A group of molecules containing four different monosaccharides (glucose, galactose, N-acetyl-glucosamine, and N-acetyl-galactosamine) was synthesized and used to investigate the extent and nature of this carbohydrate-arene interaction, as well as the effect on the overall 3D structure of the molecules involved. The sugar-aromatic distance was evaluated by rigorous NMR studies supported by molecular modeling and found to be constant throughout the series, independent of the nature of the sugar and of the conformational behavior of the fragment connecting the two elements. Ab initio calculations at the B3LYP/DZV(2d,p) level of theory enable the analysis of the electronic nature of the interaction. The study shows that, given the opportunity, persistent intramolecular aromatic-sugar interactions can be established and can significantly influence overall molecular shape and energetics. These results have important implications in the design of structural mimics of oligosaccharides.     

Solitary wave solutions to nonlinear evolution equations in mathematical physics

This paper obtains solitons as well as other solutions to a few nonlinear evolution equations that appear in various areas of mathematical physics. The two analytical integrators that are applied to extract solutions are tan–cot method and functional variable approaches. The soliton solutions can be used in the further study of shallow water waves in (1+1) as well as (2+1) dimensions.