Mixed Tetrahedral Elements for the Analysis of Structures with Material and Geometric Nonlinearities

A new mixed tetrahedral element, particularly suited for the analysis of structures exhibiting nonlinear material and geometric behavior, is here presented. Its derivation is based on a Hu–Washizu type formulation, including also rotation and skew-symmetric stress fields as independent variables, instrumental to equip the element with nodal rotational degrees of freedom. A Gauss-point-discontinuous interpolation is selected for the total strain field, in order to account for its possibly highly nonlinear spatial distribution due to inelastic strains. Accordingly, the resulting tetrahedron can properly describe inelastic effects occurring over a space scale smaller than the element size. An original and efficient iterative procedure is proposed to perform the element state determination. Geometric nonlinearities are treated by means of the corotational approach. A numerical simulation is presented to analyze the element performances. (© 2015 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim)     

Fibril Structure Demonstrates the Role of Iodine Labelling on a Pentapeptide Self-Assembly

Iodination has long been employed as a successful labelling strategy to gain structural insights into proteins and other biomolecules via several techniques, including Small Angle X-ray Scattering, Inductively Coupled Plasma Mass Spectrometer (ICP-MS), and single-crystal crystallography. However, when dealing with smaller biomolecular systems, interactions driven by iodine may significantly alter their self-assembly behaviour. The engineering of amyloidogenic peptides for the development of ordered nanomaterials has greatly benefitted from this possibility. Still, to date, iodination has exclusively been applied to aromatic residues. In this work, an aliphatic bis-iodinated amino acid was synthesized and included into a custom pentapeptide, which showed enhanced fibrillogenic behaviour. Peptide single crystal X-ray structure and powder X-ray diffraction on its dried water solution demonstrated the key role of iodine atoms in promoting intermolecular interactions that drive the peptide self-assembly into amyloid fibrils. These findings enlarge the library of halogenated moieties available for directing and engineering the self-assembly of amyloidogenic peptides.     

Light‐Controlled Regioselective Synthesis of Fullerene Bis‐Adducts

Multi‐functionalization and isomer‐purity of fullerenes are crucial tasks for the development of their chemistry in various fields. In both current main approaches—tether‐directed covalent functionalization and supramolecular masks—the control of regioselectivity requires multi‐step synthetic procedures to prepare the desired tether or mask. Herein, we describe light‐responsive tethers, containing an azobenzene photoswitch and two malonate groups, in the double cyclopropanation of [60]fullerene. The formation of the bis‐adducts and their spectroscopic and photochemical properties, as well as the effect of azobenzene photoswitching on the regiochemistry of the bis‐addition, have been studied. The behavior of the tethers depends on the geometry of the connection between the photoactive core and the malonate moieties. One tether lead to a strikingly different adduct distribution for the E and Z isomers, indicating that the covalent bis‐functionalization of C₆₀ can be controlled by light.     

Terpyridine-Functionalized Calixarenes: Synthesis,Characterization and Anion Sensing Applications

Lanthanide complexes have been developed and are reported herein. These complexes were derived from a terpyridine-functionalized calix[4]arene ligand, chelated with Tb³⁺ and Eu³⁺. Synthesis of these complexes was achieved in two steps from a calix[4]arene derivative: (1) amide coupling of a calix[4]arene bearing carboxylic acid functionalities and (2) metallation with a lanthanide triflate salt. The ligand and its complexes were characterized by NMR (¹H and ¹³C), fluorescence and UV-vis spectroscopy as well as MS. The photophysical properties of these complexes were studied; high molar absorptivity values, modest quantum yields and luminescence lifetimes on the ms timescale were obtained. Anion binding results in a change in the photophysical properties of the complexes. The anion sensing ability of the Tb(III) complex was evaluated via visual detection, UV-vis and fluorescence studies. The sensor was found to be responsive towards a variety of anions, and large binding constants were obtained for the coordination of anions to the sensor.     

A Metabolomic Approach to Beer Characterization

The consumers’ interest towards beer consumption has been on the rise during the past decade: new approaches and ingredients get tested, expanding the traditional recipe for brewing beer. As a consequence, the field of “beeromics” has also been constantly growing, as well as the demand for quick and exhaustive analytical methods. In this study, we propose a combination of nuclear magnetic resonance (NMR) spectroscopy and chemometrics to characterize beer. ¹H-NMR spectra were collected and then analyzed using chemometric tools. An interval-based approach was applied to extract chemical features from the spectra to build a dataset of resolved relative concentrations. One aim of this work was to compare the results obtained using the full spectrum and the resolved approach: with a reasonable amount of time needed to obtain the resolved dataset, we show that the resolved information is comparable with the full spectrum information, but interpretability is greatly improved.     

Interests diffusion on a semantic multiplex

Exploiting the information about members of a Social Network (SN) represents one of the most attractive and dwelling subjects for both academic and applied scientists. The community of Complexity Science and especially those researchers working on multiplex social systems are devoting increasing efforts to outline general laws, models, and theories, to the purpose of predicting emergent phenomena in SN’s (e.g. success of a product). On the other side the semantic web community aims at engineering a new generation of advanced services tailored to specific people needs. This implies defining constructs, models and methods for handling the semantic layer of SNs. We combined models and techniques from both the former fields to provide a hybrid approach to understand a basic (yet complex) phenomenon: the propagation of individual interests along the social networks. Since information may move along different social networks, one should take into account a multiplex structure. Therefore we introduced the notion of “Semantic Multiplex”. In this paper we analyse two different semantic social networks represented by authors publishing in the Computer Science and those in the American Physical Society Journals. The comparison allows to outline common and specific features.     

Novel binding material for supercapacitor electrodes

Environmentally friendly water-based composite material has been investigated as a novel binder for manufacturing supercapacitor electrodes. The performance of these electrodes and those with the conventional polyvinylidene fluoride (PVDF) binder were studied. Results obtained from cyclic voltammetry, electrochemical impedance spectrometry, and charge/discharge measurements showed that the electrodes with the new binder performed significantly better than the electrodes with the conventional PVDF binder; the specific capacitance increased by 51 % in an aqueous electrolyte while in an organic electrolyte, it increased by 15 %. This increase in capacitance was attributed to the electrophilic and hydrophilic nature of the new binding composite. The main reason for the improvement in capacitance was ascribed to reduction of equivalent series resistance (ESR). The presence of highly amorphous polyvinylpyrrolidone (PVP), a polymeric component of the new composite binder, was responsible for the reduction in ESR.     

Heterocycles from α‐Aminonitriles

Owing to their various modes of reactivity, α‐aminonitriles represent versatile building blocks for the construction of a wide range of nitrogen heterocycles. The present Concept article focuses on synthetic methodologies using their bifunctional nature which is the basis of their reactivity as α‐amino carbanions and as iminium ions. Reactions exclusively taking place on either the amine or on the nitrile moiety will not be considered.