Polydispersity index of polymers revealed by DOSY NMR

The polydispersity of a polymer chain is usually measured by its polydispersity index (PDI). In this study we present a method which allows to estimate the PDI of linear polymers from a simple diffusion experiment. The approach is based on the differential diffusion profile observed for the main polymer chain signal versus the extremity signal. From this difference, a statistical analysis of the DOSY spectrum allows the PDI to be estimated accurately, to the condition that the Flory coefficient of the polymer chain is known. Alternatively, the mass average molar mass Mw and the number average molar mass Mn can be extracted separately from the same spectrum. Results on PEO mixes reveal that, using this new method, PDI can be estimated with a very good accuracy. This method can easily be applied to almost any kind of linear polymers.     

A semi-microscopic model of the heat conduction law

We give two very simple quantum models for the heat conduction law using a master equation approach for the probability distribution of the quantum numbers of the oscillators. The probability of interaction of the oscillators is given by the Landau-Teller formula.     

Variation in the accumulation levels of N,N-dimethyltryptamine in micropropagated trees and in in vitro cultures of Mimosa tenuiflora

The present article reports the accumulation of N,N-dimethyltryptamine and its metabolic precursors (tryptophan, tryptamine) in different organs of micropropagated Mimosa tenuiflora trees (leaves, flowers and bark) subjected to seasonal variations (January and June), as well as in in vitro cultures (plantlets and calluses) of this plant species. The accumulation of all the tested compounds varied according to the organ, the month of collection, and age of the plant material. In all cases, the neurotoxic compound N,N-dimethyltryptamine (DMT) was detected with the lowest concentration 0.01% dry weight (DW) in flowers, and the highest 0.33% DW in bark. For the in vitro cultures, DMT was present in high yields in plantlets (0.1-0.2% DW), while in calluses this compound was initially detected but its concentration decreased significantly in the subsequent subcultures.     

Activation in prochiral reaction assemblies on Pt(111)

Trifluoroacetophenone (TFAP) forms C O...H-C bonded dimers and trimers at room temperature on Pt(111). It is proposed that these systems mimic the prochiral carbonyl-chiral modifier interaction in the enantioselective hydrogenation of TFAP on cinchona-modified Pt catalysts. That is, the activation of TFAP in homomolecular assemblies at racemic sites is expected to be roughly the same as in the diastereomeric complex formed at chiral sites. This interpretation suggests a reason why alpha-phenyl ketones do not display a strong measured rate enhancement effect in the Orito reaction.     

Aspects of a direct homogenization procedure for electro-mechanically coupled problems

The aim of this work is to discuss a micro–macro homogenization procedure for electro–mechanically coupled problems. In this context a two–scale homogenization ansatz for ferroelectric ceramics based on an FE²-approach is presented. The microscopic discretization of the heterogeneous structure of the polycrystalline material allows for the incorporation of microscopic effects, which are necessary to determine the corresponding overall macroscopic material response. (© 2008 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim)     

Adaptive Fuzzy Sliding Mode Controller and Observer for a Dive Cell

We present an adaptive fuzzy sliding mode control strategy in combination with a sliding mode observer for a dive cell. Numerical results demonstrate the outperformance of the presented controller compared to a conventional sliding mode approach. (© 2015 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim)     

On the generation of soft magneto-electric effects through Maxwell interactions

This contribution presents a finite-strain computational homogenization framework for soft magneto-electro-elastic solids. We use it in order to determine effective magneto-electric coupling coefficients of soft composites, which are driven by the interconnection of electrical and magnetical Maxwell stresses. (© 2015 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim)     

Phase-field simulation of the electro-mechanical response of ferroelectrics during Piezoresponse Force Microscopy

The contribution adresses the simulation of ferroelectric matrials in the framework of the Piezoresponse Force Microscopy (PFM). Based on the PFM, ferroelectric domain structures can be analyzed in great detail by measuring the electrically induced mechanical deformations of the surface of a ferroelectric. We employ a flexible continuum-mechanical model based on the phase-field method in order to analyze the behavior of ferroelectric microstructures numerically. Since ferroelectric materials are often highly anisotropic, the phase-field formulation will account for transversely isotropic symmetry. (© 2013 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim)     

CRAACK: consensus program for NMR amino acid type assignment

Protein peak spectrum assignment is a prerequisite of the nuclear magnetic resonance study of a molecule. We present here a computer tool which proposes the determination of the amino acid type from the values of the chemical shifts. This tool is based on two consensus algorithms based on several published typing algorithms and was trained and extensively tested against the Biological Magnetic Resonance Bank chemical shift data bank. The first one accomplishes the analysis with support vector machine technology, grouping related amino acids together, and presents a mean rate of success above 90% on the test set. The second one uses a classical consensus algorithm of vote. Furthermore, secondary structural prediction is available. This tool can be used for assisting manual assignment of peptides and proteins and can also be used as a step in an automated approach to assignment. This program has been called CRAACK and is publicly available at the following URL: http://abcis.cbs.cnrs.fr/craack.