A condensed microelectromechanical constitutive and damage model for tetragonal ferroelectrics

A condensed model for ferroelectric solids with tetragonal unit cells is presented. The approach is microelectromechanically and physically motivated, considering discrete switching processes on the level of unit cells and quasi-continuous evolution of inelastic fields on the domain wall level. To calculate multiple grain interactions an interaction tensor is introduced. Hysteresis loops are simulated for pure electric and electromechanical loading, demonstrating e.g. the influence of a compressive preload on the poling process and interaction between statistically arranged crystallits. The residual stresses and the corresponding principle stresses are used to simulate fatigue damage in ferroelectric materials. (© 2014 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim)     

Studies on the MxiH Protein in T3SS Needles Using DNP‐Enhanced ssNMR Spectroscopy

Bacterial T3SS needles formed by the protein MxiH are studied using DNP‐enhanced ssNMR spectroscopy at 14.1 T (600 MHz). This technique provides spectra of good resolution, allowing us to draw conclusions about the protein dynamics. With the obtained signal enhancement, samples of limited quantity now get within reach of ssNMR studies.     

Conducting polymers in chemical sensors and arrays

The review covers main applications of conducting polymers in chemical sensors and biosensors. The first part is focused on intrinsic and induced receptor properties of conducting polymers, such as pH sensitivity, sensitivity to inorganic ions and organic molecules as well as sensitivity to gases. Induced receptor properties can be also formed by molecularly imprinted polymerization or by immobilization of biological receptors. Immobilization strategies are reviewed in the second part. The third part is focused on applications of conducting polymers as transducers and includes usual optical (fluorescence, SPR, etc.) and electrical (conductometric, amperometric, potentiometric, etc.) transducing techniques as well as organic chemosensitive semiconductor devices. An assembly of stable sensing structures requires strong binding of conducting polymers to solid supports. These aspects are discussed in the next part. Finally, an application of combinatorial synthesis and high-throughput analysis to the development and optimization of sensing materials is described.     

Interactions of the 3ppi u c1Pi u(v=2) Rydberg-complex member in isotopic N2

The 3ppi u c1Pi u-X 1Sigmag+(2,0) Rydberg and b' 1Sigmau+-X 1Sigmag+(7,0) valence transitions of 14N2, 14N15N, and 15N2 are studied using laser-based 1 extreme ultraviolet (XUV)+1' UV two-photon-ionization spectroscopy, supplemented by synchrotron-based hotoabsorption measurements in the case of 14N2. For each isotopomer, effective rotational interactions between the c(v=2) and b'(v=7) levels are found to cause strong Lambda-doubling in c(v=2) and dramatic P/R-branch intensity anomalies in the b'-X(7,0) band due to the effects of quantum interference. Local perturbations in energy and predissociation line width for the c(v=2) Rydberg level are observed and attributed to a spin-orbit interaction with the crossing, short-lived C 3Pi u(v=17) valence level.     

One-step catalyst-free generation of carbon nanospheres via laser-induced pyrolysis of anthracene

Carbon nanospheres with diameters between 100 and 400 nm have been successfully synthesized via low-power laser-assisted pyrolysis of anthracene in a nitrogen atmosphere. The developed facile route yields homogeneous nanoparticles and requires no supplementary carbon feedstock or catalyst. The sharp thermal gradient afforded by the laser results in two kinds of carbon products that differ in crystallinity and mean particle size. Our detailed findings point to the carbon nanospheres being comprised of small-unclosed aromatic layers that are connected together by simple organic linkers. C-H bonds in the anthracene molecules are partially broken by the laser beam energy, and as the newly created large radicals aggregate, carbon nanospheres are formed.     

Cannabinoid CB1 receptor antagonists in therapeutic and structural perspectives

The observed antiobesity effect of rimonabant ( 1 ) in a pharmacological rodent model 10 years ago has led to a surge in the search for novel cannabinoid CB₁ antagonists as a new therapeutic target for the treatment of obesity. Rimonabant showed clinical efficacy in the treatment of obesity and also improved cardiovascular and metabolic risk factors. Cannabinoid CB₁ receptor antagonists have also good prospects in other therapeutic areas, including smoking and alcohol addiction as well as cognitive impairment. Solvay's research achievements in this fast‐moving field are reported in relation with the current state of the art. Several medicinal chemistry strategies have been pursued. The application of the concept of conformational constraint led to the discovery of more rigid analogs of the prototypic CB₁ receptor antagonist rimonabant. Replacement of the central heterocyclic pyrazole ring in rimonabant yielded imidazoles, triazoles, and thiazoles as selective CB₁ receptor antagonists. Dedicated medium‐throughput screening efforts delivered one 3,4‐diarylpyrazoline hit. Its poor pharmacokinetic properties were successfully optimized which led to the discovery of orally active and highly CB₁/CB₂ receptor selective analogs in this series. Regioisomeric 1,5‐diarylpyrazolines, 1,2‐diarylimidazolines, and water‐soluble imidazoles have been designed as novel CB₁ receptor antagonist structure classes. © 2008 The Japan Chemical Journal Forum and Wiley Periodicals, Inc. Chem Rec 8: 156–168; 2008: Published online in Wiley InterScience ( www.interscience.wiley.com ) DOI 10.1002/tcr.20147     

β-Sheet Core of Tau Paired Helical Filaments Revealed by Solid-State NMR

One of the hallmarks of Alzheimer's disease is the self-assembly of the microtubule-associated protein tau into fibers termed "paired helical filaments" (PHFs). However, the structural basis of PHF assembly at atomic detail is largely unknown. Here, we applied solid-state nuclear magnetic resonance (ssNMR) spectroscopy to investigate in vitro assembled PHFs from a truncated three-repeat tau isoform (K19) that represents the core of PHFs. We found that the rigid core of the fibrils is formed by amino acids V306 to S324, only 18 out of 99 residues, and comprises three β-strands connected by two short kinks. The first β-strand is formed by the well-studied hexapeptide motif VQIVYK that is known to self-aggregate in a steric zipper arrangement. Results on mixed [(15)N:(13)C]-labeled K19 fibrils show that β-strands are stacked in a parallel, in-register manner. Disulfide bridges formed between C322 residues of different molecules lead to a disturbance of the β-sheet structure, and polymorphism in ssNMR spectra is observed. In particular, residues K321-S324 exhibit two sets of resonances. Experiments on K19 C322A PHFs further confirm the influence of disulfide bond formation on the core structure. Our structural data are supported by H/D exchange NMR measurements on K19 as well as a truncated four-repeat isoform of tau (K18). Site-directed mutagenesis studies show that single-point mutations within the three different β-strands result in a significant loss of PHF aggregation efficiency, highlighting the importance of the β-structure-rich regions for tau aggregation.