Synthesis and Catalytic Application of Bimetallic and Trimetallic Magnetic Nanoalloys for the Preparation of Bis(indolyl)methanes

Russian Journal of Organic Chemistry - Some bimetallic and trimetallic magnetic nanoalloys based on cobalt, copper, and silver have been synthesized and used as and green catalysts for the...     

Synthesis of micro and nanostructured MnO2 and their comparative study in lithium battery

Micro and nanostructured ??-MnO₂ are synthesized to investigate the size effect of cathode active materials in battery performance. MnSO₄ and (NH₄)₂S₂O₈ were used as starting materials to prepare micro and nanostructured samples in the presence of stirring and ultrasonic irradiation, respectively. Structure optimization is done by changing values for temperature and manganese sulphate concentration. The MnO₂ micro and nanoparticles are characterized by scanning electron microscopy and X-ray diffraction (XRD). The XRD results reveal that only ??-MnO₂ is formed under the reaction conditions. Under the optimized conditions, manganese dioxide nanoparticles, with an average particle size of 56?nm, are obtained. Both micro and nanostructured MnO₂ is used as the cathode active material in Li/MnO₂ battery. Discharge profiles of stirrer-based cathode material (micro) and ultrasonic instrument-based one (nano) compared with each other in constant discharge currents of 50 and 100?mA?g^?1. The results demonstrated that nanosized materials show higher specific capacities and energies. Electrochemical impedance spectroscopy is used to investigate the size effect of cathode material on battery resistance and the results show a copious decrease in total resistance.     

Thiazole Orange Dimers in DNA: Fluorescent Base Substitutions with Hybridization Readout

By using (S)‐2‐amino‐1,3‐propanediol as a linker, thiazole orange (TO) was incorporated in a dimeric form into DNA. The green fluorescence (λ=530 nm) of the intrastrand TO dimer is quenched, whereas the interstrand TO dimer shows a characteristic redshifted orange emission (λ=585 nm). Steady‐state optical spectroscopic methods reveal that the TO dimer fluorescence is independent of the sequential base contexts. Time‐resolved pump–probe measurements and excitation spectra reveal the coexistence of conformations, including mainly stacked TO dimers and partially unstacked ones, which yield exciton and excimer contributions to the fluorescence, respectively. The helicity of the DNA framework distorts the excitonic coupling. In particular, the interstrand TO dimer could be regarded as an excitonically interacting base pair with fluorescence readout for DNA hybridization. Finally, the use of this fluorescent readout was representatively demonstrated in molecular beacons.     

Inhibitors of Bacterial Swarming Behavior

Bacteria can migrate in groups of flagella-driven cells over semisolid surfaces. This coordinated form of motility is called swarming behavior. Swarming is associated with enhanced virulence and antibiotic resistance of various human pathogens and may be considered as favorable adaptation to the diverse challenges that microbes face in rapidly changing environments. Consequently, the differentiation of motile swarmer cells is tightly regulated and involves multi-layered signaling networks. Controlling swarming behavior is of major interest for the development of novel anti-infective strategies. In addition, compounds that block swarming represent important tools for more detailed insights into the molecular mechanisms of the coordination of bacterial population behavior. Over the past decades, there has been major progress in the discovery of small-molecule modulators and mechanisms that allow selective inhibition of swarming behavior. Herein, an overview of the achievements in the field and future directions and challenges will be presented.     

Multi-objective Antenna Selection in a Full Duplex Base Station

Wireless Personal Communications - The use of full-duplex (FD) communication systems is a new way to increase spectral efficiency. For this reason, it has received serious attention in the new...     

On the Structure of Sulfur/1,3-Diisopropenylbenzene Co-Polymer Cathodes for Li-S Batteries: Insights from Density-Functional Theory Calculations

Sulfur co-polymers have recently drawn considerable attention as alternative cathode materials for lithium-sulfur batteries, thanks to their flexible atomic structure and the ability to provide high reversible capacity. Here, we report on the atomic structure of sulfur/1,3-diisopropenylbenzene co-polymers (poly(S-co-DIB)) based on the insights obtained from density-functional theory calculations. The focus is set on studying the local structural properties, namely the favorable sulfur chain length (S_n with ) connecting two DIBs. In order to investigate the effects of the organic groups and sulfur chains separately, we perform series of atomic structure optimizations. We start from simple organic groups connected via sulfur chains and gradually change the structure of the organic groups until we reach a structure in which two DIB molecules are attached via sulfur chains. Additionally, to increase the structural sampling, we perform temperature-assisted minimum-energy structure search on slightly simpler model systems. We find that in DIB-S_n-DIB co-polymers, shorter sulfur chains with are preferred, where the stabilization is mostly brought about by the sulfur chains rather than the organic groups. The presented results, corresponding to the fully charged state of the cathode in the thermodynamic limit, have direct applications in the field of lithium-sulfur batteries with sulfur-polymer cathodes.     

A pH‐sensitive,strong double‐network hydrogel: Poly(ethylene glycol) methyl ether methacrylates–poly(acrylic acid)

We here describe new double network (DN) hydrogels with excellent mechanical strength and high sensitivity to pH changes. The first polymer network has a bottle brush structure and is formed from oligo‐monomers of poly(ethylene glycol) methyl ether methacrylate (PEGMA). Poly(acrylic acid) (PAA) is used as the second network. This double network features strong intermolecular interactions between the neutral poly(ethylene glycol) (PEG) side chains of PPEGMA and the non‐ionized carboxylic acid groups of the PAA second network. When immersed in solutions with a pH below ～4 the DN hydrogels have a low swelling ratio and are opaque as a result of solvent‐polymer phase separation driven by the formation of dense hydrogen‐bonded clusters. The compression strength (～8 MPa) is at least 14 times higher than the analogous single networks. When immersed in solutions with a pH >4, the hydrogels are transparent and exhibit a high swelling ratio with a compression strength of ～1 MPa. The PEG side chain length can be readily controlled without greatly altering the overall DN topology by choosing PEGMA monomers having different PEG side chain lengths. Longer PEG side branches give higher compression and tensile strengths at pH <4 when hydrogen bonded clusters form. The robust nature of these DN gels over a wide pH range may be useful for applications such as artificial muscles and controlled release devices. © 2011 Wiley Periodicals, Inc. J Polym Sci Part B: Polym Phys, 2012     

NOUF6 Revisited: A Comprehensive Study of a Hexafluoridouranate(V) Salt

We have synthesized NOUF₆ by direct reaction of NO with UF₆ in anhydrous HF (aHF). Based on the unit cell volume and powder diffraction data, the compound was previously reported to be isotypic to O₂PtF₆, however, detailed structural data, such as the atom positions and all information that can be derived from those, were unavailable. We have therefore investigated the compound by using single‐crystal and powder X‐ray diffraction, IR, Raman, NMR, EPR, and photoluminescence spectroscopy, magnetic measurements, as well as chemical analysis, density determination, and quantum chemical calculations.