Electrochemistry with alkyl-linked oligothiophenes

Two pairs of β,β′-didodecyl substituted quinquethiophenes linked via a tri- (3) and tetramethylene spacer (4) at their α-positions have been synthesized and their electrochemical behavior investigated with cyclic voltammetry in solution and in solid films. Both compounds can be charged to a tetracation in two two-electron transfer steps, which are reversible at room temperature but become partially irreversible at low temperatures. Concentration and scan rate dependent measurements support an intramolecular coupling of the oligothiophene units preferentially next to their bridging site with σ-bond formation. In solution no electropolymerization can be observed. In the solid state upon oxidation intermolecular coupling of the oligothiophene segments takes place. Conductance measurements confirm the voltammetric findings. Obviously, the mechanism of conductance is based on hopping processes within mixed valence states.     

A priori and a posteriori analyses of algebraic flame surface density modeling in the context of Large Eddy Simulation of turbulent premixed combustion

The flame surface density (FSD) based reaction rate closure is one of the most important methodologies of turbulent premixed flame modeling in the context of Large Eddy Simulations (LES). The transport equation for the Favre-filtered reaction progress variable needs closure of the filtered reaction rate and the subgrid scalar flux (SGSF). The SGSF in premixed turbulent flames has both gradient and countergradient components, where the former is typically modeled using eddy diffusivity and the latter can be modeled either on its own or in combination with the filtered reaction rate term using an appropriate wrinkling factor. The scope of the present work is to identify an explicit SGSF closure for the optimum performance in combination with an already established LES FSD model. The performance of different SGSF models for premixed turbulent combustion has been assessed recently by the authors using a Direct Numerical Simulation (DNS) database of freely propagating turbulent premixed flames with a range of different values of turbulent Reynolds number. The two most promising models have been implemented in the LES code. The modeling methodology identified based on a priori DNS analysis is assessed further a posteriori by comparing the LES simulation results of turbulent methane Bunsen flames with the well-documented experimental data. A significant change of the overall flame speed is not observed for different SGSF models. However, the flame shape and thickness respond to the modeling of SGSF. Considering the fact that the SGSF models have very different characteristics, the overall effect on the LES results in this work is smaller than expected. An extension of a previous a priori DNS analysis provides detailed explanations for the observed behavior.     

Core/Shell and Hollow Ultra High Molecular Weight Polyethylene Nanofibers and Nanoporous Polyethylene Prepared by Mesoscopic Shape Replication Catalysis

Polyvinyl alcohol (PVA) nanofibers, produced by electrospinning, represent attractive high‐surface‐area supports for olefin polymerization catalysts. Tethered with metal alkyls, PVA nanofibers immobilize a great variety of transition metal compounds, thus producing highly active nanofiber‐supported Ziegler‐, metallocene‐, and post‐metallocene catalysts. Whereas most conventional heterogeneous polymerization catalysts form particles, PVA‐nanofiber‐supported catalysts enable polyolefin nanofiber and nanostructure formation by mesoscopic shape replication using electrospun nanofibers as templates. At low ethylene pressure, linear correlation between average PE/PVA core/shell fiber diameter and polymerization time are made. At elevated pressure, this control is lost, accounting for the formation of reactor blends consisting of PE granules and built‐in PE/PVA nanofibers. Whereas conventional catalysts produce micrometer‐sized particles of ultrahigh molecular weight PE (UHMWPE), PVA‐nanofiber supported chromium catalysts afford new families UHMWPE materials. They range from UHMWPE/PVA core/shell nanofibers and nonwovens to hollow UHMWPE fibers and nanoporous UHMWPE, obtained by removing the PVA component.     

Structural Integrity of the A147T Polymorph of Mammalian TSPO

Ligands of the transmembrane protein TSPO are used for imaging of brain inflammation, but a common polymorphism in TSPO complicates their application to humans. Here we determined the three‐dimensional structure and side‐chain dynamics of the A147T polymorph of mammalian TSPO in complex with the first‐generation ligand PK11195. We show that A147T TSPO is able to retain the same structural and dynamic profile as the wild‐type protein and thus binds PK11195 with comparable affinity. Our study is important for the design of more potent diagnostic and therapeutic ligands of TSPO.     

Methods for the Trace Oxygen Removal from Methane‐Rich Gas Streams

Oxygen removal to very low residual contents in methane‐rich gas streams and carbon dioxide as co‐component (simulated biogas) was achieved via three different methods at various temperatures, namely, by reduction with hydrogen admixtures on Pt/γ‐Al₂O₃ catalysts, by oxygen absorption affinity of YBaCo₄O_7+δ, and by the catalytic reaction with methane on both the materials, respectively. The three methods have characteristic advantages and disadvantages which are discussed in the context of existing methods for gas treatments focused on oxygen removal. Finally, the advantage of dielectric radio‐frequency heating on the powdered functional materials is suggested as alternative to conventional routes.     

Comparison of different propagation steps for lattice Boltzmann methods

Several possibilities exist to implement the propagation step of lattice Boltzmann methods. This paper describes common implementations and compares the number of memory transfer operations they require per lattice node update. A performance model based on the memory bandwidth is then used to obtain an estimation of the maximum achievable performance on different machines. A subset of the discussed implementations of the propagation step are benchmarked on different Intel- and AMD-based compute nodes using the framework of an existing flow solver that is specially adapted to simulate flow in porous media, and the model is validated against the measurements. Advanced approaches for the propagation step like “A–A pattern” or “Esoteric Twist” require more programming effort but often sustain significantly better performance than non-naïve but straightforward implementations.     

MiR-205 Is Progressively Down-Regulated in Lymph Node Metastasis but Fails as a Prognostic Biomarker in High-Risk Prostate Cancer

The treatment of high-risk prostate cancer (HRPCa) is a tremendous challenge for uro-oncologists. The identification of predictive moleculobiological markers allowing risk assessment of lymph node metastasis and systemic progression is essential in establishing effective treatment. In the current study, we investigate the prognostic potential of miR-205 in HRPCa study and validation cohorts, setting defined clinical endpoints for both. We demonstrate miR-205 to be significantly down-regulated in over 70% of the HRPCa samples analysed and that reconstitution of miR-205 causes inhibition of proliferation and invasiveness in prostate cancer (PCa) cell lines. Additionally, miR-205 is increasingly down-regulated in lymph node metastases compared to the primary tumour indicating that miR-205 plays a role in migration of PCa cells from the original location into extraprostatic tissue. Nevertheless, down-regulation of miR-205 in primary PCa was not correlated to the synchronous presence of metastasis and failed to predict the outcome for HRPCa patients. Moreover, we found a tendency for miR-205 up-regulation to correlate with an adverse outcome of PCa patients suggesting a pivotal role of miR-205 in tumourigenesis. Overall, we showed that miR-205 is involved in the development and metastasis of PCa, but failed to work as a useful clinical biomarker in HRPCa. These findings might have implications for the use of miR-205 as a prognostic or therapeutic target in HRPCa.     

YedY: A Mononuclear Molybdenum Enzyme with a Redox‐Active Ligand?

A recent electrochemical investigation suggests that the mononuclear molybdenum enzyme YdeY utilizes redox‐active ligands during catalysis.