Correlation Between Segmental Dynamics,Glass Transition,and Lithium Ion Conduction in Poly(Methyl Methacrylate)/Ionic Liquid Mixture

A solid-state membrane of a polymer/ionic liquid miscible mixture, poly(methyl methacrylate) (PMMA) and 1-butyl-3-methylimidazolium hexafluorophosphate (BMIMPF₆) doped with lithium perchlorate (LiClO₄), was prepared and characterized. Miscibility, segmental dynamics, glass transition and ionic conductivity were investigated. Based on the results from differential scanning calorimetry (DSC) and dynamic mechanical thermal analysis (DMTA), the system is fully miscible and of single phase. Broadening of the glass transition was observed when increasing the amount of ionic liquid, which can be attributed to mobility and flexibility differences between the polymer and ionic liquid. A large dynamical asymmetry and intrinsic mobility difference allow segmental and structural motion/relaxation over a wider temperature range by increasing the amount of ionic liquid. Saturation recovery spin–lattice relaxation time (T₁) versus temperature obtained from ⁷Li nuclear magnetic resonance (NMR) showed high mobility of lithium ions, which was almost temperature independent. Lithium ion conductivity significantly increases with increasing ionic liquid amount. It is concluded that lithium ion mobility and its conduction is positively correlated to segmental dynamics of ion carriers in this model system, which is more noticeable in mixtures with higher amounts of the ionic liquid.     

Observation of turbulent-driven shear flow in a cylindrical laboratory plasma device

An azimuthally symmetric radially sheared plasma fluid flow is observed to spontaneously form in a cylindrical magnetized helicon plasma device with no external sources of momentum input. A turbulent momentum conservation analysis shows that this shear flow is sustained by the Reynolds stress generated by collisional drift turbulence in the device. The results provide direct experimental support for the basic theoretical picture of drift-wave-shear-flow interactions.     

Evidence for a transition in deformation mechanism in nanocrystalline pure titanium processed by high-pressure torsion

Nanocrystalline titanium with an average grain size of about 60–70 nm was prepared by high-pressure torsion. The results of hardness and structural evolutions indicate that a strain-induced hardening–softening–hardening–softening behaviour occurs. For coarse-grained titanium, 〈a〉-type dislocation multiplication, twinning and a high pressure-induced α-to-ω phase transformation play major roles to accommodate deformation, leading to a significant strain hardening. As deformation proceeds, dynamic recrystallisation leads to a decrease in dislocation density, especially for 〈a〉-type dislocations, leading to a slight strain softening. The 〈c〉-component dislocation multiplication dominates the deformation when the grain size decreases to 100 nm and 〈c〉-component dislocation multiplication, grain refinement and the α-to-ω phase transformation contribute to the second strain hardening. The following strain softening is attributed to dynamic recovery.     

Analysis and design of simple low-loss wide-angle waveguide bends

In this paper a simple low-loss planar waveguide wide-angle bend is proposed and analyzed. The waveguide bend of this work consists of a curved tapered angle such that its tapering can be adjusted for a minimum loss (maximum transmission coefficient) and small dimension of bend. The analysis is done using wide-angle BPM (beam propagation method) type Pade (4,4). The simulated results of different bends show that at the same transmission coefficient the area required for the proposed bends are smaller than those of the abrupt bends.     

Local chemical state change in Co–O resistance random access memory

Kelvin probe force microscopy (KFM) and conductive atomic force microscopy (C‐AFM) together with micro X‐ray photoelectron spectroscopy (XPS) were performed for the stacking structure comprising of the transition metal oxide Co–O and metal electrode, which exhibits large reproducible resistance switching. The application of the external voltage by the C‐AFM cantilever decreases the resistance of Co–O, which well accords with the non‐polar forming process observed in the Pt/Co–O/Pt trilayer, known as the candidate of resistance random access memory (ReRAM). Furthermore, the KFM and micro XPS experimentally revealed that the local reductive reaction of Co–O possibly nucleates the defect related energy levels which dominates the current conduction in the low resistance state. (© 2008 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)     

Ammonium chloride-catalyzed green multicomponent synthesis of dihydropyrazine and tetrahydrodiazepine derivatives “on water”

Molecular Diversity - This research describes a simple and efficient one-pot synthetic approach for the preparation of tetrahydrodiazepine and dihydropyrazine (or dihydroquinoxaline) derivatives in...     

Strategies for synthesis of 1,2,4-triazole-containing scaffolds using 3-amino-1,2,4-triazole

Molecular Diversity - 1,2,4-Triazole-containing scaffolds are unique heterocyclic compounds present in an array of pharmaceuticals and biologically important compounds used in the drug-discovery...