High Sensitivity Stress Sensor Based on Hybrid Materials

A sensing device is used to detect the spatial distributions of stresses applied by physical contact with the surface of the sensor or induced by pressure, temperature gradients, and surface absorption. The sensor comprises a hybrid active layer that includes luminophores doped in a polymeric or organic host, altogether embedded in a matrix. Under an electrical bias, the sensor simultaneously converts stresses into electrical and optical signals. Among many applications, the device may be used for tactile sensing and biometric imaging

Two-Level Brezzi-Pitkäranta Discretization Method Based on Newton Iteration for Navier-Stokes Equations with Friction Boundary Conditions

We present a new stabilized finite element method for Navier-Stokes equations with friction slip boundary conditions based on Brezzi-Pitkäranta stabilized method. The stability and error estimates of numerical solutions in some norms are derived for standard one-level method. Combining the techniques of two-level discretization method, we propose two-level Newton iteration method and show the stability and error estimate. Finally, the numerical experiments are given to support the theoretical results and to check the efficiency of this two-level iteration method

Bis(μ-biphenyl-2,2′-dicarboxyl­ato)bis­[(2,2′-bipyridine)cobalt(II)]

In the title compound, [Co2(C14H8O4)2(C10H8N2)2], the CoII atom is coordinated by two N atoms from one 2,2′-bipyridine ligand and two O atoms from two biphenyl-2,2′-dicarboxyl­ate (2,2′-dpa) ligands in a distorted planar geometry. Longer Co—O contacts [2.437 (3) and 2.552 (3) Å] are formed to the second O atom of each coordinated carboxyl­ate group so that these groups approximate a bidentate coordination mode and the coordination geometry around CoII approaches distorted octa­hedral. The 2,2′-dpa ligands bridge two CoII atoms, forming a cyclic dinuclear complex around a centre of inversion

Tetra­imidazolium piperazinediium bis­(benzene-1,3,5-tricarboxyl­ate) dihydrate

During the crystallization of the title compound, 4C3H5N2 +·C4H12N2 +·2C9H3O6 3−·2H2O, the acidic protons were transferred to the imidazole and piperazine N atoms, forming the final 4:1:2:2 hydrated mixed salt. The mean planes of the three carboxyl­ate groups in the anion are twisted with respect to the the central benzene ring, making dihedral angles of 13.5 (1), 14.5 (1) and 16.9 (1)°. In the crystal, the component ions are linked into a three-dimensional network by a combination of inter­molecular N—H⋯O, O—H⋯O and weak C—H⋯O hydrogen bonds. Further stabilization is provided by π-π stacking inter­actions with centroid–centroid distances of 3.393 (2) Å and weak C=O⋯π inter­actions [O–centroid = 3.363 (2) Å]

catena-Poly[[diaqua­(2,2′-bipyridine-κ2 N,N′)nickel(II)]-μ-biphenyl-2,2′-dicarboxyl­ato-κ2 O:O′]

In the title compound, [Ni(C14H8O4)(C10H8N2)(H2O)2]n, the NiII atom is coordinated in a slightly distorted octa­hedral geometry by two water mol­ecules, two N atoms from a 2,2′-bipyridine ligand and two O atoms from the carboxyl­ate groups of two 2,2′-biphenyl­dicarboxyl­ate (2,2′-dpa) ligands. The 2,2′-dpa ligand acts as a bridge between neighbouring NiII atoms, forming one-dimensional coordination polymers along [100]. The coordinated water mol­ecules form hydrogen bonds to the carboxyl­ate O atoms of 2,2′-dpa within the same coordination polymer, and one O—H⋯π inter­action is also formed to 2,2′-dpa

Rigid vortices in MgB2

Magnetic relaxation of high-pressure synthesized MgB$_2$ bulks with different thickness is investigated. It is found that the superconducting dia-magnetic moment depends on time in a logarithmic way; the flux-creep activation energy decreases linearly with the current density (as expected by Kim-Anderson model); and the activation energy increases linearly with the thickness of sample when it is thinner than about 1 mm. These features suggest that the vortices in the MgB$_2$ are rather rigid, and the pinning and creep can be well described by Kim-Anderson model.Comment: Typo corrected & reference adde

Current-voltage characteristics of NdFeAsO0.85F0.15 and NdFeAsO0.85 superconductors

The vortex phase diagrams of NdFeAsO0.85F0.15 and NdFeAsO0.85 superconductors are determined from the analysis of resistivity and current-voltage (I-V) measurements in magnetic fields up to 9 T. A clear vortex glass to liquid transition is identified only in the oxygen deficient NdFeAsO0.85, in which I-V curves can be well scaled onto liquid and glass branches consistent with the vortex glass theory. With increasing magnetic field, the activation energy U0, deduced from the Arrhenius plots of resistivity based on the thermally activated flux-flow model (TAFF), decays more quickly for NdFeAsO0.85F0.15 than for NdFeAsO0.85. Moreover, the irreversibility field Hirr of NdFeAsO0.85 increases more rapidly than that of NdFeAsO0.85F0.15 with decreasing temperature. These observations evidence the strong vortex pinning effects, presumably caused by the enhanced defects and disorders in the oxygen deficient NdFeAsO0.85. It is inferred that the enhanced defects and disorder can be also responsible for the vortex glass to liquid transition in the NdFeAsO0.85.Comment: 19 pages, 5 figure