35,998 research outputs found
Effect of charged impurities on graphene thermoelectric power near the Dirac point
In graphene devices with a varying degree of disorders as characterized by
their carrier mobility and minimum conductivity, we have studied the
thermoelectric power along with the electrical conductivity over a wide range
of temperatures. We have found that the Mott relation fails in the vicinity of
the Dirac point in high-mobility graphene. By properly taking account of the
high temperature effects, we have obtained good agreement between the Boltzmann
transport theory and our experimental data. In low-mobility graphene where the
charged impurities induce relatively high residual carrier density, the Mott
relation holds at all gate voltages
Growth rate of YBCO single grains containing Y-2411(M)
Y-Ba-Cu-O (YBCO) single grains have the potential to generate large trapped magnetic fields for a variety of engineering applications, and research on the processing and properties of this material has attracted world-wide interest. In particular, the introduction of flux pinning centres to the large grain microstructure to improve its current density, Jc, and hence trapped field, has been investigated extensively over the past decade. Y 2Ba4CuMOx [Y-2411(M)], where M = Nb, Ta, Mo, W, Ru, Zr, Bi and Ag, has been reported to form particularly effective flux pinning centres in YBCO due primarily to its ability to exist as nano-size inclusions in the superconducting phase matrix. However, the addition of the Y-2411(M) phase to the precursor composition complicates the melt-processing of single grains. We report an investigation of the growth rate of single YBCO grains containing Y-2411(Bi) phase inclusions and Y2O3. The superconducting properties of these large single grains have been measured specifically to investigate the effect of Y2O3 on broadening the growth window of these materials
The Antimicrobial Effect of Silver Ion Impregnation into Endodontic Sealer against Streptococcus mutans.
Pulpal and periradicular diseases are primarily caused by bacterial invasion of the root canal system as a result of caries progression. The presence of residual bacteria at the time of root canal completion (obturation) is associated with significantly higher rate of treatment failure. Re-infection of obturated root canals can be potentially prevented by enhancing the antibacterial activities of root canal obturation materials. We evaluated, in an in vitro model, the antimicrobial efficacy of silver ions added to a common endodontic sealer. For that purpose we performed growth inhibition studies and bacterial viability tests. We measured the zone of inhibition, optical density and performed confocal laser scanning microscopy. Our results show that the silver ions enhance the antimicrobial activity of the root canal sealer against Streptococcus mutans. This study approach may hold promise for studying other biologically based therapies and therefore increasing the success rate of routine orthograde root canal treatment
Energy transfer, pressure tensor and heating of kinetic plasma
Kinetic plasma turbulence cascade spans multiple scales ranging from
macroscopic fluid flow to sub-electron scales. Mechanisms that dissipate large
scale energy, terminate the inertial range cascade and convert kinetic energy
into heat are hotly debated. Here we revisit these puzzles using fully kinetic
simulation. By performing scale-dependent spatial filtering on the Vlasov
equation, we extract information at prescribed scales and introduce several
energy transfer functions. This approach allows highly inhomogeneous energy
cascade to be quantified as it proceeds down to kinetic scales. The pressure
work, , can
trigger a channel of the energy conversion between fluid flow and random
motions, which is a collision-free generalization of the viscous dissipation in
collisional fluid. Both the energy transfer and the pressure work are strongly
correlated with velocity gradients.Comment: 28 pages, 10 figure
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