1,012 research outputs found
Dynamics vs electronic states of vortex core of high-T_c superconductors investigated by high-frequency impedance measurement
Dynamics of vortices reflects the electronic states of quasiparticles in the
core. To understand this, we investigated the following three issues. (1) We
investigated the complex surface impedance, Zs, of YBa2Cu3Oy as a function of
magnetic field, H. The total features were well expressed by the Coffey-Clem
model. From the data, we estimated the viscosity and pinning frequency, which
were found to be independent of frequency. In particular, the obtained
viscosity definitely shows that the core of vortex of YBa2Cu3Oy is moderately
clean. This result suggests that new physics will show up, for the physics of
quantum moderately clean vortex core is unknown at all. (2) An anomaly found in
the surface reactance at the first order transition (FOT) of vortex lattice was
investigated in Bi2Sr2CaCu2Oy with various doping levels. As a result, the
anomaly was found only in the samples exhibiting the FOT. On the other hand, we
did not observe the anomaly in YBa2Cu3Oy. These suggest that the anomaly is due
to the change in the electronic states of the vortices characteristic of
materials with very strong anisotropy. (3) We measured H dependence of both the
thermal conductivity \kappa(H) and Zs(H) in exactly the same pieces of crystal.
We could not find any anomaly in Zs(H) even at the onset of the plateau. This
result suggests that the origin of the plateau in \kappa(H) is not a drastic
phase transition but is rather gradual crossover.Comment: 6 pages, 5 figures, Proceedings of Plasma2000(Sendai), to be
published in Physica
Role of carbon dioxide and ion transport in the formation of sub-embryonic fluid by the blastoderm of the Japanese quail
1. The explanted blastoderm of the Japanese quail was used to explore the role of ions and carbon dioxide in determining the rate of sub-embryonic fluid (SEF) production between 54 and 72 h of incubation.
2. Amiloride, an inhibitor of Na+/H+ exchange, at concentrations of 10-3 to 10-6 M substantially decreased the rate of SEF production when added to the albumen culture medium. N-ethylmaleimide, an inhibitor of V type H+ ATPase, also decreased this rate but only to a small extent at the highest dose applied, 10-3 M. Both inhibitors had no effect on SEF production when added to the SEF. 3. The inhibitors of cellular bicarbonate and chloride exchange, 4-acetamido-4-'isothiocyano-2, 2-'disulphonic acid (SITS) and 4,4'diisothiocyanostilbene-2,2-'disulphonic acid (DIDS), had no effect upon SEF production.
4. Ouabain, an inhibitor of Na+/K+ ATPase, decreased SEF production substantially at all concentrations added to the SEF (10-3 to 10-6 M). Three sulphonamide inhibitors of carbonic anhydrase, acetazolamide, ethoxzolamide and benzolamide, decreased SEF production when added to the SEF at concentrations of 10-3 to 10-6 M. Benzolamide was by far the most potent. Neither ouabain nor the sulphonamides altered SEF production when added to the albumen culture medium.
5. Using a cobalt precipitation method, carbonic anhydrase activity was localised to the endodermal cells of the area vasculosa. The carbonic anhydrase activity was primarily associated with the lateral plasma membranes, which together with the potent inhibitory effect of benzolamide, suggests the carbonic anhydrase of these cells is the membrane-associated form, CA IV.
6. The changes in SEF composition produced by inhibitors were consistent with the production of SEF by local osmotic gradients.
7. It is concluded that a Na+/K+ ATPase is located on the basolateral membranes of the endodermal cells of the area vasculosa , and that a sodium ion/hydrogen ion exchanger is located on their apical surfaces. Protons for this exchanger would be provided by the hydration of CO2 catalysed by the membrane-associated carbonic anhydrase. Furthermore, it is proposed that the prime function of the endodermal cells of the area vasculosa is the production of SEF
Vortex Collisions: Crossing or Recombination?
We investigate the collision of two vortex lines moving with viscous dynamics
and driven towards each other by an applied current. Using London theory in the
approach phase we observe a non-trivial vortex conformation producing
anti-parallel segments; their attractive interaction triggers a violent
collision. The collision region is analyzed using the time-dependent
Ginzburg-Landau equation. While we find vortices will always recombine through
exchange of segments, a crossing channel appears naturally through a double
collision process.Comment: 4 pages, 3 figure
Collaboration and the Emerging Craft Brewing Industry: An Exploratory Study
In adopting various elements associated with the theory of collaboration, this exploratory study investigates collaboration in the context of predominantly micro- and small craft breweries. The findings revealed that collaboration within other brewers helped increase product quality, gain basic knowledge of new recipes, and enhance strategic knowledge about the industry. The applicability of the elements related to the theory of collaboration was confirmed. For instance, the element of stakeholders of a problem domain was aligned with the notion that craft brewery operators’ actions, including collaboration, can have significant impacts on the problem domain that brought them together. © 2018 Taylor & Francis Group, LL
Absence of a Finite-Temperature Melting Transition in the Classical Two-Dimensional One-Component Plasma
Vortices in thin-film superconductors are often modelled as a system of
particles interacting via a repulsive logarithmic potential. Arguments are
presented to show that the hypothetical (Abrikosov) crystalline state for such
particles is unstable at any finite temperature against proliferation of
screened disclinations. The correlation length of crystalline order is
predicted to grow as as the temperature is reduced to zero, in
excellent agreement with our simulations of this two-dimensional system.Comment: 3 figure
Disorder Induced Transitions in Layered Coulomb Gases and Superconductors
A 3D layered system of charges with logarithmic interaction parallel to the
layers and random dipoles is studied via a novel variational method and an
energy rationale which reproduce the known phase diagram for a single layer.
Increasing interlayer coupling leads to successive transitions in which charge
rods correlated in N>1 neighboring layers are nucleated by weaker disorder. For
layered superconductors in the limit of only magnetic interlayer coupling, the
method predicts and locates a disorder-induced defect-unbinding transition in
the flux lattice. While N=1 charges dominate there, N>1 disorder induced defect
rods are predicted for multi-layer superconductors.Comment: 4 pages, 2 figures, RevTe
Evaporation of the pancake-vortex lattice in weakly-coupled layered superconductors
We calculate the melting line of the pancake-vortex system in a layered
superconductor, interpolating between two-dimensional (2D) melting at high
fields and the zero-field limit of single-stack evaporation. Long-range
interactions between pancake vortices in different layers permit a mean-field
approach, the ``substrate model'', where each 2D crystal fluctuates in a
substrate potential due to the vortices in other layers. We find the thermal
stability limit of the 3D solid, and compare the free energy to a 2D liquid to
determine the first-order melting transition and its jump in entropy.Comment: 4 pages, RevTeX, two postscript figures incorporated using eps
Topological Defects in the Abrikosov Lattice of Vortices in Type-II Superconductors
The free energy costs for various defects within an Abrikosov lattice of
vortices are calculated using the lowest Landau level approximation (LLL).
Defect solutions with boundary conditions for lines to meet at a point
(crossing defect) and for lines to twist around each other (braid defect) are
sought for 2, 3, 6, and 12 lines. Many results have been unexpected, including
the nonexistence of a stable two- or three-line braid. This, and the high
energy cost found for a six-line braid lead us to propose that the equilibrium
vortex state is not entangled below the irreversibility line of the high-
superconductors or in a large part of the vortex-liquid phase above this line.
Also, the solution for an infinite straight screw dislocation is found, and
used to give a limiting form for the free energy cost of very large braids.
This depends on the area enclosed by the braid as well as its perimeter length.Comment: 30 pages, 17 Encapsulated PostScript figures, uses Revtex (with epsf
The effects of relative importance of user constraints in cloud of things resource discovery: a case study
Over the last few years, the number of smart objects connected to the Internet has grown exponentially in comparison to the number of services and applications. The integration between Cloud Computing and Internet of Things, named as Cloud of Things, plays a key role in managing the connected things, their data and services. One of the main challenges in Cloud of Things is the resource discovery of the smart objects and their reuse in different contexts. Most of the existent work uses some kind of multi-criteria decision analysis algorithm to perform the resource discovery, but do not evaluate the impact that the user constraints has in the final solution. In this paper, we analyse the behaviour of the SAW, TOPSIS and VIKOR multi-objective decision analyses algorithms and the impact of user constraints on them. We evaluated the quality of the proposed solutions using the Pareto-optimality concept
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