2,259 research outputs found
Origin of time reversal symmetry breaking in Y(1-y)Ca(y)Ba(2)Cu(3)O(7-x)
We have studied the Zero Bias Conductance Peak (ZBCP) of the tunneling
conductance measured on (1,1,0) oriented Y(1-y)Ca(y)Ba(2)Cu(3)O(7-x) thin films
as a function of doping and of magnetic field. A spontaneous (zero field) split
of the ZBCP was observed only in overdoped samples (either by O or by Ca). The
magnitude of this split was found to be linear in doping. All samples exhibited
a magnetic field splitting, also strongly doping dependent. The field
susceptibility chi=d(delta)/dH diverges at the point at which spontaneous ZBCP
splitting occurs, its inverse value, chi^(-1), following a linear doping
dependence on both the underdoped and overdoped sides. We discuss these results
in terms of recent theoretical models of Time Reversal Symmetry Breaking
(TRSB).Comment: 5 figure
A Taxing Settlement
Citizens sue industries for tort injuries. That is familiar. Governments sue the same industries for costs suffered in ameliorating or preventing those injuries. That is unfamiliar. This new pattern of litigation and settlement inherently puts the government in competition with its citizens
A Taxing Settlement
The following essay is based on the talk Government, Citizens, and Injurious Industries: A Case Study of the Tobacco Litigation, delivered by Hanoch Dagan last May to the Detroit Chapter of the International Association of Jewish Lawyers and Jurists, and on the article Governments, Citizens, and Injurious Industries, by Dagan and James J. White, \u2762, which appeared in 75.2 New York University Law Review 254-428 (May 2000). The authors hold conflicting view on the underlying issue of this topic: tobacco company product liability. Professor Dagan holds the position that tobacco companies are liable for harm done by their products; Professor White argues that tobacco companies are not liable for harm done by their products
Role of oxygen in the electron-doped superconducting cuprates
We report on resistivity and Hall measurements in thin films of the
electron-doped superconducting cuprate PrCeCuO.
Comparisons between x = 0.17 samples subjected to either ion-irradiation or
oxygenation demonstrate that changing the oxygen content has two separable
effects: 1) a doping effect similar to that of cerium, and 2) a disorder
effect. These results are consistent with prior speculations that apical oxygen
removal is necessary to achieve superconductivity in this compound.Comment: 5 pages, 5 figure
Use of groundwater lifetime expectancy for the performance assessment of a deep geologic waste repository: 1. Theory, illustrations, and implications
Long-term solutions for the disposal of toxic wastes usually involve
isolation of the wastes in a deep subsurface geologic environment. In the case
of spent nuclear fuel, if radionuclide leakage occurs from the engineered
barrier, the geological medium represents the ultimate barrier that is relied
upon to ensure safety. Consequently, an evaluation of radionuclide travel times
from a repository to the biosphere is critically important in a performance
assessment analysis. In this study, we develop a travel time framework based on
the concept of groundwater lifetime expectancy as a safety indicator. Lifetime
expectancy characterizes the time that radionuclides will spend in the
subsurface after their release from the repository and prior to discharging
into the biosphere. The probability density function of lifetime expectancy is
computed throughout the host rock by solving the backward-in-time solute
transport adjoint equation subject to a properly posed set of boundary
conditions. It can then be used to define optimal repository locations. The
risk associated with selected sites can be evaluated by simulating an
appropriate contaminant release history. The utility of the method is
illustrated by means of analytical and numerical examples, which focus on the
effect of fracture networks on the uncertainty of evaluated lifetime
expectancy.Comment: 11 pages, 8 figures; Water Resources Research, Vol. 44, 200
Polydisperse spray flames in vortex flows
[EN] A new mathematical analysis of the dynamics of laminar spray diffusion flames in the vicinity of a vortex flow field
is presented. The governing equations for a spray evaporating in an unsteady vortex are studied. New similarity
solutions are found for the dynamics of the spray and the flame it supports. Analytical solutions for the spray flames
are derived using Schvab-Zeldovich parameters, through which the radial evolution of the flames is found. The
results based on the solution reveal the significant influence the droplets size has on the diffusion flame dynamics
in the vicinity of vortical flows.Dagan, Y.; Katoshevski, D.; Greenberg, BJ. (2017). Polydisperse spray flames in vortex flows. En Ilass Europe. 28th european conference on Liquid Atomization and Spray Systems. Editorial Universitat Politècnica de València. 702-708. https://doi.org/10.4995/ILASS2017.2017.4716OCS70270
Field Induced Nodal Order Parameter in the Tunneling Spectrum of YBaCuO Superconductor
We report planar tunneling measurements on thin films of
YBaCuO at various doping levels under magnetic fields. By
choosing a special setup configuration, we have probed a field induced energy
scale that dominates in the vicinity of a node of the d-wave superconducting
order parameter. We found a high doping sensitivity for this energy scale. At
Optimum doping this energy scale is in agreement with an induced
order parameter. We found that it can be followed down to low fields at optimum
doping, but not away from it.Comment: 9 pages, 8 figures, accepted for publication in Phys. Rev.
Remarkable change of tunneling conductance in YBCO films in fields up to 32.4T
We studied the tunneling density of states in YBCO films under strong
currents flowing along node directions. The currents were induced by fields of
up to 32.4T parallel to the film surface and perpendicular to the
planes. We observed a remarkable change in the tunneling conductance at high
fields where the gap-like feature shifts discontinuously from 15meV to a lower
bias of 11meV, becoming more pronounced as the field increases. The effect
takes place in increasing fields around 9T and the transition back to the
initial state occurs around 5T in decreasing fields. We argue that this
transition is driven by surface currents induced by the applied magnetic field.Comment: 4 pages, 7 figure
On the resistivity at low temperatures in electron-doped cuprate superconductors
We measured the magnetoresistance as a function of temperature down to 20mK
and magnetic field for a set of underdoped PrCeCuO (x=0.12) thin films with
controlled oxygen content. This allows us to access the edge of the
superconducting dome on the underdoped side. The sheet resistance increases
with increasing oxygen content whereas the superconducting transition
temperature is steadily decreasing down to zero. Upon applying various magnetic
fields to suppress superconductivity we found that the sheet resistance
increases when the temperature is lowered. It saturates at very low
temperatures. These results, along with the magnetoresistance, cannot be
described in the context of zero temperature two dimensional
superconductor-to-insulator transition nor as a simple Kondo effect due to
scattering off spins in the copper-oxide planes. We conjecture that due to the
proximity to an antiferromagnetic phase magnetic droplets are induced. This
results in negative magnetoresistance and in an upturn in the resistivity.Comment: Accepted in Phys. Rev.
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