85 research outputs found
Emergency Contraception in the UK: Stigma as a Key Ingredient of a Fundamental Women’s Healthcare Product
Universal saturation of electron dephasing in three-dimensional disordered metals
We have systematically investigated the low-temperature electron dephasing
times in more than 40 three-dimensional polycrystalline impure
metals with distinct material characteristics. In all cases, a saturation of
the dephasing time is observed below about a (few) degree(s) Kelvin, depending
on samples. The value of the saturated dephasing time [] falls basically in the range 0.005 to 0.5 ns for
all samples. Particularly, we find that scales with the electron
diffusion constant as , with close to or
slightly larger than 1, for over two decades of from about 0.1 to 10
cm/s. Our observation suggests that the saturation behavior of
is universal and intrinsic in three-dimensional polycrystalline impure metals.
A complete theoretical explanation is not yet available.Comment: 4 pages, 3 eps figure
Effect of Iodine Doping on BiSrCaCuO: Charge Transfer or Interlayer Coupling?
A comparative study has been made of iodine-intercalated
BiSrCaCuO single crystal and 1 atm O
annealed BiSrCaCuO single crystal using AC
susceptibility measurement, X-ray photoemission (XPS) and angle-resolved
ultraviolet photoemission spectroscopy (ARUPS). AC susceptibility measurement
indicates that O-doped samples studied have T of 84 K,
whereas T of Iodine-doped samples studied are 80 K. XPS Cu 2p core
level data establish that the hole concentration in the CuO planes are
essentially the same for these two kinds of samples. ARUPS measurements show
that electronic structure of the normal states near the Fermi level has been
strongly affected by iodine intercalation. We conclude that the dominant effect
of iodine doping is to alter the interlayer coupling.Comment: LBL 9 pages, APS_Revtex. 5 Figures, available upon request.
UW-Madison preprin
Intrinsic Decoherence in Mesoscopic Systems
We present measurements of the phase coherence time in six
quasi-1D Au wires and clearly show that is temperature independent
at low temperatures. We suggest that zero-point fluctuations of the intrinsic
electromagnetic environment are responsible for the observed saturation of
. We introduce a new functional form for the temperature dependence
and present the results of a calculation for the saturation value of
. This explains the observed temperature dependence of our samples
as well as many 1D and 2D systems reported to date.Comment: 4 pages, 4 figures & 1 tabl
Phase-coherence time saturation in mesoscopic systems: wave function collapse
A finite phase-coherence time emerges from iterative
measurement onto a quantum system. For a rapid sequence, the phase-coherence
time is found explicitly. For the stationary charge conduction problem, it is
bounded. At all order, in the time-interval of measurements, we propose a
general expression for .Comment: 8 pages, 0 figures, Late
Evidence for a Two-stage Melting Transition of the Vortex Matter in Bi2Sr2Ca1Cu2O8+d Single Crystals obtained by Muon Spin Rotation
From muon spin rotation measurements on under- to overdoped Bi-2212 crystals
we obtain evidence for a two-stage transition of the vortex matter as a
function of temperature. The first transition is well known and related to the
irreversibility line (IL). The second one is located below the IL and has not
been previously observed. It occurs for all three sets of crystals and is
unrelated to the vortex mobility. Our data are consistent with a two-stage
melting scenario where the intra-planar melting of the vortex lattice and the
inter-planar decoupling of the vortex lines occur independently.Comment: 9 pages and 3 figure
Non-linear effects and dephasing in disordered electron systems
The calculation of the dephasing time in electron systems is presented. By
means of the Keldysh formalism we discuss in a unifying way both weak
localization and interaction effects in disordered systems. This allows us to
show how dephasing arises both in the particle-particle channel (weak
localization) and in the particle-hole channel (interaction effect). First we
discuss dephasing by an external field. Besides reviewing previous work on how
an external oscillating field suppresses the weak localization correction, we
derive a new expression for the effect of a field on the interaction
correction. We find that the latter may be suppressed by a static electric
field, in contrast to weak localization. We then consider dephasing due to
inelastic scattering. The ambiguities involved in the definition of the
dephasing time are clarified by directly comparing the diagrammatic approach
with the path-integral approach. We show that different dephasing times appear
in the particle-particle and particle-hole channels. Finally we comment on
recent experiments.Comment: 28 pages, 6 figures (14ps-files
The effectiveness of seated combined extension-compression and transverse load traction in increasing cervical lordosis-challenging the underlying framework
Introduction: The goal of this study was to assess the effectiveness of seated combined extension-compression and transverse load (ECTL) traction as a new method for increasing a reduced lordosis of less than 30 degrees in a Malaysian population between the ages of 18 and 60 years. Possible changes in disc height were measured in accordance with the underlying theoretical framework, that suggests the anterior cervical structures would elongate due to creep over the fulcrum of the traction device. Method: This was a single centre, randomised, blinded controlled clinical trial with parallel groups, used to test the superiority of the seated combined ECTL traction together with physiotherapy exercises when compared with the same physiotherapy exercises used as a control. Fifty randomly allocated subjects who completed the forty treatments over the fourteen weeks were analysed using non-parametric tests for changes in outcomes. Results: There were no significant changes in outcomes for disc height changes seen in this study. The findings of a greater overall increase in posterior disc height changes compared with anterior disc height changes were in contrast with the proposed underlying theoretical framework for this type of ECTL traction. The greater height changes occurring in the control group were also unexpected. Conclusion: The findings in this study of the contrasting changes in disc height of greater posterior than anterior height changes, question the underlying theoretical framework as postulated for this type of traction
Dephasing of Electrons by Two-Level Defects in Quantum Dots
The electron dephasing time in a diffusive quantum dot is
calculated by considering the interaction between the electron and dynamical
defects, modelled as two-level system. Using the standard tunneling model of
glasses, we obtain a linear temperature dependence of ,
consistent with the experimental observation. However, we find that, in order
to obtain dephasing times on the order of nanoseconds, the number of two-level
defects needs to be substantially larger than the typical concentration in
glasses. We also find a finite system-size dependence of , which
can be used to probe the effectiveness of surface-aggregated defects.Comment: two-column 9 page
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