501 research outputs found
Scaling of the conductance distribution near the Anderson transition
The single parameter scaling hypothesis is the foundation of our
understanding of the Anderson transition. However, the conductance of a
disordered system is a fluctuating quantity which does not obey a one parameter
scaling law. It is essential to investigate the scaling of the full conductance
distribution to establish the scaling hypothesis. We present a clear cut
numerical demonstration that the conductance distribution indeed obeys one
parameter scaling near the Anderson transition
Anderson transition in three-dimensional disordered systems with symplectic symmetry
The Anderson transition in a 3D system with symplectic symmetry is
investigated numerically. From a one-parameter scaling analysis the critical
exponent of the localization length is extracted and estimated to be . The level statistics at the critical point are also analyzed
and shown to be scale independent. The form of the energy level spacing
distribution at the critical point is found to be different from that
for the orthogonal ensemble suggesting that the breaking of spin rotation
symmetry is relevant at the critical point.Comment: 4 pages, revtex, to appear in Physical Review Letters. 3 figures
available on request either by fax or normal mail from
[email protected] or [email protected]
The Anderson Transition in Two-Dimensional Systems with Spin-Orbit Coupling
We report a numerical investigation of the Anderson transition in
two-dimensional systems with spin-orbit coupling. An accurate estimate of the
critical exponent for the divergence of the localization length in this
universality class has to our knowledge not been reported in the literature.
Here we analyse the SU(2) model. We find that for this model corrections to
scaling due to irrelevant scaling variables may be neglected permitting an
accurate estimate of the exponent
Randomized controlled trial to assess the effectiveness of a videotape about radiotherapy
In a randomized controlled trial, the additional provision of information on videotape was no more effective than written information alone in reducing pre-treatment worry about radiotherapy. Images of surviving cancer patients, however, may provide further reassurance to patients once therapy is completed. © 2001 Cancer Research Campaign http://www.bjcancer.co
Magnetic-Field Dependence of the Localization Length in Anderson Insulators
Using the conventional scaling approach as well as the renormalization group
analysis in dimensions, we calculate the localization length
in the presence of a magnetic field . For the quasi 1D case the
results are consistent with a universal increase of by a numerical
factor when the magnetic field is in the range
\ell\ll{\ell_{\!{_H}}}\alt\xi(0), is the mean free path,
is the magnetic length . However, for
where the magnetic field does cause delocalization there is no
universal relation between and . The effect of spin-orbit
interaction is briefly considered as well.Comment: 4 pages, revtex, no figures; to be published in Europhysics Letter
Scaling Theory of Conduction Through a Normal-Superconductor Microbridge
The length dependence is computed of the resistance of a disordered
normal-metal wire attached to a superconductor. The scaling of the transmission
eigenvalue distribution with length is obtained exactly in the metallic limit,
by a transformation onto the isobaric flow of a two-dimensional ideal fluid.
The resistance has a minimum for lengths near l/Gamma, with l the mean free
path and Gamma the transmittance of the superconductor interface.Comment: 8 pages, REVTeX-3.0, 3 postscript figures appended as self-extracting
archive, INLO-PUB-94031
The effect of a randomized 12-week soy drink intervention on everyday mood in postmenopausal women
Objective: Dietary soy may improve menopausal symptoms, and subsequently mediate mood. This novel study examines various doses of dietary soy drink on everyday mood stability and variability in postmenopausal women. Methods: Community-dwelling women (n = 101), within 7 years postmenopause, consumed daily either a low (10 mg, n = 35), medium (35 mg, n = 37), or high (60 mg, n = 29) dose of isoflavones, for 12 weeks. Menopausal symptoms and repeated measures of everyday mood (positive [PA] and negative [NA] affect) (assessed at four time points per day for 4 consecutive days, using The Positive and Negative Affect Schedule) were completed at baseline and follow-up. Results: The dietary soy intervention had no effect on everyday mood stability (for PA [F{2,70} = 0.95, P = 0.390] and NA [F{2,70} = 0.72, P = 0.489]) or variability (for PA [F{2,70} = 0.21, P = 0.807] and for NA [F{2,70} = 0.15, P = 0.864]), or on menopausal symptoms (for vasomotor [F{2,89} = 2.83, P = 0.064], psychological [F{2,88} = 0.63, P = 0.535], somatic [F{2,89} = 0.32, P = 0.729], and total menopausal symptoms [F{2,86} = 0.79, P = 0.458]). There were between-group differences with the medium dose reporting higher PA (low, mean 24.2, SD 6; and medium, mean 29.7, SD 6) and the low dose reporting higher NA (P = 0. 048) (low, mean 11.6, SD 2; and high, mean 10.6, SD 1) in mood scores. Psychological (baseline M = 18 and follow-up M = 16.5) and vasomotor (baseline M = 4.2 and follow-up M = 3.6) scores declined from baseline to follow-up for the overall sample. Conclusions: Soy isoflavones had no effect on mood at any of the doses tested. Future research should focus on the menopause transition from peri to postmenopause as there may be a window of vulnerability, with fluctuating hormones and increased symptoms which may affect mood
Localization Transition in Multilayered Disordered Systems
The Anderson delocalization-localization transition is studied in
multilayered systems with randomly placed interlayer bonds of density and
strength . In the absence of diagonal disorder (W=0), following an
appropriate perturbation expansion, we estimate the mean free paths in the main
directions and verify by scaling of the conductance that the states remain
extended for any finite , despite the interlayer disorder. In the presence
of additional diagonal disorder () we obtain an Anderson transition with
critical disorder and localization length exponent independently of
the direction. The critical conductance distribution varies,
however, for the parallel and the perpendicular directions. The results are
discussed in connection to disordered anisotropic materials.Comment: 10 pages, Revtex file, 8 postscript files, minor change
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