686 research outputs found
Numerical verification of universality for the Anderson transition
We analyze the scaling behavior of the higher Lyapunov exponents at the
Anderson transition. We estimate the critical exponent and verify its
universality and that of the critical conductance distribution for box,
Gaussian and Lorentzian distributions of the random potential
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
Universality of the critical conductance distribution in various dimensions
We study numerically the metal - insulator transition in the Anderson model
on various lattices with dimension (bifractals and Euclidian
lattices). The critical exponent and the critical conductance
distribution are calculated. We confirm that depends only on the {\it
spectral} dimension. The other parameters - critical disorder, critical
conductance distribution and conductance cummulants - depend also on lattice
topology. Thus only qualitative comparison with theoretical formulae for
dimension dependence of the cummulants is possible
Topology dependent quantities at the Anderson transition
The boundary condition dependence of the critical behavior for the three
dimensional Anderson transition is investigated. A strong dependence of the
scaling function and the critical conductance distribution on the boundary
conditions is found, while the critical disorder and critical exponent are
found to be independent of the boundary conditions
Anderson transition in the three dimensional symplectic universality class
We study the Anderson transition in the SU(2) model and the Ando model. We
report a new precise estimate of the critical exponent for the symplectic
universality class of the Anderson transition. We also report numerical
estimation of the function.Comment: 4 pages, 5 figure
Failure of single-parameter scaling of wave functions in Anderson localization
We show how to use properties of the vectors which are iterated in the
transfer-matrix approach to Anderson localization, in order to generate the
statistical distribution of electronic wavefunction amplitudes at arbitary
distances from the origin of disordered systems. For
our approach is shown to reproduce exact diagonalization results
available in the literature. In , where strips of width sites
were used, attempted fits of gaussian (log-normal) forms to the wavefunction
amplitude distributions result in effective localization lengths growing with
distance, contrary to the prediction from single-parameter scaling theory. We
also show that the distributions possess a negative skewness , which is
invariant under the usual histogram-collapse rescaling, and whose absolute
value increases with distance. We find for the
range of parameters used in our study, .Comment: RevTeX 4, 6 pages, 4 eps figures. Phys. Rev. B (final version, to be
published
Accuracy of [(18)Fluorine]-Fluoro-2-Deoxy-D-Glucose Positron Emission Tomography-Computed Tomography Response Assessment Following (Chemo) radiotherapy for Locally Advanced Laryngeal/Hypopharyngeal Carcinoma
Introduction: The accuracy of response assessment positron emission tomography (PET)-computed tomography (CT) following radiotherapy with or without chemotherapy for laryngeal/hypopharyngeal squamous cell carcinoma is uncertain. Methods: In all, 35 patients with laryngeal or hypopharyngeal squamous cell carcinoma who were treated between 2009 and 2014 with (chemo)radiotherapy were identified. The accuracy of response assessment PET-CT was made by correlation with clinical follow-up and pathological findings. Results: Of the 35 patients, 20 (57%) had an overall complete metabolic response. Sensitivity, specificity, positive predictive value (PPV), and negative predictive value (NPV) for response assessment [18Fluorine]-fluoro-2-deoxy-d-glucose (FDG) PET-CT for primary and nodal sites, respectively, were 100%, 73%, 46%, and 100% and 83%, 95%, 83%, and 95%. Conclusions: Response assessment FDG PET-CT following (chemo)radiotherapy for laryngeal and hypopharyngeal carcinomas has a high NPV for both primary site and lymph nodes and can be used to guide treatment decisions. The PPV of residual FDG uptake at the primary tumour site is limited and requires examination and biopsy confirmation
Recent Decisions
Comments on recent decisions by L. D. Wichmann, Lawrence James Bradley, John F. Beggan, John A. Slevin, Robert P. Mone, and F. James Kane
Wavelength dependent collective effects in the multiphoton ionization of atomic deuterium
This paper presents the results of an experimental investigation into collective effects in the transient plasma
formed by multiphoton ionization of atomic deuterium with a pulsed laser. The laser wavelength is varied in a
narrow range around 243 nm, so that the photoionization is resonant with the metastable 2S1/2 state. The ion
yield, the ion time-of-flight spectra, and the yield of Lyman-a photons have been measured as a function of
laser intensity ~from 1 to 340 MW/cm2! and laser detuning around the 1S1/2-2S1/2 two-photon resonance.
During and shortly after the laser pulse, collective effects resulting from the mutual interaction of the photoelectrons
and the ions affect the spatial and temporal distribution of the ions. Because of the near-degeneracy
of the 2S1/2, 2P1/2 , and 2P3/2 states, the resonant multiphoton ionization is affected by the Stark mixing of
these states in the collective field. As a result, the time-dependent yields of ions and of Lyman-a photons are
modulated by the interplay of the multiphoton ionization of the atoms and the collective effects in the plasma.
From the measurements it is deduced that collective effects are important above a critical charge density of
33108 ions/cm3. An asymmetry is observed in the line profile of the total ion yield as a function of laser
detuning. This asymmetry is interpreted to be due to the effect of the collective field upon the intermediate
resonant 2S1/2 state of the photoionization process
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