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 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 $\beta$ function.Comment: 4 pages, 5 figure

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

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 $2 < d \le 4$ (bifractals and Euclidian lattices). The critical exponent $\nu$ and the critical conductance distribution are calculated. We confirm that $\nu$ 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

Oscillating density of states near zero energy for matrices made of blocks with possible application to the random flux problem

We consider random hermitian matrices made of complex blocks. The symmetries of these matrices force them to have pairs of opposite real eigenvalues, so that the average density of eigenvalues must vanish at the origin. These densities are studied for finite $N\times N$ matrices in the Gaussian ensemble. In the large $N$ limit the density of eigenvalues is given by a semi-circle law. However, near the origin there is a region of size $1\over N$ in which this density rises from zero to the semi-circle, going through an oscillatory behavior. This cross-over is calculated explicitly by various techniques. We then show to first order in the non-Gaussian character of the probability distribution that this oscillatory behavior is universal, i.e. independent of the probability distribution. We conjecture that this universality holds to all orders. We then extend our consideration to the more complicated block matrices which arise from lattices of matrices considered in our previous work. Finally, we study the case of random real symmetric matrices made of blocks. By using a remarkable identity we are able to determine the oscillatory behavior in this case also. The universal oscillations studied here may be applicable to the problem of a particle propagating on a lattice with random magnetic flux.Comment: 47 pages, regular LateX, no figure

Prothonotary warbler demography and nest site selection in natural and artificial cavities in bottomland forests of Arkansas, USA [Démographie et sélection du site de nidification de la paruline orangée dans des cavités naturelles et artificielles en forêts sur terres basses de l\u27Arkansas, É.-U.]

Anthropogenic alterations to bottomland forests in the United States that occurred post-European settlement likely negatively affected many avian species. The Prothonotary Warbler (Protonotaria citrea), a secondary cavity nester that breeds predominantly in these forests, has steadily declined over the past 60 years, and our ability to mitigate this trend is partially limited by a lack of basic biological data. Although much research has been devoted to Prothonotary Warblers, most studies have focused on local breeding populations that use nest boxes; we lack information about habitat selection behavior and demographic parameters of individuals that use natural cavities, which includes the vast majority of the global population. We studied warblers nesting both in boxes and natural cavities in central Arkansas, USA. We aimed to evaluate: (1) microhabitat features important for nest site selection, (2) relationships between these features and nest survival, and (3) demographic parameters of individuals breeding in natural cavities versus nest boxes. We hypothesized (1) selected nest site characteristics are associated with nest survival, and (2) natural cavities and nest boxes provide similar nest features related to clutch size and number fledged, but that predation protection differs. We found that warblers preferred nesting in dead trees with cavities that were higher and shallower than available random cavities, and that canopy cover within 5 m of nests was inversely related to nest survival. Demographic parameters did not differ between natural cavities and nest boxes; however, when excluding flooded nests, boxes experienced lower rates of nest depredation. We believe that forest management strategies that increase the number of suitable dead nest trees and restore the natural hydrology of these ecosystems would create and improve habitat for this iconic species. We advocate multiscale experimental canopy cover manipulation to explore the causal mechanism(s) of the relationship we found between canopy cover and nest survival

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 $L^{d-1} \times \infty$ disordered systems. For $d=1$ our approach is shown to reproduce exact diagonalization results available in the literature. In $d=2$, where strips of width $L \leq 64$ 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 $S$, which is invariant under the usual histogram-collapse rescaling, and whose absolute value increases with distance. We find $0.15 \lesssim -S \lesssim 0.30$ 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

Probability distribution of the conductance at the mobility edge

Distribution of the conductance P(g) at the critical point of the metal-insulator transition is presented for three and four dimensional orthogonal systems. The form of the distribution is discussed. Dimension dependence of P(g) is proven. The limiting cases $g\to\infty$ and $g\to 0$ are discussed in detail and relation $P(g)\to 0$ in the limit $g\to 0$ is proven.Comment: 4 pages, 3 .eps figure

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

Public health advocacy in action: the case of unproven breast cancer screening in Australia

In recent years, nonmammographic breast imaging devices, such as thermography, electrical impedance scanning and elastography, have been promoted directly to consumers, which has captured the attention of governments, researchers and health organisations. These devices are not supported by evidence and risk undermining existing mammographic breast cancer screening services. During a 5-year period, Cancer Council Western Australia (CCWA) used strategic research combined with legal, policy and media advocacy to contest claims that these devices were proven alternatives to mammography for breast cancer screening. The campaign was successful because it had input from people with public health, academic, clinical and legal backgrounds, and took advantage of existing legal and regulatory avenues. CCWA's experience provides a useful advocacy model for public health practitioners who are concerned about unsafe consumer products, unproven medical devices, and misleading health information and advertising