Constructive Fractional-Moment Criteria for Localization in Random Operators

We present a family of finite-volume criteria which cover the regime of exponential decay for the fractional moments of Green functions of operators with random potentials. Such decay is a technically convenient characterization of localization for it is known to imply spectral localization, absence of level repulsion, dynamical localization and a related condition which plays a significant role in the quantization of the Hall conductance in two-dimensional Fermi gases. The constructive criteria also preclude fast power-law decay of the Green functions at mobility edges.Comment: Announcement and summary of results whose proofs are given elsewhere. LaTex (10 pages), uses Elsevier "elsart" files (attached

The Arecibo Methanol Maser Galactic Plane Survey - III: Distances and Luminosities

We derive kinematic distances to the 86 6.7 GHz methanol masers discovered in the Arecibo Methanol Maser Galactic Plane Survey. The systemic velocities of the sources were derived from 13CO (J=2-1), CS (J=5-4), and NH3 observations made with the ARO Submillimeter Telescope, the APEX telescope, and the Effelsberg 100 m telescope, respectively. Kinematic distance ambiguities were resolved using HI self-absorption with HI data from the VLA Galactic Plane Survey. We observe roughly three times as many sources at the far distance compared to the near distance. The vertical distribution of the sources has a scale height of ~ 30 pc, and is much lower than that of the Galactic thin disk. We use the distances derived in this work to determine the luminosity function of 6.7 GHz maser emission. The luminosity function has a peak at approximately 10^{-6} L_sun. Assuming that this luminosity function applies, the methanol maser population in the Large Magellanic Cloud and M33 is at least 4 and 14 times smaller, respectively, than in our Galaxy.Comment: Accepted by Ap

Effects of quantum well growth temperature on the recombination efficiency of InGaN/GaN multiple quantum wells that emit in the green and blue spectral regions

InGaN-based light emitting diodes and multiple quantum wells designed to emit in the green spectral region exhibit, in general, lower internal quantum efficiencies than their blue-emitting counter parts, a phenomenon referred to as the “green gap.” One of the main differences between green-emitting and blue-emitting samples is that the quantum well growth temperature is lower for structures designed to emit at longer wavelengths, in order to reduce the effects of In desorption. In this paper, we report on the impact of the quantum well growth temperature on the optical properties of InGaN/GaN multiple quantum wells designed to emit at 460 nm and 530 nm. It was found that for both sets of samples increasing the temperature at which the InGaN quantum well was grown, while maintaining the same indium composition, led to an increase in the internal quantum efficiency measured at 300 K. These increases in internal quantum efficiency are shown to be due reductions in the non-radiative recombination rate which we attribute to reductions in point defect incorporation.This work was carried out with the financial support of the United Kingdom Engineering and Physical Sciences Research Council under Grant Numbers EP/I012591/1 and EP/H011676/1.This is the final version of the article. It first appeared from AIP via http://dx.doi.org/10.1063/1.4932200 All data created during this research are openly available from the University of Manchester eScholar archive at http://dx.doi.org/10.15127/1.26974

Decay Properties of the Connectivity for Mixed Long Range Percolation Models on Zd\Z^d

In this short note we consider mixed short-long range independent bond percolation models on $\Z^{k+d}$. Let $p_{uv}$ be the probability that the edge $(u,v)$ will be open. Allowing a $x,y$-dependent length scale and using a multi-scale analysis due to Aizenman and Newman, we show that the long distance behavior of the connectivity $\tau_{xy}$ is governed by the probability $p_{xy}$. The result holds up to the critical point.Comment: 6 page

Knowing and doing vocational education and training reform: evidence, learning and the policy process

Much of VET policy internationally draws on a toolkit that has been seriously questioned for its logic, international relevance and effectiveness by considerable amounts of academic research. Reflecting primarily on our experiences of leading a complex, multi-country policy study, we develop an account that seeks to explore ways in which the apparent incommensurability between academic and policy knowledge can be addressed. This leads on to a broader discussion of key issues of contestation in the debates about knowledge for policy as they relate to international education and development more generally. We consider three key turns in the discourse of international education policy and research: to "governing by numbers", "what works" and policy learning, and ask what happens when these discursive trends travel to Southern and VET contexts. We suggest that this analysis implies that policymakers need both to be more modest and reflexive in their expectations of what knowledge can be mobilised for policy purposes and more serious in their commitment to supporting the generation of the types of knowledge that they claim to value. For international and comparative educators, we stress the importance of being clearer in seeking to shape research agendas; more rigorous in our approaches to research; and better in our external communication of our findings. Given the particular focus of this special issue on VET, we end by reiterating the particular challenge of reawakening research on VET-for-development from twenty years of slumbers

Sequential cavity method for computing free energy and surface pressure

We propose a new method for the problems of computing free energy and surface pressure for various statistical mechanics models on a lattice $\Z^d$. Our method is based on representing the free energy and surface pressure in terms of certain marginal probabilities in a suitably modified sublattice of $\Z^d$. Then recent deterministic algorithms for computing marginal probabilities are used to obtain numerical estimates of the quantities of interest. The method works under the assumption of Strong Spatial Mixing (SSP), which is a form of a correlation decay. We illustrate our method for the hard-core and monomer-dimer models, and improve several earlier estimates. For example we show that the exponent of the monomer-dimer coverings of $\Z^3$ belongs to the interval $[0.78595,0.78599]$, improving best previously known estimate of (approximately) $[0.7850,0.7862]$ obtained in \cite{FriedlandPeled},\cite{FriedlandKropLundowMarkstrom}. Moreover, we show that given a target additive error $\epsilon>0$, the computational effort of our method for these two models is $(1/\epsilon)^{O(1)}$ \emph{both} for free energy and surface pressure. In contrast, prior methods, such as transfer matrix method, require $\exp\big((1/\epsilon)^{O(1)}\big)$ computation effort.Comment: 33 pages, 4 figure

A sociological exploration of the tensions related to interprofessional collaboration in acute-care discharge planning

Patient discharge is a key concern in hospitals, particularly in acute care, given the multifaceted and challenging nature of patients' healthcare needs. Policies on discharge have identified the importance of interprofessional collaboration, yet research has described its limitations in this clinical context. This study aimed to extend our understanding of interprofessional interactions related to discharge in a general internal medicine setting by using sociological theories to illuminate the existence of, and interplay between, structural factors and microlevel practices. An ethnographic approach was employed to obtain an in-depth insight into healthcare providers' perspectives, behaviours, and interactions regarding discharge. Data collection involved observations, interviews, and document analysis. Approximately 65 hours of observations were undertaken, 23 interviews were conducted with healthcare providers, and government and hospital discharge documents were collected. Data were analysed using a directed content approach. The findings indicate the existence of a medically dominated division of healthcare labour in patient discharge with opportunities for some interprofessional negotiations; the role of organizational routines in facilitating and challenging interprofessional negotiations in patient discharge; and tensions in organizational priorities that impact an interprofessional approach to discharge. The findings provide insight into the various levels at which interventions can be targeted to improve interprofessional collaboration in discharge while recognizing the organizational tensions that challenge an interprofessional approach

Zeros of the i.i.d. Gaussian power series: a conformally invariant determinantal process

Consider the zero set of the random power series f(z)=sum a_n z^n with i.i.d. complex Gaussian coefficients a_n. We show that these zeros form a determinantal process: more precisely, their joint intensity can be written as a minor of the Bergman kernel. We show that the number of zeros of f in a disk of radius r about the origin has the same distribution as the sum of independent {0,1}-valued random variables X_k, where P(X_k=1)=r^{2k}. Moreover, the set of absolute values of the zeros of f has the same distribution as the set {U_k^{1/2k}} where the U_k are i.i.d. random variables uniform in [0,1]. The repulsion between zeros can be studied via a dynamic version where the coefficients perform Brownian motion; we show that this dynamics is conformally invariant.Comment: 37 pages, 2 figures, updated proof