The hidden burden of adult allergic rhinitis : UK healthcare resource utilisation survey

Funding Funding for this survey was provided by Meda Pharma.Peer reviewedPublisher PD

First-principles study of the ferroelectric Aurivillius phase Bi2WO6

In order to better understand the reconstructive ferroelectric-paraelectric transition of Bi2WO6, which is unusual within the Aurivillius family of compounds, we performed first principles calculations of the dielectric and dynamical properties on two possible high-temperature paraelectic structures: the monoclinic phase of A2/m symmetry observed experimentally and the tetragonal phase of I4/mmm symmetry, common to most Aurivillius phase components. Both paraelectric structures exhibits various unstable modes, which after their condensation bring the system toward more stable structures of lower symmetry. The calculations confirms that, starting from the paraelectric A2/m phase at high temperature, the system must undergo a reconstructive transition to reach the P2_1ab ferroelectric ground state.Comment: added Appendix and two table

A Cost-based Optimizer for Gradient Descent Optimization

As the use of machine learning (ML) permeates into diverse application domains, there is an urgent need to support a declarative framework for ML. Ideally, a user will specify an ML task in a high-level and easy-to-use language and the framework will invoke the appropriate algorithms and system configurations to execute it. An important observation towards designing such a framework is that many ML tasks can be expressed as mathematical optimization problems, which take a specific form. Furthermore, these optimization problems can be efficiently solved using variations of the gradient descent (GD) algorithm. Thus, to decouple a user specification of an ML task from its execution, a key component is a GD optimizer. We propose a cost-based GD optimizer that selects the best GD plan for a given ML task. To build our optimizer, we introduce a set of abstract operators for expressing GD algorithms and propose a novel approach to estimate the number of iterations a GD algorithm requires to converge. Extensive experiments on real and synthetic datasets show that our optimizer not only chooses the best GD plan but also allows for optimizations that achieve orders of magnitude performance speed-up.Comment: Accepted at SIGMOD 201

Joint Kernel Maps

We develop a methodology for solving high dimensional dependency estimation problems between pairs of data types, which is viable in the case where the output of interest has very high dimension, e.g. thousands of dimensions. This is achieved by mapping the objects into continuous or discrete spaces, using joint kernels. Known correlations between input and output can be defined by such kernels, some of which can maintain linearity in the outputs to provide simple (closed form) pre-images. We provide examples of such kernels and empirical results on mass spectrometry prediction and mapping between images

Integrability of graph combinatorics via random walks and heaps of dimers

We investigate the integrability of the discrete non-linear equation governing the dependence on geodesic distance of planar graphs with inner vertices of even valences. This equation follows from a bijection between graphs and blossom trees and is expressed in terms of generating functions for random walks. We construct explicitly an infinite set of conserved quantities for this equation, also involving suitable combinations of random walk generating functions. The proof of their conservation, i.e. their eventual independence on the geodesic distance, relies on the connection between random walks and heaps of dimers. The values of the conserved quantities are identified with generating functions for graphs with fixed numbers of external legs. Alternative equivalent choices for the set of conserved quantities are also discussed and some applications are presented.Comment: 38 pages, 15 figures, uses epsf, lanlmac and hyperbasic

Analyse du comportement électrique d'une électrode de mise à la terre de forme géométrique complexe

Le travail présenté porte sur l’étude de l’analyse du comportement électrique d’une électrode de mise à la terre où sa particularité dépend de sa forme géométrique. L’étude se focalise sur la répartition du potentiel électrique ainsi que la détermination de la résistance de mise à la terre dans un sol avec différents paramètres (résistivités, nombre de couches…). Plusieurs configurations d’électrodes de système de mise à la terre ont été reproduites afin d’étudier leurs comportements dans un sol homogène et hétérogène. Le calcul analytique de la résistance de certaines configurations avec certains paramètres du sol a été fait grâce aux relations trouvées dans la littérature et ce qui a permis de valider le modèle utilisé par les simulations. Le calcul le plus complexe, qui s’explique par les paramètres du sol hétérogène et par la forme géométrique comme celle de l’électrode proposée, a été effectué par le traitement numérique basé sur la méthode des éléments finis vu qu’elle est bien adaptée pour résoudre ce type de problème. Cette approche a pour but de comparer l’électrode proposée à ceux de forme standard de manière à connaitre laquelle qui dissipe mieux le courant de défaut dans le sol pour éviter les perturbations dans les réseaux de télécommunication et assurer la sécurité du matériel et les personnes aux alentour