Extraction of Airways with Probabilistic State-space Models and Bayesian Smoothing

Segmenting tree structures is common in several image processing applications. In medical image analysis, reliable segmentations of airways, vessels, neurons and other tree structures can enable important clinical applications. We present a framework for tracking tree structures comprising of elongated branches using probabilistic state-space models and Bayesian smoothing. Unlike most existing methods that proceed with sequential tracking of branches, we present an exploratory method, that is less sensitive to local anomalies in the data due to acquisition noise and/or interfering structures. The evolution of individual branches is modelled using a process model and the observed data is incorporated into the update step of the Bayesian smoother using a measurement model that is based on a multi-scale blob detector. Bayesian smoothing is performed using the RTS (Rauch-Tung-Striebel) smoother, which provides Gaussian density estimates of branch states at each tracking step. We select likely branch seed points automatically based on the response of the blob detection and track from all such seed points using the RTS smoother. We use covariance of the marginal posterior density estimated for each branch to discriminate false positive and true positive branches. The method is evaluated on 3D chest CT scans to track airways. We show that the presented method results in additional branches compared to a baseline method based on region growing on probability images.Comment: 10 pages. Pre-print of the paper accepted at Workshop on Graphs in Biomedical Image Analysis. MICCAI 2017. Quebec Cit

The potential of Antheraea pernyi silk for spinal cord repair

This work was supported by the Institute of Medical Sciences of the University of Aberdeen, Scottish Rugby Union and RS McDonald Charitable Trust. We are grateful to Mr Nicholas Hawkins from Oxford University and Ms Annette Raffan from the University of Aberdeen for assistance with tensile testing. We thank Ms Michelle Gniβ for her help with the microglial response experiments. We also thank Mr Gianluca Limodio for assisting with the MATLAB script for automation of tensile testing’s data analysis.Peer reviewedPublisher PD

Topo-Geometric Filtration Scheme for Geometric Active Contours and Level Sets: Application to Cerebrovascular Segmentation

One of the main problems of the existing methods for the segmentation of cerebral vasculature is the appearance in the segmentation result of wrong topological artefacts such as the kissing vessels. In this paper, a new approach for the detection and correction of such errors is presented. The proposed technique combines robust topological information given by Persistent Homology with complementary geometrical information of the vascular tree. The method was evaluated on 20 images depicting cerebral arteries. Detection and correction success rates were 81.80% and 68.77%, respectively

The long delayed solution of the Bukhvostov Lipatov model

In this paper I complete the solution of the Bukhvostov Lipatov model by computing the physical excitations and their factorized S matrix. I also explain the paradoxes which led in recent years to the suspicion that the model may not be integrable.Comment: 9 page

Évaluation des habiletés de vie autonome chez les personnes psychotiques

Ce texte détaille les caractéristiques métrologiques de l'Échelle des habiletés de Vie Autonome (EHVA) mesurant les habiletés requises chez des personnes psychotiques, pour fonctionner de façon autonome au sein de la communauté. Ce questionnaire, qui comprend 65 items répartis en dix échelles d'habiletés, a été administré à 276 personnes psychotiques. Les résultats indiquent que, dans l'ensemble, la fidélité de cet instrument est bonne, mesurée par l'accord interjuges et les coefficients alpha. Trois des 10 échelles, soit les échelles Déplacement, Recherche d'emploi et Maintien de l'emploi, n'ont pu être conservées dans la version finale. Les quatre aspects de la validité examinés dans cette étude se révèlent très satisfaisants; il s'agit du degré de convergence entre l'évaluation faite par les participants eux-mêmes et par un membre du personnel soignant, des analyses discriminantes, des corrélations convergentes-divergentes avec d'autres instruments de mesure du fonctionnement psychosocial et de l'analyse factorielle exploratoire. Après ces analyses, la version finale de l'EHVA comprend 48 items répartis sous sept échelles. La discussion fait ressortir les qualités psychométriques d'un tel instrument en langue française et suggère des pistes de recherche pour poursuivre le développement de l'EHVA.This article studies in detail the metrological characteristics of the "Autonomous Life Skills Test" ("Echelle des Habiletés de Vie Autonome" or "EHVA") which measures the skills required of psychotic patients to function on their own in the community. The questionnaire, distributed to 276 psychotic patients, made use of 10 parameters of skills broken down into 65 items. Results show that, overall, this instrument is quite reliable, as measured by the inter-rater reliability and alpha coefficients. Three of the ten parameters, namely Mobility, Employment Search and Employment Holding, were not retained in the final version. The four validity aspects were found to be very satisfactory, namely the degree of convergence between the participant's self-evaluation and the evaluation provided by healthcare personnel, (discriminating analysis), convergent-divergent correlations with other instruments measuring psychosocial functioning and the exploratory factorial analysis. Following these analysis, the final version of the "EHVA" includes 48 items covering seven parameters. A discussion of results underscores the psychometric qualities of such a French-language instrument and suggests avenues to pursue the development of the "EHVA"

Single particle Green's function in the Calogero-Sutherland model for rational couplings β=p/q\beta=p/q

We derive an exact expression for the single particle Green function in the Calogero-Sutherland model for all rational values of the coupling $\beta$. The calculation is based on Jack polynomial techniques and the results are given in the thermodynamical limit. Two type of intermediate states contribute. The firts one consists of a particle propagating out of the Fermi sea and the second one consists of a particle propagating in one direction, q particles in the opposite direction and p holes.Comment: 9 pages, RevTeX, epsf.tex, 4 figures, files uuencode

Coherence correlations in the dissipative two-state system

We study the dynamical equilibrium correlation function of the polaron-dressed tunneling operator in the dissipative two-state system. Unlike the position operator, this coherence operator acts in the full system-plus-reservoir space. We calculate the relevant modified influence functional and present the exact formal expression for the coherence correlations in the form of a series in the number of tunneling events. For an Ohmic spectral density with the particular damping strength $K=1/2$, the series is summed in analytic form for all times and for arbitrary values of temperature and bias. Using a diagrammatic approach, we find the long-time dynamics in the regime $K<1$. In general, the coherence correlations decay algebraically as $t^{-2K}$ at T=0. This implies that the linear static susceptibility diverges for $K\le 1/2$ as $T\to 0$, whereas it stays finite for $K>1/2$ in this limit. The qualitative differences with respect to the asymptotic behavior of the position correlations are explained.Comment: 19 pages, 4 figures, to be published in Phys. Rev.

Données récentes d’études scandinaves. Traiter la dépression : une stratégie efficace de prévention du suicide?

Cet article vise à éclairer les planificateurs en santé publique, le personnel clinique et les intervenants en prévention du suicide au Québec ainsi que les familles et le public francophone à propos de récentes études sur le traitement de la dépression comme stratégie de prévention du suicide. Les auteurs en résument les conclusions, passent en revue les méthodes et examinent les résultats dans une perspective de santé publique visant à établir une stratégie efficace de prévention. Ils soulignent que le traitement de la dépression pourrait non seulement réduire les taux de suicide mais avoir des effets importants sur la santé publique en réduisant les incapacités liées à la dépression, en plus d'avoir un impact sur les futures générations à risque. Les obstacles au développement d'une telle stratégie sont soulignés en référence spécifique à la situation du Québec.Treating depression is an effective population suicide prevention strategy: recent evidence from Scandinavian studies This article's objective is to signal to the Quebec and the francophone audience of public planners and decision makers, clinical and suicide prevention workers, staff, relatives as well as the public of these recent breakthrough findings that provides strong evidence now that increasing the treatment of depression is an effective suicide prevention strategy. The article summarizes the evidence published recently and then critically reviews the methods and if the evidence fits within a complete public health perspective demonstration of an effective suicide prevention strategy. It highlights that the treatment of depression may not only decrease suicide rates but have much more larger public health effects by decreasing the disability associated with depression and have impact on future generations at risk of depression and suicide. The obstacles to developing such nation-wide strategy of increasing the treatment of depression will be highlighted with specific reference to the situation in Quebec.Datos recientes de investigaciones escandinavas. Tratar la depresión: ¿una estragegia eficaz de prevención del suicidio? El artículo quiere alumbrar los planificadores en salud pública, el personal clínico y los intervenantes en prevención del suicidio en Quebec asi que las familias y el público francófono sobre estudios recientes tocando el tratamiento de la depresión como estrategia de prevención del suicidio. Los autores resumen las conclusiones, pasan revista las métodas y examinan los resultados desde una perspectiva de salud pública con objeto de establecer una estrategia eficaz de prevención. Subrayan que el tratamiento de la depresión podria no solamente reducir las tasas del suicidio pero tener efectos importantes sobre la salud pública reduciendo las incapacidades ligadas a la depresión y además tener un impacto sobre generaciones futuras a riesgo. Los obstáculos al desarrollo de tal estrategia estan subrayados con referencia específica a la situación del Québec.Dados recentes de estudos escandinavos. Tratar a depressão: uma estratégia eficaz de prevenção contra o suicídio? Este artigo visa informar os promotores em saúde pública, os funcionários clínicos e os assistentes em prevenção contra o suicídio no Quebec, e também as famílias e o público francófono a respeito dos estudos recentes sobre o tratamento da depressão como estratégia na prevenção contra o suicídio. Os autores resumem aqui as conclusões, analisam os métodos e examinam os resultados em uma perspectiva de saúde pública visando estabelecer uma estratégia eficaz de prevenção. Eles ressaltam que o tratamento da depressão poderia, não apenas diminuir a taxa de suicídio, mas ter efeitos importantes na saúde pública, reduzindo a incapacidade ligada à depressão, além de ter um impacto nas futuras gerações em risco. Os obstáculos ao desenvolvimento de tal estratégia são ressaltados fazendo referência específica à situação do Quebec

Estimating local car ownership models

Many studies in the transport demand literature have shown that income is an important factor in determining how many cars a household owns. When the models used to measure the strength of this relationship are estimated on cross-sectional data, they typically yield one overall value as the estimate. Local circumstances will, however, vary. This paper illustrates the use of the Geographically Weighted Regression technique to estimate the individual strength of this relationship for each of the United Kingdom electoral wards. Use of this type of model enables a wards’ income elasticity to be based on both the local estimate of the strength of this relationship and the current local level of car ownership. How the use of this local elasticity changes future forecasts of the size of the vehicle fleet is illustrated

Correlation functions of disorder operators in massive ghost theories

The two-dimensional ghost systems with negative integral central charge received much attention in the last years for their role in a number of applications and in connection with logarithmic conformal field theory. We consider the free massive bosonic and fermionic ghost systems and concentrate on the non-trivial sectors containing the disorder operators. A unified analysis of the correlation functions of such operators can be performed for ghosts and ordinary complex bosons and fermions. It turns out that these correlators depend only on the statistics although the scaling dimensions of the disorder operators change when going from the ordinary to the ghost case. As known from the study of the ordinary case, the bosonic and fermionic correlation functions are the inverse of each other and are exactly expressible through the solution of a non-linear differential equation.Comment: 8 pages, late