3,101 research outputs found
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
Towards sketch-based exploration of terrain : a feasibility study
CISRG discussion paper ; 1
PATRIMÔNIO ARQUEOLÓGICO HURON-WENDAT: CONSTRUINDO RELAÇÕES PARA A COLABORAÇÃO
L’intérêt universitaire pour la population Huron-Wendat du dix-septième siècle en Ontario est loin d’être nouveau. Malgré cela, ce n’est que très récemment que les archéologues et autres chercheurs travaillent avec la communauté Huron-Wendat autour des excavations de sites Huron-Wendat en Ontario. Cette implication est un premier pas, mais ne peut être vue comme une réelle collaboration car dans la plupart des cas les investigations ne sont pas des partenariats et ne répondent pas à de questions directement posées par les membres de la Nation. En 2015, pour le quatre-centième anniversaire de l’arrivée de Champlain en Ontario, les membres de la Nation Huron-Wendat et des archéologues ont co-organisé un colloque autour de sujets significatifs pour la nation, parmi lesquels la relation avec les « Iroquoiens du Saint-Laurent », les Wendat et l’histoire Wyandot après 1650, ainsi que les analyses bio-archéologiques. Cet article présente une brève histoire de la recherche archéologique sur le passé Huron-Wendat et dégage de nouvelles et plus collaboratives voies de recherche présentes et à venir.There is a long history of academic interest in the Huron-Wendat people of the seventeenth century in Ontario. Despite this interest, archaeologists and other academics have only recently begun to engage with the Huron-Wendat community regarding excavations of Huron-Wendat sites in Ontario. This engagement is a first step, and it does not represent true collaboration, because in most cases investigations are not partnerships and do not arise from questions posed by members of the Nation. In 2015, to mark the four-hundredth anniversary of the arrival of Champlain in Ontario, members of the Huron-Wendat Nation and archaeologists co-organized a conference focussed on subjects of interest to the Nation, including their relationship with the “St. Lawrence Iroquoians,” Wendat and Wyandot history after 1650, and bioarchaeological analyses. This paper presents a brief history of archaeological research on the Huron-Wendat past and outlines some new, more collaborative avenues of present and future research.Existe uma história longa de estudo acadêmico do povo Huron-Wendat no século dezessete no Ontario. Apesar disso, é muito recente o engajamento dos arqueólogos e de outros acadêmicos com a comunidade Huron-Wendat em relação às escavações de sítios Huron-Wendat no Ontario. Este engajamento constitui um primeiro passo, porém não representa uma verdadeira colaboração considerando que na maioria dos casos as investigações não são parcerias e não se baseiam em perguntas diretamente formuladas pelos membros da Nação. Em 2015, para marcar o aniversario de quatrocentos anos da chegada de Champlain no Ontario, membros da Nação Huron-Wendat e arqueólogos co-organizaram um colóquio sobre temas de grande interesse para a Nação, incluindo a relação com os “St. Lawrence Iroquoians,” os Wendat e a história dos Wyandot depois de 1650, assim como análises bio-arqueológicas. Este artigo apresenta uma breve história da pesquisa arqueológica sobre o passado dos Huron-Wendat e revela alguns novos, e mais colaborativos, caminhos de pesquisas presentes e futuras
Avancée de Diabrotica virgifera virgifera [Coleoptera : Chrysomelidae] dans les champs de maïs au Québec et collecte dans le soja à Ottawa, Ontario
La chrysomèle des racines du maïs de l’Ouest, Diabrotica virgifera virgifera, a été trouvée au Québec en septembre 2000 dans la région de la Montérégie. Ceci constitue une extension vers le nord de son aire de répartition. De plus, à Ottawa, quelques individus se sont développés à partir du soja. Ceci constitue la première mention de développement de cet insecte sur du soja au Canada.The western corn rootworm, Diabrotica virgifera virgifera, was found in the Monteregie region in the province of Quebec in September 2000. This finding constitutes a northern extension of the species distribution. Moreover, at Ottawa, some specimens were found developing from soybean plants. This constitutes the first mention of development of this insect on soybean in Canada
Exact Friedel oscillations in the g=1/2 Luttinger liquid
A single impurity in the 1D Luttinger model creates a local modification of
the charge density analogous to the Friedel oscillations. In this paper, we
present an exact solution of the case (the equivalent of the
Toulouse point) at any temperature and impurity coupling, expressing the
charge density in terms of a hypergeometric function. We find in particular
that at , the oscillatory part of the density goes as at small
distance and at large distance.Comment: 1 reference added. 13 pages, harvma
Boundary interactions changing operators and dynamical correlations in quantum impurity problems
Recent developments have made possible the computation of equilibrium
dynamical correlators in quantum impurity problems. In many situations however,
one is rather interested in correlators subject to a non equilibrium initial
preparation; this is the case for instance for the occupation probability
in the double well problem of dissipative quantum mechanics (DQM). We
show in this paper how to handle this situation in the framework of integrable
quantum field theories by introducing ``boundary interactions changing
operators''. We determine the properties of these operators by using an
axiomatic approach similar in spirit to what is done for form-factors. This
allows us to obtain new exact results for ; for instance, we find that
that at large times (or small ), the leading behaviour for g < 1/2} is
, with the universal ratio.
.Comment: 4 pages, revte
3D Geometric Analysis of Tubular Objects based on Surface Normal Accumulation
This paper proposes a simple and efficient method for the reconstruction and
extraction of geometric parameters from 3D tubular objects. Our method
constructs an image that accumulates surface normal information, then peaks
within this image are located by tracking. Finally, the positions of these are
optimized to lie precisely on the tubular shape centerline. This method is very
versatile, and is able to process various input data types like full or partial
mesh acquired from 3D laser scans, 3D height map or discrete volumetric images.
The proposed algorithm is simple to implement, contains few parameters and can
be computed in linear time with respect to the number of surface faces. Since
the extracted tube centerline is accurate, we are able to decompose the tube
into rectilinear parts and torus-like parts. This is done with a new linear
time 3D torus detection algorithm, which follows the same principle of a
previous work on 2D arc circle recognition. Detailed experiments show the
versatility, accuracy and robustness of our new method.Comment: in 18th International Conference on Image Analysis and Processing,
Sep 2015, Genova, Italy. 201
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Anti-Reflection Coating for Nitrogen-Vacancy Optical Measurements in Diamond
We realize anti-reflection (AR) coatings for optical excitation and fluorescence measurements of nitrogen-vacancy (NV) color centers in bulk diamond by depositing quarter-wavelength thick silica layers on the diamondsurface. These AR coatings improve NV-diamond optical measurements by reducing optical reflection at the diamond-air interface from ≈17% to ≈2%, which allows more effective NV optical excitation and more efficient detection of NV fluorescence. We also show that diamondAR coatings eliminate standing-wave interference patterns of excitation laser intensity within bulk diamond, and thereby greatly reduce spatial variations in NV fluorescence, which can degrade spatially resolved magnetic field sensing using NV centers.Engineering and Applied SciencesPhysic
Colored noise in the fractional Hall effect: duality relations and exact results
We study noise in the problem of tunneling between fractional quantum Hall
edge states within a four probe geometry. We explore the implications of the
strong-weak coupling duality symmetry existent in this problem for relating the
various density-density auto-correlations and cross-correlations between the
four terminals. We identify correlations that transform as either ``odd'' or
``anti-symmetric'', or ``even'' or ``symmetric'' quantities under duality. We
show that the low frequency noise is colored, and that the deviations from
white noise are exactly related to the differential conductance. We show
explicitly that the relationship between the slope of the low frequency noise
spectrum and the differential conductance follows from an identity that holds
to {\it all} orders in perturbation theory, supporting the results implied by
the duality symmetry. This generalizes the results of quantum supression of the
finite frequency noise spectrum to Luttinger liquids and fractional statistics
quasiparticles.Comment: 14 pages, 3 figure
Mapping the use of computational modelling and simulation in clinics: A survey
In silico medicine describes the application of computational modelling and simulation (CM&S) to the study, diagnosis, treatment or prevention of a disease. Tremendous research advances have been achieved to facilitate the use of CM&S in clinical applications. Nevertheless, the uptake of CM&S in clinical practice is not always timely and accurately reflected in the literature. A clear view on the current awareness, actual usage and opinions from the clinicians is needed to identify barriers and opportunities for the future of in silico medicine. The aim of this study was capturing the state of CM&S in clinics by means of a survey toward the clinical community. Responses were collected online using the Virtual Physiological Human institute communication channels, engagement with clinical societies, hospitals and individual contacts, between 2020 and 2021. Statistical analyses were done with R. Participants (n = 163) responded from all over the world. Clinicians were mostly aged between 35 and 64 years-old, with heterogeneous levels of experience and areas of expertise (i.e., 48% cardiology, 13% musculoskeletal, 8% general surgery, 5% paediatrics). The CM&S terms “Personalised medicine” and “Patient-specific modelling” were the most well-known within the respondents. “In silico clinical trials” and “Digital Twin” were the least known. The familiarity with different methods depended on the medical specialty. CM&S was used in clinics mostly to plan interventions. To date, the usage frequency is still scarce. A well-recognized benefit associated to CM&S is the increased trust in planning procedures. Overall, the recorded level of trust for CM&S is high and not proportional to awareness level. The main barriers appear to be access to computing resources, perception that CM&S is slow. Importantly, clinicians see a role for CM&S expertise in their team in the future. This survey offers a snapshot of the current situation of CM&S in clinics. Although the sample size and representativity could be increased, the results provide the community with actionable data to build a responsible strategy for accelerating a positive uptake of in silico medicine. New iterations and follow-up activities will track the evolution of responses over time and contribute to strengthen the engagement with the medical community
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