786 research outputs found
The spectrum of radial, orbital and gluonic excitations of charmonium
We present results for the charmonium spectrum from dynamical QCD
simulations on anisotropic lattices. Using all-to-all
propagators we determine the ground and excited states of S, P and D waves and
hybrids. We also evaluate the disconnected (OZI suppressed) contribution to the
and Comment: 6 pages, 3 figures, Presented at 24th International Symposium on
Lattice Field Theory (Lattice 2006), Tucson, Arizona, 23-28 Jul 200
Explainable Anatomical Shape Analysis through Deep Hierarchical Generative Models
Quantification of anatomical shape changes currently relies on scalar global indexes which are largely insensitive to regional or asymmetric modifications. Accurate assessment of pathology-driven anatomical remodeling is a crucial step for the diagnosis and treatment of many conditions. Deep learning approaches have recently achieved wide success in the analysis of medical images, but they lack interpretability in the feature extraction and decision processes. In this work, we propose a new interpretable deep learning model for shape analysis. In particular, we exploit deep generative networks to model a population of anatomical segmentations through a hierarchy of conditional latent variables. At the highest level of this hierarchy, a two-dimensional latent space is simultaneously optimised to discriminate distinct clinical conditions, enabling the direct visualisation of the classification space. Moreover, the anatomical variability encoded by this discriminative latent space can be visualised in the segmentation space thanks to the generative properties of the model, making the classification task transparent. This approach yielded high accuracy in the categorisation of healthy and remodelled left ventricles when tested on unseen segmentations from our own multi-centre dataset as well as in an external validation set, and on hippocampi from healthy controls and patients with Alzheimer's disease when tested on ADNI data. More importantly, it enabled the visualisation in three-dimensions of both global and regional anatomical features which better discriminate between the conditions under exam. The proposed approach scales effectively to large populations, facilitating high-throughput analysis of normal anatomy and pathology in large-scale studies of volumetric imaging
Topological susceptibility with the asqtad action
Chiral perturbation theory predicts that in quantum chromodynamics (QCD),
light dynamical quarks suppress the gauge-field topological susceptibility of
the vacuum. The degree of suppression depends on quark multiplicity and masses.
It provides a strong consistency test for fermion formulations in lattice QCD.
Such tests are especially important for staggered fermion formulations that
lack a full chiral symmetry and use the "fourth-root" procedure to achieve the
desired number of sea quarks. Over the past few years we have measured the
topological susceptibility on a large database of 18 gauge field ensembles,
generated in the presence of 2+1 flavors of dynamical asqtad quarks with up and
down quark masses ranging from 0.05 to 1 in units of the strange quark mass and
lattice spacings ranging from 0.045 fm to 0.12 fm. Our study also includes
three quenched ensembles with lattice spacings ranging from 0.06 to 0.12 fm. We
construct the topological susceptibility from the integrated point-to-point
correlator of the discretized topological charge density F-Fdual. To reduce its
variance, we model the asymptotic tail of the correlator. The continuum
extrapolation of our results for the topological susceptibility agrees nicely
at small quark mass with the predictions of lowest-order SU(3) chiral
perturbation theory, thus lending support to the validity of the fourth-root
procedure.Comment: 28 pp, 6 figs. Version 2 corrects some discussion, some numbers, and
some figures and adds some reference
Automatic Alignment of pre and intraoperative Data using Anatomical Landmarks for Augmented Laparoscopic Liver Surgery
International audienceEach year in Europe 50,000 new liver cancer cases are diagnosed for which hepatic surgery combined to chemotherapy is the most common treatment. In particular the number of laparoscopic liver surgeries has increased significantly over the past years. This type of minimally invasive procedure which presents many benefits for the patient is challenging for the surgeons due to the limited field of view. Recently new augmented reality techniques which merge preoperative data and intraoperative images and permit to visualize internal structures have been proposed to help surgeons during this type of surgery. One of the difficulties is to align preoperative data with the intraoperative images. We propose in this paper a semi-automatic approach for solving the ill-posed problem of initial alignment for Augmented Reality systems during liver surgery. Our registration method relies on anatomical landmarks extracted from both the laparoscopic images and three-dimensional model, using an image-based soft-tissue reconstruction technique and an atlas-based approach, respectively. The registration evolves automatically from a quasi-rigid to a non-rigid registration. Furthermore, the surface-driven deformation is induced in the volume via a patient specific biomechanical model. The experiments conducted on both synthetic and in vivo data show promising results with a registration error of 2 mm when dealing with a visible surface of 30% of the whole liver
Symanzik flow on HISQ ensembles
We report on a scale determination with gradient-flow techniques on the HISQ ensembles generated by the MILC collaboration. The lattice
scale , originally proposed by the BMW collaboration, is computed using
Symanzik flow at four lattice spacings ranging from 0.15 to 0.06 fm. With a
Taylor series ansatz, the results are simultaneously extrapolated to the
continuum and interpolated to physical quark masses. We give a preliminary
determination of the scale in physical units, along with associated
systematic errors, and compare with results from other groups. We also present
a first estimate of autocorrelation lengths as a function of flowtime for these
ensembles.Comment: 7 pages, 6 pdf figures, 2 tables, presented at the 31st International
Symposium on Lattice Field Theory (Lattice 2013), 29 July - 3 August 2013,
Mainz, German
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