Upper gastro-intestinal fibre-optic endoscopy

A study of 3 000 upper gastro-intestinal fibre-optic endoscopies over a 3-year period is reported. The majority of patients were endoscoped after barium meals and in 69% of the cases the endoscopic findings correlated well with the radiological findings. In 28% of the cases the endoscopic findings differed from the radiological findings. Endoscopy is more accurate than radiology in the examination of the postgastrectomy stomach, in acute gastro-intestinal haemorrhage, in the radiologically distorted gastric antrum and in the follow-up of gastric ulcer healing. The localisation, healing rate and incidence of recurrence in gastric ulcers and the accuracy of endoscopic biopsy and cytology are reported. The value of endoscopic examination of the stomach and duodenum is shown, but it is stressed that endoscopy is complementary to and not exclusive of radiology.S. Afr. Med. J., 48, 857 (1974)

6th-order finite volume approximation for the steady-state burger and euler equations: the mood approach

We propose an innovative method based on the MOOD technology (Multi-dimensional Optimal Order Detection) to provide a 6th-order finite volume approximation for the one-dimensional steady-state Burger and Euler equations. The main ingredient consists in using an 'a posteriori' limiting strategy to eliminate non physical oscillations deriving from the Gibbs phenomenon while keeping a high accuracy for the smooth part. A short overview of the MOOD method will be presented and numerical tests with regular or discontinuous solutions will assess the method capacity to produce excellent approximations. In the latter situation, the numerical results enable to detect the zone where it is necessary to reduce the degree of the polynomial reconstructions to preserve the scheme robustness.Fundação para a Ciência e a Tecnologia (FCT

Soft tissue modelling for analysis of errors in breast reduction surgery

Breast reduction is one of the most common procedures in breast surgery. The aim of this work is to develop a computational model allowing one to forecast the final breast geometry according to the incision marking parameters. This model can be used in surgery simulators that provide preoperative planning and training, allowing the study of the errors origin in breast reduction

Structural schemes for one dimension stationary equations

In this paper, we propose a new paradigm for finite differences numerical methods, based on compact schemes to provide high order accurate approximations of a smooth solution. The method involves its derivatives approximations at the grid points and the construction of structural equations deriving from the kernels of a matrix that gathers the variables belonging to a small stencil. Numerical schemes involve combinations of physical equations and the structural relations. We have analysed the spectral resolution of the most common structural equations and performed numerical tests to address both the stability and accuracy issues for popular linear and non-linear problems. Several benchmarks are presented that ensure that the developed technology can cope with several problems that may involve non-linearity.S. Clain acknowledges the financial support by Portuguese Funds through Foundation for Science and Technology (FCT) in the framework of the Strategic Funding UIDB/00324/2020. R. M. S. Pereira acknowledges the financial support by Portuguese Funds through Foundation for Science and Technology (FCT) in the framework of the Strategic Funding UIDB/04650/2020. P. A. Pereira acknowledges the financial support by Portuguese Funds through Foundation for Science and Technology (FCT) in the framework of the Strategic Funding UIDB/00013/2020. Diogo Lopes acknowledges the financial support by national funds (PIDDAC), through the FCT – Fundação para a Ciência e a Tecnologia and FCT/MCTES under the scope of the projects UIDB/05549/2020 and UIDP/05549/2020. S. Clain and R. M.Pereira acknowledge the financial support by FEDER – Fundo Europeu de Desenvolvimento Regional, through COMPETE 2020 – Programa Operacional Fatores de Competitividade, and the National Funds through FCT, project N◦. POCI-01-0145-FEDER-028118

Numerical simulation of breast reduction with a new knitting condition

SUMMARY Breast reduction is one of the most common procedures in breast surgery. The aim of this work is to develop a computational model allowing one to forecast the final breast geometry according to the incision marking parameters. This model can be used in surgery simulators that provide preoperative planning and training, allowing the study of the errors origin in breast reduction. From the mathematical point of view this is a problem of calculus of variations with unusual boundary conditions, known as knitting conditions. The breast tissue is considered as a hyperelastic material, discretized with three-dimensional finite elements for the body whereas the skin is modelled with two-dimensional finite elements on the curved surface. Although the model is of low precision, we show that it is sufficient for a satisfactory analysis of errors frequently done during breast reduction surgery and allows to understand how to avoid or correct them

Improved Detection Criteria for the Multi-dimensional Optimal Order Detection (MOOD) on unstructured meshes with very high-order polynomials

This paper extends the MOOD method proposed by the authors in ["A high-order finite volume method for hyperbolic systems: Multidimensional Optimal Order Detection (MOOD)", J. Comput. Phys. 230, pp 4028-4050, (2011)], along two complementary axes: extension to very high-order polynomial reconstruction on non-conformal unstructured meshes and new Detection Criteria. The former is a natural extension of the previous cited work which confirms the good behavior of the MOOD method. The latter is a necessary brick to overcome limitations of the Discrete Maximum Principle used in the previous work. Numerical results on advection problems and hydrodynamics Euler equations are presented to show that the MOOD method is effectively high-order (up to sixth-order), intrinsically positivity-preserving on hydrodynamics test cases and computationally efficient

A Very High-Order Accurate Staggered Finite Volume Scheme for the Stationary Incompressible Navier–Stokes and Euler Equations on Unstructured Meshes

International audienceWe propose a sixth-order staggered finite volume scheme based on polynomial reconstructions to achieve high accurate numerical solutions for the incompressible Navier-Stokes and Euler equations. The scheme is equipped with a fixed-point algorithm with solution relaxation to speed-up the convergence and reduce the computation time. Numerical tests are provided to assess the effectiveness of the method to achieve up to sixth-order con-2 Ricardo Costa et al. vergence rates. Simulations for the benchmark lid-driven cavity problem are also provided to highlight the benefit of the proposed high-order scheme

Mellin-Barnes Representation for the Genus-g Finite Temperature String Theory

The Mellin-Barnes representation for the free energy of the genus-$g$ string is constructed. It is shown that the interactions of the open bosonic string do not modify the critical (Hagedorn) temperature. However,for the sectors having a spinor structure, the critical temperature exists also for all $g$ and depends on the windings. The appearance of a periodic structure is briefly discussed.Comment: 9 pages, report UTF 294 (1993

Etude rhéologique et thermique d'une boucle de réfrigération secondaire par coulis d'hydrates

14e édition du congrès de la Société française du génie des procédés, Lyon, FRA, 08-/10/2013 - 10/10/2013International audienceLes fluides réfrigérants classiques sont néfastes pour l'environnement en raison de leur potentiel de réchauffement global (GWP), c'est pourquoi leur utilisation doit être réduite. L'une des solutions est d'employer des fluides frigoporteurs diphasiques, comme les coulis d'hydrates, pour transporter le froid. Le travail réalisé a pour objectif d'étudier les propriétés rhéologiques et thermiques des coulis de CO2. Le dispositif expérimental est constitué d'une boucle pilote permettant la circulation des fluides. Les hydrates sont formés par refroidissement à des températures de l'ordre de 275 K et des pressions allant jusqu'à 3 MPa. Les coefficients d'échange thermique locaux et moyens du coulis ont également été évalués par l'utilisation d'un tube chauffant. La rhéologie a montré que le coulis présentait un comportement de type rhéofluidifiant pour des fractions d'hydrates en volume allant jusqu'à 22 %. L'étude thermique a quant à elle montré que le coulis présentait des coefficients d'échange locaux de l'ordre de 2900 W.m-2.K-1 pour une fraction en hydrates de 19 %, ce qui est supérieur à l'eau et légèrement plus élevé que le coulis de glace. Ainsi, ces résultats permettent de mettre en évidence les bonnes capacités du coulis d'hydrates à stocker, à véhiculer et à restituer l'énergie emmagasinée