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Distribution by Scientific Domains

Medical Sciences	40%
Engineering	40%

Selected Abstracts

How to design perforated polymeric films for modified atmosphere packs (MAP)

PACKAGING TECHNOLOGY AND SCIENCE, Issue 6 2001
Luciano ZanderighiArticle first published online: 12 APR 200
Abstract Increasing proportions of fresh produce are being sold in modified atmosphere packs (MAP) with the aim of preserving product quality longer and reducing freight costs. A rigorous theoretical analysis was made of the transport phenomena across packaging film (composite, perforated, etc.) in order to find out whether polymeric film will permit a stationary modified atmosphere (MA) inside the pack, and if so when, and to investigate the effect of the size and shape of the holes in the perforated film. The continuity equations of the pack, for all diffusing species, were written and solved for stationary conditions, with the boundary conditions that species not involved in metabolic processes do not diffuse across polymeric film. After a detailed analysis of the transport phenomena across both continuous and perforated film, and of the metabolic rate processes, it transpires that no stationary conditions compatible with any MA can be found for continuous film, owing to the permeation characteristics of the film and the rate of the metabolic processes. With perforated film it is possible to find, at least for certain metabolic process rates, a stationary state where a constant MA is maintained inside the pack. A proposal is given, provided the rate of the metabolic process is known, for the design of a pack in terms of polymeric materials and of the pinhole size. Two case studies, strawberry and cabbage, are presented and discussed, along with the optimization of the polymeric film and the size and length of the pinholes of the packs. Another point raised deals with the advantages of using perforated film and/or of making holes or openings along the edges where the polymeric film is welded. Copyright © 2001 John Wiley & Sons, Ltd. [source]

A variational multiscale model for the advection,diffusion,reaction equation

INTERNATIONAL JOURNAL FOR NUMERICAL METHODS IN BIOMEDICAL ENGINEERING, Issue 7 2009
Guillaume Houzeaux
Abstract The variational multiscale (VMS) method sets a general framework for stabilization methods. By splitting the exact solution into coarse (grid) and fine (subgrid) scales, one can obtain a system of two equations for these unknowns. The grid scale equation is solved using the Galerkin method and contains an additional term involving the subgrid scale. At this stage, several options are usually considered to deal with the subgrid scale equation: this includes the choice of the space where the subgrid scale would be defined as well as the simplifications leading to compute the subgrid scale analytically or numerically. The present study proposes to develop a two-scale variational method for the advection,diffusion,reaction equation. On the one hand, a family of weak forms are obtained by integrating by parts a fraction of the advection term. On the other hand, the solution of the subgrid scale equation is found using the following. First, a two-scale variational method is applied to the one-dimensional problem. Then, a series of approximations are assumed to solve the subgrid space equation analytically. This allows to devise expressions for the ,stabilization parameter' ,, in the context of VMS (two-scale) method. The proposed method is equivalent to the traditional Green's method used in the literature to solve residual-free bubbles, although it offers another point of view, as the strong form of the subgrid scale equation is solved explicitly. In addition, the authors apply the methodology to high-order elements, namely quadratic and cubic elements. The proposed model consists in assuming that the subgrid scale vanishes also on interior nodes of the element and applying the strategy used for linear element in the segment between these interior nodes. The proposed scheme is compared with existing ones through the solution of a one-dimensional numerical example for linear, quadratic and cubic elements. In addition, the mesh convergence is checked for high-order elements through the solution of an exact solution in two dimensions. Copyright © 2008 John Wiley & Sons, Ltd. [source]

Using matching distance in size theory: A survey

INTERNATIONAL JOURNAL OF IMAGING SYSTEMS AND TECHNOLOGY, Issue 5 2006
Michele d'Amico
Abstract In this survey we illustrate how the matching distance between reduced size functions can be applied for shape comparison. We assume that each shape can be thought of as a compact connected manifold with a real continuous function defined on it, that is a pair (,,, : , , ,), called size pair. In some sense, the function , focuses on the properties and the invariance of the problem at hand. In this context, matching two size pairs (,, ,) and (,,, ,) means looking for a homeomorphism between , and ,, that minimizes the difference of values taken by , and , on the two manifolds. Measuring the dissimilarity between two shapes amounts to the difficult task of computing the value , = inff maxP,, |,(P) , ,(f(P))|, where f varies among all the homeomorphisms from , to ,,. From another point of view, shapes can be described by reduced size functions associated with size pairs. The matching distance between reduced size functions allows for a robust to perturbations comparison of shapes. The link between reduced size functions and the dissimilarity measure , is established by a theorem, stating that the matching distance provides an easily computable lower bound for ,. Throughout this paper we illustrate this approach to shape comparison by means of examples and experiments. © 2007 Wiley Periodicals, Inc. Int J Imaging Syst Technol, 16, 154,161, 2006 [source]

Numerical analysis of a non-singular boundary integral method: Part II: The general case

MATHEMATICAL METHODS IN THE APPLIED SCIENCES, Issue 7 2002
P. Dreyfuss
In order to numerically solve the interior and the exterior Dirichlet problems for the Laplacian operator, we have presented in a previous paper a method which consists in inverting, on a finite element space, a non-singular integral operator for circular domains. This operator was described as a geometrical perturbation of the Steklov operator, and we have precisely defined the relation between the geometrical perturbation and the dimension of the finite element space, in order to obtain a stable and convergent scheme in which there are non-singular integrals. We have also presented another point of view under which the method can be considered as a special quadrature formula method for the standard piecewise linear Galerkin approximation of the weakly singular single-layer potential. In the present paper, we extend the results given in the previous paper to more general cases for which the Laplace problem is set on any ,,, domains. We prove that the properties of stability and convergence remain valid. Copyright © 2002 John Wiley & Sons, Ltd. [source]

Evaluation of soft tissue around single-tooth implant crowns: the pink esthetic score

CLINICAL ORAL IMPLANTS RESEARCH, Issue 6 2005
Rudolf Fürhauser
Abstract Aim: In this study, the reproducibility of a newly developed pink esthetic score (PES) for evaluating soft tissue around single-tooth implant crowns was assessed. The effect of observer specialization was another point of interest. Material and methods: Twenty observers (five prosthodontists, five oral surgeons, five orthodontists and five dental students) were given photographs of 30 single-tooth implant crowns. Seven variables were evaluated vs. a natural reference tooth: mesial papilla, distal papilla, soft-tissue level, soft-tissue contour, alveolar process deficiency, soft-tissue color and texture. Using a 0-1-2 scoring system, 0 being the lowest, 2 being the highest value, the maximum achievable PES was 14. Each observer was requested to make two assessments at an interval of 4 weeks. At the second assessment, the photographs were scored in the reverse order. Results: The mean PES of evaluations at the first assessment (n=600) was 9.46 (±3.81 SD), and 9.24 (±3.8 SD) at the second one. The difference between these two means was not significant statistically (P=0.6379). Implant-related mean PES for single-tooth implants varied from 2.28 to 13.8, with standard deviations between 0.46 and 3.51. Very poor and very esthetic restorations showed the smallest standard deviations. The mean total PES was 10.6 for the prosthodontists, 9.2 for the oral surgeons, 9.9 for the dental students and 7.6 for the orthodontists. Conclusions: The PES reproducibly evaluates peri-implant soft tissue around single-tooth implants. Thus, an objective outcome of different surgical or prosthodontic protocols can be assessed. Orthodontists were clearly more critical than the other observers. Résumé Dans cette étude la reproduction d'un nouveau Score d'Esthétique Rose (PES) pour l'évaluation des tissus mous autour des couronnes d'implants uniques a étéévaluée. L'effet de la spécialisation de l'observateur était un autre point d'intérêt. Vingt observateurs (cinq spécialistes en prothèse, cinq chirurgiens, cinq orthodontistes et cinq étudiants en médecine dentaire) ont reçu des photographies de 30 couronnes sur implant unique. Sept variables ont étéévaluées vs une dent de référence naturelle : papille mésiale, papille distale, niveau du tissu mou, couleur du tissu mou, perte du processus alvéolaire, couleur du tissu mou et texture. En utilisant un système 0,1,2, zéro étant le plus bas et deux étant la plus haute valeur, le score maximum PES était donc de 14. Chaque observateur a reçu comme instruction de réaliser deux évaluations à un intervalle de quatre semaines. A la seconde évaluation les photographies ont étéévaluées dans un ordre inverse. Les PES moyens des évaluations de la première fois (n=600) étaient de 9,46±3,81 et 9,24±3,80 la seconde fois. La différence entre ces deux moyennes n'était pas significative (P=0,6379). Le PS moyen en relation pour les implants sur dent unique variait de 2,28 à 13,8 avec des déviations standards de 0,46 à 3,51. Les restaurations de moindre qualité et les excellentes affichaient les plus petites déviations standards. Le PES total moyen était de 10,6 pour les spécialistes en prothèse, 9,2 pour les chirurgiens, 9,9 pour les étudiants et 7,6 pour les orthodontistes. Le PES évalue donc les tissus mous paraïmplantaires autour des implants uniques. Un aboutissement objectif de différents protocoles chirurgicaux ou prothétiques peut donc être estimé. Les orthodontistes étaient clairement plus critiques que les autres observateurs. Zusammenfassung Ziel: In dieser Arbeit wird die Reproduzierbarkeit eines neu entwickelten Pink Esthetic Index (PES) zur Evaluation vom Weichgewebe um Kronen auf Einzelzahnimplantaten untersucht. Zusätzlich interessierte der Einfluss des Spezialisierungsgrades eines Untersuchers. Material und Methoden: Man gab zwanzig Untersuchern (5 Prothetiker, 5 Oralchirurgen, 5 Orthodonten und 5 Zahnmedizinstudenten) Fotoaufnahmen von 30 Kronen auf Einzelzahnimplantaten. Sie hatten 7 Variabeln gegenüber einem natürlichen Referenzzahn zu beurteilen: mesiale Papille, distale Papille, Niveau der Weichgewebe, Form der Weichgewebe, Defizit an Alveolarkamm, Farbe und Struktur der Weichgewebe. Man definierte eine Bewertungsskala 0-1-2, wobei 0 für den schlechtesten und 2 für den besten Wert stehen, so dass man einen maximalen PES von 14 erreichen konnte. Jeder Untersucher war angehalten, im Abstand von 4 Wochen zwei Beurteilungen durchzuführen. Anlässlich des zweiten Untersuchungstermins wurden die Fotoaufnahmen in ungekehrter Reihenfolge beurteilt. Resultate: Der mittlere PES bei den Untersuchungen im ersten Umgang (n=600) betrug 9.46 (±3.81 SD) und 9.24 (±3.8 SD) im zweiten Umgang. Der Unterschied zwischen diesen zwei Mittelwerten war statistisch nicht signifikant (P=0.6379). Der mittlere implantatspezifische PES für die Einzelzahnimplantate variierte zwischen 2.28 und 13.8 mit Standardabweichungen zwischen 0.46 und 3.51. Sehr schlechte und sehr schöne Rekonstruktionen zeigten die kleinesten Standardabweichungen. Der mittlere Gesamt-PES war bei den Prothetikern 10.6, bei den Oralchirurgen 9.2, bei den Zahnmedizinstudenten 9.9 und bei den Orthodonten 7.6. Zusammenfassung: Der Pink Esthetic Index untersucht die periimplantären Weichgewebe um Einzelzahnimplantate und wird auf seine Reproduzierbarkeit überprüft. Damit kann man die Ergebnisse von verschiedenen chirurgischen und prothetischen Protokollen objektivieren. Die Orthodonten waren deutlich kritischer bei ihrer Beurteilung als die anderen Behandler. Resumen Intencion: En este estudio se valoró la reproductibilidad de una nueva Valor de Rosado Estético (PES) para evaluar el tejido blando alrededor de coronas de implantes unitarios. El efecto de la especialización del observador fue otro punto de interés. Material y metodos: Se entregó a veinte observadores (5 prostodoncistas, 5 cirujanos orales, 5 ortodoncistas y 5 estudiantes dentales) fotografías de 30 coronas de implantes unitarios. Se evaluaron 7 variables frente a dientes naturales de referencia: papila mesial, papila distal, nivel de tejido blando, contorno de tejido blando, deficiencia del proceso alveolar, color y textura del tejido blando. Usando un sistema de puntuación de 0-1-2, siendo 0 el valor más bajo, 2 el valor más alto, el PES más alto alcanzable era de 14. Se solicitó a cada observador que llevara a cabo dos valoraciones en un intervalo de 4 semanas. En la segunda valoración las fotografías se valoraron en orden inverso. Resultados: El PES medio de evaluaciones a la primera valoración (n=600) fue 9.46 (±3.81 SD) y 9.24 (±3.8 SD) en la segunda. La diferencia entre estas dos medias no fue estadísticamente significativo (P=0.6379). El PES medio relacionado al implante para implantes unitarios varió desde 2.28 a 13.8 con desviaciones estándar entre 0.46 y 3.51. Las restauraciones más pobres y más estéticas mostraron las desviaciones estándar más bajas. El PES total fue de 10.6 para los prostodoncistas, 9.2 para los cirujanos orales, 9.9 para los estudiantes dentales y 7.6 para los ortodoncistas. Conclusiones: Las Puntuaciones de Estética Rosa evalúa reproduciblemente el tejido blando periimplantario alrededor de implantes unitarios. De este modo, se puede valorar un resultado objetivo de diferentes protocolos quirúrgicos o prostodónticos. Los ortodoncistas fueron claramente más críticos que los otros observadores. [source]