Inverse identification of constitutive parameters from heat source fields: A local approach applied to hyperelasticity

In this paper, a new inverse identification method of constitutive parameters is developed from full kinematic and thermal field measurements. It consists in reconstructing the heat source field from two different approaches by using the heat diffusion equation. The first one requires the temperature field measurement and the value of the thermophysical parameters. The second one is based on the kinematic field measurement and the choice of a thermo-hyperelastic model that contains the parameters to be identified. The identification is carried out at the local scale, ie, at any point of the heat source field, without using the boundary conditions. In the present work, the method is applied to the challenging case of hyperelasticity from a heterogeneous test. Due to large deformations undergone by the rubber specimen tested, a motion compensation technique is developed to plot the kinematic and the thermal fields at the same points before reconstructing the heterogeneous heat source field. In the present case, the constitutive parameter of the Neo-Hookean model has been identified, and its distribution has been characterized with respect to the strain state at the surface of a cross-shaped specimen.     

Diagnostic value of fundus examination in familial adenomatous polyposis

BACKGROUND: Multiple, bilateral lesions of congenital hypertrophy of the retinal pigment epithelium (CHRPE) have been described in patients suffering from familial adenomatous polyposis (FAP) since 1980. This study aimed to determine a reliable diagnostic criterion, based on the size and number of retinal CHRPE lesions, allowing the screening of patient carriers of the gene responsible for FAP. METHODS: 32 control subjects and 144 patients belonging to 85 FAP families were studied, divided into 124 carriers of the genetic alteration and 20 non-carriers. RESULTS: In carriers of the deleted gene, multiple, bilateral retinal lesions were consistently observed. Lesion situation, size, shape, and degree of pigmentation were variable however. A positive criterion for FAP was defined as the presence of at least four lesions whatever their size, or at least two lesions one of which is large. This criterion showed a high sensitivity (0.68) and a maximal specificity (1). Within each family, the retinal phenotypic expression was homogeneous. CHRPE lesions were observed in two thirds of the FAP families and absent from the remaining third. CONCLUSION: By using this new positive diagnostic criterion, fundus examination allows early detection of those children carrying the gene responsible for FAP in families positive at ocular examination.     

Canadian research activity in aquaculture: A bibliometric analysis

Analysis of the Canadian publications in the field of aquaculture reveals that Canada is one of the word's major contributors in this area. This confirms that Canada's expertise in science and technology often finds its stimulus in its resource-based industries. Several bibliometric indicators were used to enlighten the peculiar features of the Canadian research system. These include the channels of communication used by scientists, the authorship pattern, the level of collaboration, the identification of the institutions in which the research is performed and the uneven research effort distribution inside the country. The relevance of such quantitative measures for science policy-making is emphasized. The present study shows how bibliometric analysis, by describing the actual strengths and weaknesses of Canadian research and identifying the agents of this research activity, might foster a better understanding of the Canadian research enterprise as a whole.     

Polyvinylidene fluoride monofilament sutures: can they be used safely for long-term anastomoses in the thoracic aorta?

Polyvinylidene fluoride (PVDF) represents an attractive alternative to polypropylene as a monofilament vascular suture because of its satisfactory physicochemical properties, it ease of handling, and its good biocompatibility. However, the polymer's ability to remain mechanically and chemically stable when exposed to a mild hydrolytic environment over the long term has yet to be demonstrated. One in vitro study involved the comparison of the long-term relative resistance of PVDF and polypropylene sutures to hydrolysis for a period of 9 years. The PVDF suture showed major molecular rearrangements from the original ratio of three crystalline structures to the single beta crystalline phase. The observation of some surface oxidation and water inhibition did not significantly modify the tensile strength of the PVDF suture, which retained 92.5% of its original value. In contrast, the polypropylene sample did not undergo any recrystallization but was associated with more oxidation byproducts and more water molecules near the surface, which contributed to a 46.6% loss in initial tensile strength. An in vivo study confirmed that PVDF sutures are biocompatible and are able to maintain satisfactory biostability when used to anastomose thoracic aortic allografts for a period of 6 months in the dog. The cellular reaction of fresh allografts as well as the control autografts to PVDF sutures was minimal. In other allografts that had been preserved in a supplemented medium for 1 week prior to implantation, the PVDF sutures healed satisfactorily with the formation of neocollagen and few macrophages surrounding the monofilament. No evidence of instability at the allograft-host artery junction was observed, confirming that the PVDF sutures were able to ensure a secure anastomosis in the thoracic aorta. PVDF sutures have demonstrated superior long-term biostability in vitro and minimal tissue response in vivo. These are two essential requirements when evaluating the use of a suture for vascular surgery in general and thoracic aortic surgery in particular.     

Nodular and granulomatous form of periarteritis nodosa caused by the hepatitis B virus

Human herpesvirus type 6 DNA derived from human breath was discovered to contaminate PCR reactions during routine reaction preparation. Parallel PCR experiments were conducted in which expiratory secretions were blocked by a surgical mask, while others were performed without any attempt to circumvent respiratory contamination. The experimenter was previously determined to harbor HHV-6 DNA in the saliva. All reactions in which expiration was obstructed were negative for HHV-6 DNA via PCR. Reactions in which there was no attempt to obstruct respiratory secretions were positive for HHV-6 DNA. These data suggest that PCR assays investigating the presence of HHV-6 may be highly susceptible to contamination from the experimenter leading to false positive results.     

Coverage-biased random exploration of large models and application to testing

This paper presents several randomised algorithms for generating paths in large models according to a given coverage criterion. Using methods for counting combinatorial structures, these algorithms can efficiently explore very large models, based on a graphical representation by an automaton or by a product of several automata. This new approach can be applied to random exploration in order to optimise path coverage and can be generalised to take into account other coverage criteria, via the definition of a notion of randomised coverage satisfaction. Our main contributions are a method for drawing paths uniformly at random in composed models, i.e. models that are given as products of automata, first without and then with synchronisation; a new efficient approach to draw paths at random taking into account some other coverage criterion. Experimental results show promising agreement with theoretical predictions and significant improvement over previous randomised approaches. This work opens new perspectives for future studies of statistical testing and model checking, mainly to fight the combinatorial explosion problem.     

Comparison of a contactor catalytic membrane reactor with a conventional reactor: example of wet air oxidation

A wet air oxidation reaction was carried out in a gas/liquid catalytic membrane reactor of the contactor type. The oxidation of formic acid was used as a model reaction. The mesoporous top-layer of a ceramic tubular membrane was used as catalyst (Pt) support, and was placed at the interface of the gas (air) and liquid (HCOOH solution) phases.

A similar reaction was carried out in a conventional batch reactor, using a steering rate high enough to avoid gas-diffusion limitations, and exactly identical conditions than for the CMR (amount of catalyst, pressure, etc.). At room temperature, the CMR showed an initial activity three to six times higher than the conventional reactor. This activity increase was attributed to an easier oxygen access to the catalytic sites. Nevertheless, the catalytic membrane gradually deactivated after a few hours of operation. Different deactivation mechanisms are presented.     

Effects of the sintering atmosphere on Nb-based dielectrics

The effects of a forming atmosphere on the stability, the sintering and the dielectric properties of Ba₅Nb₄O₁₅, BaNb₂O₆, ZnNb₂O₆ and Zn₃Nb₂O₈ ceramics were investigated, because of the primary importance of the sintering atmosphere in relation to copper sintering. These Nb-based materials were sintered in air and in Ar/H₂10%. Zn-containing samples are very sensitive to the reductive atmosphere. ZnO volatilises at 800–850 °C and the resulting compound does not exhibit the expected properties. BaNb₂O₆ and Ba₅Nb₄O₁₅ are more stable in term of relative weight loss. Nevertheless, the phase analysis reveals a modification of the BaNb₂O₆ phase, what induces the degradation of the dielectric property stability versus temperature. The properties of Ba₅Nb₄O₁₅ are not modified by a sintering in reductive atmosphere. A relative permittivity of 38.8, a permittivity temperature coefficient of −150 ppm °C⁻¹ and an insulating resistivity of 10^10.9 Ω cm were obtained for this latter.     

The Failure of the Strong Pumping Lemma for Multiple Context-Free Languages

Seki et al. (Theor. Comput. Sci. 88(2):191–229, 1991) showed that every m-multiple context-free language L is weakly 2m-iterative in the sense that either L is finite or L contains a subset of the form \(\{ u_{0} w_{1}^{i} u_{1} \cdots w_{2m}^{i} u_{2m} \mid i \in \mathbb {N}\}\) , where w ₁?w _2n ≠ε. Whether every m-multiple context-free language L is 2m-iterative, that is to say, whether all but finitely many elements z of L can be written as z=u ₀ w ₁ u ₁?w _2m u _2m with w ₁?w _2m ≠ε and \(\{ u_{0} w_{1}^{i} u_{1} \cdots w_{2m}^{i} u_{2m} \mid i \in \mathbb {N}\} \subseteq L\) , has been open. We show that there is a 3-multiple context-free language that is not k-iterative for any k.