Showing papers by "Conservatoire national des arts et métiers published in 2003"

Electrochemical Characteristics and Impedance Spectroscopy Studies of Carbon-Carbon Supercapacitors

Abstract: This paper presents the results obtained on the electrochemical behavior of electrochemical capacitors assembled in nonaqueous electrolyte. The first part is devoted to the electrochemical characterization of carbon-carbon 4 cm2 cells systems in terms of capacitance, resistance, and cyclability. The second part is focused on the electrochemical impedance spectroscopy study of the cells. Nyquist plots are presented and the impedance of the supercapacitors is discussed in terms of complex capacitance and complex power. This allows the determination of a relaxation time constant of the systems, and the real and the imaginary part of the complex power vs. the frequency plots give information on the supercapacitor cells frequency behavior. The complex impedance plots for both a supercapacitor and a tantalum dielectric capacitor cells are compared. © 2003 The Electrochemical Society. All rights reserved.

Activated Carbon/Conducting Polymer Hybrid Supercapacitors

Abstract: This paper presents the work carried out within a European Union (EU) project which led to the development of 3 V and 1.5 kF preseries supercapacitor modules and 2 kW stacks based on hybrid cells with poly(3-methylthiophene) as positive electrode and activated carbon as the negative electrode with propylene carhonate-tetraethylammonium tetrafluoroborate electrolyte. These prototypes, which display a concept of hybrid cell operating with a high-surface-area activated carbon and a conventional electronically conducting polymer, both commercially available, and with a nontoxic and nonvolatile electrolyte, provide a successful response to the market demand for high power and energy supercapacitors operating with an environmentally friendly electrolyte.

Association of selenium with thyroid volume and echostructure in 35- to 60-year-old French adults.

Abstract: Objective: To investigate the relationship between selenium status, thyroid volume and gland echostructure. Design: Cross-sectional. Methods: In 792 men (45 – 60 years) and 1108 women (35 – 60 years) from the SU.VI.MAX study, thyroid volume and gland echostructure were determined ultrasonographically. At baseline, thyrotropin, free thyroxine, selenium, zinc, a-tocopherol, b-carotene, retinol, urinary iodine and thiocyanate concentrations were measured. Alcohol consumption, smoking, and menopausal status were assessed by a questionnaire. A stepwise linear and a logistic regression model were used, adjusting for antioxidant vitamins, trace elements status and age. Results: In women, there was an inverse association between selenium status and thyroid volume ðP ¼ 0:003Þ: A protective effect of selenium against goiter (odds ratio ðOR Þ¼ 0:07; 95% confidence interval ðCI Þ¼ 0:008 – 0:6) and thyroid tissue damage ðOR ¼ 0:2; 95% CI ¼ 0:06 – 0:7Þ was observed. There was no evidence of an association between menopausal status and other antioxidant elements, thyroid volume or thyroid hypoechogenicity. Smoking, but not alcohol consumption, was associated with an increased risk of thyroid enlargement in women ðOR ¼ 3:94; 95% CI ¼ 1:64 – 9:48Þ: No association between thyroid volume, thyroid structure or selenium was found in men. Conclusion: Our findings suggest that selenium may protect against goiter. Selenium was related to thyroid echostructure, suggesting it may also protect against autoimmune thyroid disease.

Differences between clinical trials and postmarketing use

Abstract: Aims Clinical trials constitute the gold standard to assess the efficacy and safety of new medicines. However, because they are conducted in standardized conditions far from the real world of prescription and use, discrepancies in patient selection or treatment conditions may alter both the effectiveness and risks. On the basis of three examples, our objectives were to study the differences between the characteristics of treated populations and treatment patterns in clinical trials and in postmarketing settings and to discuss the potential consequences on actual efficacy and safety. Methods Treated populations were compared with patients included in premarketing clinical trials. Comparisons were made on the basis of demographic characteristics and treatment patterns. Results Whatever the indicator and the drug studied, differences were observed: from 0.04% to 63% for tacrine, from 0% to 37% for celecoxib and from 6% to 52% for simvastatin, with possible consequences on the effectiveness and safety of the drug concerned. Our results confirm the under-representation of women and elderly patients in premarketing clinical trials, e.g. an M : F ratio of 4.6 in clinical trails of simvastatin vs 1.0 in the joint population. Moreover, the concomitant use of medicines was made extremely restrictive by the protocols of these trials while this was not the case in the postmarketing phase. This has possible consequences on the effectiveness and safety of the drug concerned. Conclusions These results plead for systematic ad hoc observational postmarketing studies for any novel and/or expensive medicine to assess the relevance of premarketing data.

Query-preserving watermarking of relational databases and XML documents

Abstract: Watermarking allows robust and unobtrusive insertion of information in a digital document. Very recently, techniques have been proposed for watermarking relational databases or XML documents, where information insertion must preserve a specific measure on data (e.g. mean and variance of numerical attributes.)In this paper we investigate the problem of watermarking databases or XML while preserving a set of parametric queries in a specified language, up to an acceptable distortion.We first observe that unrestricted databases can not be watermarked while preserving trivial parametric queries. We then exhibit query languages and classes of structures that allow guaranteed watermarking capacity, namely 1) local query languages on structures with bounded degree Gaifman graph, and 2) monadic second-order queries on trees or tree-like structures. We relate these results to an important topic in computational learning theory, the VC-dimension. We finally consider incremental aspects of query-preserving watermarking.

Setoids in type theory

Abstract: Formalising mathematics in dependent type theory often requires to represent sets as setoids, i.e. types with an explicit equality relation. This paper surveys some possible definitions of setoids and assesses their suitability as a basis for developing mathematics. According to whether the equality relation is required to be reflexive or not we have total or partial setoid, respectively. There is only one definition of total setoid, but four different definitions of partial setoid, depending on four different notions of setoid function. We prove that one approach to partial setoids in unsuitable, and that the other approaches can be divided in two classes of equivalence. One class contains definitions of partial setoids that are equivalent to total setoids; the other class contains an inherently different definition, that has been useful in the modeling of type systems. We also provide some elements of discussion on the merits of each approach from the viewpoint of formalizing mathematics. In particular, we exhibit a difficulty with the common definition of subsetoids in the partial setoid approach.

Neurosteroids: Cerebrospinal fluid levels for Alzheimer's disease and vascular dementia diagnostics.

Abstract: A neurodegenerative disease such as Alzheimer’s disease (AD) is associated with significantly higher dehydroepiandrosterone (DHEA) levels in cerebrospinal fluid (CSF). Because the human brain is known to transform DHEA into DHEA sulfate (DHEAS), 7α-hydroxy-DHEA, 7β-hydroxy-DHEA, and 16α-hydroxy-DHEA, it is possible that DHEA accumulation in the brain results from a decreased production of such metabolites. To test this hypothesis, we have measured and compared CSF levels of DHEA, DHEAS, 7α-hydroxy-DHEA, 7β-hydroxy-DHEA, and 16α-hydroxy-DHEA in 14 patients with AD, 12 controls, and eight patients with another common dementia, vascular dementia (VD). Results indicated that DHEAS CSF levels were significantly decreased in AD and VD (P < 0.007), whereas other metabolite levels were not significantly changed. Use of steroid level ratios, such as DHEA/(7α-hydroxy-DHEA + 7β-hydroxy-DHEA), 7β-hydroxy-DHEA/DHEA, and DHEAS/DHEA ratios, resulted in significant differences between diseased and control patients (P < 0...

Réflexions méthodologiques sur l'autoconfrontation croisée

Abstract: We have studied and developed a methodological procedure, named cruised auto confrontation, in order to analyze work situations, with the purpose of recovering the process of production, through the understanding of the activity purpose itself. The principles of the Bakhtinian dialogism and the Vigotskyan development psychology were applied to understand linguistic interventions in professional activities. The five subsequent parts of the method help the analyst orientate his work in order to develop an action towards the subject, which is confronted with himself and with others in the activity. The method succeeded in shedding light on the relation between real activity and represented activity, taking into account speech genders and activity gender.

Selective Concentration of Uranium from Seawater by Nanofiltration

Abstract: A new procedure for the concentration of uranium, dissolved in seawater with extremely low concentration, was studied. Plate module membrane filtration equipment was operated to evaluate the performance and selectivity of four different nanofiltration flat sheet membranes. Experiments were first carried out using different model waters. The membranes were discriminating by the rejection of uranium, calcium, and sodium. Then, a uranium concentration test using a nanofiltration membrane showing the highest selectivity for uranium toward alkaline and alkaline-earth ions has been performed on natural seawater. A nanofiltration membrane shows a high selectivity for U(VI), illustrating the advantageous use of nanofiltration for the concentration of uranium from seawater.

Semantic integration in Xyleme: a uniform tree-based approach

Abstract: Xyleme is a huge warehouse integrating XML data of the Web. Xyleme considers a simple data model with data trees and tree types for describing the data sources, and a simple query language based on tree queries with boolean conditions. The main components of the data model are a mediated schema modeled by an abstract tree type, as a view of a set of tree types associated with actual data trees, called concrete tree types, and a mapping expressing the connection between the mediated schema and the concrete tree types. The first contribution of this paper is formal: we provide a declarative model-theoretic semantics for Xyleme tree queries, a way of checking tree query containment, and a characterization of tree queries as a composition of branch queries. The other contributions are algorithmic and handle the potentially huge size of the mapping relation which is a crucial issue for semantic integration and query evaluation in Xyleme. First, we propose a method for pre-evaluating queries at compile time by storing some specific meta-information about the mapping into map translation tables. These map translation tables summarize the set of all the branch queries that can be generated from the mediated schema and the set of all the mappings. Then, we propose different operators and strategies for relaxing queries which, having an empty map translation table, will have no answer if they are evaluated against the data. Finally, we present a method for semi-automatically generating the mapping relation.

Heterodyne interferometric technique for displacement control at the nanometric scale

Abstract: We propose a method of displacement control that addresses the measurement requirements of the nanotechnology community and provide a traceability to the definition of the meter at the nanometric scale. The method is based on the use of both a heterodyne Michelson’s interferometer and a homemade high frequency electronic circuit. The system so established allows us to control the displacement of a translation stage with a known step of 4.945 nm. Intrinsic relative uncertainty on the step value is 1.6×10−9. Controls of the period of repetition of these steps with a high-stability quartz oscillator permits to impose an uniform speed to the translation stage with the same accuracy. This property will be used for the watt balance project of the Bureau National de Metrologie of France.

Fragment charge correlations and spinodal decomposition in finite nuclear systems

Abstract: Enhanced production of events with almost equal-sized fragments is experimentally revealed by charge correlations in the multifragmentation of a finite nuclear system selected in 129Xe central collisions on nat Sn. The evolution of their weight with the incident energy: 32, 39, 45, 50 AMeV, is measured. Dynamical stochastic mean-field simulations performed at 32 AMeV, in which spinodal instabilities are responsible for multifragmentation, exhibit a similar enhancement of this kind of events. The above experimental observation evidences the spinodal decomposition of hot finite nuclear matter as the origin of multifragmentation in the Fermi energy regime.

Cost Allocation Methods

Abstract: This chapter deals with the key issue of cost allocation, namely: how to allocate costs across services or market segments within a given industry, in order to set prices exhibiting desirable properties?

Multidimensional Schemas Quality: Assessing and Balancing Analyzability and Simplicity

Abstract: A data warehouse is a database focused on decision making. Decision makers typically access data warehouses through OLAP tools, based on a multidimensional representation of data. In the past, the key issue of data warehouse quality has often been centered on data quality. However, since OLAP tool users directly access multidimensional schemas, multidimensional schema quality evaluation is also crucial. This paper focuses on the quality of multidimensional schemas, more specifically on the analyzability and simplicity criteria. We present the underlying multidimensional model and address the problem of measuring and finding the right balance between analyzability and simplicity of multidimensional schemas. Analyzability and simplicity are assessed using quality metrics which are described and illustrated based on a case study. The main objective of our approach is to provide the data warehouse designer with precise measures to support him in the choice among several alternative multidimensional schemas.

Dehydroepiandrosterone 7α‐ and 7β‐Hydroxylation in Mouse Brain Microsomes. Effects of Cytochrome P450 Inhibitors and Structure‐Specific Inhibition by Steroid Hormones

Abstract: Presently, several works question the effects of dehydroepiandrosterone (DHEA) reported in vivo and designate its 7-hydroxylated metabolites as native antiglucocorticoids and potent mediators in the triggering of immune response. Among mouse tissues and organs, and second to liver, the largest production of 7alpha-and 7beta-hydroxylated derivatives of DHEA takes place in brain microsomes. To contribute to identification of cytochromes P450 (CYPs) responsible for 7alpha- and 7beta-hydroxy-DHEA production, effects of CYP inhibitors and of several steroid hormones on DHEA 7-hydroxylation were examined. Using mouse brain microsomes as a source of enzyme, we report now that strong and smaller inhibitions of DHEA 7alpha-hydroxylation were obtained with ketoconazole and alpha-naphthoflavone, respectively, and that neither changed DHEA 7beta-hydroxylation. Metyrapone and antipyrine also inhibited 7alpha-hydroxylation, but by contrast, significantly increased 7beta-hydroxylation of DHEA. This indicated that at least, two different CYPs were responsible for 7alpha- and 7beta-hydroxylation of DHEA. Steroids sharing a 3beta-hydroxylated structure with DHEA, namely pregnenolone, 5-androstene-3beta,17beta-diol and 3beta-hydroxy-5alpha-androstan-17-one, were strong inhibitors of DHEA 7alpha-hydroxylation (non-competitive inhibition with pregnenolone, Ki=2.0 +/- 0.3 microM). In contrast, 7beta-hydroxylation yields were not decreased by the 3beta-hydroxysteroids tested. Moderate inhibition of 7alpha- and 7beta-hydroxylation was obtained with 3-oxosteroids, namely testosterone, progesterone, corticosterone and 4-androsten-3,17-dione. Taken together, these data indicate specific inhibition patterns of DHEA 7alpha- and 7beta-hydroxylation by CYP inhibitors and steroid hormones in mouse brain microsomes and may be used as criteria necessary for identification of the responsible CYP species.

Filling-in phenomenon in patients with age-related macular degeneration: differences regarding uni- or bilaterality of central scotoma

Abstract: The purpose of this study was to explore the presence of the filling-in phenomenon in patients with uni- or bilateral central scotoma (CS) resulting from natural history or laser photocoagulation of choroidal neovascularization in age-related macular degeneration (AMD). Sixteen consecutive patients with unilateral CS and 14 patients with bilateral CS were assessed (44 eyes) with a scanning laser ophthalmoscope (SLO). Scotoma was delineated by scotometry with a point (1°×1°) moving radially from the periphery to the center of the lesion. In addition, patients underwent a line test, consisting of a horizontal line moving vertically and a vertical line moving horizontally, from the periphery to the center. The lines were longer than the macular lesion and were projected onto the retina. Patients were asked to indicate when the lines seemed interrupted. The perceptual filling-in phenomenon was considered to be present when limits of the perceived scotoma, determined by the line test, were smaller than those assessed by scotometry. In patients with bilateral CS, the results were analyzed to distinguish the less or more severely affected eye. In all eyes, the limits of the scotoma obtained with the scotometry test corresponded to the anatomic edges of the macular lesion. In patients with bilateral CS, the filling-in phenomenon was observed in 12 out of 14 (85%) less severely affected eyes, but only in one (7%) of their more severely affected eyes. In patients with unilateral CS, the phenomenon was observed in only one out of 16 (6%) eyes. These results suggest that the filling-in phenomenon mostly occurs in patients with bilateral central scotoma, and almost always in their less affected eye. Thus, it did usually not occur in an eye if the fellow eye was better.