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Showing papers by "Conservatoire national des arts et métiers published in 1992"


Journal ArticleDOI
TL;DR: In this article, it was shown that the network representation of non-resistive physical systems in interaction with their environment leads to a well defined class of control systems, called port-controlled Hamiltonian systems.

381 citations


Journal ArticleDOI
TL;DR: In this paper, an intrinsic Hamiltonian formulation of the equations of motion of network models of non-resistive physical systems is provided. But the connection between the Hamiltonian formalism and network dynamics is investigated through the representation of the invariants of the system.
Abstract: The aim of this paper is to provide an intrinsic Hamiltonian formulation of the equations of motion of network models of non-resistive physical systems. A recently developed extension of the classical Hamiltonian equations of motion considers systems with state space given by Poisson manifolds endowed with degenerate Poisson structures, examples of which naturally appear in the reduction of systems with symmetry. The link with network representations of non-resistive physical systems is established using the generalized bond graph formalism which has the essential feature of symmetrizing all the energetic network elements into a single class and introducing a coupling unit gyrator. The relation between the Hamiltonian formalism and network dynamics is then investigated through the representation of the invariants of the system, either captured in the degeneracy of the Poisson structure or in the topological constraints at the ports of the gyrative type network structure. This provides a Hamiltonian formulation of dimension equal to the order of the physical system, in particular, for odd dimensional systems. A striking example is the direct Hamiltonian formulation of electrical LC networks.

171 citations


Journal ArticleDOI
TL;DR: The digestive gland of cephalopods (carnivorous molluscs whose age can be easily calculated with great accuracy) would seem to constitute a good potential indicator of heavy metal concentrations in the marine environment.
Abstract: The concentrations of 11 heavy metals (Ag, Cd, Co, Cr, Cu, Fe, Mn, Ni, Pb, V and Zn) were measured in the tissues (digestive gland, branchial hearts, gills, digestive tract, kidney, genital tract, muscle, skin, shell) of the two cephalopods Eledone cirrhosa (d'Orb.) and Sepia officinalis (L.) collected from the French coast of the English Channel in October 1987. The tissues of both species displayed a similar pattern of heavy-metal accumulation: the digestive gland, branchial hearts and kidney were the major sites of concentration for all 11 metals; the digestive gland accumulated silver, cadmium, cobalt, copper, iron, lead and zinc, the branchial hearts high concentrations of copper, nickel and vanadium, and the kidney high concentrations of manganese, nickel and lead. The digestive gland, which constituted 6 to 10% of the whole-animal tissue, contained >80% of the total body burden of Ag, Cd and Co and from 40 to 80% of the total body burden of the other metals. The ratios between heavy metal concentrations in the digestive gland and those in the muscle separated the elements into three groups, those with a ratio ≤10 (Cr, Mn, Ni, Pb, V, Zn), those with a ratio >10 to <50 (Co, Cu, Fe), and those with a ratio ≥50 (Ag, Cd). The digestive gland of cephalopods (carnivorous molluscs whose age can be easily calculated with great accuracy) would seem to constitute a good potential indicator of heavy metal concentrations in the marine environment.

156 citations


Journal ArticleDOI
TL;DR: In this article, the complexation ability of coumarin 153 linked to monoaza-15-crown-5 was studied and the stability of the complexes remains high enough in acetonitrile-water mixtures for practical application to the determination of cation concentrations in aqueous samples.

95 citations


Journal ArticleDOI
TL;DR: The results suggest that a competitive interrelation between methanogenic archaea and sulfate-reducing bacteria occurs in the human colon, however, it does not lead to a complete exclusion of the two populations.
Abstract: In humans, CH4 is produced in the colon by methanogenic archaea and is detected in breath samples from approximately 50% of healthy adults, identified as CH4-excretors. Methanogenesis and sulfate reduction have been described as two mutually exclusive processes, potentially regulated by sulfate reduction have been described as two mutually exclusive processes, potentially regulated by sulfate availability. To determine whether microbial population balances reflected these apparently co-regulated activities, we compared sulfate-reducing bacteria, methanogenic archaea, sulfate and sulfide concentrations in faeces of 10 CH4-excretors (CH4+) and 9 non-CH4-excretors (CH4−). The mean ±SE of the logarithm of methanogenic archaea per gram wet weight were 9.0 ± 0.2 and 4.0 ± 0.7 for CH4+ and CH4−, respectively (P < 0.001). Sulfate-reducing bacterial counts were 6.5 ± 0.1 and 7.3 ± 0.2, respectively (P < 0.001). Fecal sulfate and sulfide concentrations did not differ between groups. These results suggest that a competitive interrelation between methanogenic archaea and sulfate-reducing bacteria occurs in the human colon. However, it does not lead to a complete exclusion of the two populations.

67 citations


Journal ArticleDOI
TL;DR: The reduction in IL-2 production by activated lymphocytes observed in the study of iron-deficient children may be responsible for impairments in immunity found by other authors, particularly in cell-mediated immunity.
Abstract: The relationship between iron status and capacity for IL-2 production by lymphocytes was assessed in 81 children from 6 mo to 3 yr of age selected at random from a population with low socioeconomic status, undergoing free systematic examination in four children's health centers in the Paris area. Iron deficiency was defined by the existence of at least two abnormal values among the three indicators of iron status: serum ferritin level ≤12 μg/L, transferrin saturation 3 μg/g hemoglobin. According to this definition, 53 children were classified as iron deficient and 28 as iron sufficient. No differences were observed between the iron-deficient and iron-sufficient groups in terms of the IL-2 concentration without stimulation by PHA. IL-2 production by lymphocytes stimulated with PHA, as well as the stimulation index (ratio of IL-2 concentration following stimulation by PHA to that of IL-2 concentration without stimulation by PHA) were significantly lower in iron-deficient children. The reduction in IL-2 production by activated lymphocytes observed in our study of iron-deficient children may be responsible for impairments in immunity found by other authors, particularly in cell-mediated immunity.

59 citations


Journal ArticleDOI
TL;DR: The highest values found in samples are within the range of lower values reported for other regions of the world, indicating an area not, or only slightly, influenced by industrial activities.

52 citations


Book ChapterDOI
22 Jun 1992
TL;DR: It is shown that testing whether a bounded Extended Free Choice net or a Non Self-Controlling net is structurally live can be reduced to the search for a strongly connected deadlock which is not a trap.
Abstract: This paper is related to structural analysis of Petri nets where liveness and boundedness issues are addressed through the analysis of the combinatorial properties of the underlying graph. We first recall a number of basic results about liveness and boundedness involving combinatorial substructures (deadlocks and traps). It is then shown that testing whether a bounded Extended Free Choice net or a Non Self-Controlling net is structurally live can be reduced to the search for a strongly connected deadlock which is not a trap. This problem, in turn, is shown to be solvable in polynomial time through a purely combinatorial algorithm making combined use of Tarjan's strong connectivity algorithm and Minoux's LTUR algorithm for solving Horn satisfiability problems. Once structural liveness has been proved, testing liveness for a given initial marking is already known to be polynomially solvable.

48 citations


Journal ArticleDOI
TL;DR: In this paper, a biprotonic transfer mechanism was proposed to transfer 4-methylumbelliferone to the neutral keto form, where the intermediate species cannot be the cationic form as stated by other authors.

47 citations


Journal ArticleDOI
TL;DR: Women are highly represented in those computer service jobs which are supposed to require the lowest level of qualification, but study of the real tasks involved revealed that the job required a great deal of innovative thinking, all of it unrecognized by the employer, and some of it actually forbidden.
Abstract: Women are highly represented in those computer service jobs which are supposed to require the lowest level of qualification. The complexity of the activities which contribute to accomplishing such tasks in real life is usually unrecognized, as are the skills needed to perform these activities. The requirements of one such job, held by 7 women in a university administration, have been documented by ergonomic analysis. According to the supervisors, little mental effort was required, and "the employees do the job without even thinking about it." However, study of the real tasks involved revealed that the job required a great deal of innovative thinking, all of it unrecognized by the employer, and some of it actually forbidden. However, because the knowledge was not arrived at through systematic training, it is fragmentary and does not permit the employee to be fully autonomous or to transfer her skills to other jobs.

29 citations


Journal ArticleDOI
TL;DR: In this paper, a ring-opening of racemic styrene oxide was achieved by lithium azide in the presence of β-cyclodextrin in aqueous media.
Abstract: Regioselective ring-opening of racemic styrene oxide was achieved by lithium azide in the presence of β-cyclodextrin in aqueous media. Kinetic resolution of racemic epoxide was observed and 1-phenyl-2-azido-ethanol was obtained with 78 % ee.

Journal ArticleDOI
TL;DR: In this article, several chiral triethoxysilanes, easily prepared from acidic or basic chiral compounds and aminopropyltriethioxysilane or isocyanatepropyltriethyldisilazanc were bonded onto silica gel.


Book ChapterDOI
24 Aug 1992
TL;DR: The strong normalization of its subcalculus σ which computes substitutions is proved, which proves that λσ-calculus is an extended λ-Calculus where substitutions are handled explicity.
Abstract: λσ-calculus is an extended λ-calculus where substitutions are handled explicity. We prove the strong normalization of its subcalculus σ which computes substitutions.

Journal ArticleDOI
TL;DR: Diet restriction lowered the TBARS level in the small intestine or liver of young rats and no variations were found for the superoxide dismutase and catalase activities; only liver seleno-dependent glutathione peroxidase was enhanced by the restriction.

Journal ArticleDOI
TL;DR: In this paper, seven chiral stationary phases obtained from (S )-phenylalanine derivatives, ( R )-Mosher's acid and ( S )-naproxen were prepared and evaluated.

Book ChapterDOI
01 Jan 1992
TL;DR: In this paper, the authors presented the FT-IR spectra in the hydroxyl region in reversed micelles where the sodium counterions of the surfactant Aerosol-OT have been replaced by Ca2+ and Zn2+ ions.
Abstract: FT-IR spectra in the hydroxyl region in reversed micelles where the sodium counterions of the surfactant Aerosol-OT have been replaced by Ca2+ and Zn2+ ions are presented. The IR spectra, taken as a function of the molar ratio R = [H2O]/[surfactant], are analzyed in the framework of a twostate model for the water molecules in which the O-H vibration can be split into two contributions: one originated by the water “tightly-bonded” to the surfactant ions, and the other induced by the “bulk” water of the micellar water pool. We also evaluate the percentage a(R) of the bond water in the micellar growth process. Furthermore, an explanation of the O-H stretching band features is suggested by comparison between our spectra and those simulated through an MD “experiment”.

Journal ArticleDOI
TL;DR: InP layers were grown by chemical beam epitaxy (CBE) using high purity thermally precracked tertiarybutylphosphine (TBP) and trimethylindium (TMI) as the source of the group III element as mentioned in this paper.

Journal ArticleDOI
TL;DR: This study shows that the polychlorinated biphenyl with the 3-methylcholanthrene-type pattern of induction of cytochrome P-450 has more profound effects on B group vitamins and particularly vitamin A homeostasis than does the phenobarbital-type inducer.

Journal ArticleDOI
TL;DR: In this article, the authors describe a set of new thiophenes having various perfluorinated alkyl groups attached via spacers to the 3-position of a thiophene.

Book ChapterDOI
02 Sep 1992
TL;DR: It is proved that the confluent λσ-calculus, augmented by cη, remains confluent and that the ground confluent version[1], extended by c η, is still groundConfluent, by the interpretation method introduced in [10].
Abstract: Some new calculi [1, 12, 8], referred to by the collective name of λσ-calculus, have been recently introduced to provide an explicit treatment of substitutions in the λ-calculus. They are term rewriting systems, with two sorts: substitution and term. The λ-terms are exactly the ground λσ-terms of sort term containing no substitutions and the β-reduction is decomposed in these calculi, into a starting reduction with a rule called (Beta) followed by a derivation computing explicitly the substitution. These calculi differ by their treatment of substitution. In this paper, we extend the λσ-calculi with a conditional rewriting relation, called cη. This relation coincides, on λ-terms, with the classical η-reduction of λ-calculus. We prove that the confluent λσ-calculus, augmented by cη, remains confluent and that the ground confluent version[1], extended by cη, is still ground confluent. The proof is done by the interpretation method introduced in [10].

Journal ArticleDOI
TL;DR: High hearing thresholds were more commonly associated with lower iodine excretion, suggesting mild hearing defects, and in spite of iodine prophylaxis, the risk of mild to moderate iodine deficiency still exists in France and in a number of European countries.
Abstract: Urinary iodine excretion was assessed in 642 healthy children aged 10 mo (n = 243), 2 yr (n = 183), and 4 yr (n = 216) living in the Paris area and originating from continental France (60.3%), North Africa (13.8%), the West Indies (9.1%), West Africa (8.3%), Southeast Asia (4.8%), and southern Europe (3.8%). Mild impairment of neurological (reflexes, tone, audiometry) and intellectual development (Brunet-Lezine scale) was assessed in relation to iodine status. Iodine excretions (median values) were 18.4, 11.9, and 10.9 micrograms/100 mL at 10 mo, 2 yr, and 4 yr, respectively, and risk of mild iodine deficiency (5-10 micrograms/100 mL) was 18.1%, 34.8%, and 38.3% for the same age groups. No relationship was found between anthropometry, global development quotient, and iodine status. High hearing thresholds were more commonly associated with lower iodine excretion, suggesting mild hearing defects. In spite of iodine prophylaxis, the risk of mild to moderate iodine deficiency still exists in France and in a number of European countries. Evaluation of neurological sequels of borderline iodine status is a major public health problem in European communities.

Journal ArticleDOI
01 Dec 1992-Wear
TL;DR: In this article, the effect of five initial surface roughnesses of silicon nitride is studied on an alternating “pin-on-plate” tribometer and the results show that the surface finish of the ceramic determines the friction response only during a short transitory stage, whereas the reactional film never occurs on the ceramic and is no longer observed on the steel after long sliding times.

Journal ArticleDOI
TL;DR: In this paper, strategies implemented by 12-13 year olds to solve electricity problems are examined, and three factors account for observed strategies:==================�τργαρατραβαταγαβραγβαβγαγγατ βαββαγ βααβ βα ββα β β βγα βα α β ββ β β α ββββ ββγ ββ α βγ βγβ βγγ β βGA βγ α β
Abstract: Strategies implemented by 12–13 year olds to solve electricity problems are examined. Three factors account for observed strategies: a) type of problem representation, itself dependent on the knowledge base; b) cognitive personality dimensions; c) form of problem statement.

Book ChapterDOI
01 Jan 1992
TL;DR: The aim of the work is to develop a new approach based on a partial exploration of the reachability set that can demonstrate, for a given period of operation, that assertions about the behaviour of the system are verified with an acceptable probability level.
Abstract: This paper presents a new concept of validation of distributed or safety-critical systems. The main problem of existing methods is related to the exponential growth of the analysis complexity with the model size. Our method relies on a state transition model which includes a description of operation duration and frequency of events (stochastic Petri nets). The aim of our work is to develop a new approach based on a partial exploration of the reachability set. At the end of the partial exploration we can demonstrate, for a given period of operation, that assertions about the behaviour of the system are verified with an acceptable probability level.

Journal ArticleDOI
TL;DR: In this paper, the fatigue strength of Al-7Si-O.6Mg and Al-5Si-3Cu-1Mg composites randomly reinforced with Al 2 O 3, short fibres were determined using a stress ratio of 0.1.
Abstract: The room temperature fatigue strengths of Al-7Si-O.6Mg and Al-5Si-3Cu-1Mg composites randomly reinforced with Al 2 O 3 , short fibres were determined using a stress ratio of 0. 1, a frequency of 50 Hz. The fatigue strength of the composites under these testing conditions can be expressed by a single curve-fitting equation. The effect of surface roughness on fatigue strength was also studied and the results show that these composites are not sensitive to surface roughness. The orthogonal growth of cracks is an important fatigue fracture mechanism in these composites. The residual strength decreased as the fatigue load increased

Journal ArticleDOI
TL;DR: In this article, a method for the preparation of N-Benzyl allylamines is described, where Selenophenol generated in catalytic quantities from diphenyldiselenide and sodium borohydride leads to reductive amination of allylamine by substituted benzaldehydes.

Journal ArticleDOI
TL;DR: In this paper, the relationship between geometrical parameters, acoustical criteria and subjecive characteristics of sound spatialisation in concert halls was investigated using multiple correspondence analysis.

Journal ArticleDOI
TL;DR: A bichomophoric molecule consisting of two coumarins linked by a penta(ethylene oxide) spacer is able to bind cooperative three Pb2+ ions in propylene carbonate.