Showing papers by "Paul Sabatier University published in 1988"

Representation and combination of uncertainty with belief functions and possibility measures

Abstract: The theory of evidence proposed by G Shafer is gaining more and more acceptance in the field of artificial intelligence, for the purpose of managing uncertainty in knowledge bases One of the crucial problems is combining uncertain pieces of evidence stemming from several sources, whether rules or physical sensors This paper examines the framework of belief functions in terms of expressive power for knowledge representation It is recalled that probability theory and Zadeh's theory of possibility are mathematically encompassed by the theory of evidence, as far as the evaluation of belief is concerned Empirical and axiomatic foundations of belief functions and possibility measures are investigated Then the general problem of combining uncertain evidence is addressed, with focus on Dempster rule of combination It is pointed out that this rule is not very well adapted to the pooling of conflicting information Alternative rules are proposed to cope with this problem and deal with specific cases such as nonreliable sources, nonexhaustive sources, inconsistent sources, and dependent sources It is also indicated that combination rules issued from fuzzy set and possibility theory look more flexible than Dempster rule because many variants exist, and their numerical stability seems to be better La theorie des fonctions de credibilite proposee par G Shafer est de plus en plus reconnue, dans le domaine de l'intelligence artificielle, pour le traitement de l'incertitude dans les bases de connaissances Un des problemes cruciaux est la combinaison d'informations issues de plusieurs sources (regles ou capteurs) Cet article etudie le cadre propose par les fonctions de credibilite quant a son pouvoir expressif pour la representation de connaissances On rappelle que d'un point de vue mathematique la theorie des probabilites et la theorie des possibilites sont des cas particuliers de la theorie des fonctions de credibilite pour ce qui est de l'evaluation de l'incertitude Les fondements empiriques et axiomatiques des fonctions de credibilite et de possibilite sont discutes Puis le probleme general de la combinaison est aborde en mettant l'accent sur la regle de Dempster On met en evidence le fait que cette regle est peu adaptee a la combinaison d'informations conflictuelles D'autres regles sont proposees pour traiter ce probleme dans diverses situations telles que sources inegalement fiables, incompletes, incoherentes, dependantes On indique aussi que les regles de combinaison proposees par la theorie des ensembles flous et des possibilites semblent plus flexibles que la regle de Dempster, car de nombreuses variantes existent; de plus leur stabilite numerique semble meilleure

Clinical Pharmacokinetics of Doxycycline and Minocycline

Abstract: Doxycycline and minocycline are second-generation tetracyclines. They are readily absorbed, distributed throughout the organism as a function of their lipophilicity and eliminated in both the urine and the faeces. The influence of age, renal disease, malnutrition and hyperlipidaemia is reviewed, together with the main pharmacokinetic interactions.

Extended gaussian-type valence basis sets for calculations involving non-empirical core pseudopotentials

Abstract: Revised values of core pseudopotential parameters are presented together with optimized PS-31 G valence basis sets for atoms from Li to Ca and from Ga to Kr. Studies with more than thirty test molecules indicate a very good agreement with 6–31 G results for atomization energies, geometries, dipole moments and force constants.

Monoclonal Antibodies in the Diagnosis of Hodgkin's Disease: The Search for a Rational Panel

Abstract: A novel, comprehensive panel of monoclonal antibodies was tested in a large series of routinely processed lymph node biopsy specimens from patients with Hodgkin's disease (69 cases), with the object of developing either definitive or adjunctive diagnostic criteria. B- and T-cell lymphomas and reactive states that could mimic Hodgkin's disease were also assessed with the same monoclonal antibody panel. In addition to the popularly used anti-Leu-M1 (CD15), the panel included the recently produced Ber-H2 (CD30) antibody, which detects a formalin-resistant epitope of the Ki-1 antigen. The other monoclonal antibodies were directed against epithelial membrane antigen (Dako-EMA) and leukocyte common antigen (Dako-LC) (CD45), as well as B-cell (LN-1 and LN-2) and T-cell (MT1) associated antigens. The results showed clear phenotypic separation of nodular lymphocyte predominant subtype of Hodgkin's disease from other subtypes. The lymphocytic and histiocytic cells of nodular lymphocyte predominant Hodgkin's disease were reactive for LN-1 (all cases) and anti-EMA (most cases) but negative for anti-Leu-M1 and Ber-H2. Within the other subtypes--i.e. nodular sclerosis and mixed cellularity--nearly all Reed-Sternberg cells and Hodgkin's cells were positive for both anti-Leu-M1 and Ber-H2. Ber-H2 monoclonal antibody was observed to react more frequently with Reed-Sternberg cells and Hodgkin's cells in Bouin's- or formalin-fixed tissues. Pleomorphic T-cell lymphomas, which could mimic Hodgkin's disease on morphology, created the same problem on phenotypic analysis. However, MT1 identified a significant proportion of T-cell lymphomas with Reed-Sternberg-like cells, having proven negative for Reed-Sternberg cells and Hodgkin's cells in Hodgkin's disease. Thus, a combination of anti-Leu-M1, Ber-H2, anti-EMA, LN-1, and MT1 monoclonal antibodies appears at present to be the most useful panel for the diagnosis and the differential diagnosis of Hodgkin's disease.

OPAL: A Knowledge-Based System for Industrial Job-Shop Scheduling

Abstract: A job-shop scheduling software currently under development is described, based on Artificial Intelligence programming techniques. The idea is to be able to make three kinds of knowledge cooperate in the derivation of a feasible schedule : theoretical knowledge (issued form scheduling theory) which achieves the management of time ; empirical knowledge about priority rules and their influence on production objectives; and practical knowledge (provided by shop-floor managers) about technological constraints to be satisfied in a given application. The latter is usually not considered in pure Operations Research algorithms. The system is actually implemented in COMMON LISP and runs on a Texas Explorer LISP Machine and a SUN workstation. Computational results are reported.

On fuzzy syllogisms

Abstract: This paper provides a systematic treatment of possibly imprecisely or vaguely specified numerical quantifiers in default syllogisms, following an approach initiated by Zadeh. The obtained propagation rules are derived from simple properties of relative cardinality or, equivalently, conditional probability. Uncertainty in the description of numerical quantifiers is handled using possibility theory and, particularly, fuzzy arithmetic. The advantages of this default reasoning method are its ability to model any kind of quantifier and to build new defaults by chaining existing ones, in a rigorous manner. This approach also emphasizes the difference between two types of uncertain pieces of knowledge, i.e., conjectures versus general rules. Cet article presente un traitement systematique des quantificateurs numeriques eventuellement imprecisement ou vaguement specifie dans des syllogismes avec exceptions, selon l'approche proposee par Zadeh. Les regles de propagation obtenues derivent de proprietes elementaires des cardinalites relatives ou, de facon equivalente, des probabilites conditionnelles. L'incertitude dans la definition des quantificateurs numeriques est traitee a l'aide de la theorie des possibilites et, plus particulierement, de l'arithmetique floue. L'avantage de cette technique de raisonnement par defaut est son aptitude a prendre en compte n'importe quel quantificateur et a construire de nouvelles regles par defaut a partir de regles par defaut connues, par chainage. Cette approche met l'accent sur la difference entre deux types d'informations incertaines: les conjectures et les lois generales avee exceptions (ou regles par defaut).

Spin-lattice relaxation in p-type gallium arsenide single crystals.

Abstract: An optical-pumping technique is used to measure the spin-relaxation time of photogenerated conduction electrons in several p-type GaAs single crystals doped with various amounts of acceptors in the 1.7--300 K temperature range. Our experimental results are compared with those of the literature and with the predictions of the existing theoretical calculations. From about 10 K, the Bir-Aronov-Pikus (BAP) mechanism is found to be relevant for moderately doped ${(10}^{17}$--${10}^{18}$ ${\mathrm{cm}}^{\mathrm{\ensuremath{-}}3}$), up to about 150 K, or degenerate (up to 300 K) semiconductors, using the electronic temperature, deduced from the luminescence spectra, rather than the sample temperature. The D'yakonov-Perel' (DP) process was found to be active above 200 K for moderately doped samples and from about 80 K to room temperature for samples doped in the (1.6--6)\ifmmode\times\else\texttimes\fi{}${10}^{16}$-${\mathrm{cm}}^{\mathrm{\ensuremath{-}}3}$ acceptor-concentration range. Our original results obtained at liquid-helium temperatures at whatever the doping level cannot be explained either by the DP mechanism or by the BAP process.

One-center expansion for pseudopotential matrix elements

Abstract: Semilocal pseudopotential operators can be expressed as a linear combination of nonlocal (projection) operators. Pseudopotential operator integrals over a molecular basis set are therefore reduced to linear combinations of overlap integrals products. Molecular calculations indicate that sufficient precision can be achieved with a limited number of nonlocal operators. Analytic derivatives of pseudopotential integrals are easily deduced and implemented in a standard quantum chemistry program.

Phleomycin resistance as a dominant selectable marker in CHO cells

Abstract: The Tn5 and the Streptoalloteichus hindustanus (Sh) ble genes conferring resistance to bleomycin-phleomycin antibiotics have been cloned into a mammalian vector under the RSV-LTR promoter. The resulting plasmids, pUT506 and pUT507 respectively, were used to transfect CHO cells by either the calcium phosphate or the recently described polybrene-DMSO method. Phleomycin- or bleomycin-resistant clones arose with a higher frequency after transfection with pUT507, and pUT507 transfectants were more resistant to both antibiotics than pUT506 transfectants. Phleomycin resistance in pUT507 transfectants was stable and associated with integration of plasmid sequences in genomic DNA. The Sh ble gene, which confers a dominant phleomycin-resistance phenotype, should provide a useful transferable selectable marker in CHO cells as well as in other animal cell lines.

Alpha 2-antagonist compounds and lipid mobilization: evidence for a lipid mobilizing effect of oral yohimbine in healthy male volunteers.

Abstract: Investigations were carried out to analyse the interactions of alpha 2-antagonists (yohimbine, idazoxan, SK & F-86,466) with human fat cell alpha 2-adrenoceptors. All the alpha 2-antagonists enhanced the lipolytic potencies of epinephrine with an order of potency: yohimbine greater than idazoxan greater than SK & F-86,466; the same order was also found in 3H-yohimbine competition studies on human fat cell membranes. The most potent agent, yohimbine, was administered orally in humans to define the conditions of appearance and the time-course of a putative lipid-mobilizing action. Oral yohimbine administration (0.2 mg kg-1) elevated plasma glycerol and non-esterified fatty acids in fasting healthy subjects without significant action on heart rate or blood pressure during the time-course of the experiment. The lipid-mobilizing action of yohimbine was reinforced during physical exercise, completely suppressed after a meal and partially blocked by administration of propranolol (0.5 mg kg-1; 60 min before yohimbine). Plasma norepinephrine concentrations were increased (40-50%) after oral yohimbine administration. The rise in plasma catecholamine concentration elicited by yohimbine was not modified by propranolol treatment. The lipid-mobilizing effect of yohimbine could be attributable to: (i) the increase in synaptic norepinephrine with a resultant increment in lipolysis by beta-adrenergic agonism; (ii) a decrease in alpha 2-adrenoceptor stimulation of human fat cell alpha 2-adrenoceptors; (iii) a blockade of presynaptic alpha 2-adrenoceptors. The use of highly selective alpha 2-antagonists will allow investigations into alpha 2-adrenoceptors, which may represent a novel locus for pharmacological intervention in lipid-mobilization strategies.(ABSTRACT TRUNCATED AT 250 WORDS)

The dielectric constant approach to speciation and ion pairing at high temperature and pressure

Abstract: Fluids in the Earth's crust commonly contain, in addition to the solvent, H2O, high concentrations of other volatiles (such as CO2, CH4 or N2) and/or salts (such as NaCl, KC1 or CaCl2). The solubility of minerals in these fluids is of prime importance for understanding metasomatic processes. Many theoretical and empirical relations have been proposed to account for various aspects of solubility behaviour and speciation. Here we show that quartz solubility behaviour in solutions where the activity of H2O is reduced from unity is easily modelled from knowledge of changes in the dielectric constant of the solvent. The approach may be generalized to all neutral aqueous species. We further demonstrate the usefulness of considering a modified form of the Fuoss equation1 for the calculation of the dielectric-constant dependence of ion pairing at high temperatures and pressures. This approach thus allows the prediction of speciation in complex fluids at high temperature and pressure for reduced activities of H2O.

Control of brood male production in the Argentine antIridomyrmex humilis (Mayr)

Abstract: The influence of various social factors on the production of males was investigated in the Argentine ant,Iridomyrmex humilis.

Corrosion inhibition study of a carbon steel in acidic media containing hydrogen sulphide and organic surfactants

Abstract: Inhibition of the corrosion of a carbon steel (0.4% C) by 2-hexadecyl imidazoline and 2-hexadecyl imidazole has been evaluated by electrochemical techniques and correlated with surface tension measurements. Plots of inhibitor efficiency versus surfactant concentration produce S-shaped curves which are assumed to represent adsorption isotherms. A sharp increase in slope was observed at concentrations below the critical micellar concentration. This increase in slope is accounted for by changes in conformation of the adsorbed molecules: horizontal orientations (with respect to the surface) at lower concentrations reflecting cathodic behaviour and perpendicular orientations at the higher concentrations reflecting mixed cathodic and anodic behaviour. At increasing concentrations the inhibitory effect remained constant, suggesting complete saturation of the surface in a bilayered arrangement. Electrochemical impedance measurements, carried out for concentrations greater than the critical micellar concentration, corroborate this assumption: the inhibitors form a thick but adherent micellar film which acts as a diffusion barrier.

Incomplete conjunctive information

Abstract: Many information systems capable of handling incomplete or fuzzy information manipulate objects with single-valued attributes. Information is then said to be disjunctive. Information is said to be conjunctive when pertaining to many-valued attributes. While a piece of incomplete disjunctive information is easily represented by means of a set of mutually exclusive possible values, modeling incomplete conjunctive information theoretically leads to consider families of sets, since attributes are then set-valued under complete information. Some proposals are made in order to efficiently and rigorously represent incomplete conjunctive information, and deal with query evaluation, especially in the case where only upper and/or lower bounds of the set of values of a many-valued attribute are known. Applications of this approach can be expected for the processing of time intervals, as well as spatial reasoning, among other topics, in knowledge base management.