Showing papers by "Paul Sabatier University published in 1999"
TL;DR: This paper focuses on semantic approaches to approximate reasoning based on fuzzy sets, commonly exemplified by the generalized modus ponens, but also considers applications to current topics in Artificial Intelligence such as default reasoning and qualitative process modeling.
804 citations
TL;DR: Some of the most important papers of the first workshop about ANNs in ecological modelling are presented, including two algorithms frequently used; one supervised network, the backpropagation algorithm; and one unsupervisednetwork, the Kohonen self-organizing mapping algorithm.
782 citations
TL;DR: The approximation problem, issued from a discretization of a second order elliptic equation in 2D, is nonetheless well posed and provides a discrete solution that satisfies optimal error estimates with respect to natural norms.
Abstract: The present paper deals with a variant of a non conforming domain decomposition technique: the mortar finite element method. In the opposition to the original method this variant is never conforming because of the relaxation of the matching constraints at the vertices (and the edges in 3D) of subdomains. It is shown that, written under primal hybrid formulation, the approximation problem, issued from a discretization of a second order elliptic equation in 2D, is nonetheless well posed and provides a discrete solution that satisfies optimal error estimates with respect to natural norms. Finally the parallelization advantages consequence of this variant are also addressed.
705 citations
TL;DR: The history of Stigmergy is described in the context of social insects and the general properties of two distinct stigmergic mechanisms are discussed: quantitative stIGmergy and qualitative stigMERgy.
Abstract: Stigmergy is a class of mechanisms that mediate animal-animal interactions. Its introduction in 1959 by Pierre-Paul Grasse made it possible to explain what had been until then considered paradoxical observations: In an insect society individuals work as if they were alone while their collective activities appear to be coordinated. In this article we describe the history of stigmergy in the context of social insects and discuss the general properties of two distinct stigmergic mechanisms: quantitative stigmergy and qualitative stigmergy.
618 citations
TL;DR: In this article, an estimator of regression by means of a functional principal component analysis analogous to the one introduced by Bosq in the case of Hilbertian AR processes was proposed and both convergence in probability and almost sure convergence of this estimator are stated.
539 citations
TL;DR: Labeling patterns observed in lipids and carbohydrates after substrates were supplied to the mycorrhizal roots or the extraradical mycelium indicated that 13C-labeled glucose and fructose are effectively taken up by the fungus within the root and are metabolized to yield labeled carbohydrates and lipids.
Abstract: Both the plant and the fungus benefit nutritionally in the arbuscular mycorrhizal symbiosis: The host plant enjoys enhanced mineral uptake and the fungus receives fixed carbon. In this exchange the uptake, metabolism, and translocation of carbon by the fungal partner are poorly understood. We therefore analyzed the fate of isotopically labeled substrates in an arbuscular mycorrhiza (in vitro cultures of Ri T-DNA-transformed carrot [Daucus carota] roots colonized by Glomus intraradices) using nuclear magnetic resonance spectroscopy. Labeling patterns observed in lipids and carbohydrates after substrates were supplied to the mycorrhizal roots or the extraradical mycelium indicated that: (a) 13C-labeled glucose and fructose (but not mannitol or succinate) are effectively taken up by the fungus within the root and are metabolized to yield labeled carbohydrates and lipids; (b) the extraradical mycelium does not use exogenous sugars for catabolism, storage, or transfer to the host; (c) the fungus converts sugars taken up in the root compartment into lipids that are then translocated to the extraradical mycelium (there being little or no lipid synthesis in the external mycelium); and (d) hexose in fungal tissue undergoes substantially higher fluxes through an oxidative pentose phosphate pathway than does hexose in the host plant.
361 citations
TL;DR: Data on modelling of DNA damage induced by electrons, protons and alpha-particles to provide an insight into factors which determine the biological effectiveness of radiations of high and low linear energy transfer (LET) are presented.
Abstract: This paper presents data on modelling of DNA damage induced by electrons, protons and alpha-particles to provide an insight into factors which determine the biological effectiveness of radiations of high and low linear energy transfer (LET). These data include the yield of single- and double-strand breaks (ssb, dsb) and base damage in a cellular environment. We obtain a ratio of 4–15 for ssb:dsb for solid and cellular DNA and a preliminary ratio of about 2 for base damage to strand breakage. Data are also given on specific characteristics of damage at the DNA level in the form of clustered damage of varying complexity, that challenge the repair processes and if not processed adequately could lead to the observed biological effects. It is shown that nearly 30% of dsb are of complex form for low-LET radiation, solely by virtue of additional breaks, rising to about 70% for high-LET radiation. Inclusion of base damage increases the complex proportion to about 60% and 90% for low- and high-LET radiation, respectively. The data show a twofold increase in frequencies of complex dsb from low-LET radiation when base damage is taken into account. It is shown that most ssb induced by high-LET radiation have associated base damages, and also a substantial proportion is induced by low-energy electrons.
312 citations
TL;DR: Data demonstrate that: (i) antigen 85C is involved directly or indirectly in the transfer of mycolates onto the cell wall of the whole bacterium; (ii) the enzyme is not specific for a given type of my colate; and (iii) the cellwall‐linked mycolate layer may represent a barrier for the diffusion of small hydrophobic and hydrophilic molecules.
Abstract: The antigen 85 complex of Mycobacterium tuberculosis consists of three abundantly secreted proteins. The recent characterization of a mycoloyltransferase activity associated in vitro with each of these antigens suggested that they are potentially important for the building of the unusual cell envelope of mycobacteria. To define the physiological role of these proteins, the gene coding for antigen 85C was inactivated by transposon mutagenesis. The resulting mutant was shown to transfer 40% fewer mycolates to the cell wall with no change in the types of mycolates esterifying arabinogalactan or in the composition of non-covalently linked mycolates. As a consequence, the diffusion of the hydrophobic chenodeoxycholate and the hydrophilic glycerol, but not that of isoniazid, was found to be much faster through the cell envelope of the mutant than that of the parent strain. Taken together, these data demonstrate that: (i) antigen 85C is involved directly or indirectly in the transfer of mycolates onto the cell wall of the whole bacterium; (ii) the enzyme is not specific for a given type of mycolate; and (iii) the cell wall-linked mycolate layer may represent a barrier for the diffusion of small hydrophobic and hydrophilic molecules.
254 citations
TL;DR: In this paper, a H2-CH4 mixture over oxide spinels containing two transition elements as in Mg0.8MyM'zAl2O4 (M, M' = Fe, Co or Ni, y + z = 0.2) at 1070°C produces small alloy nanoparticles which enable the formation of carbon nanotubes.
249 citations
TL;DR: This study suggests that the underlying neural basis associated with processing faces matures in a gradual, quantitative manner throughout childhood.
220 citations
TL;DR: The geochemical implications of thermally driven flow of seawater through oceanic crust on the mid-ocean ridge flank have been examined on a well-studied 80 km transect across the eastern flank of the Juan de Fuca Ridge at 48-N, using porewater and basement fluid samples obtained on ODP Leg 168.
TL;DR: It is shown that, for half the cells recorded in area V1 of behaving monkeys, the classically described visual responses are strongly modulated by gaze direction, and neural changes were most often present at the beginning of the visual response, suggesting a feedforward gain control by eye position signals.
Abstract: To localize objects in space, the brain needs to combine information about the position of the stimulus on the retinae with information about the location of the eyes in their orbits. Interaction between these two types of information occurs in several cortical areas, but the role of the primary visual cortex (area V1) in this process has remained unclear. Here we show that, for half the cells recorded in area V1 of behaving monkeys, the classically described visual responses are strongly modulated by gaze direction. Specifically, we find that selectivity for horizontal retinal disparity-the difference in the position of a stimulus on each retina which relates to relative object distance-and for stimulus orientation may be present at a given gaze direction, but be absent or poorly expressed at another direction. Shifts in preferred disparity also occurred in several neurons. These neural changes were most often present at the beginning of the visual response, suggesting a feedforward gain control by eye position signals. Cortical neural processes for encoding information about the three-dimensional position of a stimulus in space therefore start as early as area V1.
TL;DR: In this article, the results of ultrafiltration experiments (0.20 μm-300,000 Da-5000 Da-1000 Da) performed on natural rich-organic waters (30-40 mg l−1 of dissolved organic carbon) sampled in wetland area of Cameroon (Nsimi-Zoetele site).
TL;DR: In this paper, the authors used a new thermodynamic model to compute the barite saturation index of ocean waters, mainly from GEOSECS data, and showed that equilibrium between barite and seawater is reached in a number of places: cold surface waters of the Southern Ocean, waters at intermediate depths (2000-3500 m) in the Pacific, deep waters (2000 -3500m) of the Gulf of Bengal.
01 Jun 1999
TL;DR: In the present work, agents are very similar to those proposed by Schoonderwoerd et al.
Abstract: A simple mechanism is presented, based on ant-like agents, for routing and load balancing in telecommunications networks, following the initial works of Appleby and Stewart [1] and Schoonderwoerd et al. [32,33]. In the present work, agents are very similar to those proposed by Schoonderwoerd et al. [32,33], but are supplemented with the ability to perform more computations at switching nodes, which significantly improves the network's relaxation and its response to perturbations.
TL;DR: It is shown by experiments under natural conditions that the level of background noise increases in windy conditions and thus leads to a diminution of the signal–to-noise ratio, and for the first time, to the authors' knowledge, a bird species takes into account the constraints imposed by wind on their acoustic communication.
Abstract: In the king penguin ( Aptenodytes patagonicus ), both pair members alternate in incubating and rearing their chick. Mates can recognize each other among thousands of other birds in the hubbub of the colony using only acoustic signalling: the display call. Large penguin colonies are found on sub–Antarctic islands where strong winds blow throughout the year. We have shown by experiments under natural conditions that the level of background noise increases in windy conditions and thus leads to a diminution of the signal–to–noise ratio. Moreover the emergence level of the signal revealed by entropy calculation is statistically weaker in windy conditions. To achieve breeding success, birds must continue communicating in spite of the significant decrease in the total amount of information that can be transmitted in windy situations. For the first time, to our knowledge, we have shown that a bird species takes into account the constraints imposed by wind on their acoustic communication. In windy conditions, birds try to maintain the efficiency of communication by increasing both the number of calls emitted and the number of syllables per call. This result conforms with predictions from the mathematical theory of communication: increased redundancy in a signal improves the probability of receiving a message in a noisy channel.
TL;DR: The FHA coatings showed good integration in the bone tissue and lasted much longer than classic calcium phosphate coatings, which almost totally degraded within the implantation period.
Abstract: Calcium phosphate coatings on dental implants enhance integration of the material. Resorption of the ceramic coatings has raised some concern about the behavior of the bone-implant interfaces after the coating disappearance. Substitution of the OH- ions by fluoride in the hydroxylapatite (HA) lattice makes the calcium phosphate more stable. We investigated the degradation rate of dental implants with 50- and 100-microm coatings of HA, fluorapatite (FA), or fluorhydroxylapatite (FHA). The implants were inserted in dog jaws and retrieved for histological analysis after 3, 6, and 12 months. The thickness of the calcium phosphate coatings was evaluated using an image analysis device. A relative resorption index and its standard deviation were studied. HA and FA coatings (even at 100-microm thickness) were almost totally degraded within the implantation period. In contrast, the FHA coatings did not show significant degradation during the same period. The standard deviation showed that the resorption process for FHA with thicknesses of 50 or 100 microm was the same. Such a difference was not observed between the 50- and 100-microm thick coatings of FA and HA. In conclusion, the FHA coatings showed good integration in the bone tissue and lasted much longer than classic calcium phosphate coatings.
TL;DR: In this paper, a model for barite and celestite solubilities in the Na-K-Ca-Mg-Ba-Sr-Cl-SO4-H2O system to 200°C and to 1 kbar is presented.
TL;DR: In this paper, the authors analyzed observations made in the solar wind near the Lagrange point L1 and observed three kinds of electrostatic (e.g., coherent wave packets of Langmuir waves with frequencies f ~ fpe, coherent wave packet with frequencies in the ion acoustic range fpi f ~ 25λD, there is a small but finite electric potential drop, implying an average electric field generally directed away from the Sun.
Abstract: . The time domain sampler (TDS) experiment on WIND measures electric and magnetic wave forms with a sampling rate which reaches 120 000 points per second. We analyse here observations made in the solar wind near the Lagrange point L1. In the range of frequencies above the proton plasma frequency fpi and smaller than or of the order of the electron plasma frequency fpe, TDS observed three kinds of electrostatic (e.s.) waves: coherent wave packets of Langmuir waves with frequencies f ~ fpe, coherent wave packets with frequencies in the ion acoustic range fpi f ~ 25λD, there is a small but finite electric potential drop, implying an average electric field generally directed away from the Sun. The IES wave forms, which have not been previously reported in the solar wind, are similar, although with a smaller amplitude, to the weak double layers observed in the auroral regions, and to the electrostatic solitary waves observed in other regions in the magnetosphere. We have also studied the solar wind conditions which favour the occurrence of the three kinds of waves: all these e.s. waves are observed more or less continuously in the whole solar wind (except in the densest regions where a parasite prevents the TDS observations). The type (wave packet or IES) of the observed LF waves is mainly determined by the proton temperature and by the direction of the magnetic field, which themselves depend on the latitude of WIND with respect to the heliospheric current sheet. Key words. Interplanetary physics (plasma waves and turbulence; solar wind plasma). Space plasma physics (electrostatic structures).
TL;DR: It is reported here that incubation of SMC with oxLDL increased the activities of both acidic and alkaline ceramidases as well as sphingosine kinase, and elevated cellular sphingoine and S1P, suggesting that S1p is a key mediator of the mitogenic effect of oxLDl.
TL;DR: After disruption of the RNT1 gene, the yeast ortholog of bacterial RNase III, production of the seven mature snoRNAs was abolished, while the polycistronic snoRNA precursor accumulated, in cells lacking functional Rat1p, an exonuclease involved in the processing of both pre-rRNA and intron-encoded sno RNAs accumulated.
Abstract: Through a computer search of the genome of the yeast Saccharomyces cerevisiae, the coding sequences of seven different box C/D antisense small nucleolar RNAs (snoRNAs) with the structural hallmarks of guides for rRNA ribose methylation have been detected clustered over a 1.4-kb tract in an inter-open reading frame region of chromosome XIII. The corresponding snoRNAs have been positively identified in yeast cells. Disruption of the nonessential snoRNA gene cluster specifically suppressed the seven cognate rRNA ribose methylations but did not result in any growth delay under the conditions of yeast culture tested. The seven snoRNAs are processed from a common polycistronic transcript synthesized from an independent promoter, similar to some plant snoRNAs but in marked contrast with their vertebrate functional homologues processed from pre-mRNA introns containing a single snoRNA. Processing of the polycistronic precursor requires nucleases also involved in rRNA processing, i.e., Rnt1p and Rat1p. After disruption of the RNT1 gene, the yeast ortholog of bacterial RNase III, production of the seven mature snoRNAs was abolished, while the polycistronic snoRNA precursor accumulated. In cells lacking functional Rat1p, an exonuclease involved in the processing of both pre-rRNA and intron-encoded snoRNAs, several processing intermediates of the polycistronic precursor accumulated. This allowed for the mapping in the precursor of the presumptive Rnt1p endonucleolytic cuts which provide entry sites for subsequent exonucleolytic trimming of the pre-snoRNAs. In line with known properties of double-stranded RNA-specific RNase III, pairs of Rnt1p cuts map next to each other on opposite strands of long double-helical stems in the secondary structure predicted for the polycistronic snoRNA precursor.
TL;DR: This paper examines ten concrete propositional update operations of the literature, completely characterizing their relative strength and their computational complexity, and concludes that only two of the update operations are satisfactory.
TL;DR: Carbon isotope distribution of citrinin from Damascus ruber incubated with [13C]acetate revealed that the biosynthesis of the toxin originated from a tetraketide, instead of a pentaketide as has been shown for Penicillium and Aspergillus species.
Abstract: Carbon isotope distribution of [13C]citrinin from Monascus ruber incubated with [13C]acetate revealed that the biosynthesis of the toxin originated from a tetraketide, instead of a pentaketide as has been shown for Penicillium and Aspergillus species. The production of polyketide red pigments and citrinin by M. ruber may therefore be regulated at the level of the tetraketide branch point.
TL;DR: As shown here, Megazol interferes with the oxygen metabolism of the parasite, but its extra activity when compared to Nifurtimox may be related to other features not yet identified.
TL;DR: In this paper, stable-state dissolution rates of Magnesite (MgCO3) were measured at 25°C as a function of pH (from 0.2 to 12), total dissolved carbonate concentration (10−5 8 and ΣCO2 > 10−3 M. The surface complexation model developed by Pokrovsky et al. was used to correlate magnesite dissolution kinetics with its surface speciation.
TL;DR: This paper surveys refinements of the ordering of solutions supplied by the max–min formulation, namely the discrimin partial ordering and the leximin complete preordering and gives a general algorithm which computes all maximal solutions in the sense of these relations.
TL;DR: Two tetrahydroquinoline alkaloids have been isolated from the bark of Galipea officinalis Hancock by spectroscopic methods and are named angustureine and galipeine.
TL;DR: In this paper, chemical analysis performed on water samples collected monthly from different localities between 1994-1997 and on soil samples taken during a well drilling in December 1997 showed that a significant amount of Al does not leave the system due to kaolinite recrystallisation in the swamp zone soils.
TL;DR: In this article, the authors studied optimal control problems governed by semilinear parabolic equations and obtained necessary optimality conditions in the form of an exact Pontryagin's minimum principle for distributed and boundary controls (which can be unbounded) and bounded initial controls.
Abstract: In this paper we study optimal control problems governed by semilinear parabolic equations. We obtain necessary optimality conditions in the form of an exact Pontryagin's minimum principle for distributed and boundary controls (which can be unbounded) and bounded initial controls. These optimality conditions are obtained thanks to new regularity results for linear and nonlinear parabolic equations.
TL;DR: CPT-11 is a prodrug activated by carboxylesterases to the active metabolite SN-38 which is a potent inhibitor of topoisomerase I which is of clinical interest in the treatment of colorectal cancer.
Abstract: CPT-11 is a prodrug activated by carboxylesterases to the active metabolite SN-38 which is a potent inhibitor of topoisomerase I. CPT-11 is of clinical interest in the treatment of colorectal cancer. We evaluated the activities of CPT-11 converting carboxylesterase (CPT-CE) and topoisomerase I (topo I) in 53 colorectal tumours, in eight liver metastases and in normal tissue adjacent to the tumours. Both CPT-CE and topo I activities were widely variable in the malignant and the normal tissue of patients with colorectal carcinomas. CPT-CE was only two to threefold lower in primary tumours compared to normal liver, suggesting that a local conversion to SN-38 might occur in tumour cells. CPT-CE was similar in liver and in normal colon tissues. Levels of topo I in tumour ranged from 580 to 84 900 U mg protein−1 and was above 40 000 U mg protein−1 in 11 of 53 patients. Similarly, a very high ratio (> 5) between tumour and normal tissues were observed in 12 of 53 patients. An inverse correlation was observed between the topo I activity and the clinical stage of disease. Clinical studies are in progress in our institution to explore a possible relationship between CPT-CE and topo I activities in tumour cells and the response to CPT-11-based chemotherapy in patients with colorectal cancer. © 1999 Cancer Research Campaign