Showing papers by "University of Mons published in 2004"

Enumeration, measurement, and identification of net zooplankton samples using the ZOOSCAN digital imaging system

Abstract: Grosjean, P., Picheral, M., Warembourg, C., and Gorsky, G. 2004. Enumeration,measurement, and identification of net zooplankton samples using the ZOOSCAN digitalimaging system. e ICES Journal of Marine Science, 61: 518e525.Identifying and counting zooplankton are labour-intensive and time-consuming processesthat are still performed manually. However, a new system, known as ZOOSCAN, has beendesigned for counting zooplankton net samples. We describe image-processing and theresults of (semi)-automatic identification of taxa with various machine-learning methods.Each scan contains between 1500 and 2000 individuals !0.5 mm. We used two trainingsets of about 1000 objects each divided into 8 (simplified) and 29 groups (detailed),respectively. The new discriminant vector forest algorithm, which is one of the mostefficient methods, discriminates between the organisms in the detailed training set with anaccuracy of 75% at a speed of 2000 items per second. A supplementary algorithm tagsobjects that the method classified with low accuracy (suspect items), such that they could bechecked by taxonomists. This complementary and interactive semi-automatic processcombines both computer speed and the ability to detect variations in proportions and greylevels with the human skills to discriminate animals on the basis of small details, such aspresence/absence or number of appendages. After this checking process, total accuracyincreases to between 80% and 85%. We discuss the potential of the system as a standard foridentification, enumeration, and size frequency distribution of net-collected zooplankton.

Parkinson's disease home diary: further validation and implications for clinical trials.

Abstract: We provide further validation of a Parkinson's disease (PD) home diary and explore implications for practical use in clinical trials. We previously developed and published a home PD diary that includes the categories ASLEEP, off, on without dyskinesia, on with nontroublesome dyskinesia, and on with troublesome dyskinesia [Hauser et al., J Clin Neuropharmacol 2000;23:75-81] and demonstrated that patients generally consider off time and on time with troublesome dyskinesia "bad time" and on time without dyskinesia or with nontroublesome dyskinesia "good time". We suggested that that on time without dyskinesia or with nontroublesome dyskinesia would be an appropriate outcome measure in clinical trials of advanced PD patients. In the current study, PD patients with motor fluctuations and dyskinesia (present more than 25% of the awake day and at least moderately disabling) completed daily diaries on 3 consecutive days in each of 2 consecutive weeks. In addition, patients provided responses to five questions regarding dyskinesia and their motor response through the day on visual analog scales (VAS). Three hundred two patients from 10 countries participated. Eighty-three percent (n = 252) completed six diaries without missing or duplicate entries. Seventy-six percent of the missing or duplicate entries occurred after Day 3. Mean percent of the awake day on without dyskinesia or with nontroublesome dyskinesia ("good on", ONG%) was observed to be very stable over time (repeated measure analysis of variance, P = 0.99). Coefficients of reliability as calculated by Cronbach's alpha were as follows: 2 days, r = 0.806; 3 days, r = 0.868; 4 days, r = 0.918; 5 days, r = 0.934; 6 days, r = 0.946. The standard error of measurement (SEM) was calculated to be 10.75%. VAS responses to the question, "How much of the day today did you experience a good response?" more strongly correlated with ONG% (0.41) than ON% (0.24). The diary appears to be sufficiently simple and feasible. Test-retest reliability was good, and reliability increased with increasing number of diary days but compliance diminished beyond 3 days. Good on time (ONG = on time without dyskinesia or with nontroublesome dyskinesia) most strongly correlated with patients' perceived duration of a good response through the day and is an important outcome variable.

1,3,6,8-tetraphenylpyrene derivatives: Towards fluorescent liquid-crystalline columns?

Abstract: Tetraphenylpyrene has been selected as a discotic core to promote liquid-crystalline fluorescent columns in view of its high fluorescence quantum yield in solution and ease of substitution by flexible lateral side chains. The synthesis and characterization of ten new derivatives of pyrene have been carried out; the pyrene core has been substituted at the 1,3,6,8-positions by phenylene rings bearing alkoxy, ester, thioether, or tris(alkoxy)benzoate groups on the para position; the compounds have been characterized by mass spectrometry and H-1 NMR and UV-vis spectroscopies. In order to generate liquid-crystalline phases, the nature, number. and size of the side chains as well as the degree of polarity around the tetraphenylpyrene core have been varied. However, the desired liquid-crystal line behavior has not been observed. The supramolecular order together with the absorption and emission properties in solution and the solid state are discussed and compared to theoretical predictions. Quantum-chemical calculations rationalize the high solid-state fluorescence of a tetraphenylpyrene derivative for which the crystal structure has been determined.

Characterization of the molecular parameters determining charge transport in anthradithiophene

Abstract: The molecular parameters that govern charge transport in anthradithiophene (ADT) are studied by a joint experimental/theoretical approach involving high-resolution gas-phase photoelectron spectroscopy and quantum-mechanical methods. The hole reorganization energy of ADT has been determined by an analysis of the vibrational structure of the lowest ionization band in the gas-phase photoelectron spectrum as well as by density-functional theory calculations. In addition, various dimers and clusters of ADT molecules have been considered in order to understand the effect of molecular packing on the hole and electron intermolecular transfer integrals. The results indicate that the intrinsic electronic structure, the relevant intramolecular vibrational modes, and the intermolecular interactions in ADT are very similar to those in pentacene.

Study of tau-pair production in photon-photon collisions at LEP and limits on the anomalous electromagnetic moments of the tau lepton

Abstract: Tau-pair production in the process e(+)e(-) --> e(+)e(-) tau(+)tau(-) was studied using data collected by the DELPHI experiment at LEP2 during the years 1997 - 2000. The corresponding integrated luminosity is 650 pb(-1). The values of the cross-section obtained are found to be in agreement with QED predictions. Limits on the anomalous magnetic and electric dipole moments of the tau lepton are deduced.

On O-Minimal Hybrid Systems

Abstract: This paper is driven by a general motto: bisimulate a hybrid system by a finite symbolic dynamical system. In the case of o-minimal hybrid systems, the continuous and discrete components can be decoupled, and hence, the problem reduces in building a finite symbolic dynamical system for the continuous dynamics of each location. We show that this can be done for a quite general class of hybrid systems defined on o-minimal structures. In particular, we recover the main result of a paper by Lafferriere G., Pappas G.J. and Sastry S. on o-minimal hybrid systems.

STAR: an algorithm to Search for Tandem Approximate Repeats

Abstract: Motivation: Tandem repeats consist in approximate and adjacent repetitions of a DNA motif. Such repeats account for large portions of eukaryotic genomes and have also been found in other life kingdoms. Owing to their polymorphism, tandem repeats have proven useful in genome cartography, forensic and population studies, etc. Nevertheless, they are not systematically detected nor annotated in genome projects. Partially because of this lack of data, their evolution is still poorly understood. Results: In this work, we design an exact algorithm to locate approximate tandem repeats (ATR) of a motif in a DNA sequence. Given a motif and a DNA sequence, our method named STAR, identifies all segments of the sequence that correspond to significant approximate tandem repetitions of the motif. In our model, an Exact Tandem Repeat (ETR) comes from the tandem duplication of the motif and an ATR derives from an ETR by a series of point mutations. An ATR can then be encoded as a number of duplications of the motif together with a list of mutations. Consequently, any sequence that is not an ATR cannot be encoded efficiently by this description, while a true ATR can. Our method uses the minimum description length criterion to identify which sequence segments are ATR. Our optimization procedure guarantees that STAR finds a combination of ATR that minimizes this criterion. Availability: for use at http://atgc.lirmm.fr/star Supplementary information: an appendix is available at http://atgc.lirmm.fr/star under 'Paper and contacts'.

Searches for Neutral Higgs Bosons in Extended Models

Abstract: Searches for neutral Higgs bosons produced at LEP in association with Z bosons, in pairs and in the Yukawa process are presented in this paper. Higgs boson decays into b quarks, tau leptons, or other Higgs bosons are considered, giving rise to four-b, four-b+jets, six-b and four-tau final states, as well as mixed modes with b quarks and tau leptons. The whole mass domain kinematically accessible at LEP in these topologies is searched. The analysed data set covers both the LEP1 and LEP2 energy ranges and exploits most of the luminosity recorded by the DELPHI experiment. No convincing evidence for a signal is found, and results are presented in the form of mass-dependent upper bounds on coupling factors (in units of model-independent reference cross-sections) for all processes, allowing interpretation of the data in a large class of models.

Spin asymmetries for events with high p(T) hadrons in DIS and an evaluation of the gluon polarization

Abstract: We present a measurement of the longitudinal spin cross section asymmetry for deep-inelastic muon-nucleon interactions with two high transverse momentum hadrons in the final state. Two methods of event classification are used to increase the contribution of the photon-gluon fusion process to above 30%. The most effective one, based on a neural network approach, provides the asymmetries A(p)lN(-->)lhhX=0.030+/-0.057(stat)+/-0.010(syst) and A(d)lN(-->)lhhX=0.070+/-0.076(stat)+/-0.010(syst). From these values we derive an averaged gluon polarization DeltaG/G=-0.20+/-0.28(stat)+/-0.10(syst) at an average fraction of nucleon momentum carried by gluons =0.07.

Modeling mid-aged women's sexual functioning: a prospective, population-based study.

Abstract: This article uses a prospectively, annually collected sexuality questionnaire from an 8-year study of 340 mid-aged Melbourne women. We modeled the interactions of sexuality domains, the effect of prior level of sexual functioning, and the effects of change in partner-related factors. We found that we were unable to separate items denoting sexual interest from those denoting responsiveness. Using the statistical technique of auto-correlation, we determined that the most important predictor of female sexual functioning is prior level of sexual functioning. Partner-related factors (change in partner status and feelings for partner) also had significant effects.

Search for extraterrestrial point sources of neutrinos with AMANDA-II.

Abstract: The results of a search for point sources of high energy neutrinos in the northern hemisphere were presented using AMANDA-II data collected in the year 2000. The results included the flux limits on several active-galactic-nuclei blazars, microquasars, magnetars, and other candidate neutrino sources. A search for excesses above a random background of cosmic ray induced atmospheric neutrinos and misreconstructed downgoing cosmic-rays muons, which revealed no statistically significant neutrino point sources was also presented. It was shown that AMANDA-II had achieved the sensitivity required to probe known TeV γ-ray sources such as the blazar Markarian 501 in its 1997 flaring state at a level where neutrino and γ-ray fluxes were equal.

Multichromophoric dendrimers as single-photon sources: A single-molecule study

Abstract: Single-molecule fluorescence spectroscopy was performed on a number of multi-peryleneimide substituted polyphenylene dendrimers for the purpose of investigating the parameters which influence the efficiency of the dendrimers as single-photon sources at room temperature. Analysis of fluorescence intensity, lifetime, and interphoton arrival time distribution revealed that all measured first-generation dendrimers behave as single-photon emitters when more than one chromophore is excited by a single excitation pulse regardless of the number of constituent chromophores. This is a result of efficient singlet-singlet annihilation, which becomes less efficient in higher-generation dendrimers when the interchromophoric distance increases. The efficiency of the investigated dendrimers as single-photon sources depends on several other parameters, such as the nature of the surrounding polymer matrix, the number of chromophores, and the extent of interchromophoric interactions. These parameters mainly affect the frequency of singlet-triplet annihilation, which in turn dominates the quality of these multichromophoric dendrimers as single-photon sources. The results reported here are important not only for the design of single-photon sources based on single organic molecules but also for a fundamental understanding of natural and artificial multichromophoric systems.

Microscopic morphology of polyfluorene-poly(ethylene oxide) block copolymers: Influence of the block ratio

Abstract: In this paper, we describe the synthesis and characterization of poly(9,9′-dioctylfluorene)–poly(ethylene oxide) (PF-PEO) block copolymers with different block ratio and molecular architectures (diblock or triblock copolymers). Tapping-mode atomic force microscopy is used to investigate the relationship between the molecular structure and the microscopic morphology of thin deposits. Copolymers with a low average volume ratio of PEO (fEO from 0.1 to 0.3) exhibit a well-defined organization into nanoribbons. A model of chain packing is proposed; these structures arise from the interplay of π–π interactions between conjugated PF segments and the interactions of PEO with the mica substrate surface. For copolymers with higher average volume ratio of PEO (fEO > 0.4), the organized structures disappear and lead to untextured aggregates, probably because long-range, regular π–π stacking of the segments can no longer take place. We also observe that the nature of the solvent from which deposits are grown and the substrate polarity have a strong impact on the microscopic morphology.

K-shell Photoabsorption of Oxygen Ions

Abstract: Extensive calculations of the atomic data required for the spectral modelling of the K-shell photoabsorption of oxygen ions have been carried out in a multi-code approach. The present level energies and wavelengths for the highly ionized species (electron occupancies 2 4, lack of measurements, wide experimental scatter, and discrepancies among theoretical values are handicaps in reliable accuracy assessments. The radiative and Auger rates are expected to be accurate to 10% and 20%, respectively, except for transitions involving strongly mixed levels. Radiative and Auger dampings have been taken into account in the calculation of photoabsorption cross sections in the K-threshold region, leading to overlapping lorentzian shaped resonances of constant widths that cause edge smearing. The behavior of the improved opacities in this region has been studied with the XSTAR modelling code using simple constant density slab models, and is displayed for a range of ionization parameters.

Two-photon absorption in quadrupolar π-conjugated molecules: Influence of the nature of the conjugated bridge and the donor-acceptor separation

Abstract: Quadrupolar-type substitution of pi-conjugated chromophores with donor and acceptor groups has been shown to increase their two-photon absorption (TPA) response by up to two orders of magnitude. Here, we apply highly correlated quantum-chemical calculations to evaluate the impact of the nature of conjugated bridge and the charge-transfer distance on that enhancement. We compare chromophores with phenylenevinylene-, thienylenevinylene-, polyene-, and indenofluorene-type backbones substituted by dimethylamino and cyano groups. In all compounds, we find a strongly TPA-active A(g) state (either 2A(g) or 3A(g)) in the low-energy region, as well as a higher lying TPA-active state (mA(g)) at close to twice the energy of the lowest lying one-photon allowed state; the smaller energy detuning in the mA(g) states results in very large TPA cross sections delta. We also investigate the influence of the degree of ground-state polarization on TPA. Independent of the nature of the backbone and the donor-acceptor separation, delta displays the same qualitative evolution with a maximum before the cyanine-like limit; the highest TPA cross sections are calculated for distirylbenzene- and polyene-based systems.

Controlled polymer grafting on single clay nanoplatelets.

Abstract: We report on the controlled chemical grafting of well-defined polymer chains onto individual montmorillonite-type clay nanoplatelets and the direct visualization of the formed hybrid material at the nanoscale level. Our approach is based on the use of a surfactant mixture that contains varying proportions of hydroxyl-substituted alkylammonium and unsubstituted alkylammonium cations to exchange the initial Na+ counterions of the natural montmorillonite. This allows for the exchange of Na+ by a tunable amount of hydroxyl functions at the surface of the clays. Those functions are then derivatized into aluminum alkoxides in order to initiate the ring-opening polymerization of e-caprolactone directly from the clay surface that was swollen in an organic solvent. Atomic force microscopy measurements on the resulting polymer-grafted nanoplatelets demonstrate the strong dependence of the coating of the individual clay particles with the composition of the surfactant mixture used for the cationic exchange. This all...

Model-checking for weighted timed automata

Abstract: We study the model-checking problem for weighted timed automata and the weighted CTL logic by the bisimulation approach. Weighted timed automata are timed automata extended with costs on both edges and locations. When the costs act as stopwatches, we get stopwatch automata with the restriction that the stopwatches cannot be reset nor tested. The weighted CTL logic is an extension of TCTL that allow to reset and test the cost variables. Our main results are (i) the undecidability of the proposed model-checking problem for discrete and dense time, (ii) its PSpace-Completeness in the discrete case for a slight restriction of the logic, (iii) the precise frontier between finite and infinite bisimulations in the dense case for the subclass of stopwatch automata.

In vitro behavior of osteoblastic cells cultured in the presence of pseudowollastonite ceramic.

Abstract: Pseudowollastonite ceramic (psW) is a bioactive ceramic that binds to bone when implanted in vivo and may be useful for the treatment of skeletal defects. However, there have been no studies that examined the interaction between psW and osteoblastic cells in vitro. This study investigated the suitability of psW as a substratum for cell attachment and the ability of the material to effect osteoblasts at a distance from the material surface. Fetal rat calvarial cells were plated onto the ceramic and examined by scanning electron microscopy. The findings reported show that cells attached and proliferated on the surface to the ceramic. Attachment by cells to the material can be enhanced by preincubation of psW in serum or media containing fibronectin. The adhesion of cells can be inhibited by addition of GRGDS peptides suggesting that adhesion to psW is mediated by integrin binding to adsorbed proteins. To study the effects of psW at a distance, cells were cultured in the presence but not in direct contact with the material. Subsequent changes in proliferation, alkaline phosphatase expression, and bone nodule formation were assessed. Cells grown in wells containing psW demonstrated an increase in both the rate and total numbers of bone nodules formed, although there were no differences in proliferation or alkaline phosphatase expression. Overall, these results suggest that psW is biocompatible and osteoconductive.

Measurement of ionic and neutral densities in amplified magnetron discharges by pulsed absorption spectroscopy

Abstract: Resonant absorption diagnostic has been used to estimate densities of neutral and ionic titanium, both in ground and metastable states, in a rf coil amplified magnetron sputtering process. The conventional optical source dc supply has been replaced by a high voltage pulsed power supply to allow absorption experiments onto ionic and neutral species, in a broad range of discharge conditions (500 W are applied onto the magnetron cathode and 0–500 W on the rf coil, for a 30 mTorr argon pressure). The obtained densities are used to compare the magnetron and the amplified discharges. The total ionization degree of the metallic vapor is found to increase from ∼3% in the magnetron regime to ∼24% in the amplified magnetron discharge. The Ti (a5F) neutral metastable density is found to be partially enhanced when the rf coil is power supplied.

Surface-controlled self-assembly of chiral sexithiophenes

Abstract: We report on the self-assembly of two enantiomeric sexithiophenes in solution and on surfaces. Circular dichromism of aggregated sexithiophenes and drop-cast films reveals, as expected, mirror image spectra for both enantiomers. The aggregation in thin deposits from sexithiophenes molecularly dispersed in a solution on different types of substrates was investigated by atomic force microscopy (AFM). On graphite, one-dimensional objects (nanowires) are formed while on mica platelets are generated. Remarkably, we found that both enantiomers form left-handed helices on silicon. This observation depends on the hydrophilicity of the silicon. Furthermore, the achiral sexithiophene did not form helical aggregates suggesting that the stereocenter is required to obtain chirality in the fibers.

Key Role of Ser562/661 in Snf1-Dependent Regulation of Cat8p in Saccharomyces cerevisiae and Kluyveromyces lactis

Abstract: Utilization of nonfermentable carbon sources by Kluyveromyces lactis and Saccharomyces cerevisiae requires the Snf1p kinase and the Cat8p transcriptional activator, which binds to carbon source-responsive elements of target genes. We demonstrate that KlSnf1p and KlCat8p from K. lactis interact in a two-hybrid system and that the interaction is stronger with a kinase-dead mutant form of KlSnf1p. Of two putative phosphorylation sites in the KlCat8p sequence, serine 661 was identified as a key residue governing KlCat8p regulation. Serine 661 is located in the middle homology region, a regulatory domain conserved among zinc cluster transcription factors, and is part of an Snf1p consensus phosphorylation site. Single mutations at this site are sufficient to completely change the carbon source regulation of the KlCat8p transactivation activity observed. A serine-to-glutamate mutant form mimicking constitutive phosphorylation results in a nearly constitutively active form of KlCat8p, while a serine-to-alanine mutation has the reverse effect. Furthermore, it is shown that KlCat8p phosphorylation depends on KlSNF1. The Snf1-Cat8 connection is evolutionarily conserved: mutation of corresponding serine 562 of ScCat8p gave similar results in S. cerevisiae. The enhanced capacity of ScCat8S562E to suppress the phenotype caused by snf1 strengthens the hypothesis of direct phosphorylation of Cat8p by Snf1p. Unlike that of S. cerevisiae ScCAT8, KlCAT8 transcription is not carbon source regulated, illustrating the prominent role of posttranscriptional regulation of Cat8p in K. lactis.