Showing papers by "University of Mons published in 2003"

Origin of high second- and third-order nonlinear optical response in ammonio/borato diphenylpolyene zwitterions: the remarkable role of polarized aromatic groups.

Abstract: We present a quantum-chemical analysis of the molecular structure and second- and third-order polarizabilities in a series of promising nonlinear optical (NLO) chromophores, the zwitterionic ammonio/borato diphenylpolyenes, R3N+Ph(C═C)nPhB-R3, whose synthesis has been reported recently. The molecular geometries are obtained via MP2/6-31G optimization, while the NLO properties are calculated with the INDO Hamiltonian using the sum-over-states and finite-field real-space methods. The real-space approach allows the direct evaluation of the NLO-active segments of the molecules, while the sum-over-states results illustrate the virtual excitations and charge-transfer pathways that are essential in the NLO response. Both methods highlight the remarkable and unexpected result that it is the strongly polarized phenylene groups that play the key role in generating a high NLO response.

Ralstonia metallidurans, a bacterium specifically adapted to toxic metals: towards a catalogue of metal-responsive genes

Abstract: Ralstonia metallidurans, formerly known as Alcaligenes eutrophus and thereafter as Ralstonia eutropha, is a β-Proteobacterium colonizing industrial sediments, soils or wastes with a high content of heavy metals. The type strain CH34 carries two large plasmids (pMOL28 and pMOL30) bearing a variety of genes for metal resistance. A chronological overview describes the progress made in the knowledge of the plasmid-borne metal resistance mechanisms, the genetics of R. metallidurans CH34 and its taxonomy, and the applications of this strain in the fields of environmental remediation and microbial ecology. Recently, the sequence draft of the genome of R. metallidurans has become available. This allowed a comparison of these preliminary data with the published genome data of the plant pathogen Ralstonia solanacearum, which harbors a megaplasmid (of 2.1 Mb) carrying some metal resistance genes that are similar to those found in R. metallidurans CH34. In addition, a first inventory of metal resistance genes and operons across these two organisms could be made. This inventory, which partly relied on the use of proteomic approaches, revealed the presence of numerous loci not only on the large plasmids pMOL28 and pMOL30 but also on the chromosome. It suggests that metal-resistant Ralstonia, through evolution, are particularly well adapted to the harsh environments typically created by extreme anthropogenic situations or biotopes.

Effects of short-term treatment with metformin on serum concentrations of homocysteine, folate and vitamin B12 in type 2 diabetes mellitus: a randomized, placebo-controlled trial.

Abstract: . Wulffele MG, Kooy A, Lehert P, Bets D, Ogterop JC, Borger van der Burg B, Donker AJM, Stehouwer CDA (Bethesda General Hospital, Hoogeveen, The Netherlands; University of Mons, Mons, Belgium; Merck Nederland B.V., Amsterdam; Deaconesses’ Hospital, Meppel; Aleida Kramer Hospital, Coevorden; and Vrije Universiteit Medical Centre, Amsterdam; The Netherlands). Effects of short-term treatment with metformin on serum concentrations of homocysteine, folate and vitamin B12 in type 2 diabetes mellitus: a randomized, placebo-controlled trial. J Intern Med 2003; 254: 455–463. Objective. Metformin is a key treatment option in type 2 diabetes. However, metformin may decrease vitamin B12 levels and increase levels of homo-cysteine, a cardiovascular risk factor. We investigated whether 16 weeks of treatment with metformin affects serum concentrations of homo-cysteine, folate and vitamin B12 in subjects with type 2 diabetes treated with insulin. Design. Placebo-controlled, randomized trial. Measurements: at baseline and 16 weeks later. Setting. This trial was conducted in the outpatient clinics of three general hospitals in The Netherlands. Subjects. A total of 745 patients with type 2 diabetes, treated with insulin and not known with a contraindication for the use of metformin, were approached; 390 gave informed consent and entered the study. Thirty-seven subjects dropped out (12 placebo and 25 metformin users). Intervention. Addition of metformin or placebo to insulin therapy. Primary outcome parameters. Serum homocysteine, folate, vitamin B12, indices of glycaemic control and body weight. Results. Amongst those who completed 16 weeks of treatment, metformin use, as compared with placebo, was associated with an increase in homocysteine of 4% (0.2 to 8; P = 0.039) and with decreases in folate [−7% (−1.4 to −13); P = 0.024] and vitamin B12 [−14% (−4.2 to −24); P < 0.0001]. In addition, the increase in homocysteine could be explained by the decreases in folate and vitamin B12. Conclusion. In patients with type 2 diabetes, 16 weeks of treatment with metformin reduces levels of folate and vitamin B12, which results in a modest increase in homocysteine. The clinical significance of these findings remains to be investigated.

Using Description Logic to Maintain Consistency between UML Models

Abstract: A software design is often modelled as a collection of UML diagrams. There is an inherent need to preserve consistency between these diagrams. Moreover, through evolution those diagrams get modified leading to possible inconsistency between different versions of the diagrams. State-of-the-art UML CASE tools provide poor support for consistency maintenance. To solve this problem, an extension of the UML metamodel enabling support for consistency maintenance and a classification of inconsistency problems is proposed. To achieve the detection and resolution of consistency conflicts, the use of description logic (DL) is presented. DL has the important property of being a decidable fragment of first-order predicate logic. By means of a number of concrete experiments in Loom, we show the feasibility of using this formalism for the purpose of maintaining consistency between (evolving) UML models.

Condensed Representation of Database Repairs for Consistent Query Answering

Abstract: Repairing a database means bringing the database in accordance with a given set of integrity constraints by applying modifications that are as small as possible. In the seminal work of Arenas et al. on query answering in the presence of inconsistency, the possible modifications considered are deletions and insertions of tuples. Unlike earlier work, we also allow tuple updates as a repair primitive. Update-based repairing is advantageous, because it allows rectifying an error within a tuple without deleting the tuple, thereby preserving other consistent values in the tuple. At the center of the paper is the problem of query answering in the presence of inconsistency relative to this refined repair notion. Given a query, a trustable answer is obtained by intersecting the query answers on all repaired versions of the database. The problem arising is that, in general, a database can be repaired in infinitely many ways. A positive result is that for conjunctive queries and full dependencies, there exists a condensed representation of all repairs that permits computing trustable query answers.

Towards automating source-consistent UML refactorings

Abstract: With the increased interest in refactoring, UML tool vendors seek ways to support software developers in applying a (sequence of) refactoring(s) The problem with such tools is that the UML metamodel – on which their repository is based – is inadequate to maintain the consistency between the model and the code while one of them gets refactored Therefore, we propose a set of minimal extensions to the UML metamodel, which is sufficient to reason about refactoring for all common OO languages For instance, by specifying pre- and postconditions in OCL, we are able to compose primitive refactorings, verify preservation of program behavior, and trigger refactorings based on code smells This way, we provide future MDA tools with the ability to improve existing UML designs, yet keeping them in synch with the underlying code base

Recent Advances in the Study of Lanthanide Atoms and Ions

Abstract: We present an overview of the recent developments concerning the spectroscopic properties of lanthanide atoms and ions (Z = 57–71) This review is focussed on the advances made during the past twenty years regarding the analysis of the spectra, the transition probabilities, the radiative lifetimes and also the hyperfine structures and isotope shifts Theoretical aspects as well as experimental measurements are both covered in this paper including bibliographical references up to the end of 2001 Some astrophysical implications of the new atomic data concerning the chemical composition of the sun are briefly reviewed Emphasis is also put on the new database DREAM developed on a web site of Mons University in Belgium

Oligothiophene radical cations: Polaron structure in hybrid DFT and MP2 calculations

Abstract: We investigate the geometric and electronic structure of radical cations in oligothiophene chains by performing hybrid DFT (BHandHLYP) calculations on chains with up to 13 thiophene rings and ab initio MP2 calculations. The BHandHLYP-optimized structures indicate a self-localization of charge, spin, and geometric distortion around the middle of the chain, i.e., the formation of a polaron even in the case of the longer chains. This result contrasts with previous pure DFT findings that indicate complete delocalization of the radical cation over the whole chain. The MP2-optimized structure of octathiophene, an oligomer long enough to allow for possible polaron formation, confirms the presence of a well-localized polaron structure, similar to that obtained at the Hartree–Fock level. © 2002 Wiley Periodicals, Inc. Int J Quantum Chem, 2002

Limits on diffuse fluxes of high energy extraterrestrial neutrinos with the AMANDA-B10 detector.

Abstract: A report on the limits, which could be placed on diffuse fluxes of high energy extraterrestrial neutrinos, was presented. The incorporation of neutrino oscillations was necessary for interpreting the limits in terms of the flux from a cosmological distributions of sources. The energetic accelerated environments were presented as the sources of high energy extraterrestrial neutrinos.

The yggH gene of Escherichia coli encodes a tRNA (m7G46) methyltransferase.

Abstract: We cloned, expressed, and purified the Escherichia coli YggH protein and show that it catalyzes the S-adenosyl-L-methionine-dependent formation of N(7)-methylguanosine at position 46 (m(7)G46) in tRNA. Additionally, we generated an E. coli strain with a disrupted yggH gene and show that the mutant strain lacks tRNA (m(7)G46) methyltransferase activity.

Study of ZrN layers deposited by reactive magnetron sputtering

Abstract: Zirconium nitride films are deposited onto borosilicate wafers by reactive magnetron sputtering. The films are analysed in situ by X-ray photoelectron spectroscopy (XPS). We have studied by XPS the effects of the nitrogen partial pressure (1–100%), the subtract temperature (ambient to 450 °C), and biasing (0–80 W) on the stoichiometry of ZrN films. The N1s peak is composed of three components at 397.2, 396.4 and 395.8 eV in binding energy. These components are correlated with the three existing phases of zirconium nitride (ZrN, Zr3N4 and ZrN2). With an increase of the nitrogen partial pressure, a shift of the Zr3d line to the high binding energy and the increase of the N1s component at 395.8 eV are observed. These observations are explained by the charge transfer between Zr to N which increases with P(N2) as previously described for the Ti–N2 system [1]. The bulk stoichiometry is calculated by Rutherford backscattering and nuclear reaction measurements. The resistivity of the films is measured by the four-point probes technique. The reflectivity of the films are recorded by a spectrophotometer in the IR–Vis range. A correlation between the reflectivity and the resistivity is observed. The roughness of the films is measured by atomic force microscopy. The bias voltage has a great influence on the surface roughness and on the reflectivity of the films. The dependence of the ZrNx films structure and morphology with the discharge parameters is established.

Dewetting near the glass transition: transition from a capillary force dominated to a dissipation dominated regime.

Abstract: Dynamics and corresponding morphology of dewetting of thin polystyrene films at temperatures close to the glass transition were investigated by measuring simultaneously dewetted distance and width of the rim. Comparing the opening of cylindrical holes with the retraction of a straight contact line revealed (i) a drastic influence of the geometry (planar or radial symmetry) on the dynamics at early stages, (ii) a new logarithmic dewetting regime, and (iii) transitions between four dewetting regimes clearly indicated by changes in the shape of the rim. The complete dewetting scenario can be understood as an initial dominance of capillary driving forces, which is progressively overtaken by dissipation related to the increasing size of the rim.

Does Acamprosate Improve Reduction of Drinking As Well As Aiding Abstinence

Abstract: The study aimed to discover whether acamprosate reduces the severity of relapse for those patients undergoing abstinence-orientated treatment who are unable to abstain completely. Data on patients' alcohol consumption from 15 placebo-controlled treatment studies (n = 3309) were examined to test whether, at a given time point, patients who have taken one or more drinks since the last assessment ('relapsers', n = 1010) take alcohol on fewer days, report lower average number of drinks per day, and consume less alcohol in total with acamprosate compared to placebo. These studies had varying duration (90 days, 180 days and 360 days). There were four dates that were common to some studies (days 30, 90, 180 and 360). Among relapsers, acamprosate was significantly associated with less quantity (Q) and frequency (F) of drinking compared to placebo in each of the four follow-up periods (p < 0.001). The differences were most marked for the product Q x F (overall weekly consumption). For each period, there were fewer who were drinking an average of five or more drinks per day in the acamprosate compared to the placebo groups. Acamprosate helps reduce the severity of relapse in patients undergoing abstinence-orientated treatment.

Echinoderms as bioindicators, bioassays, and impact assessment tools of sediment-associated metals and PCBs in the North Sea.

Abstract: The study assessed the occurrence, possible toxicity, and impact of sediment-associated metals and PCBs in the coastal zone of the southern North Sea using echinoderms as representatives of the macrobenthos. Metals and PCBs were analyzed in the sediments and in the body compartments of the starfish Asterias rubens from 11 stations. The general toxicity of sediment-associated contaminants was assessed by bioassays using embryonic and larval developments of both A. rubens and the sea urchin Psammechinus miliaris. The impact of contamination was assessed by measuring cellular immune responses of A. rubens collected in the same stations. Contamination of the starfish by metals and PCBs closely reflected that of the sediments. However, bioaccumulation was element-specific for metals and depended on the chlorination pattern for PCBs. The sediment-associated contaminants appeared to be toxic in both the A. rubens and P. miliaris developmental assays. Moreover, metals were shown to affect the immune responses of starfishes living in contaminated stations. The most significant effects on biological responses were recorded in the plumes of the Scheldt/Rhine/North Sea Canal and the Elbe/Weser Rivers.

Density functional theory and Hartree–Fock studies of the geometric and electronic structure of neutral and doped ethylenedioxythiophene (EDOT) oligomers

Abstract: The geometric and electronic structure of 3,4-ethylenedioxythiophene oligomers, ranging in size up to the decamer, have been calculated with density functional theory according to Becke's three-parameter exchange functional and the gradient-corrected functional of Lee, Yang, and Paar (DFT/B3LYP/6-31G) and ab initio Hartree–Fock (HF/6-31G) methods. A comparison between the energetics of the aromatic and quinoid forms in the neutral state shows as expected that the former is more stable. For both the singly and doubly positively charged compounds, HF is found to localize the excess charge around the center of the molecule, whereas DFT leads to delocalization of the charge all along the conjugated path. The optical properties calculated at the semiempirical level (intermediate neglect of differential overlap/single configuration, (INDO/SCI) on the basis of the geometries provided by DFT and HF are also analyzed. © 2003 Wiley Periodicals, Inc. Int J Quantum Chem, 2002

Indirect cytotoxicity evaluation of pseudowollastonite.

Abstract: This study aimed to evaluate the cytotoxicity of substances leached by pseudowollastonite (CaSiO(3)). It has been previously shown that calcium (Ca(2+)) and silicate (SiO(3)(-)) ions are released from pseudowollastonite into biological solutions. Both of these ions are known to influence the biological metabolism of osteoblastic cells essential in the mineralization process and bone-bonding mechanism. The indirect toxicity evaluation was performed by extraction method, according to International Standard Organization (ISO). Pseudowollastonite pellets obtained by solid-state reaction were incubated, in culture medium, during 24, 48, 72 or 168 h at different concentrations (5, 10, 15, 50, 100, 200 mg/ml). The cytotoxicity of each extract in presence of human osteoblastic cell line (SaOS-2) was quantitatively assessed by measuring the viability (succinate dehydrogenase activity, MTT), the membrane integrity (the uptake of the neutral red by viable cells, NR) as well as the cell necrosis by measuring the lactate dehydrogenase (LDH) released in the culture medium. No significant alteration of membrane integrity or cell suffering was detectable. However, increased cell metabolism was observed for cells exposed to pseudowollastonite extract with longest extraction time (168 h). In conclusion, mineral elements leached by pseudowollastonite do not significantly affect the metabolism of osteoblastic cells.

How many Hipparcos Variability-Induced Movers are genuine binaries?

Abstract: Hipparcos observations of some variable stars, and especially of long-period (e.g. Mira) variables, reveal a motion of the photocenter correlated with the brightness variation (variability-induced mover - VIM), suggesting the presence of a binary companion. A re-analysis of the Hipparcos photometric and astrometric data does not confirm the VIM solution for 62 among the 288 VIM objects (21%) in the Hipparcos catalogue. Most of these 288 VIMs are long-period (e.g. Mira) variables (LPV). The eect of a revised chromaticity correction, which accounts for the color variations along the light cycle, was then investigated. It is based on "instantaneous" V I color indices derived from Hipparcos and Tycho-2 epoch photometry. Among the 188 LPVs flagged as VIM in the Hipparcos catalogue, 89 (47%) are not confirmed as VIM after this improved chromaticity correction is applied. This dramatic decrease in the number of VIM solutions is not surprising, since the chromaticity correction applied by the Hipparcos reduction consortia was based on a fixed V I color. Astrophysical considerations lead us to adopt a more stringent criterion for accepting a VIM solution (first-kind risk of 0.27% instead of 10% as in the Hipparcos catalogue). With this more severe criterion, only 27 LPV stars remain VIM, thus rejecting 161 of the 188 (86%) of the LPVs defined as VIMs in the Hipparcos catalogue.

Synthesis and Characterization of Random Copolyesters of ε-Caprolactone and 2-Oxepane-1,5-dione

Abstract: 2-Oxepane-1,5-dione (OPD) has been synthesized by the Baeyer−Villiger oxidation of 1,4-cyclohexanedione and copolymerized with e-caprolactone. This random copolymerization has been initiated by different metal derivatives, i.e., tin octanoate, dibutyltin dimethoxide, and aluminum isopropoxide. Dibutyltin dimethoxide is the preferred initiator, and the course of polymerization is controlled by the competition of the ketone of OPD and the ester of the lactones for coordination to the initiator. Semicrystalline copolymers are formed, whose the randomness has been confirmed by DSC, 1H NMR, and 13C NMR analysis. A single melting temperature (Tm) has been observed, which varies regularly and monotonically with the OPD content as result of a cocrystallization phenomenom. The single glass transition temperature (Tg) obeys the Fox equation.

Particle-like solutions to higher-order curvature Einstein–Yang–Mills systems in d dimensions

Abstract: We consider the superposition of the first two members of the gravitational hierarchy (Einstein plus first Gauss–Bonnet (GB)) interacting with the superposition of the first two members of the Yang–Mills (YM) hierarchy, in d dimensions. The YM fields are taken to be in the chiral representations of the gauge groups, (i) SO(±)(d), and (ii) SO(±)(d − 1), respectively, for (i) even d and (ii) odd d. Such systems can occur in the low energy effective action of string theory. Particle-like solutions in dimensions d = 6, 8, and d = 7, are constructed, respectively. Our results reveal qualitatively new properties featuring double-branch solutions with critical behaviour. In this preliminary study, we have restricted numerical study to one-node solutions.

Automated Support for Framework-Based Software Evolution

Abstract: In this paper, we show how elaborate support forframework-based software evolution can be provided basedon explicit documentation of the hot spots of object-orientedapplication frameworks. Such support includes high-leveltransformations that guide a developer when instantiatingapplications from a framework by propagating the necessarychanges, as well as application upgrading facilitiesbased on these transformations. The approach relies on activedeclarative documentation of the design and evolutionof the framework's hot spots, by means of metapatterns andtheir associated transformations.

Feeding preferences, seasonal gut repletion indices, and diel feeding patterns of the sea urchin Tripneustes gratilla (Echinodermata: Echinoidea) on a coastal habitat off Toliara (Madagascar)

Abstract: The feeding biology of the echinoid Tripneustes gratilla from a seagrass bed off Toliara, on the south-west coast of Madagascar, was investigated during the summer and winter seasons. Repletion indices of the gut of T. gratilla varied seasonally, in such a way that higher amounts of food occurred in the gut in winter than in other seasons. Conversely, a more detailed analysis of one summer and one winter sample of the gut tissue dry weights revealed higher weights in summer (February) than in winter (August). This was interpreted as a varying capability of nutrient storage and closely related to the feeding activity of the echinoid. This inverse relationship between feeding activity and nutrient storage was suggested to be dependent on gonadal growth. Indeed, higher food consumption was observed during the post-spawning period (August), that is, when most of the energy accumulated was used up for gonadal growth. Low feeding activity occurred when a sufficient amount of energy was accumulated in gut tissues (February), the time corresponding to the initiation of gonadal growth. Investigations on the feeding habits, using Ivlev's electivity index, revealed preferential feeding of T. gratilla on Syringodium isoetifolium, the dominant seagrass species found in the gut. This was partly related to the higher availability of that particular seagrass species in the field. However, its soft and terete leaf blade's morphology also makes it easier to manipulate and ingest. Studies on the feeding behaviour indicated the presence of a diel feeding cycle in T. gratilla individuals in both summer and winter seasons. Yet, its pattern varied between the two studied months (one summer and one winter) as the cycle was less contrasted during period of active feeding, i.e. in winter compared to summer. This study provides novel information on how intrinsic factors, such as physiological state, can govern the feeding activity of T. gratilla living in a seagrass habitat.