References of "1997"
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See detailA Computer Aided Design of a Secure Registration Protocol
Germeau, François; Leduc, Guy ULg

in Formal Description Techniques and Protocol Specification, Testing and Verification (1997, November)

We use the formal language LOTOS to specify a registration protocol between a user and a Trusted Third Party, that requires mutual authentication. We explain how a model-based verification method can be ... [more ▼]

We use the formal language LOTOS to specify a registration protocol between a user and a Trusted Third Party, that requires mutual authentication. We explain how a model-based verification method can be used to verify its robustness to attacks by an intruder. This method is also used to find a simpler protocol that remains secure. [less ▲]

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See detailLipopeptides alter Bacillus subtilis hydrophobicity by adsorbing onto cell surfaces
Ahimou, François; Razafindralambo, Hary ULg; Paquot, Michel ULg

Poster (1997, October 29)

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See detailNitrogen deposition and nitrification in coniferous forests’
Carnol, Monique ULg

Doctoral thesis (1997)

The increased inorganic nitrogen (N) deposition in the last decades has become a major concern for the health of forest ecosystems. High anthropogenic N emissions, mainly from fossil fuel combustion and ... [more ▼]

The increased inorganic nitrogen (N) deposition in the last decades has become a major concern for the health of forest ecosystems. High anthropogenic N emissions, mainly from fossil fuel combustion and livestock agriculture, have resulted in both high gaseous concentrations and high deposition in rainfall and throughfall. In forest ecosystem, where N is no longer limiting to primary production due to high inputs, the excess N is thought to be related to forest decline and a concept of ‘N saturation ‘ has been developed. In particular, N in the form of NH4, in excess to plant and microbial demands could lead to soil acidification if nitrified in the soil and leached, causing loss of base cations or mobilisation of phytotoxic aluminium. Nutrient imbalances due to high soil solution NH4/cation ratios or damaged root systems may also occur. The fate of the incoming NH4 is central to determining the effects on the ecosystem, and is closely related to the controls of nitrification. Although this process has been intensely studied in pure cultures for some nitrifying bacteria, the organisms responsible and controlling factors in acid forest soils are still poorly understood. A better comprehension of the fate of NH4 deposition is necessary to determine ‘Critical Loads for N’, the threshold deposition not damaging to the ecosystem, which is used as a political tool for quantifying pollution limits. In this thesis, I focused on a) the effects of increased (NH4)2SO4 deposition on soil solution chemistry of six coniferous forest sites the presence of live roots, b) the impacts of (NH4)2SO4 deposition on Norway spruce (Picea abies [L.] Karst) and Scots pine (Pinus sylvestris L.) fine roots, and c) the controls of nitrification in an acid forest soil. The work was part of the CEC project ‘CORE’, investigating the effects of atmospheric pollution on nutrient turnover in soils. An identical field experiment was performed in six coniferous sites, situated in five European countries. Chronically increased NH4 deposition by 75 kg N ha-1 a-1 through (NH4)2SO4 application, demonstrated the contrasting responses of the different ecosystems. Soil solution concentrations and yearly ionic fluxes were analysed. (NH4)2SO4 treatment resulted in deposition of 79 to 93 kg N ha-1 a-1 at the different sites. In the two less acidic, clay/clay loam soils, only 6% of the added NH4 was lost through leaching. The two sandy soils lost up to 75% of the added NH4, and the two remaining sites lost ca. 25%. Leaching of added NH4 was thought to be related to soil physico-chemical characteristics, such as pH, C and N content and texture. NO3 leaching was increased at three sites, only 4-9 months after starting the (NH4)2SO4 treatment, with a maximum doubling of concentrations. One sandy soil failed to nitrify under any condition, and the other sandy soil showed high NO3 leaching under all treatments, but no increase due to increased N inputs. The presence of live roots reduced NO3 leaching in two sites, delaying the increase in soil solution NO3 concentrations in response to the (NH4)2SO4 deposition in one of them. In all nitrifying soils, soil solution NO3 concentrations were related to cation concentrations, with Al being the dominant cation in the more acid soils with low base saturation. This experiment demonstrated the importance of soil N storage capacity and nitrification potential in determining the consequences of increased NH4 deposition, and the strong relationship between NO3 and cation leaching. Ionic fluxes and soil solution chemistry were further analysed in one of the six sites (Grizedale, UK). In this Norway spruce stand on clay soil, NO3 fluxes were increased by increased (NH4)2SO4 deposition, and mainly balanced by increased Al losses. This soil had a pHH2O around 3.6, and was characterised by over 90% of the exchange complex being occupied by Al. Independent of treatment, soil solution changed from Ca to Al leaching during the 18 month field experiment, with a decrease in soil solution pH from 4.9 to 3.8. At the end of the experiment, soil solution Al concentrations were higher for the (NH4)2SO4 treatments. It was suggested that nitrification had caused the pH decrease, with a further lowering of the base saturation, linked to a abrupt increase in soil solution Al concentrations. The impacts of increased (NH4)2SO4 deposition and soil characteristics on Norway spruce root biomass and vitality, and on Norway spruce and Scots pine fine root chemistry, were investigated with an ingrowth core technique. The same experiment was performed in a Norway spruce stand on clay soil (Grizedale, UK) and a Scots pine stand on sandy soil (Wekerom, NL), using soil from each of the two sites. For Norway spruce, root biomass and numbers of fine root tips were higher in the organic than in the mineral horizon of the clay and sandy soils. This was related to higher fine root Al and lower Ca contents in the mineral horizon. Root biomass and the proportion of dead roots were higher in the clay soil, compared to the sandy soil, with higher root Al contents, despite lower soil solution Al concentrations than in the sandy soil. For Norway spruce, a negative correlation between root biomass and fine root Al content was established. Enhanced N deposition caused an increase in the total number of root tips and in the proportion of dead roots in the sandy soil. Effects of increased (NH4)2SO4 deposition on root biomass were not significant for the clay soil, yet caused increased fine root N content in the organic horizon for both species. Scots pine fine roots also showed higher Al and lower Ca contents in the mineral horizon. (NH4)2SO4 treatment caused increased fine root Al content and a decreased Mg/Al ratio in the mineral layer of the sandy soil, with opposite effects in the clay soil. This (NH4)2SO4 treatment effect in the sandy soil for Scots pine was the only indication of a potential adverse effect of (NH4)2SO4 deposition on fine roots. Results demonstrated the dominant importance of inherent soil characteristics and the stratification into soil horizons on fine root growth and chemical composition. The effects of temperature, throughfall volume and NH4 deposition on soil solution NO3 concentrations, N2O emissions and numbers of NH4 oxidisers were investigated for the Grizedale soil in a controlled laboratory experiment. Multiple regression and surface response analysis revealed temperature as the most important factor, with an optimum for NO3 leaching and numbers of NH4 oxidisers in the mineral horizon at 11°C. Volume acted independently of temperature with a minimum at 870 mm throughfall 2 weeks-1. The relatively low optimum temperature compared to other studies was explained by the minimum disturbance of the soil in the current study. NO3 fluxes increased quadratically with throughfall volume. N2O fluxes increased quadratically with temperature and throughfall volume, and showed high variability. It was suggested that the temperature optimum for net nitrification depended on the physico-chemical characteristics of the soil and on the activity of decomposers, by competition for O2 and NH4. Optimum temperatures may have been overestimated in previous studies using disturbed soils. The regression model for NO3 leaching derived from the laboratory experiment was applied to data from the previous field experiment and tested with different time intervals for temperature input parameters. A model including two-monthly mean temperatures yielded the best fit between measured and simulated values, as determined by correlation and minimum sum of squared residuals. Simulated NO3 leaching was over-estimated in the second part of the field study. The good correspondence between field temperature frequency distribution and the optimum temperature determined by the regression model, as well as the high correlation between measured and simulated values, demonstrated the adequacy of a quadratic model with a relatively low temperature optimum to describe field NO3 leaching, determined for the same soil with an identical sampling design. [less ▲]

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See detailOptimisation et Scale up des Fermentations de Production de Starters Lactiques.
Hamdi, M.; Hamza, S.; Amor, L. et al

Poster (1997, October 27)

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See detailLes applications des bactéries lactiques
Thonart, Philippe ULg

Conference (1997, October 27)

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See detailIdentification de la flore lactique du lait fermenté traditionnel tunisien (lben) et évaluation des composés aromatisants
Ben Amor, K.; Cornelius, C.; Mahjoub, A. et al

Poster (1997, October 27)

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See detailX ray in RDS with HFOV and surfactant: what has changed ?
Battisti, Oreste ULg; Rausin, L.; Khamis, J. et al

Conference (1997, October 24)

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See detailspontaneous pneumothorax treated by HFOV
Battisti, Oreste ULg; Petermans, M. F.; François, A. et al

Conference (1997, October 24)

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See detailA two year experience with primary high frequency ventilation in neonatal respiratory distress syndrome
Battisti, Oreste ULg; Detaille, T.; François, A. et al

Conference (1997, October 24)

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See detailA comparison of two methods for pulmonary function testing in horses with upper and lower airway obstruction
Van Erck, Emmanuelle; Duvivier, D. H.; Art, Tatiana ULg et al

Poster (1997, October 24)

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See detailMolecular weight effects on polystyrene fingerprint time-of-flight secondary ion mass spectroscopy (ToF-SIMS) spectra
Vanden Eynde, X.; Bertrand, P.; Jérôme, Robert ULg

in Macromolecules (1997), 30(21), 6407-6416

Monodisperse polystyrenes (PS) of different molecular weights (Mn) synthesized by living anionic polymerization with three types of butyllithium initiator (linear, n; secondary, sec; and tertiary, tert ... [more ▼]

Monodisperse polystyrenes (PS) of different molecular weights (Mn) synthesized by living anionic polymerization with three types of butyllithium initiator (linear, n; secondary, sec; and tertiary, tert) were analyzed by ToF-SIMS (time-of-flight secondary ion mass spectrometry). The influence of the molecular weight on the secondary ion intensities was studied in detail for the fingerprint part of the mass spectra (with m/z < 200). A drastic effect was observed for Mn values below 104, related to the presence of the saturated butyl end group. An extra hydrogen transfer originating from this end group during the secondary ion formation must be invoked to explain the data. Only the first neighbor monomer repeat units seem to be affected. This H exchange increases the intensity of ions containing more hydrogen or needing H transfer for their formation as the tropylium ion (C7H7+ at m/z = 91). The molecular structure of the butyl end group is found to influence greatly not only the intensity of their parent ion but also the PS characteristic ion intensities. Indeed, the tert-butyl end group is seen unable to produce the H transfer observed for the n- and sec-butyl ones. A model is proposed to take the influence of the end group on the PS SIMS fragmentation pattern into account. The parameters of this model allow the quantification of the end group interaction. [less ▲]

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See detailPoly[poly(isobornyl methacrylate-co-methyl methacrylate) (poly(IBMA-co-MMA))-b-polybutadiene-b-poly(IBMA-co-MMA)] Copolymers: synthesis, morphology, and properties
Yu, J. M.; Dubois, Philippe ULg; Jérôme, Robert ULg

in Macromolecules (1997), 30(21), 6536-6543

Anionic random and block copolymerization of isobornyl methacrylate (IBMA) and methyl methacrylate (MMA) has been studied in THF at −78 °C by using (1,1-diphenyl-3,3-dimethylbutyl)lithium (DDBLi) as ... [more ▼]

Anionic random and block copolymerization of isobornyl methacrylate (IBMA) and methyl methacrylate (MMA) has been studied in THF at −78 °C by using (1,1-diphenyl-3,3-dimethylbutyl)lithium (DDBLi) as initiator in the presence of LiCl. The random copolymerization of MMA and IBMA has also been carried out at 0 °C, all the other conditions being kept unchanged. Poly[poly(IBMA)-b-poly(BD)-b-poly(IBMA)] (IBI), poly[poly(IBMA-co-MMA)-b-poly(BD)-b-poly(MMA-co-IBMA)] (I/MBM/I), and poly[poly(IBMA)-b-poly(MMA)-b-poly(BD)-b-poly(MMA)-b-poly(IBMA)] (IMBMI) block copolymers have been synthesized by sequential anionic polymerization of butadiene, MMA, and IBMA initiated by the m-diisopropenylbenzene (m-DIB)/tert-butyllithium (t-BuLi) diadduct. These block copolymers of a monomodal and narrow molecular weight distribution (M̄w/M̄n = 1.1) have been analyzed by size exclusion chromatography (SEC), NMR, differential scanning calorimetry (DSC), dynamic mechanical analysis (DMA), and transmission electron microscopy (TEM). Stereocomplexation of IMBMA and I/MBM/I with iPMMA has also been studied by DSC. Although IBI triblock copolymers show a lamellar morphology even for relatively low hard block content (33 wt %), cylindrical and lamellar morphologies have been observed for the other block copolymers under consideration. These new block copolymers exhibit high ultimate tensile strength (30 MPa), elongation at break (1000%), and upper service temperature (140−200 °C). [less ▲]

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See detailDiscrepancy in hemoglobin A1c results obtained by HPLC and CE: influence of carbamyl HB
Gougnard, Th; Chapelle, Jean-Paul ULg; Charlier, Corinne ULg et al

Poster (1997, October 18)

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See detailLa loi du 4 mars 1997 instituant le collège des procureurs généraux et créant la fonction de magistrat national : que reste-t-il de l’indépendance du Ministère public?
Masset, Adrien ULg

in Journal des Tribunaux (1997), 5856(32), 649-651

La loi du 4 mars 1997 instituant le collège des procureurs généraux et créant la fonction de magistrat national est présentée, par le législateur lui-même, comme la traduction de la volonté d’entériner ... [more ▼]

La loi du 4 mars 1997 instituant le collège des procureurs généraux et créant la fonction de magistrat national est présentée, par le législateur lui-même, comme la traduction de la volonté d’entériner une situation de fait existante. Le propos n'est pas de détailler la teneur de cette loi, mais plutôt de mettre en exergue l’expropriation croissante, au bénéfice du ministre de la Justice, de l’indépendance du ministère public par rapport à ce même ministre de la Justice, dans le domaine de la politique criminelle [less ▲]

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See detailLes hypertensions artérielles d'origine endocrinienne
Beckers, Albert ULg

Scientific conference (1997, October 17)

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See detailPsychrophilic Enzymes: A Thermodynamic Challenge
Gerday, Charles ULg; Aittaleb, Mohamed; Arpigny, Jean Louis et al

in Biochimica et Biophysica Acta (1997), 1342(2), 119-31

Psychrophilic microorganisms, hosts of permanently cold habitats, produce enzymes which are adapted to work at low temperatures. When compared to their mesophilic counterparts, these enzymes display a ... [more ▼]

Psychrophilic microorganisms, hosts of permanently cold habitats, produce enzymes which are adapted to work at low temperatures. When compared to their mesophilic counterparts, these enzymes display a higher catalytic efficiency over a temperature range of roughly 0-30 degrees C and a high thermosensitivity. The molecular characteristics of cold enzymes originating from Antarctic bacteria have been approached through protein modelling and X-ray crystallography. The deduced three-dimensional structures of cold alpha-amylase, beta-lactamase, lipase and subtilisin have been compared to their mesophilic homologs. It appears that the molecular adaptation resides in a weakening of the intramolecular interactions, and in some cases in an increase of the interaction with the solvent, leading to more flexible molecular edifices capable of performing catalysis at a lower energy cost. [less ▲]

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See detailSite-Directed Mutagenesis of the Actinomadura R39 DD-Peptidase
Zhao, GuoHua; Duez, Colette ULg; Forceille, Christine et al

in Biochemical Journal (1997), 327(2), 377-381

The role of various residues in the conserved structural elements of the Actinomadura R39 penicillin-sensitive dd-peptidase has been studied by site-directed mutagenesis. Replacement of Ser-298 of the ... [more ▼]

The role of various residues in the conserved structural elements of the Actinomadura R39 penicillin-sensitive dd-peptidase has been studied by site-directed mutagenesis. Replacement of Ser-298 of the 'SDN loop' by Ala or Gly significantly decreased the kcat/Km value for the peptide substrate, but only by a factor of 15 and had little effect on the other catalytic properties. Mutations of Asn-300 of the same loop and of Lys-410 of the KTG triad yielded very unstable proteins. However, the N300S mutant could be purified as a fusion protein with thioredoxin that exhibited decreased rates of acylation by the peptide substrate and various cephalosporins. Similar fusion proteins obtained with the N300A, K410H and K410N mutants were unstable and their catalytic and penicillin-binding properties were very strongly affected. In transpeptidation reactions, the presence of the acceptor influenced the kcat/Km values, which suggested a catalytic pathway more complex than a simple partition of the acyl-enzyme between hydrolysis and aminolysis. These results are compared with those obtained with two other penicillin-sensitive enzymes, the Streptomyces R61 dd-peptidase and Escherichia coli penicillin-binding protein (PBP) 5. [less ▲]

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