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See detailCharacterization of Tunisian pomegranatenext term (Punica granatum L.) cultivars using amplified fragment length polymorphism analysis
Jbir, Rania; Hasnaoui, Nejib ULg; Mars, Messaoud et al

in Scientia Horticulturae (2008), 115(3), 231-237

The amplified fragment length polymorphism (AFLP) analysis of DNA was used to characterize 34 previous termpomegranatenext term cultivars. By using a combination of six primers, a total of 327 markers ... [more ▼]

The amplified fragment length polymorphism (AFLP) analysis of DNA was used to characterize 34 previous termpomegranatenext term cultivars. By using a combination of six primers, a total of 327 markers were scored with a mean of 57.5. The high percentage of polymorphic bands (ppb) of 94.7 and the resolving power (Rp) collective rate value of 129.14 were scored. Data proved that the tested primers were informative to discriminate among cultivars and to survey the genetic diversity in this fruit crop. It has been assumed that the local previous termpomegranatenext term germplasm is characterized by a typically continuous genetic diversity. The derived dendrogram proved that cultivars are clustered independently from their geographical origin and their denomination. In addition, AFLP permitted the generation of a nearly unlimited number of molecular markers that are reliable in differentiating the cultivars and/or the polyclonal varieties. [less ▲]

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See detailCharacterization of two Acacia gums and their fractions using a Langmuir film balance
Fauconnier, Marie-Laure ULg; Blecker, Christophe ULg; Groyne, J. et al

in Journal of Agricultural and Food Chemistry (2000), 48(7), 2709-2712

The mechanical properties of monolayers from two Acacia gums [Acacia senegal (L.) Willd. and Acacia seyal Del.] and their three fractions isolated by hydrophobic interaction chromatography were studied ... [more ▼]

The mechanical properties of monolayers from two Acacia gums [Acacia senegal (L.) Willd. and Acacia seyal Del.] and their three fractions isolated by hydrophobic interaction chromatography were studied with a Langmuir film balance to obtain a more complete understanding of their action mode. The analysis of compression isotherms revealed that A. senegal gums globally exhibit better interfacial properties than A. seyal ones. The behavior of the whole gums appeared to be strongly influenced by their arabinogalactan-protein complex. [less ▲]

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See detailCharacterization of two genes encoding the mitochondrial alternative oxidase in Chlamydomonas reinhardtii
Dinant, Monique; Baurain, Denis ULg; Coosemans, Nadine ULg et al

in Current Genetics (2001), 39(2), 101-108

Two cDNA clones (AOX1 and AOX2) and the corresponding genes encoding the alternative oxidases (AOXs) from Chlamydomonas reinhardtii were isolated and sequenced. The cDNAs, AOX1 and AOX2, contained open ... [more ▼]

Two cDNA clones (AOX1 and AOX2) and the corresponding genes encoding the alternative oxidases (AOXs) from Chlamydomonas reinhardtii were isolated and sequenced. The cDNAs, AOX1 and AOX2, contained open reading frames (ORFs) encoding putative proteins of 360 amino acids and 347 amino acids, respectively. For each of the ORFs, a potential mitochondrial-targeting sequence was found in the 5'-end regions. In comparison to AOX enzymes from plants and fungi, the predicted amino acid sequences of the ORFs showed their highest degree of identity with proteins from Aspergillus niger (38.1% and 37.2%) and Ajellomyces capsulatus (37% and 34.9%). Several residues supposed either to be Fe ligands or to be involved in the ubiquinol-binding site were fully conserved in both C. reinhardtii putative AOX proteins. In contrast, a cysteine residue conserved in the sequences of all higher plants and probably involved in the regulation of the enzyme activity was missing both from the AOX1 and AOX2 amino acid sequences and from protein sequences from various other microorganisms. The transcriptional expression of the AOX1 and AOX2 genes in wild-type cells and in mutant cells deficient in mitochondrial complex III activity was also investigated. [less ▲]

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See detailCharacterization of two structural aberrations in the horse by FISH with BAC clones.
Durkin, Keith ULg; Raudsepp, T; Chowdhary, B.P.

in Chromosome Research : An International Journal on the Molecular, Supramolecular and Evolutionary Aspects of Chromosome Biology (2006), 14

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See detailCharacterization of UDP-glucose : protein transglucosylase genes from potato.
Wald, F. A.; Kissen, R.; du Jardin, Patrick ULg et al

in Plant Molecular Biology (2003), 52

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See detailCharacterization of variable importance measures derived from decision trees
Sutera, Antonio ULg

Master's dissertation (2013)

In the context of machine learning, tree-based ensemble methods are common techniques used for prediction and explanation purposes in many research fields such as genetics for instance. These methods ... [more ▼]

In the context of machine learning, tree-based ensemble methods are common techniques used for prediction and explanation purposes in many research fields such as genetics for instance. These methods consist in building, by randomization, several decision trees and then aggregating their predictions. From an ensemble of trees, one can derive an importance score for each variable of the problem that assesses its relevance for predicting the output. Although these importance scores have been successfully exploited in many applications, they are not well understood and in particular, they lack a theoretical characterization. In this context, this work is a first step towards providing a better understanding of these measures from a theoretical and an empirical point of view. First, we derive, and verify empirically, an analytical formulation of the importance scores obtained from an ensemble of totally randomized trees in asymptotic conditions (i.e, infinite number of trees and infinite sample size). We then study empirically importance score distributions derived from totally randomized tree ensembles in non asymptotic conditions for several simple input-output models. In particular, we show theoretically and empirically the insensitivity of importance scores with respect to the introduction of irrelevant variables for these simple models. We then evaluate the effect of a reduction of the randomization on importance scores and their distribution. Finally, tree-based importance measures are illustrated on a digit recognition problem. [less ▲]

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See detailCharacterization of Venom Peptides using Microfluidic Separation Techniques coupled to Mass Spectrometry (LC-MS and CE-MS)
Degueldre, Michel ULg; Delvaux, Cédric ULg; Far, Johann ULg et al

Poster (2015, March)

More than the half of the principal sub-kingdoms of the animal world contains species that produce venom whose purposes are to immobilize, kill and pre-digest the preys. These venoms represent an ... [more ▼]

More than the half of the principal sub-kingdoms of the animal world contains species that produce venom whose purposes are to immobilize, kill and pre-digest the preys. These venoms represent an exceptionally rich source of various biologically active peptides, both in their structures and their effects, which are more and more useful for human being1. Yet, the total characterization of such complex samples require advanced analytical techniques mainly due to the complexity of the sample (hundreds of compounds), the limited quantities usually available and the presence of numerous PTMs, especially disulfide bridges and specific folding. Here we present a method that combines LC and CE separation techniques coupled to mass spectrometry (MS) to characterize the peptide composition of the snake venom Naja atra. The characterization will not only focus on the toxin sequencing (LC-MS and LC-MS/MS), but will also aim at analyzing the folding of the toxins (CE-MS). To this end, native and reduced/alkylated toxins will be analyzed by both techniques. Final result targets the determination of the global hydrophobic pattern and native tridimensional folding of these strongly reticulated peptides. (1) Richard J. Lewis & Maria L. Garcia, Therapeutic potential of venom peptides. Nature Reviews Drug Discovery 2003, 2, 790-802. [less ▲]

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See detailCharacterization of volatile organic compounds emitted by Barley (Hordeum vulgare L.) roots and their attractiveness to wireworms
Gfeller, Aurélie; Laloux, Morgan; Barsics, Fanny ULg et al

in Journal of Chemical Ecology (2013), 39(8), 1129-1139

Root volatile organic compounds (VOCs), their chemistry and ecological functions have garnered less attention than aboveground emitted plant VOCs. We report here for the first time on the identification ... [more ▼]

Root volatile organic compounds (VOCs), their chemistry and ecological functions have garnered less attention than aboveground emitted plant VOCs. We report here for the first time on the identification of VOCs emitted by barley roots (Hordeum vulgare L.). Twenty nine VOCs were identified from isolated 21-d-old roots. The detection of root volatiles was dependent on the medium used for root cultivation. From 7-d-old roots cultivated on sterile Hoagland gelified medium, 24 VOCs were identified, on sterile vermiculite 33 VOCs, and on non-sterile vermiculite 34 VOCs. The major VOCs identified were fatty acid derived compounds, including hexanal, methyl hexanoate, (E)-hex-2-enal, 2-pentylfuran, pentan-1-ol, (Z)-2-(pentenyl)-furan, (Z)-pent-2-en-1-ol, hexan-1-ol, (Z)-hex-3-en-1-ol, (E)-hex-2-en-1-ol, oct-1-en-3-ol, 2-ethylhexan-1-ol (likely a contaminant), (E)-non-2-enal, octan-1-ol, (2E,6Z)-nona-2,6-dienal), methyl (E)-non-2-enoate, nonan-1-ol, (Z)-non-3-en-1-ol, (E)-non-2-en-1-ol, nona-3,6-dien-1-ol and nona-2,6-dien-1-ol. In an olfactometer assay, wireworms (larvae of Agriotes sordidus Illiger, Coleoptera: Elateridae) were attracted to chemical cues emanating from barley seedlings. We discuss the role of individual root volatiles or a blend of the root volatiles detected here and their interaction with CO2for wireworm attraction. [less ▲]

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See detailCharacterization of Volatile Organic Compounds from Human Analogue Decomposition Using Thermal Desorption Coupled to Comprehensive Two-Dimensional Gas Chromatography-Time-of-Flight Mass Spectrometry
Stadler, Sonja; Stefanuto, Pierre-Hugues ULg; Brokl, Michal et al

in Analytical Chemistry (2013), 85(2), 998-1005

Complex processes of decomposition produce a variety of chemicals as soft tissues, and their component parts are broken down. Among others, these decomposition byproducts include volatile organic ... [more ▼]

Complex processes of decomposition produce a variety of chemicals as soft tissues, and their component parts are broken down. Among others, these decomposition byproducts include volatile organic compounds (VOCs) responsible for the odor of decomposition. Human remains detection (HRD) canines utilize this odor signature to locate human remains during police investigations and recovery missions in the event of a mass disaster. Currently, it is unknown what compounds or combinations of compounds are recognized by the HRD canines. Furthermore, a comprehensive decomposition VOC profile remains elusive. This is likely due to difficulties associated with the nontarget analysis of complex samples. In this study, cadaveric VOCs were collected from the decomposition headspace of pig carcasses and were further analyzed using thermal desorption coupled to comprehensive two-dimensional gas chromatography time-of-flight mass spectrometry (TD-GC × GC−TOFMS). Along with an advanced data handling methodology, this approach allowed for enhanced characterization of these complex samples. The additional peak capacity of GC × GC, the spectral deconvolution algorithms applied to unskewed mass spectral data, and the use of a robust data mining strategy generated a characteristic profile of decomposition VOCs across the various stages of soft-tissue decomposition. The profile was comprised of numerous chemical families, particularly alcohols, carboxylic acids, aromatics, and sulfides. Characteristic compounds identified in this study, e.g., 1-butanol, 1-octen-3-ol, 2-and 3-methyl butanoic acid, hexanoic acid, octanal, indole, phenol, benzaldehyde, dimethyl disulfide, and trisulfide, are potential target compounds of decomposition odor. This approach will facilitate the comparison of complex odor profiles and produce a comprehensive VOC profile for decomposition. [less ▲]

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See detailCharacterization of YbjG, a pyrophosphate phosphatase from E. coli involved in the lipid carrier undecaprenyl phosphate metabolism
Delbrassine, François ULg; Auger, Rodolphe; El Ghachi, Meriem ULg et al

Poster (2015, June 08)

•Background Undecaprenyl phosphate (C55-P) is an essential lipid carrier involved in the biosynthesis of cell surface carbohydrate polymers such as the peptidoglycan. C55-P is the result of the ... [more ▼]

•Background Undecaprenyl phosphate (C55-P) is an essential lipid carrier involved in the biosynthesis of cell surface carbohydrate polymers such as the peptidoglycan. C55-P is the result of the dephosphorylation of the undecaprenyl pyrophosphate (C55-PP) by specific phosphatases. In Escherichia coli this dephosphorylation can be performed by four integral membrane proteins, BacA, and three members of the type 2 phosphatidic acid phosphatase family (PAP2), PgpB, YbjG, and LpxT. •Objectives The aim of this project is to characterize YbjG and contributes to the understanding of the physiological role and mechanism of action of this enzyme in the C55-P metabolism. The C55-PP phosphatases could become an interesting target in the search for new molecules with antibacterial activity. •Methods In parallel the stability of YbjG and its activity against C15-PP were assessed in 94 different detergents. Moreover the enzymatic activity of YbjG was studied: substrate specificity, optimum pH and temperature, effect of detergent concentration. •Conclusions For the first time, YbjG has been purified and we show its ability to dephosphorylate C15-PP, DGPP and C55-PP in vitro with respectively decreasing efficiency. No activity has been detected on five other potential substrates (PPi, PA, C5-PP, G6P & PNPP). The phosphatase activity on C15-PP is maximum at pH 6,5 and 25 °C. Moreover Cymal6, LMNG, & ωUDM are good detergent both for the stability and the C15-PP phosphatase activity of YbjG, but approximately half of the 94 tested detergents show C15-PP phosphatase activity on the qualitative enzymatic test. [less ▲]

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See detailCharacterization of YKL165c a new essential gene of the yeast Saccharomyces cerevisiae.
Delbecq, X.; Godrie, Thérèse ULg; Portetelle, Daniel ULg et al

in Current Genetics (1999), 35

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See detailCharacterization of YKL165c a new essential gene of the yeast Saccharomyces cerevisiae.
Delbecq, Xavier; Godrie, Thérèse ULg; Portetelle, Daniel ULg et al

in Archives Internationales de Physiologie et de Biochimie (1999), 107

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See detailCharacterization study of Halaf ceramic production at Tell Amarna (Euphrates Valley, Syria)
Clop Garcia, X.; Alvarez Perez, A.; Hatert, Frédéric ULg

in Tunca, Önhan; Molist, Miquel (Eds.) Tell Amarna (Syrie) – La période de Halaf (2004)

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See detailCharacterization, dynamics and trophic ecology of macrofauna associated to seagrass macrophytodetritus accumulations (Calvi Bay, Mediterranean Sea)
Remy, François ULg

Doctoral thesis (2016)

Posidonia oceanica meadows are a major coastal Mediterranean ecosystem. Although highly productive this Mediterranean marine flower plant is not much consumed by herbivore organisms. During autumnal ... [more ▼]

Posidonia oceanica meadows are a major coastal Mediterranean ecosystem. Although highly productive this Mediterranean marine flower plant is not much consumed by herbivore organisms. During autumnal senescence, most (up to 90%) of the foliar primary production of P. oceanica ends in the “detrital compartment”. These dead leaves, also called “macrophytodetritus”, begin to degrade immediately inside the meadow, but a large amount will be rapidly exported to adjacent unvegetated accumulation zones, such as bare sand patches. Associated to drift macroalgae, living detached P. oceanica shoots, micro-organisms and fine sediment, these macrophytoderitus form what we call “exported P. oceanica litter”. This exported litter is a highly dynamic habitat for a whole community of invertebrates: meiofauna (38µm < size < 500µm) and macrofauna (size ≥ 500µm) on which we focused on. This dynamic nature of exported litter could play a major structuring role in terms of abundance, diversity and trophic ecology of this vagile macrofauna community at a seasonal, annual or spatial scale, but also during stochastic, brief and very strong perturbations: resource pulses. In this context, this PhD Thesis had 7 main objectives: i. Characterize for the first time exhaustively the macrofauna community. ii. Evaluate the spatiotemporal changes occurring at two different time scales in the detritus themselves and in the macrofauna community. iii. Relating these variations with measured environmental parameters. iv. Experimentally demonstrate the stratification occurring in a stable P. oceanica litter accumulation and the impact of this stratification on environmental conditions and on the macrofauna. v. Experimentally demonstrate the impact of resource pulses on the exported P. oceanica litter macrofauna community. vi. Unravel for the first time the global P. oceanica litter macrofauna food web using gut contents examinations and stable isotopes (C and N). vii. Evaluate the spatiotemporal changes of diet preferences of this community and determine if the observed changes are really synonym of true diet changes. This PhD Thesis demonstrated that exported P. oceanica litter was mainly composed of dead P. oceanica leaves (70-80%). It followed the natural annual cycle of P. oceanica and presented a maximum abundance in autumn just after leaves senescence. Measured environmental parameters also showed important variations linked to different factors such as force and direction of the wind, litter abundance and probably temperature. The continuous presence of the vagile macrofauna community throughout the year was demonstrated as well. This community was composed of 115 species and largely dominated by arthropods (77%), followed by annelids (12%) and mollusks (7%), while other taxa were much more anecdotal. Even if diversity is quite important, only a few species dominate largely the community. Indeed, 19 species represent more than 90% of the total abundance. One species to keep in mind: Gammarella fucicola, the most typical dominant and abundant amphipod species, representing 40-50% of the total abundance. In addition to this general pattern, litter vagile macrofauna presented important seasonal and annual variations. In the case of several species, these variations could be linked to some measured environmental parameters, but we had to recognize that most species did not seem to be influenced by environmental parameters measured during this PhD. However, oxygen concentration was the most important environmental parameter, potentially influencing 7 of the 19 most dominant and abundant species. The experimentally demonstrated physico-chemical stratification occurring inside litter accumulations was strongly related to this oxygen parameter. Indeed we demonstrated that several species were distributed in the different layers of a litter accumulation according to oxygen concentration and to a lesser extent, to nutrients concentration (mostly NH4). Besides, smaller time scale sampling allowed the identification of several stormy events corresponding to the definition of resource pulses. These pulses were demonstrated to play a potentially important role on the structure of the macrofauna community, favoring importantly the detritivore species and hypoxia tolerant species. It was also demonstrated that resource pulses could induce diet switching increasing the consumption of dead P. oceanica leaves just after the events, potentially increasing the litter decomposition by the macrofauna. The trophic web described in this PhD Thesis was composed of several trophic levels, from the primary herbivore/detritivore consumer, to second order carnivore predators. Different dietary preferences were highlighted, but major information was that dead P. oceanica leaves were ingested by a majority (85%) of the sampled species. Moreover, stable isotope analysis confirmed that P. oceanica litter was assimilated by most primary consumers and this “detrital signal” could be identified to the upper trophic levels, which is an argument in favor of the importance of macrofauna as major dead P. oceanica leaves decomposers. This also highlighted their potential role in terms of organic matter transfer from the P. oceanica meadow itself to the Mediterranean coastal food webs. Seasonal variations were observed in terms of trophic niches, and SIAR mixing model confirmed that this variability was sometimes caused by real diet modifications, potentially linked to the variable availability of food sources. This PhD Thesis, combining standardized sampling at two different time scales, trophic web analysis (gut contents and stable isotopes) and original experimentation allowed us to describe a diverse and abundant macrofauna community associated to P. oceanica exported litter, its temporal variations, potential responses to resource pulses as well as the link existing between some species and measured environmental parameters. This PhD also described the food web of this community and demonstrated the importance of dead P. oceanica leaves as food source for many invertebrates composing this community. These invertebrates thus seemed to play an important role in both litter decomposition and organic matter flux from the P. oceanica meadow to the Mediterranean coastal food webs. [less ▲]

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See detailCharacterizations by automorphism groups of some rank 3 buildings - I. Some properties of half strongly-transitive triangle buildings
Van Maldeghem, H.; Van Steen, Kristel ULg

in Geometriae Dedicata (1998), 73(2), 119-142

In a sequence of papers, we will show that the existence of a (half) strongly-transitive automorphism group acting on a locally finite triangle building Delta forces Delta to be one of the examples ... [more ▼]

In a sequence of papers, we will show that the existence of a (half) strongly-transitive automorphism group acting on a locally finite triangle building Delta forces Delta to be one of the examples arising from PSL3(K) for a locally finite local skewfield K. Furthermore, we introduce some Moufang-like conditions in affine buildings of rank 3, and characterize those examples arising from algebraic,classical or mixed type groups over a local field. In particular, we characterize the p-adic-like affine rank 3 buildings by a certain p-adic Moufang condition, and show that such a condition has zero probability to survive in hyperbolic rank 3 buildings. This shows that a construction of hyperbolic buildings as analogues of p-adic affine buildings is very unlikely to exist. Mathematics Subject Classifications (1991): 51E24, 51C05. [less ▲]

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See detailCharacterizations by automorphism groups of some rank 3 buildings - II: A half strongly-transitive locally finite triangle building is a Bruhat-Tits building
Van Maldeghem, H.; Van Steen, Kristel ULg

in Geometriae Dedicata (1999), 74(2), 113-133

We complete the proof of the fact that every locally finite triangle building Delta with a half strongly-transitive automorphism group G (e.g., this happens when Delta is defined via a (B, N)-pair in G ... [more ▼]

We complete the proof of the fact that every locally finite triangle building Delta with a half strongly-transitive automorphism group G (e.g., this happens when Delta is defined via a (B, N)-pair in G) is a Bruhat-Tits building associated with a classical linear group over a locally finite local skewfield. [less ▲]

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See detailCharacterizations by automorphism groups of some rank 3 buildings - IV: Hyperbolic p-adic Moufang buildings of rank 3
Van Maldeghem, H.; Van Steen, Kristel ULg

in Geometriae Dedicata (1999), 75(2), 115-122

In this paper, we introduce the p-adic Moufang condition for hyperbolic buildings of rank 3. It is the most obvious and simplest generalization of the p-adic Moufang condition for affine buildings ... [more ▼]

In this paper, we introduce the p-adic Moufang condition for hyperbolic buildings of rank 3. It is the most obvious and simplest generalization of the p-adic Moufang condition for affine buildings, introduced in Part III of this sequence of papers. We show that p is very restricted, which confirms (but does not prove) the conjecture that no p-adic analogue is possible for the construction of Moufang (hyperbolic) buildings by Ronan and Tits. [less ▲]

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