Browsing
     by title


0-9 A B C D E F G H I J K L M N O P Q R S T U V W X Y Z

or enter first few letters:   
OK
Full Text
Peer Reviewed
See detailThe Critical Neighbourhood Range for Asymptotic Overlay Connectivity in Ad Hoc Networks
Calomme, Sandrine; Leduc, Guy ULg

in Ad Hoc & Sensor Wireless Networks (2006), 2(2), 169-187

We first motivate the use of ad hoc overlays. In particular, we argue that overlay routing could play a role in the spreading of ad hoc networks. We then define a simple criterion for neighbourhood: two ... [more ▼]

We first motivate the use of ad hoc overlays. In particular, we argue that overlay routing could play a role in the spreading of ad hoc networks. We then define a simple criterion for neighbourhood: two overlay nodes are neighbours if and only if there exists a path between them of at most R hops, and R is called the (overlay) neighbourhood range. A small R may result in a disconnected overlay, while an unnecessarily large R would generate extra control traffic. We are interested in the minimum R ensuring overlay connectivity, the so-called critical R. We study conditions on R to achieve asymptotic connectivity of the overlay almost surely, i.e. connectivity with probability 1 when the number of nodes in the underlying ad hoc network tends to infinity (so-called dense networks) or when the size of the field tends to infinity (socalled sparse networks), under the hypothesis that the underlying ad hoc network is itself asymptotically almost surely connected. For dense networks, we derive a necessary and sufficient condition on R, and for sparse networks we derive distinct necessary and sufficient conditions that are however asymptotically tight. These conditions, though asymptotic, shed some light on the relation linking the critical R to the number of nodes n, the field size the radio transmission range r and the overlay density D (i.e., the proportion of overlay nodes). These conditions can be considered as approximations when the number of nodes (resp. the field) is large enough. Since r is considered as a function of n or l , we are able to study the impact of topology control mechanisms, by showing how the shape of this function impacts the critical R. [less ▲]

Detailed reference viewed: 29 (4 ULg)
Full Text
Peer Reviewed
See detailThe Critical Neighbourhood Range for Asymptotic Overlay Connectivity in Dense Ad Hoc Networks
Calomme, Sandrine; Leduc, Guy ULg

in Challenges in Ad Hoc Networking (2005, June)

We define, for an overlay built on top of an ad hoc network, a simple criterion for neighbourhood: two overlay nodes are neighbours if and only if there exists a path between them of at most R hops, and R ... [more ▼]

We define, for an overlay built on top of an ad hoc network, a simple criterion for neighbourhood: two overlay nodes are neighbours if and only if there exists a path between them of at most R hops, and R is called the (overlay) neighbourhood range. A small R may result in a disconnected overlay, while an unnecessarily large R would generate extra control traffic. We are interested in the minimum R ensuring overlay connectivity, the so-called critical R. We derive a necessary and sufficient condition on R to achieve asymptotic connectivity of the overlay almost surely, i.e. connectivity with probability 1 when the number of overlay nodes tends to infinity, under the hypothesis that the underlying ad hoc network is itself asymptotically almost surely connected. This condition, though asymptotic, sheds some light on the relation linking the critical R to the number of nodes n, the normalized radio transmission range r and the overlay density D (i.e., the proportion of overlay nodes). This condition can be considered as an approximation when the number of nodes is large enough. Since r is considered as a function of n, we are able to study the impact of topology control mechanisms, by showing how the shape of this function impacts the critical R. [less ▲]

Detailed reference viewed: 13 (2 ULg)
Full Text
Peer Reviewed
See detailCritical opalescence points to thermodynamic instability:relevance to small-angle X-ray scattering of resorcinol–formaldehyde gel formation at low pH
Gommes, Cédric ULg; Job, Nathalie ULg; Pirard, Jean-Paul ULg et al

in Journal of Applied Crystallography (2008), 41(4), 663-668

During the formation at low pH of resorcinol–formaldehyde gels with a structure in the micrometre range, small-angle X-ray scattering exhibits a nonmonotonic intensity variation as a function of reaction ... [more ▼]

During the formation at low pH of resorcinol–formaldehyde gels with a structure in the micrometre range, small-angle X-ray scattering exhibits a nonmonotonic intensity variation as a function of reaction time. The data are analyzed in terms of scattering by statistical fluctuations of polymer concentration, the amplitude of which is maximal close to the critical point for phase separation between polymer and solvent. The data do not carry any morphological information, but they unambiguously show that the driving force of the gel formation is a thermodynamic instability of the polymerizing solution. [less ▲]

Detailed reference viewed: 73 (17 ULg)
Full Text
Peer Reviewed
See detailCritical parameters for the partial coalescence of a droplet
Gilet, Tristan ULg; Mulleners, Karen; Lecomte, Jean-Paul et al

in Physical Review E (2007), 75(3, Pt 2), 36303

The partial coalescence of a droplet onto a planar liquid-liquid interface is investigated experimentally by tuning the viscosities of both liquids. The problem mainly depends on four dimensionless ... [more ▼]

The partial coalescence of a droplet onto a planar liquid-liquid interface is investigated experimentally by tuning the viscosities of both liquids. The problem mainly depends on four dimensionless parameters: The Bond number (gravity vs surface tension), the Ohnesorge numbers (viscosity in both fluids vs surface tension), and the density relative difference. The ratio between the daughter droplet size and the mother droplet size is investigated as a function of these dimensionless numbers. Global quantities such as the available surface energy of the droplet have been measured during the coalescence. The capillary waves propagation and damping are studied in detail. The relation between these waves and the partial coalescence is discussed. Additional viscous mechanisms are proposed in order to explain the asymmetric role played by both viscosities. [less ▲]

Detailed reference viewed: 49 (10 ULg)
Full Text
Peer Reviewed
See detailCritical points and reaction paths characterization on a potential energy hypersurface
Ramquet, Marie-Noëlle; Dive, Georges ULg; Dehareng, Dominique ULg

in Journal of Chemical Physics (2000), 112(11), 4923-4934

Most of the time, the definitions of minima, saddle points or more generally order p (p=0,...,n) critical points, do not mention the possibility of having zero Hessian eigenvalues. This feature reflects ... [more ▼]

Most of the time, the definitions of minima, saddle points or more generally order p (p=0,...,n) critical points, do not mention the possibility of having zero Hessian eigenvalues. This feature reflects some flatness of the potential energy hypersurface in a special eigendirection which is not often taken into account. Thus, the definitions of critical points are revisited in a more general framework within this context. The concepts of bifurcation points, branching points, and valley ridge inflection points are investigated. New definitions based on the mathematical formulation of the reaction path are given and some of their properties are outlined. (C) 2000 American Institute of Physics. [S0021-9606(00)01110-7]. [less ▲]

Detailed reference viewed: 27 (0 ULg)
Peer Reviewed
See detailCritical points for Salmonella contamination during slaughter process in Belgian slaughterhouses.
De Saedeleer, L.; Maes, D.; Dewulf, J. et al

in International Pig Veterinary Society Congress (2006, July)

Detailed reference viewed: 11 (0 ULg)
Full Text
See detailCritical points in glucosinolates analysis in seed and plant tis Critical points in glucosinolates analysis in seed and plant tissues by HPLC of desulfo-derivatives
Leoni, O.; Iori, R.; Wathelet, Jean-Paul ULg et al

Poster (2004)

In the EU the ISO 9167-1 is the reference method for glucosinolates content determination in rapeseed. This method is widely used also for other seeds or Brassica plant tissues analysis also in order to ... [more ▼]

In the EU the ISO 9167-1 is the reference method for glucosinolates content determination in rapeseed. This method is widely used also for other seeds or Brassica plant tissues analysis also in order to the large diffusion of HPLC instrumentation in analytical laboratories. Anyway, in our experience the use of this method has revealed some critical points which can considerably affect the final result, thus when this method is used to analyse materials different from seeds of B. napus some methodological modifications must be done especially in reason of the kind of glucosinolate present in the sample. [less ▲]

Detailed reference viewed: 32 (1 ULg)
Full Text
Peer Reviewed
See detailCritical Re-Examination of the Distribution of Aromatase-Immunoreactive Cells in the Quail Forebrain Using Antibodies Raised against Human Placental Aromatase and against the Recombinant Quail, Mouse or Human Enzyme
Foidart, Agnès ULg; Reid, J.; Absil, Philippe ULg et al

in Journal of Chemical Neuroanatomy (1995), 8(4), 267-82

Mouse and quail aromatase cDNAs were isolated from libraries of mouse ovary and quail brain by using a human aromatase cDNA fragment (hA-24) as a probe. These three cDNAs were inserted into plasmid ... [more ▼]

Mouse and quail aromatase cDNAs were isolated from libraries of mouse ovary and quail brain by using a human aromatase cDNA fragment (hA-24) as a probe. These three cDNAs were inserted into plasmid vectors and expressed in Escherichia coli. Antisera against these purified recombinant proteins were raised in rabbit and purified by ammonium sulfate fractionation and affinity chromatography. The three antibodies directed against recombinant human, mouse and quail proteins were used to visualize aromatase-immunoreactive cells in the quail brain. They were compared with the antibody raised against human placental aromatase used in previous experiments and with another antibody recently developed by similar methods. The signal obtained with all antibodies was completely abolished by preadsorption with the homologous recombinant antigens and the signal produced by the two antibodies raised against placental aromatase was similarly abolished by a preadsorption with recombinant quail aromatase. The antibodies raised against recombinant proteins identified the major groups of aromatase cells previously described in the quail brain. The antibodies directed against the mouse and quail antigen identified more positive cells and stained them more densely than the antibodies raised against human recombinant antigen or purified placental aromatase. The new cell groups identified by the antibody raised against quail recombinant aromatase were located in an area ventral to the fasciculus prosencephali lateralis, the nucleus accumbens, the paleostriatum ventrale, the nucleus taeniae, the area around the nucleus ovoidalis, the caudal tuber and the mesencephalic central gray. A critical re-examination of the distribution and nomenclature of the aromatase-positive cells is proposed based on these new findings. [less ▲]

Detailed reference viewed: 13 (2 ULg)
Full Text
Peer Reviewed
See detailCritical Reflections on the Treaty on the Non-Proliferation of Nuclear Weapons
Michel, Quentin ULg

in Nuclear Law Bulletin (2007)

Detailed reference viewed: 12 (1 ULg)
Full Text
Peer Reviewed
See detailCritical Review of Near-Infrared Spectroscopic Methods Validations in Pharmaceutical Applications
De Bleye, Charlotte ULg; Chavez, Pierre-François ULg; Mantanus, Jérôme ULg et al

in Journal of Pharmaceutical & Biomedical Analysis (2012), 69

Based on the large number of publications reported over the past five years, near-infrared spectroscopy (NIRS) is more and more considered an attractive and promising analytical tool regarding Process ... [more ▼]

Based on the large number of publications reported over the past five years, near-infrared spectroscopy (NIRS) is more and more considered an attractive and promising analytical tool regarding Process Analytical Technology and Green Chemistry. From the reviewed literature, few of these publications present a thoroughly validated NIRS method even if some guidelines have been published by different groups and regulatory authorities. However, as any analytical method, the validation of NIRS method is a mandatory step at the end of the development in order to give enough guarantees that each of the future results during routine use will be close enough to the true value. Besides the introduction of PAT concepts in the revised document of the European Pharmacopoeia (2.2.40) dealing with near-infrared spectroscopy recently published in Pharmeuropa, it agrees very well with this mandatory step. Indeed, the latter suggests to use similar analytical performance characteristics than those required for any analytical procedure based on acceptance criteria consistent with the intended use of the method. In this context, this review gives a comprehensive and critical overview of the methodologies applied to assess the validity of quantitative NIRS methods used in pharmaceutical applications. [less ▲]

Detailed reference viewed: 150 (59 ULg)
Peer Reviewed
See detailA critical review of surgery techniques for implanting telemetry devices into the body cavity of fish
Baras, Etienne; Birtles, Cymon; Westerloppe, Luc et al

Conference (1996, August)

Based on literature survey and personal experience, this paper presents a critical review of surgery procedures to implant telemetry devices (transmitters, transponders) into the body cavity of fish ... [more ▼]

Based on literature survey and personal experience, this paper presents a critical review of surgery procedures to implant telemetry devices (transmitters, transponders) into the body cavity of fish species. It debates on the relative adequacy of techniques which may compromise or enhance tagging success with respect to fish health and transmitter retention: anaesthesia, incision (position and length of incision), transmitter features (size and weight ratios, coating), ways of closing the incision (stitches, staples, adhesives), prophylaxy, pre- and postoperative care. Behavioural and physiological biases originating from tagging or internal presence of the transmitter are reviewed, evaluated and integrated to determine the actual duration of the post-operative perturbation and subsequent validation of telemetry data. [less ▲]

Detailed reference viewed: 156 (10 ULg)
Full Text
Peer Reviewed
See detailCritical Review: Biological functions of thiamine derivatives: Focus on non-coenzyme roles
Bettendorff, Lucien ULg; Wins, Pierre

in OA Biochemistry (2013), 1(1), 10

Thiamine (vitamin B1) is mainly known for its diphosphorylated derivatives (ThDP), an essential coenzyme in energy metabolism. However non-coenzyme roles have been suggested for this vitamin for many ... [more ▼]

Thiamine (vitamin B1) is mainly known for its diphosphorylated derivatives (ThDP), an essential coenzyme in energy metabolism. However non-coenzyme roles have been suggested for this vitamin for many years. Such roles have remained hypothetical, but recent data from various sources have shed a new light on this hypothesis. First, the existence of other phosphorylated thiamine derivatives, most prominently thiamine triphosphate (ThTP) and adenosine thiamine triphosphate (AThTP) can reach significant levels in E. coli, respectively during amino acid starvation and energy stress. Though much less is known about these compounds in animals, mammalian cells contain a highly specific soluble thiamine triphosphatase controlling cytosolic ThTP concentrations. Second, there is now growing evidence in favour of the existence of thiamine-binding proteins with specific roles in the nervous system, possibly in the regulation of in neurotransmitter release. Thiamine and some of its synthetic precursors with higher bioavailability have beneficial effects in several models of Alzheimer’s disease and may be beneficial for patients suffering from Alzheimer's or Parkinson's diseases. These effects might be related to non-coenzyme roles of thiamine, possibly involving thiamine-binding proteins. [less ▲]

Detailed reference viewed: 40 (3 ULg)
Full Text
Peer Reviewed
See detailThe critical role of carbohydrate administration in safe, effective TGC
PREISER, Jean-Charles ULg; Suhaimi, F; Chase, JG et al

in Clinical Nutrition (2010), 5 (Suppl 2):111

Detailed reference viewed: 8 (2 ULg)
Full Text
Peer Reviewed
See detailA critical role of plastidial glycolytic glyceraldehyde-3-phosphate dehydrogenase in the control of plant metabolism and development
Muñoz-Bertomeu, Jesús; Cascales - Miñana, Borja ULg; Alaiz, Manuel et al

in Plant Signaling & Behavior (2010), 5(1), 67-69

Glycolysis is a central metabolic pathway that provides energy and generates precursors for the synthesis of primary metabolites such as amino acids and fatty acids.1-3 In plants, glycolysis occurs in the ... [more ▼]

Glycolysis is a central metabolic pathway that provides energy and generates precursors for the synthesis of primary metabolites such as amino acids and fatty acids.1-3 In plants, glycolysis occurs in the cytosol and plastids, which complicates the understanding of this essential process.1 As a result, the contribution of each glycolytic pathway to the specific primary metabolite production and the degree of integration of both pathways is still unresolved. The glycolytic glyceraldehyde-3-phosphate dehydrogenase (GAPDH) catalyzes the conversion of glyceraldehyde-3-phosphate to 1,3-bisphosphoglycerate. Both cytosolic (GAPCs) and plastidial (GAPCps) GAPDH activities have been described biochemically. But, up to now, little attention had been paid to GAPCps, probably because they have been considered as "minor isoforms" that catalyze a reversible reaction in plastids where it has been assumed that key glycolytic intermediates are in equilibrium with the cytosol. In the associated study,4 we have elucidated the crucial role of Arabidopsis GAPCps in the control of primary metabolism in plants. GAPCps deficiency affects amino acid and sugar metabolism and impairs plant development. Specifically, GAPCp deficiency affects the serine supply to roots, provoking a drastic phenotype of arrested root development. Also, we show that the phosphorylated serine biosynthesis pathway is critical to supply serine to non-photosynthetic organs such as roots. These studies provide new insights of the contribution of plastidial glycolysis to plant metabolism and evidence the complex interactions existing between metabolism and development. © 2010 Landes Bioscience. [less ▲]

Detailed reference viewed: 3 (1 ULg)
Full Text
Peer Reviewed
See detailCritical role of tryptophan 154 for the activity and stability of class D beta-lactamases.
Baurin, Stephane; Vercheval, Lionel ULg; Bouillenne, Fabrice ULg et al

in Biochemistry (2009), 48(47), 11252-63

The catalytic efficiency of the class D beta-lactamase OXA-10 depends critically on an unusual carboxylated lysine as the general base residue for both the enzyme acylation and deacylation steps of ... [more ▼]

The catalytic efficiency of the class D beta-lactamase OXA-10 depends critically on an unusual carboxylated lysine as the general base residue for both the enzyme acylation and deacylation steps of catalysis. Evidence is presented that the interaction between the indole group of Trp154 and the carboxylated lysine is essential for the stability of the posttranslationally modified Lys70. Substitution of Trp154 by Gly, Ala, or Phe yielded noncarboxylated enzymes which displayed poor catalytic efficiencies and reduced stability when compared to the wild-type OXA-10. The W154H mutant was partially carboxylated. In addition, the maximum values of k(cat) and k(cat)/K(M) were shifted toward pH 7, indicating that the carboxylation state of Lys70 is dependent on the protonation level of the histidine. A comparison of the three-dimensional structures of the different proteins also indicated that the Trp154 mutations did not modify the overall structures of OXA-10 but induced an increased flexibility of the Omega-loop in the active site. Finally, the deacylation-impaired W154A mutant was used to determine the structure of the acyl-enzyme complex with benzylpenicillin. These results indicate a role of the Lys70 carboxylation during the deacylation step and emphasize the importance of Trp154 for the ideal positioning of active site residues leading to an optimum activity. [less ▲]

Detailed reference viewed: 51 (11 ULg)
Full Text
Peer Reviewed
See detailCritical specific stream power in gravel-bed rivers
Petit, François ULg; Gob, Frédéric ULg; Houbrechts, Geoffrey ULg et al

in Geomorphology (2005), 69(1-4), 92-101

Experiments with marked pebbles were carried out on different sized rivers of the Belgian Ardenne (catchment areas varying from less than I km(2) to 2700 km(2)). Specific stream power required to cause ... [more ▼]

Experiments with marked pebbles were carried out on different sized rivers of the Belgian Ardenne (catchment areas varying from less than I km(2) to 2700 km(2)). Specific stream power required to cause bedload movement was evaluated and critical values were obtained. Three types of relationship between critical specific stream power (omega(0)) and grain size (D) were established. The values for coo in the largest river (the Ourthe) were the lowest and were close to the values obtained for mountainous rivers carrying large boulders. In medium sized rivers (catchment area between 40 and 500 km(2)), the critical unit stream power was higher. It is likely that it is due to the bedform's greater resistance. This resistance would use up some of the energy that can cause movement and transport of bedload. The amount of resistance of the bedform can be expressed as bedform shear stress (tau ''), determined by the relationship between grain shear stress (tau'-that determines movement and transport of the bedload) and the total shear stress (tau). This ratio varies between 0.4 and 0.5 in the medium sized rivers, compared to 0.7 in the Ourthe. In headwater streams (less than 20 km(2)), there is greater loss of energy due to bedform resistance (tau'/tau < 0.3). Critical specific stream power is higher in this third type of river than in the other two. (c) 2005 Elsevier B.V. All rights reserved. [less ▲]

Detailed reference viewed: 186 (26 ULg)
Full Text
Peer Reviewed
See detailCritical state modelling of crossed field demagnetisation in HTS materials
Swartz, J. P.; Mc Culloch, M. D.; Pecher, R. et al

in Andreone, A.; Pepe, G. P.; Cristiano, R. (Eds.) et al Applied Superconductivity 2003 (Proceedings of the 6th European Conference on Applied Superconductivity) (2004)

Large magnetic fields can be trapped in high temperature superconductor material, enabling their use as permanent magnets in various applications. It has, however, been observed that these materials ... [more ▼]

Large magnetic fields can be trapped in high temperature superconductor material, enabling their use as permanent magnets in various applications. It has, however, been observed that these materials experience a decay in magnetisation when a field is applied in a direction transverse to the trapped field. This paper presents the results of critical state modelling of an infinite slab of superconductor that is first fully magnetised and then exposed to magnetic field in the transverse direction. The bean and double critical state model are implemented and the results compared to each other and to that of physical experiment. The convergence of the decay is investigated as well as the effect of the magnitude of the crossed field on the final decay value. Diamagnetic and paramagnetic initial conditions are applied to the material and the results used to compare the accuracy of the bean and double critical state model. [less ▲]

Detailed reference viewed: 28 (4 ULg)
Full Text
Peer Reviewed
See detailA Critical Study of Primate Reintroduction Projects in the Mesoamerican Region.
Martin, Sarah ULg; Huynen, Marie-Claude ULg; Libois, Roland ULg

Poster (2008)

Very little is known about primate reintroduction projects in Mesoamerica. The aim of this study was to focus on existing projects concerning primate re-introductions, conservation-introduction ... [more ▼]

Very little is known about primate reintroduction projects in Mesoamerica. The aim of this study was to focus on existing projects concerning primate re-introductions, conservation-introduction, translocation, as well as on reinforcement-supplementation of parallel initiatives. In order to create a database, a survey was sent to a panel of scientists in Mexico, Belize, Guatemala, Honduras, El Salvador, Nicaragua, Costa Rica and Panama, and we visited five projects in Costa Rica from March to August 2006. A total of 19 projects were found: Costa Rica hosted the higher number (7) while Salvador and Nicaragua did not host any. Fourteen out of those 19 projects concerned confiscated animals. Six of the 7 Costa Rican projects used confiscated primates; the other ones came from wild populations or were born in captivity. Alouatta palliata and Ateles geoffroyi are the most common species subject to reintroduction effort in the Mesoamerican region. A wide range of factors seem to influence reintroduction success such as: the project’s budget, the release site, the mode of transportation, the caging setting, the support from local communities, the presence of environmental education programs, but also the age of primates, etc. Each project seems to work as a completely separated entity, with its own definition of reintroduction success and its own policy. There’s no communication between the projects, no matter if they are based in the same country or work on the same species. A reintroduction guideline for this region should be established as well as a regional network coordinating the information. [less ▲]

Detailed reference viewed: 108 (11 ULg)
Peer Reviewed
See detailCritical survey of hierarchical methods for state estimation of electric power systems
Van Cutsem, Thierry ULg; Pavella, Mania ULg

in IEEE Transactions on Power Apparatus and Systems (1983), 102

Detailed reference viewed: 11 (0 ULg)