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Peer Reviewed
See detailCharacterization of somatostatin transactivating factor-1, a novel homeobox factor that stimulates somatostatin expression in pancreatic islet cells.
Peers, Bernard ULg; Johnson, T.; Ferreri, K. et al

in Molecular Endocrinology (1993), 7(10), 1275-83

The endocrine pancreas consists of several differentiated cell types that are distinguished by their selective expression of peptide hormones such as insulin, glucagon, and somatostatin. Although a number ... [more ▼]

The endocrine pancreas consists of several differentiated cell types that are distinguished by their selective expression of peptide hormones such as insulin, glucagon, and somatostatin. Although a number of homeobox-type factors have been proposed as key regulators of individual peptide genes in the pancreas, their cellular distribution and relative abundance remain uncharacterized. Also, their overlapping DNA binding specificities have further obscured the regulatory functions these factors perform during development. In this report we characterize a novel homeobox-type somatostatin transactivating factor termed STF-1, which is uniformly expressed in cells of the endocrine pancreas and small intestine. The 283-amino acid STF-1 protein binds to tissue-specific elements within the somatostatin promoter and stimulates somatostatin gene expression both in vivo and in vitro. Remarkably, STF-1 comprises the predominant tissue-specific element-binding activity in nuclear extracts from somatostatin-producing pancreatic islet cells, suggesting that this protein may have a primary role in regulating peptide hormone expression and specifying endocrine cell lineage in the developing gut. [less ▲]

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See detailCharacterization of some functions stable for positive linear transformations
Marichal, Jean-Luc; Mathonet, Pierre ULg; Tousset, E.

in Fuzzy Sets & Systems (1999), 102

This paper deals with a characterization of a class of aggregation operators. This class concerns operators which are symmetric, increasing, stable for the same positive linear transformations and present ... [more ▼]

This paper deals with a characterization of a class of aggregation operators. This class concerns operators which are symmetric, increasing, stable for the same positive linear transformations and present a property close to the bisymmetry property: the ordered bisymmetry property. It is proved that the class investigated contains exactly the ordered weighted averaging operators (OWA) introduced by Yager in 1988. [less ▲]

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See detailCharacterization of spatio-temporal organization of slow waves during human NREM sleep
Schrouff, Jessica ULg; Leclercq, Yves ULg; Foret, Ariane et al

Poster (2009, December 14)

Sleep is a behavior commonly observed in a large number of animal species. However, neuroscientists still poorly understand the meaning of this loss of consciousness absolutely needed for life. In the ... [more ▼]

Sleep is a behavior commonly observed in a large number of animal species. However, neuroscientists still poorly understand the meaning of this loss of consciousness absolutely needed for life. In the present work, we established different methods to characterize the Slow Wave Sleep most recognizable patterns: the Slow Waves (SWs). Since the anatomical structure of white matter tracts that connect various brain regions is not random and thus must constraint the propagation of waves (Hagmann et al., 2008), our basic hypothesis was that large white matter bundles would bias the propagation of SW along specific patterns, which could be identified in homogeneous clusters of waves. To investigate our hypothesis, SWs were detected automatically on the three first periods of SWS using an algorithm based on Massimini et al., 2004. They were then clustered using a two steps procedure involving a hierarchical clustering based on delay maps and a k-means clustering based on the SWs potential in a given time interval around the maximum power of the SW negative peak. To compute the relevance of the final clusters, a mathematical criterion was implemented as well as a visual check. Results of the multisubjects study showed that only bad quality and small clusters could be obtained, suggesting that there is no particular organization of SWs across the night and inforcing the hypothesis that SWs are local phenomena, each one decreasing the homeostatic pressure in only one specific area. [less ▲]

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See detailCharacterization of spontaneous bone marrow recovery after sublethal total body irradiation: importance of the osteoblastic/adipocytic balance.
Poncin, Géraldine ULg; Beaulieu, Aurore ULg; Humblet, Chantal ULg et al

in PLoS ONE (2012), 7(2), 30818

Many studies have already examined the hematopoietic recovery after irradiation but paid with very little attention to the bone marrow microenvironment. Nonetheless previous studies in a murine model of ... [more ▼]

Many studies have already examined the hematopoietic recovery after irradiation but paid with very little attention to the bone marrow microenvironment. Nonetheless previous studies in a murine model of reversible radio-induced bone marrow aplasia have shown a significant increase in alkaline phosphatase activity (ALP) prior to hematopoietic regeneration. This increase in ALP activity was not due to cell proliferation but could be attributed to modifications of the properties of mesenchymal stem cells (MSC). We thus undertook a study to assess the kinetics of the evolution of MSC correlated to their hematopoietic supportive capacities in mice treated with sub lethal total body irradiation. In our study, colony-forming units - fibroblasts (CFU-Fs) assay showed a significant MSC rate increase in irradiated bone marrows. CFU-Fs colonies still possessed differentiation capacities of MSC but colonies from mice sacrificed 3 days after irradiation displayed high rates of ALP activity and a transient increase in osteoblastic markers expression while ppargamma and neuropilin-1 decreased. Hematopoietic supportive capacities of CFU-Fs were also modified: as compared to controls, irradiated CFU-Fs significantly increased the proliferation rate of hematopoietic precursors and accelerated the differentiation toward the granulocytic lineage. Our data provide the first evidence of the key role exerted by the balance between osteoblasts and adipocytes in spontaneous bone marrow regeneration. First, (pre)osteoblast differentiation from MSC stimulated hematopoietic precursor's proliferation and granulopoietic regeneration. Then, in a second time (pre)osteoblasts progressively disappeared in favour of adipocytic cells which down regulated the proliferation and granulocytic differentiation and then contributed to a return to pre-irradiation conditions. [less ▲]

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See detailCharacterization of spontaneous collagen fibrillogenesis in a cell-free and tension-free environment.
PIERARD, Gérald ULg; Hermanns-Lê, Trinh ULg; Delvenne, Philippe ULg et al

in Clinical & Experimental Dermatology (2013)

The collagen fibril packing that forms threads and bundles is poorly defined, despite the fact that it is important for distinct aspects of the adventitial and reticular dermis. The present study explored ... [more ▼]

The collagen fibril packing that forms threads and bundles is poorly defined, despite the fact that it is important for distinct aspects of the adventitial and reticular dermis. The present study explored an in vitro fibrillogenesis model using the property of heat polymerization. The process was performed on glass slides with mixtures of collagen I and III, and the material was viewed by scanning electron microscopy. In all instances, collagen I and III formed fibrils with regular sizes. The formation of threads was influenced by the relative proportions of collagen I and III; increasing the relative proportion of collagen I resulted in the formation of threads showing increasing variations in thickness. These findings are in line with the differential presentation and compositions of the different parts of the dermis. The possible interventions of stromal cells and of other macromoleules of the extracellular matrix were not considered in this study. [less ▲]

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See detailCHARACTERIZATION OF STONY SOILS’ HYDRAULIC PROPERTIES AND REPRESENTATIVE ELEMENTARY VOLUME USING FIELD, LABORATORY AND NUMERICAL EXPERIMENTS
Pichault, Mathieu ULg

Master's dissertation (2015)

Determining soil hydraulic properties is of major concern in various fields of study such as soil physics, hydrology, ecology and agronomy. Though stony soils are widespread across the globe, most studies ... [more ▼]

Determining soil hydraulic properties is of major concern in various fields of study such as soil physics, hydrology, ecology and agronomy. Though stony soils are widespread across the globe, most studies deal with gravel-free soils so that the literature describing the impact of stones on a soil’s hydraulic characteristics is still rather scarce. The aim of this study is to assess, through a case study of a clayey soil in Thailand, the effect of rock fragments on the main hydraulic characteristics, i.e. hydraulic conductivity and retention curves, and on related physical properties of the soil. This was done by means of field, laboratory and numerical experiments involving different amounts and types of coarse fragments. Results were compared with those predicted by several models assuming that stones are non-porous and only reduce the cross-sectional area available for water flow. These models further consider that the shape parameters of the retention and hydraulic conductivity curves are not dependent on the stoniness. We tested the validity of such assumptions. We did not find evidence against the assumption stating that stones might be considered as non-porous. However, our results suggest that the shape parameters of the retention curve vary according to the stone content. Furthermore, considering that stones only reduce the cross-sectional area available for water flow might also be ill-founded. We pointed out several significant drivers of the saturated hydraulic conductivity which are not considered by these models. First of all, the effect due to the creation of voids at the fine earth-stone interface combined with an increased difficulty to repack the fine earth can counteract and even overcome the effect of a reduced cross-sectional area in some cases. Moreover, the shape and the size of inclusions may also affect substantially hydraulic conductivity. Finally, we developed a code destined to quantify the representative elementary volume of soils containing different amounts of stones of various diameters. [less ▲]

Detailed reference viewed: 102 (29 ULg)
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See detailCharacterization of stream - aquifer interaction in carbonate rocks
Briers, Pierre ULg; Sohier, Catherine ULg; Schmit, Flore et al

Poster (2014, September 30)

Groundwater - surface water interactions play a fundamental role in terms of quantity and quality of water and in terms of ecological quality of rivers. Despite many research efforts and the necessity to ... [more ▼]

Groundwater - surface water interactions play a fundamental role in terms of quantity and quality of water and in terms of ecological quality of rivers. Despite many research efforts and the necessity to better understand such interactions in order to reach effective management of water resources, stream-aquifer exchanges remain poorly understood, in particular in fractured carbonate environments. [less ▲]

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See detailCharacterization of structures with a complex disposition of YBCO coated conductors for magnetic shielding applications
Wera, Laurent ULg; Fagnard, Jean-François ULg; Levin, G. A. et al

Poster (2013, September 16)

An efficient superconducting magnetic shield can be built as an assembly of YBCO 2G coated conductor sections. Each section is milled and placed around a cylindrical support in order to form a joint free ... [more ▼]

An efficient superconducting magnetic shield can be built as an assembly of YBCO 2G coated conductor sections. Each section is milled and placed around a cylindrical support in order to form a joint free superconducting loop where persistent currents can flow and provide a strong attenuation of a magnetic field. Our previous works have shown that this assembly is able to shield an axial quasi static (“DC”) magnetic field and that the shielding performances depend on the aspect ratio and the number of layers. The purpose of the present work is to study experimentally the shielding efficiency of several structures with a more complex orientation and position of YBCO coated conductors. Our aim is to design a magnetic shield that would be able to shield a magnetic field directed at any angle with respect to the superconducting loops. Such a structure can be obtained by placing pairs of coated conductors sections along three orthogonal axes. All experiments are carried out at 77K. The structure is subjected to a quasi-static (“DC”) magnetic field. A Hall probe measures the three components of the local magnetic induction inside the assembly as a function of the applied magnetic induction. The shielding efficiency of the structure is characterized as a function of (i) the magnetic field amplitude, (ii) the position of the Hall probe along the three axes, and (iii) the angles between the applied magnetic field and each axis. The experimental results allow us to determine the shielding efficiency in the central part of the new 3-axes structure. Although the shielding efficiency is lowered with respect to that of the traditional 1-axis-coil geometry, measurements at different field orientations allow us to identify the role played by each of the pairs of coils in screening the external magnetic field. [less ▲]

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See detailCharacterization of sugar beet pectic-derived oligosaccharides obtained by enzymatic hydrolysis.
Combo, Agnan Marie Michel ULg; Aguedo, Mario ULg; Quiévy, N et al

in International Journal of Biological Macromolecules (2013), 52(1), 148-156

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See detailCharacterization of superficial deposits using electrical resistivity tomography (ERT) and horizontal-to-vertical spectral ratio (HVSR) geophysical methods: A case study
Sauret, Elie; Beaujean, Jean; Nguyen, Frédéric ULg et al

in Journal of Applied Geophysics (2015), 121

In developing countries, superficial aquifers are potential water resources for irrigation in agriculture. Cost effective methodologies are required to characterize those deposits in order to identify ... [more ▼]

In developing countries, superficial aquifers are potential water resources for irrigation in agriculture. Cost effective methodologies are required to characterize those deposits in order to identify better locations for groundwater abstraction. This study has investigated the potential use of combined electrical resistivity tomography (ERT) and horizontal-to-vertical spectral ratio (HVSR) to characterize the heterogeneity and thickness of superficial deposits deployed along of a river. The ERT and HVSRmethods are non-invasive geophysical techniques, simple, efficient, robust and easy-to-use in alluvial environment contexts. Using these geophysicalmethods in the Kou basin in Burkina Faso (West Africa), a good correspondence is obtained between ERT images and resonance frequencies determined on theHVSR profiles perpendicular to the Kou River. The superficial deposits and the bedrock depth have been characterized and mapped. The role of faulting andmagmatic intrusions in the accumulation of fractured, deconsolidated andweathered bedrockmaterials and the filling of superficial deposits have been observed and highlighted. Froma hydrogeological point of view, the thickness of (clay-free) superficial deposits presents a relatively important groundwater reservoir and potentially high productivity. The ERT and HVSR were proven to be efficient and complementary methods in superficial deposit environment characterization, and a viable option for exploration of superficial deposits in terms of groundwater reservoir in environments where the bedrock exhibits strong lateral variation due to faulting or volcanic activities. [less ▲]

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See detailCharacterization of surface and porous properties of synthetic hybrid lamellar silica
Toussaint, Gilles ULg; Rodriguez, Miguel Angel; Cloots, Rudi ULg et al

in Journal of Non-Crystalline Solids (2011), 357

Synthetic lamellar silica and hybrid lamellar silicas have been prepared by liquid crystal templating, template extraction and silanization. The samples have been characterized by thermogravimetric ... [more ▼]

Synthetic lamellar silica and hybrid lamellar silicas have been prepared by liquid crystal templating, template extraction and silanization. The samples have been characterized by thermogravimetric analysis (TGA), carbon analysis, spectroscopy, X-ray diffraction (XRD) and nitrogen adsorption. The XRD analyses have shown that the lamellar periodic stacking is preserved for all samples. The quantity and type of organic molecules at the silica surface have been evaluated by carbon analysis, TGA and spectroscopy. The covalent grafting of the solvent used for extraction of the initial surfactant has been highlighted by these analyses. The nitrogen adsorption analyses have revealed three categories of pores and two types of samples. The initial lamellar silica exhibits a very low specific surface area and plate-like type of pores. The second type of samples is made up of the hybrid samples and the initial substrate from whom the surfactant has been extracted. These samples show a significantly higher specific surface area with interlamellar spaces corresponding to narrow-slit like mesopores around 4 nm. The nitrogen adsorption data analysis has highlighted the presence of micropores within the silica sheets. The difference of the specific surface is due to pore blocking by the surfactant impeding the access to nitrogen into interlamellar spaces and by the silanes covering the pores once the surface modified. The presence of micro and mesopores combined to a high BET specific surface of 612 m²/g makes these lamellar silicas interesting materials for catalysis applications. [less ▲]

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See detailCharacterization of synovial angiogenesis in osteoarthritis patients and its modulation by chondroitin sulfate
Lambert, Cécile ULg; Mathy-Hartert, Marianne; Dubuc, JE et al

in Arthritis Research & Therapy (2012), 14(2), 58

INTRODUCTION: This work aimed at comparing the production of inflammatory and pro- and anti-angiogenic factors by normal/reactive (N/R) or inflammatory (I) areas of the osteoarthritic synovial membrane ... [more ▼]

INTRODUCTION: This work aimed at comparing the production of inflammatory and pro- and anti-angiogenic factors by normal/reactive (N/R) or inflammatory (I) areas of the osteoarthritic synovial membrane. The effects of interleukin (IL)-1β and chondroitin sulfate (CS) on the expression of pro- and anti-angiogenic factors by synovial fibroblasts cells (SFC) were also studied. METHODS: Biopsies from N/R or from I areas of osteoarthritic synovial membrane were collected at the time of surgery. The inflammatory status of the synovial membrane was characterized by the surgeon according to macroscopic criteria, including the synovial vascularization, the villi formation and the hypertrophic aspect of the tissue. We assessed the expression of CD45, von Willebrand factor and vascular endothelial growth factor (VEGF) antigen by immunohistochemistry in both N/R and I biopsies. The production of IL-6, -8, VEGF and thrombospondin (TSP)-1 by N/R or I synovial cells was quantified by ELISA. SFC were cultured in the absence or in the presence of IL-1β (1 ng/ml) and with or without CS (10, 50, 200 μg/ml). Gene expression of pro-angiogenic factors (VEGF, basic fibroblast growth factor (bFGF), nerve growth factor (NGF), matrix metalloproteinase (MMP)-2 and angiopoietin (ang)-1) and anti-angiogenic factors (vascular endothelial growth inhibitor (VEGI), TSP-1 and -2) were determined by real time RT-PCR. Production of VEGI and TSP-1 was also estimated by ELISA. RESULTS: Immunohistochemistry showed the increase of lymphocyte infiltration, vascular density and VEGF expression in I compared to N/R synovial biopsies. Synovial cells from I areas produced more IL-6, IL-8 and VEGF but less TSP-1 than cells isolated from N/R synovial biopsies. The expression of pro-angiogenic factors by SFC was stimulated by IL-1β. A time dependent regulation of the expression of anti-angiogenic factor genes was observed. IL-1β stimulated the expression of anti-angiogenic factor genes but inhibited it after 24 h. CS reversed the inhibitory effect of IL-1β on anti-angiogenic factors, VEGI and TSP-1. CONCLUSIONS: We demonstrated that synovial biopsies from I areas expressed a pro-angiogenic phenotype. IL-1β induced an imbalance between pro- and anti-angiogenic factors in SFC and CS tended to normalize this IL-1β-induced imbalance, providing a new possible mechanism of action of this drug. [less ▲]

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See detailCharacterization of talcschist's weathering Materials in Henguegue (Cameroon)
Woguia, Damaris Laure ULg; Ngo Bidjeck, Louise Marie

Poster (2015, August 25)

Detailed reference viewed: 22 (10 ULg)
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See detailCharacterization of tap intensity for granular compaction
Ludewig, François ULg; Dorbolo, Stéphane ULg; Vandewalle, Nicolas ULg

in Powders and Grains 2009 (2009)

Detailed reference viewed: 17 (6 ULg)
See detailCHARACTERIZATION OF TEN STRAINS OF FILAMENTOUS CYANOBACTERIA FROM THE SOUTH SHETLAND ISLANDS, MARITIME ANTARCTICA
Kovacik, Lubomir; Pereira, Antonio; Dusinsky, Roman et al

Poster (2015, September 07)

The evolutionary relationships of ten Antarctic cyanobacterial strains of the order Oscillatoriales isolated from King George Island and Deception Island, South Shetland Islands were studied by a ... [more ▼]

The evolutionary relationships of ten Antarctic cyanobacterial strains of the order Oscillatoriales isolated from King George Island and Deception Island, South Shetland Islands were studied by a polyphasic approach. Phenotypic observations of the morphological features and genotypic analyses (16S rRNA and ITS sequences) were performed. Based on major phenotypic features, the strains were divided into four distinct morphotypes: Leptolyngbya borchgrevinkii (A), Leptolyngbya frigida (B), Phormidium autumnale (C) and Wilmottia murrayi (D). This morphological identification was in global agreement with the evolutionary relationships. According to the phylogenetic analysis, the ten strains were divided into two major clades, containing related strain sequences with Leptolyngbya morphotypes in one clade and with morphotypes corresponding to Phormidium, Wilmottia and Microcoleus spp. in the other clade. Each major clade was divided into two sub-clades. For the first time, the 16S rRNA gene sequence of a strain corresponding to the Leptolyngbya borchgrevinkii morphotype (A) was determined, on the basis of strain KOVACIK-ANT 1990/4. The closest sequence to our morphotype A is the clone Fr252 isolated from microbial mat of Antarctic Lake Fryxell. Morphotype B is closest to sequences assigned to Leptolyngbya frigida isolated from microbial mats of lakes in continental East Antarctica. Morphotype C belongs to a cluster including strains with morphotypes corresponding to Phormidium autumnale from Antarctica, but also from Europe. Morphotype D is grouped with sequences of the morphotype assigned to Wilmottia murrayi isolated from Antarctica. [less ▲]

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See detailCharacterization of the antimicrobial activity of mycosubtilin on the plasma membranes. A biomimetic approach
Nasir, Mehmet Nail ULg; Besson, Françoise

Poster (2010)

Mycosubtilin, an antimicrobial lipopeptide, is produced by Bacillus subtilis strains. It belongs to the iturin family, which is characterized by the presence of a peptide part, constituted of a constant ... [more ▼]

Mycosubtilin, an antimicrobial lipopeptide, is produced by Bacillus subtilis strains. It belongs to the iturin family, which is characterized by the presence of a peptide part, constituted of a constant chiral amino acid sequence cycled by a β-amino fatty acid (Fig. 1). As all the iturinic lipopeptides, mycosubtilin exhibits its biocide activities on cytoplasmic membrane of target cells [1]. Recently, the activity of mycosubtilin on pathogenic strains resistant to classical agents was shown [2]. However, despite many works focused on its structure and the optimization of its production, only a few studies are conducted to analyze mycosubtilin-membrane interactions. The purpose of our work was to better understand, at the molecular level, the mechanisms of the mycosubtilin activity on cytoplasmic membranes. Firstly, we modelled the mycosubtilin-membrane interactions by using biomimetic monolayers and their associated techniques (tensiometry and PM-IRRAS). After characterizing the interfacial properties of pure mycosubtilin [3], we used Langmuir films to investigate the mycosubtilin behavior when the lipopeptide reaches the external leaflet of the membrane. We found that the mycosubtilin adsorption to lipid monolayers depended on their lipid composition and the lipopeptide interaction with the membrane was facilitated by the presence of sterols. Then, we mimicked the insertion of the lipopeptide in the whole membrane by using multilamellar vesicles. FT-IR spectroscopy analysis showed that the interaction of mycosubtilin with the artificial membranes induced conformational changes of the lipopeptide only in the presence of sterol. 1. Maget-Dana R, Peypoux F. (1994) Toxicology 87:151-74. 2. Fickers P, Guez JS, Damblon C, Leclère V, Béchet M, Jacques P, Joris B. (2009) Appl. Environ. Microbiol. 75:4636-40. 3. Nasir MN, Thawani A, Kouzayha A, Besson F. (2010) Colloids Surf. B Biointerfaces 78 :17-23. [less ▲]

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See detailCharacterization of the Behaviour of a Simple Aeroservoelastic System with Control Nonlinearities
Dimitriadis, Grigorios ULg; Cooper, Jonathan E

in Journal of Fluids & Structures (2000), 14(8), 1173-1193

The characterization of the behaviour of nonlinear aeroelastic systems has become a very important research topic in the Aerospace Industry. However, most work carried to-date has concentrated upon ... [more ▼]

The characterization of the behaviour of nonlinear aeroelastic systems has become a very important research topic in the Aerospace Industry. However, most work carried to-date has concentrated upon systems containing structural or aerodynamic nonlinearities. The purpose of this paper is to study the stability of a simple aeroservoelastic system with nonlinearities in the control system and power control unit. The work considers both structural and control law nonlinearities and assesses the stability of the system response using bifurcation diagrams. It is shown that simple feedback systems designed to increase the stability of the linearized system also stabilize the nonlinear system, although their effects can be less pronounced. Additionally, a nonlinear control law designed to limit the control surface pitch response was found to increase the flutter speed considerably by forcing the system to undergo limit cycle oscillations instead of fluttering. Finally, friction was found to affect the damping of the system but not its stability, as long as the amplitude of the frictional force is low enough not to cause stoppages in the motion. [less ▲]

Detailed reference viewed: 20 (1 ULg)