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See detailFlow and sedimentation in shallow reservoirs
Dewals, Benjamin ULg

Scientific conference (2011, October 03)

Les recherches présentées ici portent sur la prédiction de la sédimentation dans des bassins rectangulaires peu profonds. Ceux-ci sont fréquemment utilisés en hydraulique urbaine et constituent une ... [more ▼]

Les recherches présentées ici portent sur la prédiction de la sédimentation dans des bassins rectangulaires peu profonds. Ceux-ci sont fréquemment utilisés en hydraulique urbaine et constituent une idéalisation pertinente de multiples configurations plus complexes. Des campagnes expérimentales complémentaires ont été menées de concert à l’Université de Liège ainsi que dans d’autres laboratoires européens. Ces modélisations physiques, réalisées sur fond fixe et mobile, ont été complétées par des simulations numériques tant hydrodynamiques qu’hydrosédimentaires. Les analyses ont d’emblée révélé la complexité des écoulements dans de tels bassins, qui présentent des recirculations asymétriques malgré la symétrie hydraulique et géométrique du dispositif. La typologie des écoulements est caractérisée par plusieurs transitions, de type « bifurcations », entre écoulement symétrique et écoulement dévié. Ce faisant, nous avons abouti à une unification des critères de prédiction du type d’écoulement pour des nombres de Reynolds élevés, la formulation proposée s’appliquant à l’ensemble des résultats expérimentaux connus dans la littérature. L’étude des dépôts et du taux de rétention des sédiments dans les bassins a démontré la corrélation forte entre ces paramètres et la configuration de l’écoulement, ce qui confirme a posteriori l’importance de critères prédictifs du type d’écoulement. Ces recherches ont finalement permis d’identifier des recommandations pratiques, destinées soit à éviter les instabilités d’écoulement lors du design de bassins ou, a contrario, à exploiter pleinement ces instabilités afin de maximiser l’efficacité du bassin (stockage ou décantation). [less ▲]

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See detailFlow and Transport Monitoring in Soils and Aquifers using Electrical Resistivity Tomography
Vanderborght, J.; Kemna, A.; Köstel, J. et al

(2007)

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See detailFlow and turbulence characterization as an onset for assessing the stability of gravel beds
Duma, Diana ULg; Erpicum, Sébastien ULg; Archambeau, Pierre ULg et al

in 7th International Conference on Fluvial Hydraulics (2014, September)

The flow characteristics, such as velocity profiles and turbulence intensities, are of high practical relevance in the assessment of riverbed stability. So far, the Shields diagram remains the most widely ... [more ▼]

The flow characteristics, such as velocity profiles and turbulence intensities, are of high practical relevance in the assessment of riverbed stability. So far, the Shields diagram remains the most widely accepted approach for defining the initiation of sediment motion. However, it faces a number of shortcomings. In principle, it is only valid for uniform flow conditions and, under non-uniform flow conditions, it fails to account properly for the influence of turbulence in sediment entrainment. In this paper, we focus on a more detailed description of quasi-uniform and non-uniform flow characteristics in the vicinity of the critical flow conditions for inception of motion of gravel beds. Laboratory experiments were designed, involving two configurations. First, the entire bottom of the flume was paved with stones of uniform diameter (8 or 15 mm), leading to quasi-uniform flow conditions. Second, the flume bottom was smooth upstream of the zone of measurement while the downstream part was covered with gravels, leading to a sudden smooth-to-rough transition. The flow velocity was obtained by acoustic measurements and the turbulence intensity was calculated for both configurations. By fitting the velocity profile to a modified logarithmic law, the shear velocity was estimated. Standard approaches for predicting the threshold of motion, initially developed for uniform flows, were compared to other methods, based on depth-averaged turbulence kinetic energy, recently proposed in literature for non-uniform flow conditions. [less ▲]

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See detailFlow bi-stability around stay cable's sheath: Impact of roughness and circularity defect in the critical regime
Benidir, Adel; Flamand, Olivier; Gaillet, Laurent et al

in Journal of Wind Engineering & Industrial Aerodynamics (in press)

The stay cables on cable-stayed bridges have been the subject of considerable research in order to understand the origins of the dry galloping phenomenon. Surface irregularity is one of the last ... [more ▼]

The stay cables on cable-stayed bridges have been the subject of considerable research in order to understand the origins of the dry galloping phenomenon. Surface irregularity is one of the last parameters that have not been thoroughly examined. This paper focuses on static wind tunnel tests on original High Density Polyethylene cable covers in a range of Reynolds numbers from the sub-critical regime to the critical, corresponding to values ranging from Re = 9.6x104 to Re = 3.3x105. The experiment consists in testing cable covers of various diameters in order to investigate the effect of surface irregularity (roughness and circularity defect) on the mechanism of dry galloping excitation. Previous studies reported that dry galloping is caused by the appearance of a negative pressure bubble on one side of the circular cylinder at the critical Reynolds number range, leading to a rapid drop in the drag coefficient and the appearance of a non-negligible lift force. The results of the present investigation demonstrate that there is a clear correlation between the single bubble pressure pattern and the circularity defect along the tube. They further show that surface roughness has little effect on the location of the bubble. The paper also treats the spatial and temporal correlation of the instantaneous pressure pattern along the tube with respect to the circularity defect. [less ▲]

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See detailFlow cytometric cerebrospinal fluid analysis in children
Häusler, M.; Sellhaus, B.; Schweizer, K. et al

in Pathology Research and Practice (2003), 199(10), 667-675

Flow cytometry (FC) is of increasing importance for the analysis of cerebrospinal fluid (CSF) lymphocytes because of its ability to detect a large spectrum of cellular characteristics (granularity, volume ... [more ▼]

Flow cytometry (FC) is of increasing importance for the analysis of cerebrospinal fluid (CSF) lymphocytes because of its ability to detect a large spectrum of cellular characteristics (granularity, volume, surface antigen expression) even in small amounts of cells. Data on CSF FC in children are very limited. Here, we summarize our 3-year experience of CSF FC routinely performed in pediatric patients with assumed inflammatory central nervous system (CNS) disease. Among 109 samples sent for analysis, flow cytometric detection of major leukocyte subsets was possible in 78% (85 out of 109), which exceeds the 31% rate of our retrospective microscopic pediatric control group. Apart from physiologic lymphocytes (100%) or monocytes (48%), 11 out of these 85 samples showed granulocytes, two showed proliferated monocytes, and nine displayed proliferated lymphocytes. In most children, the proliferated lymphocytes consisted of a polyclonal population of CD4+ and CD8+ T cells. Compared with literature data, eight children showed abnormally composed lymphocyte subsets (surface antigen expression) within the main lymphocyte population. However, none of these changes was specific for distinct diseases or allowed a distinction between patients with and without primary inflammatory processes. These data suggest that CSF FC may be the most effective modality to differentiate major CSF leukocyte subsets. At present, further differentiation of distinct cell populations, such as proliferated lymphocytes, is of limited clinical impact. This may, however, gain increasing interest in the future. [less ▲]

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See detailFlow cytometric detection of myeloperoxidase in horse neutrophils: a novel technique in equine diagnostic research.
Wauters, Jella; Franck, Thierry ULg; Pille, Frederik et al

in Veterinary Immunology and Immunopathology (2011), 144(3-4), 417-22

Myeloperoxidase (MPO) is a protein of interest due to its involvement in equine pathologies. Until now, results in equine diagnostic research were achieved through extracellular MPO detection. However ... [more ▼]

Myeloperoxidase (MPO) is a protein of interest due to its involvement in equine pathologies. Until now, results in equine diagnostic research were achieved through extracellular MPO detection. However, studying the cellular MPO content in neutrophils has revealed important insights in human diseases. This study aimed to develop a technique for the specific detection of MPO on the single cell level defining a flow cytometric protocol for the detection of both equine surface-bound and cellular MPO. Both indirect and direct labeling techniques are described which include the comparison of two secondary antibodies and two linking-fluorochromes, respectively. [less ▲]

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See detailFlow cytometric enumeration of parasitaemia and haematologic changes in trypanosoma-infected mice.
Antoine-Moussiaux, Nicolas ULg; Saerens, Dirk; Desmecht, Daniel ULg

in Acta Tropica (2008), 107(2), 139-44

African trypanosomiasis is a severe parasitic disease affecting both man and livestock. It is crucial to expand our fundamental knowledge of the intimate interactions between trypanosomes and their ... [more ▼]

African trypanosomiasis is a severe parasitic disease affecting both man and livestock. It is crucial to expand our fundamental knowledge of the intimate interactions between trypanosomes and their vertebrate hosts in order to develop new and efficient control strategies. The mouse model of trypanosomiasis is the most popular for research purposes because of all the logistic advantages of using this species. Studies of any aspect of trypanosomiases in the mouse systematically require the quantification of some phenotypic traits which translate its degree of resistance/susceptibility to the disease, as blood cell counts. The present study presents a methodological approach combining everyday microsampling of tail blood and its analysis by flow cytometry. The technical options and conditions permitting a fast, reliable and reproducible daily quantification of erythrocyte, reticulocyte, leucocyte and trypanosome counts in the inoculated mouse were established. The protocol proposed allows the multiplication of blood samplings without being exposed to the time-consuming constraint of visual countings, without causing iatrogenic blood cell alterations in the mouse and without requiring specific anti-trypanosome antibodies. [less ▲]

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See detailFlow cytometric method for the detection of gpI antigens of varicella zoster virus and evaluation of anti-VZV agents
Snoeck, R.; Schols, D.; Sadzot-Delvaux, Catherine ULg et al

in Journal of Virological Methods (1992), 38(2), 243-254

Varicella zoster virus (VZV) is responsible for a primary infection (varicella.) and, upon reactivation, zoster, which in immunocompromised patients, may both lead to life-threatening disseminated disease ... [more ▼]

Varicella zoster virus (VZV) is responsible for a primary infection (varicella.) and, upon reactivation, zoster, which in immunocompromised patients, may both lead to life-threatening disseminated disease. There is a great need for antiviral compounds that are effective inhibitors of VZV replication and for rapid and accurate methods for evaluating viral sensitivity to candidate anti-VZV drugs. With the monoclonal antibody (mAb) (VL8), which is directed against the gpI of VZV, and using the fluorescence-activated cell sorter (FACS) we could readily demonstrate expression of the VZV gpI antigen at 3-4 days after VZV infection. (E)-5-(2-Bromovinyl)-2'-deoxyuridine (BVDU), (S)-9-(3-hydroxy-2-phosphonylmethoxypropyl)adenine (HPMPA) and (S)-1-(3-hydro-xy-2-phosphonylmethoxypropyl)cytosine (HPMC) were shown to be potent inhibitors of VZV replication by this assay. HPMPA and HPMPC were also active against thymidine kinase-deficient (TK-) VZV whereas BVDU was not. The flow cytometric method based on the use of mAb VL8 may be of considerable help for the early diagnosis of VZV infection and evaluation of viral sensitivity to antiviral drugs. [less ▲]

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See detailFlow Cytometric Probing of Mitochondrial Function in Equine Peripheral Blood Mononuclear Cells
Cassart, Dominique ULg; Fett, Thomas ULg; Sarlet, Michaël ULg et al

in BMC Veterinary Research (2007), 3

BACKGROUND: The morphopathological picture of a subset of equine myopathies is compatible with a primary mitochondrial disease, but functional confirmation in vivo is still pending. The cationic dye JC-1 ... [more ▼]

BACKGROUND: The morphopathological picture of a subset of equine myopathies is compatible with a primary mitochondrial disease, but functional confirmation in vivo is still pending. The cationic dye JC-1 exhibits potential-dependent accumulation in mitochondria that is detectable by a fluorescence shift from green to orange. As a consequence, mitochondrial membrane potential can be optically measured by the orange/green fluorescence intensity ratio. A flow cytometric standardized analytic procedure of the mitochondrial function of equine peripheral blood mononuclear cells is proposed along with a critical appraisal of the crucial questions of technical aspects, reproducibility, effect of time elapsed between blood sampling and laboratory processing and reference values. RESULTS: The JC-1-associated fluorescence orange and green values and their ratio were proved to be stable over time, independent of age and sex and hypersensitive to intoxication with a mitochondrial potential dissipator. Unless time elapsed between blood sampling and laboratory processing does not exceed 5 hours, the values retrieved remain stable. Reference values for clinically normal horses are given. CONCLUSION: Whenever a quantitative measurement of mitochondrial function in a horse is desired, blood samples should be taken in sodium citrate tubes and kept at room temperature for a maximum of 5 hours before the laboratory procedure detailed here is started. The hope is that this new test may help in confirming, studying and preventing equine myopathies that are currently imputed to mitochondrial dysfunction. [less ▲]

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See detailA flow cytometric study on the effect of myeloperoxidase on stallion spermatozoal motility and structure
Ponthier, Jérôme ULg; Parrilla Hernandez, Sonia ULg; Van Den Berghe, Femke ULg et al

in Journal of Equine Veterinary Science (2012, August), 32(8), 509

Myeloperoxidase (MPO) is a pro-oxidant enzyme that is normally contained in neutrophils. MPO has recently been associated with keratinized cells and with decreased post-thaw motility in stallion semen [1 ... [more ▼]

Myeloperoxidase (MPO) is a pro-oxidant enzyme that is normally contained in neutrophils. MPO has recently been associated with keratinized cells and with decreased post-thaw motility in stallion semen [1]. The aim of the study was to determine effects of experimental addition of active MPO on motility, mitochondrial potential, apoptosis induction, membrane and acrosome integrity in equine semen. Three stallions were used and semen was collected four times. Extended (INRA96TM) semen was processed for density gradient centrifugation (Equipure Bottom Layer®) [2]. Purified pellet was re-extended to 100x106spermatozoa/ml in INRA96TM and divided in 3 samples. One sample was used for control and active human MPO (Calbiochem, Merck) was added in the other two samples to final concentration of 5 or 50 ng/ml. After incubation (2 hours, 20°C), motility was analysed with Computer Assisted Semen Analysis (IVOS, Hamilton-Throne, Beverly, MA, USA) and cytometric analyzes were perfomed with EasyCyte (IMV). Mitochondrial potential and apoptosis were assayed using Guava Mitopotential JC-1 and 7-AAD kit (Millipore). Membrane and acrosome integrity were respectively assayed with PI (Propidium Iodide) (Invitrogen) and PNA (Peanut Agglutinin-Fluorescein Iso Thio Cyanate) (Sigma-Aldrich). Statistical differences (p<0.05) were determined using Kruskall-Wallis test. No effect of the stallions was observed on parameters assayed in this study. Unlike total motility, progressive motility was decreased in both MPO concentrations (p<0.001). MPO addition had no effect on membrane and acrosome integrity. No differences were detected for the percentages of spermatozoa having polarised or depolarised mitochondria. Apoptosis, assayed by 7-AAD fluorescence, was not increased by the treatments. Our results agree with previously published effects of in vitro ROS production systems with xanthine oxidase [3], showing an effect on motility but no influence on mitochondria and membrane or acrosome integrity. However, membrane lipoperoxidation was increased by ROS in this study [3], and it could be linked to the impaired motility also observed in our protocol. Further studies with increasing concentrations of added MPO should be conducted to correlate motility with lipoperoxidation. References [1] Ponthier J, Desvals M, Franck T, de la Rebiere de Pouyade G, Spalart M, Palmer E, Serteyn D, Deleuze S. Myeloperoxidase in equine semen: Concentration and Localization during freezing processing. Journal of Equine Veterinary Science 2012;32: 32-37. [2] Edmond AJ, Teague SR, Brinsko SP, Comerford KL, Waite JA, Mancill SS, Love CC, Varner DD. Effect of density-gradient centrifugation on quality and recovery rate of equine spermatozoa. Animal Reproduction Science 2008;107: 318-318. [3] Baumber J, Ball BA, Gravance CG, Medina V, Davies-Morel MC. The effect of reactive oxygen species on equine sperm motility, viability, acrosomal integrity, mitochondrial membrane potential, and membrane lipid peroxidation. J Androl 2000;21: 895-902. [less ▲]

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See detailFlow cytometry estimation of nuclear size and ploidy level of habituated calli of sugar beet
Kevers, Claire ULg; Greimers, Roland ULg; Franck, Thierry ULg et al

in Biologia Plantarum (1999), 42(3), 321-332

A fully habituated (auxin- and cytokinin-independent) self-regenerating (organogenic) sugar beet cell line (HO) and a fully habituated non-organogenic one (HNO) derived from the former one, were analyzed ... [more ▼]

A fully habituated (auxin- and cytokinin-independent) self-regenerating (organogenic) sugar beet cell line (HO) and a fully habituated non-organogenic one (HNO) derived from the former one, were analyzed as to their nuclear size and DNA content. Flow cytometry and image analysis were used and cells of certified diploid leaves of the same sugar beet strain served as controls. The HNO cells had been shown previously to have many characteristics of cancerous cells. The analyses made on leaves and HNO cells indicated the presence of only one population of cycling cells. In HO cells. two cycling populations were detected: the first one had the same DNA content as the leaves while the second one contained two fold more DNA than the first population. HNO cells showed the higher nuclear size and DNA content. HNO cells also showed evidence of aneuploidy. Thus, nuclear size, DNA content and ploidy level increase together with the neoplasic progression to culminate in HNO cells with the loss of organogenic totipotency. [less ▲]

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See detailFlow Cytometry for the follow-up of Trypanosoma evansi infection in a mouse model
Antoine-Moussiaux, Nicolas ULg; Leroy, ; Faisca, et al

Poster (2005, November 18)

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See detailFlow cytometry for the follow-up of Trypanosoma evansi infection in a mouse model
Antoine-Moussiaux, Nicolas ULg; Leroy, ; Faisca, et al

Poster (2006, April)

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See detailFlow cytometry in prostate cancer: Histological and clinical correlation
de Leval, Laurence ULg; Waltregny, David ULg; Greimers, Roland ULg et al

in Acta Urologica Belgica (1994), 62(1), 37-43

DNA histograms were obtained by flow cytometry for 39 human prostate carcinomas (27 total prostatectomy specimens, 5 biopsies and 7 transuretral resections). The study was performed on formalin-fixed and ... [more ▼]

DNA histograms were obtained by flow cytometry for 39 human prostate carcinomas (27 total prostatectomy specimens, 5 biopsies and 7 transuretral resections). The study was performed on formalin-fixed and paraffin-embedded material. In this report, ploidy index did not seem to be a good marker of prognosis as no significant variation in ploidy was found neither among the different stages nor among the different Gleason categories. Proliferative index of the tumors seemed to be a more sensitive parameter; a significant relation was observed between proliferative index and stage of the tumor. The authors discuss these results under the light of previously reported observations. [less ▲]

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See detailFlow in shallow rectangular basins: experimental study and 2D numerical simulations
Kantoush, Sameh A.; Dewals, Benjamin ULg; Erpicum, Sébastien ULg et al

in Proc. 8th International Conference on Hydro-Science and Engineering (ICHE) (2008)

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See detailFlow interruption effects on intake rate and rill erosion in two soils
Sirjacobs, Damien ULg; Shainberg, Itzhak; Rapp, Ido et al

in Soil Science Society of America Journal (2001), 65

Efficiency of surface irrigation is often low because of poor infiltration uniformity, resulting from relatively long periods of infiltration at the upstream end and short periods of infiltration at the ... [more ▼]

Efficiency of surface irrigation is often low because of poor infiltration uniformity, resulting from relatively long periods of infiltration at the upstream end and short periods of infiltration at the downstream end of the field. Surge irrigation, the intermittent supply of water to furrows, generally reduces soil intake rate (IR) and improves moisture uniformity over the entire field. However, IR reduction varies from one irrigation scheme to another, depends on soil and water properties, and is difficult to predict. A laboratory study using miniflumes was designed to investigate the effect of interrupted flow on IR and soil loss from short rills. Two soils differing in their textures, a silt loam (Calcic Haploxeralf) derived from loess and a clay soil (Typic Haploxerert), were studied. Intake rate in the clay soil was greater than that in the silt loam. Therefore, different inflow rates were applied to the two soils to achieve similar runoff flow rates from the two soils. Cumulative infiltration decreased from 646 mL in continuous flow to 539 mL in interrupted flow for the silt loam and from 1142 to 1068 mL in the clay soil. Interrupted flow also reduced cumulative soil loss by 84% in the clay soil but had only a small effect on soil loss from the silt loam. However, when flow rate was increased from 80 to 320 mL min−1, interrupted flow reduced soil loss in the silt loam as much as in the clay soil. Consolidation of the soil surface and formation of cohesive forces between soil particles of the silt loam with unstable structure during flow interruption was suggested as the explanation for the effect of flow interruption on intake rate and soil detachment. These results need to be verified in field experiments. [less ▲]

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See detailFlow modeling in an underground gasifier at great depth by the Boundary-Element Method
MATHY, B.; PIRLOT, Pierre; Pirard, Jean-Paul ULg et al

in In Situ (1994), 18(4), 399-418

In order to simulate the cavity growth of an underground gasifier in thin seams at great depth, Wilks1 has developed an original model that solves the continuity equation in the horizontal plane with the ... [more ▼]

In order to simulate the cavity growth of an underground gasifier in thin seams at great depth, Wilks1 has developed an original model that solves the continuity equation in the horizontal plane with the hypothesis of radial fluid flow around the injection well. In the model presented here, the continuity equation in the horizontal plane has been taken into account, removing the limiting assumption on flow (radial direction) assumed by Wilks. The simultaneous solution of the continuity equation and the Darcy law has been carried out using the Boundary Element Method (BEM); this method is particularly suitable for solving problems where boundary conditions are of prime importance. The model enables the influences of the permeability of the medium and gasifier geometry to be demonstrated. [less ▲]

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