Filter backwashing mechanisms

An investigation of filter backwashing mechanisms was undertaken. High speed video recording equipment, operating at 200 frames/s, in conjunction with a rigid endoscope (borescope) has been used to obtain detailed visual information from inside the filter bed during backwash. In addition, experimental measurements of mass balance and backwash water turbidity have provided efficiency information. Experiments were performed using standard filter sand, either clean or clogged with a suspension of kaolin clay, or kaolin clay flocculated with alum and polymer in London tap water. Backwashing with water or water and air scour was recorded on video for subsequent analysis. A total of 30 experiments were performed backwashing with water only and 38 using combined air and water wash of the clogged bed. Using the XY Coordinator and a PC velocities of the sand grains were obtained from the video tapes for different backwash regimes. The results indicate that the majority of detachment is due to the fluid shear forces acting on deposits on the grain surfaces, particularly when a water only wash is employed. Kaolin and flocculated kaolin deposits are easily detached without fluidising the bed, but some remain trapped in areas where there is no flow, or, where the shear forces are insufficient for detachment. Fluidisation serves: (i) to mobilise grains and expose new faces to the shearing effects of the flow, and (ii) to allow flushing out of the resuspended deposits. Grain collisions and abrasion do take place, particularly as the bed undergoes expansion, but these were not the major cause of deposit detachment in the experiments described. When simultaneous air and subfluidising water flow are used, then the bed behaves in a way described as collapse-pulsing. A high degree of bed circulation is created and higher grain velocities with consequent shear stress leads to rapid deposit detachment. Following air scour it is necessary to fluidise the bed with water in order to flush out deposits and trapped air. The velocity data correlates well with the backwashing efficiency data, i.e. higher grain velocities result in better cleaning. This thesis includes a video recording of selected representative experiments and copies of publications from this work

Rapport annuel du Conseil supérieur des bibliothèques (1995)

Rapport annuel du président du CSB. État des bibliothèques françaises, propositions d\u27action, études particulières : Les difficultés des bibliothèques universitaires françaises, Les usages des documents électroniques en bibliothèque, Développement des relations internationales, Publics empêchés, etc

Rapport annuel du Conseil supérieur des bibliothèques (1994)

Rapport annuel du président [Michel Melot] du CSB. État et perspectives des bibliothèques françaises, études particulières : Bibliothèque nationale de France, CCFR, Patrimoine des bibliothèques, Documentation électronique, Bibliothèques universitaires, etc

Rapport annuel du Conseil supérieur des bibliothèques (1993)

Rapport annuel du CSB : Bibliothèque de France, BNF, Bibliothèques universitaires, Droit de prêt, Le rôle de l\u27Etat vis-à-vis des bibliothèques territoriales, Traitement de la littérature grise, Les bibliothèques jeunesse etc

Rapport annuel du Conseil supérieur des bibliothèques (2000-2001)

Rapport du CSB rédigé par le secrétaire général. Etat et perspectives des bibliothèques françaises, statistiques nationales et étrangères. Etudes particulières : Documentation électronique, Politiques documentaires, Violence et bibliothèques, Architecture des bibliothèques, etc

Rapport annuel du Conseil supérieur des bibliothèques (1991)

Rapport annuel du Conseil supérieur des bibliothèques : Charte des bibliothèques, Historique des projets de lois sur les bibliothèques, Coopérations entre bibliothèques, Projet de la Bibliothèque de France, etc

Rapport annuel du Conseil supérieur des bibliothèques (1992)

Rapport annuel du président du CSB : Projet de la Bibliothèque de France, CCFR, Pôles associés, Bibliothèques universitaires, Programme des BMVR, Politique européenne, Droit de prêt, Collections scientifiques et techniques en bibliothèque publique

Epigenetic inactivation of mir-34b/c in addition to mir-34a and DAPK1 in chronic lymphocytic leukemia

BACKGROUND: TP53 mutation/deletion is uncommon in chronic lymphocytic leukemia (CLL). We postulated that components of TP53-centered tumor suppressor network, miR-34b/c, in addition to DAPK1 and miR-34a might be inactivated by DNA hypermethylation. Moreover, we tested if miR-34b/c methylation might correlate with miR-203 or miR-124-1 methylation in CLL. METHODS: miR-34b/c, miR-34a and DAPK1 methylation was studied in 11 normal controls, 7 CLL cell lines, and 78 diagnostic CLL samples by methylation-specific polymerase chain reaction. MEC-1 cells were treated with 5-Aza-2'-deoxycytidine for reversal of methylation-associated miRNA silencing. Tumor suppressor properties of miR-34b were demonstrated by over-expression of precursor miR-34b in MEC-1 cells. RESULTS: miR-34b/c promoter was unmethylated in normal controls, but completely methylated in 4 CLL cell lines. miR-34b/c expression was inversely correlated with miR-34b/c methylation. Different MSP statuses of miR-34b/c, including complete methylation and complete unmethylation, were verified by quantitative bisulfite pyrosequencing. 5-Aza-2'-deoxycytidine treatment resulted in promoter demethylation and miR-34b re-expression in MEC1 cells. Moreover, over-expression of miR-34b resulted in inhibition of cellular proliferation and increased cell death. In primary CLL samples, miR-34a, miR-34b/c and DAPK1 methylation was detected in 2.6%, 17.9% and 34.6% of patients at diagnosis respectively. Furthermore, 39.7%, 3.8% and 2.6% patients had methylation of one, two or all three genes respectively. Overall, 46.2% patients had methylation of at least one of these three genes. Besides, miR-34b/c methylation was associated with methylation of miR-34a (P = 0.03) and miR-203 (P = 0.012) in CLL. CONCLUSIONS: Taken together, miR-34b/c is a tumor suppressor miRNA frequently methylated, and hence silenced in CLL. Together with DAPK1 methylation, miR-34b/c methylation is implicated in the disruption of the TP53-centered tumor suppressor network. Moreover, the association of miRNA methylation warrants further study.published_or_final_versio

Rapport annuel du Conseil supérieur des bibliothèques (1996-1997)

Rapport du CSB : évaluation et propositions pour les bibliothèques françaises, Environnements administratifs, activités du CSB. Etudes particulières : Formation, Identité professionnelles, Normalisation, Statistiques internationales, etc

Rapport annuel du Conseil supérieur des bibliothèques (1998-1999)

Rapport du CSB : État et perspectives des bibliothèques françaises, statistiques nationales et internationales, formation et personnel. Etudes particulières : Normalisation, Histoire de la Direction du Livre et des politiques de la lecture, Services bibliographiques nationaux