Fluid dynamic treatment of thixotropic debris flows and avalanches

Some forms of mud flows and debris flows exhibit a non-Newtonian thixotropic behaviour, and this study describes a basic study of dam break wave with thixotropic fluid. Theoretical considerations were developed based upon a kinematic wave approximation of the Saint-Venant equations down a prismatic sloping channel and combined with the thixotropic rheological model of Coussot et al. (2002). The analytical solution of basic flow motion and rheology equations predicts three basic flow regimes depending upon the fluid properties and flow conditions, including the initial degree of jamming of the fluid. The present work is the first theoretical analysis combining successfully the basic principles of unsteady flow motion with a thixotropic fluid model, which was verified with systematic laboratory experiments

Francis Affergan, Martinique : les identités remarquables. Anthropologie d’un terrain revisité

C’est le sous-titre de ce nouvel ouvrage de Francis Affergan, plus que son titre (dont le contenu est plus induit dans le texte que véritablement explicité) qui retient en premier l’attention. La « re-visitation » anthropologique du terrain de prédilection de l’auteur, la Martinique, trente ans après ses premières collectes, est en soi un projet original attractif pour le lecteur. Exercice à vrai dire peu courant chez les anthropologues, souvent heureux de « boucler » définitivement leur terr..

« Rien n’est plus fort que le Bon Dieu ! »

Le conte créole est l’exemple d’un phénomène historique de traduction engageant plus qu’un fait religieux: le référent croyant ultime qu’est le Dieu d’une religion – en l’occurrence celle du christianisme. Parole de résistance sous son apparence ludique, il tient le rôle de substitut de mythe qu’il reconstitue au sein des sociétés antillo-guyanaises issues de la traite, soumises à l’esclavage et recréées à partir d’une situation de dépossession anthropologique totale. C’est de cette mémoire blessée – et théologiquement blessée – qu’il a pris corps. Habilement convoqué par le conteur, champion des paroles de détour prononcées autrefois dans la nuit de la Plantation (à la barbe des maîtres colons!) s’y est inscrit, traduit et pérennisé le dieu chrétien sous une forme inévitablement et stratégiquement associée à la figure du maître esclavagiste, présence omnipotente qu’il faut à la fois se concilier et tenter de rouler. En ce sens, le conte créole, qui exige une lecture palimpseste, reste le témoin original d’une traduction culturelle et spirituelle sans aucun doute totalement imprévue par le colonialisme mais dont les effets pérennes sont toujours latents en pays créoles.Creole storytelling is an example of a historical phenomenon of translation which involves more than just religious facts: as the ultimate referent believer is the God of a religion–in this case the God of Christianity. A resistance speech hidden under a playful appearance, Creole storytelling plays the role of a surrogate myth that it recreates at the heart of West Indies-Guyanese communities which were born out of trafficking, subjected to slavery and were then recreated from a situation of total anthropological dispossession. It is from this wounded memory–also theologically wounded–that the Creole storytelling took shape. Skilfully convened by the storyteller, a champion of wandering words, once uttered in the darkness of the Plantation (under the noses of the colonial masters), the Christian God is described, translated and perpetuated in a form which is inevitably and strategically associated with the figure of the slave master, an omnipotent presence which both needs to be won over and fooled. In this sense, Creole storytelling, which requires a palimpsest interpretation, remains the original witness of a cultural and spiritual translation that was without a doubt completely unforeseen by colonialism, but whose lasting effects are still dormant in Creole communities.El cuento creole es el ejemplo de un fenómeno histórico de traducción que implica más de un hecho religioso: el referente último de las creencias que es el Dios de una religión–en este caso el del cristianismo. Palabra de resistencia bajo su apariencia lúdica, ocupa un rol de sustituto del mito que reconstituye dentro de las sociedades antillo-guayanesas salidas de la trata, sometidas al esclavismo y recreadas a partir de una situación de deposesión antropológica total. Es a partir de esta memoria herida–y teológicamente herida-que el cuento creole ha tomado cuerpo. Hábilmente convocado por el cuentista, campeón de palabras del disimulo pronunciadas en otro tiempo en la noche de la Plantación (¡bajo las barbas de los amos colonos!) se inscribió en él, traducido y perennizado el dios cristiano bajo una forma inevitable y estratégicamente asociada a la figura del amo esclavista, presencia omnipotente con el cual es necesario conciliar y a la vez tratar de dar vuelta. En este sentido, el cuento creole, que exige una lectura palimpsesto, sigue siendo el testimonio original de una traducción cultural y espiritual sin ninguna duda totalmente imprevista por el colonialismo pero cuyos efectos perennes están siempre latentes en países creoles. (trad. Véronica Giménez Béliveau

An Experimental Study of Sudden Release of Bentonite Suspensions down an Inclined Chute

Bentonite suspensions, used in the construction industry, are non-Newtonian fluids with a thixotropic behaviour. Sudden releases of bentonite suspensions were systematically investigated down a sloping chute, to quantify the effects of bentonite concentrations and initial rest period on flow motion. Experiments observations highlighted four types of flows, that differ substantially from Newtonian fluid motion. Quantitative informations were documented in terms of the fluid thickness, wave front position and wave front curvature during motion and after stoppage. It is believed that the present study is the first systematic study of its kind in a large-size facility

A Study of Dam Break Wave of Thixotropic Fluid: Bentonite Surges down an Inclined plane

Thixotropic fluids are commonly used in the construction industry (e.g. liquid cements, liquid concrete, drilling fluids), industrial applications (e.g. muds, paints) and the food industry (e.g. liquid dairy products, ketchup). Related applications include some forms of mud flows and debris flows, pasty sewage sludges and some wastewater treatment residues. Thixotropy is the characteristic of a fluid to form a gelled structure over time when it is not subjected to shearing and to liquefy when agitated. A thixotropic fluid is a non-Newtonian fluid with a viscosity that is a function of both shear rate y and instantaneous state(s) of structure of the material. Such a fluid exhibits a reversible time-dependent decrease in apparent viscosity under shear rate and a gradual recovery when the shear stress is removed. This report describes a basic study of dam break wave with thixotropic fluid. A dam break wave is a sudden release of a mass of fluid in a channel. This type of flows has not been studied to date with thixotropic fluid, despite its practical applications : e.g., mudflow release, concrete tests including L-Box and J-Ring for self-consolidating concrete testing, paint applications. Theoretical considerations were developed based upon a kinematic wave approximation of the Saint-Venant equations for a thixotropic fluid down a prismatic sloping channel. The thixotropic fluid model of COUSSOT et al. (2002a) was used since it describes the instantaneous state of fluid structure by a single parameter. The analytical solution of the basic flow motion and rheology equations predict three basic flow regimes depending upon the fluid properties and flow conditions, including the initial degree of jamming of the fluid : (1) a short motion with relatively-rapid flow stoppage for relatively small mass of fluid, (2) a fast flow motion for a large mass of fluid, or (3) an intermediate motion initially rapid before final fluid stoppage for intermediate mass of fluid and intermediate initial rest period To. Physical experiments were performed with bentonite suspensions. Systematic experiments showed four types of flows. For small bentonite mass concentrations and short relaxation times To, the fluid flowed rapidly down the slope and spilled into the overflow container (Flow Type I). For intermediate concentrations and rest periods, the suspension flowed rapidly initially, decelerated relatively suddenly, continued to flow slowly for sometimes before complete stoppage (Flow Type II). For large mass concentrations and long rest periods, the mass of fluid stretched down the slope, until the head separated from the tail (Flow Type III). The last flow pattern (Type IV) corresponded to an absence of flow for large bentonite concentrations and long rest times. Quantitative informations were documented in terms of the final fluid thickness, wave front position, wave front curvature, side profile of the wave front during motion and after stoppage, as well as the flow motion immediately after gate opening. Some freesurface instabilities are also discussed and illustrated. It is believed that the present study is the first theoretical analysis combining successfully the basic principles of unsteady flow motion (i.e. Saint-Venant equations) with a thixotropic fluid model, which was validated with large-size systematic laboratory experiments. It is the belief of the writers that, for such complex systems this kind of approach, combining both rheology and fluid dynamics, is necessary to gain new insights of these complicated flow motions

Epithelial sodium channel is a key mediator of growth hormone-induced sodium retention in acromegaly.: Antinatriuretic action of growth hormone

International audienceAcromegalic patients present with volume expansion and arterial hypertension, but the renal sites and molecular mechanisms of direct antinatriuretic action of GH remain unclear. Here, we show that acromegalic GC rats, which are chronically exposed to very high levels of GH, exhibited a decrease of furosemide-induced natriuresis and an increase of amiloride-stimulated natriuresis compared with controls. Enhanced Na(+),K(+)-ATPase activity and altered proteolytic maturation of epithelial sodium channel (ENaC) subunits in the cortical collecting ducts (CCDs) of GC rats provided additional evidence for an increased sodium reabsorption in the late distal nephron under chronic GH excess. In vitro experiments on KC3AC1 cells, a murine CCD cell model, revealed the expression of functional GH receptors and IGF-I receptors coupled to activation of Janus kinase 2/signal transducer and activator of transcription 5, ERK, and AKT signaling pathways. That GH directly controls sodium reabsorption in CCD cells is supported by: 1) stimulation of transepithelial sodium transport inhibited by GH receptor antagonist pegvisomant; 2) induction of alpha-ENaC mRNA expression; and 3) identification of signal transducer and activator of transcription 5 binding to a response element located in the alpha-ENaC promoter, indicative of the transcriptional regulation of alpha-ENaC by GH. Our findings provide the first evidence that GH, in concert with IGF-I, stimulates ENaC-mediated sodium transport in the late distal nephron, accounting for the pathogenesis of sodium retention in acromegaly

International Multicenter Validation Study of the SAGIT® Instrument in Acromegaly.

Abstract Context The SAGIT® instrument (SAGIT) has been developed to enable accurate characterization of acromegaly disease activity. Objective We evaluated the ability of SAGIT to discriminate acromegaly disease control status. Methods This multicenter, noninterventional, prospective and retrospective, longitudinal study, conducted at academic and private clinical practice sites, included patients aged ≥ 18 years with a diagnosis of controlled (n = 109) or non-controlled (n = 105) acromegaly, assessed by clinical global evaluation of disease control (CGE-DC) questionnaire, investigator therapeutic decision, and international guidelines. Control status was not determined at baseline for 13 patients. Since 9 patients were enrolled retrospectively, all presented analyses are based on the prospective population (N = 227). Patients were assessed over a 2-year follow-up period. Classification and regression tree (CART) analyses were performed to investigate how SAGIT components at baseline (signs/symptoms [S], associated comorbidities [A], growth hormone levels [G], insulin-like growth factor 1 levels [I], tumor features [T]) discriminate between controlled and non-controlled acromegaly. Results Baseline mean subscores S, G, I, and T were significantly lower in patients with CGE-DC controlled vs CGE-DC non-controlled acromegaly. SAGIT components I and G for CGE-DC and S, A, G, I, and T for the clinician's therapeutic decision were retained by CART analyses. For international guidelines, only SAGIT component I was retained. The risk for undergoing ≥ 1 treatment change during the study was 3.44 times greater for CGE-DC non-controlled acromegaly relative to CGE-DC controlled acromegaly. Conclusion The SAGIT instrument is a valid and sensitive tool to comprehensively and accurately assess acromegaly severity

Sex-Related Differences in Lactotroph Tumor Aggressiveness Are Associated With a Specific Gene-Expression Signature and Genome Instability

Sex-related differences have been reported in various cancers, in particular men with lactotroph tumors have a worse prognosis than women. While the underlying mechanism of this sexual dimorphism remains unclear, it has been suggested that a lower estrogen receptor alpha expression may drive the sex differences observed in aggressive and malignant lactotroph tumors that are resistant to dopamine agonists. Based on this observation, we aimed to explore the molecular importance of the estrogen pathway through a detailed analysis of the transcriptomic profile of lactotroph tumors from 20 men and 10 women. We undertook gene expression analysis of the selected lactotroph tumors following their pathological grading using the five-tiered classification. Chromosomic alterations were further determined in 13 tumors. Functional analysis showed that there were differences between tumors from men and women in gene signatures associated with cell morphology, cell growth, cell proliferation, development, and cell movement. Hundred-forty genes showed an increased or decreased expression with a minimum 2-fold change. A large subset of those genes belonged to the estrogen receptor signaling pathway, therefore confirming the potent role of this pathway in lactotroph tumor sex-associated aggressiveness. Genes belonging to the X chromosome, such as CTAG2, FGF13, and VEGF-D, were identified as appealing candidates with a sex-linked dysregulation in lactotroph tumors. Through our comparative genomic hybridization analyses (CGH), chromosomic gain, in particular chromosome 19p, was found only in tumors from men, while deletion of chromosome 11 was sex-independent, as it was found in most (5/6) of the aggressive and malignant tumors. Comparison of transcriptomic and CGH analysis revealed four genes (CRB3, FAM138F, MATK, and STAP2) located on gained regions of chromosome 19 and upregulated in lactotroph tumors from men. MATK and STAP2 are both implicated in cell growth and are reported to be associated with the estrogen signaling pathway. Our work confirms the proposed involvement of the estrogen signaling pathway in favoring the increased aggressiveness of lactotroph tumors in men. More importantly, we highlight a number of ER-related candidate genes and further identify a series of target molecules with sex-specific expression that could contribute to the aggressive behavior of lactotroph tumors in men