Non-local rheology in dense granular flows -- Revisiting the concept of fluidity

Granular materials belong to the class of amorphous athermal systems, like foams, emulsion or suspension they can resist shear like a solid, but flow like a liquid under a sufficiently large applied shear stress. They exhibit a dynamical phase transition between static and flowing states, as for phase transitions of thermodynamic systems, this rigidity transition exhibits a diverging length scales quantifying the degree of cooperatively. Several experiments have shown that the rheology of granular materials and emulsion is non-local, namely that the stress at a given location does not depend only on the shear rate at this location but also on the degree of mobility in the surrounding region. Several constitutive relations have recently been proposed and tested successfully against numerical and experimental results. Here we use discrete elements simulation of 2D shear flows to shed light on the dynamical mechanism underlying non-locality in dense granular flows

Intoxicação por organoclorados (endosulfan) em bovinos no Uruguai

Descreve-se um surto de intoxicação por organoclorados (Endosulfan) em bovinos ocorrido em abril de 2009, em uma propriedade de recria de bezerros localizada no departamento de Paisandú, Uruguai. O quadro clínico foi observado um dia depois de haver ocorrido na propriedade, uma descarga acidental de 700 litros de um pesticida formulado em solução a base de água mais endosulfan e cipermetrina por dano em um avião pulverizador. A morbidade foi de 7,7% e mortalidade de 6,0%. Os sinais clínicos se caracterizaram por salivação, ataxia, hipersensibilidade, tremores musculares, movimentos de pedalagem, ranger de dentes, excitação, convulsão, decúbito e morte. Na necropsia dos animais e ao exame histopatológico não se observaram lesões. Na mesma propriedade foi observada, também, mortalidade de peixes em um arroio próximo ao local onde o pesticida foi derramado. Amostras de gordura, fígado e conteúdo ruminal de bovinos mortos e de peixes foram analisadas pela técnica de cromatografia gasosa sendo detectada a presença de endosulfan e/ou seus metabólitos em quantidades de 0,16-3,7mg/kg, superiores aos níveis de referência aceitáveis de 0,05-0,2mg/kg, confirmando-se a ocorrência da intoxicação por este organoclorado

Occurrence and Distribution of Banana bunchy top virus Related Agro-Ecosystem in South Western, Democratic Republic of Congo

Banana bunchy top virus (BBTV) is one of the most severe and widespread virus limiting produc- tion and distribution of planting material of banana (Musa spp.) crops in the world. In Democratic Republic of Congo (DRC), these crops play a major role in daily life of almost 70% of citizen. Many factors influence banana production negatively such as Banana bunchy top disease. Epidemiol- ogical survey was conducted in experimental stations and farmers’ fields for two consecutive sea- sons covering 72 sites in five provinces of south western of RDC. The objective of this study was to evaluate the presence and distribution of the Banana bunchy top virus in five provinces of South Western of DRC, with emphasis on the agro-ecological factors. A total of 174 Musa spp. leaves samples were collected and analyzed by PCR. The results revealed the presence of BBTV in all provinces investigated. The frequency of BBTV was 6.3% in Bandundu, 12.1% in Kasaï Oriental, 17.8% Bas Congo, 1.1% in Katanga and 7.5% Kinshasa Urban and Peri-urban. Results also re- vealed that BBTV occurred in experimental station and farmers’ fields, both having all cooking and dessert bananas. The high prevalence of BBTV seemed to be linked to multiple introductions of planting materials in the Bas Congo province during 1990 and 2002. However, the province of Katanga had not experienced the introduction of planting material. This factor would explain the lowest prevalence of Banana bunchy top virus in this province. The results indicated that there was a real need to facilitate access to genetically improved and healthy certified planting material in these provinces

Milk fatty acid profile of holstein cows when changed from a mixed system to a confinement system or mixed system with overnight grazing

This study is aimed at comparing the milk fatty acid profile (FAP) of cows that changed from a mixed system (MS) of double grazing plus total mixed ration (TMR) to a total confinement system (TCS, 100% TMR) with cows that changed to another MS with one overnight grazing plus TMR and compare with cows that were kept unchanged in TCS. The diet change was made in the second month of lactation. The milk samples were collected at one (M1-spring) and three months of lactation (M3-summer). Three treatments are as follows (each n=10 ): confined cows fed with TMR throughout the period (GTMR), cows that changed from MS with double grazing plus TMR in M1 to TCS in M3 (GCHD), and cows that changed from a MS with double grazing plus TMR in M1 to a MS with overnight grazing plus TMR in M3 (GTMR+P). Unlike GTMR+P, GCHD improved milk production after change (increased 14% from M1 to M3), but milk FAP was impaired. In M3, conjugated linoleic acid (C18 : 2-CLA) in GTMR and GCHD was lower than GTMR+P (p < 0.05), and linolenic (C18 : 3-n-3) was lower in GCHD than GTMR+P. Maintaining grazing in summer overnight sustained milk fat quality, evidenced by higher C18 : 3 (n-3); C18 : 2 (CLA); and n-6/n-3 ratio than cows that changed to TCS

Milk fatty acid profile of holstein cows when changed from a mixed system to a confinement system or mixed system with overnight grazin

This study is aimed at comparing the milk fatty acid profile (FAP) of cows that changed from a mixed system (MS) of double grazing plus total mixed ration (TMR) to a total confinement system (TCS, 100% TMR) with cows that changed to another MS with one overnight grazing plus TMR and compare with cows that were kept unchanged in TCS. The diet change was made in the second month of lactation. The milk samples were collected at one (M1-spring) and three months of lactation (M3-summer). Three treatments are as follows (each ): confined cows fed with TMR throughout the period (GTMR), cows that changed from MS with double grazing plus TMR in M1 to TCS in M3 (GCHD), and cows that changed from a MS with double grazing plus TMR in M1 to a MS with overnight grazing plus TMR in M3 (GTMR+P). Unlike GTMR+P, GCHD improved milk production after change (increased 14% from M1 to M3), but milk FAP was impaired. In M3, conjugated linoleic acid (C18 : 2-CLA) in GTMR and GCHD was lower than GTMR+P (), and linolenic (C18 : 3-n-3) was lower in GCHD than GTMR+P. Maintaining grazing in summer overnight sustained milk fat quality, evidenced by higher C18 : 3 (n-3); C18 : 2 (CLA); and n-6/n-3 ratio than cows that changed to TCS

Le delta du fleuve Sénégal Une gestion de l'eau dans l'incertitude chronique

International audienceL'incertitude peut être définie comme l'état de ce qui n'est pas déterminé, fixé, et par extension comme le doute vis à vis d'un avenir inconnu. Souvent teintée d'inquiétude, cette préoccupation est inhérente au mode de vie des populations sahéliennes puisque la variabilité interannuelle des pluies, qui commandent les ressources agricole et pastorale, est la règle. Comme telle, elle a déterminé toutefois dans ces sociétés des stratégies de défense, d'adaptation, patiemment mises en place au long de l'histoire, propres à limiter le risque climatique. Par ailleurs, cette incertitude liée à différents paramètres successifs (date de début des pluies efficaces, épisodes secs au sein de la saison pluvieuse, durée) s'inscrit dans un cadre temporel cerné, saisonnier. L'incertitude est en quelque sorte «normale», attendue et comprise. Attendue également mais moins bien comprise est celle vécue par tous ceux qui dépendent d'une ressource en eau fluviale, dont la production résulte de conditions climatiques dans un amont lointain, peu ou pas connu. Une même incertitude climatique présente en outre des degrés plus ou moins contraignants : une sécheresse accusée, répétée durant plusieurs années, n'est plus supportable et n'apparaît plus aujourd'hui acceptable. Dès lors, il est tentant pour nos sociétés techniciennes d'appliquer à ce mal chronique un remède tel que le barrage. Cela a été le cas dans le bassin du fleuve Sénégal avec la construction des deux ouvrages de Diama (1985) et de Manantali (1988), à la fin d'une longue période de sécheresse de vingt années. De nouveaux « désordres » apparaissent toutefois liés à des tâtonnements successifs dans la gestion des ouvrages hydrauliques ainsi qu'à des impacts négatifs pour lesquels les solutions de compensation, d'atténuation n'avaient pas été prévues en tant que telles ou dans leur financement. Enfin, en octobre 2003, une inondation dans la ville de St Louis a provoqué le recours à une intervention bénéfique dans l'instant mais désormais redoutable : le percement artificiel de la langue de Barbarie, accompagné d'une forte intrusion marine dans le bas estuaire. Ainsi les incertitudes changent de nature, l'homme n'apparaissant pas tout à fait maître des outils ou des solutions qu'il se donne. Les scientifiques eux-mêmes ont peu de certitude, s'interrogeant sur de possibles effets de seuil, sur les temps de réponse de tel ou tel paramètre. Les adaptations répétées nécessaires pour les acteurs vivant au plus près du fleuve provoquent lassitude, désillusion ou pour le moins des difficultés économiques dans le cadre de modes de production nouveaux

Milk casein and fatty acid fractions in early lactation are affected by nutritional regulation of body condition score at the beginning of the transition period in primiparous and multiparous cows under grazing conditions

The objective was to evaluate the effect of body condition score (BCS) at 30 days before calving ()30 days) induced by a differential nutritional management, parity and week of lactation (WOL) on milk yield and composition, and milk casein and fatty acid composition. Primiparous and multiparous Holstein cows with high BCS (PH, n = 13; MH, n = 9) and low BCS (PL, n = 9; ML = 8) under grazing conditions were sampled at WOL 2 and 8 (before and after peak of lactation). Milk yield was greater in multiparous than in primiparous cows and tended to decrease from WOL 2 to 8 only in ML cows. Milk protein, fat and casein yields were greater in multiparous than in primiparous cows and decreased from WOL 2 to 8. Milk casein concentration in milk protein was greater in MH cows than in ML, PH and PL cows at WOL 2. Milk j-casein was greater, and b-casein was less in multiparous than in primiparous cows. As lactation progressed, proportion of casein fractions were not altered. Only j-casein fraction was affected by BCS at )30 days as PL showed a higher concentration than PH. The de novo (4:0–15:1) and mixed-origin fatty acids (16:0–16:1) in milk fat increased, whereas preformed fatty acids (‡17:0) decreased from WOL 2 to 8. Saturated (SAT) fatty acids tended to be greater and monounsaturated fatty acids (MUFA) were less in multiparous than in primiparous cows. High-BCS cows had greater concentrations of polyunsaturated (PUFA), conjugated linoleic acid (CLA) as well as n-6 and n-3 fatty acids in milk fat than low-BCS cows. The results indicate that casein and fatty acid fractions in milk were affected by parity and may be modified by a differential nutritional management during the pre-calving period (BCS at )30 days) in cows under grazing conditions

CRITICAL PEAT project : The importance of hydrology for Carbon Reactivity along with atmosphere - peatland interactions. Preliminary results from the Frasne peatland monitoring (Jura Mountains, France).

International audienceIn the framework of climate changes, peatland ecosystems are compartments of the Critical Zone of growing importance for greenhouse gas (GHG) exchanges with the atmosphere. Peatlands contain about 30 % of the total organic soil carbon worldwide. Interactions of GHG between atmosphere and peatland are potentially controlled by organic matter production and degradation controlled by biotic functiuns, which are in turn influenced by diverse abiotic factors including (1) water saturation, (2) peat humification degree, and (3) water quality conditioning electron acceptor availability. Delineating the detailed roles of these mechanisms is therefore challenging for long-term peatland management, requiring a detailed spatio-temporal monitoring of a wide range of hydrological and biogeochemical parameters.The Frasne peatland (Jura mountains, eastern France), belonging to a regional natural reserve is an outstanding site for such studies as it is monitored since 2008 in the framework of the national observatory of peatlands (SNO Tourbières),and belongs to the Zones Ateliers (RZA) and French Critical Zone (OZCAR) networks supplying the Europe Long-Term Ecosystem Research (eLTER) database (DEIMS-SDR). The peatland took place in a periglacial context on groundmoraines covering a large-scale karstified synclinal structure. This complex geological setting is combined with eco-physical (peat thicknesses and maturity), and hydrological (water-table depth) heterogeneities at the peatland scale.Based on daily hydrometeorological data (P, T, potential evapotranspiration, groundwater level) and monthly monitoring (hydrochemistry; peat lability, GHG fluxes) in 25 piezometers, the goal of the CRITICAL PEAT project is to identify the hydrological and biogeochemical drivers controlling GHG exchanges between peatland and atmosphere. In this perspective, this contribution aims at presenting preliminary results on the hydroclimatic sensitivity of the system inferred from correlation analyses, and its relationships with water origin and chemistry