Sedimentology and magnetic susceptibility of the Couvin Formation (Eifelian, South Western Belgium): Carbonate platform initiation in a hostile world

The Eifelian of Belgium is mainly characterised by a mixed siliciclastic-carbonate sedimentation on a ramp profile. In this context, the Couvin Formation is the more important and remarkable exception. It represents a carbonate platform initiation in a hostile environment. This work is mainly based on the stratotype, corresponding to two stratigraphic sections located in Couvin, along the southern border of the Dinant Synclinorium. These sections are the Eau Noire and Falaise de l'Abime sections. Unfortunately, they are discontinuous. To allow a better understanding of the sedimentary dynamics, the data are complemented by a shorter but continuous section located in Villers-la-Tour (3.5 km West of Chimay). Petrographic study leads to the definition of 14 microfacies which are integrated in a palaeogeographical model. It corresponds to a platform setting where the reef complex is mainly constituted by an accumulation of crinoids, stromatoporoids and tabulate corals. The microfacies evolution is interpreted in terms of bathymetrical variations. It shows a general shallowing-upward trend encompassing the vertical succession of fore-reef settings, reef development, back-reef and then lagoon environment. This interpretation is supported by trends in mean magnetic susceptibility data, providing a better understanding of the sedimentary dynamics. Moreover, these data show positive correlation with concentrations of detritic minerals, but an inverse relationship with well washed skeletal limestones. The comparison of the three studied sections leads to considerations concerning the lateral variability in the Couvin Formation indicating more agitated conditions in the Abime Member in Villers-le-Tour section

Neutrophils enhance early Trypanosoma brucei infection onset.

In this study, Trypanosoma brucei was naturally transmitted to mice through the bites of infected Glossina morsitans tsetse flies. Neutrophils were recruited rapidly to the bite site, whereas monocytes were attracted more gradually. Expression of inflammatory cytokines (il1b, il6), il10 and neutrophil chemokines (cxcl1, cxcl5) was transiently up-regulated at the site of parasite inoculation. Then, a second influx of neutrophils occurred that coincided with the previously described parasite retention and expansion in the ear dermis. Congenital and experimental neutropenia models, combined with bioluminescent imaging, indicate that neutrophils do not significantly contribute to dermal parasite control and elicit higher systemic parasitemia levels during the infection onset. Engulfment of parasites by neutrophils in the skin was rarely observed and was restricted to parasites with reduced motility/viability, whereas live parasites escaped phagocytosis. To our knowledge, this study represents the first description of a trypanosome infection promoting role of early innate immunological reactions following an infective tsetse fly bite. Our data indicate that the trypanosome is not hindered in its early development and benefits from the host innate responses with the neutrophils being important regulators of the early infection, as already demonstrated for the sand fly transmitted Leishmania parasite

The 1958–2009 Greenland ice sheet surface melt and the mid-tropospheric atmospheric circulation

peer reviewedaudience: researcherIn order to assess the impact of the mid-tropospheric circulation over the Greenland ice sheet (GrIS) on surface melt, as simulated by the regional climate model MAR, an automatic Circulation type classification (CTC) based on 500 hPa geopotential height from reanalyses is developed. General circulation correlates significantly with the surface melt anomalies for the summers in the period 1958–2009. The record surface melt events observed during the summers of 2007–2009 are linked to the exceptional persistence of atmospheric circulations favouring warm air advection. The CTC emphasizes that summer 500 hPa circulation patterns have changed since the beginning of the 2000s; this process is partly responsible for the recent warming observed over the GrIS

Monodisperse fragmentation in emulsions: Mechanisms and kinetics

How can a crude polydisperse emulsion be transformed into a monodisperse one? Mason and Bibette (Phys. Rev. Lett., 77 (1996) 3481) have experimentally discovered this phenomenon by applying a shear step on a crude emulsion. In this paper, we examine how this transformation occurs. Our strategy is to prepare calibrated emulsions and to examine the fragmentation kinetics as a function of the initial droplet size. We show that the fragmentation process involves two distinct regimes. At short time (shorter than one second), the droplet diameter decreases abruptly. The droplets deform into long threads that undergo a Rayleigh instability. The obtained diameter is mainly determined by the applied stress and weakly depends on the viscosity ratio between the dispersed and continuous phases. After this first step, the resulting droplets can, once again, break up into daughter droplets. This second mechanism is much slower with a characteristic time of several hundred seconds. Depending on the initial size, the first step can vanish and only the second slow step subsists

Mechanical modeling of wheat hardness and fragmentation

International audienceThe mechanical origin of the wheat hardness used to classify wheat flours is an open issue. We propose a cohesive granular model of wheat endosperm involving a discrete phase composed of starch granules, a continuous phase representing the protein matrix, and pores. A lattice element method is employed to simulate the behavior of numerical samples with variable matrix volume fraction and starch-protein adherence subjected to axial tension and compression. We show that the effective stiffness is a linear function of matrix volume fraction but is higher in compression than in tension. Crack formation is analyzed in terms of particle damage as a function of matrix volume fraction and particle-matrix adherence. Our data provide evidence for three regimes of crack propagation depending on the crack path through the material. These regimes are associated with the three hardness classes of soft, hard and durum wheat. We also show that starch damage scales well with the relative toughness of the starch-protein interface. The interface toughness appears therefore to be strongly correlated with particle damage and determines transition from soft to hard behavior

Influence of instrument rigidity and specimen geometry on calculations of compressive strength poperties of wheat endosperm

IATE Axe 5 : Application intégrée de la connaissance, de l’information et des technologies permettant d’accroître la qualité et la sécurité des alimentsEndosperm texture is one of the most important quality features in wheat; it defines milling energy requirements and end-use suitability. From an engineering perspective, texture can be quantified by measuring the physical property of the resistance force to crushing of precisely machined specimens of endosperm. In such procedures, cylindrical or parallelepiped blocks are crushed under a constant rate of strain, in which values are reported of maximum stress, strain at maximum stress, Young's modulus, and the energy of compression to the point of maximum stress. Generally overlooked, however, is the instrument itself, which can significantly affect the apparent values of the latter three properties. Because no instrument is infinitely rigid, departures between apparent and actual strength properties occur. In this study, the physical principles for compressive strength measurement with respect to corrections for instrument rigidity are developed. Results show that the departures are exacerbated in specimens of small slenderness ratio and elevated hardness. This issue is demonstrated in a small collaborative study involving three laboratories and three instruments with low, intermediate, and high rigidity. Specimens were prepared from wheat kernels from hard and soft near-isogenic lines derived from the cultivar Alpowa. For strain at maximum stress, the implementation of a correction for instrument rigidity reduced the range across laboratories from 6.03-47.7% (before correction) to 4.49-7.35% (after correction) for the hard genotype, and the corresponding ranges for the soft genotype were 3.29-18.6% and 2.07-6.01%, respectively. For Young's modulus, instrument rigidity correction resulted in a tenfold correction for the hard genotype measured on the least rigid instrument, going from 0.21 GPa (before) to 4.9 GPa (after). Likewise, with this instrument, the imparted energy density to maximum stress was reduced from an average apparent value of 23 MJ/m(3) (before) to 3.8 MJ/m(3) (after). Because of these large differences between apparent and actual values for these physical-strength properties, it is recommended that future strength property measurements should account for instrument rigidity by implementation of the correction procedure described herein