Colloidal brazil nut effect in sediments of binary charged suspensions

Equilibrium sedimentation density profiles of charged binary colloidal suspensions are calculated by computer simulations and density functional theory. For deionized samples, we predict a colloidal ``brazil nut'' effect: heavy colloidal particles sediment on top of the lighter ones provided that their mass per charge is smaller than that of the lighter ones. This effect is verifiable in settling experiments.Comment: 4 pages, 4 figure

Presa de Djatiluhur, Indonesia

This dam is located in Java, close to Djakarta, on the Tjitarum river. The dam consists of a stone dyke and an internal watertight screen, of suitably chosen and compacted soil. The width of the dyke at the base is 600 m, and the dam rises 100 m above its foundations. The reservoir that will be formed will hold 3,000 X 106 m3 of water, at 107 m height. A special feature of this project is that the power station and spillway are related to a concrete cylindrical body, of 90 m diameter and 110 m height. At the top of this is the surface spillway, and on the outside are the water intakes for each of the 6 generator groups located along the inner bottom rim of the concrete cylinder.Se halla situada en la isla de Java, próxima a Djakarta y sobre el río Tjitarum. La presa de cierre está constituida por un dique de piedra y una pantal la interior, de impermeabilización, formada con tierras convenientemente seleccionadas y compactadas. El espesor del dique en su base es de 600 m, y tiene una altura respecto a cimientos de 100 m. Este dique crea un embalse de 3.000 x 166 m3 con un nivel de agua a la cota 107 metros. La particularidad de esta obra consiste en disponer la central y el aliviadero en un cuerpo cilíndrico de hormigón, de 90 m de diámetro exterior y 110 m de altura, en cuya parte superior están el aliviadero de superficie, y en el exterior se hallan las tomas de agua para cada uno de los 6 grupos instalados y la central en un anillo circular inferior

Aging and memory properties of topologically frustrated magnets

The model 2d kagome system (H3O)Fe3(SO4)2(OH)6 and the 3d pyrochlore Y2Mo2O7 are two well characterized examples of low-disordered frustrated antiferromagnets which rather then condensing into spin liquid have been found to undergo a freezing transition with spin glass-like properties. We explore more deeply the comparison of their properties with those of spin glasses, by the study of characteristic rejuvenation and memory effects in the non-stationary susceptibility. While the pyrochlore shows clear evidence for these non-trivial effects, implying temperature selective aging, that is characteristic of a wide hierarchical distribution of equilibration processes, the kagome system does n not show clearly these effects. Rather, it seems to evolve towards the same final state independently of temperature.Comment: submitted for the proceedings of the 46th MMM conference (Seattle, 2001

Recent tectonic reorganization of the Nubia-Eurasia convergent 2 boundary heading for the closure of the western Mediterranean

: In the western Mediterranean area, after a long period (late Paleogene-Neogene) of Nubian northward subduction beneath Eurasia, subduction is almost ceased as well as convergence accommodation in the subduction zone. With the progression of Nubia-Eurasia convergence, a tectonic reorganization is therefore necessary to accommodate future contraction. Previously-published tectonic, seismological, geodetic, tomographic, and seismic reflection data (integrated by some new GPS velocity data) are reviewed to understand the reorganization of the convergent boundary in the western Mediterranean. Between northern Morocco, to the west, and northern Sicily, to the east, contractional deformation has shifted from the former subduction zone to the margins of the two backarc oceanic basins (Algerian-Liguro-Provençal and Tyrrhenian basins) and it is now active in the south-Tyrrhenian (northern Sicily), northern Liguro-Provençal, Algerian, and Alboran (partly) margins. Compression and basin inversion has propagated in a scissor-like manner from the Alboran (c. 8 Ma) to the Tyrrhenian (younger than c. 2 Ma) basins following a similar propagation of the subduction cessation and slab breakoff, i.e., older to the west and younger to the east. It follows that basin inversion is rather advanced in the Algerian margin, where a new southward subduction seems to be in its very infant stage, while it has still to properly start in the Tyrrhenian margin, where contraction has resumed at the rear of the fold-thrust belt and may soon invert the Marsili oceanic basin. GPS-derived strain rates higher in the Tyrrhenian margin than in the Algerian boundary suggest that this latter manner of contraction accommodation (contraction resumption at the rear of the orogenic wedge) is more efficient than subduction inception and basin inversion along newly-generated reverse faults (Algeria), but the differential strain rates may also be explained with the heterogeneous distribution of GPS stations. Part of the contractional deformation may have shifted toward the north in the Liguro-Provençal basin possibly because of its weak rheological properties compared with the area between Tunisia and Sardinia, where no oceanic crust occurs and seismic deformation is absent or limited compared with the adjacent strands of the Nubia-Eurasia boundary. The tectonic reorganization of the Nubia-Eurasia boundary in the study area is still strongly controlled by the inherited tectonic fabric and rheological attributes, which are both discontinuous and non-cylindrical along the boundary. These features prevent, at present, the development of long and continuous thrust faults. In an extreme and approximate synthesis, the evolution of the western Mediterranean is inferred as being similar to a Wilson Cycle in the following main steps: (1) northward Nubian subduction with Mediterranean backarc extension (since ~35 Ma); (2) progressive cessation, from west to east, of Nubian main subduction (since ~15 Ma); (3) progressive compression, from west to east, in the former backarc domain and consequent basin inversion (since ~8-10 Ma); (4) possible future subduction of former backarc basins

Une occupation de la fin du Dernier Maximum Glaciaire dans les Pyrénées : le Magdalénien inférieur de la grotte des Scilles (Lespugue, Haute-Garonne)

International audienceThe excavations by R. and S. Saint-Périer at the Grotte des Scilles (Lespugue, Haute-Garonne, France) in 1923-1924 yielded archaeological material attributed to the Magdalenian. The re-examination of this old collection now allows a more precise characterization of it, in light of recent research on this period. This article presents the different artefact types found (lithic and osseous tools, faunal remains, personal ornaments, portable art items and one sandstone lamp) in order to consider all activities documented at the site. Particular attention is given to typological and technological data, the analyses of which point to a Lower Magdalenian chronological attribution. A SMA 14C date shows that occupation took place around 16,000 years BP (19,400 years cal BP) at the Grotte des Scilles. The identification, for the first time, of a Lower Magdalenian presence in the Pyrenees raises new questions concerning Magdalenian occupation at the end of the Last Glacial Maximum in southwestern France and northern Spain.Les fouilles menées par R. et S. Saint-Périer dans les années 1920 à la grotte des Scilles (Lespugue, Haute-Garonne) ont livré un ensemble de vestiges attribués au Magdalénien. L'étude de cette collection ancienne offre désormais la possibilité de préciser cette caractérisation à la lumière de travaux récents sur cette période. La présentation des différentes catégories de vestiges (industries lithique et osseuse, faune, parure, art mobilier et lampe) permet d'appréhender l'ensemble des registres d'activités documentés sur le site. En particulier, cet article présente les éléments typo-technologiques qui fournissent des arguments pour rattacher l'occupation de cette cavité au Magdalénien inférieur. Une date 14C par SMA situe cette période autour de 16 000 BP (19 400 cal BP) à la grotte des Scilles. La mise en évidence de ce premier jalon pyrénéen conduit ensuite les auteurs à discuter du peuplement magdalénien à la fin du dernier maximum glaciaire dans le sud-ouest de la France et le nord de l'Espagne

The relative influences of disorder and of frustration on the glassy dynamics in magnetic systems

The magnetisation relaxations of three different types of geometrically frustrated magnetic systems have been studied with the same experimental procedures as previously used in spin glasses. The materials investigated are Y$_2$Mo$_2$O$_7$ (pyrochlore system), SrCr$_{8.6}$Ga$_{3.4}$O$_{19}$ (piled pairs of Kagom\'e layers) and (H$_3$O)Fe$_3$(SO$_4$)$_2$(OH)$_6$ (jarosite compound). Despite a very small amount of disorder, all the samples exhibit many characteristic features of spin glass dynamics below a freezing temperature $T_g$, much smaller than their Curie-Weiss temperature $\theta$. The ageing properties of their thermoremanent magnetization can be well accounted for by the same scaling law as in spin glasses, and the values of the scaling exponents are very close. The effects of temperature variations during ageing have been specifically investigated. In the pyrochlore and the bi-Kagom\'e compounds, a decrease of temperature after some waiting period at a certain temperature $T_p$ re-initializes ageing and the evolution at the new temperature is the same as if the system were just quenched from above $T_g$. However, as the temperature is raised back to $T_p$, the sample recovers the state it had previously reached at that temperature. These features are known in spin glasses as rejuvenation and memory effects. They are clear signatures of the spin glass dynamics. In the Kagom\'e compound, there is also some rejuvenation and memory, but much larger temperature changes are needed to observe the effects. In that sense, the behaviour of this compound is quantitatively different from that of spin glasses.Comment: latex VersionCorrigee4.tex, 4 files, 3 figures, 5 pages (Proceedings of the International Conference on Highly Frustrated Magnetism (HFM2003), August 26-30, 2003, Institut Laue Langevin (ILL), Grenoble, France

Preparation of large biological samples for high-resolution, hierarchical, synchrotron phase-contrast tomography with multimodal imaging compatibility

Imaging across different scales is essential for understanding healthy organ morphology and pathophysiological changes. The macro- and microscale three-dimensional morphology of large samples, including intact human organs, is possible with X-ray microtomography (using laboratory or synchrotron sources). Preparation of large samples for high-resolution imaging, however, is challenging due to limitations such as sample shrinkage, insufficient contrast, movement of the sample and bubble formation during mounting or scanning. Here, we describe the preparation, stabilization, dehydration and mounting of large soft-tissue samples for X-ray microtomography. We detail the protocol applied to whole human organs and hierarchical phase-contrast tomography at the European Synchrotron Radiation Facility, yet it is applicable to a range of biological samples, including complete organisms. The protocol enhances the contrast when using X-ray imaging, while preventing sample motion during the scan, even with different sample orientations. Bubbles trapped during mounting and those formed during scanning (in the case of synchrotron X-ray imaging) are mitigated by multiple degassing steps. The sample preparation is also compatible with magnetic resonance imaging, computed tomography and histological observation. The sample preparation and mounting require 24-36 d for a large organ such as a whole human brain or heart. The preparation time varies depending on the composition, size and fragility of the tissue. Use of the protocol enables scanning of intact organs with a diameter of 150 mm with a local voxel size of 1 μm. The protocol requires users with expertise in handling human or animal organs, laboratory operation and X-ray imaging

Mycobacterium tuberculosis ClpP Proteases Are Co-transcribed but Exhibit Different Substrate Specificities

PMCID: PMC3613350This is an open-access article distributed under the terms of the Creative Commons Attribution License, which permits unrestricted use, distribution, and reproduction in any medium, provided the original author and source are credited

Structural Controls on Crustal Fluid Circulation and Hot Spring Geochemistry Above a Flat‐Slab Subduction Zone, Peru

Hot spring geochemistry from the Cordillera Blanca and Cordillera Huayhuash, Peru, reveal the influence of crustal‐scale structures on geothermal fluid circulation in an amagmatic region located above a flat‐slab subduction zone. To test the influence of contrasting modes of faulting in these regions, springs were targeted along the Cordillera Blanca detachment fault, within its hanging wall, in the footwall of the detachment, and in the Cordillera Huayhuash. Hot springs along the Cordillera Blanca detachment fault zone are associated with recent extension and normal faulting, and those in its footwall and the Cordillera Huayhuash are located in the Marañon fold and thrust belt where compressional structures dominate. Springs along and in the hanging wall of the Cordillera Blanca detachment fault yield brackish‐saline, alkaline‐chloride waters, with oxygen, hydrogen, carbon, and chlorine stable isotope values that suggest mixing between meteoric groundwater and saline brine affected by high water‐rock interaction. Geothermometry reservoir temperature estimates (RTEs) of 91–226°C indicate maximum flow path depths of 8.7 or 11 km, depending on geothermal gradient, associated with the Cordillera Blanca detachment fault. In contrast, springs in the footwall and in the Cordillera Huayhuash exhibit a wide range of water types with an isotopic affinity to meteoric water, suggesting a greater influence from shallow groundwater and less water‐rock interaction. For these springs, RTEs of 40–98°C correspond to much shallower circulation (1.6–4 km). Results indicate that the Cordillera Blanca detachment system accommodates significantly deeper circulation of crustal fluids compared to other regional compressional structures