Sorption of Eu(III) on Attapulgite Studied by Batch, XPS and EXAFS Techniques.

The effects of pH, ionic strength and temperature on sorption of Eu(III) on attapulgite were investigated in the presence and absence of fulvic acid (FA) and humic acid (HA). The results indicated that the sorption of Eu(III) on attapulgite was strongly dependent on pH and ionic strength, and independent of temperature. In the presence of FA/HA, Eu(III) sorption was enhanced at pH 7. The X-ray photoelectron spectroscopy (XPS) analysis suggested that the sorption of Eu(III) might be expressed as ≡X3Eu0 ≡SwOHEu3+ and ≡SOEu-OOC-/HA in the ternary Eu/HA/attapulgite system. The extended X-ray absorption fine structure (EXAFS) analysis of Eu-HA complexes indicated that the distances of d(Eu-O) decreased from 2.451 to 2.360 Å with increasing pH from 1.76 to 9.50, whereas the coordination number (N) decreased from ~9.94 to ~8.56. Different complexation species were also found for the different addition sequences of HA and Eu(III) to attapulgite suspension. The results are important to understand the influence of humic substances on Eu(III) behavior in the natural environment

Baryons: What, When and Where?

We review the current state of empirical knowledge of the total budget of baryonic matter in the Universe as observed since the epoch of reionization. Our summary examines on three milestone redshifts since the reionization of H in the IGM, z = 3, 1, and 0, with emphasis on the endpoints. We review the observational techniques used to discover and characterize the phases of baryons. In the spirit of the meeting, the level is aimed at a diverse and non-expert audience and additional attention is given to describe how space missions expected to launch within the next decade will impact this scientific field.Comment: Proceedings Review for "Astrophysics in the Next Decade: JWST and Concurrent Facilities", ed. X. Tielens, 38 pages, 10 color figures. Revised to address comments from the communit

Flux-rope twist in eruptive flares and CMEs : due to zipper and main-phase reconnection

Funding: UK Science and Technology Facilities CouncilThe nature of three-dimensional reconnection when a twisted flux tube erupts during an eruptive flare or coronal mass ejection is considered. The reconnection has two phases: first of all, 3D “zipper reconnection” propagates along the initial coronal arcade, parallel to the polarity inversion line (PIL); then subsequent quasi-2D “main phase reconnection” in the low corona around a flux rope during its eruption produces coronal loops and chromospheric ribbons that propagate away from the PIL in a direction normal to it. One scenario starts with a sheared arcade: the zipper reconnection creates a twisted flux rope of roughly one turn (2π radians of twist), and then main phase reconnection builds up the bulk of the erupting flux rope with a relatively uniform twist of a few turns. A second scenario starts with a pre-existing flux rope under the arcade. Here the zipper phase can create a core with many turns that depend on the ratio of the magnetic fluxes in the newly formed flare ribbons and the new flux rope. Main phase reconnection then adds a layer of roughly uniform twist to the twisted central core. Both phases and scenarios are modeled in a simple way that assumes the initial magnetic flux is fragmented along the PIL. The model uses conservation of magnetic helicity and flux, together with equipartition of magnetic helicity, to deduce the twist of the erupting flux rope in terms the geometry of the initial configuration. Interplanetary observations show some flux ropes have a fairly uniform twist, which could be produced when the zipper phase and any pre-existing flux rope possess small or moderate twist (up to one or two turns). Other interplanetary flux ropes have highly twisted cores (up to five turns), which could be produced when there is a pre-existing flux rope and an active zipper phase that creates substantial extra twist.PostprintPublisher PDFPeer reviewe

Query translation from XPath to SQL in the presence of recursive DTDs

The interaction between recursion in XPATH and recursion in DTDs makes it challenging to answer XPATH queries on XML data that is stored in an RDBMS via schema-based shredding. We present a new approach to translating XPATH queries into SQL queries with a simple least fixpoint (LFP) operator, which is already supported by most commercial RDBMS. The approach is based on our algorithm for rewriting XPATH queries into regular XPATH expressions, which are capable of capturing both DTD recursion and XPATH queries in a uniform framework. Furthermore, we provide an algorithm for translating regular XPATH queries to SQL queries with LFP, and optimization techniques for minimizing the use of the LFP operator. The novelty of our approach consists in its capability to answer a large class of XPATH queries by means of only low-end RDBMS features already available in most RDBMS. Our experimental results verify the effectiveness of our techniques

The morphology of Au@MgO nanopeapods

Nanotechnology2045-NNOT

Permeability inversion using induced microseismicity: A case study for Longmaxi shale gas reservoir

We predict the flow permeability and its spatial distribution for the Longmaxi shale gas reservoir using microseismicity induced during hydraulic fracturing stimulation. In the time-of-occurrence versus distance-from-injector plot, we find that microseismic points exhibit a parabolic envelope, which we interpret as a triggering front. This reveals that fluid pressure diffusion is at least one of underlying mechanisms of microseismicity generation. We derive the large-scale equivalent diffusivity from the triggering front plot and thereafter obtain a 3D diffusivity map of the heterogeneous reservoir by solving an eikonal-like equation suggested previously. During this process, we apply kriging interpolation to increase the density of sparsely distributed microseismic points. The resulting diffusivity ranges between 1.0 m2·s-1 and 25.85 m2 s-1 with the peak probability attained at 1.8 m2 s-1, which is consistent with the estimate we obtain from the triggering front analysis. We transform the diffusivity map into a permeability map using three different theories of fluid pressure diffusion in porous media. These are the seismicity-based-reservoir-characterization method (SBRC) based on Biot's theory of poroelasticity, the quasi-rigid medium approximation (QRMA) and the deformable medium approximation (DMA) based on the de la Cruz-Spanos theory. The permeability according to QRMA is slightly higher than that from SBRC, yet we observe no significant difference. However, these estimates are both by one order of magnitude higher compared with the permeability estimate from DMA. Furthermore, the permeability from all three theories is much higher than that from previously reported core sample measurements. We interpret this as the difference between large-scale equivalent and matrix permeability and therefore lend weight to the hypothesis that there exist highly conducting fluid pathways, such as natural fractures