Rainfall patterns in the Southern Amazon: a chronological perspective (1971–2010)     

Nathan S. Debortoli  Vincent Dubreuil  Beatriz Funatsu  Florian Delahaye  Carlos Henke de Oliveira  Saulo Rodrigues-Filho  Carlos Hiroo Saito  Raquel Fetter 《Climatic change》2015,132(2):251-264

  相似文献   

Carbon-saturated monosulfide melting in the shallow mantle: solubility and effect on solidus     

Zhou Zhang  Nathan Lentsch  Marc M. Hirschmann 《Contributions to Mineralogy and Petrology》2015,170(5-6):1-13

  相似文献   

A census of the Carina Nebula – I. Cumulative energy input from massive stars     

Nathan Smith † 《Monthly notices of the Royal Astronomical Society》2006,367(2):763-772

  相似文献   

A census of the Carina Nebula – II. Energy budget and global properties of the nebulosity     

Nathan Smith  Kate J. Brooks 《Monthly notices of the Royal Astronomical Society》2007,379(4):1279-1292

  相似文献   

Reply: Late Quaternary deglacial history of the Mérida Andes,Venezuela: response to comment     

Nathan D. Stansell  Mark B. Abbott  Pratigya J. Polissar  Alexander P. Wolfe  Maximiliano Bezada  Valenti Rull 《第四纪科学杂志》2007,22(8):823-825

  相似文献   

Poroelastic two‐phase material modeling: theoretical formulation and embedded finite element method implementation          下载免费PDF全文

Nathan Benkemoun  Rachel Gelet  Emmanuel Roubin  Jean‐Baptiste Colliat 《国际地质力学数值与分析法杂志》2015,39(12):1255-1275

This paper presents the formulation of FEMs for the numerical modeling of a poroelastic two‐phase (aggregates/mixture phase) solid. The displacement and pressure fields are decomposed, following the Enhanced Assumed Strain (EAS) method, into a regular part and an enhanced part. This leads to discontinuous strain and pressure gradient fields allowing to capture the jump in mechanical and hydrical properties passing through the interface between the aggregates and the mixture phase. All these enhanced fields are treated in the context of the embedded FEM through a local enhancement of the finite element interpolations as these jumps appear. The local character of these interpolations leads after a static condensation of the enhanced fields to a problem exhibiting the same structure as common poroelastic finite element models but incorporating now the mechanical and hydrical properties of a two‐phase solid. Copyright © 2015 John Wiley & Sons, Ltd.  相似文献   

Spatial variations of the décollement/protodécollement zone and their implications: A 3-D seismic inversion study of the northern Barbados accretionary prism     

Zhiyong Zhao  Gregory F. Moore  Nathan L. B. Bangs and  Thomas H. Shipley 《Island Arc》2000,9(2):219-236

We conducted a 3‐D seismic inversion study to investigate spatial variations of physical properties of the décollement zone (DZ) and protodécollement zone (PDZ) under the northern Barbados accretionary prism. Significant spatial variations of physical properties were observed in the PDZ seaward of the thrust front from the inversion data. The density generally increases southward with a few localized low‐density patches. A lower density commonly corresponds to a thicker PDZ, suggesting that the paleomorphology may at least partially control the variations of the physical properties. Similar low‐density patches were also found in the DZ. These features may be inherited from those of the PDZ and enhanced after subduction through localized arrested consolidation. Under the prism toe, the density of the DZ increases landward. This trend may mainly result from shear‐induced consolidation of the DZ but may also be related to landward increasing tectonic loading. Significant north–south differences in density and, thus, porosity and strength of the PDZ, are observed and these differences may continue into the DZ. A stronger DZ is likely responsible for a larger prism taper observed in the southern area of the prism toe. The larger taper, thus more horizontal shortening, coupled with a thinner sediment sheet above the PDZ in the southern area, may cause a relative retreat of the thrust front and a pronounced change in strike of the sequence thrusts south of seismic Line 690. The north–south differences may ultimately have originated in the approach of a structurally higher segment of the Tiburon Rise. The Tiburon Rise affects regional morphology and, thus, it controls the sedimentation and physical properties of the PDZ. It may also control sediment accumulation above the PDZ. Therefore, the sedimentational change induced by the structural high of the Tiburon Rise, in turn, resulted in structural change of the prism in the southern area.  相似文献   

Sediments,porewaters and diagenesis in an urban water body,Salford, UK: impacts of remediation     

Kevin G. Taylor  Nathan A. Boyd  Stephen Boult 《水文研究》2003,17(10):2049-2061

Contaminated sediments deposited within urban water bodies commonly exert a significant negative effect on overlying water quality. However, our understanding of the processes operating within such anthropogenic sediments is currently poor. This paper describes the nature of the sediment and early diagenetic reactions in a highly polluted major urban water body (the Salford Quays of the Manchester Ship Canal) that has undergone remediation focused on the water column. The style of sedimentation within Salford Quays has been significantly changed as a result of remediation of the water column. Pre‐remediation sediments are composed of a range of natural detrital grains, predominantly quartz and clay, and anthropogenic detrital material dominated by industrial furnace‐derived metal‐rich slag grains. Post‐remediation sediments are composed of predominantly autochthonous material, including siliceous algal remains and clays. At the top of the pre‐remediation sediments and immediately beneath the post‐remediation sediments is a layer significantly enriched in furnace‐derived slag grains, input into the basin as a result of site clearance prior to water‐column remediation. These grains contain a high level of metals, resulting in a significantly enhanced metal concentration in the sediments at this depth. Porewater analysis reveals the importance of both bacterial organic matter oxidation reactions and the dissolution of industrial grains upon the mobility of nutrient and chemical species within Salford Quays. Minor release of iron and manganese at shallow depths is likely to be taking place as a result of bacterial Fe(III) and Mn(IV) reduction. Petrographic analysis reveals that the abundant authigenic mineral within the sediment is manganese‐rich vivianite, and thus Fe(II) and Mn(II) released by bacterial reactions may be being taken up through the precipitation of this mineral. Significant porewater peaks in iron, manganese and silicon deeper in the sediment column are most probably the result of dissolution of furnace‐derived grains in the sediments. These species have subsequently diffused into porewater above and below the metal‐enriched layer. This study illustrates that the remediation of water quality in anthropogenic water bodies can significantly impact upon the physical and chemical nature of sedimentation. Additionally, it also highlights how diagenetic processes in sediments derived from anthropogenic grains can be markedly different from those in sediments derived from natural detrital material. Copyright © 2003 John Wiley & Sons, Ltd.  相似文献   

Heavy metal levels in New Zealand molluscs     

Stephen A. Nielsen  Adrienne Nathan 《新西兰海洋与淡水研究杂志》2013,47(4):467-481

Cadmium, lead, copper, mercury, zinc and iron were analysed by atomic absorption spectrophotometry in 13 species of edible molluscs from 199 sites around New Zealand; these included all molluscs commonly eaten in New Zealand. From each sampling site, a minimum of 14 specimens were combined and analysed together, so that the result would be representative of the population in that area. Wide variations are shown to occur in heavy metals from one location to another, and explanations for some of these variations are given.  相似文献   

Sedna and the Oort Cloud around a migrating Sun     

Nathan A. Kaib  Rok Roškar  Thomas Quinn 《Icarus》2011,215(2):491-507

Recent numerical simulations have demonstrated that the Sun’s dynamical history within the Milky Way may be much more complex than that suggested by its current low peculiar velocity (Sellwood, J.A., Binney, J.J. [2002]. Mon. Not. R. Astron. Soc. 336, 785-796; Roškar, R., Debattista, V.P., Quinn, T.R., Stinson, G.S., Wadsley, J. [2008]. Astrophys. J. 684, L79-L82). In particular, the Sun may have radially migrated through the galactic disk by up to 5-6 kpc (Roškar, R., Debattista, V.P., Quinn, T.R., Stinson, G.S., Wadsley, J. [2008]. Astrophys. J. 684, L79-L82). This has important ramifications for the structure of the Oort Cloud, as it means that the Solar System may have experienced tidal and stellar perturbations that were significantly different from its current local galactic environment. To characterize the effects of solar migration within the Milky Way, we use direct numerical simulations to model the formation of an Oort Cloud around stars that end up on solar-type orbits in a galactic-scale simulation of a Milky Way-like disk formation. Surprisingly, our simulations indicate that Sedna’s orbit may belong to the classical Oort Cloud. Contrary to previous understanding, we show that field star encounters play a pivotal role in setting the Oort Cloud’s extreme inner edge, and due to their stochastic nature this inner edge sometimes extends to Sedna’s orbit. The Sun’s galactic migration heightens the chance of powerful stellar passages, and Sedna production occurs around ∼20-30% of the solar-like stars we study. Considering the entire Oort Cloud, we find its median distance depends on the minimum galactocentric distance attained during the Sun’s orbital history. The inner edge also shows a similar dependence but with increased scatter due to the effects of powerful stellar encounters. Both of these Oort Cloud parameters can vary by an order of magnitude and are usually overestimated by an Oort Cloud formation model that assumes a fixed galactic environment. In addition, the amount of material trapped in outer Oort Cloud orbits (a > 20,000 AU) can be extremely low and may present difficulties for traditional models of Oort Cloud formation and long-period comet production.  相似文献