Corrigendum to “Trajectories of sinking particles in the Sargasso Sea: modeling of statistical funnels above deep-ocean sediment traps” [Deep-Sea Research I 44, 1519–1541]     

《Deep Sea Research Part I: Oceanographic Research Papers》2002,49(6):1115-1116

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Dynamical evolutuion of planetesimals driven by a massive planet: First simulations     

《Physics and Chemistry of the Earth, Part C: Solar, Terrestrial & Planetary Science》1999,24(5):557-559

N-body simulations of the dynamical evolution of proto-planets embedded in a swarm of planetesimals and perturbed by a massive Jupiter-like planet were performed with the GRAPE-4 system recently installed in Marseille observatory. Initially both the protoplanets and the planetesimals are on circular and coplanar orbits distributed in a ring located within the orbital radius of the perturber. The first simulations show that, for a perturber significantly more massive than Jupiter, the system of the proto-planets becomes strongly unstable with the possibility of orbit crossing.  相似文献   

The Hadley circulation: assessing NCEP/NCAR reanalysis and sparse in-situ estimates   总被引：1，自引：1，他引：0  

D. E. Waliser  Zhixiong Shi  J. R. Lanzante  A. H. Oort 《Climate Dynamics》1999,15(10):719-735

 We present a comparison of the zonal mean meridional circulations derived from monthly in situ data (i.e. radiosondes and ship reports) and from the NCEP/NCAR reanalysis product. To facilitate the interpretation of the results, a third estimate of the mean meridional circulation is produced by subsampling the reanalysis at the locations where radiosonde and surface ship data are available for the in situ calculation. This third estimate, known as the subsampled estimate, is compared to the complete reanalysis estimate to assess biases in conventional, in situ estimates of the Hadley circulation associated with the sparseness of the data sources (i.e., radiosonde network). The subsampled estimate is also compared to the in situ estimate to assess the biases introduced into the reanalysis product by the numerical model, initialization process and/or indirect data sources such as satellite retrievals. The comparisons suggest that a number of qualitative differences between the in situ and reanalysis estimates are mainly associated with the sparse sampling and simplified interpolation schemes associated with in situ estimates. These differences include: (1) a southern Hadley cell that consistently extends up to 200 hPa in the reanalysis, whereas the bulk of the circulation for the in situ and subsampled estimates tends to be confined to the lower half of the troposphere, (2) more well-defined and consistent poleward limits of the Hadley cells in the reanalysis compared to the in-situ and subsampled estimates, and (3) considerably less variability in magnitude and latitudinal extent of the Ferrel cells and southern polar cell exhibited in the reanalysis estimate compared to the in situ and subsampled estimates. Quantitative comparison shows that the subsampled estimate, relative to the reanalysis estimate, produces a stronger northern Hadley cell (∼20%), a weaker southern Hadley cell (∼20–60%), and weaker Ferrel cells in both hemispheres. These differences stem from poorly measured oceanic regions which necessitate significant interpolation over broad regions. Moreover, they help to pinpoint specific shortcomings in the present and previous in situ estimates of the Hadley circulation. Comparisons between the subsampled and in situ estimates suggest that the subsampled estimate produces a slightly stronger Hadley circulation in both hemispheres, with the relative differences in some seasons as large as 20–30%. 6These differences suggest that the mean meridional circulation associated with the NCEP/NCAR reanalysis is more energetic than observations suggest. Examination of ENSO-related changes to the Hadley circulation suggest that the in situ and subsampled estimates significantly overestimate the effects of ENSO on the Hadley circulation due to the reliance on sparsely distributed data. While all three estimates capture the large-scale region of low-level equatorial convergence near the dateline that occurs during El Nino, the in situ and subsampled estimates fail to effectively reproduce the large-scale areas of equatorial mass divergence to the west and east of this convergence area, leading to an overestimate of the effects of ENSO on the zonal mean circulation. Received: 16 September 1998 / Accepted: 22 April 1999  相似文献   

Calculating field weathering rates using a mechanistic geochemical model PROFILE     

《Applied Geochemistry》1993,8(3):273-283

A new model for base cation release due to chemical weathering of soil minerals has been developed based on transition state theory, and included in the integrated soil chemistry model PROFILE. The data required for model application can be operationally determined on soil samples, making the model generally applicable and independent of any type of calibration. The model considers the contribution to the weathering rate from 12 groups of the most common primary and secondary minerals of soils, reacting in separate reactions with H⁺-ion, H₂O, CO₂ and organic acids expressed as dissolved organic carbon (DOC). The weathering rate sub-model couples the effects of dissolved Al and base cations on the reaction mechanisms. The model takes into account changes in soil temperature, different chemical conditions, the effect of vegetation interactions with the soil and N transformations. The kinetic coefficients and reaction orders are based on a complete re-evaluation of weathering data available in the literature, and additional kinetic data determined by the authors.Data from 23 different independent determinations of the field weathering rate from 15 sites in Scandinavia, Central Europe and North America were compiled and used to verify the model. The model is capable of estimating the release rate of base cations due to chemical weathering from information on soil mineralogy, texture and geochemical properties of the order of ±20% of the rate determined by independent methods. The results indicate that small amounts of dark minerals like epidote and hornblende, and the plagioclase content, largely determine the field weathering rate.  相似文献   

Chemical forms and dynamics of amino acid-containing particulate organic matter in Pacific surface waters     

《Deep Sea Research Part I: Oceanographic Research Papers》2005,52(10):1865-1884

Particulate combined amino acids (PCAA) are the most abundant identified constituents of particulate organic matter (POM) in Pacific Ocean surface waters, but their chemical forms are unclear. In the present study, chemical characterization of amino acid-containing materials in surface POM from subarctic to subtropical waters along 165 °E in the Pacific was carried out by one- and two-dimensional gel electrophoresis. At least four chemical forms of amino acid-containing POM were distinguished: proteins, acidic materials containing peptides, protein/peptide-specific dye-stainable low-molecular-mass materials (stainable materials) and non-stainable materials, all of which were considered to be major components of detrital POM. Seventeen distinct protein containing components were distinguished in samples across the transect. A majority of stainable materials was estimated to comprise 6–8 amino acid residues, while less than six amino acid residues made up the non-stainable materials. Among the four chemical forms, acidic materials and non-stainable materials were major components, accounting for 31–42% and 49–63% of PCAA, respectively, along the transect. Proteins were common, but they were quantitatively less than 2% of PCAA. Stainable materials were regionally variable and more abundant in subarctic waters than in subtropical waters. The mechanistic processes by which such amino acid-containing POM occurs as detrital POM are discussed.  相似文献   

Vertical distribution of prokaryote production and abundance in the mesopelagic and bathypelagic layers of the Canada Basin,western Arctic: Implications for the mode and extent of organic carbon delivery     

《Deep Sea Research Part I: Oceanographic Research Papers》2013

The vertical distributions of prokaryote heterotrophic production (³H-leucine incorporation rate) and abundance were investigated in the meso- and bathy-pelagic layers of the Canada Basin, western Arctic Ocean, during September 2009. Prokaryote production and abundance were high in the Pacific-origin water mass located in the upper mesopelagic layer (depth, 100–200 m). Below the halocline layer (depth, 300–3000 m), both the production and abundance decreased with depth, with log–log regression slopes of −1.33 and −0.77, respectively. Depth-integrated production and biomass in the meso- and bathy-pelagic layers was three- to five-fold lower than the corresponding values reported in the subpolar regions, whereas they were close to or lower than the corresponding values in oligotrophic subtropical regions. Prokaryote turnover times were estimated to be 1.1 and 6.1 years for meso- and bathy-pelagic layers, respectively, with the latter being among the longest turnover times reported for oceanic basins. We estimated prokaryote carbon demand in the water column (100–3000 m) to be on the order of 11 mg C m⁻² d⁻¹, which largely exceeds (by 38-fold) the sinking particulate organic carbon flux at depths of 120–200 m reported in the literature. This large carbon imbalance may be partly explained by organic carbon delivery by lateral intrusion of the Pacific-origin water mass into the upper mesopelagic layer.  相似文献   

First postcranial remains of Multituberculata (Allotheria,Mammalia) from Gondwana     

《Cretaceous Research》2017

Multituberculates (Allotheria) are generally regarded as the evolutionarily most successful and longest-lived (Middle Jurassic to late Eocene) clade of Mesozoic and early Paleogene mammals. Despite this “reputation” and the fact that the group is particularly well represented in both taxonomic diversity and relative abundance on Laurasian landmasses during the Cretaceous and Paleocene, multituberculates are exceedingly poorly represented on the southern supercontinent Gondwana. Previous records on Gondwanan landmasses have been based on fragmentary dental remains and all except the three most recently published (each represented by a single isolated tooth or fragment of tooth) have been disputed and allocated to either Haramiyida or Gondwanatheria. Furthermore, several previous records, disputed or not, are based on fragmentary dental remains of a type (plagiaulacoid) that has evolved independently several times in mammalian evolution.Here we place on record a multituberculate femur from the Upper Cretaceous (Maastrichtian) Maevarano Formation of the Mahajanga Basin, Madagascar. This specimen, although fragmentary as well, exhibits a number of features common to all multituberculate femora: neck cylindrical in cross section and set apart from shaft; greater trochanter prominent, extending proximally beyond head, inclined dorsally, and separated from neck by deep incisure; lesser trochanter prominent and protruding ventrally; posttrochanteric fossa present on ventral aspect, lateral to lesser trochanter; subtrochanteric tubercle present on dorsal aspect, distal to incisure between greater trochanter and neck; diaphysis straight, elliptical in cross section (slightly compressed dorsoventrally); and third trochanter absent. Three of these features (prominent, ventrally placed lesser trochanter; presence of posttrochanteric fossa; presence of subtrochanteric tubercle) are regarded as autapomorphies of Multituberculata. This specimen therefore not only independently and conclusively confirms the presence of the clade on Madagascar—previously based on a small molar fragment—but on the entire supercontinent as well.  相似文献   

Effect of non-linear soil deformation on the interaction among energy piles     

《Computers and Geotechnics》2017

This study investigates the effect of non-linear soil deformation on the displacement interaction among energy piles. The work is based on interaction factor analyses of full-scale pile group tests, whose results are compared with experimental evidence. The results presented highlight the tendency of interaction factor analyses that ignore non-linear soil deformation to overestimate the interaction and the displacement of energy pile groups. This outcome, in accordance with previous studies for conventional pile groups subjected to mechanical loads, may be considered in the analysis and design of energy pile groups subjected to thermal (and mechanical) loads through the interaction factor method.  相似文献   

Evaluating the use of 3'-(p-Aminophenyl) fluorescein for determining the formation of highly reactive oxygen species in particle suspensions     

Corey A Cohn  Christopher E Pedigo  Shavonne N Hylton  Sanford R Simon  Martin AA Schoonen 《Geochemical transactions》2009,10(1):8-9

Background  

Given the importance of highly reactive oxygen species (hROS) as reactants in a wide range of biological, photochemical, and environmental systems there is an interest in detection and quantification of these species. The extreme reactivity of the hROS, which includes hydroxyl radicals, presents an analytical challenge. 3'-(p-Aminophenyl) fluorescein (APF) is a relatively new probe used for measuring hROS. Here, we further evaluate the use of APF as a method for the detection of hydroxyl radicals in particle suspensions.  相似文献   

Peculiarities of the within-year distribution of earthquakes in the Kuril region     

M. Yu. Andreeva  E. V. Sasorova  B. W. Levin 《Russian Journal of Pacific Geology》2009,3(5):491-500

Recent investigations have shown that the probability of the occurrence of earthquakes in a specified region depends on several factors, such as the latitude of the study region, as well as the lunar and solar tidal forces, which are governed by the mutual arrangement of bodies in the Sun-Earth-Moon system. The objective of our work is to prove that the irregularity of the within-year distribution of seismic events in the Pacific regions (the Kuril Islands and Hokkaido Island) is a statistically significant process, which is manifested in different ways for earthquakes with various source depths and energy levels. The hypothesis about the uniform within-year distribution of earthquakes is refuted for shallow events. However, it is shown that deep earthquakes are distributed uniformly. This work attempts for the first time to determine the stability degree of the within-year irregularity of seismic events with respect to the observation time interval (from 28 to 5 years). Two peaks are noted in the annual distribution of the earthquakes. The relation of the peaks of the within-year seismic activity to the Earth’s position on the ecliptic plane, as well as the relationships between the peaks, the magnitude range of the events, and the position of the specified subregion, is considered. The principal maximum of the seismic activity falls in the November-March period, which matches the minimum Earth-Sun distance.  相似文献