The shape of the magnetosphere has been calculated self-consistently for inclinations of the Earth's magnetic dipole from perpendicular to the solar wind. Inclination angles of 0–35° have been chosen in steps of 5° and various smooth trends in the surface characteristics with increasing inclination angle noted. The surface points and the complete field at the surface points have been calculated for the entire surfaces. The neutral point region has been given precise study in one degree steps and is found to be tangent to the solar wind velocity and to have a smooth continuous curvature. The inclusion of the Earth's bow shock pressure and other sources of current have not been included at this stage of our program. 相似文献
Imposex was measured in the rock shell, Thais clavigera, from the coast of the Korean peninsula. Frequency of imposex was 0% at two reference sites, but at 47 out of 61 sites, frequency of imposex was recorded as 100%. The degree of imposex was relatively high at the sites near a harbor and a shipyard. Tributyltin (TBT) and triphenyltin (TPT) concentrations in T. clavigera ranged from 5 to 508 ng/g and from 3 to 2460 ng/g, respectively. A significant positive relationship was found between degree of imposex and organotin concentration, whereas a significant negative relationship was obtained between female-to-male sex ratio and the degree of imposex. During a field transplantation of T. clavigera from a pristine area to a port, TBT and TPT were accumulated in T. clavigera, and imposex was induced. T. clavigera shows considerable potential as a bioindicator species of the adverse effects of TBT and TPT contamination. 相似文献
1.IntroductionAmong various control devices,Tuned Mass Damper(TMD)has been mostfrequently usedtothecontrol of structural vibration induced by oscillating loads such as earthquakes,winds,and waves.This is due to the fact that it operates without external e… 相似文献
Previous research has suggested that competitive bottlenecks may exist for the Mediterranean grey mullets (Osteichthyes, Mugilidae) at the fry stage with the exotic Cyprinus carpio (Osteichthyes, Cyprinidae) playing a central role. As a consequence, the structure of grey mullet assemblages at later stages is thought to reflect previous competition as well as differences in osmoregulatory skills. This paper tests that hypothesis by examining four predictions about the relative abundance of five grey mullet species in 42 Western Mediterranean estuary sites from three areas (Aiguamolls de l'Empordà, Ebro Delta and Minorca) differing in the salinity level and occurrence of C. carpio. Field data confirmed the predictions as: (1) Liza aurata and Mugil cephalus were scarce everywhere and never dominated the assemblage; (2) Liza saliens dominated the assemblage where the salinity level was higher than 13; (3) Liza ramado always dominated the assemblage where the salinity level was lower than 13 and C. carpio was present; and (4) Chelon labrosus dominated the assemblage only where the salinity level was lower than 13 and C. carpio was absent. The catch per unit effort of C. labrosus of any size was smaller in the presence of C. carpio than where it had not been introduced, which is in agreement with the juvenile competitive bottleneck hypothesis. Discriminant analysis confirmed that the assemblage structure was linked to the salinity level and the occurrence of C. carpio for both early juveniles and late juveniles as well as adults. The data reported here reveal that the structure of grey mullet assemblages inhabiting Mediterranean estuaries is determined by salinity and competitive interactions at the fry stage. 相似文献
We investigated the distribution of δ13C and δ15N of organic matter among benthic communities from the upper estuary of Yura River to offshore of Tango Sea, Japan, to determine spatial variation in utilization of organic matter by benthic communities. The δ13C values of benthic animals ranged from −27 to −15‰ in the upper estuary, −21 to −15‰ in the lower estuary, −20 to −16‰ in the shallow coast (5–10 m depths), −18 to −16‰ in the deep coast (30–60 m depths) and −19 to −15‰ in offshore (100–150 m depths) stations. Adapting the dual isotope values to mixing models, we estimated the relative contributions of potential food sources to the benthos diet. Phytoplankton and macroalgae that intruded the estuary in summer were utilized as alternative food aside from the terrestrial-origin organic matter assimilated by the estuarine benthic consumers. Resuspended benthic microalgae were important source of energy in the shallow coastal stations, while abundant supply of phytodetritus fueled the deep coastal and offshore benthic food webs. Spatial difference in the diet of benthic communities depends largely on the shifts in the primary carbon source. Thus, benthic communities are important link of autochthonous/allochthonous production and secondary production in the continuous river–estuary–marine system. 相似文献
Understanding contaminant transport in clay-containing soils is critical for accurate prediction of the travel distances of contaminants and for the design and implementation of corresponding remediation plans. This study examined the breakthrough behavior of methylene blue (MB) through sand-illite mixtures using laboratory soil-column experiments at five inlet concentrations, three flow rates, and five illite contents. Kinetic and equilibrium adsorption tests were performed to evaluate the maximum adsorption capacities of the sand and illite used in the soil-column experiments. In addition, the bed efficiency, MB saturation, and adsorption rate were calculated to quantitatively describe the observed breakthrough curves. The observed breakthrough curves, bed efficiencies, MB saturations, and adsorption rates in this study demonstrated the presence of a threshold illite content of ~10% for the adsorption efficiency of contaminants. This implies the need to evaluate the threshold clay content for accurate predictions of contaminant transport through gap-graded clay-containing soils.
This study aims to examine the favorable conditions for an ocean effect snowstorm across the Yellow Sea over the southwestern coast of Korea on 21 December 2005, using a coupled model with a Coupled Ocean/Atmosphere Mesoscale Prediction System as the atmospheric component and the Regional Ocean Modeling System as the oceanic component. Simulation of heavy snowfall event, which was 44.3 cm of snow accumulated in 24-hour, was performed to investigate the mesoscale structure, dynamics and development mechanisms in the snowstorm. As a result from 48-hour integration, the results of simulation showed that barotropic instability and turbulent heat fluxes played important roles in the formation of snowstorm. The enhanced surface diabatic heating was dominant in the latent heat flux, and eventually induced convective instability. An additional factor was the favorable condition of synoptic environment, accessing the cold air transport by the approach of the upper-level cold vortex over the warm ocean. Besides these factors, conditional symmetric instability (CSI) is a mechanism which can result in a heavy snowfall with sufficient moisture and upward vertical motion. A slantwise convection from the release of CSI could support a complex snowfall event with heavier than expected amounts. The result comparison between a coupled model and an uncoupled model supports that airsea coupling has an impact of decreasing of about 10% in a snowfall amount on the snowstorm. 相似文献
Ore beds with fluorite and sphalerite occur in the Cave-In-Rock fluorite district, Illinois in the upper part of the Mississippian System; in the upper parts of the Fredonia and Joppa Members of the Ste. Genevieve Formation and in the upper part of the Downeys Bluff Formation. Sedimentary structures within the upper two horizons are described and discussed. Primary cut-and-fill channels usually contain broken pieces of dolomite, limestone, shale, sandstone, fluorite and sphalerite. Some of the channels show geopetal features. Horizontal stylolitic seams bend downward and their thicknesses increase while their amplitudes decrease near and along the channel slopes. Another geopetal feature consists of clastic shale fragments which have mechanically filled from above into an open crack formed in the hydroplastic carbonate mud below. A number of features known as collapsed structures prove to be cut-and-fill structures of primary origin. During the compaction, carbonate beds were reduced in thickness by at least 37% through styloitization. The relationships between primary sedimentary channels and fluorite-sphalerite ore rocks suggest that the latter may have been deposited during or after the formation of such sedimentary structures, i. e., during various stages of diagenesis.
Zusammenfassung Die Fluorit-Zinkblende-Vorkommen des Cave-In-Rock Distrikts von Illinois treten stratigraphisch in den oberen Partien des Mississippian System, speziell in der Fredonia und Joppa Serie der Ste. Genevieve Formation und in der Downeys Bluff Formation auf. Einige sedimentäre Strukturen in diesen beiden oberen Horizonten werden beschrieben und diskutiert. Primäre cut-and-fill channels enthalten im allgemeinen Bruchstücke von Dolomit, Kalk- und Sandstein, Schieferton, Fluorit und Zinkblende. Einige channels zeigen geopetale Gefüge, d. h. horizontale stylolithische Lagen sind mit zunehmender Mächtigkeit und abnehmender Amplitude der Fältelung in der Nähe oder entlang der Flanken der channel Strukturen nach unten durchgebogen. Ein weiteres geopetales Gefüge besteht aus Schieferton-Fragmenten, die mechanisch in eine offene Spalte des darunterliegenden hydroplastischen Karbonatschlammes eingesunken sind. Eine Anzahl von Gefügen, bekannt als collapsed structures scheinen cut-and-fill und slump Strukturen von primär subaquatischer Herkunft zu sein. Während der Diagenese wurden Karbonatbänke durch Stylolithbildung um mindestens 37% der ursprünglichen Mächtigkeit reduziert. Die Beziehungen zwischen den primären sedimentären channels und dem Fluorit-Zinkblende-Erz deuten darauf hin, daß das letztere während oder nach der Bildung der sedimentären Strukturen abgelagert wurde, d. h., während verschiedener Perioden der Diagenese.