Global zoogeography of fragile macrozooplankton in the upper 100-1000 m inferred from the underwater video profiler     

Stemmann  Lars; Youngbluth  Marsh; Robert  Kevin; Hosia  Aino; Picheral  Marc; Paterson  Harriet; Ibanez  Frederic; Guidi  Lionel; Lombard  Fabien; Gorsky  Gabriel 《ICES Journal of Marine Science》2008,65(3):433-442

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Simulations of 3D Magnetic Merging: Resistive Scalings for Null Point and QSL Reconnection     

Frederic Effenberger  I. J. D. Craig 《Solar physics》2016,291(1):143-153

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Experimental investigation of the alluaudite?+?triphylite assemblage, and development of the Na-in-triphylite geothermometer: applications to natural pegmatite phosphates     

Frederic Hatert  Luisa Ottolini  Peter Schmid-Beurmann 《Contributions to Mineralogy and Petrology》2011,161(4):531-546

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Monitoring the effects of disposal of fine sediments from maintenance dredging on suspended particulate matter concentration in the Belgian nearshore area (southern North Sea)     

Fettweis M  Baeye M  Francken F  Lauwaert B  Van den Eynde D  Van Lancker V  Martens C  Michielsen T 《Marine pollution bulletin》2011,62(2):258-269

The impact of continuous disposal of fine-grained sediments from maintenance dredging works on the suspended particulate matter concentration in a shallow nearshore turbidity maximum was investigated during dredging experiment (port of Zeebrugge, southern North Sea). Before, during and after the experiment monitoring of SPM concentration using OBS and ADV altimetry was carried out at a location 5 km west of the disposal site. A statistical analysis, based on the concept of populations and sub-sampling, was applied to evaluate the effect. The data revealed that the SPM concentration near the bed was on average more than two times higher during the dredging experiment. The disposed material was mainly transported in the benthic layer and resulted in a long-term increase of SPM concentration and formation of fluid mud layers. The study shows that SPM concentration can be used as an indicator of environmental changes if representative time series are available.  相似文献   

Substantial stream–disc overflow found in three-dimensional SPH simulations of cataclysmic variables     

Stefan Kunze  Roland Speith  Frederic V. Hessman 《Monthly notices of the Royal Astronomical Society》2001,322(3):499-514

We study numerically the interaction of the infalling gas stream and the rim of the accretion disc in cataclysmic variables. The simulations were performed with a smoothed particle hydrodynamics scheme with high spatial resolution. Parameters of the systems AM CVn, OY Car, DQ Her, U Gem and IP Peg were used for the simulations. The simulations cover a wide range of orbital periods, mass ratios and mass transfer rates, as well as different thermal states of the accretion disc. The main result of this study is that the accretion stream is not stopped at the impact region (the bright spot at the outer rim of the disc). In fact, after undergoing the shock interaction, most of the matter is deflected vertically and flows in a more or less diffuse stream to inner parts of the disc, hitting the disc surface close to the circularization radius at orbital phase 0.5. This is a common feature in all systems for all simulated parameters. This stream overflow can cause the X-ray absorption dips observed in cataclysmic variables (CVs) and low-mass X-ray binaries (LMXBs) around orbital phase 0.7, if the inclination is at least 65°. Under certain circumstances, namely a sudden increase of the mass transfer rate from the secondary or a rather small disc, parts of the overflowing stream bounce off the disc surface after hitting it at orbital phase ≈0.5. Another absorption region can be expected around orbital phase 0.2.
In our simulations most of the infalling matter reaches the inner disc very quickly. This must alter the evolution of the quiescent disc and the outburst behaviour considerably compared with purely viscous transport of the material through the disc from the outer rim, and therefore should be taken into account in dwarf nova outburst cycle calculations. To our knowledge, the consequences of such a massive stream overflow for the dwarf nova outburst cycle have not been considered yet.  相似文献   

Tidal interactions and disruptions of giant planets on highly eccentric orbits     

Joshua A. Faber  Frederic A. Rasio  Bart Willems 《Icarus》2005,175(1):248-262

We calculate the evolution of planets undergoing a strong tidal encounter using smoothed particle hydrodynamics (SPH), for a range of periastron separations. We find that outside the Roche limit, the evolution of the planet is well-described by the standard model of linear, non-radial, adiabatic oscillations. If the planet passes within the Roche limit at periastron, however, mass can be stripped from it, but in no case do we find enough energy transferred to the planet to lead to complete disruption. In light of the three new extrasolar planets discovered with periods shorter than two days, we argue that the shortest-period cases observed in the period-mass relation may be explained by a model whereby planets undergo strong tidal encounters with stars, after either being scattered by dynamical interactions into highly eccentric orbits, or tidally captured from nearly parabolic orbits. Although this scenario does provide a natural explanation for the edge found for planets at twice the Roche limit, it does not explain how such planets will survive the inevitable expansion that results from energy injection during tidal circularization.  相似文献   

Spatial impulse waves: wave height decay experiments at laboratory scale   总被引：1，自引：1，他引：0  

Frederic M. Evers  Willi H. Hager 《Landslides》2016,13(6):1395-1403

Impulse waves generated by rapid subaerial landslides into water bodies may pose a threat to riparian settlements and infrastructure. Empirically derived prediction equations based on experiments at laboratory scale provide information on key wave characteristics for preliminary hazard assessment. This research discusses existing prediction methods for spatial wave propagation features and compares their results with own impulse wave height decay experiments. While some prediction methods are based on simplified approaches for wave generation such as rigid body slides, others take only limited sets of slide parameters into account, narrowing their range of applicability considerably. The prediction methods are intentionally applied outside their ranges of applicability with the aim to assess their characteristics on an extended parameter range. It is found that a combination of separate terms for wave generation and wave propagation from two different existing prediction methods provides the best representation of the experimental data.  相似文献   

Numerical evidence of site effects contributing to triggering the Las Colinas landslide during the 2001 <Emphasis Type="Italic">M</Emphasis><Subscript>w</Subscript> = 7.7 El Salvador earthquake     

Zezhong Zhang  Jean-Alain Fleurisson  Frederic L. Pellet 《Landslides》2018,15(12):2373-2384

The Las Colinas landslide, which was triggered by the 13 January 2001, M_w?=?7.7 El Salvador earthquake, was highly destructive. The local site is composed of pyroclastic flows, brown cinders, soft pyroclastic fall deposits and a thin palaeosol and is characterised by steep slopes. The extremely high ground motions recorded near the landslide location are assumed to be both produced by site effects and responsible for the landslide. To characterise the ground motion amplifications due to site effects in terms of the variation in geometrical and geological settings, parametric studies were conducted with a linear elastic slope model, which was vertically subjected to the scattering SV wave of the Gabor wavelet. The results show that a maximum amplification is obtained when the model slope angle is approximately 30° (similar to the actual slope angle), and the maximum amplification is located approximately 20 m behind the crest, where the actual movement was initiated. Additionally, a slope with a height of approximately 160 m enhances ground motion amplification. The subsurface geology is found to induce a greater effect on amplification than that of the slope topography. In particular, a soft pyroclastic fall deposit is observed to contribute most of the ground motion amplification. According to the numerical results, it can be concluded that the local site conditions induced extremely high ground motions that then contributed to the slope movement. Although the thin, buried layer of palaeosol did not cause any significant amplification, its weak cohesion enhanced movement.  相似文献   

Abundance fluctuations among benthic invertebrates in two pacific estuaries     

Frederic H. Nichols 《Estuaries and Coasts》1985,8(2):136-144

Long-term studies were used to examine (1) contrasting time scales and mechanisms of structural variations within two benthic communities and (2) the usefulness of long data sets for evaluating human impact. A 10-year study of a San Francisco Bay mudflat, the details of which are reported elsewhere, has revealed large short-term (on the order of months) variations in species abundances within a community composed predominantly of opportunistic species. The study site, located in a highly urbanized estuary, is subject to the influence of a nearby sewage-treatment facility. However, rapid changes in population size of the common species, in part due to periodic natural habitat disturbance, impedes the detection of anthropogenic influences on community composition. Only a very long-term data set may provide evidence of progressive change. Data collected for a 20-year period on the benthic community at 200 m depth in the main basin of Puget Sound, an environment subject to little apparent habitat disturbance show that numerical abundance of the common species can also change markedly. Here, however, numerical dominance shifts from one species to another at irregular, multiyear intervals. Recent increases in two heretofore rare species, and a significant increase in total numbers of individuals suggest that long-term changes may be occurring in this community. These two long-term data sets demonstrate the importance of measuring both the amplitude and the periodicity of fluctuations in population size of aquatic species as well as long-term fluctuations and patterns in environmental factors before attempting to demonstrate the effect of anthropogenic influences on aquatic communities. The results of these studies also demonstrate the usefulness of long-term data sets for revealing the potential importance of interactions among species in determining abundance patterns in the soft-bottom benthos.  相似文献   

Resident fishes and macrobenthos in mangrove-rimmed habitats: Evaluation of habitat restoration by hydrologic modification     

Frederic E. Vose  Susan S. Bell 《Estuaries and Coasts》1994,17(3):585-596

An impounded area (Cabbagehead Bayou) in Upper Tampa Bay, Florida, was studied for 13 mo prior to and 22 mo after berm removal. Sampling for small fish and macrobenthos was conducted both at Cabbagehead Bayou and at a nearby control site, Double Branch Bay. Before and After Control and Impact (BACI) analyses, as well as similarity indices, were used to evaluate faunal characteristics in control versus impacted areas. Berm removal drastically changed periodicity of water cover in the impacted site, with the previously impounded site becoming almost entirely exposed during low tide. Fish abundances, biomass, and mean monthly number of species decreased in Cabbagehead Bayou after tidal flow was established as compared to when it was impounded. Responses of macrofauna varied among taxa, but total amphipod and polychaete abundance displayed a relative increase in the impacted site after berm removal. BACI analyses indicated that the relationship between mean values for almost all polychaete and amphipod taxa in the impacted and control sites changed significantly after berm removal. Additional differences were apparent in BACI analyses, which showed a significant change in the relationship of fish abundance and biomass at both sites for prebreach vs post-breach samples. The changes in relationships were generally not indicative of convergence of control and impacted sites, however. Community similarity of fish, amphipod, and polychaete assemblages increased during the last year of the post-breach sampling but remained generally very low. These findings suggest that distinct faunal responses to alteration of tidal periodicity can be detected within less than 2 yr after reestablishment of tidal flow. However, attainment of close correspondence to control conditions for certain fauna may require more than 22 mo. Therefore, future studies attempting to document recovery of restored wetlands may benefit from extended duration.  相似文献