Fecundity and spawning of the Atlantic horseshoe crab, Limulus polyphemus, in Pleasant Bay, Cape Cod, Massachusetts, USA     

Alison S. Leschen  Sara P. Grady  & Ivan Valiela 《Marine Ecology》2006,27(1):54-65

This study provided the first comprehensive analysis of Atlantic horseshoe crab (Limulus polyphemus) fecundity. Limulus appear to be a determinate spawner, maturing all eggs for the breeding season before spawning begins. On average, larger females held a larger number of eggs (63,500) than smaller females (14,500). By the end of the breeding season there was an average of 11,600 mature eggs per female left undeposited, regardless of female size. Larger females laid a higher percentage of the eggs they contained. Thus they not only contain more eggs, but are more effective at laying them as well. Size of spawning females ranged from about 185–300 mm prosomal width, with by far the highest concentration in the mid‐size ranges. Although on an individual basis large females carry and lay the greatest number of eggs, mid‐size crabs as a group contributed more to the horseshoe crab population in Pleasant Bay because they were more plentiful (net fecundity was highest for mid‐size crabs). These results have implications for the management of this important species, which is harvested for bait, scientific, and biomedical uses. Incorporation of these results into models and other management tools can help predict growth rates, effects of size‐selective harvest, reproductive value, and stable stage distribution of populations.  相似文献   

Airborne Laser Sensing of Scottish Coastal Waters     

Grigorii Kokhanenko  Geoff Ludbrook  Ivan Penner  Vitalii Shamanaev 《Marine Geodesy》2001,24(4):195-207

An Nd:YAG-based airborne lidar system has been used to measure the optical properties of littoral waters off the northwest Scottish coast. The small-scale structure of subsurface scattering layers was also investigated. Methods of solving the Lidar Sensing Equation in the single scattering approximation are described and the values of the derived extinction indices presented. The extinction index averaged over a series of five flights to the northeast of the Gulf Stream was ε= 0.224 m -1 with a standard deviation of 0.212 m -1 . Further, it was demonstrated that, in coastal waters, optical inhomogeneities with dimensions between 50 m and 200 km obey the power law Sp ε ~ k -P with the parameter P close to two. In turbid or transparent areas, the water extinction index can change by several tenths of a percent with respect to the surrounding water mass. This suggests that the observed nonmonotonic behavior of the power spectra of the water extinction index fluctuations is caused by the outer scale of turbulence, in particular, by the bottom depth at the measurement site.  相似文献   

Computational validation of static and dynamic plate load testing   总被引：1，自引：1，他引：0  

Christoph Adam  Dietmar Adam  Fritz Kopf  Ivan Paulmichl 《Acta Geotechnica》2009,4(1):35-55

In this paper, the static load plate test and the dynamic load plate test by means of the light falling weight device are assessed utilizing numerical simulations. Simplified computational models of the tested subsoil and of the testing devices are developed, which capture the main effects of both the static and the dynamic load plate test. In extensive parametric studies, the impact of various subsoil conditions on the test results and several sources of error are evaluated and discussed. Computational test results of the static load plate test and of the dynamic load plate test are set in contrast to an effort to demonstrate the differences and the common features of the outcomes.  相似文献   

Advances in extreme value analysis and application to natural hazards     

Haigh  Ivan D.  Wahl  Thomas 《Natural Hazards》2019,98(3):819-822

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Simultaneous measurements of the two-dimensional distribution of infrared laser intensity and temperature in a single-sided laser-heated diamond anvil cell     

Kamil M. Bulatov  Pavel V. Zinin  Yulia V. Mantrova  Aleksey A. Bykov  Maksim I. Gaponov  Alexsandr S. Machikhin  Ivan A. Troyan  Igor B. Kutuza 《Comptes Rendus Geoscience》2019,351(2-3):286-294

In this report, we demonstrate that combining the laser heating system in a diamond anvil cell (LH-DAC) with a tandem acoustic-optical tunable filter (LH-DAC–TAOTF) allows for the simultaneous measurement of (a) the relative infrared (IR, 1070 nm) power distribution on a specimen surface in the DAC; (b) the temperature distribution under laser heating of a specimen under high-pressure in a DAC; it also (c) provides an opportunity to control the shape of the IR laser spot on the surface of the heated specimen. The effect of the π-shaper on the shape and the position of the focus of the IR laser beam on a specimen using a TAOTF is also presented. For a 10× long-working distance objective, the smallest diameter of the IR laser was found to be around 10 μm, when the focal plane coincides with that of the imaging optical system of LH-DAC. The highest diameter of the IR laser was shown to be 20 μm when the rim of the π-shaper was set at 3 μm. It is demonstrated also that the TAOFT not only permits to measure the two-dimensional (2-D) distribution of the IR laser power, but also allows for the alignment of the laser before each heating event at different pressures.  相似文献   

The effect of surface irregularities on a falling rock motion     

Ivan Gratchev  Somayeh Saeidi 《Geomechanics and Geoengineering》2019,14(1):52-58

This laboratory study seeks to investigate the effect of surface irregularities on the motion characteristics of a falling rock. The irregularly-shaped surfaces of greywacke with a range of joint roughness coefficient (JRC) from 2 to 18 were used in an experimental setup where a falling rock was dropped from a height of 110 cm. A high-speed camera was utilised to capture the trajectory of the falling rock upon its impact with the rock surface. The data from 287 tests were statistically analysed to determine the dominant type of motion and to establish relationships between JRC and the coefficient of restitution (CoR). The effect of surface roughness was seen in different modes of motion of the falling rock with more irregular surfaces often produced ‘sliding’ or ‘rolling’ instead of ‘bouncing’. The obtained data indicated that the rock surface roughness did not seem to have a significant effect on CoR; however, it affected the rebound angle of the falling rock.  相似文献   

Ray tracing and inhomogeneous dynamic ray tracing for anisotropy specified in curvilinear coordinates     

Einar Iversen  Ivan P&#;en&#;ík 《Geophysical Journal International》2008,174(1):316-330

Ray tracing has recently been expressed for anisotropy specified in a local Cartesian coordinate system, which may vary continuously in a model specified by elastic parameters. It takes advantage of the fact that anisotropy is often of a simpler nature locally (and is thus specified by a smaller number of elastic parameters) and that the orientation of its symmetry elements may vary. Here we extend this approach by replacing the local Cartesian coordinate system with a curvilinear coordinate system of global extent and by applying the new approach to ray tracing and inhomogeneous dynamic ray tracing. The curvilinear coordinate system is orthogonal and is constructed so that the coordinate axes are consistent with the considered anisotropy of the medium. Our formulation allows for computation of ray attributes (e.g. ray velocity vector and paraxial ray attributes) in the curvilinear coordinate system, while rays are computed in global Cartesian coordinates. Compared to the classic formulation in terms of 21 elastic moduli in global Cartesian coordinates, the main advantages are improved efficiency, lower computer-memory requirements, and conservation of anisotropic symmetry throughout the model.  相似文献   

Petrology and geochemistry of lava and ash erupted from Volcán Colima, Mexico, during 1998–2005     

Ivan P. Savov  James F. Luhr  Carlos Navarro-Ochoa 《Journal of Volcanology and Geothermal Research》2008,174(4):241-256

Lava (n = 8) and bulk ash samples (n = 6) erupted between July 1999 and June 2005 were investigated to extend time-series compositional and textural studies of the products erupted from Volcán Colima since 1869. In particular, we seek to evaluate the possibility that the current activity will culminate in major explosive Plinian-style event similar to that in 1913. Lava samples continue to show relatively heterogeneous whole-rock compositions with some significant mafic spikes (1999, 2001) as have prevailed since 1976. Groundmass SiO₂ contents continue trends to lower levels that have prevailed since 1961, in the direction of the still lower groundmass SiO₂ contents found in 1913 scoriae. Importantly, ash samples from investigated Vulcanian-style explosive eruptions in 2005 are devoid of particles with micro-vesiculated groundmass textures; such textures characterized the 1913 scoriae, signifying expansion of in-situ magmatic gas as the propellant of the 1913 eruption. All magmas erupted since 1913 appear to have arrived in the upper volcanic conduit system in a degassed state. The small to moderate Vulcanian-style explosive eruptions, which have been common since 1999 (> 16,000 events), have blasted ash clouds as high as 11 km a.s.l. and sent pyroclastic flows out to distances of 5 km. These eruptions do not appear to be powered by expansion of in-situ magmatic gas. New small lava domes have been observed in the crater prior to many explosive eruptions. These plugs of degassed lava may temporarily seal the conduit and allow the build-up of magmatic gases streaming upward from below ahead of rising and degassing magma. In this interpretation, when gas pressure exceeds the strength of the plug seal in the upper conduit, an explosive Vulcanian-style eruption occurs. Alternatively these explosive eruptions may represent interactions of hot rock and groundwater (phreato-magmatic).  相似文献   

Soil water dynamics at a midlatitude test site: Field measurements and box modeling approaches     

Mara Baudena  Ivan Bevilacqua  Davide Canone  Stefano Ferraris  Maurizio Previati  Antonello Provenzale 《Journal of Hydrology》2012

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Environmental Assessment of Heavy Metal Pollution in Freshwater Sediment,Serbia          下载免费PDF全文

Sanja M. Sakan  Gordana J. Dević  Dubravka J. Relić  Ivan B. Anđelković  Nenad M. Sakan  Dragana S. Đorđević 《洁净——土壤、空气、水》2015,43(6):838-845

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