X-ray computed tomography and petrographic thin sectioning were used to study internal features of the plates of the thyreophoran
dinosaur Stegosaurus and the osteoderms of Alligator. Infrared thermographic imaging of basking caimans was used to examine possible differential blood flow to osteoderms and
other parts of the skin. Multiple large openings in the Stegosaurus plate base lead to a linear, mesiodistally oriented vestibule, which in turn apically sends off multiply branching “pipes”.
The pipes are best developed in the basal half of the plate, and communicate with cancellous regions (some of which presumably
were vascular spaces) throughout the plate interior. Some internal vascular features also connect with vascular pits and grooves
on the plate surface. Alligator osteoderms show a similar internal vascularity. In crocodylians, the osteoderms serve as armor
and help to stiffen the back for terrestrial locomotion, but their vascularity enables them to be used as sources of calcium
for egg shelling, as sites of lactate sequestration, and possibly for heat exchange with the external environment, as suggested
by our infrared thermographic imaging of basking caimans. Thyreophoran osteoderms presumably had multiple functions as well.
In Stegosaurus the potential thermoregulatory role of the plates may have been greater than in other thyreophorans, by virtue of their extensive
external and internal vascularity, their large size, thin cross-sections above the plate base, dorsal position, and alternating
arrangement. 相似文献
A new traveltime tomographic method was developed with hierarchical shape functions of the finite element method as slowness or velocity interpolation functions. The degree of the approximation of velocity modelling is adjusted by selecting a set of hierarchical shape functions in each element. The ray density parameter of each element controls the selection to make the approximation fine or coarse in the high- or low-ray-density area. The proposed method is applied to both synthetic traveltime data and actual data. The AIC is used to determine the number of model parameters. The result of the synthetic data shows that low-resolution model parameters can be eliminated by the ray density parameter. The result of the actual data shows that the velocity pattern is approximately the same in the fine approximation area and that the velocity fluctuation is suppressed in the coarse approximation area, compared with that obtained from a full set of hierarchical shape functions. The number of model parameters is drastically reduced. The resolution can be estimated by the checkerboard restoration test. The result of the real data set was compared with that of the linear velocity grid model. 相似文献
Abstract The Isabela ophiolite, the Philippines, is characterized by a lherzolite‐dominant mantle section, which was probably formed beneath a slow‐spreading mid‐ocean ridge. Several podiform chromitites occur in the mantle section and grade into harzburgite to lherzolite. The chromitites show massive, nodular, layered and disseminated textures. Clinopyroxene (±orthopyroxene/amphibole) inclusions within chromian spinel (chromite hereafter) are commonly found in the massive‐type chromitites. Large chromitites are found in relatively depleted harzburgite hosts having high‐Cr? (Cr/(Cr + Al) atomic ratio = ~0.5) chromite. Light rare earth element (LREE) contents of clinopyroxenes in harzburgites near the chromitites are higher than those in lherzolite with low‐Cr? chromite, whereas heavy REE (HREE) contents of clinopyroxenes are lower in harzburgite than in lherzolite. The harzburgite near the chromitites is not a residual peridotite after simple melt extraction from lherzolite but is formed by open‐system melting (partial melting associated with influx of primitive basaltic melt of deeper origin). Clinopyroxene inclusions within chromite in chromitites exhibit convex‐shaped REE patterns with low HREE and high LREE (+Sr) abundances compared to the host peridotites. The chromitites were formed from a hybridized melt enriched with Cr, Si and incompatible elements (Na, LREE, Sr and H2O). The melt was produced by mixing of secondary melts after melt–rock interaction and the primitive basaltic melts in large melt conduits, probably coupled with a zone‐refining effect. The Cr? of chromites in the chromitites ranges from 0.65 to 0.75 and is similar to those of arc‐related magmas. The upper mantle section of the Isabela ophiolite was initially formed beneath a slow‐spreading mid‐ocean ridge, later introduced by arc‐related magmatisms in response to a switch in tectonic setting during its obduction at a convergent margin. 相似文献
The Angélica copper deposit is situated at the southernmost sector of the Jurassic Tocopilla plutonic complex in the North Chilean Coastal Cordillera. This deposit occurs in monzonitic to monzodioritic rocks, and has platelike orebodies with no appreciable hydrothermal alteration nor sulfide mineralization. The mineralized zones are located in the western side of the two main normal faults with NE and NW orientations, and are characterized principally by impregnation of supergene copper products of atacamite and minor amounts of chrysocolla, lavendulan and “black copper”. Generally, chrysocolla is more abundant at a distal NE sector of the deposit. The black copper is Cu‐Fe‐Mn‐Si‐Cl‐rich multimineral aggregates composed of atacamite with minor amounts of quartz, pseudomalachite, dioptase, neotocite, gypsum, paratacamite and melanothallite, and its surface exhibits nanometer‐sized cylindrical morphologies. All these characteristics suggest an exotic origin for the Angélica copper deposit. A few vein‐type copper deposits situated at the southwestern sector along the NE‐oriented fault are inferred as the possible source of the Angélica copper deposit. 相似文献
I' Grade-tonnage diagrams are one of the most useful tools inthe resource assessment (e. g. St'nger, 1993). One' grade-tonnage diagram is well known as Laskys (1950) e\-7ation, whichdemonstrates the linear relation between average grade (x) andlOgarithms of cumulative ore tonnage (ac above a given gradex(0相似文献
It has been suggested that the solar differential rotation might be maintained by nearly horizontal non-spherical convective circulation called the Rossby-type waves (the wave motions characterized by the close balance of the Coriolis force and pressure gradient in horizontal motions). In this paper, such Rossby-type waves which could be excited in the upper solar convection zone are considered, and the possibility of maintenance of the solar differential rotation by such waves is examined. A numerical estimate, in terms of the rate of conversion of the kinetic energy of such wave motions into the mean rotational motion, indicates this possibility. The implications and limitations of the results are also discussed.Visiting Scientist to the High Altitude Observatory on leave of absence from the Department of Astronomy, University of Tokyo, Japan.The National Center for Atmospheric Research is sponsored by the National Science Foundation. 相似文献
Abstract 40Ar–39Ar analysis of phlogopite separated from a plagioclase lherzolite of the Horoman Peridotite Complex, Hokkaido, Japan, has yielded a plateau age of 20.6 ± 0.5 Ma in an environment where the metamorphic fluid was characterized by an almost atmospheric Ar isotopic ratio. The age spectrum is slightly saddle-shaped, implying some incorporation of excess 40Ar during the formation of the phlogopite at a depth. As the phlogopite has been inferred to have formed in veins and/or interstitials during exhumation of the peridotite body, metasomatic fluids, to which ground- and sea water might have contributed, were probably involved in the formation of phlogopite in the crustal environment. A total 40Ar–39Ar age of 129 Ma of a whole rock sample of the plagioclase lherzolite, from which the phlogopite was separated and is representative of the main lithology of the Horoman Peridotite Complex, indicates the occurrence of excess 40Ar. Hence, the age has no geological meaning. 相似文献
A simple-extended array of observation for strong motions, named ‘Small-Titan’, was installed in Sendai City, Japan in 1997. This array system consists of 20 observation sites, which have an average of about 4 km for the station-to-station distance. Each observation station was located at various kinds of soils to effectively obtain local site effects. Since its completion, the system has obtained about 160 motion records. As is well known, ground motions are influenced by the three main factors such as source, path and local site effects. An accurate prediction of ground motions should thus be performed based on the three factors. In this context, theoretical methods used commonly lack enough information related with source and path effects. A generalized inversion scheme to separate the effects of source, propagation path and local site from S-wave spectra was applied to the records of Small-Titan obtained in the Sendai region, Japan. The objective of this paper is to estimate local site effects in Sendai City and to obtain meaningful information of input motions available to earthquake-resistant design, aimed at setting in terms of local soil conditions. This paper also describes the applicability of the generalized inversion scheme to seismic zoning.
Site amplification factors estimated from the generalized inversion scheme vary significantly, reflecting the effects of soil characteristics at each site. Strong site-dependency was found in the site amplification factors. In particular, the local site amplification factors in the western side are smaller than those in the eastern side, across the Nagamachi–Rifu Fault that exists in the central part of the Sendai area. Results from the generalized inversion scheme are compared with those obtained by the direct spectral ratio scheme, the H/V method and the bootstrap inversion. There is a good agreement in the amplification factors between the generalized inversion scheme, the direct spectral ratio scheme and the bootstrap inversion scheme. The H/V method for estimating site amplification is found to extract the same dominant periods as the other methods. This paper especially emphasizes a good agreement in not only dominant period, but also amplification factor.
The generalized inversion scheme is a useful method in separating the effects of source, propagation path and local site and in revealing the site amplification. In addition, the generalized inversion scheme provides meaningful information of input motions available to earthquake-resistant design, aimed at setting in terms of local soil conditions. Moreover, this paper indicates that the generalized inversion scheme is applicable to the seismic zoning toward disaster mitigation. 相似文献