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211.
John N. H. Britton 《The Professional geographer》1981,33(1):36-47
The technological underdevelopment of secondary manufacturing in Canada is inferred from patterns of trade, industrial structure, and the range of industrial functions performed within firms in Canada. These patterns are explained by reference to the behavior of foreign subsidiaries that have major direct and indirect effects on the linkages and developmental potential of the Canadian industrial system. Canadian manufacturing is found to have a low level of innovative capability because of inadequate R & D and product and design engineering in foreign and domestic firms. In view of the strong need for new policy initiatives, the components of a techno-industrial strategy are evaluated. 相似文献
212.
213.
Jennifer L. Mays Mark Brenner Jason H. Curtis Kathryn V. Curtis David A. Hodell Alex Correa-Metrio Jaime Escobar Andrea L. Dutton Andrew R. Zimmerman Thomas P. Guilderson 《Journal of Paleolimnology》2017,57(4):307-319
Sediment core PI-6 from Lake Petén Itzá, Guatemala, possesses an ~85-ka record of climate and environmental change from lowland Central America. Variations in sediment lithology suggest large and abrupt changes in precipitation during the last glacial and deglacial periods, and into the early Holocene. We measured stable carbon isotope ratios of total organic carbon and long-chain n-alkanes from the core, the latter representing a largely allochthonous (terrestrial) source of organic matter, to reveal past shifts in the relative proportion of C3–C4 terrestrial biomass. We sought to test whether stable carbon isotope results were consistent with other paleoclimate proxies measured in the PI-6 core, and if extraction and isotope analysis of n-alkanes is warranted. The largest δ13C variations are associated with Heinrich Events. Carbon isotope values in sediments deposited during the last glacial maximum indicate moderate precipitation with little fluctuation. The deglacial was a period of pronounced climate variability, e.g. a relatively warm and moist Bølling–Allerød, but a cool and dry Younger Dryas. Arid periods of the deglacial were inferred from samples with high δ13C values in total organic carbon, which reflect times of greater proportions of C4 plants. These inferences are supported by stable isotope measurements on ostracod shells and relative abundance of grass pollen from the same depths in core PI-6. Similar trends in carbon stable isotopes measured on bulk organic carbon and n-alkanes suggest that carbon isotope measures on bulk organic carbon in sediments from this lake are sufficient to infer past climate-driven shifts in local vegetation. 相似文献
214.
B. H. Briz-Kishore 《Journal of Earth System Science》1982,91(3):219-234
The use of digital models has increased significantly in recent years with the accessibility of fast computing machines. A
variable dimensioned digital model was constructed for the Shadnagar granite basin using SPECTRUM-7 micro computer to integrate
various hydrogeological characteristics and for their quantitative evaluation. The basin has an areal extent of 437 sq km
and is demarcated with clear water divides in all directions. Transmissivity, recharge and discharge at each cell of the basin
area were estimated by trial and error simulation of the hydrogeological phenomenon under steady state condition. Dynamic
simulation at representative nodes facilitated the estimation of storage coefficient. The capability of the constructed model
was established by the conformance of the simulated hydrographs with the actual behaviour of the ground water system. The
entire studies ammended the earlier arrived estimates of various input/output hydrogeological parameters and evolved a methodology
for efficient processing of aquifer simulation data 相似文献
215.
While the natural structures of the GDR territory influenced by geological features and relief formation show a north-south sequence, variations in climate belong to a more northwest-southeast directed differentiation by maritime to continental features. Already since the Middle Ages the natural conditions of this territory have been utilized by man, at present many socially necessary functions of natural regions require rational and effective solutions for the complex utilization of nature and its resources. In order to support decisionmakers by scientific foundations for the solution of these problems, Physical Geography is concerned chiefly with three tasks: 1. Determination of the suitability and carrying capacity with regard to certain requirements of society (landscape survey). 2. Analysis of the functioning of landscape systems by the investigation of natural processes and technogene impacts on them by different forms of use. 3. Elaboration of scientific foundations in order to render possible a rational utilization and effective forms of control of natural and technogene determined landscape processes. 相似文献
216.
Nice HE 《Marine pollution bulletin》2005,50(12):661-1674
Nonylphenol, a widespread aquatic pollutant with endocrine-disrupting potential has been found to affect sperm motility in the Pacific oyster, Crassostrea gigas (Thunberg). This marine invertebrate, a global aquaculture species, was exposed to nonylphenol at concentrations of 1 and 100 μg l−1 for a duration of 72 h during the period of gametogenesis. Growth was monitored at regular intervals until sexual maturity when sperm motility was assessed. The growth rate of C. gigas remained unaffected by exposure to nonylphenol during gametogenesis. However, the number of individuals with motile sperm was significantly reduced. 相似文献
217.
218.
H. Fuchs 《Astronomische Nachrichten》1990,311(4):219-222
Tetrads which are parallelpropagated along time-like geodesics in static spherically symmetric spce-times are constructed. Its connection with the geodesic precession is explained. Moreover, we express the solution of the equations of geodesic deviation in terms of the Killing vectors and the fourvelocity. 相似文献
219.
V. L. Afanasjev I. D. Karachentsev V. A. Lipovetsky H. Lorenz 《Astronomische Nachrichten》1979,300(2):77-79
The spectra of ten objects discovered by the Tautenburg objective prism survey were obtained at a higher spectral resolution in order to refine the selection criteria. We found four objects to be quasars and three MARKARIAN -type galaxies. 相似文献
220.
A. Vela V. Pasqualini V. Leoni A. Djelouli H. Langar G. Pergent C. Pergent-Martini L. Ferrat M. Ridha H. Djabou 《Estuarine, Coastal and Shelf Science》2008,79(4):591-598
Mapping marine biocenoses is an efficient method for providing useful data for the management and conservation of Mediterranean lagoons. Fused images from two satellites, SPOT 5 and IKONOS, were tested as management tools for identifying specific ecosystems in the El Bibane lagoon, situated in southern Tunisia near the Libyan border. The objectives of this study were to provide a precise map of the entire El Bibane lagoon using fused images from SPOT 5 and to compare fused images from SPOT 5 and IKONOS over a test-area. After applying a supervised classification, pixels are automatically classified in four classes: low seagrass cover, high seagrass cover, superficial mobile sediments and deep mobile sediments. The maps of the lagoon revealed and confirmed an extremely wide distribution of seagrass meadows within the lagoon (essentially Cymodocea nodosa; 19 546 ha) and a large area of mobile sediments more or less parallel to the shore (3 697 ha). A direct comparison of overall accuracy between SPOT 5 over the entire area, SPOT 5 over the test-area and IKONOS over the test-area revealed that these tools provided accurate mapping of the lagoon environment (83.25%, 85.91% and 73.41% accuracy, respectively). The SPOT 5 images provided greater overall accuracy than the IKONOS image, but did not take into account the heterogeneous spatial structure of the seagrasses and sediments present in the lagoon environment. Although IKONOS imagery provided lower overall accuracy than SPOT 5, it proved a very useful tool for the mapping of heterogeneous structures as it enabled the patchiness of formations to be better taken into account. The use of SPOT 5 and IKONOS fused images appears to be very promising for completing the mapping of lagoons in other regions and countries of the Mediterranean Sea. 相似文献