RURAL ROAD IMPROVEMENTS: THEIR ECONOMIC IMPACT IN SIERRA LEONE     

Anthony Airey  M.A.  Ph.D. 《Singapore journal of tropical geography》1985,6(2):78-90

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NETWORKS OF RELATIONS AMONG A SET OF GEOGRAPHICAL JOURNALS*     

Anthony C. Gatrell  Anthony Smith 《The Professional geographer》1984,36(3):300-307

The network of interrelationships among a set of 22 geographic journals is investigated, using data on the frequency with which articles published in one journal cite papers published In another. The analysis considers journals published in 1970–1972 and 1980–1982. Journals with a focus on regional science weaken their connection to others in the set. The Annals retains its position at the core of the journal space that is identified using multidimensional scaling; Environment and Planning A invades the niche vacated by the regional science journals.  相似文献   

Atmospheric tides on Venus: III. The planetary boundary layer     

Anthony R. Dobrovolskis 《Icarus》1983,56(1):165-175

Diurnal solar heating of Venus' surface produces variable temperatures, winds, and pressure gradients within a shallow layer at the botton of the atmosphere. The corresponding asymmetric mass distribution experiences a tidal torque tending to maintain Venus' slow retrograde rotation. It is shown that including viscosity in the boundary layer does not materially affect the balance of torques. On the other hand, friction between the air and ground can reduce the predicted wind speeds from ∽5 to ∽1 m/sec in the lower atmosphere, more consistent with the observations from Venus landers and descent probes. Implications for aeolian activity on Venus' surface and for future missions are discussed.  相似文献   

Does Venus breathe?     

Anthony R. Dobrovolskis 《Icarus》1983,54(3):539-542

The periodic absorption and desorption of CO₂ by the soil on Venus may buffer daily temperature, pressure, and wind variations in the lower atmosphere. This would effectively eliminate the net tidal torque on the atmosphere. Nevertheless, the redistribution of mass in the crust would generate a sizable torque, which might balance that due to the gravitationally induced tide.  相似文献   

Ferric Iron in CaTiO3 Perovskite as an Oxygen Barometer for Kimberlite Magmas II: Applications     

Canil  Dante; Bellis  Anthony J. 《Journal of Petrology》2007,48(2):231-252

We apply an oxygen barometer based on the Fe content of CaTiO₃perovskite to estimate the oxygen fugacity (fO₂) during thecrystallization and emplacement of kimberlites in differenteruptive phases of a single pipe, or between different pipes,clusters or provinces. Mineral chemical data for perovskitewere compiled from the literature and obtained in our detailedstudy of perovskites from 11 kimberlites at Somerset Islandand Lac de Gras, Canada. Perovskite compositions in kimberlitesrecord a range in fO₂ of many orders of magnitude from NNO–5to NNO+6 [where log fO₂ is given relative to the nickel–nickeloxide (NNO) buffer]. The range of fO₂ recorded by differentparageneses of perovskite within a single pipe can vary up tothree orders of magnitude with trends toward both oxidationand reduction during crystallization. Kimberlites record someof the greatest ranges, and the highest known fO₂ conditionsfor any terrestrial magma. This is attributed to the presenceof deep and oxidized source regions and the variable interplayof ferric–ferrous vs carbon–fluid equilibria duringascent of kimberlite magmas. Three kimberlite pipes from theLac de Gras field show that higher fO₂ values correlate withhigher proportions of more resorbed diamonds, suggesting thatthis variable has a measurable effect on the physical propertiesof diamonds in a pipe. KEY WORDS: kimberlites; oxygen fugacity; perovskite; diamond; redox; mantle  相似文献   

Sulfur isotopic evidence for chemocline upward excursions during the end-Permian mass extinction   总被引：1，自引：0，他引：1  

Anthony L. Riccardi  Michael A. Arthur  Lee R. Kump 《Geochimica et cosmochimica acta》2006,70(23):5740-5752

The latest Permian was a time of major change in ocean chemistry, accompanying the greatest mass extinction of the Phanerozoic. To examine the nature of these changes, samples from two well-studied marine sections that span the Permian-Triassic boundary have been analyzed: the Meishan and Shangsi sections located in Southern China. Isotopic analysis of the carbonate-associated sulfate in these samples provides a detailed record of several isotopic shifts in δ³⁴S_CAS approaching and across the PTB, ranging from +30 to −15‰ (VCDT), with repeated asynchronous fluctuations at the two locations. We interpret the patterns of isotopic shifts, in conjunction with other data, to indicate a shallow unstable chemocline overlying euxinic deep-water which periodically upwelled into the photic zone. These chemocline upward excursion events introduced sulfide to the photic zone stimulating a bloom of phototrophic sulfur oxidizing bacteria. We hypothesize that elemental sulfur globules produced by these organisms and ³⁴S-depleted pyrite produced in the euxinic water column were deposited in the sediment; later oxidation led to incorporation as CAS. This created the large changes to the δ³⁴S_CAS observed in the latest Permian at these locations.  相似文献   

Impact of fabric, microcracks and stress field on shale anisotropy   总被引：2，自引：0，他引：2  

David N. Dewhurst  Anthony F. Siggins 《Geophysical Journal International》2006,165(1):135-148

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Geomorphology and ecology: Unifying themes for complex systems in biogeomorphology   总被引：2，自引：5，他引：2  

J. Anthony Stallins   《Geomorphology》2006,77(3-4):207

The interaction of geomorphic and ecologic landscape components has been largely conceptualized as independent. In one direction, geomorphic processes and landforms shape the distribution of biota. Conversely, in the other direction, biota modify geomorphic processes and landforms. Increasingly, the interactions between geomorphic and ecological components are more circular and developmentally intertwined. In this paper, I integrate these two independent perspectives within the framework of complexity theory. I outline four themes that characterize complex systems in biogeomorphology: multiple causality and the concept of recursivity, the influence of organisms that function as ecosystem engineers, the expression of an ecological topology, and ecological memory. Implicit in all of these themes is the recognition that biogeomorphic systems are open and path dependent. They may exhibit a range of assembly states, from self-reinforcing stability domains to more transient configurations of organisms and environment.  相似文献   

Fluids in early stage hydrothermal alteration of high-sulfidation epithermal systems: A view from the Vulcano active hydrothermal system (Aeolian Island,Italy)     

Adrian J. Boyce  Paolo Fulignati  Alessandro Sbrana  Anthony E. Fallick 《Journal of Volcanology and Geothermal Research》2007

High-sulfidation (HS) epithermal systems have elements in common with passively degassing volcanoes associated with high T, acid fumarole fields or acid crater lakes. They are considered to form in two stages, the first of which involves advanced argillic alteration resulting from intense, strongly acidic fluid–rock interaction. The La Fossa hydrothermal system (Vulcano Island) represents a classic example of such an active HS system and can be considered as a modern analogue of this early stage of alteration, resulting in a core of intense silicic (90–95% pure SiO₂) alteration surrounded by alunitic alteration zones.  相似文献   

The impact of resolution on the dynamics of the martian global atmosphere: Varying resolution studies with the MarsWRF GCM     

Anthony D. Toigo  Christopher Lee  Claire E. Newman  Mark I. Richardson 《Icarus》2012,221(1):276-288

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