Oxygen isotope and palaeomagnetic stratigraphy of Equatorial Pacific core V28-238: Oxygen isotope temperatures and ice volumes on a 105 year and 106 year scale     

Nicholas John Shackleton  Neil D. Opdyke 《Quaternary Research》1973,3(1):39-55

Core Vema 28-238 preserves an excellent oxygen isotope and magnetic stratigraphy and is shown to contain undisturbed sediments deposited continuously through the past 870,000 yr. Detailed correlation with sequences described by Emiliani in the Caribbean and Atlantic Ocean is demonstrated. The boundaries of 22 stages representing alternating times of high and low Northern Hemisphere ice volume are recognized and dated. The record is interpreted in terms of Northern Hemisphere ice accumulation, and is used to estimate the range of temperature variation in the Caribbean.  相似文献   

Eikonal description of internal wave interactions: A non-diffusive picture of “induced diffusion”     

Frank S. Henyey  Neil Pomphrey 《Dynamics of Atmospheres and Oceans》1983,7(4):189-219

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Toxicities of ten metals to Crassostrea gigas and Mytilus edulis embryos and Cancer magister larvae     

Michael Martin  Kenneth E. Osborn  Patricia Billig  Neil Glickstein 《Marine pollution bulletin》1981,12(9):305-308

Pacific oyster (Crassostrea gigas Thunberg) embryos, bay mussel (Mytilus edulis Linnaeus) embryos, and Dungeness crab (Cancer magister Dana) zoea I stage larvae were exposed to arsenic, cadmium, chromium, copper, lead, mercury, nickel, selenium, silver, and zinc salts. The two bivalve species were exposed through the completion of embryogenesis (48 h), and the effects of the metals upon abnormal development were monitored. The crab larval stages were exposed to the metal solutions for 96 h. Concentrations (μg l_.^?1 as metal) which caused 50% abnormal development in the two species of bivalve larvae and which were fatal to 50% of the crab larvae ranged from 5.3 (oyster) to 49 (crab) for copper; 5.8 (mussel) to 8.2 (crab) for mercury; 14 (mussel) to 55 (crab) for silver; 119 (oyster) to 456 (crab) for zinc; 232 (crab) to 3000 (mussel) for arsenic; 247 (crab) to 1200 (mussel) for cadmium; 349 (oyster) to 4360 (crab) for nickel; 476 (mussel) to 758 (oyster) for lead; 3440 (crab) to 4538 (oyster) for hexavalent chromium; and selenium greater than 10 000 for the three species. The acute toxicity testing of C. gigas embryo together with two California native species confirmed its usefulness for predicting toxicity to the latter species.  相似文献   

A note on topological matrices and characteristic polynomials of fourth-magnitude drainage net maps     

Neil L. Coleman 《地球表面变化过程与地形》1981,6(5):485-491

I suggest that a connection matrix and a characteristic polynomial, which can be formed for any drainage net, using Shreve link magnitudes, may be used in studying drainage nets. I show how the matrix and the polynomial can be formed, using selected drainage nets as examples.  相似文献   

Comments on: “Surface circulation of the Indian Ocean during the last glacial maximum approximately 18,000 yr B.P.” by Warren L. Prell et al.     

Peter J. Webster  Neil A. Streten 《Quaternary Research》1981,16(3):421-423

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Paleoenvironmental reconstruction from chemical and isotopic compositions of Permo-Pennsylvanian pedogenic minerals     

Neil John Tabor  Isabel P. MontanezRandal J. Southard 《Geochimica et cosmochimica acta》2002,66(17):3093-3107

Mineralogical and chemical analysis of Late Pennsylvanian and Early Permian paleosols from the eastern shelf of the Midland basin, north-central Texas, USA, are used to test hypothesized climate change in Late Paleozoic western equatorial Pangea, previously defined independently on the bases of sedimentologic and paleontologic proxies and climate models. The <0.2-μm size phyllosilicate fraction in the studied paleosols exhibits down-profile trends in mineralogy and chemical composition that are consistent with modern weathering profiles suggesting a dominantly pedogenic origin. A stratigraphic trend from kaolinite-dominated profiles in Upper Pennsylvanian paleosols to profiles dominated by smectite and hydroxy-interlayered 2:1 phyllosilicates in Lower Permian paleosols indicates a relatively rapid decrease in soil weathering and leaching in the latest Pennsylvanian followed by a more gradual decrease in leaching throughout the Early Permian. The chemical composition (cation ratios and exchange capacity) of these phyllosilicates further corroborates this shift toward less intensive leaching, presumably in response to climate change from humid to progressively more arid conditions.The phyllosilicates in the <0.2-μm size fraction and contemporaneous pedogenic calcites from the Permo-Pennsylvanian paleosols exhibit a long-term stratigraphic increase in their δ¹⁸O values of as much as ∼3.2‰ and ∼5.2‰, respectively. This long-term trend is consistent with a transition throughout the latest Pennsylvanian through Early Permian toward progressively more evaporatively enriched soil waters. Superimposed on the long-term trend is an apparent rapid enrichment (1.5 to 2‰) in phyllosilicate δ¹⁸O values immediately above the Pennsylvanian-Permian boundary. Observed oxygen isotope fractionation between the phyllosilicates and calcites within individual paleosols indicate isotopic disequilibrium between mineral pairs. This is attributed to a minor detrital component in the pedogenic clay-dominated phyllosilicate fraction coupled with the effects of seasonality of mineral formation. Inferred δ¹⁸O compositions of Late Paleozoic meteoric water (−2‰ to +4‰) are compatible with less intensive soil leaching under conditions of increasing aridity, possibly coupled with a shift in local precipitation from a continental source to a marine source.  相似文献   

Species diversity and emergence patterns of nematocerous flies (Insecta: Diptera) from three coastal salt marshes in prince Edward Island, Canada     

Donna J. Giberson  Bohdan Bilyj  Neil Burgess 《Estuaries and Coasts》2001,24(6):862-874

Emerging insects were monitored every 10 days between early May and late August 1993, from tidal pools in three coastal salt marshes on Prince Edward Island, Canada. The salt marsh pools ranged from about 1 m² to > 1,000 m² in surface area, and had salinities ranging from 11–27‰ Water temperatures through the study period ranged from 4–46°C. Most of the emerging insects were flies (Diptera; 85%), and two-thirds of these were in the sub-Order Nematocera, mainly Chironomidae, Ceratopogonidae, and Culicidae. Forty-three species of Nematocera were identified, although most of these were rare occurrences, and twelve of the species are undescribed. No consistent relationships were found between abundance or diversity and pool size or marsh for Nematocera species overall, although some species showed a statistical preference for a particular marsh or pool size. Emergence patterns were consistent between marshes for species found in different marshes, but overall patterns were highly variable, depending upon species.  相似文献   

From Pillar to Post? In search of the post-productivist countryside in Australia     

Neil Argent 《The Australian geographer》2002,33(1):97-114

According to a growing number of commentators, the agricultural sectors and rural areas of advanced Western nations are experiencing a transition from productivism to post-productivism. In Britain and Western Europe, where this putative transition is most evident, the salient features of the shift include: the gradual removal of farm-level subsidies and related stimulatory policies; the introduction of a range of agri-environmental programs aimed at reducing agricultural commodity surpluses and halting farm-related environmental degradation; and the development of a more socially and culturally heterogeneous rural population as counter-urbanisation has brought a new stratum of residents into rural areas. This paper explores this notion in the Australian context. In analysing a wide range of data and policy documents, the paper argues that while there is some evidence of a productivist regime operating in Australia from 1945 to the early 1980s, and some more recent incipient trends consistent with a transition to a post-productivist countryside, there is much stronger evidence that the Australian farm sector and rural landscapes are being shaped by the complex interactions between the 'productivist' ideals held by farmers and key policy makers alike, and the growing environmental regulation of farming. It is concluded that while the concept of 'post-productivism' is superficially appealing, it has little practical or conceptual application to Australian conditions. Indeed, the paper argues that 'post-productivism' is fundamentally misconceived, largely owing to its inherent binary narrative form and logic.  相似文献   

The diffraction of linear waves by a uniform vertical cylinder with cosine-type radial perturbations     

Alaa M. Mansour  A. Neil Williams  K. H. Wang 《Ocean Engineering》2002,29(3):239-259

The interaction of linear waves with a uniform, bottom-mounted, surface-piercing cylinder whose diameter exhibits a cosine-type variation is investigated. Two solution methods are presented. One method is based on a perturbation theory, using a perturbation parameter defined in terms of the surface geometry of the cylinder. The analysis includes terms up to the first-order in this parameter, where the zeroth-order solution corresponds to a circular cylinder. The velocity potentials at the zeroth and first orders are expressed as eigenfunction expansions involving unknown coefficients that are subsequently determined through the cylinder boundary conditions. The second method is based on Green's theorem and gives rise to an integral equation for the fluid velocity potential on the cylinder surface. A comparison between the results of these two methods has proved that they are in good agreement for small values of the perturbation parameter. Numerical results are presented that illustrate the influence of the magnitude and frequency of these perturbations on the resulting hydrodynamic force and the wave runup on the cylinder.  相似文献   

Sensitivity of AUV response to variations in hydrodynamic parameters     

Doug Perrault  Neil Bose  Siu O&#x;Young  Christopher D. Williams 《Ocean Engineering》2003,30(6):779-811

The sensitivity of the response of a typical AUV to changes in hydrodynamic parameters is examined. The analysis is primarily performed using a computer model of an axi-symmetric vehicle typical of many AUVs in service today. The vehicle used is the Canadian Self-Contained Off-the-shelf Underwater Testbed (C-SCOUT), designed and built by graduate and work term students. The fully nonlinear computer model is based on Newton–Euler equations of motion, and uses the component build-up method to describe the excitation forces. The hydrodynamic parameters are varied in a series of simulations with the computer model; the response being analyzed for specific performance indicators.  相似文献