Retrieving N₂O from nadir-viewing infrared spectrometers     

A. M. LUBRANO  G. MASIELLO  M. MATRICARDI  C. SERIO  V. CUOMO 《Tellus. Series B, Chemical and physical meteorology》2004,56(3):249-261

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Multicomponent magnetizations in the Foyers Old Red Sandstone (northern Scotland) and their bearing on lateral displacements along the Great Glen Fault   总被引：1，自引：0，他引：1  

K. M. Storetvedt  E. Tveit  E. R. Deutsch  G. S. Murthy 《Geophysical Journal International》1990,102(1):151-163

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The Optical Gravitational Lensing Experiment: catalogue of stellar proper motions in the OGLE-II Galactic bulge fields     

T. Sumi  X. Wu  A. Udalski  M. Szyma&#;ski  M. Kubiak  G. Pietrzy&#;ski  I. Soszy&#;ski  P. Wo&#;niak  K. &#;ebru&#;  O. Szewczyk  &#;. Wyrzykowski 《Monthly notices of the Royal Astronomical Society》2004,348(4):1439-1450

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Weathering process at the natural fission reactor of Bangombé     

G. Bracke  S. Salah  F. Gauthier-Lafaye 《Environmental Geology》2001,40(4-5):403-408

 The uranium deposits in the basin of Franceville (Gabon) host the only natural fission reactors known in the world. Unique geological conditions favoured a natural fission reaction 2 Ga ago. This was detected by anomalous isotopic compositions of uranium and rare earth elements (REE), which are produced by the fission reaction. In total, 16 reactor zones were found. Most of them are mined out. The reactor zone of Bangombé, is only 10–11 m below the surface. This site has been influenced by surface weathering processes. Six drill cores have been sampled at the site of the reactor zone of Bangombé during the course of the study and only one drill core (BAX 08) hit the core of the reactor. From these data and previous drilling campaigns, the reactor size is estimated to be 10 cm thick, 2–3 m wide and 4–6 m long. The migration of fission products can be traced by the anomalous isotope ratios of REE because of the fission process. The ¹⁴⁹Sm/¹⁴⁷Sm ratio close to the reactor zone is only 0.28 (normal: 0.92) because of the intense neutron capture of ¹⁴⁹Sm and subsequent transmutation, whereas ¹⁴⁷Sm is enriched by the fission reaction. Similar changes in isotopic patterns are detectable on other REE. The isotope ratios of Sm and Nd of whole rock and fracture samples surrounding the reactor indicate that fission-genic REE migrated only a few decimetres above and mainly below the reactor zone. Organic matter (bitumen) seems to act as a trap for fission-genic REE. Additional REE-patterns show less intense weathering with increasing depth in the log profile and support a simple weathering model. Received: 26 November 1999 · Accepted: 2 May 2000  相似文献   

Characterization of soil's structural crust by spectral reflectance in the SWIR region (1.2–2.5 μm)     

N. Goldshleger  E. Ben-Dor  Y. Benyamini  M. Agassi  & D. G. Blumberg 《地学学报》2001,13(1):12-17

Structural crust is a thin layer formed on the soil surface after a rainstorm. The crust is the result of a physical segregation and rearrangement of soil particles in a way that affects some of the soil properties, such as infiltration, runoff and soil erosion. In practice, there is no rapid, in situ method for monitoring, assessing and mapping crust intensity and quality. In this study, a controlled spectral investigation of the structural crust across the NIR–SWIR spectral region was conducted on three selected Israeli soils, to study the potential of reflectance radiation to detect structural crust in soils. Two major factors served as the driving forces for this study: (1) there is no valid method for in situ assessment of the crust's characteristics in the agriculture field, and (2) the crust might bias thematic remote sensing of soils, because the thin layer of crust blocks photon–matter interaction, which represents the relevant soil body. Through the use of a laboratory rainfall simulator and a sensitive spectrometer, it was revealed that for three selected soils, significant spectral differences occurred between the crust and its bulk soil. The spectral information was found to be related to changes in particle size distribution and texture at the surface of the soil. This conclusion was based on indications of absorption of OH in clay lattice, OH in adsorbed water and CO₃ in carbonates. It was concluded that the structural crust is a phenomenon that should not be ignored by remote-sensing users. In fact, in the field of agriculture, the spectral properties of crust can be used as tools for estimating the crust's intensity.  相似文献   

Fossil midge associations and the historical status of fish in acidified lakes     

M. G. Johnson  J. R. M. Kelso  O. C. McNeil  W. B. Morton 《Journal of Paleolimnology》1990,3(2):113-127

Chaoborid and chironomid (Diptera) fossils were examined in sediment cores form nine Ontario Precambrian Shield lakes that were fishless in 1979. An abundance of Chaoborus americamus (intolerant of predation by fish) throughout cores from four lakes indicated that they were fishless historically. Occurrence of Chaoborus punctipennis and C. flavicans and absence of C. americanus in cores, except near the surface in two cases, indicated that four other lakes were inhabited by fish historically. One of these was probably periodically fishless as suggested by fluctuations among these Chaoborus species. The ninth lake was not suitable for Chaoborus; only one specimen of C. trivittatus was found in this core. Chironomid fossil associations were substantially different in historically fishless and inhabited lakes. Fishless lakes had chironomids typical of eutrophic conditions indicating that seasonal oxygen depletion likely was inimical to fish. Chironomid associations of oligotrophic waters occurred in lakes historically inhabited by fish. Both good water quality and accessibility were required for long-term habitation by fish. Partial recovery of alkalinity and rise in pH were accompanied by substantial re-invasion by fish in two lakes which had been inhabited historically by fish. Diptera associations provide valuable information on the historical suitability of lakes for fish and the presence/absence of fish in regions where acidification of surface waters has occurred.  相似文献   

Evolution of Polytropic Reimann Disks in Halos     

M. G. Abrahamyan 《Astrophysics》2004,47(4):555-567

The equilibrium of elliptical Riemann disks with a polytropic equation of state and their evolution under the influence of viscosity and gravitational radiation inside spheroidal halos with a relative surface mass density k. The evolutionary trajectory of a disk inside a halo with k<0.5, which is analogous to the evolution of an isolated disk, differs from that of a disk inside a denser halo.  相似文献   

Frequency and time profiles of metric wave isolated Type I solar noise storm bursts at high spectral and temporal resolution     

G. A. Shanmugha Sundaram  K. R. Subramanian 《Monthly notices of the Royal Astronomical Society》2005,359(2):580-588

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Influence of inhomogeneity of the magnetic field on the excitation of longitudinal waves in pulsar magnetospheres     

A. Z. Kazbegi  G. Z. Machabeli  G. I. Melikidze 《Astrophysics》1986,25(1):425-428

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Deep-ocean vertical noise directionality     

Carey  W.M. Evans  R.B. Davis  J.A. Botseas  G. 《Oceanic Engineering, IEEE Journal of》1990,15(4):324-334

The structure of beam noise measured at the output of a vertical array in a range dependent ocean basin was investigated using the modified wide-angle parabolic equation (PE). Noise sources were distributed throughout the basin, and the field due to each noise source at an array located in the midbasin was calculated. The response of the array to the superposition of the noise sources was found by beamforming. An efficient and direct approach that superimposes the noise sources on the PE field as the field is marched toward the array was developed. Downslope calculations of the midbasin vertical directionality were made between 50 and 400 Hz with this technique. Use of a geoacoustic model shows that the bottom behaves as a low-pass filter  相似文献