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61.
M. J. Richter J. R. Graham G. S. Wright D. M. Kelly J. H. Lacy 《Astrophysics and Space Science》1995,233(1-2):67-70
We present spectroscopy of the molecular shock in the supernova remnant IC 443. The H2 level populations in IC 443 are nearly identical to Orion Peak 1 (Brand et al. 1988; Parmar et al. 1994) and are consistent with a partially dissociative J-shock. The similarity with Orion suggests the shock processes which dominate the emission in both regions are essentially identical. 相似文献
62.
Hydrogen peroxide (H2O2) has been suggested as a possible oxidizer of the martian surface. Photochemical models predict a mean column density in the range of 1015-1016 cm−2. However, a stringent upper limit of the H2O2 abundance on Mars (9×1014 cm−2) was derived in February 2001 from ground-based infrared spectroscopy, at a time corresponding to a maximum water vapor abundance in the northern summer (30 pr. μm, Ls=112°). Here we report the detection of H2O2 on Mars in June 2003, and its mapping over the martian disk using the same technique, during the southern spring (Ls=206°) when the global water vapor abundance was ∼10 pr. μm. The spatial distribution of H2O2 shows a maximum in the morning around the sub-solar latitude. The mean H2O2 column density (6×1015 cm−2) is significantly greater than our previous upper limit, pointing to seasonal variations. Our new result is globally consistent with the predictions of photochemical models, and also with submillimeter ground-based measurements obtained in September 2003 (Ls=254°), averaged over the martian disk (Clancy et al., 2004, Icarus 168, 116-121). 相似文献
63.
Jagdish Krishnaswamy Daniel D. Richter Patrick N. Halpin Michael S. Hofmockel 《水文研究》2001,15(12):2237-2257
An Erratum has been published for this article in Hydrological Processes 16(5) 2002, 1130–1131. Humid tropical regions are often characterized by extreme variability of fluvial processes. The Rio Terraba drains the largest river basin, covering 4767 km2, in Costa Rica. Mean annual rainfall is 3139±419sd mm and mean annual discharge is 2168±492sd mm (1971–88). Loss of forest cover, high rainfall erosivity and geomorphologic instability all have led to considerable degradation of soil and water resources at local to basin scales. Parametric and non‐parametric statistical methods were used to estimate sediment yields. In the Terraba basin, sediment yields per unit area increase from the headwaters to the basin mouth, and the trend is generally robust towards choice of methods (parametric and LOESS) used. This is in contrast to a general view that deposition typically exceeds sediment delivery with increase in basin size. The specific sediment yield increases from 112±11·4sd t km?2 year?1 (at 317·9 km2 on a major headwater tributary) to 404±141·7sd t km?2 year?1 (at 4766·7 km2) at the basin mouth (1971–92). The analyses of relationships between sediment yields and basin parameters for the Terraba sub‐basins and for a total of 29 basins all over Costa Rica indicate a strong land use effect related to intensive agriculture besides hydro‐climatology. The best explanation for the observed pattern in the Terraba basin is a combined spatial pattern of land use and rainfall erosivity. These were integrated in a soil erosion index that is related to the observed patterns of sediment yield. Estimated sediment delivery ratios increase with basin area. Intensive agriculture in lower‐lying alluvial fans exposed to highly erosive rainfall contributes a large part of the sediment load. The higher elevation regions, although steep in slope, largely remain under forest, pasture, or tree‐crops. High rainfall erosivity (>7400 MJ mm ha?1 h?1 year ?1) is associated with land uses that provide inadequate soil protection. It is also associated with steep, unstable slopes near the basin mouth. Improvements in land use and soil management in the lower‐lying regions exposed to highly erosive rainfall are recommended, and are especially important to basins in which sediment delivery ratio increases downstream with increasing basin area. Copyright © 2001 John Wiley & Sons, Ltd. 相似文献
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66.
S. Heynisch A. Pekdeger B. Richter M. -Th. Schafmeister W. Skala 《Mathematical Geology》1994,26(4):505-517
Computer-based risk evaluation methods are practical tools to compare automatically and evaluate contaminated sites. HYDRISK is an example of adequate knowledge-based systems: HYDRISK evaluates hydrogeological properties and chemical criteria relevant to contaminant transport with respect to the necessary remedial actions. It works at a high investigative level and enables geologists and engineers to draw differentiated conclusions for selecting remediation methods for the contaminated site. HYDRISK emphasizes space and time dependent aspects of the contaminant transport. It is supported by a geographic information system (GIS) to display the evaluation results. Some ideas on considering the spatiotemporal variability of relevant parameters by means of geostatistical methods and numerical models will be given. 相似文献
67.
The Fourier transform infrared spectra of individual conodonts with various CAI values indicate definite changes in conodont francolite during diagenesis. Steady decarbonation can be observed in the increasing intensity of the band with the wavenumber 2340 an-1 , which is assigned to trapped molecular CO2 . Carbon dioxide originates from decomposing CO2- 3 -ions occupying the B-site in francolite. Furthermore, the intensity of the water-deformation band at 1644 cm-1 decreases with higher CAI values. These changes of intensity can be quantified by calculating the maximum extinction (Emax ) for the corresponding absorption maxima and correlated with the CAI. Unaltered conodonts have a relative variable water 'content' and very little CO2 . Up to a CAI value of 4 conodont francolite continuously expells water and carbon dioxide is trapped. Conodonts with CAI = 5 have similar water 'contents' to CAI = 4 conodonts, but decarbonation continues to take place during this stage of diagenesis. 相似文献
68.
Stefano?ParolaiEmail author Andreas?F?cke Sandra?M.?Richwalski Lothar?Stempniwski 《Natural Hazards》2005,34(2):217-230
Ambient seismic noise measurements were conducted inside the Holweide Hospital (Cologne) for checking whether its frequencies of vibration fall into the range where soil amplification is expected. If this is the case, damage might increase in case of an earthquake due to an amplified structural response of the building. Two different techniques were used: the ratio between the horizontal and vertical components of the spectra recorded at stations located inside the building and the ratio between the corresponding components of the spectra recorded simultaneously inside the building and at a reference station placed outside. While the former method might be preferred because of less equipment involved, the latter has the advantage of producing more stable results and deleting automatically the influence of the sedimentary cover, which might obscure some eigenfrequencies of vibration of the building. An independently performed finite-element analysis of the hospital showed a good correlation between measured and calculated eigenmodes. 相似文献
69.
Wolfgang Kuhnt Florian Luderer Sandra Nederbragt Jürgen Thurow Thomas Wagner 《International Journal of Earth Sciences》2005,94(1):147-159
High sedimentation rates (up to 12 cm/kyear) of laminated organic carbon-rich biogenic limestones in the Tarfaya Basin provide an unusually high (millennial) resolution record of the late Cenomanian oceanic anoxic event (OAE-2). The global positive carbon-isotope excursion across the Cenomanian–Turonian corresponds to 11 light/dark sedimentary cycles. We interpret these cycles as a response to orbital obliquity variation and estimate the duration of the complete excursion as 440 kyear or one long eccentricity cycle. On this timescale, the main increase in 13C values occurred over a short time interval of less than 20 kyear in the late Cenomanian and reached a first maximum approximately 15 kyear prior to the bulk (mainly coccoliths) 18O-derived sea surface maximum temperature that occurs coeval to the extinction of Rotalipora cushmani. Organic carbon-accumulation rates follow obliquity cycles, reaching a maximum approximately 10 kyear after the last occurrence of R. cushmani, then slowly decreasing during the early Turonian. Thus, the maximum temperature and the maximum organic carbon accumulation in the Tarfaya Basin lagged by at least 15 kyear behind the global carbon-isotope shift and a proposed reduction of atmospheric CO2 content. The climate change across the Cenomanian/Turonian boundary probably occurred independent of CO2 levels and may have been controlled by different greenhouse gases (water vapour and methane) and changes in ocean circulation (i.e., opening of the Equatorial Atlantic gateway) 相似文献
70.
Allessandro Piccolo Riccardo Spaccini Rolf Nieder Joerg Richter 《Climatic change》2004,67(2-3):329-343
In a long-term (one year) experiment, a sandy Podzol and a silty-loamy Loess soil were treated with labile (polysaccharides, AG) and stable (mature compost, CMP, and two humic acids from compost, HAC, and lignite, HAL) organic matter and the organic carbon (OC) lost by mineralization was periodically evaluated. The stable materials alone induced a significant reduction of OC losses in Podzol CMP <, HAL, <, HAC, Control), whereas the same treatments, except for CMP, produced an OC loss larger than control in Loess. This was attributed to the diverse textural and physical status of the two soils. The added stable organic matter became protected in the Podzol soil within the aggregates formed by the interaction with the coarse inorganic phase, while it was more easily decomposed in the Loess soils due to the strength of the native humic-clay complexes. In both soils, when the stable organic materials were mixed with polysaccharides (AG), the OC losses from this labile fraction were significantly reduced, being CMP more OC sequestering than HAC and HAL, in the order. These results confirmed that labile organic matter in soils can be protected from biodegradation by repartition into the hydrophobic domains of the stable, humified organic matter. This study suggests that mature compost and humic acids may usefully integrate management practices aimed to sequester organic carbon in soils. 相似文献