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991.
M. A. Romanova 《Mathematical Geology》1991,23(7):959-979
A hypothesis for effects of stable tectonic elements on chemical composition of Mesozoic granitoids in northeastern Asia is tested. Chemical compositional change of granitoid rocks is examined in nine-dimensional space of rock-forming oxides. Stable geologic structures of the region are outlined by trends of Euclidean distances between rock recognized as a standard in a space of major rock-forming oxides and composition of individual samples. A data-smoothing polynomial of the fourth order corresponds closely to the geology of the region. Chemically stable masses of quartz diorite are thought to be delivered directly from magmatic sources along deep faults. A great variety of acidic granites, which occupy for each analysis separate cells in the nine-dimensional classification, are presumed to be palingenetic in origin. 相似文献
992.
Vegetation characteristics have not been sufficiently utilized in catchment runoff models. An analysis of storm hydrograph data from nested subareas of the Highland Water catchment, New Forest, U.K., indicates that depth of runoff and peak discharge from areas under heathland cover is substantially greater than from areas under woodland cover at several spatial scales. The significance of heath vegetation composition in the identification of runoff contributing areas is illustrated by an analysis of vegetation composition, water table depth, baseflow discharge and storm runoff from areas predominantly covered by heathland. Methods are proposed to employ the hydrological characteristics of heathland to refine and develop the Flood Studies Approach to discharge estimation in ungauged heathland catchments. Such an approach is greatly facilitated by the use of remotely-sensed data. 相似文献
993.
Weaver H. A. Brooke T. Y. Chin G. Kim S. J. Bockelée-Morvan D. Davies J. K. 《Earth, Moon, and Planets》1997,78(1-3):71-80
High resolution (λ/δλ ∼ 20,000) spectra of comet C/1995 O1 (Hale-Bopp) in the 2–5 μm region were obtained during UT 2–5 March
1997 using CSHELL at the NASA Infrared Telescope Facility (IRTF) on Mauna Kea. The heliocentric and geocentric distances of
the comet were ∼1.1 AU and ∼1.5 AU,respectively. We detected emission lines of the gas-phase molecules H2O, 4, C2H6, C2H2, HCN, and CO and derived absolute production rates and relative abundances for all species. We also used the 2-dimensional
nature of the CSHELL data to investigate the spatial distribution of the molecules and find evidence that CO was derived at
least partly from an extended source in the coma.
This revised version was published online in July 2006 with corrections to the Cover Date. 相似文献
994.
995.
996.
Offshore oil platforms and fouling communities in the southern Arabian Gulf (Abu Dhabi) 总被引:1,自引:0,他引:1
Stachowitsch M Kikinger R Herler J Zolda P Geutebrück E 《Marine pollution bulletin》2002,44(9):853-860
This study examined the fouling organisms on the legs of offshore oil platforms at two sites in the southern Arabian Gulf (offshore Abu Dhabi, United Arab Emirates). 100% of the metal structures was colonized by encrusting organisms. Both the number of individuals and the total biomass tended to decrease with depth. The total weight of dead shells always exceeded that of living organisms. Sessile filter feeders dominated the biomass, whereas small mobile forms had the largest number of individuals. The biomass at the deeper platform (22 m) was dominated by bivalves, barnacles and bryozoans, while polychaetes and amphipods had the greatest number of individuals. Biomass values here ranged from 1 g/0.1 m2 at 20 m to 147 g/0.1 m2 at 5 m; the corresponding individual numbers were 266 (20 m) and 11,814 indiv./0.1 m2 (5 m). The results at the shallower platform (11 m) differed in several respects: barnacles clearly dominated over bivalves, and sponges exceeded byrozoans, while total individual numbers fell due to a decline in polychaete dominance. Biomass values here ranged from 84 g/0.1 m2 at 10 m to 153 g/0.1 m2 at 0 m; the corresponding individual numbers were 695 (10 m) and 3,125 indiv./0.1 m2 (0 m). The potential role of such fouling communities on artificial structures in the Gulf is discussed. 相似文献
997.
Bernard Aumont Sasha Madronich Isabelle Bey Geoffrey S. Tyndall 《Journal of Atmospheric Chemistry》2000,35(1):59-75
Measurements show that 20–60% of the carbon mass present in fine atmospheric particulate matter consists of water soluble organic compounds (WSOC). However, only 5–20% of this WSOC has been identified, mainly as dicarboxylic acids. Because of their high solubility in water, multifunctional secondary compounds derived from the gas-phase oxidation of volatile organic compounds (VOC) are suspected to be key contributors to the WSOC. To test this assumption, an estimate of aqueous uptake of secondary VOC was included in a highly detailed gas-phase mechanism which treats explicitly the formation of the secondary VOC from a set of representative primary species. Simulations were conducted for 2 scenarios, representing typical rural and urban areas. It was observed that the uptake of secondary VOC can lead to WSOC mass concentrations in the range of a few C m–3, in fairly good agreement with typical WSOC mass concentrations measured. Speciation of WSOC was found to be mainly as tri- or higher multifunctional hydroxy-carbonyl species and hydroxy-hydroperoxide-carbonyl species, in urban and rural environments, respectively. However, it was also found that taking into account only the absorption of secondary VOC does not bring the carboxylic acids mass concentration in agreement with measurements. An attempt was made to explain this discrepancy by introducing chemistry occurring within deliquescent aerosols. 相似文献
998.
999.
The viscosity of a natural phonolitic composition with variable amounts of H2O has been experimentally determined. The starting materials were crystal-free phonolitic glasses from Montaña Blanca, situated within the Las Cañadas caldera of Teide. Dry phonolitic melt viscosities were determined using concentric cylinder viscometry in the low viscosity range. The glassy quench products of these runs were then hydrated by high pressure synthesis in a piston–cylinder apparatus to generate a suite of samples with water contents ranging from 0.02 to 3.75 wt%. Samples thus hydrated were quenched rapidly and prepared (cut and polished) for the determination of water contents by infrared spectroscopy before and after experimental viscometry. The viscosities of the melts (dry and hydrated) were determined at 1 bar using a micropenetration technique. Samples were stable under the measurement conditions up to 3.75 wt% H2O. Homogeneity of water content was confirmed by infrared spectroscopy and total water contents were calculated using absorptivity coefficients for compositions extremely close to that investigated here. The variation of viscosity as a function of water content and temperature can be described in the high viscosity interval of relevance to many welding processes by the non-Arrhenian expression:(1) whereas the high viscosity range alone is adequately described by the Arrhenian expression(2) where η is the viscosity in Pa s, H2O is the water content in wt% and T is the temperature in K.These results are particularly useful for the scaling of conditions extant during the welding of phonolitic products of Montaña Blanca. The welding of glassy phonolitic rocks is enhanced by the lower viscosity of these melts with respect to calcalkaline rhyolites. The ratio of viscosities of phonolitic to calcalkaline rhyolitic melts is a complex function of temperature and water content and reaches up to 104.5 at 0.1 wt% H2O and 500°C. Abundant evidence of welding and remobilisation of pyroclastic and spatter products of Teide system volcanism are consistent with these experimental observations. 相似文献
log10 η=−5.900−0.286 ln (H2O)+(10775.4−394.8(H2O))/(T−148.7+21.65 ln (H2O))
log10 η=−10.622−0.738 ln (H2O)+(17114.3−590.4(H2O))×1/T
1000.
Auroral and airglow emissions over Eureka (89° CGM) during the 1997/98 winter show striking variations in relation to solar wind IMF changes. The period January 19 to 22, 1998, was chosen for detailed study, as the IMF was particularly strong and variable. During most of the period, Bz was northward and polar arcs were observed. Several overpasses by DMSP satellites during the four day period provided a clear picture of the particle precipitation producing the polar arcs. The spectral character of these events indicated excitation by electrons of average energy 300 to 500 eV. Only occasionally were electrons of average energy up to 1 keV observed and these appeared transitory from the ground optical data. It is noted that polar arcs appear after sudden changes in IMF By, suggesting IMF control over arc initiation. When By is positive there is arc motion from dawn to dusk, while By is negative the motion is consistently dusk to dawn. F-region (anti-sunward) convections were monitored through the period from 630.0 nm emissions. The convection speed was low (100/150 m/s) when Bz was northward but increased to 500 m/s after Bz turned southward on January 20. 相似文献