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排序方式: 共有147条查询结果,搜索用时 15 毫秒
101.
Franois Charles Susanna Lopez-Legentil Antoine Grmare Jean Michel Amouroux Martin Desmalades Gilles Vtion Karine Escoubeyrou 《Continental Shelf Research》2005,25(19-20):2533
Environmental parameters and gross sedimentation rates (GSR) were monitored at a fixed site located in the Bay of Banyuls-sur-Mer (NW Mediterranean), between March 1997 and April 1998, together with the main biochemical characteristics of both sedimenting and sedimented particulate organic matter (POM). Three storms which occurred during this time period resulted in natural sediment resuspension. This is indicated by the corresponding increase in GSR and a decrease in the enzymatically hydrolysable amino acids/totally hydrolysable amino acids ratio (EHAA/THAA), within the sedimenting POM. Only the strongest storm resulted in (1) a transitory increase in fine-grained particles, (2) concomitant increases in organic carbon, carbohydrates, lipids and THAA, and (3) a decrease in the EHAA/THAA ratio in surficial sediments. For most of the assayed parameters, the values recorded after the December 1997 storm corresponded to extremes for the whole period under study. This emphasises the role of storms in controlling the characteristics of sedimented and sedimenting POM.Ten sediment types, with contrasting biochemical characteristics, were selected for experiments; these were based on the results of the monitoring survey and were used during adsorption and absorption experiments involving 14C tetrachlorobiphenyl (TCB). Adsorption rates differed significantly between the sediment types, but did not correlate with any of the assayed biochemical parameters. Absorption efficiency by the mussel Mytilus galloprovincialis also differed between the sediment types; it correlated positively with all the assayed biochemical parameters, except lipids. Comparison between the magnitudes of the increase in GSR, together with the decrease in absorption efficiency during resuspension events, suggests that resuspension tends to enhance the transfer of organic pollutants in the benthic food chain. 相似文献
102.
103.
目的:提高CT衬度的分辨率,30年来,医学CT经历了原始的第一代CT发展至目前第5代高分辨率CT和高速电子束CT,其成像的空间分辨率和时间分辨率均有明显提高,但CT成像的衬度(密度)分辨率提高并不显著,而衬度分辨率与图像的灰度等级(灰阶)密切相关,是图像清晰度的重要参数。本文对应用双能量光子扫描吸收法以提高CT衬度(密度)分辨率的原理进行分析,并探讨其实际应用的可行性。 相似文献
104.
油气资源的遥感勘探,可分为“直接”和“间接”两大类。红外遥感油气资源勘探技术属于“直接”勘探范畴。本研究基于工业油气藏烃类微渗漏理论,利用烃类特有的2.27—2.46μm波谱双峰吸收带,以土壤烃组分异常为标志实施探测,并从理论上排除了各种地物目标的干扰,建立了一套航空遥感计算机图像处理及油气遥感信息异常提取方法。三次大面积试验表明,与已知油流区块的符合率达70%,在未知区的油气遥感异常中,一些已被钻探证实含有油气性,业已正式列入油气勘探生产计划。 相似文献
105.
本文总结最近从Xray 观测得到的关于宽吸收线类星体一些新结果, 我们和人家的结果都表明吸收物质的柱密度比原来从紫外估计的高三个量级, 在PG1411 + 442 中, 我们发现Xray 除了吸收成分外, 还有散射成分, 其量级和UV 吸收的剩余流量一致, 从而说明以前从UV 推断的结论是有问题的。此外, 对PG1126041 的研究表明从宽吸收线类星体到Seyfert 星系的窄本征吸收线其物理性质是连续过渡的。 相似文献
106.
Francisco P. J. Valero Thomas P. Ackerman Warren J. Y. Gore 《Journal of Atmospheric Chemistry》1989,9(1-3):225-244
The interaction of the Aretic winter aerosol (Arctic haze) with solar radiation produces changes in the radiation field that result in the enhancement of scattering and absorption processes which alter the energy balance and solar energy distribution in the Arctic atmosphere-surface system. During the second Arctic Gas and Aerosols Sampling Project (AGASP II) field experiment, we measured radiation parameters using the NOAA WP-3D research aircraft as a platform. State-of-the-art instrumentation was used to measure in situ the absorption of solar radiation by the Arctic atmosphere during severe haze events. Simultaneously with the absorption measurements, we determined optical depths, and total, direct, and scattered radiation fields. All optical measurements were made at spectral bands centered at 412, 500, 675, and 778 nm and with a bandpass of 10 nm. With this selection of spectral regions we concentrated on the measurement of the radiative effects of the aerosol excluding most of the contributions by the gaseous components of the atmosphere. An additional measurement performed during these experiments was the determination of total solar spectrum fluxes. The experimentally determined parameters were used to define an aerosol model that was employed to deduce the absorption by the aerosols over the full solar spectrum and to calculate atmospheric heating rate profiles. The analyses summarized above allowed us to deduce the magnitude of the change in some important parameters. For example, we found changes in instantaneous heating rate of up to about 0.6 K/day. Besides the increased absorption (30 to 40%) and scattering of radiation by the atmosphere, the haze reduces the surface absorption of solar energy by 6 to 10% and the effective planetary albedo over ice surfaces by 3 to 6%. The vertical distribution of the absorbing aerosol is inferred from the flux measurements. Values for the specific absorption of carbon are found to be around 6 m2/g for externally mixed aerosol and about 11.7 m2/g for internally mixed aerosol. A complete study of the radiative effects of the Arctic haze should include infrared measurements and calculations as well as physics of the ice, snow, and water surfaces. 相似文献
107.
This paper reports changes in dissolved organic carbon concentration β(DOC) and the relation between UV-active and non-UV-active components determined for Elbe river water and river bank infiltrate in the Torgau river basin between 1992 and 1994. Using an ultrafiltration method, the fractionation of the DOC content was obtained for the fractions > 10 000 g/mol, 1 000…10 000 g/mol, and < 1 000 g/mol. The spectral absorption coefficient at 254 nm a254 of the molecular-weight fractions was also measured. The mean total DOC concentration of Elbe river water decreased from 6.0 mg/L to below 3.9 mg/L along two investigated flowpaths. Two thirds of the decrease occurred within the first few metres of the river bed and one third along the 350 m length of the groundwater flowpaths. The a254 values showed a significant decrease from 14.8 1/m in Elbe river water to 7.8 1/m in the aquifer. Along a flowpath, the proportion of low-molecular weight fraction of DOC increased, the proportion of high-molecular weight fraction decreased, and the proportion of the 1 000…10 000 g/mol molecular-weight fraction remained relatively stable. The Elbe river water contained the main portion of UV-active compounds in the fraction 1 000…10 000 g/mol, and this was also the case for samples of river infiltrate. For the high-molecular weight fraction, mainly non-UV-active compounds were attenuated in the river bed sediment. 相似文献
108.
翡翠透射红外光谱解析 总被引:1,自引:0,他引:1
对百余件翡翠红外光谱及历年测试原始记录研究发现:同类玉件(指A、B货)红外光谱特征不尽相同,可以归纳为典型谱和变异谱两类。将谱图分为四个区段,发现产生变异谱的因素。天然翡翠典型谱,可反映玉件质地。导致出现变异谱的主要因素是透过率低或水峰过宽。发现玉件中可能存在一种新的有机充填物,其性质介于胶与蜡之间。 相似文献
109.
含油岩石的荧光特征研究 总被引:1,自引:0,他引:1
在紫外光照射下,很多有机物质和部分无机物质能够发出不同颜色和亮度的荧光。本文研究了含油岩芯中岩石矿物的荧光特征,指出采用氯仿(或乙烷)试剂浸泡岩样是区别岩石矿物荧光的有效方法。本文着重对含油岩芯中有机质组成以及有机组分与荧光颜色的关系进行了深入的探讨,指出依据含油岩芯的荧光颜色可以进行油气水层的荧光解释。 相似文献
110.