The ultraviolet reflectance of Enceladus: Implications for surface composition     

Amanda R. Hendrix  Candice J. Hansen 《Icarus》2010,206(2):608-617

The reflectance of Saturn’s moon Enceladus has been measured at far ultraviolet (FUV) wavelengths (115-190 nm) by Cassini’s Ultraviolet Imaging Spectrograph (UVIS). At visible and near infrared (VNIR) wavelengths Enceladus’ reflectance spectrum is very bright, consistent with a surface composed primarily of H₂O ice. At FUV wavelengths, however, Enceladus is surprisingly dark - darker than would be expected for pure water ice. Previous analyses have focused on the VNIR spectrum, comparing it to pure water ice (Cruikshank, D.P., Owen, T.C., Dalle Ore, C., Geballe, T.R., Roush, T.L., de Bergh, C., Sandford, S.A., Poulet, F., Benedix, G.K., Emery, J.P. [2005] Icarus, 175, 268-283) or pure water ice plus a small amount of NH₃ (Emery, J.P., Burr, D.M., Cruikshank, D.P., Brown, R.H., Dalton, J.B. [2005] Astron. Astrophys., 435, 353-362) or NH₃ hydrate (Verbiscer, A.J., Peterson, D.E., Skrutskie, M.F., Cushing, M., Helfenstein, P., Nelson, M.J., Smith, J.D., Wilson, J.C. [2006] Icarus, 182, 211-223). We compare Enceladus’ FUV spectrum to existing laboratory measurements of the reflectance spectra of candidate species, and to spectral models. We find that the low FUV reflectance of Enceladus can be explained by the presence of a small amount of NH₃ and a small amount of a tholin in addition to H₂O ice on the surface. The presence of these three species (H₂O, NH₃, and a tholin) appears to satisfy not only the low FUV reflectance and spectral shape, but also the middle-ultraviolet to visible wavelength brightness and spectral shape. We expect that ammonia in the Enceladus plume is transported across the surface to provide a global coating.  相似文献   

不同时期再造琥珀的微细结构对比及鉴定     

李海波  陆太进  沈美冬  周军 《地质科学译丛》2012,(2):36-39,43

再造琥珀制造技术不断更新换代,并不断取得进展。市场上能见到不同时期的再造琥珀,给实验室鉴定带来挑战。为科学鉴定这些琥珀,结合前人研究和国检（NGTC）近年来的研究成果,主要从放大检查,正交偏光,紫外荧光这三方面分别对早期和近期再造琥珀的鉴定特征进行了系统研究和阐述。结果显示,早期传统再造琥珀的“血丝”状构造明显,其在正交偏光下的特征及紫外灯下的荧光特征明显。近期再造琥珀中的“血丝”变浅,其后多数又进行了一系列后期处理,掩盖了原有的再造琥珀特征,所以其在正交偏光下的特征及紫外灯下的荧光特征均不明显。但在强透射光源照射下,仍可发现局部残余的再造特征,如沿“血丝”分布的片状炸裂纹、流动的“砂糖”状构造等。这些微细结构特征有助于对不同时期再造琥珀进行正确举别。  相似文献   

CIPP紫外线固化施工的质量验收方法     

强一香 《岩土钻凿工程》2012,(2):109-111

本文概要论述了排水管道CIPP拉入法内衬修复技术采用紫外线固化的工艺过程、技术优势;并根据紫外线固化工艺存在的技术缺陷,提出了有针对性的可操作的质量验收方法,希望对管道业主同仁们在紫外线固化工程验收时有所助益,以进一步促进管道非开挖修复事业在我国的健康发展。  相似文献   

海水中胶体有机碳的测定──高温燃烧法和紫外/过硫酸钾法的比较   总被引：5，自引：0，他引：5  

王江涛  赵卫红  谭丽菊  张正斌 《海洋学报》2000,22(2):65-70

利用切向超滤(cross-flow ultrafiltration)技术对海水中胶体有机碳(COC)和真溶解有机碳(UOC)进行了分离,并分别用高温燃烧法和紫外/过硫酸钾法对胶体有机碳和真溶解有机碳进行了测定。测定结果表明,切向超滤能定量分离海水中的胶体有机碳,高温燃烧法和紫外/过硫酸钾法对胶体有机碳和真溶解有机碳的测定结果没有明显的系统误差,表明这两种方法的氧化效率基本相同,胶体粒子的存在,对紫外/过硫酸钾法的氧化效率没有显着影响。  相似文献   

The spatial distribution of coarse surface grains and the stability of gravel river beds     

MIGULE M. PIEDRA  HEATHER HAYNES  TREVOR B. HOEY 《Sedimentology》2012,59(3):1014-1029

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Ultraviolet spectroscopy of the extended solar corona     

John L. Kohl  Giancarlo Noci  Steven R. Cranmer  John C. Raymond 《Astronomy and Astrophysics Review》2006,13(1-2):31-157

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Utilization of a submersible UV fluorometer for monitoring anthropogenic inputs in the Mediterranean coastal waters     

Marc Tedetti  Catherine Guigue  Madeleine Goutx 《Marine pollution bulletin》2010,60(3):350-2210

We evaluated the performances of a submersible ultraviolet fluorometer (EnviroFlu-HC, TriOS Optical Sensors) dedicated to the real time measurement of polycyclic aromatic hydrocarbons (PAHs) in the aquatic media. We conducted calibration experiments and in situ measurements in the coastal Mediterranean Sea. We found that the EnviroFlu-HC was not strictly specific to PAHs, even though it exhibited the highest sensitivity for phenanthrene, but could response to tryptophan-like material as well, and in a much less extent, to humic substances. The sensor signal showed great spatial and temporal variations in clean and polluted sites, with likely a high contribution of PAHs in the harbors, and a high contribution of tryptophan-like and humic-like materials in the sewage effluent. We conclude that the EnviroFlu-HC is a good tool for monitoring anthropogenic inputs in the coastal waters, although its utilization should be combined to other fluorescence measurements to improve the information about the nature of the aromatic compounds detected.  相似文献   

Production of Laccase from Coriolus versicolor and Its Application in Dye Decolorization in Combination with UV/H2O2 Technique     

A. J. Damle  S. R. Shukla 《洁净——土壤、空气、水》2010,38(7):663-669

The relative ability of Coriolus versicolor to grow on coir fiber as a ligninocellulosic material was examined. Addition of yeast extract to the culture increased laccase activity, which was further enhanced to the level of 1976 U/L by addition of 1 mM copper sulfate. Laccase thus produced was used without further purification for the decolorization of various dye solutions. Decolorization efficiency was compared with the conventional environment friendly oxidation technique using hydrogen peroxide in the presence of UV radiations. Laccase showed good decolorization in most of the cases. Excellent results were achieved when the dye solution was treated successively with laccase and UV/H₂O₂ wherein more than 80% decolorization was achieved. This value is remarkably higher than that attained either by the enzyme or UV/H₂O₂ photolysis alone.  相似文献   

Photon scattering in the solar ultraviolet lines of He i and He ii     

C. Jordan  G. R. Smith  E. R. Houdebine 《Monthly notices of the Royal Astronomical Society》2005,362(2):411-423

Observations made with the Coronal Diagnostic Spectrometer (CDS) onboard the Solar and Heliospheric Observatory ( SOHO ) are used to investigate the behaviour of the intensities of the emission lines of He  i , He  ii and O  iii at the quiet Sun-centre and at  θ= 60°  towards the equatorial limb. The aim is to examine the possible effects of photon scattering on the spatial variation of the optically thick helium lines. At the quiet Sun-centre, we find that, in agreement with previous work, the ratios of the intensities of the He  i 584-Å and He  ii 304-Å lines to those of the O  iii 600-Å line decrease systematically as the intensity of the O  iii line increases. However, we find that the dependence of these ratios on the O  iii intensity is not unique, but differs between the individual regions studied. Similar results are found at  θ= 60°  . We have also used line intensities and intensity ratios to investigate limb-to-disc effects and variations across a sample of supergranulation cell boundaries and adjacent cell interiors at both locations. The results do not exclude photon scattering as the cause of the larger observed ratios in cell interiors. The differences between the apparent widths of boundaries in O  iii at Sun-centre and 60° show that the emitting material is extended in height, which will aid the process of scattering into cell interiors. Photon scattering could also account for the lack of oscillations in the He  i intensities in a cell interior studied by Pietarila & Judge. Three-dimensional radiative transfer calculations in chosen geometries are now needed to account for the observations in detail.  相似文献   

紫外光对有毒甲藻塔玛亚历山大藻的生态学效应   总被引：21，自引：1，他引：21  

齐雨藻  黄长江  应浙鸿  钱锋 《海洋与湖沼》1997,28(2):113-120

对1991年分离自南海大鹏湾海域的塔玛亚历山大藻单克隆培养林在不同光照条件、辐射强度（9.5，5．9W／m2）（辐射剂量为：95，190，380,760,1520J/m2）和营养盐（N，P）浓度下，进行紫外辐射敏感性的研究。结果表明，紫外辐射可以导致细胞变形、增大和死亡。不论在什么条件下，低剂量的紫外辐射（95J／m2）就能使该藻的存活率和生长率大幅下降。此后，随着辐射剂量的增加，虽然存活率和生长率继续下降，但下降幅度渐缓。充足的营养盐和辐射处理后的连续光照对藻群的恢复有益，但在缺氮和缺磷条件下培养的藻群，可能由于生理活性减弱而导致对紫外辐射敏感性的迟钝。辐射强度对该藻的紫外辐射敏感性的影响十分显著，而且与辐射剂量具有明显的双重效应。  相似文献