Measurements of spectral lines observed with Hinode/EIS as implications for coronal heating     

Ying Li  Ming-De Ding 《中国天文和天体物理学报》2009,9(7)

We have measured the line widths and nonthermal velocities in 12 solar regions using high resolution EUV data taken by Hinode/EIS. We find that there exists a positive correlation between the intensity and nonthermal velocity for the Fe XII emission line as well as some other lines. The correlation coefficients decrease from the disk center to the limb. However, the nonthermal velocities of a particular spectral line do not vary much in different regions, so they are considered isotropic. In particular, we find that for a coronal loop structure, the largest widths and nonthermal velocities occur at the footpoints, where outflows appear. Based on these observational results, we discuss several physical processes responsible for coronal heating.  相似文献   

Ultraviolet observations of Phoebe from the Cassini UVIS     

Amanda R. Hendrix  Candice J. Hansen 《Icarus》2008,193(2):323-333

Observations of Saturn's distant moon Phoebe were made at far-ultraviolet (FUV) (1100-1900 Å) and extreme-ultraviolet (EUV) (600-1100 Å) wavelengths by the Cassini Ultraviolet Imaging Spectrograph (UVIS) during the Cassini spacecraft flyby on June 11, 2004. These are the first UV spectra of Phoebe and the first detection of water ice on a Solar System surface using FUV wavelengths. The characteristics of water ice in the FUV are presented, and Hapke models are used to interpret the spectra in terms of composition and grain size; the use of both areal and intimate mixing models is explored. Non-ice species used in these models include carbon, ice tholin, Triton tholin, poly-HCN and kerogen. Satisfactory disk-integrated fits are obtained for intimate mixtures of ∼10% H₂O plus a non-ice species. Spatially resolved regions of higher (∼20%) and lower (∼5%) H₂O ice concentrations are also detected. Phoebe does not display any evidence of volatile activity. Upper limits on atomic oxygen and carbon are 5×¹⁰¹¹ and 2×¹⁰¹² atoms/cm², respectively, for solar photon scattering. The UVIS detection of water ice on Phoebe, and the ice amounts detected, are consistent with IR measurements and contribute to the evidence for a Phoebe origin in the outer Solar System rather than in the main asteroid belt.  相似文献   

The albedo dichotomy of Iapetus measured at UV wavelengths     

Amanda R. Hendrix  Candice J. Hansen 《Icarus》2008,193(2):344-351

The dramatic hemispheric dichotomy in albedo displayed by Saturn's moon Iapetus has intrigued astronomers for centuries. Here we report on far-ultraviolet observations of Iapetus' bright and dark terrains from Cassini. We compare the reflectance spectra of Iapetus's dark terrain, Hyperion and Phoebe and find that both Phoebe and Hyperion are richer in water ice than Iapetus' dark terrain. Spectra of the lowest latitudes of the dark terrain display the diagnostic water ice absorption feature; water ice amounts increase within the dark material away from the apex (at 90° W longitude, the center of the dark leading hemisphere), consistent with thermal segregation of water ice. The water ice in the darkest, warmest low latitude regions is not expected to be stable and may be a sign of ongoing or recent emplacement of the dark material from an exogenic source.  相似文献   

Dehydration experiments on natural omphacites: qualitative and quantitative characterization by various spectroscopic methods   总被引：1，自引：0，他引：1  

M. Koch-Müller  I. Abs-Wurmbach  D. Rhede  V. Kahlenberg  S. Matsyuk 《Physics and Chemistry of Minerals》2007,34(9):663-678

A series of natural omphacites from a wide range of P, T occurrences were investigated by electron microprobe (EMP), infrared (IR)-, Mössbauer (MS)- and optical spectroscopy in the UV/VIS spectral range (UV/VIS), secondary ion mass spectrometry (SIMS) and single crystal structure refinement by X-ray diffraction (XRD) to study the influence of hydrogen loss on valence state and site occupancies of iron. In accordance with literature data we found Fe²⁺ at M1 as well as at M2, and in a first approach assigned Fe³⁺ to M1, as indicated by MS and XRD results. Hydrogen content of three of our omphacite samples were measured by SIMS. In combination with IR spectroscopy we determined an absorption coefficient: ε _i,tot = 65,000 ± 3,000 lmol_H2O ^?1 cm^?2. Using this new ε _i,tot value, we obtained water concentrations ranging from 60 to 700 ppm H₂O (by weight). Hydrogen loss was simulated by stepwise heating the most water rich samples in air up to 800°C. After heat treatment the samples were analyzed again by IR, MS, UV/VIS, and XRD. Depending on the type of the OH defect, the grade of dehydration with increasing temperature is significantly different. In samples relatively poor in Fe³⁺ (<0.1 Fe³⁺ pfu), hydrogen associated with vacancies at M2 (OH bands around 3,450 cm^?1) starts to leave the structure at about 550°C and is completely gone at 780°C. Hydrogen associated with Al³⁺ at the tetrahedral site (OH bands around 3,525 cm^?1, Koch-Müller et al., Am Mineral, 89:921–931, 2004) remains completely unaffected by heat treatment up to 700°C. But all hydrogen vanished at about 775°C. However, this is different for a more Fe³⁺-rich sample (0.2 Fe³⁺ pfu). Its IR spectrum is characterized by a very intense OH band at 3,515 cm^?1 plus shoulder at 3,450 cm^?1. We assign this intense high-energy band to vibrations of an OH dipole associated with Fe³⁺ at M1 and a vacancy either at M1 or M2. OH release during heating is positively correlated with decrease in Fe²⁺ and combined with increase in Fe³⁺. That dehydration is correlated with oxidation of Fe²⁺ is indirectly confirmed by annealing of one sample in a gas mixing furnace at 700°C under reducing conditions keeping almost constant OH^? content and giving no indication of Fe²⁺-oxidation. Obtained data indicate that in samples with a relatively high concentration of Fe²⁺ at M2 and low-water concentrations, i.e., at a ratio of Fe^{2+ M2}/H > 10 dehydration occurs by iron oxidation of Fe²⁺ exclusively at the M2 site following the reaction: \( {\left[ {{\text{Fe}}^{{{\text{2 + [ M2]}}}}{\text{OH}}^{ - } } \right]} = {\left[ {{\text{Fe}}^{{{\text{3 + [ M2]}}}} {\text{O}}^{{{\text{2}} - }} } \right]} + {\text{1/2}}\;{\text{H}}_{{\text{2}}} \uparrow . \) In samples having relatively low concentration of Fe²⁺ at M2 but high-water concentrations, i.e., ratio of Fe^{2+ M2}/H < 5.0 dehydration occurs through oxidation of Fe²⁺ at M1.  相似文献   

Impacts of domestic sewage effluent on phytoplankton from Bedford Basin, eastern Canada   总被引：2，自引：0，他引：2  

Youlian Pan  D.V. Subba Rao 《Marine pollution bulletin》1997,34(12):1001-1005

The impact of domestic sewage effluent (SE) on the dynamics of phytoplankton assemblages from Bedford Basin was evaluated in the laboratory. Phytoplankton production and chlorophyll a increased proportionally with SE enrichment. Phytoplankton species composition also changed. The potentially harmful diatoms, Pseudonitzschia spp., present initially in small numbers (600 cells 1⁻¹) in Bedford Basin seawater, and became dominant (3–5×10⁶ cells 1⁻¹) when the seawater was enriched with 0.5–5% untreated SE. With higher proportions of SE, other harmful species such as Fragilaria spp. and Euglena spp. became dominant (7−15×10⁶ and 2.2×10⁴ cells 1⁻¹, respectively). Treatment of SE with UV light or activated charcoal seems to favour growth of benign species, such as Chaetoceros socialis, Skeletonema costatum and Thalassiosira spp., but not harmful species such as Pseudonitzschia spp. Further research on UV treatment of domestic sewage is recommended.  相似文献   

Spectroscopic Characterization of Organic Structures and Organic‐Inorganic Interactions in Paper Mill Sludge     

Claudia M. B. F. Maia  Fabio Simonelli  Antinio S. Mangrich 《洁净——土壤、空气、水》2001,28(7):372-377

The organic composition and organic‐inorganic interaction in paper mill sludge (PS) solvent extracts (hexane, ethyl acetate, acetone and ethanol) and humic fractions, humic acid (HA) and humin (HU) were studied by electron paramagnetic resonance spectroscopy (EPR), proton and carbon‐13 nuclear magnetic resonance spectroscopy (¹H NMR; ¹³C NMR), Fourier‐transformed infrared spectroscopy (FTIR), and ultraviolet‐visible spectroscopy (UV‐vis). The strategy of fractionating the PS, sequentially, with organic solvents of increasing polarity is a reliable analytical procedure for humic substance sample separation because it results in more purified fractions. FTIR, ¹H NMR and ¹³C NMR results showed that hexane extract consisted mainly of aliphatic hydrocarbon structures. Their contents in the extracts decreased as the polarity of the extracting solvent increased and the content of oxygen functional groups increased. Carboxylic and carboxylate functional groups were found in the acetone extract, and ester and ether functions were predominantly found in the ethanol extract. EPR spectra revealed some Fe³⁺ complexes with rhombic structure (g₁ = 4.3; g₂ = 9.0) in the humic fractions and in all solvent extracts, except hexane. Quasi‐octahedral Fe³⁺ complexes (g = 2.3; ΔH_pp ≤ 400 G) were found in the HU fraction and in the acetone extract. The organic free radical content in the HA fraction was higher than the non‐fractionated PS sample and HU fraction.  相似文献   

Degradation Pathway of the Photochemical Oxidation of Ethylenediaminetetraacetate (EDTA) in the UV/H2O2-process     

M. Srensen  S. Zurell  F. H. Frimmel 《洁净——土壤、空气、水》1998,26(2):109-115

The degradation pathway for the oxidation of EDTA in the UV/H₂O₂-process was investigated. In absence of iron ions, the mineralization of EDTA is dominated by the reaction of the HO-radicals generated by the photolysis of H₂O₂. The organic degradation products iminodiacetate (IMDA), glycinate, oxamate, glyoxylate, oxalate and formate, and the inorganic degradation products carbon dioxide, ammonia, nitrate, nitrite, and cyanate were found. In the presence of iron ions, photolytic decarboxylation processes inside the complex get an important role during degradation, and the organic degradation products ethylenediaminetriacetate (ED3A), ethylenediaminediacetate (EDDA), ethylenediaminemonoacetate (EDMA) were also found. By combining product studies with balances of carbon and nitrogen, the degradation pathway in the UV/H₂O₂-process could be elucidated. The degradation of EDTA was fast (k_deg = 0.012 s^–1), and no toxic degradation products were identified. Therefore, the process is well suited for the elimination of EDTA in water treatment.  相似文献   

Innovative Germicidal UV and Photocatalytic System Dedicated to Aircraft Cabin Eliminates Volatile Organic Compounds and Pathogenic Micro‐Organisms          下载免费PDF全文

Laurent Gorvel  Matthieu Yver  Evelyne Robert  Michel Harmant  Manuel Rosa‐Calatrava  Bruno Lina  Jean Pierre Gorvel  Vincent Moulès  Raphaël Albalate  Carole Gaüzère 《洁净——土壤、空气、水》2014,42(6):703-712

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The Effect and Mechanism of UV Disinfection on the Inactivation of a Planktonic Freshwater Copepods (Limnoithona sinensis)          下载免费PDF全文

Tao Lin  Jian Zhang  Wei Chen  Ying Sun 《洁净——土壤、空气、水》2014,42(1):43-50

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Influence of Biological Treatment and Ultraviolet Disinfection System on Pseudomonas spp. Diversity in Wastewater as Assessed by Denaturing Gradient Gel Electrophoresis          下载免费PDF全文

Inès Mehri  Yousra Turki  Hanène Chérif  Amel Khessairi  Abdennasser Hassen  Maher Gtari 《洁净——土壤、空气、水》2014,42(5):578-585

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