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1.
The contents of the moderately volatile elements Ga, Ge, Cu and Sb in ordinary chondrites give us some clues with regard to the metal-silicate fractionation process. Their concentration in coexisting magnetic and non-magnetic portions of members of each ordinary chondrite group will be discussed. Germanium and Sb are mostly siderophilic, but Ga is strongly lithophilic in unequilibrated chondrites; its partition coefficient between magnetic and non-magnetic portions is positively correlated with petrologic type in L and LL chondrites, but not in H4–6 chondrites. From 25 to 50% of the total Cu is found in the non-magnetic fraction of chondrites, but there is no correlation between Cu content and petrologic type. The abundances of Ga, Cu and Sb (relative to Si) are constant in ordinary chondrites, independent of the amount of metal present, indicating that these elements were not in solid solution in the metal phase of chondrites when the metal-silicate fractionation process occurred. Germanium, which is the most volatile among the four elements analyzed, is more abundant in H than in L and LL chondrites, indicating that it was fractionated by this process. Nebular oxidation processes can be responsible for the behavior of Ga if this element was in oxidized form when loss of metal occurred, but cannot explain the results for Cu and Sb which are predicted to condense as metals and accrete mostly in metallic form. It is possible that Cu and Sb, upon condensation, did not form solid solutions with metallic Ni-Fe until after the separation of metal from silicates took place. 相似文献
2.
The mineralogy, elemental and isotopic composition of the Shaw meteorite indicate that it is a highly metamorphosed L-group chondrite which has lost a portion of its metal and sulfide. The metal which remains has an unusual composition relative to that in other L-group chondrites. It is enriched in Ga, Ge, Ir, Mo, Os, Pt, Re and Ru and depleted in As, Au, Cu and Sb. A comparison of the relative enrichments and depletions in Shaw to those observed in San Cristobal, the extreme end-member of group IAB iron meteorites, shows that the metal phases in these two meteorites have complementary compositions. This implies that the metal in Shaw represents the residual solid of a partial melting process while the missing metal, which drained away, may have gone to form an iron meteorite, like San Cristobal. 相似文献
3.
Dario Del Moro Luca Giovannelli Ermanno Pietropaolo Francesco Berrilli 《Experimental Astronomy》2017,43(1):23-37
Hyperspectral imaging is an ubiquitous technique in solar physics observations and the recent advances in solar instrumentation enabled us to acquire and record data at an unprecedented rate. The huge amount of data which will be archived in the upcoming solar observatories press us to compress the data in order to reduce the storage space and transfer times. The correlation present over all dimensions, spatial, temporal and spectral, of solar data-sets suggests the use of a 3D base wavelet decomposition, to achieve higher compression rates. In this work, we evaluate the performance of the recent JPEG2000 Part 10 standard, known as JP3D, for the lossless compression of several types of solar data-cubes. We explore the differences in: a) The compressibility of broad-band or narrow-band time-sequence; I or V Stokes profiles in spectropolarimetric data-sets; b) Compressing data in [x,y, λ] packages at different times or data in [x,y,t] packages of different wavelength; c) Compressing a single large data-cube or several smaller data-cubes; d) Compressing data which is under-sampled or super-sampled with respect to the diffraction cut-off. 相似文献
4.
Abstract. A two-year ecological study in the Oliveri-Tindari (Messina) brackish water ponds evaluated the quantitative and qualitative distribution of Vibrio species in relation to the physicochemical conditions of the ponds.
The evaluation of 204 samples shows a general relationship between the halophilic vibrios and water temperature. In particular this relationship is stronger for the Vibrio fraction able to grow at 37°C, i. e. , those species related to human infections. On the other hand, the halophilic vibrios show no relation with the index of fecal contamination.
The ecology of V. parahaemolyticus is discussed in relation to the salinity of Marinello pond.
The distribution of V. cholerae non O1, isolated from all ponds, shows that this microorganism can be considered as autochthonous in coastal environments. 相似文献
The evaluation of 204 samples shows a general relationship between the halophilic vibrios and water temperature. In particular this relationship is stronger for the Vibrio fraction able to grow at 37°C, i. e. , those species related to human infections. On the other hand, the halophilic vibrios show no relation with the index of fecal contamination.
The ecology of V. parahaemolyticus is discussed in relation to the salinity of Marinello pond.
The distribution of V. cholerae non O1, isolated from all ponds, shows that this microorganism can be considered as autochthonous in coastal environments. 相似文献
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6.
Roberto G. Francese Ermanno Finzi Gianfranco Morelli 《Journal of Applied Geophysics》2009,67(1):44-51
A fast and efficient subsurface radar imaging procedure, based on a multi-channel cart system, has been developed and tested within the framework of a large-scale archaeological investigation project in northern Italy.The tested cart comprises 14 closely-spaced dipoles, rotated by 45° with respect to the dragging direction, and allows unidirectional scanning operations. Using this approach, an area of approximately 75 000m2 was surveyed daytime via recording of a dense grid of about 490km of radar profiles. Geo-referencing of the scanning trajectories was achieved operating a separate on-board differential Global Positioning System in real-time kinematic mode. In this configuration the final positioning error of the radar sweeps was less than 0.05m.The large amount of collected data, of the order of tens of GBytes, was processed, using an open-source software package, on a workstation-based environment. A set of specific codes was developed to fully automate the data processing and the image generation procedure. Critical steps during code development were the integration of positioning and radar data, the referencing of the single radar sweeps and the correction for changes in the spectral amplitude of the different channels.The processed data volume displays high signal coherency and reveals several well-defined reflectors, clearly visible both on vertical profiles and horizontal time slices. The plan of the Roman settlement could be revealed in detail proving the potential of the tested approach for assisting high-resolution archaeological investigations of large areas. 相似文献
7.
It appears that the highly unequilibrated Bishunpur ordinary chondrite preserves phase relations acquired during solar nebular processes to a relatively high degree; metamorphic temperatures may not have exceeded 300–350°C. The major categories of metal are: 3 kinds of metal in the metal matrix, three kinds in chondrule interiors and 2 kinds in chondrule rims. The fine-grained matrix metal is highly variable in composition: the kamacite Co content (7.8 ± 2.0 mg/g) is within the L-group range (6.7–8.2 mg/g) but extends well above and below; its Ni content (38 ± 5 mg/g) is considerably lower than in more equilibrated chondrites and taenite is Ni-rich ( > 450 mg/g) and unzoned. These compositions imply equilibration at very low temperatures of about 300–350°C. It seems unlikely that volume diffusion could account for the observed relatively unzoned phases; a better model involves mass transport by grain boundary diffusion and grain growth at the indicated temperatures. We find no evidence that the matrix was ever at higher temperatures. Large (50–650 μm) polycrystalline metal aggregates consisting of individually zoned crystals are also found in the matrix; they probably represent clusters formed in the solar nebula. A few large (50–250 μm) round monocrystalline grains are also present in the matrix.Metal-bearing chondrules tend to be highly reduced; they contain low-Ni metal that occasionally contains Si and/or Cr. Silicates in these chondrules tend to have low ratios. The Si-rich metal grains are never in contact with silicates and are always surrounded by troilite with a poorly characterized Ca, Cr-sulfide at the metal-troilite interface; they appear to be high temperature nebular condensates that avoided oxidation even during the chondrule forming process. Silicon contents drop below our detection limit when the sulfide coating is absent. Much more common in chondrule interiors are Si-free spheroidal metal grains not associated with sulfides. These have Ni and Co contents very similar to the Si-bearing grains, and appear to be oxidized variants of the same material. The third class of chondrule metal is fine ( ~1 μm) dusty grains inside individual olivine grains. These seem to reflect high temperature in situ reduction of FeO from the olivine.The composition of kamacite is different in sulfide-rich and sulfide-poor chondrule rims and in both cases it is dissimilar to the compositions in the chondrule interiors and matrix; this indicates that chondrule rims could not have resulted from reactions with the matrix, but are primary features acquired prior to accretton. 相似文献
8.
Ermanno Crisafi Renata Zaccone Lucrezia Genovese Rosabruna La Ferla Teresa Luciana Maugeri 《Marine Ecology》1989,10(4):365-375
Abstract. Seventy six samples of coastal sediments collected in the Straits of Messina were studied in order to evaluate the effects of an oil spill and the consequent "clean-up" operations on heterotrophic acrobic bacteria.
In addition, in vitro tests were carried out to estimate the effects of five dispersants on the growth and oil degrading capacity of marine strains isolated from the same sediments. 相似文献
In addition, in vitro tests were carried out to estimate the effects of five dispersants on the growth and oil degrading capacity of marine strains isolated from the same sediments. 相似文献
9.
Cyanobacterial toxins in Italian freshwaters 总被引：1，自引：0，他引：1
Valentina Messineo Serena Melchiorre Antonella Lugliè Maria Antonietta Mariani Antonio Di Corcia Ermanno Carloni 《Limnologica》2009,39(2):95-106
This study focuses on the occurrence and distribution of cyanobacterial toxins from 1989 to 2006 in several Italian lakes of different characteristics and human uses, the latter including drinking water abstraction and recreation. Phytoplankton and LC/MS/MS toxin analyses were performed on surface water samples collected from 28 lakes. The most widespread species associated with toxin production belonged to the genera Microcystis, Planktothrix and Anabaena. Extracellular concentrations varied from non-detectable values up to 226.16 ng/mL for microcystins (sum of all variants), to 126 ng/mL for total cylindrospermopsin, and to 100 μg/g (dry weight) for anatoxin-a.The toxin concentrations in the lake waters did not always correlate with the cyanobacteria cell densities. This implies a need for control studies including toxin detection in water together with microscopic cell evaluations, in order to avoid possible toxin underestimates. 相似文献
10.
Lucilla Alfonsi Andrew J. Kavanagh Ermanno Amata Pierre Cilliers Emilia Correia Mervyn Freeman Kirsti Kauristie Ruiyuan Liu Juha-Pekka Luntama Cathryn N. Mitchell G.A. Zherebtsov 《Journal of Atmospheric and Solar》2008,70(18):2293-2308
During the International Polar Year (IPY), one area of great interest is co-coordinated, multi-instrument probing of the ionosphere at high latitudes. This region is important not only for the applications that rely upon our understanding of it, but also because it contains the footprints of processes that have their origin in the interplanetary space. Many different techniques are now available for probing the ionosphere, from radar measurements to the analysis of very low frequency (VLF) wave paths. Combining these methods provides the ability to study the ionosphere from high in the F-region to the bottom of the D-layer. Thus, coupling processes from the magnetosphere and to the neutral atmosphere can be considered. An additional dimension is through comparisons of the response of the two polar ionospheres to similar (or the same) geomagnetic activity. With more instruments available at the South Pole inter-hemispheric, studies have become easier to accomplish such that a fuller picture of the global response to Sun–Earth coupling can be painted.This paper presents a review of the current state of knowledge in ionospheric probing. It cannot provide a comprehensive guide of the work to date due to the scale of the topic. Rather it is intended to give an overview of the techniques and recent results from some of the instruments and facilities that are a part of the IPY cluster 63—Heliosphere Impact on Geospace. In this way it is hoped that the reader will gain a flavor of the recent research performed in this area and the potential for continuing collaboration and capabilities during the IPY (2007–2009). 相似文献