Geochemical study of products associated with spontaneous oxidation of coal in the Cerro Pelado Formation,Venezuela     

M. Martínez  G. Márquez  F.J. Alejandre  J.J. Del Río  A. Hurtado 《Journal of South American Earth Sciences》2009,27(2-3):211-218

The aim of this research work is a geochemical, mineralogical, and textural characterization of spontaneously smouldered coal-derived products in northwestern Venezuela (Cerro Pelado Formation, some 10 km from Pedregal city). Several solid samples were collected from this formation, six of unweathering coal, an other six of resulting unmelted rocks forming on a surface coal bed, and the last four of mineralizations found accumulating around gas vents. The fresh coal and the unmelted material were analysed by scanning electron microscopy, X-ray diffraction, and proximate techniques. Products such as magnetite and chabazite-K were identified in the alteration rocks. Likewise, both materials were also studied in order to determine the mobilization of 17 elements into the environment; such elements were analysed through inductively coupled plasma atomic emission spectroscopy on extracts obtained by a sequential extraction method: each sample was firstly extracted with MilliQ water and then the resultant residue was washed. This and the subsequently resulting residues are extracted according to the mentioned procedure by using, respectively, ammonium acetate, chlorhydric acid, peroxide and chlorhydric acid, nitric acid and fluorhydric acid, and nitric acid. The studied elements are classified as highly mobile (Na, Ni, ...), nearly immobile (Ti, P) and partially mobile (Mg, Fe, K, ...). In regards to mineralizations around fumaroles associated with smoldering coal seams, Fourier-transform infrared spectroscopy and X-ray diffraction analyses have revealed the presence of salammoniac, mascagnite and other solid combustion compounds formed by reaction of gas emitted from coal oxidation, in addition to previously non-reported sulfur-rich by-products associated with gas fissures, particularly ammonium thiosulfate, a phase first obtained only synthetically in the laboratory. Another objective of the research was to collect and analyse gases escaping from surficial vents. Relatively high concentrations of several aromatic compounds were detected in the gas collected at the studied coal outcrop, as well as aliphatic hydrocarbons including ethane, propane, butanes, among others. High contents of carbon monoxide, methane and carbon dioxide were also measured for gas samples.  相似文献   

Erratum to: The Cusp/Core problem: supernovae feedback versus the baryonic clumps and dynamical friction model     

A. Del Popolo  F. Pace 《Astrophysics and Space Science》2016,361(7):225

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On the dark matter haloes inner structure and galaxy morphology     

A. Del Popolo 《Astrophysics and Space Science》2016,361(7):222

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Beach tar accumulation, transport mechanisms, and sources of variability at Coal Oil Point, California     

Del Sontro TS  Leifer I  Luyendyk BP  Broitman BR 《Marine pollution bulletin》2007,54(9):1461-1471

A new field method for tar quantification was used at Coal Oil Point (COP), California to study the mechanisms transporting oil/tar from the nearby COP natural marine hydrocarbon seep field. This method segregates tar pieces into six size classes and assigns them an average mass based on laboratory or direct field measurements. Tar accumulation on the 19,927m(2) survey area was well resolved spatially by recording tar mass along twelve transects segmented into 4-m(2) blocks and then integrating over the survey area. A seasonal trend was apparent in total tar in which summer accumulations were an order of magnitude higher than winter accumulations. Based on multiple regression analyses between environmental data and tar accumulation, 34% of tar variability is explained by a combination of onshore advection via wind and low swell height inhibiting slick dispersion.  相似文献   

Saturn eddy momentum fluxes and convection: First estimates from Cassini images     

Anthony D. Del Genio  John M. Barbara  Andrew P. Ingersoll  Ashwin R. Vasavada  Carolyn C. Porco 《Icarus》2007,189(2):479-492

We apply an automated cloud feature tracking algorithm to estimate eddy momentum fluxes in Saturn's southern hemisphere from Cassini Imaging Science Subsystem near-infrared continuum image sequences. Voyager Saturn manually tracked images had suggested no conversion of eddy to mean flow kinetic energy, but this was based on a small sample of <1000 wind vectors. The automated procedure we use for the Cassini data produces an order of magnitude more usable wind vectors with relatively unbiased sampling. Automated tracking is successful in and around the westward jet latitudes on Saturn but not in the vicinity of most eastward jets, where the linearity and non-discrete nature of cloud features produces ambiguous results. For the regions we are able to track, we find peak eddy fluxes and a clear positive correlation between eddy momentum fluxes and meridional shear of the mean zonal wind, implying that eddies supply momentum to eastward jets and remove momentum from westward jets at a rate . The behavior we observe is similar to that seen on Jupiter, though with smaller eddy-mean kinetic energy conversion rates per unit mass of atmosphere (). We also use the appearance and rapid evolution of small bright features at continuum wavelengths, in combination with evidence from weak methane band images where possible, to diagnose the occurrence of moist convective storms on Saturn. Areal expansion rates imply updraft speeds of over the convective anvil cloud area. As on Jupiter, convection preferentially occurs in cyclonic shear regions on Saturn, but unlike Jupiter, convection is also observed in eastward jet regions. With one possible exception, the large eddy fluxes seen in the cyclonic shear latitudes do not seem to be associated with convective events.  相似文献   

Profiles of dark matter haloes at high redshift     

A. Del Popolo 《Monthly notices of the Royal Astronomical Society》2001,325(3):1190-1196

I study the evolution of halo density profiles as a function of time in the SCDM and ΛCDM cosmologies. Following Del Popolo, I calculate the concentration parameter c = r _v / a and study its time evolution. For a given halo mass, I find that c ( z ) ∝ 1/(1+ z ) in both the ΛCDM and SCDM cosmology, in agreement with the analytic model of Bullock et al. and N -body simulations. In both models, a ( z ) is roughly constant. The present model predicts a stronger evolution of c ( z ) with respect to the Navarro, Frenk & White model. Finally I show some consequences of the results on galaxy modelling.  相似文献   

Kinematic Subsystems of the Ionized Gas in the Central Region of NGC 1068 Inferred from the [O III] λλ 4959, 5007 and [S III] λ 9069 Emission Lines     

E. Mediavilla  S. Arribas  B. Garcia-Lorenzo  C. Del Burgo 《Astrophysics and Space Science》1997,248(1-2):151-157

We discuss the multi-Gaussian decomposition of the [O III] λλ 4959,5007 emission line profiles from 2-D spectroscopy. We found that a model based on five main gaseous components can reproduce the observed line profiles consistently. The morphology of the intensity maps of some of these gaseous subsystems seems bipolar. This is in better agreement with current ideas about the alignment of the ionization in AGNs than the relatively amorphous morphology seen in filter images. The centre of the inter-pole region is sited ~ 2″ NE of the optical nucleus, close to the origin of the strong outflow of ionized gas recently reported (Arribas et al. 1996). This suggests that the putative hidden nucleus of NGC 1068 could be sited near to this point.  相似文献   

Discrete mechanics: Some remarks     

Ettore Perozzi 《Celestial Mechanics and Dynamical Astronomy》1983,30(3):249-261

A detailed investigation about Discrete Mechanics (a numerical method developed by D. Greenspan and R. A. LaBudde) in Celestial Mechanics applications has been carried out. The method shows a remarkable precession of the argument of pericentre, whose value depends mainly on the time step scaling used and on the length of the integration step. It has been found that this behaviour is due to the structure of Discrete Mechanics and that the precession, taken as a function of the length of the integration step, follows with good agreement an inverse square law. The existence of this relationship allowed the development of a modified version of the method: its consistence with respect to the original one is discussed both from an analytical and a computational point of view. Furthermore the Modified Discrete Mechanics allowed the extension of the method to the case of the potential due to an oblate spheroid.  相似文献   

Application of Spectroscopic Diagnostics to Early Observations with the SOHO Coronal Diagnostic Spectrometer     

Mason  H. E.  Young  P. R.  Pike  C. D.  Harrison  R. A.  Fludra  A.  Bromage  B. J. I.  Del Zanna  G. 《Solar physics》1997,170(1):143-161

The Coronal Diagnostic Spectrometer (CDS) has as a scientific goal the determination of the physical parameters of the solar plasma using spectroscopic diagnostic techniques. Absolute intensities and intensity ratios of the EUV spectral emission lines can be used to obtain information on the electron density and temperature structure, element abundances, and dynamic nature of different features in the solar atmosphere. To ensure that these techniques are accurate it is necessary to interface solar analysis programs with the best available atomic data calculations. Progress is reported on this work in relation to CDS observations.  相似文献   

Characteristics of the low energy seismicity of central Apulia (southern Italy) and hazard implications     

V.?Del?GaudioEmail author  P.?Pierri  G.?Calcagnile  N.?Venisti 《Journal of Seismology》2005,9(1):39-59

The central part of the Apulia region, in southern Italy, has been generally considered practically free from significant level of seismicity, but historical documentation, geological indicators and recent instrumental observations suggest that the activity of local minor tectonic structures could have been masked (and partly also induced) by that of major seismogenic structures located in the neighbouring regions. A revision of the central Apulia seismicity characteristics was conducted considering its space and time distribution, energy release rate and focal mechanisms, in view of possible hazard implications. To better constrain the seismicity rates inferable from the set of available historical data, special attention was paid to the declustering of a catalogue of low energy events (magnitude < 3.5) instrumentally detected in about 20 years: a new declustering procedure, useful for cases like to the one at hand, was purposely devised taking into account the peculiarity of local seismicity characteristics and the limitations of the available database. The results obtained by combining instrumental and historical data show that this area is affected by a rather sporadic seismicity, likely associated to a general tensional regime and possibly stimulated by the interaction with Apenninic and northern Apulia seismogenic activity. Even though less energetic, the local seismicity contributes to increase the moderately damaging shaking probability due to the activity of seismic sources located in the near areas, so to justify the adoption of at least a minimum level of caution in relation to the local definition of seismic protection measures.  相似文献