Porosity and mineralogy evolution during the decay process involved in the Chellah monument stones     

Abderrahim Samaouali  Larbi Laânab  Mohamed Boukalouch  Yves Geraud 《Environmental Earth Sciences》2010,59(6):1171-1181

The objective of this work is to study the decay process involved in the historical Roman Chellah located in the Rabat city (Morocco). This monument is made up of porous calcarenite stone. Several samples, taken from altered and unaltered blocks, were analyzed by the water saturation, the mercury intrusion porosimetry techniques and using the scanning electron microscopy coupled to energy dispersive X-ray spectrometer (SEM–EDX). To perform a reliable chemical analysis, some samples were also analyzed by inductively coupled plasma-atomic emission spectroscopy (ICP-AES). The mercury porosimetry results show a bimodal porous network for this porous material, the deterioration process of these stones involved an increase in porous volume of about 2%. The lowest porosity observed in the unaltered block is connected to the presence of sparitic cement which causes a partial inter-granular porosity clogging. The highest porosity of the deteriorated block without crust is due to the increase in inter-granular space. SEM photographs of the unaltered sample show the presence of the porous primary grains, of ovoid forms and millimeter-length sizes, and of the secondary grains, of rhombohedric forms and micro size. Porosity is essentially located between the primary grains and can be completely clogged by secondary precipitations. Various forms of deterioration are observed on the altered samples such as the dissolution of the secondary grains edges, wells of dissolution and also the presence of argillaceous residues on the surface. This last was also detected by the ICP-AES and EDX analysis which show an increase of the silicon and aluminum contents toward the surface.  相似文献   

Model-data comparisons for Titan's nightside ionosphere     

T.E. Cravens  I.P. Robertson  R.V. Yelle  A.J. Coates  K. Agren  V. De La Haye  F.M. Neubauer 《Icarus》2009,199(1):174-188

Solar and X-ray radiation and energetic plasma from Saturn's magnetosphere interact with the upper atmosphere producing an ionosphere at Titan. The highly coupled ionosphere and upper atmosphere system mediates the interaction between Titan and the external environment. A model of Titan's nightside ionosphere will be described and the results compared with data from the Ion and Neutral Mass Spectrometer (INMS) and the Langmuir probe (LP) part of the Radio and Plasma Wave (RPWS) experiment for the T5 and T21 nightside encounters of the Cassini Orbiter with Titan. Electron impact ionization associated with the precipitation of magnetospheric electrons into the upper atmosphere is assumed to be the source of the nightside ionosphere, at least for altitudes above 1000 km. Magnetospheric electron fluxes measured by the Cassini electron spectrometer (CAPS ELS) are used as an input for the model. The model is used to interpret the observed composition and structure of the T5 and T21 ionospheres. The densities of many ion species (e.g., CH⁺₅ and C₂H⁺₅) measured during T5 exhibit temporal and/or spatial variations apparently associated with variations in the fluxes of energetic electrons that precipitate into the atmosphere from Saturn's magnetosphere.  相似文献   

Multiple flaring activity in the supergiant fast X-ray transient IGR J08408−4503 observed with Swift     

P. Romano  L. Sidoli  G. Cusumano  P. A. Evans  L. Ducci  H. A. Krimm  S. Vercellone  K. L. Page  A. P. Beardmore  D. N. Burrows  J. A. Kennea  N. Gehrels  V. La Parola  V. Mangano 《Monthly notices of the Royal Astronomical Society》2009,392(1):45-51

IGR  J08408−4503  is a supergiant fast X–ray transient discovered in 2006 with a confirmed association with a O8.5Ib(f) supergiant star, HD 74194. We report on the analysis of two outbursts caught by Swift /Burst Alert Telescope (BAT) on 2006 October 4 and 2008 July 5, and followed up at softer energies with Swift /X-ray Telescope (XRT). The 2008 XRT light curve shows a multiple-peaked structure with an initial bright flare that reached a flux of  ∼10⁻⁹ erg cm⁻² s⁻¹  (2–10 keV), followed by two equally bright flares within 75 ks. The spectral characteristics of the flares differ dramatically, with most of the difference, as derived via time-resolved spectroscopy, being due to absorbing column variations. We observe a gradual decrease in the N _H, derived with a fit using absorbed power-law model, as time passes. We interpret these N _H variations as due to an ionization effect produced by the first flare, resulting in a significant decrease in the measured column density towards the source. The durations of the flares as well as the times of the outbursts suggest that the orbital period is ∼35 d, if the flaring activity is interpreted within the framework of the Sidoli et al. model with the outbursts triggered by the neutron star passage inside an equatorial wind inclined with respect to the orbital plane.  相似文献   

The Fountain Hills unique CB chondrite: Insights into thermal processes on the CB parent body     

Dante S. LAURETTA  Julia S. GOREVA  Dolores H. HILL  Marvin KILLGORE  Alyssa R. La BLUE  Andrew CAMPBELL  R. C. GREENWOOD  A. B. VERCHOVSKY  Ian A. FRANCHI 《Meteoritics & planetary science》2009,44(6):823-838

Abstract— We report the results of an extensive study of the Fountain Hills chondritic meteorite. This meteorite is closely related to the CB_a class. Mineral compositions and O‐isotopic ratios are indistinguishable from other members of this group. However, many features of Fountain Hills are distinct from the other CB chondrites. Fountain Hills contains 23 volume percent metal, significantly lower than other members of this class. In addition, Fountain Hills contains porphyritic chondrules, which are extremely rare in other CB_a chondrites. Fountain Hills does not appear to have experienced the extensive shock seen in other CB chondrites. The chondrule textures and lack of fine‐grained matrix suggests that Fountain Hills formed in a dust‐poor region of the early solar system by melting of solid precursors. Refractory siderophiles and lithophile elements are present in near‐CI abundances (within a factor of two, related to the enhancement of metal). Moderately volatile and highly volatile elements are significantly depleted in Fountain Hills. The abundances of refractory siderophile trace elements in metal grains are consistent with condensation from a gas that is reduced relative to solar composition and at relatively high pressures (10^?3bars). Fountain Hills experienced significant thermal metamorphism on its parent asteroid. Combining results from the chemical gradients in an isolated spinel grain with olivine‐spinel geothermometry suggests a peak temperature of metamorphism between 535 °C and 878 °C, similar to type‐4 ordinary chondrites.  相似文献   

On the origin of the scatter around the Fundamental Plane: correlations with stellar population parameters     

A. Gargiulo  C. P. Haines  P. Merluzzi  R. J. Smith  F. La Barbera  G. Busarello  J. R. Lucey  A. Mercurio  M. Capaccioli 《Monthly notices of the Royal Astronomical Society》2009,397(1):75-89

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Monitoring supergiant fast X-ray transients with Swift: results from the first year     

P. Romano  L. Sidoli  G. Cusumano  V. La Parola  S. Vercellone  C. Pagani  L. Ducci  V. Mangano  J. Cummings  H. A. Krimm  C. Guidorzi  J. A. Kennea  E. A. Hoversten  D. N. Burrows  N. Gehrels 《Monthly notices of the Royal Astronomical Society》2009,399(4):2021-2032

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The spectrum and position of solar noise storms at decameter wavelengths     

Jérôme De La Noë  Tomas E. Gergely 《Solar physics》1977,55(1):195-209

Decametric storm radiation during the period July–August 1970 has been observed simultaneously with a high sensitivity spectrograph at Arecibo Observatory and with the log-periodic, swept-frequency array of the Clark Lake Radio Observatory. The observations complement each other; different types of fine structure emissions can be easily identified on the spectrograph records and their position can be determined from the swept-frequency recordings. We study the relative positions of the different emissions which have been observed during the storms. Four distinct sources appeared to be present. The continuum emission, the type I bursts and the flare-related type III's were all emitted at different locations. The storm type III bursts, type IIIb's and drift pairs overlapped in position, but appeared at different locations than the previously mentioned sources.On leave of absence from Instituto Argentino de Radioastronomia, Argentina.  相似文献   

Umbral dots: A case of penetrative convection between sunspot fragments     

J. I. García De La Rosa 《Solar physics》1987,112(1):49-58

A study of the observations made on the development and, in some cases, even the decay of 15 large active regions is presented. It is shown that the mature spots result from the subphotospherically controlled attraction of several large fragments of 1–2 × 10²¹ Mx, which are themselves made of smaller elements. The fragments are more stable structures than the spots they constitute; and usually survive after the spot decay. In the process of coalescence of fragments to form the spot, the fusion is never complete and properly exposed photographs reveal light bridges or saddle-like distributions of umbral dots in the interstices between fragments. These are also the regions along which the break up of the spot occurs. For us, these observations fit within the expectations of the penetrative convection mechanism for umbral dots proposed by Parker (1979b).  相似文献   

Sunspot populations and their relation with the solar cycle     

J. I. García De La Rosa 《Solar physics》1981,74(1):117-123

The joint consideration of theoretical and observational arguments is used to conclude that two different spot populations co-exist in the Sun.Proceedings of the 14th ESLAB Symposium on Physics of Solar Variations, 16–19 September 1980, Scheveningen, The Netherlands.  相似文献   

基于空间数据库的多媒体图形查询信息系统研究——以苏州河环境综合整治为例   总被引：5，自引：2，他引：5  

张立峰  许有鹏  孙亚梅  王腊春  马劲松 《地理研究》2002,21(3):365-372

本文介绍作者自行开发的GIS软件系统———基于空间数据库的多媒体图形查询信息系统的内容、结构和功能 ,以及在环境规划管理方面的应用。阐明了系统可满足决策管理层和公共信息发布层等不同层次的应用需求 ,对环境工程项目的规划管理可作为示范和借鉴。说明本系统除具有一般GIS系统所具有的功能外 ,还把现代多媒体技术和GIS空间数据库技术结合起来 ,实现了在空间数据基础上的多媒体信息查询 ,丰富了GIS中属性数据查询的内容 ,提高了地图的可视性。详细介绍了一种地理信息系统的空间分析方法———包含分析的算法和在本系统中的具体应用———按多边形区域进行空间相关性关系查询。  相似文献