Influence of frozen conditions on the oxygen diffusion coefficient in unsaturated porous materials     

Nyameogo  Gretta Fabienne Toudanaba  Mbonimpa  Mamert  Bussière  Bruno  Awoh  Akué-Sylvette 《Acta Geotechnica》2020,15(2):409-421

The efficiency of soil covers used as oxygen barriers to control the generation of acid drainage from sulfidic mine wastes can be evaluated in terms of the diffusive oxygen flux reaching the underlying wastes. Oxygen diffusion has been extensively investigated over the last few decades for unsaturated porous materials that are not frozen. However, little attention has been paid to materials that are fully or partially frozen, and thus, the diffusion of oxygen through soil covers during the winter freezing period has been generally neglected. This paper presents a laboratory method developed to evaluate the effective diffusion coefficient of oxygen (D_e) in frozen, inert materials. The method is a modified version of the conventional double-chamber cell in which the temperature and unfrozen volumetric water content of the sample are measured in addition to the more commonly monitored change in oxygen concentration. Several tests were conducted on non-reactive materials: that is, a sand at multiple degrees of saturation (S_r?=?20, 30, 39, and 42%), a silt (S_r?=?47%), and a mixture of the two (S_r?=?90%). Experimental data were interpreted using the POLLUTE code. Values of D_e for frozen materials were slightly lower than those obtained at ambient laboratory temperatures. In addition to the development of an empirical method for determining D_e, a preliminary model based on the model proposed by Aachib et al. (Water Air Soil Pollut 156:163–193, 2004) was created for the prediction of D_e in frozen materials by defining the involved parameters as temperature-dependent. The results indicate that predicated values of D_e are slightly higher than experimental values, suggesting that there remains room for improvement in the model.

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Turbulent Structure of a Simplified Urban Fluid Flow Studied Through Stereoscopic Particle Image Velocimetry     

Bruno Monnier  Sepehr A. Goudarzi  Ricardo Vinuesa  Candace Wark 《Boundary-Layer Meteorology》2018,166(2):239-268

Stereoscopic particle image velocimetry was used to provide a three-dimensional characterization of the flow around a simplified urban model defined by a 5 by 7 array of blocks, forming four parallel streets, perpendicular to the incoming wind direction corresponding to a zero angle of incidence. Channeling of the flow through the array under consideration was observed, and its effect increased as the incoming wind direction, or angle of incidence (AOI), was changed from \(0^{\circ }\) to \(15^{\circ }\), \(30^{\circ }\), and \(45^{\circ }\). The flow between blocks can be divided into two regions: a region of low turbulence kinetic energy (TKE) levels close to the leeward side of the upstream block, and a high TKE area close to the downstream block. The centre of the arch vortex is located in the low TKE area, and two regions of large streamwise velocity fluctuation bound the vortex in the spanwise direction. Moreover, a region of large spanwise velocity fluctuation on the downstream block is found between the vortex legs. Our results indicate that the reorientation of the arch vortex at increasing AOI is produced by the displacement of the different TKE regions and their interaction with the shear layers on the sides and top of the upstream and downstream blocks, respectively. There is also a close connection between the turbulent structure between the blocks and the wind gusts. The correlations among gust components were also studied, and it was found that in the near-wall region of the street the correlations between the streamwise and spanwise gusts \(R_{uv}\) were dominant for all four AOI cases. At higher wall-normal positions in the array, the \(R_{uw}\) correlation decreased with increasing AOI, whereas the \(R_{uv}\) coefficient increased as AOI increased, and at \({\textit{AOI}}=45^{\circ }\) all three correlations exhibited relatively high values of around 0.4.  相似文献   

Sediments of Lake Vens (SW European Alps,France) record large-magnitude earthquake events     

Jade Petersen  Bruno Wilhelm  Marie Revel  Yann Rolland  Christian Crouzet  Fabien Arnaud  Elodie Brisset  Eric Chaumillon  Olivier Magand 《Journal of Paleolimnology》2014,51(3):343-355

We studied sediment cores from Lake Vens (2,327 m asl), in the Tinée Valley of the SW Alps, to test the paleoseismic archive potential of the lake sediments in this particularly earthquake-sensitive area. The historical earthquake catalogue shows that moderate to strong earthquakes, with intensities of IX–X, have impacted the Southern Alps during the last millennium. Sedimentological (X-ray images, grain size distribution) and geochemical (major elements and organic matter) analyses show that Lake Vens sediments consist of a terrigenous, silty material (minerals and organic matter) sourced from the watershed and diatom frustules. A combination of X-ray images, grain-size distribution, major elements and magnetic properties shows the presence of six homogenite-type deposits interbedded in the sedimentary background. These sedimentological features are ascribed to sediment reworking and grain sorting caused by earthquake-generated seiches. The presence of microfaults that cross-cut the sediment supports the hypothesis of seismic deposits in this system. A preliminary sediment chronology is provided by ²¹⁰Pb measurement and AMS ¹⁴C ages. According to the chronology, the most recent homogenite events are attributable to damaging historic earthquakes in AD 1887 (Ligure) and 1564 (Roquebillière). Hence, the Lake Vens sediment recorded large-magnitude earthquakes in the region and permits a preliminary estimate of recurrence time for such events of ~400 years.  相似文献   

A 16-ka δ18O record of lacustrine sugar biomarkers from the High Himalaya reflects Indian Summer Monsoon variability     

Michael Zech  Mario Tuthorn  Roland Zech  Frank Schlütz  Wolfgang Zech  Bruno Glaser 《Journal of Paleolimnology》2014,51(2):241-251

We investigated a late glacial–Holocene lacustrine sediment archive located at 4,050 m a.s.l. in the small carbonate-free catchment of Lake Panch Pokhari, Helambu Himal, Nepal. A δ¹⁸O sugar biomarker record was established by applying novel compound-specific δ¹⁸O analysis of plant sugar biomarkers (Zech and Glaser in Rapid Commun Mass Spectrom 23:3522–3532, 2009). This method overcomes analytical challenges such as extraction and purification faced by previous methods aimed at using δ¹⁸O of aquatic cellulose as a paleoclimate proxy. The δ¹⁸O results for sugar biomarkers arabinose, xylose and fucose agree well and reveal a pronounced trend towards lower δ¹⁸O values during the deglaciation and the onset of the Bølling/Allerød interstadial. By contrast, the period of the Younger Dryas is characterized by higher δ¹⁸O values. The early Holocene again reveals lower δ¹⁸O values. We suggest that our lacustrine δ¹⁸O record reflects coupled hydrological and thermal control. It is strongly related to changes in the oxygen isotopic composition of paleo-precipitation and resembles the δ¹⁸O records of Asian speleothems. With respect to the ‘amount effect,’ the record is interpreted as reflecting the Indian Summer Monsoon intensity. The precipitation signal is, however, amplified in our record by evaporative ¹⁸O enrichment that is controlled by the ratio of precipitation to evaporation. We suggest that our δ¹⁸O record reflects the variability of the Indian Summer Monsoon, which was strong during the Bølling/Allerød interstadial and early Holocene, but weak during the Younger Dryas stadial. This interpretation is corroborated by a pollen-based index for Lake Panch Pokhari that estimated the strength of the Indian Summer Monsoon versus the strength of the Westerlies. Millennial-scale synchronicity with the Greenland δ¹⁸O temperature records highlights the previously suggested strong teleconnections between the Asian Monsoon system and North Atlantic climate variability.  相似文献   

Unexpected records of ‘deep‐sea’ carnivorous sponges Asbestopluma hypogea in the shallow NE Atlantic shed light on new conservation issues          下载免费PDF全文

Pierre Chevaldonné  Thierry Pérez  Jean‐Michel Crouzet  Wilfried Bay‐Nouailhat  Anne Bay‐Nouailhat  Maïa Fourt  Bruno Almón  Jacinto Pérez  Ricardo Aguilar  Jean Vacelet 《Marine Ecology》2015,36(3):475-484

Marine cave communities have been a continued source of ecological surprises, among other things because of their close ecological and evolutionary ties with the deep sea. The discovery of cladorhizid sponges, the deepest occurring poriferan family, in shallow Mediterranean caves in the 1990s was one such surprise, leading to the generally accepted hypothesis that the whole family was carnivorous, an unprecedented feeding mode for sponges. The recent observation of the cave species Asbestopluma hypogea in the Mediterranean bathyal, confirmed the view that some shallow caves can occasionally shelter otherwise deep‐dwelling species. Here we present new distribution data of A. hypogea, from deep Mediterranean locations, and for the first time from Atlantic locations. Among the new Atlantic records, the most surprising ones are located in three different geographic areas (Ria de Arousa, Groix Island and Cherbourg) of the NW European coasts, from the Iberian Peninsula to the English Channel, where A. hypogea reaches SCUBA depths (5–50 m), while not sheltered in marine caves. The carnivorous sponge however reaches its shallowest occurrence (5 m), in a small cave at Groix Island. The ecological significance of these discoveries, particularly the very patchy distribution and peculiar dynamics, are noteworthy, and the shallow occurrence of A. hypogea, together with other deep‐water or uncommon species, constitute unique assemblages that must be considered in conservation plans.  相似文献   

PAOLO: A Polarimeter Add‐On for the LRS Optics at a Nasmyth focus of the TNG     

S. Covino  E. Molinari  P. Bruno  M. Cecconi  P. Conconi  P. D'Avanzo  L. di Fabrizio  D. Fugazza  M. Giarrusso  E. Giro  F. Leone  V. Lorenzi  S. Scuderi 《Astronomische Nachrichten》2014,335(2):117-123

We describe a new polarimetric facility available at the Istituto Nazionale di AstroFisica / Telescopio Nazionale Galileo at La Palma, Canary islands. This facility, PAOLO (Polarimetric Add‐On for the LRS Optics), is located at a Nasmyth focus of an alt‐az telescope and requires a specific modeling in order to remove the time‐ and pointing position‐dependent instrumental polarization. We also describe the opto‐mechanical structure of the instrument and its calibration and present early examples of applications. (© 2014 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)  相似文献   

The Herschel-PACS photometer calibration     

Zoltan Balog  Thomas Müller  Markus Nielbock  Bruno Altieri  Ulrich Klaas  Joris Blommaert  Hendrik Linz  Dieter Lutz  Attila Moór  Nicolas Billot  Marc Sauvage  Koryo Okumura 《Experimental Astronomy》2014,37(2):129-160

This paper provides an overview of the PACS photometer flux calibration concept, in particular for the principal observation mode, the scan map. The absolute flux calibration is tied to the photospheric models of five fiducial stellar standards (α Boo, α Cet, α Tau, β And, γ Dra). The data processing steps to arrive at a consistent and homogeneous calibration are outlined. In the current state the relative photometric accuracy is ～2 % in all bands. Starting from the present calibration status, the characterization and correction for instrumental effects affecting the relative calibration accuracy is described and an outlook for the final achievable calibration numbers is given. After including all the correction for the instrumental effects, the relative photometric calibration accuracy (repeatability) will be as good as 0.5 % in the blue and green band and 2 % in the red band. This excellent calibration starts to reveal possible inconsistencies between the models of the K-type and the M-type stellar calibrators. The absolute calibration accuracy is therefore mainly limited by the 5 % uncertainty of the celestial standard models in all three bands. The PACS bolometer response was extremely stable over the entire Herschel mission and a single, time-independent response calibration file is sufficient for the processing and calibration of the science observations. The dedicated measurements of the internal calibration sources were needed only to characterize secondary effects. No aging effects of the bolometer or the filters have been found. Also, we found no signs of filter leaks. The PACS photometric system is very well characterized with a constant energy spectrum νF _ν = λF _λ = const as a reference. Colour corrections for a wide range of sources SEDs are determined and tabulated.  相似文献   

The pointing system of the Herschel space observatory     

Miguel Sánchez-Portal  Anthony Marston  Bruno Altieri  Hervé Aussel  Helmut Feuchtgruber  Ulrich Klaas  Hendrik Linz  Dieter Lutz  Bruno Merín  Thomas Müller  Markus Nielbock  Marc Oort  Göran Pilbratt  Micha Schmidt  Craig Stephenson  Mark Tuttlebee 《Experimental Astronomy》2014,37(2):453-479

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Analytical study of a four-body configuration in exoplanet scenarios     

P. P. Campo  J. A. Docobo 《Astronomy Letters》2014,40(11):737-748

Lately, more and more exoplanets are being discovered and the number is expected to increase thanks to the excellent programs dedicated to this task. Thus it is important to study the dynamical behavior of planetary systems. Among all the problems that may be considered, we are interested in four-body planetary systems. In this article, we first examine the possible cases in four-body planetary systems including satellites, in both single and multiple stars. Step decomposition is a methodology explained by A. Abad and J.A. Docobo to deal with n-body problems with hierarchy. The use of this technique permits the reduction of the different cases to five configurations. The analytical integration of one of these cases, a double star with a planet and a satellite orbiting one of the components of the stellar system, is the objective. First the Hamiltonian of the problem is given and then we formulate it in terms of three small parameters which can be reduced to two in this case. After that, using Hori’s biparametric method, the dependence on the angular variables is removed, thereby allowing the integration of the problem.  相似文献   

Experimental determination of coexisting iron–titanium oxides in the systems FeTiAlO, FeTiAlMgO, FeTiAlMnO, and FeTiAlMgMnO at 800 and 900°C, 1–4 kbar, and relatively high oxygen fugacity     

Bernard W. Evans  Bruno Scaillet  Scott M. Kuehner 《Contributions to Mineralogy and Petrology》2006,152(2):149-167

A synthetic, low-melting rhyolite composition containing TiO₂ and iron oxide, with further separate additions of MgO, MnO, and MgO + MnO, was used in hydrothermal experiments to crystallize Ilm-Hem and Usp-Mt solid solutions at 800 and 900°C under redox conditions slightly below nickel–nickel oxide (NNO) to $\approx 3\,\log_{10} f_{{{\text{O}}_{2}}}A synthetic, low-melting rhyolite composition containing TiO₂ and iron oxide, with further separate additions of MgO, MnO, and MgO + MnO, was used in hydrothermal experiments to crystallize Ilm-Hem and Usp-Mt solid solutions at 800 and 900°C under redox conditions slightly below nickel–nickel oxide (NNO) to units above the NNO oxygen buffer. These experiments provide calibration of the FeTi-oxide thermometer + oxygen barometer at conditions of temperature and oxygen fugacity poorly covered by previous equilibrium experiments. Isotherms for our data in Roozeboom diagrams of projected %usp vs. %ilm show a change in slope at ≈ 60% ilm, consistent with the second-order transition from FeTi-ordered Ilm to FeTi-disordered Ilm-Hem. This feature of the system accounts for some, but not all, of the differences from earlier thermodynamic calibrations of the thermobarometer. In rhyolite containing 1.0 wt.% MgO, 0.8 wt.% MnO, or MgO + MnO, Usp-Mt crystallized with up to 14% of aluminate components, and Ilm-Hem crystallized with up to 13% geikielite component and 17% pyrophanite component. Relative to the FeTiAlO system, these components displace the ferrite components in Usp-Mt, and the hematite component in Ilm-Hem. As a result, projected contents of ulv?spinel and ilmenite are increased. These changes are attributed to increased non-ideality along joins from end-member hematite and magnetite to their respective Mg- and Mn-bearing titanate and aluminate end-members. The compositional shifts are most pronounced in Ilm-Hem in the range Ilm_50–80, a solvus region where the chemical potentials of the hematite and ilmenite components are nearly independent of composition. The solvus gap widens with addition of Mg and even further with Mn. The Bacon–Hirschmann correlation of Mg/Mn in Usp-Mt and coexisting Ilm-Hem is displaced toward increasing Mg/Mn in ilmenite with passage from ordered ilmenite to disordered hematite. Orthopyroxene and biotite crystallized in experiments with added MgO and MgO + MnO; their X _Fe varies with and T consistent with equilibria among ferrosilite, annite, and ferrite components, and the chemical potentials of SiO₂ and orthoclase in the liquid. Experimental equilibration rates increased in the order: Opx < Bt < Ilm-Hem < Usp-Mag.  相似文献