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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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   

Influence de l'hydrodynamique sur l'intrusion saline en aquifère karstique côtier     

Bruno Arfib  Thomas Cavalera  Eric Gilli 《Comptes Rendus Geoscience》2006,338(11):757-767

A new method of interpretation of the $Q\text{–}C$ hysteresis (discharge–salinity) during high water is proposed using the data recorded on coastal brackish karstic springs with salinity inversely proportional to the discharge. The method, based on the $Q_{\mathrm{mer}}\text{–}{C}_{\mathrm{T}}$ (seawater discharge–salinity) hysteresis, identifies the effect of the hydrodynamic changes on the flow and transport. Three phenomena are characterized: the emptying of the karstic conduit, the dilution by freshwater and the control of the seawater intrusion in the conduit by the hydraulic head variations. To cite this article: B. Arfib et al., C. R. Geoscience 338 (2006).  相似文献   

Dual polarization radar Lagrangian parameters: a statistics-based probabilistic nowcasting model     

Bruno Lisbôa Medina  Luiz A. T. Machado 《Natural Hazards》2017,89(2):705-721

The aim of this study is to present a statistics-based Lagrangian nowcasting model to predict intense rainfall convective events based on dual polarization radar parameters. The data employed in this study are from X-band radar collected during the CHUVA-Vale campaign from November 2011 to March 2012 in southeast Brazil. The model was designed to catch the important physical characteristics of storms, such as the presence of supercooled water above 0 °C isotherm, vertical ice crystals in high levels, graupel development in the mixed-phase layer and storm vertical growth, using polarimetric radar in the mixed-phase layer. These parameters are based on different polarimetric radar quantities in the mixed phase, such as negative differential reflectivity (Z _DR) and specific differential phase (K _DP), low correlation coefficient (ρ _hv) and high reflectivity Z _h values. Storms were tracked to allow the Lagrangian temporal derivation. The model is based on the estimation of the proportion of radar echo volume in the mixed phase that is likely to be associated with intense storm hydrometeors. Thirteen parameters are used in this probabilistic nowcasting model, which is able to predict the potential for future storm development. The model distinguishes two different categories of storms, intense and non-intense rain cell events by determining how many parameters reach the “intense” storm threshold.  相似文献   

A geotechnical perspective of raw earth building     

Domenico Gallipoli  Agostino Walter Bruno  Céline Perlot  Joao Mendes 《Acta Geotechnica》2017,12(3):463-478

Much research has been devoted over the past 30 years to the development of construction materials that can lower the environmental and economic costs of buildings over their entire life by reducing embodied energy, minimizing air conditioning needs and cutting down demolition waste. In this respect, raw earth is an attractive material because it is natural and largely available. In its simplest form, this material consists of a compacted mixture of soil and water which is put in place with the least possible transformation. Raw earth construction has been practised in ancient times but has only recently been rediscovered thanks to modern technology, which has improved fabrication efficiency. If properly manufactured, raw earth exhibits comparable mechanical characteristics and better hygro-thermal properties than concrete or fired bricks. After a brief historical overview, we discuss the advantages of raw earth construction in terms of environmental impact, energy consumption and indoor air quality together with the main obstacles to its wider dissemination. We also review the hydro-thermo-mechanical behaviour of raw earth in the context of the recent geotechnical literature, by examining the dependency of key parameters such as strength, stiffness and moisture retention on: (a) material variables (e.g. particle size and mineralogy), (b) manufacturing variables (e.g. density and stabilization) and (c) environmental variables (e.g. pore suction, ambient humidity and temperature).  相似文献   

Influence of wave climate on architecture and landscape characteristics of Posidonia oceanica meadows          下载免费PDF全文

Matthew Pace  Joseph A. Borg  Charles Galdies  Amit Malhotra 《Marine Ecology》2017,38(1)

Seagrass meadow characteristics, including distribution, shape, size and within‐meadow architectural features, may be influenced by various physical factors, including hydrodynamic forces. However, such influences have hardly been assessed for meadows of the ecologically important and endemic Mediterranean seagrass Posidonia oceanica. The distribution of P. oceanica meadows at five sites in the Maltese Islands was mapped to a depth of c. 15 m using a combination of aerial photography and SCUBA diving surveys. Estimates of wind‐generated wave energy and energy attenuated by depth were computed using the hydrodynamic model WEMo (Wave Exposure Model). Metrics for P. oceanica landscape features were calculated using FRAGSTATS for replicate 2500 m² subsamples taken from the seagrass habitat maps in order to explore the influence of wave dynamics at the landscape scale. Data on within‐meadow architectural attributes were collected from five sites and analysed for relationships with wave energy. The results indicate that landscape and architectural features of P. oceanica meadows located within the 6–11 m depth range are significantly influenced by wave climate. Posidonia oceanica meadows tend to be patchier and have low overall cover, more complex patch shapes and reduced within‐patch architectural complexity along a wave exposure gradient from low to high energy. The findings from the present study provide new insight into the influence of hydrodynamic factors on the natural dynamism of P. oceanica meadow landscape and architecture, which has implications for the conservation and management of the habitat.  相似文献