The role of aridification in constraining the elevation range of Holocene solifluction processes and associated landforms in the periglacial belt of the Sierra Nevada (southern Spain)     

Marc Oliva  Antonio Gómez Ortiz 《地球表面变化过程与地形》2011,36(10):1279-1291

Climate variability during the Mid‐Late Holocene has influenced the activity of geomorphic processes in the current periglacial belt of the Sierra Nevada. We studied two types of sedimentary records that reveal a synchronous timing for slope instability in this high semi‐arid massif: solifluction landforms and mountain lake sediments. Lithological and sedimentological properties of both records have recorded numerous cycles of different magnitude of slope processes in the massif. Solifluction deposits record seven phases of solifluction activity and soil development during the last 7 ka bp and lake sediments show evidence of eight periods with increased geomorphic activity in the catchments over the last 6 ka bp . Although present‐day climate conditions do not promote active solifluction processes in the Sierra Nevada, colder and wetter periods during the Holocene triggered solifluction and transported coarse‐grained sediments into the lakes. By contrast, warm phases favoured soil formation and spread an incipient vegetation cover over the headwaters of the highest valleys, diminishing the grain size of the particles reaching the lakes. Lake sediments record an aridification trend in the massif intensifying since 4·2 ka bp that has conditioned solifluction activity to shift gradually to higher elevations. During major cooler phases such as the Little Ice Age active solifluction was recorded back down to 2500 m altitude. Copyright © 2010 John Wiley & Sons, Ltd.  相似文献   

The visible and near infrared module of EChO     

A. Adriani  G. Bellucci  L. Gambicorti  M. Focardi  E. Oliva  M. Farina  A. M. Di Giorgio  F. Santoli  E. Pace  G. Piccioni  G. Filacchione  M. Pancrazzi  A. Tozzi  G. Micela 《Experimental Astronomy》2015,40(2-3):753-769

The Visible and Near Infrared (VNIR) is one of the modules of EChO, the Exoplanets Characterization Observatory proposed to ESA for an M-class mission. EChO is aimed to observe planets while transiting by their suns. Then the instrument had to be designed to assure a high efficiency over the whole spectral range. In fact, it has to be able to observe stars with an apparent magnitude M_v?=?9–12 and to see contrasts of the order of 10^?4–10^?5 necessary to reveal the characteristics of the atmospheres of the exoplanets under investigation. VNIR is a spectrometer in a cross-dispersed configuration, covering the 0.4–2.5 μm spectral range with a resolving power of about 330 and a field of view of 2 arcsec. It is functionally split into two channels respectively working in the 0.4–1.0 μm and 1.0–2.5 μm spectral ranges. Such a solution is imposed by the fact the light at short wavelengths has to be shared with the EChO Fine Guiding System (FGS) devoted to the pointing of the stars under observation. The spectrometer makes use of a HgCdTe detector of 512 by 512 pixels, 18 μm pitch and working at a temperature of 45 K as the entire VNIR optical bench. The instrument has been interfaced to the telescope optics by two optical fibers, one per channel, to assure an easier coupling and an easier colocation of the instrument inside the EChO optical bench.  相似文献   

The Effect of Human Exclusion on the Population Structure of Key-Hole Limpets Fissurella crassa and F. limbata on the Coast of Central Chile     

Doris  Oliva Juan Carlos  Castilla 《Marine Ecology》1986,7(3):201-217

Abstract. We describe the basic ecology of two key-hole limpets, Fissurella crassa and Fissurella limbata , which are heavily harvested by coastal shellfishermen (mariscadores) at the rocky intertidal of central Chile. The ecological role of human predation on these species was assessed. Anthropic exclusion from a stretch of the rocky intertidal at Las Cruces (non-harvested area) for about two and a half years resulted in changes of the densities and size distributions of these fissurelid species as compared to populations in control zones (harvested area). Differential human predation generates, on key-hole limpets, responses of different intensities related to the accessibility of man to the mesohabitats (sheltered platforms, exposed platforms and vertical walls) and fringes of the intertidal (mid-low intertidal and Lessonia nigrescens fringe). Thus, size distributions and mean densities of both fissurelids differ widely between the harvested and non-harvested areas on both platform habitats but not on vertical walls. In the mid-low intertidal fringe, differences are greater than in the less accessible L. nigrescens intertidal fringe. Moreover, we discuss the way in which other species, directly harvested by mariscadores (i. e., the mollusc Concholepas concholepas) can affect the keyhole limpet populations of central Chile rocky shores. Finally, we highlight the ecological role of these limpets on the dynamics of intertidal ecosystems and how they can modify community landscape.  相似文献   

Instruments, Detectors and the Future of Astronomy with Large Ground Based Telescopes     

Douglas A. Simons  Paola Amico  Dietrich Baade  Sam Barden  Randall Campbell  Gert Finger  Kirk Gilmore  Roland Gredel  Paul Hickson  Steve Howell  Norbert Hubin  Andreas Kaufer  Ralf Kohley  Philip MacQueen  Sergej Markelov  Mike Merrill  Satoshi Miyazaki  Hidehiko Nakaya  Darragh O'Donoghue  Tino Oliva  Andrea Richichi  Derrick Salmon  Ricardo Schmidt  Hongjun Su  Simon Tulloch  Maria Luisa García Vargas  R. Mark Wagner  Olivier Wiecha  Binxun Ye 《Experimental Astronomy》2005,19(1-3):15-44

Results of a survey of instrumentation and detector systems, either currently deployed or planned for use at telescopes larger than 3.5 m, in ground based observatories world-wide, are presented. This survey revealed a number of instrumentation design trends at optical, near, and mid-infrared wavelengths. Some of the most prominent trends include the development of vastly larger optical detector systems (> 10⁹ pixels) than anything built to date, and the frequent use of mosaics of near-infrared detectors – something that was quite rare only a decade ago in astronomy. Some future science applications for detectors are then explored, in an attempt to build a bridge between current detectors and what will be needed to support the research ambitions of astronomers in the future.  相似文献   

Rivers, chemical weathering and Earth's climate   总被引：4，自引：0，他引：4  

Bernard Dupr  Cline Dessert  Priscia Oliva  Yves Goddris  Jrme Viers  Louis Franois  Romain Millot  Jrme Gaillardet 《Comptes Rendus Geoscience》2003,335(16):1141-1160

We detail the results of recent studies describing and quantifying the large-scale chemical weathering of the main types of continental silicate rocks: granites and basalts. These studies aim at establishing chemical weathering laws for these two lithologies, describing the dependence of chemical weathering on environmental parameters, such as climate and mechanical erosion. As shown within this contribution, such mathematical laws are of primary importance for numerical models calculating the evolution of the partial pressure of atmospheric CO₂ and the Earth climate at geological timescales. The major results can be summarized as follow: (1) weathering of continental basaltic lithologies accounts for about 30% of the total consumption of atmospheric CO₂ through weathering of continental silicate rocks. This is related to their high weatherability (about eight times greater than the granite weatherability); (2) a simple weathering law has been established for basaltic lithologies, giving the consumption of atmospheric CO₂ as a function of regional continental runoff, and mean annual regional temperature; (3) no such simple weathering law can be proposed for granitic lithologies, since the effect of temperature can only be identified for regions displaying high continental runoff; (4) a general law relating mechanical erosion and chemical weathering has been validated on small and large catchments. The consequences of these major advances on the climatic evolution of the Earth are discussed. Particularly, the impacts of the onset of the Deccan trapps and the Himalayan orogeny on the global carbon cycle are reinvestigated. To cite this article: B. Dupré et al., C. R. Geoscience 335 (2003).  相似文献   

Little River Experimental Watershed,a keystone in understanding of coastal plain watersheds     

David D. Bosch  Alisa W. Coffin  Joseph Sheridan  Oliva Pisani  Dinku M. Endale  Tim C. Strickland 《水文研究》2021,35(8):e14334

The US Department of Agriculture-Agricultural Research Service Southeast Watershed Research Laboratory (SEWRL) initiated a hydrologic research program on the Little River Experimental Watershed (LREW) in 1967. Long-term (52 years) streamflow data are available for nine sites, including rainfall-runoff relationships and hydrograph characteristics regularly used in research on interactive effects of climate, vegetation, soils, and land-use in low-gradient streams of the US EPA Level III Southeastern Plains ecoregion. A summary of prior research on the LREW illustrates the impact of the watershed on building a regional understanding of hydrology and water quality. Climatic and streamflow data were used to make comparisons of scale across the nine nested LREW watersheds (LRB, LRF, LRI, LRJ, LRK, LRO, LRN, LRM, and LRO3) and two regional watersheds (Alapaha and Little River at Adel). Annual rainfall for the largest LREW, LRB, was 1200 mm while average annual streamflow was 320 mm. Annual rainfall, streamflow, and the ratio between annual streamflow and rainfall (Sratio) were similar (α = 0.05) across LREWs LRB, LRF, LRI, LRJ, LRK, and LRO. While annual rainfall within the 275 ha LRO3 was found to be similar to LRO and LRM (α = 0.05), annual streamflow and Sratio were significantly different (α = 0.05). Comparisons of annual rainfall, streamflow, and Sratio between LRB and the regional watersheds indicated no differences (α = 0.05). Based upon this analysis, most regional watersheds shared similar hydrologic characteristics. LRO3 was an exception, where increases in row crops and decreases in forest coverage resulted in increased streamflow. LREW data have been instrumental in building considerable scientific understanding of flow and transport processes for these stream systems. Continued operation of the LREW hydrologic network will support hydrologic research as well as environmental quality and riparian research programs that address emerging and high priority natural resource and environmental issues.  相似文献   

SIMPLE: A High Resolution Near IR Spectrograph for the European ELT     

L. Origlia  E. Oliva 《Earth, Moon, and Planets》2009,105(2-4):123-126

We present the main features of SIMPLE, the Phase A study of a high resolution near IR spectrograph for the European Extreme Large Telescope and we mention a few science cases which are relevant for the study of planets in the solar system and beyond.  相似文献   

Baily’s Beads Atlas in 2005 – 2008 Eclipses     

C. Sigismondi  D. W. Dunham  K. Guhl  S. Andersson  H. Bode  O. Canales  P. Colona  O. Farago  M. Fernández-Ocaña  A. Gabel  M. Haupt  C. Herold  R. Nugent  P. Oliva  M. Patel  C. Perello  W. Rothe  J. Rovira  T. Schaefer  C. Schnabel  D. Schwartz  A. Selva  W. Strickling  A. Tegtmeier  C. Tegtmeier  B. Thome  W. H. Warren 《Solar physics》2009,258(2):191-202

In the annular or total eclipses of 3 October 2005, 29 March 2006, 22 September 2006, and 1 August 2008, observational campaigns were organized to record the phenomenon of Baily’s beads. These campaigns were internationally coordinated through the International Occultation Timing Association (IOTA) at both its American and European sections. From the stations in the northern and southern zones of grazing eclipse, the eclipses have been recorded on video. Afterward, as many beads as possible have been identified by analyzing the video data of each observing station. The atlas presented in this paper includes 598 data points, obtained by 23 observers operating at 28 different observing stations. The atlas lists the geographic positions of the observing stations and the observed time instants of disappearance or reappearance of beads, identified by an angle measured relative to the Moon’s axis of rotation. The atlas will serve as a basis for determining the solar diameter. Electronic Supplementary Material  The online version of this article () contains supplementary material, which is available to authorized users.  相似文献   

Trace elements in organic- and iron-rich surficial fluids of the boreal zone: Assessing colloidal forms via dialysis and ultrafiltration     

E.V. Vasyukova  O.S. Pokrovsky  J. Viers  P. Oliva  B. Dupré  F. Martin  F. Candaudap 《Geochimica et cosmochimica acta》2010,74(2):449-468

On-site size fractionation of about 40 major and trace elements (TE) was performed on waters from boreal small rivers and their estuaries in the Karelia region of North-West Russia around the “Vetreny Belt” mountain range and in Paanajärvi National Park (Northern Karelia). Samples were filtered in the field using a progressively decreasing pore size (5 μm, 2.5 (3) μm, 0.22 (0.45) μm, 100 kDa, 10 and 1 kDa) by means of frontal filtration and ultrafiltration (UF) techniques and employing in-situ dialysis with 10 and 1 kDa membranes followed by ICP-MS analysis. For most samples, dialysis yields a systematically higher (factor of 2-3) proportion of colloidal forms compared to UF. Nevertheless, dialysis is able to provide a fast and artefact-free in-situ separation of colloidal and dissolved components.Similar to previous studies in European subarctic zones, poor correlation of iron concentration with that of organic carbon (OC) in (ultra)filtrates and dialysates reflect the presence of two pools of colloids composed of organic-rich and Fe-rich particles. All major anions and silica are present as dissolved species (or solutes) passing through the 1-kDa membrane. Size-separation ultrafiltration experiments show the existence of larger or smaller pools of colloidal particles different for each of the considered elements.The effect of rock lithology (acidic versus basic) on the colloidal speciation of TE is seen solely in the increase of Fe and some accompanying TE concentrations in catchment areas dominated by basic rocks compared to granitic catchments. Neither the ultrafiltration pattern nor the relative proportions of colloidal versus truly dissolved TE are affected by the lithology of the underlying rocks: within ±10% uncertainty, the two colloidal (10 kDa-0.22 μm and 1-10 kDa) and the truly dissolved (<1 kDa) pools show no difference in percentage of TE distribution between two types of bedrock lithology. The same conclusion is held for organic- and Fe-rich waters. In contrast, landscape context analysis demonstrated slight dominance, for most TE affected by UF, of large-size colloids (10 kDa-0.22 μm) in rivers and streams and small-size colloids and truly dissolved fractions in swamp stagnant surface waters. This supports the existence of two pathways of colloids formation: during the plant litter degradation in wetland zones and at the redox front in river riparian zone.  相似文献   

Removal of Pyridine from Aqueous Solution by Adsorption on an Activated Carbon Cloth     

Pedro Alonso‐Davila  Oliva L. Torres‐Rivera  Roberto Leyva‐Ramos  Raul Ocampo‐Perez 《洁净——土壤、空气、水》2012,40(1):45-53

Pyridine is a very toxic pollutant that has to be removed from wastewater. In this work, adsorption of pyridine on activated carbon cloth (ACC) is studied as a possible alternative for eliminating pyridine from aqueous solution. The ACC was produced from polyacrylonitrile. The adsorption equilibrium data of pyridine on ACC was obtained in a batch adsorber. The experimental data was interpreted with the isotherms of Langmuir, Freundlich, and Prausnitz‐Radke (PR), and the PR isotherm better represented the experimental data. The capacity of ACC for adsorbing pyridine was favored increasing the solution pH from 3 to 6, and this effect was due to the π–π dispersive and electrostatic interactions between the pyridine species in solution and the surface complexes of ACC. The modified Langmuir model fitted reasonably well the influence of pH on the adsorption capacity. In this model was assumed that both neutral pyridine and pyridinium were simultaneously adsorbed on ACC accordingly to the experimental results. The adsorption capacity was almost independent of temperature. The reversibility study revealed that 75% of the pyridine can be desorbed from ACC indicating that part of the pyridine was irreversibly adsorbed, and possibly chemisorbed.  相似文献