Historical political ecology: On the importance of looking back to move forward     

Diana K. Davis 《Geoforum》2009,40(3):285-286

  相似文献   

A test of Sporormiella representation as a predictor of megaherbivore presence and abundance     

Diana Raper  Mark Bush 《Quaternary Research》2009,71(3):490-496

Spores of the dung fungus Sporormiella have been suggested to indicate the presence, perhaps also the abundance of past megaherbivore populations. Nonetheless, basic studies demonstrating a correlation between Sporormiella concentration in lacustrine sediments and modern herbivore abundance are lacking. This study of Sporormiella representation in grazed and ungrazed landscapes provides supporting evidence for the application of Sporormiella as an indicator of megaherbivore presence and abundance in ancient landscapes. However, Sporormiella representation is spatially sensitive to the distance from the dung source. In lakes where Sporomiella are abundant in shoreline sediments, they decline sharply with increasing distance from the lake edge. Although this study provides supporting evidence for the application of Sporormiella as a proxy for herbivore presence and abundance, independent proxies should be applied in conjunction with Sporormiella to control for changes in lake size.  相似文献   

A New Method for Determining Compound Specific Carbon Isotope of Chlorinated Solvents in Porewater     

Jofre Herrero  Diana Puigserver  Beth L. Parker  José M. Carmona 《Ground Water Monitoring & Remediation》2021,41(3):51-57

A new method for the extraction of chlorinated solvents (CSs) from porewater with dimethylacetamide (DMA) used as a solvent and the determination of δ¹³C by gas chromatography-isotope ratio mass spectrometry (GC-IRMS) with solid-phase microextraction (SPME) are presented. This method was used for the determination of δ¹³C of chloroethenes and chloromethanes. The extraction of the CSs from porewater with DMA led to a minimal loss of mass of solvent and chlorinated compounds. The accuracy of the method was verified with the analysis of the pure injected compounds using elemental analyzer—isotope ratio mass spectrometry (EA-IRMS). It has been effectively applied in a study area in saturated soil samples of a pollutant source zone of perchloroethylene (PCE) and trichloroethylene (TCE). The limit of quantification of the new method was 0.034 μg/g for PCE and TCE for 10–20 g of soil sample. This new method allows for compound-specific isotope analysis of CSs in porewater, which can be beneficial in sites where the identification of contamination sources and the behavior of the contaminants are not clear.  相似文献   

Chemistry of chromium spinel in high-Mg rocks from the Morungava Intrusion,Cretaceous Paraná Igneous Province,southernmost Brazil     

Pinto  Viter Magalhães  Massonne  Hans-Joachim  Wildner  Wilson  Hartmann  Léo Afraneo  Debruyne  David  Theye  Thomas 《Mineralogy and Petrology》2019,113(6):765-782

Mineralogy and Petrology - Mafic-ultramafic intrusions within continental flood basalt terrains are frequently associated with Cu-Ni-PGE mineralization. This study aims to constrain the...  相似文献   

Late Quaternary vegetation and climate dynamics in central-eastern Brazil: insights from a ~35k cal a bp peat record in the Cerrado biome     

Ingrid Horák-Terra  Antonio Martínez Cortizas  Cynthia Fernandes Pinto Da Luz  Alexandre Christófaro Silva  Tim Mighall  Plínio Barbosa De Camargo  Carlos Victor Mendonça-Filho  Paulo Eduardo De Oliveira  Francisco Willian Cruz  Pablo Vidal-Torrado 《第四纪科学杂志》2020,35(5):664-676

The late Quaternary evolution of central-eastern Brazil has been under-researched. Questions remain as to the origin of the Cerrado, a highly endangered biome, and other types of vegetation, such as the Capões – small vegetation islands of semi-deciduous and mountain forests. We investigated the factors that influenced the expansion and contraction of the Cerrado and Capões during the late Quaternary (last ~35 ka), using a multi-proxy approach: stable isotopes (δ¹³C, δ¹⁵N), geochemistry, pollen and multivariate statistics derived from a peat core (Pinheiro mire, Serra do Espinhaço Meridional). Five major shifts in precipitation, temperature, vegetation and landscape stability occurred at different timescales. Our study revealed that changes in the South Atlantic Convergence Zone (SACZ) seem to have been coeval with these shifts: from the Late Glacial Maximum to mid-Holocene the SACZ remained near (~29.6 to ~16.5k cal a bp ) and over (~16.5 to ~6.1 k cal a bp ) the study area, providing humidity to the region. This challenges previous research which suggested that climate was drier for this time period. At present, the Capões are likely to be a remnant of a more humid climate; meanwhile, the Cerrado biome seems to have stablished in the late Holocene, after ~3.1 k cal a bp .  相似文献   

Ecological distribution of Stephanodiscus niagarae Ehrenberg in central Mexico and niche modeling for its last glacial maximum habitat suitability in the Nearctic realm     

Avendaño  Diana  Caballero  Margarita  Vázquez  Gabriela 《Journal of Paleolimnology》2021,66(1):1-14

Journal of Paleolimnology - Stephanodiscus niagarae Ehrenberg is currently restricted to specific regions of central Mexico, however, during the late Pleistocene, it had a wider distribution in the...  相似文献   

Pseudo‐dynamic testing with substructuring at the ELSA Laboratory     

P. Pegon  A. V. Pinto 《地震工程与结构动力学》2000,29(7):905-925

The paper describes the distinctive features of the pseudo‐dynamic test method as implemented at the ELSA reaction‐wall facility. Both hardware and software aspects are considered. Particular attention is devoted to the digital control system and to a coupled numerical–experimental substructuring technique allowing realistic earthquake testing of very large structures. Mathematical and implementation details corresponding to this testing technique are given for both synchronous and asynchronous input motion. Selected test results illustrate the advantages of the presented features. Copyright © 2000 John Wiley & Sons, Ltd.  相似文献   

Dense collection areas and terrestrial alteration of meteorites in the Atacama Desert     

Gabriel A. Pinto  Adrien Tavernier  Jérôme Gattacceca  Alexandre Corgne  Millarca Valenzuela  Béatrice Luais  Laura Flores  Felipe Olivares  Yves Marrocchi 《Meteoritics & planetary science》2024,59(2):351-367

In the last 15 years, more than 2700 meteorites have been recovered and officially classified from the Atacama Desert. Although the number of meteorites collected in the Atacama has risen, the physical and climatic properties of the dense collection areas (DCAs) have not been fully characterized. In this article, we compiled the published data of all classified meteorites found in the Atacama Desert to (i) describe the distribution by meteorite groups, (ii) compare the weathering degree of chondrites among different Atacama DCAs and other hot and cold deserts, and (iii) determine the preservation conditions of chondrites in the main Atacama DCAs in relation with the local climatic conditions. The 35 DCAs so far identified in the Atacama Desert are located in three main morphotectonic units: The Coastal Range (CR), Central Depression (CD), and Pre-Andean Range/Basement. A comparison with reported weathering data from other cold and hot deserts indicates that the mean terrestrial weathering of Atacama chondrites (W1–2), displays less alteration than other hot deserts (W2–3) and resembles the weathering distribution of the Antarctic meteorites (W1–2). The highest abundance of Atacama chondrites with low weathering (≤W2) is localized in the CD (78.8%, N = 1435), which is protected from the coastal fog influence and seasonal rainfalls and displays the oldest surfaces in the Atacama Desert. The morphogenetic classification based on present-day temperatures and precipitations of the main Atacama DCAs reveals similar regional/subregional climatic conditions in the most productive areas and a truly productive surface for meteorite recovery between 5% and 58% of the quadrangles formally defined for each Atacama DCA. Our morphogenetic classification lacks consideration of some meteorological parameters such as the coastal fog, so it cannot fully explain the differences in weathering patterns among CR chondrites. Future studies of chondrite preservation in the Atacama DCAs should consider other meteorological variables such as relative humidity, specific humidity, or dew point, in combination with exposure ages of meteorites and its surfaces.  相似文献   

Seismic displacement demand prediction in non-linear domain: Optimization of the N2 method     

Diana  Lorenzo  Manno  Andrea  Lestuzzi  Pierino 《地震工程与工程振动(英文版)》2019,18(1):141-158

In Europe, computation of displacement demand for seismic assessment of existing buildings is essentially based on a simplified formulation of the N2 method as prescribed by Eurocode 8(EC8). However, a lack of accuracy of the N2 method in certain conditions has been pointed out by several studies. This paper addresses the assessment of effectiveness of the N2 method in seismic displacement demand determination in non-linear domain. The objective of this work is to investigate the accuracy of the N2 method through comparison with displacement demands computed using non-linear timehistory analysis(NLTHA). Results show that the original N2 method may lead to overestimation or underestimation of displacement demand predictions. This may affect results of mechanical model-based assessment of seismic vulnerability at an urban scale. Hence, the second part of this paper addresses an improvement of the N2 method formula by empirical evaluation of NLTHA results based on EC8 ground-classes. This task is formulated as a mathematical programming problem in which coefficients are obtained by minimizing the overall discrepancy between NLTHA and modified formula results. Various settings of the mathematical programming problem have been solved using a global optimization metaheuristic. An extensive comparison between the original N2 method formulation and optimized formulae highlights benefits of the strategy.  相似文献   

Metals in tidal flats colonized by microbial mats within a South-American estuary (Argentina)     

Analía V. Serra  Sandra E. Botté  Diana G. Cuadrado  Noelia S. La Colla  Vanesa L. Negrin 《Environmental Earth Sciences》2017,76(6):254

In this study, we measured the concentrations of metals (Cd, Cu, Pb, Ni, Cr, Zn, Hg, Mn, and Fe) and assessed the characteristics of tidal flats (grain size and organic matter content) in sediments and their overlying microbial mats fractions to evaluate the anthropogenic impact within the Bahía Blanca Estuary (BBE). Puerto Rosales (PR) and Almirante Brown (AB), located in the middle and inner zone of the estuary, respectively, were used as sampling sites. Sediments were composed mainly of silt–clay in AB, whereas first fine-grained particles were coarser in depth in PR. Regarding the concentration of metals in both fractions, we found differences between sites: There were higher concentrations of overall metals in AB relative to PR. In addition, higher concentrations of Cu were recorded in the first centimeters of AB tidal flats, whereas higher concentration of Cd were recorded in microbial mats of PR. Considering that the grain size was similar between sites, these results are consistent with the high concentration of organic matter found in AB, probably because this site is close to a former municipal dump and sewage discharges. Also, the higher Cd content found in PR site would highlight both the influence of untreated urban discharges and port anthropogenic activities. In conclusion, this study allowed identifying high values of some metals in the presence of microbial mats in the BBE, thus suggesting a possible interaction between both, at least for metals like Cu or Cd.  相似文献