Late-Holocene paleoenvironmental change at mid-elevation on the Caribbean slope of the Cordillera Central,Dominican Republic: a multi-site,multi-proxy analysis     

Chad S. Lane  Sally P. Horn  Claudia I. Mora  Kenneth H. Orvis 《Quaternary Science Reviews》2009,28(23-24):2239-2260

High-resolution proxy records from the circum-Caribbean region indicate significant variation in Late Holocene climate, especially precipitation, attributed primarily to shifts in the mean annual position of the Intertropical Convergence Zone (ITCZ). The paleoenvironmental and cultural impacts of this Late-Holocene climate variability have been analyzed intensively in the western Caribbean, and to a lesser extent in the southern Caribbean. However, the occurrence and impacts of Late Holocene climate shifts in the eastern Caribbean, especially in island interiors, has not been well documented. Here we present sediment records of Late-Holocene paleoenvironmental change from two lakes located on the Caribbean slope of the Cordillera Central in the Dominican Republic that span the last ～3000 years. Sediment characteristics, pollen, charcoal, biogenic carbonate assemblages and isotopic composition, and bulk sedimentary carbon isotope values in Laguna Castilla and Laguna de Salvador indicate extreme shifts in hydrology, vegetation, and disturbance regimes in response to climate change and human activity in the lake watersheds. Close correspondence between the hydrological histories of the lakes and trace metal concentrations in sediments of the Cariaco Basin indicate that precipitation variability here responds to the same controls, and may similarly reflect shifts in the mean annual position of the ITCZ. Human occupation of the watersheds appears to be closely linked to severe dry periods and may indicate larger scale cultural responses to precipitation variability on the island of Hispaniola. Prehistoric human populations strongly affected vegetation and disturbance regimes in the lake watersheds. Impacts may have lasted several centuries and may have been more severe than impacts of modern populations.  相似文献   

Scales and causes of heterogeneity in bars in a large multi‐channel river: Río Paraná, Argentina     

Arnold J. H. Reesink  Philip J. Ashworth  Gregory H. Sambrook Smith  James L. Best  Daniel R. Parsons  Mario L. Amsler  Richard J. Hardy  Stuart N. Lane  Andrew P. Nicholas  Oscar Orfeo  Steven D. Sandbach  Christopher J. Simpson  Ricardo N. Szupiany 《Sedimentology》2014,61(4):1055-1085

To date, published studies of alluvial bar architecture in large rivers have been restricted mostly to case studies of individual bars and single locations. Relatively little is known about how the depositional processes and sedimentary architecture of kilometre‐scale bars vary within a multi‐kilometre reach or over several hundreds of kilometres downstream. This study presents Ground Penetrating Radar and core data from 11, kilometre‐scale bars from the Río Paraná, Argentina. The investigated bars are located between 30 km upstream and 540 km downstream of the Río Paraná – Río Paraguay confluence, where a significant volume of fine‐grained suspended sediment is introduced into the network. Bar‐scale cross‐stratified sets, with lengths and widths up to 600 m and thicknesses up to 12 m, enable the distinction of large river deposits from stacked deposits of smaller rivers, but are only present in half the surface area of the bars. Up to 90% of bar‐scale sets are found on top of finer‐grained ripple‐laminated bar‐trough deposits. Bar‐scale sets make up as much as 58% of the volume of the deposits in small, incipient mid‐channel bars, but this proportion decreases significantly with increasing age and size of the bars. Contrary to what might be expected, a significant proportion of the sedimentary structures found in the Río Paraná is similar in scale to those found in much smaller rivers. In other words, large river deposits are not always characterized by big structures that allow a simple interpretation of river scale. However, the large scale of the depositional units in big rivers causes small‐scale structures, such as ripple sets, to be grouped into thicker cosets, which indicate river scale even when no obvious large‐scale sets are present. The results also show that the composition of bars differs between the studied reaches upstream and downstream of the confluence with the Río Paraguay. Relative to other controls on downstream fining, the tributary input of fine‐grained suspended material from the Río Paraguay causes a marked change in the composition of the bar deposits. Compared to the upstream reaches, the sedimentary architecture of the downstream reaches in the top ca 5 m of mid‐channel bars shows: (i) an increase in the abundance and thickness (up to metre‐scale) of laterally extensive (hundreds of metres) fine‐grained layers; (ii) an increase in the percentage of deposits comprised of ripple sets (to >40% in the upper bar deposits); and (iii) an increase in bar‐trough deposits and a corresponding decrease in bar‐scale cross‐strata (<10%). The thalweg deposits of the Río Paraná are composed of dune sets, even directly downstream from the Río Paraguay where the upper channel deposits are dominantly fine‐grained. Thus, the change in sedimentary facies due to a tributary point‐source of fine‐grained sediment is primarily expressed in the composition of the upper bar deposits.  相似文献   

Changes to sediment sources following wildfire in a forested upland catchment,southeastern Australia     

Hugh G. Smith  Gary J. Sheridan  Patrick N. J. Lane  Philip J. Noske  Henk Heijnis 《水文研究》2011,25(18):2878-2889

Few investigations link post‐fire changes to sediment sources and erosion processes with sediment yield response at the catchment scale. This linkage is essential if downstream impacts on sediment transport after fire are to be understood in the context of fire effects across different forest environments. In this study, we quantify changing source contributions to fine sediment (<63 µm) exported from a eucalypt forest catchment (136 ha) burnt by wildfire. The study catchment is one of a pair of research catchments located in the East Kiewa River valley in southeastern Australia that have been the subject of a research program investigating wildfire effects on runoff, erosion, and catchment sediment/nutrient exports. This previous research provided the opportunity to couple insights gained from a range of measurement techniques with the application of fallout radionuclides ¹³⁷Cs and ²¹⁰Pb_ex to trace sediment sources. It was found that hillslope surface erosion dominated exports throughout the 3·5‐year post‐fire measurement period. During this time there was a pronounced decline in the proportional surface contribution from close to 100% in the first six months to 58% in the fourth year after fire. Over the study period, hillslope surface sources accounted for 93% of the fine sediment yield from the burnt catchment. The largest decline in the hillslope contribution occurred between the first and second years after fire, which corresponded with the previously reported large decline in sediment yield, breakdown of water repellency in burnt soils, substantial reduction in hillslope erodibility, and rapid surface vegetation recovery. Coupling the information on sediment sources with hillslope process measurements indicated that only a small proportion of slopes contributed sediment to the catchment outlet, with material derived from near‐channel areas dominating the post‐fire catchment sediment yield response. Copyright © 2011 John Wiley & Sons, Ltd.  相似文献   

The AMADEUS dextrous subsea hand: design, modeling, and sensorprocessing     

Lane  D.M. Davies  J.B.C. Robinson  G. O'Brien  D.J. Sneddon  J. Seaton  E. Elfstrom  A. 《Oceanic Engineering, IEEE Journal of》1999,24(1):96-111

This paper describes the mechanical design, finger modeling, and sensor signal processing for a dextrous subsea robot hand incorporating force and slip contact sensing. The hand uses a fluid-filled tentacle for each finger, which has inherent passive compliance, and no moving parts. Force sensing uses strain gauges mounted in the fingertip, potted within a silicon elastomer. Slip sensing uses a piezoelectric strip to detect vibration, embedded 1 mm below the elastomer surface. Static models of finger motion are presented and validated based on bending moments and hydraulic pressure. The design of a stochastic estimator is also described for sensor fusion of contact force magnitude and direction data, obtained using redundant strain gauges in the fingertip. Finally, linear dynamic models of the finger dynamics in contact with a rigid surface are obtained using least squares and recursive least squares parameter estimation, as a precursor to closed-loop force control during grasping  相似文献   

Photometric study of new southern SU UMa-type dwarf novae and candidates – III. NSV 10934, MM Sco, AB Nor and CAL 86     

Taichi Kato  Peter Nelson  Chris Stockdale  Berto Monard  Tom Richards  Rod Stubbings  Hitoshi Yamaoka  Bernard Heathcote  Roland Santallo 《Monthly notices of the Royal Astronomical Society》2004,347(3):861-872

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Climate change and infectious diseases: Can we meet the needs for better prediction?     

Xavier Rodó  Mercedes Pascual  Francisco J. Doblas-Reyes  Alexander Gershunov  Dáithí A. Stone  Filippo Giorgi  Peter J. Hudson  James Kinter  Miquel-Àngel Rodríguez-Arias  Nils Ch. Stenseth  David Alonso  Javier García-Serrano  Andrew P. Dobson 《Climatic change》2013,118(3-4):625-640

The next generation of climate-driven, disease prediction models will most likely require a mechanistically based, dynamical framework that parameterizes key processes at a variety of locations. Over the next two decades, consensus climate predictions make it possible to produce forecasts for a number of important infectious diseases that are largely independent of the uncertainty of longer-term emissions scenarios. In particular, the role of climate in the modulation of seasonal disease transmission needs to be unravelled from the complex dynamics resulting from the interaction of transmission with herd immunity and intervention measures that depend upon previous burdens of infection. Progress is also needed to solve the mismatch between climate projections and disease projections at the scale of public health interventions. In the time horizon of seasons to years, early warning systems should benefit from current developments on multi-model ensemble climate prediction systems, particularly in areas where high skill levels of climate models coincide with regions where large epidemics take place. A better understanding of the role of climate extremes on infectious diseases is urgently needed.  相似文献   

The thin layer of Warm Ionized Gas: towards a 3-D reconstruction of the spatial distribution of HII regions     

Roberta Paladini  Rod Davies  Gianfranco DeZotti 《Astrophysics and Space Science》2004,289(3-4):363-366

HII regions are known to contribute to the so-called thin layer of the diffuse Warm Ionized Gas. In order to constrain thiscontribution, we reconstruct the 3-D distribution of the sources.A detailed spatial analysis of the largest up-to-date sample of HIIregions is presented.  相似文献   

Neutral hydrogen surveys for high-redshift galaxy clusters and protoclusters     

Richard A. Battye  Rod D. Davies  Jochen Weller 《Monthly notices of the Royal Astronomical Society》2004,355(4):1339-1347

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A Very Small Array search for the extended Sunyaev–Zel''dovich effect in the Corona Borealis supercluster     

Ricardo Génova-Santos  José Alberto Rubiño-Martín  Rafael Rebolo †  Kieran Cleary ‡  Rod D. Davies  Richard J. Davis  Clive Dickinson §  Nelson Falcón ‡‡  Keith Grainge  Carlos M. Gutiérrez  Michael P. Hobson  Michael E. Jones ¶  Rüdiger Kneissl &#;  Katy Lancaster  Carmen P. Padilla-Torres  Richard D. E. Saunders  Paul F. Scott  Angela C. Taylor ¶  Robert A. Watson †† 《Monthly notices of the Royal Astronomical Society》2005,363(1):79-92

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First results from the Very Small Array – I. Observational methods     

Robert A. Watson  Pedro Carreira  Kieran Cleary  Rod D. Davies  Richard J. Davis  Clive Dickinson  Keith Grainge †  Carlos M. Gutiérrez  Michael P. Hobson  Michael E. Jones  Rüdiger Kneissl  Anthony Lasenby  Klaus Maisinger  Guy G. Pooley  Rafael Rebolo  José Alberto Rubiño-Martin ‡  Ben Rusholme §  Richard D. E. Saunders  Richard Savage  Paul F. Scott  An&#;e Slosar  Pedro J. Sosa Molina  Angela C. Taylor  David Titterington  Elizabeth Waldram  Althea Wilkinson 《Monthly notices of the Royal Astronomical Society》2003,341(4):1057-1065

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