The Huygens scientific data archive: Technical overview     

Olivier Witasse  Lyle Huber  Jean-Pierre Lebreton  David Heather  John Zarnecki  Roland Trautner  Piero Leon Stoppato  Chuck See  Cyril Pennanech  Lisa McFarlane  Bobby Kazeminejad  Brijen Hathi  John Haberman  Francesca Ferri  Lyn Doose  Giacomo Colombatti  Michael Bird  Alessio Aboudan 《Planetary and Space Science》2008,56(5):770-777

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Thermal evolution of an ancient subduction interface revealed by Lue Hf garnet geochronology,Halilba■? Complex(Anatolia)     

Amaury Pourteau  Erik E.Scherer  Simon Schorn  Rebecca Bast  Alexander Schmidt  Lisa Ebert 《地学前缘(英文版)》2019,(1)

The thermal structure of subduction zones exerts a major influence on deep-seated mechanical and chemical processes controlling arc magmatism, seismicity, and global element cycles. Accretionary complexes exposed inland may comprise tectonic blocks with contrasting pressureetemperature(Pe T)histories, making it possible to investigate the dynamics and thermal evolution of former subduction interfaces. With this aim, we present new Lue Hf geochronological results for mafic rocks of the Halilbag?Complex(Anatolia) that evolved along different thermal gradients. Samples include a lawsoniteeepidote blueschist, a lawsoniteeepidote eclogite, and an epidote eclogite(all with counter-clockwise Pe T paths),a prograde lawsonite blueschist with a "hairpin"-type Pe T path, and a garnet amphibolite from the overlying sub-ophiolitic metamorphic sole. Equilibrium phase diagrams suggest that the garnet amphibolite formed at w0.6 -0.7 GPa and 800 -850℃, whereas the prograde lawsonite blueschist records burial from 2.1 GPa and 420℃ to 2.6 GPa and 520℃. Well-defined Lue Hf isochrons were obtained for the epidote eclogite(92.38 ± 0.22 Ma) and the lawsoniteeepidote blueschist(90.19 ± 0.54 Ma),suggesting rapid garnet growth. The lawsoniteeepidote eclogite(87.30 ± 0.39 Ma) and the prograde lawsonite blueschist(ca. 86 Ma) are younger, whereas the garnet amphibolite(104.5 ± 3.5 Ma) is older.Our data reveal a consistent trend of progressively decreasing geothermal gradient from granulite-facies conditions at ~104 Ma to the epidote-eclogite facies around 92 Ma, and the lawsonite blueschist-facies between 90 Ma and 86 Ma. Three Lue Hf garnet dates(between 92 Ma and 87 Ma) weighted toward the growth of post-peak rims(as indicated by Lu distribution in garnet) suggest that the HP/LT rocks were exhumed continuously and not episodically. We infer that HP/LT metamorphic rocks within the Halilbag?Complex were subjected to continuous return flow, with "warm" rocks being exhumed during the tectonic burial of "cold" ones. Our results, combined with regional geological constraints, allow us to speculate that subduction started at a transform fault near a mid-oceanic spreading centre. Following its formation, this ancient subduction interface evolved thermally over more than 15 Myr, most likely as a result of heat dissipation rather than crustal underplating.  相似文献   

Revised recommended methods for analyzing crater size-frequency distributions          下载免费PDF全文

Stuart J. Robbins  Jamie D. Riggs  Brian P. Weaver  Edward B. Bierhaus  Clark R. Chapman  Michelle R. Kirchoff  Kelsi N. Singer  Lisa R. Gaddis 《Meteoritics & planetary science》2018,53(4):891-931

Impact crater populations help us to understand solar system dynamics, planetary surface histories, and surface modification processes. A single previous effort to standardize how crater data are displayed in graphs, tables, and archives was in a 1978 NASA report by the Crater Analysis Techniques Working Group, published in 1979 in Icarus. The report had a significant lasting effect, but later decades brought major advances in statistical and computer sciences while the crater field has remained fairly stagnant. In this new work, we revisit the fundamental techniques for displaying and analyzing crater population data and demonstrate better statistical methods that can be used. Specifically, we address (1) how crater size-frequency distributions (SFDs) are constructed, (2) how error bars are assigned to SFDs, and (3) how SFDs are fit to power-laws and other models. We show how the new methods yield results similar to those of previous techniques in that the SFDs have familiar shapes but better account for multiple sources of uncertainty. We also recommend graphic, display, and archiving methods that reflect computers’ capabilities and fulfill NASA's current requirements for Data Management Plans.  相似文献   

Verification of tropical cyclone deposits with oxygen isotope analyses of coeval ostracod valves     

Chad S. Lane  Brooklyn Hildebrandt  Lisa M. Kennedy  Allison LeBlanc  Kam-Biu Liu  Amy J. Wagner  Andrea D. Hawkes 《Journal of Paleolimnology》2017,57(3):245-255

Reconstruction of prehistoric tropical cyclone (TC) activity often relies on the identification of distinctive overwash deposits (tempestites) in coastal lagoon sediments. Similar sediment deposits, however, can result from high-energy events other than TCs. In this study we assessed the utility of using the geochemistry of ostracod valves, specifically their stable oxygen isotope composition (δ¹⁸O), as a potential validation variable that could reduce the chances of misidentifying an overwash deposit as having been generated by a TC, when in fact it formed from another high-energy depositional process (type 1 error). We applied this technique to a sediment core recovered from Laguna Alejandro, Dominican Republic, which had already been analyzed for other sedimentary TC proxies. Negative δ¹⁸O anomalies identified in the ostracod valve stable isotope record are associated with TC deposits and are most easily explained by large influxes of ¹⁸O-depleted meteoric waters typical of intense tropical storms. There is potential for this technique to be used to identify TC landfalls that are not represented by overwash deposits. We, however, propose a more conservative approach and suggest this technique be used to validate the origin of a storm deposit and reduce the odds of a type 1 error.  相似文献   

Uv Line Profiles of Biv from a 10-Ps Krf-Laser-Produced Plasma     

Iglesias  E.  Griem  H.  Welch  B.  Weaver  J. 《Astrophysics and Space Science》1997,256(1-2):327-331

We use a KrF laser that generates pulses up to 8 × 10¹⁴ watt/cm² when focused onto a boron nitride target. We measured the line profile of the near UV, n = 0, n = 2 transitions of helium-like boron and we studied the triplet 1s2p³P-1s2s³S at 2825.85 (J = 1), 2821.68 (J = 2) and 2824.57 (J = 0) Å, at various positions from the target surface, in order to correlate details of this profile with the presence of self-generated magnetic fields and/or dynamic turbulence among other processes. We fitted the measured profiles to a 0-D model, that includes, Stark, Doppler, Zeeman and instrumental broadening. The effect of the magnetic field was included using an intermediate field calculations. Preliminary results of these measurements are presented and discussed.  相似文献   

Summer temperature variability across four urban neighborhoods in Knoxville,Tennessee, USA     

Kelsey?N.?EllisEmail author  Jon?M.?Hathaway  Lisa?Reyes?Mason  David?A.?Howe  Thomas?H.?Epps  Vincent?M.?Brown 《Theoretical and Applied Climatology》2017,127(3-4):701-710

The urban heat island (UHI) is a well-documented effect of urbanization on local climate, identified by higher temperatures compared to surrounding areas, especially at night and during the warm season. The details of a UHI are city-specific, and microclimates may even exist within a given city. Thus, investigating the spatiotemporal variability of a city’s UHI is an ongoing and critical research need. We deploy ten weather stations across Knoxville, Tennessee, to analyze the city’s UHI and its differential impacts across urban neighborhoods: two each in four neighborhoods, one in more dense tree cover and one in less dense tree cover, and one each in downtown Knoxville and Ijams Nature Center that serve as control locations. Three months of temperature data (beginning 2 July 2014) are analyzed using paired-sample t tests and a three-way analysis of variance. Major findings include the following: (1) Within a given neighborhood, tree cover helps negate daytime heat (resulting in up to 1.19 ^°C lower maximum temperature), but does not have as large of an influence on minimum temperature; (2) largest temperature differences between neighborhoods occur during the day (0.38–1.16 ^°C difference), but larger differences between neighborhoods and the downtown control occur at night (1.04–1.88 ^°C difference); (3) presiding weather (i.e., air mass type) has a significant, consistent impact on the temperature in a given city, and lacks the differential impacts found at a larger-scale in previous studies; (4) distance from city center does not impact temperature as much as land use factors. This is a preliminary step towards informing local planning with a scientific understanding of how mitigation strategies may help minimize the UHI and reduce the effects of extreme weather on public health and well-being.  相似文献   

Improved performance‐based seismic assessment of buildings by utilizing Bayesian statistics          下载免费PDF全文

Omid Esmaili  Lisa Grant Ludwig  Farzin Zareian 《地震工程与结构动力学》2016,45(4):581-597

This paper addresses two important issues of concern to practicing engineers and researchers alike in application of performance‐based seismic assessment (PBSA) methodology on buildings: (i) the number of ground motion records required to exercise PBSA—current practice (FEMA P‐58‐1) requires eleven or more pairs of motions for this purpose, and (ii) the time and effort associated with performing the number of nonlinear response history analyses required to exercise PBSA. We present a method for exercising of PBSA that employs classical linear modal analysis to develop a first estimate (i.e., a priori) of probability distribution of loss, followed by utilizing Bayesian statistics to update this estimate using estimates of loss obtained by utilizing a small number of nonlinear response history analyses of a detailed model of the building (i.e., posterior). The proposed technique is used to assess the distribution of monetary loss of two case studies, a 4‐story reinforced concrete moment‐resisting frame building and a 20‐story steel moment‐resisting frame building, both located in Los Angeles, for a ground motion hazard with 10% probability of exceedance in 50 years. The efficiency of the proposed PBSA method is demonstrated by showing the similarity between the distribution of monetary loss at each story of case study buildings obtained from the traditional/sophisticated PBSA methodology and the proposed PBSA method in this study. Copyright © 2015 John Wiley & Sons, Ltd.  相似文献   

Species loss in the brown world: are heterotrophic systems inherently stable?     

Michael J. Rubbo  Lisa K. Belden  Sara I. Storrs-Mendez  Jonathan J. Cole  Joseph M. Kiesecker 《Aquatic Sciences - Research Across Boundaries》2012,74(3):397-404

Determining the effects of species loss on ecosystems has received considerable attention given the current threats many ecosystems are facing. A significant body of research has yielded many insights to this question, but this work has been limited by a focus on ecosystems where primary production plays a significant role in energy transfer. As many ecosystems rely on energy sources that are not derived from in situ production, there is a need to better understand how species loss will affect ecosystems of varying trophic states. To examine the effects of species loss on an ecosystem that is not reliant on in situ primary production, we manipulated the larval amphibian community of temporary forest ponds. These ponds are heterotrophic systems that rely on allochthonous inputs of detritus as a basal energy source. The larvae of two amphibian species that are prone to local extinction, wood frogs (Lithobates sylvatica) and spotted salamanders (Ambystoma maculatum), were removed from ponds and net ecosystem production was monitored. We found no effects of the removal of these top consumers on ecosystem functioning or on lower trophic groups (i.e., zooplankton, algae, bacteria). While amphibians can influence food web dynamics in other systems, their influence on system processes in temporary forest ponds appears to be limited. We hypothesize that the lack of any effects is due to the microbial degradation of detritus ??swamping?? the system, providing more than enough energy to maintain the food web, and/or due to omnivory dampening species interactions. These data indicate that the functioning of heterotrophic systems may be inherently stable due to internal dynamics that minimize interaction strengths among trophic groups.  相似文献   

The Seashell Wastes as Biosorbent for Reactive Dye Removal from Textile Effluents     

Daniela Suteu  Doina Bilba  Magdalena Aflori  Florica Doroftei  Gabriela Lisa  Marinela Badeanu  Teodor Malutan 《洁净——土壤、空气、水》2012,40(2):198-205

This study investigates structural and adsorption properties of the powdered waste shells of Rapana gastropod and their use as a new cheap adsorbent to remove reactive dye Brilliant Red HE‐3B from aqueous solutions under batch conditions. For the powder shells characterization, solubility tests in acidic solutions and X‐ray diffraction (XRD), scanning electron microscopy (SEM), energy‐dispersive X‐ray spectroscopy (EDX), Fourier transform IR spectroscopy (FT‐IR) and thermogravimetric analyses were performed. The results revealed that the adsorbent surface is heterogeneous consisting mainly from calcium carbonate layers (either calcite or aragonite) and a small amount of organic macromolecules (proteins and polysaccharides). The dye adsorptive potential of gastropod shells powder was evaluated as function of initial solution pH (1–5), adsorbent dose (6–40 g L^?1), dye concentration (50–300 mg L^?1), temperature (5–60°C), and contact time (0–24 h). It was observed that the maximum values of dye percentage removal were obtained at the initial pH of solution 1.2, shells dose of 40 g L^?1, dye initial concentration of 50–50 mg L^?1 and higher temperatures; the equilibrium time decreases with increasing of dye concentration. It is proved that the waste seashell powder can be used as low cost bioinorganic adsorbent for dyes removal from textile wastewaters.  相似文献   

A log‐normal spectral analysis of inorganic grain‐size distributions from a Canadian boreal lake core: Towards refining depositional process proxy data from high latitude lakes          下载免费PDF全文

Paul R. Gammon  Lisa A. Neville  R. Timothy Patterson  Martine M. Savard  Graeme T. Swindles 《Sedimentology》2017,64(3):609-630

Better methods for interpreting grain‐size spectra will enhance current understanding of past transport–depositional processes. A high‐resolution inorganic grain‐size dataset has been measured from a freeze core extracted from ‘Alberta Lake E’ a boreal fresh water lake 40 km east of the Athabasca Oil Sands in north‐eastern Alberta, Canada. The grain‐size spectra are remarkably consistent throughout the core, exhibiting a structure comprising six persistent grain‐size distributions below ca 250 μm, plus a rare medium‐sand distribution. Automated deconvolution of the grain‐size spectra produced poor results. Constraining the modes of two of the distributions produced deconvolution solutions that were statistically excellent and consistent with the structure of each spectrum. Statistical analysis of the ‘constrained’ solutions indicates that deconvolution successfully extracted independent grain‐size populations. Conversely, the multimodal spectra generate traditional measures (for example, mean grain size) that are inconsistent combinations of different individual populations and thus are poor proxies of transport–depositional processes. Alberta Lake E is situated in a boreal wetland landscape where sediment delivery is dominated by overland flow transport during spring melt. This context means that the Alberta Lake E grain‐size spectra can be interpreted to reflect: (i) a bedload component transported during short‐duration high discharge events that reflect the intensity of the melt; and (ii) a finer suspended load component representing material whose magnitude is controlled by the volume of the spring melt. Stratigraphically, bedload and suspended load populations demonstrate different short‐wavelength and long‐wavelength cyclicity, suggesting that spring melt is likely to be driven by cyclic external forcing factors. The links between the grain‐size spectra and spring melt have potential for generating proxy records that better capture the external controls over spring melt in boreal systems and the risks associated with these energetic hydrodynamics. This is exemplified by the coarsest Alberta Lake E distributions, which indicate that more intense spring‐melt dynamics occurred in pre‐historical times.  相似文献