How much material do the radar-bright craters at the Mercurian poles contain?     

Faith Vilas  Paul S. Cobian  Nadine G. Barlow  Susan M. Lederer 《Planetary and Space Science》2005,53(14-15):1496-1500

The depth-to-diameter (d/D) ratios were determined for 12 craters located near the Mercurian north pole that were identified by Harmon et al. (2001, Icarus 149) as having strong depolarized radar echos. We find that the mean d/D value of these radar-bright craters is the mean d/D value of the general population of non-radar-bright craters in the surrounding north polar region. Previous studies, however, show no difference between d/D values of Mercurian polar and equatorial crater populations, suggesting that no terrain softening which could modify crater structure exists at the Mercurian poles (Barlow et al., 1999, 194, Icarus 141). Thus, the change in d/D is governed by a change in crater depth, probably due to deposition of material inside the crater. The volume of infilling material, including volatiles, in the radar-bright craters is significantly greater than predicted by proposed mechanisms for the emplacement of either water ice or sulfur.  相似文献   

The retention of ammonia and sulfur dioxide during riming of ice particles and dendritic snow flakes: laboratory experiments in the Mainz vertical wind tunnel     

Nadine v. Blohn  Karoline Diehl  Anke Nölscher  Alexander Jost  Subir K. Mitra  Stephan Borrmann 《Journal of Atmospheric Chemistry》2013,70(2):131-150

Laboratory experiments were carried out in the Mainz vertical wind tunnel to determine the retention of the trace gases ammonia and sulfur dioxide dissolved in supercooled cloud droplets during riming. The conditions during riming were similar to the ones in atmospheric mixed phase clouds: temperatures from ?18 °C to ?5 °C, liquid water contents between 1 and 1.5 g m^?3, liquid drop radii between 10 and 20 μm, liquid phase concentrations from 1 to 22 mg/l. As collectors, floating ice particles and snow flakes with diameters between 6 mm and 1.5 cm were used. After riming the retention coefficients, i.e. the fractions of the species which remained in the ice phase after freezing were determined. Retention coefficients lying between 0.1 and 1.0 were measured depending on the solubility and dissociation of the trace gas, liquid phase concentration, ambient air temperature, and shape of rimed collector. This can be explained from the chemists’ point of view by the effective Henry’s law constant of the species and physically with the rate of latent heat removal from the rimed collector during freezing. Parameterizations derived from the different experimental cases describe the retention coefficients as a function of temperature. In general, an average retention of ammonia of 92?±?21 % was determined independently of liquid phase concentration while mean values for sulfur dioxide were 53?±?10 % at low liquid phase concentrations and 29?±?7 % at high liquid phase concentrations.  相似文献   

Cambrian sedimentary dykes in the Proterozoic basement of the Västervik area (southeast Sweden): episodic formation inferred from macro- and microfabrics     

Nadine Friese  Axel Vollbrecht  Bernd Leiss  Olaf Jacke 《International Journal of Earth Sciences》2011,100(4):741-752

Fabrics of Cambrian sedimentary dykes formed in Proterozoic granites of the Västervik area (Southeast Sweden) evidence repeated opening/filling and mineralisation/cementation events under varying conditions. Diagnostic features include (1) wall-parallel boundaries between epiclastic fillings and (2) early formed dyke sediments that appear as lithoclasts in subsequently formed sedimentary fillings. The psammitic components mostly consist of well-rounded quartz grains related to a coastal environment and fragments from the granitic host rock. Platy calcitic fragments embedded in the epiclastic matrix originally formed as microveins within already-lithified dyke sediments and the adjacent host rock. Convex downward-pointing, internal sagging structures, together with the preferred orientation of compositional boundaries and long axes of grains/rock fragments parallel to the dyke walls, are interpreted as the result of suction-controlled flow of unconsolidated fillings during episodes of downward dyke growth. Pressure solution of quartz grains are evidence of extensional phases with dyke propagation that were interrupted by phases of horizontal compression normal to the dyke walls. The N–S and NE–SW striking sedimentary dykes formed by opening of a pre-existing joint set during NW–SE oriented rifting during the Cambrian.  相似文献   

Stakeholders’ expectations towards a proposed marine protected area: A multi-criteria analysis of MPA performance criteria     

Nadine Heck  Philip Dearden  Adrian McDonald 《Ocean & Coastal Management》2011,54(9):687-695

In order to enable effective management of marine protected areas (MPAs), desired MPA achievements need to be identified as early as possible for the development of relevant and clear management goals, objectives and conservation targets. As the definition of MPA success is a social construct, the involvement of multiple groups in this process including government agencies, stakeholders, and other interested parties is increasingly advocated. This study investigates diverse groups’ opinions on the performance of a proposed National Marine Conservation Area (NMCA) on the West coast of Canada prior to its establishment. In order to analyse and quantify the importance of MPA performance criteria among multiple stakeholder groups, the Analytical Hierarchy Process (AHP) is applied. Findings reveal that marine stakeholder groups have distinct preferences for future MPA performance. Most differences are obvious between user and non-user groups. The study also finds that respondents’ characteristics other than stakeholder groups affiliations influence expectations towards the proposed MPA including livelihood dependency on the marine environment, amount of time spent in the area, and engagement in fishing activities.  相似文献   

Digitization and Scientific Exploitation of the Italian and Vatican Astronomical Plate Archives     

Cesare Barbieri  Carlo Blanco  Beatrice Bucciarelli  Regina Coluzzi  Andrea Di Paola  Luciano Lanteri  Gian Luca Li Causi  Ettore Marilli  Piero Massimino  Vincenzo Mezzalira  Stefano Mottola  Roberto Nesci  Alessandro Omizzolo  Fernando Pedichini  Francesca Rampazzi  Corinne Rossi  Ruggero Stagni  Milcho Tsvetkov  Roberto Viotti 《Experimental Astronomy》2003,15(1):29-43

There is a widespread interest to digitize the precious information contained in the astronomical plate archives, both for the preservation of their content and for its fast distribution to all interested researchers in order to achieve their better scientific exploitation. This paper presents the first results of our large-scale project to digitize the archive of plates of the Italian Astronomical Observatories and of the Specola Vaticana. Similar systems, composed by commercial flat-bed retro-illuminated scanners plus dedicated personal computers and acquisition and analysis software, have been installed in all participating Institutes. Ad-hoc codes have been developed to acquire the data, to test the suitability of the machines to our scientific needs, and to reduce the digital data in order to extract the astrometric, photometric and spectroscopic content. Two more elements complete the overall project: the provision of high quality BVRI CCD sequences in selected fields with the Campo Imperatore telescopes, and the distribution of the digitized information to all interested researchers via the Web. The methods we have derived in the course of this project have been already applied successfully to plates taken by other Observatories, for instance at Byurakan and at Hamburg.  相似文献   

预料之外的安第斯地震     

韩立波 《国际地震动态》2011,(10):12-14

沿南美安第斯山脉西缘的俯冲带边界预期会发生大地震。而沿东边界的地表运动测量表明,曾预期不会发生大地震的安第斯山脉东缘也具有发生同等规模大地震的潜在可能。  相似文献   

Style for the Zeitgeist: The Stealthy Revival of Historicist Housing Since the Late 1960s     

Nadine Dostrovsky  Richard Harris 《The Professional geographer》2013,65(3):314-332

A revival has occurred in the use of historical architectural styles for modern suburban houses but this has attracted little attention from journalists and academics. Those who have noted it disagree about when it began and gathered momentum. Newspaper and trade journal evidence for Canadian cities indicates that the revival began in the late 1960s; that it has reached market saturation; and that Victorian and neo-classical styles became dominant after 1980. Coinciding with the beginnings of inner-city gentrification, the historicist revival in suburban dwellings preceded the recent interest in neotraditional urban design. Not a fringe taste, it says something about the zeitgeist.  相似文献   

Tweet Me Your Talk: Geographical Learning and Knowledge Production 2.0   总被引：1，自引：0，他引：1  

Nadine Schuurman 《The Professional geographer》2013,65(3):369-377

We are in a Gutenberg moment in which we are migrating from book reading to Internet browsing. We are subtly shifting to more ephemeral, summary methods of learning and producing knowledge, shaped by how we consume information on the Web. Thus, a strong determinant of learning might be the very technology that hosts the information, such that technology is both the arbiter of our understanding of the world and how we come to gain that understanding. Based on recent evidence that the Internet is reshaping our learning processes, I argue that geographical knowledge production and translation are not so much products of individualism but rather shaped by rapidly changing work styles that favor concise and highly accessible methods of academic production. I offer examples of changes in journal formats, academic social networking, and academic reviewing to reveal that we are catering to shorter attention spans that prefer to browse.  相似文献   

Storage,mixing, and fluxes of water in the critical zone across northern environments inferred by stable isotopes of soil water          下载免费PDF全文

Matthias Sprenger  Doerthe Tetzlaff  Jim Buttle  Sean K. Carey  James P. McNamara  Hjalmar Laudon  Nadine J. Shatilla  Chris Soulsby 《水文研究》2018,32(12):1720-1737

Quantifying soil water storage, mixing, and release via recharge, transpiration, and evaporation is essential for a better understanding of critical zone processes. Here, we integrate stable isotope (²H and ¹⁸O of soil water, precipitation, and groundwater) and hydrometric (soil moisture) data from 5 long‐term experimental catchments along a hydroclimatic gradient across northern latitudes: Dry Creek (USA), Bruntland Burn (Scotland), Dorset (Canada), Krycklan (Sweden), and Wolf Creek (Canada). Within each catchment, 6 to 11 isotope sampling campaigns occurred at 2 to 4 sampling locations over at least 1 year. Analysis for ²H and ¹⁸O in the bulk pore water was done for >2,500 soil samples either by cryogenic extraction (Dry Creek) or by direct equilibration (other sites). The results showed a similar general pattern that soil water isotope variability reflected the seasonality of the precipitation input signal. However, pronounced differences among sampling locations occurred regarding the isotopic fractionation due to evaporation. We found that antecedent precipitation volumes mainly governed the fractionation signal, temperature and evaporation rates were of secondary importance, and soil moisture played only a minor role in the variability of soil water evaporation fractionation across the hydroclimatic gradient. We further observed that soil waters beneath conifer trees were more fractionated than beneath heather shrubs or red oak trees, indicating higher soil evaporation rates in coniferous forests. Sampling locations closer to streams were more damped and depleted in their stable isotopic composition than hillslope sites, revealing increased subsurface mixing towards the saturated zone and a preferential recharge of winter precipitation. Bulk soil waters generally comprised a high share of waters older than 14 days, which indicates that the water in soil pores are usually not fully replaced by recent infiltration events. The presented stable isotope data of soil water were, thus, a useful tool to track the spatial variability of water fluxes within and from the critical zone. Such data provide invaluable information to improve the representation of critical zone processes in spatially distributed hydrological models.  相似文献   

Systematic GIS-based landslide inventory as the first step for effective landslide-hazard management   总被引：1，自引：1，他引：1  

A. Colombo  L. Lanteri  M. Ramasco  C. Troisi 《Landslides》2005,2(4):291-301

The purpose of the so-called IFFI project (Inventario dei Fenomeni Franosi in Italia—Inventory of Landslides in Italy) and of many other related activities carried out by the Centro Regionale per le Ricerche Territoriali e Geologiche of ARPA Piemonte (Agenzia Regionale per la Protezione Ambientale—Regional Agency for Environmental Protection), is to map all the existing landslides in Piemonte (including both results of monitoring data and available historical data). ARPA carried out new systematic surveys using airphoto interpretation and created a specific alphanumeric geological information systems (GIS)-based database to store and process all the collected data. In order to obtain proper landslide-hazard zoning, it is necessary to provide a landslide inventory and to define the relationship between landslides and geological setting. A landslide inventory represents a fundamental base of knowledge, is a very basic tool for land planning, and strongly helps the local authorities in their decision making.  相似文献