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991.
N. G. Cameron H. J. B. Birks V. J. Jones F. Berges J. Catalan R. J. Flower J. Garcia B. Kawecka K. A. Koinig A. Marchetto P. Sánchez-Castillo R. Schmidt M. Šiško N. Solovieva E. Štefková M. Toro 《Journal of Paleolimnology》1999,22(3):291-317
A modern diatom-pH calibration data-set consisting of surface-sediment diatom assemblages from 118 lakes and 530 taxa is presented. The AL:PE data-set is from high-altitude or high-latitude lakes in the Alps, Norway, Svalbard, Kola Peninsula, UK, Slovenia, Slovakia, Poland, Portugal, and Spain (pH range = 4.5-8.0; DOC range = 0.2-3.2 mg l-1). In addition, 92 epilithon samples from 22 high-altitude or high-latitude lakes comprise an AL:PE epilithon diatom-pH data-set. Weighted averaging partial least squares regression is used to develop pH-inference models. The AL:PE data-set has a root-mean-square-error of prediction (RMSEP) of 0.33 and a maximum bias of 0.36 pH units and r2 of 0.82, as assessed by leave-one-out cross-validation. The epilithon data-set has, after data-screening and the deletion of one very obvious outlier, a RMSEP of 0.23 and a maximum bias of 0.18 pH units and r2 of 0.88. The 167 sample SWAP diatom-pH data-set from lowland or upland lakes in the UK, Norway, and Sweden has a RMSEP of 0.29 and a maximum bias of 0.23 pH units and r2 of 0.86.The pH optima, as estimated by weighted averaging and Gaussian regression, are compared for the three data-sets (AL:PE, SWAP, AL:PE epilithon). There is a good correspondence between the AL:PE and the AL:PE epilithon optima, but a consistent bias between the AL:PE and SWAP optima, with the SWAP optima being lower than the AL:PE estimates.The predictive performances of the AL:PE and SWAP calibration data-sets are compared using independent test samples and six core sequences, all from high-altitude lakes, one in south-east Siberia and five in eastern Scotland. The results show the importance of using the AL:PE data-set for inferring lake-water pH from diatom assemblages in high-altitude or high latitude lakes with low DOC concentrations. 相似文献
992.
Plomerová Jaroslava Granet Michel Judenherc Sebasten Achauer Ulrich Babuška Vladislav Jedlička Petr Kouba Daniel Vecsey Luděk 《Studia Geophysica et Geodaetica》2000,44(2):195-209
We present the first results of a comparison of deep lithosphere structure of three Variscan massifs - the Armorican Massif, French Massif Central and Bohemian Massif, as revealed by recent tomographic studies of seismic anisotropy. The data originate from several field measurements made in temporary arrays of stations equipped with both short-period and broadband seismometers with digital recording. The study is based on teleseismic body waves and a joint inversion of anisotropic data (P-residual spheres, the fast shear-wave polarizations and split times) and demonstrates that the three Variscan massifs appear to consist of at least two parts with different orientation of large-scale fabric derived from seismic anisotropy. The boundaries of anisotropic lithospheric domains are related to prominent tectonic features recognised on the surface as sutures, shear zones or transfer fault zones, as well as grabens, thus indicating that some of them extend deep through the entire lithosphere. 相似文献
993.
V. Rušin 《Solar physics》2017,292(1):24
From observations of the solar white-light corona at 65 eclipses from 1851 to 2015 we confirm earlier findings that the flattening index of the white-light corona depends on the phase, rather than the magnitude of solar cycles, which is in contrast with behavior of other major solar activity indices like the sunspot number, the 2800 MHz radio flux, etc. This indicates that mechanisms responsible for creation and distribution of helmet streamers, the most essential coronal structures influencing the flattening index, could be of different magnetic nature from those of other manifestations of solar surface activity. 相似文献
994.
Mateja Dumbović Nandita Srivastava Yamini K. Rao Bojan Vršnak Andy Devos Luciano Rodriguez 《Solar physics》2017,292(8):96
Under the European Union 7th Framework Programme (EU FP7) project Coronal Mass Ejections and Solar Energetic Particles (COMESEP, http://comesep.aeronomy.be ), an automated space weather alert system has been developed to forecast solar energetic particles (SEP) and coronal mass ejection (CME) risk levels at Earth. The COMESEP alert system uses the automated detection tool called Computer Aided CME Tracking (CACTus) to detect potentially threatening CMEs, a drag-based model (DBM) to predict their arrival, and a CME geoeffectiveness tool (CGFT) to predict their geomagnetic impact. Whenever CACTus detects a halo or partial halo CME and issues an alert, the DBM calculates its arrival time at Earth and the CGFT calculates its geomagnetic risk level. The geomagnetic risk level is calculated based on an estimation of the CME arrival probability and its likely geoeffectiveness, as well as an estimate of the geomagnetic storm duration. We present the evaluation of the CME risk level forecast with the COMESEP alert system based on a study of geoeffective CMEs observed during 2014. The validation of the forecast tool is made by comparing the forecasts with observations. In addition, we test the success rate of the automatic forecasts (without human intervention) against the forecasts with human intervention using advanced versions of the DBM and CGFT (independent tools available at the Hvar Observatory website, http://oh.geof.unizg.hr ). The results indicate that the success rate of the forecast in its current form is unacceptably low for a realistic operation system. Human intervention improves the forecast, but the false-alarm rate remains unacceptably high. We discuss these results and their implications for possible improvement of the COMESEP alert system. 相似文献
995.
Caroline Aubry-Wake Lauren D. Somers Haley Alcock Aspen M. Anderson Amin Azarkhish Samuel Bansah Nicole M. Bell Kelly Biagi Mariana Castaneda-Gonzalez Olivier Champagne Anna Chesnokova Devin Coone Tasha-Leigh J. Gauthier Uttam Ghimire Nathan Glas Dylan M. Hrach Oi Yin Lai Pierrick Lamontagne-Hallé Nicolas R. Leroux Laura Lyon Sohom Mandal Bouchra R. Nasri Nataša Popović Tracy E. Rankin Kabir Rasouli Alexis Robinson Palash Sanyal Nadine J. Shatilla Brandon Van Huizen Sophie Wilkinson Jessica Williamson Majid Zaremehrjardy 《水文研究》2020,34(8):2001-2006
996.
Jaroslav Buša Miloš Rusnák Dávid Kušnirák Vladimír Greif Martin Bednarik René Putiška 《自然地理学》2020,41(2):169-194
ABSTRACTWe employed integrated methods to assess the landslide movement in Sv. Anton town in the Western Carpathians Neogene Volcanic Field (Central Slovakia). The integrated diagnostics required study of the landslide kinematic activity by a combination of Global Navigation Satellite Systems (GNSS) and Electrical Resistivity Tomography (ERT) imaging from November 2013 to March 2015. A topographic model with 2-cm accuracy was constructed from Unmanned Aerial Vehicles (UAV) photogrammetry. Continuous spatial datasets of movement and displacement field vectors were interpolated from the measured movements over the entire study period. Although deformation studies in Slovakia have a long-term tradition, complex interdisciplinary studies in urbanized areas are still lacking. This inspired our main objectives: to identify landslide kinematics and to reconstruct and define the rates of annual landslide movement obtained from geodetic measurement at the monitoring points. Our results demonstrate how landslide integrated diagnostics contribute to the detection of slope instability, with a maximum velocity of 60.82 mm/yr during the summer period. The precipitation effects are consistent with the Sv. Anton landslide displacement acceleration, and the following increases in total monthly precipitations are staggering compared to long-term monthly averages: July precipitation increased by 175.3%, August by 203.3%, and September by 198.1%. 相似文献
997.
Thermochronological insights into the structural contact between the Tian Shan and Pamirs,Tajikistan 下载免费PDF全文
Gilby Jepson Stijn Glorie Dmitry Konopelko Jack Gillespie Martin Danišík Noreen J. Evans Yunus Mamadjanov Alan S. Collins 《地学学报》2018,30(2):95-104
Multi‐method thermochronology along the Vakhsh‐Surkhob fault zone reveals the thermotectonic history of the South Tian Shan–Pamirs boundary. Apatite U/Pb analyses yield a consistent age of 251 ± 2 Ma, corresponding to cooling below ~550–350°C, related to the final closure of the Palaeo‐Asian Ocean and contemporaneous magmatism in the South Tian Shan. Zircon (U–Th–Sm)/He ages constrain cooling below ~180°C to the end of the Triassic (~200 Ma), likely related either to deformation induced by the Qiangtang collision or to the closure of the Rushan Ocean. Apatite fission track thermochronology reveals two low‐temperature (<120°C) thermal events at ~25 Ma and ~10 Ma, which may be correlated with tectonic activity at the distant southern Eurasian margin. The late Miocene cooling is confirmed by apatite (U–Th–Sm)/He data and marks the onset of mountain building within the South Tian Shan that is ongoing today. 相似文献
998.
Scott A. SANDFORD Saša BAJT Simon J. CLEMETT George D. CODY George COOPER Bradley T. DEGREGORIO Vanessa
De VERA Jason P. DWORKIN Jamie E. ELSILA George J. FLYNN Daniel P. GLAVIN Antonio LANZIROTTI Thomas LIMERO Mildred P. MARTIN Christopher J. SNEAD Maegan K. SPENCER Thomas STEPHAN Andrew WESTPHAL Sue WIRICK Richard N. ZARE Michael E. ZOLENSKY 《Meteoritics & planetary science》2010,45(3):406-433
Abstract– Numerous potential sources of organic contaminants could have greatly complicated the interpretation of the organic portions of the samples returned from comet 81P/Wild 2 by the Stardust spacecraft. Measures were taken to control and assess potential organic (and other) contaminants during the design, construction, and flight of the spacecraft, and during and after recovery of the sample return capsule. Studies of controls and the returned samples suggest that many of these potential sources did not contribute any significant material to the collectors. In particular, contamination from soils at the recovery site and materials associated with the ablation of the heatshield do not appear to be significant problems. The largest source of concern is associated with the C present in the original aerogel. The relative abundance of this carbon can vary between aerogel tiles and even within individual tiles. This C was fortunately not distributed among a complex mixture of organics, but was instead largely present in a few simple forms (mostly as Si‐CH3 groups). In most cases, the signature of returned cometary organics can be readily distinguished from contaminants through their different compositions, nonterrestrial isotopic ratios, and/or association with other cometary materials. However, some conversion of the carbon indigenous to the flight aerogel appears to have happened during particle impact, and some open issues remain regarding how this C may be processed into new forms during the hypervelocity impact collection of the comet dust. 相似文献
999.
The article draws a comparison between different ways of landslide geometry interpretation in the scope of the statistical
landslide hazard and risk assessment processing. The landslides are included as a major input variable, which are compared
with all of the input parametric factors. Based on the above comparison the input data are classified and the final map of
landslide susceptibility is constructed. Methodology of multivariate conditional analysis has been used for the construction
of final maps. Unique condition units was developed by combination of geological map (lithological units) and slope angle
map. Lithological units were derived from geological map and subsequently reclassified into 22 classes. Slope angle map was
calculated from digital elevation model (contour map at a scale 1:10,000) and reclassified into nine classes. As a case study,
a wide area of Horná Súča (western Slovakia) strongly affected by landsliding (predominantly made of Flysch) has been chosen.
Spatial data in the form of parametric maps, as well as final statistical data set were processed in GIS GRASS environment.
Four different approaches are used for landslides interpretation: (1) area of landslide body including accumulation zone,
(2) area of depletion zone, (3) lines of elongated main scarps, (4) lines of main scarp upper edge. For each approach, a zoning
map of landslide susceptibility was compiled and these were compared with each other. Depending on the interpretation approach,
the final susceptibility zones are markedly different (in tens of percent). 相似文献
1000.
The severe bora case that lasted from 13 to 15 November 2004 has been selected for the analysis of the bora of Pag’s ribs,
which occurs in the northern part of the eastern Adriatic coast over the Pag island area (Croatia). According to the measurements
from automatic stations, the MM5 numerical model is successful in the 10-min mean wind speed prediction at 10-m height. The
vertical analysis of the wind speed and potential temperature also gave satisfactory results. At the commencement of the bora
the modelled wind had a magnitude of 20ms−1 at 10-m height in the Pag island area, which sharply attenuated in the cross direction and to the open sea. In this way the
model has proved successful in predicting the characteristics of the bora of Pag’s ribs. Potential vorticity (PV) at 600m
has lower values within PV banners than during the developed bora. The consequence is a strong jet emanating from the nearest
gap. The vertical cross-sections through the centre of the gap point out a permanent hydraulic-like flow. At the time of the
bora of Pag’s ribs the highest modelled turbulent kinetic energy is found in the jump-like region above the inversion and
within the boundary layer along the lower boundary, ranging from 6–8m2 s−2. It is concluded that the dissipation in the hydraulic jumps and the wave breaking regions are the reasons for PV generation. 相似文献