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11.
This study presents a review of recently recorded instability phenomena on the flysch slopes of Istria, Croatia. The northeastern part of the Istrian Peninsula, the so-called Gray Istria, is built of Paleogene flysch deposits, where instability phenomena are frequent and where a large number of landslides, with significant consequences, have been recorded over the past 35 years. Based on field investigations conducted for the purpose of remedial study design, a database of these landslides was created. An investigation of the documented landslides and their elements found some common features that enabled general conclusions about the conditions and causes of landslide occurrence. In total, 19 documented landslides have been analyzed as individual phenomena, and from the results of these analyses, general conclusions were drawn about sliding conditions and the main triggering factors. Geological conditions and processes on slopes where landslides occurred are shown in detail, and geotechnical properties have been systematically represented. The sliding conditions and dimensions of four recent landslide occurrences, specifically by type, have been described in detail and analyzed. 相似文献
12.
A. Šajnović K. Stojanović V. Simić G. S. Pevneva A. K. Golovko B. Jovančiećević 《Geochemistry International》2011,49(10):1022-1034
Liquid thermolysis products of various types of immature kerogen from sedimentary lacustrine rocks from the Valjevo-Mionica
basin in Serbia were studied to evaluate the generation potential of kerogen contained in the organic matter (OM) of the rocks,
determine the composition of the biomarkers and alkylaromatics in the liquid thermolysis products, and elucidate the effect
of Pt4+ and Ru3+ ions (which were added in the form of inorganic salts) on the yield and hydrocarbon composition of the liquid thermolysis
products. For this purpose, representative bitumen-free samples A and B of the sedimentary rocks were subjected to thermolysis
under various conditions. Rock A contains high amount of immature organic matter, which is dominated by kerogen type I/II
and was generated under strongly reduced sedimentation conditions at a high salinity. Sample B is poorer in immature OM than
sample A, and the OM of the former contains kerogen type II/III and was generated predominantly in a reduced environment.
The content of the liquid products and the concentrations of hydrocarbons obtained in the course of thermolysis of bitumen-free
sample A and the typical oil distribution of the biomarkers and alkylaromatics in the thermolysis products confirm a high
generation potential of OM in this rock. In all of our experiments on the thermolysis of bitumen-free sample B, the yield
of liquid products and hydrocarbons is low. According to the kerogen type, the thermolysis of this rock generates much gases.
The Pt4+ and Ru3+ ions (added in the form of simple inorganic salts) increased the yield of liquid (kerogen type I/II) and gaseous (kerogen
type II/III) products. During the thermolysis of various type of immature kerogen in the lacustrine sedimentary rocks at a
temperature of 400°C, the OM attained maturation corresponding to the early catagenesis level. Saturated biomarkers and alkylaomatics
in the thermolysis products of both samples display typical oil distributions. The type of the source OM most strongly affects
the composition of n-alkanes and alkylnaphthalenes. The metal ions used in this research served as catalysts for the methylation process during
the thermolysis of immature kerogen, regardless of its type. The effect of the Pt4+ and Ru3+ ions on other transformations of the hydrocarbons, for example, the destruction of high-molecular n-alkanes to low-molecular ones and on isomerization reactions in molecules of polycyclic biomarkers and alkylaromatics to
thermodynamically more stable isomers in the thermolysis products is controlled, first of all, by the type of the source OM. 相似文献
13.
Flow energy and channel adjustments in rills developed in loamy sand and sandy loam soils 总被引：1，自引：0，他引：1
The storms usually associated with rill development in nature are seldom prolonged, so development is often interrupted by interstorm disturbances, e.g. weathering or tillage. In laboratory simulated rainfall experiments, active rill development can be prolonged, and under these conditions typically passes through a period of intense incision, channel extension and bifurcation before reaching quasi‐stable conditions in which little form change occurs. This paper presents laboratory experiments with coarse textured soils under simulated rainfall which show how channel adjustment processes contribute to the evolution of quasi‐stability. Newly incised rills were stabilized for detailed study of links between rill configuration and flow energy. On a loamy sand, adjustment towards equilibrium occurred due to channel widening and meandering, whereas on a sandy loam, mobile knickpoints and chutes, pulsations in flow width and flow depth and changes in stream power and sediment discharge occurred as the channel adjusted towards equilibrium. The tendency of rill systems towards quasi‐stability is shown by changes in stream power values which show short‐lived minima. Differences in energy dissipation in stabilized rills indicate that minimization of energy dissipation was reached locally between knickpoints and at the downstream ends of rills. In the absence of energy gradients in knickpoints and chutes, stabilized rill sections tended toward equilibrium by establishing uniform energy expenditure. The study confirmed that energy dissipation increased with flow aspect ratio. In stabilized rills, flow acceleration reduced energy dissipation on the loamy sand but not on the sandy loam. On both soils flow deceleration tended to increase energy dissipation. Understanding how rill systems evolve towards stability is essential in order to predict how interruptions between storms may affect long‐term rill dynamics. This is essential if event‐based physical models are to become effective in predicting sediment transport on rilled hillslopes under changing weather and climatic conditions. Copyright © 2008 John Wiley and Sons, Ltd. 相似文献
14.
J. Skuljan J. B. Hearnshaw P. L. Cottrell 《Monthly notices of the Royal Astronomical Society》1999,308(3):731-740
A two-dimensional velocity distribution in the UV plane has been obtained for stars in the solar neighbourhood, using Hipparcos astrometry for over 4000 'survey' stars with parallaxes greater than 10 mas and radial velocities found in the Hipparcos Input Catalogue. In addition to the already known grouping characteristics (field stars plus young moving groups), the velocity distribution seems to exhibit a more complex structure characterized by several longer branches running almost parallel to each other across the UV plane. By using the wavelet transform technique to analyse the distribution, the branches are visible at relatively high significance levels of 90 per cent or higher. They are roughly equidistant with a separation of about 15 km s−1 for early-type stars and about 20 km s−1 for late-type stars, creating an overall quasi-periodic structure which can also be detected by means of a two-dimensional Fourier transform. This branch-like velocity distribution might be caused by the Galactic spiral structure. 相似文献
15.
I. A.Bond F.Abe R. J.Dodd J. B.Hearnshaw P. M.Kilmartin K.Masuda Y.Matsubara Y.Muraki S.Noda O. K. L.Petterson N. J.Rattenbury M.Reid To.Saito Y.Saito T.Sako J.Skuljan D. J.Sullivan T.Sumi S.Wilkinson R.Yamada T.Yanagisawa P. C. M.Yock 《Monthly notices of the Royal Astronomical Society》2002,331(2):L19-L23
Gravitational microlensing events of high magnification have been shown to be promising targets for detecting extrasolar planets. However, only a few events of high magnification have been found using conventional survey techniques. Here we demonstrate that high-magnification events can be readily found in microlensing surveys using a strategy that combines high-frequency sampling of target fields with on-line difference imaging analysis. We present 10 microlensing events with peak magnifications greater than 40 that were detected in real-time towards the Galactic bulge during 2001 by the Microlensing Observations in Astrophysics (MOA) project. We show that Earth-mass planets can be detected in future events such as these through intensive follow-up observations around the event peaks. We report this result with urgency as a similar number of such events are expected in 2002. 相似文献
16.
N. J. Rattenbury I. A. Bond J. Skuljan P. C. M. Yock 《Monthly notices of the Royal Astronomical Society》2002,335(1):159-169
Simulations of planetary microlensing at high magnification that were carried out on a cluster computer are presented. It was found that the perturbations owing to two-thirds of all planets occur in the time interval −0.5 t FWHM ,0.5 t FWHM with respect to the peak of the microlensing light curve, where t FWHM is typically ∼14 h. This implies that only this restricted portion of the light curve need be intensively monitored for planets – a very significant practical advantage. Nearly all planetary detections in high-magnification events will not involve caustic crossings. We discuss the issues involved in determining the planetary parameters in high magnification events. Earth-mass planets may be detected with 1-m class telescopes if their projected orbital radii lie within about 1.5–2.5 au. Giant planets are detectable over a much larger region. For multiplanet systems the perturbations caused by individual planets can be separated under certain conditions. The size of the source star needs to be determined independently, but the presence of spots on the source star is likely to be negligible, as is the effect of planetary motion during an event. 相似文献
17.
I. A. Bond N. J. Rattenbury J. Skuljan F. Abe R. J. Dodd J. B. Hearnshaw M. Honda J. Jugaku P. M. Kilmartin A. Marles K. Masuda Y. Matsubara Y. Muraki T. Nakamura G. Nankivell S. Noda C. Noguchi K. Ohnishi M. Reid To. Saito H. Sato M. Sekiguchi D. J. Sullivan T. Sumi M. Takeuti Y. Watase S. Wilkinson R. Yamada T. Yanagisawa P. C. M. Yock 《Monthly notices of the Royal Astronomical Society》2002,333(1):71-83
A search for extrasolar planets was carried out in three gravitational microlensing events of high magnification, MACHO 98–BLG–35 , MACHO 99–LMC–2 and OGLE 00–BUL–12 . Photometry was derived from observational images by the MOA and OGLE groups using an image subtraction technique. For MACHO 98–BLG–35 , additional photometry derived from the MPS and PLANET groups was included. Planetary modelling of the three events was carried out in a supercluster computing environment. The estimated probability for explaining the data on MACHO 98–BLG–35 without a planet is <1 per cent. The best planetary model has a planet of mass ∼(0.4–1.5)× M Earth at a projected radius of either ∼1.5 or ∼2.3 au. We show how multiplanet models can be applied to the data. We calculate exclusion regions for the three events and find that Jupiter-mass planets can be excluded with projected radii from as wide as about 30 au to as close as around 0.5 au for MACHO 98–BLG–35 and OGLE 00–BUL–12 . For MACHO 99–LMC–2 , the exclusion region extends out to around 10 au and constitutes the first limit placed on a planetary companion to an extragalactic star. We derive a particularly high peak magnification of ∼160 for OGLE 00–BUL–12 . We discuss the detectability of planets with masses as low as Mercury in this and similar events. 相似文献
18.
Charles J. Newell David T. Adamson Poonam R. Kulkarni Blossom N. Nzeribe John A. Connor Jovan Popovic Hans F. Stroo 《Ground Water Monitoring & Remediation》2021,41(4):76-89
Sites impacted by per- and polyfluoroalkyl substances (PFAS) pose significant challenges to investigation and remediation, including very low cleanup objectives, limited information on natural PFAS degradation processes in the subsurface, and the apparent mobility and persistence of PFAS. Consequently, monitored natural attenuation (MNA) may be considered less applicable to PFAS compared to biodegradable classes of chemicals such as petroleum hydrocarbons and chlorinated solvents that can completely biodegrade to innocuous end products. However, MNA has proven effective for certain non-degrading metals, metalloids, and radionuclides (e.g., chromium, arsenic, and uranium). To assess the applicability of MNA to PFAS, this paper reviews the fate and transport properties of PFAS in conjunction with the various physiochemical factors that control the subsurface movement of chemicals. This analysis demonstrates that two important retention processes: (1) chemical retention in the form of PFAS precursors, and (2) geochemical retention in the form of sorption and matrix diffusion to mitigate the movement and potential impacts of PFAS in groundwater that may form the scientific basis for applying MNA to PFAS contamination. This paper describes the scientific and regulatory basis for using MNA to manage PFAS-impacted groundwater. 相似文献
19.
K. Stojanović Br. Jovančićević Dr. Vitorovi G. S. Pevneva Ju. A. Golovko A. K. Golovko 《Geochemistry International》2007,45(8):781-797
Aiming at improved classification of crude oils, naphthalene and phenanthrene isomerization and dealkylation processes were
considered in detail as a possible basis to select new maturation parameters. Crude oils originating from the Banat depression
(Southeastern Pannonian Basin, Serbia) were used as objects of our study. Four new maturation parameters are proposed in this
paper. Two of them are based on dimethylnaphthalene (DMN) and trimethylnaphthalene (TMN) isomerization reactions: DNx = (1,3-DMN + 1,6-DMN)/(1,4-DMN + 1,5-DMN) and TNy = (1,3,6-TMN + 1,3,7-TMN)/(1,3,5-TMN + 1,4,6-TMN). The other two are based
on demethylation of dimethyl-and trimethylphenanthrenes (DMP and TMP) into corresponding methylphenanthrenes (MP): MDR = ΣMP/ΣDMP
and MTR = ΣMP/ΣTMP. The new parameters’ advantageous applicability was demonstrated by factor analysis, comparing them with
maturation parameters known from literature.
The text was submitted by the authors in English. 相似文献
20.
S. Noda M. Takeuti F. Abe I. A. Bond R. J. Dodd J. B. Hearnshaw M. Honda M. Honma J. Jugaku Y. Kan-ya Y. Kato P. M. Kilmartin Y. Matsubara K. Masuda Y. Muraki T. Nakamura K. Ohnishi M. Reid N. J. Rattenbury To. Saito Y. Saito H. Sato M. Sekiguchi J. Skuljan D. J. Sullivan T. Sumi R. Yamada T. Yanagisawa P. C. M. Yock M. Yoshizawa 《Monthly notices of the Royal Astronomical Society》2004,348(4):1120-1134