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21.
22.
M. Bossolasco A. Caneva I. Dagnino A. Elena G. Flocchini 《Pure and Applied Geophysics》1972,100(1):174-184
Summary The diurnal and seasonal variation of the VLF sferics pulse rate recorded at Roburent, Northern Italy, on 27 kHz since 1966 is derived. By analyzing the sunrise effect, the minimum distance of the thunderstorm centers providing at that time an unperturbed behaviour of the sferics pulse rate is obtained: this distance varies in azimuth and with the seasons and lies between 600 and 1300 km. In the time of the equinoxes, however, it is more stable between 700 and 900 km. The role of the groundwave propagation, generated by thunderstorm center within a radius of less than 500 km, is emphasized.
Contribution No. 241 of the Istituto Geofisico e Geodetico, Università di Genova,Genoa, Italy. This work has been supported by a grant from the Consiglio Nazionale delle Ricerche (Comitato Nazionale per le Scienze Fisiche), Roma. 相似文献
Zusammenfassung Der Tagesgang und der Jahresgang der Sferics-Impulshäufigkeit werden abgeleitet. Diese Sferics-Häufigkeit ist seit 1966 auf 27 kHz in Roburent, in Nord-Italien, registriert worden. Der Mindestabstand der Gewitterherde, welche zur Zeit des Sonnenaufgangs ein ungestörte Bild der Impulshäufigkeit geben, wird mit Hilfe des Sonnenaufgangseffekts abgeleitet: der Abstand liegt — abhängig von der Jahreszeit und der Einfallsrichtung — zwischen 600 und 1300 km; jedoch bewegt er sich in dem engeren Rahmen zwischen 700 und 900 km zur Zeit der Tag-und Nachtgleichen. Betont wird die Rolle der Bodenwelle, welche von Gewitterherden in einem Abstand von weniger als 500 km erzeugt wird.
Contribution No. 241 of the Istituto Geofisico e Geodetico, Università di Genova,Genoa, Italy. This work has been supported by a grant from the Consiglio Nazionale delle Ricerche (Comitato Nazionale per le Scienze Fisiche), Roma. 相似文献
23.
Using the standard map as a model problem and in the spirit of cluster analysis we have studied the invariance of the distributions of different indicators introduced to detect and measure weak chaos. We show that the problem is less straightforward than expected and that, except for very strong chaotic dynamical systems, all the complexities (islands, sticking phenomena, cantori) of mixed Hamiltonian systems are reflected into the indicators of convergence towards invariant distributions. 相似文献
24.
25.
Mario Bossolasco Guiseppe Cicconi Ignazio Dagnino Antonio Elena Giuseppe Flocchini 《Pure and Applied Geophysics》1965,62(1):207-214
Summary The relationship, already found by the authors, between sunspot numbers and the solar constant, as deduced from the highest global irradiance values at noon, is here reexamined and confirmed. Some attempts at explanation and further inferences are presented. 相似文献
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27.
Elena Chernysheva Tatiana Khomutova Flavio Fornasier Tatiana Kuznetsova Alexandr Borisov 《山地科学学报》2018,15(6):1171-1185
The chemical properties and biological activities of soils were studied in the vicinity of the medieval settlement Podkumskoe-3 in the Kislovodsk basin (Northern Caucasus, Russia). Between the 5th and 8th centuries this area was ploughed regularly, but it was then abandoned up to the present day. It has been established that past human activity leads to soil undergoing significant transformations in terms of microbial communities and enzyme activity, and that such changes are maintained over long periods. Long-term manuring in the middle of the first millennium AD led to an increase in organic carbon content and the accumulation of nitrate nitrogen. Soils of ancient abandoned fields are associated with increases in microbial biomass, number of saprotrophic bacteria, urease activity, and fungal mycelium biomass. The observed changes in the microbiological and biochemical properties of soil were conditioned by secondary anthropogenically induced succession after the abandonment of arable lands. 相似文献
28.
Gas hydrate disturbance fabrics of southern Hydrate Ridge sediments (ODP Leg 204): Relationship with texture and physical properties 总被引:1,自引:0,他引:1
Elena Piñero Eulàlia Gràcia Francisca Martínez-Ruiz Juan Cruz Larrasoaña Alexis Vizcaino Gemma Ercilla 《Geo-Marine Letters》2007,27(2-4):279-288
Soupy and mousse-like fabrics are disturbance sedimentary features that result from the dissociation of gas hydrate, a process
that releases water. During the core retrieval process, soupy and mousse-like fabrics are produced in the gas hydrate-bearing
sediments due to changes in pressure and temperature conditions. Therefore, the identification of soupy and mousse-like fabrics
can be used as a proxy for the presence of gas hydrate in addition to other evidence, such as pore water freshening or anomalously
cool temperature. We present here grain-size results, mineralogical composition and magnetic susceptibility data of soupy
and mousse-like samples from the southern Hydrate Ridge (Cascadia accretionary complex) acquired during Leg 204 of the Ocean
Drilling Program. In order to study the relationship between sedimentary texture and the presence of gas hydrates, we have
compared these results with the main textural and compositional data available from the same area. Most of the disturbed analyzed
samples from the summit and the western flank of southern Hydrate Ridge show a mean grain size coarser than the average mean
grain size of the hemipelagic samples from the same area. The depositional features of the sediments are not recognised due
to disturbance. However, their granulometric statistical parameters and distribution curves, and magnetic susceptibility logs
indicate that they correspond to a turbidite facies. These results suggest that gas hydrates in the southern Hydrate Ridge
could form preferentially in coarser grain-size layers that could act as conduits feeding gas from below the BSR. Two samples
from the uppermost metres near the seafloor at the summit of the southern Hydrate Ridge show a finer mean grain-size value
than the average of hemipelagic samples. They were located where the highest amount of gas hydrates was detected, suggesting
that in this area the availability of methane gas was high enough to generate gas hydrates, even within low-permeability layers.
The mineralogical composition of the soupy and mousse-like sediments does not show any specific characteristic with respect
to the other samples from the southern Hydrate Ridge. 相似文献
29.
Eugene GUROV Elena GUROVA Yuri CHERNENKO Anatoly YAMNICHENKO 《Meteoritics & planetary science》2009,44(3):389-404
Abstract— The Obolon impact structure, 18 km in diameter, is situated at the northeastern slope of the Ukrainian Shield near its margin with the Dnieper‐Donets Depression. The crater was formed in crystalline rocks of the Precambrian basement that are overlain by marine Carboniferous and continental Lower Triassic deposits. The post‐impact sediments comprise marine Middle Jurassic (Bajocian and Bathonian) and younger Mesozoic and Cenozoic deposits. Today the impact structure is buried beneath an about 300‐meter‐thick sedimentary rock sequence. Most information on the Obolon structure is derived from two boreholes in the western part of the crater. The lowest part of the section in the deepest borehole is composed by allogenic breccia of crystalline basement rocks overlain by clast‐rich impact melt rocks and suevites. Abundant shock metamorphic effects are planar deformation features (PDFs) in quartz and feldspars, kink bands in biotite, etc. Coesite and impact diamonds were found in clast‐rich impact melt rocks. Crater‐fill deposits are a series of sandstones and breccias with blocks of sedimentary rocks that are covered by a layer of crystalline rock breccia. Crystalline rock breccias, conglomeratic breccias, and sandstones with crystalline rock debris have been found in some boreholes around the Obolon impact structure to a distance of about 50 km from its center. Those deposits are always underlain by Lower Triassic continental red clay and overlain by Middle Jurassic marine clay. The K‐Ar age of impact melt glasses is 169 Ma, which corresponds to the Middle Jurassic (Bajocian) age. The composition of crater‐fill rocks within the crater and sediments outside the Obolon structure testify to its formation under submarine conditions. 相似文献
30.
Giovanni MONEGATO Matteo MASSIRONI Elena MARTELLATO Giordano TEZA 《Meteoritics & planetary science》2011,46(12):1804-1813
Abstract– The Omeonga ring structure (D.R. Congo) shows a remarkable drainage pattern encircling an area up to 45 km wide and encompassing a central smoothed relief 20 km wide. This inner circular ridge is elevated about 70 m above the ring depression corresponding to the bed of the Unia River, which flows between the inner ridge and an outer irregular ridge. Landsat 7 ETM and ASTER DEM show that the structural characteristics resemble those of several wide impact structures known on Earth. Other geological modes of origin that could produce ring structures, such as magmatic activity, salt diapirism, and karst dissolution have been considered. However, after evaluating the regional stratigraphy, the distribution of volcanism, and morphometry, these processes seem to be rather unlikely. If of impact origin, the age of the Omeonga structure can be constrained to the Late Cretaceous‐Cenozoic according to the youngest units in which the ring structure was formed. 相似文献