Evolution of the Radio Luminosities of the Tycho and Kepler Supernovae Remnants     

K. S. Stankevich  A. M. Aslanyan  V. P. Ivanov  R. M. Martirosyan  Ye. Terzian 《Astrophysics》2003,46(4):429-433

Radio emission of the historical supernovae remnants Tycho (SNR1572) and Kepler (SNR1604) and evolution of their luminosity are considered. Measurement data of secular luminosity decrease rate, obtained earlier by the authors, were corrected with account of variation in time of the flux density of the reference sources. As a result, it is found that the SNR1604 luminosity at 1667 MHz is weakening with an annual mean rate equal to (0.2 ± 0.07)%. The corresponding rate for SNR1572 is (0.47 ± 0.05)%. Since the radio luminosity evolution, as well as energy densities of magnetic field and relativistic electrons inside SNR1604 and SNR1572 are essentially different, these remnants should be considered as different types of supernovae. Bandiera classified SN1604 as type SNIb or SNII.  相似文献   

Assessment of mercury mobility and bioavailability by fractionation method in sediments from coastal zone inundated by the 26 December 2004 tsunami in Thailand     

Leonard Boszke  Artur Kowalski  Witold Szczuciński  Grzegorz Rachlewicz  Stanisław Lorenc  Jerzy Siepak 《Environmental Geology》2006,51(4):527-536

The 26 December 2004 tsunami covered significant portion of a coastal zone with a blanket of potentially contaminated sediments. In this report are presented results on mercury concentrations in sediments deposited by the tsunami in a coastal zone of Thailand. Since the total mercury concentrations are insufficient to assess mercury mobility and bioavailability in sediment, its fractionation was applied. Sediments were sampled within 50 days after the event and analyzed by sequential extraction method. The procedure of sequential extraction involved five subsequent stages performed with solutions of chloroform, deionized water, 0.5 M HCl, 0.2 M NaOH, and aqua regia. The mean concentration of total mercury in sediments was 119 ± 50 ng g⁻¹ dry mass (range 66–230). The fractionation revealed that mercury is mainly bound to the least bioavailable sulphides 75 ± 6% (range 62–86), organomercury compounds 14 ± 7% (range 4–26), and humic matter 9 ± 7% (range 1–27). The lowest contributions bring fractions of water-soluble mercury 0.8 ± 1.0% (range 0.1–3.6) and acid soluble mercury 0.9 ± 0.5% (range 0.2–2.1). Although, the total mercury content is similar in a reference sample and in the tsunami sediments, the highly toxic organomercury fraction contribution is higher in the latter. The results were compared with chemical and sedimentological properties of the sediments but no significant correlations were obtained between them.  相似文献   

Regional impact of the Armenian highland as an elevated heat source: ERA-Interim reanalysis and observations     

Artur Gevorgyan  Hamlet Melkonyan 《Climate Dynamics》2015,44(5-6):1541-1565

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Taxonomic analysis of the Quaternary archaeofauna found at The Lapa do Santo site,Lagoa Santa region,Brazil     

Artur Chahud  Gisele Ferreira Figueiredo  Gabriela Sartori Mingatos  Mercedes Okumura 《第四纪科学杂志》2021,36(7):1268-1278

The Lapa do Santo archaeological site, located in the Lagoa Santa region, Brazil, represents an important hunter-gatherer occupation dated from the Early and Middle Holocene. Prior studies of archaeofauna dating to this period are few and most of them only provide basic faunal identification with limited information on taphonomic processes. The main goal of this study is to identify the archaeofauna, record the taphonomic processes, and make inferences about its natural (interpreted as the death of the animal in the rockshelter area due to natural causes or due to predation) or anthropic origins. No extinct species (including megamastofauna) were identified. Taxonomic analysis indicated that most faunal remains consist of taxa that may be of mixed origin (natural or anthropic), such as microvertebrates and carnivorous mammals. The Cervidae are the main vertebrate family found in the studied material and these are likely the result of hunting. The Cervidae Ozotoceros support the presence of a fauna that is typical of savannah environments, although the assemblage contains mostly generalist fauna that can thrive in a variety of environments. Very few remains showed clear evidence for taphonomic processes related to human interaction, such as burnt bones.  相似文献   

The accuracy of standard enthalpies and entropies for phases of petrological interest derived from density-functional calculations     

Artur?BenisekEmail authorView author&#;s OrcID profile  Edgar?Dachs 《Contributions to Mineralogy and Petrology》2018,173(11):90

The internal energies and entropies of 21 well-known minerals were calculated using the density functional theory (DFT), viz. kyanite, sillimanite, andalusite, albite, microcline, forsterite, fayalite, diopside, jadeite, hedenbergite, pyrope, grossular, talc, pyrophyllite, phlogopite, annite, muscovite, brucite, portlandite, tremolite, and CaTiO₃–perovskite. These thermodynamic quantities were then transformed into standard enthalpies of formation from the elements and standard entropies enabling a direct comparison with tabulated values. The deviations from reference enthalpy and entropy values are in the order of several kJ/mol and several J/mol/K, respectively, from which the former is more relevant. In the case of phase transitions, the DFT-computed thermodynamic data of involved phases turned out to be accurate and using them in phase diagram calculations yields reasonable results. This is shown for the Al₂SiO₅ polymorphs. The DFT-based phase boundaries are comparable to those derived from internally consistent thermodynamic data sets. They even suggest an improvement, because they agree with petrological observations concerning the coexistence of kyanite?+?quartz?+?corundum in high-grade metamorphic rocks, which are not reproduced correctly using internally consistent data sets. The DFT-derived thermodynamic data are also accurate enough for computing the P–T positions of reactions that are characterized by relatively large reaction enthalpies (>?100 kJ/mol), i.e., dehydration reactions. For reactions with small reaction enthalpies (a few kJ/mol), the DFT errors are too large. They, however, are still far better than enthalpy and entropy values obtained from estimation methods.  相似文献   

Stochastic response of rigid foundations     

Artur Luna Pais  Eduardo Kausel 《地震工程与结构动力学》1990,19(4):611-622

While the study of kinematic interaction (i.e. the dynamic response of massless foundations to seismic loads) calls, in general, for advanced analytical and numerical techniques, an excellent approximation was proposed recently by Iguchi.^1,2 This approximation was used by the authors to analyse embedded foundations subjected to spatially random SH-wave fields, i.e. motions that exhibit some degree of incoherence. The wave fields considered ranged from perfectly coherent motions (resulting from seismic waves arriving from a single direction) to chaotic motions, resulting from waves arriving simultaneously from all directions. Additional parameters considered were the shape of the foundation (cylindrical or rectangular) and the degree of embedment. It was found that kinematic interaction usually reduces the severity of the motions transmitted to the structure, and that incoherent motions do not exhibit the frequency selectivity (i.e. narrow valleys in the foundation response spectra) that coherent motions do.  相似文献   

Icequakes and glacier motion: The hans glacier,spitsbergen     

Artur Cichowicz 《Pure and Applied Geophysics》1983,121(1):27-38

The recording of glacier icequakes has been carried out on the Hans glacier, Spitsbergen. The icequakes have been connected with the formation of open cracks. The energy of the main group of icequakes has ranged from 0.01 J to 6 J, their seismic moment being from 0.5 · 10¹⁴ dyne · cm to 26 · 10¹⁴ dyne · cm. The nonelastic volume increase corresponding to each crack has ranged from 0.2 · 10⁻² m³ to 8.8 · 10⁻² m³. The stresses released due to extensional faulting ranged from 25N/m² to 500 N/m²; these values are so small that they suggest an incomplete release of the medium. The contribution into the glacier flow rate of the deformation in the surface glacier layer due to extensional faulting is lower by 2 to 3 orders of magnitude than the total plastic deformation associated with the ice creeping.  相似文献   

Geology, coal quality, and resources of the Antaramut–Kurtan–Dzoragukh coal field, north-central Armenia     

Brenda S. Pierce  Artur Martirosyan  Gourgen Malkhasian  Samvel Harutunian  Grigory Harutunian 《International Journal of Coal Geology》2001,45(4):307

The Antaramut–Kurtan–Dzoragukh (AKD) coal deposit is a previously unrecognized coal field in north-central Armenia. Coal has been known to exist in the general vicinity since the turn of the century, but coal was thought to be restricted to a small (1 km²) area only near the village of Antaramut. However, through detailed field work and exploratory drilling, this coal deposit has been expanded to at least 20 km², and thus renamed the Antaramut–Kurtan–Dzoragukh coal field, for the three villages that the coal field encompasses. The entire coal-bearing horizon, a series of tuffaceous sandstones, siltstones, and claystones, is approximately 50 m thick. The AKD coal field contains two coal beds, each greater than 1 m thick, and numerous small rider beds, with a total resource of approximately 31,000,000 metric tonnes. The coals are late Eocene in age, high volatile bituminous in rank, relatively high in ash yield (approximately 40%, as-determined basis) and moderate in sulfur content (approximately 3%, as-determined basis). The two coal beds (No. 1 and No. 2), on a moist, mineral-matter-free basis, have high calorific values of 32.6 MJ/kg (7796 cal/g) and 36.0 MJ/kg (8599 cal/g), respectively. Coal is one of the few indigenous fossil fuel resources occurring in Armenia and thus, the AKD coal field could potentially provide fuel for heating and possibly energy generation in the Armenian energy budget.  相似文献   

Seismic quiescence before the M 7, 1988, Spitak earthquake, Armenia   总被引：7，自引：0，他引：7  

Max Wyss  & Artak H. Martirosyan 《Geophysical Journal International》1998,134(2):329-340

A detailed analysis of the 35  yr of seismicity between 1962 and 1997 using a gridding technique shows that the M 7, Spitak earthquake of 1988 December 7 was preceded by a quiescence anomaly that started at approximately 1984±0.5, and lasted about 5±0.5  yr, up to the main shock. This quiescence anomaly had a radius of about 20±3  km, estimated from circular areas with 75 per cent rate decrease, centred at the point of maximum significance of the anomaly. The quiescence was clearly present in the aftershock volume during the 5  yr before the 1988 main shock, but its statistically strongest expression was located 30  km NW of the epicentre. This anomaly fulfills the association rules between precursory quiescence anomalies and main shocks, even for a tight definition, and is therefore proposed as a case of precursory quiescence. The largest value of the standard deviate Z , found by random selection of samples by gridding, was Z =14 for a time window of T _w=3  yr, using a sample size of N =300 events. This makes this anomaly the strongest observed so far, and it is the first documented in an environment of continental collision. There are no false alarms exceeding in significance the precursor. The Armenian earthquake catalogue used for this study had 4600 earthquakes with M ≥ M _min=2.2 in the area bounded by 39.5° to 42°N/42.5° to 47°E. From the point of view of homogeneous reporting this is the best catalogue we have analysed so far. The limits of the data used and the density of the grid are dictated by the data, and have no influence on the results. The choice of free parameters does not influence the results significantly within the following limits: 100≤ N ≤500, 2≤ T _w≤7, 2.2≤ M _min≤2.8.  相似文献   

Everyday realities of climate change adaptation in Mozambique     

Luis Artur  Dorothea Hilhorst 《Global Environmental Change》2012,22(2):529-536

This paper analyzes discourses and practices of flood response and adaptation to climate change in Mozambique. It builds on recent publications on climate change adaptation that suggest that the successes and failures of adaptation highly depend on the cultural and political realms of societal perceptions and the sensitivity of institutions. To capture this, the paper adopted a multi-sited ethnographic approach. Acknowledging that there is no central locus of representation that can unveil the working of disaster response in Mozambique, the paper brings together five vignettes of research in different ‘sites’ of concern to the rise in floods in Mozambique. These are the politics of climate change adaptation at the national institutional level, societal responses to increased flooding, local people's responses to floods, the evacuation and resettlement programme following the 2007 flood. The paper finds how adaptation to climate change becomes part of everyday politics, how actors aim to incorporate responses into the continuation of their normal behavior and how elites are better positioned to take advantage of adaptation programmes than the vulnerable people that were targeted. It argues that climate change adaptation must be made consonant with historically grown and ongoing social and institutional processes. It concludes with lessons that the analysis and methodology of the research can provide for the practice of climate change adaptation.  相似文献