Cosmogenic nuclides in the Košice meteorite: Experimental investigations and Monte Carlo simulations          下载免费PDF全文

Pavel P. Povinec  Jozef Masarik  Ivan Sýkora  Andrej Kováčik  Juraj Beňo  Matthias M. M. Meier  Rainer Wieler  Matthias Laubenstein  Vladimir Porubčan 《Meteoritics & planetary science》2015,50(5):880-892

Results of nondestructive gamma‐ray analyses of cosmogenic radionuclides (⁷Be, ²²Na, ²⁶Al, ⁴⁶Sc, ⁴⁸V, ⁵⁴Mn, ⁵⁶Co, ⁵⁷Co, ⁵⁸Co, and ⁶⁰Co) in 19 fragments of the Ko?ice meteorite are presented and discussed. The activities varied mainly with position of fragments in the meteoroid body, and with fluxes of cosmic‐ray particles in the space affecting radionuclides with different half‐lives. Monte Carlo simulations of the production rates of ⁶⁰Co and ²⁶Al compared with experimental data indicate that the pre‐atmospheric radius of the meteoroid was 50 ± 5 cm. In two Ko?ice fragments, He, Ne, and Ar concentrations and isotopic compositions were also analyzed. The noble‐gas cosmic‐ray exposure age of the Ko?ice meteorite is 5–7 Myr, consistent with the conspicuous peak (or doublet peak) in the exposure age histogram of H chondrites. One sample likely contains traces of implanted solar wind Ne, suggesting that Ko?ice is a regolith breccia. The agreement between the simulated and observed ²⁶Al activities indicate that the meteoroid was mostly irradiated by a long‐term average flux of galactic cosmic rays of 4.8 particles cm^?2 s^?1, whereas the short‐lived radionuclide activities are more consistent with a flux of 7.0 protons cm^?2 s^?1 as a result of the low solar modulation of the galactic cosmic rays during the last few years before the meteorite fall.  相似文献   

MOL-D: A Collisional Database and Web Service within the Virtual Atomic and Molecular Data Center     

V. Vujčič  D. Jevremović  A. A. Mihajlov  Lj. M. Ignjatović  V. A. Srećković  M. S. Dimitrijević  M. Malović 《Journal of Astrophysics and Astronomy》2015,36(4)

MOL-D database is a collection of cross-sections and rate coefficients for specific collisional processes and a web service within the Serbian Virtual Observatory (SerVO) and the Virtual Atomic and Molecular Data Center (VAMDC). This database contains photo-dissociation cross-sections for the individual ro-vibrational states of the diatomic molecular ions and rate coefficients for the atom-Rydberg atom chemi-ionization and inverse electron–ion–atom chemi-recombination processes. At the moment it contains data for photodissociation cross-sections of hydrogen H\(_{2}^{+}\) and helium He\(_{2}^{+}\) molecular ions and the corresponding averaged thermal photodissociation cross-sections. The ro-vibrational energy states and the corresponding dipole matrix elements are provided as well. Hydrogen and helium molecular ion data are important for calculation of solar and stellar atmosphere models and for radiative transport, as well as for kinetics of other astrophysical and laboratory plasma (i.e. early Universe).  相似文献   

Inverse Bremsstrahlung in Astrophysical Plasmas: The Absorption Coefficients and Gaunt Factors     

A. A. Mihajlov  V. A. Srećković  N. M. Sakan 《Journal of Astrophysics and Astronomy》2015,36(4)

The electron–ion inverse Bremsstrahlung is considered here as a factor of the influence on the opacity of the different stellar atmospheres and other astrophysical plasmas. It is shown that this process can be successfully described in the frames of cut-off Coulomb potential model within the regions of the electron densities and temperatures. The relevant quantum mechanical method of the calculation of the corresponding spectral coefficient processes is described and discussed. The results obtained for the plasmas with the electron densities from 10¹⁴ cm ^?3 to 2?10¹⁹ cm ^?3 and temperatures from 5?10³ K to 3?10⁴ K in the wavelength region 100 nm<λ<3000 nm are presented. Also, these results can be of interest for different laboratory plasmas.  相似文献   

Cellular energy allocation in mussels (Mytilus galloprovincialis) from the stratified estuary as a physiological biomarker     

Erk M  Ivanković D  Strižak Ž 《Marine pollution bulletin》2011,62(5):1124-1129

This study demonstrates the usefulness of cellular energy allocation (CEA) evaluations as a physiological biomarker to infer the occurrence of natural stress in native populations of mussels inhabiting the stratified estuary (Krka River estuary, Croatia). Sampling sites were selected based on their differences in the salinity and temperature. The CEA value was calculated as a ratio between available energy (E_a) and energy consumption (E_c). Generally, higher values of E_a were recorded in June than in November, which were especially evident in the storage components (carbohydrates and lipids), while the constitutive component (proteins) remained relatively constant. The highest E_c was recorded in mussels at estuarine site compared to coastal site, which may be caused by the energetically costly maintenance of osmotic balance. Decrease in CEA recorded in estuarine mussels may ultimately result in a lower amount of energy available for growth, reproduction, or defence against other stresses (e.g. pollution).  相似文献   

Distribution, magnitude and characterization of the toxicity of Ukrainian estuarine sediments     

Burgess RM  Konovets IM  Kipnis LS  Lyashenko AV  Grintsov VA  Petrov AN  Terletskaya AV  Milyukin MV  Povolotskii MI  Demchenko VY  Bogoslovskaya TA  Topkin YV  Vorobyova TV  Portis LM  Ho KT 《Marine pollution bulletin》2011,62(11):2442-2462

During the Soviet era, Ukraine was an important industrial and agricultural region of the Soviet Union. This industrial and agricultural activity resulted in contamination of Ukraine’s estuaries with legacy anthropogenic pollutants. Investigations on the toxicological effects of this estuarine contamination have been limited. For this research, we measured the toxicity of contaminated sediments from four Ukrainian estuaries to several aquatic organisms over 3 years. Sediment chemical analyses and whole sediment toxicity identification evaluations (TIEs) were also performed to determine the classes of contaminants contributing to toxicity. Toxic sediments were observed in several of the Ukrainian estuaries and chemical analyses of the sediments demonstrated anthropogenic contaminants were widely distributed. Contaminants were also detected in macrobenthic organisms collected from the sediments. Several lines of evidence, including TIEs, indicated hydrophobic organic chemicals (HOCs) were contributing substantially to observed toxicity. This information can guide environmental managers to prioritize portions of the estuaries requiring remediation.  相似文献   

The Elastic Strain Energy of Damaged Solids with Applications to Non-Linear Deformation of Crystalline Rocks     

Yariv?HamielEmail author  Vladimir?Lyakhovsky  Yehuda?Ben-Zion 《Pure and Applied Geophysics》2011,168(12):2199-2210

Laboratory and field data indicate that rocks subjected to sufficiently high loads clearly deviate from linear behavior. Non-linear stress–strain relations can be approximated by including third and higher-order terms of the strain tensor in the elastic energy expression (e.g., the Murnaghan model). Such classical non-linear models are successful for calculating deformation of soft materials, for example graphite, but cannot explain with the same elastic moduli small and large non-linear deformation of stiff rocks, such as granite. The values of the third (higher-order) Murnaghan moduli estimated from acoustic experiments are one to two orders of magnitude above the values estimated from stress–strain relations in quasi-static rock-mechanics experiments. The Murnaghan model also fails to reproduce an abrupt change in the elastic moduli upon stress reversal from compression to tension, observed in laboratory experiments with rocks, concrete, and composite brittle material samples, and it predicts macroscopic failure at stress levels lower than observations associated with granite. An alternative energy function based on second-order dependency on the strain tensor, as in the Hookean framework, but with an additional non-analytical term, can account for the abrupt change in the effective elastic moduli upon stress reversal, and extended pre-yielding deformation regime with one set of elastic moduli. We show that the non-analytical second-order model is a generalization of other non-classical non-linear models, for example “bi-linear”, “clapping non-linearity”, and “unilateral damage” models. These models were designed to explain the abrupt changes of elastic moduli and non-linearity of stiff rocks under small strains. The present model produces dilation under shear loading and other non-linear deformation features of the stiff rocks mentioned above, and extends the results to account for gradual closure of an arbitrary distribution of initial cracks. The results provide a quantitative framework that can be used to model simultaneously, with a small number of coefficients, multiple observed aspects of non-linear deformation of stiff rocks. These include, in addition to the features mentioned above, stress-induced anisotropy and non-linear effects in resonance experiments with damaged materials.  相似文献   

Effect of temperature on contents of essential highly unsaturated fatty acids in freshwater zooplankton     

Michail I. Gladyshev  Vitaliy P. Semenchenko  Olga P. Dubovskaya  Elena B. Fefilova  Olesia N. Makhutova  Zhanna F. Buseva  Nadezhda N. Sushchik  Vladimir I. Razlutskij  Ekaterina V. Lepskaya  Mariya A. Baturina  Galina S. Kalachova  Olga N. Kononova 《Limnologica》2011,41(4):339-347

In 11 lakes from cold and warm regions we studied the content of highly unsaturated fatty acids (HUFA) in seston (<130 μm) and crustacean zooplankton using gas chromatography–mass spectrometry. An increase of temperature correlated with a decrease of HUFA content in zooplankton. A multivariate canonical correlation analyses revealed, that the decrease of HUFA content was related with a decrease of per cent of copepods in zooplankton communities, which are known to have higher HUFA levels in their biomass, than cladocerans. This means that temperature primarily affected the HUFA levels indirectly, via changing of taxonomic structure of zooplankton community, while the homeoviscous adaptation of zooplankton individuals had comparatively lower importance. As found, water temperature was better predictor of HUFA contents of zooplankton, than the fatty acid composition of seston. Thus, it can be predicted, that a probable climate warming will decrease the content of the essential HUFA in freshwater zooplankton with possible negative consequences for animals of higher trophic levels.  相似文献   

Distal “impact” layers and global acidification of ocean water at the Cretaceous-Paleogene boundary (KPB)     

P. I. Premović 《Geochemistry International》2011,49(1):55-65

The KPB sections at Højerup in Denmark, Agost and Caravaca in Spain and El Kef in Tunisia and (elsewhere in the world) consists of a very thin reddish biogenic calcite-poor smectite-rich “impact” layer overlain by a thicker smectite-rich marl. The massive amount of impact-generated atmospheric CO₂ at KPB would have accumulated globally in the ocean surface, leading to acidification and CaCO₃ undersaturation. These chemical changes would have induced a low biocalcification of calcareous plankton and a high dissolution of their shells. The biocalcification/dissolution crises may have played a significant role for the low abundance of biogenic calcite in the “impact” layer of the marine boundary clays at Højerup, Agost, Caravaca and El Kef (and elsewhere in the world). Experimental data and observations indicate that the deposition of the “impact” layer probably lasted only a few decades at most.  相似文献   

An energy budget for the subtidal bivalve Modiolus barbatus (Mollusca) at different temperatures     

Ezgeta-Balić D  Rinaldi A  Peharda M  Prusina I  Montalto V  Niceta N  Sarà G 《Marine environmental research》2011,71(1):79-85

Clearance rates, respiration rates and food absorption efficiencies of the commercially interesting subtidal bivalve Modiolus barbatus were measured at different temperatures under laboratory conditions and scope for growth calculated. Clearance rates were highest at temperatures from 20 °C to 28 °C, whereas respiration rate was maximal at 9 °C and minimal at 26 °C. Highest mean values of absorbed energy occurred at 20 °C and 26 °C. Scope for growth trend had negative values at 9 °C, 15 °C and 28 °C and positive values at temperatures 20 °C and 26 °C. The profitable thermal window for M. barbatus to have energy sufficient for growth and reproduction corresponded to <5 months per year. Seawater temperature increases will potentially impact the eco-physiological responses of subtidal M. barbatus causing life history traits to change with important repercussions for subtidal biodiversity in the Mediterranean.  相似文献   

Loggerhead sea turtles (Caretta caretta) as bioturbators in neritic habitats: an insight through the analysis of benthic molluscs in the diet     

Bojan Lazar  Romana Gračan  Jelena Katić  Dušan Zavodnik  Andrej Jaklin  Nikola Tvrtković 《Marine Ecology》2011,32(1):65-74

Molluscs are a diverse and ubiquitous group of organisms which contribute to the formation of biogenic sediments and are one of the major prey taxa for the neritic‐stage loggerhead sea turtles (Caretta caretta) worldwide. Here we investigated to what degree molluscs contribute to the diet of individual turtles, and what role the feeding strategy of loggerheads might play in bioturbation, one of the key processes in nutrient transport in marine ecosystems. We performed a detailed analysis of benthic molluscs from the digestive tracts of 62 loggerhead sea turtles (curved carapace length: 25.0–85.4 cm) found in the Northern Adriatic Sea. From 50 of the turtles that contained benthic molluscs, we identified 87 species representing 40 families and three classes (Gastropoda, Bivalvia and Scaphopoda), including 72 new dietary records for loggerhead turtle. Most of the identified molluscs were small‐sized species (shell length ≤ 3 cm) and were often found in a subfossil condition. Their intake may be considered a byproduct of infaunal mining, while larger molluscs were mainly found crushed into smaller fragments. Through such foraging behaviour loggerheads actively rework sediments, increase the surface area of shells and the rate of shells disintegration, acting as bioturbators in this system. We conservatively estimate that loggerheads in the neritic zone of the Adriatic Sea bioturbate about 33 tonnes of mollusc shells per year, and hypothesize about the possible effects of bioturbation reduction on environmental changes in the Northern Adriatic ecosystem.  相似文献