Thermal history of inter-cluster relativistic electron gas heated by quasars     

Flavio I. M. Pereira  Ives Do Monte Lima 《Astrophysics and Space Science》1989,158(2):265-279

The thermal evolution of an inter-cluster gas of relativistic electrons heated by quasars with redshifts up toz=3 and 4 is studied in the framework of a Friedmann-Robertson-Walker universe. The gas cools by Compton scattering with the microwave backgroud radiation and by adiabatic cooling due to the universe expansion. Power and exponential laws of cosmological evolution of the comoving density of sources are considered. The obtained temperatures are sensitive to the form of these laws and to the heating epochs. Compared to the nonrelativistic models, the results obtained in the case of the power law present strong differences. These differences decrease when the exponential law is considered. Thermalization times are compared to the characteristic time of variation of the universe energy density and to the time-scales of energy loss by bremsstrahlung radiation and by Compton scattering. It is shown that, in some cases, nonequilibrium effects may be important. The time delay effects in the propagation of electromagnetic waves in cosmic plasma are shown to be very important for the analysis of theoretical models.  相似文献   

Short‐term flood inundation prediction using hydrologic‐hydraulic models forced with downscaled rainfall from global NWP          下载免费PDF全文

Do Hoai Nam  Dang Thanh Mai  Keiko Udo  Akira Mano 《水文研究》2014,28(24):5844-5859

A short‐term flood inundation prediction model has been formulated based on the combination of the super‐tank model, forced with downscaled rainfall from a global numerical weather prediction model, and a one‐dimensional (1D) hydraulic model. Different statistical methods for downscaled rainfall have been explored, taking into account the availability of historical data. It has been found that the full implementation of a statistical downscaling model considering physically‐based corrections to the numerical weather prediction model output for rainfall prediction performs better compared with an altitudinal correction method. The integration of the super‐tank model into the 1D hydraulic model demonstrates a minimal requirement for the calibration of rainfall–runoff and flood propagation models. Updating the model with antecedent rainfall and regular forecast renewal has enhanced the model's capabilities as a result of the data assimilation processes of the runoff and numerical weather prediction models. The results show that the predicted water levels demonstrate acceptable agreement with those measured by stream gauges and comparable to those reproduced using the actual rainfall. Moreover, the predicted flood inundation depth and extent exhibit reasonably similar tendencies to those observed in the field. However, large uncertainties are observed in the prediction results in lower, flat portions of the river basin where the hydraulic conditions are not properly analysed by the 1D flood propagation model. Copyright © 2013 John Wiley & Sons, Ltd.  相似文献   

Deciphering the weathering processes using environmental mineralogy and geochemistry: Towards an integrated model of laterite and podzol genesis in the Upper Amazon Basin     

Emmanuel Fritsch  Etienne Balan  Nadia Régina Do Nascimento  Thierry Allard  Marion Bardy  Guilherme Bueno  Sylvie Derenne  Adolpho José Melfi  Georges Calas 《Comptes Rendus Geoscience》2011,343(2-3):188-198

This article reports major results from collaborative research between France and Brazil on soil and water systems, carried out in the Upper Amazon Basin. It reveals the weathering processes acting in the partly inundated, low elevation plateaus of the Basin, mostly covered by evergreen forest. Our findings are based on geochemical data and mineral spectroscopy that probe the crystal chemistry of Fe and Al in mineral phases (mainly kaolinite, Al- and Fe-(hydr)oxides) of tropical soils (laterites). These techniques reveal crystal alterations in mineral populations of different ages and changes of metal speciation associated with mineral or organic phases. These results provide an integrated model of soil formation and changes (from laterites to podzols) in distinct hydrological compartments of the Amazon landscapes and under altered water regimes.  相似文献   

Seagrass colonization: Knock-on effects on zoobenthic community,populations and individual health     

V. Tu Do  Xavier de MontaudouinNicolas Lavesque  Hugues BlanchetHervé Guyard 《Estuarine, Coastal and Shelf Science》2011

This study provided evidence that Zostera noltii presence affects macrofauna community structure independently from median sediment grain-size and that the notion of ecosystem health is rather subjective: in the present case, we recorded “good health” in terms of seagrass development, “no impact” in terms of macrobenthic biotic indices and “negative effect” for a given key-population. The occurrence and development of a Z. noltii seagrass bed was surveyed at Banc d’Arguin, Arcachon Bay (France), to estimate the modification of the macrozoobenthic community and of the dynamics of a key-population for the local ecosystem, – the cockle Cerastoderma edule. Even though median grain-size of the sediment decreased only at the very end of the survey, i.e. when seagrass totally invaded the area, most of the macrofauna community characteristics (such as abundance and biomass) increased as soon as Z. noltii patches appeared. The structure of the macrofauna community also immediately diverged between sand and seagrass habitats, without however modifying the tested biotic indices (BENTIX, BOPA, AMBI). The health of the cockle population (growth, abundance, recruitment) was impacted by seagrass development. Related parasite communities slowly diverged between habitats, with more parasites in the cockles from seagrass areas. However, the number of parasites per cockle was always insufficient to alter cockle fitness.  相似文献   

PRIMARY STUDY OF SULFATE AND CARBONACEOUS AEROSOLS IN BEIJING     

Su Weihan  Zhang Qiupeng  Song Wenzhi  R. L. Do  R. D. Giauque  T. Novakov 《大气科学进展》1987,4(2):225-232

Results of our aerosol study, performed during 1983–1984 in Beijing, demonstrate that ambient carbonaceous aerosols are derived mainly from coal combustion. Different SO₂ oxidation processes have been observed in summer and winter. The winter sulfate appears to be produced locally and associated with products of incomplete combustion.  相似文献   

Predicting water flow in fully and partially saturated porous media: a new fractal-based permeability model     

A.  Nguyen Van Nghia  Jougnot  Damien  Thanh  Luong Duy  Van Do  Phan  Thuy  Tran Thi Chung  Hue  Dang Thi Minh  Hung  Nguyen Manh 《Hydrogeology Journal》2021,29(6):2017-2031

Hydrogeology Journal - Predicting the permeability of porous media in saturated and partially saturated conditions is of crucial importance in many geo-engineering areas, from water resources to...  相似文献   

The Use of Stable Sulfur, Oxygen and Hydrogen Isotope Ratios as Geochemical Tracers of Sulfates in the Podwiśniówka Acid Drainage Area (South-Central Poland)   总被引：1，自引：0，他引：1  

Zdzisław M. Migaszewski  Agnieszka Gałuszka  Artur Michalik  Sabina Dołęgowska  Andrzej Migaszewski  Stanisław Hałas  Andrzej Trembaczowski 《Aquatic Geochemistry》2013,19(4):261-280

The paper presents the results of determinations of stable S and O isotopes of dissolved sulfates and O and H stable isotopes of waters from three ponds, that is, Marczakowe Do?y acid pond, Marczakowe Do?y fish pond and Podwi?niówka acid pit pond, located in the Holy Cross Mountains (south-central Poland). The δ³⁴S_V-CDT and δ¹⁸O_V-SMOW of SO₄ ^2? in waters of three ponds (n = 14) varied from ?16.2 to ?9.5 ‰ (mean of ?13.6 ‰) and from ?8.1 to ?3.2 ‰ (mean of ?4.8 ‰), respectively. The mean δ³⁴S–SO₄ ^2? values were closer to those of pyrite (mean of ?25.4 ‰) and efflorescent sulfate salts (mean of ?25.6 ‰), recorded previously in the Podwi?niówka quarry, than to sulfates derived from other anthropogenic or soil and bedrock sources. The SO₄ ^2? ions formed by bacterially induced pyrite oxidation combined with bacterial (dissimilatory) dissolved sulfate reduction, and presumably with subordinate mineralization of carbon-bonded sulfur compounds, especially in both Marczakowe Do?y ponds. In addition, the comparison of δ¹⁸O–SO₄ ^2? and δ¹⁸O–H₂O values indicated that 75–100 % of sulfate oxygen was derived from water. Due to the largest size, the Podwi?niówka acid pit pond revealed distinct seasonal variations in both δ¹⁸O–H₂O (?9.2 to ?1.6) and δD–H₂O (?29.7 to ?71.3) values. The strong correlation coefficient (r ² = 0.99) was noted between δ¹⁸O–H₂O and δD–H₂O values, which points to atmospheric precipitation as the only source of water. The sediments of both acid ponds display different mineral inventory: the Marczakowe Do?y acid pond sediment consists of schwertmannite and goethite, whereas Podwi?niówka acid pit pond sediment is composed of quartz, illite, chlorite and kaolinite with some admixture of jarosite reflecting a more acidic environment. Geochemical modeling of two acid ponds indicated that the saturation indices of schwertmannite and nanosized ε-Fe₂O₃ (Fe³⁺ oxide polymorph) were closest to thermodynamic equilibrium state with water, varying from ?1.44 to 3.05 and from ?3.42 to 6.04, respectively. This evidence matches well with the obtained mineralogical results.  相似文献   

Terrestrial water dynamics in the lower Ganges—estimates from ENVISAT and GRACE   总被引：1，自引：0，他引：1  

Haris Hasan Khan  Arina Khan  Shakeel Ahmed  Marie-Claude Gennero  Kien Do Minh  Anny Cazenave 《Arabian Journal of Geosciences》2013,6(10):3693-3702

In this study, the hydrodynamics of lower Ganges basin in India has been monitored using radar altimetry data from environmental satellite (ENVISAT) mission and microgravity data from the Gravity Recovery and Climate Experiment (GRACE) mission. River stage time series have been constructed for different virtual stations on the lower Ganges. Time series for the integrated water volume changes from microgravity measurements have also been constructed to characterize the seasonal and interannual fluctuation patterns in water storage and flux. The ENVISAT dataset indicates an average seasonal river stage fluctuation of 8 m in the lower Ganges River. The GRACE dataset reveals a seasonal fluctuation ranging from 0.18 to 0.40 m in the vertically integrated total water storage in the lower Ganges basin. The two independent datasets show broad similarity in the lower Ganges basin and outline the importance of space-based techniques for monitoring continental water resources.  相似文献   

Period studies of classical Algol-type binaries II: UX Leo,RW Mon,EQ Ori,XZ UMa and AX Vul     

F. Soydugan  A. Erdem  S.S. Doğru  F. Aliçavuş  E. Soydugan  C. Çiçek  O. Demircan 《New Astronomy》2011,16(4):253-264

This study presents an investigation of the orbital period variations of five Algol type binaries, UX Leo, RW Mon, EQ Ori, XZ UMa and AX Vul based on all available minima times. The O–C diagrams of all systems exhibit a periodic variation superimposed on a downward parabolic segment. The mass loss due to magnetic braking effect in the cooler components is assumed to account for the parabolic variation with a downward shape, while it is suggested that the light-time effect (LITE) due to an unseen component around the eclipsing binaries explains the tilted sinusoidal changes in their O–C diagrams. The orbital period decrease rates for the systems are estimated as approximately between about 0.7 and 2.5 s per century. It is clearly seen that mass loss effect is more dominant than the expected mass transfer for classical Algols in this study. The minimum mass of the probable third bodies around the eclipsing pairs was calculated to be ?0.5 M_⊙ except for UX Leo, in which it was estimated to be approximately 0.9 M_⊙. In order to search for third lights in the light curves of five systems, the V-light curves of the systems were analyzed and their physical and photometric parameters were determined. For UX Leo, a significant third light contribution was determined. We found a very small third light that can be tested using multi-color light curves, for RW Mon, EQ Ori and XZ UMa, while a third light for AX Vul could not be exposed.  相似文献   

Ion-cyclotron waves in solar coronal hole     

S. Do?an  E.R. Pekünlü 《New Astronomy》2012,17(3):316-324

We investigate the effect of the plume/interplume lane (PIPL) structure of the solar polar coronal hole (PCH) on the propagation characteristics of ion-cyclotron waves (ICW). The gradients of physical parameters determined by SOHO and TRACE satellites both parallel and perpendicular to the magnetic field are considered with the aim of determining how the efficiency of the ICR process varies along the PIPL structure of PCH. We construct a model based on the kinetic theory by using quasi-linear approximation. We solve the Vlasov equation for O VI ions and obtain the dispersion relation of ICW. The resonance process in the interplume lanes is much more effective than in the plumes, agreeing with the observations which show the source of fast solar wind is interplume lanes. The solution of the Vlasov equation in PIPL structure of PCH, the physical parameters of which display gradients along and perpendicular direction to the external magnetic field, is thus obtained in a more general form than the previous investigations.  相似文献