The evolution of massive close binaries     

De Grève  J. P.  De Loore  C.  Van Dessel  E. L. 《Astrophysics and Space Science》1978,53(1):105-130

The results of evolutionary computations for massive binary systems (initial masses of the primary 10M ) with mass ratios between 0.3 and 0.8 are summarized and compared with observations in order to verify how far one can go with the conservative assumption of mass exchange. It is found that conservative mass exchange leads to acceptable first-order models of W-R and massive X-ray binaries. However, the comparison between this theory and observation reveals that for the observed systems (W-R and X-ray binaries) a preference exists for low intial mass ratios; moreover, the X-ray luminosities of the theoretical models are systematically too low, though this may be due to the adopted wind model. In addition, the influences of several parameters (distance between the components, chemical composition, primary mass, mass ratio and atmosphere) are examined. These parameters influence the remnant mass and any further evolution only marginally. Attention is also given to the effect on the system parameters of a supernova explosion of the remnant of the mass-losing component. For a large range of systems a disruption probability smaller than 25% is found.  相似文献   

New Generation of Probabilistic Seismic Hazard Assessment for the Area Cologne/Aachen Considering the Uncertainties of the Input Data     

G. Grünthal  R. Wahlström 《Natural Hazards》2006,38(1-2):159-176

A new earthquake catalogue for central, northern and northwestern Europe with unified M_w magnitudes, in part derived from chi-square maximum likelihood regressions, forms the basis for seismic hazard calculations for the Lower Rhine Embayment. Uncertainties in the various input parameters are introduced, a detailed seismic zonation is performed and a recently developed technique for maximum expected magnitude estimation is adopted and quantified. Applying the logic tree algorithm, resulting hazard values with error estimates are obtained as fractile curves (median, 16% and 84% fractiles and mean) plotted for pga (peak ground acceleration; median values for Cologne 0.7 and 1.2 m/s² for probabilities of exceedence of 10% and 2%, respectively, in 50 years), 0.4 s (0.8 and 1.5 m/s²) and 1.0 s (0.3 and 0.5 m/s²) pseudoacclerations, and intensity (I₀ = 6.5 and 7.2). For the ground motion parameters, rock foundation is assumed. For the area near Cologne and Aachen, maps show the median and 84% fractile hazard for 2% probability of exceedence in 50 years based on pga (maximum median value about 1.5 m/s²), and 0.4 s (>2 m/s²) and 1.0 s (about 0.8 m/s²) pseudoaccelerations, all for rock. The pga 84% fractile map also has a maximum value above 2 m/s² and shows similarities with the median map for 0.4 s. In all maps, the maximum values fall within the area 6.2–6.3° E and 50.8–50.9° N, i.e., east of Aachen.  相似文献   

Avalanche Risk During Backcountry Skiing – An Analysis of Risk Factors     

Harpa Grímsdóttir  David Mcclung 《Natural Hazards》2006,39(1):127-153

Skier-triggered avalanches are the main cause of avalanche accidents in backcountry skiing. The risk of accidents during backcountry skiing was analysed statistically and related to factors such as elevation level, aspect, stability rating and the time of the year. The analysis is based on a database about terrain usage and avalanche accidents from a large heli-skiing operator in Canada, which makes it possible to study the conditional probability of accidents given the recorded pattern of terrain usage. This study shows that the historical risk of accidentally triggering an avalanche greater than size 1 depends highly on the stability rating, with the highest risk occurring during “poor” stability. The risk is greater at high elevations, and it is lower during the late season than earlier on. Skier risk does not depend as much on aspect as may be indicated from avalanche data alone. However, it is relatively high in the N–NE–E sector. These factors are not independent of each other and therefore analyses of combined factors were also performed. Questionnaires and interviews were used to gain knowledge about the terrain selection of professional mountain guides. These results indicate that when selecting terrain, guides first look at the overall shape and size of the terrain, but avalanche history of terrain and inclination are also important factors. Finally, remarks in avalanche reports were analysed, and common human factors identified.  相似文献   

Palaeolimnology of Lake Piene-Kuuppalanlampi (Kurkijoki, Karelian Republic, Russia): isolation history, lake ecosystem development and long-term agricultural impact     

Juha Miettinen  Elisabeth Grönlund  Heikki Simola  Pertti Huttunen 《Journal of Paleolimnology》2002,27(1):29-44

The post-glacial history of Lake Pieni-Kuuppalanlampi, western Lake Ladoga region, was studied by means of stratigraphic pollen and diatom analyses. Diatoms were analysed to track the isolation history of the basin and the limnological effects of the early land-use phases indicated by pollen analysis. Chrysophycean stomatocysts and Isoëtes spores were also employed in the limnological reconstructions. Sediment dating was provided by six conventional radiocarbon dates.The lower part of the 370-cm long sediment sequence represents early Holocene, large lake conditions: the (freshwater) Yoldia and Ancylus stages of the Baltic basin, with a short-term lagoonal or isolation phase at the end of Yoldia. The basin was isolated due to Ancylus lake regression at 9785 cal B.P. For the small-lake sequence (0–250 cm) we used diatom inferences (WA-method) for hindcasting water chemistry. The post-isolation limnology of Pieni-Kuuppalanlampi reflects the development of vegetation on its small hill-top catchment. In its early development, the lake was mesotrophic, but became more acidic (pH about 6) and oligotrophic after the decline of temperate hardwood trees and the spread of spruce to the area after around 5000 B.P. The lake ecosystem appears to have reacted sensitively to agricultural land-use in the catchment from AD 400–800 onwards: inferred total phosphorus levels and pH both rise during these periods.  相似文献   

An Mw based earthquake Catalogue for central, northern and northwestern Europe using a hierarchy of magnitude conversions   总被引：3，自引：1，他引：3  

G. Grünthal  R. Wahlström 《Journal of Seismology》2003,7(4):507-531

Data from 25 local catalogues and 30special studies of earthquakes in central,northern and northwestern Europe have beenincorporated into a Databank. The dataprocessing includes discriminating eventtypes, eliminating fake events and dupletsand converting different magnitudes andintensities to M_w if this is not givenby the original source. The magnitudeconversion is a key task of the study andimplies establishment of regressionequations where no local relations exist.The Catalogue contains tectonic events fromthe Databank within the area44°N–72°N,25°W–32°E and the time period1300–1993. The lower magnitude level forthe Catalogue entries is setat M_w == 3.50. The area covered by thedifferent catalogues are associated withpolygons. Within each polygon only datafrom one or a small number of the localcatalogues, supplemented by data fromspecial studies, enter the Catalogue. Ifthere are two or more such catalogues orstudies providing a solution for an event,a priority algorithm selects one entry forthe Catalogue. Then M_w is calculatedfrom one of the magnitude types, or frommacroseismic data, given by the selectedentry according to another priority scheme.The origin time, location, M_w magnitude and reference are specified for eachentry of the Catalogue. So is theepicentral intensity, I₀, if providedby the original source. Following thesecriteria, a total of about 5,000earthquakes constitute the Catalogue.Although originally derived for the purposeof seismic hazard calculation within GSHAP,the Catalogue provides a data base for manytypes of seismicity and seismic hazardstudies.  相似文献   

Stratigraphy of the upper cretaceous and lower tertiary strata in the Tethyan Himalayas of Tibet (Tingri area,China)   总被引：26，自引：0，他引：26  

H. Willems  Z. Zhou  B. Zhang  K. -U. Gräfe 《International Journal of Earth Sciences》1996,85(4):723-754

The 1500-m-thick marine strata of the Tethys Himalaya of the Zhepure Mountain (Tingri, Tibet) comprise the Upper Albian to Eocene and represent the sedimentary development of the passive northern continental margin of the Indian plate. Investigations of foraminifera have led to a detailed biozonation which is compared with the west Tethyan record. Five stratigraphic units can be distinguished: The Gamba group (Upper Albian - Lower Santonian) represents the development from a basin and slope to an outer-shelf environment. In the following Zhepure Shanbei formation (Lower Santonian - Middle Maastrichtian), outer-shelf deposits continue. Pebbles in the top layers point to beginning redeposition on a continental slope. Intensified redeposition continues within the Zhepure Shanpo formation (Middle Maastrichtian - Lower Paleocene). The series is capped by sandstones of the Jidula formation (Danian) deposited from a seaward prograding delta plain. The overall succession of these units represents a sea-level high at the Cenomanian/Turonian boundary followed, from the Turonian to Danian, by an overall shallowing-upward megasequence. This is followed by a final transgression — regression cycle during the Paleocene and Eocene, documented in the Zhepure Shan formation (?Upper Danian - Lutetian) and by Upper Eocene continental deposits. The section represents the narrowing and closure of the Tethys as a result of the convergence between northward-drifting India and Eurasia. The plate collision started in the Lower Maastrichtian and caused rapid changes in sedimentation patterns affected by tectonic subsidence and uplift. Stronger subsidence and deposition took place from the Middle Maastrichtian to the Lower Paleocene. The final closure of remnant Tethys in the Tingri area took place in the Lutetian.  相似文献   

Effet du vieillissement des céramiques poreuses sur leur capacité à évaluer la concentration de pesticide en solution     

Nicolas Domange  Caroline Grégoire  Véronique Gouy  Michèle Tremolières 《Comptes Rendus Geoscience》2004,336(1):49-58

The soil solution sampling by ceramic cups allows pesticide transfer monitoring in the soil during long times. The ageing of material involves a bias in the sampling results. In laboratory, the comparison of two types of ceramic suction cups, new and installed in situ during four years, shows a modification of the hydrodynamic properties and a possible evolution of the adsorption capacity of the matrix. The passage rate, as well qualitative as quantitative, is better for the old material. Recommendations about site management are finally exposed. To cite this article: N. Domange et al., C. R. Geoscience 336 (2004).  相似文献   

Effects of deglaciation on the petrology and eruptive history of the Western Volcanic Zone,Iceland     

Deborah E. Eason  John M. Sinton  Karl Grönvold  Mark D. Kurz 《Bulletin of Volcanology》2015,77(6):1-27

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Floods and livelihoods: The impact of changing water resources on wetland agro-ecological production systems in the Tana River Delta,Kenya     

Crystele Leauthaud  Stéphanie Duvail  Olivier Hamerlynck  Jean-Luc Paul  Hubert Cochet  Judith Nyunja  Jean Albergel  Olivier Grünberger 《Global Environmental Change》2013,23(1):252-263

Wetlands are highly dynamic and productive systems that have been under increased pressure from changes in land use and water management strategies. In Eastern Africa, wetlands provide resources at multiple spatial and temporal levels through farming, fishing, livestock ownership and a host of other ecosystem services that sustain the local economy and individual livelihoods. As part of a broader effort to describe future development scenarios for East African coastal wetlands, this qualitative study focuses on understanding the processes by which river water depletion has affected local food production systems in Kenya's Tana River Delta over the past 50 years, and how this situation has impacted residents’ livelihoods and well-being. Interviews performed in six villages among various ethnic groups, geographical locations and resource profiles indicated that the agro-ecological production systems formerly in place were adapted to the river's dynamic flooding patterns. As these flooding patterns changed, the local population diversified and abandoned or adopted various farming, fishing and livestock-rearing techniques. Despite these efforts, the decrease in water availability affected each subcomponent of the production systems under study, which led to their collapse in the 1990s. Water depletion negatively impacted local human well-being through the loss of food security. The current study provides a detailed account of the dynamics of agro-ecological production systems facing the effects of river water depletion in a wetland-associated environment in Sub-Saharan Africa.  相似文献   

Exploring the spatial distribution patterns of South African Cape hakes using generalised additive models     

A Grüss  D Yemane  TP Fairweather 《African Journal of Marine Science》2016,38(3):395-409

We developed delta generalised additive models (GAMs) to predict the spatial distribution of different size classes of South African hakes, Merluccius capensis and M. paradoxus, using demersal trawl survey data and geographical (latitude and longitude) and environmental features (depth, temperature, bottom dissolved oxygen and sediment type). Our approach consists of fitting, for each hake size class, two independent models, a binomial GAM and a quasi-Poisson GAM, whose predictions are then combined using the delta method. Delta GAMs were validated using an iterative cross-validation procedure, and their predictions were then employed to produce distribution maps for the southern Benguela. Delta GAM predictions confirmed existing knowledge about the spatial distribution patterns of South African hakes, and brought new insights into the factors influencing the presence/absence and abundance of these species. Our GAM approach can be used to produce distribution maps for spatially explicit ecosystem models of the southern Benguela in a rigorous and objective way. Ecosystem models are critical features of the ecosystem approach to fisheries, and distribution maps constructed using our GAM approach will enable a reliable allocation of species biomasses in spatially explicit ecosystem models, which will increase trust in the spatial overlaps and, therefore, the trophic interactions predicted by these models.  相似文献