Possible Light-Time Effect in the Eclipsing Binary System TY Boo     

A. Elmaslı  S. O. Selam  B. Albayrak  D. Özuyar 《Astrophysics and Space Science》2006,304(1-4):189-190

The O − C diagram for the eclipsing binary system TY Boo was constructed with the new minima times observed at the Ankara University Observatory along with the collected ones from the literature. The O − C diagram shows a cyclic variation superimposed on a quadratic variation. The quadratic variation can be explained in terms of mass loss/exchange mechanism in the system while the cyclic variation is attributed to a possible light-time effect caused by a third body revolving around the close binary.  相似文献   

Hydrogeochemical and isotopic investigation of the Kolan geothermal field, southeastern Turkey     

Özlem Öztekin Okan  Bahattin Çetindağ 《Environmental Geology》2005,48(2):179-188

The Kolan geothermal field is located 24 km northwest of the Karakoçan area of Elaz city in southeastern Turkey. The Keban crystallized limestone of Permo-Carboniferous age is the oldest unit in the area. This unit is overlain by the middle-upper Eocene Krkgeçit formation consisting of conglomerate, sandstone, limestone and marl alternations. The youngest unit in the area is the Upper Miocene-Lower Pliocene Karabakr formation consisting of basalt, andesite and tuffs. Thermal Springs in the Kolan field issue along two major fault zones. The temperature of the hot springs is between 38°C and 45°C. Thermal waters in the area are heated by the geothermal gradient. The waters are classified as hot or very hot and as brackish waters. On the basis of International Association of Hydrogeologists Classification (IAH), waters are grouped as Ca–Na-HCO₃–CO₂-bearing thermal and mineral waters. Chemical analyses indicate a chemical composition of Ca>(Na+K)>Mg - HCO₃>SO₄>Cl. Saturation calculations reveal that the waters are oversaturated with respect to calcite, dolomite and aragonite while undersaturated with respect to gypsum, anhydrite and halite minerals. On the basis of ¹⁸O, ²H and ³H isotope data, Kolan waters are of meteoric origin, recharged from high elevations and then circulated deeply.  相似文献   

Chemical Weathering Rates, Erosion Rates and Mobility of Major and Trace Elements in a Boreal Granitic Till   总被引：1，自引：0，他引：1  

Magnus Land  Björn Öhlander 《Aquatic Geochemistry》2000,6(4):435-460

Chemical weathering rates and erosionrates of granitic till in northern Sweden have beenestimated. The present-day chemical weathering rate iscompared with the long-term average weathering ratesince the last deglaciation approximately 8,700 yearsago. Also, the present-day release rates of major andtrace elements due to chemical weathering are comparedwith the mobility of these elements in a spodosolprofile as shown by soil water samples from the vadozezone. The estimation of the past weathering rate isbased on elemental depletion trends in a soil profile(typic haplocryod), whereas the present weatheringrate is based on elemental input/output budgets in asmall catchment (9.4 km²). The long-term averagechemical erosion rate, expressed as the sum of majorelement oxides (SiO₂, Al₂O₃, CaO,Fe₂O₃, K₂O, MgO, MnO, Na₂O,P₂O₅, TiO₂), was estimated to be4.9 gm^-2 yr^-1. The long-term base cation(Ca²⁺, Mg²⁺, Na⁺, K⁺) depletionwas 0.325 keq ha^-1 yr^-1. The currentchemical erosion rate was estimated to be2.43.0 g ^-2 yr^-1, which is at least an order ofmagnitude higher than the rate of physical erosion,and the base cation flux due to chemical weathering is0.356–0.553~keq ha^-1 yr^-1. However,0.074 keq ha^-1 yr^-1 of this flux may be related tocation exchange processes induced by atmospheric inputof acid rain. There is no evidence for any recentlyincreased weathering rate of silicates in this area.The inputs of Cd, Cu, Ni and Zn exceed the outputs,and hence, these elements are currently accumulatingin the soil.There is a distinct seasonal variation in thechemical composition of the soil water. Results fromthe soil water samples show that Na, followed by Siand S (Cl was not measured), are the most mobileelements in the spodosol profile between the E-horizonand the C-horizon, and that Al and Fe were the leastmobile elements. However, there is no simplerelationship between the mobility of an element in thespodosol profile and the current release rate due toweathering of that element. This fact may haveimplications for the validity of the comparisonbetween the past and present weathering rates asperformed in this study.  相似文献   

Comets and the formation of planets     

Ernst J. Öpik 《Astrophysics and Space Science》1973,21(2):307-398

A morphological study of the physical and dynamical processes of planet formation is presented, with emphasis on the intermediary role of comet nuclei. Although guided by a particular model of the evolution of the pre-planetary solar nebula, implying the freezing-out of hydrogen in the region of the giant planets, the derivations and conclusions are of wider import, applicable to other cosmogonic models as well as to certain phases of star formation. The items evaluated physically, dynamically, or statistically comprise: (1) the total number mass of comets in Oort's cloud; (2) a re-evaluation of the diameters and masses of cometary nuclei; (3) the processes of nucleation from gravitational and Boltzmann instabilities of gaseous media to agglomerations of particulate matter as conditioned by inbuilt angular momentum; (4) the statistical-dynamical conditions and time scales of orbital interaction of comets with the planets and the consequences of disintegration.A consistent model proposes the formation of comets and planets in pre-planetary rings of the residual solar nebula, with subsequent ejection, chiefly by Jupiter, of the comets to Oort's sphere. Screening by absorbing matter is not only probable, but necessary to protect the comets from dis-integration during the process of ejection.Paper dedicated to Prof. H. C. Urey on the occasion of his 80th birthday on 29 April, 1973.This work has been currently supported by grants from the National Aeronautics and Space Administration, Goddard Space Flight Center, Greenbelt, Maryland.  相似文献   

On the insignificance of aluminium-borate complexes in aqueous solution     

Lars-Olof Öhman  Staffan Sjöberg 《Marine Chemistry》1985,17(1):91-97

The strength of complexation in the system H⁺Al³⁺B(OH)₃ has been studied. It is shown, on the basis of three independent types of measurement (H⁺ potentiometry, ²⁷Al NMR and ¹¹B NMR), that no, or at least very weak, aluminium-borate complexes form. An apparent solubility for freshly precipitated Al(OH)₃(s) is reported.  相似文献   

Formation and composition of cemented layers in low-sulphide mine tailings, Laver, northern Sweden     

Lena Alakangas  Björn Öhlander 《Environmental Geology》2006,50(6):821-819

Cemented layers (hardpans) are common in carbonate or sulphide-rich mine tailings and where pyrrhotite is the predominating Fe-sulphide. Laver, northern Sweden, is an abandoned Cu-mine where the tailings have low pyrrhotite content, almost no pyrite and no carbonates. Two cemented layers at different locations in the Laver tailings impoundment were investigated, with the aim to determine their effects on metal mobility. The cementing agents were mainly jarosite and Fe-oxyhydroxides in the layer formed where the tailings have a barren surface, whereas only Fe-oxyhydroxides were identified below grass-covered tailings surface. Arsenic was enriched in both layers which also exhibit high concentrations of Mo, V, Hg and Pb compared to unoxidised tailings. Sequential extraction indicates that these metals and As were mainly retained with crystalline Fe-oxides, and therefore potentially will be remobilised if the oxic conditions become more reducing, for instance as a result of remediation of the tailings impoundment.An erratum to this article can be found at  相似文献   

Some views on land ownership in urban planning and housing production in Sweden     

Ella Ödmann 《Geoforum》1973,4(1):31-41

Urbanisation is a functional change in land utilisation which requires a high degree of coordination in time and space. Swedish society has not considered it possible to entrust this coordination to the free market forces. A number of measures was introduced during the latter part of the sixties with a view to coordinating housing development by means of local authority-land ownership and preventing land speculation. In a recently published report of a Government Commission it is proposed that dwellings receiving Government housing loans (more than 90 % of building construction) shall only be built on land which is owned by the local authorities. The local authorities may then be assumed to be the only purchasers of land for housing development purposes. Their housing policy can be given a more short-term character and can be better adapted to urban planning. Urban development in Sweden during recent decades is characterised by a struggle between the two groups of our mixed-economy society, i. e., a social democratic government, and capitalistic enterprise. As far as the private individual is concerned, both parties are remote decision makers. The important question is whether an improvement in town environment may be expected before the private individual has been given a chance to influence planning. The relationship between housing development and land ownership in some Swedish towns over the period 1950–1970 is presented as an example of the realization of land policy.  相似文献   

Zur Tektonik im Bereich der Brennerlinie     

Dr. Hansgeorg FÖrster  Dipl.-Min. Annemarie Schmitz-Wiechowski 《International Journal of Earth Sciences》1970,59(2):637-648

Zusammenfassung Die Verfasser entwickeln aus den Ergebnissen ihrer feldgeologischen und petrographischen Untersuchungen — gestützt auf gesteinsmechanische Überlegungen und tektonische Experimente — ein neues geologisches Konzept für das Tauernwestende.

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A new concept about the geology of the Brenner region is developed from field observations, petrographic investigations, mechanic considerations and tectonic experiments.

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Résumé Les auteurs présentent une conception géologique nouvelle de la partie occidentale des Tauern d'après leurs observations géologiques sur le terrain et leurs recherches pétrographiques, en s'appuyant sur des considérations de la mécanique des roches et des expériences tectoniques.

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FrauSchmitz-Wiechowski (Wiechowski 1968) hat die Phyllitserie östlich des Brenner untersucht und tektonische Grenzflächen verfolgt.Förster bearbeitete hauptsächlich das Gebiet westlich des Brenner.  相似文献   

Evaluation of the twenty-first century RCM simulations driven by multiple GCMs over the Eastern Mediterranean–Black Sea region     

Barış Önol  Deniz Bozkurt  Ufuk Utku Turuncoglu  Omer Lutfi Sen  H. Nuzhet Dalfes 《Climate Dynamics》2014,42(7-8):1949-1965

In this study, human-induced climate change over the Eastern Mediterranean–Black Sea region has been analyzed for the twenty-first century by performing regional climate model simulations forced with large-scale fields from three different global circulation models (GCMs). Climate projections have been produced with Special Report on Emissions Scenarios A2, A1FI and B1 scenarios, which provide greater diversity in climate information for future period. The gradual increases for temperature are widely apparent during the twenty-first century for each scenario simulation, but ECHAM5-driven simulation generally has a weaker signal for all seasons compared to CCSM3 simulations except for the Fertile Crescent. The contrast in future temperature change between the winter and summer seasons is very strong for CCSM3-A2-driven and HadCM3-A2-driven simulations over Carpathians and Balkans, 4–5 °C. In addition, winter runoff over mountainous region of Turkey, which feeds many river systems including the Euphrates and Tigris, increases in second half of the century since the snowmelt process accelerates where the elevation is higher than 1,500 m. Moreover, analysis of daily temperature outputs reveals that the gradual decrease in daily minimum temperature variability for January during the twenty-first century is apparent over Carpathians and Balkans. Analysis of daily precipitation extremes shows that positive trend is clear during the last two decades of the twenty-first century over Carpathians for both CCSM3-driven and ECHAM5-driven simulations. Multiple-GCM driven regional climate simulations contribute to the quantification of the range of climate change over a region by performing detailed comparisons between the simulations.  相似文献   

Multipurpose agroforestry as a climate change resiliency option for farmers: an example of local adaptation in Vietnam     

Quan Nguyen  Minh Ha Hoang  Ingrid Öborn  Meine van Noordwijk 《Climatic change》2013,117(1-2):241-257

Increasing frequency, intensity and duration of severe weather events are posing major challenges to global food security and livelihoods of rural people. Agriculture has evolved through adaptation to local circumstances for thousands of years. Local experience in responding to severe weather conditions, accumulated over generations and centuries, is valuable for developing adaptation options to current climate change. This study aimed to: (i) identify tree species that reduce vulnerability of cropping systems under climate variability; and (ii) develop a method for rapidly assessing vulnerability and exploring strategies of smallholder farmers in rural areas exposed to climate variability. Participatory Rural Appraisal methods in combination with Geographical Information Systems tools and statistical analysis of meteorological data were used to evaluate local vulnerability to climate change and to investigate local adaptation measures in two selected villages in Vietnam, one of the countries most vulnerable to climate change. The low predictability of severe weather events makes food crops, especially grain production, insecure. This study shows that while rice and rain-fed crops suffered over 40 % yield losses in years of extreme drought or flood, tree-based systems and cattle were less affected. 13 tree species performed well under the harsh local climate conditions in home and forest gardens to provide income, food, feed and other environmental benefits. Thus, this research suggests that maintenance and enhancement of locally evolved agroforestry systems, with high resilience and multiple benefits, can contribute to climate change adaptation.  相似文献