The theory of geomagnetic induction     

Albert T. Price 《Physics of the Earth and Planetary Interiors》1973,7(3):227-233

The theoretical basis of electromagnetic induction methods in geophysics is considered with special reference to the interplay of physical ideas and mathematical arguments. The design of mathematical problems to elucidate observed physical phenomena, and methods of solving them, are discussed. Earth models suitable for various types of investigation are considered. The importance of getting the correct physical interpretation of the solution of a mathematical problem is stressed.  相似文献   

Sédimentation récifale rythmique dans le Jurassique superieur du Grand-Saleve (Haute-Savoie,France)     

Albert Carozzi 《International Journal of Earth Sciences》1955,43(2):433-446

Résumé L'étude statistique des composants minéraux et organiques, selon les méthodes de l'auteur, a été effectuée sur plus de 600 coupes minces régulièrement distribuées dans une série récifale de 225 m d'épaisseur. Elle a révélé des soulèvements et des subsidences encadrant des récifs et se traduisant par une succession de microfaciès clastiques dont les assemblages faunistiques sont très bien délimités au point de vue bathymétrique. Une comparaison avec les formations récifales actuelles est tentée sur la base des faunes périrécifales.  相似文献   

Tektonik und zyklische Sedimentation in der helvetischen Zone der Schweizer Alpen     

Albert Carozzi 《International Journal of Earth Sciences》1954,42(2):233-237

Zusammenfassung In der helvetischen Kreide scheint es also im ganzen so zu sein, daß die einfachen Rhythmen (Feinschichtung und Kalk-Mergel-Schichtwechsel) klimatisch, d. h. exogen, die Zyklen und Großzyklen tektonisch, d. h. endogen, begründet sind (3).  相似文献   

The dose-response relationship between No. 2 fuel oil and the growth of the salt marsh grass,Spartina alterniflora   总被引：1，自引：0，他引：1  

Lin Q  Mendelssohn IA  Suidan MT  Lee K  Venosa AD 《Marine pollution bulletin》2002,44(9):897-902

The effect of No. 2 fuel oil on the biomass production of the salt marsh plant, Spartina alterniflora, was studied in a greenhouse dose-response experiment. S. alterniflora were transplanted into soil with 10 dosage levels of No. 2 fuel oil ranging from 0 to 456 mg g(-1) dry soil. Three months after transplantation, values for plant biomass, stem density, and shoot height decreased significantly with increasing fuel oil level in a dose-response fashion. Evapo-transpiration rates were correlated with the total biomass response. Relative to the control, a significant decrease in total (above- plus below-ground) plant biomass was observed at concentrations above 57 mg g(-1) dry soil. Within the 3-month experimental period, detrimental effects on below-ground biomass accumulation and bioluminescence of the marine bacterium Viberio fisheri in the Microtox Solid Phase Test were observed at oil concentrations >29 mg g(-1) dry soil, suggesting that biological effects of oil within the sediment matrix may be more pronounced than on above-ground biomass, requiring a dosage 228 mg g(-1) dry soil to elicit a significant detrimental effect. Hence, measurements of oil effects with biological end-points based solely on above-ground responses may underestimate the potential impacts of petroleum hydrocarbon spills, especially when the oil has penetrated the soil. While S. alterniflora was proved to be relatively tolerant to the No. 2 fuel oil spills, its effectiveness in phytoremediation operations may be limited at fuel oil levels 228 mg g(-1) dry soil, as both plant growth and microbial activity may be constrained.  相似文献   

An Intercomparison of Large-Eddy Simulations of the Stable Boundary Layer   总被引：2，自引：27，他引：2  

Robert J. Beare  Malcolm K. Macvean  Albert A. M. Holtslag  Joan Cuxart  Igor Esau  Jean-Christophe Golaz  Maria A. Jimenez  Marat Khairoutdinov  Branko Kosovic  David Lewellen  Thomas S. Lund  Julie K. Lundquist  Anne Mccabe  Arnold F. Moene  Yign Noh  Siegfried Raasch  Peter Sullivan 《Boundary-Layer Meteorology》2006,118(2):247-272

Results are presented from the first intercomparison of large-eddy simulation (LES) models for the stable boundary layer (SBL), as part of the Global Energy and Water Cycle Experiment Atmospheric Boundary Layer Study initiative. A moderately stable case is used, based on Arctic observations. All models produce successful simulations, in as much as they generate resolved turbulence and reflect many of the results from local scaling theory and observations. Simulations performed at 1-m and 2-m resolution show only small changes in the mean profiles compared to coarser resolutions. Also, sensitivity to subgrid models for individual models highlights their importance in SBL simulation at moderate resolution (6.25 m). Stability functions are derived from the LES using typical mixing lengths used in numerical weather prediction (NWP) and climate models. The functions have smaller values than those used in NWP. There is also support for the use of K-profile similarity in parametrizations. Thus, the results provide improved understanding and motivate future developments of the parametrization of the SBL.  相似文献   

Carbon isotopic fractionation during a mesocosm bloom experiment dominated by Emiliania huxleyi: Effects of CO₂ concentration and primary production     

Albert Benthien  Ingrid Zondervan  Jens Hefter  Ulf Riebesell 《Geochimica et cosmochimica acta》2007,71(6):1528-1541

We investigated the effect of CO₂ and primary production on the carbon isotopic fractionation of alkenones and particulate organic matter (POC) during a natural phytoplankton bloom dominated by the coccolithophore Emiliania huxleyi. In nine semi-closed mesocosms (∼11 m³ each), three different CO₂ partial pressures (pCO₂) in triplicate represented glacial (∼180 ppmv CO₂), present (∼380 ppmv CO₂), and year 2100 (∼710 ppmv CO₂) CO₂ conditions. The largest shift in alkenone isotopic composition (4-5‰) occurred during the exponential growth phase, regardless of the CO₂ concentration in the respective treatment. Despite the difference of ∼500 ppmv, the influence of pCO₂ on isotopic fractionation was marginal (1-2‰). During the stationary phase, E. huxleyi continued to produce alkenones, accumulating cellular concentrations almost four times higher than those of exponentially dividing cells. Our isotope data indicate that, while alkenone production was maintained, the interaction of carbon source and cellular uptake dynamics by E. huxleyi reached a steady state. During stationary phase, we further observed a remarkable increase in the difference between δ¹³C of bulk organic matter and of alkenones spanning 7-12‰. We suggest that this phenomenon is caused mainly by a combination of extracellular release of ¹³C-enriched polysaccharides and subsequent particle aggregation induced by the production of transparent exopolymer particles (TEP).  相似文献   

Interpreting the Ca isotope record of marine biogenic carbonates     

Neil G. Sime  Edward T. Tipper  Albert Galy 《Geochimica et cosmochimica acta》2007,71(16):3979-3989

An 18 million year record of the Ca isotopic composition (δ^44/42Ca) of planktonic foraminiferans from ODP site 925, in the Atlantic, on the Ceara Rise, provides the opportunity for critical analysis of Ca isotope-based reconstructions of the Ca cycle. δ^44/42Ca in this record averages +0.37 ± 0.05 (1σ SD) and ranges from +0.21‰ to +0.52‰. The record is a good match to previously published Neogene Ca isotope records based on foraminiferans, but is not similar to the record based on bulk carbonates, which has values that are as much as 0.25‰ lower. Bulk carbonate and planktonic foraminiferans from core tops differ slightly in their δ^44/42Ca (i.e., by 0.06 ± 0.06‰ (n = 5)), while the difference between bulk carbonate and foraminiferan values further back in time is markedly larger, leaving open the question of the cause of the difference. Modeling the global Ca cycle from downcore variations in δ^44/42Ca by assuming fixed values for the isotopic composition of weathering inputs (δ^44/42Ca_w) and for isotope fractionation associated with the production of carbonate sediments (Δ_sed) results in unrealistically large variations in the total mass of Ca²⁺ in the oceans over the Neogene. Alternatively, variations of ±0.05‰ in the Ca isotope composition of weathering inputs or in the extent of fractionation of Ca isotopes during calcareous sediment formation could entirely account for variations in the Ca isotopic composition of marine carbonates. Ca isotope fractionation during continental weathering, such as has been recently observed, could easily result in variations in δ^44/42Ca_w of a few tenths of permil. Likewise a difference in the fractionation factors associated with aragonite versus calcite formation could drive shifts in Δ_sed of tenths of permil with shifts in the relative output of calcite and aragonite from the ocean. Until better constraints on variations in δ^44/42Ca_w and Δ_sed have been established, modeling the Ca²⁺ content of seawater from Ca isotope curves should be approached cautiously.  相似文献   

The Dark Matter Problem     

Albert Bosma 《Celestial Mechanics and Dynamical Astronomy》1998,72(1-2):69-90

In these notes I will briefly summarize our knowledge about the dark matter problem, and emphasize the corresponding dynamical aspects. This covers a wide area of research, so I have been selective, and have concentrated on the subject of dark matter in nearby galaxies, in particular spirals. This revised version was published online in July 2006 with corrections to the Cover Date.  相似文献   

Crustal thickening and crustal extension as controls on the evolution of the drainage network of the central Swiss Alps between 30  Ma and the present: constraints from the stratigraphy of the North Alpine Foreland Basin and the structural evolution of the Alps     

Fritz Schlunegger  Rudy Slingerl  & Albert Matter 《Basin Research》1998,10(2):197-212

The combined information about sedimentary petrography from the North Alpine Foreland Basin and structural geology from the Alps allows a qualitative reconstruction of the drainage network of the central Swiss Alps between 30 Ma and the present. This study suggests that crustal thickening and crustal thinning significantly controlled the location of the drainage divide. It also reveals the possible controls of crustal thickening/thinning on the change of the orientation of the drainage network from across-strike between 30 and 14 Ma to along-strike thereafter. Initial crustal thickening in the rear of the wedge is considered to have formed the drainage divide between north and south at 30 Ma. Because the location of crustal thickening shifted from east to west between ≈30–20 Ma, the catchment areas of the eastern dispersal systems reached further south than those of the western Alpine palaeorivers for the same time slice. Similarly, the same crustal dynamics appear to have controlled two phases of denudation that are reflected in the Molasse Basin by petrographic trends. Uplift in the rear of the wedge caused the Alpine palaeorivers to expand further southward. This is reflected in the foreland basin by increasing admixture of detritus from structurally higher units. However, tectonic quiescence in the rear of the wedge allowed the Alpine palaeorivers to cut down into the Alpine edifice, resulting in an increase of detritus from structurally lower units. Whereas uplift in the rear of the wedge was responsible for initiation of the Alpine drainage systems, underplating of the external massifs some 50 km further north is thought to have caused along-strike deviation of the major Alpine palaeorivers. Besides crustal thickening, extension in the rear of the wedge appears to have significantly controlled the evolution of the drainage network of the western Swiss Alps. Slip along the Simplon detachment fault exposed the core of the Lepontine dome, and caused a 50-km-northward shift of the drainage divide.  相似文献   

The Most Luminous Stars in Our Galaxy     

M.R. Villamariz  A. Herrero 《Astrophysics and Space Science》1998,263(1-4):247-250

We present quantitative analyses of 7 galactic O stars of spectral types from O3 to O6. By means of classical hydrostatic and planeparallel models we find the so-called He and Mass Discrepancies for a number of stars of our sample. We also prove the need of line-blocking for the correct reproduction of these spectra. For stars with effective temperature around 50 000 K and above, there is no possibility of reproducing their spectra with these kind of models. Further analyses with unified models, including sphericity and mass loss, allow us to reproduce even the earliest spectra. They also show that the Mass Discrepancy is not only due to the neglect of sphericity and mass loss in the planeparallel analysis, and give us the mass loss rate of these stars. We find that HD15 570, with a present mass of 100 M_⊙, can be the most massive star known in the solar neighbourhood. This revised version was published online in July 2006 with corrections to the Cover Date.  相似文献