Unique solutions of solar wind models with thermal conductivity     

E. J. Weber 《Solar physics》1970,14(2):480-488

The solutions of a radially symmetrical solar wind model with thermal conductivity are discussed in the neighborhood of the loci of the critical points, called the critical line, and at infinity. It is shown that for constant mass and total energy flux the conditions at infinity are related uniquely to the conditions at the critical line. Furthermore the requirement that the solution is continuous and has the proper behavior at infinity will determine uniquely one specific point on the critical line through which the solution has to pass.Operated by the Association of Universities for Research in Astronomy, Inc., under contract with the National Science Foundation.  相似文献   

Low frequency spectra of type III solar radio bursts     

Richard R. Weber 《Solar physics》1978,59(2):377-385

Flux density spectra have been determined for ninety-one simple type III solar bursts observed by the Goddard Space Flight Center radio astronomy experiment on the IMP-6 spacecraft during 1971 and 1972. Spectral peaks were found to occur at frequencies ranging from 44 kHz up to 2500 kHz. Half of the bursts peaked between 250 kHz and 900 kHz, corresponding to emission at solar distances of about 0.3 to 0.1 AU. Maximum burst flux density sometimes exceeds 10^–14 W m^–2 Hz^–1. The primary factor controlling the spectral peak frequency of these bursts appears to be variation in intrinsic power radiated by the source as the exciter moves outward from the Sun, rather than radio propagation effects between the source and IMP-6. Thus, a burst spectrum strongly reflects the evolution of the properties of the exciting electron beam, and according to current theory, beam deceleration could help account for the observations.  相似文献   

South China karst aquifer storm-scale hydrochemistry   总被引：7，自引：0，他引：7  

Liu Z  Groves C  Yuan D  Meiman J 《Ground water》2004,42(4):491-499

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The Rise of the GIS Volunteer     

Catherine E. Jones  Nicholas J. Mount  Patrick Weber 《Transactions in GIS》2012,16(4):431-434

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Multi-metal contaminant dynamics in temporarily flooded soil under sulfate limitation   总被引：3，自引：0，他引：3  

Frank-Andreas Weber  Andreas Voegelin  Ruben Kretzschmar 《Geochimica et cosmochimica acta》2009,73(19):5513-5527

In many river basins, floodplain soils have accumulated a variety of metal contaminants, which might be released during periods of flooding. We investigated the dynamics of copper, cadmium, lead, zinc, and nickel in a contaminated freshwater floodplain soil under a realistic sulfate-limited flooding regime in microcosm experiments. We found that most contaminants were initially mobilized by processes driven by the reductive dissolution of Fe(III) and Mn(IV, III) (hydr)oxides. Subsequently, bacterial sulfate respiration resulted in the transformation of the entire available sulfate (2.3 mmol/kg) into chromous reducible sulfur (CRS). Cu K-edge X-ray absorption fine structure (XAFS) spectroscopy revealed that the soil Cu speciation changed from predominantly Cu(II) bound to soil organic matter (SOM) intermittently to 14% metallic Cu(0) and subsequently to 66% copper sulfide (Cu_xS). These Cu_xS precipitates accounted for most of the formed CRS, suggesting that Cu_xS was the dominant sulfide phase formed in the flooded soil. Sequential metal extractions, in agreement with CRS results, suggested that easily mobilizable Cd was completely and Pb partially sequestered in sulfide precipitates, controlling their dissolved concentrations to below detection limits. In contrast, Zn and Ni (as well as Fe) were hardly sequestered into sulfide phases, so that micromolar levels of dissolved Zn and Ni (and millimolar dissolved Fe(II)) persisted in the reduced soil. The finding that Cu, Cd, and Pb were sequestered (but hardly any Zn, Ni, and Fe) is consistent with the thermodynamically predicted sulfide ladder following the increasing solubility products of the respective metal sulfides. The observation that Cd and Pb were sequestered in sulfides despite the presence of remaining SOM-bound Cu(II) suggested that the kinetics of Cu(II) desorption, diffusion, and/or Cu_xS precipitation interfered with the sulfide ladder. We conclude that the dynamics of multiple metal contaminants are intimately coupled under sulfate limitation by the relative thermodynamic stabilities and formation kinetics of the respective metal sulfides.  相似文献   

Clay minerals from the sedimentary cover from the Northwest Iberian shelf     

A. Oliveira  F. Rocha  A. Rodrigues  J. Jouanneau  A. Dias  O. Weber  C. Gomes 《Progress in Oceanography》2002,52(2-4)

The Northern Iberian margin is a typical example of a continental margin subjected to seasonal highly energetic regime (waves and tides) and receiving inputs of continental sediments via riverine discharges. The principal goal of this study has been to use clay minerals as indicators of sedimentary dynamics in the open shelf system. The distributions of clay mineral in the top layer of the sedimentary cover are shown to be related to their continental sources, but also reflect the influences of winter storms and longshore currents in determining the pathways of sediment transport.The mineralogical composition of the material issuing from the rivers is very similar to the general mineralogical composition of the fine fractions of the seabed sediments. Those deposits that are directly influenced by riverine discharges have higher contents of kaolinite (>20%), whereas those that are not have higher contents of illite (>80%). The available data indicate no significant quantities of terrigenous particles are being discharged from the Spanish rias. Therefore, we conclude that physical processes are controlling the clay mineral distributions and that, despite contributions from the Minho River, the main source of fine detrital particles to the shelf region is the Douro River discharge. These particles settle on the middle shelf, below the 60 m isobath. During storm events these particles are re-suspended and advected northwards to the Galician shelf or into deeper domains. Thus the distributions of the clays indicate there is a net transport of fine sediments both northwards and off-shelf.  相似文献   

Correlation Between the Sunspot Number,the Total Solar Irradiance,and the Terrestrial Insolation     

A. Hempelmann  W. Weber 《Solar physics》2012,277(2):417-430

Our study deals with the correlations between the solar activity on the one hand and the solar irradiance above the Earth’s atmosphere and at ground level on the other. We analyzed the combined ACRIM I+II time series of the total solar irradiance (TSI), the Mauna Loa time series of terrestrial insolation data, and data of terrestrial cosmic ray fluxes. We find that the correlation between the TSI and the sunspot number is strongly non-linear. We interpret this as the net balance between brightening by faculae and darkening by sunspots where faculae dominate at low activity and sunspots dominate at high activity. Such a behavior is hitherto known from stellar analogs of the Sun in a statistical manner. We perform the same analysis for the Mauna Loa data of terrestrial insolation. Here we find that the linear relation between sunspot number and insolation shows more than 1% rise in insolation by sunspot number variations which is much stronger than for the TSI. Our conclusion is that the Earth atmosphere acts as an amplifier between space and ground, and that the amplification is probably controlled by solar activity. We suspect the cosmic rays intensity as the link between solar activity and atmospheric transparency. A Fourier analysis of the time series of insolation shows three dominant peaks: 10.5, 20.4, and 14.0 years. As a matter of fact, the cosmic rays data show the same pattern of significant peaks: 10.7, 22.4, and 14.9 years. This analogy supports our idea that the cosmic rays variation has influence on the transparency of the Earth atmosphere.  相似文献   

Distribution and Sources of Dissolved and Particulate Heavy Metals (Mn,Co, Ni,Cu, Zn,Cd, Pb) in Masan Bay,Korea     

Park  Sojung  Choi  Mansik  Jang  Dongjun  Joe  Dongjin  Park  Kyunggue 《Ocean Science Journal》2020,55(1):49-67

Ocean Science Journal - In this study, we investigated the spatial and temporal distribution and sources of dissolved and particulate heavy metals in Masan Bay, an area that for a long time has...  相似文献   

Between coercion and consent: the politics of “Cooperative Governance” at a time of “Austerity Localism” in London     

Joe Penny 《Urban geography》2017,38(9):1352-1373

At a time of “austerity localism”, this paper explores how local authorities in London, England, are simultaneously addressing the dual pressures of delivering fiscal retrenchment and of enrolling citizens in new participatory public service arrangements, asking whether “these trends pull against one another, in opposite directions, or whether they are the tough and tender dimensions of a singular process: austerian management” Drawing on empirical research into the London Borough of Lambeth’s Cooperative Council agenda, as well as Foucauldian and Gramscian critiques of participatory network governance theories and practice, this paper shows how participatory forms of governance can be folded into the logic of hierarchy and coercion through various governmental technologies of performance and agency (consent), and through tactics of administrative domination (coercion). As budget cuts continue to affect local government in England, this paper concludes that although small experiments in participatory governance may persist, the dominant mode of governance is likely to shift towards more hierarchical and coercive forms.  相似文献   

Die Protoblastese     

Maximilian Weber 《International Journal of Earth Sciences》1924,14(4):337-351

Ohne Zusammenfassung  相似文献