A simple non‐linear analytical relationship between aerosol accumulation number and sub‐micron volume, explaining their observed ratio in the clean and polluted marine boundary layer     

Rita Van Dingenen  Aki O. Virkkula  Frank Raes  Timothy S. Bates  Alfred Wiedensohler 《Tellus. Series B, Chemical and physical meteorology》2000,52(2):439-451

We propose an analytical expression for the relation between aerosol accumulation number and sub‐micron volume over the marine boundary layer (MBL), based on a simple balance equation. By providing appropriate source and sink terms which account for entrainment, coagulation, in‐cloud scavenging and condensational growth, the model is able to reproduce the observed ratio between MBL particles larger than 80 nm diameter (as a proxy for accumulation mode number) and submicron aerosol volume, from freshly polluted to background conditions. Entrainment and coagulation are essential in predicting the observed ratio. Budget and lifetime calculations show that, due to relatively low source rates of oceanic non‐sea‐salt‐sulfate and sea‐salt, the anthropogenic signature in aerosol volume remains significant even after 8 days of MBL transport.  相似文献   

Multivariate comparisons of the period–light-curve shape distributions of Cepheids in five galaxies     

C. Koen  I. Siluyele 《Monthly notices of the Royal Astronomical Society》2007,377(3):1281-1286

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A high‐resolution multi‐proxy stalagmite record from Mechara,Southeastern Ethiopia: palaeohydrological implications for speleothem palaeoclimate reconstruction     

Asfawossen Asrat  Andy Baker  Mohammed Umer Mohammed  Melanie J. Leng  Peter Van Calsteren  Claire Smith 《第四纪科学杂志》2007,22(1):53-63

An annually laminated stalagmite from Southeastern Ethiopia grew for 443±8 yr starting at 5023 yr BP (±160 yr) as determined by lamina‐tuned U‐Th dating. The speleothem shows three growth phases: (1) an initial phase where the stalagmite has a candlestick shape, deposited by relatively slow rate drip water; (2) a middle growth phase where laminae grow on the flanks, suggesting faster drip rates; and (3) a final growth phase where the speleothem becomes narrower owing to a decrease in drip water supply towards the end of deposition. Morphometry, annual growth rate, fluorescence index, and ²³⁴U/²³⁸U isotope ratio show marked differences between the growth phases, while δ¹³C and δ¹⁸O do not show significant variation, except within the third phase towards the top of the stalagmite, where they have higher values. The study indicates that the multiproxy approach is crucial as the different proxies respond to single climate forcing in different manners. Our results can be widely applied to speleothem studies distinguishing the relative importance of the various proxies in recording cave ‘external’ (climate, hydrology) and cave ‘internal’ (e.g. evaporation) processes. Copyright © 2006 John Wiley & Sons, Ltd.  相似文献   

An embedded exponentially fitted Runge–Kutta–Nyström method for the numerical solution of orbital problems     

Hans Van de Vyver   《New Astronomy》2006,11(8):577-587

A new embedded pair of explicit exponentially fitted Runge–Kutta–Nyström methods is constructed. The methods integrate exactly systems of differential equations whose solutions are linear combinations of the functions from the set {exp(μt), exp(−μt)} (). The pair has four stages and algebraic orders five and three. An application to some well-known orbital problem shows that the new pair is very competitive when it is compared with high-quality codes proposed in the scientific literature.  相似文献   

The pulsational characteristics of the λ Bootis type star BD Phe (HD 11413)     

C. Koen  E. Paunzen  F. van Wyk  F. Marang  I. V. Chernyshova  S. M. Andrievsky 《Monthly notices of the Royal Astronomical Society》2003,338(4):931-938

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What can be deduced from open cluster metallicity measurements?     

Chris Koen  Fred Lombard 《Monthly notices of the Royal Astronomical Society》2007,382(2):693-698

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Modeling and distance determination of planetary nebulae     

Peter A. M. Van Hoof  Griet C. Van De Steene 《Astrophysics and Space Science》1996,243(1):83-86

The monthly probability of occurrence of southward (B _z ^– ) component of IMF estimated independent of the sector polarity observed near earth is found to change with the magnitude of solar wind velocity. The above analysis is done for each month during two years around sunspot minima and maxima in cycle 21. The results will be interpreted in terms of association of southwardB _z events with solar wind flows of distinct solar origin such as low and high speed solar wind.  相似文献   

Late Weichselian fluvio‐aeolian sands and coversands of the type locality Grubbenvorst (southern Netherlands): sedimentary environments,climate record and age     

C. Kasse  D. Vandenberghe  F. De Corte  P. Van Den Haute 《第四纪科学杂志》2007,22(7):695-708

The Weichselian Late Pleniglacial and Lateglacial aeolian stratigraphy (Older Coversand I, Beuningen Gravel Bed, Older Coversand II, Younger Coversand I, Usselo Soil, Younger Coversand II) in the southern Netherlands has been reinvestigated in its type locality (Grubbenvorst). Sedimentary environments have been reconstructed and related to their climatic evolution based on periglacial structures. In addition, 22 optically stimulated luminescence (OSL) ages have been determined that provide an absolute chronology for the climatic evolution and environmental changes of the coversand area. From this work it appears that, prior to 25 ka fluvial deposition by the Maas dominated. After 25 ka fluvial activity reduced and deposition occurred in a fluvio‐aeolian environment with continuous permafrost (Older Coversand I). This depositional phase was dated between 25.2 ± 2.0 and 17.2 ± 1.2 ka. The upward increase of aeolian activity and cryogenic structures in this unit is related to an increase of climatic aridity and a decrease in sedimentation rate during the Last Glacial Maximum (LGM). The Beuningen Gravel Bed, that results from deflation with polar desert conditions and that represents a stratigraphic marker in northwestern Europe, was bracketed between 17.2 ± 1.2 and 15.3 ± 1.0 ka. Based on this age result a correlation with Heinrich event H1 is suggested. Permafrost degradation occurred at the end of this period. Optical ages for the Older Coversand II unit directly overlying the Beuningen Gravel Bed range from 15.3 ± 1.0 ka at the base to 12.7 ± 0.9 ka at the top. Thus this regionally important Older Coversand II unit started at the end of the Late Pleniglacial and continued throughout the early Lateglacial. Its formation after the Late Pleniglacial (LP) maximum cold and its preservation are related to rapid climatic warming around 14.7 ka cal. BP. The Allerød age of the Usselo Soil was confirmed by the optical ages. Copyright © 2007 John Wiley & Sons, Ltd.  相似文献   

Effects of ice-front collapse and flood generation on a proglacial river channel near kangerlussuaq (Søndre Strømfjord), west greenland     

Andrew J. Russell  Frank G. M. Van Tatenhove  Roderik S. W. Van De Wal 《水文研究》1995,9(2):213-226

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Radio emission from supernovae and gamma-ray bursters and the need for the SKA     

Kurt W. Weiler  Schuyler D. Van Dyk  Richard A. Sramek  Nino Panagia   《New Astronomy Reviews》2004,48(11-12):1377

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