Th sorption and export models in the water column: A review   总被引：2，自引：3，他引：2  

Nicolas Savoye  Claudia Benitez-Nelson  Adrian B. Burd  J. Kirk Cochran  Matthew Charette  Ken O. Buesseler  George A. Jackson  Matthieu Roy-Barman  Sabine Schmidt  Marc Elskens 《Marine Chemistry》2006,100(3-4):234

Over the past few decades, the radioisotope pair of ²³⁸U / ²³⁴Th has been widely and increasingly used to describe particle dynamics and particle export fluxes in a variety of aquatic systems. The present paper is one of five review articles dedicated to ²³⁴Th. It is focused on the models associated with ²³⁴Th whereas the companion papers (same issue) are focused on present and future methodologies and techniques (Rutgers van der Loeff et al.), C / ²³⁴Th ratios (Buesseler et al.), ²³⁴Th speciation (Santschi et al.) and present and future applications of ²³⁴Th [Waples, J.T., Benitez-Nelson, C.R., Savoye, N., Rutgers van der Loeff, M., Baskaran, M., Gustafsson, Ö., this issue. An Introduction to the application and future use of ²³⁴Th in aquatic systems. Marine Chemistry, FATE special issue]. In this paper, we review current ²³⁴Th scavenging models and discuss the relative importance of the non-steady state and physical terms associated with the most commonly used model to estimate ²³⁴Th flux. Based on this discussion we recommend that for future work the use of models should be accompanied by a discussion of the effect that model and data uncertainty have on the model results. We also suggest that future field work incorporate repeat occupations of sample sites on time scales of 1–4 weeks in order to evaluate steady state versus non-steady state estimates of ²³⁴Th export, especially during high flux events (> ca. 800 dpm m^− 2 d^− 1). Finally, knowledge of the physical oceanography of the study area is essential, particularly in ocean margins and in areas of established upwelling (e.g., Equatorial Pacific). These suggestions will greatly enhance the application of ²³⁴Th as a tracer of particle dynamics and flux in more complicated regimes.  相似文献   

IAG Newsletter     

Gyula Tóth 《Journal of Geodesy》2008,82(7):453-456

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IAG newsletter     

Gyula Tóth 《Journal of Geodesy》2008,82(6):385-387

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Distances to planetary nebulae with [WR]-type central stars     

Sławomir K. Górny 《Astrophysics and Space Science》1996,238(1):79-82

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Red dust rain within the Spanish Mediterranean area     

José Quereda Sala  Jorge Olcina Cantos  Enrique Montón Chiva 《Climatic change》1996,32(2):215-228

Dust rain belongs to the climatological conditions of the Iberian Peninsula's Mediterranean seaboard. Traditionally known as muddy' or bloody rains, red dust rain has become a topical issue as a result of more frequent rainfall of this kind in recent years. In spite of the difficulties that studying this phenomenon involves, owing to the lack of systematically kept records at meteorological observatories, details are provided of the high frequency of such phenomena within the Spanish Mediterranean area, using records from other phenological sources. The study analyzes the chemical composition of red dust rain and the atmospheric factors giving rise to such phenomena. Whether there is a relationship betwen the higher frequency of dust rain and possible changes in global atmospheric circulation is as yet unclear.  相似文献   

A multifractal analysis of lidar measured water vapour     

J. E. Pinzón  C. E. Puente  M. B. Parlange  W. Eichinger 《Boundary-Layer Meteorology》1995,76(4):323-347

Accurate and fast-response measurements of space-time observations of specific humidity were made above a drying land surface at the University of California at Davis, using the Los Alamos water Raman-lidar. In an attempt to quantify the space-time intermittency features of turbulent flows in the lower atmosphere, a multifractal analysis of these water vapour measurements was performed. The structure of the specific humidity, (x, t), was analyzed quantifying a scalar gradient measure both in time and space, for all possible one-dimensional cuts, i.e. and . The results confirm the multifractal nature of this scalar gradient measure (a type of scalar dissipation rate) and show that humidity measurements at fixed times (x) are more intermittent (e.g. have less entropy dimension) than those at fixed locations in space (t). Similar multifractal behaviour of the spatial data, with and without a transformation from the observed wind velocities, supports the validity of Taylor's hypothesis for the studied fields.  相似文献   

Crustal xenoliths from Calbuco Volcano,Andean Southern Volcanic Zone: implications for crustal composition and magma-crust interaction   总被引：1，自引：1，他引：0  

Rosemary Hickey-Vargas  Mohammad J. Abdollahi  Miguel A. Parada  Leopoldo López-Escobar  Fred A. Frey 《Contributions to Mineralogy and Petrology》1995,119(4):331-344

Crustal xenoliths in the 1961 andesite flow of Calbuco Volcano, in the southern Southern Volcanic Zone (SSVZ) of the Andes, consist predominantly of pyroxene granulites and hornblende gabbronorites. The granulites contain plagioclase+pyroxene+magnetite±amphibole, and have pronounced granoblastic textures. Small amounts of relict amphibole surrounded by pyroxene-plagioclase-magnetite-glass symplectites are found in some specimens. These and similar textures in the gabbronorites are interpreted as evidence of dehydration melting. Mineral and bulk rock geochemical data indicate that the granulites are derived from an incompatible trace element depleted basaltic protolith that underwent two stages of metamorphism: a moderate pressure, high temperature stage accompanied by melting and melt extraction from some samples, followed by thermal metamorphism after entrainment in the Calbuco andesite lavas. High _Nd ^T values (+4.0 to +8.6), Nd-isotope model ages of 1.7–2.0 Ga, and trace element characteristics like chondrite normalized La/Yb< and La/Nb1 indicate that the protoliths were oceanic basalts. Similar oceanic metabasalts of greenschist to amphibolite facies are found in the Paleozoic metamorphic belt that underlies the Chilean coastal ranges. Mineral and bulk rock compositions of the gabbronorite xenoliths indicate that they are cognate, crystallizing from the basaltic andesite magma at Calbuco. Crystallization pressures for the gabbros based on total Al contents in amphibole are 6–8 kbar. These pressures point to middle to lower crustal storage of the Calbuco magma. Neither granulite nor gabbro xenoliths have the appropriate geochemical characteristics to be contaminants of Calbuco andesites, although an ancient sedimentary contaminant is indicated by the lava compositions. The presence of oceanic metabasaltic xenoliths, together with the sedimentary isotopic imprint, suggests that the lower crust beneath the volcano is analogous to the coastal metamorphic belt, which is an accretionary complex of intercalated basalts and sediments that formed along the Paleozoic Gondwanan margin. If this is the case, the geochemical composition of the lower and middle crust beneath the SSVZ is significantly different from that of most recent SSVZ volcanic rocks.  相似文献   

Boundary manifolds for energy surfaces in celestial mechanics     

Ernesto A. Lacomba  Carles Simó 《Celestial Mechanics and Dynamical Astronomy》1982,28(1-2):37-48

We complete Mc Gehee's picture of introducing a boundary (total collision) manifold to each energy surface. This is done by constructing the missing components of its boundary as other submanifolds. representing now the asymptotic behavior at infinity.It is necessary to treat each caseh=0,h>0 orh<0 separately. In the first case, we repeat the known result that the behavior at total escape is the same as in total collision. In particular, we explain why the situation is radically different in theh>0 case compared with the zero energy case. In the caseh<0 we have many infinity manifold components. and the general situation is not quite well understood.Finally, our results forh0 are shown to be valid for general homogeneous potentials.Paper presented at the 1981 Oberwolfach Conference on Mathematical Methods in Celestial Mechanics.The research conducted in this paper has been partially supported by CONACYT (México), under grant PCCBNAL 790178.Partially supported by an Ajut a l'Investigacio of the University of Barcelona.  相似文献   

Window technique for climate trend analysis     

Tamás Szentimrey  Tibor Faragó  Sándor Szalai 《Climate Dynamics》1992,6(3-4):127-134

Climatic characteristics are affected by various systematic and occasional impacts: besides the changes in the observing system (locations of the stations of the meteorological network, instruments, observing procedures), the possible local-scale and global natural and antropogenic impacts on climatic conditions should be taken into account. Apart from the predictability problems, the phenomenological analysis of the climatic variability and the determination of past persistent climatic anomalies are significant problems, among other aspects, as evidence of the possible anomalous behavior of climate or for climate impact studies. In this paper, a special technique for the identification of such shifts in the observational series is presented. The existence of these significant shorter or longer term changes in the mean characteristics for the properly selected adjoining periods of time is the necessary condition for the formation of any more or less unidirectional climatic trends. Actually, the window technique is based on a complete set of orthogonal functions. The sensitivity of the proposed model on its main parameters is also investigated. This method is applied for hemispheric and Hungarian data series of the mean annual surface temperature.Contribution to Clima Locarno — Past and Present Climate Dynamics; Conference September 1990, Swiss Academy of Sciences — National Climate Program  相似文献   

Period variation of selected cepheids     

József Vinkó 《Astrophysics and Space Science》1991,183(1):17-36

The aim of the present paper is to study the period as well as -velocity changes of 12 cepheid-type variable stars in order to find possible evidence for duplicity. Light-time effect was found in the O-C diagram of RY CMa, the orbital period being about 5200 days. Furthermore, especially spectroscopic observations are needed to confirm the duplicity or render the accurate orbital solution possible.  相似文献