Dissolved Carbohydrate Concentration,Composition, and Bioavailability to Microbial Heterotrophs in Stream Water     

Th. J. Gremm  L. A. Kaplan 《洁净——土壤、空气、水》1998,26(3):167-171

Dissolved total carbohydrates (DTCH), dissolved free monosaccharides (DFMS), dissolved organic carbon (DOC), biodegradable DOC (BDOC), and humic substances (HS) were measured in White Clay Creek (WCC), a stream in southeastern Pennsylvania Piedmont, USA. Samples were collected over different seasons and under baseflow and stormflow conditions. DOC concentrations ranged from 1.0 to 12.8 mg/L C with the highest concentrations associated with stormflows. Carbohydrates ranged from 0.42 to 12.4 μM and accounted for 2.9 to 12.7% of the DOC. Humic substances represented the major DOC fraction, accounting for 55 to 72% of the DOC pool under all flow conditions. The humic fraction had a lower carbohydrate content (4.4%) than the non-humic fraction of DOC (7.2%). Stormflow DOC was enriched in carbohydrates relative to baseflow DOC, but the percentage of humic-C changed little. Carbohydrates were primarily present as dissolved polysaccharides (55%), but a significant fraction was bound to humic substances (40%), while a small proportion was present as monosaccharides (5%). The major monosaccharides in stream water, listed in order of decreasing concentration, included glucose, galactose, rhamnose, xylose, arabinose, mannose, and fucose. On average (30.6 ± 7.4)% (n = 44) of the stream water DOC was biodegradable, and carbohydrates accounted for 9.9 to 17.7% of the BDOC.  相似文献   

Tracing the Evolution of a Concept: A New Feature for the Geographical Review          下载免费PDF全文

David H. Kaplan 《Geographical review》2016,106(3):337-337

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Multiethnic Economic Activity Along Three Immigrant Corridors in Paris     

David H. Kaplan  Charlotte Recoquillon 《The Professional geographer》2016,68(1):82-91

Ethnic neighborhoods and ethnic economies do not always involve a single nationality or ethnic group. Quite often several groups operate side by side in the neighborhood and within the establishments themselves. This can give rise to a modification of the ethnic economy concept. We discuss an example of such a multiethnic residential and business district in Paris, the Goutte d’Or, with particular attention to three shopping streets. Although somewhat distinct from one another, each of these streets is multiethnic in regard to the proprietors, employees, and customers, and this multiethnicity extends within the establishments themselves. The primary questions we ask in this article are, first, what the nature of this ethnic economy is and how it fits within the different types of ethnic economy. Beyond this, we demonstrate how the activities taking place here reflect separate circuits of activity at separate spatial scales and what this ethnic business activity suggests for immigrant incorporation in Paris and the nature of cross-ethnic relations. To answer these questions, we rely on observation, interviews with several merchants in defined commercial corridors, and some official statistical and political information gleaned from various government sources. This Parisian neighborhood exemplifies strategies of immigrant incorporation into French society. As such, it provides a possible new model of a multiethnic economy, one that might become a common fixture in increasingly diverse cities in the world.  相似文献   

Ephemeris of Pluto     

P.K. Seidelmann  G.H. Kaplan  K.F. Pulkkiner  E.J. Santoro  T.C. Van Flandern 《Icarus》1980,44(1):19-28

The limited period of observational data and the long orbital period have limited the accuracy of the Pluto ephemerides. This condition will continue for some time. Ephemerides of Pluto are compared with the observational data.  相似文献   

Triterpenoids as molecular indicators of paleoseepage in recent sediments of the Southern California bight     

Bernd R.T. Simoneit  I.R. Kaplan 《Marine environmental research》1980,3(2):113-128

Petroleum-derived hydrocarbons have been identified in sediments by analysis of the n-alkanes, aromatic hydrocarbons and branched and cyclic components (humps). The detection of low levels of petroleum input to sediments can be ambiguous due to the presence of syngenetic biolipids. Triterpenoids, especially the (17αH, 21βH)-hopanes, have been proposed as sensitive molecular markers of petroleum pollution.Recent sediments from the Southern California Bight to subbottom depths of about 30 cm (pre-anthropogenic) contain lipids of syngenetic origin with major humps of branched and cyclic material and triterpenoids consisting mainly of the (17αH, 21βH)-hopanes ranging from C₂₇ to C₃₅. Extended hopanes (> C₃₁) are found as 1:1 mixtures of the 22R and 22S diastereomers. The 17α(H),18α(H), 21β(H)-28,30-bisnorhopane is the dominant triterpane for most of these sediments and appears to be a potential molecular marker characteristic of the Southern California petroleums. Extended tricyclic diterpanes ranging from C₁₉ to C₂₇ are also present and their structures make them further possible indicators of petroleum. Southern California Bight sediments therefore appear to contain petroleum products from both seepage and anthropogenic activity.Recent sediments from other areas (e.g. Guaymas Basin, Gulf of California; Cook Inlet, Alaska; Eastern Bering Sea; Walvis Bay, Southwest Africa; and Mangrove Lake, Bermuda) contain predominantly (17βH, 21βH)-hopanes and hopenes, indicating recent synthesis and no petroleum pollution.  相似文献   

WEST: A northern California study of the role of wind-driven transport in the productivity of coastal plankton communities   总被引：1，自引：0，他引：1  

J.L. Largier  C.A. Lawrence  M. Roughan  D.M. Kaplan  E.P. Dever  C.E. Dorman  R.M. Kudela  S.M. Bollens  F.P. Wilkerson  R.C. Dugdale  L.W. Botsford  N. Garfield  B. Kuebel Cervantes  D. Kora in 《Deep Sea Research Part II: Topical Studies in Oceanography》2006,53(25-26):2833

The “Wind Events and Shelf Transport” (WEST) program was an interdisciplinary study of coastal upwelling off northern California in 2000–03. WEST was comprised of modeling and field observations. The primary goal of WEST was to better describe and understand the competing influences of wind forcing on planktonic productivity in coastal waters. While increased upwelling-favorable winds lead to increased nutrient supply, they also result in reduced light exposure due to deeper surface mixed layers and increased advective loss of plankton from coastal waters. The key to understanding high levels of productivity, amidst these competing responses to wind forcing, is the temporal and spatial structure of upwelling. Temporal fluctuations and spatial patterns allow strong upwelling that favors nutrient delivery to be juxtaposed with less energetic conditions that favor stratification and plankton blooms. Observations of winds, ocean circulation, nutrients, phytoplankton and zooplankton off Bodega Bay and Point Reyes (38°N) were combined with model studies of winds, circulation and productivity. This overview of the WEST program provides an introduction to the WEST special issue of Deep-Sea Research, including the motivation for WEST, a summary of study components, an integrative synthesis of major research results to-date, and background on conditions during field studies in May–June 2001 (the upwelling period on which this special issue is focused).  相似文献   

Mesoscale simulations of dynamical factors discriminating between a tornado outbreak and non-event over the southeast US Part I: 84–48 hour precursors     

J. M. Egentowich  M. L. Kaplan  Y.-L. Lin  A. J. Riordan 《Meteorology and Atmospheric Physics》2000,74(1-4):129-157

Summary Observational analysis and mesoscale numerical simulations are in agreement concerning key dynamical processes which occurred over Mexico and the Gulf of Mexico 84 hours prior to the 1988 Raleigh (RDU), NC tornado outbreak. The subtropical jet (STJ) over northern Mexico and its associated transverse ageostrophic circulation forced air down the eastern side of the Sierra Madre Mountains creating adiabatic warming due to compressional heating. Along with this warm air, a low-level trough of low pressure formed and a low-level jet (LLJ) developed over the western Gulf of Mexico. This LLJ began the process that transported very warm and potential vorticity (PV) rich air from the Mexican plateau to the Carolina Piedmont. The low-level PV maximum over central NC at the time of the tornado was a coherent entity traceable back 84 hours to the Mexican plateau. Over the Mexican plateau, the STJ transported the PV rich air southward then down to the midlevels. There was substantial heating over the plateau producing a deep well-mixed layer and a mountain-plains solenoid. An area of strong vertical convergence developed in the 500–600 hPa layer which increased the thermal gradient and maintained the PV. This mid-level PV was transported to the low-levels by a hydrostatic mountain wave. As the PV maxima moved down the lee of the mountains it increased due to strong static stability, tilting and frictional effects. Finally, the PV maxima moved along the Gulf Coast and up the East Coast to central NC. Received December 23, 1999 Revised January 16, 2000  相似文献   

Why the Greenwich meridian moved     

Stephen Malys  John H. Seago  Nikolaos K. Pavlis  P. Kenneth Seidelmann  George H. Kaplan 《Journal of Geodesy》2015,89(12):1263-1272

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Deuterium in carbonaceous chondrites     

Y. Kolodny  J.F. Kerridge  I.R. Kaplan 《Earth and Planetary Science Letters》1980,46(2):149-158

Hydrogen isotopic compositions in seven carbonaceous chondrites lie in the range ?70 to +771‰ relative to SMOW. These values decrease, to a range from ?145 to +219‰, after low-temperature oxidation in an oxygen plasma. Deuterium enrichment is therefore concentrated in the organic matter, the hydrous silicates probably lying close to the terrestrial range for such material. Calculated values for δD of the organic fraction are +450 ‰ for Orgueil and Ivuna and up to +1600‰ for Renazzo. These enrichments, at least for Orgueil and Ivuna, suggest equilibration with protosolar hydrogen at very low temperatures. Assuming a value of 2.5 × 10^?5 for the protosolar D/H ratio, nominal equilibration temperatures of 230°K for silicates and 180°K for organic matter may be derived.  相似文献   

Light element geochemistry of the Apollo 16 site     

J.F Kerridge  I.R Kaplan  C Petrowski  S Chang 《Geochimica et cosmochimica acta》1975,39(2):137-162

Pronounced variations in abundances and isotopic compositions of some light elements in soils from the Apollo 16 site are interpreted in terms of differing degrees of solar wind exposure for an originally, and approximately, homogeneous regolith. Carbon abundances in soils are compatible with a model in which equilibrium is established, after 10⁴-10⁵ yr, between solar wind input and loss by H stripping. However, this model does not explain the observed C isotopic distribution, suggesting that other sources of C or other processes, or both, are also important. Carbon abundances in rocks from Apollo 16 are higher (average 40 ppm) than at other landing sites although their isotopic compositions, ?35 < δ¹³C < ?16%. PDB, are normal. Abundances of N and, to a less extent, He and H in soils correlate with C as does a fraction of metallic Fe attributed to in situ reduction of indigenous Fe²⁺ by solar wind H.Fillet soil 67461 apparently contains solar wind C and N in a relatively unfractionated form, yielding an upper limit to solar wind (δ¹³C of ?16%., PDB and a value of 3.4 for $\text{C}\text{N}$ in the solar wind.Sulfur at the Apollo 16 site represents a paradox in that, although abundances in soils are apparently controlled by local rock S contents, they also correlate, for all but one sample, with δ³⁴S, which itself is apparently controlled by surface exposure age. A complex lunar S cycle is suggested.  相似文献