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Geographic regions all have some degree of uncertainty, though this is seldom represented on their maps. Uncertainty of the Great Plains boundary is shown here by comparing 50 previously published maps of the region. These maps were found in a variety of sources, from classic 1930s geographic works to current regional studies on the Internet. By examining this diverse collection, a distinction can be seen between those maps using primarily physical criteria to define the region and those using cultural characteristics, or a combination of these two characteristics. This distinction is supported by trends in boundary shape, size, and even the map's date of publication. The Great Plains is shown as a complex region, subject to the interpretations of individual cartographers, and can be better understood by considering all points of view rather than any single boundary line. 相似文献
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K. I. Kellermann Y. Y. Kovalev M. L. Lister D. C. Homan M. Kadler M. H. Cohen E. Ros J. A. Zensus R. C. Vermeulen M. F. Aller H. D. Aller 《Astrophysics and Space Science》2007,311(1-3):231-239
We discuss results from a decade long program to study the fine-scale structure and the kinematics of relativistic AGN jets
with the aim of better understanding the acceleration and collimation of the relativistic plasma forming AGN jets. From the
observed distribution of brightness temperature, apparent velocity, flux density, time variability, and apparent luminosity,
the intrinsic properties of the jets including Lorentz factor, luminosity, orientation, and brightness temperature are discussed.
Special attention is given to the jet in M87, which has been studied over a wide range of wavelengths and which, due to its
proximity, is observed with excellent spatial resolution.
Most radio jets appear quite linear, but we also observe curved non-linear jets and non-radial motions. Sometimes, different
features in a given jet appear to follow the same curved path but there is evidence for ballistic trajectories as well. The
data are best fit with a distribution of Lorentz factors extending up to γ∼30 and intrinsic luminosity up to ∼1026 W Hz−1. In general, gamma-ray quasars may have somewhat larger Lorentz factors than non gamma-ray quasars. Initially the observed
brightness temperature near the base of the jet extend up to ∼5×1013 K which is well in excess of the inverse Compton limit and corresponds to a large excess of particle energy over magnetic
energy. However, more typically, the observed brightness temperatures are ∼2×1011 K, i.e., closer to equipartition. 相似文献
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Distribution of some elements in surface soil over the Kavadarci region,Republic of Macedonia 总被引:2,自引:0,他引:2
Trajče Stafilov Robert Šajn Blažo Boev Julijana Cvetković Duško Mukaetov Marjan Andreevski Sonja Lepitkova 《Environmental Earth Sciences》2010,61(7):1515-1530
The results of a first systematic study of spatial distribution of different elements in surface soil over of the Kavadarci
region, Republic of Macedonia, known for its nickel industrial activity are reported. The investigated region (360 km2) is covered by a sampling grid of 2 × 2 km2; whereas the sampling grid of 1 × 1 km2 was applied in the urban zone and around the ferronickel smelter plant (117 km2). In total 344 soil samples from 172 locations were collected. At each sampling point soil samples were collected at two
depths, topsoil (0–5 cm) and bottom soil (20–30 cm). Inductively coupled plasma-mass spectrometry (ICP-MS) was applied for
the determination of 36 elements (Ag, Al, As, Au, B, Ba, Bi, Ca, Cd, Co, Cr, Cu, Fe, Ga, Hg, K, La, Mn, Na, Mg, Mo, Ni, P,
Pb, S, Sb, Sc, Se, Sr, Th, Tl, Ti, U, V, W and Zn). Data analysis and construction of maps were performed using the Paradox
(ver. 9), Statistica (ver. 6.1), AutoDesk Map (ver. 2008) and Surfer (ver. 8.09) software. Four geogenic and three anthropogenic
geochemical associations were established. Within the research, natural and anthropogenic enrichment with heavy metals was
determined. Principally, the natural enrichment is related especially to Ni. Pollution by As, Cd, Co, Cr, Cu, Hg, Mo, Pb and
Zn is basically insignificant. 相似文献
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Sonja Jankowfsky Flora Branger Isabelle Braud Jorge Gironás Fabrice Rodriguez 《水文研究》2013,27(25):3747-3761
Suburban areas are subject to strong anthropogenic modifications, which can influence hydrological processes. Sewer systems, ditches, sewer overflow devices and retention basins are introduced and large surface areas are sealed off. The knowledge of accurate flow paths and watershed boundaries in these suburban areas is important for storm water management, hydrological modelling and hydrological data analysis. This study proposes a new method for the determination of the drainage network based on time efficient field investigations and integration of sewer system maps into the drainage network for small catchments of up to 10 km2. A new method is also proposed for the delineation of subcatchments and thus the catchment area. The subcatchments are delineated using a combination of an object‐oriented approach in the urban zone and geographical information system–based terrain analysis with flow direction forcing in the rural zone. The method is applied to the Chaudanne catchment, which belongs to the Yzeron river network and is located in the suburban area of Lyon, France. The resulting subcatchment map gives information about subcatchment response and contribution. The method is compared with six other automatic catchment delineation methods based on stream burning, flow direction forcing and calculation of subcatchments for inlet points. None of the automatic methods could correctly represent the catchment area and flow paths observed in the field. The watershed area calculated with these methods differs by as much as 25% from the area computed with the new method. Copyright © 2012 John Wiley & Sons, Ltd. 相似文献
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Barbara Vokal-Nemec Janina Szaran Andrzej Trembaczowski Stanislaw Halas Tadej Dolenec Sonja Lojen 《Aquatic Geochemistry》2006,12(3):199-220
Measurements were made of sulphur and oxygen isotope ratios of sulphate in some Slovenian rivers, lakes and tap waters. δ34S ranged from −0.2 to + 13.3‰, δ18O ranged from +4.9 to + 13.6‰, and the sulphate content varied from 0.8 to 41.4 mg/L. Rivers flowing from the Julian Alps
contain a very low amount of sulphate that is leached from a thin horizon of soil by rain. As confirmed by their low δ18O values, these sulphates do not enter the rivers directly in rain, but arise from biochemical cycling in the soil. The low
δ34S of this sulphate indicates that it originates from the oxidation of sedimentary sulphides. The evolution of sulphates along
the river course was investigated for the Sava and Ljubljanica rivers. The variations observed in sulphate from the waters
studied result from variations in the contribution of sulphates of different origin. Downstream the Sava River sulphate is
depleted in the heavy isotopes of both sulphur and oxygen, with δ-values gradually tending toward the δ-values of groundwater
sulphates in the watershed. In contrast, the δ-values of sulphate in the Ljubljanica River are almost constant and similar
to those of sulphate in local groundwater. Introduction of water from Italian and Slovenian mines was recorded in the Soča
River, where the lowest δ34S value of sulphate sulphur (−0.2‰) was observed. In addition, the influence of sulphate from the oxidation of sedimentary
sulphides was recorded in the Sotla River. No evidence was found for introduction of sulphate from factories. 相似文献