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1.
2.
The probabilities of discovering detached close binary (type DM) stars as eclipsing variables are calculated as a function
of the mass of the main component, mass ratio, major semiaxis, and angle of inclination of the orbit. The case of total limb
darkening (hypothesis “D”) is examined. This is compared with earlier results for uniformly bright stellar disks (hypothesis
“U”). Based on data from Svechnikov and Kuznetsova’s Catalog of Approximate Photometric and Absolute Elements of Eclipsing
Variables, the spatial density of stars of this type in the neighborhood of the sun is estimated to be ≈ 460 · 10
−6
pc−3.
__________
Translated from Astrofizika, Vol. 49, No. 1, pp. 151–169 (February 2006). 相似文献
3.
Nathan S. Hall R. Wayne Litaker Elizabeth Fensin Jason E. Adolf Holly A. Bowers Allen R. Place Hans W. Paerl 《Estuaries and Coasts》2008,31(2):402-418
A dense bloom of the ichthyotoxic dinoflagellate Karlodinium veneficum was discovered in the Neuse River Estuary, North Carolina, on 19 October 2006 and was associated with four subsequent fish
kills. Microscopic, photopigment, DNA, and toxicological techniques confirmed bloom identity and toxicity. High-resolution
spatio-temporal data from ship-board and fixed automated sampling stations provided a unique opportunity to investigate the
environmental conditions that initiated, maintained, and terminated the K. veneficum bloom. Bloom initiation and growth were favored by high nutrient availability and reduced dispersal during the period of
declining riverine discharge after Tropical Storm Ernesto. K. veneficum out-competed other co-occurring dinoflagellates, perhaps because of the production of karlotoxins that are known to act as
grazing deterrents and to facilitate mixotrophic feeding. Once the bloom was established, small-scale hydrodynamic processes,
coupled with vertical migration, concentrated cells along a frontal convergence to high densities (>200,000 cells per milliliter).
By 26 October 2006, wind mixing and possible nutrient stress disrupted the bloom. Release of cell-bound toxins during the
bloom collapse likely accounted for the associated fish kill events where fish were reported as exhibiting typical symptoms
of karlotoxin poisoning. The dynamics of this bloom underscore the tight control of harmful algal blooms by meteorological
forcing, hydrology, and sediment nutrient input in this shallow lagoonal estuary. 相似文献
4.
Among the three principal regional units of Croatia, i.e. the elongated and spacious Adriatic littoral (with numerous islands), the relatively small and narrow mountainous belt (the Croatian transit doorway) and the Pannonian/peri-Pannonian region, the latter is the largest and accounts for 54 percent of the surface area and 66 percent of the population of Croatia (1991 census). It is part of the Pannonian (or Carpathian) basin, or the central Danube basin, so that Croatia is simply by its position a Danube country. Its Danube character is also highlighted by the fact that the Pannonian/peri-Pannonian region of Croatia through the Sava and Drava Rivers is directly linked to the navigable Danube, which is the historical and ethnic eastern boundary of Croatia. Croatia is an old historical Danube nation and country, although it has nominally appeared as a state after the break-up of Yugoslavia, and its international recognition as an independent state (1992). 相似文献
5.
Adolf Kühnemann 《GeoJournal》1993,30(3):259-272
On the map of Europe, forming the south-western border region of Poland, is to be found the name Silesia, with in many cases its southern part emphasized — Upper Silesia. Any search for statistics as to its exact surface area and population size will be in vain. At the end of World War I, Upper Silesia found itself squeezed between two nationalistically-obsessed peoples, and economically too attractive to both to be allowed to play an idependent political role, as it had for centuries. Upper Silesia was in 1921 divided. After World War II, under the communist centralised power system, a completely colonial robber economy was pursued. Because of the coal production there is now here one of the greatest agglomeration areas in Europe, with an ageing heavy industry and a catastropihcally damaged environment. 相似文献
6.
Berman’s (1983) activity-composition model for CaO-MgO-Al2O3-SiO2 liquids is used to calculate the change in bulk chemical and isotopic composition during simultaneous cooling, evaporation, and crystallization of droplets having the compositions of reasonable condensate precursors of Types A and B refractory inclusions in CV3 chondrites. The degree of evaporation of MgO and SiO2, calculated to be faithfully recorded in chemical and isotopic zoning of individual melilite crystals, is directly proportional to evaporation rate, which is a sensitive function of PH2, and inversely proportional to the droplet radius and cooling rate. When the precursors are partially melted in pure hydrogen at peak temperatures in the vicinity of the initial crystallization temperature of melilite, their bulk chemical compositions evolve into the composition fields of refractory inclusions, mass-fractionated isotopic compositions of Mg, Si, and O are produced that are in the range of the isotopic compositions of natural inclusions, and melilite zoning profiles result that are similar to those observed in real inclusions. For droplets of radius 0.25 cm evaporating at PH2 = 10−6 bar, precursors containing 8 to 13 wt.% MgO and 20 to 23% SiO2 evolve into objects similar to compact Type A inclusions at cooling rates of 2 to 12 K/h, depending on the precise starting composition. Precursors containing 13 to 14 wt.% MgO and 23 to 26% SiO2 evolve into objects with the characteristics of Type B1 inclusions at cooling rates of 1.5 to 3 K/h. The relatively SiO2-poor members of the Type B2 group can be produced from precursors containing 14 to 16 wt.% MgO and 27 to 33% SiO2 at cooling rates of <1 K/h. Type B2’s containing 27 to 35 wt.% SiO2 and <12% MgO require precursors with higher SiO2/MgO ratios at MgO > 15% than are found on any condensation curve. The characteristics of fluffy Type A inclusions, including their reversely zoned melilite, can only be understood in the context of this model if they contain relict melilite. 相似文献
7.
Synthesis of soil‐hydraulic properties and infiltration timescales in wildfire‐affected soils
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We collected soil‐hydraulic property data from the literature for wildfire‐affected soils, ash, and unburned soils. These data were used to calculate metrics and timescales of hydrologic response related to infiltration and surface runoff generation. Sorptivity (S) and wetting front potential (Ψf) were significantly different (lower) in burned soils compared with unburned soils, whereas field‐saturated hydraulic conductivity (Kfs) was not significantly different. The magnitude and duration of the influence of capillarity during infiltration was greatly reduced in burned soils, causing faster ponding times in response to rainfall. Ash had large values of S and Kfs but moderate values of Ψf, compared with unburned and burned soils, indicating ash has long ponding times in response to rainfall. The ratio of S2/Kfs was nearly constant (~100 mm) for unburned soils but more variable in burned soils, suggesting that unburned soils have a balance between gravity and capillarity contributions to infiltration that may depend on soil organic matter, whereas in burned soils the gravity contribution to infiltration is greater. Changes in S and Kfs in burned soils act synergistically to reduce infiltration and accelerate and amplify surface runoff generation. Synthesis of these findings identifies three key areas for future research. First, short timescales of capillary influences on infiltration indicate the need for better measurements of infiltration at times less than 1 min to accurately characterize S in burned soils. Second, using parameter values, such as Ψf, from unburned areas could produce substantial errors in hydrologic modeling when used without adjustment for wildfire effects, causing parameter compensation and resulting underestimation of Kfs. Third, more thorough measurement campaigns that capture soil‐structural changes, organic matter impacts, quantitative water repellency trends, and soil‐water content along with soil‐hydraulic properties could drive the development of better techniques for numerically simulating infiltration in burned areas. 相似文献
8.
9.
L. W. HardingJr. C. L. Gallegos E. S. Perry W. D. Miller J. E. Adolf M. E. Mallonee H. W. Paerl 《Estuaries and Coasts》2016,39(3):664-681
Climate effects on hydrology impart high variability to water-quality properties, including nutrient loadings, concentrations, and phytoplankton biomass as chlorophyll-a (chl-a), in estuarine and coastal ecosystems. Resolving long-term trends of these properties requires that we distinguish climate effects from secular changes reflecting anthropogenic eutrophication. Here, we test the hypothesis that strong climatic contrasts leading to irregular dry and wet periods contribute significantly to interannual variability of mean annual values of water-quality properties using in situ data for Chesapeake Bay. Climate effects are quantified using annual freshwater discharge from the Susquehanna River together with a synoptic climatology for the Chesapeake Bay region based on predominant sea-level pressure patterns. Time series of water-quality properties are analyzed using historical (1945–1983) and recent (1984–2012) data for the bay adjusted for climate effects on hydrology. Contemporary monitoring by the Chesapeake Bay Program (CBP) provides data for a period since mid-1984 that is significantly impacted by anthropogenic eutrophication, while historical data back to 1945 serve as historical context for a period prior to severe impairments. The generalized additive model (GAM) and the generalized additive mixed model (GAMM) are developed for nutrient loadings and concentrations (total nitrogen—TN, nitrate?+?nitrate—NO2?+?NO3) at the Susquehanna River and water-quality properties in the bay proper, including dissolved nutrients (NO2?+?NO3, orthophosphate—PO4), chl-a, diffuse light attenuation coefficient (K D (PAR)), and chl-a/TN. Each statistical model consists of a sum of nonlinear functions to generate flow-adjusted time series and compute long-term trends accounting for climate effects on hydrology. We present results identifying successive periods of (1) eutrophication ca. 1945–1980 characterized by approximately doubled TN and NO2?+?NO3 loadings, leading to increased chl-a and associated ecosystem impairments, and (2) modest decreases of TN and NO2?+?NO3 loadings from 1981 to 2012, signaling a partial reversal of nutrient over-enrichment. Comparison of our findings with long-term trends of water-quality properties for a variety of estuarine and coastal ecosystems around the world reveals that trends for Chesapeake Bay are weaker than for other systems subject to strenuous management efforts, suggesting that more aggressive actions than those undertaken to date will be required to counter anthropogenic eutrophication of this valuable resource. 相似文献
10.
The environmental impacts generated by shipping operations have increasingly become an important research topic, where its pollutants often pose negative externalities to natural habitats and economic losses to coastal areas. While the environmental impact costs generated by shipping disasters, notably large scale accidental oil spills, have been widely studied, hitherto, works dedicated to the assessment of environmental impact costs of pollutants generated by routine shipping operations remain scarce due to their relatively implicit nature and thus delays of consequential risks. Hence, by proposing an economic model and calibrating it to Port of Rotterdam, this paper assesses the environmental impact costs generated by routine shipping operations on ports. By shedding light on this important, but under-researched, issue critical to the well-being of the global shipping industry, this paper provides a decent framework for further research in sustainable shipping and port management for future generations. 相似文献