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11.
Recently, Zhang slightly modified the standard big bang theory and developed a new cosmological model called black hole universe, which is consistent with Mach’s principle, governed by Einstein’s general theory of relativity, and able to explain all observations of the universe. Previous studies accounted for the origin, structure, evolution, expansion, and cosmic microwave background radiation of the black hole universe, which grew from a star-like black hole with several solar masses through a supermassive black hole with billions of solar masses to the present state with hundred billion-trillions of solar masses by accreting ambient matter and merging with other black holes. This paper investigates acceleration of the black hole universe and provides an alternative explanation for the redshift and luminosity distance measurements of type Ia supernovae. The results indicate that the black hole universe accelerates its expansion when it accretes the ambient matter in an increasing rate. In other words, i.e., when the second-order derivative of the mass of the black hole universe with respect to the time is positive $\ddot{M}(t) > 0$ . For a constant deceleration parameter $q = -M(t) \ddot{M}(t)/\dot{M}(t) \sim-0.6$ , we can perfectly explain the type Ia supernova measurements with the reduced chi-square to be very close to unity, χ red~1.0012. The expansion and acceleration of black hole universe are driven by external energy. 相似文献
12.
Charles T. Roman Norbert Jaworski Frederick T. Short Stuart Findlay R. Scott Warren 《Estuaries and Coasts》2000,23(6):743-764
Geographic signatures are physical, chemical, biotic, and human-induced characteristics or processes that help define similar or unique features of estuaries along latitudinal or geographic gradients. Geomorphologically, estuaries of the northeastern U.S., from the Hudson River estuary and northward along the Gulf of Maine shoreline, are highly diverse because of a complex bedrock geology and glacial history. Back-barrier estuaries and lagoons occur within the northeast region, but the domiant type is the drowned-river valley, often with rocky shores. Tidal range and mean depth of northeast estuaries are generally greater when compared to estuaries of the more southern U.S. Atlantic coast and Gulf of Mexico. Because of small estuarine drainage basins, low riverine flows, a bedrock substrate, and dense forest cover, sediment loads in northeast estuaries are generally quite low and water clarity is high. Tidal marshes, seagrass meadows, intertidal mudflats, and rocky shores represent major habitat types that fringe northeast estuaries, supporting commercially-important fauna, forage nekton and benthos, and coastal bird communities, while also serving as links between deeper estuarine waters and habitats through detritus-based pathways. Regarding land use and water quality trends, portions of the northeast have a history of over a century of intense urbanization as reflected in increased total nitrogen and total phosphorus loadings to estuaries, with wastewater treatment facilities and atmospheric deposition being major sources. Agricultural inputs are relatively minor throughout the northeast, with relative importance increasing for coastal plain estuaries. Identifying geographic signatures provides an objective means for comparing the structure, function, and processes of estuaries along latitudinal gradients. 相似文献
13.
Frederick W. Oliver 《Planetary and Space Science》1978,26(3):289-290
The Mossbauer spectra has been measured for the Leoville meteorite. Experimental results identify it as a type III carbonaceous meteorite. The spectrum shows the principle iron components to be olivine, magnetite, metallic iron, troilite and phyllosilicate material. 相似文献
14.
Cunners, a common inshore teleost fish of the north-east coast of the United States, were exposed to various concentrations of silver for 96 h. At the end of this exposure period measurements of gill-tissue oxygen consumption were made. Significant respiratory depression was noted after exposure to concentrations as low as 0.12 ppm. These results are compared to those of similar studies using cadmium and mercury as the test metals. 相似文献
15.
16.
Understanding the impact of past climatic changes on landscape stability is crucial in order to predict and mitigate the effects of future changes. However, in arid and semi‐arid environments, reconstructions are often hampered by a poor understanding of the relationship between sediment deposition and climate. We present here data from central Texas, a region that is sensitive to environmental change but has received relatively little attention. The study integrates a chronology of 29 optically stimulated luminescence (OSL) ages from six sedimentary sites in a range of depositional contexts with a 19 000 a climate record derived from pollen extracted from the adjacent Boriack Bog. By comparing the two records, we aimed to assess the relationship between climate change and geomorphic activity. Data show that extensive aeolian and colluvial deposition occurred during the mid to late Holocene, with sedimentation generally increasing during more arid phases. However, a number of depositional events on slopes were associated with moister episodes, and sediment was also deposited in a summit setting immediately after phases of increased precipitation. Linkages between climate change and geomorphic response were therefore complex, being controlled by both sediment supply and transport energy. The climatic fluctuations identified in the Boriack Bog record highlight the sensitivity of central Texas to environmental change, while disparities in conditions recorded between it and other palaeoenvironmental sites in the southern USA emphasise the need for further work in order to enhance understanding of landscape sedimentary response to climate. Copyright © 2010 John Wiley & Sons, Ltd. 相似文献
17.
J. Stephen Hopkins Paul A. Sandifer M. Richard DeVoe A. Frederick Holland Craig L. Browdy Alvin D. Stokes 《Estuaries and Coasts》1995,18(1):25-42
Shrimp culture technology has resulted in development of a major shrimp farming industry worldwide. Without the shrimp farming industry, increasing demands for shrimp by consumers could not be met, resulting in increased pressure on wild shrimp resources. Unfortunately, there are realized and potential adverse environmental effects on estuarine ecosystems as a result of shrimp farming. The effects can be categorized as wetland destruction for construction of shrimp farms, hypernutrification of estuarine ecosystems by shrim pond effluent, “biological pollution” of native shrimp stocks through escapement of aquaculture stocks, water use and entrainment of estuarine biota, and impacts of shrimp farm chemicals on estuarine systems. While the shrimp farming industry in the United States is small, the United States is effectively addressing all the realized and potential environmental impacts through regulation and research at the federal and state levels. Areas of regulation and research include stringent prohibitions on wetland destruction, regulation of effluents and support of research to eliminate and/or reduce effluents, escapement prevention technology and development of high-health stocks, minimizing entrainment of estuarine biota through water conservation and screening technology, and regulation of chemical use in the shrimp farming industry and support of research on shrimp pathology and environmentally safe disease control. Work is still in progress and not all problems have been resolved to the complete satisfaction of shrimp farmers and estuarine conservationists. However, the situation in the United States should serve as a model of how to encourage sustainable economic development through commercial shrimp farming while abating adverse environmental impacts on estuarine systems. To further improve the situation, the development and adoption of “best management practices” for shrimp aquaculture are recommended. 相似文献
18.
Li Li Yang Hong Jiahu Wang Robert F. Adler Frederick S. Policelli Shahid Habib Daniel Irwn Tesfaye Korme Lawrence Okello 《Natural Hazards》2009,50(1):109-123
Many researchers seek to take advantage of the recently available and virtually uninterrupted supply of satellite-based rainfall
information as an alternative and supplement to the ground-based observations in order to implement a cost-effective flood
prediction in many under-gauged regions around the world. Recently, NASA Applied Science Program has partnered with USAID
and African-RCMRD to implement an operational water-hazard warning system, SERVIR-Africa. The ultimate goal of the project
is to build up disaster management capacity in East Africa by providing local governmental officials and international aid
organizations a practical decision-support tool in order to better assess emerging flood impacts and to quantify spatial extent
of flood risk, as well as to respond to such flood emergencies more expediently. The objective of this article is to evaluate
the applicability of integrating NASA’s standard satellite precipitation product with a flood prediction model for disaster
management in Nzoia, sub-basin of Lake Victoria, Africa. This research first evaluated the TMPA real-time rainfall data against
gauged rainfall data from the year 2002 through 2006. Then, the gridded Xinanjiang Model was calibrated to Nzoia basin for
period of 1985–2006. Benchmark streamflow simulations were produced with the calibrated hydrological model using the rain
gauge and observed streamflow data. Afterward, continuous discharge predictions forced by TMPA 3B42RT real-time data from
2002 through 2006 were simulated, and acceptable results were obtained in comparison with the benchmark performance according
to the designated statistic indices such as bias ratio (20%) and NSCE (0.67). Moreover, it is identified that the flood prediction
results were improved with systematically bias-corrected TMPA rainfall data with less bias (3.6%) and higher NSCE (0.71).
Although the results justify to suggest to us that TMPA real-time data can be acceptably used to drive hydrological models
for flood prediction purpose in Nzoia basin, continuous progress in space-borne rainfall estimation technology toward higher
accuracy and higher spatial resolution is highly appreciated. Finally, it is also highly recommended that to increase flood
forecasting lead time, more reliable and more accurate short- or medium-range quantitative precipitation forecasts is a must. 相似文献
19.
A. P. le Roex Frederick A. Frey Stephen H. Richardson 《Contributions to Mineralogy and Petrology》1996,124(2):167-184
Basaltic lavas from the AMAR Valley and the Narrowgate region of the FAMOUS Valley on the Mid-Atlantic Ridge (36° to 37°?N) range in texture from aphyric to highly plagioclase phyric (>25% large plagioclase phenocrysts). Based on 87Sr/86Sr and 143Nd/144Nd ratios, most of these lavas can be subdivided into two distinct, isotopically homogeneous, groups: Group I has lower 87Sr/86Sr (0.70288±1) and higher 143Nd/144Nd (0.51312±1) ratios; Group II has higher 87Sr/86Sr (0.70296±1) and lower 143Nd/144Nd (0.51309±2) ratios. Most Group II lavas are aphyric, whereas Group I lavas are primarily plagioclase phyric. Lavas from both groups show a wide range in incompatible element abundance ratios (e.g., Zr/Nb =6–29; (La/Sm)n=0.6–1.7). Aphyric lavas have relatively constant Sc (40±1.5?ppm) abundances and CaO/Al2O3 ratios (0.80±0.02). Group I lavas are confined primarily to the AMAR rift valley floor whereas Group II lavas are found along the east and west marginal highs. We interpret the isotopic differences between the two groups as reflecting a temporal change in the upwelling mantle beneath this region of the Mid-Atlantic Ridge which is south of the Azore Islands. For each group, a petrogenetic model consistent with the geochemical data is multi-stage decompression melting of an initially enriched, homogeneous, mantle source region. If the early derived, incompatible-element enriched, melt increments are not always pooled with subsequent increments, the erupted magma batches may have the major element characteristics of melts derived by 10 to 20% melting, but with incompatible element abundance ratios reflecting the change from an enriched to depleted source during the incremental melting process. In this process an initially homogeneous source can generate primary magmas with the required range in incompatible element abundance ratios shown by each group. The nearly constant CaO/Al2O3 ratios and Sc contents of the aphyric lavas with decreasing Mg?? reflects subsequent polybaric fractionation of clinopyroxene, plagioclase and olivine over the pressure interval 8–6?kbar (24–18?km), followed by rapid transport to the surface and eruption. There is no geochemical evidence for a crustal magma chamber beneath this section of the Mid-Atlantic Ridge. 相似文献
20.