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991.
Anirudh?PradhanEmail author Sudhir?Kumar?Srivastav Mahesh?Kumar?Yadav 《Astrophysics and Space Science》2005,298(3):419-432
Some Bianchi type IX viscous fluid cosmological models are investigated. To get a solution, a supplementary condition between
metric potentials is used. The viscosity coefficient of bulk viscous fluid is assumed to be a power function of mass density,
whereas the coefficient of shear viscosity is considered as proportional to scale of expansion in the model. The cosmological
constant Λ is found to be positive and is a decreasing function of time, which is supported by results from recent supernovae
observations. Some physical and geometric properties of the models are also discussed. 相似文献
992.
993.
Martin?Reich Miguel?A.?ParadaEmail author Carlos?Palacios Andreas?Dietrich Frank?Schultz Bernd?Lehmann 《Mineralium Deposita》2003,38(7):876-885
Adakite-like features are recognized in the Late Miocene (~10 Ma) porphyritic intrusions of the Los Pelambres giant porphyry copper deposit, central Chile (32°S). Located within the southern portion of the flat-slab segment (28–33°S) of the Chilean Andes, the Al- and Na-rich porphyries of Los Pelambres display distinctly higher Sr/Y (~100–300) and LaN/YbN (~25–60) ratios than contemporaneous and barren magmatic units (e.g., La Gloria pluton, Cerro Aconcagua volcanic rocks) of the same Andean magmatic belt. Strong fractionation of heavy rare earth elements (HREE), absence of Eu anomalies, high Sr/Y and Zr/Sm and low Nb/Ta ratios suggest melt extraction from a garnet-amphibolite source. The Late-Miocene adakite-like porphyritic intrusions at Los Pelambres formed closely related in time and space to the subduction of the Juan Fernández Ridge (JFR) hotspot chain along the Chilean margin. Current tectonic reconstructions reveal that, at the time of formation of the Los Pelambres rocks, a W-E segment of the JFR started to subduct beneath them, producing a slow-down of a previously rapid southward migration of a NE-ridge—trench collision. These particular tectonic conditions are favorable for the origin of the Los Pelambres porphyry suite by melting of subducting young hotspot rocks under flat-slab conditions. The incorporation of crustal components into the oceanic lithopheric magma source by subduction erosion is evidenced by the Sr-Nd isotope composition of the Los Pelambres rocks different from the MORB signatures of true adakites. A close relationship apparently exists between the origin of this adakite-like magmatism and the source of the mineralization in the Los Pelambres porphyry copper deposit.Editorial handling: R.J. Goldfarb 相似文献
994.
In this paper, the application of a homemade Nation and Co(Salen) modified platinum microelectrode and an ISO-NOPMC microsensor (World Precision Instruments, USA ) to measure nitric oxide in natural seawater is reported. These two microelectrodes are suitable for the measurement. In natural seawater, the sensitivity and stability of the ISO-NOPMC microsensor are higher than that of the homemade Nation and Co(Salen) modified platinum microelectrode. 相似文献
995.
Application of multiple sublethal stress indicators to assess the health of fish in Pamlico Sound following extensive flooding 总被引:1,自引:0,他引:1
S.?Marshall?AdamsEmail author Mark?S.?Greeley J.?McHugh?Law Edward?J.?Noga Judith?T.?Zelikoff 《Estuaries and Coasts》2003,26(5):1365-1382
Multiple indicators of sublethal stress (bioindicators) were used to assess the health and condition of two important estuarine fish species in the Pamlico Sound estuary following extensive flooding from three sequential hurricanes that occurred during early fall 1999. Bioindicators ranging from the biochemical to the reproductive and organism-level were used to assess the health of southern flounder and spot in Pamlico Sound compared to the health of these same species sampled from a relatively unaffected references site in lower Core Sound. Many of the physiological, reproductive, immunological, histopathological, and general condition indices suggested that both species, and particularly spot, in Pamlico Sound were sublethally stressed and in poorer condition than fish sampled from Core Sound. The major environmental stressors causing these sublethal stress responses in Pamlico Sound fish appears to be those related to episodic hypoxic exposure or a combination of effects associated with hypoxic conditions such as alterations in preferred habitat and food availability. Although fish populations in Pamlico Sound do not appear to be severely damaged or impaired at this time, organisms that are sublethally stressed can incur increased vulnerability to additional or future stressors such as modified physicochemical regimes, changes in food and habitat availability, and increases in infectious pathogens. Because of the low flushing rate (~1 yr) of Pamlico Sound, recovery rate may be exceptionally slow, prolonging any adverse effects of altered nutrient regimes (such as hypoxia) on the health and fitness of resident fish populations. Flooding from the 1999 hurricanes may have contributed to the short-term health and condition of finfish species in Pamlico Sound and also influenced longer-term recovery and ecological status of this system. Longer-term manifestation of effects from flooding may be of particular concern as the frequency of hurricanes is expected to increase over the next few years and the accelerated uses of the coastal zone places further stress on estuarine resources. 相似文献
996.
Climate changes at the multi-decadal scale are often associated with multi-decadal phase shifts of the dominant sea surface temperature (SST) pattern, such as the Pacific Decadal Oscillation (PDO). The PDO may be associated with the North Pacific branch of the Thermohaline Circulation (THC). Great earthquakes (M 〉8), particularly along the route of the THC, might modulate the vertical mixing and bring deep, cold water to surface, contributing to multi-decadal changes in surface currents and the PDO. This may eventually lead to multi-decadal climate changes. We tested this hypothesis for the Pacific Ocean where great earthquakes have been frequently recorded. We found associations between the PDO and recurrent earthquakes along the route of the deep currents of the THC in the modern period since 1900, and relationships between hydroclimate change in Monsoonal Asia and historical earthquakes since 1300. However, it should be noted that this hypothesis is very preliminary and has many gaps that needs further evidences from more observational records and modeling studies. 相似文献
997.
CMEs and flares are the two energetic phenomena on the Sun responsible for generating shocks. Our main aim is to study the relation between the physical properties of CMEs and flares associated with and without type II radio bursts. We considered a set of 290 SOHO/LASCO CMEs associated with GOES X-ray flares observed during the period from January 1997 to December 2000. The relationship between the flares and CMEs is examined for the two sets i) with metric-type IIs and ii) without metric-type IIs. Physical properties such as rise time, duration, and strength of the flares and width, speed, and acceleration of CMEs are considered. We examined the energy relationship and temporal relationship between the CMEs and flares. First, all the events in each group were considered, and then the limb events in each group were considered separately. While there is a relationship between the temporal characteristics of flares and CME properties in the case of with-type IIs, it is absent in the case of all without-type IIs. Among all the relations studied, the correlation between flare duration and CME properties is found to be highly significant compared to the other relations. Also, the relationship between flare strength and CME speed found in the with-type II events is absent in the case of all without-type II events. However, when the limb without-type II events (with reduced time window between flare and CME) are studied separately, we found the energy relationship and the temporal relationship. 相似文献
998.
999.
Preliminary study on PAH degradation by bacteria from contaminated sediments in Xiamen Western Sea,Fujian, China 总被引:1,自引:0,他引:1
In order to estimate the biodegradation of three polycyclic aromatic hydrocarbons (PAHs) compounds, bacterial strains were isolated from marine sediments in three heavily contaminated sites (Yuandang Lake, Dongdu Port and Aquacultural zones in Maluan Bay) in Xiamen Western Sea. The results show three bacterial strains, which used pyrene as the sole carbon source, were identified as strains of Aureobacterium sp.,Arthrobacter sp., Rhodococcus sp. The PAH-degrading bacteria isolated had a strong ability to degrade phenanhrene, fluoranthene and pyrene at different degradation rates. The highest degradation rate was observed when three PAH compounds were mixed with an individual strain in the medium. The three PAHs were degraded after one week with a degradation rate of 89.94 % for phenanthrene and 93.4 % for both of fluoranthene and pyrene.In addition, after 25 days of incubation, the degradation rate was 99.98 % for phenanthrene and 99.97 % for both of fluoranthene and pyrene. Optical density was measured to estimate bacterial growth during the degradation of PAHs. Highest levels of bacterial growth were observed with a three PAH mixture in the culture, suggesting that the concentration of PAHs influenced bacterial growth and the highest levels of degradation for most series were detected after one week of incubation. 相似文献
1000.
旅游信息系统建设模式探讨——以佛山市为例 总被引:6,自引:0,他引:6
作为当前旅游信息系统开发的两种主要基础平台,地理信息系统和多媒体制作系统都存在一定的缺陷。多媒体制作系统缺乏旅游地图的有效管理,空间查询,分析和统计功能,旅游地理信息系统则缺乏旅游信息的多媒体表达能力。从实用性和普及性出发,集合二者优点开发模式具有更大的推广应用价值。因此,论文提出在同一界面下基于GIS和多媒体集成的旅游信息系统开发模式;(1)在GIS中增加多媒体信息表达能力,以关系数据库为核心,把多媒体文件名信息存储在地理信息系统属性库,依靠多媒休段实现多媒体数据与地理信息系统图形和属性的关联,实现查询的基本概念;(2)在多媒体系统中开发部分GIS空间查询功能。以此思路,佛山科技学院GIS技术实验室利用VB进行GIS和多媒体二次开发,成功地完成了佛山旅游信息系统的设计和开发。 相似文献