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41.
介绍了云南丽江高美古天文候选点,1995年12月~1996年11月全夜视宁度观测结果:全年平均r0=16.50cm(FWHM=0.67″),夜平均极大值rmax=22.41cm(0.49″),夜平均极小值rmin=12.95cm(0.85″)。 相似文献
42.
生物的染色和对其可能附着的基底的详细调查能够对Terebratulinaretusa进行准确的普查,并促进对其群体动态的研究。从深水腕足动物Modiolus组合中对Terebratulinaretusa的季节性取样中总是以小的(<1mm)个体为主,从群组的平均长度变化估计,幼年期后的生长速度突然放慢。幼虫在下沉6个月后,动物体在其长度、生长速度方面与实验室的研究一致,但种类比通常估计的要少。就其保护程度而言,腕足动物个体达到一定的大小是其唯一的生存对策,据此可干扰或抑制其过度生长,这对其生存有重要影响。Lorn地区的Firth附近,不同的附着层,T.retusa的死亡率有着意想不到的情况。实际上,尽管附在M.modiolus壳表面的幼年T.retusa个体有较高的死亡率,可它又是成年T.retusa个体的唯一附着基层。认为在复杂的表面上,摄食压力和空间竞争可以减小,这或许表明被附着的腕足动物M.modiolus首先达到2mm长度的巨大保护程度时,幼年期后的个体死亡率升高。 相似文献
43.
44.
This report describes a scoping study conducted in order to establish whether pharmaceutical compounds may be present in UK estuaries. Surface water samples collected from five UK estuaries were analysed for the presence of 14 pharmaceutical compounds selected from the priority lists of the UK Environment Agency and the Oslo and Paris Commission (OSPAR). The pharmaceutical compounds/metabolites clofibric acid, clotrimazole, dextropropoxyphene, diclofenac, ibuprofen, mefenamic acid, propranolol, tamoxifen and trimethoprim were detected at measurable concentrations in the samples collected. The concentrations of erythromycin, lofepramine, paracetamol, sulfamethoxazole and acetyl-sulfamethoxazole were all below the limits of detection of the methods used (between 4 and 20 ng l(-1)). The anti-fungal agent clotrimazole was the most frequently detected at a maximal concentration of 22 ng l(-1) and a median concentration of 7 ng l(-1). The analgesic compound ibuprofen was detected at a maximal concentration of approximately 930 ng l(-1) and a median concentration of 48 ng l(-1), whilst the other pharmaceutical compounds were detected between the limits of detection of the method used and 570 ng l(-1). 相似文献
45.
Application of harmonic analysis of water levels to determine vertical hydraulic conductivities in clay-rich aquitards 总被引:1,自引:0,他引:1
A harmonic analysis method was used to determine vertical hydraulic conductivities (Kv) in geologic media between vertically separated piezometers using water level measurements. In this method, each water level time series was filtered and then decomposed using harmonic analysis into a sum of trigonometric components. The phase and amplitude of each harmonic function were calculated. These data were used to estimate Kv values between vertically separated data sets assuming one-dimensional transient flow. The method was applied to water level data collected from nested piezometers at two thick clay-rich till aquitards in Saskatchewan, Canada. At one site, routine water levels were measured in 12 piezometers (installed between 1 and 29 m below ground surface) since installation (1995). At the other site, water levels were measured in seven piezometers (installed between 4 and 53 m below ground surface) since installation (1998-1999). The Kv calculated using harmonic analysis decreased with depth below the water table at both sites, approaching matrix estimates of hydraulic conductivity between 10 and 11 m and between 21 and 43 m below ground surface. These depths reflected the depth of extensive vertical fracturing at the sites and showed that the depth of fracturing may be site specific. 相似文献
46.
Interbasin ground water movement of 200 to 240 L/sec occurs as underflow beneath a mountainous surface water divide separating the topographically higher Salar de Michincha from the topographically lower Salar de Coposa internally drained basins in the Altiplano of northern Chile. Salt-encrusted flats (salars) and saline lakes occur on the lowest parts of the basin floors and comprise the principal evaporative discharge areas for the basins. Because a surface water divide separates the basins, surface water drainage boundaries do not coincide with ground water drainage boundaries. In the region, interbasin ground water movement is usually not recognized, but occurs for selected basins, and at places is an important component of ground water budgets. With increasing development of water for mining industry and potential exportation of ground water from the Altiplano for use at coastal cities, demonstration and quantification of interbasin movement is important for assessment of sustainable ground water development in a region of extreme aridity. Recognition and quantification of interbasin ground water underflow will assist in management of ground water resources in the arid Chilean Altiplano environment. 相似文献
47.
Moore MJ Mitrofanov IV Valentini SS Volkov VV Kurbskiy AV Zhimbey EN Eglinton LB Stegeman JJ 《Marine pollution bulletin》2003,46(1):107-119
Roach, goby and sturgeon were examined for cytochrome P4501A (CYP1A) expression and histopathology, in relation to contaminant burdens in fish and sediment. Gradients of induction of CYP1A were observed. Roach from the Ural and Ily River Deltas and roach and goby from the two stations nearest the Caspian Sea oil fields displayed higher levels of CYP1A expression in several organs than was observed in fish from further offshore. Great sturgeon and Russian sturgeon showed higher levels of CYP1A expression than was seen in starred sturgeon and gobies in the Ural delta. No fish showed evidence of contaminant-related histopathologies in the organs examined, despite the elevated CYP1A levels. Low levels of polychlorinated biphenyls and elevated levels of inshore and riverine petroleum hydrocarbons from these habitats suggest that this ongoing hydrocarbon exposure, and that from natural sources and long-term oil exploration on the Northeastern Caspian shore, contributed to the CYP1A induction observed. 相似文献
48.
Large amounts of marine debris are present in shallow reefs adjacent to beach haulouts of the critically endangered Hawaiian monk seal, Monachus schauinslandi. These areas serve as seal pup nurseries, and injury and death caused by entanglement in marine debris are undermining population recovery efforts. We investigated the extent of this threat by measuring the accumulation of potentially entangling derelict fishing gear in nursery zones, 1999-2001. Plots of reef 1.0-1.3 km2 at three Northwestern Hawaiian Islands were initially cleaned of derelict fishing gear in 1999 then resurveyed in 2000 and 2001. Submerged debris densities across sites ranged from 16 to 165 debris items/km2. Resurveyed sites yielded annual marine debris accumulation rates from 0 to 141 debris items/km2. This large range was attributed to the physiography of reef areas surveyed. Trawl net webbing was significantly more common than other types of debris recovered and represented 84% of all debris encountered, suggesting that much of the debris originated from distant North Pacific Ocean fisheries. The likely source of most debris is the multinational trawl fisheries of the North Pacific Ocean. An international solution to this problem is needed. Targeted marine debris removal is a short-term, successful, entanglement mitigation strategy. 相似文献
49.
Caue铁矿位于Sao Francisco地盾南部Itabira地区。在该区已确定出其变质程度达到角闪岩相三个地质单元:(1)太古代火山沉积层序;(2)元代含铁建筑单元;(3)元古代石曲岩单元。含铁建造单元被角闪岩脉切割,在构造上被火山沉积层序内的滑石片岩和角闪岩叠。 相似文献