Nutrient regimes and their effect on distribution of phytoplankton in the Bay of Bengal

The seasonal dynamics of nutrient ratios and abundance of phytoplankton cells from the central (CB) and western (WB) Bay of Bengal (BOB) were studied during the fall intermonsoon (FIM; September-October 2002) and spring intermonsoon (SpIM; April-May 2003). The nutrient molar ratios of macronutrients such as nitrate to phosphate (N:P), nitrate to silicate (N:Si) and silicate to phosphate (Si:P) in the top 120m were calculated for both FIM and SpIM. During both the seasons, the N:P ratios along the CB and WB were lower than 16, indicating nitrate deficiency. Whereas, along both transects the N:Si ratio was <1 and Si:P >3 in the top 20 and 40m during FIM and SpIM, respectively, indicating Si enrichment. Relatively greater nutrient concentrations along the WB than the CB appear to contribute to higher phytoplankton abundance. The preponderance of diatoms in the Bay could be attributed to rapid utilization of available nutrients in particular during FIM thus resulting in low N:Si ratios in the water column. Among diatoms, pennales were predominantly controlled by nutrients and their ratios. While, apart from nutrients, physical stratification, light and eddies also seem to influence the distribution and abundance of centrales.     

西秦岭白依沟群形成环境及其时代的初步探讨

本文根据西秦岭白依沟群中火山-沉积岩系的结构、构造和其中所夹的火山碎屑岩的岩性、岩石化学、地球化学特征。初步认为它是一套陆相沉积夹有夭折裂谷型火山岩的火山-沉积岩系。并结合白依沟群中英安质凝灰岩所测的Rb-Sr等时线年龄为738.59Ma,因此其时代应归属于早震旦世,与川西乌斯大桥群相当。     

Variations of bromide in potable ground water in the United States

Concentrations of bromide in potable ground water that has <10 mg/L chloride range from 0.0032 to 0.058 mg/L with a median value of 0.016 mg/L. The chloride/bromide mass ratio for the same water ranges from 43 to 285 with a median value of 101. The ratios, which resulted from screening approximately 165 analyses of water from 32 locations in 24 states in the United States, show a distinct geographic variation with highest values near the coast and trending toward a value of approximately 50 in the continental interior.     

Using high hydraulic conductivity nodes to simulate seepage lakes

In a typical ground water flow model, lakes are represented by specified head nodes requiring that lake levels be known a priori. To remove this limitation, previous researchers assigned high hydraulic conductivity (K) values to nodes that represent a lake, under the assumption that the simulated head at the nodes in the high-K zone accurately reflects lake level. The solution should also produce a constant water level across the lake. We developed a model of a simple hypothetical ground water/lake system to test whether solutions using high-K lake nodes are sensitive to the value of K selected to represent the lake. Results show that the larger the contrast between the K of the aquifer and the K of the lake nodes, the smaller the error tolerance required for the solution to converge. For our test problem, a contrast of three orders of magnitude produced a head difference across the lake of 0.005 m under a regional gradient of the order of 10(-3) m/m, while a contrast of four orders of magnitude produced a head difference of 0.001 m. The high-K method was then used to simulate lake levels in Pretty Lake, Wisconsin. Results for both the hypothetical system and the application to Pretty Lake compared favorably with results using a lake package developed for MODFLOW (Merritt and Konikow 2000). While our results demonstrate that the high-K method accurately simulates lake levels, this method has more cumbersome postprocessing and longer run times than the same problem simulated using the lake package.     

Impact of polychlorinated biphenyls (PCBs) on the immune function of fish: age as a variable in determining adverse outcome

Polychlorinated biphenyls (PCBs) are a major contaminant of global extent in water resources and aquatic biota. Due to its high lipid solubility, PCBs fail to be degraded and, therefore, continue to bioaccumulate throughout the environment and food chain. To determine the impact of PCBs on the immune system of aged and juvenile Japanese medaka (Oryzias latipes), fish were injected with the coplanar PCB congener 126 and examined after 3 and 14 days. PCB 126 produced oxidative stress in both age groups of fish 14 days post-injection; however, juvenile medaka appeared more susceptible than aged fish. Humoral immunity, as determined by antibody forming cell (AFC) numbers, was significantly depressed for up to 14 days post-injection in both age groups. These results demonstrate the sensitivity of the fish immune response for predicting PCB-induced immunotoxicity and identify age as a variable in determining adverse outcome.     

Suppressive effects of benzo[a]pyrene upon fish immune function: evolutionarily conserved cellular mechanisms of immunotoxicity

Knowledge gained through the use of alternative animal models has significantly enhanced our understanding of life at all levels of biological organization. The discipline of toxicology is under considerable pressure to develop such models due to increasing public concern regarding the experimental use of mammals. Studies in this laboratory have focused on the utility of a small laboratory fish model, the Japanese medaka (Oryzias latipes), to investigate immunotoxicological effects of benzo[a]pyrene (BaP). BaP is a ubiquitous environmental contaminant and known mammalian immunotoxicant. This laboratory has demonstrated that in vivo exposure of medaka to BaP (2-200 microg/g BW) significantly depresses both innate and humoral immunity. Further studies have indicated that BaP activates its own biotransformation pathway within medaka immune cells following both in vivo and in vitro exposure. In addition, reduction of BaP metabolism with alpha-naphthoflavone results in the reversal of BaP-induced suppression of antibody production in vitro. Inhibition of CYPlA-mediated metabolism within medaka immune cells also alleviates the immunotoxicity induced by benzo[a]pyrene-7,8-dihydrodiol, but not benzo[a]pyrene-7,8-dihydrodiol-9,10-epoxide (BPDE). This suggests that BPDE may be an ultimate immunotoxicant. Results from this study in medaka are in agreement with previously conducted rodent studies that indicated a role for immunotoxic BaP metabolites in BaP-induced suppression of humoral immunity.     

注过氧化氢提高原油采收率

新颖的注过氧化氢开采稠油的方法是ＮＯＶＡＴＥＣ接受的一项美国专利。这种方法似乎比目前热力采油技术在若干方面均有显著的改善。Ｔｅｊａｓ石油工程公司与ＮＯＶＡＴＥＣ联合对这一方法进行室内试验，并扩展到现场实际应用和制定有关步骤。