Implications of seasonal priming and reproductive activity on the interpretation of Comet assay data derived from the clam, Tapes semidecussatus Reeves 1864, exposed to contaminated sediments     

Hartl MG  Coughlan BM  Sheehan D  Mothersill C  van Pelt FN  O'Reilly SJ  Heffron JJ  O'Halloran J  O'Brien NM 《Marine environmental research》2004,57(4):295-310

We explore the use of the clam Tapes semidecussatus Reeves 1864 as an indicator for the presence of potentially genotoxic substances in estuarine sediments. The limitations associated with the interpretation of Comet assay data (expressed as % DNA in tail) in terms of clam reproductive state, size (age) and thermal exposure history following laboratory acclimation are discussed. Hatchery-reared clams, subjected to ambient temperature fluctuations during growth, were exposed in vivo under laboratory conditions for three weeks to sediment samples collected from a polluted site and a "clean" reference site. The DNA damage observed in haemocytes, gill and digestive gland cells was significantly higher in animals exposed to contaminated sediment compared to those exposed to sediment from the reference site. The extent of DNA damage recorded was not correlated with size (age). Spawning was not observed during the experiment. Nevertheless, clams with well-developed gonads showed a statistically higher degree of DNA damage in gill and digestive gland cells- but not haemocytes, demonstrating an increased sensitivity to potential genotoxic compounds, possibly caused by impaired DNA repair capacity due to reproductive activity. Furthermore, the degree of DNA damage in clams exposed to contaminated sediments was higher in autumn and winter compared to spring and summer, suggesting an effect of seasonal priming.  相似文献   

Studies on isoenzymes of glutathione S-transferase in the digestive gland of Mytilus galloprovincialis with exposure to pollution     

Patrick J. Fitzpatrick  David Sheehan  David R. Livingstone 《Marine environmental research》1995,39(1-4)

The possible utility of glutathione S-transferase isoenzymes in affinity purified extracts of digestive gland from Mytilus galloprovincialis as indicators of exposure to organic pollution has been assessed by fast protein liquid chromatography (FPLC) using a Mono-Q ion exchange column. Four main peaks of protein (isoenzymes 1–4) were detected in these chromatographic studies all of which displayed detectable catalytic activity with 1-chloro-2,4-dinitrobenzene and glutathione as substrates. The bulk of the activity with these substrates was associated with isoenzyme 1. The specific activity of cytosolic extracts from six sites in Venice Lagoon and the Adriatic Sea (UNESCO-MURST Venice Lagoon Ecosystem Project) decreased slightly with increasing tissue levels of chemical contaminants (hydrocarbons, PCBs and organochlorines). FPLC of affinity purified extracts from three of these sites was used to assess the possible variation in the levels of individual isoenzymes relative to pollution status. No difference was observed in the levels of these isoenzymes.  相似文献   

Chemical Petrology of Grenville Schists near Fernleigh, Ontario     

HOUNSLOW  A. W.; MOORE  J. M.  JR 《Journal of Petrology》1967,8(1):1-28

A suite of mica schists from the staurolite zone was studiedin detail. Phase rule considerations and distribution relationsindicate that chemical equilibrium was attained within the samplevolume. Iron-magnesium ratios of the silicates vary greatly,and correlate with rock ferrous-ferric ratio, as does the oxidemineral mode. Rock oxidation state varies locally, and is probablydependent on the composition of the original sediment. Distribution coefficients for Fe, Mg, and Mn among garnet, biotote,and staurolite show no vaiation attributable to temperature.Partition of Fe and Mg between staurolite and biotite is regular,but non-ideal. The staurolite structure permits only limited(15–35 percent) substitution of Mg for Fe.  相似文献   

Contrasting morphological trends of islands in Central Philippines: Speculation on their origin     

Graciano P. Yumul JR    Carla B. Dimalanta  Rodolfo A. Tamayo JR    Jenny Anne L. Barretto 《Island Arc》2000,9(4):627-637

Abstract The Palawan microcontinental block collided with the Philippine Mobile Belt in the Central Philippine region resulting in the counterclockwise rotation of Mindoro– Marinduque and clockwise rotation of Panay. The collision also brought about the clockwise rotation of north-east Negros, Cebu, north-west Masbate and Bohol (collectively called the Western Visayan block), resulting into their present-day northeast–southwest trend. This suggests a far more dramatic role of the collision than was previously recognized. Furthermore, the south-east Sulu Sea sub-basin is inferred to have also undergone collision-related clockwise rotation which can account for the observed east-west trending magnetic lineations in the basin. Aside from explaining the contrasting morphological trends of the different islands in Central Philippines, the rotation can also explain, albeit in a different way, how the belts of sedimentary basins, ophiolites and arcs in Panay and Negros can extend to Northern Luzon. Published paleomagnetic data suggest that the collision-related rotation commenced during the early to middle Miocene and had ceased by the late Miocene.  相似文献   

腾格里沙漠区盐湖物质成分研究   总被引：8，自引：2，他引：6       下载免费PDF全文

肖应凯  B.D.Vocke JR  魏海珍 《盐湖研究》2000,8(3):21-26

腾格里沙漠面积广阔 ,区内分布着数十个盐湖 ,盐湖面积大的为十余平方千米 ,小的仅为 0 .0 18km2 。盐湖卤水主要为湖表卤水 ,其矿化度较高 ,大部分盐湖卤水含盐量已达饱和 ,因而进入了自析盐阶段。盐湖卤水化学成分以 Na+ 、K+ 、Cl-、SO4 2 -、HCO3 -、CO3 2 -为主 ,占卤水总含盐量的 99% ,卤水中还有 B2 O3 、L i、I、Br等微量元素。盐湖盐类沉积有碳酸盐类、硫酸盐类和氯化物型盐类、主要盐类矿物为芒硝、钾芒硝、天然碱、泡碱、碳钾钠矾、石盐等。盐湖粘土矿物组合以蒙脱石的普遍存在为特征 ,含有少量的伊利石和水云母。  相似文献   

甘露醇对石墨存在下Cs2BO2^＋离子热电离质谱法测定硼同位素的影响   总被引：3，自引：2，他引：1       下载免费PDF全文

肖应凯 JR  BDV 《盐湖研究》2000,8(3):14-20

对石墨涂样检测Ｃｓ２ＢＯ２＾＋离子条件下甘露醇对硼同位素测定的影响进行了研究,结果表明在甘露醇存在下＾１１Ｂ／＾１０Ｂ比值明显高于只有石墨存在时的比值。硼－甘露醇络合物的形成可能改变了Ｃｓ２Ｂ０２＾＋－石墨方法的电离和蒸发条件。  相似文献   

Cultural responses to the altithermal: The role of aquifer-related water resources     

Michael S. Sheehan 《Geoarchaeology》1994,9(2):113-137

The focus of this research is Early Archaic adaptation to the hot and dry Altithermal in the North American Great Plains. The view presented here suggests a direct link between Altithermal climatic conditions and cultural responses to those conditions. Water was a key factor in cultural adaptation to arid Altithermal conditions. Statistical analysis reveals a significant relationship between Early Archaic site location and certain sources of groundwater that is not apparent during the periods preceding and succeeding the Altithermal. The distribution of Early Archaic sites may reflect increased emphasis on predictable water supplies offered by aquifers. © 1994 John Wiley & Sons, Inc.  相似文献   

Geographical information systems and planning in the USA: selected municipal adoption trends and educational concerns     

WILLIAM R. GORDON JR  NADER M. SOUBRA 《International journal of geographical information science》2013,27(4):267-278

Abstract

Practitioners and academics from many fields of study are currently facing numerous issues involving the diffusion of technologies from geographical information systems within their respective professions. This paper has two aims. The first is to report the partial results of a postal survey of selected municipal planning departments in the U.S.A. In measuring trends related to the adoption of computer and geographical information system technologies, the survey focuses on the availability of trained geographical information system and computer literate staff and on alternative means of training existing staff, as well as on the adequacy of collegiate education. The presentation of survey results is used to establish a framework for the principal discussion of this paper. The second part examines the relationship between planning and education in geographical information systems. Parallels within other disciplines and professions are derived. Curricula and training considerations within academic programmes and professional practice are suggested.  相似文献   

WMO     

LLOYD W. SWIFT JR  WAYNE T. SWANK 《水文科学杂志》2013,58(3):245-246

ABSTRACT

Long term changes in streamflow following forest cutting are presented for three experimental basins at Coweeta Hydrologic Laboratory, North Carolina, USA. Previous analyses have shown that, following forest cutting, streamflow increases and then declines with the logarithm of time as the forest regrows. Recent data indicate that the streamflow decline following cutting is related to vegetation regrowth, but the relationship is not a consistent function of simple stand measurements. The mixed hardwood forest of one basin was clearcut twice in the past 40 years. During the second regrowth period, streamflow increases after the first year were about one-half the increases at the same points in time after the first treatment. Concurrent with the second cutting, two other basins were cut whose mid-elevations are 400 m higher. The increases for the upper basins were similar, even though basal area was reduced by only 65% on one. Both streamflow increases were less than for either cutting on the lower basin. Variability of flow increases for the three concurrent treatments is similar and appears partly related to precipitation.  相似文献   

The new global growth path: implications for climate change analysis and policy     

Peter Sheehan 《Climatic change》2008,91(3-4):211-231

In recent years the world has moved to a new path of rapid global growth, largely driven by the developing countries, which is energy intensive and heavily reliant on the use of coal—global coal use will rise by nearly 60% over the decade to 2010. It is likely that, without changes to the policies in place in 2006, global CO₂ emissions from fuel combustion would nearly double their 2000 level by 2020 and would continue to rise beyond 2030. Neither the SRES marker scenarios nor the reference cases assembled in recent studies using integrated assessment models capture this abrupt shift to rapid growth based on fossil fuels, centred in key Asian countries. While policy changes must and will occur, the realism of the reference case is critical for analysis and policy formulation. Using such a reference path will have significant effects on impact and damage estimates, on the analysis of achievable stabilisation paths and on estimates of the costs of achieving stabilisation at a given GHG concentration level. Use of a realistic reference path is also essential for the international negotiations, arising out of the COP13 meeting in Bali, to achieve widely desired stabilisation goals: both the level of emission reductions to be achieved, and the preferred distribution of those reductions over countries and regions, will be heavily influenced by the reference case assumed.  相似文献