خيارات البحث
النتائج 331 - 340 من 373
Polar narcosis: Designing a suitable training set for QSAR studies النص الكامل
1997
Ramos, Eñaut Urrestarazu | Vaes, Wouter H. J. | Verhaar, H. J. M. | Hermens, Joop L. M.
Substituted phenols, anilines, pyridines and mononitrobenzenes can be classified as polar narcotics. These chemicals differ from non-polar narcotic compounds not only in their toxic potency (normalized by log Kₒw), but also in their Fish Acute Toxicity Syndrome profiles, together suggesting a different mode of action.For 97 polar narcotics, which are not ionized under physiological conditions, 11 physico-chemical and quantum-chemical descriptors were calculated. Using principal component analysis, 91 % of the total variance in this descriptor space could be explained by three principal components which were subsequently used as factors in a statistical design. Eleven compounds were selected based on a two-level full factorial design including three compounds near the center of the chemical domain (a 2³+3 design).QSARs were developed for both the design set and the whole set of 63 polar narcotics for which guppy and/or fathead minnow data were available in the literature. Both QSARs, based on partial least squares regression (3 latent variables), resulted in good models (R²=0.96 and Q²=0.82; R²=0.86 and Q²=0.83 respectively) and provided similar pseudo-regression coefficients. In addition, the model based on the design chemicals was able to predict the toxicity of the 63 compounds (R² =0.85).Models show that acute fish toxicity is determined by hydrophobicity, HOMO-LUMO energy gap and hydrogen-bond acceptor capacity.
اظهر المزيد [+] اقل [-]Long-term changes in forest soil acidity in Pennsylvania, U.S.A.
1997
Drohan, J.R. (Pennsylvania State Univ., University Park, PA (USA).) | Sharpe, W.E.
Ion leaching before and after clear-cutting in a Norway spruce stand: effects of long-term application of ammonium nitrate and superphosphate
1997
Berden, M. (Swedish Univ. of Agricultural Sciences, Uppsala (Sweden). Dept. of Soil Sciences) | Nilsson, S.I. | Nyman, P.
Effects of watershed liming on Picea rubens seedling biomass and nutrient element concentration
1997
Smallidge, P.J. (Frostburg State Univ., Frostburg, MD (USA). Dept. of Biology) | Leopold, D.J.
Effects of metals on the microbial mineralization of organic acids
1997
Brynhildsen, L. (Linkoeping Univ. (Sweden). Dept. of Water and Environmental Studies) | Rosswall, T.
Heavy metals in allotment gardens close to an oil refinery in Plock
1997
Mikula, W. (Warsaw Agricultural Univ., Warszawa (Poland). Faculty of Horticulture, Dept. of Environmental Protection) | Indeka, L.
The difference in brown trout (Salmo trutta L.) blood composition from acidic and limed sites of two rivers in western Norway
1997
Galina, M.S. (Moscow State Univ. (Russian Federation). Faculty of Biology, Dept. of Hydrobiology)
Influence of a mycorrhizal fungus and/or rhizobium on growth and biomass partitioning of subterranean clover exposed to ozone
1997
Miller, J.E. (North Carolina State Univ., Raleigh, NC (USA). Dept. of Forestry) | Shafer, S.R. | Schoeneberger, M.M. | Pursley, W.A. | Horton, S.J. | Davey, C.B.
Monitoring nitrogen pollution from sugarcane runoff using (15)N analysis
1997
Lindau, C.W. (Louisiana State Univ., Baton Rouge, LA (USA). Nuclear Science Center, Wetland Biogeochemistry Inst.) | Delaune, R.D. | Alford, D.P.
Ash from cereal and rape straw used for heat production: liming effect and contents of plant nutrients and heavy metals
1997
Sander, M.L. (Swedish Univ. of Agricultural Sciences, Uppsala (Sweden). Dept. of Ecology and Environmental Research) | Andren, O.
