خيارات البحث
النتائج 301 - 310 من 374
The accumulation of arsenic, bromine and iodine in needles of Norway spruce (Picea abies [L.] Karst.) at sites with low pollution
1997
Wyttenbach, A. (Paul Scherrer Inst., Villigen (Switzerland).) | Bajo, S. | Furrer, V. | Langenauer, M. | Tobler, L.
Sulphur and heavy metal concentrations in Scots pine bark in northern Finland and the Kola Peninsula
1997
Poikolainen, J. (Finnish Forest Research Inst., Muhos (Finland). Muhos Research Station)
Variations in sulphur and nitrogen foliar concentration of deciduous and conifers vegetation in Slovakia
1997
Mankovska, B. (Forest Research Inst., Zvolen (Slovak Republic).)
Relationship between sugar maple decline and corresponding chemical changes in the stem tissue
1997
Mohamed, H.K. (Toronto Univ., Toronto, Ont. (Canada). Faculty of Forestry) | Pathak, S. | Roy, D.N. | Hutchinson, T.C. | McLaughlin, D.L. | Kinch, J.C.
Tree bark as a bioindicator of air pollution in Navarra, Spain
1997
Santamaria, J.M. (Navarra Univ., Pamplona (Spain). Dept. of Chemistry and Soil Science) | Martin, A.
Possibilities for increased carbon sequestration through the implementation of rational forest management in Russia
1997
Shvidenko, A. (International Inst. for Applied Systems Analysis, Laxenburg (Austria).) | Nilsson, S. | Roshkov, V.
Photolytic degradation of fluoroquinolone carboxylic acids in aqueous solution : Part I: Primary photoproducts and half-lives (ESPR 1/1997, pp. 10–15) Part II: Isolation and structural elucidation of polar photometabolites (ESPR 2/1997, pp. 61–67)
1997
Burhenne, Jürgen | Ludwig, Marc | Spiteller, M. (Michael)
Subsequent to irradiation with a xenon lamp simulating sunlight, fluoroquinolone carboxylic acids in aqueous solution form polar pyridone dicarboxylic and tricarboxylic acids. After liquid/liquid partition with chloroform/water these substances can be isolated by ion exchange chromatography of the aqueous phase. They can be regarded as intermediate compounds on the route to a complete photomineralization. The structural elucidation is performed by such mass spectroscopic methods as MS, GC/MS and HPLC/MS, whereby HPLC/MS shows the highest reliability. Additionally¹H- and¹³C-NMR measurements confirm the structure of the main polar degradation product.
اظهر المزيد [+] اقل [-]Platinum emission rate of automobiles with catalytic converters : Comparison and assessment of results from various approaches
1997
Helmers, Eckard
Inconsistent data presently available on the platinum emission rate of cars in Germany equipped with catalytic converters are evaluated. Automobile sources of Pt other than autocatalysts are quantified and found to be 1–6 orders of magnitudes lower than the Pt emissions attributed to catalytic converters. A transfer of emission rates derived from test stand experiments to more realistic street conditions reaches 0.8 μg Pt/km. In this manner, data from test stand experiments and from environmental investigations meet in the range of 0.5–0.8 μg Pt/km.
اظهر المزيد [+] اقل [-]Supercritical recovery of eicosapentaenoic acid and docosahexaenoic acid from fish oil
1997
Borch-Jensen, C. | Henriksen, O. | Mollerup, J.
Phase equilibrium measurements in systems of CO2 and fish oil fatty acid ethyl esters (FAEEs) at 70 degrees C are presented. Three different mixtures were investigated, a natural FAEE mixture from the oil of the sand eel (Ammodytes sp.), a urea fractionated mixture prepared from the natural FAEE mixture, and a concentrate of omega 3 FAEEs. The measurements were performed in a static type apparatus making it possible to sample both the vapor and liquid phases. The results presented include solubilities and equilibrium ratios. The experimental results are used to evaluate a process for the recovery of C20:5 omega 3 (EPA) and C22:6 omega 3 (DHA) at 70 degrees C.
اظهر المزيد [+] اقل [-]The suitability of gastropods as biomarkers : Induction of ethoxy-, pentoxy- and benzoxyresorufin-O-dealkylase in limnetic gastropods via aroclor 1254
1997
Meimberg, Harald | Schrenk, Christiane | Steinberg, Christian | Klarenberg, Albert | Kettrup, A. A.
The measurement and induction of mixed function oxyigenases (MFOs) of limnetic gastropods were investigated to estimate their suitability as biomarkers. A determination of MFO activities was performed through the measurement of ethoxyresorufin-O-dealkylase (EROD), pentoxy-(PROD) and benzoxyresorufin-O-dealkylase-activity (BROD). Optimal measuring conditions of these activities were investigated in preparations of the digestive gland of 4 species of limnetic gastropods. Results indicate that MFO-activity inhibiting substances are accumulating in the microsomal pellet, the fraction commonly used for the measurement of MFO-activities. Therefore, the fraction used for induction studies was the postmitochondrial supernatant (PMS). EROD, PROD, and BROD activity ofPlanorbis planorbis andPlanorbis carinatus were measured after a treatment with Aroclor 1254 for 1–17 days. Maximal induction of EROD and PROD were 6 and 10 times the value in the control group ofP. carinatus, respectively induction inP. planorbis was lower. BROD-activity could not been measured inP. planorbis. InP. carinatus, BROD-activity increased to a maximum of 2 times after traetment with Aroclor 1254. The level of induction of EROD-activity is comparable to results described in analog studies with fish.
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