Temporal changes in metal levels of the lichens Parmotrema praesorediosum and Ramalina stenospora,Southwest Louisiana     

Dorothy A. Walther  Gerald J. Ramelow  James N. Beck  John C. Young  James D. Callahan  Michael F. Maroon 《Water, air, and soil pollution》1990,53(1-2):189-200

Two species of lichen native to southwest Lousiana, Parmotrema praesorediosum (Nyl.) Hale and Ramalina stenospora, Mull. Arg. have been investigated as air pollution monitors. Over the period 1983–88 samples were collected at 18 stations in the Lake Charles/Westlake/Sulphur area. The samples were analyzed for A1, Fe, Cu, Pb, Cd, Hg, Cr, and Zn. When metal concentrations in lichens were plotted vs year for certain representative stations, a dramatic reduction in the concentrations of certain metals was seen after 1983. When the most recent data are compared with those previously obtained, the effects of the industrial zone, which was previously demonstrated, have now all but disappeared.  相似文献   

Ecology: The Convention on Biological Diversity's 2010 target     

Balmford A  Bennun L  Brink BT  Cooper D  Côte IM  Crane P  Dobson A  Dudley N  Dutton I  Green RE  Gregory RD  Harrison J  Kennedy ET  Kremen C  Leader-Williams N  Lovejoy TE  Mace G  May R  Mayaux P  Morling P  Phillips J  Redford K  Ricketts TH  Rodríguez JP  Sanjayan M  Schei PJ  van Jaarsveld AS  Walther BA 《Science (New York, N.Y.)》2005,307(5707):212-213

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Phase equilibria     

Walther JV 《Science (New York, N.Y.)》1993,262(5141):1911-1912

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Rates of hydrothermal reactions   总被引：1，自引：0，他引：1  

Wood BJ  Walther JV 《Science (New York, N.Y.)》1983,222(4622):413-415

The rates of reactions of silicates and aqueous fluids follow zero-order kinetics controlled by the reacting surface area with the rate constant given by the equation: log k[unknown] -2900/T -6.85, where T is temperature and where k has the unit's gram-atoms of oxygen per square centimeter per second. This expression appears to hold for all silicates and for reactions involving dissolution, fluid production, or solid-solid transformations in the presence of a fluid of moderate to high pH.  相似文献   

Characterization of a pancreatic DNase from pyloric caeca of atlantic cod (Gadus morhua L.)     

Knut O. Strætkvern  Arnt J. Raae  Bernt T. Walther 《Fish physiology and biochemistry》1992,9(5-6):439-452

An alkaline deoxyribonuclease (DNase) from cod pancreatic tissue has been characterized. The enzyme is a DNase I type endonuclease and hydrolyzes effectively both native and denatured DNA. Monomeric actin inhibits the enzyme reaction. The enzyme obeys Michaelis-Menten kinetics and the apparent K_m value for native linear duplex DNA is 33 µg/ml. The cod DNase opens supercoiled plasmid DNA, by introducing adjacent nicks in both strands, possibly separated by 5–10 nucleotides. DNA hydrolyzed by cod DNase functions as substrates both for DNA polymerase and ligase, and the nicks therefore contain 5-phosphoryl and 3-hydroxyl groups. Optimum concentrations of divalent cations are 5 mM Mg²⁺, 0.63 mM Mn²⁺ and 0.075 mM Ca²⁺. However, Ca²⁺ is apparently not essential for the enzymatic functions. The enzyme has a narrow temperature optimum at 42°C and is thermolabile above 50°C; however, Mn²⁺ shifts the optimum slightly to 45°C by causing increased temperature stability. The cod DNase reaction is inhibited by the DNA intercalating compounds actinomycin D and ethidium bromide. Histidine-modifying reagents such as tosyl phenylalanyl chloromethylketone and diethyl pyrocarbonate inhibit the enzyme activity, but the cod DNase is insensitive to disulfide-reducing agents.  相似文献   

Untersuchungen zur Frage der Diagnose der Rinderzystizerkose mit Hilfe der indirekten Hämagglutination     

M. Walther  D. Grossklaus 《Zoonoses and public health》1972,19(4):309-319

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Zur Serodiagnose der Zystizerkose des Rindes*     

D. Grossklaus  M. M. Walther 《Zoonoses and public health》1970,17(8):828-839

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Comparison of different extractants for the determination of inorganic sulphate in gypsum‐free agricultural soils     

Viktor Schmalz  Thomas Grischek  Grit Gerstcker  Eckard Worch 《植物养料与土壤学杂志》2001,164(5):577-578

Four frequently used extractants (H₂O, 0.1 M NaCl, 0.016 M KH₂PO₄, and 0.5 M NaHCO₃) as well as different extraction conditions have been tested for sulphate extraction from gypsum‐free agricultural soils. Water is the preferable extractant for soils with pH > 6. Two extraction steps have to be carried out for complete extraction (> 95%). A 0.016 M KH₂PO₄ solution was found to be the most efficient extractant for soils with a pH < 6 within a single extraction step. A shaking frequency of 170 min^‐1 and a duration of extraction of 4 hours are the optimized conditions for the sulphate extraction with H₂O and KH₂PO₄ solution.  相似文献   

Substrate specificity of the glutathione dehydrogenase (dehydroascorbate reductase) from wheat flour     

Cornella Walther  Werner Grosch   《Journal of Cereal Science》1987,5(3)

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Determination of arsenic and selenium in whole fish by continuous-flow hydride generation atomic absorption spectrophotometry     

W G Brumbaugh  M J Walther 《Journal of the Association of Official Analytical Chemists》1989,72(3):484-486

A combined wet chemical and dry ash digestion and use of a continuous-flow hydride generator coupled with a flame-heated quartz cell enabled the simple, precise, and highly automated atomic absorption determination of arsenic and selenium in tissues of whole fish. Percent relative standard deviation averaged 4% for each element; method detection limits (micrograms/g dry wt) were about 0.06 for arsenic and 0.04 for selenium. Digestion of samples proceeded with little operator attention and without perchloric acid. Analysis for arsenic as As(V) simplified sample preparation but care had to be exercised to avoid interferences from high concentrations of selenium.  相似文献