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Adsorption and desorption of imazapyr by soil
No full textThe adsorption and desorption of imazapyr, (+/-)-2-[4,5-dihydro-4-methyl-4-(1-methylethyl)-5-oxo-1H- imidazol-2-yl]-3-pyridinecarboxylic acid, by six soils were studied. Adsorption isotherms conformed to the Freundlich equation. A multiple regression analysis indicated that K-f(ads) values were better correlated if cation exchange capacity and pH (r = 0.984) were simultaneously taken into account. The results show that the herbicide adsorption is strongly affected by the pH and the charge of the adsorbing component. The organic matter is effective in imazapyr retention, but only at pH <5. Enhanced adsorption was observed in amorphous iron oxide, most likely because of a ligand exchange process
Montmorillonite surface-catalyzed hydrolysis of fenoxaprop-ethyl
No full textThe degradation of the herbicide fenoxaprop-ethyl [ethyl 2-[4-[(6-chloro-2-benzoxazolyl)oxy]phenoxy]propanoate] on homoionic Fe3+, Al3+, Ca2+, and Na+ montmorillonite in aqueous medium was studied. The results show that the hydrolysis of the pesticide may involve two different mechanisms, both depending on the nature of the exchangeable cations. The herbicide hydrolyzes to 6-chlorobenzoxazolinone and ethyl 2-(4-hydroxyphenoxy)propanoate on Fe3+ and Al3+ clays, whereas the fenoxaprop acid [2-[4-[(6-chloro-2-benzoxazolyl)oxy]phenoxy]propanoic acid] is the main hydrolysis product on Ca2+ and Na+ clays with minor amounts of 6-chlorobenzoxazolinone and 2-(4-hydroxyphenoxy)propanoic acid. The protonation of the benzoxazole ring nitrogen of the herbicide can be responsible for the cleavage of the ether bridge of fenoxaprop-ethyl in the Fe3+ and Al3+ systems. Instead, the hydrolysis of the ester bond appears to be favored by the coordination of the carbonyl oxygen of fenoxaprop-ethyl with the hydrated exchangeable metal ions in the Ca2+ and Na+ systems
Photodegradation of herbicide triasulfuron
No full textTriasulfuron was degraded in aqueous solution by ultraviolet irradiation to yield 2-chloroethoxybenzene and (4-methoxy-6-methyl-1,3,5-triazin-2-yl)urea. The reaction followed first-order kinetics. In sunlight, the reaction was slower and afforded these two photoproducts together with 2-amino-4-methoxy-6-methyltriazine and 2-(2-chloroethoxy)benzenesulfonamide. The latter compounds arise from hydrolytic cleavage of the sulfonylurea bridge of triasulfuron because of the acidity of the reaction medium due to the loss of sulfur dioxide. A mechanism which accounts for the formation of the photoproducts is proposed. (C) 1999 Society of Chemical Industry
INTERACTION OF DICLOFOP AND DICLOFOP-METHYL WITH AL3+-, FE3+-, AND CU2+-SATURATED MONTMORILLONITE
No full textINTERACTION OF FLUAZIFOP WITH AL-SATURATED FE-3+-SATURATED, AND CU-2+-SATURATED MONTMORILLONITE
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ADSORPTION AND DESORPTION OF DIMEPIPERATE BY SOILS
No full textThe adsorption and desorption of dimepiperate, S-(alpha,alpha-dimethylbenzyl)-1-piperidinecarbothioate, on three soils of various physical and chemical properties was studied. Adsorption isotherms conformed to Freundlich equation. The k(f) values increased with increasing organic carbon content of the soils. To confirm the effect of organic matter, the adsorption of the herbicide was studied after removal of organic matter by peroxidation. This soil treatment caused a sequential loss of adsorptive capacity. Desorption isotherms also conformed to Freundlich equation, but K(des) values were higher than those for adsorption and increased with increase in concentration of initially adsorbed dimepiperate. Hysteresis was indicated by the decrease in slope of desorption compared to adsorption isotherms. Hysteresis decreased with increasing methanol content in the extracting solution. The factors involved are discussed
Going Beyond Counting First Authors in Author Co-citation Analysis
Get PDFThe present study examines one of the fundamental aspects of author co-citation analysis (ACA) - the way co-citation
counts are defined. Co-citation counting provides the data on which all subsequent statistical analyses and mappings
are based, and we compare ACA results based on two different types of co-citation counting - the traditional type that
only counts the first one among a cited work's authors on the one hand and a non-traditional type that takes into
account the first 5 authors of a cited work on the other hand. Results indicate that the picture produced through this non-traditional author co-citation counting contains more coherent author groups and is therefore considerably clearer. However, this picture represents fewer specialties in the research field being studied than that produced through the traditional first-author co-citation counting when the same number of top-ranked authors is selected and analyzed. Reasons for these effects are discussed
Variations on the Author
Get PDF“Variations on the Author” discusses two of Eduardo Coutinho’s recent films (Um Dia na Vida, from 2010, and Últimas Conversas, posthumously released in 2015) and their contribution to the general question of documentary authorship. The director’s filmography is characterized by a consistent yet self-effacing form of authorial self-inscription: Coutinho often features as an interviewer that rather than express opinions propels discourses; an interviewer that is good at listening. This mode of self-inscription characterizes him as an author who is not expressive but who is nonetheless markedly present on the screen. In Um Dia na Vida, however, Coutinho is completely absent form the image, while Últimas Conversas, on the contrary, includes a confessional prologue that moves the director from the margins to the center of his films. This article examines the ways in which these works stand out in the filmography of a director who offers new insights into the notion of cinematic authorship
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