Surface and rheological properties of as-received colloidal goethite (α-FeOOH) suspensions: pH and polyethylenimine effects

The yield stress and zeta potential (ζ) of slurries prepared from as-received goethite were evaluated as a function of pH, solids concentration, cationic polyethylenimine (PEI) concentration and molecular weight (Mw). The goethite slurries displayed a maximum yield stress at the isoelectric point (pI). These slurries do not have a low pH dispersed region. The yield stress obeyed the yield stress–DLVO force model. The maximum yield stress displayed a dependence on the solids volume fraction to a power of 3.8.PEI adsorbed and changed both the surface chemistry and rheological yield stress of the slurries. At most additive concentration ranging from 0.1 to 0.4dwb% for PEI of Mw 600, 1800 and 70,000, the maximum yield stress of the slurries is larger than that with no adsorbed additives. At low PEI concentration of 0.1dwb%, the same maximum yield stress of 30 Pa was obtained for three Mws; 600, 1800 and 70,000 representing a 1.5-fold increase. The increased attraction between particles was attributed to charge patch attraction at low surface coverages and hydrogen bonding at high coverages. Adsorbed PEI decreased the yield stress at low pH. However complete dispersion was observed only for 0.4dwb% PEI with Mw 70,000, at pH below 7. Complete dispersion was not observed at high pH for the same polymer at all concentrations.     

Understanding and contextualizing social impacts from the privatization of fisheries: An overview

Fisheries management around the world has experimented with regulations to promote privatization, in order to reach such multifaceted goals as ending overfishing and reducing economic inefficiencies. This review surveys a wide range of empirical experiences in different contexts around the world to help provide a fuller picture of potential and sometimes disparate consequences from privatization in general and new ways of organizing around fishing that can follow in the wake of such measures. Looking at the many different participants in the fishing industry—from crew, small-boat owners, to households and communities—as well as the diverse sociocultural contexts in which fishing takes place, enables a better understanding of who and what is impacted, how they are impacted, why and with what further consequences, such that communities come to be seen less oppositional to economy, but rather constituted by multiple scalar processes and by economic relations comprising different motivations and behaviors.     

CYTOTOXICITY AND GENOTOXICITY OF POLYETHYLENIMINE AND NICKEL CHLORIDE IN RED SEA BREAM (Pagrosomus major) FIN CELL LINE RSBF

ＩＮＴＲＯＤＵＣＴＩＯＮＡｃｃｕｍｕｌａｔｅｄｅｖｉｄｅｎｃｅｓｓｕｇｇｅｓｔｅｄａｃｌｏｓｅｃｏｒｒｅｌａｔｉｏｎｂｅｔｗｅｅｎｎｅｏｐｌａｓｔｉｃｄｉｓｅａｓｅｏｆａｑｕａｔｉｃｏｒ ｇａｎｉｓｍｓａｎｄｔｈｅｉｎｃｒｅａｓｉｎｇｒｅｌｅａｓｅｏｆｇｅｎｏｔｏｘｉｎｓｂｙａｎｔｈｒｏｐｏｇｅｎｉｃａｃｔｉｖｉｔｉｅｓｉｎｔｏａｑｕａｔｉｃｅｎｖｉｒｏｎｍｅｎｔ(Ｍｉｘ ,1 986;Ｇａｒｄｎｅｒｅｔａｌ.,1 991 ;ＧＥＳＡＭＰ ,1 991 ) .Ｉｔｈａｓ,ｔｈｅｒｅｆｏｒｅ,ｂｅｃｏｍｅｎｅｃｅｓｓａｒｙｔｏｅ…     

CYTOTOXICITY AND GENOTOXICITY OF POLYETHYLENIMINE AND NICKEL CHLORIDE IN RED SEA BREAM（Pagrosomus major）FIN CELL LINE RSBF

A continuous marine fish cell line RSBF(i.e.Red Sea Bream Fin)was utilized to screen the cytotoxicity and genotoxicity of polyethylenimine(PEI)and nickel cholride(NiCl2)in this study on the deleterious effects of aquatic genotoxins on fish.At the 0.01 to 1μgml concentration tested,PEI had acute toxicity to the treated RSBF cells(IC50=1.12,0.92,0.88 and 0.64μg/ml PEI for time 0 h,24 h,48 h and 72 h after treatment,respectively)and markedly inhibited their proliferation in a dose-dependent manner.At the 0.001 to 5 μmol/L concentration tested,NiCl2 posed no acute toxicity but significantly stimulated their growth(107?214?of control).Random amplified polymorphic DNA(RAPD)technique was used to detect the genotoxic effects of PEI and NiCl2 by comparing the RAPD banding patterns of the control and treated cells.RAPD analysis indicated that at the concentrations tested,PEI was more genotoxic than NiCl2 to RSBF cells;that there was a slight dose-dependent response in the genotoxic effect of PEI bue not NiCl2;and that RAPD technique might provide a sensitive,non-specif-ic gentoxic endpoint.And the potent cytotoxicity and genotoxicity of PEI on fish cells showed that we should be cautious in utilizing it as gene vector in fish gene transfer and human gene therapy.