University of Port Elizabeth

About: University of Port Elizabeth is a based out in . It is known for research contribution in the topics: Population & Estuary. The organization has 1067 authors who have published 1538 publications receiving 38560 citations. The organization is also known as: UPE & Universiteit van Port Elizabeth.

Variations in size compositions of populations of Upogebia africana (Ortmann) (Decapoda, Crustacea) within the Swartkops estuary and possible influencing factors

Abstract: The size frequencies of various populations of the mud prawn Upogebia africana sampled within the Swartkops estuary were determined and the size compositions of these populations varied along the length of the estuary, as well as vertically within the intertidal zone. Ovigerous prawns were recorded from sites representing the extremes in population structures and their mean sizes differed significantly (P < 0,05) from each other. The variations in the size compositions were therefore attributed to differences in the growth of the prawns, rather than a spatial separation of adults and juveniles. The mean sizes of the adult prawns from the various stations were determined and plotted against factors such as water temperatures and salinities, nitrogen and organic contents of the substrata, population densities and distances of the populations from the estuarine mouth. The latter factor, which was used to give a relative measure of the exposure (in terms of duration and current velocity) of the populations to...

A DSC study of the crosslinking of polychloroprene with ZnO and MgO

Abstract: Polychloroprene and compounds of polychloroprene with ZnO and MgO were crosslinked by heating in a DSC at a programmed rate. The reaction was stopped at points along the thermogram and the crosslink density of the compound determined. The amount of chlorine evolved during reaction was measured as ZnCl2 and/or MgCl2. Two crosslinking processes were identified, both involving reaction of the 1,2 units in the polymer chain; the first comprising a rapid crosslinking reaction that occurs prior to the isomerization of 1,2 units and the second, a much slower reaction of isomerized 1,2 units. ZnCl2, which forms during compounding and on crosslinking, catalyzes the first reaction, while ZnO promotes the allylic rearrangment of 1,2 units. MgO increases the scorch time by trapping HCl evolved during compounding, thus limiting the amount of the crosslinking catalyst (ZnCl2) formed. © 1995 John Wiley & Sons, Inc.

Purification and characterization of ostrich pancreatic secretory trypsin inhibitor

Abstract: Ostrich pancreatic secretory trypsin inhibitor was isolated and purified using acid extraction, salt fractionation. SP-Sephadex C-50 and QAE-Sephadex A-25 chromatography and RP-HPLC. The amino acid sequence of ostrich PSTI showed it is a single peptide chain containing 69 amino acid residues with the highest homology between ostrich and chicken PSTI. The molecular weight, as determined by electronspray mass spectrometry and from amino acid sequence data, is 7650 Da. The isoelectric point of ostrich PSTI was found to be 5.7. Ostrich PSTI specifically inhibited ostrich and commercial bovine trypsin with Ki values of 8.0 x 10(-9) and 2.4 x 10(-7) M, respectively, while no inhibitory effects were observed with other serine proteases.