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.

Effect of carboxylic acids on 2‐bisbenzothiazole‐2,2′‐disulfide‐ and tetramethylthiuram disulfide‐accelerated sulfur vulcanization. IV. Vulcanization of polyisoprene compounds with ZnO

Abstract: The effect of benzoic and stearic acids on 2-bisbenzothiazole-2,2'-disulfide (MBTS)- and tetramethylthiuram disulfide (TMTD)-accelerated sulfur vulcanization of polyisoprene compounds, containing ZnO, was studied at 150°C. In the presence of ZnO, the acids are rapidly converted to their zinc salts that, unlike the acids, do not attack accelerator polysulfides and, instead, promote vulcanization. The addition of accelerator polysulfides to the chain is not affected by zinc salts, but the rate of crosslinking of pendent groups is facilitated. In MBTS vulcanization, the promotion of crosslinking reactions reduces the number of pendent groups involved in cyclization reactions and higher crosslink densities are attained. In TMTD compounds, crosslink densities are increased on addition of ZnO and of ZnO/carboxylic acids. A mechanism is suggested to account for the promotion of crosslinking by the zinc salts. Bis(2-mercaptobenzothiazolo)zinc(II) and bis(dimethyldithiocarbamato)zinc(II) can act similarly to zinc benzoate or stearate to promote the crosslinking of pendent groups, but are less efficient. With benzoic acid, a limited attack by zinc benzoate on TMTP leads to a slightly lower increase in crosslink density than is achieved with the addition of ZnO alone.

Purification and primary structure of ostrich pancreatic polypeptide

Abstract: Pancreatic polypeptide has been isolated from ostrich pancreas by gel filtration, ion exchange chromatography and high pressure liquid chromatography. The ostrich peptide contains 36 amino acids and has an amino acid composition similar to pancreatic polypeptide of other avian species. The primary structure of ostrich pancreatic polypeptide differs from that of the chicken peptide only at residues 3 and 18 where the ostrich peptide contains an alanine and a valine residue compared to the serine and isoleucine residues found in those positions in the chicken peptide.

Catch composition and catch per unit effort of anglers' catches off St Croix Island, Algoa Bay

Abstract: Anglers' catches off St Croix Island were examined on a monthly basis, for the period December 1975 to February 1978, to establish the catch composition and catch per unit effort. A total of 343 anglers caught 2,7 metric tons bony fish and 0,7 metric tons cartilaginous fish in 95697 man-hours, over the entire sampling period. Trends in the catch per unit effort (CPUE) were examined and expressed in three ways: number of fish caught per man-hour; mass of fish caught per man-hour and mass of P.saltatrix and C. nufar, respectively, per man-hour. The fish (bony and cartilaginous) appear to be most abundant in the summer months and least abundant in mid-winter (July). However, the seasonal appearance of P. saltatrix and presence of C. nufar in the catches, increase the CPUE greatly. The cartilaginous component has little or no significance in terms of numbers caught per man-hour, but due to the larger mass of individual cartilaginous fish, the CPUE of certain months was subsequently higher. A comprehensive list of all fish species caught and the frequency occurrence of each species in the catches is also given.