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.

Subtidal occurrences of ladder‐back ripples: their significance in palaeo‐environmental reconstruction

Abstract: Ladder-back ripples are common on modern intertidal flats and have been thought to be diagnostic of deposition in this environment. Recognition of superimposed, asymmetric ladder-back ripples in a subtidal back-barrier estuary and superimposed, symmetric ladder-back ripples in an embayed, shallow marine environment indicates that these features are not diagnostic of deposition in the intertidal zone only, but can occur in other depositional environments, produced by different mechanisms and on different scales. The presence of ladder-back ripples in the subtidal zones challenges aspects of a model used to determine the palaeotidal range of ancient tidal sequences.

Factors influencing the magnitude of phytoplankton primary production in a high-energy surf zone

Abstract: The main factors influencing phytoplankton primary production in the surf zone of the Sundays River Beach, Algoa Bay have been characterized. These factors include cell concentration, chlorophyll concentration, irradiance, temperature and salinity. Good relationships have been obtained between cell concentration, chlorophyll concentration and primary production. The P-I curves showed dependence on temperature with a linear regression between temperature and Ik values. Light saturation was shown to occur between 300 and 510 μmol m−2 s−1 at normal field temperatures. Tmax and Tmin were found to be 34°C and 0°C, respectively; Pmax was 25°C. Salinity had a marked effect on primary production with Smax occurring at 60 ppt and an extrapolated Smin at 0 ppt. Pmax was found to occur at 30 ppt.

Complete amino acid sequence of a VLDV‐type neurophysin from ostrich differs markedly from known mammalian neurophysins

Abstract: The neurohypophyseal hormones vasopressin and oxytocin are known to be synthesized in eutherian mammals as part of larger precursors containing either MSEL- or VLDV-neurophysins. A neurophysin has been isolated from ostrich neurohypophyses and shown by partial amino acid sequence determination to be related to mammalian VLDV-neurophysin. The present report describes the complete amino acid sequence of this ostrich neurophysin containing 93 residues. This amino acid sequence, the first reported in birds, differs in a remarkable manner from its mammalian homolog. Indeed, it contains a large number of substitutions, including one insertion, distributed throughout the polypeptide chain when compared to known VLDV-neurophysins. Whereas many of these substitutions are localized inside the so-called constant region of the neurophysin, the highest variation can be found in the COOH-terminal region.