https://vital.seals.ac.za/vital/access/manager/Index en-us 5 https://vital.seals.ac.za/vital/access/manager/Repository/vital:43639 Wed 30 Jun 2021 11:27:41 SAST ]]> https://vital.seals.ac.za/vital/access/manager/Repository/vital:46549 Wed 23 Feb 2022 18:14:57 SAST ]]> https://vital.seals.ac.za/vital/access/manager/Repository/vital:51913 Wed 19 Oct 2022 09:27:41 SAST ]]> https://vital.seals.ac.za/vital/access/manager/Repository/vital:26991 Wed 12 May 2021 23:32:34 SAST ]]> https://vital.seals.ac.za/vital/access/manager/Repository/vital:26858 Wed 12 May 2021 23:27:01 SAST ]]> https://vital.seals.ac.za/vital/access/manager/Repository/vital:26834 Wed 12 May 2021 22:45:07 SAST ]]> https://vital.seals.ac.za/vital/access/manager/Repository/vital:34223 Wed 12 May 2021 20:26:09 SAST ]]> https://vital.seals.ac.za/vital/access/manager/Repository/vital:26990 Wed 12 May 2021 20:05:12 SAST ]]> https://vital.seals.ac.za/vital/access/manager/Repository/vital:26839 Wed 12 May 2021 19:29:39 SAST ]]> https://vital.seals.ac.za/vital/access/manager/Repository/vital:26855 Wed 12 May 2021 19:14:47 SAST ]]> https://vital.seals.ac.za/vital/access/manager/Repository/vital:29236 Wed 12 May 2021 19:09:58 SAST ]]> https://vital.seals.ac.za/vital/access/manager/Repository/vital:4909 11Oppm) are the most evolved. They are tholeiitic andesites which display fairly limited compositional variation. It is likely that more evolved compositions are present in other areas where the porphyritic lavas which characterize this unit are better developed. The overlying Orkney lavas are characterized by 110ppm>Zr>90ppm. They are tholeiitic andesites of similar composition to the Alberton lavas, but have lower incompatible element levels, higher siderophile element levels, and are of extremely uniform composition. The uppermost Loraine/Edenville lavas range from magnesian tholeiites to tholeiitic andesites. They are distinguished by Zr< 90ppm, and contain the most primitive magmas af the Witwatersrand triad, with up to 17,5% MgO, 2600ppm Cr, 600ppm Ni and M-values up to 77. The most primitive liquids evolved by 38% fractional crystallization of orthopyroxene ∓ chromite, followed by 35% fractional crystallization of an extract containing clinopyroxene and plagioclase. The absence of olivine precipitation is a result of the inherently high Si0₂ content of the magma. The Loraine/Edenville, Orkney and Alberton lavas do not lie on a common liquid line of descent, but are probably consanguinous. The Platberg Group overlies the Kliprivierberg Group, and has a coarse-clastic sedimentary unit, the Kameeldoorns Formation, at the base. Three petrographically distinct porphyritic lava sequences overlie the Kameeldoorns Formation, namely the informal "Goedgenoeg formation", the Makwassie quartz-feldspar porphyries and the Rietgat Formation. Despite petrographic differences, the Goedgenoeg and Rietgat lavas are chemically indistinguishable and thus form a single magma-type. The Makwassie porphyries are dacitic in composition with a high proportion of feldspar and quartz phenocrysts. Rational variation trends are attributed to a nett loss of Si0₂ during secondary alteration. The porphyries are probably of crustal origin. The Goedgenoeg/Rietgat lavas display unusual chemistry and a broad, irrational compositional spectrum. They contain very high incompatible element levels, high nonnative quartz, as well as high MgO, M-values, Cr and Ni relative to the other tholeiitic andesites of the Witwatersrand triad. It is tentatively suggested that they are hybrid magmas containing both crust and mantle components, the former possibly represented by the Makwassie porphyries. Field evidence suggests that Platberg volcanism commenced directly after Klipriviersberg volcanism ceased, and was accompanied by a period of enhanced tectonic activity. The Platberg lavas thus probably reflect a crustal melting cycle associated with the Klipriviersberg magmatic event. The Allanridge lavas are the youngest rocks of the Witwatersrand triad. They are separated from the Platberg Group by a unit of flat-lying sediments, the Bothaville Formation, which was deposited after an extended period of peneplanation. The Allanridge lavas form a separate magma-type. They are tholeiitic andesites of similar composition to the Alberton lavas, but have higher incompatible element levels and are not consanguinous. The compositional similarities amongst the basic magma-types of the Witwatersrand triad suggests that all were generated in an hydrous mantle. Interelement ratio differences between the various magma-types nevertheless support the concept that the mantle was chemically heterogeneous during the early Proterozoic.]]> Wed 12 May 2021 18:23:53 SAST ]]> https://vital.seals.ac.za/vital/access/manager/Repository/vital:26857 Wed 12 May 2021 17:45:07 SAST ]]> https://vital.seals.ac.za/vital/access/manager/Repository/vital:26874 Wed 12 May 2021 17:41:37 SAST ]]> https://vital.seals.ac.za/vital/access/manager/Repository/vital:28127 Wed 12 May 2021 17:38:27 SAST ]]> https://vital.seals.ac.za/vital/access/manager/Repository/vital:26849 Wed 12 May 2021 17:13:14 SAST ]]> https://vital.seals.ac.za/vital/access/manager/Repository/vital:26862 Wed 12 May 2021 17:11:25 SAST ]]> https://vital.seals.ac.za/vital/access/manager/Repository/vital:15635 Wed 12 May 2021 17:08:36 SAST ]]> https://vital.seals.ac.za/vital/access/manager/Repository/vital:1337 Wed 12 May 2021 16:43:58 SAST ]]> https://vital.seals.ac.za/vital/access/manager/Repository/vital:26679 Wed 12 May 2021 16:33:29 SAST ]]> https://vital.seals.ac.za/vital/access/manager/Repository/vital:26867 Wed 12 May 2021 16:31:14 SAST ]]> https://vital.seals.ac.za/vital/access/manager/Repository/vital:2903 Wed 12 May 2021 16:19:26 SAST ]]> https://vital.seals.ac.za/vital/access/manager/Repository/vital:26848 Wed 12 May 2021 16:08:58 SAST ]]> https://vital.seals.ac.za/vital/access/manager/Repository/vital:26638 Wed 12 May 2021 15:57:00 SAST ]]> https://vital.seals.ac.za/vital/access/manager/Repository/vital:62356 Wed 08 Mar 2023 15:38:38 SAST ]]> https://vital.seals.ac.za/vital/access/manager/Repository/vital:51916 Wed 08 Jun 2022 12:18:05 SAST ]]> https://vital.seals.ac.za/vital/access/manager/Repository/vital:51915 Wed 08 Jun 2022 11:29:12 SAST ]]> https://vital.seals.ac.za/vital/access/manager/Repository/vital:51914 Wed 08 Jun 2022 10:33:05 SAST ]]> https://vital.seals.ac.za/vital/access/manager/Repository/vital:52594 Tue 28 Jun 2022 13:27:44 SAST ]]> https://vital.seals.ac.za/vital/access/manager/Repository/vital:45689 Tue 19 Jul 2022 17:52:06 SAST ]]> https://vital.seals.ac.za/vital/access/manager/Repository/vital:57617 Tue 18 Oct 2022 10:44:28 SAST ]]> https://vital.seals.ac.za/vital/access/manager/Repository/vital:46603 Tue 15 Feb 2022 10:04:52 SAST ]]> https://vital.seals.ac.za/vital/access/manager/Repository/vital:43883 Tue 03 Aug 2021 10:18:39 SAST ]]> https://vital.seals.ac.za/vital/access/manager/Repository/vital:47442 Tue 01 Mar 2022 10:53:40 SAST ]]> https://vital.seals.ac.za/vital/access/manager/Repository/vital:46021 RhMo-AA/Al2O3 (73%) > RhMo-CA/Al2O3 (72%) > RhMo-EDTA/Al2O3 (68%). This could be that the addition of chelating ligand complexed both metallic species retarding sulfidation of both metals, hence lowering the HDS activity. Studies show that it is possible for the citric acid to complex with both promoter and an active metal (Mo), and this might result in the formation of molybdenum dimers, trimers and tetramers which are difficult to sulfide. XPS analysis showed that unchelated catalyst have more MoS2 phases of 63%, hence higher dispersion than the chelated catalyst, this could be the reason for high activity in RhMo/Al2O3 (88%) catalyst.]]> Tue 01 Feb 2022 12:45:40 SAST ]]> https://vital.seals.ac.za/vital/access/manager/Repository/vital:45984 Tue 01 Feb 2022 12:10:53 SAST ]]> https://vital.seals.ac.za/vital/access/manager/Repository/vital:69295 Thu 26 Oct 2023 11:11:29 SAST ]]> https://vital.seals.ac.za/vital/access/manager/Repository/vital:45680 Thu 20 Jan 2022 19:03:38 SAST ]]> https://vital.seals.ac.za/vital/access/manager/Repository/vital:45142 Thu 18 Nov 2021 14:58:30 SAST ]]> https://vital.seals.ac.za/vital/access/manager/Repository/vital:67833 Thu 14 Sep 2023 11:13:52 SAST ]]> https://vital.seals.ac.za/vital/access/manager/Repository/vital:26921 Thu 13 May 2021 08:19:31 SAST ]]> https://vital.seals.ac.za/vital/access/manager/Repository/vital:33741 Thu 13 May 2021 07:39:01 SAST ]]> https://vital.seals.ac.za/vital/access/manager/Repository/vital:26993 Thu 13 May 2021 06:49:06 SAST ]]> https://vital.seals.ac.za/vital/access/manager/Repository/vital:16078 Thu 13 May 2021 06:48:33 SAST ]]> https://vital.seals.ac.za/vital/access/manager/Repository/vital:1363 Thu 13 May 2021 06:32:07 SAST ]]> https://vital.seals.ac.za/vital/access/manager/Repository/vital:26621 Thu 13 May 2021 06:31:03 SAST ]]> https://vital.seals.ac.za/vital/access/manager/Repository/vital:26644 Thu 13 May 2021 06:29:15 SAST ]]> https://vital.seals.ac.za/vital/access/manager/Repository/vital:1358 Thu 13 May 2021 05:34:04 SAST ]]> https://vital.seals.ac.za/vital/access/manager/Repository/vital:26852 Thu 13 May 2021 05:30:19 SAST ]]> https://vital.seals.ac.za/vital/access/manager/Repository/vital:26856 Thu 13 May 2021 05:29:01 SAST ]]> https://vital.seals.ac.za/vital/access/manager/Repository/vital:5596 Thu 13 May 2021 05:07:48 SAST ]]> https://vital.seals.ac.za/vital/access/manager/Repository/vital:26851 Thu 13 May 2021 04:57:18 SAST ]]> https://vital.seals.ac.za/vital/access/manager/Repository/vital:549 Thu 13 May 2021 04:51:37 SAST ]]> https://vital.seals.ac.za/vital/access/manager/Repository/vital:16067 Thu 13 May 2021 04:40:17 SAST ]]> https://vital.seals.ac.za/vital/access/manager/Repository/vital:2756 Thu 13 May 2021 04:39:16 SAST ]]> https://vital.seals.ac.za/vital/access/manager/Repository/vital:15784 Thu 13 May 2021 04:32:11 SAST ]]> https://vital.seals.ac.za/vital/access/manager/Repository/vital:26850 Thu 13 May 2021 02:47:34 SAST ]]> https://vital.seals.ac.za/vital/access/manager/Repository/vital:26853 Thu 13 May 2021 02:26:05 SAST ]]> https://vital.seals.ac.za/vital/access/manager/Repository/vital:26620 Thu 13 May 2021 01:36:38 SAST ]]> https://vital.seals.ac.za/vital/access/manager/Repository/vital:26860 Thu 13 May 2021 01:23:48 SAST ]]> https://vital.seals.ac.za/vital/access/manager/Repository/vital:26859 Thu 13 May 2021 01:17:44 SAST ]]> https://vital.seals.ac.za/vital/access/manager/Repository/vital:26854 Thu 13 May 2021 00:56:11 SAST ]]> https://vital.seals.ac.za/vital/access/manager/Repository/vital:45131 Thu 11 Nov 2021 14:03:30 SAST ]]> https://vital.seals.ac.za/vital/access/manager/Repository/vital:62418 Thu 09 Mar 2023 15:18:58 SAST ]]> https://vital.seals.ac.za/vital/access/manager/Repository/vital:51990 Thu 09 Jun 2022 17:32:36 SAST ]]> https://vital.seals.ac.za/vital/access/manager/Repository/vital:51988 40) individually, using logistic regression. A strong linear relationship between dNBR and stem fire severity (r2 = 0.69, p < 0.001) confirmed the accuracy of dNBR as a measure of fire severity in Afrotemperate forest. In the fire investigated, 4 628 ha of Afrotemperate forest burnt of which 67% burnt at low severity, 21% at medium severity and 12% at high severity. The dNBR values associated with fire severity categories were comparable between Afrotemperate and North American forests, suggesting that dNBR values are relatively standard across forest types. Information on the distribution of fire severity facilitates investigation of further questions regarding past and future fire regimes and the fire ecology of Afrotemperate forest. The post-fire survival rate of Afrotemperate forest trees was 45% which is comparable to that in coniferous forests of North America but lower than that in temperate forests of Australia and Portugal and the neighbouring dune thicket which shares several species with Afrotemperate forest. Fire severity had a significant negative effect on survival and tree size a significant positive effect. Total variance explained by the model (for species collectively) was 40.8%, of which fire severity and tree size combined explained 13.2%, and species as random factor, 27.6%. Respective tree species showed differential survival responses – four species showed high survival (> 60% of individuals), while five species showed low survival (< 40%). This study was the first post-fire assessment of the resprouting ability of Afrotemperate forest trees and a third of the trees surveyed (for species collectively) resprouted from the stem. This suggested that resprouting from the stem is a primary means of post-fire recovery in Afrotemperate forest trees, in contrast with previous assertions that several common canopy species, including Podocarpus latifolius, Afrocarpus falcatus, Scutia myrtina, Scolopia mundii and Rapanea melanophloeos, are unable to resprout. Varying resilience to fire among species supports previous suggestions that fire affects species’ composition and diversity in these forests and calls for careful management of fire regimes in the face of global change.]]> Thu 09 Jun 2022 16:02:39 SAST ]]> https://vital.seals.ac.za/vital/access/manager/Repository/vital:70969 Thu 07 Mar 2024 09:01:13 SAST ]]> https://vital.seals.ac.za/vital/access/manager/Repository/vital:63985 Thu 04 May 2023 10:37:59 SAST ]]> https://vital.seals.ac.za/vital/access/manager/Repository/vital:46027 Thu 03 Feb 2022 11:49:30 SAST ]]> https://vital.seals.ac.za/vital/access/manager/Repository/vital:45691 Mon 31 Jan 2022 13:44:08 SAST ]]> https://vital.seals.ac.za/vital/access/manager/Repository/vital:52374 Mon 14 Nov 2022 08:43:49 SAST ]]> https://vital.seals.ac.za/vital/access/manager/Repository/vital:46584 Mon 14 Feb 2022 15:39:48 SAST ]]> https://vital.seals.ac.za/vital/access/manager/Repository/vital:46577 Mon 14 Feb 2022 15:26:49 SAST ]]> https://vital.seals.ac.za/vital/access/manager/Repository/vital:46541 Mon 14 Feb 2022 12:03:49 SAST ]]> https://vital.seals.ac.za/vital/access/manager/Repository/vital:46517 Mon 14 Feb 2022 10:36:11 SAST ]]> https://vital.seals.ac.za/vital/access/manager/Repository/vital:52014 Mon 13 Jun 2022 15:11:00 SAST ]]> https://vital.seals.ac.za/vital/access/manager/Repository/vital:52017 Mon 13 Jun 2022 12:24:52 SAST ]]> https://vital.seals.ac.za/vital/access/manager/Repository/vital:45690 Mon 11 Jul 2022 11:36:49 SAST ]]> https://vital.seals.ac.za/vital/access/manager/Repository/vital:58191 Mon 07 Nov 2022 11:07:45 SAST ]]> https://vital.seals.ac.za/vital/access/manager/Repository/vital:44878 Fri 29 Oct 2021 12:59:35 SAST ]]> https://vital.seals.ac.za/vital/access/manager/Repository/vital:45688 Fri 28 Jan 2022 11:06:50 SAST ]]> https://vital.seals.ac.za/vital/access/manager/Repository/vital:45683 Fri 28 Jan 2022 10:32:56 SAST ]]> https://vital.seals.ac.za/vital/access/manager/Repository/vital:45682 Fri 28 Jan 2022 09:32:18 SAST ]]> https://vital.seals.ac.za/vital/access/manager/Repository/vital:45686 Fri 28 Jan 2022 09:28:09 SAST ]]> https://vital.seals.ac.za/vital/access/manager/Repository/vital:45685 Fri 28 Jan 2022 09:25:32 SAST ]]> https://vital.seals.ac.za/vital/access/manager/Repository/vital:45684 Fri 28 Jan 2022 09:22:49 SAST ]]> https://vital.seals.ac.za/vital/access/manager/Repository/vital:69318 Fri 27 Oct 2023 11:22:03 SAST ]]> https://vital.seals.ac.za/vital/access/manager/Repository/vital:69316 Fri 27 Oct 2023 11:15:40 SAST ]]> https://vital.seals.ac.za/vital/access/manager/Repository/vital:44031 Fri 13 Aug 2021 10:53:37 SAST ]]> https://vital.seals.ac.za/vital/access/manager/Repository/vital:45141 Sr>Ca. Effects of partial dissolution of and structural changes to the alumina particles at high pH cannot be excluded. In order to better understanding the different effects, it was attempted to measure the zeta potential of the slurries at different pH values. This resulted in highly positive zeta potential values over the complete pH range, without the observationof an iso-electric point. This does not fit to the observed changes in rheology and contrasts withliterature data. One explanation would be that the measurement system used is unsuitable to yield correct zeta potential values for the materials under investigation.]]> Fri 12 Nov 2021 15:48:44 SAST ]]> https://vital.seals.ac.za/vital/access/manager/Repository/vital:45143 Fri 12 Nov 2021 15:06:09 SAST ]]> https://vital.seals.ac.za/vital/access/manager/Repository/vital:45132 Fri 12 Nov 2021 09:30:45 SAST ]]> https://vital.seals.ac.za/vital/access/manager/Repository/vital:45136 Fri 12 Nov 2021 09:09:50 SAST ]]> https://vital.seals.ac.za/vital/access/manager/Repository/vital:45138 Fri 12 Nov 2021 08:27:50 SAST ]]> https://vital.seals.ac.za/vital/access/manager/Repository/vital:45135 Fri 12 Nov 2021 07:52:44 SAST ]]> https://vital.seals.ac.za/vital/access/manager/Repository/vital:46477 Fri 11 Feb 2022 14:49:33 SAST ]]> https://vital.seals.ac.za/vital/access/manager/Repository/vital:66484 Fri 11 Aug 2023 11:43:05 SAST ]]> https://vital.seals.ac.za/vital/access/manager/Repository/vital:51996 Fri 10 Jun 2022 11:50:14 SAST ]]> https://vital.seals.ac.za/vital/access/manager/Repository/vital:47657 Fri 04 Mar 2022 11:35:45 SAST ]]> https://vital.seals.ac.za/vital/access/manager/Repository/vital:47653 Fri 04 Mar 2022 11:00:44 SAST ]]>