Showing items 41 - 60 of 1574

Your selections:

Carel's Rust Farm

- Brown, William J

Sketch map of the portion of the territory of East Griqualand : traversed while settling locations by the vacant Land Commissioners

- Brownlee, C, Strachan, Donald, Watermeyer, C P, Watermeyer, F S, Cape of Good Hope (Colony). Surveyor General, Surveyor General's Department, Saul Solomon & Co.

The largest volcanic eruptions on Earth

- Bryan, Scott E, Peate, Ingrid Ukstins, Peate, David W, Self, Stephen, Jerram, Dougal A, Mawby, Michael R, Marsh, Julian S, Miller, Jodie A

  • Authors: Bryan, Scott E , Peate, Ingrid Ukstins , Peate, David W , Self, Stephen , Jerram, Dougal A , Mawby, Michael R , Marsh, Julian S , Miller, Jodie A
  • Date: 2010
  • Language: English
  • Type: text , article
  • Identifier: http://hdl.handle.net/10962/132887 , vital:36902 , https://doi.org/10.1016/j.earscirev.2010.07.001
  • Description: Large igneous provinces (LIPs) are sites of the most frequently recurring, largest volume basaltic and silicic eruptions in Earth history. These large-volume (> 1000 km3 dense rock equivalent) and large-magnitude (> M8) eruptions produce really extensive (104–105 km2) basaltic lava flow fields and silicic ignimbrites that are the main building blocks of LIPs.
  • Full Text: false
  • Date Issued: 2010

Plan of territories formerly known as Kaffraria proper

- Burton, Alfred William

  • Authors: Burton, Alfred William
  • Date: 1884
  • Subjects: Kaffraria Maps , South Africa History 1836-1909 Maps
  • Language: English
  • Type: maps , cartographic
  • Identifier: http://hdl.handle.net/10962/115759 , vital:34227 , Cory Library for Humanities Research, Rhodes University Library, Grahamstown, South Africa , MP1877
  • Description: Plan of Territories formerly known as Kaffraria proper: simplified handdrawn copy of the 1884 map of the territories formerly known as Kaffraria, with additional information inserted by Alfred William Burton. Surveyors C.P. Watermeyer; Fletcher ; MacDonald, Schunke, Tilney, Norris, Greeff, Greathead, F. Watermeyer; Erskine, Hughes R.N., Changuion, Pritchard and O. Mehliss, and military sketches by Messrs Colley and Grant and the Intelligence Branch of the Quartermaster General's Department. Photocopy stuck on card. Transkeian territories. First produced in 1884 by 14 surveyors and 3 others.See MP 307, L (77) d 1 for the original map by fourteen surveyors and Military sketches.
  • Full Text: false
  • Date Issued: 1884

Education, Training and Capacity-Building in the Field of Biological Invasions in South Africa:

- Byrne, Marcus J, du Plessis, Dorette, Ivey, Philip J, Measey, John, Robertson, Mark P, Robinson, Tamara B, Weaver, Kim N

  • Authors: Byrne, Marcus J , du Plessis, Dorette , Ivey, Philip J , Measey, John , Robertson, Mark P , Robinson, Tamara B , Weaver, Kim N
  • Date: 2020
  • Language: English
  • Type: text , book
  • Identifier: http://hdl.handle.net/10962/176250 , vital:42678 , ISBN 978-3-030-32394-3 , 10.1007/978-3-030-32394-3
  • Description: Our changing relationship with the biosphere is one of many anxieties that human society currently confronts. The paradox that some biodiversity that has been moved across the planet by human trade could actually be harmful is unknown to many people. They are either oblivious, or perceive nature as being under threat, rather than as threatening in itself.
  • Full Text: false
  • Date Issued: 2020

Map marking the boundaries of Stellaland and Goshen and showing surrounding areas

- Cape of Good Hope. Ministerial Department of Crown Lands and Public Works

Going to university: the Influence of higher education on the lives of young South Africans

- Case, Jennifer M, Marshall, Delia, McKenna, Sioux, Mogashana, Disaapele

From contradictions to complementarities: a social realist analysis of the evolution of academic development within a department

- Case, Jennifer M, Heydenrych, Hilton, Kotta, Linda, Marshall, Delia, McKenna, Sioux, Willliams, Kevin

  • Authors: Case, Jennifer M , Heydenrych, Hilton , Kotta, Linda , Marshall, Delia , McKenna, Sioux , Willliams, Kevin
  • Date: 2017
  • Language: English
  • Type: text , article
  • Identifier: http://hdl.handle.net/10962/66752 , vital:28990 , ISSN 1470-1294 , https://doi.org/10.1080/03075079.2015.1045479
  • Description: Publisher version , Academic development is a recent project in the university, intended to enable the university to respond to the needs of a more diverse student body. In South Africa, such work arose during late apartheid, and has now moved to a more central institutional position advocating responsiveness in the light of the educational disparities that are the legacy of apartheid. The present study uses a social realist perspective to analyse the 25-year evolution of an academic development project within an engineering department at a South African university. The findings show that while academic development initially posed a contradictory logic to the department, the response was to reform the nature of this project into one that suited the other commitments of the department: a logic of complementarity. The department's relationships with industry were shown to have played a key role in fostering this form of change.
  • Full Text: false
  • Date Issued: 2017

Kenhart

- Casgrain, P H du P, Great Britain. Army. Field Intelligence Department

Maclear

- Casgrain, P H du P, Great Britain. War Office. Intelligence Division

Salt pan

- Casgrain, P H du P, Great Britain. War Office. Intelligence Division

Murraysburg

- Casgrave, P H du P, Great Britain. War Office. Intelligence Division

Thermoluminescence of SrAl2O4: Eu2+, Dy3+: kinetic analysis of a composite-peak

- Chithambo, Makaiko L, Wako, A H, Finch, A A

  • Authors: Chithambo, Makaiko L , Wako, A H , Finch, A A
  • Date: 2017
  • Language: English
  • Type: text , article
  • Identifier: http://hdl.handle.net/10962/124157 , vital:35571 , https://doi.org/10.1016/j.radmeas.2016.12.009
  • Description: The kinetic analysis of thermoluminescence of beta-irradiated SrAl2O4:Eu2+,Dy3+ is reported. The glow-curve is dominated by an apparently-single peak. It has been demonstrated using a number of tests including partial dynamic-heating, isothermal heating, phosphorescence and, the effect of fading, that the peak and the glow-curve consists of a set of closely-spaced peaks. In view of the peak being complex, its first few components were abstracted and analysed and for comparison, the peak was also analysed assuming it is genuinely single.
  • Full Text: false
  • Date Issued: 2017

Temperature-dependence of time-resolved optically stimulated luminescence and composition heterogeneity of synthetic α-Al2O3: C

- Chithambo, Makaiko L, Costin, G

  • Authors: Chithambo, Makaiko L , Costin, G
  • Date: 2017
  • Language: English
  • Type: text , article
  • Identifier: http://hdl.handle.net/10962/124172 , vital:35573 , https://doi.org/10.1016/j.jlumin.2016.10.038
  • Description: The relationship of pulse-width, lifetime and measurement temperature in describing intensity of time-resolved luminescence optically stimulated at 470 nm from α-Al2O3:C is reported. The change of luminescence intensity with stimulation temperature is discussed in terms of the signal integrated over a complete time-resolved luminescence spectrum or in terms of ratios of the signal emitted either during or after pulsed stimulation to the total signal obtained per spectrum. The temperature-induced change in these parameters depends on whether the pulse-width is less or more than the luminescence lifetime. This is because the lifetime in α-Al2O3:C varies with measurement temperature. We have developed and applied new models to distinguish thermal assistance from different traps and to use this information as an additional means to analyse thermal quenching by using the luminescence intensity integrated from time-resolved spectra. Using a model based on use of the throughput, the activation energy for thermal assistance was determined for the shallow trap as 0.054±0.001 eV and as 0.53±0.03 eV for the main trap. The activation energy for thermal quenching was then evaluated using luminescence yield during the pulse as 1.09±0.01 eV and as 1.12±0.01 eV using the throughput after the pulse. Using the new analytical method based on integrated intensity, the activation energy for thermal quenching was found as 1.00±0.07 eV. These values are self-consistent and show that the methods for analyzing temperature-induced changes in intensity and the attendant thermal effects, such as thermal assistance can be successfully applied. We have also reported a general mathematical model that accounts for the temperature-dependence of time-resolved luminescence from α-Al2O3:C. The luminescence study was complemented by investigation of the phase and composition heterogeneity of the samples.
  • Full Text: false
  • Date Issued: 2017

Time-resolved luminescence from quartz: an overview of contemporary developments and applications

- Chithambo, Makaiko L, Pagonis, Vasilis, Ankjærgaard, Christina

  • Authors: Chithambo, Makaiko L , Pagonis, Vasilis , Ankjærgaard, Christina
  • Date: 2016
  • Language: English
  • Type: text , article
  • Identifier: http://hdl.handle.net/10962/124743 , vital:35658 , https://doi.org/10.1016/j.physb.2015.10.014
  • Description: Time-resolved optical stimulation of luminescence has become established as a key method for measurement of optically stimulated luminescence from quartz, feldspar and α-Al2O3:C, all materials of interest in dosimetry. The aim of time-resolved optical stimulation is to separate in time the stimulation and emission of luminescence. The luminescence is stimulated from a sample using a brief light pulse and the emission monitored during stimulation in the presence of scattered stimulating light or after pulsing, over photomultiplier noise only. Although the use of the method in retrospective dosimetry has been somewhat limited, the technique has been successfully applied to study mechanisms in the processes leading up to luminescence emission. The main means for this has been the temperature dependence of the luminescence intensity as well as the luminescence lifetimes determined from time-resolved luminescence spectra. In this paper we review some key developments in theory and applications to quartz including methods of evaluating lifetimes, techniques of evaluating kinetic parameters using both the dependence of luminescence intensity and lifetime on measurement temperature, and of lifetimes on annealing temperature. We then provide an overview of some notable applications such as separation of quartz signals from a quartz–feldspar admixture and the utility of the dynamic throughput, a measure of luminescence measured as a function of the pulse width. The paper concludes with some suggestions of areas where further exploration would advance understanding of dynamics of luminescence in quartz and help address some outstanding problems in its application.
  • Full Text: false
  • Date Issued: 2016

Thermoluminescence of the main peak in SrAl2O4: Eu2+, Dy3+: spectral and kinetics features of secondary emission detected in the ultra-violet region

- Chithambo, Makaiko L

  • Authors: Chithambo, Makaiko L
  • Date: 2017
  • Language: English
  • Type: text , article
  • Identifier: http://hdl.handle.net/10962/124197 , vital:35575 , https://doi.org/10.1016/j.radmeas.2016.12.001
  • Description: We report the thermoluminescence of SrAl2O4:Eu2+,Dy3+ measured in the ultra-violet region of the spectrum between 300 and 400 nm. Complementary measurements of X-ray excited optical luminescence confirm emission bands of stimulated luminescence in this region. As a further test, optically stimulated luminescence was also measured in this region. The glow curve measured at 1 °C s−1 following irradiation to various doses appears simple and single but is in reality a collection of several components. This was shown by results from the Tm-Tstop method on both ends of the peak, application of thermal cleaning beyond the peak maximum as well as the dependence of the peak on fading. The latter shows that new peaks appear as preceding ones fade. Kinetic analysis of some of the main peaks was carried out giving an activation energy of 0.6 eV. The implication of the results on measurement of phosphorescence, interpretation of dose response and fading is discussed.
  • Full Text: false
  • Date Issued: 2017

Time-resolved luminescence: progress in development of theory and analytical methods

- Chithambo, Makaiko L

  • Authors: Chithambo, Makaiko L
  • Date: 2019
  • Language: English
  • Type: text , book chapter
  • Identifier: http://hdl.handle.net/10962/105403 , vital:32509 , https://doi.org/10.1142/9781786345790_0007
  • Description: Time-resolved optical stimulation is an important method for measurement of optically stimulated luminescence. The aim of time-resolved optical stimulation is to separate the stimulation and emission of luminescence in time. The luminescence is stimulated from a sample using a short light pulse of constant intensity. The ensuing luminescence can be monitored either during stimulation in the presence of scattered stimulating light, or after the light-pulse. The time-resolved luminescence spectrum produced in this way can be resolved into components, each with a distinct lifetime. The lifetimes are linked to physical processes of luminescence. Time-resolved optical stimulation has thus been used to study dynamics of luminescence in various materials, particularly ones of interest in dosimetry such as quartz, feldspar, α-Al2O3:C and BeO. This chapter will review the theory of time-resolved luminescence, look at the instrumentation involved and discuss advances in analytical methods of time-resolved luminescence spectra.
  • Full Text: false
  • Date Issued: 2019

Phototransferred thermoluminescence of synthetic quartz: analysis of illumination-time response curves

- Chithambo, Makaiko L, Niyonzima, P, Kalita, Jitumani M

  • Authors: Chithambo, Makaiko L , Niyonzima, P , Kalita, Jitumani M
  • Date: 2018
  • Language: English
  • Type: text , article
  • Identifier: http://hdl.handle.net/10962/111020 , vital:33364 , https://doi.org/10.1016/j.jlumin.2018.02.029
  • Description: Phototransferred thermoluminescence (PTTL) induced in synthetic quartz by 470 nm blue light is reported. The glow curve measured at 5 °C/s up to 500 °C after irradiation to 100 Gy shows six peaks at 94, 116, 175, 212, 280 and 348 °C labelled I through VI and another one at 80 °C (labelled A1). PTTL is only observed for peaks A1 and I and is induced at peak A1 as long as peak III has been removed by preheating and at peak I after preheating to deplete peak VI. The inducement of PTTL even when all peaks have been removed points to deep electron traps in the quartz also acting as donors in addition to the putative ones below 500 °C. The PTTL intensity as a function of duration of illumination for A1 goes through a peak and decreases monotonically or to a stable value depending on the preheating temperature. The change of PTTL intensity as a function of illumination time is described using a set of coupled linear differential equations. The number of acceptors and donors in a particular system described in this way is influenced by the preheating temperature.
  • Full Text: false
  • Date Issued: 2018

Optically stimulated luminescence of ultra-high molecular weight polyethylene: a study of dosimetric features

- Chithambo, Makaiko L, Kalita, Jitumani M

  • Authors: Chithambo, Makaiko L , Kalita, Jitumani M
  • Date: 2018
  • Language: English
  • Type: text , article
  • Identifier: http://hdl.handle.net/10962/110035 , vital:33217 , https://doi.org/10.1016/j.radmeas.2018.06.006
  • Description: We report the dosimetric features of ultra-high molecular weight polyethylene (UHMWPE) using luminescence optically stimulated using 470 nm blue light. Samples irradiated to between 1 and 1000 Gy produces luminescence that increases with irradiation dose to produce a linear dose response between 1 and 1000 Gy. The sample was determined not to be affected by pre-dose in tests using a pre-dose of 4000 Gy. This characteristic precludes the need for elaborate background erasing routines typical of dosimetry experiments. The signal has good reproducibility. We used this property to test recovery of ‘unknown’ doses with encouraging results. It was observed that luminescence can also be stimulated using 870 nm infrared light. The dose response, fading, pre-dose effect and the ability to optically stimulate luminescence from the polymer is discussed in terms of curing involving free-radicals.
  • Full Text: false
  • Date Issued: 2018

Phototransferred thermoluminescence of α-Al2O3: C: experimental results and empirical models

- Chithambo, Makaiko L, Seneza, Cleophace, Kalita, Jitumani M

  • Authors: Chithambo, Makaiko L , Seneza, Cleophace , Kalita, Jitumani M
  • Date: 2017
  • Language: English
  • Type: text , article
  • Identifier: http://hdl.handle.net/10962/115681 , vital:34215 , https://doi.org/10.1016/j.radmeas.2017.08.009
  • Description: The thermoluminescence glow curve of α-Al2O3:C consists of a prominent apparently-single peak and a number of weaker intensity secondary peaks. Phototransferred thermoluminescence (PTTL) from secondary glow peaks in α-Al2O3:C is reported. For completeness and to aid discussion, complementary results for the main peak are included. The problem studied is one of phototransferred thermoluminescence for a system of multiple acceptors and multiple donors. A TL glow curve recorded at 5 °C/s following irradiation to 0.5 Gy shows the main peak (labelled II) at 240 °C and two secondary peaks at 86 °C (peak I) and 360 °C (peak III). Peak I is reproduced under phototransfer after any preheating between 100 and 500 °C. Peak II is also reproduced as a PTTL peak after preheating to any temperature up to 800 °C. For the latter, the duration of preheating matters because if the sample is preheated at 800 °C for say, 6 min, PTTL is obtained but not when this is extended to say, 15 min. No PTTL was observed from peak III at all. A study of the time dependence of the PTTL intensity from peak III, following preheating that removes peaks I and II, shows that its electron trap acts as an acceptor when the duration of illumination to stimulate electrons from deep traps is brief but that when the illumination time is extended, the electron trap for peak III loses some of its trapped electrons to the shallower traps thus acting as a donor trap.
  • Full Text: false
  • Date Issued: 2017
  • Disclaimer
  • Privacy
  • Copyright
  • Contact