529 research outputs found
Physical properties of the magnetically frustrated very-heavy-fermion compound YbCu<sub>4</sub>Ni
No full textThe physical properties of the very-heavy-fermion compound YbCu4Ni were characterized through structural, magnetic, thermal, and transport studies along nearly four decades of temperature ranging between 50 mK and 300 K. At high temperature, the crystal electric field level splitting was determined with Δ1(Γ6)=85K and Δ2(Γ8)≈200K, the latter being a quartet in this cubic symmetry. An effective magnetic moment μeff≈3μB is evaluated for the Γ7 ground state, while at high temperature the value for a Yb3+ ion is observed. At low temperature this compound shows the typical behavior of a magnetically frustrated system undergoing a change of regime at a characteristic temperature T∗≈200mK into of Fermi-liquid-type "plateau" of the specific heat: Cm/T|T→0 = const. The change in the temperature dependence of the specific heat coincides with a maximum and a discontinuity in respective inductive and dissipative components of the ac susceptibility. More details about the nature of this ground state are revealed by the specific heat behavior under applied magnetic field.Fil: Sereni, Julian Gustavo Renzo. Comisión Nacional de Energía Atómica. Centro Atómico Bariloche; Argentina. Consejo Nacional de Investigaciones Científicas y Técnicas; ArgentinaFil: Curlík, I.. University of Prešov; EslovaquiaFil: Giovannini, M.. Università degli Studi di Genova; ItaliaFil: Strydom, A.. University of Johannesbur; SudáfricaFil: Reiffers, M.. Max Planck Institute for Chemical Physics of Solids; Alemania. University of Prešov; Eslovaqui
Critical Challenges Of The South African School System
No full textThe emphasis in the new curriculum after 1996 in South Africa was placed on the transition from the traditional aims and objectives approach to Outcomes-based education (OBE) and Curriculum 2005. This paradigm shift was interpreted as a prerequisite for achievement of the vision of an internationally competitive country. When analysing the school system in South Africa it became clear that the education system was flawed, with poorly performing teachers, poor work ethics, lack of community and parental support, poor control by education authorities, poor support for teachers and very low levels of accountability. These factors further spilled over into the morale of learners and could be seen in the lack of discipline, brutal violence in schools, low moral values, truancy, absenteeism, late coming and high dropout rates from Grade 1 to Grade 12 and very poor performance in essential areas such as Mathematics and Literacy. Citizens in historically disadvantaged areas tend to become victims of poverty, gangs and drug abuse. These factors further blend with the evil of politics in South African schools which are furthermore plagued by various forms of corruption and socio-economic challenges. Eighteen years after the end of the apartheid dispensation, apartheid is still blamed by many for any real or imagined ills in society, but the reality is that there is no political will to enforce the law or to meet public expectations of accountability, efficiency and delivery. In the light hereof, recommendations are proposed that will address these challenges. The critical message of this article will convey that the fact of the matter is that learner enrolment is not the same as attendance and attendance does not imply learning. Therefore, teaching in South Africa must become a profession of preference and pride as opposed to the present very lackadaisical attitude
Influence of added potassium and sodium carbonates on CO2 reactivity of the char from a demineralized inertinite rich bituminous coal
No full textAbstractThe addition of K2CO3, Na2CO3 and a mixture of the two catalysts showed an increase in the CO2 reactivity of the char prepared from the demineralized inertinite rich bitumious coal at 900°C in nitrogen. The CO2 reactivity of the char is higher when the catalysts are added to the coal before preparing the char in comparison to addition of the catalyst to the prepared char. The distribution of the catalyst on the char particles thus seems to be better upon addition of the catalyst to the coal (before charring). An added effect could be the evolution of CO2 during charring that may increase the surface area of the produced char. The surface area values of the chars (>400m2/g) were higher than the values for the demineralized coal samples (approximately 150m2/g) and the values for the char prepared from the coal with added catalysts increased from 413 to 445m2/g. XRF, XRD and QEMSCAN analyses were performed to determine the species of K2CO3 and Na2CO3 formed during thermal treatment of the samples. KCl, NaCl, K2O and Na2O are some of the species that were detected
Restructuring And Mergers Of The South African Post-Apartheid Tertiary System (1994-2011): A Critical Analysis
No full textSocio-economic and vocational needs of communities, governments and individuals change over the years and these discourses served as a compass for restructuring of higher institutions in South Africa from 1994. Before 1994, the claim to legitimacy for government policies in higher education rested on meeting primarily the interests of the white minority. From 1996 onwards, the newly established government considered education a major vehicle of societal transformation. The main objective had been to focus on reducing inequality and fostering internationalisation. Therefore, the rationale for the restructuring of South African universities included a shift from science systems to global science networks. Various challenges are associated with restructuring and include access, diversity, equity and equality. Thus, the restructuring and mergers between former technikons and traditional universities were probably the most difficult to achieve in terms of establishing a common academic platform, as transitional conditions also had to be taken into account and had a twin logic: It was not only the legacy of apartheid that had to be overcome but the incorporation of South Africa into the globalised world was equally important as globalisation transforms the economic, political, social and environmental dimensions of countries and their place in the world. Initially, the post-apartheid higher education transformation started with the founding policy document on higher education, the Report of the National Commission on Higher Education and this report laid the foundation for the 1997 Education White Paper 3 on Higher Education in which a transformed higher education system is described. Restructuring and mergers also had a far-reaching impact, positive and negative, on the various tertiary institutions. This article also reflects on the impact of restructuring and mergers of higher education and reaches the conclusion that higher education faces many more challenges than initially anticipated prior to transformation
The Association between Physical Activity and CAMDEX-DS Changes Prior to the Onset of Alzheimer’s Disease in Down Syndrome
No full text© 2021 S. Pape, R. Baksh, C. Startin, S. Hamburg, R. Hithersay, A. Strydom. This is an open-access article distributed under the terms of the Creative Commons Attribution 4.0 International License (CC BY 4.0), which permits unrestricted use, distribution, and reproduction in any medium, provided the original author and source are credited. See http://creativecommons.org/licenses/by/4.0
A complicated grief intervention model
No full textComplicated grief refers to a prolonged state of grief and indicates the inability of the client to incorporate the death into his or her life. Few social workers in South Africa assess the possibility of complicated grief as a contributing factor to impaired social functioning. This can be as a result of limited knowledge, ignorance and/or insufficient skills on the part of the social worker to assess and identify complicated grief. In this article, the researchers tabulate some of the models and approaches to bereavement and discusses its applicability to complicated grief. Specific attention is given to the Dual Process Model (Stroebe & Schut 1999) and the Task-Centred approach (a social work approach to therapy) in an attempt to develop a model for complicated grief intervention. This article furthermore proposes the Complicated Grief Intervention Model through the integration of the Dual Process Model and the Task-Centred approach while drawing on intervention techniques from other therapeutic approaches.
Opsomming
Gekompliseerde rou verwys na ‘n verlengde staat van rou en impliseer ‘n onvermoë by die klient om die dood van ‘n geliefde in sy/haar lewe te integreer. Gekompliseerde rou word deur min maatskaplike werkers as bydraende faktor tot verlaagde maatskaplike funksionering geassesseer. Dit kan toegeskryf word aan beperkte kennis, ignorering van/of ontoereikende vaardighede by die maatskaplike werker in die identifisering en assessering van gekompliseerde rou. Die outeurs tabuleer sommige van die rouberadingsmodelle en –benaderings in hierdie artikel en bespreek die toepaslikheid daarvan op gekompliseerde rou. Spesifieke aandag word aan die Tweeledige Prosesmodel (Dual Process Model) (Stroebe & Schut 1999) verleen, asook aan die taakgesentreerde benadering (‘n maatskaplike werkbenadering) in ‘n poging om ‘n model te ontwikkel vir gekompliseerde rou intervensie. Die artikel beveel aan dat die Gekompliseerde Rou Intervensie Model (GRIM) deur middel van die integrasie van die Tweeledige Prosesmodel en die taakgesentreerde maatskaplike werkbenadering aangebied word, terwyl intervensietegnieke van verskeie terapeutiese benaderings benut word
Policing Standard Form Contracts in Germany and South Africa: A Comparison
No full textThe aim of this dissertation is to compare South African law on standard form contracts against the corresponding German law. Thus, the responses of both legal systems to the special situation occurring in cases of standard form contracts will be compared and evaluated. Thereby, the focus of this dissertation is to determine whether South African law on standard form contracts provides adequate protection for the submitting party. German law on standard form contracts provides the basis and outline against which South African law will be critically evaluated. German law was selected for this task, as it was one of the first legal systems, which enacted legislation, and addresses the issue systematically. It should be noted that this dissertation does not aim to evaluate German law on standard form contracts. In the first part of this dissertation I will provide a brief definition of the notion of freedom of contract and consumer protection. I will then proceed to highlight the relevance of standard form contracts in modern society and outline the problems associated with such contracts. This will be followed by a discussion of whether standard form contracts can be considered as classical contracts. In the second part of this dissertation I will outline the law on standard form contracts in both jurisdictions. Concerning the German law, I will give a brief overview of what the relevant provisions state. Concerning South African law, I will briefly illustrate what the relevant common law appears to be without going into far too much depth. Such outlines of the applicable laws are necessary in order to acquaint the reader with some of the important themes that this dissertation will discuss in detail. In part three the actual comparison and evaluation will follow. The comparison will include a detailed illustration of the law on standard form contracts in both jurisdictions. Thereby, some repetition in regard to the applicable law cannot be avoided. Thereafter, the evaluation will more specifically investigate whether South African law is effective in achieving its aims and whether South Africa should introduce legislation on standard form contract terms
The symbolic uniqueness of wilderness participation
No full textIn the field of adventure therapy the curative powers of natural environments are too often not recognised as therapeutic in itself. Compared with the ecological and experiential values of wilderness the symbolic values thereof have largely been overlooked. Through restoration, physical self, primitiveness, humility, timelessness, solitude, privacy, freedom of choice, personal self and spiritual upliftment, this study aims at determining whether wilderness can be experienced as symbolically unique and whether this natural world can be considered a necessity for achieving therapeutic outcomes. In doing so, this study compared a centre-based adventure programme with an expedition-based wilderness programme, using a crossover research design with a mixed-method approach. For a meaningful adventure experience, results showed that the experience of above-mentioned components made the most important contribution during the expedition-based wilderness programme and that this programme is most effective in creating this very aspect. However, it is possible to also experience the above components during a centre-based adventure programme, but to a lesser extent and with a different meaning
Magnetic vortices in gauge/gravity duality
No full textWir untersuchen stark gekoppelte Phänomene unter Verwendung der Dualität
zwischen Eich- und Gravitationstheorien. Dabei liegt ein besonderer Fokus
einerseits auf Vortex Lösungen, die von einem magnetischem Feld verursacht
werden, und andererseits auf zeitabhängigen Problemen in holographischen
Modellen. Das wichtigste Ergebnis ist die Entdeckung eines unerwarteten Effektes
in einem einfachen holografischen Modell: ein starkes nicht abelsches
magnetisches Feld verursacht die Entstehung eines Grundzustandes in der Form
eines dreieckigen Gitters von Vortices.
Die Dualität zwischen Eich- und Gravitationstheorien ist ein mächtiges Werkzeug
welches bereits verwendet wurde um stark gekoppelte Systeme vom Quark-Gluonen
Plasma in Teilchenbeschleunigern bis hin zu Festkörpertheorien zu beschreiben.
Die wichtigste Idee ist dabei die der Dualität: Eine stark gekoppelte
Quantenfeldtheorie kann untersucht werden, indem man die Eigenschaften eines aus
den Einsteinschen Feldgleichungen folgenden Gravitations-Hintergrundes bestimmt.
Eine der Gravitationstheorien, die in dieser Arbeit behandelt werden, ist eine
Einstein--Yang--Mills Theorie in einem AdS--Schwarzschild Hintergrund mit
SU(2)-Eichsymmetrie. Der Ansatz für das Eichfeld ist so gewählt, dass die
zugehörige Quantenfeldtheorie einem externen Magnetfeld ausgesetzt ist. Oberhalb
eines kritischen Magnetfeldes wird die Konfiguration instabil und zeigt einen
Phasenübergang zu einem Supraleiter.
Die Instabilität wird mit zwei Ansätzen untersucht. Zum einen werden
Fluktuationen des Hintergrunds betrachtet und die Quasinormalmoden analysiert.
Zum anderen zeigt die numerische Analyse der Bewegungsgleichungen, dass das
effektive Schrödinger-Potential mit stärker werdendem Magnetfeld sich so lange
verändert, bis ein gebundener Zustand möglich wird. Der sich ergebende
supraleitende Grundzustand ist durch ein dreieckiges Vortexgitter gegeben, wie
eine störungstheoretische Entwicklung über einem kleinen Parameter proportional
zur Größe des Kondensats zeigt. Zur Bestimmung des energetisch bevorzugten
Zustands wird mithilfe der holographischen Übersetzungsvorschrift die
Gesamtenergie verschiedener Lösungen berechnet. Hierfür wird die Lösung der
Bewegungsgleichungen zur dritten Ordnung in oben genanntem Parameter berechnet.
Zusätzlich wird gezeigt, dass dieses Ergebnis auch für den Fall einer AdS--hard
wall Geometrie gilt, also einer Feldtheorie mit Confinement.
Als nächstes erweitern wir das einfache Gravitationsmodell um ein chemisches
Potential und wiederholen die Untersuchung. Sind das chemische Potential, das
magnetische Feld oder beide groß genug, so befindet sich das System in einer
supraleitenden Phase. Wir berechnen das Phasendiagramm des Systems numerisch.
Der Grundzustand der supraleitenden Phase nahe dem Phasenübergang ist ein
dreieckiges Vortexgitter, wobei der Gitterabstand nur von der Stärke des
magnetischen Feldes abhängt. Die Relevanz dieser Ergebnisse wird im Zusammenhang
mit inhomogenen Grundzuständen in holographischen Supraleitern diskutiert, einem
Themengebiet welches in letzter Zeit viel Interesse auf sich gezogen hat. Die
erhaltenen Resultate sind nicht nur aufgrund der vorher unbekannten inhomogenen
Lösung der Gravitationstheorie mit Schwarzem Loch neuartig. Es ist auch
interessant, dass ein großes magnetisches Feld die Vortexstruktur im
Grundzustand induziert anstatt sie zu unterdrücken.
Des Weiteren untersuchen wir zeitabhängige Phänomene in einer holographischen
Erweiterung des Kondomodells. Letzteres beschreibt ein einfaches Modell in der
Festkörperphysik, in welchem eine magnetische Verunreinigung stark an ein
Elektronenreservoir koppelt. Die holographische Beschreibung erfordert Techniken
der numerischen Relativitätstheorie und erlaubt uns die Entwicklung des Systems
nach einem plötzlichen Sprung in der Kopplungskonstante zu simulieren.
Diese Doktorarbeit basiert auf Ergebnissen, die der Autor während des Studiums
am Max-Planck-Institut-für-Physik in München, Deutschland unter der Betreuung
von PD Dr. J. K. Erdmenger von August 2011 bis Mai 2014 erreicht hat. Die
relevanten Veröffentlichungen sind:
[1] M. Ammon, J. Erdmenger, P. Kerner, and M. Strydom,
“Black Hole Instability Induced by a Magnetic Field,”
Phys.Lett. B706 (2011) 94–99, arXiv:1106.4551 [hep-th],
[2] Y.-Y. Bu, J. Erdmenger, J. P. Shock, and M. Strydom,
“Magnetic field induced lattice ground states from holography,”
JHEP 1303 (2013) 165, arXiv:1210.6669 [hep-th].We study strongly-coupled phenomena using gauge/gravity duality, with a
particular focus on vortex solutions produced by magnetic field and
time-dependent problems in holographic models. The main result is the discovery
of a counter-intuitive effect where a strong non-abelian magnetic field induces
the formation of a triangular vortex lattice ground state in a simple
holographic model.
Gauge/gravity duality is a powerful theoretical tool that has been used to study
strongly-coupled systems ranging from the quark-gluon plasma produced at
particle colliders to condensed matter theories. The most important idea is that
of duality: a strongly coupled quantum field theory can be studied by
investigating the properties of a particular gravity background described by
Einstein's equations.
One gravity background we study in this dissertation is AdS--Schwarzschild with
an SU(2) gauge field. We switch on the gauge field component that gives the
field theory an external magnetic field. When the magnetic field is above a
critical value, we find that the system is unstable, indicating a
superconducting phase transition.
We find the instability in two ways. Firstly, we do a quasinormal mode analysis,
studying fluctuations about the background. Secondly, we rewrite the equations
in Schrödinger form and numerically find that, as the magnetic field is
increased, the potential deepens until it is capable of supporting a bound
state. Next we show that the resulting superconducting ground state is a
triangular vortex lattice. This is done by performing a perturbative expansion
in a small parameter proportional to the condensate size. After solving the
equations to third order, we use the holographic dictionary to calculate the
total energy of different lattice solutions and identify the minimum energy
state. In addition, we show that the result holds in an AdS--hard wall model as
well, which is dual to a confining theory.
Next we extend the simple gravity model to include a chemical potential and
repeat the analysis. When the chemical potential, magnetic field or both are
large, the system is in a superconducting phase. We calculate the precise phase
diagram numerically. The ground state in the superconducting phase near the
phase transition line is shown to be a triangular vortex lattice with lattice
spacing depending only on the magnetic field strength. We comment on the
relevance of the results to the study of inhomogeneous ground states in
holographic superconductors, a topic in which there has been much interest
recently. Our results are novel not only because of the previously unknown
inhomogeneous black hole solution, but also because of the effect of a large
magnetic field inducing rather than inhibiting the vortex lattice ground state
in a holographic model.
We also study time-dependent phenomena in a holographic generalisation of the
Kondo model, a simple condensed matter model of a magnetic impurity coupled
strongly to a sea of electrons. This requires techniques from numerical
relativity and allows us to determine the response of the system to a quench in
the coupling.
This dissertation is based on work the author did during a PhD fellowship under
the supervision of PD Dr. J. K. Erdmenger at the Max-Planck-Institut für Physik
in Munich, Germany from August 2011 to May 2014. The relevant publications are:
[1] M. Ammon, J. Erdmenger, P. Kerner, and M. Strydom,
“Black Hole Instability Induced by a Magnetic Field,”
Phys.Lett. B706 (2011) 94–99, arXiv:1106.4551 [hep-th],
[2] Y.-Y. Bu, J. Erdmenger, J. P. Shock, and M. Strydom,
“Magnetic field induced lattice ground states from holography,”
JHEP 1303 (2013) 165, arXiv:1210.6669 [hep-th].Ons bestudeer sterk gekoppelde fenomene deur die gebruik van dualiteit tussen
ykteorieë en gravitasieteorieë. Ons fokus spesifiek op vorteks oplossings wat
deur magnetiese velde voortgebring word, asook tyd-afhanklike probleme in
holografiese modelle. Die belangrikste resultaat is die ontdekking van 'n
onverwagte effek waar sterk nie-abelse magnetiese velde 'n driehoekige
vorteksrooster grondtoestand uitlok in 'n holografiese model.
Die dualiteit tussen ykteorieë en gravitasie is 'n nuttige instrument wat al
gebruik is om sterk-gekoppelde stelsels te bestudeer wat wissel van die
kwark-gluon plasma, wat geproduseer is by deeltjieversnellers, tot
gekondenseerde materie teorieë. Die belangrikste begrip is dualiteit: 'n sterk
gekoppelde kwantumveldteorie kan bestudeer word deur die eienskappe van 'n
spesifieke swaartekrag agtergrond, wat beskryf word deur Einstein se
vergelykings, te ondersoek.
Een swaartekrag agtergrond wat ons bestudeer is AdS--Schwarzschild met 'n SU(2)
ykveld. Ons skakel die ykveld komponent aan wat in die veldteorie duaal is aan
'n eksterne magnetiese veld. Wanneer die magnetiese veld bo 'n spesifieke waarde
val, vind ons dat die stelsel onstabiel is, wat dui op 'n supergeleidende fase
oorgang.
Ons vind die onstabiliteit op twee maniere. Eerstens, doen ons 'n quasinormale
modus analise, waarin ons versteurings van die agtergrond bestudeer. Tweedens,
herskryf ons die vergelykings in Schrödinger vorm en vind numeries dat soos
die magnetiese veld sterker word, verdiep die potensiaal totdat dit diep genoeg
is vir 'n gebonde toestand om te vorm. Volgende wys ons dat die gevolglike
supergeleidende grondtoestand 'n rooster van driehoekige vortekse is. Dit word
gedoen deur die uitvoering van 'n versteuringsuitbreiding in 'n klein parameter
wat proporsioneel is tot die grootte van die kondensaat. Na die oplossing van
die vergelykings tot op die derde orde, gebruik ons die holografiese
vertalingsvoorskrif om die totale energie van verskillende rooster oplossings te
bereken en~die minimum energie toestand te identifiseer. Daarna wys ons dat
die gevolge in 'n AdS--hard wall model ook waar is. Die AdS--hard muur model is
duaal tot 'n teorie met confinement.
Volgende brei ons die eenvoudige swaartekrag model uit sodat dit 'n chemiese
potensiaal in sluit en dan herhaal ons die analise. Wanneer die chemiese
potensiaal, magnetiese veld of albei groot is, is die stelsel in 'n
supergeleidende fase. Ons bereken die fase diagram numeries. Die grondtoestand
in die supergeleidende fase naby die fase-oorgangslyn vorm 'n driehoekige
vorteksrooster met rooster spasiëring wat afhang van die sterkte van die
magnetiese veld. Ons lewer kommentaar op die toepaslikheid van die resultate tot
nie-homogene grondtoestande in holografiese supergeleiers, 'n onderwerp waarin
daar onlangs baie belangstelling was. Die nuwigheid van ons resultate l\^e in
beide die voorheen onbekende swartkolk oplossing en die effek van 'n groot
magnetiese veld wat die vorteksrooster grondtoestand in 'n holografiese model
eerder voortbring as verhinder.
Ons bestudeer ook tyd-afhanklike fenomene in 'n holografiese veralgemening
van die Kondo model, 'n eenvoudige gekondenseerde materie model van 'n
magnetiese onreinheid wat sterk koppel aan 'n see van elektrone. Dit vereis
tegnieke van numeriese relatiwiteit en laat ons toe om die reaksie van die
stelsel te bepaal na 'n vinnige sprong in die koppeling.
Hierdie verhandeling is gebaseer op die werk wat die skrywer tydens 'n PhD
program onder die toesig van PD Dr JK Erdmenger by die Max Planck-Institut-für
Physik in München, Duitsland vanaf Augustus 2011 tot Mei 2014 gedoen het. Die
toespaslike publikasies is:
[1] M. Ammon, J. Erdmenger, P. Kerner, and M. Strydom,
“Black Hole Instability Induced by a Magnetic Field,”
Phys.Lett. B706 (2011) 94–99, arXiv:1106.4551 [hep-th],
[2] Y.-Y. Bu, J. Erdmenger, J. P. Shock, and M. Strydom,
“Magnetic field induced lattice ground states from holography,”
JHEP 1303 (2013) 165, arXiv:1210.6669 [hep-th]
Stressors among South African soccer officials: a profile analysis
No full textThe purpose of this study was to determine the contribution of selected stressors to the level of stress experienced by South African soccer officials. Forty-two South African Football Association (SAFA) accredited officials, attending a training camp in Potchefstroom, participated in this study. The group comprised of 40 male and two female officials. The average age of the officials was 37.52 (±6.09) years, and the period for which they were accredited as a SAFA official ranged from 2 to 27 years. The Ontario Soccer Officials’ Survey (OSOS) was used to determine the perceived levels of stress. The results indicated that fitness concerns were rated as the highest contributor to the stress experienced followed by role-culture conflicts, fear of failure, peer conflicts, interpersonal conflict, time pressures and lastly, fear of physical harm. The Spearman Rank Order Correlation showed a high correlation between the number of years the officials were accredited with SAFA and the total level of stress they experienced. Furthermore, the results indicated that 60% of the officials, who served as an accredited official for longer than 12 years, experienced five to seven stressors, which contributed to the total level of perceived stres
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