2,101 research outputs found
Charassognathus gracilis Botha & Abdala & Smith 2007
No full text<i>CHARASSOGNATHUS GRACILIS</i> GEN. ET SP. NOV. <p> <i>Diagnosis</i>: This new cynodont is distinguished by the presence of a small notch in the base of the coronoid process, located in a similar position to the base of the masseteric fossa in <i>Dvinia</i> and <i>Procynosuchus</i>. The angle of the dentary is prominent, appearing more developed than in <i>Procynosuchus</i> and <i>Dvinia</i>, but less so than in <i>Nanictosaurus</i>. The dental formula is?4·1· 8/3·1·?, and it is distinguished from <i>Procynosuchus</i> and <i>Dvinia</i> by the absence of maxillary precanine teeth. The anterior postcanines have a single high cusp in labial view, whereas the posterior postcanines exhibit a main cusp directed slightly backward, and tiny anterior and posterior accessory cusps, with the anterior accessory cusps positioned slightly higher than the posterior accessory cusps.</p> <p> <i>Comments</i>: The combined presence of the following characters indicates that <i>C. gracilis</i> is a cynodont: multicuspidated postcanines; groove in the squamosal for the quadratojugal; two occipital condyles; elongated ascending process of the epipterygoid; frontal excluded from the orbital margin; prominent angle of the dentary; reflected laminar of the angular with small lateral crests and femoral head set off dorsally from the shaft (see Description for more details).</p> <p> <i>Holotype</i>: SAM-PK-K10369 consists of a complete skull with lower jaw in occlusion, the axis, third cervical vertebra,?cervical ribs and a few indeterminate bones. Associated material includes a right articulated femur, tibia and fibula.</p> <p> <i>Etymology</i>: Greek, <i>charasso</i>, prefix meaning ‘notch’ and <i>gnathus</i>, ‘jaw’, referring to the characteristic notch on the dentary. The specific epithet, <i>gracilis</i>, Latin, meaning ‘slender’, refers to the delicate nature of the specimen.</p> <p> <i>Locality and horizon</i>: The specimen was found in a roadside cutting of highway R 353 in Teekloof Pass, between the towns Leeu Gamka and Fraserburg in the Beaufort West District, Western Cape Province, South Africa. The locality lies on the farm Willowdene, a portion of Beato 238 (Fig. 1); exact coordinates are given in the Iziko South African Museum. It is stratigraphically positioned in the upper half of a thick mudrockdominated succession of fluvio-lacustrine strata, known locally as the Hoedemaker Member of the Teekloof Formation (Rubidge, 1995; Figs 1A, 2A), which is considered to be early Late Permian (Wuchiapingian) in age (Catuneanu <i>et al</i>., 2005). The few laterally extensive sandstone bodies in the Hoedemaker Member (Fig. 2B) are interpreted as having been deposited as amalgamated point bars within high-sinuosity Mississippi-sized meandering rivers (Smith, 1987). Most of the vertebrate fossils are found in the thick greenish-grey massively bedded siltstone with minor mudstone intercalations that occur between the main channel sandstones. These sediments occur in 5– 10-m-thick coarsening-upward sequences interpreted as prograding crevasse splay sequences. They were laid down by repeated overbank flood events emanating from the channel banks and ponding in the lowland flood basins. The new cynodont specimen was recovered from a 0.25-m-thick lens of fissile, dark purple, mudstone on a parting between two 1-m-thick beds of massive grey siltstone with purple mottles. The massive siltstones contain scattered oblate pedogenic carbonate nodules and are interpreted as proximal floodplain deposits laid down at the base of the meanderbelt slope. The fissile mudstone interlayer in which the study specimen was found is interpreted as a small pond deposit within the splay sequence.</p> <p> Numerous skulls and skeletons of <i>Diictodon galeops</i>, along with other dicynodonts, namely <i>Oudenodon baini</i>, <i>Emydops minor</i> and <i>Pristerodon mackayi</i>, and, most significantly, the biozone indicator fossil <i>Tropidostoma microtrema</i> were collected from nearby outcrops (see Fig. 1B and Table 1). The gorgonopsians <i>Lycaenops ornatus</i> and <i>Cyonosaurus longiceps</i>, the therocephalian <i>Ictidosuchoides longiceps</i> and a new burnetiamorph comprise the carnivore fossil fauna collected in the vicinity. The presence of <i>Tropidostoma</i> as well as the abundant <i>Diictodon galeops</i>, and the absences of <i>Pristerognathus</i>, which characterizes the underlying zone, and <i>Cistecephalus</i> and <i>Aulacephalodon</i> from the succeeding biozone, biostratigraphically positions this specimen in the upper half of the 180-m-thick <i>Tropidostoma</i> Assemblage Zone (Rubidge, 1995).</p>Published as part of <i>Botha, J., Abdala, F. & Smith, R., 2007, The oldest cynodont: new clues on the origin and early diversification of the Cynodontia, pp. 477-492 in Zoological Journal of the Linnean Society 149 (3)</i> on pages 478-480, DOI: 10.1111/j.1096-3642.2007.00268.x, <a href="http://zenodo.org/record/5429120">http://zenodo.org/record/5429120</a>
The evolutionary linguist's divining-rod : restrictive theory
No full textCITATION: Botha, R. P. 2004. The evolutionary linguist's divining-rod : restrictive theory. Stellenbosch Papers in Linguistics, 35:43-54, doi:10.5774/35-0-10.The original publication is available at http://spil.journals.ac.zaNo abstract available.https://spil.journals.ac.za/pub/article/view/10Publisher’s versio
Extreme ultraviolet emission lines of Ni xii in laboratory and solar spectra
No full textA linear force-free field solution is presented in cylindrical coordinates, formulated in terms of trigonometric and Bessel functions. A numerical exploration has revealed that this solution describes magnetic field lines that meander in Cartesian space, as well as field lines that lie on toroidal flux surfaces. These tori are in (or close to) the plane perpendicular to the cylindrical axis. Nested tori, as well as tori with shells that have finite thickness, were found. The parameter space of the solution shows that the tori exist within a bounded range of values
The oldest cynodont: new clues on the origin and early diversification of the Cynodontia
No full textBotha, J., Abdala, F., Smith, R. (2007): The oldest cynodont: new clues on the origin and early diversification of the Cynodontia. Zoological Journal of the Linnean Society 149 (3): 477-492, DOI: 10.1111/j.1096-3642.2007.00268.x, URL: https://academic.oup.com/zoolinnean/article-lookup/doi/10.1111/j.1096-3642.2007.00268.
Review: W.F. Botha (Hoofredakteur): <i>Woordeboek van die Afrikaanse Taal</i>, 750 Dertiende Deel: R.
No full textW.F. Botha (Hoofredakteur). Woordeboek van die Afrikaanse Taal, Dertiende Deel: R. 2009, xxi + 541 pp. ISBN-13: 978-0-9584971-7-6 (plastiekband), ISBN-13: 978-0-9584971-8-3 (leerband). Stellenbosch: Buro van die WAT. Prys: R290 (plastiekband) / R590 (leerband)
The neglected purposes of educating art history: isomorphism and facilitation.
No full textDie basiese vertrekpunt van argumentasie van hierdie artikel is gesetel in die
suggestie dat die huidige stand van kunsgeskiedkundige onderwys nie totaal in
voeling is nie met die ontsaglike moontlikhede wat binne hierdie vakdissipline
verskuild lê. Dit wil dan as rigtingwyser dien om minstens een moontlike
aspek van die toekomstige belangrikheid van kunsgeskiedkundige opvoeding
te beklemtoon, met spesifieke verwysing na die wyse waarop ’n visuele kultuur
van toenemende belang word. Hier word ten doel gestel om te dui op die
wyse waarop kunsgeskiedenis beter geposisioneer kan wees om aan die behoeftes
van ’n post-moderne gemeenskap (spesifiek leerders en/of studente) te
voldoen, en dit impliseer ’n hertaksering van wat ten beste beskryf kan word
as die persoonlike funksies met kuns.
Die argument ontplooi verder deur die rol van fasilitering wat moontlik gemaak
word deur die boodskap wat in die (‘n) kunswerk vervat is, te benut
met die oog op homeostase van die persona. Die begrip wat hiervoor gebruik
word, is isomorfisme, en die metode of tegniek waardeur dit gebeur, kan beskryf
word as isomorfiese fasilitering. Kortliks gestel kom dit neer op die aan wending van feite wat met die omstandigheidsfaktore van kunsgeskiedenis en
kunswerke verband hou. Hierdie feite word vervolgens as gereedskap gebruik
ten einde dialoog te stimuleer en ‘n atmosfeer te skep waarbinne die leerder of
student kunswerke mag gebruik ten einde tot isomorfiese identifikasie te kom
ten opsigte van soortgelyke aspekte binne haar- of homself. Hierdie identifikasie
word wederkerend gebruik om die proses van homeostase te bevorder,
en dit impliseer dat die onderwyser of dosent kuns(geskiedenis) kan gebruik in
die proses van fasilitering ten einde stres te verlig. Hierdeur word uiteraard ’n
enorme bydrae gelewer tot die geestesgesondheid van die individu
Digital Image Correlation : applications in Vehicle Dynamics
No full textThesis (PhD)--University of Pretoria, 2015.Except for aerodynamics forces, all vehicle excitation forces are generated at the tyre-road interface.
Considering low speed applications, such as terramechanics where the aerodynamics force
are negligible, the road-tyre interaction is of extreme importance. Crucial variables which govern the
forces generated at the tyre-road interface are tyre side-slip angle, tyre longitudinal slip ratio and
terrain pro le. Solutions to measure these variables exist for smooth hard roads but the solutions
experience challenges on rough and o -road terrain.
Digital Image Correlation is concerned with tracking the changes of a scene in a sequence of
images or in images obtained from multiple viewpoints. These methods are frequently used in micro
and nano-scale mechanical testing due to its ease of implementation and use as well as its non-contact
approach. As a result these techniques are being implemented in many elds from material testing,
physics, lm animations and engineering. The aim of this thesis is to investigate the applications
of Digital Image Correlation in vehicle dynamics using cost e cient o -the-shelf digital cameras and
lenses. The following three vehicle dynamic problems are investigated: The measurement of the
vehicle side-slip angle, longitudinal slip-ratio of a pneumatic tyre and high delity terrain pro ling.
The vehicle side-slip angle can be used as a measure of the vehicle stability and therefore be
used to improve the e ectiveness of vehicle stability controllers. The tyre side-slip angle is also
a vital measurement in characterising the lateral force characteristics of pneumatic tyres. A planar
measuring method using Digital Image Correlation is shown to accurately measure the side-slip angle.
The method is expanded by developing two additional algorithms which can measure all translational
and rotational velocities. These methods are validated on both smooth surfaces and rough o -road
terrain.
A method is also implemented whereby the longitudinal slip ratio of a tyre can be measured using
a single camera. Therefore, doing away with the conventional method of using three independent measurement systems. Features in the contact patch, encompassing both the tyre and the road, are
tracked in a sequence of images. The features are classi ed into features lying on the tyre, road
and outliers using a clustering algorithm. This enables the system to determine the tyre and road
velocities from which the slip ratio is determined.
High delity terrain pro ling is performed using a calibrated stereographic rig to obtain a three
dimensional point cloud of the scene which is being viewed. The point cloud generated at one sample
contains a grid of points encompassing a large area with points spaced both laterally and longitudinally.
Overlapping point clouds are generated and joined using various registration techniques. The joined
point clouds are sub-sampled to obtain a regularised grid of point containing a single point cloud of
non overlapping points.
The proposed techniques create new possibilities in the eld of vehicle dynamics. Enabling the
side-slip angle to be measured in rough of road conditions while providing additional measurements.
The longitudinal slip ratio which is measured directly at the contact patch could pave the way for
better understanding the mechanism of the longitudinal tyre force generation. The inexpensive road
pro ling systems enables multiple sensors to be used in terramechanics tests to determine the impact
of a vehicle on the environment. The thesis presents the mere tip of the ice berg concerning digital
image correlation used in vehicle dynamics with many more possibilities waiting to be discovered.tm2015Mechanical and Aeronautical EngineeringPhDUnrestricte
Failed states, fading dreams and a failing democracy : the critical role of public law academics
No full textText of inaugural address by Prof. Christoffel Botha, Department of Public Law on 17 October 2007.With reference to incidents where rule of law has been disregarded by the South African government and pointing to the danger of paraliament becoming a mere rubber stamp for the executive, the author urges legal academics - and particularly public law academics - to become involved through criticism
Windows on language evolution : how are they constructed?
No full textCITATION: Botha, R. P. 2004. Windows on language evolution : how are they constructed? Stellenbosch Papers in Linguistics, 35:23-41, doi:10.5774/35-0-9.The original publication is available at http://spil.journals.ac.zaNo abstract available.https://spil.journals.ac.za/pub/article/view/9Publisher’s versio
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