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A study of the transdermal drug diffusion properties of rooperol tetra-acetate

- Pefile, Sibongile C.

  • Authors: Pefile, Sibongile C.
  • Date: 1998 , 2013-08-29
  • Subjects: Transdermal medication , Skin absorption , Dermatologic agents
  • Language: English
  • Type: Thesis , Masters , MSc
  • Identifier: vital:3838 , http://hdl.handle.net/10962/d1007649 , Transdermal medication , Skin absorption , Dermatologic agents
  • Description: The rapidly growing interest in the potential use of topical drug delivery formulations has resulted in increased use of the skin as a vital port for drug delivery. Extensive research has been conducted in designing vehicles capable of delivering a desired amount of drug to a specific site, to produce the desired pharmacological response. Rooperol tetra-acetate is a lipophilic, cytotoxic drug with the potential for use in the treatment of solar keratosis. For effective pharmacological action, delivery of the drug to the epidermal/dermal junction of the skin is required. A study of the topical penetration properties of rooperol tetra-acetate from different topical bases, each possessing different physico-chemical properties, was performed. The assessment involved a comparison of the diffusion properties under occlusive and non occlusive conditions when the drug was formulated into a gel, Cetomacrogol Cream B.P. (oil-inwater), Simple Ointment B.P. and an extemporaneously prepared water-in-oil topical cream. The in vitro experiments were conducted using polydimethylsiloxane and rat membrane mounted in a Franz diffusion cell. The topical permeation kinetics of rooperol tetra-acetate were determined by exploring the release characteristics of the active ingredient from the vehicles formulated and the permeability properties of the drug through the membranes employed. Further studies involved investigating the utilization of supersaturated systems intended to increase the thermodynamic activity of the drug when formulated into a propylene glycol/water vehicle (with and without polymer). To measure the release of rooperol tetra-acetate into the skin from a topical base it was necessary to, firstly, develop a suitable quantitative method for the analysis of the active drug in the aqueous receptor phase of in vitro diffusion cells. The second stage of product development was the design of an effective delivery system to facilitate the release of the diffusant from its base. A high performance liquid chromatographic method was utilized for the identification and quantification of the active drug. As validation is an important aspect in the development and subsequent utilization of an analytical procedure, the developed HPLC technique was validated by determining the precision, accuracy, range, limit of quantitation and sensitivity of the system. Lastly, the stability of rooperol tetra-acetate at elevated temperatures was assessed and a stability profile of the drug was generated for the three-month period of analysis. The results obtained following chromatographic analysis of the receptor phase sampled during the diffusion experiments indicate that the gel and oil-in-water formulations most effectively promoted the diffusion of rooperol tetra-acetate across polydimethylsiloxane membrane. The water-in-oil system exhibited lower flux rates and the ointment showed the least drug release. Occlusion of the topical vehicle increased the diffusitivity of the permeant from all formulations analysed. The permeation assessment results of the supersaturated systems showed enhanced diffusion of rooperol tetra-acetate across polydimethylsiloxane and rat membrane. The high thermodynamic activity existing in supersaturated systems most effectively increased the driving force for drug diffusion resulting in enhanced percutaneous penetration of rooperol tetra-acetate beyond the release and transport limitations of saturated solutions. These results provide the basis on which an effective topical drug delivery vehicle may be designed for this new drug entity.
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  • Date Issued: 1998

A survey of the development of pitch perception theories, their application to bell sounds and an investigation of perceived differences between ringing and chiming bells

- Botha, Alison

  • Authors: Botha, Alison
  • Date: 1998
  • Subjects: Music -- Acoustics and physics , Musical pitch , Change ringing , Chimes , Bells
  • Language: English
  • Type: Thesis , Masters , MSc
  • Identifier: vital:2631 , http://hdl.handle.net/10962/d1002296 , Music -- Acoustics and physics , Musical pitch , Change ringing , Chimes , Bells
  • Description: A brief overview of the workings of the human auditory system is followed by a review of literature concerning both the theories and experimental investigations of human pitch perception. The application of these theories to the inharmonic complex tones produced by bells is discussed, and further experiments using bell sounds are reviewed. A methodology for psychoacoustic experiments with specific reference to those investigating pitch perception of inharmonic complex tones is presented. This methodology is then implemented in an experimental investigation of pitch perception of ringing and chiming bell sounds. A pitch matching experiment using ringing and chiming sounds from four bells aimed to determine perceived pitch differences between ringing and chiming bells. This experiment was inconclusive because insufficient data was collected. Known experimental results, such as the inability of non-musicians to match the pitches of sounds with different timbres were confirmed. Spectral analyses of the stimuli were performed. The presentation of stimuli at a low level of sensation is questioned, as this might have prevented pseudo high frequency noise resulting from stronger upper partials in the ringing sound from being audible, and hence the pitch differences between ringing and chiming bells would not be observed.
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  • Date Issued: 1998

A synthetic and spectrometric study of the initial phases in urea-formaldehyde resin formation

- Nocanda, Xolani Wittleton

  • Authors: Nocanda, Xolani Wittleton
  • Date: 1998
  • Subjects: Phenolic resins , Gums and resins, Synthetic
  • Language: English
  • Type: Thesis , Masters , MSc
  • Identifier: vital:4383 , http://hdl.handle.net/10962/d1005048 , Phenolic resins , Gums and resins, Synthetic
  • Description: In a series ofpreIiminary studies of urea-formaldehyde reactions, the influence of the U:F molar ratio, the temperature and the catalyst were investigated. Subsequently, in a more rigorous evaluation of the influence of four variables on urea-formaldehyde resin formation, viz., U:F molar ratio, pH, temperature and reaction time, a set of twenty reactions were performed using a statistical approach. The results indicate that high resin viscosity is best achieved by using a high U:F molar ratio (1:2) and conducting the reaction at 90°C. Several basic components produced in urea-formaldehyde reactions have been synthesised, characterised by NMR spectroscopy, silylated using bis(trimethylsilyl)trifluoroacetamide and analysed by low resolution mass spectrometry. The use oftriazones as cross-linking agents has been investigated, and a series of 5-substituted triazones have been prepared and their mass fragmentation patterns explored using a combination of low and high resolution mass spectrometry. In order to facilitate interpretation of ¹³C NMR data obtained for U-F resins, internal rotation in various urea derivatives was investigated using variable temperature ¹H and ¹³C NMR spectroscopic study. Signal splittings observed below 247 K have been rationalised in terms of various rotameric structures.
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  • Date Issued: 1998

Abiban

- Dieneba Seck (lead vocal, chorus), Nanou Coul, Wande Kouyate, Yves Ndjock (chorus), Djely Moussa Kouyate (rhythm guitar), Tom Toumani Diakite (ngamole, ngomi, percussion), Thio Mbaye (percussion, djembe, tama), Maka Tounkara "Badie" (ngomi), Jean Luc Pinot (violon), Ben's Belinga (saxophone), Yves Ndjock (bass, snare drum, guitar), Syllart Production

Adama

- Kenza Batoma Diallo (author, composer, lead singer), Aliou Traore (violin), Benogo Diakite (ngoni, kangnan), Kabin Kaba Diakite (guitar, bass, yabara), Halima Sangare (chorus), Souleymane Dembele (balafon), Kalibou Diarra (djembe), MALI K7 S.A. Ali Furka Toure Associe, Bamako

Ahoussa Kabun

- TP Audiorama Orchestra (performers), Showbiz

  • Authors: TP Audiorama Orchestra (performers) , Showbiz
  • Date: 1998
  • Subjects: Popular music , Popular music--Africa, West , Africa Cote d'Ivoire Abidjan f-iv
  • Language: French
  • Type: sound recordings , field recordings , sound recording-musical
  • Identifier: http://hdl.handle.net/10962/129583 , vital:36309 , International Library of African Music, Rhodes University, Grahamstown, South Africa , SDC30-04
  • Description: Ako music from Cote d'Ivoire performed by the TP Audiorama Orchestra, the first orchestra to develp this genre of Ivorian music
  • Full Text: false
  • Date Issued: 1998

Albany Rugby Voetbal Klub Eerste Span, 1998

  • Date: 1998
  • Subjects: Rugby football -- South Africa -- Eastern Cape -- Photographs , Albany Rugby Football Club -- Photographs
  • Type: still image
  • Identifier: http://hdl.handle.net/10962/50455 , vital:25989 , This image is held at the Cory Library for Humanities Research at Rhodes University. For further information contact cory@ru.ac.za. The digitisation of this image was made possible through a generous grant received from the Andrew W. Mellon Foundation 2014-2017. , PIC/M 6739
  • Description: Albany Rugby Voetbal Klub Eerste Span 1998, Eerste span – 1998, Team photograph with rugby/football players, in rugby uniform (blue and white checked jersey, white shorts, red socks), Group photograph, Colour photograph, Indoor photograph, Players standing have arms in front of themselves, by their sides or behind their back while those sitting have their hands in their laps, Agter (van links na regs): J. Lourens, S. Everton, W. Verwey, C. Kidson, M. Sweeny, D. Crous, R. van Vuuren, Middel (van links na regs): S. Thompson, H. Hayman, R. van Tonder, D. Brits, A. Annandale, T. Pretorius, Voor (van links na regs): S. Sawyer, H. Germishuys (Vise-President), G. Sawyer (President), P. du Preez (Kaptein), J. Vos (Afrigter), L. Germishuys (Addisionele Lid), R. Loots.
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  • Date Issued: 1998

Albany Rugby Voetbal Klub Troefee Wenners, 1998

  • Date: 1998
  • Subjects: Rugby football -- South Africa -- Eastern Cape -- Photographs , Albany Rugby Football Club -- Photographs
  • Type: still image
  • Identifier: http://hdl.handle.net/10962/49759 , vital:25920 , This image is held at the Cory Library for Humanities Research at Rhodes University. For further information contact cory@ru.ac.za. The digitisation of this image was made possible through a generous grant received from the Andrew W. Mellon Foundation 2014-2017. , PIC/M 6740
  • Description: Albany Rugby Voetbal Klub Troefee Wenners 1998, Troefee Wenners – 1998, trophy cups displayed in front, Team photograph with rugby/football players, in rugby uniform (blue and white checked jersey, white shorts, red socks), Group photograph, Colour photograph, Indoor photograph, President wearing a suit, Agter (van links na regs): A. Annadale (Adidas Birch’s Trofee – Speler van die jaar 1ste span), R. van Tonder (Albany Ford Trofee – meeste driee gedruk), Voor (van links na regs): T. W. Pretorius (Glynn Webber Trofee – Meeste punte aangeteken), R van Vuuren (Nick Thiart Wisseltrofee – Sportman op en van die veld & Louis Germishuys Wisseltrofee – Speler van die jaar 2de span), G. Sawyer (President), D. Crous (Maurice Clayton Wisseltrofee – Mees gevorderde speler), F. Zeelie (Spanghero Wisseltrofee – Mees vooruitstrewende speler 2de span).
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  • Date Issued: 1998

Albany Rugby Voetbal Klub Tweede Span, 1998

  • Date: 1998
  • Subjects: Rugby football -- South Africa -- Eastern Cape -- Photographs , Albany Rugby Football Club -- Photographs
  • Type: still image
  • Identifier: http://hdl.handle.net/10962/49699 , vital:25914 , This image is held at the Cory Library for Humanities Research at Rhodes University. For further information contact cory@ru.ac.za. The digitisation of this image was made possible through a generous grant received from the Andrew W. Mellon Foundation 2014-2017. , PIC/M 6741
  • Description: Albany Rugby Voetbal Klub Tweede Span 1998, Tweede span - 1998, Team photograph with rugby/football players, in rugby uniform (blue jersey, white shorts, red socks), Group photograph, Colour photograph, Indoor photograph, Players standing have arms in front of themselves, by their sides or behind their back while those sitting have their hands in their laps, Agter (van links na regs): D. Potgieter, G. Dyson, G. Petser, M. Sweeny, D. Crous, Middel (van links na regs): A. Estruis, S. Thompson, J. Botha, H. Warrington, N. van Vuuren, J. Lourens, Voor (van links na regs): F. Zeelie, P. Demmers, G. Sawyer (President), N. van Vuuren (Kaptein), Joos Vos (Afrigter), I Dorfling, T. Pretorius.
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  • Date Issued: 1998

Alexandria district, 70 km NNE Port Elizabeth

- Skead, C J (Cuthbert John)

  • Authors: Skead, C J (Cuthbert John)
  • Date: 1998
  • Subjects: Paterson (South Africa) , Plants -- South Africa -- Eastern Cape
  • Type: still image
  • Identifier: vital:26364 , http://hdl.handle.net/10962/d1013657
  • Description: A stretch of sandy mounds typical of the sandflats (Zand vlakte, now Paterson) area, 2 km north of Paterson village. Others reach both west and east of those depicted for a kilometre or two each way, They lie below the foothills of the Suurberge.
  • Full Text: false
  • Date Issued: 1998

Allah Akbar 6'15

- MC-Zotto (lead, vocal, rap, ragga), Lamso (rap, composition), Poupson (rap), Bouttas (ragga), David (rap, sing), Dene, Izebere (chorus), MALI K7 S.A.

Ammophila arenaria (L.) Link (marram grass) in South Africa and its potential invasiveness

- Hertling, Ursula Margret

  • Authors: Hertling, Ursula Margret
  • Date: 1998
  • Subjects: Grasses -- South Africa Alien plants -- South Africa Sand dune plants -- South Africa Grasses -- Ecology -- South Africa Sand dune ecology -- South Africa
  • Language: English
  • Type: Thesis , Doctoral , PhD
  • Identifier: vital:4198 , http://hdl.handle.net/10962/d1003767
  • Description: Ammophila arenaria (L.) Link is a European sand binding plant which was introduced to South Africa in the 1870's for the purpose of dune stabilisation. Because of its known invasiveness along the west coast of North America, and the problems South African ecosystems experience with alien invader plants, it was deemed necessary to study the biology and ecology of this species in South Africa. The aim of this thesis is to establish the potential invasiveness of A. arenaria on Cape coastal dunes and assess whether its use for dune stabilisation is still justifiable. A. arenaria occurs nowadays between the Langebaan area on the west coast and Gonubie in the Eastern Cape. Although widespread, the grass appears to occur only in areas where it has been planted. Its unaided spread may be prevented by adverse climatic conditions. Studies on the community biology of South African A. arenaria communities as compared to indigenous dune plant communities and natural A. arenaria communities in Europe cannot confirm the aggressive behaviour that A. arenaria shows in California and Oregon. In South Africa, A. arenaria does not exert strong floristic control over other species or outcompete and replace them, neither does it alter the topography of South African beaches and dunes. It forms weaker species associations and tends to develop communities of little species variability along the coast, thereby proving its alienness in South Africa, but this does not imply its invasiveness. Studies on succession of A. arenaria stabilisation areas show that monospecific A. arenaria plantings can be succeeded by a species-rich indigenous dune scrub or dune fynbos within a few decades. Plant-parasitic nematodes have been recorded, which may play an important role in the succession of A. arenaria stands in South Africa as was observed in Europe. Monitoring of A. arenaria communities and indigenous communities over nearly three years shows that A. arenaria is not spreading and replacing indigenous plants but in fact rather being replaced by the latter. A. arenaria profits from a superior sand burial tolerance but is affected by adverse climatic factors, mostly the lack of rainfall and strong radiation. In comparison to the indigenous dune grasses Thinopyrum distichum and Ehrharta villosa, it does not show any superior demographic traits such as an unusually high growth rate or large aboveground biomass production. Although A. arenaria produces viable seed in South Africa, the indigenous grasses show better germination and seedling establishment in the field. This study indicates that A. arenaria is not invasive in South Africa, nor likely to become an invader species in the near future. However, more research is required to confirm these results and more caution recommended regarding the further use of this alien grass for dune stabilisation.
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  • Date Issued: 1998

An account of second language teaching and learning in a multi-standard farm school classroom, utilising an ethnographic approach

- Krause, Siobbhan Karen

  • Authors: Krause, Siobbhan Karen
  • Date: 1998
  • Subjects: English language -- Study and teaching -- South Africa -- Foreign speakers Rural schools -- South Africa Community and school -- South Africa English language -- Study and teaching -- Foreign speakers Education, Rural -- South Africa Black people -- Education -- South Africa
  • Language: English
  • Type: Thesis , Masters , MEd
  • Identifier: vital:1416 , http://hdl.handle.net/10962/d1003297
  • Description: Multi-standard classrooms are a distinctive feature of many South African farm schools. This study adopts an ethnographic approach in order to explore how classroom life in one particular Eastern Cape multistandard farm school classroom is shaped by a set of circumstances which influence the nature of teaching and learning in that classroom. The research focuses on the extent to which the difficulties associated with teaching a multi-standard class dictate the teacher's approach to lesson planning and style of teaching and how the resultant pattern of interaction influences language learning within a second language context. Data from a variety of sources, obtained primarily through classroom observations, interviews and questionnaires, is presented. Findings tend to indicate that the demands made on the teachers and pupils in terms of large, multi-standard classes, second language medium of instruction and lack of teaching aids, encourages the use of rote learning techniques which are not conducive to language learning. The pattern of interaction that predominates is a teacher-led series of questions and prompts followed by a chorus response from the pupils. This pattern tends to undermine the communicative aspects of language learning by reducing natural interaction and results in pupil passivity as language learners.
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  • Date Issued: 1998

An assessment of the South African east coast linefishery from Kei Mouth to Stil Bay

- Brouwer, Stephen Leonard

  • Authors: Brouwer, Stephen Leonard
  • Date: 1998
  • Subjects: Fisheries -- Research -- South Africa , Fisheries -- Environmental aspects -- Research -- South Africa
  • Language: English
  • Type: Thesis , Masters , MSc
  • Identifier: vital:5233 , http://hdl.handle.net/10962/d1005076 , Fisheries -- Research -- South Africa , Fisheries -- Environmental aspects -- Research -- South Africa
  • Description: During the period April 1994 and February 1996 as part of an investigation into the national Iinefishery, the east coast shore fishery and the recreational and commercial ski-boat fisheries were surveyed, at eight sites between Kei Mouth in the East and Stil Bay in the West. Roving creel, access point and aerial surveys were used. A questionnaire was developed for each sector to gather data on catch and effort, fisher demographics, economics, fisher attitudes towards, and knowledge of, the current management regulations and assess the efficacy of the fisheries inspectorate. During the access point survey the catch of 3273 fishers was inspected and 1556 interviews were conducted. Questionnaires were conducted on 118 recreational ski-boaters and the catch of 165 boats was inspected. 96 commercial skippers were interviewed and 230 had their catch inspected. Three aerial surveys of the entire area were conducted during which a total of 1067 shore fishers were counted giving a shore fisher density of 0.39 fishers.km⁻¹. The majority (99%) of participants in all sectors of the linefishery were male. The greatest number of participants were white, shore fishery 77% recreational ski-boat 98% commercial skiboat 89%, followed by coloured, asian and black people. To a large extent this reflects the income of various racial groups. Most fishers supported the current linefish management plan. However, when tested on their knowledge of the size limits, bag limits and closed seasons of their target species many shore fishers (59%) did not know them and a high proportion of fishers in all sectors had disobeyed at least one of the regulations (shore 50%, recreational ski-boat 70%, commercial ski-boat 56%). When compared to historical data the present catch per unit effort (CPUE) in all sectors has decreased. Most interviewees in the various sectors did not accept responsibility for the decline in CPUE, but attributed it to three principal reasons vis their perceived direct competitors, trawling and pollution. Analysis of the catch revealed that all sectors were multispecies fisheries, with each sector being characterised by a small number of target species. Catch composition differed significantly between the shore and ski-boat sectors, but there was significant overlap between the two skiboat sectors. Analysis of the catch in comparison to that reported to the National Marine Linefish System (NMLS) revealed that there was a substantial degree of under-reporting. There was little seasonal difference in effort in the shore fishery while the recreational ski-boat effort was highest in the summer and the commercial ski-boat effort was high in the winter. Effort in the shore and recreational ski-boat fisheries was concentrated over weekends while the commercial ski-boat effort was highest during weekdays. Total effort for the entire area was estimated at 903 186 (±1913) fisher days per annum in the shore fishery, 24 357 (±685) recreational ski-boat fisher days and 64 266 (±1686) commercial ski-boat fisher days. Expenditure and capital investment in the various sectors was calculated, as were earnings of the participants in the commercial ski-boat sector. The linefishery in the Eastern Cape was estimated to have a minimum capital investment in excess of R210 million and more than R32 million is spent annually on running costs. The commercial ski-boat fishery directly employed an estimated 3184 people. The economic implications of changes in CPUE for the commercial ski-boat fishery are considered, as are the benefits of a recreational angling licence. Management of the linefishery is discussed in relation to the findings of this study.
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  • Date Issued: 1998

An examination of patients' responses to framework breaks in psychotherapy in an institutional context

- Rees, Christopher Lewis

  • Authors: Rees, Christopher Lewis
  • Date: 1998
  • Subjects: Psychotherapy patients Psychotherapy -- Research Psychotherapy Case studies Psychiatric hospital care
  • Language: English
  • Type: Thesis , Doctoral , PhD
  • Identifier: vital:3042 , http://hdl.handle.net/10962/d1002551
  • Description: This study examines the workings of the ground rules which make up the framework of psychotherapy, in an institutional context, by analysing transcripts of twelve audio taped sessions of therapy conducted in a psychiatric hospital. The breaks in the ground rules of the sessions are noted and the patients' responses to these breaks are analysed using Langs's (1982, 1988) method for decoding patients' material, suitably modified for use as a hermeneutic research method. Although all of the ground rules are broken in the institutional context, only one of the ten ground rules appears to be essentially affected by this particular institutional context. Other ground rules are broken out of choice of technique or through error. The institutional context has a structural impact only on the ground rule requiring a one to one relationship with privacy and confidentiality and this ground rule is transgressed in a number of ways in all twelve sessions examined in this study. However the patients' responses to this breach only occur in ways predicted by communicative theory when the break in the ground rule involves actual entry into the therapy space by another person. Other contraventions to this ground rule that do not involve such an entry do not elicit the predicted patient responses. The many other ground rule breaks occurring in the institutional context evoke the predicted responses in the patients' material. In the study, no therapist interventions are found to comply with the communicative therapy requirements for sound interventions; concomitantly it was found that no therapist interventions receive the required derivative validation. The results indicate that it is possible to conduct therapy of a substantially secure frame variety in this institutional context with minimum effort on the part of therapists and given proper training and supervision of therapists in the techniques of communicative psychotherapy. Furthermore the results lend weight to the importance of the communicative methodology for listening to patients' material in psychotherapy in an institutional context. However, further rigorous study of competently performed therapy, executed within the context of a secure frame within an institutional context, is needed in order to demonstrate the benefits of the communicative psychotherapy interventions and interpretations in this context.
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  • Date Issued: 1998

An exploration of the psychological significance of soap opera viewing

- Moodley, Prevan

  • Authors: Moodley, Prevan
  • Date: 1998
  • Subjects: Television -- Psychological aspects , Television soap operas -- Psychological aspects
  • Language: English
  • Type: Thesis , Masters , MA
  • Identifier: vital:3023 , http://hdl.handle.net/10962/d1002532 , Television -- Psychological aspects , Television soap operas -- Psychological aspects
  • Description: In traditional research approaches, soap opera viewing has been studied quantitatively. Such studies ignore the subjectivities, the sociocultural contexts, and life contexts of individual viewers. To account for such shortcomings and to offer a qualitative research approach, an investigation was conducted into the engagement that viewers have with a particular soap opera, The bold and the beautiful. The collective case study research method was used. Three subjects were interviewed using in-depth phenomenological interviewing and the data obtained was subjected to.a hermeneutic method of investigation. This involved using a reading guide that extracted firstly, how pleasure is experienced in soap opera viewing, and secondly how the viewers' interpretations of the soap opera are linked to their everyday life contexts. Pleasure was found to be related to experiencing the soap opera world as real, the social context of the viewer, the openness of the text, selecting textual elements, identification and opening up the viewer's world. The viewers' interpretations were related to their life contexts in terms of the meanings that were constructed around emotions, identities, interpersonal relations and a cultural interface. Most notable for the South African context, is that viewing The bold and the beautiful provides a cultural interface because African identities are brought to this practice.
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  • Date Issued: 1998

An investigation into factors influencing immersion in interactive virtual reality environments

- Bangay, Shaun D, Preston, Louise

  • Authors: Bangay, Shaun D , Preston, Louise
  • Date: 1998
  • Subjects: To be catalogued
  • Language: English
  • Type: text , article
  • Identifier: http://hdl.handle.net/10962/432864 , vital:72908 , https://pubmed.ncbi.nlm.nih.gov/10350927/
  • Description: Two interactive virtual reality environments were used to identify factors that may affect, or be affected by, the degree of immersion in a virtual world. In particular, the level of stress in a "swimming with dolphins" simulation is measured, as is the degree of simulator sickness resulting form a virtual roller coaster. Analysis of the results indicates that a relationship between the degree of immersion and the following factors: excitement, comfort, quality and age. The following factors are found to depend on the degree of immersion: simulator sickness, control, excitement and desire to repeat the experience.
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  • Date Issued: 1998

An investigation into the antioxidative potential and regulatory aspects of liver tryptophan 2,3-dioxygenase by tryptophan and related analogues

- Antunes, Ana Paula Martins

  • Authors: Antunes, Ana Paula Martins
  • Date: 1998
  • Subjects: Tryptophan -- Physiological effect , Antioxidants , Liver
  • Language: English
  • Type: Thesis , Masters , MSc
  • Identifier: vital:4010 , http://hdl.handle.net/10962/d1004070 , Tryptophan -- Physiological effect , Antioxidants , Liver
  • Description: The amino acid, tryptophan, obtained through dietary means, is metabolised by the enzymes tryptophan 2,3-dioxygenase (TDO), indoleamine 2,3-dioxygenase (IDO) and tryptophan hydroxylase. All the enzymes have an effect on circulating tryptophan levels, especially TDO, since it is the major site of tryptophan catabolism in the liver and results in the production of kynurenine metabolites, viz. kynurenine, kynurenic acid, 3-hydroxyanthranilic acid and quinolinic acid. Extrahepatically, IDO is responsible for the synthesis of the kynurenine metabolites. Tryptophan 2,3-dioxygenase and IDO activity is increased by hormones or substrates such as tryptophan, and inflammation, in the case of IDO. Tryptophan availability for serotonin (5-HT) synthesis by the enzyme tryptophan hydroxylase is primarily dependent on TDO activity. A study was attempted in order to ascertain whether any of the endogenous metabolites of the kynurenine and serotonergic pathways would be able to inhibit TDO activity. Results showed that although the kynurenines had no effect, the indoleamines, except for the indoleacetic acids, were able to reduce TDO activity. 6-Methoxy-2-benzoxazolinone (6-MBOA), a structural analogue to melatonin, was the most potent inhibitor with a reduction in activity of 55 % compared with the control. The pineal gland in the rat brain has been shown to have the highest IDO activity. With induction, the kynurenine metabolite concentrations of kynurenic acid and quinolinic acid are increased. The effects of both compounds were determined on the serotonergic pathway. Although kynurenic acid produced no significant effect, quinolinic acid significantly reduced N-acetylserotonin and melatonin synthesis at concentrations of lOJLM and 100 JLM respectively. Many authors have implicated oxygen derived species as causative agents in the important neurodegenerative disorders such as Parkinson's and Huntington's disease. Increased radical generation and lipid peroxidation have been suggested to be responsible for the toxic destruction of neurons, especially in the brain because of its high lipid content and oxygen demand. The brain is therefore vulnerable to oxidative attack. During inflammatory diseases, IDO is induced with a resultant increase in kynurenines. This study was also an attempt at determining the effect of kynurenines on lipid peroxidation. All metabolites of the kynurenine pathway were able to induce lipid peroxidation significantly. The antioxidative potential of various tryptophan analogues, viz. serotonin, melatonin and 6-methoxy-2-benzoxazolinone, was determined using quinolinic acid-induced lipid peroxidation. Serotonin, melatonin and 6-MBOA were able to significantly reduce quinolinic acid-induced lipid peroxidation.
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  • Date Issued: 1998

An Investigation into the feasibility of Human Facial Modeling

- Panagou, Sotcri, Bangay, Shaun D

  • Authors: Panagou, Sotcri , Bangay, Shaun D
  • Date: 1998
  • Subjects: To be catalogued
  • Language: English
  • Type: text , article
  • Identifier: http://hdl.handle.net/10962/432711 , vital:72894 , https://citeseerx.ist.psu.edu/document?repid=rep1ype=pdfoi=c305c27d16322208e0e6815ca261d61019a4cbd0
  • Description: In this paper, virtual videoconferencing is investigated. The goal of the project is to develop a cheap, realistic yet real-time 3D face-modeling tool using a number of camera feeds. Bandwidth utilisation can then be minimised by transferring only the actual model (and subsequently, changes to the model) of the actor's face. Using a virtual reality system, reconstruction of a human face is performed and transmitted, thereby reducing bandwidth requirements. The modeling process is discussed, with results.
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  • Date Issued: 1998

Analysis of chromameter results obtained from corticosteroid-induced skin blanching. I. Manipulation of data

- Smith, Eric W, Haigh, John M, Walker, Roderick B

  • Authors: Smith, Eric W , Haigh, John M , Walker, Roderick B
  • Date: 1998
  • Language: English
  • Type: text , Article
  • Identifier: vital:6424 , http://hdl.handle.net/10962/d1006559
  • Description: Purpose. One of the unresolved issues in the FDA Guidance document for topical corticosteroid bioequivalence testing is the method of manipulation suggested for the chromameter data. The purpose of this study was to manipulate the instrumental data from a typical blanching study in a number of ways to investigate the appropriateness of these procedures for comparison with the subjective visually-assessed results. Methods. The human skin blanching assay methodology routinely practiced in our laboratories was utilised and the vasoconstriction produced by two corticosteroid formulations of different potency was assessed visually and instrumentally by use of a Minolta chromameter. The instrumental data were corrected for zero-time and unmedicated site readings. In addition, Euclidean distances were calculated using all data generated by the instrument. Results. Individually the a-, b- and L-scale chromameter values are imprecise and there is negligible vasoconstriction response recorded for the moderately potent formulation. Arithmetical manipulation of the data as suggested by the FDA does not appear to improve the quality of the data in any way. Euclidean distance analysis more closely resembles the visual data and appears to have better precision. Conclusions. It is clear that mathematical correction of chromameter data is unnecessary, especially since the instrumental data are extremely imprecise. Furthermore, the assessment of each individual chromameter index does not adequately characterise the blanching response profile. It is therefore suggested that Euclidean distance may be a better measure on which to base an analysis of bioequivalence than the truncated data set methodology currently suggested by the FDA.
  • Full Text: false
  • Date Issued: 1998
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