Les travaux portent sur les multiplexeurs optiques fonctionnant à mi-IR pour la source à large bande dans l'application de détection de gaz. Deux configurations ont été étudiées: réseau de guides d'onde (AWG) et réseau concave planaire (PCG). Premièrement, le principe du fonctionnement a été compris afin de développer une solution analytique pour le champ de sortie en utilisant une approximation gaussienne du champ et de l'optique de Fourier. Ensuite, un outil de simulation semi-analytique de la réponse spectrale pour les deux configurations de multiplexeur a été développé dans MATLAB. La distribution normale des erreurs de phase a été introduite dans le modèle semi-analytique AWG, ce qui nous a permis d'étudier la corrélation entre l'écart-type des erreurs de phase et le niveau de diaphonie de la réponse spectrale AWG. AWG à 5,65 μm a été fabriqué à partir de la technologie SiGe / Si à l'aide de l'outil MATLAB pour le calcul des paramètres de conception et de l'outil P.Labeye pour le calcul de la géométrie AWG. Les dispositifs avec des paramètres légèrement variables ont été caractérisés: AWG1 avec guides d'ondes de 4,6 μm et MMI de 9 μm; AWG2 avec guides d'ondes de 4,6 μm et MMI de 11 μm; AWG3 avec guides d'ondes de 4,8 μm et MMI de 9 μm. Des mesures des dispositifs sur la puce 36 (centre de la plaquette) et sur la puce 32 (côté de la plaquette) ont été effectuées et analysées. Les mesures de température de AWG2 et AWG3 (puce 32 et puce 36) aux points cinq points de température ont montré une dépendance linéaire du déplacement spectral avec la température qui a une bonne corrélation avec les prédictions de simulation. / The work focuses on optical multiplexers operating in mid-IR for broadband source in gas sensing application. Two configurations were studies – arrayed waveguide grating (AWG) and planar concave grating (PCG). First, principle of operation was understood in order to develop analytical solution for output field using Gaussian approximation of the field and Fourier Optics. Then, semi-analytical simulation tool of the spectral response for both multiplexer configurations was developed in MATLAB. Normal distribution of phase errors was introduced to semi-analytical AWG model, which allowed us to study the correlation between standard deviation of phase errors and the level of crosstalk of AWG spectral response. AWG at 5.65 µm was fabricated based on SiGe/Si technology using the MATLAB tool for design parameters calculation and P.Labeye’s tool for AWG geometry calculation. Devices with slightly varying parameters were characterized: AWG1 with 4.6 µm waveguides and 9µm MMI; AWG2 with 4.6 µm waveguides and 11µm MMI; AWG3 with 4.8 µm waveguides and 9µm MMI. Measurements of devices on chip 36 (center of the wafer) and chip 32 (side of the wafer) were performed and analyzed. Temperature measurements of AWG2 and AWG3 (chip 32 and chip 36) at points five temperature points showed linear dependence of spectral shift with the temperature which has a good correlation with simulation predictions.

In this work, an electrochemical method based on a cyt c biosensor has been developed, for the detection of selected arsenic and cyanide compounds. Boron Doped Diamond (BDD) electrode was used as a transducer, onto which cyt c was immobilised and used for direct determination of Prussian blue, potassium cyanide and arsenic trioxide by inhibition mechanism. The sensitivity as calculated from cyclic voltammetry (CV) and square wave voltammetry (SWV), for each analyte in phosphate buffer (pH= 7) was found to be (1.087- 4.488 ×10-9 M) and the detection limits ranging from 0.0043- 9.1 μM. These values represent a big improvement over the current Environmental Protection Agency (EPA) and World Health Organisation (WHO) guidelines.

In this work, an electrochemical method based on a cyt c biosensor has been developed, for the detection of selected arsenic and cyanide compounds. Boron Doped Diamond (BDD) electrode was used as a transducer, onto which cyt c was immobilised and used for direct determination of Prussian blue, potassium cyanide and arsenic trioxide by inhibition mechanism. The sensitivity as calculated from cyclic voltammetry (CV) and square wave voltammetry (SWV), for each analyte in phosphate buffer (pH= 7) was found to be (1.087- 4.488 ×10-9 M) and the detection limits ranging from 0.0043- 9.1 μM. These values represent a big improvement over the current Environmental Protection Agency (EPA) and World Health Organisation (WHO) guidelines.

Magister Scientiae - MSc / In this work, an electrochemical method based on a cyt c biosensor has been developed, for the detection of selected arsenic and cyanide compounds. Boron Doped Diamond (BDD) electrode was used as a transducer, onto which cyt c was immobilised and used for direct determination of Prussian blue, potassium cyanide and arsenic trioxide by inhibition mechanism. The sensitivity as calculated from cyclic voltammetry (CV) and square wave voltammetry (SWV), for each analyte in phosphate buffer (pH= 7) was found to be (1.087- 4.488 ×10-9 M) and the detection limits ranging from 0.0043- 9.1 μM. These values represent a big improvement over the current Environmental Protection Agency (EPA) and World Health Organisation (WHO) guidelines. / South Africa

Formaldehyde-based adhesives have been reported to be detrimental to health. Petrochemical-based adhesives are non-renewable, limited and costly. Therefore, the improvement of environmental-friendly adhesive from natural agricultural products has awakened noteworthy attention. A novel adhesive for wood application was successfully prepared with enhanced shear strength and water resistance. The Fourier transmform infrared spectra showed the surface functionalities of the functionalized carbon nanotubes (FCNTs) and soy protein isolate nanocomposite adhesive. The attachment of carboxylic functional group on the surface of the carbon nanotubes (CNTs) after purification contributed to the effective dispersion of the CNTs in the nanocomposite adhesive. Hence, enhanced properties of FCNTs were successfully transferred into the SPI/CNTs nanocomposite adhesive. These unique functionalities on FCNTs however, improved the mechanical properties of the adhesive. The shear strength and water resistance of SPI/FCNTs was higher than that of the SPI/CNTs. SEM images showed the homogenous dispersion of CNTs in the SPI/CNTs nanocomposite adhesive. The carbon nanotubes were distributed uniformly in the soy protein adhesive with no noticeable clusters at relatively reduced fractions of CNTs as shown in the SEM images, which resulted into better adhesion on wood surface. Mechanical (shear) mixing and ultrasonication with 30 minutes of shear mixing both showed an improved dispersion of CNTs in the soy protein matrix. However, ultrasonication method of dispersion showed higher tensile shear strength and water resistance than in mechanical (shear) mixing method. Thermogravimetric analysis of the samples also showed that the CNTs incorporated increases the thermal stability of the nanocomposite adhesive at higher loading fraction. Incorporation of CNTs into soy protein isolate adhesive improved both the shear strength and water resistance of the adhesive prepared at a relatively reduced concentration of 0.3%.The result showed that tensile shear strength of SPI/FCNTs adhesive was 0.8 MPa and 7.25MPa at dry and wet state respectively, while SPI/CNTs adhesive had 6.91 MPa and 5.48MPa at dry and wet state respectively. There was over 100% increase in shear strength both at dry and wet state compared to the pure SPI adhesive. The 19% decrease in value of the new adhesive developed compared to the minimum value of ≥10MPa of European standard for interior wood application may be attributed to the presence of metallic particles remaining after purification of CNTs. The presence of metallic particles will prevent the proper penetration of the adhesive into the wood substrate. The type of wood used in this study as well as the processing parameters could also result into lower value compared to the value of European standard. Therefore, optimization of the processing parameter as well as the conversion of carboxylic acid group on the surface of the CNTs into acyl chloride group may be employed in future investigation. However, the preparation of new nanocomposite adhesive from soy protein isolate will replace the formaldehyde and petrochemical adhesive in the market and be of useful application in the wood industry. / Civil and Chemical Engineering / M. Tech. (Chemical Engineering)

La fonction barrière de la peau, qui protège l’organisme contre les molécules exogènes, limite la pénétration des actifs cosmétiques, ce qui réduit l’efficacité des molécules actives dans les couches profondes de l’épiderme. Il est alors apparu essentiel d'optimiser l'administration des actifs cosmétiques déjà existants afin d’en tirer tout le bénéfice escompté. Certaines innovations sont développées pour répondre à ce défi, notamment l’encapsulation des actifs cosmétiques dans des nanosystemes. En parallèle, il est nécessaire de s’intéresser aux méthodes analytiques capables de fournir une information qualitative et quantitative sur ces systèmes dispersés dans un produit fini complexe et de permettre une évaluation biologique à différents stades de développement des formulations. / The barrier function of the skin, which protects the body against exogenous molecules, limits the penetration of active cosmetic ingredients (ACI), thus reduce the effectiveness of molecules with a deep cellular target. Therefore, it appeared crucial to optimize the administration of existing active cosmetic in order to get the full benefits expected. Some innovations are explored to bypass this issue, including the encapsulation of existing active cosmetic in nanocarriers. In parallel, it is important to also focus on the development of analytical methodologies that could provide qualitative and quantitative information, in particular the determination of ACI contents and potentially excipients incorporated in a final form, and biological evaluation at different stages of formulation.

Thesis submitted in fulfilment of the requirements for the degree Master of Technology Chemistry in the Faculty of (Science) Supervisor: Professor T.N. van der Walt Bellville campus Date submitted: October 2011 / It is important to quantify polymeric components in a coating because they greatly influence the performance of a coating. The difficulty associated with analysis of polymers by Fourier transform infrared (FTIR) analysis’s is that colinearities arise from similar or overlapping spectral features. A quantitative FTIR method with attenuated total reflectance coupled to multivariate/ chemometric analysis is presented. It allows for simultaneous quantification of 3 polymeric components; a rheology modifier, organic opacifier and styrene acrylic binder, with no prior extraction or separation from the paint. The factor based methods partial least squares (PLS) and principle component regression (PCR) permit colinearities by decomposing the spectral data into smaller matrices with principle scores and loading vectors. For model building spectral information from calibrators and validation samples at different analysis regions were incorporated. PCR and PLS were used to inspect the variation within the sample set. The PLS algorithms were found to predict the polymeric components the best. The concentrations of the polymeric components in a coating were predicted with the calibration model. Three PLS models each with different analysis regions yielded a coefficient of correlation R2 close to 1 for each of the components. The root mean square error of calibration (RMSEC) and root mean square error of prediction (RMSEP) was less than 5%. The best out-put was obtained where spectral features of water was included (Trial 3). The prediction residual values for the three models ranged from 2 to -2 and 10 to -10. The method allows paint samples to be analysed in pure form and opens many opportunities for other coating components to be analysed in the same way.

Les triterpènes sont un groupe important et structurellement diversifié de produits naturels issus du squalène. Les progestatifs et les glucocorticoïdes sont des triterpènes oxygénés ayant un squelette tétracyclique et reconnus pour leurs diverses propriétés thérapeutiques. Par ailleurs, l'érythrodiol et l'uvaol sont des triterpènes pentacycliques reconnus pour leurs effets bénéfiques dans l'alimentation humaine. Dans ce travail, l'interaction avec les membranes des vésicules lipidiques et la liaison à la sérum albumine humaine de ces molécules sont étudiées dans le but de mieux comprendre leurs propriétés pharmacologiques. Les vésicules lipidiques ont été caractérisées par DSC, spectroscopie Raman, FTIR et polarisation de fluorescence du DPH pour comprendre l'effet des molécules sélectionnées sur la fluidité membranaire.Également, nous avons étudié la liaison du cholestérol, d'une série de progestatifs et de glucocorticoïdes à l'albumine humaine par la spectroscopie de fluorescence.Les résultats ont démontré que les progestatifs, les glucocorticoïdes, l'érythrodiol et l'uvaol altèrent les propriétés physiques de la bicouche lipidique.Les progestatifs et les glucocorticoïdes démontrent un attachement modéré à l'albumine. Par ailleurs, la dydrogestérone présente la constante de liaison la plus importante. Enfin, notre étude a démontré que la constante de liaison du cholestérol à l'albumine est faible en comparaison avec les autres molécules étudiées. Notre étude a conduit à une connaissance approfondie des mécanismes moléculaires et des caractéristiques structurales impliqués dans l'interaction des triterpènes avec les protéines et les membranes synthétiques / The triterpenoids are a large and structurally diverse group of natural products derived from squalene. Progesterone derivatives and glucocorticoids are a group of oxygenated triterpenes having a tetracyclic skeleton and identified for their therapeutic properties. Whereas, erythrodiol and uvaol are pentacyclic triterpenes, known for their beneficial effects on human diet. In this thesis, we studied their interaction with the membranes of lipid vesicles and with human serum albumin to better understand their pharmacological properties. DSC, Raman spectroscopy, FTIR and fluorescence polarization of DPH were used to investigate the effect of triterpenes on the membrane fluidity. Besides, we used fluorescence spectroscopy to study the binding of cholesterol, a series of progesterone derivatives and another series of glucocorticoids to albumin. The results revealed that progesterone derivatives, glucocorticoids, erythrodiol and uvaol changed the physical properties of the bilayers. Progesterone derivatives and glucocorticoids have been proven to bind moderately to albumin. Dydrogesterone showed the highest binding constant. Finally, our study demonstrated that cholesterol exhibited a much weaker interaction with albumin compared to progesterone derivatives and glucocorticoids.Our work has led to a better understanding of triterpenes molecular mechanisms of their interaction with proteins and biological membranes and structural features controlling these interactions

O ranelato de estrôncio (RS) diminui a reabsorção óssea e ao mesmo tempo age como um agente anabólico deste tecido. Este estudo foi realizado para avaliar os efeitos da ovariectomia e do tratamento com RS na reparação de defeitos ósseos em fêmures e nos componentes moleculares do osso em ratas. Vinte e sete ratas adultas foram submetidas a ovariectomia ou cirurgia Sham e, após trinta dias, defeitos ósseos em fêmures foram confeccionados e os animais divididos em três grupos: ovariectomizadas (OVZ), cirurgia Sham (SHAM) e ovariectomizadas + tratamento com 625 mg/kg/dia de RS (RS). A eutanásia foi realizada quatro semanas após a cirurgia do defeito ósseo. A reparação do defeito ósseo foi analisada por microtomografia computadorizada (?CT) e a composição química do tecido ósseo foi verificada por espectroscopia de infravermelho com transformada de Fourier (FTIR) e espectroscopia de energia dispersiva de raios-X (EDS). O grupo SHAM apresentou em média volume ósseo (BV) superior ao grupo OVZ (p=0,014) e o volume ósseo relativo (BV/TV) foi cerca de 8% superior ao grupo OVZ. A comparação entre SHAM e RS apresentou valores limítrofes para essas variáveis. A espessura trabecular (Tb.Th) no grupo RS foi significativamente maior que no grupo OVZ cerca de 1,8% (p = 0,049) e não diferiu em média do grupo SHAM. Não houve diferenças significativas nas relações que avaliam compostos inorgânicos sobre orgânicos nos grupos. A razão das áreas das bandas em 1057 e 1023 cm-1 para o cálculo do IC foi 1.024 no grupo SHAM, 1.015 no grupo RS e 1.108 no grupo OVZ. No estudo da banda de amida III foi observado nos animais ovariectomizados uma possível mudança na estrutura secundária das proteínas da matriz devido a uma diminuição das estruturas ?-hélice e random coil (RC) e aumento de ?-sheet. A maturidade do colágeno estimada pela relação de sub-bandas de amida I (1660/1690) foi menor no grupo RS. Neste grupo houve um aumento significativo de estrôncio (Sr) incorporado ao tecido ósseo e uma diminuição de cálcio (Ca) avaliados pela técnica do EDS. Os resultados demonstram que o tratamento sistêmico com RS promoveu a reparação óssea e melhorou a microarquitetura do osso neoformado no interior do defeito. No entanto, os resultados das análises com FTIR sugerem que o RS não reverteu as alterações na matriz orgânica ocasionadas pela ovariectomia e diminuiu as ligações cruzadas de colágeno maturas. / Strontium ranelate (SR) decreases bone resorption and at the same time acts as an anabolic agent in this tissue. This study was conducted to evaluate the effects of ovariectomy and treatment with SR on the repair of bone defects and molecular components of bones in femurs. Adult female rats (n=27) were subjected to ovariectomy or Sham surgery. Thirty days after surgery, a defect was made in the femur and the animals were divided into three groups: ovariectomy (OVZ), Sham surgery (SHAM) and ovariectomy plus treatment with SR, 625 mg / kg / day (SR). Euthanasia was performed four weeks after surgery to cause the bone defect. Repair in bone defect was assessed by computed microtomography (?CT) and the chemical composition of bone tissue was analyzed by Fourier transform infrared (FTIR) spectroscopy and energy dispersive X-ray spectroscopy (EDS). The SHAM group showed mean values for bone volume (BV) higher than those of the OVZ group (p = 0.014) and the relative bone volume (BV / TV) was about 8% higher than that of the OVZ group. Comparison between SHAM and SR showed borderline values for these variables. In the SR group, the average value for trabecular thickness (Tb.Th) was significantly higher (~1.8%) than that in the OVZ (p = 0.049) group and did not differ from that of the SHAM group. Significant difference was not observed in the relation between inorganic and organic compounds in the three groups. The ratio of the areas of the bands in 1057 and 1023 cm-1 for the calculation of IC was 1,024 in the SHAM group, 1,015 in the RS group and 1,108 in OVZ group. In the study of the amide III band, a change in the proportion of secondary structure of matrix proteins was observed in ovariectomized animals, possibly a decrease in of ?-helical and random coil (RC) and an increase in ?-sheet structures. The collagen cross-linking network maturity estimated by the relation between amide I subbands (1660/1690) showed the smaller number in the SR group. In this group, a significant increase in the amount of strontium (Sr) and a decrease in the amount of calcium (Ca) embedded to bone tissue, as assessed by the EDS technique, were also observed. The results demonstrate that systemic treatment with SR promoted bone repair and improved microarchitecture of the newly formed bone within the defect. However, results of analyses with FTIR suggest that the SR has not reversed the alterations caused by ovariectomy in the organic matrix and decreased cross-linking of collagen mature.

O ranelato de estrôncio (RS) diminui a reabsorção óssea e ao mesmo tempo age como um agente anabólico deste tecido. Este estudo foi realizado para avaliar os efeitos da ovariectomia e do tratamento com RS na reparação de defeitos ósseos em fêmures e nos componentes moleculares do osso em ratas. Vinte e sete ratas adultas foram submetidas a ovariectomia ou cirurgia Sham e, após trinta dias, defeitos ósseos em fêmures foram confeccionados e os animais divididos em três grupos: ovariectomizadas (OVZ), cirurgia Sham (SHAM) e ovariectomizadas + tratamento com 625 mg/kg/dia de RS (RS). A eutanásia foi realizada quatro semanas após a cirurgia do defeito ósseo. A reparação do defeito ósseo foi analisada por microtomografia computadorizada (?CT) e a composição química do tecido ósseo foi verificada por espectroscopia de infravermelho com transformada de Fourier (FTIR) e espectroscopia de energia dispersiva de raios-X (EDS). O grupo SHAM apresentou em média volume ósseo (BV) superior ao grupo OVZ (p=0,014) e o volume ósseo relativo (BV/TV) foi cerca de 8% superior ao grupo OVZ. A comparação entre SHAM e RS apresentou valores limítrofes para essas variáveis. A espessura trabecular (Tb.Th) no grupo RS foi significativamente maior que no grupo OVZ cerca de 1,8% (p = 0,049) e não diferiu em média do grupo SHAM. Não houve diferenças significativas nas relações que avaliam compostos inorgânicos sobre orgânicos nos grupos. A razão das áreas das bandas em 1057 e 1023 cm-1 para o cálculo do IC foi 1.024 no grupo SHAM, 1.015 no grupo RS e 1.108 no grupo OVZ. No estudo da banda de amida III foi observado nos animais ovariectomizados uma possível mudança na estrutura secundária das proteínas da matriz devido a uma diminuição das estruturas ?-hélice e random coil (RC) e aumento de ?-sheet. A maturidade do colágeno estimada pela relação de sub-bandas de amida I (1660/1690) foi menor no grupo RS. Neste grupo houve um aumento significativo de estrôncio (Sr) incorporado ao tecido ósseo e uma diminuição de cálcio (Ca) avaliados pela técnica do EDS. Os resultados demonstram que o tratamento sistêmico com RS promoveu a reparação óssea e melhorou a microarquitetura do osso neoformado no interior do defeito. No entanto, os resultados das análises com FTIR sugerem que o RS não reverteu as alterações na matriz orgânica ocasionadas pela ovariectomia e diminuiu as ligações cruzadas de colágeno maturas. / Strontium ranelate (SR) decreases bone resorption and at the same time acts as an anabolic agent in this tissue. This study was conducted to evaluate the effects of ovariectomy and treatment with SR on the repair of bone defects and molecular components of bones in femurs. Adult female rats (n=27) were subjected to ovariectomy or Sham surgery. Thirty days after surgery, a defect was made in the femur and the animals were divided into three groups: ovariectomy (OVZ), Sham surgery (SHAM) and ovariectomy plus treatment with SR, 625 mg / kg / day (SR). Euthanasia was performed four weeks after surgery to cause the bone defect. Repair in bone defect was assessed by computed microtomography (?CT) and the chemical composition of bone tissue was analyzed by Fourier transform infrared (FTIR) spectroscopy and energy dispersive X-ray spectroscopy (EDS). The SHAM group showed mean values for bone volume (BV) higher than those of the OVZ group (p = 0.014) and the relative bone volume (BV / TV) was about 8% higher than that of the OVZ group. Comparison between SHAM and SR showed borderline values for these variables. In the SR group, the average value for trabecular thickness (Tb.Th) was significantly higher (~1.8%) than that in the OVZ (p = 0.049) group and did not differ from that of the SHAM group. Significant difference was not observed in the relation between inorganic and organic compounds in the three groups. The ratio of the areas of the bands in 1057 and 1023 cm-1 for the calculation of IC was 1,024 in the SHAM group, 1,015 in the RS group and 1,108 in OVZ group. In the study of the amide III band, a change in the proportion of secondary structure of matrix proteins was observed in ovariectomized animals, possibly a decrease in of ?-helical and random coil (RC) and an increase in ?-sheet structures. The collagen cross-linking network maturity estimated by the relation between amide I subbands (1660/1690) showed the smaller number in the SR group. In this group, a significant increase in the amount of strontium (Sr) and a decrease in the amount of calcium (Ca) embedded to bone tissue, as assessed by the EDS technique, were also observed. The results demonstrate that systemic treatment with SR promoted bone repair and improved microarchitecture of the newly formed bone within the defect. However, results of analyses with FTIR suggest that the SR has not reversed the alterations caused by ovariectomy in the organic matrix and decreased cross-linking of collagen mature.