Thesis (PhD)--Stellenbosch University, 2013. / ENGLISH ABSTRACT: Heterophasic copolymers (also known as HECO polymers) or often referred to only as impact copolymers or block copolymers comprise a polymer matrix with a dispersed rubbery copolymer phase. The polymer under investigation in this study consists of a polypropylene homopolymer matrix and ethylene-propylene copolymers (EPCs). Due to its diverse range of applications and unique properties, polypropylene is the choice of polymer for a vast array of applications. This has led to the development of an entire class of polypropylene materials known as visbroken or controlled rheology polypropylene. By adding a suitable peroxide to the polymer in the presence of heat, radicals are formed which will attack the polymer chains in a random fashion. The resultant polymers generally have a higher melt flow rate (MFR), a narrower molecular weight distribution than the parent polymer, and good impact-stiffness balance. The main focus of this investigation was to determine if there exist any differences in the molecular structure and physical properties of controlled rheology HECO polymers and if differences do exist, how they influence the physical characteristics of the polymer. Eight HECO polymers with equal ethylene contents were visbroken to varying degrees by making use of two different types of organic peroxide. The effects of the amount of visbreaking on the molecular characteristics and physical properties were subsequently studied by making use various types of fractionation techniques, including preparative temperature rising elution fractionation (PTREF) and crystallisation analysis fractionation (CRYSTAF). Subsequent offline analysis was then done on the fractionated samples that included nuclear magnetic resonance spectroscopy (NMR), differential scanning calorimetry (DSC), high temperature size exclusion chromatography (HT-SEC), Fourier transform infrared spectroscopy (FTIR) and deposition of the SEC fractions via the LC Transform Interface (SEC-FTIR) as well as high temperature high performance liquid chromatography (HT-HPLC), a novel technique for the characterization of olefins according to their chemical composition. / AFRIKAANSE OPSOMMING: Heterofase kopolimere, ook bekend as HECO polimere, of dikwels na verwys net as impak kopolimere of blok kopolimere bestaan uit 'n polimeer matriks met 'n verspreide rubberagtige kopolimeer fase. Die polimeer wat in hierdie studie ondersoek was het bestaan uit 'n polipropileen homopolimeer matriks en etileen-propileen kopolimere (EPCs). As gevolg van sy veelseidigheid van toepassings en unieke eienskappe is polipropileen die keuse van polimeer vir 'n wye verskeidenheid van toepassings. Hierdie veelseidigheid het gelei tot die ontwikkeling van 'n hele klas van polipropileen materiaal bekend as gevisbreekte of beheerde reologie polipropileen. Deur die byvoeging van 'n geskikte peroksied tot die polimeer in die teenwoordigheid van hitte, word radikale gevorm wat die polimeerkettings in 'n ewekansige wyse sal aanval. Die gevolglike polimere in die algemeen het 'n hoë smelt vloeitempo (MFR), 'n smaller molekulêre gewig verspreiding as die moeder polimeer, en 'n goeie impak/styfheid balans. Agt HEKO polimere met gelyke etileen inhoude was gevisbreek in wisselende hoeveelhede deur gebruik te maak van twee verskillende tipes organiese peroksiedes. Die gevolge van die hoeveelheid van visbreeking op die molekulêre eienskappe en fisiese eienskappe was vervolgens gebestudeer deur gebruik te maak van verskillende fraksionasie tegnieke, insluitend preparatiewe TREF (P-TREF) en CRYSTAF. Daaropvolgende analiese is gedoen op die gefraktioneerde monsters en sluit in kernmagnetiese resonansie spektroskopie (KMR), differensiële skandeer kalorimetrie (DSC), 'n hoë temperatuur grootte uitsluitings chromatografie (HT-SEC), Fourier transform infrarooi spektroskopie (FTIR) met deponeering van die SEC fraksies via die LC transform koppelvlak (SEC-FTIR) sowel as 'n hoë temperatuur hoë werkverrigting vloeistof chromatografie (HT-HPLC), 'n nuwe tegniek vir die karakterisering van olefiene volgens hul chemiese samestelling.

Thesis (PhD)--Stellenbosch University, 2013. / ENGLISH ABSTRACT: Polymer composites, and in particular wood-polymer composites have become commercially and environmentally important materials. Studies in polyolefin-wood composites have mostly focused on polypropylene (PP) and polyethylene (PE). To our knowledge, no study has been undertaken on advancing impact polypropylene copolymer (IPPC)-wood composites as a suitable alternative to using PP and PE. IPPC have proven to be a suitable alternative to PP at low temperatures to improve impact resistance for manufactured polymer products, and could be a great addition to improved properties for wood polymer composites. This study shows that the physical properties of IPPC-wood composites can be markedly improved when compatibilizer(s) are used to improve the distribution of the wood within the matrix, as well as improving the interaction between the wood and the polymer matrix.. The use of different compatibilizers, vi polypropylene-graft-maleic anhydride (PPgMA) and poly(ethylene-co-vinyl alcohol) (EvOH) results in different physical properties. Using simple admixtures of the PPgMA and EvOH in IPPC-wood composites result in a large spread of results, while pre-reacting the PPgMA and EvOH to form a joint compatibilizer gives reproducible results w.r.t the physical testing. A study of the fundamental interactions of the compatibilizer(s) with the molecular components of the IPPCs was undertaken. The IPPCs used were fractionated by preparative temperature rising elution fractionation, and the fractions were mixed with the compatibilizers. To this end, fluorescence microscopy was utilized to study the interaction. The results clearly indicate that the interaction of the PPgMA with the fractions differ from that of the EvOH. These differences can be explained in terms of the chemical composition distribution within the IPPC fractions. Atomic force microscopy (AFM) was used to study adhesive forces between compatibilizer, polymer and cellulose and lignin. Successful coating of AFM tips with PPgMA and EvOH was achieved. Whilst interactions based on chemical force microscopy (CFM) could not be quantified, the AFM results in conjunction with fluorescence spectroscopy provided meaningful insight in the way that compatibilizers interact with both the wood and the impact copolymers used in this study. / AFRIKAANSE OPSOMMING: Polimeer saamgestelde material, en meer spesifiek hout-polimeer saamgestelde material het die afgelope tyd belangrike produkte geword, beide kommersieel en in verband met omgewingvriendelikheid. Navorsing op die gebied van poli(olefien)-hout komposiete het tot op hede meestal gefokus op die grbruik van poli(propileen) (PP) en poli(etileen) (PE). Sover dit on kennis strek is daar nog geen studie gedoen om die gebied van impak polipropileen kopolimere (IPPK)-hout komposiete uit te bou nie. IPPKs is ‘n geskikte alternatief vir PP in veral laetemperatuur aanwendings. Die gebruik van IPPKs as matriks vir die hout komposiete kan ‘n groot staqp vorentoe beteken. Hierdie studie wys dat die fisiese eienskappe van iPPK-hout komposiete merkwaardig verbeter kan word waneer versoeningmateriale gebruik word om die verspreiding van die hout in die polimeermatriks sowel as die interaksie tussen die hout en polimeer te verbeter. Die gebruik van verskillende versoenings material, t.w poli(propileen-ent-maleinsuur anhidried) (PPeMA) en pol(etlieen-ko-viniel alkohol) (EVOH). Deur gebruik te maak van eenvoudige mengsels van PPeMA en EVOH in IPPK-hout composite het ‘n geweldige wye verpreiding van resultate tot gevolg gehad, terwyl ‘n voorafgaande reaksie tussen die PPeMA en die EVOH om ‘n saamgestelde versoeningmateriaal te maak tot gevolg gehad het dat reproduseerbare resultate verkry kon word. ‘n Studie van die fundamentele interaksies van die versoeningsmateriale met die molkulêre komponente van die IPPKs is uitgevoer. Die IPPKs is gefraksioneer deur preparatiewe temperatuur-stygende uitloog frakasionering en die fraksies is gemeng met die versoeningmateriale. Fluoressensie mikroskopie is gebruik om hierdie interaksies te bestudeer. Die resultate dui duidelik daarop dat die interaksie van die PPeMA met die fraksies verskil met die van die EVOH. Die verskille kan verduidelik word aan die hand van die chemiese samestelling verspreiding van die IPPK fraksies. Atoomkrag mikroskopie (AKM) is gebruik om die adhesive-kragte tussen die versoeningmateriale, polimere, sellulose en lignien. AKM tippe is suksesvol bedek met PPeMA en EVOH, onderskeidelik. Alhoewel interaksies gebaseer op chemiese krag mikroskopie (CKM) nie gekwantifiseer kon word nie, lewer hierdie resultate tesame met die fluoressensie spektroskopie unieke insig in die manier wat versoeningmateriale met beide die hout en die polimeer reageer.

Thesis (PhD)--Stellenbosch University, 2014. / ENGLISH ABSTRACT: Impact copolymers or heterophasic polypropylene-ethylene-co-propylene copolymers (HEPCs) commonly produced in industry are valued for their good mechanical properties, combining the rigidity of the polypropylene matrix with the toughness of the dispersed ethylene-propylene copolymer. The potential for further optimisation and tailoring of product properties can be realised through an improved understanding of how the copolymer phase produced in the second reactor develops with increasing ethylene incorporation, providing an intermediate link between predicted physical behaviour and the process parameters required to achieve this. To this end, the morphological development of heterophasic or impact copolymers, has been a topic of interest of many studies to date, yet due to the complexity of these polymers, there is still some uncertainty with regards to the mechanism of copolymer growth as well as the structure-function relationships that exist. These studies were limited either due to the use of autoclave products or final impact copolymer products obtained from industry. The work presented in this study was aimed at understanding how the nascent copolymer phase develops during a transition from homopolymer to the final copolymer. This was done by selecting samples at certain intervals from two different commercial gas-phase processes, yielding two sets of four samples, each with a range of increasing ethylene contents. These samples provided the unique opportunity to study the early development of copolymer in a sequential manner (as each sample builds on the morphology of the previous one). The morphological development of copolymer in these samples was investigated by high resolution FE-SEM and it was observed that the copolymers showed different degrees of internal and external distribution as well as porosity for the different sets, determined by the initial porosity of the homopolymer. It was also found that the copolymer was radially distributed throughout the particle in all instances, suggesting that ethylene monomer diffusion limitations did not play a significant role in the copolymerization process. A further aim of the study was to determine the effect of ethylene incorporation on bulk sample crystallinity, microstructure and chemical composition. It was observed by SCALLS and TREF that increasing ethylene incorporation attenuated the crystallinity of the homopolymer, resulting in a distribution of components with different crystallinities within the samples, suggesting some interaction between the developing copolymer and existing homopolymer. During the microstructural development of these samples, longer or more blocky ethylene sequences seemed to be favoured above isolated ethylene sequences with increasing ethylene incorporation and it was shown by solid-state NMR that ethylene partitioning between both amorphous and rigid environments occurred. Detailed characterization (solution and solid-state 13C NMR, HT-SEC and HT-HPLC) of the semi-crystalline copolymer fractions provided some information on the development of microstructure and chemical composition in these fractions that are responsible for compatibilization between the homopolymer matrix and dispersed rubber phase. Based on the different observations from the investigations outlined above, a model for copolymer development in each set was proposed and related to the physical property development observed for these samples. / AFRIKAANSE OPSOMMING: Die impak-kopolimere – ook bekend as heterofase polipropileen-etileen-kopropileen kopolimere (HEPC’s) – wat tans in die bedryf vervaardig word, is bekend vir hul goeie meganiese eienskappe, naamlik om die styfheid van ’n polipropileenmatriks met die sterkte van ’n etileen-propileen kopolimeer, wat in die matriks versprei is, te kombineer. Die potensiaal vir die optimisering en pasmaak van produkeienskappe kan bewerkstellig word deur beter begrip ten opsigte van hoe die kopolimeerfase wat in die tweede reaktor vervaardig word, ontwikkel as gevolg van toenemende inkorporasie van etileen, en hoe dit ’n skakel skep tussen voorspelbare fisiese gedrag en die prosesparameters wat nodig is hiervoor. Tot datum het heelparty studies gefokus op die morfologiese ontwikkeling van heterofase of impak-kopolimere, maar as gevolg van die komplekse aard van hierdie polimere is daar nog steeds onsekerheid oor die meganisme van kopolimeerontwikkeling, asook die verwantskappe tussen die polimeerstruktuur en -funksie. Sodanige studies was beperk omdat óf outoklaafprodukte óf finale produkte van industriële prosesse gebruik is. Die doel van hierdie studie was om begrip te kry vir hoe die kopolimeerfase ontwikkel tydens ’n oorgang van homopolimeer tot die finale produk. Hiervoor is twee stelle van vier monsters met toenemende etileeninhoude tydens die oorgang in twee verskillende gasfaseprosesse verkry. Hierdie monsters het die unieke geleentheid gebied vir die opvolgende bestudering van die vroeë ontwikkeling van die kopolimeer, deurdat elke monster voortgebou het op die morfologie van die vorige monster. Die morfologiese ontwikkeling van die kopolimeer is ondersoek deur van hoëresolusie FE-SEM gebruik te maak. Verskillende wyses van interne en eksterne verspreiding, sowel as porositeit van die onderskeie stelle (soos bepaal deur die aanvanklike porositeit van die homopolimeer), is vir die verskillende prosesse waargeneem. Daar is ook waargeneem dat die kopolimeer in alle gevalle op verskeie straalposisies binne die partikel versprei is, waarvan afgelei kan word dat monomeerdiffusiebeperking nie ’n beduidende rol in die kopolimerisasieproses speel nie. ’n Verdere doel van hierdie studie was om die uitwerking van etileen-inkorporasie op die kristalliniteit, mikrostruktuur en chemiese samestelling van die polimeer te bepaal. Deur middel van SCALLS en TREF is bevind dat toenemende etileen-inkorporasie die kristalliniteit van die homopolimeer verswak het. Die gevolg was die vorming van ’n verskeidenheid komponente met verskillende kristalliniteite, wat dui op ’n interaksie tussen die groeiende kopolimeer en die bestaande homopolimeer. Tydens die ontwikkeling van die mikrostruktuur van die monsters het dit geblyk dat lang, opeenvolgende etileeneenhede tydens toenemende etileen-inkorporasie vinniger ontwikkel as afgesonderde etileen- en propileeneenhede. Deur middel van soliedefase-KMR is daar bewys dat die etileen in beide amorfe en kristalagtige areas versprei is. Die semi-kristallyne kopolimere wat deur TREF verkry is, is verder gekarakteriseer met behulp van KMR in oplossing sowel as die soliede fase, HT-SEC en HT-HPLC, wat meer inligting verskaf oor die ontwikkeling van die mikrostruktuur en chemiese samestelling van hierdie fraksies wat normaalweg verantwoordelik is vir die interaksies tussen die homopolimeermatriks en die verspreide rubberfase. Op grond van die waarnemings soos hierbo vermeld, word ’n model vir die kopolimeerfase-ontwikkeling van elke stel monsters in hierdie studie voorgestel en verbind met die ontwikkeling van die waargenome fisiese eienskappe.

Thesis (MSc)--Stellenbosch University, 2013. / ENGLISH ABSTRACT: A comparative study of the chemical composition of linear low density polyethylene polymers, synthesised with 1 - hexene as comonomer was conducted. Catalyst trials were conducted on the linear low density 1 - hexene polymer grade material to evaluate alternative catalysts. A comparative analysis was performed in order to investigate if the samples synthesised under catalyst trial conditions showed any significant differences in terms of crystallinity and mechanical properties with the reference sample that was synthesised using the reference catalyst. The results showed that the macro product properties, namely melt flow Index, density, and level of hexene extractables are different for the trial samples in comparison with the reference sample. The differences observed implied that the trial samples were synthesised with differences on a molecular level. The differences in the chemical composition between the reference sample and the comparative samples were fully explored using a wide range of analytical techniques, namely crystallisation analysis by fractionation (CRYSTAF), temperature rising elution fractionation (TREF), differential scanning calorimetry (DSC), Carbon 13 nuclear magnetic resonance (13C NMR), Size exclusion chromatography (SEC), Positron analysis lifetime spectroscopy (PALS) and micro hardness analysis. The results of the characterisation studies indicated the following: - Crystallinity and hardness analysis of the reference sample, catalyst trial sample 1 and catalyst trial sample 2 indicate that the catalyst trial sample 2 having a low cocatalyst concentration is the most crystalline of all the samples. - The reference sample, catalyst trial sample 1 and catalyst trial sample 2 were further fractionated using TREF at fractionation temperature intervals of 10°C. TREF analysis indicates that the bulk of the material is observed to elute between 70°C - 10°C. - 13C NMR analyses of the TREF fractions identified four populations of fractions that could be selectively removed, allowing the bulk of the material to be recombined. As these highly crystalline fractions were removed, there was an observed decrease in the total crystallinity of the bulk recombined material. This trend was further verified by the free volume analysis. - Free volume analysis indicated of the bulk recombined material indicated a general increase in the T3 lifetime and T4 lifetime intervals. Free volume analysis further confirmed a decrease in crystallinity of the bulk recombined material as highly crystalline material was removed. - Micro hardness analysis of the polymers further verified the crystallinity trends observed. As the molecular composition of the polymer changed due to removal of highly crystalline fractions, the total mechanical strength of the material indicated by the hardness value decreased. The study showed that by changing the chemical composition of the polymer by removing highly crystalline fractions, there was an observed change in the mechanical properties of the polymer. It can be concluded that the samples synthesised under catalyst trial conditions show significant differences in terms of crystallinity and mechanical properties in comparison with the sample that was synthesised using the standard reference catalyst. / AFRIKAANSE OPSOMMING: ‘n Vergelykende analise studie is onderneem van die chemiese samestellings van lineêre lae digtheid poliëtileen polimere, gesintetiseer met 1-hekseen as ko-monomeer. Alternatiewe kataliste is ge-evavuleer ten opsigte van lineêre lae digtheid 1-hekseen Sasol polimeer graad materiaal. Die vergelykende analise is uitgevoer om die monsters onder katalis proef kondisies te evalueer en te merk of enige beduidende verskille in terme van kristalliniteit en meganiese eienskappe met die verwysings monster voorkom. Die resultate toon dat die makro-produk eienskappe, naamlik smelt vloei indeks, digtheid en vlak van hekseen onttrekking, verskillend is vir die proef monsters in vergelyking met die verwysings monster. Die waargenome verskille impliseer dat die proef monsters op molekulêre vlak verskil. Die verskille in chemiese samestelling tussen die verwysings monster en die vergelykende monsters is ten volle ondersoek deur gebruik te maak van 'n wye verskeidenheid van analitiese tegnieke, naamlik kristallisasie analise fraksionering (CRYSTAF), temperatuur stygende eluering fraksionering (TREF), differensiële skandeer kalorimetrie (DSC), koolstof 13 kernmagnetiese resonansie (13C KMR), gelpermeasie chromatografie (SEC), positron analise leeftyd spektroskopie (PALS) en mikro-hardheid analise. Die resultate van die karakterisering studies het die volgende aangedui:- Kristalliniteit en hardheid analises van die verwysings monster en katalis proef monsters 1 en 2 het getoon dat katalis proef monster 2, wat ‘n lae ko-katalis konsentrasie bevat, die mees kristallyn is. - Die verwysings monster en katalis proef monster 1 en 2 is gefraksioneer met behulp van ‘n TREF met temperatuur tussenposes van 10°C. TREF analise toon dat oormaat materiaal ge-elueer word tussen 70°C en 100°C. - 13C KMR analise van die TREF fraksies het 4 verskillende fraksies geidentifiseer wat selektief verwyder kan word. Dit laat ook toe dat die grootste deel van die materiaal weer geherkombineer kan word. Soos die hoogs kristallyne fraksies verwyder is, is ‘n afname in die totale kristalliniteit van die geherkombineerde materiaal waargeneem. Hierdie tendens is bevestig deur vrye volume analises. - Vrye volume analises van die geherkombineerde materiaal toon ‘n algemene toename in die T3en T4 leeftyd aan. Vrye volume analises toon verder dat ‘n afname in die kristalliniteit van die geherkombineerde materiaal plaasvind soos meer kristallyne fraksies verwyder word. - Verdere mikro-hardheid analises van die polimere bevestig die waargenome kristalliniteit tendense. Soos die molekulêre samestelling van die polimere verander as gevolg van die verwydering van die hoogs kristallyne fraksies, so neem die totale meganiese sterkte van die materiaal af; soos aangedui deur die afname in hardheid waarde. Die studie toon dat die verandering van die chemiese samestelling van die polimeer, deur die verwydering van hoogs kristallyne fraksies, 'n waargenome verandering in die meganiese eienskappe van die polimeer laat plaasvind. Daar kan afgelei word dat die monsters, vervaardig onder die katalis proef voorwaardes, beduidende verskille toon in terme van kristalliniteit en meganiese eienskappe in vergelyking met die monster vervaardig deur die huidige verwysings katalis.

This work focuses on the integration of microfluidics and dielectrophoresis(DEP) with the principles of field flow fractionation (FFF) to create a continuous-flow isolator for rare and viable circulating tumor cells (CTCs) from peripheral blood mononuclear cells (PBMNs) drawn from cancer patients. The method exploits differences in the plasma membrane capacitances of tumor and blood cells, which correspond to differences in the membrane surface areas of these cell types. DEP-FFF was first adapted to measure cell membrane capacitance, cell density and deformability profiles of cell populations. These properties of the NCI-60 panel of cancer cell types, which represents the wide functional diversity of cancers from 9 organs and leukemia, were compared with the normal cell subpopulations of peripheral blood. In every case, the NCI-60 cells exhibited membrane capacitance characteristics that were distinct from blood and, as a result, they could be isolated from blood by DEP. The heightened cancer cell membrane capacitances correlated strongly with membrane-rich morphological characteristics at their growth sites, including cell flattening, dendritic projections, and surface wrinkling. Following harvest from culture and maintenance in suspension, cancer cells were found to shed cytoplasm and membrane area over time and the suspended cell populations developed considerable morphological diversity. The shedding changed the cancer cell DEP properties but they could still be isolated from blood cells. A similar shedding process in the peripheral blood could account for the surprisingly wide morphological diversity seen among circulating cells isolated from clinical specimens. A continuous flow DEP-FFF method was devised to exploit these findings by allowing CTCs to be isolated from the nucleated cells of 10 mL clinical blood specimens in 40 minutes, an extremely high throughput rate for a microfluidic-based method. Cultured cancer cells could be isolated at 70-80% efficiency using this approach and the isolation of CTCs from clinical specimens was demonstrated. The results showed that the continuous DEP-FFF method delivers unmodified, viable CTCs for analysis, is perhaps universally applicable to isolation of CTCs from different cancer types and is independent of surface antigens - making it suitable for cells lacking the epithelial markers used in currently accepted CTC isolation methods. / text

Wastewater activated sludge is produced during the biological treatment of wastewater. After treating the sewage, the sludge is allowed to settle. Part of the settled material is returned to the treatment process as return activated sludge (RAS) and the excess is removed as waste activated sludge (WAS). The handling and disposal of the sludge are energy and capital-intensive treatments, with a significant environmental impact. This work studies the possibility to utilize RAS (an example of wastewater sludge) as a source of surface active agents. The results indicate that higly surface active materials can be extracted from RAS, and that the RAS extract has potential applications as a detergent and wood adhesive. The results also suggest that recovering a suite of products from RAS, a biological heterogenous source, can be technically feasible. An effective alkaline treatment was developed (at pH>12) that can extract up to 75% of the sludge’s organic matter, a yield higher than previously reported. Increasing the extraction pH increased the extract surface activity, which is linked to increasing the amount of higher molecular weight molecules and the presence of phospholipids. Increasing the extraction pH beyond 11 was also related to extensive cell lysis, increasing significantly the amount of recovered material and the surface activity of the extract. The alkaline extract has properties comparable to commercial detergents. Without further purification, the extract has a low surface tension (37 mN/m on average) and performs similarly to synthetic detergents. Further assessment of the RAS extract (insensitivity to pH, surface tension, interfacial tension) suggests that it may be suitable for commercial applications. The RAS extract can also be formulated into wood adhesives using glutaraldehyde as a crosslinker. The extract fraction with 10-50 kDa constituents at pH 9 achieves high adhesive shear strengths (4.5 MPa on average, at 30% relative humidity and 25°C) with 40% of wood failure. The adhesive strength of RAS-based adhesives is strongly correlated to its protein content.

Constructed wetlands are considered an inefficient technology for long-term phosphorus (P) removal. The P retention effectiveness of subsurface wetlands can be improved by using appropriate substrates. The objectives of this study were to: (i) use sorption isotherms to estimate the P sorption capacity of the two materials, masonry sand and light weight expanded shale; (ii) describe dissolved P removal in small (2.7 m3) subsurface flow wetlands; (iii) quantify the forms of P retained by the substrates in the pilot cells; and (iv) use resulting data to assess the technical and economic feasibility of the most promising system to remove P. The P sorption capacity of masonry sand and expanded shale, as determined with Langmuir isotherms, was 60 mg/kg and 971 mg/kg respectively. In the pilot cells receiving secondarily treated wastewater, cells containing expanded shale retained a greater proportion of the incoming P (50.8 percent) than cells containing masonry sand (14.5 percent). After a year of operation, samples were analyzed for total P (TP) and total inorganic P (TIP). Subsamples were fractionated into labile-P, Fe+Al-bound P, humic-P, Ca+Mg-bound P, and residual-P. Means and standard deviations of TP retained by the expanded shale and masonry sand were 349 + 169 and 11.9 + 18.6 mg/kg respectively. The largest forms of P retained by the expanded shale pilot cells were Fe+Al- bound P (108 mg/kg), followed by labile-P (46.7 mg/kg) and humic-P (39.8). Increases in the P forms of masonry sand were greatest in labile-P (7.5 mg/kg). The cost of an expanded shale wetland is within the range of costs conventional technologies for P removal. Accurate cost comparisons are dependent upon expansion capacity of the system under consideration. Materials with a high P sorption capacity also have potential for enhancing P removal in other constructed wetland applications such as stormwater wetlands and wetlands for treating agricultural runoff.

La gélatine est un ingrédient utilisé dans de nombreuses industries et sa solubilité influence beaucoup ses propriétés fonctionnelles. Des défauts de solubilité sont parfois constatés, notamment suite à un stockage de la gélatine en grains à température élevée et humidité importante. Cette perte de solubilité pourrait être due à la présence de molécules de haut poids moléculaire. L'objectif de ce travail est d’apporter des éléments de compréhension sur la perte de solubilité observée dans les solutions de gélatine. L'utilisation d’une technique de Fractionnement par Flux-Force couplée à une diffusion de la lumière Multiangulaire, a mis en évidence la présence d’agrégats de haut poids moléculaires dans les solutions de gélatine (de 9.5 à 30.2.105 g.mol-1). Ces agrégats n’avaient jamais pu être identifiés par les techniques classiques d'exclusion stérique car elles sont souvent éliminées dans le volume d'exclusion des colonnes. La quantité d'agrégats formés ne cesse d'augmenter lors d'un traitement thermique à 75 °C, aboutissant à l'insolubilité de la gélatine. La compréhension du mécanisme à l’origine de cette perte de solubilité montre l'implication de la lysine disponible, dans l'apparition des agrégats. La lysine libre réagissant au cours du traitement thermique provoquerait la formation d'agrégats qui modifient le comportement de la gélatine en solution aqueuse. Les paramètres de caractérisation de l’AFlFFF-MALS permettent de discriminer partiellement des échantillons de gélatine dont les comportements en solubilité sont différents. Rajoutés aux paramètres classiques de caractérisation comme la viscosité à 6.67% et au dosage de la lysine disponible, la discrimination devient parfaite. / Gelatin is an important product for several industries and its solubility dramatically influences its functional properties. The lack of solubility observed in gelatine is supposed to be due to the occurrence of molecules with high molecular weights, especially after heat treatments. In order to be able to predict the gelatin behaviour, a new technique for its analysis has been developed with an Asymmetrical Flow Field-Flow Fractionation (AFlFFF-MALS) coupled to a multiangular light scattering. The AFlFFF-MALS analysis showed high molecular weight fractions in gelatin ranging from 9.5 to 30.2 105 g.mol-1 which has not been shown previously with alternative techniques such as size exclusion chromatography. After heat treatment of dry gelatine in an oven at 75°C, some huge aggregates appeared, of which size and density increased and led to partial insolubilisation of gelatin into water. The mechanism responsible for this phenomenon involved lysine residues which plays a very important role in gelatin properties. Quantification of available lysine in gelatin samples by LC-UV has been developed. Thermal treatment during 8 days led to a decrease of free lysine content whereas, at the same time, the molecular weight of gelatin fractions increased and α helixes formation in solution was strongly affected. Intermolecular cross-links led to high molar mass compounds and limited protein chain unfolding. From an industrial point of view, AFlFFF-MALS analysis can help to discriminate gelatine samples in regard to their solubility. If other parameters are added (6.67 % viscosity and free lysine) the discrimination was perfect.

Chronic lower back pain is a major public health problem, with direct and indirect economic costs comparable to those of heart disease, depression and diabetes. In many cases this pain derives from degeneration of the intervertebral disc (IVD), a fibrous, avascular tissue that sits between the vertebrae in the spinal column. A novel treatment approach for this ‘discogenic’ pain is the injection of a hydrogel that hybridises in situ and restores the normal biomechanical function of the disc. While a number of promising materials are currently under development, existing approaches to removing degenerate material from the disc prior to injection are invasive and compromise the structural integrity of the disc. Mechanical fractionation of the tissue using acoustic cavitation generated by high intensity focussed ultrasound (HIFU) has the potential to be non-invasive, and to enhance the effectiveness of the procedure by preserving the outer regions of the disc. The primary goal of this thesis is to investigate the feasibility of this approach. The acoustic properties of the disc were first measured using a modified scanning acoustic microscope. The outer region of the disc, the annulus fibrosus (AF) was found to be highly attenuative compared to the central nucleus pulposus (NP). These measured properties were then used in a simplified two-dimensional model to simulate the shape of the acoustic pressure field within the disc. A configuration using two confocal spherically focussed 0.5 MHz single-element transducers was able to produce a tightly focused field suitable for use in the IVD. As preliminary experiments suggested that high pressure amplitudes were required to initiate cavitation inside the disc, the use of exogenous nuclei to lower this threshold was investigated. A novel class of solid sonosensitive nanoparticles (SNPs) suitable for use in the IVD were developed and characterised. These SNPs comprise a layer of hydrophobic silica particles deposited onto a polystyrene core, and are thought to trap small gas pockets in surface crevices. Coated particles were found to reduce the cavitation threshold significantly in both water and blood, from some 2.0 - 2.5 MPa at 1.067 MHz to below 1.0 MPa. The particles were also found to provide repeatable initiation of cavitation activity during prolonged or repeated exposures, and to exhibit good storage stability, suggesting that they they may be appropriate for use within the IVD. Finally, a combined therapy and monitoring system was designed, built and validated. The system comprised two confocal 0.5 MHz spherically focussed HIFU transducers with central openings, each co-axially aligned with either a single element passive cavitation detector or a 64-element array that could be used for both active and passive imaging. The system was found to be capable of initiating inertial cavitation in the disc at pressures as low as 2.5MPa in the presence of sonosensitive nanoparticles. Use of the array in active mode enables creation of a B-mode image that provides anatomical information on the boundaries of the IVD, whist the same array could be used for passive mapping of acoustic emissions arising fromthe HIFU focus during therapy. Two different exposure regimes were found to be capable of producing sizeable perforations within the NP without significantly damaging the AF, and preliminary investigations were carried out into themechanism of damage. The location and extent of cavitation as seen on passive maps acquired during treatment was found to coincide with the regions of NP fractionation. This confirms that passive acoustic mapping can provide the real-time treatment monitoring necessary to ensure both safety and efficacy of ultrasonic IVD fractionation. Prior to clinical application, a significant amount of further development is required to further validate non-invasive disc fractionation by HIFU and the subsequent steps for minimally invasive disc replacement using injectable hydrogels. The present work has nonetheless demonstrated for the first time that minimally invasive removal of degenerate disc tissue is feasible trough the combined use of sonosensitive nanoparticles and a relatively low-cost therapeutic ultrasound system that provides simultaneous anatomical imaging and real-time treatment monitoring by passive acoustic mapping.

The global marine distributions of Cd and phosphate are closely correlated, which has led to Cd being considered as a marine micronutrient. Recent developments in Cd stable isotope mass spectrometry have revealed that Cd uptake by phytoplankton causes isotopic fractionation in the open ocean and in culture. The explanation for this nutrient-like behaviour is unknown as there is only one identified biochemical function for Cd, an unusual Cd/Zn carbonic anhydrase (CdCA1). This thesis investigates why Cd appears to act as an algal nutrient by performing subcellular analyses of microorganisms genetically-modified to express the CdCA1 gene. It was found that CdCA1 was not a significant contributor to whole-cell Cd isotope compositions. Instead, a large proportion of the internalized Cd is sequestered into cell membranes with a similar direction and magnitude of Cd isotopic fractionation as seen in surface seawater. This observation is explained if Cd is mistakenly imported with other divalent metals and subsequently managed by binding within the cell to avoid toxicity. This result implies that surface seawater Cd isotope compositions, if captured by an appropriate archive, may be invaluable for reconstructions of past marine productivity. The role of environmental factors in modulating the inorganic partitioning of Cd isotopes into calcite was investigated through a series of laboratory analogue experiments. In seawater, the light isotopes of Cd are always preferred in calcite. The magnitude of fractionation showed no response to temperature, ambient [Mg], or precipitation rate. To further identify suitable palaeaoceanographic archives, the Cd isotopic composition of a suite of modern deep-sea corals were investigated. It was found that the Cd/Ca and Cd isotope composition of coralline calcium carbonate followed the predicted trend for closed-system Rayleigh fractionation in the calcifying space. The lack of isotopic offsets between some corals and seawater will simplify the application of Cd isotopes in deep-sea corals -- and potentially other marine calcifying organisms that vacuolize seawater prior to calcium carbonate precipitation -- to palaeoceanography.