Azidothymidin (AZT) ist ein nukleosidischer Reverse-Transkriptase-Inhibitor (NRTI), der bei HIV-Infektionen in Kombination mit anderen antiretroviralen Substanzen eingesetzt wird. AZT zeigt darüberhinaus auch eine gute Wirksamkeit gegen Foamyviren, eine Subfamilie der Retroviren mit charakteristischen Besonderheiten in ihrer Molekularbiologie und ihrem Replikationszyklus, deren Vertreter verschiedene Affenarten und andere Säugetiere infizieren, wobei sie sich sowohl im jeweils natürlichen Wirt als auch bei seltener zufälliger Infektion des Menschen apathogen zeigen. In der vorliegenden Arbeit wurde das AZT-resistente Foamyvirus SFVmacAZTres untersucht, das in Anwesenheit steigender AZT-Konzentrationen in Zellkultur selektiert worden war. Hierzu wurde SFVmacAZTres zunächst einer genotypischen Analyse unterzogen, wobei im Vergleich mit der wildtypischen Ausgangssequenz zwei Mutationen in gag und vier Mutationen in pol nachgewiesen wurden, die zu Änderungen auf Aminosäureebene führten. Mittels PCR wurden Fragmente, die alle sechs Mutationen oder nur die vier pol-Mutationen enthielten, aus der Sequenz von SFVmacAZTres amplifiziert und jeweils in einen SFVmac-Klon eingefügt. Im weiteren Verlauf zeigte sich dabei kein Unterschied zwischen diesen beiden Konstrukten bezüglich der Replikation in Abwesenheit oder Anwesenheit von AZT, so dass gefolgert werden konnte, dass die gag-Mutationen keinen Beitrag zur AZT-Resistenz leisten. Die pol-Mutationen befanden sich sämtlich im für die Reverse Transkriptase kodierenden Bereich und führten zu den Aminosäuresubstitutionen K211I, I224T, S345T und E350K. An Position 224 fand sich dabei in einer veröffentlichten Sequenz bereits ein Threonin, so dass hier unabhängig von der Selektion in Anwesenheit von AZT möglicherweise ein Polymorphismus vorliegt. Der Vergleich der vier Mutationen der RT von SFVmacAZTres mit den bei HIV bekannten Mustern an Mutationen wie den TAMs und dem Q151M-Komplex zeigte keine Übereinstimmungen. Um den jeweiligen Beitrag der vier nachgewiesenen pol-Mutationen zur AZT-Resistenz zu untersuchen, wurden sie einzeln und in Kombinationen mittels zielgerichteter Mutagenese in einen SFVmac-Klon eingefügt und die entsprechenden Konstrukte auf ihre Replikation in Abwesenheit und Anwesenheit von 0,5 µM, 5µM und 50 µM AZT untersucht. Hierfür wurden 293T-Zellen mit dem jeweiligen Plasmid transfiziert und nach Überprüfung der gleichmäßigen Expression von Gag und Pol mittels Western Blot der virushaltige Überstand auf Zielzellen gegeben und der Titer ausgezählt. Es konnte gezeigt werden, dass keines der Konstrukte mit Einzel , Doppel- und Dreifachmutationen eine ähnlich ausgeprägte AZT-Resistenz wie die Vierfachmutante aufwies, allerdings einige in unterschiedlichen Ausmaß teilresistent waren, während andere weder ohne noch mit AZT gut replizierten. S345T erwies sich vor E350K als die Mutation mit dem größten Beitrag zur AZT-Resistenz, I224T erhöhte den Titer in Abwesenheit und Anwesenheit um etwa den gleichen Faktor, wohingegen sich K211I in den meisten Kombinationen eher negativ auswirkte. Der Klon, in den alle vier Mutationen mittels zielgerichteter Mutagenese eingeführt worden waren, zeigte die gleiche AZT-Resistenz wie das in Zellkultur selektierte Virus. Damit war gezeigt, dass diese vier Mutationen sowohl notwendig als auch hinreichend für die AZT-Resistenz von SFVmacAZTres sind. Die pol-Mutationen von SFVmacAZTres wurden weiterhin soweit möglich an entsprechenden Stellen in Klon des prototypischen Foamyvirus PFV eingeführt, bei dem es zuvor nicht gelungen war, ein resistentes Isolat in Zellkultur zu generieren. Das PFV-Konstrukt mit den Mutationen aus SFVmacAZTres zeigte sich jedoch nicht AZT-resistent, sondern wies einen Replikationsdefekt auf. Einige HIV-Mutationen, die in den PFV-Klon eingefügt wurden, führten ebenfalls zu keiner AZT-Resistenz. Es bestehen also bezüglich AZT-Resistenz und damit gewisser Eigenschaften der Reversen Transkriptase deutliche Unterschiede zwischen PFV und SFVmac. Die durchgeführten Arbeiten stellen die Grundlage für weitere Untersuchungen dar, in denen beispielsweise dem biochemischen Mechanismus der AZT-Resistenz von SFVmacAZTres nachgegangen werden kann. Die gewonnenen Erkenntnisse können zum Verständnis allgemeiner Mechanismen der NRTI-Resistenz bei Retroviren ebenso beitragen wie zur weiteren Charakterisierung der foamyviralen Reversen Transkriptase an sich. / Zidovudine or azidothymidine (AZT) is a nucleoside analog reverse transcriptase inhibitor (NRTI) which is used together with other substances for therapy of HIV infections. AZT can also be used to suppress foamy virus replication, a subfamily of retroviruses with distinct molecular biology and replication. AZT resistant foamy virus (SFVmacAZTres) which was generated in cell culture in presence of increasing AZT concentrations was analyzed in this study. First, a genotypic analysis was conducted, which showed 2 mutations in gag and 4 mutations in pol of this resistant virus when compared to the wildtype sequence. Infectious clones harbouring all 6 mutations or only the pol-mutations were constructed by amplifying the corresponding sequence of the resistant virus and cloning them into the wildtype sequence. There was no difference regarding virus replication in absence or presence of AZT between the virus with gag- and pol-mutations and the virus only harbouring the pol-mutations. Using site directed mutagenesis, the four pol mutations, namely K211I, I224T, S345T and E350K and double and triple combinations thereof were inserted into the infectious clone of SFVmac. These mutants, as well as the wildtype clone and the clone with all 4 mutations were compared in absence of AZT and at AZT concentrations of 0,5, 5, and 50 µM, using these concentrations in the virusproducing 293T-cell as well as in the target cells, BHKLTRlacZ. By counting of blue, and thereby, virus infected cells, it was demonstrated that no single, double or triple mutant displayed the same AZT resistance as the original resistant virus with all 4 mutations. Some combinations displayed deleterious effects, others partial resistance. S345T was identified as the most important mutation regarding AZT-resistance, while E350K and K211I only showed effects in combinations with other mutations and at high AZT concentrations. I224T raised the viral titre, which is reduced in absence of AZT by the other mutations, in absence or presence of AZT by the same factor. The mutations identified in SFVmac were also cloned in PFV. However, a AZT resistant PFV could not be generated.

The main technology currently used in diabetic care, monitors blood glucose and involves an invasive “fingerstick” step. However, low patient compliance and non-continuous glucose monitoring imply poor management of diabetes through this technology, which could lead to adverse and potentially life threatening conditions. In this context, non-invasive glucose sensing appears as an alternative that can bring a change in the prevention and management of the diabetic condition, promising to eliminate patient resistance towards more frequent monitoring and, hence, considerably improving diabetic’s control over glycaemia. However, no non-invasive technology has yet succeeded on the market over the long term. The research field is therefore open to innovative and performant non-invasive technologies. This thesis presents the development of a non-invasive biosensor which as a core principle accesses individual, privileged glucose pathways in the skin (such as hair follicles), allowing the extraction of glucose directly from the interstitial fluid, via reverse iontophoresis (RI). The transdermally extracted glucose is then electrochemically detected in a small size sensor with very high sensitivity. A fully developed technology based on this principle will not require fingerpricking and would thus eliminate users’ main barrier to glucose monitoring. The developed sensor is enzymatic (using glucose oxidase), which electrochemically detects the produced H2O2; while the electrode material is graphene produced by Chemical Vapour Deposition, a promising carbon nanomaterial platform for biofunctionalisation and biosensing. The sensor is a miniature one (typically of 9 mm2 area, containing 24 μL of gel encasing the enzyme), with demonstrated performance parameters that are highly competitive (sensitivity of 2.89 μA.mM-1.cm-2 and limit of detection down to 1 μM), with high specificity towards glucose. The combination of this sensor with glucose extraction by reverse iontophoresis was then validated (with proportionality between subdermal and extracted glucose concentrations demonstrated); as well as enhanced extraction through targeting of hair follicles with the miniature device. The electrochemical determination of glucose concentration was further confirmed by 1H quantitative-NMR detection of glucose. Finally, several such sensors were integrated in a multiplex configuration, and independent sensing, with no cross-talk was demonstrated. The steps demonstrated and implemented so far are proof-of-concept of a highly promising non-invasive, transdermal, future technology for diabetic care.

Reverse Osmosis membranes have been successfully proven to remove almost 99% of chemicals dissolved in seawater. However, removal of certain trace elements, such as boron is challenging and relatively low for seawater reverse osmosis desalination plants compared to thermal desalination plants. Boron is naturally occurring and is present in seawater at an average concentration of 4.5-5 mg/L. While boron is a vital element, its toxicity has been proven on crops, animals and possibly humans. Additionally, boron should be removed to comply with the current guideline value of 0.5 mg/L, for drinking water, issued by the World Health Organization (WHO), which is barely attained by a single-pass process seawater reverse osmosis plant. Currently, multipass reverse osmosis membrane operations with pH modifications are the only valid method for boron removal. However, this is not economically efficient as it requires higher energy and chemicals consumptions. The objective of this study was to investigate boron removal by commercial TFC RO membranes in addition to custom-made KAUST-synthesized TFC membrane. Five membrane samples were examined: Toray, Sepro, Koch, and KAUST in-house synthesized membrane. Three different feed pH conditions were used: pH6, pH8, and pH10. Filtration experiments were conducted in two parts. In experiment 1, all five membranes were examined for boron rejection in a dead-end permeation system, whereas in experiment 2 the two membranes with the highest boron rejection from experiment 1 were tested in a cross-flow system. Permeate and feed samples were taken continuously and analyzed for boron concentration, rejection calculation. Membrane surfaces were characterized according to hydrophilicity, roughness and surface charge. The results showed for all the tested membranes that boron rejection increased as the feed pH increased. KAUST, defect-free TFC, showed the highest performance for boron rejection for all pH conditions, although, it shows the roughest surface. Toray membranes 80LB and 80B exhibited the second highest boron rejection and had the most negatively charged membrane surfaces. It was observed in this study that the rejection of boron by a membrane is due to size exclusion and charge repulsion mechanisms. It was concluded that, the KAUST, defect free TFC has the potential to be applicable for boron rejection in industrial application as it has better boron rejection than commercially available RO membranes.

The ordering processes of ferroelectric and multiferroic materials were investigated via neutron total scattering and the reverse Monte Carlo method. The results presented in this thesis are from three materials where ferroelectric behaviour is a result of ordering of molecular groups rather than individual atoms. Two of the materials are metal-organic frameworks, three dimensional cage-like structures with guest ions inside the pores; the third material, is a room temperature ferroelectric. In the high-temperature phase of dimethylammonium manganese formate, the framework distorts around the disordered cation, and the cations form shorter hydrogen bonds with the formate framework than the average structure suggests. Framework deformations became increasingly unfavourable as the material cooled. The cations continue to order as the material was cooled below Tc. Analysis of the high-temperature phase atomistic configurations showed that in addition to the three known orientations about the threefold axis, a significant minority of the cations lie mid-way between these positions, a feature which could not have been observed via standard crystallographic techniques. The mechanisms for thermal expansion of potassium imidazolium hexacyanoferrate change between the intermediate-temperature phase and the high-temperature phase. In the hightemperature phase the framework distorts around the disordered guest, but in the intermediatetemperature phase the framework stiffens. I propose that the temperature of the dielectric transition is dependent of the volume inside the framework, but that the temperature range of the intermediate-temperature phase is dependent on the rate of contraction of the framework around the guest cation. For triglycine sulfate no correlation was observed between the orientation of the polar molecules and the motion of the intermediate deuterium. Furthermore, in the high temperature phase the atomistic configurations produced models with macroscopic polarisation. I propose that this material forms domains of aligned polar molecules above Tc and that these domains are larger than the atomistic configurations.

<p>The task to this thesis has been to create an application, Katana-databas 1.0, for analysing c-code. The generated output gets stored in a data structure which content in the end of the program run gets written in a textfile which gets used by Katana. It's a tool for reverse engineering, developed by Johan Kraft at Mälardalens institute.</p><p>Katana-databas has got the following limitations. (1) It can only handle preprocessed files, meaning it doesn't contain any rows beginning with "#". (2) Only complete files can be handled. (3) No references to unknown functions or variables are allowed. (4) A further limitation is that the application can't handle any ADT's. It can only handle primitive types. (5) Finally the application is only written for pure c-code, and thus doesn't handle code written C++.</p><p>The task has been solved by creating an automatically generated lexer with Flex and Bison rules in Visual Studio. There after a limited parser has been developed which purpose is to process the lexemes which the lexer generates.</p><p>The underlying causes for the thesis is to replace Understand with Katana-databas. Katana has this far used the database in Understand, but it contains closed source code. What is seeked is open source code, which Katana-databas is based on.</p> / <p>Programmeringsuppgiften till detta arbete har bestått i att skapa en applikation, Katana-databas 1.0, för analys av C-kod. Utflödet som applikationen skapar sparas i en datastruktur vars innehåll i slutet av programkörningen skrivs ut i en textfil som används av Katana. Det är ett verktyg för reverse engineering, utvecklat av Johan Kraft på Mälardalens högskola.</p><p>Katana-databas har fått följande begränsningar. (1) Den kan bara hantera filer som är preprocessade, dvs. den innehåller inga rader som inleds med ”#”. (2) Endast kompletta filer kan hanteras. (3) Inga referenser till okända funktioner eller variabler är tillåtna. (4) En ytterligare begränsning är att applikationen inte kan hantera ADT:er. Den kan bara hantera primitiva typer. (5) Tillsist är applikationen endast skriven för ren c-kod, och klarar således inte av att hantera kod skriven i C++.</p><p>Uppgiften har lösts genom att skapa en automatgenererad lexer med Flex och Bisonrules i Visual Studio. Därefter har en limiterad parser utvecklats vars syfte är att bearbeta de lexem som lexern genererar.</p><p>Det bakomliggande syftet med arbetet är att ersätta Understand med Katana-databas. Katana har hittills använt sig av databasen i Understand, men den består av sluten källkod. Det som eftersträvas är öppen källkod, vilket Katana-databas baseras på.</p>

A novel reverse microemulsion (RM) mediated synthesis of glucose-responsive nanoparticles was developed for controlled insulin delivery. Nanoparticles were constructed using a model system comprised of dextran, poly(α-1,6 glucose), physically crosslinked with the tetrafunctional glucose-binding protein, Con A. A rapid-screening technique was used to quantify RM phase behavior in the presence of dextran, Con A and insulin. The extent of the RM existence region diminishes with increasing dextran and Con A concentrations and with increasing dextran molecular weight. Crosslinking efficiency between Con A and fluorescein isothiocyanate dextran (FITC-Dex) was found to depend on the total concentration of Con A as well as the ratio of Con A to FITC-Dex. Functionalizing dextran with higher affinity mannose ligands and increasing dextran molecular weight both improved crosslinking efficiency. The nanoparticles dissolved when dispersed in buffered saline solutions containing elevated glucose concentrations and were most responsive within the physiological range. Finally, insulin was encapsulated in select formulations and found to release preferentially at these elevated glucose concentrations. / Singapore-MIT Alliance (SMA)

Thesis (Ph. D.)--University of Hong Kong, 2006. / Title proper from title frame. Also available in printed format.

No description available.

Crevice corrosion generally occurs on the crevice surface while the exterior or bold surfaces are not damaged. However, for copper and its alloys, the opposite is true; the bold surface is corroded while the crevice remains relatively corrosion-free. This unique type of corrosion is referred to as reverse crevice corrosion (RCC). In this research, commercially pure copper was chosen as the target metal to investigate RCC. Based on electrochemical measurements and surface analysis, reverse crevice corrosion was found to occur at room temperature. At elevated temperature only uniform corrosion was observed while under a deoxygenated environment, as expected, no corrosion was observed.<p> A multiple crevice assembly and a working electrode were designed especially for this research. Exposure test experiments were first performed at room temperature and 50 ºC. Several types of electrochemical tests were conducted including open circuit potential measurement, potentiodynamic measurement and electrochemical impendence spectroscopy (EIS). Atomic Force Microscopy (AFM) and Raman Spectroscopy were used to analyze the surfaces of the copper coupon.<p>The results of the exposure tests showed that RCC occurred at room temperature, but not at elevated temperature. Only uniform corrosion was observed at elevated temperature and no corrosion was occurred under a deoxygenated environment. It was found, based on the open circuit potential measurement, that the RCC process can be divided into three steps, a uniform corrosion phase, a corrosion slow-down step and a reverse crevice corrosion step. The first two steps can be combined into one phase, incubation phase. This hypothesis is supported with the results from Raman spectra and AFM. The EIS measurements revealed that the diffusion process from bulk solution to copper coupon surface is the rate controlling step for incubation phase and this diffusion process combined with the reduction of Cu (I) oxide in the crevice are the rate-controlling step corresponding to the last step.

Crevice corrosion generally occurs on the crevice surface while the exterior or bold surfaces are not damaged. However, for copper and its alloys, the opposite is true; the bold surface is corroded while the crevice remains relatively corrosion-free. This unique type of corrosion is referred to as reverse crevice corrosion (RCC). In this research, commercially pure copper was chosen as the target metal to investigate RCC. Based on electrochemical measurements and surface analysis, reverse crevice corrosion was found to occur at room temperature. At elevated temperature only uniform corrosion was observed while under a deoxygenated environment, as expected, no corrosion was observed.<p> A multiple crevice assembly and a working electrode were designed especially for this research. Exposure test experiments were first performed at room temperature and 50 ºC. Several types of electrochemical tests were conducted including open circuit potential measurement, potentiodynamic measurement and electrochemical impendence spectroscopy (EIS). Atomic Force Microscopy (AFM) and Raman Spectroscopy were used to analyze the surfaces of the copper coupon.<p>The results of the exposure tests showed that RCC occurred at room temperature, but not at elevated temperature. Only uniform corrosion was observed at elevated temperature and no corrosion was occurred under a deoxygenated environment. It was found, based on the open circuit potential measurement, that the RCC process can be divided into three steps, a uniform corrosion phase, a corrosion slow-down step and a reverse crevice corrosion step. The first two steps can be combined into one phase, incubation phase. This hypothesis is supported with the results from Raman spectra and AFM. The EIS measurements revealed that the diffusion process from bulk solution to copper coupon surface is the rate controlling step for incubation phase and this diffusion process combined with the reduction of Cu (I) oxide in the crevice are the rate-controlling step corresponding to the last step.