No description available.

No description available.

No description available.

Octa-heme cytochrome c tetrathionate reductase (OTR) from Shewanella oneidensis MR-1 is a periplasmic protein and shows several extraordinary structural features around its active-site heme. OTR has been found able to catalyse the in vitro reduction of tetrathionate, nitrite, hydroxylamine and hydrogen peroxide. However the physiological function of this novel protein remains unknown. The subject of this thesis is the in vitro catalytic mechanism and the in vivo function of OTR. As OTR displays great similarity with bacterial penta-heme cytochrome c nitrite reductase (NrfA) in several aspects, it has been proposed that OTR might be physiologically involved in the metabolism of nitrite or other nitrogenous compounds. However kinetics assays and phenotypes studies carried out in this project suggest this is not the case. In vitro kinetic assays of the reduction of nitrite and hydroxylamine catalysed by OTR showed no significant difference in enzyme activities among the wild-type OTR and its mutant forms which have one active site residue replaced by alanine, namely OTR K153A, C64A, N61A and D150A. And the nitrite reductase activity of OTR (kcat/Km = 1.0×105 M-1•s-1) are much lower than that of NrfA (kcat/Km = ~108 M-1•s-1). These results indicate that OTR is not specifically adapted to reduce nitrite and it cannot compete for nitrite against NrfA in vivo. No phenotype difference was identified between the wild-type and the Δotr strain of Shewanella oneidensis MR-1 when nitrite or nitrate served as the sole electron acceptor. OTR appears not to be involved in the respiration or detoxification of nitrite, which is consistent with previous transcriptional and phenotype reports that involve OTR or its homologues. The in vitro tetrathionate reduction activity of OTR was unable to be reproduced in this project for unknown reasons. Although transcriptomic data from the literature suggest that OTR may be related to the metabolism of sulphur-containing compounds, kinetic and phenotype studies reveal that OTR does not directly participate in the respiration of thiosulfate, sulfite, tetrathionate, polysulfide or elemental sulphur. Cysteine 64 is a highly-conserved amino acid residue of OTR close to the active site and its side-chain sulphur atom is covalently bonded by either an oxygen or a sulphur atom as observed in the crystal structure. Such a modification is potentially important to the function of OTR. ESI mass spectroscopy results show that in native OTR the modified form is around 48 Da heavier than the unmodified form, and the MALDITOF peptide mass spectra show that the modified form could be converted into the unmodified form by reducing agent DTT. These results suggest that the modification could be a cysteine persulfide attaching an extra oxygen atom in the form of water or hydroxide anion.

This diploma thesis is focused on preparation and characterization of parylene C barrier properties. The layers were prepared by chemical vapour deposition (CVD). The interest in characterization of those layers is huge mainly because of their possible use in museology for the protection of the museum archives against the corrosion. Chlorinated dimer of para-xylylene was used as a precursor. Polypropylene foils, metal sheets and silica wafers were used as tested substrates for thin film preparation. Polypropylene foils were used for oxygen transmission rate measurements, metal sheets were used for corrosion tests and silica wafers were used for Fourier transform infrared spectroscopy (FTIR), confocal laser scanning microscopy (CLSM), scanning electron microscopy (SEM) and stylus profilometry.

Every day there are internet users all over the world who sends a total sum of millions of emails and instant messages and a majority of these are sent and transmitted without any form of encryption. When we send an unencrypted message it can be monitored, analyzed and even stored by organiza-tions and individuals. Therefore using encrypted communication is vital for not having our privacy violated. One of the problems that needs to be solved is to allow two persons to communicate in (near) real time through text over internet in a secure and easy way for the user, while at the same time allowing the user to have a good experience and maintaining confidentiality. The chat client should be able to communicate with other platforms than only itself and must therefore use and fol-low an existing protocol for instant messaging. To receive a true end-to-end encryption, all data needs to be encrypted and decrypted locally on the user's computer before it is sent out on the inter-net. SSL / TLS can be used as a protective layer, but it must be complemented by an extra and sepa-rate layer of encryption since SSL / TLS is not an authentic end-to-end encryption. This is because of the SSL data is decrypted when they land on the server, while true end-to-end data is only de-crypted locally on the receivers computer. This thesis have resulted in a working chat client built on the XMPP protocol with support for using OTR encryption that offers true end-to-end encryption. / Varje dag finns det internetanvändare världen över som sammanlagt skickar miljontals email och direktmeddelanden vilka majoriteten skickas och överförs utan någon form utav kryptering. När vi skickar ett okrypterat meddelande kan det bli övervakat, analyserat och till och med lagrat utav or-ganisationer och individer. Därför är användande utav krypterad kommunikation avgörande för att inte vår integritet ska kränkas. Ett utav problemen som behöver lösas är att tillåta två personer att kommunicera i (nära) realtid genom text över internet på ett säkert och enkelt sätt för användaren. Detta samtidigt som användaren har en bra användarupplevelse och bibehåller konfidentialitet. Chattklienten ska kunna kommunicera med andra plattformar än sig själv och måste därmed an-vända sig utav och följa ett existerande protokoll för direktmeddelanden. För att få en riktig end-to-end kryptering måste all data krypteras och dekrypteras lokalt på användarens dator innan det skickas över internet. SSL / TLS kan användas som ett skyddande lager, men måste kompletteras av ett extra och separat lager av kryptering då SSL / TLS inte är äkta "end-to-end" kryptering. Detta är på grund utav att SSL data är dekrypterad när det kommer till servern, medan äkta "end-to-end" kryptering endast är dekrypterat lokalt på mottagarens dator. Denna avhandling resulterade i en fungerande chattklient byggt på XMPP protokollet med stöd för OTR kryptering som erbjuder äkta "end-to-end" kryptering.

Optimising illumination is essential for optimising the growth of phototrophic cells and their production of desired metabolites and/or biomass. This requires appropriate modulation of light and other key inputs and continuous online monitoring of their metabolic activities. Powerful non-invasive systems for cultivating heterotrophic organisms include shake flasks in online monitoring units, but they are rarely used for phototrophs because they lack the appropriate illumination design and necessary illuminatory power. This study presents the design and characterisation of a photosynthetic shake flask unit, illuminated from below by warm white light-emitting diodes with variable light intensities up to 2300 μmol m-2 s-1. The photosynthetic unit was successfully used, in combination with online monitoring of oxygen production, to cultivate Arthrospira platensis. In phototrophic growth under continuous light and a 16 h light/8 h dark cycle (light intensity: 180 μmol m-2 s-1), the oxygen transfer rate and biomass-related oxygen production were - 1.5 mmol L-1 h-1 and 0.18 mmol O2 gx-1 h-1, respectively. The maximum specific growth rate was 0.058 h-1, during the exponential growth phase, after which the biomass concentration reached 0.75 g L-1.

Optimising illumination is essential for optimising the growth of phototrophic cells and their production of desired metabolites and/or biomass. This requires appropriate modulation of light and other key inputs and continuous online monitoring of their metabolic activities. Powerful non-invasive systems for cultivating heterotrophic organisms include shake flasks in online monitoring units, but they are rarely used for phototrophs because they lack the appropriate illumination design and necessary illuminatory power. This study presents the design and characterisation of a photosynthetic shake flask unit, illuminated from below by warm white light-emitting diodes with variable light intensities up to 2300 μmol m-2 s-1. The photosynthetic unit was successfully used, in combination with online monitoring of oxygen production, to cultivate Arthrospira platensis. In phototrophic growth under continuous light and a 16 h light/8 h dark cycle (light intensity: 180 μmol m-2 s-1), the oxygen transfer rate and biomass-related oxygen production were - 1.5 mmol L-1 h-1 and 0.18 mmol O2 gx-1 h-1, respectively. The maximum specific growth rate was 0.058 h-1, during the exponential growth phase, after which the biomass concentration reached 0.75 g L-1.

With growing environmental concerns, efforts are made to replace petroleum based products with renewable alternatives. This is particularly evident in the packaging industry, where replacing synthetic polymers with renewable materials is of considerable interest. Materials for food packaging need to give protection, acting as a barrier against substances that can adversely affect the food quality such as water and oxygen. In this work, barrier dispersion coatings based on starch were used to produce coated papers which act as barrier against water and oxygen. However, since starch is both a hydrophilic and hygroscopic material, this barrier material becomes problematic to use at high relative humidity. In order to reduce this problem and improve the barrier properties enabling starch based barrier materials to be used in food packaging applications, two approaches were studied. Citric acid was utilized as a cross-linker of the starch and it was found to reduce the moisture sorption, the molecular movement and swelling at high relative humidity. It was seen that cross-linking and hydrolysis due to the low pH both affected the barrier properties significantly, but in opposing directions. By controlling these two reactions it was seen that this could lead to reduced gas permeability. It was also seen that cross-linking of starch by citric acid occurs at low temperatures, 70 °C at pH as high as 6.5. Starch nano-composites were produced by incorporating montmorillonite, to the barrier dispersion to improve the barrier properties. It was seen that the suspension viscosity was reduced by poly(ethylene glycol) and citric acid adsorption on the montmorillonite particles. Also, a tendency for improved barrier properties with reduced aggregate volume fraction and reduced swelling was observed. It was also seen that up scaling this formulation to pilot scale was possible and that promising results were achieved. / Baksidestext With growing environmental concerns, efforts are made to replace petroleum based materials with renewable alternatives such as starch. In this work, dispersions based on starch were used to produce coated papers which act as barrier against substances that can adversely affect the food quality such as water and oxygen. However, since starch is both a hydrophilic and hygroscopic material, this barrier material becomes problematic to use at high relative humidity. Citric acid was utilized as cross-linker for starch and it was found to reduce the moisture sorption, diffusion and swelling at high relative humidity. Both cross-linking and hydrolysis due to the low pH affected the barrier properties significantly, but in opposing directions. By controlling these two reactions it was possible to achieve reduced gas permeability. Starch nano-composites were produced by incorporating montmorillonite clay, to the barrier dispersion. It was seen that the suspension viscosity was reduced by poly(ethylene glycol) and citric acid adsorption on the clay. Also, a tendency for improved barrier properties with reduced aggregate volume fraction and reduced swelling was observed. It was also seen that up scaling this formulation to pilot scale was possible and promising results were achieved. / Renewable Functional Barriers

A megawatt class electron linear accelerator (e-linac) will be constructed at TRIUMF as part of the new ARIEL facility which will produce rare ion beams for the study of nuclear structure and astrophysics, and material science. The 50MeV, 10mA, continuous wave e-linac will drive gamma ray induced fissioning of a Uranium target for the production of neutron rich beam species. View Screens located at a number of places along the e-linac beam-line will acquire two dimensional images of the transverse electron beam profiles, providing measurements of the size, position, and shape of the incident e-linac beam. The design of the View Screens will be presented, based on design studies and simulations performed to evaluate the performance of the View Screens under various operating conditions. These studies include GEANT simulations of the energy loss and scattering of the electron beam as it passes through the scintillation and Optical Transition Radiation beam targets, the subsequent thermal response of the targets, and a ray tracing optics simulation to optimize the configuration of the imaging optics. Bench test have been performed on the resulting optics design to evaluate the imaging characteristics, verifying fulfillment of the design requirements. Construction of a prototype View Screen device is currently underway, with beam tests scheduled for Fall 2011. A total of 14 View Screens will be constructed and installed along the e-linac beam-line. / Graduate