The mucus-dwelling bacteria previously isolated from the surface of a freshwater fish species (Alburnus alburnus from Lake Mogan, Ankara), were studied to discover their cobalt resistance. The minimum inhibitory concentrations (MIC) were determined for a total of thirty six bacterial isolates. The results of the resistance studies led us to design experiments on adaptation to cobalt and subsequent memory retention. Three selected isolates were exposed to an inhibitory cobalt concentration as a mixed culture and individually. The delayed formation of colonies along with competitive exclusion of one of the isolates in the mixed culture were recorded. The delay for colony formation was followed up for liquid culture conditions. After some of our isolates acclimated to cobalt and started to exhibit constant time of growth period, it is assumed that they were adapted. We regarded adaptation as a result of memory formation. Next, we did a further study to find out how long this memory could be retained via serial multiple passages in cobalt free medium. We expressed our observations quantitatively by measuring the growth by using spectrophotometer and by performing viable counts. Interestingly, where there was a high CFU, the photometric values were very low. We interpreted the finding such that the presence of cobalt above tolerance limits were causing size reduction in the cells. So that their presence was underestimated by optic devices in visible range. Our study hinted that freshwater bacteria was adapting cobalt in a memory based mechanism and able to retain this memory for some time.

In this study, polyelectrolyte membranes were prepared by layer-by-layer self-assembly on top of an interfacially polymerized polyamide substrate, and these thin-film-composite membranes were studied for pervaporative dehydration of ethylene glycol, ethanol and isopropanol. The performance of composite membranes based on polyethylenimine/poly(acrylic acid) (PEI/PAA) multilayers on a polyamide substrate showed good selectivity and stability for ethylene glycol dehydration. In order to understand the formation process of the polyelectrolyte multilayers, the growth of polyelectrolyte multilayers fabricated on the inner surface of cuvette was investiagted. The membrane surface became increasingly hydrophilic with an increase in the number of polyelectrolyte double layers, which favored water permeation for pervaporative dehydration of organic solvents. Water contact angle on the membrane surface decreased from 68?? to 20?? when 7 polyelectrolyte bilayers were deposited on the polyamide substrate. Although the (PEI/PAA) based polyelectrolyte membranes showed good performance for dehydration of ethylene glycol, these membranes did not perform well for the dehydration of ethanol and isopropanol at relatively high feed alcohol concentrations. This was found to be caused by insufficient stability of PEI/PAA bilayers and the polyamide substrate in the ethanol and isopropanol. To improve the performance of the composite membranes for dehydration of ethanol and isopropanol, the outermost surface layer was deposited with PEI, followed by crosslinking. A further improvement in the membrane selectivity was accomplished by substituting the PEI with partially protonated chitosan in the last few polyelectrolyte bilayers during membrane fabrication. It was demonstrated that using interfacially polymerized polyamide membrane as a substrate, polyelectrolyte membranes with less than 8 bilayers could be fabricated for the dehydration of alcohol and diol. This represents a siginificant advancement as a large number of polyelectrolyte bilayers (as many as 60) are often needed. Glutaraldehyde crosslinked polyelectrolyte self-assembled membranes comprising of chitosan and PAA were also prepared for isopropanol/water separation. The resulting membrane showed stable performance with good permeation flux and separation factor. The effects of crosslinking conditions (e.g., concentration and temperature of crosslinking agent, and crosslinking time) on the membrane performance were studied. Alternatively, using PEI as polycation, when anionic PAA was substituted with alginate in the last few polyelectrolyte bilayers during membrane fabrication, stable membranes with a good performance were obtained without the need of chemical crosslinking. The polyethylenimine/alginate self-assembly membranes showed good selectivity and stability for dehydration of ethanol. For instance, a permeation flux of 0.24 kg/(??? h) and a separation factor of 206 were obtained at room temperature at 10 wt% feed water concentration with a membrane comprising of 10 double layers of polyelectrolytes.

Submitted by Maike Costa (maiksebas@gmail.com) on 2016-05-10T13:37:38Z No. of bitstreams: 1 arquivo total.pdf: 3109388 bytes, checksum: 647810f9fb25d144a271d5f256240096 (MD5) / Made available in DSpace on 2016-05-10T13:37:38Z (GMT). No. of bitstreams: 1 arquivo total.pdf: 3109388 bytes, checksum: 647810f9fb25d144a271d5f256240096 (MD5) Previous issue date: 2015-08-27 / Coordenação de Aperfeiçoamento de Pessoal de Nível Superior - CAPES / A spectrophotometer for absorption measurements / emission, simple, portable and as partially partial dual mode for quantitative experiments was constructed using cheap and available materials is proposed in this paper. The instrument, here called SpectroPhone consists of modules made of MDF, one DVD as a diffraction grating media, two mini white incandescent lamps as radiation source and a Smartphone to acquire images and perform data processing, such as detector. The pixels of a region produced in a spectral images provide qualitative and quantitative information after the application of the concepts and HSV color model RGB, respectively. A simple algorithm based on HSV was developed for the conversion of the hue values (H) in their corresponding λ. Its analytical performance was assessed by quantitative analysis based on analytical curves, specimens of which have been validated by analysis of variance (ANOVA). The SpectroPhone was applied to the determination of Fe2+ in the absorption mode in pharmaceutical samples, and Na+, in emission mode and in natural saline water. For comparison purposes, a commercial spectrophotometer for absorption mode and a photometer for commercial flame emission mode were used to construct the calibration curves of the reference instrument. Applying the paired t test at 95% confidence for the results of concentrations obtained with the instruments, it is observed that there was no statistically significant difference showing high precision and accuracy. SpectroPhone can be considered a good alternative to instrumental spectrometric measurements, not just limited to educational and academic purposes. / Um espectrofotômetro para medidas de absorção/emissão, simples, parciamente portátil e modo duplo parcial para experimentos quantitativos foi construído usando materiais baratos e disponíveis é proposto neste trabalho. O instrumento, aqui chamado de SpectroPhone é composto por módulos confeccionados em MDF, uma mídia de DVD como rede de difração, duas mini lâmpadas incadescentes branca como fonte de radiação e um Smartphone para adquirir imagens e realizar tratamento de dados, como detector. Os pixels de uma região produzida em uma imagens digital fornecem informações qualitativas e quantitativas após a aplicações do HSV e conceitos do modelo de cor RGB, respectivamente. Um simples algoritmo baseado em HSV foi desenvolvido para a conversão dos valores do matiz (H) em seu λ correspondentes. Seu desempenho analítico foi avaliado por meio de análises quantitativas baseados em curvas analíticas, cujos modelos foram validados por meio da análise de variância (ANOVA). O SpectroPhone foi aplicado na determinação de Fe2+ no modo de absorção em amostras farmacêuticas, e Na+, no modo de emissão em soro fisiológico e em água naturais. Para fins de comparação, um espectrofotômetro comercial para o modo de absorção e um fotômetro em chama comercial para o modo de emissão foram empregados para construir as curvas analíticas do instrumento de referência. Aplicando o teste t pareado ao nível de 95% de confiança para os resultados de concentrações obtidas com os instrumentos, observa-se que não houve diferença estatisticamente significativa apresentando alta precisão e exatidão. O SpectroPhone pode ser considerado uma boa alternativa instrumental para medições espectrométricas, não apenas limitada para fins didáticos e acadêmicos.

Commercially available organic and conventionally grown vegetables were studied by quantitative determination of selected metals in them and to determine if any differences found are statistically significant. These findings can help the consumers to determine if the vegetable products are within the recommended maximum limits as proposed by the joint FAO/WHO Expert committee on organic foods designation. Eight edible vegetables were purchased from local stores in both the organic and conventionally grown categories. Samples were digested with concentrated nitric acid and the metals monitored were zinc, copper, lead, iron, cadmium, and nickel using flame atomic absorption. The concentration range for the heavy metals found are as follows: Zn, 2.04-69.4; Cu, 0.35-15.1; Pb, 0.00-3.99; Cd, 0.00-0.74; Fe, 2.52-319; and Ni, 39.9-53.8 μg/g. It was found that in general, conventional vegetables contain higher amounts of most of the heavy metals studied as compared to their organic counterparts. The study also showed that all vegetables products contain below the permissible limits for Zn, Cu, Ni, and Fe. For Pb all vegetables exceeded the safe limit except organic cucumber and conventional cabbage. For Cd, organic lettuce and green pepper, and conventional leafy green, green pepper, and spinach all exceeded the limit recommended by FAO/WHO.

No description available.

Syfte: Syftet med föreliggande studie är  att undersöka högtranslucent zirkonias benägenhet till missfärgning beroende på ytbehandling och hur detta påverkar materialets färgstabilitet över tid. Material och metod: Totalt frästes och sintrades 40 cylindriska provkroppar av högtranslucent zirkonia. Provkropparna delades slumpmässigt in i grupp G (glansbrända provkroppar) och grupp P (mekaniskt polerade provkroppar). Ytbehandling utfördes genom mekanisk polering eller glansbränning. Därefter utsattes provkropparna för vätskeförvaring i svart kaffe eller svart te under 288 timmar. Provkropparna mättes med en dental spektrofotometer efter 72, 144, 216 och 288 timmar. Mätningarna utfördes tre gånger centralt på varje provkropp. Mätvärdena L*c*h och ΔEab användes för att beskriva och analysera eventuell missfärgning och färgskillnad hänvisat till NBS-klassificering. Resultat: Det fanns inte någon signifikant skillnad vad gäller missfärgning på högtranslucent zirkonia. Detta var oberoende ytbehandling och förvaring i svart kaffe eller svart te, under en tidsperiod som motsvarade ett års oral exponering. De mekaniskt polerade provkropparna som förvarades i svart te uppvisade störst färgskillnad, det högsta ΔE-värdet, efter 288 timmars förvaring. Resultatet visade på en liten färgförändring enligt NBS-klassificeringen. Slutsats: Ytbehandling genom polering eller glansbränning ger bra egenskaper när det gäller motstånd mot missfärgning. En glansbränd yta visar en tendens att inte påverkas av missfärgning lika mycket som en mekaniskt polerad yta. / Purpose: The purpose of the present study is to investigate the tendency of highly translucent zirconia to discolour depending on surface treatment and how this affects the color stability of the material over time. Material and method: A total of 40 cylindrical specimens of high translucent zirconia were milled and sintered. The specimens were randomly divided into group G (glazed specimens) and group P (mechanically polished specimens). Surface treatments were performed by mechanical polishing or glazing. Subsequently, the specimens were subjected to liquid storage in black coffee or black tea for 288 hours. The specimens were measured using a dental spectrophotometer after 72, 144, 216, and 288 hours. The measurements were performed three times centrally on each specimen. The L*c*h and ΔEab values were used to describe and analyze any discoloration and color difference referred to NBS classification. Results: There was no significant difference in discoloration of high-translucent zirconia. This was independent of surface treatment and storage in black coffee or black tea, for a period equivalent to one year of oral exposure. The mechanically polished specimens stored in black tea showed the highest ΔE value (color difference) after 288 hours of storage. However, the results showed a slight change according to the NBS classification. Conclusion: Surface treatment by polishing or burnishing gives good properties in terms of resistance to discoloration. A burnished surface shows a tendency not to be affected by discoloration as much as a mechanically polished surface.

Thesis (MScEng (Process Engineering))--University of Stellenbosch, 2010. / Thesis submitted in partial fulfilment of the requirements for the degree of MASTER OF SCIENCE IN ENGINEERING (MINERAL PROCESSING) in the Department of Processing Engineering at the University of Stellenbosch / ENGLISH ABSTRACT: This work evaluates the use of inverse least squares (ILS) and classical least squares (CLS) models for calibration of a diffuse reflectance spectrophotometer for on-line monitoring of the aqueous phase in a flotation cells. Both models use a Beer's law for the quantification of the metals. The formulated statistical models are compared to a proprietary Blue Cube model in terms of prediction ability to determine the potential applicability of the models. A diffuse reflectance spectrophotometry was used for simultaneous analysis of copper (Cu), cobalt (Co) and zinc (Zn) in the solutions. The laboratory set-up of Blue Cube instrument was used for the experimental analysis. The concentrations and matrix compositions of the samples are simulated according to Skorpion zinc mine plant conditions. The calibration samples were prepared using a simplex-centroid mixture design with the triplicates of the centroid run. The unknown or test samples were prepared randomly within the same concentration of the calibration samples. The effects of temperature and nickel concentration on absorption of the metals were evaluated in the following range, 20 - 80 °C and 125 - 400 ppm, respectively. The statistical models (ILS and CLS) were calibrated from visible and near infrared (VNIR) spectra data of the calibration samples. A modified Beer's method was used as a preprocessing technique to convert the raw data into absorbance values. The manual wavelength selection procedure was used to select the wavelengths to be used in both models. The quality of the models was evaluated based on Rª and % root mean squared error (RMSE) values with 0.90 and 10% used as the guideline for the respective statistical parameters. Both ILS and CLS models showed good results for all three metals (Cu, Co and Zn) during their calibration steps. It was further shown that both models give worse predictions for Zn as compared to other metals due to its low relative intensity in the mixture. The derivative orders of absorbance spectra that were used to enhance the prediction results of Zn had no positive effect but they rather lowered accuracy of predictions. An increase in temperature was found to increase the intensities of the absorption spectra of all the metals while an increase in nickel concentration decreases the prediction ability of model. The developed statistical models were compared to a Blue Cube model in terms of prediction ability using analysis of variance (ANOVA) test. The ANOVA results revealed that there is no statistical difference between the developed models and Blue Cube model since the F-values for all the metals were below the critical F-value. Furthermore, the partial least squares (PLS) model shows an increased accuracy results for prediction of zinc metal as compared to both the ILS and CLS models. Finally, good comparisons of the statistical models results with atomic absorption spectroscopy (AAS) analyses were establish for the unknown samples. The study demonstrates that chemometric models (ILS and CLS) developed here can be used for quantification of several metals in real hydrometallurgical solutions as samples were simulated according to a plant conditions. However, in order to have confidence in the results of the models, a factorial-mixture design must be used to study the effect of temperature and nickel concentration. Moreover the models must be further tested and validated on the real samples from a plant. / AFRIKAANSE OPSOMMING: Hierdie werkstuk evalueer die gebruik van inverse kleinste kwadraatmetodes (IKK) en klassieke kleinste kwadraatmetodes (KKK) vir die kalibrasie van 'n diffuse reflektansiespektrofotometer vir die aanlyn monitering van die waterige fase in flottasieselle. Beer se wet word vir die kwantifisering van metale vir albei modelle gebruik. Die omskrewe data-gebaseerde modelle is op grond van voorspellingsvermoë vergelyk met'n. Blue Cube model, sodat die moontlike toepaslikheid van hierdie modelle bepaal kan word. 'n Diffuse reflectantie spektrofotometrie is ingespan vir die gelyktydige analise van koper (Cu), kobalt (Co) en sink (Zn) in oplossing. Eksperimentele analises is met behulp van 'n laboratoriumopstelling met 'n Blue Cube instrument uitgevoer. Die konsentrasies en matriks-samestellings van monsters is gesimuleer om Skorpion sinkmyn aanlegkondisies na te boots. Kalibrasie monsters is voorberei volgens . simpleks-sentroïed mengselontwerp met drievoudige sentroïede lopies. Onbekende (toets) monsters is ewekansig voorberei binne dieselfde konsentrasie spesifikasies as die kalibrasie monsters. Die invloed van temperatuur en nikkelkonsenstrasie op die absorpsie van die metale is in die bestek van 20 - 80 °C en 125 - 400 dpm, onderskeidelik, bepaal. Die data-gebaseerde modelle (IKK en KKK) is met sigbare en naby infrarooi (SNIR) spektra data van die kalibrasie monsters gekalibreer. 'n Gewysigde Beer metode is vir data voorbereiding benut om rou data na absorbansie waardes om te skakel. Die handgolflengte-seleksieprosedure is vir beide modelle gebruik om die golflengtes te kies. Die kwaliteit van die modelle is op grond van Rª en % wortel gemiddelde kwadratiese fout (WGKF) geevalueer, met waardes van 0.90 en 10% (onderskeidelik) as riglyne vir hierdie statistiese parameters. Beide IKK en KKK modelle het vir hul kalibrasie stappe vir al drie metale (Cu, Co en Zn) goeie resultate getoon. Dit is verder getoon dat albei modelle die slegste voorspellings lewer vir Zn (vergeleke met die ander metale) as gevolg van Zn se lae relatiewe intensiteit in die mengsel. Afgeleide ordes van absorbansie spektra is gebruik om die Zn voorspellings te versterk, maar het geen positiewe effek gehad nie; inteendeel, voorspellingakkuraatheid is verlaag. ʼn Verhoging in temperatuur het die intensiteite van die absorpsie spektra van alle metale verhoog, terwyl ʼn verhoging in nikkelkonsentrasie die voorspellingakkuraatheid van die modelle verlaag het. Die ontwikkelde data-gebaseerde modelle is met ʼn Blue Cube model vergelyk in terme van voorspellingsvermoë met behulp van variansie-analise (ANOVA). Die ANOVA resultate toon dat daar geen statistiese verskil tussen die ontwikkelde modelle en die Blue Cube model is nie, aangesien die F-waardes vir al die metale onder die kritiese F-waarde is. Die gedeeltelike kleinste kwadraatmodel (GKK) toon verder verhoogde voorspellingakkuraat-heid vir sinkmetaal tenoor beide die IKK en KKK modelle. Ten slotte, goeie ooreenstemming van die data-gebaseerde modelresultate met atoomabsorpsie spektroskopie (AAS) analise is vir die onbekende monsters gevind. Hierdie werkstuk toon dat die chemometriese modelle (IKK en KKK) wat hier ontwikkel is, gebruik kan word vir die kwantifisering van verskeie metale in werklike hidrometallurgiese oplossings, aangesien monsters gesimuleer is volgens aanlegkondisies. Om egter verdere vertroue te hê in die modelresultate, sal ʼn faktoriaal-mengselontwerp toegepas moet word om die effek van temperatuur en nikkelkonsentrasie te ondersoek. Voorts moet die modelle verder getoets en gevalideer word op werklike monsters van ʼn aanleg.

My master's thesis deals with creating of a suitable evaluation technique that optimizes the optical parameters of the thin films according to the specified requirements of the proposer. This technique will be used at the Faculty of Mechanical Engineering and it should facilitate the evaluation of measurement results of the The Institute of Physical Engineering workers. Research workers use a digital imaging spectrophotometer for some measurements of optical properties of thin films at the institute. My most important task is to process the output data of the spectrophotometer concerning selected thin film. Construed master's thesis describes all the tools and techniques that have been used for the implementation of the program including evolutionary techniques and basics of the thin films optics (within the framework of the electromagnetic optics). As an enclosure, an electronic medium with the source codes of the whole application is provided.

[pt] A avaliação de artigos brancos tratados com alvejantes ópticos, como eles são comuns em substratos têxteis, plásticos e de papel, é uma tarefa que tradicionalmente resulta em muitas divergências entre avaliações visuais realizadas em uma cabine padronizada e avaliações instrumentais realizadas com espectrofotômetros de refletância. Mesmo entre as avaliações visuais ou entre as avaliações instrumentais são encontradas diferenças muito além do aceitável. Uma das principais causas é a fluorescência dos alvejantes ópticos que é influenciada pela quantidade de radiação UV em relação com a radiação na faixa visível do espectro. O trabalho apresentado analisa as diferentes formas de avaliação, principalmente do ponto de vista da qualidade da distribuição espectral de potência do simulador de luz do dia. No caso das avaliações visuais, são testadas diferentes lâmpadas fluorescentes. Para as avaliações instrumentais, a calibração e o ajuste de UV em conjunto com as diferentes aberturas de medição são analisados. O objetivo é aprimorar os aspectos metrológicos da avaliação e contribuir para a sua padronização a fim de garantir a maior reprodutibilidade de resultados, um procedimento importante e almejado por todos os segmentos industriais que utilizam os alvejantes ópticos. / [en] The evaluation of white objects treated with fluorescent whitening agents, such as they are commonly found on substrates like textiles, plastics and paper, is a task that traditionally leads to frequent controversy between the visual evaluations performed in a standardized light booth and the instrumental evaluations performed on reflectance spectrophotometers. Even between visual or instrumental evaluations the differences encountered are far beyond the acceptable. One of the main reasons is the fluorescence of the optical brightening agents that is influenced by the amount of UV radiation in relation to the amount of radiation in the visible range of the spectrum. The work presented analyses the different forms of evaluation, mainly from the point of view of the quality of the daylight simulators´ spectral power distribution. In the case of the visual evaluations, different fluorescent lamps are tested. For the instrumental evaluations, the UV calibration and adjustment are analyzed together with the different measurement apertures. The objective is to improve the metrological aspects of the evaluation and contribute to its standardization with the aim to guarantee better reproducibility of results, an important procedure that is desired by all the industrial segments that use optical brighteners.

Para a fabricação de filtros ópticos com característica espectral crítica, utiliza-se a tecnologia de filmes finos multicamadas, a qual exige o monitoramento e controle de espessura dos filmes com alta precisão. O sistema tradicional de monitoramento de espessura de filmes, baseado em cristal ressonante, não atende aos requisitos de precisão e repetibilidade do processo exigidos para a fabricação deste tipo de filtro. Já o monitoramento óptico, por sua vez, é um sistema que atende aos requisitos de fabricação destes filtros. Neste trabalho apresenta-se o desenvolvimento de um sistema automático de monitoramento óptico banda larga, para fabricação de filtros com filmes finos multicamadas, que se baseia na utilização de equipamentos ópticos de uso geral disponíveis no mercado. Para realizar análises de desempenho referentes exclusivamente ao algoritmo de automatização, um ambiente de simulação foi preparado, no qual os dados fornecidos pelo equipamento de aquisição de características ópticas durante a deposição efetiva foram substituídos por dados gerados por um algoritmo de simulação de crescimento do filme. Deste modo, o algoritmo de automatização e seus sistemas de segurança puderam ser exercitados. As simulações mostraram que o sistema proposto possui potencial para tornar mais preciso e repetitivo o processo de fabricação de filtros, de modo que atendam aos requisitos das aplicações especiais. / Optical filter manufacturing with critical spectral characteristics uses multilayer thin film technology, which demandas film thickness monitoring and control with high precision. Traditional monitoring systems based on oscillating crystal do not fulfill requirements of accuracy and process repeatability for manufacturing such type of filter. On the other hand, optical broadband monitoring system fulfills the manufacturing requirements to produce these filters. This work presents the development of a broadband optical monitoring system for multilayer thin film filters production, based on general optical equipment commercially available. In order to make the performance analysis related to automation algorithm, a simulation environment has been prepared, where the data supplied by optical data acquisition equipment has been replaced by simulating signals of film growing. Thus the automation algorithm and security systems could be worked. Simulations showed that the system has potential to improve the accuracy and repeatability of the manufacturing process so that the produced filters are able to fulfill the requirements of special applications.