Measurement of urine absorbance which has been irradiate by a dose of ionising radiation with addition of Mn2+ should serve to find the dose of radiation. This method could work quickly and reliably for homogeneous irradiation of person or as a rough estimate of the dose which the person received during a radiation accident. This method should serve for quick classification of the person. The target of this thesis is to find out if the irradiated urine with the addition of a solution of manganese chloride will change absorbance according to radiation dose. And if urine can be used as a biological dosimeter. In the theoretical part I describe the basic areas related to the topic and target of my thesis. This part is divided to seven subchapters: ionising radiation, radiation protection, radiotherapy, particle accelerators, spectrophotometry, excretion and urine, and dosimetry and its methods. Methods of this thesis are not clear. I tried different procedures during experiments with different results. First, I always prepared samples of urine in tubes and irradiated it in a linear accelerator Clinac 2100C/D in České Budějovice, a.s. hospital with doses from 1 to 25 Gy. Before each measurement I had two sets of tubes with these doses: 0, 1, 2, 3, 5, 7, 10, 15, 20 and 25 Gy. The following procedure was different in each experiment. Sometimes I tried adding a solution of manganese chloride to all tubes at once. Sometimes I tried to adding a solution of manganese chloride to each tube separately. I added the solution to irradiated urine at various concentrations of solution (from 1 do 5 mols) and different amounts (from 1 to 3 ml). Another difference was the use of centrifuges. A centrifuge was use in about half of experiments. Other measurements were made without centrifugation.In discussion I propose recommended methods. I recommend measuring only without centrifuges. Each cell should be measured as soon as possible after irradiation and simultaneously as soon as possible after adding the solution of manganese chloride. Results of the thesis are not clear. Only some experiments which were measuring with centrifuge were clear. I can say that this method does not work when a centrifuge is used at any tested concentration of solution of manganese chloride. The absorbance of single doses of ionising radiation does not change and the values were the same when using 1M, 3M and 5M solutions of MnCl2. The resulting graphs from all experiments have a constant absorbance value of all measured doses. (subchapter 3.1).In the remaining experiments measured without the centrifuge the results were much more interesting. In some experiments the measured absorbance really changed with the dose of ionising radiation so the hypothesis of this study was confirmed. But the differences were too small for this method to be used for measuring radiation doses (subchapter 3.2).The results were compared with the results of the thesis ?Measurement of urine extinction in depending on ionising radiation? from author Š. Radová. She performed a similar experiment, but with a different indicator - FeSO4. 7 H20. It was found that the indicator FeSO4. 7 H20 is preferable to measuring doses of ionising radiation in urine. In conclusion I can say that the hypothesis of this study was confirmed, but the method could not be used in practice and irradiated urine with added MnCl2 indicator does not function as a biological dosimeter.

No description available.

Our cells are constantly dealing with DNA damage generated by endogenous cellular activity (e.g. DNA replication) and exogenous agents (e.g. ultraviolet and ionizing radiation (IR)). The cellular stress response to DNA damage requires strict co-ordination between cell cycle checkpoint control and DNA repair. In response to DNA double-strand breaks (DNA-dsbs), members of the phosphatidylinositol 3-kinase–related kinase family (e.g. ATM and DNA-PKcs kinases) have been shown to redundantly phosphorylate substrates including the DNA-dsb marker, gamma-H2AX, and the p53 tumour suppressor protein. The p53 protein is best known as the guardian of the genome through its transcriptional-dependent and -independent functions. Despite a clear link between ATM-dependent phosphorylation of p53 with cell cycle checkpoint control and various modes of DNA damage repair, the intracellular biology and sub-cellular localization of p53 and specifically its phosphoforms during DNA damage induction and repair remains poorly characterized. Using G0/G1 confluent primary human diploid fibroblast cultures, this thesis shows that endogenous p53, phosphorylated at serine 15 (p53Ser15), accumulates as discrete, dose-dependent and chromatin-bound foci within 30 minutes following the induction of DNA breaks. This biologically distinct sub-pool of p53Ser15 is ATM-dependent and resistant to 26S-proteasomal degradation. p53Ser15 co-localizes and co-immunoprecipitates with gamma-H2AX with kinetics similar to that of biochemical DNA-dsb rejoining. Sub-nuclear microbeam irradiation studies confirm that p53Ser15 is recruited to sites of DNA damage containing gamma-H2AX, ATMSer1981 and DNA-PKcsThr2609 in vivo. Furthermore, studies using isogenic human and murine cells, which express Ser15 or Ser18 phosphomutant proteins, respectively, show defective nuclear foci formation, decreased induction of p21WAF, decreased gamma-H2AX-association and altered DNA-dsb kinetics following DNA damage. We further hypothesized that the non-specific DNA binding activity of the p53 carboxy-terminus mediates chromatin anchoring at sites of DNA damage. YFP-p53 fusion constructs expressing carboxy-terminus deletion mutants of p53 were transfected into p53-null H1299 cells to determine the role of the carboxy-terminus in chromatin-binding pre- and post-IR, independent of transcriptional activity. Within this isogenic human cell system, we observed exogenous YFP-p53WT associated with ATMSer1981 and 53BP1 within cellular chromatin in a dynamic manner. We confirmed that these associations also occurred between endogenous WTp53 with ATMSer1981 and 53BP1 within the chromatin of primary human diploid fibroblasts. YFP-p53del1-299 fusion proteins, which lack transcriptional activity and the Ser15-residue, also associated within chromatin. Ser15-phosphorylation was found not to be essential for DNA damage-induced association of p53 with chromatin or with ATMSer1981 and 53BP1. These data suggest a unique biology for p53Ser15 phosphoforms in the initial steps of DNA damage signaling and implicates ATM-p53-53BP1 chromatin-based interactions as mediators of cell cycle checkpoint control and DNA repair. And we propose a model whereby a pre-existing pool of p53 that constantly scans the genome, responds immediately to radiation-induced DNA damage by virtue of its association with chromatin through its carboxy-terminus. The consequences for these p53-ATMSer1981-53BP1 complexes following DNA damage remains to be investigated: could residual complexes be associated with decreased DNA-dsb rejoining or error-prone repair, or could these complexes signal for cell survival or cell death? Since altered p53 function and biology is an important factor in cellular carcinogenesis and response to cancer therapy, this study provides a step towards a greater understanding of WTp53 and MTp53 biology in tumour development and therapeutic resistance, in the hopes to contribute towards predicting therapeutic response and/or improving p53-targeted therapies.

Currently, it is very challenging to accurately monitor the response of patients to radiation therapy over the course of treatment. The initial response to ionizing radiation occurs in the cells at a molecular level, and effects of the response are not typically noticeable on short time scales. Surface-enhanced Raman Spectroscopy, or SERS, has proven to be a useful technique in the analysis of tissues and cells at a molecular level. Specifically, the use of targeted SERS probes allows for the detection of specific proteins on the cell membrane. The work presented here looks to assess the feasibility of using targeted SERS probes and two-dimensional SERS microscopy to measure the response of tumour cells to ionizing radiation, by identifying changes in the distribution of membrane proteins following exposure to clinically relevant doses of ionizing radiation (≤ 60Gy). Two different types of targeted SERS probes were investigated, based on the work of Grubisha et al. ([1]; Type I) and Qian et al. ([2]; Type II), both containing a gold nanoparticle core. In a simplified cellular experiment, biotin on the surface of biotinylated OVCAR5 cells was targeted with streptavidin-SERS probes, and the Type-II SERS probes showed the most promising results. However, SERS maps still provided less characteristic spectral signal than expected, and challenges remain in the development of a reproducible cellular imaging technique. Despite difficulties in cellular imaging, the functionality of the Type-II SERS probes was verified separately, using gold slides with a biotin monolayer in place of cells. Following verification, the SERS intensities provided by differently sized clusters of the SERS probes were characterized. To begin, both SERS maps and scanning electron microscope (SEM) images of gold slides were acquired after incubation with Type-II SERS probes for multiple times (1hr, 2hr, 3hr, 12hr). Data analysis of the SEM images provided a measure of the physical distribution of the SERS probes on the surface of the slide, while analysis of the SERS maps provided information about the spectral distribution of the probes. By relating the information provided by the SEM images and SERS maps, a simple polynomial relationship between SERS intensity and the number of clustered SERS probes providing the enhancement was determined, providing a framework for quantifiable SERS imaging. Finally, an independent experiment was devised to ensure that exposure to clinically relevant doses of ionizing radiation would affect the ability of the targeted protein to bind to SERS probes, thus leading to measurable differences in SERS maps of irradiated and unirradiated cells. A series of experiments utilizing the enzyme-linked immunosorbant assay (ELISA) was performed to test the effect of ionizing radiation-induced damage on the ability of streptavidin to bind to biotin, and the results confirmed that a noticeable reduction in binding could be detected at doses as low as 10 Gy. The results of this work demonstrate that following the development of a suitable cell/SERS probe incubation technique, Type-II SERS probes would be appropriate for use in quantifiable SERS imaging. Also, it is suggested that a measurable change in protein function will be present when comparing SERS maps of control cells to those of cells irradiated to clinically relevant doses. / Graduate

Humans are constantly exposed to different types of radiations. It has been suggested that low dose and low dose rate of γ-radiation as well as ultra violet A (UVA) induce oxidative stress in cells that may promote mutations. The mechanisms behind radiation-induced oxidative stress and its relation to genotoxicity and cancer induction are not well understood. In the majority of investigations, the DNA molecule has been studied as the target for mutations, however the results obtained in our group point out that DNA bases in the cytoplasm could also be a significant target. MTH1 and MYH are two of the key proteins of the repair pathway that prevent mutations arising from oxidized DNA bases. In this thesis, we studied the role of MTH1 and MYH in genotoxicity of UVA and γ-radiation. The adaptive response to low dose rates of γ-radiation was also investigated. MTH1 and/or MYH were knockdown in human lymphoblastoid TK6 cells. The clonogenic survival, mutant frequency and chromosomal aberration assays were performed following UVA or γ-radiation exposure. Our results indicated that acute exposure to UVA or γ-radiation affects cell survival and also increases the mutant frequency above the background. The mutant frequency in MTH1 deficient cells was higher than that in wild types after UVA exposure. Following γ-radiation exposure, a higher mutant frequency was observed in the MYH and MTH1 deficient cells, in comparison to either MYH or MTH1 deficient or wild type cells. No dose rate effect of γ-radiation for mutations was observed. An adaptive response to γ-radiation was observed at the mutation level in MCF-10A cells but not at the survival level. In summary, our results suggest that; a) MYH and MTH1 cooperatively protect cells against genotoxic effects of γ-radiation; b) MTH1 protects cells from UVA-induced mutations; c) low dose rates of γ-radiation may induce an adaptive response at the mutation level; d) there is no dose rate effect for γ-radiation at the mutation level. / <p>At the time of the doctoral defense, the following papers were unpublished and had a status as follows: Paper 2: Manuscript. Paper 3: Manuscript.</p>

The Wilms' tumor 1 gene is overexpressed in many types of cancer and is associated with poor prognosis and resistance to anti-cancer therapies. In vitro studies in non-glioma cells types have demonstrated that WTl plays a role in increased proliferation, resistance to apoptosis, and increased cellular invasion. We aimed to thoroughly characterize the expression pattern of Wilms' tumor 1 in human malignant glioma and discern its function in this complex disease process. We screened a large sample of established human malignant glioma cell lines and glioma tissue specimens of all grades for WT1 expression. The majority of cell lines and 80% of all glioma tissue expressed WTI mRNA, all of which expressed WTl(+KTS) isoforms. Further screening of the glioblastoma specimens for p53 mutation followed by logistic regression analysis demonstrated a positive correlation between WTl expression and wild-type p53 (p = 0.04). To determine if WTl and p53 functionally interacted, we generated LN-229 glioblastoma cells that stably expressed WTl. As LN-229 cells harbor a p53 mutation, transient transfection with wild-type p53 induced apoptosis. However, stable WTI expression did not protect cells from p53-mediated cell death. We then generated U87MG cells (p53 wild-type) that stably expressed WT1 to model an endogenous p53 response. It is well known that after treatment with ionizing radiation, U87MG cells readily undergo p53-mediated apoptosis. Again, WTI expression did not protect against ionizing radiation induced p53-mediated cell death. We next examined the effect of transient WTI silencing on ionizing radiation induced cell death in T98G and LN-18 cells which express endogenous WTl. Combination treatment with ionizing radiation and silencing of WTI using short interfering RNA caused a decrease in viability and clonogenic survival relative to radiation alone in both cell lines. Lastly, we studied the effect of stable WTl silencing using short hairpin RNA on glioblastoma cell tumorigenicity. Stable transduction of U25 1MG and LN-18 cells with WTI short hairpin RNA resulted in a marked decrease in proliferation. WTI silencing in U251MG cells also caused a decrease in in vitro invasion. WTl silencing in U251MG cells caused an increase in tumor latency and a decrease in tumor growth rate when cells were used to subcutaneously inoculate nude mice. Not only do these studies support an oncogenic role for WTI in glioma biology, they provide encouraging evidence that WTl may be a therapeutic target for molecular treatment of glioblastoma.

Os agentes físicos e químicos presentes nos ambientes de trabalho podem colocar a saúde dos colaboradores em risco. A radiação ionizante é um dos agentes físicos aos quais os trabalhadores podem estar expostos. Esta radiação possui energia superior à energia de ligação dos elétrons e, desta forma, pode causar a ionização de moléculas, ou seja, causar o rompimento das ligações moleculares. A exposição de tecidos vivos a este agente pode provocar mutações genéticas nas células e a doença mais comum que pode ocorrer é o câncer. Grande parte da exposição à radiação ionizante ocorre devido à presença de radônio nos ambientes de trabalho. Ambientes de mineração são mais suscetíveis a conter este gás pois ele é emanado a partir do solo ou das rochas, principalmente quando há cominuição destes materiais. Para identificar a condição perigosa e propor medidas de controle desta exposição, é necessário que seja aplicada uma metodologia para fazer um levantamento qualitativo e quantitativo. Este trabalho tem como objetivo avaliar uma proposta de medição, além de avaliar o risco de exposição a este gás. O estudo foi realizado em ambientes de mineração, mais especificamente nos postos de trabalho onde foi identificado que a exposição ao agente pode ser maior. As amostragens foram realizadas utilizando o equipamento RadonMapper e os resultados foram analisados e correlacionados. Foi observado que há correlação estatística no método utilizado, também pôde ser observado que as gerências dos locais em que as amostragens foram realizadas desconheciam a possibilidade de exposição ao este gás. Também foi possível indicar que em ambientes abertos, o risco da exposição a este gás é baixo. Desta forma, conclui-se que os objetivos desta dissertação foram atingidos. / Physical and chemical agents in work environments can be a risk for the health of employees. The ionizing radiation is one of the physical agents to which the workers can be exposed. This radiation have more energy than the binding of electrons and, in this way, can cause the ionization of molecules, which is to cause the molecular connections to break. The exposure of living tissue to this agent can cause genetic mutations in them and the most common disease that can occur is cancer. Much of the exposure to ionizing radiation occurs because of the presence of radon in the workplace. Mining environments are more susceptible to contain this gas because it is emanated from soil or rocks. To identify the risk and propose measures to control this exposure, it is necessary to apply a methodology to make a qualitative and quantitative analysis, this is the objective of this study, in addition to assessing the risk of exposure to this gas. The study was conducted in mining environments, more specifically in the workplace where it was identified that exposure to the agent may be higher. Samplings were performed using the RadonMapper equipment and the results were analyzed and correlated. The results indicated that there is statistical correlation in the method used, it could also be observed that the management of the locations where the samples were taken did not know the possibility of exposure to this gas. It was also possible to indicate that in open environments, the risk of exposure to this gas is low. In this way, it is concluded that the objectives of this study have been achieved.

O resveratrol, encontrando principalmente sob as formas trans-3,5,4\',5-trihidroxiestilbeno e cis-3,5,4\'-trihidroxiestilbeno é uma substância que possui muitas propriedades benéficas a saúde, entre elas, vasodilatação, metabolismo de lipoproteínas, inibição da agregação de plaquetas e até mesmo possui ação terapêutica e preventiva de câncer. Um importante destaque é a sua capacidade de agir como antioxidante, o tornando atraente para uso como substância radiomodificadora. A radiação ionizante (RI), que é utilizada na radioterapia, pode ocasionar diversos danos a células saudáveis, seus componentes e estruturas moleculares, dependendo da dose absorvida e do tipo de célula. O Danio rerio é um modelo animal ideal para avaliação dos efeitos biológicos da RI. Neste trabalho, o resveratrol foi avaliado como potencial radiomodificador em ensaios com embriões de Danio rerio expostos em diferentes horas pós fertilização(hpf), com e sem o córion, a radiação gama. Todos os ensaios foram baseados no protocolo da OECD 236. Para entender os efeitos na mortalidade dos embriões expostos ao resveratrol a radiação separados, foram obtidos valores de CL50 e DL50, respectivamente. Os resultados foram: CL50 de 154 &mu;M (para embriões de 2hpf), 283 &mu;M (para embriões de 12hpf), 699 &mu;M (para embriões de 24 hpf sem córion). E DL50 de 11,50Gy e 12,18Gy (embriões de 4 e 6hpf), 24,8Gy (embriões de 24hpf com córion) e 16,99(embriões de 24 hpf sem o córion). A partir destes resultados foram escolhidas as concentrações de 15, 30 e 60 &mu;M de resveratrol e as doses 5 e 15 Gy (para embriões de 4 e 6 e 24 hpf sem córion) 10 e 20 Gy (para embriões de 24hpf com córion) de radiação gama para observar a atividade radiomodificadora do resveratrol em ensaios com duração de 144 horas, a cada 24 horas foram contabilizados os embriões mortos para comparação estatística por meio do teste Z. Houve diferença na porcentagem de mortalidade em todos os ensaios, mas para embriões expostos a radiação com 24hpf sem córion na presença de 30&mu;M de resveratrol essa diferença foi estatisticamente significativa apontando um indício de radioproteção. Nos embriões de 24hpf sem córion irradiados na presença de 60&mu;M a mortalidade dos embriões irradiados é foi maior quando comparada apenas aos irradiados, indicando que em concentrações mais altas o resveratrol pode exercer a função de radiosensibilizador, embora neste caso não tenha sido estatisticamente significativo, o resultado corrobora com dados na literatura que indicam ação sensibilizadora do composto em células expostas a radiação nessa mesma concentração. / Resveratrol, mainly found in the forms trans-3,5,4 \', 5-trihydroxystilbene and cis-3,5,4\'-trihydroxystilbene is a substance that has many beneficial health properties, among them, vasodilation, lipoprotein metabolism, inhibition of platelet aggregation and even has therapeutic and preventive action of cancer. An important highlight is its ability to act as an antioxidant, making it attractive for use as a radiomodifying substance. Ionizing radiation (IR), which is used in radiotherapy, can cause various damage to healthy cells, their components and molecular structures, depending on the absorbed dose and the cell type. Danio rerio (paulistinha)is an ideal animal model to evaluate the biological effects of IR. In this work, resveratrol was evaluated as a potential radiomodifier in assays with embryos exposed at different hours post-fertilization (hpf), with and without the chorion, to different doses of gamma radiation. All assays were based on the protocol of OECD 236. To understand the effects on mortality of embryos exposed to resveratrol and radiation apart, values of LC50 and LD50, respectively, were obtained. The results were: LC50 of 154 &mu;M (for 2hpf embryos), 283 &mu;M (for 12hpf embryos), 699 &mu;M (for embryos of 24 hpf without chorion). And DL50 of 11.50Gy and 12.18Gy (embryos of 4 and 6hpf), 24.8Gy (embryos of 24hpf with chorion) and 16.99 (embryos of 24 hpf without the chorion). From these results, concentrations of 15, 30 and 60 &mu;M of resveratrol and doses 5 and 15 Gy (for embryos of 4 and 6 and 24 hpf without chorion) 10 and 20 Gy (for 24hpf embryos with chorion) were chosen from gamma radiation to observe the radiomodifying activity of resveratrol in trials with a duration of 144 hours, the dead embryos were counted every 24 hours and these results were compared with a Z test. There was difference in the percentage of mortality in all the trials, but for the exposed to radiation with 24hpf without chorion in the presence of 30&mu;M of resveratrol the number of dead embryos was less and statistically significant indicating radioprotection of resveratrol. In the 24hpf embryos irradiated in the presence of 60&mu;M, the mortality of irradiated embryos was higher when compared to irradiated embryos, indicating that in higher concentrations resveratrol may exert the radiosensitizer function, although in this case it was not statistically significant, these result corroborates with data in the literature that indicate the sensitizing action of the compound in cells exposed to radiation in this same concentration.

Neste trabalho, a irradiação por feixe de elétrons foi estudada como uma ferramenta para a reticulação do tecido de pericárdio bovino (PB). A conjugação de quitosana e fibroína de seda no tecido de PB liofilizado também foi objeto de estudo deste trabalho. Para isto, amostras de PB foram liofilizadas e irradiadas em um acelerador de elétrons utilizando-se diferentes doses e taxas de dose. Essas amostras foram analisadas por calorimetria exploratória diferencial (DSC), análises termogravimétricas (TGA), espectroscopia Raman, teste de intumescimento, microscopia eletrônica de varredura (MEV), microscopia eletrônica de transmissão (MET), testes de tração e quanto sua biofuncionalidade. Após as análises foi possível concluir que a irradiação do tecido na ausência de oxigênio favorece a reticulação das fibras de colágeno, enquanto na presença de oxigênio observou-se preferencialmente a cisão das fibras de colágeno. Ambas as amostras apresentaram diminuição de suas propriedades mecânicas. Também pôde-se concluir que a irradiação tanto na ausência quanto na presença de oxigênio produz um novo biomaterial cuja adesão e proliferação de células endoteliais é favorecida ao longo do tecido. Na segunda etapa deste trabalho amostras de PB liofilizadas foram incorporadas em soluções de quitosana, fibroína de seda e suas misturas (1:3, 1:1, 3:1). Depois de modificadas, as amostras foram novamente liofilizadas e submetidas à irradiação. Estas amostras foram caracterizadas por espectroscopia Raman, e avaliadas quanto sua citotoxicidade, biofuncionalidade e potencial de calcificação. Após lavagens das amostras de biomaterial com solução aquosa (NaCl 0,9%), as mesmas não apresentaram toxicidade. O teste de biofuncionalidade mostrou que as amostras de PQSFI (todas as proporções) favoreceram a adesão e crescimento das células endoteliais. Todas as amostras induziram a calcificação, entretanto apresentaram uma relação Ca/P menor do que a da hidroxiapatita. / In this work, electron beam irradiation was studied as a crosslinker of bovine pericardium tissue (BP). The treatment of BP with chitosan and silk fibroin was also the goal of this study. Samples of BP were freeze-dried and irradiated in an electron beam accelerator using different doses and dose rates. Samples were analyzed by differential scanning calorimetry (DSC), thermogravimetric analysis (TGA), Raman spectroscopy, water uptake tests, scanning electron microscopy (SEM), transmission electron microscopy (TEM), tensile tests and evaluation as biofunctionality. After analysis, it was concluded that irradiation of the tissue in the absence of oxygen promotes crosslinking of collagen fibers. On the other hand, in the presence of oxygen the chain scission of the collagen fibers was observed, and both samples suffered a decrease in their mechanical properties. It was also concluded that irradiation, both in the absence or presence of oxygen, promotes the adhesion and proliferation of endothelial cells throughout the tissue. In the second part of this work, lyophilized BP were incorporated into chitosan, silk fibroin solutions and mixtures of chitosan/silk fibroin in the ratio of 1:3, 1:1, 3:1. Then, the samples were again lyophilized and submitted to irradiation. These samples were characterized by Raman spectroscopy, and tested for their cytotoxicity, biofunctionality, and calcification. After washing the biomaterial with aqueous solution (NaCl 0.9%), the samples did not show cytotoxicity. Biofunctionality test showed that PQSFI samples (all proportions) promoted the adhesion and growth of endothelial cells. All samples induced calcification, but they exhibited a Ca/P ratio lower than hydroxyapatite.

The efforts addressed in this thesis refer to assaying the degradations in modern solar cells used in space-borne and/or nuclear environment applications. This study is motivated to address the following: 1. Modeling degradations in Si pn-junction solar cells (devices-under-test or DUTs) under different ionizing radiation dosages 2. Preemptive and predictive testing to determine the aforesaid degradations that decide eventual reliability of the DUTs; and 3. Using electrical overstressing (EOS) to emulate the fluence of ionizing radiation dosage on the DUT. Relevant analytical methods, computational efforts and experimental studies are described. Forward/reverse characteristics as well as ac impedance performance of a set of DUTs under pre- and post- electrical overstressings are evaluated. Change in observed DUT characteristics are correlated to equivalent ionizing-radiation dosages. The results are compiled and cause-effect considerations are discussed. Conclusions are enumerated and inferences are made with direction for future studies. / by George A. Thengum Pallil. / Thesis (M.S.C.S.)--Florida Atlantic University, 2010. / Includes bibliography. / Electronic reproduction. Boca Raton, Fla., 2010. Mode of access: World Wide Web.