Orientador: Solange Maria de Almeida / Tese (doutorado) - Universidade Estadual de Campinas, Faculdade de Odontologia de Piracicaba / Made available in DSpace on 2018-08-04T04:01:51Z (GMT). No. of bitstreams: 1 Silva_MarilianiChicarellida_D.pdf: 2982400 bytes, checksum: 4a42cb3e53e884e2e38412e79724b993 (MD5) Previous issue date: 2005 / Resumo: Sendo a osteoporose uma condição que acarreta fragilidade óssea e a radiação ionizante dificuldades no processo de reparação, o experimento foi idealizado com a finalidade de verificar-se o efeito da associação da deficiência de estrogênio e da radiação ionizante no processo de reparação óssea. Rattus Norvegicus Albinus Wistar, compuseram 4 grupos experimentais: controle, ovariectomizado, irradiado e ovariectomizado/irradiado, cuja deficiênica de estrogênio foi induzida através da ovariectomia. Após a comprovação da deficiência de estrogênio, nos grupos ovariectomizados, todos os grupos de animais foram submetidos à confecção de defeito ósseo em suas tíbias. Os grupos irradiado e ovariectomizado/irradiado tiveram irradiados os membros inferiores com 8 Gy de radiação gama, após 3 dias do procedimento cirúrgico. Transcorrido 7, 14, 21, 28 e 45 dias, o processo de reparação óssea foi avaliado, utilizando-se para a avaliação morfológica a Hematoxilina-Eosina e o Tricrômico de Mallory. Também foram realizadas a análise da birrefringência (coloração com Picrosírius); a análise da densidade volumétrica (coloração com Hematoxilina- Eosina) e a análise ultra-estrutural (Microscopia Eletrônica de Varredura). Os resultados encontrados indicaram que houve atraso do processo de reparação, no grupo ovariectomizado/irradiado, no qual a associação da deficiência de estrogênio e radiação ionizante acarretou uma diminuição na produção de osso neoformado e acelerou o processo de reabsorção / Abstract: As osteoporosis is a condition that causes bone fragility and ionization radiation makes the repair process difficult, the experiment was carried out to check the effect of the association of estrogen deficiency and ionization radiation on the bone repair process. The 4 experimental groups of female Wistar rats were subjected to the following conditions: control, ovariectomized, irradiated and ovariectomized/irradiated, with estrogen deficiency being induced through ovariectomy. After estrogen deficiency was confirmed, all the animals in the ovariectomized groups had a bone defect made in their tibias. The irradiated groups and ovariectomized/irradiated had their inferior members irradiated with 8 Gy of gama radiation 3 days after the surgical procedure. After 7, 14, 21, 28 and 45 days had elapsed, the bone repair process was evaluated, Hematoxylin-Eosin and Mallory¿s Tricomic being used for the morphologic evaluation. The following analyses were also carried out: birefringence analysis (Picrosirius Stain); the volumetrical density analysis (hematoxylin-eosin stain) and the ultra-structural analysis (Electronic Scanning Microscopy). The results found indicated that there was delay in the repair process in the ovariectomized/irradiated group, in which the association of the estrogen deficiency and ionization radiation caused a decrease in the production of neo- formed bone and accelerated the reabsorption process / Doutorado / Radiologia Odontologica / Doutor em Radiologia Odontológica

A computer controlled weld quality assurance system has been developed to detect weld defects ultrasonically whilst welding is in progress. This system, including a flash analogue to digital converter and built-in memories to store sampled data, a peak characters extractor and a welding process controller, enabled welding processes to be controlled automatically and welding defects to be detected concurrently with welding. In this way, the weld quality could be satisfactorily assured if no defect was detected and the welding cost was minimised either through avoiding similar defects to occur or by stopping the welding process if repair was necessary. This work demonstrated that the high temperature field around the weld pool was the major source of difficulties and unreliabilities in defect detection during welding and, had to be taken into account in welding control by ultrasonic means. The high temperatures not only influence ultrasonic characteristic parameters which are the defect judgement and assessment criterion, but also introduce noise into signals. The signal averaging technique and statistical analysis based on B-scan data have proved their feasibility to increase 'signal to noise ratio' effectively and to judge or assess weld defects. The hardware and the software for the system is explained in this work. By using this system, real-time 'A-scan' signals on screen display, and, A-scan, B-scan or three dimensional results can be printed on paper, or stored on disks, and, as a result, weld quality could be fully computerized.

Nematic liquid crystals are mesogenic materials that are popular working materials for optical displays. There has been an increased interest in bistable liquid crystal devices which support two optically distinct stable equilibria. These devices typically exploit a complex geometry or anchoring conditions, which often induces defects in the equilibria. There remains a great deal to be understood about the structure of the defects and how they stabilize multiple equilibria in modern devices. This thesis focuses on four problems: the first three explore the effect of confinement and defects on nematic equilibria in simple geometries, with the aim of exploring multistability in these geometries; the fourth problem concerns the fine structure of point defects, essential for future modelling of nematic equilibria in more complex geometries. Firstly, we study nematic liquid crystals confined to two-dimensional rectangular wells using the Oseen-Frank theory. Secondly, we study equilibria within a semi-infinite rectangular domain with weak tangential anchoring on the surfaces. Thirdly, we study nematic equilibria within two-dimensional annuli. We derive explicit expressions for the director fields and free energies of equilibria within these geometries and discuss the stability of the predicted states. These three problems are motivated by the experimental work on colloidal nematic liquid crystals, which we interpret in the context of our results. Finally, we study the fine structure and stability of the radial hedgehog defect in the Landau-de Gennes theory with a sixth order bulk potential, relevant to the observability of global biaxial phases in a model with higher order potential terms.

In the United States, approximately 3% of infants are diagnosed with a major birth defect each year. Whereas prevention efforts have led to decreases in some birth defects, the cause of approximately 70% of birth defects remains unknown. More recently, there has been increasing concern regarding exposures to environmental agents, such as air pollution during pregnancy, and the risk of birth defects. Over the past decade, there has been an increase in research studies examining the association between air pollution and birth defects. The results have been inconsistent, with some studies reporting that higher levels of exposure from the same pollutant increase the risk of birth defects, whereas others report no risk or even a decrease in risk. These inconsistencies may arise from differences in exposure assessment methods across epidemiological studies. A comprehensive series of sensitivity analyses were conducted to evaluate the impact of different exposure estimation decisions on the adjusted measures of associations between ambient air pollution exposure and birth defects. For each of six decisions – spatial scale, spatial limit, temporal scale, temporal limit, data aggregation sequence, and weighting scheme – two alternative choices were considered, and maternal exposure to PM2.5 and benzene were estimated for each ‘sensitivity case' (unique combination of choices across all decisions). For each sensitivity case, adjusted prevalence ratios (aPRs) and 95% confidence intervals (CI) were estimated from multivariable regression models comparing each exposure quartile to the first quartile; each measure of association represented the associations between either benzene or PM2.5 and one of the birth defects under study. To then evaluate the impact of selecting alternative choices for each exposure assessment decision, three metrics were used: 1) the percent difference in the aPR point estimates between alternative choices for a specific decision (calculated for each sensitivity case pairing); 2) the percent of sensitivity cases in which the aPR 95% CIs for alternative choices for a specific decision overlapped (i.e., were not statistically significantly different); and 3) the percent of sensitivity cases in which there was agreement in the substantive conclusion of the association between exposure (pollutant) and outcome (defect), the conclusion being either statistically significant increased risk, statistically significant decreased risk, or no statistically significant difference in risk. Second, a retrospective cohort study was conducted to investigate the association between maternal exposure to ambient benzene and PM2.5 and the risk of musculoskeletal birth defects in offspring. For both analyses, data on singleton infants born from 2000 to 2013 were obtained from the Florida Birth Defects Registry and air pollution data were obtained from the Environmental Protection Agency Air Quality System database. Exposure estimates were calculated for all birth defect cases and non-affected births during etiologically relevant time windows and multivariable regression models were used to obtain aPRs and 99% CIs comparing each quartile of exposure to the first. For PM2.5, across all exposure-outcome pairs under study, the alternative choices for the decision of spatial scale resulted in the largest median percent difference in aPRs (e.g., between county and block group) when results were aggregated for all quartiles. This was followed by the temporal scale and spatial limit decisions. For benzene, spatial limit resulted in largest median percent difference in aPRs, followed by spatial scale and temporal scale. However, for both pollutants, when evaluating the agreement in aPRs between alternative choices on the direction and significance of the association (i.e., statistically significant increase, decrease, or no risk), the decision of spatial limit resulted in the lowest percent agreement (biggest impact). Temporal limit had the second lowest percent agreement for PM2.5, whereas spatial scale had the second lowest for benzene. Finally, the metric assessing the level of overlap in 95% CIs for the measures of association was inconsequential, suggesting little impact of any exposure assessment decision, and doing little to differentiate between the relative impacts of each decision. That is because, for all exposure-outcome pairs, when comparing alternative choices for each decision, there was 100% overlapping intervals (i.e., no aPRs were statistically significantly different from each other). Lastly, exposure assessment decisions impacted the analytic sample sizes, with some decisions resulting in a three-fold difference in the sample size alone. Mothers of singleton infants exposed to higher levels of ambient PM2.5 were more likely than mothers with lower exposure levels to give birth to an infant with isolated anomalies of the skull and face bones, any rib and sternum anomalies, any skull and face anomalies, any spine anomaly, and other congenital anomalies of lower limb including pelvic girdle. Higher PM2.5 exposure was also associated with an increased risk of non-isolated anomalies of skull and face bones, any skull and face anomalies, and reduction deformities of the upper limb. Exposure to higher levels of benzene was associated with an increased risk of isolated congenital hip dislocation and congenital valgus deformities of feet as well as multiple inverse associations. The findings presented here indicate that measures of association between maternal pollutant exposures (PM2.5 and benzene) and selected birth defect outcomes in offspring are sensitive to exposure assessment decisions, with some decisions more impactful than others. The findings can be used, not only to explain the lack of consistency in results across existing epidemiological studies, but to guide decision-making in future studies. This study also adds to the growing body of epidemiological studies suggesting an association between specific air pollutants and birth defects. In the current political climate, it is important that researchers continue to provide evidence of the detrimental health effects of air pollution in order to circumvent change in current policies established to regulate and reduce pollution emissions.

M.Sc. (Physics) / The way we live has been fundamentally changed by technological innovations based on optical, electronic and magnetic materials. Without the continuous increase of scienti c understanding on phenomena that occur in materials, together with the processing and synthesis of materials, these technological revolutions would be impossible. Thus, the search of new materials is still the key driving force for the continuous blooming of modern technology...

Since the development of deep level transient spectroscopy (DLTS) in the 1970’s by Lang and others, the technique has become a powerful analytical tool to characterise the electrical properties of defects in semiconductors. With the development of more powerful computers and improved data acquisition systems, it has become possible to replace the original analogue boxcar analysers and lock-in amplifiers that were commonly used in early DLTS systems with digitisers and digital signal processing equipment. The use of a computer for signal processing allows for much more flexibility in the DLTS system. For instance, a digital DLTS system is capable of measuring a much wider range of emission rates than an analogue system. Furthermore, since the digital DLTS system does not rely on a repetitive signal, such a system can observe phenomena such as defect metastability that cannot be observed in an analogue system. In this thesis, the design and characterisation of a digital DLTS system is described. The results of a number of experiments that illustrated the capabilities of the system are reported. The extended range of emission rates that could be measured by the system were illustrated by the measuring of the EL2 defect in GaAs over the temperature range 270 – 380 K (corresponding to emission rates ranging from less than 10–3 s–1 to more than 103 s–1). The results compared well with previous results obtained by means of an analogue DLTS system. Further low temperature measurements on the E2 defect in GaAs showed that in the low temperature region, thermal radiation from the cryostat shroud influenced carrier emission. The field dependence of the emission rate of a number of defects, including defects in as-grown n-GaN, He-ion irradiated n-GaN and Si, was investigated as well. The ability of the digital DLTS system to measure single transients was used to investigate configurationally bistable defects in He-ion irradiated p-Si and a sputter-induced defect with negative-U properties in n-GaN. In both of these cases, the results proved far superior to those obtained by means of an analogue system. / Thesis (PhD (Physics))--University of Pretoria, 2007. / Physics / unrestricted

The electrically active defects introduced in GaAs by electron beam deposition (EB) of Ta were characterised. The effect of electron beam deposition on the electrical properties of GaAs was evaluated by current-voltage (I-V), capacitance¬voltage (C- V) and deep level transient spectroscopy (DL TS). However, when electronic devices are formed by EB, defects may be introduced into the semiconductor material, depending on the properties of the metal being deposited. Depending on the application, these defects may have either advantages or detrimental effects on the performance of such a device. I-V measurements indicated that the EB induced damage results in an increase in ideality factor and decrease in the barrier height with increasing the applied substrate bias, while C- V measurements showed that EB deposition also caused a decrease in the barrier height. DL TS studies on the same material in the temperature range of 20 - 350 K showed that at least three electrically active defects are introduced during EB deposition, with energies (0.102 ± 0.004, 0.322 ± 0.014 and 0.637 ± 0.029 eV) within the band gap. DL TS data was used to construct concentration profiles of these defects as a function of depth below the surface. It was found that the defect concentration increases with increasing substrate bias during the deposition, irrespective of the direction of the applied bias. This may be related to the I-V characteristics of the SBDs. The SBDs investigated by IV measurements showed that GaAs yields SBDs with poorer characteristic. The influence of EB deposition on the device properties of SBDs fabricated on GaAs is presented. These device properties were monitored using a variable temperature I-V and C- V apparatus. In order to have an understanding of the change in electrical properties of these contacts after EB deposition, it is necessary to characterise the EB induced defects. DL TS was used to characterise the defects in terms of their D L TS signature and defect concentration. / Dissertation (MSc (Physics))--University of Pretoria, 2006. / Physics / unrestricted

The development of science and technology have provided a lifestyle completely dependent on energy consumption. Devices such as computers and mobile phones are good examples of how our daily life depends on electric energy. In this scenario, energy storage technologies emerge with strategic importance providing efficient ways to transport and commercialize the produced energy. Rechargeable batteries come as the most suitable alternative to fulfill the market demand due to their higher energy- and power- density when compared with other electrochemical energy storage systems. In this context, during the production of this thesis, promising compounds for advanced batteries application were investigated from the theoretical viewpoint. The framework of the density functional theory has been employed together with others theoretical tools to study properties such as ionic diffusion, redox potential, electronic structure and crystal structure prediction. Different organic materials were theoretically characterized with quite distinct objectives. For instance, a protocol able to predict the redox potential in solution of long oligomers were developed and tested against experimental measurements. Strategies such as anchoring of small active molecules on polymers backbone have also been investigated through a screening process that determined the most promising candidates. Methods such as evolutionary simulation and basin-hopping algorithm were employed to search for global minimum crystal structures of small molecules and inorganic compounds working as a cathode of advanced sodium batteries. The crystal structure evolution of C6Cl4O2 upon Na insertion was unveiled and the main reasons behind the lower specific capacity obtained in the experiment were clarified. Ab initio molecular dynamics and the nudged elastic band method were employed to understand the underlying ionic diffusion mechanisms in the recently proposed Alluaudite and Eldfellite cathode materials. Moreover, it was demonstrated that electronic conduction in Na2O2, a byproduct of the Na-O2 battery, occurs via hole polarons hopping. Important physical and chemical insights were obtained during the production of this thesis. It finally supports the development of low production cost, environmental friendliness and efficient electrode compounds for advanced secondary batteries.

Tomography of crystal defects in the electron microscope was first attempted in 2005 by the author and colleagues. This thesis further develops the technique, using a variety of samples and methods. Use of a more optimised, commercial tomographic reconstruction program on the original GaN weak beam dark-field (WBDF) tilt series gave a finer reconstruction with lower background, line width 10-20 nm. Four WBDF tilt series were obtained of a microcrack surrounded by dislocations in a sample of indented silicon, tilt axes parallel to g = 220, 220, 400 and 040. Moiré fringes in the defect impaired alignment and reconstruction. The effect on reconstruction of moiré fringe motion with tilt was simulated, resulting in an array of rods, not a flat plane. Dislocations in a TiAl alloy were reconstructed from WBDF images with no thickness contours, giving an exceptionally clear reconstruction. The effect of misalignment of the tilt axis with systematic row g(ng) was assessed by simulating tilt series with diffraction condition variation across the tilt range of Δn = 0, 1 and 2. Misalignment changed the inclination of the reconstructed dislocation with the foil surfaces, and elongated the reconstruction in the foil normal direction; this may explain elongation additional to the missing wedge effect in experiments. Tomography from annular dark-field (ADF) STEM dislocation images was also attempted. A tilt series was obtained from the GaN sample; the reconstructed dislocations had a core of bright intensity of comparable width to WBDF reconstructions, with a surrounding region of low intensity to 60 nm width. An ADF STEM reconstruction was obtained from the Si sample at the same microcrack as for WBDF; here automatic specimen drift correction in tomography acquisition software succeeded, a significant improvement. The microcrack surfaces in Si reconstructed as faint planes and dislocations were recovered as less fragmented lines than from the WBDF reconstruction. ADF STEM tomography was also carried out on the TiAl sample, using a detector inner angle (βin) that included the first order Bragg spots (in other series βin had been 4-6θ B). Extinctions occurred which were dependent on tilt; this produced only weak lines in the reconstruction. Bragg scattering in the ADF STEM image was estimated by summing simulated dark-field dislocation images from all Bragg beams at a zone axis; a double line was produced. It was hypothised that choosing the inner detector angle to omit these first Bragg peaks may preclude most dynamical image features. Additional thermal diffuse scattering (TDS) intensity due to dilatation around an edge dislocation was estimated and found to be insignificant. The Huang scattering cross section was estimated and found to be 9Å, ten times thinner than experimental ADF STEM dislocation images. The remaining intensity may be from changes to TDS from Bloch wave transitions at the dislocation; assessing this as a function of tilt is for further work. On simple assessment, only three possible axial channeling orientations were found over the tilt range for GaN; if this is typical, dechanneling contrast probably does not apply to defect tomography.

This thesis deals with influence of stress during transport on selected species of transported animals especially on pigs, cattle and poultry. Each animal deals with stress differently according to its anatomical, physiological and ethological predispositions. Requirements according to these predispositions are described in the theoretical part of thesis. In the end of theoretical part defects of meat which occur as a result of stress are described. In practical part there is a summary of current laws related to transport of living animals, both Czech and European. Current laws are compared with anatomical, physiological and ethological requirements of animals. In the end of thesis the quality of current laws is evaluated and possible future development of transport of living animals is outlined.