Made available in DSpace on 2014-06-11T19:23:41Z (GMT). No. of bitstreams: 0 Previous issue date: 2003Bitstream added on 2014-06-13T20:50:52Z : No. of bitstreams: 1 coradazzi_lf_me_araca.pdf: 2222457 bytes, checksum: d4df3c1b61fe6c5d468f78b6582caafb (MD5) / Foi realizado um estudo histomorfométrico para avaliar o reparo ósseo em cavidades experimentais criadas na tíbia de coelhos, preenchidas com dois tipos de partículas de osso autógeno. Foram utilizados 12 coelhos, nos quais foram realizadas 3 cavidades unicorticais de 7 mm de diâmetro, com uma broca trefina, na face lateral da tíbia direita. Os defeitos ósseos foram preenchidos respectivamente com partículas de osso autógeno obtidas com um triturador manual, com partículas de osso autógeno recolhidas com um coletor ósseo durante o preparo de cavidades com a seqüência de brocas de implantes e com coagulo sangüíneo servindo como controle. Os animais foram igualmente distribuídos em 3 grupos e sacrificados nos períodos de 7, 15 e 30 dias. De acordo com os resultados obtidos, aos 7 dias todos os grupos apresentaram-se preenchidos por coágulo sangüíneo, sendo observada a presença de partículas ósseas autógenas nos grupos triturado ( 44,75% ) e coletado ( 24% ). No período de 15 dias, notou-se a diferenciação conjuntiva em todos os grupos, com ausência de neoformação óssea no grupo controle ( 0% ), presença de partículas ósseas e início de formação óssea nos grupos coletado (38,88%) e triturado (46%). No período de 30 dias observou-se a neoformação óssea nos grupos controle (50%), coletado (64,63%) e triturado (66%) com a presença de um trabeculado ósseo imaturo. De acordo com a metodologia utilizada, concluiu-se que: a diferença entre a neoformação óssea nas cavidades dos grupos triturado e coletado não foi estatisticamente significante, porem mostrou-se superior a do grupo controle no aspecto quantitativo e qualitativo. As partículas ósseas do grupo triturado não foram totalmente reabsorvidas nos períodos analisados, enquanto que no grupo coletado houve uma reabsorção das partículas ósseas e neoformação óssea superiores aos do grupo triturado. / A histomorphometric study was carried out to evaluate the bone repair in experimental cavities created in rabbits tibiae and filled with two types of particulate autogenous bone grafts. Twelve rabbits were used. In each tibia, on the right lateral face, three 7 mm diameter unicortical cavities were performed with a trephine bur. The bone defects were respectively filled with particles of autogenous bone obtained with manual bone mill, with autogenous bone particles collected with a bone collector during the cavities preparation with implant burs, and with the blood clot serving as a control group. The animals were equally divided in three groups and sacrificed on 7, 15 and 30 days. According to the obtained results, on the seventh day all the groups showed to be filled with blood clots with the presence of autogenous bone particles observed on the triturated group (44,75%) and collected group (24%). At the fifteenth day period it was noted connective tissue differentiation in all the groups, with no bone neoformation noted on the control group (0%). Presence of bone particles and beginning of osteogenesis was noted in the collected (38,88%) and triturated (46%) groups. On the thirtieth day bone neoformation was observed in the control (50%), collected (64,63%) and triturated (66,63%) groups as well as the presence of immature trabecular bone. According to the methodology utilized, it was concluded that the bone formation occurred in the cavities of the triturated and collected groups did not show statistical significance, however being superior to the control group as to the quantitative and qualitative aspect. The bone particles of the triturated group were not totally reabsorbed in the analyzed periods, while in the collected group there was a bone particles resorption and bone neoformation in a higher degree than in the triturated group.

FundaÃÃo Cearense de Apoio ao Desenvolvimento Cientifico e TecnolÃgico / The use of stainless steels has intensified with the industrial demand growing, which extends its application for various sectors such as the oil and gas, desalination equipment in industry, sugar industry, among others. In that context, the use of ferritic stainless steels has grown in recent years on account of its excellent relationship between corrosion resistance and cost, and a great option in substitution of austenitic stainless steels. Intending to study the connection of dissimilar stainless steels by means of a welding process, this paper will lay the submit the ferritic stainless steel AISI 444 and AISI 316L austenitic stainless steel with TIG welding autogenous (without filler metal) with pulsed current. That union seeks to get a fused zone with better mechanical properties together with the correction of possible related to welding those steels problems, such as grain growth in ferritic steels, to which its refinement is possible through the use of pulsed current during the procedure. The choice of these two materials was based on the characteristics of each one separately for they possess closest properties, despite having different classifications, allowing the combined use of both, and thus ferritic act in order to partially replace the austenitic stainless steel in situations where the combination of high corrosion resistance and mechanical strength are not relevant. That action combined, and does not affect the characteristics of the set of negative way is to use lower cost benefit, because the presence of nickel austenitic stainless steels by more expensive finishes them. Thus, it is expected to provide, through this work, further deepening the respect of dissimilar welding between stainless steel AISI 444 ferritic and austenitic stainless steel AISI 316L, evaluating operational parameters such as the pulse of current and heat input on obtained microstructure and mechanical properties. / A utilizaÃÃo dos aÃos inoxidÃveis tem se intensificado juntamente com a crescente demanda industrial, em que sua aplicaÃÃo se estende pelos mais variados setores, como por exemplo, na indÃstria de petrÃleo e gÃs, em equipamentos de dessalinizaÃÃo, na indÃstria sucroalcooleira, entre outros. Neste contexto, o uso de aÃos inoxidÃveis ferrÃticos tem crescido nos Ãltimos anos devido a sua excelente relaÃÃo entre resistÃncia à corrosÃo e custo, sendo uma Ãtima opÃÃo em substituiÃÃo aos aÃos inoxidÃveis austenÃticos. Objetivando estudar a uniÃo de aÃos inoxidÃveis dissimilares por meio de um processo de soldagem, o presente trabalho submeterà o aÃo inoxidÃvel ferrÃtico AISI 444 e o aÃo inoxidÃvel austenÃtico AISI 316L à soldagem TIG autÃgeno (sem metal de adiÃÃo) com corrente pulsada. Essa uniÃo visa obter uma zona fundida com melhores propriedades mecÃnicas juntamente com a correÃÃo dos possÃveis problemas relacionado à soldagem desses aÃos, como por exemplo, o crescimento de grÃo nos aÃos inoxidÃveis ferrÃticos, em que seu refinamento se torna possÃvel atravÃs da utilizaÃÃo de corrente pulsada durante o procedimento. A escolha desses dois materiais baseou-se nas caracterÃsticas inerentes a cada um separadamente e tambÃm por possuÃrem propriedades muito prÃximas, apesar de possuÃrem classificaÃÃes diferentes, permitindo a utilizaÃÃo combinada de ambos e dessa forma o aÃo inoxidÃvel ferrÃtico atuarà de forma a substituir parcialmente o aÃo inoxidÃvel austenÃtico nas situaÃÃes em que a combinaÃÃo de elevada resistÃncia à corrosÃo e resistÃncia mecÃnica nÃo sÃo tÃo relevantes. Essa utilizaÃÃo combinada, alÃm de nÃo afetar as caracterÃsticas do conjunto de maneira negativa tem como benefÃcio reduzir custos, visto que a presenÃa de nÃquel nos aÃos inoxidÃveis austenÃticos acaba por encarecÃ-los. Dessa forma, espera-se fornecer atravÃs deste trabalho um maior aprofundamento a respeito da soldagem dissimilar entre o aÃo inoxidÃvel ferrÃtico AISI 444 e o aÃo inoxidÃvel austenÃtico AISI 316L, avaliando os parÃmetros operacionais, como a pulsaÃÃo da corrente e a energia de soldagem sobre a microestrutura obtida, bem como as propriedades mecÃnicas.

As moagens autógena (AG) e semiautógena (SAG) mostram-se como opções cada vez mais consideradas na seleção de novos circuitos de cominuição. A flexibilidade de operação, assim como a combinação de grandes capacidades de processamento e altas relações de redução obtidas, são algumas das vantagens destes circuitos. Este trabalho procurou descrever o método utilizado na condução de ensaios de moagem semiautógena em escala piloto e de caracterização tecnológica, empregando o minério de ouro da Rio Paracatu Mineração S/A (RPM). A moagem semiautógena foi investigada considerando diferentes condições de operação e às especificidades do minério da RPM. Foram conduzidos 69 ensaios em planta piloto que permitiram o estudo do efeito das variáveis de operação sobre parâmetros de moagem SAG, como taxa de processamento, consumo energético específico, qualidade do produto, entre outros. As informações obtidas na campanha de ensaios em planta piloto e nos trabalhos de caracterização das amostras mostraram-se consistentes e fundamentaram o dimensionamento e projeto do circuito de Expansão da RPM, com capacidade de processamento adicional de 41 Mtpa. / The autogenous (AG) and semi-autogenous (SAG) mills have increasingly been considered options in the selection of new comminution circuits. The flexibility of the operation, as well as the combination of high processing capacity and high reduction rates obtained, are some of the advantages of these circuits. This study sought to describe the method used in conducting semi-autogenous grinding pilot plant and technological characterization, using the gold ore from the Rio Paracatu Mineração S/A (RPM) mine. The semi-autogenous grinding was investigated considering different operating conditions and specific characteristics of the ore from the Rio Paracatu Mineração mine. Were conducted 69 tests in a pilot plant that enabled the study of the effects of the operating variables of the SAG grinding parameters such as processing rates, specific energy consumption, product quality, among others. Information obtained in the test campaign of the pilot plant and the characterization work of the samples were consistent and supported the design and project of the circuit of the expansion of the Rio Paracatu Mineração mine, with additional processing capacity of 41 Mtpy.

Estudos sugerem que a cafeína atua sobre o osso promovendo aumento da excreção de cálcio e inibição da proliferação de osteoblastos, aumentando o risco de fraturas, osteoporose e doença periodontal. Os efeitos da cafeína sobre o tecido ósseo dificultam a aplicação de implantes dentários devido à presença de grandes defeitos ósseos ou volume ósseo insuficiente. Vários métodos são propostos para a regeneração de defeitos ósseos, entre eles, o uso de diferentes tipos de enxertos, os quais demonstram capacidade em promover a formação óssea A despeito das desvantagens, o osso autógeno ainda é considerado a referência padrão como enxerto ósseo, devido ao seu potencial osteogênico, osteoindutor e osteocondutor. A engenharia tecidual óssea tem sido utilizada como uma estratégia para a regeneração óssea. As células tronco mesenquimais são consideradas multipotentes e podem replicar como células indiferenciadas, possuindo potencial para se diferenciarem em linhagens de osso, cartilagem, gordura e cartilagem. O objetivo deste estudo foi quantificar histomorfometricamente a reparação óssea pelo enxerto de uma associação de osso autógeno obtido da calota craniana e células osteoblásticas em defeitos ósseos produzidos pela extração dental de ratos submetidos à administração diária de cafeína. Os animais foram divididos em: Controle (c), osso autógeno (oa) e osso autógeno + células osteoblásticas (oa+co) e receberam injeções diárias intraperitonealmente de 30 mg/kg/dia de cafeína durante trinta dias, os homólogos receberam de solução salina. Os ratos foram sacrificados nos períodos de 7, 21 e 42 dias pós-cirurgia e as amostras teciduais foram processadas para a obtenção de secções finas (5 m) e coradas com HE. Através de um sistema de análise de imagens se estimou a fração de volume de osso, conjuntivo e coágulo, no defeito ósseo. Os resultados histológicos e histométricos mostraram que nos animais sob tratamento com cafeína houve uma menor formação óssea estatisticamente significante a 1%, e um retardo na reabsorção do coágulo sanguíneo quando comparado aos alvéolos dos animais sob tratamento com soro fisiológico. A análise qualitativa do fragmento de osso autógeno isoladamente ou associado às células osteoblásticas mostrou uma osteointegração progressiva e sem reação de corpo estranho nos animais tratados com soro fisiológico e, as células implantadas não propiciaram reações imunogênicas nem a formação tumoral, possibilitando um aumento (25%) na reparação óssea dos animais tratados com a cafeína. Conclui-se que o enxerto/implante das células osteoblásticas associadas ao osso autógeno da calota craniana foi capaz de compensar, nos períodos tardios, os efeitos deletérios da cafeína na reparação óssea alveolar. / Studies suggest that caffeine acts on the bone for increasing the excretion of calcium and inhibition of osteoblasts proliferation, increasing the risk of fractures, osteoporosis and periodontal disease. The effects of caffeine on bone difficult the application of dental implants due to large bone defects and insufficient bone volume. Several methods are proposed for the regeneration of bone defects, including the use of different types of grafts, which show ability to promote bone formation. Despite the disadvantages, the autogenous bone is still considered the gold standard as bone graft because the potential osteogenic, osteoinductive and osteoconductive. The bone tissue engineering has been used as a strategy for bone regeneration. The mesenchymal stem cells are considered multipotent and can replicate as undifferentiated cells, with potential to differentiate into lineages of bone, cartilage, fat and cartilage. This study aimed to quantify histomorphometrycally bone repair by grafts of a combination of autogenous bone obtained from the skull and osteoblastic cells in bone defects produced by dental extraction in rats subjected to daily administration of caffeine. The animals were divided into: Control (c), autogenous bone (ab) and autogenous bone + osteoblastic cells (ab + oc) and received daily injections intraperitoneally of 30 mg/kg/day of caffeine for thirty days, the counterparts received saline solution. The rats were sacrificed at times of 7th, 21st and 42nd days post-surgery and tissue samples were processed to obtain thin sections (5 m) and stained with HE. Through an image analysis system was estimated the fraction of volume of bone, collagen and blood clot in the bone defect. The histological and histometric results showed that in animals under treatment with caffeine had a lower bone formation statistically significant at 1%, and a delay in the resorption of blood clots when compared to the alveoli of animals under treatment with saline. The qualitative analysis of the fragment of autogenous bone alone or associated with osteoblastic cells showed a progressive osteointegration and no foreign body reaction in animals treated with saline, and implanted the cells not provided immunogenic reactions or tumor formation, allowing an increase (25%) on bone repair in animals treated with caffeine. It was concluded that the graft/implant of osteoblastic cells associated with autogenous bone from the skull was able to compensate in later periods, the deleterious effects of caffeine on alveolar boné repair.

Abstract This study focuses on the development of a bone collecting device for intra-oral bone harvesting and on the introduction of a new bone graft donor site, zygomatic bone. A bone collector was constructed and tested in vitro. This bone collector is suitable and efficient in dental implant related bone grafting surgery. It was also found to be more efficient and with a larger capacity in bone harvesting when compared to the two commercially available bone collectors. A zygomatic bone harvesting technique is introduced in this study. The safety and morbidity of the method was assessed in a cadaver and a prospective clinical study. In the cadaver study, 40 procedures were performed. The complications during the cadaver harvesting included 15 perforations into the maxillary sinus and 7 perforations into the infratemporal fossa. The only intra-operative complication in 32 clinical operations was perforation of the maxillary sinus in 33% of the zygomatic sites. None of these patients experienced any post-operative problems related to the perforation. Patients needed pain medication for a mean time of four days and they did not demonstrate any paresthesias or altered sensations in the donor area. The yield of the bone graft from zygomatic bone was quantified in cadaver and clinical studies. In the cadaver study, the average yield of the graft was 0.59 ml. In the clinical study the average graft volume was 0.90 ml. The required reconstructions were accomplished in all clinical cases. In the prospective clinical study, the bone grafts from the zygomatic bone were used simultaneously with one-stage dental implants placement. Bone grafting was employed at 72 of the 82 implant sites. Two of the bone grafted implants failed, yielding a survival rate of 97.2% for bone grafted implants and 97.6% for the whole study group. Grafted sites healed remarkably well, and no obvious signs of graft resorption were noted during the 26.9 months follow-up period. The bone collector developed in this study is an effective instrument in intra-oral bone harvesting. The zygomatic bone can be regarded as a safe bone harvesting donor site and the yield of bone graft from this area is sufficient for moderate defects in resorbed alveolar ridges.

Autogenous (AG) milling is utilised around the world for rst stage particle size reduction. The system exhibits highly non-linear behaviour in addition to being subject to unmeasured variability associated with most ore bodies. Anglo American Platinum aimed at improving online optimisation of the circuit by implementing industrial model predictive control to reduce system variability and continuously drive towards the optimal operating point within system constraints. A dimensional analysis of the circuit was conducted to explain the relationships between the various milling parameters discussed in the literature survey. The measured variables used in the analysis satis ed Buckingham's theorem, indicating that a complete subset of dimensionless groups were present and suitably able to describe process movement. These relationships were used as a reference point in determining the dynamic step response models between these variables necessary for model based control. The industrial dynamic matrix controller commissioned on the AG mill resulted in a 66 % reduction in power and a 40 % reduction in load. These are the main controlled variables of the mill. The controller also managed to reduce its objective function, e ective power utilisation, by 11 %. This stability improvement enabled a test campaign where the mill was controlled at various operating regions in order to establish the conditions conducive to the nest product size at a given mill feed rate. Moving the mill's operating region from the benchmarked plant to this optimal grind environment (at benchmarked variability) provided an estimated potential recovery increase of 0.27 % (absolute) due to better precious metal liberation. Stabilising the mill at this point with the model predictive controller resulted in a further 0.04 % potential recovery increase (absolute). The 0.31 % potential recovery increase is estimated at a monetary value of $93.1 million per annum. Copyright / Dissertation (MEng)--University of Pretoria, 2013. / Chemical Engineering / unrestricted

Magister Scientiae Dentium - MSc(Dent) / Autologous bone grafting in conjunction with dental implant therapy is a well-accepted procedure in oral and maxillofacial rehabilitation. A variety of intraoral donor sites, such as the mandibular symphysis, the mandibular ramus and the maxillary tuberosity have been used in oral and maxillofacial reconstruction. However these sites are associated with complications. In order to reduce these complications, the anterior palate has been proposed as a potential donor site. However, the scientific literature in this regard is sparse, and larger studies are required to investigate the clinical potential of this proposed site. Aim: To determine the volume and density of available bone in the anterior palate that may be used for bone harvesting using cone-beam computed tomography (CBCT) in a select South African population. Materials and methods: One hundred previously acquired CBCT scans taken at the Diagnostic and Radiology Department of Tygerberg Oral Health Centre were analyzed for the required data. These were all acquired from a single CBCT machine (Newtom VGI®, Verona, Italy). The study sample included 52 females and 48 males ranging from ages 20 years to 80 years. The CBCT scans were divided into 3 different age groups. The first age group was between the ages of 20 and 39 years, the second age group was from 40 to 59 years and the third age group was ≥ 60 years. The volume and density of the anterior palate of the different age groups were analyzed using specific criterion. CBCT specific software (Simplant Pro Crystal®) Dentsply implants, Mannheim, Germany was used to standardize the data collection. All data was stored in a Microsoft Excel spreadsheet (Microsoft Corporation, Washington, USA). Results: The mean volume of the anterior palate in this study was 2.11 ± 0.55 cm3, with a minimum volume of 1.04 cm3 and a maximum volume of 3.82 cm3. There was no significant difference in the volume and density of the anterior palate between different age groups and no significant difference in the volume between males and females (p value = 0.227). Conclusions: The anterior palate affords a considerable amount of bone volume which is similar or even more than other intraoral donor sites. The anterior palate is a potential donor site for bone harvesting and CBCT may be regarded as an ideal tool to analyze the amount of bone available for harvesting.

Aitik is a large copper porphyry type deposit located in northern Sweden, currently exploited at an annual rate of approximately 45Mt. The ore's exceptionally low head grade of 0.22 % Cu and varying degrees of hardness across the entire deposit pose challenges to the two fully autogenous grinding lines, each of which comprises a 22.5 MW primary autogenous mill in series with a pebble mill. The variability in ore grindability frequently leads to fluctuations in mill throughput.  Within the framework of a geometallurgical approach, the present study investigated the relationships between ore grindability and modal mineralogy. For this purpose, drill core samples from different lithologies were subjected to Boliden AB's in-house grindability tests. This laboratory-scale autogenous grinding test generates a grindability index Ks mainly related to abrasion breakage, which is a significant breakage mechanism within autogenous mills. The test results suggested divergent degrees of grindability within and across the selected rock types. Furthermore, subsequent sieve analyses identified a relationship between the grindability index, PSD, and the proportions of fines generated by abrasive grinding. A combination of scanning electron microscopy, X-ray powder diffraction, and X-ray fluorescence analyses was performed for the grinding products and bulk mineral samples. The resulting mineralogical and elemental properties were correlated to the parameters from the grindability tests. It was shown that the main mineral phases, such as plagioclase, quartz, and micas, correlate well with the grindability indices. Similar correlations were found regarding the sample's chemical composition, attributable to the main mineral phases. Derived from the previous findings, two exemplary linear empirical models for the calculation of grindability based on either mineral contents or chemical composition were presented. Careful examination of the mineralogical data revealed that the prevalent abrasion breakage mechanism leads to constant and continuous removal of mineral particles from the sample's surface. No indications for a preferential abrasion of any mineral phases were found.  A further inverse correlation between the sample's calculated average weighted Mohs hardness based on modal mineralogy and the grindability index Ks was established. Hence, it was proposed that a higher Mohs hardness results in a finer grinding product, oppositional to the Ks-values. Since Ks can be interpreted as a measure of abrasiveness, it can be stated that abrasiveness decreases with an increasing average sample hardness and vice versa.  Moreover, mineral liberation information provided by scanning electron microscopy was associated with the parameters mentioned earlier. It was determined that different degrees of mineral liberation were reached within specific particle size classes. The identified relationships between grindability, modal mineralogy, and element grades may help Boliden develop a predictive throughput model for Aitik to be integrated into the mine's block model. Based on this information, a strategy for smart blending could be developed, where run of mine material from ore blocks of varying grindabilities could be blended to attain the target plant throughput.

Objectives: To compare optical values in the osteotomy gap created after a Tibial Tuberosity Advancement (TTA) treated with autogenous cancellous bone graft (ACBG), extracorporeal shock wave therapy (ESWT), a combination of ACBG and ESWT, and absence of both ACBG and ESWT using densitometry. Methods: Dogs presenting for surgical repair of a cranial cruciate ligament rupture were randomly assigned to one of four groups; TTA with ACBG (TTA-G), TTA with ACBG and ESWT (TTA-GS), TTA with ESWT (TTA-S), and TTA with no additional therapy (TTA-O). Mediolateral radiographs at 0, 4 and 8 weeks after surgery were evaluated to compare healing of the osteotomy gap via densitometry. An analysis of variance (ANOVA) statistical analysis was used to compare the densitometric values between groups. Results: At 4 weeks after surgery, a significant difference in osteotomy gap density was noted between TTA-GS (8.4 millimeters of Aluminum equivalent [mmAleq]) and TTA-S (6.1mmAleq), and between TTA-GS (8.4 mmAleq) and TTA-O (6.4 mmAleq). There were no significant differences noted between groups at the 8 week recheck. Clinical Significance: There were no significant differences in the osteotomy gap density at 8 weeks after surgery regardless of the treatment modality used. The combination of ACBG and ESWT may lead to increased density of the osteotomy gap in the first 4 weeks after surgery. Densitometry using an aluminum step wedge is a feasible method for comparison of bone healing after TTA in dogs. / Master of Science

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