24 research outputs found
O Atlântico Sul para além da miragem de um espaço homogêneo (séculos XV-XIX)
No full textA abertura do Atlântico no século XV representou a integração das regiões africanas costeiras e das povoações que habitavam o interior do continente com sociedades com as quais anteriormente não havia contato. No caso da África Centro-Ocidental essa abertura representou a descoberta de “novos mundos”, anteriormente isolados do contato com a Europa e as Américas. A História Atlântica tem inspirado centenas de novos trabalhos com seu olhar transnacional sobre este espaço. Esse olhar instrumentaliza o historiador a trabalhar as redes mercantis que muitas vezes transpunham os limites impostos pelos Estados, operando para além do projeto “colonial” europeu para a região. O Atlântico Sul – embora possa ser visto como um espaço integrado por meio de correntes marítimas particulares e rotas de navegação bem desenhadas – caracteriza-se por sua heterogeneidade e a pela constante transformação de seus espaços durante os séculos do comércio de escravos
Dossiê histórias angolanas, séculos XVI-XX: introdução
No full textIntrodução do dossiê histórias angolanas, séculos XVI-X
O programa troca-troca e a politica de assistencia e incentivo ao pequeno produtor rural do estado de Santa Catarina no periodo 1983-1987
No full textDissertação (mestrado) - Universidade Federal de Santa Catarina. Centro Socio-Economic
Avaliação da influência da ingestão de lixo plástico nos indicadores de estresse oxidativo no sangue de tratarugas verdes (Chelonia mydas)
No full textDissertação (mestrado) - Universidade Federal de Santa Catarina, Centro de Ciências Biológicas, Programa de Pós-Graduação em Ecologia, Florianópolis, 2012O presente estudo analisou biomarcadores de estresse oxidativo, como as enzimas catalase (CAT), superóxido dismutase (SOD), glutationa peroxidase (GPx), glutationa redutase (GR) e glutationa S-transferase (GST), níveis de glutationa reduzida (GSH), de proteínas carboniladas (PC) e de lipoperoxidação (TBARS), presentes no sangue de tartarugas verdes (Chelonia mydas), vítimas de ingestão de lixo plástico, bem como o peso e volume dos resíduos ingeridos. A obstrução no trato gástrointestinal decorrente promove processos de isquemia-reperfusão associados ao estresse oxidativo sistêmico. Foram amostradas 27 tartarugas, coletadas na região da Ilha de Santa Catarina, Florianópolis, SC. Após a coleta sanguínea realizada durante exame clínico, quando se observou a presença/ausência de alguns sintomas. As tartarugas foram mantidas em tanques individuais e observadas diariamente para a constatação de lixo plástico em suas fezes: os indivíduos que realizaram três evacuações consecutivas livres de lixo plástico e não apresentaram nenhum sintoma formaram o grupo controle (n=7); os indivíduos que apresentaram as mesmas condições do grupo controle, porém em que foi constatado lixo plástico em suas fezes ao menos em uma das evacuações, foram considerados do grupo 2 (n=10); os indivíduos que apresentaram ao menos um dos sintomas avaliados durante o exame clínico e também lixo plástico em ao menos uma das evacuações, foram consideradas do grupo 3 (n=10). Foi verificada a presença de lixo plástico em 74% das tartarugas amostradas e um alto índice de ingestão de resíduos foi verificado em tartarugas sem sintomas (63%). Houve uma diferença significativa, em termos estatísticos, em relação à massa e o volume de resíduos ingeridos entre os grupos 2 e 3 (pAbstract : The aim of this study was to analyze oxidative stress biomarkers such as the enzymes catalase (CAT), superoxide dismutase (SOD), glutathione peroxidase (GPx), glutathione reductase (GR) e glutathione S-transferase (GST), levels of reduced glutathione (GSH), protein carbonyls (PC), lipoperoxidation (TBARS), in the blood of green turtles (Chelonia mydas) victims of plastic debris ingestion, as well as measuring weight and volume of such material. The consequent gastrointestinal obstruction promote an ischemia-reperfusion process associated with systemic oxidative stress, A total of 27 turtles were collected in the region of the Island of Santa Catarina, SC. After blood collection performed during clinical examination, which showed the presence/absence of some symptoms, the turtles were kept in individual tanks and were observed daily for confirmation of plastic debris in their feces: animals that underwent three consecutive evacuations free of plastic debris and that showed no symptoms formed the control group (n=7); those that exhibited similar conditions as in the control group but presented plastic debris in their feces at least in one of the evacuations, were considered group 2 (n=10); and individuals that showed at least one symptom evaluated during clinical examination and also plastic debris in at least one of the evacuations were considered in group 3 (n=10). The presence of plastic debris was detected in 74% of the turtles sampled and a high intake of residues in turtles without symptoms (63%) was also observed. The mean weight and volume of plastic debris ingested by this group were 0.8 g and 3.0 ml, respectively. There was a significant difference regarding mass and volume of waste taken between group 2 and 3 (p<0.0007 and p<0.002, respectively). The volume of waste ingested and the enzyme activities of GPx (R=-0.48) and GR (R=-0.69) were negatively correlated. In group 2, only CAT activity showed a significant decrease (p=0.02), while GR activity showed a significant increase (p=0.04), compared to controls. No statistical variation was detected for the biomarkers studied in animals from group 3 compared to controls, only a tendency of increase in TBARS and PC levels. The means of plastic debris ingested by group 3 were 11.02 g and 19.65 ml, respectively. The results found in this study suggest that the amount of waste ingested by animals in group 2, which presented a survival rate of 100%, was not enough to cause an ischemia-reperfusion of the intestine sufficient to promote a pronounced oxidative stress. The catalase activity was apparently sufficient to detoxify the excess of H2O2. On the other hand, the high mortality of group 3 (100%) seemed to be related to the failure of antioxidant defense system, because the deleterious consequences from the oxidative stress associated with the ischemia-reperfusion injury of the gastrointestinal tract. The development of biomarkers of oxidative stress to assess the health status of marine turtles may provide an important tool in the conservation of these species
Slow cooling protocol improves fatigue life of zirconia crowns
No full textOBJECTIVE: To compare the fatigue life and damage modes of zirconia crowns fabricated with and without framework design modification when porcelain veneered using a fast or slow cooling protocol.METHODS: Composite resin replicas of a first molar full crown preparation were fabricated. Zirconia copings were milled as conventional (0.5mm even thickness, Zr-C, n=20,) or modified (lingual margin of 1.0mm thickness, 2.0mm height connected to two proximal struts of 3.5mm height, Zr-M, n=20). These groups were subdivided (n=10 each) according to the veneer cooling protocol employed: fast cooling (Zr-CFast and Zr-MFast) and slow cooling (Zr-CSlow and Zr-MSlow). Crowns were cemented and fatigued for 10(6) cycles in water. The number of cycles to failure was recorded and used to determine the interval databased 2-parameter probability Weibull distribution parameter Beta (β) and characteristic life value Eta (η).RESULTS: 2-parameter Weibull calculation presented β=5.53 and β=4.38 for Zr-MFast and Zr-CFast, respectively. Slow cooled crowns did not fail by completion of 10(6) cycles, thereby Weibayes calculation was applied. Increased fatigue life was observed for slow cooled crowns compared to fast cooled ones. Groups Zr-MFast and Zr-MSlow presented no statistical difference. Porcelain cohesive fractures were mainly observed in fast cooled groups. Slow cooled crowns presented in some instances inner cone cracks not reaching the zirconia/veneer interface.SIGNIFICANCE: Improved fatigue life in tandem with the absence of porcelain fractures were observed in slow cooled crowns, regardless of framework design. Crowns fast cooled chiefly failed by porcelain cohesive fractures.</p
Fatigue and damage accumulation of veneer porcelain pressed on Y-TZP
No full textObjectives: This study compared the reliability and fracture patterns of zirconia cores veneered with pressable porcelain submitted to either axial or off-axis sliding contact fatigue. Methods: Forty-two Y-TZP plates (12 mm x 12 mm x 0.5 mm) veneered with pressable porcelain (12 mm x 12 mm x 1.2 mm) and adhesively luted to water aged composite resin blocks (12 mm x 12 mm x 4 mm) were stored in water at least 7 days prior to testing. Profiles for step-stress fatigue (ratio 3:2:1) were determined from single load to fracture tests (n = 3). Fatigue loading was delivered on specimen either on axial (n = 18) or off-axis 30 degrees angulation (n = 18) to simulate posterior tooth cusp inclination creating a 0.7 mm slide. Single load and fatigue tests utilized a 6.25 mm diameter WC indenter. Specimens were inspected by means of polarized-light microscope and SEM. Use level probability Weibull curves were plotted with 2-sided 90% confidence bounds (CB) and reliability for missions of 50,000 cycles at 200 N (90% CB) were calculated. Results: The calculated Weibull Beta was 3.34 and 2.47 for axial and off-axis groups, respectively, indicating that fatigue accelerated failure in both loading modes. The reliability data for a mission of 50,000 cycles at 200 N load with 90% CB indicates no difference between loading groups. Deep penetrating cone cracks reaching the core-veneer interface were observed in both groups. Partial cones due to the sliding component were observed along with the cone cracking for the off-axis group. No Y-TZP core fractures were observed. Conclusions: Reliability was not significantly different between axial and off-axis mouth-motion fatigued pressed over Y-TZP cores, but incorporation of sliding resulted in more aggressive damage on the veneer. (C) 2009 Elsevier Ltd. All rights reserved.Nobel Biocare[2007-622]Nobel Biocare[2007-623
Monolithic CAD/CAM Lithium Disilicate Versus Veneered Y-TZP Crowns: Comparison of Failure Modes and Reliability After Fatigue
No full textPurpose: The aim of this research was to evaluate the fatigue behavior and reliability of monolithic computer-aided design/computer-assisted manufacture (CAD/CAM) lithium disilicate and hand-layer-veneered zirconia all-ceramic crowns. Materials and Methods: A CAD-based mandibular molar crown preparation, fabricated using rapid prototyping, served as the master die. Fully anatomically shaped monolithic lithium disilicate crowns (IPS e.max CAD, n = 19) and hand-layer-veneered zirconia-based crowns (IPS e.max ZirCAD/Ceram, n = 21) were designed and milled using a CAD/CAM system. Crowns were cemented on aged dentinlike composite dies with resin cement. Crowns were exposed to mouth-motion fatigue by sliding a WC-indenter (r = 3.18 mm) 0.7 mm lingually down the distobuccal cusp using three different step-stress profiles until failure occurred. Failure was designated as a large chip or fracture through the crown. If no failures occurred at high loads (> 900 N), the test method was changed to staircase r ratio fatigue. Stress level probability curves and reliability were calculated. Results: Hand-layer-veneered zirconia crowns revealed veneer chipping and had a reliability of < 0.01 (0.03 to 0.00, two-sided 90% confidence bounds) for a mission of 100,000 cycles and a 200-N load. None of the fully anatomically shaped CAD/CAM-fabricated monolithic lithium disilicate crowns failed during step-stress mouth-motion fatigue (180,000 cycles, 900 N). CAD/CAM lithium disilicate crowns also survived r ratio fatigue (1,000,000 cycles, 100 to 1,000 N). There appears to be a threshold for damage/bulk fracture for the lithium disilicate ceramic in the range of 1,100 to 1,200 N. Conclusion: Based on present fatigue findings, the application of CAD/CAM lithium disilicate ceramic in a monolithic/fully anatomical configuration resulted in fatigue-resistant crowns, whereas hand-layer-veneered zirconia crowns revealed a high susceptibility to mouth-motion cyclic loading with early veneer failures. Int J Prosthodont 2010; 23: 434-442.NIDCR[P01 DE01976]Ivoclar Vivaden
