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Introduction: To verify the literature concerning the mechanical properties, measuring methods and the resultant force system developed by closing loops (CL). The effectiveness of a certain CL is related to its geometry and the nature of the wire material. To obtain the necessary performance CL must work in the elastic range and be geometrically configured to express an adequate force system, which is the result of compensatory gable bends and preactivation. It was performed a literature search in MEDLINE from 1974 to 2014 using search for “orthodontic AND retraction AND springs” and “orthodontic AND closing AND loops”. From the 147 papers resulted from Pubmed, 50 were chosen. Overall, many works seek not only improve the knowledge about the force system, but also a better understanding of their mechanical behavior. FEM, Holographic and Photoelastic studies, are tests commonly used before testing them experimentally. Wire material and the cross-section show a great influence in the choice of the geometric variables because the modulus of elasticity (E), modulus of resiliency (R) and the moment of inertia (I). Experimental tests should be preceded by numerical methods because the latter idealize a particular setting, and allows modifying variables.

This study aimed at the mechanical characterization, on a nanometric scale, of the constituents obtained for different fractions in duplex stainless-steel plates subjected to 850, 950, 1000, and 1150 °C heating treatments via hardness measurements and determining their influences on the fretting wear behavior of the studied steel. The obtained ferrite (α)-, austenite (γ)-, and sigma (σ)-phase fractions were determined using optical microscopy, scanning electron microscopy (SEM), and X-ray diffraction (XRD) techniques. The mechanical characterization was carried out using hardness measurement and fretting wear techniques via nanoindentation. For comparison purposes, the Vickers microhardness was also characterized to determine the effect of the σ phase, which eventually formed, on the obtained microstructure properties as a whole. Two distinct behaviors were observed, depending on the eventual formation of σ phase as a function of the treatment temperature: (i) specimens treated at 850 and 950 °C showed a hardening effect (HV0.5 values of 333 ± 15 and 264 ± 13, respectively) due to σ-phase precipitation (hereafter termed ‘as-aged’), and (ii) specimens treated at 1000 and 1150 °C (with HV0.5 values of 240 ± 13 and 249 ± 4, respectively) showed no σ-phase precipitation (hereafter termed ‘as-solubilized’). The increases in the microhardness values for the as-aged specimens were attributed to the hardness of the σ-phase precipitates (which showed nanohardness values varying in the 8.0–8.5 GPa range), which was approximately twice that of the austenite and ferrite grains (both phases showed nanohardness values in the 3.6–4.1 GPa range, on average). When formed (for fractions on the order of 8% and 3% at 850 and 950 °C, respectively), σ phase was mainly observed at the α/γ grain interfaces or boundaries. Fretting wear tests, using a diamond sphere with a radius of 10 μm as the counter body and a load of 20 mN, revealed the same wear mechanisms in the α/γ matrix for all studied conditions. However, as-solubilized specimens (heat-treated at 1000 and 1150 °C) displayed higher resistance to fretting micro-wear in the austenitic grains compared to the ferritic grains, indicating lower plastic deformation in the respective wear scars on the obtained tracks. In particular, as-aged specimens (heat-treated at 850 and 950 °C) exhibited lower coefficients of friction due to their higher surface resistances. The localized wear at σ-phase grains was much less pronounced than at ferrite and austenite grains. Overall, this study provides valuable insights into the mechanical behavior of microstructural changes in duplex steel at the nanometric scale.

O contexto escolar e o público adolescente foram bastante impactados pelo novo cenário de pandemia. Objetivo: Analisar quais fatores decorrentes da pandemia tem repercutido na saúde mental dos adolescentes em contexto escolar, bem como averiguar as principais estratégias promotoras de saúde mental no contexto escolar em tempos de pandemia. Método: Trata-se de um relato de experiência de práticas multiprofissionais no contexto escolar, envolvendo as áreas da psicologia e da enfermagem com os alunos do ensino médio de uma escola filantrópica da cidade de Teresina - PI. Resultados: Foram identificadas demandas relacionadas í saúde do adolescente e a partir das práticas dos respectivos profissionais foi possí­vel oportunizar estratégias de promoção í saúde dos mesmos. Conclusão: Ficou evidente que mesmo diante da situação pandêmica e das adversidades, a preocupação com a saúde e bem estar dos alunos é única e impulsionou para o desenvolvimento de novas ações dentro da escola.

O novo coronavírus surgiu na China em dezembro de 2019, o bloqueio pandêmico interrompeu a continuidade do aprendizado e desencadeou o isolamento social, mudanças na rotina, cancelamento das atividades fora de casa, perda da sensação de segurança e temores sobre o futuro. O objetivo deste estudo foi realizar uma revisão narrativa a fim de identificar como a pandemia e o aumento do uso dos dispositivos tecnológicos emissores de luz azul interferem na qualidade do sono de crianças e adolescentes. Foram analisados artigos científicos sobre a referida temática e a busca nas bases de dados Pubmed, Science Direct e Scielo.Identificou-se 252 artigos, onde 30 foram utilizados na construção. A pandemia de COVID-19 aumentou os níveis de estresse psicológico em crianças e adolescentes em todo o mundo e interferiu na qualidade do sono, o qual desempenha papel fundamental para a saúde mental e física, onde a duração e qualidade adequadas são essenciais. Devido ao isolamento, fechamento das atividades comerciais e adesão ao ensino remoto, houve um aumento e uso generalizado de dispositivos eletrônicos portáteis, dessa forma, o impacto na qualidade do sono desse público alvo tem se mostrado expressivo. Portanto, o controle e tempo de uso das telas devem ser observados na qualidade do sono entre crianças e adolescentes, como prioridade nos contextos familiar, escolar e clínico.

Metal conditioners (MC) are friction, wear, and heat-reducing agents between metal components in motion and are mainly used in engines and transmission boxes as aftermarket additives. Laboratory and field tests were conducted to assess the performance of a commercial MC. Laboratory tribotests revealed the MC’s potential to reduce wear and friction in lubricated steel contacts. Field studies were performed on two new motorcycles (160 cc) under urban driving conditions for 15,000 km. The physico-chemical properties of the used oils were similar and within the acceptable limits provided in the literature. The FTIR results showed that specific components in the MC formulation do not allow for a direct comparison between oils and their mixtures with MC. Regarding engine wear, MC provided overall aluminum and iron metal parts protection, mainly in the first 7000 km of engine break-in, but a higher wear of copper-containing parts, although at levels below the warning limits. Accurate measurements of engine components demonstrated there were changes of less than 0.05% in the cylinder, piston, and transmission system pieces, except for gear #5. The lubrication of the crown, pinion, transmission chain and gear #5 with the MC significantly increased their wear resistance. The motorcycle driven with MC maintained higher average fuel economy improvements (+1 km/L), representing a 2.5% gain compared to the other motorcycle. Although only two motorcycles were tested, the laboratory and field results suggested that mixing MC with the fully formulated oil (10W-30) reduces wear and friction during the break-in period.

Resumo: O presente artigo discute o conceito de “mundo da vida cotidiana”, uma das mais importantes contribuições da “sociologia fenomenológica” de A. Schutz para a teoria social contemporânea. Argumentamos que a premissa fundamental desse conceito se refere prioritariamente à questão de ação (fluxo de atividades sempre em vias de transformação e de concretização) e não apenas de significação. Partimos do pressuposto que a sua teoria assume um “caráter ontológico”: a existência humana consiste em ser/estar no mundo e é próprio do ser humano atuar. A ação é sempre circunstancial, requer um “ímpeto inicial” (motivo) e se constitui essencialmente como processo em curso (trajeto), o que difere do “ato” (o resultado desse percurso, a ação realizada). As significações, produzidas no fluxo de atividades, são interpretações de experiências passadas. Tal premissa levanta um desafio para a sociologia: como lidar com uma realidade que em si mesma é temporal, plural, incerta? Abstract: This article discusses the concept of “word of daily life”, one of the most important contributions of A. Schutz's “phenomenological sociology” to contemporary social theory. We argue that the fundamental premise of this concept refers primarily to the question of action (the flow of activities always in the process of transformation and realization) and not only of meaning. We start from the assumption that his theory assumes an “ontological character”: human existence consists in being in the world and it is proper to the human being to act. Action is always circumstantial, requires an “initial impetus” (motive) and is essentially constituted as an ongoing process (path), which differs from the “act” (the result of this path, the action taken). The meanings, produced in the flow of activities, are interpretations of past experiences. This premise raises a challenge for sociology: how to deal with a reality that in itself is temporal, plural, uncertain? Resumen: Este artículo discute el concepto de “mundo de la vida cotidiana”, una de las contribuciones más importantes de la “sociología fenomenológica” de A. Schutz a la teoría social contemporánea. Sostenemos que la premisa fundamental de este concepto se refiere principalmente a la cuestión de la acción (el flujo de actividades siempre en proceso de transformación y realización) y no sólo al significado. Partimos del supuesto de que su teoría asume un “carácter ontológico”: la existencia humana consiste en estar/ser en el mundo y es propio del ser humano actuar. La acción es siempre circunstancial, requiere un “impulso inicial” (motivo) y se constituye esencialmente como un proceso continuo (camino), que difiere del “acto” (el resultado de este camino, la acción tomada). Los significados, producidos en el flujo de actividades, son interpretaciones de experiencias pasadas. Esta premisa plantea un desafío a la sociología: ¿cómo tratar una realidad que en sí misma es temporal, plural, incierta?

O presente artigo discute o conceito de “mundo da vida cotidiana”, uma das mais importantes contribuições da “sociologia fenomenológica” de A. Schutz para a teoria social contemporânea. Argumentamos que a premissa fun-damental desse conceito se refere prioritariamente à questão de ação (fluxo de atividades sempre em vias de transformação e de concretização) e não apenas de significação. Partimos do pressuposto que a sua teoria assume um “caráter ontológico”: a existência humana consiste em ser/estar no mundo e é próprio do ser humano atuar. A ação é sempre circunstancial, requer um “ímpeto inicial” (motivo) e se constitui essencialmente como processo em curso (trajeto), o que difere do “ato” (o resultado desse percurso, a ação realizada). As significações, produzidas no fluxo de atividades, são interpretações de experiências passadas. Tal premissa levanta um desafio para a sociologia: como lidar com uma realidade que em si mesma é temporal, plural, incerta?

The duplex stainless steel UNS S32205 was plasma nitrided at 380 °C for 10 h using a gas mixture of 25% N2-75% H2. The thickness of the nitrided layer was 4.5 ± 0.5 μm, composed mainly of nitrogen-expanded austenite and iron nitrides precipitates. There was an increase in surface hardness around 2.6 and 3.8 times in the nitrided layer formed on the austenite and the ferrite phases, respectively, in relation to the untreated samples. The surface texture parameters skewness (Ssk), maximum peak height (Sp) and texture aspect ratio (Str) were the most appropriate parameters for studying the topography changes after treatment. An improvement in the localized corrosion properties after the nitriding treatment was revealed by the cyclic polarization curves. The nitrided samples showed higher pitting corrosion and repassivation potentials compared to the untreated material. The ferritic phases and grain boundaries were more susceptible to corrosion in the nitrided samples. The potentiodynamic curves of the nitrided samples exhibited a hillside on the passive-to-transpassive transition. This feature was already observed by other researchers, but it has not been well investigated. Potentiostatic studies demonstrated that metastable pitting took place on this transition.

Resumo Objetivo Análise biomecânica comparativa da resistência da fixação tibial para reconstrução ligamentar com parafuso de interferência, comparada com parafuso do tipo poste com arruela, e com fixação associada entre os métodos (fixação híbrida). Métodos Foram utilizados 54 corpos de prova (tíbia suína e tendão digital bovino), que foram divididos em 3 grupos com tipos de fixação semelhantes àqueles utilizados na reconstrução do ligamento cruzado anterior: 1) fixação com parafuso de interferência; 2) fixação com parafuso do tipo poste com arruela dentada sobre nó e fios de sutura; e 3) fixação com parafuso do tipo poste com arruela combinada com parafuso de interferência (fixação híbrida). Os testes foram realizados por meio de ensaios biomecânicos de tração tipo pull-out para determinação da rigidez e carga para falha (yield load) do sistema. Resultados O grupo com fixação híbrida apresentou maior rigidez final (59,10 ± 3,45 N/mm) do que os demais grupos (p Conclusão A fixação híbrida apresentou vantagens biomecânicas com relação ao sistema de fixação do enxerto de flexor digital bovino em tíbia suína durante os ensaios de tração.

Corrosion resistance of plasma carburized AISI 420 martensitic stainless steel was evaluated by cyclic polarization test in 3.5% NaCl solution. Two distinct treatment groups were studied with the purpose of evaluating the influence of the carburizing temperature and time on the corrosion behavior of treated material (one at 350–500 °C temperature range for 8, and 12 h times; and other one at 400 °C for 12–48 h time range, and at 450 °C for 4–16 h time range). To support the discussions on electrochemical test results, microstructural characterization was carried out using metallographic analysis and XRD techniques. Microstructural characterization results show that low temperature and short time treatments produce outer layer composed by α′C and Fe3C phases. High temperature and/or long time treatments promote outer layer Cr7C3 and Cr23C6 phases precipitation. Corrosion test results show improved carburized samples resistance, which is related to chromium-carbides precipitation-free outer layer formation. The Cr-carbides formation promotes a reduction on carburized samples corrosion resistance due to depletion of Cr in the solid solution of carburized layer. Finally, by confronting the behavior of untreated and carburized samples, it is verified the potentialities of the low-temperature plasma carburizing to enhance the corrosion resistance of AISI 420 MSS.

Samples of AISI 409 were thermochemically treated by the Solution Heat Treatment after Plasma Nitriding (SHTPN) process. SHTPN process consisted of a nitriding step followed by solution annealing at 1100 °C and rapid cooling down to room temperature. The second cycle of quenching (950 or 1050 °C), followed by tempering (250, 450, or 650 °C), was performed sequentially to SHTPN. Lubricated reciprocating tests were employed to analyze friction and wear behaviors. A bearing steel ball was used as a counterpart. The analysis of worn surfaces was assessed using optical interferometry and depth-sensing indentation. The last technique allows determining the work hardening caused by the wear process. Friction behavior was related to the deformation component: the higher the hardening, the higher the friction coefficient. Abrasion is the primary mechanism observed in all specimens, but there is a transitional behavior that depends on the original hardness of the surface. Samples with a similar hardness of bearing ball presented delaminated regions caused by highly deformed thin layer fatigue. Amongst SHTPN conditions NS-Q950-T2 and NS-Q1050-T2 presented the best balance of wear and corrosion performances.

The present paper verified the effect of the interbracket distance on the force system developed by orthodontic retraction springs with two delta geometries measured during space closure when spaces between teeth are present. By using a platform transducer, five different interbracket distances were tested. Also the finite element method was applied to know the von Mises stress during spring activation/deactivation process. It was concluded that the interbracket distance and spring geometry variables have not caused significant influence on the force system resulting from activations, but activation has produced a statistical difference.

Duplex surface treatments involving plasma nitriding (PN) followed by laser hardening (LH) were performed in this work on grade 450 compacted graphite iron (CGI) to investigate the effects of PN duration (1 and 3 h) and LH power (400, 449, and 514 W) on microstructure evolution, nitrogen profile, and hardening depth of CGI. X-ray diffraction (XRD) phase analysis indicated a reduction in and partial decomposition of e and γ’ nitrides corresponding to an increase in laser power. The existence of a new nitrogen-rich austenitic phase—FeN0.076—was observed along with the identification of certain iron oxides. The proposed duplex treatment of CGI was found to facilitate the establishment of duplex layers with higher surface hardness (826–951 HK 0.05) and greater hardening depths (300–750 μm). Additionally, a reduction in the hardness gradient was observed between the surface and substrate. This affords a major advantage in applications involving operations on mechanical components.

The reactions that can occur on organic materials treated in plasma enviorement are strongly affected by surface temperature, thus the sharp determination of this variable is extremely important to process control. In situ temperature measurements are often employed; however, the measured point is generally under the treated surface. If in metallic materials the high thermal conductivity minimizes this problem, in non-metallic materials processing it becomes important, because its thermal resistivity besides a high sensibility to small temperature variations. The present work uses a simulation tool to extract thermal data on Ar+O2 RF plasma processing of Stearic Acid. Experimental data were obtained by thermocouples placed inside the samples. The extrapolation of surface temperature was performed by numerical simulation with Autodesk CFD software v.15.1. Results show that the temperature of the surface reaches values higher than the ones measured inside the sample holder. This difference of temperature is in good agreement with the visual observation of the phase transformations in the treated material, showing a simple and valuable tool to better control of plasma treatments.

The UNS S32750 super duplex stainless steel (SDSS) was low temperature plasma nitrided at 350 °C and 400 °C for 4 h. Pitting and crevice corrosion resistance was evaluated using electrochemical techniques in a NaCl neutral solution. Nitriding treatments resulted in increased in hardness, general corrosion resistance and in the passive layer breakdown potential. Regarding crevice corrosion tests, the nitrided surfaces showed lower current densities during the potentiostatic polarization and lower corrosion depths when compared to the untreated surface. The nitrogen played a fundamental role in the passivation behavior and in the susceptibility to repassivation of localized corrosion.

The purposes of this study were to evaluate the effects of different preactivation bends on the force system and the mechanical stresses of beta-titanium T-loop orthodontic springs. A tridimensional T-loop spring finite element model was built aiming to obtain reactive forces and moments in the three directions (x, y and z) as well as the moment–force ratios (M/F) for the sagittal and occlusal planes considering different gable bends. Using a transducer designed to measure forces in the x- and y-axis and moment around the z-axis, experimental tests were performed to validate the numerical analysis. It was observed that F x increases as the angle between extremities increases. The F x magnitude changed from 0.2 to 2.0 N. F y forces presented very low magnitude while in z direction they were null. In the sagittal plane, decreasing the gable bends increases the M/F ratio. On the other hand, in the occlusal plane, no change in the M/F ratio values was observed with the variation of the gable bends. The results obtained from the analyses showed that the M/F ratio presented different values because of different preactivation bends formed between alpha and beta extremities, consequently different types of dental movement can be produced. In the occlusal plane, no movement tendency was observed while in the sagittal plane there was a movement tendency to produce uncontrolled tipping, controlled tipping, translation and finally root correction. Translation tendency was observed during deactivation starting at 5.0 mm without crown rotation.

The properties of the “nitrogen expanded ferrite” or αN phase have been scarcely studied to date. This phase was obtained here on a super ferritic stainless steel (SFSS) by plasma immersion ion implantation (PIII), which is a suitable technique to produce near to surface modifications on the Fe Cr alloys due to the control of energy delivered to the surface. The UNS S44400 SFSS, a special alloy developed for extreme corrosion environments, was nitrided by PIII at temperatures from 300 °C to 400 °C resulting in the αN phase as the main product of nitriding on the modified layer. The surface hardness measured by nanoindentation was investigated in the modified layers, reaching up to 3.5 times (the 400 °C condition) the hardness value presented by the untreated sample. The nitrided surfaces also presented improved corrosion resistance in comparison to the untreated sample, inferred by potentiodynamic polarization tests in NaCl electrolyte. This was evidenced by increased corrosion and pitting potentials (Ecorr and Ep, respectively) and decreased corrosion and passive current densities (icorr and ip, respectively). Moreover, through of the analysis in the polarization curves of the nitrided samples, a greater stability of the passive layer and repassivation processes were identified. The best corrosion resistance was obtained for the sample nitrided at 300 °C, which presented the greatest reduction in icorr and ip (6.6 μA/cm2 and 43 μA/cm2, respectively) and increase in Ecorr and Ep (108 mV and 214 mV, respectively), when compared to the untreated sample. In both untreated and nitrided samples, the addition of Nb and Ti in this alloy to prevent intergranular corrosion led to the formation of N- Ti-Nb-Mo precipitates that acted as initiators of pitting corrosion.

This work presents the application of Solution Heat Treatment after Plasma Nitriding (SHTPN) followed by requenching and tempering to the AISI 409 stainless steel aiming to increase hardness with no compromise of corrosion resistance. The SHTPN process consists of applying solution treatment to a previously plasma nitrided surface, promoting the dissolution of nitrides and the formation of a nitrogen-rich layer, in which nitrogen is in solid solution. When applied to ferritic stainless steels, SHTPN allows the obtention of a high‑nitrogen martensitic layer. It is presented an evaluation of the effects of requenching (from 950 and 1050 °C) and tempering (at 250, 450 and 650 °C) processes on the microstructure, hardness, and corrosion resistance of the nitrided layer of samples previously treated by SHTPN. Corrosion resistance was assessed through cyclic potentiodynamic polarization tests carried out in NaCl 0.5 mol/L, according to ASTM G150 . Optical and scanning electron microscopy, wavelength dispersive spectroscopy, and X-ray diffraction were applied to microstructural and phase characterization. Surface hardening was evaluated by Vickers microhardness tests. Results have shown that the requenching of SHTPN samples promoted a deepening of the nitrided layer and microstructure refinement. The process with requenching from 1050 °C and tempering at 250 °C led to increasing both hardness and corrosion resistance. These results confirmed that nitrogen in solid solution increases the hardness and the potential for pit nucleation in the AISI 409 stainless steel.

Compacted graphite iron is an interesting material class for automotive applications. CGI-450 grade cast iron was subjected to various surface treatments: plasma nitriding (PN), laser hardening (LH), and PN followed by LH (PN+LH). The resulting tribological behaviors were evaluated by means of linear scratch testing under progressive loading (40–70 and 70–95 N). The PN+LH treatment yielded the lowest friction coefficient and shallowest scratching. In this case, the outermost layer was composed of oxide phases (Fe2O3 and Fe3O4), underlain by a compound layer (oxides + nitrides + martensite) and a high-resistance martensitic layer with accompanying nitrides and carbides. These underlying layers provided high load capacity for the external layers, allowing them to function as solid lubricants.

RESUMO A adição de nitrogênio em aços inoxidáveis tem sido estudada como alternativa à produção de materiais que combinem boas propriedades mecânicas, resistência à corrosão e ao desgaste. Alguns métodos de enriquecimento de nitrogênio se respaldam em processos difusivos como nitretação a baixa e alta temperatura. Dentre estes, a nitretação seguida do Tratamento Térmico de Solubilização (NTTS), que consiste na realização de nitretação, com o objetivo de inserir o nitrogênio no material, seguido de um tratamento térmico de solubilização, que dissolve os nitretos, fazendo com que o nitrogênio se apresente em solução sólida intersticial. Neste trabalho aplicou-se o NTTS ao aço inoxidável martensítico ASTM CA-6NM. A nitretação a plasma foi realizada a uma temperatura de 630 °C por 3 horas e a solubilização em três diferentes condições (1200 °C por 30 minutos, 1200 °C por 1 hora e 1100 °C por 1 hora). As amostras foram analisadas através de difração de raios-x, microscopia ótica e medições de microdureza na região transversal da amostra. Foi verificado um aumento da dureza superficial dos aços CA-6NM, porém não foi observada a estabilização da fase austenita na região superficial mais rica em nitrogênio. O ensaio de cavitação foi realizado conforme norma ASTM G32/09, porém utilizando o método indireto, no qual a amostra não é fixada diretamente no sonotrodo. A região cavitada das amostras foi caracterizada através de microscopia eletrônica de varredura. Foi verificado que as amostras tratadas obtiveram menores taxas de erosão, e que houve diferença entre as diferentes condições de solubilização.

To verify whether the combination of tibial cross pin fixation and femoral screw fixation presents biomechanical advantages when compared to femoral cross pin fixation and tibial screw fixation for the reconstruction of the anterior cruciate ligament (ACL).Thirty-eight porcine knees and bovine extensor digitorum tendons were used as the graft materials. The tests were performed in three groups: (1) standard, used fourteen knees, and the grafts were fixated with the combination of femoral cross pin and a tibial screw; (2) inverted, used fourteen knees with an inverted combination of tibial cross pin and a femoral screw; (3) control, ten control tests performed with intact ACL. After the grafts fixation, all the knees were subjected to tensile testing to determine yield strength and ultimate strength.There was no statistically significant difference in survival techniques in regard to strength, yield load and tension. There was a higher survival compared in the standard curves of yield stress (p 0.05).There is no biomechanical advantage, observed in animal models testing, in the combination of tibial cross pin fixation and femoral screw when compared to femoral cross pin fixation and tibial screw.Investigar se a fixação transversa tibial com parafuso femoral apresenta vantagens biomecânicas sobre a fixação transversa femoral com parafuso tibial na reconstrução do ligamento cruzado anterior (LCA).Foram usados como modelos de testes joelhos suínos e tendões extensores digitais bovinos. Foram submetidos à reconstrução do LCA 28 joelhos: 14 foram fixados com parafuso na tíbia e implante transverso no fêmur (grupo padrão) e 14 com parafuso no fêmur e fixação transversa na tíbia (grupo invertido). Os modelos foram submetidos aos testes de tração.Não houve diferença estatisticamente significante na sobrevivência das técnicas no que tange a força, força máxima sem falha e tensão. Houve uma sobrevivência maior no grupo padrão na comparação das curvas de tensão de limite elástico (p 0,05).Não há vantagem biomecânica da fixação transversa tibial com parafuso femoral em relação à fixação transversa femoral com parafuso tibial, observada em testes com modelos animais.

Plasma surface cleaning is an alternative process that aims at the fully removal of organic contaminants on several kinds of materials. Despite its advantages, there are still lacks on the comprehension of the complex relations between plasma-generated species and organic molecules during plasma cleaning. In the present work, a linear alkane (hexatriacontane - C36H74), used as a contaminant model, was exposed to an Argon radiofrequency (RF) inductively coupled plasma (ICP). The by-products from degradation were monitored by optical emission spectroscopy (OES) and residual gas analysis (RGA), to identify the influence of sample positioning on E and H discharge modes regions. The exposition to H-mode discharge resulted in more intense and profuse emissions of C-H and C2 systems. RGA results show similar byproducts from degradation in both modes; however, the intensity from treatment in H-mode is largely greater. It was also observed that plasma etching in H-mode is enough to melt the sample, while E-type discharge leaves the surface of the sample apparently unchanged.

OBJECTIVE: A systematic review on nickel-titanium wires was performed. The strategy was focused on Entrez-PubMed-OLDMEDLINE, Scopus and BioMed Central from 1963 to 2008. METHODS: Papers in English and French describing the behavior of these wires and laboratorial methods to identify crystalline transformation were considered. A total of 29 papers were selected. RESULTS: Nickel-titanium wires show exceptional features in terms of elasticity and shape memory effects. However, clinical applications request a deeper knowledge of these properties in order to allow the professional to use them in a rational manner. In addition, the necessary information regarding each alloy often does not correspond to the information given by the manufacturer. Many alloys called "superelastic" do not present this effect; they just behave as less stiff alloys, with a larger springback if compared to the stainless steel wires. CONCLUSIONS: Laboratory tests are the only means to observe the real behavior of these materials, including temperature transition range (TTR) and applied tensions. However, it is also possible to determine in which TTR these alloys change the crystalline structure.

OBJETIVO: Determinar a resistência inicial de fixação do sistema RigidFix® e comparar com o método tradicional de fixação que utiliza parafusos de interferência metálicos. Avaliar a resistência da fixação com o sistema RigidFix® ao se modificar o posicionamento rotacional do bloco ósseo no interior do túnel femoral. MÉTODOS: 40 espécimes de joelhos (soldras) de ovinos, foram submetidos à reconstrução do ligamento cruzado anterior (LCA)utilizando enxerto osso-tendão-osso. Em 20 espécimes utilizou-se o método RigidFix®, este grupo foi subdividido em dois, 10 joelhos foram utilizados para fixação através da esponjosa e 10 para fixação cruzando a tábua óssea cortical. Nos 20 espécimes restantes fixou-se o enxerto com parafusos de interferência metálico de 9mm. RESULTADOS: A comparação do método RigidFix® com o método de fixação com parafuso de interferência metálico não mostrou diferenças estatisticamente significativas ao se considerar carga máxima e rigidez, também não houve diferenças estatisticamente significativas ao se modificar o posicionamento rotacional do bloco ósseo no interior do túnel femoral. Para estas avaliações considerou-se o p < 0,017. CONCLUSÃO: A fixação do enxerto osso-tendão-osso com dois pinos bioabsorvíveis, independente do posicionamento rotacional no túnel femoral, permite uma fixação comparável em termos de resistência inicial ao parafuso de interferência metálico neste modelo experimental.OBJECTIVE: to determine the initial resistance of fixation using the Rigid Fix® system, and compare it with traditional fixation methods using metal interference screws; and to evaluate the resistance of the fixation with the rigid fix system when the rotational position of the bone block is altered in the interior of the femoral tunnel. METHODS: forty ovine knee specimens (stifle joints) were submitted to anterior cruciate ligament reconstruction (ACL) using a bone-tendon-bone graft. In twenty specimens, the RigidFix® method was used; this group was subdivided into two groups: ten knees used for fixation with trabecular bone screw, and ten for fixation passing through the layer of cortical bone. In the twenty remaining specimens, the graft was fixed with 9mm metal interference screws. RESULTS: comparison of the Rigidfix® method with the metal interference screw fixation method did not show any statistically significant differences in terms of maximum load and rigidity; also, there were no statistically significant differences when the rotational position of the bone block was altered inside the femoral tunnel. For these evaluations, a level of significance of p < 0.017 was considered. CONCLUSION: fixation of the bone-tendon-bone graft with 2 bioabsorbable pines, regardless of the rotational position inside the femoral tunnel, gave a comparable fixation in terms of initial resistance to the metal interference screw, in this experimental model.

OBJETIVO: Determinar a resistência inicial de fixação do sistema RigidFix® e comparar com o método tradicional de fixação que utiliza parafusos de interferência metálicos. Avaliar a resistência da fixação com o sistema RigidFix® ao se modificar o posicionamento rotacional do bloco ósseo no interior do túnel femoral. MÉTODOS: 40 espécimes de joelhos (soldras) de ovinos, foram submetidos à reconstrução do ligamento cruzado anterior (LCA)utilizando enxerto osso-tendão-osso. Em 20 espécimes utilizou-se o método RigidFix®, este grupo foi subdividido em dois, 10 joelhos foram utilizados para fixação através da esponjosa e 10 para fixação cruzando a tábua óssea cortical. Nos 20 espécimes restantes fixou-se o enxerto com parafusos de interferência metálico de 9mm. RESULTADOS: A comparação do método RigidFix® com o método de fixação com parafuso de interferência metálico não mostrou diferenças estatisticamente significativas ao se considerar carga máxima e rigidez, também não houve diferenças estatisticamente significativas ao se modificar o posicionamento rotacional do bloco ósseo no interior do túnel femoral. Para estas avaliações considerou-se o p < 0,017. CONCLUSÃO: A fixação do enxerto osso-tendão-osso com dois pinos bioabsorvíveis, independente do posicionamento rotacional no túnel femoral, permite uma fixação comparável em termos de resistência inicial ao parafuso de interferência metálico neste modelo experimental. OBJECTIVE: to determine the initial resistance of fixation using the Rigid Fix® system, and compare it with traditional fixation methods using metal interference screws; and to evaluate the resistance of the fixation with the rigid fix system when the rotational position of the bone block is altered in the interior of the femoral tunnel. METHODS: forty ovine knee specimens (stifle joints) were submitted to anterior cruciate ligament reconstruction (ACL) using a bone-tendon-bone graft. In twenty specimens, the RigidFix® method was used; this group was subdivided into two groups: ten knees used for fixation with trabecular bone screw, and ten for fixation passing through the layer of cortical bone. In the twenty remaining specimens, the graft was fixed with 9mm metal interference screws. RESULTS: comparison of the Rigidfix® method with the metal interference screw fixation method did not show any statistically significant differences in terms of maximum load and rigidity; also, there were no statistically significant differences when the rotational position of the bone block was altered inside the femoral tunnel. For these evaluations, a level of significance of p < 0.017 was considered. CONCLUSION: fixation of the bone-tendon-bone graft with 2 bioabsorbable pines, regardless of the rotational position inside the femoral tunnel, gave a comparable fixation in terms of initial resistance to the metal interference screw, in this experimental model.

The influence of hydrogen loading temperature on the mechanical strength of optical fibers is investigated. Fibers subjected to high-pressure hydrogen loading at different temperatures were submitted to bend tests, and the results compared with those for pristine fibers. The Weibull probability distribution function was used to analyze the data of the mechanical bending strength of the fibers. Fiber strength is reduced by the presence of hydrogen, and this decrease is greater for higher hydrogen loading temperatures. The mechanical properties of the polymers used to coat fibers are affected by the hydrogen loading process and also by the increase in temperature. However, there is no evidence of cracks formation that might allow water to penetrate to the surface of the glass. Observation using scanning electron microscopy revealed that the morphology of fractures in nonhydrogen-loaded fibers have distinct fracture characteristics to that of fibers that are hydrogen loaded at 90°C and 120°C.

Austenitic stainless steels, although highly resistant to general corrosion, are susceptible to localized pitting or crevice corrosion. Corrosion resistance and mechanical properties could be enhanced by adding nitrogen to the alloy in solid solution. The methods currently in use involve fusion and solidification of the material, which may often be a deterrent, from the cost–benefit analysis stand point. In this article, the solution heat treatment after plasma nitriding (SHTPN) is presented as a new method to increase the surface nitrogen content in the solid state. The results obtained demonstrated the efficiency of this technique, by which the achieved thickness of the nitrided steel reaches up to 200 μm with 0.45 wt% of nitrogen.

Ao se situar no campo da metateoria, o presente trabalho tem por objetivo discutir uma das principais premissas que está subjacente à sociologia contemporânea: a historicidade. Contrapondo-se à teoria sociológica desenvolvida entre as décadas de 1940 e 1970, as "novas sociologias" têm procurado ultrapassar um pressuposto epistemológico daquele período - a superdeterminação pela teoria. Nesse esforço, têm outorgado à ideia de historicidade uma posição central no entendimento da ação humana. Constituindo-se como aberturas para o futuro (seu componente de "liberdade"), a ação, longe de ser um processo "cego", sempre revela necessariamente tanto o seu enraizamento no mundo social e físico quanto a possibilidade de transcender essa situação.Situated in the field of metatheory, the present paper aims to discuss one of the main premisses underlying contemporary sociology: the idea of historicity. As opposed to the sociological theory produced being the 1940s and 1970s, the new sociologies have sought to overcome the dominant epistemological premise of that period - overdeterminantion by theory. In their effort, they have granted the idea of historicity a central role in the understanding of human action. Action is not a blind process: as an opening to the future (component of liberty), it reveals both its grounding on the social and physical situation and its possibility of transcending that situation.

The crescent search for production time reduction is a factor that stimulates the improvement of the existent manufacturing techniques. In this work, a combined process using tools that perform punching followed by broaching in only one operation is studied in order to obtain holes with improved precision and surface finish. This researched combo process should make possible the manufacturing of pieces in less time with better use of material and equipment. This allows the use of only one process for heavy-duty jobs on thick sheet metal. In order to study this process, eighteen tools with three types of geometry with parallel and nonparallel cutting angle were made. Tool lubrication/cooling conditions were also analyzed using cutting fluids with concentrations of 100, 75 and 50% Hislip with respective 0, 25 and 50% of water. The hole final surface roughness, diameter and conical form, cutting tool angles, tool temperatures and cutting tool degradation were analyzed. The data obtained through the analysis of the variance (ANOVA), showed that this process is viable due holes obtained with overall superior quality, when compared with the ones generated in conventional stamping processes. Holes produced by tools types I, II and III presented good results in the holes overall precision. Nevertheless, in general, the best results were seen using tools type I, with punch angle of 22.5° and, lubrication/cooling conditions using 75% Hislip concentration as cutting fluid (water emulsion).