Objective: The aim of the study was to evaluate the effect of aging through different thermocycling protocols on the flexural strength of a feldspathic ceramic. Material and Methods: Fifty ceramic ...bars, Vitablock Mark II (VITA), with dimensions of 18X4X2mm were prepared. The bars were randomly distributed to the groups (n = 10), which were defined according to the number of thermal cycles (TCy): G0 - no TCy; G500 - 500 cycles of TCy; G6000 - 6000 TCy; G10000 - 10000 TCy; G15000 - 15000 TCy. After aging, the specimens were subjected to the three point bending test in a universal testing machine (EMIC DL 1000), under 0.5mm/min speed and loading of 50kgf, until catastrophic failure. A sample of each group was evaluated for topographic morphology under Scanning Electron Microscopy. Results: For mechanical testing, the following mean values and standard deviation (MPa) were obtained: G0 (99.78 ± 5.07); G500 (101.64 ± 5.59); G6000 (98.13 ± 4.95); G10000 (91.77 ± 9.68); G15000 (101.51 ± 4.22). An analysis of variance by regression equation (p = 0.387) was performed, demonstrating a weak and non-significant correlation between flexural strength and number of thermal cycles. Conclusion: It can be concluded that aging in water solely by different numbers of temperature cycles did not influence on the flexural strength of a feldspathic ceramic. Keywords Material resistance; Aging; Ceramics.
This paper examines the spiritual works and practices of the German artist Anselm Kiefer and the lessons they provide to architectural thinking and doing in educational settings more and more driven ...by reductive material control. Considering Kiefer’s emotionally charged works, and their ability to speak about a larger totality, the text examines the relationships between material and space, material and history, material and language, that emerge in the artist’s working methods as a model for architects concerned with achieving spiritual awareness in a secular world. Through works and spaces experienced during the author’s visit to Kiefer’s former home and studio, La Ribaute, the paper examines how his work is a part of greater paradigmatic, spiritual works of theoretical architecture. By virtue of questioning the more banal practices of modernity, the author discusses how Kiefer’s acts of creation enrich our understanding of the processes used to conceive architectural atmospheres that involve linguistic, expressive, and indeed spiritual possibilities that have not been previously considered in relation to representational making.
Abstract To evaluate the flexural strength (FS) and flexural modulus (FM) of a commercial 3Y-TZ0P ceramic after artificial aging and either without or with two application times of non-thermal plasma ...treatments (NTP). In addition, changes in crystalline phase transformation and surface nano-topography after NTP application, during different aging periods, were evaluated. Ninety 3Y-TZP bars (45x4x3 mm) were made for FS and FM testing, and assigned to nine groups (n=10): no NTP/no aging (Control); no NTP/4h aging; no NTP/30h aging; 10s NTP/no aging; 10s NTP/4h aging; 10s NTP/30h aging; 60s NTP/no aging; 60s NTP/4h aging and 60s NTP/30h aging. Artificial accelerated aging was simulated using an autoclave (134º C at 2 bar) for up to 30h. FS and FM were assessed using a universal testing machine and data analyzed using a ANOVA and Tukey test (α=0.05). The volume change in zirconia monoclinic phase (MPV) was evaluated using X-ray diffraction and surface nano-topography was assessed using atomic force microscopy (baseline until 30h-aging). NTP application did not influence the FS and FM of zirconia. Compared to the Control (no NTP/no aging), the FS of zirconia samples treated for 30 hours in autoclave (“no NTP/30h aging” group) increased. Artificial aging for 30 hours significantly increased the FM of zirconia, regardless of NTP application. MPV tended to increase following the increase in aging time, which might result in the surface irregularities observed at 30h-aging. NTP did not alter the zirconia properties tested, but 30h-aging can change the zirconia FS, FM and MPV.
Resumo Avaliar a resistência à flexão (FS) e o módulo de flexão (FM) de uma cerâmica comercial 3Y-TZP após envelhecimento artificial, e com ou sem dois tempos de aplicação de plasma não térmico (NTP). Além disso, a transformação de fase cristalina e a nano-topografia de superfície após a aplicação de NTP, durante diferentes períodos de envelhecimento, foram avaliadas. Noventa barras 3Y-TZP (45x4x3 mm) foram feitas para testes de FS e FM, e distribuídas em nove grupos (n=10): sem NTP/sem envelhecimento (Controle); sem NTP/4h de envelhecimento; sem NTP/30h de envelhecimento; 10sNTP/sem envelhecimento; 10sNTP/4h; 10sNTP/30h; 60sNTP/sem envelhecimento; 60sNTP/4h e 60sNTP/30h. O envelhecimento artificial acelerado foi simulado em autoclave (134º C a 2 bar) por até 30 horas. FS e FM foram avaliados em máquina de ensaio universal e os dados analisados pela ANOVA e teste de Tukey (α = 0,05). A mudança de volume da fase monoclínica de zircônia (MPV) foi avaliada usando difração de raios-X e nano-topografia de superfície foi avaliada utilizando microscopia de força atômica (baseline até 30h). A aplicação do NTP não influenciou a FS e FM da zircônia. Comparado ao Controle (“sem NTP/sem envelhecimento”), a FS das amostras de zircônia tratadas por 30 horas em autoclave (“sem NTP/30h de envelhecimento”) aumentou. O envelhecimento artificial por 30 horas aumentou significativamente a FM da zircônia, independente do tempo de aplicação do NTP. O MPV tendeu a aumentar em função do aumento do tempo de envelhecimento para todos os grupos, que pode ter resultado nas irregularidades superficiais observadas com 30 horas de envelhecimento. O NTP não afetou as propriedades da zircônia testadas, mas o envelhecimento por 30 horas pode alterar a FS, FM e MPV da zircônia.
This case study examines how material resistance (limitations posed by the physical world) and graph interpretation intersected during a high school biology investigation using digital sensors. We ...use an extended episode from a small group to illustrate how, in an inquiry-based unit, measuring near the resolution limit of a sensor caused scaling issues in graphs. Qualitative videotape analysis focuses on both the students' attempts to make sense of a perceived lack of variation in the collected data and the teacher's and classroom researchers' misinterpretation of the students' difficulties with graph interpretation. We suggest that these educators, though experienced, could have benefited from additional strategies to help them recognise and respond to graph interpretation issues introduced by digital representations of real-world data, and that the students could have benefited from explicit prompts to discuss the limitations of their equipment. We describe several implications for researchers, teachers, and curriculum developers interested in implementing inquiry-based biology investigations using sensor data. We argue that students should be supported to recognise that encountering unexpected results from their investigations and working to understand what these results have to say about the real world is an important and valid part of the practice of real science.
•Masonry buildings represent half of the building stock in the education sector in Romania.•Comparing numerical models for subsequent retrofitting highlights their efficiency.•Premature failure of ...URM is avoided for confined masonry and jacketed masonry.
In order to study how retrofitting techniques applied to URM structures influence the failure modes and the displacement capacity of the buildings, a school building from Bucharest was modelled using 3DMacro software. The mixed structural system required a particular approach for the calculation model, in a software able to capture the interaction between the reinforced concrete elements (columns and tie beams) and the URM masonry panels.
Damage pattern evolution was analyzed for the three models capturing the gradual seismic improvements done in the past century, transforming the unreinforced masonry structure into a confined masonry one, with few RC elements, and eventually into a fully jacketed structure with densely spaced RC columns. The results obtained from the nonlinear static analyses were validated by means of global and local displacement limits associated with specific damage criteria.
The damage suffered after 1977 Vrancea earthquake and the current performance requirements in terms of seismic safety led to structural changes aimed at improving the behavior of masonry structures by means of interventions that marked the transition from an unreinforced masonry structural system to a retrofitted masonry structural system. The comparative analyses carried out between the behavior of the initial and the strengthened structure of the school intend to highlight the benefits of the retrofitting interventions performed, but also the situations in which the applied strengthening measures might prove to be excessive. Considering the case study is representative for the existing building stock in the education sector in Romania which needed subsequent seismic retrofitting in order to reach the required seismic safety, the results highlight the improved behavior after these interventions. The present works represent a topic of interest at national level, since it targets a large part of the existing building stock subjected to losses in case of an earthquake. Moreover, the past retrofitting interventions assessed in this paper represent a typical intervention done for similar structures, and therefore, the results obtained are representative for the Romanian building stock.
Objectives
To assess the probability of survival of crowns made with a 3Y-TZP, a 5Y-TZP, and a lithium disilicate.
Materials and methods
CAD-CAM premolar crowns with occlusal thicknesses of 1.0 mm or ...1.5 mm and cemented on a metal dye. Step-stress accelerated life testing (SSALT) was performed to access the use level probability Weibull curves and reliability were calculated for the completion of a mission of 100,000 cycles at 300 to 1200 N.
Results
All ceramics showed a high probability of survival (87–99%) at 300 N, irrespective of thickness. 3Y-TZP shows no significant decrease in the probability of survival up to 1200 N (83–96%). Lithium disilicate presented lower reliability than zirconia under the 600 N mission. 5Y-TZP showed lower reliability than 3Y-TZP at 1200 N. There was no significant difference in the Weibull modulus (3.23–7.12). 3Y-TZP had the highest characteristic strength (2483–2972 N), followed by 5Y-TZP (1512–1547 N) and lithium disilicate (971–1154 N).
Conclusion
Zirconia ceramics have a high probability of survival (up to 900 N-load), while lithium disilicate survives up to 300 N load only, irrespective of the thickness (1.0 mm or 1.5 mm).
Clinical relevance
The probability of survival of posterior crowns made with zirconia ceramics resists extreme loads while glass ceramics resist normal chewing loads. In addition, crowns with thinner occlusal face showed sufficient mechanical behavior.
Abstract
Introduction
This work aimed to demonstrate the resistance of the femoral-tibial joint collaterals of 60 dogs of undefned breed, euthanized at the Zoonoses Control Centre of the city of ...Petrolina (PE), North-Eastern Brazil.
Materials and Methods
The femur-tibial articulation was dissected to expose the collateral ligaments. Bones were cut on the distal third of the femur and the proximal third of tibia and fibula. The knee joint was kept bound only by the collateral ligaments and then submitted to destructive mechanical tests, evaluating the deformation of the ligaments (mm) per unit of time, (seconds), and the joint resistance.
Results
We could observe no side effects of contralateral joints. In a destructive mechanical assay, we detected that the medial collateral ligaments ruptured earlier than the lateral ones. The resistance of the lateral and medial ligament of the right limb of females was respectively 537.1N ± 413.6 and 360.1N ± 228.6; while in males, were of 632.4N ± 333.4 e 440.4N ± 227.1. About the left antimere, the females presented 442.4N ± 288 resistance on the lateral ligament and 417.4N ± 190.6. In males, the resistance was 605.8N ± 316.1 e 548.6N ± 2,333.7, respectively.
Conclusion
The results of our research will allow the development of synthetic tissues to replace the natural ligament of dogs in cases of rupture or degeneration.
Recently interest in lightweight concrete (LWC) has increased for its cost effectiveness and design reduction, however it has low resistance to external forces. Carbon nanotube (CNT) was incorporated ...to overcome this disadvantage and achieve high-strength in LWC. The structural response of CNT reinforced high-strength lightweight concrete (HSLC) beams was investigated considering specimen size, tensile reinforcement ratio, and stirrup spacing. As the tensile reinforcement ratio increased from 0.008 to 0.019, yielding and peak load of specimens improved by 92% and 73%, respectively. Interestingly, nanocrack bridging induced by CNT increased the ductility index of reinforced HSLC beams compared to conventional reinforced HSC and LWC beams in the low longitudinal reinforcement index range. At the end, a flexural design model for CNT reinforced HSLC beams was proposed and validated. This study aims to reinforce feasibility by providing both a basic reference for structural response and a cost analysis of CNT reinforced HSLC.
ABSTRACT Objective The aim of this study was to evaluate the in situ hardness, compressive strength and resilience of soft lining materials used in total removable prostheses in different time ...intervals Methods total of 48 rectangular test specimens (10 x 3 x 2 mm) were fabricated of each of the polyvinylsiloxane-based soft liner (Mucopren Soft) and acrylic resin-based material (Trusoft), which were placed on total removable prostheses bases of 12 volunteers (n = 12). The hardness (Shore A), compressive strength (in MPa) and resilience (in Kgf/cm2) were evaluated in different time intervals: 0, 7, 30 and 60 days, at three different locations of the specimens surface. Results The two-way ANOVA and Tukey test showed that the polyvinylsiloxane-based soft liner presented higher hardness values (p = 0.0113) and higher compressive strength (p=0.0252) than the acrylic resin-based material at immediate and 7 days evaluations. The polyvinylsiloxane-based soft liner presented higher resilience values than the acrylic resin-based material at all times (p = 0.0133). Hardness and compressive strength were similar for both materials at 30 and 60 days evaluations. Conclusions For both materials,there was a tendency for an increase of hardness, compressive strength and resilience over time, influenced by the composition of the tissue conditioner. The polyvinylsiloxane-based soft liner presented higher hardness, compressive strength and resilience than the acrylic resin-based material, specially considering a long-term evaluation up to 60 days.
RESUMO Objetivo O objetivo deste estudo foi avaliar in situ a dureza, resistência à compressão e resiliência de materiais para reembasamento utilizadas em próteses totais removíveis em diferentes intervalos de tempo. Métodos Um total de 48 corpos de prova retangulares (10 x 3 x 2 mm) foram confeccionados de cada uma dos reembasadores a base de polivinilsiloxano (Mucopren Soft, Kettenbach GmbH & Co) e resina acrílica (Trusoft, Bosworth), os quais foram posicionados na base de próteses totais removíveis de 12 voluntários (n = 12). A dureza (Shore A), resistência à compressão (em MPa) e resiliência (em Kgf/cm2) foram avaliadas em diferentes intervalos de tempo: 0, 7, 30 e 60 dias, em três diferentes localizações da superfície do corpo de prova. Resultados A ANOVA a dois critérios e o teste de Tukey mostraram que o reembasador a base de polivinilsiloxano apresentou maiores valores de dureza (p = 0,0113) e maior resistência à compressão (p=0,0252) do que o a base de resina acrílica nas avaliações nos tempos imediato e 7 dias. O reembasador a base de polivinilsiloxano apresentou maior resiliência que o a base de resina acrílica em todos os tempos (p = 0,0133). Dureza e resistência à compressão foram semelhantes para ambos os materiais nos tempos 30 e 60 dias de avaliação. Conclusões Para ambos os materiais, houve tendência de aumento da dureza, resistência à compressão e resiliência com o passar do tempo, influenciado pela composição dos materiais de rembasamento tecidual. O reembasador a base de polivinilsiloxano apresentou maior dureza, resistência à compressão e resiliência que o a base de resina acrílica, considerando-se especialmente o tempo de avaliação de 60 dias.
The service life of wood in outdoor use under humid conditions is mainly determined by its material resistance and the exposure situation. Different standards such as EN 350 (2016) point on the ...relevance of wood’s resistance against moisture for its expected service life. Recently, different standardized but also numerous nonstandardized methods were suggested to test the water permeability of wooden materials. In the context of this study, different European-grown soft- and hardwoods, tropical hardwoods, modified wood and wood treated with water- and oil-borne preservatives were subjected to floating and submersion tests according to CEN/TS 16818 (2018) and different short-term water uptake and release tests. Moisture performance data from field tests with the same materials were analyzed and used to assess the predictive power of different laboratory moisture indicators. The moisture characteristics suggested by CEN/TS 16818 (2018)—rm168 (residual moisture content after water uptake and release processes) and res312 (residue as a percentage of the absorbed moisture)—showed the little potential to predict the outdoor moisture performance of the tested materials. In contrast, the mean moisture content during absorption and desorption (MCmean) predicted well the outdoor moisture performance of the materials under test. Short-term water uptake and release of small specimens also showed high predictive power.
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