Your browser doesn't support javascript.
loading
Mostrar: 20 | 50 | 100
Resultados 1 - 20 de 28
Filtrar
1.
Rom J Morphol Embryol ; 65(2): 349-352, 2024.
Artigo em Inglês | MEDLINE | ID: mdl-39020551

RESUMO

In this comprehensive case report, we examine a 29-year-old male who suffered a high-energy vehicular accident, resulting in a type III Hawkins fracture of the talus. This specific fracture type is critically associated with a greater than 90% risk of progressing to avascular necrosis (AVN) of the talus, a severe and debilitating condition. Alongside this, the patient sustained fractures of the medial and lateral malleolus. Due to extensive swelling and severe circulatory disorders, an immediate emergency surgical procedure was necessitated, employing nail fixation as a stabilizing intervention. Over the course of 12 months following the surgery, despite routine post-operative imaging including X-rays and computed tomography (CT) scans, the patient continued to experience significant pain and impairment. This condition led to further investigations, culminating in a magnetic resonance imaging (MRI) that revealed an area of 19.8∕20.9 mm of AVN on the talus dome's upper-lateral facet. Interestingly, earlier CT scans had indicated multiple osteitic lesions, but these findings lacked a clear clinical correspondence, presenting a diagnostic challenge. To resolve this ambiguity and to definitively distinguish between necrosis and infection, a targeted histopathological analysis was deemed necessary. This analysis was conducted on a bone fragment extracted during a follow-up surgical procedure for nail removal. The results from this analysis present an area of bone and myeloid tissue necrosis unequivocally confirming the presence of AVN, effectively ruling out osteitis as a potential diagnosis. This critical diagnostic clarification allowed for a shift in therapeutic strategy, enabling the initiation of a more focused and potentially curative treatment regimen.


Assuntos
Osteonecrose , Tálus , Humanos , Masculino , Adulto , Osteonecrose/patologia , Osteonecrose/etiologia , Osteonecrose/diagnóstico por imagem , Tálus/patologia , Tálus/lesões , Tomografia Computadorizada por Raios X
2.
Nanomaterials (Basel) ; 14(13)2024 Jul 06.
Artigo em Inglês | MEDLINE | ID: mdl-38998760

RESUMO

A Ni2MnSn Heusler alloy was obtained as a single B2 phase after 12 h of mechanical milling. The influence of prolonged milling on the phase stability was analysed for milling times up to 50 h, related to mean crystallite size, lattice strain, and electrical resistivity. The nature of the powders in the milled range was found to be nanocrystalline, with a mean crystallite size of about 33 ± 2 nm. An evaluation of the internal stresses induced by milling was performed, a linear behaviour was found, and a coefficient of the internal stress increase with milling time was proposed. Particle size distributions of milled samples were analysed, and the morphology of the powders was visualised by scanning electron microscopy. The elemental distribution of milled samples was quantified by energy-dispersive X-ray spectroscopy. Electrical resistivity measurements were performed on compacted samples, and their behaviour with milling time was analysed.

3.
Bioengineering (Basel) ; 10(12)2023 Dec 13.
Artigo em Inglês | MEDLINE | ID: mdl-38136010

RESUMO

BACKGROUND: Breast cancer is arguably one of the leading causes of death among women around the world. The automation of the early detection process and classification of breast masses has been a prominent focus for researchers in the past decade. The utilization of ultrasound imaging is prevalent in the diagnostic evaluation of breast cancer, with its predictive accuracy being dependent on the expertise of the specialist. Therefore, there is an urgent need to create fast and reliable ultrasound image detection algorithms to address this issue. METHODS: This paper aims to compare the efficiency of six state-of-the-art, fine-tuned deep learning models that can classify breast tissue from ultrasound images into three classes: benign, malignant, and normal, using transfer learning. Additionally, the architecture of a custom model is introduced and trained from the ground up on a public dataset containing 780 images, which was further augmented to 3900 and 7800 images, respectively. What is more, the custom model is further validated on another private dataset containing 163 ultrasound images divided into two classes: benign and malignant. The pre-trained architectures used in this work are ResNet-50, Inception-V3, Inception-ResNet-V2, MobileNet-V2, VGG-16, and DenseNet-121. The performance evaluation metrics that are used in this study are as follows: Precision, Recall, F1-Score and Specificity. RESULTS: The experimental results show that the models trained on the augmented dataset with 7800 images obtained the best performance on the test set, having 94.95 ± 0.64%, 97.69 ± 0.52%, 97.69 ± 0.13%, 97.77 ± 0.29%, 95.07 ± 0.41%, 98.11 ± 0.10%, and 96.75 ± 0.26% accuracy for the ResNet-50, MobileNet-V2, InceptionResNet-V2, VGG-16, Inception-V3, DenseNet-121, and our model, respectively. CONCLUSION: Our proposed model obtains competitive results, outperforming some state-of-the-art models in terms of accuracy and training time.

4.
Medicina (Kaunas) ; 59(10)2023 Oct 09.
Artigo em Inglês | MEDLINE | ID: mdl-37893515

RESUMO

Background and Objectives: Although fiber posts are widely used in the restoration of endodontically treated teeth (ETT), their ideal cementation depth into the root canal is still debated in literature. The aim of the present study was to evaluate whether the different intra-radicular insertion lengths of the fiber posts influence the fracture strength of ETT. Materials and Methods: A total of 10 permanent human lower incisors with straight roots of similar length and volume extracted for periodontal reason were sectioned 2 mm above the cement-enamel junction (CEJ) to a total length of 18 mm and endodontically treated in the same manner, then randomly divided into two groups of five each (Groups 1 and 2, n = 5). Two sound incisors, with no endodontic treatment, were used as the control group (Group 3, n = 2). After one week of storage in a humid environment, spaces for fiber post no. 1 (Reforpost, Angelus, Londrina, PR, Brazil) were prepared in the first two groups at a depth of 5 mm (Group 1) and 7 mm (Group 2), and the fiber posts were adhesively cemented using self-adhesive resin cement (Maxcem Elite, Kerr GmbH, Herzogenrath, Germany). After 7 days, the samples were vertically positioned and fixed in a self-curing transparent acrylic resin, up to 2 mm below the CEJ level, and mechanically tested in compression after another week of storage using a displacement-controlled testing machine up to each sample's fracture. The force-displacement curves were recorded for each sample, the means were calculated for each group and a statistical comparative analysis between groups was conducted. Results: Although no statistically significant differences between groups were observed, the highest mean fracture force (N) was recorded in Group 2 (1099.41 ± 481.89) in comparison to Group 1 (985.09 ± 330.28), even when compared to the sound, non-treated teeth (1045.69 ± 146.19). Conclusions: Within the limitations of this in vitro study, teeth where fiber posts were placed deeper into the root canal (7 mm) recorded slightly higher fracture forces in comparison with shorter lengths (5 mm). However, similar biomechanical performances obtained in the mechanical tests showed no statistical differences between the 7 mm and the 5 mm inserted posts.


Assuntos
Fraturas dos Dentes , Dente não Vital , Humanos , Resistência à Flexão , Resinas Compostas , Dente não Vital/terapia , Incisivo
5.
Materials (Basel) ; 16(17)2023 Aug 25.
Artigo em Inglês | MEDLINE | ID: mdl-37687525

RESUMO

The purpose of this paper is to compare the fracture behavior of interfaces obtained using fourth-generation and universal dental adhesives. The study relies on optic and SEM to evaluate the dentin-adhesive-restoration material interface of the samples and also on FEA simulation of fracture behavior. Specimen fabrication relied on 20 extracted teeth, in which class I cavities were created according to a protocol established based on the rules of minimally invasive therapy. For the direct adhesive technique, the adhesives used were: three-step All Bond, three-batch A and one-step Clearfil Universal Bond Quick-batch B. The restoration was performed with the same composite for both adhesives: Gradia direct posterior. The simulation used a 3D reconstructed molar on which geometric operations were performed to obtain an assembly that replicated a physical specimen. Material properties were applied to each component based on the information found in the literature. A simplified model for crack propagation was constructed, and using the fracture mechanics tool in Ansys 2019, the stress intensity factors that act at the crack tip of the adhesive interface were obtained. Mechanical simulation and microscopic investigation showed us how the interface of the dentine-adhesive-filling material performed in cases of both dental adhesives and for a certain loading condition. Important differences were identified among the adhesives, the fourth generation being superior to the fourth generation especially due to the separate steps in which the tooth surface was prepared for adhesion.

6.
Genes (Basel) ; 14(5)2023 04 22.
Artigo em Inglês | MEDLINE | ID: mdl-37239315

RESUMO

Lamiaceae is one of the largest botanical families, encompassing over 6000 species that include a variety of aromatic and medicinal spices. The current study is focused on three plants within this botanical family: basil (Ocimum basilicum L.), thyme (Thymus vulgaris L.), and summer savory (Satureja hortensis L.). These three species contain primary and secondary metabolites such as phenolic and flavonoid compounds, fatty acids, antioxidants, and essential oils and have traditionally been used for flavoring, food preservation, and medicinal purposes. The goal of this study is to provide an overview of the nutraceutical, therapeutic, antioxidant, and antibacterial key features of these three aromatics to explore new breeding challenges and opportunities for varietal development. In this context, a literature search has been performed to describe the phytochemical profile of both primary and secondary metabolites and their pharmacological uses, as well as to further explore accession availability in the medicine industry and also to emphasize their bioactive roles in plant ecology and biotic and abiotic stress adaptability. The aim of this review is to explore future perspectives on the development of new, highly valuable basil, summer savory, and thyme cultivars. The findings of the current review emphasize the importance of identifying the key compounds and genes involved in stress resistance that can also provide valuable insights for further improvement of these important medicinal plants.


Assuntos
Lamiaceae , Ocimum basilicum , Óleos Voláteis , Plantas Medicinais , Thymus (Planta) , Humanos , Melhoramento Vegetal , Óleos Voláteis/farmacologia , Óleos Voláteis/química , Ocimum basilicum/química , Estresse Fisiológico
7.
Materials (Basel) ; 16(7)2023 Mar 23.
Artigo em Inglês | MEDLINE | ID: mdl-37048854

RESUMO

Finite element analysis of complex bodies is frequently used in design to determine the size of deformations. Successive iterations, with progressive refinement of mesh densities, are most often required to obtain a sufficiently accurate convergent numerical solution. This process is costly, time consuming, and requires superior hardware and software. The paper presents a quick and effortless way to determine a sufficiently accurate value of the numerical solution. The mentioned solution is obtained by amending the numerical solution resulting for a certain value of the mesh density of the studied body with an adequate proportionality coefficient determined following the deformation study of simple bodies differently subject to external forces. It is assumed that the elastic displacement of the various bodies has a similar evolution as the mesh density increases and that the values of the proportionality coefficients considered are approximately equal for identical mesh densities. Examples presented are related to the reference body of the mechanical press PAI 25.

8.
Materials (Basel) ; 15(24)2022 Dec 09.
Artigo em Inglês | MEDLINE | ID: mdl-36556613

RESUMO

Through the approaches in this article, an attempt was made to analyze the bonding of Al-Cu bimetallic composite layers and the highlight of the diffusion at the boundary between the layers, by hot rolling. An aluminum alloy 6060 plate (EN-AW AlMgSi) and a Cu-ETP ½ hard (CW004A) plate were used. All of these layers of materials were TIG-welded, at both ends, into a heat-treated layered composite and subsequently subjected to the hot-rolling process. The Al-Cu composite material obtained was analyzed by scanning electronic microscopy (SEM) analysis, after being subjected to the tensile test, as well as energy-dispersive X-ray (EDX) analysis. The obtained results highlighted the diffusion at the boundary between the layers of the Al-Cu composite as well as its ductile breakage and the distribution of the amount of Al and Cu at the interface of the layers.

9.
Front Psychol ; 13: 945707, 2022.
Artigo em Inglês | MEDLINE | ID: mdl-36092071

RESUMO

Recently, social media marketing has become one of the most significant growth channels for many businesses. However, many companies are still unclear about using social media marketing to their advantage, particularly in an e-commerce environment. In this background, this study examines the effect of website quality, consumer satisfaction, and eWOM on online purchase intention. An online survey was conducted with 789 online Chinese shoppers from four cities-Harbin, Shenyang, Guangzhou, and Shenzhen. Structural equation modeling (SEM) was used to analyze the hypotheses. The findings show that each variable had a high impact on eWOM with website quality (information quality, system quality, and service quality), which in turn positively increased consumer online purchase intentions in China's e-commerce business. Additionally, findings show a significant gender gap in online shopping behavior. This novel research provides several managerial guidelines that support managers in improving their business performance in the e-commerce industry. This research also highlighted some limitations.

10.
Front Pediatr ; 10: 869628, 2022.
Artigo em Inglês | MEDLINE | ID: mdl-35722493

RESUMO

Kidney transplantation (KT) is currently the elective approach for patients with end-stage renal disease. Although it is a safe choice for these patients, the early complications can lead to graft dysfunction. One of the most redoubtable complications is delayed graft function (DGF), having no specific treatment. The effects of DGF on the graft survival are large enough to justify the formulation of specific biological protocols. Therefore, discovering biomarkers of acute impairment in renal transplanted patients is required. Creatinine is a poor marker to establish the kidney injury. Estimated glomerular filtration rate together with creatinine is ready to approximately measure the kidney function. Different serum and urine proteins are being studied as possible predictive biomarkers for delayed graft function. This review will concentrate on recent and existing research which provide insight concerning the contribution of some molecules for the estimation and evaluation of graft function after kidney transplantation. Further studies examining various aspects of DGF after KT are urgently needed to address a hitherto less-known clinical question.

11.
Nanomaterials (Basel) ; 11(11)2021 Oct 29.
Artigo em Inglês | MEDLINE | ID: mdl-34835662

RESUMO

Alloys possessing nominal compositions Mn53Al45C2 and Mn52Al46C2 were prepared by the melt spinning method and were subjected to complex structural, morphological and magnetic investigations. As these alloys can exhibit tetragonal L10-type and τ phase, they have good potential as rare earth (RE)-free magnets. It is, therefore, important to monitor the ε-τ phase transformation and the stability and the magnetic features of the tetragonal phase in an entire temperature interval. By using synchrotron X-ray diffraction, it has been proven that the ε-τ phase transformation occurs gradually, with the τ phase becoming predominant only after 450 °C. Moreover, this phase has been proven to be quite stable without any grain growth even at the highest temperature investigated at 800 °C. Low temperature behavior was thoroughly investigated by using a complex combination of major and minor hysteresis loops combined with the zero field cooled-field cooled magnetization protocols (ZFC-FC). Two different regimes, blocking and superparamagnetic, were documented. A spin reorientation transition was proven to occur at 55 K while a maximum magnetization observed in ZFC-FC curves proved that at about 75 K, a transition from ferro to superparamagnetic state occurs. The existence of a blocking regime below 55 K that is characteristic to nanogranular systems with superparamagnetic behavior has shown further development towards obtaining RE-free magnets.

12.
Materials (Basel) ; 14(17)2021 Sep 03.
Artigo em Inglês | MEDLINE | ID: mdl-34501143

RESUMO

The purpose of this study is to identify the stress levels that act in inlay and onlay restorations, according to the direction and value of the external force applied. The study was conducted using the Finite Element Method (FEM) of three types of ceramics: pressed lithium disilicate and monolith, zirconia, and three different adhesive systems: self-adhesive, universal, and dual-cure cements. In addition to FEM, the inlay/onlay-dental structure interface analysis was performed by means of Scanning Electron Microscopy (SEM). The geometric models were reconstructed based on computer tomography images of an undamaged molar followed by geometrical procedures of inducing the inlay and onlay reconstructions. The two functional models were then simulated for different orientations of external force and different material properties, according to the considered adhesives and ceramics. The Scanning Electron Microscopy (SEM) was conducted on 30 extracted teeth, divided into three groups according to the adhesive cement type. Both FEM simulation and SEM investigations reveal very good mechanical behavior of the adhesive-dental structure and adhesive-ceramic interfaces for inlay and onlay reconstructions. All results lead to the conclusion that a physiological mastication force applied, regardless of direction, cannot produce a mechanical failure of either inlay or onlay reconstructions. The adhesive bond between the restorations and the dental structure can stabilize the ceramic restorations, resulting in a higher strength to the action of external forces.

13.
Artigo em Inglês | MEDLINE | ID: mdl-34299984

RESUMO

Order increases, supply chain disruptions, changing customer behavior, store closures, and more that have been caused by the coronavirus epidemic (COVID-19) will undoubtedly affect the online commerce forms of business. The coronavirus pandemic has a significant impact on digitalization and customer experience and well-being in mobile commerce. Since the beginning of the coronavirus pandemic, online sales and the number of online shoppers using wireless internet-enabled devices have increased tremendously. The article develops, an experimental study that captures COVID-19 and digital commerce's impact in terms of customers' experience and well-being during the pandemic period. The study explores the synergy between technology evolution and the effects of the COVID-19 pandemic on customers' behavior based on survey data collection and the technology acceptance model (TAM). The results reveal that, for millennials, digital commerce seems to be the typical way of shopping and paying in the pandemic period since the oldest generations adopted in a smaller proportion the use of mobile devices for shopping and payments. Besides, retailers are confronted with great challenges raised by millennials' expectations. The result confirms four of the six hypotheses based on the technology acceptance model (TAM). As a result, it shows that the easiness of use, trust, mobility, and customer involvement influences the behavioral intention of the customer to use mobile commerce, and that usefulness and customization does not influence the behavioral intention.


Assuntos
COVID-19 , Pandemias , Comércio , Comportamento do Consumidor , Humanos , SARS-CoV-2 , Inquéritos e Questionários
14.
Nanomaterials (Basel) ; 11(4)2021 Mar 31.
Artigo em Inglês | MEDLINE | ID: mdl-33807428

RESUMO

Melt spun ribbons of Mn53Al45C2 and Mn52Al46C2 have been synthesized by rapid quenching of the melt with the purpose of monitoring the ε-τ phase transformation to show technologically feasible ways to increase magnetic parameters and to illustrate the viability of these alloys as the next generation of rare earth (RE)-free magnets. By differential scanning calorimetry (DSC), activation energies and temperatures of onset of the ε-τ phase transformation were obtained. Structural analysis was performed using X-ray diffraction (XRD) and the resulting XRD patterns were quantitatively assessed using full profile Rietveld-type analysis. Appropriate annealing was performed in order to enable the ε-τ phase transformation. While hcp ε-phase was found to be predominant in the as-cast samples, after appropriate annealing, the tetragonal τ-phase, the one that furnishes the relevant magnetic response, was found to be predominant with an abundance of about 90%. The data suggested a mechanism of hcp ε-phase decomposition controlled by the segregation towards the interfacial regions, having the rate of transformation governed by antiphase boundary diffusion processes. Magnetic measurements of annealed sample Mn53Al45C2, consisting of predominant tetragonal τ-phase, showed high values of magnetization and increased coercivity, consistent with an energy product of about 10 MGOe, similar with previously reported magnetization measurements, providing further insight into the realization of future class of RE-free low-cost permanent magnets.

15.
J Med Life ; 13(3): 410-417, 2020.
Artigo em Inglês | MEDLINE | ID: mdl-33072217

RESUMO

Risk assessment is an essential component of the occupational health and safety event prevention activity.The purpose of this study is to choose the most appropriate risk assessment method for hospitals. The main methods were compared. There are many assessment methods, each with its advantages and disadvantages, but none has been adapted to the specificities of hospital activity. We adapted the workplace assessment sheet from the INCDPM (National Research and Development Institute for Labor Protection Bucharest) method to the specific of the hospital units and used this method at the level of jobs, within the hospital's departments, calculating the global risk level per job position, workplace (department), and hospital. The clinical departments global risk level exceeds the average (3.00) for all jobs, but does not exceed, however, 3.50, representing an acceptable security level. For assess the psychosocial risks we used the ELVIE method. Looking ahead, the methods should be adapted to allow both numerical presentation of the results and graphic.


Assuntos
Prevenção de Acidentes , Acidentes , Doenças Profissionais/prevenção & controle , Saúde Ocupacional , Recursos Humanos em Hospital , Medição de Risco , Local de Trabalho , Acidentes/psicologia , Humanos , Doenças Profissionais/psicologia , Recursos Humanos em Hospital/psicologia , Inquéritos e Questionários
16.
Int J Mol Sci ; 21(9)2020 May 01.
Artigo em Inglês | MEDLINE | ID: mdl-32369940

RESUMO

Wheat protein is considered a major type of food allergen in many countries including the USA. The mechanisms of allergenicity of wheat proteins are not well understood at present. Both adjuvant-based and adjuvant-free mouse models are reported for this food allergy. However, it is unclear whether the mechanisms underlying wheat allergenicity in these two types of models are similar or different. Therefore, we compared the molecular mechanisms in a novel adjuvant-free (AF) model vs. a conventional alum-adjuvant (AA) model of wheat allergy using salt-soluble wheat protein (SSWP). In the AF model, Balb/cJ mice were sensitized with SSWP via skin exposure. In the AA model, mice were sensitized by an intraperitoneal injection of SSWP with alum. In both models, allergic reactions were elicited using an identical protocol. Robust IgE as well as mucosal mast cell protein-1 responses were elicited similarly in both models. However, an analysis of the spleen immune markers identified strikingly different molecular activation patterns in these two models. Furthermore, a number of immune markers associated with intrinsic allergenicity were also identified in both models. Since the AF model uses skin exposure without an adjuvant, the mechanisms in the AF model may more closely simulate the human wheat allergenicity mechanisms from skin exposure in occupational settings such as in the baking industry.


Assuntos
Adjuvantes Imunológicos , Alérgenos/imunologia , Hipersensibilidade a Trigo/imunologia , Compostos de Alúmen , Animais , Especificidade de Anticorpos/imunologia , Antígenos de Plantas/imunologia , Citocinas/metabolismo , Modelos Animais de Doenças , Imunização , Imunoglobulina E/sangue , Imunoglobulina E/imunologia , Imunoglobulina G/sangue , Imunoglobulina G/imunologia , Camundongos , Proteínas de Plantas/efeitos adversos , Hipersensibilidade a Trigo/sangue , Hipersensibilidade a Trigo/metabolismo
17.
Polymers (Basel) ; 12(3)2020 Mar 11.
Artigo em Inglês | MEDLINE | ID: mdl-32168974

RESUMO

Selective Laser Sintering is a flexible additive manufacturing technology that can be used for the fabrication of high-resolution parts. Alongside the shape and dimension of the parts, the mechanical properties are essential for the majority of applications. Therefore, this paper investigates dimensional accuracy and mode I fracture toughness (KIC) of Single Edge Notch Bending samples under a Three Point Bending fixture, according to the ASTM D5045-14 standard. The work focuses on the influence of two major aspects of additive manufacturing: material type (Polyamide PA2200 and Alumide) and part orientation in the building environment (orientations of 0°, 45° and 90° are considered). The rest of the controllable parameters remains constant for all samples. The results reveal a direct link between the sample densities and the dimensional accuracy with orientation. The dimensional accuracy of the samples is also material dependent. For both materials, the angular orientation leads to significant anisotropic behavior in terms of KIC. Moreover, the type of material fundamentally influences the KIC values and the fracture mode. The obtained results can be used in the development of additive manufactured parts in order to obtain predictable dimensional tolerances and fracture properties.

18.
Polymers (Basel) ; 11(11)2019 Nov 09.
Artigo em Inglês | MEDLINE | ID: mdl-31717539

RESUMO

As additive manufacturing (AM) becomes more accessible, correlating process parameters with geometric and mechanical properties is an important topic. Because the number of process variables in AM is large, extensive studies must be conducted in order to underline every particular influence. The study focuses on two variables-part orientation in the orthogonal horizontal plane and energy density-and targets two outcomes-geometric and tensile properties of the parts. The AM process was conducted on selective laser sintering (SLS) machine EOS Formiga P100 using EOS white powder polyamide (PA2200). After finishing the sinterization process, the parts were postprocessed, measured, weighted, and mechanically tested. The geometric evaluation and mass measurements of every sample allowed us to compute the density of all parts according to the sinterization energy and orientation, and to determine the relative error of every dimension. By conducting the tensile testing, the elastic and strength properties were determined according to process variables. A linear trend regarding sample density and energy density was identified. Also, large relative dimensional errors were recorded for the lowest energy density. Mechanical properties encountered the highest value for the highest energy density at a 45° orientation angle.

19.
Materials (Basel) ; 12(7)2019 Apr 06.
Artigo em Inglês | MEDLINE | ID: mdl-30959903

RESUMO

A case study of a failed humeral shaft locking compression plate is presented, starting with a clinical case where failure occurred and an implant replacement was required. This study uses finite element method (FEM) in order to determine the failure modes for the clinical case. Four loading scenarios that simulate daily life activities were considered for determining the stress distribution in a humeral shaft locking compression plate (LCP). Referring to the simulation results, the failure analysis was performed on the explant. Using fracture surface investigation methods, stereomicroscopy and scanning electron microscopy (SEM), a mixed mode failure was determined. An initial fatigue failure occurred followed by a sudden failure of the plate implant as a consequence of patient's fall. The fracture morphology was mostly masked by galling; the fractured components were in a sliding contact. Using information from simulations, the loading was inferred and correlated with fracture site and surface features.

20.
Materials (Basel) ; 12(6)2019 Mar 15.
Artigo em Inglês | MEDLINE | ID: mdl-30875894

RESUMO

This paper presents a study on the tensile properties of Alumide and polyamide PA2200 standard samples produced by Additive manufacturing (AM) based on selective laser sintering (SLS). Because of the orthogonal trajectories of the laser beam during exposure, different orientations of the samples may lead to different mechanical properties. In order to reveal this process issue, four orientations of the samples in building envelope were investigated. For data reliability, all the other process parameters were constant for each material and every orientation. The tensile tests highlight small differences in elastic properties of the two materials, while significant differences in strength properties and energy absorption were observed. Nevertheless, Young modulus indicates high stiffness of the Alumide comparing to PA2200 samples. The stereo microscopy reveals a brittle fracture site for Alumide and a ductile fracture with longitudinal splitting zones for PA2200. From the orientation point of view, similar properties of samples oriented at 0 and 90 degrees for all investigated mechanical properties were observed. However, tensile strength was less influenced by the sample orientations.

SELEÇÃO DE REFERÊNCIAS
DETALHE DA PESQUISA