Análisis del efecto entalla y validación de la teoría de distancias críticas en ABS fabricado por impresión 3D

Máster en Integridad y Durabilidad de Materiales, Componentes y Estructura

Effect of graphene on the fracture behaviour of 3D printed PLA SENB specimens

ABSTRACT: This paper analyses the effect of graphene addition on the fracture behaviour of 3D printed PLA SENB specimens containing crack-like defects. The addition of graphene is assumed to improve the tensile behaviour of 3D printed PLA material, but the integrity of structural components strongly depends on the material fracture resistance. Tensile and fracture SENB specimens have been tested with different raster orientations (0/90, 30/-60 and 45/-45), showing that the effect of graphene addition (1 wt. %) is very sensitive to the raster orientation: this effect is significant for raster orientation 45/-45 and very limited for 0/90 (with 30/-60 providing intermediate results).The authors of this work would like to express their gratitude to the Spanish Ministry of Science and Innovation for the financial support of the project PGC2018-095400-B-I00 “Comportamiento en fractura de materiales compuestos nano-reforzados con defectos tipo entalla”

Analysis of notch effect in 3D-printed ABS fracture specimens containing U-notches

In this paper a fracture assessment in additive manufactured acrylonitrile butadiene styrene (ABS) fracture specimens containing U-notches is performed. We performed 33 fracture tests and 9 tensile tests, combining five different notch radii (0 mm, 0.25 mm, 0.50 mm, 1 mm and 2 mm) and three different raster orientations: 0/90, 30/-60 and 45/-45. The theory of critical distances (TCD) was then used in the analysis of fracture test results, obtaining additional validation of this theoretical framework. Different versions of TCD provided suitable results contrasting with the experimental tests performed. Moreover, the fracture mechanisms were evaluated using scanning electron microscopy in order to establish relationships with the behaviour observed. It was demonstrated that 3D-printed ABS material presents a clear notch effect, and also that the TCD, through both the point method and the line method, captured the physics of the notch effect in 3D-printed ABS. Finally, it was observed that the change in the fracture mechanisms when introducing a finite notch radius was limited to a narrow band behind the original defect, which appeared in cracked specimens but not in notched specimens.This research received funding from the Spanish Ministry of Science and Innovation, grant PGC2018-095400-B-I00 “Comportamiento en fractura de materiales compuestos nano-reforzados con defectos tipo entalla”

Analysis of additively manufactured PLA containing notches using Failure Assessment Diagrams

ABSTRACT: This paper provides a methodology for the estimation of the load-bearing capacity of additively manufactured (AM) PLA specimens that may be applied to both cracked and notched conditions. The methodology is based on the use of Failure Assessment Diagrams (FADs), which are, in practice, the main fracture-plastic collapse assessment tool provided by structural integrity assessment procedures. When dealing with notch-type defects, the methodology requires, additionally, the application of a notch correction that it is based on the Theory of Critical Distances (TCD) and the Creager-Paris stress distribution ahead of the cracktip. The results show that the FAD methodology (alone, in cracked conditions, or in combination with the TCD in notched conditions) can be successfully applied in this AM polymer.This publication is part of the project “Comportamiento en fractura de materiales compuestos nano-reforzados con defectos tipo entalla, PGC2018-095400-B-I00” funded by MCIN/ AEI /10.13039/501100011033/ FEDER "Una manera de hacer Europa

Structural integrity assessment of additively manufactured ABS, PLA and graphene reinforced PLA notched specimens combining Failure Assessment Diagrams and the Theory of Critical Distances

ABSTRACT: Failure Assessment Diagrams (FADs) are a widely used engineering tool for the analysis of structural components containing cracks, and are included in recognised structural integrity assessment procedures such as BS7910 and API 579 1/ASME FFS 1. Their consistency and reliability has been demonstrated over the years through numerous laboratory validation tests and industrial applications. Nevertheless, both their theoretical definition and their subsequent validation have been performed in metallic materials and, therefore, their use in other types of materials still requires theoretical support and experimental validation. Moreover, FADs have been initially defined for the analysis of crack-like defects, whereas there are many situations where the defects that are, or might be, responsible for structural failure are not necessarily cracks. This is the case of (non-sharp) defects with a finite radius on their tip, which here will be referred to as notches. Simultaneously, additive manufacturing (AM) is an emergent technology that allows practically any type of geometry to be fabricated through a relatively simple process. One of the main AM techniques is fused deposition modelling (FDM), which consists in the extrusion of heated feedstock plastic filaments through a nozzle tip. The resultant printed materials have rather particular properties that are very dependent on the printing parameters and on the final state of internal defects. Concerning AM polymers and polymer-matrix composites, their use as structural materials, beyond their main current use in prototyping, requires the development of specific structural integrity assessment procedures. This paper provides FAD analyses for three additively manufactured (FDM) materials containing U-shaped notches: ABS, PLA and graphene reinforced PLA. The results show that the FAD methodology may be applied for the estimation of fracture loads in these particular materials, as long as linear-elastic fracture toughness values are used.This publication is part of the project “Comportamiento en fractura de materiales compuestos nano-reforzados con defectos tipo entalla, PGC2018-095400-B-I00” funded by MCIN/ AEI /10.13039/ 501100011033/ FEDER “Una manera de hacer Europa

Peripheral desmoplastic ameloblastoma : histopathological and immunohistochemical profile of a case

In this study we present a rare case of peripheral desmoplastic ameloblastoma and discuss its clinical features, histopathology, and inmunoshistochemical profile. This article reports a new case of this unusual neoplasm in a 66 year-old woman in which the main complaint was an asymptomatic swelling located in the right body of mandible. Histopathological findings were similar to the two previously reported cases of this tumor. Positive immunohistochemical stain for laminin V and type IV collagen suggests an inductive effect of the epithelium over the stroma while the low index of p53 protein and Ki-67 expression in epithelium and stromal cells, as well as CD138 uniform positive-stain in epithelial cells, support the benign biological behavior of this lesion. Including this new case, currently there are only three reports of this rare neoplasm. Reports of new cases of peripheral desmoplastic ameloblastoma are necessary for a better understanding of the origin and behavior of this particular subtype of ameloblastoma

Effects of semen processing on sperm function: Differences between swim-up and density gradient centrifugation

Purpose: Andrology research has evolved notoriously in the latest years, particularly since male factor contribution to couple infertility has been undoubtedly demonstrated. However, sperm function investigations results are sometimes contradictory, probably as a result of the use of different sperm processing techniques. In this work, we underwent a systematic functional comparison of human sperm samples simultaneously processed by swim-up and density gradient centrifugation, which are the preferred sperm processing methods used in basic and clinical laboratories. Materials and Methods: To compare functional characteristics of sperm isolated by swim-up and density gradient centrifugation followed by incubation at different times under capacitating conditions. Results: Semen samples processed in parallel by these two procedures resulted in sperm preparations with significant differences in redox state, spontaneous intracellular calcium oscillations, hyperactivation, protein tyrosine phosphorylation, and acrosome reaction responsivity to calcium ionophore. Such differences showed time-dependent specific patterns for spontaneous intracellular calcium oscillations, hyperactivation and protein tyrosine phosphorylation. Sperm retrieved by density gradient centrifugation showed more hyperactivation and tyrosine phosphorylation than swim-up sperm, suggesting a higher degree of capacitation. Conclusions: Our results account for functional differences observed in spermatozoa processed with these two methods and therefore may contribute to a better interpretation of outcomes obtained in different laboratories as well as to improve experimental designs aimed to study sperm physiology and fertility potential.Fil: Hernández Silva, Gabriela. Instituto Nacional de Ciencias Médicas y Nutrición Salvador Zubirán; MéxicoFil: López Torres, Aideé S.. Instituto Nacional de Ciencias Médicas y Nutrición Salvador Zubirán; MéxicoFil: Maldonado Rosas, Israel. Centro de Innovación Tecnológica y Medicina Reproductiva; MéxicoFil: Mata Martínez, Esperanza. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - Mendoza. Instituto de Histología y Embriología de Mendoza Dr. Mario H. Burgos. Universidad Nacional de Cuyo. Facultad de Ciencias Médicas. Instituto de Histología y Embriología de Mendoza Dr. Mario H. Burgos; ArgentinaFil: Larrea, Fernando. Instituto Nacional de Ciencias Médicas y Nutrición Salvador Zubirán; MéxicoFil: Torres Flores, Víctor. Universidad Nacional Autónoma de México; MéxicoFil: Treviño, Claudia L.. Universidad Nacional Autónoma de México; MéxicoFil: Chirinos, Mayel. Instituto Nacional de Ciencias Médicas y Nutrición Salvador Zubirán; Méxic

Correlation between obesity and severity of distal radius fractures

Introduction: The incidence of obesity has increased significantly worldwide. Our hypothesis was that patients with obesity have a more severe distal radius fracture and we realized a study to evaluate this correlation between obesity and severity of distal radius fractures caused by low-energy injuries. Materials and methods: A total of 114 patients with distal radius fracture were examined in

Ultrasound-Assisted Melt Extrusion of Polymer Nanocomposites

A review of the latest developments in ultrasound-assisted melt extrusion of polymer nanocomposites is presented. In general, the application of ultrasound waves during melt extrusion of polymer in the presence of nanoparticles results in a more homogeneous dispersion of the nanoparticles in the polymer matrix. In spite of this, a lack of understanding in the field has hindered the development of this processing technique. Based on the analysis of literature on the field, key aspects are identified for a better understanding of the physical and chemical effects of ultrasound waves and the fabrication of polymer nanocomposites by means of melt extrusion

HGUE-C-1 is an atypical and novel colon carcinoma cell line

Background: Colorectal carcinoma is a common cause of cancer. Adjuvant treatments include: 5-fluorouracil administered together with folinic acid, or more recently, oral fluoropyrimidines such as capecitabine, in combination with oxaliplatin or irinotecan. Metastatic colorectal cancer patients can benefit from other additional treatments such as cetuximab or bevacizumab. Methods: Using cell culture techniques, we isolated clonal populations from primary cultures of ascitic effusion derived from a colon cancer patient and after several passages an established cell line, HGUE-C-1, was obtained. Genetic analysis of HGUE-C-1 cells was performed by PCR of selected exons and sequencing. Cell proliferation studies were performed by MTT assays and cell cycle analyses were performed by flow cytometry. Retinoblastoma activity was measured by luciferase assays and proteins levels and activity were analysed by Western blot or immunohistochemistry. Results: We have established a new cell line from ascitic efussion of a colon cancer patient who did not respond to 5-fluorouracil or irinotecan. HGUE-C-1 cells did not show microsatellite instability and did not harbour mutations in KRAS, BRAF, PI3KCA or TP53. However, these cells showed loss of heterozygosity affecting Adenomatous Polyposis Coli and nuclear staining of β-catenin protein. The HGUE-C-1 cell line was sensitive to erlotinib, gefitinib, NVP-BEZ235, rapamycin and trichostatin, among other drugs, but partially resistant to heat shock protein inhibitors and highly resistant to AZD-6244 and oxaliplatin, even though the patient from which this cell line was derived had not been exposed to these drugs. Molecular characterization of this cell line revealed low expression levels and activity of Retinoblastoma protein and elevated basal levels of Erk1/2 activity and p70S6K expression and activity, which may be related to chemoresistance mechanisms. Conclusions: HGUE-C-1 represents a novel and peculiar colon carcinoma model to study chemoresistance to chemotherapeutic agents and to novel anti-neoplasic drugs that interrupt signalling pathways such as the APC/βcatenin, Ras/Raf/Mek/Erk, PI3K/mTOR/p70S6K pathways as well as histone regulation mechanisms.This article has been funded by grants from the Instituto de Salud Carlos III FIS PI080901and FIS PI01202025 to Miguel Saceda