The optimized consolidated nanocomposite material exhibited an excellent combination of various mechanical properties for a polymer-based structure that under the extreme state they can express as the tensile strength of up to ~120 MPa, bending strength of up to ~90 MPa, and absorbed impact energy of up to ~17 J/m.Extracellular matrix (ECM)-derived scaffolds have shown promise as tissue-engineered grafts for promoting cartilage repair. However, there has been a lack of focus on fine-tuning the frictional properties of scaffolds for cartilage tissue engineering as well as understanding their interactions with synovial fluid constituents. Proteoglycan-4 (PRG4) and hyaluronan (HA) are macromolecules within synovial fluid that play key roles as boundary mode lubricants during cartilage surface interactions. The overall objective of this study was to characterize the role PRG4 and HA play in the lubricating function of collagen-glycosaminoglycan (GAG) scaffolds for cartilage repair. As a first step towards this goal, we aimed to develop a suitable in vitro friction test to establish the boundary mode lubrication parameters for collagen-GAG scaffolds articulated against glass in a phosphate buffered saline (PBS) bath. Subsequently, we sought to leverage this system to determine the effect of physiological synovial fluid lubrlity as potential tissue-engineered cartilage replacements. To conclude, this study reports the development of an in vitro friction test capable of characterizing the coefficient of friction of ECM-derived scaffolds tested in a range of synovial fluid lubricants and demonstrates frictional properties as a potential design parameter for implants and materials for soft tissue replacement.Development of optimal shaping processes for pre-sintered and sintered zirconia materials requires a fundamental understanding of damage and deformation mechanisms at small-scale contacts with diamond tools. This paper reports on responses of zirconia materials with distinct microstructures to nanoindentation associated with diamond machining using a Berkovich diamond indenter. In-situ nanoindentation was performed in a scanning electron microscope (SEM) and in-process filmed to record small contact events. Indentation morphology was SEM-mapped at high-magnifications. Although both pre-sintered porous and sintered dense zirconia materials mechanically revealed the quasi-plastic behavior in indentation, there were distinct responses of the two materials to quasi-plasticity at the microstructural level. For pre-sintered porous zirconia, the quasi-plasticity was attributed to shear faults resulting from breaking pore networks as microstructurally discrete interfaces, to lead to compression, fragmentation, pulverization and microcracking of zirconia crystals in indentation imprints. In contrast, sintered dense zirconia had shear band-induced quasi-plastic deformation, accompanied with localized tensile microfracture. A material index associated with the mechanical properties ranked the lower quasi-plasticity for pre-sintered porous zirconia than its sintered dense state, predicting more machining-induced damage in the former than the latter. Significantly higher indentation imprint volumes induced in indented pre-sintered porous zirconia than sintered dense state previses higher machining efficiency for the former than the latter. The microstructure-dependent indentation mechanisms provide the fundamental knowledge into micromechanics of abrasive machining of zirconia materials and may lead to a new microstructural design for zirconia materials to achieve a balanced machining efficiency and damage control.
  To investigate the impact of hydrothermal aging on Martens parameter (Martens hardness HM/elastic indentation modulus E
  ) and biaxial flexural strength (BFS) of recently available CAD/CAM silicate ceramics.
 
  220 specimens (diameter 12mm, thickness 0.95mm) were fabricated from six CAD/CAM ceramics in two translucency levels (LT/HT) (a) two lithium disilicate (Amber Mill, ABM; IPS e.max CAD, IEM), (b) one lithium metasilicate (Cetra Duo, CEL), (c) one lithium alumina silicate (n!ce, NIC), and (d) two leucite ceramics (Initial LRF Block, LRF; IPS Empress CAD, IPR). HM/E
  and BFS were measured initially and after hydrothermal aging (134°C/0.2 MPa/100h) in an autoclave. The Kolmogorov-Smirnov-test, t-test, one-way ANOVA with post-hoc Scheffé test, Kruskal-Wallis-test, Mann-Whitney-U-test with Bonferroni correction and Weibull statistics were performed (α=0.05).
 
  CEL and IEM showed the highest and the leucite ceramics the lowest Martens parameter. Within HT, ABM and NIC were in same initial HM value range witterm stability of restorations CAD/CAM lithium disilicate ceramics presented the highest and leucite ceramics the lowest mechanical properties, whereas the reliability was better for leucite than for lithium silicate ceramics.Osseointegrated trans-femoral fixations have been used as alternatives for conventional sockets in recent years. Despite numerous advantages, the dissimilarity of the mechanical properties between bone and implant has led to issues in periprosthetic bone adaptation.  https://www.selleckchem.com/products/ins018-055-ism001-055.html  This study aims to address these issues by proposing fixations made of functionally graded materials (FGMs). The computational study of bone remodeling was performed by linking a bone remodeling algorithm to the finite element analysis. The 3D model of the femur was created by computerized tomography (CT) scan images, and a Titanium fixture, along with nine Titanium/Hydroxyapatite FGM fixtures, were modeled. The analyses revealed evident advantages for the FGM fixtures over the conventionally used Titanium fixtures. Furthermore, it was shown that the gradation direction considerably affects the bone adaptation procedure. The results showed that using a radial FGM with low-stiffness material in the outer layer and less metal composition significantly improves the bone remodeling behavior.Cells possess two major DNA damage tolerance pathways that allow them to duplicate their genomes despite the presence of replication blocking lesions translesion synthesis (TLS) and daughter strand gap repair (DSGR). The TLS pathway involves specialized DNA polymerases that are able to synthesize past DNA lesions while DSGR relies on Recombinational Repair (RR). At least two mechanisms are associated with RR Homologous Recombination (HR) and RecA Mediated Excision Repair (RAMER). While HR and RAMER both depend on RecFOR and RecA, only the HR mechanism should involve Holliday Junctions (HJs) resolvase reactions. In this study we investigated the role of HJ resolvases, RuvC, TopIII and RusA on the balance between RAMER and HR in E. coli MG1655 derivatives. Using UV survival measurements, we first clearly establish that, in this genetic background, topB and ruvC define two distinct pathways of HJ resolution. We observed that a recA mutant is much more sensitive to UV than the ruvC topB double mutant which is deficient in HR because of its failure to resolve HJs.