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https://www.readbyqxmd.com/read/28549214/griffith-criterion-for-nanoscale-stress-singularity-in-brittle-silicon
#1
Takashi Sumigawa, Takahiro Shimada, Shuuhei Tanaka, Hiroki Unno, Naoki Ozaki, Shinsaku Ashida, Takayuki Kitamura
Brittle materials such as silicon fail via the crack nucleation and propagation, which is characterized by the singular stress field formed near the crack tip according to Griffith or fracture mechanics theory. The applicability of these continuum-based theories is, however, uncertain and questionable in nanoscale system due to its extremely small singular stress field of only a few nanometers. Here, we directly characterize the mechanical behavior of a nano-crack via the development of in situ nanomechanical testing using a transmission electron microscope, and demonstrate that Griffith or fracture mechanics theory can be applied to even 4-nm stress singularity despite their continuum-based concept...
May 26, 2017: ACS Nano
https://www.readbyqxmd.com/read/28545871/reinforcing-effect-of-glass-fiber-mesh-on-complete-dentures-in-a-test-model-with-a-simulated-oral-mucosa
#2
Sang-Hui Yu, Seunghan Oh, Hye-Won Cho, Ji-Myung Bae
STATEMENT OF PROBLEM: Studies that evaluated the strength of complete dentures reinforced with glass-fiber mesh or metal mesh on a cast with a simulated oral mucosa are lacking. PURPOSE: The purpose of this in vitro study was to compare the mechanical properties of maxillary complete dentures reinforced with glass-fiber mesh with those of metal mesh in a new test model, using a simulated oral mucosa. MATERIAL AND METHODS: Complete dentures reinforced with 2 types of glass-fiber mesh, SES mesh (SES) and glass cloth (GC) and metal mesh (metal) were fabricated...
May 23, 2017: Journal of Prosthetic Dentistry
https://www.readbyqxmd.com/read/28542539/a-leishmania-secretion-system-for-the-expression-of-major-ampullate-spidroin-mimics
#3
Todd A Lyda, Elizabeth L Wagner, Andre X Bourg, Congyue Peng, Golnaz Najaf Tomaraei, Delphine Dean, Marian S Kennedy, William R Marcotte
Spider major ampullate silk fibers have been shown to display a unique combination of relatively high fracture strength and toughness compared to other fibers and show potential for tissue engineering scaffolds. While it is not possible to mass produce native spider silks, the potential ability to produce fibers from recombinant spider silk fibers could allow for an increased innovation rate within tissue engineering and regenerative medicine. In this pilot study, we improved upon a prior fabrication route by both changing the expression host and additives to the fiber pulling precursor solution to improve the performance of fibers...
2017: PloS One
https://www.readbyqxmd.com/read/28532898/toughening-of-fibrous-scaffolds-by-mobile-mineral-deposits
#4
Justin Lipner, John J Boyle, Younan Xia, Victor Birman, Guy M Genin, Stavros Thomopoulos
Partially mineralized fibrous tissue situated between tendon and bone is believed to be tougher than either tendon or bone, possibly serving as a compliant, energy absorptive, protective barrier between the two. This tissue does not reform following surgical repair (e.g., rotator cuff tendon-to-bone re-attachment) and might be a factor in the poor outcomes following such surgeries. Towards our long-term goal of tissue engineered solutions to functional tendon-to-bone re-attachment, we tested the hypotheses that partially mineralized fibrous matrices can derive toughness from mobility of mineral along their fibers, and that in such cases toughness is maximized at levels of mineralization sufficiently low to allow substantial mobility...
May 19, 2017: Acta Biomaterialia
https://www.readbyqxmd.com/read/28531971/graphene-oxide-versus-graphene-for-optimisation-of-pmma-bone-cement-for-orthopaedic-applications
#5
E Paz, F Forriol, J C Del Real, N Dunne
Graphene (G) and graphene oxide (GO) nano-sized powders with loadings ranging from 0.1 to 1.0wt% were investigated as reinforced agents for polymethyl methacrylate (PMMA) bone cements. The mechanical properties (i.e. bend strength, bend modulus, compression strength, fracture toughness and fatigue performance) and the thermal properties (i.e. maximum temperature, setting time, curing heat and residual monomer) of the resultant nanocomposites were characterised. The mechanical performance of G-PMMA and GO-PMMA bone cements has been improved at low loadings (≤0...
August 1, 2017: Materials Science & Engineering. C, Materials for Biological Applications
https://www.readbyqxmd.com/read/28526443/mechanical-properties-of-polymer-infiltrated-ceramic-sodium-aluminum-silicate-composites-for-dental-restoration
#6
Bencang Cui, Jing Li, Huining Wang, Yuanhua Lin, Yang Shen, Ming Li, Xuliang Deng, Cewen Nan
OBJECTIVE: To fabricate indirect restorative composites for CAD/CAM applications and evaluate the mechanical properties. METHODS: Polymer-infiltrated-ceramic composites were prepared through infiltrating polymer into partially sintered sodium aluminum silicate ceramic blocks and curing. The corresponding samples were fabricated according to standard ISO-4049 using for mechanical properties measurement. The flexural strength and fracture toughness were measured using a mechanical property testing machine...
May 16, 2017: Journal of Dentistry
https://www.readbyqxmd.com/read/28522235/a-review-of-terrestrial-aerial-and-aquatic-keratins-the-structure-and-mechanical-properties-of-pangolin-scales-feather-shafts-and-baleen-plates
#7
Bin Wang, Tarah N Sullivan
Keratinous materials, omnipresent as the hard and durable epidermal appendages of animals, are one of the toughest biological materials. They exhibit diverse morphologies and structures that serve a variety of amazing and inspiring mechanical functions. In this work, we provide a review of representative terrestrial, aerial and aquatic keratinous materials, pangolin scales, feather shafts and baleen plates, and correlate their hierarchical structures to respective functions of dermal armor, flight material and undersea filter...
May 8, 2017: Journal of the Mechanical Behavior of Biomedical Materials
https://www.readbyqxmd.com/read/28489301/hyperelastic-tough-gels-through-macrocross-linking
#8
Shailesh K Goswami, Christopher John McAdam, Lyall R Hanton, Stephen C Moratti
The wet and soft nature of hydrogels makes them useful as a mimic for biological tissues, and in uses such as actuators and drug delivery vehicles. For many applications the mechanical performance of the gel is critical, but gels are notoriously weak and prone to fracture. Free radical polymerization is a very powerful technique allowing for fine spatial and temporal control of polymerization, but also allows for the use of a wide range of monomers and mixtures. In this work, it is demonstrated that extremely tough and extensible hydrogels can be readily produced through simple radical polymerization of acrylamide or acrylic acid with a poly(ethylene oxide) macrocross-linker...
May 10, 2017: Macromolecular Rapid Communications
https://www.readbyqxmd.com/read/28484774/fracture-mechanisms-in-multilayer-phosphorene-assemblies-from-brittle-to-ductile
#9
Ning Liu, Jiawang Hong, Xiaowei Zeng, Ramana Pidaparti, Xianqiao Wang
The outstanding mechanical performance of nacre has stimulated numerous studies on the design of artificial nacres. Phosphorene, a new two-dimensional (2D) material, has a crystalline in-plane structure and non-bonded interaction between adjacent flakes. Therefore, multi-layer phosphorene assemblies (MLPs), in which phosphorene flakes are piled up in a staggered manner, may exhibit outstanding mechanical performance, especially exceptional toughness. Therefore, molecular dynamics simulations are performed to study the dependence of the mechanical properties on the overlap distance between adjacent phosphorene layers and the number of phosphorene flakes per layer...
May 24, 2017: Physical Chemistry Chemical Physics: PCCP
https://www.readbyqxmd.com/read/28482476/schiff-base-bond-linked-polysaccharide-doxorubicin-conjugate-for-upregulated-cancer-therapy
#10
Xiangru Feng, Di Li, Jiandong Han, Xiuli Zhuang, Jianxun Ding
The pH-responsive polymer prodrugs were designed to maintain sufficient stability in the bloodstream and promptly release the active drugs when entering the acidic microenvironments, such as tumor tissue and cells. This kind of polymer-drug conjugates has become increasingly intriguing given the specific advantages over traditional drug delivery system. In our work, dextran (Dex) was oxidized into aldehyde-functionalized Dex-CHO before conjugating with doxorubicin (DOX) via efficient Schiff base reaction. The amphiphilic product Dex-DOX aggregated into uniform spherical nanoparticle in aqueous condition...
July 1, 2017: Materials Science & Engineering. C, Materials for Biological Applications
https://www.readbyqxmd.com/read/28463496/interfacial-phenomena-and-mechanical-behavior-of-polyetheretherketone-polybenzimidazole-blend-under-hygrothermal-environment
#11
Peng Liu, Michael Mullins, Tim Bremner, Natalie Benner, Hung-Jue Sue
Demands for engineering applications of high performance polymers, such as the polyaryletherketone families, have grown significantly in recent years. Fundamental knowledge on the mechanical behavior of such polymers, especially under harsh environments, is still lacking. In this study, the mechanical behavior and interfacial phenomena of a blend of polybenzimidazole (PBI) particles having sizes of about 50 μm and polyetheretherketone (PEEK) matrix at 50:50 weight ratio was characterized. PBI and PEEK are known to be incompatible with each other in the dry state...
May 22, 2017: Journal of Physical Chemistry. B
https://www.readbyqxmd.com/read/28462520/zirconia-phase-transformation-in-retrieved-wear-simulated-and-artificially-aged-ceramic-femoral-heads
#12
Maria Parkes, Kathryn Sayer, Markus Goldhofer, Philippa Cann, William L Walter, Jonathan Jeffers
Zirconia in Zirconia toughened alumina ceramic hip replacements exists in an unstable state and can transform in response to stress giving the material improved fracture toughness. Phase transformation also occurs under hydrothermal conditions such as exist in vivo. To predict the hydrothermal aging that will occur in vivo accelerated aging procedures have been used, but validation of these models requires the study of retrieved hip joints. Here 26 retrievals are analysed to determine the degree of phase transformation in vivo...
April 29, 2017: Journal of Orthopaedic Research: Official Publication of the Orthopaedic Research Society
https://www.readbyqxmd.com/read/28461887/recovery-property-of-double-network-hydrogel-containing-mussel-inspired-adhesive-moiety-and-nano-silicate
#13
Yuan Liu, Bruce P Lee
Altough double network (DN) hydrogels are extremly tough, they are irreversibly softened during large strain deformation. We incorporated mussel-inspired adhesive moiety, catechol, and a synthetic nano-silicate, Laponite, into DN to examine the effect of strong, reversible crosslinks on the DN's ability to recover its mechanical properties during successive loading cycles. The introduction of catechol and Laponite drastically increased the compressive strength and toughness of DN without compromising the compliance of the hydrogel...
October 28, 2016: Journal of Materials Chemistry. B, Materials for Biology and Medicine
https://www.readbyqxmd.com/read/28457593/a-review-of-cutting-mechanics-and-modeling-techniques-for-biological-materials
#14
REVIEW
Behrouz Takabi, Bruce L Tai
This paper presents a comprehensive survey on the modeling of tissue cutting, including both soft tissue and bone cutting processes. In order to achieve higher accuracy in tissue cutting, as a critical process in surgical operations, the meticulous modeling of such processes is important in particular for surgical tool development and analysis. This review paper is focused on the mechanical concepts and modeling techniques utilized to simulate tissue cutting such as cutting forces and chip morphology. These models are presented in two major categories, namely soft tissue cutting and bone cutting...
April 27, 2017: Medical Engineering & Physics
https://www.readbyqxmd.com/read/28454145/yb-sup-3-sup-doped-caf-sub-2-sub-laf-sub-3-sub-ceramics-laser
#15
Shotaro Kitajima, Kentaro Yamakado, Akira Shirakawa, Ken-Ichi Ueda, Yoshinobu Ezura, Hitoshi Ishizawa
Highly transparent ceramic is an attractive gain medium for high-power lasers due to its high fracture toughness, homogeneity, and size scalability. Here we report the first Yb<sup>3+</sup>-doped CaF<sub>2</sub>-LaF<sub>3</sub> ceramics laser. Codoping of La<sup>3+</sup> ion can reduce the formation of Yb<sup>2+</sup> ions and enhance the laser efficiency. In the laser experiment, the maximum output power of 4.36 W and the maximum slope efficiency of 69...
May 1, 2017: Optics Letters
https://www.readbyqxmd.com/read/28442711/temperature-dependent-fracture-properties-of-shape-memory-alloys-novel-findings-and-a-comprehensive-model
#16
Carmine Maletta, Emanuele Sgambitterra, Fabrizio Niccoli
Temperature dependent fracture properties of NiTi-based Shape Memory Alloys (SMAs), within the pseudoelastic regime, were analyzed. In particular, the effective Stress Intensity Factor (SIF) was estimated, at different values of the testing temperature, by a fitting of the William's expansion series, based on Digital Image Correlation (DIC) measurements. It was found that temperature plays an important role on SIF and on critical fast fracture conditions. As a consequence, Linear Elastic Fracture Mechanics (LEFM) approaches are not suitable to predict fracture properties of SMAs, as they do not consider the effects of temperature...
December 21, 2016: Scientific Reports
https://www.readbyqxmd.com/read/28439575/polymerization-efficacy-affects-the-long-term-mini-interfacial-fracture-toughness
#17
Pong Pongprueksa, Jan De Munck, Bruno C Barreto, Bart Van Meerbeek
PURPOSE: To evaluate the effect of the type and concentration of photo-initiator on the long-term bonding efficacy to dentin in terms of mini-interfacial fracture toughness (mini-iFT). MATERIALS AND METHODS: The bonding efficacy of the one-step self-etch (SE) adhesive Clearfil S3 Bond Plus and four derivative experimental adhesives (Leuven University Bond [LUB]), which were similar in composition except for the (co)photo-initiators (all prepared by Kuraray Noritake), containing 2...
April 21, 2017: Journal of Adhesive Dentistry
https://www.readbyqxmd.com/read/28433242/freeform-extrusion-fabrication-of-titanium-fiber-reinforced-13-93-bioactive-glass-scaffolds
#18
Albin Thomas, Krishna C R Kolan, Ming C Leu, Gregory E Hilmas
Although implants made with bioactive glass have shown promising results for bone repair, their application in repairing load-bearing long bone is limited due to their poor mechanical properties in comparison to human bone. This work investigates the freeform extrusion fabrication of bioactive silicate 13-93 glass scaffolds reinforced with titanium (Ti) fibers. A composite paste prepared with 13-93 glass and Ti fibers (~16µm in diameter and lengths varying from ~200µm to ~2 mm) was extruded through a nozzle to fabricate scaffolds (0-90° filament orientation pattern) on a heated plate...
June 2017: Journal of the Mechanical Behavior of Biomedical Materials
https://www.readbyqxmd.com/read/28432999/effect-of-intra-oral-aging-on-t%C3%A2-m-phase-transformation-microstructure-and-mechanical-properties-of-y-tzp-dental-ceramics
#19
Luciana Meireles Miragaya, Renato Bastos Guimarães, Rodrigo Othávio de Assunção E Souza, Glauco Dos Santos Botelho, José Guilherme Antunes Guimarães, Eduardo Moreira da Silva
The aim of the present study was to evaluate the influence of intra-oral aging on the tetragonal-to-monoclinic (t→m) phase transformation of two Y-TZP dental ceramics - Lava Frame (Frame) and Lava Plus (Plus) - and determine the impact of this response on their microstructures and mechanical properties: flexural strength, Young's modulus, microhardness and fracture toughness. Standardized ceramic specimens were analyzed by X-ray diffraction (XRD), scanning electron microscopy (SEM) and atomic force microscopy (AFM)...
April 13, 2017: Journal of the Mechanical Behavior of Biomedical Materials
https://www.readbyqxmd.com/read/28420829/bonding-measurement-strength-and-fracture-mechanics-approaches
#20
Chuchai Anunmana, Wiroj Wansom
This study investigated the effect of cross-sectional areas on interfacial fracture toughness and bond strength of bilayered dental ceramics. Zirconia core ceramics were veneered and cut to produce specimens with three different cross-sectional areas. Additionally, monolithic specimens of glass veneer were also prepared. The specimens were tested in tension until fracture at the interface and reported as bond strength. Fracture surfaces were observed, and the apparent interfacial toughness was determined from critical crack size and failure stress...
April 18, 2017: Dental Materials Journal
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