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The current gold standard of identifying yield points from stress strain curves involves identifying a significant change in elastic modulus or using an arbitrary strain offset (0.1%, 0.2% or 2%) of the elastic modulus. The development of the offset method was due to the ambiguous definitions of yield point. The result is an arbitrary yield point which is prone to various human-related errors. This article presents a method to identify a unique yield point consistently using energy absorbed by the material up to first peak stress. This mathematical process idealises the stress strain curve for easy identification of the yield point. The method was tested on three possible types of stress strain curves with either a distinct yield point or without a distinct yield point (with peak stress closer to elastic region or closer to fracture). The yield points obtained by the proposed method are shown to be robust, consistent and unaffected by variations of the stress strain curves and data noises. [ABSTRACT FROM AUTHOR]

Polypropylene/metallocene polyethylene (PP/mPE) thermoplastic elastomer nanocomposites were prepared by a melt blending process. Metallocene polyethylenes grafted with vinyltriethoxy silane (mPE-g-silane) and neat mPE, both premixed with commercial organoclay (20A) to serve as the elastomer domains, were compared to investigate the silane curing effect on the prepared nanocomposites. According to X-ray diffraction and transmission electron microscopy analyses, the mPE-g-silane was of help in facilitating the intercalation and partial exfoliation of clay for PP/mPE-g-silane/clay system. A slight melting temperature depression of mPE and its nanocomposites was observed with the introduction of the silane curing due to the induced imperfect crystals. There was no silane curing effect found on the thermal stability, but the incorporation of clay increased the thermal stabilities. The PP/mPE-g-silane/clay system conferred higher tensile strength and tear strength than that of PP/mPE/clay system, mainly attributed to the better dispersion in the case of PP/mPE-g-silane. In general, the addition of clay gave more positive enhancement to the tensile and tear properties of the PP/mPE-g-silane/clay system in comparison with the PP/mPE/clay system. [ABSTRACT FROM AUTHOR]

The basic mechanism of reinforcement in tendons addresses the transfer of stress, generated by the deforming proteoglycan (PG)- rich matrix, to the collagen fibrils. Regulating this mechanism involves the interactions of PGs on the fibril with those in the surrounding matrix and between PGs on adjacent fibrils. This understanding is key to establishing new insights on the biomechanics of tendon in various research domains. However, the experimental designs in many studies often involved long sample preparation time. To minimise biological degradation the tendons are usually stored by freezing. Here, we have investigated the effects of commonly used frozen storage temperatures on the mechanical properties of tendons from the tail of a murine model (C57BL6 mouse). Fresh (unfrozen) and thawed samples, frozen at temperatures of -20°C and -80°C, respectively, were stretched to rupture. Freezing at -20°C revealed no effect on the maximum stress (σ), stiffness (E ), the corresponding strain (ε) at σ and strain energy densities up to ε (μ) and from ε until complete rupture (μp). On the other hand, freezing at -80°C led to higher σ,E and μ; ε and μp were unaffected. The results implicate changes in the long-range order of radially packed collagen molecules in fibrils, resulting in fibril rupture at higher stresses, and changes to the composition of extrafibrillar matrix, resulting in an increase in the interaction energy between fibrils via collagen-bound PGs. [ABSTRACT FROM AUTHOR]

Tissue engineering, often referred to as regenerative medicine and reparative medicine, is an interdisciplinary field that necessitates the combined effort of cell biologists, engineers, material scientists, mathematicians, geneticists, and clinicians toward the development of biological substitutes that restore, maintain, or improve tissue function. It has emerged as a rapidly expanding approach to address the organ shortage problem and comprises tissue regeneration and organ substitution. Cells placed on/or within constructs is the most common strategy in tissue engineering. Successful cell seeding depends on fast attachment of cell to scaffolds, high cell survival and uniform cell distribution. The seeding time is strongly dependent on the scaffold material and architecture. Scaffolds provide an initial biochemical substrate for the novel tissue until cells can produce their own extra-cellular matrix (ECM). Thus scaffolds not only define the 3D space for the formation of new tissues, but also serve to provide tissues with appropriate functions. These scaffolds are often critical, both in vivo (within the body) or in vitro (outside the body) mimicking in vivo conditions. Additive fabrication processes represent a new group of non-conventional fabrication techniques recently introduced in the biomedical engineering field. In tissue engineering, additive fabrication processes have been used to produce scaffolds with customised external shape and predefined internal morphology, allowing good control of pore size and pore distribution. This article provides a comprehensive state-of-the-art review of the application of biomanufacturing additive processes in the field of tissue engineering. New and moving trends in biomanufacturing technologies and the concept of direct cell-printing technologies are also discussed. [ABSTRACT FROM AUTHOR]

Corticosteroid injection using hypodermic needles is one of the commonly accepted treatments for patients with hand conditions. However, in some cases the needle perforations may cause tendon ruptures. This paper aims to investigate the relationships between a tendon's ultimate tensile strength (UTS) and the number of hypodermic needle perforations as well as needle sizes. The UTS was determined for all specimens at the loading rate of 0.4 mm/s. Tendon specimens with perforations punctured by large-sized (19 G) hypodermic needles were found to have significantly lower UTS than those with perforations punctured by medium-sized (23 G) and small-sized (27 G) needles. For specimens punctured by medium- and small-sized needles, no significant difference in UTS was observed between tendons with three perforations and those with one perforation. [ABSTRACT FROM AUTHOR]

Gripping is a major challenge faced in the tensile testing of tendons. As soft and aqueous materials, tendons are prone to slip and experience premature failure during mechanical testing. Several gripping methods were attempted and evaluated, including serrated jaw, sandpaper, frozen ends, and air-dried ends. It was found that 1 kN pneumatic grips (Shimadzu Company) lined with cardboard provided an adequate grip without perceptible slip and damage to the tendons. It was found that using the pneumatic grips with cardboard lining the stress concentration at the grip-specimen interface reduced substantially. An analysis of specimens that failed at the grip-specimen interface versus those that failed at mid-substance shows that there was no significant difference in their tensile properties. [ABSTRACT FROM AUTHOR]

The purpose of this study is to evaluate the effect of strain rate on the failure properties of tendons. Seventy-five chicken flexor digitorum profundus (FDP) tendons were tensile tested at 15 strain rates, ranging from 0.05 to 150 per cent/s. Results showed that strain rate had little effect on the shape of the stress-strain curve. No significant change was observed in the toe region, while the slope of the linear region increased with the increase in strain rate. Generally, the ultimate tensile strength (UTS) and elastic modulus increased significantly as strain rate increased (p < 0.01), while no significant change in strain at UTS (p > 0.01) was observed. It was found the change in failure properties of tendons was not significant, with small change in strain rate. [ABSTRACT FROM AUTHOR]

A unique case of an ependymal cyst on the anterior aspect of the thoracic spinal cord in a woman aged 68 years is described. Clinical signs were precipitated by trauma. Recovery of function, while incomplete, was remarkably good after extirpation of the cyst. [ABSTRACT FROM AUTHOR]