scholarly journals A Horse of a Different Color?: Tensile Strength and Elasticity of Sloth Flexor Tendons

2020 ◽  
Vol 2 (1) ◽  
Author(s):  
A M Mossor ◽  
B L Austin ◽  
J A Avey-Arroyo ◽  
M T Butcher
Keyword(s):  
Tensile Strength ◽  
Muscle Activation ◽  
Flexor Tendons ◽  
Tensile Forces ◽  
Low Levels ◽  
Bradypus Variegatus ◽  
Strength And Stiffness ◽  
Different Color ◽  
Muscle Contractile ◽  
Tendon Collagen

Abstract Tendons must be able to withstand the tensile forces generated by muscles to provide support while avoiding failure. The properties of tendons in mammal limbs must therefore be appropriate to accommodate a range of locomotor habits and posture. Tendon collagen composition provides resistance to loading that contributes to tissue strength which could, however, be modified to not exclusively confer large strength and stiffness for elastic energy storage/recovery. For example, sloths are nearly obligate suspenders and cannot run, and due to their combined low metabolic rate, body temperature, and rate of digestion, they have an extreme need to conserve energy. It is possible that sloths have a tendon “suspensory apparatus” functionally analogous to that in upright ungulates, thus allowing for largely passive support of their body weight below-branch, while concurrently minimizing muscle contractile energy expenditure. The digital flexor tendons from the fore- and hindlimbs of two-toed (Choloepus hoffmanni) and three-toed (Bradypus variegatus) sloths were loaded in tension until failure to test this hypothesis. Overall, tensile strength and elastic (Young’s) modulus of sloth tendons were low, and these material properties were remarkably similar to those of equine suspensory “ligaments.” The results also help explain previous findings in sloths showing relatively low levels of muscle activation in the digital flexors during postural suspension and suspensory walking.

In Situ Formation of Poly(ethylene naphthalate) Microfibres in Polyethylene and Polypropylene during Extrusion

2007 ◽  
Vol 334-335 ◽  
pp. 161-164 ◽  
Author(s):  
Ka Lok Leung ◽  
Allan J. Easteal ◽  
Debes Bhattacharyya
Keyword(s):  
Tensile Strength ◽  
Scanning Electron Micrographs ◽  
Polyolefin Blends ◽  
Extrusion Die ◽  
Order Of Magnitude ◽  
Poly Ethylene ◽  
Strength And Stiffness ◽  
The Relationship ◽  
Fibre Morphology

Tensile properties and morphology of poly(ethylene naphthalate)/polyolefin blends and the relationship with the extrusion die size were investigated. Scanning electron micrographs of the blends reveal that the fibre morphology is developed during extrusion through the die. Skin-core morphology has been observed. As die diameter decreases, a droplet-to-fibre transition in morphology increases tensile strength and stiffness. After microfibrillization, up to 100% increase in the tensile stiffness was observed and the tensile strength could increase by one order of magnitude.

Development of poplar glued–laminated timber. I: Tensile strength and stiffness of poplar laminating stock

1986 ◽  
Vol 13 (4) ◽  
pp. 445-459 ◽  
Author(s):  
M. M. Lepper ◽  
F. J. Keenan
Keyword(s):  
Tensile Strength ◽  
Volume Effect ◽  
The Other ◽  
Regression Analyses ◽  
Frequency Data ◽  
Glulam Beam ◽  
Full Size ◽  
Glued Laminated Timber ◽  
Strength And Stiffness ◽  
General Slope

The tensile strength and stiffness of 263 full-size pieces of 38 × 80 mm in-grade poplar lumber from two mills in Ontario were determined. Prior to testing, complete maps of all grade-related defects in each piece were made; these defects included general slope of grain, centre knots, and edge knots. Specific gravity and moisture content were also recorded for each piece. After testing, the defects that triggered each piece's failure were noted. This information led, through regression analyses and the assumption of a Weibull distribution, to models for tensile strength and stiffness. The models were developed for the pieces from one mill and were tested against the results obtained from pieces from the other mill; agreement was very good. The knot frequency and slope frequency data were used in a modified form of the Foschi and Barrett glulam beam simulation model to predict the fifth fractile value of a population of poplar glulam beams. Taking the volume effect into account, the predicted beam strengths and stiffnesses are close to those of glulam beams of stress grade 20f–E.

Links between the Mechanics of Ventilation and Spine Stability

2008 ◽  
Vol 24 (2) ◽  
pp. 166-174 ◽  
Author(s):  
Simon Wang ◽  
Stuart M. McGill
Keyword(s):  
Muscle Activation ◽  
Stability Index ◽  
Motor Patterns ◽  
Lung Inflation ◽  
Spine Stability ◽  
Hand Force ◽  
Low Levels ◽  
Male Subjects ◽  
Back Extensor

Spine stability is ensured through isometric coactivation of the torso muscles; however, these same muscles are used cyclically to assist ventilation. Our objective was to investigate this apparent paradoxical role (isometric contraction for stability or rhythmic contraction for ventilation) of some selected torso muscles that are involved in both ventilation and support of the spine. Eight, asymptomatic, male subjects provided data on low back moments, motion, muscle activation, and hand force. These data were input to an anatomically detailed, biologically driven model from which spine load and a lumbar spine stability index was obtained. Results revealed that subjects entrained their torso stabilization muscles to breathe during demanding ventilation tasks. Increases in lung volume and back extensor muscle activation coincided with increases in spine stability, whereas declines in spine stability were observed during periods of low lung inflation volume and simultaneously low levels of torso muscle activation. As a case study, aberrant ventilation motor patterns (poor muscle entrainment), seen in one subject, compromised spine stability. Those interested in rehabilitation of patients with lung compromise and concomitant back troubles would be assisted with knowledge of the mechanical links between ventilation during tasks that impose spine loading.

Tensile and Impact Properties of Sugarcane Bagasse/Poly(vinyl Chloride) Composites

2011 ◽  
Vol 471-472 ◽  
pp. 167-172 ◽  
Author(s):  
Riza Wirawan ◽  
S.M. Sapuan ◽  
Khalina Abdan ◽  
Robiah Bt. Yunus
Keyword(s):  
Tensile Strength ◽  
Vinyl Chloride ◽  
Sugarcane Bagasse ◽  
Outer Part ◽  
Fibre Content ◽  
Composite Fibre ◽  
Impact Properties ◽  
Poly Vinyl Chloride ◽  
Strength And Stiffness ◽  
Main Components

Sugarcane bagasse is divided into two main components, pith and rind, with “pith” representing the inner part of the sugarcane bagasse and “rind” as the outer part. In this study, the tensile and impact properties of untreated pith/ poly(vinyl chloride) composites were compared to that of untreated rind composites using the same matrix with variation of fibre content. It was observed that the tensile strength and modulus of rind/PVC composites are higher than the unfilled PVC at composite fibre contents of 30% and 40%. Additionally, the rind composites exhibited superior strength and stiffness in comparison with the pith composites.

scholarly journals Thermo-Mechanical and Morphological Properties of Water Hyacinth Reinforced Polypropylene Composites

2018 ◽  
Vol 3 (3) ◽  
pp. 151-161
Author(s):  
Manabendra Saha ◽  
Ali Md. Afsar
Keyword(s):  
Mechanical Properties ◽  
Tensile Strength ◽  
Water Hyacinth ◽  
Thermal Analyses ◽  
Morphological Properties ◽  
Sem Images ◽  
Pull Out ◽  
Chemically Treated ◽  
Pp Composites ◽  
Strength And Stiffness

This paper focusses on the analysis of thermo-mechanical and morphological properties of water hyacinth (WH) fiber reinforced polypropylene (PP) biocomposites manufactured by using a single screw extruder and an injection molding machine. With a view to increasing the compatibility between the WH fibers and polypropylene matrix, raw WH fibers were chemically treated with Benzenediazonium salt in base media. Composites were manufactured with five different levels of loading (15, 20, 25, 30 and 35 wt%) of both the raw and treated WH fibers. Thermal properties of WH-PP composites were evaluated by thermogravimetric and differential thermal analyses. To analyze mechanical properties of composites, tests of tensile strength and stiffness, flexural strength and stiffness, and Charpy impact strength were carried out following ASTM standards. It was found that thermal stability and all the mechanical properties except tensile strength were improved considerably for chemically treated WH fiber composites in comparison with untreated ones. Fracture surfaces of the tensile and flexural specimens were scanned with scanning electron microscopy (SEM) to understand their surface morphologies. The SEM images clearly revealed that there were fewer fiber agglomerations, microvoids, and fiber pull out traces in treated WH-PP composites than in the untreated ones indicating better distribution of the fibers into the matrix as well as stronger fiber matrix interfacial adhesion due to treatment of WH fibers. Water absorption properties were studied to evaluate the viability of these biocomposites under specified conditions.

scholarly journals Distinct matrix composition and mechanics in aged and estrogen-deficient mouse skin

2019 ◽  
Author(s):  
Charis R Saville ◽  
Venkatesh Mallikarjun ◽  
David F Holmes ◽  
Elaine Emmerson ◽  
Brian Derby ◽  
...  
Keyword(s):  
Mechanical Properties ◽  
Extracellular Matrix ◽  
Tensile Strength ◽  
Mouse Skin ◽  
Hormone Deficiency ◽  
Matrix Composition ◽  
Estrogen Deprivation ◽  
Skin Loss ◽  
Aged Skin ◽  
Strength And Stiffness

ABSTRACTHormone deficiency has been widely linked to accelerated tissue ageing, and increased incidence of chronic degenerative disease. Furthermore, age-associated hormonal dysregulation is thought to be a major contributing factor to the increased fragility of aged skin. The ageing process is driven by an aggregation of damage to cells and extracellular matrix, which can directly influence the mechanical properties of the tissue. Here we report on the correlation between mechanical properties and composition of skin from ovariectomised and aged mice, to assess the extent to which estrogen deprivation drives dermal ageing. We found that age and estrogen abrogation affected skin mechanical properties in contrasting ways: ageing led to increased tensile strength and stiffness while estrogen deprivation had the opposite effect. Mass spectrometry proteomics showed that the quantity of extractable fibrillar collagen-I decreased with ageing, but no change was observed in ovariectomised mice. This observation, in combination with measurements of tensile strength, was interpreted to reflect changes to the extent of extracellular matrix crosslinking, supported by a significant increase in the staining of advanced glycation endpoints in aged skin. Loss of mechanical strength in the skin following ovariectomy was consistent with a loss of elastic fibres. Other changes in extracellular matrix composition broadly correlated between aged and ovariectomised mice, confirming the important role of estrogen-related pathways in ageing. This study offers new insight into the relationship between tissue composition and mechanics, and suggests that the deleterious effects of intrinsic skin ageing are compounded by factors beyond hormonal dysregulation.

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