scholarly journals Determinants of mechanical properties in the developing ovine thoracic aorta

1999 ◽  
Vol 277 (4) ◽  
pp. H1385-H1391 ◽  
Author(s):  
Sarah M. Wells ◽  
B. Lowell Langille ◽  
J. Michael Lee ◽  
S. Lee Adamson
Keyword(s):  
Mechanical Properties ◽  
Elastic Modulus ◽  
Tensile Stress ◽  
Thoracic Aorta ◽  
Adult Life ◽  
Perinatal Period ◽  
Developmental Changes ◽  
Cross Linking ◽  
Postnatal Life ◽  
Collagen Cross Linking

We previously reported changes in mechanical properties and collagen cross-linking of the ovine thoracic aorta during perinatal development and postnatal maturation, and we now report changes in biochemical composition (elastin, collagen, and DNA contents per mg wet wt) over the same developmental intervals. A comparison of results from the present and previous studies has yielded novel and important observations concerning the relationship between aortic mechanics and composition during maturation. Developmental changes in aortic incremental elastic modulus at low tensile stress ( E low) closely followed changes in relative elastin content (i.e., per mg wet wt). An 89% increase in E low during the perinatal period was associated with a 69% increase in relative elastin content, whereas neither variable changed during postnatal life. Incremental elastic modulus at high tensile stress ( E high) did not change during the perinatal period but increased 88% during postnatal life. This pattern closely paralleled changes in collagen cross-linking index, which did not change perinatally but almost doubled postnatally. In contrast, relative collagen content (per mg wet wt) increased only slightly from fetal to adult life, a trend that was unrelated to aortic mechanics. Substantial, progressive decreases in measures of wall viscosity (pressure wave attenuation coefficient and viscoelastic phase angle) from fetal to adult life followed the pattern observed for relative DNA (smooth muscle cell) content (per mg wet wt). Our findings suggest that accumulation of elastin per milligram wet weight contributes most to developmental changes in E low, change in collagen cross-linking is the primary determinant of developmental changes in E high, and cell accumulation contributes most to developmental changes in wall viscosity.

PEG Cross-Linked Alginate Hydrogels with Controlled Mechanical Properties

1998 ◽  
Vol 530 ◽  
Author(s):  
Petra Eiselt ◽  
Jon A. Rowley ◽  
David J. Mooney
Keyword(s):  
Mechanical Properties ◽  
Tissue Engineering ◽  
Molecular Weight ◽  
Elastic Modulus ◽  
Cell Transplantation ◽  
Cross Linking ◽  
Cross Link ◽  
Link Density ◽  
A Cell ◽  
Cross Link Density

AbstractReconstruction of tissues and organs utilizing cell transplantation offers an attractive approach for the treatment of patients suffering from organ failure or loss. Highly porous synthetic materials are often used to mimic the function of the extracellular matrix (ECM) in tissue engineering, and serve as a cell delivery vehicle for the formation of tissues in vivo. Alginate, a linear copolysaccharide composed of D-mannuronic acid (M) and L-guluronic acid (G) units is widely used as a cell transplantation matrix. Alginate is considered to be biocompatible, and hydrogels are formed in the presence of divalent cations such as Ca2+, Ba2+ and Sr2+. However, ionically cross-linked alginate gels continuously lose their mechanical properties over time with uncontrollable degradation behavior. We have modified alginate via covalent coupling of cross-linking molecules to expand and stabilize the mechanical property ranges of these gels. Several diamino PEG molecules of varying molecular weight (200, 400, 1000, 3400) were synthesized utilizing carbodiimide chemistry. Sodium alginate was covalently cross-linked with these cross-linking molecules, and mechanical properties of the resulting hydrogels were determined. The elastic modulus of the cross-linked alginates depended on the molecular weight of the cross-linking molecules, and ranged from 10-110 kPa. The theoretical cross-link density in the hydrogels was also varied from 3 to 47% (relative to the carboxylic groups in the alginate) and the mechanical properties were measured. The elastic modulus increased gradually and reached a maximum at a cross-link density of 15%. In summary, covalently coupled hydrogels can be synthesized which exhibit a wide range of mechanical properties, and these materials may be useful in a number of tissue engineering applications.

scholarly journals The mechanical properties of fin whale arteries are explained by novel connective tissue designs.

1996 ◽  
Vol 199 (4) ◽  
pp. 985-997 ◽  
Author(s):  
J M Gosline ◽  
R E Shadwick
Keyword(s):  
Mechanical Properties ◽  
Elastic Modulus ◽  
Aortic Arch ◽  
Thoracic Aorta ◽  
Collagen Fibre ◽  
External Diameter ◽  
Collagen Fibres ◽  
Descending Aorta ◽  
Fin Whale ◽  
Terrestrial Mammals

The aortic arch and the descending aorta in the fin whale (Balaenoptera physalus) are structurally and mechanically very different from comparable vessels in other mammals. Although the external diameter of the whale's descending thoracic aorta (approximately 12 cm) is similar to that predicted by scaling relationships for terrestrial mammals, the wall thickness:diameter ratio in the whale (0.015) is much smaller than the characteristic value for other mammals (0.05). In addition, the elastic modulus of the thoracic aorta (12 MPa at 13 kPa blood pressure) is about 30 times higher than in other mammals. In contrast, the whale's aortic arch has a wall thickness/diameter ratio (0.055) and an elastic modulus (0.4 MPa) that are essentially identical to those for other mammals. However, the aortic arch is unusual in that it can be deformed biaxially to very large strains without entering a region of high stiffness caused by the recruitment of fully extended collagen fibres. Chemical composition studies indicate that the elastin:collagen ratio is high in the aortic arch (approximately 2:1) and that this ratio falls in the thoracic (approximately 1:2) and abdominal (approximately 1:3) aortas, but the magnitude of the change in composition does not account for the dramatic difference in mechanical properties. This suggests that there are differences in the elastin and collagen fibre architecture of these vessels. The descending aorta contains dense bands of tendon-like, wavy collagen fibres that run in the plane of the arterial wall, forming a fibre-lattice that runs in parallel to the elastin lamellae and reinforces the wall, making it very stiff. The aortic arch contains a very different collagen fibre-lattice in which fibres appear to have a component of orientation that runs through the thickness of the artery wall. This suggests that the collagen fibres may be arranged in series with elastin-containing elements, a difference in tissue architecture that could account for both the lower stiffness and the extreme extensibility of the whale's aortic arch. Thus, both the structure and the mechanical behaviour of the lamellar units in the aortic arch and aorta of the whale have presumably been modified to produce the unusual mechanical and haemodynamic properties of the whale circulation.

Developmental changes in respiratory, febrile, and cardiovascular responses to PGE2 in newborn lambs

2000 ◽  
Vol 278 (6) ◽  
pp. R1460-R1473 ◽  
Author(s):  
T. C. Tai ◽  
S. L. Adamson
Keyword(s):  
Adult Life ◽  
Lung Ventilation ◽  
Cardiovascular Effects ◽  
Cardiovascular Responses ◽  
Periodic Breathing ◽  
Developmental Changes ◽  
Postnatal Life ◽  
Newborn Period ◽  
Arterial Blood ◽  
Thyroarytenoid Muscle

PGE2 has centrally mediated respiratory, febrile, and cardiovascular effects that markedly differ between fetal and adult life. We hypothesized that the transition from fetal to adult responses to PGE2 occurs in the newborn period. Thus effects of an intracarotid infusion of PGE2 (3 μg/min for 60 min) were determined in unanesthetized newborn lambs at 5, 10, and 15 days after birth. At 5 days, PGE2 reduced central CO2 sensitivity, reduced lung ventilation due to a decrease in breathing frequency, and induced hypercapnia. By 15 days, these effects of PGE2 had waned significantly. In contrast, phasic (expiratory) thyroarytenoid muscle electromyogram activity, number of short apneas, and incidence of Biot periodic breathing were similarly increased at all three ages. PGE2 induced a sustained fever at 10 and 15 days. Heart rate and mean arterial blood pressure were unchanged in contrast to marked increases observed by others in adults. Results showed that the transition from fetal to adult respiratory and febrile responses to PGE2 occurs in early postnatal life, whereas adult cardiovascular responses develop later in life in sheep.

Mechanical properties and residual stress of HVOF sprayed nanostructured WC-17Co coatings

2019 ◽  
Vol 34 (01n03) ◽  
pp. 2040041
Author(s):  
Hairong Sun ◽  
Jinpeng Yu ◽  
Guoqing Gou ◽  
Wei Gao
Keyword(s):  
Mechanical Properties ◽  
Fracture Toughness ◽  
Residual Stress ◽  
Elastic Modulus ◽  
Tensile Stress ◽  
Compressive Residual Stress ◽  
Hvof Spray ◽  
Spray Technique ◽  
Oxygen Flame ◽  
Conventional Coating

Nanostructured WC-17Co, 2C-12Co coatings and conventional WC-17Co coating were prepared by High Velocity Oxygen Flame (HVOF) spray technique. The elastic modulus, fracture toughness and crack spread path were studied. The residual stress, different phases, microstructure from surface to the depth of coatings were also analyzed. While the nanostructured WC-12Co coating showed the highest elastic modulus, the nanostructured WC-17Co coating has the highest fracture toughness. The compressive residual stress of the nanostructured coatings was higher than the conventional coating. Both WC and W2C phases showed compressive residual stress, but Co6W6C phase showed tensile stress. The distribution of residual stress showed that the stress is the lowest at the surface and the highest close to the interface.

Role of Copper in Collagen Cross-linking and Its Influence on Selected Mechanical Properties of Chick Bone and Tendon

1982 ◽  
Vol 112 (4) ◽  
pp. 708-716 ◽  
Author(s):  
William Opsahl ◽  
Haig Zeronian ◽  
Mike Ellison ◽  
Davis Lewis ◽  
Robert B. Rucker ◽  
...  
Keyword(s):  
Mechanical Properties ◽  
Cross Linking ◽  
Collagen Cross Linking

scholarly journals Load magnitude affects patellar tendon mechanical properties but not collagen or collagen cross-linking after long-term strength training in older adults

2019 ◽  
Vol 19 (1) ◽  
Author(s):  
Christian S. Eriksen ◽  
Rene B. Svensson ◽  
Anne T. Gylling ◽  
Christian Couppé ◽  
S. Peter Magnusson ◽  
...  
Keyword(s):  
Mechanical Properties ◽  
Older Adults ◽  
Strength Training ◽  
Patellar Tendon ◽  
Cross Linking ◽  
Term Strength ◽  
Collagen Cross Linking

scholarly journals Mechanical properties of the cement of the stalked barnacle Dosima fascicularis (Cirripedia, Crustacea)

2015 ◽  
Vol 5 (1) ◽  
pp. 20140049 ◽  
Author(s):  
Vanessa Zheden ◽  
Waltraud Klepal ◽  
Stanislav N. Gorb ◽  
Alexander Kovalev
Keyword(s):  
Mechanical Properties ◽  
Elastic Modulus ◽  
Tensile Stress ◽  
Mechanical Damage ◽  
Morphological Structure ◽  
Dual Use ◽  
Barnacle Species ◽  
Compact Zone ◽  
Inner Region

The stalked barnacle Dosima fascicularis secretes foam-like cement, the amount of which usually exceeds that produced by other barnacles. When Dosima settles on small objects, this adhesive is additionally used as a float which gives buoyancy to the animal. The dual use of the cement by D. fascicularis requires mechanical properties different from those of other barnacle species. In the float, two regions with different morphological structure and mechanical properties can be distinguished. The outer compact zone with small gas-filled bubbles (cells) is harder than the interior one and forms a protective rind presumably against mechanical damage. The inner region with large, gas-filled cells is soft. This study demonstrates that D. fascicularis cement is soft and visco-elastic. We show that the values of the elastic modulus, hardness and tensile stress are considerably lower than in the rigid cement of other barnacles.

scholarly journals Effects of Organophosphate Insecticides on Mechanical Properties of Rat Aorta

2011 ◽  
pp. 39-46 ◽  
Author(s):  
B. GUVENC TUNA ◽  
N. OZTURK ◽  
U. COMELEKOGLU ◽  
B. C. YILMAZ
Keyword(s):  
Mechanical Properties ◽  
Elastic Modulus ◽  
Thoracic Aorta ◽  
High Stress ◽  
Chronic Administration ◽  
Female Rats ◽  
Control Group ◽  
Stress Strain ◽  
High Stress Region ◽  
Stress Region

The present study was carried out to search whether organophosphate pesticides affect the mechanical properties of the thoracic aorta. Wistar female rats (aged 6-8 weeks) were assigned randomly to a control group and groups treated with either dichlorvos or chlorpyriphos for 90 days at a dose of 5 mg/kg/day. After that period, animals were killed and thoracic aorta strips in longitudinal direction were isolated. The stress, strain and elastic modulus were obtained from the strips. Our results showed that chronic administration of chlorpyriphos and dichlorvos caused downward shift of the stress-strain relations compared to the control curve. The elastic modulus-stress curve revealed distinct characteristics in the low and high stress regions. A power function was used to simulate the low stress region while a line was fit to the high stress region. Curve fitting procedure illustrated that both pesticides influenced mainly the high stress region, but they had diverse effects at the low stress region. The results also imply that chlorpyriphos and dichlorvos decrease the strength of the aorta and therefore might influence the response of the aorta to mechanical loading induced by blood pressure.

A Study on Tensile Mechanical Properties of Bamboo Plywood

2011 ◽  
Vol 291-294 ◽  
pp. 1009-1014 ◽  
Author(s):  
Jian Han ◽  
Xi Tao Gao
Keyword(s):  
Mechanical Properties ◽  
Elastic Modulus ◽  
Tensile Stress ◽  
Elastic Deformation ◽  
Modulus Of Elasticity ◽  
Tensile Deformation ◽  
Tensile Modulus ◽  
Stress And Strain ◽  
Load Increase ◽  
Tensile Elastic Modulus

The tensile mechanical properties of bamboo mat and curtain plywood（for short bamboo plywood）were studied through “electrometric method”. It was proved that in the range of elastic deformation，the Poisson′s ratio and the elastic modulus of the bamboo plywood were not constant. The Poisson′s ratio of the bamboo plywood decreased nonlinearly with the load increase that Poisson′s ratio decreased markedly when the load was less than 1kN，and decreased gently when more than 1kN.The tensile elastic modulus of the bamboo plywood also increased nonlinearly with the load increase that the tensile modulus of elasticity increased drastically when the load was less than 800N，and increased less when exceeded 800N. In the process of loading，the tensile deformation、the tensile stress and strain all increased linearly with the load increase，and the tensile stress and strain both were linearly relevant to tensile deformation.

Sign in / Sign up

Export Citation Format

Share Document