Mechanical properties of the collagenous framework of skin in rats of different ages

1964 ◽  
Vol 206 (6) ◽  
pp. 1425-1429 ◽  
Author(s):  
Phyllis Fry ◽  
Margaret L. R. Harkness ◽  
R. D. Harkness
Keyword(s):  
Mechanical Properties ◽  
Tensile Strength ◽  
Unit Area ◽  
Constant Load ◽  
Cross Sectional Area ◽  
Mechanical Resistance ◽  
Sectional Area ◽  
Cross Sectional ◽  
Constant Rate ◽  
Zero Time

The collagen content, tensile strength, and extensibility of the skin of rats have been examined in rats 3–85 weeks of age. Tensile strength calculated per unit cross-sectional area of collagen increased with age, the maximal value in the oldest group (5.5 kg/mm2 collagen) being about three times that in the youngest. The quantity present per unit area of surface also increased with age. An estimate of the total "surface mechanical resistance" obtained by multiplying collagen per unit area of skin and tensile strength rose continuously about twentyfold between the youngest to oldest of the groups. Application of a load produces after a time an elongation at constant rate ( K). Extensibility, measured by the ratio of this rate to length at zero time ( l0) obtained by extrapolation, and corrected to constant load of 100 g/mm2 cross-sectional area of collagen, was found to fall with age, the range being about eightyfold.

Comparison of the Cross Sectional Area, the Loss in Volume and the Mechanical Properties of LAE442 and MgCa0.8 as Resorbable Magnesium Alloy Implants after 12 Months Implantation Duration

2010 ◽  
Vol 638-642 ◽  
pp. 675-680 ◽  
Author(s):  
Martina Thomann ◽  
Nina von der Höh ◽  
Dirk Bormann ◽  
Dina Rittershaus ◽  
C. Krause ◽  
...  
Keyword(s):  
Mechanical Properties ◽  
Cross Sections ◽  
Degradation Process ◽  
Cross Sectional Area ◽  
Bending Test ◽  
Sectional Area ◽  
Cross Sectional ◽  
Initial Strength ◽  
Three Point Bending ◽  
The Cross

Current research focuses on magnesium based alloys in the course of searching a resorbable osteosynthetic material which provides sufficient mechanical properties besides a good biocompatibility. Previous studies reported on a favorable biocompatibility of the alloys LAE442 and MgCa0.8. The present study compared the degradation process of cylindrical LAE442 and MgCa0.8 implants after 12 months implantation duration. Therefore, 10 extruded implants (2.5 x 25 mm, cross sectional area 4.9 mm²) of both alloys were implanted into the medullary cavity of both tibiae of rabbits for 12 months. After euthanization, the right bone-implant-compound was scanned in a µ-computed tomograph (µCT80, ScancoMedical) and nine uniformly distributed cross-sections of each implant were used to determine the residual implants´ cross sectional area (Software AxioVisionRelease 4.5, Zeiss). Left implants were taken out of the bone carefully. After weighing, a three-point bending test was carried out. LAE442 implants degraded obviously slower and more homogeneously than MgCa0.8. The mean residual cross sectional area of LAE442 implants was 4.7 ± 0.07 mm². MgCa0.8 showed an area of only 2.18 ± 1.03 mm². In contrast, the loss in volume of LAE442 pins was more obvious. They lost 64 % of their initial weight. The volume of MgCa0.8 reduced clearly to 54.4 % which corresponds to the cross sectional area results. Three point bending tests revealed that LAE442 showed a loss in strength of 71.2 % while MgCa0.8 lost 85.6 % of its initial strength. All results indicated that LAE442 implants degraded slowly, probably due to the formation of a very obvious degradation layer. Degradation of MgCa0.8 implants was far advanced.

Habitual loading results in tendon hypertrophy and increased stiffness of the human patellar tendon

2008 ◽  
Vol 105 (3) ◽  
pp. 805-810 ◽  
Author(s):  
C. Couppé ◽  
M. Kongsgaard ◽  
P. Aagaard ◽  
P. Hansen ◽  
J. Bojsen-Moller ◽  
...  
Keyword(s):  
Mechanical Properties ◽  
Patellar Tendon ◽  
Cross Sectional Area ◽  
Isometric Contractions ◽  
Sectional Area ◽  
Cross Sectional ◽  
Strength Difference ◽  
Distal Tendon

The purpose of this study was to examine patellar tendon (PT) size and mechanical properties in subjects with a side-to-side strength difference of ≥15% due to sport-induced loading. Seven elite fencers and badminton players were included. Cross-sectional area (CSA) of the PT obtained from MRI and ultrasonography-based measurement of tibial and patellar movement together with PT force during isometric contractions were used to estimate mechanical properties of the PT bilaterally. We found that distal tendon and PT, but not mid-tendon, CSA were greater on the lead extremity compared with the nonlead extremity (distal: 139 ± 11 vs. 116 ± 7 mm2; mid-tendon: 85 ± 5 vs. 77 ± 3 mm2; proximal: 106 ± 7 vs. 83 ± 4 mm2; P < 0.05). Distal tendon CSA was greater than proximal and mid-tendon CSA on both the lead and nonlead extremity ( P < 0.05). For a given common force, stress was lower on the lead extremity (52.9 ± 4.8 MPa) compared with the nonlead extremity (66.0 ± 8.0 MPa; P < 0.05). PT stiffness was also higher in the lead extremity (4,766 ± 716 N/mm) compared with the nonlead extremity (3,494 ± 446 N/mm) ( P < 0.05), whereas the modulus did not differ (lead 2.27 ± 0.27 GPa vs. nonlead 2.16 ± 0.28 GPa) at a common force. These data show that a habitual loading is associated with a significant increase in PT size and mechanical properties.

scholarly journals Sex Differences in the Morphological and Mechanical Properties of the Achilles Tendon

2021 ◽  
Vol 18 (17) ◽  
pp. 8974
Author(s):  
Xini Zhang ◽  
Liqin Deng ◽  
Songlin Xiao ◽  
Lu Li ◽  
Weijie Fu
Keyword(s):  
Mechanical Properties ◽  
Achilles Tendon ◽  
Maximum Voluntary Contraction ◽  
Voluntary Contraction ◽  
Cross Sectional Area ◽  
Morphological Properties ◽  
Sectional Area ◽  
Cross Sectional ◽  
Force Peak ◽  
Strain Stress

Background: Patients with Achilles tendon (AT) injuries are often engaged in sedentary work because of decreasing tendon vascularisation. Furthermore, men are more likely to be exposed to AT tendinosis or ruptures. These conditions are related to the morphological and mechanical properties of AT, but the mechanism remains unclear. This study aimed to investigate the effects of sex on the morphological and mechanical properties of the AT in inactive individuals. Methods: In total, 30 inactive healthy participants (15 male participants and 15 female participants) were recruited. The AT morphological properties (cross-sectional area, thickness, and length) were captured by using an ultrasound device. The AT force–elongation characteristics were determined during isometric plantarflexion with the ultrasonic videos. The AT stiffness was determined at 50%–100% maximum voluntary contraction force. The AT strain, stress, and hysteresis were calculated. Results: Male participants had 15% longer AT length, 31% larger AT cross-sectional area and 21% thicker AT than female participants (p < 0.05). The plantarflexion torque, peak AT force, peak AT stress, and AT stiffness were significantly greater in male participants than in female participants (p < 0.05). However, no significant sex-specific differences were observed in peak AT strain and hysteresis (p > 0.05). Conclusions: In physically inactive adults, the morphological properties of AT were superior in men but were exposed to higher stress conditions. Moreover, no significant sex-specific differences were observed in peak AT strain and hysteresis, indicating that the AT of males did not store and return elastic energy more efficiently than that of females. Thus, the mechanical properties of the AT should be maintained and/or improved through physical exercise.

Effects of cross-sessional area and aspect ratio coupled with orientation on mechanical properties and deformation behavior of Cu nanowires

2021 ◽  
Author(s):  
Hui Cao ◽  
Wenke Chen ◽  
Zhiyuan Rui ◽  
Changfeng Yan
Keyword(s):  
Mechanical Properties ◽  
Aspect Ratio ◽  
Yield Stress ◽  
Young’S Modulus ◽  
Young's Modulus ◽  
Cross Sectional Area ◽  
Sectional Area ◽  
Cross Sectional ◽  
Cu Nanowires ◽  
The Cross

Abstract Metal nanomaterials exhibit excellent mechanical properties compared with corresponding bulk materials and have potential applications in various areas. Despite a number of studies of the size effect on Cu nanowires mechanical properties with square cross-sectional, investigations of them in rectangular cross-sectional with various sizes at constant volume are rare, and lack of multifactor coupling effect on mechanical properties and quantitative investigation. In this work, the dependence of mechanical properties and deformation mechanisms of Cu nanowires/nanoplates under tension on cross-sessional area, aspect ratio of cross-sectional coupled with orientation were investigated using molecular dynamics simulations and the semi-empirical expressions related to mechanical properties were proposed. The simulation results show that the Young’s modulus and the yield stress sharply increase with the aspect ratio except for the <110>{110}{001} Cu nanowires/nanoplates at the same cross-sectional area. And the Young’s modulus increases while the yield stress decreases with the cross-sectional area of Cu nanowires. However, both of them increase with the cross-sectional area of Cu nanoplates. Besides, the Young’s modulus increases with the cross-sectional area at all the orientations. The yield stress shows a mildly downward trend except for the <111> Cu nanowires with increased cross-sectional area. For the Cu nanowires with a small cross-sectional area, the surface force increases with the aspect ratio. In contrast, it decreases with the aspect ratio increase at a large cross-sectional area. At the cross-sectional area of 13.068 nm2, the surface force decreases with the aspect ratio of the <110> Cu nanowires while it increases at other orientations. The surface force is a linearly decreasing function of the cross-sectional area at different orientations. Quantitative studies show that Young’s modulus and yield stress to the aspect ratio of the Cu nanowires satisfy exponent relationship. In addition, the main deformation mechanism of Cu nanowires is the nucleation and propagation of partial dislocations while it is the twinning-dominated reorientation for Cu nanoplates.

scholarly journals Enterochromaffin Cells and Mast Cells in Acute Appendicitis

2020 ◽  
Vol 12 (02) ◽  
pp. 141-146
Author(s):  
Bhavya P. Mohan ◽  
K.P. Aravindan
Keyword(s):  
Mast Cell ◽  
Mast Cells ◽  
Acute Appendicitis ◽  
Toluidine Blue ◽  
Unit Area ◽  
Cross Sectional Area ◽  
Sectional Area ◽  
Cross Sectional ◽  
Cell Counts ◽  
Ec Cells

Abstract Background and Objective Serotonin levels are increased in acute appendicitis. We investigated the possible source of this increase. The aim of this study was to compare the distribution and density of epithelial and nonepithelial enterochromaffin (EC) cells as well as numbers of degranulated and nondegranulated mast cells in different layers of normal appendices and acute appendicitis. Methods Sections from 15 cases of acute appendicitis and 10 cases where the appendix was morphologically normal were stained with Hematoxylin & Eosin, Toluidine blue, and immunohistochemically for chromogranin and CD-117. EC cells stained by chromogranin were counted per crypt and extraepithelial EC cells counted and expressed as cells per unit area (mm2). Mast cells stained by Toluidine blue and CD-117 were counted in lamina propria, submucosa, and muscle layers. The difference between Toluidine blue and CD117 stained mast cells was taken to be an estimate of degranulated cells. The cell counts were expressed per unit area (mm2) as well as per cross-sectional area of the appendix. Results There was no statistically significant difference in epithelial and extraepithelial EC cells between acute appendicitis and normal appendix. Estimated mast cell degranulation as indicated by mast cell counts per cross-sectional area is greatly increased in acute appendicitis when compared with normal. Conclusion Degranulated mast cells rather than EC cells may be the main source of raised serotonin in acute appendicitis.

scholarly journals Effects of Advanced Glycation Endproducts on the Mechanical Properties of Posterior Tibialis in Individuals with Diabetes Mellitus

2019 ◽  
Vol 4 (4) ◽  
pp. 2473011419S0045
Author(s):  
Jennifer A. Zellers ◽  
Jeremy Eekhoff ◽  
Remy Walk ◽  
Simon Y. Tang ◽  
Mary K. Hastings ◽  
...  
Keyword(s):  
Diabetes Mellitus ◽  
Mechanical Properties ◽  
Mechanical Testing ◽  
Advanced Glycation Endproducts ◽  
Cross Sectional Area ◽  
Sectional Area ◽  
Advanced Glycation ◽  
Cross Sectional ◽  
Glycation Endproducts ◽  
Wet Weight

Category: Diabetes Introduction/Purpose: Advanced glycation endproducts (AGEs) accumulate in tendon tissue in individuals with diabetes mellitus (DM). Although AGEs have been shown to impact tendon function by decreasing collagen sliding, this relationship has not been explored in humans with diabetes. Despite the prevalence of foot deformity in this population and implications of posterior tibialis dysfunction, the mechanical behavior of the posterior tibialis tendon has only been reported in a small (n=5), cadaveric study that did not report DM status. Therefore, the purpose of this study is to determine the effects of DM-associated AGEs accumulation on the mechanical properties of the posterior tibialis tendon. Methods: Posterior tibialis tendons were collected from individuals with and without DM undergoing lower extremity amputation. A 1-2 mm tendon transection was used for AGEs quantification. AGEs were quantified via fluorescence following papain digestion and hydrolyzation as described previously. Fluorescence was compared to a quinine standard to calculate AGEs content, which was normalized to sample wet weight. Tensile mechanical testing was completed with the remaining specimen (˜25 mm long). Tendon cross-sectional area was measured with a non-contact laser scanning device. Specimens were preloaded to 10 N and preconditioned for 10 cycles at 6% strain, subjected to stress-relaxation at 6% strain for 10 minutes, and loaded with a triangular waveform to a maximum of 10% strain at a rate of 1% strain per second. Individual values and group descriptive statistics are reported for AGEs content and mechanical testing. Relationships between AGEs content and various mechanical testing parameters were evaluated using Spearman correlation. Results: Six individuals (5 with DM, 4 male, mean(SD) age: 56(5)years) were included. AGEs content was increased in DM tendon (DM: 20.5(5.1), non-DM: 9.5 ng quinine/mg wet weight). Compared to non-DM tendon, DM tendons had larger cross-sectional area (DM: 44.3(4.9), non-DM: 11mm2). From stress relaxation, DM tendons had smaller peak (DM: 0.41(0.25), non-DM: 1.16 MPa) and equilibrium stress (DM: 0.23(0.13), non-DM: 0.83 MPa), and larger percent relaxation (DM: 46(6)%, non-DM: 29%)(Figure 1-A). DM tendons had decreased maximum stress at 10% strain (DM: 0.63(0.45), non-DM: 1.75 MPa), increased linear stiffness (DM: 35.2(27.6), non-DM: 19.2N/mm), and decreased linear modulus (DM: 8.5(7.0), non-DM: 20.1 MPa)(Figure 1-B, C) compared to non- DM tendon. Hysteresis (i.e., energy loss upon unloading) was higher in DM tendons (DM: 0.35(0.05), non-DM: 0.22), and positively correlated to AGEs (rho=0.943, p=0.005, Figure 1-D). Conclusion: Posterior tibialis tendons with DM exhibited increased AGEs content and altered mechanical properties. DM tendons were less stiff when accounting for cross-sectional area but had 2-4x the cross-sectional area of non-DM tendon, with inconsistent patterns in total tendon stiffness potentially attributable to several factors. DM tendons showed impaired energy storage and return, which was most strongly associated with AGEs. Non-DM samples were limited and the linear modulus was smaller than previously reported, however, all but one DM tendon had a modulus less than 50% of the non-DM sample. Future work will explore the mechanisms of AGEs-associated DM tendon impairments.

Effect of Weld Defects on Tensile Properties of Lightweight Materials and Correlations With Phased Array Ultrasonic Nondestructive Evaluation

2014 ◽  
Author(s):  
Mohammad W. Dewan ◽  
M. A. Wahab ◽  
Ayman M. Okeil
Keyword(s):  
Tensile Strength ◽  
Aluminum Alloy ◽  
Tensile Properties ◽  
Phased Array ◽  
Critical Value ◽  
Area Ratio ◽  
Cross Sectional Area ◽  
Sectional Area ◽  
Cross Sectional ◽  
Strength And Toughness

Fusion welding of Aluminum and its alloys is a great challenge for the structural integrity of lightweight material structures. One of the major shortcomings of Aluminum alloy welding is the inherent existence of defects in the welded area. In the current study, tests have been conducted on tungsten inert gas (TIG) welded AA6061-T651 aluminum alloy to determine the effects of defect sizes and its distribution on fracture strength. The information will be used to establish weld acceptance/rejection criteria. After welding, all specimens were non-destructively inspected with phased array ultrasonic and measured the projected area of the defects. Tensile testing was performed on inspected specimens containing different weld defects: such as, porosity, lack of fusion, and incomplete penetration. Tensile tested samples were cut along the cross section and inspected with Optical Microscope (OM) to measure actual defect sizes. Tensile properties were correlated with phased array ultrasonic testing (PAUT) results and through microscopic evaluations. Generally, good agreement was found between PAUT and microscopic defect sizing. The tensile strength and toughness decreased with the increase of defect sizes. Small voids (area ratio <0.04) does not have significant effect on the reduction of tensile strength and toughness values. Once defective “area ratio (cross sectional area of the defect) / (total specimen cross sectional area)” reached a certain critical value (say, 0.05), both strength and toughness values decline sharply. After that critical value both the tensile strength and toughness values decreases linearly with the increase of defect area ratio.

Effect of Estrogen on the Mechanical Properties of Prepubertal Rabbit ACL

2004 ◽  
Author(s):  
Courtney Cowden ◽  
Naveen Chandrashekar ◽  
Javad Hashemi ◽  
Vaughan H. Lee ◽  
Daniel M. Hardy ◽  
...  
Keyword(s):  
Mechanical Properties ◽  
Tensile Strength ◽  
Anterior Cruciate Ligament ◽  
Growth Factor ◽  
Material Properties ◽  
Cruciate Ligament ◽  
Sectional Area ◽  
Cross Sectional ◽  
Epidermal Growth ◽  
Anterior Cruciate

Recent research suggests that estradiol affects the material properties of the Anterior Cruciate Ligament (ACL). Here we experimentally determine the cross-sectional area and tensile properties of ACLs from the groups of prepubertal rabbits: untreated control (C), estrogen treated (E) and estrogen and epidermal growth factor treated (E+EGF). Estradiol decreased the ultimate tensile strength and toughness of the ACL. Addition of EGF decreased the modulus of elasticity.

Fleece characters and their influence on wool production per unit area of skin in Merino sheep

1958 ◽  
Vol 9 (3) ◽  
pp. 363 ◽  
Author(s):  
SSY Young ◽  
RE Chapman
Keyword(s):  
Unit Area ◽  
Fibre Diameter ◽  
Fibre Volume ◽  
Cross Sectional Area ◽  
The Body ◽  
Sectional Area ◽  
Cross Sectional ◽  
Fibre Density ◽  
Wool Production ◽  
Staple Length

The variations in fleece characters and the dependence of wool production per unit area of skin on these characters were studied with 15 sheep in both a medium and a strong-wool strain of Merino. Small but significant differences in staple length and fibre diameter were found between regions on the body, whereas differences in density were large. The variation in density was about three times as large as those in staple length and fibre diameter. Distinct dorsoventral and anteroposterior gradients over the body existed for fibre density, but not for staple length and fibre diameter. The influences of the fleece characters on wool production per unit area were somewhat different in the two strains, and changed with level of production. Among the medium-wool sheep, fibre density had the largest effect on production, with staple length less and mean fibre cross-sectional area least. Among the strong-wool sheep, length was more important than density, which in turn was more important than fibre cross-sectional area. The combined data indicated that as mean wool weight per unit area increased, the influence of density rose to a maximum and then diminished, whereupon mean fibre volume became the main contributor to wool weight. For different positions on the body of individual sheep, the dependence of wool production per unit area on the fleece characters was found to be similar in the two strains. Fibre density had the major effect in determining the level of production, whereas the influences of staple length and fibre area were negligible.

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