The Experts below are selected from a list of 41295 Experts worldwide ranked by ideXlab platform
Taihao Quan - One of the best experts on this subject based on the ideXlab platform.
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physical properties of the photodamaged human skin dermis rougher collagen surface and stiffer harder mechanical properties
Experimental Dermatology, 2019Co-Authors: Yuan Shao, James Alexander Wilks, Rebecca Mutesi Balimunkwe, Gary J Fisher, John J Voorhees, Taihao QuanAbstract:Fragmentation of collagen fibrils and aberrant elastic material (solar elastosis) in the dermal extracellular matrix (ECM) is among the most prominent features of photodamaged human skin. These alterations impair the structural integrity and create a dermal microenvironment prone to skin disorders. The objective of this study was to determine the physical properties (surface roughness, Stiffness and hardness) of the dermal ECM in photodamaged and subject-matched sun-protected human skin. Skin samples were sectioned and analysed by histology, atomic force microscopy and nanoindentation. Dermal ECM collagen fibrils were more disorganized (ie, rougher surface), and the dermal ECM was stiffer and harder, in photodamaged forearm, compared to sun-protected underarm skin. Cleavage of collagen fibrils in sun-protected underarm dermis by recombinant human matrix metalloproteinase-1 resulted in rougher collagen fibril surface and Reduced dermal Stiffness and hardness. Degradation of elastotic material in photodamaged skin by treatment with purified neutrophil elastase Reduced Stiffness and hardness, without altering collagen fibril surface roughness. Additionally, expression of two members of the lysyl oxidase gene family, which insert cross-links that stiffen and harden collagen fibrils, was elevated in photodamaged forearm dermis. These data elucidate the contributions of fragmented collagen fibrils, solar elastosis and elevated collagen cross-linking to the physical properties of the dermal ECM in photodamaged human skin. This new knowledge extends current understanding of the impact of photodamage on the dermal ECM microenvironment.
Byeoungju Ha - One of the best experts on this subject based on the ideXlab platform.
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capacitive type surface micromachined silicon accelerometer with Stiffness tuning capability
Sensors and Actuators A-physical, 1999Co-Authors: Kyuyeon Park, Hyunsuk Jang, Yongsoo Oh, Byeoungju HaAbstract:Abstract A surface-micromachined silicon accelerometer with a novel concept, which has a Stiffness tuning capability to improve the sensor resolution, is developed. Imposing an electrostatic force to the electrodes reduces the Stiffness of the sensor structure. By adopting the Stiffness tuning, the initially stiff structure guarantees the stability of fabrication, and the Reduced Stiffness, only along the sensing direction, produces the improved resolution. One of the major improvements in the developed accelerometer is the branched comb-finger type electrode which senses the relative position between the mass and the electrode. Maintaining the same capacitance variation, such electrodes allow a larger initial gap between the mass and the electrode, so that the clash problem can be easily eliminated. The accelerometer was successfully fabricated with the active size of 650×530 μm 2 , the 7-μm thick polysilicon structure, and a proof mass of about 1 μg. Experimental results show that the equivalent noise level of the accelerometer is improved by 30 dB through the Stiffness tuning. The accelerometer has the bandwidth of 350 Hz, linearity of 0.3% FS, and sensing range of 50 g.
Christof Birkenmaier - One of the best experts on this subject based on the ideXlab platform.
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modification of pmma vertebroplasty cement for Reduced Stiffness by addition of normal saline a material properties evaluation
European Spine Journal, 2017Co-Authors: Christian Schroder, Mai Nguyen, Michael Kraxenberger, Yan Chevalier, Carolin Melcher, Bernd Wegener, Christof BirkenmaierAbstract:Purpose Vertebral augmentation is an established treatment for patients with pathological vertebral compression fractures. These procedures typically employ a PMMA-based bone cement, which possesses a high compressive Stiffness. Because of the increased risk of subsequent fractures after vertebral augmentations, there is a desire for reducing this Stiffness. The goal of our study was to examine the influence of adding isotonic saline on the biomechanical properties of PMMA vertebroplasty cement.
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modification of pmma vertebroplasty cement for Reduced Stiffness by addition of normal saline a material properties evaluation
European Spine Journal, 2017Co-Authors: Christian Schroder, Mai Nguyen, Michael Kraxenberger, Yan Chevalier, Carolin Melcher, Bernd Wegener, Christof BirkenmaierAbstract:Vertebral augmentation is an established treatment for patients with pathological vertebral compression fractures. These procedures typically employ a PMMA-based bone cement, which possesses a high compressive Stiffness. Because of the increased risk of subsequent fractures after vertebral augmentations, there is a desire for reducing this Stiffness. The goal of our study was to examine the influence of adding isotonic saline on the biomechanical properties of PMMA vertebroplasty cement. A PMMA-based vertebroplasty cement was prepared according to the manufacturer’s recommendations after which isotonic saline was mixed into the cement at 10, 20, and 30% (volume:volume). Testing bodies were cast, and compression and bending tests were performed. Fracture surfaces were studied using SEM. Measurements of injectability, setting temperature, and radioopacity were also performed. The addition of saline solution (of up to vol-30%) led to a pronounced reduction in the compression modulus of the cement from 3409 ± 312 to 1131 ± 127 MPa. In parallel, maximal compression strength was Reduced from 86 ± 4 to 33 ± 3 MPa and bending strength from 40 ± 4 to 24 ± 3 MPa. The differences regarding injectability, setting temperature, and radioopacity were small and probably of no clinical relevance. The compressive Stiffness of PMMA-based vertebroplasty cement can be Reduced to almost a third by the addition of saline. The probable explanation is an increase in microporosity. Future simulator experiments will show whether the achieved reduction in Stiffness is large enough to reduce the rate of subsequent vertebral fractures.
Yuan Shao - One of the best experts on this subject based on the ideXlab platform.
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physical properties of the photodamaged human skin dermis rougher collagen surface and stiffer harder mechanical properties
Experimental Dermatology, 2019Co-Authors: Yuan Shao, James Alexander Wilks, Rebecca Mutesi Balimunkwe, Gary J Fisher, John J Voorhees, Taihao QuanAbstract:Fragmentation of collagen fibrils and aberrant elastic material (solar elastosis) in the dermal extracellular matrix (ECM) is among the most prominent features of photodamaged human skin. These alterations impair the structural integrity and create a dermal microenvironment prone to skin disorders. The objective of this study was to determine the physical properties (surface roughness, Stiffness and hardness) of the dermal ECM in photodamaged and subject-matched sun-protected human skin. Skin samples were sectioned and analysed by histology, atomic force microscopy and nanoindentation. Dermal ECM collagen fibrils were more disorganized (ie, rougher surface), and the dermal ECM was stiffer and harder, in photodamaged forearm, compared to sun-protected underarm skin. Cleavage of collagen fibrils in sun-protected underarm dermis by recombinant human matrix metalloproteinase-1 resulted in rougher collagen fibril surface and Reduced dermal Stiffness and hardness. Degradation of elastotic material in photodamaged skin by treatment with purified neutrophil elastase Reduced Stiffness and hardness, without altering collagen fibril surface roughness. Additionally, expression of two members of the lysyl oxidase gene family, which insert cross-links that stiffen and harden collagen fibrils, was elevated in photodamaged forearm dermis. These data elucidate the contributions of fragmented collagen fibrils, solar elastosis and elevated collagen cross-linking to the physical properties of the dermal ECM in photodamaged human skin. This new knowledge extends current understanding of the impact of photodamage on the dermal ECM microenvironment.
Maria Kashtalyan - One of the best experts on this subject based on the ideXlab platform.
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Stiffness degradation in cross ply laminates damaged by transverse cracking and splitting
Composites Part A-applied Science and Manufacturing, 2000Co-Authors: Maria KashtalyanAbstract:Abstract In contrast to the few existing theoretical models (Highsmith and Reifsnider, ASTM STP 1986;907:233–251; Hashin, Trans ASME J Appl Mech 1987;54:872–879; Daniel and Tsai, Comp Eng 1991;1(6):355–362; Tsai and Daniel, Int J Solid Structures 1992;29(24)3251–3267; Henaff-Gardin et al., Comp Structures 1996;36:113–130; 1996;36:131–140), based on the consideration of a repeated laminate element defined by the intersecting pairs of transverse cracks and splits, the new approach for evaluating the Stiffness degradation in [0 m /90 n ] s laminates due to matrix cracking both in the 90° (transverse cracking) and 0° (splitting) plies employs the Equivalent Constraint Model (Fan and Zhang, Composites Science and Technology 1993;47:291–298). It also uses an improved 2-D shear lag analysis (Zhang et al., Composites 1992;23(5):291–298; 1992;23(5):299–304) for determination of stress field in the cracked or split lamina and In-situ Damage Effective Functions for description of Stiffness degradation. Reduced Stiffness properties of the damaged lamina are found to depend explicitly upon the crack density of that lamina and implicitly upon the crack density of the neighbouring lamina. Theoretical predictions for carbon and glass fibre reinforced plastic cross-ply laminates with matrix cracking in the 90° ply revealed significant reduction in the Poisson's ratio and shear modulus due to additional damage (splitting) in the 0° ply.
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The effect of delaminations induced by transverse cracks and splits on Stiffness properties of composite laminates
Composites Part A: Applied Science and Manufacturing, 2000Co-Authors: Maria Kashtalyan, Constantinos SoutisAbstract:Abstract In an effort to evaluate Stiffness degradation due to delaminations growing at the 0°/90° interface from the tips of transverse cracks in the 90° plies and splits in the 0° plies of cross-ply [0m/90n]s laminates, a new theoretical approach was developed. It employs the Equivalent Constraint Model of the damaged lamina [Fan J, Zhang J. In-situ damage evolution and micro/macro transition for laminated composites. Composites Science and Technology 1993;47:107–118], which allows one to avoid cumbersome consideration of the repeated laminate element defined by the intersecting pairs of transverse cracks and splits. It also uses an improved 2D shear-lag analysis [Zhang J, Soutis C, Fan J. Strain energy release rate associated with local delamination in cracked composite laminates. Composites 1994;25(9):851–862] to determine the stress fields in the explicitly damaged lamina and the In situ Damage Effective Functions to describe its Reduced Stiffness properties. Reduced Stiffness properties of the damaged lamina are found to depend explicitly upon the crack density and relative delamination area associated with that lamina and implicitly upon two damage parameters associated with the neighbouring lamina. Theoretical predictions reveal that transverse crack tip delaminations cause significant reduction in the shear modulus and Poisson's ratio of cross-ply and symmetric balanced [±θm/90n]s laminates. Dependence of the laminate Reduced elastic properties on the orientation angle of the constraining ply is examined. Contribution of each damage mode (transverse cracking, transverse crack tip delaminations, splitting and split tip delaminations) into Stiffness loss is established.