MRI-derived bone porosity index correlates to bone composition and mechanical stiffness

Abstract Magnetic gels and elastomers consist of magnetic or magnetizable colloidal particles embedded in an elastic polymeric matrix. Outstanding properties of these materials comprise reversible changes in their mechanical stiffness or magnetostrictive distortions under the influence of external magnetic fields. To understand such types of overall material behavior from a theoretical point of view, it is essential to characterize the substances starting from the discrete colloidal particle level. It turns out that the macroscopic material response depends sensitively on the mesoscopic particle arrangement. We have utilized and developed several theoretical approaches to this end, allowing us both to reproduce experimental observations and to make theoretical predictions. Our hope is that both these paths help to further stimulate the interest in these fascinating materials.

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Cu2Se-based thermoelectric cellular architectures for efficient and durable power generation

Nature Communications ◽

10.1038/s41467-021-23944-w ◽

2021 ◽

Vol 12 (1) ◽

Author(s):

Seungjun Choo ◽

Faizan Ejaz ◽

Hyejin Ju ◽

Fredrick Kim ◽

Jungsoo Lee ◽

...

Keyword(s):

Power Generation ◽

3D Printing ◽

Power Output ◽

Waste Heat ◽

Computational Simulation ◽

Mechanical Stiffness ◽

Higher Power ◽

Printing Inks ◽

Binder Free ◽

Sustainable Power

AbstractThermoelectric power generation offers a promising way to recover waste heat. The geometrical design of thermoelectric legs in modules is important to ensure sustainable power generation but cannot be easily achieved by traditional fabrication processes. Herein, we propose the design of cellular thermoelectric architectures for efficient and durable power generation, realized by the extrusion-based 3D printing process of Cu2Se thermoelectric materials. We design the optimum aspect ratio of a cuboid thermoelectric leg to maximize the power output and extend this design to the mechanically stiff cellular architectures of hollow hexagonal column- and honeycomb-based thermoelectric legs. Moreover, we develop organic binder-free Cu2Se-based 3D-printing inks with desirable viscoelasticity, tailored with an additive of inorganic Se82− polyanion, fabricating the designed topologies. The computational simulation and experimental measurement demonstrate the superior power output and mechanical stiffness of the proposed cellular thermoelectric architectures to other designs, unveiling the importance of topological designs of thermoelectric legs toward higher power and longer durability.

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Mechanical Pressure Driving Proteoglycan Expression in Mammographic Density: a Self-perpetuating Cycle?

Journal of Mammary Gland Biology and Neoplasia ◽

10.1007/s10911-021-09494-3 ◽

2021 ◽

Cited By ~ 1

Author(s):

Gina Reye ◽

Xuan Huang ◽

Larisa M. Haupt ◽

Ryan J. Murphy ◽

Jason J. Northey ◽

...

Keyword(s):

Mammographic Density ◽

Positive Feedback ◽

Weight Bearing ◽

Fibrous Tissue ◽

Feedback Mechanism ◽

Mechanical Force ◽

Mechanical Stiffness ◽

Mechanical Pressure ◽

Fibrous Stroma ◽

High Mammographic Density

AbstractRegions of high mammographic density (MD) in the breast are characterised by a proteoglycan (PG)-rich fibrous stroma, where PGs mediate aligned collagen fibrils to control tissue stiffness and hence the response to mechanical forces. Literature is accumulating to support the notion that mechanical stiffness may drive PG synthesis in the breast contributing to MD. We review emerging patterns in MD and other biological settings, of a positive feedback cycle of force promoting PG synthesis, such as in articular cartilage, due to increased pressure on weight bearing joints. Furthermore, we present evidence to suggest a pro-tumorigenic effect of increased mechanical force on epithelial cells in contexts where PG-mediated, aligned collagen fibrous tissue abounds, with implications for breast cancer development attributable to high MD. Finally, we summarise means through which this positive feedback mechanism of PG synthesis may be intercepted to reduce mechanical force within tissues and thus reduce disease burden.

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Mechanical stiffness control of a three DOF wrist joint that mimics musculo-skeletal system

2017 IEEE International Conference on Advanced Intelligent Mechatronics (AIM) ◽

10.1109/aim.2017.8013993 ◽

2017 ◽

Cited By ~ 1

Author(s):

Koichi Koganezawa

Keyword(s):

Wrist Joint ◽

Skeletal System ◽

Mechanical Stiffness ◽

Stiffness Control

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Comparison of Biomechanical and Anatomical Effects Following Eccentric and Concentric Exertions

Proceedings of the Human Factors and Ergonomics Society Annual Meeting ◽

10.1177/154193120504901405 ◽

2005 ◽

Vol 49 (14) ◽

pp. 1287-1291

Author(s):

Amrish O. Chourasia ◽

Mary E. Sesto ◽

Youngkyoo Jung ◽

Robert S. Howery ◽

Robert G. Radwin

Keyword(s):

Signal Intensity ◽

Intensity Ratio ◽

Maximum Voluntary Contraction ◽

Magnetic Resonance Images ◽

Voluntary Contraction ◽

Work Place ◽

Signal Intensity Ratio ◽

Mechanical Stiffness ◽

Average Decrease ◽

Muscle Shortening

Work place exertions may include muscle shortening (concentric) or muscle lengthening (eccentric) contractions. This study investigates the upper limb mechanical properties and magnetic resonance images (MRI) of the involved muscles following submaximal eccentric and concentric exertions. Twelve participants were randomly assigned to perform at 30° per second eccentric or concentric forearm supination exertions at 50% isometric maximum voluntary contraction (MVC) for 30 minutes. Measurement of mechanical stiffness, isometric MVC, localized discomfort and MRI supinator: extensor signal intensity ratio was done before, immediately after, 1 hour after and 24 hours after the bout of exercise. A 53% average decrease in mechanical stiffness after 1 hour was observed for the eccentric group (p< 0.05) compared to a 1% average decrease for the concentric group (p> 0.05). Edema, indicative of swelling, was observed 24 hrs after exercise, with an average increase in the MRI supinator: extensor signal intensity ratio of 36% for the eccentric group and less than 10% for the concentric group (p<0.05).

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Cortical bone composition and orientation as a function of animal and tissue age in mice by Raman spectroscopy

Bone ◽

10.1016/j.bone.2010.04.608 ◽

2010 ◽

Vol 47 (2) ◽

pp. 392-399 ◽

Cited By ~ 93

Author(s):

Sonja Gamsjaeger ◽

A. Masic ◽

P. Roschger ◽

M. Kazanci ◽

J.W.C. Dunlop ◽

...

Keyword(s):

Raman Spectroscopy ◽

Cortical Bone ◽

Bone Composition

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Poly(HDDA)-Based Polymers for Microfabrication and Mechanobiology

MRS Advances ◽

10.1557/adv.2017.57 ◽

2017 ◽

Vol 2 (24) ◽

pp. 1315-1321 ◽

Cited By ~ 3

Author(s):

Daniela Espinosa-Hoyos ◽

Huifeng Du ◽

Nicholas X. Fang ◽

Krystyn J. Van Vliet

Keyword(s):

Polyethylene Glycol ◽

Additive Manufacturing ◽

Progenitor Cell ◽

Materials Processing ◽

Biological Applications ◽

Post Processing ◽

Mechanical Stiffness ◽

Processing Times ◽

Low Stiffness ◽

Cell Material Interactions

ABSTRACTMaterials processing and additive manufacturing afford exciting opportunities in biomedical research, including the study of cell-material interactions. However, some of the most efficient materials for microfabrication are not wholly suitable for biological applications, require extensive post-processing or exhibit high mechanical stiffness that limits the range of applications. Conversely, materials exhibiting high cytocompatibility and low stiffness require long processing times with typically decreased spatial resolution of features. Here, we investigated the use of hexanediol diacrylate (HDDA), a classic and efficient polymer for stereolithography, for oligodendrocyte progenitor cell (OPC) culture. We developed composite HDDA-polyethylene glycol acrylate hydrogels that exhibited high biocompatibility, mechanical stiffness in the range of muscle tissue, and high printing efficiency at ∼5 μm resolution.

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In Vivo and ex Vivo Approaches to Studying the Biomechanical Properties of Healing Wounds in Rat Skin

Journal of Biomechanical Engineering ◽

10.1115/1.4025109 ◽

2013 ◽

Vol 135 (10) ◽

Cited By ~ 14

Author(s):

Clare Y. L. Chao ◽

Gabriel Y. F. Ng ◽

Kwok-Kuen Cheung ◽

Yong-Ping Zheng ◽

Li-Ke Wang ◽

...

Keyword(s):

Wound Healing ◽

Ex Vivo ◽

Normal Skin ◽

Biomechanical Properties ◽

Skin Wound ◽

Sprague Dawley ◽

Rat Skin ◽

Mechanical Stiffness ◽

Air Jet

An evaluation of wound mechanics is crucial in reflecting the wound healing status. The present study examined the biomechanical properties of healing rat skin wounds in vivo and ex vivo. Thirty male Sprague-Dawley rats, each with a 6 mm full-thickness circular punch biopsied wound at both posterior hind limbs were used. The mechanical stiffness at both the central and margins of the wound was measured repeatedly in five rats over the same wound sites to monitor the longitudinal changes over time of before wounding, and on days 0, 3, 7, 10, 14, and 21 after wounding in vivo by using an optical coherence tomography-based air-jet indentation system. Five rats were euthanized at each time point, and the biomechanical properties of the wound tissues were assessed ex vivo using a tensiometer. At the central wound bed region, the stiffness measured by the air-jet system increased significantly from day 0 (17.2%), peaked at day 7 (208.3%), and then decreased progressively until day 21 (40.2%) as compared with baseline prewounding status. The biomechanical parameters of the skin wound samples measured by the tensiometer showed a marked reduction upon wounding, then increased with time (all p < 0.05). On day 21, the ultimate tensile strength of the skin wound tissue approached 50% of the normal skin; while the stiffness of tissue recovered at a faster rate, reaching 97% of its prewounded state. Our results suggested that it took less time for healing wound tissues to recover their stiffness than their maximal strength in rat skin. The stiffness of wound tissues measured by air-jet could be an indicator for monitoring wound healing and contraction.

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