Degradation of Terfenol-D particle epoxy composites under low frequency cyclic magneto-mechanical loading: comparisons of matrix polymer

2005 ◽  
Author(s):  
William D. Armstrong ◽  
Manikantan Shanmugham
Keyword(s):  
Mechanical Loading ◽  
Low Frequency ◽  
Epoxy Composites ◽  
Matrix Polymer

Mechanical Properties of Piezoelectric Stack Actuators under Electro-Mechanical Loading

2007 ◽  
Vol 336-338 ◽  
pp. 331-334 ◽  
Author(s):  
Shao Ze Yan ◽  
Kai Zheng ◽  
Jian Xun
Keyword(s):  
Mechanical Loading ◽  
Piezoelectric Coefficient ◽  
Strong Dependence ◽  
Dynamic Test ◽  
Low Frequency ◽  
Input Voltage ◽  
Experimental Results ◽  
Phase Lag ◽  
Driving Frequency ◽  
Piezoelectric Stack Actuator

The responses of the piezoelectric stack actuator under electro-mechanical loading are investigated. Two types of tests are performed: influences of the preload on characteristics of the stack and dynamic test. Experimental results indicate strong dependence of the stack properties on the electro-mechanical loading conditions. The displacement output is initially enhanced with an increase of the mechanical preload, and the maximum value is obtained at the preload of about 0.4 kN. But much higher preload will cause the decrease of the displacement output. The effective piezoelectric coefficient and the hysteresis degree are employed to describe the variations of the stack’s performances caused by the mechanical preload. The effective piezoelectric coefficient under different preloads can be calculated by using experimental results of the displacement output and input voltage. Within low frequency band of about 400 Hz, the displacement magnitude of the stack is nearly constant, and the phase lag increases with the increase of the driving frequency at the applied sine sweep voltage with the amplitude of 150V.

scholarly journals Optimizing Mechanical Stretching Protocols for Hypertrophic and Anti-apoptotic Responses in H9c2 Cardiomyocytes

2020 ◽  
Author(s):  
Evangelos Zevolis ◽  
Anastassios Philippou ◽  
Athanasios Moustogiannis ◽  
Antonis Chatzigeorgiou ◽  
Michael Koutsilieris
Keyword(s):  
Mechanical Loading ◽  
Low Frequency ◽  
Signaling Proteins ◽  
Mechanical Stimuli ◽  
Elastic Membranes ◽  
H9c2 Cardiomyocytes ◽  
H9c2 Cardiomyoblasts ◽  
Mechanical Stretching ◽  
Strain Frequency

Abstract Background: Cardiomyocytes are sensitive to mechanical loading, possessing the ability to respond to mechanical stimuli by reprogramming their gene expression. In this study, signaling as well as expression responses of myogenic, anabolic, inflammatory, atrophy and pro-apoptotic genes to different mechanical stretching protocols were examined in differentiated cardiomyocytes.Methods: H9C2 cardiomyoblasts were cultured on elastic membranes up to their 5th day of differentiation (myotubes) and then subjected to three different stretching protocols by altering their strain, frequency and duration characteristics, using an in vitro cell tension system. cells were harvested and lysed 24 hours after the completion of each stretching protocol and Real Time-PCR was used to monitor changes in mRNA expression of myogenic regulatory factors (MyoD, Myogenin, MRF4), the IGF-1 isoforms (IGF-1Ea, IGF-1Eb), as well as atrophy (Atrogin-1), pro-apoptotic (FoxO, Fuca), and inflammatory (IL-6) factors in response to the different mechanical loading conditions. The activation of Akt and Erk 1/2 signaling proteins following the various stretching protocols was also evaluated by Western blot analysis.Results: We documented that the low strain (2.7% elongation), low frequency (0.25 Hz) and intermediate duration (12 hrs) stretching protocol was overall the most effective in inducing beneficial responses in differentiated cardiomyoblasts as it increased the expression of IGF-1 isoforms and phosphorylation of Akt and Erk1/2 (p<0.05), while it provoked the downregulation of all the other factors examined (p<0.05-0.001). Conclusion: These findings demonstrated that a low strain, low frequency of intermediate duration stretching protocol is the most effective in inducing a hypertrophic and anti-apoptotic response in H9C2 cardiomyotubes, in vitro.

scholarly journals Communication—Tunable Negative Permittivity of Cobalt and Epoxy Composites at 3 kHz ~ 1 MHz Frequency Regions

2021 ◽  
Author(s):  
Min Chen ◽  
Kai Sun ◽  
Xuai Wang ◽  
Yanmin Wang
Keyword(s):  
Potential Application ◽  
Low Frequency ◽  
Negative Permittivity ◽  
Epoxy Composites ◽  
Conductive Network ◽  
Free Electrons ◽  
Metal Composites ◽  
Large Numbers

Abstract Negative permittivity in percolation composites has drawn much attention owing to their potential application. This study set out to explore whether tunable negative permittivity can be realized in metal composites at 3 kHz ~ 1 MHz frequency regions. When the content of cobalt is 80 wt%, the permittivity turns to negative in the test band. These findings show that the Co conductive network has formed and provides large numbers of free electrons. Meanwhile, the percolation composites with negative permittivity show inductive characteristic. This research supports the idea that tunable low-frequency negative permittivity can be realized in metal composites.

scholarly journals In vivo assessment of the effect of controlled high- and low-frequency mechanical loading on peri-implant bone healing

2012 ◽  
Vol 9 (72) ◽  
pp. 1697-1704 ◽  
Author(s):  
Xiaolei Zhang ◽  
Katleen Vandamme ◽  
Antonia Torcasio ◽  
Toru Ogawa ◽  
G. Harry van Lenthe ◽  
...  
Keyword(s):  
Mechanical Loading ◽  
Bone Healing ◽  
Ex Vivo ◽  
Low Frequency ◽  
Constant Strain Rate ◽  
Titanium Implants ◽  
Cortical Level ◽  
Bone Response ◽  
Custom Made ◽  
40 Hz

The aim of this study was to investigate the effect of controlled high- (HF) and low-frequency (LF) mechanical loading on peri-implant bone healing. Custom-made titanium implants were inserted in both tibiae of 69 adult Wistar rats. For every animal, one implant was loaded by compression through the axis of tibia (test), whereas the other one was unloaded (control). The test implants were randomly distributed among four groups receiving different loading regimes, which were determined by ex vivo calibration. Within the HF (40 Hz) or LF (2 Hz) loading category, the magnitudes were chosen as low- (LM) and high-magnitude (HM), respectively, leading to constant strain rate amplitudes for the two frequency groups. This resulted in the four loading regimes: (i) HF-LM (40 Hz–0.5 N); (ii) HF-HM (40 Hz–1 N); (iii) LF-LM (2 Hz–10 N); and (iv) LF-HM (2 Hz–20 N) loading. Loading was performed five times per week and lasted for one or four weeks. Tissue samples were processed for histology and histomorphometry (bone-to-implant contact, BIC; and peri-implant bone fraction, BF) at the cortical and medullar level. Data were analysed statistically with ANOVA and paired t -tests with the significance level set at 0.05. For the one-week experiments, an increased BF adjacent to the implant surface at the cortical level was exclusively induced by the LF-HM loading regime (2 Hz–20 N). Four weeks of loading resulted in a significant effect on BIC (and not on BF) in case of HF-LM loading (40 Hz–0.5 N) and LF-HM loading (2 Hz–20 N): BIC at the cortical level significantly increased under both loading regimes, whereas BIC at the medullar level was positively influenced only in case of HF-LM loading. Mechanical loading at both HF and LF affects osseointegration and peri-implant BF. Higher loading magnitudes (and accompanying elevated tissue strains) are required under LF loading to provoke a positive peri-implant bone response, compared with HF loading. A sustained period of loading at HF is needed to result in an overall enhanced osseointegration.

A Study on the Fine Structure of the Lateral Line Organ of the Sea Eel

1973 ◽  
Vol 31 ◽  
pp. 648-649
Author(s):  
K. Hama
Keyword(s):  
Fine Structure ◽  
Electron Microscope ◽  
Lateral Line ◽  
Low Frequency ◽  
Sensory Cells ◽  
Apical Surface ◽  
Voltage Electron ◽  
Sensory Epithelia ◽  
Low Frequency Vibration ◽  
Transmission Electron

The lateral line organs of the sea eel consist of canal and pit organs which are different in function. The former is a low frequency vibration detector whereas the latter functions as an ion receptor as well as a mechano receptor.The fine structure of the sensory epithelia of both organs were studied by means of ordinary transmission electron microscope, high voltage electron microscope and of surface scanning electron microscope.The sensory cells of the canal organ are polarized in front-caudal direction and those of the pit organ are polarized in dorso-ventral direction. The sensory epithelia of both organs have thinner surface coats compared to the surrounding ordinary epithelial cells, which have very thick fuzzy coatings on the apical surface.

Lectin Binding to Human Breast Tumor Cells

1976 ◽  
Vol 34 ◽  
pp. 34-35
Author(s):  
Robert E. Nordquist ◽  
J. Hill Anglin ◽  
Michael P. Lerner
Keyword(s):  
Carcinoma Cell ◽  
Ricinus Communis ◽  
Lectin Binding ◽  
Low Frequency ◽  
Breast Carcinoma Cell Line ◽  
Human Breast ◽  
Human Breast Tumor ◽  
Duct Carcinoma ◽  
Specific Antigens ◽  
Ricin Agglutinin

A human breast carcinoma cell line (BOT-2) was derived from an infiltrating duct carcinoma (1). These cells were shown to have antigens that selectively bound antibodies from breast cancer patient sera (2). Furthermore, these tumor specific antigens could be removed from the living cells by low frequency sonication and have been partially characterized (3). These proteins have been shown to be around 100,000 MW and contain approximately 6% hexose and hexosamines. However, only the hexosamines appear to be available for lectin binding. This study was designed to use Concanavalin A (Con A) and Ricinus Communis (Ricin) agglutinin for the topagraphical localization of D-mannopyranosyl or glucopyranosyl and D-galactopyranosyl or DN- acetyl glactopyranosyl configurations on BOT-2 cell surfaces.

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