Effects Of Static Compression Research Articles

Effect of static compression on near-field tsunami waves: Three-dimensional solution

An analytical solution of three-dimensional surface wave profiles due to arbitrary spatio-temporal disturbance of a circular ocean bottom in a compressible ocean is obtained by incorporating the influence of the static ocean background compression under the assumptions of linearized water wave theory. Time-domain simulations of the surface profile in three dimensions and the pressure distribution within the water column for a circular uniform rise and tilt are shown. The corresponding animation movies depict the temporal evolution of the surface profile and pressure field inside the water column eloquently, which was not shown in earlier literature. The impact of static compression is also discussed through the simulations. A novel analytical expression of the potential function for a generic tilted motion (rmcos(mθ),m∈Z) of the circular ocean floor is derived. An efficient numerical code is developed to find surface elevation and pressure distribution, implementing the inverse Fourier integral as matrix multiplication. Validation is performed for the specific case of a rising flat ocean floor, showing the oscillations due to acoustic-gravity modes. Initially, a simplified problem of a flat rising ocean bottom is solved using the eigenfunction matching method, which involves finding a particular solution for the nonhomogeneous ocean bottom condition and the solution for its homogeneous counterpart. Solutions are obtained using a newly developed inner product between the depth-dependent functions. Later, a Green function technique is used to incorporate the impact of the arbitrary spatio-temporal motion of the circular portion of the ocean bed. The solution obtained from the eigenfunction matching method is utilized to obtain the analytical form of Green’s function and, eventually, an expression of surface elevation and pressure distribution inside the ocean water column.

Effect of static compression on tsunami waves: Two-dimensional solution

This study provides an analytical solution for the surface wave profile resulting from an arbitrary temporal ocean bottom disturbance in a compressible ocean. The solution also considers the impact of static compression of the ocean background. The problem is formulated in two dimensions and solved using the Fourier transformation and eigenfunction matching method, which requires a new inner product and determining a particular solution to account for the non-homogeneous boundary condition. To verify the solution's validity, it is compared with the corresponding Green's function formulation, which employs the movement of the ocean floor as a source. The Green's function technique can handle the ocean floor's arbitrary spatial movement, which is demonstrated through two specific profiles. Additionally, the shallow water limit is derived to provide further validation. A time-domain simulation of the surface profile is presented, comparing the case with and without static compression. The effect of static compression is found to be small but non-negligible for typical ocean depths.

The Effect of Static Compression via Vibration Foam Rolling on Eccentrically Damaged Muscle.

Previous research has shown that vibration foam rolling (VFR) on damaged muscle can result in improvements in muscle soreness and range of motion (ROM). Furthermore, static compression via VFR (i.e., VFR without rolling) can increase the ROM and decrease the muscle stiffness of non-damaged muscle. Therefore, it is likely that static compression via VFR on eccentrically damaged muscle can mitigate muscle soreness and the decrease in ROM, and the decrease in muscle strength. The purpose of this study was to investigate the acute effects of a 90 s bout of VFR applied as a static compression on an eccentrically damaged quadriceps muscle, measuring ROM, muscle soreness, muscle strength, and jump performance. This study was a single-arm repeated measure design. Study participants were sedentary healthy male volunteers (n = 14, 20.4 ± 0.8 years) who had not performed habitual exercise activities or any regular resistance training for at least 6 months before the experiment. All participants performed a bout of eccentric exercise of the knee extensors with the dominant leg and then received a 90 s bout of static compression via VFR of the quadriceps 48 h after the eccentric exercise. The knee flexion ROM, muscle soreness at palpation, and countermovement jump height were measured before the eccentric exercise (baseline), before (pre-intervention) and after the VFR intervention (post-intervention), and 48 h after the eccentric exercise. The results showed that the static compression via VFR significantly (p < 0.05) improved the knee flexion ROM (6.5 ± 4.8%, d = 0.76), muscle soreness at palpation (−10.7 ± 8.6 mm, d = −0.68), and countermovement jump height (15.6 ± 16.0%, d = 0.49). Therefore, it can be concluded that static compression via VFR can improve muscle soreness and function.

In situ Raman spectroscopic study of the pressure induced structural changes in ammonia borane

The effect of static compression up to 65 GPa at ambient temperature on ammonia borane, BH(3)NH(3), has been investigated using in situ Raman spectroscopy in a diamond anvil cells. Two phase transitions were observed at approximately 12 GPa and previously not reported transition at 27 GPa. It was demonstrated that ammonia borane behaves differently under compression at quasi-hydrostatic and non-hydrostatic conditions. The ability of BH(3)NH(3) to generate second harmonic of the laser light observed up to 130 GPa suggests that the non-centrosymmetric point group symmetry is preserved in the material up to very high pressures.

Unraveling the role of preformed epidermal growth factor receptor dimers by site-directed mutatgenesis

The effect of static compression on the release of superoxide (SO) and nitric oxide (NO) from cartilage obtained from rabbit knee joints with tissue defects was studied. The rabbits were divided into two groups: (1) those that had 5 mm diameter full chondral defects (defect group) and (2) those in which chondral defects were filled with autogenous perichondrial grafts (grafted group). Histologically, cartilage was regenerated in the grafted group 3 weeks after the operation, although only a fibrous tissue filled the defects in the defect group even 16 weeks after the operation. A static pressure of 5 kg for 10 minutes applied to the cartilage chips obtained from the area surrounding the defects released significant amounts of SO and NO into the medium. Maximum increases were observed in the defect group 3 weeks after the operation.

Development of Attenuated Total Reflection Based Compression Modulation Step-Scan Fourier Transform Infrared Spectroscopy and its Applications to Rheo-Spectral Characterizations of Polymer Films

Dynamic compression modulation attenuated total reflection Fourier transform infrared (ATR FT-IR) spectroscopic methods have been developed in this paper for characterizing polymer films. To obtain dynamic compression polarized ATR spectra, internal reflection element (IRE) secure assemblies made of tungsten carbide with very high hardness (Knoop hardness of > 1000 kgf/mm(2)) have been designed. These assemblies are mounted on the Harrick Seagull ATR attachment and measured by step-scan FT-IR spectroscopy. The effect of static compression, air gaps, and refractive index changes were examined. Experimental and simulated results showed that the effect of air gaps between the sample and IRE and refractive index changes of the sample and IRE are negligible at values larger than a static torque of 40 cN m and good signal-to-noise ratios (SNR) and reproducible data can be obtained. Uniaxially and biaxially drawn poly(ethylene terephthalate) films were measured by the presented method. Both bipolar and unipolar bands were observed in the dynamic in-phase ATR spectra, which can be associated with their micro-structural environmental changes. This technique shows promise in evaluating various polymer film materials, including biaxially oriented films, multilayer coated film surfaces, and molecular interactions between polymer-polymer and polymer-additives at the film surface.

Effects of Static Compression on the Vibration Modes of a Fingertip

The vibrotactile perception threshold measurement technique is used to diagnose sensory neuropathy of the hand. The vibration perception threshold of a human finger could be most sensitive in the vicinity of one or more of its resonant frequency. The purpose of the present study is to investigate, theoretically, the effects of deformation (compression) on the free vibration behaviour of fingertips. An in-plane finite element model of the fingertip tissue has been formulated on the basis of the anatomical structure and the nonlinear elastic material properties of the soft tissue. The vibration modes of a fingertip model have been analyzed under different deformation states. Our results show that the modal vibration characteristics of the fingertip are deformation-dependent; the eigenfrequencies of the fingertip increase with the increasing preload. The present study suggests, from a theoretical point of view, that the static deformation state will influence the vibration modes and thus the perception threshold of fingertips.

Effect of compression on the cochlear nerve: A short- and long-term electrophysiological and histological study

The short- and long-term effects of static compression of the cochlear nerve were studied in dogs. The nerve was exposed in the cerebellopontine angle and a modified aneurysm clip was applied to reduce the diameter of the nerve trunk to 50%, 40%, 30% or 20% of normal (designated respectively as 50%, 60%, 70%, and 80% compression). Brainstem auditory evoked potentials (BAEPs) were monitored intra- operatively and post-operatively. The animals were sacrificed between 5 and 7 7 9 days after nerve compression and temporal bones were examined histologically. In the 50% compression group, all peaks except peak I disappeared immediately after nerve compression. After release of the clip, however, peak II and subsequent components recovered and prolonged interpeak latency (IPL) between peaks I and IV normalized within 7 days. In the 60% compression group, recovery was incomplete for as long as 49 days after compression. Significant histological changes were not always reflected in the electrophysiological recordings, as shown by the finding of multiple cavitations at the compressed portion of the cochlear nerve in cases in which conduction block of cochlear nerve impulses was reversible. In the 70% compression group, peak IV did not reappear for more than 7 week, and histological examination revealed severe damage to all cochlear nerve fibers except those from the apical turn, which lie in the center of the cochlear nerve trunk. Severe injury occurred to the cochlear nerve fibers that are situated more superficially in the nerve, which are tonotopically responsible for the perception of high-frequency sound and the generation of BAEPs. This means that the BAEP changes due to cochlear nerve compression would be detectable by BAEP monitoring, although changes in the apical region of the cochlea are not fully detectable by BAEP monitoring. In the 80% compression group, all peaks except peak I were lost permanently and the amplitude of peak I, which had been preserved in the acute phase, gradually decreased. Reversibility of impaired cochlear nerve impulse conduction was related to the severity of compression, and at some level of compression between 70% and 80% the nerve fibers generating BAEPs permanently lost the ability to conduct electrical impulses proximal to the site of compression. In the 70% and 80% compression groups, the amplitude of peak I gradually decreased over the first 30 days after compression and did not change significantly thereafter. Histologically, the branches of the internal auditory artery were resilient to compression, although they are easily avulsed due to stretch force. Furthermore, retrograde degeneration of cochlear neurons triggered by compression at the cisternal portion of the cochlear nerve was apparent. Such slowly progressive degeneration of nerve fibers may play a part in development of the delayed postoperative hearing disturbance. [Neurol Res 1999; 21: 599–610]

Effect of static compression on proteoglycan biosynthesis by chondrocytes transplanted to articular cartilage in vitro.

Transplantation of chondrocytes by injection or within carrier matrices has shown promise for augmenting the repair of articular cartilage defects. In vivo, transplanted chondrocytes are exposed to mechanical forces. This in vitro study examined the effect of a step application of compressive load to chondrocytes after the cells had been seeded onto a cartilage surface. Bovine chondrocytes were transplanted onto bovine cartilage disks, allowed to attach for 1 hour or 4 days, and subjected to compression through overlying cartilage disks in a confined compression configuration. Before use, the disks were lyophilized to lyse the endogenous chondrocytes and thereby allow assessment of the metabolic activity of the transplanted cells. During a 16-hour application of compressive stress of 0.24-0.72 MPa, proteoglycan synthesis, assessed as [35S]sulfate incorporation into macromolecules, was inhibited by approximately 68% after the 1-hour attachment and by approximately 45% after the 4-day attachment. Cell retention after the application of load was assessed by use of [3H]thymidine-tagged chondrocytes and quantitation of the displacement of radioactivity. After the 1-hour seeding period, loading induced a dose-dependent dislodgment of [3H]radioactivity (as much as 35%) from the tissue bilayer. In contrast, after the 4-day seeding period, there was no detectable effect of loading on chondrocyte dislodgment with an 8-12% release of radioactivity. The inhibitory effect of a 16-hour compression of 0.48 MPa applied after the 4-day seeding period was studied further. This protocol did not appear to have an irreversible effect on chondrocyte metabolism; at 2 days after the release of load, proteoglycan synthesis by the loaded cells was stimulated by 41% compared with transplanted cells that were not subjected to loading. These results suggest that the application of static compressive stress to chondrocytes at a cartilage surface may affect biosynthesis by these cells and thus subsequent integrative cartilage repair. Such an effect may have implications for optimization of the tightness of the press fit of a cell-laden cartilaginous construct into an articular defect.

Auto-destruction of the articular cartilage and free radical mediators

The effect of static compression on the release of superoxide (SO) and nitric oxide (NO) from cartilage obtained from rabbit knee joints with tissue defects was studied. The rabbits were divided into two groups: (1) those that had 5 mm diameter full chondral defects (defect group) and (2) those in which chondral defects were filled with autogenous perichondrial grafts (grafted group). Histologically, cartilage was regenerated in the grafted group 3 weeks after the operation, although only a fibrous tissue filled the defects in the defect group even 16 weeks after the operation. A static pressure of 5 kg for 10 minutes applied to the cartilage chips obtained from the area surrounding the defects released significant amounts of SO and NO into the medium. Maximum increases were observed in the defect group 3 weeks after the operation.

Mechanical and physiochemical determinants of the chondrocyte biosynthetic response.

The relation between mechanical loading of cartilage and chondrocyte activity in vivo may be mediated by several physical transduction mechanisms including: cell deformation, hydrostatic pressure gradients, fluid flow, streaming currents, and physicochemical changes. We have developed an organ culture system designed to study chondrocyte biosynthetic response to such physical stimuli. This study focuses on the effects of static compression and physicochemical changes. Cartilage disks harvested from the reserve zone of the epiphyseal plate of 1-2-week-old calves were subjected to static compressive stresses of 0-3 MPa in unconfined compression and the incorporation of [35S]sulfate and [3H]proline was measured during the 12-h loading period. Incorporation of both proline and sulfate decreased monotonically with increasing stress. Compressive loading also produces physicochemical changes including a decreased water content and increased matrix fixed-charge density, with a concomitant increase in interstitial counterion concentrations (e.g., K+, H+) and decreased coion concentrations (e.g., SO4(2-). We therefore examined the possibility that specific changes in interstitial mobile ion concentrations may be linked to chondrocyte response to static compression by measuring biosynthesis in the absence of mechanical compression while independently altering the SO4(2-), K+, and H+ composition of the bathing medium. We found that proline and sulfate incorporation were strongly dependent on pH, but independent of [SO4(2-)] and [K+] in the range studied. These results suggest that compression-induced changes in local, interstitial pH may account for the observed biosynthetic response to static compression.