Properties Of Single Fibers Research Articles

713 単離ストレスファイバの引張特性と局所ひずみ分布(S07-2 マイクロ・ナノバイオメカニクス(2),S07 マイクロ・ナノバイオメカニクス)

In our previous study, tensile properties of single stress fibers (SF) chemically isolated from vascular smooth muscle cells have been investigated. Tensile tests were performed at a single strain rate of 0.02s^<-1>. In this study, the strain rate dependency of tensile properties of SF was investigated. The results showed that averaged force-strain relationships were found to be almost linear in the physio-logical strain range of 0.0-0.4 for 0.01s^<-1> and 0.05s^<-1>. In contrast, the force-strain relationship was nonlinear for the 0.1s^<-1> strain rate. The reason for this difference is unclear, however possibly due to a presence of threshold in strain rate between 0.01s^<-1> and 0.1s^<-1>. Moreover, microstructural canges of SF during stretching were investigated using a speckle fluorescent microscopy technique. SF were labeled using Quantum Dot in dotted pattern to analyze local strain in SF. The results showed that local stretch ratio was nonuniformly distributed through the length of the SF. This approach may provide further insights to SF biomechanics.

Polarization mode dispersion: Characterization of optical fiber using cross-correlation interferometry

The interferometric measurement technique is known to be a quick and reliable method for accurately measuring polarization mode dispersion (PMD) in an optical fiber. In this paper we present the means by which this technique may further be used to obtain qualitative information about the birefringent properties of the fiber under test. Polarization maintaining fiber segments are used to show that a concatenation of n birefringent segments gives rise to an interferogram with 3n interference peaks. The peak positions are further related to the total birefringent contribution of each of the fiber segments. These findings are then used to interpret measurement results and comment on the PMD and related birefringent properties of numerous single mode fibers. Stress is shown to introduce PMD in uncabled single mode fiber. Interferometric measurements are also used to determine the number of birefringent segments in both undeployed and deployed cabled fibers. Polarization optical time domain reflectometry is used successfully to verify these results.

Tensile properties of single stress fibers isolated from cultured vascular smooth muscle cells

Stress fibers (SFs), a contractile bundle of actin filaments, play a critical role in mechanotransduction in adherent cells; yet, the mechanical properties of SFs are poorly understood. Here, we measured tensile properties of single SFs by in vitro manipulation with cantilevers. SFs were isolated from cultured vascular smooth muscle cells with a combination of low ionic-strength extraction and detergent extraction and were stretched until breaking. The breaking force and the Young's modulus (assuming that SFs were isotropic) were, on average, 377 nN and 1.45 MPa, which were approximately 600-fold greater and three orders of magnitude lower, respectively, than those of actin filaments reported previously. Strain-induced stiffening was observed in the force–strain curve. We also found that the extracted SFs shortened to approximately 80% of the original length in an ATP-independent manner after they were dislodged from the substrate, suggesting that SFs had preexisting strain in the cytoplasm. The force required for stretching the single SFs from the zero-stress length back to the original length was approximately 10 nN, which was comparable with the traction force level applied by adherent cells at single adhesion sites to maintain cell integrity. These results suggest that SFs can bear intracellular stresses that may affect overall cell mechanical properties and will impact interpretation of intracellular stress distribution and force-transmission mechanism in adherent cells.

The characterization of step index single mode silica fiber for long haul signal communication

The optical properties of single mode fibers, which are drawn from the silica preform made by MCVD technique, have been studied. The properties such as cutoff wavelength, chromatic dispersion, and polarization mode dispersion (PMD) were studied for 2.3 km length of single mode fiber (SMF). The cutoff wavelength was measured by fiber optic test procedure (FOTP)-80 which was found to be 1179 nm. The chromatic dispersion was measured by FOTP-169 at various wavelengths, the zero dispersion being observed at 1503 nm. The PMD was measured by interferometric method, and exhibited the magnitude of 0.07 ps at 1550 nm. The results are discussed to assess the suitability of these fibers for long haul communication systems.

Contractile properties of mouse single muscle fibers, a comparison with amphibian muscle fibers

Single fibers, 25-40 microm wide and 0.5-0.7 mm long, were isolated from the flexor digitorum brevis muscle of the mouse. Force and movement were recorded (21-27 degrees C) from the fiber as a whole and, in certain experiments, from a short marked segment that was held at constant length by feedback control. The maximum tetanic force, 368+/-57 kN/m2 (N = 10), was not significantly different from that recorded in frog muscle fibers at equal temperature. However, the rising phase of the tetanus was considerably slower in the mammalian fibers, 202+/-20 ms (N = 17) being required to reach 90% of maximum tetanic force as compared with 59+/-4 ms (N = 20) in the frog muscle fibers. Similar to the situation in frog muscle fibers, the force-velocity relation exhibited two distinct curvatures located on either side of a breakpoint near 80% of the isometric force. Maximum speed of shortening was 4.0+/-0.3 fiber lengths s(-1) (N = 6). The relationship between tetanic force and sarcomere length was studied between 1.5 and 4.0 microm sarcomere spacings, based on length-clamp recordings that were free of 'tension creep'. There was a flat maximum (plateau) of the length-tension relation between approximately 2.0 and 2.4 microm sarcomere lengths. The descending limb of the length-tension relation (linear regression) intersected the length axis (zero force) at 3.88 microm and reached maximum force at 2.40 microm sarcomere length. The slope of the descending limb is compatible with a thick filament length of 1.63 microm and an average thin filament length of 1.10 microm. These values accord well with recent electron microscope measurements of myofilament length in mammalian muscle.

Tensile properties of twisted hair fibers

Hair is routinely twisted during grooming processes, which can cause tangles and lead to breakage of hair fibers. To evaluate the damage caused by twisting hair, the tensile stress-strain properties of single twisted hair fibers were measured by two different experimental procedures: (A) twist at constant length, followed by extension to break (without untwisting); and (B) twist and untwist at constant length, followed by extension to break. In procedure (A), the strength, extension, and initial modulus decreased with increase in twist factor, whereas in procedure (B), the strength and extension did not significantly change from control values, although the initial modulus decreased with increase in twist factor. Furthermore, the degree of recovery from torsional deformation was studied by a variant of procedure (B), where the fiber after untwisting was relaxed for 5 and 10 minutes, respectively, prior to extension to break. The major conclusion from this study was that at low and moderate twist levels, the tensile mechanical properties of human hair are recoverable.

Effects of spinning processes on HVI fiber characteristics and spun yarn properties

The effects of opening, carding, and repeated drawings on single fiber and bundle cotton characteristics were studied by employing Mantis®, AFIS® and HVI Testers. Some of the significant changes in single fiber properties were found to be due to process parameters as well as the changes in the fiber crimps, parallelness of fibers within HVI beards, and the actual changes in the tensile properties of the fibers. The study showed that the HVI test data taken just prior to spinning had the highest correlation with the yarn tensile properties. Based on the study results, we point out the potential of HVI for future quality and process control in spinning by recommending a set of expanded HVI output that is more scientific and comprehensive for the future control needs.

Flax fiber surface modifications: Effects on fiber physico mechanical and flax/polypropylene interface properties

This study arises on the opportunities of using flax fibers as reinforcement for polypropylene (PP) matrix composites. For this purpose, untreated flax fiber bundles obtained by a retting process have been used. For improving compatibility between flax fiber bundles and PP matrix, fiber surface treatments such as maleic anhydride, maleic anhydride polypropylene copolymer, and vinyltrimethoxy silane have been carried out. On the other hand, alkali treatment has also been carried out for fiber modification. The effect of surface modification on tensile properties of single fibers and also on fiber-matrix interfacial shear strength (IFSS) has been analyzed. Finally, both optical microscopy and atomic force microscopy have been used for characterizing flax fiber microstructural features. The current study completes previous results to elucidate the influence of treatments on fiber surface and flax fiber-PP interface. POLYM. COMPOS. 26:324–332, 2005. © 2005 Society of Plastics Engineers.

Coding of acoustic particle motion by utricular fibers in the sleeper goby, Dormitator latifrons.

It is unknown whether the fish utricle contributes to directional hearing. Here, we report response properties of single utricular fibers in a teleost fish ( Dormitator latifrons) to linear accelerations at various stimulus frequencies and axes. Characteristic frequencies ranged from < or =50-400 Hz (median=80 Hz), and best frequencies shifted from 50 to 250 Hz with stimulus level. Best sensitivity of utricular fibers was distributed from -70 to -40 dB re: 1 g (mean=-52 dB), which is about 30 dB less sensitive than saccular fibers. Q50% fell between 0.16 and 11.50 (mean=2.04) at 15 dB above threshold. We observed temporal response patterns of entrained phase-locking, double phase-locking, phase-locked bursting, and non-phase-locked bursting. Most utricular fibers were directionally selective with various directional response profiles, and directional selectivity was stimulus-level dependent. Horizontal best-response axes were distributed in a 152 degrees range while mid-sagittal best-response axes were clustered around the fish longitudinal axis, which is consistent with the horizontal orientation of the utricle and morphological polarizations of utricular hair cells. Therefore, results of this study indicate that the utricle in this vertebrate plays an auditory role in azimuth and that utricular fibers extend the response dynamic range of this species in directional hearing.

Mechanical Properties of Electrospun Silk Fibers

The morphology and microstructure of electrospun B. mori silk/poly(ethylene oxide) (PEO) fibers with diameters less than 1 μm were characterized using birefringence, wide-angle X-ray diffraction, differential scanning calorimetry, and atomic force microscopy (AFM). In the as-spun fibers, silk fibroin is present in a coil conformation due to rapid fiber formation during electrospinning. After treatment with methanol, the silk fibroin was transformed into a β-sheet-containing structure. Evidence for nanofibrils within the as-spun fibers was observed by AFM, and the PEO phase was dispersed as small, elongated islands within the silk fibroin matrix and oriented along the fiber direction. The mechanical properties of single fibers were characterized by AFM nanoindentation. The results were consistent with uniaxial tensile tests and with the morphological analysis. After methanol treatment and extraction with water, the electrospun silk fiber exhibits a lateral modulus of 8.0 GPa, within a factor of 2 of degumm...

Sedimentation Method to Evaluate PFI Mill Beating Degree of Wood Pulp Fibers

A sedimentation experiment was used as a simple method to evaluate the PFI mill beating degree of wood pulp fibers. The sedimentation volume decayed exponentially with elapsed time. The sedimentation rate, k, changed with the beating degree, though the equilibrium sedimentation volume remained relatively constant. The rate k decreased with the increasing concentration, c, and the beating degree; and moreover, k-1 was proportional to c. This result suggests that k-1c-1 can be a unique factor for the beating degree. The factor expresses the beating degree well and can also tell us that the single fiber properties are more important than inter-fiber interactions during the sedimentation process of the CSF measurement.

Failure of fiber bundles

The paper investigates the discrepancy between experimental data and theory on the tensile behavior and strength of fiber tows. Experimental data were compared to predictions from single fiber properties. A numerical model allowed the scatter in tow strength data to be generated, and the influence of the following factors to be examined: uncertainty in fiber statistical parameters estimation, and in the number of fibers within tows, non-uniform loading and equal or imperfect local load sharing conditions when a fiber fails. This approach was applied to SiC (Nicalon NLM 202 and Hi-Nicalon) fiber tows containing 500 filaments. It was shown that local load sharing was a preponderant factor that influenced tow strength data and the associated scatter. Implications in composite failure are finally discussed.

Effect of proteolytic enzyme activity and heating on the mechanical properties of bovine single muscle fibres

The effect of proteolysis and heating on the mechanical properties of single muscle fibres isolated from bovine M. semitendinosus was investigated. Short incubations with μ-calpain (pH 7.5) and cathepsin B (pH 5.6) at room temperature reduced ( P<0.01) the raw fibre strength by 50%. After subsequent heating, μ-calpain-incubated fibres were 20% weaker and cathepsin B-incubated fibres 50% weaker than heated controls. Fibres were incubated for 8 days at 2 °C under post-mortem like pH conditions (pH 5.6) or pH conditions optimal for the calpains (pH 7.5). At pH 5.6 no significant weakening of the fibres was observed when incubations were performed in 0.1, 1 or 10 mM Ca 2+. In contrast, incubation in 1 or 10 mM Ca 2+ at pH 7.5 decreased the strength of the fibres. Addition of the protease inhibitors E-64 or PD150,606 prevented this weakening, suggesting that the weakening is caused by proteolyses and not directly by Ca 2+.

Myosin heavy-chain isoform composition of human single jaw-muscle fibers.

Diversity in muscle contractile properties is based on the variability of contractile properties of single muscle fibers which in turn is related to the presence of different myosin heavy-chain (MyHC) isoforms. Human jaw muscles are featured by many hybrid fibers expressing more than one MyHC isoform. The purpose of this study was to determine the proportion of each isoform within these fibers for evaluation of the fiber's capacity of producing a large diversity in contractile properties. Electrophoretic separation of MyHC isoforms was performed on 218 single fibers of the temporalis and digastric muscles. Of these fibers, 100 were classified as hybrid fibers. Most hybrid fibers co-expressed MyHC-IIA and -IIX (n = 62); a smaller number co-expressed MyHC-I and -IIA (n = 14), MyHC-I and -IIX (n = 12), and MyHC-I, -IIA, and -IIX (n = 12). The proportions of the individual MyHC isoforms in the hybrid fibers varied highly, suggesting a large range of contractile properties among these fibers.

Effect of added μ-calpain and post-mortem storage on the mechanical properties of bovine single muscle fibres extended to fracture

The effects of μ-calpain and post-mortem storage on the strength of single muscle fibres were investigated. During the 10 min of incubation at pH 7.5, μ-calpain became evenly distributed throughout the fibre. μ-Calpain-incubation resulted in thinner ( P <0.001) Z-lines and reduced ( P <0.001) the strength of the fibres compared to controls. These results demonstrate that μ-calpain is capable of mechanically weakening the muscle fibres. Post-mortem storage of meat for 10 days at 2 °C weakened ( P <0.001) the muscle fibres compared to 24-h fibres. The presence or absence of Ca 2+ affected fibre stiffness. Fibres incubated at pH 7.5 in 100 μM Ca 2+ were less stiff than fibres incubated in 200 μM EGTA. Breaking stress and strain were not affected by Ca 2+. We hypothesise that Ca 2+ causes conformational changes in some of the load-bearing proteins, which alters their initial resistance to extension, but does not affect the breaking strength of the fibres.

Contractile properties of rat single muscle fibers and myosin and troponin isoform expression after hypergravity.

The effects of 19 days of hypergravity (HG) were investigated on the biochemical and physiological properties of the slow soleus muscle and its fast agonist, the plantaris. HG was induced by rotational centrifugation that led to a 2-G gravity level. The HG rats were characterized by a slower body growth than control, whereas the soleus muscle mass was increased by 15%. Using electrophoretic techniques, we showed that the distribution of myosin heavy chain and troponin T isoforms was not modified after HG in both soleus and plantaris. In contrast, the isoform expression pattern of two troponin subunits, troponin I and troponin C, was changed in a slow-to-fast manner only in the soleus. From tension-pCa relationships, changes in Ca(2+) activation threshold by 0.18 pCa unit indicated a decrease in Ca(2+) sensitivity and an increase in the slope of the curve, attesting to a higher cooperativity along the thin filament after HG. Comparison of our HG data with previous results in microgravity conditions indicated that muscle characteristics, except muscle mass, did not evolve linearly from 0 to 2 G.

Mechanics of thin ultra-light stainless steel sandwich sheet material: Part II. Resistance to delamination

This study concerns three variants of a novel type of thin sandwich sheet. Details of the core structures, and also the results of an investigation into elastic properties, were presented in the first part of this pair of papers. A study was also made of the tensile properties of single fibres of the type present in the core of these sheets. In this second paper, an investigation is presented of the resistance offered by these materials to delamination of the two faceplates. In one variant of the material, in which the fibres lie approximately normal to the plane of the sheet, delamination occurs predominantly by frictional pull-out of fibres from their sockets in the adhesive. The mode I fracture energy has been measured at about 340 J m −2. This value is consistent with predictions from a model based on shear-lag theory, with a fibre–adhesive interfacial shear strength of about 5 MPa. It is noted that there should be scope for improving the fracture energy somewhat by raising the strength of the fibre–adhesive bond. For the other two variants studied, in which the fibres are softer (as a result of heat treatment during sintering) and are inclined close to the plane of the sheet, the measured fracture energy is appreciably lower at about 30 J m −2. In this case, delamination occurs by fracture of the fibres near the mid-plane. Application of a simple model for prediction of the fracture energy in this case leads to the conclusion that some of the fracture was probably of sintered necks between fibres, rather than the fibres themselves, and that this process required considerably less energy.

A112 ストレスファイバの粘弾性特性の計測

A112 ストレスファイバの粘弾性特性の計測

Mechanical properties of single muscle fibers from patients with spasticity

Mechanical properties of single muscle fibers from patients with spasticity

Metabolic Modulation of Muscle Fiber Properties Unrelated to Mechanical Stimuli

The effects of chronically increasing (creatine-fed) or decreasing (beta-guanidinopropionic acid [beta-GPA]-fed) high-energy phosphates for up to 8 weeks on daily voluntary activity levels, swimming endurance capacity, electromyogram (EMG) activity, and the morphological and metabolic properties of single fibers in the soleus and extensor digitorum longus (EDL) muscles in young rats were determined. High-energy phosphate, voluntary activity, and soleus-integrated EMG levels were lower in beta-GPA-fed rats than in control rats. Endurance capacity was higher at a relatively low intensity of swimming and lower at a relatively high intensity in beta-GPA-fed rats than in control rats. Muscle mass and fiber size were smaller, and the percentage of slow fibers was higher in the soleus and EDL of beta-GPA-fed rats than in control rats. Succinate dehydrogenase activity was higher in both the fast and slow fibers of the EDL of beta-GPA-fed rats than in control rats. Thus, a reduction in high-energy phosphates transformed some fast fibers toward a slow phenotype. Creatine supplementation had minimal effects: The only significant change was an increase in alpha-glycerophosphate dehydrogenase activity in the fast fibers of the EDL. These results indicate that the metabolic environment of a muscle fiber can influence the prominence of a given muscle fiber independent of the activity level of muscle.