Showing papers on "Fiber published in 1994"

Relationship between muscle fiber types and sizes and muscle architectural properties in the mouse hindlimb

Abstract: Skeletal muscle fiber and architectural properties both contribute to the functional behavior of a muscle. This study uses discriminant analysis and mathematical modeling to identify the structurally and functionally significant properties. The architectural properties of fiber length, muscle length, and pennation angle are found to be the most structurally significant parameters, whereas fiber length, muscle length, and fiber type distribution are found to be most functionally determining. Architectural speed and fiber type do not appear to be complimentary (i.e., the architectural determinant of speed, fiber length, is not associated with fibers of high intrinsic velocity). However, there does seem to be a synergistic relation between the two property classes and force production. Muscles with large physiological cross sectional areas (PCSAs) tend to contain a greater proportion of larger, faster fibers. Structurally or morphologically significant parameters are not always found to have a large functional effect. Pennation angle, though one of the most structurally significant variables, was found to have very little functional effect.

Carbon fiber composites

Abstract: Introduction to Carbon Fibers Processing of Carbon Fibers Structure of Carbon Fibers Properties of Carbon Fibers Carbon Fiber Composites Introduction to Carbon Fiber Composites Polymer-Matrix Composites Metal-Matrix Composites Ceramic-Matrix Composites Hybrid Composites

Mechanical properties of kaolinite/fiber soil composite

Abstract: The mechanical properties of a kaolinite/fiber soil composite were evaluated by a series of laboratory unconfined‐compression, splitting‐tension, three‐point‐bending, and hydraulic‐conductivity tests. The inclusion of randomly distributed fibers significantly increased the peak compressive strength, ductility, splitting tensile strength, and flexural toughness of kaolinite clay. The increase in strength and toughness was a function of fiber length and content, and the water content of the composite. Increasing fiber content increased the compressive and tensile strength, and the toughness index of kaolinite clay, with the effect being more pronounced at lower water contents. The contribution of fibers to peak compressive and tensile strengths were reduced, and ductility increased, with increasing fiber length. The fiber inclusion increased the hydraulic conductivity of the composite and the increase was more pronounced at higher fiber contents. Despite the increase, the hydraulic conductivity of the compo...

Melt-blown fibrous web

Abstract: The present invention provides a melt-blown fibrous nonwoven web comprising fibers ranging in average fiber diameters to about 2 microns or less, with a narrow fiber diameter distribution, and a high degree of weight uniformity. The present invention also provides methods of preparing, processing and using such fibrous webs, as well as products incorporating such fibrous webs.

Environmental durability of glass-fiber composites

Abstract: Durability of glass-fiber/polymer composites is dictated by the durability of the components: glass fiber, matrix, and the interface. Environmental attack by moisture, for example, can degrade the strength of the glass fiber; plasticize, swell, or microcrack the resin; and degrade the fiber/ matrix interface by either chemical or mechanical attack. The relative rates of these degradation processes are a function of the chemistry of the resin, temperature, length of time of exposure, degree of stress (whether cyclic or static), chemistry and morphology of coating of coupling agent on the glass fiber, and type of glass fiber. Several examples illustrate how the chemistry and morphology of the coatings of coupling agents that are on the glass fiber influence the strength and durability of the interfacial region.

Ten Different Dietary Fibers Have Significantly Different Effects on Serum and Liver Lipids of Cholesterol-Fed Rats

Abstract: The comparative effects of 10 different dietary fibers on serum and liver lipids were investigated by feeding male Sprague-Dawley rats diets containing 10 g cholesterol + 2 g cholic acid/kg diet, with 60 g fiber/kg diet. Diets were fed for 3 wk; cellulose was the control fiber. Rats fed psyllium (rich in soluble fiber) had the lowest serum and liver cholesterol concentrations. Rats fed other soluble fiber-rich fibers (oat gum, guar gum and pectin) also had significantly lower serum and liver cholesterol concentrations than rats fed cellulose. Although feeding diets containing both soluble and insoluble fibers (soybean fiber and oat bran) did not significantly alter serum cholesterol, liver cholesterol values were significantly lower than those of cellulose-fed rats. Rats fed rice bran, predominantly an insoluble fiber source, had significantly higher liver cholesterol and significantly lower body weight gains and serum triglyceride concentrations than cellulose-fed rats. Values for serum and liver cholesterol were similar for rats were fed insoluble-rich fibers (corn bran, cellulose and wheat bran). These observations indicate that feeding dietary fibers rich in soluble fiber produces lower serum and liver cholesterol concentrations than does feeding commonly available sources of water-insoluble fiber.

Review of Chitin and Chitosan as Fiber and Film Formers

Abstract: Chitin is one of the most abundant polysaccharides found in nature. It is often considered a cellulose derivative although it does not occur in organisms producing cellulose. Cellulose consists of β-(1→4)-D-glucopyranose units. In contrast, chitin has the same backbone but the 2-hydroxy has been replaced by an acetamide group, resulting in mainly β-(1→4)-2-acetamido-2-deoxy-D- glucopyranose structural units (GLcNAc). Chitosan is the N-deacetylated derivative of chitin, though this N-deacetylation is almost never complete. A sharp nomenclature border has not been defined between chitin and chitosan based on the degree of N-acetylation [1, 2]. Structural examples of cellulose, chitin, and chitosan can be found in Fig. 1. The structural and chemical features will be elaborated on in a later section.

Oxidation Mechanisms and Kinetics of 1D-SiC/C/SiC Composite Materials: II, Modeling

Abstract: A model, based on a simple axisymmetrical fiber/interphase/matrix assembly, is derived to depict the oxidation behavior of 1D-SiC/C/SiC composites within the temperature range 900-1300°C and for 10

Parallel optical interconnect

Abstract: An optical interconnect is disclosed that couples multiple optical fibers to an array of optoelectronic devices. The interconnect includes a multiple optical fiber connector and an optoelectronic board. The multiple fiber connector can be mechanically attached to or detached from the board.

Growth of manganese filled carbon nanofibers in the vapor phase

Abstract: We report the vapor phase growth of partially filled graphitic fibers, 20-30 nm in diameter and up to a micron in length, during a manganese catalyzed carbon electric arc discharge. The fiber morphology resembles that of catalytic chemical vapor deposited carbon filaments but the inside hollow contains intermittent precipitates and continuous filling of Mn that at times occupy g50% of fiber lengths. Transmission electron microscopy and electron energy loss line spectra show that the fillings form as solid cores and may correspond to pure metal.

Stereocomplex formation between enantiomeric poly(lactic acid). VIII. Complex fibers spun from mixed solution of poly(D‐lactic acid) and poly(L‐lactic acid)

Abstract: To obtain poly(lactic acid) (PLA) complex fibers, spinning was performed by wet and dry methods from 5–10 g/dL chloroform solutions of poly(D-lactic acid) (PDLA) and poly(L-lactic), both with a viscosity-average molecular weight of 3 × 105. The dope was extruded from a monohole nozzle into coagulation baths from ethanol and chloroform for wet spinning and into a drying column kept at 60°C for dry spinning. Scanning electron microscopic observation of the as-spun fibers showed that the surface of the wet-spun fiber had large basins with diameters of 50–100 μm and many pores with diameters from sub μm to 10 μm, whereas the surface of dry-spun fiber had a microporous structure with the pore diameter of 1–3 μm. The tensile strength of the wet-spun complex fiber was very low and could not be drawn at high temperatures, in contrast to the dry-spun fiber. The tensile strength of dry-spun complex fiber increased upon hot drawing and showed the tensile strength of 94 kg/mm2 by drawing at 160°C to the draw ratio of 13. Differential scanning calorimetry revealed that the complex fibers contained both the stereocomplex crystallites (racemic crystallites) and the crystallites of the single polymers, PDLA and PLLA, regardless of the spinning methods. The ratio of the racemic crystallites to the single-polymer crystallites increased with the draw ratio of the complex fiber. © 1994 John Wiley & Sons, Inc.

Influence of water uptake on the mechanical properties of jute fiber‐reinforced polypropylene

Abstract: Jute fiber-reinforced polypropylene composites have been produced and characterized in order to investigate the influence of water on their mechanical properties. Being hydrophilic, jute fibers absorb a high amount of water causing swelling of fibers. On the other hand, the thermal shrinkage of polypropylene melt leaves some gaps between jute fibers and matrix material. We investigated whether these gaps could be filled by the swelling of wetted fibers. The fillup of these gaps would result in a higher shear strength between fibers and matrix during fracture. Our results suggest that swelling of jute fibers in a composite material can have positive effects on mechanical properties. © 1994 John Wiley & Sons, Inc.

Shortening velocity and ATPase activity of rat skeletal muscle fibers: effects of endurance exercise training

Abstract: Mechanical properties were measured in single skinned fibers from rat hindlimb muscle to test the hypothesis that the fast type IIb fiber exhibits a higher maximal shortening velocity (Vo) than the fast type IIa fiber and that the difference is directly attributable to a higher myofibrillar adenosinetriphosphatase (ATPase) activity in the type IIb fiber. Additional measurements were made to test the hypotheses that regular endurance exercise increases and decreases the Vo of the type I and IIa fiber, respectively, and that the altered Vo is associated with a corresponding change in the fiber ATPase activity. Rats were exercised by 8-12 wk of treadmill running for 2 h/day, 5 day/wk, up a 15% grade at a speed of 27 m/min. Fiber Vo was determined by the slack test, and the ATPase was measured fluorometrically in the same fiber. The myosin isozyme profile of each fiber was subsequently determined by sodium dodecyl sulfate-polyacrylamide gel electrophoresis. The mean +/- SE Vo (7.9 +/- 0.22 fiber lengths/s) of the type IIb fiber was significantly greater than the type IIa fiber (4.4 +/- 0.21 fiber lengths/s), and the higher Vo was associated with a higher ATPase activity (927 +/- 70 vs. 760 +/- 60 microM.min-1.mm-3). The exercise program induced cardiac hypertrophy and an approximately twofold increase in the mitochondrial marker enzyme citrate synthase. Exercise had no effect on fiber diameter or peak tension per cross-sectional area in any fiber type, but, importantly, it significantly increased (23%) both the Vo and the ATPase activity of the slow type I fiber of the soleus.(ABSTRACT TRUNCATED AT 250 WORDS)

Fiber reinforced thermoplastic resin structure, process for production of same, and extruder for production of same

Abstract: A fiber reinforced thermoplastic resin structure comprising a thermoplastic resin and reinforcing fibers, having a ratio (Lw/Ln) of the number average fiber length (Ln) to the weight average fiber length (Lw) of the uniformly dispersed reinforcing fibers of 1.1 to 5, and having a weight average fiber length of 1.0 mm to 200 mm as well as a process and extruder for the production thereof.

Microvascular compression during myocardial ischemia: mechanistic basis for no-reflow phenomenon.

Abstract: Alterations in fiber size and capillary diameter were highly correlated with perfusion deficits after myocardial ischemia. After 5 (n = 3) and 30 (n = 5) min of global normothermic ischemia, isolated rabbit hearts were perfused with India ink and then with glutaraldehyde. Morphometric techniques were used to determine mean fiber cross-sectional area [a(f)], mean effective capillary diameter [d(c)], total and perfused capillary number per fiber area, and capillary length per fiber volume in subepicardium (Epi) and subendocardium (Endo). Sarcomere length was measured to differentiate between effects of fiber shortening and intracellular edema on a(f). After 30 min of ischemia, a(f) increased 41 (Epi) and 36% (Endo). Of these percentages, fiber shortening accounted for 2 (Epi) and 25% (Endo). Decreased d(c) was correlated with increased a(f) as well as reductions in perfused capillary number and length. Whereas intracellular edema had the greatest overall effect on a(f), fiber shortening accounted for a significant increase of a(f) in Endo, where perfusion deficits were most pronounced. These data support the hypothesis that microvascular compression consequent to increased a(f) contributes to perfusion deficits after myocardial ischemia.

Birefringence reduction in side-written photoinduced fiber devices by a dual-exposure method.

Abstract: An in situ birefringence measurement in conjunction with an atomic force microscope study shows that the geometric asymmetry of the side-writing process is a major cause of the induced birefringence in grating-based fiber devices. Measured refractive-index profiles of UV-exposed fibers clearly show the asymmetry in the induced index change. We demonstrate the use of a dual-exposure technique for producing low-birefringence devices.

Electric Double‐Layer Capacitor Composed of Activated Carbon Fiber Cloth Electrodes and Solid Polymer Electrolytes Containing Alkylammonium Salts

Abstract: Solid polymer electrolytes consisting of complexes of poly(ethylene oxide)‐grafted poly(methyl)‐methacrylate (PEO‐PMMA) and tetraalkylammonium salts [tetrabutylammonium perchlorate, tetraethylammonium perchlorate, and tetraethylammonium tetrafluoroborate (TEABF4)] have been investigated for electric double‐layer capacitors with activated carbon fiber cloth electrodes. The PEO‐PMMA and tetraalkylammonium composites obtained showed high ionic conductivity (>10−4 S cm−1 at 298 K). The ionic conductivity depended on both the concentration and the size of each ion. The composites had good stability over a wide potential range (ca. 5.0 V). When the PEO‐PMMA and TEABF4 composites were used in solid‐state electric double‐layer capacitors with activated carbon fiber cloths as polarizable electrodes, the capacitors showed charge/discharge behavior with large values of capacitance and high coulombic efficiency. The long voltage retention was observed in the self‐discharge test of the capacitor with TEABF4.

Environmentally stable Kerr-type mode-locked erbium fiber laser producing 360-fs pulses.

Abstract: We demonstrate an environmentally stable Kerr-type mode-locked erbium fiber laser producing 360-fs near-bandwidth-limited pulses. Environmentally stable operation is possible in the presence of nonpolarization-maintaining fiber components provided that their overall length is short compared with the length of the polarization-maintaining fiber components. The pulses are generated at a stable repetition rate of 27 MHz and have an energy content of 60 pJ.

A coupling arrangement between a multi-mode light source and an optical fiber through an intermediate optical fiber length

Abstract: A coupling arrangement for non-axial transfer of light power between a multi-mode light source (LS), having a substantially circu lar emission with a divergence angle αs, and a multi-mode optical fiber (FF) with a cross section Ac, through a length of an intermediate feeding multi-mode optical fiber (IF) having an end with cross section area Af coupled with said light source (LS) and one portion fused to said optical fiber (FF). Said feeding fiber (IF) has a progressively tapered portion and is fused to said multi-mode optical fiber (FF) at a region of the tapered fiber, and in that the relationship between the acceptance angle αf of the feeding fiber (IF) and the emission angle αs of the light source (LS) is expressed by: αf = k . αs where k is a positive constant greater than 1.

Inorganic fiber composition

Abstract: Inorganic fibers which have a silicon extraction of greater than about 002 wt % Si/day in physiological saline solutions The fiber contains SiO 2 , MgO, CaO, and at least one of Al 2 O 3 , ZrO 2 , TiO 2 , B 2 O 3 , iron oxides, or mixtures thereof Also disclosed are inorganic fibers which have diameters of less than 35 microns and which pass the ASTM E-119 two hour fire test when processed into a fiber blanket having a bulk density in the range of about 15 to 3 pcf

Oxidation of NO into NO2 over active carbon fibers

Abstract: Catalytic oxidation of NO (400 ppm) into NO 2 was studied over active carbon fibers at room temperature to trap the unreacted NO as well as the oxidized product in forms of nitric acid or its salts to develop an oxidative removal of NO in the flue gas. The heat treatment of a particular pitch-based active carbon fiber of rather small surface area was found to enhance markedly the activity to allow the conversion of 82% in dry, 65% in 80% relative humidity (rh) and 21% in wet (100% rh) air, respectively, at 25°C by W/F of 1.0 × 10% g min mL −1 . The rate of oxidation was examined by varying humidity to reveal marked decrease of the activity above 80% rh. The strong retardation by humidity of the activity of as-received fiber was moderated by the heat treatment of the fiber at 800°C.

Processing and characterization of absorbable polylactide polymers for use in surgical implants.

Abstract: Absorbable fibers of linear poly-α-hydroxy acids have been used successfully in providing temporary scaffolds for tissue regeneration. In some surgical applications, degradation rates for poly(glycolide) (PGA) are too high, but implants of poly(L-lactide) (PLLA) fibers may degrade too slowly for optimal function. Polymers produced by copolymerization of L-lactide with varying amounts of D-lactide may offer an alternative choice for absorbable fiber based implants. Poly(L/D-lactide) stereocopolymers with L/D lactide molar ratios of 95/5, 90/10, and 85/15 were considered. Melt-spun/hot-drawn fibers with L/D molar ratios of 90/10 and 85/15 and draw ratios ranging from 3.0 to 8.9 were further evaluated by mechanical testing, differential scanning calorimetry, birefringence, x-ray diffraction, and in vitro exposure to pH 7.4 phosphate buffered saline at 37°C. Fabrication was reproducible and results indicated that tensile strength, modulus, and birefringence all increased with increasing draw ratio up to a draw ratio of 6.7 and declined thereafter; elongation to failure decreased for the entire range studied. For fibers with a draw ratio of 6.7, there was a 10% relative difference in crystallinity between the 90/10 and 85/15 lactide fibers (90/10 was higher). Wet strength retention after 12 weeks in vitro exposure was approximately 10% for the 90/10 fibers and 30% for the 85/15 fibers. The intermediate wet strength retention of lactide stereocopolymer fibers when compared to reported values for PGA and PLLA fibers, suggests these materials may be useful in absorbable surgical implants for tissue repair and regeneration. © 1994 John Wiley & Sons, Inc.