Showing papers on "Fiber published in 1987"

Skeletal muscle capillary density and fiber type are possible determinants of in vivo insulin resistance in man.

Abstract: We have compared the capillary density and muscle fiber type of musculus vastus lateralis with in vivo insulin action determined by the euglycemic clamp (M value) in 23 Caucasians and 41 Pima Indian nondiabetic men. M value was significantly correlated with capillary density (r = 0.63; P less than or equal to 0.0001), percent type I fibers (r = 0.29; P less than 0.02), and percent type 2B fibers (r = -0.38; P less than 0.003). Fasting plasma glucose and insulin concentrations were significantly negatively correlated with capillary density (r = -0.46, P less than or equal to 0.0001; r = -0.47, P less than or equal to 0.0001, respectively). Waist circumference/thigh circumference ratio was correlated with percent type 1 fibers (r = -0.39; P less than 0.002). These results suggest that diffusion distance from capillary to muscle cells or some associated biochemical change, and fiber type, could play a role in determining in vivo insulin action. The association of muscle fiber type with body fat distribution may indicate that central obesity is only one aspect of a more generalized metabolic syndrome. The data may provide at least a partial explanation for the insulin resistance associated with obesity and for the altered kinetics of insulin action in the obese.

High-gain erbium-doped traveling-wave fiber amplifier

Abstract: Traveling-wave amplification of a lambda = 1.53 microm signal with +22-dB gain is achieved at 295 K in an Er(3+)-doped single-mode fiber using a lambda = 514.5 nm pump source. The optimum fiber length for maximum gain is determined experimentally. A limit in signal-to-noise ratio that is due to concurrent amplification of spontaneous emission is observed. By cooling the fiber to 77 K, the amplifier gain is increased to +29 dB as a result of depopulation of the lower laser level.

Self-organized phase-matched harmonic generation in optical fibers.

Abstract: We generated second-harmonic light from a single-mode fiber after a few minutes of seeding with 532-nm harmonic light along with 1.064-μm pump light. This experiment supports a mechanism for photoinducing an alternating second-order nonlinearity in the fiber.

Bicomponent fibers and webs made therefrom

Abstract: Biocomponent fibers, and webs made therefrom, are taught in which one component of the fibers is a crystallizable material. When a web of the fibers is heated in a mold above the temperature at which crystallization occurs, the fibers tend to be set in the position they are held in the mold. A preferred fiber comprises blown fibers comprising as one component amorphous, crystallizable polyethylene terephthalate, and as the other component polypropylene. A web of such fibers not only becomes formed into a shape-retaining form by crystallization during the molding process, but also can be further established in its shape-retaining character by heating the web above the softening point of the polypropylene, whereupon the fibers become bonded at their points of intersection.

Analysis of Progressive Matrix Cracking In Composite Laminates II. First Ply Failure

Abstract: The mechanics of transverse cracking in an elastic fibrous composite ply is explored for the case of low crack density. Cracks are assumed to initiate from a nucleus created by localized fiber debo...

Optical fiber distribution panel

Abstract: An improved fiber distribution panel including fiber connecting and splicing modules which are slidable into and out of a housing which is formed to support a plurality of said modules. Each module is provided with means for supporting a fiber connector at an angle with respect to the front edge thereof allowing access to the connectors and supports a booklet for storing slack fiber and for supporting permanent fiber connectors within said module.

Interactions of hydrogen and deuterium with silica optical fibers: A review

Abstract: This paper reviews all the interactions of hydrogen and deuterium with silica-based optical fibers. Included in the discussion are H 2 overtone absorption, OH formation, increased UV and IR absorption, radiation effects on H 2 -treated fibers, the gas-in-glass laser and applications, the reduction of OH absorption by isotope exchange OH → OD and other isotope-exchange related effects, and applications of isotope exchange and substitution for diagnostic purposes. Also included is a description of common sources of H 2 in materials used in fiber and cable manufacture, and countermeasures against hydrogen generation and intrusion into the fiber.

Fiber-optic evanescent-wave methane-gas sensor using optical absorption for the 3.392-μm line of a He–Ne laser

Abstract: Gas sensing using evanescent waves of optical fibers is investigated. Methane gas is detected by means of its strong optical absorption of the 3.392-μm line of a He–Ne laser. A single fiber is used as both a sensor and an optical transmission line. The sensor has a small diameter, ranging from 1.8 to 7 μm, made by heating and expanding a part of a step-index silica fiber. An evanescent wave of 5 to 40% of the total propagating power is generated outside the fiber. When a sensor fiber of 1.8-μm diameter and 10-mm length is used, the minimum detectable concentration of methane is less than the lowest explosive limit of 5%.

Soluble vs insoluble fiber: different physiological responses.

Abstract: A brief review on the physiological gastrointestinal response of soluble and insoluble dietary fiber concludes that the type of dietary fiber appears to have an influence on the physiological response. Human and animal studies have shown that insoluble fiber can slow gastric emptying and may slow nutrient uptake, and can blunt the rise in plasma glucose after a glucose load. Soluble fiber, owing to its high water-holding capacity, can be readily fermented by intestinal bacteria which may lead to a modest increase in fecal bulk. In contrast, insoluble fiber cannot be fermented, resulting in maintenance of the fiber mass in the large bowel. It is speculated that the differences in bacterial metabolism may explain some of the physiological effects of different types of dietary fibers.(wz).

Optical probe for measuring pH and oxygen in blood and employing a composite membrane

Abstract: An optical probe is presented for use in measuring pH and oxygen content in blood in a blood vessel within a living body. An elongated flexible optical fiber means is provided which has a proximal end and a distal end. The distal end is adapted to be inserted into a blood vessel. A membrane is secured to the distal end of the optical fiber and receives light from the distal end of the fiber and returns light therethrough to the proximal end. The membrane is constructed of hydrophilic porous material containing a pH sensitive dye. A plurality of microspheres are embedded in and carried by the membrane. These microspheres are constructed hydrophobic material and each carries a fluorescent dye quenchable with oxygen. Consequently, when light is supplied to the proximal end of the optical fiber, it is conveyed to the membrane. This causes the pH sensitive dye to react and light is conveyed through the optical fiber having an intensity level indicative of the pH level in the blood. The oxygen sensitive dye fluoresces and light is transmitted to the proximal end of an intensity which varies with the partial pressure of oxygen.

Twisting of fibrin fibers limits their radial growth

Abstract: Electron microscopy of freeze-dried, shadowed fibrin fibers has demonstrated that these structures are twisted. The pitch and radius of many fibers were measured from the micrographs. Although there is some variability, the average pitch of 1930 +/- 280 (SD) nm is independent of radius. The distribution of observed radii of fibers assembled in vitro is highly skewed, suggesting that individual fibers grow to a maximum radius of about 50 nm, except when both pH and ionic strength are high; fibers aggregate to form thicker fiber bundles under some conditions. The observed twisting may be responsible for limiting the lateral growth of individual fibers. Protofibrils near the surface of a twisted fiber are stretched relative to those near the center. Consequently, the degree to which a protofibril can be stretched limits the radius of a fiber; protofibrils can be added to a growing fiber until the energy required to stretch an added protofibril exceeds the energy of binding. These properties of assembly arise directly from the intrinsic twist of the fibrinogen molecule determined from structural evidence. Simple geometric considerations lead to conclusions regarding the locations of the binding sites for assembly of the protofibril and the flexibility of the fibrin molecule.

Dynamic mechanical analysis studies of the interphase

Abstract: The dynamic mechanical properties of unidirectional glass-fiber-reinforced polyester measured along the fiber direction were recently investigated In the same polyester, the type of organosilane coated on the glass fiber, the amount of organosilane, the fiber volume fraction, and the fiber diameter affect the value of the loss tangent, tan δ, at the glass-transition temperature of the glass-fiber-reinforced polyester The interfacial shear strength and the tan δ at the glass-transition temperature of the glass-fiber-reinforced polyester show good correlation suggesting that the latter can be used to characterize the quality of the interphase Factors affecting the glass-transition temperature and the application of Zorowski and Murayama's equation in the characterization of the interfacial adhesion are also discussed

Optical-fiber type power transmission device

Abstract: An optical-fiber type power transmission device, comprises an optical fiber for transmitting the power from a power input end through a power output end of the optical fiber; an opaque protective sleeve over the optical fiber and having an inner diameter larger than the outer diameter of the optical fiber to define a gas passageway therebetween; and a tubular waveguide secured to the protective sleeve at the power output end of the optical fiber and projecting past the power output end. The tubular waveguide is unattached to the optical fiber to permit the fiber to move with respect to the tubular waveguide and protective sleeve during the bending of the device.

Dietary fiber: classification, chemical analyses, and food sources.

Abstract: Dietary fiber's role in the prevention and treatment of constipation has long been known, but now fiber is touted as a cure for many of the ills in Western countries. Although some data exist to relate dietary fiber intake to certain diseases, lack of agreement on what dietary fiber is and how it should be measured make interpreting the data difficult. Further, not all dietary fiber is created equal. Water-soluble fibers, such as pectin and gums, have little effect on stool weight and hence are not appropriate treatment for patients with constipation. Water-insoluble fibers, such as cellulose and hemicellulose, are most effective in aiding laxation but may also limit absorption of minerals and possibly vitamins. Wheat bran is a good source of hemicellulose; vegetables supply cellulose to the diet. Most agencies are recommending a doubling or tripling of dietary fiber intake. Typical recommendations are set at 25 to 50 grams of dietary fiber daily. Different analytical methods for dietary fiber yield conflicting fiber values, and dietary fiber values do not exist for many foods, making fiber recommendations controversial and difficult to achieve. Fiber in the diet should ideally be increased by the consumption of unrefined breads and cereals and more fruits and vegetables. Vegetarians routinely consume 40 to 50 gm dietary fiber daily without ill effect. Fiber supplements may be appropriate for some patients, but the composition of the fiber should be known and be appropriate for the disease being treated. Before fiber supplements are marketed, clinical trials should be conducted to support the use of the supplements in the prevention and treatment of disease.(ABSTRACT TRUNCATED AT 250 WORDS)

Fiber-containing composite

Abstract: Fibrous material is coated with boron nitride and a silicon-wettable material, the coated fibrous material is admixed with an infiltration-promoting material which is at least partly elemental carbon and the mixture is formed into a preform which is infiltrated with a molten solution of boron and silicon producing a composite containing boron nitride coated fibrous material.

In vitro chemical degradation of poly(glycolic acid) pellets and fibers

Abstract: The influence of macroscopic dimensions, heat treatment, and polymer morphology on the chemical degradation of poly(glycolic acid) (PGA) fibers and pellets was examined in media of different pH values by monitoring the sample mass, dimensions, crystallinity, mechanical strength, and surface character. The degradation was found to be chemically controlled and independent of fiber size. The rate was an order of magnitude faster in alkaline vs. acidic media. In general, the pellets degraded faster than fibers, and while the latter showed little surface deterioration, scanning electron photomicrographs of the pellets revealed considerable surface degradation with circumferential microcracks progressing into longitudinal cracks with increasing immersion times and pH. Concomitantly, DSC measurements showed a steady increase in crystallinity for both fibers and pellets. The fiber tensile strength decline was independent of diameter and more drastic in alkaline media. Additionally, the heat-treated fiber was always stronger than the non-heat-treated one. It is concluded that crystallinity and polymer chain orientation, in addition to immersion media, influence PGA degradation. Also, the loss in strength results from chain scission in the amorphous regions while mass loss occurs when polymer chains become small enough to be soluble. These different variables offer a means of modifying PGA fiber tensile properties.

Carbon/graphite fiber reinforced poly(methyl methacrylate): properties under dry and wet conditions.

Abstract: The flexural properties of poly(methyl methacrylate) (PMMA) reinforced with carbon/graphite (C/G) fibers with three different surface treatments were investigated by transverse bend testing after dry and wet storage. The fibers used were (1) commercially available fibers, (2) cleaned fibers, and (3) cleaned and sized fibers. The coating agents of commercial unidirectional and braided C/G fibers as well as impurities on C/G fibers for medical uses were characterized by means of high-performance liquid chromatography (HPLC). The agar overlay technique was used to assess the cytotoxicity of leachable elements from different fibers and processed composites. Composites with both unidirectional and braided tubular C/G fibers were investigated after storage in water. Fracture stress and flexural modulus decreased when "commercial" fibers were used as reinforcing material. Composites with cleaned and sized fibers gave only minor differences in flexural properties after dry and wet storage. By means of SEM micrographs the adhesion behavior of unsized C/G fibers, epoxy sized fibers, cleaned fibers, and cleaned and sized fibers were assessed. After water storage a substantial part of the cleaned fibers adhered to the matrix material. The adhesion capacity of the other fibers was reduced since the water absorption caused separation of fiber and matrix.

Silver-coated nylon fiber as an antibacterial agent.

Abstract: A blend of nylon fiber and silver-coated nylon fiber (the latter known as X-static) was used in these experiments. This fiber was bactericidal when bacteria were exposed to it directly or to an extract derived from its prior incubation in salt solution. At ambient temperatures, a rapid exponential decrease of survival occurred, usually after a delay of approximately 1 h. The rate of killing (decrease of survival) increased with an increase in X-static percentage of the fiber blend, temperature of fiber extraction, concentration of Tris buffer present during extraction, and temperature at which bacteria were exposed to the extract. When bacteria were exposed to the extract at 37 degrees C as opposed to ambient temperature, there was no delay in onset of killing. Escherichia coli was generally the indicator organism tested, but comparable results were also found for Pseudomonas, Klebsiella, Staphylococcus, and Streptococcus species. The rate of killing increased with increasing silver ion concentration of the fiber extract, as determined through atomic absorption spectrophotometry. The rate of killing was greater and the onset was earlier with an extract containing silver ions from fiber than with a salt solution containing the same concentration of silver ions from silver nitrate. Studies of the kinetics of ion release suggested that X-static may be an effective, sustained-release antibacterial agent.

The neurophysiologic investigation of small fiber neuropathies.

Abstract: We have applied our technique for the measurement of thermal thresholds to 25 patients referred with symptoms and signs of small fiber peripheral neuropathy in whom conventional electrophysiological indices were individually within the range of normal values for our laboratory. Vibration threshold determinations were also within normal range. Significant abnormalities of thermal thresholds were noted in all patients. The results indicate that the technique provides an accurate, easily performed and reproducible index of function in small Aδ and C groups of nerve fibers.

High‐Temperature Mechanical Properties of a Ceramic Matrix Composite

Abstract: The change in mechanical properties of a fiber-reinforced ceramic from notch insensitivity at room temperature to notch sensitivity at elevated temperature has been investigated. The change in behavior has been attributed primarily to a correspondingly large variation in the shear resistance of the fiber/matrix interface caused by oxidation effects at that interface. The transition in behavior has been correlated with a fracture model based on the incidence of fiber failure in the crack wake.

Effect of uniaxial stress on the Raman spectra of graphite fibers

Abstract: Measurements of the effect of uniaxial stress on the frequency of the k≊0 optical phonons in heat‐treated benzene‐derived graphite fibers have been performed using first‐order Raman scattering. Application of uniaxial stress along the fiber axis is found to cause polarization‐dependent splittings and shifts of the Raman peaks of the k≊0 doubly degenerate optical phonons. From these observed splittings and shifts, experimental values for the phenomenological coefficients which describe the changes in the elastic constant of these phonons with strain are determined. It is concluded that Raman spectroscopy can be used to characterize the local stress or strain conditions of graphite fibers nondestructively.