Showing papers on "Fiber published in 1984"

Orientation Behavior of Fibers in Concentrated Suspensions

Abstract: A mathematical model is developed to predict the orientation distribution function of rigid fibers in concentrated suspensions. The model contains a phenomenological term to account for interactions between fibers. Predictions of the model are tested against experiments in simple shear flow, using suspensions of nylon monofilaments in silicone oil. The results compare favorably for steady-state distributions, though the theory predicts a more rapid approach to steady state than actually occurs. The model predicts, and experiments show, that fiber orientation is not reversible when the flow is reversed. The model is useful for predicting the effects of processing on fiber orienta tion in short fiber composites.

A Rheological Equation of State for Semiconcentrated Fiber Suspensions

Abstract: A rheological equation of state is developed for a semiconcentrated suspension of stiff fibers in a Newtonian solvent with volume fraction φ in the range (D/L)2<φ<(D/L), where L/D is the length‐to‐diameter ratio of the fibers. The constitutive equation gives the stress in terms of an integral over a function of the Cauchy strain tensor and the orientation vector for a fiber. An expression is also obtained for the evolution of the fiber orientation. The development is restricted to homogeneous flows. It is found that in start‐up of steady shear or elongational flow the orientation of the fibers and the measurable rheological properties both depend only on the total applied strain. For a fiber number density of n the contribution of the fibers to the stress is roughly nL3 times that of the solvent when the fibers are randomly oriented, as for example at the beginning of a flow. In the model presented here the viscosity (at steady state) is identical to that of the Newtonian solvent, because of the alignment...

Development of the Cotton Fiber

Abstract: Publisher Summary This chapter discusses the various facets of cotton-fiber development and focuses on some currently critical areas of investigation. In addition to its commercial importance, cotton fiber has several attributes that make it an experimental system of choice for the investigation of physiological and biochemical changes accompanying cell elongation and/or maturation. The fiber originates and ends as a single cell, and thus elongation can be studied free of any complications from cell division. The variability in fiber length and secondary wall thickness of fibers among different cotton varieties depends upon the interplay of a complex pattern of metabolic processes and regulating mechanisms that govern fiber growth. The in vitro methodology of cotton ovule culture holds considerable promise for investigating the effects of a number of plant growth substances on cell growth. The developing cotton fibers provide a rich source of homogeneous single cells, which should be preferred for structural and biosynthetic studies of the cell wall.

Laser-heated miniature pedestal growth apparatus for single-crystal optical fibers

Abstract: We have designed and built a single‐crystal fiber growth apparatus. The apparatus employs novel optical, mechanical, and electronic control systems that enable the growth of high optical quality single‐crystal fibers. We have grown oriented single‐crystal fibers of four refractory oxide materials, Al2O3, Cr:Al2O3, Nd:YAG, and LiNbO3. These materials exhibit similar growth characteristics and yield fibers of comparable quality. Fibers as small as 20 μm in diameter and as long as 20 cm have been grown. Measured optical losses at 1.06 μm for a 10‐cm‐long, 170‐μm‐diam Cr:Al2O3 fiber were 0.074 dB/cm.

Dependence of Asbestos- and Mineral Dust-induced Transformation of Mammalian Cells in Culture on Fiber Dimension

Abstract: The abilities of chrysotile and crocidolite asbestos, glass fibers of differing dimensions, and nonfibrous mineral particulates to induce morphological transformation of Syrian hamster embryo cells in culture were compared. Chrysotile and crocidolite asbestos induced morphologically transformed colonies which were indistinguishable from transformed colonies observed following treatment with known chemical carcinogens. A linear, dose-dependent increase in the frequency of transformed colonies was observed. The slope of the dose-response curve on a log-log scale was approximately 1, which is consistent with a one-hit mechanism for their induction. The transforming potency of chrysotile asbestos was decreased by milling of the fibers but not by extraction with an organic solvent. Chrysotile asbestos was nearly twice as potent in inducing morphological transformation as crocidolite asbestos. Glass fibers were also very active in this assay. Thin glass fibers with an average diameter of 0.1 to 0.2 micrometer were as active as asbestos. In contrast, two nonfibrous particulates, alpha-quartz and Min-U-Sil, were inactive over the same concentration range used for the fibrous dusts; however, both were active at higher doses. The effect of varying fiber dimension on induction of morphological transformation was examined with glass fibers. When compared on a per-weight basis, thick glass fibers [average diameter, 0.8 plus/minus 0.06 micrometer (S.E.)] were 20-fold less potent than thin fibers [average diameter, 0.13 plus/minus 0.005 micrometer] in inducing cell transformation. When the average fiber length of thin glass fibers was reduced from 9.5 to 1.7 micrometer by milling the fibers in a mortar and pestle, a 10-fold decrease in transforming activity resulted. When the average fiber length was reduced to 0.95 micrometer, transforming ability was totally absent. The cytotoxic potencies of the various mineral dusts correlated with their transforming potencies. The varying abilities of the mineral dusts to induce cell transformation in vitro are similar to their abilities to induce mesotheliomas in vivo. Thus, this system provides a unique model for studying the mechanism of mineral fiber tumorigenesis and for comparing the relative risks of mineral dusts.

An Indentation Method for Measuring Matrix‐Fiber Frictional Stresses in Ceramic Composites

Abstract: A simple method for measuring frictional stresses between the mairix and individual fibers in a ceramic composite is described. A standard microhardness indenter is used to apply a force to the end of the fiber and depress it below the matrix surface. The frictional stress is calculated from measurement of the applied force and the amount of slipping between the fiber and matrix.

Optical fiber hydrogen sensor

Abstract: A new type of hydrogen sensor is reported in which an optical fiber is used as the sensing element. The fiber is coated with palladium which expands on exposure to hydrogen. This changes the effective optical path length of the fiber, which is detected by interferometric techniques. Preliminary experiments have demonstrated the effect and suggest a high sensitivity and a wide dynamic range for this kind of sensor. The experimental results are compared to calculated optical path length changes. Application of this kind of sensor to the detection of other chemicals appears feasible.

The effect of carbon fiber orientation on the fatigue resistance and bending properties of two denture resins

Abstract: The following conclusions were made concerning the effects of carbon fiber orientation on the flexural fatigue resistance and bending properties of two denture base acrylic resins. Hi-I resin, regardless of fiber presence or orientation, was more resistant to flexural fatigue than Lucitone resin. Carbon fibers placed perpendicular to the direction of applied stress produced the most favorable combination of increased resistance to bending and to flexural fatigue. Production of properly oriented fibers that are well centered within the resin is technically difficult and yields less predictable property improvements than result from randomly dispersed fibers.

Chalcogenide glass fibers for mid-infrared transmission

Abstract: Chalcogenide glass fibers for mid-infrared transmission have been fabricated in As-S, As-Ge-Se, and Ge-S glass systems using high purity materials. The preparation of unclad, Teflon FEP clad, and chalcogenide glass clad fibers and their transmission loss characteristics are reported. It is found that appropriate glass compositions for drawing low-loss fibers are limited to the narrow ranges in the glass-forming regions. The minimum losses obtained are 35 dB/km at 2.44μm for As 40 S 60 unclad fiber, 182 dB/km at 2.12 μm for As 38 Ge 5 Se 57 unclad fiber, and 148 dB/km at 1.68 μm for Ge 20 S 80 unclad fiber. It is shown that hydrogen impurity absorptions and short-wavelength weak absorption tails seriously enhance loss in the fibers. It is also suggested that ultralow loss cannot be achieved due to the existence of the weak absorption tail. However, it is expected that the chalcogenide glass fibers can be used in short fiber-length applications such as in the remote monitoring and delivery of CO laser radiation. This is due to their wide operating wavelength ranges of 0.9-6\mu m for As-S, 1.3-9\mu m for As-Ge-Se, and 0.8-5\mu m for Ge-S, in which losses can be reduced to below 1 dB/m.

Producing high tenacity, high modulus crystalline article such as fiber or film

Abstract: Solutions of ultrahigh molecular weight polymers such as polyethylene in a relatively non-volatile solvent are extruded through an aperture at constant concentration through the aperture and cooled to form a first gel of indefinite length. The first gels are extracted with a volatile solvent to form a second gel and the second gel is dried to form a low porosity xerogel. The first gel, second gel or xerogel, or a combination, are stretched. Among the products obtainable are polyethylene fibers of greater than 30 or even 40 g/denier tenacity and of modulus greater than 1000 or even 1600 or 2000 g/denier.

The study of model polydiacetylene/epoxy composites: Part 1 The axial strain in the fibre

Abstract: Le compose modele est soumis a une deformation d'etirage dans une direction parallele a la fibre. On determine la deformation tout au long de la fibre par spectroscopie Raman et de la matrice par les techniques classiques

Dietary fiber food products and method of manufacture

Abstract: A dietary fiber composition is prepared by coating an insoluble fiber with a soluble fiber. The insoluble fiber is preferably derived from cereal bran by enzymatically and chemically purifying the bran. The soluble fiber is preferably pectin or an alginate. The dietary fiber composition can be used to prepare low calorie, high fiber content dietary food products.

In vivo metal-ion release from porous titanium-fiber material

Abstract: Dense and porous Ti, Ti-alloy, and stainless steel specimens were implanted in canine trabecular bone. After 6 and 12 months the specimens were retrieved together with bone tissue immediately adjacent. The trace metal content in the tissue samples was determined using neutron activation analysis, differential pulse polarography, graphite furnace atomic-absorption spectrophotometry, electron microprobe analysis, and laser microprobe analysis. The results are discussed in view of (i) the release of Ti ions, which is larger for porous than for bulk specimens, (ii) the various artifacts arising in electron microprobe (EMP) and laser microprobe mass analysis (LAMMA) determination of compositional gradients of trace metal-ion content in bone tissue, (iii) the absence of measurable quantities of V in bone tissue, and (iv) the difference in local tissue accumulation between Ti, released from Ti specimens, and Ni, released from stainless steel specimens.

The speed of sound in DNA

Abstract: We have used Brillouin scattering to determine the speed of sound in (and hence longitudinal modulus of) A- and B-DNA fibers. The speed of sound is very sensitive to the degree of hydration of the fibers, and measurements have to be made at laser powers below 5 mW to avoid local heating and dehydration. Under those conditions, we obtain sound speed perpendicular to the fiber axis of about 2.2 and 1.9 km/s in A- and B-DNA fibers, respectively. A-DNA fibers show a small anisotropy with sound speeds along the fiber axis higher by up to 10% B-DNA fibers appear to be isotropic.

Resorbable materials of poly(L‐lactide). V. Influence of secondary structure on the mechanical properties and hydrolyzability of poly(L‐lactide) fibers produced by a dry‐spinning method

Abstract: Fibers of poly(L-lactide) (PLLA) with a loosened fibrillar structure were produced by solution spinning from a good solvent (chloroform) in the presence of various additives (camphor, polyurethanes). No decrease in mechanical properties was observed as compared with PLLA fibers spun from a good solvent only. In vitro degradation studies showed that the rate of degradation of PLLA fibers with the loosened fibrillar structure was increased approaching that found for fibers composed of the homopolymer of glycolide or copolymers of glycolide and L-lactide. Helices on the fiber surface caused by melt fracture during spinning of the fibers leads to higher knot strengths of the hot-drawn PLLA fiber up to 70% of the tensile strength.

Microdeformation losses of single-mode fibers.

Abstract: In this paper, we consider the scattering losses of single-mode fibers that are caused by microdeformations such as microbends of the fiber axis and random fluctuations of the fiber core diameter. Since very little is known about the statistics of microdeformations of actual fibers, we assume that the autocorrelation functions of random bends and random core diameter fluctuations are Gaussian, characterized by the rms deviation and the correlation length of the random function. We consider single-mode fibers with step, parabolic, and triangular (linear) refractive-index profiles and reach the following conclusions: (1) Whereas for equal (large) mode radii the microbending losses of all three fiber types are the same, losses due to random core diameter fluctuations can be three times as high in step-index fibers as in triangular-index fibers. Since triangular-index fibers have sometimes been observed to have lower scattering losses than step-index fibers, one might conclude that, in these cases, excess losses may be caused by random radius fluctuations rather than by microbends. (2) Radial refractive-index ripples, which tend to be present in the deposited claddings of single-mode fibers, seem unlikely to be a major source of microdeformation losses. (3) The wavelength dependence of microdeformation losses depends strongly on the value of the correlation length of the Gaussian autocorrelation function of the fiber deformations. If the correlation length is of the same order of magnitude as the fiber radius, the losses are only slightly wavelength dependent. For very long correlation lengths the losses are very much smaller (for the same rms variation of the random functions), but they become strongly wavelength dependent, increasing sharply with increasing wavelength.

Methods and apparatus for optical fiber systems

Abstract: Methods, apparatus and articles for systems comprising optical fibers, in particular for feeding an optical signal into an optical fiber through the buffer thereof and for withdrawing an optical signal from an optical fiber through the buffer thereof. Preferably this is achieved with the aid of an optical coupling means which contacts and conforms to the surface of the buffer at a bent portion of the fiber. The coupling means can for example be a resiliently deformable material such as a polysiloxane. In a preferred aspect, the invention provides an apparatus and method for axially aligning, and preferably joining, the ends of optical fibers. The apparatus comprises means for holding two fibers so that the fiber ends are approximately abutting and axially aligned, adjacent means for passing an optical signal into one of the fibers through the buffer thereof, and adjacent means for withdrawing that signal from the other fiber through the buffer thereof. At least one of the holding means is movable to maximize the withdrawn optical signal and thus to align the fibers. The invention also includes novel splices which can be made in this way and novel splicing aids for use in the method.

Morphological and structural changes in a copolymer of glycolide and lactide occurring as a result of hydrolysis

Abstract: The changes in the structure and morphology of a random copolymer containing 92 mol % glycolide units and 8 mol % lactide units as a function of in vitro hydrolysis have been studied. A number of techniques, such as wide-angle x-ray diffraction, small-angle x-ray scattering, density measurements, infrared spectroscopy, and viscometry were employed in this study. The results showed that the hydrolytic attack was initiated in the amorphous areas of the polymer. After 28 days in the in vitro medium most of the amorphous areas had been chemically converted to lower-molecular-weight species such as oligomers of poly(glycolide-co-lactide). These low-molecular-weight species become water solble and are removed rapidly after day 28. Thus the fiber takes on a Swiss cheese character as the amorphous matter is hydrolyzed and eventually dissolved. As hydrolysis proceeds further, the crystalline areas of the polymer are attacked and eventually removed from the fiber by solubilization. The resulting voids in the fiber are eventually filled by a “collapse” of the structure. The role of the amorphous areas of the polymer in controlling the tensile strength of the suture is discussed.

Slurry Infiltrated Fiber Concrete (SIFCON): Properties and Applications

Abstract: Steel fiber reinforced concretes (SFRC) are typically prepared by adding the fiber along with the other concrete ingredients in the mixing operation. At fiber contents in excess of 2 volume percent, the SFRC becomes difficult or impossible to mix and place. Inasmuch as improvements in concrete properties attributed to the fibers increase as a function of increasing fiber content, this situation places a limit on the ultimate property development in SFRC prepared using the premix approach. Recently, a procedure has been developed wherein steel fiber contents up to 20 volume percent have been provided. Slurry Infiltrated Fiber Concrete (SIFCCN) composites possess outstanding strength, ductility, and crack/spall resistant properties. Equally: important, the ability to construct with SIFCON has been demonstrated.

Carbon composite article and method of making same

Abstract: A composite structural ceramic article and method of fabrication thereof. The article of the invention is specifically designed for use in high temperature, corrosive and erosive environments such as those found in heat engines, heat exchangers, stationary power equipments and industrial process equipments. The article comprises a porous carbon fibrous substrate or other suitable high temperature fibrous substrate which may include: a pyrolytic carbon or appropriate chemical vapor deposited sheath formed about each fiber of the substrate; a chemically vapor deposited metallic carbide, oxide, boride or nitride coating over the coated fibers of the substrate; and an impermeable metallic carbide, oxide, boride or nitride outer protective layer formed about the entire periphery of the coated substrate. In accordance with the method of the invention, the metallic coating is applied to the fibers in such a manner such that internal porosity of the article is precisely controlled and a flaw resistant, tough, non-catastrophic failing structural ceramic body is formed.

Dietary fiber composition and process of manufacture

Abstract: A dietary fiber composition is prepared by coating an insoluble fiber with a soluble fiber. The insoluble fiber is preferably derived from cereal bran by enzymatically and chemically purifying the bran. The soluble fiber is preferably pectin or an alginate. The dietary fiber composition can be used to prepare low calorie, high fiber content dietary food products. The process of preparing the dietary food composition and the food products made therefrom is also disclosed.

Characterization of fiber orientation in short‐fiber composites

Abstract: A method for measuring intermediate states of fiber orientation in short‐fiber composites is described. The technique is based on the observation that a representative fiber distribution, for example, the negative of a photomicrograph from a specimen, resembles a collection of diffraction apertures. Diffraction masks for a Fraunhofer diffractometer made from the representative fiber distributions produce diffraction patterns characteristic of the state of orientation. Analyses are presented which relate the features of the diffraction pattern to (i) the orientation distribution, (ii) shape, and (iii) aspect ratio of the fibers. The results from these analyses are in good agreement with experimental diffraction patterns from masks made from simulated fiber distribution patterns.

Interconnecting and distributing box for optical fibers

Abstract: An optical fiber interconnecting and distributing box includes a base, a cover, and a movable pivotable panel dividing the box into two compartments. Rack-mounted connectors each connect an end section of a first optical fiber from an array of cables to an end section of a second optical fiber from another array of cables. The base contains practically circular flat loops of the first fibers that enter the first compartment through holes in a base wall. The cover contains the connectors. End sections of the first fibers run through an aperture in the panel. The second fibers are arranged as circular flat loops and have end portions entering the second compartment through sides of the cover. The first fibers are intended to be pre-wired, i.e. each first fiber is definitively ascribed to a connector. Distributing involves withdrawing the end section of a second fiber that is initially inserted in a connector into another connector. In one embodiment, the panel carries two racks for connecting the first and second optical fibers via optical fiber jumpers.

Effects of fiber and virginiamycin on nutrient absorption, nutrient retention and rate of passage in growing swine.

Abstract: Three balance trials, each involving 12 crossbred gilts averaging 35.2 kg body weight, were conducted to determine the effects of dietary fiber and virginiamycin on nutrient digestibility, mineral absorption and retention, and digesta rate of passage (RP). Two levels of fiber (13.5 and 20.2% neutral detergent fiber) and two levels of virginiamycin (0 and 11 ppm) were used in a 2 X 2 factorial arrangement of treatments. All diets were isonitrogenous and isocaloric. The RP was determined by observing the time required for a change in feces color after the addition of .5% chromic oxide to the diet. The high fiber diet had a faster (P less than .01) RP, which was associated with depressions (P less than .001) in the digestibility of dry matter (DM), energy (E), cell contents, neutral detergent fiber (NDF), acid detergent fiber (ADF), hemicellulose (HC), cellulose, permanganate lignin and ash. Virginiamycin supplementation slowed (P less than .004) the RP of both low and high fiber diets, but improved (P less than .05) the DM, E, NDF, ADF, HC and cellulose digestibility of the high fiber diet only. Fiber increased (P less than .06) fecal N excretion, whereas virginiamycin supplementation decreased (P less than .08) fecal N excretion. The addition of virginiamycin improved the absorption and retention of P, Ca, Mg, Cu, Fe, Zn and Mn when added to the high fiber diet, but had little or no effect when added to the low fiber diet even though absorption and retention values for most minerals were similar or slightly higher for the unsupplemented high fiber diet compared with the unsupplemented low fiber diet.(ABSTRACT TRUNCATED AT 250 WORDS)

Entangled nonwoven fabric made of two fibers having different lengths in which the shorter fiber is a conjugate fiber in which an exposed component thereof has a lower melting temperature than the longer fiber and method of making same

Abstract: There is disclosed a fabric made up of short conjugate fusible fibers and longer, base fibers. The conjugate fibers have an exposed low melting point component having a lower melting point than the remainder of said fibers and said base fibers. In the method of the present invention, a web of short conjugate fibers and longer base fibers is passed through an entangling mechanism where the short fusible fibers are concentrated and intertwined in heavily entangled knot areas. The entangled web is heated to thermobond at least the low melting point component of the conjugate fibers to each other and preferably to the surrounding base fibers to reinforce and strengthen the fabric.

Modified polyolefin fiber

Abstract: Fibers prepared by spinning, drawing and drying dilute solutions of ultrahigh molecular weight polyethylene or polypropylene are modified by including in the dilute solution a polymeric additive. The polyethylene fibers so prepared have melting points above 140° C. and exhibit improved adherence to matrices, resistance to fibrillation and other advantageous properties. Additives include lower molecular weight polyolefins, oxidized polyolefins, olefin copolymers, polyolefin graft copolymers and polyoxymethylenes.

Fiber reinforced glass matrix composites

Abstract: What is disclosed is a method of preparing fiber reinforced glass composites from high modulus fibers and organopolysiloxane resins. The composites are obtained by firing a partially cured, pressed, and post-cured prepreg to an elevated temperature in an inert atmosphere. A simple, low temperature laminating procedure is used in the composite preparation in place of the standard hot pressing technique.