Showing papers on "Fiber published in 1977"

Carcinogenicity of Fibrous Glass: Pleural Response in the Rat in Relation to Fiber Dimension

Abstract: Seventeen fibrous glasses of diverse type or dimensional distribution induced different incidences of malignant mesenchymal neoplasms when implanted in the pleurae of female Osborne-Mendel rats for periods of more than 1 year. Neoplastic response correlated well with the dimensional distribution of fibers. Fibers less than or equal to 1.5 mu in diameter and greater than 8 mu in length yielded the highest probability of pleural sarcomas, and probability trends suggested that pleural sarcoma incidence increased with increasing lengths of fibers with diameters of less than 1.5 mu, Morphologic observations indicated that fibers less than or equal to 8 mu in length were inactivated by phagocytosis. In fibers greater than 8 mu in length, the correlation of carcinogenicity witth increasing length was difficult to explain. Since neoplastic response to a variety of types of durable fibers, particularly asbestos fibers, was similar, our experiments reinforce the idea that the carcinogenicity of fibers depends on dimension and durability rather than physicochemical properties and emphasize that all respirable fibers be viewed with caution.

Changes in Biochemical Composition of the Cell Wall of the Cotton Fiber During Development

Abstract: The composition of the cell wall of the cotton fiber ( Gossypium hirsutum L. Acala SJ-1) has been studied from the early stages of elongation (5 days postanthesis) through the period of secondary wall formation, using cell walls derived both from fibers developing on the plant and from fibers obtained from excised, cultured ovules. The cell wall of the elongating cotton fiber was shown to be a dynamic structure. Expressed as a weight per cent of the total cell wall, cellulose, neutral sugars (rhamnose, fucose, arabinose, mannose, galactose, and noncellulosic glucose), uronic acids, and total protein undergo marked changes in content during the elongation period. As a way of analyzing absolute changes in the walls with time, data have also been expressed as grams component per millimeter of fiber length. Expressed in this way for plant-grown fibers, the data show that the thickness of the cell wall is relatively constant until about 12 days postanthesis; after this time it markedly increases until secondary wall cellulose deposition is completed. Between 12 and 16 days postanthesis increases in all components contribute to total wall increase per millimeter fiber length. The deposition of secondary wall cellulose begins at about 16 days postanthesis (at least 5 days prior to the cessation of elongation) and continues until about 32 days postanthesis. At the time of the onset of secondary wall cellulose deposition, a sharp decline in protein and uronic acid content occurs. The content of some of the individual neutral sugars changes during development, the most prominent change being a large increase in noncellulosic glucose which occurs just prior to the onset of secondary wall cellulose deposition. Methylation analyses indicate that this glucose, at least in part, is 3-linked. In contrast to the neutral sugars, no significant changes in cell wall amino acid composition are observed during fiber development. Compositional analyses of cell walls derived from culture-grown fibers indicate that these walls are remarkably similar to those derived from fibers grown on the plant, both in terms of composition and in terms of relative changes in composition during development. A comparison of our results on total cell wall composition and linkages of sugars as determined by a preliminary methylation analysis of unfractionated fiber walls indicates that the primary cell wall of cotton fibers is similar to that of primary cell walls of other dicotyledons and of gymnosperms as reported in the literature.

Capillary supply of skeletal muscle fibers in untrained and endurance-trained men

Abstract: Muscle fiber diameters and numbers of capillaries per fiber, per square millimeter, and around each fiber were determined in needle biopsies from the lateral part of the quadriceps muscle of 23 young men. Twelve subjects were untrained (UT) and eleven were endurance-trained (ET) athletes. Average values for maximal oxygen uptake were 51.3 (UT) and 72.0 ml/kg-min (ET). Mean fiber diameters were not significantly different in the two groups (48.8 and 49.1 micron). The capillaries per fiber ratios were 1.77+/-0.10 and 2.49+/-0.08 (mean+/-SE) in the UT and ET groups, respectively. The numbers of capillaries around each fiber were 4.43+/-0.19 (UT) and 5.87+/-0.18 (ET). The numbers of capillaries per mm2 were 585+/-40 (UT) and 821+/-28 (ET). Fiber diameters were 28% smaller in ultrathin than in fresh-frozen sections from the same biopsies. After correction for this difference, the numbers of capillaries per mm2 were 305 and 425 in the UT and ET, respectively. The capillaries per fiber ratio increased with increasing fiber diameter, but not sufficiently to maintain the number of capillaries per mm2. Fibers containing many mitochondria are surrounded by more capillaries than fibers with few mitochondria.

Numbers of Fiber-to-Fiber Contacts in General Fiber Assemblies:

Abstract: General formulas are derived for the estimation of the number of fiber-to-fiber contacts in fiber assemblies with arbitrary distributions of orientation and fiber length The average number of contacts per unit volume of an assembly nv is given bywhereIn this equation fi is the density function of orientation, D is the diameter of the cross section of the fiber, Lv is the total length of fiber per unit volume, and θ, φ, and θ', φ' are respective polar angles characterizing the orientation of two fibers to be brought into contact each other The application of this general result is shown to lead to the same results in the special cases considered by van Wyk, and Kallmes and Corte

Photon probe — an optical-fiber time-domain reflectometer

Abstract: This paper describes an optical time-domain reflectometer that incorporates a gated photomultiplier receiver. The instrument can detect extremely weak reflections from fiber breaks (more than 65 dB below the 4-percent reflection of a perfect break) with 0.5-m distance resolution. In addition, backward Rayleigh scattering, which occurs roughly uniformly along a fiber, can be used to estimate the attenuation vs position within a fiber. Therefore, regions of high attenuation can be located nondestructively from one end of the fiber.

Polysulfone hollow fibers. II. Morphology

Abstract: The morphology of porous polysulfone hollow fibers which were spun by the dry–wet spinning process is discussed. It was demonstrated that a relatively moderate quenching medium should be employed in the bore of the nascent fiber in order to produce an isotropic fiber free of macrovoids and intrusion cells. A rather delicate quantitative balance between the internal precipitant and the spinning solution has to be maintained, especially when low-viscosity polymeric solutions are employed. Scanning electron micrographs of fiber cross sections display highly porous, spongestructured walls which in some instances exhibit a rather dense interface skin. However, control of the extrusion/coagulation procedure allows the formation of skinned, porous skinned, and nonskinned fibers.

Processes for coating bundles of hollow fiber membranes

Abstract: Processes are disclosed for coating the exteriors of a plurality of hollow fibers which are suitable for fluid separations and which are assembled in the form of a bundle. The processes involve immersing the bundle of hollow fibers in a coating liquid containing material suitable for forming the coating and a substantial amount of solvent. A pressure drop from the exteriors to the interiors of the hollow fibers is provided to result in the formation of a deposit on the exteriors of the hollow fibers. The processes of this invention enable essentially the entire exterior surfaces of the hollow fibers to be coated without undue sticking of the hollow fibers or providing undesirably thick coatings on the hollow fibers in any portion of the bundle or on a portion of any of the hollow fibers.

Short-Fiber-Reinforced Elastomer Composites

Abstract: The reinforcement of elastomers with short fibers results in composites with a wide variety of properties. The performance and properties are a function of fiber type, fiber content, fiber...

Mechanochemical studies of enzymatic degradation of insoluble collagen fibers.

Abstract: A mechanochemical method was developed for studying the enzymatic degradation of insoluble collagen fibers. The method involves stretching the collagen fiber to a fixed extension in the presence of a solution of collagenase and measuring the rate of relaxation of the force induced in the fiber. In this work, bacterial collagenase was used for reasons of availability. We observed invariably an exponential decrease in force with respect to ttime. The slope of the linear plot of logarithm of the force versus time was taken as a measure of the rate of enzymatic degradation. This rate was found a) to vary linearly with collagenase concentration; b) to be maximal at pH 7-8; c) to vary with temperature according to the Arrhenius relationship in the range 10-56 degrees C; d) to be reduced to varying extent by addition of EDTA omicron-phenanthroline, 2,3-dimercaptopropanolol, and D,L-cysteine; e) to be minimal when the strain on the fiber was ca. 4%; f) to be increased dramatically by denaturation of the collagen fiber; and g) to be reduced by an increase in the crosslink density of the collagen fiber. Except for the effect of strain, which can not be conveniently studied by existing methods these results are consistent with those observed by other methods for the study of the enzymatic degradation of collagen. The mechanochemical method is, however, uniquely suited to monitor continuously the enzymatically induced decay in the stress-bearing ability of collagen fibers. It has also been found useful in the design of collagenous implants with specified resistance to enzymatic degradation in vivo.

X-Ray diffraction data for β-(1 → 3)-D-glucan

Abstract: The conformation of a bacterial β-(1 → 3)-D-glucan (curdlan) was studied by X-ray diffraction measurements on fiber diagrams. The glucan fiber, prepared by extruding a dimethyl sulfoxide solution o...

Effects of Cellulose Added to Diets of Low and High Fiber Content upon the Metabolism of Calcium, Magnesium, Zinc and Phosphorus by Man

Abstract: Addition of 10 g of cellulose dispersed in 150 g of apple compote to the daily diet with a low fiber content for a 20-day period caused the fecal excretion of calcium and zinc of three men to increase significantly Balances of both metals became negative and their concentrations in plasma decreased Magnesium balances became negative in two subjects while phosphorus balance changed to negative in one In a similar experiment in which the cellulose was added to a fiber-rich diet, fecal excretions of calcium and zinc increased significantly in each of two men and excretion of magnesium in one Previously negative balances became more negative, and calcium and zinc concentrations decreased in plasma The dependence of fecal dry weight upon fecal fiber content measured by the acid-detergent method was confirmed However, increments of dry matter per g of fiber were less fecal fiber concentrations were high Fecal calcium content correlated significantly with fecal fiber in two subjects, and fecal fiber and zinc in one No correlations were demonstrated in the subject who apparently digested fiber most effectively Our findings indicate that high intakes of fiber can explain to a considerable extent the impaired utilization of zinc, calcium, and magnesium among villagers in rural Iran

Numerical Solution of the Coupled-Power Equation in Step-Index Optical Fibers

Abstract: By use of the finite-difference method of numerical analysis, a simple numerical solution is obtained for the coupled-power equation in optical fibers. For a specified arbitrary coupling coefficient and launching condition, the solution yields all the quantities of interest in the interior of the fiber: power distribution, attenuation, and far-field radiation pattern as functions of length. Results for buffered and cabled Corning fibers are reported. Attention is mainly focused on the influence of the microbends on the optical losses.

Optical fiber Raman oscillator

Abstract: A tunable radiation source employing the stimulated Raman-scattering process is disclosed. The source generates several orders of Stokes radiation in an optical-fiber oscillator cavity, which Stokes radiation may be independently tuned by incorporating separate tuning elements for the several Stokes orders. Several different arrangements of fiber and tuning elements are disclosed.

Process for continuous preparation of fibrous polymer crystals

Abstract: Filament-like polymer crystal fibers are prepared from a solution of a crystallizable polymer, such as polyethylene or polypropylene, in a vessel containing a spinning rotor, preferably having a slightly roughened surface, according to the disclosed invention. The fiber thus formed is taken up and removed at a rate equal to the crystal growth rate. The longitudinal crystal growth rate is of sufficient speed for commercial application while at the same time yielding fibers of outstanding mechanical properties.

Alternate Hybrid-Stress Elements for Analysis of Multilayer Composite Plates

Abstract: Two quadrilateral-shaped multilayer plate bending/stretching elements based on the assumed-stress hybrid finite-element model are presented. These elements may be applied to the analysis of fiber composite plates and shells composed of an arbitrary number of layers and arbitrary mate rial properties and fiber direction within each layer. Both elements incor porate the effects of transverse shear by including the transverse shear stresses τxz and τyz, and by assuming independent rotations of the normals to the plate midsurface, so that normals to the midsurface in the un deformed state need not be normal to the midsurface after deformation. In the formulation of an element based on the assumed-stress hybrid model, the stress distribution in the interior of the element is expressed in terms of a finite number of stress parameters such that equilibrium is satisfied, and the displacement distribution on the boundary of the element is expressed in terms of generalized nodal displacements such that interelement...

Method for forming tubesheets on hollow fiber tows and forming hollow fiber bundle assemblies containing same

Abstract: A method of potting in a single or multi-cavity mold a plurality of fibers in continuous tow form to encapsulate the fibers, fill the interstices and form a solid tubesheet of selected shape and length. After transversely cutting through the thus formed tubesheet and the fibers therein a pair of tubesheets are formed each attached to and forming the end portion of a length of fibers. Potting at spaced longitudinal locations on the continuous tow, and transverse cutting, produces fiber bundle assemblies having a length of the tow of hollow fibers between a pair of axially spaced tubesheets. The process is semi-continuous or continuous, as desired.

Photoassisted heterogeneous catalysis with optical fibers: I. Isolated single fiber

Abstract: Recently reported varieties of photoassisted heterogeneous catalysts are summarized. A cylindrical, light carrying, optical fiber coated with a catalyst layer is evaluated as a novel configuration for all such light assisted catalysis. Equations are obtained which describe the light intensity in the fiber and its surrounding catalyst layer. A dimensionless group of the form phi = (4..cap alpha../sub c/..beta../sub c/dL)/(d/sub f/) (d = d/sub c/ for d/sub c/lambda) determines the relative influence of light loss by all absorption and scattering to light transported in the fiber length. An effectiveness factor eta/sub I/ for heterogeneous photoassisted catalysis is determined for reactions which are first order in intensity and without mass transport limitations. Asymptotic forms of eta/sub I/ are eta/sub I/ = 1.0 (phi > ..integral..1.0). 58 references.

High-speed noncontact fiber-diameter measurement using forward light scattering.

Abstract: The forward scattering of light by an optical fiber produces an interference fringe pattern, and the fringe period is inversely proportional to the fiber diameter. An electrooptic system has been developed to produce and detect this scattering pattern to provide an instrument which will measure fiber diameter during the drawing operation. The system measures the fiber diameter at a 1-kHz rate with a precision of 0.25 μm and an accuracy of ±0.25 μm over a range of 50–150-μm diams. The instrument allows the fiber to move laterally in a 1-cm diam window maintaining the above accuracy. The system can be calibrated optically and does not need a standard fiber for this procedure. The instrument has been used for months without the need for recalibration. In addition to the digital diameter output, the system employs a microprocessor to compute mean and standard deviation values for various sample lengths and provides suitable signals for feedback control of fiber diameter.

Superabsorbent cellulosic fibers having a coating of a water insoluble, water absorbent polymer and method of making the same

Abstract: Products having high absorbency for use in absorbent dressings and the like are prepared by precipitating a water-insoluble but water-swellable superabsorbent polymer onto the surface of a long fiber cellulose from an aqueous slurry and drying the resulting coated fibers by dehydration with a water-miscible nonsolvent for the polymer.

A high‐efficiency tunable cw Raman oscillator

Abstract: Continuously tunable cw Raman oscillation has been achieved in the visible by pumping a single‐mode fused silica fiber with several lines from an argon ion laser. The 100‐m‐long fiber has a core diameter of 3.3 μm and a loss of 17 dB/km at 5145 A. Threshold was achieved with ∼1.0 W of pump power in the fiber. With 4 W of 5145‐A power coupled into the fiber, the Raman oscillator was prism tuned over 80 A. Typical linewidths were ∼2 A. At 5280 A, net input to output power conversion efficiencies of ∼9% and pump depletion of over 80% have been achieved. The simplicity, efficiency, and broadband tunability of fiber Raman oscillators both in the visible and in the near infrared make them potential rivals to other coherent sources of tunable radiation, such as dye lasers and parametric oscillators.

Carbon adsorptive filter material with layers of reinforcing non woven fabrics needle punched

Abstract: An adsorptive filter material having deodorizing, degassing and decolorizing properties which comprises an adsorptive sheet layer of active carbon fibers of which the active carbon fiber content is not less than about 20% by weight and reinforcing sheet layers of fibers having a single yarn strength of not less than about 2 g/denier and an elongation of not less than about 2% provided on the surfaces of the adsorptive sheet layer, the adsorptive sheet layer and the reinforcing sheet layers each weighing from about 20 to 2,000 g/m 2 .

Porosity and pore size determination in polysulfone hollow fibers

Abstract: Average pore sizes and effective porosity of microporous polysulfone hollow fibers were determined by the gas permeability method. Surface structure and porosity were determined by scanning electron microscopy. The values of effective porosity e/q2 (porosity/tortuosity factor) are approximately one order of magnitude lower than those reported previously for flat sheet porous membrane. These lower values are a direct outcome of a higher polymer concentration in the spinning dope. Correlations between the wall void volume, equivalent pore size, and hydraulic permeabilities of the hollow fibers have been determined. Rather low values of e/q2 have been calculated compared to those of the void volume; these effective porosity values indicate either a very high tortuosity factor or a large number of “dead end” pores. Exposure of the fibers to elevated temperature (110°C) for a short period of time drastically reduces the surface pore size and narrows the pore size distributions, whereas overall fiber dimensions are reduced only by 1%, and 85% of the fiber's hydraulic permeability is retained. The scanning electron microscopy study reveals the formation of a relatively dense skin in some spun fibers. For such “skinned” fibers, kinetic (permeability) evaluation of static structure such as mean pore size is not realistic and is further generalized to the term “equivalent pore size.”

Fresnel-Fizeau effect in a rotating optical fiber ring interferometer

Abstract: Measurements of the Fresnel-Fizeau effect in a fiber ring interferometer gyroscope are reported. The presence of the dispersion term in the Fresnel drag coefficient was discernable. The temperature dependence of the coefficient bears on the temperature sensitivity of the optical fiber gyroscope. An alternate approach to measuring fiber dispersion is an added benefit, leading to determination of maximum pulse rate transmitted through single-mode fibers.

Catalytic process utilizing hollow fiber membranes

Abstract: Catalysts of various types, preferably enzymes, are immobilized on hollow fiber membranes in novel way to provide a new system for performing catalytic reactions. In preferred embodiments, novel processes for catalyzing reactions utilizing hollow fiber techniques are disclosed.

Multistrand carbon coated sutures

Abstract: Multistrand carbon coated sutures comprising a plurality of small diameter fibers having a tensile modulus of at least about 2×10 6 psi, and a thin, smooth, adherent, isotropic carbon coating on the substrate fiber having particular properties including a tensile fracture strain of at least about 5%.

Fiber reinforcing composites comprising portland cement having embedded therein precombined absorbent and reinforcing fibers

Abstract: Fibre reinforced composites of cementitious materials or gypsum are reinforced with pre-combined mixtures of strong reinforcing fibres eg, glass or steel, and water absorbent fibres, eg, cotton Examples of composites are cement pipes, wall boards, etc

Short Fiber orientation and its Effects on the Properties of Thermoplastic Composite Materials

Abstract: I. INTRODUCTION While it is true that preform processes involving the use of long or continuous fibers are known and used in the manufacture of reinforced thermoplastic articles–Azdel [1] or STX sheet [2], for example–it is generally the case that such articles are formed by injection molding. Both the feedstock requirements for this process and the occurrence of high melt shear during it ensure that only short fibers will be present in the finished article. Although the use of slow screw speeds, slow injection rates, low back pressure, wide sprues, runners, and gates, and large radii of curvature avoids fiber breakage during molding, such conditions are not often found in practice. Furthermore, the necessity of incorporating reground material into the feedstock also ensures short fiber lengths in the final part, lengths not greatly in excess of the critical length required for effective stress transfer from polymer matrix to reinforcing fiber. In a practical part, design uncertainties caused by fiber len...