Range Of Fiber Diameters Research Articles

Millimeter-wavelength investigation of fibrous aerosol absorption and scattering properties

The measurements here are used to examine agreement with a recently developed theory for long-wavelength fibrous aerosol attenuative properties (extinction and components absorption, scattering). This is intended to be the final phase of a long and systematic examination of the theory's key features. In this case the parameters are high conductivities coupled with a broad range of fiber diameters. It is clear that there is a limit on the extinction efficiency or effective extinction cross section per unit fiber volume. This limit is represented by the fiber diameter of translucency, that is, the diameter at which the fiber is not completely opaque to the electromagnetic energy. The transition is approximated by the classical skin depth of the fiber. Above this diameter the peak extinction efficiency decreases with an increase in diameter at approximately the same rate for all conductors. The scattering resonance producing this peak becomes stronger as the diameter increases. Our data confirm that for fiber diameters below the skin depth the character of the attenuation is that of absorption.

Generation of fibrous aerosols from thin films

A method of producing relatively monodisperse, small-diameter (sub-500 nm diameter) aerosol fibers is described. This method involves the separation of porous thin films from their substrate. It was found that fibers with diameters of less than several hundred nm and lengths of several micrometers can be formed that do not adhere to one-another. Two μ m thick columnar thin films were fabricated and processed, yielding aerosol fibers with lengths up to 2 μ m and diameters up to 170 nm. Diameter and length distributions of a collected aerosol showed that a broad range of fiber lengths and diameters are formed by this method. Further modification of the method, however, is expected to greatly narrow the range of effective diameters and lengths obtained.

Levator palpebrae superioris fibre size in normals and patients with congenital ptosis.

A study of the histochemical staining of levator palpebrae superioris (LPS) was undertaken to measure the muscle fibre size in normal individuals and in patients with congenital dystrophic ptosis in order to see whether there is an alteration in muscle fibre size in congenital ptosis. Eight LPS specimens were obtained: 4 from normal patients (3 from normal levator divided in a bilateral brow suspension procedure and 1 from an exenteration specimen) and 4 from levator resection procedures for treatment of unilateral congenital ptosis. Cryostat sections from these specimens were stained histochemically to reveal muscle fibre types. The orthogonal diameters were measuring using a computer-generated program and the two groups compared using the Mann-Whitney mu-test. No statistically significant difference in muscle fibre diameter was found between normals and patients with congenital ptosis. There was also no change in the distribution or range of muscle fibre diameter in patients with congenital ptosis. Our findings do not support the classification of congenital ptosis as a dystrophy.

Optical fibre sensors for process tomography

This paper describes an investigation into the use of an optical fibre sensor to measure the flow of pneumatically conveyed solid particles. Typical results for the mass flow rate of dry sand versus transducer output voltage are presented for a 1 mm diameter sensor fibre. The frequency bandwidth of the sensor is determined for a range of fibre diameters and compared with the calculated response obtained using spatial filtering considerations.

Glass fiber manufacturing and fiber safety: the producer's perspective.

Historically, the potential health effects of airborne fibers have been associated with the dose, dimension, and durability. Increasing focus is being placed on the latter category. Concern about airborne fiber safety could be reduced by manufacturing fibers that are not respirable; however, due to performance and manufacturing constraints on glasswool insulations, this is not possible today. These products are an important part of today's economy and as a major manufacturer, Owens-Corning is committed to producing and marketing materials that are both safe and effective in their intended use. To this end, manufacturing technology seeks to produce materials that generate low concentrations of airborne fibers, thus minimizing exposure and irritation. The range of fiber diameters is controlled to assure effective product performance and, as far as possible, to minimize respirability. Glass compositions are designed to allow effective fiber forming and ultimate product function. Fiber dissolution is primarily a function of composition; this too, can be controlled within certain constraints. Coupled with these broad parameters is an extensive product stewardship program to assure the safety of these materials. This article will discuss the factors that influence glasswool insulation production, use, and safety.

Fabric-Evoked Prickle

A simple subjective test method is described to evaluate the prickliness of fabric samples, and its reproducibility and consistency are assessed. The test is used to evaluate the prickliness of a set of wool knitted samples covering a range of fiber diameters. The finer (19 micron) wool samples are nonprickly, and prickle increases as the mean fiber diameter increases. Reducing fiber/fiber friction with silicones reduces prickle, suggesting that a reduction of fiber/fiber friction is an important mechanism in antiprickle treatments.

The number of fibers and range of fiber diameters in the cochlear nerve of three odontocete species

The total number of fibers and the range of fiber diameters in the cochlear nerve of three species of toothed whales were determined. There are 90 672 fibers in Lipotes vexillifer, 82 570 in Neophocaena phocaenoides, and 77 171 in Sousa chinensis. In Lipotes the fiber diameters range from 0.4 to 25.8 μm, with a modal diameter of 9.5 μm, and the largest fiber measures 35.2 μm; in Neophocaena, the diameter ranges from 0.6 to 36.0 μm, with a mode of 9.5 μm, and the largest fiber measures 54.9 μm; in Sousa the diameter ranges from 0.3 to 39.7 μm, with a mode of 8.5 μm and the largest fiber measures 50.3 μm. In Lipotes, Neophocaena, and Sousa, 1.5, 8.5, and 14.2%, respectively, of the cochlear fibers are ≥ 20 μm in diameter. Almost all the fibers are myelinated, and the ratio of the diameter of the axis cylinder to the outer diameter of the fiber in each species averages between 0.6 and 0.7. The high percentage of large fibers and the very wide range of fiber diameters indicate that the odontocete cochlear nerve is specialized for high-speed communication with the brain. The maximum diameters of the myelinated fibers of the cochlear nerve reported in this paper are the largest diameters recorded for the cranial nerve, or any other nerve, among the vertebrates.

Structure and properties of ceramic fibers prepared from organosilicon polymers

This paper is a review of structure and properties of ceramic fibers derived from organosilicon polymers, with emphasis on the author's research. Ceramic fibers are prepared from organosilicon polymers by melt-spinning, cross-linking, and pyrolysis. Desirable polymeric precursors display the following properties: high char yield of desired composition, thermal stability at melt-spinning temperature, stable rheology, high purity and freedom from particulate impurities, and ability to undergo rapid cure (cross-linking). Ceramic fibers in the Si-C-O or Si-C-N-O systems display a rich nanostructure consisting of some or all of the following metastable phases: (1) an amorphous, continuous siliconoxycarbide or siliconoxycarbonitride phase; (2) dispersed carbon nanocrystallites; (3) dispersed β-SiC or Si3N4 nanocrystallites; and (4) closed, globular nanopores. The crystalline phases increase in volume fraction and crystallite size as stoichiometry approaches the crystalline composition and as pyrolysis temperature increases. The Si-C-N-O fibers are amorphous. Pore size increases and total pore volume decreases with increasing pyrolysis temperature. Considerable variation in ceramic fiber composition can be achieved by varying cure conditions and pyrolysis atmosphere. Polycrystalline SiC fibers can be produced by pyrolysis above 1600°C. Fiber diameters range from 7 to 20 µm. Elastic moduli vary from 140 to >420 GPa (20 to >60 Msi) and are controlled by composition, nanostructure, and fiber density. Fiber densities range from ∼2.2 to >3.1 g/cm3. Tensile strengths range up to ∼5 GPa (700 ksi) and are Griffith flaw-controlled.

A computational test of the requirements for conduction in demyelinated axons

Conduction in demyelinated and remyelinating axons has been simulated with a computational model. The calculations made use of recent determinations of ionic channel densities in the internodal axolemma of Xenopus fibers. Several new morphological measurements reduced the number of parameters not directly obtained from experimental data. Action potentials and ionic currents were calculated for a wide range of fiber diameters and internodal lengths. The earliest stage of remyelination, characterized by Schwann cell attachment and extension of processes, was simulated by covering just a small percentage of the internode by a single cell layer. Conduction invariably failed if the internodal Na+ channel density was zero. The minimum density required for successful propagation agreed well with that measured in loose patch clamp experiments. Lateral diffusion of Na+ channels from nodes of Ranvier into the demyelinated internode did not restore conduction in blocked axons, and this was true regardless of the initial internodal Na+ channel density. Decreases in the internodal K+ channel density improved the safety factor for conduction, but this was significant only in the largest axons. Simulating minimal paranodal demyelination by eliminating the axo-glial junctional seals did not result in conduction block, but did produce large conduction delays.

Neutron measurements on ZFX

The NRL ZFX Facility is being used to form dense Z pinches from single fibers composed of cryogenically frozen deuterium (D2) or deuterated polyethylene (CD2). Fiber diameters range from 40 to 125 μm. Maximum current through all these pinches has been about 1 MA with a rise time of 670 ns. Total neutron yields per shot are measured with a pair of rhodium foil activation counters mounted coaxial and perpendicular to the fiber axis. In order to include the effects of external scattering and absorption these detectors are calibrated in situ using a 252Cf neutron source at the pinch location. Total neutron yields have also been determined using bubble detector dosimeters. This is believed to be the first application of these detectors on a pulsed plasma source. Neutron energy spectroscopy and production time are determined with either a pair of scintillator/photomultiplier detectors located at two different perpendicular distances from the pinch axis or a single microchannel plate photomultiplier (μcp-pmt) detector. Both x-ray shielding and neutron flux collimation are required on these detectors. Typically the detected neutrons (up to 2×109 per shot) were emitted in two to four distinct but overlapping 150–200 ns wide bursts starting 300–400 ns after the current initiation.

SUBSTITUTION BETWEEN WOOLS OF DIFFERENT FIBRE DIAMETER1

The extent to which wools with different fibre characteristics can be substituted in textile production and consumption holds implications for Australia's international and domestic marketing policies. An analysis of price‐induced substitution between Australian wools of different fibre diameters was conducted. Fibre diameter was used to parameterise cross‐price relationships in order to estimate a system of demand equations for wools by diameter class. The results indicate that direct substitution takes place within a very limited range of fibre diameters. The use of product characteristics to parameterise price relationships may be extended to other graded commodities.

Motor and sensory fibers of the superior laryngeal nerve in the rat. A light and electron microscopic study.

A quantitative and qualitative study of the superior laryngeal nerve (SLN) and its branches was performed on the intact nerve and after experimental denervation procedures. The distribution patterns of the myelinated fibers of the intact internal (SLNI) and external (SLNE) branches in the rat were unimodal with a fiber diameter range of 0.5-12 microns and with peaks at 2-4 microns. Numerous unmyelinated fibers, ranging in diameter from 0.1-2.3 microns, were evenly distributed all over the nerve. The SLNI contained no degenerated myelinated fibers after intracranial vagotomy, but about 25% of the unmyelinated fibers showed degenerative features. In the SLNE 2-10% of the myelinated fibers and about 25% of the unmyelinated fibers were degenerated after the same procedure. Extracranial vagotomy caused degeneration of nearly all fibers in the SLNI and SLNE. Single unmyelinated fibers appeared normal after this procedure. Occasional myelinated and a few unmyelinated fibers were degenerated after excision of the superior cervical ganglion. It is inferred from the results that a majority of the myelinated fibers in the SLN (96-99%) are sensory, with the cell bodies in the extracranial vagal ganglia. The SLNE was also found to be predominantly sensory, as only 2-10% of the myelinated fibers and about 25% of the unmyelinated fibers had their cell bodies in the brainstem. Single myelinated and a few unmyelinated fibers in both the SLNI and SLNE had their origin in the superior cervical ganglion.

Monte Carlo model of microporous plane membranes

A Monte Carlo based membrane model has been developed to predict the pore characteristics of microporous plane polytetrafluoroethylene membranes. Various correlations have been established to calculate the hydraulic and equivalent radii, the area and perimeter of the pores from the porosity (range 50% – 90%) and fibre diameter (range 0.1 – 0.3 μm). Good agreement is obtained when comparison is made with real gas membranes examined by microphotography.

Mechanical properties of vapour-grown carbon fibres

Vapour-grown carbon fibres are formed by depositing layers of carbon from hydrocarbon pyrolysis on precursors of filamentous carbon. They are partially graphitic with the basal planes preferentially oriented as nested coaxial cylinders. As the fibres are axially strained, their stiffness increases by about 28%, probably due to strain-induced increase in the preferred orientation. Vapour-grown fibres 7.5 mu m in diameter have a tensile strength of 2.92 GPa (0.42*106 PSI) and a modulus of 237 GPa (34*106 PSI). Both the tensile strength and the modulus shows an apparent dependence on fibre diameter. Larger-diameter fibres have a lower modulus and tensile strength than smaller-diameter fibres. This apparent dependence of fibre mechanical properties on diameter is shown to be due to nonuniform carbon deposition rates along the length of the fibre growth reactor. In a given growth experiment, a range of fibre diameters are produced in a fixed period with the larger-diameter fibres deposited at a higher rate. X-ray studies of fibres having a range of diameters and hence deposition rates show that the graphitic ordering of small-diameter fibres (low deposition rates) is more complete than that of large-diameter fibres, thus accounting for the larger modulus of small-diameter fibres.

Fibre Diameter and the Transfer of Wool Fibres

The possibility that fibre diameter is a factor in the transfer of wool fibres is discussed in relation to a recent case. Fibre diameter may be important in the fragmentation of fibres under pressure, and may result in a greater proportion of fine, as opposed to coarse, woollen fibres being transferred to a recipient garment. Therefore, there may be selective transfer of fine over coarse woollen fibres when there is a wide range of fibre diameters in the donor item.

Myelination determines the caliber of dorsal root ganglion neurons in culture

In order to understand the relationship of supporting cells to the differentiation of neurons in culture, we have used morphometry to study myelination of dorsal root ganglion (DRG) neurons by central or peripheral supporting cells. Dissociated DRG cultures from 15-day rat embryos, free of Schwann cells and fibroblasts, were prepared, and supporting cells were added from spinal cord or DRG; myelination commenced after 2 weeks. Control cultures received no supporting cells. At 7, 14, and 24 days, a total of 22 cultures were processed for electron microscopy. Three fascicles from defined points were sampled from each culture. In cultures containing glial cells, smaller fibers (p less than 0.001) were myelinated (mean of median diameter, 1.13 +/- 0.13 (SD) micron) than in cultures containing Schwann cells (1.67 +/- 0.17 micron), although there was no difference (p greater than 0.1) in the degree of myelination expressed as number of myelin lamellae/fiber. A new finding concerned the relationship of axonal diameter to the presence or absence of myelinating cells. In control cultures without supporting cells or in areas where supporting cells were absent, the range of neurite diameter (0.05 to 1.25 micron) and the median diameter (mean of median, 0.24 +/- 0.03 micron) were similar at different times (7, 14, and 24 days), demonstrating a stable population of neurite diameters throughout the period. In myelinated fascicles, a different distribution of neurite diameters was present. Myelinated neurites had a greater median diameter (measured to inner border of myelin) and a different range of fiber diameters compared to bare neurites. For Schwann cells, this range was 0.7 to 3.4 micron, and the mean of median diameters was 1.67 +/- 0.17 micron; for glial cells, the range was 0.6 to 2.4 micron, and the mean of median diameters 1.13 +/- 0.13 micron. Differences between myelinated and bare fibers were all highly significant (p less than 0.001).(ABSTRACT TRUNCATED AT 250 WORDS)

Changes in electrical properties and quantal current during growth of identified muscle fibres in the crayfish.

The muscle fibre electrical properties, miniature excitatory junctional current (m.e.j.c.) and miniature excitatory junctional potential (m.e.j.p.) were studied during growth of an identified crayfish muscle fibre from a diameter of 20 to 400 microns. The specific membrane resistance (Rm), and the specific internal resistance (Ri), of the muscle fibre were independent of fibre diameter (d) during growth. The current-voltage relation has a similar shape in large and small fibres, indicating that voltage dependence of Rm does not change during growth. The input resistance (R0) was approximately proportional to d-1.5, as predicted theoretically. The specific membrane capacitance (Cm) and the membrane time constant (Tm) increased linearly with fibre diameter, apparently as a result of the contribution of the tubular capacitance to Cm. The decrease in R0 and the increase in Tm should have resulted in a 90-fold decrease in m.e.j.p. amplitude during growth of the fibre from a diameter of 20 to 240 microns. However, m.e.j.p. amplitude was found to decrease only 21-fold. This discrepancy was shown to result from an increase in m.e.j.c. amplitude and duration during growth. There was 2.9-fold increase in m.e.j.c. amplitude and a 2.7-fold increase in m.e.j.c. duration over the range of muscle fibre growth studied. This increase in the m.e.j.c. apparently results from an increase in the magnitude and duration of the synaptic conductance change produced by a quantum of transmitter. Throughout the range of muscle fibre diameters studied, the muscle fibre effective input impedance for the m.e.j.c. was 17-19% of R0. This is due to the relatively large Cm and the short duration of the m.e.j.c.

20—PROCESSING TRIALS ON WOOL CLASSED BY OBJECTIVE CLIP PREPARATION

This paper describes part of a programme of worsted processing trials of wools prepared by objective clip preparation (OCP) in accordance with the Australian Clip Preparation Standards. In each of four merino clips, chosen to cover the range of mean fibre diameter encountered in Australian merino wools, fleece wool prepared by OCP and by traditional methods was compared for processing performance. It is concluded that the variability of diameter of an OCP line is essentially the same as that of traditional lines classed from the same mob; that the properties of tops made from individual OCP lines are similar to those of tops made from traditional lines of the same mob, spinning performance and yarn characteristics being normal; and that, on average, the weight of card losses from OCP lines is the same as the combined weight of carding losses that would be obtained if the wool had been classed into quality-number lines and processed separately; a similar conclusion can be drawn for combing noil.

Routing of transported materials in the dorsal root and nerve fiber branches of the dorsal root ganglion

After injection of the L7 dorsal root ganglion with 3H-leucine, fast axoplasmic transport carries some 3--5 x more labeled materials down the sensory fibers branches entering the sciatic nerve as compared to the dorsal root fiber branches of the neurons. Freeze-substitution preparations taken from the two sides of the lumbar seventh dorsal root ganglia of cats and monkeys showed little difference in the histograms of nerve fiber diameters of the sensory nerve fiber branch of these neurons as compared to the dorsal root fiber branches. A similar density of microtubules and of neurofilaments in the dorsal root and sensory nerve fiber branches over a wide range of fiber diameters was found in electron micrograph preparations. In the absence of an anatomical difference in the fibers to account for the asymmetrical outflow, a functional explanation based on the transport filament model was advanced.

La Responsibilite Medicale (5th Edn)

In order to understand the relationship of supporting cells to the differentiation of neurons in culture, we have used morphometry to study myelination of dorsal root ganglion (DRG) neurons by central or peripheral supporting cells. Dissociated DRG cultures from 15-day rat embryos, free of Schwann cells and fibroblasts, were prepared, and supporting cells were added from spinal cord or DRG; myelination commenced after 2 weeks. Control cultures received no supporting cells. At 7, 14, and 24 days, a total of 22 cultures were processed for electron microscopy. Three fascicles from defined points were sampled from each culture. In cultures containing glial cells, smaller fibers (p less than 0.001) were myelinated (mean of median diameter, 1.13 +/- 0.13 (SD) micron) than in cultures containing Schwann cells (1.67 +/- 0.17 micron), although there was no difference (p greater than 0.1) in the degree of myelination expressed as number of myelin lamellae/fiber. A new finding concerned the relationship of axonal diameter to the presence or absence of myelinating cells. In control cultures without supporting cells or in areas where supporting cells were absent, the range of neurite diameter (0.05 to 1.25 micron) and the median diameter (mean of median, 0.24 +/- 0.03 micron) were similar at different times (7, 14, and 24 days), demonstrating a stable population of neurite diameters throughout the period. In myelinated fascicles, a different distribution of neurite diameters was present. Myelinated neurites had a greater median diameter (measured to inner border of myelin) and a different range of fiber diameters compared to bare neurites. For Schwann cells, this range was 0.7 to 3.4 micron, and the mean of median diameters was 1.67 +/- 0.17 micron; for glial cells, the range was 0.6 to 2.4 micron, and the mean of median diameters 1.13 +/- 0.13 micron. Differences between myelinated and bare fibers were all highly significant (p less than 0.001).