K.E. Duckett

The study of ciliary frequencies with an optical spectrum analysis system

Abstract The cilia of rabbit tracheal epithelial cells beat at the rate of from 6 to 21 cycles/sec at physiological temperatures. The cilia of each cell show a frequency response which fluctuates within a frequency range specific to that cell. Cells from the same area of the trachea tend to fluctuate in the same frequency range. The frequency may be constant for several seconds or it may vary second-by-second in the range appropriate to the cell being measured. The frequency range can be altered in part by temperature. At 37 °C the frequency range may fluctuate by ± 3.5 beats/sec. As the temperature is decreased ciliary beat becomes more coherent and the frequency range decreases to ± 0.5 beats/sec at 5 °C. Frequencies are obtained with a photomultiplier system attached to a phase-contrast microscope. The mixed population of frequencies produced by the cilia passing through the transmitted light are sorted by Fast Fourier Transform analysis into discrete frequencies. With this system, frequencies of individual ciliated cells can be analysed in real time and for unlimited duration.

Torsional Fatigue and the Initiation Mechanism of Pilling

Torsional fatigue studies in polyester fibers have revealed that the fracture morphology of ruptured fiber surfaces is influenced by the level of torsional strain amplitude. At relatively high strain ampli tude the mechanism of fracture seems to be governed by the propagation of a single large crack. However, at low strain amplitudes, the fibers exhibit a slow and gradual breakdown of structure, starting with the surface layers. The surface morphology and the fracture phenomenon observed in the later case essentially resemble what happens in the formation of pills from polyester fibers in garments.

Biodegradable and Tensile Properties of Cotton/Cellulose Acetate Nonwovens

A possible candidate as an environmentally friendly nonwoven fabric is one that can be formed from the thermal calendering of a cotton/cellulose acetate blend. Our results focus on biodegradable properties of the fibers as well as tensile properties of the fabric. Cotton, which is a comfortable, absorbent, biodegradable fiber, is the base fiber in the nonwovens. Cellulose acetate, which is a thermoplastic, hydrophilic, mod ified cellulosic fiber, is used for the binder fiber. We examine the biodegradability of cellulose acetate, cotton, and these fibers in the blend using an ASTM standard pro cedure in which the amount of CO 2 evolved from the decomposition of cellulose acetate and cotton fibers due to microbial activity is monitored. Increased biodegra dation rates in fiber blends are attributed to the synergistic effects of multi-enzyme systems. Opening, blending, carding, and thermal calendering processes are used to fabricate the nonwovens. Pretreatment with solvent vapors is introduced to modify the softening temperatures of the cellulose acetate and to lower the calendering tem peratures. The success of this procedure is demonstrated in enhanced tensile strength of the nonwoven. In addition, modifying tensile properties with solvent vapor pre treatment shows how enhanced strength can be obtained with lower calendering tem peratures.

Mechanical Properties of Cotton/Polyester Yarns Part I: Contributions of Interfiber Friction to Breaking Energy

Samples of two cotton cultivars were spun with high- and normal-tenacity polyester staple fibers in cotton/polyester blend ratios of 100:0, 67:33, 50:50, 33:67, and 0:100. Stress-strain measurements provided tenacities, elongations, and breaking energies. Based on the stress-strain response of the pure cotton and pure polyester yarns, breaking energies were calculated for the yarn blends, with the assumption that the two different components did not interact. Differences between calculated and experimental values, which were maximum when the polyester content was about 60%, were attributed primarily to the interaction between the constituent cotton and polyester fibers. Support for this attribution was provided through measurements of energy lost when an oscillatory shearing motion was applied to 50-gram blended specimens of carded lap.

X-Ray and Optical Orientation Measurements on Single Cotton Fibers:

Diffraction patterns from single fibers have shown sufficient resolution in the 002 density peaks expected from near perfect spiral structures that direct measurements may be made independently of any theory. Single walls from fractured weakened fibers are observed between crossed polarizers and give an easy measure of fibril orientation. Both sets of measurements are used to corroborate the results obtained from a theoretical analysis of the 002 diffraction arcs recorded for bundle samples.

Color Grading of Cotton Part I: Spectral and Color Image Analysis:

Spectrometer measurements of the color of cotton based on CIE standards are investi gated and compared with high volume instrumentation (HVI) methods. Additionally, color imaging and spatial interpretation are examined with the intent of demonstrating the importance of color uniformity, trash content, and yellow spots on classer color grading. The result is that agreement between HVI color grading and the cotton classer can likely be enhanced by including the CIE color space redness parameter α*, trash content, and yellowness variability.

An Examination of the Fibrogram

The theory of the fibrogram has been derived based on the probability of randomly catching and holding a fiber. The amount axis has been shown to be proportional to the relative mass when related to the original specimen. Tangential equations are used to show that theoretically, for a length l or longer, the proportional mass, the mean length by number, the relative number, and the mean length by mass of fibers in the sample can be obtained from the fibrogram, as well as the number and mass arrays. Finally, the theoretical percentage of fiber by number or by mass extending a length l or longer from a clamped random sliver of the sample is obtainable from the fibrogram.

A Continuum Mechanics Approach to Twisted Yarns

A new formulation of the mechanics of deformation of continuous filament textile yarns has been carried out which utilizes the concepts of classical continuum mechanics, particularly the stress tensor. The stresses acting on a fiber are divided into a tensile stress T acting along its axial direction, and compressive stresses Pn and Pb acting in the direction of the normal and binormal vectors of the equivalent space curve. The resulting expressions for the stress distribution in the yarn and the applied tensile force and torque are more general than those derived by earlier researchers.

Energy Losses within Sheared Fiber Assemblies

A theoretical treatment of fiber-to-fiber frictional character and internal energy losses within an oscillating fibrous mass is presented. Experimental evaluation of the theoretical result is given and discussed in terms of the correlations ob tained by extending over a wide range of the variables involved. A single measurable parameter obtained from the energy loss mechanism is derived which characterizes the processibiliy of the fibrous material.

The Detection of Cotton Fiber Convolutions by the Reflection of Light

A device which allows the azimuthal monitoring of reflected light is described. The results of measuring the azimuthal angles between maximum reflected light and one-half of maximum reflected light are given for nineteen varieties of cotton of the G. barbadense and G. hirsutum species. This angle is shown to be a function of the induced convolutions in cotton fibers. These measurements by a new technique are compared separately with x-ray and microscopic orientation results. Also, comparisons are made between zero-gage tenacity versus 40% x-ray angle and zero-gage tenacity versus 50% optical angle.