Average Fiber Density Research Articles

Modifying the Sand Concrete with Recycled Tyre Polymer Fiber to Increase the Crack Resistance of Building Structures

Recently, the use of recycled tyre polymer fiber derived from waste tires as a concrete reinforcement has received a great deal of attention. The recycled tyre polymer fiber is a promising additive to concrete for building materials which require resistance against cracking. In this work, the effect of treated and untreated fiber on the properties of sand concrete was studied. It was shown that recycled tyre polymer fiber consists mainly of different fractions of crumb rubber, fiber, and metal fiber. The main polymer components in the fiber are polyamide and polyester threads of 6.5 mm length (l) and 0.05 mm diameter (d); the ratio l/d = 150; and the average fiber density is 0.923 g/cm3. It was established that the addition of untreated recycled tyre polymer fiber in the amounts of 11 and 19 kg/m3 into sand concrete leads to a decrease in compressive and flexural strengths by 15% and 21%, respectively. The reinforcement of concrete with the treated fiber in the amounts of 5 and 10 kg/m3 increases the flexural strength by 14% and 23.4%, respectively. The prismatic strength of the concrete which contents 5 and 10 kg/m3 of the treated polymer fiber was lower than that of ordinary concrete by 10.8% and 4.6%, respectively. The obtained results showed that the use of recycled tyre polymer fiber increases the crack resistance of concrete. The recycled tyre polymer fiber can be used as a cost-effective alternative to other types of low-modulus fibers to produce durable building materials.

Improving the precision in estimating cotton seed fibre density

An increasing demand for lightweight casual garments has driven the need for cotton with lower fibre fineness to facilitate production of finer yarns in the spinning mill. Breeding cottons with finer fibre (lower linear density) to address this target will reduce lint yield unless there is a concomitant change in another yield component. One yield component to consider is seed fibre density (FD) which is the number of fibres per unit seed surface area (SSA). FD can be measured also as the number of fibre initials on the seed coat at fibre initiation by scanning electron microscopy (SEM). In order for a cotton breeder to apply selection during breeding, an accurate measure of FD is required.Micronaire is a common, indirect measurement of cotton fineness but it is confounded by fibre maturity. This paper compares the use of micronaire with a direct measure of fineness in calculating FD. It compares mature seed estimated FD to FD determined by SEM imagery of one day old ovules, and determines the most reliable stage during flowering for quantifying FD. Data from five field experiments provided 1469 samples in which micronaire and fineness were compared for estimating FD. When using fibre fineness for calculation, the average FPS was 17,017, and the average FD was 157mm−2. The average FD by SEM was 5108mm−2, it was higher than FDfin because ovules were ∼4% of the final seed surface area due to growth dilution. Although micronaire and fineness were correlated, there was scatter in that relationship due to differences in fibre maturity. As a result, there were many instances where FD was overestimated when calculated by micronaire, compared with using fineness, such that less than 50% of the top 20% FD measured by fineness were identified by the top 20% of the samples in FD measured by micronaire. Results indicated FD measured by fineness on mature seeds obtained similar ranking to direct measures by SEM of FD on one day old ovules and the mid flowering stage was more reliable than early or late flowering. It was concluded that FD should be estimated by using fineness rather than micronaire because micronaire is not a reliable measure of fineness.

Stereological Study of the External Urethral Sphincter in the Female Urethra of the Lamb: A New Model for Studies on Urinary Continence

Some of the morphometrical features and functional properties of the lamb external urethral sphincter (EUS) were determined by means of ATPase histochemistry. In this study, eight female urethras of 2- to 3-month-old lambs were used. The samples were studied by using an unbiased stereological design and were statistically evaluated with a Kolmogorov-Smirnov test. Additionally, the mechanical activity of the different fibre types was analysed by measuring the isometric changes in tension induced by electrical field stimulation (EFS) of intrinsic nerves. The lamb EUS has an average fibre density of 1142.37 fibres/mm(2) (SD = 279.33). Our data showed the predominance of fast-twitch fibres or type II fibres, with a proportion of 30% (type I) and 70% (type II) in all cases. These percentages remained the same along the length of the EUS. However, a clear tendency to increase the number of both fibre types in the mid-EUS was observed. Interestingly, type I and II fibres are intermingled throughout the whole lamb EUS. Dynamic parameters of the contraction induced in lamb EUS preparations by EFS of intramural nerves, were intermediate between fast- and slow-twitch muscles. Furthermore, contractile activity showed no decrease in amplitude upon repetitive stimulation, suggesting the presence of a mixture of fibre types, in which fast but fatigue-resistant fibres (probably type IIA) seem to predominate. Our results indicate that lambs could be suggested as a new biological model to study those pathological processes, which involve the sphincteric regulation of the EUS.

Microstructure and property of Czochralski-grown Si–TaSi 2 eutectic in situ composite for field emission

Directional solidification of eutectic alloys yields various kinds of in situ composites with interesting and excellent properties, among which the semiconductor–metal eutectic with three-dimensional array of Schottky junctions grown in the composite is useful in electronic applications. This paper reports the experimental research on the Si/TaSi 2 rod-like eutectic composite for field emission. By the Czochralski crystal growth technique, the composite with highly oriented TaSi 2 fibres embedded in the (1 1 1) monocrystal n-type Si matrix is obtained. The average fibre diameter is 1.79 μm, the average fibre spacing is 10.0 μm and the average fibre density is 9.25×10 5/cm 2. The fibre distribution characteristic is also studied. The TaSi 2 fibres with hexagonal crystal structure present various cross-section shapes. Furthermore, the composite is preferentially etched to form the cone-shaped TaSi 2 field emission array protruding above the Si matrix and the field emission property measurement shows that the turn-on field is about 4.4 MV/m which is quite well.

Differences of morphometrical parameters in hind limb muscle fibres between ovarectomized and sexually intact female dogs

Slow and fast twitch fibres of the Mm. tibialis cranialis, semitendinosus and sartorius of seven sexually intact and seven ovarectomized female beagles were histochemically and morphometrically analysed. Along with type I and type IIA fibres, another main type II fibre (IIS), which seems to be peculiar to the dog, was found in the Mm. semitendinosus and tibialis cranialis. Type I fibers comprised 26% and type II fibres 74% of all recorded muscle fibres in the M. tibialis cranialis, 29% (type I) and 71% (type II) in the M. semitendinosus and 51% (type I) and 49% (type II) in the M. sartorius, respectively. The average single profile area and the corresponding mean diameter of fibre types I and II in the investigated hind limb muscles were generally larger in ovarectomized than in sexually intact animals. This was more evident in type II than in type I fibres. However only the type II fibres of the M. tibialis cranialis and sartorius exhibited a statistically significant increase in diameter (p < 0.01 and p < 0.05, respectively). Accordingly, the mean density (number of fibres/mm2) of both fibre types in the hind limb muscles of spayed dogs was generally reduced. Again, this reduction attained statistical relevance in the type I and II fibres of the tibialis cranialis. In addition, the fibre densities of type I in the semitendinosus and type II in the sartorius muscles were also significantly reduced in ovarectomized dogs. In conclusion, ovarectomized beagles showed a generally increased mean diameter of the investigated type I and II hind limb muscle fibres and a concomitant decreased average fibre density of the respective types when compared to sexually intact animals.

Distribution of Serotonin Immunoreactivitiy in the Main Olfactory Bulb of the Mongolian Gerbil

The distribution of serotonin immunoreactivity in the main olfactory bulb (MOB) of the Mongolian gerbil (Meriones unguiculatus) was examined by immunohistochemistry. Seven distinct layers of the Mongolian gerbil MOB-stained with cresyl violet were identified. Serotonin-immunoreactive (IR) cell bodies were not found in the MOB. The serotonin-IR nerve fibres had a specific laminar distribution and morphology in the gerbil MOB. Serotonin-IR nerve fibres were observed in the glomerular, external plexiform and granule cell layers of the MOB. These serotonin-IR nerve fibres showed varicosities that were larger than the thickness of the axon. The highest density of serotonin-IR nerve fibres was in glomeruli of the glomerular layer. The average fibre density in the glomerular layer was more than three to four times the density in the infraglomerular layers. Glomerular serotonin-IR fibres were much more intensively stained than infraglomerular serotonin-IR fibres. This result suggests that serotonin-IR nerve fibres of Mongolian gerbil MOB are extrinsic and may act to modulate the olfactory transmission.

Characterization of Asbestos Fiber Distribution on Membrane Filters from 25- and 37-mm Sampling Cassettes

Abstract In the occupational assessment of airborne asbestos fibers, non-uniform fiber distributions on membrane filters could be a significant factor in the overall precision of the analytical method because counting is allowed in any region of the filter and because only a small portion of the membrane filter is selected for counting. A laboratory study was conducted to characterize fiber distribution properly both within and among filter sectors (wedges) for two 25-mm cassettes with and without air flow trenches in the cassette bases, a 37-mm cassette with air flow trenches in the base, and a 37-mm circumferential orifice cassette. Chrysotile asbestos fibers were sampled at a 70 percent relative humidity to minimize electrostatic effects. Sampling variables were adjusted to obtain a fiber density which was statistically valid for counting purposes and approximately equivalent between filters of differently sized sampling cassettes. Fiber identification and counting conditions conformed to OSHA and NIOSH specifications. Along each of 6 (60°) radial sectors, 9 counting fields in the 25-mm filters and 20 counting fields in the 37-mm filters were selected in the middle of rings of equivalent area so that no region of the filter, on a per unit area basis, was under or over sampled relative to another region. In the 25-mm cassettes, no differences in fiber density among sectors attributable to cassette design were found. In the 37-mm cassettes with air flow trenches, fiber densities in on-trench sectors were greater than some, but not all, off-trench sectors. Fiber density in the region directly above the air flow channel in the base of the circumferential orifice cassette was greater than that observed in adjacent regions. In all cassette types examined, a trend of decreasing fiber density was observed from the middle to the outer regions of filters. This trend was especially prominent in the outer one-fourth to one-third, by distance, of the 25-mm filters. When filters were counted along a randomly selected radial line according to NIOSH counting rules, average fiber density did not differ from the average fiber density obtained in the detailed characterization. The results of the study suggest that the selection of radial or nearly radial counting lines, which can be made in 25-mm filters without regard for location relative to air flow trenches in the cassette base, are probably necessary to minimize the variability of the method and to make comparisons among different samples more meaningful.

Measurement of nerve fiber diameters in the region of the dorsal spinocerebellar and spinocervical tracts in the cat.

AbstractNerve fibers in the region of the dorsal spinocerebellar tract (DSCT) and the spinocervical tract (SCT) in the adult cat were measured at various spinal levels. Fiber measurements were made from photographs of transverse sections of Epon embedded material that had been fixed by vascular perfusion with a paraformaldehyde solution, post‐fixed in osmium tetroxide, and stained with Azur II‐methylene blue.The fiber diameter histograms from the region of the DSCT exhibited a bimodal distribution and between 50 to 75% of the fibers had a diameter of less than 5 μ. The presence of a subpopulation of large sized nerve fibers was identified between the 10 to 15 μ diameter intervals and this subpopulation appeared to decrease in size at the rostral spinal segments. This observation agrees with the electrophysiological studies of Lundberg and Oscarsson ('60) who found that the conduction velocity of the DSCT decreases at rostral levels.The fiber diameter measurements from the region of the SCT appeared to exhibit a unimodal distribution and between 40 to 75% of the fibers in this region had a diameter of less than 5 μ. By omission of fibers less than 5 μ, it could be shown that the mean values of the SCT decreased at successively rostral spinal levels. However, when the cumulative frequency distributions of the SCT data from different spinal levels were compared, a definite trend of statistically significant differences at the 0.05 level could not be established.The average fiber density (number of fibers/mm2) of the DSCT was 16,617 and the average fiber density of the SCT was 15,927.The heterogeneous organization of the dorsolateral fasciculus is discussed.

Wool Fiber Density of Shropshire Lambs

Wool fiber densities are discussed, results being obtained from 10 Shropshire lambs, sampled at 20 and 52 weeks of age. Seven body regions were considered: neck, back, dock, shoulder, side, hip, and belly. Fiber measurements were made near the base end of each lock by the method proposed by Hardy and Wolf (1942). The average fiber density at 20 weeks of age was 2517 fibers per square centimeter compared with 1970 fibers per square centimeter at 52 weeks of age. The high and low density regions when the lambs were 20 weeks of age were also high and low regions at the age of 52 weeks. The density at 20 weeks was highly correlated with density at 52 weeks. However, certain individual regions were not significantly correlated at the two periods. The dock, back, and shoulder fiber densities at 20 weeks are significantly correlated with the fiber density at 52 weeks for the same locations. From all considerations, analysis was to be limited to only one region. From weight of clean wool and body measurements, it was possible to estimate the fiber density of the sheep at 52 weeks of age. The estimated value ranked the sheep in practically the same order as did the measured fiber density. The wool producing area upon which the fiber density was estimated was based on a formula developed from sheep volume measurements. Differences between sheep, body regions, locks and ages are all highly significant. The differences within the regions may be due to order of sampling or more likely to gradients within the 16 square inch area sampled. The fiber density moreover changed during the growth period from 20 to 52 weeks. Indications were that the number of wool producing follicles remained constant but that they were spread out by the skin growth. A method for early selection of sheep for wool production has been developed, use being made of fiber density, fiber diameter, fiber length, body weight and body size. The correlations between the estimates and scoured value of clean wool at 52 weeks were highly significant. A significant regression relationship existed between these estimates and clean wool at 52 weeks. This provides a method of estimating from weanling measurements the clean wool content of a fleece at 52 weeks.