Fibre Diameter Profiles Research Articles

Connecting in situ cone/jet length in electrospinning to fiber diameter and drug release for the rational design of electrospun drug carriers

Towards enabling the rational design of electrospun drug carriers, this study investigated relationships between cone/jet features in electrospinning and operating/solution parameters, fiber diameter or drug release profiles. Cone/jet length were visualized real-time during electrospinning of budesonide (BUD)-loaded poly(caprolactone) (PCL) and poly(D,L-lactide-co-glycolide) (PLGA) solutions. Voltage was varied for BUD-PCL at fixed drug/polymer ratio of 7.4 %, while solution concentration was modulated for BUD-PLGA resulting in drug/polymer ratios of 3.3–4.3 %. In both the BUD-PCL and BUD-PLGA systems, cone length and fiber diameter shared a strong linear relationship (R2 = 0.99, 0.98 respectively). PCL meshes exhibited bi-phasic release profiles, releasing ∼ 95 % BUD over 7 days regardless of fiber diameter, while PLGA meshes exhibited diameter-dependent controlled release. Despite the inconsistent relationship between fiber diameter and release, straight jet length in electrospinning was well-correlated with the Korsmeyer-Peppas parameter for BUD-PCL and the zero-order release parameter for BUD-PLGA (R2 = 0.71, 0.94 respectively). This approach of cone/jet visualization can reduce trial–error experiments and circumvent the cumbersome optimization of several electrospinning parameters for the design of drug-loaded electrospun meshes.

Environmental influence on Merino sheep wool quality through the lens of seasonal variations in fibre diameter

Wool production in arid and semiarid rangelands is strongly affected by environmental variability. Seasonal fluctuations of the environmental conditions drive variations in the nutritional status of the sheep, wool growth and quality. The variation of fibre diameter during the annual growth period can be observed through the Fibre Diameter Profiles (FDP). The FDP provide a retrospective description of animal responses to varying environmental and management conditions during the wool growth period. Certain characteristics of FDP influence wool quality because this is associated with the performance during processing. The aim of this paper was to assess the variation of the FDP during the 2014–2015 wool growth period on farms located in a longitudinal environmental gradient of Northern Patagonia, Argentina. Some features of the FDPs were found to be associated to the geographical location of the farms. For example, the minimal fibre diameter occurred at different times on the farms during the annual wool growth. The results of this paper support the relevance of the environment in generating seasonal variations in fibre diameter, which might be associated to animal stressful circumstances. However, future research is needed to better understand the influence of climatic conditions and other stressful circumstances for animals.

Generation of 2 μm radiation due to single-mode fibers with longitudinally varying diameter

Abstract We report on numerical modeling of the spectral dynamics of telecom range laser pulse of moderate power in a silica fiber with a flattened dispersion and longitudinally varying diameter. In the simulation experiments, the optimal fiber profile has been proposed for more than 60% energy transfer from the initial telecom range pulse to subpicosecond pulse at 2.2–2.3 μm. Another option of the fiber diameter profile provides flat radiation spectrum in the range 2–2.5 μm.

Subpicosecond pulse generation above 2 μm in longitudinally inhomogeneous single-mode fibres

We consider the evolution of the spectrum of a medium-power input telecom laser pulse during propagation in a longitudinally inhomogeneous flattened dispersion silica fibre. Using modelling results, we find an optimal longitudinal fibre diameter profile ensuring transfer of more than 60 % of the input pulse energy to a subpicosecond pulse in the range 2.2 – 2.3 μm.

Response of fiber diameter to a continuously changing draw ratio in a laser drawing process

The controllability of the fiber diameter profile with a changing draw ratio in a laser drawing process is discussed in comparison with model calculations. The take-up speed in the continuous drawing process was changed under constant acceleration, and the diameter profile of the resultant fiber was monitored on-line. It was revealed that the diameter profile was consistent with a profile predicted by a model calculation up to a certain acceleration. The profile was calculated by assuming a stationary neck-drawing point and elastic deformation of the fiber in the drawing system. Video observation revealed that the neck-drawing point did in fact move with changes in the draw ratio. Moreover, it moved faster at higher accelerations, particularly when the draw ratio was increased from low to high. It seems that the faster movement of the neck-drawing point causes the observed diameter change to lag behind that predicted by the model. The responsiveness of the diameter change could be further improved by shortening the distance between the feed and take-up rollers. The minimum response length was 5 cm as the draw ratio decreased from 8.0 to 4.0.

Melt-spinning basalt fibers based on dielectric heating and steady-state process characteristics

In this study, we introduce a new melt-spinning technology for producing basalt fibers on a laboratory scale and provide a dynamic model describing the basalt-fiber spinning process with the thermal effect in terms of an Arrhenius equation. The new trial system for basalt melt-spinning was established, while a microwave furnace was used to melt the quarried basalt rocks. And a susceptor, i.e., silicon carbide (SiC) was applied. A crucible with a one-hole bushing took the role of the spinning block, which was placed in the heating zone. A take-up device controlled by a PC was installed and the take-up speed was varied in order to investigate the fiber drawing effect on the thickness produced. Experimental results demonstrated that this new system is feasible for producing basalt fibers. The theoretical estimate of the fiber diameter profile with the Arrhenius viscosity description along the spinning line agreed well with the measurement. The diameter profile of the basalt fibers decreased with a funnel-shaped profile along the spinning line, while it changed very rapidly near the bushing hole up to the position 15 mm downwards, and then the fiber diameter decreased further up to the position 30 mm. In the remaining spinning zone the diameter reduction was very small. The gravitational effect of the molten basalt in the crucible on the fiber diameter was negligible.

The effects of pasture inputs and intensive rotational grazing on superfine wool production, quality and income

A farmlet experiment was conducted between July 2000 and December 2006 as part of the Cicerone Project, which sought to enhance the profitability and sustainability of grazing enterprises on the Northern Tablelands of New South Wales, Australia. A self-replacing Merino enterprise was grazed as the dominant livestock enterprise, together with ~20% of the carrying capacity as cattle, on each of three farmlet treatments: higher levels of soil fertility and pasture renovation with flexible rotational grazing over eight paddocks (farmlet A), moderate soil fertility and pasture renovation with flexible rotational grazing over eight paddocks (farmlet B) and moderate soil fertility and pasture renovation with intensive rotational grazing over 37 paddocks (farmlet C). Prior to commencement of the trial, the three 53-ha farmlets were allocated equivalent areas of land based on soil type, slope and recent fertiliser history. This paper describes the effects of the three pasture and grazing management strategies on the production, quality and value of the wool produced per head, per ha and per farmlet. Up until 2001 there were no differences in wool production between farmlets. Thereafter, significant differences between farmlets emerged in greasy fleece weight per head and price received per kg of fleece wool. For example, the clean fleece value averaged over the 2003–05 shearings for all hoggets, ewes and wethers was 1531, 1584 and 1713 cents/kg for farmlets A, B and C, respectively. There were small but significant differences, which varied between sheep class and year, between the farmlets in average fibre diameter and staple length but less so with staple strength. In general, while the differences between farmlets in staple strength varied over time, farmlets A and B tended to have wool with longer staple length and broader fibre diameter than farmlet C and this affected wool value per kg. Differences in wool income per ha between farmlets grew in later years as the farmlet treatments took effect. In spite of farmlet A having a slightly lower wool value per kg, after taking into account its greater fleece weight per head and its higher stocking rate, the total wool income per ha was higher than on either farmlets B or C. The average gross wool income per ha from 2003 to 2005 was $303, $215 and $180 for farmlets A, B and C, respectively. The highest amount of greasy wool produced was in 2004 when 38.2, 26.5 and 21.5 kg/ha was harvested from farmlets A, B and C, respectively. The fibre diameter profiles of 2-year-old ewes showed similar profiles for farmlets A and B but a significantly finer fibre diameter profile for farmlet C ewes due to intensive rotational grazing. However, sheep on all three farmlets produced wool with high staple strength. Multivariate analyses revealed that greasy fleece weight, staple length and staple strength were significantly positively correlated with the proportion of the farm grazed at any one time, and with soil phosphorus, legume herbage and green digestible herbage thus highlighting the significant influence of pasture and soil inputs and of grazing management on wool production and quality.

Optical nanofibers and spectroscopy

We review our recent progress in the production and characterization of tapered optical fibers with a sub-wavelength diameter waist. Such fibers exhibit a pronounced evanescent field and are therefore a useful tool for highly sensitive evanescent wave spectroscopy of adsorbates on the fiber waist or of the medium surrounding. We use a carefully designed flame pulling process that allows us to realize preset fiber diameter profiles. In order to determine the waist diameter and to verify the fiber profile, we employ scanning electron microscope measurements and a novel accurate in situ optical method based on harmonic generation. We use our fibers for linear and nonlinear absorption and fluorescence spectroscopy of surface-adsorbed organic molecules and investigate their agglomeration dynamics. Furthermore, we apply our spectroscopic method to quantum dots on the surface of the fiber waist and to cesium vapor surrounding the fiber. Finally, toward dispersive measurements, we present our first results on building and testing a single-fiber bimodal interferometer.

Measurement Precision and Evaluation of the Diameter Profiles of Single Wool Fibers

A recent model of the Single Fiber Analyzer 3001 (SIFAN3001) was firstly employed to obtain the single wool fiber diameter profiles (SfFDPs) at multiple orientations. The results showed that using SIFAN3001 to measure fiber diameter at four orientations for 50 single fibers randomly sub-sampled from each mid-side sample can produce average fiber diameter profiles (AS fFDPs) of fibers within staples. Within the testing regime used, the precision estimates for the total samples were ±1.3 µm for the mean fiber diameter of staples and 1.4 µm for the average fiber diameter of the AS fFDPs at each scanned step in the diameter profile. The mean diameter ratio (ellipticity) obtained from the four orientations was 1.08±0.01, confirming that the Merino wool fibers under review were elliptical rather than circular. The elliptical morphology of wool fibers and the precision of the fiber diameter measurement at each point along a fiber will be considered in the development of a mechanical model of Staple Strength testing.

Modeling Melt Spinning of PLA Fibers

A modified version of a model for fiber spinning was developed for poly(lactic acid) (PLA) based on earlier models that predicted the spinline behavior of poly(ethylene terephthalate) (PET) and Nylon 6.6. Comparisons were made to melt‐spinning data of Takasaki and coworkers for high lactic acid (L)‐content PLA (PLLA) and racemic mixtures of the L‐ and D‐ forms over a range of spin speeds from high‐ to low‐speed conditions. The characteristic necking and “freeze off” under high‐speed conditions is not as severe with PLA as that observed in the earlier model systems, most likely due to the more highly entangled nature of PLA. To address this, the extended pom‐pom model was utilized to model the melt phase. Because of the stereochemistry of PLA, mixtures of the L‐ and D‐ forms result in an additional stereo‐crystal formation with a higher melting temperature than the normal alpha‐crystal formation. In addition to accurately capturing fiber diameter profiles for the PLLA, all the important features of spinning of the racemic mixture (r‐PLA) were also successfully captured with our model. Besides diameter predictions, the model also successfully predicts the elongation to break of the spun fiber by correlating it to the calculated ratio of amorphous to total stress at the freeze off point. In modeling both PLLA and r‐PLA, further insight was gained into the relationship between thermally induced crystallization and flow‐enhanced crystallization.

Environmental responsiveness of fibre diameter in grazing fine wool Merino sheep

Fibre diameter, fibre length, and the ratio of fibre length growth to mean fibre diameter (L/D), fibre diameter profile characteristics, and staple strength were examined in 16 fine wool Merino wethers in a 12-month field experiment. Variations in fibre diameter, fibre length, and L/D were shown to be associated with fibre diameter profile characteristics and staple strength. At constant fibre diameter, L/D was significantly positively related to variation in fibre diameter along the staple. A positive correlation between seasonal variation in L/D and variation in diameter between fibres was also observed. Staple length was significantly positively correlated with along-staple variation in fibre diameter and negatively correlated with variation in fibre diameter among fibres. Among-fibre variation in fibre diameter was not significantly correlated with along-staple variation in fibre diameter. Seasonal variation in fibre length growth, fibre diameter, and the ratio of length to diameter throughout the year was associated with increased variation in fibre diameter along the fibre diameter profile and reduced staple strength in grazing sheep. Seasonal variation in fibre diameter was mostly related to mean fibre diameter, L/D, and seasonal variation in fibre length growth rate. Changes in fibre diameter throughout the year were also related to seasonal changes in body weight, fat depth, and skin thickness.

Comparison of the 'Measure as you Grow' technique for measuring fibre diameter profiles between two laboratories and two sample sites

Fibre diameter (FD) was measured on 2 mm snippets of wool from the base of staples and compared between 2 laboratories and 2 sample sites for 6 flocks. The base snippets were taken at regular intervals during the year, and the FD was plotted against staple length to produce a FD profile. There was a mean bias of 0.4 µm between laboratories in estimating the mean FD of the profile. The hipbone sample site was 0.96 µm broader than the mid-side, although this differed significantly between flocks. The staple length estimates between both laboratories were strongly correlated (research2 = 0.99). There was no difference in the precision of estimating FD profile between the sample sites. The confidence limit of a mean FD estimate at a point along the staple profile was ± 0.54 µm within a sample site. The 'measure as you grow' technique for estimating FD profile parameters appears precise enough to be used as a guide to growers. However, other alternatives need to be investigated which provide a more accurate and precise estimate of the FD profile.

Diameter Profile Measurements for CO2 Laser Heated Drawing Process of PET Fiber

Abstract Poly (ethylene terephthalate) (PET) fiber was heated by carbon dioxide laser radiation in the continuous drawing process. By this procedure, the position of the deformation region could be fixed precisely in the air. The location of neck-like deformation fluctuated within a range of about 0.2 mm for draw ratios of 4.0 to 4.5 and within a range of about 0.5 mm for draw ratios of 5.5 to 6.0, but the location fluctuated over a range of 1.0 mm for a draw ratio of 5.0. Fiber diameter profiles, which were used to calculate Hencky strain rate profiles and apparent elongational viscosity profiles, were obtained from high-speed video camera images of the deformation region. Regardless of draw ratio, apparent elongational viscosity exhibited almost the same minimum value. Apparent elongational viscosity is much lower than the value obtained by measurement at a low, constant strain rate, but the elongational stress acting at the point where apparent elongational viscosity begins to increase steeply (Hencky strain of about 1.0) is of the same order of magnitude as the reported value. For draw ratios less than 5.0, the temperature where apparent viscosity is lowest is about 100 to 120°C, which corresponds to the flow temperature of amorphous PET, whereas for draw ratios exceeding 5.0 the temperature where apparent viscosity is lowest is about 80°C, which corresponds to the glass transition temperature. Thus, the former corresponds to so-called neck-like deformation typically observed in high-speed spinning, and the latter corresponds to necking typically observed in cold drawing. These two types of deformation appear in turns for a draw ratio of 5.0, and therefore the location of the deformation region fluctuates greatly. This measurement system can be used as a high-strain-rate elongational rheometer for analyzing practical polymer processing systems, which can easily measure the precise on-line deformation history with a time resolution in the μs level.

The effect of ration sequence on the staple strength of genetically high and low wool producing Merino wethers

A controlled feeding experiment, designed to maintain liveweight while changing dietary crude protein content, was conducted with medium wool Merino wethers of high (fleece-plus) and low (fleece-minus) wool growing capacity. The sheep were split into 3 groups and offered a ration of medium (17%) protein content throughout the experiment (Control), a sequence in which the ration changed from medium to high (27%) then low (7%) protein content, or a ration sequence of medium–low–high protein content. While diets were offered at a level designed to be isoenergetic, incomplete intake of the low protein ration resulted in the energy intake of sheep receiving this ration being significantly (P < 0.05) less than the energy intake of sheep receiving the other two rations.Feeding regime significantly influenced staple strength of fleece-plus, but not fleece-minus sheep. Fleece-plus sheep receiving the ration sequence that changed from medium to low to high protein content grew wool with significantly (P < 0.05) lower staple strength than fleece-plus sheep receiving either of the other ration sequences. Liveweight changes throughout the experiment were small and did not explain any of the variance in staple strength. Analysis of fibre diameter profiles measured using autoradiography indicated along-fibre variation in diameter was influenced by genotype and feeding sequence, while between-fibre variation in diameter was influenced by feeding sequence only. Regression analysis indicated two models, one containing between-fibre variation in diameter and standard deviation of fibre diameter, and another including along-fibre variation in diameter, rate of fibre diameter increase during ration changes, and clean fleece weight explained a significant part of the variation in staple strength. The results are discussed in relation to mechanisms affecting staple strength.

Differences in fibre diameter profile characteristics in wool staples from Merino sheep and their relationship with staple strength between years, environments, and bloodlines

This study examined differences in fibre diameter profiles (FDPs) and midside characteristics of Merino sheep in 2 environments, 4 bloodlines, 3 years, and 44 sire groups. Environment significantly (P < 0.05) influenced all characteristics except one measure of fibre diameter change and staple length. Bloodline also significantly (P < 0.05) influenced all characteristics except staple strength. The maximum fibre diameter, one measure of fibre diameter change, and staple length were significantly different (P < 0.05) between sires. Variation in fibre diameter profile characteristics between bloodlines and sires changed across the environment in which the sheep are maintained. Despite these differences between bloodlines and sires in the FDP, midside mean fibre diameter, fibre diameter variation, and staple length, there were no significant differences between bloodlines in staple strength. The relationships between the FDP and midside characteristics with staple strength were also examined over these bloodlines and environments. Along-staple variation in fibre diameter (r = –0.32 to –0.50), between-fibre fibre diameter variation (r = –0.25 to –0.48), rate of fibre diameter change (r = –0.16 to –0.38), and midside variation in fibre diameter (r = –0.25 to –0.51) were all negatively correlated with staple strength. Maximum fibre diameter (r = 0.08 to 0.18), minimum fibre diameter (r = 0.25 to 0.49), and midside mean fibre diameter (r = 0.09 to 0.35) were positively associated with staple strength. FDP characteristics explained 5–30% more variation in staple strength than could be explained using the standard midside characteristics of mean fibre diameter, fibre diameter variation, and staple length alone. These relationships were also different between environments and bloodlines. The inclusion of the FDP characteristics as explanatory variables provided an alternative interpretation for how absolute fibre diameter and fibre diameter variation combine to explain staple strength. These results suggested that animals and sires might be able to be selected on FDP characteristics to improve staple strength. More detailed genetic studies are required before these selection strategies can be recommended.

Simultaneous measurements of small- and wide-angle X-ray scattering during low speed spinning of poly(propylene) using synchrotron radiation

Simultaneous measurements of small- and wide-angle X-ray scattering (SAXS and WAXD) were performed during the melt spinning of isotactic poly(propylene). The extruder assembly was mounted on a platform, which could be moved horizontally and vertically allowing variations of the measuring point between distances of 28 and 90 cm from the spinneret. The SAXS and WAXD pattern were taken simultaneously with two two-dimensional detectors. Additionally, the fiber diameter profile was measured. The development of the crystallization and the orientation of the crystallites were studied as a function of the distance from the spinneret. The wide-angle data revealed that highly oriented crystals grow out of an apparently unoriented amorphous matrix. Moreover, the orientation of the crystallites was found to be constant along the spin line. Both crystalline WAXD and SAXS peaks were found to occur at the same distance from the spinneret within the resolution of the apparatus. A comparison of WAXD and SAXS shows that the crystallization and the formation of a superstructure follow the same kinetics.

An isothermal model for high-speed spinning of liquid crystalline polymer fibers – coupling of flow, orientation, and crystallization

Experiments show high-speed spinning of many synthetic fibers is accompanied by the partial crystallization of the initially amorphous melt. This crystallization is induced by some combination of the extensional flow, molecular orientation and extension, and temperature dependence. The crystallization of the material couples back to affect the fiber rheology, through a process of stress-hardening. Recently Forest, Wang and Bechtel have derived isothermal 1-D equations from macroscopic approximations of Doi-type liquid crystalline polymer (LCP) kinetic equations; their equations model the coupling between the extensional flow and the molecular orientation. Here we extend that model to include a fully three-way coupling of flow, orientation and crystallization mechanics, adopting an Avrami crystallization law with an orientation-dependent rate constant as proposed by Ziabicki, and the Kikutani stress-hardening law. We show that there is a significant difference in the fiber diameter profile, orientation and crystallinity with the inclusion of the stress-hardening to the extensional flow. Of interest here also is the role of crystallization in localizing the drawdown into a so-called `neck' region. We illustrate important qualitative and quantitative effects due to the development of crystallization: a pronounced drop in the fiber radius, an increased rapid fluid acceleration, and enhanced molecular alignment with the fiber centerline axis. These three features all occur over the short orientation-induced crystallization lengthscale, and are isolated in the first 20% of the crystallizing region along the spinline for draw ratios typical of high-speed spinning.

Measuring the Diameter Profile of Single Wool Fibres by Using the Single Fibre Analyser (SIFAN)

An instrument named the Single Fibre Analyser (SIFAN) was built to measure the diameter profile of single wool fibres. By scanning every 40 μm along the length of a 100-mm fibre, a detailed diameter profile of a fibre could be measured in less than 2 minutes. The measurement error of the SIFAN was low (s.d. = 0.6 μm) in view of the large variation in diameter over relatively short lengths of fibre. Fibre-diameter profiles measured along single fibres by the SIFAN were compared and correlated closely with single-fibre and 2-mm-snippet profiles measured with the Optical Fibre Diameter Analyser.

Fleece metrology of Liaoning cashmere goats

Details of cashmere and hair fibre metrology of Liaoning cashmere goats at the Gai County Cashmere Goat Farm, Liaoning Province, China, are reported. Midside fleece samples were taken from five adult bucks, five yearling bucks and five adult pregnant does (live weights 60 kg, 23 kg and 35 kg, respectively). Fibre length, fibre diameter, fibre diameter distribution, cashmere yield (% by weight), estimated secondary/primary skin follicle ratios (S/P) and crimping of cashmere were measured. Adult bucks had longer ( P < 0.001) and coarser cashmere ( P < 0.001) and had higher ( P < 0.05) cashmere yields ((mean ± SE) 120±5 μm, 17.5±0.4 μm, 58±3.6%, respectively) than adult does (67±4 mm, 15.4±0.3 μm, 33±6.8%) and yearling bucks (50±3 mm, 13.3±0.1 μm, 45±2.6%). Cashmere from adult goats had four to six crimps cm −1. Adult bucks had coarser hair, 66.4±3.3 μm, than kid bucks, 48.9±2.4 μm ( P<0.001). The ratio of hair to cashmere fibre diameter was 3.8:1. Adult bucks had twice the S/P ratio of adult does ( P < 0.05). Cashmere fibre diameter could be predicted from cashmere length ( R 2=0.83). Cashmere yield was related to S/P ratio and cashmere length ( R 2=0.70). Cashmere grown during winter and spring under poorer nutritional conditions was significantly finer ( P < 0.05) than cashmere grown in summer and autumn. Fibre diameter profiles show adult bucks having a significantly coarser distribution of cashmere and hair ( P < 0.05) with 0.6% of cashmere fibre > 30 μm. The implications of these observations for processing cashmere and managing cashmere goats are discussed and estimates of the commercial cashmere production of Liaoning goats are given.

Skeletal muscle pathology in ovine congenital progressive muscular dystrophy. 2. Myofiber morphometry.

Fiber-type proportions were determined in 12 skeletal muscles (peronaeus tertius, tibialis cranialis, tensor fascia lata, psoas major, extensor digitorum lateralis, tensor fascia antibrachii, vastus intermedius, soleus, anconaeus, and flexor digitorum superficialis of fore and hind limb) from infantile (20 weeks), juvenile (16 months) and adult (2.5 and 3.5 years) Merino sheep with ovine congenital progressive muscular dystrophy and in age-matched controls. Although confined to type I fibers, lesions were severe not only in type I fiber dominant muscles (vastus intermedius, soleus and anconaeus) but also in the type II dominant medial triceps brachii and in the superficial digital flexors which had approximately equal proportions of both fiber types. The frequency distribution curves of myofiber diameter in dystrophic anconaeus and superficial digital flexor of the fore limb altered as the disease progressed. In young sheep (20 weeks) type I fibers increased in size, then in juvenile and adult sheep the curves became flatter and broader and lost symmetry due to the presence of hypertrophic and atrophic fibers. The fiber diameter profiles were similar to those seen in Duchenne dystrophy in humans.