Single Fiber Bundle Research Articles

Second generation slit-based photoacoustic tomography system for vascular imaging in human.

Slit-based photoacoustic tomography is a newly developed technique that improves the elevation numerical aperture of a linear array through acoustic diffraction. The slit, placed at the acoustic focus of a linear array, effectively forms an array of virtual detectors with high receiving angle, which subsequently improves the elevation resolution. However, due to the complex implementation, our original system could only image phantoms and sacrificed animals. In this report, the system has been significantly improved. In particular, we designed a slit holder that can be directly mounted to the transducer array for easy adjustment of slit width and simultaneous scanning of both the array and the slit. To enlarge the imaging field of view, we replaced the single circular optical fiber bundle with a bifurcated line fiber bundle which moved simultaneously with the array and the slit. The data acquisition system has also been updated to double the imaging speed. With these improvements, the new system can image a 3.8 × 4cm2 region within 40 seconds and the object only needs to be coupled through ultrasound gel. We successfully used the system to image vasculatures in the palm and forearm of human volunteers. 3D palm vascular image of human palm.

Relationship between chemical composition, crystallinity, orientation and tensile strength of kenaf fiber

The physical properties of natural growth fibers such as chemical composition content and fiber diameter are highly affected by environmental issues such as environmental changes and fiber extraction methods. These irregularities of the natural fibers seriously affect its utilization in composite as reinforcements. In this study, taking into account the importance of the fiber tensile strength, the correlation degrees between the kenaf fiber tensile strength and the fiber chemical composition, crystallinity, orientation degree were analyzed by the grey relational analysis method. Both the kenaf single fiber and fiber bundle were used as XRD and tensile strength test sample. The chemical composition content and the FTIR were carried out to obtain a correct result of the chemical composition content. It found that for the different XRD and tensile strength test samples, the single fiber showed lower crystallinity, higher orientation degree and tensile strength compared with the fiber bundle. The cellulose content and the orientation degree got the higher correlation degree with single fiber tensile strength, which was 0.674 and 0.640. The highest factor associated with the fiber bundle tensile strength was the orientation degree, the correlation degree was 0.747. The hemicellulose content and the crystallinity also got high correlation degree with the fiber bundle strength, which was 0.687 and 0.640.

Windmill Palm Fiber/Polyvinyl Alcohol Coated Nonwoven Mats with Sound Absorption Characteristics

Windmill palm single fibers (WPSFs) and fiber bundles (WPFBs) were extracted from a windmill sheath mesh. For the palm fiber acoustic application, WPSFs/WPFBs nonwoven materials and windmill palm fiber (WPF)/polyvinyl alcohol (PVA) coated nonwoven mats were developed. The effects of conditions such as the thickness and surface density of the materials and the concentration of PVA were studied. The sound absorption coefficients of all of the samples were measured using an impedance tube instrument. The statistical significance of the differences between these materials was tested using Duncan’s grouping method. Based on the results, the windmill palm fiber can be regarded as appropriate for use as a sound absorbing material. The addition of PVA was an effective way to improve the acoustic properties of the WPF/PVA coated nonwoven mats. This coated mat exhibited a greater ability to absorb sound than WPSFs/WPFBs nonwoven materials. The acoustic properties of the materials exhibited good results, with an average sound absorption coefficient of 0.38 when the concentration of PVA was 1 wt.%.

Quantitative representation and description of intravoxel fiber complexity in HARDI

Diffusion tensor imaging and high angular resolution diffusion imaging are often used to analyze the fiber complexity of tissues. In these imaging techniques, the most commonly calculated metric is anisotropy, such as fractional anisotropy (FA), generalized anisotropy (GA), and generalized fractional anisotropy (GFA). The basic idea underlying these metrics is to compute the deviation from free or spherical diffusion. However, in many cases, the question is not really to know whether it concerns spherical diffusion. Instead, the main concern is to describe and quantify fiber complexity such as fiber crossing in a voxel. In this context, it would be more direct and effective to compute the deviation from a single fiber bundle instead of a sphere. We propose a new metric, called PEAM (PEAnut Metric), which is based on computing the deviation of orientation diffusion functions (ODFs) from a single fiber bundle ODF represented by a peanut. As an example, the proposed PEAM metric is used to classify intravoxel fiber configurations. The results on simulated data, physical phantom data and real brain data consistently showed that the proposed PEAM provides greater accuracy than FA, GA and GFA and enables parallel and complex fibers to be better distinguished.

Chemical–mechanical pretreatment of wood: Reducing downsizing energy and increasing enzymatic digestibility

A chemimechanical (CM) pretreatment method was devised, wherein wood chips are acid-treated to weaken the physical structure then disc-refined to produce a fibrous substrate. CM pretreatment was directly compared with a common dilute acid (DA) pretreatment method, wherein wood is mechanically downsized to a powder or fiber substrate and then acid-treated. It was hypothesized that the CM pretreatment sequence would reduce the energy required for size reduction and increase enzymatic digestibility of the pretreated substrate. By treating wood chips in a dilute sulfuric acid liquor before the mechanical downsizing step, the net specific energy (NSE) of disc-refining was reduced by up to 95%. At the optimal acid treatment and disc-refining conditions determined within this work, CM pretreatment could produce a highly digestible lignocellulose substrate (95% cellulose conversion) while requiring less than 100 kWh/tonne od NSE for mechanical downsizing. A comparison of CM and DA pretreated hardwood revealed that CM pretreatment produced a significantly more digestible substrate than DA pretreatment. Differences in the digestibility of CM and DA pretreated substrates were attributed to differences in physical structure. CM pretreatment produced a substrate that consisted primarily of single fibers and small fiber bundles, while DA pretreatment produced larger fiber bundles. Furthermore, the CM pretreated substrate had a more accessible pore structure, and an altered distribution of surface lignin.

UV protection performance of textiles affected by fiber cross-sectional shape

In this study, a model was set up for simulating the effects of varying fiber cross-sectional shapes on ultraviolet protection of fibers. The fiber diameter and fiber type were also involved in the model setting. Experiments of diffuse reflectance spectra measurement on natural (wool, cotton, silk), regenerated (bamboo viscose) and synthetic (polyester, nylon) fibers were conducted to verify the model predicted results. When a more complex shape was assumed as the fiber cross-section for model calculation, the predicted results have a better agreement with the actual results. The effects on ultraviolet absorption from fibers with different cross-sectional shapes were investigated at a single fiber, fiber bundle and yarn levels. With the same material, when the fiber cross-sectional area and the areal coverage of a single fiber were constant, the triangular shape had the lowest ultraviolet transmittance and the highest ultraviolet reflectance for a single fiber and also for a fiber bundle. The difference of fiber cross-sectional shapes was also significant in the ultraviolet protection of a single yarn.

Topological and Euclidean metrics reveal spatially nonuniform structure in the entanglement of stochastic fiber bundles

Data acquired from synchrotron-based X-ray computed tomography provide complete descriptions of the stochastic positions of each fiber in large bundles within composite samples. The data can be accumulated for distances along the nominal fiber direction that are long enough to reveal meandering or misalignment. Data are analyzed for a single fiber bundle consolidated as a mini-composite specimen and a block of fibers embedded within a single ply in a tape laminate specimen. The fibers in these materials differ markedly in their departure from alignment and the patterns formed by fiber deviations. The tape laminate specimen exhibits evidence of fibers that have slipped laterally through the bundle in narrow shear bands, which may be a mechanism of bundle deformation under transverse compression and shear. This pattern is absent in the single-tow specimen, which was not subject to transverse loads in processing. We propose a combination of topological and Euclidean metrics to quantify these and other stochastic bundle characteristics. Topological metrics are based on the neighbor map of fibers, which is constructed on cross-sections of the bundle by Delaunay triangulation (or Voronoi tessellation). Variations of the neighbor map along the fiber direction describe fiber meandering, twist, etc. Euclidean metrics include factors such as local fiber density and fiber orientation. The metrics distinguish bundle types, enable quantification of the effects of the manufacturing history of bundles, and provide target statistics to be matched by virtual specimens that might be generated for use in fiber-scale virtual tests.

Microstructural Study, Tensile Properties, and Scanning Electron Microscopy Fractography Failure Analysis of Various Agricultural Residue Fibers

This paper presents an approach to examine the microstructural properties and mechanical behavior of coconut husks, banana pseudo-stem, pineapple leaf, and sugarcane bagasse fibers by scanning electron microscope and mini-tensile tester, respectively. Single fiber bundles were examined by using scanning electron microscope. Tensile tests were performed at different diameters (0.15–0.55 mm) and gauge lengths (10, 15, 20, and 30 mm/min) to assess the effects of diameter and gauge length on tensile properties. It was found that fibers consisted of different types of regularly arranged cells. The tensile strength (310 MPa) and Young’s modulus (7.4 GPa) of pineapple leaf fiber bundles showed the highest value compared to the other fibers. The tensile strength and Young’s modulus decreased with the increase of diameter and gauge length of fiber bundles. Scanning electron microscopic fractography analysis showed comparatively heterogeneous ruptures associated with more participants of microfibrils for pineapple leaf and banana pseudo-stem fibers compared to coconut husk and sugarcane bagasse fibers. These fractographic observations were discussed in the light of current knowledge of the microstructure of each fiber and the corresponding mechanical properties.

Counting carbon fibres by electrical resistance measurement

Electrical Impedance Measurement has been used to measure the diameter of single carbon fibres to within 3% of the actual value measured by Scanning Electron Microscopy (SEM). The precision of the technique developed also allows for the accurate determination of the number of fibres present in a carbon fibre bundle, such data are important for the calculation of fibre tensile strength from the tensile force applied to carbon fibre bundles. The impedance of a single carbon fibre and carbon fibre bundles of up to 20 fibres have been measured, with results showing good agreement with theoretical values. The impedance of multiple lengths of carbon fibres ranging from 80 to 300mm has also been studied, with the impedance being directly proportional to the fibre length, as per electrical theory. This technique will be suitable for determining the number of fibres in a virgin or recycled carbon fibre bundle.

Skeletal muscle fibrosis and stiffness increase after rotator cuff tendon injury and neuromuscular compromise in a rat model.

Rotator cuff tears can cause irreversible changes (e.g., fibrosis) to the structure and function of the injured muscle(s). Fibrosis leads to increased muscle stiffness resulting in increased tension at the rotator cuff repair site. This tension influences repairability and healing potential in the clinical setting. However, the micro- and meso-scale structural and molecular sources of these whole-muscle mechanical changes are poorly understood. Here, single muscle fiber and fiber bundle passive mechanical testing was performed on rat supraspinatus and infraspinatus muscles with experimentally induced massive rotator cuff tears (Tenotomy) as well as massive tears with chemical denervation (Tenotomy + BTX) at 8 and 16 weeks post-injury. Titin molecular weight, collagen content, and myosin heavy chain profiles were measured and correlated with mechanical variables. Single fiber stiffness was not different between controls and experimental groups. However, fiber bundle stiffness was significantly increased at 8 weeks in the Tenotomy + BTX group compared to Tenotomy or control groups. Many of the changes were resolved by 16 weeks. Only fiber bundle passive mechanics was weakly correlated with collagen content. These data suggest that tendon injury with concomitant neuromuscular compromise results in extra-cellular matrix production and increases in stiffness of the muscle, potentially complicating subsequent attempts for surgical repair.

Comparative mechanical and thermal study of chemically treated and untreated single sugarcane fiber bundle

Natural fiber as a reinforcing constituent can play a dominant role in the field of fiber reinforced polymer composites (FRPC) due to its availability, eco-friendliness, renewability, CO2-neutrality, flexibility, low density, and low cost. Sugarcane fiber can be a potential candidate to replace the synthetic FRPC. The objective of this study is to evaluate the effect of chemical treatment on the tensile, thermal, and morphological properties of single sugarcane fiber bundles. Locally grown sugarcane was cut into specific lengths from the internode section and the single fiber bundles were extracted from the rind region. These fiber bundles were then dried in an oven to remove the moisture. Surface modification of fiber bundles was accomplished by performing alkali treatment and neutralized by acetic acid solution. The fiber bundles were then rinsed with water and dried at 80°C for about 24h in an oven. Optical Microscopy (OM) was employed to measure the diameter of the single fiber bundle which ranged from 0.260mm (untreated) to 0.155mm (treated). Tensile tests were carried out on single fiber bundles according to the ASTM standard. Correction factors were also applied for machine displacement and slippage of the fiber bundle. Data from tensile tests showed that maximum improvement in the tensile strength and modulus for the treated fiber bundles were observed to be 106.83% and 20.46%, respectively, compared to those of untreated ones. Strain to maximum strength was enhanced by 25.92% in the treated fiber bundles compared to that of the untreated one. Untreated fiber bundles were observed in Thermogravimetric Analysis (TGA) studies to start decomposing at around 200°C compared to about 250°C for treated ones. Differential Scanning Calorimetry (DSC) provided the amount of moisture content present in treated and untreated fiber bundles which matched with the TGA results. Fourier Transformed Infrared Spectroscopy (FTIR) revealed structural modification after treatment. Scanning Electron Microscopy (SEM) was used to evaluate the fracture morphology of failed samples. Fracture morphology of the treated fiber bundles revealed cleaner and rougher fracture surfaces compared to those of untreated ones.

Gel formation in protein amyloid aggregation: a physical mechanism for cytotoxicity.

Amyloid fibers are associated with disease but have little chemical reactivity. We investigated the formation and structure of amyloids to identify potential mechanisms for their pathogenic effects. We incubated lysozyme 20 mg/ml at 55C and pH 2.5 in a glycine-HCl buffer and prepared slides on mica substrates for examination by atomic force microscopy. Structures observed early in the aggregation process included monomers, small colloidal aggregates, and amyloid fibers. Amyloid fibers were observed to further self-assemble by two mechanisms. Two or more fibers may merge together laterally to form a single fiber bundle, usually in the form of a helix. Alternatively, fibers may become bound at points where they cross, ultimately forming an apparently irreversible macromolecular network. As the fibers assemble into a continuous network, the colloidal suspension undergoes a transition from a Newtonian fluid into a viscoelastic gel. Addition of salt did not affect fiber formation but inhibits transition of fibers from linear to helical conformation, and accelerates gel formation. Based on our observations, we considered the effects of gel formation on biological transport. Analysis of network geometry indicates that amyloid gels will have negligible effects on diffusion of small molecules, but they prevent movement of colloidal-sized structures. Consequently gel formation within neurons could completely block movement of transport vesicles in neuronal processes. Forced convection of extracellular fluid is essential for the transport of nutrients and metabolic wastes in the brain. Amyloid gel in the extracellular space can essentially halt this convection because of its low permeability. These effects may provide a physical mechanism for the cytotoxicity of chemically inactive amyloid fibers in neurodegenerative disease.

Alternate Relationship between Single Fiber Properties and Both of Fiber Microscopic and Physical Properties

Current study was carried out in Cotton Research Institute, Agricultural Research Center, Egypt and Textechno company labs Monchengladbach, Germany during 2013 season. The materials used in this study comprised 16 different genotypes produced by cotton research institute. In addition to, two upland cotton varieties from Sudan. Aiming to study the effect of environmental conditions, genotypes and thier interaction on each characters under study beside studyig the relationship between single fiber prroperties and bundle properties. Giza 93 variety showed the lowest micronaire, fineness and area of cross section. On contrast, it showed the highest upper half mean. Giza 87 variety exhibited the highest bundle strength, the lowest reversals number per mm and the narrowest convolution angle. As for single fiber properties. Giza 45 variety followed by Giza 87 variety exhibited the lowest single fiber linear density readings. Single fiber strength is a little bit lower than bundle strength. Giza 87 variety surpassed the other genotypes on single fiber strength. Upland cotton varieties showed the worst bundle and single fiber properties. As maturity ratio increased bundle and single fiber properties improved and vice versa. According to, the relationship between single fiber prroperties and bundle properties, there was a nearly linear relation¬ship between fiber properties and single fiber properties. After excluding the weak correlated characters 3 linear multiple regression models for single fiber tenacity, single fiber linear density and single fiber elongation were produced. Fineness and degree of thickness were the predictor variables for single fiber strength parameters. However, fiber fineness per mtex and micronaire values were the most important factors for single fiber linear density, both of them proportionate directly with single fiber linear density. While, single fiber elongation contains 7 predictors i.e. Micronaire reading, UI, area of cross section, theta, fiber strength, fiber elongation and UHM characters. Nevertheless, it showed the weakest relation, UI, area of cross section, and fiber Strength proportionate inversely with single fiber elongation. The model is not reliable enough for single fiber elongation prediction.

Fiber bundle endocytoscopy.

Endocytoscopy is an optical biopsy technique which uses a miniaturized camera to capture white light microscopy images through an endoscope. We have developed an alternative design that instead relays images to an external camera via a coherent fiber bundle. In this paper we characterize the device and demonstrate microscopy of porcine tissue ex vivo. One advantage of our approach is the ease with which other bundle-compatible imaging modalities can be deployed simultaneously. We show this by acquiring quasi-simultaneous endocytoscopy and fluorescence confocal endomicroscopy images through a single fiber bundle. This opens up possibilities for multi-modal endomicroscopy, combining white light and fluorescence imaging.

Chemical and Mechanical Properties Studies of Chinese Linen Flax and Its Composites

To improve the mechanical performance of flax polymer composites, different surface modifications on flax fibres have been investigated by many researchers. In this study, the effects of alkaline treatment on the properties of Chinese linen flax were evaluated by different chemical and mechanical test techniques. Chemical detergents, stains and FTIR were used to investigate the chemical constituent changes in the Chinese linen flax. Moreover, the elastic properties of untreated and treated flax fibres were evaluated using a single fibre bundle tensile test. The elastic properties of their composites were accessed also using tensile tests. In addition, the theoretical elastic properties of alkaline treated flax were calculated using Halpin-Tsai equations. The theoretical elastic properties of flax/vinyl ester composites were also obtained to compare against the experimental results. An optimal/ultimate elastic modulus of flax/vinyl ester composites was predicted.

Probing white-matter microstructure with higher-order diffusion tensors and susceptibility tensor MRI.

Diffusion MRI has become an invaluable tool for studying white matter microstructure and brain connectivity. The emergence of quantitative susceptibility mapping and susceptibility tensor imaging (STI) has provided another unique tool for assessing the structure of white matter. In the highly ordered white matter structure, diffusion MRI measures hindered water mobility induced by various tissue and cell membranes, while susceptibility sensitizes to the molecular composition and axonal arrangement. Integrating these two methods may produce new insights into the complex physiology of white matter. In this study, we investigated the relationship between diffusion and magnetic susceptibility in the white matter. Experiments were conducted on phantoms and human brains in vivo. Diffusion properties were quantified with the diffusion tensor model and also with the higher order tensor model based on the cumulant expansion. Frequency shift and susceptibility tensor were measured with quantitative susceptibility mapping and susceptibility tensor imaging. These diffusion and susceptibility quantities were compared and correlated in regions of single fiber bundles and regions of multiple fiber orientations. Relationships were established with similarities and differences identified. It is believed that diffusion MRI and susceptibility MRI provide complementary information of the microstructure of white matter. Together, they allow a more complete assessment of healthy and diseased brains.

Phenomenological consequences of sectioning and bathing on passive muscle mechanics of the New Zealand white rabbit tibialis anterior

Skeletal muscle tissue provides support and mobility of the musculoskeletal system. Numerical modeling of muscle tissue aids in understanding disease pathophysiology, however, the effectiveness is dependent on accurately accounting for various tissue phenomena. Muscle modeling is made difficult due to the multitude of constituents that contribute to elastic and viscous mechanisms. Often, deterministic single fiber or fiber bundle studies are undertaken to examine these contributions. However, examination of whole, intact and structurally altered tissue and comparison to findings at the myofibril scale can help elucidate tissue mechanics. Stress relaxation tests at 10% strain were performed on 28 New Zealand White rabbit's tibialis anterior muscles for whole, intact muscle and sub-sectioned muscle samples. Additionally, to aid in examining viscous effects, sub groups were tested with and without a phosphate buffered saline bath. The steady-state elastic modulus was not significantly different between groups. Interestingly, sectioning did result in a negative Poisson’s ratio following tensile loading. Additionally, sectioning resulted in altering the viscous tissue response as the time to reach steady-state was significantly faster than whole muscle samples (p<0.05), as well as the linear relaxation rate from 0 to 0.1 (p<0.01), 1 to 10 (p<0.05), and 10 to 100s (p<0.05). Bathing tissue resulted in a significantly greater amount of percent stress relaxation for whole muscle (p<0.01). These findings provide new insight into the differing mechanical characteristics of whole and sectioned muscle tissue.

Modeling of fiber-optic fluorescence probes for strongly absorbing samples

The dynamic range of fiber-optic fluorescent probes such as single fibers and fiber bundles is calculated for strongly absorbing samples, such as process liquids, foodstuffs, and lubricants. The model assumes an excitation beam profile based on a Lambertian light source and uses analytical forms of the collection efficiency, followed by an Abel transformation and numerical integration. It is found that the effect of primary absorption of the excitation light and secondary absorption of the fluorescence is profound. For fiber bundles and bifurcated fiber probes, the upper accessible concentration limit is roughly given by the absorption length of the primary and secondary absorption. Fluorescence detectors that are placed at right angles to the excitation beam axis or collinear to the beam axis are equally strongly affected by secondary absorption. A probe in which the same fiber is used for excitation and for collection of the fluorescence emerges as the fiber probe with the largest accessible concentration range.

Muscle excursion does not correlate with increased serial sarcomere number after muscle adaptation to stretched tendon transfer

Chronic skeletal muscle stretch typically increases serial muscle fiber sarcomere number. Since serial sarcomere number correlates with functional excursion in normal muscle, observed changes in sarcomere number are often extrapolated to their new assumed function. However, this has not been well demonstrated experimentally. Thus, we measured the functional properties of muscles stretched due to tendon transfer surgery. Muscle active and passive length-tension curves were measured 1 week and 4 weeks after surgery, and then each muscle was further examined to determine structural adaptation as well as single fiber and fiber bundle passive mechanical properties. We found a disconnect between the functional and structural muscle properties. Specifically, muscle excursion was significantly lower in the transferred muscle compared to controls, even though serial sarcomere number had increased. Furthermore, maximum tetanic tension was significantly reduced, though the two groups had similar physiological cross sectional areas. Passive tension increased in the transferred muscle, which was deemed to be due to proliferation of extracellular matrix. These data are the first to report that muscle morphological adaptation after chronic stretch does not accurately predict the muscle's functional properties. These data have significant implications for examining muscle physiological properties under surgical interventions.

Observation of transcrystalline growth of PLA crystals on sisal fibre bundles and the effect of crystal structure on interfacial shear strength

Hot-stage microscopy was used to characterise crystal growth at the interface between sisal fibre bundles and a polylactic acid (PLA) matrix in order to better understand the mechanical properties of sisal fibre–PLA composites. Cooling rates and crystallisation temperatures and times were varied to influence crystalline morphology at the interface. Single sisal fibre bundles were evaluated in their as received state or treated with 6 wt.% caustic soda solution for 48 h at room temperature. A microbond shear test was used to characterise the shear strength of the interface as a function of fibre surface treatment. These tests were performed on sisal fibre bundles carefully embedded in flat films of PLA supported on card mounts. Fibre bundles in a PLA matrix were cooled from 180 °C at rates from 2 to 9 °C/min and then crystallised isothermally. For as received fibre bundles uneven growth of PLA spherulites occurred at all cooling rates and crystallisation temperatures. For caustic soda treated fibres, uneven spherulitic growth was observed at crystallisation temperatures at and above 125 °C. In contrast, transcrystalline growth was observed for samples cooled to 120 °C at cooling rates from 2 to 6 °C/min and then allowed to crystallise. The microbond shear strengths of untreated and caustic soda treated fibre bundles were evaluated using Weibull statistics and the caustic soda treated fibres exhibited higher interfacial shear strengths in comparison to untreated fibres, reflecting the development of a transcrystalline layer at the fibre to matrix interface.