Structure-based discovery of fiber-binding compounds that reduce the cytotoxicity of amyloid beta

DOE PAGES

Jiang, Lin; Liu, Cong; Leibly, David; ...

2013-07-16

Amyloid protein aggregates are associated with dozens of devastating diseases including Alzheimer’s, Parkinson’s, ALS, and diabetes type 2. While structure-based discovery of compounds has been effective in combating numerous infectious and metabolic diseases, ignorance of amyloid structure has hindered similar approaches to amyloid disease. Here we show that knowledge of the atomic structure of one of the adhesive, steric-zipper segments of the amyloid-beta (Aβ) protein of Alzheimer’s disease, when coupled with computational methods, identifies eight diverse but mainly flat compounds and three compound derivatives that reduce Aβ cytotoxicity against mammalian cells by up to 90%. Although these compounds bind tomore » Aβ fibers, they do not reduce fiber formation of Aβ. Structure-activity relationship studies of the fiber-binding compounds and their derivatives suggest that compound binding increases fiber stability and decreases fiber toxicity, perhaps by shifting the equilibrium of Aβ from oligomers to fibers.« less

Influence of fiber packing structure on permeability

NASA Technical Reports Server (NTRS)

Cai, Zhong; Berdichevsky, Alexander L.

1993-01-01

The study on the permeability of an aligned fiber bundle is the key building block in modeling the permeability of advanced woven and braided preforms. Available results on the permeability of fiber bundles in the literature show that a substantial difference exists between numerical and analytical calculations on idealized fiber packing structures, such as square and hexagonal packing, and experimental measurements on practical fiber bundles. The present study focuses on the variation of the permeability of a fiber bundle under practical process conditions. Fiber bundles are considered as containing openings and fiber clusters within the bundle. Numerical simulations on the influence of various openings on the permeability were conducted. Idealized packing structures are used, but with introduced openings distributed in different patterns. Both longitudinal and transverse flow are considered. The results show that openings within the fiber bundle have substantial effect on the permeability. In the longitudinal flow case, the openings become the dominant flow path. In the transverse flow case, the fiber clusters reduce the gap sizes among fibers. Therefore the permeability is greatly influenced by these openings and clusters, respectively. In addition to the porosity or fiber volume fraction, which is commonly used in the permeability expression, another fiber bundle status parameter, the ultimate fiber volume fraction, is introduced to capture the disturbance within a fiber bundle.

Mechanically induced long period fiber gratings in Er3+ fiber for structural health monitoring

NASA Astrophysics Data System (ADS)

Pulido-Navarro, M. G.; Alvarez-Chavez, J. A.; Ceballos-Herrera, D. E.; Escamilla-Ambrosio, P. J.

2013-09-01

This work presents preliminary results on wavelength sensitivity due to mechanically induced long period fiber grating (LPFG) on both standard single-mode and Er-doped fibers. The work presents and compares results for both types of fibers under different torsion conditions. In order to apply the torsion one of the fiber ends is fixed while torsion is applied on the other end. A LPFG whose period is 503μm is used to press on the fiber after the torsion, this will allow for micro curvatures to be formed on the fiber, which will in turn generate a periodical index perturbation on it. Here, it was noted that the rejection band shifts to shorter wavelengths for Er-doped fibers. It was detected that for torsion of 6 turns applied to 10cm doped fiber the wavelength peaks can shift up to 25nm, which is longer than similar results reported on standard fibers. Therefore, by using Er-doped fibers this technique will give more sensitive and accurate results on the real conditions of the structure under study. These results can be employed for sensing applications, especially for small to medium size structures, being these structures mechanical, civil or aeronautical. Theoretical calculations and simulations are employed for experimental results validation.

Monitoring of Structural Integrity of Composite Structures by Embedded Optical Fiber Sensors

NASA Technical Reports Server (NTRS)

Osei, Albert J.

2002-01-01

advanced structural materials expected to become the mainstay of the current and future generation space structures. Since carbon-epoxy composites are the materials of choice for the current space structures, the initial study is concentrated on this type of composite. The goals of this activity are to use embedded FBG sensors for measuring strain and temperature of composite structures, and to investigate the effects of various parameters such as composite fiber orientation with respect to the optical sensor, unidirectional fiber composite, fabrication process etc., on the optical performance of the sensor. This paper describes an experiment to demonstrate the use of an embedded FBG for measuring strain in a composite material. The performance of the fiber optic sensor is determined by direct comparison with results from more conventional instrumentation.

Age-related structural alterations in human skeletal muscle fibers and mitochondria are sex specific: relationship to single-fiber function.

PubMed

Callahan, Damien M; Bedrin, Nicholas G; Subramanian, Meenakumari; Berking, James; Ades, Philip A; Toth, Michael J; Miller, Mark S

2014-06-15

Age-related loss of skeletal muscle mass and function is implicated in the development of disease and physical disability. However, little is known about how age affects skeletal muscle structure at the cellular and ultrastructural levels or how such alterations impact function. Thus we examined skeletal muscle structure at the tissue, cellular, and myofibrillar levels in young (21-35 yr) and older (65-75 yr) male and female volunteers, matched for habitual physical activity level. Older adults had smaller whole muscle tissue cross-sectional areas (CSAs) and mass. At the cellular level, older adults had reduced CSAs in myosin heavy chain II (MHC II) fibers, with no differences in MHC I fibers. In MHC II fibers, older men tended to have fewer fibers with large CSAs, while older women showed reduced fiber size across the CSA range. Older adults showed a decrease in intermyofibrillar mitochondrial size; however, the age effect was driven primarily by women (i.e., age by sex interaction effect). Mitochondrial size was inversely and directly related to isometric tension and myosin-actin cross-bridge kinetics, respectively. Notably, there were no intermyofibrillar or subsarcolemmal mitochondrial fractional content or myofilament ultrastructural differences in the activity-matched young and older adults. Collectively, our results indicate age-related reductions in whole muscle size do not vary by sex. However, age-related structural alterations at the cellular and subcellular levels are different between the sexes and may contribute to different functional phenotypes in ways that modulate sex-specific reductions in physical capacity with age. Copyright © 2014 the American Physiological Society.

Activated Carbon Fibers with Hierarchical Nanostructure Derived from Waste Cotton Gloves as High-Performance Electrodes for Supercapacitors.

PubMed

Wei, Chao; Yu, Jianlin; Yang, Xiaoqing; Zhang, Guoqing

2017-12-01

One of the most challenging issues that restrict the biomass/waste-based nanocarbons in supercapacitor application is the poor structural inheritability during the activating process. Herein, we prepare a class of activated carbon fibers by carefully selecting waste cotton glove (CG) as the precursor, which mainly consists of cellulose fibers that can be transformed to carbon along with good inheritability of their fiber morphology upon activation. As prepared, the CG-based activated carbon fiber (CGACF) demonstrates a surface area of 1435 m 2  g -1 contributed by micropores of 1.3 nm and small mesopores of 2.7 nm, while the fiber morphology can be well inherited from the CG with 3D interconnected frameworks created on the fiber surface. This hierarchically porous structure and well-retained fiber-like skeleton can simultaneously minimize the diffusion/transfer resistance of the electrolyte and electron, respectively, and maximize the surface area utilization for charge accumulation. Consequently, CGACF presents a higher specific capacitance of 218 F g -1 and an excellent high-rate performance as compared to commercial activated carbon.

Performance characterization of active fiber-composite actuators for helicopter rotor blade applications

NASA Astrophysics Data System (ADS)

Wickramasinghe, Viresh K.; Hagood, Nesbitt W.

2002-07-01

The primary objective of this work was to characterize the performance of the Active Fiber Composite (AFC) actuator material system for the Boeing Active Material Rotor (AMR) blade application. The AFCs were a new structural actuator system consisting of piezoceramic fibers embedded in an epoxy matrix and sandwiched between interdigitated electrodes to orient the driving electric field in the fiber direction to use the primary piezoelectric effect. These actuators were integrated directly into the blade spar laminate as active plies within the composite structure to perform structural actuation for vibration control in helicopters. Therefore, it was necessary to conduct extensive electromechanical material characterization to evaluate AFCs both as actuators and as structural components of the rotor blade. The characterization tests designed to extract important electromechanical properties under simulated blade operating conditions included stress-strain tests, free strain tests and actuation under tensile load tests. This paper presents the test results as well as the comprehensive testing process developed to evaluate the relevant AFC material properties. The results from this comprehensive performance characterization of the AFC material system supported the design and operation of the Boeing AMR blade scheduled for hover and forward flight wind tunnel tests.

A forty-year history of fiber optic smart structures

NASA Astrophysics Data System (ADS)

Udd, Eric; Scheel, Ingrid U.

2017-04-01

In 1977 McDonnell Douglas Astronautics Company began a project on using fiber optic sensors to support the Delta Rocket program. This resulted in a series of fiber sensors to support the measurement of rotation, acoustics, vibration, strain, and temperature for a variety of applications and early work on fiber optic smart structures. The work on fiber optic smart structures transitioned in part to Blue Road Research in 1993 and continued in 2006 to the present at Columbia Gorge Research. This paper summarizes some of the efforts made by these companies to implement fiber optic smart structures over this forty year period.

Plasmonic structure: fiber grating formed by gold nanorods on a tapered fiber.

PubMed

Trevisanutto, J O; Linhananta, A; Das, G

2016-12-15

The authors demonstrated the fabrication of a fiber Bragg grating-like plasmonic nanostructure on the surface of a tapered optical fiber using gold nanorods (GNRs). A multimode optical fiber with core and cladding diameters of 105 and 125 μm, respectively, was used to make a tapered fiber using a dynamic etching process. The tip diameter was ∼100  nm. Light from a laser was coupled to the untapered end of the fiber, which produced a strong evanescent field around the tapered section of the fiber. The gradient force due to the evanescent field trapped the GNRs on the surface of the tapered fiber. The authors explored possible causes of the GNR distribution. The plasmonic structure will be a good candidate for sensing based on surface enhanced Raman scattering.

Fiber networks amplify active stress

PubMed Central

Ronceray, Pierre; Broedersz, Chase P.

2016-01-01

Large-scale force generation is essential for biological functions such as cell motility, embryonic development, and muscle contraction. In these processes, forces generated at the molecular level by motor proteins are transmitted by disordered fiber networks, resulting in large-scale active stresses. Although these fiber networks are well characterized macroscopically, this stress generation by microscopic active units is not well understood. Here we theoretically study force transmission in these networks. We find that collective fiber buckling in the vicinity of a local active unit results in a rectification of stress towards strongly amplified isotropic contraction. This stress amplification is reinforced by the networks’ disordered nature, but saturates for high densities of active units. Our predictions are quantitatively consistent with experiments on reconstituted tissues and actomyosin networks and shed light on the role of the network microstructure in shaping active stresses in cells and tissue. PMID:26921325

Combined electromechanical impedance and fiber optic diagnosis of aerospace structures

NASA Astrophysics Data System (ADS)

Schlavin, Jon; Zagrai, Andrei; Clemens, Rebecca; Black, Richard J.; Costa, Joey; Moslehi, Behzad; Patel, Ronak; Sotoudeh, Vahid; Faridian, Fereydoun

2014-03-01

Electromechanical impedance is a popular diagnostic method for assessing structural conditions at high frequencies. It has been utilized, and shown utility, in aeronautic, space, naval, civil, mechanical, and other types of structures. By contrast, fiber optic sensing initially found its niche in static strain measurement and low frequency structural dynamic testing. Any low frequency limitations of the fiber optic sensing, however, are mainly governed by its hardware elements. As hardware improves, so does the bandwidth (frequency range * number of sensors) provided by the appropriate enabling fiber optic sensor interrogation system. In this contribution we demonstrate simultaneous high frequency measurements using fiber optic and electromechanical impedance structural health monitoring technologies. A laboratory specimen imitating an aircraft wing structure, incorporating surfaces with adjustable boundary conditions, was instrumented with piezoelectric and fiber optic sensors. Experiments were conducted at different structural boundary conditions associated with deterioration of structural health. High frequency dynamic responses were collected at multiple locations on a laboratory wing specimen and conclusions were drawn about correspondence between structural damage and dynamic signatures as well as correlation between electromechanical impedance and fiber optic sensors spectra. Theoretical investigation of the effect of boundary conditions on electromechanical impedance spectra is presented and connection to low frequency structural dynamics is suggested. It is envisioned that acquisition of high frequency structural dynamic responses with multiple fiber optic sensors may open new diagnostic capabilities for fiber optic sensing technologies.

Optical Fiber Sensors for Advanced Civil Structures

NASA Astrophysics Data System (ADS)

de Vries, Marten Johannes Cornelius

1995-01-01

The objective of this dissertation is to develop, analyze, and implement optical fiber-based sensors for the nondestructive quantitative evaluation of advanced civil structures. Based on a comparative evaluation of optical fiber sensors that may be used to obtain quantitative information related to physical perturbations in the civil structure, the extrinsic Fabry-Perot interferometric (EFPI) optical fiber sensor is selected as the most attractive sensor. The operation of the EFPI sensor is explained using the Kirchhoff diffraction approach. As is shown in this dissertation, this approach better predicts the signal-to-noise ratio as a function of gap length than methods employed previously. The performance of the optical fiber sensor is demonstrated in three different implementations. In the first implementation, performed with researchers in the Civil Engineering Department at the University of Southern California in Los Angeles, optical fiber sensors were used to obtain quantitative strain information from reinforced concrete interior and exterior column-to-beam connections. The second implementation, performed in cooperation with researchers at the United States Bureau of Mines in Spokane, Washington, used optical fiber sensors to monitor the performance of roof bolts used in mines. The last implementation, performed in cooperation with researchers at the Turner-Fairbanks Federal Highway Administration Research Center in McLean, Virginia, used optical fiber sensors, attached to composite prestressing strands used for reinforcing concrete, to obtain absolute strain information. Multiplexing techniques including time, frequency and wavelength division multiplexing are briefly discussed, whereas the principles of operation of spread spectrum and optical time domain reflectometery (OTDR) are discussed in greater detail. Results demonstrating that spread spectrum and OTDR techniques can be used to multiplex optical fiber sensors are presented. Finally, practical

Manufacturing of Smart Structures Using Fiber Placement Manufacturing Processes

NASA Technical Reports Server (NTRS)

Thomas, Matthew M.; Glowasky, Robert A.; McIlroy, Bruce E.; Story, Todd A.

1996-01-01

Smart structures research and development, with the ultimate aim of rapid commercial and military production of these structures, are at the forefront of the Synthesis and Processing of Intelligent Cost-Effective Structures (SPICES) program. As part of this ARPA-sponsored program, MDA-E is using fiber placement processes to manufacture integrated smart structure systems. These systems comprise advanced composite structures with embedded fiber optic sensors, shape memory alloys, piezoelectric actuators, and miniature accelerometers. Cost-effective approaches and solutions to smart material synthesis in the fiber-placement process, based upon integrated product development, are discussed herein.

Adjusted active carbon fibers for solid phase microextraction.

PubMed

Jia, Jinping; Feng, Xue; Fang, Nenghu; Wang, Yalin; Chen, Hongjin; Dan, Wu

2002-01-01

Adjusted active carbon fiber (AACF) was evaluated for Solid Phase Microextraction (SPME), which showed higher sensitivity and stability than traditional coating fibers. The characteristics of AACF result from two different activation methods (chemical and water vapor) and from variable activation conditions (temperature and time). The fiber treated by water vapor appears to have stronger affinity to polar compounds, while that treated by chemical activation appears to have stronger affinity to non-polar compounds. For different target compounds ranged from non-polar to polar, AACF design could be effective with specific selections and sensitivities. As applications in this paper, benzoic acid in soy sauce was extracted onto water-vapor-activated-fiber, then analyzed using gas chromatograph-mass spectrometer (GC-MS). The chemical-activated-fiber SPME was applied in the analysis of benzene series compounds (BTEX) in water matrix. Compared with standard carbon disulfide extraction method, chemical-activated-fiber SPME is more convenient due to its simple process and turns to be of relative low detection limits.

Design and fabrication of advanced fiber alignment structures for field-installable fiber connectors

NASA Astrophysics Data System (ADS)

Van Erps, Jürgen; Vervaeke, Michael; Sánchez Martínez, Alberto; Beri, Stefano; Debaes, Christof; Watté, Jan; Thienpont, Hugo

2012-06-01

Fiber-To-The-Home (FTTH) networks have been adopted as a potential replacement of traditional electrical connections for the 'last mile' transmission of information at bandwidths over 1Gb/s. However, the success and adoption of optical access networks critically depend on the quality and reliability of connections between optical fibers. In particular a further reduction of insertion loss of field-installable connectors must be achieved without a significant increase in component cost. This requires precise alignment of fibers that can differ in terms of ellipticity, eccentricity or diameter and seems hardly achievable using today's widespread ferrule-based alignment systems. Novel low-cost structures for bare fiber alignment with outstanding positioning accuracies are strongly desired as they would allow reducing loss beyond the level achievable with ferrule-bore systems. However, the realization of such alignment system is challenging as it should provide sufficient force to position the fiber with sub-micron accuracy required in positioning the fiber. In this contribution we propose, design and prototype a bare-fiber alignment system which makes use of deflectable/compressible micro-cantilevers. Such cantilevers behave as springs and provide self-centering functionality to the structure. Simulations of the mechanical properties of the cantilevers are carried out in order to get an analytical approximation and a mathematical model of the spring constant and stress in the structure. Elastic constants of the order of 104 to 105N/m are found out to be compatible with a proof stress of 70 MPa. Finally a first self-centering structure is prototyped in PMMA using our Deep Proton Writing technology. The spring constants of the fabricated cantilevers are in the range of 4 to 6 × 104N/m and the stress is in the range 10 to 20 MPa. These self-centering structures have the potential to become the basic building blocks for a new generation of field-installable connectors.

Adenosine triphosphatase activity of cutaneous nerve fibers.

PubMed

Idé, C; Saito, T

1980-02-01

The histochemical study of Mg++-activated adenosine triphosphatase (Mg++-ATPase) activity was carried out on the peripheral nerves of mouse digital skin by light and electron microscopy. Under the light microscope, the ATPase activity was clearly demonstrated on the nerve fibers as a fine network in the subepidermal regions. Under the electron microscope, the reaction product of enzyme activity was located in the interspace between axolemma and the surrounding Schwann cells of the unmyelinated nerve fibers. No reaction product was observed in the space between the axolemma and the Schwann cells associated with myelinated nerve fibers. Demonstrable activity was absent at the nodes of Ranvier as well as on the para- and internodal regions of these myelinated axons. The part of the axolemma lacking a Schwann cell sheath failed to show a reaction product. The perineural epithelial cells surrounding the nerve fibers displayed reaction product in the caveolae. These results suggest a functional difference in the axon-Schwann interface of myelinated as compared to unmyelinated nerve fibers. The function of the perineural epithelial cell would be expected to be a regulatory one in transferring materials across the epithelium to keep the proper humoral environment around nerve fibers.

Infrared Fibers for Use in Space-Based Smart Structures

NASA Technical Reports Server (NTRS)

Tucker, Dennis S.; Nettles, Alan T.; Brantley, Lott W. (Technical Monitor)

2001-01-01

Infrared optical fibers are finding a number of applications including laser surgery, remote sensing, and nuclear radiation resistant links. Utilizing these fibers in space-based structures is another application, which can be exploited. Acoustic and thermal sensing are two areas in which these fibers could be utilized. In particular, fibers could be embedded in IM7/8552 toughened epoxy and incorporated into space structures both external and internal. ZBLAN optical fibers are a candidate, which have been studied extensively over the past 20 years for terrestrial applications. For the past seven years the effects of gravity on the crystallization behavior of ZBLAN optical fiber has been studied. It has been found that ZBLAN crystallization is suppressed in microgravity. This lack of crystallization leads to a fiber with better transmission characteristics than its terrestrial counterpart.

Influence of heating procedures on the surface structure of stabilized polyacrylonitrile fibers

NASA Astrophysics Data System (ADS)

Zhao, Rui-Xue; Sun, Peng-fei; Liu, Rui-jian; Ding, Zhan-hui; Li, Xiang-shan; Liu, Xiao-yang; Zhao, Xu-dong; Gao, Zhong-min

2018-03-01

The stabilized polyacrylonitrile (PAN) fibers were obtained after heating the precursor PAN fibers under air atmosphere by different procedures. The surface structures and compositions of as-prepared stabilized PAN fibers have been investigated by SEM, SSNMR, XPS and Raman spectroscopy. The results show that 200 °C, 220 °C, 250 °C, and 280 °C are key temperatures for the preparation of stabilized PAN fibers. The effect of heating gradient on the structure of stabilized PAN fibers has been studied. The possible chemical structural formulas for the PAN fibers is provided, which include the stable and unstable structure. The stable structure (α-type) could endure the strong chemical reactions and the unstable structure (β- or γ-type) could mitigate the drastic oxidation reactions. The inferences of chemical formula of stabilized PAN fibers are benefit to the design of appropriate surface structure for the production for high quality carbon fibers.

Spectral engineering of optical fiber through active nanoparticle doping

NASA Astrophysics Data System (ADS)

Lindstrom-James, Tiffany

The spectral engineering of optical fiber is a method of intentional doping of the core region in order to absorb/emit specific wavelengths of light therby providing enhanced performance over current fibers. Efforts here focused on developing an understanding of optically active nanoparticles based on alkaline earth fluorides that could be easily and homogeneously incorporated into the core of a silica based optical fiber preform and result in efficient and tailorable spectral emissions. Doped and undoped calcium, strontium and barium fluoride nanoparticles were successfully synthesized and characterized for their physical, chemical, and optical behavior. Distinct spectroscopic differences as a result of different host materials, varying rare earth doping levels and processing conditions, indicated the ability to influence the spectral behavior of the doped nanoparticle. By using photoluminescence to predict diffusion behavior, the application of a simple one dimensional model for diffusion provided a method for predicting the diffusion coefficient of europium ions in alkaline earth fluorides with order of magnitude accuracy. Modified chemical vapor deposition derived silica preforms were individually solution doped with europium doped alkaline earth fluoride nanoparticles. By using the rare earth doped alkaline earth fluoride nanoparticles as the dopant materials in the core of optical fiber preforms, the resultant optical properties of the glass were significantly influenced by their presence in the core. The incorporation of these rare earth doped alkaline earth fluoride nanoparticles was found to significantly influence the local chemical and structural environment about the rare earth ion, demonstrated homogeneity and uniform distribution of the rare earth dopant and resulted in specifically unique spectral behavior when compared to conventional doping methods. A more detailed structural model of the doped core glass region has been developed based on the

Functional, structural, and chemical changes in myosin associated with hydrogen peroxide treatment of skeletal muscle fibers.

PubMed

Prochniewicz, Ewa; Lowe, Dawn A; Spakowicz, Daniel J; Higgins, LeeAnn; O'Conor, Kate; Thompson, LaDora V; Ferrington, Deborah A; Thomas, David D

2008-02-01

To understand the molecular mechanism of oxidation-induced inhibition of muscle contractility, we have studied the effects of hydrogen peroxide on permeabilized rabbit psoas muscle fibers, focusing on changes in myosin purified from these fibers. Oxidation by 5 mM peroxide decreased fiber contractility (isometric force and shortening velocity) without significant changes in the enzymatic activity of myofibrils and isolated myosin. The inhibitory effects were reversed by treating fibers with dithiothreitol. Oxidation by 50 mM peroxide had a more pronounced and irreversible inhibitory effect on fiber contractility and also affected enzymatic activity of myofibrils, myosin, and actomyosin. Peroxide treatment also affected regulation of contractility, resulting in fiber activation in the absence of calcium. Electron paramagnetic resonance of spin-labeled myosin in muscle fibers showed that oxidation increased the fraction of myosin heads in the strong-binding structural state under relaxing conditions (low calcium) but had no effect under activating conditions (high calcium). This change in the distribution of structural states of myosin provides a plausible explanation for the observed changes in both contractile and regulatory functions. Mass spectroscopy analysis showed that 50 mM but not 5 mM peroxide induced oxidative modifications in both isoforms of the essential light chains and in the heavy chain of myosin subfragment 1 by targeting multiple methionine residues. We conclude that 1) inhibition of muscle fiber contractility via oxidation of myosin occurs at high but not low concentrations of peroxide and 2) the inhibitory effects of oxidation suggest a critical and previously unknown role of methionines in myosin function.

Activated carbon fibers and engineered forms from renewable resources

DOEpatents

Baker, Frederick S

2013-02-19

A method of producing activated carbon fibers (ACFs) includes the steps of providing a natural carbonaceous precursor fiber material, blending the carbonaceous precursor material with a chemical activation agent to form chemical agent-impregnated precursor fibers, spinning the chemical agent-impregnated precursor material into fibers, and thermally treating the chemical agent-impregnated precursor fibers. The carbonaceous precursor material is both carbonized and activated to form ACFs in a single step. The method produces ACFs exclusive of a step to isolate an intermediate carbon fiber.

Activated carbon fibers and engineered forms from renewable resources

DOEpatents

Baker, Frederick S.

2010-06-01

A method of producing activated carbon fibers (ACFs) includes the steps of providing a natural carbonaceous precursor fiber material, blending the carbonaceous precursor material with a chemical activation agent to form chemical agent-impregnated precursor fibers, spinning the chemical agent-impregnated precursor material into fibers, and thermally treating the chemical agent-impregnated precursor fibers. The carbonaceous precursor material is both carbonized and activated to form ACFs in a single step. The method produces ACFs exclusive of a step to isolate an intermediate carbon fiber.

Structure and mechanics of aegagropilae fiber network.

PubMed

Verhille, Gautier; Moulinet, Sébastien; Vandenberghe, Nicolas; Adda-Bedia, Mokhtar; Le Gal, Patrice

2017-05-02

Fiber networks encompass a wide range of natural and manmade materials. The threads or filaments from which they are formed span a wide range of length scales: from nanometers, as in biological tissues and bundles of carbon nanotubes, to millimeters, as in paper and insulation materials. The mechanical and thermal behavior of these complex structures depends on both the individual response of the constituent fibers and the density and degree of entanglement of the network. A question of paramount importance is how to control the formation of a given fiber network to optimize a desired function. The study of fiber clustering of natural flocs could be useful for improving fabrication processes, such as in the paper and textile industries. Here, we use the example of aegagropilae that are the remains of a seagrass ( Posidonia oceanica ) found on Mediterranean beaches. First, we characterize different aspects of their structure and mechanical response, and second, we draw conclusions on their formation process. We show that these natural aggregates are formed in open sea by random aggregation and compaction of fibers held together by friction forces. Although formed in a natural environment, thus under relatively unconstrained conditions, the geometrical and mechanical properties of the resulting fiber aggregates are quite robust. This study opens perspectives for manufacturing complex fiber network materials.

Relationship between Fiber Furnish and the Structural Performance of MDF

Treesearch

Leslie H. Groom; Laurence Mott; Stephen Shaler

1999-01-01

The structural performance of medium density fiberboard (MDF) is attributable to three primary variables which are: physical and mechanical properties of individual wood fibers; fiber-to-fiber stress transfer; and fiber orientation. These origins of fiber properties and stress transfer can be traced to the fiber generation method wherein fiber orientation is associated...

Specialty fibers for fiber optic sensor application

NASA Astrophysics Data System (ADS)

Bennett, K.; Koh, J.; Coon, J.; Chien, C. K.; Artuso, A.; Chen, X.; Nolan, D.; Li, M.-J.

2007-09-01

Over the last several years, Fiber Optic Sensor (FOS) applications have seen an increased acceptance in many areas including oil & gas production monitoring, gyroscopes, current sensors, structural sensing and monitoring, and aerospace applications. High level optical and mechanical reliability of optical fiber is necessary to guarantee reliable performance of FOS. In this paper, we review recent research and development activities on new specialty fibers. We discuss fiber design concepts and present both modeling and experimental results. The main approaches to enhancing fiber attributes include new index profile design and fiber coating modification.

Self-centering fiber alignment structures for high-precision field installable single-mode fiber connectors

NASA Astrophysics Data System (ADS)

Van Erps, Jürgen; Ebraert, Evert; Gao, Fei; Vervaeke, Michael; Berghmans, Francis; Beri, Stefano; Watté, Jan; Thienpont, Hugo

2014-05-01

There is a steady increase in the demand for internet bandwidth, primarily driven by cloud services and high-definition video streaming. Europe's Digital Agenda states the ambitious objective that by 2020 all Europeans should have access to internet at speeds of 30Mb/s or above, with 50% or more of households subscribing to connections of 100Mb/s. Today however, internet access in Europe is mainly based on the first generation of broadband, meaning internet accessed over legacy telephone copper and TV cable networks. In recent years, Fiber-To-The-Home (FTTH) networks have been adopted as a replacement of traditional electrical connections for the `last mile' transmission of information at bandwidths over 1Gb/s. However, FTTH penetration is still very low (< 5%) in most major Western economies. The main reason for this is the high deployment cost of FTTH networks. Indeed, the success and adoption of optical access networks critically depend on the quality and reliability of connections between optical fibers. In particular a further reduction of insertion loss of field- installable connectors must be achieved without a significant increase in component cost. This requires precise alignment of fibers that can differ in terms of ellipticity, eccentricity or diameter and seems hardly achievable using today's widespread ferrule-based alignment systems. In this paper, we present a field-installable connector based on deflectable/compressible spring structures, providing a self-centering functionality for the fiber. This way, it can accommodate for possible fiber cladding diameter variations (the tolerance on the cladding diameter of G.652 fiber is typically +/-0.7μm). The mechanical properties of the cantilever are derived through an analytical approximation and a mathematical model of the spring constant, and finite element-based simulations are carried out to find the maximum first principal stress as well as the stress distribution distribution in the fiber alignment

Optical fiber curvature sensor based on MMF-SCF-MMF structure

NASA Astrophysics Data System (ADS)

Wang, Qi; Liu, Yu

2018-07-01

A sensitive curvature sensor based on MMF-SCF-MMF (MMF: multimode fiber; SCF: seven core fiber) structure is proposed. The multimode fiber (MMF) are used to improve the light coupling efficiency between the input singlemode fiber (SMF) and the seven-core fiber (SCF), and the seven-core fiber is used as the main element for curvature measurement. Experimental results show that the best curvature sensitivity reaches 41.46453 nm/m-1 in the range of 0.094 m-1-0.567 m-1. The temperature sensitivity is up to 59.02 pm/°C in the range of 20 °C-55 °C. The optical curvature sensors are widely used for buildings structure health monitoring and mechanical engineering due to the advantages of compact structure, anti-electromagnetic interference, and low cost.

Block copolymer hollow fiber membranes with catalytic activity and pH-response.

PubMed

Hilke, Roland; Pradeep, Neelakanda; Madhavan, Poornima; Vainio, Ulla; Behzad, Ali Reza; Sougrat, Rachid; Nunes, Suzana P; Peinemann, Klaus-Viktor

2013-08-14

We fabricated block copolymer hollow fiber membranes with self-assembled, shell-side, uniform pore structures. The fibers in these membranes combined pores able to respond to pH and acting as chemical gates that opened above pH 4, and catalytic activity, achieved by the incorporation of gold nanoparticles. We used a dry/wet spinning process to produce the asymmetric hollow fibers and determined the conditions under which the hollow fibers were optimized to create the desired pore morphology and the necessary mechanical stability. To induce ordered micelle assembly in the doped solution, we identified an ideal solvent mixture as confirmed by small-angle X-ray scattering. We then reduced p-nitrophenol with a gold-loaded fiber to confirm the catalytic performance of the membranes.

Optical-fiber strain sensors with asymmetric etched structures.

PubMed

Vaziri, M; Chen, C L

1993-11-01

Optical-fiber strain gauges with asymmetric etched structures have been analyzed, fabricated, and tested. These sensors are very sensitive with a gauge factor as high as 170 and a flat frequency response to at least 2.7 kHz. The gauge factor depends on the asymmetry of the etched structures and the number of etched sections. To understand the physical principles involved, researchers have used structural analysis programs based on a finite-element method to analyze fibers with asymmetric etched structures under tensile stress. The results show that lateral bends are induced on the etched fibers when they are stretched axially. To relate the lateral bending to the optical attenuation, we have also employed a ray-tracing technique to investigate the dependence of the attenuation on the structural deformation. Based on the structural analysis and the ray-tracing study parameters affecting the sensitivity have been studied. These results agree with the results of experimental investigations.

Optical Fiber Sensors for Aircraft Structural Health Monitoring

PubMed Central

García, Iker; Zubia, Joseba; Durana, Gaizka; Aldabaldetreku, Gotzon; Illarramendi, María Asunción; Villatoro, Joel

2015-01-01

Aircraft structures require periodic and scheduled inspection and maintenance operations due to their special operating conditions and the principles of design employed to develop them. Therefore, structural health monitoring has a great potential to reduce the costs related to these operations. Optical fiber sensors applied to the monitoring of aircraft structures provide some advantages over traditional sensors. Several practical applications for structures and engines we have been working on are reported in this article. Fiber Bragg gratings have been analyzed in detail, because they have proved to constitute the most promising technology in this field, and two different alternatives for strain measurements are also described. With regard to engine condition evaluation, we present some results obtained with a reflected intensity-modulated optical fiber sensor for tip clearance and tip timing measurements in a turbine assembled in a wind tunnel. PMID:26134107

Optical Fiber Sensors for Aircraft Structural Health Monitoring.

PubMed

García, Iker; Zubia, Joseba; Durana, Gaizka; Aldabaldetreku, Gotzon; Illarramendi, María Asunción; Villatoro, Joel

2015-06-30

Aircraft structures require periodic and scheduled inspection and maintenance operations due to their special operating conditions and the principles of design employed to develop them. Therefore, structural health monitoring has a great potential to reduce the costs related to these operations. Optical fiber sensors applied to the monitoring of aircraft structures provide some advantages over traditional sensors. Several practical applications for structures and engines we have been working on are reported in this article. Fiber Bragg gratings have been analyzed in detail, because they have proved to constitute the most promising technology in this field, and two different alternatives for strain measurements are also described. With regard to engine condition evaluation, we present some results obtained with a reflected intensity-modulated optical fiber sensor for tip clearance and tip timing measurements in a turbine assembled in a wind tunnel.

Mechanochromic Fibers with Structural Color.

PubMed

Li, Houpu; Sun, Xuemei; Peng, Huisheng

2015-12-21

Responsive photonic crystals have been widely developed to realize tunable structural colors by manipulating the flow of light. Among them, mechanochromic photonic crystals attract increasing attention due to the easy operation, high safety and broad applications. Recently, mechanochromic photonic crystal fibers were proposed to satisfy the booming wearable smart textile market. In this Concept, the fundamental mechanism, fabrication, and recent progress on mechanochromic photonic crystals, especially in fiber shape, are summarized to represent a new direction in sensing and displaying. © 2015 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

Ceramic Fiber Structures for Cryogenic Load-Bearing Applications

NASA Technical Reports Server (NTRS)

Jaskowiak, Martha H.; Eckel, Andrew J.

2009-01-01

This invention is intended for use as a load-bearing device under cryogenic temperatures and/or abrasive conditions (i.e., during missions to the Moon). The innovation consists of small-diameter, ceramic fibers that are woven or braided into devices like ropes, belts, tracks, or cables. The fibers can be formed from a variety of ceramic materials like silicon carbide, carbon, aluminosilicate, or aluminum oxide. The fiber architecture of the weave or braid is determined by both the fiber properties and the mechanical requirements of the application. A variety of weave or braid architectures is possible for this application. Thickness of load-bearing devices can be achieved by using either a 3D woven structure, or a layered, 2D structure. For the prototype device, a belt approximately 0.10 in. (0.25 cm) thick, and 3.0 in. (7.6 cm) wide was formed by layering and stitching a 2D aluminosilicate fiber weave.

Microstructure of the smart composite structures with embedded fiber optic sensing nerves

NASA Astrophysics Data System (ADS)

Liu, Jingyuan; Luo, Fei; Li, Changchun; Ma, Naibin

1997-11-01

The composite structures with embedded optical fiber sensors construct a smart composite structure system, which may have the characteristics of the in-service self-measurement, self- recognition and self-judgement action. In the present work, we studied the microstructures of carbon/epoxy composite laminates with embedded sensing optical fibers, and the integration of optical fiber with composites was also discussed. The preliminary experiment results show that because of the difference between the sensing optical fibers and the reinforcing fibers in their size, the microstructure of the composites with embedded optical fibers will produce partial local changes in the area of embedded optical fiber, these changes may affect the mechanical properties of composite structures. When the optical fibers are embedded parallel to the reinforcing fibers, due to the composite prepregs are formed under a press action during its curing process, the reinforcing fibers can be arranged equably around the optical fibers. But when the optical fibers are embedded perpendicularly to the reinforcement fibers, the resin rich pocket will appear in the composite laminates surrounding the embedded optical fiber. The gas holes will be easily produced in these zones which may produce a premature failure of the composite structure. The photoelastic experiments are also given in the paper.

Numerical simulation of actuation behavior of active fiber composites in helicopter rotor blade application

NASA Astrophysics Data System (ADS)

Paik, Seung Hoon; Kim, Ji Yeon; Shin, Sang Joon; Kim, Seung Jo

2004-07-01

Smart structures incorporating active materials have been designed and analyzed to improve aerospace vehicle performance and its vibration/noise characteristics. Helicopter integral blade actuation is one example of those efforts using embedded anisotropic piezoelectric actuators. To design and analyze such integrally-actuated blades, beam approach based on homogenization methodology has been traditionally used. Using this approach, the global behavior of the structures is predicted in an averaged sense. However, this approach has intrinsic limitations in describing the local behaviors in the level of the constituents. For example, the failure analysis of the individual active fibers requires the knowledge of the local behaviors. Microscopic approach for the analysis of integrally-actuated structures is established in this paper. Piezoelectric fibers and matrices are modeled individually and finite element method using three-dimensional solid elements is adopted. Due to huge size of the resulting finite element meshes, high performance computing technology is required in its solution process. The present methodology is quoted as Direct Numerical Simulation (DNS) of the smart structure. As an initial validation effort, present analytical results are correlated with the experiments from a small-scaled integrally-actuated blade, Active Twist Rotor (ATR). Through DNS, local stress distribution around the interface of fiber and matrix can be analyzed.

Biobased Nano Porous Active Carbon Fibers for High-Performance Supercapacitors.

PubMed

Huang, Yuxiang; Peng, Lele; Liu, Yue; Zhao, Guangjie; Chen, Jonathan Y; Yu, Guihua

2016-06-22

Activated carbon fibers (ACFs) with different pore structure have been prepared from wood sawdust using the KOH activation method. A study was conducted to examine the influence of the activation parameters (temperature, alkali/carbon ratio, and time) on the morphology and structure of the as-prepared ACFs developed in the process of pore generation and evolution. Activation temperature was very essential for the formation of utramicropores (<0.6 nm), which greatly contributed to the electric double layer capacitance. The significance of metallic potassium vapor evolved when the temperature was above 800 °C, since the generation of 0.8- and 1.1 nm micropores cannot be ignored. When the the KOH/fiber ratio was increased and the activation time was prolonged, to some extent, the micropores were enlarged to small mesopores within 2-5 nm. The sample with the optimal condition exhibited the highest specific capacitance (225 F g(-1) at a current density of 0.5 A g(-1)). Its ability to retain capacitance corresponding to 10 A g(-1) and 6 M KOH was 85.3%, demonstrating a good rate capability. With 10 000 charge-discharge cycles at 3 A g(-1), the supercapacitor kept 94.2% capacity, showing outstanding electrochemical performance as promising electrode material.

Fiber-Optic Sensor And Smart Structures Research At Florida Institute Of Technology

NASA Astrophysics Data System (ADS)

Grossman, Barry G.; Alavie, A. Tino; Ham, Fredric M.; Franke, Jorge E.; Thursby, Michael H.

1990-02-01

This paper discusses the fundamental issues being investigated by Florida Institute of Technology (F.I.T.) to implement the technology of smart structural systems for DoD, NASA, and commercial applications. Embedded sensors and actuators controlled by processors can provide a modification of the mechanical characteristics of composite structures to produce smart structures1-3. Recent advances in material science have spurred the development and use of composite materials in a wide range of applications from rotocraft blades and advanced tactical fighter aircraft to undersea and aerospace structures. Along with the advantages of an increased strength-to-weight ratio, the use of these materials has raised a number of questions related to understanding their failure mechanisms. Also, being able to predict structural failures far enough in advance to prevent them and to provide real-time structural health and damage monitoring has become a realistic possibility. Unfortunately, conventional sensors, actuators, and digital processors, although highly developed and well proven for other systems, may not be best suited for most smart structure applications. Our research has concentrated on few-mode and polarimetric single-fiber strain sensors4-7 and optically activated shape memory alloy (SMA) actuators controlled by artificial neural processors. We have constructed and characterized both few-mode and polarimetric sensors for a variety of fiber types, including standard single-mode, high-birefringence polarization preserving, and low-birefringence polarization insensitive fibers. We have investigated signal processing techniques for these sensors and have demonstrated active phase tracking for the high- and low-birefringence polarimetric sensors through the incorporation into the system of an electrooptic modulator designed and fabricated at F.I.T.. We have also started the design and testing of neural network architectures for processing the sensor signal outputs to

FIBER-TEX 1991: The Fifth Conference on Advanced Engineering Fibers and Textile Structures for Composites

NASA Technical Reports Server (NTRS)

Buckley, John D. (Editor)

1992-01-01

This document is a compilation of papers presented at a joint NASA/North Carolina State University/DoD/Clemson University/Drexel University conference on Fibers, Textile Technology, and Composites Structures held at the College of Textiles Building on Centennial Campus of North Carolina State University, Raleigh, North Carolina on October 15-17, 1991. Conference papers presented information on advanced engineering fibers, textile processes and structures, structural fabric production, mechanics and characteristics of woven composites, pultruded composites, and the latest requirements for the use of textiles in the production of composite materials and structures.

All-fiber intensity bend sensor based on photonic crystal fiber with asymmetric air-hole structure

NASA Astrophysics Data System (ADS)

Budnicki, Dawid; Szostkiewicz, Lukasz; Szymanski, Michal O.; Ostrowski, Lukasz; Holdynski, Zbigniew; Lipinski, Stanislaw; Murawski, Michal; Wojcik, Grzegorz; Makara, Mariusz; Poturaj, Krzysztof; Mergo, Pawel; Napierala, Marek; Nasilowski, Tomasz

2017-10-01

Monitoring the geometry of an moving element is a crucial task for example in robotics. The robots equipped with fiber bend sensor integrated in their arms can be a promising solution for medicine, physiotherapy and also for application in computer games. We report an all-fiber intensity bend sensor, which is based on microstructured multicore optical fiber. It allows to perform a measurement of the bending radius as well as the bending orientation. The reported solution has a special airhole structure which makes the sensor only bend-sensitive. Our solution is an intensity based sensor, which measures power transmitted along the fiber, influenced by bend. The sensor is based on a multicore fiber with the special air-hole structure that allows detection of bending orientation in range of 360°. Each core in the multicore fiber is sensitive to bend in specified direction. The principle behind sensor operation is to differentiate the confinement loss of fundamental mode propagating in each core. Thanks to received power differences one can distinguish not only bend direction but also its amplitude. Multicore fiber is designed to utilize most common light sources that operate at 1.55 μm thus ensuring high stability of operation. The sensitivity of the proposed solution is equal 29,4 dB/cm and the accuracy of bend direction for the fiber end point is up to 5 degrees for 15 cm fiber length. Such sensitivity allows to perform end point detection with millimeter precision.

Study of the Peripheral Nerve Fibers Myelin Structure Changes during Activation of Schwann Cell Acetylcholine Receptors

PubMed Central

Verdiyan, Ekaterina E.; Allakhverdiev, Elvin S.; Maksimov, Georgy V.

2016-01-01

In the present paper we consider a new type of mechanism by which neurotransmitter acetylcholine (ACh) regulates the properties of peripheral nerve fibers myelin. Our data show the importance of the relationship between the changes in the number of Schwann cell (SC) acetylcholine receptors (AChRs) and the axon excitation (different intervals between action potentials (APs)). Using Raman spectroscopy, an effect of activation of SC AChRs on the myelin membrane fluidity was investigated. It was found, that ACh stimulates an increase in lipid ordering degree of the myelin lipids, thus providing evidence for specific role of the “axon-SC” interactions at the axon excitation. It was proposed, that during the axon excitation, the SC membrane K+- depolarization and the Ca2+—influx led to phospholipase activation or exocytosis of intracellular membrane vesicles and myelin structure reorganization. PMID:27455410

Laser printed glass planar lightwave circuits with integrated fiber alignment structures

NASA Astrophysics Data System (ADS)

Desmet, A.; Radosavljevic, A.; Missinne, J.; Van Thourhout, D.; Van Steenberge, G.

2018-02-01

Femtosecond laser inscription allows straightforward manufacturing of glass planar lightwave circuits such as waveguides, interferometers, directional couplers, resonators and more complex structures. Fiber alignment structures are needed to facilitate communication with the glass planar lightwave circuit. In this study, a technique is described to create optical waveguides and alignment structures in the same laser exposure step. Using an industrial ytterbium-doped 1030 nm fiber laser pulses of 400 fs were focused into glass with a 0.4 NA objective causing permanent alteration of the material. Depending on laser parameters this modification allows direct writing of waveguides or the creation of channels after exposing the irradiated volumes to an etchant such as KOH. Writing of channels and waveguides with different laser powers, frequencies, polarisations, stage translation speeds and scan densities were investigated in fused silica and borosilicate glass. Waveguides with controlled dimensions were created, as well as etched U-grooves with a diameter of 126 μm and a sidewall roughness Ra of 255 nm. Cut back measurements were performed giving a waveguide propagation loss of 1.1 dB/cm in borosilicate glass. A coupling loss of 0.7 dB was measured for a transition between the waveguide and standard single mode fiber at 1550 nm, using index matching liquid. The described technique eliminates active alignment requirements and is useful for many applications such as microfluidic sensing, PLCs, fan-out connectors for multicore fibers and quantum optical networks.

Robust, Brillouin Active Embedded Fiber-Is-The-Sensor System in Smart Composite Structures

NASA Technical Reports Server (NTRS)

Yu, Chung

1996-01-01

Extensive review of our proposed sensing scheme, based mainly on the forward Guided Acoustic Wave Brillouin Scattering (GAWBS) with backward stimulated Brillouin scattering (sBs) as an auxiliary scheme for system fault tolerance has been completed during this project period. This preliminary study is conducted for a number of reasons. The most significant reasons lie in the essential capability of the system to measure temperature and pressure. These two measurands have been proposed to be sensed by sBs in our proposal. Temperature and pressure/strain are important measurands in structural monitoring, so that the effectiveness of sensing by sBs needs to be further examined. It has been pointed out initially that sBs shift will be dependent on temperature and pressure/strain simultaneously. The shift versus temperature or strain is linear. Now, the question is how can these two measurands be separated when sBs is used to sense an environment, in which both temperature and strain are changing simultaneously. Typical sBs shift plotted versus strain and varying temperature is shown in Fig. 1. As is clear, a fiber initially stressed will relax with rising temperature. This is verified by a displacement to the right with rising temperature of the sBs shift vs strain curves in the figure. A way to circumvent this ambiguity is by employing two fibers, one pre-stressed and the other is a free fiber. The latter will measure temperature and subtracting data in the latter fiber from those of the former will give us net strain readings. This is a laborious approach, since it involves the use of two identical fibers, and this is hard to accomplish, especially when many sensors are needed. Additional multiplexing of the data stream for data subtraction becomes a necessity.

Energy storage in structural composites by introducing CNT fiber/polymer electrolyte interleaves.

PubMed

Senokos, Evgeny; Ou, Yunfu; Torres, Juan Jose; Sket, Federico; González, Carlos; Marcilla, Rebeca; Vilatela, Juan J

2018-02-21

This work presents a method to produce structural composites capable of energy storage. They are produced by integrating thin sandwich structures of CNT fiber veils and an ionic liquid-based polymer electrolyte between carbon fiber plies, followed by infusion and curing of an epoxy resin. The resulting structure behaves simultaneously as an electric double-layer capacitor and a structural composite, with flexural modulus of 60 GPa and flexural strength of 153 MPa, combined with 88 mF/g of specific capacitance and the highest power (30 W/kg) and energy (37.5 mWh/kg) densities reported so far for structural supercapacitors. In-situ electrochemical measurements during 4-point bending show that electrochemical performance is retained up to fracture, with minor changes in equivalent series resistance for interleaves under compressive stress. En route to improving interlaminar properties we produce grid-shaped interleaves that enable mechanical interconnection of plies by the stiff epoxy. Synchrotron 3D X-ray tomography analysis of the resulting hierarchical structure confirms the formation of interlaminar epoxy joints. The manuscript discusses encapsulation role of epoxy, demonstrated by charge-discharge measurements of composites immersed in water, a deleterious agent for ionic liquids. Finally, we show different architectures free of current collector and electrical insulators, in which both CNT fiber and CF act as active electrodes.

Highly Stretchable Waterproof Fiber Asymmetric Supercapacitors in an Integrated Structure.

PubMed

Guo, Kai; Wang, Xianfu; Hu, Lintong; Zhai, Tianyou; Li, Huiqiao; Yu, Neng

2018-06-01

Fiber supercapacitors have attracted tremendous attention as promising power source candidates for the next generation of wearable electronics, which are flexible, stretchable, and washable. Although asymmetric fiber supercapacitors with a high energy density have been achieved, their stretchability is no more than 200%, and they still face mechanical instability and an unreliable waterproof structure. This work develops a highly integrated structure for a waterproof, highly stretchable, and asymmetric fiber-shaped supercapacitor, which is assembled by integrating a helix-shaped asymmetric fiber supercapacitor into a bifunctional polymer. The asymmetric fiber supercapacitor demonstrates a working voltage of 1.6 V, a high energy density of 2.86 mW h/cm 3 , has unchanged capacitance after being immersed in water for 50 h, and retains 95% of its initial capacitance after 3000 cycles of stretching-releasing at a maximum strain of 400%. The extraordinary waterproof capability, the large stretching strain, and excellent stretching stability are attributed to the highly integrated structure design, which can also simplify the assembly process of stretchable, waterproof fiber supercapacitors.

Preparation and photo Fenton-like activities of high crystalline CuO fibers

NASA Astrophysics Data System (ADS)

Zhang, Yan; He, Jing; Shi, Ruixia; Yang, Ping

2017-11-01

CuO fibers were successfully fabricated by a simple electrospinning method, followed by calcination. Some experimental parameters such as the content of Cu(NO3)2•3H2O, the content of PVP, the stirring time, the applied voltage, as well the calcination temperature were investigated, respectively, and their influences on the morphologies of fibers and the spinnability of precursor solution were analyzed. The CuO fibers calcined at 550 °C consisted of numerous CuO grains exhibited a well-crystalline structure. Furthermore, the CuO fibers demonstrated effective photo-Fenton degradation to methyl orange with the assist of H2O2 and the adding volume of H2O2 affects the degradation activities greatly. The degradation rate of methyl orange by the CuO fibers in the presence of 238.8 mmol/L H2O2 is 3.8 times as much as one by P25 alone under the irradiation of Xe lamp. The degradation ratio of methyl orange could achieve 83% in 180 min. The enhanced photocatalytic activities of the CuO fibers were attributed to two aspects: one is the well-crystalline of CuO fibers; the other is that H2O2 accepted the photogenerated electrons and holes effectively, which not only prevented the recombination of charge carriers but also produced additional rad OH. In this work, the formation and photocatalysis mechanisms of CuO fibers were also investigated.

Material characterization of active fiber composites for integral twist-actuated rotor blade application

NASA Astrophysics Data System (ADS)

Wickramasinghe, Viresh K.; Hagood, Nesbitt W.

2004-10-01

The primary objective of this work was to perform material characterization of the active fiber composite (AFC) actuator system for the Boeing active material rotor (AMR) blade application. The purpose of the AMR was to demonstrate active vibration control in helicopters through integral twist-actuation of the blade. The AFCs were a new structural actuator system consisting of piezoceramic fibers embedded in an epoxy matrix and sandwiched between interdigitated electrodes to enhance actuation performance. These conformable actuators were integrated directly into the blade spar laminate as active plies within the composite structure to perform structural control. Therefore, extensive electromechanical material characterization was required to evaluate AFCs both as actuators and as structural components of the blade. The characterization tests designed to extract important electromechanical properties under simulated blade operating conditions included nominal actuation tests, stress-strain tests and actuation under tensile load tests. This paper presents the test results as well as the comprehensive testing procedure developed to evaluate the relevant properties of the AFCs for structural application. The material characterization tests provided an invaluable insight into the behavior of the AFCs under various electromechanical conditions. The results from this comprehensive material characterization of the AFC actuator system supported the design and operation of the AMR blades scheduled for wind tunnel tests.

An SMS (single mode - multi mode - single mode) fiber structure for vibration sensing

NASA Astrophysics Data System (ADS)

Waluyo, T. B.; Bayuwati, D.

2017-04-01

We describe an SMS (single mode - multi mode - single mode) fiber structure to be used in a vibration sensing system. The fiber structure was fabricated by splicing a section (about 300 mm in length) of a step index multi mode fiber between two single mode fibers obtained from a communication grade fiber patchcord. Interference between higher order modes occurs while light from a narrow band light source travels along the multi mode fiber. When the multi mode fiber vibrates, the refractive index profile is changed because of the photo-elastics effect and the amplitude of the interference pattern is changed accordingly. To simulate a vibrating structure we used a loudspeaker to vibrate a wooden table. By using a digital oscilloscope, we recorded and analysed the vibrating signals obtained from the SMS fiber structure as well as from a GS-32CT geophone for referencing. We observed that this SMS fiber structure was potential to be used in a vibration sensing system with a measurement range from 30 to 180 Hz with inherent optical fiber sensor advantages such as light weight, immune to electromagnetic interference, and no electricity in the sensing part.

Distributed fiber-optic laser-ultrasound generation based on ghost-mode of tilted fiber Bragg gratings.

PubMed

Tian, Jiajun; Zhang, Qi; Han, Ming

2013-03-11

Active ultrasonic testing is widely used for medical diagnosis, material characterization and structural health monitoring. Ultrasonic transducer is a key component in active ultrasonic testing. Due to their many advantages such as small size, light weight, and immunity to electromagnetic interference, fiber-optic ultrasonic transducers are particularly attractive for permanent, embedded applications in active ultrasonic testing for structural health monitoring. However, current fiber-optic transducers only allow effective ultrasound generation at a single location of the fiber end. Here we demonstrate a fiber-optic device that can effectively generate ultrasound at multiple, selected locations along a fiber in a controllable manner based on a smart light tapping scheme that only taps out the light of a particular wavelength for laser-ultrasound generation and allow light of longer wavelengths pass by without loss. Such a scheme may also find applications in remote fiber-optic device tuning and quasi-distributed biochemical fiber-optic sensing.

Optical Sensing: Fiber Structures and Interrogation Techniques

NASA Astrophysics Data System (ADS)

Carvalho, Joel Pedro

The work described in this PhD Thesis focuses on the post-processing of optical fibers and their enhancement as sensing element. Since the majority of sensors presented are based in Fabry-Perot interferometers, an historical overview of this category of optical fiber sensors is firstly presented. This review considers the works published since the early years, in the beginning of the 1980s, until the middle of 2015. The incorporation of microcavities at the tip of a single mode fiber was extensively studied, particularly for the measurement of nitrogen and methane gas pressure. These cavities were fabricated using hollow core silica tubes and a hollow core photonic crystal fiber. Following a different approach, the microcavities were incorporated between two sections of single mode fiber. In this case, the low sensitivity to temperature makes these microcavities highly desirable for the measurement of strain at high temperatures. Competences in post-processing techniques such as the chemical etching and the writing of periodical structures in the fiber core by means of an excimer or a femtosecond laser were also acquired in the course of the PhD programme. One of the works consisted in the design and manufacturing of a double clad optical fiber. The refractive index of the inner cladding was higher than the one of the outer cladding and the core. Thus, light was guided in the inner cladding instead of propagating in the core. This situation was overcome by applying chemical etching, thus removing the inner cladding. The core, surrounded by air, was then able to guide light. Two different applications were found for this fiber, as a temperature sensor and as an optical refractometer. In the last, the optical phase changes with the liquid refractive index. Two different types of fiber Bragg gratings were characterized in strain and temperature. Sensing structures obtained through the phase mask technique at the tip of an optical fiber were subjected to chemical

Dynamic pesticide removal with activated carbon fibers.

PubMed

Martín-Gullón, I; Font, R

2001-02-01

Rapid small-scale minicolumn tests were carried out to simulate the atrazine adsorption in water phase with three pelletized pitch-based activated carbon fibers (ACF) and one commercial granular activated carbon (GAC). Initial atrazine solutions were prepared with pretreated ground water. Minicolumn tests showed that the performance of highly activated carbon fibers (surface area of 1700 m2/g) is around 7 times better than the commercial GAC (with surface area at around 1100 m2/g), whereas carbon fibers with medium activation degree (surface area of 1500 m2/g) had a removal efficiency worse than the commercial carbon. The high removal efficiency of the highly activated ACF is due to the wide-opened microstructure of the material, with an appreciable contribution of the low size mesopores, maintaining at these conditions a fast kinetic adsorption rate rather than a selective adsorbent for micropollutants vs. natural organic matter.

Optical fiber sensors for materials and structures characterization

NASA Technical Reports Server (NTRS)

Lindner, D. K.; Claus, R. O.

1991-01-01

The final technical report on Optical Fiber Sensors for Materials and Structures Characterization, covering the period August 1990 through August 1991 is presented. Research programs in the following technical areas are described; sapphire optical fiber sensors; vibration analysis using two-mode elliptical core fibers and sensors; extrinsic Fabry-Perot interferometer development; and coatings for fluorescent-based sensor. Research progress in each of these areas was substantial, as evidenced by the technical publications which are included as appendices.

Polymer optical fiber grating as water activity sensor

NASA Astrophysics Data System (ADS)

Zhang, Wei; Webb, David J.

2014-05-01

Controlling the water content within a product has long been required in the chemical processing, agriculture, food storage, paper manufacturing, semiconductor, pharmaceutical and fuel industries. The limitations of water content measurement as an indicator of safety and quality are attributed to differences in the strength with which water associates with other components in the product. Water activity indicates how tightly water is "bound," structurally or chemically, in products. Water absorption introduces changes in the volume and refractive index of poly(methyl methacrylate) PMMA. Therefore for a grating made in PMMA based optical fiber, its wavelength is an indicator of water absorption and PMMA thus can be used as a water activity sensor. In this work we have investigated the performance of a PMMA based optical fiber grating as a water activity sensor in sugar solution, saline solution and Jet A-1 aviation fuel. Samples of sugar solution with sugar concentration from 0 to 8%, saline solution with concentration from 0 to 22%, and dried (10ppm), ambient (39ppm) and wet (68ppm) aviation fuels were used in experiments. The corresponding water activities are measured as 1.0 to 0.99 for sugar solution, 1.0 to 0.86 for saline solution, and 0.15, 0.57 and 1.0 for the aviation fuel samples. The water content in the measured samples ranges from 100% (pure water) to 10 ppm (dried aviation fuel). The PMMA based optical fiber grating exhibits good sensitivity and consistent response, and Bragg wavelength shifts as large as 3.4 nm when the sensor is transferred from dry fuel to wet fuel.

Strain of optic-fiber/giant magnetostrictive film structure in magnetic field by finite element analysis

NASA Astrophysics Data System (ADS)

Hu, Jiafei; Pan, Mengchun; Xin, Jianguang; Chen, Dixiang

2008-12-01

The magnetostrictive transducer is the most important part of the optic-fiber magnetic field sensor, and the optic-fiber/giant magnetostrictive(GMS) film coupled structure is a novel coupling form of the magnetostrictive transducer. Always we analyze the coupled structure based on the entire coupled structure being sputtered GMS material without tail-fibers. In practical application, the coupled structure has tail-fibers without films at two ends. When the entire coupled structure is immersed in the detected magnetic field, the detected magnetic field causes the GMS film strain then causing optic-fiber strain. This strain transmission process is different from it in the coupled structure entirely with GMS films without tail-fibers. The strain transmission relationship can be calculated theoretically in the coupled structure without tail-fibers, but it's complicated to theoretically calculate the strain transmission relationship in the coupled structure with tail-fibers. After large numbers of calculations and analyses by ANSYS software, we figure out some relationships of the two strain transmission processes in the respective structures and the stress distribution in the tail-fibers. These results are helpful to the practical application of the optic-fiber/ GMS film coupled structure.

Highly sensitive rotation sensing based on orthogonal fiber-optic structures

NASA Astrophysics Data System (ADS)

Yang, Yi; Wang, Zi-nan; Xu, Lian-yu; Wang, Cui-yun; Jia, Lei; Yu, Xiao-qi; Shao, Shan; Li, Zheng-bin

2011-08-01

In traditional fiber-optic gyroscopes (FOG), the polarization state of counter propagating waves is critically controlled, and only the mode polarized along one particular direction survives. This is important for a traditional single mode fiber gyroscope as the requirement of reciprocity. However, there are some fatal defects such as low accuracy and poor bias stability in traditional structures. In this paper, based on the idea of polarization multiplexing, a double-polarization structure is put forward and experimentally studied. In highly birefringent fibers or standard single mode fibers with induced anisotropy, two orthogonal polarization modes can be used at the same time. Therefore, in polarization maintaining fibers (PMF), each pair of counter propagating beams preserve reciprocity within their own polarization state. Two series of sensing results are gotten in the fast and slow axes in PMF. The two sensing results have their own systematic drifts and the correlation of random noise in them is approximately zero. So, beams in fast and slow axes work as two independent and orthogonal gyroscopes. In this way, amount of information is doubled, providing opportunity to eliminate noise and improve sensitivity. Theoretically, this double-polarization structure can achieve a sensitivity of 10-18 deg/h. Computer simulation demonstrates that random noise and systematic drifts are largely reduced in this novel structure. In experiment, a forty-hour stability test targeting the earth's rotation velocity is carried out. Experiment result shows that the orthogonal fiber-optic structure has two big advantages compared with traditional ones. Firstly, the structure gets true value without any bias correction in any axis and even time-varying bias does not affect the acquisition of true value. The unbiasedness makes the structure very attractive when sudden disturbances or temperature drifts existing in working environment. Secondly, the structure lowers bias for more than

Axial strain and temperature sensing characteristics of the single-coreless-single mode fiber structure-based fiber ring laser

NASA Astrophysics Data System (ADS)

Liu, Zhi-bo; Yin, Bin; Liang, Xiao; Bai, Yunlong; Tan, Zhongwei; Liu, Shuo; Li, Yang; Liu, Yan; Jian, Shuisheng

2014-06-01

This paper experimentally demonstrated a singlemode-coreless-singlemode (SCS) fiber structure-based fiber ring cavity laser for strain and temperature measurement. The basis of the sensing system is the multimodal interference occurs in coreless fiber, and the transmission spectrum is sensitive to the ambient perturbation. In this sensing system, the SCS fiber structure not only acts as the sensing head of the sensor but also the band-pass filter of the ring laser. Blue shift with strain sensitivity of ˜ -2 pm/μɛ ranging from 0 to 730 μɛ and red shift with temperature sensitivity of ˜ 11 pm/°C ranging from 5 to 75 °C have been achieved. Experimental results also show the proposal has great potential in using long-distance operation. The fiber ring laser sensing system has a optical signal to noise ratio (OSNR) more than 50 and 3 dB bandwidth less than 0.05 nm. The result shows that the coreless fiber has no improvement of the temperature and axial strain sensitivity. However, compared to the common singlemode-multimode-singlemode fiber structure sensors, the laser sensing system has the additional advantages of high OSNR, high intensity and narrow 3 dB bandwidth, and thus improves the accuracy.

Structural health monitoring using smart optical fiber sensors

NASA Astrophysics Data System (ADS)

Davies, Heddwyn; Everall, Lorna A.; Gallon, Andrew M.

2001-04-01

This paper describes the potential of a smart monitoring system, incorporating optical fiber sensing techniques, to provide important structural information to designers and users alike. This technology has application in all areas including aerospace, civil, maritime and automotive engineering. In order to demonstrate the capability of the sensing system it has been installed in a 35 m free-standing carbon fiber yacht mast, where a complete optical network of strain and temperature sensors were embedded into a composite mast and boom during lay-up. The system was able to monitor the behavior of the composite rig through a range of handling conditions and the resulting strain information could be used by engineers to improve the structural design process. The optical strain sensor system comprises of three main components: the sensor network, the opto-electronic data acquisition unit (OFSSS) and the external PC which acts as a data log and display. Embedded fiber optic sensors have wide ranging application for structural load monitoring. Due to their small size, optical fiber sensors can be readily embedded into composite materials. Other advantages include their immediate multiplexing capability and immunity to electromagnetic interference. The capability of this system has been demonstrated within the maritime environment, but can be adapted for any application.

Transmural gradients of myocardial structure and mechanics: Implications for fiber stress and strain in pressure overload.

PubMed

Carruth, Eric D; McCulloch, Andrew D; Omens, Jeffrey H

2016-12-01

Although a truly complete understanding of whole heart activation, contraction, and deformation is well beyond our current reach, a significant amount of effort has been devoted to discovering and understanding the mechanisms by which myocardial structure determines cardiac function to better treat patients with cardiac disease. Several experimental studies have shown that transmural fiber strain is relatively uniform in both diastole and systole, in contrast to predictions from traditional mechanical theory. Similarly, mathematical models have largely predicted uniform fiber stress across the wall. The development of this uniform pattern of fiber stress and strain during filling and ejection is due to heterogeneous transmural distributions of several myocardial structures. This review summarizes these transmural gradients, their contributions to fiber mechanics, and the potential functional effects of their remodeling during pressure overload hypertrophy. Copyright © 2016 Elsevier Ltd. All rights reserved.

Fiber networks amplify active stress

NASA Astrophysics Data System (ADS)

Lenz, Martin; Ronceray, Pierre; Broedersz, Chase

Large-scale force generation is essential for biological functions such as cell motility, embryonic development, and muscle contraction. In these processes, forces generated at the molecular level by motor proteins are transmitted by disordered fiber networks, resulting in large-scale active stresses. While fiber networks are well characterized macroscopically, this stress generation by microscopic active units is not well understood. I will present a comprehensive theoretical study of force transmission in these networks. I will show that the linear, small-force response of the networks is remarkably simple, as the macroscopic active stress depends only on the geometry of the force-exerting unit. In contrast, as non-linear buckling occurs around these units, local active forces are rectified towards isotropic contraction and strongly amplified. This stress amplification is reinforced by the networks' disordered nature, but saturates for high densities of active units. I will show that our predictions are quantitatively consistent with experiments on reconstituted tissues and actomyosin networks, and that they shed light on the role of the network microstructure in shaping active stresses in cells and tissue.

Active and separate secretion of fiber and penton base during the early phase of Ad2 or Ad5 infection

DOE Office of Scientific and Technical Information (OSTI.GOV)

Yan, Yuhua; Zhang, Bo; Hou, Weihong

Fiber and penton base overproduced in adenovirus (Ad) infected cells can be secreted prior to progeny release and thereby regulate progeny spread. We aimed to investigate the mechanisms of fiber and penton base secretion in Ad2- or Ad5-infected A549 cells. Our flow cytometry analyses detected abundant surface fiber molecules, but little penton base molecules at 12 h post infection. Immunogold staining combined with transmission electron microscopic analyses revealed separate, non-co-localized release of fiber and penton base in the proximity of the plasma membrane. Depolymerization of microtubule and actin cytoskeletons, and inhibition of Rock kinase and myosin II activity together demonstratedmore » cytoskeletal network-dependent fiber secretion. Inhibition of intracellular calcium [Ca{sup 2+}]{sub i} signaling caused diminished fiber secretion, which was associated with diminished progeny production. Thus, fiber and penton base are actively and separately secreted during the early stages of Ad2 or Ad5 infection, their secretion may play important role in Ad life cycle. - Highlights: •Excessive production of structural proteins is common to viral infection, which may regulate the host-virus equilibrium and the spreading of viruses. •The adenovirus (Ad) structural proteins, fiber and penton base, are respectively important for Ad binding to its receptor and subsequent internalization in host cells. In Ad infected cells, these two structural proteins are excessively produced. •The mechanisms underlying the release of fiber and penton base molecules at the early phase of Ad infection is yet poorly understood. •Our studies show that in Ad5 or Ad2 infected A549 cells, fiber and penton base molecules are actively and separately secreted. •Fiber secretion is dependent on cytoskeleton-mediated protein traffic. •Inhibition of myosin II motor and Ca{sup 2+} signaling activity significantly diminishes fiber secretion. •These findings could contribute to our

Graphite fiber reinforced structure for supporting machine tools

DOEpatents

Knight, Jr., Charles E.; Kovach, Louis; Hurst, John S.

1978-01-01

Machine tools utilized in precision machine operations require tool support structures which exhibit minimal deflection, thermal expansion and vibration characteristics. The tool support structure of the present invention is a graphite fiber reinforced composite in which layers of the graphite fibers or yarn are disposed in a 0/90.degree. pattern and bonded together with an epoxy resin. The finished composite possesses a low coefficient of thermal expansion and a substantially greater elastic modulus, stiffness-to-weight ratio, and damping factor than a conventional steel tool support utilized in similar machining operations.

Effects of annealing on the structure and magnetic properties of Fe80B20 magnetostrictive fibers.

PubMed

Zhu, Qianke; Zhang, Shuling; Geng, Guihong; Li, Qiushu; Zhang, Kewei; Zhang, Lin

2016-07-04

Fe80B20 amorphous alloys exhibit excellent soft magnetic properties, high abrasive resistance and outstanding corrosion resistance. In this work, Fe80B20 amorphous micro-fibers with HC of 3.33 Oe were firstly fabricated and the effects of annealing temperature on the structure and magnetic properties of the fibers were investigated. In this study, Fe80B20 amorphous fibers were prepared by the single roller melt-spinning method. The structures of as-spun and annealed fibers were investigated by X-ray diffractometer (XRD) (PANalytical X,Pert Power) using Cu Kα radiation. The morphology of the fibers was observed by scanning electron microscopy (SEM) (HITACHI-S4800). Differential scanning calorimetry (DSC) measurements of the fibers were performed on Mettler Toledo TGA/DSC1 device under N2 protection. Vibrating sample magnetometer (VSM, Versalab) was used to examine the magnetic properties of the fibers. The resonance behavior of the fibers was characterized by an impedance analyzer (Agilent 4294A) with a home-made copper coil. The X-ray diffusion (XRD) patterns show that the fibers remain amorphous structure until the annealing temperature reaches 500°C. The differential scanning calorimetry (DSC) results show that the crystallization temperature of the fibers is 449°C. The crystallization activation energy is calculated to be 221 kJ/mol using Kissinger formula. The scanning electron microscopy (SEM) images show that a few dendrites appear at the fiber surface after annealing. The result indicates that the coercivity HC (//) and HC (⊥) slightly increases with increasing annealing temperature until 400°C, and then dramatically increases with further increasing annealing temperature which is due to significant increase in magneto-crystalline anisotropy and magneto-elastic anisotropy. The Q value firstly increases slightly when the annealing temperature rises from room temperature (RT) to 300°C, then decreases until 400°C. Eventually, the value of Q increases to

Erbium-doped fiber amplifier elements for structural analysis sensors

NASA Technical Reports Server (NTRS)

Hanna-Hawver, P.; Kamdar, K. D.; Mehta, S.; Nagarajan, S.; Nasta, M. H.; Claus, R. O.

1992-01-01

The use of erbium-doped fiber amplifiers (EDFA's) in optical fiber sensor systems for structural analysis is described. EDFA's were developed for primary applications as periodic regenerator amplifiers in long-distance fiber-based communication systems. Their in-line amplification performance also makes them attractive for optical fiber sensor systems which require long effective lengths or the synthesis of special length-dependent signal processing functions. Sensor geometries incorporating EDFA's in recirculating and multiple loop sensors are discussed. Noise and polarization birefringence are also considered, and the experimental development of system components is discussed.

Automated determination of fibrillar structures by simultaneous model building and fiber diffraction refinement.

PubMed

Potrzebowski, Wojciech; André, Ingemar

2015-07-01

For highly oriented fibrillar molecules, three-dimensional structures can often be determined from X-ray fiber diffraction data. However, because of limited information content, structure determination and validation can be challenging. We demonstrate that automated structure determination of protein fibers can be achieved by guiding the building of macromolecular models with fiber diffraction data. We illustrate the power of our approach by determining the structures of six bacteriophage viruses de novo using fiber diffraction data alone and together with solid-state NMR data. Furthermore, we demonstrate the feasibility of molecular replacement from monomeric and fibrillar templates by solving the structure of a plant virus using homology modeling and protein-protein docking. The generated models explain the experimental data to the same degree as deposited reference structures but with improved structural quality. We also developed a cross-validation method for model selection. The results highlight the power of fiber diffraction data as structural constraints.

Preparation of activated carbon hollow fibers from ramie at low temperature for electric double-layer capacitor applications.

PubMed

Du, Xuan; Zhao, Wei; Wang, Yi; Wang, Chengyang; Chen, Mingming; Qi, Tao; Hua, Chao; Ma, Mingguo

2013-12-01

Activated carbon hollow fibers (ACHFs) with high surface area were prepared from inexpensive, renewable ramie fibers (RFs) by a single-step activation method under lower temperature than that of other reports. The effects of activation conditions on the pore structure and turbostratic structure of ACHFs were investigated systematically. The results show that ACHFs surface area decreased but micropore volume and conductivity increased as the increase of activation temperature and activation time. The electrochemical measurements of supercapacitors fabricated from these ACHFs electrodes reveal that the electrochemical properties improved with the enhancing of activation degree. However, too high activation temperature can make the ion diffusion resistance increase. It suggests that pore structure and conductivity are as important as surface area to decide the electrochemical performances of ACHFs electrode materials. A maximum capacity of 287 F g(-1) at 50 mA g(-1) was obtained for the ACHFs electrode prepared under suitable conditions. Copyright © 2013 Elsevier Ltd. All rights reserved.

Bactericidal Activity of Usnic Acid-Loaded Electrospun Fibers.

PubMed

Araújo, Evando S; Pereira, Eugênia C; da Costa, Mateus M; da Silva, Nicácio H; de Oliveira, Helinando P

2016-01-01

Usnic acid has been progressively reported in the literature as one of the most important lichen metabolites characterized by a rich diversity of applications such as antifungal, antimicrobial, antiprotozoal and antiviral agent. Particularly, antimicrobial activity of usnic acid can be improved by encapsulation of active molecules in enteric electrospun fibers, allowing the controlled release of active molecule at specific pH. Few relevant patents to the topic have been reviewed and cited. Bactericidal activity of usnic acid-loaded electrospun fibers of Eudragit L-100 and polyvinylpyrrolidone was examined against Staphylococcus aureus using inhibition hales methodology. The controlled release of active material at high pH is established after 10 minutes of interaction with media and results in reasonable activity against S. aureus, as detected by inhibition hales. The strong biological activity of usnic acid-loaded electrospun fibers provides a promising application for corresponding material as a bactericidal agent for wound healing treatment.

Adsorption Properties of Lignin-derived Activated Carbon Fibers (LACF)

DOE Office of Scientific and Technical Information (OSTI.GOV)

Contescu, Cristian I.; Gallego, Nidia C.; Thibaud-Erkey, Catherine

The object of this CRADA project between Oak Ridge National Laboratory (ORNL) and United Technologies Research Center (UTRC) is the characterization of lignin-derived activated carbon fibers (LACF) and determination of their adsorption properties for volatile organic compounds (VOC). Carbon fibers from lignin raw materials were manufactured at Oak Ridge National Laboratory (ORNL) using the technology previously developed at ORNL. These fibers were physically activated at ORNL using various activation conditions, and their surface area and pore-size distribution were characterized by gas adsorption. Based on these properties, ORNL did down-select five differently activated LACF materials that were delivered to UTRC formore » measurement of VOC adsorption properties. UTRC used standard techniques based on breakthrough curves to measure and determine the adsorption properties of indoor air pollutants (IAP) - namely formaldehyde and carbon dioxide - and to verify the extent of saturated fiber regenerability by thermal treatments. The results are summarized as follows: (1) ORNL demonstrated that physical activation of lignin-derived carbon fibers can be tailored to obtain LACF with surface areas and pore size distributions matching the properties of activated carbon fibers obtained from more expensive, fossil-fuel precursors; (2) UTRC investigated the LACF potential for use in air cleaning applications currently pursued by UTRC, such as building ventilation, and demonstrated their regenerability for CO2 and formaldehyde, (3) Both partners agree that LACF have potential for possible use in air cleaning applications.« less

Fiber grating systems used to measure strain in cylindrical structures

NASA Astrophysics Data System (ADS)

Udd, Eric; Corona-Bittick, Kelli; Slattery, Kerry T.; Dorr, Donald J.; Crowe, C. Robert; Vandiver, Terry L.; Evans, Robert N.

1997-07-01

Fiber optic grating systems are described that have been used to measure strain in cylindrical structures. The applications of these systems to a composite utility pole and to a composite missile body are described. Composite utility poles have significant advantages with respect to wooden utility poles that include superior strength and uniformity; light weight for ease of deployment; the ability to be recycled, reducing hazardous waste associated with chemically treated wooden poles; and compatibility with embedded fiber optic sensors, allowing structural loads to be monitored. Tests conducted of fiber optic grating sensors in combination with an overcoupled coupler demodulation system to support structural testing of a 22-ft composite pole are reported. Monitoring strain in composite missile bodies has the potential to improve the quality of manufactured parts, support performance testing, and enhance safety during long periods of storage. Strain measurements made with fiber optic grating and electrical strain gauges are described.

Natural Kenaf Fiber Reinforced Composites as Engineered Structural Materials

NASA Astrophysics Data System (ADS)

Dittenber, David B.

The objective of this work was to provide a comprehensive evaluation of natural fiber reinforced polymer (NFRP)'s ability to act as a structural material. As a chemical treatment, aligned kenaf fibers were treated with sodium hydroxide (alkalization) in different concentrations and durations and then manufactured into kenaf fiber / vinyl ester composite plates. Single fiber tensile properties and composite flexural properties, both in dry and saturated environments, were assessed. Based on ASTM standard testing, a comparison of flexural, tensile, compressive, and shear mechanical properties was also made between an untreated kenaf fiber reinforced composite, a chemically treated kenaf fiber reinforced composite, a glass fiber reinforced composite, and oriented strand board (OSB). The mechanical properties were evaluated for dry samples, samples immersed in water for 50 hours, and samples immersed in water until saturation (~2700 hours). Since NFRPs are more vulnerable to environmental effects than synthetic fiber composites, a series of weathering and environmental tests were conducted on the kenaf fiber composites. The environmental conditions studied include real-time outdoor weathering, elevated temperatures, immersion in different pH solutions, and UV exposure. In all of these tests, degradation was found to be more pronounced in the NFRPs than in the glass FRPs; however, in nearly every case the degradation was less than 50% of the flexural strength or stiffness. Using a method of overlapping and meshing discontinuous fiber ends, large mats of fiber bundles were manufactured into composite facesheets for structural insulated panels (SIPs). The polyisocyanurate foam cores proved to be poorly matched to the strength and stiffness of the NFRP facesheets, leading to premature core shear or delamination failures in both flexure and compressive testing. The NFRPs were found to match well with the theoretical stiffness prediction methods of classical lamination

Catalytic property of fiber media supported palladium containing alloy nanoparticles and electrospun ceramic fibers biodurability study

NASA Astrophysics Data System (ADS)

Shin, Hyeon Ung

The nanoscale of the supporting fibers may provide enhancements such as restricting the migration of metal catalyst particles. In this work, palladium nanoparticle doped alumina fibers were electrospun into template submicron fibers. These fibers were calcined at temperatures between 650°C and 1150°C to vary the crystal structures of the calcined fibers with the Pd particle size. Higher calcination temperatures led to higher reaction temperatures from 250 to about 450°C for total conversion, indicating the effective reactivity of the fiber-supported catalysts decreased with increase in calcination temperature. Pd-Au alloy nanoparticle doped titania fibers were also fabricated using an electrospinning method and assembled into a fibrous porous medium structure by a vacuum molding process. In reactor tests, the fiber media with Pd-Au alloy nanoparticle catalyst had greater reactivity in conversion of NO and CO gases than that of fiber media with Pd monometallic catalyst alone, attributed to a lower activation energy of the Pd-Au catalyst particles. In carbon monoxide oxidation reaction tests, the results showed that the performance was optimal for a catalyst of composition Pd2Au1 molar ratio that was active at 125°C, which had higher dispersion of active components and better catalytic performance compared to monometallic particle Au/TiO 2 and Pd/TiO2 fiber media. Moreover, the improved reaction activity of Pd2Au1/TiO2 fiber medium was attributed to a decreased in the activation energy. Further experiments were conducted using the electrospun ceramic fibers biodurability study. The properties of nano-sized fiber structures have attracted the attention of recent research on ceramic nanostructures as nonwoven media for applications in hazardous chemical and high temperature environments. However, health and safety concerns of micro and nano scale ceramic materials have not been fully investigated. Little is known about the physicochemical effects of the properties

Femtosecond laser-induced surface structures on carbon fibers.

PubMed

Sajzew, Roman; Schröder, Jan; Kunz, Clemens; Engel, Sebastian; Müller, Frank A; Gräf, Stephan

2015-12-15

The influence of different polarization states during the generation of periodic nanostructures on the surface of carbon fibers was investigated using a femtosecond laser with a pulse duration τ=300  fs, a wavelength λ=1025  nm, and a peak fluence F=4  J/cm². It was shown that linear polarization results in a well-aligned periodic pattern with different orders of magnitude concerning their period and an alignment parallel and perpendicular to fiber direction, respectively. For circular polarization, both types of uniform laser-induced periodic surface structures (LIPSS) patterns appear simultaneously with different dominance in dependence on the position at the fiber surface. Their orientation was explained by the polarization-dependent absorptivity and the geometrical anisotropy of the carbon fibers.

Investigation of Carbon-Polymer Structures with Embedded Fiber-Optic Bragg Gratings

NASA Technical Reports Server (NTRS)

Grant, Joseph; Kaul, R.; Taylor, S.; Myers, G.; Sharma, A.

2003-01-01

Several Bragg-grating sensors fabricated within the same optical fiber are buried within multiple-ply carbon-epoxy planar and cylindrical structures. Effect of different orientation of fiber-sensors with respect to carbon fibers in the composite structure is investigated. This is done for both fabric and uni-tape material samples. Response of planar structures to axial and transverse strain up to 1 millistrain is investigated with distributed Bragg-grating sensors. Material properties like Young's Modulus and Poisson ratio is measured. A comparison is made between response measured by sensors in different ply-layers and those bonded on the surface. The results from buried fiber- sensors do not completely agree with surface bonded conventional strain gauges. A plausible explanation is given for observed differences. The planar structures are subjected to impacts with energies up to 10 ft-lb. Effect of this impact on the material stiffness is also investigated with buried fiber-optic Bragg sensors. The strain response of such optical sensors is also measured for cylindrical carbon-epoxy composite structures. The sensors are buried within the walls of the cylinder as well as surface bonded in both the axial as well as hoop directions. The response of these fiber-optic sensors is investigated by pressurizing the cylinder up to its burst pressure of around 1500 psi. This is done at both room temperature as well as cryogenic temperatures. The recorded response is compared with that from a conventional strain gauge.

Fiber optic shape sensing for monitoring of flexible structures

NASA Astrophysics Data System (ADS)

Lally, Evan M.; Reaves, Matt; Horrell, Emily; Klute, Sandra; Froggatt, Mark E.

2012-04-01

Recent advances in materials science have resulted in a proliferation of flexible structures for high-performance civil, mechanical, and aerospace applications. Large aspect-ratio aircraft wings, composite wind turbine blades, and suspension bridges are all designed to meet critical performance targets while adapting to dynamic loading conditions. By monitoring the distributed shape of a flexible component, fiber optic shape sensing technology has the potential to provide valuable data during design, testing, and operation of these smart structures. This work presents a demonstration of such an extended-range fiber optic shape sensing technology. Three-dimensional distributed shape and position sensing is demonstrated over a 30m length using a monolithic silica fiber with multiple optical cores. A novel, helicallywound geometry endows the fiber with the capability to convert distributed strain measurements, made using Optical Frequency-Domain Reflectometry (OFDR), to a measurement of curvature, twist, and 3D shape along its entire length. Laboratory testing of the extended-range shape sensing technology shows

Active control for vibration suppression in a flexible beam using a modal domain optical fiber sensor

NASA Technical Reports Server (NTRS)

Cox, D. E.; Lindner, D. K.

1991-01-01

An account is given of the use of a modal-domain (MD) fiber-optic sensor as an active control system component for vibration suppression, whose output is proportional to the integral of the axial strain along the optical fiber. When an MD sensor is attached to, or embedded in, a flexible structure, it senses the strain in the structure along its gage length. On the basis of the present integration of the sensor model into a flexible-structure model, it becomes possible to design a control system with a dynamic compensator which adds damping to the low-order modes of the flexible structure. This modeling procedure has been experimentally validated.

Analysis of Plasmonics Based Fiber Optic Sensing Structures

NASA Astrophysics Data System (ADS)

Moayyed, Hamed

The work described in this PhD Thesis focuses on the post-processing of optical fibers and their enhancement as sensing element. Since the majority of sensors presented are based in Fabry-Perot interferometers, an historical overview of this category of optical fiber sensors is firstly presented. This review considers the works published since the early years, in the beginning of the 1980s, until the middle of 2015. The incorporation of microcavities at the tip of a single mode fiber was extensively studied, particularly for the measurement of nitrogen and methane gas pressure. These cavities were fabricated using hollow core silica tubes and a hollow core photonic crystal fiber. Following a different approach, the microcavities were incorporated between two sections of single mode fiber. In this case, the low sensitivity to temperature makes these microcavities highly desirable for the measurement of strain at high temperatures. Competences in post-processing techniques such as the chemical etching and the writing of periodical structures in the fiber core by means of an excimer or a femtosecond laser were also acquired in the course of the PhD programme. One of the works consisted in the design and manufacturing of a double clad optical fiber. The refractive index of the inner cladding was higher than the one of the outer cladding and the core. Thus, light was guided in the inner cladding instead of propagating in the core. This situation was overcome by applying chemical etching, thus removing the inner cladding. The core, surrounded by air, was then able to guide light. Two different applications were found for this fiber, as a temperature sensor and as an optical refractometer. In the last, the optical phase changes with the liquid refractive index. Two different types of fiber Bragg gratings were characterized in strain and temperature. Sensing structures obtained through the phase mask technique at the tip of an optical fiber were subjected to chemical

Activated Carbon Fibers For Gas Storage

DOE Office of Scientific and Technical Information (OSTI.GOV)

Burchell, Timothy D; Contescu, Cristian I; Gallego, Nidia C

The advantages of Activated Carbon Fibers (ACF) over Granular Activated Carbon (GAC) are reviewed and their relationship to ACF structure and texture are discussed. These advantages make ACF very attractive for gas storage applications. Both adsorbed natural gas (ANG) and hydrogen gas adsorption performance are discussed. The predicted and actual structure and performance of lignin-derived ACF is reviewed. The manufacture and performance of ACF derived monolith for potential automotive natural gas (NG) storage applications is reported Future trends for ACF for gas storage are considered to be positive. The recent improvements in NG extraction coupled with the widespread availability ofmore » NG wells means a relatively inexpensive and abundant NG supply in the foreseeable future. This has rekindled interest in NG powered vehicles. The advantages and benefit of ANG compared to compressed NG offer the promise of accelerated use of ANG as a commuter vehicle fuel. It is to be hoped the current cost hurdle of ACF can be overcome opening ANG applications that take advantage of the favorable properties of ACF versus GAC. Lastly, suggestions are made regarding the direction of future work.« less

Civionics specifications for fiber optic sensors for structural health monitoring

NASA Astrophysics Data System (ADS)

Rivera, Evangeline; Mufti, Aftab A.; Thomson, Douglas J.

2004-07-01

As the design and construction of civil structures continue to evolve, it is becoming imperative that these structures be monitored for their health. In order to meet this need, the discipline of Civionics has emerged. It involves the applications to civil structures and aims to assist engineers in realizing the full benefits of structural health monitoring (SHM). Therefore, the goal of the specification outlined in this work is to ensure that correct installation and operating of fiber optic sensors, such as bridges, will be discussed that motivated the writing of these specifications. The main reason for the failure of FOS based monitoring systems can be traced directly to the installation of the fiber sensor itself. Therefore, by creating a standard procedure for SHM, several ambiguities are eliminated such as fiber sensor specifications and the types of cables required. As a result, these specifications will help ensure that the sensors will survive the installation process and eventually prove their value over years of monitoring the health of the structure. The Civionics FOS specifications include the requirements for fiber sensors, specifically Bragg grating sensors, and their corresponding readout unit. It also includes specifications on the cables, conduits, junction boxes, cable termination and the environmental.

Three-Axis Distributed Fiber Optic Strain Measurement in 3D Woven Composite Structures

NASA Technical Reports Server (NTRS)

Castellucci, Matt; Klute, Sandra; Lally, Evan M.; Froggatt, Mark E.; Lowry, David

2013-01-01

Recent advancements in composite materials technologies have broken further from traditional designs and require advanced instrumentation and analysis capabilities. Success or failure is highly dependent on design analysis and manufacturing processes. By monitoring smart structures throughout manufacturing and service life, residual and operational stresses can be assessed and structural integrity maintained. Composite smart structures can be manufactured by integrating fiber optic sensors into existing composite materials processes such as ply layup, filament winding and three-dimensional weaving. In this work optical fiber was integrated into 3D woven composite parts at a commercial woven products manufacturing facility. The fiber was then used to monitor the structures during a VARTM manufacturing process, and subsequent static and dynamic testing. Low cost telecommunications-grade optical fiber acts as the sensor using a high resolution commercial Optical Frequency Domain Reflectometer (OFDR) system providing distributed strain measurement at spatial resolutions as low as 2mm. Strain measurements using the optical fiber sensors are correlated to resistive strain gage measurements during static structural loading. Keywords: fiber optic, distributed strain sensing, Rayleigh scatter, optical frequency domain reflectometry

Research on dual-parameter optical fiber sensor based on thin-core fiber and spherical structure

NASA Astrophysics Data System (ADS)

Tong, Zhengrong; Wang, Xue; Zhang, Weihua; Xue, Lifang

2018-04-01

A novel dual-parameter optical fiber sensor is proposed and experimentally demonstrated. The proposed sensor is based on a fiber in-line Mach-Zehnder interferometer, which is fabricated by sandwiching a section of thin-core fiber between two spherical structures made of single-mode fibers. The transmission spectrum exhibits the response of the interference between the core and the different cladding modes. Due to the different wavelength shifts of the two selected dips, the simultaneous measurement of temperature and the surrounding refractive index can be achieved. The measured temperature sensitivities are 0.067 nm/°C and 0.050 nm/°C, and the refractive index sensitivities are  -119.9 nm/RIU and  -69.71 nm/RIU, respectively. In addition, the compact size, simple fabrication and cost-effectiveness of the fiber sensor are also advantages.

Structure and morphology of regenerated silk nano-fibers produced by electrospinning

NASA Astrophysics Data System (ADS)

Zarkoob, Shahrzad

The impressive physical and mechanical properties of natural silk fiberssp1 and the possibility of producing these proteins using biotechnology,sp2 have provided the impetus for recent efforts in both the biosynthesissp{3,4} and the spinning of these protein based biopolymers.sp{5,6,7} The question still remains: whether fibers spun from solutions with similar chemical makeup can produce fibers with similar structures and therefore with the possibility of improved properties. Since genetically engineered silk solutions were not readily available, the first objective of this project was to completely dissolve the Bombyx mori cocoon and the Nephila clavipes dragline silk while maintaining the molecular weight integrity of the polymer. The second objective was to develop a system for re-spinning from very small amount of the resulting silk solutions by the process of electrospinning. The third objective was, to produce regenerated silk fibers with diameters that are several orders of magnitude smaller than the original fibers, suitable for direct observation and analysis by transmission electron microscopy and electron diffraction. And finally, to compare these results to structural information obtained from natural (as spun by the organism) fibers to see if the regenerated solutions are able to form the same structure as the original fibers. Both types of silk fibers were successfully dissolved while maintaining the polymer integrity. Small quantities (25-50 mul) of these solutions were used to electrospin fibers with diameters ranging from 8nm-200nm. The fibers were observed by optical, scanning electron, and transmission electron microscopy. These nano fibers showed optical retardation, appeared to have a circular cross-section, and were dimensionally stable at temperatures above 280sp°C. Electron diffraction patterns of annealed electrospun fibers of B. mori and N. clavipes showed reflections, demonstrating orientational and semicrystalline order in the material

Damage to lens fiber cells causes TRPV4-dependent Src family kinase activation in the epithelium.

PubMed

Shahidullah, M; Mandal, A; Delamere, N A

2015-11-01

The bulk of the lens consists of tightly packed fiber cells. Because mature lens fibers lack mitochondria and other organelles, lens homeostasis relies on a monolayer of epithelial cells at the anterior surface. The detection of various signaling pathways in lens epithelial cells suggests they respond to stimuli that influence lens function. Focusing on Src Family Kinases (SFKs) and Transient Receptor Potential Vanilloid 4 (TRPV4), we tested whether the epithelium can sense and respond to an event that occurs in fiber mass. The pig lens was subjected to localized freeze-thaw (FT) damage to fibers at posterior pole then the lens was incubated for 1-10 min in Krebs solution at 37 °C. Transient SFK activation in the epithelium was detectable at 1 min. Using a western blot approach, the ion channel TRPV4 was detected in the epithelium but was sparse or absent in fiber cells. Even though TRPV4 expression appears low at the actual site of FT damage to the fibers, SFK activation in the epithelium was suppressed in lenses subjected to FT damage then incubated with the TRPV4 antagonist HC067047 (10 μM). Na,K-ATPase activity was examined because previous studies report changes of Na,K-ATPase activity associated with SFK activation. Na,K-ATPase activity doubled in the epithelium removed from FT-damaged lenses and the response was prevented by HC067047 or the SFK inhibitor PP2 (10 μM). Similar changes were observed in response to fiber damage caused by injection of 5 μl hyperosmotic NaCl or mannitol solution beneath the surface of the posterior pole. The findings point to a TRPV4-dependent mechanism that enables the epithelial cells to detect remote damage in the fiber mass and respond within minutes by activating SFK and increasing Na,K-ATPase activity. Because TRPV4 channels are mechanosensitive, we speculate they may be stimulated by swelling of the lens structure caused by damage to the fibers. Increased Na,K-ATPase activity gives the lens greater capacity to

Activation of Arabidopsis Seed Hair Development by Cotton Fiber-Related Genes

PubMed Central

Pang, Mingxiong; Shi, Xiaoli; Stelly, David M.; Chen, Z. Jeffrey

2011-01-01

Each cotton fiber is a single-celled seed trichome or hair, and over 20,000 fibers may develop semi-synchronously on each seed. The molecular basis for seed hair development is unknown but is likely to share many similarities with leaf trichome development in Arabidopsis. Leaf trichome initiation in Arabidopsis thaliana is activated by GLABROUS1 (GL1) that is negatively regulated by TRIPTYCHON (TRY). Using laser capture microdissection and microarray analysis, we found that many putative MYB transcription factor and structural protein genes were differentially expressed in fiber and non-fiber tissues. Gossypium hirsutum MYB2 (GhMYB2), a putative GL1 homolog, and its downstream gene, GhRDL1, were highly expressed during fiber cell initiation. GhRDL1, a fiber-related gene with unknown function, was predominately localized around cell walls in stems, sepals, seed coats, and pollen grains. GFP:GhRDL1 and GhMYB2:YFP were co-localized in the nuclei of ectopic trichomes in siliques. Overexpressing GhRDL1 or GhMYB2 in A. thaliana Columbia-0 (Col-0) activated fiber-like hair production in 4–6% of seeds and had on obvious effects on trichome development in leaves or siliques. Co-overexpressing GhRDL1 and GhMYB2 in A. thaliana Col-0 plants increased hair formation in ∼8% of seeds. Overexpressing both GhRDL1 and GhMYB2 in A. thaliana Col-0 try mutant plants produced seed hair in ∼10% of seeds as well as dense trichomes inside and outside siliques, suggesting synergistic effects of GhRDL1 and GhMYB2 with try on development of trichomes inside and outside of siliques and seed hair in A. thaliana. These data suggest that a different combination of factors is required for the full development of trichomes (hairs) in leaves, siliques, and seeds. A. thaliana can be developed as a model a system for discovering additional genes that control seed hair development in general and cotton fiber in particular. PMID:21779324

Femtosecond-pulse inscription of fiber Bragg gratings with single or multiple phase-shifts in the structure

NASA Astrophysics Data System (ADS)

Wolf, Alexey; Dostovalov, Alexandr; Skvortsov, Mikhail; Raspopin, Kirill; Parygin, Alexandr; Babin, Sergey

2018-05-01

In this work, long high-quality fiber Bragg gratings with phase shifts in the structure are inscribed directly in the optical fiber by point-by-point technique using femtosecond laser pulses. Phase shifts are introduced during the inscription process with a piezoelectric actuator, which rapidly shifts the fiber along the direction of its movement in a chosen point of the grating with a chosen shift value. As examples, single and double π phase shifts are introduced in fiber Bragg gratings with a length up to 34 mm in passive fibers, which provide corresponding transmission peaks with bandwidth less than 1 pm. It is shown that 37 mm π -phase-shifted grating inscribed in an active Er-doped fiber forms high-quality DFB laser cavity generating single-frequency radiation at 1550 nm with bandwidth of 20 kHz and signal-to-noise ratio of >70 dB. The inscription technique has a high degree of performance and flexibility and can be easily implemented in fibers of various types.

Seismic damage identification for steel structures using distributed fiber optics.

PubMed

Hou, Shuang; Cai, C S; Ou, Jinping

2009-08-01

A distributed fiber optic monitoring methodology based on optic time domain reflectometry technology is developed for seismic damage identification of steel structures. Epoxy with a strength closely associated to a specified structure damage state is used for bonding zigzagged configured optic fibers on the surfaces of the structure. Sensing the local deformation of the structure, the epoxy modulates the signal change within the optic fiber in response to the damage state of the structure. A monotonic loading test is conducted on a steel specimen installed with the proposed sensing system using selected epoxy that will crack at the designated strain level, which indicates the damage of the steel structure. Then, using the selected epoxy, a varying degree of cyclic loading amplitudes, which is associated with different damage states, is applied on a second specimen. The test results show that the specimen's damage can be identified by the optic sensors, and its maximum local deformation can be recorded by the sensing system; moreover, the damage evolution can also be identified.

A new biodegradable sisal fiber-starch packing composite with nest structure.

PubMed

Xie, Qi; Li, Fangyi; Li, Jianfeng; Wang, Liming; Li, Yanle; Zhang, Chuanwei; Xu, Jie; Chen, Shuai

2018-06-01

A new completely biodegradable sisal fiber-starch packing composite was proposed. The effects of fiber content and alkaline treatment on the cushioning property of the composites were studied from energy absorption efficiency, cellular microstructure and compatibility between fiber and starch. With increasing fiber content, the nest structure of composites becomes dense first and then loosens, resulting in initial enhancement and subsequent weakening of the cushioning property of the composites. The composite with 4:13 mass ratio of fiber and thermoplastic starch (TPS) exhibit the optimal cushioning property. Alkaline treatment increases the compatibility between sisal fiber and TPS, promotes the formation of dense nest structure, thereby enhances the cushioning property of the composites. After biodegradability tests for 28 days, the weight loss of the composites was 62.36%. It's found that the composites are a promising replacement for expandable polystyrene (EPS) as packing material, especially under large compression load (0.7-6 MPa). Copyright © 2018 Elsevier Ltd. All rights reserved.

Deformation behavior of carbon-fiber reinforced shape-memory-polymer composites used for deployable structures (Conference Presentation)

NASA Astrophysics Data System (ADS)

Lan, Xin; Liu, Liwu; Li, Fengfeng; Pan, Chengtong; Liu, Yanju; Leng, Jinsong

2017-04-01

Shape memory polymers (SMPs) are a new type of smart material, they perform large reversible deformation with a certain external stimulus (e.g., heat and electricity). The properties (e.g., stiffness, strength and other mechanically static or quasi-static load-bearing capacity) are primarily considered for conventional resin-based composite materials which are mainly used for structural materials. By contrast, the mechanical actuating performance with finite deformation is considered for the shape memory polymers and their composites which can be used for both structural materials and functional materials. For shape memory polymers and their composites, the performance of active deformation is expected to further promote the development in smart active deformation structures, such as deployable space structures and morphing wing aircraft. The shape memory polymer composites (SMPCs) are also one type of High Strain Composite (HSC). The space deployable structures based on carbon fiber reinforced shape memory polymer composites (SMPCs) show great prospects. Considering the problems that SMPCs are difficult to meet the practical applications in space deployable structures in the recent ten years, this paper aims to research the mechanics of deformation, actuation and failure of SMPCs. In the overall view of the shape memory polymer material's nonlinearity (nonlinearity and stress softening in the process of pre-deformation and recovery, relaxation in storage process, irreversible deformation), by the multiple verifications among theory, finite element and experiments, one obtains the deformation and actuation mechanism for the process of "pre-deformation, energy storage and actuation" and its non-fracture constraint domain. Then, the parameters of SMPCs will be optimized. Theoretical analysis is realized by the strain energy function, additionally considering the interaction strain energy between the fiber and the matrix. For the common resin-based or soft

The Transport Properties of Activated Carbon Fibers

DOE R&D Accomplishments Database

di Vittorio, S. L.; Dresselhaus, M. S.; Endo, M.; Issi, J-P.; Piraux, L.

1990-07-01

The transport properties of activated isotropic pitch-based carbon fibers with surface area 1000 m{sup 2}/g have been investigated. We report preliminary results on the electrical conductivity, the magnetoresistance, the thermal conductivity and the thermopower of these fibers as a function of temperature. Comparisons are made to transport properties of other disordered carbons.

Application of smart optical fiber sensors for structural load monitoring

NASA Astrophysics Data System (ADS)

Davies, Heddwyn; Everall, Lorna A.; Gallon, Andrew M.

2001-06-01

This paper describes a smart monitoring system, incorporating optical fiber sensing techniques, capable of providing important structural information to designers and users alike. This technology has wide industrial and commercial application in areas including aerospace, civil, maritime and automotive engineering. In order to demonstrate the capability of the sensing system it has been installed in a 35m free-standing carbon fiber yacht mast, where a complete optical network of strain and temperature sensors were embedded into a composite mast and boom during lay-up. The system was able to monitor the behavior of the composite rig through a range of handling conditions. The resulting strain information can be used by engineers to improve the structural design process. Embedded fiber optic sensors have wide ranging application for structural load monitoring. Due to their small size, optical fiber sensors can be readily embedded into composite materials. Other advantages include their immediate multiplexing capability and immunity to electro-magnetic interference. The capability of this system has been demonstrated within the maritime and industrial environment, but can be adapted for any application.

Fabrication and photoluminescence properties of graphite fiber/ZnO nanorod core-shell structures.

PubMed

Liu, Xianbin; Du, Hejun; Liu, Bo; Wang, Jianxiong; Sun, Xiao Wei; Sun, Handong

2011-08-01

Graphite fiber/ZnO nanorod core-shell structures were synthesized by thermal evaporation process. The core-shell hybrid architectures were comprised of ZnO nanorods grown on the surface of graphite fiber. In addition, Hollow ZnO hierarchical structure can be obtained by oxidizing the graphite fiber. Room temperature photoluminescence (PL) of the as-made graphite fiber/ZnO nanorod structures shows two UV peaks at around 3.274 eV and 3.181 eV. The temperature-dependent photoluminescence spectra demonstrate the two UV emissions are attributed to the intrinsic optical transitions and extrinsic defect-related emissions in ZnO. These hybrid structures may be used as the building block for fabrication of nanodevices.

Fabrication of locally micro-structured fiber Bragg gratings by fs-laser machining

NASA Astrophysics Data System (ADS)

Dutz, Franz J.; Stephan, Valentin; Marchi, Gabriele; Koch, Alexander W.; Roths, Johannes; Huber, Heinz P.

2018-06-01

Here, we describe a method for producing locally micro-structured fiber Bragg gratings (LMFGB) by fs-laser machining. This technique enables the precise and reproducible ablation of cladding material to create circumferential grooves inside the claddings of optical fibers. From initial ablation experiments we acquired optimized process parameters. The fabricated grooves were located in the middle of uniform type I fiber Bragg gratings. LMFBGs with four different groove widths of 48, 85, 135 and 205 μ { {m}} were produced. The grooves exhibited constant depths of about 30 μ {m} and steep sidewall angles. With the combination of micro-structures and fiber Bragg gratings, fiber optic sensor elements with enhanced functionalities can be achieved.

Structure of the bacteriophage T4 long tail fiber receptor-binding tip

PubMed Central

Bartual, Sergio G.; Otero, José M.; Garcia-Doval, Carmela; Llamas-Saiz, Antonio L.; Kahn, Richard; Fox, Gavin C.; van Raaij, Mark J.

2010-01-01

Bacteriophages are the most numerous organisms in the biosphere. In spite of their biological significance and the spectrum of potential applications, little high-resolution structural detail is available on their receptor-binding fibers. Here we present the crystal structure of the receptor-binding tip of the bacteriophage T4 long tail fiber, which is highly homologous to the tip of the bacteriophage lambda side tail fibers. This structure reveals an unusual elongated six-stranded antiparallel beta-strand needle domain containing seven iron ions coordinated by histidine residues arranged colinearly along the core of the biological unit. At the end of the tip, the three chains intertwine forming a broader head domain, which contains the putative receptor interaction site. The structure reveals a previously unknown beta-structured fibrous fold, provides insights into the remarkable stability of the fiber, and suggests a framework for mutations to expand or modulate receptor-binding specificity. PMID:21041684

The effect of woven and non-woven fiber structure on mechanical properties polyester composite reinforced kenaf

NASA Astrophysics Data System (ADS)

Ratim, S.; Bonnia, N. N.; Surip, S. N.

2012-07-01

The effects of woven and non-woven kenaf fiber on mechanical properties of polyester composites were studied at different types of perform structures. Composite polyester reinforced kenaf fiber has been prepared via hand lay-up process by varying fiber forms into plain weave, twill and mats structure. The reinforcing efficiency of different fiber structure was compared with control of unreinforced polyester sample. It was found that the strength and stiffness of the composites are largely affected by fiber structure. A maximum value for tensile strength of composite was obtained for twill weave pattern of fiber structure while no significant different for plain weave and mat structure. The elastic modulus of composite has shown some improvement on plain and twill weave pattern. Meanwhile, lower value of modulus elasticity achieved by mats structure composite as well as control sample. The modulus of rupture and impact resistance were also analyzed. The improvement of modulus of rupture value can be seen on plain and twill weave pattern. However impact resistance doesn't show significant improvement in all types of structure except for mat fiber. The mechanical properties of kenaf fiber reinforced polyester composite found to be increased with woven and non-woven fiber structures in composite.

Ultrahigh resolution radiation imaging system using an optical fiber structure scintillator plate.

PubMed

Yamamoto, Seiichi; Kamada, Kei; Yoshikawa, Akira

2018-02-16

High resolution imaging of radiation is required for such radioisotope distribution measurements as alpha particle detection in nuclear facilities or high energy physics experiments. For this purpose, we developed an ultrahigh resolution radiation imaging system using an optical fiber structure scintillator plate. We used a ~1-μm diameter fiber structured GdAlO 3 :Ce (GAP) /α-Al 2 O 3 scintillator plate to reduce the light spread. The fiber structured scintillator plate was optically coupled to a tapered optical fiber plate to magnify the image and combined with a lens-based high sensitivity CCD camera. We observed the images of alpha particles with a spatial resolution of ~25 μm. For the beta particles, the images had various shapes, and the trajectories of the electrons were clearly observed in the images. For the gamma photons, the images also had various shapes, and the trajectories of the secondary electrons were observed in some of the images. These results show that combining an optical fiber structure scintillator plate with a tapered optical fiber plate and a high sensitivity CCD camera achieved ultrahigh resolution and is a promising method to observe the images of the interactions of radiation in a scintillator.

Al-Coated Conductive Fiber Filters for High-Efficiency Electrostatic Filtration: Effects of Electrical and Fiber Structural Properties.

PubMed

Choi, Dong Yun; An, Eun Jeong; Jung, Soo-Ho; Song, Dong Keun; Oh, Yong Suk; Lee, Hyung Woo; Lee, Hye Moon

2018-04-10

Through the direct decomposition of an Al precursor ink AlH 3 {O(C 4 H 9 ) 2 }, we fabricated an Al-coated conductive fiber filter for the efficient electrostatic removal of airborne particles (>99%) with a low pressure drop (~several Pascals). The effects of the electrical and structural properties of the filters were investigated in terms of collection efficiency, pressure drop, and particle deposition behavior. The collection efficiency did not show a significant correlation with the extent of electrical conductivity, as the filter is electrostatically charged by the metallic Al layers forming electrical networks throughout the fibers. Most of the charged particles were collected via surface filtration by Coulombic interactions; consequently, the filter thickness had little effect on the collection efficiency. Based on simulations of various fiber structures, we found that surface filtration can transition to depth filtration depending on the extent of interfiber distance. Therefore, the effects of structural characteristics on collection efficiency varied depending on the degree of the fiber packing density. This study will offer valuable information pertaining to the development of a conductive metal/polymer composite air filter for an energy-efficient and high-performance electrostatic filtration system.

Strength Analysis of Coconut Fiber Stabilized Earth for Farm Structures

NASA Astrophysics Data System (ADS)

Enokela, O. S.; P. O, Alada

2012-07-01

Investigation of the strength characteristic of soil from alluvial deposit of River Benue in makurdi stabilized with coconut fiber as a stabilizer was carried as local building material for farm structure. Processed coconut fibers were mixed with the soil at four different mix ratios of 1% fiber, 2% fiber, 3% fiber and 4% fiber by percentage weight with 0% fiber as control. Compaction test and compressive strength were carried out on the various stabilizing ratio. From the compaction test, the correlation between the maximum dry density and optimum moisture content is a second order polynomial with a coefficient of 63% obtained at1.91kg/m3and 20.0% respectively while the compressive strength test shows an optimum failure load of 8.62N/mm2 at 2%fibre:100% soil mix ratio at 2.16 maximum dry density.

Nitrogen-Doped Carbon Fiber Paper by Active Screen Plasma Nitriding and Its Microwave Heating Properties.

PubMed

Zhu, Naishu; Ma, Shining; Sun, Xiaofeng

2016-12-28

In this paper, active screen plasma nitriding (ASPN) treatment was performed on polyacrylonitrile carbon fiber papers. Electric resistivity and microwave loss factor of carbon fiber were described to establish the relationship between processing parameters and fiber's ability to absorb microwaves. The surface processing effect of carbon fiber could be characterized by dynamic thermal mechanical analyzer testing on composites made of carbon fiber. When the process temperature was at 175 °C, it was conducive to obtaining good performance of dynamical mechanical properties. The treatment provided a way to change microwave heating properties of carbon fiber paper by performing different treatment conditions, such as temperature and time parameters. Atomic force microscope, scanning electron microscope, and X-ray photoelectron spectroscopy analysis showed that, during the course of ASPN treatment on carbon fiber paper, nitrogen group was introduced and silicon group was removed. The treatment of nitrogen-doped carbon fiber paper represented an alternative promising candidate for microwave curing materials used in repairing and heating technology, furthermore, an efficient dielectric layer material for radar-absorbing structure composite in metamaterial technology.

An Intrinsic Fiber-Optic Sensor for Structure Lightning Current Measurement

NASA Technical Reports Server (NTRS)

Nguyen, Truong X.; Ely, Jay J.; Szatkowski, George N.; Mata, Carlos T.; Mata, Angel. G.; Snyder, Gary P.

2014-01-01

An intrinsic optical-fiber sensor based on Faraday Effect is developed that is highly suitable for measuring lightning current on aircraft, towers and complex structures. Originally developed specifically for aircraft installations, it is light-weight, non-conducting, structure conforming, and is immune to electromagnetic interference, hysteresis and saturation. It can measure total current down to DC. When used on lightning towers, the sensor can help validate other sensors and lightning detection network measurements. Faraday Effect causes light polarization to rotate when the fiber is exposed to a magnetic field in the direction of light propagation. Thus, the magnetic field strength can be determined from the light polarization change. By forming closed fiber loops and applying Ampere's law, measuring the total light rotation yields the total current enclosed. A broadband, dual-detector, reflective polarimetric scheme allows measurement of both DC component and AC waveforms with a 60 dB dynamic range. Two systems were built that are similar in design but with slightly different sensitivities. The 1310nm laser system can measure 300 A - 300 kA, and has a 15m long sensing fiber. It was used in laboratory testing, including measuring current on an aluminum structure simulating an aircraft fuselage or a lightning tower. High current capabilities were demonstrated up to 200 kA at a lightning test facility. The 1550nm laser system can measure 400 A - 400 kA and has a 25m fiber length. Used in field measurements, excellent results were achieved in the summer of 2012 measuring rocket-triggered lightning at the International Center for Lightning Research and Testing (ICLRT), Camp Blanding, Florida. In both systems increased sensitivity can be achieved with multiple fiber loops. The fiber optic sensor provides many unique capabilities not currently possible with traditional sensors. It represents an important new tool for lightning current measurement where low weight

Narrowband random lasing in a Bismuth-doped active fiber

PubMed Central

Lobach, Ivan A.; Kablukov, Sergey I.; Skvortsov, Mikhail I.; Podivilov, Evgeniy V.; Melkumov, Mikhail A.; Babin, Sergey A.; Dianov, Evgeny M.

2016-01-01

Random fiber lasers operating via the Rayleigh scattering (RS) feedback attract now a great deal of attention as they generate a high-quality unidirectional laser beam with the efficiency and performance comparable and even exceeding those of fiber lasers with conventional cavities. Similar to other random lasers, both amplification and random scattering are distributed here along the laser medium being usually represented by a kilometers-long passive fiber with Raman gain. However, it is hardly possible to utilize normal gain in conventional active fibers as they are usually short and RS is negligible. Here we report on the first demonstration of the RS-based random lasing in an active fiber. This became possible due to the implementation of a new Bi-doped fiber with an increased amplification length and RS coefficient. The realized Bi-fiber random laser generates in a specific spectral region (1.42 μm) exhibiting unique features, in particular, a much narrower linewidth than that in conventional cavity of the same length, in agreement with the developed theory. Lasers of this type have a great potential for applications as Bi-doped fibers with different host compositions enable laser operation in an extremely broad range of wavelengths, 1.15–1.78 μm. PMID:27435232

Alcohol sensor based on u-bent hetero-structured fiber optic

NASA Astrophysics Data System (ADS)

Patrialova, Sefi N.; Hatta, Agus M.; Sekartedjo, Sekartedjo

2016-11-01

A sensor based on a fiber optic hetero-structure to determine the concentration of alcohol has been proposed. The structure of the sensing probe in this research is a singlemode-multimode-singlemode (SMS) which bent into Ushaped and soon called as SMS u-bent. The SMS structure was chosen to get a higher sensitivity. This research utilizes the principle of multimode interference and evanescent field by modifying the cladding with various alcohol concentration. Testing of the sensor's performance has been done by measuring the sensor's power output response to the length of the SMS fiber optic, bending diameter, and alcohol concentration. Based on the experiment result, the ubent SMS fiber optic with 50 mm bending diameter and 63 mm MMF lenght has the highest sensitivity, 3.87 dB/% and the minimum resolution, 0.26 x 10-3 %.

Photonic-structured fibers assembled from cellulose nanocrystals with tunable polarized selective reflection.

PubMed

Meng, Xin; Pan, Hui; Lu, Tao; Chen, Zhixin; Chen, Yanru; Zhang, Di; Zhu, Shenmin

2018-08-10

Fibers with self-assembled photonic structures are of special interest due to their unique photonic properties and potential applications in the smart textile industry. Inspired by nature, the photonic-structured fibers were fabricated through the self-assembly of chiral nematic cellulose nanocrystals (CNCs) and the fibers showed tunably brilliant and selectively reflected colors under crossed-polarization. A simple wet-spinning method was applied to prepare composite fibers of the mixed CNC matrix and polyvinyl alcohol (PVA) additions. During the processing, a cholesteric CNC phase formed photonic fibers through a self-assembly process. The selective color reflection of the composite fibers in the polarized condition showed a typical red-shift tendency with an increase in the PVA content, which was attributed to the increased helical pitch of the CNC. Furthermore, the polarized angle could also alter the reflected colors. Owing to their excellent selective reflection properties under the polarized condition, CNC-based photonic fibers are promising as the next-generation of smart fibers, applied in the fields of specific display and sensing.

Fiber optic sensor technology - An opportunity for smart aerospace structures

NASA Technical Reports Server (NTRS)

Heyman, J. S.; Rogowski, R. S.; Claus, R. O.

1988-01-01

Fiber optic sensors provide the opportunity for fabricating materials with internal sensors which can serve as lifetime health monitors, analogous to a central nervous system. The embedded fiber optic sensors can be interrogated by various techniques to measure internal strain, temperature, pressure, acoustic waves and other parameters indicative of structural integrity. Experiments have been conducted with composite samples with embedded sensors to measure strain using optical time domain reflectometry, modal interference and an optical phase locked loop. Fiber optic sensors have been developed to detect acoustic emission and impact damage and have been demonstrated for cure monitoring. These sensors have the potential for lifetime monitoring of structural properties, providing real time nondestructive evaluation.

Influence of BN fiber coatings on the interfacial structure of sapphire fiber reinforced NiAl composites

NASA Astrophysics Data System (ADS)

Reichert, K.; Wen, K.; Cremer, R.; Hu, W.; Neuschütz, D.; Gottstein, G.

2001-07-01

A new concept for a tailored fiber-matrix interface for sapphire fiber reinforced NiAl matrix composites is proposed, consisting of an initial hexagonal boron nitride (hBN) fiber coating. For this, single crystal Al 2O 3 fibers were coated with hBN by chemical vapor deposition (CVD). Following a comprehensive characterization of the CVD coating as to composition and structure by means of X-ray photoelectron spectroscopy (XPS) and grazing incidence X-ray diffraction (GIXRD), the fiber reinforced NiAl matrix composites were fabricated by diffusion bonding at 1400°C. The interfaces NiAl/BN and BN/Al 2O 3 were analyzed by scanning electron microscopy (SEM), analytical transmission electron microscopy (TEM), and selected area diffraction (SAD). An interfacial reaction between NiAl and hBN to form AlN was revealed using these analytical techniques.

Adsorption of SOx and NOx in activated viscose fibers.

PubMed

Plens, Ana Carolina O; Monaro, Daniel L G; Coutinho, Aparecido R

2015-01-01

SOx and NOx are emissions resulting from combustion processes and are the main agents that contribute to the formation of acid rain, which causes harm to humans and the environment. Several techniques for removing these pollutants are applied in i.e. oil refineries, thermoelectric that use petroleum oils and vehicular pollution. Among these, highlight the adsorption of contaminants by the usage of activated carbon fibers and activated carbon, which are characterized by high surface area and uniform distribution of pores, providing appropriate conditions for application in processes of removing environmental contaminants. In the present work, activated viscose fibers (AVF) were prepared and applied in adsorption experiments of NO and SO2. The materials produced showed high values of surface area, with a predominance of micro pores with diameters in the range of 1.0 nm. The AVF had satisfactory performance in the removal of contaminants and are compatible with other synthetic fibers. Thus, the formation of active sites of carbon provides contaminants adsorption, demonstrating that carbon fibers cloth can be applied for the removal of pollutants.

Modulation of skeletal muscle fiber type by mitogen-activated protein kinase signaling.

PubMed

Shi, Hao; Scheffler, Jason M; Pleitner, Jonathan M; Zeng, Caiyun; Park, Sungkwon; Hannon, Kevin M; Grant, Alan L; Gerrard, David E

2008-08-01

Skeletal muscle is composed of diverse fiber types, yet the underlying molecular mechanisms responsible for this diversification remain unclear. Herein, we report that the extracellular signal-regulated kinase (ERK) 1/2 pathway, but not p38 or c-Jun NH(2)-terminal kinase (JNK), is preferentially activated in fast-twitch muscles. Pharmacological blocking of ERK1/2 pathway increased slow-twitch fiber type-specific reporter activity and repressed those associated with the fast-twitch fiber phenotype in vitro. Overexpression of a constitutively active ERK2 had an opposite effect. Inhibition of ERK signaling in cultured myotubes increased slow-twitch fiber-specific protein accumulation while repressing those characteristic of fast-twitch fibers. Overexpression of MAP kinase phosphatase-1 (MKP1) in mouse and rat muscle fibers containing almost exclusively type IIb or IIx fast myosin heavy chain (MyHC) isoforms induced de novo synthesis of the slower, more oxidative type IIa and I MyHCs in a time-dependent manner. Conversion to the slower phenotype was confirmed by up-regulation of slow reporter gene activity and down-regulation of fast reporter activities in response to forced MKP1 expression in vivo. In addition, activation of ERK2 signaling induced up-regulation of fast-twitch fiber program in soleus. These data suggest that the MAPK signaling, most likely the ERK1/2 pathway, is necessary to preserve the fast-twitch fiber phenotype with a concomitant repression of slow-twitch fiber program.

Preparation and study on the structure of keratin/PVA membrane containing wool fibers

NASA Astrophysics Data System (ADS)

Wu, Min; Shen, Shuming; Yang, Xuhong; Tang, Rencheng

2017-10-01

The urea / sodium sulfide / sodium dodecyl sulfate (SDS) method was used to dissolve the wool in this study. Then the Wool fiber/keratin/PVA composites with different proportions were prepared, and the surface morphology, molecular structure, mechanical property of the composite films and the influence of the proportions on their structure and properties were studied. The results showed that, there are α-helix structure, β-sheet and random coil conformations in the pure keratin film, as well as in the wool fiber. Compared with wool fiber, the crystallinity of keratin decreased. PVA can obviously improve the mechanical property of the blended film. When the blended ratio of keratin/PVA is 20/80, the mechanical property of the blended film is greatly improved. The composite films with 8%-16% of wool fibers have better flexibility than those without wool fibers.

Investigation of Structural Properties of Carbon-Epoxy Composites Using Embedded Fiber-Optic Bragg Gratings

NASA Technical Reports Server (NTRS)

Osei, Albert J.

2003-01-01

coupled into the optical fiber sensor, a reflection peak will be obtained centered around a wavelength called Bragg-wavelength. The Bragg-wavelength depends on the refractive index and the period of the grating, which both change due to mechanical and thermal strain applied to the sensor. The shift in the Bragg-wavelength is directly proportional to the strain. Researchers at NASA MSFC are currently developing techniques for using FBGs for monitoring the integrity of advanced structural materials expected to become the mainstay of the current and future generation space structures. Since carbon-epoxy composites are the materials of choice for the current space structures, the initial study is concentrated on this type of composite. The goals of this activity are to use embedded FBG sensors for measuring strain and temperature of composite structures, and to investigate the effects of various parameters such as composite fiber orientation with respect to the optical sensor, unidirectional fiber composite, fabrication process etc., on the optical performance of the sensor. This paper describes an experiment to demonstrate the use of an embedded FBG for measuring strain in a composite material. The performance of the fiber optic sensor is determined by direct comparison with results from more conventional instrumentation.

Innovative design of composite structures: Use of curvilinear fiber format to improve structural efficiency

NASA Technical Reports Server (NTRS)

Hyer, M. W.; Charette, R. F.

1987-01-01

To increase the effectiveness and efficiency of fiber-reinforced materials, the use of fibers in a curvilinear rather than the traditional straightline format is explored. The capacity of a laminated square plate with a central circular hole loaded in tension is investigated. The orientation of the fibers is chosen so that the fibers in a particular layer are aligned with the principle stress directions in that layer. Finite elements and an iteration scheme are used to find the fiber orientation. A noninteracting maximum strain criterion is used to predict load capacity. The load capacities of several plates with different curvilinear fibers format are compared with the capacities of more conventional straightline format designs. It is found that the most practical curvilinear design sandwiches a group of fibers in a curvilinear format between a pair of +/-45 degree layers. This design has a 60% greater load capacity than a conventional quasi-isotropic design with the same number of layers. The +/-45 degree layers are necessary to prevent matrix cracking in the curvilinear layers due to stresses perpendicular to the fibers in those layers. Greater efficiencies are achievable with composite structures than now realized.

Novel electric double-layer capacitor with a coaxial fiber structure.

PubMed

Chen, Xuli; Qiu, Longbin; Ren, Jing; Guan, Guozhen; Lin, Huijuan; Zhang, Zhitao; Chen, Peining; Wang, Yonggang; Peng, Huisheng

2013-11-26

A coaxial electric double-layer capacitor fiber is developed from the aligned carbon nanotube fiber and sheet, which functions as two electrodes with a polymer gel sandwiched between them. The unique coaxial structure enables a rapid transportation of ions between the two electrodes with a high electrochemical performance. These energy storage fibers are also flexible and stretchable, and can be woven into and widely used for electronic textiles. © 2013 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

An all fiber-optic multi-parameter structure health monitoring system

DOE PAGES

Hu, Chennan; Yu, Zhihao; Wang, Anbo

2016-08-24

In this article, we present an all fiber-optics based multi-parameter structure health monitoring system, which is able to monitor strain, temperature, crack and thickness of metal structures. This system is composed of two optical fibers, one for laser-acoustic excitation and the other for acoustic detection. A nano-second 1064 nm pulse laser was used for acoustic excitation and a 2 mm fiber Bragg grating was used to detect the acoustic vibration. The feasibility of this system was demonstrated on an aluminum test piece by the monitoring of the temperature, strain and thickness changes, as well as the appearance of an artificialmore » crack. The multiplexing capability of this system was also preliminarily demonstrated.« less

An all fiber-optic multi-parameter structure health monitoring system

DOE Office of Scientific and Technical Information (OSTI.GOV)

Hu, Chennan; Yu, Zhihao; Wang, Anbo

In this article, we present an all fiber-optics based multi-parameter structure health monitoring system, which is able to monitor strain, temperature, crack and thickness of metal structures. This system is composed of two optical fibers, one for laser-acoustic excitation and the other for acoustic detection. A nano-second 1064 nm pulse laser was used for acoustic excitation and a 2 mm fiber Bragg grating was used to detect the acoustic vibration. The feasibility of this system was demonstrated on an aluminum test piece by the monitoring of the temperature, strain and thickness changes, as well as the appearance of an artificialmore » crack. The multiplexing capability of this system was also preliminarily demonstrated.« less

Fiber optic structures for refractive index and gas sensing

NASA Astrophysics Data System (ADS)

Silva, Susana Ferreira de Oliveira

The work described in this PhD Thesis focuses on the post-processing of optical fibers and their enhancement as sensing element. Since the majority of sensors presented are based in Fabry-Perot interferometers, an historical overview of this category of optical fiber sensors is firstly presented. This review considers the works published since the early years, in the beginning of the 1980s, until the middle of 2015. The incorporation of microcavities at the tip of a single mode fiber was extensively studied, particularly for the measurement of nitrogen and methane gas pressure. These cavities were fabricated using hollow core silica tubes and a hollow core photonic crystal fiber. Following a different approach, the microcavities were incorporated between two sections of single mode fiber. In this case, the low sensitivity to temperature makes these microcavities highly desirable for the measurement of strain at high temperatures. Competences in post-processing techniques such as the chemical etching and the writing of periodical structures in the fiber core by means of an excimer or a femtosecond laser were also acquired in the course of the PhD programme. One of the works consisted in the design and manufacturing of a double clad optical fiber. The refractive index of the inner cladding was higher than the one of the outer cladding and the core. Thus, light was guided in the inner cladding instead of propagating in the core. This situation was overcome by applying chemical etching, thus removing the inner cladding. The core, surrounded by air, was then able to guide light. Two different applications were found for this fiber, as a temperature sensor and as an optical refractometer. In the last, the optical phase changes with the liquid refractive index. Two different types of fiber Bragg gratings were characterized in strain and temperature. Sensing structures obtained through the phase mask technique at the tip of an optical fiber were subjected to chemical

Dual-wavelength nano-engineered Thulium-doped fiber laser via bending of singlemode-multimode-singlemode fiber structure

NASA Astrophysics Data System (ADS)

Zulkifli, A. Z.; Latiff, A. A.; Paul, M. C.; Yasin, M.; Ahmad, H.; Harun, S. W.

2016-12-01

In this paper, a dual-wavelength fiber laser (DWFL) using nano-engineered Thulium-doped fiber as a gain medium with a bent singlemode-multimode-singlemode fiber structure (SMS) is demonstrated. The SMS structure is packaged systematically using Cr-39 polymer plates to provide linear bending via applied load. Experimental results have proved that the bent SMS is capable to provide highly effective wavelength filter and wavelengths stabilizer by balancing the net cavity gain between the two wavelengths. The DWFL provides very narrow spacing of 0.9 nm, narrow 3 dB spectral linewidth of ∼0.07 nm and SNR of ∼42 dB. Based on stability test, very small mode hopping is observed at the two wavelengths having deviations of ±0 nm and ±0.04 nm respectively. In conjunction, the DWFL provides very stable relative wavelength spacing with a deviation of ±0.04 nm.

Study of distributed fiber-optic laser-ultrasound generation based on ghost-mode of tilted fiber Bragg gratings

NASA Astrophysics Data System (ADS)

Tian, Jiajun; Zhang, Qi; Han, Ming

2013-05-01

Fiber-optic ultrasonic transducers are an important component of an active ultrasonic testing system for structural health monitoring. Fiber-optic transducers have several advantages such as small size, light weight, and immunity to electromagnetic interference that make them much more attractive than the current available piezoelectric transducers, especially as embedded and permanent transducers in active ultrasonic testing for structural health monitoring. In this paper, a distributed fiber-optic laser-ultrasound generation based on the ghost-mode of tilted fiber Bragg gratings is studied. The influences of the laser power and laser pulse duration on the laser-ultrasound generation are investigated. The results of this paper are helpful to understand the working principle of this laser-ultrasound method and improve the ultrasonic generation efficiency.

Tutorial for Collecting and Processing Images of Composite Structures to Determine the Fiber Volume Fraction

NASA Technical Reports Server (NTRS)

Conklin, Lindsey

2017-01-01

Fiber-reinforced composite structures have become more common in aerospace components due to their light weight and structural efficiency. In general, the strength and stiffness of a composite structure are directly related to the fiber volume fraction, which is defined as the fraction of fiber volume to total volume of the composite. The most common method to measure the fiber volume fraction is acid digestion, which is a useful method when the total weight of the composite, the fiber weight, and the total weight can easily be obtained. However, acid digestion is a destructive test, so the material will no longer be available for additional characterization. Acid digestion can also be difficult to machine out specific components of a composite structure with complex geometries. These disadvantages of acid digestion led the author to develop a method to calculate the fiber volume fraction. The developed method uses optical microscopy to calculate the fiber area fraction based on images of the cross section of the composite. The fiber area fraction and fiber volume fraction are understood to be the same, based on the assumption that the shape and size of the fibers are consistent in the depth of the composite. This tutorial explains the developed method for optically determining fiber area fraction performed at NASA Langley Research Center.

Carbon nanotube-based structural health monitoring for fiber reinforced composite materials

NASA Astrophysics Data System (ADS)

Liu, Hao; Liu, Kan; Mardirossian, Aris; Heider, Dirk; Thostenson, Erik

2017-04-01

In fiber reinforced composite materials, the modes of damage accumulation, ranging from microlevel to macro-level (matrix cracks development, fiber breakage, fiber-matrix de-bonding, delamination, etc.), are complex and hard to be detected through conventional non-destructive evaluation methods. Therefore, in order to assure the outstanding structural performance and high durability of the composites, there has been an urgent need for the design and fabrication smart composites with self-damage sensing capabilities. In recent years, the macroscopic forms of carbon nanotube materials have been maturely investigated, which provides the opportunity for structural health monitoring based on the carbon nanotubes that are integrated in the inter-laminar areas of advanced fiber composites. Here in this research, advanced fiber composites embedded with laminated carbon nanotube layers are manufactured for damage detection due to the relevant spatial electrical property changes once damage occurs. The mechanical-electrical coupling response is recorded and analyzed during impact test. The design and manufacturing of integrating the carbon nanotubes intensely affect the detecting sensitivity and repeatability of the integrated multifunctional sensors. The ultimate goal of the reported work is to develop a novel structural health monitoring method with the capability of reporting information on the damage state in a real-time way.

Non-synaptic signaling from cerebellar climbing fibers modulates Golgi cell activity.

PubMed

Nietz, Angela K; Vaden, Jada H; Coddington, Luke T; Overstreet-Wadiche, Linda; Wadiche, Jacques I

2017-10-13

Golgi cells are the principal inhibitory neurons at the input stage of the cerebellum, providing feedforward and feedback inhibition through mossy fiber and parallel fiber synapses. In vivo studies have shown that Golgi cell activity is regulated by climbing fiber stimulation, yet there is little functional or anatomical evidence for synapses between climbing fibers and Golgi cells. Here, we show that glutamate released from climbing fibers activates ionotropic and metabotropic receptors on Golgi cells through spillover-mediated transmission. The interplay of excitatory and inhibitory conductances provides flexible control over Golgi cell spiking, allowing either excitation or a biphasic sequence of excitation and inhibition following single climbing fiber stimulation. Together with prior studies of spillover transmission to molecular layer interneurons, these results reveal that climbing fibers exert control over inhibition at both the input and output layers of the cerebellar cortex.

Single mode fibers with antireflective surface structures for high power laser applications

NASA Astrophysics Data System (ADS)

Busse, Lynda E.; Florea, Catalin M.; Shaw, L. Brandon; Aggarwal, Ishwar D.; Sanghera, Jasbinder S.

2014-03-01

We present results for increased transmission of ~99.5% in the near-IR through the end faces of silica single mode fibers by creating a random antireflective microstructure etched into the end face of the fiber. We demonstrate high laser damage thresholds for these fibers with AR structured surfaces.

Carbon fiber epoxy composites for both strengthening and health monitoring of structures.

PubMed

Salvado, Rita; Lopes, Catarina; Szojda, Leszek; Araújo, Pedro; Gorski, Marcin; Velez, Fernando José; Castro-Gomes, João; Krzywon, Rafal

2015-05-06

This paper presents a study of the electrical and mechanical behavior of several continuous carbon fibers epoxy composites for both strengthening and monitoring of structures. In these composites, the arrangement of fibers was deliberately diversified to test and understand the ability of the composites for self-sensing low strains. Composites with different arrangements of fibers and textile weaves, mainly unidirectional continuous carbon reinforced composites, were tested at the dynamometer. A two-probe method was considered to measure the relative electrical resistance of these composites during loading. The measured relative electrical resistance includes volume and contact electrical resistances. For all tested specimens, it increases with an increase in tensile strain, at low strain values. This is explained by the improved alignment of fibers and resulting reduction of the number of possible contacts between fibers during loading, increasing as a consequence the contact electrical resistance of the composite. Laboratory tests on strengthening of structural elements were also performed, making hand-made composites by the "wet process", which is commonly used in civil engineering for the strengthening of all types of structures in-situ. Results show that the woven epoxy composite, used for strengthening of concrete elements is also able to sense low deformations, below 1%. Moreover, results clearly show that this textile sensor also improves the mechanical work of the strengthened structural elements, increasing their bearing capacity. Finally, the set of obtained results supports the concept of a textile fabric capable of both structural upgrade and self-monitoring of structures, especially large structures of difficult access and needing constant, sometimes very expensive, health monitoring.

Optical fiber sensor having a sol-gel fiber core and a method of making

DOEpatents

Tao, Shiquan; Jindal, Rajeev; Winstead, Christopher; Singh, Jagdish P.

2006-06-06

A simple, economic wet chemical procedure is described for making sol-gel fibers. The sol-gel fibers made from this process are transparent to ultraviolet, visible and near infrared light. Light can be guided in these fibers by using an organic polymer as a fiber cladding. Alternatively, air can be used as a low refractive index medium. The sol-gel fibers have a micro pore structure which allows molecules to diffuse into the fiber core from the surrounding environment. Chemical and biochemical reagents can be doped into the fiber core. The sol-gel fiber can be used as a transducer for constructing an optical fiber sensor. The optical fiber sensor having an active sol-gel fiber core is more sensitive than conventional evanescent wave absorption based optical fiber sensors.

Nondestructive imaging of fiber structure in articular cartilage using optical polarization tractography

NASA Astrophysics Data System (ADS)

Yao, Xuan; Wang, Yuanbo; Ravanfar, Mohammadreza; Pfeiffer, Ferris M.; Duan, Dongsheng; Yao, Gang

2016-11-01

Collagen fiber orientation plays an important role in determining the structure and function of the articular cartilage. However, there is currently a lack of nondestructive means to image the fiber orientation from the cartilage surface. The purpose of this study is to investigate whether the newly developed optical polarization tractography (OPT) can image fiber structure in articular cartilage. OPT was applied to obtain the depth-dependent fiber orientation in fresh articular cartilage samples obtained from porcine phalanges. For comparison, we also obtained collagen fiber orientation in the superficial zone of the cartilage using the established split-line method. The direction of each split-line was quantified using image processing. The orientation measured in OPT agreed well with those obtained from the split-line method. The correlation analysis of a total of 112 split-lines showed a greater than 0.9 coefficient of determination (R2) between the split-line results and OPT measurements obtained between 40 and 108 μm in depth. In addition, the thickness of the superficial layer can also be assessed from the birefringence images obtained in OPT. These results support that OPT provides a nondestructive way to image the collagen fiber structure in articular cartilage. This technology may be valuable for both basic cartilage research and clinical orthopedic applications.

Self-diagnosis of structures strengthened with hybrid carbon-fiber-reinforced polymer sheets

NASA Astrophysics Data System (ADS)

Wu, Z. S.; Yang, C. Q.; Harada, T.; Ye, L. P.

2005-06-01

The correlation of mechanical and electrical properties of concrete beams strengthened with hybrid carbon-fiber-reinforced polymer (HCFRP) sheets is studied in this paper. Two types of concrete beams, with and without reinforcing bars, are strengthened with externally bonded HCFRP sheets, which have a self-structural health monitoring function due to the electrical conduction and piezoresistivity of carbon fibers. Parameters investigated include the volume fractions and types of carbon fibers. According to the investigation, it is found that the hybridization of uniaxial HCFRP sheets with several different types of carbon fibers is a viable method for enhancing the mechanical properties and obtaining a built-in damage detection function for concrete structures. The changes in electrical resistance during low strain ranges before the rupture of carbon fibers are generally smaller than 1%. Nevertheless, after the gradual ruptures of carbon fibers, the electrical resistance increases remarkably with the strain in a step-wise manner. For the specimens without reinforcing bars, the electrical behaviors are not stable, especially during the low strain ranges. However, the electrical behaviors of the specimens with reinforcing bars are relatively stable, and the whole range of self-sensing function of the HCFRP-strengthened RC structures has realized the conceptual design of the HCFRP sensing models and is confirmed by the experimental investigations. The relationships between the strain/load and the change in electrical resistance show the potential self-monitoring capacity of HCFRP reinforcements used for strengthening concrete structures.

Embedded fiber optic ultrasonic sensors and generators

NASA Astrophysics Data System (ADS)

Dorighi, John F.; Krishnaswamy, Sridhar; Achenbach, Jan D.

1995-04-01

Ultrasonic sensors and generators based on fiber-optic systems are described. It is shown that intrinsic fiber optic Fabry-Perot ultrasound sensors that are embedded in a structure can be stabilized by actively tuning the laser frequency. The need for this method of stabilization is demonstrated by detecting piezoelectric transducer-generated ultrasonic pulses in the presence of low frequency dynamic strains that are intentionally induced to cause sensor drift. The actively stabilized embedded fiber optic Fabry-Perot sensor is also shown to have sufficient sensitivity to detect ultrasound that is generated in the interior of a structure by means of a high-power optical fiber that pipes energy from a pulsed laser to an embedded generator of ultrasound.

Calpain expression and activity during lens fiber cell differentiation.

PubMed

De Maria, Alicia; Shi, Yanrong; Kumar, Nalin M; Bassnett, Steven

2009-05-15

In animal models, the dysregulated activity of calcium-activated proteases, calpains, contributes directly to cataract formation. However, the physiological role of calpains in the healthy lens is not well defined. In this study, we examined the expression pattern of calpains in the mouse lens. Real time PCR and Western blotting data indicated that calpain 1, 2, 3, and 7 were expressed in lens fiber cells. Using controlled lysis, depth-dependent expression profiles for each calpain were obtained. These indicated that, unlike calpain 1, 2, and 7, which were most abundant in cells near the lens surface, calpain 3 expression was strongest in the deep cortical region of the lens. We detected calpain activities in vitro and showed that calpains were active in vivo by microinjecting fluorogenic calpain substrates into cortical fiber cells. To identify endogenous calpain substrates, membrane/cytoskeleton preparations were treated with recombinant calpain, and cleaved products were identified by two-dimensional difference electrophoresis/mass spectrometry. Among the calpain substrates identified by this approach was alphaII-spectrin. An antibody that specifically recognized calpain-cleaved spectrin was used to demonstrate that spectrin is cleaved in vivo, late in fiber cell differentiation, at or about the time that lens organelles are degraded. The generation of the calpain-specific spectrin cleavage product was not observed in lens tissue from calpain 3-null mice, indicating that calpain 3 is uniquely activated during lens fiber differentiation. Our data suggest a role for calpains in the remodeling of the membrane cytoskeleton that occurs with fiber cell maturation.

Fuselage structure using advanced technology fiber reinforced composites

NASA Technical Reports Server (NTRS)

Robinson, R. K.; Tomlinson, H. M. (Inventor)

1982-01-01

A fuselage structure is described in which the skin is comprised of layers of a matrix fiber reinforced composite, with the stringers reinforced with the same composite material. The high strength to weight ratio of the composite, particularly at elevated temperatures, and its high modulus of elasticity, makes it desirable for use in airplane structures.

Investigation of Structural Properties of Carbon-Epoxy Composites Using Fiber-Bragg Gratings

NASA Technical Reports Server (NTRS)

Grant, J.; Kaul, R.; Taylor, S.; Jackson, K.; Sharma, A.; Burdine, Robert V. (Technical Monitor)

2002-01-01

Fiber Bragg-gratings are embedded in carbon-epoxy laminates as well as bonded on the surface of cylindrical structures fabricated out of such composites. Structural properties of such composites is investigated. The measurements include stress-strain relation in laminates and Poisson's ratio in several specimens with varying orientation of the optical fiber Bragg-sensor with respect to the carbon fiber in an epoxy matrix. Additionally, Bragg gratings are bonded on the surface of cylinders fabricated out of carbon-epoxy composites and longitudinal and hoop strain on the surface is measured.

Preparation of thick silica coatings on carbon fibers with fine-structured silica nanotubes induced by a self-assembly process.

PubMed

Baumgärtner, Benjamin; Möller, Hendrik; Neumann, Thomas; Volkmer, Dirk

2017-01-01

A facile method to coat carbon fibers with a silica shell is presented in this work. By immobilizing linear polyamines on the carbon fiber surface, the high catalytic activity of polyamines in the sol-gel-processing of silica precursors is used to deposit a silica coating directly on the fiber's surface. The surface localization of the catalyst is achieved either by attaching short-chain polyamines (e.g., tetraethylenepentamine) via covalent bonds to the carbon fiber surface or by depositing long-chain polyamines (e.g., linear poly(ethylenimine)) on the carbon fiber by weak non-covalent bonding. The long-chain polyamine self-assembles onto the carbon fiber substrate in the form of nanoscopic crystallites, which serve as a template for the subsequent silica deposition. The silicification at close to neutral pH is spatially restricted to the localized polyamine and consequently to the fiber surface. In case of the linear poly(ethylenimine), silica shells of several micrometers in thickness can be obtained and their morphology is easily controlled by a considerable number of synthesis parameters. A unique feature is the hierarchical biomimetic structure of the silica coating which surrounds the embedded carbon fiber by fibrillar and interconnected silica fine-structures. The high surface area of the nanostructured composite fiber may be exploited for catalytic applications and adsorption purposes.

Structural health monitoring of civil infrastructure using optical fiber sensing technology: a comprehensive review.

PubMed

Ye, X W; Su, Y H; Han, J P

2014-01-01

In the last two decades, a significant number of innovative sensing systems based on optical fiber sensors have been exploited in the engineering community due to their inherent distinctive advantages such as small size, light weight, immunity to electromagnetic interference (EMI) and corrosion, and embedding capability. A lot of optical fiber sensor-based monitoring systems have been developed for continuous measurement and real-time assessment of diversified engineering structures such as bridges, buildings, tunnels, pipelines, wind turbines, railway infrastructure, and geotechnical structures. The purpose of this review article is devoted to presenting a summary of the basic principles of various optical fiber sensors, innovation in sensing and computational methodologies, development of novel optical fiber sensors, and the practical application status of the optical fiber sensing technology in structural health monitoring (SHM) of civil infrastructure.

Ectopic Activation of Wnt/β-Catenin Signaling in Lens Fiber Cells Results in Cataract Formation and Aberrant Fiber Cell Differentiation

PubMed Central

Antosova, Barbora; Smolikova, Jana; Borkovcova, Romana; Strnad, Hynek; Lachova, Jitka; Machon, Ondrej; Kozmik, Zbynek

2013-01-01

The Wnt/β-catenin signaling pathway controls many processes during development, including cell proliferation, cell differentiation and tissue homeostasis, and its aberrant regulation has been linked to various pathologies. In this study we investigated the effect of ectopic activation of Wnt/β-catenin signaling during lens fiber cell differentiation. To activate Wnt/β-catenin signaling in lens fiber cells, the transgenic mouse referred to as αA-CLEF was generated, in which the transactivation domain of β-catenin was fused to the DNA-binding protein LEF1, and expression of the transgene was controlled by αA-crystallin promoter. Constitutive activation of Wnt/β-catenin signaling in lens fiber cells of αA-CLEF mice resulted in abnormal and delayed fiber cell differentiation. Moreover, adult αA-CLEF mice developed cataract, microphthalmia and manifested downregulated levels of γ-crystallins in lenses. We provide evidence of aberrant expression of cell cycle regulators in embryonic lenses of αA-CLEF transgenic mice resulting in the delay in cell cycle exit and in the shift of fiber cell differentiation to the central fiber cell compartment. Our results indicate that precise regulation of the Wnt/β-catenin signaling activity during later stages of lens development is essential for proper lens fiber cell differentiation and lens transparency. PMID:24205179

Structural characterization and mechanical properties of polypropylene reinforced natural fibers

NASA Astrophysics Data System (ADS)

Karim, M. A. A.; Zaman, I.; Rozlan, S. A. M.; Berhanuddin, N. I. C.; Manshoor, B.; Mustapha, M. S.; Khalid, A.; Chan, S. W.

2017-10-01

Recently the development of natural fiber composite instead of synthetics fiber has lead to eco-friendly product manufacturing to meet various applications in the field of automotive, construction and manufacturing. The use of natural fibers offer an alternative to the reinforcing fibers because of their good mechanical properties, low density, renewability, and biodegradability. In this present research, the effects of maleic anhydride polypropylene (MAPP) on the mechanical properties and material characterization behaviour of kenaf fiber and coir fiber reinforced polypropylene were investigated. Different fractions of composites with 10wt%, 20wt% and 30wt% fiber content were prepared by using brabender mixer at 190°C. The 3wt% MAPP was added during the mixing. The composites were subsequently molded with injection molding to prepare the test specimens. The mechanical properties of the samples were investigated according to ISO 527 to determine the tensile strength and modulus. These results were also confirmed by the SEM machine observations of fracture surface of composites and FTIR analysis of the chemical structure. As the results, the presence of MAPP helps increasing the mechanical properties of both fibers and 30wt% kenaf fiber with 3wt% MAPP gives the best result compare to others.

Carbon Fiber Epoxy Composites for Both Strengthening and Health Monitoring of Structures

PubMed Central

Salvado, Rita; Lopes, Catarina; Szojda, Leszek; Araújo, Pedro; Gorski, Marcin; Velez, Fernando José; Castro-Gomes, João; Krzywon, Rafal

2015-01-01

This paper presents a study of the electrical and mechanical behavior of several continuous carbon fibers epoxy composites for both strengthening and monitoring of structures. In these composites, the arrangement of fibers was deliberately diversified to test and understand the ability of the composites for self-sensing low strains. Composites with different arrangements of fibers and textile weaves, mainly unidirectional continuous carbon reinforced composites, were tested at the dynamometer. A two-probe method was considered to measure the relative electrical resistance of these composites during loading. The measured relative electrical resistance includes volume and contact electrical resistances. For all tested specimens, it increases with an increase in tensile strain, at low strain values. This is explained by the improved alignment of fibers and resulting reduction of the number of possible contacts between fibers during loading, increasing as a consequence the contact electrical resistance of the composite. Laboratory tests on strengthening of structural elements were also performed, making hand-made composites by the “wet process”, which is commonly used in civil engineering for the strengthening of all types of structures in-situ. Results show that the woven epoxy composite, used for strengthening of concrete elements is also able to sense low deformations, below 1%. Moreover, results clearly show that this textile sensor also improves the mechanical work of the strengthened structural elements, increasing their bearing capacity. Finally, the set of obtained results supports the concept of a textile fabric capable of both structural upgrade and self-monitoring of structures, especially large structures of difficult access and needing constant, sometimes very expensive, health monitoring. PMID:25954955

High-performance wearable supercapacitors fabricated with surface activated continuous filament graphite fibers

NASA Astrophysics Data System (ADS)

Jia, Dedong; Yu, Xin; Chen, Tinghan; Wang, Shu; Tan, Hua; Liu, Hong; Wang, Zhong Lin; Li, Linlin

2017-08-01

Generally, carbon or graphite fibers (GFs) are used as the supporting materials for the preparation of flexible supercapacitors (SCs) by assembling various electrochemically active nanomaterials on them. A facile and rapid electrochemical oxidation method with a voltage of 3 V in a mixed H2SO4-HNO3 solution for 2-15 min is proposed to active continuous filament GFs. Detailed structural characterization, SEM, TEM, XRD, Raman and XPS demonstrate that the GFs-8 (oxidized for 8 min) possessing high specific surface area which provided numerous electrochemical sites and a large number of oxygen-containing functional groups producing pseudocapacitance. Cyclic voltammetric (CV), galvanostatic charge-discharge measurements and electrochemical impedance spectroscopy (EIS) are conducted to test the capacitive of GFs and activated GFs. The capacitance of GFs-8 reaches as high as 570 mF cm-1 at the current density of 1 mA cm-1 in LiCl electrolyte, a 1965-fold enhancement with respect to the pristine GFs (0.29 mF cm-1). The fabricated fiber solid-state supercapacitors (SSCs) provide high energy density of 0.68 mWh cm-3 at the power density 3.3 W cm-3 and have excellent durability with 90% capacitance retention after 10000 cycles. In addition, such fiber SSCs features flexibility and mechanical stability, which may have wide applications in wearable electronic devices.

Control systems using modal domain optical fiber sensors for smart structure applications

NASA Technical Reports Server (NTRS)

Lindner, Douglas K.; Reichard, Karl M.

1991-01-01

Recently, a new class of sensors has emerged for structural control which respond to environmental changes over a significant gauge length; these sensors are called distributed-effect sensors. These sensors can be fabricated with spatially varying sensitivity to the distributed measurand, and can be configured to measure a variety of structural parameters which can not be measured directly using point sensors. Examples of distributed-effect sensors include piezoelectric film, holographic sensors, and modal domain optical fiber sensors. Optical fiber sensors are particularly attractive for smart structure applications because they are flexible, have low mass, and can easily be embedded directly into materials. In this paper we describe the implementation of weighted modal domain optical fiber sensors. The mathematical model of the modal domain optical fiber sensor model is described and used to derive an expression for the sensor sensitivity. The effects of parameter variations on the sensor sensitivity are demonstrated to illustrate methods of spatially varying the sensor sensitivity.

Buckling Modes of Structural Elements of Off-Axis Fiber-Reinforced Plastics

NASA Astrophysics Data System (ADS)

Paimushin, V. N.; Polyakova, N. V.; Kholmogorov, S. A.; Shishov, M. A.

2018-05-01

The structures of two types of unidirectional fiber-reinforced composites — with an ELUR-P carbon fiber tape, an XT-118 cold-cure binder with an HSE 180 REM prepreg, and a hot-cure binder — were investigated. The diameters of fibers and fiber bundles (threads) of both the types of composites were measured, and their mutual arrangement was examined both in the semifinished products (in the uncured state) and in the finished composites. The defects characteristic of both the types of binder and manufacturing technique were detected in the cured composites. Based on an analysis of the results obtained, linearized problems on the internal multiscale buckling modes of an individual fiber (with and without account of its interaction with the surrounding matrix) or of a fiber bundle are formulated. In the initial atate, these structural elements of the fibrous composites are in a subcritical (unperturbed) state under the action of shear stresses and tension (compression) in the transverse direction. Such an initial stress state is formed in them in tension and compression tests on flat specimens made of off-axis-reinforced composites with straight fibers. To formulate the problems, the equations derived earlier from a consistent variant of geometrically nonlinear equations of elasticity theory by reducing them to the one-dimensional equations of the theory of straight rods on the basis of a refined Timoshenko shear model with account of tensile-compressive strains in the transverse direction are used. It is shown that, in loading test specimens, a continuous rearrangement of composite structure can occur due to the realization and continuous change of internal buckling modes as the wave-formation parameter varies continuously, which apparently explain the decrease revealed in the tangential shear modulus of the fibrous composites with increasing shear strains.

Active phase compensation system for fiber optic holography

NASA Technical Reports Server (NTRS)

Mercer, Carolyn R.; Beheim, Glenn

1988-01-01

Fiber optic delivery systems promise to extend the application of holography to severe environments by simplifying test configurations and permitting the laser to be remotely placed in a more benign location. However, the introduction of optical fiber leads to phase stability problems. Environmental effects cause the pathlengths of the fibers to change randomly, preventing the formation of stationary interference patterns which are required for holography. An active phase control system has been designed and used with an all-fiber optical system to stabilize the phase difference between light emitted from two fibers, and to step the phase difference by 90 deg without applying any constraints on the placement of the fibers. The accuracy of the phase steps is shown to be better than 0.02 deg., and a stable phase difference can be maintained for 30 min. This system can be applied to both conventional and electro-optic holography, as well as to any system where the maintenance of an accurate phase difference between two coherent beams is required.

Active phase compensation system for fiber optic holography

NASA Technical Reports Server (NTRS)

Mercer, Carolyn R.; Beheim, Glenn

1989-01-01

Fiber optic delivery systems promise to extend the application of holography to severe environments by simplifying test configurations and permitting the laser to be remotely placed in a more benign location. However, the introduction of optical fiber leads to phase stability problems. Environmental effects cause the pathlengths of the fibers to change randomly, preventing the formation of stationary interference patterns which are required for holography. An active phase control system has been designed and used with an all-fiber optical system to stabilize the phase difference between light emitted from two fibers, and to step the phase difference by 90 deg without applying any constraints on the placement of the fibers. The accuracy of the phase steps is shown to be better than 0.02 deg., and a stable phase difference can be maintained for 30 min. This system can be applied to both conventional and electro-optic holography, as well as to any system where the maintenance of an accurate phase difference between two coherent beams is required.

All-fiber, long-active-length Fabry-Perot strain sensor.

PubMed

Pevec, Simon; Donlagic, Denis

2011-08-01

This paper presents a high-sensitivity, all-silica, all-fiber Fabry-Perot strain-sensor. The proposed sensor provides a long active length, arbitrary length of Fabry-Perot cavity, and low intrinsic temperature sensitivity. The sensor was micro-machined from purposely-developed sensor-forming fiber that is etched and directly spliced to the lead-in fiber. This manufacturing process has good potential for cost-effective, high-volume production. Its measurement range of over 3000 µε, and strain-resolution better than 1 µε were demonstrated by the application of a commercial, multimode fiber-based signal processor.

Structural dissipative solitons in passive mode-locked fiber lasers.

PubMed

Komarov, Andrey; Sanchez, François

2008-06-01

On the basis of numerical simulation of fiber laser passive mode locking with anomalous dispersion we have found the dissipative solitons with powerful pedestals having oscillating structure. The pedestal structure causes a complex structural spectrum. These solitons can be multistable: with the same laser parameters the pedestals can have different structures. For some nonlinear-dispersion parameters there exist solitons with asymmetric structural pedestals moving relatively solitons with symmetric ones.

Structural Health Monitoring of Civil Infrastructure Using Optical Fiber Sensing Technology: A Comprehensive Review

PubMed Central

Ye, X. W.; Su, Y. H.; Han, J. P.

2014-01-01

In the last two decades, a significant number of innovative sensing systems based on optical fiber sensors have been exploited in the engineering community due to their inherent distinctive advantages such as small size, light weight, immunity to electromagnetic interference (EMI) and corrosion, and embedding capability. A lot of optical fiber sensor-based monitoring systems have been developed for continuous measurement and real-time assessment of diversified engineering structures such as bridges, buildings, tunnels, pipelines, wind turbines, railway infrastructure, and geotechnical structures. The purpose of this review article is devoted to presenting a summary of the basic principles of various optical fiber sensors, innovation in sensing and computational methodologies, development of novel optical fiber sensors, and the practical application status of the optical fiber sensing technology in structural health monitoring (SHM) of civil infrastructure. PMID:25133250

Instrumentation by distributed optical fiber sensors of a new ballastless track structure

NASA Astrophysics Data System (ADS)

Chapeleau, Xavier; Cottineau, Louis-Marie; Sedran, Thierry; Gueguen, Ivan; Cailliau, Joël

2013-04-01

While relatively expensive to build, ballastless track structures are presently seen as an attractive alternative to conventional ballast. With its service life of at least 60 years, they require little maintenance and hence they offer great availability. Other reasons for using ballastless tracks instead of ballasted tracks are the lack of suitable ballast material and the need of less noise and vibration for high-speed, in particularly. A new ballastless track structure has been designed to be circulated up to 300km/h, with a target life of 100 years. It is an interoperable way on concrete slabs that are cast-in-place and slip formed. This structure has been built and tested at the scale one in our laboratory. Indeed, ten millions cyclic loads were applied at 2.5Hz to evaluate the fatigue behaviour under selected mechanical and thermal conditions. To monitor the thermo-mechanical behavior of this new structure and to verify the numerical simulations used for its design, a lot of sensors have been embedded. In particularly, we have tested an optical fiber as distributed sensors to measure strain distribution in the railway model. This sensor can also be used to detect, localize and monitor cracks in concrete slabs. The optical fiber sensing technique ("Rayleigh technique") used in this experimentation has a centimetric spatial resolution which allows to measure complex strain profiles unlike electrical strain gauges which only give local information. Firstly, optical cables used as sensors have been successfully embedded and attached to the reinforcing steel bars in the structure. We have noted that they are resistant enough to resist concrete pouring and working activities. Secondly, strains measured by conventional strain gauges has confirmed the quality of the strain profiles measurements obtained by optical fiber sensors. Moreover, we have found a good agreement between experimental profiles measurements and those obtained by numerical simulations. Early

Hole-pin joining structure with fiber-round-hole distribution of lobster cuticle and biomimetic study.

PubMed

Chen, Bin; Fan, Jinghong; Gou, Jihua; Lin, Shiyun

2014-12-01

Observations of the cuticle of the Boston Spiny Lobster using scanning electron microscope (SEM) show that it is a natural biocomposite consisting of chitin fibers and sclerotic-protein matrix with hierarchical and helicoidal structure. The SEM images also indicate that there is a hole-pin joining structure in the cuticle. In this joining structure, the chitin fibers in the neighborhood of the joining holes continuously round the holes to form a fiber-round-hole distribution. The maximum pullout force of the fibers in the fiber-round-hole distribution, which is closely related to the fracture toughness of the cuticle, is investigated and compared with that of the fibers in non-fiber-round-hole distribution based on their representative models. It is revealed that the maximum pullout force of the fibers in the fiber-round-hole distribution is significantly larger than that of the fibers in the non-fiber-round-hole distribution, and that a larger diameter of the hole results in a larger difference in the maximum pullout forces of the fibers between the two kinds of the fiber distributions. Inspired by the fiber-round-hole distribution found in the cuticle, composite specimens with the fiber-round-hole distribution were fabricated with a special mold and process to mirror the fiber-round-hole distribution. The fracture toughness of the biomimetic composite specimens is tested and compared with that of the conventional composite specimens with the non-fiber-round-hole distribution. It is demonstrated that the fracture toughness of the biomimetic composite specimens with the fiber-round-hole distribution is significantly larger than that of the conventional composite specimens with the non-fiber-round-hole distribution. Copyright © 2014 Elsevier Ltd. All rights reserved.

Active Q switching of a fiber laser with a microsphere resonator

NASA Astrophysics Data System (ADS)

Kieu, Khanh; Mansuripur, Masud

2006-12-01

We propose and demonstrate an active Q-switched fiber laser using a high-Q microsphere resonator as the Q-switching element. The laser cavity consists of an Er-doped fiber as the gain medium, a glass microsphere reflector (coupled through a fiber taper) at one end of the cavity, and a fiber Bragg grating reflector at the other end. The reflectivity of the microsphere is modulated by changing the gap between the microsphere and the fiber taper. Active Q switching is realized by oscillating the microsphere in and out of contact with the taper. Using this novel technique, we have obtained giant pulses (maximum peak power ˜102W, duration ˜160ns) at a low pump-power threshold (˜3mW).

Analysis of the connection of the timber-fiber concrete composite structure

NASA Astrophysics Data System (ADS)

Holý, Milan; Vráblík, Lukáš; Petřík, Vojtěch

2017-09-01

This paper deals with an implementation of the material parameters of the connection to complex models for analysis of the timber-fiber concrete composite structures. The aim of this article is to present a possible way of idealization of the continuous contact model that approximates the actual behavior of timber-fiber reinforced concrete structures. The presented model of the connection was derived from push-out shear tests. It was approved by use of the nonlinear numerical analysis, that it can be achieved a very good compliance between results of numerical simulations and results of the experiments by a suitable choice of the material parameters of the continuous contact. Finally, an application for an analytical calculation of timber-fiber concrete composite structures is developed for the practical use in engineering praxis. The input material parameters for the analytical model was received using data from experiments.

Codon optimization of the adenoviral fiber negatively impacts structural protein expression and viral fitness

NASA Astrophysics Data System (ADS)

Villanueva, Eneko; Martí-Solano, Maria; Fillat, Cristina

2016-06-01

Codon usage adaptation of lytic viruses to their hosts is determinant for viral fitness. In this work, we analyzed the codon usage of adenoviral proteins by principal component analysis and assessed their codon adaptation to the host. We observed a general clustering of adenoviral proteins according to their function. However, there was a significant variation in the codon preference between the host-interacting fiber protein and the rest of structural late phase proteins, with a non-optimal codon usage of the fiber. To understand the impact of codon bias in the fiber, we optimized the Adenovirus-5 fiber to the codon usage of the hexon structural protein. The optimized fiber displayed increased expression in a non-viral context. However, infection with adenoviruses containing the optimized fiber resulted in decreased expression of the fiber and of wild-type structural proteins. Consequently, this led to a drastic reduction in viral release. The insertion of an exogenous optimized protein as a late gene in the adenovirus with the optimized fiber further interfered with viral fitness. These results highlight the importance of balancing codon usage in viral proteins to adequately exploit cellular resources for efficient infection and open new opportunities to regulate viral fitness for virotherapy and vaccine development.

Preparation of thick silica coatings on carbon fibers with fine-structured silica nanotubes induced by a self-assembly process

PubMed Central

Baumgärtner, Benjamin; Möller, Hendrik; Neumann, Thomas

2017-01-01

A facile method to coat carbon fibers with a silica shell is presented in this work. By immobilizing linear polyamines on the carbon fiber surface, the high catalytic activity of polyamines in the sol–gel-processing of silica precursors is used to deposit a silica coating directly on the fiber’s surface. The surface localization of the catalyst is achieved either by attaching short-chain polyamines (e.g., tetraethylenepentamine) via covalent bonds to the carbon fiber surface or by depositing long-chain polyamines (e.g., linear poly(ethylenimine)) on the carbon fiber by weak non-covalent bonding. The long-chain polyamine self-assembles onto the carbon fiber substrate in the form of nanoscopic crystallites, which serve as a template for the subsequent silica deposition. The silicification at close to neutral pH is spatially restricted to the localized polyamine and consequently to the fiber surface. In case of the linear poly(ethylenimine), silica shells of several micrometers in thickness can be obtained and their morphology is easily controlled by a considerable number of synthesis parameters. A unique feature is the hierarchical biomimetic structure of the silica coating which surrounds the embedded carbon fiber by fibrillar and interconnected silica fine-structures. The high surface area of the nanostructured composite fiber may be exploited for catalytic applications and adsorption purposes. PMID:28685115

Fiber-reinforced concretes with a high fiber volume fraction — a look in future. Can a design determine the fiber amount in concrete in real time in every part of a structure in production?

NASA Astrophysics Data System (ADS)

Tepfers, R.

2010-09-01

In near future, when the control of the load-bearing capacity of fiber-only-reinforced concrete members will be safely guaranteed, the deletion of the ordinary continuous steel reinforcing bars might be possible. For the time being, it is difficult to change the fiber amount during the casting with today's techniques. Therefore, the fiber concentration has to be determined by the maximum tensile stress in concrete structural members, resulting in an unnecessary fiber addition in compressed zones. However, if the right amount of fibers could be regulated and added to concrete in real time at the pump outlet, a future vision could be to design and produce a structure by using FEM-controlled equipment. The signals from calculation results could be transmitted to a concrete casting system for addition of a necessary amount of fibers to take care of the actual tensile stresses in the right position in the structure. The casting location could be determined by using a GPS for positioning the pump outlet for targeting the casting location horizontally and a laser vertically. The addition of fibers to concrete at the outlet of a concrete pump and proportioning them there according to the actual needs of the stress situation in a structure, given by a FEM analysis in real time, is a future challenge. The FEM analysis has to be based on material properties of fiber-only-reinforced concrete. This means that the resistance and stiffness of different-strength concrete members with a varying fiber content has to be determined in tests and conveyed to the FEM analysis. The FEM analysis has to be completed before the casting and controlled. Then it can be used as the base for adding a correct amount of fibers to concrete in every part of the structure. Thus, a system for introducing a correct amount of fibers into concrete has to be developed. The fibers have to be added at the outlet of concrete pump. Maybe a system to shotcrete concrete with electronically controlled fiber

Alcohol sensor based on single-mode-multimode-single-mode fiber structure

NASA Astrophysics Data System (ADS)

Mefina Yulias, R.; Hatta, A. M.; Sekartedjo, Sekartedjo

2016-11-01

Alcohol sensor based on Single-mode -Multimode-Single-mode (SMS) fiber structure is being proposed to sense alcohol concentration in alcohol-water mixtures. This proposed sensor uses refractive index sensing as its sensing principle. Fabricated SMS fiber structure had 40 m of multimode length. With power input -6 dBm and wavelength 1550 nm, the proposed sensor showed good response with sensitivity 1,983 dB per % v/v with measurement range 05 % v/v and measurement span 0,5% v/v.

Fiber sensing based on new structures and post-processing enhancement

NASA Astrophysics Data System (ADS)

Ferreira, Marta Sofia dos Anjos

The work described in this PhD Thesis focuses on the post-processing of optical fibers and their enhancement as sensing element. Since the majority of sensors presented are based in Fabry-Perot interferometers, an historical overview of this category of optical fiber sensors is firstly presented. This review considers the works published since the early years, in the beginning of the 1980s, until the middle of 2015. The incorporation of microcavities at the tip of a single mode fiber was extensively studied, particularly for the measurement of nitrogen and methane gas pressure. These cavities were fabricated using hollow core silica tubes and a hollow core photonic crystal fiber. Following a different approach, the microcavities were incorporated between two sections of single mode fiber. In this case, the low sensitivity to temperature makes these microcavities highly desirable for the measurement of strain at high temperatures. Competences in post-processing techniques such as the chemical etching and the writing of periodical structures in the fiber core by means of an excimer or a femtosecond laser were also acquired in the course of the PhD programme. One of the works consisted in the design and manufacturing of a double clad optical fiber. The refractive index of the inner cladding was higher than the one of the outer cladding and the core. Thus, light was guided in the inner cladding instead of propagating in the core. This situation was overcome by applying chemical etching, thus removing the inner cladding. The core, surrounded by air, was then able to guide light. Two different applications were found for this fiber, as a temperature sensor and as an optical refractometer. In the last, the optical phase changes with the liquid refractive index. Two different types of fiber Bragg gratings were characterized in strain and temperature. Sensing structures obtained through the phase mask technique at the tip of an optical fiber were subjected to chemical

CVD of silicon carbide on structural fibers - Microstructure and composition

NASA Technical Reports Server (NTRS)

Veitch, Lisa C.; Terepka, Francis M.; Gokoglu, Suleyman A.

1992-01-01

Structural fibers are currently being considered as reinforcements for intermetallic and ceramic materials. Some of these fibers, however, are easily degraded in a high temperature oxidative environment. Therefore, coatings are needed to protect the fibers from environmental attack. Silicon carbide (SiC) was chemically vapor deposited (CVD) on Textron's SCS6 fibers. Fiber temperatures ranging from 1350 to 1500 C were studied. Silane (SiH4) and propane (C2H8) were used for the source gases and different concentrations of these source gases were studied. Deposition rates were determined for each group of fibers at different temperatures. Less variation in deposition rates were observed for the dilute source gas experiments than the concentrated source gas experiments. A careful analysis was performed on the stoichiometry of the CVD SiC coating using electron microprobe. Microstructures for the different conditions were compared. At 1350 C, the microstructures were similar; however, at higher temperatures, the microstructure for the more concentrated source gas group were porous and columnar in comparison to the cross sections taken from the same area for the dilute source gas group.

CVD of silicon carbide on structural fibers: Microstructure and composition

NASA Technical Reports Server (NTRS)

Veitch, Lisa C.; Terepka, Francis M.; Gokoglu, Suleyman A.

1992-01-01

Structural fibers are currently being considered as reinforcements for intermetallic and ceramic materials. Some of these fibers, however, are easily degraded in a high temperature oxidative environment. Therefore, coatings are needed to protect the fibers from environmental attack. Silicon carbide (SiC) was chemically vapor deposited (CVD) on Textron's SCS6 fibers. Fiber temperatures ranging from 1350 to 1500 C were studied. Silane (SiH4) and propane (C2H8) were used for the source gases and different concentrations of these source gases were studied. Deposition rates were determined for each group of fibers at different temperatures. Less variation in deposition rates were observed for the dilute source gas experiments than the concentrated source gas experiments. A careful analysis was performed on the stoichiometry of the CVD SiC coating using electron microprobe. Microstructures for the different conditions were compared. At 1350 C, the microstructures were similar; however, at higher temperatures, the microstructure for the more concentrated source gas group were porous and columnar in comparison to the cross sections taken from the same area for the dilute source gas group.

Tunable Laser Development for In-Flight Fiber Optic Based Structural Health Monitoring Systems

NASA Technical Reports Server (NTRS)

Richards, Lance; Parker, Allen; Chan, Patrick

2013-01-01

Briefing based on tunable laser development for in flight fiber optic based structural health monitoring systems. The objective of this task is to investigate, develop, and demonstrate a low-cost swept lasing light source for NASA DFRC's fiber optics sensing system (FOSS) to perform structural health monitoring on current and future aerospace vehicles.

Regional mechanics determine collagen fiber structure in healing myocardial infarcts.

PubMed

Fomovsky, Gregory M; Rouillard, Andrew D; Holmes, Jeffrey W

2012-05-01

Following myocardial infarction, the mechanical properties of the healing infarct are an important determinant of heart function and the risk of progression to heart failure. In particular, mechanical anisotropy (having different mechanical properties in different directions) in the healing infarct can preserve pump function of the heart. Based on reports of different collagen structures and mechanical properties in various animal models, we hypothesized that differences in infarct size, shape, and/or location produce different patterns of mechanical stretch that guide evolving collagen fiber structure. We tested the effects of infarct shape and location using a combined experimental and computational approach. We studied mechanics and collagen fiber structure in cryoinfarcts in 53 Sprague-Dawley rats and found that regardless of shape or orientation, cryoinfarcts near the equator of the left ventricle stretched primarily in the circumferential direction and developed circumferentially aligned collagen, while infarcts at the apex stretched similarly in the circumferential and longitudinal directions and developed randomly oriented collagen. In a computational model of infarct healing, an effect of mechanical stretch on fibroblast and collagen alignment was required to reproduce the experimental results. We conclude that mechanical environment determines collagen fiber structure in healing myocardial infarcts. Our results suggest that emerging post-infarction therapies that alter regional mechanics will also alter infarct collagen structure, offering both potential risks and novel therapeutic opportunities. Copyright © 2012 Elsevier Ltd. All rights reserved.

Regional Mechanics Determine Collagen Fiber Structure in Healing Myocardial Infarcts

PubMed Central

Fomovsky, Gregory M.; Rouillard, Andrew D.; Holmes, Jeffrey W.

2012-01-01

Following myocardial infarction, the mechanical properties of the healing infarct are an important determinant of heart function and the risk of progression to heart failure. In particular, mechanical anisotropy (having different mechanical properties in different directions) in the healing infarct can preserve pump function of the heart. Based on reports of different collagen structures and mechanical properties in various animal models, we hypothesized that differences in infarct size, shape, and/or location produce different patterns of mechanical stretch that guide evolving collagen fiber structure. We tested the effects of infarct shape and location using a combined experimental and computational approach. We studied mechanics and collagen fiber structure in cryoinfarcts in 53 Sprague-Dawley rats and found that regardless of shape or orientation, cryoinfarcts near the equator of the left ventricle stretched primarily in the circumferential direction and developed circumferentially aligned collagen, while infarcts at the apex stretched similarly in the circumferential and longitudinal direction and developed randomly oriented collagen. In a computational model of infarct healing, an effect of mechanical stretch on fibroblast and collagen alignment was required to reproduce the experimental results. We conclude that mechanical environment determines collagen fiber structure in healing myocardial infarcts. Our results suggest that emerging post-infarction therapies that alter regional mechanics will also alter infarct collagen structure, offering both potential risks and novel therapeutic opportunities. PMID:22418281

Thermal stability characterization of SiC ceramic fibers. II. Fractography and structure

DOE Office of Scientific and Technical Information (OSTI.GOV)

Sawyer, L.C.; Chen, R.T.; Haimbach, F.,IV

1986-08-01

SiC ceramic fibers (Nicalon) exhibit tensile strength reduction following thermal treatment in air, argon and nitrogen environments above 1200 C. Grain-size variations have been observed in the treated fibers by X-ray diffraction and electron microscopy. Fractography studies show that strength reduction occurs in all thermal treatments, although the mechanism of fiber failure varies depending upon the specific environment. Structure-property relations will be developed as mechanical testing and fractography of the thermally treated fibers are associated with tensile strength loss mechanisms. 16 references.

Effects of glass fiber mesh with different fiber content and structures on the compressive properties of complete dentures.

PubMed

Yu, Sang-Hui; Cho, Hye-Won; Oh, Seunghan; Bae, Ji-Myung

2015-06-01

No study has yet evaluated the strength of complete dentures reinforced with glass fiber meshes with different content and structures. The purpose of this study was to compare the reinforcing effects of glass fiber mesh with different content and structures with that of metal mesh in complete dentures. Two types of glass fiber mesh were used: SES mesh (SES) and glass cloth (GC2, GC3, and GC4). A metal mesh was used for comparison. The complete dentures were made by placing the reinforcement 1 mm away from the tissue surface. A control group was prepared without any reinforcement (n=10). The compressive properties were measured by a universal testing machine at a crosshead speed of 5 mm/min. The results were analyzed with the Kruskal-Wallis test and the Duncan multiple range test (α=.05). The fracture resistance of the SES group was significantly higher than that of the control, GC4, and metal groups (asymptotic P=.004), but not significantly different from the GC2 and GC3 groups. The toughness of the SES and GC3 groups was significantly higher than that of the others (asymptotic P<.001), but not significantly different from that of the GC4 group. SES and GC3, which have different structures but similar volume content, were the most effective in reinforcing complete dentures. The content of the glass fiber mesh seemed more important than the structures. Copyright © 2015 Editorial Council for the Journal of Prosthetic Dentistry. Published by Elsevier Inc. All rights reserved.

Nanoimprint of a 3D structure on an optical fiber for light wavefront manipulation.

PubMed

Calafiore, Giuseppe; Koshelev, Alexander; Allen, Frances I; Dhuey, Scott; Sassolini, Simone; Wong, Edward; Lum, Paul; Munechika, Keiko; Cabrini, Stefano

2016-09-16

Integration of complex photonic structures onto optical fiber facets enables powerful platforms with unprecedented optical functionalities. Conventional nanofabrication technologies, however, do not permit viable integration of complex photonic devices onto optical fibers owing to their low throughput and high cost. In this paper we report the fabrication of a three-dimensional structure achieved by direct nanoimprint lithography on the facet of an optical fiber. Nanoimprint processes and tools were specifically developed to enable a high lithographic accuracy and coaxial alignment of the optical device with respect to the fiber core. To demonstrate the capability of this new approach, a 3D beam splitter has been designed, imprinted and optically characterized. Scanning electron microscopy and optical measurements confirmed the good lithographic capabilities of the proposed approach as well as the desired optical performance of the imprinted structure. The inexpensive solution presented here should enable advancements in areas such as integrated optics and sensing, achieving enhanced portability and versatility of fiber optic components.

Structure of bacteriophage [phi]29 head fibers has a supercoiled triple repeating helix-turn-helix motif

DOE Office of Scientific and Technical Information (OSTI.GOV)

Xiang, Ye; Rossmann, Michael G.

2011-12-22

The tailed bacteriophage {phi}29 capsid is decorated with 55 fibers attached to quasi-3-fold symmetry positions. Each fiber is a homotrimer of gene product 8.5 (gp8.5) and consists of two major structural parts, a pseudohexagonal base and a protruding fibrous portion that is about 110 {angstrom} in length. The crystal structure of the C-terminal fibrous portion (residues 112-280) has been determined to a resolution of 1.6 {angstrom}. The structure is about 150 {angstrom} long and shows three distinct structural domains designated as head, neck, and stem. The stem region is a unique three-stranded helix-turn-helix supercoil that has not previously been described.more » When fitted into a cryoelectron microscope reconstruction of the virus, the head structure corresponded to a disconnected density at the distal end of the fiber and the neck structure was located in weak density connecting it to the fiber. Thin section studies of Bacillus subtilis cells infected with fibered or fiberless {phi}29 suggest that the fibers might enhance the attachment of the virions onto the host cell wall.« less

Tunable Laser Development for In-flight Fiber Optic Based Structural Health Monitoring Systems

NASA Technical Reports Server (NTRS)

Richards, Lance; Parker, Allen; Chan, Patrick

2014-01-01

The objective of this task is to investigate, develop, and demonstrate a low-cost swept lasing light source for NASA DFRC's fiber optics sensing system (FOSS) to perform structural health monitoring on current and future aerospace vehicles. This is the regular update of the Tunable Laser Development for In-flight Fiber Optic Based Structural Health Monitoring Systems website.

Analysis of structure of hyperfine poly(3-hydroxybutyrate) fibers (PHB) for controlled drug delivery

NASA Astrophysics Data System (ADS)

Olkhov, A. A.; Kosenko, R. Yu; Markin, V. S.; Zykova, A. K.; Pantyukhov, P. V.; Karpova, S. G.; Iordanskii, A. L.

2017-12-01

Hyperfine fibers based on biodegradable poly (3-hydroxybutyrate) with encapsulated drug substance (dipyridamol) were obtained by using electrospinning method. Addition of dipyridamol has a significant effect on geometrical shape and structure of microfibers as well as total porosity of fibrous material. Observation of fibers using scanning electron microscopy (SEM) method showed that without or at lower dipyridamol content (<3%) fibers consisted of interleaved ellipsoid and cylindrical fragments. At higher dipyridamol content (3-5%) anomalous ellipsoid structures did not practically form, and fiber’s shape became cylindrical. The totality of morphological and structural characteristics determined the rate of dipyridamol diffusive transports. The simplified model of drug desorption from fibrous matrix was presented. In current work it was showed that the rate-limiting stage of transport was the diffusion of dipyridamol in the bulk of cylindrical fibers.

Nano-structured wild moth cocoon fibers as radiative cooling and waveguiding optical materials

NASA Astrophysics Data System (ADS)

Shi, Norman Nan; Tsai, Cheng-Chia; Bernard, Gary D.; Craig, Catherine; Yu, Nanfang

2017-09-01

The study shows that comet moth cocoon fibers exhibit radiative cooing properties with enhanced solar reflectivity and thermal emissivity. Nanostructured voids inside the cocoon fiber enables the cocoons to exhibit strong scattering in the visible and near-infrared. These structures also allow the fibers to exhibit strong shape birefringence and directional reflectivity. Optical waveguiding due to transverse Anderson localization is observed in these natural fibers, where the invariance and large concentration of the voids in the longitudinal direction allow the fiber to confine light in the transverse direction. To mimic the optical effects generated by these natural silk fibers, nanostructured voids are introduced into regenerated silk fibers through wet spinning to enhance reflectivity in the solar spectrum.

Arterial elastic fiber structure. Function and potential roles in acute aortic dissection.

PubMed

Pratt, B; Curci, J

2010-10-01

The lethality of acute aortic dissection is well recognized. Successful treatment and prevention of aortic dissection is going to be dependent upon an improved understanding of the molecular and physiologic events which predispose to dissection development and propagation. In this review, we will focus on the elastic fiber, one of the critical elements of the aortic wall matrix. Mechanical or functional failure of the elastin in the wall of the aorta likely predisposes to dissection as well as the post-dissection aortic degeneration with aneurysm formation. Insight into the role of the elastin and the elastic fiber in aortic dissection has recently been accelerated by research into the molecular mechanisms associated with hereditary propensity for aortic dissection, such as Marfan syndrome. These studies have implicated both structural and metabolic contributions of alterations in the scaffolding proteins in matrix elastic fibers. In particular, increased transforming growth factor-β (TGF-β) activity may play a prominent role in predisposing the aortic wall to dissection. The events which predispose to post-dissection aortic degeneration are somewhat less well defined. However, the loss of the structural integrity of the remaining elastic fibers leaves the wall weaker and prone to dilatation and rupture. It appears likely that the upregulation of several potent proteases, particularly those of the matrix metalloproteinase (MMP) family such as MMP-9, are participating in the subsequent matrix damage. Novel medical treatments based on this pathologic data have been proposed and in some cases have made it to clinical trials. The ongoing study evaluating whether therapeutic inhibition of TGF-β may be useful in reducing the risk of aortic dissection in patients at high risk represents one promising new strategy in the treatment of this deadly disease.

Technique for writing of fiber Bragg gratings over or near preliminary formed macro-structure defects in silica optical fibers

NASA Astrophysics Data System (ADS)

Evtushenko, Alexander S.; Faskhutdinov, Lenar M.; Kafarova, Anastasia M.; Kazakov, Vadim S.; Kuznetzov, Artem A.; Minaeva, Alina Yu.; Sevruk, Nikita L.; Nureev, Ilnur I.; Vasilets, Alexander A.; Andreev, Vladimir A.; Morozov, Oleg G.; Burdin, Vladimir A.; Bourdine, Anton V.

2017-04-01

This work presents method for performing precision macro-structure defects "tapers" and "up-tapers" written in conventional silica telecommunication multimode optical fibers by commercially available field fusion splicer with modified software settings and following writing fiber Bragg gratings over or near them. We developed technique for macrodefect geometry parameters estimation via analysis of photo-image performed after defect writing and displayed on fusion splicer screen. Some research results of defect geometry dependence on fusion current and fusion time values re-set in splicer program are represented that provided ability to choose their "the best" combination. Also experimental statistical researches concerned with "taper" and "up-taper" diameter stability as well as their insertion loss values during their writing under fixed corrected splicer program parameters were performed. We developed technique for FBG writing over or near macro-structure defect. Some results of spectral response measurements produced for short-length samples of multimode optical fiber with fiber Bragg gratings written over and near macro-defects prepared by using proposed technique are presented.

The role of local interaction mechanics in fiber optic smart structures

NASA Astrophysics Data System (ADS)

Sirkis, J. S.; Dasgupta, A.

1993-04-01

The concept of using 'smart' composite materials/structures with built-in self-diagnostic capabilities for health monitoring involves embedding discrete and/or distributed sensory networks in the host composite material, along with a central and/or distributed artificial intelligence capability for signal processing, data collection, interpretation and diagnostic evaluations. This article concentrates on the sensory functions in 'smart' structure applications and concentrates in particular on optical fiber sensors. Specifically, we present an overview of recent research dealing with the basic mechanics of local interactions between the embedded optical fiber sensors and the surrounding host composite. The term 'local' is defined by length scales on the order of several optical fiber diameters. We examine some generic issues, such as the 'calibration' and 'obtrusivity' of the sensor, and the inherent damage caused by the sensor inclusions to the surrounding host and vice-versa under internal and/or external applied loads. Analytical, numerical and experimental results are presented regarding the influence of local strain concentrations caused by the sensory inclusions on sensor and host performance. The important issues examined are the local mechanistic effects of optical fiber coatings on the behavior of the sensor and the host, and mechanical survivability of optical fibers experiencing quasi-static and time-varying thermomechanical loading.

Analysis of structure and dynamics of superfine polyhydroxybutyrate fibers for targeted drug delivery

NASA Astrophysics Data System (ADS)

Olkhov, A.; Kucherenko, E.; Pantyukhov, P.; Zykova, A.; Karpova, S.; Iordanskii, A.

2017-02-01

Creation of polymer matrix systems for targeted drug delivery into a living organism is a challenging problem of modern treatment of various diseases and injuries. Poly-3-hydroxybutyrate (PHB) is commonly used for development of therapeutic systems. The aim of this article is to examine the changes in structure and morphology of fibers in presence of dipyridamole (DPD) as model drug for controlled release. It was found that addition of dipyridamole led to disappearance of spindle-shaped nodules on fibers of PHB in comparison with pure PHB. The research of thermophysical parameters showed that specific melting enthalpy (and the degree of crystallinity) of PHB fibers increased with the addition of DPD. With the increasing of DPD content in PHB fibers, more perfect and equilibrium crystal structure was formed. According to analysis of intercrystalline regions of PHB fibers, it was found that as the crystallinity of PHB in intergranular regions rose, the corresponding decrease of radical rotation speed was observed. It was concluded that fibers of PHB can be used for creating therapeutic systems for targeted and prolonged drug delivery.

Structural Evolution of Silicon Oxynitride Fiber Reinforced Boron Nitride Matrix Composite at High Temperatures

NASA Astrophysics Data System (ADS)

Zou, Chunrong; Li, Bin; Zhang, Changrui; Wang, Siqing; Xie, Zhengfang; Shao, Changwei

2016-02-01

The structural evolution of a silicon oxynitride fiber reinforced boron nitride matrix (Si-N-Of/BN) wave-transparent composite at high temperatures was investigated. When heat treated at 1600 °C, the composite retained a favorable bending strength of 55.3 MPa while partially crystallizing to Si2N2O and h-BN from the as-received amorphous structure. The Si-N-O fibers still performed as effective reinforcements despite the presence of small pores due to fiber decomposition. Upon heat treatment at 1800 °C, the Si-N-O fibers already lost their reinforcing function and rough hollow microstructure formed within the fibers because of the accelerated decomposition. Further heating to 2000 °C led to the complete decomposition of the reinforcing fibers and only h-BN particles survived. The crystallization and decomposition behaviors of the composite at high temperatures are discussed.

Fiber Optic Thermal Health Monitoring of Aerospace Structures and Materials

NASA Technical Reports Server (NTRS)

Wu, Meng-Chou; Winfree, William P.; Allison, Sidney G.

2009-01-01

A new technique is presented for thermographic detection of flaws in materials and structures by performing temperature measurements with fiber Bragg gratings. Individual optical fibers with multiple Bragg gratings employed as surface temperature sensors were bonded to the surfaces of structures with subsurface defects or thickness variations. Both during and following the application of a thermal heat flux to the surface, the individual Bragg grating sensors measured the temporal and spatial temperature variations. The investigated structures included a 10-ply composite specimen with subsurface delaminations of various sizes and depths. The data obtained from grating sensors were further analyzed with thermal modeling to reveal particular characteristics of the interested areas. These results were found to be consistent with those from conventional thermography techniques. Limitations of the technique were investigated using both experimental and numerical simulation techniques. Methods for performing in-situ structural health monitoring are discussed.

The effects of embedded piezoelectric fiber composite sensors on the structural integrity of glass-fiber-epoxy composite laminate

NASA Astrophysics Data System (ADS)

Konka, Hari P.; Wahab, M. A.; Lian, K.

2012-01-01

Piezoelectric fiber composite sensors (PFCSs) made from micro-sized lead zirconate titanate (PZT) fibers have many advantages over the traditional bulk PZT sensors for embedded sensor applications. PFCSs as embedded sensors will be an ideal choice to continuously monitor the stress/strain levels and health conditions of composite structures. PFCSs are highly flexible, easily embeddable, have high compatibility with composite structures, and also provides manufacturing flexibility. This research is focused on examining the effects of embedding PFCS sensors (macro-fiber composite (MFC) and piezoelectric fiber composite (PFC)) on the structural integrity of glass-fiber-epoxy composite laminates. The strengths of composite materials with embedded PFCSs and conventional PZT sensors were compared, and the advantages of PFCS sensors over PZTs were demonstrated. Initially a numerical simulation study is performed to understand the local stress/strain field near the embedded sensor region inside a composite specimen. High stress concentration regions were observed near the embedded sensor corner edge. Using PFCS leads to a reduction of 56% in longitudinal stress concentration and 38% in transverse stress concentration, when compared to using the conventional PZTs as embedded sensors. In-plane tensile, in-plane tension-tension fatigue, and short beam strength tests are performed to evaluate the strengths/behavior of the composite specimens containing embedded PFCS. From the tensile test it is observed that embedding PFCS and PZT sensors in the composite structures leads to a reduction in ultimate strength by 3 and 6% respectively. From the fatigue test results it is concluded that both embedded PFCS and PZT sensors do not have a significant effect on the fatigue behavior of the composite specimens. From the short beam strength test it is found that embedding PFCS and PZT sensors leads to a reduction in shear strength by 7 and 15% respectively. Overall the pure PZT sensors

Erbium-doped fiber ring laser based on few-mode-singlemode-few-mode fiber structure for refractive index measurement

NASA Astrophysics Data System (ADS)

Liu, Jingxuan; Wang, Muguang; Liang, Xiao; Dong, Yue; Xiao, Han; Jian, Shuisheng

2017-08-01

A novel Erbium-doped fiber ring cavity laser sensor for refractive index (RI) measurement based on a special designed few-mode-singlemode-few-mode structure is proposed and experimentally demonstrated. The few-mode fiber is a home-made concentric ring core fiber (CRCF) which can only support two scalar modes. Thus a stable mode interference occurs which functions as a sensing head and band-pass filter to select the lasing wavelength simultaneously. A sensitivity of -45.429 nm/RIU is obtained in the range of 1.333-1.363. High optical signal to noise ratio (OSNR) of ∼45 dB and narrow 3-dB bandwidth of ∼0.1 nm indicate that the fiber ring laser sensing system has a high resolution and accuracy RI measurement.

Energy Absorption Capacity in Natural Fiber Reinforcement Composites Structures

PubMed Central

López-Alba, Elías; Díaz, Francisco

2018-01-01

The study of natural fiber reinforcement composite structures has focused the attention of the automobile industry due to the new regulation in relation to the recyclability and the reusability of the materials preserving and/or improving the mechanical characteristics. The influence of different parameters on the material behavior of natural fiber reinforced plastic structures has been investigated, showing the potential for transport application in energy absorbing structures. Two different woven fabrics (twill and hopsack) made of flax fibers as well as a non-woven mat made of a mixture of hemp and kenaf fibers were employed as reinforcing materials. These reinforcing textiles were impregnated with both HD-PE (high-density polyethylen) and PLA (polylactic acid) matrix, using a continuous compression molding press. The impregnated semi-finished laminates (so-called organic sheets) were thermoformed in a second step to half-tubes that were assembled through vibration-welding process to cylindric crash absorbers. The specimens were loaded by compression to determine the specific energy absorption capacity. Quasi-static test results were compared to dynamic test data obtained on a catapult arrangement. The differences on the specific energies absorption (SEA) as a function of different parameters, such as the wall thickness, the weave material type, the reinforced textiles, and the matrix used, depending on the velocity rate application were quantified. In the case of quasi-static analysis it is observed a 20% increment in the SEA value when wove Hopsack fabric reinforcement is employed. No velocity rate influence from the material was observed on the SEA evaluation at higher speeds used to perform the experiments. The influence of the weave configuration (Hopsack) seems to be more stable against buckling effects at low loading rates with 10% higher SEA values. An increase of SEA level of up to 72% for PLA matrix was observed when compared with HD-PE matrix. PMID

Energy Absorption Capacity in Natural Fiber Reinforcement Composites Structures.

PubMed

López-Alba, Elías; Schmeer, Sebastian; Díaz, Francisco

2018-03-13

The study of natural fiber reinforcement composite structures has focused the attention of the automobile industry due to the new regulation in relation to the recyclability and the reusability of the materials preserving and/or improving the mechanical characteristics. The influence of different parameters on the material behavior of natural fiber reinforced plastic structures has been investigated, showing the potential for transport application in energy absorbing structures. Two different woven fabrics (twill and hopsack) made of flax fibers as well as a non-woven mat made of a mixture of hemp and kenaf fibers were employed as reinforcing materials. These reinforcing textiles were impregnated with both HD-PE (high-density polyethylen) and PLA (polylactic acid) matrix, using a continuous compression molding press. The impregnated semi-finished laminates (so-called organic sheets) were thermoformed in a second step to half-tubes that were assembled through vibration-welding process to cylindric crash absorbers. The specimens were loaded by compression to determine the specific energy absorption capacity. Quasi-static test results were compared to dynamic test data obtained on a catapult arrangement. The differences on the specific energies absorption (SEA) as a function of different parameters, such as the wall thickness, the weave material type, the reinforced textiles, and the matrix used, depending on the velocity rate application were quantified. In the case of quasi-static analysis it is observed a 20% increment in the SEA value when wove Hopsack fabric reinforcement is employed. No velocity rate influence from the material was observed on the SEA evaluation at higher speeds used to perform the experiments. The influence of the weave configuration (Hopsack) seems to be more stable against buckling effects at low loading rates with 10% higher SEA values. An increase of SEA level of up to 72% for PLA matrix was observed when compared with HD-PE matrix.

Study of Structural Morphology of Hemp Fiber from the Micro to the Nanoscale

NASA Astrophysics Data System (ADS)

Wang, Bei; Sain, Mohini; Oksman, Kristiina

2007-03-01

The focus of this work has been to study how high pressure defibrillation and chemical purification affect the hemp fiber morphology from micro to nanoscale. Microscopy techniques, chemical analysis and X-ray diffraction were used to study the structure and properties of the prepared micro and nanofibers. Microscopy studies showed that the used individualization processes lead to a unique morphology of interconnected web-like structure of hemp fibers. The nanofibers are bundles of cellulose fibers of widths ranging between 30 and 100 nm and estimated lengths of several micrometers. The chemical analysis showed that selective chemical treatments increased the α-cellulose content of hemp nanofibers from 75 to 94%. Fourier transform infrared spectroscopy (FTIR) study showed that the pectins were partially removed during the individualization treatments. X-ray analysis showed that the relative crystallinity of the studied fibers increased after each stage of chemical and mechanical treatments. It was also observed that the hemp nanofibers had an increased crystallinity of 71 from 57% of untreated hemp fibers.

Cryo-transmission electron microscopy structure of a gigadalton peptide fiber of de novo design

PubMed Central

Sharp, Thomas H.; Bruning, Marc; Mantell, Judith; Sessions, Richard B.; Thomson, Andrew R.; Zaccai, Nathan R.; Brady, R. Leo; Verkade, Paul; Woolfson, Derek N.

2012-01-01

Nature presents various protein fibers that bridge the nanometer to micrometer regimes. These structures provide inspiration for the de novo design of biomimetic assemblies, both to address difficulties in studying and understanding natural systems, and to provide routes to new biomaterials with potential applications in nanotechnology and medicine. We have designed a self-assembling fiber system, the SAFs, in which two small α-helical peptides are programmed to form a dimeric coiled coil and assemble in a controlled manner. The resulting fibers are tens of nm wide and tens of μm long, and, therefore, comprise millions of peptides to give gigadalton supramolecular structures. Here, we describe the structure of the SAFs determined to approximately 8 Å resolution using cryotransmission electron microscopy. Individual micrographs show clear ultrastructure that allowed direct interpretation of the packing of individual α-helices within the fibers, and the construction of a 3D electron density map. Furthermore, a model was derived using the cryotransmission electron microscopy data and side chains taken from a 2.3 Å X-ray crystal structure of a peptide building block incapable of forming fibers. This was validated using single-particle analysis techniques, and was stable in prolonged molecular-dynamics simulation, confirming its structural viability. The level of self-assembly and self-organization in the SAFs is unprecedented for a designed peptide-based material, particularly for a system of considerably reduced complexity compared with natural proteins. This structural insight is a unique high-resolution description of how α-helical fibrils pack into larger protein fibers, and provides a basis for the design and engineering of future biomaterials. PMID:22847414

Study on structure and morphology (Boehmeria nivea) in the irregular and regular parts of the fiber after biodegumming

NASA Astrophysics Data System (ADS)

Wulandari, A. P.; Septarini, D.; Zainuddin, A.

2017-05-01

Ramie is a natural fiber that is very potential to be developed in Indonesia. Decorticated-fiber which has been known as china grass produce different structures irregular part but shows a long straight section in the middle. This study aims to determine differences in chemical components, morphology and microstructure of two different parties after biodegumming process. China grass has been processed to remove gum using pectinolytic fungus. The microstructure of the treated was further tested by Fourier Transform InfraRed (FTIR), X-Ray Diffraction (XRD), and Scanning Electron Microscope (SEM). The FTIR study indicated that during the biodegumming process, chemical bonding of non-cellulose components most removed by the activity of pectinase from the fungus. XRD analysis reflects an increase in the crystallinity of the fiber after biodegumming. Scanning electron microscopy (SEM) was used to confirm a reduction in the size of the fiber after biodegumming either in the irregular and regular part of the fiber after biodegumming.

Amyloid fibers provide structural integrity to Bacillus subtilis biofilms.

PubMed

Romero, Diego; Aguilar, Claudio; Losick, Richard; Kolter, Roberto

2010-02-02

Bacillus subtilis forms biofilms whose constituent cells are held together by an extracellular matrix. Previous studies have shown that the protein TasA and an exopolysaccharide are the main components of the matrix. Given the importance of TasA in biofilm formation, we characterized the physicochemical properties of this protein. We report that purified TasA forms fibers of variable length and 10-15 nm in width. Biochemical analyses, in combination with the use of specific dyes and microscopic analyses, indicate that TasA forms amyloid fibers. Consistent with this hypothesis, TasA fibers required harsh treatments (e.g., formic acid) to be depolymerized. When added to a culture of a tasA mutant, purified TasA restored wild-type biofilm morphology, indicating that the purified protein retained biological activity. We propose that TasA forms amyloid fibers that bind cells together in the biofilm.

Research, development and application of noncombustible Beta fiber structures. [for Apollo

NASA Technical Reports Server (NTRS)

Dillon, J. J.; Cobb, E. S.

1975-01-01

Beta fiber was selected as the primary material for flexible fibrous structures used in spacecraft and crew systems applications in the Apollo program because it was noncombustible in a 100 percent oxygen atmosphere up to 16.5 psia. It met NASA criteria for outgassing, toxicity, odor, and crew comfort, and possessed sufficient durability to last through the mission. Topics discussed include: study of spacecraft applications; design of Beta fiber textile structures to meet the requirements; selection of surface treatments (finishes, coatings, and printing systems) to impart the required durability and special functional use to the textile structures; development of sewing and fabrication techniques; and testing and evaluation programs, and development of production sources.

Functional characteristics of the rat jaw muscles: daily muscle activity and fiber type composition.

PubMed

Kawai, Nobuhiko; Sano, Ryota; Korfage, Joannes A M; Nakamura, Saika; Tanaka, Eiji; van Wessel, Tim; Langenbach, Geerling E J; Tanne, Kazuo

2009-12-01

Skeletal muscles have a heterogeneous fiber type composition, which reflects their functional demand. The daily muscle use and the percentage of slow-type fibers have been shown to be positively correlated in skeletal muscles of larger animals but for smaller animals there is no information. The examination of this relationship in adult rats was the purpose of this study. We hypothesized a positive relationship between the percentage of fatigue-resistant fibers in each muscle and its total duration of use per day. Fourteen Wistar strain male rats (410-450 g) were used. A radio-telemetric device was implanted to record muscle activity continuously from the superficial masseter, deep masseter, anterior belly of digastric and anterior temporalis muscles. The degree of daily muscle use was quantified by the total duration of muscle activity per day (duty time) exceeding specified levels of the peak activity (2, 5, 20 and 50%). The fiber type composition of the muscles was examined by the myosin heavy chain content of the fibers by means of immunohistochemical staining. At lower activity levels (exceeding 2 and 5% of the peak activity), the duty time of the anterior belly of digastric muscle was significantly (P < 0.01) longer than those of the other muscles. The anterior belly of digastric muscle also contained the highest percentage of slow-type fibers (type I fiber and hybrid fiber co-expressing myosin heavy chain I + IIA) (ca. 11%; P < 0.05). By regression analysis for all four muscles, an inter-muscular comparison showed a positive relationship between the duty time (exceeding 50% of the peak activity) and the percentage of type IIX fibers (P < 0.05), which demonstrate intermediate physiological properties relative to type IIA and IIB fibers. For the jaw muscles of adult male rats, the variations of fiber type composition and muscle use suggest that the muscle containing the largest amounts of slow-type fibers (the anterior belly of digastric muscle) is mainly

Quantitative analysis of animal model lens anatomy: accommodative range is related to fiber structure and organization.

PubMed

Kuszak, J R; Mazurkiewicz, M; Jison, L; Madurski, A; Ngando, A; Zoltoski, R K

2006-01-01

The results of a recent study on accommodation in humans and baboons has revealed that lens fiber structure and organization are key components of the mechanism of accommodation. Dynamic focusing involves the controlled displacement and replacement, or realignment, of cortical fiber-ends at sutures as the mechanism of accommodation at the fiber level. This emended explanation of the mechanism of accommodation raises the following question: as the structure of crystalline lenses are only similar, not identical between species, is accommodative amplitude related to differences in the structure and organization of fibers between species? To address this question, we have quantitatively examined the structure and organization of fibers in a number of the more commonly used animal models (mice, cattle, frogs, rabbits and chickens) for lens research. Lenses (a minimum of 12-18 lenses/species) from mice, cattle, frogs and rabbits were used for this study. Prior to fixation for structural analysis, measurements of the gross shape of the lenses (equatorial diameter, anterior and posterior minor radii [anterior + posterior minor radius = polar axis]) were taken directly through a stereo surgical dissecting microscope equipped with an ocular reticle. Lenses were then prepared for and examined by light (LM), transmission (TEM) and scanning electron microscopy (SEM). Scale computer-assisted drawings (CADs) of lenses and lens fibers were then constructed from quantitative data as described above and from quantitative data contained in micrographs. The differences in fiber structure and organization that effect accommodative range arise early in development and are continued throughout lifelong lens growth. In umbilical suture lenses (avian) secondary fibers develop with almost completely tapered anterior ends (85-90% reduction of their measures of width and thickness at the equator). By comparison, in lenses with line sutures (e.g. frogs and rabbits) secondary fibers develop

Hydrothermally Activated Graphene Fiber Fabrics for Textile Electrodes of Supercapacitors.

PubMed

Li, Zheng; Huang, Tieqi; Gao, Weiwei; Xu, Zhen; Chang, Dan; Zhang, Chunxiao; Gao, Chao

2017-11-28

Carbon textiles are promising electrode materials for wearable energy storage devices owing to their conductive, flexible, and lightweight features. However, there still lacks a perfect choice for high-performance carbon textile electrodes with sufficient electrochemical activity. Graphene fiber fabrics (GFFs) are newly discovered carbon textiles, exhibiting various attractive properties, especially a large variability on the microstructure. Here we report the fabrication of hierarchical GFFs with significantly enlarged specific surface area using a hydrothermal activation strategy. By carefully optimize the activation process, the hydrothermally activated graphene fiber fabrics (HAGFFs) could achieve an areal capacitance of 1060 mF cm -2 in a very thin thickness (150 μm) and the capacitance is easily magnified by overlaying several layers of HAGFFs, even up to a record value of 7398 mF cm -2 . Meanwhile, a good rate capability and a long cycle life are also attained. As compared with other carbon textiles, including the commercial carbon fiber cloths, our HAGFFs present much better capacitive performance. Therefore, the mechanically stable, flexible, conductive, and highly active HAGFFs have provided an option for high-performance textile electrodes.

Damage detection in bridges through fiber optic structural health monitoring

NASA Astrophysics Data System (ADS)

Doornink, J. D.; Phares, B. M.; Wipf, T. J.; Wood, D. L.

2006-10-01

A fiber optic structural health monitoring (SHM) system was developed and deployed by the Iowa State University (ISU) Bridge Engineering Center (BEC) to detect gradual or sudden damage in fracture-critical bridges (FCBs). The SHM system is trained with measured performance data, which are collected by fiber optic strain sensors to identify typical bridge behavior when subjected to ambient traffic loads. Structural responses deviating from the trained behavior are considered to be signs of structural damage or degradation and are identified through analytical procedures similar to control chart analyses used in statistical process control (SPC). The demonstration FCB SHM system was installed on the US Highway 30 bridge near Ames, IA, and utilizes 40 fiber bragg grating (FBG) sensors to continuously monitor the bridge response when subjected to ambient traffic loads. After the data is collected and processed, weekly evaluation reports are developed that summarize the continuous monitoring results. Through use of the evaluation reports, the bridge owner is able to identify and estimate the location and severity of the damage. The information presented herein includes an overview of the SHM components, results from laboratory and field validation testing on the system components, and samples of the reduced and analyzed data.

Composite structural materials. [fiber reinforced composites for aircraft structures

NASA Technical Reports Server (NTRS)

Ansell, G. S.; Loewy, R. G.; Wiberly, S. E.

1981-01-01

Physical properties of fiber reinforced composites; structural concepts and analysis; manufacturing; reliability; and life prediction are subjects of research conducted to determine the long term integrity of composite aircraft structures under conditions pertinent to service use. Progress is reported in (1) characterizing homogeneity in composite materials; (2) developing methods for analyzing composite materials; (3) studying fatigue in composite materials; (4) determining the temperature and moisture effects on the mechanical properties of laminates; (5) numerically analyzing moisture effects; (6) numerically analyzing the micromechanics of composite fracture; (7) constructing the 727 elevator attachment rib; (8) developing the L-1011 engine drag strut (CAPCOMP 2 program); (9) analyzing mechanical joints in composites; (10) developing computer software; and (11) processing science and technology, with emphasis on the sailplane project.

A preliminary investigation of textile fibers in smothering scenarios and alternative legitimate activities.

PubMed

Schnegg, Michael; Turchany, Morgane; Deviterne, Marie; Gueissaz, Line; Hess, Sabine; Massonnet, Geneviève

2017-10-01

Was this group of target fibers transferred during a criminal action? Is it possible that it was transferred during another legitimate activity? Acquiring knowledge about the activity, whether legitimate or criminal, leading to the transfer of a group of fibers is a recurring challenge encountered throughout the evidence interpretation process. Trace evidence such as fibers may assist with generating a reasoning of the activity which produced the trace, but this assumes that one already has a thorough understanding of the transfer phenomenon. How to generate and then use such relevant knowledge? What are the influencing parameters and which ones should (or can) be controlled? The present work focuses on homicides by smothering using a pillow and the transfer of fibers on the face of the victim in such events. A legitimate activity - represented by a night's sleep on a pillow - was also investigated since such legitimate, alternative explanations concerning the presence of fibers could likely be formulated by the suspect. The number and distribution of fibers transferred onto the victim's face in either scenario were investigated and interpreted using a Bayesian approach. Results showed that the shedding capacity of the pillowcase strongly impact the number of fibers recovered. The nature of the action, modus operandi and amount of friction could not be excluded in their influence on the transfer of fibers. Finally, likelihood ratios indicating the number of fibers recovered from the victim's face can provide relevant information by supporting either criminal or legitimate proposition (i.e., smothering or night's sleep scenario). Copyright © 2017 Elsevier B.V. All rights reserved.

In-Depth Analysis of the Structure and Properties of Two Varieties of Natural Luffa Sponge Fibers

PubMed Central

Chen, Yuxia; Su, Na; Zhang, Kaiting; Zhu, Shiliu; Zhao, Lei; Fang, Fei; Ren, Linyan; Guo, Yong

2017-01-01

The advancement in science and technology has led to luffa sponge (LS) being widely used as a natural material in industrial application because of its polyporous structure and light texture. To enhance the utility of LS fibers as the reinforcement of lightweight composite materials, the current study investigates their water absorption, mechanical properties, anatomical characteristics and thermal performance. Hence, moisture regain and tensile properties of LS fiber bundles were measured in accordance with American Society for Testing and Materials (ASTM) standards while their structural characteristics were investigated via microscopic observation. Scanning electron microscopy (SEM) was used to observe the surface morphology and fractured surface of fiber bundles. The test results show that the special structure where the phloem tissues degenerate to cavities had a significant influence on the mechanical properties of LS fiber bundles. Additionally, the transverse sectional area occupied by fibers in a fiber bundle (SF), wall thickness, ratio of wall to lumen of fiber cell, and crystallinity of cellulose had substantial impact on the mechanical properties of LS fiber bundles. Furthermore, the density of fiber bundles of LS ranged within 385.46–468.70 kg/m3, significantly less than that of jute (1360.40 kg/m3) and Arenga engleri (950.20 kg/m3). However, LS fiber bundles demonstrated superior specific modulus than Arenga engleri. PMID:28772838

Effects of high-speed homogenization and high-pressure homogenization on structure of tomato residue fibers.

PubMed

Hua, Xiao; Xu, Shanan; Wang, Mingming; Chen, Ying; Yang, Hui; Yang, Ruijin

2017-10-01

Tomato residue fibers obtained after derosination and deproteinization were processed by high-speed homogenization (HSH) and high-pressure homogenization (HPH), and their effects on fiber structure was investigated, respectively. Characterizations including particle size distribution, SEM, TEM and XRD were performed. HSH could break raw fibers to small particles of around 60μm, while HPH could reshape fibers to build network structure. Microfibrils were released and their nanostructure consisting of elementary fibrils was observed by TEM. XRD patterns indicated both HSH and HPH could hardly alter the nanostructure of the fibers. Physicochemical properties including expansibility, WHC and OHC were determined. Both HSH and HPH could increase the soluble fiber content by about 8%, but HSH-HPH combined processing did not show better result. Acid (4mol/L HCl) was used in replacement of water medium and the acidic degradation of fibers could be promoted by high speed shearing or high pressure processing. Copyright © 2017 Elsevier Ltd. All rights reserved.

Methods for Producing High-Performance Silicon Carbide Fibers, Architectural Preforms, and High-Temperature Composite Structures

NASA Technical Reports Server (NTRS)

Yun, Hee-Mann (Inventor); DiCarlo, James A. (Inventor)

2014-01-01

Methods are disclosed for producing architectural preforms and high-temperature composite structures containing high-strength ceramic fibers with reduced preforming stresses within each fiber, with an in-situ grown coating on each fiber surface, with reduced boron within the bulk of each fiber, and with improved tensile creep and rupture resistance properties tier each fiber. The methods include the steps of preparing an original sample of a preform formed from a pre-selected high-strength silicon carbide ceramic fiber type, placing the original sample in a processing furnace under a pre-selected preforming stress state and thermally treating the sample in the processing furnace at a pre-selected processing temperature and hold time in a processing gas having a pre-selected composition, pressure, and flow rate. For the high-temperature composite structures, the method includes additional steps of depositing a thin interphase coating on the surface of each fiber and forming a ceramic or carbon-based matrix within the sample.

Structural Laminate Aluminum-Glass-Fiber Materials 1441-Sial

NASA Astrophysics Data System (ADS)

Shestov, V. V.; Antipov, V. V.; Senatorova, O. G.; Sidel'nikov, V. V.

2014-01-01

The structure, composition and set of properties of specimens and components, and some parameters of the process of production of a promising FML class of metallic polymers based on sheets of high-modulus ( E 79 GPa) alloy 1441 with reduced density ( d 2.6 g/cm3) and an optimized glued prepreg reinforced with fibers of high-strength high-modulus VMPglass are described. Results of fire and fatigue tests of a promising 1441-SIAL structural laminate are presented.

High-power fiber optic cable with integrated active sensors for live process monitoring

NASA Astrophysics Data System (ADS)

Blomster, Ola; Blomqvist, Mats; Bergstrand, Hans; Pålsson, Magnus

2012-03-01

In industrial applications using high-brilliance lasers at power levels up to and exceeding 20 kW and similarly direct diode lasers of 10 kW, there is an increasing demand to continuously monitor component status even in passive components such as fiber-optic cables. With fiber-optic cables designed according to the European Automotive Industry fiber standard interface there is room for integrating active sensors inside the connectors. In this paper we present the integrated active sensors in the new Optoskand QD fiber-optic cable designed to handle extreme levels of power losses, and how these sensors can be employed in industrial manufacturing. The sensors include photo diodes for detection of scattered light inside the fiber connector, absolute temperature of the fiber connector, difference in temperature of incoming and outgoing cooling water, and humidity measurement inside the fiber connector. All these sensors are connected to the fiber interlock system, where interlock break enable functions can be activated when measured signals are higher than threshold levels. It is a very fast interlock break system as the control of the signals is integrated in the electronics inside the fiber connector. Also, since all signals can be logged it is possible to evaluate what happened inside the connector before the interlock break instance. The communication to the fiber-optic connectors is via a CAN interface. Thus it is straightforward to develop the existing laser host control to also control the CAN-messages from the QD sensors.

Reflectance Speckle of Retinal Nerve Fiber Layer Reveals Axonal Activity

PubMed Central

Huang, Xiang-Run; Knighton, Robert W.; Zhou, Ye; Zhao, Xiao-Peng

2013-01-01

Purpose. This study investigated the retinal nerve fiber layer (RNFL) reflectance speckle and tested the hypothesis that temporal change of RNFL speckle reveals axonal dynamic activity. Methods. RNFL reflectance speckle of isolated rat retinas was studied with monochromatic illumination. A series of reflectance images was collected every 5 seconds for approximately 15 minutes. Correlation coefficients (CC) of selected areas between a reference and subsequent images were calculated and plotted as a function of the time intervals between images. An exponential function fit to the time course was used to evaluate temporal change of speckle pattern. To relate temporal change of speckle to axonal activity, in vitro living retina perfused at a normal (34°C) and a lower (24°C) temperature, paraformaldehyde-fixed retina, and retina treated with microtubule depolymerization were used. Results. RNFL reflectance was not uniform; rather nerve fiber bundles had a speckled texture that changed with time. In normally perfused retina, the time constant of the CC change was 0.56 ± 0.26 minutes. In retinas treated with lower temperature and microtubule depolymerization, the time constants increased by two to four times, indicating that the speckle pattern changed more slowly. The speckled texture in fixed retina was stationary. Conclusions. Fixation stops axonal activity; treatments with either lower temperature or microtubule depolymerization are known to decrease axonal transport. The results obtained in this study suggest that temporal change of RNFL speckle reveals structural change due to axonal activity. Assessment of RNFL reflectance speckle may offer a new means of evaluating axonal function. PMID:23532525

Determination of bacterial activity by use of an evanescent-wave fiber-optic sensor

NASA Astrophysics Data System (ADS)

John, M. Shelly; Kishen, Anil; Sing, Lim Chu; Asundi, Anand

2002-12-01

A novel technique based on fiber-optic evanescent-wave spectroscopy is proposed for the detection of bacterial activity in human saliva. The sensor determines the specific concentration of Streptococcus mutans in saliva, which is a major causative factor in dental caries. In this design, one prepares the fiber-optic bacterial sensor by replacing a portion of the cladding region of a multimode fiber with a dye-encapsulated xerogel, using the solgel technique. The exponential decay of the evanescent wave at the core-cladding interface of a multimode fiber is utilized for the determination of bacterial activity in saliva. The acidogenic profile of Streptococcus mutans is estimated by use of evanescent-wave absorption spectra at various levels of bacterial activity.

Effect of сopper сoating on fibers made of aluminum alloy, titanium, and FeCrAl alloy on surface morphology and activity in CO oxidation

NASA Astrophysics Data System (ADS)

Lukiyanchuk, I. V.; Rudnev, V. S.; Serov, M. M.; Krit, B. L.; Lukiyanchuk, G. D.; Nedozorov, P. M.

2018-04-01

The catalytic activity of both copper fibers and copper-coated fibers of a diameter of 50-100 μm made of aluminum alloy, technical grade titanium, and FeCrAl alloy in CO oxidation has been estimated. Metal fibers have been fabricated by the method of pendant drop melt extraction (PDME). The fibers copper plating was carried out by chemical and electrochemical methods. The composition and structure of samples and coatings before and after catalytic tests have been characterized by the methods of scanning electron microscopy, energy-dispersive analysis, and X-ray fluorescence analysis. It has been shown that the catalytic activity of copper-coated fibers made of FeCrAl alloy in the reaction of CO oxidation is not inferior to that of copper fibers.

Process and Structural Health Monitoring of Composite Structures with Embedded Fiber Optic Sensors and Piezoelectric Transducers

NASA Astrophysics Data System (ADS)

Keulen, Casey James

Advanced composite materials are becoming increasingly more valuable in a plethora of engineering applications due to properties such as tailorability, low specific strength and stiffness and resistance to fatigue and corrosion. Compared to more traditional metallic and ceramic materials, advanced composites such as carbon, aramid or glass reinforced plastic are relatively new and still require research to optimize their capabilities. Three areas that composites stand to benefit from improvement are processing, damage detection and life prediction. Fiber optic sensors and piezoelectric transducers show great potential for advances in these areas. This dissertation presents the research performed on improving the efficiency of advanced composite materials through the use of embedded fiber optic sensors and surface mounted piezoelectric transducers. Embedded fiber optic sensors are used to detect the presence of resin during the injection stage of resin transfer molding, monitor the degree of cure and predict the remaining useful life while in service. A sophisticated resin transfer molding apparatus was developed with the ability of embedding fiber optics into the composite and a glass viewing window so that resin flow sensors could be verified visually. A novel technique for embedding optical fiber into both 2- and 3-D structures was developed. A theoretical model to predict the remaining useful life was developed and a systematic test program was conducted to verify this model. A network of piezoelectric transducers was bonded to a composite panel in order to develop a structural health monitoring algorithm capable of detecting and locating damage in a composite structure. A network configuration was introduced that allows for a modular expansion of the system to accommodate larger structures and an algorithm based on damage progression history was developed to implement the network. The details and results of this research are contained in four manuscripts that

Carbon fiber polymer-matrix structural composites tailored for multifunctionality by filler incorporation

NASA Astrophysics Data System (ADS)

Han, Seungjin

This dissertation provides multifunctional carbon fiber polymer-matrix structural composites for vibration damping, thermal conduction and thermoelectricity. Specifically, (i) it has strengthened and stiffened carbon fiber polymer-matrix structural composites by the incorporation of halloysite nanotubes, carbon nanotubes and silicon carbide whiskers, (ii) it has improved mechanical energy dissipation using carbon fiber polymer-matrix structural composites with filler incorporation, (iii) it has increased the through-thickness thermal conductivity of carbon fiber polymer-matrix composite by curing pressure increase and filler incorporation, and (iv) it has enhanced the thermoelectric behavior of carbon fiber polymer-matrix structural composites. Low-cost natural halloysite nanotubes (0.1 microm diameter) were effective for strengthening and stiffening continuous fiber polymer-matrix composites, as shown for crossply carbon fiber (5 microm diameter, ˜59 vol.%) epoxy-matrix composites under flexure, giving 17% increase in strength, 11% increase in modulus and 21% decrease in ductility. They were less effective than expensive multiwalled carbon nanotubes (0.02 microm diameter), which gave 25% increase in strength, 11% increase in modulus and 14% decrease in ductility. However, they were more effective than expensive silicon carbide whiskers (1 microm diameter), which gave 15% increase in strength, 9% increase in modulus and 20% decrease in ductility. Each filler, at ˜2 vol.%, was incorporated in the composite at every interlaminar interface by fiber prepreg surface modification. The flexural strength increase due to halloysite nanotubes incorporation related to the interlaminar shear strength increase. The measured values of the composite modulus agreed roughly with the calculated values based on the Rule of Mixtures. Continuous carbon fiber composites with enhanced vibration damping under flexure are provided by incorporation of fillers between the laminae

Single-mode annular chirally-coupled core fibers for fiber lasers

NASA Astrophysics Data System (ADS)

Zhang, Haitao; Hao, He; He, Linlu; Gong, Mali

2018-03-01

Chirally-coupled core (CCC) fiber can transmit single fundamental mode and effectively suppresses higher-order mode (HOM) propagation, thus improve the beam quality. However, the manufacture of CCC fiber is complicated due to its small side core. To decrease the manufacture difficulty in China, a novel fiber structure is presented, defined as annular chirally-coupled core (ACCC) fiber, replacing the small side core by a larger side annulus. In this paper, we designed the fiber parameters of this new structure, and demonstrated that the new structure has a similar property of single mode with traditional CCC fiber. Helical coordinate system was introduced into the finite element method (FEM) to analyze the mode field in the fiber, and the beam propagation method (BPM) was employed to analyze the influence of the fiber parameters on the mode loss. Based on the result above, the fiber structure was optimized for efficient single-mode transmission, in which the core diameter is 35 μm with beam quality M2 value of 1.04 and an optical to optical conversion efficiency of 84%. In this fiber, fundamental mode propagates in an acceptable loss, while the HOMs decay rapidly.

Cytoplasm-to-myonucleus ratios and succinate dehydrogenase activities in adult rat slow and fast muscle fibers

NASA Technical Reports Server (NTRS)

Tseng, B. S.; Kasper, C. E.; Edgerton, V. R.

1994-01-01

The relationship between myonuclear number, cellular size, succinate dehydrogenase activity, and myosin type was examined in single fiber segments (n = 54; 9 +/- 3 mm long) mechanically dissected from soleus and plantaris muscles of adult rats. One end of each fiber segment was stained for DNA before quantitative photometric analysis of succinate dehydrogenase activity; the other end was double immunolabeled with fast and slow myosin heavy chain monoclonal antibodies. Mean +/- S.D. cytoplasmic volume/myonucleus ratio was higher in fast and slow plantaris fibers (112 +/- 69 vs. 34 +/- 21 x 10(3) microns3) than fast and slow soleus fibers (40 +/- 20 vs. 30 +/- 14 x 10(3) microns3), respectively. Slow fibers always had small volumes/myonucleus, regardless of fiber diameter, succinate dehydrogenase activity, or muscle of origin. In contrast, smaller diameter (< 70 microns) fast soleus and plantaris fibers with high succinate dehydrogenase activity appeared to have low volumes/myonucleus while larger diameter (> 70 microns) fast fibers with low succinate dehydrogenase activity always had large volume/myonucleus. Slow soleus fibers had significantly greater numbers of myonuclei/mm than did either fast soleus or fast plantaris fibers (116 +/- 51 vs. 55 +/- 22 and 44 +/- 23), respectively. These data suggest that the myonuclear domain is more limited in slow than fast fibers and in the fibers with a high, compared to a low, oxidative metabolic capability.

Designing for fiber composite structural durability in hygrothermomechanical environment

NASA Technical Reports Server (NTRS)

Chamis, C. C.

1985-01-01

A methodology is described which can be used to design/analyze fiber composite structures subjected to complex hygrothermomechanical environments. This methodology includes composite mechanics and advanced structural analysis methods (finite element). Select examples are described to illustrate the application of the available methodology. The examples include: (1) composite progressive fracture; (2) composite design for high cycle fatigue combined with hot-wet conditions; and (3) general laminate design.

Structural Health Monitoring in Composite Structures by Fiber-Optic Sensors.

PubMed

Güemes, Alfredo; Fernández-López, Antonio; F Díaz-Maroto, Patricia; Lozano, Angel; Sierra-Perez, Julian

2018-04-04

Fiber-optic sensors cannot measure damage; to get information about damage from strain measurements, additional strategies are needed, and several alternatives are available in the existing literature. This paper discusses two independent procedures. The first is based on detecting new strains appearing around a damage spot. The structure does not need to be under loads, the technique is very robust, and damage detectability is high, but it requires sensors to be located very close to the damage, so it is a local technique. The second approach offers wider coverage of the structure; it is based on identifying the changes caused by damage on the strain field in the whole structure for similar external loads. Damage location does not need to be known a priori, and detectability is dependent upon the sensor's network density, the damage size, and the external loads. Examples of application to real structures are given.

Reconstruction and Visualization of Fiber and Laminar Structure inthe Normal Human Heart from Ex Vivo DTMRI Data

DOE Office of Scientific and Technical Information (OSTI.GOV)

Rohmer, Damien; Sitek, Arkadiusz; Gullberg, Grant T.

2006-12-18

Background - The human heart is composed of a helicalnetwork of muscle fibers. These fibers are organized to form sheets thatare separated by cleavage surfaces. This complex structure of fibers andsheets is responsible for the orthotropic mechanical properties ofcardiac muscle. The understanding of the configuration of the 3D fiberand sheet structure is important for modeling the mechanical andelectrical properties of the heart and changes in this configuration maybe of significant importance to understand the remodeling aftermyocardial infarction.Methods - Anisotropic least square filteringfollowed by fiber and sheet tracking techniques were applied to DiffusionTensor Magnetic Resonance Imaging (DTMRI) data of the excisedmore » humanheart. The fiber configuration was visualized by using thin tubes toincrease 3-dimensional visual perception of the complex structure. Thesheet structures were reconstructed from the DTMRI data, obtainingsurfaces that span the wall from the endo- to the epicardium. Allvisualizations were performed using the high-quality ray-tracing softwarePOV-Ray. Results - The fibers are shown to lie in sheets that haveconcave or convex transmural structure which correspond to histologicalstudies published in the literature. The fiber angles varied depending onthe position between the epi- and endocardium. The sheets had a complexstructure that depended on the location within the myocardium. In theapex region the sheets had more curvature. Conclusions - A high-qualityvisualization algorithm applied to demonstrated high quality DTMRI datais able to elicit the comprehension of the complex 3 dimensionalstructure of the fibers and sheets in the heart.« less

Dual-point reflective refractometer based on parallel no-core fiber/FBG structure

NASA Astrophysics Data System (ADS)

Guo, Cuijuan; Niu, Panpan; Wang, Juan; Zhao, Junfa; Zhang, Cheng

2018-01-01

A novel dual-point reflective fiber-optic refractometer based on multimode interference (MMI) effect and fiber Bragg grating (FBG) reflection is proposed and experimentally demonstrated, which adopts parallel structure. Each point of the refractometer consists of a single mode-no core-single mode fiber (SNS) structure cascaded with a FBG. Assisted by the reflection of FBG, refractive index (RI) measurement can be achieved by monitoring the peak power variation of the reflected FBG spectrum. By selecting different length of the no core fiber and center wavelength of the FBG, independent dual-point refractometer is easily realized. Experiment results show that the refractometer has a nonlinear relationship between the surrounding refractive index (SRI) and the peak power of the reflected FBG spectrum in the RI range of 1.3330-1.4086. Linear relationship can be approximately obtained by dividing the measuring range into 1.3330-1.3611 and 1.3764-1.4086. In the RI range of 1.3764-1.4086, the two sensing points have higher RI sensitivities of 319.34 dB/RIU and 211.84 dB/RIU, respectively.

Exploring the atomic structure and conformational flexibility of a 320 Å long engineered viral fiber using X-ray crystallography

DOE Office of Scientific and Technical Information (OSTI.GOV)

Bhardwaj, Anshul; Casjens, Sherwood R.; Cingolani, Gino, E-mail: gino.cingolani@jefferson.edu

2014-02-01

This study presents the crystal structure of a ∼320 Å long protein fiber generated by in-frame extension of its repeated helical coiled-coil core. Protein fibers are widespread in nature, but only a limited number of high-resolution structures have been determined experimentally. Unlike globular proteins, fibers are usually recalcitrant to form three-dimensional crystals, preventing single-crystal X-ray diffraction analysis. In the absence of three-dimensional crystals, X-ray fiber diffraction is a powerful tool to determine the internal symmetry of a fiber, but it rarely yields atomic resolution structural information on complex protein fibers. An 85-residue-long minimal coiled-coil repeat unit (MiCRU) was previously identifiedmore » in the trimeric helical core of tail needle gp26, a fibrous protein emanating from the tail apparatus of the bacteriophage P22 virion. Here, evidence is provided that an MiCRU can be inserted in frame inside the gp26 helical core to generate a rationally extended fiber (gp26-2M) which, like gp26, retains a trimeric quaternary structure in solution. The 2.7 Å resolution crystal structure of this engineered fiber, which measures ∼320 Å in length and is only 20–35 Å wide, was determined. This structure, the longest for a trimeric protein fiber to be determined to such a high resolution, reveals the architecture of 22 consecutive trimerization heptads and provides a framework to decipher the structural determinants for protein fiber assembly, stability and flexibility.« less

Structural considerations in design of lightweight glass-fiber composite pressure vessels

NASA Technical Reports Server (NTRS)

Faddoul, J. R.

1973-01-01

The development of structurally efficient, metal-lined, glass-fiber composite pressure vessels. Both the current state-of-the-art and current problems are discussed along with fracture mechanics considerations for the metal liner. The design concepts used for metal-lined, glass-fiber, composite pressure vessels are described and the structural characteristics of the composite designs are compared with each other and with homogeneous metal pressure vessels. Specific design techniques and available design data are identified. Results of a current program to evaluate flaw growth and fracture characteristics of the metal liners are reviewed and the impact of these results on composite pressure vessel designs is discussed.

Performance assessment of geotechnical structural elements using distributed fiber optic sensing

NASA Astrophysics Data System (ADS)

Monsberger, Christoph; Woschitz, Helmut; Lienhart, Werner; Račanský, Václav; Hayden, Martin

2017-04-01

Geotechnical structural elements are used to underpin heavy structures or to stabilize slopes and embankments. The bearing capacity of these components is usually verified by geotechnical load tests. It is state of the art to measure the resulting deformations with electronic sensors at the surface and therefore, the load distribution along the objects cannot be determined. This paper reports about distributed strain measurements with an optical backscatter reflectometer along geotechnical elements. In addition to the installation of the optical fiber in harsh field conditions, results of investigations of the fiber optic system in the laboratory and the most significant results of the field trials are presented.

Fiber Optic Sensor Components and Systems for Smart Materials and Structures

NASA Technical Reports Server (NTRS)

Lyons, R.

1999-01-01

The general objective of the funded research effort has been the development of discrete and distributed fiber sensors and fiber optic centered opto-electronic networks for the intelligent monitoring of phenomena in various aerospace structures related to NASA Marshall specific applications. In particular, we have proposed and have been developing technologies that we believe to be readily transferrable and which involve new fabrication techniques. The associated sensors developed can be incorporated into the matrix or on the surfaces of structures for the purpose of sensing stress, strain, temperature-both low and high, pressure field variations, phase changes, and the presence of various chemical constituents.

Using different fibers to replace fat in sponge cakes: In vitro starch digestion and physico-structural studies.

PubMed

Diez-Sánchez, Elena; Llorca, Empar; Quiles, Amparo; Hernando, Isabel

2018-01-01

This study assessed the effect of substituting 30% of fat by soluble, insoluble fiber, or a mix of both fibers in sponge cake quality, structure, acceptability, and starch digestibility. The apparent viscosity of the different formulations was measured and micro-baking was simulated. Texture profile tests were carried out and the crumb structure was examined. In vitro digestion was performed to study the digestibility of starch and a sensory test was carried out to know consumer acceptance. The soluble fiber (maltodextrin) affected the structure and quality of the cakes less than the insoluble fiber (potato fiber) and the use of soluble fiber in the formulation resulted in lower glucose release under in vitro conditions. Moreover, the consumer did not find differences among the control cake and the cakes prepared with soluble fiber. Considering the results as a whole, soluble fiber may be used for partial replacement of fat in sponge cake formulations and may constitute an appropriate strategy for obtaining healthy sponge cakes.

Detecting eavesdropping activity in fiber optic networks

NASA Astrophysics Data System (ADS)

MacDonald, Gregory G.

The secure transmission of data is critical to governments, military organizations, financial institutions, health care providers and other enterprises. The primary method of securing in-transit data is though data encryption. A number of encryption methods exist but the fundamental approach is to assume an eavesdropper has access to the encrypted message but does not have the computing capability to decrypt the message in a timely fashion. Essentially, the strength of security depends on the complexity of the encryption method and the resources available to the eavesdropper. The development of future technologies, most notably quantum computers and quantum computing, is often cited as a direct threat to traditional encryption schemes. It seems reasonable that additional effort should be placed on prohibiting the eavesdropper from coming into possession of the encrypted message in the first place. One strategy for denying possession of the encrypted message is to secure the physical layer of the communications path. Because the majority of transmitted information is over fiber-optic networks, it seems appropriate to consider ways of enhancing the integrity and security of the fiber-based physical layer. The purpose of this research is to investigate the properties of light, as they are manifested in single mode fiber, as a means of insuring the integrity and security of the physical layer of a fiber-optic based communication link. Specifically, the approach focuses on the behavior of polarization in single mode fiber, as it is shown to be especially sensitive to fiber geometry. Fiber geometry is necessarily modified during the placement of optical taps. The problem of detecting activity associated with the placement of an optical tap is herein approached as a supervised machine learning anomaly identification task. The inputs include raw polarization measurements along with additional features derived from various visualizations of the raw data (the inputs are

Method for rapid fabrication of fiber preforms and structural composite materials

DOEpatents

Klett, James W.; Burchell, Timothy D.; Bailey, Jeffrey L.

1998-01-01

A densified carbon matrix carbon fiber composite preform is made by vacuum molding an aqueous slurry of carbon fibers and carbonizable organic powder to form a molded part. The molded part is dried in an oven at 50.degree. C. for 14 hours and hot pressed at 2000 psi at 400.degree. C. for 3 hours. The hot pressed part is carbonized at 650.degree. C. under nitrogen for 3 hours and graphitized at 2400.degree. C. to form a graphitic structure in the matrix of the densified carbon matrix carbon fiber composite preform. The densified preform has a density greater than 1.1 g/cc.

Method for rapid fabrication of fiber preforms and structural composite materials

DOEpatents

Klett, J.W.; Burchell, T.D.; Bailey, J.L.

1998-04-28

A densified carbon matrix carbon fiber composite preform is made by vacuum molding an aqueous slurry of carbon fibers and carbonizable organic powder to form a molded part. The molded part is dried in an oven at 50 C for 14 hours and hot pressed at 2,000 psi at 400 C for 3 hours. The hot pressed part is carbonized at 650 C under nitrogen for 3 hours and graphitized at 2,400 C to form a graphitic structure in the matrix of the densified carbon matrix carbon fiber composite preform. The densified preform has a density greater than 1.1 g/cc. 12 figs.

Method for rapid fabrication of fiber preforms and structural composite materials

DOEpatents

Klett, J.W.; Burchell, T.D.; Bailey, J.L.

1999-02-16

A densified carbon matrix carbon fiber composite preform is made by vacuum molding an aqueous slurry of carbon fibers and carbonizable organic powder to form a molded part. The molded part is dried in an oven at 50 C for 14 hours and hot pressed at 2000 psi at 400 C for 3 hours. The hot pressed part is carbonized at 650 C under nitrogen for 3 hours and graphitized at 2400 C to form a graphitic structure in the matrix of the densified carbon matrix carbon fiber composite preform. The densified preform has a density greater than 1.1 g/cc. 12 figs.

Method for rapid fabrication of fiber preforms and structural composite materials

DOEpatents

Klett, James W.; Burchell, Timothy D.; Bailey, Jeffrey L.

1999-01-01

A densified carbon matrix carbon fiber composite preform is made by vacuum molding an aqueous slurry of carbon fibers and carbonizable organic powder to form a molded part. The molded part is dried in an oven at 50.degree. C. for 14 hours and hot pressed at 2000 psi at 400.degree. C. for 3 hours. The hot pressed part is carbonized at 650.degree. C. under nitrogen for 3 hours and graphite at 2400.degree. C. to form a graphitic structure in the matrix of the densified carbon matrix carbon fiber composite preform. The densified preform has a density greater than 1.1 g/cc.

Surface characterization of carbon fiber polymer composites and aluminum alloys after laser interference structuring

DOE PAGES

Sabau, Adrian S.; Greer, Clayton M.; Chen, Jian; ...

2016-05-03

Here, the increasing use of Carbon Fiber-reinforced Polymer matrix Composites (CFPC) and aluminum alloys as lightweight materials in the automotive and aerospace industries demands enhanced surface preparation and control of surface morphology prior to joining. In this study, surfaces of both composite and aluminum were prepared for joining using an Nd:YAG laser in a two-beam interference setup, enabling the (a) structuring of the AL 5182 surface, (b) removal of the resin layer on top of carbon fibers, and (c) structuring of the carbon fibers. CFPC specimens of T700S carbon fiber, Prepreg - T8 3 epoxy, 5 ply thick, 0/90o plaquesmore » were used. The effect of laser fluence, scanning speed, and number of shots-per-spot was investigated on the removal rate of the resin without an excessive damage of the fibers. Optical micrographs, 3D imaging, and scanning electron microscope (SEM) imaging were used to study the effect of the laser processing on surface morphology.« less

Fabrication of bundle-structured tube-leaky optical fibers for infrared thermal imaging

NASA Astrophysics Data System (ADS)

Kobayashi, T.; Katagiri, T.; Matsuura, Y.

2017-02-01

Bundled glass tubular fibers were fabricated by glass drawing technique for endoscopic infrared-thermal imaging. The bundle fibers were made of borosilicate glass and have a structure like a photonic crystal fiber having multiple hollow cores. Fabricated fibers have a length of 90 cm and each pixel sizes are less than 80 μm. By setting the thickness of glass wall to a quarter-wavelength optical thickness, light is confined in the air core as a leaky mode with a low loss owing to the interference effect of the thin glass wall and this type of hollow-core fibers is known as tube leaky fibers. The transmission losses of bundled fibers were firstly measured and it was found that bundled tube-leaky fibers have reasonably low transmission losses in spite of the small pixel size. Then thermal images were delivered by the bundled fibers combining with an InSb infrared camera. Considering applications with rigid endoscopes, an imaging system composed of a 30-cm long fiber bundle and a half-ball lens with a diameter of 2 mm was fabricated. By using this imaging system, a metal wire with a thickness of 200 μm was successfully observed and another test showed that the minimum detected temperature was 32.0 °C and the temperature resolution of the system was around 0.7 °C.

Analysis of flavonoids and the flavonoid structural genes in brown fiber of upland cotton.

PubMed

Feng, Hongjie; Tian, Xinhui; Liu, Yongchang; Li, Yanjun; Zhang, Xinyu; Jones, Brian Joseph; Sun, Yuqiang; Sun, Jie

2013-01-01

As a result of changing consumer preferences, cotton (Gossypium Hirsutum L.) from varieties with naturally colored fibers is becoming increasingly sought after in the textile industry. The molecular mechanisms leading to colored fiber development are still largely unknown, although it is expected that the color is derived from flavanoids. Firstly, four key genes of the flavonoid biosynthetic pathway in cotton (GhC4H, GhCHS, GhF3'H, and GhF3'5'H) were cloned and studied their expression profiles during the development of brown- and white cotton fibers by QRT-PCR. And then, the concentrations of four components of the flavonoid biosynthetic pathway, naringenin, quercetin, kaempferol and myricetin in brown- and white fibers were analyzed at different developmental stages by HPLC. The predicted proteins of the four flavonoid structural genes corresponding to these genes exhibit strong sequence similarity to their counterparts in various plant species. Transcript levels for all four genes were considerably higher in developing brown fibers than in white fibers from a near isogenic line (NIL). The contents of four flavonoids (naringenin, quercetin, kaempferol and myricetin) were significantly higher in brown than in white fibers and corresponding to the biosynthetic gene expression levels. Flavonoid structural gene expression and flavonoid metabolism are important in the development of pigmentation in brown cotton fibers.

Analysis of Flavonoids and the Flavonoid Structural Genes in Brown Fiber of Upland Cotton

PubMed Central

Liu, Yongchang; Li, Yanjun; Zhang, Xinyu; Jones, Brian Joseph; Sun, Yuqiang; Sun, Jie

2013-01-01

Backgroud As a result of changing consumer preferences, cotton (Gossypium Hirsutum L.) from varieties with naturally colored fibers is becoming increasingly sought after in the textile industry. The molecular mechanisms leading to colored fiber development are still largely unknown, although it is expected that the color is derived from flavanoids. Experimental Design Firstly, four key genes of the flavonoid biosynthetic pathway in cotton (GhC4H, GhCHS, GhF3′H, and GhF3′5′H) were cloned and studied their expression profiles during the development of brown- and white cotton fibers by QRT-PCR. And then, the concentrations of four components of the flavonoid biosynthetic pathway, naringenin, quercetin, kaempferol and myricetin in brown- and white fibers were analyzed at different developmental stages by HPLC. Result The predicted proteins of the four flavonoid structural genes corresponding to these genes exhibit strong sequence similarity to their counterparts in various plant species. Transcript levels for all four genes were considerably higher in developing brown fibers than in white fibers from a near isogenic line (NIL). The contents of four flavonoids (naringenin, quercetin, kaempferol and myricetin) were significantly higher in brown than in white fibers and corresponding to the biosynthetic gene expression levels. Conclusions Flavonoid structural gene expression and flavonoid metabolism are important in the development of pigmentation in brown cotton fibers. PMID:23527031

A study on the crushing behavior of basalt fiber reinforced composite structures

NASA Astrophysics Data System (ADS)

Pandian, A.; Veerasimman, A. P.; Vairavan, M.; Francisco, C.; Sultan, M. T. H.

2016-10-01

The crushing behavior and energy absorption capacity of basalt fiber reinforced hollow square structure composites are studied under axial compression. Using the hand layup technique, basalt fiber reinforced composites were fabricated using general purpose (GP) polyester resin with the help of wooden square shaped mould of varying height (100 mm, 150 mm and 200 mm). For comparison, similar specimens of glass fiber reinforced polymer composites were also fabricated and tested. Axial compression load is applied over the top end of the specimen with cross head speed as 2 mm/min using Universal Testing Machine (UTM). From the experimental results, the load-deformation characteristics of both glass fiber and basalt fiber composites were investigated. Crashworthiness and mode of collapse for the composites were determined from load-deformation curve, and they were then compared to each other in terms of their crushing behaviors.

Dynamic Sensing Performance of a Point-Wise Fiber Bragg Grating Displacement Measurement System Integrated in an Active Structural Control System

PubMed Central

Chuang, Kuo-Chih; Liao, Heng-Tseng; Ma, Chien-Ching

2011-01-01

In this work, a fiber Bragg grating (FBG) sensing system which can measure the transient response of out-of-plane point-wise displacement responses is set up on a smart cantilever beam and the feasibility of its use as a feedback sensor in an active structural control system is studied experimentally. An FBG filter is employed in the proposed fiber sensing system to dynamically demodulate the responses obtained by the FBG displacement sensor with high sensitivity. For comparison, a laser Doppler vibrometer (LDV) is utilized simultaneously to verify displacement detection ability of the FBG sensing system. An optical full-field measurement technique called amplitude-fluctuation electronic speckle pattern interferometry (AF-ESPI) is used to provide full-field vibration mode shapes and resonant frequencies. To verify the dynamic demodulation performance of the FBG filter, a traditional FBG strain sensor calibrated with a strain gauge is first employed to measure the dynamic strain of impact-induced vibrations. Then, system identification of the smart cantilever beam is performed by FBG strain and displacement sensors. Finally, by employing a velocity feedback control algorithm, the feasibility of integrating the proposed FBG displacement sensing system in a collocated feedback system is investigated and excellent dynamic feedback performance is demonstrated. In conclusion, our experiments show that the FBG sensor is capable of performing dynamic displacement feedback and/or strain measurements with high sensitivity and resolution. PMID:22247683

Propagation characteristics of optical fiber structures with arbitrary shape and index variation

NASA Technical Reports Server (NTRS)

Manshadi, F.

1990-01-01

The application of the scalar wave-fast Fourier transform (SW-FFT) technique to the computation of the propagation characteristics of some complex optical fiber structures is presented. The SW-FFT technique is based on the numerical solution of the scalar wave equation by a forward-marching fast Fourier transform method. This solution yields the spatial configuration of the fields as well as its modal characteristics in and around the guiding structure. The following are treated by the SW-FFT method: analysis of coupled optical fibers and computation of their odd and even modes and coupling length; the solution of tapered optical waveguides (transitions) and the study of the effect of the slope of the taper on mode conversion; and the analysis of branching optical fibers and demonstration of their mode-filtering and/or power-dividing properties.

Near-field optical technique applied for investigation of the characteristics of polymer fiber and waveguide structures.

PubMed

Ming, Hai; Tang, Lin; Sun, Xiaohong; Zhang, Jiangying; Wang, Pei; Lu, Yonghua; Bai, Ming; Guo, Yang; Xie, Aifang; Zhang, Zebo

2004-01-01

This article summarizes the near-field optical technique applied for investigating the characteristics of polymer fiber and waveguide structures. The near-field optical technique is used to analyze multimode interference structures of fiber. The localized fluctuation of the transmission caused by fractal cluster is carried out in Nd3+- and Eu3+-doped polymer fiber and film by means of a scanning near-field optical microscopy. The near-field optical spectrum of Nd3+-doped polymer fiber is investigated. The topography and near-field intensity images of Azo-polymer liquid crystal film for waveguide are obtained simultaneously.

Effect of dietary fiber on the activity of intestinal and fecal beta-glucuronidase activity during 1,2-dimethylhydrazine induced colon carcinogenesis.

PubMed

Manoj, G; Thampi, B S; Leelamma, S; Menon, P V

2001-01-01

The effects of fiber isolated from black gram (Phaseolus mungo) and coconut (Cocos nucifera) kernel on the metabolic activity of intestinal and fecal beta glucuronidase activity during 1,2-dimethylhydrazine induced colon carcinogenesis were studied. The results indicated that the inclusion of fiber from black gram and coconut kernel generally supported lower specific activities and less fecal output of beta-glucuronidase than did the fiber free diet. This study suggests that the fibers isolated from coconut or black gram may potentially play a role in preventing the formation of colon tumors induced by the carcinogen 1,2-dimethylhydrazine by reducing the activity of the intestinal as well as fecal beta-glucuronidase.

Nonlinear analysis for high-temperature multilayered fiber composite structures. M.S. Thesis; [turbine blades

NASA Technical Reports Server (NTRS)

Hopkins, D. A.

1984-01-01

A unique upward-integrated top-down-structured approach is presented for nonlinear analysis of high-temperature multilayered fiber composite structures. Based on this approach, a special purpose computer code was developed (nonlinear COBSTRAN) which is specifically tailored for the nonlinear analysis of tungsten-fiber-reinforced superalloy (TFRS) composite turbine blade/vane components of gas turbine engines. Special features of this computational capability include accounting of; micro- and macro-heterogeneity, nonlinear (stess-temperature-time dependent) and anisotropic material behavior, and fiber degradation. A demonstration problem is presented to mainfest the utility of the upward-integrated top-down-structured approach, in general, and to illustrate the present capability represented by the nonlinear COBSTRAN code. Preliminary results indicate that nonlinear COBSTRAN provides the means for relating the local nonlinear and anisotropic material behavior of the composite constituents to the global response of the turbine blade/vane structure.

Structured polarized light microscopy (SPLM) for mapping collagen fiber orientation of ocular tissues

NASA Astrophysics Data System (ADS)

Yang, Bin; Brazile, Bryn; Jan, Ning-Jiun; Voorhees, Andrew P.; Sigal, Ian A.

2018-02-01

Glaucoma is a disease characterized by progressive and irreversible vision loss leading to blindness. This vision loss is believed to be largely determined by the biomechanics of the optic nerve head region. Optic nerve head biomechanics, in turn, is determined by the properties of the constituent collagen. However, it is challenging to visualize and quantify collagen morphology and orientation in situ, and therefore often studies of the region collagen have used histological sections. Here we describe SPLM, a novel imaging technique that combines structured light illumination and polarized light microscopy (PLM) to enable collagen fiber visualization and fiber orientation mapping without requiring tissue sectioning. We developed a custom automated SPLM imaging system based on an upright microscope and a digital micromirror device (DMD) projector. The high spatial frequency patterns were used to achieve effective background suppression. Enhanced scattering sensitivity with SPLM resulted in images with highly improved visibility of collagen structures, even of tissues covered by pigment. SPLM produced improved fiber orientation maps from superficial layers compared to depth-averaged orientation from regular PLM. SPLM imaging provides valuable information of collagen fiber morphology and orientation in situ thus strengthening the study of ocular collagen fiber biomechanics and glaucoma.

Review structure of silk by raman spectromicroscopy: from the spinning glands to the fibers.

PubMed

Lefèvre, Thierry; Paquet-Mercier, François; Rioux-Dubé, Jean-François; Pézolet, Michel

2012-06-01

Raman spectroscopy has long been proved to be a useful tool to study the conformation of protein-based materials such as silk. Thanks to recent developments, linearly polarized Raman spectromicroscopy has appeared very efficient to characterize the molecular structure of native single silk fibers and spinning dopes because it can provide information relative to the protein secondary structure, molecular orientation, and amino acid composition. This review will describe recent advances in the study of the structure of silk by Raman spectromicroscopy. A particular emphasis is put on the spider dragline and silkworm cocoon threads, other fibers spun by orb-weaving spiders, the spinning dope contained in their silk glands and the effect of mechanical deformation. Taken together, the results of the literature show that Raman spectromicroscopy is particularly efficient to investigate all aspects of silk structure and production. The data provided can lead to a better understanding of the structure of the silk dope, transformations occurring during the spinning process, and structure and mechanical properties of native fibers. Copyright © 2011 Wiley Periodicals, Inc.

Innovative Design for Composite Spacecraft Structure Thanks to Automatic Fiber Placement Technology

NASA Astrophysics Data System (ADS)

Brindeau, Aymeric; Khalfi, Thomas

2014-06-01

The innovative design for composite spacecraft structure thanks to automatic fiber placement technology takes place in the frame of the development of a new launcher. A heavy loaded spacecraft carrying structure is developed in order to allow performance and big payload volumes.This kind of structure already exists on a current launcher, but performances are not compatible with the new requirements. Indeed, in spite of a sandwich design made of carbon and aluminium honeycomb, mass and stiffness requirements are not fulfilled.Consequently, for the new structure, an innovative design has been set-up. The materials are still sandwich made of carbon and aluminium honeycomb in order to obtain the best ratio mass / stiffness, but major evolutions have been implemented of the geometry of the structure in order to increase the performance of the product. These evolutions are allowed thanks to the use of the fiber placement technology, which allows manufacturing geometries that are not reachable with standard lay-up by hands. The main progress deals with the manufacturing of revolution sub-structures, in one shot, with double curvature areas. Moreover, beyond the technical performance of the new product and the gains in terms of manufacturing time and quality, the integration of sub-structures is extremely simplified compared to the existing process. As a result, the technology of fiber placement is the opportunity to imagine new designs which allows increasing the performances, to reduce manufacturing cycles, and to simplify integration operations.

Fog Collection on Polyethylene Terephthalate (PET) Fibers: Influence of Cross Section and Surface Structure.

PubMed

Azad, M A K; Krause, Tobias; Danter, Leon; Baars, Albert; Koch, Kerstin; Barthlott, Wilhelm

2017-06-06

Fog-collecting meshes show a great potential in ensuring the availability of a supply of sustainable freshwater in certain arid regions. In most cases, the meshes are made of hydrophilic smooth fibers. Based on the study of plant surfaces, we analyzed the fog collection using various polyethylene terephthalate (PET) fibers with different cross sections and surface structures with the aim of developing optimized biomimetic fog collectors. Water droplet movement and the onset of dripping from fiber samples were compared. Fibers with round, oval, and rectangular cross sections with round edges showed higher fog-collection performance than those with other cross sections. However, other parameters, for example, width, surface structure, wettability, and so forth, also influenced the performance. The directional delivery of the collected fog droplets by wavy/v-shaped microgrooves on the surface of the fibers enhances the formation of a water film and their fog collection. A numerical simulation of the water droplet spreading behavior strongly supports these findings. Therefore, our study suggests the use of fibers with a round cross section, a microgrooved surface, and an optimized width for an efficient fog collection.

Fabrication and Properties of Carbon Fibers

PubMed Central

Huang, Xiaosong

2009-01-01

This paper reviews the research and development activities conducted over the past few decades on carbon fibers. The two most important precursors in the carbon fiber industry are polyacrylonitrile (PAN) and mesophase pitch (MP). The structure and composition of the precursor affect the properties of the resultant carbon fibers significantly. Although the essential processes for carbon fiber production are similar, different precursors require different processing conditions in order to achieve improved performance. The research efforts on process optimization are discussed in this review. The review also attempts to cover the research on other precursor materials developed mainly for the purpose of cost reduction.

Optical modeling of fiber organic photovoltaic structures using a transmission line method.

PubMed

Moshonas, N; Stathopoulos, N A; O'Connor, B T; Bedeloglu, A Celik; Savaidis, S P; Vasiliadis, S

2017-12-01

An optical model has been developed and evaluated for the calculation of the external quantum efficiency of cylindrical fiber photovoltaic structures. The model is based on the transmission line theory and has been applied on single and bulk heterojunction fiber-photovoltaic cells. Using this model, optimum design characteristics have been proposed for both configurations, and comparison with experimental results has been assessed.

Integrated fiber optic structural health sensors for inflatable space habitats

NASA Astrophysics Data System (ADS)

Ohanian, Osgar John; Garg, Naman; Castellucci, Matthew A.

2017-04-01

Inflatable space habitats offer many advantages for future space missions; however, the long term integrity of these flexible structures is a major concern in harsh space environments. Structural Health Monitoring (SHM) of these structures is essential to ensure safe operation, provide early warnings of damage, and measure structural changes over long periods of time. To address this problem, the authors have integrated distributed fiber optic strain sensors to measure loading and to identify the occurrence and location of damage in the straps and webbing used in the structural restraint layer. The fiber optic sensors employed use Rayleigh backscatter combined with optical frequency domain reflectometry to enable measurement of strain every 0.65 mm (0.026 inches) along the sensor. The Kevlar woven straps that were tested exhibited large permanent deformation during initial cycling and continued to exhibit hysteresis thereafter, but there was a consistent linear relationship between the sensor's measurement and the actual strain applied. Damage was intentionally applied to a tensioned strap, and the distributed strain measurement clearly identified a change in the strain profile centered on the location of the damage. This change in structural health was identified at a loading that was less than half of the ultimate loading that caused a structural failure. This sensing technique will be used to enable integrated SHM sensors to detect loading and damage in future inflatable space habitat structures.

Surface Characterization of Carbon Fiber Polymer Composites and Aluminum Alloys After Laser Interference Structuring

NASA Astrophysics Data System (ADS)

Sabau, Adrian S.; Greer, Clayton M.; Chen, Jian; Warren, Charles D.; Daniel, Claus

2016-07-01

The increasing use of carbon fiber-reinforced polymer matrix composites (CFPC) and aluminum alloys as lightweight materials in the automotive and aerospace industries demands enhanced surface preparation and control of surface morphology prior to joining. In this study, surfaces of both composite and aluminum were prepared for joining using an Nd:YAG laser in a two-beam interference setup, enabling the (1) structuring of the AL 5182 surface, (2) removal of the resin layer on top of carbon fibers, and (3) structuring of the carbon fibers. CFPC specimens of T700S carbon fiber, Prepreg—T83 epoxy, 5 ply thick, 0°/90° plaques were used. The effects of laser fluence, scanning speed, and number of shots-per-spot were investigated on the removal rate of the resin without an excessive damage of the fibers. Optical micrographs, 3D imaging, and scanning electron microscope imaging were used to study the effect of the laser processing on the surface morphology. It was found that an effective resin ablation and a low density of broken fibers for CFPC specimens was attained using laser fluences of 1-2 J/cm2 and number of 2-4 pulses per spot. A relatively large area of periodic line structures due to energy interference were formed on the aluminum surface at laser fluences of 12 J/cm2 and number of 4-6 pulses per spot.

On the pull-out of fibers with fractal-tree structure and the interference of strength and fracture toughness of composites

NASA Astrophysics Data System (ADS)

Fe, Shaoyun; Zhou, Benlian; Lung, Chiwei

1992-06-01

An approximate theory of pull-out of fiber with fractal-tree structure from a matrix is developed with the aim of quantifying the effects of the fractal-tree structure of the fiber. In the experimental investigation of the pull-out of the synthetic fiber with fractal-tree structure, it was generally observed that the force and energy of fiber pullout increase with the branching angle. The application of this theory to experiment is successful. The strength and fracture toughness of composites reinforced by this kind of fiber are inferred to be greater than those of composites reinforced by plane fibers.

Production of continuous piezoelectric ceramic fibers for smart materials and active control devices

NASA Astrophysics Data System (ADS)

French, Jonathan D.; Weitz, Gregory E.; Luke, John E.; Cass, Richard B.; Jadidian, Bahram; Bhargava, Parag; Safari, Ahmad

1997-05-01

Advanced Cerametrics Inc. has conceived of and developed the Viscous-Suspension-Spinning Process (VSSP) to produce continuous fine filaments of nearly any powdered ceramic materials. VSSP lead zirconate titanate (PZT) fiber tows with 100 and 790 filaments have been spun in continuous lengths exceeding 1700 meters. Sintered PZT filaments typically are 10 - 25 microns in diameter and have moderate flexibility. Prior to carrier burnout and sintering, VSSP PZT fibers can be formed into 2D and 3D shapes using conventional textile and composite forming processes. While the extension of PZT is on the order of 20 microns per linear inch, a woven, wound or braided structure can contain very long lengths of PZT fiber and generate comparatively large output strokes from relatively small volumes. These structures are intended for applications such as bipolar actuators for fiber optic assembly and repair, vibration and noise damping for aircraft, rotorcraft, automobiles and home applications, vibration generators and ultrasonic transducers for medical and industrial imaging. Fiber and component cost savings over current technologies, such as the `dice-and-fill' method for transducer production, and the range of unique structures possible with continuous VSSP PZT fiber are discussed. Recent results have yielded 1-3 type composites (25 vol% PZT) with d33 equals 340 pC/N, K equals 470, and g33 equals 80 mV/N, kt equals 0.54, kp equals 0.19, dh equals 50.1pC/N and gh equals 13 mV/N.

Muscle Activation During Peripheral Nerve Field Stimulation Occurs Due to Recruitment of Efferent Nerve Fibers, Not Direct Muscle Activation.

PubMed

Frahm, Ken Steffen; Hennings, Kristian; Vera-Portocarrero, Louis; Wacnik, Paul W; Mørch, Carsten Dahl

2016-08-01

Peripheral nerve field stimulation (PNFS) is a potential treatment for chronic low-back pain. Pain relief using PNFS is dependent on activation of non-nociceptive Aβ-fibers. However, PNFS may also activate muscles, causing twitches and discomfort. In this study, we developed a mathematical model, to investigate the activation of sensory and motor nerves, as well as direct muscle fiber activation. The extracellular field was estimated using a finite element model based on the geometry of CT scanned lumbar vertebrae. The electrode was modeled as being implanted to a depth of 10-15 mm. Three implant directions were modeled; horizontally, vertically, and diagonally. Both single electrode and "between-lead" stimulation between contralateral electrodes were modeled. The extracellular field was combined with models of sensory Aβ-nerves, motor neurons and muscle fibers to estimate their activation thresholds. The model showed that sensory Aβ fibers could be activated with thresholds down to 0.563 V, and the lowest threshold for motor nerve activation was 7.19 V using between-lead stimulation with the cathode located closest to the nerves. All thresholds for direct muscle activation were above 500 V. The results suggest that direct muscle activation does not occur during PNFS, and concomitant motor and sensory nerve fiber activation are only likely to occur when using between-lead configuration. Thus, it may be relevant to investigate the location of the innervation zone of the low-back muscles prior to electrode implantation to avoid muscle activation. © 2016 International Neuromodulation Society.

A perspective on the complexity of dietary fiber structures and their potential effect on the gut microbiota.

PubMed

Hamaker, Bruce R; Tuncil, Yunus E

2014-11-25

Even though there are many factors that determine the human colon microbiota composition, diet is an important one because most microorganisms in the colon obtain energy for their growth by degrading complex dietary compounds, particularly dietary fibers. While fiber carbohydrates that escape digestion in the upper gastrointestinal tract are recognized to have a range of structures, the vastness in number of chemical structures from the perspective of the bacteria is not well appreciated. In this article, we introduce the concept of "discrete structure" that is defined as a unique chemical structure, often within a fiber molecule, which aligns with encoded gene clusters in bacterial genomes. The multitude of discrete structures originates from the array of different fiber types coupled with structural variations within types due to genotype and growing environment, anatomical parts of the grain or plant, discrete regions within polymers, and size of oligosaccharides and small polysaccharides. These thousands of discrete structures conceivably could be used to favor bacteria in the competitive colon environment. A global framework needs to be developed to better understand how dietary fibers can be used to obtain predicted changes in microbiota composition for improved health. This will require a multi-disciplinary effort that includes biological scientists, clinicians, and carbohydrate specialists. Copyright © 2014 Elsevier Ltd. All rights reserved.

Structure and properties of novel fibers spun from cellulose in NaOH/thiourea aqueous solution.

PubMed

Ruan, Dong; Zhang, Lina; Zhou, Jinping; Jin, Huiming; Chen, Hui

2004-12-15

Cellulose was dissolved rapidly in a NaOH/thiourea aqueous solution (9.5:4.5 in wt.-%) to prepare a transparent cellulose solution, which was employed, for the first time, to spin a new class of regenerated cellulose fibers by wet spinning. The structure and mechanical properties of the resulting cellulose fibers were characterized, and compared with those of commercially available viscose rayon, cuprammonium rayon and Lyocell fibers. The results from wide angle X-ray diffraction and CP/MAS 13C NMR indicated that the novel cellulose fibers have a structure typical for a family II cellulose and possessed relatively high degrees of crystallinity. Scanning electron microscopy (SEM) and optical microscopy images revealed that the cross-section of the fibers is circular, similar to natural silk. The new fibers have higher molecular weights and better mechanical properties than those of viscose rayon. This low-cost technology is simple, different from the polluting viscose process. The dissolution and regeneration of the cellulose in the NaOH/thiourea aqueous solutions were a physical process and a sol-gel transition rather than a chemical reaction, leading to the smoothness and luster of the fibers. This work provides a potential application in the field of functional fiber manufacturing.

Thermally induced structural transitions in cotton fiber revealed by a finite mixture model of fiber tenacity distribution

USDA-ARS?s Scientific Manuscript database

Much processing of cotton fibrous materials accompanies heat treatments. Despite their critical influence on the properties of the material, the structural responses of cotton fiber to elevated temperatures remain uncertain. This study demonstrated that modeling the temperature dependence of the fib...

Correlating Detergent Fiber Analysis and Dietary Fiber Analysis Data for Corn Stover

DOE Office of Scientific and Technical Information (OSTI.GOV)

Wolfrum, E. J.; Lorenz, A. J.; deLeon, N.

There exist large amounts of detergent fiber analysis data [neutral detergent fiber (NDF), acid detergent fiber (ADF), acid detergent lignin (ADL)] for many different potential cellulosic ethanol feedstocks, since these techniques are widely used for the analysis of forages. Researchers working in the area of cellulosic ethanol are interested in the structural carbohydrates in a feedstock (principally glucan and xylan), which are typically determined by acid hydrolysis of the structural fraction after multiple extractions of the biomass. These so-called dietary fiber analysis methods are significantly more involved than detergent fiber analysis methods. The purpose of this study was to determinemore » whether it is feasible to correlate detergent fiber analysis values to glucan and xylan content determined by dietary fiber analysis methods for corn stover. In the detergent fiber analysis literature cellulose is often estimated as the difference between ADF and ADL, while hemicellulose is often estimated as the difference between NDF and ADF. Examination of a corn stover dataset containing both detergent fiber analysis data and dietary fiber analysis data predicted using near infrared spectroscopy shows that correlations between structural glucan measured using dietary fiber techniques and cellulose estimated using detergent techniques, and between structural xylan measured using dietary fiber techniques and hemicellulose estimated using detergent techniques are high, but are driven largely by the underlying correlation between total extractives measured by fiber analysis and NDF/ADF. That is, detergent analysis data is correlated to dietary fiber analysis data for structural carbohydrates, but only indirectly; the main correlation is between detergent analysis data and solvent extraction data produced during the dietary fiber analysis procedure.« less

Effect of Hindlimb Unweighting on Single Soleus Fiber Maximal Shortening Velocity and ATPase Activity

NASA Technical Reports Server (NTRS)

McDonald, K. S.; Fitts, R. H.

1993-01-01

This study characterizes the time course of change in single soleus muscle fiber size and function elicited by hindlimb un weighting (HU) and analyzes the extent to which varying durations of HU altered maximal velocity of shortening (V(sub o)), myofibrillar adenosinetriphosphatase (ATPase), and relative content of slow and fast myosin in individual soleus fibers. After 1, 2, or 3 weeks of HU, soleus muscle bundles were prepared and stored in skinning solution at -20 C. Single fibers were isolated and mounted between a motor arm and a transducer, and fiber force, V(sub o), and ATPase activity were measured. Fiber myosin content was determined by one-dimensional sodium dodecyl sulfate- (SDS) polyacrylamide gel electrophoresis. After 1, 2, and 3 weeks of HU, soleus fibers exhibited a progressive reduction in fiber diameter (16, 22, and 42%, respectively) and peak force (42, 48, and 7%, respectively). Peak specific tension was significantly reduced after 1 week of HU (18%) and showed no further change in 2-3 weeks of HU. During 1 and 3 wk of HU, fiber V(sub o) and ATPase showed a significant increase. By 3 week, V(sub o) had increased from 1.32 +/- 0.04 to 2.94 +/- 0.17 fiber lengths/s and fiber ATPase from 291 +/- 16 to 1064 +/- 128 micro-M min(sub -1) mm(sub -3). The percent fibers expressing fast myosin heavy chain increased from 4% to 29% by 3 week of HU, and V(sub o) and ATPase activity within a fiber were highly correlated. However, a large population of fibers after 1, 2, and 3 weeks of HU showed increases in V(sub o) and ATPase but displayed the same myosin protein profile on SDS gels as control fibers. The mechanism eliciting increased fiber V(sub o) and ATPase activity was not obvious but may have been due to increases in fast myosin that went undetected on SDS gels and/or other factors unrelated to the myosin filament.

Fiber Optic Sensors for Structural Health Monitoring of Air Platforms

PubMed Central

Guo, Honglei; Xiao, Gaozhi; Mrad, Nezih; Yao, Jianping

2011-01-01

Aircraft operators are faced with increasing requirements to extend the service life of air platforms beyond their designed life cycles, resulting in heavy maintenance and inspection burdens as well as economic pressure. Structural health monitoring (SHM) based on advanced sensor technology is potentially a cost-effective approach to meet operational requirements, and to reduce maintenance costs. Fiber optic sensor technology is being developed to provide existing and future aircrafts with SHM capability due to its unique superior characteristics. This review paper covers the aerospace SHM requirements and an overview of the fiber optic sensor technologies. In particular, fiber Bragg grating (FBG) sensor technology is evaluated as the most promising tool for load monitoring and damage detection, the two critical SHM aspects of air platforms. At last, recommendations on the implementation and integration of FBG sensors into an SHM system are provided. PMID:22163816

Optical fiber sensors and signal processing for intelligent structure monitoring

NASA Technical Reports Server (NTRS)

Rogowski, Robert; Claus, R. O.; Lindner, D. K.; Thomas, Daniel; Cox, Dave

1988-01-01

The analytic and experimental performance of optical fiber sensors for the control of vibration of large aerospace and other structures are investigated. In particular, model domain optical fiber sensor systems, are being studied due to their apparent potential as distributed, low mass sensors of vibration over appropriate ranges of both low frequency and low amplitude displacements. Progress during the past three months is outlined. Progress since September is divided into work in the areas of experimental hardware development, analytical analysis, control design and sensor development. During the next six months, tests of a prototype closed-loop control system for a beam are planned which will demonstrate the solution of several optical fiber instrumentation device problems, the performance of the control system theory which incorporates the model of the modal domain sensor, and the potential for distributed control which this sensor approach offers.

Exploring the atomic structure and conformational flexibility of a 320 Å long engineered viral fiber using X-ray crystallography.

PubMed

Bhardwaj, Anshul; Casjens, Sherwood R; Cingolani, Gino

2014-02-01

Protein fibers are widespread in nature, but only a limited number of high-resolution structures have been determined experimentally. Unlike globular proteins, fibers are usually recalcitrant to form three-dimensional crystals, preventing single-crystal X-ray diffraction analysis. In the absence of three-dimensional crystals, X-ray fiber diffraction is a powerful tool to determine the internal symmetry of a fiber, but it rarely yields atomic resolution structural information on complex protein fibers. An 85-residue-long minimal coiled-coil repeat unit (MiCRU) was previously identified in the trimeric helical core of tail needle gp26, a fibrous protein emanating from the tail apparatus of the bacteriophage P22 virion. Here, evidence is provided that an MiCRU can be inserted in frame inside the gp26 helical core to generate a rationally extended fiber (gp26-2M) which, like gp26, retains a trimeric quaternary structure in solution. The 2.7 Å resolution crystal structure of this engineered fiber, which measures ∼320 Å in length and is only 20-35 Å wide, was determined. This structure, the longest for a trimeric protein fiber to be determined to such a high resolution, reveals the architecture of 22 consecutive trimerization heptads and provides a framework to decipher the structural determinants for protein fiber assembly, stability and flexibility.

Formation and chemical reactivity of carbon fibers prepared by defluorination of graphite fluoride

NASA Technical Reports Server (NTRS)

Hung, Ching-Cheh

1994-01-01

Defluorination of graphite fluoride (CFX) by heating to temperatures of 250 to 450 C in chemically reactive environments was studied. This is a new and possibly inexpensive process to produce new carbon-based materials. For example, CF 0.68 fibers, made from P-100 carbon fibers, can be defluorinated in BrH2C-CH = CH-CH2Br (1,4-dibromo-2butene) heated to 370 C, and graphitized to produce fibers with an unusually high modulus and a graphite layer structure that is healed and cross-linked. Conversely, a sulfur-doped, visibly soft carbon fiber was produced by defluorinating CF 0.9 fibers, made from P-25, in sulfur (S) vapor at 370 C and then heating to 660 C in nitrogen (N2). Furthermore, defluorination of the CF 0.68 fibers in bromine (Br2) produced fragile, structurally damaged carbon fibers. Heating these fragile fibers to 1100 C in N2 caused further structural damage, whereas heating to 150 C in bromoform (CHBr3) and then to 1100 C in N2 healed the structural defects. The defluorination product of CFX, tentatively called activated graphite, has the composition and molecular structure of graphite, but is chemically more reactive. Activated graphite is a scavenger of manganese (Mn), and can be intercalated with magnesium (Mg). Also, it can easily collect large amounts of an alloy made from copper (Cu) and type 304 stainless steel to form a composite. Finally, there are indications that activated graphite can wet metals or ceramics, thereby forming stronger composites with them than the pristine carbon fibers can form.

Damage evaluation and analysis of composite pressure vessels using fiber Bragg gratings to determine structural health

NASA Astrophysics Data System (ADS)

Ortyl, Nicholas E.

2005-11-01

The application of MEMS and nanotechnology (MNT) to the field of structural health monitoring (SHM) is a fairly recent development. The recent change in this focus for MNT has been driven by the need to expand the applications for much of the technologies that were developed in the late 1990s. In addition, many companies desire to expand beyond their target high volume market segments of automotive, wireless communications, and computer peripherals, since these market segments were not as lucrative as first predicted. Most of the aerospace structural health monitoring developmental activity has been sponsored by agencies of the U.S. Government, which serves to pace the examination of these newer technologies to some degree. With that said, efforts are underway by companies such as Acellent Technologies and Blue Road Research to explore various MNT structural health monitoring approaches. The MNT under test include embedded piezoelectric sensors, MEMS accelerometers, time domain region sensors, and topical and embedded single and multi-axis fiber optic Bragg grating sensors. The promise of MNT for the SHM market segment is very enticing. The many wireless communication developments and miniaturization developments of the past five years is very attractive to the SHM community, especially those that are able to reduce the cost and complexity of integration. The main challenge for the community is one of selective integration. That is, certain pieces may be appropriate for SHM systems and certain pieces may not be. The better companies will chose wisely and put forth an approach that can be seamlessly integrated into the larger structure. For over a decade, Blue Road Research has been developing technologies aimed at structural health monitoring of both composite and non-composite parts, through the use of single and multiaxis fiber optic Bragg grating sensors. These sensors are 80 to 120 microns in diameter making them smaller than the diameter of a human hair

Development of nanoparticle embedded sizing for enhanced structural health monitoring of carbon fiber composites

NASA Astrophysics Data System (ADS)

Bowland, Christopher C.; Wang, Yangyang; Naskar, Amit K.

2017-04-01

Carbon fiber composites experience sudden, catastrophic failure when exposed to sufficient stress levels and provide no obvious visual indication of damage before they fail. With the commercial adoption of these high-performance composites in structural applications, a need for in-situ monitoring of their structural integrity is paramount. Therefore, ways in which to monitor these systems has gathered research interest. A common method for accomplishing this is measuring through-thickness resistance changes of the composite due to the fact that carbon fiber composites are electrically conductive. This provides information on whole-body stress levels imparted on the composite and can help identify the presence of damage. However, this technique relies on the carbon fiber and polymer matrix to reveal a resistance change. Here, an approach is developed that increases damage detection sensitivity. This is achieved by developing a facile synthesis method of integrating semiconducting nanomaterials, such as silicon carbide, into carbon fiber sizing. The piezoresistive effect exhibited by these nanomaterials provides more pronounced resistance changes in response to mechanical stress as compared to carbon fiber alone. This is investigated through fabricating a unidirectional composite and subsequently monitoring the electrical resistance during mechanical testing. By establishing this route for integrating nanomaterials into carbon fiber composites, various nanomaterials can see future composite integration to realize novel properties.

Understanding the Mechanical Properties and Structure Transition of Antheraea pernyi Silk Fiber Induced by Its Contraction.

PubMed

Wang, Yu; Wen, Jianchuan; Peng, Bo; Hu, Bingwen; Chen, Xin; Shao, Zhengzhong

2018-02-23

Like most major ampullate silks of spider, the length of Antheraea pernyi silkworm silk can shrink to a certain degree when the fiber is in contact with water. However, what happens in terms of molecule chain level and how it correlates to the mechanical properties of the silk during its contraction is not yet fully understood. Here, we investigate the water-induced mechanical property changes as well as the structure transition of two kinds of A. pernyi silk fiber, which are forcibly reeled from two different individuals (silkworm a and silkworm b; the silk fiber from either one represents the lower and upper limit of the distribution of mechanical properties, respectively). The tensile test results present that most of the mechanical parameters except the post-yield modulus and breaking strain for both silk fibers have the same variation trend before and after their water contraction. Synchrotron FTIR and Raman spectra show that the native filament from silkworm a contains more α-helix structures than that in silkworm b filament, and these α-helices are partially converted to β-sheet structures after the contraction of the fibers, while the order of both β-sheet and α-helix slightly increase. On the other side, the content and orientation of both secondary structural components in silkworm b fiber keep unchanged, no matter if it is native or contracted. 13 C CP/MAS NMR results further indicate that the α-helix/random coil to β-sheet conformational transition that occurred in the silk of silkworm a corresponds the Ala residues. Based upon these results, the detailed structure transition models of both as-reeled A. pernyi silk fibers during water contraction are proposed finally to interpret their properties transformation.

Structural Health Monitoring in Composite Structures by Fiber-Optic Sensors †

PubMed Central

Güemes, Alfredo; Díaz-Maroto, Patricia F.; Lozano, Angel; Sierra-Perez, Julian

2018-01-01

Fiber-optic sensors cannot measure damage; to get information about damage from strain measurements, additional strategies are needed, and several alternatives are available in the existing literature. This paper discusses two independent procedures. The first is based on detecting new strains appearing around a damage spot. The structure does not need to be under loads, the technique is very robust, and damage detectability is high, but it requires sensors to be located very close to the damage, so it is a local technique. The second approach offers wider coverage of the structure; it is based on identifying the changes caused by damage on the strain field in the whole structure for similar external loads. Damage location does not need to be known a priori, and detectability is dependent upon the sensor’s network density, the damage size, and the external loads. Examples of application to real structures are given. PMID:29617345

Digitally controlled chirped pulse laser for sub-terahertz-range fiber structure interrogation.

PubMed

Chen, Zhen; Hefferman, Gerald; Wei, Tao

2017-03-01

This Letter reports a sweep velocity-locked laser pulse generator controlled using a digital phase-locked loop (DPLL) circuit. This design is used for the interrogation of sub-terahertz-range fiber structures for sensing applications that require real-time data collection with millimeter-level spatial resolution. A distributed feedback laser was employed to generate chirped laser pulses via injection current modulation. A DPLL circuit was developed to lock the optical frequency sweep velocity. A high-quality linearly chirped laser pulse with a frequency excursion of 117.69 GHz at an optical communication band was demonstrated. The system was further adopted to interrogate a continuously distributed sub-terahertz-range fiber structure (sub-THz-fs) for sensing applications. A strain test was conducted in which the sub-THz-fs showed a linear response to longitudinal strain change with predicted sensitivity. Additionally, temperature testing was conducted in which a heat source was used to generate a temperature distribution along the fiber structure to demonstrate its distributed sensing capability. A Gaussian temperature profile was measured using the described system and tracked in real time, as the heat source was moved.

Radiation tolerant passive and active optical fiber products for use in space environments

NASA Astrophysics Data System (ADS)

Hill, Mark; Hankey, Judith; Gray, Rebecca

2017-11-01

This paper reports the radiation performance results of several new product types designed for high radiation environments. The products tested include radiation hardened highly birefringent (HiBi) passive products for polarised applications and radiation tolerant active erbium doped fiber products for amplifiers. Radiation hardened, short beatlength HiBi fiber products have been developed for high accuracy polarisation maintaining (PM) gyros and sensors at both 1310nm and 1550nm operation in the space environment. The fibers have been tested up to 5kGy (500krad) - levels which could be expected in extreme, extra-terrestrial space environments. Results show a consistently low Radiation Induced Attenuation (RIA) of <7dB/km at 5kGy, giving a RIA value of 1.37×10-2 dB/km/krad at 1550nm for this product range. Radiation tolerant EDF AstroGain™ fibers are intended for use in multichannel amplifiers in optical intersatellite communications. The structure of the fibers have been designed to deliver an accelerated recovery of radiation damage through photo-annealing using only the residual energy already available in an amplifier using a 980nm pumping regime. These products have been tested up to 200Gy (20krad) - levels which can be expected in Earth orbit environments over a 20-30 mission lifetime. Results show up to 100% recovery under continuous use for dose rates of 0.11rad/hr. It has also been demonstrated through analysis of the optical spectral output that this effect reverses the gain tilt, or spectral narrowing, induced by radiation damage through the C and L band. These combined fiber characteristics allow performance stability of the amplifier over the lifetime of the space mission.

Seamless metal-clad fiber-reinforced organic matrix composite structures and process for their manufacture

NASA Technical Reports Server (NTRS)

Bluck, Raymond M. (Inventor); Bush, Harold G. (Inventor); Johnson, Robert R. (Inventor)

1990-01-01

A metallic outer sleeve is provided which is capable of enveloping a hollow metallic inner member having continuous reinforcing fibers attached to the distal end thereof. The inner member is then introduced into outer sleeve until inner member is completely enveloped by outer sleeve. A liquid matrix member is then injected into space between inner member and outer sleeve. A pressurized heat transfer medium is flowed through the inside of inner member, thereby forming a fiber reinforced matrix composite material. The wall thicknesses of both inner member and outer sleeve are then reduced to the appropriate size by chemical etching, to adjust the thermal expansion coefficient of the metal-clad composite structure to the desired value. thereby forming a fiber reinforced matrix composite material. The wall thicknesses of both inner member and outer sleeve are then reduced to the appropriate size by chemical etching, to adjust the thermal expansion coefficient of the metal-clad composite structure to the desired value. The novelty of this invention resides in the development of a efficient method of producing seamless metal clad fiber reinforced organic matrix composite structures.

Miniature optical fiber temperature sensor based on FMF-SCF structure

NASA Astrophysics Data System (ADS)

Zhang, Chuanbiao; Ning, Tigang; Zheng, Jingjing; Gao, Xuekai; Lin, Heng; Li, Jing; Pei, Li; Wen, Xiaodong

2018-03-01

We proposed and experimentally demonstrated a miniature optical fiber temperature sensor consisting of a seven core fiber (SCF) and a few mode fiber (FMF). The device is fabricated by splicing a section of FMF with a segment of SCF to form a FMF-SCF based sensing structure, and during the FMF region, few modes can be excited and will propagate within the SCF. In experiment, the proposed device has good quality interferometric spectra, and the highest extinction ratio of 27 dB was achieved. When the temperature increases from room temperature to 110 °C, the temperature response properties of the sensor have been investigated, the wavelength sensitivity of about 91.8 pm/°C and the amplitude sensitivity of about 1.57 × 10-2 a.u./°C are obtained, respectively. Due to its easy and controllable fabrication, the sensor can be a suitable candidate in temperature sensing applications.

Natural fibers

Treesearch

Craig M. Clemons

2010-01-01

The term “natural fibers” covers a broad range of vegetable, animal, and mineral fibers. However, in the composites industry, it usually refers to wood fiber and plant-based bast, leaf, seed, and stem fibers. These fibers often contribute greatly to the structural performance of the plant and, when used in plastic composites, can provide significant reinforcement....

Natural fibers

Treesearch

Craig M. Clemons; Daniel F. Caulfield

2005-01-01

The term “natural fibers” covers a broad range of vegetable, animal, and mineral fibers. However, in the composites industry, it usually refers to wood fiber and agrobased bast, leaf, seed, and stem fibers. These fibers often contribute greatly to the structural performance of the plant and, when used in plastic composites, can provide significant reinforcement. Below...

Structural analysis of Gossypium hirsutum fibers grown under greenhouse and hydroponic conditions.

PubMed

Natalio, Filipe; Tahir, Muhammad Nawaz; Friedrich, Norman; Köck, Margret; Fritz-Popovski, Gerhard; Paris, Oskar; Paschke, Reinhard

2016-06-01

Cotton is the one of the world's most important crops. Like any other crop, cotton growth/development and fiber quality is highly dependent on environmental factors. Increasing global weather instability has been negatively impacting its economy. Cotton is a crop that exerts an intensive pressure over natural resources (land and water) and demands an overuse of pesticides. Thus, the search for alternative cotton culture methods that are pesticide-free (biocotton) and enable customized standard fiber quality should be encouraged. Here we describe a culture of Gossypium hirsutum ("Upland" Cotton) utilizing a greenhouse and hydroponics in which the fibers are morphological similar to conventional cultures and structurally fit into the classical two-phase cellulose I model with 4.19nm crystalline domains surrounded by amorphous regions. These fibers exhibit a single crystalline form of cellulose I-Iß, monoclinic unit cell. Fiber quality bulk analysis shows an improved length, strength, whiteness when compared with soil-based cultures. Finally, we show that our fibers can be spun, used for production of non-woven fabrics and indigo-vat stained demonstrating its potential in industrial and commercial applications. Copyright © 2016 Elsevier Inc. All rights reserved.

Activated carbon fiber felt and polymer fiber as biofilm carrier in a modified University of Cape Town process for sewage treatment.

PubMed

Zhou, Dongkai

2013-01-01

Biofilms on fiber-based carriers have attracted much concern in wastewater treatment processes recently. In this study: (1) a novel sandwich structure fiber-based biofilm carrier was produced, which consisted of an inner core composed of polyacrylonitrile-based activated carbon fiber felt (PAN-ACFF) and an outer coat made of polyester reticular cloth with polypropylene fiber loops; (2) the novel carrier was filled in a step-feeding pilot-scale modified University of Cape Town process (MUCT) for sewage treatment; the MUCT contained a series of pre-anoxic/anaerobic/anoxic-1/anoxic-2/oxic tanks, wherein nitrification liquor was recycled to the anoxic-2 tank and an extra liquor return from the anoxic-1 to the pre-anoxic tank was set up; and (3) the removal efficiencies of chemical oxygen demand (COD), total nitrogen (TN) and total phosphorus (TP) were continuously tested for two periods as operational parameters alternated. The optimum values were collected in Period II, when the influent loads were 2,100.6 ± 120.3 gCOD/(d m(3)), 205.5 ± 20.4 gTN/(d m(3)), 39.9 ± 3.9 gTP/(d m(3)), the removal percentages were 93.1 ± 1.1% of COD, 39.4 ± 3.5% of TN, and 84.6 ± 3.4% of TP. For COD, NH4(+)-N, and TP, the specific removal loads of filler were 291.5 ± 18.2, 22.9 ± 3.1, 4.8 ± 0.5 (g d)/kg.

In-fiber modal interferometer based on multimode and double cladding fiber segments for tunable fiber laser applications

NASA Astrophysics Data System (ADS)

Prieto-Cortés, P.; Álvarez-Tamayo, R. I.; Durán-Sánchez, M.; Castillo-Guzmán, A.; Salceda-Delgado, G.; Ibarra-Escamilla, B.; Kuzin, E. A.; Barcelata-Pinzón, A.; Selvas-Aguilar, R.

2018-02-01

We report an in-fiber structure based on the use of a multimode fiber segment and a double cladding fiber segment, and its application as spectral filter in an erbium-doped fiber laser for selection and tuning of the laser line wavelength. The output transmission of the proposed device exhibit spectrum modulation of the input signal with free spectral range of 21 nm and maximum visibility enhanced to more than 20 dB. The output spectrum of the in-fiber filter is wavelength displaced by bending application which allows a wavelength tuning of the generated laser line in a range of 12 nm. The use of the proposed in-fiber structure is demonstrated as a reliable, simple, and low-cost wavelength filter for tunable fiber lasers design and optical instrumentation applications.

A novel structure photonic crystal fiber based on bismuth-oxide for optical parametric amplification

NASA Astrophysics Data System (ADS)

Jin, Cang; Yuan, Jinhui; Yu, Chongxiu

2010-11-01

The heavy metal oxide glasses containing bismuth such as bismuth sesquioxide show unique high refractive index. In addition, the bismuth-oxide based glass does not include toxic elements such as Pb, As, Se, Te, and exhibits well chemical, mechanical and thermal stability. Hence, it is used to fabricate high nonlinear fiber for nonlinear optical application. Although the bismuth-oxide based high nonlinear fiber can be fusion-spliced to conventional silica fibers and have above advantages, yet it suffers from large group velocity dispersion because of material chromatic dispersion which restricts its utility. In regard to this, the micro-structure was introduced to adjust the dispersion of bismuth-oxide high nonlinear fiber in the 1550nm wave-band. In this paper, a hexagonal solid-core micro-structure is developed to balance its dispersion and nonlinearity. Our simulation and calculation results show that the bismuth-oxide based photonic crystal fiber has near zero dispersion around 1550nm where the optical parametric amplification suitable wavelength is. Its dispersion slop in the communication wavelength range is also relatively flat. Moreover, both nonlinear coefficient and model filed distribution were simulated, respectively.

Fiber-reinforced scaffolds in soft tissue engineering

PubMed Central

Wang, Wei; Fan, Yubo; Wang, Xiumei; Watari, Fumio

2017-01-01

Abstract Soft tissue engineering has been developed as a new strategy for repairing damaged or diseased soft tissues and organs to overcome the limitations of current therapies. Since most of soft tissues in the human body are usually supported by collagen fibers to form a three-dimensional microstructure, fiber-reinforced scaffolds have the advantage to mimic the structure, mechanical and biological environment of natural soft tissues, which benefits for their regeneration and remodeling. This article reviews and discusses the latest research advances on design and manufacture of novel fiber-reinforced scaffolds for soft tissue repair and how fiber addition affects their structural characteristics, mechanical strength and biological activities in vitro and in vivo. In general, the concept of fiber-reinforced scaffolds with adjustable microstructures, mechanical properties and degradation rates can provide an effective platform and promising method for developing satisfactory biomechanically functional implantations for soft tissue engineering or regenerative medicine. PMID:28798872

Activation of parallel fiber feedback by spatially diffuse stimuli reduces signal and noise correlations via independent mechanisms in a cerebellum-like structure.

PubMed

Simmonds, Benjamin; Chacron, Maurice J

2015-01-01

Correlations between the activities of neighboring neurons are observed ubiquitously across systems and species and are dynamically regulated by several factors such as the stimulus' spatiotemporal extent as well as by the brain's internal state. Using the electrosensory system of gymnotiform weakly electric fish, we recorded the activities of pyramidal cell pairs within the electrosensory lateral line lobe (ELL) under spatially localized and diffuse stimulation. We found that both signal and noise correlations were markedly reduced (>40%) under the latter stimulation. Through a network model incorporating key anatomical features of the ELL, we reveal how activation of diffuse parallel fiber feedback from granule cells by spatially diffuse stimulation can explain both the reduction in signal as well as the reduction in noise correlations seen experimentally through independent mechanisms. First, we show that burst-timing dependent plasticity, which leads to a negative image of the stimulus and thereby reduces single neuron responses, decreases signal but not noise correlations. Second, we show trial-to-trial variability in the responses of single granule cells to sensory input reduces noise but not signal correlations. Thus, our model predicts that the same feedback pathway can simultaneously reduce both signal and noise correlations through independent mechanisms. To test this prediction experimentally, we pharmacologically inactivated parallel fiber feedback onto ELL pyramidal cells. In agreement with modeling predictions, we found that inactivation increased both signal and noise correlations but that there was no significant relationship between magnitude of the increase in signal correlations and the magnitude of the increase in noise correlations. The mechanisms reported in this study are expected to be generally applicable to the cerebellum as well as other cerebellum-like structures. We further discuss the implications of such decorrelation on the neural

Is fast fiber innervation responsible for increased acetylcholinesterase activity in reinnervating soleus muscles?

NASA Technical Reports Server (NTRS)

Misulis, K. E.; Dettbarn, W. D.

1985-01-01

An investigation was conducted as to whether the predominantly slow SOL, which is low in AChE activity, is initially reinnervated by axons that originally innervated fast muscle fibers with high AChE activity, such as those of the EDL. Local denervation of the SOL in the guinea pig was performed because this muscle is composed solely of slow (type I) fibers; thereby virtually eliminating the possibility of homologous muscle fast fiber innervation. The overshoot in this preparation was qualitatively similar to that seen with distal denervation in the guinea pig and local and distal denervation in the rat. Thus, initial fast fiber innvervation is not responsible for the patterns of change in AChE activity seen with reinnervation in the SOL. It is concluded that the neural control of AChe is different in these two muscles and may reflect specific differences in the characteristics of AChE regulation in fast and slow muscle.

Nondestructive testing of externally reinforced structures for seismic retrofitting using flax fiber reinforced polymer (FFRP) composites

NASA Astrophysics Data System (ADS)

Ibarra-Castanedo, C.; Sfarra, S.; Paoletti, D.; Bendada, A.; Maldague, X.

2013-05-01

Natural fibers constitute an interesting alternative to synthetic fibers, e.g. glass and carbon, for the production of composites due to their environmental and economic advantages. The strength of natural fiber composites is on average lower compared to their synthetic counterparts. Nevertheless, natural fibers such as flax, among other bast fibers (jute, kenaf, ramie and hemp), are serious candidates for seismic retrofitting applications given that their mechanical properties are more suitable for dynamic loads. Strengthening of structures is performed by impregnating flax fiber reinforced polymers (FFRP) fabrics with epoxy resin and applying them to the component of interest, increasing in this way the load and deformation capacities of the building, while preserving its stiffness and dynamic properties. The reinforced areas are however prompt to debonding if the fabrics are not mounted properly. Nondestructive testing is therefore required to verify that the fabric is uniformly installed and that there are no air gaps or foreign materials that could instigate debonding. In this work, the use of active infrared thermography was investigated for the assessment of (1) a laboratory specimen reinforced with FFRP and containing several artificial defects; and (2) an actual FFRP retrofitted masonry wall in the Faculty of Engineering of the University of L'Aquila (Italy) that was seriously affected by the 2009 earthquake. Thermographic data was processed by advanced signal processing techniques, and post-processed by computing the watershed lines to locate suspected areas. Results coming from the academic specimen were compared to digital speckle photography and holographic interferometry images.

Development of Coconut Trunk Fiber Geopolymer Hybrid Composite for Structural Engineering Materials

NASA Astrophysics Data System (ADS)

Amalia, F.; Akifah, N.; Nurfadilla; Subaer

2017-03-01

A research on the influence of coconut fiber trunk on mechanical properties based on fly ash has been conducted. The aims of this study was to examine the mechanical properties of geopolymer composites by varrying the concentration of coconut trunk fiber. Geopolymer synthesized by alkali activated (NaOH+H2O+Na2O.3SiO2) and cured at the temperature 700C for one hour. Specimens were synthesized into 5 different mass of fiber 0 g, 0.25 g, 0.50 g, 0.75 g, and 1.00 g keeping fly ash constant. The highest compressive strength was 89.44 MPa for specimen added with 0.50 g of fiber. The highest flexural strength was 7.64 MPa for the same sample. The interfacial transition zone (ITZ) between the matrix of geopolymers and coconut fiber was conducted by using Scanning Electron Microscopy-Energy Dispersive Spectroscopy (SEM-EDS). The chemical composition of the specimen was examined by using X-Ray Diffraction (XRD). The thermal properties of coconut fiber trunk was analyzed using Differential Scanning Calorimetry (DSC). It was found that coconut fiber was able to improve the mechanical and microstructure properties of geopolymers composites.

Nerve Fiber Activation During Peripheral Nerve Field Stimulation: Importance of Electrode Orientation and Estimation of Area of Paresthesia.

PubMed

Frahm, Ken Steffen; Hennings, Kristian; Vera-Portocarrero, Louis; Wacnik, Paul W; Mørch, Carsten Dahl

2016-04-01

Low back pain is one of the indications for using peripheral nerve field stimulation (PNFS). However, the effect of PNFS varies between patients; several stimulation parameters have not been investigated in depth, such as orientation of the nerve fiber in relation to the electrode. While placing the electrode parallel to the nerve fiber may give lower activation thresholds, anodal blocking may occur when the propagating action potential passes an anode. A finite element model was used to simulate the extracellular potential during PNFS. This was combined with an active cable model of Aβ and Aδ nerve fibers. It was investigated how the angle between the nerve fiber and electrode affected the nerve activation and whether anodal blocking could occur. Finally, the area of paresthesia was estimated and compared with any concomitant Aδ fiber activation. The lowest threshold was found when nerve and electrode were in parallel, and that anodal blocking did not appear to occur during PNFS. The activation of Aβ fibers was within therapeutic range (<10V) of PNFS; however, within this range, Aδ fiber activation also may occur. The combined area of activated Aβ fibers (paresthesia) was at least two times larger than Aδ fibers for similar stimulation intensities. No evidence of anodal blocking was observed in this PNFS model. The thresholds were lowest when the nerves and electrodes were parallel; thus, it may be relevant to investigate the overall position of the target nerve fibers prior to electrode placement. © 2015 International Neuromodulation Society.

A Novel Terminal Web-Like Structure in Cortical Lens Fibers: Architecture and Functional Assessment

PubMed Central

Al-Ghoul, Kristin J.; Lindquist, Timothy P.; Kirk, Spencer S.; Donohue, Sean T.

2010-01-01

This study describes a novel cytoskeletal array in fiber cells of the ocular lens of the rat and shows its relationship to the classical terminal web of other epithelial tissues. Naive adult Sprague-Dawley rats (n=28) were utilized. F-actin, fodrin, myosin IIA and CP49 distribution was assessed in anterior and posterior polar sections. For functional analysis, lenses were cultured with or without cytochalasin-D for 3 hours, then processed for confocal microscopy or assessed by laser scan analysis along sutures. Phalloidin labeling demonstrated a dense mesh of F-actin adjacent to posterior sutural domains to a subcapsular depth of 400 μm. Anterior polar sections revealed a comparable actin structure adjacent to anterior suture branches however, it was not developed in superficial fibers. Fodrin and myosin were localized within the web-like actin apparatus. The data was used to construct a model showing that the cytoskeletal array is located within the blunt, variable-width fiber ends that abut at sutures such that the ‘terminal web’ flanks the suture on either side. Treatment with cytochalasin-D resulted in partial disassembly of the ‘terminal web’ and perturbed cellular organization. Laser scan analysis revealed that cytochalasin-D treated lenses had significantly greater focal variability than control lenses (p=0.020). We conclude that cortical fibers of rat lenses contain a bipolar structure that is structurally and compositionally analogous to classical terminal webs. The results indicate that the lens ‘terminal web’ functions to stabilize lens fiber ends at sutures thus minimizing structural disorder, which in turn, promotes the establishment and maintenance of lens transparency. PMID:20730867

Adaptive Crack Modeling with Interface Solid Elements for Plain and Fiber Reinforced Concrete Structures.

PubMed

Zhan, Yijian; Meschke, Günther

2017-07-08

The effective analysis of the nonlinear behavior of cement-based engineering structures not only demands physically-reliable models, but also computationally-efficient algorithms. Based on a continuum interface element formulation that is suitable to capture complex cracking phenomena in concrete materials and structures, an adaptive mesh processing technique is proposed for computational simulations of plain and fiber-reinforced concrete structures to progressively disintegrate the initial finite element mesh and to add degenerated solid elements into the interfacial gaps. In comparison with the implementation where the entire mesh is processed prior to the computation, the proposed adaptive cracking model allows simulating the failure behavior of plain and fiber-reinforced concrete structures with remarkably reduced computational expense.

Adaptive Crack Modeling with Interface Solid Elements for Plain and Fiber Reinforced Concrete Structures

PubMed Central

Zhan, Yijian

2017-01-01

The effective analysis of the nonlinear behavior of cement-based engineering structures not only demands physically-reliable models, but also computationally-efficient algorithms. Based on a continuum interface element formulation that is suitable to capture complex cracking phenomena in concrete materials and structures, an adaptive mesh processing technique is proposed for computational simulations of plain and fiber-reinforced concrete structures to progressively disintegrate the initial finite element mesh and to add degenerated solid elements into the interfacial gaps. In comparison with the implementation where the entire mesh is processed prior to the computation, the proposed adaptive cracking model allows simulating the failure behavior of plain and fiber-reinforced concrete structures with remarkably reduced computational expense. PMID:28773130

Bent-core fiber structure: Experimental and theoretical studies of fiber stability

NASA Astrophysics Data System (ADS)

Bailey, C.; Gartland, E.; Jakli, A.

2007-03-01

Recent studies have shown that bent core liquid crystals in the B7 and B2 phases can form stable freestanding fibers with a so called ``jelly-roll'' layer configuration, which means that the smectic layers would be arranged in concentric cylindrical shells. This configuration shows layer curvature is necessary for fiber stability. Classically this effect would destabilize the fiber configuration because of the energy cost of layer distortions and surface tension. We propose a model that can predict fiber stability in the experimentally observed range of a few micrometers, by assuming that layer curvature can be stabilized by including a term dealing with the linear divergence of the polarization direction if the polarization is allowed to have a component normal to the smectic layers. We show that this term can stabilize the fiber configuration if its strength is larger than the surface tension. We also propose an entropic model to explain the strength of this term by considering steric effects. Finally we will take results from this model and apply them to better understand experimental findings of bent-core fibers. Financial support by NSF FRG under contract DMS-0456221. Prof. Daniel Phillips, Particia Bauman and Jie Shen at Purdue Univ., Prof. Maria Carme Calderer at Univ. of Minnesota, and Prof. Jonathan Selinger at Kent State Univ. Liou Qiu and Dr. O.D. Lavrentovich, Characterization Facilities, Liquid Crystal Institute, Kent State Univ. Julie Kim and Dr. Quan Li, Chemical Synthesis Facilities, Liquid Crystal Institute, Kent State Univ.

An actively Q-switched fiber laser with cylindrical vector beam generation

NASA Astrophysics Data System (ADS)

Zhang, Jiaojiao; Zhang, Zuxing; Cai, Yu; Wan, Hongdan; Wang, Zhiqiang; Zhang, Lin

2018-03-01

We demonstrate an actively Q-switched fiber laser with cylindrical vector beam (CVB) emission using a few-mode fiber Bragg grating as the mode selection component and an acousto-optic modulator to achieve Q-switching. To the best of our knowledge, this is the first such demonstration. Using a linear cavity configuration, an actively Q-switched CVB with a pulse width of about 64 ns, a pulse energy of 4.25 µJ and a repetition rate of 20 kHz has been obtained. Moreover, by tuning the polarization controllers radially and azimuthally, polarized Q-switched beams can be excited separately with a polarization purity of  >94.5%. This compact Q-switched fiber laser with ns CVB pulse output could find potential applications in the field of material processing, nonlinear optics and so on.

A fiber-optic sensor based on no-core fiber and Faraday rotator mirror structure

NASA Astrophysics Data System (ADS)

Lu, Heng; Wang, Xu; Zhang, Songling; Wang, Fang; Liu, Yufang

2018-05-01

An optical fiber sensor based on the single-mode/no-core/single-mode (SNS) core-offset technology along with a Faraday rotator mirror structure has been proposed and experimentally demonstrated. A transverse optical field distribution of self-imaging has been simulated and experimental parameters have been selected under theoretical guidance. Results of the experiments demonstrate that the temperature sensitivity of the sensor is 0.0551 nm/°C for temperatures between 25 and 80 °C, and the correlation coefficient is 0.99582. The concentration sensitivity of the device for sucrose and glucose solutions was found to be as high as 12.5416 and 6.02248 nm/(g/ml), respectively. Curves demonstrating a linear fit between wavelength shift and solution concentration for three different heavy metal solutions have also been derived on the basis of experimental results. The proposed fiber-optic sensor design provides valuable guidance for the measurement of concentration and temperature.

Vibration sensing in flexible structures using a distributed-effect modal domain optical fiber sensor

NASA Technical Reports Server (NTRS)

Reichard, Karl M.; Lindner, Douglas K.; Claus, Richard O.

1991-01-01

Modal domain optical fiber sensors have recently been employed in the implementation of system identification algorithms and the closed-loop control of vibrations in flexible structures. The mathematical model of the modal domain optical fiber sensor used in these applications, however, only accounted for the effects of strain in the direction of the fiber's longitudinal axis. In this paper, we extend this model to include the effects of arbitrary stress. Using this sensor model, we characterize the sensor's sensitivity and dynamic range.

Analysis of structural transformation in wool fiber resulting from oxygen plasma treatment using vibrational spectroscopy

NASA Astrophysics Data System (ADS)

Barani, Hossein; Haji, Aminoddin

2015-01-01

The aim of this study was to investigate the influence of oxygen plasma procedure at different time treatments on wool fiber using the micro-Raman spectroscopy as a non-destructive vibrational spectroscopic technique and Fourier transform infrared spectroscopy. The amide I and III regions, Csbnd C skeletal vibration region, and Ssbnd S and Csbnd S bonds vibration regions were analyzed with the Raman microscope. The Fourier transform infrared spectroscope analysis was employed to find out the effect of oxygen plasma treatment on the cysteic acid residues content of the wool fiber sample. The results indicated that the α-helix structure was the highest component content of wool fiber. Moreover, the protein secondary structure of wool fibers was transformed from α-helical arrangement to the β-pleated sheet configuration during the oxygen plasma treatment. Also, the disulphide bonds content in the treated wool fiber reduced because they were fractured and oxidized during oxygen plasma treatment. The oxygen plasma treated samples presented higher cysteic acid compared to the untreated wool samples due to produce more cleavage of disulfide linkages.

High sensitivity refractive index sensor based on a tapered small core single-mode fiber structure.

PubMed

Liu, Dejun; Mallik, Arun Kumar; Yuan, Jinhui; Yu, Chongxiu; Farrell, Gerald; Semenova, Yuliya; Wu, Qiang

2015-09-01

A high sensitivity refractive index (RI) sensor based on a tapered small core single-mode fiber (SCSMF) structure sandwiched between two traditional single-mode fibers (SMF28) is reported. The microheater brushing technique was employed to fabricate the tapered fiber structures with different waist diameters of 12.5, 15.0, and 18.8 μm. Experiments demonstrate that the fiber sensor with a waist diameter of 12.5 μm offers the best sensitivity of 19212.5  nm/RIU (RI unit) in the RI range of 1.4304 to 1.4320. All sensors fabricated in this Letter show good linearity in terms of the spectral wavelength shift versus changes in RI. Furthermore, the sensor with the best sensitivity to RI was also used to measure relative humidity (RH) without any coating materials applied to the fiber surface. Experimental results show that the spectral wavelength shift changes exponentially as the RH varies from 60% to 95%. A maximum sensitivity of 18.3 nm per relative humidity unit (RHU) was achieved in the RH range of 90.4% to 94.5% RH.

A civil structural monitoring system based on fiber grating sensors

NASA Astrophysics Data System (ADS)

Zhang, Yan; Cai, Haiwen; Pastore, Robert; Ju, Jing; Zeng, Debing; Yin, Zhifan; Cui, Hong-Liang

2003-08-01

Optical fiber sensors based on Fiber Bragg Grating (FBG) technology have found many applications in the area of civil structural monitoring systems, such as in bridge monitoring and maintenance. FBG sensors can measure the deformation, overload and cracks on bridge with a high sensitivity. In this paper we report on our recent work a structural monitoring system using FBG sensors. Basic theoretical background and design of the system is described here, including the light source, FBG sensors, demodulator sensors, signal detection and processing schemes. The system will be installed on a major arch bridge currently under construction in Shanghai, China for long-term in situ health monitoring. The system schematic arrangement on the bridge is introduced in brief. Simulation experiments in the laboratory were carried out to test the performance of FBG strain sensors. The sensor response shows excellent linearity against the strain imposed on it. Traffic and overload monitoring on bridge using FBG sensors is also discussed and planned for the near future.

Bio-composites of cassava starch-green coconut fiber: part II-Structure and properties.

PubMed

Lomelí-Ramírez, María Guadalupe; Kestur, Satyanarayana G; Manríquez-González, Ricardo; Iwakiri, Setsuo; de Muniz, Graciela Bolzon; Flores-Sahagun, Thais Sydenstricker

2014-02-15

Development of any new material requires its complete characterization to find potential applications. In that direction, preparation of bio-composites of cassava starch containing up to 30 wt.% green coconut fibers from Brazil by thermal molding process was reported earlier. Their characterization regarding physical and tensile properties of both untreated and treated matrices and their composites were also reported. Structural studies through FTIR and XRD and thermal stability of the above mentioned composites are presented in this paper. FT-IR studies revealed decomposition of components in the matrix; the starch was neither chemically affected nor modified by either glycerol or the amount of fiber. XRD studies indicated increasing crystallinity of the composites with increasing amount of fiber content. Thermal studies through TGA/DTA showed improvement of thermal stability with increasing amount of fiber incorporation, while DMTA showed increasing storage modulus, higher glass transition temperature and lower damping with increasing fiber content. Improved interfacial bonding between the matrix and fibers could be the cause for the above results. Copyright © 2013 Elsevier Ltd. All rights reserved.

Twistable and Stretchable Sandwich Structured Fiber for Wearable Sensors and Supercapacitors.

PubMed

Choi, Changsoon; Lee, Jae Myeong; Kim, Shi Hyeong; Kim, Seon Jeong; Di, Jiangtao; Baughman, Ray H

2016-12-14

Twistable and stretchable fiber-based electrochemical devices having high performance are needed for future applications, including emerging wearable electronics. Weavable fiber redox supercapacitors and strain sensors are here introduced, which comprise a dielectric layer sandwiched between functionalized buckled carbon nanotube electrodes. On the macroscopic scale, the sandwiched core rubber of the fiber acts as a dielectric layer for capacitive strain sensing and as an elastomeric substrate that prevents electrical shorting and irreversible structural changes during severe mechanical deformations. On the microscopic scale, the buckled CNT electrodes effectively absorb tensile or shear stresses, providing an essentially constant electrical conductance. Consequently, the sandwich fibers provide the dual functions of (1) strain sensing, by generating approximately 115.7% and 26% capacitance changes during stretching (200%) and giant twist (1700 rad·m -1 or 270 turns·m -1 ), respectively, and (2) electrochemical energy storage, providing high linear and areal capacitances (2.38 mF·cm -1 and 11.88 mF·cm -2 ) and retention of more than 95% of initial energy storage capability under large mechanical deformations.

Laser interrogation techniques for high-sensitivity strain sensing by fiber-Bragg-grating structures

NASA Astrophysics Data System (ADS)

Gagliardi, G.; Salza, M.; Ferraro, P.; De Natale, P.

2017-11-01

Novel interrogation methods for static and dynamic measurements of mechanical deformations by fiber Bragg-gratings (FBGs) structures are presented. The sensor-reflected radiation gives information on suffered strain, with a sensitivity dependent on the interrogation setup. Different approaches have been carried out, based on laser-frequency modulation techniques and near-IR lasers, to measure strain in single-FBG and in resonant high-reflectivity FBG arrays. In particular, for the fiber resonator, the laser frequency is actively locked to the cavity resonances by the Pound-Drever-Hall technique, thus tracking any frequency change due to deformations. The loop error and correction signals fed back to the laser are used as strain monitor. Sensitivity limits vary between 200 nɛ/√Hz in the quasi-static domain (0.5÷2 Hz), and between 1 and 4 nɛ/√Hz in the 0.4-1 kHz range for the single-FBG scheme, while strain down to 50 pɛ can be detected by using the laser-cavity-locked method.

Photogrammetric Verification of Fiber Optic Shape Sensors on Flexible Aerospace Structures

NASA Technical Reports Server (NTRS)

Moore, Jason P.; Rogge, Matthew D.; Jones, Thomas W.

2012-01-01

Multi-core fiber (MCF) optic shape sensing offers the possibility of providing in-flight shape measurements of highly flexible aerospace structures and control surfaces for such purposes as gust load alleviation, flutter suppression, general flight control and structural health monitoring. Photogrammetric measurements of surface mounted MCF shape sensing cable can be used to quantify the MCF installation path and verify measurement methods.

Fiber distributed feedback laser

NASA Technical Reports Server (NTRS)

Elachi, C.; Evans, G. A.; Yeh, C. (Inventor)

1976-01-01

Utilizing round optical fibers as communication channels in optical communication networks presents the problem of obtaining a high efficiency coupling between the optical fiber and the laser. A laser is made an integral part of the optical fiber channel by either diffusing active material into the optical fiber or surrounding the optical fiber with the active material. Oscillation within the active medium to produce lasing action is established by grating the optical fiber so that distributed feedback occurs.

Structural Health Monitoring Using High-Density Fiber Optic Strain Sensor and Inverse Finite Element Methods

NASA Technical Reports Server (NTRS)

Vazquez, Sixto L.; Tessler, Alexander; Quach, Cuong C.; Cooper, Eric G.; Parks, Jeffrey; Spangler, Jan L.

2005-01-01

In an effort to mitigate accidents due to system and component failure, NASA s Aviation Safety has partnered with industry, academia, and other governmental organizations to develop real-time, on-board monitoring capabilities and system performance models for early detection of airframe structure degradation. NASA Langley is investigating a structural health monitoring capability that uses a distributed fiber optic strain system and an inverse finite element method for measuring and modeling structural deformations. This report describes the constituent systems that enable this structural monitoring function and discusses results from laboratory tests using the fiber strain sensor system and the inverse finite element method to demonstrate structural deformation estimation on an instrumented test article

Effect of different fibers on mechanical properties and ductility of alkali-activated slag cementitious material

NASA Astrophysics Data System (ADS)

Zhu, J.; Zheng, W. Z.; Qin, C. Z.; Xu, Z. Z.; Wu, Y. Q.

2018-01-01

The effect of different fibers on mechanical properties and ductility of alkali-activated slag cementitious material (AASCM) is studied. The research contents include: fiber type (plant fiber, polypropylene fiber), fiber content, mechanical property index, tensile stress-strain relationship curve, treating time. The test results showed that the compressive strength of two fibers reinforced AASCM was about 90 ~ 110MPa, and the tensile strength was about 3 ~ 5MPa. The reinforcement effect of polypropylene fiber is superior to that of plant fiber, and the mechanical properties of polypropylene fiber reinforced AASCM are superior to those of plant fiber, According to the comparison of SEM pictures, the plant fiber and polypropylene fiber are both closely bound with the matrix, and the transition zones are complete and close. Thus, it is proved that plant fiber and polypropylene fiber delay the crack extension and enhance the ductility of AASCM.

Active polymer materials for optical fiber CO2 sensors

NASA Astrophysics Data System (ADS)

Wysokiński, Karol; Filipowicz, Marta; Stańczyk, Tomasz; Lipiński, Stanisław; Napierała, Marek; Murawski, Michał; Nasiłowski, Tomasz

2017-04-01

CO2 optical fiber sensors based on polymer active materials are presented in this paper. Ethyl cellulose was proven to be a good candidate for a matrix material of the sensor, since it gives porous, thick and very sensitive layers. Low-cost sensors based on polymer optical fibers have been elaborated. Sensors have been examined for their sensitivity to CO2, temperature and humidity. Response time during cyclic exposures to CO2 have been also determined. Special layers exhibiting irreversible change of color during exposure to carbon dioxide have been developed. They have been verified for a possible use in smart food packaging.

Matched metal die compression molded structural random fiber sheet molding compound flywheel

DOEpatents

Kulkarni, Satish V.; Christensen, Richard M.; Toland, Richard H.

1985-01-01

A flywheel (10) is described that is useful for energy storage in a hybrid vehicle automotive power system or in some stationary applications. The flywheel (10) has a body of essentially planar isotropic high strength structural random fiber sheet molding compound (SMC-R). The flywheel (10) may be economically produced by a matched metal die compression molding process. The flywheel (10) makes energy intensive efficient use of a fiber/resin composite while having a shape designed by theory assuming planar isotropy.

High Sensitivity Refractometer Based on Reflective Smf-Small Diameter No Core Fiber Structure.

PubMed

Zhou, Guorui; Wu, Qiang; Kumar, Rahul; Ng, Wai Pang; Liu, Hao; Niu, Longfei; Lalam, Nageswara; Yuan, Xiaodong; Semenova, Yuliya; Farrell, Gerald; Yuan, Jinhui; Yu, Chongxiu; Zeng, Jie; Tian, Gui Yun; Fu, Yong Qing

2017-06-16

A high sensitivity refractive index sensor based on a single mode-small diameter no core fiber structure is proposed. In this structure, a small diameter no core fiber (SDNCF) used as a sensor probe, was fusion spliced to the end face of a traditional single mode fiber (SMF) and the end face of the SDNCF was coated with a thin film of gold to provide reflective light. The influence of SDNCF diameter and length on the refractive index sensitivity of the sensor has been investigated by both simulations and experiments, where results show that the diameter of SDNCF has significant influence. However, SDNCF length has limited influence on the sensitivity. Experimental results show that a sensitivity of 327 nm/RIU (refractive index unit) has been achieved for refractive indices ranging from 1.33 to 1.38, which agrees well with the simulated results with a sensitivity of 349.5 nm/RIU at refractive indices ranging from 1.33 to 1.38.

Multimaterial Acoustic Fibers

NASA Astrophysics Data System (ADS)

Chocat, Noemie

The emergence of multimaterial fibers that combine a multiplicity of solid materials with disparate electrical, optical, and mechanical properties into a single fiber presents new opportunities for extending fiber applications well beyond optical transmission. Fiber reflectors, thermal detectors, photodetectors, chemical sensors, surface-emitting fiber lasers, fiber diodes, and other functional fiber devices have been demonstrated with this approach. Yet, throughout this development and indeed the development of fibers in general, a key premise has remained unchanged : that fibers are essentially static devices incapable of controllably changing their properties at high frequencies. Unique opportunities would arise if a rapid, electrically-driven mechanism for changing fiber properties existed. A wide spectrum of hitherto passive fiber devices could at once become active with applications spanning electronics, mechanics, acoustics, and optics, with the benefits of large surface-area, structural robustness, and mechanical flexibility. This thesis addresses the challenges and opportunities associated with the realization of electromechanical transduction in fibers through the integration of internal piezoelectric and electrostrictive domains. The fundamental challenges related to the fabrication of piezoelectric devices in fiber form are analyzed from a materials perspective, and candidate materials and geometries are selected that are compatible with the thermal drawing process. The first realization of a thermally drawn piezoelectric fiber device is reported and its piezoelectric response is established over a wide range of frequencies. The acoustic properties of piezoelectric fiber devices are characterized and related to their mechanical and geometric properties. Collective effects in multi-fiber constructs are discussed and demonstrated by the realization of a linear phased array of piezoelectric fibers capable of acoustic beam steering. High strain actuation

From kinetic-structure analysis to engineering crystalline fiber networks in soft materials.

PubMed

Wang, Rong-Yao; Wang, Peng; Li, Jing-Liang; Yuan, Bing; Liu, Yu; Li, Li; Liu, Xiang-Yang

2013-03-07

Understanding the role of kinetics in fiber network microstructure formation is of considerable importance in engineering gel materials to achieve their optimized performances/functionalities. In this work, we present a new approach for kinetic-structure analysis for fibrous gel materials. In this method, kinetic data is acquired using a rheology technique and is analyzed in terms of an extended Dickinson model in which the scaling behaviors of dynamic rheological properties in the gelation process are taken into account. It enables us to extract the structural parameter, i.e. the fractal dimension, of a fibrous gel from the dynamic rheological measurement of the gelation process, and to establish the kinetic-structure relationship suitable for both dilute and concentrated gelling systems. In comparison to the fractal analysis method reported in a previous study, our method is advantageous due to its general validity for a wide range of fractal structures of fibrous gels, from a highly compact network of the spherulitic domains to an open fibrous network structure. With such a kinetic-structure analysis, we can gain a quantitative understanding of the role of kinetic control in engineering the microstructure of the fiber network in gel materials.

Evaluation of Ultrasonic Fiber Structure Extraction Technique Using Autopsy Specimens of Liver

NASA Astrophysics Data System (ADS)

Yamaguchi, Tadashi; Hirai, Kazuki; Yamada, Hiroyuki; Ebara, Masaaki; Hachiya, Hiroyuki

2005-06-01

It is very important to diagnose liver cirrhosis noninvasively and correctly. In our previous studies, we proposed a processing technique to detect changes in liver tissue in vivo. In this paper, we propose the evaluation of the relationship between liver disease and echo information using autopsy specimens of a human liver in vitro. It is possible to verify the function of a processing parameter clearly and to compare the processing result and the actual human liver tissue structure by in vitro experiment. In the results of our processing technique, information that did not obey a Rayleigh distribution from the echo signal of the autopsy liver specimens was extracted depending on changes in a particular processing parameter. The fiber tissue structure of the same specimen was extracted from a number of histological images of stained tissue. We constructed 3D structures using the information extracted from the echo signal and the fiber structure of the stained tissue and compared the two. By comparing the 3D structures, it is possible to evaluate the relationship between the information that does not obey a Rayleigh distribution of the echo signal and the fibrosis structure.

Loss of calretinin immunoreactive fibers in subcortical visual recipient structures of the RCS dystrophic rat.

PubMed

Vugler, Anthony A; Coffey, Peter J

2003-11-01

The retinae of dystrophic Royal College of Surgeons (RCS) rats exhibit progressive photoreceptor degeneration accompanied by pathology of ganglion cells. To date, little work has examined the consequences of retinal degeneration for central visual structures in dystrophic rats. Here, we use immunohistochemistry for calretinin (CR) to label retinal afferents in the superior colliculus (SC), lateral geniculate nucleus, and olivary pretectal nucleus of RCS rats aged between 2 and 26 months of age. Early indications of fiber loss in the medial dystrophic SC were apparent between 9 and 13 months. Quantitative methods reveal a significant reduction in the level of CR immunoreactivity in visual layers of the medial dystrophic SC at 13 months (P < 0.02). In dystrophic animals aged 19-26 months the loss of CR fibers in SC was dramatic, with well-defined patches of fiber degeneration predominating in medial aspects of the structure. This fiber degeneration in SC was accompanied by increased detection of cells immunoreactive for CR. In several animals, regions of fiber loss were also found to contain strongly parvalbumin-immunoreactive cells. Loss of CR fibers was also observed in the lateral geniculate nucleus and olivary pretectal nucleus. Patterns of fiber loss in the dystrophic SC compliment reports of ganglion cell degeneration in these animals and the response of collicular neurons to degeneration is discussed in terms of plasticity of the dystrophic visual system and properties of calcium binding proteins.

A Robust Distributed Multipoint Fiber Optic Gas Sensor System Based on AGC Amplifier Structure.

PubMed

Zhu, Cunguang; Wang, Rende; Tao, Xuechen; Wang, Guangwei; Wang, Pengpeng

2016-07-28

A harsh environment-oriented distributed multipoint fiber optic gas sensor system realized by automatic gain control (AGC) technology is proposed. To improve the photoelectric signal reliability, the electronic variable gain can be modified in real time by an AGC closed-loop feedback structure to compensate for optical transmission loss which is caused by the fiber bend loss or other reasons. The deviation of the system based on AGC structure is below 4.02% when photoelectric signal decays due to fiber bending loss for bending radius of 5 mm, which is 20 times lower than the ordinary differential system. In addition, the AGC circuit with the same electric parameters can keep the baseline intensity of signals in different channels of the distributed multipoint sensor system at the same level. This avoids repetitive calibrations and streamlines the installation process.

Prebiotics, Fermentable Dietary Fiber, and Health Claims.

PubMed

Delcour, Jan A; Aman, Per; Courtin, Christophe M; Hamaker, Bruce R; Verbeke, Kristin

2016-01-01

Since the 1970s, the positive effects of dietary fiber on health have increasingly been recognized. The collective term "dietary fiber" groups structures that have different physiologic effects. Since 1995, some dietary fibers have been denoted as prebiotics, implying a beneficial physiologic effect related to increasing numbers or activity of the gastrointestinal microbiota. Given the complex composition of the microbiota, the demonstration of such beneficial effects is difficult. In contrast, an exploration of the metabolites of dietary fiber formed as a result of its fermentation in the colon offers better perspectives for providing mechanistic links between fiber intake and health benefits. Positive outcomes of such studies hold the promise that claims describing specific health benefits can be granted. This would help bridge the "fiber gap"-that is, the considerable difference between recommended and actual fiber intakes by the average consumer. © 2016 American Society for Nutrition.

Making Plant-Support Structures From Waste Plant Fiber

NASA Technical Reports Server (NTRS)

Morrow, Robert C.; < oscjmocl. < attjew K/; {ertzbprm. A,amda; Ej (e. Cjad); Hunt, John

2006-01-01

Environmentally benign, biodegradable structures for supporting growing plants can be made in a process based on recycling of such waste plant fiber materials as wheat straw or of such derivative materials as paper and cardboard. Examples of structures that can be made in this way include plant plugs, pots, planter-lining mats, plant fences, and root and shoot barriers. No chemical binders are used in the process. First, the plant material is chopped into smaller particles. The particles are leached with water or steam to remove material that can inhibit plant growth, yielding a fibrous slurry. If the desired structures are plugs or sheets, then the slurry is formed into the desired shapes in a pulp molding subprocess. If the desired structures are root and shoot barriers, pots, or fences, then the slurry is compression-molded to the desired shapes in a heated press. The processed materials in these structures have properties similar to those of commercial pressboard, but unlike pressboard, these materials contain no additives. These structures have been found to withstand one growth cycle, even when wet

Flexible filamentous virus structure from fiber diffraction

DOE Office of Scientific and Technical Information (OSTI.GOV)

Stubbs, Gerald; Kendall, Amy; McDonald, Michele

2008-10-24

Fiber diffraction data have been obtained from Narcissus mosaic virus, a potexvirus from the family Flexiviridae, and soybean mosaic virus (SMV), a potyvirus from the family Potyviridae. Analysis of the data in conjunction with cryo-electron microscopy data allowed us to determine the symmetry of the viruses and to make reconstructions of SMV at 19 {angstrom} resolution and of another potexvirus, papaya mosaic virus, at 18 {angstrom} resolution. These data include the first well-ordered data ever obtained for the potyviruses and the best-ordered data from the potexviruses, and offer the promise of eventual high resolution structure determinations.

A Fiber Optic Doppler Sensor and Its Application in Debonding Detection for Composite Structures

PubMed Central

Li, Fucai; Murayama, Hideaki; Kageyama, Kazuro; Meng, Guang; Ohsawa, Isamu; Shirai, Takehiro

2010-01-01

Debonding is one of the most important damage forms in fiber-reinforced composite structures. This work was devoted to the debonding damage detection of lap splice joints in carbon fiber reinforced plastic (CFRP) structures, which is based on guided ultrasonic wave signals captured by using fiber optic Doppler (FOD) sensor with spiral shape. Interferometers based on two types of laser sources, namely the He-Ne laser and the infrared semiconductor laser, are proposed and compared in this study for the purpose of measuring Doppler frequency shift of the FOD sensor. Locations of the FOD sensors are optimized based on mechanical characteristics of lap splice joint. The FOD sensors are subsequently used to detect the guided ultrasonic waves propagating in the CFRP structures. By taking advantage of signal processing approaches, features of the guided wave signals can be revealed. The results demonstrate that debonding in the lap splice joint results in arrival time delay of the first package in the guided wave signals, which can be the characteristic for debonding damage inspection and damage extent estimation. PMID:22219698

A fiber optic Doppler sensor and its application in debonding detection for composite structures.

PubMed

Li, Fucai; Murayama, Hideaki; Kageyama, Kazuro; Meng, Guang; Ohsawa, Isamu; Shirai, Takehiro

2010-01-01

Debonding is one of the most important damage forms in fiber-reinforced composite structures. This work was devoted to the debonding damage detection of lap splice joints in carbon fiber reinforced plastic (CFRP) structures, which is based on guided ultrasonic wave signals captured by using fiber optic Doppler (FOD) sensor with spiral shape. Interferometers based on two types of laser sources, namely the He-Ne laser and the infrared semiconductor laser, are proposed and compared in this study for the purpose of measuring Doppler frequency shift of the FOD sensor. Locations of the FOD sensors are optimized based on mechanical characteristics of lap splice joint. The FOD sensors are subsequently used to detect the guided ultrasonic waves propagating in the CFRP structures. By taking advantage of signal processing approaches, features of the guided wave signals can be revealed. The results demonstrate that debonding in the lap splice joint results in arrival time delay of the first package in the guided wave signals, which can be the characteristic for debonding damage inspection and damage extent estimation.

Groove micro-structure optical fiber refractive index sensor with nanoscale gold film based on surface plasmon resonance

NASA Astrophysics Data System (ADS)

Zhang, Zhen; Li, Shuguang; Liu, Qiang; Feng, Xinxing; Zhang, Shuhuan; Wang, Yujun; Wu, Junjun

2018-07-01

A groove micro-structure optical fiber refractive index sensor with nanoscale gold film based on surface plasmon resonance (SPR) is proposed and analyzed by the finite element method (FEM). Numerical results show that the average sensitivity is 15,933 nm/refractive index unit (RIU) with the refractive index of analyte ranging from 1.40 to 1.43 and the maximum sensitivity is 28,600 nm/RIU and the resolution of the sensor is 3.50 × 10-8 RIU. The groove micro-structure optical fiber refractive index sensor do some changes on the D-shaped fiber sensor, compared with conventional D-shaped fiber sensor, it has a higher sensitivity and it is easier to produce than the traditional SPR sensor.

Biomimetic Branched Hollow Fibers Templated by Self-assembled Fibrous Polyvinylpyrrolidone (PVP) Structures in Aqueous Solution

PubMed Central

Qiu, Penghe; Mao, Chuanbin

2010-01-01

Branched hollow fibers are common in nature, but to form artificial fibers with a similar branched hollow structure is still a challenge. We discovered that polyvinylpyrrolidone (PVP) could self-assemble into branched hollow fibers in an aqueous solution after aging the PVP solution for about two weeks. Based on this finding, we demonstrated two approaches by which the self-assembly of PVP into branched hollow fibers could be exploited to template the formation of branched hollow inorganic fibers. First, inorganic material such as silica with high affinity against the PVP could be deposited on the surface of the branched hollow PVP fibers to form branched hollow silica fibers. To extend the application of PVP self-assembly in templating the formation of hollow branched fibers, we then adopted a second approach where the PVP molecules bound to inorganic nanoparticles (using gold nanoparticles as a model) co-self-assemble with the free PVP molecules in an aqueous solution, resulting in the formation of the branched hollow fibers with the nanoparticles embedded in the PVP matrix constituting the walls of the fibers. Heating the resultant fibers above the glass transition temperature of PVP led to the formation of branched hollow gold fibers. Our work suggests that the self-assembly of the PVP molecules in the solution can serve as a general method for directing the formation of branched hollow inorganic fibers. The branched hollow fibers may find potential applications in microfluidics, artificial blood vessel generation, and tissue engineering. PMID:20158250

Stiffness and force in activated frog skeletal muscle fibers.

PubMed Central

Cecchi, G.; Griffiths, P. J.; Taylor, S.

1986-01-01

cross-bridge model of force generation proposed by Huxley, A. F., and R. M. Simmons (1971, Nature (Lond.), 213:533-538). However, stiffness in short fibers developed markedly faster than force during the tetanus rise. Thus our findings show the presence of one or more noteworthy cross-bridge states at the onset and during the rise of active tension towards a plateau in that attachment apparently is followed by a relatively long delay before force generation occurs. A set of equations is given in the Appendix that describes the frequency dependence of the applied sinusoid and its response. This model predicts that frequency dependent changes can be used as a measure of a change in stiffness. PMID:3955178

A Novel Optical Fiber Sensor for Steel Corrosion in Concrete Structures.

PubMed

Leung, Christopher K Y; Wan, Kai Tai; Chen, Liquan

2008-03-20

Steel corrosion resulting from the penetration of chloride ions or carbon dioxide is a major cause of degradation for reinforced concrete structures,. The objective of the present investigation was to develop a low-cost sensor for steel corrosion, which is based on a very simple physical principle. The flat end of a cut optical fiber is coated with an iron thin film using the ion sputtering technique. Light is then sent into a fiber embedded in concrete and the reflected signal is monitored. Initially, most of the light is reflected by the iron layer. When corrosion occurs to remove the iron layer, a significant portion of the light power will leave the fiber at its exposed end, and the reflected power is greatly reduced. Monitoring of the reflected signal is hence an effective way to assess if the concrete environment at the location of the fiber tip may induce steel corrosion or not. In this paper, first the principle of the corrosion sensor and its fabrication are described. The sensing principle is then verified by experimental results. Sensor packaging for practical installation will be presented and the performance of the packaged sensors is assessed by additional experiments.

A Novel Optical Fiber Sensor for Steel Corrosion in Concrete Structures

PubMed Central

Leung, Christopher K.Y.; Wan, Kai Tai; Chen, Liquan

2008-01-01

Steel corrosion resulting from the penetration of chloride ions or carbon dioxide is a major cause of degradation for reinforced concrete structures,. The objective of the present investigation was to develop a low-cost sensor for steel corrosion, which is based on a very simple physical principle. The flat end of a cut optical fiber is coated with an iron thin film using the ion sputtering technique. Light is then sent into a fiber embedded in concrete and the reflected signal is monitored. Initially, most of the light is reflected by the iron layer. When corrosion occurs to remove the iron layer, a significant portion of the light power will leave the fiber at its exposed end, and the reflected power is greatly reduced. Monitoring of the reflected signal is hence an effective way to assess if the concrete environment at the location of the fiber tip may induce steel corrosion or not. In this paper, first the principle of the corrosion sensor and its fabrication are described. The sensing principle is then verified by experimental results. Sensor packaging for practical installation will be presented and the performance of the packaged sensors is assessed by additional experiments. PMID:27879805

Application of smart BFRP bars with distributed fiber optic sensors into concrete structures

NASA Astrophysics Data System (ADS)

Tang, Yongsheng; Wu, Zhishen; Yang, Caiqian; Wu, Gang; Zhao, Lihua; Song, Shiwei

2010-04-01

In this paper, the self-sensing and mechanical properties of concrete structures strengthened with a novel type of smart basalt fiber reinforced polymer (BFRP) bars were experimentally studied, wherein the sensing element is Brillouin scattering-based distributed optical fiber sensing technique. First, one of the smart bars was applied to strengthen a 2m concrete beam under a 4-points static loading manner in the laboratory. During the experiment, the bar can measure the inner strain changes and monitor the randomly distributed cracks well. With the distributed strain information along the bar, the distributed deformation of the beam can be calculated, and the structural health can be monitored and evaluated as well. Then, two smart bars with a length of about 70m were embedded into a concrete airfield pavement reinforced by long BFRP bars. In the field test, all the optical fiber sensors in the smart bars survived the whole concrete casting process and worked well. From the measured data, the concrete cracks along the pavement length can be easily monitored. The experimental results also confirmed that the bars can strengthen the structures especially after the yielding of steel bars. All the results confirm that this new type of smart BFRP bars show not only good sensing performance but also mechanical performance in the concrete structures.

Innovative design of composite structures: Design, manufacturing, and testing of plates utilizing curvilinear fiber trajectories

NASA Technical Reports Server (NTRS)

Hyer, M. W.; Rust, R. J.; Waters, W. A., Jr.

1994-01-01

As a means of improving structural design, the concept of fabricating flat plates containing holes by incorporating curvilinear fiber trajectories to transmit loads around the hole is studied. In the present discussion this concept is viewed from a structural level, where access holes, windows, doors, and other openings are of significant size. This is opposed to holes sized for mechanical fasteners. Instead of cutting the important load-bearing fibers at the hole edge, as a conventional straightline design does, the curvilinear design preserves the load-bearing fibers by orienting them in smooth trajectories around the holes, their loading not ending abruptly at the hole edge. Though the concept of curvilinear fiber trajectories has been studied before, attempts to manufacture and test such plates have been limited. This report describes a cooperative effort between Cincinnati Milacron Inc., NASA Langley Research Center, and Virginia Polytechnic Institute and State University to design, manufacture, and test plates using the curvilinear fiber trajectory concept. The paper discusses details of the plate design, details of the manufacturing, and a summary of results from testing the plates with inplane compressive buckling loads and tensile loads. Comparisons between the curvilinear and conventional straightline fiber designs based on measurements and observation are made. Failure modes, failure loads, strains, deflections, and other key responses are compared.

A new strategy toward Internet of Things: structural health monitoring using a combined fiber optic and acoustic emission wireless sensor platform

NASA Astrophysics Data System (ADS)

Nguyen, A. D.; Page, C.; Wilson, C. L.

2016-04-01

This paper investigates a new low-power structural health monitoring (SHM) strategy where fiber Bragg grating (FBG) rosettes can be used to continuously monitor for changes in a host structure's principal strain direction, suggesting damage and thus enabling the immediate triggering of a higher power acoustic emissions (AE) sensor to provide for better characterization of the damage. Unlike traditional "always on" AE platforms, this strategy has the potential for low power, while the wireless communication between different sensor types supports the Internet of Things (IoT) approach. A combination of fiber-optic sensor rosettes for strain monitoring and a fiber-optic sensor for acoustic emissions monitoring was attached to a sample and used to monitor crack initiation. The results suggest that passive principal strain direction monitoring could be used as a damage initiation trigger for other active sensing elements such as acoustic emissions. In future work, additional AE sensors can be added to provide for damage location; and a strategy where these sensors can be powered on periodically to further establish reliability while preserving an energy efficient scheme can be incorporated.

High sensitivity cascaded preamplifier with an optical bridge structure in Brillouin distributed fiber sensing system

NASA Astrophysics Data System (ADS)

Bi, Weihong; Lin, Hang; Fu, Xinghu; Fu, Guangwei

2013-12-01

Fiber amplifiers such as Erbium-doped fiber amplifier (EDFA) played a key role in developing long-haul transmission system and have been an important element for enabling the development of optical communication system. EDFA amplifies the optical signal directly, without the optical-electric-optical switch and has the advantages such as high gain, broad band, low noise figure. It is widely used in repeaterless submarine system, smart grid and community antenna television system. This article describe the application of optical-fiber amplifiers in distributed optical fiber sensing system, focusing on erbium-doped fiber preamplifiers in modern transmission optical systems. To enhance the measurement range of a spontaneous Brillouin intensity based distributed fiber optical sensor and improve the receiver sensitivity, a two cascaded EDFAs C-band preamplifier with an optical bridge structure is proposed in this paper. The first cascaded EDFA is consisted of a length of 4.3m erbium-doped fiber and pumped in a forward pump light using a laser operating at 975nm. The second one made by using a length of 16m erbium-doped fiber is pumped in a forward pump light which is the remnant pump light of the first cascaded EDFA. At the preamplifier output, DWDM, centered at the signal wavelength, is used to suppress unwanted amplified spontaneous emission. The experimental results show that the two cascade preamplifier with a bridge structure can be used to amplify for input Brillouin backscattering light greater than about -43dBm. The optical gain is characterized and more than 26dB is obtained at 1549.50nm with 300mW pump power.

Fiber optic strain measurements using an optically-active polymer

NASA Astrophysics Data System (ADS)

Buckley, Leonard J.; Neumeister, Gary C.

1992-03-01

A study encompassing the use of an optically-active polymer as the strain-sensing medium in an organic matrix composite was performed. Several compounds were synthesized for use as the inner cladding material for silica fiber-optic cores. These materials include a diacetylene containing polyamide. It is possible to dynamically modify the optical properties of these materials through changes in applied strain or temperature. By doing so the characteristic absorption in the visible is reversibly shifted to a higher energy state. The polymer-coated fiber-optic cores were initially studied in epoxy resin. Additionally, one of the polyamide/diacetylene polymers was studied in a spin-fiber form consisting of 15 micron filaments assembled in multifilament tows. The most promising configuration and materials were then investigated further by embedding in graphite/epoxy composite laminates. In each case the shift in the visible absorption peak was monitored as a function of applied mechanical strain.

Experimental and Numerical Evaluation of the Mechanical Behavior of Strongly Anisotropic Light-Weight Metallic Fiber Structures under Static and Dynamic Compressive Loading

PubMed Central

Andersen, Olaf; Vesenjak, Matej; Fiedler, Thomas; Jehring, Ulrike; Krstulović-Opara, Lovre

2016-01-01

Rigid metallic fiber structures made from a variety of different metals and alloys have been investigated mainly with regard to their functional properties such as heat transfer, pressure drop, or filtration characteristics. With the recent advent of aluminum and magnesium-based fiber structures, the application of such structures in light-weight crash absorbers has become conceivable. The present paper therefore elucidates the mechanical behavior of rigid sintered fiber structures under quasi-static and dynamic loading. Special attention is paid to the strongly anisotropic properties observed for different directions of loading in relation to the main fiber orientation. Basically, the structures show an orthotropic behavior; however, a finite thickness of the fiber slabs results in moderate deviations from a purely orthotropic behavior. The morphology of the tested specimens is examined by computed tomography, and experimental results for different directions of loading as well as different relative densities are presented. Numerical calculations were carried out using real structural data derived from the computed tomography data. Depending on the direction of loading, the fiber structures show a distinctively different deformation behavior both experimentally and numerically. Based on these results, the prevalent modes of deformation are discussed and a first comparison with an established polymer foam and an assessment of the applicability of aluminum fiber structures in crash protection devices is attempted. PMID:28773522

Experimental and Numerical Evaluation of the Mechanical Behavior of Strongly Anisotropic Light-Weight Metallic Fiber Structures under Static and Dynamic Compressive Loading.

PubMed

Andersen, Olaf; Vesenjak, Matej; Fiedler, Thomas; Jehring, Ulrike; Krstulović-Opara, Lovre

2016-05-21

Rigid metallic fiber structures made from a variety of different metals and alloys have been investigated mainly with regard to their functional properties such as heat transfer, pressure drop, or filtration characteristics. With the recent advent of aluminum and magnesium-based fiber structures, the application of such structures in light-weight crash absorbers has become conceivable. The present paper therefore elucidates the mechanical behavior of rigid sintered fiber structures under quasi-static and dynamic loading. Special attention is paid to the strongly anisotropic properties observed for different directions of loading in relation to the main fiber orientation. Basically, the structures show an orthotropic behavior; however, a finite thickness of the fiber slabs results in moderate deviations from a purely orthotropic behavior. The morphology of the tested specimens is examined by computed tomography, and experimental results for different directions of loading as well as different relative densities are presented. Numerical calculations were carried out using real structural data derived from the computed tomography data. Depending on the direction of loading, the fiber structures show a distinctively different deformation behavior both experimentally and numerically. Based on these results, the prevalent modes of deformation are discussed and a first comparison with an established polymer foam and an assessment of the applicability of aluminum fiber structures in crash protection devices is attempted.

Drawing dependent structures, mechanical properties and cyclization behaviors of polyacrylonitrile and polyacrylonitrile/carbon nanotube composite fibers prepared by plasticized spinning.

PubMed

Li, Xiang; Qin, Aiwen; Zhao, Xinzhen; Liu, Dapeng; Wang, Haiye; He, Chunju

2015-09-14

Drawing to change the structural properties and cyclization behaviors of the polyacrylonitrile (PAN) chains in crystalline and amorphous regions is carried out on PAN and PAN/carbon nanotube (CNT) composite fibers. Various characterization methods including Fourier transform infrared spectroscopy, differential scanning calorimetry, X-ray diffraction and thermal gravimetric analysis are used to monitor the structural evolution and cyclization behaviors of the fibers. With an increase of the draw ratio during the plasticized spinning process, the structural parameters of the fibers, i.e. crystallinity and planar zigzag conformation, are decreased at first, and then increased, which are associated with the heat exchange rate and the oriented-crystallization rate. A possible mechanism for plasticized spinning is proposed to explain the changing trends of crystallinity and planar zigzag conformation. PAN and PAN/CNT fibers exhibit various cyclization behaviors induced by drawing, e.g., the initiation temperature for the cyclization (Ti) of PAN fibers is increased with increasing draw ratio, while Ti of PAN/CNT fibers is decreased. Drawing also facilitates cyclization and lowers the percentage of β-amino nitrile for PAN/CNT fibers during the stabilization.

A novel fiber optic Fabry-Perot structure with a micrometric diameter tip

NASA Astrophysics Data System (ADS)

Wang, Xingwei; Xu, Juncheng; Wang, Zhuang; Cooper, Kristie L.; Wang, Anbo

2006-08-01

This paper presents a novel fiber optic Fabry-Perot (FP) structure with a micrometric diameter tip. The fabrication of micro scale probes has become essential in intracellular surgery, in cell sensing, manipulation, and injection. It is of great importance in many fields, such as genetics, pathology, criminology, pharmacogenetics, and food safety. With such a tiny protrusion, the sensor can be inserted into micron size cells, say, for DNA analysis. With the FP cavity inside the fiber, the change of optical path difference (OPD) caused by the environment can be demodulated. In addition, the structure is intrinsically capable of temperature compensation. What's more, it is simple, cost-efficient, and compact. Last but not the least, the structure shows promise for nanometric protrusion. Once this goal is achieved, the sensor can be inserted into most cells. The sensor could pave the way for faster, more accurate medical diagnostic tests for countless conditions and may ultimately save lives by allowing earlier disease detection and intervention.

Piezoelectric Micro- and Nanostructured Fibers Fabricated from Thermoplastic Nanocomposites Using a Fiber Drawing Technique: Comparative Study and Potential Applications.

PubMed

Lu, Xin; Qu, Hang; Skorobogatiy, Maksim

2017-02-28

We report an all-polymer flexible piezoelectric fiber that uses both judiciously chosen geometry and advanced materials in order to enhance fiber piezoelectric response. The microstructured/nanostructured fiber features a soft hollow polycarbonate core surrounded by a spiral multilayer cladding consisting of alternating layers of piezoelectric nanocomposites (polyvinylidene enhanced with BaTiO 3 , PZT, or CNT) and conductive polymer (carbon-filled polyethylene). The conductive polymer layers serve as two electrodes, and they also form two spatially offset electric connectors on the fiber surface designed for the ease of connectorization. Kilometer-long piezoelectric fibers of sub-millimeter diameters are thermally drawn from a macroscopic preform. The fibers exhibit high output voltage of up to 6 V under moderate bending, and they show excellent mechanical and electrical durability in a cyclic bend-release test. The micron/nanosize multilayer structure enhances in-fiber poling efficiency due to the small distance between the conducting electrodes sandwiching the piezoelectric composite layers. Additionally, the spiral structure greatly increases the active area of the piezoelectric composite, thus promoting higher voltage generation and resulting in 10-100 higher power generation efficiency over the existing piezoelectric cables. Finally, we weave the fabricated piezoelectric fibers into technical textiles and demonstrate their potential applications in power generation when used as a sound detector, smart car seat upholstery, or wearable materials.

Development of Active Microwave Thermography for Structural Health Monitoring

NASA Astrophysics Data System (ADS)

Foudazi, Ali

Active Microwave Thermography (AMT) is an integrated nondestructive testing and evaluation (NDT&E) method that incorporates aspects of microwave NDT and thermography techniques. AMT uses a microwave excitation to generate heat and the surface thermal profile of the material or structure under test is subsequently measured using a thermal camera (or IR camera). Utilizing a microwave heat excitation provides advantages over traditional thermal excitations (heat lamps, etc.) including the potential for non-contact, selective and focused heating. During an AMT inspection, two heating mechanisms are possible, referred to as dielectric and induction heating. Dielectric heating occurs as a result of the interaction of microwave energy with lossy dielectric materials which results in dissipated microwave energy and a subsequent increase in temperature. Induction heating is a result of induced surface current on conductive materials with finite conductivity under microwave illumination and subsequently ohmic loss. Due to the unique properties of microwave signals including frequency of operation, power level, and polarization, as well as their interaction with different materials, AMT has strong potential for application in various industries including infrastructure, transportation, aerospace, etc. As such, this Dissertation explores the application of AMT to NDT&E needs in these important industries, including detection and evaluation of defects in single- or multi-layered fiber-reinforced polymer-strengthened cement-based materials, evaluation of steel fiber percentage and distributions in steel fiber reinforced structures, characterization of corrosion ratio on corroded reinforcing steel bars (rebar), and evaluation of covered surface cracks orientation and size in metal structures.

NDE of Fiber Reinforced Foam Composite Structures for Future Aerospace Vehicles

NASA Technical Reports Server (NTRS)

Walker, james; Roth, Don; Hopkins, Dale

2010-01-01

This slide presentation reviews the complexities of non-destructive evaluation (NDE) of fiber reinforced foam composite structures to be used for aerospace vehicles in the future.Various views of fiber reinforced foam materials are shown and described. Conventional methods of NDE for composites are reviewed such as Micro-computed X-Ray Tomography, Thermography, Shearography, and Phased Array Ultrasonics (PAUT). These meth0ods appear to work well on the face sheet and face sheet ot core bond, they do not provide adequate coverage for the webs. There is a need for additional methods that will examine the webs and web to foam core bond.

Fiber stress values for design of glulam timber utility structures

Treesearch

R. Hernandez; R. C. Moody; R. H. Falk

In this study, we developed a simple equation to calculate average fiber stress values for design of glued-laminated (glulam) timber utility structures as a function of design bending stress. We took design stress in bending values specified by the American Institute of Timber Construction (AITC) for various combinations of glulam timber, applied appropriate end-use...

Natural Fiber Composite Retting, Preform Manufacture and Molding (Project 18988/Agreement 16313)

DOE Office of Scientific and Technical Information (OSTI.GOV)

Simmons, Kevin L.; Howe, Daniel T.; Laddha, Sachin

2009-12-31

Plant-based natural fibers can be used in place of glass in fiber reinforced automotive composites to reduce weight, cost and provide environmental benefits. Current automotive applications use natural fibers in injection molded thermoplastics for interior, non-structural applications. Compression molded natural fiber reinforced thermosets have the opportunity to extend natural fiber composite applications to structural and semi-structural parts and exterior parts realizing further vehicle weight savings. The development of low cost molding and fiber processing techniques for large volumes of natural fibers has helped in understanding the barriers of non-aqueous retting. The retting process has a significant effect on the fibermore » quality and its processing ability that is related to the natural fiber composite mechanical properties. PNNL has developed a compression molded fiber reinforced composite system of which is the basis for future preforming activities and fiber treatment. We are using this process to develop preforming techniques and to validate fiber treatment methods relative to OEM provided application specifications. It is anticipated for next fiscal year that demonstration of larger quantities of SMC materials and molding of larger, more complex components with a more complete testing regimen in coordination with Tier suppliers under OEM guidance.« less

Active and passive interaction mechanism of smart materials for health monitoring of engineering structures: a review

NASA Astrophysics Data System (ADS)

Annamdas, Venu Gopal Madhav; Annamdas, Kiran Kumar

2009-03-01

Smart materials when interact with engineering structures, should have the capability to sense, measure, process, and detect any change in the selected variables (stress, damage) at critical locations. These smart materials can be classified into active and passive depending on the type of the structure, variables to be monitored, and interaction mechanism due to surface bonding or embedment. Some of the prominent smart materials are piezoelectric materials, micro fiber composite, polymers, shape memory alloys, electrostrictive and magnetostrictive materials, electrorheological and magnetorheological fluids and fiber optics. In addition, host structures do have the properties to support or repel the usage of smart materials inside or on it. This paper presents some of the most widely used smart materials and their interaction mechanism for structural health monitoring of engineering structures.

Structural dynamics of the skeletal muscle fiber by second harmonic generation

NASA Astrophysics Data System (ADS)

Nucciotti, V.; Stringari, C.; Sacconi, L.; Vanzi, F.; Linari, M.; Piazzesi, G.; Lombardi, V.; Pavone, F. S.

2008-02-01

The high degree of structural order in skeletal muscle allows imaging of this tissue by Second Harmonic Generation (SHG). As previously found (Vanzi et al., J. Muscle Cell Res. Motil. 2006) by fractional extraction of proteins, myosin is the source of SHG signal. A full characterization of the polarization-dependence of the SHG signal can provide very selective information on the orientation of the emitting proteins and their dynamics during contraction. We developed a line scan polarization method, allowing measurements of a full polarization curve in intact muscle fibers from skeletal muscle of the frog to characterize the SHG polarization dependence on different physiological states (resting, rigor and isometric tetanic contraction). The polarization data have been interpreted by means of a model in terms of the average orientation of SHG emitters.The different physiological states are characterized by distinct patterns of SHG polarization. The variation of the orientation of emitting molecules in relation to the physiological state of the muscle demonstrates that one part of SHG signal arises from the globular head of the myosin molecule that cross-links actin and myosin filaments. The dependence of the SHG modulation on the degree of overlap between actin and myosin filaments during an isometric contraction, provides the constraints to estimate the fraction of myosin heads generating the isometric force in the active muscle fiber.

Thermal oxidation induced degradation of carbon fiber reinforced composites and carbon nanotube sheet enhanced fiber/matrix interface for high temperature aerospace structural applications

NASA Astrophysics Data System (ADS)

Haque, Mohammad Hamidul

Recent increase in the use of carbon fiber reinforced polymer matrix composite, especially for high temperature applications in aerospace primary and secondary structures along with wind energy and automotive industries, have generated new challenges to predict its failure mechanisms and service life. This dissertation reports the experimental study of a unidirectional carbon fiber reinforced bismaleimide (BMI) composites (CFRC), an excellent candidate for high temperature aerospace components, undergoing thermal oxidation at 260 °C in air for over 3000 hours. The key focus of the work is to investigate the mechanical properties of the carbon fiber BMI composite subjected to thermal aging in three key aspects - first, studying its bulk flexural properties (in macro scale), second, characterizing the crack propagation along the fiber direction, representing the interfacial bonding strength between fiber and matrix (in micro scale), and third, introducing nano-structured materials to modify the interface (in nano scale) between the carbon fiber and BMI resin and mechanical characterization to study its influence on mitigating the aging effect. Under the first category, weight loss and flexural properties have been monitored as the oxidation propagates through the fiber/matrix interface. Dynamic mechanical analysis and micro-computed tomography analysis have been performed to analyze the aging effects. In the second category, the long-term effects of thermal oxidation on the delamination (between the composite plies) and debonding (between fiber and matrix) type fracture toughness have been characterized by preparing two distinct types of double cantilever beam specimens. Digital image correlation has been used to determine the deformation field and strain distribution around the crack propagation path. Finally the resin system and the fiber/matrix interface have been modified using nanomaterials to mitigate the degradations caused by oxidation. Nanoclay modified

Application of fiber-reinforced bismaleimide materials to aircraft nacelle structures

NASA Technical Reports Server (NTRS)

Peros, Vasilios; Ruth, John; Trawinski, David

1992-01-01

Existing aircraft engine nacelle structures employ advanced composite materials to reduce weight and thereby increase overall performance. Use of advanced composite materials on existing aircraft nacelle structures includes fiber-reinforced epoxy structures and has typically been limited to regions furthest away from the hot engine core. Portions of the nacelle structure that are closer to the engine require materials with a higher temperature capability. In these portions, existing nacelle structures employ aluminum sandwich construction and skin/stringer construction. The aluminum structure is composed of many detail parts and assemblies and is usually protected by some form of ablative, insulator, or metallic thermal shield. A one-piece composite inner cowl for a new-generation engine nacelle structure has been designed using fiber-reinforced bismaleimide (BMI) materials and honeycomb core in a sandwich construction. The new composite design has many advantages over the existing aluminum structure. Multiple details were integrated into the one-piece composite design, thereby significantly reducing the number of detail parts and fasteners. The use of lightweight materials and the reduction of the number of joints result in a significant weight reduction over the aluminum design; manufacturing labor and the overall number of tools required have also been reduced. Several significant technical issues were addressed in the development of a BMI composite design. Technical evaluation of the available BMI systems led to the selection of a toughened BMI material which was resistant to microcracking under thermal cyclic loading and enhanced the damage tolerance of the structure. Technical evaluation of the degradation of BMI materials in contact with aluminum and other metals validated methods for isolation of the various materials. Graphite-reinforced BMI in contact with aluminum and some steels was found to degrade in salt spray testing. Isolation techniques such as

Spinning, structure and properties of PP/CNTs and PP/carbon black composite fibers

NASA Astrophysics Data System (ADS)

Marcincin, A.; Hricova, M.; Ujhelyiova, A.

2014-08-01

In this paper, the effect of the compatibilisers-dispersants and other nanofillers on melt spinning of the polypropylene (PP) composites, containing carbon nanotubes (CNTs), and carbon black pigment (CBP) has been investigated. Further, the structure and selected properties of composite fibers, such as mechanical and electrical have been studied. The results revealed, that percolation threshold for PP/CBP composite fibres was situated within the concentration of 15 - 20 wt%, what is several times higher than for PP/CNTs fibers.

Use it or Lose It: Tonic Activity of Slow Motoneurons Promotes Their Survival and Preferentially Increases Slow Fiber-Type Groupings in Muscles of Old Lifelong Recreational Sportsmen

PubMed Central

Mosole, Simone; Carraro, Ugo; Kern, Helmut; Loefler, Stefan; Zampieri, Sandra

2016-01-01

Histochemistry, immuno-histochemistry, gel electrophoresis of single muscle fibers and electromyography of aging muscles and nerves suggest that: i) denervation contributes to muscle atrophy, ii) impaired mobility accelerates the process, and iii) lifelong running protects against loss of motor units. Recent corroborating results on the muscle effects of Functional Electrical Stimulation (FES) of aged muscles will be also mentioned, but we will in particular discuss how and why a lifelong increased physical activity sustains reinnervation of muscle fibers. By analyzing distribution and density of muscle fibers co-expressing fast and slow Myosin Heavy Chains (MHC) we are able to distinguish the transforming muscle fibers due to activity related plasticity, to those that adapt muscle fiber properties to denervation and reinnervation. In muscle biopsies from septuagenarians with a history of lifelong high-level recreational activity we recently observed in comparison to sedentary seniors: 1. decreased proportion of small-size angular myofibers (denervated muscle fibers); 2. considerable increase of fiber-type groupings of the slow type (reinnervated muscle fibers); 3. sparse presence of muscle fibers co-expressing fast and slow MHC. Immuno-histochemical characteristics fluctuate from those with scarce fiber-type modulation and groupings to almost complete transformed muscles, going through a process in which isolated fibers co-expressing fast and slow MHC fill the gaps among fiber groupings. Data suggest that lifelong high-level exercise allows the body to adapt to the consequences of the age-related denervation and that it preserves muscle structure and function by saving otherwise lost muscle fibers through recruitment to different slow motor units. This is an opposite behavior of that described in long term denervated or resting muscles. These effects of lifelong high level activity seems to act primarily on motor neurons, in particular on those always more active

Use it or Lose It: Tonic Activity of Slow Motoneurons Promotes Their Survival and Preferentially Increases Slow Fiber-Type Groupings in Muscles of Old Lifelong Recreational Sportsmen.

PubMed

Mosole, Simone; Carraro, Ugo; Kern, Helmut; Loefler, Stefan; Zampieri, Sandra

2016-09-15

Histochemistry, immuno-histochemistry, gel electrophoresis of single muscle fibers and electromyography of aging muscles and nerves suggest that: i) denervation contributes to muscle atrophy, ii) impaired mobility accelerates the process, and iii) lifelong running protects against loss of motor units. Recent corroborating results on the muscle effects of Functional Electrical Stimulation (FES) of aged muscles will be also mentioned, but we will in particular discuss how and why a lifelong increased physical activity sustains reinnervation of muscle fibers. By analyzing distribution and density of muscle fibers co-expressing fast and slow Myosin Heavy Chains (MHC) we are able to distinguish the transforming muscle fibers due to activity related plasticity, to those that adapt muscle fiber properties to denervation and reinnervation. In muscle biopsies from septuagenarians with a history of lifelong high-level recreational activity we recently observed in comparison to sedentary seniors: 1. decreased proportion of small-size angular myofibers (denervated muscle fibers); 2. considerable increase of fiber-type groupings of the slow type (reinnervated muscle fibers); 3. sparse presence of muscle fibers co-expressing fast and slow MHC. Immuno-histochemical characteristics fluctuate from those with scarce fiber-type modulation and groupings to almost complete transformed muscles, going through a process in which isolated fibers co-expressing fast and slow MHC fill the gaps among fiber groupings. Data suggest that lifelong high-level exercise allows the body to adapt to the consequences of the age-related denervation and that it preserves muscle structure and function by saving otherwise lost muscle fibers through recruitment to different slow motor units. This is an opposite behavior of that described in long term denervated or resting muscles. These effects of lifelong high level activity seems to act primarily on motor neurons, in particular on those always more active

From single fiber to macro-level mechanics: A structural finite-element model for elastomeric fibrous biomaterials

PubMed Central

D'Amore, Antonio; Amoroso, Nicholas; Gottardi, Riccardo; Hobson, Christopher; Carruthers, Christopher; Watkins, Simon; Wagner, William R.; Sacks, Michael S.

2014-01-01

In the present work, we demonstrate that the mesoscopic in-plane mechanical behavior of membrane elastomeric scaffolds can be simulated by replication of actual quantified fibrous geometries. Elastomeric electrospun polyurethane (ES-PEUU) scaffolds, with and without particulate inclusions, were utilized. Simulations were developed from experimentally-derived fiber network geometries, based on a range of scaffold isotropic and anisotropic behaviors. These were chosen to evaluate the effects on macro-mechanics based on measurable geometric parameters such as fiber intersections, connectivity, orientation, and diameter. Simulations were conducted with only the fiber material model parameters adjusted to match the macro-level mechanical test data. Fiber model validation was performed at the microscopic level by individual fiber mechanical tests using AFM. Results demonstrated very good agreement to the experimental data, and revealed the formation of extended preferential fiber orientations spanning the entire model space. We speculate that these emergent structures may be responsible for the tissue-like macroscale behaviors observed in electrospun scaffolds. To conclude, the modeling approach has implications for (1) gaining insight on the intricate relationship between fabrication variables, structure, and mechanics to manufacture more functional devices/materials, (2) elucidating the effects of cell or particulate inclusions on global construct mechanics, and (3) fabricating better performing tissue surrogates that could recapitulate native tissue mechanics. PMID:25128869

Development of eddy current probe for fiber orientation assessment in carbon fiber composites

NASA Astrophysics Data System (ADS)

Wincheski, Russell A.; Zhao, Selina

2018-04-01

Measurement of the fiber orientation in a carbon fiber composite material is crucial in understanding the load carrying capability of the structure. As manufacturing conditions including resin flow and molding pressures can alter fiber orientation, verification of the as-designed fiber layup is necessary to ensure optimal performance of the structure. In this work, the development of an eddy current probe and data processing technique for analysis of fiber orientation in carbon fiber composites is presented. A proposed directional eddy current probe is modeled and its response to an anisotropic multi-layer conductor simulated. The modeling results are then used to finalize specifications of the eddy current probe. Experimental testing of the fabricated probe is presented for several samples including a truncated pyramid part with complex fiber orientation draped to the geometry for resin transfer molding. The inductively coupled single sided measurement enables fiber orientation characterization through the thickness of the part. The fast and cost-effective technique can be applied as a spot check or as a surface map of the fiber orientations across the structure. This paper will detail the results of the probe design, computer simulations, and experimental results.

Physico-chemical studies of hardened cement paste structure with micro-reinforcing fibers

DOE Office of Scientific and Technical Information (OSTI.GOV)

Steshenko, Aleksei, E-mail: steshenko.alexey@gmail.com; Kudyakov, Aleksander; Konusheva, Viktoriya

The results of physico-chemical studies of modified hardened cement paste with micro-reinforcing fibers are given in this article. The goal was to study the reasons of the increase of strength properties of modified hardened cement paste by the method of X-ray diffraction and electron microscopy. It is shown that the use of mineral fibers in the production of cement based material has positive effect on its properties. The study found out that the increase in the strength of the hardened cement paste with micro-reinforcing fibers is due to the increase of the rate of hydration of cement without a significantmore » change in the phase composition in comparison with hardened cement paste without additive. The results of microstructure investigation (of control samples and samples of the reinforced hardened cement paste) have shown that introduction of mineral fibers in the amount of 0.1-2 % by weight of cement provides the structure of the homogeneous microporous material with uniform distribution of the crystalline phase provided by densely packed hydrates.« less

Hierarchical structural health monitoring system combining a fiber optic spinal cord network and distributed nerve cell devices

NASA Astrophysics Data System (ADS)

Minakuchi, Shu; Tsukamoto, Haruka; Takeda, Nobuo

2009-03-01

This study proposes novel hierarchical sensing concept for detecting damages in composite structures. In the hierarchical system, numerous three-dimensionally structured sensor devices are distributed throughout the whole structural area and connected with the optical fiber network through transducing mechanisms. The distributed "sensory nerve cell" devices detect the damage, and the fiber optic "spinal cord" network gathers damage signals and transmits the information to a measuring instrument. This study began by discussing the basic concept of the hierarchical sensing system thorough comparison with existing fiber optic based systems and nerve systems in the animal kingdom. Then, in order to validate the proposed sensing concept, impact damage detection system for the composite structure was proposed. The sensor devices were developed based on Comparative Vacuum Monitoring (CVM) system and the Brillouin based distributed strain sensing was utilized to gather the damage signals from the distributed devices. Finally a verification test was conducted using prototype devices. Occurrence of barely visible impact damage was successfully detected and it was clearly indicated that the hierarchical system has better repairability, higher robustness, and wider monitorable area compared to existing systems utilizing embedded optical fiber sensors.

Structural Health Monitoring of Composite Materials Using Distributed Fiber Bragg Sensors

NASA Technical Reports Server (NTRS)

Grant, Joseph; Kual, Raj; Taylor, Scott; Jackson, Kurt V.; Myers, George; Wang, Y.; Sharma, A.; Burdine, Robert (Technical Monitor)

2002-01-01

Health monitoring of polymer matrix composite materials using fiber optic Bragg grating (FBG) sensors is accomplished using a tunable IR (infrared) laser via transmission mode. Results are presented from experiments of composite structures with FBG's embedded at various orientations, and surface measurements of various cryogenic composite vessels.

Structural Behavior of Concrete Beams Reinforced with Basalt Fiber Reinforced Polymer (BFRP) Bars

NASA Astrophysics Data System (ADS)

Ovitigala, Thilan

The main challenge for civil engineers is to provide sustainable, environmentally friendly and financially feasible structures to the society. Finding new materials such as fiber reinforced polymer (FRP) material that can fulfill the above requirements is a must. FRP material was expensive and it was limited to niche markets such as space shuttles and air industry in the 1960s. Over the time, it became cheaper and spread to other industries such as sporting goods in the 1980-1990, and then towards the infrastructure industry. Design and construction guidelines are available for carbon fiber reinforced polymer (CFRP), aramid fiber reinforced polymer (AFRP) and glass fiber reinforced polymer (GFRP) and they are currently used in structural applications. Since FRP is linear elastic brittle material, design guidelines for the steel reinforcement are not valid for FRP materials. Corrosion of steel reinforcement affects the durability of the concrete structures. FRP reinforcement is identified as an alternative to steel reinforcement in corrosive environments. Although basalt fiber reinforced polymer (BFRP) has many advantages over other FRP materials, but limited studies have been done. These studies didn't include larger BFRP bar diameters that are mostly used in practice. Therefore, larger beam sizes with larger BFRP reinforcement bar diameters are needed to investigate the flexural and shear behavior of BFRP reinforced concrete beams. Also, shear behavior of BFRP reinforced concrete beams was not yet studied. Experimental testing of mechanical properties and bond strength of BFRP bars and flexural and shear behavior of BFRP reinforced concrete beams are needed to include BFRP reinforcement bars in the design codes. This study mainly focuses on the use of BFRP bars as internal reinforcement. The test results of the mechanical properties of BFRP reinforcement bars, the bond strength of BFRP reinforcement bars, and the flexural and shear behavior of concrete beams

One-year follow-up of the phagocytic activity of leukocytes after exposure of rats to asbestos and basalt fibers.

PubMed Central

Hurbánková, M

1994-01-01

The phagocytic activity of leukocytes in peripheral blood was investigated after 2, 24, and 48 hr; 1, 2, 4, and 8 weeks; and 6 and 12 months following intraperitoneal administration of asbestos and basalt fibers to Wistar rats. Asbestos and basalt fibers differed in their effects on the parameters studied. Both granulocyte count and phagocytic activity of leukocytes during the 1-year dynamic follow-up in both dust-exposed groups of animals changed in two phases, characterized by the initial stimulation of the acute phase I, followed by the suppression of the parameters in the chronic phase II. Exposure to asbestos and basalt fibers led, in phase II, to impairment of the phagocytic activity of granulocytes. Asbestos fibers also significantly decreased phagocytic activity of monocytes. Exposure to basalt fibers did not affect the phagocytic activity of monocytes in phase II. Results suggest that the monocytic component of leukocytes plays an important role in the development of diseases caused by exposure to fibrous dusts, but basalt fibers have lesser biological effects than asbestos fibers. PMID:7882931

Structural characterization of guaiacyl-rich lignins in flax (Linum usitatissimum) fibers and shives.

PubMed

del Río, José C; Rencoret, Jorge; Gutiérrez, Ana; Nieto, Lidia; Jiménez-Barbero, Jesús; Martínez, Ángel T

2011-10-26

The structural characteristics of the lignins from flax (Linum usitatissimum) fibers and shives were studied. Significant differences in the content and composition of the lignin from both parts were observed. The lignin contents were 3.8% in the fibers and 29.0% in the shives. Analysis by Py-GC/MS indicated a H:G:S molar ratio of 13:72:15 in the milled wood lignin (MWL) isolated from flax fibers and a molar ratio of 5:87:8 in the MWL isolated from flax shives. In addition, 2D-NMR showed a predominance of β-O-4' aryl ether linkages, followed by β-5' phenylcoumaran and β-β' resinol-type linkages in both MWLs, with a higher content of condensed linkages in flax shives. Thioacidolysis (followed by Raney nickel desulfurization) gave further information on the lignin units involved in the different linkages and confirmed the enrichment of G units. The thioacidolysis dimers released were similar from both lignins, with a predominance of the β-5' followed by β-1' and 5-5' structures.

Enhancement of hippocampal mossy fiber activity in zinc deficiency and its influence on behavior.

PubMed

Takeda, Atsushi; Itoh, Hiromasa; Yamada, Kohei; Tamano, Haruna; Oku, Naoto

2008-10-01

The extracellular concentration of glutamate in the hippocampus is increased by hippocampal perfusion with CaEDTA, a membrane-impermeable zinc chelator, suggesting that the activity of glutamatergic neurons in the hippocampus are influenced by the extracellular concentrations of zinc. In the present study, the relationship between the extracellular concentrations of zinc and mossy fiber activity in the hippocampus was examined in mice and rats fed a zinc-deficient diet for 4 weeks. Timm's stain, by which histochemically reactive zinc in the presynaptic vesicles is detected, was attenuated in the hippocampus in zinc deficiency. The extracellular signal of ZnAF-2, a membrane-impermeable zinc indicator, was also lower in the hippocampal CA3, suggesting that the basal extracellular concentrations of zinc are lower maintained in zinc deficiency. To check mossy fiber activity after 4-week zinc deprivation, the decrease in the signal of FM4-64, an indicator of presynaptic activity (exocytosis), at mossy fiber synapses was measured under the condition of spontaneous depolarization. The decrease was significantly facilitated by zinc deficiency, suggesting that the basal exocytosis at mossy fiber synapses is enhanced by zinc deficiency. On the other hand, the increase in anxiety-like behavior was observed in the open-field test after 4-week zinc deprivation. The present study demonstrates that the decrease in the basal extracellular concentrations of zinc may be linked to the enhancement of the basal mossy fiber activity in zinc deficiency. This decrease seems to be also involved in neuropsychological behavior in zinc deficiency.

Review of natural fiber composites

NASA Astrophysics Data System (ADS)

Rohan, T.; Tushar, B.; T, Mahesha G.

2018-02-01

Development of new alternative materials to the existing traditional metals, alloys and synthetic materials is the new buzz in recent research activities at the academic and industrial level taking place all over the world. Earning carbon credits by minimizing the atmospheric pollution is getting an increase in attention by industries. One small step to conserve the atmosphere around us is to use natural resources in making fully bio degradable or partially bio degradable composite materials. Such prepared alternative materials can find applications in interior housing, automotive, marine, domestic, and other applications. Composites made by using appropriate natural fibers as reinforcements is a possibility that ensures such a reality as they can be well received in multiple disciplines of engineering. Results published from various research activities illustrates that natural fiber composites can successfully be adapted for non-structural, moderate load bearing indoor applications. Further, the few deficiencies in the natural fibers can be overcome by subjecting them to morphological changes by various physical or chemical treatment methods. The overall objective of this paper is to provide a comprehensive overview of the property profiles of Natural Fiber Composites.

Direct writing of fiber optic components in photonic crystal fibers and other specialty fibers

NASA Astrophysics Data System (ADS)

Fernandes, Luis Andre; Sezerman, Omur; Best, Garland; Ng, Mi Li; Kane, Saidou

2016-04-01

Femtosecond direct laser writing has recently shown great potential for the fabrication of complex integrated devices in the cladding of optical fibers. Such devices have the advantage of requiring no bulk optical components and no breaks in the fiber path, thus reducing the need for complicated alignment, eliminating contamination, and increasing stability. This technology has already found applications using combinations of Bragg gratings, interferometers, and couplers for the fabrication of optical filters, sensors, and power monitors. The femtosecond laser writing method produces a local modification of refractive index through non-linear absorption of the ultrafast laser pulses inside the dielectric material of both the core and cladding of the fiber. However, fiber geometries that incorporate air or hollow structures, such as photonic crystal fibers (PCFs), still present a challenge since the index modification regions created by the writing process cannot be generated in the hollow regions of the fiber. In this work, the femtosecond laser method is used together with a pre-modification method that consists of partially collapsing the hollow holes using an electrical arc discharge. The partial collapse of the photonic band gap structure provides a path for femtosecond laser written waveguides to couple light from the core to the edge of the fiber for in-line power monitoring. This novel approach is expected to have applications in other specialty fibers such as suspended core fibers and can open the way for the integration of complex devices and facilitate miniaturization of optical circuits to take advantage of the particular characteristics of the PCFs.

Reduced fiber size, capillary supply and mitochondrial activity in constitutional thinness' skeletal muscle.

PubMed

Galusca, Bogdan; Verney, Julien; Meugnier, Emmanuelle; Ling, Yiin; Edouard, Pascal; Feasson, Leonard; Ravelojaona, Marion; Vidal, Hubert; Estour, Bruno; Germain, Natacha

2018-05-13

Constitutional thinness (CT) is a rare condition of natural low bodyweight, with no psychological issues, no marker of undernutrition and a resistance to weight gain. This study evaluated the skeletal muscle phenotype of CT women by comparison to a normal BMI control group. 10 CT women (BMI< 17.5 kg/m2) and 10 female controls (BMI: 18.5-25 kg/m2) underwent metabolic and hormonal assessment along with muscle biopsies to analyse the skeletal muscular fibers pattern, capillarity, enzymes activities and transcriptomics. CTs displayed similar energy balance metabolic and hormonal profile to controls. CTs presented with lower mean area of all the skeletal muscular fibers (-24%, p= 0.01) and percentage of slow-twitch type I fibers (-25%, p=0.02, respectively). Significant down regulation of the mRNA expression of several mitochondrial related genes and triglycerides metabolism was found along with low Cytochrome C Oxydase (COX) activity and capillary network in type I fibers. Pre and post mitochondrial respiratory chain enzymes levels were found similar to controls. Transcriptomics also revealed downregulation of cytoskeletal related genes. Diminished type I fibers, decreased mitochondrial and metabolic activity suggested by these results are discordant with normal resting metabolic rate of CT subjects. Downregulated genes related to cytoskeletal proteins and myocyte differentiation could account for CT's resistance to weight gain. This article is protected by copyright. All rights reserved. This article is protected by copyright. All rights reserved.

Dietary Fiber-Induced Changes in the Structure and Thermal Properties of Gluten Proteins Studied by Fourier Transform-Raman Spectroscopy and Thermogravimetry.

PubMed

Nawrocka, Agnieszka; Szymańska-Chargot, Monika; Miś, Antoni; Wilczewska, Agnieszka Z; Markiewicz, Karolina H

2016-03-16

Interactions between gluten proteins and dietary fiber supplements at the stage of bread dough formation are crucial in the baking industry. The dietary fiber additives are regarded as a source of polysaccharides and antioxidants, which have positive effects on human health. The fiber enrichment of bread causes a significant reduction in its quality, which is connected with changes in the structure of gluten proteins. Changes in the structure of gluten proteins and their thermal properties induced by seven commercial dietary fibers (fruit, vegetable, and cereal) were studied by FT-Raman spectroscopy and thermogravimetry (TGA), respectively. For this aim the bread dough at 500 FU consistency was made of a blend of wheat starch and wheat gluten as well as the fiber, the content of which ranged from 3 to 18% w/w. The obtained results revealed that all dietary fibers apart from oat caused similar changes in the secondary structure of gluten proteins. The most noticeable changes were observed in the regions connected with hydrogen-bonded β-sheets (1614 and 1684 cm(-1)) and β-turns (1640 and 1657 cm(-1)). Other changes observed in the gluten structure, concerning other β-structures, conformation of disulfide bridges, and aromatic amino acid microenvironment, depend on the fibers' chemical composition. The results concerning structural changes suggested that the observed formation of hydrogen bonds in the β-structures can be connected with aggregation or abnormal folding. This hypothesis was confirmed by thermogravimetric results. Changes in weight loss indicated the formation of a more complex and strong gluten network.

Differentiation of molecular chain entanglement structure through laser Raman spectrum measurement of High strength PET fibers under stress

NASA Astrophysics Data System (ADS)

Go, D.; Takarada, W.; Kikutani, T.

2017-10-01

The aim of this study was to investigate the mechanism for the improvement of mechanical properties of poly(ethylene terephthalate) (PET) fibers based on the concept of controlling the state of molecular entanglement. For this purpose, five different PET fibers were prepared through either the conventional melt spinning and drawing/annealing process or the high-speed melt spinning process. In both cases, the melt spinning process was designed so as to realize different Deborah number conditions. The prepared fibers were subjected to the laser Raman spectroscopy measurement and the characteristics of the scattering peak at around 1616 cm-1, which corresponds to the C-C/C=C stretching mode of the aromatic ring in the main chain, were investigated in detail. It was revealed that the fibers drawn and annealed after the melt spinning process of lower Deborah number showed higher tensile strength as well as lower value of full width at half maximum (FWHM) in the laser Raman spectrum. Narrow FWHM was considered to represent the homogeneous state of entanglement structure, which may lead to the higher strength and toughness of fibers because individual molecular chains tend to bare similar level of tensile stress when the fiber is stretched. In case of high-speed spun fibers prepared with a high Deborah number condition, the FWHM was narrow presumably because much lower tensile stress in comparison with the drawing/annealing process was applied when the fiber structure was developed, however the value increased significantly upon applying tensile load to the fibers during the laser Raman spectrum measurement. From these results, it was concluded that the Laser Raman spectroscopy could differentiate molecular chain entanglement structure of various fiber samples, in that low FWHM, which corresponds to either homogeneous state of molecular entanglement or lower level of mean residual stress, and small increase of FWTH upon applying tensile stress are considered to be the key

Conceptual study on maillardized dietary fiber in coffee.

PubMed

Silván, José Manuel; Morales, Francisco J; Saura-Calixto, Fulgencio

2010-12-08

There is a methodological and conceptual overlap between coffee melanoidins and dietary fiber. Green Uganda coffee beans were roasted in a range from 8.1 to 21.6% of weight loss to evaluate melanoidins and dietary fiber. Samples were characterized by color, moisture, solubility, water activity, carbohydrates, polyphenols, protein, soluble dietary fiber (SDF), and melanoidins content. Hydroxymethylfurfural and chlorogenic acids were also measured as chemical markers of the extent of roasting. Melanoidins rapidly increased from 5.6 (light roasting) to 29.1 mg/100 mg soluble dry matter (dark roasting). A melanoidins-like structure was already present in green coffee that might overestimate up to 21.0% of the melanoidins content as determined by colorimetric methods. However, its contribution is variable and very likely depends on the method of drying applied to green coffee. SDF content (mg/100 mg soluble dry matter) gradually increased from 39.4 in green coffee to 64.9 at severe roasting conditions due to incorporation of neoformed colored structures and polyphenols. Then, SDF progressively turns to a maillardized structure, which increased from 11.0 to 45.0% according to the roasting conditions. It is concluded that the content of coffee melanoidins includes a substantial part of dietary fiber and also that coffee dietary fiber includes melanoidins. A conceptual discussion on a new definition of coffee melanoidins as a type of maillardized dietary fiber is conducted.

Fiber optic smart structures and skins V; Proceedings of the Meeting, Boston, MA, Sept. 8, 9, 1992

NASA Technical Reports Server (NTRS)

Claus, Richard O. (Editor); Rogowski, Robert S. (Editor)

1993-01-01

The present conference discusses the materials used in applications of fiber-optics (F-O) to smart structures, extrinsic Fabry-Perot interferometric F-O sensors, sapphire F-O sensors, two-mode F-O sensors with photoinduced refractive index, an F-O accelerometer using two-mode fibers, and embedded F-O acoustic sensors for flaw detection. Also discussed are an optoelectronic smart structure interface, F-O sensors for simultaneous detection of strain and temperature, an optical Mach-Zehnder interferometer for smart skins, a split-cavity cross-coupled extrinsic fiber interferometer, and an embedded Bragg grating F-O sensor for composite flexbeams, an Er-doped ring-laser strain sensor.

Compressive Behavior of Fiber-Reinforced Concrete with End-Hooked Steel Fibers.

PubMed

Lee, Seong-Cheol; Oh, Joung-Hwan; Cho, Jae-Yeol

2015-03-27

In this paper, the compressive behavior of fiber-reinforced concrete with end-hooked steel fibers has been investigated through a uniaxial compression test in which the variables were concrete compressive strength, fiber volumetric ratio, and fiber aspect ratio (length to diameter). In order to minimize the effect of specimen size on fiber distribution, 48 cylinder specimens 150 mm in diameter and 300 mm in height were prepared and then subjected to uniaxial compression. From the test results, it was shown that steel fiber-reinforced concrete (SFRC) specimens exhibited ductile behavior after reaching their compressive strength. It was also shown that the strain at the compressive strength generally increased along with an increase in the fiber volumetric ratio and fiber aspect ratio, while the elastic modulus decreased. With consideration for the effect of steel fibers, a model for the stress-strain relationship of SFRC under compression is proposed here. Simple formulae to predict the strain at the compressive strength and the elastic modulus of SFRC were developed as well. The proposed model and formulae will be useful for realistic predictions of the structural behavior of SFRC members or structures.

Compressive Behavior of Fiber-Reinforced Concrete with End-Hooked Steel Fibers

PubMed Central

Lee, Seong-Cheol; Oh, Joung-Hwan; Cho, Jae-Yeol

2015-01-01

In this paper, the compressive behavior of fiber-reinforced concrete with end-hooked steel fibers has been investigated through a uniaxial compression test in which the variables were concrete compressive strength, fiber volumetric ratio, and fiber aspect ratio (length to diameter). In order to minimize the effect of specimen size on fiber distribution, 48 cylinder specimens 150 mm in diameter and 300 mm in height were prepared and then subjected to uniaxial compression. From the test results, it was shown that steel fiber-reinforced concrete (SFRC) specimens exhibited ductile behavior after reaching their compressive strength. It was also shown that the strain at the compressive strength generally increased along with an increase in the fiber volumetric ratio and fiber aspect ratio, while the elastic modulus decreased. With consideration for the effect of steel fibers, a model for the stress–strain relationship of SFRC under compression is proposed here. Simple formulae to predict the strain at the compressive strength and the elastic modulus of SFRC were developed as well. The proposed model and formulae will be useful for realistic predictions of the structural behavior of SFRC members or structures. PMID:28788011

Micro-structured optical fiber sensor for simultaneous measurement of temperature and refractive index

NASA Astrophysics Data System (ADS)

Liu, Ying-gang; Liu, Xin; Ma, Cheng-ju; Zhou, Yu-min

2018-03-01

Through using micro-machining method for optical fiber sensor, a kind of miniature, compact and composite structural all-fiber sensor is presented. Based on manufacturing two micro-holes with certain distance in ordinary single-mode fiber Bragg grating (FBG) by excimer laser processing technique, we fabricate a dual Fabry-Perot-FBG (FP-FBG) composite fiber interferometric sensor, which can be used in simultaneous measurement for liquid's refractive index (RI) and temperature change. Due to every micro-hole and the dual micro-holes in fiber acting as different Fabry-Perot (FP) cavities, this kind of sensor has not only different RI sensitivities but also different temperature sensitivities, which are corresponding to the wavelength shifts of the fine interference fringes and spectral envelope, respectively. The experimental results show that the spectral wavelength shift keep better linear response for temperature and RI change, so that we can select the higher temperature and RI sensitivities as well as the analyzed sensitivities of FBG to utilize them for constituting a sensitivity coefficients matrix. Finally, the variations of liquid's temperature and RI are detected effectively, and the resolutions can reach to 0.1 °C and 1.0 ×10-5 RIU. These characteristics are what other single-type sensors don't have, so that this kind of all-fiber dual FP-FBG composite fiber interferometric sensor can be used in extremely tiny liquid environment for measuring different physical quantities simultaneously.

A state-of-the-art assessment of active structures

NASA Technical Reports Server (NTRS)

1992-01-01

A state-of-the-art assessment of active structures with emphasis towards the applications in aeronautics and space is presented. It is felt that since this technology area is growing at such a rapid pace in many different disciplines, it is not feasible to cover all of the current research but only the relevant work as relates to aeronautics and space. Research in smart actuation materials, smart sensors, and control of smart/intelligent structures is covered. In smart actuation materials, piezoelectric, magnetostrictive, shape memory, electrorheological, and electrostrictive materials are covered. For sensory materials, fiber optics, dielectric loss, and piezoelectric sensors are examined. Applications of embedded sensors and smart sensors are discussed.

Radiation Effects on an Active Ytterbium doped Fiber Laser

DTIC Science & Technology

laser. While the gain medium of the laser was irradiated , the power was measured in-situ and the spectrum was recorded intermittently. The results...with a lower initial power. Power recovery experiments were conducted post- irradiation with the fiber laser off and actively lasing. Passively, the...total power recovery of 12.6 and 4.4 for YDF1 and YDF2 respectively. The active recovery rate declined as the number of days following irradiation

In-Line Fiber Optic Interferometric Sensors in Single-Mode Fibers

PubMed Central

Zhu, Tao; Wu, Di; Liu, Min; Duan, De-Wen

2012-01-01

In-line fiber optic interferometers have attracted intensive attention for their potential sensing applications in refractive index, temperature, pressure and strain measurement, etc. Typical in-line fiber-optic interferometers are of two types: Fabry-Perot interferometers and core-cladding-mode interferometers. It's known that the in-line fiber optic interferometers based on single-mode fibers can exhibit compact structures, easy fabrication and low cost. In this paper, we review two kinds of typical in-line fiber optic interferometers formed in single-mode fibers fabricated with different post-processing techniques. Also, some recently reported specific technologies for fabricating such fiber optic interferometers are presented. PMID:23112608

Magnetic field sensor based on the magnetic-fluid-clad combined with singlemode-multimode-singlemode fiber and large core-offset splicing structure

NASA Astrophysics Data System (ADS)

Lv, Ri-qing; Qian, Jun-kai; Zhao, Yong

2018-03-01

A simple, compact optical fiber magnetic field sensor is proposed and experimentally demonstrated in this paper. It is based on the magnetic-fluid-clad combined with singlemode-multimode-singlemode fiber structure and large core-offset splicing structure. It was protected by a section of capillary tube and was sealed by UV glue. A sensing property study of the combined optical fiber structure and the proposed sensor were carried out. The experimental results show that the sensitivity of the refractive index of the optical fiber sensing structure is up to 156.63 nm/RIU and the magnetic field sensitivity of the proposed sensor is up to -97.24 pm/Oe in the range from 72.4 Oe to 297.8 Oe. The proposed sensor has several other advantages, such as simple structure, small size, easy fabrication and low cost.

Insertion of linear 8.4 μm diameter 16 channel carbon fiber electrode arrays for single unit recordings

PubMed Central

Patel, Paras R.; Na, Kyounghwan; Zhang, Huanan; Kozai, Takashi D. Y.; Kotov, Nicholas A.; Yoon, Euisik; Chestek, Cynthia A.

2016-01-01

Objective Single carbon fiber electrodes (d=8.4 μm) insulated with parylene-c and functionalized with PEDOT:pTS have been shown to record single unit activity but manual implantation of these devices with forceps can be difficult. Without an improvement in the insertion method any increase in the channel count by fabricating carbon fiber arrays would be impractical. In this study, we utilize a water soluble coating and structural backbones that allow us to create, implant, and record from fully functionalized arrays of carbon fibers with ~150 μm pitch. Approach Two approaches were tested for the insertion of carbon fiber arrays. The first method used a PEG coating that temporarily stiffened the fibers while leaving a small portion at the tip exposed. The small exposed portion (500 μm – 1 mm) readily penetrated the brain allowing for an insertion that did not require the handling of each fiber by forceps. The second method involved the fabrication of silicon support structures with individual shanks spaced 150 μm apart. Each shank consisted of a small groove that held an individual carbon fiber. Main results Our results showed that the PEG coating allowed for the chronic implantation of carbon fiber arrays in 5 rats with unit activity detected at 31 days post-implant. The silicon support structures recorded single unit activity in 3 acute rat surgeries. In one of those surgeries a stacked device with 3 layers of silicon support structures and carbon fibers was built and shown to readily insert into the brain with unit activity on select sites. Significance From these studies we have found that carbon fibers spaced at ~150 μm readily insert into the brain. This greatly increases the recording density of chronic neural probes and paves the way for even higher density devices that have a minimal scarring response. PMID:26035638

Structural alterations of thin actin filaments in muscle contraction by synchrotron X-ray fiber diffraction.

PubMed

Wakabayashi, Katsuzo; Sugimoto, Yasunobu; Takezawa, Yasunori; Ueno, Yutaka; Minakata, Shiho; Oshima, Kanji; Matsuo, Tatsuhito; Kobayashi, Takakazu

2007-01-01

Strong evidence has been accumulated that the conformational changes of the thin actin filaments are occurring and playing an important role in the entire process of muscle contraction. The conformational changes and the mechanical properties of the thin actin filaments we have found by X-ray fiber diffraction on skeletal muscle contraction are explored. Recent studies on the conformational changes of regulatory proteins bound to actin filaments upon activation and in the force generation process are also described. Finally, the roles of structural alterations and dynamics of the actin filaments are discussed in conjunction with the regulation mechanism and the force generation mechanism.

Reduction of the Radiating Sound of a Submerged Finite Cylindrical Shell Structure by Active Vibration Control

PubMed Central

Kim, Heung Soo; Sohn, Jung Woo; Jeon, Juncheol; Choi, Seung-Bok

2013-01-01

In this work, active vibration control of an underwater cylindrical shell structure was investigated, to suppress structural vibration and structure-borne noise in water. Finite element modeling of the submerged cylindrical shell structure was developed, and experimentally evaluated. Modal reduction was conducted to obtain the reduced system equation for the active feedback control algorithm. Three Macro Fiber Composites (MFCs) were used as actuators and sensors. One MFC was used as an exciter. The optimum control algorithm was designed based on the reduced system equations. The active control performance was then evaluated using the lab scale underwater cylindrical shell structure. Structural vibration and structure-borne noise of the underwater cylindrical shell structure were reduced significantly by activating the optimal controller associated with the MFC actuators. The results provide that active vibration control of the underwater structure is a useful means to reduce structure-borne noise in water. PMID:23389344

Reduction of the radiating sound of a submerged finite cylindrical shell structure by active vibration control.

PubMed

Kim, Heung Soo; Sohn, Jung Woo; Jeon, Juncheol; Choi, Seung-Bok

2013-02-06

In this work, active vibration control of an underwater cylindrical shell structure was investigated, to suppress structural vibration and structure-borne noise in water. Finite element modeling of the submerged cylindrical shell structure was developed, and experimentally evaluated. Modal reduction was conducted to obtain the reduced system equation for the active feedback control algorithm. Three Macro Fiber Composites (MFCs) were used as actuators and sensors. One MFC was used as an exciter. The optimum control algorithm was designed based on the reduced system equations. The active control performance was then evaluated using the lab scale underwater cylindrical shell structure. Structural vibration and structure-borne noise of the underwater cylindrical shell structure were reduced significantly by activating the optimal controller associated with the MFC actuators. The results provide that active vibration control of the underwater structure is a useful means to reduce structure-borne noise in water.

From single fiber to macro-level mechanics: A structural finite-element model for elastomeric fibrous biomaterials.

PubMed

D'Amore, Antonio; Amoroso, Nicholas; Gottardi, Riccardo; Hobson, Christopher; Carruthers, Christopher; Watkins, Simon; Wagner, William R; Sacks, Michael S

2014-11-01

In the present work, we demonstrate that the mesoscopic in-plane mechanical behavior of membrane elastomeric scaffolds can be simulated by replication of actual quantified fibrous geometries. Elastomeric electrospun polyurethane (ES-PEUU) scaffolds, with and without particulate inclusions, were utilized. Simulations were developed from experimentally-derived fiber network geometries, based on a range of scaffold isotropic and anisotropic behaviors. These were chosen to evaluate the effects on macro-mechanics based on measurable geometric parameters such as fiber intersections, connectivity, orientation, and diameter. Simulations were conducted with only the fiber material model parameters adjusted to match the macro-level mechanical test data. Fiber model validation was performed at the microscopic level by individual fiber mechanical tests using AFM. Results demonstrated very good agreement to the experimental data, and revealed the formation of extended preferential fiber orientations spanning the entire model space. We speculate that these emergent structures may be responsible for the tissue-like macroscale behaviors observed in electrospun scaffolds. To conclude, the modeling approach has implications for (1) gaining insight on the intricate relationship between fabrication variables, structure, and mechanics to manufacture more functional devices/materials, (2) elucidating the effects of cell or particulate inclusions on global construct mechanics, and (3) fabricating better performing tissue surrogates that could recapitulate native tissue mechanics. Copyright © 2014 Elsevier Ltd. All rights reserved.

Interaction of gelatin with polyenes modulates antifungal activity and biocompatibility of electrospun fiber mats

PubMed Central

Lakshminarayanan, Rajamani; Sridhar, Radhakrishnan; Loh, Xian Jun; Nandhakumar, Muruganantham; Barathi, Veluchamy Amutha; Kalaipriya, Madhaiyan; Kwan, Jia Lin; Liu, Shou Ping; Beuerman, Roger Wilmer; Ramakrishna, Seeram

2014-01-01

Topical application of antifungals does not have predictable or well-controlled release characteristics and requires reapplication to achieve therapeutic local concentration in a reasonable time period. In this article, the efficacy of five different US Food and Drug Administration-approved antifungal-loaded (amphotericin B, natamycin, terbinafine, fluconazole, and itraconazole) electrospun gelatin fiber mats were compared. Morphological studies show that incorporation of polyenes resulted in a two-fold increase in fiber diameter and the mats inhibit the growth of yeasts and filamentous fungal pathogens. Terbinafine-loaded mats were effective against three filamentous fungal species. Among the two azole antifungals compared, the itraconazole-loaded mat was potent against Aspergillus strains. However, activity loss was observed for fluconazole-loaded mats against all of the test organisms. The polyene-loaded mats displayed rapid candidacidal activities as well. Biophysical and rheological measurements indicate strong interactions between polyene antifungals and gelatin matrix. As a result, the polyenes stabilized the triple helical conformation of gelatin and the presence of gelatin decreased the hemolytic activity of polyenes. The polyene-loaded fiber mats were noncytotoxic to primary human corneal and sclera fibroblasts. The reduction of toxicity with complete retention of activity of the polyene antifungal-loaded gelatin fiber mats can provide new opportunities in the management of superficial skin infections. PMID:24920895

Preparation of active 3D film patches via aligned fiber electrohydrodynamic (EHD) printing

PubMed Central

Wang, Jun-Chuan; Zheng, Hongxia; Chang, Ming-Wei; Ahmad, Zeeshan; Li, Jing-Song

2017-01-01

The design, preparation and application of three-dimensional (3D) printed structures have gained appreciable interest in recent times, particularly for drug dosage development. In this study, the electrohydrodynamic (EHD) printing technique was developed to fabricate aligned-fiber antibiotic (tetracycline hydrochloride, TE-HCL) patches using polycaprolactone (PCL), polyvinyl pyrrolidone (PVP) and their composite system (PVP-PCL). Drug loaded 3D patches possessed perfectly aligned fibers giving rise to fibrous strut orientation, variable inter-strut pore size and controlled film width (via layering). The effect of operating parameters on fiber deposition and alignment were explored, and the impact of the film structure, composition and drug loading was evaluated. FTIR demonstrated successful TE-HCL encapsulation in aligned fibers. Patches prepared using PVP and TE-HCL displayed enhanced hydrophobicity. Tensile tests exhibited changes to mechanical properties arising from additive effects. Release of antibiotic from PCL-PVP dosage forms was shown over 5 days and was slower compared to pure PCL or PVP. The printed patch void size also influenced antibiotic release behavior. The EHDA printing technique provides an exciting opportunity to tailor dosage forms in a single-step with minimal excipients and operations. These developments are crucial to meet demands where dosage forms cannot be manufactured rapidly or when a personalized approach is required. PMID:28272513

Preparation of active 3D film patches via aligned fiber electrohydrodynamic (EHD) printing

NASA Astrophysics Data System (ADS)

Wang, Jun-Chuan; Zheng, Hongxia; Chang, Ming-Wei; Ahmad, Zeeshan; Li, Jing-Song

2017-03-01

The design, preparation and application of three-dimensional (3D) printed structures have gained appreciable interest in recent times, particularly for drug dosage development. In this study, the electrohydrodynamic (EHD) printing technique was developed to fabricate aligned-fiber antibiotic (tetracycline hydrochloride, TE-HCL) patches using polycaprolactone (PCL), polyvinyl pyrrolidone (PVP) and their composite system (PVP-PCL). Drug loaded 3D patches possessed perfectly aligned fibers giving rise to fibrous strut orientation, variable inter-strut pore size and controlled film width (via layering). The effect of operating parameters on fiber deposition and alignment were explored, and the impact of the film structure, composition and drug loading was evaluated. FTIR demonstrated successful TE-HCL encapsulation in aligned fibers. Patches prepared using PVP and TE-HCL displayed enhanced hydrophobicity. Tensile tests exhibited changes to mechanical properties arising from additive effects. Release of antibiotic from PCL-PVP dosage forms was shown over 5 days and was slower compared to pure PCL or PVP. The printed patch void size also influenced antibiotic release behavior. The EHDA printing technique provides an exciting opportunity to tailor dosage forms in a single-step with minimal excipients and operations. These developments are crucial to meet demands where dosage forms cannot be manufactured rapidly or when a personalized approach is required.

Structure-based engineering of a pectate lyase with improved specific activity for ramie degumming.

PubMed

Zhou, Zhanping; Liu, Yang; Chang, Zhenying; Wang, Huilin; Leier, André; Marquez-Lago, Tatiana T; Ma, Yanhe; Li, Jian; Song, Jiangning

2017-04-01

Biotechnological applications of microbial pectate lyases (Pels) in plant fiber processing are promising, eco-friendly substitutes for conventional chemical degumming processes. However, to potentiate the enzymes' use for industrial applications, resolving the molecular structure to elucidate catalytic mechanisms becomes necessary. In this manuscript, we report the high resolution (1.45 Å) crystal structure of pectate lyase (pelN) from Paenibacillus sp. 0602 in apo form. Through sequence alignment and structural superposition with other members of the polysaccharide lyase (PL) family 1 (PL1), we determined that pelN shares the characteristic right-handed β-helix and is structurally similar to other members of the PL1 family, while exhibiting key differences in terms of catalytic and substrate binding residues. Then, based on information from structure alignments with other PLs, we engineered a novel pelN. Our rational design yielded a pelN mutant with a temperature for enzymatic activity optimally shifted from 67.5 to 60 °C. Most importantly, this pelN mutant displayed both higher specific activity and ramie fiber degumming ability when compared with the wild-type enzyme. Altogether, our rational design method shows great potential for industrial applications. Moreover, we expect the reported high-resolution crystal structure to provide a solid foundation for future rational, structure-based engineering of genetically enhanced pelNs.

High sensitivity optical fiber liquid level sensor based on a compact MMF-HCF-FBG structure

NASA Astrophysics Data System (ADS)

Zhang, Yunshan; Zhang, Weigang; Chen, Lei; Zhang, Yanxin; Wang, Song; Yan, Tieyi

2018-05-01

An ultra-high sensitivity fiber liquid level sensor based on wavelength demodulation is proposed and demonstrated. The sensor is composed of a segment of multimode fiber and a large aperture hollow-core fiber assisted by a fiber Bragg grating (FBG). Interference occurs due to core mismatching and different modes with different effective refractive indices. The experimental results show that the liquid level sensitivity of the sensor is 1.145 nm mm‑1, and the linearity is up to 0.996. The dynamic temperature compensation of the sensor can be achieved by cascading an FBG. Considering the high sensitivity and compact structure of the sensor, it can be used for real-time intelligent monitoring of tiny changes in liquid level.

Use of nondestructive inspection and fiber optic sensing for damage characterization in carbon fiber fuselage structure

NASA Astrophysics Data System (ADS)

Neidigk, Stephen; Le, Jacqui; Roach, Dennis; Duvall, Randy; Rice, Tom

2014-04-01

To investigate a variety of nondestructive inspection technologies and assess impact damage characteristics in carbon fiber aircraft structure, the FAA Airworthiness Assurance Center, operated by Sandia National Labs, fabricated and impact tested two full-scale composite fuselage sections. The panels are representative of structure seen on advanced composite transport category aircraft and measured approximately 56"x76". The structural components consisted of a 16 ply skin, co-cured hat-section stringers, fastened shear ties and frames. The material used to fabricate the panels was T800 unidirectional pre-preg (BMS 8-276) and was processed in an autoclave. Simulated hail impact testing was conducted on the panels using a high velocity gas gun with 2.4" diameter ice balls in collaboration with the University of California San Diego (UCSD). Damage was mapped onto the surface of the panels using conventional, hand deployed ultrasonic inspection techniques, as well as more advanced ultrasonic and resonance scanning techniques. In addition to the simulated hail impact testing performed on the panels, 2" diameter steel tip impacts were used to produce representative impact damage which can occur during ground maintenance operations. The extent of impact damage ranges from less than 1 in2 to 55 in2 of interply delamination in the 16 ply skin. Substructure damage on the panels includes shear tie cracking and stringer flange disbonding. It was demonstrated that the fiber optic distributed strain sensing system is capable of detecting impact damage when bonded to the backside of the fuselage.

Structural Health Monitoring Using Textile Reinforcement Structures with Integrated Optical Fiber Sensors

PubMed Central

Bremer, Kort; Weigand, Frank; Zheng, Yulong; Alwis, Lourdes Shanika; Helbig, Reinhard; Roth, Bernhard

2017-01-01

Optical fiber-based sensors “embedded” in functionalized carbon structures (FCSs) and textile net structures (TNSs) based on alkaline-resistant glass are introduced for the purpose of structural health monitoring (SHM) of concrete-based structures. The design aims to monitor common SHM parameters such as strain and cracks while at the same time acting as a structural strengthening mechanism. The sensor performances of the two systems are characterized in situ using Mach-Zehnder interferometric (MZI) and optical attenuation measurement techniques, respectively. For this purpose, different FCS samples were subjected to varying elongation using a tensile testing machine by carefully incrementing the applied force, and good correlation between the applied force and measured length change was observed. For crack detection, the functionalized TNSs were embedded into a concrete block which was then exposed to varying load using the three-point flexural test until destruction. Promising results were observed, identifying that the location of the crack can be determined using the conventional optical time domain reflectometry (OTDR) technique. The embedded sensors thus evaluated show the value of the dual achievement of the schemes proposed in obtaining strain/crack measurement while being utilized as strengthening agents as well. PMID:28208636

Fiber optic system for deflection and damage detection in morphing wing structures

NASA Astrophysics Data System (ADS)

Scheerer, M.; Djinovic, Z.; Schüller, M.

2013-04-01

Within the EC Clean Sky - Smart Fixed Wing Aircraft initiative concepts for actuating morphing wing structures are under development. In order for developing a complete integrated system including the actuation, the structure to be actuated and the closed loop control unit a hybrid deflection and damage monitoring system is required. The aim of the project "FOS3D" is to develop and validate a fiber optic sensing system based on low-coherence interferometry for simultaneous deflection and damage monitoring. The proposed system uses several distributed and multiplexed fiber optic Michelson interferometers to monitor the strain distribution over the actuated part. In addition the same sensor principle will be used to acquire and locate the acoustic emission signals originated from the onset and growth of defects like impact damages, cracks and delamination's. Within this paper the authors present the concept, analyses and first experimental results of the mentioned system.

Structural health monitoring of IACC yachts using fiber optic distributed strain sensors: a technical challenge for America's Cup 2000