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Sample records for abnormal elastic fibers

  1. Penicillamine-induced elastosis perforans serpiginosa with abnormal "lumpy-bumpy" elastic fibers in lesional and non-lesional skin.

    PubMed

    Khatu, Swapna S; Dhurat, Rachita S; Nayak, Chitra S; Pereira, Rickson R; Kagne, Rucha B

    2011-01-01

    Four types of elastosis perforans serpiginosa (EPS) have been described in literature: 1) idiopathic EPS, 2) reactive perforating elastosis associated with connective tissue disorders, 3) in some instances of pseudoxanthoma elasticum (PXE), disease-specific calcified elastic tissue is extruded, producing a clinical picture indistinguishable from other types, may also be seen in patients undergoing hemodialysis and 4) EPS induced by long-term treatment with D-penicillamine is observed in patients suffering from Wilson's disease. Long term D-penicillamine therapy causes an alteration in the dermal elastic tissue. D-penicillamine induced EPS has a distinctive histopathologic feature - serrated appearance of elastic fibers due to perpendicular budding from their surface giving a "lumpy-bumpy" look. D-penicillamine induced elastic fiber alteration may not always manifest clinically as EPS. We report a case of D-penicillamine induced widespread alteration in skin elastic tissue with distinct histopathologic features.

  2. Studies in cutaneous aging: I. The elastic fiber network

    SciTech Connect

    Braverman, I.M.; Fonferko, E.

    1982-05-01

    We studied by light and electron microscopy the elastic fibers in he sun exposed and sun protected skin of normal and psoriatic individuals of different ages in order to separate the changes of actinic damage from those of chronological aging. The sun exposed skin showed 2 types of elastic fiber abnormalities-one related to actinic damage and the other to chronological aging. The sun protected buttock skin showed only the latter. From ages 30 to 70, a minority of the elastic fibers exhibited abnormalities that appeared to represent a process of fiber disintegration. After age 70, the majority of elastic fibers showed these abnormalities. These abnormalities were present without accompanying inflammatory cells. Also, there was morphological evidence of continuing synthesis of elastic fibers during the lifetime of these subjects, except that from ages 50-93, the fibers appeared to be loosely, rather than compactly, assembled. Incubation of dermal slices from buttock skin of young adults with porcine pancreatic elastase and bovine chymotrypsin produced elastic fiber degradation that closely simulated the changes that were observed in aged sun protected skin. Researcher propose that one of the features of cutaneous aging is a slow, spontaneous, progressive degradative process inherent in the elastic fiber that can be enzymatically accelerated from decades to hours by elastase and chymotrypsin.

  3. Elasticity of Poissonian fiber networks

    NASA Astrophysics Data System (ADS)

    Åström, J. A.; Mäkinen, J. P.; Alava, M. J.; Timonen, J.

    2000-05-01

    An effective-medium model is introduced for the elasticity of two-dimensional random fiber networks. These networks are commonly used as basic models of heterogeneous fibrous structures such as paper. Using the exact Poissonian statistics to describe the microscopic geometry of the network, the tensile modulus can be expressed by a single-parameter function. This parameter depends on the network density and fiber dimensions, which relate the macroscopic modulus to the relative importance of axial and bending deformations of the fibers. The model agrees well with simulation results and experimental findings. We also discuss the possible generalizations of the model.

  4. Capillary stretching of elastic fibers

    NASA Astrophysics Data System (ADS)

    Protiere, Suzie; Stone, Howard A.; Duprat, Camille

    2014-11-01

    Fibrous media consisting of constrained flexible fibers can be found in many engineered systems (membranes in filters, woven textile, matted paper). When such materials interact with a liquid, the presence of liquid/air interfaces induces capillary forces that deform the fibers. To model this interaction we study the behaviour of a finite volume of liquid deposited on two parallel flexible fibers clamped at both ends. A tension along the fibers is imposed and may be varied. We show that the system undergoes various morphological changes as the interfiber distance, the elasticity and the tension of the fibers are varied. For a certain range of parameters, the liquid spreads along the fibers and pulls them together, leading to the ``zipping'' of the fibers. This capillary adhesion can then be enhanced or reduced by changing the tension within the fibers. We will show that balancing stretching and capillary forces allows the prediction of this transition as well as the conditions for which detachment of the fibers occurs. These results may be used to prevent the clogging of fibrous membranes or to optimize the capture of liquids.

  5. Linear Lumbar Localized Lysis of Elastic Fibers

    PubMed Central

    Tschen, Jaime A.

    2013-01-01

    Background: The absence or loss of elastic fibers in the skin is referred to as dermal elastolysis. Purpose: This paper describes a woman with a distinctive clinical presentation of mid-dermal elastolysis characterized morphologically by multiple horizontal raised bands on the lower back. Methods: A 20-year-old Filipino woman presented with multiple asymptomatic, flesh-colored, raised, firm, linear, cord-like bands on the lumbar area of her back. There were neither similar lesions elsewhere nor a family member with this condition. Results: Microscopic examination of the raised band showed nearly complete absence of elastic fibers in the mid dermis. In contrast, a biopsy of symmetrically located normal-appearing skin showed a uniform distribution of elastic fibers throughout the dermis. Linear lumbar localized elastolysis is a descriptive designation that accurately reflects a correlation of the clinical and pathological changes of this condition. Conclusion: The clinical differential of raised horizontal cord-like bands on the lower back (without a family history of an inherited elastic fiber disorder, a prior history of trauma, or a significant change in weight or exercise habit) includes linear focal elastosis and linear lumbar localized elastolysis. Microscopic evaluation of a Verhoeff-van Gieson stained lesion specimen (which may be accompanied by a biopsy of normal-appearing skin for comparison) will readily differentiate these conditions. The former is usually characterized by increased elastic fibers, whereas the latter, as in this patient, shows a paucity or absence of elastic fibers in the mid dermis. PMID:23882313

  6. Filament-length-controlled elasticity in 3D fiber networks.

    PubMed

    Broedersz, C P; Sheinman, M; Mackintosh, F C

    2012-02-17

    We present a model for disordered 3D fiber networks to study their linear and nonlinear elasticity. In contrast to previous 2D models, these 3D networks with binary crosslinks are underconstrained with respect to fiber stretching elasticity, suggesting that bending may dominate their response. We find that such networks exhibit a bending-dominated elastic regime controlled by fiber length, as well as a crossover to a stretch-dominated regime for long fibers. Finally, by extending the model to the nonlinear regime, we show that these networks become intrinsically nonlinear with a vanishing linear response regime in the limit of flexible or long filaments.

  7. Accurate estimation of the elastic properties of porous fibers

    SciTech Connect

    Thissell, W.R.; Zurek, A.K.; Addessio, F.

    1997-05-01

    A procedure is described to calculate polycrystalline anisotropic fiber elastic properties with cylindrical symmetry and porosity. It uses a preferred orientation model (Tome ellipsoidal self-consistent model) for the determination of anisotropic elastic properties for the case of highly oriented carbon fibers. The model predictions, corrected for porosity, are compared to back-calculated fiber elastic properties of an IM6/3501-6 unidirectional composite whose elastic properties have been determined via resonant ultrasound spectroscopy. The Halpin-Tsai equations used to back-calculated fiber elastic properties are found to be inappropriate for anisotropic composite constituents. Modifications are proposed to the Halpin-Tsai equations to expand their applicability to anisotropic reinforcement materials.

  8. Energy in elastic fiber embedded in elastic matrix containing incident SH wave

    NASA Technical Reports Server (NTRS)

    Williams, James H., Jr.; Nagem, Raymond J.

    1989-01-01

    A single elastic fiber embedded in an infinite elastic matrix is considered. An incident plane SH wave is assumed in the infinite matrix, and an expression is derived for the total energy in the fiber due to the incident SH wave. A nondimensional form of the fiber energy is plotted as a function of the nondimensional wavenumber of the SH wave. It is shown that the fiber energy attains maximum values at specific values of the wavenumber of the incident wave. The results obtained here are interpreted in the context of phenomena observed in acousto-ultrasonic experiments on fiber reinforced composite materials.

  9. Elastic and viscoelastic properties of a type I collagen fiber.

    PubMed

    Sopakayang, Ratchada; De Vita, Raffaella; Kwansa, Albert; Freeman, Joseph W

    2012-01-21

    A new mathematical model is presented to describe the elastic and viscoelastic properties of a single collagen fiber. The model is formulated by accounting for the mechanical contribution of the collagen fiber's main constituents: the microfibrils, the interfibrillar matrix and crosslinks. The collagen fiber is modeled as a linear elastic spring, which represents the mechanical contribution of the microfibrils, and an arrangement in parallel of elastic springs and viscous dashpots, which represent the mechanical contributions of the crosslinks and interfibrillar matrix, respectively. The linear elastic spring and the arrangement in parallel of elastic springs and viscous dashpots are then connected in series. The crosslinks are assumed to gradually break under strain and, consequently, the interfibrillar is assumed to change its viscous properties. Incremental stress relaxation tests are conducted on dry collagen fibers reconstituted from rat tail tendons to determine their elastic and viscoelastic properties. The elastic and total stress-strain curves and the stress relaxation at different levels of strain collected by performing these tests are then used to estimate the parameters of the model and evaluate its predictive capabilities.

  10. Elastic fibers and collagen distribution in human aorta

    NASA Astrophysics Data System (ADS)

    Vieira-Damiani, G.; Ferro, D. P.; Adam, R. L.; de Thomaz, A. A.; Pelegati, V.; Cesar, C. L.; Metze, K.

    2011-03-01

    Elastic and collagen fibers are essential components of the aorta, the remodeling of these structures is accompanied with aging in various diseases and life-threatening events. While the elastic fibers confer resilience to major blood vessels collagen confers resistance to the same. Elastic fibers are easily visualized in the fluorescent light when stained with hematoxylin eosin. Second Harmonic Generation (SHG) is a non linear signal that occurs only in molecules without inversion symmetry and is particularly strong in the collagen fibers arranged in triple helices. The aim of this paper is to describe the distribution of collagen in the thickness of the thoracic aorta, and to demonstrate the distribution of between elastic fibers. The images were acquired in a multifoton microscopy and both signals, Two-phtoton excitaded fluorescence (TPEF) and SHG, were excited by a Ti:Sapphire laser. We used a band pass filter to filter the SHG signal from the TPEF signal. The thickness of the aorta varies 2-3 mm, and the image was composed of the juxtaposition of images of 220 x 220 microns. We acquired images of a histological slide of the thoracic aorta stained with picrosirius red (specific for collagen) at a wavelength of 670nm SHG subsequently acquired images with the same region and observed that the images are overlapping. Therefore, the following images were acquired by confocal microscopy (fluorescence of eosin for visualization of elastic fibers) and for collagen SHG. After reconstruction of the images, we observed the distribution of collagen along the aorta.

  11. Dynamics of enzymatic digestion of elastic fibers and networks under tension.

    PubMed

    Araújo, Ascânio D; Majumdar, Arnab; Parameswaran, Harikrishnan; Yi, Eunice; Spencer, Jean L; Nugent, Matthew A; Suki, Béla

    2011-06-07

    We study the enzymatic degradation of an elastic fiber under tension using an anisotropic random-walk model coupled with binding-unbinding reactions that weaken the fiber. The fiber is represented by a chain of elastic springs in series along which enzyme molecules can diffuse. Numerical simulations show that the fiber stiffness decreases exponentially with two distinct regimes. The time constant of the first regime decreases with increasing tension. Using a mean field calculation, we partition the time constant into geometrical, chemical and externally controllable factors, which is corroborated by the simulations. We incorporate the fiber model into a multiscale network model of the extracellular matrix and find that network effects do not mask the exponential decay of stiffness at the fiber level. To test these predictions, we measure the force relaxation of elastin sheets stretched to 20% uniaxial strain in the presence of elastase. The decay of force is exponential and the time constant is proportional to the inverse of enzyme concentration in agreement with model predictions. Furthermore, the fragment mass released into the bath during digestion is linearly related to enzyme concentration that is also borne out in the model. We conclude that in the complex extracellular matrix, feedback between the local rate of fiber digestion and the force the fiber carries acts to attenuate any spatial heterogeneity of digestion such that molecular processes manifest directly at the macroscale. Our findings can help better understand remodeling processes during development or in disease in which enzyme concentrations and/or mechanical forces become abnormal.

  12. Submillisecond Elastic Recoil Reveals Molecular Origins of Fibrin Fiber Mechanics

    PubMed Central

    Hudson, Nathan E.; Ding, Feng; Bucay, Igal; O’Brien, E. Timothy; Gorkun, Oleg V.; Superfine, Richard; Lord, Susan T.; Dokholyan, Nikolay V.; Falvo, Michael R.

    2013-01-01

    Fibrin fibers form the structural scaffold of blood clots. Thus, their mechanical properties are of central importance to understanding hemostasis and thrombotic disease. Recent studies have revealed that fibrin fibers are elastomeric despite their high degree of molecular ordering. These results have inspired a variety of molecular models for fibrin’s elasticity, ranging from reversible protein unfolding to rubber-like elasticity. An important property that has not been explored is the timescale of elastic recoil, a parameter that is critical for fibrin’s mechanical function and places a temporal constraint on molecular models of fiber elasticity. Using high-frame-rate imaging and atomic force microscopy-based nanomanipulation, we measured the recoil dynamics of individual fibrin fibers and found that the recoil was orders of magnitude faster than anticipated from models involving protein refolding. We also performed steered discrete molecular-dynamics simulations to investigate the molecular origins of the observed recoil. Our results point to the unstructured αC regions of the otherwise structured fibrin molecule as being responsible for the elastic recoil of the fibers. PMID:23790375

  13. Measurement of Elastic Modulus of Collagen Type I Single Fiber.

    PubMed

    Dutov, Pavel; Antipova, Olga; Varma, Sameer; Orgel, Joseph P R O; Schieber, Jay D

    2016-01-01

    Collagen fibers are the main components of the extra cellular matrix and the primary contributors to the mechanical properties of tissues. Here we report a novel approach to measure the longitudinal component of the elastic moduli of biological fibers under conditions close to those found in vivo and apply it to type I collagen from rat tail tendon. This approach combines optical tweezers, atomic force microscopy, and exploits Euler-Bernoulli elasticity theory for data analysis. This approach also avoids drying for measurements or visualization, since samples are freshly extracted. Importantly, strains are kept below 0.5%, which appear consistent with the linear elastic regime. We find, surprisingly, that the longitudinal elastic modulus of type I collagen cannot be represented by a single quantity but rather is a distribution that is broader than the uncertainty of our experimental technique. The longitudinal component of the single-fiber elastic modulus is between 100 MPa and 360 MPa for samples extracted from different rats and/or different parts of a single tail. Variations are also observed in the fibril-bundle/fibril diameter with an average of 325±40 nm. Since bending forces depend on the diameter to the fourth power, this variation in diameter is important for estimating the range of elastic moduli. The remaining variations in the modulus may be due to differences in composition of the fibril-bundles, or the extent of the proteoglycans constituting fibril-bundles, or that some single fibrils may be of fibril-bundle size.

  14. NDE Elastic Properties of Fiber-Reinforced Composite Materials

    NASA Technical Reports Server (NTRS)

    Bar-Cohen, Y.

    1995-01-01

    Fiber-reinforced composites are increasingly replacing metallic alloys as structural materials for primary components of fracture-critical structures. This trend is a result of the growing understanding of material behavior and recognition of the desirable properties of composites. A research program was conducted on NDE methods for determining the elastic properties of composites.

  15. Elastic/viscoplastic constitutive model for fiber reinforced thermoplastic composites

    NASA Technical Reports Server (NTRS)

    Gates, T. S.; Sun, C. T.

    1991-01-01

    A constitutive model to describe the elastic/viscoplastic behavior of fiber-reinforced thermoplastic composites under plane stress conditions is presented. Formulations are given for quasi-static plasticity and time-dependent viscoplasticity. Experimental procedures required to generate the necessary material constants are explained, and the experimental data is compared to the predicted behavior.

  16. Compressive elastic modulus of natural fiber based binary composites

    NASA Astrophysics Data System (ADS)

    Widayani, Susanah, Y.; Utami, L. S.; Khotimah, S. N.; Viridi, S.

    2012-06-01

    The composites made of bamboo apus fiber - epoxy resin and charcoal - tapioca starch with several compositions have been synthesized. Bamboo fiber powder as the rest of cutting process was refined and filtered by mesh 40 before used. Epoxy resin 1021A and hardener 1021B has been used as resin. The synthesis of epoxy resin-based composites was carried out via simple mixing method by adding adequate 70% ethanol solution before drying. The 100 mesh-filtered dry charcoal was mixed with tapioca mixture before it was pressed and dried to produce briquette composites. To study the compressive elastic modulus of the composites, pressure tests using Mark 10 Pressure Test Machine have been carried out. It was found that all the composites show maximum compressive elastic modulus at certain component compositions. The maximum elastic modulus for bamboo fiber-epoxy resin, charcoal - epoxy resin and charcoal-tapioca starch were observed at 52.9%, 56.3%, and 25.0% of mass fraction of bamboo fiber, charcoal and tapioca starch, respectively.

  17. Confocal microscopy for automatic texture analysis of elastic fibers in histologic preparations

    NASA Astrophysics Data System (ADS)

    Adam, R. L.; Vieira, G.; Ferro, D. P.; de Thomaz, A. A.; Cesar, C., L.; Metze, K.

    2009-07-01

    Elastic fibers are an important component of many organs and tissues, such as skin, lungs, arteries, ligaments, intervertebral discs and cartilage Their function is to endow tissues with elastic recoil and resilience, to act as an important adhesion template for cells, and to regulate growth factor availability (1,2). Loss or remodeling of the elastic fiber texture occurs in many diseases. Degeneration and fragmentation of elastic fibers and aging are intimately related (3). Recently, the importance of elastin for the study of malignant tumor progression has been emphasized (4,5). Elastic tissue may be a significant reservoir of angiostatic molecules and soluble elastin as well as elastin peptides, that are inhibitors of the metastatic process in experimental tumor models (4). Elastic fibers are involved in the anatomic remodeling of chronic pulmonary diseases (6) and, especially, of diseases of the arterial wall (7, 8). The study of these phenomena is important for the understanding of the pathophysiologic basis of the diseases. Recently the role of elastic fibers in small diameter vascular graft design has been emphasized (2). The possibility to regenerate or engineer elastic fibres and tissues creates an important challenge, not only to understand the molecular basis of elastic-fibre biology (1,2), but also of its spatial arrangement and remodeling in the diseased tissues. Subtle changes of the complex elastic fiber network may be involved in the pathogenesis of diseases. Therefore a precise and objective histopathologic description is necessary.

  18. Abnormal Elasticity of Single-Crystal Magnesiosiderite across the Spin Transition in Earth's Lower Mantle

    NASA Astrophysics Data System (ADS)

    Fu, Suyu; Yang, Jing; Lin, Jung-Fu

    2017-01-01

    Brillouin light scattering and impulsive stimulated light scattering have been used to determine the full elastic constants of magnesiosiderite [(Mg0.35Fe0.65)CO3 ] up to 70 GPa at room temperature in a diamond-anvil cell. Drastic softening in C11 , C33 , C12 , and C13 elastic moduli associated with the compressive stress component and stiffening in C44 and C14 moduli associated with the shear stress component are observed to occur within the spin transition between ˜42.4 and ˜46.5 GPa . Negative values of C12 and C13 are also observed within the spin transition region. The Born criteria constants for the crystal remain positive within the spin transition, indicating that the mixed-spin state remains mechanically stable. Significant auxeticity can be related to the electronic spin transition-induced elastic anomalies based on the analysis of Poisson's ratio. These elastic anomalies are explained using a thermoelastic model for the rhombohedral system. Finally, we conclude that mixed-spin state ferromagnesite, which is potentially a major deep-carbon carrier, is expected to exhibit abnormal elasticity, including a negative Poisson's ratio of -0.6 and drastically reduced VP by 10%, in Earth's midlower mantle.

  19. Micromechanics Solution for the Elastic Moduli of Fiber-Reinforced Concrete

    NASA Astrophysics Data System (ADS)

    Huan, Yu Jia; Yang, Liu; Jin, Yu; Guang, Jia Lian; Ming, Liu

    2014-09-01

    The overall elastic moduli of fiber-reinforced concrete composite materials are investigated by employing the theory of micromechanics. A method based on the Mori-Tanaka theory and triple inhomogeneities is found to provide a sufficiently accurate evaluation of the average elastic properties of fiber-reinforced concrete composite materials. The inhomogeneities of the materials are divided into three groups: a fine aggregate, a coarse aggregate, and fibers (steel or polymer). The elastic moduli of fiber-reinforced concrete composite materials are determined as functions of the physical properties and volume fraction of sand, gravel, fibers (steel or polymer), and cement paste as a matrix. The theoretical results obtained are compared with published experimental data. The parameters affecting the elastic moduli of fiber-reinforced concrete are discussed in detail.

  20. Fetal development of the elastic-fiber-mediated enthesis in the human middle ear.

    PubMed

    Takanashi, Yoshitaka; Shibata, Shunichi; Katori, Yukio; Murakami, Gen; Abe, Shinichi; Rodríguez-Vázquez, Jose Francisco; Kawase, Tetsuaki

    2013-10-01

    In the human middle ear, the annular ligament of the incudostapedial joint and the insertions of the tensor tympani and stapedius muscles contain abundant elastic fibers; i.e., the elastic-fiber-mediated entheses. Hyaluronan also coexists with the elastic fibers. In the present study using immunohistochemistry, we demonstrated the distribution of elastin not only in the incudostapedial joint but also in the other two joints of the middle ear in adults and fetuses. In adults, the expression of elastin did not extend out of the annular ligament composed of mature elastic fibers but clearly overlapped with it. Electron microscopic observations of the annular ligament demonstrated a few microfibrils along the elastic fibers. Thus, in contrast to the vocal cord, the middle ear entheses seemed not to contain elaunin and oxytalan fibers. In mid-term fetuses (at approximately 15-16 weeks of gestation) before opening of the external acoustic meatus, the incudostapedial joint showed abundant elastic fibers, but the incudomalleolar and stapediovestibular joints did not. At this stage, hyaluronan was not colocalized, but distributed diffusely in loose mesenchymal tissues surrounding the ear ossicles. Therefore, fetal development of elastin and elastic fibers in the middle ear entheses is unlikely to require acoustic oscillation. In late-stage fetuses (25-30 weeks), whose ear ossicles were almost the same size as those in adults, we observed bundling and branching of elastic fibers. However, hyaluronan expression was not as strong as in adults. Colocalization between elastic fibers and hyaluronan appeared to be a result of postnatal maturation of the entheses.

  1. An Elastic-Plastic Damage Model for Long-Fiber Thermoplastics

    SciTech Connect

    Nguyen, Ba Nghiep; Kunc, Vlastimil

    2009-08-11

    This article proposes an elastic-plastic damage model that combines micromechanical modeling with continuum damage mechanics to predict the stress-strain response of injection-molded long-fiber thermoplastics. The model accounts for distributions of orientation and length of elastic fibers embedded in a thermoplastic matrix whose behavior is elastic-plastic and damageable. The elastic-plastic damage behavior of the matrix is described by the modified Ramberg-Osgood relation and the three-dimensional damage model in deformation assuming isotropic hardening. Fiber/matrix debonding is accounted for using a parameter that governs the fiber/matrix interface compliance. A linear relationship between this parameter and the matrix damage variable is assumed. First, the elastic-plastic damage behavior of the reference aligned-fiber composite containing the same fiber volume fraction and length distribution as the actual composite is computed using an incremental Eshelby-Mori-Tanaka mean field approach. The incremental response of the latter is then obtained from the solution for the aligned-fiber composite by averaging over all fiber orientations. The model is validated against the experimental stress-strain results obtained for long-glass-fiber/polypropylene specimens.

  2. Modeling of Distributed Sensing of Elastic Waves by Fiber-Optic Interferometry

    PubMed Central

    Agbodjan Prince, Just; Kohl, Franz; Sauter, Thilo

    2016-01-01

    This paper deals with the transduction of strain accompanying elastic waves in solids by firmly attached optical fibers. Stretching sections of optical fibers changes the time required by guided light to pass such sections. Exploiting interferometric techniques, highly sensitive fiber-optic strain transducers are feasible based on this fiber-intrinsic effect. The impact on the actual strain conversion of the fiber segment’s shape and size, as well as its inclination to the elastic wavefront is studied. FEM analyses show that severe distortions of the interferometric response occur when the attached fiber length spans a noticeable fraction of the elastic wavelength. Analytical models of strain transduction are presented for typical transducer shapes. They are used to compute input-output relationships for the transduction of narrow-band strain pulses as a function of the mechanical wavelength. The described approach applies to many transducers depending on the distributed interaction with the investigated object. PMID:27608021

  3. Modeling of Distributed Sensing of Elastic Waves by Fiber-Optic Interferometry.

    PubMed

    Agbodjan Prince, Just; Kohl, Franz; Sauter, Thilo

    2016-09-06

    This paper deals with the transduction of strain accompanying elastic waves in solids by firmly attached optical fibers. Stretching sections of optical fibers changes the time required by guided light to pass such sections. Exploiting interferometric techniques, highly sensitive fiber-optic strain transducers are feasible based on this fiber-intrinsic effect. The impact on the actual strain conversion of the fiber segment's shape and size, as well as its inclination to the elastic wavefront is studied. FEM analyses show that severe distortions of the interferometric response occur when the attached fiber length spans a noticeable fraction of the elastic wavelength. Analytical models of strain transduction are presented for typical transducer shapes. They are used to compute input-output relationships for the transduction of narrow-band strain pulses as a function of the mechanical wavelength. The described approach applies to many transducers depending on the distributed interaction with the investigated object.

  4. Unraveling the mechanism of elastic fiber assembly: The roles of short fibulins

    PubMed Central

    Yanagisawa, Hiromi; Davis, Elaine C.

    2010-01-01

    Evolution of elastic fibers is associated with establishment of the closed circulation system. Primary roles of elastic fibers are to provide elasticity and recoiling to tissues and organs and to maintain the structural integrity against mechanical strain over a lifetime. Elastic fibers are comprised of an insoluble elastin core and surrounding mantle of microfibrils. Elastic fibers are formed in a regulated, stepwise manner, which includes the formation of a microfibrillar scaffold, deposition and integration of tropoelastin monomers into the scaffold, and cross-linking of the monomers to form an insoluble, functional polymer. In recent years, an increasing number of glycoproteins have been identified and shown to be located on or surrounding elastic fibers. Among them, the short fibulins-3, -4 and -5 particularly drew attention because of their potent elastogenic activity. Fibulins-3, -4 and -5 are characterized by tandem repeats of calcium binding EGF-like motifs and a C-terminal fibulin module, which is conserved throughout fibulin family members. Initial biochemical characterization and gene expression studies predicted that fibulins might be involved in structural support and/or matrix-cell interactions. Recent analyses of short fibulin knockout mice have revealed their critical roles in elastic fiber development in vivo. We review recent findings on the elastogenic functions of short fibulins and discuss the molecular mechanism underlying their activity in vitro and in vivo. PMID:20236620

  5. Degradation of elastic fiber and elevated elastase expression in long head of biceps tendinopathy.

    PubMed

    Wu, Yen-Ting; Su, Wei-Ren; Wu, Po-Ting; Shen, Po-Chuan; Jou, I-Ming

    2016-12-09

    Tendinopathy of the long head of the biceps (TLHB) involves various types of extracellular matrix degeneration, but previous studies have not evaluated elastic fibers. The purpose of this study was to investigate elastic fiber distribution in long head of the biceps (LHB). The TLHB tendons of 16 consecutive patients (eight men and eight women; average age of 55.75 years; age range of 40-71 years) were transected and harvested. Three cadaveric LHB tendons were used as the control group. The expression of collagen type I was decreased, but type III was increased in TLHB. Disruption of elastic fibers was particularly observed in grade II specimens where the level of elastase-positive staining was significantly higher than in grade I specimens. Elastic fibers were not observed in the grade III area, implying a higher expression of elastase than in the grade I area. Results of Western blotting showed that the expression of elastin was higher in the control group and the levels of elastin significantly decreased in grades II and III of TLHB. Levels of osteopontin and elastase were increased in primary culture of human tenocytes after experiencing elastic derived peptide treatment. These results suggested that elastase may be caused by the disruption of elastic fibers in the development of chronic tendinopathy and that elastic derived peptide may enhance elastase and osteopontin expression. © 2016 Orthopaedic Research Society. Published by Wiley Periodicals, Inc. J Orthop Res.

  6. Three-dimensional arrangement of elastic fibers in the human corneal stroma.

    PubMed

    Lewis, Philip N; White, Tomas L; Young, Robert D; Bell, James S; Winlove, C Peter; Meek, Keith M

    2016-05-01

    The cornea is the main refracting lens in the eye. As part of the outer tunic it has to be resilient, a property conferred by the organisation of the constituent collagen. It also has to be sufficiently elastic to regain its exact shape when deformed, in order not to distort the retinal image. The basis of this elasticity is not fully understood. The purpose of this study was to characterise in three dimensions the arrangement and distribution of elastic fibers in the human corneal stroma, using serial block face scanning electron microscopy. We have demonstrated that there exists a complex network of elastic fibers that appear to originate in the sclera or limbus. These appear as elastic sheets in the limbus and peripheral cornea immediately above the trabecular meshwork which itself appears to extend above Descemet's membrane in the peripheral stroma. From these sheets, elastic fibers extend into the cornea; moving centrally they bifurcate and trifurcate into narrower fibers and are concentrated in the posterior stroma immediately above Descemet's membrane. We contend that elastic sheets will play an important role in the biomechanical deformation and recovery of the peripheral cornea. The network may also have practical implications for understanding the structural basis behind a number of corneal surgeries.

  7. A biomaterial composed of collagen and solubilized elastin enhances angiogenesis and elastic fiber formation without calcification.

    PubMed

    Daamen, Willeke F; Nillesen, Suzan T M; Wismans, Ronnie G; Reinhardt, Dieter P; Hafmans, Theo; Veerkamp, Jacques H; van Kuppevelt, Toin H

    2008-03-01

    Elastin is the prime protein in elastic tissues that contributes to elasticity of, for example, lung, aorta, and skin. Upon injury, elastic fibers are not readily replaced, which hampers tissue regeneration. Incorporation of solubilized elastin (hydrolyzed insoluble elastin fibers or elastin peptides) in biomaterials may improve regeneration, because solubilized elastin is able to promote proliferation as well as elastin synthesis. Porous biomaterials composed of highly purified collagen without and without elastin fibers or solubilized elastin were prepared by freezing and lyophilization. Solubilized elastin formed spherical structures that were incorporated in the collagenous part of the scaffolds and that persisted after chemical crosslinking of the scaffolds. Crosslinked scaffolds were subcutaneously implanted in young Sprague Dawley rats. Collagen-solubilized elastin and collagen scaffolds showed no calcification in this sensitive calcification model, in contrast to scaffolds containing elastin fibers. Collagen-solubilized elastin scaffolds also induced angiogenesis, as revealed by type IV collagen staining, and promoted elastic fiber synthesis, as shown with antibodies against rat elastin and fibrillin-1. It is concluded that scaffolds produced from collagen and solubilized elastin present a non-calcifying biomaterial with a capacity for soft-tissue regeneration, especially in relation to elastic fiber synthesis.

  8. Elastomeric optical fiber sensors and method for detecting and measuring events occurring in elastic materials

    DOEpatents

    Muhs, Jeffrey D.; Capps, Gary J.; Smith, David B.; White, Clifford P.

    1994-01-01

    Fiber optic sensing means for the detection and measurement of events such as dynamic loadings imposed upon elastic materials including cementitious materials, elastomers, and animal body components and/or the attrition of such elastic materials are provided. One or more optical fibers each having a deformable core and cladding formed of an elastomeric material such as silicone rubber are embedded in the elastic material. Changes in light transmission through any of the optical fibers due the deformation of the optical fiber by the application of dynamic loads such as compression, tension, or bending loadings imposed on the elastic material or by the attrition of the elastic material such as by cracking, deterioration, aggregate break-up, and muscle, tendon, or organ atrophy provide a measurement of the dynamic loadings and attrition. The fiber optic sensors can be embedded in elastomers subject to dynamic loadings and attrition such as commonly used automobiles and in shoes for determining the amount and frequency of the dynamic loadings and the extent of attrition. The fiber optic sensors are also useable in cementitious material for determining the maturation thereof.

  9. To improve the flame resistance of spandex elastic elastomeric fiber

    NASA Technical Reports Server (NTRS)

    1972-01-01

    Strength characteristics of fibers were improved to pass the 70% oxygen/30% nitrogen specification. Spinning techniques and information about incorporating these fibers in fabric structures using wrapping materials of Beta Fiberglas, Nomex, and PBI were developed.

  10. Matrix Gla protein is involved in elastic fiber calcification in the dermis of pseudoxanthoma elasticum patients.

    PubMed

    Gheduzzi, Dealba; Boraldi, Federica; Annovi, Giulia; DeVincenzi, Chiara Paolinelli; Schurgers, Leon J; Vermeer, Cees; Quaglino, Daniela; Ronchetti, Ivonne Pasquali

    2007-10-01

    Mature MGP (Matrix gamma-carboxyglutamic acid protein) is known to inhibit soft connective tissues calcification. We investigated its possible involvement in pseudoxanthoma elasticum (PXE), a genetic disorder whose clinical manifestations are due to mineralization of elastic fibers. PXE patients have lower serum concentration of total MGP compared to controls (P<0.001). Antibodies specific for the noncarboxylated (Glu-MGP) and for the gamma-carboxylated (Gla-MGP) forms of MGP were assayed on ultrathin sections of dermis from controls and PXE patients. Normal elastic fibers in controls and patients were slightly positive for both forms of MGP, whereas Gla-MGP was more abundant within control's than within patient's elastic fibers (P<0.001). In patients' calcified elastic fibers, Glu-MGP intensively colocalized with mineral precipitates, whereas Gla-MGP precisely localized at the mineralization front. Data suggest that MGP is present within elastic fibers and is associated with calcification of dermal elastic fibers in PXE. To investigate whether local cells produce MGP, dermal fibroblasts were cultured in vitro and MGP was assayed at mRNA and protein levels. In spite of very similar MGP mRNA expression, cells from PXE patients produced 30% less of Gla-MGP compared to controls. Data were confirmed by immunocytochemistry on ultrathin sections. Normal fibroblasts in vitro were positive for both forms of MGP. PXE fibroblasts were positive for Glu-MGP and only barely positive for Gla-MGP (P<0.001). In conclusion, MGP is involved in elastic fiber calcification in PXE. The lower ratio of Gla-MGP over Glu-MGP in pathological fibroblasts compared to controls suggests these cells may play an important role in the ectopic calcification in PXE.

  11. Development of a rapid matrix digestion technique for ultrastructural analysis of elastic fibers in the intervertebral disc.

    PubMed

    Tavakoli, Javad; Costi, John J

    2017-03-21

    Collagen and elastic fibers are two major fibrous constituents of the annulus fibrosus (AF) in the disc that contribute to its mechanical and viscoelastic properties. It was thought that elastic fibers play no substantial role in the function and properties of the disc as these fibers were irregularly distributed. Studies that have revealed highly organized elastic fibers with different regional orientation and distribution, while being strongly crosslinked with matrix, suggesting their contribution to disc structure-function properties. These studies that were performed by light microscopic analysis of histologically prepared samples, have not been able to reveal the fine-scale architectural details of the elastic fiber network. Since elastic fibers are intermingled with other fibrous components of the disc and mostly obscured by the extracellular matrix, it is difficult to demonstrate their ultra-structural organization using scanning electron microscopy (SEM). Therefore the aim of this study was to develop a rapid matrix digestion technique for ultrastructural analysis of the disc elastic fibers. This study provides a new method for fundamental visualization of elastic fibers and their architecture in the disc. Through the ultra-structural analysis, the relationship between structure and function, as well as the role of elastic fibers on AF mechanical properties can be studied. This method may be used to develop a three-dimensional map of elastic fibers distribution within the disc, which would provide valuable information for designing tissue engineered scaffolds for AF repair and replacement.

  12. Histological Comparison of the Human Trunk Skin Creases: The Role of the Elastic Fiber Component

    PubMed Central

    Kakagia, Despoina; Yiacoumettis, Andreas; Vasilakaki, Thivi; Drougou, Aggeliki; Lambropoulou, Maria; Simopoulos, Constantinos; Tsaroucha, Alexandra K.

    2016-01-01

    Objective: Skin creases are features of major anatomical, morphological, surgical, and functional interest. This study focuses on the histological comparison of creases of the trunk and participation of the elastic fibers in their formation. The histological structure is a key consideration for the reconstructive planning of the relevant area and its knowledge may contribute in such direction. Methods: Fresh cadaver specimens were collected from the inframammary (n = 15), infragluteal (n = 16), and inguinal creases (n = 14), the anterior axillary fold (n = 14), and the surrounding skin (n = 10). Specimens were fixed in 10% buffered formaldehyde. Collagen and muscle fibers were stained by Masson Trichrome and Van Gieson stains, reticular and collagen type III fibers by Reticulin stain, and elastic fibers by Verhoef and Orcein stains. Results: Skin creases of the trunk present well-defined dense bundles of collagen fibers, creating a beehive pattern with broad attachment to the dermis and denser in deeper sites related to the fascia of the underlying muscle. The elastic fibers participate in the collagen pattern and radiate in a parallel pattern in the reticular dermis and in a perpendicular fashion in the papillary dermis. The skin surrounding the creases lacks such organization. Conclusions: Creases of the trunk are formed by well-organized collagen bundles in a beehive pattern, attached to the dermis and related to the underlying muscle fascia. The elastic fibers participate in this structure and radiate in a parallel fashion in the reticular dermis and perpendicularly in the papillary dermis. PMID:27081433

  13. The stumbling block in lung repair of emphysema: elastic fiber assembly.

    PubMed

    Shifren, Adrian; Mecham, Robert P

    2006-07-01

    The mechanical properties of the lung are largely determined by the connective tissue networks laid down during development. The macromolecules most important for lung mechanics and structural integrity are collagen, elastin, and proteoglycans. Members of the fibrillar collagen gene family provide the structural framework of the various lung compartments and elastic fibers provide elastic recoil. Elastin is also an important architectural component that influences lung development, predominantly during the alveolar stage. Previous studies have conclusively shown that elastin degradation is a key step in the pathogenesis of chronic obstructive pulmonary disease. Exacerbating the disease process is the inability of lung cells to repair damaged elastic fibers, which leads to permanently compromised lung function and ongoing degenerative disease. Elastic fibers are among the most difficult matrix structures to repair because of their size, molecular complexity, and the requirement for numerous helper proteins to facilitate fiber assembly. Recent studies of elastin assembly combined with new insight into the functional role of elastic fiber proteins obtained from gene inactivation studies and linkage of human disease to elastin mutations provide new insight into the molecular and cellular complexities of elastin homeostasis.

  14. An Elastic-Plastic and Strength Prediction Model for Injection-Molded Long-Fiber Thermoplastics

    SciTech Connect

    Nguyen, Ba Nghiep; Kunc, Vlastimil; Phelps, Jay; Tucker III, Charles L.; Bapanapalli, Satish K.

    2008-09-01

    This paper applies a recently developed model to predict the elastic-plastic stress/strain response and strength of injection-molded long-fiber thermoplastics (LFTs). The model combines a micro-macro constitutive modeling approach with experimental characterization and modeling of the composite microstructure to determine the composite stress/strain response and strength. Specifically, it accounts for elastic fibers embedded in a thermoplastic resin that exhibits the elastic-plastic behavior obeying the Ramberg-Osgood relation and J-2 deformation theory of plasticity. It also accounts for fiber length, orientation and volume fraction distributions in the composite formed by the injection-molding process. Injection-molded-long-glass-fiber/polypropylene (PP) specimens were prepared for mechanical characterization and testing. Fiber length, orientation, and volume fraction distributions were then measured at some selected locations for use in the computation. Fiber orientations in these specimens were also predicted using an anisotropic rotary diffusion model developed for LFTs. The stress-strain response of the as-formed composite was computed by an incremental procedure that uses the Eshelby’s equivalent inclusion method, the Mori-Tanaka assumption and a fiber orientation averaging technique. The model has been validated against the experimental stress-strain results obtained for these long-glass-fiber/PP specimens.

  15. Spatial pattern of nerve fiber abnormality indicative of pathologic mechanism.

    PubMed Central

    Dyck, P. J.; Karnes, J.; O'Brien, P.; Nukada, H.; Lais, A.; Low, P.

    1984-01-01

    Estimates of the number, density, and size distribution of myelinated fibers at selected levels of roots, spinal tracts, and sampled levels of peripheral nerves may be used in the detection and characterization of alterations of motor, sensory, and autonomic neurons and their axons with development, aging and disease. Use of imaging techniques, now available, increases the reliability, versatility, and speed of such analysis. In this study, the authors evaluated the spatial pattern of fibers in sampled frames and contour areas of transverse sections of nerve fascicles, utilizing, the coefficient of variation and index of dispersion (ID), the latter extensively employed by plant ecologists. The ID was used for recognization of increased, normal, or decreased variability of density within fascicles, between fascicles, and between nerves in health and in various experimental neuropathies. In addition, various morphometric measurements were made in transverse sections at defined levels along the hind limb nerves of rats in acute and chronic ischemia, after rhizotomy and in galactose neuropathy. These stereomorphometric studies, emphasizing the number, size, shape, and spatial pattern of fibers, revealed differences among experimental neuropathies and may be found to be helpful in the characterization and prediction of pathologic mechanisms in neuropathies of unknown cause. Specifically, these approaches could be used for study of whether fiber loss in human diabetic neuropathy is multifocal and determination of the levels of such losses. PMID:6333825

  16. Improved bounds on elastic and transport properties of fiber-reinforced composites - Effect of polydispersivity in fiber radius

    NASA Technical Reports Server (NTRS)

    Miller, C. A.; Torquato, S.

    1991-01-01

    Improved rigorous bounds were computed on the effective elastic and transport properties (including the effective axial shear modulus, effective transverse bulk modulus, and effective transverse shear modulus) of a transversely isotropic fiber-reinforced material composed of infinitely-long oriented multisized impenetrable circular cylinders distributed throughout a matrix. Results were used to study the effect of fiber-radius polydispersivity on the elastic and transport properties of such unidirectional composites. It was found that increasing the degree of polydispersivity increases the effective transverse conductivity (or axial shear modulus) and the effective transverse bulk modulus, and slightly decreases the effective transverse shear modulus for cases in which the fibers are more conducting or stiffer than the matrix.

  17. Homeostatic maintenance via degradation and repair of elastic fibers under tension

    PubMed Central

    Alves, Calebe; Araújo, Ascanio D.; Oliveira, Cláudio L. N.; Imsirovic, Jasmin; Bartolák-Suki, Erzsébet; Andrade, José S.; Suki, Béla

    2016-01-01

    Cellular maintenance of the extracellular matrix requires an effective regulation that balances enzymatic degradation with the repair of collagen fibrils and fibers. Here, we investigate the long-term maintenance of elastic fibers under tension combined with diffusion of general degradative and regenerative particles associated with digestion and repair processes. Computational results show that homeostatic fiber stiffness can be achieved by assuming that cells periodically probe fiber stiffness to adjust the production and release of degradative and regenerative particles. However, this mechanism is unable to maintain a homogeneous fiber. To account for axial homogeneity, we introduce a robust control mechanism that is locally governed by how the binding affinity of particles is modulated by mechanical forces applied to the ends of the fiber. This model predicts diameter variations along the fiber that are in agreement with the axial distribution of collagen fibril diameters obtained from scanning electron microscopic images of normal rat thoracic aorta. The model predictions match the experiments only when the applied force on the fiber is in the range where the variance of local stiffness along the fiber takes a minimum value. Our model thus predicts that the biophysical properties of the fibers play an important role in the long-term regulatory maintenance of these fibers. PMID:27279029

  18. Homeostatic maintenance via degradation and repair of elastic fibers under tension.

    PubMed

    Alves, Calebe; Araújo, Ascanio D; Oliveira, Cláudio L N; Imsirovic, Jasmin; Bartolák-Suki, Erzsébet; Andrade, José S; Suki, Béla

    2016-06-09

    Cellular maintenance of the extracellular matrix requires an effective regulation that balances enzymatic degradation with the repair of collagen fibrils and fibers. Here, we investigate the long-term maintenance of elastic fibers under tension combined with diffusion of general degradative and regenerative particles associated with digestion and repair processes. Computational results show that homeostatic fiber stiffness can be achieved by assuming that cells periodically probe fiber stiffness to adjust the production and release of degradative and regenerative particles. However, this mechanism is unable to maintain a homogeneous fiber. To account for axial homogeneity, we introduce a robust control mechanism that is locally governed by how the binding affinity of particles is modulated by mechanical forces applied to the ends of the fiber. This model predicts diameter variations along the fiber that are in agreement with the axial distribution of collagen fibril diameters obtained from scanning electron microscopic images of normal rat thoracic aorta. The model predictions match the experiments only when the applied force on the fiber is in the range where the variance of local stiffness along the fiber takes a minimum value. Our model thus predicts that the biophysical properties of the fibers play an important role in the long-term regulatory maintenance of these fibers.

  19. Homeostatic maintenance via degradation and repair of elastic fibers under tension

    NASA Astrophysics Data System (ADS)

    Alves, Calebe; Araújo, Ascanio D.; Oliveira, Cláudio L. N.; Imsirovic, Jasmin; Bartolák-Suki, Erzsébet; Andrade, José S.; Suki, Béla

    2016-06-01

    Cellular maintenance of the extracellular matrix requires an effective regulation that balances enzymatic degradation with the repair of collagen fibrils and fibers. Here, we investigate the long-term maintenance of elastic fibers under tension combined with diffusion of general degradative and regenerative particles associated with digestion and repair processes. Computational results show that homeostatic fiber stiffness can be achieved by assuming that cells periodically probe fiber stiffness to adjust the production and release of degradative and regenerative particles. However, this mechanism is unable to maintain a homogeneous fiber. To account for axial homogeneity, we introduce a robust control mechanism that is locally governed by how the binding affinity of particles is modulated by mechanical forces applied to the ends of the fiber. This model predicts diameter variations along the fiber that are in agreement with the axial distribution of collagen fibril diameters obtained from scanning electron microscopic images of normal rat thoracic aorta. The model predictions match the experiments only when the applied force on the fiber is in the range where the variance of local stiffness along the fiber takes a minimum value. Our model thus predicts that the biophysical properties of the fibers play an important role in the long-term regulatory maintenance of these fibers.

  20. Ultrasonic Determination of the Elastic Constants of Epoxy-natural Fiber Composites

    NASA Astrophysics Data System (ADS)

    Valencia, C. A. Meza; Pazos-Ospina, J. F.; Franco, E. E.; Ealo, Joao L.; Collazos-Burbano, D. A.; Garcia, G. F. Casanova

    This paper shows the applications ultrasonic through-transmission technique to determine the elastic constants of two polymer-natural fiber composite materials with potential industrial application and economic and environmental advantages. The transversely isotropic coconut-epoxy and fique-epoxy samples were analyzed using an experimental setup which allows the sample to be rotated with respect to transducers faces and measures the time-of-flight at different angles of incidence. Then, the elastic properties of the material were obtained by fitting the experimental data to the Christoffel equation. Results show a good agreement between the measured elastic constants and the values predicted by an analytical model. The velocities as a function of the incidence angle are reported and the effect of the natural fiber on the stiffness of the composite is discussed.

  1. Critical buckling pressure in mouse carotid arteries with altered elastic fibers.

    PubMed

    Luetkemeyer, Callan M; James, Rhys H; Devarakonda, Siva Teja; Le, Victoria P; Liu, Qin; Han, Hai-Chao; Wagenseil, Jessica E

    2015-06-01

    Arteries can buckle axially under applied critical buckling pressure due to a mechanical instability. Buckling can cause arterial tortuosity leading to flow irregularities and stroke. Genetic mutations in elastic fiber proteins are associated with arterial tortuosity in humans and mice, and may be the result of alterations in critical buckling pressure. Hence, the objective of this study is to investigate how genetic defects in elastic fibers affect buckling pressure. We use mouse models of human disease with reduced amounts of elastin (Eln+/-) and with defects in elastic fiber assembly due to the absence of fibulin-5 (Fbln5-/-). We find that Eln+/- arteries have reduced buckling pressure compared to their wild-type controls. Fbln5-/- arteries have similar buckling pressure to wild-type at low axial stretch, but increased buckling pressure at high stretch. We fit material parameters to mechanical test data for Eln+/-, Fbln5-/- and wild-type arteries using Fung and four-fiber strain energy functions. Fitted parameters are used to predict theoretical buckling pressure based on equilibrium of an inflated, buckled, thick-walled cylinder. In general, the theoretical predictions underestimate the buckling pressure at low axial stretch and overestimate the buckling pressure at high stretch. The theoretical predictions with both models replicate the increased buckling pressure at high stretch for Fbln5-/- arteries, but the four-fiber model predictions best match the experimental trends in buckling pressure changes with axial stretch. This study provides experimental and theoretical methods for further investigating the influence of genetic mutations in elastic fibers on buckling behavior and the development of arterial tortuosity.

  2. Critical Buckling Pressure in Mouse Carotid Arteries with Altered Elastic Fibers

    PubMed Central

    Luetkemeyer, Callan M.; James, Rhys H.; Devarakonda, Siva Teja; Le, Victoria P.; Liu, Qin; Han, Hai-Chao; Wagenseil, Jessica E.

    2015-01-01

    Arteries can buckle axially under applied critical buckling pressure due to a mechanical instability. Buckling can cause arterial tortuosity leading to flow irregularities and stroke. Genetic mutations in elastic fiber proteins are associated with arterial tortuosity in humans and mice, and may be the result of alterations in critical buckling pressure. Hence, the objective of this study is to investigate how genetic defects in elastic fibers affect buckling pressure. We use mouse models of human disease with reduced amounts of elastin (Eln+/−) and with defects in elastic fiber assembly due to the absence of fibulin-5 (Fbln5−/−). We find that Eln+/− arteries have reduced buckling pressure compared to their wild-type controls. Fbln5−/− arteries have similar buckling pressure to wild-type at low axial stretch, but increased buckling pressure at high stretch. We fit material parameters to mechanical test data for Eln+/−, Fbln5−/− and wild-type arteries using Fung and four-fiber strain energy functions. Fitted parameters are used to predict theoretical buckling pressure based on equilibrium of an inflated, buckled, thick-walled cylinder. In general, the theoretical predictions underestimate the buckling pressure at low axial stretch and overestimate the buckling pressure at high stretch. The theoretical predictions with both models replicate the increased buckling pressure at high stretch for Fbln5−/− arteries, but the four-fiber model predictions best match the experimental trends in buckling pressure changes with axial stretch. This study provides experimental and theoretical methods for further investigating the influence of genetic mutations in elastic fibers on buckling behavior and the development of arterial tortuosity. PMID:25771258

  3. Engineering of PHB synthesis causes improved elastic properties of flax fibers.

    PubMed

    Wróbel-Kwiatkowska, Magdalena; Zebrowski, Jacek; Starzycki, Michał; Oszmiański, Jan; Szopa, Jan

    2007-01-01

    Flax stem is a source of fiber used by the textile industry. Flax fibers are separated from other parts of stems in the process called retting and are probably the first plant fibers used by man for textile purposes (1). Nowadays flax cultivation is often limited because of its lower elastic property compared to cotton fibers. Thus the goal of this study was to increase the flax fiber quality using a transgenic approach. Expression of three bacterial genes coding for beta-ketothiolase (phb A), acetoacetyl-CoA reductase (phb B), and PHB synthase (phb C) resulted in poly-beta-hydroxybutyrate (PHB) accumulation in the plant stem. PHB is known as a biodegradable thermoplastic displaying chemical and physical properties similar to those of conventional plastics (i.e., polypropylene). The fibers isolated from transgenic flax plants cultivated in the field and synthesizing PHB were then studied for biomechanical properties. All measured parameters, strength, Young's modulus, and energy for failure of flax fibers, were significantly increased. Thus the substantial improvement in elastic properties of fibers from the transgenic line has been achieved. Since the acetyl CoA, substrate for PHB synthesis, is involved not only for energy production but also for synthesis of many cellular constituents, the goal of this study was also the analysis of those metabolites, which interfere with plant physiology and thus fiber quality. The analyzed plants showed that reduction in lignin, pectin, and hemicellulose levels resulted in increased retting efficiency. A significant increase in phenolic acids was also detected, and this was the reason for improved plant resistance to pathogen infection. However, a slight decrease in crop production was detected.

  4. Nondestructive characterization of the elastic constants of fiber reinforced composites

    NASA Technical Reports Server (NTRS)

    Mal, Ajit K.; Lih, Shyh-Shiuh; Bar-Cohen, Yoseph

    1993-01-01

    Composite structural components may be subjected to a variety of defects resulting in a sharp reduction in their load carrying capacity or even catastrophic failure. Thus, it is extremely important to have the means to monitor the degradation suffered by critical components of a structure for safe operation during its service life. A nondestructive method based on ultrasonics has recently been developed for the quantitative evaluation of composite structural components during service. The experimental part of the technique uses a two-transducer, pitch-catch type arrangement to generate a variety of elastic waves within the specimen immersed in water. The recorded reflection data are then analyzed by means of a theoretical model to back out the relevant properties. In this paper the method is applied to determine the stiffness constants of unidirectional graphite/epoxy materials. The measurements are shown to be efficient and sufficiently accurate so that it can be used for early detection of material degradation in composite structural elements during service.

  5. A new constitutive theory for fiber-reinforced incompressible nonlinearly elastic solids

    NASA Astrophysics Data System (ADS)

    Horgan, Cornelius O.; Saccomandi, Giuseppe

    2005-09-01

    We consider an incompressible nonlinearly elastic material in which a matrix is reinforced by strong fibers, for example fibers of nylon or carbon aligned in one family of curves in a rubber matrix. Rather than adopting the constraint of fiber inextensibility as has been previously assumed in the literature, here we develop a theory of fiber-reinforced materials based on the less restrictive idea of limiting fiber extensibility. The motivation for such an approach is provided by recent research on limiting chain extensibility models for rubber. Thus the basic idea of the present paper is simple: we adapt the limiting chain extensibility concept to limiting fiber extensibility so that the usual inextensibility constraint traditionally used is replaced by a unilateral constraint. We use a strain-energy density composed with two terms, the first being associated with the isotropic matrix or base material and the second reflecting the transversely isotropic character of the material due to the uniaxial reinforcement introduced by the fibers. We consider a base neo-Hookean model plus a special term that takes into account the limiting extensibility in the fiber direction. Thus our model introduces an additional parameter, namely that associated with limiting extensibility in the fiber direction, over previously investigated models. The aim of this paper is to investigate the mathematical and mechanical feasibility of this new model and to examine the role played by the extensibility parameter. We examine the response of the proposed models in some basic homogeneous deformations and compare this response to those of standard models for fiber reinforced rubber materials. The role of the strain-stiffening of the fibers in the new models is examined. The enhanced stability of the new models is then illustrated by investigation of cavitation instabilities. One of the motivations for the work is to apply the model to the biomechanics of soft tissues and the potential merits

  6. Structural and Functional Small Fiber Abnormalities in the Neuropathic Postural Tachycardia Syndrome

    PubMed Central

    Gibbons, Christopher H.; Bonyhay, Istvan; Benson, Adam; Wang, Ningshan; Freeman, Roy

    2013-01-01

    Objective To define the neuropathology, clinical phenotype, autonomic physiology and differentiating features in individuals with neuropathic and non-neuropathic postural tachycardia syndrome (POTS). Methods Twenty-four subjects with POTS and 10 healthy control subjects had skin biopsy analysis of intra-epidermal nerve fiber density (IENFD), quantitative sensory testing (QST) and autonomic testing. Subjects completed quality of life, fatigue and disability questionnaires. Subjects were divided into neuropathic and non-neuropathic POTS, defined by abnormal IENFD and abnormal small fiber and sudomotor function. Results Nine of 24 subjects had neuropathic POTS and had significantly lower resting and tilted heart rates; reduced parasympathetic function; and lower phase 4 valsalva maneuver overshoot compared with those with non-neuropathic POTS (P<0.05). Neuropathic POTS subjects also had less anxiety and depression and greater overall self-perceived health-related quality of life scores than non-neuropathic POTS subjects. A sub-group of POTS patients (cholinergic POTS) had abnormal proximal sudomotor function and symptoms that suggest gastrointestinal and genitourinary parasympathetic nervous system dysfunction. Conclusions and Relevance POTS subtypes may be distinguished using small fiber and autonomic structural and functional criteria. Patients with non-neuropathic POTS have greater anxiety, greater depression and lower health-related quality of life scores compared to those with neuropathic POTS. These findings suggest different pathophysiological processes underlie the postural tachycardia in neuropathic and non-neuropathic POTS patients. The findings have implications for the therapeutic interventions to treat this disorder. PMID:24386408

  7. A cell model for homogenization of fiber-reinforced composites: General theory and nonlinear elasticity effects

    SciTech Connect

    Aidun, J.B.; Addessio, F.L.

    1995-11-01

    The theoretical basis of the homogenization technique developed by Aboudi is presented and assessed. Given the constitutive relations of the constituents, this technique provides an equivalent, homogeneous, constitutive model of unidirectional, continuous-fiber-reinforced composites. The expressions that comprise the first-order version of the technique are given special attention as this treatment has considerable practical value. Nonlinear elasticity effects are added to it. This extension increases the accuracy of numerical simulations of high strain-rate loadings. It is particularly important for any dynamic loading in which shock waves might be produced, including crash safety, armor, and munitions applications. Examples illustrate that elastic nonlinearity can make substantial contributions at strains of only a few per cent. These contributions are greatest during post-yield inelastic deformation. The micromechanics-based homogenization technique is shown to facilitate use of an efficient approximate treatment of elastic nonlinearity in composites with isotropic matrix materials.

  8. Elastosis and fragmentation of fibers of the elastic system in fatal asthma.

    PubMed

    Mauad, T; Xavier, A C; Saldiva, P H; Dolhnikoff, M

    1999-09-01

    Fibers of the elastic system (FES) are important in regulating airway patency and lung elastic recoil. Their possible role in modulating bronchoconstriction is not fully understood. Chronic inflammation and mechanical stretching present in asthma could lead to conformational alterations in the FES, participating in the mechanism of airway remodeling observed in this disease. In airway mucosa, two layers of FES are discernible: one superficial network, attached to the basement membrane, and a deeper network, lying close to the airway smooth muscle. Using image analysis and conventional morphometry, we analyzed airway content of FES in central and peripheral airways in 31 cases of fatal asthma and in 10 control lungs. Slides were stained using the oxidized resorcin-fuchsin method. Optical analysis revealed fragmentation of the FES in the superficial network of central asthmatic airways. Morphometry showed the presence of elastosis in central asthmatic airways when the entire thickness of the mucosa was considered. In the superficial network elastic fiber content was significantly decreased. These results indicate that FES participate in airway remodeling in asthma. We also suggest that disrupture of fiber attachments at the basement membrane in the superficial layer could impair the mechanism of airway recoil in asthmatic patients.

  9. Multiphoton microscopy study of the morphological and quantity changes of collagen and elastic fiber components in keloid disease

    NASA Astrophysics Data System (ADS)

    Chen, Jianxin; Zhuo, Shuangmu; Jiang, Xingshan; Zhu, Xiaoqin; Zheng, Liqin; Xie, Shusen; Lin, Bifang; Zeng, Haishan

    2011-05-01

    Multiphoton microscopy was used to study the extracellular matrix of keloid at the molecular level without tissue fixation and staining. Direct imaging of collagen and elastin was achieved by second harmonic generation and two-photon excited fluorescence, respectively. The morphology and quantity of collagen and elastin in keloid were characterized and quantitatively analyzed in comparison to normal skin. The study demonstrated that in keloid, collagen content increased in both the upper dermis and the deep dermis, while elastin mostly showed up in the deep dermis and its quantity is higher compared to normal skin. This suggests the possibility that abnormal fibroblasts synthesized an excessive amount of collagen and elastin at the beginning of keloid formation, corresponding to the observed deep dermis, while after a certain time point, the abnormal fibroblast produced mostly collagen, corresponding to the observed upper dermis. The morphology of collagen and elastin in keloid was disrupted and presented different variations. In the deep dermis, elastic fibers showed node structure, while collagen showed obviously regular gaps between adjacent bundles. In the upper dermis, collagen bundles aligned in a preferred direction, while elastin showed as sparse irregular granules. This new molecular information provided fresh insight about the development process of keloid.

  10. Prediction of the Elastic-Plastic Stress/Strain Response for Injection-Molded Long-Fiber Thermoplastics

    SciTech Connect

    Nguyen, Ba Nghiep; Bapanapalli, Satish K.; Kunc, Vlastimil; Phelps, Jay; Tucker III, Charles L.

    2009-01-26

    This paper proposes a model to predict the elastic-plastic response of injection-molded long-fiber thermoplastics (LFTs). The model accounts for elastic fibers embedded in a thermoplastic resin that exhibits the elastic-plastic behavior obeying the Ramberg-Osgood relation and J-2 deformation theory of plasticity. It also accounts for fiber length and orientation distributions in the composite formed by the injection-molding process. Fiber orientation was predicted using the anisotropic rotary diffusion model recently developed by Phelps and Tucker for LFTs. An incremental procedure using the Eshelby’s equivalent inclusion method and the Mori-Tanaka model is proposed to compute the overall stress increment resulting from an overall strain increment for an aligned fiber composite that contains the same fiber volume fraction and length distribution as the actual composite. The incremental response of the later is then obtained from the solution for the aligned fiber composite that is averaged over all possible fiber orientations using the orientation averaging method. Failure during incremental loading is predicted using the Van Hattum-Bernado model. The elastic-plastic and strength prediction model for LFTs was validated against the experimental stress-strain results obtained for long glass fiber/polypropylene specimens.

  11. Deformation and strength of silica fibers in three-point bending in consideration of nonlinear elasticity of glass

    NASA Astrophysics Data System (ADS)

    Baikova, L. G.; Pesina, T. I.; Mansyrev, E. I.; Kireenko, M. F.; Tikhonova, L. V.

    2017-01-01

    We consider the problem of asymmetric strain and stress distribution in silica fiber under threepoint bending. The parameters of nonlinear elasticity of silica glass under tension and compression are estimated using available data from the literature. It has been found that consideration of the nonlinear elasticity of silica glass leads to a slight increase in the calculated values of strength compared to the data obtained from estimates based on the linear theory of elasticity.

  12. Dynamic interrogator for elastic wave sensing using Fabry Perot filters based on fiber Bragg gratings.

    PubMed

    Harish, Achar V; Varghese, Bibin; Rao, Babu; Balasubramaniam, Krishnan; Srinivasan, Balaji

    2015-07-01

    Use of in-fiber Fabry-Perot (FP) filters based on fiber Bragg gratings as both sensor as well as an interrogator for enhancing the detection limit of elastic wave sensing is investigated in this paper. The sensitivity of such a demodulation scheme depends on the spectral discrimination of the sensor and interrogator gratings. Simulations have shown that the use of in-fiber FP filters with high finesse provide better performance in terms of sensitivity compared to the demodulation using fiber Bragg gratings. Based on these results, a dynamic interrogator capable of sensing acoustic waves with amplitude of less than 1 micro-strain over frequencies of 10 kHz to several 100 kHz has been implemented. Frequency response of the fiber Bragg gratings in the given experimental setup has been compared to that of the conventional piezo sensors demonstrating that fiber Bragg gratings can be used over a relatively broad frequency range. Dynamic interrogator has been packaged in a compact box without any degradation in its performance.

  13. Stochastic mechanical degradation of multi-cracked fiber bundles with elastic and viscous interactions.

    PubMed

    Manca, Fabio; Giordano, Stefano; Palla, Pier Luca; Cleri, Fabrizio

    2015-05-01

    The mechanics of fiber bundles has been largely investigated in order to understand their complex failure modes. Under a mechanical load, the fibers fail progressively while the load is redistributed among the unbroken fibers. The classical fiber bundle model captures the most important features of this rupture process. On the other hand, the homogenization techniques are able to evaluate the stiffness degradation of bulk solids with a given population of cracks. However, these approaches are inadequate to determine the effective response of a degraded bundle where breaks are induced by non-mechanical actions. Here, we propose a method to analyze the behavior of a fiber bundle, undergoing a random distribution of breaks, by considering the intrinsic response of the fibers and the visco-elastic interactions among them. We obtain analytical solutions for simple configurations, while the most general cases are studied by Monte Carlo simulations. We find that the degradation of the effective bundle stiffness can be described by two scaling regimes: a first exponential regime for a low density of breaks, followed by a power-law regime at increasingly higher break density. For both regimes, we find analytical effective expressions described by specific scaling exponents.

  14. Biaxial Stretch Improves Elastic Fiber Maturation, Collagen Arrangement, and Mechanical Properties in Engineered Arteries.

    PubMed

    Huang, Angela H; Balestrini, Jenna L; Udelsman, Brooks V; Zhou, Kevin C; Zhao, Liping; Ferruzzi, Jacopo; Starcher, Barry C; Levene, Michael J; Humphrey, Jay D; Niklason, Laura E

    2016-06-01

    Tissue-engineered blood vessels (TEVs) are typically produced using the pulsatile, uniaxial circumferential stretch to mechanically condition and strengthen the arterial grafts. Despite improvements in the mechanical integrity of TEVs after uniaxial conditioning, these tissues fail to achieve critical properties of native arteries such as matrix content, collagen fiber orientation, and mechanical strength. As a result, uniaxially loaded TEVs can result in mechanical failure, thrombus, or stenosis on implantation. In planar tissue equivalents such as artificial skin, biaxial loading has been shown to improve matrix production and mechanical properties. To date however, multiaxial loading has not been examined as a means to improve mechanical and biochemical properties of TEVs during culture. Therefore, we developed a novel bioreactor that utilizes both circumferential and axial stretch that more closely simulates loading conditions in native arteries, and we examined the suture strength, matrix production, fiber orientation, and cell proliferation. After 3 months of biaxial loading, TEVs developed a formation of mature elastic fibers that consisted of elastin cores and microfibril sheaths. Furthermore, the distinctive features of collagen undulation and crimp in the biaxial TEVs were absent in both uniaxial and static TEVs. Relative to the uniaxially loaded TEVs, tissues that underwent biaxial loading remodeled and realigned collagen fibers toward a more physiologic, native-like organization. The biaxial TEVs also showed increased mechanical strength (suture retention load of 303 ± 14.53 g, with a wall thickness of 0.76 ± 0.028 mm) and increased compliance. The increase in compliance was due to combinatorial effects of mature elastic fibers, undulated collagen fibers, and collagen matrix orientation. In conclusion, biaxial stretching is a potential means to regenerate TEVs with improved matrix production, collagen organization, and mechanical

  15. Evaporation of drops on two parallel fibers: influence of the liquid morphology and fiber elasticity.

    PubMed

    Duprat, Camille; Bick, Alison D; Warren, Patrick B; Stone, Howard A

    2013-06-25

    We investigate experimentally the evaporation of liquid accumulated on a pair of parallel fibers, rigid or flexible. The liquid wetting the fibers can adopt two distinct morphologies: a compact drop shape, whose evaporation dynamics is similar to that of an isolated aerosol droplet, or a long liquid column of constant cross-section, whose evaporation dynamics depends upon the aspect ratio of the column. We thus find that the evaporation rate is constant for drops, while it increases strongly for columns as the interfiber distance decreases, and we propose a model to explain this behavior. When the fibers are flexible, the transition from drops to columns can be induced by the deformation of the fibers because of the capillary forces applied by the drop. Thus, we find that the evaporation rate increases with increasing flexibility. Furthermore, complex morphology transitions occur upon drying, which results in spreading of the drop as it evaporates.

  16. The Effects of Elastic Fiber Protein Insufficiency and Treatment on the Modulus of Arterial Smooth Muscle Cells

    PubMed Central

    Gabriela Espinosa, M.; Gardner, William S.; Bennett, Lisa; Sather, Bradley A.; Yanagisawa, Hiromi; Wagenseil, Jessica E.

    2014-01-01

    Elastic fibers are critical for the mechanical function of the large arteries. Mechanical effects of elastic fiber protein deficiency have been investigated in whole arteries, but not in isolated smooth muscle cells (SMCs). The elastic moduli of SMCs from elastin (Eln-/-) and fibulin-4 (Fbln4-/-) knockout mice were measured using atomic force microscopy. Compared to control SMCs, the modulus of Eln-/- SMCs is reduced by 40%, but is unchanged in Fbln4-/- SMCs. The Eln-/- SMC modulus is rescued by soluble or α elastin treatment. Altered gene expression, specifically of calponin, suggests that SMC phenotypic modulation may be responsible for the modulus changes. PMID:24322348

  17. Dynamic effective elastic modulus of polymer matrix composites with dense piezoelectric nano-fibers considering surface/interface effect

    NASA Astrophysics Data System (ADS)

    Fang, XueQian; Huang, MingJuan; Zhu, ZiTao; Liu, JinXi; Feng, WenJie

    2015-01-01

    Based on effective field method, the dynamic effective elastic modulus of polymer matrix composites embedded with dense piezoelectric nano-fibers is obtained, and the interacting effect of piezoelectric surfaces/interfaces around the nano-fibers is considered. The multiple scattering effects of harmonic anti-plane shear waves between the piezoelectric nano-fibers with surface/interface are averaged by effective field method. To analyze the interacting results among the random nano-fibers, the problem of two typical piezoelectric nano-fibers is introduced by employing the addition theorem of Bessel functions. Through numerical calculations, the influence of the distance between the randomly distributed piezoelectric nano-fibers under different surface/interface parameters is analyzed. The effect of piezoelectric property of surface/interface on the effective shear modulus under different volume fractions is also examined. Comparison with the simplified cases is given to validate this dynamic electro-elastic model.

  18. Ultrashort optical waveguide excitations in uniaxial silica fibers: elastic collision scenarios.

    PubMed

    Kuetche, Victor K; Youssoufa, Saliou; Kofane, Timoleon C

    2014-12-01

    In this work, we investigate the dynamics of an uniaxial silica fiber under the viewpoint of propagation of ultimately ultrashort optical waveguide channels. As a result, we unveil the existence of three typical kinds of ultrabroadband excitations whose profiles strongly depend upon their angular momenta. Looking forward to surveying their scattering features, we unearth some underlying head-on scenarios of elastic collisions. Accordingly, we address some useful and straightforward applications in nonlinear optics through secured data transmission systems, as well as laser physics and soliton theory with optical soliton dynamics.

  19. On the elastic properties of fiber composite laminates with statistically dispersed fiber and ply orientations.

    NASA Technical Reports Server (NTRS)

    Robinson, E. Y.

    1973-01-01

    Structural application of advanced composite filamentary materials requires lamination of the basic orthotropic plies into angle-ply laminates. This article reviews the effect on elastic properties of orientation dispersion. The conventional constitutive relations are recast in a homologous form to account for uniform orientation dispersion by addition of a single parameter. Graphical results are presented to show the behavior of the most important advanced composite materials. The results are directly useful for estimating effects of manufacturing inaccuracy and for design of partially oriented reinforced structures.

  20. Extremely Elastic Wearable Carbon Nanotube Fiber Strain Sensor for Monitoring of Human Motion.

    PubMed

    Ryu, Seongwoo; Lee, Phillip; Chou, Jeffrey B; Xu, Ruize; Zhao, Rong; Hart, Anastasios John; Kim, Sang-Gook

    2015-06-23

    The increasing demand for wearable electronic devices has made the development of highly elastic strain sensors that can monitor various physical parameters an essential factor for realizing next generation electronics. Here, we report an ultrahigh stretchable and wearable device fabricated from dry-spun carbon nanotube (CNT) fibers. Stretching the highly oriented CNT fibers grown on a flexible substrate (Ecoflex) induces a constant decrease in the conductive pathways and contact areas between nanotubes depending on the stretching distance; this enables CNT fibers to behave as highly sensitive strain sensors. Owing to its unique structure and mechanism, this device can be stretched by over 900% while retaining high sensitivity, responsiveness, and durability. Furthermore, the device with biaxially oriented CNT fiber arrays shows independent cross-sensitivity, which facilitates simultaneous measurement of strains along multiple axes. We demonstrated potential applications of the proposed device, such as strain gauge, single and multiaxial detecting motion sensors. These devices can be incorporated into various motion detecting systems where their applications are limited to their strain.

  1. Egestion of asbestos fibers in Tetrahymena results in early morphological abnormalities. A step in the induction of heterogeneous cell lines?

    PubMed

    Hjelm, K K

    1989-01-01

    In Tetrahymena populations exposed to crocidolite asbestos fibers, many cells develop morphological abnormalities within 1-2 hours. The abnormalities are mainly large or small protrusions or indentations, or flattened parts of the cell surface and most often located in the posterior part of the cell. They are formed repeatedly in all cells but are also continuously repaired so that the fraction of cells affected represents an equilibrium between these two processes. Their formation is connected with egestion of the large bundles of fibers formed by phagocytosis. Such effects of egestion of fibers do not seem to have been reported previously. Egestion of a bundle of fibers is much slower than for other types of undigestible residues. In contrast to normal exocytosis occurring invariably at the cytoproct, egestion of asbestos often occurs in the posterior part of the cell outside the cytoproct. To my knowledge this is the first reported case of either very slow or extra-cytoproctal egestion in Tetrahymena. Cells with large abnormalities have a greater tendency to develop into "early heterogeneous" cells than the average abnormal cell. Some of these give rise to hereditarily stable heterogeneous cell lines of Tetrahymena. The morphological abnormalities are probably caused by mechanical action of the crocidolite fibers resulting in local damage of the cytoskeletal elements responsible for normal cell shape. The heterogenous cell lines may arise when cellular structures carrying non-genic cytotactically inherited information are modified. The relevance of these ideas to the induction of cancer by asbestos is briefly discussed.

  2. Influence of fiber architecture on the elastic an d inelastic response of metal matrix composites

    NASA Technical Reports Server (NTRS)

    Arnold, Steven M.; Pindera, Marek-Jerzy; Wilt, Thomas E.

    1995-01-01

    This three part paper focuses on the effect of fiber architecture (i.e., shape and distribution) on the elastic and inelastic response of metal matrix composites. The first part provides an annotative survey of the literature, presented as a historical perspective, dealing with the effects of fiber shape and distribution on the response of advanced polymeric matrix and metal matrix composites. Previous investigations dealing with both continuously and discontinuously reinforced composites are included. A summary of the state-of-the-art will assist in defining new directions in this quickly reviving area of research. The second part outlines a recently developed analytical micromechanics model that is particularly well suited for studying the influence of these effects on the response of metal matrix composites. This micromechanics model, referred to as the generalized method of cells (GMC), is capable of predicting the overall, inelastic behavior of unidirectional, multi-phased composites given the properties of the constituents. In particular, the model is sufficiently general to predict the response of unidirectional composites reinforced by either continuous or discontinuous fibers with different inclusion shapes and spatial arrangements in the presence of either perfect or imperfect interfaces and/or interfacial layers. Recent developments regarding this promising model, as well as directions for future enhancements of the model's predictive capability, are included. Finally, the third pan provides qualitative results generated using GMC for a representative titanium matix composite system, SCS-6/TlMETAL 21S. Results are presented that correctly demonstrate the relative effects of fiber arrangement and shape on the longitudinal and transverse stress-strain and creep response, with both strong and weak fiber/matrix interfacial bonds. The fiber arrangements include square, square diagonal, hexagonal and rectangular periodic arrays, as well as a random array. The

  3. Effect of carbon and glass fiber posts on the flexural strength and modulus of elasticity of a composite resin.

    PubMed

    Pereira, Jefferson Ricardo; de Oliveira, Jonas Alves; do Valle, Accacio Lins; Zogheib, Lucas Villaca; Ferreira, Paulo Martins; Bastos, Luiz Gustavo Cavalcanti

    2011-01-01

    The aim of this study was to evaluate the effect of prefabricated fiber posts on the flexural strength and modulus of elasticity of a composite resin. Thirty bar-shaped specimens measuring 25 x 2.0 x 2.0 mm were made, containing posts that were 1.3 mm in diameter and 20 mm long. Each group contained 10 specimens: Group 1, resin without post; Group 2, resin with carbon fiber post; Group 3, resin with glass fiber post. The samples were immersed in water at 37 degrees C until the three-point loading test was performed at a speed of 1.0 mm/minute. The results were statistically analyzed by ANOVA and Tukey's test (P = 0.05). Both fiber posts were similar in strength and both were stronger than the control. Group 3 obtained a higher mean modulus of elasticity than Groups 1 and 2, which were similar. The results of this study demonstrated that the presence of a fiber post significantly raised flexural strength values and the glass fiber post significantly increased the modulus of elasticity of the evaluated composite resin.

  4. Cutis laxa: intersection of elastic fiber biogenesis, TGFβ signaling, the secretory pathway and metabolism.

    PubMed

    Urban, Zsolt; Davis, Elaine C

    2014-01-01

    Cutis laxa (CL), a disease characterized by redundant and inelastic skin, displays extensive locus heterogeneity. Together with geroderma osteodysplasticum and arterial tortuosity syndrome, which show phenotypic overlap with CL, eleven CL-related genes have been identified to date, which encode proteins within 3 groups. Elastin, fibulin-4, fibulin-5 and latent transforming growth factor-β-binding protein 4 are secreted proteins which form elastic fibers and are involved in the sequestration and subsequent activation of transforming growth factor-β (TGFβ). Proteins within the second group, localized to the secretory pathway, perform transport and membrane trafficking functions necessary for the modification and secretion of elastic fiber components. Key proteins include a subunit of the vacuolar-type proton pump, which ensures the efficient secretion of tropoelastin, the precursor or elastin. A copper transporter is required for the activity of lysyl oxidases, which crosslink collagen and elastin. A Rab6-interacting goglin recruits kinesin motors to Golgi-vesicles facilitating the transport from the Golgi to the plasma membrane. The Rab and Ras interactor 2 regulates the activity of Rab5, a small guanosine triphosphatase essential for the endocytosis of various cell surface receptors, including integrins. Proteins of the third group related to CL perform metabolic functions within the mitochondria, inhibiting the accumulation of reactive oxygen species. Two of these proteins catalyze subsequent steps in the conversion of glutamate to proline. The third transports dehydroascorbate into mitochondria. Recent studies on CL-related proteins highlight the intricate connections among membrane trafficking, metabolism, extracellular matrix assembly, and TGFβ signaling.

  5. Second- and Third-Order Elastic Constants of Filaments of HexTow® IM7 Carbon Fiber

    NASA Astrophysics Data System (ADS)

    Oliveira, L.; Hitchcock, D.; Behlow, H.; Podila, R.; Skove, M. J.; Serkiz, S. M.; Rao, A. M.

    2014-03-01

    Single filaments of HexTow® IM7-12K carbon fiber were subjected to tensile measurements on a device which applies a known stress σ, and measures the resulting strain ɛ, and the change in resistivity Δρ. Young's modulus E, the resistivity ρ, the piezoresistivity Δρ/ρɛ, and the nonlinearity in the stress-strain relation δ, were determined to be 264.1 ± 16.0 GPa, 1.5 ± 0.1 × 10-3 Ω cm, 1.3 ± 0.1, and -4.96 ± 0.23, respectively. The values obtained for Young's modulus and the resistivity of the fiber are in reasonable agreement with the values reported by the manufacturer. To the best of our knowledge, this is the first report of a measurement of a third-order elastic constant of a single filament of HexTow® IM7-12K. Given the high elastic strains attainable in these fibers and the negative value of δ, the usual calculation of E from a linear fit to the stress-strain data leads to an incorrect higher value of E. According to the accepted thermodynamic definition of the elastic constants, one must use the initial slope of the stress-strain curve to evaluate E. We also observed that the glue used to secure the fiber has an influence on the apparent modulus of the fiber.

  6. EMTA’s Evaluation of the Elastic Properties for Fiber Polymer Composites Potentially Used in Hydropower Systems

    SciTech Connect

    Nguyen, Ba Nghiep; Paquette, Joshua

    2010-08-01

    Fiber-reinforced polymer composites can offer important advantages over metals where lightweight, cost-effective manufacturing and high mechanical performance can be achieved. To date, these materials have not been used in hydropower systems. In view of the possibility to tailor their mechanical properties to specific applications, they now have become a subject of research for potential use in hydropower systems. The first step in any structural design that uses composite materials consists of evaluating the basic composite mechanical properties as a function of the as-formed composite microstructure. These basic properties are the elastic stiffness, stress-strain response, and strength. This report describes the evaluation of the elastic stiffness for a series of common discontinuous fiber polymer composites processed by injection molding and compression molding in order to preliminarily estimate whether these composites could be used in hydropower systems for load-carrying components such as turbine blades. To this end, the EMTA (Copyright © Battelle 2010) predictive modeling tool developed at the Pacific Northwest National Laboratory (PNNL) has been applied to predict the elastic properties of these composites as a function of three key microstructural parameters: fiber volume fraction, fiber orientation distribution, and fiber length distribution. These parameters strongly control the composite mechanical performance and can be tailored to achieve property enhancement. EMTA uses the standard and enhanced Mori-Tanaka type models combined with the Eshelby equivalent inclusion method to predict the thermoelastic properties of the composite based on its microstructure.

  7. Channelling of elastic waves in an eight-ply fiber composite plate

    NASA Astrophysics Data System (ADS)

    Green, E. Rhian; Green, W. A.

    2000-05-01

    The paper is concerned with the channeling of elastic waves propagating in an eight-ply quasi-isotropic laminate arising from impulsive line sources of dislocation located at each of the seven interfaces in turn. The laminate is composed of identical layers of fiber composite material which is modeled as a transversely isotropic continuum with the axis of transverse isotropy along the fiber direction. The line sources set up a straight crested wave travelling along the laminate in the direction normal to the load line and the elastodynamic equations within each layer are solved by taking Laplace transforms with respect to time and Fourier transforms with response to the co-ordinate in the propagation direction. The resulting system of six first order differential equations in each layer are solved to obtain the transforms of the displacement and stress components throughout the laminate. The time history of any displacement or stress component at any location may then be recovered by numerical inversion of the double transform. This numerical inversion involves a summation over the normal modes of Rayleigh-Lamb waves and in an earlier paper, it has been shown that for some locations of the line source, the contribution to the upper surface normal displacement from the fundamental mode is swamped by contributions from some of the higher modes. Here, details are presented of the displacement variation through the laminate associated with the different Rayleigh-Lamb modes showing how the disturbance is channelled in some layers for specific locations of the source line.

  8. A micromechanical approach to elastic and viscoelastic properties of fiber reinforced concrete

    SciTech Connect

    Pasa Dutra, V.F.; Maghous, S. Campos Filho, A.; Pacheco, A.R.

    2010-03-15

    Some aspects of the constitutive behavior of fiber reinforced concrete (FRC) are investigated within a micromechanical framework. Special emphasis is put on the prediction of creep of such materials. The linear elastic behavior is first examined by implementation of a Mori-Tanaka homogenization scheme. The micromechanical predictions for the overall stiffness prove to be very close to finite element solutions obtained from the numerical analysis of a representative elementary volume of FRC modeled as a randomly heterogeneous medium. The validation of the micromechanical concepts based on comparison with a set of experiments, shows remarkable predictive capabilities of the micromechanical representation. The second part of the paper is devoted to non-ageing viscoelasticity of FRC. Adopting a Zener model for the behavior of the concrete matrix and making use of the correspondence principle, the homogenized relaxation moduli are derived analytically. The validity of the model is established by mean of comparison with available experiment measurements of creep strain of steel fiber reinforced concrete under compressive load. Finally, the model predictions are compared to those derived from analytical models formulated within a one-dimensional setting.

  9. A mechanical model of actin stress fiber formation and substrate elasticity sensing in adherent cells.

    PubMed

    Walcott, Sam; Sun, Sean X

    2010-04-27

    Tissue cells sense and respond to the stiffness of the surface on which they adhere. Precisely how cells sense surface stiffness remains an open question, though various biochemical pathways are critical for a proper stiffness response. Here, based on a simple mechanochemical model of biological friction, we propose a model for cell mechanosensation as opposed to previous more biochemically based models. Our model of adhesion complexes predicts that these cell-surface interactions provide a viscous drag that increases with the elastic modulus of the surface. The force-velocity relation of myosin II implies that myosin generates greater force when the adhesion complexes slide slowly. Then, using a simple cytoskeleton model, we show that an external force applied to the cytoskeleton causes actin filaments to aggregate and orient parallel to the direction of force application. The greater the external force, the faster this aggregation occurs. As the steady-state probability of forming these bundles reflects a balance between the time scale of bundle formation and destruction (because of actin turnover), more bundles are formed when the cytoskeleton time-scale is small (i.e., on stiff surfaces), in agreement with experiment. As these large bundles of actin, called stress fibers, appear preferentially on stiff surfaces, our mechanical model provides a mechanism for stress fiber formation and stiffness sensing in cells adhered to a compliant surface.

  10. Abnormal Skeletal Muscle Regeneration plus Mild Alterations in Mature Fiber Type Specification in Fktn-Deficient Dystroglycanopathy Muscular Dystrophy Mice

    PubMed Central

    Foltz, Steven J.; Modi, Jill N.; Melick, Garrett A.; Abousaud, Marin I.; Luan, Junna; Fortunato, Marisa J.; Beedle, Aaron M.

    2016-01-01

    Glycosylated α-dystroglycan provides an essential link between extracellular matrix proteins, like laminin, and the cellular cytoskeleton via the dystrophin-glycoprotein complex. In secondary dystroglycanopathy muscular dystrophy, glycosylation abnormalities disrupt a complex O-mannose glycan necessary for muscle structural integrity and signaling. Fktn-deficient dystroglycanopathy mice develop moderate to severe muscular dystrophy with skeletal muscle developmental and/or regeneration defects. To gain insight into the role of glycosylated α-dystroglycan in these processes, we performed muscle fiber typing in young (2, 4 and 8 week old) and regenerated muscle. In mice with Fktn disruption during skeletal muscle specification (Myf5/Fktn KO), newly regenerated fibers (embryonic myosin heavy chain positive) peaked at 4 weeks old, while total regenerated fibers (centrally nucleated) were highest at 8 weeks old in tibialis anterior (TA) and iliopsoas, indicating peak degeneration/regeneration activity around 4 weeks of age. In contrast, mature fiber type specification at 2, 4 and 8 weeks old was relatively unchanged. Fourteen days after necrotic toxin-induced injury, there was a divergence in muscle fiber types between Myf5/Fktn KO (skeletal-muscle specific) and whole animal knockout induced with tamoxifen post-development (Tam/Fktn KO) despite equivalent time after gene deletion. Notably, Tam/Fktn KO retained higher levels of embryonic myosin heavy chain expression after injury, suggesting a delay or abnormality in differentiation programs. In mature fiber type specification post-injury, there were significant interactions between genotype and toxin parameters for type 1, 2a, and 2x fibers, and a difference between Myf5/Fktn and Tam/Fktn study groups in type 2b fibers. These data suggest that functionally glycosylated α-dystroglycan has a unique role in muscle regeneration and may influence fiber type specification post-injury. PMID:26751696

  11. The time-dependent magneto-visco-elastic behavior of a magnetostrictive fiber actuated viscoelastic polymer matrix composite.

    PubMed

    Hogea, Cosmina S; Armstrong, William D

    2002-11-01

    The paper develops a one-dimensional magneto-elastic model of a magnetostrictive fiber actuated polymer matrix composite material which accounts for a strong viscoelastic response in the polymer matrix. The viscoelastic behavior of the composite polymer matrix is modeled with a three parallel Maxwell element viscoelastic model, the magnetoelastic behavior of the composite fibers is modeled with an anhysteric directional potential based domain occupation theory. Example calculations are performed to identify and explain the dynamical behavior of the composite. These calculations assume that a constant stress and the oscillating magnetic field are applied in the fiber longitudinal direction. The inclusion of matrix viscosity results in an apparent hysteresis loop in the magnetization and magnetostriction curves even though the model does not include magnetoelastic hysteresis in the fibers. The apparent hysteresis is a consequence of the interaction of the time varying fiber stress caused by matrix viscosity with a multidomain state in the fiber. The small increase in fiber longitudinal compressive stress due to matrix viscosity under increasing field inhibits the occupation of domains with magnetization orientations near the fiber longitudinal [112] direction. As a consequence, the summed longitudinal magnetization and magnetostriction is reduced as compared to the decreasing field limb.

  12. Elastic anisotropy of uniaxial mineralized collagen fibers measured using two-directional indentation. Effects of hydration state and indentation depth

    PubMed Central

    Spiesz, Ewa M.; Roschger, Paul; Zysset, Philippe K.

    2012-01-01

    Mineralized turkey leg tendon (MTLT) is an attractive model of mineralized collagen fibers, which are also present in bone. Its longitudinal structure is advantageous for the relative simplicity in modeling, yet its anisotropic elastic properties remain unknown. The aim of this study was to quantify the extent of elastic anisotropy of mineralized collagen fibers by using nano- and microindentation to probe a number on MTLT samples in two orthogonal directions. The large dataset allowed the quantification of the extent of anisotropy, depending on the final indentation depth and on the hydration state of the sample. Anisotropy was observed to increase with the sample re-hydration process. Artifacts of indentation in a transverse direction to the main axis of the mineralized tendons in re-hydrated condition were observed. The indentation size effect, that is, the increase of the measured elastic properties with decreasing sampling volume, reported previously on variety of materials, was also observed in MTLT. Indentation work was quantified for both directions of indentation in dried and re-hydrated conditions. As hypothesized, MTLT showed a higher extent of anisotropy compared to cortical and trabecular bone, presumably due to the alignment of mineralized collagen fibers in this tissue. PMID:22664658

  13. Generation of narrowband elastic waves with a fiber laser and its application to the imaging of defects in a plate.

    PubMed

    Hayashi, Takahiro; Ishihara, Ken

    2017-01-26

    Pulsed laser equipment can be used to generate elastic waves through the instantaneous reaction of thermal expansion or ablation of the material; however, we cannot control the waveform generated by the laser in the same manner that we can when piezoelectric transducers are used as exciters. This study investigates the generation of narrowband tone-burst waves using a fiber laser of the type that is widely used in laser beam machining. Fiber lasers can emit laser pulses with a high repetition rate on the order of MHz, and the laser pulses can be modulated to a burst train by external signals. As a consequence of the burst laser emission, a narrowband tone-burst elastic wave is generated. We experimentally confirmed that the elastic waves agreed well with the modulation signals in time domain waveforms and their frequency spectra, and that waveforms can be controlled by the generation technique. We also apply the generation technique to defect imaging with a scanning laser source. In the experiments, with small laser emission energy, we were not able to obtain defect images from the signal amplitude due to low signal-to-noise ratio, whereas using frequency spectrum peaks of the tone-burst signals gave clear defect images, which indicates that the signal-to-noise ratio is improved in the frequency domain by using this technique for the generation of narrowband elastic waves. Moreover, even for defect imaging at a single receiving point, defect images were enhanced by taking an average of distributions of frequency spectrum peaks at different frequencies.

  14. Light-intensity-induced characterization of elastic constants and d33 piezoelectric coefficient of PLZT single fiber based transducers.

    PubMed

    Kozielski, Lucjan; Erhart, Jiri; Clemens, Frank Jörg

    2013-02-12

    Enhanced functionality of electro-optic devices by implementing piezoelectric micro fibers into their construction is proposed. Lanthanum-modified lead zirconate titanate (PLZT) ceramics are known to exhibit high light transparency, desirable electro-optic properties and fast response. In this study PLZT fibers with a diameter of around 300 microns were produced by a thermoplastic processing method and their light-induced impedance and piezoelectric coefficient were investigated at relatively low light intensity (below 50 mW/cm2). The authors experimentally proved higher performance of light controlled microfiber transducers in comparison to their bulk form. The advantage of the high surface area to volume ratio is shown to be an excellent technique to design high quality light sensors by using fibrous materials. The UV absorption induced change in elastic constants of 3% and 4% for the piezoelectric coefficient d(33).

  15. Light-Intensity-Induced Characterization of Elastic Constants and d33 Piezoelectric Coefficient of PLZT Single Fiber Based Transducers

    PubMed Central

    Kozielski, Lucjan; Erhart, Jiri; Clemens, Frank Jörg

    2013-01-01

    Enhanced functionality of electro-optic devices by implementing piezoelectric micro fibers into their construction is proposed. Lanthanum-modified lead zirconate titanate (PLZT) ceramics are known to exhibit high light transparency, desirable electro-optic properties and fast response. In this study PLZT fibers with a diameter of around 300 microns were produced by a thermoplastic processing method and their light-induced impedance and piezoelectric coefficient were investigated at relatively low light intensity (below 50 mW/cm2). The authors experimentally proved higher performance of light controlled microfiber transducers in comparison to their bulk form. The advantage of the high surface area to volume ratio is shown to be an excellent technique to design high quality light sensors by using fibrous materials. The UV absorption induced change in elastic constants of 3% and 4% for the piezoelectric coefficient d33. PMID:23403643

  16. Anogenital Mammary-Like Glands: A Study of Their Normal Histology With Emphasis on Glandular Depth, Presence of Columnar Epithelial Cells, and Distribution of Elastic Fibers.

    PubMed

    Konstantinova, Anastasia M; Kyrpychova, Liubov; Belousova, Irena E; Spagnolo, Dominic V; Kacerovska, Denisa; Michal, Michal; Kerl, Katrin; Kazakov, Dmitry V

    2016-10-18

    The normal histology of anogenital mammary-like glands (AGMLG) has been studied previously, but some aspects, including glandular depth, presence of columnar epithelium resembling columnar cell change/hyperplasia as defined in mammary pathology, and distribution of elastic fibers, have not been previously investigated. To address these issues, we studied 148 AGMLG identified in 133 paraffin blocks sampled from 64 vulvar wide excision or vulvectomy specimens (64 patients, various indications for surgery). The depth of AGMLG ranged from 0.64 to 3.9 mm. Epithelial columnar cell change was noted in 33.1% of all AGMLG, whereas columnar cell hyperplasia was detected in 10.1%. Occasionally, combinations of cuboidal epithelium and columnar cell change were seen within 1 histological section. Of 22 specimens stained for elastic fibers, in only 6 (27.3%) cases were elastic fibers found around glands. Periductal elastic fibers were demonstrated around 3 of the only 5 ducts, which were available for analysis in slides stained for elastic fibers. The depth of AGMLG should be taken into account when planning topical and surgical therapies for lesions derived or evolving from AGMLG. Alterations identical to columnar cell change may represent a normal variation of AGMLG.

  17. Lysosomal sialidase (neuraminidase-1) is targeted to the cell surface in a multiprotein complex that facilitates elastic fiber assembly.

    PubMed

    Hinek, Aleksander; Pshezhetsky, Alexey V; von Itzstein, Mark; Starcher, Barry

    2006-02-10

    We have established previously that the 67-kDa elastin-binding protein (EBP), identical to the spliced variant of beta-galactosidase, acts as a recyclable chaperone that facilitates secretion of tropoelastin. (Hinek, A., Keeley, F. W., and Callahan, J. W. (1995) Exp. Cell Res. 220, 312-324). We now demonstrate that EBP also forms a cell surface-targeted molecular complex with protective protein/cathepsin A and sialidase (neuraminidase-1), and provide evidence that this sialidase activity is a prerequisite for the subsequent release of tropoelastin. We found that treatment with sialidase inhibitors repressed assembly of elastic fibers in cultures of human skin fibroblasts, aortic smooth muscle cells, and ear cartilage chondrocytes and caused impaired elastogenesis in developing chick embryos. Fibroblasts derived from patients with congenital sialidosis (primary deficiency of neuraminidase-1) and galactosialidosis (secondary deficiency of neuraminidase-1) demonstrated impaired elastogenesis, which could be reversed after their transduction with neuraminidase-1 cDNA or after treatment with bacterial sialidase, which has a similar substrate specificity to human neuraminidase-1. We postulate that neuraminidase-1 catalyzes removal of the terminal sialic acids from carbohydrate chains of microfibrillar glycoproteins and other adjacent matrix glycoconjugates, unmasking their penultimate galactosugars. In turn, the exposed galactosugars interact with the galectin domain of EBP, thereby inducing the release of transported tropoelastin molecules and facilitating their subsequent assembly into elastic fibers.

  18. Determination of Elastic Moduli of Fiber-Resin Composites Using an Impulse Excitation Technique

    NASA Technical Reports Server (NTRS)

    Viens, Michael J.; Johnson, Jeffrey J.

    1996-01-01

    The elastic moduli of graphite/epoxy and graphite/cyanate ester composite specimens with various laminate lay-ups was determined using an impulse excitation/acoustic resonance technique and compared to those determined using traditional strain gauge and extensometer techniques. The stiffness results were also compared to those predicted from laminate theory using uniaxial properties. The specimen stiffnesses interrogated ranged from 12 to 30 Msi. The impulse excitation technique was found to be a relatively quick and accurate method for determining elastic moduli with minimal specimen preparation and no requirement for mechanical loading frames. The results of this investigation showed good correlation between the elastic modulus determined using the impulse excitation technique, strain gauge and extensometer techniques, and modulus predicted from laminate theory. The flexural stiffness determined using the impulse excitation was in good agreement with that predicted from laminate theory. The impulse excitation/acoustic resonance interrogation technique has potential as a quality control test.

  19. On the elastic properties of fiber composite laminates with statistically dispersed ply orientations

    NASA Technical Reports Server (NTRS)

    Robinson, E. Y.

    1972-01-01

    Structural application of advanced composite filamentary materials requires lamination of the basic orthotropic plies into angle-ply laminates. The resulting elastic and strength properties depend on the pattern of orientation and are influenced by inevitable errors and inaccuracy in placement of the angle plies. Reviewed is the effect on elastic properties of orientation dispersion. The conventional constitutive relations are recast in a homologous form to account for orientation dispersion by addition of a single parameter. Graphical results are presented to show the behavior of the most important advanced composite materials. The results are directly useful for estimating effects of manufacturing inaccuracy and for design of partially oriented reinforced structures.

  20. Radial variation of elastic properties of SCS-6 silicon carbide fiber

    NASA Technical Reports Server (NTRS)

    Sathish, Shamachary; Cantrell, John H.; Yost, William T.

    1994-01-01

    The upper and lower bounds of the bulk, shear, and Young's moduli are calculated point-by-point along the radius of SCS-6 silicon carbide fibers using the Hashin-Shtrikman equations from considerations of the Auger spectra along the fiber radius. The calculated values are in agreement with measurements of the average Young modulus obtained over relatively large radial regions of the fiber using scanning acoustic microscopy (SAM). The validity of the Hashin-Shtrikman bounds calculations is enhanced by the agreement found between experimental SAM V(z) curves for fixed z along the fiber radius and the theoretical bounds of such curves obtained from the bounds of the calculated bulk and shear moduli.

  1. Radial Variation of Elastic Properties of SCS-6 Silicon Carbide Fiber

    NASA Technical Reports Server (NTRS)

    Sathish, Shamachary; Cantrell, John H.; Yost, William T.

    1994-01-01

    The upper and lower bounds of the bulk, shear, and Young's moduli are calculated point-by-point along the radius of SCS-6 silicon carbide fibers using the Hashin-Shtrikman equations from considerations of the Auger spectra along the fiber radius. The calculated values are in agreement with measurements of the average Young modulus obtained over relatively large radial regions of the fiber using scanning acoustic microscopy (SAM). The validity of the Hashin-Shtrikman bounds calculations is enhanced by the agreement found between experimental SAM V(z) curves for fixed z along the fiber radius and the theoretical bounds of such curves obtained from the bounds of the calculated bulk and shear moduli.

  2. Size effects and internal length scales in the elasticity of random fiber networks

    NASA Astrophysics Data System (ADS)

    Picu, Catalin; Berkache, Kamel; Shahsavari, Ali; Ganghoffer, Jean-Francois

    Random fiber networks are the structural element of many biological and man-made materials, including connective tissue, various consumer products and packaging materials. In all cases of practical interest the scale at which the material is used and the scale of the fiber diameter or the mean segment length of the network are separated by several orders of magnitude. This precludes solving boundary value problems defined on the scale of the application while resolving every fiber in the system, and mandates the development of continuum equivalent models. To this end, we study the intrinsic geometric and mechanical length scales of the network and the size effect associated with them. We consider both Cauchy and micropolar continuum models and calibrate them based on the discrete network behavior. We develop a method to predict the characteristic length scales of the problem and the minimum size of a representative element of the network based on network structural parameters and on fiber properties.

  3. Influence of Copper Layer Content in the Elastic and Damping Behavior of Glass-Fiber/Epoxy-Resin Composites

    NASA Astrophysics Data System (ADS)

    Carneiro, V. H.; Capela, P.; Teixeira, J. C.; Teixeira, S.; Cerqueira, F.; Macedo, F.; Ribas, L.; Soares, D.

    2016-12-01

    The impact in the elastic behavior and internal friction, caused by the introduction of Copper layers in Glass-Fiber/Epoxy Resin composites and temperature effects, were studied and evaluated recurring to Dynamic Mechanical Analysis. It is shown that the introduction of Copper layers increases the storage modulus of the composites and delays their glass transition temperature, however, it allows a faster transformation. Additionally, it is concluded that the introduction of Copper layers elevates the internal friction during the glass transition phase by the inversion of the deformation mechanism due to thermal expansion and increase in the Poisson's ratio of the epoxy resin to a value near 0.5 where its deformation is approximately isochoric. This increase in damping capacity is relevant in application with cyclic fatigue and mechanical vibration.

  4. Measurement of the elastic-optic effect of crystal using PM fiber optic low coherence interferometry

    NASA Astrophysics Data System (ADS)

    Xing, J. H.

    2011-06-01

    The elasticooptic effect of crystal is analyzed by the method of index ellipsoid. The relationship between the stress along the optical axis of trigonal crystallographic system and the refractive index is then established. Considering the optical anisotropic property of crystal and very small change of refractive index with the stress, the optic low coherence interferometry technique can be extended to measure the refractive index of anisotropic material, beause of its high spatial resolving power. Moreover, all polarization-maintaining fiber Michelson interferometer for measuring the elasticooptic coefficient of crystal has been sucessfully constructed. Unlike a common fiber low coherence interferometer, all the components are connected via polarization-maintaining fibers. Besides, an improved method using low coherence interferometry and Michelson interferometer to measure group refractive index is introduced, using grating displacement sensor and all polarization-maintaining fiber to greatly increase the displacement precision of scanning mirror. The refractive index change of LiNbO3 crystal under different external force has been measured and the elasticooptic coefficient is determined. It is shown that the elasticooptic coefficients P13 and P33 of LiNbO3 crystal are 0.110 and 0.089, respectively. The precision reaches 0.001.

  5. Elastic response of water-filled fiber composite tubes under shock wave loading

    SciTech Connect

    Perotti, Luigi E.; Deiterding, Ralf; Inaba, Kazuaki; Shepherd, Joseph E; Ortiz, Michael

    2013-01-01

    We experimentally and numerically investigate the response of fluid-filled filament-wound composite tubes subjected to axial shock wave loading in water. Our study focuses on the fluid structure interaction occurring when the shock wave in the fluid propagates parallel to the axis of the tube, creating pressure waves in the fluid coupled to flexural waves in the shell. The in-house-developed computational scheme couples an Eulerian fluid solver with a Lagrangian shell solver, which includes a new and simple material model to capture the response of fiber composites in finite kinematics. In the experiments and simulations we examine tubes with fiber winding angles equal to 45 and 60 , and we measure the precursor and primary wave speeds, hoop and longitudinal strains, and pressure. The experimental and computational results are in agreement, showing the validity of the computational scheme in complex fluid structure interaction problems involving fiber composite materials subjected to shock waves. The analyses of the measured quantities show the strong coupling of axial and hoop deformations and the significant effect of fiber winding angle on the composite tube response, which differs substantially from that of a metal tube in the same configuration.

  6. Elastic poly(ε-caprolactone)-polydimethylsiloxane copolymer fibers with shape memory effect for bone tissue engineering.

    PubMed

    Kai, Dan; Prabhakaran, Molamma P; Chan, Benjamin Qi Yu; Liow, Sing Shy; Ramakrishna, Seeram; Xu, Fujian; Loh, Xian Jun

    2016-02-02

    A porous shape memory scaffold with biomimetic architecture is highly promising for bone tissue engineering applications. In this study, a series of new shape memory polyurethanes consisting of organic poly(ε-caprolactone) (PCL) segments and inorganic polydimethylsiloxane (PDMS) segments in different ratios (9 : 1, 8 : 2 and 7 : 3) was synthesised. These PCL-PDMS copolymers were further engineered into porous fibrous scaffolds by electrospinning. With different ratios of PCL: PDMS, the fibers showed various fiber diameters, thermal behaviour and mechanical properties. Even after being processed into fibrous structures, these PCL-PDMS copolymers maintained their shape memory properties, and all the fibers exhibited excellent shape recovery ratios of  >90% and shape fixity ratios of  >92% after 7 thermo-mechanical cycles. Biological assay results corroborated that the fibrous PCL-PDMS scaffolds were biocompatible by promoting osteoblast proliferation, functionally enhanced biomineralization-relevant alkaline phosphatase expression and mineral deposition. Our study demonstrated that the PCL-PDMS fibers with excellent shape memory properties are promising substrates as bioengineered grafts for bone regeneration.

  7. Portable polarimetric fiber stress sensor system for visco-elastic and biomimetic material analysis

    NASA Astrophysics Data System (ADS)

    Harrison, Mark C.; Armani, Andrea M.

    2015-05-01

    Non-destructive materials characterization methods have significantly changed our fundamental understanding of material behavior and have enabled predictive models to be developed. However, the majority of these efforts have focused on crystalline and metallic materials, and transitioning to biomaterials, such as tissue samples, is non-trivial, as there are strict sample handling requirements and environmental controls which prevent the use of conventional equipment. Additionally, the samples are smaller and more complex in composition. Therefore, more advanced sample analysis methods capable of operating in these environments are needed. In the present work, we demonstrate an all-fiber-based material analysis system based on optical polarimetry. Unlike previous polarimetric systems which relied on free-space components, our method combines an in-line polarizer, polarization-maintaining fiber, and a polarimeter to measure the arbitrary polarization state of the output, eliminating all free-space elements. Additionally, we develop a more generalized theoretical analysis which allows more information about the polarization state to be obtained via the polarimeter. We experimentally verify our system using a series of elastomer samples made from polydimethylsiloxane (PDMS), a commonly used biomimetic material. By adjusting the base:curing agent ratio of the PDMS, we controllably tune the Young's modulus of the samples to span over an order of magnitude. The measured results are in good agreement with those obtained using a conventional load-frame system. Our fiber-based polarimetric stress sensor shows promise for use as a simple research tool that is portable and suitable for a wide variety of applications.

  8. ["Elastic osteosynthesis" with autocompression plates of carbon fiber reinforced thermoplastic material].

    PubMed

    Stange, J; Mittelmeier, H

    1989-06-01

    The problem of atrophic bone that occurs in osteosynthesis employing rigid plates is first depicted. Attempts at fabricating "simirigid" plates, which, however, have so far failed to gain any practical importance are then discussed. The reason for this seems to be that made of duroplastics cannot be molded during the operation and the thermoplastics do not have sufficient strength. The production of semirigid plates made of thermoplastic Polyethersulfon (PES), reinforced with 20% short carbon fibres, results in plates which are made moldable by heating in a small oven, white retaining sufficient static strength, although only limited fatigue strength. Biomechanical examinations revealed that with appropriate dimensioning of the plates, "elastic osteosynthesis" results in less loss of mechanical function of the stabilized bones, so that less atrophy of the bone may be expected. During more pronounced exercise loading, a reversible "springiness" of the fracture results, which might stimulate callus formation and improved stability.

  9. Elastic Properties of UHMWPE-SWCNT Nanocomposites' Fiber: An Experimental, Theoretic, and Molecular Dynamics Evaluation

    NASA Astrophysics Data System (ADS)

    Khan, Mujibur R.; Mahfuz, Hassan; Adnan, Ashfaq; Shabib, Ishraq; Leventouri, Theodora

    2013-06-01

    Ultrahigh molecular weight polyethylene (PE) filaments were reinforced with 2 wt.% of single-walled carbon nanotubes (SWCNTs). The solution spinning method was used to produce both neat and reinforced PE filaments. Tensile tests and strain hardening through repeated loading-unloading cycles of the filaments revealed a spectacular contribution of the SWCNTs in enhancing the elastic properties, e.g., strength and modulus. The theoretic strength and modulus of the reinforced PE were predicted using the shear lag model and micromechanics-based model, respectively, and verifying with experimental results. It was observed that the predicted strength and modulus were comparable only with those obtained after strain hardening. In the next step, a molecular dynamic simulation was conducted by simulating a unit cell containing a SWCNT surrounded by PE matrix subjected to uniaxial tensile strain. The strength and modulus of the simulated structure showed an agreement, to certain extent, with experimental observations of strain-hardened nanocomposites.

  10. Brittle-to-quasibrittle transition in bundles of nonlinear elastic fibers

    NASA Astrophysics Data System (ADS)

    Roy, Chandreyee; Manna, S. S.

    2016-09-01

    Properties of the fiber bundle model have been studied using equal load-sharing dynamics where each fiber obeys a nonlinear stress (s )-strain (x ) characteristic function s =G (x ) till its breaking threshold. In particular, four different functional forms have been studied: G (x ) =eα x , 1 +xα , xα, and x eα x where α is a continuously tunable parameter of the model in all cases. Analytical studies, supported by extensive numerical calculations of this model, exhibit a brittle to quasibrittle phase transition at a critical value of αc only in the first two cases. This transition is characterized by the weak power law modulated logarithmic (brittle) and logarithmic (quasibrittle) dependence of the relaxation time on the two sides of the critical point. Moreover, the critical load σc(α ) for the global failure of the bundle depends explicitly on α in all cases. In addition, four more cases have also been studied, where either the nonlinear functional form or the probability distribution of breaking thresholds has been suitably modified. In all these cases similar brittle to quasibrittle transitions have been observed.

  11. Identification of the elastic and damping characteristics of carbon fiber-reinforced plastic based on a study of damping flexural vibrations of test specimens

    NASA Astrophysics Data System (ADS)

    Paimushin, V. N.; Firsov, V. A.; Gyunal, I.; Shishkin, V. M.

    2016-07-01

    A theoretical and experimental method for determining the elastic and damping characteristics of materials is proposed based on analysis of vibrograms of damping flexural vibrations of test specimens with different structures. It is shown that during tension-compression and shear of a carbon fiber-reinforced plastic made of Porcher 3692 carbon fabric and EDT-69NM polymer binder, its dynamic elastic modulus decreases considerably with increasing frequency of deformation in the range of 0-120 Hz. The amplitude dependences of the logarithmic vibration decrements of the carbon fiber-reinforced plastic are determined by minimizing the discrepancy between the experimental and calculated internal-damping parameters of the test specimens in tension-compression and shear.

  12. Adaptive Optics Imaging of Healthy and Abnormal Regions of Retinal Nerve Fiber Bundles of Patients With Glaucoma

    PubMed Central

    Chen, Monica F.; Chui, Toco Y. P.; Alhadeff, Paula; Rosen, Richard B.; Ritch, Robert; Dubra, Alfredo; Hood, Donald C.

    2015-01-01

    Purpose. To better understand the nature of glaucomatous damage of the macula, especially the structural changes seen between relatively healthy and clearly abnormal (AB) retinal regions, using an adaptive optics scanning light ophthalmoscope (AO-SLO). Methods. Adaptive optics SLO images and optical coherence tomography (OCT) vertical line scans were obtained on one eye of seven glaucoma patients, with relatively deep local arcuate defects on the 10-2 visual field test in one (six eyes) or both hemifields (one eye). Based on the OCT images, the retinal nerve fiber (RNF) layer was divided into two regions: (1) within normal limits (WNL), relative RNF layer thickness within mean control values ±2 SD; and (2) AB, relative thickness less than −2 SD value. Results. As seen on AO-SLO, the pattern of AB RNF bundles near the border of the WNL and AB regions differed across eyes. There were normal-appearing bundles in the WNL region of all eyes and AB-appearing bundles near the border with the AB region. This region with AB bundles ranged in extent from a few bundles to the entire AB region in the case of one eye. All other eyes had a large AB region without bundles. However, in two of these eyes, a few bundles were seen within this region of otherwise missing bundles. Conclusions. The AO-SLO images revealed details of glaucomatous damage that are difficult, if not impossible, to see with current OCT technology. Adaptive optics SLO may prove useful in following progression in clinical trials, or in disease management, if AO-SLO becomes widely available and easy to use. PMID:25574048

  13. Elastic vibrations of a fiber due to impact of an aerosol particle and their influence on the efficiency of fibrous filters

    NASA Astrophysics Data System (ADS)

    Chernyakov, A. L.; Kirsch, A. A.; Kirsch, V. A.

    2011-05-01

    The excitation of sound vibrations of a cylindrical fine fiber due to the impact of a spherical aerosol particle is investigated. The equations describing the dynamics of impact are derived for an arbitrary shooting parameter. The coefficient of restitution is calculated, and its analytical approximation is obtained. It is shown, for the case of long fibers, that the coefficient of restitution depends upon a single parameter λc. The parameter λc depends on the particle radial velocity component near the fiber surface, the mass of the particle, the density of the fiber, the modulus of elasticity, and the geometric parameters of the fiber and the particle. The inertial deposition of submicron aerosol particles on fine fibers in a filter is considered. The efficiency of filtration is studied as a function of the gas flow velocity. The existence of a critical flow velocity U*, below which the losses of particle energy during collision have no effect on the efficiency, is demonstrated. For velocities higher than the critical velocity, the filtration efficiency is dependent on the mechanisms of nonelastic losses of the particle's energy. Its value can be significantly lower than that estimated when particle rebound effects are neglected. After they have rebounded, some particles are not able to attain the initial high velocities in the stream, thus depositing on neighboring fibers. The dynamics of these particles is investigated. For this case, it is shown that the filtration efficiency is dependent on the velocity distribution of the rebounded particles and that it increases with the packing density of fibers. A qualitative difference between the asymptotic behavior of a fiber and that of a flat plate is found long after the initial impulse.

  14. Elastic-plastic finite element analyses of an unidirectional, 9 vol percent tungsten fiber reinforced copper matrix composite

    NASA Technical Reports Server (NTRS)

    Sanfeliz, Jose G.

    1993-01-01

    Micromechanical modeling via elastic-plastic finite element analyses were performed to investigate the effects that the residual stresses and the degree of matrix work hardening (i.e., cold-worked, annealed) have upon the behavior of a 9 vol percent, unidirectional W/Cu composite, undergoing tensile loading. The inclusion of the residual stress-containing state as well as the simulated matrix material conditions proved to be significant since the Cu matrix material exhibited plastic deformation, which affected the subsequent tensile response of the composite system. The stresses generated during cooldown to room temperature from the manufacturing temperature were more of a factor on the annealed-matrix composite, since they induced the softened matrix to plastically flow. This event limited the total load-carrying capacity of this matrix-dominated, ductile-ductile type material system. Plastic deformation of the hardened-matrix composite during the thermal cooldown stage was not considerable, therefore, the composite was able to sustain a higher stress before showing any appreciable matrix plasticity. The predicted room temperature, stress-strain response, and deformation stages under both material conditions represented upper and lower bounds characteristic of the composite's tensile behavior. The initial deformation stage for the hardened material condition showed negligible matrix plastic deformation while for the annealed state, its initial deformation stage showed extensive matrix plasticity. Both material conditions exhibited a final deformation stage where the fiber and matrix were straining plastically. The predicted stress-strain results were compared to the experimental, room temperature, tensile stress-strain curve generated from this particular composite system. The analyses indicated that the actual thermal-mechanical state of the composite's Cu matrix, represented by the experimental data, followed the annealed material condition.

  15. Micromechanical analysis of a hybrid composite—effect of boron carbide particles on the elastic properties of basalt fiber reinforced polymer composite

    NASA Astrophysics Data System (ADS)

    Krishna Golla, Sai; Prasanthi, P.

    2016-11-01

    A fiber reinforced polymer (FRP) composite is an important material for structural application. The diversified application of FRP composites has become the center of attention for interdisciplinary research. However, improvements in the mechanical properties of this class of materials are still under research for different applications. The reinforcement of inorganic particles in a composite improves its structural properties due to their high stiffness. The present research work is focused on the prediction of the mechanical properties of the hybrid composites where continuous fibers are reinforced in a micro boron carbide particle mixed polypropylene matrix. The effectiveness of the addition of 30 wt. % of boron carbide (B4C) particle contributions regarding the longitudinal and transverse properties of the basalt fiber reinforced polymer composite at various fiber volume fractions is examined by finite element analysis (FEA). The experimental approach is the best way to determine the properties of the composite but it is expensive and time-consuming. Therefore, the finite element method (FEM) and analytical methods are the viable methods for the determination of the composite properties. The FEM results were obtained by adopting a micromechanics approach with the support of FEM. Assuming a uniform distribution of reinforcement and considering one unit-cell of the whole array, the properties of the composite materials are determined. The predicted elastic properties from FEA are compared with the analytical results. The results suggest that B4C particles are a good reinforcement for the enhancement of the transverse properties of basalt fiber reinforced polypropylene.

  16. Fiber

    MedlinePlus

    ... it can help with weight control. Fiber aids digestion and helps prevent constipation . It is sometimes used ... fiber attracts water and turns to gel during digestion. This slows digestion. Soluble fiber is found in ...

  17. Solid-phase microextraction-gas chromatography-time-of-flight mass spectrometry utilized for the evaluation of the new-generation super elastic fiber assemblies.

    PubMed

    Setkova, Lucie; Risticevic, Sanja; Linton, Christopher M; Ouyang, Gangfeng; Bragg, Leslie M; Pawliszyn, Janusz

    2007-01-09

    The aim of this study was to evaluate the performance characteristics of the recently developed super elastic solid-phase microextraction (SPME) fibers. The fiber needle, plunger and fiber core are manufactured with a special type of flexible alloy that exhibits excellent shape memory and tensile strength. This material makes the assemblies more robust, permitting several hundreds of analyses in a sequence, which is one of the ways to improve the robustness and sample throughput of automated SPME methods. The design and size of the needle utilized in the new fiber assemblies is discussed here, as well as the use of a septum-free injector replacement and a low-volume direct injection glass liner placed in the GC inlet. Deionized water and pump oil samples spiked with target volatile compounds (McReynold's probes and toluene) were used for the purposes of the presented study. A fully automated SPME sample preparation technique was combined with the GC-TOFMS system for the chromatographic separation and identification/quantification of the target analytes.

  18. An auxiliary graph based dynamic traffic grooming algorithm in spatial division multiplexing enabled elastic optical networks with multi-core fibers

    NASA Astrophysics Data System (ADS)

    Zhao, Yongli; Tian, Rui; Yu, Xiaosong; Zhang, Jiawei; Zhang, Jie

    2017-03-01

    A proper traffic grooming strategy in dynamic optical networks can improve the utilization of bandwidth resources. An auxiliary graph (AG) is designed to solve the traffic grooming problem under a dynamic traffic scenario in spatial division multiplexing enabled elastic optical networks (SDM-EON) with multi-core fibers. Five traffic grooming policies achieved by adjusting the edge weights of an AG are proposed and evaluated through simulation: maximal electrical grooming (MEG), maximal optical grooming (MOG), maximal SDM grooming (MSG), minimize virtual hops (MVH), and minimize physical hops (MPH). Numeric results show that each traffic grooming policy has its own features. Among different traffic grooming policies, an MPH policy can achieve the lowest bandwidth blocking ratio, MEG can save the most transponders, and MSG can obtain the fewest cores for each request.

  19. Neuronal fiber pathway abnormalities in autism: An initial MRI diffusion tensor tracking study of hippocampo-fusiform and amygdalo-fusiform pathways

    PubMed Central

    CONTURO, THOMAS E.; WILLIAMS, DIANE L.; SMITH, CHARLES D.; GULTEPE, EREN; AKBUDAK, ERBIL; MINSHEW, NANCY J.

    2012-01-01

    MRI diffusion-tensor tracking (DTT) was performed in 17 high-functioning adolescents/adults with autism and 17 pairwise-matched controls. White matter pathways involved in face processing were examined due to the relevance of face perception to the social symptoms of autism, and due to known behavioral and functional imaging findings in autism. The hippocampo-fusiform (HF) and amygdalo-fusiform (AF) pathways had normal size and shape but abnormal microstructure in the autism group. The right HF had reduced across-fiber diffusivity (D-min) compared with controls, opposite to the whole-brain effect of increased D-min. In contrast, left HF, right AF, and left AF had increased D-min and increased along-fiber diffusivity (D-max), more consistent with the whole-brain effect. There was a general loss of lateralization compared with controls. The right HF D-min was markedly low in the autism subgroup with lower Benton face recognition scores, compared with the lower-Benton control subgroup, and compared with the higher-Benton autism subgroup. Similar behavioral relationships were found for performance IQ. Such results suggest an early functionally-significant pathological process in right HF consistent with small-diameter axons (with correspondingly slower neural transmission) and/or higher packing density. In left AF and HF, changes were interpreted as secondary, possibly reflecting axonal loss and/or decreased myelination. PMID:18954474

  20. Congenital Abnormalities

    MedlinePlus

    ... Listen Español Text Size Email Print Share Congenital Abnormalities Page Content Article Body About 3% to 4% ... of congenital abnormalities earlier. 5 Categories of Congenital Abnormalities Chromosome Abnormalities Chromosomes are structures that carry genetic ...

  1. Statistical analysis of blocking probability and fragmentation based on Markov modeling of elastic spectrum allocation on fiber link

    NASA Astrophysics Data System (ADS)

    Rosa, A. N. F.; Wiatr, P.; Cavdar, C.; Carvalho, S. V.; Costa, J. C. W. A.; Wosinska, L.

    2015-11-01

    In Elastic Optical Network (EON), spectrum fragmentation refers to the existence of non-aligned, small-sized blocks of free subcarrier slots in the optical spectrum. Several metrics have been proposed in order to quantify a level of spectrum fragmentation. Approximation methods might be used for estimating average blocking probability and some fragmentation measures, but are so far unable to accurately evaluate the influence of different sizes of connection requests and do not allow in-depth investigation of blocking events and their relation to fragmentation. The analytical study of the effect of fragmentation on requests' blocking probability is still under-explored. In this work, we introduce new definitions for blocking that differentiate between the reasons for the blocking events. We developed a framework based on Markov modeling to calculate steady-state probabilities for the different blocking events and to analyze fragmentation related problems in elastic optical links under dynamic traffic conditions. This framework can also be used for evaluation of different definitions of fragmentation in terms of their relation to the blocking probability. We investigate how different allocation request sizes contribute to fragmentation and blocking probability. Moreover, we show to which extend blocking events, due to insufficient amount of available resources, become inevitable and, compared to the amount of blocking events due to fragmented spectrum, we draw conclusions on the possible gains one can achieve by system defragmentation. We also show how efficient spectrum allocation policies really are in reducing the part of fragmentation that in particular leads to actual blocking events. Simulation experiments are carried out showing good match with our analytical results for blocking probability in a small scale scenario. Simulated blocking probabilities for the different blocking events are provided for a larger scale elastic optical link.

  2. Elastic-plastic stress concentrations around crack-like notches in continuous fiber reinforced metal matrix composites

    NASA Technical Reports Server (NTRS)

    Johnson, W. S.; Bigelow, C. A.

    1987-01-01

    Continuous fiber silicon-carbide/aluminum composite laminates with slits were tested statically to failure. Five different layups were examined: (0) sub 8, (0 sub 2/ + or - 45) sub s, (0/90) sub 2s), (0/ + or - 45/90 sub s), and (+ or - 45) sub 2s. Either a 9.5 or a 19 mm slit was machined in the center of each specimen. The strain distribution ahead of the slit tip was found experimentally with a series of strain gages bonded ahead of the slit tip. A three-dimensional finite element program (PAFAC) was used to predict the strain distribution ahead of the slit tip for several layups. For all layups, except the (0) sub 8, the yielding of the metal matrix caused the fiber stress concentration factor to increase with increasing load. This is contrary to the behavior seen in homogeneous materials where yielding causes the stress concentration to drop. For the (0) sub 8 laminate, yielding of the matrix caused a decrease in the fiber stress concentration. The finite element analysis predicted these trends correctly.

  3. Elastic-plastic stress concentrations around crack-like notches in continuous fiber reinforced metal matrix composites

    NASA Technical Reports Server (NTRS)

    Johnson, W. S.; Bigelow, C. A.

    1989-01-01

    Continuous fiber silicon-carbide/aluminum composite laminates with slits were tested statically to failure. Five different layups were examined: (0) sub 8, (0 sub 2/ + or - 45) sub s, (0/90) sub 2s), (0/ + or - 45/90 sub s), and (+ or - 45) sub 2s. Either a 9.5 or a 19 mm slit was machined in the center of each specimen. The strain distribution ahead of the slit tip was found experimentally with a series of strain gages bonded ahead of the slit tip. A three-dimensional finite element program (PAFAC) was used to predict the strain distribution ahead of the slit tip for several layups. For all layups, except the (0) sub 8, the yielding of the metal matrix caused the fiber stress concentration factor to increase with increasing load. This is contrary to the behavior seen in homogeneous materials where yielding causes the stress concentration to drop. For the (0) sub 8 laminate, yielding of the matrix caused a decrease in the fiber stress concentration. The finite element analysis predicted these trends correctly.

  4. Dynamic virtual optical network embedding in spectral and spatial domains over elastic optical networks with multicore fibers

    NASA Astrophysics Data System (ADS)

    Zhu, Ruijie; Zhao, Yongli; Yang, Hui; Tan, Yuanlong; Chen, Haoran; Zhang, Jie; Jue, Jason P.

    2016-08-01

    Network virtualization can eradicate the ossification of the infrastructure and stimulate innovation of new network architectures and applications. Elastic optical networks (EONs) are ideal substrate networks for provisioning flexible virtual optical network (VON) services. However, as network traffic continues to increase exponentially, the capacity of EONs will reach the physical limitation soon. To further increase network flexibility and capacity, the concept of EONs is extended into the spatial domain. How to map the VON onto substrate networks by thoroughly using the spectral and spatial resources is extremely important. This process is called VON embedding (VONE).Considering the two kinds of resources at the same time during the embedding process, we propose two VONE algorithms, the adjacent link embedding algorithm (ALEA) and the remote link embedding algorithm (RLEA). First, we introduce a model to solve the VONE problem. Then we design the embedding ability measurement of network elements. Based on the network elements' embedding ability, two VONE algorithms were proposed. Simulation results show that the proposed VONE algorithms could achieve better performance than the baseline algorithm in terms of blocking probability and revenue-to-cost ratio.

  5. Energy-momentum conserving higher-order time integration of nonlinear dynamics of finite elastic fiber-reinforced continua

    NASA Astrophysics Data System (ADS)

    Erler, Norbert; Groß, Michael

    2015-05-01

    Since many years the relevance of fibre-reinforced polymers is steadily increasing in fields of engineering, especially in aircraft and automotive industry. Due to the high strength in fibre direction, but the possibility of lightweight construction, these composites replace more and more traditional materials as metals. Fibre-reinforced polymers are often manufactured from glass or carbon fibres as attachment parts or from steel or nylon cord as force transmission parts. Attachment parts are mostly subjected to small strains, but force transmission parts usually suffer large deformations in at least one direction. Here, a geometrically nonlinear formulation is necessary. Typical examples are helicopter rotor blades, where the fibres have the function to stabilize the structure in order to counteract large centrifugal forces. For long-run analyses of rotor blade deformations, we have to apply numerically stable time integrators for anisotropic materials. This paper presents higher-order accurate and numerically stable time stepping schemes for nonlinear elastic fibre-reinforced continua with anisotropic stress behaviour.

  6. Alveolar abnormalities

    MedlinePlus

    ... page: //medlineplus.gov/ency/article/001093.htm Alveolar abnormalities To use the sharing features on this page, please enable JavaScript. Alveolar abnormalities are changes in the tiny air sacs in ...

  7. Nail abnormalities

    MedlinePlus

    Beau's lines; Fingernail abnormalities; Spoon nails; Onycholysis; Leukonychia; Koilonychia; Brittle nails ... 2012:chap 71. Zaiac MN, Walker A. Nail abnormalities associated with systemic pathologies. Clin Dermatol . 2013;31: ...

  8. Marked longevity of human lung parenchymal elastic fibers deduced from prevalence of D-aspartate and nuclear weapons-related radiocarbon

    SciTech Connect

    Shapiro, S.D.; Endicott, S.K.; Province, M.A.; Pierce, J.A.; Campbell, E.J. )

    1991-05-01

    Normal structure and function of the lung parenchyma depend upon elastic fibers. Amorphous elastin is biochemically stable in vitro, and may provide a metabolically stable structural framework for the lung parenchyma. To test the metabolic stability of elastin in the normal human lung parenchyma, we have (a) estimated the time elapsed since the synthesis of the protein through measurement of aspartic acid racemization and (b) modeled the elastin turnover through measurement of the prevalence of nuclear weapons-related {sup 14}C. Elastin purified by a new technique from normal lung parenchyma was hydrolyzed; then the prevalences of D-aspartate and {sup 14}C were measured by gas chromatography and accelerator-mass spectrometry, respectively. D-aspartate increased linearly with age; Kasp (1.76 x 10{sup {minus} 3} yr{sup {minus} 1}) was similar to that previously found for extraordinarily stable human tissues, indicating that the age of lung parenchymal elastin corresponded with the age of the subject. Radiocarbon prevalence data also were consistent with extraordinary metabolic stability of elastin; the calculated mean carbon residence time in elastin was 74 yr (95% confidence limits, 40-174 yr). These results indicate that airspace enlargement characteristic of 'aging lung' is not associated with appreciable new synthesis of lung parenchymal elastin. The present study provides the first tissue-specific evaluation of turnover of an extracellular matrix component in humans and underscores the potential importance of elastin for maintenance of normal lung structure. Most importantly, the present work provides a foundation for strategies to directly evaluate extracellular matrix injury and repair in diseases of lung (especially pulmonary emphysema), vascular tissue, and skin.

  9. Meiotic abnormalities

    SciTech Connect

    1993-12-31

    Chapter 19, describes meiotic abnormalities. These include nondisjunction of autosomes and sex chromosomes, genetic and environmental causes of nondisjunction, misdivision of the centromere, chromosomally abnormal human sperm, male infertility, parental age, and origin of diploid gametes. 57 refs., 2 figs., 1 tab.

  10. An innovative approach to achieve re-centering and ductility of cement mortar beams through randomly distributed pseudo-elastic shape memory alloy fibers

    NASA Astrophysics Data System (ADS)

    Shajil, N.; Srinivasan, S. M.; Santhanam, M.

    2012-04-01

    Fibers can play a major role in post cracking behavior of concrete members, because of their ability to bridge cracks and distribute the stress across the crack. Addition of steel fibers in mortar and concrete can improve toughness of the structural member and impart significant energy dissipation through slow pull out. However, steel fibers undergo plastic deformation at low strain levels, and cannot regain their shape upon unloading. This is a major disadvantage in strong cyclic loading conditions, such as those caused by earthquakes, where self-centering ability of the fibers is a desired characteristic in addition to ductility of the reinforced cement concrete. Fibers made from an alternative material such as shape memory alloy (SMA) could offer a scope for re-centering, thus improving performance especially after a severe loading has occurred. In this study, the load-deformation characteristics of SMA fiber reinforced cement mortar beams under cyclic loading conditions were investigated to assess the re-centering performance. This study involved experiments on prismatic members, and related analysis for the assessment and prediction of re-centering. The performances of NiTi fiber reinforced mortars are compared with mortars with same volume fraction of steel fibers. Since re-entrant corners and beam columns joints are prone to failure during a strong ground motion, a study was conducted to determine the behavior of these reinforced with NiTi fiber. Comparison is made with the results of steel fiber reinforced cases. NiTi fibers showed significantly improved re-centering and energy dissipation characteristics compared to the steel fibers.

  11. Oxynitride glass fibers

    NASA Technical Reports Server (NTRS)

    Patel, Parimal J.; Messier, Donald R.; Rich, R. E.

    1991-01-01

    Research at the Army Materials Technology Laboratory (AMTL) and elsewhere has shown that many glass properties including elastic modulus, hardness, and corrosion resistance are improved markedly by the substitution of nitrogen for oxygen in the glass structure. Oxynitride glasses, therefore, offer exciting opportunities for making high modulus, high strength fibers. Processes for making oxynitride glasses and fibers of glass compositions similar to commercial oxide glasses, but with considerable enhanced properties, are discussed. We have made glasses with elastic moduli as high as 140 GPa and fibers with moduli of 120 GPa and tensile strengths up to 2900 MPa. AMTL holds a U.S. patent on oxynitride glass fibers, and this presentation discusses a unique process for drawing small diameter oxynitride glass fibers at high drawing rates. Fibers are drawn through a nozzle from molten glass in a molybdenum crucible at 1550 C. The crucible is situated in a furnace chamber in flowing nitrogen, and the fiber is wound in air outside of the chamber, making the process straightforward and commercially feasible. Strengths were considerably improved by improving glass quality to minimize internal defects. Though the fiber strengths were comparable with oxide fibers, work is currently in progress to further improve the elastic modulus and strength of fibers. The high elastic modulus of oxynitride glasses indicate their potential for making fibers with tensile strengths surpassing any oxide glass fibers, and we hope to realize that potential in the near future.

  12. Leukocyte abnormalities.

    PubMed

    Gabig, T G

    1980-07-01

    Certain qualitative abnormalities in neutrophils and blood monocytes are associated with frequent, severe, and recurrent bacterial infections leading to fatal sepsis, while other qualitative defects demonstrated in vitro may have few or no clinical sequelae. These qualitative defects are discussed in terms of the specific functions of locomotion, phagocytosis, degranulation, and bacterial killing.

  13. Ultrasonic System Measures Elastic Properties Of Composites

    NASA Technical Reports Server (NTRS)

    Bar-Cohen, Yoseph; Mal, Ajit K.

    1993-01-01

    Measurements with leaky Lamb waves yield data on properties and defects of panels. System nondestructively measures elastic properties of, and defects in, panel of laminated fiber/matrix material. Ultrasonic transducers operating in pitch/catch mode excite and detect leaky Lamb waves in specimen. Elastic properties of specimen and defects within it characterized from dispersion curves of Lamb waves.

  14. Medial medullary infarction: abnormal ocular motor findings.

    PubMed

    Kim, J Soo; Choi, K-D; Oh, S-Y; Park, S-H; Han, M-K; Yoon, B-W; Roh, J-K

    2005-10-25

    In 20 consecutive patients with isolated medial medullary infarction, abnormal ocular motor findings included nystagmus (n = 8), ocular contrapulsion (n = 5), and contralesional ocular tilt reaction (n = 2). The nystagmus was ipsilesional (n = 4), gaze-evoked (n = 5), upbeating (n = 4), and hemiseesaw (n = 1). The ocular motor abnormalities may be explained by involvements of the nucleus prepositus hypoglossi, medial longitudinal fasciculus or efferent fibers from the vestibular nuclei, climbing fibers, and cells of the paramedian tracts.

  15. Micro-mechanics of fiber reinforced bounded and unbounded solids: effective local and non-local thermo-elastic properties, stress concentration factors, and edge effect

    DTIC Science & Technology

    2005-07-01

    in finite elasticity and applications to black- filled elastomers // Ibid.-2000.-48.-pp. 1389-1411. 4. Guz A.N. Two-level model of meso-mechanics... polyamide . J. Polym. Sci. Part. B: Polyme. Phys. 40, 272—283. Meisner, M.J. and Kouris, D.A., 1995. Interaction of two elliptic inclusions. Interna...of Young’s modulus of layered silicate- elastomer nanocomposites. Polym Composite, 19, 608–617. Stevenson, A.C., 1942. On the equilibrium of plates

  16. Fatigue damage evaluation of plain woven carbon fiber reinforced plastic (CFRP) modified with MFC (micro-fibrillated cellulose) by thermo-elastic damage analysis (TDA)

    NASA Astrophysics Data System (ADS)

    Aoyama, Ryohei; Okubo, Kazuya; Fujii, Toru

    2013-04-01

    The aim of this study is to investigate characteristics of fatigue damage of CFRP modified with MFC by TDA under tensile cyclic loading. In this paper, fatigue life of CFRP modified with MFC was investigated under cyclic loading. Characteristics of fatigue damage of CFRP modified with MFC were evaluated by thermo-elastic damage analysis. Maximum improvement in fatigue life was also obtained under cyclic loading when epoxy matrix was enhanced with 0.3wt% of MFC as well as under static loading. Result of TDA showed same tendency as the result of fatigue test, and the result of TDA well expressed the fatigue damage behavior of plain woven CFRP plate. Eventually, TDA was effective for clear understanding the degree of fatigue damage progression of CFRP modified with MFC.

  17. Inhibition of versican expression by siRNA facilitates tropoelastin synthesis and elastic fiber formation by human SK-LMS-1 leiomyosarcoma smooth muscle cells in vitro and in vivo

    PubMed Central

    Keire, Paul A.; Bressler, Steven L.; Mulvihill, Eileen R.; Starcher, Barry C.; Kang, Inkyung; Wight, Thomas N.

    2016-01-01

    Versican is an extracellular matrix (ECM) molecule that interacts with other ECM components to influence ECM organization, stability, composition, and cell behavior. Versican is known to increase in a number of cancers, but little is known about how versican influences the amount and organization of the ECM components in the tumor microenvironment. In the present study, we modulated versican expression using siRNAs in the human leiomyosarcoma (LMS) smooth muscle cell line SK-LMS-1, and observed the formation of elastin and elastic fibers in vitro and also in vivo in a nude mouse tumor model. Constitutive siRNA-directed knockdown of versican in LMS cells resulted in increased levels of elastin, as shown by immunohistochemical staining of the cells in vitro, and by mRNA and protein analyses. Moreover, versican siRNA LMS cells, when injected into nude mice, generated smaller tumors that had significantly greater immunohistochemical and histochemical staining for elastin when compared to control tumors. Additionally, microarray analyses were used to determine the influence of versican isoform modulation on gene expression profiles, and to identify genes that influence and relate to the process of elastogenesis. cDNA microarray analysis and TaqMan low density array validation identified previously unreported genes associated with downregulation of versican and increased elastogenesis. These results highlight an important role for the proteoglycan versican in regulating the expression and assembly of elastin and the phenotype of LMS cells. PMID:26723257

  18. How an Elastic Body Reduces its Drag

    NASA Astrophysics Data System (ADS)

    Alben, Silas; Shelley, Michael; Zhang, Jun

    2002-11-01

    Recent studies from bio-fluid dynamics have quantified dramatic decreases in fluid drag on flexible organic structures (including tree leaves and underwater plants) as they deform in high-Reynolds-number flows. Our simple experiment considers the role of elastic bending in the steady case. Using a thin glass fiber wetted into a planar soap-film flow, we identify a transition in flow speed beyond which the fluid forces dominate the elastic response, and yield large deformations that greatly reduce drag. We construct a free-streamline model coupling fluid and elastic forces and solve it numerically. Self-similarity emerges on a shrinking length scale, resulting in a transition from the U^2 growth of rigid bodies to a U^4/3 law as the fiber exhibits large deformation. The theory gives a good rationalization of the experimental data in terms of a single non-dimensional parameter.

  19. Highly Stretchable, Strain Sensing Hydrogel Optical Fibers.

    PubMed

    Guo, Jingjing; Liu, Xinyue; Jiang, Nan; Yetisen, Ali K; Yuk, Hyunwoo; Yang, Changxi; Khademhosseini, Ali; Zhao, Xuanhe; Yun, Seok-Hyun

    2016-12-01

    A core-clad fiber made of elastic, tough hydrogels is highly stretchable while guiding light. Fluorescent dyes are easily doped into the hydrogel fiber by diffusion. When stretched, the transmission spectrum of the fiber is altered, enabling the strain to be measured and also its location.

  20. Urine - abnormal color

    MedlinePlus

    ... medlineplus.gov/ency/article/003139.htm Urine - abnormal color To use the sharing features on this page, please enable JavaScript. The usual color of urine is straw-yellow. Abnormally colored urine ...

  1. Tooth - abnormal colors

    MedlinePlus

    ... medlineplus.gov/ency/article/003065.htm Tooth - abnormal colors To use the sharing features on this page, please enable JavaScript. Abnormal tooth color is any color other than white to yellowish- ...

  2. Abnormal Head Position

    MedlinePlus

    ... cause. Can a longstanding head turn lead to any permanent problems? Yes, a significant abnormal head posture could cause permanent ... occipitocervical synostosis and unilateral hearing loss. Are there any ... postures? Yes. Abnormal head postures can usually be improved depending ...

  3. Skeletal limb abnormalities

    MedlinePlus

    ... medlineplus.gov/ency/article/003170.htm Skeletal limb abnormalities To use the sharing features on this page, please enable JavaScript. Skeletal limb abnormalities refers to a variety of bone structure problems ...

  4. The optimal fiber volume fraction and fiber-matrix property compatibility in fiber reinforced composites

    NASA Technical Reports Server (NTRS)

    Pan, Ning

    1992-01-01

    Although the question of minimum or critical fiber volume fraction beyond which a composite can then be strengthened due to addition of fibers has been dealt with by several investigators for both continuous and short fiber composites, a study of maximum or optimal fiber volume fraction at which the composite reaches its highest strength has not been reported yet. The present analysis has investigated this issue for short fiber case based on the well-known shear lag (the elastic stress transfer) theory as the first step. Using the relationships obtained, the minimum spacing between fibers is determined upon which the maximum fiber volume fraction can be calculated, depending on the fiber packing forms within the composites. The effects on the value of this maximum fiber volume fraction due to such factors as fiber and matrix properties, fiber aspect ratio and fiber packing forms are discussed. Furthermore, combined with the previous analysis on the minimum fiber volume fraction, this maximum fiber volume fraction can be used to examine the property compatibility of fiber and matrix in forming a composite. This is deemed to be useful for composite design. Finally some examples are provided to illustrate the results.

  5. Abnormal Uterine Bleeding FAQ

    MedlinePlus

    ... PROBLEMS Abnormal Uterine Bleeding • What is a normal menstrual cycle? • When is bleeding abnormal? • At what ages is ... treat abnormal bleeding? •Glossary What is a normal menstrual cycle? The normal length of the menstrual cycle is ...

  6. Fiber-matrix interface failures

    NASA Technical Reports Server (NTRS)

    Rabenberg, Lew; Marcus, Harris L.; Park, Hun Sub; Zong, Gui Sheng; Brown, Lloyd D.

    1989-01-01

    Interface fractures of aluminum-graphite composites under transverse loading are expected to occur within the graphite fibers, but very near the interface. Residual stresses in aluminum, reinforced with the new high modulus pitch-based fibers, are much lower than would be expected based on simple elasticity calculations. The excess stress may be relaxed by shearing internal to the fibers or at the interface rather than by plastic flow of the matrix. The internal shearing also occurs during repeated thermal cycling of these composites; the fibers are repeatedly intruded, then extruded, during repeated temperature excursions.

  7. Structural abnormality of the corticospinal tract in major depressive disorder

    PubMed Central

    2014-01-01

    Background Scientists are beginning to document abnormalities in white matter connectivity in major depressive disorder (MDD). Recent developments in diffusion-weighted image analyses, including tractography clustering methods, may yield improved characterization of these white matter abnormalities in MDD. In this study, we acquired diffusion-weighted imaging data from MDD participants and matched healthy controls. We analyzed these data using two tractography clustering methods: automated fiber quantification (AFQ) and the maximum density path (MDP) procedure. We used AFQ to compare fractional anisotropy (FA; an index of water diffusion) in these two groups across major white matter tracts. Subsequently, we used the MDP procedure to compare FA differences in fiber paths related to the abnormalities in major fiber tracts that were identified using AFQ. Results FA was higher in the bilateral corticospinal tracts (CSTs) in MDD (p’s < 0.002). Secondary analyses using the MDP procedure detected primarily increases in FA in the CST-related fiber paths of the bilateral posterior limbs of the internal capsule, right superior corona radiata, and the left external capsule. Conclusions This is the first study to implicate the CST and several related fiber pathways in MDD. These findings suggest important new hypotheses regarding the role of CST abnormalities in MDD, including in relation to explicating CST-related abnormalities to depressive symptoms and RDoC domains and constructs. PMID:25295159

  8. Structurally abnormal human autosomes

    SciTech Connect

    1993-12-31

    Chapter 25, discusses structurally abnormal human autosomes. This discussion includes: structurally abnormal chromosomes, chromosomal polymorphisms, pericentric inversions, paracentric inversions, deletions or partial monosomies, cri du chat (cat cry) syndrome, ring chromosomes, insertions, duplication or pure partial trisomy and mosaicism. 71 refs., 8 figs.

  9. Elastically Decoupling Dark Matter.

    PubMed

    Kuflik, Eric; Perelstein, Maxim; Lorier, Nicolas Rey-Le; Tsai, Yu-Dai

    2016-06-03

    We present a novel dark matter candidate, an elastically decoupling relic, which is a cold thermal relic whose present abundance is determined by the cross section of its elastic scattering on standard model particles. The dark matter candidate is predicted to have a mass ranging from a few to a few hundred MeV, and an elastic scattering cross section with electrons, photons and/or neutrinos in the 10^{-3}-1  fb range.

  10. Morphological abnormalities among lampreys

    USGS Publications Warehouse

    Manion, Patrick J.

    1967-01-01

    The experimental control of the sea lamprey (Petromyzon marinus) in the Great Lakes has required the collection of thousands of lampreys. Representatives of each life stage of the four species of the Lake Superior basin were examined for structural abnormalities. The most common aberration was the presence of additional tails. The accessory tails were always postanal and smaller than the normal tail. The point of origin varied; the extra tails occurred on dorsal, ventral, or lateral surfaces. Some of the extra tails were misshaped and curled, but others were normal in shape and pigment pattern. Other abnormalities in larval sea lampreys were malformed or twisted tails and bodies. The cause of the structural abnormalities is unknown. The presence of extra caudal fins could be genetically controlled, or be due to partial amputation or injury followed by abnormal regeneration. Few if any lampreys with structural abnormalities live to sexual maturity.

  11. Nanomechanics of electrospun phospholipid fiber

    NASA Astrophysics Data System (ADS)

    Mendes, Ana C.; Nikogeorgos, Nikolaos; Lee, Seunghwan; Chronakis, Ioannis S.

    2015-06-01

    Electrospun asolectin phospholipid fibers were prepared using isooctane as a solvent and had an average diameter of 6.1 ± 2.7 μm. Their mechanical properties were evaluated by nanoindentation using Atomic Force Microscopy, and their elastic modulus was found to be approximately 17.2 ± 1 MPa. At a cycle of piezo expansion-retraction (loading-unloading) of a silicon tip on a fiber, relatively high adhesion was observed during unloading. It is proposed that this was primarily due to molecular rearrangements at the utmost layers of the fiber caused by the indentation of the hydrophilic tip. The phospholipid fibers were shown to be stable in ambient conditions, preserving the modulus of elasticity up to 24 h.

  12. A Investigation of the Elastic and Dielectric Anisotropy of Paper.

    NASA Astrophysics Data System (ADS)

    Fleischman, Elmer Henry, Jr.

    This investigation was undertaken to learn more about the way in which fiber orientation and drying restraint affect the elastic and dielectric properties in all three principal directions of paper. It was found that both variables affect the in -plane elastic anisotropy by similar magnitudes. What was surprising, however, was that wet straining has the greatest effect in the z-direction. The z-direction stiffness was reduced 50% as a result of only a moderate 2.4% wet strain in the plane of the sheet. On the other hand, the dielectric anisotropy was affected very little by wet straining. In fact, the dielectric results could be explained in terms of mixture theories. The anisotropy in the dielectric constant when measured at microwave frequencies could largely be explained as being the result of fiber orientation alone without having to assume that the fiber has an anisotropic dielectric constant. From comparison of the elastic and dielectric results, it may be concluded that the mechanism by which wet straining enhances the elastic anisotropy does not involve a large fiber orientation in the direction of wet straining. From a practical standpoint, one could use the dielectric anisotropy measured at microwave frequencies as a measure of the fiber orientation distribution in the sheet. On the basis of the results presented here, this measurement should be quite insensitive to any stresses imposed on the sheet as it dries.

  13. Elastic properties of minerals

    SciTech Connect

    Aleksandrov, K.S.; Prodaivoda, G.T.

    1993-09-01

    Investigations of the elastic properties of the main rock-forming minerals were begun by T.V. Ryzhova and K.S. Aleksandrov over 30 years ago on the initiative of B.P. Belikov. At the time, information on the elasticity of single crystals in general, and especially of minerals, was very scanty. In the surveys of that time there was information on the elasticity of 20 or 30 minerals. These, as a rule, did not include the main rock-forming minerals; silicates were represented only by garnets, quartz, topaz, tourmaline, zircon, beryl, and staurolite, which are often found in nature in the form of large and fairly high-quality crystals. Then and even much later it was still necessary to prove a supposition which now seems obvious: The elastic properties of rocks, and hence the velocities of elastic (seismic) waves in the earth`s crust, are primarily determined by the elastic characteristics of the minerals composing these rocks. Proof of this assertion, with rare exceptions of mono-mineralic rocks (marble, quartzite, etc.) cannot be obtained without information on the elasticities of a sufficiently large number of minerals, primarily framework, layer, and chain silicates which constitute the basis of most rocks. This also served as the starting point and main problem of the undertakings of Aleksandrov, Ryzhova, and Belikov - systematic investigations of the elastic properties of minerals and then of various rocks. 108 refs., 7 tabs.

  14. Biochemical and Cellular Determinants of Renal Glomerular Elasticity

    PubMed Central

    Embry, Addie E.; Mohammadi, Hamid; Niu, Xinying; Liu, Liping; Moe, Borren; Miller-Little, William A.; Lu, Christopher Y.; Bruggeman, Leslie A.; McCulloch, Christopher A.; Janmey, Paul A.; Miller, R. Tyler

    2016-01-01

    The elastic properties of renal glomeruli and their capillaries permit them to maintain structural integrity in the presence of variable hemodynamic forces. Measured by micro-indentation, glomeruli have an elastic modulus (E, Young’s modulus) of 2.1 kPa, and estimates from glomerular perfusion studies suggest that the E of glomeruli is between 2 and 4 kPa. F-actin depolymerization by latrunculin, inhibition of acto-myosin contractility by blebbistatin, reduction in ATP synthesis, and reduction of the affinity of adhesion proteins by EDTA reduced the glomerular E to 1.26, 1.7, 1.5, and 1.43 kPa, respectively. Actin filament stabilization with jasplakinolide and increasing integrin affinity with Mg2+ increased E to 2.65 and 2.87 kPa, respectively. Alterations in glomerular E are reflected in commensurate changes in F/G actin ratios. Disruption of vimentin intermediate filaments by withaferin A reduced E to 0.92 kPa. The E of decellularized glomeruli was 0.74 kPa, indicating that cellular components of glomeruli have dominant effects on their elasticity. The E of glomerular basement membranes measured by magnetic bead displacement was 2.4 kPa. Podocytes and mesangial cells grown on substrates with E values between 3 and 5 kPa had actin fibers and focal adhesions resembling those of podocytes in vivo. Renal ischemia and ischemia-reperfusion reduced the E of glomeruli to 1.58 kPa. These results show that the E of glomeruli is between 2 and 4 kPa. E of the GBM, 2.4 kPa, is consistent with this value, and is supported by the behavior of podocytes and mesangial cells grown on variable stiffness matrices. The podocyte cytoskeleton contributes the major component to the overall E of glomeruli, and a normal E requires ATP synthesis. The reduction in glomerular E following ischemia and in other diseases indicates that reduced glomerular E is a common feature of many forms of glomerular injury and indicative of an abnormal podocyte cytoskeleton. PMID:27942003

  15. [Visco-elastic characteristics of the aorta in conscious dogs in a model of experimental calcinosis].

    PubMed

    Armentano, R; Levenson, J; Cabrera, E; Pichel, R; Simon, A

    1989-07-01

    Effects of experimental calcinosis induced by daily overdose of 500.000 IU Vit D3 during 10 days were studied in 6 mongrel conscious dogs chronically instrumented with intra-aortic Konigsberg microtransducer and two ultrasonic piezo-electric crystals diametrically opposed in the adventitia of the descending thoracic aorta. Simultaneous recording of instantaneous aortic pressure and diameter waves in basal state and during transient acute hypertension induced by intravenous angiotensin bolus (0.1 microgram/kg) allowed to obtain the pressure (y) diameter (x) relationship of the aorta according to an exponential regression: P = expo (beta D + A), with a highly significant correlation coefficient in all animals (r greater than 0.99). (table; see text) Anatomopathological studies of aortas revealed abnormal calcium deposition, ruptures of elastic fibers and disorganization of collagen. Thus, a striking decrease in aortic rigidity is observed after calcinosis in relation with structural changes of elastic materials and responsible in part for a reduction in pulsatile pressure; moreover this unexpected phenomena might represent an initiative process of development of aortic aneurysms.

  16. "Jeopardy" in Abnormal Psychology.

    ERIC Educational Resources Information Center

    Keutzer, Carolin S.

    1993-01-01

    Describes the use of the board game, Jeopardy, in a college level abnormal psychology course. Finds increased student interaction and improved application of information. Reports generally favorable student evaluation of the technique. (CFR)

  17. Capillary adhesion forces between flexible fibers

    NASA Astrophysics Data System (ADS)

    Duprat, Camille; Protière, Suzie

    2016-11-01

    We consider the capillary adhesion produced by a drop placed between two elastic fibers. We measure the force exerted by the drop as we vary the inter-fiber distance, and report two types of wet adhesion: a weak capillary adhesion, where a liquid drop bridges the fibers, and a strong elastocapillary adhesion where the liquid is spread between two collapsed fibers. The weak adhesion is characterized by a force that increases linearly with the liquid length. With flexible fibers, the force exerted by the drop can induce deformation and rapid collapse, or zipping, of the fibers. This zipping results in a sudden increase of the wetted length and a force that departs from the linear evolution. As the inter-fiber distance is subsequently increased, the liquid length decreases while the fibers deformation increases, and the force actually reaches a plateau, i.e. remains constant until unzipping, or detachment of the fibers occurs. We measure the value of this plateau, i.e. the maximal adhesion force, as we vary the drop volume and the fibers elasticity. We also show that flexibility extends capillary adhesion to inter-fiber distances impossible to reach with rigid fibers, while keeping a constant pull-out force characteristic of the elastocapillary coupling.

  18. On granular elasticity

    PubMed Central

    Sun, Qicheng; Jin, Feng; Wang, Guangqian; Song, Shixiong; Zhang, Guohua

    2015-01-01

    Mesoscopic structures form in dense granular materials due to the self-organisation of the constituent particles. These structures have internal structural degrees of freedom in addition to the translational degree of freedom. The resultant granular elasticity, which exhibits intrinsic variations and inevitable relaxation, is a key quantity that accounts for macroscopic solid- or fluid-like properties and the transitions between them. In this work, we propose a potential energy landscape (PEL) with local stable basins and low elastic energy barriers to analyse the nature of granular elasticity. A function for the elastic energy density is proposed for stable states and is further calibrated with ultrasonic measurements. Fluctuations in the elastic energy due to the evolution of internal structures are proposed to describe a so-called configuration temperature Tc as a counterpart of the classical kinetic granular temperature Tk that is attributed to the translational degrees of freedom. The two granular temperatures are chosen as the state variables, and a fundamental equation is established to develop non-equilibrium thermodynamics for granular materials. Due to the relatively low elastic energy barrier in the PEL, granular elasticity relaxes more under common mechanical loadings, and a simple model based on mean-field theory is developed to account for this behaviour. PMID:25951049

  19. Elastic membranes in confinement

    NASA Astrophysics Data System (ADS)

    Bostwick, Joshua; Miksis, Michael; Davis, Stephen

    2014-11-01

    An elastic membrane stretched between two walls takes a shape defined by its length and the volume of fluid it encloses. Many biological structures, such as cells, mitochondria and DNA, have finer internal structure in which a membrane (or elastic member) is geometrically ``confined'' by another object. We study the shape stability of elastic membranes in a ``confining'' box and introduce repulsive van der Waals forces to prevent the membrane from intersecting the wall. We aim to define the parameter space associated with mitochondria-like deformations. We compare the confined to `unconfined' solutions and show how the structure and stability of the membrane shapes changes with the system parameters.

  20. Kinetics of stress fibers

    NASA Astrophysics Data System (ADS)

    Stachowiak, Matthew R.; O'Shaughnessy, Ben

    2008-02-01

    Stress fibers are contractile cytoskeletal structures, tensile actomyosin bundles which allow sensing and production of force, provide cells with adjustable rigidity and participate in various processes such as wound healing. The stress fiber is possibly the best characterized and most accessible multiprotein cellular contractile machine. Here we develop a quantitative model of the structure and relaxation kinetics of stress fibers. The principal experimentally known features are incorporated. The fiber has a periodic sarcomeric structure similar to muscle fibers with myosin motor proteins exerting contractile force by pulling on actin filaments. In addition the fiber contains the giant spring-like protein titin. Actin is continuously renewed by exchange with the cytosol leading to a turnover time of several minutes. In order that steady state be possible, turnover must be regulated. Our model invokes simple turnover and regulation mechanisms: actin association and dissociation occur at filament ends, while actin filament overlap above a certain threshold in the myosin-containing regions augments depolymerization rates. We use the model to study stress fiber relaxation kinetics after stimulation, as observed in a recent experimental study where some fiber regions were contractile and others expansive. We find that two distinct episodes ensue after stimulation: the turnover-overlap system relaxes rapidly in seconds, followed by the slow relaxation of sarcomere lengths in minutes. For parameter values as they have been characterized experimentally, we find the long time relaxation of sarcomere length is set by the rate at which actin filaments can grow or shrink in response to the forces exerted by the elastic and contractile elements. Consequently, the stress fiber relaxation time scales inversely with both titin spring constant and the intrinsic actin turnover rate. The model's predicted sarcomere velocities and contraction-expansion kinetics are in good

  1. Probabilistic Fiber Composite Micromechanics

    NASA Technical Reports Server (NTRS)

    Stock, Thomas A.

    1996-01-01

    Probabilistic composite micromechanics methods are developed that simulate expected uncertainties in unidirectional fiber composite properties. These methods are in the form of computational procedures using Monte Carlo simulation. The variables in which uncertainties are accounted for include constituent and void volume ratios, constituent elastic properties and strengths, and fiber misalignment. A graphite/epoxy unidirectional composite (ply) is studied to demonstrate fiber composite material property variations induced by random changes expected at the material micro level. Regression results are presented to show the relative correlation between predictor and response variables in the study. These computational procedures make possible a formal description of anticipated random processes at the intra-ply level, and the related effects of these on composite properties.

  2. Stiffness transition in anisotropic fiber nets

    NASA Astrophysics Data System (ADS)

    Åström, J. A.; Sunil Kumar, P. B.; Karttunen, Mikko

    2012-08-01

    We demonstrate the existence of a percolationlike stiffness transition in fiber networks with a bidisperse orientation distribution and with fiber densities clearly above the geometrical and the ordinary stiffness transition. The fibers are oriented parallel and perpendicular to a strain direction and they have a large fiber aspect ratio. The stiffness K of the fiber nets can be described by a scaling relation, K∝ταg[(ɛ-ɛc)/τ-β], where τ is the fraction of fibers parallel to strain. g is a scaling function that is roughly described by a power law g(x)∝xγ for stiffness above the transition and by a constant below the transition. The transition point is characterized by qualitative changes in the distribution of the elastic deformation energy of the fibers, the deformation mode of the fibers, the effective Poisson ratio of the nets, the distribution of elastic energy on fibers and cross links, and the ratio of elastic and viscous dissipation energy. This transition opens the possibility of extreme stiffness variations with minimal mesh manipulations in the vicinity of the transition (i.e., a stiffness gate). It is possible that this transition affects the mechanical behavior of the cytoskeleton in cells.

  3. Stiffness of compressed fiber mats

    NASA Astrophysics Data System (ADS)

    Åström, J. A.; Mäkinen, J. P.; Hirvonen, H.; Timonen, J.

    2000-11-01

    We investigate, using an analytical and a numerical model, the in-plane stiffness of fiber mats. A mat is modeled by randomly depositing thin linear-elastic fibers on top of each other under the influence of an external pressure. The external pressure has the effect of bending the fibers over each other. The fibers are assumed rigidly bonded at contacts. For a low external pressure the stiffness of the mat deviates from that of its two-dimensional projection only by a geometrical factor, and the effective Poisson contraction is close to zero. For higher pressures, stiffness is governed by two competing effects and a maximum appears in the stiffness. The effective Poisson ratio is clearly negative in this range. An approximative analytical description is developed for the stiffness of mats formed under low external pressure. The stiffness is given as a function of only a few parameters: the degree of bonding, the dimensions of the fibers, the elastic constants of the fiber material, and the density of fibers.

  4. Mechanism of Resilin Elasticity

    PubMed Central

    Qin, Guokui; Hu, Xiao; Cebe, Peggy; Kaplan, David L.

    2012-01-01

    Resilin is critical in the flight and jumping systems of insects as a polymeric rubber-like protein with outstanding elasticity. However, insight into the underlying molecular mechanisms responsible for resilin elasticity remains undefined. Here we report the structure and function of resilin from Drosophila CG15920. A reversible beta-turn transition was identified in the peptide encoded by exon III and for full length resilin during energy input and release, features that correlate to the rapid deformation of resilin during functions in vivo. Micellar structures and nano-porous patterns formed after beta-turn structures were present via changes in either the thermal or mechanical inputs. A model is proposed to explain the super elasticity and energy conversion mechanisms of resilin, providing important insight into structure-function relationships for this protein. Further, this model offers a view of elastomeric proteins in general where beta-turn related structures serve as fundamental units of the structure and elasticity. PMID:22893127

  5. Elastic-plastic behavior of non-woven fibrous mats

    NASA Astrophysics Data System (ADS)

    Silberstein, Meredith N.; Pai, Chia-Ling; Rutledge, Gregory C.; Boyce, Mary C.

    2012-02-01

    Electrospinning is a novel method for creating non-woven polymer mats that have high surface area and high porosity. These attributes make them ideal candidates for multifunctional composites. Understanding the mechanical properties as a function of fiber properties and mat microstructure can aid in designing these composites. Further, a constitutive model which captures the membrane stress-strain behavior as a function of fiber properties and the geometry of the fibrous network would be a powerful design tool. Here, mats electrospun from amorphous polyamide are used as a model system. The elastic-plastic behavior of single fibers are obtained in tensile tests. Uniaxial monotonic and cyclic tensile tests are conducted on non-woven mats. The mat exhibits elastic-plastic stress-strain behavior. The transverse strain behavior provides important complementary data, showing a negligible initial Poisson's ratio followed by a transverse:axial strain ratio greater than -1:1 after an axial strain of 0.02. A triangulated framework has been developed to emulate the fibrous network structure of the mat. The micromechanically based model incorporates the elastic-plastic behavior of single fibers into a macroscopic membrane model of the mat. This representative volume element based model is shown to capture the uniaxial elastic-plastic response of the mat under monotonic and cyclic loading. The initial modulus and yield stress of the mat are governed by the fiber properties, the network geometry, and the network density. The transverse strain behavior is linked to discrete deformation mechanisms of the fibrous mat structure including fiber alignment, fiber bending, and network consolidation. The model is further validated in comparison to experiments under different constrained axial loading conditions and found to capture the constraint effect on stiffness, yield, post-yield hardening, and post-yield transverse strain behavior. Due to the direct connection between

  6. Deflation of elastic surfaces

    NASA Astrophysics Data System (ADS)

    Quilliet, Catherine; Quemeneur, François; Marmottant, Philippe; Imhof, Arnout; Pépin-Donat, Brigitte; van Blaaderen, Alfons

    2010-03-01

    The deflation of elastic spherical surfaces has been numerically investigated, and show very different types of deformations according the range of elastic parameters, some of them being quantitatively explained through simple calculations. This allows to retrieve various shapes observed on hollow shells (from colloidal to centimeter scale), on lipid vesicles, or on some biological objects. The extension of this process to other geometries allows to modelize vegetal objects such as the ultrafast trap of carnivorous plants.

  7. Advances in biomimetic regeneration of elastic matrix structures

    PubMed Central

    Sivaraman, Balakrishnan; Bashur, Chris A.

    2012-01-01

    Elastin is a vital component of the extracellular matrix, providing soft connective tissues with the property of elastic recoil following deformation and regulating the cellular response via biomechanical transduction to maintain tissue homeostasis. The limited ability of most adult cells to synthesize elastin precursors and assemble them into mature crosslinked structures has hindered the development of functional tissue-engineered constructs that exhibit the structure and biomechanics of normal native elastic tissues in the body. In diseased tissues, the chronic overexpression of proteolytic enzymes can cause significant matrix degradation, to further limit the accumulation and quality (e.g., fiber formation) of newly deposited elastic matrix. This review provides an overview of the role and importance of elastin and elastic matrix in soft tissues, the challenges to elastic matrix generation in vitro and to regenerative elastic matrix repair in vivo, current biomolecular strategies to enhance elastin deposition and matrix assembly, and the need to concurrently inhibit proteolytic matrix disruption for improving the quantity and quality of elastogenesis. The review further presents biomaterial-based options using scaffolds and nanocarriers for spatio-temporal control over the presentation and release of these biomolecules, to enable biomimetic assembly of clinically relevant native elastic matrix-like superstructures. Finally, this review provides an overview of recent advances and prospects for the application of these strategies to regenerating tissue-type specific elastic matrix structures and superstructures. PMID:23355960

  8. Mesoscale elastic properties of marine sponge spicules.

    PubMed

    Zhang, Yaqi; Reed, Bryan W; Chung, Frank R; Koski, Kristie J

    2016-01-01

    Marine sponge spicules are silicate fibers with an unusual combination of fracture toughness and optical light propagation properties due to their micro- and nano-scale hierarchical structure. We present optical measurements of the elastic properties of Tethya aurantia and Euplectella aspergillum marine sponge spicules using non-invasive Brillouin and Raman laser light scattering, thus probing the hierarchical structure on two very different scales. On the scale of single bonds, as probed by Raman scattering, the spicules resemble a combination of pure silica and mixed organic content. On the mesoscopic scale probed by Brillouin scattering, we show that while some properties (Young's moduli, shear moduli, one of the anisotropic Poisson ratios and refractive index) are nearly the same as those of artificial optical fiber, other properties (uniaxial moduli, bulk modulus and a distinctive anisotropic Poisson ratio) are significantly smaller. Thus this natural composite of largely isotropic materials yields anisotropic elastic properties on the mesoscale. We show that the spicules' optical waveguide properties lead to pronounced spontaneous Brillouin backscattering, a process related to the stimulated Brillouin backscattering process well known in artificial glass fibers. These measurements provide a clearer picture of the interplay of flexibility, strength, and material microstructure for future functional biomimicry.

  9. Nonaffine rubber elasticity for stiff polymer networks.

    PubMed

    Heussinger, Claus; Schaefer, Boris; Frey, Erwin

    2007-09-01

    We present a theory for the elasticity of cross-linked stiff polymer networks. Stiff polymers, unlike their flexible counterparts, are highly anisotropic elastic objects. Similar to mechanical beams, stiff polymers easily deform in bending, while they are much stiffer with respect to tensile forces ("stretching"). Unlike in previous approaches, where network elasticity is derived from the stretching mode, our theory properly accounts for the soft bending response. A self-consistent effective medium approach is used to calculate the macroscopic elastic moduli starting from a microscopic characterization of the deformation field in terms of "floppy modes"-low-energy bending excitations that retain a high degree of nonaffinity. The length scale characterizing the emergent nonaffinity is given by the "fiber length" lf, defined as the scale over which the polymers remain straight. The calculated scaling properties for the shear modulus are in excellent agreement with the results of recent simulations obtained in two-dimensional model networks. Furthermore, our theory can be applied to rationalize bulk rheological data in reconstituted actin networks.

  10. 16 CFR 303.10 - Fiber content of special types of products.

    Code of Federal Regulations, 2011 CFR

    2011-01-01

    ... 16 Commercial Practices 1 2011-01-01 2011-01-01 false Fiber content of special types of products... CONGRESS RULES AND REGULATIONS UNDER THE TEXTILE FIBER PRODUCTS IDENTIFICATION ACT § 303.10 Fiber content... other yarns or materials used therein. Where a textile fiber product is made in part of elastic...

  11. 16 CFR 303.10 - Fiber content of special types of products.

    Code of Federal Regulations, 2010 CFR

    2010-01-01

    ... 16 Commercial Practices 1 2010-01-01 2010-01-01 false Fiber content of special types of products... CONGRESS RULES AND REGULATIONS UNDER THE TEXTILE FIBER PRODUCTS IDENTIFICATION ACT § 303.10 Fiber content... other yarns or materials used therein. Where a textile fiber product is made in part of elastic...

  12. [The relativity of abnormity].

    PubMed

    Nilson, Annika

    2006-01-01

    In the late 19th century and in the beginning of the 20th century, mental diseases and abnormal behavior was considered to be a great danger to culture and society. "Degeneration" was the buzzword of the time, used and misused by artists and scientists alike. At the same time, some scientists saw abnormity as the key to unlock the mysteries of the ordinary mind. Naturalistic curiosity left Pandoras box open when religion declined in Darwins wake. Two swedish scientists, the physician Bror Gadelius (1862-1938) and his friend the philosopher Axel Herrlin (1870-1937), inspired by the French psychologist Theodule Ribots (1839-1916) "psychology without a soul", denied all fixed demarcation lines between abnormity and normality. All humans are natures creatures ruled by physiological laws, not ruled by God or convention. Even ordinary morality was considered to be an utterly backward explanation and guideline for complex human behavior. Different forms of therapy, not various kinds of penalties for wicked and disturbing behavior, are the now the solution for lots of people, "normal" as well as "abnormal". Psychiatry is expanding.

  13. Abnormalities of gonadal differentiation.

    PubMed

    Berkovitz, G D; Seeherunvong, T

    1998-04-01

    Gonadal differentiation involves a complex interplay of developmental pathways. The sex determining region Y (SRY) gene plays a key role in testis determination, but its interaction with other genes is less well understood. Abnormalities of gonadal differentiation result in a range of clinical problems. 46,XY complete gonadal dysgenesis is defined by an absence of testis determination. Subjects have female external genitalia and come to clinical attention because of delayed puberty. Individuals with 46,XY partial gonadal dysgenesis usually present in the newborn period for the valuation of ambiguous genitalia. Gonadal histology always shows an abnormality of seminiferous tubule formation. A diagnosis of 46,XY true hermaphroditism is made if the gonads contain well-formed testicular and ovarian elements. Despite the pivotal role of the SRY gene in testis development, mutations of SRY are unusual in subjects with a 46,XY karyotype and abnormal gonadal development. 46,XX maleness is defined by testis determination in an individual with a 46,XX karyotype. Most affected individuals have a phenotype similar to that of Klinefelter syndrome. In contrast, subjects with 46,XX true hermaphroditism usually present with ambiguous genitalia. The majority of subjects with 46,XX maleness have Y sequences including SRY in genomic DNA. However, only rare subjects with 46,XX true hermaphroditism have translocated sequences encoding SRY. Mosaicism and chimaerism involving the Y chromosome can also be associated with abnormal gonadal development. However, the vast majority of subjects with 45,X/46,XY mosaicism have normal testes and normal male external genitalia.

  14. Elasticity of plagioclase feldspars

    NASA Astrophysics Data System (ADS)

    Brown, J. Michael; Angel, Ross J.; Ross, Nancy L.

    2016-02-01

    Elastic properties are reported for eight plagioclase feldspars that span compositions from albite (NaSi3AlO8) to anorthite (CaSi2Al2O8). Surface acoustic wave velocities measured using Impulsive Stimulated Light Scattering and compliance sums from high-pressure X-ray compression studies accurately determine all 21 components of the elasticity tensor for these triclinic minerals. The overall pattern of elasticity and the changes in individual elastic components with composition can be rationalized on the basis of the evolution of crystal structures and chemistry across this solid-solution join. All plagioclase feldspars have high elastic anisotropy; a* (the direction perpendicular to the b and c axes) is the softest direction by a factor of 3 in albite. From albite to anorthite the stiffness of this direction undergoes the greatest change, increasing twofold. Small discontinuities in the elastic components, inferred to occur between the three plagioclase phases with distinct symmetry (C1>¯, I1>¯, and P1>¯), appear consistent with the nature of the underlying conformation of the framework-linked tetrahedra and the associated structural changes. Measured body wave velocities of plagioclase-rich rocks, reported over the last five decades, are consistent with calculated Hill-averaged velocities using the current moduli. This confirms long-standing speculation that previously reported elastic moduli for plagioclase feldspars are systematically in error. The current results provide greater assurance that the seismic structure of the middle and lower crusts can be accurately estimated on the basis of specified mineral modes, chemistry, and fabric.

  15. Recurrent chromosome 6 abnormalities in malignant mesothelioma.

    PubMed

    Ribotta, M; Roseo, F; Salvio, M; Castagneto, B; Carbone, M; Procopio, A; Giordano, A; Mutti, L

    1998-04-01

    The long latency period between asbestos exposure and the onset of malignant mesothelioma (MM) suggests that a multistep tumorigenesis process occurs whilst the capability of asbestos fibres to interfere directly with chromosomes focuses on the critical role of the chromosomal abnormalities in this neoplasm. The aim of our study was to identify any recurrent chromosomal changes in ten primary MM cell cultures derived from pleural effusions of patients with MM from the same geographic area and environmental and/or occupational exposure to asbestos fibers. Cytogenetic analysis was performed in accordance with International System for Human Cytogenetic Nomenclature. Our results confirmed a great number of cytogenetic abnormalities in MM cells. Recurrent loss of the long arms of chromosome 6 (6q-) was the most frequent abnormality detected (four epithelial and two mixed subtypes) while, on the whole, abnormalities of chromosome 6 were found in nine out of ten cases whereas chromosome 6 was normal only in the case with fibromatous subtype. Monosomy 13 and 17 was found in five cases, monosomy 14 in four cases and 22 in three cases. Since deletion of 6q- was detected even in relatively undisturbed karyotype, we hypothesize a multistep carcinogenic process in which deletion of 6q- is an early event in the development and progression of malignant mesothelioma.

  16. Ultrasonic characterization of the nonlinear elastic properties of unidirectional graphite/epoxy composites

    NASA Technical Reports Server (NTRS)

    Prosser, William H.; Green, Robert E., Jr.

    1987-01-01

    The theoretical treatment of linear and nonlinear elasticity in a unidirectionally fiber reinforced composite as well as measurements for a unidirectional graphite/epoxy composite (T300/5208) are presented. Linear elastic properties were measured by both ultrasonic and strain gage measurements. The nonlinear properties were determined by measuring changes in ultrasonic natural phase velocity with a pulsed phase locked loop interferometer as a function of stress and temperature. These measurements provide the basis for further investigations into the relationship between nonlinear elastic properties and other important properties such as strength and fiber-matrix interfacial strength in graphite/epoxy composites.

  17. Ultrasonic characterization of the nonlinear elastic properties of unidirectional graphite/epoxy composites

    NASA Technical Reports Server (NTRS)

    Prosser, William H.

    1987-01-01

    The theoretical treatment of linear and nonlinear elasticity in a unidirectionally fiber reinforced composite as well as measurements for a unidirectional graphite/epoxy composite (T300/5208) are presented. Linear elastic properties were measured by both ultrasonic and strain gage measurements. The nonlinear properties were determined by measuring changes in ultrasonic natural phase velocity with a pulsed phase locked loop interferometer as a function of stress and temperature. These measurements provide the basis for further investigations into the relationship between nonlinear elastic properties and other important properties such as strength and fiber-matrix interfacial stength in graphite/epoxy composites.

  18. Elastic properties of pyrope

    NASA Astrophysics Data System (ADS)

    O'Neill, Bridget; Bass, Jay D.; Rossman, George R.; Geiger, Charles A.; Langer, Klaus

    1991-03-01

    Brillouin spectroscopy was used to measure the single crystal elastic properties of a pure synthetic pyrope and a natural garnet containing 89.9 mol% of the pyrope end member (Mg3Al2Si3O12). The elastic moduli, c ij , of the two samples are entirely consistent and agree with previous estimates of the elastic properties of pyrope based upon the moduli of solid solutions. Our results indicate that the elastic moduli of pyrope end-member are c 11=296.2±0.5, c 12=111.1±0.6, c 44=91.6±0.3, Ks=172.8±0.3, μ=92.0±0.2, all in units of GPa. These results differ by several percent from those reported previously for synthetic pyrope, but are based upon a much larger data set. Although the hydrous components of the two samples from the present study are substantially different, representing both ‘dry’ and ‘saturated’ samples, we find no discernable effect of structurally bound water on the elastic properties. This is due to the small absolute solubility of water in pyrope, as compared with other garnets such as grossular.

  19. Nonlinear dynamics of laser-induced bubble near elastic boundaries

    NASA Astrophysics Data System (ADS)

    Liu, Xiu Mei; He, Jie; Lu, Jian; Ni, Xiao Wu

    2008-01-01

    Nonlinear dynamics of a laser-generated single cavitation bubble near an elastic boundary is investigated by a fiber-optic diagnostic technique based on optical beam deflection (OBD). The maximum bubble radii and the bubble life-time for each oscillation cycle are determined according to the characteristic signals. It is shown that with the increase of the number of oscillating cycles, the maximum radii and the life-time of the bubble are decreased sharply. Furthermore, the effect of material elasticity on nonlinear dynamics of cavitation bubble has also been investigated in some detail. The maximum bubble size and thus the bubble life time decreases with an increase in elastic modulus. In addition, increasing elastic modulus leads to a significant decrease of the collapse amplitude and the bubble energy. These results are valuable in the fields of cavitation erosion, collateral damage in laser surgery, and cavitation-mediated enhancement of pulsed laser ablation of tissue.

  20. An elastic second skin

    NASA Astrophysics Data System (ADS)

    Yu, Betty; Kang, Soo-Young; Akthakul, Ariya; Ramadurai, Nithin; Pilkenton, Morgan; Patel, Alpesh; Nashat, Amir; Anderson, Daniel G.; Sakamoto, Fernanda H.; Gilchrest, Barbara A.; Anderson, R. Rox; Langer, Robert

    2016-08-01

    We report the synthesis and application of an elastic, wearable crosslinked polymer layer (XPL) that mimics the properties of normal, youthful skin. XPL is made of a tunable polysiloxane-based material that can be engineered with specific elasticity, contractility, adhesion, tensile strength and occlusivity. XPL can be topically applied, rapidly curing at the skin interface without the need for heat- or light-mediated activation. In a pilot human study, we examined the performance of a prototype XPL that has a tensile modulus matching normal skin responses at low strain (<40%), and that withstands elongations exceeding 250%, elastically recoiling with minimal strain-energy loss on repeated deformation. The application of XPL to the herniated lower eyelid fat pads of 12 subjects resulted in an average 2-grade decrease in herniation appearance in a 5-point severity scale. The XPL platform may offer advanced solutions to compromised skin barrier function, pharmaceutical delivery and wound dressings.

  1. Elastic constants of calcite

    USGS Publications Warehouse

    Peselnick, L.; Robie, R.A.

    1962-01-01

    The recent measurements of the elastic constants of calcite by Reddy and Subrahmanyam (1960) disagree with the values obtained independently by Voigt (1910) and Bhimasenachar (1945). The present authors, using an ultrasonic pulse technique at 3 Mc and 25??C, determined the elastic constants of calcite using the exact equations governing the wave velocities in the single crystal. The results are C11=13.7, C33=8.11, C44=3.50, C12=4.82, C13=5.68, and C14=-2.00, in units of 1011 dyncm2. Independent checks of several of the elastic constants were made employing other directions and polarizations of the wave velocities. With the exception of C13, these values substantially agree with the data of Voigt and Bhimasenachar. ?? 1962 The American Institute of Physics.

  2. Fiber biology

    Technology Transfer Automated Retrieval System (TEKTRAN)

    Cotton fiber cells arising from seed epidermis is the most important agricultural textile commodity in the world. To produce fully mature fibers, approximately two months of fiber developmental process are required. The timing of four distinctive fiber development stages consisting of initiation, ...

  3. Heritable bovine fetal abnormalities.

    PubMed

    Whitlock, B K; Kaiser, L; Maxwell, H S

    2008-08-01

    The etiologies for congenital bovine fetal anomalies can be divided into heritable, toxic, nutritional, and infectious categories. Although uncommon in most herds, inherited congenital anomalies are probably present in all breeds of cattle and propagated as a result of specific trait selection that inadvertently results in propagation of the defect. In some herds, the occurrence of inherited anomalies has become frequent, and economically important. Anomalous traits can affect animals in a range of ways, some being lethal or requiring euthanasia on humane grounds, others altering structure, function, or performance of affected animals. Veterinary practitioners should be aware of the potential for inherited defects, and be prepared to investigate and report animals exhibiting abnormal characteristics. This review will discuss the morphologic characteristics, mode of inheritance, breeding lines affected, and the availability of genetic testing for selected heritable bovine fetal abnormalities.

  4. Liver abnormalities in pregnancy.

    PubMed

    Than, Nwe Ni; Neuberger, James

    2013-08-01

    Abnormalities of liver function (notably rise in alkaline phosphatase and fall in serum albumin) are common in normal pregnancy, whereas rise in serum bilirubin and aminotransferase suggest either exacerbation of underlying pre-existing liver disease, liver disease related to pregnancy or liver disease unrelated to pregnancy. Pregnant women appear to have a worse outcome when infected with Hepatitis E virus. Liver diseases associated with pregnancy include abnormalities associated hyperemesis gravidarum, acute fatty liver disease, pre-eclampsia, cholestasis of pregnancy and HELLP syndrome. Prompt investigation and diagnosis is important in ensuring a successful maternal and foetal outcome. In general, prompt delivery is the treatment of choice for acute fatty liver, pre-eclampsia and HELLP syndrome and ursodeoxycholic acid is used for cholestasis of pregnancy although it is not licenced for this indication.

  5. Morphological abnormalities in elasmobranchs.

    PubMed

    Moore, A B M

    2015-08-01

    A total of 10 abnormal free-swimming (i.e., post-birth) elasmobranchs are reported from The (Persian-Arabian) Gulf, encompassing five species and including deformed heads, snouts, caudal fins and claspers. The complete absence of pelvic fins in a milk shark Rhizoprionodon acutus may be the first record in any elasmobranch. Possible causes, including the extreme environmental conditions and the high level of anthropogenic pollution particular to The Gulf, are briefly discussed.

  6. Prediction of fiber composite mechanical behavior made simple. [using a rocket calculator

    NASA Technical Reports Server (NTRS)

    Chamis, C. C.

    1980-01-01

    The elastic properties and failure stresses of angleplied fiber composite laminates were determined using a pocket calculator. The procedure uses simple equations and appropriate graphs of elastic properties versus angle plies, and can handle all types of fiber composites including hybrids. The versatility and generality of the method is illustrated in several step-by-step numerical examples.

  7. Anatomical Abnormalities in Autism?

    PubMed

    Haar, Shlomi; Berman, Sigal; Behrmann, Marlene; Dinstein, Ilan

    2016-04-01

    Substantial controversy exists regarding the presence and significance of anatomical abnormalities in autism spectrum disorders (ASD). The release of the Autism Brain Imaging Data Exchange (∼1000 participants, age 6-65 years) offers an unprecedented opportunity to conduct large-scale comparisons of anatomical MRI scans across groups and to resolve many of the outstanding questions. Comprehensive univariate analyses using volumetric, thickness, and surface area measures of over 180 anatomically defined brain areas, revealed significantly larger ventricular volumes, smaller corpus callosum volume (central segment only), and several cortical areas with increased thickness in the ASD group. Previously reported anatomical abnormalities in ASD including larger intracranial volumes, smaller cerebellar volumes, and larger amygdala volumes were not substantiated by the current study. In addition, multivariate classification analyses yielded modest decoding accuracies of individuals' group identity (<60%), suggesting that the examined anatomical measures are of limited diagnostic utility for ASD. While anatomical abnormalities may be present in distinct subgroups of ASD individuals, the current findings show that many previously reported anatomical measures are likely to be of low clinical and scientific significance for understanding ASD neuropathology as a whole in individuals 6-35 years old.

  8. Elastic model of supercoiling.

    PubMed Central

    Benham, C J

    1977-01-01

    An elastic model for the supercoiling of duplex DNA is developed. The simplest assumptions regarding the elastic properties of double-helical DNA (homogeneous, isotropic, of circular cross section, and remaining straight when unstressed) will generate two orders of superhelicity when stressed. Recent experimental results [Brady, G.W., Fein, D.B. & Brumberger, H. (1976) Nature 264, 231-234] suggest that in supercoiled DNA molecules there are regions where two distinct orders of supercoiling arise, as predicted by this model. PMID:267934

  9. Abnormal pressures as hydrodynamic phenomena

    USGS Publications Warehouse

    Neuzil, C.E.

    1995-01-01

    So-called abnormal pressures, subsurface fluid pressures significantly higher or lower than hydrostatic, have excited speculation about their origin since subsurface exploration first encountered them. Two distinct conceptual models for abnormal pressures have gained currency among earth scientists. The static model sees abnormal pressures generally as relict features preserved by a virtual absence of fluid flow over geologic time. The hydrodynamic model instead envisions abnormal pressures as phenomena in which flow usually plays an important role. This paper develops the theoretical framework for abnormal pressures as hydrodynamic phenomena, shows that it explains the manifold occurrences of abnormal pressures, and examines the implications of this approach. -from Author

  10. [Molecular abnormalities in lymphomas].

    PubMed

    Delsol, G

    2010-11-01

    Numerous molecular abnormalities have been described in lymphomas. They are of diagnostic and prognostic value and are taken into account for the WHO classification of these tumors. They also shed some light on the underlying molecular mechanisms involved in lymphomas. Overall, four types of molecular abnormalities are involved: mutations, translocations, amplifications and deletions of tumor suppressor genes. Several techniques are available to detect these molecular anomalies: conventional cytogenetic analysis, multicolor FISH, CGH array or gene expression profiling using DNA microarrays. In some lymphomas, genetic abnormalities are responsible for the expression of an abnormal protein (e.g. tyrosine-kinase, transcription factor) detectable by immunohistochemistry. In the present review, molecular abnormalities observed in the most frequent B, T or NK cell lymphomas are discussed. In the broad spectrum of diffuse large B-cell lymphomas microarray analysis shows mostly two subgroups of tumors, one with gene expression signature corresponding to germinal center B-cell-like (GCB: CD10+, BCL6 [B-Cell Lymphoma 6]+, centerine+, MUM1-) and a subgroup expressing an activated B-cell-like signature (ABC: CD10-, BCL6-, centerine-, MUM1+). Among other B-cell lymphomas with well characterized molecular abnormalies are follicular lymphoma (BCL2 deregulation), MALT lymphoma (Mucosa Associated Lymphoid Tissue) [API2-MALT1 (mucosa-associated-lymphoid-tissue-lymphoma-translocation-gene1) fusion protein or deregulation BCL10, MALT1, FOXP1. MALT1 transcription factors], mantle cell lymphoma (cycline D1 [CCND1] overexpression) and Burkitt lymphoma (c-Myc expression). Except for ALK (anaplastic lymphoma kinase)-positive anaplastic large cell lymphoma, well characterized molecular anomalies are rare in lymphomas developed from T or NK cells. Peripheral T cell lymphomas not otherwise specified are a heterogeneous group of tumors with frequent but not recurrent molecular abnormalities

  11. Elastic properties and fracture strength of quasi-isotropic graphite/epoxy composites

    NASA Technical Reports Server (NTRS)

    Sullivan, T. L.

    1977-01-01

    A research program is described which was devised to determine experimentally the elastic properties in tension and bending of quasi-isotropic laminates made from high-modulus graphite fiber and epoxy. Four laminate configurations were investigated, and determinations were made of the tensile modulus, Poisson's ratio, bending stiffness, fracture strength, and fracture strain. The measured properties are compared with those predicted by laminate theory, reasons for scatter in the experimental data are discussed, and the effect of fiber misalignment on predicted elastic tensile properties is examined. The results strongly suggest that fiber misalignment in combination with variation in fiber volume content is responsible for the scatter in both elastic constants and fracture strength.

  12. Buckling transitions of an elastic filament in a viscous stagnation point flow

    NASA Astrophysics Data System (ADS)

    Guglielmini, Laura; Kushwaha, Amit; Shaqfeh, Eric S. G.; Stone, Howard A.

    2012-12-01

    The interplay of viscous and elastic stresses is relevant to a number of flow problems involving slender elastic fibers. These range from the swimming of microorganisms to the transport of pulp fibers in processing flow as well as from nanotube and nanocarpet applications to semi-flexible polymer behavior. In some applications, slender fibers are attached to walls where they experience externally applied flows. In this paper, we focus on the model problem of a wall mounted filament in a (compressive) extensional flow and characterize the flow-induced bending and buckling of the fiber. Using a combination of stability analysis and numerical simulations (with the latter based on a discretized beam model), we show that, for a critical value of the ratio between viscous and elastic forces, the filament is susceptible to bending and buckling instabilities at supercritical bifurcation points.

  13. Feeling Abnormal: Simulation of Deviancy in Abnormal and Exceptionality Courses.

    ERIC Educational Resources Information Center

    Fernald, Charles D.

    1980-01-01

    Describes activity in which student in abnormal psychology and psychology of exceptional children classes personally experience being judged abnormal. The experience allows the students to remember relevant research, become sensitized to the feelings of individuals classified as deviant, and use caution in classifying individuals as abnormal.…

  14. Effects of EB irradiation on stress-strain curves for carbon fiber reinforced composite materials

    NASA Astrophysics Data System (ADS)

    Kobayashi, H.; Yamada, K.; Mizutani, A.; Uchida, N.; Tanaka, K.; Nishi, Yoshitake

    2004-02-01

    In order to evaluate influence of electron beam (EB) irradiation on elasticity and stress- strain curve of composite materials reinforced by carbon fiber (CF), carbon fiber reinforced polymer (CFRP) and carbon fiber reinforced graphite (C/C) were treated by EB irradiation of 0.3 MGy. Since the EB strengthening was mainly dominated by the ductility enhancements of carbon fiber and matrix of epoxy resin, EB irradiation enlarged fracture stress and enhanced fracture strain of CFRP. Furthermore, EB irradiation slightly enhanced bending elasticity of CFRP and largely enhanced the initial spring constant related to elasticity of C/C coil. Although the elasticity enhancement of carbon fibers did not largely contribute that of CFRP, that of treated graphite matrix in C/C mainly caused the C/C coil elasticity enhancement by EB irradiation. Such a new treatment is a dream-worthy technology for structural materials to be applied in the fields of future engineering.

  15. The Law of Elasticity

    ERIC Educational Resources Information Center

    Cocco, Alberto; Masin, Sergio Cesare

    2010-01-01

    Participants estimated the imagined elongation of a spring while they were imagining that a load was stretching the spring. This elongation turned out to be a multiplicative function of spring length and load weight--a cognitive law analogous to Hooke's law of elasticity. Participants also estimated the total imagined elongation of springs joined…

  16. Elastic swimming I: Optimization

    NASA Astrophysics Data System (ADS)

    Lauga, Eric; Yu, Tony; Hosoi, Anette

    2006-03-01

    We consider the problem of swimming at low Reynolds number by oscillating an elastic filament in a viscous liquid, as investigated by Wiggins and Goldstein (1998, Phys Rev Lett). In this first part of the study, we characterize the optimal forcing conditions of the swimming strategy and its optimal geometrical characteristics.

  17. Elastic swimming II: Experiments

    NASA Astrophysics Data System (ADS)

    Yu, Tony; Lauga, Eric; Hosoi, Anette

    2006-03-01

    We consider the problem of swimming at low Reynolds number by oscillating an elastic filament in a viscous liquid, as investigated by Wiggins and Goldstein (1998, Phys Rev Lett). In this second part of the study, we present results of a series of experiments characterizing the performance of the propulsive mechanism.

  18. Hydrodynamic Elastic Magneto Plastic

    SciTech Connect

    Wilkins, M. L.; Levatin, J. A.

    1985-02-01

    The HEMP code solves the conservation equations of two-dimensional elastic-plastic flow, in plane x-y coordinates or in cylindrical symmetry around the x-axis. Provisions for calculation of fixed boundaries, free surfaces, pistons, and boundary slide planes have been included, along with other special conditions.

  19. Elastic and Inelastic Collisions

    ERIC Educational Resources Information Center

    Gluck, Paul

    2010-01-01

    There have been two articles in this journal that described a pair of collision carts used to demonstrate vividly the difference between elastic and inelastic collisions. One cart had a series of washers that were mounted rigidly on a rigid wooden framework, the other had washers mounted on rubber bands stretched across a framework. The rigidly…

  20. Elastic Granular Flows

    NASA Astrophysics Data System (ADS)

    Campbell, Charles

    2006-03-01

    There is no fundamental understanding of the mechanics of granular solids. Partially this is because granular flows have historically been divided into two very distinct flow regimes, (1) the slow, quasistatic regime, in which the bulk friction coefficient is taken to be a material constant, and (2) the fast, rapid-flow regime, where the particles interact collisionally. But slow hopper flow simulations indicate that the bulk friction coefficient is not a constant. Rapidly moving large scale landslide simulations never entered the collisional regime and operate in a separate intermediate flow regime. In other words, most realistic granular flows are not described by either the quasistatic or rapid flow models and it is high time that the field look beyond those early models. This talk will discuss computer simulation studies that draw out the entire flowmap of shearing granular materials, spanning the quasistatic, rapid and the intermediate regimes. The key was to include the elastic properties of the solid material in the set of rheological parameters; in effect, this puts solid properties back into the rheology of granular solids. The solid properties were previously unnecessary in the plasticity and kinetic theory formalisms that respectively form the foundations of the quasistatic and rapid-flow theories. Granular flows can now be divided into two broad categories, the Elastic Regimes, in which the particles are locked in force chains and interact elastically over long duration contact with their neighbors and the Inertial regimes, where the particles have broken free of the force chains. The Elastic regimes can be further subdivided into the Elastic-Quasistatic regime (the old quasistatic regime) and the Elastic-Inertial regime. The Elastic-Inertial regime is the ``new'' regime observed in the landslide simulations, in which the inertially induced stresses are significant compared to the elastically induced stresses. The Inertial regime can also be sub

  1. Exercises to Improve Gait Abnormalities

    MedlinePlus

    ... Home About iChip Articles Directories Videos Resources Contact Exercises to Improve Gait Abnormalities Home » Article Categories » Exercise and Fitness Font Size: A A A A Exercises to Improve Gait Abnormalities Next Page The manner ...

  2. Abnormal human sex chromosome constitutions

    SciTech Connect

    1993-12-31

    Chapter 22, discusses abnormal human sex chromosome constitution. Aneuploidy of X chromosomes with a female phenotype, sex chromosome aneuploidy with a male phenotype, and various abnormalities in X chromosome behavior are described. 31 refs., 2 figs.

  3. Epilepsy and chromosomal abnormalities

    PubMed Central

    2010-01-01

    Background Many chromosomal abnormalities are associated with Central Nervous System (CNS) malformations and other neurological alterations, among which seizures and epilepsy. Some of these show a peculiar epileptic and EEG pattern. We describe some epileptic syndromes frequently reported in chromosomal disorders. Methods Detailed clinical assessment, electrophysiological studies, survey of the literature. Results In some of these congenital syndromes the clinical presentation and EEG anomalies seems to be quite typical, in others the manifestations appear aspecific and no strictly linked with the chromosomal imbalance. The onset of seizures is often during the neonatal period of the infancy. Conclusions A better characterization of the electro clinical patterns associated with specific chromosomal aberrations could give us a valuable key in the identification of epilepsy susceptibility of some chromosomal loci, using the new advances in molecular cytogenetics techniques - such as fluorescent in situ hybridization (FISH), subtelomeric analysis and CGH (comparative genomic hybridization) microarray. However further studies are needed to understand the mechanism of epilepsy associated with chromosomal abnormalities. PMID:20438626

  4. Rac1 GTPase-deficient mouse lens exhibits defects in shape, suture formation, fiber cell migration and survival.

    PubMed

    Maddala, Rupalatha; Chauhan, Bharesh K; Walker, Christopher; Zheng, Yi; Robinson, Michael L; Lang, Richard A; Rao, Ponugoti V

    2011-12-01

    Morphogenesis and shape of the ocular lens depend on epithelial cell elongation and differentiation into fiber cells, followed by the symmetric and compact organization of fiber cells within an enclosed extracellular matrix-enriched elastic capsule. The cellular mechanisms orchestrating these different events however, remain obscure. We investigated the role of the Rac1 GTPase in these processes by targeted deletion of expression using the conditional gene knockout (cKO) approach. Rac1 cKO mice were derived from two different Cre (Le-Cre and MLR-10) transgenic mice in which lens-specific Cre expression starts at embryonic day 8.75 and 10.5, respectively, in both the lens epithelium and fiber cells. The Le-Cre/Rac1 cKO mice exhibited an early-onset (E12.5) and severe lens phenotype compared to the MLR-10/Rac1 cKO (E15.5) mice. While the Le-Cre/Rac1 cKO lenses displayed delayed primary fiber cell elongation, lenses from both Rac1 cKO strains were characterized by abnormal shape, impaired secondary fiber cell migration, sutural defects and thinning of the posterior capsule which often led to rupture. Lens fiber cell N-cadherin/β-catenin/Rap1/Nectin-based cell-cell junction formation and WAVE-2/Abi-2/Nap1-regulated actin polymerization were impaired in the Rac1 deficient mice. Additionally, the Rac1 cKO lenses were characterized by a shortened epithelial sheet, reduced levels of extracellular matrix (ECM) proteins and increased apoptosis. Taken together, these data uncover the essential role of Rac1 GTPase activity in establishment and maintenance of lens shape, suture formation and capsule integrity, and in fiber cell migration, adhesion and survival, via regulation of actin cytoskeletal dynamics, cell adhesive interactions and ECM turnover.

  5. Magnetically Responsive Bone Marrow Mesenchymal Stem Cell-Derived Smooth Muscle Cells Maintain Their Benefits to Augmenting Elastic Matrix Neoassembly.

    PubMed

    Swaminathan, Ganesh; Sivaraman, Balakrishnan; Moore, Lee; Zborowski, Maciej; Ramamurthi, Anand

    2016-04-01

    Abdominal aortic aneurysms (AAA) represent abnormal aortal expansions that result from chronic proteolytic breakdown of elastin and collagen fibers by matrix metalloproteases. Poor elastogenesis by adult vascular smooth muscle cells (SMCs) limits regenerative repair of elastic fibers, critical for AAA growth arrest. Toward overcoming these limitations, we recently demonstrated significant elastogenesis by bone marrow mesenchymal stem cell-derived SMCs (BM-SMCs) and their proelastogenesis and antiproteolytic effects on rat aneurysmal SMCs (EaRASMCs). We currently investigate the effects of super paramagnetic iron oxide nanoparticle (SPION) labeling of BM-SMCs, necessary to magnetically guide them to the AAA wall, on their functional benefits. Our results indicate that SPION-labeling is noncytotoxic and does not adversely impact the phenotype and elastogenesis by BM-SMCs. In addition, SPION-BM-SMCs showed no changes in the ability of the BM-SMCs to stimulate elastin regeneration and attenuate proteolytic activity by EaRASMCs. Together, our results are promising toward the utility of SPIONs for magnetic targeting of BM-SMCs for in situ AAA regenerative repair.

  6. Fiber Techniques

    ERIC Educational Resources Information Center

    Nalle, Leona

    1976-01-01

    Describes a course in fiber techniques, which covers design methods involving fibers and fabric, that students in the Art Department at Sleeping Giant Junior High School had the opportunity to learn. (Author/RK)

  7. Linear Elastic Waves

    NASA Astrophysics Data System (ADS)

    Revenough, Justin

    Elastic waves propagating in simple media manifest a surprisingly rich collection of phenomena. Although some can't withstand the complexities of Earth's structure, the majority only grow more interesting and more important as remote sensing probes for seismologists studying the planet's interior. To fully mine the information carried to the surface by seismic waves, seismologists must produce accurate models of the waves. Great strides have been made in this regard. Problems that were entirely intractable a decade ago are now routinely solved on inexpensive workstations. The mathematical representations of waves coded into algorithms have grown vastly more sophisticated and are troubled by many fewer approximations, enforced symmetries, and limitations. They are far from straightforward, and seismologists using them need a firm grasp on wave propagation in simple media. Linear Elastic Waves, by applied mathematician John G. Harris, responds to this need.

  8. Series elastic actuators

    NASA Astrophysics Data System (ADS)

    Williamson, Matthew M.

    1995-01-01

    This thesis presents the design, construction, control and evaluation of a novel for controlled actuator. Traditional force controlled actuators are designed from the premise that 'Stiffer is better'. This approach gives a high bandwidth system, prone to problems of contact instability, noise, and low power density. The actuator presented in this thesis is designed from the premise that 'Stiffness isn't everything'. The actuator, which incorporates a series elastic element, trades off achievable bandwidth for gains in stable, low noise force control, and protection against shock loads. This thesis reviews related work in robot force control, presents theoretical descriptions of the control and expected performance from a series elastic actuator, and describes the design of a test actuator constructed to gather performance data. Finally the performance of the system is evaluated by comparing the performance data to theoretical predictions.

  9. Elastic plate spallation

    NASA Technical Reports Server (NTRS)

    Oline, L.; Medaglia, J.

    1972-01-01

    The dynamic finite element method was used to investigate elastic stress waves in a plate. Strain displacement and stress strain relations are discussed along with the stiffness and mass matrix. The results of studying point load, and distributed load over small, intermediate, and large radii are reported. The derivation of finite element matrices, and the derivation of lumped and consistent matrices for one dimensional problems with Laplace transfer solutions are included. The computer program JMMSPALL is also included.

  10. Skeletal abnormalities in homocystinuria.

    PubMed Central

    Brenton, D. P.

    1977-01-01

    The skeletal changes of thirty-four patients with the biochemical and clinical features of cystathionine synthase deficiency are described. It is emphasized that there is clinical evidence of excessive bone growth and the formation for bone which is structurally weaker than normal. The similarities and differences between this condition and Marfan's syndrome are stressed and the possible nature of the connective tissue defect leading to the skeletal changes discussed. The most characteristic skeletal changes in homocystinuria are the skeletal disproportion (pubis-heel length greater than crown-pubis length), the abnormal vertebrae, sternal deformities, genu valgum and large metaphyses and epiphyses. Images Fig. 2 Fig. 3 Fig. 4 Fig. 8 Fig. 9 Fig. 10 PMID:917963

  11. Eye movement abnormalities.

    PubMed

    Moncayo, Jorge; Bogousslavsky, Julien

    2012-01-01

    Generation and control of eye movements requires the participation of the cortex, basal ganglia, cerebellum and brainstem. The signals of this complex neural network finally converge on the ocular motoneurons of the brainstem. Infarct or hemorrhage at any level of the oculomotor system (though more frequent in the brain-stem) may give rise to a broad spectrum of eye movement abnormalities (EMAs). Consequently, neurologists and particularly stroke neurologists are routinely confronted with EMAs, some of which may be overlooked in the acute stroke setting and others that, when recognized, may have a high localizing value. The most complex EMAs are due to midbrain stroke. Horizontal gaze disorders, some of them manifesting unusual patterns, may occur in pontine stroke. Distinct varieties of nystagmus occur in cerebellar and medullary stroke. This review summarizes the most representative EMAs from the supratentorial level to the brainstem.

  12. Dietary Fiber

    MedlinePlus

    Fiber is a substance in plants. Dietary fiber is the kind you eat. It's a type of carbohydrate. You may also see it listed on a food label as soluble ... types have important health benefits. Good sources of dietary fiber include Whole grains Nuts and seeds Fruit and ...

  13. Effect of diameter of glass fibers on flexural properties of fiber-reinforced composites.

    PubMed

    Obukuro, Motofumi; Takahashi, Yutaka; Shimizu, Hiroshi

    2008-07-01

    This study investigated the effect of the diameter of glass fibers on the flexural properties of fiber-reinforced composites. Bar-shaped test specimens of highly filled fiber-reinforced composites (FRCs) and FRC of 30 vol% fiber content were made from a light-cured dimethacrylate monomer liquid (mixture of urethane dimethacrylate and triethylene glycol dimethacrylate) with silanized E-glass fibers (7, 10, 13, 16, 20, 25, 30, and 45 microm in diameter). Flexural strength and elastic modulus were measured. The flexural strength of the highly filled FRCs increased with increasing fiber diameter. In particular, the strengths of highly filled FRCs with 20-, 25-, 30-, and 45-microm-diameter fibers was significantly higher than the others (p<0.05). The flexural strength of FRC of 30 vol% fiber content increased with increasing fiber diameter, except for the FRC with 45-microm-diameter fibers; FRCs with 20-, 25-, and 30-microm-diameter fibers were significantly stronger than the others (p<0.05). Therefore, it was revealed that the diameter of glass fibers significantly affected the flexural properties of fiber-reinforced composites.

  14. Body forces and pressures in elastic models of the myocardium.

    PubMed Central

    Pierce, W H

    1981-01-01

    Tension strands are introduced to represent active myocardial fibers. They create one body force proportional to the divergence of the tension-direction vector, and a second equal to the tension divided by the radius of curvature. Explicit solutions to isotropic linearly elastic tensor equations with these body forces are found for the radially-symmetric, linearly-isotropic, elastic spherical heart with arbitrary radial body force. They confirm experiments showing supraluminal intramural pressures. Such pressures may affect coronary perfusion. A tension strand model which is a reasonable compromise between actual myofibrillar geometry and analytical simplicity is the iso-oblique, terminating, nonintersecting model. The body force from that or any other axially symmetric body force can be the forcing term for equations in which the heart is modeled as a thin, ellipsoidal, elastic membrane. PMID:7213931

  15. Probabilistic elastography: estimating lung elasticity.

    PubMed

    Risholm, Petter; Ross, James; Washko, George R; Wells, William M

    2011-01-01

    We formulate registration-based elastography in a probabilistic framework and apply it to study lung elasticity in the presence of emphysematous and fibrotic tissue. The elasticity calculations are based on a Finite Element discretization of a linear elastic biomechanical model. We marginalize over the boundary conditions (deformation) of the biomechanical model to determine the posterior distribution over elasticity parameters. Image similarity is included in the likelihood, an elastic prior is included to constrain the boundary conditions, while a Markov model is used to spatially smooth the inhomogeneous elasticity. We use a Markov Chain Monte Carlo (MCMC) technique to characterize the posterior distribution over elasticity from which we extract the most probable elasticity as well as the uncertainty of this estimate. Even though registration-based lung elastography with inhomogeneous elasticity is challenging due the problem's highly underdetermined nature and the sparse image information available in lung CT, we show promising preliminary results on estimating lung elasticity contrast in the presence of emphysematous and fibrotic tissue.

  16. Development of a continuous spinning process for producing silicon carbide - silicon nitride precursor fibers

    NASA Technical Reports Server (NTRS)

    1985-01-01

    An apparatus was designed for the continuous production of silicon carbide - silicon nitride precursor fibers. The precursor polymer can be fiberized, crosslined and pyrolyzed. The product is a metallic black fiber with the composition of the type C sub x Si sub y n sub z. Little, other than the tensile strength and modulus of elasticity, is known of the physical properties.

  17. Mechanics of soft composites of rods in elastic gels

    NASA Astrophysics Data System (ADS)

    Das, Moumita; Mackintosh, F. C.

    2011-12-01

    We report detailed theoretical investigations of the micromechanics and bulk elastic properties of composites consisting of randomly distributed stiff fibers embedded in an elastic matrix in two and three dimensions. Recent experiments [V. Pelletier, N. Gal, P. Fournier, and M. L. Kilfoil, Phys. Rev. Lett.PRLTAO0031-900710.1103/PhysRevLett.102.188303 102, 188303 (2009)] have suggested that the inclusion of stiff microtubules in a softer, nearly incompressible biopolymer matrix can lead to emergent compressibility. This can be understood in terms of the enhancement of the compressibility of the composite relative to its shear compliance as a result of the addition of stiff rodlike inclusions. We show that the Poisson's ratio ν of such a composite evolves with increasing rod density toward a particular value, or fixed point, independent of the material properties of the matrix, as long as it has a finite initial compressibility. This fixed point is ν=1/4 in three dimensions and ν=1/3 in two dimensions. Our results suggest an important role for stiff filaments such as microtubules and stress fibers in cell mechanics. At the same time, our work has a wider elasticity context, with potential applications to composite elastic media with a wide separation of scales in stiffness of its constituents such as carbon nanotube-polymer composites, which have been shown to have highly tunable mechanics.

  18. Carbon Fiber Reinforced Glass Matrix Composites for Satellite Applications

    DTIC Science & Technology

    1992-06-01

    graphite basal planes. On the other hand, a high elastic modulus fiber derived from a mesophase pitch precursor, such as P-100, has a radial...and B. V. Perov. Elsevier Science Publishers B. V., Amsterdam, 1985. 2. B. Rand, "Carbon Fibres from Mesophase Pitch " pp. 495-575 in ibid.. 3. W. K...HMU fiber and the other reinforced with pitch -based fiber (P- 100 or FT700), will be described and compared with respect to various features of the

  19. Microstructural design of fiber composites

    NASA Astrophysics Data System (ADS)

    Chou, Tsu-Wei

    The optimum performance design of composite microstructures is discussed. The forces driving progress in fiber composites are examined, and recent developments in the mechanics of laminated composites are surveyed, emphasizing thick laminates, hygrothermal effects, and thermal transient effects. The strength of continuous-fiber composites is discussed, presenting analyses of local load redistribution due to fiber breakages and treatments of statistical tensile strength theories. Modes of failure of laminated composites are examined. Elastic, physical, and viscoelastic properties as well as the strength and fracture behavior of short-fiber composites are studied, and it is shown how the performance of composites can be controlled by selecting material systems and their geometric distributions. 2D textile structural composites based on woven, knitted, and braided preforms are considered, and techniques for analyzing and modeling the thermomechanical behavior of 2D textile composites are presented. Recent developments in the processing of 3D textile preforms are introduced and the processing-microstructure relationship is demonstrated. Finite elastic deformation of flexible composites is addressed.

  20. Buckling conditions for a dual-coated optical fiber

    NASA Astrophysics Data System (ADS)

    Suhir, Ephraim

    2013-03-01

    The elastic stability (buckling) condition for a short dual-coated optical-fiber experiencing mechanical and/or thermally induced compression is established based on the developed analytical (mathematical) predictive model. The problem is reduced to a situation when a cantilever beam of finite length is supported by a continuous elastic foundation and is subjected to a compressive force applied to the beam's free end. Easy-to-use practical guidelines and a simple diagram are suggested for choosing the adequate length of the fiber and/or its flexural rigidity and/or the characteristics of the coating materials, so that the fiber remains elastically stable. The developed model can be used also in the design and reliability evaluations of composites, including nano-composites, and in flexible (large area) photonics when high-modulus and lowexpansion fibers are embedded into a high-modulus-and-low-expansion matrix and experience axial compression at low temperature conditions.

  1. Design guidance for elastic followup

    SciTech Connect

    Naugle, F.V.

    1983-01-01

    The basic mechanism of elastic followup is discussed in relation to piping design. It is shown how mechanistic insight gained from solutions for a two-bar problem can be used to identify dominant design parameters and to determine appropriate modifications where elastic followup is a potential problem. It is generally recognized that quantitative criteria are needed for elastic followup in the creep range where badly unbalanced lines can pose potential problems. Approaches for criteria development are discussed.

  2. Theory of epithelial elasticity

    NASA Astrophysics Data System (ADS)

    Krajnc, Matej; Ziherl, Primož

    2015-11-01

    We propose an elastic theory of epithelial monolayers based on a two-dimensional discrete model of dropletlike cells characterized by differential surface tensions of their apical, basal, and lateral sides. We show that the effective tissue bending modulus depends on the apicobasal differential tension and changes sign at the transition from the flat to the fold morphology. We discuss three mechanisms that stabilize the finite-wavelength fold structures: Physical constraint on cell geometry, hard-core interaction between non-neighboring cells, and bending elasticity of the basement membrane. We show that the thickness of the monolayer changes along the waveform and thus needs to be considered as a variable rather than a parameter. Next we show that the coupling between the curvature and the thickness is governed by the apicobasal polarity and that the amplitude of thickness modulation along the waveform is proportional to the apicobasal differential tension. This suggests that intracellular stresses can be measured indirectly by observing easily measurable morphometric parameters. We also study the mechanics of three-dimensional structures with cylindrical symmetry.

  3. Elastic emission polishing

    SciTech Connect

    Loewenthal, M.; Loseke, K.; Dow, T.A.; Scattergood, R.O.

    1988-12-01

    Elastic emission polishing, also called elastic emission machining (EEM), is a process where a stream of abrasive slurry is used to remove material from a substrate and produce damage free surfaces with controlled surface form. It is a noncontacting method utilizing a thick elasto-hydrodynamic film formed between a soft rotating ball and the workpiece to control the flow of the abrasive. An apparatus was built in the Center, which consists of a stationary spindle, a two-axis table for the workpiece, and a pump to circulate the working fluid. The process is controlled by a programmable computer numerical controller (CNC), which presently can operate the spindle speed and movement of the workpiece in one axis only. This apparatus has been used to determine material removal rates on different material samples as a function of time, utilizing zirconium oxide (ZrO{sub 2}) particles suspended in distilled water as the working fluid. By continuing a study of removal rates the process should become predictable, and thus create a new, effective, yet simple tool for ultra-precision mechanical machining of surfaces.

  4. Mutation of the myosin converter domain alters cross-bridge elasticity.

    PubMed

    Köhler, Jan; Winkler, Gerhard; Schulte, Imke; Scholz, Tim; McKenna, William; Brenner, Bernhard; Kraft, Theresia

    2002-03-19

    Elastic distortion of a structural element of the actomyosin complex is fundamental to the ability of myosin to generate motile forces. An elastic element allows strain to develop within the actomyosin complex (cross-bridge) before movement. Relief of this strain then drives filament sliding, or more generally, movement of a cargo. Even with the known crystal structure of the myosin head, however, the structural element of the actomyosin complex in which elastic distortion occurs remained unclear. To assign functional relevance to various structural elements of the myosin head, e.g., to identify the elastic element within the cross-bridge, we studied mechanical properties of muscle fibers from patients with familial hypertrophic cardiomyopathy with point mutations in the head domain of the beta-myosin heavy chain. We found that the Arg-719 --> Trp (Arg719Trp) mutation, which is located in the converter domain of the myosin head fragment, causes an increase in force generation and fiber stiffness under isometric conditions by 48-59%. Under rigor and relaxing conditions, fiber stiffness was 45-47% higher than in control fibers. Yet, kinetics of active cross-bridge cycling were unchanged. These findings, especially the increase in fiber stiffness under rigor conditions, indicate that cross-bridges with the Arg719Trp mutation are more resistant to elastic distortion. The data presented here strongly suggest that the converter domain that forms the junction between the catalytic and the light-chain-binding domain of the myosin head is not only essential for elastic distortion of the cross-bridge, but that the main elastic distortion may even occur within the converter domain itself.

  5. Abnormal pressure in hydrocarbon environments

    USGS Publications Warehouse

    Law, B.E.; Spencer, C.W.

    1998-01-01

    Abnormal pressures, pressures above or below hydrostatic pressures, occur on all continents in a wide range of geological conditions. According to a survey of published literature on abnormal pressures, compaction disequilibrium and hydrocarbon generation are the two most commonly cited causes of abnormally high pressure in petroleum provinces. In young (Tertiary) deltaic sequences, compaction disequilibrium is the dominant cause of abnormal pressure. In older (pre-Tertiary) lithified rocks, hydrocarbon generation, aquathermal expansion, and tectonics are most often cited as the causes of abnormal pressure. The association of abnormal pressures with hydrocarbon accumulations is statistically significant. Within abnormally pressured reservoirs, empirical evidence indicates that the bulk of economically recoverable oil and gas occurs in reservoirs with pressure gradients less than 0.75 psi/ft (17.4 kPa/m) and there is very little production potential from reservoirs that exceed 0.85 psi/ft (19.6 kPa/m). Abnormally pressured rocks are also commonly associated with unconventional gas accumulations where the pressuring phase is gas of either a thermal or microbial origin. In underpressured, thermally mature rocks, the affected reservoirs have most often experienced a significant cooling history and probably evolved from an originally overpressured system.

  6. Systemic abnormalities in liver disease

    PubMed Central

    Minemura, Masami; Tajiri, Kazuto; Shimizu, Yukihiro

    2009-01-01

    Systemic abnormalities often occur in patients with liver disease. In particular, cardiopulmonary or renal diseases accompanied by advanced liver disease can be serious and may determine the quality of life and prognosis of patients. Therefore, both hepatologists and non-hepatologists should pay attention to such abnormalities in the management of patients with liver diseases. PMID:19554648

  7. An Investigation of Voice Quality in Individuals with Inherited Elastin Gene Abnormalities

    ERIC Educational Resources Information Center

    Watts, Christopher R.; Awan, Shaheen N.; Marler, Jeffrey A.

    2008-01-01

    The human elastin gene (ELN) is responsible for the generation of elastic fibres in the extracellular matrix of connective tissue throughout the body, including the vocal folds. Individuals with Supravalvular aortic stenosis (SVAS) and Williams syndrome (WS) lack one normal ELN allele due to heterozygous ELN abnormalities, resulting in a…

  8. Elastic instabilities in rubber

    NASA Astrophysics Data System (ADS)

    Gent, Alan

    2009-03-01

    Materials that undergo large elastic deformations can exhibit novel instabilities. Several examples are described: development of an aneurysm on inflating a rubber tube; non-uniform stretching on inflating a spherical balloon; formation of internal cracks in rubber blocks at a critical level of triaxial tension or when supersaturated with a dissolved gas; surface wrinkling of a block at a critical amount of compression; debonding or fracture of constrained films on swelling, and formation of ``knots'' on twisting stretched cylindrical rods. These various deformations are analyzed in terms of a simple strain energy function, using Rivlin's theory of large elastic deformations, and the results are compared with experimental measurements of the onset of unstable states. Such comparisons provide new tests of Rivlin's theory and, at least in principle, critical tests of proposed strain energy functions for rubber. Moreover the onset of highly non-uniform deformations has serious implications for the fatigue life and fracture resistance of rubber components. [4pt] References: [0pt] R. S. Rivlin, Philos. Trans. Roy. Soc. Lond. Ser. A241 (1948) 379--397. [0pt] A. Mallock, Proc. Roy. Soc. Lond. 49 (1890--1891) 458--463. [0pt] M. A. Biot, ``Mechanics of Incremental Deformations'', Wiley, New York, 1965. [0pt] A. N. Gent and P. B. Lindley, Proc. Roy. Soc. Lond. A 249 (1958) 195--205. [0pt] A. N. Gent, W. J. Hung and M. F. Tse, Rubb. Chem. Technol. 74 (2001) 89--99. [0pt] A. N. Gent, Internatl. J. Non-Linear Mech. 40 (2005) 165--175.

  9. The First Law of Elasticity

    ERIC Educational Resources Information Center

    Girill, T. R.

    1972-01-01

    The Boyle-Mariotte gas law was formulated in terms of pneumatic springs," subsumed by Hooke under his own stress-strain relation, and generally regarded as a law of elasticity. The subsequent development of Boyle's principle and elasticity provide thought-provoking test cases for Kuhn's notations of paradigm and puzzle solving in physics.…

  10. Valve designed with elastic seat

    NASA Technical Reports Server (NTRS)

    Mac Glashan, W. F., Jr.

    1965-01-01

    Absolute valve closure is accomplished by a machined valve with an axially annular channel which changes the outlet passage into a thin tubular elastic seat member with a retainer backup ring. The elasticity of the seat provides tight conformity to ball irregularity.

  11. PAGOSA Sample Problem. Elastic Precursor

    SciTech Connect

    Weseloh, Wayne N.; Clancy, Sean Patrick

    2016-02-03

    A PAGOSA simulation of a flyer plate impact which produces an elastic precursor wave is examined. The simulation is compared to an analytic theory for the Mie-Grüneisen equation of state and an elastic-perfectly-plastic strength model.

  12. Chromosomal abnormalities and mental illness.

    PubMed

    MacIntyre, D J; Blackwood, D H R; Porteous, D J; Pickard, B S; Muir, W J

    2003-03-01

    Linkage studies of mental illness have provided suggestive evidence of susceptibility loci over many broad chromosomal regions. Pinpointing causative gene mutations by conventional linkage strategies alone is problematic. The breakpoints of chromosomal abnormalities occurring in patients with mental illness may be more direct pointers to the relevant gene locus. Publications that describe patients where chromosomal abnormalities co-exist with mental illness are reviewed along with supporting evidence that this may amount to an association. Chromosomal abnormalities are considered to be of possible significance if (a) the abnormality is rare and there are independent reports of its coexistence with psychiatric illness, or (b) there is colocalisation of the abnormality with a region of suggestive linkage findings, or (c) there is an apparent cosegregation of the abnormality with psychiatric illness within the individual's family. Breakpoints have been described within many of the loci suggested by linkage studies and these findings support the hypothesis that shared susceptibility factors for schizophrenia and bipolar disorder may exist. If these abnormalities directly disrupt coding regions, then combining molecular genetic breakpoint cloning with bioinformatic sequence analysis may be a method of rapidly identifying candidate genes. Full karyotyping of individuals with psychotic illness especially where this coexists with mild learning disability, dysmorphism or a strong family history of mental disorder is encouraged.

  13. Chromosomal abnormalities in human sperm

    SciTech Connect

    Martin, R.H.

    1985-01-01

    The ability to analyze human sperm chromosome complements after penetration of zona pellucida-free hamster eggs provides the first opportunity to study the frequency and type of chromosomal abnormalities in human gametes. Two large-scale studies have provided information on normal men. We have studied 1,426 sperm complements from 45 normal men and found an abnormality rate of 8.9%. Brandriff et al. (5) found 8.1% abnormal complements in 909 sperm from 4 men. The distribution of numerical and structural abnormalities was markedly dissimilar in the 2 studies. The frequency of aneuploidy was 5% in our sample and only 1.6% in Brandriff's, perhaps reflecting individual variability among donors. The frequency of 24,YY sperm was low: 0/1,426 and 1/909. This suggests that the estimates of nondisjunction based on fluorescent Y body data (1% to 5%) are not accurate. We have also studied men at increased risk of sperm chromosomal abnormalities. The frequency of chromosomally unbalanced sperm in 6 men heterozygous for structural abnormalities varied dramatically: 77% for t11;22, 32% for t6;14, 19% for t5;18, 13% for t14;21, and 0% for inv 3 and 7. We have also studied 13 cancer patients before and after radiotherapy and demonstrated a significant dose-dependent increase of sperm chromosome abnormalities (numerical and structural) 36 months after radiation treatment.

  14. Haematological abnormalities in mitochondrial disorders

    PubMed Central

    Finsterer, Josef; Frank, Marlies

    2015-01-01

    INTRODUCTION This study aimed to assess the kind of haematological abnormalities that are present in patients with mitochondrial disorders (MIDs) and the frequency of their occurrence. METHODS The blood cell counts of a cohort of patients with syndromic and non-syndromic MIDs were retrospectively reviewed. MIDs were classified as ‘definite’, ‘probable’ or ‘possible’ according to clinical presentation, instrumental findings, immunohistological findings on muscle biopsy, biochemical abnormalities of the respiratory chain and/or the results of genetic studies. Patients who had medical conditions other than MID that account for the haematological abnormalities were excluded. RESULTS A total of 46 patients (‘definite’ = 5; ‘probable’ = 9; ‘possible’ = 32) had haematological abnormalities attributable to MIDs. The most frequent haematological abnormality in patients with MIDs was anaemia. 27 patients had anaemia as their sole haematological problem. Anaemia was associated with thrombopenia (n = 4), thrombocytosis (n = 2), leucopenia (n = 2), and eosinophilia (n = 1). Anaemia was hypochromic and normocytic in 27 patients, hypochromic and microcytic in six patients, hyperchromic and macrocytic in two patients, and normochromic and microcytic in one patient. Among the 46 patients with a mitochondrial haematological abnormality, 78.3% had anaemia, 13.0% had thrombopenia, 8.7% had leucopenia and 8.7% had eosinophilia, alone or in combination with other haematological abnormalities. CONCLUSION MID should be considered if a patient’s abnormal blood cell counts (particularly those associated with anaemia, thrombopenia, leucopenia or eosinophilia) cannot be explained by established causes. Abnormal blood cell counts may be the sole manifestation of MID or a collateral feature of a multisystem problem. PMID:26243978

  15. Elasticity of Flowing Soap films

    NASA Astrophysics Data System (ADS)

    Kim, Ildoo; Mandre, Shreyas

    2016-11-01

    The robustness of soap films and bubbles manifests their mechanical stability. The single most important factor underlying the mechanical stability of soap films is its elasticity. Non-destructive measurement of the elasticity in these films has been cumbersome, because of its flowing nature. Here we provide a convenient, reproducible, and non-destructive method for measuring the elasticity by generating and inspecting Marangoni waves. Our method is based on generating an oblique shock by inserting a thin cylindrical obstacle in the flowing film, and converting the measured the shock angle to elasticity. Using this method, we find a constant value for the elasticity of 22 dyne/cm in the commonly used range of film widths, thicknesses or flow rates, implying that the surface of the film is chemically saturated with soap molecules.

  16. Deformation of a flexible fiber in a viscous flow past an obstacle

    NASA Astrophysics Data System (ADS)

    López, H. M.; Hulin, J.-P.; Auradou, H.; D'Angelo, M. V.

    2015-01-01

    We study the deformation and transport of elastic fibers in a viscous Hele-Shaw flow with curved streamlines. The variations of the global velocity and orientation of the fiber follow closely those of the local flow velocity. The ratios of the curvatures of the fibers by the corresponding curvatures of the streamlines reflect a balance between elastic and viscous forces: this ratio is shown experimentally to be determined by a dimensionless Sperm number Sp combining the characteristic parameters of the flow (transverse velocity gradient, viscosity, fiber diameter/cell gap ratio) and those of the fiber (diameter, effective length, Young's modulus). For short fibers, the effective length is that of the fiber; for long ones, it is equal to the transverse characteristic length of the flow. For Sp ≲ 250, the ratio of the curvatures increases linearly with Sp; for Sp ≳ 250, the fiber reaches the same curvature as the streamlines.

  17. Relative sliding durability of candidate high temperature fiber seal materials

    NASA Technical Reports Server (NTRS)

    Dellacorte, Christopher; Steinetz, Bruce M.

    1992-01-01

    The relative sliding durability behavior of six candidate ceramic fibers for high temperature sliding seal applications is reviewed and compared. Pin on disk tests were used to evaluate potential seal materials by sliding a tow or bundle of the candidate ceramic fiber against a superalloy test disk. Tests were conducted in air under a 2.65 N load, at a sliding velocity of 0.025 m/sec and at temperatures from 25 to 900 C. Friction was measured during the tests and fiber wear, indicated by the extent of fibers broken in the tow or bundle, was measured at the end of each test. For most of the fibers, friction and wear increase with test temperature. The relative fiber durability ranking correlates with tensile strength, indicating that tensile data, which is more readily available than sliding durability data, may be useful in predicting fiber wear behavior under various conditions. A dimensional analysis of the wear data shows that the fiber durability is related to a dimensionless durability ratio which represents the ratio of the fiber strength to the fiber stresses imposed by sliding. The analysis is applicable to fibers with similar diameters and elastic moduli. Based upon the results of the research program, three fiber candidates are recommended for further study as potential seal materials. They are a silicon based complex carbide-oxide fiber, an alumina-boria-silica and an aluminosilicate fiber.

  18. Reincarnation in cultured muscle of mitochondrial abnormalities. Two patients with epilepsy and lactic acidosis.

    PubMed

    Askanas, V; Engel, W K; Britton, D E; Adornato, B T; Eiben, R M

    1978-12-01

    Two unrelated 9-year-old boys failed to thrive from ages 5 and 4 years, and had focal cerebral seizures followed by transcent hemipareses. Histochemistry of their muscle biopsies showed "ragged-red" fibers, which ultrastructurally contained clusters of mitochondria having loss of crisp delineation of crista membranes and contained amorphous inclusion material and parallel-packed cristae and sometimes paracrystalline inclusions. In the patients' cultured muscles, similar mitochondrial abnormalities were present. 2,4-Dinitrophenol, introduced to the medium of cultures of normal human muscle, produced mitochondrial abnormalities similar to those of the patients', and the medium of the patients' muscle cultures worsened the mitochondrial abnormalities. This study, in demonstrating a mitochondrial defect reproducible in the cultured muscle fibers and, therefore, intrinsic to the ragged-red muscle fibers themselves, raises the possibility of a collateral mitochondrial defect in CNS cells as part of a multicellular mitochondriopathy.

  19. An analytical solution for the elastoplastic response of a continuous fiber composite under uniaxial loading

    NASA Technical Reports Server (NTRS)

    Lee, Jong-Won; Allen, David H.

    1990-01-01

    A continuous fiber composite is modelled by a two-element composite cylinder in order to predict the elastoplastic response of the composite under a monotonically increasing tensile loading parallel to fibers. The fibers and matrix are assumed to be elastic-perfectly plastic materials obeying Hill's and Tresca's yield criteria, respectively. Here, the composite behavior when the fibers yield prior to the matrix is investigated.

  20. Two Fiber Optical Fiber Thermometry

    NASA Technical Reports Server (NTRS)

    Jones, Mathew R.; Farmer, Jeffery T.; Breeding, Shawn P.

    2000-01-01

    An optical fiber thermometer consists of an optical fiber whose sensing tip is given a metallic coating. The sensing tip of the fiber is essentially an isothermal cavity, so the emission from this cavity will be approximately equal to the emission from a blackbody. Temperature readings are obtained by measuring the spectral radiative heat flux at the end of the fiber at two wavelengths. The ratio of these measurements and Planck's Law are used to infer the temperature at the sensing tip. Optical fiber thermometers have high accuracy, excellent long-term stability and are immune to electromagnetic interference. In addition, they can be operated for extended periods without requiring re-calibration. For these reasons. it is desirable to use optical fiber thermometers in environments such as the International Space Station. However, it has recently been shown that temperature readings are corrupted by emission from the fiber when extended portions of the probe are exposed to elevated temperatures. This paper will describe several ways in which the reading from a second fiber can be used to correct the corrupted temperature measurements. The accuracy and sensitivity to measurement uncertainty will be presented for each method.

  1. Nonlinear elastic effects on the energy flux deviation of ultrasonic waves in gr/ep composites

    NASA Technical Reports Server (NTRS)

    Prosser, William H.; Kriz, R. D.; Fitting, Dale W.

    1992-01-01

    The effects of nonlinear elasticity on energy flux deviation in undirectional gr/ep composites are examined. The shift in the flux deviation is modeled using acoustoelasticity theory and the second- and third-order elastic stiffness coefficients for T300/5208 gr/ep. Two conditions of applied uniaxial stress are considered. In the first case, the direction of applied uniaxial stress was along the fiber axis (x3), while in the second case it was perpendicular to the fiber axis along the laminate stacking direction (x1). For both conditions, the change in the energy flux deviation angle from the condition of zero applied stress is computed over the range of propagation directions of 0 to 60 deg from the fiber axis at two-degree intervals. A positive flux deviation angle implies the energy deviates away from the fiber direction toward the x1 axis, while a negative deviation means that the energy deviates toward the fibers. Over this range of fiber orientation angles, the energy of the quasi-longitudinal and pure mode transverse waves deviates toward the fibers, while that of the quasi-transverse mode deviates away from the fibers.

  2. Congenital abnormalities and selective abortion.

    PubMed

    Seller, M J

    1976-09-01

    The technique of amniocentesis, by which an abnormal fetus can be detected in utero, has brought a technological advance in medical science but attendant medical and moral problems. Dr Seller describes those congenital disabilities which can be detected in the fetus before birth, for which the "remedy" is selective abortion. She then discusses the arguments for and against selective abortion, for the issue is not simple, even in the strictly genetic sense of attempting to ensure a population free of congenital abnormality.

  3. Flow of a flexible fiber past an obstacle

    NASA Astrophysics Data System (ADS)

    Lopez, Hector; Hulin, Jean Pierre; Auradou, Harold; D'Angelo, Veronica

    2014-11-01

    The transport of flexible biological or man made fibers by a flow is of interest in view of their potential applications in many different industrial fields. Here we study the deformation and transport of elastic fibers in a viscous Hele-Shaw flow with curved streamlines. The variations of the global velocity and orientation of the fiber follow closely those of the local flow velocity. The ratios of the curvatures of the fibers by the corresponding curvatures of the streamlines reflect a balance between elastic and viscous forces: this ratio is shown experimentally to be determined by a dimensionless Sperm number (Sp) combining the characteristic parameters of the flow (transverse velocity gradient, viscosity, fiber diameter/cell gap ratio) and those of the fiber (diameter, effective length, Young's modulus). The effective length is either the fiber length (short fiber case) or the characteristic size of the obstacle (long fiber case). For low values of Sp the ratio of the curvatures increases linearly with Sp. For values higher than 250, the fiber and the streamlines have the same curvature.

  4. Stromal fibers in oral squamous cell carcinoma: A possible new prognostic indicator?

    PubMed Central

    Kardam, Priyanka; Mehendiratta, Monica; Rehani, Shweta; Kumra, Madhumani; Sahay, Khushboo; Jain, Kanu

    2016-01-01

    Background: Many studies have been carried out to study the role of extracellular matrix proteins, growth factors and matrix metalloproteinases on tumor invasion. However, literature related to the analysis of connective tissue fibers in varying grades of oral squamous cell carcinoma (OSCC) is very limited. Aim: To analyze the changes in collagen and elastic fibers in varying grades of (OSCC). Settings and Design: This retrospective study was carried out using a light and polarizing microscope. Materials and Methods: Three sections each were cut from fifty samples of varying grades of OSCC and ten samples of control followed by staining with H and E, Picrosirius-Red and Verhoeff–Van Gieson. Qualitative and quantitative analysis of collagen and elastic fibers were accomplished using set criteria. Statistical Analysis: Data were entered into the Statistical Package for Social Sciences (SPSS) version 13.5 for analysis. Results: A change in colors of collagen fibers was seen on progressing from well to poorly differentiated OSCC. Thin collagen fibers predominantly exhibited greenish yellow, but the thick fibers exhibited a variety of colors. As the grade of OSCC progressed, collagen fibers were loosely packed haphazardly arranged. Statistically insignificant results were obtained for quantitative analysis of collagen and qualitative analysis of elastic fibers. Conclusion: The collagen fibers undergo a change in color, orientation and packing in the stroma of varying grades of OSCC. The uniqueness of this study lies in the exploration of elastic fibers in OSCC which has not been done so far. PMID:27721605

  5. Ductility of nonmetallic hybrid fiber composite reinforcement for concrete

    NASA Astrophysics Data System (ADS)

    Tepfers, R.; Tamužs, V.; Apinis, R.; Vilks, U.; Modniks, J.

    1996-03-01

    Reinforcing units, FRP, of unidirectional fiber composites for concrete have elastic behavior up to tensile failure. For safety reasons an elongation of 3% at maximum load is usually required for the reinforcement. Ductile behavior with the necessary elongation and stress hardening could be obtained with braided fiber strands around a core of foam plastic, thin glass fiber cylindrical shell, or unidirectional carbon fibers. Braids around a porous core reveal the ductility when epoxy resin breaks up and collapse of core enables the braids to rotate. The same seems to happen at that cross section, where carbon fiber core breaks in tension. The best result is obtained using a cylindrical glass fiber reinforced core shell surrounded with aramid fiber braid.

  6. [Diagnosticum of abnormalities of plant meiotic division].

    PubMed

    Shamina, N V

    2006-01-01

    Abnormalities of plant meiotic division leading to abnormal meiotic products are summarized schematically in the paper. Causes of formation of monads, abnormal diads, triads, pentads, polyads, etc. have been observed in meiosis with both successive and simultaneous cytokinesis.

  7. Elastic properties of hybrid composites by the effective field approach

    NASA Astrophysics Data System (ADS)

    Kanaun, S. K.; Jeulin, D.

    2001-10-01

    The work is dedicated to the calculation of the overall elastic properties of matrix composite materials containing two different populations of inclusions (three phase hybrid composites). The application of the well known Mori-Tanaka method or self-consistent effective medium method to the solution of this problem gives overall elastic moduli tensors of such composites that do not have the necessary symmetry (the symmetry with respect to the first and second pairs of indices). In this work, a new version of the effective field method that takes into account specific features of the microstructure of three phase composites is developed. In this version, the field that acts on every inclusion in the composite is assumed to be different for inclusions of different populations. It is shown that the modified effective field method gives a correct symmetry of the overall elastic moduli tensors of three phase composites. The method allows us to describe the influence of the peculiarities in spatial distributions of inclusions on the overall elastic constants. The cases of media containing infinite cylindrical fibers and thin ellipsoidal disks or spherical pores are considered. Various boolean type probabilistic models of random sets of such inclusions are proposed and the elastic moduli tensors of the corresponding three phase composites are obtained and analyzed. It turns out that these tensors strongly depend on statistical properties of the random fields of inclusions. It is shown that for two phase composites, the Mori-Tanaka method is a particular case of the effective field method. In the case of three phase composites, the formulas of the Mori-Tanaka method follow from the equations of the effective field method if a general property of the symmetry of cross-correlation functions of different populations of inclusions is violated. As a result, the overall elastic moduli tensors obtained by Mori-Tanaka method lose their natural symmetry.

  8. Fireblocking Fibers

    NASA Technical Reports Server (NTRS)

    1986-01-01

    PBI was originally developed for space suits. In 1980, the need for an alternative to asbestos and stricter government anti-pollution standards led to commercialization of the fire blocking fiber. PBI is used for auto racing driver suits and aircraft seat covers. The fiber does not burn in air, is durable and easily maintained. It has been specified by a number of airliners and is manufactured by Hoechst-Celanese Corporation.

  9. Dietary fiber.

    PubMed

    Madar, Z; Thorne, R

    1987-01-01

    Studies done on dietary fiber (DF) over the past five years are presented in this Review. The involvement of dietary fiber in the control of plasma glucose and lipid levels is now established. Two dietary fiber sources (soybean and fenugreek) were studied in our laboratory and are discussed herein. These sources were found to be potentially beneficial in the reduction of plasma glucose in non-insulin dependent diabetes mellitus subjects. They are shown to be acceptable by human subjects and are easy to use either in a mixture of milk products and in cooking. The mechanism by which dietary fiber alters the nutrient absorption is also discussed. The effect of DF on gastric emptying, transit time, adsorption and glucose transport may contribute to reducing plasma glucose and lipid levels. DF was found to be effective in controlling blood glucose and lipid levels of pregnant diabetic women. Dietary fiber may also be potentially beneficial in the reduction of exogenous insulin requirements in these subjects. However, increased consumption of DF may cause adverse side effects; the binding capabilities of fiber may affect nutrient availability, particularly that of minerals and prolonged and high DF dosage supplementation must be regarded cautiously. This is particularly true when recommending such a diet for pregnant or lactating women, children or subjects with nutritional disorders. Physiological effects of DF appear to depend heavily on the source and composition of fiber. Using a combination of DF from a variety of sources may reduce the actual mass of fiber required to obtain the desired metabolic effects and will result in a more palatable diet. Previously observed problems, such as excess flatus, diarrhea and mineral malabsorption would also be minimized.

  10. Nanocomposite Fibers

    DTIC Science & Technology

    2003-01-01

    attempts to prepare carbon nanotube , CNT, containing fiber material. Modulus and tenacity tests on experimentally prepared nanosilica filled PET...individual entities of nanofibers, such as carbon nanotubes and SiC whiskers, silica and clay, into polymers with the goal of producing new forms of...if carbon nanotube (CNT) particle implanted fibers are used, one would expect a great increase in the electrical conductivity of the so-reinforced

  11. Elastic protectors for ultrasound injection

    SciTech Connect

    Barkhatov, V.A.; Nesterova, L.A.

    1995-07-01

    A new material has been developed for elastic protectors on ultrasonic probes: sonar rubber. This combines low ultrasonic absorption, high strength, and wear resistance, and so the rubber can be used in sensor designs.

  12. Measuring How Elastic Arteries Function.

    ERIC Educational Resources Information Center

    DeMont, M. Edwin; MacGillivray, Patrick S.; Davison, Ian G.; McConnell, Colin J.

    1997-01-01

    Describes a procedure used to measure force and pressure in elastic arteries. Discusses the physics of the procedure and recommends the use of bovine arteries. Explains the preparation of the arteries for the procedure. (DDR)

  13. Elasticity of crystalline molecular explosives

    DOE PAGES

    Hooks, Daniel E.; Ramos, Kyle J.; Bolme, C. A.; ...

    2015-04-14

    Crystalline molecular explosives are key components of engineered explosive formulations. In precision applications a high degree of consistency and predictability is desired under a range of conditions to a variety of stimuli. Prediction of behaviors from mechanical response and failure to detonation initiation and detonation performance of the material is linked to accurate knowledge of the material structure and first stage of deformation: elasticity. The elastic response of pentaerythritol tetranitrate (PETN), cyclotrimethylene trinitramine (RDX), and cyclotetramethylene tetranitramine (HMX), including aspects of material and measurement variability, and computational methods are described in detail. Experimental determinations of elastic tensors are compared, andmore » an evaluation of sources of error is presented. Furthermore, computed elastic constants are also compared for these materials and for triaminotrinitrobenzene (TATB), for which there are no measurements.« less

  14. Elasticity of crystalline molecular explosives

    SciTech Connect

    Hooks, Daniel E.; Ramos, Kyle J.; Bolme, C. A.; Cawkwell, Marc J.

    2015-04-14

    Crystalline molecular explosives are key components of engineered explosive formulations. In precision applications a high degree of consistency and predictability is desired under a range of conditions to a variety of stimuli. Prediction of behaviors from mechanical response and failure to detonation initiation and detonation performance of the material is linked to accurate knowledge of the material structure and first stage of deformation: elasticity. The elastic response of pentaerythritol tetranitrate (PETN), cyclotrimethylene trinitramine (RDX), and cyclotetramethylene tetranitramine (HMX), including aspects of material and measurement variability, and computational methods are described in detail. Experimental determinations of elastic tensors are compared, and an evaluation of sources of error is presented. Furthermore, computed elastic constants are also compared for these materials and for triaminotrinitrobenzene (TATB), for which there are no measurements.

  15. Elastic waves in quasiperiodic structures

    NASA Astrophysics Data System (ADS)

    Velasco, V. R.; Zárate, J. E.

    2001-08-01

    We study the transverse and sagittal elastic waves in different quasiperiodic structures by means of the full transfer-matrix technique and surface Green-function matching method. The quasiperiodic structures follow Fibonacci, Thue-Morse and Rudin-Shapiro sequences, respectively. We consider finite structures having stress-free bounding surfaces and different generation orders, including up to more than 1000 interfaces. We obtain the dispersion relations for elastic waves and spatial localization of the different modes. The fragmentation of the spectrum for different sequences is evident for intermediate generation orders, in the case of transverse elastic waves, whereas, for sagittal elastic waves, higher generation orders are needed to show clearly the spectrum fragmentation. The results of Fibonacci and Thue-Morse sequences exhibit similarities not present in the results of Rudin-Shapiro sequences.

  16. Hilbert complexes of nonlinear elasticity

    NASA Astrophysics Data System (ADS)

    Angoshtari, Arzhang; Yavari, Arash

    2016-12-01

    We introduce some Hilbert complexes involving second-order tensors on flat compact manifolds with boundary that describe the kinematics and the kinetics of motion in nonlinear elasticity. We then use the general framework of Hilbert complexes to write Hodge-type and Helmholtz-type orthogonal decompositions for second-order tensors. As some applications of these decompositions in nonlinear elasticity, we study the strain compatibility equations of linear and nonlinear elasticity in the presence of Dirichlet boundary conditions and the existence of stress functions on non-contractible bodies. As an application of these Hilbert complexes in computational mechanics, we briefly discuss the derivation of a new class of mixed finite element methods for nonlinear elasticity.

  17. Tensile strain measurements of ceramic fibers using scanning laser acoustic microscopy

    NASA Astrophysics Data System (ADS)

    Kent, Renee M.; Vary, Alex

    1992-08-01

    A noncontacting technique using scanning laser acoustic microscopy for making in situ tensile strain measurements of small diameter fibers was implemented for the tensile strain analysis of individual Nicalon SiC fibers (nominal diameter 15 microns). Stress vs strain curves for the fibers were plotted from the experimental data. The mean elastic modulus of the fibers was determined to be 185.3 GPa. Similar measurements were made for Carborundum SiC fibers (nominal diameter 28 microns) and Saphikon sapphire fibers (nominal diameter 140 microns).

  18. Comparison of methods for predicting fiber stresses in a cracked Kevlar/epoxy monolayer

    SciTech Connect

    Reedy, E.D. Jr.

    1984-01-01

    Shear-lag and 3-D finite element predictions for the fiber stresses in a cracked Kevlar 49/epoxy monolayer are compared. Results are given for a 5-fiber wide monolayer containing a single broken fiber. Both methods of analysis are found to predict nearly the same fiber stress distribution along the crack-tip fiber when the monolayer is fully elastic. Results for highly loaded monolayers with extensive matrix yielding are not in quite as good agreement, but even then the predicted stress distributions are within 5%. These calculations show that a shear-lag analysis is accurate even though the Kevlar 49 fiber is highly anisotropic.

  19. Elastic Properties of Mantle Minerals

    NASA Astrophysics Data System (ADS)

    Duffy, T. S.; Stan, C. V.

    2012-12-01

    The most direct information about the interior structure of the Earth comes from seismic wave velocities. Interpretation of seismic data requires an understanding of how sound velocities and elastic properties of minerals vary with pressure, temperature, crystal structure, and composition as well as the role of anelasticity, melts, etc. More generally, elastic moduli are important for understanding many solid-state phenomena including mechanical stability, interatomic interactions, material strength, compressibility, and phase transition mechanisms. The database of mineral elasticity measurements has been growing rapidly in recent years. In this work, we report initial results of an ongoing survey of our current knowledge of mineral elasticity at both ambient conditions and high pressures and temperatures. The analysis is selective, emphasizing single crystal measurements but also incorporating polycrystalline measurements and volume compression data as appropriate. The goal is to synthesize our current understanding of mineral elasticity in terms of structure and composition, and to identify the major remaining needs for experimental and theoretical work. Clinopyroxenes (Cpx) provide an example of our approach. A wide range of clinopyroxene compositions are found geologically and Mg-, Ca-, and Na-rich clinopyroxenes are expected to be important components in the upper mantle. The single-crystal elastic properties of a number of endmember Cpx compositions have been measured and these exhibit a range of ~25% in shear velocity. Those with monovalent cations (spodumene, jadeite) in the M2 site exhibit the highest velocities while Fe-rich (hendenbergit, acmite) compositions have the lowest velocities. The effects on velocity due to a wide range of chemical substitutions can be defined, but there are important discrepancies and omissions in the database. New measurements of omphacites, intermediate diopside-hedenbergite compositions, aegerine/acmite, augite, etc. are

  20. Elastic Wave Transmission and Stop Band Characteristics in Unidirectional Composites

    NASA Astrophysics Data System (ADS)

    Nakashima, Kazuhiro; Biwa, Shiro; Matsumoto, Eiji

    Elastic wave transmission characteristics in unidirectional fiber-reinforced composites are studied based on the two-dimensional finite element analysis. The composite is assumed to be a lay-up of a finite number of monolayers, each of which contains a single row of fibers spaced at equal distance. Influences of the stacking number and misalignment of monolayers as well as the presence of coating layer around the fibers on the wave transmission spectra are demonstrated for unidirectional SiC-fiber-reinforced Ti-alloy composites. It is shown that the transmission coefficients fall to low values in certain bands of frequency, i.e., stop bands in terminology analogous to perfectly periodic structures. This feature is found to appear more clearly for the transverse wave incidence, irrespective of the misalignment of monolayers. The stiffness reduction of the coating layer is shown to shift the stop bands to lower frequencies, which can be a useful feature for the monitoring of the fiber/matrix interfacial damage.

  1. Elastic image registration via rigid object motion induced deformation

    NASA Astrophysics Data System (ADS)

    Zheng, Xiaofen; Udupa, Jayaram K.; Hirsch, Bruce E.

    2011-03-01

    In this paper, we estimate the deformations induced on soft tissues by the rigid independent movements of hard objects and create an admixture of rigid and elastic adaptive image registration transformations. By automatically segmenting and independently estimating the movement of rigid objects in 3D images, we can maintain rigidity in bones and hard tissues while appropriately deforming soft tissues. We tested our algorithms on 20 pairs of 3D MRI datasets pertaining to a kinematic study of the flexibility of the ankle complex of normal feet as well as ankles affected by abnormalities in foot architecture and ligament injuries. The results show that elastic image registration via rigid object-induced deformation outperforms purely rigid and purely nonrigid approaches.

  2. Effects of crystal orientation on cellulose nanocrystals-cellulose acetate nanocomposite fibers prepared by dry spinning.

    PubMed

    Chen, Si; Schueneman, Greg; Pipes, R Byron; Youngblood, Jeffrey; Moon, Robert J

    2014-10-13

    This work presents the development of dry spun cellulose acetate (CA) fibers using cellulose nanocrystals (CNCs) as reinforcements. Increasing amounts of CNCs were dispersed into CA fibers in efforts to improve the tensile strength and elastic modulus of the fiber. A systematic characterization of dispersion of CNCs in the polymer fiber and their effect on the nanocomposites' mechanical properties is described. The birefringence, thermal properties, and degree of CNC orientation of the fibers are discussed. 2D X-ray diffraction was used to quantify the degree of CNC alignment within the fibers. It is shown that the CNC alignment directly correlates to the mechanical properties of the composite. Maximum improvements of 137% in tensile strength and 637% in elastic modulus were achieved. Empirical micromechanical models Halpin-Tsai equation and an orientation modified Cox model were used to predict the fiber performance and compared with experimental results.

  3. Abnormal insulin levels and vertigo.

    PubMed

    Proctor, C A

    1981-10-01

    Fifty patients with unexplained vertigo (36) or lightheadedness (14) are evaluated, all of whom had abnormal ENGs and normal audiograms. Five hour insulin glucose tolerance tests were performance on all patients, with insulin levels being obtained fasting and at one-half, one, two, and three hours. The results of this investigation were remarkable. Borderline or abnormal insulin levels were discovered in 82% of patients; 90% were found to have either an abnormal glucose tolerance test or at least borderline insulin levels. The response to treatment in these dizzy patients was also startling, with appropriate low carbohydrate diets improving the patient's symptoms in 90% of cases. It is, therefore, apparent that the earliest identification of carbohydrate imbalance with an insulin glucose tolerance test is extremely important in the work-up of the dizzy patients.

  4. Complex patterns of abnormal heartbeats

    NASA Technical Reports Server (NTRS)

    Schulte-Frohlinde, Verena; Ashkenazy, Yosef; Goldberger, Ary L.; Ivanov, Plamen Ch; Costa, Madalena; Morley-Davies, Adrian; Stanley, H. Eugene; Glass, Leon

    2002-01-01

    Individuals having frequent abnormal heartbeats interspersed with normal heartbeats may be at an increased risk of sudden cardiac death. However, mechanistic understanding of such cardiac arrhythmias is limited. We present a visual and qualitative method to display statistical properties of abnormal heartbeats. We introduce dynamical "heartprints" which reveal characteristic patterns in long clinical records encompassing approximately 10(5) heartbeats and may provide information about underlying mechanisms. We test if these dynamics can be reproduced by model simulations in which abnormal heartbeats are generated (i) randomly, (ii) at a fixed time interval following a preceding normal heartbeat, or (iii) by an independent oscillator that may or may not interact with the normal heartbeat. We compare the results of these three models and test their limitations to comprehensively simulate the statistical features of selected clinical records. This work introduces methods that can be used to test mathematical models of arrhythmogenesis and to develop a new understanding of underlying electrophysiologic mechanisms of cardiac arrhythmia.

  5. Optimization of multilayered composite pressure vessels using exact elasticity solution

    SciTech Connect

    Adali, S.; Verijenko, V.E.; Tabakov, P.Y.; Walker, M.

    1995-11-01

    An approach for the optimal design of thick laminated cylindrical pressure vessels is given. The maximum burst pressure is computed using an exact elasticity solution and subject to the Tsai-Wu failure criterion. The design method is based on an accurate 3-D stress analysis. Exact elasticity solutions are obtained using the stress function approach where the radial, circumferential and shear stresses are determined taking the closed ends of the cylindrical shell into account. Design optimization of multilayered composite pressure vessels are based on the use of robust multidimensional methods which give fast convergence. Two methods are used to determine the optimum ply angles, namely, iterative and gradient methods. Numerical results are given for optimum fiber orientation of each layer for thick and thin-walled multilayered pressure vessels.

  6. Sprayable Elastic Conductors Based on Block Copolymer Silver Nanoparticle Composites

    PubMed Central

    2015-01-01

    Block copolymer silver nanoparticle composite elastic conductors were fabricated through solution blow spinning and subsequent nanoparticle nucleation. The reported technique allows for conformal deposition onto nonplanar substrates. We additionally demonstrated the ability to tune the strain dependence of the electrical properties by adjusting nanoparticle precursor concentration or localized nanoparticle nucleation. The stretchable fiber mats were able to display electrical conductivity values as high as 2000 ± 200 S/cm with only a 12% increase in resistance after 400 cycles of 150% strain. Stretchable elastic conductors with similar and higher bulk conductivity have not achieved comparable stability of electrical properties. These unique electromechanical characteristics are primarily the result of structural changes during mechanical deformation. The versatility of this approach was demonstrated by constructing a stretchable light emitting diode circuit and a strain sensor on planar and nonplanar substrates. PMID:25491507

  7. Ectodermal dysplasia and abnormal thumbs.

    PubMed

    Lucky, A W; Esterly, N B; Tunnessen, W W

    1980-05-01

    Two unrelated children, a girl and a boy, with alopecia, anomalous cutaneous pigmentation, abnormal thumbs, and endocrine disorders, including short stature and delayed bone age in one patient and juvenile onset diabetes mellitus in the other, are described. In one instance, the mother and the maternal grandmother had similar abnormalities, although of a less severe nature. Both children had normal nails and no unusual susceptibility to infections. We believe these two patients represent a previously undescribed syndrome of ectodermal dysplasia that may be inherited as an autosomal-dominant trait.

  8. Physicochemical properties of surimi gels fortified with dietary fiber.

    PubMed

    Debusca, Alicia; Tahergorabi, Reza; Beamer, Sarah K; Matak, Kristen E; Jaczynski, Jacek

    2014-04-01

    Although dietary fiber provides health benefits, most Western populations have insufficient intake. Surimi seafood is not currently fortified with dietary fiber, nor have the effects of fiber fortification on physicochemical properties of surimi been thoroughly studied. In the present study, Alaska pollock surimi was fortified with 0-8 g/100 g of long-chain powdered cellulose as a source of dietary fiber. The protein/water concentrations in surimi were kept constant by adding an inert filler, silicon dioxide in inverse concentrations to the fiber fortification. Fiber-fortified surimi gels were set at 90 °C. The objectives were to determine (1) textural and colour properties; (2) heat-induced gelation (dynamic rheology); and (3) protein endothermic transitions (differential scanning calorimetry) of surimi formulated with constant protein/water, but variable fiber content. Fiber fortification up to 6 g/100 g improved (P<0.05) texture and colour although some decline occurred with 8 g/100g of fiber. Dynamic rheology correlated with texture and showed large increase in gel elasticity, indicating enhanced thermal gelation of surimi. Differential scanning calorimetry showed that fiber fortification did not interfere with thermal transitions of surimi myosin and actin. Long-chain fiber probably traps water physically, which is stabilized by chemical bonding with protein within surimi gel matrix. Based on the present study, it is suggested that the fiber-protein interaction is mediated by water and is physicochemical in nature.

  9. Designing the Structure of Carbon Fibers for Optimal Mechanical Properties

    SciTech Connect

    Ozcan, Soydan; Vautard, Frederic; Naskar, Amit K

    2014-01-01

    Carbon fiber manufacturing follows generic processing steps: formation of thermoplastic fibers, stabilization, and carbonization. The final structures and end properties of the carbon fiber can differ significantly depending on the precursor chemistry and the associated processing sciences. Polyacrylonitrile (PAN) and mesophase pitch are the predominant precursors used in the production of carbon fibers. PAN-based carbon fibers consist of nanocrystalline graphitic domains typically 1.5 5 nm in size surrounded by amorphous carbon; in contrast, pitch-based carbon fibers are 10 50 nm crystallites with the graphitic (002) planes mostly aligned parallel to the fiber axis. It has been seen that the skin core structure of PAN-based carbon fibers plays a significant role in their mechanical properties. Designing a more homogenous carbon fiber microstructure by controlling the starting polymer and process parameters results in a different set of tensile strengths and elastic moduli. In this study the microstructural defect distribution (0.1 200 nm), measured by small-angle X-ray scattering, was shown to be directly related to the tensile strength of the carbon fibers. Here the formation of carbon structures from various polymer precursors is reviewed. Such a comprehensive understanding offers the opportunity to design carbon fiber microstructures with improved properties and to ultimately create new types of carbon fibers from alternative precursors at reduced cost.

  10. Nonlinear Elastic Effects on the Energy Flux Deviation of Ultrasonic Waves in GR/EP Composites

    NASA Technical Reports Server (NTRS)

    Prosser, William H.; Kriz, R. D.; Fitting, Dale W.

    1992-01-01

    In isotropic materials, the direction of the energy flux (energy per unit time per unit area) of an ultrasonic plane wave is always along the same direction as the normal to the wave front. In anisotropic materials, however, this is true only along symmetry directions. Along other directions, the energy flux of the wave deviates from the intended direction of propagation. This phenomenon is known as energy flux deviation and is illustrated. The direction of the energy flux is dependent on the elastic coefficients of the material. This effect has been demonstrated in many anisotropic crystalline materials. In transparent quartz crystals, Schlieren photographs have been obtained which allow visualization of the ultrasonic waves and the energy flux deviation. The energy flux deviation in graphite/epoxy (gr/ep) composite materials can be quite large because of their high anisotropy. The flux deviation angle has been calculated for unidirectional gr/ep composites as a function of both fiber orientation and fiber volume content. Experimental measurements have also been made in unidirectional composites. It has been further demonstrated that changes in composite materials which alter the elastic properties such as moisture absorption by the matrix or fiber degradation, can be detected nondestructively by measurements of the energy flux shift. In this research, the effects of nonlinear elasticity on energy flux deviation in unidirectional gr/ep composites were studied. Because of elastic nonlinearity, the angle of the energy flux deviation was shown to be a function of applied stress. This shift in flux deviation was modeled using acoustoelastic theory and the previously measured second and third order elastic stiffness coefficients for T300/5208 gr/ep. Two conditions of applied uniaxial stress were considered. In the first case, the direction of applied uniaxial stress was along the fiber axis (x3) while in the second case it was perpendicular to the fiber axis along the

  11. Vestibular abnormalities in congenital disorders.

    PubMed

    Sando, I; Orita, Y; Miura, M; Balaban, C D

    2001-10-01

    This paper reviews the histopathologic features of vestibular abnormalities in congenital disorders affecting the inner ear, based upon a comprehensive literature survey and a review of cases in our temporal bone collection. The review proceeds in three systematic steps. First, we surveyed associated diseases with the major phenotypic features of congenital abnormalities of the inner ear (including the internal auditory canal and otic capsule). Second, the vestibular anomalies are examined specifically. Finally, the anomalies are discussed from a developmental perspective. Among vestibular anomalies, a hypoplastic endolymphatic duct and sac are observed most frequently. Anomalies of the semicircular canals are also often observed. From embryological and clinical viewpoints, many of these resemble the structural features from fetal stages and appear to be associated with vestibular dysfunction. It is expected that progress in genetic analysis and accumulation of temporal bone specimens with vestibular abnormalities in congenital diseases will provide crucial information not only for pathology of those diseases, but also for genetic factors that are responsible for the specific vestibular abnormalities.

  12. Optical fiber technique for in-reactor mechanical properties measurement

    SciTech Connect

    Schley, R. S.; Hurley, D. H.; Hua, Z. A.

    2013-01-25

    In-reactor measurement of material properties is required for a better understanding of radiation effects on materials. We present an optical fiber based technique for measuring changes in elastic properties which involves exciting and measuring flexural vibrations in a thin cantilever beam. By exciting the beam and measuring the resonant frequency, changes in the modulus of elasticity can be monitored. The technique is demonstrated by monitoring the elastic property changes of a beam fabricated from copper, as the copper undergoes recrystallization at elevated temperature.

  13. Optical Fiber Technique for In-Reactor Mechanical Properties Measurement

    SciTech Connect

    Robert S. Schley; Zilong Hua; David H. Hurley; Heng Ban

    2012-07-01

    In-reactor measurement of material properties is required for a better understanding of radiation effects on materials. We present an optical fiber based technique for measuring changes in elastic properties which involves exciting and measuring flexural vibrations in a thin cantilever beam. By exciting the beam and measuring the natural frequency, changes in the modulus of elasticity can be monitored. The technique is demonstrated by monitoring the elastic property changes of a beam fabricated from copper, as the copper undergoes recrystallization at elevated temperature.

  14. Optical fiber technique for in-reactor mechanical properties measurement

    NASA Astrophysics Data System (ADS)

    Schley, R. S.; Hurley, D. H.; Hua, Z. A.

    2013-01-01

    In-reactor measurement of material properties is required for a better understanding of radiation effects on materials. We present an optical fiber based technique for measuring changes in elastic properties which involves exciting and measuring flexural vibrations in a thin cantilever beam. By exciting the beam and measuring the resonant frequency, changes in the modulus of elasticity can be monitored. The technique is demonstrated by monitoring the elastic property changes of a beam fabricated from copper, as the copper undergoes recrystallization at elevated temperature.

  15. Diamagnetic studies on as-processed carbon fibers

    NASA Technical Reports Server (NTRS)

    Scott, C. B.; Fischbach, D. B.

    1976-01-01

    The Faraday method has been used to measure the diamagnetic susceptibilities of small bundles of aligned carbon fibers of different types at room temperature. It was found that the tensor trace susceptibility of the fibers varies systematically over the range 0.8-20 (in units of -10 to the -6th emu/g) as a function of precursor type and processing history. The susceptibility increases, in general, with increasing nominal treatment temperature and hot stretching, and with increasing tensile elastic modulus. The anisotropy ratio of fibers increases approximately linearly with tensile elastic modulus for all fibers from about 1 for a modulus of about 70 GN/sq m to about 22 for a modulus of 700 GN/sq m in air, and is quantitatively consistent with the layer-plane orientation textures determined by X-ray diffraction when appropriate values of the crystallite principal susceptibilities are used.

  16. Elastic wavefield migration and tomography

    NASA Astrophysics Data System (ADS)

    Duan, Yuting

    Wavefield migration and tomography are well-developed under the acoustic assumption; however, multicomponent recorded seismic data include shear waves (S-modes) in addition to the compressional waves (P-modes). Constructing multicomponent wavefields and considering multiparameter model properties make it possible to utilize information provided by various wave modes, and this information allows for better characterization of the subsurface. In my thesis, I apply popular wavefield imaging and tomography to elastic media, and propose methods to address challenges posed by elastic multicomponent wavefields and multiparameter models. The key novelty of my research consists of new elastic imaging conditions, which generate elastic images with improved qualities and clear physical meaning. Moreover, I demonstrate an elastic wavefield tomography method to obtain realistic elastic models which benefits elastic migration. Migration techniques, including conventional RTM, extended RTM, and least-squares RTM (LSRTM), provide images of subsurface structures. I propose one imaging condition that computes potential images (PP, PS, SP, and SS). This imaging condition exploits pure P- and S-modes obtained by Helmholtz decomposition and corrects for the polarity reversal in PS and SP images. Using this imaging condition, I propose methods for conventional RTM and extended RTM. The extended imaging condition makes it possible to compute angle gathers for converted waves. The amplitudes of the scalar images indicate reflectivities, which can be used for amplitude verse offset (AVO) analysis; however, this imaging condition requires knowledge of the geologic dip. I propose a second imaging condition that computes perturbation images, i.e., P and S velocity perturbations. Because these images correspond to perturbations to material properties that are angle-independent, they do not have polarity reversals; therefore, they do not need dip information for polarity correction. I use this

  17. Photovoltaic fibers

    NASA Astrophysics Data System (ADS)

    Gaudiana, Russell; Eckert, Robert; Cardone, John; Ryan, James; Montello, Alan

    2006-08-01

    It was realized early in the history of Konarka that the ability to produce fibers that generate power from solar energy could be applied to a wide variety of applications where fabrics are utilized currently. These applications include personal items such as jackets, shirts and hats, to architectural uses such as awnings, tents, large covers for cars, trucks and even doomed stadiums, to indoor furnishings such as window blinds, shades and drapes. They may also be used as small fabric patches or fiber bundles for powering or recharging batteries in small sensors. Power generating fabrics for clothing is of particular interest to the military where they would be used in uniforms and body armor where portable power is vital to field operations. In strong sunlight these power generating fabrics could be used as a primary source of energy, or they can be used in either direct sunlight or low light conditions to recharge batteries. Early in 2002, Konarka performed a series of proof-of-concept experiments to demonstrate the feasibility of building a photovoltaic cell using dye-sensitized titania and electrolyte on a metal wire core. The approach taken was based on the sequential coating processes used in making fiber optics, namely, a fiber core, e.g., a metal wire serving as the primary electrode, is passed through a series of vertically aligned coating cups. Each of the cups contains a coating fluid that has a specific function in the photocell. A second wire, used as the counter electrode, is brought into the process prior to entering the final coating cup. The latter contains a photopolymerizable, transparent cladding which hardens when passed through a UV chamber. Upon exiting the UV chamber, the finished PV fiber is spooled. Two hundred of foot lengths of PV fiber have been made using this process. When the fiber is exposed to visible radiation, it generates electrical power. The best efficiency exhibited by these fibers is 6% with an average value in the 4

  18. Early White-Matter Abnormalities of the Ventral Frontostriatal Pathway in Fragile X Syndrome

    ERIC Educational Resources Information Center

    Haas, Brian W.; Barnea-Goraly, Naama; Lightbody, Amy A.; Patnaik, Swetapadma S.; Hoeft, Fumiko; Hazlett, Heather; Piven, Joseph; Reiss, Allan L.

    2009-01-01

    Aim: Fragile X syndrome is associated with cognitive deficits in inhibitory control and with abnormal neuronal morphology and development. Method: In this study, we used a diffusion tensor imaging (DTI) tractography approach to reconstruct white-matter fibers in the ventral frontostriatal pathway in young males with fragile X syndrome (n = 17;…

  19. Photoacoustic elastic oscillation and characterization.

    PubMed

    Gao, Fei; Feng, Xiaohua; Zheng, Yuanjin

    2015-08-10

    Photoacoustic imaging and sensing have been studied extensively to probe the optical absorption of biological tissue in multiple scales ranging from large organs to small molecules. However, its elastic oscillation characterization is rarely studied and has been an untapped area to be explored. In literature, photoacoustic signal induced by pulsed laser is commonly modelled as a bipolar "N-shape" pulse from an optical absorber. In this paper, the photoacoustic damped oscillation is predicted and modelled by an equivalent mass-spring system by treating the optical absorber as an elastic oscillator. The photoacoustic simulation incorporating the proposed oscillation model shows better agreement with the measured signal from an elastic phantom, than conventional photoacoustic simulation model. More interestingly, the photoacoustic damping oscillation effect could potentially be a useful characterization approach to evaluate biological tissue's mechanical properties in terms of relaxation time, peak number and ratio beyond optical absorption only, which is experimentally demonstrated in this paper.

  20. Nanofiber alignment of a small diameter elastic electrospun scaffold

    NASA Astrophysics Data System (ADS)

    Patel, Jignesh

    Cardiovascular disease is the leading cause of death in western countries with coronary heart disease making up 50% of these deaths. As a treatment option, tissue engineered grafts have great potential. Elastic scaffolds that mimic arterial extracellular matrix (ECM) may hold the key to creating viable vascular grafts. Electrospinning is a widely used scaffold fabrication technique to engineer tubular scaffolds. In this study, we investigated how the collector rotation speed altered the nanofiber alignment which may improve mechanical characteristics making the scaffold more suitable for arterial grafts. The scaffold was fabricated from a blend of PCL/Elastin. 2D Fast Fourier Transform (FFT) image processing tool and MatLab were used to quantitatively analyze nanofiber orientation at different collector speeds (13500 to 15500 rpm). Both Image J and MatLab showed graphical peaks indicating predominant fiber orientation angles. A collector speed of 15000 rpm was found to produce the best nanofiber alignment with narrow peaks at 90 and 270 degrees, and a relative amplitude of 200. This indicates a narrow distribution of circumferentially aligned nanofibers. Collector speeds below and above 15000 rpm caused a decrease in fiber alignment with a broader orientation distribution. Uniformity of fiber diameter was also measured. Of 600 measures from the 15000 rpm scaffolds, the fiber diameter range from 500 nm to 899 nm was most prevalent. This diameter range was slightly larger than native ECM which ranges from 50 nm to 500 nm. The second most prevalent diameter range had an average of 404 nm which is within the diameter range of collagen. This study concluded that with proper electrospinning technique and collector speed, it is possible to fabricate highly aligned small diameter elastic scaffolds. Image J 2D FFT results confirmed MatLab findings for the analyses of circumferentially aligned nanofibers. In addition, MatLab analyses simplified the FFT orientation data

  1. Hydrostatic compression in glycerinated rabbit muscle fibers.

    PubMed

    Ranatunga, K W; Fortune, N S; Geeves, M A

    1990-12-01

    Glycerinated muscle fibers isolated from rabbit psoas muscle, and a number of other nonmuscle elastic fibers including glass, rubber, and collagen, were exposed to hydrostatic pressures of up to 10 MPa (100 Atm) to determine the pressure sensitivity of their isometric tension. The isometric tension of muscle fibers in the relaxed state (passive tension) was insensitive to increased pressure, whereas the muscle fiber tension in rigor state increased linearly with pressure. The tension of all other fiber types (except rubber) also increased with pressure; the rubber tension was pressure insensitive. The pressure sensitivity of rigor tension was 2.3 kN/m2/MPa and, in comparison with force/extension relation determined at atmospheric pressure, the hydrostatic compression in rigor muscle fibers was estimated to be 0.03% Lo/MPa. As reported previously, the active muscle fiber tension is depressed by increased pressure. The possible underlying basis of the different pressure-dependent tension behavior in relaxed, rigor, and active muscle is discussed.

  2. Cellular Uptake of Elastic Nanoparticles

    NASA Astrophysics Data System (ADS)

    Yi, Xin; Shi, Xinghua; Gao, Huajian

    2011-08-01

    A fundamental understanding of cell-nanomaterial interaction is of essential importance to nanomedicine and safe applications of nanotechnology. Here we investigate the adhesive wrapping of a soft elastic vesicle by a lipid membrane. We show that there exist a maximum of five distinct wrapping phases based on the stability of full wrapping, partial wrapping, and no wrapping states. The wrapping phases depend on the vesicle size, adhesion energy, surface tension of membrane, and bending rigidity ratio between vesicle and membrane. These results are of immediate interest to the study of vesicular transport and endocytosis or phagocytosis of elastic particles into cells.

  3. Dynamic Modulus and Damping of Boron, Silicon Carbide, and Alumina Fibers

    NASA Technical Reports Server (NTRS)

    Dicarlo, J. A.; Williams, W.

    1980-01-01

    The dynamic modulus and damping capacity for boron, silicon carbide, and silicon carbide coated boron fibers were measured from-190 to 800 C. The single fiber vibration test also allowed measurement of transverse thermal conductivity for the silicon carbide fibers. Temperature dependent damping capacity data for alumina fibers were calculated from axial damping results for alumina-aluminum composites. The dynamics fiber data indicate essentially elastic behavior for both the silicon carbide and alumina fibers. In contrast, the boron based fibers are strongly anelastic, displaying frequency dependent moduli and very high microstructural damping. Ths single fiber damping results were compared with composite damping data in order to investigate the practical and basic effects of employing the four fiber types as reinforcement for aluminum and titanium matrices.

  4. Material and Flexural Properties of Fiber-reinforced Rubber Concrete

    NASA Astrophysics Data System (ADS)

    Helminger, Nicholas P.

    The purpose of this research is to determine the material properties of rubber concrete with the addition of fibers, and to determine optimal mixture dosages of rubber and fiber in concrete for structural applications. Fiber-reinforced concrete and rubberized concrete have been researched separately extensively, but this research intends to combine both rubber and fiber in a concrete matrix in order to create a composite material, fiber-reinforced rubber concrete (FRRC). Sustainability has long been important in engineering design, but much of the previous research performed on sustainable concrete does not result in a material that can be used for practical purposes. While still achieving a material that can be used for structural applications, economical considerations were given when choosing the proportions and types of constituents in the concrete mix. Concrete mixtures were designed, placed, and tested in accordance with common procedures and standards, with an emphasis on practicality. Properties that were investigated include compressive strength, tensile strength, modulus of elasticity, toughness, and ductility. The basis for determining the optimal concrete mixture is one that is economical, practical, and exhibits ductile properties with a significant strength. Results show that increasing percentages of rubber tend to decrease workability, unit weight, compressive strength, split tensile strength, and modulus of elasticity while the toughness is increased. The addition of steel needle fibers to rubber concrete increases unit weight, compressive strength, split tensile strength, modulus of elasticity, toughness, and ductility of the composite material.

  5. Using blocking peptides to control and analyze the mechanical properties of single fibrin fibers

    NASA Astrophysics Data System (ADS)

    Maddi, Pranav; O'Brien, E. Tim, III; Gorkun, Oleg; Falvo, Michael R.

    2011-10-01

    Fibrin is the main structural protein involved in blood clotting, and exhibits high strength and elasticity. Fibrin study traditionally focuses on fully formed clots, whereas we employ new AFM nanoManipulation techniques to study single fibrin fiber mechanics. We used 4 and 10 residue peptides to interfere with the knob-hole and αC interactions involved in fibrin polymerization to evaluate the contribution of each interaction to the fiber's mechanical properties. We varied the concentration of each peptide present during polymerization to find the concentration that inhibited polymerization by half. The presence of either peptide during fibrin polymerization did not affect single fiber breaking strain (δLL0). The breaking force of all treated fibers reduced from 10-50nN to 2-10nN, suggesting treated fibers are thinner or are the same diameter with some inhibition of interactions. Fibers polymerized with the knob-hole targeting peptide visibly lost elasticity after 100% strain, while fibers polymerized with the αC targeting peptide lost elasticity after reaching 150% strain, suggesting that the knob-hole interactions control single fiber elasticity.

  6. Fiber reinforced glasses and glass-ceramics for high performance applications

    NASA Technical Reports Server (NTRS)

    Prewo, K. M.; Brennan, J. J.; Layden, G. K.

    1986-01-01

    The development of fiber reinforced glass and glass-ceramic matrix composites is described. The general concepts involved in composite fabrication and resultant composite properties are given for a broad range of fiber and matrix combinations. It is shown that composite materials can be tailored to achieve high levels of toughness, strength, and elastic stiffness, as well as wear resistance and dimensional stability.

  7. The effects of non-elastic taping on muscle tone in stroke patients: a pilot study

    PubMed Central

    Kim, Ji Young; Chung, Jun Sub; Jang, Gwon Uk; Park, Seol; Park, Ji Won

    2015-01-01

    [Purpose] Hemiplegia occurs when posturing with a dominant flexor tone is present in the upper limbs, thus preventing increased abnormal tone. We attempted to improve the side effects of this condition using elbow re-positioning with non-elastic tape; this method is used to modulate abnormal muscle tone in chronic hemiplegic stroke patients. [Subjects and Methods] Fourteen post-stroke patients were included in this study. Non-elastic tape was applied to the elbow joint in a spiral manner. Before and after the tape was applied, the degree of spasticity (hypertonia) was measured in the elbow flexor muscles using the Modified Ashworth Scale (MAS). Global synkinesis (GS) intensity using electromyography (EMG) was measured in the biceps brachii and triceps brachii during voluntary isometric elbow contractions of the contralateral upper limbs. [Results] Application of non-elastic tape at the elbow joint significantly changed the GS intensity, but no significant changes were found when compared with the MAS. [Conclusion] This study demonstrates that non-elastic tape can be used to decrease abnormal elbow flexor tone. The findings may be used to influence the choice of intervention regarding muscle tone and spastic elbow flexion. PMID:26834377

  8. Small Fiber Neuropathy: Differential Diagnosis and Treatment Implications.

    PubMed

    Barrett, Stephen L; Dellon, A Lee

    2016-04-01

    Burning sensation in the feet is a common problem encountered in podiatric medicine. When this pain is bilateral, symmetric, and includes the top and bottom of both feet, small nerve fiber involvement must be considered in the differential diagnosis. With the now available, in-office, skin biopsy quantification of intraepidermal nerve fibers, documentation of the presence of small fiber involvement in the pain mechanism is possible. Technical details of performing the skin biopsy are reviewed and the legal implications of a positive abnormal skin biopsy for intraepidermal nerve fibers is discussed.

  9. Optimization of Elastically Tailored Tow-Placed Plates with Holes

    NASA Technical Reports Server (NTRS)

    Jegley, Dawn C.; Tatting, Brian F.; Guerdal, Zafer

    2003-01-01

    Elastic stiffness tailoring of laminated composite panels by allowing the fibers to curve within the plane of the laminate is a design concept that has been demonstrated to be both beneficial and practical. The objective of the present paper is to demonstrate the effectiveness of stiffness tailoring through the use of curvilinear fibers to reduce stress concentrations around the hole and improve the load carrying capability of panels. Preliminary panel designs that are to be manufactured and tested were determined through design studies for flat plates without holes under axial compression using an optimization program. These candidate designs were then analyzed with finite element models that accurately reflect the test conditions and geometries in order to decide upon the final designs for manufacture and testing. An advanced tow-placement machine is used to manufacture the test panels with varying fiber orientation angles. A total of six large panels measuring three feet by six feet, each of which is used to produce four specimens with or without holes, are fabricated. The panels were machined into specimens with holes and tested at NASA Langley Research Center. Buckling response and failure of panels without holes and with two different hole dimensions are presented. Buckling and failure loads of tow-steered specimens are significantly greater than the buckling and failure loads of traditional straight-fiber specimens.

  10. SIZE EFFECTS IN THE TENSILE STRENGTH OF UNIDIRECTIONAL FIBER COMPOSITES

    SciTech Connect

    M. SIVASAMBU; ET AL

    1999-08-01

    Monte Carlo simulation and theoretical modeling are used to study the statistical failure modes in unidirectional composites consisting of elastic fibers in an elastic matrix. Both linear and hexagonal fiber arrays are considered, forming 2D and 3D composites, respectively. Failure is idealized using the chain-of-bundles model in terms of {delta}-bundles of length {delta}, which is the length-scale of fiber load transfer. Within each {delta}-bundle, fiber load redistribution is determined by local load-sharing models that approximate the in-plane fiber load redistribution from planar break clusters as predicted from 2D and 3D shear-lag models. As a result these models are 1D and 2D, respectively. Fiber elements have random strengths following either the Weibull or the power-law distribution with shape and scale parameters {rho} and {sigma}{sub {delta}}, respectively. Simulations of {delta}-bundle failure, reveal two regimes. When fiber strength variability is low (roughly {rho} > 2) the dominant failure mode is by growing clusters of fiber breaks up to instability. When this variability is high (roughly 0 < {rho} < 1) cluster formation is suppressed by a dispersed fiber failure mode. For these two cases, closed-form approximations to the strength distribution of a {delta}-bundle are developed under the local load-sharing model and an equal load-sharing model of Daniels, respectively. The results compare favorably with simulations on {delta}-bundles with up to 1500 fibers. The location of the transition in terms of {rho} is affected by the upper tail properties of the fiber strength distributions as well as the number of fibers.

  11. Fabrication of Composite Material Using Gettou Fiber by Injection Molding

    NASA Astrophysics Data System (ADS)

    Setsuda, Roy; Fukumoto, Isao; Kanda, Yasuyuki

    This study investigated the mechanical properties of composite using gettou (shell ginger) fiber as reinforcement fabricated from injection molding. Gettou fiber is a natural fiber made from gettou, a subtropical plant that is largely abundant in Okinawa, Japan. We used the stem part of gettou plant and made the gettou fiber by crushing the stem. The composite using gettou fiber contributed to low shrinkage ratio, high bending strength and high flexural modulus. The mechanical strength of composite using long gettou fiber showed higher value than composite using short gettou fiber. Next, because gettou is particularly known for its anti-mold characteristic, we investigated the characteristic in gettou plastic composite. The composite was tested against two molds: aspergillius niger and penicillium funiculosum. The 60% gettou fiber plastic composite was found to satisfy the JISZ2801 criterion. Finally, in order to predict the flexural modulus of composite using gettou fiber by Halpin-Tsai equation, the tensile elastic modulus of single gettou fiber was measured. The tendency of the experimental results of composite using gettou fiber was in good agreement with Halpin-Tsai equation.

  12. The preparation and investigation into properties of ionomer fiber

    NASA Astrophysics Data System (ADS)

    Ejigiri, Everest Emmanuel

    The purpose of this study was to demonstrate the preparation and characterization of ionomer fiber. Two outstanding features of oriented-fiber composites are their high strength-to- weight ratio and controlled anisotropy which is because fibers are formed when polymer chains (in case of polymeric materials) are all lined up in the same direction. And the chains can pack together tightly. Materials can be made into fiber for the purpose of getting better properties and to make the application flexible. In this study, ionomer fiber was prepared. The physical and mechanical properties were examined through a variety of tests- including tensile test, dynamic mechanical analysis (DMA), differential scanning calorimetry (DSC), free shape recovery test, and constrained stress recovery test. The ionomer fibers were made into muscles fiber, and the tensile actuation behavior of the muscle was studied. From the DMA, Storage modulus, loss modulus, tan delta and glass transition temperature were obtained. DSC was also used to obtain the glass transition temperature which also closely aligned with glass transition obtained from DMA. Also according to the test results, ionomer fiber (filament) demonstrated considerable stress recovery, high ductility and however, the filament did not produce high recovery ratio. The fiber was made into artificial muscle and actuation test was also carried out, which indicated that because the fiber being too much elastic - the fiber was not able to expand and contract when heat was applied to it. Instead it showed continuous expansion.

  13. Endocrine abnormalities in anorexia nervosa.

    PubMed

    Lawson, Elizabeth A; Klibanski, Anne

    2008-07-01

    Anorexia nervosa (AN) is a psychiatric disease associated with notable medical complications and increased mortality. Endocrine abnormalities, including hypogonadotropic hypogonadism, hypercortisolemia, growth hormone resistance and sick euthyroid syndrome, mediate the clinical manifestations of this disease. Alterations in anorexigenic and orexigenic appetite-regulating pathways have also been described. Decreases in fat mass result in adipokine abnormalities. Although most of the endocrine changes that occur in AN represent physiologic adaptation to starvation, some persist after recovery and might contribute to susceptibility to AN recurrence. In this Review, we summarize key endocrine alterations in AN, with a particular focus on the profound bone loss that can occur in this disease. Although AN is increasingly prevalent among boys and men, the disorder predominantly affects girls and women who are, therefore, the focus of this Review.

  14. Eye abnormalities in Fryns syndrome.

    PubMed

    Pierson, Diane M; Taboada, Eugenio; Butler, Merlin G

    2004-03-15

    Fryns syndrome is a rare, generally lethal, autosomal recessive multiple congenital anomaly (MCA) syndrome first described in 1979. Patients with the syndrome present with the classical findings of cloudy cornea, brain malformations, diaphragmatic defects, and distal limb deformities. Over 70 patients have been reported revealing a wide variety of phenotypic features. Although initially considered a major feature of Fryns syndrome, cloudy cornea has been relegated as a minor diagnostic sign and not commonly reported in patients since the original description. However, eye findings per se are not uncommon. Abnormal eye findings occasionally reported in Fryns syndrome potentially result in amblyopia and blindness, profoundly affecting neurologic outcome of those who survive the neonatal period. We reviewed 77 reported patients with Fryns syndrome and summarized the abnormal eye findings identified in 12 of the reported cases. In addition, we contribute three new patients with Fryns syndrome, one of which demonstrated unilateral microphthalmia and cloudy cornea.

  15. [Chromosome abnormalities in human cancer].

    PubMed

    Salamanca-Gómez, F

    1995-01-01

    Recent investigation on the presence of chromosome abnormalities in neoplasias has allowed outstanding advances in the knowledge of malignant transformation mechanisms and important applications in the clinical diagnosis and prognosis of leukaemias, lymphomas and solid tumors. The purpose of the present paper is to discuss the most relevant cytogenetic aberrations, some of them described at the Unidad de Investigación Médica en Genética Humana, Instituto Mexicano del Seguro Social, and to correlate these abnormalities with recent achievements in the knowledge of oncogenes, suppressor genes or antioncogenes, their chromosome localization, and their mutations in human neoplasia; as well as their perspectives in prevention and treatment of cancer that such findings permit to anticipate.

  16. Neuroendocrine abnormalities in Parkinson's disease.

    PubMed

    De Pablo-Fernández, Eduardo; Breen, David P; Bouloux, Pierre M; Barker, Roger A; Foltynie, Thomas; Warner, Thomas T

    2017-02-01

    Neuroendocrine abnormalities are common in Parkinson's disease (PD) and include disruption of melatonin secretion, disturbances of glucose, insulin resistance and bone metabolism, and body weight changes. They have been associated with multiple non-motor symptoms in PD and have important clinical consequences, including therapeutics. Some of the underlying mechanisms have been implicated in the pathogenesis of PD and represent promising targets for the development of disease biomarkers and neuroprotective therapies. In this systems-based review, we describe clinically relevant neuroendocrine abnormalities in Parkinson's disease to highlight their role in overall phenotype. We discuss pathophysiological mechanisms, clinical implications, and pharmacological and non-pharmacological interventions based on the current evidence. We also review recent advances in the field, focusing on the potential targets for development of neuroprotective drugs in Parkinson's disease and suggest future areas for research.

  17. Monte Carlo investigations of elastic scattering spectroscopy applied to latex spheres used as tissue phantoms

    SciTech Connect

    Boyer, J.; Mourant, J.R.; Bigio, I.J.

    1995-05-01

    An optical-fiber-coupled, elastic-scatter spectrometer has proven effective in discriminating between malignant and non-malignant tissue in the human bladder and gastrointestinal tract. The system injects broadband light into the tissue with an optical fiber and spectrally analyzes the returning light collected by an adjacent fiber. The collected photons have experienced multiple scattering events and therefore arrive at the analysis fiber after traveling varied paths.the diameter of the source fiber is comparable to its separation from the collection fiber. The diffusion model is inappropriate for this geometry; therefore, Monte Carlo simulations are used. In addition, the size of the scattering sites in tissue are expected to be of the same order as the excitation wavelengths, and Mie theory is expected to provide the best description of the scattering and extinction. The authors will present and compare the results of simulations and measurements of the elastic scatter signal for suspensions of latex spheres in hemoglobin solutions of varying concentrations.

  18. On the elastic buckling of rod-shaped particles in sheared suspensions

    SciTech Connect

    DeTeresa, S.J. )

    1993-09-01

    The rheology of rod-shaped particle suspensions is of practical importance for the processing of discontinuous fiber composites. A correction of the original work by Forgacs and Mason describing the elastic buckling of rod-shaped particles in sheared suspensions is presented. Although the qualitative relationship among critical buckling conditions and the fiber aspect ratio and elastic modulus is unaltered, the new result for the predicted critical buckling condition shows that the resistance of suspended rods to buckling is more than five times greater than had been believed. Reexamination of experimental results using the corrected solution yielded mixed conclusions concerning the validity of the model. The agreement with results of the original experiments by Forgacs and Mason using Dacron fibers suspended in corn syrup and the new result was found to be excellent and quantitative. The results of experiments with glass fibers suspended in glucose solutions were found to be in poor agreement with predictions. The ability of the proposed result to account for an unusual degradation due to shearing in polystyrene melts of Kevlar 29 fibers was also found to be quantitative and excellent. The Kevlar fibers exhibited permanent bends spaced with a uniform spacing which was predicted by application of the new buckling relationship.

  19. Modeling shock waves in orthotropic elastic materials

    NASA Astrophysics Data System (ADS)

    Vignjevic, Rade; Campbell, James C.; Bourne, Neil K.; Djordjevic, Nenad

    2008-08-01

    A constitutive relationship for modeling of shock wave propagation in orthotropic materials is proposed for nonlinear explicit transient large deformation computer codes (hydrocodes). A procedure for separation of material volumetric compression (compressibility effects equation of state) from deviatoric strain effects is formulated, which allows for the consistent calculation of stresses in the elastic regime as well as in the presence of shock waves. According to this procedure the pressure is defined as the state of stress that results in only volumetric deformation, and consequently is a diagonal second order tensor. As reported by Anderson et al. [Comput. Mech. 15, 201 (1994)], the shock response of an orthotropic material cannot be accurately predicted using the conventional decomposition of the stress tensor into isotropic and deviatoric parts. This paper presents two different stress decompositions based on the assumption that the stress tensor is split into two components: one component is due to volumetric strain and the other is due to deviatoric strain. Both decompositions are rigorously derived. In order to test their ability to describe shock propagation in orthotropic materials, both algorithms were implemented in a hydrocode and their predictions were compared to experimental plate impact data. The material considered was a carbon fiber reinforced epoxy material, which was tested in both the through-thickness and longitudinal directions. The ψ decomposition showed good agreement with the physical behavior of the considered material, while the ζ decomposition significantly overestimated the longitudinal stresses.

  20. Congenital abnormalities of the goat.

    PubMed

    Basrur, P K

    1993-03-01

    Congenital abnormalities of genetic and environmental causes constitute a striking proportion of the afflictions seen in goats. These include a variety of malformations and metabolic diseases that could occur in all breeds but tend to exhibit predisposition in some breeds of goats. Genetic abnormalities for which the carrier state is detectable with the aid of enzymes and surface protein markers can be eliminated from goat populations, whereas common polygenic disorders including udder problems in does and gynecomastia in bucks are more difficult to eradicate because the mutant genes responsible for these traits generally do not declare themselves until inbreeding brings together a critical concentration of liability genes to create a crisis. A substantial reduction of common abnormalities in this species, such as intersexuality in dairy breeds, abortion in Angora breed, and arthritis in the Pygmy breed, will require a change in breeders' preference and selection practice. In making these changes, however, the beneficial traits will have to be balanced against the undesirable effects of the selected mutant genes (pleiotropy), which hold the key to success or failure of a breed under domestication.

  1. Meiotic abnormalities in infertile males.

    PubMed

    Egozcue, J; Sarrate, Z; Codina-Pascual, M; Egozcue, S; Oliver-Bonet, M; Blanco, J; Navarro, J; Benet, J; Vidal, F

    2005-01-01

    Meiotic anomalies, as reviewed here, are synaptic chromosome abnormalities, limited to germ cells that cannot be detected through the study of the karyotype. Although the importance of synaptic errors has been underestimated for many years, their presence is related to many cases of human male infertility. Synaptic anomalies can be studied by immunostaining of synaptonemal complexes (SCs), but in this case their frequency is probably underestimated due to the phenomenon of synaptic adjustment. They can also be studied in classic meiotic preparations, which, from a clinical point of view, is still the best approach, especially if multiplex fluorescence in situ hybridization is at hand to solve difficult cases. Sperm chromosome FISH studies also provide indirect evidence of their presence. Synaptic anomalies can affect the rate of recombination of all bivalents, produce achiasmate small univalents, partially achiasmate medium-sized or large bivalents, or affect all bivalents in the cell. The frequency is variable, interindividually and intraindividually. The baseline incidence of synaptic anomalies is 6-8%, which may be increased to 17.6% in males with a severe oligozoospermia, and to 27% in normozoospermic males with one or more previous IVF failures. The clinical consequences are the production of abnormal spermatozoa that will produce a higher number of chromosomally abnormal embryos. The indications for a meiotic study in testicular biopsy are provided.

  2. Helical graphene oxide fibers as a stretchable sensor and an electrocapillary sucker

    NASA Astrophysics Data System (ADS)

    Hua, Chunfei; Shang, Yuanyuan; Li, Xiying; Hu, Xiaoyang; Wang, Ying; Wang, Xinchang; Zhang, Yingjiu; Li, Xinjian; Duan, Huiling; Cao, Anyuan

    2016-05-01

    Fibers made from carbon nanotubes or graphene are strong and conductive; encoding helical structures into these fibers may render useful properties such as high stretchability. Here, we directly spin freestanding graphene oxide (GO) films into helical fibers consisting of uniformly arranged loops with tunable diameters, under controlled environmental humidity. Reduced GO fibers with a helical shape are stretched elastically with a reversible electrical resistance change for many strain cycles. Stretchable temperature sensors built on helical fibers work at large strains (up to 50%) and high temperature (up to 300 °C), with a reliable deformation-independent response. The GO fibers also contain through-channels inside with suitable pore size, which can take up an aqueous electrolyte quickly under a low bias, resulting in a fiber-shaped, on-off switchable electrocapillary sucker. Our multifunctional helical and hollow GO fibers have potential applications in stretchable fiber-shaped sensors, actuators and nano-fluid systems.Fibers made from carbon nanotubes or graphene are strong and conductive; encoding helical structures into these fibers may render useful properties such as high stretchability. Here, we directly spin freestanding graphene oxide (GO) films into helical fibers consisting of uniformly arranged loops with tunable diameters, under controlled environmental humidity. Reduced GO fibers with a helical shape are stretched elastically with a reversible electrical resistance change for many strain cycles. Stretchable temperature sensors built on helical fibers work at large strains (up to 50%) and high temperature (up to 300 °C), with a reliable deformation-independent response. The GO fibers also contain through-channels inside with suitable pore size, which can take up an aqueous electrolyte quickly under a low bias, resulting in a fiber-shaped, on-off switchable electrocapillary sucker. Our multifunctional helical and hollow GO fibers have potential

  3. [Use of elastic compression stockings].

    PubMed

    Kallestrup, Lisbeth; Søgaard, Tine; Schjødt, Inge; Grove, Erik Lerkevang

    2014-08-04

    Post-thrombotic syndrome (PTS) is caused by venous insufficiency and is a frequent complication of deep venous thrombosis. Patients with PTS have reduced quality of life and an increased risk of recurrent deep venous thrombosis. Importantly, the risk of PTS is halved by the use of elastic compression stockings. This review outlines important practical aspects related to correct clinical use of these stockings.

  4. HEMP. Hydrodynamic Elastic Magneto Plastic

    SciTech Connect

    Wilkins, M.L.; Levatin, J.A.

    1985-02-01

    The HEMP code solves the conservation equations of two-dimensional elastic-plastic flow, in plane x-y coordinates or in cylindrical symmetry around the x-axis. Provisions for calculation of fixed boundaries, free surfaces, pistons, and boundary slide planes have been included, along with other special conditions.

  5. Duration of an Elastic Collision

    ERIC Educational Resources Information Center

    de Izarra, Charles

    2012-01-01

    With a pedagogical goal, this paper deals with a study of the duration of an elastic collision of an inflatable spherical ball on a planar surface suitable for undergraduate studies. First, the force generated by the deformed spherical ball is obtained under assumptions that are discussed. The study of the motion of the spherical ball colliding…

  6. Robustness Elasticity in Complex Networks

    PubMed Central

    Matisziw, Timothy C.; Grubesic, Tony H.; Guo, Junyu

    2012-01-01

    Network robustness refers to a network’s resilience to stress or damage. Given that most networks are inherently dynamic, with changing topology, loads, and operational states, their robustness is also likely subject to change. However, in most analyses of network structure, it is assumed that interaction among nodes has no effect on robustness. To investigate the hypothesis that network robustness is not sensitive or elastic to the level of interaction (or flow) among network nodes, this paper explores the impacts of network disruption, namely arc deletion, over a temporal sequence of observed nodal interactions for a large Internet backbone system. In particular, a mathematical programming approach is used to identify exact bounds on robustness to arc deletion for each epoch of nodal interaction. Elasticity of the identified bounds relative to the magnitude of arc deletion is assessed. Results indicate that system robustness can be highly elastic to spatial and temporal variations in nodal interactions within complex systems. Further, the presence of this elasticity provides evidence that a failure to account for nodal interaction can confound characterizations of complex networked systems. PMID:22808060

  7. Buckling transition of a flexible fiber at a surface stagnation point

    NASA Astrophysics Data System (ADS)

    Guglielmini, Laura; Autrusson, Nicolas; Kushwaha, Amit; Shaqfeh, Eric; Stone, Howard

    2011-11-01

    The interplay of viscous and elastic stresses is relevant to a number of flow problems involving slender elastic fibers. These range from the swimming of microorganisms to the transport of pulp fibers in processing flow as well as from nanotube and nanocarpet applications to semi-flexible polymer behavior. In this work, we discuss the response of an elastic fiber tethered to a plane wall and subjected to a stagnation point flow. Using a combination of stability analysis and numerical simulations, (with the latter based on a discretized beam model), we show that, for a critical value of the ratio between viscous and elastic forces, the filament is susceptible to a buckling instability at a bifurcation point which may be subcritical. Further, we discuss the effect of thermal fluctuations on the buckling transition, thus demonstrating the dynamic effect of small fluctuations on a filament whose persistence length is much longer than its contour length.

  8. Visual pathway abnormalities in tuberculous meningitis.

    PubMed

    Maurya, Pradeep Kumar; Singh, Ajai Kumar; Sharma, Lalit; Kulshreshtha, Dinkar; Thacker, Anup Kumar

    2016-11-01

    Ophthalmological complications are common and disabling in patients with tuberculous meningitis. We aimed to study the visual pathway abnormalities in patients with tuberculous meningitis. Forty-three patients with tuberculous meningitis were subjected to visual evoked responses (VER) and neuroophthalmologic assessment. Neuroophthalmologic assessment revealed abnormalities in 22 (51.3%) patients. VER were found to be abnormal in 27 (62.8%) patients. The VER abnormalities included prolonged P100 latencies with relatively normal amplitude and significant interocular latency differences. Visual pathways abnormalities are common in patients with tuberculous meningitis and are often subclinical. Pathophysiologic explanations for electrophysiological abnormalities on VER in these patients are incompletely understood and needs further exploration.

  9. A nano-cheese-cutter to directly measure interfacial adhesion of freestanding nano-fibers

    NASA Astrophysics Data System (ADS)

    Wang, Xin; Najem, Johnny F.; Wong, Shing-Chung; Wan, Kai-tak

    2012-01-01

    A nano-cheese-cutter is fabricated to directly measure the adhesion between two freestanding nano-fibers. A single electrospun fiber is attached to the free end of an atomic force microscope cantilever, while a similar fiber is similarly prepared on a mica substrate in an orthogonal direction. External load is applied to deform the two fibers into complementary V-shapes, and the force measurement allows the elastic modulus to be determined. At a critical tensile load, "pull-off" occurs when the adhering fibers spontaneously detach from each other, yielding the interfacial adhesion energy. Loading-unloading cycles are performed to investigate repeated adhesion-detachment and surface degradation.

  10. Crystalline and tensile properties of carbon nanotube and graphene reinforced polyamide 12 fibers

    NASA Astrophysics Data System (ADS)

    Chatterjee, S.; Nüesch, F. A.; Chu, B. T. T.

    2013-02-01

    The influence of carbon nanotubes (CNTs) and graphene nanoplatelets (GnPs) on the structure and mechanical properties of polyamide 12 (PA12) fibers was investigated. As seen from wide-angle X-ray diffraction analysis the crystallinity index increases with incorporation of nanofillers due to nucleation effects. Marked improvement was noted for mechanical properties of the composites with increase in elastic modulus, yield stress and strength of the fibers. The most significant improvement of a factor of 4 could be observed for elastic modulus with the inclusion of 0.5 wt.% GnP. A comparative study was made between the fibers reinforced with CNTs and GnPs.

  11. Anisotropic elasticity and abnormal Poisson's ratios in super-hard materials

    NASA Astrophysics Data System (ADS)

    Huang, Chuanwei; Li, Rongpeng; Chen, Lang

    2014-12-01

    We theoretically investigated the variable mechanical properties such as Young's modulus, Poisson's ratios and compressibility in super-hard materials. Our tensorial analysis reveals that the mechanical properties of super-hard materials are strongly sensitive to the anisotropy index of materials. In sharp contrast to the traditional positive constant as thought before, the Poisson's ratio of super-hard materials could be unexpectedly negative, zero, or even positive with a value much larger than the isotropic upper limit of 0.5 along definite directions. Our results uncover a correlation between compressibility and hardness, which offer insights on the prediction of new super-hard materials.

  12. Polyimide Fibers

    NASA Technical Reports Server (NTRS)

    St.Clair, Terry L. (Inventor); Fay, Catharine C. (Inventor); Working, Dennis C. (Inventor)

    1997-01-01

    A polyimide fiber having textile physical property characteristics and the process of melt extruding same from a polyimide powder. Polyimide powder formed as the reaction product of the monomers 3.4'-ODA and ODPA, and endcapped with phthalic anhydride to control the molecular weight thereof, is melt extruded in the temperature range of 340? C. to 360? C. and at heights of 100.5 inches, 209 inches and 364.5 inches. The fibers obtained have a diameter in the range of 0.0068 inch to 0.0147 inch; a mean tensile strength in the range of 15.6 to 23.1 ksi; a mean modulus of 406 to 465 ksi; and a mean elongation in the range of 14 to 103%.

  13. Polyimide Fibers

    NASA Technical Reports Server (NTRS)

    St.Clair, Terry L. (Inventor); Fay, Catharine C. (Inventor); Working, Dennis C. (Inventor)

    1998-01-01

    A polyimide fiber having textile physical property characteristics and the process of melt extruding same from a polyimide powder. Polyimide powder formed as the reaction product of the monomers 3.4'-ODA and ODPA, and end- capped with phthalic anhydride to control the molecular weight thereof, is melt extruded in the temperature range of 340 C. to 360 C. and at heights of 100.5 inches. 209 inches and 364.5 inches. The fibers obtained have a diameter in the range of 0.0068 inch to 0.0147 inch; a mean tensile strength in the range of 15.6 to 23.1 ksi; a mean modulus of 406 to 465 ksi, and a mean elongation in the range of 14 to 103%.

  14. The sequential addition and migration method to generate representative volume elements for the homogenization of short fiber reinforced plastics

    NASA Astrophysics Data System (ADS)

    Schneider, Matti

    2017-02-01

    We present an algorithm for generating volume elements of short fiber reinforced plastic microstructures for prescribed fourth order fiber orientation tensor, fiber aspect ratio and solid volume fraction. The algorithm inserts fibers randomly into an existing microstructure, and removes the resulting overlap systematically based on a gradient descent method. In contrast to existing methods, large fiber aspect ratios (up to 150) and large volume fractions (60 vol% for isotropic orientation and aspect ratio of 33) can be reached. We study the effective linear elastic properties of the resulting microstructures, depending on fiber orientation, volume fraction as well as aspect ratio, and examine the size of a corresponding representative volume element.

  15. Nonlinear characterization of elasticity using quantitative optical coherence elastography

    PubMed Central

    Qiu, Yi; Zaki, Farzana R.; Chandra, Namas; Chester, Shawn A.; Liu, Xuan

    2016-01-01

    Optical coherence elastography (OCE) has been used to perform mechanical characterization on biological tissue at the microscopic scale. In this work, we used quantitative optical coherence elastography (qOCE), a novel technology we recently developed, to study the nonlinear elastic behavior of biological tissue. The qOCE system had a fiber-optic probe to exert a compressive force to deform tissue under the tip of the probe. Using the space-division multiplexed optical coherence tomography (OCT) signal detected by a spectral domain OCT engine, we were able to simultaneously quantify the probe deformation that was proportional to the force applied, and to quantify the tissue deformation. In other words, our qOCE system allowed us to establish the relationship between mechanical stimulus and tissue response to characterize the stiffness of biological tissue. Most biological tissues have nonlinear elastic behavior, and the apparent stress-strain relationship characterized by our qOCE system was nonlinear an extended range of strain, for a tissue-mimicking phantom as well as biological tissues. Our experimental results suggested that the quantification of force in OCE was critical for accurate characterization of tissue mechanical properties and the qOCE technique was capable of differentiating biological tissues based on the elasticity of tissue that is generally nonlinear. PMID:27896009

  16. 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.

  17. Mechanical strength of additive manufactured carbon fiber reinforced polyetheretherketone

    NASA Astrophysics Data System (ADS)

    Chumaevskii, A. V.; Tarasov, S. Yu.; Filippov, A. V.; Kolubaev, E. A.; Rubtsov, V. E.; Eliseev, A. A.

    2016-11-01

    Mechanical properties of both pure and chopped carbon fiber reinforced polyetheretherketone samples have been carried out. It was shown that the reinforcement resulted in increasing the elasticity modulus, compression and tensile ultimate strength by a factor of 3.5, 2.9 and 2.8, respectively. The fracture surfaces have been examined using both optical and scanning electron microscopy.

  18. On the anisotropic elastic properties of hydroxyapatite.

    NASA Technical Reports Server (NTRS)

    Katz, J. L.; Ukraincik, K.

    1971-01-01

    Experimental measurements of the isotropic elastic moduli on polycrystalline specimens of hydroxyapatite and fluorapatite are compared with elastic constants measured directly from single crystals of fluorapatite in order to derive a set of pseudo single crystal elastic constants for hydroxyapatite. The stiffness coefficients thus derived are given. The anisotropic and isotropic elastic properties are then computed and compared with similar properties derived from experimental observations of the anisotropic behavior of bone.

  19. Comparison of carbon fiber and stainless steel root canal posts.

    PubMed

    Purton, D G; Payne, J A

    1996-02-01

    This in vitro study compared physical properties of root canal posts made of carbon fiber-reinforced epoxy resin with those of stainless steel posts. Three-point bending tests were used to derive the transverse modulus of elasticity of the posts. Resin composite cores on the posts were subjected to tensile forces to test the bonds between the cores and posts. Carbon fiber posts appeared to have adequate rigidity for their designed purpose. The bond strength of the resin composite cores to the carbon fiber posts was significantly less than that to the stainless steel posts.

  20. Low-set ears and pinna abnormalities

    MedlinePlus

    Low-set ears; Microtia; "Lop" ear; Pinna abnormalities; Genetic defect-pinna; Congenital defect-pinna ... most cases, a health care provider finds pinna abnormalities during the first well-baby exam. This exam ...

  1. Abnormalities of the erythrocyte membrane.

    PubMed

    Gallagher, Patrick G

    2013-12-01

    Primary abnormalities of the erythrocyte membrane are characterized by clinical, laboratory, and genetic heterogeneity. Among this group, hereditary spherocytosis patients are more likely to experience symptomatic anemia. Treatment of hereditary spherocytosis with splenectomy is curative in most patients. Growing recognition of the long-term risks of splenectomy has led to re-evaluation of the role of splenectomy. Management guidelines acknowledge these considerations and recommend discussion between health care providers, patient, and family. The hereditary elliptocytosis syndromes are the most common primary disorders of erythrocyte membrane proteins. However, most elliptocytosis patients are asymptomatic and do not require therapy.

  2. Foot abnormalities of wild birds

    USGS Publications Warehouse

    Herman, C.M.; Locke, L.N.; Clark, G.M.

    1962-01-01

    The various foot abnormalities that occur in birds, including pox, scaly-leg, bumble-foot, ergotism and freezing are reviewed. In addition, our findings at the Patuxent Wildlife Research Center include pox from dove, mockingbird, cowbird, grackle and several species of sparrows. Scaly-leg has been particularly prevalent on icterids. Bumble foot has been observed in a whistling swan and in a group of captive woodcock. Ergotism is reported from a series of captive Canada geese from North Dakota. Several drug treatments recommended by others are presented.

  3. Synergistic stiffening in double-fiber networks.

    PubMed

    Rombouts, Wolf H; Giesbers, Marcel; van Lent, Jan; de Wolf, Frits A; van der Gucht, Jasper

    2014-04-14

    Many biological materials are composite structures, interpenetrating networks of different types of fibers. The composite nature of such networks leads to superior mechanical properties, but the origin of this mechanical synergism is still poorly understood. Here we study soft composite networks, made by mixing two self-assembling fiber-forming components. We find that the elastic moduli of the composite networks significantly exceed the sum of the moduli of the two individual networks. This mechanical enhancement is in agreement with recent simulations, where it was attributed to a suppression of non-affine deformation modes in the most rigid fiber network due to the reaction forces in the softer network. The increase in affinity also causes a loss of strain hardening and an increase in the critical stress and stain at which the network fails.

  4. Elastocapillarity and the curling of fibers

    NASA Astrophysics Data System (ADS)

    Pandey, Anupam; Protiere, Suzie; Holmes, Douglas

    2014-03-01

    Coalescence of paintbrush bristles removed from a bath of fluid is the result of competing elastic and surface energies. The lengthscale that emerges out of this energy balance is called the ``elastocapillary'' lengthscale. This phenomenon has been well studied both experimentally and theoretically at the desktop scale as well as microscale. But in many natural and synthetic systems, the fluid between the flexible fibers can swell the material and causes the fibers to curl. A natural example is human hair, which swells in humid conditions, dilating and becoming frizzy. In this presentation, we demonstrate experimental results on this coupled ``elastocapillary-elastoswelling'' system. Specifically, we identify two distinct regimes dominated by capillarity and swellability, and the transition between these two regimes is governed by the ``elastoswelling'' lengthscale. We also show that in the swelling dominated regime a small fluid droplet is being carried upward by the curling fibers that mimic a pipetting mechanism.

  5. Instabilities of soft elastic microtubes filled with viscous fluids: Pearls, wrinkles, and sausage strings

    NASA Astrophysics Data System (ADS)

    Tomar, Gaurav; Bandopadhayay, Dipankar; Sharma, Ashutosh

    2011-09-01

    A linear stability analysis is presented to study the self-organized instabilities of a highly compliant elastic cylindrical shell filled with a viscous liquid and submerged in another viscous medium. The prototype closely mimics many components of micro- or nanofluidic devices and biological processes such as the budding of a string of pearls inside cells and sausage-string formation of blood vessels. The cylindrical shell is considered to be a soft linear elastic solid with small storage modulus. When the destabilizing capillary force derived from the cross-sectional curvature overcomes the stabilizing elastic and in-plane capillary forces, the microtube can spontaneously self-organize into one of several possible configurations; namely, pearling, in which the viscous fluid in the core of the elastic shell breaks up into droplets; sausage strings, in which the outer interface of the mircrotube deforms more than the inner interface; and wrinkles, in which both interfaces of the thin-walled mircrotube deform in phase with small amplitudes. This study identifies the conditions for the existence of these modes and demonstrates that the ratios of the interfacial tensions at the interfaces, the viscosities, and the thickness of the microtube play crucial roles in the mode selection and the relative amplitudes of deformations at the two interfaces. The analysis also shows asymptotically that an elastic fiber submerged in a viscous liquid is unstable for Y=γ/(GeR)>6 and an elastic microchannel filled with a viscous liquid should rupture to form spherical cavities (pearling) for Y>2, where γ, Ge, and R are the surface tension, elastic shear modulus, and radius, respectively, of the fiber or microchannel.

  6. An all-fiber spectroscopic Raman lidar system for atmospheric water vapor measurements

    NASA Astrophysics Data System (ADS)

    Wang, Yufeng; Zhao, Meina; Fu, Qiang; Li, Zhao; Di, Huige; Wang, Li; Hua, Dengxin

    2016-01-01

    Aimed to establish a Raman lidar system with high-reliability and high anti-interference performance, an newly all-fiber spectroscopic Raman lidar system was proposed for atmospheric water vapor measurement, in which optical fiber couplers, fiber band-width filters and fiber F-P filters constitute the all-fiber spectroscopic system. On the basis of the design of fiber F-P filters and its transmission analysis, the series connection of optical fiber coupler is designed as fiber optics splitter, which is not only to obtain fiber coupling of the input and output of lidar returns, and also to achieve the optimal energy output ratio at three fiber channels. Furthermore, fiber band-width filters are proposed to replace the dichroic mirrors, and the structure of fiber band-width filters and fiber F-P filters is to constitute the secondary cascade filter system, achieving the fine extraction of interested spectrum and high rejection rate to elastic scattering signals. Preliminary test results indicated that, the energy at the three output ports is %sim;5: 2.5: 2.5, and the two fiber band-width filters are provided with the central wavelength of 606nm and 660nm, the bandwidth of 20nm, and the out of band inhibition of >0.5%, which met the design requirements. The design and results will provide a reliable basis for the integration and experiment of the subsequent all-fiber spectroscopic system.

  7. Disruption of the gene encoding the latent transforming growth factor-beta binding protein 4 (LTBP-4) causes abnormal lung development, cardiomyopathy, and colorectal cancer.

    PubMed

    Sterner-Kock, Anja; Thorey, Irmgard S; Koli, Katri; Wempe, Frank; Otte, Jürgen; Bangsow, Thorsten; Kuhlmeier, Katharina; Kirchner, Thomas; Jin, Shenchu; Keski-Oja, Jorma; von Melchner, Harald

    2002-09-01

    Transforming growth factor-betas (TGF-betas) are multifunctional growth factors that are secreted as inactive (latent) precursors in large protein complexes. These complexes include the latency-associated propeptide (LAP) and a latent transforming growth factor-beta binding protein (LTBP). Four isoforms of LTBPs (LTBP-1-LTBP-4) have been cloned and are believed to be structural components of connective tissue microfibrils and local regulators of TGF-beta tissue deposition and signaling. By using a gene trap strategy that selects for integrations into genes induced transiently during early mouse development, we have disrupted the mouse homolog of the human LTBP-4 gene. Mice homozygous for the disrupted allele develop severe pulmonary emphysema, cardiomyopathy, and colorectal cancer. These highly tissue-specific abnormalities are associated with profound defects in the elastic fiber structure and with a reduced deposition of TGF-beta in the extracellular space. As a consequence, epithelial cells have reduced levels of phosphorylated Smad2 proteins, overexpress c-myc, and undergo uncontrolled proliferation. This phenotype supports the predicted dual role of LTBP-4 as a structural component of the extracellular matrix and as a local regulator of TGF-beta tissue deposition and signaling.

  8. Do Xylem Fibers Affect Vessel Cavitation Resistance?1

    PubMed Central

    Jacobsen, Anna L.; Ewers, Frank W.; Pratt, R. Brandon; Paddock, William A.; Davis, Stephen D.

    2005-01-01

    Possible mechanical and hydraulic costs to increased cavitation resistance were examined among six co-occurring species of chaparral shrubs in southern California. We measured cavitation resistance (xylem pressure at 50% loss of hydraulic conductivity), seasonal low pressure potential (Pmin), xylem conductive efficiency (specific conductivity), mechanical strength of stems (modulus of elasticity and modulus of rupture), and xylem density. At the cellular level, we measured vessel and fiber wall thickness and lumen diameter, transverse fiber wall and total lumen area, and estimated vessel implosion resistance using (t/b)h2, where t is the thickness of adjoining vessel walls and b is the vessel lumen diameter. Increased cavitation resistance was correlated with increased mechanical strength (r2 = 0.74 and 0.76 for modulus of elasticity and modulus of rupture, respectively), xylem density (r2 = 0.88), and Pmin (r2 = 0.96). In contrast, cavitation resistance and Pmin were not correlated with decreased specific conductivity, suggesting no tradeoff between these traits. At the cellular level, increased cavitation resistance was correlated with increased (t/b)h2 (r2 = 0.95), increased transverse fiber wall area (r2 = 0.89), and decreased fiber lumen area (r2 = 0.76). To our knowledge, the correlation between cavitation resistance and fiber wall area has not been shown previously and suggests a mechanical role for fibers in cavitation resistance. Fiber efficacy in prevention of vessel implosion, defined as inward bending or collapse of vessels, is discussed. PMID:16100359

  9. Microscopic and macroscopic instabilities in hyperelastic fiber composites

    NASA Astrophysics Data System (ADS)

    Slesarenko, Viacheslav; Rudykh, Stephan

    2017-02-01

    In this paper, we study the interplay between macroscopic and microscopic instabilities in 3D periodic fiber reinforced composites undergoing large deformations. We employ the Bloch-Floquet analysis to determine the onset of microscopic instabilities for composites with hyperelastic constituents. We show that the primary mode of buckling in the fiber composites is determined by the volume fraction of fibers and the contrast between elastic moduli of fiber and matrix phases. We find that for composites with volume fraction of fibers exceeding a threshold value, which depends on elastic modulus contrast, the primary buckling mode corresponds to the long wave or macroscopic instability. However, composites with a lower amount of fibers experience microscopic instabilities corresponding to wavy or helical buckling shapes. Buckling modes and critical wavelengths are shown to be highly tunable by material composition. A comparison between the instability behavior of 3D fiber composites and laminates, subjected to uniaxial compression, reveals the significant differences in critical strains, wavelengths, and transition points from macro- to microscopic instabilities in these composites.

  10. Lower extremity abnormalities in children.

    PubMed

    Sass, Pamela; Hassan, Ghinwa

    2003-08-01

    Rotational and angular problems are two types of lower extremity abnormalities common in children. Rotational problems include intoeing and out-toeing. Intoeing is caused by one of three types of deformity: metatarsus adductus, internal tibial torsion, and increased femoral anteversion. Out-toeing is less common than intoeing, and its causes are similar but opposite to those of intoeing. These include femoral retroversion and external tibial torsion. Angular problems include bowlegs and knock-knees. An accurate diagnosis can be made with careful history and physical examination, which includes torsional profile (a four-component composite of measurements of the lower extremities). Charts of normal values and values with two standard deviations for each component of the torsional profile are available. In most cases, the abnormality improves with time. A careful physical examination, explanation of the natural history, and serial measurements are usually reassuring to the parents. Treatment is usually conservative. Special shoes, cast, or braces are rarely beneficial and have no proven efficacy. Surgery is reserved for older children with deformity from three to four standard deviations from the normal.

  11. Normal and abnormal lid function.

    PubMed

    Rucker, Janet C

    2011-01-01

    This chapter on lid function is comprised of two primary sections, the first on normal eyelid anatomy, neurological innervation, and physiology, and the second on abnormal eyelid function in disease states. The eyelids serve several important ocular functions, the primary objectives of which are protection of the anterior globe from injury and maintenance of the ocular tear film. Typical eyelid behaviors to perform these functions include blinking (voluntary, spontaneous, or reflexive), voluntary eye closure (gentle or forced), partial lid lowering during squinting, normal lid retraction during emotional states such as surprise or fear (startle reflex), and coordination of lid movements with vertical eye movements for maximal eye protection. Detailed description of the neurological innervation patterns and neurophysiology of each of these lid behaviors is provided. Abnormal lid function is divided by conditions resulting in excessive lid closure (cerebral ptosis, apraxia of lid opening, blepharospasm, oculomotor palsy, Horner's syndrome, myasthenia gravis, and mechanical) and those resulting in excessive lid opening (midbrain lid retraction, facial nerve palsy, and lid retraction due to orbital disease).

  12. Abnormal retinal development associated with FRMD7 mutations

    PubMed Central

    Thomas, Mervyn G.; Crosier, Moira; Lindsay, Susan; Kumar, Anil; Araki, Masasuke; Leroy, Bart P.; McLean, Rebecca J.; Sheth, Viral; Maconachie, Gail; Thomas, Shery; Moore, Anthony T.; Gottlob, Irene

    2014-01-01

    Idiopathic infantile nystagmus (IIN) is a genetically heterogeneous disorder, often associated with FRMD7 mutations. As the appearance of the retina is reported to be normal based on conventional fundus photography, IIN is postulated to arise from abnormal cortical development. To determine whether the afferent visual system is involved in FRMD7 mutations, we performed in situ hybridization studies in human embryonic and fetal stages (35 days post-ovulation to 9 weeks post-conception). We show a dynamic retinal expression pattern of FRMD7 during development. We observe expression within the outer neuroblastic layer, then in the inner neuroblastic layer and at 9 weeks post-conception a bilaminar expression pattern. Expression was also noted within the developing optic stalk and optic disk. We identified a large cohort of IIN patients (n = 100), and performed sequence analysis which revealed 45 patients with FRMD7 mutations. Patients with FRMD7 mutations underwent detailed retinal imaging studies using ultrahigh-resolution optical coherence tomography. The tomograms were compared with a control cohort (n = 60). The foveal pit was significantly shallower in FRMD7 patients (P < 0.0001). The optic nerve head morphology was abnormal with significantly decreased optic disk area, retinal nerve fiber layer thickness, cup area and cup depth in FRMD7 patients (P < 0.0001). This study shows for the first time that abnormal afferent system development is associated with FRMD7 mutations and could be an important etiological factor in the development of nystagmus. PMID:24688117

  13. Abnormal retinal development associated with FRMD7 mutations.

    PubMed

    Thomas, Mervyn G; Crosier, Moira; Lindsay, Susan; Kumar, Anil; Araki, Masasuke; Leroy, Bart P; McLean, Rebecca J; Sheth, Viral; Maconachie, Gail; Thomas, Shery; Moore, Anthony T; Gottlob, Irene

    2014-08-01

    Idiopathic infantile nystagmus (IIN) is a genetically heterogeneous disorder, often associated with FRMD7 mutations. As the appearance of the retina is reported to be normal based on conventional fundus photography, IIN is postulated to arise from abnormal cortical development. To determine whether the afferent visual system is involved in FRMD7 mutations, we performed in situ hybridization studies in human embryonic and fetal stages (35 days post-ovulation to 9 weeks post-conception). We show a dynamic retinal expression pattern of FRMD7 during development. We observe expression within the outer neuroblastic layer, then in the inner neuroblastic layer and at 9 weeks post-conception a bilaminar expression pattern. Expression was also noted within the developing optic stalk and optic disk. We identified a large cohort of IIN patients (n = 100), and performed sequence analysis which revealed 45 patients with FRMD7 mutations. Patients with FRMD7 mutations underwent detailed retinal imaging studies using ultrahigh-resolution optical coherence tomography. The tomograms were compared with a control cohort (n = 60). The foveal pit was significantly shallower in FRMD7 patients (P < 0.0001). The optic nerve head morphology was abnormal with significantly decreased optic disk area, retinal nerve fiber layer thickness, cup area and cup depth in FRMD7 patients (P < 0.0001). This study shows for the first time that abnormal afferent system development is associated with FRMD7 mutations and could be an important etiological factor in the development of nystagmus.

  14. Elastic modulus of viral nanotubes

    NASA Astrophysics Data System (ADS)

    Zhao, Yue; Ge, Zhibin; Fang, Jiyu

    2008-09-01

    We report an experimental and theoretical study of the radial elasticity of tobacco mosaic virus (TMV) nanotubes. An atomic force microscope tip is used to apply small radial indentations to deform TMV nanotubes. The initial elastic response of TMV nanotubes can be described by finite-element analysis in 5nm indentation depths and Hertz theory in 1.5nm indentation depths. The derived radial Young’s modulus of TMV nanotubes is 0.92±0.15GPa from finite-element analysis and 1.0±0.2GPa from the Hertz model, which are comparable with the reported axial Young’s modulus of 1.1GPa [Falvo , Biophys. J. 72, 1396 (1997)].

  15. Structure and elasticity of glaucophane

    NASA Astrophysics Data System (ADS)

    Bezacier, L.; Mookherjee, M.

    2012-12-01

    We report equation of state and elasticity of glaucophane amphibole [Na2Mg3Al2Si8O22(OH)2] up to 9 GPa, which encompasses its experimentally observed stability field. The full elastic constant tensor reveals significantly larger stiffness along (100) plane. The [100] direction is relatively softer. This anisotropy is related to the stacking of the stiffer tetrahedral units along [010] and [001] directions within the crystal structure. Glaucophane is a dominant mineral constituent of blueschist facies rock, and has significantly lower velocities compared to garnet bearing eclogites. In addition, glaucophane is anisotropic and could account for the observed low velocity layer (LVL) in the subducting slabs at depth range within the thermodynamic stability of glaucophane.

  16. Elastic sealants for surgical applications.

    PubMed

    Annabi, Nasim; Yue, Kan; Tamayol, Ali; Khademhosseini, Ali

    2015-09-01

    Sealants have emerged as promising candidates for replacing sutures and staples to prevent air and liquid leakages during and after the surgeries. Their physical properties and adhesion strength to seal the wound area without limiting the tissue movement and function are key factors in their successful implementation in clinical practice. In this contribution, the advances in the development of elastic sealants formed from synthetic and natural materials are critically reviewed and their shortcomings are pointed out. In addition, we highlight the applications in which elasticity of the sealant is critical and outline the limitations of the currently available sealants. This review will provide insights for the development of novel bioadhesives with advanced functionality for surgical applications.

  17. Vibrations of elastically restrained frames

    NASA Astrophysics Data System (ADS)

    Albarracín, Carlos Marcelo; Grossi, Ricardo Oscar

    2005-07-01

    This paper deals with the determination of eigenfrequencies of a frame which consists of a beam supported by a column and is submitted to intermediate elastic constraints. The ends of the frame are elastically restrained against rotation and translation. The individual members of the frame are assumed to be governed by the transverse and axial vibration theory of an Euler-Bernoulli beam. The boundary and eigenvalue problem which governs the dynamical behavior of the frame structure is derived using the techniques of calculus of variations. Exact values of eigenfrequencies are determined by the application of the separation of variables method. Also, results are obtained by the use of the finite element method. The natural frequencies and mode shapes are presented for a wide range of values of the restraint parameters. Several particular cases are presented and some of these have been compared with those available in the literature.

  18. Elastic heterogeneity in metallic glasses.

    SciTech Connect

    Dmowski, , W.; Iwashita, T.; Chuang, C.-P.; Almer, J. D; Egami, T.; X-Ray Science Division; Univ. of Tennessee; ORNL

    2010-01-01

    When a stress is applied on a metallic glass it deforms following Hook's law. Therefore it may appear obvious that a metallic glass deforms elastically. Using x-ray diffraction and anisotropic pair-density function analysis we show that only about 3/4 in volume fraction of metallic glasses deforms elastically, whereas the rest of the volume is anelastic and in the experimental time scale deform without resistance. We suggest that this anelastic portion represents residual liquidity in the glassy state. Many theories, such as the free-volume theory, assume the density of defects in the glassy state to be of the order of 1%, but this result shows that it is as much as a quarter.

  19. Elastic Heterogeneity in Metallic Glasses

    NASA Astrophysics Data System (ADS)

    Dmowski, W.; Iwashita, T.; Chuang, C.-P.; Almer, J.; Egami, T.

    2010-11-01

    When a stress is applied on a metallic glass it deforms following Hook’s law. Therefore it may appear obvious that a metallic glass deforms elastically. Using x-ray diffraction and anisotropic pair-density function analysis we show that only about (3)/(4) in volume fraction of metallic glasses deforms elastically, whereas the rest of the volume is anelastic and in the experimental time scale deform without resistance. We suggest that this anelastic portion represents residual liquidity in the glassy state. Many theories, such as the free-volume theory, assume the density of defects in the glassy state to be of the order of 1%, but this result shows that it is as much as a quarter.

  20. Linear elastic fracture mechanics primer

    NASA Technical Reports Server (NTRS)

    Wilson, Christopher D.

    1992-01-01

    This primer is intended to remove the blackbox perception of fracture mechanics computer software by structural engineers. The fundamental concepts of linear elastic fracture mechanics are presented with emphasis on the practical application of fracture mechanics to real problems. Numerous rules of thumb are provided. Recommended texts for additional reading, and a discussion of the significance of fracture mechanics in structural design are given. Griffith's criterion for crack extension, Irwin's elastic stress field near the crack tip, and the influence of small-scale plasticity are discussed. Common stress intensities factor solutions and methods for determining them are included. Fracture toughness and subcritical crack growth are discussed. The application of fracture mechanics to damage tolerance and fracture control is discussed. Several example problems and a practice set of problems are given.

  1. Stability of elastically supported columns

    NASA Technical Reports Server (NTRS)

    Niles, Alfred S; Viscovich, Steven J

    1942-01-01

    A criterion is developed for the stiffness required of elastic lateral supports at the ends of a compression member to provide stability. A method based on this criterion is then developed for checking the stability of a continuous beam-column. A related method is also developed for checking the stability of a member of a pin-jointed truss against rotation in the plane of the truss.

  2. Gender-related difference in arterial elastance during exercise in patients with hypertension.

    PubMed

    Park, Sungha; Ha, Jong-Won; Shim, Chi Young; Choi, Eui-Young; Kim, Jin-Mi; Ahn, Jeong-Ah; Lee, Se-Wha; Rim, Se-Joong; Chung, Namsik

    2008-04-01

    Exercise intolerance and heart failure with preserved ejection fraction are common in females. Recently, arterial stiffness has been suggested to be a significant contributor in the development of heart failure. How gender difference affects arterial stiffening and its response to exercise is not well known. We hypothesized that arterial elastance index during exercise would be more abnormal in females with hypertension than males. Arterial elastance index was estimated as arterial end systolic pressure/stroke volume controlled for body surface area and was measured at rest and during graded supine bicycle exercise (25 watts, 3-minute increments) in 298 patients with hypertension (149 males; 149 females; mean age, 59). The subjects were divided into 2 groups by gender. Exercise duration was significantly shorter in females compared to males (692+/-222 versus 483+/-128 seconds, P<0.001). Although arterial elastance index at baseline was significantly higher in males, the magnitude of increase was steeper in females with the magnitude of change at 75 W of exercise being significantly higher in females compared to males (0.69+/-0.83 versus 0.43+/-0.69, P=0.018). Arterial elastance index at each stage of exercise up to 75 W was independently associated with decreased exercise duration. In conclusion, despite lower arterial elastance index at rest, the increase during exercise was steeper in women with hypertension, suggesting a gender-related difference in dynamic arterial stiffness. The arterial elastance index during exercise was significantly associated with exercise duration in patients with hypertension.

  3. Improved Indentation Test for Measuring Nonlinear Elasticity

    NASA Technical Reports Server (NTRS)

    Eldridge, Jeffrey I.

    2004-01-01

    A cylindrical-punch indentation technique has been developed as a means of measuring the nonlinear elastic responses of materials -- more specifically, for measuring the moduli of elasticity of materials in cases in which these moduli vary with applied loads. This technique offers no advantage for characterizing materials that exhibit purely linear elastic responses (constant moduli of elasticity, independent of applied loads). However, the technique offers a significant advantage for characterizing such important materials as plasma-sprayed thermal-barrier coatings, which, in cyclic loading, exhibit nonlinear elasticity with hysteresis related to compaction and sliding within their microstructures.

  4. Teaching nonlinear dynamics through elastic cords

    NASA Astrophysics Data System (ADS)

    Chacón, R.; Galán, C. A.; Sánchez-Bajo, F.

    2011-01-01

    We experimentally studied the restoring force of a length of stretched elastic cord. A simple analytical expression for the restoring force was found to fit all the experimental results for different elastic materials. Remarkably, this analytical expression depends upon an elastic-cord characteristic parameter which exhibits two limiting values corresponding to two nonlinear springs with different Hooke's elastic constants. Additionally, the simplest model of elastic cord dynamics is capable of exhibiting a great diversity of nonlinear phenomena, including bifurcations and chaos, thus providing a suitable alternative model system for discussing the basic essentials of nonlinear dynamics in the context of intermediate physics courses at university level.

  5. Phase diagram of elastic spheres.

    PubMed

    Athanasopoulou, L; Ziherl, P

    2017-02-15

    Experiments show that polymeric nanoparticles often self-assemble into several non-close-packed lattices in addition to the face-centered cubic lattice. Here, we explore theoretically the possibility that the observed phase sequences may be associated with the softness of the particles, which are modeled as elastic spheres interacting upon contact. The spheres are described by two finite-deformation theories of elasticity, the modified Saint-Venant-Kirchhoff model and the neo-Hookean model. We determine the range of indentations where the repulsion between the spheres is pairwise additive and agrees with the Hertz theory. By computing the elastic energies of nine trial crystal lattices at densities far beyond the Hertzian range, we construct the phase diagram and find the face- and body-centered cubic lattices as well as the A15 lattice and the simple hexagonal lattice, with the last two being stable at large densities where the spheres are completely faceted. These results are qualitatively consistent with observations, suggesting that deformability may indeed be viewed as a generic property that determines the phase behavior in nanocolloidal suspensions.

  6. Thermo-elastic behavior of deformed woven fabric composites at elevated temperatures: Part 1

    SciTech Connect

    Vu-Khanh, T.; Liu, B.

    1994-12-31

    This paper presents the results of a study on the effects of temperature on the thermo-elastic properties of woven fabric composites. The thermo-mechanical behavior of woven fabric composites is characterized by a laminate composed of four fictional unidirectional plies, called the sub-plies model. The model allows determination of the thermo-elastic properties of deformed fabric composites (non-orthogonal structure) and direct use of layered shell elements in finite element codes. A special procedure is also proposed to measure the fiber undulation effect and to predict the on-axis thermo-elastic coefficients of the equivalent constituent plies. The thermo-elastic behavior at elevated temperature was investigated on graphite/epoxy fabric composites. Experimental measurements were carried out from 23 C to 177 C. The results revealed that the equivalent thermal expansion coefficients of the sub-plies remain almost constant over a wide range of temperature. However, the equivalent elastic moduli and Poison`s ratio of the sub-plies vary nonlinearly with temperature. Semiempirical equations based on the experimental data were also developed to predict the equivalent on-axis thermo-elastic properties of the fictional constituent plies in the sub-plies model as a function of temperature.

  7. Creep of chemically vapor deposited SiC fibers

    NASA Technical Reports Server (NTRS)

    Dicarlo, J. A.

    1984-01-01

    The creep, thermal expansion, and elastic modulus properties for chemically vapor deposited SiC fibers were measured between 1000 and 1500 C. Creep strain was observed to increase logarithmically with time, monotonically with temperature, and linearly with tensile stress up to 600 MPa. The controlling activation energy was 480 + or - 20 kJ/mole. Thermal pretreatments near 1200 and 1450 C were found to significantly reduce fiber creep. These results coupled with creep recovery observations indicate that below 1400 C fiber creep is anelastic with neglible plastic component. This allowed a simple predictive method to be developed for describing fiber total deformation as a function of time, temperature, and stress. Mechanistic analysis of the property data suggests that fiber creep is the result of beta-SiC grain boundary sliding controlled by a small percent of free silicon in the grain boundaries.

  8. Ordering in stretch-tunable polymeric opal fibers.

    PubMed

    Finlayson, Chris E; Goddard, Chris; Papachristodoulou, Elpida; Snoswell, David R E; Kontogeorgos, Andreas; Spahn, Peter; Hellmann, G P; Hess, Ortwin; Baumberg, Jeremy J

    2011-02-14

    We demonstrate the production of high-quality polymer opal fibers in an industrially-scalable process. These fibers exhibit structural color, based on the self-assembly of sub-micron core-shell particles, with a spectrum which is stretch-tunable across the visible region. The internal substructure and ordering of fibers, as inferred from variations in spectral bandwidth, is studied using dark-field microscopy. We employ a granular model to examine flow and shear forces during the extrusion process, and the effects on particle ordering. In both theory and experiment, a concentric zone of the fiber near the exposed surface develops particularly strong structural color. Such elastically-tuned structurally colored fibers are of interest for many applications.

  9. Elastic proteins: biological roles and mechanical properties.

    PubMed Central

    Gosline, John; Lillie, Margo; Carrington, Emily; Guerette, Paul; Ortlepp, Christine; Savage, Ken

    2002-01-01

    The term 'elastic protein' applies to many structural proteins with diverse functions and mechanical properties so there is room for confusion about its meaning. Elastic implies the property of elasticity, or the ability to deform reversibly without loss of energy; so elastic proteins should have high resilience. Another meaning for elastic is 'stretchy', or the ability to be deformed to large strains with little force. Thus, elastic proteins should have low stiffness. The combination of high resilience, large strains and low stiffness is characteristic of rubber-like proteins (e.g. resilin and elastin) that function in the storage of elastic-strain energy. Other elastic proteins play very different roles and have very different properties. Collagen fibres provide exceptional energy storage capacity but are not very stretchy. Mussel byssus threads and spider dragline silks are also elastic proteins because, in spite of their considerable strength and stiffness, they are remarkably stretchy. The combination of strength and extensibility, together with low resilience, gives these materials an impressive resistance to fracture (i.e. toughness), a property that allows mussels to survive crashing waves and spiders to build exquisite aerial filters. Given this range of properties and functions, it is probable that elastic proteins will provide a wealth of chemical structures and elastic mechanisms that can be exploited in novel structural materials through biotechnology. PMID:11911769

  10. Lamb Wave Assessment of Fiber Volume Fraction in Composites

    NASA Technical Reports Server (NTRS)

    Seale, Michael D.; Smith, Barry T.; Prosser, W. H.; Zalameda, Joseph N.

    1998-01-01

    Among the various techniques available, ultrasonic Lamb waves offer a convenient method of examining composite materials. Since the Lamb wave velocity depends on the elastic properties of a material, an effective tool exists to evaluate composites by measuring the velocity of these waves. Lamb waves can propagate over long distances and are sensitive to the desired in-plane elastic properties of the material. This paper discusses a study in which Lamb waves were used to examine fiber volume fraction variations of approximately 0.40-0.70 in composites. The Lamb wave measurements were compared to fiber volume fractions obtained from acid digestion tests. Additionally, a model to predict the fiber volume fraction from Lamb wave velocity values was evaluated.

  11. Artificial neural network for modeling the elastic modulus of electrospun polycaprolactone/gelatin scaffolds.

    PubMed

    Vatankhah, Elham; Semnani, Dariush; Prabhakaran, Molamma P; Tadayon, Mahdi; Razavi, Shahnaz; Ramakrishna, Seeram

    2014-02-01

    Scaffolds for tissue engineering (TE) require the consideration of multiple aspects, including polymeric composition and the structure and mechanical properties of the scaffolds, in order to mimic the native extracellular matrix of the tissue. Electrospun fibers are frequently utilized in TE due to their tunable physical, chemical, and mechanical properties and porosity. The mechanical properties of electrospun scaffolds made from specific polymers are highly dependent on the processing parameters, which can therefore be tuned for particular applications. Fiber diameter and orientation along with polymeric composition are the major factors that determine the elastic modulus of electrospun nano- and microfibers. Here we have developed a neural network model to investigate the simultaneous effects of composition, fiber diameter and fiber orientation of electrospun polycaprolactone/gelatin mats on the elastic modulus of the scaffolds under ambient and simulated physiological conditions. The model generated might assist bioengineers to fabricate electrospun scaffolds with defined fiber diameters, orientations and constituents, thereby replicating the mechanical properties of the native target tissue.

  12. Investigation and modeling of the elastic-plastic fracture behavior of continuous woven fabric-reinforced ceramic composites

    SciTech Connect

    Kahl, W.K.

    1997-03-01

    The paper describes a study which attempted to extrapolate meaningful elastic-plastic fracture toughness data from flexure tests of a chemical vapor-infiltrated SiC/Nicalon fiber-reinforced ceramic matrix composite. Fibers in the fabricated composites were pre-coated with pyrolytic carbon to varying thicknesses. In the tests, crack length was not measured and the study employed an estimate procedure, previously used successfully for ductile metals, to derive J-R curve information. Results are presented in normalized load vs. normalized displacements and comparative J{sub Ic} behavior as a function of fiber precoating thickness.

  13. Design and Manufacture of Elastically Tailored Tow Placed Plates

    NASA Technical Reports Server (NTRS)

    Tatting, Brain F.; Guerdal, Zafer; Jegley, Dawn (Technical Monitor)

    2002-01-01

    Elastic stiffness tailoring of laminated composite panels by allowing the fibers to curve within the plane of the laminate is a relatively novel design concept that has been demonstrated to be both beneficial and practical. In particular, for structures with highly non-uniform stress states, such as the case of a flat panel with a central hole subjected to in-plane loading, the concept is likely to provide substantial improvements in load carrying capability. The objective of the present study is to determine the effectiveness of stiffness tailoring through the use of curvilinear fibers to reduce stress concentrations around the hole and improve the load carrying capability of panels with holes. In this study software was created that translates standard finite element models with traditional laminate definitions into ones that possess stacking sequences with curvilinear fiber paths that are directly manufacturable using an advanced tow placement machine. Preliminary designs for the manufacturing and testing phase were determined through rudimentary design studies for flat plates without holes under axial compression. These candidate designs were then analyzed using finite element models that accurately reflect the test conditions and geometries in order to select final designs for testing. A total of six large panels, measuring three feet by six feet, each of which are used to produce four specimens with or without holes, were fabricated and delivered to NASA for machining and testing.

  14. Breathing Monitor Using Dye-Doped Optical Fiber

    NASA Astrophysics Data System (ADS)

    Muto, Shinzo; Fukasawa, Akihiko; Ogawa, Takayuki; Morisawa, Masayuki; Ito, Hiroshi

    1990-08-01

    A new monitoring system of human breathing using umbelliferon dye-doped plastic fiber has been studied. Under UV light pumping, the fiber which was used as a sensor head generates blue fluorescence depending on human expiration. By converting the light signal to electronic pulses, the counting of breathing and real-time monitoring of abnormal breathing such as a heavy cough or a cloggy sputum have easily been obtained.

  15. Dynamics of Mechanical Signal Transmission through Prestressed Stress Fibers

    PubMed Central

    Hwang, Yongyun; Barakat, Abdul I.

    2012-01-01

    Transmission of mechanical stimuli through the actin cytoskeleton has been proposed as a mechanism for rapid long-distance mechanotransduction in cells; however, a quantitative understanding of the dynamics of this transmission and the physical factors governing it remains lacking. Two key features of the actin cytoskeleton are its viscoelastic nature and the presence of prestress due to actomyosin motor activity. We develop a model of mechanical signal transmission through prestressed viscoelastic actin stress fibers that directly connect the cell surface to the nucleus. The analysis considers both temporally stationary and oscillatory mechanical signals and accounts for cytosolic drag on the stress fibers. To elucidate the physical parameters that govern mechanical signal transmission, we initially focus on the highly simplified case of a single stress fiber. The results demonstrate that the dynamics of mechanical signal transmission depend on whether the applied force leads to transverse or axial motion of the stress fiber. For transverse motion, mechanical signal transmission is dominated by prestress while fiber elasticity has a negligible effect. Conversely, signal transmission for axial motion is mediated uniquely by elasticity due to the absence of a prestress restoring force. Mechanical signal transmission is significantly delayed by stress fiber material viscosity, while cytosolic damping becomes important only for longer stress fibers. Only transverse motion yields the rapid and long-distance mechanical signal transmission dynamics observed experimentally. For simple networks of stress fibers, mechanical signals are transmitted rapidly to the nucleus when the fibers are oriented largely orthogonal to the applied force, whereas the presence of fibers parallel to the applied force slows down mechanical signal transmission significantly. The present results suggest that cytoskeletal prestress mediates rapid mechanical signal transmission and allows

  16. Dynamics of mechanical signal transmission through prestressed stress fibers.

    PubMed

    Hwang, Yongyun; Barakat, Abdul I

    2012-01-01

    Transmission of mechanical stimuli through the actin cytoskeleton has been proposed as a mechanism for rapid long-distance mechanotransduction in cells; however, a quantitative understanding of the dynamics of this transmission and the physical factors governing it remains lacking. Two key features of the actin cytoskeleton are its viscoelastic nature and the presence of prestress due to actomyosin motor activity. We develop a model of mechanical signal transmission through prestressed viscoelastic actin stress fibers that directly connect the cell surface to the nucleus. The analysis considers both temporally stationary and oscillatory mechanical signals and accounts for cytosolic drag on the stress fibers. To elucidate the physical parameters that govern mechanical signal transmission, we initially focus on the highly simplified case of a single stress fiber. The results demonstrate that the dynamics of mechanical signal transmission depend on whether the applied force leads to transverse or axial motion of the stress fiber. For transverse motion, mechanical signal transmission is dominated by prestress while fiber elasticity has a negligible effect. Conversely, signal transmission for axial motion is mediated uniquely by elasticity due to the absence of a prestress restoring force. Mechanical signal transmission is significantly delayed by stress fiber material viscosity, while cytosolic damping becomes important only for longer stress fibers. Only transverse motion yields the rapid and long-distance mechanical signal transmission dynamics observed experimentally. For simple networks of stress fibers, mechanical signals are transmitted rapidly to the nucleus when the fibers are oriented largely orthogonal to the applied force, whereas the presence of fibers parallel to the applied force slows down mechanical signal transmission significantly. The present results suggest that cytoskeletal prestress mediates rapid mechanical signal transmission and allows

  17. Carbon-fiber technology

    NASA Technical Reports Server (NTRS)

    Hansen, C. F.; Parker, J. A.

    1980-01-01

    The state of the art of PAN based carbon fiber manufacture and the science of fiber behavior is surveyed. A review is given of the stabilization by oxidation and the subsequent carbonization of fibers, of the apparent structure of fibers deduced from scanning electron microscopy, from X-ray scattering, and from similarities with soft carbons, and of the known relations between fiber properties and heat treatment temperature. A simplified model is invoked to explain the electrical properties of fibers and recent quantum chemical calculations on atomic clusters are used to elucidate some aspects of fiber conductivity. Some effects of intercalation and oxidative modification of finished fibers are summarized.

  18. Optical diagnostics based on elastic scattering: An update of clinical demonstrations with the Optical Biopsy System

    SciTech Connect

    Bigio, I.J.; Boyer, J.; Johnson, T.M.; Lacey, J.; Mourant, J.R.; Conn, R.; Bohorfoush, A.

    1994-10-01

    The Los Alamos National Laboratory has continued the development of the Optical Biopsy System (OBS) for noninvasive, real-time in situ diagnosis of tissue pathologies. Our clinical studies have expanded since the last Biomedical Optics Europe conference (Budapest, September 1993), and we report here on the latest results of clinical tests in gastrointestinal tract. The OBS invokes a unique approach to optical diagnosis of tissue pathologies based on the elastic scattering properties, over a wide range of wavelengths, of the tissue. The use of elastic scattering as the key to optical tissue diagnostics in the OBS is based on the fact that many tissue pathologies, including a majority of cancer forms, manifest significant architectural changes at the cellular and sub-cellular level. Since the cellular components that cause elastic scattering have dimensions typically on the order of visible to near-IR wavelengths, the elastic (Mie) scattering properties will be wavelength dependent. Thus, morphology and size changes can be expected to cause significant changes in an optical signature that is derived from the wavelength-dependence of elastic scattering. The OBS employs a small fiberoptic probe that is amenable to use with any endoscope or catheter, or to direct surface examination. The probe is designed to be used in optical contact with the tissue under examination and has separate illuminating and collecting fibers. Thus, the light that is collected and transmitted to the analyzing spectrometer must first scatter through a small volume of the tissue before entering the collection fiber(s). Consequently, the system is also sensitive to the optical absorption spectrum of the tissue, over an effective operating range of <300 to 950 nm, and such absorption adds valuable complexity to the scattering spectral signature.

  19. Degradation of recycled PET fibers in Portland cement-based materials

    SciTech Connect

    Silva, D.A. . E-mail: denise@ecv.ufsc.br; Betioli, A.M.; Gleize, P.J.P.; Roman, H.R.; Gomez, L.A.; Ribeiro, J.L.D.

    2005-09-01

    In order to investigate the durability of recycled PET fibers embedded in cement-based materials, fiber-reinforced mortar specimens were tested until 164 days after mixing. Compressive, tensile, and flexural strengths, elasticity modulus, and toughness of the specimens were determined. The mortars were also analyzed by SEM. The results have shown that PET fibers have no significant influence on mortars strengths and elasticity modulus. However, the toughness indexes I {sub 5}, I {sub 10}, and I {sub 20} decreased with time due to the degradation of PET fibers by alkaline hydrolysis when embedded in the cement matrix. Fourier transform infrared spectroscopy (FT-IR) and SEM analysis of PET fibers immersed and kept for 150 days in alkaline solutions supported the conclusions.

  20. Mechanochromic photonic-crystal fibers based on continuous sheets of aligned carbon nanotubes.

    PubMed

    Sun, Xuemei; Zhang, Jing; Lu, Xin; Fang, Xin; Peng, Huisheng

    2015-03-16

    A new family of mechanochromic photonic-crystal fibers exhibits tunable structural colors under stretching. This novel mechanochromic fiber is prepared by depositing polymer microspheres onto a continuous aligned-carbon-nanotube sheet that has been wound on an elastic poly(dimethylsiloxane) fiber, followed by further embedding in poly(dimethylsiloxane). The color of the fiber can be tuned by varying the size and the center-to-center distance of the polymer spheres. It further experiences reversible and rapid multicolor changes during the stretch and release processes, for example, between red, green, and blue. Both the high sensitivity and stability were maintained after 1000 deformation cycles. These elastic photonic-crystal fibers were woven into patterns and smart fabrics for various display and sensing applications.

  1. Penny-shaped crack in a fiber-reinforced matrix. [elastostatics

    NASA Technical Reports Server (NTRS)

    Narayanan, T. V.; Erdogan, F.

    1974-01-01

    Using a slender inclusion model developed earlier, the elastostatic interaction problem between a penny-shaped crack and elastic fibers in an elastic matrix is formulated. For a single set and for multiple sets of fibers oriented perpendicularly to the plane of the crack and distributed symmetrically on concentric circles, the problem was reduced to a system of singular integral equations. Techniques for the regularization and for the numerical solution of the system are outlined. For various fiber geometries numerical examples are given, and distribution of the stress intensity factor along the crack border was obtained. Sample results showing the distribution of the fiber stress and a measure of the fiber-matrix interface shear are also included.

  2. Autosomal recessive micrencephaly with simplified gyral pattern, abnormal myelination and arthrogryposis.

    PubMed

    Sztriha, L; Al-Gazali, L I; Várady, E; Goebel, H H; Nork, M

    1999-06-01

    The clinical courses, neuroimaging and muscle biopsy findings of two infants born to an inbred Arab family are described. They had a syndrome of micrencephaly with simplified gyral pattern, abnormal myelin formation and arthrogryposis. Increased variation of fiber size was seen in the muscle biopsy, creatine kinase, however was normal. Large areas of muscle were replaced by adipofibrous tissue. The infants had dysmorphic features consistent with the fetal akinesia/hypokinesia sequence. The abnormalities were suggestive of microlissencephaly probably associated with a dysgenetic process in the muscles. The syndrome showed an autosomal recessive inheritance.

  3. Reversibly Actuating Solid Janus Polymeric Fibers.

    PubMed

    Ionov, Leonid; Stoychev, Georgi; Jehnichen, Dieter; Sommer, Jens Uwe

    2017-02-08

    It is commonly assumed that the substantial element of reversibly actuating soft polymeric materials is chemical cross-linking, which is needed to provide elasticity required for the reversible actuation. On the example of melt spun and three-dimensional printed Janus fibers, we demonstrate here for the first time that cross-linking is not an obligatory prerequisite for reversible actuation of solid entangled polymers, since the entanglement network itself can build elasticity during crystallization. Indeed, we show that not-cross-linked polymers, which typically demonstrate plastic deformation in melt, possess enough elastic behavior to actuate reversibly. The Janus polymeric structure bends because of contraction of the polymer and due to entanglements and formation of nanocrystallites upon cooling. Actuation upon melting is simply due to relaxation of the stressed nonfusible component. This approach opens perspectives for design of solid active materials and actuator for robotics, biotechnology, and smart textile applications. The great advantage of our principle is that it allows design of non-cross-linked self-moving materials, which are able to actuate in both water and air, which are not cross-linked. We demonstrate application of actuating fibers for design of walkers, structures with switchable length, width, and thickness, which can be used for smart textile applications.

  4. Parametric studies on effective elastic modulus of nano-clay/polymer composites

    NASA Astrophysics Data System (ADS)

    Thakur, Arvind Kumar; Srinivas, J.

    2016-04-01

    This paper proposes a methodology of finding effective elastic properties of nanoclay-reinforced polymer composites with aligned clay particles. When interphase regions exist between nanoclay platelets and polymer, numerical homogenization is initially required to identify the properties of effective particle consisting of both clay and interface regions. Once the elastic properties of equivalent particle are obtained, Mori-Tanaka approach is employed to identify all the effective properties of resultant composite. The methodology is implemented with a modular based computer program developed in MATLAB and the variation of longitudinal modulus as a function of weight fraction of nanoclay, aspect ratio of fibers, number of stacks, nanoclay volume fraction etc is reported. The empirical results are validated with a numerical model developed in ANSYS using a representative volume element for prediction of the elastic modulus. Results are illustrated with two cases of exfoliated morphology.

  5. Euler-Lagrange Elasticity: elasticity without stress or strain

    NASA Astrophysics Data System (ADS)

    Hardy, Humphrey

    2014-03-01

    A Euler-Lagrange (E-L) approach to elasticity is proposed that produces differential equations of elasticity without the need to define stress or strain tensors. The positions of the points within the body are the independent parameters instead of strain. Force replaces stress. The advantage of this approach is that the E-L differential equations are the same for both infinitesimal and finite deformations. Material properties are expressed in terms of the energy of deformation. The energy is expressed as a function of the principal invariants of the deformation gradient tensor. This scalar invariant representation of the energy of deformation enters directly into the E-L differential equations so that there is no need to define fourth order tensor material properties. By experimentally measuring the force and displacement of materials the functional form of the energy of deformation can be determined. The E-L differential equations can be input directly into finite element, finite difference, or other numerical models. If desired, stress and stain can be calculated as dependent parameters.

  6. Muscle fiber characteristics of broiler breast fillets with the wooden breast condition.

    Technology Transfer Automated Retrieval System (TEKTRAN)

    Broiler breast fillets exhibiting the wooden breast condition are described as having a rigid feel and abnormal texture attributes; however, changes at the muscle fiber level in wooden breast fillets are not well understood. The objective of this study was to compare the histochemical muscle fiber ...

  7. Time-temperature-stress dependence of boron fiber deformation

    NASA Technical Reports Server (NTRS)

    Dicarlo, J. A.

    1976-01-01

    The time-dependent deformation of boron fibers over the temperature range from -190 to 800 C is studied by flexural stress relaxation and flexural internal friction techniques on 203-micron diam specimen fibers commercially produced by chemical vapor deposition (CVD) on a 13-micron tungsten substrate. It is shown that up to at least 800 C all nonelastic behavior observed during axial deformation of CVD boron fibers can be explained solely by anelastic mechanisms and that although creep strains are small, boron fiber anelasticity can produce significant mechanical effects which would otherwise be neglected under the elastic approximation. Relations are obtained to demonstrate the considerable effects of anelasticity on such fiber/composite properties as modulus, creep, creep recovery, stress relaxation, and damping capacity. For an elastic-core/anelastic-sheath model, boron fibers on tungsten substrates are shown to have predictable fracture stresses for time-temperature conditions ranging from impact to long-time stress rupture. Possible techniques for altering these stresses are discussed.

  8. Fiber reinforced concrete: Characterization of flexural toughness and some studies on fiber-matrix bond-slip interaction

    NASA Astrophysics Data System (ADS)

    Dubey, Ashish

    frictional shear stress over the debonded interface is modeled using Coulomb's Law. Stresses required to cause initial, partial and complete debonding of the fiber-matrix interface are analyzed, and closed form solutions are derived to predict the complete fiber pullout response. Analysis shows that the initial debonding stress strongly depends upon fiber length and fiber elastic modulus. The process of interfacial debonding turns catastrophic at the instant the fiber pullout stress begins to drop with an increase in debond length. The magnitude of interfacial frictional shear stress along the embedded fiber length is found to vary as a result of the Poisson's contraction of the fiber. Moreover, Poisson's effect manifests itself in the form of a non-linear relationship between the peak pullout stress versus embedded fiber length plot. Based on energy considerations, an analytical solution is derived to compute the interfacial coefficient of friction. For both steel and polypropylene fibers, interfacial coefficient of friction is found to decrease exponentially with increase in pullout distance. Matrix wear resulting from fiber pullout appears to be responsible for the aforementioned physical phenomena. Parametric studies are carried out to investigate the influence of fiber-matrix interfacial properties (adhesional bond shear strength, normal contact stress and coefficient of friction) and elastic modulus of the fiber. (Abstract shortened by UMI.)

  9. Piezoresistive effect in carbon nanotube fibers.

    PubMed

    Lekawa-Raus, Agnieszka; Koziol, Krzysztof K K; Windle, Alan H

    2014-11-25

    The complex structure of the macroscopic assemblies of carbon nanotubes and variable intrinsic piezoresistivity of nanotubes themselves lead to highly interesting piezoresistive performance of this new type of conductive material. Here, we present an in-depth study of the piezoresistive effect in carbon nanotube fibers, i.e., yarnlike assemblies made purely of aligned carbon nanotubes, which are expected to find applications as electrical and electronic materials. The resistivity changes of carbon nanotube fibers were measured on initial loading, through the elastic/plastic transition, on cyclic loading and on stress relaxation. The various regimes of stress/strain behavior were modeled using a standard linear solid model, which was modified with an additional element in series to account for the observed creep behavior. On the basis of the experimental and modeling results, the origin of piezoresistivity is discussed. An additional effect on the resistivity was found as the fiber was held under load which led to observations of the effect of humidity and the associated water adsorption level on the resistivity. We show that the equilibrium uptake of moisture leads to the decrease in gauge factor of the fiber decrease, i.e., the reduction in the sensitivity of fiber resistivity to loading.

  10. Evaluation of a Hybrid Elastic EVA Glove

    NASA Technical Reports Server (NTRS)

    Korona, F. Adam; Akin, David

    2002-01-01

    The hybrid elastic design is based upon an American Society for Engineering Education (ASEE) glove designed by at the Space Systems Laboratory (SSL) in 1985. This design uses an elastic restraint layer instead of convolute joints to achieve greater dexterity and mobility during EVA (extravehicular activity). Two pilot studies and a main study were conducted using the hybrid elastic glove and 4000-series EMU (extravehicular activity unit) glove. Data on dexterity performance, joint range of motion, grip strength and perceived exertion was assessed for the EMU and hybrid elastic gloves with correlations to a barehanded condition. During this study, 30 test subjects performed multiple test sessions using a hybrid elastic glove and a 4000- series shuttle glove in a 4.3psid pressure environment. Test results to date indicate that the hybrid elastic glove performance is approximately similar to the performance of the 4000-series glove.

  11. Elastic, Conductive, Polymeric Hydrogels and Sponges

    PubMed Central

    Lu, Yun; He, Weina; Cao, Tai; Guo, Haitao; Zhang, Yongyi; Li, Qingwen; Shao, Ziqiang; Cui, Yulin; Zhang, Xuetong

    2014-01-01

    As a result of inherent rigidity of the conjugated macromolecular chains resulted from the delocalized π-electron system along the polymer backbone, it has been a huge challenge to make conducting polymer hydrogels elastic by far. Herein elastic and conductive polypyrrole hydrogels with only conducting polymer as the continuous phase have been simply synthesized in the indispensable conditions of 1) mixed solvent, 2) deficient oxidant, and 3) monthly secondary growth. The elastic mechanism and oxidative polymerization mechanism on the resulting PPy hydrogels have been discussed. The resulting hydrogels show some novel properties, e.g., shape memory elasticity, fast functionalization with various guest objects, and fast removal of organic infectants from aqueous solutions, all of which cannot be observed from traditional non-elastic conducting polymer counterparts. What's more, light-weight, elastic, and conductive organic sponges with excellent stress-sensing behavior have been successfully achieved via using the resulting polypyrrole hydrogels as precursors. PMID:25052015

  12. Electrocardiographic abnormalities in patients with Lassa fever.

    PubMed

    Cummins, D; Bennett, D; Fisher-Hoch, S P; Farrar, B; McCormick, J B

    1989-10-01

    Electrocardiograms from 32 patients with acute Lassa fever were abnormal in over 70% of cases. The changes noted included non-specific ST-segment and T-wave abnormalities, ST-segment elevation, generalized low-voltage complexes, and changes reflecting electrolyte disturbance. None of the abnormalities correlated with clinical severity of infection, serum transaminase levels, or eventual outcome. ECG changes are common in Lassa fever, but usually unassociated with clinical manifestations of myocarditis.

  13. Electrochemical Skin Conductance Correlates with Skin Nerve Fiber Density

    PubMed Central

    Novak, Peter

    2016-01-01

    Purpose: Electrochemical skin conductance (ESC) using reverse iontophoresis and chronoamperometry has been used to evaluate abnormal function of small fibers. How ESC correlates with loss of small fibers in skin is unclear. Methods: This was a prospective, blinded study. The primary outcome measure was the correlation between ESC at the feet and results of skin biopsies including epidermal nerve fiber density (ENFD) and sweat gland nerve fiber density (SGNFD) at the distal leg. ESC, ENFD, and SGNFD data were normalized by adjusting for weight. The secondary outcome measures were the correlation between ESC and the following variables: quantitative sudomotor axon reflex test (QSART) and symptom scales (neuropathy, pain and autonomic). Results: Eighty-one patients (mean ± sd): age = 53.3 ± 17.3, men/women = 25/56 were enrolled in the study. ESC was reduced in subjects with abnormally low ENFD (ENFD normal/abnormal, ESC = 1.17 ± 0.27/0.87 ± 0.34 μSiemens/kg, p < 0.0008) and abnormally low SGNFD (SGNFD normal/abnormal ESC = 1.09 ± 0.34/0.78 ± 0.3 μSiemens/kg, p < 0.0003). ESC correlated with ENFD (ρ = 0.73, p = 0.0001) and SGNFD (ρ = 0.64, p = 0.0001). ESC did not correlate with symptom scales. Conclusion: ESC is diminished in subjects who have a reduced number of small fibers in the skin and the ESC reduction is proportional to ENFD and SGNFD. ESC can be useful in detecting loss of small nerve fibers. PMID:27605912

  14. Detecting skin malignancy using elastic light scattering spectroscopy

    NASA Astrophysics Data System (ADS)

    Canpolat, Murat; Akman, Ayşe; Çiftçioğlu, M. Akif; Alpsoy, Erkan

    2007-07-01

    We have used elastic light scattering spectroscopy to differentiate between malign and benign skin lesions. The system consists of a UV spectrometer, a single optical fiber probe and a laptop. The single optical fiber probe was used for both delivery and detection of white light to tissue and from the tissue. The single optical fiber probe received singly scattered photons rather than diffused photons in tissue. Therefore, the spectra are correlated with morphological differences of the cells. It has been shown that spectra of malign skin lesions are different than spectra of benign skin lesions. While slopes of the spectra taken on benign lesions or normal skin tissues were positive, slopes of the spectra taken on malign skin lesions tissues were negative. In vivo experiments were conducted on 20 lesions from 18 patients (11 men with mean age of 68 +/- 9 years and 7 women with mean age of 52 +/- 20 years) applied to the Department of Dermatology and Venerology. Before the biopsy, spectra were taken on the lesion and adjacent (approximately 1 cm distant) normal-appearing skin. Spectra of the normal skin were used as a control group. The spectra were correlated to the pathology results with sensitivity and specificity of 82% and 89%, respectively. Due to small diameter of fiber probe and limited number of sampling (15), some positive cases are missed, which is lowered the sensitivity of the system. The results are promising and could suggest that the system may be able to detect malignant skin lesion non-invasively and in real time.

  15. [Renal abnormalities in ankylosing spondylitis].

    PubMed

    Samia, Barbouch; Hazgui, Faiçal; Abdelghani, Khaoula Ben; Hamida, Fethi Ben; Goucha, Rym; Hedri, Hafedh; Taarit, Chokri Ben; Maiz, Hedi Ben; Kheder, Adel

    2012-07-01

    We will study the epidemiologic, clinical, biological, therapeutic, prognostic characteristics and predictive factors of development of nephropathy in ankylosing spondylitis patients. We retrospectively reviewed the medical record of 32 cases with renal involvement among 212 cases of ankylosing spondylitis followed in our service during the period spread out between 1978 and 2006. The renal involvement occurred in all patients a mean of 12 years after the clinical onset of the rheumatic disease. Thirty-two patients presented one or more signs of renal involvement: microscopic hematuria in 22 patients, proteinuria in 23 patients, nephrotic syndrome in 11 patients and decreased renal function in 24 patients (75%). Secondary renal amyloidosis (13 patients), which corresponds to a prevalence of 6,1% and tubulointerstitial nephropathy (7 patients) were the most common cause of renal involvement in ankylosing spondylitis followed by IgA nephropathy (4 patients). Seventeen patients evolved to the end stage renal disease after an average time of 29.8 ± 46 months. The average follow-up of the patients was 4,4 years. By comparing the 32 patients presenting a SPA and renal disease to 88 with SPA and without nephropathy, we detected the predictive factors of occurred of nephropathy: tobacco, intense inflammatory syndrome, sacroileite stage 3 or 4 and presence of column bamboo. The finding of 75% of the patients presented a renal failure at the time of the diagnosis of renal involvement suggests that evidence of renal abnormality involvement should be actively sought in this disease.

  16. Abnormal band of lateral meniscus.

    PubMed

    Giordano, Brian; Goldblatt, John

    2009-01-01

    This article describes a case of an "abnormal band" of the lateral meniscus, extending from the posterior horn of the true lateral meniscus to its antero-mid portion, observed during arthroscopy in a 45-year-old white man of Bosnian descent. The periphery of the aberrant lateral meniscus was freely mobile, and not connected to the underlying true lateral meniscus. Preoperative physical examination findings were consistent with medial-sided meniscal pathology only; however, evidence of an anomalous lateral meniscus was seen with magnetic resonance imaging. This anatomical pattern is rare and has been reported in the literature only once, in a report of 2 Asian patients. This article illustrates an anatomical variant of the lateral meniscus in a non-Asian patient with a clinical presentation that has not been previously described. In addition to the case report, the article presents a comprehensive review of the existing body of literature on anomalous lateral meniscus patterns. We believe that the definitions of the types of aberrant meniscus can be clarified to establish improved accuracy in reporting.

  17. Biochemical abnormalities in Pearson syndrome.

    PubMed

    Crippa, Beatrice Letizia; Leon, Eyby; Calhoun, Amy; Lowichik, Amy; Pasquali, Marzia; Longo, Nicola

    2015-03-01

    Pearson marrow-pancreas syndrome is a multisystem mitochondrial disorder characterized by bone marrow failure and pancreatic insufficiency. Children who survive the severe bone marrow dysfunction in childhood develop Kearns-Sayre syndrome later in life. Here we report on four new cases with this condition and define their biochemical abnormalities. Three out of four patients presented with failure to thrive, with most of them having normal development and head size. All patients had evidence of bone marrow involvement that spontaneously improved in three out of four patients. Unique findings in our patients were acute pancreatitis (one out of four), renal Fanconi syndrome (present in all patients, but symptomatic only in one), and an unusual organic aciduria with 3-hydroxyisobutyric aciduria in one patient. Biochemical analysis indicated low levels of plasma citrulline and arginine, despite low-normal ammonia levels. Regression analysis indicated a significant correlation between each intermediate of the urea cycle and the next, except between ornithine and citrulline. This suggested that the reaction catalyzed by ornithine transcarbamylase (that converts ornithine to citrulline) might not be very efficient in patients with Pearson syndrome. In view of low-normal ammonia levels, we hypothesize that ammonia and carbamylphosphate could be diverted from the urea cycle to the synthesis of nucleotides in patients with Pearson syndrome and possibly other mitochondrial disorders.

  18. Composite Fiber Hazards

    DTIC Science & Technology

    1990-12-01

    34L boton Ion a tungsten boride core, and appear more like fine wires ,tin fibers. The fibers are combined with an epoxy matrix to form a prepreg j i...a 8-hour TWA Recommended Exposure Limit (REL) for fibrous glass of 3 fibers/cm3 for fibers with length >10 Jim and diameter ɛ.5 pm, and total

  19. Radiologic atlas of pulmonary abnormalities in children

    SciTech Connect

    Singleton, E.B.; Wagner, M.L.; Dutton, R.V.

    1988-01-01

    This book is an atlas about thoracic abnormalities in infants and children. The authors include computed tomographic, digital subtraction angiographic, ultrasonographic, and a few magnetic resonance (MR) images. They recognize and discuss how changes in the medical treatment of premature infants and the management of infection and pediatric tumors have altered some of the appearances and considerations in these diseases. Oriented toward all aspects of pulmonary abnormalities, the book starts with radiographic techniques and then discusses the normal chest, the newborn, infections, tumors, and pulmonary vascular diseases. There is comprehensive treatment of mediastinal abnormalities and a discussion of airway abnormalities.

  20. Inversion of elastic impedance for unconsolidated sediments

    USGS Publications Warehouse

    Lee, Myung W.

    2006-01-01

    Elastic properties of gas-hydrate-bearing sediments are important for quantifying gas hydrate amounts as well as discriminating the gas hydrate effect on velocity from free gas or pore pressure. This paper presents an elastic inversion method for estimating elastic properties of gas-hydrate-bearing sediments from angle stacks using sequential inversion of P-wave impedance from the zero-offset stack and S-wave impedance from the far-offset stack without assuming velocity ratio.

  1. Multi-spectral photoacoustic elasticity tomography

    PubMed Central

    Liu, Yubin; Yuan, Zhen

    2016-01-01

    The goal of this work was to develop and validate a spectrally resolved photoacoustic imaging method, namely multi-spectral photoacoustic elasticity tomography (PAET) for quantifying the physiological parameters and elastic modulus of biological tissues. We theoretically and experimentally examined the PAET imaging method using simulations and in vitro experimental tests. Our simulation and in vitro experimental results indicated that the reconstructions were quantitatively accurate in terms of sizes, the physiological and elastic properties of the targets. PMID:27699101

  2. Elastic scattering with weakly bound projectiles

    SciTech Connect

    Figueira, J. M.; Abriola, D.; Arazi, A.; Capurro, O. A.; Marti, G. V.; Martinez Heinmann, D.; Pacheco, A. J.; Testoni, J. E.; Barbara, E. de; Fernandez Niello, J. O.; Padron, I.; Gomes, P. R. S.; Lubian, J.

    2007-02-12

    Possible effects of the break-up channel on the elastic scattering threshold anomaly has been investigated. We used the weakly bound 6,7Li nuclei, which is known to undergo break-up, as projectiles in order to study the elastic scattering on a 27Al target. In this contribution we present preliminary results of these experiments, which were analyzed in terms of the Optical Model and compared with other elastic scattering data using weakly bound nuclei as projectile.

  3. Microscopic theory of rubber elasticity.

    PubMed

    Oyerokun, Folusho T; Schweizer, Kenneth S

    2004-05-15

    A microscopic integral equation theory of elasticity in polymer liquids and networks is developed which addresses the nonclassical problem of the consequences of interchain repulsive interactions and packing correlations on mechanical response. The theory predicts strain induced softening, and a nonclassical intermolecular contribution to the linear modulus. The latter is of the same magnitude as the classical single chain entropy contribution at low polymer concentrations, but becomes much more important in the melt state, and dominant as the isotropic-nematic liquid crystal phase transition is approached. Comparison of the calculated stress-strain curve and induced nematic order parameter with computer simulations show good agreement. A nearly quadratic dependence of the linear elastic modulus on segmental concentration is found, as well as a novel fractional power law dependence on degree of polymerization. Quantitative comparison of the theory with experiments on polydimethylsiloxane networks are presented and good agreement is found. However, a nonzero modulus in the long chain limit is not predicted since quenched chemical crosslinks and trapped entanglements are not explicitly taken into account. The theory is generalizable to treat the structure, thermodynamics and mechanical response of nematic elastomers.

  4. Electron-Hydrogen Elastic Scattering

    NASA Technical Reports Server (NTRS)

    Bhatia, A. K.

    2004-01-01

    Scattering by single-electron systems is always of interest because the wave function of the target is known exactly. Various approximations have been employed to take into account distortion produced in the target. Among them are the method of polarized orbitals and the close coupling approximation. Recently, e-H and e-He+ S-wave scattering in the elastic region has been studied using the Feshbach projection operator formalism. In this approach, the usual Hartree-Fock and exchange potentials are augmented by an optical potential and the resulting phase shifts have rigorous lower bounds. Now this method is being applied to the e-H P-wave scattering in the elastic region. The number of terms in the Hylleraas-type wave function for the 1,3 P phase shifts is 84 and the resulting phase shifts (preliminary) are given. The results have been given up to five digits because to that accuracy they are rigorous lower bounds. They are in general agreement with the variational (VAR) results of Armstead, and those obtained from the intermediate energy R-matrix method (RM) of Scholz et al., and the finite element method (FEM) of Botero and Shertzer. The later two methods do not provide any bounds on phase shifts.

  5. Pneumatic Variable Series Elastic Actuator.

    PubMed

    Zheng, Hao; Wu, Molei; Shen, Xiangrong

    2016-08-01

    Inspired by human motor control theory, stiffness control is highly effective in manipulation and human-interactive tasks. The implementation of stiffness control in robotic systems, however, has largely been limited to closed-loop control, and suffers from multiple issues such as limited frequency range, potential instability, and lack of contribution to energy efficiency. Variable-stiffness actuator represents a better solution, but the current designs are complex, heavy, and bulky. The approach in this paper seeks to address these issues by using pneumatic actuator as a variable series elastic actuator (VSEA), leveraging the compressibility of the working fluid. In this work, a pneumatic actuator is modeled as an elastic element with controllable stiffness and equilibrium point, both of which are functions of air masses in the two chambers. As such, for the implementation of stiffness control in a robotic system, the desired stiffness/equilibrium point can be converted to the desired chamber air masses, and a predictive pressure control approach is developed to control the timing of valve switching to obtain the desired air mass while minimizing control action. Experimental results showed that the new approach in this paper requires less expensive hardware (on-off valve instead of proportional valve), causes less control action in implementation, and provides good control performance by leveraging the inherent dynamics of the actuator.

  6. Hummingbird tongues are elastic micropumps.

    PubMed

    Rico-Guevara, Alejandro; Fan, Tai-Hsi; Rubega, Margaret A

    2015-08-22

    Pumping is a vital natural process, imitated by humans for thousands of years. We demonstrate that a hitherto undocumented mechanism of fluid transport pumps nectar onto the hummingbird tongue. Using high-speed cameras, we filmed the tongue-fluid interaction in 18 hummingbird species, from seven of the nine main hummingbird clades. During the offloading of the nectar inside the bill, hummingbirds compress their tongues upon extrusion; the compressed tongue remains flattened until it contacts the nectar. After contact with the nectar surface, the tongue reshapes filling entirely with nectar; we did not observe the formation of menisci required for the operation of capillarity during this process. We show that the tongue works as an elastic micropump; fluid at the tip is driven into the tongue's grooves by forces resulting from re-expansion of a collapsed section. This work falsifies the long-standing idea that capillarity is an important force filling hummingbird tongue grooves during nectar feeding. The expansive filling mechanism we report in this paper recruits elastic recovery properties of the groove walls to load nectar into the tongue an order of magnitude faster than capillarity could. Such fast filling allows hummingbirds to extract nectar at higher rates than predicted by capillarity-based foraging models, in agreement with their fast licking rates.

  7. Hummingbird tongues are elastic micropumps

    PubMed Central

    Rico-Guevara, Alejandro; Fan, Tai-Hsi; Rubega, Margaret A.

    2015-01-01

    Pumping is a vital natural process, imitated by humans for thousands of years. We demonstrate that a hitherto undocumented mechanism of fluid transport pumps nectar onto the hummingbird tongue. Using high-speed cameras, we filmed the tongue–fluid interaction in 18 hummingbird species, from seven of the nine main hummingbird clades. During the offloading of the nectar inside the bill, hummingbirds compress their tongues upon extrusion; the compressed tongue remains flattened until it contacts the nectar. After contact with the nectar surface, the tongue reshapes filling entirely with nectar; we did not observe the formation of menisci required for the operation of capillarity during this process. We show that the tongue works as an elastic micropump; fluid at the tip is driven into the tongue's grooves by forces resulting from re-expansion of a collapsed section. This work falsifies the long-standing idea that capillarity is an important force filling hummingbird tongue grooves during nectar feeding. The expansive filling mechanism we report in this paper recruits elastic recovery properties of the groove walls to load nectar into the tongue an order of magnitude faster than capillarity could. Such fast filling allows hummingbirds to extract nectar at higher rates than predicted by capillarity-based foraging models, in agreement with their fast licking rates. PMID:26290074

  8. Joint strength measurements of individual fiber-fiber bonds: An atomic force microscopy based method

    NASA Astrophysics Data System (ADS)

    Schmied, Franz J.; Teichert, Christian; Kappel, Lisbeth; Hirn, Ulrich; Schennach, Robert

    2012-07-01

    We are introducing a method to measure tensile strength of individual fiber-fiber bonds within a breaking force range of 0.01 mN-1 mN as well as the energy consumed during breaking. Until now, such a method was not available. Using a conventional atomic force microscope and a specifically designed sample holder, the desired force and the breaking behavior can be analyzed by two different approaches. First, dynamic loading can be applied, where force-versus-distance curves are employed to determine the proportions of elastic energy and energy dissipated in the bond. Second, static loading is utilized to study viscoelastic behavior and calculate viscoelastic energy contributions. To demonstrate the capability of the proposed method, we are presenting results for breaking strength of kraft pulp fiber-fiber bonds in tensile opening mode. The procedure is by no means restricted to cellulose fibers, it has the potential to quantify joint strength of micrometer-sized fibers in general.

  9. An overview of self-consistent methods for fiber-reinforced composites

    NASA Technical Reports Server (NTRS)

    Gramoll, Kurt C.; Freed, Alan D.; Walker, Kevin P.

    1991-01-01

    The Walker et al. (1989) self-consistent method to predict both the elastic and the inelastic effective material properties of composites is examined and compared with the results of other self-consistent and elastically based solutions. The elastic part of their method is shown to be identical to other self-consistent methods for non-dilute reinforced composite materials; they are the Hill (1965), Budiansky (1965), and Nemat-Nasser et al. (1982) derivations. A simplified form of the non-dilute self-consistent method is also derived. The predicted, elastic, effective material properties for fiber reinforced material using the Walker method was found to deviate from the elasticity solution for the v sub 31, K sub 12, and mu sub 31 material properties (fiber is in the 3 direction) especially at the larger volume fractions. Also, the prediction for the transverse shear modulus, mu sub 12, exceeds one of the accepted Hashin bounds. Only the longitudinal elastic modulus E sub 33 agrees with the elasticity solution. The differences between the Walker and the elasticity solutions are primarily due to the assumption used in the derivation of the self-consistent method, i.e., the strain fields in the inclusions and the matrix are assumed to remain constant, which is not a correct assumption for a high concentration of inclusions.

  10. Fiber optic connector

    DOEpatents

    Rajic, Slobodan; Muhs, Jeffrey D.

    1996-01-01

    A fiber optic connector and method for connecting composite materials within which optical fibers are imbedded. The fiber optic connector includes a capillary tube for receiving optical fibers at opposing ends. The method involves inserting a first optical fiber into the capillary tube and imbedding the unit in the end of a softened composite material. The capillary tube is injected with a coupling medium which subsequently solidifies. The composite material is machined to a desired configuration. An external optical fiber is then inserted into the capillary tube after fluidizing the coupling medium, whereby the optical fibers are coupled.

  11. Fiber optic temperature sensor

    NASA Technical Reports Server (NTRS)

    Sawatari, Takeo (Inventor); Gaubis, Philip A. (Inventor)

    2000-01-01

    A fiber optic temperature sensor uses a light source which transmits light through an optical fiber to a sensor head at the opposite end of the optical fiber from the light source. The sensor head has a housing coupled to the end of the optical fiber. A metallic reflective surface is coupled to the housing adjacent the end of the optical fiber to form a gap having a predetermined length between the reflective surface and the optical fiber. A detection system is also coupled to the optical fiber which determines the temperature at the sensor head from an interference pattern of light which is reflected from the reflective surface.

  12. Fiber optic temperature sensor

    NASA Technical Reports Server (NTRS)

    Sawatari, Takeo (Inventor); Gaubis, Philip A. (Inventor); Mattes, Brenton L. (Inventor); Charnetski, Clark J. (Inventor)

    1999-01-01

    A fiber optic temperature sensor uses a light source which transmits light through an optical fiber to a sensor head at the opposite end of the optical fiber from the light source. The sensor head has a housing coupled to the end of the optical fiber. A metallic reflective surface is coupled to the housing adjacent the end of the optical fiber to form a gap having a predetermined length between the reflective surface and the optical fiber. A detection system is also coupled to the optical fiber which determines the temperature at the sensor head from an interference pattern of light which is reflected from the reflective surface.

  13. Fiber optic connector

    DOEpatents

    Rajic, S.; Muhs, J.D.

    1996-10-22

    A fiber optic connector and method for connecting composite materials within which optical fibers are imbedded are disclosed. The fiber optic connector includes a capillary tube for receiving optical fibers at opposing ends. The method involves inserting a first optical fiber into the capillary tube and imbedding the unit in the end of a softened composite material. The capillary tube is injected with a coupling medium which subsequently solidifies. The composite material is machined to a desired configuration. An external optical fiber is then inserted into the capillary tube after fluidizing the coupling medium, whereby the optical fibers are coupled. 3 figs.

  14. Elastic moduli of pyrope rich garnets

    NASA Astrophysics Data System (ADS)

    Pandey, B. K.; Pandey, A. K.; Singh, C. K.

    2013-06-01

    The elastic properties of minerals depend on its composition, crystal structure, temperature and level of defects. The elastic parameters are important for the interpretation of the structure and composition of the garnet rich family. In present work we have calculated the elastic moduli such as isothermal bulk modulus, Young's modulus and Shear modulus over a wide range of temperature from 300 K to 1000 K by using Birch EOS and Poirrier Tarantola equation of state. The obtained results are compared with the experimental results obtained by measuring the elastic moduli of single crystal. The calculated results show that the logarithmic isothermal EOS does not cooperate well with experimental results.

  15. Faraday wave lattice as an elastic metamaterial.

    PubMed

    Domino, L; Tarpin, M; Patinet, S; Eddi, A

    2016-05-01

    Metamaterials enable the emergence of novel physical properties due to the existence of an underlying subwavelength structure. Here, we use the Faraday instability to shape the fluid-air interface with a regular pattern. This pattern undergoes an oscillating secondary instability and exhibits spontaneous vibrations that are analogous to transverse elastic waves. By locally forcing these waves, we fully characterize their dispersion relation and show that a Faraday pattern presents an effective shear elasticity. We propose a physical mechanism combining surface tension with the Faraday structured interface that quantitatively predicts the elastic wave phase speed, revealing that the liquid interface behaves as an elastic metamaterial.

  16. Rubber Elasticity in Highly Crosslinked Polyesters.

    DTIC Science & Technology

    Esters, *Polymers, *Elastic properties, Rubber, Propylene glycol , Maleic acid, Anhydrides, Phthalic acids, Mechanical properties, Molecular structure, Crosslinking(Chemistry), Polymerization, Styrenes, Temperature, Transition temperature, Molecular weight

  17. Coatings for graphite fibers

    NASA Technical Reports Server (NTRS)

    Galasso, F. S.; Scola, D. A.; Veltri, R. D.

    1980-01-01

    Graphite fibers released from composites during burning or an explosion caused shorting of electrical and electronic equipment. Silicon carbide, silica, silicon nitride and boron nitride were coated on graphite fibers to increase their electrical resistances. Resistances as high as three orders of magnitude higher than uncoated fiber were attained without any significant degradation of the substrate fiber. An organo-silicone approach to produce coated fibers with high electrical resistance was also used. Celion 6000 graphite fibers were coated with an organo-silicone compound, followed by hydrolysis and pyrolysis of the coating to a silica-like material. The shear and flexural strengths of composites made from high electrically resistant fibers were considerably lower than the shear and flexural strengths of composites made from the lower electrically resistant fibers. The lower shear strengths of the composites indicated that the coatings on these fibers were weaker than the coating on the fibers which were pyrolyzed at higher temperature.

  18. Characterization and modeling of performance of Polymer Composites Reinforced with Highly Non-Linear Cellulosic Fibers

    NASA Astrophysics Data System (ADS)

    Rozite, L.; Joffe, R.; Varna, J.; Nyström, B.

    2012-02-01

    The behaviour of highly non-linear cellulosic fibers and their composite is characterized. Micro-mechanisms occurring in these materials are identified. Mechanical properties of regenerated cellulose fibers and composites are obtained using simple tensile test. Material visco-plastic and visco-elastic properties are analyzed using creep tests. Two bio-based resins are used in this study - Tribest and EpoBioX. The glass and flax fiber composites are used as reference materials to compare with Cordenka fiber laminates.

  19. Modeling fiber dynamics and transport in the carding process

    NASA Astrophysics Data System (ADS)

    Wibberly, Leonard Daniel

    1999-12-01

    A carding machine processes short, crimped fibers by feeding disorganized tufts onto a rotating cylinder coated with wires that engage the fibers. This cylinder works in conjunction with pun of smaller cylinders (carding stations) dig are simply coated and rotating at carefully calibrated speeds in order to separate, redistribute, align and straighten the fibers. This process produces a relatively uniform sheet of fibers with properties desirable for the textile industry. One method used to analyze the processing of the fibers is to insert a small number of easily identified tracer fibers in the card and observe their behavior at different stages throughout the card. In a similar manner, this research develops a technique to follow a representative sampling of theoretical fibers through a structure simulating the card, complete with forces attributable to the presence of other fibers, the surrounding air, and the wires on the surfaces. In this work a model of the card is proposed consisting of three essential elements. First, equations are developed to estimate the density and velocity of the overall fiber mass with a partial differential equation (PDE) derived from a random-walk formulation of the fiber motion in an interface between two surfaces. Next, a numerical solution is obtained for the steady state Navier-Stokes equations for air-flow in the space between the three rotating cylinders of a single carding station. Finally, these velocities and densities are applied to the dynamics of individual fibers, each represented as a chain of elastic-jointed segments in a moving fluid, subject to viscous drag, with the possibility of being tugged at some point with a fixed velocity by either a wire on the surface or another fiber. All of these elements are tied into the overall structure of a simple card with three rotating Cylinders, interfaces between cylinders, triangular cavity, fiber input and output points and the transfer of fibers between surfaces. Fibers are

  20. Alumina fiber strength improvement

    NASA Technical Reports Server (NTRS)

    Pepper, R. T.; Nelson, D. C.

    1982-01-01

    The effective fiber strength of alumina fibers in an aluminum composite was increased to 173,000 psi. A high temperature heat treatment, combined with a glassy carbon surface coating, was used to prevent degradation and improve fiber tensile strength. Attempts to achieve chemical strengthening of the alumina fiber by chromium oxide and boron oxide coatings proved unsuccessful. A major problem encountered on the program was the low and inconsistent strength of the Dupont Fiber FP used for the investigation.

  1. Fiber optic monitoring device

    DOEpatents

    Samborsky, James K.

    1993-01-01

    A device for the purpose of monitoring light transmissions in optical fibers comprises a fiber optic tap that optically diverts a fraction of a transmitted optical signal without disrupting the integrity of the signal. The diverted signal is carried, preferably by the fiber optic tap, to a lens or lens system that disperses the light over a solid angle that facilitates viewing. The dispersed light indicates whether or not the monitored optical fiber or system of optical fibers is currently transmitting optical information.

  2. Photonic Crystal Fibers

    DTIC Science & Technology

    2005-12-01

    passive and active versions of each fiber designed under this task. Crystal Fibre shall provide characteristics of the fiber fabricated to include core...passive version of multicore fiber iteration 2. 15. SUBJECT TERMS EOARD, Laser physics, Fibre Lasers, Photonic Crystal, Multicore, Fiber Laser 16...9 00* 0 " CRYSTAL FIBRE INT ODUCTION This report describes the photonic crystal fibers developed under agreement No FA8655-o5-a- 3046. All

  3. Antimicrobial Acrylic Fiber

    DTIC Science & Technology

    2006-08-01

    hydantoin). The fibers were extruded from a single solvent, dimenthyl acetamide. The fibers could be chlorinated to produce halamines and thus... chlorine adsorption was shown to be proportional to the specific surface area of the fibers, as might be expected for hydrophobic materials which can react...hydantoin). The fibers were extruded from a single solvent, dimethyl acetamide. The fibers could be chlorinated to produce halamines and thus rendered

  4. Underwater propulsion of an internally actuated elastic plate

    NASA Astrophysics Data System (ADS)

    Yeh, Peter; Cen, Lejun; Erturk, Alper; Alexeev, Alexander

    2013-03-01

    Combining experiments and numerical simulations we examine underwater locomotion of an active (internally powered) flexible bimorph composite. We use Macro-Fiber Composite (MFC) piezoelectric laminates that are actuated by a sinusoidally varying voltage generating thrust similar to that of a flapping fin in carangiform motion. In our fully-coupled three dimensional simulations, we model this MFC bimorph fin as a thin, elastic plate that is actuated by a time-varying internal moment producing periodic fin bending and oscillations. The steady state swim velocity and thrust are experimentally measured and compared to the theoretical predictions. Our simulations provide detailed information about the flow structures around the swimming fin and show how they affect the forward motion. The results are useful for designing self-propelling fish-like robots driven by internally powered fins.

  5. Nonlinear elastic properties of various man-made materials

    SciTech Connect

    Darvennes, C.M.; Hou, X.

    1998-12-31

    Second harmonic generation was measured in several man-made materials for possible application of nonlinear elastic properties to non-destructive testing. Samples included several thicknesses of two types of carbon fiber/polymer matrix composites, three types of concretes, and plywood. Steel and Aluminum specimens were used as references and one of the composite samples was evaluated before and after fatigue cycles. Some interesting observations were made: (1) the two composites were much more nonlinear than the metals, (2) the concretes and the wood were extremely absorptive, (3) one of the concrete samples exhibited a third harmonic but no second harmonic, and (4) fatigue cycles significantly increased the second harmonic, even though no damage was observed by C-scan. The possible applications of these results to NDE will be discussed.

  6. Microsurgery-aided in-situ force probing reveals extensibility and viscoelastic properties of individual stress fibers

    PubMed Central

    Labouesse, Céline; Gabella, Chiara; Meister, Jean-Jacques; Vianay, Benoît; Verkhovsky, Alexander B.

    2016-01-01

    Actin-myosin filament bundles (stress fibers) are critical for tension generation and cell shape, but their mechanical properties are difficult to access. Here we propose a novel approach to probe individual peripheral stress fibers in living cells through a microsurgically generated opening in the cytoplasm. By applying large deformations with a soft cantilever we were able to fully characterize the mechanical response of the fibers and evaluate their tension, extensibility, elastic and viscous properties. PMID:27025817

  7. Strain-rate dependence of the compressive properties of normal and carbon-fiber-reinforced bone cement.

    PubMed

    Saha, S; Pal, S

    1983-11-01

    Normal and carbon-fiber-reinforced (1 wt. %) bone cement samples were tested in compression at various strain rates. Both the compressive strength and proportional limit increased in general with increasing strain rate. Similar strain-rate sensitivity was also shown by the carbon-fiber-reinforced bone cement. The mechanical properties, namely the modulus of elasticity, the proportional limit, and the compressive strength of the carbon-fiber-reinforced bone cement showed highly significant positive correlations with the strain rate.

  8. Effects of nitrogen doping from pyrolyzed ionic liquid in carbon nanotube fibers: enhanced mechanical and electrical properties

    NASA Astrophysics Data System (ADS)

    Park, Ok-Kyung; Kim, Hwa Jung; Hwang, Jun Yeon; Kim, Seung Min; Jeong, Youngjin; Lee, Jae Kwan; Ku, Bon-Cheol

    2015-02-01

    Nitrogen doping in carbon nanotube (CNT) fibers using pyrolyzed ionic liquid induced interfacial hydrogen bonding between individual CNTs, enhancing mechanical properties and electrical conductivity simultaneously. In particular, the nitrogen doped CNT fiber using the ionic liquid BMI-I exhibited about 104%, 714%, and 38% increased tensile strength (0.65 N/tex), elastic modulus (83 N/tex), and electrical conductivity (1350 S cm-1), respectively, compared to pristine CNT fiber.

  9. An Elastic Model of Blebbing in Nuclear Lamin Meshworks

    NASA Astrophysics Data System (ADS)

    Funkhouser, Chloe; Sknepnek, Rastko; Shimi, Takeshi; Goldman, Anne; Goldman, Robert; Olvera de La Cruz, Monica

    2013-03-01

    A two-component continuum elastic model is introduced to analyze a nuclear lamin meshwork, a structural element of the lamina of the nuclear envelope. The main component of the lamina is a meshwork of lamin protein filaments providing mechanical support to the nucleus and also playing a role in gene expression. Abnormalities in nuclear shape are associated with a variety of pathologies, including some forms of cancer and Hutchinson-Gilford progeria syndrome, and are often characterized by protruding structures termed nuclear blebs. Nuclear blebs are rich in A-type lamins and may be related to pathological gene expression. We apply the two-dimensional elastic shell model to determine which characteristics of the meshwork could be responsible for blebbing, including heterogeneities in the meshwork thickness and mesh size. We find that if one component of the lamin meshwork, rich in A-type lamins, has a tendency to form a larger mesh size than that rich in B-type lamins, this is sufficient to cause segregation of the lamin components and also to form blebs rich in A-type lamins. The model produces structures with comparable morphologies and mesh size distributions as the lamin meshworks of real, pathological nuclei. Funded by US DoE Award DEFG02-08ER46539 and by the DDR&E and AFOSR under Award FA9550-10-1-0167; simulations performed on NU Quest cluster

  10. Strength limit of entropic elasticity in beta-sheet protein domains.

    PubMed

    Keten, Sinan; Buehler, Markus J

    2008-12-01

    Elasticity and strength of individual beta-sheet protein domains govern key biological functions and the mechanical properties of biopolymers including spider silk, amyloids, and muscle fibers. The worm-like-chain (WLC) model is commonly used to describe the entropic elasticity of polypeptides and other biomolecules. However, force spectroscopy experiments have shown pronounced deviations from the ideal WLC behavior, leading to controversial views about the appropriate elastic description of proteins at nanoscale. Here we report a simple model that explains the physical mechanism that leads to the breakdown of the WLC idealization in experiments by using only two generic parameters of the protein domain, the H-bond energy and the protein backbone's persistence length. We show that a rupture initiation condition characterized by the free energy release rate of H-bonds characterizes the limit of WLC entropic elasticity of beta-sheet protein domains and the onset of rupture. Our findings reveal that strength and elasticity are coupled and cannot be treated separately. The predictions of the model are compared with atomic force microscopy experiments of protein rupture.

  11. Strength limit of entropic elasticity in beta-sheet protein domains

    NASA Astrophysics Data System (ADS)

    Keten, Sinan; Buehler, Markus J.

    2008-12-01

    Elasticity and strength of individual beta-sheet protein domains govern key biological functions and the mechanical properties of biopolymers including spider silk, amyloids, and muscle fibers. The worm-like-chain (WLC) model is commonly used to describe the entropic elasticity of polypeptides and other biomolecules. However, force spectroscopy experiments have shown pronounced deviations from the ideal WLC behavior, leading to controversial views about the appropriate elastic description of proteins at nanoscale. Here we report a simple model that explains the physical mechanism that leads to the breakdown of the WLC idealization in experiments by using only two generic parameters of the protein domain, the H-bond energy and the protein backbone’s persistence length. We show that a rupture initiation condition characterized by the free energy release rate of H-bonds characterizes the limit of WLC entropic elasticity of beta-sheet protein domains and the onset of rupture. Our findings reveal that strength and elasticity are coupled and cannot be treated separately. The predictions of the model are compared with atomic force microscopy experiments of protein rupture.

  12. Transient elastic deformation detection on the metal surface induced by nanosecond laser pulse

    NASA Astrophysics Data System (ADS)

    Tong, Yanqun; Huang, Jianyu; Wu, Xiaoyi; Shi, Lin

    2016-10-01

    It is difficult to detect the elastic deformation on the metal surface induced by nanosecond laser pulse. Optical fiber sensor system is suitable for detecting the elastic deformation, which has many advantages such as the high sensitivity, fast speed (GHz), non-contact, non-loss and point-measurement. We set up the measuring system to analyze the deformation mechanism firstly. Then, the elastic deformation on the metal surface was investigated. The relation between the shock-wave and elastic deformation was analyzed. The result of the present work implicated that as the nanosecond laser pulse radiated to the metal surface, elastic deformation had a delay time which was around 320ns. And the deformation presented the damped oscillation law. The data of laser-induced plasma shock wave were fitted and the fitting degree was 97.696%.The variation law of laser-induced plasma shock-wave was obtained. These results helped to make the laser removal applied to the manufacturing technique better.

  13. Actin Cytoskeleton Contributes to the Elastic Modulus of Embryonic Tendon During Early Development

    PubMed Central

    Schiele, Nathan R.; von Flotow, Friedrich; Tochka, Zachary L.; Hockaday, Laura A.; Marturano, Joseph E.; Thibodeau, Jeffrey J.; Kuo, Catherine K.

    2016-01-01

    Tendon injuries are common and heal poorly. Strategies to regenerate or replace injured tendons are challenged by an incomplete understanding of normal tendon development. Our previous study showed that embryonic tendon elastic modulus increases as a function of developmental stage. Inhibition of enzymatic collagen crosslink formation abrogated increases in tendon elastic modulus at late developmental stages, but did not affect increases in elastic modulus of early stage embryonic tendons. Here, we aimed to identify potential contributors to the mechanical properties of these early stage embryonic tendons. We characterized tendon progenitor cells in early stage embryonic tendons, and the influence of actin cytoskeleton disruption on tissue elastic modulus. Cells were closely packed in embryonic tendons, and did not change in density during early development. We observed an organized network of actin filaments that seemed contiguous between adjacent cells. The actin filaments exhibited a crimp pattern with a period and amplitude that matched the crimp of collagen fibers at each developmental stage. Chemical disruption of the actin cytoskeleton decreased tendon tissue elastic modulus, measured by atomic force microscopy. Our results demonstrate that early developmental stage embryonic tendons possess a well organized actin cytoskeleton network that contributes significantly to tendon tissue mechanical properties. PMID:25721681

  14. Actin cytoskeleton contributes to the elastic modulus of embryonic tendon during early development.

    PubMed

    Schiele, Nathan R; von Flotow, Friedrich; Tochka, Zachary L; Hockaday, Laura A; Marturano, Joseph E; Thibodeau, Jeffrey J; Kuo, Catherine K

    2015-06-01

    Tendon injuries are common and heal poorly. Strategies to regenerate or replace injured tendons are challenged by an incomplete understanding of normal tendon development. Our previous study showed that embryonic tendon elastic modulus increases as a function of developmental stage. Inhibition of enzymatic collagen crosslink formation abrogated increases in tendon elastic modulus at late developmental stages, but did not affect increases in elastic modulus of early stage embryonic tendons. Here, we aimed to identify potential contributors to the mechanical properties of these early stage embryonic tendons. We characterized tendon progenitor cells in early stage embryonic tendons, and the influence of actin cytoskeleton disruption on tissue elastic modulus. Cells were closely packed in embryonic tendons, and did not change in density during early development. We observed an organized network of actin filaments that seemed contiguous between adjacent cells. The actin filaments exhibited a crimp pattern with a period and amplitude that matched the crimp of collagen fibers at each developmental stage. Chemical disruption of the actin cytoskeleton decreased tendon tissue elastic modulus, measured by atomic force microscopy. Our results demonstrate that early developmental stage embryonic tendons possess a well organized actin cytoskeleton network that contributes significantly to tendon tissue mechanical properties.

  15. An Abnormal Psychology Community Based Interview Assignment

    ERIC Educational Resources Information Center

    White, Geoffry D.

    1977-01-01

    A course option in abnormal psychology involves students in interviewing and observing the activities of individuals in the off-campus community who are concerned with some aspect of abnormal psychology. The technique generates student interest in the field when they interview people about topics such as drug abuse, transsexualism, and abuse of…

  16. Immune Abnormalities in Patients with Autism.

    ERIC Educational Resources Information Center

    Warren, Reed P.; And Others

    1986-01-01

    A study of 31 autistic patients (3-28 years old) has revealed several immune-system abnormalities, including decreased numbers of T lymphocytes and an altered ratio of helper-to-suppressor T cells. Immune-system abnormalities may be directly related to underlying biologic processes of autism or an indirect reflection of the actual pathologic…

  17. Nail abnormalities in patients with vitiligo*

    PubMed Central

    Topal, Ilteris Oguz; Gungor, Sule; Kocaturk, Ozgur Emek; Duman, Hatice; Durmuscan, Mustafa

    2016-01-01

    Background Vitiligo is an acquired pigmentary skin disorder affecting 0.1-4% of the general population. The nails may be affected in patients with an autoimmune disease such as psoriasis, and in those with alopecia areata. It has been suggested that nail abnormalities should be apparent in vitiligo patients. Objective We sought to document the frequency and clinical presentation of nail abnormalities in vitiligo patients compared to healthy volunteers. We also examined the correlations between nail abnormalities and various clinical parameters. Methods This study included 100 vitiligo patients and 100 healthy subjects. Full medical histories were collected from the subjects, who underwent thorough general and nail examinations. All nail changes were noted. In the event of clinical suspicion of a fungal infection, additional mycological investigations were performed. Results Nail abnormalities were more prevalent in the patients (78%) than in the controls (55%) (p=0.001). Longitudinal ridging was the most common finding (42%), followed by (in descending order): leukonychia, an absent lunula, onycholysis, nail bed pallor, onychomycosis, splinter hemorrhage and nail plate thinning. The frequency of longitudinal ridging was significantly higher in patients than in controls (p<0.001). Conclusions Nail abnormalities were more prevalent in vitiligo patients than in controls. Systematic examination of the nails in such patients is useful because nail abnormalities are frequent. However, the causes of such abnormalities require further study. Longitudinal ridging and leukonychia were the most common abnormalities observed in this study. PMID:27579738

  18. Polarized spatial frequency domain imaging of heart valve fiber structure

    NASA Astrophysics Data System (ADS)

    Goth, Will; Yang, Bin; Lesicko, John; Allen, Alicia; Sacks, Michael S.; Tunnell, James W.

    2016-03-01

    Our group previously introduced Polarized Spatial Frequency Domain Imaging (PSFDI), a wide-field, reflectance imaging technique which we used to empirically map fiber direction in porcine pulmonary heart valve leaflets (PHVL) without optical clearing or physical sectioning of the sample. Presented is an extended analysis of our PSFDI results using an inverse Mueller matrix model of polarized light scattering that allows additional maps of fiber orientation distribution, along with instrumentation permitting increased imaging speed for dynamic PHVL fiber measurements. We imaged electrospun fiber phantoms with PSFDI, and then compared these measurements to SEM data collected for the same phantoms. PHVL was then imaged and compared to results of the same leaflets optically cleared and imaged with small angle light scattering (SALS). The static PHVL images showed distinct regional variance of fiber orientation distribution, matching our SALS results. We used our improved imaging speed to observe bovine tendon subjected to dynamic loading using a biaxial stretching device. Our dynamic imaging experiment showed trackable changes in the fiber microstructure of biological tissue under loading. Our new PSFDI analysis model and instrumentation allows characterization of fiber structure within heart valve tissues (as validated with SALS measurements), along with imaging of dynamic fiber remodeling. The experimental data will be used as inputs to our constitutive models of PHVL tissue to fully characterize these tissues' elastic behavior, and has immediate application in determining the mechanisms of structural and functional failure in PHVLs used as bio-prosthetic implants.

  19. The mechanical properties of individual, electrospun fibrinogen fibers

    PubMed Central

    Carlisle, Christine R.; Coulais, Corentin; Namboothiry, Manoj; Carroll, David L.; Hantgan, Roy R.; Guthold, Martin

    2010-01-01

    We used a combined atomic force microscopic (AFM)/fluorescence microscopic technique to study the mechanical properties of individual, electrospun fibrinogen fibers in aqueous buffer. Fibers (average diameter 208 nm) were suspended over 12 μm-wide grooves in a striated, transparent substrate. The AFM, situated above the sample, was used to laterally stretch the fibers and to measure the applied force. The fluorescence microscope, situated below the sample, was used to visualize the stretching process. The fibers could be stretched to 2.3 times their original length before breaking; the breaking stress was 22 × 106 Pa. We collected incremental stress–strain curves to determine the viscoelastic behavior of these fibers. The total stretch modulus was 17.5 × 106 Pa and the relaxed elastic modulus was 7.2 × 106 Pa. When held at constant strain, electrospun fibrinogen fibers showed a fast and slow stress relaxation time of 3 and 55 s. Our fibers were spun from the typically used 90% 1,1,1,3,3,3-hexafluoro-2-propanol (90-HFP) electrospinning solution and re-suspended in aqueous buffer. Circular dichroism spectra indicate that α-helical content of fibrinogen is ~70% higher in 90-HFP than in aqueous solution. These data are needed to understand the mechanical behavior of electrospun fibrinogen structures. Our technique is also applicable to study other nanoscopic fibers. PMID:19058845

  20. Elasticity and Extensibility Determine Printability and Spinnability of Polymer Solutions

    NASA Astrophysics Data System (ADS)

    Dinic, Jelena; Jimenez, Leidy; Sharma, Vivek

    Many advanced manufacturing technologies like inkjet and 3D printing, nano-fiber spinning involve complex free-surface flows, and the formation of columnar necks that undergo spontaneous capillary-driven thinning and pinch-off. The progressive self-thinning of neck is often characterized by self-similar profiles and scaling laws that depend on the relative magnitude of capillary, inertial and viscous stresses for simple (Newtonian and inelastic) fluids. Stream-wise velocity gradients that arise within the thinning columnar neck create an extensional flow field that can orient and stretch macromolecules, contributing extra elastic stresses and extensional viscosity that change thinning and pinch-off dynamics for polymeric complex fluids. Characterizing the filament thinning and break-up kinetics in jetting, dripping and stretching liquid bridge provides invaluable insight into the interplay of elastic, viscous, capillary and inertial stresses relevant for these applications. We elucidate how polymer composition, flexibility and molecular weight determine the thinning and pinch-off kinetics in our experiments. Both effective relaxation time and transient extensional viscosity are found to be strongly concentration dependent even for dilute solutions.

  1. Adaptive Quality of Transmission Control in Elastic Optical Network

    NASA Astrophysics Data System (ADS)

    Cai, Xinran

    Optical fiber communication is becoming increasingly important due to the burgeoning demand in the internet capacity. However, traditional wavelength division multiplexing (WDM) technique fails to address such demand because of its inefficient spectral utilization. As a result, elastic optical networking (EON) has been under extensive investigation recently. Such network allows sub-wavelength and super-wavelength channel accommodation, and mitigates the stranded bandwidth problem in the WDM network. In addition, elastic optical network is also able to dynamically allocate the spectral resources of the network based on channel conditions and impairments, and adaptively control the quality of transmission of a channel. This application requires two aspects to be investigated: an efficient optical performance monitoring scheme and networking control and management algorithms to reconfigure the network in a dynamic fashion. This thesis focuses on the two aspects discussed above about adaptive QoT control. We demonstrated a supervisory channel method for optical signal to noise ratio (OSNR) and chromatic dispersion (CD) monitoring. In addition, our proof-of-principle testbed experiments show successful impairment aware reconfiguration of the network with modulation format switching (MFS) only and MFS combined with lightpath rerouting (LR) for hundred-GHz QPSK superchannels undergoing time-varying OSNR impairment.

  2. Elasticity of polymeric nanocolloidal particles

    NASA Astrophysics Data System (ADS)

    Riest, Jonas; Athanasopoulou, Labrini; Egorov, Sergei A.; Likos, Christos N.; Ziherl, Primož

    2015-11-01

    Softness is an essential mechanical feature of macromolecular particles such as polymer-grafted nanocolloids, polyelectrolyte networks, cross-linked microgels as well as block copolymer and dendrimer micelles. Elasticity of individual particles directly controls their swelling, wetting, and adsorption behaviour, their aggregation and self-assembly as well as structural and rheological properties of suspensions. Here we use numerical simulations and self-consistent field theory to study the deformation behaviour of a single spherical polymer brush upon diametral compression. We observe a universal response, which is rationalised using scaling arguments and interpreted in terms of two coarse-grained models. At small and intermediate compressions the deformation can be accurately reproduced by modelling the brush as a liquid drop, whereas at large compressions the brush behaves as a soft ball. Applicable far beyond the pairwise-additive small-strain regime, the models may be used to describe microelasticity of nanocolloids in severe confinement including dense disordered and crystalline phases.

  3. High elastic modulus polymer electrolytes

    DOEpatents

    Balsara, Nitash Pervez; Singh, Mohit; Eitouni, Hany Basam; Gomez, Enrique Daniel

    2013-10-22

    A polymer that combines high ionic conductivity with the structural properties required for Li electrode stability is useful as a solid phase electrolyte for high energy density, high cycle life batteries that do not suffer from failures due to side reactions and dendrite growth on the Li electrodes, and other potential applications. The polymer electrolyte includes a linear block copolymer having a conductive linear polymer block with a molecular weight of at least 5000 Daltons, a structural linear polymer block with an elastic modulus in excess of 1.times.10.sup.7 Pa and an ionic conductivity of at least 1.times.10.sup.-5 Scm.sup.-1. The electrolyte is made under dry conditions to achieve the noted characteristics.

  4. Elastic Suppression of Viscous Fingering

    NASA Astrophysics Data System (ADS)

    Peng, Gunnar; Lister, John

    2016-11-01

    Consider peeling an elastic tape or beam away from a rigid base to which it is stuck by a film of viscous liquid. The peeling motion requires air to invade the viscous liquid and is thus susceptible to the Saffman-Taylor fingering instability. We analyse the fundamental travelling-wave solution and show that the advancing air-liquid interface remains linearly stable at higher capillary numbers than in a standard Hele-Shaw cell. A short-wavelength expansion yields an analytical expression for the growth rate which is valid for all unstable modes throughout the parameter space, allowing us to identify and quantify four distinct physical mechanisms that each help suppress the instability. Applying our method to the experiments by Pihler-Puzovic et al. (2012) reveals that the radial geometry and time-variation stabilize the system further.

  5. Can transcutaneous recordings detect gastric electrical abnormalities?

    PubMed Central

    Familoni, B O; Bowes, K L; Kingma, Y J; Cote, K R

    1991-01-01

    The ability of transcutaneous recordings of gastric electrical activity to detect gastric electrical abnormalities was determined by simultaneous measurements of gastric electrical activity with surgically implanted serosal electrodes and cutaneous electrodes in six patients undergoing abdominal operations. Transient abnormalities in gastric electrical activity were seen in five of the six patients during the postoperative period. Recognition of normal gastric electrical activity by visual analysis was possible 67% of the time and with computer analysis 95% of the time. Ninety four per cent of abnormalities in frequency were detected by visual analysis and 93.7% by computer analysis. Abnormalities involving a loss of coupling, however, were not recognised by transcutaneous recordings. Transcutaneous recordings of gastric electrical activity assessed by computer analysis can usually recognise normal gastric electrical activity and tachygastria. Current techniques, however, are unable to detect abnormalities in electrical coupling. PMID:1864531

  6. Rheological properties of molten flax- and Tencel{sup ®}-polypropylene composites: Influence of fiber morphology and concentration

    SciTech Connect

    Abdennadher, Ahmed; Vincent, Michel; Budtova, Tatiana

    2016-01-15

    The rheological properties of short fiber reinforced polypropylene were investigated. Flax and Tencel{sup ®} are two cellulose based fibers used in this study. Flax fibers are extracted from the bast of plants. They are composed of thin elementary fibers and rigid thick bundles made of elementary fibers “glued” together. Tencel{sup ®} is a man-made cellulosic fiber spun from cellulose solution, with a uniform diameter, thin, and flexible. First, fiber dimensions before and after compounding were analyzed. Both types of fibers were broken during compounding. Flax shows larger length and diameter than Tencel{sup ®}, but aspect ratio of flax is smaller. The reason is that after compounding flax remained in bundles. Dynamic viscosity, elastic and viscous moduli were studied as a function of fiber type, concentration (from 0 to 30 wt. %), and composite temperature (from 180 to 200 °C). All Tencel{sup ®}-based composites showed higher apparent yield stress, viscosity, and moduli compared to flax-based composites at the same fiber concentrations. The results are analyzed in terms of the influence of fiber type, aspect ratio, and flexibility. The importance of considering fiber morphology is demonstrated as far as it controls fiber flexibility and fiber-fiber interactions.

  7. Abnormal lateral geniculate nucleus and optic chiasm in human albinism.

    PubMed

    Mcketton, Larissa; Kelly, Krista R; Schneider, Keith A

    2014-08-01

    Our objective was to measure how the misrouting of retinal ganglion cell (RGC) fibers affects the organization of the optic chiasm and lateral geniculate nuclei (LGN) in human albinism. We compared the chiasmal structures and the LGN in both pigmented controls and patients with albinism by using high-resolution structural magnetic resonance imaging (MRI). We studied 12 patients with oculocutaneous albinism and 12 age-matched pigmented controls. Using a 3T MRI scanner, we acquired a T1 -weighted three-dimensional magnetization-prepared rapid gradient-echo (MPRAGE) image of the whole brain, oriented so that the optic nerves, chiasm, and tracts were in the same plane. We acquired multiple proton density-weighted images centered on the thalamus and midbrain, and averaged them to increase the signal, enabling precise manual tracing of the anatomical boundaries of the LGN. Albinism patients exhibited significantly smaller diameters of the optic nerves, chiasm and tracts, and optic chiasm and LGN volume compared with controls (P < 0.001 for all). The reductions in chiasmal diameters in the albinism compared with the control group can be attributed to the abnormal crossing of optic fibers and the reduction of RGCs in the central retina. The volume of the LGN devoted to the center of the visual field may be reduced in albinism due to fewer RGCs representing the area where the fovea would normally lie. Our data may be clinically useful in addressing how genetic deficits compromise proper structural and functional development in the brain.

  8. Study of Nonlinear Oscillations of Elastic Membrane

    DTIC Science & Technology

    2006-09-26

    Nonlinear Elastic Membrane Oscillations by Eigenfunction Expansion, WSEAS Transactions of Systems, 3 (4) (2004), 1430-1435. 2.V. Varlamov, Convolution...proceedings 1. A. Balogh and V. Varlamov, Analysis of Nonlinear Elastic Membrane Oscillations by Eigenfunction Expansion, 6th WSEAS International...Eigenfunction Expansion, 6th WSEAS International Conference on Algorithms, Scientific Computing, Modelling and Simulation, Cancun, Mexico, May 12--15

  9. 7 CFR 29.6013 - Elasticity.

    Code of Federal Regulations, 2010 CFR

    2010-01-01

    ... 7 Agriculture 2 2010-01-01 2010-01-01 false Elasticity. 29.6013 Section 29.6013 Agriculture Regulations of the Department of Agriculture AGRICULTURAL MARKETING SERVICE (Standards, Inspections, Marketing... INSPECTION Standards Definitions § 29.6013 Elasticity. The flexible, springy nature of the tobacco leaf...

  10. Simulation and control problems in elastic robots

    NASA Technical Reports Server (NTRS)

    Tadikonda, S. S. K.; Baruh, H.

    1989-01-01

    Computational issues associated with modeling and control of robots with revolute joints and elastic arms are considered. A manipulator with one arm and pinned at one end is considered to investigate various aspects of the modeling procedure and the model, and the effect of coupling between the rigid-body and the elastic motions. The rigid-body motion of a manipulator arm is described by means of a reference frame attached to the shadow beam, and the linear elastic operator denoting flexibility is defined with respect to this reference frame. The small elastic motion assumption coupled with the method of assumed modes is used to model the elasticity in the arm. It is shown that only terms up to quadratic in these model amplitudes need to be retained. An important aspect of the coupling between the rigid-body and the elastic motion is the centrifugal stiffening effect. This effect stiffens the elastic structure, as to be expected on physical grounds, gives rise to a time-varying inertia term for the rigid-body motion, and, in general, results in an effective inertia term smaller than the rigid-body inertia term. Simulation results are presented for an elastic beam pinned at one end and free at the other, and rotating in a horizontal plane, and control issues such as the order of the model, number of sensors, and modal extraction are examined within this context.

  11. Celestial mechanics of elastic bodies II

    NASA Astrophysics Data System (ADS)

    Beig, Robert; Schmidt, Bernd G.

    2017-04-01

    We construct time independent configurations describing a small elastic body moving in a circular orbit in the Schwarzschild spacetime. These configurations are relativistic versions of Newtonian solutions constructed by us previously. In the process we simplify and sharpen previous results of ours concerning elastic bodies in rigid rotation.

  12. Traveling Lamb wave in elastic metamaterial layer

    NASA Astrophysics Data System (ADS)

    Shu, Haisheng; Xu, Lihuan; Shi, Xiaona; Zhao, Lei; Zhu, Jie

    2016-10-01

    The propagation of traveling Lamb wave in single layer of elastic metamaterial is investigated in this paper. We first categorized the traveling Lamb wave modes inside an elastic metamaterial layer according to different combinations (positive or negative) of effective medium parameters. Then the impacts of the frequency dependence of effective parameters on dispersion characteristics of traveling Lamb wave were studied. Distinct differences could be observed when comparing the traveling Lamb wave along an elastic metamaterial layer with one inside the traditional elastic layer. We further examined in detail the traveling Lamb wave mode supported in elastic metamaterial layer, when the effective P and S wave velocities were simultaneously imaginary. It was found that the effective modulus ratio is the key factor for the existence of special traveling wave mode, and the main results were verified by FEM simulations from two levels: the level of effective medium and the level of microstructure unit cell.

  13. Breakdown of elasticity in amorphous solids

    NASA Astrophysics Data System (ADS)

    Biroli, Giulio; Urbani, Pierfrancesco

    2016-12-01

    What characterizes a solid is the way that it responds to external stresses. Ordered solids, such as crystals, exhibit an elastic regime followed by a plastic regime, both understood microscopically in terms of lattice distortion and dislocations. For amorphous solids the situation is instead less clear, and the microscopic understanding of the response to deformation and stress is a very active research topic. Several studies have revealed that even in the elastic regime the response is very jerky at low temperature, resembling very much the response of disordered magnetic materials. Here we show that in a very large class of amorphous solids this behaviour emerges upon decreasing temperature, as a phase transition, where standard elastic behaviour breaks down. At the transition all nonlinear elastic moduli diverge and standard elasticity theory no longer holds. Below the transition, the response to deformation becomes history- and time-dependent.

  14. Elasticity-based determination of isovolumetric phases in the human heart

    PubMed Central

    2010-01-01

    Background/Motivation To directly determine isovolumetric cardiac time intervals by magnetic resonance elastography (MRE) using the magnitude of the complex signal for deducing morphological information combined with the phase of the complex signal for tension-relaxation measurements. Methods Thirty-five healthy volunteers and 11 patients with relaxation abnormalities were subjected to transthoracic wave stimulation using vibrations of approximately 25 Hz. A k-space-segmented, ECG-gated gradient-recalled echo steady-state sequence with a 500-Hz bipolar motion-encoding gradient was used for acquiring a series of 360 complex images of a short-axis view of the heart at a frame rate of less than 5.2 ms. Magnitude images were employed for measuring the cross-sectional area of the left ventricle, while phase images were used for analyzing the amplitudes of the externally induced waves. The delay between the decrease in amplitude and onset of ventricular contraction was determined in all subjects and assigned to the time of isovolumetric tension. Conversely, the delay between the increase in wave amplitude and ventricular dilatation was used for measuring the time of isovolumetric elasticity relaxation. Results Wave amplitudes decreased during systole and increased during diastole. The variation in wave amplitude occurred ahead of morphological changes. In healthy volunteers the time of isovolumetric elasticity relaxation was 75 ± 31 ms, which is significantly shorter than the time of isovolumetric tension of 136 ± 36 ms (P < 0.01). In patients with relaxation abnormalities (mild diastolic dysfunction, n = 11) isovolumetric elasticity relaxation was significantly prolonged, with 133 ± 57 ms (P < 0.01), whereas isovolumetric tension time was in the range of healthy controls (161 ± 45 ms; P = 0.053). Conclusion The complex MRE signal conveys complementary information on cardiac morphology and elasticity, which can be combined for directly measuring isovolumetric tension

  15. SiC/SiC Composites: The Effect of Fiber Type and Fiber Architecture on Mechanical Properties

    NASA Technical Reports Server (NTRS)

    Morscher, Gregory N.

    2008-01-01

    Woven SiC/SiC composites represent a broad family of composites with a broad range of properties which are of interest for many energy-based and aero-based applications. Two important features of SiC/SiC composites which one must consider are the reinforcing fibers themselves and the fiber-architecture they are formed into. The range of choices for these two features can result in a wide range of elastic, mechanical, thermal, and electrical properties. In this presentation, it will be demonstrated how the effect of fiber-type and fiber architecture effects the important property of "matrix cracking stress" for slurry-cast melt-infiltrated SiC matrix composites, which is often considered to be a critical design parameter for this system of composites.

  16. Composite laminates with spatially varying fiber orientations - 'Variable stiffness panel concept'

    NASA Technical Reports Server (NTRS)

    Guerdal, Zafer; Olmedo, Reynaldo

    1992-01-01

    A solution has been obtained to the plane elasticity problem for a symmetrically laminated composite panel with spatially varying fiber orientations. Since variation of the fiber angles along the length of a composite laminate results in stiffness properties that change as a function of location, the laminates are called variable stiffness panels. An analysis of the stiffness variation and its effect on the elastic response of the panel is presented here. A numerical solution has been obtained using an iterative collocation technique. Corresponding closed-form solutions are given for three different sets of boundary conditions. Two of the cases considered have exact solutions and thus serve to validate the numerical model.

  17. Cutis laxa with pulmonary emphysema, conjunctivochalasis, nasolacrimal duct obstruction, abnormal hair, and a novel FBLN5 mutation.

    PubMed

    Kantaputra, Piranit Nik; Kaewgahya, Massupa; Wiwatwongwana, Atchareeya; Wiwatwongwana, Damrong; Sittiwangkul, Rekwan; Iamaroon, Anak; Dejkhamron, Prapai

    2014-09-01

    We report on a 4-year-old girl with autosomal recessive cutis laxa, type IA, or pulmonary emphysema type (ARCL1A; OMIM #219100), with loose and wrinkled skin, mitral and tricuspid valve prolapse, conjunctivochalasis, obstructed nasolacrimal ducts, hypoplastic maxilla, and early childhood-onset pulmonary emphysema. Mutation analysis of FBLN5 showed a homozygous c.432C>G missense mutation, and heterozygosity in the parents. This is predicted to cause amino acid substitution p.Cys144Trp. Conjunctivochalasis or redundant folds of conjunctiva and obstructed nasolacrimal ducts have not been reported to be associated with FBLN5 mutations. Histopathological study of the conjunctival biopsy showed that most blood vessels had normal elastic fibers. The gingiva appeared normal, but histologically elastic fibers were defective. Scanning electron micrography of scalp hair demonstrated hypoplastic hair follicles. The cuticles appear intact underneath the filamentous meshwork.

  18. 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.

  19. Underwater Acoustic Sensors Based on Fiber Bragg Gratings

    PubMed Central

    Campopiano, Stefania; Cutolo, Antonello; Cusano, Andrea; Giordano, Michele; Parente, Giuseppe; Lanza, Giuseppe; Laudati, Armando

    2009-01-01

    We report on recent results obtained with a fiber optic hydrophone based on the intensity modulation of the laser light in a FBG (Fiber Bragg Grating) under the influence of the sound pressure. In order to control the behavior of the hydrophone in terms of sensitivity and bandwidth, FBGs have been coated with proper materials, characterized by different elastic modulus and shapes. In particular, new experiments have been carried out using a cylindrical geometry with two different coating, showing that the sensitivity is not influenced by the shape but by the transversal dimension and the material characteristics of the coating. PMID:22408534

  20. High strain-rate model for fiber-reinforced composites

    SciTech Connect

    Aidun, J.B.; Addessio, F.L.

    1995-07-01

    Numerical simulations of dynamic uniaxial strain loading of fiber-reinforced composites are presented that illustrate the wide range of deformation mechanisms that can be captured using a micromechanics-based homogenization technique as the material model in existing continuum mechanics computer programs. Enhancements to the material model incorporate high strain-rate plastic response, elastic nonlinearity, and rate-dependent strength degradation due to material damage, fiber debonding, and delamination. These make the model relevant to designing composite structural components for crash safety, armor, and munitions applications.

  1. Ceramic fiber reinforced filter

    DOEpatents

    Stinton, David P.; McLaughlin, Jerry C.; Lowden, Richard A.

    1991-01-01

    A filter for removing particulate matter from high temperature flowing fluids, and in particular gases, that is reinforced with ceramic fibers. The filter has a ceramic base fiber material in the form of a fabric, felt, paper of the like, with the refractory fibers thereof coated with a thin layer of a protective and bonding refractory applied by chemical vapor deposition techniques. This coating causes each fiber to be physically joined to adjoining fibers so as to prevent movement of the fibers during use and to increase the strength and toughness of the composite filter. Further, the coating can be selected to minimize any reactions between the constituents of the fluids and the fibers. A description is given of the formation of a composite filter using a felt preform of commercial silicon carbide fibers together with the coating of these fibers with pure silicon carbide. Filter efficiency approaching 100% has been demonstrated with these filters. The fiber base material is alternately made from aluminosilicate fibers, zirconia fibers and alumina fibers. Coating with Al.sub.2 O.sub.3 is also described. Advanced configurations for the composite filter are suggested.

  2. Modeling the Elastic Modulus of 2D Woven CVI SiC Composites

    NASA Technical Reports Server (NTRS)

    Morscher, Gregory N.

    2006-01-01

    The use of fiber, interphase, CVI SiC minicomposites as structural elements for 2D-woven SiC fiber reinforced chemically vapor infiltrated (CVI) SiC matrix composites is demonstrated to be a viable approach to model the elastic modulus of these composite systems when tensile loaded in an orthogonal direction. The 0deg (loading direction) and 90deg (perpendicular to loading direction) oriented minicomposites as well as the open porosity and excess SiC associated with CVI SiC composites were all modeled as parallel elements using simple Rule of Mixtures techniques. Excellent agreement for a variety of 2D woven Hi-Nicalon(TradeMark) fiber-reinforced and Sylramic-iBN reinforced CVI SiC matrix composites that differed in numbers of plies, constituent content, thickness, density, and number of woven tows in either direction (i.e, balanced weaves versus unbalanced weaves) was achieved. It was found that elastic modulus was not only dependent on constituent content, but also the degree to which 90deg minicomposites carried load. This depended on the degree of interaction between 90deg and 0deg minicomposites which was quantified to some extent by composite density. The relationships developed here for elastic modulus only necessitated the knowledge of the fractional contents of fiber, interphase and CVI SiC as well as the tow size and shape. It was concluded that such relationships are fairly robust for orthogonally loaded 2D woven CVI SiC composite system and can be implemented by ceramic matrix composite component modelers and designers for modeling the local stiffness in simple or complex parts fabricated with variable constituent contents.

  3. Mechanical Behavior of Homogeneous and Composite Random Fiber Networks

    NASA Astrophysics Data System (ADS)

    Shahsavari, Ali

    Random fiber networks are present in many biological and non-biological materials such as paper, cytoskeleton, and tissue scaffolds. Mechanical behavior of networks is controlled by the mechanical properties of the constituent fibers and the architecture of the network. To characterize these two main factors, different parameters such as fiber density, fiber length, average segment length, nature of the cross-links at the fiber intersections, ratio of bending to axial behavior of fibers have been considered. Random fiber networks are usually modeled by representing each fiber as a Timoshenko or an Euler-Bernoulli beam and each cross-link as either a welded or rotating joint. In this dissertation, the effect of these modeling options on the dependence of the overall linear network modulus on microstructural parameters is studied. It is concluded that Timoshenko beams can be used for the whole range of density and fiber stiffness parameters, while the Euler-Bernoulli model can be used only at relatively low densities. In the low density-low bending stiffness range, elastic strain energy is stored in the bending mode of the deformation, while in the other extreme range of parameters, the energy is stored predominantly in the axial and shear deformation modes. It is shown that both rotating and welded joint models give the same rules for scaling of the network modulus with different micromechanical parameters. The elastic modulus of sparsely cross-linked random fiber networks, i.e. networks in which the degree of cross-linking varies, is studied. The relationship between the micromechanical parameters - fiber density, fiber axial and bending stiffness, and degree of cross-linking - and the overall elastic modulus is presented in terms of a master curve. It is shown that the master plot with various degrees of cross-linking can be collapsed to a curve which is also valid for fully cross-linked networks. Random fiber networks in which fibers are bonded to each other are

  4. Shear-wave elastography of invasive breast cancer: correlation between quantitative mean elasticity value and immunohistochemical profile.

    PubMed

    Youk, Ji Hyun; Gweon, Hye Mi; Son, Eun Ju; Kim, Jeong-Ah; Jeong, Joon

    2013-02-01

    To compare the mean elasticity value, as measured by shear-wave elastography (SWE), with immunohistochemical profile of invasive breast cancer. This was an institutional review board-approved retrospective study, with a waiver of informed consent. A total of 166 invasive breast cancers in 152 women undergoing preoperative SWE and surgery were included. Quantitative mean elasticity values in kPa were measured for each lesion by using SWE. Medical records were reviewed to determine palpability, invasive size, lymphovascular invasion, histologic grade, and axillary lymph node status. Based on the immunohistochemical profiles, tumor subtypes were categorized as triple-negative (TN), luminal A and B, or human epidermal growth factor receptor 2-enriched cancer. The mean elasticity value was correlated with clinicopathological features using univariate regression models and multivariate linear regression analysis. Palpability (P < 0.0001), larger size (P = 0.013), lymphovascular invasion (P < 0.0001), higher histologic grade (P < 0.0001), and lymph node involvement (P = 0.018) were significantly associated with the mean elasticity value. For the immunohistochemical profiles and tumor subtypes, the estrogen receptor (P = 0.015), progesterone receptor (P = 0.002), Ki-67 (P = 0.009), and the TN (P = 0.009) tumor subtype were correlated with the mean elasticity value. Multivariate logistic regression analysis showed that the following variables were significantly associated with the mean elasticity value: palpable abnormality, histologic grade, and lymphovascular invasion. No immunohistochemical profile of the cancers was independently correlated with the mean elasticity value. For invasive breast cancers, clinicopathological features of poor prognosis showed higher mean elasticity values than those of good prognosis. However, the immunohistochemical profile showed no independent association with the mean elasticity value.

  5. Sleep Physiology, Abnormal States, and Therapeutic Interventions

    PubMed Central

    Wickboldt, Alvah T.; Bowen, Alex F.; Kaye, Aaron J.; Kaye, Adam M.; Rivera Bueno, Franklin; Kaye, Alan D.

    2012-01-01

    Sleep is essential. Unfortunately, a significant portion of the population experiences altered sleep states that often result in a multitude of health-related issues. The regulation of sleep and sleep-wake cycles is an area of intense research, and many options for treatment are available. The following review summarizes the current understanding of normal and abnormal sleep-related conditions and the available treatment options. All clinicians managing patients must recommend appropriate therapeutic interventions for abnormal sleep states. Clinicians' solid understanding of sleep physiology, abnormal sleep states, and treatments will greatly benefit patients regardless of their disease process. PMID:22778676

  6. Congenital abnormalities of the ovine paramesonephric ducts.

    PubMed

    Smith, K C; Long, S E; Parkinson, T J

    1995-01-01

    A 15 month survey of ovine reproductive tracts was undertaken in slaughterhouses in southwest England. A total of 33506 tracts were examined; 23536 from lambs and 9970 from adults. In total, 3.4% of tracts were pregnant and 3.3% exhibited abnormalities. Twenty cases of uterus unicornis, six of uterus didelphys and 11 of segmental aplasia were encountered, such that partial aplasia of the paramesonephric ducts accounted for 3.3% of all abnormalities. Although developmental abnormalities of the ovine female genital system are relatively uncommon, a substantial proportion of these can be accounted for by development defects of the paramesonephric ducts.

  7. [Radionuclide studies of congenital kidney abnormalities].

    PubMed

    Vlakhov, N

    1984-06-01

    Using the potentialities of isotope nephrograms as a screening test a total of 4746 patients suspected of renal abnormalities were examined. The author established pathological deviations in 561 cases (11.8%). During further verification using scintigraphy unsuspected congenital renal abnormalities (aplasia, hypoplasia, dystopia, double kidney, horseshoe kidney, solitary cyst and polycystic renal disease) were found in 46 patients (8.2%). The diagnosis was confirmed at subsequent venous x-ray urography. A conclusion has been made as to the role of comprehensive nephrographic-scintigraphic examination in the diagnosis of congenital renal abnormalities.

  8. Numerically abnormal chromosome constitutions in humans

    SciTech Connect

    1993-12-31

    Chapter 24, discusses numerically abnormal chromosome constitutions in humans. This involves abnormalities of human chromosome number, including polyploidy (when the number of sets of chromosomes increases) and aneuploidy (when the number of individual normal chromosomes changes). Chapter sections discuss the following chromosomal abnormalities: human triploids, imprinting and uniparental disomy, human tetraploids, hydatidiform moles, anomalies caused by chromosomal imbalance, 13 trisomy (D{sub 1} trisomy, Patau syndrome), 21 trisomy (Down syndrome), 18 trisomy syndrome (Edwards syndrome), other autosomal aneuploidy syndromes, and spontaneous abortions. The chapter concludes with remarks on the nonrandom participation of chromosomes in trisomy. 69 refs., 3 figs., 4 tabs.

  9. Bond characteristics of steel fiber and deformed reinforcing steel bar embedded in steel fiber reinforced self-compacting concrete (SFRSCC)

    NASA Astrophysics Data System (ADS)

    Aslani, Farhad; Nejadi, Shami

    2012-09-01

    Steel fiber reinforced self-compacting concrete (SFRSCC) is a relatively new composite material which congregates the benefits of the self-compacting concrete (SCC) technology with the profits derived from the fiber addition to a brittle cementitious matrix. Steel fibers improve many of the properties of SCC elements including tensile strength, ductility, toughness, energy absorption capacity, fracture toughness and cracking. Although the available research regarding the influence of steel fibers on the properties of SFRSCC is limited, this paper investigates the bond characteristics between steel fiber and SCC firstly. Based on the available experimental results, the current analytical steel fiber pullout model (Dubey 1999) is modified by considering the different SCC properties and different fiber types (smooth, hooked) and inclination. In order to take into account the effect of fiber inclination in the pullout model, apparent shear strengths (τ (app)) and slip coefficient (β) are incorporated to express the variation of pullout peak load and the augmentation of peak slip as the inclined angle increases. These variables are expressed as functions of the inclined angle (ϕ). Furthurmore, steel-concrete composite floors, reinforced concrete floors supported by columns or walls and floors on an elastic foundations belong to the category of structural elements in which the conventional steel reinforcement can be partially replaced by the use of steel fibers. When discussing deformation capacity of structural elements or civil engineering structures manufactured using SFRSCC, one must be able to describe thoroughly both the behavior of the concrete matrix reinforced with steel fibers and the interaction between this composite matrix and discrete steel reinforcement of the conventional type. However, even though the knowledge on bond behavior is essential for evaluating the overall behavior of structural components containing reinforcement and steel fibers

  10. Bond characteristics of steel fiber and deformed reinforcing steel bar embedded in steel fiber reinforced self-compacting concrete (SFRSCC)

    NASA Astrophysics Data System (ADS)

    Aslani, Farhad; Nejadi, Shami

    2012-09-01

    Steel fiber reinforced self-compacting concrete (SFRSCC) is a relatively new composite material which congregates the benefits of the self-compacting concrete (SCC) technology with the profits derived from the fiber addition to a brittle cementitious matrix. Steel fibers improve many of the properties of SCC elements including tensile strength, ductility, toughness, energy absorption capacity, fracture toughness and cracking. Although the available research regarding the influence of steel fibers on the properties of SFRSCC is limited, this paper investigates the bond characteristics between steel fiber and SCC firstly. Based on the available experimental results, the current analytical steel fiber pullout model (Dubey 1999) is modified by considering the different SCC properties and different fiber types (smooth, hooked) and inclination. In order to take into account the effect of fiber inclination in the pullout model, apparent shear strengths ( τ ( app)) and slip coefficient ( β) are incorporated to express the variation of pullout peak load and the augmentation of peak slip as the inclined angle increases. These variables are expressed as functions of the inclined angle ( ϕ). Furthurmore, steel-concrete composite floors, reinforced concrete floors supported by columns or walls and floors on an elastic foundations belong to the category of structural elements in which the conventional steel reinforcement can be partially replaced by the use of steel fibers. When discussing deformation capacity of structural elements or civil engineering structures manufactured using SFRSCC, one must be able to describe thoroughly both the behavior of the concrete matrix reinforced with steel fibers and the interaction between this composite matrix and discrete steel reinforcement of the conventional type. However, even though the knowledge on bond behavior is essential for evaluating the overall behavior of structural components containing reinforcement and steel fibers

  11. Extinction efficiency of "elastic-sheet" beams by a cylindrical (viscous) fluid inclusion embedded in an elastic medium and mode conversion—Examples of nonparaxial Gaussian and Airy beams

    NASA Astrophysics Data System (ADS)

    Mitri, F. G.

    2016-10-01

    . Moreover, the efficiencies for the embedded circular viscous fluid cylinder in the field of an Airy elastic-sheet display a spatial parabolic (nonlinear) type of absorption, scattering, and extinction, representative of the intrinsic property of the curved accelerating beam in the elastic matrix. The present analysis provides an improved method for the computations of energy efficiency factors in elastodynamics for finite beams in 2D, which can be used as a priori information in the direct or inverse characterization of the mechanical properties of cylindrical fiber-reinforced materials, pipes, vessels, etc., embedded in an elastic medium.

  12. Differentiating cancerous tissues from noncancerous tissues using single-fiber reflectance spectroscopy with different fiber diameters

    NASA Astrophysics Data System (ADS)

    Sircan-Kuçuksayan, Aslinur; Denkceken, Tuba; Canpolat, Murat

    2015-11-01

    Elastic light-scattering spectra acquired with single-fiber optical probes with diameters of 100, 200, 400, 600, 800, 1000, 1200, and 1500 μm were used to differentiate cancerous from noncancerous prostate tissues. The spectra were acquired ex vivo on 24 excised prostate tissue samples collected from four patients. For each probe, the spectra and histopathology results were compared in order to investigate the correlation between the core diameters of the single-fiber optical probe and successful differentiation between cancerous and noncancerous prostate tissues. The spectra acquired using probes with a fiber core diameter of 400 μm or smaller successfully differentiated cancerous from noncancerous prostate tissues. Next, the spectra were acquired from monosized polystyrene microspheres with a diameter of 5.00±0.01 μm to investigate the correlation between the core diameters of the probes and the Mie oscillations on the spectra. Monte Carlo simulations of the light distribution of the tissue phantoms were run to interrogate whether the light detected by the probes with different fiber core diameters was in the ballistic or diffusive regime. If the single-fiber optical probes detect light in the ballistic regime, the spectra can be used to differentiate between cancerous and noncancerous tissues.

  13. Partial elastodynamic cloaking by means of fiber-reinforced composites

    NASA Astrophysics Data System (ADS)

    Olsson, P.; Wall, David J. N.

    2011-04-01

    In this paper, we show that if inextensible fibers are embedded in an elastic material (or the material is by some other means made considerably stiffer in a particular but possibly variable direction), one may obtain equations of motion which are form invariant under certain diffeomorphism, allowing for partial cloaking (or 'illusion optics') schemes in both 2D and 3D. The schemes are valid at all frequencies without requiring any active material properties, and will thus work in the time domain without requiring active materials. While being mathematically exact at all frequencies, the applicability is of course limited to where the continuum approximation holds. Additional limits, set by idealization in the modeling of fibers and core material, are also present. However, contrary to some other approaches, the solution does not require metamaterials with non-scalar mass densities, nor does it require the breaking of the supersymmetry of the elasticity tensor.

  14. Sources of fiber (image)

    MedlinePlus

    ... to avoid constipation. Vegetables, fresh fruits (especially dried fruits) and whole wheat, bran, or oatmeal cereals are excellent sources of fiber. To reap the benefits of fiber, it is very important to drink ...

  15. Fiber Optics Instrumentation Development

    NASA Technical Reports Server (NTRS)

    Chan, Patrick Hon Man; Parker, Allen R., Jr.; Richards, W. Lance

    2010-01-01

    This is a general presentation of fiber optics instrumentation development work being conducted at NASA Dryden for the past 10 years and recent achievements in the field of fiber optics strain sensors.

  16. Fiber Optics Technology.

    ERIC Educational Resources Information Center

    Burns, William E.

    1986-01-01

    Discusses various applications of fiber optics technology: information systems, industrial robots, medicine, television, transportation, and training. Types of jobs that will be available with fiber optics training (such as electricians and telephone cable installers and splicers) are examined. (CT)

  17. Soluble vs. insoluble fiber

    MedlinePlus

    ... soluble and insoluble. Both are important for health, digestion, and preventing diseases. Soluble fiber attracts water and turns to gel during digestion. This slows digestion. Soluble fiber is found in ...

  18. Omnidirectional fiber optic tiltmeter

    DOEpatents

    Benjamin, B.C.; Miller, H.M.

    1983-06-30

    A tiltmeter is provided which is useful in detecting very small movements such as earth tides. The device comprises a single optical fiber, and an associated weight affixed thereto, suspended from a support to form a pendulum. A light source, e.g., a light emitting diode, mounted on the support transmits light through the optical fiber to a group of further optical fibers located adjacent to but spaced from the free end of the single optical fiber so that displacement of the single optical fiber with respect to the group will result in a change in the amount of light received by the individual optical fibers of the group. Photodetectors individually connectd to the fibers produce corresponding electrical outputs which are differentially compared and processed to produce a resultant continuous analog output representative of the amount and direction of displacement of the single optical fiber.

  19. Elastic metamaterial beam with remotely tunable stiffness

    NASA Astrophysics Data System (ADS)

    Qian, Wei; Yu, Zhengyue; Wang, Xiaole; Lai, Yun; Yellen, Benjamin B.

    2016-02-01

    We demonstrate a dynamically tunable elastic metamaterial, which employs remote magnetic force to adjust its vibration absorption properties. The 1D metamaterial is constructed from a flat aluminum beam milled with a linear array of cylindrical holes. The beam is backed by a thin elastic membrane, on which thin disk-shaped permanent magnets are mounted. When excited by a shaker, the beam motion is tracked by a Laser Doppler Vibrometer, which conducts point by point scanning of the vibrating element. Elastic waves are unable to propagate through the beam when the driving frequency excites the first elastic bending mode in the unit cell. At these frequencies, the effective mass density of the unit cell becomes negative, which induces an exponentially decaying evanescent wave. Due to the non-linear elastic properties of the membrane, the effective stiffness of the unit cell can be tuned with an external magnetic force from nearby solenoids. Measurements of the linear and cubic static stiffness terms of the membrane are in excellent agreement with experimental measurements of the bandgap shift as a function of the applied force. In this implementation, bandgap shifts by as much as 40% can be achieved with ˜30 mN of applied magnetic force. This structure has potential for extension in 2D and 3D, providing a general approach for building dynamically tunable elastic metamaterials for applications in lensing and guiding elastic waves.

  20. Elastic metamaterial beam with remotely tunable stiffness

    SciTech Connect

    Qian, Wei; Yu, Zhengyue; Wang, Xiaole; Lai, Yun; Yellen, Benjamin B.

    2016-02-07

    We demonstrate a dynamically tunable elastic metamaterial, which employs remote magnetic force to adjust its vibration absorption properties. The 1D metamaterial is constructed from a flat aluminum beam milled with a linear array of cylindrical holes. The beam is backed by a thin elastic membrane, on which thin disk-shaped permanent magnets are mounted. When excited by a shaker, the beam motion is tracked by a Laser Doppler Vibrometer, which conducts point by point scanning of the vibrating element. Elastic waves are unable to propagate through the beam when the driving frequency excites the first elastic bending mode in the unit cell. At these frequencies, the effective mass density of the unit cell becomes negative, which induces an exponentially decaying evanescent wave. Due to the non-linear elastic properties of the membrane, the effective stiffness of the unit cell can be tuned with an external magnetic force from nearby solenoids. Measurements of the linear and cubic static stiffness terms of the membrane are in excellent agreement with experimental measurements of the bandgap shift as a function of the applied force. In this implementation, bandgap shifts by as much as 40% can be achieved with ∼30 mN of applied magnetic force. This structure has potential for extension in 2D and 3D, providing a general approach for building dynamically tunable elastic metamaterials for applications in lensing and guiding elastic waves.

  1. Estimation of In vivo Cancellous Bone Elasticity

    NASA Astrophysics Data System (ADS)

    Otani, Takahiko; Mano, Isao; Tsujimoto, Toshiyuki; Yamamoto, Tadahito; Teshima, Ryota; Naka, Hiroshi

    2009-07-01

    The effect of decreasing bone density (a symptom of osteoporosis) is greater for cancellous bone than for dense cortical bone, because cancellous bone is metabolically more active. Therefore, the bone density or bone mineral density of cancellous bone is generally used to estimate the onset of osteoporosis. Elasticity or elastic constant is a fundamental mechanical parameter and is directly related to the mechanical strength of bone. Accordingly, elasticity is a preferable parameter for assessing fracture risk. A novel ultrasonic bone densitometer LD-100 has been developed to determine the mass density and elasticity of cancellous bone with a spatial resolution comparable to that of peripheral quantitative computed tomography. Bone density and bone elasticity are evaluated using ultrasonic parameters based on fast and slow waves in cancellous bone by modeling the ultrasonic wave propagation path. Elasticity is deduced from the measured bone density and the propagation speed of the fast wave. Thus, the elasticity of cancellous bone is approximately expressed by a cubic equation of bone density.

  2. Application of numerical methods to elasticity imaging.

    PubMed

    Castaneda, Benjamin; Ormachea, Juvenal; Rodríguez, Paul; Parker, Kevin J

    2013-03-01

    Elasticity imaging can be understood as the intersection of the study of biomechanical properties, imaging sciences, and physics. It was mainly motivated by the fact that pathological tissue presents an increased stiffness when compared to surrounding normal tissue. In the last two decades, research on elasticity imaging has been an international and interdisciplinary pursuit aiming to map the viscoelastic properties of tissue in order to provide clinically useful information. As a result, several modalities of elasticity imaging, mostly based on ultrasound but also on magnetic resonance imaging and optical coherence tomography, have been proposed and applied to a number of clinical applications: cancer diagnosis (prostate, breast, liver), hepatic cirrhosis, renal disease, thyroiditis, arterial plaque evaluation, wall stiffness in arteries, evaluation of thrombosis in veins, and many others. In this context, numerical methods are applied to solve forward and inverse problems implicit in the algorithms in order to estimate viscoelastic linear and nonlinear parameters, especially for quantitative elasticity imaging modalities. In this work, an introduction to elasticity imaging modalities is presented. The working principle of qualitative modalities (sonoelasticity, strain elastography, acoustic radiation force impulse) and quantitative modalities (Crawling Waves Sonoelastography, Spatially Modulated Ultrasound Radiation Force (SMURF), Supersonic Imaging) will be explained. Subsequently, the areas in which numerical methods can be applied to elasticity imaging are highlighted and discussed. Finally, we present a detailed example of applying total variation and AM-FM techniques to the estimation of elasticity.

  3. Intramuscular pressures beneath elastic and inelastic leggings

    NASA Technical Reports Server (NTRS)

    Murthy, G.; Ballard, R. E.; Breit, G. A.; Watenpaugh, D. E.; Hargens, A. R.

    1994-01-01

    Leg compression devices have been used extensively by patients to combat chronic venous insufficiency and by astronauts to counteract orthostatic intolerance following spaceflight. However, the effects of elastic and inelastic leggings on the calf muscle pump have not been compared. The purpose of this study was to compare in normal subjects the effects of elastic and inelastic compression on leg intramuscular pressure (IMP), an objective index of calf muscle pump function. IMP in soleus and tibialis anterior muscles was measured with transducer-tipped catheters. Surface compression between each legging and the skin was recorded with an air bladder. Subjects were studied under three conditions: (1) control (no legging), (2) elastic legging, and (3) inelastic legging. Pressure data were recorded for each condition during recumbency, sitting, standing, walking, and running. Elastic leggings applied significantly greater surface compression during recumbency (20 +/- 1 mm Hg, mean +/- SE) than inelastic leggings (13 +/- 2 mm Hg). During recumbency, elastic leggings produced significantly higher soleus IMP of 25 +/- 1 mm Hg and tibialis anterior IMP of 28 +/- 1 mm Hg compared to 17 +/- 1 mm Hg and 20 +/- 2 mm Hg, respectively, generated by inelastic leggings and 8 +/- 1 mm Hg and 11 +/- 1 mm Hg, respectively, without leggings. During sitting, walking, and running, however, peak IMPs generated in the muscular compartments by elastic and inelastic leggings were similar. Our results suggest that elastic leg compression applied over a long period in the recumbent posture may impede microcirculation and jeopardize tissue viability.(ABSTRACT TRUNCATED AT 250 WORDS).

  4. Hysteresis and nonlinear elasticity in rocks

    SciTech Connect

    McCall, K.R.; Guyer, R.A.

    1993-12-01

    The purpose of this paper is to describe a theory of the propagation of elastic waves in hysteretic nonlinear elastic materials, e.g., rock. In the next section, we introduce the Priesach-Mayergoyz (P-M) model [6,7] of hysteretic systems and adapt it to describe the hysteretic mesoscopic elastic units (HMEU) determining the elastic properties of a rock. We combine the P-M model with effective medium theory (EMT) [8] to find the elastic response of a rock that has experienced a specified pressure history. Next, we consider elastic wave propagation in a hysteretic nonlinear elastic system governed by a history dependent equation of state. We consider one-dimensional propagation of compressional waves. The equation of motion for the longitudinal displacement field contains the same hysteretic nonlinear interactions that characterize the equation of state. We solve the equation of motion using the Green function technique developed by McCall [9]. This solution lets us identify the qualitative features in harmonic generation that are signatures of nonlinearity and hysteresis.

  5. Fiber length distributions and fiber quality

    Technology Transfer Automated Retrieval System (TEKTRAN)

    Cotton (Gossypium hirsutum L.) is grown in Georgia on ~1 million acres by producers as a raw material input for textile mills. Georgia cotton fiber qualities continue to improve through crop management, genetic, and ginning improvements. Competition from synthetic fibers, mill modernization, and g...

  6. Role of elasticity in stagnant lid convection

    NASA Astrophysics Data System (ADS)

    Patocka, Vojtech; Tackley, Paul; Cadek, Ondrej

    2016-04-01

    A present limitation of global thermo-chemical convection models is that they assume a purely viscous or visco-plastic flow law for solid rock, i.e. elasticity is ignored. This may not be a good assumption in the cold, outer boundary layer known as the lithosphere, where elastic deformation may be important. Elasticity in the lithosphere plays at least two roles: It changes surface topography, which changes the relationship between topography and gravity, and it alters the stress distribution in the lithosphere, which may affect dynamical behaviour such as the formation of plate boundaries and other tectonics features. In the present work we study these effects in the context of stagnant lid convection. We use StagYY (Tackley, 2008) enhanced to include elasticity through adding advected elastic stresses to the momentum equation and replacing viscosity by the "effective" one (the method described in e.g. Moresi et al., 2002). First, a test example with a cylinder rising below the lithosphere (Crameri et al., 2012) is considered in various geometries and the effect of elasticity on the resulting topography and geoid is evaluated. Both free-slip and free-surface upper boundary condition is considered. Second, comparison of stagnant lid convection models with and without elasticity is performed. It is shown that global characteristics of the convection do not change when a realistic value of shear modulus is employed and that the stress pattern in the lithosphere is very similar. The most important effect is that stresses build up gradually when elasticity is considered and thus the stress picture is more stable in the time domain in the elastic than in the viscous case. Viscoelastic lithosphere thus filters internal dynamics more effectively than a purely viscous one, responding only to features which stay stable for times comparable to its relaxation time. This effect is clearly recognizable only when free-surface upper boundary condition is considered. The role of

  7. Graphite Fibers from Pitch

    DTIC Science & Technology

    1975-07-01

    carbon fibers derived from pitch (Type-P fibers). But even if such perfect mesophase pitch fibers could be obtained, the subsequent carbonization... mesophase pitch filaments with diameters below lOfim was demonstrated in the preceding contract period. Further effort was aimed at reproducibly...Isotropie pitch fibers. ’ It seemed prudent for us to establish whether some of these agents could be used to advantage with the mesophase pitch

  8. Helical Fiber Amplifier

    DOEpatents

    Koplow, Jeffrey P.; Kliner, Dahy; Goldberg, Lew

    2002-12-17

    A multi-mode gain fiber is provided which affords substantial improvements in the maximum pulse energy, peak power handling capabilities, average output power, and/or pumping efficiency of fiber amplifier and laser sources while maintaining good beam quality (comparable to that of a conventional single-mode fiber source). These benefits are realized by coiling the multimode gain fiber to induce significant bend loss for all but the lowest-order mode(s).

  9. Graphite Fibers from Pitch

    DTIC Science & Technology

    1976-09-01

    yarn filaments may cause early fiber failure, particularly when the crack follows a tight spiral along the fiber axis, as it was observed in isolated...ray Results 4. Mechanical Properties 5. Conclusions V. STRUCTURE OF FILAMENTS IN TYPE P YARN 1. Fiber Structure Terminology 2. Correlation of...Fiber Structure with Single Filament Properties 3. Optical Microscopy of Filaments with Variable Structure 4. SEM Studies of Yarn Samples with

  10. Diode Pumped Fiber Laser

    DTIC Science & Technology

    1983-07-01

    acousto - optic beam deflector for greater absolute accuracy. The detection system was also upgraded to a response time of • 1 usec. The... 2 C. SUMMARY OF RESULTS.., 3 D . GENERAL PLAN 5 II. Nd:YAG FIBER PREPARATION 7 A. FIBER GROWTH 7 B. PHYSICAL PROPERTIES OF Nd:YAG...A. INTRODUCTION 25 B. GENERAL FORMALISM 26 C. FREE-SPACE LASERS 35 D . FIBER LASERS 43 1. Fiber Laser Configuration 43 2 . F

  11. Graphite fiber reinforced thermoplastic glass matrix composites for use at 1000 F

    NASA Technical Reports Server (NTRS)

    Prewo, K. M.; Minford, E. J.

    1985-01-01

    The fabrication and properties of the graphite fiber reinforced glass matrix composite system are described. By reinforcing borosilicate glass with graphite fibers it has been possible to develop a composite whose properties can be compared favorably with resin matrix counterparts. Both high elastic modulus and strength can be obtained and maintained to temperatures of approximately 600 C. In addition, composite dimensional stability is superior to resin or metal matrix systems due to the low thermal expansion behavior of the glass matrix.

  12. Structural basis of spectrin elasticity

    SciTech Connect

    Shen, B.W.; Stevens, F.J.; Luthi, U.; Goldin, S.B.

    1991-10-17

    A new model of human erythrocyte {alpha}-spectrin is proposed. The secondary structure of human erythrocyte {alpha}-spectrin and its folding into a condensed structure that can convert reversibly in situ, into an elongated configuration is predicted from its deduced protein sequence. Results from conformational and amphipathicity analyses suggest that {alpha}-spectrin consists mainly of short amphipathicity helices interconnected by flexible turns and/or coils. The distribution of charges and amphipathicity of the helices can facilitate their folding into stable domains of 4 and 3 helices surrounding a hydrophobic core. The association between adjacent four- and three-helix domains further organize them into recurring seven-helix motifs that might constitute the basic structural units of the extended {alpha}-spectrin. The elongated spectrin molecule packs, in a sinusoidal fashion, through interactions between neighboring motifs into a compact structure. We suggest that the reversible extension and contraction of this sigmoidally packed structure is the molecular basis of the mechanism by which spectrin contributes to the elasticity of the red cell membrane.

  13. Elasticity and Binding of Adenovirus

    NASA Astrophysics Data System (ADS)

    Matthews, Garrett; Negishi, Atsuko; Seeger, Adam; McCarty, Doug; Taylor, Russell; Samulshi, Jude; Superfine, Richard

    1999-11-01

    Adenovirus was the first human virus found to cause the transformation of cells and is one of the more common vectors being used for the development of gene therapy. As such, much is known about the viral structure and genome; however, the events of the early infection cycle, such as binding of the virus to the cell membrane and the release of genetic material from the capsid, for this and other nonenveloped viruses, are not fully understood. With the atomic force microscope (AFM) we are able to image the virus in both air and liquids, allowing us to change the surrounding environment, varying such physiologically relevant parameters as osmolality or pH. We additionally have the ability to do manipulations on single virus particles in these environments using the nanoManipulator. The nanoManipulator is an advanced interface for AFM that allows real time three dimensional rendering of the topographical data, allows the sample surface to be non-destructively felt using a hand held stylus that responds to the information being sensed at the tip, and allows controlled modification of the surface. Using this tool we have translated single virions over various surfaces, allowing us to measure the adhesion between the capsid and these surfaces. Additionally, we are able to place the tip directly atop individual viruses and measure their elasticity under a compressive load being supplied by that tip. We can explore how this property changes as a function of the properties of the surrounding liquid.

  14. Elasticity of polymeric nanocolloidal particles

    PubMed Central

    Riest, Jonas; Athanasopoulou, Labrini; Egorov, Sergei A.; Likos, Christos N.; Ziherl, Primož

    2015-01-01

    Softness is an essential mechanical feature of macromolecular particles such as polymer-grafted nanocolloids, polyelectrolyte networks, cross-linked microgels as well as block copolymer and dendrimer micelles. Elasticity of individual particles directly controls their swelling, wetting, and adsorption behaviour, their aggregation and self-assembly as well as structural and rheological properties of suspensions. Here we use numerical simulations and self-consistent field theory to study the deformation behaviour of a single spherical polymer brush upon diametral compression. We observe a universal response, which is rationalised using scaling arguments and interpreted in terms of two coarse-grained models. At small and intermediate compressions the deformation can be accurately reproduced by modelling the brush as a liquid drop, whereas at large compressions the brush behaves as a soft ball. Applicable far beyond the pairwise-additive small-strain regime, the models may be used to describe microelasticity of nanocolloids in severe confinement including dense disordered and crystalline phases. PMID:26522242

  15. Elastic/Inelastic Measurement Project

    SciTech Connect

    Yates, Steven; Hicks, Sally; Vanhoy, Jeffrey; McEllistrem, Marcus

    2016-03-01

    The work scope involves the measurement of neutron scattering from natural sodium (23Na) and two isotopes of iron, 56Fe and 54Fe. Angular distributions, i.e., differential cross sections, of the scattered neutrons will be measured for 5 to 10 incident neutron energies per year. The work of the first year concentrates on 23Na, while the enriched iron samples are procured. Differential neutron scattering cross sections provide information to guide nuclear reaction model calculations in the low-­energy (few MeV) fast-­neutron region. This region lies just above the isolated resonance region, which in general is well studied; however, model calculations are difficult in this region because overlapping resonance structure is evident and direct nuclear reactions are becoming important. The standard optical model treatment exhibits good predictive ability for the wide-­region average cross sections but cannot treat the overlapping resonance features. In addition, models that do predict the direct reaction component must be guided by measurements to describe correctly the strength of the direct component, e.g., β2 must be known to describe the direct component of the scattering to the first excited state. Measurements of the elastic scattering differential cross sections guide the optical model calculations, while inelastic differential cross sections provide the crucial information for correctly describing the direct component. Activities occurring during the performance period are described.

  16. Highly elastic conductive polymeric MEMS

    PubMed Central

    Ruhhammer, J; Zens, M; Goldschmidtboeing, F; Seifert, A; Woias, P

    2015-01-01

    Polymeric structures with integrated, functional microelectrical mechanical systems (MEMS) elements are increasingly important in various applications such as biomedical systems or wearable smart devices. These applications require highly flexible and elastic polymers with good conductivity, which can be embedded into a matrix that undergoes large deformations. Conductive polydimethylsiloxane (PDMS) is a suitable candidate but is still challenging to fabricate. Conductivity is achieved by filling a nonconductive PDMS matrix with conductive particles. In this work, we present an approach that uses new mixing techniques to fabricate conductive PDMS with different fillers such as carbon black, silver particles, and multiwalled carbon nanotubes. Additionally, the electrical properties of all three composites are examined under continuous mechanical stress. Furthermore, we present a novel, low-cost, simple three-step molding process that transfers a micro patterned silicon master into a polystyrene (PS) polytetrafluoroethylene (PTFE) replica with improved release features. This PS/PTFE mold is used for subsequent structuring of conductive PDMS with high accuracy. The non sticking characteristics enable the fabrication of delicate structures using a very soft PDMS, which is usually hard to release from conventional molds. Moreover, the process can also be applied to polyurethanes and various other material combinations. PMID:27877753

  17. Highly elastic conductive polymeric MEMS

    NASA Astrophysics Data System (ADS)

    Ruhhammer, J.; Zens, M.; Goldschmidtboeing, F.; Seifert, A.; Woias, P.

    2015-02-01

    Polymeric structures with integrated, functional microelectrical mechanical systems (MEMS) elements are increasingly important in various applications such as biomedical systems or wearable smart devices. These applications require highly flexible and elastic polymers with good conductivity, which can be embedded into a matrix that undergoes large deformations. Conductive polydimethylsiloxane (PDMS) is a suitable candidate but is still challenging to fabricate. Conductivity is achieved by filling a nonconductive PDMS matrix with conductive particles. In this work, we present an approach that uses new mixing techniques to fabricate conductive PDMS with different fillers such as carbon black, silver particles, and multiwalled carbon nanotubes. Additionally, the electrical properties of all three composites are examined under continuous mechanical stress. Furthermore, we present a novel, low-cost, simple three-step molding process that transfers a micro patterned silicon master into a polystyrene (PS) polytetrafluoroethylene (PTFE) replica with improved release features. This PS/PTFE mold is used for subsequent structuring of conductive PDMS with high accuracy. The non sticking characteristics enable the fabrication of delicate structures using a very soft PDMS, which is usually hard to release from conventional molds. Moreover, the process can also be applied to polyurethanes and various other material combinations.

  18. Report to Congress on abnormal occurrences

    SciTech Connect

    Not Available

    1991-03-01

    Section 208 of the Energy Reorganization Act of 1974 identified an abnormal occurrence as an unscheduled incident or event that the Nuclear Regulatory Commission determines to be significant from the standpoint of public health or safety and requires a quarterly report of such events to be made to Congress. This report covers the period from October 1 through December 31, 1990. The report discusses five abnormal occurrences, none of which involved a nuclear power plant. Two involved significant overexposures to the hands of two radiographers, two involved medical therapy misadministrations, and one involved a medical diagnostic misadministration. No abnormal occurrences were reported by the Agreement States. The report also contains information that updates a previously reported abnormal occurrence. 8 refs.

  19. MRI Helps Assess Fetal Brain Abnormalities

    MedlinePlus

    ... decisions about their pregnancy," said lead author Paul Griffiths. He's a professor of radiology at the University ... the fetus may have a suspected brain abnormality," Griffiths said in a journal news release. In this ...

  20. Abnormal Position and Presentation of the Fetus

    MedlinePlus

    ... Interest (Quiz) Breast Cancer (Video) Overview of the Female Reproductive System (News) Study: Plenty of IV Fluids May Make Childbirth Safer, Easier (News) Zejula Approved for Certain Female Cancers Additional Content Medical News Abnormal Position and ...

  1. Abnormalities of lung function in hay fever.

    PubMed Central

    Morgan, E J; Hall, D R

    1976-01-01

    Twenty subjects with symptoms of hay fever were studied to see whether abnormalities could be detected in the function of small airways. The investigations included dynamic compliance at varying respiratory frequencies, closing capacity, residual volume, transfer factor, and maximal expiratory flow-volume curves. The tests were repeated in the winter when symptoms had resolved. Frequency dependence of compliance was found in eight subjects with symptoms (40%), closing capacities being abnormal in only two instances. Conventional pulmonary function tests, including expiratory flow rates at mid vital capacity, were within the predicted range of all subjects. When tests were repeated in the winter, frequency dependence of compliance was no longer present in subjects whose symptoms had resolved. The study suggests that reversible small airway abnormalities are present in a significant proportion of subjects with symptoms of hay fever and that such abnormalities are best detected by the measurement of dynamic compliance at varying respiratory frequencies. PMID:769243

  2. Fiber optic coupled optical sensor

    DOEpatents

    Fleming, Kevin J.

    2001-01-01

    A displacement sensor includes a first optical fiber for radiating light to a target, and a second optical fiber for receiving light from the target. The end of the first fiber is adjacent and not axially aligned with the second fiber end. A lens focuses light from the first fiber onto the target and light from the target onto the second fiber.

  3. Elastic properties of polycrystalline dense matter

    NASA Astrophysics Data System (ADS)

    Kobyakov, D.; Pethick, C. J.

    2015-04-01

    Elastic properties of the solid regions of neutron star crusts and white dwarfs play an important role in theories of stellar oscillations. Matter in compact stars is presumably polycrystalline and, since the elastic properties of single crystals of such matter are very anisotropic, it is necessary to relate elastic properties of the polycrystal to those of a single crystal. We calculate the effective shear modulus of polycrystalline matter with randomly oriented crystallites using a self-consistent theory that has been very successful in applications to terrestrial materials and show that previous calculations overestimate the shear modulus by approximately 28 per cent.

  4. Polycrystalline gamma plutonium's elastic moduli versus temperature

    SciTech Connect

    Migliori, Albert; Betts, J; Trugman, A; Mielke, C H; Mitchell, J N; Ramos, M; Stroe, I

    2009-01-01

    Resonant ultrasound spectroscopy was used to measure the elastic properties of pure polycrystalline {sup 239}Pu in the {gamma} phase. Shear and longitudinal elastic moduli were measured simultaneously and the bulk modulus was computed from them. A smooth, linear, and large decrease of all elastic moduli with increasing temperature was observed. They calculated the Poisson ratio and found that it increases from 0.242 at 519 K to 0.252 at 571 K. These measurements on extremely well characterized pure Pu are in agreement with other reported results where overlap occurs.

  5. Deterministic Folding in Stiff Elastic Membranes

    NASA Astrophysics Data System (ADS)

    Tallinen, T.; Åström, J. A.; Timonen, J.

    2008-09-01

    Crumpled membranes have been found to be characterized by complex patterns of spatially seemingly random facets separated by narrow ridges of high elastic energy. We demonstrate by numerical simulations that compression of stiff elastic membranes with small randomness in their initial configurations leads to either random ridge configurations (high entropy) or nearly deterministic folds (low elastic energy). For folding with symmetric ridge configurations to appear in part of the crumpling processes, the crumpling rate must be slow enough. Folding stops when the thickness of the folded structure becomes important, and crumpling continues thereafter as a random process.

  6. Failure of classical elasticity in auxetic foams

    NASA Astrophysics Data System (ADS)

    Roh, J. H.; Giller, C. B.; Mott, P. H.; Roland, C. M.

    2013-04-01

    Poisson's ratio, ν, was measured for four materials, a rubbery polymer, a conventional soft foam, and two auxetic foams. We find that for the first two materials, having ν ≥ 0.2, the experimental determinations of Poisson's ratio are in good agreement with values calculated from the shear and tensile moduli using the equations of classical elasticity. However, for the two auxetic materials (ν < 0), the equations of classical elasticity give values significantly different from the measured ν. We offer an interpretation of these results based on a recently published analysis of the bounds on Poisson's ratio for classical elasticity to be applicable.

  7. Full Elasticity Tensor from Thermal Diffuse Scattering

    NASA Astrophysics Data System (ADS)

    Wehinger, Björn; Mirone, Alessandro; Krisch, Michael; Bosak, Alexeï

    2017-01-01

    We present a method for the precise determination of the full elasticity tensor from a single crystal diffraction experiment using monochromatic x rays. For the two benchmark systems calcite and magnesium oxide, we show that the measurement of thermal diffuse scattering in the proximity of Bragg reflections provides accurate values of the complete set of elastic constants. This approach allows for a reliable and model-free determination of the elastic properties and can be performed together with crystal structure investigation in the same experiment.

  8. Quantum-elastic bump on a surface

    NASA Astrophysics Data System (ADS)

    Atanasov, Victor; Dandoloff, Rossen

    2017-01-01

    We use an exact solution of the elastic membrane shape equation, representing the curvature, which will serve as a quantum potential in the quantum mechanical two dimensional Schrödinger equation for a (quasi-) particle on the surface of the membrane. Surface curvature in the quasi one-dimensional case is related to an unexpected static formation: on one hand the elastic energy has a maximum where surface curvature has a maximum and on the other hand the concentration of the expectation value to find the (quasi-) particle is again where the elastic energy is concentrated, namely where surface curvature has a maximum. This represents a particular form of a conformon.

  9. Intra-Ocular Pressure Measurement in a Patient with a Thin, Thick or Abnormal Cornea

    PubMed Central

    Clement, Colin I.; Parker, Douglas G.A.; Goldberg, Ivan

    2016-01-01

    Accurate measurement of intra-ocular pressure is a fundamental component of the ocular examination. The most common method of measuring IOP is by Goldmann applanation tonometry, the accuracy of which is influenced by the thickness and biomechanical properties of the cornea. Algorithms devised to correct for corneal thickness to estimate IOP oversimplify the effects of corneal biomechanics. The viscous and elastic properties of the cornea influence IOP measurements in unpredictable ways, a finding borne out in studies of patients with inherently abnormal and surgically altered corneal biomechanics. Dynamic contour tonometry, rebound tonometry and the ocular response analyzer provide useful alternatives to GAT in patients with abnormal corneas, such as those who have undergone laser vision correction or keratoplasty. This article reviews the various methods of intra-ocular pressure measurement available to the clinician and the ways in which their utility is influenced by variations in corneal thickness and biomechanics. PMID:27014386

  10. Probing axial orientation of collagen fibers with Brillouin microspectroscopy

    NASA Astrophysics Data System (ADS)

    Meng, Zhaokai; Yakovlev, Vladislav V.

    2015-03-01

    Collagen is an important structural component in many biological tissues including bone, teeth, skin, and vascular endothelial layer. Its fibrillar arrangement can produce tissues with distinct anisotropies and is responsible for its unique elastic properties. However, current methods of retrieving orientation of those fibers show low sensitivity to the out-of-plane orientations. In this report, we employed Brillouin microspectroscopy to probe the local sound velocity, which, in its turn, is found to have a strong correlation to the local fibrillar arrangements.

  11. Rate dependent response and failure of a ductile epoxy and carbon fiber reinforced epoxy composite

    SciTech Connect

    Brown, Eric N; Rae, Philip J; Dattelbaum, Dana M; Stahl, David B

    2010-01-01

    An extensive characterization suite has been performed on the response and failure of a ductile epoxy 55A and uniaxial carbon fiber reinforced epoxy composite of IM7 fibers in 55A resin from the quasistatic to shock regime. The quasistatic and intermediate strain rate response, including elastic modulus, yield and failure have are characterized by quasistatic, SHPB, and DMA measurements as a function of fiber orientation and temperature. The high strain rate shock effect of fiber orientation in the composite and response of the pure resin are presented for plate impact experiments. It has previously been shown that at lower impact velocities the shock velocity is strongly dependent on fiber orientation but at higher impact velocity the in-plane and through thickness Hugoniots converge. The current results are compared with previous studies of the shock response of carbon fiber composites with more conventional brittle epoxy matrices. The spall response of the composite is measured and compared with quasistatic fracture toughness measurements.

  12. Mineral Fiber Toxicology

    EPA Science Inventory

    The chemical and physical properties of different forms of mineral fibers impact biopersistence and pathology in the lung. Fiber chemistry, length, aspect ratio, surface area and dose are critical factors determining mineral fiber-associated health effects including cancer and as...

  13. The Fiber Optic Connection.

    ERIC Educational Resources Information Center

    Reese, Susan

    2003-01-01

    Describes the fiber optics programs at the Career and Technical Center in Berlin, Pennsylvania and the Charles S. Monroe Technology Center in Loudoun County, Virginia. Discusses the involvement of the Fiber Optic Association with education, research and development, manufacturing, sales, distribution, installation, and maintenance of fiber optic…

  14. Advanced Engineering Fibers.

    ERIC Educational Resources Information Center

    Edie, Dan D.; Dunham, Michael G.

    1987-01-01

    Describes Clemson University's Advanced Engineered Fibers Laboratory, which was established to provide national leadership and expertise in developing the processing equipment and advance fibers necessary for the chemical, fiber, and textile industries to enter the composite materials market. Discusses some of the laboratory's activities in…

  15. SYNTHETIC FIBERS, 1965,

    DTIC Science & Technology

    The following groups of fibers are each briefly discussed: Glass and other inorganic fibers, viscose rayon, cuprammonium rayon, saponified acetate rayon, alginate rayon, regenerated protein fibers, cellulose nitrate, cellulose acetate rayon, cellulose triacetate, polyamides, acrylics, modacrylics, polyvinyls, polyvinylidenes, polyesters, polyolefins, polyurethanes, fluorocarbons.

  16. Congenital abnormalities associated with extrahepatic portal hypertension.

    PubMed Central

    Odièvre, M; Pigé, G; Alagille, D

    1977-01-01

    Congenital abnormalities were present in 12 out of 30 (40%) children with extrahepatic portal hypertension of unknown cause, but in only 2 out of 17 (12%) children with extnahepatic portal hypertension secondary to umbilical vein catheterization or omphalitis. The most frequent abnormalities in this series and in published reports were atrial septal defect, malformation of the biliary tract, and anomalous inferior vena cava. These findings are consistent with the view that some cases with extrahepatic portal hypertension are congenital in origin. PMID:869567

  17. Congenital abnormalities associated with extrahepatic portal hypertension.

    PubMed

    Odièvre, M; Pigé, G; Alagille, D

    1977-05-01

    Congenital abnormalities were present in 12 out of 30 (40%) children with extrahepatic portal hypertension of unknown cause, but in only 2 out of 17 (12%) children with extnahepatic portal hypertension secondary to umbilical vein catheterization or omphalitis. The most frequent abnormalities in this series and in published reports were atrial septal defect, malformation of the biliary tract, and anomalous inferior vena cava. These findings are consistent with the view that some cases with extrahepatic portal hypertension are congenital in origin.

  18. Basilar artery migraine and reversible imaging abnormalities.

    PubMed

    Maytal, J; Libman, R B; Lustrin, E S

    1998-01-01

    We report a case of a basilar artery migraine in a 17-year-old boy with transient CT and MR abnormalities after each of two migraine episodes. A repeat MR study 6 months after the last event showed complete resolution of the lesion. Transient abnormalities on brain images similar to those shown in our case have been reported in patients with migraine and other neurologic conditions and are most likely related to cerebral vasogenic edema.

  19. Highly Elastic and Suturable Electrospun Poly(Glycerol Sebacate) Fibrous Scaffolds

    PubMed Central

    Jeffries, Eric M.; Allen, Robert A.; Gao, Jin; Pesce, Matt; Wang, Yadong

    2015-01-01

    Poly(glycerol sebacate) (PGS) is a thermally-crosslinked elastomer suitable for tissue regeneration due to its elasticity, degradability, and pro-regenerative inflammatory response. Pores in PGS scaffolds are typically introduced by porogen leaching, which compromises strength. Methods for producing fibrous PGS scaffolds are very limited. Electrospinning is the most widely used method for laboratory scale production of fibrous scaffolds. Electrospinning PGS by itself is challenging, necessitating a carrier polymer which can affect material properties if not removed. We report a simple electrospinning method to produce distinct PGS fibers while maintaining the desired mechanical and cytocompatibility properties of thermally crosslinked PGS. Fibrous PGS demonstrated 5 times higher tensile strength and increased suture retention compared to porous PGS foams. Additionally, similar modulus and elastic recovery were observed. A final advantage of fibrous PGS sheets is the ability to create multi-laminate constructs due to fiber bonding that occurs during thermal crosslinking. Taken together, these highly elastic fibrous PGS scaffolds will enable new approaches in tissue engineering and regenerative medicine. PMID:25686558

  20. Highly elastic and suturable electrospun poly(glycerol sebacate) fibrous scaffolds.

    PubMed

    Jeffries, Eric M; Allen, Robert A; Gao, Jin; Pesce, Matt; Wang, Yadong

    2015-05-01

    Poly(glycerol sebacate) (PGS) is a thermally-crosslinked elastomer suitable for tissue regeneration due to its elasticity, degradability, and pro-regenerative inflammatory response. Pores in PGS scaffolds are typically introduced by porogen leaching, which compromises strength. Methods for producing fibrous PGS scaffolds are very limited. Electrospinning is the most widely used method for laboratory scale production of fibrous scaffolds. Electrospinning PGS by itself is challenging, necessitating a carrier polymer which can affect material properties if not removed. We report a simple electrospinning method to produce distinct PGS fibers while maintaining the desired mechanical and cytocompatibility properties of thermally crosslinked PGS. Fibrous PGS demonstrated 5 times higher tensile strength and increased suture retention compared to porous PGS foams. Additionally, similar modulus and elastic recovery were observed. A final advantage of fibrous PGS sheets is the ability to create multi-laminate constructs due to fiber bonding that occurs during thermal crosslinking. Taken together, these highly elastic fibrous PGS scaffolds will enable new approaches in tissue engineering and regenerative medicine.

  1. Elasticity and inelasticity of silicon nitride/boron nitride fibrous monoliths.

    SciTech Connect

    Smirnov, B. I.; Burenkov, Yu. A.; Kardashev, B. K.; Singh, D.; Goretta, K. C.; de Arellano-Lopez, A. R.; Energy Technology; Russian Academy of Sciences; Univer. de Sevilla

    2001-01-01

    A study is reported on the effect of temperature and elastic vibration amplitude on Young's modulus E and internal friction in Si{sub 3}N{sub 4} and BN ceramic samples and Si{sub 3}N{sub 4}/BN monoliths obtained by hot pressing of BN-coated Si{sub 3}N{sub 4} fibers. The fibers were arranged along, across, or both along and across the specimen axis. The E measurements were carried out under thermal cycling within the 20-600 C range. It was found that high-modulus silicon-nitride specimens possess a high thermal stability; the E(T) dependences obtained under heating and cooling coincide well with one another. The low-modulus BN ceramic exhibits a considerable hysteresis, thus indicating evolution of the defect structure under the action of thermoelastic (internal) stresses. Monoliths demonstrate a qualitatively similar behavior (with hysteresis). This behavior of the elastic modulus is possible under microplastic deformation initiated by internal stresses. The presence of microplastic shear in all the materials studied is supported by the character of the amplitude dependences of internal friction and the Young's modulus. The experimental data obtained are discussed in terms of a model in which the temperature dependences of the elastic modulus and their features are accounted for by both microplastic deformation and nonlinear lattice-atom vibrations, which depend on internal stresses.

  2. Templated Biomineralization on Self-Assembled Protein Fibers

    SciTech Connect

    Subburaman,K.; Pernodet, N.; Kwak, S.; DiMasi, E.; Ge, S.; Zaitsev, V.; Ba, X.; Yang, N.; Rafailovich, M.

    2006-01-01

    Biological mineralization of tissues in living organisms relies on proteins that preferentially nucleate minerals and control their growth. This process is often referred to as 'templating', but this term has become generic, denoting various proposed mineral-organic interactions including both chemical and structural affinities. Here, we present an approach using self-assembled networks of elastin and fibronectin fibers, similar to the extracellular matrix. When induced onto negatively charged sulfonated polystyrene surfaces, these proteins form fiber networks of {approx}10-{mu}m spacing, leaving open regions of disorganized protein between them. We introduce an atomic force microscopy-based technique to measure the elastic modulus of both structured and disorganized protein before and during calcium carbonate mineralization. Mineral-induced thickening and stiffening of the protein fibers during early stages of mineralization is clearly demonstrated, well before discrete mineral crystals are large enough to image by atomic force microscopy. Calcium carbonate stiffens the protein fibers selectively without affecting the regions between them, emphasizing interactions between the mineral and the organized protein fibers. Late-stage observations by optical microscopy and secondary ion mass spectroscopy reveal that Ca is concentrated along the protein fibers and that crystals form preferentially on the fiber crossings. We demonstrate that organized versus unstructured proteins can be assembled mere nanometers apart and probed in identical environments, where mineralization is proved to require the structural organization imposed by fibrillogenesis of the extracellular matrix.

  3. Templated biomineralization on self-assembled protein fibers.

    PubMed

    Subburaman, K; Pernodet, N; Kwak, S Y; DiMasi, E; Ge, S; Zaitsev, V; Ba, X; Yang, N L; Rafailovich, M

    2006-10-03

    Biological mineralization of tissues in living organisms relies on proteins that preferentially nucleate minerals and control their growth. This process is often referred to as "templating," but this term has become generic, denoting various proposed mineral-organic interactions including both chemical and structural affinities. Here, we present an approach using self-assembled networks of elastin and fibronectin fibers, similar to the extracellular matrix. When induced onto negatively charged sulfonated polystyrene surfaces, these proteins form fiber networks of approximately 10-mum spacing, leaving open regions of disorganized protein between them. We introduce an atomic force microscopy-based technique to measure the elastic modulus of both structured and disorganized protein before and during calcium carbonate mineralization. Mineral-induced thickening and stiffening of the protein fibers during early stages of mineralization is clearly demonstrated, well before discrete mineral crystals are large enough to image by atomic force microscopy. Calcium carbonate stiffens the protein fibers selectively without affecting the regions between them, emphasizing interactions between the mineral and the organized protein fibers. Late-stage observations by optical microscopy and secondary ion mass spectroscopy reveal that Ca is concentrated along the protein fibers and that crystals form preferentially on the fiber crossings. We demonstrate that organized versus unstructured proteins can be assembled mere nanometers apart and probed in identical environments, where mineralization is proved to require the structural organization imposed by fibrillogenesis of the extracellular matrix.

  4. Templated biomineralization on self-assembled protein fibers

    PubMed Central

    Subburaman, K.; Pernodet, N.; Kwak, S. Y.; DiMasi, E.; Ge, S.; Zaitsev, V.; Ba, X.; Yang, N. L.; Rafailovich, M.

    2006-01-01

    Biological mineralization of tissues in living organisms relies on proteins that preferentially nucleate minerals and control their growth. This process is often referred to as “templating,” but this term has become generic, denoting various proposed mineral–organic interactions including both chemical and structural affinities. Here, we present an approach using self-assembled networks of elastin and fibronectin fibers, similar to the extracellular matrix. When induced onto negatively charged sulfonated polystyrene surfaces, these proteins form fiber networks of ≈10-μm spacing, leaving open regions of disorganized protein between them. We introduce an atomic force microscopy-based technique to measure the elastic modulus of both structured and disorganized protein before and during calcium carbonate mineralization. Mineral-induced thickening and stiffening of the protein fibers during early stages of mineralization is clearly demonstrated, well before discrete mineral crystals are large enough to image by atomic force microscopy. Calcium carbonate stiffens the protein fibers selectively without affecting the regions between them, emphasizing interactions between the mineral and the organized protein fibers. Late-stage observations by optical microscopy and secondary ion mass spectroscopy reveal that Ca is concentrated along the protein fibers and that crystals form preferentially on the fiber crossings. We demonstrate that organized versus unstructured proteins can be assembled mere nanometers apart and probed in identical environments, where mineralization is proved to require the structural organization imposed by fibrillogenesis of the extracellular matrix. PMID:17003131

  5. CREEP MODELING FOR INJECTION-MOLDED LONG-FIBER THERMOPLASTICS

    SciTech Connect

    Nguyen, Ba Nghiep; Kunc, Vlastimil; Bapanapalli, Satish K.

    2008-06-30

    This paper proposes a model to predict the creep response of injection-molded long-fiber thermoplastics (LFTs). The model accounts for elastic fibers embedded in a thermoplastic resin that exhibits the nonlinear viscoelastic behavior described by the Schapery’s model. It also accounts for fiber length and orientation distributions in the composite formed by the injection-molding process. Fiber length and orientation distributions were measured and used in the analysis that applies the Eshelby’s equivalent inclusion method, the Mori-Tanaka assumption (termed as the Eshelby-Mori-Tanaka approach) and the fiber orientation averaging technique to compute the overall strain increment resulting from an overall constant applied stress during a given time increment. The creep model for LFTs has been implemented in the ABAQUS finite element code via user-subroutines and has been validated against the experimental creep data obtained for long-glass-fiber/polypropylene specimens. The effects of fiber orientation and length distributions on the composite creep response are determined and discussed.

  6. 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.

  7. Human mesenchymal stem cells are sensitive to abnormal gravity and exhibit classic apoptotic features.

    PubMed

    Meng, Rui; Xu, Hui-yun; Di, Sheng-meng; Shi, Dong-yan; Qian, Ai-rong; Wang, Jin-fu; Shang, Peng

    2011-02-01

    The aim of the present study was to investigate the effects of abnormal gravity on human mesenchymal stem cells (hMSCs). Strong magnetic field and magnetic field gradient generate a magnetic force that can add to or subtract from the gravitational force. In this study, this is defined as a high-magneto-gravitational environment (HMGE). The HMGE provides three apparent gravity levels, i.e. hypogravity (μg), hypergravity (2g) and normal gravity with strong magnetic field (1g) conditions. After hMSCs were subject to HMGE for 12 h, the proliferation, morphology, structure and apoptosis were investigated. Results showed that the proliferation of hMSCs was inhibited under μg condition. The abnormal gravity induced morphologic characteristics of apoptosis cells, such as cell shrinkage, membrane blebbing, nuclear chromatin condensation and margination, decreased cell viability, and increased caspase-3/7 activity. The rate of apoptosis under μg condition is up to 56.95%. The F-actin stress fibers and microtubules were disrupted under abnormal gravity condition. Under μg-condition, the expression of p53 at mRNA and protein levels was up-regulated more than 9- and 6 folds, respectively. The Pifithrin-α, an specific inhibitor of p53, inhibited the apoptosis and prevented the disruption of cytoskeleton induced by abnormal gravity. These results implied that hMSCs were sensitive to abnormal gravity and exhibited classic apoptotic features, which might be associated with p53 signaling.

  8. The trampoline aftereffect: the motor and sensory modulations associated with jumping on an elastic surface.

    PubMed

    Márquez, Gonzalo; Aguado, Xavier; Alegre, Luis M; Lago, Angel; Acero, Rafael M; Fernández-del-Olmo, Miguel

    2010-08-01

    After repeated jumps over an elastic surface (e.g. a trampoline), subjects usually report a strange sensation when they jump again overground (e.g. they feel unable to jump because their body feels heavy). However, the motor and sensory effects of exposure to an elastic surface are unknown. In the present study, we examined the motor and perceptual effects of repeated jumps over two different surfaces (stiff and elastic), measuring how this affected maximal countermovement vertical jump (CMJ). Fourteen subjects participated in two counterbalanced sessions, 1 week apart. Each experimental session consisted of a series of maximal CMJs over a force plate before and after 1 min of light jumping on an elastic or stiff surface. We measured actual motor performance (height jump and leg stiffness during CMJ) and how that related to perceptual experience (jump height estimation and subjective sensation). After repeated jumps on an elastic surface, the first CMJ showed a significant increase in leg stiffness (P < or = 0.01), decrease in jump height (P < or = 0.01) increase in perceptual misestimation (P < or = 0.05) and abnormal subjective sensation (P < or = 0.001). These changes were not observed after repeated jumps on a rigid surface. In a complementary experiment, continuous surface transitions show that the effects persist across cycles, and the effects over the leg stiffness and subjective experience are minimized (P < or = 0.05). We propose that these aftereffects could be the consequence of an erroneous internal model resulting from the high vertical forces produced by the elastic surface.

  9. Effective dynamic moduli and density of fiber-reinforced composites

    NASA Astrophysics Data System (ADS)

    Caleap, Mihai; Drinkwater, Bruce W.; Wilcox, Paul D.

    2013-01-01

    A multiple scattering theory is developed to predict the effective dynamic material properties of elastic composites in two dimensions. The system consists of circular fibers distributed randomly in an elastic solid. The coherent wave propagation in the elastic composite is analyzed under the quasi-crystalline approximation. The effective medium equivalent to the original composite material is a medium with space and time dispersion, and hence, its parameters are functions of frequency of the incident field. Although the effective medium is homogeneous and isotropic, its effective dynamic moduli and density depend on the type of propagating wave, e.g., they are different for longitudinal and transverse incident waves. However, they coincide in the long-wave region as expected on physical grounds. Furthermore, the effective material properties are found to be complexvalued, in addition to their dynamic nature. For in-plane waves and in the long-wave limit the effective bulk modulus, mass density and shear modulus are independently determined by a set of monopolar, dipolar and quadrupolar scattering coefficients of the embedded fibers alone, respectively. Likewise, for anti-plane waves, the effective mass density and the shear modulus are specified, respectively, in terms of the monopolar and dipolar scattering coefficients of the corresponding fiberscattering problem. The emerging possibility of designing composite materials to form elastic metamaterials is discussed.

  10. Dissecting Regional Variations in Stress Fiber Mechanics in Living Cells with Laser Nanosurgery

    SciTech Connect

    Tanner, Kandice; Boudreau, Aaron; Bissell, Mina J; Kumar, Sanjay

    2010-03-02

    The ability of a cell to distribute contractile stresses across the extracellular matrix in a spatially heterogeneous fashion underlies many cellular behaviors, including motility and tissue assembly. Here we investigate the biophysical basis of this phenomenon by using femtosecond laser nanosurgery to measure the viscoelastic recoil and cell-shape contributions of contractile stress fibers (SFs) located in specific compartments of living cells. Upon photodisruption and recoil, myosin light chain kinase-dependent SFs located along the cell periphery display much lower effective elasticities and higher plateau retraction distances than Rho-associated kinase-dependent SFs located in the cell center, with severing of peripheral fibers uniquely triggering a dramatic contraction of the entire cell within minutes of fiber irradiation. Image correlation spectroscopy reveals that when one population of SFs is pharmacologically dissipated, actin density flows toward the other population. Furthermore, dissipation of peripheral fibers reduces the elasticity and increases the plateau retraction distance of central fibers, and severing central fibers under these conditions triggers cellular contraction. Together, these findings show that SFs regulated by different myosin activators exhibit different mechanical properties and cell shape contributions. They also suggest that some fibers can absorb components and assume mechanical roles of other fibers to stabilize cell shape.

  11. Damage of the Interface Between an Orthodontic Bracket and Enamel - the Effect of Some Elastic Properties of the Adhesive Material

    NASA Astrophysics Data System (ADS)

    Durgesh, B. H.; Alkheraif, A. A.; Al Sharawy, M.; Varrela, J.; Vallittu, P. K.

    2016-01-01

    The aim of this study was to investigate the magnitude of debonding stress of an orthodontic bracket bonded to the enamel with resin systems having different elastic properties. For the same purpose, sixty human premolars were randomly divided into four groups according to the adhesive system used for bonding brackets: G Fix flowable resin (GFI) with Everstick NET (ESN), GFI, G Aenial Universal Flow (GAU) with ESN, and GAU. The brackets were stressed in the occlusogingival direction on a universal testing machine. The values of debonding load and displacement were determined at the point of debonding. The elastic modulus of the tested materials was determined using nanoindentation. An analysis of variance showed a significant difference in the loads required to debond the bracket among the groups tested. The GAU group had the highest elastic modulus, followed by the GFI and ESN groups. ARI (Adhesive Remnant Index) scores demonstrated more remnants of the adhesive material on the bracket surface with adhesives having a higher elastic modulus. Taking into consideration results of the present in-vitro study, it can be concluded that the incorporation of a glass-fiber-reinforced composite resin (FRC) with a low elastic modulus between the orthodontic bracket and enamel increases the debonding force and strain more than with adhesive systems having a higher elastic modulus.

  12. Effect of fiber content on flexural properties of glass fiber-reinforced polyamide-6 prepared by injection molding.

    PubMed

    Nagakura, Manamu; Tanimoto, Yasuhiro; Nishiyama, Norihiro

    2017-02-11

    The use of non-metal clasp denture (NMCD) materials may seriously affect the remaining tissues because of the low rigidity of NMCD materials such as polyamides. The purpose of this study was to develop a high-rigidity glass fiber-reinforced thermoplastic (GFRTP) composed of E-glass fiber and polyamide-6 for NMCDs using an injection molding. The reinforcing effects of fiber on the flexural properties of GFRTPs were investigated using glass fiber content ranging from 0 to 50 mass%. Three-point bending tests indicated that the flexural strength and elastic modulus of a GFRTP with a fiber content of 50 mass% were 5.4 and 4.7 times higher than those of unreinforced polyamide-6, respectively. The result showed that the physical characteristics of GFRTPs were greatly improved by increasing the fiber content, and the beneficial effects of fiber reinforcement were evident. The findings suggest that the injection-molded GFRTPs are adaptable to NMCDs because of their excellent mechanical properties.

  13. Hi-Nicalon Fiber-Reinforced Celsian Matrix Composites: Influence of Interface Modification

    NASA Technical Reports Server (NTRS)

    Bansal, Narottam P.; Eldridge, Jeffrey I.

    1998-01-01

    Unidirectional celsian matrix composites having 42-45 vol % of uncoated or BN-SIC coated Hi-Nicalon fibers were tested in three-point bend at room temperature. The uncoated fiber-reinforced composites showed catastrophic failure with strength of 210 35 MPa and a flat fracture surface. In contrast, composites reinforced with coated fibers exhibited graceful failure with extensive fiber pullout. Values of first matrix cracking stress and strain were 435 +/- 35 MPa and 0.27 +/- 0.01%, respectively, with ultimate strength as high as 960 MPa. The elastic Young modulus of the uncoated and coated fiber-reinforced composites were 184 +/- 4 GPa and 165 +/- 5 GPa, respectively. Fiber push-through tests and microscopic examination indicated no chemical reaction at the uncoated or coated fiber-matrix interface. The low strength of composite with uncoated fibers is due to degradation of the fiber strength from mechanical damage during processing. Because both the coated- and uncoated-fiber-reinforced composites exhibited weak interfaces, the beneficial effect of the BN-SIC dual layer is primarily the protection of fibers from mechanical damage during processing.

  14. Micro-Mechanical Analysis About Kink Band in Carbon Fiber/Epoxy Composites Under Longitudinal Compression

    NASA Astrophysics Data System (ADS)

    Zhang, Mi; Guan, Zhidong; Wang, Xiaodong; Du, Shanyi

    2016-12-01

    Kink band is a typical phenomenon for composites under longitudinal compression. In this paper, theoretical analysis and finite element simulation were conducted to analyze kink angle as well as compressive strength of composites. Kink angle was considered to be an important character throughout longitudinal compression process. Three factors including plastic matrix, initial fiber misalignment and rotation due to loading were considered for theoretical analysis. Besides, the relationship between kink angle and fiber volume fraction was improved and optimized by theoretical derivation. In addition, finite element models considering fiber stochastic strength and Drucker-Prager constitutive model for matrix were conducted in ABAQUS to analyze kink band formation process, which corresponded with the experimental results. Through simulation, the loading and failure procedure can be evidently divided into three stages: elastic stage, softening stage, and fiber break stage. It also shows that kink band is a result of fiber misalignment and plastic matrix. Different values of initial fiber misalignment angle, wavelength and fiber volume fraction were considered to explore the effects on compressive strength and kink angle. Results show that compressive strength increases with the decreasing of initial fiber misalignment angle, the decreasing of initial fiber misalignment wavelength and the increasing of fiber volume fraction, while kink angle decreases in these situations. Orthogonal array in statistics was also built to distinguish the effect degree of these factors. It indicates that initial fiber misalignment angle has the largest impact on compressive strength and kink angle.

  15. Modeling of Low Velocity Impact Damage in Injection-Molded Long Fiber Composites

    SciTech Connect

    Bapanapalli, Satish K.; Nguyen, Ba Nghiep; Kunc, Vlastimil

    2009-09-15

    Apart from increase in failure strength, increase in the impact resistance is one of the major reasons for the interest in long-fiber polymer composites for automotive structural applications. The in-house code EMTA has been adapted to accommodate dynamic problems. It combines with ABAQUS Explicit solver to model impact behavior of long-fiber thermoplastics. At the present stage, the model captures the elastic behavior of LFTs in a dynamic formulation that incorporates the Eshelby equivalent inclusion method, the Mori-Tanaka assumption and the fiber orientation averaging technique. The effect of average fiber length on the impact behavior of discontinuous fiber composites has been studied with the aid of the preliminary model. Fiber lengths from short fiber range to long fiber range were explored with fiber orientation distributions from obtained from previous studies. The numerical examples indicate a slight improvement in the energy absorption capabilities of long fiber thermoplastics over short fiber thermoplastics. Advanced impact models need to be incorporated into the current code to model impact behavior with greater accuracy.

  16. Mechanics of finite cracks in dissimilar anisotropic elastic media considering interfacial elasticity

    NASA Astrophysics Data System (ADS)

    Juan, Pierre-Alexandre; Dingreville, Rémi

    2017-02-01

    Interfacial crack fields and singularities in bimaterial interfaces (i.e., grain boundaries or dissimilar materials interfaces) are considered through a general formulation for two-dimensional (2-D) anisotropic elasticity while accounting for the interfacial structure by means of an interfacial elasticity paradigm. The interfacial elasticity formulation introduces boundary conditions that are effectively equivalent to those for a weakly bounded interface. This formalism considers the 2-D crack-tip elastic fields using complex variable techniques. While the consideration of the interfacial elasticity does not affect the order of the singularity, it modifies the oscillatory effects associated with problems involving interface cracks. Constructive or destructive "interferences" are directly affected by the interface structure and its elastic response. This general formulation provides an insight on the physical significance and the obvious coupling between the interface structure and the associated mechanical fields in the vicinity of the crack tip.

  17. Mechanics of finite cracks in dissimilar anisotropic elastic media considering interfacial elasticity

    SciTech Connect

    Juan, Pierre -Alexandre; Dingreville, Remi

    2016-10-31

    Interfacial crack fields and singularities in bimaterial interfaces (i.e., grain boundaries or dissimilar materials interfaces) are considered through a general formulation for two-dimensional (2-D) anisotropic elasticity while accounting for the interfacial structure by means of an interfacial elasticity paradigm. The interfacial elasticity formulation introduces boundary conditions that are effectively equivalent to those for a weakly bounded interface. This formalism considers the 2-D crack-tip elastic fields using complex variable techniques. While the consideration of the interfacial elasticity does not affect the order of the singularity, it modifies the oscillatory effects associated with problems involving interface cracks. Constructive or destructive “interferences” are directly affected by the interface structure and its elastic response. Furthermore, this general formulation provides an insight on the physical significance and the obvious coupling between the interface structure and the associated mechanical fields in the vicinity of the crack tip.

  18. Mechanics of finite cracks in dissimilar anisotropic elastic media considering interfacial elasticity

    DOE PAGES

    Juan, Pierre -Alexandre; Dingreville, Remi

    2016-10-31

    Interfacial crack fields and singularities in bimaterial interfaces (i.e., grain boundaries or dissimilar materials interfaces) are considered through a general formulation for two-dimensional (2-D) anisotropic elasticity while accounting for the interfacial structure by means of an interfacial elasticity paradigm. The interfacial elasticity formulation introduces boundary conditions that are effectively equivalent to those for a weakly bounded interface. This formalism considers the 2-D crack-tip elastic fields using complex variable techniques. While the consideration of the interfacial elasticity does not affect the order of the singularity, it modifies the oscillatory effects associated with problems involving interface cracks. Constructive or destructive “interferences” aremore » directly affected by the interface structure and its elastic response. Furthermore, this general formulation provides an insight on the physical significance and the obvious coupling between the interface structure and the associated mechanical fields in the vicinity of the crack tip.« less

  19. Single-Crystal Elastic Constants of Yttria (Y2O3) Measured to High Temperatures

    NASA Technical Reports Server (NTRS)

    Sayir, Ali; Palko, James W.; Kriven, Waltraud M.; Sinogeikin, Sergey V.; Bass, Jay D.

    2001-01-01

    Yttria, or yttrium sesquioxide (Y2O3), has been considered for use in nuclear applications and has gained interest relatively recently for use in infrared optics. Single crystals of yttria have been grown successfully at the NASA Glenn Research Center using a laser-heated float zone technique in a fiber and rod. Such samples allow measurement of the single-crystal elastic properties, and these measurements provide useful property data for the design of components using single crystals. They also yield information as to what degree the elastic properties of yttria ceramics are a result of the intrinsic properties of the yttria crystal in comparison to characteristics that may depend on processing, such as microstructure and intergranular phases, which are common in sintered yttria. The single-crystal elastic moduli are valuable for designing such optical components. In particular, the temperature derivatives of elastic moduli allow the dimensional changes due to heating under physical constraints, as well as acoustic excitation, to be determined. The single-crystal elastic moduli of yttria were measured by Brillouin spectroscopy up to 1200 C. The room-temperature values obtained were C(sub 11) = 223.6 + 0.6 GPa, C(sub 44) = 74.6 + 0.5 GPa, and C(sub 12) = 112.4 + 1.0 GPa. The resulting bulk and (Voigt-Reuss-Hill) shear moduli were K = 149.5 + 1.0 GPa and G(sub VRH) = 66.3 + 0.8 GPa, respectively. Linear least-squares regressions to the variation of bulk and shear moduli with temperature resulted in derivatives of dK/dT = -17 + 2 MPa/C and dG(sub VRH)/dT = -8 + 2 MPa/ C. Elastic anisotropy was found to remain essentially constant over the temperature range studied.

  20. Dynamic response of visco-elastic plates

    NASA Astrophysics Data System (ADS)

    Kadıoǧlu, Fethi; Tekin, Gülçin

    2016-12-01

    In this study, a comprehensive analysis about the dynamic response characteristics of visco-elastic plates is given. To construct the functional in the Laplace-Carson domain for the analysis of visco-elastic plates based on the Kirchhoff hypothesis, functional analysis method is employed. By using this new energy functional in the Laplace-Carson domain, moment values that are important for engineers can be obtained directly with excellent accuracy and element equations can be written explicitly. Three-element model is considered for modelling the visco-elastic material behavior. The solutions obtained in the Laplace-Carson domain by utilizing mixed finite element formulation are transformed to the time domain using the Durbin's inverse Laplace transform technique. The proposed mixed finite element formulation is shown to be simple to implement and gives satisfactory results for dynamic response of visco-elastic plates.